File: rfc3108.txt

package info (click to toggle)
doc-rfc 20181229-2
  • links: PTS, VCS
  • area: non-free
  • in suites: buster
  • size: 570,944 kB
  • sloc: xml: 285,646; sh: 107; python: 90; perl: 42; makefile: 14
file content (6163 lines) | stat: -rw-r--r-- 248,037 bytes parent folder | download | duplicates (5)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578
2579
2580
2581
2582
2583
2584
2585
2586
2587
2588
2589
2590
2591
2592
2593
2594
2595
2596
2597
2598
2599
2600
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
2612
2613
2614
2615
2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
2637
2638
2639
2640
2641
2642
2643
2644
2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
2682
2683
2684
2685
2686
2687
2688
2689
2690
2691
2692
2693
2694
2695
2696
2697
2698
2699
2700
2701
2702
2703
2704
2705
2706
2707
2708
2709
2710
2711
2712
2713
2714
2715
2716
2717
2718
2719
2720
2721
2722
2723
2724
2725
2726
2727
2728
2729
2730
2731
2732
2733
2734
2735
2736
2737
2738
2739
2740
2741
2742
2743
2744
2745
2746
2747
2748
2749
2750
2751
2752
2753
2754
2755
2756
2757
2758
2759
2760
2761
2762
2763
2764
2765
2766
2767
2768
2769
2770
2771
2772
2773
2774
2775
2776
2777
2778
2779
2780
2781
2782
2783
2784
2785
2786
2787
2788
2789
2790
2791
2792
2793
2794
2795
2796
2797
2798
2799
2800
2801
2802
2803
2804
2805
2806
2807
2808
2809
2810
2811
2812
2813
2814
2815
2816
2817
2818
2819
2820
2821
2822
2823
2824
2825
2826
2827
2828
2829
2830
2831
2832
2833
2834
2835
2836
2837
2838
2839
2840
2841
2842
2843
2844
2845
2846
2847
2848
2849
2850
2851
2852
2853
2854
2855
2856
2857
2858
2859
2860
2861
2862
2863
2864
2865
2866
2867
2868
2869
2870
2871
2872
2873
2874
2875
2876
2877
2878
2879
2880
2881
2882
2883
2884
2885
2886
2887
2888
2889
2890
2891
2892
2893
2894
2895
2896
2897
2898
2899
2900
2901
2902
2903
2904
2905
2906
2907
2908
2909
2910
2911
2912
2913
2914
2915
2916
2917
2918
2919
2920
2921
2922
2923
2924
2925
2926
2927
2928
2929
2930
2931
2932
2933
2934
2935
2936
2937
2938
2939
2940
2941
2942
2943
2944
2945
2946
2947
2948
2949
2950
2951
2952
2953
2954
2955
2956
2957
2958
2959
2960
2961
2962
2963
2964
2965
2966
2967
2968
2969
2970
2971
2972
2973
2974
2975
2976
2977
2978
2979
2980
2981
2982
2983
2984
2985
2986
2987
2988
2989
2990
2991
2992
2993
2994
2995
2996
2997
2998
2999
3000
3001
3002
3003
3004
3005
3006
3007
3008
3009
3010
3011
3012
3013
3014
3015
3016
3017
3018
3019
3020
3021
3022
3023
3024
3025
3026
3027
3028
3029
3030
3031
3032
3033
3034
3035
3036
3037
3038
3039
3040
3041
3042
3043
3044
3045
3046
3047
3048
3049
3050
3051
3052
3053
3054
3055
3056
3057
3058
3059
3060
3061
3062
3063
3064
3065
3066
3067
3068
3069
3070
3071
3072
3073
3074
3075
3076
3077
3078
3079
3080
3081
3082
3083
3084
3085
3086
3087
3088
3089
3090
3091
3092
3093
3094
3095
3096
3097
3098
3099
3100
3101
3102
3103
3104
3105
3106
3107
3108
3109
3110
3111
3112
3113
3114
3115
3116
3117
3118
3119
3120
3121
3122
3123
3124
3125
3126
3127
3128
3129
3130
3131
3132
3133
3134
3135
3136
3137
3138
3139
3140
3141
3142
3143
3144
3145
3146
3147
3148
3149
3150
3151
3152
3153
3154
3155
3156
3157
3158
3159
3160
3161
3162
3163
3164
3165
3166
3167
3168
3169
3170
3171
3172
3173
3174
3175
3176
3177
3178
3179
3180
3181
3182
3183
3184
3185
3186
3187
3188
3189
3190
3191
3192
3193
3194
3195
3196
3197
3198
3199
3200
3201
3202
3203
3204
3205
3206
3207
3208
3209
3210
3211
3212
3213
3214
3215
3216
3217
3218
3219
3220
3221
3222
3223
3224
3225
3226
3227
3228
3229
3230
3231
3232
3233
3234
3235
3236
3237
3238
3239
3240
3241
3242
3243
3244
3245
3246
3247
3248
3249
3250
3251
3252
3253
3254
3255
3256
3257
3258
3259
3260
3261
3262
3263
3264
3265
3266
3267
3268
3269
3270
3271
3272
3273
3274
3275
3276
3277
3278
3279
3280
3281
3282
3283
3284
3285
3286
3287
3288
3289
3290
3291
3292
3293
3294
3295
3296
3297
3298
3299
3300
3301
3302
3303
3304
3305
3306
3307
3308
3309
3310
3311
3312
3313
3314
3315
3316
3317
3318
3319
3320
3321
3322
3323
3324
3325
3326
3327
3328
3329
3330
3331
3332
3333
3334
3335
3336
3337
3338
3339
3340
3341
3342
3343
3344
3345
3346
3347
3348
3349
3350
3351
3352
3353
3354
3355
3356
3357
3358
3359
3360
3361
3362
3363
3364
3365
3366
3367
3368
3369
3370
3371
3372
3373
3374
3375
3376
3377
3378
3379
3380
3381
3382
3383
3384
3385
3386
3387
3388
3389
3390
3391
3392
3393
3394
3395
3396
3397
3398
3399
3400
3401
3402
3403
3404
3405
3406
3407
3408
3409
3410
3411
3412
3413
3414
3415
3416
3417
3418
3419
3420
3421
3422
3423
3424
3425
3426
3427
3428
3429
3430
3431
3432
3433
3434
3435
3436
3437
3438
3439
3440
3441
3442
3443
3444
3445
3446
3447
3448
3449
3450
3451
3452
3453
3454
3455
3456
3457
3458
3459
3460
3461
3462
3463
3464
3465
3466
3467
3468
3469
3470
3471
3472
3473
3474
3475
3476
3477
3478
3479
3480
3481
3482
3483
3484
3485
3486
3487
3488
3489
3490
3491
3492
3493
3494
3495
3496
3497
3498
3499
3500
3501
3502
3503
3504
3505
3506
3507
3508
3509
3510
3511
3512
3513
3514
3515
3516
3517
3518
3519
3520
3521
3522
3523
3524
3525
3526
3527
3528
3529
3530
3531
3532
3533
3534
3535
3536
3537
3538
3539
3540
3541
3542
3543
3544
3545
3546
3547
3548
3549
3550
3551
3552
3553
3554
3555
3556
3557
3558
3559
3560
3561
3562
3563
3564
3565
3566
3567
3568
3569
3570
3571
3572
3573
3574
3575
3576
3577
3578
3579
3580
3581
3582
3583
3584
3585
3586
3587
3588
3589
3590
3591
3592
3593
3594
3595
3596
3597
3598
3599
3600
3601
3602
3603
3604
3605
3606
3607
3608
3609
3610
3611
3612
3613
3614
3615
3616
3617
3618
3619
3620
3621
3622
3623
3624
3625
3626
3627
3628
3629
3630
3631
3632
3633
3634
3635
3636
3637
3638
3639
3640
3641
3642
3643
3644
3645
3646
3647
3648
3649
3650
3651
3652
3653
3654
3655
3656
3657
3658
3659
3660
3661
3662
3663
3664
3665
3666
3667
3668
3669
3670
3671
3672
3673
3674
3675
3676
3677
3678
3679
3680
3681
3682
3683
3684
3685
3686
3687
3688
3689
3690
3691
3692
3693
3694
3695
3696
3697
3698
3699
3700
3701
3702
3703
3704
3705
3706
3707
3708
3709
3710
3711
3712
3713
3714
3715
3716
3717
3718
3719
3720
3721
3722
3723
3724
3725
3726
3727
3728
3729
3730
3731
3732
3733
3734
3735
3736
3737
3738
3739
3740
3741
3742
3743
3744
3745
3746
3747
3748
3749
3750
3751
3752
3753
3754
3755
3756
3757
3758
3759
3760
3761
3762
3763
3764
3765
3766
3767
3768
3769
3770
3771
3772
3773
3774
3775
3776
3777
3778
3779
3780
3781
3782
3783
3784
3785
3786
3787
3788
3789
3790
3791
3792
3793
3794
3795
3796
3797
3798
3799
3800
3801
3802
3803
3804
3805
3806
3807
3808
3809
3810
3811
3812
3813
3814
3815
3816
3817
3818
3819
3820
3821
3822
3823
3824
3825
3826
3827
3828
3829
3830
3831
3832
3833
3834
3835
3836
3837
3838
3839
3840
3841
3842
3843
3844
3845
3846
3847
3848
3849
3850
3851
3852
3853
3854
3855
3856
3857
3858
3859
3860
3861
3862
3863
3864
3865
3866
3867
3868
3869
3870
3871
3872
3873
3874
3875
3876
3877
3878
3879
3880
3881
3882
3883
3884
3885
3886
3887
3888
3889
3890
3891
3892
3893
3894
3895
3896
3897
3898
3899
3900
3901
3902
3903
3904
3905
3906
3907
3908
3909
3910
3911
3912
3913
3914
3915
3916
3917
3918
3919
3920
3921
3922
3923
3924
3925
3926
3927
3928
3929
3930
3931
3932
3933
3934
3935
3936
3937
3938
3939
3940
3941
3942
3943
3944
3945
3946
3947
3948
3949
3950
3951
3952
3953
3954
3955
3956
3957
3958
3959
3960
3961
3962
3963
3964
3965
3966
3967
3968
3969
3970
3971
3972
3973
3974
3975
3976
3977
3978
3979
3980
3981
3982
3983
3984
3985
3986
3987
3988
3989
3990
3991
3992
3993
3994
3995
3996
3997
3998
3999
4000
4001
4002
4003
4004
4005
4006
4007
4008
4009
4010
4011
4012
4013
4014
4015
4016
4017
4018
4019
4020
4021
4022
4023
4024
4025
4026
4027
4028
4029
4030
4031
4032
4033
4034
4035
4036
4037
4038
4039
4040
4041
4042
4043
4044
4045
4046
4047
4048
4049
4050
4051
4052
4053
4054
4055
4056
4057
4058
4059
4060
4061
4062
4063
4064
4065
4066
4067
4068
4069
4070
4071
4072
4073
4074
4075
4076
4077
4078
4079
4080
4081
4082
4083
4084
4085
4086
4087
4088
4089
4090
4091
4092
4093
4094
4095
4096
4097
4098
4099
4100
4101
4102
4103
4104
4105
4106
4107
4108
4109
4110
4111
4112
4113
4114
4115
4116
4117
4118
4119
4120
4121
4122
4123
4124
4125
4126
4127
4128
4129
4130
4131
4132
4133
4134
4135
4136
4137
4138
4139
4140
4141
4142
4143
4144
4145
4146
4147
4148
4149
4150
4151
4152
4153
4154
4155
4156
4157
4158
4159
4160
4161
4162
4163
4164
4165
4166
4167
4168
4169
4170
4171
4172
4173
4174
4175
4176
4177
4178
4179
4180
4181
4182
4183
4184
4185
4186
4187
4188
4189
4190
4191
4192
4193
4194
4195
4196
4197
4198
4199
4200
4201
4202
4203
4204
4205
4206
4207
4208
4209
4210
4211
4212
4213
4214
4215
4216
4217
4218
4219
4220
4221
4222
4223
4224
4225
4226
4227
4228
4229
4230
4231
4232
4233
4234
4235
4236
4237
4238
4239
4240
4241
4242
4243
4244
4245
4246
4247
4248
4249
4250
4251
4252
4253
4254
4255
4256
4257
4258
4259
4260
4261
4262
4263
4264
4265
4266
4267
4268
4269
4270
4271
4272
4273
4274
4275
4276
4277
4278
4279
4280
4281
4282
4283
4284
4285
4286
4287
4288
4289
4290
4291
4292
4293
4294
4295
4296
4297
4298
4299
4300
4301
4302
4303
4304
4305
4306
4307
4308
4309
4310
4311
4312
4313
4314
4315
4316
4317
4318
4319
4320
4321
4322
4323
4324
4325
4326
4327
4328
4329
4330
4331
4332
4333
4334
4335
4336
4337
4338
4339
4340
4341
4342
4343
4344
4345
4346
4347
4348
4349
4350
4351
4352
4353
4354
4355
4356
4357
4358
4359
4360
4361
4362
4363
4364
4365
4366
4367
4368
4369
4370
4371
4372
4373
4374
4375
4376
4377
4378
4379
4380
4381
4382
4383
4384
4385
4386
4387
4388
4389
4390
4391
4392
4393
4394
4395
4396
4397
4398
4399
4400
4401
4402
4403
4404
4405
4406
4407
4408
4409
4410
4411
4412
4413
4414
4415
4416
4417
4418
4419
4420
4421
4422
4423
4424
4425
4426
4427
4428
4429
4430
4431
4432
4433
4434
4435
4436
4437
4438
4439
4440
4441
4442
4443
4444
4445
4446
4447
4448
4449
4450
4451
4452
4453
4454
4455
4456
4457
4458
4459
4460
4461
4462
4463
4464
4465
4466
4467
4468
4469
4470
4471
4472
4473
4474
4475
4476
4477
4478
4479
4480
4481
4482
4483
4484
4485
4486
4487
4488
4489
4490
4491
4492
4493
4494
4495
4496
4497
4498
4499
4500
4501
4502
4503
4504
4505
4506
4507
4508
4509
4510
4511
4512
4513
4514
4515
4516
4517
4518
4519
4520
4521
4522
4523
4524
4525
4526
4527
4528
4529
4530
4531
4532
4533
4534
4535
4536
4537
4538
4539
4540
4541
4542
4543
4544
4545
4546
4547
4548
4549
4550
4551
4552
4553
4554
4555
4556
4557
4558
4559
4560
4561
4562
4563
4564
4565
4566
4567
4568
4569
4570
4571
4572
4573
4574
4575
4576
4577
4578
4579
4580
4581
4582
4583
4584
4585
4586
4587
4588
4589
4590
4591
4592
4593
4594
4595
4596
4597
4598
4599
4600
4601
4602
4603
4604
4605
4606
4607
4608
4609
4610
4611
4612
4613
4614
4615
4616
4617
4618
4619
4620
4621
4622
4623
4624
4625
4626
4627
4628
4629
4630
4631
4632
4633
4634
4635
4636
4637
4638
4639
4640
4641
4642
4643
4644
4645
4646
4647
4648
4649
4650
4651
4652
4653
4654
4655
4656
4657
4658
4659
4660
4661
4662
4663
4664
4665
4666
4667
4668
4669
4670
4671
4672
4673
4674
4675
4676
4677
4678
4679
4680
4681
4682
4683
4684
4685
4686
4687
4688
4689
4690
4691
4692
4693
4694
4695
4696
4697
4698
4699
4700
4701
4702
4703
4704
4705
4706
4707
4708
4709
4710
4711
4712
4713
4714
4715
4716
4717
4718
4719
4720
4721
4722
4723
4724
4725
4726
4727
4728
4729
4730
4731
4732
4733
4734
4735
4736
4737
4738
4739
4740
4741
4742
4743
4744
4745
4746
4747
4748
4749
4750
4751
4752
4753
4754
4755
4756
4757
4758
4759
4760
4761
4762
4763
4764
4765
4766
4767
4768
4769
4770
4771
4772
4773
4774
4775
4776
4777
4778
4779
4780
4781
4782
4783
4784
4785
4786
4787
4788
4789
4790
4791
4792
4793
4794
4795
4796
4797
4798
4799
4800
4801
4802
4803
4804
4805
4806
4807
4808
4809
4810
4811
4812
4813
4814
4815
4816
4817
4818
4819
4820
4821
4822
4823
4824
4825
4826
4827
4828
4829
4830
4831
4832
4833
4834
4835
4836
4837
4838
4839
4840
4841
4842
4843
4844
4845
4846
4847
4848
4849
4850
4851
4852
4853
4854
4855
4856
4857
4858
4859
4860
4861
4862
4863
4864
4865
4866
4867
4868
4869
4870
4871
4872
4873
4874
4875
4876
4877
4878
4879
4880
4881
4882
4883
4884
4885
4886
4887
4888
4889
4890
4891
4892
4893
4894
4895
4896
4897
4898
4899
4900
4901
4902
4903
4904
4905
4906
4907
4908
4909
4910
4911
4912
4913
4914
4915
4916
4917
4918
4919
4920
4921
4922
4923
4924
4925
4926
4927
4928
4929
4930
4931
4932
4933
4934
4935
4936
4937
4938
4939
4940
4941
4942
4943
4944
4945
4946
4947
4948
4949
4950
4951
4952
4953
4954
4955
4956
4957
4958
4959
4960
4961
4962
4963
4964
4965
4966
4967
4968
4969
4970
4971
4972
4973
4974
4975
4976
4977
4978
4979
4980
4981
4982
4983
4984
4985
4986
4987
4988
4989
4990
4991
4992
4993
4994
4995
4996
4997
4998
4999
5000
5001
5002
5003
5004
5005
5006
5007
5008
5009
5010
5011
5012
5013
5014
5015
5016
5017
5018
5019
5020
5021
5022
5023
5024
5025
5026
5027
5028
5029
5030
5031
5032
5033
5034
5035
5036
5037
5038
5039
5040
5041
5042
5043
5044
5045
5046
5047
5048
5049
5050
5051
5052
5053
5054
5055
5056
5057
5058
5059
5060
5061
5062
5063
5064
5065
5066
5067
5068
5069
5070
5071
5072
5073
5074
5075
5076
5077
5078
5079
5080
5081
5082
5083
5084
5085
5086
5087
5088
5089
5090
5091
5092
5093
5094
5095
5096
5097
5098
5099
5100
5101
5102
5103
5104
5105
5106
5107
5108
5109
5110
5111
5112
5113
5114
5115
5116
5117
5118
5119
5120
5121
5122
5123
5124
5125
5126
5127
5128
5129
5130
5131
5132
5133
5134
5135
5136
5137
5138
5139
5140
5141
5142
5143
5144
5145
5146
5147
5148
5149
5150
5151
5152
5153
5154
5155
5156
5157
5158
5159
5160
5161
5162
5163
5164
5165
5166
5167
5168
5169
5170
5171
5172
5173
5174
5175
5176
5177
5178
5179
5180
5181
5182
5183
5184
5185
5186
5187
5188
5189
5190
5191
5192
5193
5194
5195
5196
5197
5198
5199
5200
5201
5202
5203
5204
5205
5206
5207
5208
5209
5210
5211
5212
5213
5214
5215
5216
5217
5218
5219
5220
5221
5222
5223
5224
5225
5226
5227
5228
5229
5230
5231
5232
5233
5234
5235
5236
5237
5238
5239
5240
5241
5242
5243
5244
5245
5246
5247
5248
5249
5250
5251
5252
5253
5254
5255
5256
5257
5258
5259
5260
5261
5262
5263
5264
5265
5266
5267
5268
5269
5270
5271
5272
5273
5274
5275
5276
5277
5278
5279
5280
5281
5282
5283
5284
5285
5286
5287
5288
5289
5290
5291
5292
5293
5294
5295
5296
5297
5298
5299
5300
5301
5302
5303
5304
5305
5306
5307
5308
5309
5310
5311
5312
5313
5314
5315
5316
5317
5318
5319
5320
5321
5322
5323
5324
5325
5326
5327
5328
5329
5330
5331
5332
5333
5334
5335
5336
5337
5338
5339
5340
5341
5342
5343
5344
5345
5346
5347
5348
5349
5350
5351
5352
5353
5354
5355
5356
5357
5358
5359
5360
5361
5362
5363
5364
5365
5366
5367
5368
5369
5370
5371
5372
5373
5374
5375
5376
5377
5378
5379
5380
5381
5382
5383
5384
5385
5386
5387
5388
5389
5390
5391
5392
5393
5394
5395
5396
5397
5398
5399
5400
5401
5402
5403
5404
5405
5406
5407
5408
5409
5410
5411
5412
5413
5414
5415
5416
5417
5418
5419
5420
5421
5422
5423
5424
5425
5426
5427
5428
5429
5430
5431
5432
5433
5434
5435
5436
5437
5438
5439
5440
5441
5442
5443
5444
5445
5446
5447
5448
5449
5450
5451
5452
5453
5454
5455
5456
5457
5458
5459
5460
5461
5462
5463
5464
5465
5466
5467
5468
5469
5470
5471
5472
5473
5474
5475
5476
5477
5478
5479
5480
5481
5482
5483
5484
5485
5486
5487
5488
5489
5490
5491
5492
5493
5494
5495
5496
5497
5498
5499
5500
5501
5502
5503
5504
5505
5506
5507
5508
5509
5510
5511
5512
5513
5514
5515
5516
5517
5518
5519
5520
5521
5522
5523
5524
5525
5526
5527
5528
5529
5530
5531
5532
5533
5534
5535
5536
5537
5538
5539
5540
5541
5542
5543
5544
5545
5546
5547
5548
5549
5550
5551
5552
5553
5554
5555
5556
5557
5558
5559
5560
5561
5562
5563
5564
5565
5566
5567
5568
5569
5570
5571
5572
5573
5574
5575
5576
5577
5578
5579
5580
5581
5582
5583
5584
5585
5586
5587
5588
5589
5590
5591
5592
5593
5594
5595
5596
5597
5598
5599
5600
5601
5602
5603
5604
5605
5606
5607
5608
5609
5610
5611
5612
5613
5614
5615
5616
5617
5618
5619
5620
5621
5622
5623
5624
5625
5626
5627
5628
5629
5630
5631
5632
5633
5634
5635
5636
5637
5638
5639
5640
5641
5642
5643
5644
5645
5646
5647
5648
5649
5650
5651
5652
5653
5654
5655
5656
5657
5658
5659
5660
5661
5662
5663
5664
5665
5666
5667
5668
5669
5670
5671
5672
5673
5674
5675
5676
5677
5678
5679
5680
5681
5682
5683
5684
5685
5686
5687
5688
5689
5690
5691
5692
5693
5694
5695
5696
5697
5698
5699
5700
5701
5702
5703
5704
5705
5706
5707
5708
5709
5710
5711
5712
5713
5714
5715
5716
5717
5718
5719
5720
5721
5722
5723
5724
5725
5726
5727
5728
5729
5730
5731
5732
5733
5734
5735
5736
5737
5738
5739
5740
5741
5742
5743
5744
5745
5746
5747
5748
5749
5750
5751
5752
5753
5754
5755
5756
5757
5758
5759
5760
5761
5762
5763
5764
5765
5766
5767
5768
5769
5770
5771
5772
5773
5774
5775
5776
5777
5778
5779
5780
5781
5782
5783
5784
5785
5786
5787
5788
5789
5790
5791
5792
5793
5794
5795
5796
5797
5798
5799
5800
5801
5802
5803
5804
5805
5806
5807
5808
5809
5810
5811
5812
5813
5814
5815
5816
5817
5818
5819
5820
5821
5822
5823
5824
5825
5826
5827
5828
5829
5830
5831
5832
5833
5834
5835
5836
5837
5838
5839
5840
5841
5842
5843
5844
5845
5846
5847
5848
5849
5850
5851
5852
5853
5854
5855
5856
5857
5858
5859
5860
5861
5862
5863
5864
5865
5866
5867
5868
5869
5870
5871
5872
5873
5874
5875
5876
5877
5878
5879
5880
5881
5882
5883
5884
5885
5886
5887
5888
5889
5890
5891
5892
5893
5894
5895
5896
5897
5898
5899
5900
5901
5902
5903
5904
5905
5906
5907
5908
5909
5910
5911
5912
5913
5914
5915
5916
5917
5918
5919
5920
5921
5922
5923
5924
5925
5926
5927
5928
5929
5930
5931
5932
5933
5934
5935
5936
5937
5938
5939
5940
5941
5942
5943
5944
5945
5946
5947
5948
5949
5950
5951
5952
5953
5954
5955
5956
5957
5958
5959
5960
5961
5962
5963
5964
5965
5966
5967
5968
5969
5970
5971
5972
5973
5974
5975
5976
5977
5978
5979
5980
5981
5982
5983
5984
5985
5986
5987
5988
5989
5990
5991
5992
5993
5994
5995
5996
5997
5998
5999
6000
6001
6002
6003
6004
6005
6006
6007
6008
6009
6010
6011
6012
6013
6014
6015
6016
6017
6018
6019
6020
6021
6022
6023
6024
6025
6026
6027
6028
6029
6030
6031
6032
6033
6034
6035
6036
6037
6038
6039
6040
6041
6042
6043
6044
6045
6046
6047
6048
6049
6050
6051
6052
6053
6054
6055
6056
6057
6058
6059
6060
6061
6062
6063
6064
6065
6066
6067
6068
6069
6070
6071
6072
6073
6074
6075
6076
6077
6078
6079
6080
6081
6082
6083
6084
6085
6086
6087
6088
6089
6090
6091
6092
6093
6094
6095
6096
6097
6098
6099
6100
6101
6102
6103
6104
6105
6106
6107
6108
6109
6110
6111
6112
6113
6114
6115
6116
6117
6118
6119
6120
6121
6122
6123
6124
6125
6126
6127
6128
6129
6130
6131
6132
6133
6134
6135
6136
6137
6138
6139
6140
6141
6142
6143
6144
6145
6146
6147
6148
6149
6150
6151
6152
6153
6154
6155
6156
6157
6158
6159
6160
6161
6162
6163






Network Working Group                                           R. Kumar
Request for Comments: 3108                                    M. Mostafa
Category: Standards Track                                  Cisco Systems
                                                                May 2001


   Conventions for the use of the Session Description Protocol (SDP)
                       for ATM Bearer Connections

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2001).  All Rights Reserved.

Abstract

   This document describes conventions for using the Session Description
   Protocol (SDP) described in RFC 2327 for controlling ATM Bearer
   Connections, and any associated ATM Adaptation Layer (AAL).  The AALs
   addressed are Type 1, Type 2 and Type 5.  This list of conventions is
   meant to be exhaustive.  Individual applications can use subsets of
   these conventions.  Further, these conventions are meant to comply
   strictly with the SDP syntax as defined in RFC 2327.

Table of Contents

   1. Introduction...................................................  3
   1.1  Key words to indicate Requirement Levels.....................  5
   2. Representation of Certain Fields within SDP description lines..  5
   2.1  Representation of Extension Attributes.......................  5
   2.2  Representation of Parameter Values...........................  5
   2.3  Directionality Convention....................................  6
   2.4 Case convention...............................................  7
   2.5 Use of special characters in SDP parameter values.............  8
   3. Capabilities Provided by SDP conventions.......................  8
   4. Format of the ATM Session Description..........................  9
   5.  Structure of the Session Description Lines.................... 11
   5.1  The Origin Line.............................................. 11
   5.2  The Session Name Line........................................ 12
   5.3  The Connection Information Line.............................. 13
   5.4  The Timestamp Line........................................... 15



Kumar & Mostafa             Standards Track                     [Page 1]

RFC 3108                        ATM SDP                         May 2001


   5.5  Media Information Line for ATM connections................... 16
   5.5.1  The Virtual Connection ID.................................. 16
   5.5.2  The Transport Parameter.................................... 19
   5.5.3  The Format List for AAL1 and AAL5 applications............. 21
   5.5.4  The Format List for AAL2 applications...................... 21
   5.5.5  Media information line construction........................ 22
   5.6  The Media Attribute Lines.................................... 27
   5.6.1  ATM bearer connection attributes........................... 28
   5.6.1.1  The 'eecid' attribute.................................... 30
   5.6.1.2  The 'aalType' attribute.................................. 31
   5.6.1.3  The 'capability' attribute............................... 32
   5.6.1.4  The 'qosClass' attribute................................. 33
   5.6.1.5  The 'bcob' attribute..................................... 34
   5.6.1.6  The 'stc' attribute...................................... 34
   5.6.1.7  The 'upcc' attribute..................................... 35
   5.6.1.8  The 'atmQOSparms' attribute.............................. 35
   5.6.1.9  The 'atmTrfcDesc'  attribute............................. 37
   5.6.1.10 The 'abrParms' attribute................................. 39
   5.6.1.11 The 'abrSetup' attribute................................. 40
   5.6.1.12 The 'bearerType' attribute............................... 41
   5.6.1.13 The 'lij' attribute...................................... 42
   5.6.1.14 The 'anycast' attribute.................................. 43
   5.6.1.15 The 'cache' attribute.................................... 43
   5.6.1.16 The 'bearerSigIE' attribute.............................. 44
   5.6.2  ATM Adaptation Layer (AAL) attributes...................... 45
   5.6.2.1  The 'aalApp' attribute................................... 46
   5.6.2.2  The 'cbrRate' attribute.................................. 48
   5.6.2.3  The 'sbc' attribute...................................... 49
   5.6.2.4  The 'clkrec' attribute................................... 51
   5.6.2.5  The 'fec' attribute...................................... 51
   5.6.2.6  The 'prtfl' attribute.................................... 51
   5.6.2.7  The 'structure' attribute................................ 52
   5.6.2.8  The 'cpsSDUsize' attribute............................... 53
   5.6.2.9  The 'aal2CPS' attribute.................................. 53
   5.6.2.10 The 'aal2CPSSDUrate' attribute........................... 54
   5.6.2.11 The 'aal2sscs3661unassured' attribute.................... 54
   5.6.2.12 The 'aal2sscs3661assured' attribute...................... 55
   5.6.2.13 The 'aal2sscs3662' attribute............................. 56
   5.6.2.14 The 'aal5sscop' attribute................................ 58
   5.6.3  Service attributes......................................... 58
   5.6.3.1  The 'atmmap' attribute................................... 60
   5.6.3.2  The 'silenceSupp' attribute.............................. 63
   5.6.3.3  The 'ecan' attribute..................................... 65
   5.6.3.4  The 'gc' attributes...................................... 66
   5.6.3.5  The 'profileDesc' attribute.............................. 67
   5.6.3.6  The 'vsel' attribute..................................... 68
   5.6.3.7  The 'dsel' attribute..................................... 70
   5.6.3.8  The 'fsel' attribute..................................... 72



Kumar & Mostafa             Standards Track                     [Page 2]

RFC 3108                        ATM SDP                         May 2001


   5.6.3.9  The 'onewaySel' attribute................................ 73
   5.6.3.10 The 'codecconfig' attribute.............................. 75
   5.6.3.11 The 'isup_usi' attribute................................. 76
   5.6.3.12 The 'uiLayer1_Prot' attribute............................ 76
   5.6.4  Miscellaneous media attributes............................. 77
   5.6.4.1 The 'chain' attribute..................................... 77
   5.6.5  Use of the second media-level part in H.323 Annex C
          applications............................................... 78
   5.6.6  Use of the eecid media attribute in call establishment
          procedures................................................. 78
   6. List of Parameters with  Representations....................... 83
   7. Examples of ATM session descriptions using SDP................. 93
   8. Security Considerations........................................ 94
   8.1  Bearer Security.............................................. 94
   8.2  Security of the SDP description.............................. 95
   9. ATM SDP Grammar................................................ 95
   References........................................................104
   Acknowledgements..................................................109
   Authors' Addresses................................................109
   Full Copyright Statement..........................................110

1. Introduction

   SDP will be used in conjunction with a connection handling /device
   control protocol such as Megaco (H.248) [26], SIP [18] or MGCP [25]
   to communicate the information needed to set up ATM and AAL2 bearer
   connections.  These connections include voice connections, voiceband
   data connections, clear channel circuit emulation connections, video
   connections and baseband data connections (such as fax relay, modem
   relay, SSCOP, frame relay etc.).

   These conventions use standard SDP syntax as defined in RFC 2327 [1]
   to describe the ATM-level and AAL-level connections, addresses and
   other parameters.  In general, parameters associated with layers
   higher than the ATM adaptation layer are included only if they are
   tightly coupled to the ATM or AAL layers.  Since the syntax conforms
   to RFC 2327, standard SDP parsers should react in a well-defined and
   safe manner on receiving session descriptions based on the SDP
   conventions in this document.  This is done by extending the values
   of fields defined in RFC 2327 rather than by defining new fields.
   This is true for all SDP lines except the of the media attribute
   lines, in which case new attributes are defined.  The SDP protocol
   allows the definition of new attributes in the media attribute lines
   which are free-form.  For the remaining lines, the fact that the
   <networkType> field in an SDP descriptor is set to "ATM" should
   preclude the misinterpretation of extended parameter values by RFC
   2327-compliant SDP parsers.




Kumar & Mostafa             Standards Track                     [Page 3]

RFC 3108                        ATM SDP                         May 2001


   These conventions are meant to address the following ATM
   applications:

      1. Applications in which a new SVC is set-up for each service
         connection.  These SVCs could be AAL1 or AAL5 SVCs or single-
         CID AAL2 SVCs.

      2. Applications in which existing path resources are assigned to
         service connections.  These resources could be:

         *  AAL1/AAL5 PVCs, SPVCs or cached SVCs,
         *  AAL2 single-CID PVCs, SPVCs or cached SVCs,
         *  CIDs within AAL2 SVCs/PVCs/SPVCs that multiplex multiple
            CIDs.
         *  Subchannels (identified by CIDs) within AAL1 [8] or AAL2
            [11] SVCs/PVCs/SPVCs.

   Note that the difference between PVCs and SPVCs is in the way the
   bearer virtual circuit connection is set up.  SPVCs are a class of
   PVCs that use bearer signaling, as opposed to node-by-node
   provisioning, for connection establishment.

   This document is limited to the case when the network type is ATM.
   This includes raw RTP encapsulation [45] or voice sample
   encapsulation [46] over AAL5 with no intervening IP layer.  It does
   not address SDP usage for IP, with or without ATM as a lower layer.

   In some cases, IP connection set-up is independent of lower layers,
   which are configured prior to it.  For example, AAL5 PVCs that
   connect IP routers can be used for VoIP calls.  In other cases, VoIP
   call set-up is closely tied to ATM-level connection set-up.  This
   might require a chaining of IP and ATM descriptors, as described in
   section 5.6.4.1.

   This document makes no assumptions on who constructs the session
   descriptions (media gateway, intermediate ATM/AAL2 switch, media
   gateway controller etc.).  This will be different in different
   applications.  Further, it allows the use of one session description
   for both directions of a connection (as in SIP and MGCP applications)
   or the use of separate session descriptions for different directions.
   It also addresses the ATM multicast and anycast capabilities.

   This document makes no assumptions about how the SDP description will
   be coded.  Although the descriptions shown here are encoded as text,
   alternate codings are possible:

   -  Binary encoding such as ASN.1.  This is an option (in addition to
      text encoding) in the Megaco context.



Kumar & Mostafa             Standards Track                     [Page 4]

RFC 3108                        ATM SDP                         May 2001


   -  Use of extended ISUP parameters [36] to encode the information in
      SDP descriptors, with conversion to/from binary/text-based SDP
      encoding when needed.

1.1 Key words to indicate Requirement Levels

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [62].

2. Representation of Certain Fields within SDP description lines

   This document conforms to the syntactic conventions of standard SDP
   as defined in RFC 2327 [1].

2.1  Representation of Extension Attributes

   The SDP protocol [1] requires that non-standard attributes and codec
   names use an "X-" prefix.

   In this internet document, the "X-" prefix is used consistently for
   codec names (Table 2) that have not been registered with the IANA.
   The IANA-registered codec names listed in [31] do not use this
   prefix, regardless of  whether they are statically or dynamically
   assigned payload types.

   However, this prefix is not used for the extension SDP attributes
   defined in this document.  This has been done to enhance legibility.

   This document suggests that parsers be flexible in the use of the
   "X-" prefix convention.  They should accept codec names and attribute
   names with or without the "X-" prefix.

2.2 Representation of Parameter Values

   Depending on the format of their representation in SDP, the
   parameters defined in this document fall into the following classes:

   (1) Parameters always represented in a decimal format.
   (2) Parameters always represented in a hexadecimal format.
   (3) Parameters always represented as character strings.
   (4) Parameters that can be represented in either decimal or
       hexadecimal format.

   No prefixes are needed for classes 1 - 3, since the format is fixed.
   For class 4, a "0x" prefix shall always be used to differentiate the
   hexadecimal from the decimal format.




Kumar & Mostafa             Standards Track                     [Page 5]

RFC 3108                        ATM SDP                         May 2001


   For both decimal and hex representations, if the underlying bit field
   is smaller or larger than the binary equivalent of the SDP
   representation, then leading 0 bits should be added or removed as
   needed.  Thus, 3 and 0x3 translate into the following five-bit
   pattern: 0 0011.  The SDP representations 0x12 and 18 translate into
   the following five-bit pattern: 1 0010.

   Leading 0 digits shall not be used in decimal representations.
   Generally, these are also not used in hexadecimal representations.
   Exceptions are when an exact number of hex digits is expected, as in
   the case of NSAP addresses.  Parsers shall not reject leading zeros
   in hex values.

   Both single-character and multi-character string values are enclosed
   in double quotes (i.e., ").  By contrast, single quotes (i.e., ') are
   used for emphasizing keywords rather than to refer to characters or
   strings.

   In the text representation of decimal and hex numbers, digits to the
   left are more significant than digits to the right.

2.3 Directionality Convention

   This section defined the meaning of the terms 'forward' and
   'backward' as used in this document.  This is specially applicable to
   parameters that have a specific direction associated with them.

   In this document, 'forward' refers to the direction away from the ATM
   node under consideration, while 'backward' refers to the direction
   towards the ATM node.  This convention must be used in all SDP-based
   session descriptions regardless of whether underlying bearer is an
   SVC, a dynamically allocated PVC/SPVC or a dynamically allocated CID.
   This is regardless of which side originates the service connection.
   If ATM SVC or AAL2 Q.2630.1 signaling is used, the directionality
   convention is independent of which side originates the SVC or AAL2
   connection.

   This provides a simple way of identifying the direction in which a
   parameter is applicable, in a manner that is independent of the
   underlying ATM or AAL2 bearer.  This simplicity comes at a price,
   described below.

   The convention used by all ATM/AAL2 signaling specifications (e.g.,
   Q.2931 Section 1.3.3 and Q.2630.1) mandates that forward direction is
   from the end initiating setup/establishment via bearer signaling
   towards the end receiving the setup/establishment request.  The
   backward direction is in the opposite direction.  In some cases, the
   'forward' and 'backward' directions of the ATM signaling convention



Kumar & Mostafa             Standards Track                     [Page 6]

RFC 3108                        ATM SDP                         May 2001


   might be the exact opposite of the SDP convention described above,
   requiring the media gateway to perform the necessary translation.  An
   example case in which this is needed is described below.

   Consider an SDP description sent by a media gateway controller to the
   gateway originating a service-level call.  In the backward SVC call
   set-up model, this gateway terminates (rather than originates) an SVC
   call.  The media gateway refers to the traffic descriptor (and hence
   the PCR) in the direction away from this gateway as the forward
   traffic descriptor and forward PCR.  Clearly, this is at odds with
   ATM SVC signaling which refers to this very PCR as the backward PCR.
   The gateway needs to be able to perform the required swap of
   directions.  In this example, the media gateway terminating the
   service level call (and hence originating the SVC call) does not need
   to perform this swap.

   Certain parameters within attributes are defined exclusively for the
   forward or  backward directions.  Examples for the forward direction
   are the <fsssar> subparameter within the 'aal2sscs3661unassured'
   media attribute line, the <fsssar>, <fsscopsdu> and <fsscopuu>
   subparameters within the 'aal2sscs3661assured' media attribute line,
   the <fsscopsdu> and <fsscopuu> subparameters within the 'aal5sscop'
   media attribute line, and the <fmaxFrame> parameter within the
   'aal2sscs3662' media attribute line.  Examples for the backward
   direction are the <bsssar> subparameter within the
   'aal2sscs3661unassured' media attribute line, the <bsssar>,
   <bsscopsdu> and <bsscopuu> subparameters within the
   'aal2sscs3661assured' media attribute line, the <bsscopsdu> and
   <bsscopuu> subparameters within the 'aal5sscop' media attribute line,
   and the <bmaxFrame> parameter within the 'aal2sscs3662' media
   attribute line.

2.4 Case convention

   As defined in RFC 2327 [1], SDP syntax is case-sensitive.  Since
   these ATM conventions conform strictly with SDP syntax, they are
   case-sensitive.  SDP line types (e.g., "c", "m", "o", "a") and fields
   in the SDP lines should be built according to the case conventions in
   [1] and in this document.  It is suggested, but not required, that
   SDP parsers for ATM applications be case-tolerant where ignoring case
   does not result in ambiguity.  Encoding names, which are defined
   outside the SDP protocol, are case-insensitive.









Kumar & Mostafa             Standards Track                     [Page 7]

RFC 3108                        ATM SDP                         May 2001


2.5 Use of special characters in SDP parameter values

   In general, RFC 2327-conformant string values of SDP parameters [1]
   do not include special characters that are neither alphabets nor
   digits.  An exception is the "/" character used in the value
   "RTP/AVP" of transport sub-field of the 'm' line.

   String values used in SDP descriptions of ATM connections retain this
   convention, while allowing the use of the special character "/" in a
   manner commensurate with [1].  In addition, the special characters
   "$" and "-" are used in the following manner.  A "$" value is a
   wildcard that allows the recipient of the SDP description to select
   any permitted value of the parameter.  A "-" value indicates that it
   is not necessary to specify the value of the parameter in the SDP
   description because this parameter is irrelevant for this
   application, or because its value can be known from another source
   such as provisioning, defaults, another protocol, another SDP
   descriptor or another part of the same SDP descriptor.  If the use of
   these special characters is construed as a violation of RFC 2327 [1]
   syntax, then reserved string values can be used.  The string "CHOOSE"
   can be used in lieu of "$".  The string "OMIT" can be used in lieu of
   "-" for an omitted parameter.

3. Capabilities Provided by SDP conventions

   To support the applications listed in section 1, the SDP conventions
   in this document provide the following session control capabilities:

      *  Identification of the underlying bearer network type as ATM.

      *  Identification by an ATM network element of its own address, in
         one of several possible formats.  A connection peer can
         initiate SVC set-up to this address.  A call agent or
         connection peer can select an pre-established bearer path to
         this address.

      *  Identification of the ATM bearer connection that is to be bound
         to the service-level connection.  Depending on the application,
         this is either a VCC or a subchannel (identified by a CID)
         within a VCC.

      * Identification of media type: audio, video, data.

      *  In AAL1/AAL5  applications, declaration of a set of payload
         types that can be bound to the ATM bearer connection.  The
         encoding names and payload types defined for use in the RTP
         context [31] are re-used for AAL1 and AAL5, if applicable.




Kumar & Mostafa             Standards Track                     [Page 8]

RFC 3108                        ATM SDP                         May 2001


      *  In AAL2 applications, declaration of a set of profiles that can
         be bound to the ATM bearer connection.  A mechanism for
         dynamically defining custom profiles within the SDP session
         description is included.  This allows the use of custom
         profiles for connections that span multi-network interfaces.

      *  A means of correlating service-level connections with
         underlying ATM bearer connections.  The backbone network
         connection identifier or bnc-id specified in ITU Q.1901 [36]
         standardization work is used for this purpose.  In order to
         provide a common SDP base for applications based on Q.1901 and
         SIP/SIP+, the neutral term 'eecid' is used in lieu of 'bnc-id'
         in the SDP session descriptor.

      *  A means of  mapping codec types and packetization periods into
         service types (voice, voiceband data and facsimile).  This is
         useful in determining the encoding to use when the connection
         is upspeeded in response to modem or facsimile tones.

      *  A means of describing the adaptation type, QoS class, ATM
         transfer capability/service category, broadband bearer class,
         traffic parameters, CPS parameters and SSCS parameters related
         the underlying bearer connection.

      *  Means for enabling or describing special functions such as
         leaf- initiated-join, anycast and SVC caching.

      *  For H.323 Annex C applications, a means of specifying the IP
         address and port number on which the node will receive RTCP
         messages.

      *  A means of chaining consecutive SDP descriptors so that they
         refer to different layers of the same connection.

4. Format of the ATM Session Description

   The sequence of lines in the session descriptions in this document
   conforms to RFC 2327 [1].  In general, a session description consists
   of a  session-level part followed by zero or more media-level parts.
   ATM session descriptions consist of a session-level part followed by
   one or two media-level parts.  The only two media applicable are the
   ATM bearer medium and RTCP control (where applicable).

   The session level part consists of the following lines:

   v=  (protocol version, zero or one line)
   o=  (origin, zero or one line)
   s=  (session name, zero or one line)



Kumar & Mostafa             Standards Track                     [Page 9]

RFC 3108                        ATM SDP                         May 2001


   c=  (connection information, one line)
   b=  (bandwidth, zero or more lines)
   t=  (timestamp, zero or one line)
   k=  (encryption key, zero or one line)

   In ATM session descriptions, there are no media attribute lines in
   the session level part.  These are present in the media-level parts.

   The media-level part for the ATM bearer consists of the following
   lines:

   m=  (media information and transport address, one line)
   b=  (bandwidth, zero or more lines)
   k=  (encryption key, zero or more lines)
   a=  (media attribute, zero or more lines)

   The media-level part for RTCP control consists of the following
   lines:

   m=  (media information and transport address, one line)
   c=  (connection information for control only, one line)

   In general, the 'v', 'o', 's', and 't' lines are mandatory.  However,
   in the Megaco [26] context, these lines have been made optional.  The
   'o', 's', and 't' lines are omitted in most MGCP [25] applications.

   Note that SDP session descriptors for ATM can contain bandwidth (b=)
   and encryption key (k=) lines.  Like all other lines, these lines
   should strictly conform to the SDP standard [1].

   The bandwidth (b=) line is not necessarily redundant in the ATM
   context since, in some applications, it can be used to convey
   application-level information which does not map directly into the
   atmTrfcDesc media attribute line.  For instance, the 'b' line can be
   used in SDP descriptors in RTSP commands to describe content
   bandwidth.

   The encryption key line (k=) can be used to indicate an encryption
   key for the bearer, and a method to obtain the key.  At present, the
   encryption of ATM and AAL2 bearers has not been conventionalized,
   unlike the encryption of RTP payloads.  Nor has the authentication or
   encryption of ATM or AAL2 bearer signaling.  In the ATM and AAL2
   contexts, the term 'bearer' can include 'bearer signaling' as well as
   'bearer payloads'.

   The order of lines in an ATM session description is exactly in the
   RFC 2327-conformant order depicted above.  However, there is no order
   of the media attribute ('a') lines with respect to other 'a' lines.



Kumar & Mostafa             Standards Track                    [Page 10]

RFC 3108                        ATM SDP                         May 2001


   The SDP protocol version for session descriptions using these
   conventions is 0.  In conformance with standard SDP, it  is strongly
   recommended that the 'v' line be included at the beginning of each
   SDP session description.  In some contexts such as Megaco, the
   'v' line is optional and may be omitted unless several session
   descriptions are provided in sequence, in which case the 'v' line
   serves as a delimiter.  Depending on the application, sequences of
   session descriptions might refer to:

   -  Different connections or sessions.
   -  Alternate ways of realizing the same connection or session.
   -  Different layers of the same session (section 5.6.4.1).

   The 'o', 's' and 't' lines are included for strict conformance with
   RFC 2327.  It is possible that these lines might not carry useful
   information in some ATM-based applications.  Therefore, some
   applications might omit these lines, although it is recommended that
   they not do so.  For maximum interoperability, it is preferable that
   SDP parsers not reject session descriptions that do not contain these
   lines.

5. Structure of the Session Description Lines

5.1 The Origin Line

   The origin line for an ATM-based session is structured as follows:

         o=<username> <sessionID> <version> <networkType>
           <addressType> <address>

   The <username> is set to "-".

   The <sessionID> can be  set to one of the following:

      *  an NTP timestamp referring to the moment when the SDP session
         descriptor was created.
      *  a Call ID, connection ID or context ID that uniquely identifies
         the session within the scope of the ATM node.  Since calls can
         comprise multiple connections (sessions), call IDs are
         generally not suitable for this purpose.

   NTP time stamps can be represented as decimal or hex integers.  The
   part of the NTP timestamp that refers to an integer number of seconds
   is sufficient.  This is a 32-bit field

   On the other hand, call IDs, connection IDs and context IDs can be
   can be 32 hex digits long.




Kumar & Mostafa             Standards Track                    [Page 11]

RFC 3108                        ATM SDP                         May 2001


   The <sessionID> field is represented as a decimal or hex number of up
   to 32 digits.  A "0x" prefix is used before the hex representation.
   The <version> refers to the version of the SDP session descriptor
   (not that of the SDP protocol).  This is can be set to one of the
   following:

      *  0.
      *  an NTP timestamp referring to the moment when the SDP session
         descriptor was modified.  If the SDP session descriptor has not
         been modified by an intermediate entity (such as an MGC), then
         the <version> timestamp will be the same as the <sessionId>
         timestamp, if any.  As with the <sessionId>, only the integer
         part of the NTP timestamp is used.

   When equated to the integer part of an NTP timestamp, the <version>
   field is 10 digits wide.  This is more restricted than [1], which
   allows unlimited size.  As in [1], the most significant digit is
   non-zero when an NTP timestamp is used.

   The <networkType> in SDP session descriptions for ATM applications
   should be assigned the string value "ATM" or wildcarded to a "$" or
   "-".

   The <addressType> and <address>  parameters are identical to those
   for the connection information ('c') line (Section 5.3).  Each of
   these parameters can be wildcarded per the conventions described for
   the 'c' line in Section 5.3.  These parameters should not me omitted
   since this would violate SDP syntax [1].

   As with the 'c' line, SDP parsers are not expected to check the
   consistency of <networkType> with <addressType>, <address> pairs.
   The <addressType> and <address> need to be consistent with each
   other.

5.2 The Session Name Line

   In general, the session name line is structured as follows:

        s=<sessionName>

   For ATM-based sessions, the <sessionName> parameter is set to a "-".
   The resulting line is:

        s=-







Kumar & Mostafa             Standards Track                    [Page 12]

RFC 3108                        ATM SDP                         May 2001


5.3 The Connection Information Line

   In general, the connection information line [1] is structured as
   follows:

        c=<networkType> <addressType> <address>

   For ATM networks, additional values of <networkType>, <addressType>
   and <address> are defined, over and above those listed in [1].  The
   ABNF syntax (Section 9) for ATM SDP does not limit the ways in which
   <networkType> can be combined with <addressType>, <address> pairs.
   However, some combinations will not be valid in certain applications,
   while others will never be valid.  Invalid combinations should be
   rejected by application-specific functions, and not by generic
   parsers.  The ABNF syntax does limit the ways in which <addressType>
   and <address> can be paired.

   For ATM networks, the value of <networkType> should be set to "ATM".
   Further, this may be wildcarded to "$" or "-".  If this is done, an
   node using ATM as the basic transport mechanism will select a value
   of "ATM".  A node that interfaces with multiple network types ("IN",
   "ATM" etc.) that include ATM can also choose a value of "ATM".

   When the SDP description is built by a node such as a media gateway,
   the <address> refers to the address of the node building the SDP
   description.  When this description is forwarded to another node, it
   still contains the original node's address.  When the media gateway
   controller builds part or all of the SDP description, the local
   descriptor contains the address of the local node, while the remote
   descriptor contains the address of the remote node.  If the <address>
   and/or <addressType> are irrelevant or are known by other means, they
   can be set to a "$" or a "-", as described below.

   Additionally, in all contexts, the 'm' line can have an ATM address
   in the <virtualConnectionId> subparameter which, if present, is the
   remote address if the 'c' line address is local, and vice versa.

   For ATM networks, the <addressType> can be NSAP, E164 or GWID
   (ALIAS).  For ATM networks, the <address> syntax depends on the
   syntax of the <addressType>.  SDP parsers should check the
   consistency of <addressType> with <address>.

   NSAP: If the addressType is NSAP, the address is expressed in the
   standard dotted hex form.  This is a string of 40 hex digits, with
   dots after the 2nd, 6th, 10th, 14th, 18th, 22nd, 26th, 30th, 34th and
   38th digits.  The last octet of the NSAP address is the 'selector'
   field that is available for non-standard use.  An example of a line
   with an NSAP address is:



Kumar & Mostafa             Standards Track                    [Page 13]

RFC 3108                        ATM SDP                         May 2001


       c=ATM NSAP 47.0091.8100.0000.0060.3e64.fd01.0060.3e64.fd01.00

   A "0x" prefix shall not be used in this case since this is always in
   hexadecimal format.

   E164: If the addressType is E164, the address is expressed as a
   decimal number  with up to 15 digits.  For example:

        c=ATM E164 9738294382

   The use of E.164 numbers in the B-ISDN context is defined in ITU
   E.191.  There is a disparity between the ATM forum and the ITU in the
   use of E.164 numbers for ATM addressing.  The ATM forum (e.g., UNI
   Signaling 4.0) allows only International Format E.164 numbers, while
   the ITU (e.g., Q.2931) allows private numbering plans.  Since the
   goal of this SDP specification is to interoperate with all bearer
   signaling protocols, it allows the use of numbers that do not conform
   to the E.164 International Format.  However, to maximize overall
   consistency, network administrators can restrict the provisioning of
   numbers to the E.164 International Format.

   GWID (ALIAS): If the addressType is GWID, it means that the address
   is a Gateway Identifier or Node Alias.  This may or may not be
   globally unique.  In this format, the address is expressed as an
   alphanumeric string ("A"-"Z", "a"-"z", "0" - "9",".","-","_").  For
   example:

       c=ATM GWID officeABCmgx101vism12

   Since these SDP conventions can be used for more than gateways, the
   string "ALIAS" can be used instead of "GWID" in the 'c' line.  Thus,
   the example above is equivalent to:

       c=ATM ALIAS officeABCmgx101vism12

   An example of a GWID (ALIAS)is the CLLI code used for telecom
   equipment.  For all practical purposes, it should be adequate for the
   GWID (ALIAS) to be a variable length string with a maximum size of 32
   characters.

   The connection information line is always present in an SDP session
   descriptor.  However, each of the parameters on this line can be
   wildcarded to a "$" or a "-", independently of whether other
   parameters on this line are wildcarded or not.  Not all syntactically
   legal wildcard combinations are meaningful in a particular
   application.





Kumar & Mostafa             Standards Track                    [Page 14]

RFC 3108                        ATM SDP                         May 2001


   Examples of meaningful wildcard combinations in the ATM context are:

         c=- - -
         c=$ $ $
         c=ATM - -
         c=ATM $ $
         c=ATM <addressType> -
         c=ATM <addressType> $

   Specifying the ATM address type without specifying the ATM address is
   useful when the recipient is asked to select an ATM address of a
   certain type (NSAP, E.164 etc.).

   Examples of syntactically legal wildcard combinations of dubious
   utility are:

         c=- $ -
         c=- $ $
         c=- <addressType> -
         c=$ <addressType> $
         c=- <addressType> <address>
         c=$ <addressType> <address>

   Note that <addressType> and/or <address> should not omitted without
   being set to a "-" or "$" since this would violate basic SDP syntax
   [1].

5.4 The Timestamp Line

   The timestamp line for an SDP session descriptor is structured as
   follows:

         t= <startTime> <stopTime>

   Per Ref. [49], NTP time stamps use a 32 bit unsigned representation
   of seconds, and a 32 bit unsigned representation of fractional
   seconds.  For ATM-based sessions, the <startTime>parameter can be
   made equal to the NTP timestamp referring to the moment when the SDP
   session descriptor was created.  It can also be set to 0 indicating
   its irrelevance.  If it made equal to the NTP timestamp in seconds,
   the fractional part of the NTP timestamp is omitted.  When equated to
   the integer part of an NTP timestamp, the <startTime> field is 10
   digits wide.  This is more restricted than [1], which allows
   unlimited size.  As in [1], the most significant digit is non-zero
   when an NTP timestamp is used.

   The <stopTime> parameter is set to 0 for ATM-based SDP descriptors.




Kumar & Mostafa             Standards Track                    [Page 15]

RFC 3108                        ATM SDP                         May 2001


5.5 Media Information Line for ATM connections

   The general format of the media information line adapted for AAL1 and
   AAL5 applications is:

   m=<media> <virtualConnectionId> <transport> <format list>

   The general format of the media information line adapted for AAL2
   applications is:

m=<media> <virtualConnectionId> <transport#1> <format list#1>
         <transport#2> <format list#2> ... <transport#M> <format list#M>

   Note that <virtualConnectionId> is equivalent to <port> in [1].

   The subparameter <media> can take on all the values defined in [1].
   These are: "audio", "video", "application", "data" and "control".

   When the <transport> parameter has more than one value in the 'm'
   line, the <transport> <format list> pairs can be arranged in
   preferential order.

5.5.1 The Virtual Connection ID

   In applications in which the media-level part of a session descriptor
   is bound to an ATM virtual circuit, the <virtualConnectionId> can be
   in one of the following formats:

         * <ex_vcci>
         * <addressType>-<address>/<ex_vcci>
         * <address>/<ex_vcci>
         * <ex_bcg>/<ex_vcci>
         * <ex_portId>/<ex_vpi>/<ex_vci>
         * <ex_bcg>/<ex_vpi>/<ex_vci>
         * <ex_vpci>/<ex_vci>
         * <addressType>-<address>/<ex_vpci>/<ex_vci>
         * <address>/<ex_vpci>/<ex_vci>

   In applications in which the media-level part of a session descriptor
   is bound to a subchannel within an ATM virtual circuit, the
   <virtualConnectionId> can be in one of the following formats:

         * <ex_vcci>/<ex_cid>
         * <addressType>-<address>/<ex_vcci>/<ex_cid>
         * <address>/<ex_vcci>/<ex_cid>
         * <ex_bcg>/<ex_vcci>/<ex_cid>
         * <ex_portId>/<ex_vpi>/<ex_vci>/<ex_cid>
         * <ex_bcg>/<ex_vpi>/<ex_vci>/<ex_cid>



Kumar & Mostafa             Standards Track                    [Page 16]

RFC 3108                        ATM SDP                         May 2001


         * <ex_vpci>/<ex_vci>/<ex_cid>
         * <addressType>-<address>/<ex_vpci>/<ex_vci>/<ex_cid>
         * <address>/<ex_vpci>/<ex_vci>/<ex_cid>

   Here,

          <ex_vcci> = VCCI-<vcci>
          <ex_vpci> = VPCI-<vpci>
          <ex_bcg> = BCG-<bcg>
          <ex_portId> = PORT-<portId>
          <ex_vpi> = VPI-<vpi>
          <ex_vci> = VCI-<vci>
          <ex_cid> = CID-<cid>

   The <vcci>, <vpi>, <vci>, <vpci> and <cid> are decimal numbers or
   hexadecimal numbers.  An "0x" prefix is used before their values when
   they are in the hex format.

   The <portId> is always a hexadecimal number.  An "0x" prefix is not
   used with it.

   The <addressType> and <address> are identical to their definitions
   above for the connection information line with the difference that
   this address refers to the remote peer in the media information line.
   Since the <virtualConnectionId>, as defined here, is meant for use in
   ATM networks, the values of <addressType> and <address> in the
   <virtualConnectionId> are limited to ATM-specific values.

   The <vpi>, <vci> and <cid> are the Virtual Path Identifier, Virtual
   Circuit Identifier and Channel Identifier respectively. The <vpi> is
   an 8 or 12 bit field. The <vci> is a 16-bit field. The <cid> is an
   8-bit field ([8] and [11]). For AAL1 applications, it corresponds to
   the channel number defined in Annex C of [8].

   The <vpci> is a 16-bit field defined in Section 4.5.16 of ITU Q.2931
   [Ref. 15].  The <vpci> is similar to the <vpi>, except for its width
   and the fact that it retains its value across VP crossconnects.  In
   some applications, the size of the <vpci> is the same as the size of
   the <vpi> (8 or 12 bits).  In this case, the most significant 8 or 4
   bits are ignored.

   The <vcci> is a 16-bit field defined in ITU Recommendation Q.2941.2
   [32].  The <vcci> is similar to the <vci>, except for the fact that
   it retains its value across VC crossconnects.

   In general, <vpci> and <vcci> values are unique between a pair of
   nodes.  When they are unique between a pair of nodes but not unique
   within a network, they need to be qualified, at any node, by the ATM



Kumar & Mostafa             Standards Track                    [Page 17]

RFC 3108                        ATM SDP                         May 2001


   address of the remote node.  These parameters can be pre-provisioned
   or signaled.  When signaled, the <vpci> is encapsulated in the
   connection identifier information element of SVC signaling messages.
   The <vcci> is encapsulated in the Generic Information Transport (GIT)
   information element of SVC signaling messages.  In an ATM node pair,
   either node can assign <vcci> values and signal it to the other end
   via SVC signaling.  A glare avoidance scheme is defined in [32] and
   [44].  This mechanism works in SVC applications.  A different glare
   avoidance technique is needed when a pool of existing PVCs/SPVCs is
   dynamically assigned to calls.  One such scheme for glare reduction
   is the assignment of <vcci> values from different ends of the <vcci>
   range, using the lowest or highest available value as applicable.

   When <vpci> and <vcci> values are pre-provisioned, administrations
   have the option of provisioning them uniquely in a network.  In this
   case, the ATM address of the far end is not needed to qualify these
   parameters.

   In the AAL2 context, the definition of a VCC implies that there is no
   CID-level switching between its ends.  If either end can assign <cid>
   values, then a glare reduction mechanism is needed.  One such scheme
   for glare reduction is the assignment of <cid> values from different
   ends of the <cid> range, using the lowest or highest available value
   as applicable.

   The <portId> parameter is used to identify the physical trunk port on
   an ATM module.  It can be represented as a hexadecimal number of up
   to 32 hex digits.

   In some applications, it is meaningful to bundle a set of connections
   between a pair of ATM nodes into a bearer connection group.  The
   <bcg> subparameter is an eight bit field that allows the bundling of
   up to 255 VPCs or VCCs.

   In some applications, it is necessary to wildcard the
   <virtualConnectionId> parameter, or some elements of this parameter.
   The "$" wildcard character can be substituted for the entire
   <virtualConnectionId> parameter, or some of its terms.  In the latter
   case, the constant strings that qualify the terms in the
   <virtualConnectionId> are retained.  The concatenation
   <addressType>-<address> can be wildcarded in the following ways:

      *  The entire concatenation, <addressType>-<address>, is replaced
         with a "$".
      *  <address> is replaced with a "$", but <addressType> is not.






Kumar & Mostafa             Standards Track                    [Page 18]

RFC 3108                        ATM SDP                         May 2001


   Examples of wildcarding the <virtualConnectionId> in the AAL1 and
   AAL5 contexts are: $, VCCI-$, BCG-100/VPI-20/VCI-$.  Examples of
   wildcarding the <virtualConnectionId> in the AAL2 context are: $,
   VCCI-40/CID-$, BCG-100/VPI-20/VCI-120/CID-$, NSAP-$/VCCI-$/CID-$,
   $/VCCI-$/CID-$.

   It is also permissible to set the entire <virtualConnectionId>
   parameter to a "-" indicating its irrelevance.

5.5.2 The Transport Parameter

   The <transport> parameter indicates the method used to encapsulate
   the service payload.  These methods are not defined in this document,
   which refers to existing ATMF and ITU-T standards, which, in turn,
   might refer to other standards.  For ATM applications, the following
   <transport> values are defined:



































Kumar & Mostafa             Standards Track                    [Page 19]

RFC 3108                        ATM SDP                         May 2001


   Table 1: List of Transport Parameter values used in SDP in the ATM
            context

+---------------------------------------------------------------------+
|                        |       Controlling Document for             |
|   Transport            |    Encapsulation of Service Payload        |
+------------------------+--------------------------------------------+
|    AAL1/ATMF           |          af-vtoa-0078.000 [7]              |
+------------------------+--------------------------------------------+
|    AAL1/ITU            |          ITU-T H.222.1 [51]                |
+------------------------+--------------------------------------------+
|    AAL5/ATMF           |          af-vtoa-0083.000 [46]             |
+------------------------+--------------------------------------------+
|    AAL5/ITU            |          ITU-T H.222.1 [51]                |
+------------------------+--------------------------------------------+
|    AAL2/ATMF           |          af-vtoa-0113.000 [44]  and        |
|                        |          af-vmoa-0145.000 [52]             |
+------------------------+--------------------------------------------+
|    AAL2/ITU            |          ITU-T I.366.2 [13]                |
+------------------------+--------------------------------------------+
|    AAL1/custom         |         Corporate document or              |
|    AAL2/custom         |   application-specific interoperability    |
|    AAL5/custom         |              statement.                    |
+------------------------+--------------------------------------------+
|  AAL1/<corporateName>  |                                            |
|  AAL2/<corporateName>  |                                            |
|  AAL5/<corporateName>  |                                            |
|  AAL1/IEEE:<oui>       |          Corporate document                |
|  AAL2/IEEE:<oui>       |                                            |
|  AAL5/IEEE:<oui>       |                                            |
+------------------------+--------------------------------------------+
|     RTP/AVP            |          Annex C of H.323 [45]             |
+------------------------+--------------------------------------------+

   In H.323 Annex C applications [45], the <transport> parameter has a
   value of "RTP/AVP".  This is because these applications use the RTP
   protocol [2] and audio/video profile [3].  The fact that RTP is
   carried directly over AAL5 per [45] can be indicated explicitly via
   the aalApp media attribute.

   A value of "AAL1/custom", "AAL2/custom" or "AAL5/custom" for the
   <transport> parameter can indicate non-standard or semi-standard
   encapsulation schemes defined by a corporation or a multi-vendor
   agreement.  Since there is no standard administration of this
   convention, care should be taken to preclude inconsistencies within
   the scope of a deployment.





Kumar & Mostafa             Standards Track                    [Page 20]

RFC 3108                        ATM SDP                         May 2001


   The use of <transport> values "AAL1/<corporateName>",
   "AAL2/<corporateName>", "AAL5/<corporateName>", "AAL1/IEEE:<oui>",
   "AAL2/IEEE:<oui>" and "AAL5/IEEE:<oui>" is similar.  These indicate
   non-standard transport mechanisms or AAL2 profiles which should be
   used consistently within the scope of an application or deployment.
   The parameter <corporateName> is the registered, globally unique name
   of a corporation (e.g., Cisco, Telcordia etc.).  The parameter <oui>
   is the hex representation of a three-octet field identical to the OUI
   maintained by the IEEE.  Since this is always represented in hex, the
   "0x" prefix shall not be used.  Leading zeros can be omitted.  For
   example, "IEEE:00000C" and "IEEE:C" both refer to Cisco Systems, Inc.

5.5.3 The Format List for AAL1 and AAL5 applications

   In the AAL1 and AAL5 contexts, the <format list> is a list of payload
   types:

      <payloadType#1> <payloadType#2>...<payloadType#n>

   In most AAL1 and AAL5 applications, the ordering of payload types
   implies a preference (preferred payload types before less favored
   ones).  The payload type can be statically assigned or dynamically
   mapped.  Although the transport is not the same, SDP in the ATM
   context leverages the encoding names and payload types registered
   with IANA [31] for RTP.  Encoding names not listed in [31] use a "X-"
   prefix.  Encodings that are not statically mapped to payload types in
   [31] are to be dynamically mapped at the time of connection
   establishment to payload types in the decimal range 96-127.  The SDP
   'atmmap' attribute (similar to 'rtpmap') is used for this purpose.

   In addition to listing the IANA-registered encoding names and payload
   types found in [31], Table 2 defines a few non-standard encoding
   names(with "X-" prefixes).

5.5.4 The Format List for AAL2 applications

   In the AAL2 context, the <format list> is a list of AAL2 profile
   types:

      <profile#1> <profile#2>...<profile#n>

   In most applications, the ordering of profiles implies a preference
   (preferred profiles before less favored ones).  The <profile>
   parameter is expressed as a decimal number in the range 1-255.







Kumar & Mostafa             Standards Track                    [Page 21]

RFC 3108                        ATM SDP                         May 2001


5.5.5 Media information line construction

   Using the parameter definitions above, the 'm' for AAL1-based audio
   media can be constructed as follows:

      m=audio <virtualConnectionId> AAL1/ATMF  <payloadType#1>
                <payloadType#2>...<payloadType #n>

   Note that only those payload types, whether statically mapped or
   dynamically assigned, that are consistent with af-vtoa-78 [7] can be
   used in this construction.

   Backwards compatibility note: The transport value "AAL1/AVP" used in
   previous versions of this document should be considered equivalent to
   the value "AAL1/ATMF" defined above.  "AAL1/AVP" is unsuitable
   because the AVP profile is closely tied to RTP.

   An example 'm' line use for audio media over AAL1 is:

      m=audio VCCI-27 AAL1/ATMF 0

   This indicates the use of an AAL1 VCC with VCCI=24 to carry PCMU
   audio that is encapsulated according to ATMF's af-vtoa-78 [7].

   Another example of the use of the 'm' line use for audio media over
   AAL1 is:

      m=audio $  AAL1/ATMF 0 8

   This indicates that any AAL1 VCC may be used.  If it exists already,
   then its selection is subject to glare rules.  The audio media on
   this VCC is encapsulated according to ATMF's af-vtoa-78 [7].  The
   encodings to be used are either PCMU or PCMA, in preferential order.

   The 'm' for AAL5-based audio media can be constructed as follows:

      m=audio <virtualConnectionId> AAL5/ATMF  <payloadType#1>
                <payloadType#2>...<payloadType #n>

   An example 'm' line use for audio media over AAL5 is:

      m=audio PORT-2/VPI-6/$  AAL5/ITU  9  15

   implies that any VCI on VPI= 6 of trunk port #2 may be used.  The
   identities of the terms in the virtual connection ID are implicit in
   the application context.  The audio media on this VCC is encapsulated
   according to ITU-T H.222.1 [51].  The encodings to be used are either
   ITU-T G.722 or ITU-T G.728 (LD-CELP), in preferential order.



Kumar & Mostafa             Standards Track                    [Page 22]

RFC 3108                        ATM SDP                         May 2001


   The 'm' for AAL5-based H.323 Annex C audio [45] can be constructed as
   follows:

      m=audio <virtualConnectionId> RTP/AVP <payloadType#1>
                    <payloadType#2>...<payloadType #n>

   For example:

         m=audio PORT-9/VPI-3/VCI-$  RTP/AVP 2 96
         a=rtpmap:96 X-G727-32
         a=aalType:AAL5
         a=aalApp:itu_h323c - -

   implies that any VCI on VPI= 3 of trunk port #9 may be used.  This VC
   encapsulates RTP packets directly on AAL5 per [45].  The 'rtpmap'
   (rather than the 'atmmap') attribute is used to dynamically map the
   payload type of 96 into the codec name X-G727-32 (Table 2).  This
   name represents 32 kbps EADPCM.

   The 'm' line for AAL5-based video media can be constructed as
   follows:

      m=video <virtualConnectionId> AAL5/ITU  <payloadType#1>
                <payloadType#2>...<payloadType #n>

   In this case, the use of AAL5/ITU as the transport points to H.222.1
   as the controlling standard [51].  An example 'm' line use for video
   media is:

      m=video PORT-9/VPI-3/VCI-$  AAL5/ITU  33

   This indicates that any VCI on VPI= 3 of trunk port #9 may be used.
   The video media on this VCC is encapsulated according to ITU-T
   H.222.1 [51].  The encoding scheme is an MPEG 2 transport stream
   ("MP2T" in Table 1).  This is statically mapped per [31] to a payload
   type of 33.

   Using the parameter definitions in the previous subsections, the
   media information line for AAL2-based audio media can be constructed
   as follows:

m=<media> <virtualConnectionId> <transport#1> <format list#1>
        <transport#2> <format list#2> ... <transport#M> <format list#M>

   where <format list#i> has the form <profile#i_1>...<profile#i_N>
   Unlike the 'm' line for AAL1 or AAL5 applications, the 'm' line for
   AAL2 applications can have multiple <transport> parameters, each
   followed by a <format list>.  This is because it is possible to



Kumar & Mostafa             Standards Track                    [Page 23]

RFC 3108                        ATM SDP                         May 2001


   consider definitions from multiple sources (ATMF, ITU and non-
   standard documents) when selecting AAL2 profile to be bound to a
   connection.

   In most applications, the ordering of profiles implies a preference
   (preferred profiles before less favored ones).  Therefore, there can
   be multiple instances of the same <transport> value in the same 'm'
   line.

   An example 'm' line use for audio media over AAL2 is:

      m=audio VCCI-27/CID-19 AAL2/ITU 7 AAL2/custom 100 AAL2/ITU 1

   This indicates the use of CID #19 on VCCI #27 to carry audio.  It
   provides a preferential list of profiles for this connection: profile
   AAL2/ITU 7 defined in [13], AAL2/custom 100 defined in an
   application-specific or interoperability document and profile
   AAL2/ITU 1 defined in [13].

   Another example of the use of the 'm' line use for audio media over
   AAL2 is:

      m=audio VCCI-$/CID-$  AAL2/ATMF 6 8

   This indicates that any AAL2 CID may be used, subject to any
   applicable glare avoidance/reduction rules.  The profiles that can be
   bound to this connection are AAL2/ATMF 6 defined in af-vtoa-0113.000
   [44] and AAL2/ATMF 8 defined in af-vmoa-0145.000 [52].  These sources
   use non-overlapping profile number ranges.  The profiles they define
   fall under the <transport> category "AAL2/ATMF".  This application
   does not order profiles preferentially.  This rule is known a priori.
   It is not embedded in the 'm' line.

   Another example of the use of the 'm' line use for audio media over
   AAL2 is:

      m=audio VCCI-20/CID-$  AAL2/xyzCorporation 11

   AAL2 VCCs in this application are single-CID VCCs.  Therefore, it is
   possible to wildcard the CID.  The single-CID VCC with VCCI=20 is
   selected.  The AAL2 profile to be used is AAL2/xyzCorporation 11
   defined by xyzCorporation.

   In some applications, an "-" can be used in lieu of:

   -  <format list>
   -  <transport> and <format list>




Kumar & Mostafa             Standards Track                    [Page 24]

RFC 3108                        ATM SDP                         May 2001


   This implies that these parameters are irrelevant or are known by
   other means (such as defaults).  For example:

         m=audio VCCI-234 - -
         a=aalType:AAL1

   indicates the use of VCCI=234 with AAL1 adaptation and unspecified
   encoding.

   In another example application, the 'aal2sscs3662' attribute can
   indicate <faxDemod> = "on" and any other competing options as "off",
   and the <aalType> attribute can indicate AAL2.  Thus:

      m=audio VCCI-123/CID-5 - -
      a=aalType:AAL2
      a=aal2sscs3662:audio off off on off on off off off - - -

   Besides indicating an audio medium, a VCCI of 123 and a CID of 5, the
   'm' line indicates an unspecified profile.  The media attribute lines
   indicate an adaptation layer of AAL2, and the use of the audio SAP
   [13] to carry demodulated facsimile.

   The media information line for "data" media has one of the following
   the following formats:

      m=data <virtualConnectionId> - -
      m=data - - -

   The data could be circuit emulation data carried over AAL1 or AAL2,
   or packet data carried over AAL5.  Media attribute lines, rather than
   the 'm' line, are used to indicate the adaptation type for the data
   media.  Examples of the representation of data media are listed
   below.

         m=data  PORT-7/VPI-6/VCI-$  - -
         a=aalApp:AAL5_SSCOP-                             -

   implies that any VCI on VPI= 6 of trunk port #7 may be used.  This VC
   uses SSCOP on AAL5 to transport data.

         m=data  PORT-7/VPI-6/VCI-50  - -
         a=aalType:AAL1_SDT
         a=sbc:6

   implies that VCI 50 on VPI 6 on port 7 uses structured AAL1 to
   transfer 6 x 64 kbps circuit emulation data.  This may be alternately
   represented as:




Kumar & Mostafa             Standards Track                    [Page 25]

RFC 3108                        ATM SDP                         May 2001


         m=data  PORT-7/VPI-6/VCI-50  - -
         b=AS:384
         a=aalType:AAL1_SDT

   The following lines:

         m=data VCCI-123/CID-5 - -
         a=aalType:AAL2
         a=sbc:2

   imply that CID 5 of VCCI 123 is used to transfer 2 x 64 kbps circuit
   emulation data.

   In the AAL1 context, it is also permissible to represent circuit mode
   data as an "audio" codec.  If this is done, the codec types used are
   X-CCD or X-CCD-CAS.  These encoding names are dynamically mapped into
   payload types through the 'atmmap' attribute.  For example:

         m=audio VCCI-27 AAL1/AVP 98
         a=atmmap:98 X-CCD
         a=sbc:6

   implies that AAL1 VCCI=27 is used for 6 x 64 transmission.

   In the AAL2 context, the X-CCD codec can be assigned a profile type
   and number.  Even though it is not possible to construct a profile
   table as described in ITU I.366.2 for this "codec", it is preferable
   to adopt the common AAL2 profile convention in its case.  An example
   AAL2 profile mapping for the X-CCD codec could be as follows:

      PROFILE TYPE         PROFILE NUMBER        "CODEC" (ONLY ONE)
        "custom"                200                     X-CCD

   The profile does not identify the number of subchannels ('n' in
   nx64).  This is known by other means such as the 'sbc' media
   attribute line.

   For example, the media information line:

         m=audio $ AAL2/custom 200
         a=sbc:6

   implies 384 kbps circuit emulation using AAL2 adaptation.

   It is not necessary to define a profile with the X-CCD-CAS codec,
   since this method of CAS transport [7] is not used in AAL2
   applications.




Kumar & Mostafa             Standards Track                    [Page 26]

RFC 3108                        ATM SDP                         May 2001


5.6 The Media Attribute Lines

   In an SDP line sequence, the media information line 'm' is followed
   by one or more media attribute or 'a' lines.  Media attribute lines
   are per the format below:

      a=<attribute>:<value>

   or

      a=<value>

   In general, media attribute lines are optional except when needed to
   qualify the media information line.  This qualification is necessary
   when the "m" line for an AAL1 or AAL5 session specifies a payload
   type that needs to be dynamically mapped.  The 'atmmap' media
   attribute line defined below is used for this purpose.

   In attribute lines, subparameters that are meant to be left
   unspecified are set to a "-".  These are generally inapplicable or,
   if applicable, are known by other means such as provisioning.  In
   some cases, a media attribute line with all parameters set to "-"
   carries no information and should be preferably omitted.  In other
   cases, such as the 'lij' media attribute line, the very presence of
   the media attribute line conveys meaning.

   There are no restrictions placed by RFC 2327 [1] regarding the order
   of 'a' lines with respect to other 'a' lines.  However, these lines
   must not contradict each other or the other SDP lines.
   Inconsistencies are not to be ignored and should be flagged as
   errors.  Repeated media attribute lines can carry additional
   information.  These should not be inconsistent with each other.

   Applications will selectively use the optional media attribute lines
   listed below.  This is meant to be an exhaustive list for describing
   the general attributes of ATM bearer networks.

   The base specification for SDP, RFC 2327 [1], allows the definition f
   new attributes.  In keeping with this spirit, some of the attributes
   defined in this document can also be used in SDP descriptions of IP
   nd other non-ATM sessions.  For example, the 'vsel', 'dsel' and
   'fsel' attributes defined below refer generically to codec-s.  These
   can be bed for service-specific codec negotiation and assignment in
   non-ATM s well as ATM applications.

   SDP media attributes defined in this document for use in the ATM
   context are classified as:




Kumar & Mostafa             Standards Track                    [Page 27]

RFC 3108                        ATM SDP                         May 2001


      *  ATM bearer connection attributes (Section 5.6.1)
      *  AAL attributes (Section 5.6.2)
      *  Service attributes (Section 5.6.3).
      *  Miscellaneous media attributes, that cannot be classified as
         ATM, AAL or service attributes (Section 5.6.4).

   In addition to these, the SDP attributes defined in [1] can also be
   used in the ATM context.  Examples are:

      *  The attributes defined in RFC 2327 which allow indication of
         the direction in which a session is active.  These are
         a=sendonly, a=recvonly, a=sendrecv, a=inactive.

      *  The 'Ptime' attribute defined in RFC 2327.  It indicates the
         packet period.  It is not recommended that this attribute be
         used in ATM applications since packet period information is
         provided with other parameters (e.g., the profile type and
         number in the 'm' line, and the 'vsel', 'dsel' and 'fsel'
         attributes).  Also, for AAL1 applications, 'ptime' is not
         applicable and should be flagged as an error.  If used in AAL2
         and AAL5 applications, 'ptime' should be consistent with the
         rest of the SDP description.

      *  The 'fmtp' attribute used to designate format-specific
         parameters.

5.6.1 ATM bearer connection attributes

   The following is a summary list of the SDP media attributes that can
   be used to describe ATM bearer connections.  These are detailed in
   subsequent subsections.

      *  The 'eecid' attribute.  This stands for 'end-to-end connection
         identifier'.  It provides a means of correlating service-level
         connections with underlying ATM bearer connections.  In the
         Q.1901 [36] context, the eecid is synonymous with the bnc-id
         (backbone network connection identifier).

      *  The 'aalType' attribute.  This is used to indicate the nature
         of the ATM adaptation layer (AAL).

      *  The 'capability' attribute, which indicates the ATM transfer
         capability (ITU nomenclature), synonymous with the ATM Service
         Category (ATMF nomenclature).

      *  The 'qosClass' attribute, which indicates the QoS class of the
         ATM bearer connection.




Kumar & Mostafa             Standards Track                    [Page 28]

RFC 3108                        ATM SDP                         May 2001


      *  The 'bcob' attribute, which indicates the broadband connection
         oriented bearer class, and whether end-to-end timing is
         required.

      *  The 'stc' attribute, which indicates susceptibility to
         clipping.

      *  The 'upcc' attribute, which indicates the user plane connection
         configuration.

      *  The 'atmQOSparms' attribute, which is used to describe certain
         key ATM QoS parameters.

      *  The 'atmTrfcDesc' attribute, which is used to describe ATM
         traffic descriptor parameters.

      *  The 'abrParms' attribute, which is used to describe  ABR-
         specific parameters.  These parameters are per the UNI 4.0
         signaling  specification [5].

      *  The 'abrSetup' attribute, which is used to indicate the ABR
         parameters needed during call/connection establishment.

      *  The 'bearerType' attribute, which is used to indicate whether
         the underlying bearer is an ATM PVC/SPVC, an ATM SVC, or a
         subchannel within an existing ATM SVC/PVC/SPVC.

      *  The 'lij' attribute, which is used to indicate the presence of
         a connection that uses the Leaf-initiated-join capability
         described in UNI 4.0 [5], and to optionally describe parameters
         associated with this capability.

      *  The 'anycast' attribute, which is used to indicate the
         applicability of the anycast function described in UNI 4.0 [5],
         and to optionally qualify it with certain parameters.

      *  The 'cache' attribute, which is used to enable SVC caching and
         to specify an inactivity timer for SVC release.

      *  The 'bearerSigIE' attribute, which can be used to represent ITU
         Q-series information elements in bit-map form.  This is useful
         in describing parameters that are not closely coupled to the
         ATM and AAL layers.  Examples are the B-HLI and B-LLI IEs
         specified in ITU Q.2931 [15], and the user-to-user information
         element described in ITU Q.2957 [48].






Kumar & Mostafa             Standards Track                    [Page 29]

RFC 3108                        ATM SDP                         May 2001


5.6.1.1 The 'eecid' attribute

   The 'eecid' attribute is synonymous with the 4-byte 'bnc-id'
   parameter used by T1SI, the ATM forum and the ITU (Q.1901)
   standardization effort.  The term 'eecid' stands for 'end-to-end
   connection identifier', while 'bnc-id' stands for 'backbone network
   connection identifier'.  The name "backbone" is slightly misleading
   since it refers to the entire ATM network including the ATM edge and
   ATM core networks.  In Q.1901 terminology, an ATM "backbone" connects
   TDM or analog edges.

   While the term 'bnc-id' might be used in the bearer signaling plane
   and in an ISUP (Q.1901) call control plane, SDP session descriptors
   use the neutral term 'eecid'.  This provides a common SDP baseline
   for applications that use ISUP (Q.1901) and applications that use
   SIP/SIP+.

   Section 5.6.6 depicts the use of the eecid in call establishment
   procedures.  In these procedures, the eecid is used to correlate
   service-level calls with SVC set-up requests.

   In the forward SVC establishment model, the call-terminating gateway
   selects an eecid and transmits it via SDP to the call-originating
   gateway.  The call originating gateway transmits this eecid to the
   call terminating gateway via the bearer set-up message (SVC set-up or
   Q.2630.1 establish request).

   In the backward SVC establishment model, the call-originating gateway
   selects an eecid and transmits it via SDP to the call-terminating
   gateway.  The call terminating gateway transmits this eecid to the
   call originating gateway via the bearer set-up message (SVC set-up or
   Q.2630.1 establish request).

   The value of the eecid attribute values needs to be unique within the
   node terminating the SVC set-up but not across multiple nodes.
   Hence, the SVC-terminating gateway has complete control over using
   and releasing values of this parameter.  The eecid attribute is used
   to correlate, one-to-one, received bearer set-up requests with
   service-level call control signaling.

   Within an SDP session description, the eecid attribute is used as
   follows:

         a=eecid:<eecid>

   where <eecid> consists of up to 8 hex digits (equivalent to 4
   octets).  Since this is always represented in hex, the "0x" prefix
   shall not be used.



Kumar & Mostafa             Standards Track                    [Page 30]

RFC 3108                        ATM SDP                         May 2001


   Within the text representation of the <eecid> parameter, hex digits
   to the left are more significant than hex digits to the right
   (Section 2.2).

   This SDP document does not specify how the eecid (synonymous with
   bnc-id) is to be communicated through bearer signaling (Q.931, UNI,
   PNNI, AINI, IISP, proprietary signaling equivalent, Q.2630.1).  This
   is a task of these bearer signaling protocols.  However, the
   following informative statements are made to convey a sense of the
   interoperability that is a goal of current standardization efforts:

   -  ITU Q.2941.3 and the ATMF each recommend the use of the GIT IE for
      carrying the eecid (synonymous with bnc-id) in the set-up message
      of ATM signaling protocols (Q.2931, UNI 4.0, PNNI, AINI, IISP).
      The coding for carrying the eecid (bnc-id) in the GIT IE is
      defined in ITU Q.2941.3 and accepted by the ATM forum.

   -  Another alternate method is to use the called party subaddress IE.
      In some networks, this might be considered a protocol violation
      and is not the recommended means of carrying the eecid (bnc-id).
      The GIT IE is the preferred method of transporting the eecid
      (bnc-id) in ATM signaling messages.

   -  The establish request (ERQ) message of the Q.2630.1 [37] signaling
      protocol can use the SUGR (Served User Generated Reference) IE to
      transport the eecid (bnc-id).

   The node assigning the eecid can release and re-use it when it
   receives a Q.2931 [15] set-up message or a Q.2630.1 [37] establish
   request message containing the eecid.

   However, in both cases (backward and forward models), it is
   recommended that this eecid be retained until the connection
   terminates.  Since the eecid space is large enough, it is not
   necessary to release it as soon as possible.

5.6.1.2 The 'aalType' attribute

   When present, the 'aalType' attribute is used to indicate the ATM
   adaptation layer.  If this information is redundant with the 'm'
   line, it can be omitted.  The format of the 'aalType' media attribute
   line is as follows:

      a=aalType: <aalType>







Kumar & Mostafa             Standards Track                    [Page 31]

RFC 3108                        ATM SDP                         May 2001


   Here, <aalType> can take on the following string values: "AAL1",
   "AAL1_SDT", "AAL1_UDT", "AAL2", "AAL3/4", "AAL5" and
   "USER_DEFINED_AAL".  Note that "AAL3/4" and "USER DEFINED AAL" are
   not addressed in this document.

5.6.1.3 The 'capability' attribute

   When present, the 'capability' attribute indicates the ATM Transfer
   Capability described in ITU I.371 [28], equivalent to the ATM Service
   Category described in the UNI 4.1 Traffic Management specification
   [6].

   The 'capability' media attribute line is structured in one of the
   following ways:

      a=capability:<asc> <subtype>

      a=capability:<atc> <subtype>

   Possible values of the <asc> are enumerated below:

      "CBR", "nrt-VBR", "rt-VBR", "UBR", "ABR", "GFR"

   Possible values of the <atc> are enumerated below:

      "DBR","SBR","ABT/IT","ABT/DT","ABR"

   Some applications might use non-standard <atc> and <asc> values not
   listed above.  Equipment designers will need to agree on the meaning
   and implications of non-standard transfer capabilities / service
   capabilities.

   The <subtype> field essentially serves as a subscript to the <asc>
   and <atc> fields.  In general, it can take on any integer value, or
   the "-" value indicating that it does not apply or that the
   underlying data is to be known by other means, such as provisioning.

   For an <asc> value of CBR and an <atc> value of DBR, the <subtype>
   field can be assigned values from Table 4-6 of ITU Q.2931 [15].
   These are:











Kumar & Mostafa             Standards Track                    [Page 32]

RFC 3108                        ATM SDP                         May 2001


      <asc>/<atc>    <subtype>   Meaning

       "CBR"/"DBR"      1        Voiceband signal transport
                                 (ITU G.711, G.722, I.363)
       "CBR"/"DBR"      2        Circuit transport (ITU I.363)
       "CBR"/"DBR"      4        High-quality audio signal transport
                                 (ITU I.363)
       "CBR"/"DBR"      5        Video signal transport (ITU I.363)

   Note that [15] does not define a <subtype> value of 3.

   For other values of the <asc> and <atc> parameters, the following
   values can be assigned to the <subtype> field, based on [6] and [28].

         <asc>/<atc>              <subtype>     Meaning

           nrt-VBR                   1          nrt-VBR.1
           nrt-VBR                   2          nrt-VBR.2
           nrt-VBR                   3          nrt-VBR.3
           rt-VBR                    1          rt-VBR.1
           rt-VBR                    2          rt-VBR.2
           rt-VBR                    3          rt-VBR.3
           UBR                       1          UBR.1
           UBR                       2          UBR.2
           GFR                       1          GFR.1
           GFR                       2          GRR.2
           SBR                       1          SBR1
           SBR                       2          SBR2
           SBR                       3          SBR3

   It is beyond the scope of this specification to examine the
   equivalence of some of the ATMF and ITU definitions.  These need to
   be recognized from the ATMF and ITU source specifications and
   exploited, as much as possible, to simplify ATM node design.

   When the bearer connection is a single AAL2 CID connection within a
   multiplexed AAL2 VC, the 'capability' attribute does not apply.

5.6.1.4 The 'qosClass' attribute

   When present, the 'qosClass' attribute indicates the QoS class
   specified in ITU I.2965.1 [34].

   The 'qosClass' media attribute line is structured as follows:

      a=qosClass:<qosClass>

   Here, <qosClass> is an integer in the range 0 - 5.



Kumar & Mostafa             Standards Track                    [Page 33]

RFC 3108                        ATM SDP                         May 2001


      <qosClass>      Meaning

           0            Default QoS
           1            Stringent
           2            Tolerant
           3            Bi-level
           4            Unbounded
           5            Stringent bi-level

5.6.1.5 The 'bcob' attribute

   When present, the 'bcob' attribute represents the broadband
   connection oriented bearer class defined in [5], [15] and [33].  It
   can also be used to indicate whether end-to-end timing is required.

   The 'bcob' media attribute line is structured as follows:

      a=bcob:<bcob> <eetim>

   Here, <bcob> is the decimal or hex representation of a 5-bit field.
   The following values are currently defined:

         <bcob>          Meaning

         0x01             BCOB-A
         0x03             BCOB-C
         0x05             Frame relaying bearer service
         0x10             BCOB-X
         0x18             BCOB-VP (transparent VP service)

   The <eetim> parameter can be assigned a value of "on" or "off"
   depending on whether end-to-end timing is required or not (Table 4-8
   of [15]).

   Either of these parameters can be left unspecified by setting it to a
   "-".  A 'bcob' media attribute line with all parameters set to "-"
   carries no information and should be omitted.

5.6.1.6 The 'stc' attribute

   When present, the 'stc' attribute represents susceptibility to
   clipping.  The 'stc' media attribute line is structured as follows:

      a=stc:<stc>

   Here, <stc> is the decimal equivalent of a 2-bit field.  Currently,
   all values are unused and reserved with the following exceptions:




Kumar & Mostafa             Standards Track                    [Page 34]

RFC 3108                        ATM SDP                         May 2001


      <stc> value      Binary Equivalent     Meaning

           0                   00            Not susceptible to clipping
           1                   01            Susceptible to clipping

5.6.1.7 The 'upcc' attribute

   When present, the 'upcc' attribute represents the user plane
   connection configuration.  The 'upcc' media attribute line is
   structured as follows:

      a=upcc:<upcc>

   Here, <upcc> is the decimal equivalent of a 2-bit field.  Currently,
   all values are unused and reserved with the following exceptions:

      <upcc> value     Binary Equivalent    Meaning

           0                 00             Point to point
           1                 01             Point to multipoint

5.6.1.8 The 'atmQOSparms' attribute

   When present, the 'atmQOSparms' attribute is used to describe certain
   key ATM QoS parameters.

   The 'atmQOSparms' media attribute line is structured as follows:

   a=atmQOSparms:<directionFlag><cdvType><acdv><ccdv><eetd><cmtd><aclr>

   The <directionFlag> can be assigned the following string values: "f",
   "b" and "fb".  "f" and "b" indicate the forward and backward
   directions respectively.  "fb" refers to both directions (forward and
   backward).  Conventions for the forward and backward directions are
   per section 2.3.

   The <cdvType> parameter can take on the string values of "PP" and
   "2P".  These refer to the peak-to-peak and two-point CDV as defined
   in UNI 4.0 [5] and ITU Q.2965.2 [35] respectively.

   The CDV parameters, <acdv> and <ccdv>, refer to the acceptable and
   cumulative CDVs respectively.  These are expressed in units of
   microseconds and represented as the decimal equivalent of a 24-bit
   field.  These use the cell loss ratio, <aclr>, as the "alpha"
   quantiles defined in the ATMF TM 4.1 specification [6] and in ITU
   I.356 [47].





Kumar & Mostafa             Standards Track                    [Page 35]

RFC 3108                        ATM SDP                         May 2001


   The transit delay parameters, <eetd> and <cmtd>, refer to the end-
   to-end and cumulative transit delays respectively in milliseconds.
   These are represented as the decimal equivalents of 16-bit fields.
   These parameters are defined in Q.2965.2 [35], UNI 4.0 [5] and Q.2931
   [15].

   The <aclr> parameter refers to forward and backward acceptable cell
   loss ratios.  This is the ratio between the number of cells lost and
   the number of cells transmitted.  It is expressed as the decimal
   equivalent of an 8-bit field.  This field expresses an order of
   magnitude n, where n is an integer in the range 1-15.  The Cell Loss
   Ratio takes on the value 10 raised to the power of minus n.

   The <directionFlag> is always specified.  Except for the
   <directionFlag>, the remaining parameters can be set to "-" to
   indicate that they are not specified, inapplicable or implied.
   However, there must be some specified parameters for the line to be
   useful in an SDP description.

   There can be several 'atmQOSparms' lines in an SDP description.

   An example use of these attributes for an rt-VBR, single-CID AAL2
   voice VC is:

      a=atmQOSparms:f PP  8125 3455 32000 -  11
      a=atmQOSparms:b PP  4675 2155 18000 -  12

   This implies a forward acceptable peak-to-peak CDV of 8.125 ms, a
   backward acceptable peak-to-peak CDV of 4.675 ms, forward cumulative
   peak-to-peak CDV of 3.455 ms, a backward cumulative peak-to-peak CDV
   of 2.155 ms, a forward end-to-end transit delay of 32 ms, a backward
   end-to-end transit delay of 18 ms, an unspecified forward cumulative
   transit delay, an unspecified backward cumulative transit delay, a
   forward cell loss ratio of 10 raised to minus 11 and a backward cell
   loss ratio of 10 to the minus 12.

   An example of specifying the same parameters for the forward and
   backward directions is:

      a=atmQOSparms:fb PP  8125 3455 32000 -  11

   This implies a forward and backward acceptable peak-to-peak CDV of
   8.125 ms, a forward and backward cumulative peak-to-peak CDV of 3.455
   ms, a forward and backward end-to-end transit delay of 32 ms, an
   unspecified cumulative transit delay in the forward and backward
   directions, and a cell loss ratio of 10 raised to minus 11 in the
   forward and backward directions.




Kumar & Mostafa             Standards Track                    [Page 36]

RFC 3108                        ATM SDP                         May 2001


5.6.1.9 The 'atmTrfcDesc'  attribute

   When present, the 'atmTrfcDesc' attribute is used to indicate ATM
   traffic descriptor parameters.  There can be several 'atmTrfcDesc'
   lines in an SDP description.

   The 'atmTrfcDesc' media attribute line is structured as follows:

      a=atmTrfcDesc:<directionFlag><clpLvl>
                <pcr><scr><mbs><cdvt><mcr><mfs><fd><te>

   The <directionFlag> can be assigned the following string values: "f",
   "b" and "fb".  "f" and "b" indicate the forward and backward
   directions respectively.  "fb" refers to both directions (forward and
   backward).  Conventions for the forward and backward directions are
   per section 2.3.

   The <directionFlag> is always specified.  Except for the
   <directionFlag>, the remaining parameters can be set to "-" to
   indicate that they are not specified, inapplicable or implied.
   However, there must be some specified parameters for the line to be
   useful in an SDP description.

   The <clpLvl> (CLP level) parameter indicates whether the rates and
   bursts described in these media attribute lines apply to CLP values
   of 0 or (0+1).  It can take on the following string values: "0",
   "0+1" and "-".  If rates and bursts for both <clpLvl> values are to
   be described, then it is necessary to use two separate media
   attribute lines for each direction in the same session descriptor.
   If the <clpLvl> parameter is set to "-", then it implies that the CLP
   parameter is known by other means such as default, MIB provisioning
   etc.

   The meaning, units and applicability of the remaining parameters are
   per [6] and [28]:

   PARAMETER      MEANING       UNITS         APPLICABILITY

   <pcr>          PCR           Cells/        CBR, rt-VBR, nrt-VBR,
                                second        ABR, UBR, GFR;
                                              CLP=0,0+1

   <scr>          SCR           Cells/        rt-VBR, nrt-VBR;
                                second        CLP=0,0+1

   <mbs>          MBS           Cells         rt-VBR, nrt-VBR,
                                              GFR;
                                              CLP=0,0+1



Kumar & Mostafa             Standards Track                    [Page 37]

RFC 3108                        ATM SDP                         May 2001


   <cdvt>        CDVT           Microsec.     CBR, rt-VBR, nrt-VBR,
                                              ABR, UBR, GFR;
                                              CLP=0,0+1

   <mcr>         MCR            Cells/        ABR,GFR;
                                second        CLP=0+1


   <mfs>         MFS            Cells         GFR;
                                              CLP=0,0+1


   <fd>         Frame          "on"/"off"     CBR, rt-VBR, nrt-VBR,
                Discard                       ABR, UBR, GFR;
                Allowed                       CLP=0+1


   <te>         CLP            "on"/"off"     CBR, rt-VBR, nrt-VBR,
                tagging                       ABR, UBR, GFR;
                Enabled                       CLP=0

   <fd> indicates that frame discard is permitted.  It can take on the
   string values of "on" or "off".  Note that, in the GFR case, frame
   discard is always enabled.  Hence, this subparameter can be set to
   "-" in the case of GFR.  Since the <fd> parameter is independent of
   CLP, it is meaningful in the case when <clpLvl> = "0+1".  It should
   be set to "-" for the case when <clpLvl> = "0".

   <te> (tag enable) indicates that CLP tagging is allowed.  These can
   take on the string values of "on" or "off".  Since the <te> parameter
   applies only to cells with a CLP of 0, it is meaningful in the case
   when <clpLvl> = "0".  It should be set to "-" for the case when
   <clpLvl> = "0+1".

   An example use of these media attribute lines for an rt-VBR, single-
   CID AAL2 voice VC is:

      a=atmTrfcDesc:f 0+1 200   100  20   - - - on  -
      a=atmTrfcDesc:f 0   200   80   15   - - - -  off
      a=atmTrfcDesc:b 0+1 200   100  20   - - - on -
      a=atmTrfcDesc:b 0   200   80   15   - - - -  off

   This implies a forward and backward PCR of 200 cells per second all
   cells regardless of CLP, forward and backward PCR of 200 cells per
   second for cells with CLP=0, a forward and backward SCR of 100 cells
   per second for all cells regardless of CLP, a forward and backward
   SCR of 80 cells per second for cells with CLP=0, a forward and
   backward MBS of 20 cells for all cells regardless of CLP, a forward



Kumar & Mostafa             Standards Track                    [Page 38]

RFC 3108                        ATM SDP                         May 2001


   and backward MBS of 15 cells for cells with CLP=0, an unspecified
   CDVT which can be known by other means, and an MCR and MFS which are
   unspecified because they are inapplicable.  Frame discard is enabled
   in both the forward and backward directions.  Tagging is not enabled
   in either direction.

   The <pcr>, <scr>, <mbs>, <cdvt>, <mcr> and <mfs> are represented as
   decimal integers, with range as defined in Section 6.  See section
   2.2 regarding the omission of leading zeros in decimal
   representations.

5.6.1.10 The 'abrParms' attribute

   When present, the 'abrParms' attribute is used to indicate the '
   additional' ABR parameters specified in the UNI 4.0 signaling
   specification [5].  There can be several 'abrParms' lines in an SDP
   description.

   The 'abrParms' media attribute line is structured as follows:

      a=abrParms:<directionFlag><nrm><trm><cdf><adtf>

   The <directionFlag> can be assigned the following string values: "f",
   "b" and "fb".  "f" and "b" indicate the forward and backward
   directions respectively.  "fb" refers to both directions (forward and
   backward).  Conventions for the forward and backward directions are
   per section 2.3.

   The <directionFlag> is always specified.  Except for the
   <directionFlag>, the remaining parameters can be set to "-" to
   indicate that they are not specified, inapplicable or implied.
   However, there must be some specified parameters for the line to be
   useful in an SDP description.

   These parameters are mapped into the ABR service parameters in [6] in
   the manner described below.  These parameters can be represented in
   SDP as decimal integers, with fractions permitted for some.  Details
   of the meaning, units and applicability of these parameters are in
   [5] and [6].

   In SDP, these parameters are represented as the decimal or hex
   equivalent of the binary fields mentioned below.









Kumar & Mostafa             Standards Track                    [Page 39]

RFC 3108                        ATM SDP                         May 2001


+-----------+----------------------------------+-----------------------+
| PARAMETER |            MEANING               | FIELD SIZE            |
+-----------+----------------------------------+-----------------------+
| <nrm>     | Maximum number of cells per      |    3 bits             |
|           | forward Resource Management cell |                       |
+-----------+----------------------------------+-----------------------+
| <trm>     | Maximum time between             |    3 bits             |
|           | forward Resource Management cells|                       |
+-----------+----------------------------------+-----------------------+
| <cdf>     | Cutoff Decrease Factor           |    3 bits             |
+-----------+----------------------------------+-----------------------+
| <adtf>    | Allowed Cell Rate Decrease       |    10 bits            |
|           | Time Factor                      |                       |
+-----------+----------------------------------+-----------------------+

5.6.1.11 The 'abrSetup' attribute

   When present, the 'abrSetup' attribute is used to indicate the ABR
   parameters needed during call/connection establishment (Section
   10.1.2.2 of the UNI 4.0 signaling specification [5]).  This line is
   structured as follows:

   a=abrSetup:<ficr><bicr><ftbe><btbe><crmrtt><frif><brif><frdf><brdf>

   These parameters are defined as follows:


























Kumar & Mostafa             Standards Track                    [Page 40]

RFC 3108                        ATM SDP                         May 2001


+-----------+----------------------------------+-----------------------+
| PARAMETER |            MEANING               | REPRESENTATION        |
+-----------+----------------------------------+-----------------------+
| <ficr>    | Forward Initial Cell Rate        | Decimal equivalent    |
|           | (Cells per second)               | of 24-bit field       |
+-----------+----------------------------------+-----------------------+
| <bicr>    | Backward Initial Cell Rate       | Decimal equivalent    |
|           | (Cells per second)               | of 24-bit field       |
+-----------+----------------------------------+-----------------------+
| <ftbe>    | Forward transient buffer         | Decimal equivalent    |
|           | exposure (Cells)                 | of 24-bit field       |
+-----------+----------------------------------+-----------------------+
| <btbe>    | Backward transient buffer        | Decimal equivalent    |
|           | exposure (Cells)                 | of 24-bit field       |
+-----------+----------------------------------+-----------------------+
| <crmrtt>  | Cumulative RM round-trip time    | Decimal equivalent    |
|           | (Microseconds)                   | of 24-bit field       |
+-----------+----------------------------------+-----------------------+
| <frif>    | Forward rate increase factor     | Decimal integer       |
|           | (used to derive cell count)      | 0 -15                 |
+-----------+----------------------------------+-----------------------+
| <brif>    | Backward rate increase factor    | Decimal integer       |
|           | (used to derive cell count)      | 0 -15                 |
+-----------+----------------------------------+-----------------------+
| <frdf>    | Forward rate decrease factor     | Decimal integer       |
|           | (used to derive cell count)      | 0 -15                 |
+-----------+----------------------------------+-----------------------+
| <brdf>    | Backward rate decrease factor    | Decimal integer       |
|           | (used to derive cell count)      | 0 -15                 |
+-----------+----------------------------------+-----------------------+

   See Section 2.3 for a definition of the terms 'forward' and
   'backward'.

   If any of these parameters in the 'abrSetup' media attribute line is
   not specified, is inapplicable or is implied, then it is set to h "-
   ".

5.6.1.12 The 'bearerType' attribute

   When present, the 'bearerType' attribute is used to indicate whether
   the underlying bearer is an ATM PVC/SPVC, an ATM SVC, or a subchannel
   within an existing ATM SVC/PVC/SPVC.  Additionally, for ATM SVCs and
   AAL2 CID connections, the 'bearerType' attribute can be used to
   indicate whether the media gateway initiates connection set-up via
   bearer signaling (Q.2931-based or Q.2630.1 based).  The format of the
   'bearerType' media attribute line is as follows:




Kumar & Mostafa             Standards Track                    [Page 41]

RFC 3108                        ATM SDP                         May 2001


      a=bearerType: <bearerType> <localInitiation>

   The <bearerType> field can take on the following string values:

   "PVC", "SVC", "CID", with semantics as defined above.  Here, "PVC"
   includes both the PVC and SPVC cases.

   In the case when the underlying bearer is a PVC/SPVC, or a CID
   assigned by the MGC rather than through bearer signaling, the
   <localInitiation> flag can be omitted or set to "-".  In the case
   when bearer signaling is used, this flag can be omitted when it is
   known by default or by other means whether the media gateway
   initiates the connection set-up via bearer signaling.  Only when this
   is to be indicated explicitly that the <localInitiation> flag takes
   on the values of "on" or "off".  An "on" value indicates that the
   media gateway is responsible for initiating connection set-up via
   bearer signaling (SVC signaling or Q.2630.1 signaling), an "off"
   value indicates otherwise.

5.6.1.13 The 'lij' attribute

   When present, the 'lij' attribute is used to indicate the presence of
   a connection that uses the Leaf-initiated-join capability described
   in UNI 4.0 [5], and to optionally describe parameters associated with
   this capability.  The format of the 'lij' media attribute line is as
   follows:

      a=lij: <sci><lsn>

   The <sci> (screening indication) is a 4-bit field expressed as a
   decimal or hex integer.  It is defined in the UNI 4.0 signaling
   specification [5].  It is possible that the values of this field will
   be defined later by the ATMF and/or ITU.  Currently, all values are
   reserved with the exception of 0, which indicates a 'Network Join
   without Root Notification'.

   The <lsn> (leaf sequence number) is a 32-bit field expressed as a
   decimal or hex integer.  Per the UNI 4.0 signaling specification [5],
   it is used by a joining leaf to associate messages and responses
   during LIJ (leaf initiated join) procedures.

   Each of these fields can be set to a "-" when the intention is to not
   specify them in an SDP descriptor.








Kumar & Mostafa             Standards Track                    [Page 42]

RFC 3108                        ATM SDP                         May 2001


5.6.1.14 The 'anycast' attribute

   When present, the 'anycast' attribute line is used to indicate the
   applicability of the anycast function described in UNI 4.0 [5].
   Optional parameters to qualify this function are provided. The format
   of the 'anycast' attribute is:

      a=anycast: <atmGroupAddress> <cdStd> <conScpTyp> <conScpSel>

   The <atmGroupAddress> is per Annex 5 of UNI 4.0 [5].  Within an SDP
   descriptor, it can be represented in one of the formats (NSAP, E.164,
   GWID/ALIAS) described elsewhere in this document.

   The remaining subparameters mirror the connection scope selection
   information element in UNI 4.0 [5].  Their meaning and representation
   is as shown below:

   PARAMETER      MEANING                                 REPRESENTATION

   <cdStd>        Coding standard for the                 Decimal or hex
                  connection scope selection IE           equivalent of
                  Definition: UNI 4.0 [5]                 2 bits

   <conScpTyp>    Type of connection scope                Decimal or hex
                  Definition: UNI 4.0 [5]                 equivalent of
                                                          4 bits

   <conScpSel>    Connection scope selection              Decimal or hex
                  Definition: UNI 4.0 [5]                 equivalent of
                                                          8 bits

   Currently, all values of <cdStd> and <conScpTyp> are reserved with
   the exception of <cdStd> = 3 (ATMF coding standard) and <conScpTyp> =
   1 (connection scope type of 'organizational').

   Each of these fields can be set to a "-" when the intention is to not
   specify them in an SDP descriptor.

5.6.1.15 The 'cache' attribute

   This attribute is used to enable SVC caching.  This attribute has the
   following format:

      a=cache:<cacheEnable><cacheTimer>







Kumar & Mostafa             Standards Track                    [Page 43]

RFC 3108                        ATM SDP                         May 2001


   The <cacheEnable> flag indicates whether caching is enabled or not,
   corresponding to the string values of "on" and "off" respectively.

   The <cacheTimer> indicates the period of inactivity following which
   the SVC is to be released by sending an SVC release message into the
   network.  This is specified as the decimal or hex equivalent of a
   32-bit field, indicating the timeout in seconds.  As usual, leading
   zeros can be omitted.  For instance,

      a=cache:on 7200

   implies that the cached SVC is to be deleted if it is idle for 2
   hours.

   The <cacheTimer> can be set to "-" if it is inapplicable or implied.

5.6.1.16 The 'bearerSigIE' attribute

   ATM signaling standards provide 'escape mechanisms' to represent,
   signal and negotiate higher-layer parameters.  Examples are the B-HLI
   and B-LLI IEs specified in ITU Q.2931 [15], and the user-to-user
   information element described in ITU Q.2957 [48].

   The 'bearerSigIE'(bearer signaling information element) attribute is
   defined to allow a similar escape mechanism that can be used with
   these ATM SDP conventions.  The format of this media attribute line
   is as follows:

      a=bearerSigIE: <bearerSigIEType> <bearerSigIELng> <bearerSigIEVal>

   When an 'bearerSigIE' media attribute line is present, all its
   subparameters are mandatory.  The "0x" prefix is not used since these
   are always represented in hex.

   The <bearerSigIEType> is represented as exactly 2 hex digits.  It is
   the unique IE identifier as defined in the ITU Q-series standards.
   Leading zeros are not omitted.  Some pertinent values are 7E (User-
   user IE per ITU Q.2957 [48]), 5F (B-LLI IE) and 5D (B-HLI IE).  B-LLI
   and B-HLI, which stand for Broadband Low-layer Information and
   Broadband High-layer Information respectively, are defined in ITU
   Q.2931 [15].  Both of these refer to layers above the ATM adaptation
   layer.

   The <bearerSigIELng> consists of 1-4 hex digits.  It is the length of
   the information element in octets.  Leading zeros may be omitted.






Kumar & Mostafa             Standards Track                    [Page 44]

RFC 3108                        ATM SDP                         May 2001


   The <bearerSigIEVal> is the value of the information element,
   represented as a hexadecimal bit map.  Although the size of this bit
   map is network/ service dependent, setting an upper bound of 256
   octets (512 hex digits) is adequate.  Since this a bit map, leading
   zeros should not be omitted. The number of hex digits in this bit map
   is even.

5.6.2 ATM Adaptation Layer (AAL) attributes

   The following is a summary list of the SDP media attributes that can
   be used to describe the ATM Adaptation Layer (AAL).  These are
   detailed in subsequent subsections.

      *  The 'aalApp' attribute, which is used to point to the
         controlling standard for an application layer above the ATM
         adaptation layer.

      *  The 'cbrRate' attribute, which represents the CBR rate octet
         defined in Table 4-6 of ITU Q.2931  [15].

      *  The 'sbc' attribute, which denotes the subchannel count in the
         case of n x 64 clear channel communication.

      *  The 'clkrec' attribute, which indicates the clock recovery
         method for AAL1 unstructured data transfer (UDT).

      *  The 'fec' attribute, which indicates the use of forward error
         correction.

      *  The 'prtfl' attribute, which indicates indicate the fill level
         of partially filled cells.

      *  The 'structure' attribute, which is used to indicate the
         presence or absence of AAL1 structured data transfer (SDT), and
         the size of the SDT blocks.

      *  The 'cpsSDUsize' attribute, which is used to indicate the
         maximum size of the CPCS SDU payload.

      *  The 'aal2CPS' attribute, which is used to indicate that an AAL2
         CPS sublayer as defined in ITU I.363.2 [13] is associated with
         the VCC referred to in the 'm' line.  Optionally, it can be
         used to indicate selected CPS options and parameter values for
         this VCC.

      *  The 'aal2CPSSDUrate' attribute, which is used to place an upper
         bound on the SDU bit rate for an AAL2 CID.




Kumar & Mostafa             Standards Track                    [Page 45]

RFC 3108                        ATM SDP                         May 2001


      *  The 'aal2sscs3661unassured' attribute, which is used to
         indicate the presence of an AAL2 SSCS sublayer with unassured
         transmission as defined in ITU I.366.1 [12].  Optionally, it
         can be used to indicate selected options and parameter values
         for this SSCS.

      *  The 'aal2sscs3661assured' attribute, which is used to indicate
         the presence of an AAL2 SSCS sublayer with assured transmission
         as defined in ITU I.366.1 [12].  Optionally, it can be used to
         indicate selected options and parameter values for this SSCS.

      *  The 'aal2sscs3662' attribute, which is used to indicate the
         presence of an AAL2 SSCS sublayer as defined in ITU I.366.2.
         Optionally, it can be used to indicate selected options and
         parameter values for this SSCS.

      *  The 'aal5sscop' attribute, which is used to indicate the
         existence of an SSCOP protocol layer over an AAL5 CPS layer,
         and the parameters which pertain to this SSCOP layer.

5.6.2.1 The 'aalApp' attribute

   When present, the 'aalApp' attribute is used to  point to the
   controlling standard for an application layer above the ATM
   adaptation layer.  The format of the 'aalApp' media attribute line is
   as follows:

      a=aalApp: <appClass> <oui> <appId>

   If any of the subparameters, <appClass>, <oui> or <appId>, is meant
   to be left, unspecified, it is set to "-".  However, an 'aalApp'
   attribute line with all subparameters set to "-" carries no
   information and should be omitted.

   The <appClass>, or application class, field can take on the string
   values listed below.

   This list is not exhaustive.  An "X-" prefix should be used with
   <appClass> values not listed here.

     <appClass>            Meaning

     "itu_h323c"           Annex C of H.323 which specifies direct
                           RTP on AAL5 [45].

      "af83"               af-vtoa-0083.001, which specifies
                           variable size AAL5 PDUs with PCM voice
                           and a null SSCS [46].



Kumar & Mostafa             Standards Track                    [Page 46]

RFC 3108                        ATM SDP                         May 2001


     "AAL5_SSCOP"          SSCOP as defined in ITU Q.2110 [43]
                           running over an AAL5 CPS [21].
                           No information is provided regarding
                           any layers above SSCOP such as Service
                           Specific Coordination Function  (SSCF)
                           layers.

   "itu_i3661_unassured"   SSCS with unassured transmission,
                           per ITU I.366.1 [12].

   "itu_i3661_assured"     SSCS with assured transmission,
                           per ITU I.366.1 [12].  This uses SSCOP [43].

      "itu_i3662"          SSCS per ITU I.366.2 [13].

      "itu_i3651"          Frame relay SSCS per ITU I.365.1 [39].

      "itu_i3652"          Service-specific coordination function,
                           as defined in ITU I.365.2, for Connection
                           Oriented Network Service (SSCF-CONS) [40].
                           This uses SSCOP [43].

      "itu_i3653"          Service-specific coordination function,
                           as defined in ITU I.365.3, for Connection
                           Oriented Transport Service (SSCF-COTS) [41].
                           This uses SSCOP [43].

      "itu_i3654"          HDLC Service-specific coordination function,
                           as defined in ITU I.365.4 [42].

      "FRF5"               Use of the FRF.5 frame relay standard [53],
                           which references ITU I.365.1 [39].

      "FRF8"               Use of the FRF.8.1 frame relay standard [54].
                           This implies a null SSCS and the mapping of
                           the frame relay header into the ATM header.

      "FRF11"              Use of the FRF.11 frame relay standard [55].

      "itu_h2221"          Use of the ITU standard H.222.1 for
                           audiovisual communication over AAL5 [51].

   The <oui>, or Organizationally Unique Identifier, refers to the
   organization responsible for defining the <appId>, or Application
   Identifier.  The <oui> is maintained by the IEEE.  One of its uses is
   in 802 MAC addresses.  It is a three-octet field represented as one
   to six hex digits.  Since this is always represented in hex, the "0x"
   prefix is not used.  Leading zeros may be omitted.



Kumar & Mostafa             Standards Track                    [Page 47]

RFC 3108                        ATM SDP                         May 2001


   The <appId> subparameter refers to the application ID, a hex number
   consisting of up to 8 digits.  Leading zeros may be omitted.  The
   "0x" prefix is not used, since the representation is always
   hexadecimal.  Currently, the only organization that has defined
   application identifiers is the ATM forum.  These have been defined in
   the context of AAL2 ([44], [52], Section 5 of [61]).  Within SDP,
   these can be used with <appClass> = itu_i3662.  The <oui> value for
   the ATM forum is 0x00A03E.

   In the following example, the aalApp media attribute line is used to
   indicate 'Loop Emulation Service using CAS (POTS only) without the
   Emulated Loop Control Protocol (ELCP) [52].  The Application ID is
   defined by the ATM forum [61].  The SSCS used is per ITU I.366.2
   [13].

      a=aalApp:itu_i3662 A03E A

   If leading zeros are not dropped, this can be represented as:

      a=aalApp:itu_i3662 00A03E 0000000A

   Since application identifiers have been specified only in the context
   of the AAL2 SSCS defined in ITU I.366.2 [13],the <appClass> can be
   set to '-' without ambiguity.  The aalApp media attribute line can be
   reduced to:

      a=aalApp:- A03E A

   or

      a=aalApp:- 00A03E 0000000A

5.6.2.2 The 'cbrRate' attribute

   When present, the 'cbrRate' attribute is used to represent the CBR
   rate octet defined in Table 4-6 of ITU Q.2931 [15].  The format of
   this media attribute line is:

      a=cbrRate: <cbrRate>

   Here, <cbrRate> is represented as exactly two hex digits.  The "0x"
   prefix is omitted since this parameter is always represented in hex.
   Values currently defined by the ITU are:








Kumar & Mostafa             Standards Track                    [Page 48]

RFC 3108                        ATM SDP                         May 2001


         +------------+-----------------------------------------------+
         |  VALUE     |             MEANING                           |
         |  (hex)     |                                               |
         +------------+-----------------------------------------------+
         |     01     |  64 kbps                                      |
         +------------+-----------------------------------------------+
         |     04     |  1544 kbps                                    |
         +------------+-----------------------------------------------+
         |     05     |  6312 kbps                                    |
         +------------+-----------------------------------------------+
         |     06     |  32064 kbps                                   |
         +------------+-----------------------------------------------+
         |     07     |  44736 kbps                                   |
         +------------+-----------------------------------------------+
         |     08     |  97728 kbps                                   |
         +------------+-----------------------------------------------+
         |     10     |  2048 kbps                                    |
         +------------+-----------------------------------------------+
         |     11     |  8448 kbps                                    |
         +------------+-----------------------------------------------+
         |     12     |  34368 kbps                                   |
         +------------+-----------------------------------------------+
         |     13     |  139264 kbps                                  |
         +------------+-----------------------------------------------+
         |     40     |  n x 64  kbps                                 |
         +------------+-----------------------------------------------+
         |     41     |  n x 8 kbps                                   |
         +------------+-----------------------------------------------+

   It is preferable that the cbrRate attribute be omitted rather than
   set to an unspecified value of "-", since it conveys no information
   in the latter case.

5.6.2.3 The 'sbc' attribute

   The 'sbc' media attribute line denotes the subchannel count and is
   meaningful only in the case of n x 64 clear channel communication.  A
   clear n x 64 channel can use AAL1 (ATM forum af-vtoa-78) or AAL2
   adaptation (ITU I.366.2).  Although no such standard definition
   exists, it is also possible to use AAL5 for this purpose.  An n x 64
   clear channel is represented by the encoding names of "X-CCD" and
   "X-CCD-CAS" in Table 2.

   The format of the 'sbc' media attribute line is as follows:

      a=sbc:<sbc>





Kumar & Mostafa             Standards Track                    [Page 49]

RFC 3108                        ATM SDP                         May 2001


   Here, <sbc> can be expressed as a decimal or hex integer.  This
   attribute indicates the number of DS0s in a T1 or E1 frame that are
   aggregated for transmitting clear channel data.  For T1-based
   applications, it can take on integral values in the inclusive range
   [1...24].  For E1-based applications, it can take on integral values
   in the inclusive range [1...31].  When omitted, other means are to be
   used to determine the subchannel count.

   Use of the 'sbc' attribute provides a direct way to indicate the
   number of 64 kbps subchannels bundled into an n x 64 clear channel.
   An alternate mechanism to indicate this exists within the SDP
   bandwidth information, or 'b', line [1].  In this case, instead of
   specifying the number of subchannels, the aggregate bandwidth in kbps
   is specified.  The syntax of the 'b' line, copied verbatim from [1],
   is as follows:

      b=<modifier>:<bandwidth-value>

   In the case of n x 64 clear channels, the <modifier> is assigned a
   text string value of "AS", indicating that the 'b' line is
   application-specific.  The <bandwidth-value> parameter, which is a
   decimal number indicating the bandwidth in kbps, is limited to one of
   the following values in the n x 64 clear channel application context:

      64, 128, 192, 256, 320, 384, 448, 512, 576, 640, 704, 768, 832,
      896, 960, 1024, 1088, 1152, 1216, 1280, 1344, 1408, 1472, 1600,
      1664, 1728, 1792, 1856, 1920, 1984

   Thus, for n x 64 circuit mode data service,

      a=sbc:6

   is equivalent to

      b=AS:384

   The media attribute line

      a=sbc:2

   is equivalent to

      b=AS:128








Kumar & Mostafa             Standards Track                    [Page 50]

RFC 3108                        ATM SDP                         May 2001


5.6.2.4 The 'clkrec' attribute

   When present, the 'clkrec' attribute is used to indicate the clock
   recovery method.  This attribute is meaningful in the case of AAL1
   unstructured data transfer (UDT).  The format of the 'clkrec' media
   attribute line is as follows:

      a=clkrec:<clkrec>

   The <clkrec> field can take on the following string values: "NULL",
   "SRTS" or "ADAPTIVE".  SRTS and adaptive clock recovery are defined
   in ITU I.363.1 [10].  "NULL" indicates that the stream (e.g., T1/E1)
   encapsulated in ATM is synchronous to the ATM network or is retimed,
   before AAL1 encapsulation, via slip buffers.

5.6.2.5 The 'fec' attribute

   When present, the 'fec' attribute is used to indicate the use of
   forward error correction.  Currently, there exists a forward error
   correction method defined for AAL1 in ITU I.363.1 [10].  The format
   of the 'fec' media attribute line is as follows:

      a=fec:<fecEnable>

   The <fecEnable> flag indicates the presence of absence of Forward
   Error Correction.  It can take on the string values of "NULL",
   "LOSS_SENSITIVE" and "DELAY_SENSITIVE".  An "NULL" value implies
   disabling this capability.  FEC can be enabled differently for
   delay-sensitive and loss-sensitive connections.

5.6.2.6 The 'prtfl' attribute

   When present, the 'prtfl' attribute is used to indicate the fill
   level of cells.  When this attribute is absent, then other means
   (such as provisionable defaults) are used to determine the presence
   and level of partial fill.

   This attribute indicates the number of non-pad payload octets, not
   including any AAL SAR or convergence sublayer octets.  For example,
   in some AAL1 applications that use partially filled cells with
   padding at the end, this attribute indicates the number of leading
   payload octets not including any AAL overhead.

   The format of the 'prtfl' media attribute line is as follows:

      a=prtfl:<partialFill>

   Here, <partialFill> can be expressed as a decimal or a hex integer.



Kumar & Mostafa             Standards Track                    [Page 51]

RFC 3108                        ATM SDP                         May 2001


   In general, permitted values are integers in the range 1 - 48
   inclusive.  However, this upper bound is different for different
   adaptations since the AAL overhead, if any, is different.  If the
   specified partial fill is greater than or equal to the maximum fill,
   then complete fill is used.  Using a 'partial' fill of 48 always
   disables partial fill.

   In the AAL1 context, this media attribute line applies uniformly to
   both P and non-P cells.  In AAL1 applications that do not distinguish
   between P and non-P cells, a value of 47 indicates complete fill
   (i.e., the absence of partial fill).  In AAL1 applications that
   distinguish between P and non-P cells, a value of 46 indicates no
   padding in P-cells and a padding of one in non-P cells.

   If partial fill is enabled (i.e there is padding in at least some
   cells), then AAL1 structures must not be split across cell
   boundaries.  These shall fit in any cell.  Hence, their size shall be
   less than or equal to the partial fill size.  Further, the partial
   fill size is preferably an integer multiple of the structure size.
   If not, then the partial fill size stated in the SDP description
   shall be truncated to an integer multiple (e.g., a partial fill size
   of 40 is truncated to 36 to support six 6 x 64 channels).

5.6.2.7 The 'structure' attribute

   This attribute applies to AAL1 connections only.  When present, the '
   structure' attribute is used to indicate the presence or absence of
   structured data transfer (SDT), and the size in octets of the SDT
   blocks.  The format of the 'structure' media attribute line is as
   follows:

      a=structure: <structureEnable> <blksz>

   where the <structureEnable> flag indicates the presence of absence of
   SDT.  It can take on the values of "on" or "off".  An "on" value
   implies AAL1 structured data transfer (SDT), while an "off" value
   implies AAL1 unstructured data transfer (UDT).

   The block size field, <blksz>, is an optional 16-bit field [15] that
   can be represented in decimal or hex.  It is set to a "-" when not
   applicable, as in the case of unstructured data transfer (UDT).  For
   SDT, it can be set to a "-" when <blksz> is known by other means.
   For instance, af-vtoa-78 [7] fixes the structure size for n x 64
   service, with or without CAS.  The theoretical maximum value of
   <blksz> is 65,535, although most services use much less.






Kumar & Mostafa             Standards Track                    [Page 52]

RFC 3108                        ATM SDP                         May 2001


5.6.2.8 The 'cpsSDUsize' attribute

   When present, the 'cpsSDUsize' attribute is used to indicate the
   maximum size of the CPCS SDU payload.  There can be several '
   cpsSDUsize' lines in an SDP description.

   The format of this media attribute line is as follows:

      a=cpsSDUsize:<directionFlag><cpcs>

   The <directionFlag> can be assigned the following string values: "f",
   "b" and "fb".  "f" and "b" indicate the forward and backward
   directions respectively.  "fb" refers to both directions (forward and
   backward).  Conventions for the forward and backward directions are
   per section 2.3.

   The <cpcs> fields is a 16-bit integer that can be represented in
   decimal or in hex.  The meaning and values of these fields are as
   follows:

   Application    Field      Meaning                         Values

   AAL5           <cpcs>    Maximum CPCS-SDU size           1- 65,535


   AAL2           <cpcs>    Maximum CPCS-SDU size           45 or 64

5.6.2.9 The 'aal2CPS' attribute

   When present, the 'aal2CPS' attribute is used to describe parameters
   associated with the AAL2 CPS layer.

   The format of the 'aal2CPS' media attribute line is as follows:
   a=aal2CPS:<cidLowerLimit><cidUpperLimit><timerCU> <simplifiedCPS>

   Each of these fields can be set to a "-" when the intention is to not
   specify them in an SDP descriptor.

   The <cidLowerLimit> and <cidUpperLimit> can be assigned integer
   values between 8 and 255 [11], with the limitation that
   <cidUpperLimit> be greater than or equal to <cidLowerLimit>.  For
   instance, for POTS applications based on [52], <cidLowerLimit> and
   <cidUpperLimit> can have values of 16 and 223 respectively.

   The <timerCU> integer represents the "combined use" timerCU defined
   in ITU I.363.2.  This timer is represented as an integer number of
   microseconds.  It is represented as the decimal integer equivalent of
   32 bits.



Kumar & Mostafa             Standards Track                    [Page 53]

RFC 3108                        ATM SDP                         May 2001


   The <simplifiedCPS> parameter can be assigned the values "on" or
   "off".  When it is "on", the AAL2 CPS simplification described in
   [52] is adopted.  Under this simplification, each ATM cell contains
   exactly on AAL2 packet.  If necessary, octets at the end of the cell
   are padded with zeros.  Since the <timerCU> value in this context is
   always 0, it can be set to "-".

5.6.2.10 The 'aal2CPSSDUrate' attribute

   When present, the 'aal2CPSSDUrate' attribute is used to place an
   upper bound on the SDU bit rate for an AAL2 CID.  This is useful for
   limiting the bandwidth used by a CID, specially if the CID is used
   for frame mode data defined in [13], or with the SSSAR defined in
   [12].  The format of this media attribute line is as follows:

      a=aal2CPSSDUrate: <fSDUrate><bSDUrate>

   The fSDUrate and bSDUrate are the maximum forward and backward SDU
   rates in bits/second.  These are represented as decimal integers,
   with range as defined in Section 6.  If any of these parameters in
   these media attribute lines is not specified, is inapplicable or is
   implied, then it is set to "-".

5.6.2.11 The 'aal2sscs3661unassured' attribute

   When present, the 'aal2sscs3661unassured' attribute is used to
   indicate the options that pertain to the unassured transmission SSCS
   defined in ITU I.366.1 [12].  This SSCS can be selected via the
   aalApp attribute defined below, or by virtue of the presence of the '
   aal2sscs3661unassured' attribute.  The format of this media attribute
   line is as follows:

      a=aal2sscs3661unassured: <ted> <rastimer> <fsssar> <bsssar>

   Each of these fields can be set to a "-" when the intention is to not
   specify them in an SDP descriptor.

   The <ted> flag indicates the presence or absence of transmission
   error detection as defined in I.366.1.  It can be assigned the values
   of "on" or "off".  An "on" value indicates presence of the
   capability.

   The <rastimer> subparameter indicates the SSSAR reassembly timer in
   microseconds.  It is represented as the decimal equivalent of 32
   bits.






Kumar & Mostafa             Standards Track                    [Page 54]

RFC 3108                        ATM SDP                         May 2001


   The <fsssar> and <bsssar> fields are 24-bit integers that can be
   represented in decimal or in hex.  The meaning and values of the
   <fsssar> and <bsssar> fields are as follows:

   Field      Meaning                         Values

   <fsssar>   Maximum SSSAR-SDU size           1- 65,568
              forward direction

   <bsssar>   Maximum SSSAR-SDU size           1- 65,568
              backward direction

   If present, the SSTED (Service-Specific Transmission Error Detection)
   sublayer is above the SSSAR (Service-Specific Segmentation and
   Reassembly) sublayer [12].  Since the maximum size of the SSTED-SDUs
   can be derived from the maximum SSSAR-SDU size, it need not be
   specified separately.

5.6.2.12 The 'aal2sscs3661assured' attribute

   When present, the 'aal2sscs3661assured' attribute is used to indicate
   the options that pertain to the assured transmission SSCS defined in
   ITU I.366.1 [12] on the basis of ITU Q.2110 [43].  This SSCS can be
   selected via the aalApp attribute defined below, or by virtue of the
   presence of the 'aal2sscs3661assured' attribute.  The format of this
   media attribute line is as follows:

      a=aal2sscs3661assured: <rastimer> <fsssar> <bsssar> <fsscopsdu>
                             <bsscopsdu><fsscopuu> <bsscopuu>

   Each of these fields can be set to a "-" when the intention is to not
   specify them in an SDP descriptor.

   The <rastimer> subparameter indicates the SSSAR reassembly timer in
   microseconds.  It is represented as the decimal equivalent of 32
   bits.

   The <fsssar> and <bsssar> fields are 24-bit integers that can be
   represented in decimal or in hex.  The <fsscopsdu>, <bsscopsdu>,
   <fsscopuu> and <bsscopuu> fields are 16-bit integers that can be
   represented in decimal or in hex.  The meaning and values of these
   fields is as follows:

   Field       Meaning                          Values

   <fsssar>    Maximum SSSAR-SDU size           1- 65,568
               forward direction




Kumar & Mostafa             Standards Track                    [Page 55]

RFC 3108                        ATM SDP                         May 2001


   <bsssar>    Maximum SSSAR-SDU size           1- 65,568
               backward direction

   <fsscopsdu> Maximum SSCOP-SDU size           1- 65,528
               forward direction

   <bsscopsdu> Maximum SSCOP-SDU size           1- 65,528
               backward direction

   <fsscopuu>  Maximum SSCOP-UU field           1- 65,524
               size, forward direction

   <bsscopuu>  Maximum SSCOP-UU field           1- 65,524
               size, backward direction

   The SSTED (Service-Specific Transmission Error Detection) sublayer is
   above the SSSAR (Service-Specific Segmentation and Reassembly)
   sublayer [12].  The SSADT (Service-Specific Assured Data Transfer)
   sublayer is above the SSTED sublayer.  Since the maximum size of the
   SSTED-SDUs and SSADT-SDUs can be derived from the maximum SSSAR-SDU
   size, they need not be specified separately.

   The SSCOP protocol defined in [43] is used by the Assured Data
   Transfer service defined in [12].  In the context of the ITU I.366.1
   SSCS, it is possible to use the 'aal2sscs3661assured' attribute to
   limit the maximum sizes of the SSCOP SDUs and UU (user-to-user)
   fields in either direction.  Note that it is necessary for the
   parameters on the 'aal2sscs3661assured' media attribute line to be
   consistent with each other.

5.6.2.13 The 'aal2sscs3662' attribute

   When present, the 'aal2sscs3662' attribute is used to indicate the
   options that pertain to the SSCS defined in ITU I.366.2 [13].  This
   SSCS can be selected via the aalApp attribute defined below, or by
   the presence of the 'aal2sscs3662' attribute.

   The format of this media attribute line is as follows:

      a=aal2sscs3662: <sap> <circuitMode> <frameMode> <faxDemod>
                      <cas> <dtmf> <mfall> <mfr1> <mfr2>
                      <PCMencoding> <fmaxFrame> <bmaxFrame>

   Each of these fields can be set to a "-" when the intention is to not
   specify them in an SDP descriptor.  Additionally, the values of these
   fields need to be consistent with each other.  Inconsistencies should
   be flagged as errors.




Kumar & Mostafa             Standards Track                    [Page 56]

RFC 3108                        ATM SDP                         May 2001


   The <sap> field can take on the following string values: "AUDIO" and
   "MULTIRATE".  These correspond to the audio and multirate Service
   Access Points (SAPs) defined in ITU I.366.2.

   For the multirate SAP, the following parameters on the aal2sscs3662
   attribute line do not apply: <faxDemod>,<cas>, <dtmf>, <mfall>,
   <mfr1>,  <mfr2> and <PCMencoding>.  These are set to "-" for the
   multirate SAP.

   The <circuitMode> flag indicates whether the transport of circuit
   mode data is enabled or disabled, corresponding to the string values
   of "on" and "off" respectively.  For the multirate SAP, it cannot
   have a value of "off".  For the audio SAP, it can be assigned a value
   of "on", "off" or "-".  Note that the <sbc> attribute, defined
   elsewhere in this document, can be used to specify the number of 64
   kbps subchannels bundled into a circuit mode data channel.

   The <frameMode> flag indicates whether the transport of frame mode
   data is enabled or disabled, corresponding to the string values of
   "on" and "off" respectively.

   The <faxDemod> flag indicates whether facsimile demodulation and
   remodulation are enabled or disabled, corresponding to the string
   values of "on" and "off" respectively.

   The <cas> flag indicates whether the transport of Channel Associated
   Signaling (CAS) bits in AAL2 type 3 packets is enabled or disabled,
   corresponding to the string values of "on" and "off" respectively.

   The <dtmf> flag indicates whether the transport of DTMF dialled
   digits in AAL2 type 3 packets is enabled or disabled, corresponding
   to the string values of "on" and "off" respectively.

   The <mfall> flag indicates whether the transport of MF dialled digits
   in AAL2 type 3 packets is enabled or disabled, corresponding to the
   string values of "on" and "off" respectively.  This flag enables MF
   dialled digits in a generic manner, without specifying type (e.g.,
   R1, R2 etc.).

   The <mfr1> flag indicates whether the transport, in AAL2 type 3
   packets, of MF dialled digits for signaling system R1 is enabled or
   disabled, corresponding to the string values of "on" and "off"
   respectively.

   The <mfr2> flag indicates whether the transport, in AAL2 type 3
   packets, of MF dialled digits for signaling system R2 is enabled or
   disabled, corresponding to the string values of "on" and "off"
   respectively.



Kumar & Mostafa             Standards Track                    [Page 57]

RFC 3108                        ATM SDP                         May 2001


   The <PCMencoding> field indicates whether PCM encoding, if used, is
   based on the A-law or the Mu-law.  This can be used to qualify the '
   generic PCM' codec stated in some of the AAL2 profiles.  The
   <PCMencoding> field can take on the string values of "PCMA" and
   "PCMU".

   The <fmaxFrame> and <bmaxFrame> fields are 16-bit integers that can
   be represented in decimal or in hex.  The meaning and values of the
   <fmaxFrame> and <bmaxFrame> fields are as follows:

   Field         Meaning                         Values

   <fmaxFrame>   Maximum length of a             1- 65,535
                 frame mode data unit,
                 forward direction

   <bmaxFrame>   Maximum length of a             1- 65,535
                 frame mode data unit,
                 backward direction

5.6.2.14 The 'aal5sscop' attribute

   When present, the 'aal5sscop' attribute is used to indicate the
   existence of an SSCOP [43] protocol layer over an AAL5 CPS layer
   [21], and the parameters which pertain to this SSCOP layer.  SSCOP
   over AAL5 can also be selected via the aalApp attribute defined
   below.  The format of the 'aal5sscop' media attribute line is as
   follows:

      a=aal5sscop: <fsscopsdu> <bsscopsdu> <fsscopuu> <bsscopuu>

   Each of these fields can be set to a "-" when the intention is to not
   specify them in an SDP descriptor.

   The representation, meaning and values of the <fsscopsdu>,
   <bsscopsdu>, <fsscopuu> and <bsscopuu> fields are identical to those
   for the 'aal2sscs3661assured' media attribute line (Section
   5.6.2.12).  Note that it is necessary for the parameters on the '
   aal5sscop' media attribute line to be consistent with each other.

5.6.3 Service attributes

   The following is a summary list of the SDP media attributes that can
   be used to describe the services that use the ATM Adaptation Layer
   (AAL).  These attributes are detailed in subsequent subsections.

      *  The 'atmmap' attribute.  In the AAL1 and AAL5 contexts, this is
         used to dynamically map payload types into codec strings.



Kumar & Mostafa             Standards Track                    [Page 58]

RFC 3108                        ATM SDP                         May 2001


      *  The 'silenceSupp' attribute, used to indicate the use of of
         voice activity detection for silence suppression, and to
         optionally parameterize the silence suppression function.

      *  The 'ecan'  attribute, used to indicate the use of of echo
         cancellation, and to parameterize the this function.

      *  The 'gc' attribute, used to indicate the use of of gain
         control, and to parameterize the this function.

      *  The 'profileDesc' attribute, which can be used to describe AAL2
         profiles.  Although any AAL2 profile can be so described, this
         attribute is useful for describing, at connection establishment
         time, custom profiles that might not be known to the far end.
         This attribute applies in the AAL2 context only.

      *  The 'vsel' attribute, which indicates a prioritized list of 3-
         tuples for voice service.  Each 3-tuple indicates a codec, an
         optional packet length and an optional packetization period.
         This complements the 'm' line information and should be
         consistent with it.

      *  The 'dsel' attribute, which indicates a prioritized list of 3-
         tuples for voiceband data service.  Each 3-tuple indicates a
         codec, an optional packet length and an optional packetization
         period.  This complements the 'm' line information and should
         be consistent with it.

      *  The 'fsel' attribute, which indicates a prioritized list of 3-
         tuples for facsimile service.  Each 3-tuple indicates a codec,
         an optional packet length and an optional packetization period.
         This complements the 'm' line information and should be
         consistent with it.

      *  The 'onewaySel' attribute, which indicates a prioritized list
         of 3-tuples for one direction of an asymmetric connection.
         Each 3-tuple indicates a codec, an optional packet length and
         an optional packetization period.  This complements the 'm'
         line information and should be consistent with it.

      *  The 'codecconfig' attribute, which is used to represent the
         contents of the single codec information element (IE) defined
         in ITU Q.765.5 [57].

      *  The 'isup_usi' attribute which is used to represent the bearer
         capability information element defined in Section 4.5.5 of ITU
         Q.931 [59], and reiterated as the user service information
         element (IE) in Section 3.57  of ITU Q.763 [60].



Kumar & Mostafa             Standards Track                    [Page 59]

RFC 3108                        ATM SDP                         May 2001


      *  The 'uiLayer1_Prot' attribute, which is used to represent the '
         User Information Layer 1 protocol' field within the bearer
         capability information element defined in Section 4.5.5 of ITU
         Q.931 [59].

5.6.3.1 The 'atmmap' attribute

   The 'atmmap' attribute is defined on the basis of the 'rtpmap'
   attribute used in RFC 2327.

      a=atmmap:<payloadType> <encodingName>

   The 'atmmap' attribute is used to dynamically map encoding names into
   payload types.  This is necessary for those encoding names which have
   not been assigned a static payload type through IANA [31].  Payload
   types and encoding techniques that have been registered with IANA for
   RTP are retained for AAL1 and AAL5.

   The range of statically defined payload types is in the range 0-95.
   All static assignments of payload types to codecs are listed in [31].
   The range of payload types defined dynamically via the 'atmmap'
   attribute is 96-127.

   In addition to reiterating the payload types and encoding names in
   [31], Table 2 defines non-standard encoding names (with "X-"
   prefixes).  Note that [31], rather than Table 2, is the authoritative
   list of standard codec names and payload types in the ATM context.

               Table 2: Encoding Names and Payload Types

      |---------------------|--------------|---------------------------|
      | Encoding Technique  | Encoding Name|    Payload type           |
      |---------------------|--------------|---------------------------|
      | PCM - Mu law        | "PCMU"       |    0 (Statically Mapped)  |
      |---------------------|--------------|---------------------------|
      | 32 kbps ADPCM       | "G726-32"    |    2 (Statically Mapped)  |
      |---------------------|--------------|---------------------------|
      |Dual rate 5.3/6.3kbps| "G723"       |    4 (Statically Mapped)  |
      |---------------------|--------------|---------------------------|
      | PCM- A law          | "PCMA"       |    8 (Statically Mapped)  |
      |---------------------|--------------|---------------------------|
      | 7 KHz audio coding  | "G722"       |    9 (Statically Mapped)  |
      | within 64 kbps      |              |                           |
      |---------------------|--------------|---------------------------|
      | LD-CELP             | "G728"       |    15 (Statically Mapped) |
      |---------------------|--------------|---------------------------|
      | CS-ACELP            | "G729"       |    18 (Statically Mapped) |
      |(normal/low-complexity)             |                           |



Kumar & Mostafa             Standards Track                    [Page 60]

RFC 3108                        ATM SDP                         May 2001


      |---------------------|--------------|---------------------------|
      | Low-complexity      | "X-G729a"    |    None, map dynamically  |
      | CS-ACELP            |              |                           |
      |---------------------|--------------|---------------------------|
      |Normal               | "X-G729b"    |    None, map dynamically  |
      |CS-ACELP w/ ITU      |              |                           |
      |defined silence      |              |                           |
      |suppression          |              |                           |
      +---------------------+--------------+---------------------------+
      |Low-complexity       | "X-G729ab"   |    None, map dynamically  |
      |CS-ACELP w/ ITU      |              |                           |
      |defined silence      |              |                           |
      |suppression          |              |                           |
      |---------------------|--------------|---------------------------|
      | 16 kbps ADPCM       | "X-G726-16"  |    None, map dynamically  |
      |---------------------|--------------|---------------------------|
      | 24 kbps ADPCM       | "X-G726-24"  |    None, map dynamically  |
      |---------------------|--------------|---------------------------|
      | 40 kbps ADPCM       | "X-G726-40"  |    None, map dynamically  |
      |---------------------|--------------|---------------------------|
      | Dual rate 5.3/6.3   |"X-G7231-H"   |    None, map dynamically  |
      | kbps - high rate    |              |                           |
      |---------------------|--------------|---------------------------|
      | Dual rate 5.3/6.3   |"X-G7231-L"   |   None, map dynamically   |
      | kbps - low rate     |              |                           |
      |---------------------|--------------|---------------------------|
      | Dual rate 5.3/6.3   |"X-G7231a-H"  |   None, map dynamically   |
      | kbps - high rate w/ |              |                           |
      | ITU-defined silence |              |                           |
      | suppression         |              |                           |
      |----------------------------------------------------------------|
      +---------------------+--------------+---------------------------+
      | Dual rate 5.3/6.3   |"X-G7231a-L"  |   None, map dynamically   |
      | kbps - high rate w/ |              |                           |
      | ITU-defined silence |              |                           |
      | suppression         |              |                           |
      |---------------------|--------------|---------------------------|
      | 16 kbps EADPCM      | "X-G727-16"  |    None, map dynamically  |
      |---------------------|--------------|---------------------------|
      | 24 kbps EADPCM      | "X-G727-24"  |    None, map dynamically  |
      |---------------------|--------------|---------------------------|
      | 32 kbps EADPCM      | "X-G727-32"  |    None, map dynamically  |
      |---------------------|--------------|---------------------------|
      |n x 64 kbps Clear    | "X-CCD"      |    None, map dynamically  |
      |Channel without CAS  |              |                           |
      |per af-vtoa-78 [7]   |              |                           |
      |---------------------|--------------|---------------------------|




Kumar & Mostafa             Standards Track                    [Page 61]

RFC 3108                        ATM SDP                         May 2001


      |n x 64 kbps Clear    | "X-CCD-CAS"  |    None, map dynamically  |
      |Channel with CAS     |              |                           |
      |per af-vtoa-78 [7]   |              |                           |
      |---------------------|--------------|---------------------------|
      |GSM Full Rate        | "GSM"        |    3 (Statically Mapped)  |
      |---------------------|--------------|---------------------------|
      |GSM Half Rate        |    "GSM-HR"  |    None, map dynamically  |
      |---------------------|--------------|---------------------------|
      |GSM-Enhanced Full Rate    "GSM-EFR" |    None, map dynamically  |
      |---------------------|--------------|---------------------------|
      |GSM-Enhanced Half Rate  "GSM-EHR"   |    None, map dynamically  |
      |---------------------|--------------|---------------------------|
      |Group 3 fax demod.   | "X-FXDMOD-3" |    None, map dynamically  |
      |---------------------|--------------|---------------------------|
      | Federal Standard    |    "1016"    |   1 (Statically Mapped)   |
      | FED-STD 1016 CELP   |              |                           |
      |---------------------|--------------|---------------------------|
      | DVI4, 8 KHz [3]     |    "DVI4"    |   5 (Statically Mapped)   |
      |---------------------|--------------|---------------------------|
      | DVI4, 16 KHz [3]    |    "DVI4"    |   6 (Statically Mapped)   |
      |---------------------|--------------|---------------------------|
      | LPC [3], Linear     |    "LPC"     |   7 (Statically Mapped)   |
      | Predictive Coding   |              |                           |
      |---------------------|--------------|---------------------------|
      | L16 [3], Sixteen    |    "L16"     |   10 (Statically Mapped)  |
      | Bit Linear PCM,     |              |                           |
      | Double channel      |              |                           |
      |---------------------|--------------|---------------------------|
      | L16 [3], Sixteen    |    "L16"     |   11 (Statically Mapped)  |
      | Bit Linear PCM,     |              |                           |
      | Single channel      |              |                           |
      |---------------------|--------------|---------------------------|
      | QCELP [3]           |    "QCELP"   |   12 (Statically Mapped)  |
      |---------------------|--------------|---------------------------|
      | MPEG1/MPEG2 audio   |    "MPA"     |   14 (Statically Mapped)  |
      |---------------------|--------------|---------------------------|
      +---------------------+--------------+---------------------------+
      | DVI4, 11.025 KHz[3] |    "DVI4"    |   16 (Statically Mapped)  |
      |---------------------|--------------|---------------------------|
      | DVI4, 22.05 KHz [3] |    "DVI4"    |   17 (Statically Mapped)  |
      |---------------------|--------------|---------------------------|
      | MPEG1/MPEG2 video   |    "MPV"     |   32 (Statically Mapped)  |
      |---------------------|--------------|---------------------------|
      | MPEG 2 audio/video  |    "MP2T"    |   33 (Statically Mapped)  |
      | transport stream    |              |                           |
      |---------------------|--------------|---------------------------|
      | ITU H.261 video     |    "H261"    |   31 (Statically Mapped)  |
      |---------------------|--------------|---------------------------|



Kumar & Mostafa             Standards Track                    [Page 62]

RFC 3108                        ATM SDP                         May 2001


      | ITU H.263 video     |    "H263"    |   33 (Statically Mapped)  |
      |---------------------|--------------|---------------------------|
      | ITU H.263 video     |"H263-1998"   | None, map dynamically     |
      | 1998 version        |              |                           |
      |---------------------|--------------|---------------------------|
      |MPEG 1 system stream |    "MP1S"    | None, map dynamically     |
      |---------------------|--------------|---------------------------|
      |MPEG 2 program stream|    "MP2P"    | None, map dynamically     |
      |---------------------|--------------|---------------------------|
      |Redundancy           |    "RED"     | None, map dynamically     |
      |---------------------|--------------|---------------------------|
      |Variable rate DVI4   |    "VDVI"    | None, map dynamically     |
      |---------------------|--------------|---------------------------|
      |Cell-B               |    "CelB"    | 25                        |
      |---------------------|--------------|---------------------------|
      |JPEG                 |    "JPEG"    | 26                        |
      |---------------------|--------------|---------------------------|
      |nv                   |    "nv"      | 28                        |
      |---------------------|--------------|---------------------------|
      |L8, Eight Bit Linear |    "L8"      | None, map dynamically     |
      |PCM                  |              |                           |
      |---------------------|--------------|---------------------------|
      | ITU-R Recommendation|   "BT656"    | None, map dynamically     |
      | BT.656-3 for        |              |                           |
      | digital video       |              |                           |
      |---------------------|--------------|---------------------------|
      | Adaptive Multirate  |   "FR-AMR"   | None, map dynamically     |
      |-Full Rate (3GPP)[58]|              |                           |
      |---------------------|--------------|---------------------------|
      | Adaptive Multirate  |   "HR-AMR"   | None, map dynamically     |
      |-Half Rate (3GPP)[58]|              |                           |
      |---------------------|--------------|---------------------------|
      | Adaptive Multirate  |   "UMTS-AMR" | None, map dynamically     |
      |- UMTS(3GPP)  [58]   |              |                           |
      |---------------------|--------------|---------------------------|
      | Adaptive Multirate  |   "AMR"      | None, map dynamically     |
      |- Generic     [58]   |              |                           |
      |---------------------|--------------|---------------------------|

5.6.3.2 The 'silenceSupp' attribute

   When present, the 'silenceSupp' attribute is used to indicate the use
   or non-use of silence suppression.  The format of the 'silenceSupp'
   media attribute line is as follows:

   a=silenceSupp: <silenceSuppEnable> <silenceTimer> <suppPref> <sidUse>
                   <fxnslevel>




Kumar & Mostafa             Standards Track                    [Page 63]

RFC 3108                        ATM SDP                         May 2001


   If any of the parameters in the silenceSupp media attribute line is
   not specified, is inapplicable or is implied, then it is set to "-".

   The <silenceSuppEnable> can take on values of "on" or "off".  If it
   is "on", then silence suppression is enabled.

   The <silenceTimer> is a 16-bit field which can be represented in
   decimal or hex.  Each increment (tick) of this timer represents a
   millisecond.  The maximum value of this timer is between 1 and 3
   minutes.  This timer represents the time-lag before silence
   suppression kicks in.  Even though this can, theoretically, be as low
   as 1 ms, most DSP algorithms take more than that to detect silence.
   Setting <silenceTimer> to a large value (say 1 minute> is equivalent
   to disabling silence suppression within a call.  However, idle
   channel suppression between calls on the basis of silence suppression
   is still operative in non-switched, trunking applications if
   <silenceSuppEnable> = "on" and <silenceTimer> is a large value.

   The <suppPref> specifies the preferred silence suppression method
   that is preferred or already selected.  It can take on the string
   values of "standard" and "custom".  If its value is "standard", then
   a standard method (e.g., ITU-defined) is preferred to custom methods
   if such a standard is defined.  Otherwise, a custom method may be
   used.  If <suppPref> is set to "custom", then a custom method, if
   available, is preferred to the standard method.

   The <sidUse> indicates whether SIDs (Silence Insertion Descriptors)
   are to be used, and whether they use fixed comfort noise or sampled
   background noise.  It can take on the string values of "No SID",
   "Fixed Noise", "Sampled Noise".

   If the value of <sidUse> is "Fixed Noise", then <fxnslevel> provides
   its level.  It can take on integer values in the range 0-127, as
   follows:

         +-----------------------+---------------------+
         | <fxnslevel> value     |         Meaning     |
         +-----------------------+---------------------+
         |  0-29                 |          Reserved   |
         |   30                  |          -30 dBm0   |
         |   31                  |          -31 dBm0   |
         |   . . .               |           . . .     |
         |   77                  |          -77 dBm0   |
         |   78                  |          -78 dBm0   |
         |  79-126               |          reserved   |
         |   127                 | Idle Code (no noise)|
         +-----------------------+---------------------+




Kumar & Mostafa             Standards Track                    [Page 64]

RFC 3108                        ATM SDP                         May 2001


   In addition to the decimal representation of <fxnslevel>, a hex
   representation, preceded by a "0x" prefix, is also allowed.

5.6.3.3 The 'ecan' attribute

   When present, the 'ecan' attribute s is used to indicate the use or
   non-use of echo cancellation.  There can be several 'ecan' lines in
   an SDP description.

   The format of the 'ecan' media attribute line is as follows:

      a=ecan:<directionFlag><ecanEnable><ecanType>

   The <directionFlag> can be assigned the following string values: "f",
   "b" and "fb".  "f" and "b" indicate the forward and backward
   directions respectively.  "fb" refers to both directions (forward and
   backward).  Conventions for the forward and backward directions are
   per section 2.3.

   The <directionFlag> is always specified.  Except for the
   <directionFlag>, the remaining parameters can be set to "-" to
   indicate that they are not specified, inapplicable or implied.
   However, there must be some specified parameters for the line to be
   useful in an SDP description.

   If the 'ecan' media attribute lines is not present, then means other
   than the SDP descriptor must be used to determine the applicability
   and nature of echo cancellation for a connection direction.  Examples
   of such means are MIB provisioning, the local connection options
   structure in MGCP etc.

   The <ecanEnable> parameter can take on values of "on" or "off".  If
   it is "on", then echo cancellation is enabled.  If it is "off", then
   echo cancellation is disabled.

   The <ecanType> parameter can take on the string values "G165" and
   "G168" respectively.

   When SDP is used with some media gateway control protocols such as
   MGCP and Megaco [26], there exist means outside SDP descriptions to
   specify the echo cancellation properties of a connection.
   Nevertheless, this media attribute line is included for completeness.
   As a result, the SDP can be used for describing echo cancellation in
   applications where alternate means for this are unavailable.







Kumar & Mostafa             Standards Track                    [Page 65]

RFC 3108                        ATM SDP                         May 2001


5.6.3.4 The 'gc' attributes

   When present, the 'gc' attribute is used to indicate the use or non-
   use of gain control.  There can be several 'gc' lines in an SDP
   description.

   The format of the 'gc' media attribute line is as follows:

      a=gc:<directionFlag><gcEnable><gcLvl>

   The <directionFlag> can be assigned the following string values: "f",
   "b" and "fb".  "f" and "b" indicate the forward and backward
   directions respectively.  "fb" refers to both directions (forward and
   backward).  Conventions for the forward and backward directions are
   per section 2.3.

   The <directionFlag> is always specified.  Except for the
   <directionFlag>, the remaining parameters can be set to "-" to
   indicate that they are not specified, inapplicable or implied.
   However, there must be some specified parameters for the line to be
   useful in an SDP description.

   If the 'gc' media attribute lines is not present, then means other
   than the SDP descriptor must be used to determine the applicability
   and nature of gain control for a connection direction.  Examples of
   such means are MIB provisioning, the local connection options
   structure in MGCP etc.

   The <gcEnable> parameter can take on values of "on" or "off".  If it
   is "on", then gain control is enabled.  If it is "off", then gain
   control is disabled.

   The <gcLvl> parameter is represented as the decimal or hex equivalent
   of a 16-bit binary field.  A value of 0xFFFF implies automatic gain
   control.  Otherwise, this number indicates the number of decibels of
   inserted loss.  The upper bound, 65,535 dB (0xFFFE) of inserted loss,
   is a large number and is a carryover from Megaco [26].  In practical
   applications, the inserted loss is much lower.

   When SDP is used with some media gateway control protocols such as
   MGCP and Megaco [26], there exist means outside SDP descriptions to
   specify the gain control properties of a connection.  Nevertheless,
   this media attribute line is included for completeness.  As a result,
   the SDP can be used for describing gain control in applications where
   alternate means for this are unavailable.






Kumar & Mostafa             Standards Track                    [Page 66]

RFC 3108                        ATM SDP                         May 2001


5.6.3.5 The 'profileDesc' attribute

   There is one 'profileDesc' media attribute line for each AAL2 profile
   that is intended to be described.  The 'profileDesc' media attribute
   line is structured as follows:

      a=profileDesc: <aal2transport> <profile>  <uuiCodeRange#1>
        <encodingName#1> <packetLength#1> <packetTime#1>
        <uuiCodeRange#2> <encodingName#2> <packetLength#2>
        <packetTime#2>... <uuiCodeRange#N> <encodingName#N>
        <packetLength#N> <packetTime#N>

   Here, <aal2transport> can have those values of <transport> (Table 1)
   that pertain to AAL2.  These are:

            AAL2/ATMF
            AAL2/ITU
            AAL2/custom
            AAL2/<corporateName>
            AAL2/IEEE:<oui>

   The parameter <profile> is identical to its definition for the 'm'
   line (Section 5.5.4).

   The profile elements (rows in the profile tables of ITU I.366.2 or
   AF-VTOA-0113) are represented as four-tuples following the <profile>
   parameter in the 'profileDesc' media attribute line.  If a member of
   one of these four-tuples is not specified or is implied, then it is
   set to "-".

   The <uuiCodeRange> parameter is represented by D1-D2, where D1 and D2
   are decimal integers in the range 0 through 15.

   The <encodingName> parameter can take one of the values in column 2
   of Table 2.  Additionally, it can take on the following descriptor
   strings: "PCMG", "SIDG" and "SID729".  These stand for generic PCM,
   generic SID and G.729 SID respectively.

   The <packetLength> is a decimal integer representation of the AAL2
   packet length in octets.

   The <packetTime> is a decimal integer representation of the AAL2
   packetization interval in microseconds.

   For instance, the 'profileDesc' media attribute line below defines
   the AAL2/custom 100 profile.  This profile is reproduced in the Table
   3 below.  For a description of the parameters in this profile such as
   M and the sequence number interval, see ITU I.366.2 [13].



Kumar & Mostafa             Standards Track                    [Page 67]

RFC 3108                        ATM SDP                         May 2001


   a=profileDesc:AAL2/custom 100 0-7 PCMG 40 5000 0-7 SIDG 1 5000 8-15
       G726-32 40 10000 8-15 SIDG 1 5000

   If the <packetTime> parameter is to be omitted or implied, then the
   same profile can be represented as follows:

   a=profileDesc:AAL2/custom 100 0-7 PCMG 40 - 0-7 SIDG 1 - 8-15
        G726-32 40 - 8-15 SIDG 1 -

   If a gateway has a provisioned or hard coded definition of a profile,
   then any definition provided via the 'profileDesc' line overrides it.
   The exception to this rule is with regard to standard profiles such
   as ITU-defined profiles and ATMF-defined profiles.  In general, these
   should not be defined via a 'profileDesc' media attribute line.  If
   they are, then the definition needs to be consistent with the
   standard definition else the SDP session descriptor should be
   rejected with an appropriate error code.

             Table 3: Example of a  custom AAL2 profile

   |---------------------------------------------------------------|
   | UUI  | Packet |Encoding |               |     |Packet|Seq.No. |
   | Code | Length |per ITU  |Description of |  M  |Time  |Interval|
   |point |(octets)|I.366.2  |  Algorithm    |     |(ms)  |(ms)    |
   |Range |        |  2/99   |               |     |      |        |
   |      |        | version |               |     |      |        |
   |---------------------------------------------------------------|
   | 0-7  |    40  |  Figure | PCM, G.711-64,|   1 |    5 |    5   |
   |      |        |  B-1    |  generic      |     |      |        |
   |------|--------|---------|---------------|-----|------|--------|
   | 0-7  |    1   |  Figure | Generic SID   |   1 |    5 |    5   |
   |      |        |  I-1    |               |     |      |        |
   |------|--------|---------|---------------|-----|------|--------|
   | 8-15 |    40  |  Figure | ADPCM,        |   2 |   10 |    5   |
   |      |        |  E-2    | G.726-32      |     |      |        |
   |------|--------|---------|---------------|-----|------|--------|
   | 8-15 |    1   |  Figure | Generic SID   |   1 |    5 |    5   |
   |      |        |  I-1    |               |     |      |        |
   |------|--------|---------|---------------|-----|------|--------|

5.6.3.6 The 'vsel' attribute

   The 'vsel' attribute indicates a prioritized list of one or more 3-
   tuples for voice service.  Each 3-tuple indicates a codec, an
   optional packet length and an optional packetization period.  This
   complements the 'm' line information and should be consistent with
   it.




Kumar & Mostafa             Standards Track                    [Page 68]

RFC 3108                        ATM SDP                         May 2001


   The 'vsel' attribute refers to all directions of a connection.  For a
   bidirectional connection, these are the forward and backward
   directions.  For a unidirectional connection, this can be either the
   backward or forward direction.

   The 'vsel' attribute is not meant to be used with bidirectional
   connections that have asymmetric codec configurations described in a
   single SDP descriptor.  For these, the 'onewaySel' attribute (section
   5.6.3.9) should be used.  See section 5.6.3.9 for the requirement to
   not use the 'vsel' and 'onewaySel' attributes in the same SDP
   descriptor.

   The 'vsel' line is structured as follows:

      a=vsel:<encodingName #1> <packetLength #1><packetTime #1>
                <encodingName #2> <packetLength #2><packetTime #2>
                ...
               <encodingName #N> <packetLength #N><packetTime #N>

   where the <encodingName> parameter can take one of the values in
   column 2 of Table 2.  The <packetLength> is a decimal integer
   representation of the packet length in octets.  The <packetTime> is a
   decimal integer representation of the packetization interval in
   microseconds.  The parameters <packetLength> and <packetTime> can be
   set to "-" when not needed.  Also, the entire 'vsel' media attribute
   line can be omitted when not needed.

   For example,

      a=vsel:G729 10 10000 G726-32 40 10000

   indicates first preference of G.729 or G.729a (both are
   interoperable) as the voice encoding scheme.  A packet length of 10
   octets and a packetization interval of 10 ms are associated with this
   codec.  G726-32 is the second preference stated in this line, with an
   associated packet length of 40 octets and a packetization interval of
   10 ms.  If the packet length and packetization interval are intended
   to be omitted, then this media attribute line becomes

      a=vsel:G729 - - G726-32 - -

   The media attribute line

      a=vsel:G726-32 40 10000

   indicates preference for or selection of 32 kbps ADPCM with a packet
   length of 40 octets and a packetization interval of 10 ms.




Kumar & Mostafa             Standards Track                    [Page 69]

RFC 3108                        ATM SDP                         May 2001


   This media attribute line can be used in ATM as well as non-ATM
   contexts.  Within the ATM context, it can be applied to the AAL1,
   AAL2 and AAL5 adaptations.  The <packetLength> and <packetTime> are
   not meaningful in the AAL1 case and should be set to "-".  In the
   AAL2 case, this line determines the use of some or all of the rows in
   a given profile table.  If multiple 3-tuples are present, they can
   indicate a hierarchical assignment of some rows in that profile to
   voice service (e.g., row A preferred to row B etc.).  If multiple
   profiles are present on the 'm' line, the profile qualified by this
   attribute is the first profile.  If a single profile that has been
   selected for a connection is indicated in the 'm' line, the 'vsel'
   attribute qualifies the use, for voice service, of codecs within that
   profile.

   With most of the encoding names in Figure 2, the packet length and
   packetization period can be derived from each other.  One of them can
   be set to "-" without a loss of information.  There are some
   exceptions such as the IANA-registered encoding names G723, DVI4 and
   L16 for which this is not true.  Therefore, there is a need to retain
   both the packet length and packetization period in the definition of
   the 'vsel' line.

5.6.3.7 The 'dsel' attribute

   The 'dsel' attribute indicates a prioritized list of one or more 3-
   tuples for voiceband data service.  The <fxIncl> flag indicates
   whether this definition of voiceband data includes fax ("on" value)
   or not ("off" value).  If <fxIncl> is "on", then the 'dsel' line must
   be consistent with any 'fsel' line in the session description.  In
   this case, an error event is generated in the case of inconsistency.
   Each 3-tuple indicates a codec, an optional packet length and an
   optional packetization period.  This complements the 'm' line
   information and should be consistent with it.

   The 'dsel' attribute refers to all directions of a connection.  For a
   bidirectional connection, these are the forward and backward
   directions.  For a unidirectional connection, this can be either the
   backward or forward direction.

   The 'dsel' attribute is not meant to be used with bidirectional
   connections that have asymmetric codec configurations described in a
   single SDP descriptor.  For these, the 'onewaySel' attribute (section
   5.6.3.9) should be used.  See section 5.6.3.9 for the requirement to
   not use the 'dsel' and 'onewaySel' attributes in the same SDP
   descriptor.






Kumar & Mostafa             Standards Track                    [Page 70]

RFC 3108                        ATM SDP                         May 2001


   The 'dsel' line is structured as follows:

      a=dsel:<fxIncl> <encodingName #1> <packetLength #1><packetTime #1>
                <encodingName #2> <packetLength #2><packetTime #2>
                ...
               <encodingName #N> <packetLength #N><packetTime #N>


   where the <encodingName> parameter can take one of the values in
   column 2 of Table 2. The <packetLength> and <packetTime> parameters
   are per their definition, above, for the 'vsel' media attribute line.
   The parameters <packetLength> and <packetTime>) can be set to "-"
   when not needed.  The <fxIncl> flag is presumed to be "off" if it is
   set to "-".  Also, the entire 'dsel' media attribute line can be
   omitted when not needed.

   For example,

      a=dsel:-  G726-32 20 5000 PCMU 40 5000

   indicates that this line does not address facsimile, and that the
   first preference for the voiceband data codes is 32 kbps ADPCM, while
   the second preference is PCMU.  The packet length and the
   packetization interval associated with G726-32 are 20 octets and 5 ms
   respectively.  For PCMU, they are 40 octets and 5 ms respectively.

   This media attribute line can be used in ATM as well as non-ATM
   contexts.  Within the ATM context, it can be applied to the AAL1,
   AAL2 and AAL5 adaptations.  The <packetLength> and <packetTime> are
   not meaningful in the AAL1 case and should be set to "-".  In the
   AAL2 case, this line determines the use of some or all of the rows in
   a given profile table.  If multiple 3-tuples are present, they can
   indicate a hierarchical assignment of some rows in that profile to
   voiceband data service (e.g., row A preferred to row B etc.)  If
   multiple profiles are present on the 'm' line, the profile qualified
   by this attribute is the first profile.  If a single profile that has
   been selected for a connection is indicated in the 'm' line, the '
   dsel' attribute qualifies the use, for voiceband data service, of
   codecs within that profile.

   With most of the encoding names in Figure 2, the packet length and
   packetization period can be derived from each other.  One of them can
   be set to "-" without a loss of information.  There are some
   exceptions such as the IANA-registered encoding names G723, DVI4 and
   L16 for which this is not true.  Therefore, there is a need to retain
   both the packet length and packetization period in the definition of
   the 'dsel' line.




Kumar & Mostafa             Standards Track                    [Page 71]

RFC 3108                        ATM SDP                         May 2001


5.6.3.8 The 'fsel' attribute

   The 'fsel' attribute indicates a prioritized list of one or more 3-
   tuples for facsimile service.  If an 'fsel' line is present, any '
   dsel' line with <fxIncl> set to "on" in the session description must
   be consistent with it.  In this case, an error event is generated in
   the case of inconsistency.  Each 3-tuple indicates a codec, an
   optional packet length and an optional packetization period.  This
   complements the 'm' line information and should be consistent with
   it.

   The 'fsel' attribute refers to all directions of a connection.  For a
   bidirectional connection, these are the forward and backward
   directions.  For a unidirectional connection, this can be either the
   backward or forward direction.

   The 'fsel' attribute is not meant to be used with bidirectional
   connections that have asymmetric codec configurations described in a
   --single SDP descriptor.  For these, the 'onewaySel' attribute
   (section 5.6.3.9) should be used.  See section 5.6.3.9 for the
   requirement to not use the 'fsel' and 'onewaySel' attributes in the
   same SDP descriptor.

   The 'fsel' line is structured as follows:

      a=fsel:<encodingName #1> <packetLength #1><packetTime #1>
                <encodingName #2> <packetLength #2><packetTime #2>
                ...
               <encodingName #N> <packetLength #N><packetTime #N>

   where the <encodingName> parameter can take one of the values in
   column 2 of Table 2.  The <packetLength> and <packetTime> parameters
   are per their definition, above, for the 'vsel' media attribute line.
   The parameters <packetLength> and <packetTime> can be set to "-" when
   not needed.  Also, the entire 'fsel' media attribute line can be
   omitted when not needed.

   For example,

      a=fsel:FXDMOD-3 - -

   indicates demodulation and remodulation of ITU-T group 3 fax at the
   gateway.

      a=fsel:PCMU 40 5000 G726-32 20 5000






Kumar & Mostafa             Standards Track                    [Page 72]

RFC 3108                        ATM SDP                         May 2001


   indicates a first and second preference of Mu-law PCM and 32 kbps
   ADPCM as the facsimile encoding scheme.  The packet length and the
   packetization interval associated with G726-32 are 20 octets and 5 ms
   respectively.  For PCMU, they are 40 octets and 5 ms respectively.

   This media attribute line can be used in ATM as well as non-ATM
   contexts.  Within the ATM context, it can be applied to the AAL1,
   AAL2 and AAL5 adaptations.  The <packetLength> and <packetTime> are
   not meaningful in the AAL1 case and should be set to "-".  In the
   AAL2 case, this line determines the use of some or all of the rows in
   a given profile table.  If multiple 3-tuples are present, they can
   indicate a hierarchical assignment of some rows in that profile to
   facsimile service (e.g., row A preferred to row B etc.).  If multiple
   profiles are present on the 'm' line, the profile qualified by this
   attribute is the first profile.  If a single profile that has been
   selected for a connection is indicated in the 'm' line, the 'fsel'
   attribute qualifies the use, for facsimile service, of codecs within
   that profile.

   With most of the encoding names in Figure 2, the packet length and
   packetization period can be derived from each other.  One of them can
   be set to "-" without a loss of information.  There are some
   exceptions such as the IANA-registered encoding names G723, DVI4 and
   L16 for which this is not true.  Therefore, there is a need to retain
   both the packet length and packetization period in the definition of
   the 'fsel' line.

5.6.3.9 The 'onewaySel' attribute

   The 'onewaySel' (one way select) attribute can be used with
   connections that have asymmetric codec configurations.  There can be
   several 'onewaySel' lines in an SDP description.  The 'onewaySel'
   line is structured as follows:

      a=onewaySel:<serviceType> <directionFlag>
                <encodingName #1> <packetLength #1><packetTime #1>
                <encodingName #2> <packetLength #2><packetTime #2>
                ...
                <encodingName #N> <packetLength #N><packetTime #N>

   The <serviceType> parameter can be assigned the following string
   values: "v", "d", "f", "df" and "all".  These indicate voice,
   voiceband data (fax not included), fax, voiceband data (fax included)
   and all services respectively.

   The <directionFlag> can be assigned the following string values: "f",
   "b" and "fb".  "f" and "b" indicate the forward and backward
   directions respectively.  "fb" refers to both directions (forward and



Kumar & Mostafa             Standards Track                    [Page 73]

RFC 3108                        ATM SDP                         May 2001


   backward) and shall not be used with the 'onewaySel' line.
   Conventions for the forward and backward directions are per section
   2.3.

   Following <directionFlag>, there is a prioritized list of one or more
   3-tuples.  Each 3-tuple indicates a codec, an optional packet length
   and an optional packetization period.  This complements the 'm' line
   information and should be consistent with it.

   Within each 3-tuple, the <encodingName> parameter can take one of the
   values in column 2 of Table 2.  The <packetLength> is a decimal
   integer representation of the packet length in octets.  The
   <packetTime> is a decimal integer representation of the packetization
   interval in microseconds.

   The 'onewaySel' attribute must not be used in SDP descriptors that
   have one or more of the following attributes: 'vsel', 'dsel', 'fsel'.
   If it is present, then command containing the SDP description may be
   rejected.  An alternate response to such an ill-formed SDP descriptor
   might the selective ignoring of some attributes, which must be
   coordinated via an application-wide policy.

   The <serviceType>, <directionFlag> and <encodingName> parameters may
   not be set to "-".  However, the parameters <packetLength> and
   <packetTime> can be set to "-" when not needed.

   For example,

      a=onewaySel:v f G729 10 10000
      a=onewaySel:v b G726-32 40 10000

   indicates that for voice service, the codec to be used in the forward
   direction is G.729 or G.729a (both are interoperable), and the codec
   to be used in the backward direction is G726-32.  A packet length of
   10 octets and a packetization interval of 10 ms are associated with
   the G.729/G.729a codec.  A packet length of 40 octets and a
   packetization interval of 10 ms are associated with the G726-32
   codec.

   For example,

      a=onewaySel:d f G726-32 20 5000
      a=onewaySel:d b PCMU 40 5000

   indicates that for voiceband service (fax not included), the codec to
   be used in the forward direction is G726-32), and the codec to be
   used in the backward direction is PCMU.  A packet length of 20 octets




Kumar & Mostafa             Standards Track                    [Page 74]

RFC 3108                        ATM SDP                         May 2001


   and a packetization interval of 5 ms are associated with the G726-32
   codec.  A packet length of 40 octets and a packetization interval of
   5 ms are associated with the PCMU codec.

   This media attribute line can be used in ATM as well as non-ATM
   contexts.  Within the ATM context, it can be applied to the AAL1,
   AAL2 and AAL5 adaptations.  The <packetLength> and <packetTime> are
   not meaningful in the AAL1 case and should be set to "-".  In the
   AAL2 case, these lines determine the use of some or all of the rows
   in a given profile table.  If multiple 3-tuples are present, they can
   indicate a hierarchical assignment of some rows in that profile to
   voice service (e.g., row A preferred to row B etc.).  If multiple
   profiles are present on the 'm' line, the profile qualified by this
   attribute is the first profile.

   With most of the encoding names in Figure 2, the packet length and
   packetization period can be derived from each other.  One of them can
   be set to "-" without a loss of information.  There are some
   exceptions such as the IANA-registered encoding names G723, DVI4 and
   L16 for which this is not true.  Therefore, there is a need to retain
   both the packet length and packetization period in the definition of
   the 'onewaySel' line.

5.6.3.10 The 'codecconfig' attribute

   When present, the 'codecconfig' attribute is used to represent the
   contents of the single codec information element (IE) defined in
   [57].  The contents of this IE are: a single-octet Organizational
   Identifier (OID) field, followed by a single-octet Codec Type field,
   followed by zero or more octets of a codec configuration bit-map.
   The semantics of the codec configuration bit-map are specific to the
   organization [57, 58].  The 'codecconfig' attribute is represented as
   follows:

      a=codecconfig:<q7655scc>

   The <q7655scc> (Q.765.5 single codec IE contents) parameter is
   represented as a string of hex digits.  The number of hex digits is
   even (range 4 -32).  The "0x" prefix shall be omitted since this
   value is always hexadecimal.  As with other hex values [Section 2.2],
   digits to the left are more significant than digits to the right.
   Leading zeros shall not be omitted.

   An example of the use of this media attribute is:

      a=codecconfig:01080C





Kumar & Mostafa             Standards Track                    [Page 75]

RFC 3108                        ATM SDP                         May 2001


   The first octet indicates an Organizational Identifier of 0x01 (the
   ITU-T).  Using ITU Q.765.5 [57], the second octet (0x08) indicates a
   codec type of G.726 (ADPCM).  The last octet, 0x0C indicates that 16
   kbps and 24 kbps rates are NOT supported, while the 32 kbps and 40
   kbps rates ARE supported.

5.6.3.11 The 'isup_usi' attribute

   When present, the 'isup_usi' attribute is used to represent the
   bearer capability information element defined in Section 4.5.5 of ITU
   Q.931 [59] (excluding the information element identifier and length).
   This information element is reiterated as the user service
   information element (IE) in Section 3.57 of ITU Q.763 [60].  The '
   isup_usi' attribute is represented as follows:

      a=isup_usi:<isupUsi>

   The <isupUsi> parameter is represented as a string of hex digits.
   The number of hex digits is even (allowed range 4 -24).  The "0x"
   prefix shall be omitted since this value is always hexadecimal.  As
   with other hex values [Section 2.2], digits to the left are more
   significant than digits to the right.  Leading zeros shall not be
   omitted.

5.6.3.12 The 'uiLayer1_Prot' attribute

   When present, the 'uiLayer1_Prot' attribute is used to represent the
   'User Information Layer 1 protocol' field within the bearer
   capability information element defined in Section 4.5.5 of [59], and
   reiterated as the user service information element (IE) in Section
   3.57 of [60].  The 'User Information Layer 1 protocol' field consists
   of the five least significant bits of Octet 5 of this information
   element.

   Within SDP, the 'uiLayer1_Prot' attribute is represented as follows:

      a='uiLayer1_Prot':<uiLayer1Prot>

   The <uiLayer1Prot> parameter is represented as a string of two hex
   digits.  The "0x" prefix shall be omitted since this value is always
   hexadecimal.  As with other hex values [Section 2.2], digits to the
   left are more significant than digits to the right.  These hex digits
   are constructed from an octet with three leading '0' bits and last
   five bits equal to the 'User Information Layer 1 protocol' field
   described above.  As specified in [59] and [26], bit 5 of this field
   is the most significant bit.  The resulting values of the
   <uiLayer1Prot> parameter are as follows:




Kumar & Mostafa             Standards Track                    [Page 76]

RFC 3108                        ATM SDP                         May 2001


   VALUE   MEANING
   0x01    CCITT standardized rate adaption V.110 and X.30
   0x02    Recommendation G.711 Mu-law
   0x03    Recommendation G.711 A-law
   0x04    Recommendation G.721 32 kbps ADPCM and Recommendation I.460
   0x05    Recommendations H.221 and H.242
   0x06    Recommendation  H.223 and H.245
   0x07    Non-ITU-T standardized rate adaption
   0x08    ITU-T standardized rate adaption V.120
   0x09    CCITT standardized rate adaption X.31 HDLC flag stuffing

5.6.4 Miscellaneous media attributes

   The 'chain' media attribute line, which is used to chain consecutive
   SDP descriptions, cannot be classified as an ATM, AAL or service
   attribute.  It is detailed in the following subsection.

5.6.4.1 The 'chain' attribute

   The start of an SDP descriptor is marked by a 'v' line.  In some
   applications, consecutive SDP descriptions are alternative
   descriptions of the same session.  In others, these describe
   different layers of the same connection (e.g., IP, ATM, frame relay).
   This is useful when these connectivity at these layers are
   established at the same time (e.g., an IP-based session over an ATM
   SVC).  To distinguish between the alternation and concatenation of
   SDP descriptions, a 'chain' attribute can be used in the case of
   concatenation.

   When present, the 'chain' attribute binds an SDP description to the
   next or previous SDP description.  The next or previous description
   is separated from the current one by a 'v' line.  It is not necessary
   that this description also have a 'chain' media attribute line.

   Chaining averts the need to set up a single SDP description for a
   session that is simultaneously created at multiple layers.  It allows
   the SDP descriptors for different layers to remain simple and clean.
   Chaining is not needed in the Megaco context, where it is possible to
   create separate terminations for the different layers of a
   connection.

   The 'chain' media attribute line has the following format:

      a=chain:<chainPointer>

   The <chainPointer> field can take on the following string values:
   "NEXT", "PREVIOUS" and "NULL".  The value "NULL" is not equivalent to
   omitting the chain attribute from a description since it expressly



Kumar & Mostafa             Standards Track                    [Page 77]

RFC 3108                        ATM SDP                         May 2001


   precludes the possibility of chaining.  If the 'chain' attribute is
   absent in an SDP description, chaining can still be realized by the
   presence of a chain media attribute line in the previous or next
   description.

5.6.5 Use of the second media-level part in H.323 Annex C applications

   Section 4 mentions that H.323 annex C applications have a second
   media level part for the ATM session description.  This is used to
   convey information about the RTCP stream.  Although the RTP stream is
   encapsulated in AAL5 with no intervening IP layer, the RTCP stream is
   sent to an IP address and RTCP port.  This media-level part has the
   following format:

      m= control <rtcpPortNum> H323c -
      c= IN IP4 <rtcpIPaddr>

   Consistency with RFC 2327 is maintained in the location and format of
   these lines.  The <fmt list> in the 'm' line is set to "-".  The 'c'
   line in the second media-level part pertains to RTCP only.

   The <rtcpPortNum> and <rtcpIPaddr> subparameters indicate the port
   number and IP address on which the media gateway is prepared to
   receive RTCP packets.

   Any of the subparameters on these lines can be set to "-" if they are
   known by other means.

   The range and format of the <rtcpPortNum> and <rtcpIPaddr>
   subparameters is per [1].  The <rtcpPortNum> is a decimal number
   between 1024 and 65535.  It is an odd number.  If an even number in
   this range is specified, the next odd number is used.  The
   <rtcpIPaddr> is expressed in the usual dotted decimal IP address
   representation, from 0.0.0.0 to 255.255.255.255.

5.6.6 Use of the eecid media attribute in call establishment
     procedures

   This informative section supplements the definition of the eecid
   attribute (Section 5.6.1.1) by describing example procedures for its
   use.  These procedures assume a bearer-signaling mechanism for
   connection set-up that is independent of service-level call control.
   These procedures are independent of the media gateway control
   protocol (MGCP, Megaco, SIP etc.), the protocol used between media
   gateway controllers (ITU Q.1901, SIP etc.) and the protocol used for
   bearer connection set-up (Q.2931, UNI, PNNI, AINI, IISP, Q.2630.1
   etc.).




Kumar & Mostafa             Standards Track                    [Page 78]

RFC 3108                        ATM SDP                         May 2001


                            Inter-MGC
               +---------+  Protocol        +---------+
               |   MGC   |------------------|   MGC   |
               +---------+                  +---------+
                    |                            |
                    |Media Gateway               |Media Gateway
                    |Control Protocol            |Control Protocol
                    |                            |
                +------------+  (ATM Network)   +------------+
                |Originating |------------------|Terminating |
                |Media       |  Bearer Setup    |Media       |
                |Gateway     |  Protocol        |Gateway     |
                +------------+                  +------------+

   In the diagram above, the originating media gateway originates the
   service-level call.  The terminating media gateway terminates it.  In
   the forward bearer connection set-up model, the originating media
   gateway initiates bearer connection set-up.  In the backward bearer
   connection set-up model, the terminating gateway initiates bearer
   connection set-up.

   Example use of the Backward Bearer Connection Set-up Model:

   (1)  The originating media gateway controller (OMGC) initiates
        service-level call establishment by sending the appropriate
        control message to the originating media gateway (OMG).

   (2)  The originating media gateway (OMG) provides its NSAP address
        and an eecid value to the OMGC, using the following SDP
        description:

   v=0
   o=- 2873397496 0 ATM NSAP
      47.0091.8100.0000.0060.3E64.FD01.0060.3E64.FD01.00
   s=-
   c=ATM NSAP
     47.0091.8100.0000.0060.3E64.FD01.0060.3E64.FD01.00
   t=0 0
   m=audio $ AAL2/ITU 8
   a=eecid:B3D58E32

   (3)  The originating media gateway controller (OMGC) signals the
        terminating media gateway controller (TMGC) through the
        appropriate mechanism (ISUP with Q.1901 extensions, SIP etc.).
        It provides the TMGC with the NSAP address and the eecid
        provided by the OMG.





Kumar & Mostafa             Standards Track                    [Page 79]

RFC 3108                        ATM SDP                         May 2001


   (4)  The TMGC sends the appropriate control message to the TMG.  This
        includes the session descriptor received from the OMG.  This
        descriptor contains the NSAP address of the OMG and the EECID
        assigned by the OMG.  Additionally, the TMGC instructs the TMG
        to set up an SVC to the OMG.  It also requests the TMG to notify
        the TMGC when SVC set-up is complete.  Depending on the control
        protocol used, this can be done through a variety of means.  In
        the Megaco context, the request to set-up an SVC (not the
        notification request for the SVC set-up event) can be made
        through the following local descriptor:

   v=0
   o=- 2873397497 0 ATM - -
   s=-
   c=ATM - -
   t=0 0
   m=audio $ - -
   a=bearerType:SVC on

   The 'bearerType' attribute indicates that an SVC is to be used and
   that the <localInitiation> flag is on i.e., the SVC is to be set up
   by the TMG.

   (5)  The TMG acknowledges the control message from the TMGC.  It
        returns the following SDP descriptor with the acknowledge:

   v=0
   o=- 2873397498 0 ATM NSAP
      47.0091.8100.0000.0040.2A74.EB03.0020.4421.2A04.00
   s=-
   c=ATM NSAP
     47.0091.8100.0000.0040.2A74.EB03.0020.4421.2A04.00
   t=0 0
   m=audio $ AAL2/ITU 8

   The NSAP address information provided in this descriptor is not
   needed.  It can be omitted (by setting it to "- -").

   (6)  The TMG sends an SVC set-up message to the OMG.  Within the GIT
        information element, it includes eecid (B3D58E32) received from
        the OMG.

   (7)  The OMG uses the eecid to correlate the SVC set-up request with
        service-level control message received before from the OMGC.

   (8)  The OMG returns an SVC connect message to the TMG.  On receiving
        this message, the TMG sends an event notification to the TMGC
        indicating successful SVC set-up.



Kumar & Mostafa             Standards Track                    [Page 80]

RFC 3108                        ATM SDP                         May 2001


        Note that, for this example, the "v=", "o=", "s=" and "t=" lines
        can be omitted in the Megaco context.

   Example use of the Forward Bearer Connection Set-up Model:

   (1)  The originating media gateway controller (OMGC) initiates
        service-level call establishment by sending the appropriate
        controlsmessage to the originating media gateway (OMG).

   (2)  The originating media gateway (OMG) provides its NSAP address to
        the OMGC, using the following SDP description:

   v=0
   o=- 2873397496 0 ATM NSAP
      47.0091.8100.0000.0060.3E64.FD01.0060.3E64.FD01.00
   s=-
   c=ATM NSAP
     47.0091.8100.0000.0060.3E64.FD01.0060.3E64.FD01.00
   t=0 0
   m=audio $ AAL2/ITU 8

   The NSAP address information provided in this descriptor is not
   needed.  It can be omitted (by setting it to "- -").

   (3)  The originating media gateway controller (OMGC) signals the
        terminating media gateway controller (TMGC) through the
        appropriate mechanism (ISUP with Q.1901 extensions, SIP etc.).
        Although this is not necessary, it can provide the TMGC with the
        NSAP address provided by the OMG.

   (4)  The TMGC sends the appropriate control message to the TMG.  This
        includes the session descriptor received from the OMG.  This
        descriptor contains the NSAP address of the OMG.

   (5)  The TMG acknowledges the control message from the TMGC.  Along
        with the acknowledgement, it provides an SDP descriptor with a
        locally assigned eecid.

   v=0
   o=- 2873397714 0 ATM NSAP
      47.0091.8100.0000.0040.2A74.EB03.0020.4421.2A04.00
   s=-
   c=ATM NSAP
     47.0091.8100.0000.0040.2A74.EB03.0020.4421.2A04.00
   t=0 0
   m=audio $ AAL2/ITU 8
   a=eecid:B3D58E32




Kumar & Mostafa             Standards Track                    [Page 81]

RFC 3108                        ATM SDP                         May 2001


   (6)  The terminating media gateway controller (TMGC) signals the
        originating media gateway controller (OMGC) through the
        appropriate mechanism (ISUP with Q.1901 extensions, SIP etc.).
        It provides the OMGC with the NSAP address and the eecid
        provided by the TMG.

   (7)  The OMGC sends the appropriate control message to the OMG.  This
        includes the session descriptor received from the TMG.  This
        descriptor contains the NSAP address of the TMG and the EECID
        assigned by the TMG.  Additionally, the OMGC instructs the OMG
        to set up an SVC to the TMG.  It also requests the OMG to notify
        the OMGC when SVC set-up is complete.  Depending on the control
        protocol used, this can be done through a variety of means.  In
        the Megaco context, the request to set-up an SVC (not the
        notification request for the SVC set-up event) can be made
        through the following local descriptor:

   v=0
   o=- 2873397874 0 ATM - -
   s=-
   c=ATM - -
   t=0 0
   m=audio $ - -
   a=bearerType:SVC on

   The 'bearerType' attribute indicates that an SVC is to be used and
   that the <localInitiation> flag is on i.e., the SVC is to be set up
   by the TMG.

   (8)  The OMG acknowledges the control message from the OMGC.

   (9)  The OMG sends an SVC set-up message to the TMG.  Within the GIT
        information element, it includes eecid (B3D58E32) received from
        the TMG.

   (10) The TMG uses the eecid to correlate the SVC set-up request with
        the service-level control message received before from the TMGC.

   (11) The TMG returns an SVC connect message to the OMG.  On receiving
        this message, the OMG sends an event notification to the OMGC
        indicating successful SVC set-up.

        Note that, for this example,  the "v=", "o=", "s=" and "t="
        lines can be omitted in the Megaco context.







Kumar & Mostafa             Standards Track                    [Page 82]

RFC 3108                        ATM SDP                         May 2001


6. List of Parameters with  Representations

   This section provides a list of the parameters used in this document,
   and the formats used to represent them in SDP descriptions.  In
   general, a "-" value can be used for any field that is not specified,
   is inapplicable or is implied.

PARAMETER           MEANING              REPRESENTATION

<username>          User name            Constant "-"

<sessionID>         Session ID           Up to 32 decimal or
                                         hex digits

<version>           Version of           "0" or 10 decimal digits
                    SDP descriptor

<networkType>       Network type        Constant "ATM" for ATM transport

<addressType>       Address type         String values:
                                         "NSAP", "E164", "GWID",
                                         "ALIAS"

<address>           Address             "NSAP":  40 hex digits, dotted
                                        "E164":  up to 15 decimal digits
                                        "GWID":  up to 32 characters
                                        "ALIAS": up to 32 characters

<sessionName>       Session name         Constant "-"

<startTime>         Session start        "0" or 10 decimal digits
                    time

<stopTime>          Session stop         Constant "0"
                    time

<vcci>              Virtual Circuit      Decimal or hex equivalent
                    Connection           of 16 bits
                    Identifier

<ex_vcci>           Explicit             "VCCI-" prefixed to <vcci>
                    representation
                    of <vcci>

<bcg>               Bearer Connection    Decimal or hex equivalent
                    Group                of 8 bits





Kumar & Mostafa             Standards Track                    [Page 83]

RFC 3108                        ATM SDP                         May 2001


<ex_bcg>            Explicit             "BCG-" prefixed to <bcg>
                    representation
                    of <bcg>

<portId>            Port ID              Hex number of up to 32 digits


<ex_portId>         Explicit             "PORT-" prefixed to <portId>
                    representation
                    of <portId>

<vpi>               Virtual Path         Decimal or hex equivalent
                    Identifier           of 8 or 12 bits

<ex_vpi>            Explicit             "VPI-" prefixed to <vpi>
                    representation
                    of <vpi>

<vci>                Virtual Circui t    Decimal or hex equivalent
                     Identifier          of 16 bits

<ex_vci>             Explicit            "VCI-" prefixed to <vci>
                     representation
                     of <vci>

<vpci>               Virtual Path        Decimal or hex equivalent
                     Connection          of 16 bits
                     Identifier

<ex_vpci>            Explicit            "VPCI-" prefixed to <vpci>
                     representation
                     of <vpci>

<cid>                Channel             Decimal or hex equivalent
                     Identifier          of 8 bits

<ex_cid>             Explicit            "CID-" prefixed to <cid>
                     representation
                     of <cid>

<payloadType>        Payload              Decimal integer 0-127
                     Type

<transport>          Transport            Values listed in
                                          Table 1.

<profile>            Profile              Decimal integer 1-255




Kumar & Mostafa             Standards Track                    [Page 84]

RFC 3108                        ATM SDP                         May 2001


<eecid>              End-to-end           Up to 8 hex digits
                     Connection
                     Identifier

<aalType>            AAL type             String values:
                                          "AAL1","AAL1_SDT","AAL1_UDT",
                                          "AAL2", "AAL3/4",
                                          "AAL5", "USER_DEFINED_AAL"

<asc>               ATM service           String values:
                    category defined      "CBR", "nrt-VBR", "rt-VBR",
                    by the ATMF           "UBR", "ABR", "GFR"

<atc>               ATM transfer          String values:
                    capability            "DBR","SBR","ABT/IT","ABT/DT",
                    defined by the        "ABR"
                    ITU

<subtype>            <asc>/<atc>          Decimal integer 1-10
                     subtype

<qosClass>           QoS Class            Decimal integer 0-5

<bcob>               Broadband Bearer     Decimal or hex representation
                     Class                of 5-bit field

<eetim>              End-to-end timing    String values: "on",
                     required             "off".

<stc>                Susceptibility       Decimal equivalent of
                     to clipping          a 2-bit field

<upcc>               User plane           Decimal equivalent of
                     connection           a 2-bit field
                     configuration

<directionFlag>      Direction Flag       String values: "f", "b",
                                          "fb"

<cdvType>            CDV type             String values:
                                          "PP", "2P"

<acdv>               Acceptable CDV       Decimal equivalent
                                          of 24-bit field

<ccdv>               Cumulative CDV       Decimal equivalent
                                          of 24-bit field




Kumar & Mostafa             Standards Track                    [Page 85]

RFC 3108                        ATM SDP                         May 2001


<eetd>               End-to-end transit   Decimal equivalent
                     delay                of 16-bit field


<cmtd>               Cumulative transit   Decimal equivalent
                     delay                of 16-bit field

<aclr>               Acceptable           Decimal equivalent
                     Cell Loss Ratio      of 8-bit field

<clpLvl>             CLP level            String values:
                                          "0", "0+1"

<pcr>                Peak                 Decimal
                     Cell Rate            equivalent of a 24-bit field.

<scr>                Sustained            Decimal
                     Cell Rate            equivalent of a 24-bit field

<mbs>                Maximum              Decimal
                     Burst Size           equivalent of 16-bit field

<cdvt>               CDVT                 Decimal equivalent of 24-bit
                                          field.

<mcr>                Minimum              Decimal
                     Cell Rate            equivalent of a 24-bit field

<mfs>                Maximum              Decimal
                     Frame Size           equivalent of a 16-bit field

<fd>                 Frame Discard        String Values:
                     Allowed              "on", "off"

<te>                 CLP tagging          String Values:
                                          "on", "off"

<nrm>                NRM                  Decimal/hex equivalent
                                          of 3 bit field

<trm>                TRM                  -ditto-

<cdf>                CDF                  -ditto-

<adtf>               ADTF                 Decimal/Hex  equivalent
                                          of 10 bit field





Kumar & Mostafa             Standards Track                    [Page 86]

RFC 3108                        ATM SDP                         May 2001


<ficr>               Forward Initial      Decimal equivalent of
                     Cell Rate            24-bit field

<bicr>               Backward Initial     Decimal equivalent of
                     Cell Rate            24-bit field

<ftbe>               Forward Transient    Decimal equivalent of
                     Buffer Exposure      24-bit field

<btbe>               Backward Transient   Decimal equivalent of
                     Buffer Exposure      24-bit field

<crmrtt>             Cumulative RM        Decimal equivalent of
                     round-trip time      24-bit field
                     (Microseconds)

<frif>               Forward rate         Decimal integer
                     increase factor      0 -15

<brif>               Backward rate        Decimal integer
                     increase factor      0 -15

<frdf>               Forward rate         Decimal integer
                     decrease factor      0 -15

<brdf>               Backward rate        Decimal integer
                     decrease factor      0 -15

<bearerType>         Bearer Type          String Values:
                                          "PVC", "SVC", "CID"

<localInitiation>    Local Initiation      String values:
                                           "on", "off"

<sci>                Screening Indication  Decimal or hex
                                           equivalent of 4  bits.

<lsn>                Leaf Sequence Number  Decimal or hex
                                           equivalent of 32 bits.

<cdStd>              Coding standard for          Decimal or hex
                     connection scope             equivalent of 2 bits.
                     selection IE
                     Definition: UNI 4.0 [5]

<conScpTyp>          Type of connection scope     Decimal or hex
                     Definition: UNI 4.0 [5]      equivalent of 4 bits




Kumar & Mostafa             Standards Track                    [Page 87]

RFC 3108                        ATM SDP                         May 2001


<conScpSel>          Connection scope selection   Decimal or hex
                     Definition: UNI 4.0 [5]      equivalent of 8 bits

<cacheEnable>        Enable SVC caching           String values: "on",
                                                  "off"

<cacheTimer>        Timer for cached SVC       Decimal or hex equivalent
                    deletion                   of 32-bit field

<bearerSigIEType>   Bearer Signaling IE Type      2 hex digits

<bearerSigIELng>    Bearer Signaling IE Length    1-4 hex digits

<bearerSigIEVal>    Bearer Signaling IE Value     Even number of hex
                                                  digits, 2-512

<appClass>          Application                String values:
                    specification              "itu_h323c","af83",
                                               "AAL5_SSCOP",
                                               "itu_i3661_unassured",
                                               "itu_i3661_assured",
                                               "itu_i3662",
                                               "itu_i3651", "itu_i3652",
                                               "itu_i3653", "itu_i3654",
                                               "FRF5", "FRF8","FRF11",
                                               "itu_h2221"

<oui>               Organizationally         1 to  6 hex digits
                    Unique Identifier

<appId>             Application Identifier   1 to 8 digits

<cbrRate>           CBR Rate                 Two hex digits.

<sbc>               Subchannel Count         T1: Decimal integer 1-24
                                             or hex equivalent
                                             E1: Decimal integer 1-31
                                             or hex equivalent

<clkrec>             Clock Recovery          String values:
                     Method                  "NULL", "SRTS",
                                             "ADAPTIVE"

<fecEnable>          Forward Error           String values:
                     Correction Enable       "NULL", "LOSS_SENSITIVE"
                                             "DELAY_SENSITIVE"





Kumar & Mostafa             Standards Track                    [Page 88]

RFC 3108                        ATM SDP                         May 2001


<partialFill>        Partial Fill            Decimal integer 1-48
                                             or hex equivalent

<structureEnable>    Structure Present       String values:
                                             "on", "off"

<blksz>              Block Size              Decimal or hexadecimal
                                             equivalent of 16 bits

<cpcs>              Maximum                  AAL5: Decimal or hex
                    CPCS SDU size            equivalent of 16 bits
                                             AAL2: 45 or 64, decimal
                                             or hex representation

<cidLowerLimit>     AAL2 CID lower limit     Decimal integer 8-255
                                             or hex equivalent

<cidUpperLimit>     AAL2 CID upper limit     Decimal integer 8-255
                                             or hex equivalent


<timerCU>           Timer, combined use      Integer decimal; range
                    (microseconds)           determined by application.
                                             Use decimal equivalent of
                                             32 bits.

<simplifiedCPS>     Simplified CPS [52]      String values:
                                             "on", "off"

<fSDUrate>          Forward SDU rate         Decimal equivalent of
                    (bits per second)        24-bit field

<bSDUrate>          Backward SDU rate        Decimal equivalent of
                    (bits per second)        24-bit field

<ted>               Transmission Error       String values:
                    Detection Enable         "on", "off"

<rastimer>          SSSAR reassembly         Integer decimal,
                    (microseconds)           Range determined by
                                             application.  Use decimal
                                             equivalent of 32 bits.

<fsssar>            Maximum SSSAR-SDU        Decimal 1- 65568
                    size, forward            or hex equivalent
                    direction





Kumar & Mostafa             Standards Track                    [Page 89]

RFC 3108                        ATM SDP                         May 2001


<bsssar>            Maximum SSSAR-SDU        Decimal 1- 65568
                    size, backward           or hex equivalent
                    direction

<fsscopsdu>         Maximum SSCOP-SDU        Decimal 1- 65528
                    size, forward            or hex equivalent
                    direction

<bsscopsdu>         Maximum SSCOP-SDU        Decimal 1- 65528
                    size, backward           or hex equivalent
                    direction

<fsscopuu>          Maximum SSCOP-UU         Decimal 1- 65524
                    field size, forward      or hex equivalent
                    direction

<bsscopuu>          Maximum SSCOP-UU         Decimal 1- 65524
                    field size, backward     or hex equivalent
                    direction

<sap>               Service Access           String values:
                    Point                    "AUDIO", "MULTIRATE"

<circuitMode>       Circuit Mode             String values:
                    Enable                   "on", "off"

<frameMode>         Frame Mode               String values:
                    Enable                   "on", "off"

<faxDemod>          Fax Demodulation         String values:
                    Enable                   "on", "off"

<cas>               Enable CAS transport     String values:
                    via Type 3 packets       "on", "off"

<dtmf>              Enable DTMF transport    String values:
                    via Type 3 packets       "on", "off"

<mfall>             Enable MF transport      String values:
                    via Type 3 packets       "on", "off"

<mfr1>              Enable MF (R1)           String values:
                    transport via             "on", "off"
                    Type 3 packets

<mfr2>              Enable MF (R2)           String values:
                    transport via             "on", "off"
                    Type 3 packets



Kumar & Mostafa             Standards Track                    [Page 90]

RFC 3108                        ATM SDP                         May 2001


<PCMencoding>       PCM encoding             String values:
                                             "PCMA", "PCMU"

<fmaxFrame>         Maximum length of a      Decimal or hex
                    frame mode data unit,    equivalent of
                    forward direction        16-bit field

<bmaxFrame>         Maximum length of a      -ditto-
                    frame mode data unit,
                    backward direction

<silenceSuppEnable>  Silence suppression  String values:
                     Enable               "on", "off"

<silenceTimer>       Kick-in timer        Decimal or hex representation
                     for silence          of 16-bit field
                     suppression


<suppPref>          Preferred Silence     String values:
                    Suppression Method    "standard", "custom"

<sidUse>            SID Use               String values:
                    Method                "No SID", "Fixed Noise",
                                          "Sampled Noise"

<fxnslevel>         Fixed Noise           Decimal or hex representation
                    Level                 of a 7-bit field

<ecanEnable>        Enable Echo           String values:
                    Cancellation          "on", "off"

<ecanType>           Type of Echo         String values:
                     Cancellation         "G165", "G168"

<gcEnable>           Enable Gain          String values:
                     Control              "on", "off"

<gcLvl>              Level of inserted    Decimal or hex equivalent
                     Loss                 of 16-bit field

<aal2transport>      AAL2 transport       Values listed in Table 1
                                          that begin with the string
                                          "AAL2"

<uuiCodeRange>       UUI code range       Decimal integer 0-15





Kumar & Mostafa             Standards Track                    [Page 91]

RFC 3108                        ATM SDP                         May 2001


<encodingName>       Encoding name        String values:
                                          "PCMG", "SIDG", "SID729",
                                          any value from column 2
                                          of Table 2

<packetLength>      Packet length         Decimal integer 0-45

<packetTime>        Packetization         Decimal integer 1-65,536
                    Interval in microsec.

<fxIncl>            Facsimile included    String values: "on", "off"

<serviceType>       Service type          String values: "v", "d", "f",
                                          "df", "all"

<q7655scc>          Contents of the       Even number of hex
                    Q.765.5 Single        digits (4-32)
                    Codec IE

<isupUsi>           ISUP User Service     Even number of hex digits
                    Information           (4-24)

<uiLayer1Prot>      User Information      Two hex digits
                    Layer 1 Protocol

<chainPointer>     Chain pointer          String values: "NEXT",
                                          "PREVIOUS", "NULL"

<rtcpPortNum>      RTCP port number for    Odd decimal in range 1,024 to
                   H.323 Annex C           65,535.
                   applications            Preferred: Odd number in
                                           the range 49,152 to 65,535

<rtcpIPaddr>      IP address for  receipt  Dotted decimal, 7-15 chars
                  of RTCP packets
















Kumar & Mostafa             Standards Track                    [Page 92]

RFC 3108                        ATM SDP                         May 2001


7. Examples of ATM session descriptions using SDP

   An example of a complete AAL1 session description in SDP is:

      v=0
      o=- A3C47F21456789F0 0 ATM NSAP
         47.0091.8100.0000.0060.3e64.fd01.0060.3e64.fd01.00
      s=-
      c=ATM NSAP
          47.0091.8100.0000.0060.3e64.fd01.0060.3e64.fd01.00
      t=0 0
      m=audio $ AAL1/AVP 18 0 96
      a=atmmap:96 X-G727-32
      a=eecid:B3D58E32

   An example of a complete AAL2 session description in SDP is:

      v=0
      o=- A3C47F21456789F0 0 ATM NSAP
      47.0091.8100.0000.0060.3e64.fd01.0060.3e64.fd01.00
      s=-
      c=ATM NSAP
           47.0091.8100.0000.0060.3e64.fd01.0060.3e64.fd01.00
      t=0 0
      m=audio $ AAL2/ITU 8 AAL2/custom 100 AAL2/ITU 1
      a=eecid:B3E32

   The AAL2 session descriptor below is the same as the one above except
   that it states an explicit preference for a voice codec, a voiceband
   data codec and a voiceband fax codec.  Further, it defines the
   profile AAL2/custom 100 rather than assume that the far-end is
   cognizant of the elements of this profile.

      v=0
      o=- A3C47F21456789F0 0 ATM NSAP
      47.0091.8100.0000.0060.3e64.fd01.0060.3e64.fd01.00
      s=-
      c=ATM NSAP
      47.0091.8100.0000.0060.3e64.fd01.0060.3e64.fd01.00
      t=0 0
      m=audio $ AAL2/ITU 8 AAL2/custom 100 AAL2/ITU 1
      a=eecid:B3E32
      a=profileDesc:AAL2/custom 100 0-7 PCMG 40 5000 0-7 SIDG 1
      5000 8-15 G726-32 40 10000 8-15 SIDG 1 5000
      a=vsel:G726-32 40 10000
      a=dsel:off PCMU - -
      a=fsel:G726-32 40 10000




Kumar & Mostafa             Standards Track                    [Page 93]

RFC 3108                        ATM SDP                         May 2001


   An example of an SDP session descriptor for an AAL5 switched virtual
   circuit for delivering MPEG-2 video:

      v=0
      o=- A3C47F21456789F0 0 ATM NSAP
      47.0091.8100.0000.0060.3e64.fd01.0060.3e64.fd01.00
      s=-
      c=ATM NSAP 47.0091.8100.0000.0060.3e64.fd01.0060.3e64.fd01.00
      t=0 0
      m=video $ AAL5/ITU 33
      a=eecid:B3E32
      a=aalType:AAL5
      a=bearerType:SVC on
      a=atmTrfcDesc:f 0+1 7816 - - - - - off -
      a=atmTrfcDesc:b 0+1 0 - - - - - on -
      a=cpsSDUsize:f 20680
      a=aalApp:itu_h2221 - -

   An example of an SDP session descriptor for an AAL5 permanent virtual
   circuit for delivering MPEG-2 video:

      v=0
      o=- A3C47F21456789F0 0 ATM - -
      s=-
      c=ATM - -
      t=0 0
      m=video PORT-$/VPI-0/VCI-$ AAL5/ITU 33
      a=bearerType:PVC -
      a=atmTrfcDesc:f 0+1 7816 - - - - - off -
      a=atmTrfcDesc:b 0+1 0 - - - - - on -
      a=cpsSDUsize:f 20680
      a=aalApp:itu_h2221 - -

8. Security Considerations

8.1 Bearer Security

   At present, standard means of encrypting ATM and AAL2 bearers are not
   conventionalized in the same manner as means of encrypting RTP
   payloads.  Nor has the authentication of ATM or AAL2 bearer
   signaling.

   The SDP encryption key line (k=) defined in RFC 2327 can be used to
   represent the encryption key and the method of obtaining the key.  In
   the ATM and AAL2 contexts, the term 'bearer' can include 'bearer
   signaling' as well as 'bearer payloads'.





Kumar & Mostafa             Standards Track                    [Page 94]

RFC 3108                        ATM SDP                         May 2001


8.2 Security of the SDP description

   The SDP session descriptions might originate in untrusted areas such
   as equipment owned by end-subscribers or located at end-subscriber
   premises.  SDP relies on the security mechanisms of the encapsulating
   protocol or layers below the encapsulating protocol.  Examples of
   encapsulating protocols are the Session Initiation Protocol (SIP),
   MGCP and Multimedia Gateway Control Protocol (MEGACO).  No additional
   security mechanisms are needed.  SIP, MGCP and MEGACO can use IPSec
   authentication as described in RFC 1826 [Ref.  27].  IPSec encryption
   can be optionally used with authentication to provide an additional,
   potentially more expensive level of security.  IPSec security
   associations can be made between equipment located in untrusted areas
   and equipment located in trusted areas through configured shared
   secrets or the use of a certificate authority.

9. ATM SDP Grammar

   This appendix provides an Augmented BNF (ABNF) grammar for the ATM
   conventions for SDP. ABNF is defined in rfc2234. This is not a
   complete ABNF description of SDP. Readers are referred to [1] for an
   ABNF description of the SDP base line protocol, and to rfc2848,
   rfc2543, rfc2045 and rfc2326 for application-specific conventions for
   SDP use. For case conventions, see section 2.4.

; Constant definitions

safe = alpha-numeric / "'" / "-" / "." / "/" / ":" / "?" / DQUOTE /
   "#" / "$" / "&" / "*" / ";" / "=" / "@" / "[" / "]" / "^" / "_" /
   "`" / "{" / "|" / "}" / "+" / "~"
DQUOTE = %x22 ; double quote
alpha-numeric = ALPHA / DIGIT
ALPHA = "a" / "b" / "c" / "d" / "e" / "f" / "g" / "h" / "i" / "j" /
        "k" / "l" / "m" / "n" / "o" / "p" / "q" / "r" / "s" / "t" /
        "u" / "v" / "w" / "x" / "y" / "z" /
        "A" / "B" / "C" / "D" / "E" / "F" / "G" / "H" / "I" / "J" /
        "K" / "L" / "M" / "N" / "O" / "P" / "Q" / "R" / "S" / "T" /
        "U" / "V" / "W" / "X" / "Y" / "Z"
DIGIT = "0" / POS-DIGIT
POS-DIGIT = "1" / "2" / "3" / "4" / "5" / "6" / "7" / "8" / "9"
hex-prefix = "0" ("x"  /  "X")
HEXDIG = DIGIT  /  "a" / "b" / "c" / "d" / "e" / "f" /
                      "A" / "B" / "C" / "D" / "E" / "F"
space = %d32
EOL = (CR / LF / CRLF) ; as per Megaco RFC
CR = %d13
LF = %d10




Kumar & Mostafa             Standards Track                    [Page 95]

RFC 3108                        ATM SDP                         May 2001


decimal-uchar =       DIGIT
                         / POS-DIGIT DIGIT
                         / ("1" 2*(DIGIT))
                         / ("2" ("0"/"1"/"2"/"3"/"4") DIGIT)
                         / ("2" "5" ("0"/"1"/"2"/"3"/"4"/"5"))

generic-U8  = (hex-prefix hex-U8) / decimal-uchar
generic-U12 = (hex-prefix hex-U12) / 1*4 (DIGIT)
generic-U16 = (hex-prefix hex-U16) / 1*5(DIGIT)
generic-U24 = (hex-prefix hex-U24) / 1*8(DIGIT)
generic-U32 = (hex-prefix hex-U32) / 1*10(DIGIT)
hex-U8  = 1*2(HEXDIG)
hex-U12 = 1*3(HEXDIG)
hex-U16 = 1*4(HEXDIG)
hex-U24 = 1*6(HEXDIG)
hex-U32 = 1*8(HEXDIG)
generic-U8-or-null  = generic-U8 / "-"
generic-U12-or-null = generic-U12 / "-"
generic-U16-or-null = generic-U16 / "-"
generic-U24-or-null = generic-U24 / "-"
generic-U32-or-null = generic-U32 / "-"
decimal-U8-or-null =  decimal-uchar / "-"
decimal-U12-or-null = 1*4(DIGIT) / "-"
decimal-U16-or-null = 1*5(DIGIT) / "-"
decimal-U24-or-null = 1*8 (DIGIT) / "-"
decimal-U32-or-null = 1*10(DIGIT) / "-"
on-off-or-null = "on" / "off" / "-"

; ABNF definition of SDP with ATM conventions

SDP-infoset    =  1*(announcement)announcement  =  proto-version
origin-field   session-name-field   information-field   uri-field
email-fields   phone-fields   connection-field bandwidth-fields
time-fields key-field attribute-fields media-descriptions

proto-version = ["v=" 1*4(DIGIT) EOL] ; use "v=0" for ATM SDP

origin-field = ["o=" username space sess-id space sess-version space
   net-type-addr EOL]

username = 1* safe ; for ATM use "-"

sess-id = (1*32 DIGIT) / (hex-prefix 1*32 HEXDIG)
sess-version = (1*10 DIGIT) / (hex-prefix 1*8 HEXDIG)

net-type-addr= nettype space addrtype-addr

netttype = "ATM" / "IN" / "TN" / "-" / "$"



Kumar & Mostafa             Standards Track                    [Page 96]

RFC 3108                        ATM SDP                         May 2001


 ; Other nettype values may be defined in the future in other documents
 ; Validity of  nettype and addrtype-addr combination to be checked at
 ;      application level, not protocol syntax level

addrtype-addr = atm-addrtype-addr / ip-addrtype-addr / tn-addrtype-addr
   ; ip-addrtype-addr per rfc2327
   ; tn-addrtype-addr per rfc2848

; ATM address definition

atm-addrtype-addr =  atm-nsap-addr / atm-e164-addr / atm-alias-addr

atm-nsap-addr = ("NSAP" / "-" / "$")  space (nsap-addr / "-" / "$")
atm-e164-addr = ("E164" / "-" / "$") space (e164-addr / "-" / "$")
atm-alias-addr = ("GWID" / "ALIAS" / "-" / "$") space (alias-addr /
                  "-" / "$")

nsap-addr = 2(HEXDIG) "." 9(4(HEXDIG) ".") 2(HEXDIG)

e164-addr = 1*15 (DIGIT)
alias-addr = 1*32(alpha-numeric / "-" / "." / "_")

session-name-field = ["s=" text EOL] ; for ATM use "s=-"
text = byte-string
byte-string = 1*(byte-string-char) ; definition per rfc2327
byte-string-char = %x01-09/ %x0B/ %x0C/ %x0E-FF ; all ASCII except
                   NUL, CR & LF
; Definitions of information-field, uri-field, email-fields,
; phone-fields per rfc2327.  These fields are omitted in
; ATM SDP descriptions.  If received, they are ignored in the ATM
; context

connection-field = ["c=" c-net-type-addr]

         ; connection-field required, not optional, in ATM

c-net-type-addr = nettype space c-addrtype-addr
c-addrtype-addr = atm-addrtype-addr / c-ip-addrtype-addr /
                  tn-addrtype-addr

   ; atm-addrtype-addr defined above

   ; c-ip-addrtype-addr per rfc2327
   ; difference in address usage between 'o' and 'c' lines per rfc2327

   ; tn-addrtype-addr per rfc2848

bandwidth-fields = *("b=" bwtype ":" bandwidth EOL)



Kumar & Mostafa             Standards Track                    [Page 97]

RFC 3108                        ATM SDP                         May 2001


bwtype = 1*(alpha-numeric)
bandwidth = 1*(DIGIT)

time-fields = *( "t=" start-time space stop-time
              *(EOL repeat-fields) EOL)
              [zone-adjustments EOL]
start-time = time / "0"
stop-time = time / "0" ; always "0" in ATM
time = POS-DIGIT 9*(DIGIT) ; same as rfc2327
 ; repeat-fields and zone-adjustments per rfc2327, not used in ATM

 ; Definition of optional key-field per rfc2327
 ;

attribute-fields = *("a=" attribute EOL)

 ; SDP descriptors for ATM do not have session-level media attribute
 ; lines.  If these are provided, they should be ignored.

media-descriptions = *(media-description)
media-description  = media-field information-field *(connection-field)
                     bandwidth-fields key-field attribute-fields

; Definitions of information-field per RFC 2327.  These fields are
; omitted in ATM SDP descriptions.  If received, they are ignored in
; the ATM context
;
; In ATM, the connection-field is used in media-description to indicate
; the IP address associated with the RTCP control protocol in H.323.C
; applications.  In this case,  the connection field is per the RFC 2327
; definition for IP v4-based connections.  Otherwise, it is not used in
; media-description.  If received as part of  media-description,
; it is ignored.
;
; Definition of optional bandwidth-fields as above.
: Definition of optional key-field as in RFC 2327

media-field = rfc2327-media-field / rfc2848-media-field /
              atm-media-field
    ; rfc2327-media-field and rfc2848-media-field defined in those rfc's
atm-media-field = "m=" media space vcId space transport-fmts EOL
   ; superset of rfc2327 definition

media = "audio" / "video" / "data" / "application" / "control" /
        1*(alpha-numeric)

vcId = "$" / "-" / ex-vcci / (ex-vcci "/" ex-cid) /
     (atm-type-addr-m  "/" ex-vcci) /



Kumar & Mostafa             Standards Track                    [Page 98]

RFC 3108                        ATM SDP                         May 2001


     (atm-type-addr-m "/" ex-vcci "/" ex-cid) /
     (ex-bcg "/" ex-vcci) / (ex-bcg "/" ex-vcci "/" ex-cid)
     (ex-portid "/" ex-vpi "/" ex-vci) /
     (ex-portid "/" ex-vpi "/" ex-vci "/" ex-cid) /
     (ex-bcg "/" ex-vpi "/" ex-vci) /
     (ex-bcg "/" ex-vpi "/" ex-vci "/" ex-cid) /
     (ex-vpci "/" ex-vci) /
     (ex-vpci "/" ex-vci "/" ex-cid) /
     (atm-type-addr-m  "/" ex-vpci "/" ex-vci) /
     (atm-type-addr-m  "/" ex-vpci "/" ex-vci "/" ex-cid)

atm-type-addr-m = atm-nsap-addr-m / atm-e164-addr-m / atm-alias-addr-m
atm-nsap-addr-m =  ["NSAP-"] (nsap-addr / "$")
atm-e164-addr-m =  ["E164-"] (e164-addr / "$")
atm-alias-addr-m = ["GWID-" / "ALIAS-"] (alias-addr / "$")
 ; The -m at the end indicates use in the media field
 ; Wildcarding rules different from ATM address on 'o' and 'c' lines

ex-vcci    = "VCCI-"  vcci
ex-cid     = "CID-"   cid
ex-bcg     = "BCG-"   bcg
ex-portid  = "PORT-"  portid
ex-vpi     = "VPI-"   vpi
ex-vci     = "VCI-"   vci
ex-vpci    = "VPCI-"  vpci

vcci   = generic-U16
cid    = generic-U8
bcg    = generic-U8
portid = 1*32 (HEXDIG)
vpi    = generic-U12
vci    = generic-U16
vpci   = generic-U16


transport-fmts = generic-transport-fmts / known-transport-fmts / "- -"
generic-transport-fmts = generic-transport 1*(space fmt)
generic-transport = 1*(alpha-numeric / "/")
fmt = 1*(alpha-numeric)

known-transport-fmts = aal1-transport space aal1-fmt-list /
                       aal2-transport space aal2-fmt-list
                       *(space aal2-transport space aal2-fmt-list) /
                       aal5-transport space aal5-fmt-list /
                       rtp-transport space rtp-fmt-list /
                       tn-proto space tn-fmt-list /
                       h323c-proto "-"
h323c-proto = "H323c"



Kumar & Mostafa             Standards Track                    [Page 99]

RFC 3108                        ATM SDP                         May 2001


    ; h323c-proto used for RTCP control ports in H.323 annex C
    ; applications.  tn-proto and tn-fmt-list per rfc2848

aal1-transport = "AAL1" "/" aal1-transport-list
aal1-transport-list = "ATMF" / "ITU" / "custom" / "IEEE:" oui /
                      corporate-name
corporate-name = 1*(safe)
aal2-transport = "AAL2" "/" aal2-transport-list
aal2-transport-list = aal1-transport-list
aal5-transport = "AAL5" "/" aal5-transport-list
aal5-transport-list = aal1-transport-list
rtp-transport = "RTP" "/" rtp-transport-list
rtp-transport-list = "AVP"

aal1-fmt-list = (payload-type *(space payload-type)) / "-"
payload-type = decimal-uchar
aal5-fmt-list = aal1-fmt-list
rtp-fmt-list = aal1-fmt-list
aal2-fmt-list = (profile *(space profile)) / "-"
profile = decimal-uchar
attribute-fields = *("a=" attribute EOL)
attribute = known-attribute / (generic-att-field ":" att-value) /
            generic-att-field
generic-att-field = 1*(alpha-numeric)
att-value = byte-string
known-attribute = atm-attribute / PINT-attribute / rfc2327-attribute
         ; PINT-attribute as defined in rfc2848
         ; rfc2327 attribute as defined in that rfc

atm-attribute =
      "eecid" ":" eecid /
      "aalType" ":" aalType /
      "capability" ":" (asc / atc) space subtype /
      "qosclass" ":" qosclass /
      "bcob" ":" bcob space eetim /
      "stc" ":" stc /
      "upcc" ":" upcc /
      "atmQOSparms" ":" directionFlag space cdvType
                      space acdv space ccdv space eetd space cmtd
                      space aclr /
      "atmTrfcDesc" ":" directionFlag space clpLvl
                      space pcr space scr space mbs space cdvt space
                      mcr space mfs space fd space te /
      "abrParms" ":" directionFlag  space nrm space trm space cdf
                    space adtf /
      "abrSetup" ":" ficr space bicr space ftbe space btbe space
             crmrtt space frif space brif space frdf space brdf /
      "bearertype" ":" bearerType space localInitiation  /



Kumar & Mostafa             Standards Track                   [Page 100]

RFC 3108                        ATM SDP                         May 2001


      "lij" ":" sci space lsn /
      "anycast" ":" atmGroupAddress space cdStd space
                 conScpTyp space conScpSel /
      "cache" ":" cacheEnable space cacheTimer /
      "bearerSigIE" ":" bearerSigIEType space
               bearerSigIELng space bearerSigIEVal /
      "aalApp" ":" appClass space oui space appId /
      "cbrRate" ":" cbrRate /
      "sbc" ":" sbc /
      "clkrec" ":" clkrec /
      "fec" ":" fecEnable /
      "prtfl" ":" partialFill /
      "structure" ":" structureEnable space blksz /
      "cpsSDUsize" ":" directionFlag space cpcs /
      "aal2CPS" ":" cidLowerLimit space cidUpperLimit space
               timerCU space simplifiedCPS /
      "aal2CPSSDUrate" ":" fSDUrate space bSDUrate /
      "aal2sscs3661unassured" ":" ted space rastimer space fsssar
                space bsssar /
      "aal2sscs3661assured" ":" rastimer space fsssar space bsssar
           space fsscopsdu space bsscopsdu space fsscopuu
           space bsscopuu  /
      "aal2sscs3662" ":" sap space circuitMode space frameMode
           space faxDemod space cas space dtmf space mfall space mfr1
           space mfr2 space PCMencoding space fmaxFrame
           space bmaxFrame /
      "aal5sscop" ":" fsscopsdu space bsscopsdu space fsscopuu
             space bsscopuu  /
      "atmmap" ":" payload-type space encoding-name /
      "silenceSupp" ":" silenceSuppEnable space silenceTimer
               space suppPref space sidUse space fxnslevel /
      "ecan" ":" directionFlag space ecanEnable space ecanType /
      "gc" ":" directionFlag space gcEnable space gcLvl /
      "profileDesc" ":" aal2-transport space profile space
         1*(profile-row) /
      "vsel" ":" 1*(encoding-name space packet-length space
                                  packet-time space) /
      "dsel" ":" fxIncl space
                 1*(encoding-name space packet-length space
                                  packet-time space) /
      "fsel" ":" 1*(encoding-name space packet-length space
                                  packet-time space) /
      "onewaySel" ":" serviceType space directionFlag space
                 1*(encoding-name space packet-length space
                                  packet-time space) /

      "codecconfig" ":" q7655scc /
      "isup_usi" ":" isupUsi /



Kumar & Mostafa             Standards Track                   [Page 101]

RFC 3108                        ATM SDP                         May 2001


      "uiLayer1_Prot" ":" uiLayer1Prot /
      "chain" ":" chainPointer

eecid =  8 (HEXDIG)
aalType = "AAL1" / "AAL2" / "AAL3/4" / "AAL5" / "USER_DEFINED_AAL"
asc = "CBR" / "nrt-VBR" / "rt-VBR" / "UBR" / "ABR" / "GFR"
atc = "DBR" / "SBR" / "ABT/IT" / "ABT/DT" / "ABR"
subtype = decimal-U8-or-null
qosclass = decimal-U8-or-null
bcob = generic-U8
eetim = on-off-or-null
stc = decimal-uchar
upcc = decimal-uchar
directionFlag = "f" / "b" / "fb"
cdvType = "PP" / "2P" / "-"
acdv = decimal-U32-or-null
ccdv = decimal-U32-or-null
eetd = decimal-U16-or-null
cmtd = decimal-U16-or-null
aclr = decimal-U8-or-null
clpLvl = "0" / "0+1" / "-"
pcr = decimal-U24-or-null
scr = decimal-U24-or-null
mbs = decimal-U16-or-null
cdvt = decimal-U24-or-null
mcr = decimal-U24-or-null
mfs = decimal-U16-or-null
fd = on-off-or-null
te = on-off-or-null
nrm = generic-U8-or-null
trm = generic-U8-or-null
cdf = generic-U8-or-null
adtf = generic-U16-or-null
ficr = decimal-U24-or-null
bicr = decimal-U24-or-null
ftbe = decimal-U24-or-null
btbe = decimal-U24-or-null
crmrtt = decimal-U24-or-null
frif = 1*2 (DIGIT)
brif = 1*2 (DIGIT)
frdf = 1*2 (DIGIT)
brdf = 1*2 (DIGIT)
bearerType =  "PVC" / "SVC" / "CID"
localInitiation = on-off-or-null
sci = generic-U8-or-null
lsn = generic-U32-or-null
atmGroupAddress = atm-type-addr
cdStd = generic-U8-or-null



Kumar & Mostafa             Standards Track                   [Page 102]

RFC 3108                        ATM SDP                         May 2001


conScpTyp = generic-U8-or-null
conScpSel = generic-U8-or-null
cacheEnable = on-off-or-null
cacheTimer = generic-U32-or-null
bearerSigIEType = 2 * (HEXDIG)
bearerSigIELng = 1*4 (HEXDIG)
bearerSigIEVal = 2*512 (HEXDIG)
appClass =  "-" /
          "itu_h323c" / "af83" / "AAL5_SSCOP" / "itu_i3661_unassured" /
          "itu_ i3661_assured"/ "itu_i3662"/ "itu_i3651" /
          "itu_i3652" / "itu_i3653" / "itu_i3654" / "FRF11" / "FRF5" /
          "FRF8" / "itu_h2221"
oui = "-" / 1*6 (HEXDIG)
appId = "-" / 1*8 (HEXDIG)
cbrRate = 2 (HEXDIG)
sbc = generic-U8
clkrec = "NULL" / "SRTS" / "ADAPTIVE"
fecEnable = "NULL" / "LOSS_SENSITIVE"  / "DELAY_SENSITIVE"
partialFill = generic-U8
structureEnable = on-off-or-null
blksz = generic-U16-or-null
cpcs = generic-U16
cidLowerLimit = generic-U8-or-null
cidUpperLimit = generic-U8-or-null
timerCU = decimal-U32-or-null
simplifiedCPS = on-off-or-null
fSDUrate = decimal-U24-or-null
bSDUrate = decimal-U24-or-null
ted = on-off-or-null
rastimer = decimal-U32-or-null
fsssar = generic-U24-or-null
bsssar = generic-U24-or-null
fsscopsdu = generic-U16-or-null
bsscopsdu = generic-U16-or-null
fsscopuu = generic-U16-or-null
bsscopuu = generic-U16-or-null
sap = "AUDIO" / "MULTIRATE" / "-"
circuitMode = on-off-or-null
frameMode = on-off-or-null
faxDemod = on-off-or-null
cas = on-off-or-null
dtmf = on-off-or-null
mfall = on-off-or-null
mfr1 = on-off-or-null
mfr2 = on-off-or-null
PCMencoding = "PCMA" / "PCMU" / "-"
fmaxframe = generic-U16-or-null
bmaxframe = generic-U16-or-null



Kumar & Mostafa             Standards Track                   [Page 103]

RFC 3108                        ATM SDP                         May 2001


silenceSuppEnable = on-off-or-null
silenceTimer = generic-U16-or-null
suppPref = "standard" / "custom" / "-"
sidUse = "No SID" / "Fixed Noise" / "Sampled Noise" / "-"
fxnslevel = generic-U8-or-null
ecanEnable = on-off-or-null
ecanType = "G165" / "G168" / "-"
gcEnable = on-off-or-null
gcLvl = generic-U16-or-null

profile-row  = uuiCodeRange space encoding-name space packet-length
                   space packet-time space
uuiCodeRange = decimal-uchar "-" decimal-uchar / "-"
encoding-name = "-" /
                "PCMG" / "SIDG" / "SID729" /
                "PCMU" / "G726-32" / "G723" / "PCMA" / "G722" / "G728" /
                "G729" / "X-G729a" / "X-G729b" / "X-G729ab" /
                "X-G726-16" / "X-G726-24" / "X-G726-40" / "X-G7231-H" /
                "X-G7231-L" / "X-G7231a-H" / "X-G7231a-L" /
                "X-G727-16" / "X-G727-24" / "X-G727-32" /
                "X-CCD" / "X-CCD-CAS" / "GSM" / "GSM-HR" / "GSM-EFR" /
                "GSM-EHR" / "X-FXDMOD-3" / "1016" / "DVI4" / "L16" /
                "LPC" / "MPA" / "QCELP" / "H263" / "H263-1998" /
                "JPEG" / "H261" / "MPV" / "MP2T" / "nv" / "RED" /
                "CelB" / "L8" / "VDVI" / "MP1S" / "MP2P" / "BT656" /
                "FR-AMR" / "HR-AMR" / "UMTS-AMR" / "AMR"
packet-length = decimal-U8-or-null
packet-time = decimal-U16-or-null
fxIncl = on-off-or-null
serviceType = "v" / "d" / "f" / "df" / "all"
q7655scc = 4*32 (HEXDIG)
isupUsi = 4*24 (HEXDIG)
uiLayer1Prot = 2 (HEXDIG)

chainPointer = "NEXT" / "PREVIOUS" / "NULL"

References

   [1]  Handley, M. and V. Jacobson, "SDP: Session Description
        Protocol", RFC 2327, April 1998.

   [2]  Schulzrinne, H., Casner, S., Frederick, R. and V. Jacobson,
        "RTP:  A Transport Protocol for Real-Time Applications", RFC
        1889, January 1996.

        RFC 1889 will be obsoleted, in a substantially backwards
        compatible manner, by a work in progress that will become an
        RFC.



Kumar & Mostafa             Standards Track                   [Page 104]

RFC 3108                        ATM SDP                         May 2001


   [3]  Schulzrinne, H., "RTP Profile for Audio and Video Conferences
        with Minimal Control", RFC 1890, January 1996.

        RFC 1890 will be obsoleted, in a fully backwards compatible
        manner, by a work in progress that will become an RFC.

   [4]  ATMF UNI 3.1 Specification,  af-uni-0010.002. Of special
        interest for this document is  Section 5.4.5.5,  ATM Adaptation
        Layer Parameters.

   [5]  ATMF UNI 4.0 Signaling Specification, af-sig-0061.000.

   [6]  ATMF Traffic Management Specification, Version 4.1, af-tm-
        0121.000.

   [7]  ATMF Circuit Emulation Service (CES) Interoperability
        Specification, version 2.0, af-vtoa-0078.000, Jan. 97.

   [8]  ATMF Voice and Telephony over ATM - ATM Trunking using AAL1 for
        Narrowband Services, version 1.0, af-vtoa-0089.000, July 1997.

   [9]  ATMF Specifications of (DBCES) Dynamic Bandwidth Utilization -
        in 64kbps Timeslot Trunking over ATM  - using CES, af-vtoa-
        0085.000, July 1997.

   [10] ITU-T I.363.1, B-ISDN ATM Adaptation Layer Specification: Type 1
        AAL, August 1996.

   [11] ITU-T I.363.2, B-ISDN ATM Adaptation Layer Specification: Type 2
        AAL, Sept. 1997.

   [12] ITU-T I.366.1, Segmentation and Reassembly Service Specific
        Convergence Sublayer  for AAL Type 2, June 1998.

   [13] ITU-T I.366.2, AAL Type 2 Reassembly Service Specific
        Convergence Sublayer  for Trunking, Feb. 99.

   [14] Petrack, S., "RTP payloads for Telephone Signal Events", Work in
        Progress.

   [15] ITU-T Q.2931, B-ISDN Application Protocol for Access Signaling.

   [16] Amendment 1, 2, 3 and 4 to ITU-T Q.2931, B-ISDN Application
        Protocol for Access Signaling.

   [17] Handley, M., Perkins C. and E. Whelan, "Session Announcement
        Protocol", RFC 2974, October 2000.




Kumar & Mostafa             Standards Track                   [Page 105]

RFC 3108                        ATM SDP                         May 2001


   [18] Handley, M., Schulzrinne, H., Schooler, E. and J. Rosenberg,
        "Session Initiation Protocol (SIP)", RFC 2543, March 1999.

   [19] Almquist, P., "Type of Service in the Internet Protocol Suite",
        July 1992.

   [20] Nichols, K., Blake, S., Baker, F. and D. Black, "Definition of
        the Differentiated Services Field (DS Field) in the IPv4 and
        IPv6 Headers", December 1998.

   [21] ITU-T I.363.5, B-ISDN ATM Adaptation Layer Specification: Type 5
        AAL, Aug. 1996.

   [22] ATMF PNNI 1.0, af-pnni-0055.000, March 1996.

   [23] Schulzrinne, H., Casner, S., Frederick, R. and V. Jacobson,
        "RTP: A Transport Protocol for Real-Time Applications", Work in
        Progress.

   [24] Schulzrinne, H. and S. Casner, "RTP Profile for Audio and Video
        Conferences with Minimal Control", Work in Progress.

   [25] Arango, M., Dugan, A., Elliott, I., Huitema, C. and S. Pickett,
        "Media Gateway Control Protocol (MGCP)", RFC 2705, October 1999.

   [26] Cuervo, F., Greene, N., Rayhan, A., Huitema, C., Rosen, B. and
        J.  Segers, "Megaco Protocol Version 1.0", RFC 3015, November
        2000.

   [27] Atkinson, R., "IP Authentication Header", RFC 1826, August 1995.

   [28] ITU I.371, Traffic Control and Congestion Control in the BISDN.

   [29] ITU E.191, BISDN Numbering and Addressing.

   [30] ATM Forum Addressing: Reference Guide, af-ra-0106.000.

   [31] http://www.iana.org/assignments/rtp-parameters for a list of
        codecs with static payload types.

   [32] ITU Q.2941-2, Digital Subscriber Signalling System No. 2 (DSS
        2): Generic identifier transport extensions.

   [33] ITU Q.2961, Digital subscriber signalling system no.2 (DSS 2) -
        additional traffic parameters. Also, Amendment 2 to Q.2961.

   [34] ITU Q. 2965.1, Digital subscriber signalling system no.2 (DSS 2)
        - Support of Quality of Service classes.



Kumar & Mostafa             Standards Track                   [Page 106]

RFC 3108                        ATM SDP                         May 2001


   [35] ITU Q. 2965.2, Digital subscriber signalling system no.2 (DSS 2)
        - Signalling of individual Quality of Service parameters.

   [36] ITU Q.1901, Bearer Independent Call Control Protocol.

   [37] ITU Q.2630.1, AAL type 2 signaling protocol - capability set 1.

   [38] ITU I.363.5, B-ISDN ATM Adaptation Layer specification: Type 5
        AAL.

   [39] I.365.1,Frame relaying service specific convergence sublayer
        (FR-SSCS).

   [40] I.365.2, B-ISDN ATM adaptation layer sublayers: service specific
        coordination function to provide the connection oriented network
        service.

   [41] I.365.3, B-ISDN ATM adaptation layer sublayers: service specific
        coordination function to provide the connection-oriented
        transport service.

   [42] I.365.4, B-ISDN ATM adaptation layer sublayers: Service specific
        convergence sublayer for HDLC applications.

   [43] Q.2110, B-ISDN ATM adaptation layer - service specific
        connection oriented  protocol (SSCOP).

   [44] af-vtoa-0113.000, ATM trunking using AAL2 for narrowband
        services.

   [45] H.323-2, Packet-based multimedia communications systems.

   [46] af-vtoa-0083.000, Voice and Telephony Over ATM to the Desktop.

   [47] I.356, BISDN ATM layer cell transfer performance.

   [48] ITU Q.2957, Digital Subscriber Signaling System No. 2, User to
        user signaling.

   [49] Mills, D., "Network Time Protocol (Version 3) Specification,
        Implementation and Analysis", RFC 1305, March 1992.

   [50] TIA/EIA/IS-J-STD-025-A, Lawfully Authorized Electronic
        Surveillance, May 2000.

   [51] ITU-T H.222.1, Multimedia multiplex and synchronization for
        audiovisual communication in ATM environments.




Kumar & Mostafa             Standards Track                   [Page 107]

RFC 3108                        ATM SDP                         May 2001


   [52] af-vmoa-0145.000, Voice and Multimedia over ATM, Loop Emulation
        Service using AAL2.

   [53] FRF.5, Frame Relay/ATM PVC Network Interworking Implementation
        Agreement.

   [54] FRF.8.1, Frame Relay/ATM PVC Service Interworking Implementation
        Agreement.

   [55] FRF.11, Voice over Frame Relay Implementation Agreement.

   [56] Crocker, D. and P. Overell, "Augmented BNF for Syntax
        Specifications: ABNF", RFC 2234, November 1997.

   [57] ITU Q.765.5, Application Transport Mechanism - Bearer
        Independent Call Control.

   [58] http://www.3gpp.org/ftp/Specs for specifications related to
        3GPP, including AMR codecs.

   [59] ITU Q.931, Digital Subscriber Signaling System No. 1: Network
        Layer.

   [60] ITU Q.763, SS7 - ISUP formats and codes.

   [61] http://www.atmforum.com/atmforum/specs/specs.html, ATM Forum,
        Well-known addresses and assigned codes.

   [62] Bradner, S., "Keywords for use in RFCs to indicate requirement
        levels", BCP 14, RFC 2119, March 1997.





















Kumar & Mostafa             Standards Track                   [Page 108]

RFC 3108                        ATM SDP                         May 2001


Acknowledgements

   The authors wish to thank several colleagues at Cisco and in the
   industry who have contributed towards the development of these SDP
   conventions, and who have reviewed, implemented and tested these
   constructs.  Valuable technical ideas that have been incorporated
   into this internet document have been provided by Hisham Abdelhamid,
   Flemming Andreasen, David Auerbach, Robert Biskner, Bruce Buffam,
   Steve Casner, Alex Clemm, Bill Foster, Snehal Karia, Raghu Thirumalai
   Rajan, Joe Stone, Bruce Thompson, Dan Wing and Ken Young of Cisco,
   Michael Brown, Rade Gvozdanovic, Graeme Gibbs, Tom-PT Taylor, Mark
   Watson and Sophia Scoggins of Nortel Networks, Brian Rosen, Tim
   Dwight and Michael Mackey of Marconi, Ed Guy and Petros Mouchtaris of
   Telcordia, Christian Groves of Ericsson, Charles Eckel of Vovida
   Networks, Tom Jepsen, Dal Chohan, Sagar Gordhan and Chris Gallon of
   Fujitsu, Mahamood Hussain of Hughes Software Systems and Sean Sheedy
   of nCUBE Corporation, Narendra Tulpule of Intel, Albrecht Schwarz of
   Alcatel, and Jonathan Rosenberg of Dynamicsoft.  The authors also
   wish to thank the ISC device control group, and the MMUSIC and MEGACO
   subgroups of the IETF, especially Bill Foster, Joerg Ott, Sean Sheedy
   and Brian Rosen for their help in the preparation of this document.
   Finally, thanks are due to Narendra Tulpule of Intel whose ABNF
   grammar was adapted for this document.

Authors' Addresses

   Rajesh Kumar
   Cisco Systems, Inc.
   M/S SJC01/3
   170 West Tasman Drive
   San Jose, CA 95134-1706

   Phone: 1-800-250-4800
   EMail: rkumar@cisco.com


   Mohamed Mostafa
   Cisco Systems, Inc.
   M/S SJC01/3
   170 West Tasman Drive
   San Jose, CA 95134-1706

   Phone: 1-800-250-4800
   EMail: mmostafa@cisco.com







Kumar & Mostafa             Standards Track                   [Page 109]

RFC 3108                        ATM SDP                         May 2001


Full Copyright Statement

   Copyright (C) The Internet Society (2001).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.



















Kumar & Mostafa             Standards Track                   [Page 110]