File: rfc1841.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 (3699 lines) | stat: -rw-r--r-- 146,206 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






Network Working Group                                         J. Chapman
Request For Comments: 1841                           Cisco Systems, Inc.
Category: Informational                                          D. Coli
                                                     Cisco Systems, Inc.
                                                               A. Harvey
                                                     Cisco Systems, Inc.
                                                               B. Jensen
                                                     Cisco Systems, Inc.
                                                               K. Rowett
                                                     Cisco Systems, Inc.
                                                          September 1995


            PPP Network Control Protocol for LAN Extension

Status of Memo

   This memo provides information for the Internet community.  This memo
   does not specify an Internet standard of any kind.  Distribution of
   this memo is unlimited.

Abstract

   Telecommunications infrastructure is improving to offer higher
   bandwidth connections at lower cost. Access to the network is
   changing from modems to more intelligent devices. This informational
   RFC discusses a PPP Network Control Protocol for one such intelligent
   device. The protocol is the LAN extension interface protocol.

Table of Contents

   1.0    Introduction ...........................................    3
      1.1   LAN Extension Interface Topology .....................    4
      1.2   LAN Extension Interface Architecture .................    5
      1.3   LAN Extension Interface Protocol .....................    6

   2.0    LAN Extension Interface Protocol Control Packets........    8
      2.1   Startup Options ......................................    8
      2.2   Remote Command Options ...............................   14
      2.3   Conditions for Sending PPP-LEX Packet ................   17

   3.0    Filter Protocol Type ...................................   18
      3.1   LEX_RCMD_REQUEST - Filter Protocol Type...............   19
      3.2   Response Packets - Filter Protocol Type...............   21

   4.0    Filter MAC Address .....................................   22
      4.1   LEX_RCMD_REQUEST - Filter MAC Address ................   23
      4.2   Response Packets - Filter MAC Address.................   25



Chapman, et al               Informational                      [Page 1]

RFC 1841           LAN Extension Interface Protocol       September 1995


   5.0    Set Priority ...........................................   27
      5.1   LEX_RCMD_REQUEST - Set Priority ......................   27
      5.2   Response Packets - Set Priority ......................   29

   6.0    Disable LAN Extension Ethernet Interface ...............   30
      6.1   LEX_RCMD_REQUEST - Disable LAN Extension
            Ethernet Interface ...................................   31
      6.2   Response Packets - Disable LAN Extension
            Ethernet Interface ...................................   32

   7.0    Enable LAN Extension Ethernet Interface ................   33
      7.1   LEX_RCMD_REQUEST - Enable LAN Extension
            Ethernet Interface ...................................   33
      7.2   Response Packets - Enable LAN Extension
            Ethernet Interface ...................................   34

   8.0    Reboot LAN Extension Interface Unit ....................   35
      8.1   LEX_RCMD_REQUEST - Reboot LAN Extension Interface
            Unit .................................................   35
      8.2   Response Packets - Reboot LAN Extension
            Interface Unit .......................................   36

   9.0    Request Statistics .....................................   37
      9.1   LEX_RCMD_REQUEST - Request Statistics ................   37
      9.2   LEX_RCMD_ACK - Request Statistics ....................   39
      9.3   LEX_RCMD_NAK/LEX_RCMD_REJ - Request Statistics .......   44

   10.0    Download Request ......................................   45
      10.1   LEX_RCMD_REQUEST - Download Request .................   46
      10.2   Response Packets - Download Request..................   48

   11.0    Download Data .........................................   49
      11.1   LEX_RCMD_REQUEST - Download Request .................   49
      11.2   Response Packets - Download Data ....................   51

   12.0    Download Status .......................................   52
      12.1   LEX_RCMD_REQUEST - Download Status ..................   53
      12.2   LEX_RCMD_ACK - Download Status ......................   54
      12.3   LEX_RCMD_NAK/LEX_RCMD_REJ - Download Status .........   56

   13.0    Inventory Request .....................................   56
      13.1   LEX_RCMD_REQUEST - Inventory Request ................   57
      13.2   LEX_RCMD_ACK - Inventory Request ....................   58
      13.3   LEX_RCMD_NAK/LEX_RCMD_REJ - Inventory Request .......   61

   14.0    LAN Extension Interface Protocol Data Packets .........   62
      14.1   Frame Format ........................................   62
      14.2   Summary Field Descriptions...........................   63



Chapman, et al               Informational                      [Page 2]

RFC 1841           LAN Extension Interface Protocol       September 1995


   NOTES ......................................................      65
   REFERENCES .................................................      65
   SECURITY CONSIDERATIONS ....................................      66
   AUTHORS' ADDRESSES .........................................      66

1.0 Introduction

   An increasing number of corporations allow their employees to
   telecommute to work due to local government regulations on traffic
   and air pollution. Additionally, many businesses are run out of
   internetworked home offices and small branch offices. With these
   changes in the workplace, more people and businesses require Internet
   access from small LANs.

   Today, routers serve the LAN-to-LAN traffic using high-speed WAN
   links such as leased lines, ISDN, or Frame Relay. This new breed of
   Internet users from home offices and small branch offices may have a
   different, less network-literate skill set than those connecting up
   to the Internet today. These new users need an alternative to the
   complex and hard-to-configure routers currently employed for
   connectivity. One such alternative is a LAN extension interface unit.

   A LAN extension interface unit is a hardware device installed at
   remote sites (such as a home office or small branch office) that
   connects a LAN across a WAN link to a router at a central site. The
   following sections introduce a LAN extension interface topology,
   architecture, and protocol.
























Chapman, et al               Informational                      [Page 3]

RFC 1841           LAN Extension Interface Protocol       September 1995


1.1 LAN Extension Interface Topology

   Figure 1 shows the topology of LAN extension interfaces. The figure
   shows two LAN extension interface units connected via a WAN link to a
   central or "host router."

                 Figure 1 LAN Extension Interface Topology

                  -----------------------------------------
                                    Router
                  -----------------------------------------
                     Virtual Interface   Virtual Interface
                        123.123.78.1        123.123.89.1
                  .........................................
                           Serial 0           Serial n
                  -----------------------------------------
                             |<---- WAN Link ---->|
                ------------------                    ------------------
                | LAN Extension  |                    | LAN Extension  |
                | Interface Unit |                    | Interface Unit |
                ------------------                    ------------------
                        |                                     |
                ------------------                    ------------------
                  |                                      |
                ------------                          ------------
                | End node |                          | End node |
                ------------                          ------------
                123.123.78.2                          123.123.46.2

   Each LAN extension interface unit maps to a virtual interface at the
   host router. The virtual interface mirrors the characteristics of the
   LAN extension interface unit. To the routing protocols, the virtual
   interface looks just like a local interface, but with the bandwidth
   of a serial line. The virtual interface keeps the state (up or down)
   of the LAN extension interface unit, and identifies each LAN
   extension interface unit by its MAC address.

   A LAN extension interface protocol transfers MAC frames from the LAN
   extension interface unit across the serial line to the host router.
   At the termination point in the router, the router routes the
   packets. This topology uses only one subnet per remote LAN rather
   than two, as is the case when routers exist on both ends of a WAN
   link. Figure 1 shows this subnetting structure. The IP addresses of
   the virtual interfaces on the router are in the same subnet as the IP
   addresses of the end nodes on the LAN of the LAN extension interface
   unit. The LAN extension interface unit itself has no IP address.





Chapman, et al               Informational                      [Page 4]

RFC 1841           LAN Extension Interface Protocol       September 1995


   LAN extension interface units resemble bridges, but with the
   following distinct differences:

   *  LAN extension interface units always depend on a host router.
      They cannot operate standalone or even back-to-back with other
      LAN extension interface units.

   *  LAN extension interface units need not employ any spanning tree
      algorithm.

   *  (LAN extension interface units transfer MAC frames across a
      serial line (like bridges), but a router can either route or
      bridge the LAN extension interface data packets.

1.2 LAN Extension Interface Architecture

   Figure 2 shows the basic LAN extension interface architecture.

               Figure 2 LAN Extension Interface Architecture

                 Router                        LAN Extension Interface
          -------------------                  -------------------
          |   Network Layer |                  |     MAC Layer   |
          -------------------                  -------------------
                  |                                       |
          -------------------                  -------------------
     |    |Virtual Interface|                  |       Filters   |   |
     |    -------------------                  -------------------   |
     |            |                                 |                |
     |    -------------------                  -------------         |
     |    |      PPP        |                  |   RCMD    |         |
     |    |                 |                  |   Handler |         |
     |    -------------------                  -------------         |
     |            |                                 |                |
     |    -------------------                  -------------------   |
     |    |Serial Interface |                  |        PPP      |   |
     |    -------------------                  -------------------   |
     |            |                                      |           |
     |            |                            -------------------   |
     |            |                            | Serial Interface|   |
     |            |                            -------------------   |
     |            |          WAN Link                    |           |
     |            ---------------------------------------            |
     |                                                               |
     |   Outbound                                          Inbound   |
     -------------->                                  <---------------





Chapman, et al               Informational                      [Page 5]

RFC 1841           LAN Extension Interface Protocol       September 1995


   In the inbound direction (from the remote LAN, to the LAN extension
   interface unit, across the WAN link, to the host router), the LAN
   extension interface unit can filter received frames to optimize WAN
   utilization. The LAN extension interface unit can filter frames by
   protocol type or by MAC address. Frames that pass through the LAN
   extension interface filters go to the WAN protocol state machine. In
   Figure 2, this state machine is PPP. The LAN extension interface unit
   adds PPP encapsulation and forwards the packet to the router via the
   WAN serial link.

   Upon receiving the frame, the host router decapsulates the PPP header
   and passes the packet to the virtual interface. From there the
   virtual interface handles the packet like any packet received on a
   local interface -- by routing or bridging the packet to another
   interface, depending on configuration.

   In the outbound direction (from the host router, across the WAN link,
   to the LAN extension interface unit, to the LAN), the host router's
   virtual interface builds the full MAC header, before adding PPP
   encapsulation. The router then sends the packet across the WAN serial
   link to the LAN extension interface unit. The LAN extension interface
   unit strips the PPP header and forwards the packet directly onto the
   LAN. The host router has already determined that the packet needs to
   be forwarded to the LAN extension interface unit, hence there is no
   need for additional filtering or processing at that end.

   Embedded in the data stream is a control stream for configuring and
   managing the LAN extension interface unit from the host router. The
   virtual interface makes the remote LAN extension interface unit
   appear like a local router interface to the routing protocols.

   Configuration commands and statistics gathering commands are issued
   on the router to the virtual interface. The virtual interface formats
   the LAN extension interface remote commands into encoded messages and
   transfers them in-band with the data packets. The LAN extension
   interface unit decodes the remote commands and executes them.
   Responses are similarly formatted messages sent by the LAN extension
   interface unit to the host router. The remote command messages use a
   different encapsulation type than the data packets, as described
   later in this document in the "LAN Extension Interface Protocol
   Control Packets" and "LAN Extension Interface Protocol Data Packets"
   sections.

1.3 LAN Extension Interface Protocol

   To accommodate this LAN extension interface architecture, a new
   Network Control Protocol (NCP) for PPP exists. This NCP is called
   PPP-LEX. The basic functionality of PPP-LEX is to encapsulate LAN



Chapman, et al               Informational                      [Page 6]

RFC 1841           LAN Extension Interface Protocol       September 1995


   extension interface control and data packets. The IETF has assigned
   two new protocol types for these functions, as shown in Table 1.

                 Table 1  IETF Protocol Types for PPP-LEX

   Protocol Type       Function

   0x8041              Encapsulates control packets
   0x0041              Encapsulates data packets (MAC frames)

   PPP is a natural choice for a LAN extension interface protocol
   because it allows for negotiating a specific control protocol and
   options at connection time. This means that network administrators do
   not have to statically configure the router interface for remote
   interfaces. Rather, remote interfaces negotiate the link at
   connection time.

   The LAN extension interface protocol employs PPP link operation as
   described in RFC 1331, which reads as follows:

      In order to establish communications of a point-to-point link,
      each end of the PPP link must first send [Link Control Protocol]
      LCP packets to configure and test the data link. After the link
      has been established,the peer may be authenticated. Then PPP must
      send NCP packets to choose and configure one or more network layer
      protocols. Once each of the chosen network-layer protocols has
      been configured, datagrams from each network layer protocol can be
      sent over the link.

      The link will remain configured for communications until explicit
      LCP or NCP packets close the link down, or until some external
      event occurs (an inactivity timer expires or network administrator
      intervention). (References, [1])

   Thus, the LAN extension interface unit and the host router exchange
   PPP-LCP packets at connection time to dynamically configure and test
   the WAN serial link. Once the link reaches an "opened" state, the LAN
   extension interface unit and host router exchange PPP-LEX NCP packets
   to configure the LAN extension interface protocol. Once it is
   configured, the NCP (PPP-LEX) reaches an "opened" state, and PPP
   carries the PPP-LEX control and data packets across the serial link.
   At this point, link traffic is a any combination of LCPs, PPP-LEX
   NCPs, PPP-LEX control packets, and PPP-LEX data packets.

   Note that the LAN extension interface protocol is not a bridging
   protocol. The only similarity to the PPP Bridging Control Protocol
   (References. [2]) is that the LAN extension interface protocol also
   encapsulates MAC frames.



Chapman, et al               Informational                      [Page 7]

RFC 1841           LAN Extension Interface Protocol       September 1995


   The following sections detail PPP-LEX control packets and data
   packets.

2.0 LAN Extension Interface Protocol Control Packets

   There are two types of PPP-LEX control packets, as follows:

      *  Startup options packet
      *  Remote command options packets

   The startup options packet is the first PPP-LEX NCP packet that the
   LAN extension interface unit sends to the host router after the LCP
   has reached an "opened" state. This required startup options packet
   configures the LAN extension interface protocol and puts the PPP-LEX
   NCP in an "opened" state.

   Remote command options are the PPP-LEX NCP packets that control the
   functioning and statistics gathering of the LAN extension interface
   protocol.

2.1 Startup Options

   The LAN extension interface unit sends a startup options packet to
   the host router to negotiate the following startup options:

      *  MAC Type
      *  MAC Address
      *  LAN Extension

   The MAC Type startup option informs the host router of the type of
   media that the LAN extension interface unit is connected to. For
   example, the LAN extension interface unit may be connected to an
   Ethernet LAN or a Token Ring LAN. Currently, only Ethernet is
   supported. The MAC type tells the host router what type of traffic
   the LAN extension interface unit is prepared to receive. If the host
   router rejects the MAC type, the LAN extension interface unit sends
   the Configure-Request again.

   The MAC Address startup option sends the MAC address of the LAN
   extension interface unit to the host router to authenticate the LAN
   extension interface unit and bind it to the corresponding virtual
   interface at the host router. The host router also inserts the MAC
   address in outbound packets. The MAC address is represented in IEEE
   802.3 canonical format.

   The LAN Extension startup option establishes the network layer
   protocol (NCP) as PPP-LEX and provides the host router with the LAN
   extension interface protocol version number.



Chapman, et al               Informational                      [Page 8]

RFC 1841           LAN Extension Interface Protocol       September 1995


   Each startup option is transmitted in a series of three fields:
   Option-Type, Option-Length, and Option-Data fields. The fields are
   concatenated in the startup options Configure-Request packet.

   Frame Format

   Figure 3 shows a summary of the frame format for the startup options
   packet. The LAN extension interface unit sends this startup options
   packet to the host router. The LAN extension interface unit transmits
   these fields from left to right.

        Figure 3  Startup Options Frame Format (Configure-Request)

                     PPP Header
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|    Address    |     Control   |          Protocol Type        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     (1 octet)          (1)                      (2)

               LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|     Code      |   Identifier  |             Length            |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     (1 octet)         (1)                      (2)

            LAN Extension Interface Startup Options
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|  Option-Type  | Option-Length |          Option-Data          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     (1 octet)          (1)

   Address

   This PPP-specified field is one octet and contains the binary
   sequence 11111111 (hexadecimal 0xFF), the All-Stations address. PPP
   does not assign individual station addresses. The All-Stations
   address must be recognized and received by all devices. For more
   information on this field, refer to "The Point-to-Point Protocol
   (PPP) for the Transmission of Multi-protocol Datagrams over Point-
   to-Point Links." (References, [1])





Chapman, et al               Informational                      [Page 9]

RFC 1841           LAN Extension Interface Protocol       September 1995


   Control

   This PPP-specified field is one octet and contains the binary
   sequence 00000011 (hexadecimal 0x03), the Unnumbered Information (UI)
   command with the P/F bit set to zero.

   For more information on this field, refer to "The Point-to-Point
   Protocol (PPP) for the Transmission of Multi-protocol Datagrams over
   Point-to Point Links." (References, [1])

   Protocol-Type

   The Protocol-Type field is two octets and contains the IETF-assigned
   protocol type value. Valid LAN extension interface protocol type
   values are as follows:

      *  0x8041 (for control packets)
      *  0x0041 (for data packets)

   Because the startup options packet encapsulates LAN extension
   interface control data, the valid value for this field is 0x8041.

   Code

   The Code field is one octet and identifies the type of LCP packet
   that the LAN extension interface packet is sending. Valid values are
   as follows:

      *  0x01 - Configure-Request
      *  0x02 - Configure-Ack
      *  0x03 - Configure-Nak
      *  0x04 - Configure-Rej

   The LAN extension interface unit initiates the startup options
   packet; therefore, the valid value for this field is 1.

   Identifier

   The Identifier field is one octet and contains a randomly generated
   value. The value aids matching requests and replies. It is
   recommended that a non-zero value be used for the identifier. That
   is, zero could be used in the future for unsolicited messages from
   the LAN extension interface unit. Valid values are 0x01-0xFF.








Chapman, et al               Informational                     [Page 10]

RFC 1841           LAN Extension Interface Protocol       September 1995


   Length

   The Length field is two octets and indicates the length of the entire
   packet in octets, including the Code, Identifier, Length, and startup
   options fields.

   Option-Type

   The Option-Type field is one octet and identifies the startup option
   being negotiated. Valid values are as follows:

      *  0x01 - MAC Type
      *  0x03 - MAC Address
      *  0x05 - LAN Extension

   Option-Length

   The Option-Length field is one octet and specifies the length of the
   startup option fields, including the Option-Type, Option-Data, and
   Option-Length fields.

   Option-Data

   The Option-Data field contains the data relating to the value
   specified in the Option-Type field. That is, if the Option-Type field
   specifies MAC type (0x01), then the Option-Data field contains the
   MAC type (Ethernet, Token Ring, and so on). If the Option-Type field
   specifies MAC address (0x03), then the Option-Data field contains the
   actual MAC address. If the Option-Type field specifies LAN Extension
   (0x05), then the Option-Data field contains LAN extension interface
   software information. The following table defines the contents of the
   Option-Data field for each possible Option-Type field value:

   Option-Type Field Value   Option-Data

   0x01 (MAC Type)           The most up-to-date value of the MAC type as
                             specified in the most recent "Assigned
                             Numbers" RFC. The current valid value from
                             that RFC follows:
                             *  0x01: IEEE 802.3/Ethernet with canonical
                                addresses
   0x03 (MAC Address)        The burned-in MAC address in IEEE 802.3
                              canonical format.
   0x05 (LAN Extension)      The LAN extension interface protocol version
                             number. 0x01 is the current protocol version
                             supported.





Chapman, et al               Informational                     [Page 11]

RFC 1841           LAN Extension Interface Protocol       September 1995


   Example

   In the Configure-Request packet that it sends to the host router, the
   LAN extension interface unit concatenates the Option-Type, Option-
   Data, and Option-Length fields for each startup option, as shown in
   Figure 4. The LAN extension interface unit transmits these fields
   from left to right.

         Figure 4 Sample Startup Options Configure-Request Packet

                         PPP Header
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      0xFF     |      0x03     |             0x8041            |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     Address          Control             Protocol-Type

                LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|     0x01      |      0x09     |             0x12              |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   Option-Type      Identifier               Length

              LAN Extension Interface Startup Options
<------------------------------------------------
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      0x01     |               0x03            |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   Option-Type             Option-Length

                                  ------------------------------>
                                  4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
                                 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                               0x01             |
                                 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                             Option-Data











Chapman, et al               Informational                     [Page 12]

RFC 1841           LAN Extension Interface Protocol       September 1995


 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      0x03     |               0x08            |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   Option-Type             Option-Length        |

                                  4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
                                 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                    0A  0A  0A  0A  0B  0C      |
                                 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                 ---------- Option-Data --------|

 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      0x05     |               0x03            |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   Option-Type             Option-Length

                                  4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
                                 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                                0x01            |
                                 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                           Option-Data

   In Figure 4, the Address field always contains 0xFF, and the Control
   field always contains 0x03. The Protocol-Type field value is 0x8041
   because the startup options packet is a LAN extension interface
   control packet. The Code field value is 0x01 because the LAN
   extension interface unit is sending an LCP Configure-Request packet
   to configure or negotiate PPP-LEX. The Identifier field contains a
   randomly generated number. The Length field gives the total length of
   the entire packet.

   The first startup option is the MAC Type startup option. The Option-
   Type value for MAC Type is 0x01. The Option-Length field value for
   the MAC type startup option is 3 octets. The Option-Data field value
   is 0x01 because, in this example, the LAN extension interface unit
   connects to an Ethernet LAN using 802.3 canonical addresses.

   The next startup option transmitted is the MAC Address. Its Option-
   Type field value is 0x03, its Option-Length field value is 8 octets,
   and its Option-Data field value is the actual MAC address.

   Lastly, the LAN Extension startup option is transmitted. Its Option-
   Type field value is 0x05, its Option-Length field value is 3 octets,
   and its Option-Data field value is the LAN extension interface
   protocol version number (0x01).




Chapman, et al               Informational                     [Page 13]

RFC 1841           LAN Extension Interface Protocol       September 1995


   The host router responds to this LCP Configure-Request packet with an
   LCP Configure-Ack packet, Configure-Nak packet, or Configure-Rej
   packet. For more information on these packets, refer to "The Point-
   to-Point Protocol (PPP) for the Transmission of Multi-protocol
   Datagrams over Point-to-Point Links" RFC. (References, [1])

2.2 Remote Command Options

   Once the host router responds to the startup options Configure-
   Request packet with a Configure-Ack packet, the PPP-LEX NCP is in an
   "opened" state, and the LAN extension interface unit and the host
   router freely exchange PPP-LEX data packets and remote command
   options packets.

   The host router initiates PPP-LEX remote command options packets to
   control the configuration of the LAN extension interface unit and to
   gather statistics. There are 11 types of remote command options that
   the host router can send in a LEX_RCMD_REQUEST packet to the LAN
   extension interface unit. The LAN extension interface unit responds
   to a LEX_RCMD_REQUEST packet with a LEX_RCMD_ACK, LEX_RCMD_NAK, or
   LEX_RCMD_REJ packet.

   Frame Format

   Figure 5 shows a summary of the frame format for a remote command
   options packet. These fields are transmitted from left to right.

               Figure 5 Remote Command Options Frame Format

                        PPP Header
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|    Address    |     Control   |          Protocol Type        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     (1 octet)          (1)                      (2)

                  LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|     Code      |   Identifier  |             Length            |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     (1 octet)          (1)                      (2)







Chapman, et al               Informational                     [Page 14]

RFC 1841           LAN Extension Interface Protocol       September 1995


               LAN Extension Interface Remote Command Options
<--------------------------------
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|  Option-Type  |  Option-Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     (1 octet)          (1)

                 ---------------------------------------------->
                 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
                 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                          Option-Length        |  Option-Data  |
                 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                (2)

   Address

   This PPP-specified field is a single octet and contains the binary
   sequence 11111111 (hexadecimal 0xFF), the All-Stations address. PPP
   does not assign individual station addresses. The All-Stations
   address must be recognized and received by all devices. For more
   information on this field, refer to "The Point-to-Point Protocol
   (PPP) for the Transmission of Multi-protocol Datagrams over Point-
   to-Point Links." (References, [1])

   Control

   This PPP-specified field is a single octet and contains the binary
   sequence 00000011 (hexadecimal 0x03), the Unnumbered Information (UI)
   command with the P/F bit set to zero.

   For more information on this field, refer to "The Point-to-Point
   Protocol (PPP) for the Transmission of Multi-protocol Datagrams over
   Point-to Point Links." (References, [1])

   Note:  Hereafter the Address and Control fields will be represented
   together as a 2-octet field containing "0xFF03".

   Protocol-Type

   The Protocol-Type field is two octets and contains the IETF-assigned
   protocol type value. Valid LAN extension interface protocol type
   values follow:

      *  0x8041 (for control packets)
      *  0x0041 (for data packets)





Chapman, et al               Informational                     [Page 15]

RFC 1841           LAN Extension Interface Protocol       September 1995


   Because the remote command options packet encapsulates LAN extension
   interface control data, the valid value for this field is 0x8041.

   Code

   The Code field is one octet and identifies the type of PPP-LEX
   packet. Valid values are as follows:

      *  0x40 - LEX_RCMD_REQUEST packet
      *  0x41 - LEX_RCMD_ ACK packet
      *  0x42 - LEX_RCMD_NAK packet
      *  0x43 - LEX_RCMD_REJ packet

   The host router sends the LEX_RCMD_REQUEST packet, and the LAN
   extension interface unit sends the LEX_RCMD_ACK, LEX_RCMD_NAK, and
   LEX_RCMD_REJ packets.

   Identifier

   The Identifier field is one octet and contains a randomly generated
   value. The value aids matching requests and replies. It is
   recommended that a non-zero value be used for the identifier. That
   is, zero could be used in the future for unsolicited messages from
   the LAN extension interface unit. Valid values are 0x01-0xFF.

   Length

   The Length field is two octets and indicates the length in octets of
   the entire packet, including the Code, Identifier, Length, and remote
   command options fields.

   Option-Type

   The Option-Type field is one octet and identifies the remote command
   option being transmitted. Valid values are as follows:

      *  0x01 - Filter Protocol Type
      *  0x02 - Filter MAC Address
      *  0x03 - Set Priority
      *  0x04 - Disable LAN Extension Ethernet Interface
      *  0x05 - Enable LAN Extension Ethernet Interface
      *  0x06 - Reboot LAN Extension Interface Unit
      *  0x07 - Request Statistics
      *  0x08 - Download Request
      *  0x09 - Download Data
      *  0x0A - Download Status
      *  0x0B- Inventory Request




Chapman, et al               Informational                     [Page 16]

RFC 1841           LAN Extension Interface Protocol       September 1995


   Each remote command option is discussed in detail in its own section
   later in this document.

   Option-Flags

   This field is one octet and further specifies the remote command
   option, containing specific actions that must be followed.

   Option-Length

   The Option-Length field is two octets and specifies the length in
   octets of the remote command option fields, including the Option-
   Type, Option-Flags, Option-Length, and Option-Data fields.

   Option-Data

   Option-Data field contains data relating to the remote command option
   specified in the Option-Type field.

2.3 Conditions for Sending PPP-LEX Packet

   This section describes the general conditions under which PPP-LEX
   packet types are sent. For specific information by remote command,
   refer to the appropriate remote command section later in this
   document.

   LEX RCMD_REQUEST Packet

   The host router sends LEX_RCMD_REQUEST packets to the LAN extension
   interface unit to initiate a remote command request. Until the host
   router receives a LEX_RCMD_ACK, LEX_RCMD_NAK, or LEX_RCMD_REJ packet
   from the LAN extension interface unit, the host router continues to
   send the LEX_RCMD_REQUEST packet a default number of times, at which
   point the host router times out.

   LEX_RCMD_ACK Packet

   The LAN extension interface unit responds to a LEX_RCMD_REQUEST
   packet with a LEX_RCMD_ACK packet when it correctly receives the
   request and is able to perform the request.

   LEX RCMD_NAK Packet

   The LAN extension interface unit responds to a LEX_RCMD_REQUEST
   packet with a LEX_RCMD_NAK packet when the LAN extension interface
   unit recognizes all the elements of the remote command option, but
   some elements are not acceptable. Upon receipt of a LEX_RCMD_NAK
   packet, the host router immediately stops sending the request.



Chapman, et al               Informational                     [Page 17]

RFC 1841           LAN Extension Interface Protocol       September 1995


   LEX RCMD_REJ Packet

   The LAN extension interface unit responds to a LEX_RCMD_REQUEST
   packet with a LEX_RCMD_REJ packet when the Option-Type value in the
   request packet is invalid. Invalid Option-Type values are those less
   than 0x01 or greater than 0x0B. Currently, this is the only condition
   under which the LAN extension interface unit sends a LEX_RCMD_REJ
   packet. Upon receipt of a LEX_RCMD_REJ packet, the host router
   immediately stops sending the request.

   The following sections detail each of the 11 remote command options.
   The sections provide a general description of the option and then
   specify the option's Option-Type, Option-Flags, Option-Length, and
   Option-Data fields. In addition, the sections describe the return
   messages from the LAN extension interface unit.

3.0 Filter Protocol Type

   The host router sends a LEX_RCMD_REQUEST packet with an Option-Type
   of 0x01 to the LAN extension interface unit to configure the LAN
   extension interface unit to filter inbound packets by protocol type.
   A protocol type filter determines whether or not the LAN extension
   interface unit forwards packets of a specific protocol type to the
   host router. A protocol type filter consists of a 16-bit value, 16-
   bit mask, and a permit or deny field. (See the "Option-Data Field
   Descriptions" section for more information on these filter fields.)

   A LEX_RCMD_REQUEST packet can contain 0 to 200 (depending on MTU
   size) protocol type filters. When a LEX_RCMD_REQUEST packet contains
   multiple filters, they are concatenated.

   The LAN extension interface unit applies the protocol type filters to
   each inbound packet's protocol type field in the order in which the
   filters exist in the filter table. A packet must be permitted by one
   of the filters before the LAN extension interface unit can forward
   the packet across the serial link.

   The following example is a filtering algorithm:

   if (protocol_type_field & (~filter_mask)) == filter_value)
    if (permit/deny_field == PERMIT) <forward packet on serial LAN>
   else <DROP PACKET>

   The protocol type filter should also be applied to the DIX type code
   field of Ethernet II frames as well as to IEEE 802.2 SNAP packets.






Chapman, et al               Informational                     [Page 18]

RFC 1841           LAN Extension Interface Protocol       September 1995


3.1 LEX RCMD_REQUEST-Filter Protocol Type

   Figure 6 shows a frame format summary of a LEX_RCMD_REQUEST packet
   for the Filter Protocol Type remote command option. The host router
   transmits the fields from left to right.

   Figure 6 LEX_RCMD_REQUEST Packet Frame Format - Filter Protocol Type

                              PPP Header
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|              0xFF03           |          Protocol-Type        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              (2 octets)                         (2)

                LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      Code     |   Identifier  |             Length            |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         (1)            (1)                    (2)

                   LAN Extension Interface Remote Command Options
<--------------------------------
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|  Option-Type  |  Option-Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         (1)            (1)

                 ---------------------------------------------->
                 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
                -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                        Option-Length          |  Option-Data  |
                -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                              (2)

   Where the Option-Data field contains the following fields:

 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|         Value (16 bits)       |          Value (16 bits)      |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|     Permit/Deny (16 bits)     |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+




Chapman, et al               Informational                     [Page 19]

RFC 1841           LAN Extension Interface Protocol       September 1995


   Summary Field Descriptions

   For a complete description of the fields in the PPP Header, the LAN
   Extension Interface Protocol Header, and the LAN Extension Interface
   Remote Command Options, refer to the "Remote Command Options" section
   earlier in this document. The following table provides a summary of
   these fields when sending a LEX_RCMD_REQUEST packet that configures
   the LAN extension interface unit to filter by protocol type.

   Table 2  Field Values for LEX_RCMD_REQUEST Packet-Filter Protocol Type
   Field               Value
   Address/Control     0xFF03 (Broadcast address/Unnumbered
                       information)
   Protocol-Type       0x8041 (Control packet)
   Code                0x40 (LEX_RCMD_REQUEST packet)
   Identifier          Valid values: 0x01-0xFF
   Length              Minimum length = 12 octets
                       Maximum length = 1212 octets
   Option-Type         0x01 (Filter Protocol Type)
   Option-Flags        None
   Option-Length       Minimum length = 4 octets
                       Maximum length = 1204 octets
   Option-Data         Zero or more filters to be applied at
                       the LAN extension interface unit. See the
                       following "Option-Data Field Descriptions"
                       for details.

   Option-Data Field Descriptions

   The following three Option-Data fields are used in conjunction to
   specify a protocol type filter:

   *  Value

   The Value field contains a 16-bit value that is any Ethernet type
   code. Refer to the "Assigned Numbers" RFC for valid Ethernet type
   codes. (References, [4]).

   *  Mask

   The Mask field contains a 16-bit "wild card" mask. That is, this
   field contains a 16-bit number whose ones bits correspond to the type
   code bits to be ignored during the comparison. Thus, the mask
   excludes bits from the comparison in the protocol type filter.







Chapman, et al               Informational                     [Page 20]

RFC 1841           LAN Extension Interface Protocol       September 1995


   *  Permit/Deny

   The Permit/Deny field determines whether a protocol type filter
   permits or denies inbound frames to pass to the host router. A permit
   value is a non-zero value that allows frames of a specific protocol
   type to pass to the host router. A deny value is a zero value that
   does not allow frames of a specific protocol type to pass to the host
   router.

   Implementation Notes

   Each LEX_RCMD_REQUEST packet is a complete specification of all
   protocol type filters and replaces any previously established
   filters.

   Note the following special cases:

   *  A LEX_RCMD_REQUEST packet with an Option-Length field equal
      to four (without any filter entries) instructs the LAN extension
      interface unit to turn off protocol type filtering. All MAC
      protocol types are forwarded.

   *  A LEX_RCMD_REQUEST packet with a filter entry of 0x0000 in the
      Value field, 0xFFFF in the Mask field, and a positive value in the
      Permit/Deny field means that if previous filters in the filter list
      do not permit the inbound packet then this filter entry will. This
      filter entry is typically the last filter in a list of filters
      contained within the Option-Data field.

   *  A LEX_RCMD_REQUEST packet with a filter entry of 0x0000 in the
      Value field, 0xFFFF in the Mask field, and a zero in the
      Permit/Deny field, means that the LAN extension interface unit must
      deny all protocol types. This filter is typically the last filter in
      a list of filters contained within the Option-Data field.

3.2 Response Packets - Filter Protocol Type

   The following packets are valid responses to the Filter Protocol Type
   LEX_RCMD_REQUEST packet:

   *  LEX_RCMD_ACK - Filter Protocol Type

   The LAN extension interface unit sends a LEX_RCMD_ACK packet in
   response to the Filter Protocol Type LEX_RCMD_REQUEST packet when the
   LAN extension interface unit correctly receives the Filter Protocol
   Type remote command option and applies all filter entries to its
   filter table. All filter entries are returned to the host router in
   the LEX_RCMD_ACK packet.



Chapman, et al               Informational                     [Page 21]

RFC 1841           LAN Extension Interface Protocol       September 1995


   *  LEX_RCMD_NAK - Filter Protocol Type

   The LAN extension interface unit sends a LEX_RCMD_NAK packet in
   response to the Filter Protocol Type LEX_RCMD_REQUEST packet when the
   request contains an incorrect number of bytes in the filter or when
   there are no more filter entries available. The LAN extension
   interface unit continues to use the previous filter table (that is,
   the filter table that existed prior to the receipt of the request).
   The host router should signal an error to the user/network
   administrator. All filter entries are returned to the host router in
   the LEX_RCMD_NAK packet.

   *  LEX_RCMD-REJ - Filter Protocol Type

   See the "Conditions for Sending PPP-LEX Packets" section earlier in
   this document for more information on this packet type.

   Table 3 summarizes the field values of Filter Protocol Type
   LEX_RCMD_ACK, LEX_RCMD_NAK, and LEX_RCMD_REJ packets.

     Table 3  Field Values for Response Packets - Filter Protocol Type

   Field                Value
   Address/Control      0xFF03 (Broadcast address/Unnumbered
                        information)
   Protocol-Type        0x8041 (Control packet)
   Code                 Valid values:
                        * 0x41 (LEX_RCMD_ACK packet)
                        * 0x42 (LEX_RCMD_NAK packet)
                        * 0x43 (LEX_RCMD_REJ packet)
   Identifier           The same value as that sent by the
                        LEX_RCMD_REQUEST packet
   Length               The same value as that sent by the
                        LEX_RCMD_REQUEST packet
   Option-Type          0x01 (Filter Protocol Type)
   Option-Flags         None
   Option-Length        The same value as that sent by the
                        LEX_RCMD_REQUEST packet
   Option-Data          The filter entries sent in the
                        LEX_RCMD_REQUEST packet

4.0 Filter MAC Address

   The host router sends a LEX_RCMD_REQUEST packet with an Option-Type
   of 0x02 to the LAN extension interface unit to configure the LAN
   extension interface unit to filter inbound packets by source MAC
   address. A MAC address filter determines whether or not the LAN
   extension interface unit forwards packets with a specific source MAC



Chapman, et al               Informational                     [Page 22]

RFC 1841           LAN Extension Interface Protocol       September 1995


   address to the host router. A MAC address filter consists of MAC
   address, a MAC address mask, and a permit or deny field. (See the
   "Option-Data Field Descriptions" section later in this section for
   more information on these filter fields.)

   A LEX_RCMD_REQUEST packet can contain 0 to 100 (depending on MTU
   size) MAC address filters. When a LEX_RCMD_REQUEST packet contains
   multiple filters, they are concatenated.

   The LAN extension interface unit applies MAC address filters to each
   inbound packet's source MAC address in the order in which the filters
   exist in the filter entry list. A packet must be permitted by one of
   the filters before the LAN extension interface unit can forward the
   packet across the serial link.

4.1 LEX RCMD_REQUEST - Filter MAC Address

   Figure 7 shows a frame format summary of a LEX_RCMD_REQUEST packet
   for the Filter MAC Address remote command option. The host router
   transmits the fields from left to right.

    Figure 7 LEX_RCMD_REQUEST Packet Frame Format - Filter MAC Address

                            PPP Header
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|              0xFF03           |          Protocol-Type        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              (2 octets)                         (2)

                LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      Code     |   Identifier  |              Length           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         (1)            (1)                     (2)













Chapman, et al               Informational                     [Page 23]

RFC 1841           LAN Extension Interface Protocol       September 1995


                   LAN Extension Interface Remote Command Options
<--------------------------------
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|  Option-Type  |  Option-Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         (1)            (1)

                 ---------------------------------------------->
                 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
                 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
                         Option-Length          |  Option-Data |
                 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
                               (2)

Where the Option-Data field contains the following fields:

 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                      MAC Address (48 bits)....
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                      MAC Address Mask (48 bits)....
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      Permit/Deny (16 bits)    |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Summary Field Descriptions

   For a complete description of the fields in the PPP Header, the LAN
   Extension Interface Protocol Header, and the LAN Extension Interface
   Remote Command Options, refer to the "Remote Command Options" section
   earlier in this document. Table 4 provides a summary of these fields
   when sending a LEX_RCMD_REQUEST packet that configures the LAN
   extension interface unit to filter by source MAC address.

   Table 4  Field Values for LEX_RCMD_REQUEST Packet - Filter MAC Address

   Field                Value
   Address/Control      0xFF03 (Broadcast address/Unnumbered
                        information)
   Protocol-Type        0x8041 (Control packet)
   Code                 0x40 (LEX_RCMD_REQUEST packet)
   Identifier           Valid values: 0x01-0xFF
   Length               Minimum length = 12 octets
                        Maximum length = 1412 octets
   Option-Type          0x02 (Filter MAC Address)
   Option-Flags         None
   Option-Length        Minimum length = 4 octets



Chapman, et al               Informational                     [Page 24]

RFC 1841           LAN Extension Interface Protocol       September 1995


                        Maximum length = 1404 octets
   Option-Data          Zero or more filters to be applied at the
                        LAN extension interface unit. See the
                        following "Option-Data Field Description
                        section for details.

   Option-Data Field Descriptions

   The following three Option-Data fields are used in conjunction to
   specify a MAC address filter:

   *  MAC Address

   The MAC Address field contains a 48-bit IEEE 802.3 MAC address in
   canonical format.

   *  MAC Address Mask

   The MAC Address Mask field contains a "wild card" mask. The mask is a
   48-bit hexadecimal number whose ones bits correspond to the MAC
   address bits to be ignored during the comparison. The mask excludes
   bits from the comparison in the MAC address filter.

   *  Permit/Deny

   The Permit/Deny field determines whether or not a MAC address filter
   permits or denies inbound frames of a specific MAC address to pass to
   the host router. A permit value is a non-zero value that allows
   frames of a specific MAC address to pass to the host router. A deny
   value is a zero value that does not allow frames of a specific MAC
   address to pass to the host router.

   Implementation Notes

   Each LEX_RCMD_REQUEST packet is a complete specification of all MAC
   address filters and replaces any previously established filters.

   A LEX_RCMD_REQUEST packet with an Option-Length field equal to four
   (without any filter entries) instructs the LAN extension interface
   unit to turn off filtering. All MAC addresses, except local
   destination addresses cached in the self-learning filter, are
   forwarded.

4.2 Response Packets - Filter MAC Address

   The following packets are valid responses to the Filter MAC Address
   LEX_RCMD_REQUEST packet:




Chapman, et al               Informational                     [Page 25]

RFC 1841           LAN Extension Interface Protocol       September 1995


   *  LEX_RCMD_ACK - Filter MAC Address

   The LAN extension interface unit sends a LEX_RCMD_ACK packet in
   response to a Filter MAC Address LEX_RCMD_REQUEST packet when the LAN
   extension interface unit correctly receives the Filter MAC Address
   remote command option and applies the entries to its filter table.
   All MAC address filter entries are returned in the LEX_RCMD_ACK
   packet.

   *  LEX_RCMD_NAK - Filter MAC Address

   The LAN extension interface unit sends a LEX_RCMD_NAK packet in
   response to the Filter MAC Address LEX_RCMD_REQUEST packet when the
   request contains an incorrect number of bytes in the filter or when
   there are no more filter entries available. The LAN extension
   interface unit continues to use the previous filter table (that is,
   the filter table that existed prior to the receipt of the request).
   The host router should signal an error to the user/network
   administrator. All filter entries are returned in the LEX_RCMD_NAK
   packet.

   *  LEX_RCMD-REJ - Filter MAC Address

   See the "Conditions for Sending PPP-LEX Packets" section earlier in
   this document for more information on this packet type.

   Table 5 summarizes the field values of Filter MAC Address
   LEX_RCMD_ACK, LEX_RCMD_NAK, and LEX_RCMD_REJ packets.

      Table 5  Field Values for Response Packets - Filter MAC Address

   Field                Value
   Address/Control      0xFF03 (Broadcast address/Unnumbered
                        information)
   Protocol-Type        0x8041 (Control packet)
   Code                 Valid values:
                        * 0x41 (LEX_RCMD_ACK packet)
                        * 0x42 (LEX_RCMD_NAK packet)
                        * 0x43 (LEX_RCMD_REJ packet)
   Identifier           The same value as that sent by the
                        LEX_RCMD_REQUEST packet
   Length               The same value as that sent by the
                        LEX_RCMD_REQUEST packet
   Option-Type          0x02 (Filter MAC Address)
   Option-Flags         None
   Option-Length        The same value as that sent by the
                        LEX_RCMD_REQUEST packet
   Option-Data          The filter entries sent in the



Chapman, et al               Informational                     [Page 26]

RFC 1841           LAN Extension Interface Protocol       September 1995


                        LEX_RCMD_REQUEST packet

5.0 Set Priority

   The host router sends a LEX_RCMD_ REQUEST with an Option-Type of 0x03
   to the LAN extension interface unit to establish the sending priority
   of different protocol type packets from the LAN extension interface
   unit to host router. There are four levels of priority:

      *  High
      *  Medium
      *  Normal
      *  Low

   Packets are classified according to protocol type and then are queued
   to one of four output queues on the LAN extension interface unit that
   correspond to the above priority levels. When the LAN extension
   interface unit is ready to transmit a packet, it scans the priority
   queues in order, from the highest to lowest, to find the highest
   priority packet.

5.1 LEX RCMD_REQUEST - Set Priority

   To establish priority queues for each protocol type, the host router
   sends a Set Priority LEX_RCMD_REQUEST packet. Figure 8 shows a frame
   format summary of such a LEX_RCMD_REQUEST packet. The host router
   transmits the fields from left to right.

       Figure 8 LEX_RCMD_REQUEST Packet Frame Format - Set Priority

                            PPP Header
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|              0xFF03           |          Protocol-Type        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              (2 octets)                         (2)

                LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      Code     |   Identifier  |              Length           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         (1)            (1)                     (2)






Chapman, et al               Informational                     [Page 27]

RFC 1841           LAN Extension Interface Protocol       September 1995


                   LAN Extension Interface Remote Command Options
<--------------------------------
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|  Option-Type  |  Option-Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         (1)            (1)

                 ---------------------------------------------->
                 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
                 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
                         Option-Length          |  Option-Data |
                 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
                               (2)

   Where the Option-Data field contains the following fields:

 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|     Protocol Type (16 bits)   |    Protocol Value (16 bits)   |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Summary Field Descriptions

   For a complete descriptions of the fields in the PPP Header, the LAN
   Extension Interface Protocol Header, and the LAN Extension Interface
   Remote Command Options, refer to the "Remote Command Options" section
   earlier in this document. The following table provides a summary of
   these fields when sending a LEX_RCMD_REQUEST packet that sets
   priority queuing.

     Table 6  Field Values for LEX_RCMD_REQUEST Packet - Set Priority

   Field                Value
   Address/Control      0xFF03 (Broadcast address/Unnumbered
                        information)
   Protocol-Type        0x8041 (Control packet)
   Code                 0x40 (LEX_RCMD_REQUEST packet)
   Identifier           Valid values: 0x01-0xFF
   Length               Minimum length = 12 octets
                        Maximum length = 1028 octets
   Option-Type          0x03 (Set Priority)
   Option-Flags         None
   Option-Length        Minimum length = 4 octets
                        Maximum length = 1020 octets
   Option-Data          Protocol Type and Priority Value. See the
                        following "Option-Data Field Description"
                        section for details.



Chapman, et al               Informational                     [Page 28]

RFC 1841           LAN Extension Interface Protocol       September 1995


   Option-Data Field Descriptions

   The following Option-Data fields set the priority queuing of
   different protocol type packets.

   *  Protocol Type

   The Protocol Type field contains a 16-bit number that is any Ethernet
   type code. See the most recent "Assigned Numbers" RFC for the correct
   Ethernet type code.

   *  Priority Value

   The Priority Value field specifies the priority queue for the
   protocol type specified in the Protocol Type field. Valid values are
   as follows:

      - 0 - High priority queue
      - 1 - Medium priority queue
      - 2 - Normal priority queue
      - 3 - Low priority queue

   Sending a LEX_RCMD_REQUEST packet with an Option-Length of four (no
   priority entries) disables priority queuing. When disabled, the LAN
   extension interface unit transfers all packets at a normal (2)
   priority level. When a new priority is specified, it overwrites the
   previous setting.

5.2 Response Packets - Set Priority

   The following packets are valid responses to the Set Priority

   LEX_RCMD_REQUEST packet.

   *  LEX_RCMD_ACK - Set Priority

   See the "Conditions for Sending PPP-LEX Packets" section earlier in
   this document for more information on this packet type.

   *  LEX_RCMD_NAK - Set Priority

   The LAN extension interface unit sends a LEX_RCMD_NAK packet in
   response to the Set Priority LEX_RCMD_REQUEST packet when the request
   contains an incorrect number of bytes in the message, when necessary
   resources are not available, or when the specified priority is
   invalid.





Chapman, et al               Informational                     [Page 29]

RFC 1841           LAN Extension Interface Protocol       September 1995


   *  LEX_RCMD-REJ - Set Priority

   See the "Conditions for Sending PPP-LEX Packets" section earlier in
   this document for more information on this packet type.  Table 7
   summarizes the field values of Set Priority LEX_RCMD_ACK,
   LEX_RCMD_NAK, and LEX_RCMD_REJ packets.

         Table 7  Field Values for Response Packets - Set Priority

   Field                Value
   Address/Control      0xFF03 (Broadcast address/Unnumbered
                        information)
   Protocol-Type        0x8041 (Control packet)
   Code                 Valid values:
                        * 0x41 (LEX_RCMD_ACK packet)
                        * 0x42 (LEX_RCMD_NAK packet)
                        * 0x43 (LEX_RCMD_REJ packet)
   Identifier           A randomly generated value that aids in
                        matching requests with replies
   Length               Minimum length = 12 octets
                        Maximum length = 1028 octets
   Option-Type          0x03 (Set Priority)
   Option-Flags         None
   Option-Length        Minimum length = 4 octets
                        Maximum length = 1020 octets
   Option-Data          Protocol Type and Priority Value sent
                        in the LEX_RCMD_REQUEST packet

6.0 Disable LAN Extension Ethernet Interface

   The host router sends a LEX_RCMD_ REQUEST with an Option-Type of 0x04
   to the LAN extension interface unit to disable the LAN extension
   Ethernet interface. This remote command option stops data traffic
   from the LAN extension interface unit to the host router for
   troubleshooting or for reconfiguring the LAN extension interface
   unit. This remote command option only affects data traffic. PPP-LEX
   control packets can still be transferred over the serial link.














Chapman, et al               Informational                     [Page 30]

RFC 1841           LAN Extension Interface Protocol       September 1995


6.1 LEX RCMD_REQUEST - Disable LAN Extension Ethernet Interface

   Figure 9 shows a frame format summary of a LEX_RCMD_REQUEST packet
   for the Disable LAN Extension Ethernet Interface remote command
   option. The host router transmits the fields from left to right.

             Figure 9  LEX_RCMD_REQUEST Packet Frame Format -
                 Disable LAN Extension Ethernet Interface

                            PPP Header
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|              0xFF03           |          Protocol-Type        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              (2 octets)                         (2)

                LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      Code     |   Identifier  |              Length           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         (1)            (1)                     (2)

            LAN Extension Interface Remote Command Options
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|  Option-Type  |  Option-Flags |        Option-Length          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         (1)            (1)                    (2)

   Summary Field Descriptions

   For complete descriptions of the fields in the PPP Header, the LAN
   Extension Interface Protocol Header, and the LAN Extension Interface
   Remote Command Option, refer to the "Remote Command Options" section
   earlier in this document. The following table provides a summary of
   these fields when sending a LEX_RCMD_REQUEST packet that disables the
   LAN extension interface unit.










Chapman, et al               Informational                     [Page 31]

RFC 1841           LAN Extension Interface Protocol       September 1995


           Table 8  Field Values for LEX_RCMD_REQUEST Packet -
                 Disable LAN Extension Ethernet Interface

   Field                Value
   Address/Control      0xFF03 (Broadcast address/Unnumbered
                        information)
   Protocol-Type        0x8041 (Control packet)
   Code                 0x40 (LEX_RCMD_REQUEST packet)
   Identifier           Valid values: 0x01-0xFF
   Length               12 octets
   Option-Type          0x04 (Disable LAN Extension Ethernet
                        Interface)
   Option-Flags         None
   Option-Length        4 octets
   Option-Data          None

6.2 Response Packets - Disable LAN Extension Ethernet Interface

   LEX_RCMD_ACK, LEX_RCMD_NAK, and LEX_RCMD-REJ packets are valid
   responses to the Disable LAN Extension Ethernet Interface
   LEX_RCMD_REQUEST packet. Refer to the "Conditions for Sending PPP-LEX
   Packets" section earlier in this document for more information on
   when the LAN extension interface unit sends each of these response
   packets. Note that the LAN extension interface unit sends the
   LEX_RCMD_ACK packet after shutting down the interface.

   Table 9 summarizes the field values of Disable LAN Extension Ethernet
   Interface LEX_RCMD_ACK, LEX_RCMD_NAK, and LEX_RCMD_REJ packets.

               Table 9  Field Values for Response Packets -
                 Disable LAN Extension Ethernet Interface

   Field                Value
   Address/Control      0xFF03 (Broadcast address/Unnumbered
                        information)
   Protocol-Type        0x8041 (Control packet)
   Code                 Valid values:
                        * 0x41 (LEX_RCMD_ACK packet)
                        * 0x42 (LEX_RCMD_NAK packet)
                        * 0x43 (LEX_RCMD_REJ packet)
   Identifier           The same value as that sent by the
                        LEX_RCMD_REQUEST packet
   Length               12 octets
   Option-Type          0x04 (Disable LAN Extension Ethernet
                        Interface)
   Option-Flags         None
   Option-Length        4 octets
   Option-Data          None



Chapman, et al               Informational                     [Page 32]

RFC 1841           LAN Extension Interface Protocol       September 1995


7.0 Enable LAN Extension Ethernet Interface

   The host router sends a LEX_RCMD_ REQUEST with an Option-Type of 0x05
   to the LAN extension interface unit to enable the LAN extension
   Ethernet interface. This remote command option allows LAN traffic to
   flow into the LAN extension interface unit after the interface has
   been disabled.

7.1 LEX RCMD_REQUEST - Enable LAN Extension Ethernet Interface

   Figure 10 shows a frame format summary of a LEX_RCMD_REQUEST packet
   for an Enable LAN Extension Ethernet Interface remote command option.
   The host router transmits the fields from left to right.

   Figure 10 LEX_RCMD_REQUEST Packet Frame Format - Enable LAN Extension
   Ethernet Interface

                            PPP Header
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|              0xFF03           |          Protocol-Type        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              (2 octets)                         (2)

                LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      Code     |   Identifier  |              Length           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         (1)            (1)                     (2)

            LAN Extension Interface Remote Command Options
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|  Option-Type  |  Option-Flags |        Option-Length          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         (1)            (1)                    (2)

   Summary Field Descriptions

   For complete descriptions of the fields in the PPP Header, the LAN
   Extension Interface Protocol Header, and the LAN Extension Interface
   Remote Command Option, refer to the "Remote Command Options" section
   earlier in this document. Table 10 provides a summary of these fields
   when sending a LEX_RCMD_REQUEST packet that enables the LAN extension



Chapman, et al               Informational                     [Page 33]

RFC 1841           LAN Extension Interface Protocol       September 1995


   Ethernet interface.

           Table 10  Field Values for LEX_RCMD_REQUEST Packet -
                  Enable LAN Extension Ethernet Interface

   Field                Value
   Address/Control      0xFF03 (Broadcast address/Unnumbered
                        information)
   Protocol-Type        0x8041 (Control packet)
   Code                 0x40 (LEX_RCMD_REQUEST packet)
   Identifier           Valid values: 0x01-0xFF
   Length               12octets
   Option-Type          0x05 (Enable LAN Extension Ethernet
                        Interface)
   Option-Flags         None
   Option-Length        4 octets
   Option-Data          None

7.2 Response Packets - Enable LAN Extension Ethernet Interface

   LEX_RCMD_ACK, LEX_RCMD_NAK, and LEX_RCMD-REJ packets are valid
   responses to the Enable LAN Extension Ethernet Interface
   LEX_RCMD_REQUEST packet. Refer to the "Conditions for Sending PPP-LEX
   Packets" section earlier in this document for more information on
   when the LAN extension interface unit sends each of these response
   packets. Note that the LAN extension interface unit sends the
   LEX_RCMD_ACK packet after enabling the interface.

   The frame format of the response packets mirrors that of the request.
   Table 11 summarizes the field values of Enable LAN Extension Ethernet
   Interface LEX_RCMD_ACK, LEX_RCMD_NAK, and LEX_RCMD_REJ packets.

              Table 11  Field Values for Response Packets -
                  Enable LAN Extension Ethernet Interface

   Field                Value
   Address/Control      0xFF03 (Broadcast address/Unnumbered
                        information)
   Protocol-Type        0x8041 (Control packet)
   Code                 Valid values:
                        * 0x41 (LEX_RCMD_ACK packet)
                        * 0x42 (LEX_RCMD_NAK packet)
                        * 0x43 (LEX_RCMD_REJ packet)
   Identifier           The same value as that sent by the
                        LEX_RCMD_REQUEST packet
   Length               12 octets
   Option-Type          0x05 (Enable LAN Extension Ethernet
                        Interface)



Chapman, et al               Informational                     [Page 34]

RFC 1841           LAN Extension Interface Protocol       September 1995


   Option-Flags         None
   Option-Length        4 octets
   Option-Data          None

8.0 Reboot LAN Extension Interface Unit

   The host router sends a LEX_RCMD_REQUEST packet with an Option-Type
   of 0x06 to the LAN extension interface unit to cause the LAN
   extension interface unit to reboot itself. The Option-Flags field
   specifies the boot mode for the LAN extension interface unit. There
   are two boot modes:

   * The first boot mode (Option-Flag 0x00) is the default. The
     default boot mode causes the LAN extension interface unit to
     check for a valid Flash image and to boot from it if it exists.
     If a valid Flash image does not exist, the default boot mode
     causes the LAN extension interface unit to boot from the PROM
     image. Similarly, if the Flash image is bad, then the LAN
     extension interface unit recovers by booting from the PROM image.

   * The second boot mode (Option-Flag 0x01) forces the LAN extension
     interface unit to boot from the PROM image.

8.1 LEX RCMD_REQUEST - Reboot LAN Extension  Interface Unit

   Figure 11 shows a frame format summary of a LEX_RCMD_REQUEST packet
   for a Reboot LAN Extension Interface Unit remote command option. The
   host router transmits the fields from left to right.

             Figure 11 LEX_RCMD_REQUEST Packet Frame Format -
                    Reboot LAN Extension Interface Unit

                            PPP Header
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|              0xFF03           |          Protocol-Type        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              (2 octets)                         (2)

                LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      Code     |   Identifier  |            Length             |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         (1)            (1)                   (2)




Chapman, et al               Informational                     [Page 35]

RFC 1841           LAN Extension Interface Protocol       September 1995


            LAN Extension Interface Remote Command Options
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|  Option-Type  |  Option-Flags |        Option-Length          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         (1)            (1)                    (2)

   Summary Field Descriptions

   For complete descriptions of the fields in the PPP Header, the LAN
   Extension Interface Protocol Header, and the LAN Extension Interface
   Remote Command Option, refer to the "Remote Command Options" section
   earlier in this document. Table 12 provides a summary of these fields
   when sending a LEX_RCMD_REQUEST packet that instructs the LAN
   extension interface unit to reboot.

           Table 12  Field Values for LEX_RCMD_REQUEST Packet -
                    Reboot LAN Extension Interface Unit

   Field                Value
   Address/Control      0xFF03 (Broadcast address/Unnumbered
                        information)
   Protocol-Type        0x8041 (Control packet)
   Code                 0x40 (LEX_RCMD_REQUEST packet)
   Identifier           Valid values: 0x01-0xFF
   Length               12 octets
   Option-Type          0x06 (Reboot LAN Extension Interface Unit)
   Option-Flags         Valid values:
                        * 0x00 - Reboot from Flash image if it
                          exists. If not, reboot from PROM. (This
                          value does not force the LAN extension
                          interface unit to reboot from PROM.)
                        * 0x01 - Reboot from PROM explicitly.
   Option-Length        4 octets
   Option-Data          None

8.2 Response Packets - Reboot LAN Extension Interface Unit

   LEX_RCMD_ACK, LEX_RCMD_NAK, and LEX_RCMD-REJ packets are valid
   responses to the Reboot LAN Extension Interface Unit LEX_RCMD_REQUEST
   packet. Refer to the "Conditions for Sending PPP-LEX Packets" section
   earlier in this document for more information on when the LAN
   extension interface unit sends each of these response packets. Note
   that the LAN extension interface unit reboots after sending the
   LEX_RCMD_ACK packet.





Chapman, et al               Informational                     [Page 36]

RFC 1841           LAN Extension Interface Protocol       September 1995


   The frame format for the response packets mirrors that of the
   request. Table 13 summarizes the field values for Reboot LAN
   Extension Interface Unit LEX_RCMD_ACK, LEX_RCMD_NAK, and LEX_RCMD_REJ
   packets.

              Table 13  Field Values for Response Packets -
                    Reboot LAN Extension Interface Unit

   Field                Value
   Address/Control      0xFF03 (Broadcast address/Unnumbered
                        information)
   Protocol-Type        0x8041 (Control packet)
   Code                 Valid values:
                        * 0x41 (LEX_RCMD_ACK packet)
                        * 0x42 (LEX_RCMD_NAK packet)
                        * 0x43 (LEX_RCMD_REJ packet)
   Identifier           The same value as that sent in the
                        LEX_RCMD_REQUEST packet
   Length               12 octets
   Option-Type          0x06 (Reboot LAN Extension Interface Unit)
   Option-Flags         Valid values:
                        * 0x00 - Reboot from Flash image if it
                          exists. If not, reboot from PROM. (This
                          value does not force the LAN extension
                          interface unit to reboot from PROM.)
                        * 0x01 - Reboot from PROM explicitly.
   Option-Length        4 octets
   Option-Data          None

9.0 Request Statistics

   The host router issues a LEX_RCMD_REQUEST packet with an Option-Type
   of 0x07 to obtain statistics information from the LAN extension
   interface unit. The host router may want statistics information about
   the following:

      *  Serial interface only
      *  LAN interface only
      *  Both the serial and LAN interfaces

   The host router may also send a Statistics Request LEX_RCMD_REQUEST
   packet to reset statistics in the LAN extension interface unit.

9.1 LEX RCMD_REQUEST - Request Statistics

   Figure 12 shows a summary frame format of a LEX_RCMD_REQUEST packet
   for a Statistics Request remote command option. The host router
   transmits the fields from left to right.



Chapman, et al               Informational                     [Page 37]

RFC 1841           LAN Extension Interface Protocol       September 1995


    Figure 12 LEX_RCMD_REQUEST Packet Frame Format - Request Statistics

                            PPP Header
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|              0xFF03           |          Protocol-Type        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              (2 octets)                         (2)

                LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      Code     |   Identifier  |              Length           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        (1)             (1)                     (2)

            LAN Extension Interface Remote Command Option
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 0 1 2
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|  Option-Type  |  Option-Flags |        Option-Length          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         (1)            (1)                    (2)

Summary Field Descriptions

   For complete descriptions of the fields in the PPP Header, the LAN
   Extension Interface Protocol Header, and the LAN Extension Interface
   Remote Command Option, refer to the "Remote Command Options" section
   earlier in this document. Table 14 provides a summary of these fields
   when sending a LEX_RCMD_REQUEST packet that requests statistics of
   the LAN extension interface unit.

           Table 14  Field Values for LEX_RCMD_REQUEST Packet -
                            Request Statistics

   Field                Value
   Address/Control      0xFF03 (Broadcast address/Unnumbered
                        information)
   Protocol-Type        0x8041 (Control packet)
   Code                 0x40 (LEX_RCMD_REQUEST packet)
   Identifier           Valid values: 0x01-0xFF
   Length               12 octets
   Option-Type          0x07 (Request Statistics)
   Option-Flags         Valid values:
                        * 0x01 - Resets serial statistics in the LAN



Chapman, et al               Informational                     [Page 38]

RFC 1841           LAN Extension Interface Protocol       September 1995


                          extension interface unit
                        * 0x02 - Returns serial statistics from the
                          LAN extension interface unit
                        * 0x04 - Returns LAN statistics from the LAN
                          extension interface unit
                        * 0x08 - Resets LAN statistics in the LAN
                        * extension interface unit
                        If both serial and LAN statistics are
                        desired, the corresponding bits of this
                        field should be set (that is, 0x06). The
                        serial interface statistics appear in the
                        response packet before the LAN statistics.
   Option-Length        4 octets
   Option-Data          None

9.2 LEX RCMD_ACK - Request Statistics

   The normal response to a Statistics Request LEX_RCMD_REQUEST packet
   is a LEX_RCMD_ACK packet. This acknowledgment packet has an Option-
   Type, an Option-Flags, and an Option-Length field followed by one or
   two blocks of statistics data. The value in the Option-Flags field
   indicates whether the packet has one or two blocks of statistics. For
   more information on these values, see the following "Summary Field
   Descriptions" section.

   The frame format for the Statistics Request LEX_RCMD_ACK packet
   follows. The LAN extension interface unit transmits the fields from
   left to right.

      Figure 13 LEX_RCMD_ACK Packet Frame Format - Request Statistics

                            PPP Header
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|              0xFF03           |          Protocol-Type        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              (2 octets)                         (2)

                LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      Code     |   Identifier  |              Length           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        (1)             (1)                     (2)





Chapman, et al               Informational                     [Page 39]

RFC 1841           LAN Extension Interface Protocol       September 1995


            LAN Extension Interface Remote Command Options
<--------------------------------
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|  Option-Type  |  Option-Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         (1)            (1)

                ----------------------------------------------->
                 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
                -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                       Option-Length          |  Option-Data   |
                -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                              (2)

   Where the Option-Data fields contains one or both of the following
   statistics blocks:

   Serial Interface Statistics Block:

                       (32 bits)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Number of Packets Received                 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Number of CRC Erros                        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Number of Framing Errors                   |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Number of Overruns                         |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Number of Packets Dropped                  |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Number of Frame Aborts                     |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Number of Packets in Error                 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Number of Packets Dropped Due to Lack of   |
| Buffer Descriptors                                            |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Time of Last Packet Received               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Average Data Rate                          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Average Packet Rate                        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Number of Octets Received                  |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Number of Packets Dropped Due to No Buffers|



Chapman, et al               Informational                     [Page 40]

RFC 1841           LAN Extension Interface Protocol       September 1995


+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Packets Transmitted             |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Packets with Error Transmissions|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Under-run Errors                |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Packets in Low Priority Queue   |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Size of Low Priority Queue                |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Packets Dropped in Low Priority |
| Queue                                                         |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Packets in Normal Priority Queue|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Size of Normal Priority Queue             |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Packets Dropped in Normal       |
| Priority Queue                                                |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Packets in Medium Priority Queue|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Size of Medium Priority Queue             |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Packets Dropped in              |
| Medium Priority Queue                                         |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Packets in High Priority Queue  |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Size of High Priority Queue               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Packets Dropped in High         |
| Priority Queue                                                |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Time of Last Packet Transmitted           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Carrier Transitions             |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Transmitted Data Rate                     |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Octets Transmitted              |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+






Chapman, et al               Informational                     [Page 41]

RFC 1841           LAN Extension Interface Protocol       September 1995


   Lan Interface Statistics Block:

                        (32 bits)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Number of Packets Received                         |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Number of Packets Received with CRC Errors         |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Number of Packets Received with Framing Errors     |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Number of Overruns                                 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Number of Packets Dropped Due to Congestion        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Number of Frame Aborts                             |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Number of Broadcast Packets Received               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Number of Packets Received with Errors             |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Number of Packets Dropped Due to Lack of Buffer    |
| Descriptors                                                   |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Number of Runts (Too Small Packets) Received       |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Time of Last Packet Received                       |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Average Data Rate                                  |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Average Packet Rate                                |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Number of Octets Received                          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Number of Packets Dropped Due to Lack of Buffers   |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Output, Number of Packets Transmitted                     |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Output, Number of Packets Transmitted with Errors         |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Output, Number of Under-runs                              |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Output, Number of Collisions (Ethernet)                   |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Output, Number of Packets in Queue                        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



Chapman, et al               Informational                     [Page 42]

RFC 1841           LAN Extension Interface Protocol       September 1995


| LAN Output, Queue Size                                        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Output, Number of Packets Dropped in Queue                |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Output, Time of Last Packet Transmitted                   |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Output, Transmit Data Rate                                |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Output, Transmit Packet Rate                              |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Output, Number of Octets Transmitted                      |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN, Number of Interface Resets                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Note:  Counts are cumulative since last counter reset. Time stamps
   are in milliseconds since last given event. Packet rates are in
   packets per second (averaged).

   Summary Field Descriptions

   For complete descriptions of the fields in the PPP Header, the LAN
   Extension Protocol Header, and the LAN Extension Remote Command
   Option, refer to the "Remote Command Options" section earlier in this
   document. The following table provides a summary of these fields for
   a LEX_RCMD_ACK packet that sends statistics to the host router.

    Table 15  Field Values for LEX_RCMD_ACK Packet - Request Statistics

   Field                Value
   Address/Control      0xFF03 (Broadcast address/Unnumbered
                        information)
   Protocol-Type        0x8041 (Control packet)
   Code                 0x41 (LEX_RCMD_ACK packet)
   Identifier           The same value as that sent by the
                        LEX_RCMD_REQUEST packet
   Length               Minimum length = 120 octets
                        Maximum length = 140 octets
   Option-Type          0x07 (Request Statistics)
   Option-Flags         The LAN extension interface unit always sets
                        this field to reflect the actions taken in
                        response to the LEX_RCMD_ACK packet. Valid
                        values:
                        * 0x01 - Reset serial statistics in the LAN
                          extension interface unit
                        * 0x02 - Return serial statistics from the
                          LAN extension interface unit
                        * 0x04 - Return LAN statistics from the LAN



Chapman, et al               Informational                     [Page 43]

RFC 1841           LAN Extension Interface Protocol       September 1995


                          extension interface unit
                        * 0x08 - Reset LAN statistics in the LAN
                          extension interface unit
                          If both serial and LAN statistics are
                          returned, the corresponding bits of this
                          field should are set (that is, 0x06). The
                          serial interface statistics appear in the
                          response packet before the LAN statistics.
   Option-Length        Minimum length = 116 octets
                        Maximum length = 136 octets
   Option-Data          The Serial Interface Statistics Block, the
                        LAN Interface Statistics Block, or both the
                        Serial Interface and LAN Interface
                        Statistics blocks. When the Option-Data
                        contains both blocks, the Serial Interface
                        Block precedes the LAN Interface Block.
                        Statistics values that the LAN extension
                        interface unit does not collect/support
                        are retuned with a value of zero.

   Implementation Notes

   If the LAN extension interface unit does not implement the capability
   of sending the serial and LAN interface statistics blocks separately,
   the implementation may always return both statistics blocks (with the
   Option-Flags and Option-Length fields containing the appropriate
   corresponding values).

   An implementation, such as a Token Ring LAN implementation, can
   collect a different set of statistics than shown above by defining a
   new statistics request type remote command option.

9.3 LEX RCMD_NAK/LEX RCMD_REJ - Request Statistics

   The LAN extension interface unit sends a LEX_RCMD_NAK packet when the
   Statistics Request LEX_RCMD_REQUEST packet did not specify the type
   of statistics the host router wants. That is, the request's Option-
   Flags field equals zero.

   Refer to the "Conditions for Sending PPP-LEX Packets" section earlier
   in this document for information on when the LAN extension interface
   unit sends a Request Statistics LEX_RCMD_REJ packet.

   The frame format for the LEX_RCMD_NAK and LEX_RCMD_REJ packets is the
   same as that of the Statistics Request LEX_RCMD_REQUEST packet. Table
   16 summarizes the appropriate field values for the Statistics Request
   LEX_RCMD_NAK and LEX_RCMD_REJ packets.




Chapman, et al               Informational                     [Page 44]

RFC 1841           LAN Extension Interface Protocol       September 1995


      Table 16  Field Values for LEX_RCMD_NAK/LEX_RCMD_REJ Packets -
                            Request Statistics

   Field                Value
   Address/Control      0xFF03 (Broadcast address/Unnumbered
                        information)
   Protocol-Type        0x8041 (Control packet)
   Code                 Valid values:
                        * 0x42 (LEX_RCMD_NAK packet)
                        * 0x43 (LEX_RCMD_REJ packet)
   Identifier           The same value as that sent by the
                        LEX_RCMD_REQUEST packet
   Length               12 octets
   Option-Type          0x07 (Request Statistics)
   Option-Flags         The same value as that sent by the
                        LEX_RCMD_REQUEST packet
   Option-Length        4 octets
   Option-Data          None

10.0 Download Request

   The host router sends a LEX_RCMD_REQUEST packet with an Option-Type
   of 0x08 to alert the LAN extension interface unit that the host
   router will be issuing a software download to Flash memory. When the
   LAN extension interface unit acknowledges the command, the host
   router starts sending download data.

























Chapman, et al               Informational                     [Page 45]

RFC 1841           LAN Extension Interface Protocol       September 1995


10.1 LEX RCMD_REQUEST - Download Request

   Figure 14 shows a summary frame format of a LEX_RCMD_REQUEST packet
   for a Download Request remote command option. The host router
   transmits the fields from left to right.

    Figure 14  LEX_RCMD_REQUEST Packet Frame Format - Download Request

                          PPP Header
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|              0xFF03           |          Protocol-Type        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              (2 octets)                         (2)

                LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      Code     |   Identifier  |              Length           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        (1)             (1)                     (2)

            LAN Extension Interface Remote Command Option
<--------------------------------
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|  Option-Type  |  Option-Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         (1)            (1)

                ----------------------------------------------->
                 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
                -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                        Option-Length          |  Option-Data  |
                -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                              (2)

   Where the Option-Data field contains the following fields:

 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|     Block Number (16 bits)    |        File Size (32 bits)....
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|     Filename (Max. 64 octets).......
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+




Chapman, et al               Informational                     [Page 46]

RFC 1841           LAN Extension Interface Protocol       September 1995


   Summary Field Descriptions

   For a complete description of the fields in the PPP Header, the LAN
   Extension Interface Protocol Header, and the LAN Extension Interface
   Remote Command Option, refer to the "Remote Command Options" section
   earlier in this document. Table 17 provides a summary of these fields
   when sending a LEX_RCMD_REQUEST packet that informs the LAN extension
   interface unit of an upcoming software download to Flash memory.

   Table 17  Field Values for LEX_RCMD_REQUEST Packet - Download Request

   Field                Value
   Address/Control      0xFF03 (Broadcast address/Unnumbered
                        information)
   Protocol-Type        0x8041 (Control packet)
   Code                 0x40 (LEX_RCMD_REQUEST packet)
   Identifier           Valid values: 0x01-0xFF
   Length               Variable depending on size of filename in
                        the Filename field. Valid range:
                        Minimum length = 19 octets
                        Maximum length = 82 octets
   Option-Type          0x08 (Download Request)
   Option-Flags         None
   Option-Length        Variable depending on size of filename in
                        the Filename field. Valid range:
                        Minimum length = 11 octets
                        Maximum length = 74 octets
   Option-Data          Block Number, File Size, and Filename of
                        the code/image to be downloaded. See the
                        following "Option-Data Field Descriptions"
                        section for details.

   Option-Data Field Descriptions

   The Option-Data field contains the following fields:

   *  Block Number

   The Block Number field contains a value that identifies a contiguous
   group of code bits to be downloaded to the LAN extension interface
   unit. In the LEX_RCMD_REQUEST packet, the Block Number is always
   zero.

   *  File Size

   The File Size field contains the size (in octets) of the code to be
   downloaded to the LAN extension interface unit.




Chapman, et al               Informational                     [Page 47]

RFC 1841           LAN Extension Interface Protocol       September 1995


   *  Filename

   The Filename field contains the name of the image to be transferred
   to the LAN extension interface unit.

10.2 Response Packets - Download Request

   The following packets are valid responses to a Download Request
   LEX_RCMD_REQUEST packet:

   *  LEX_RCMD_ACK - Download Request

   Refer to the "Conditions for Sending PPP-LEX Packets" section earlier
   in this document for more information on when the LAN extension
   interface unit sends this packet.

   *  LEX_RCMD_NAK - Download Request

   The LAN extension interface unit sends a Download Request
   LEX_RCMD_NAK packet when the LAN Extension interface unit is
   currently programming Flash, when the File Size field value in the
   request is greater than the unit's available Flash bytes, when the
   LAN extension interface unit is out of memory, or when the Block
   Number field value in the request is not zero.

   *  LEX_RCMD_REJ - Download Request

   Refer to the "Conditions for Sending PPP-LEX Packets" section earlier
   in this document for more information on when the LAN extension
   interface unit sends this packet.

   Table 18 summarizes the field values of the Download Request
   LEX_RCMD_ACK, LEX_RCMD_NAK, and LEX_RCMD_REJ packets.

      Table 18  Field Values for Response Packets - Download Request

   Field                Value
   Address/Control      0xFF03 (Broadcast address/Unnumbered
                        information)
   Protocol-Type        0x8041 (Control packet)
   Code                 Valid values:
                        * 0x41 (LEX_RCMD_ACK packet)
                        * 0x42 (LEX_RCMD_NAK packet)
                        * 0x43 (LEX_RCMD_REJ packet)
   Identifier           The same value as that sent by the
                        LEX_RCMD_REQUEST packet
   Length               The same value as that sent by the
                        LEX_RCMD_REQUEST packet



Chapman, et al               Informational                     [Page 48]

RFC 1841           LAN Extension Interface Protocol       September 1995


   Option-Type          0x08 (Download Request)
   Option-Flags         None
   Option-Length        The same value as that sent by the
                        LEX_RCMD_REQUEST packet
   Option-Data          Block Number, File Size, and Filename of
                        the code/image to be downloaded.

11.0 Download Data

   Once the host router receives a Download Request LEX_RCMD_ACK packet
   from the LAN extension interface unit, the host router downloads the
   data to be written to Flash memory by sending a LEX_RCMD_REQUEST
   packet with an Option-Type of 0x09. The host router sends multiple
   Download Data LEX_RCMD_REQUEST packets, each with 512 octets of
   Option-Data containing the binary data to be programmed into Flash
   memory.

   A packet containing Option-Data with less than 512 octets signals the
   end of the download data (that is, the end of tile). If the size of
   the file being downloaded is an even multiple of 512 bytes, then the
   last packet transferred should have an Option-Length of 6. That is,
   the last packet transferred should have Option-Data containing the
   Block Number field value but no data. A Block Number field value
   without data alerts the LAN extension interface unit that this is the
   last block to be transmitted.

11.1 LEX RCMD_REQUEST - Download Data

   The frame format for the Download Data LEX_RCMD_REQUEST packet is
   similar to a TFTP frame format. Figure 15 shows a summary frame
   format. The host router transmits the fields from left to right.

      Figure 15 LEX_RCMD_REQUEST Packet Frame Format - Download Data

                           PPP Header
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|              0xFF03           |          Protocol-Type        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              (2 octets)                         (2)










Chapman, et al               Informational                     [Page 49]

RFC 1841           LAN Extension Interface Protocol       September 1995


                LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      Code     |   Identifier  |              Length           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        (1)             (1)                     (2)

            LAN Extension Interface Remote Command Option
<--------------------------------
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|  Option-Type  |  Option-Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         (1)            (1)

                ----------------------------------------------->
                 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
                -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                        Option-Length          |  Option-Data  |
                -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                              (2)

   Where the Option-Data field contains the following fields:

 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|     Block Number (16 bits)    |                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
|       Binary Download Data (Max. 512 octets).....             |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Summary Field Descriptions

   For a complete descriptions of the fields in the PPP Header, the LAN
   Extension Interface Protocol Header, and the LAN Extension Interface
   Remote Command Option, refer to the "Remote Command Options" section
   earlier in this document. The following table provides a summary of
   these fields when sending a LEX_RCMD_REQUEST packet that download
   software to the LAN extension interface unit.

      Table 19  Field Values for LEX_RCMD_REQUEST Packet - Download Data

   Field                Value
   Address/Control      0xFF03 (Broadcast address/Unnumbered
                        information)
   Protocol-Type        0x8041 (Control packet)
   Code                 0x40 (LEX_RCMD_REQUEST packet)



Chapman, et al               Informational                     [Page 50]

RFC 1841           LAN Extension Interface Protocol       September 1995


   Identifier           Valid values: 0x01-0xFF
   Length               Minimum length = 14 octets
                        Maximum length = 526 octets
   Option-Type          0x09 (Download Data)
   Option-Flags         None
   Option-Length        Minimum length = 6 octets (signals end of
                        data transfer for a file with a file size
                        of an even multiple of 512 bytes)
                        Maximum length = 518 octets
   Option-Data          Block Number and Download Data. See the
                        following "Option-Data Field Descriptions"
                        section for details.

   Option-Data Field Descriptions

   The following Option-Data fields provide the LAN extension interface
   unit with download data:

   *  Block Number

   The Block Number identifies the contiguous group of code bits to be
   downloaded. The host router automatically generates this number. The
   first Download Data packet gets a block number of one. The host
   router increments this Block Number value by one with every Download
   Data LEX_RCMD_REQUEST packet sent to the LAN extension interface
   unit. The maximum value of the Block Number is dependent on the
   unit's Flash memory size.

   *  Download Data

   The Download Data are the actual code bits being downloaded to the
   LAN extension interface unit. A maximum of 512 octets of download
   data can sent in one Download Data LEX_RCMD_REQUEST packet.

11.2 Response Packets - Download Data

   The following packets are valid responses to a Download Data
   LEX_RCMD_REQUEST packet:

   *  LEX_RCMD_ACK - Download Data

   Refer to the "Conditions for Sending PPP-LEX Packets" section earlier
   in the document for more information on this packet.








Chapman, et al               Informational                     [Page 51]

RFC 1841           LAN Extension Interface Protocol       September 1995


   *  LEX_RCMD_NAK - Download Data

   The LAN extension interface unit sends a Download Data LEX_RCMD_NAK
   packet when the LAN extension interface unit is not in the proper
   state or when accepting the data will over-run the download buffer.

   *  LEX_RCMD_REJ - Download Data

   Refer to the "Conditions for Sending PPP-LEX Packets" section earlier
   in the document for more information on this packet.

   Table 20 summarizes the field values of the Download Data
   LEX_RCMD_ACK, LEX_RCMD_NAK, and LEX_RCMD_REJ packets.

       Table 20  Field Values for Response Packets - Download Data

   Field                Value
   Address/Control      0xFF03 (Broadcast address/Unnumbered
                        information)
   Protocol-Type        0x8041 (Control packet)
   Code                 Valid values:
                        * 0x41 (LEX_RCMD_ACK packet)
                        * 0x42 (LEX_RCMD_NAK packet)
                        * 0x43 (LEX_RCMD_REJ packet)
   Identifier           The same value as that sent by the
                        LEX_RCMD_REQUEST packet
   Length               14 octets
   Option-Type          0x09 (Download Data)
   Option-Flags         None
   Option-Length        6 octets
   Option-Data          Block Number only

12.0 Download Status

   Upon completion of a Download Data sequence, the host router issues a
   LEX_RCMD_REQUEST packet with an Option-Type of 0x0A to request status
   of the success or failure of the download. A bad checksum of the
   image or a malfunctioning Flash memory could cause the download to
   fail.












Chapman, et al               Informational                     [Page 52]

RFC 1841           LAN Extension Interface Protocol       September 1995


12.1 LEX RCMD_REQUEST - Download Status

   Figure 16 shows the frame format summary of a LEX_RCMD_REQUEST packet
   for a Download Status remote command option. The host router
   transmits the fields from left to right.

    Figure 16  LEX_RCMD_REQUEST Packet Frame Format - Download Status

                           PPP Header
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|              0xFF03           |          Protocol-Type        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              (2 octets)                         (2)

                LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      Code     |   Identifier  |              Length           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        (1)             (1)                     (2)

            LAN Extension Interface Remote Command Option
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|  Option-Type  |  Option-Flags |        Option-Length          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         (1)            (1)                    (2)

   Summary Field Descriptions

   For a complete descriptions of the fields in the PPP Header, the LAN
   Extension Interface Protocol Header, and the LAN Extension Interface
   Remote Command Option, refer to the "Remote Command Options" section
   earlier in this document. Table 21 provides a summary of these fields
   when sending a LEX_RCMD_REQUEST packet that requests the download
   status of the LAN extension interface unit.

   Table 21  Field Values for LEX_RCMD_REQUEST Packet - Download Status

   Field                Value
   Address/Control      0xFF03 (Broadcast address/Unnumbered
                        information)
   Protocol-Type        0x8041 (Control packet)
   Code                 0x40 (LEX_RCMD_REQUEST packet)



Chapman, et al               Informational                     [Page 53]

RFC 1841           LAN Extension Interface Protocol       September 1995


   Identifier           Valid values: 0x01-0xFF
   Length               12 octets
   Option-Type          0x0A (Download Status)
   Option-Flags         None
   Option-Length        4 octets
   Option-Data          None

12.2 LEX RCMD_REQUEST - Download Status

   When the LAN extension interface unit correctly receives the Download
   Status LEX_RCMD_REQUEST packet, it returns a LEX_RCMD_ACK packet
   containing the appropriate status information in the Option-Data
   field.

   Figure 17 shows the frame format for the Download Status LEX_RCMD_ACK
   packet. The LAN extension interface unit transmits the fields from
   left to right.

      Figure 17  LEX_RCMD_ACK Packet Frame Format - Download Status

                            PPP Header
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|              0xFF03           |          Protocol-Type        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              (2 octets)                         (2)

                LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      Code     |   Identifier  |              Length           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        (1)             (1)                     (2)
















Chapman, et al               Informational                     [Page 54]

RFC 1841           LAN Extension Interface Protocol       September 1995


            LAN Extension Interface Remote Command Option
<--------------------------------
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|  Option-Type  |  Option-Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         (1)            (1)

                ----------------------------------------------->
                 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
                -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                        Option-Length          |  Option-Data  |
                -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                              (2)

   Where the Option-Data field contains the following fields:

 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|        Status (16 bits)       |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Summary Field Descriptions

   For a complete descriptions of the fields in the PPP Header, the LAN
   Extension Interface Protocol Header, and the LAN Extension Interface
   Remote Command Option, refer to the "Remote Command Options" section
   earlier in this document. Table 22 provides a summary of these fields
   when sending a status information to the host router.

     Table 22  Field Values for LEX_RCMD_ACK Packet - Download Status

   Field                Value
   Address/Control      0xFF03 (Broadcast address/Unnumbered
                        information)
   Protocol-Type        0x8041 (Control packet)
   Code                 0x41 (LEX_RCMD_ACK packet)
   Identifier           The same value as that sent by the
                        LEX_RCMD_REQUEST packet
   Length               14 octets
   Option-Type          0x0A (Download Status)
   Option-Flags         None
   Option-Length        6 octets
   Option-Data          Status information. See the following
                        "Option-Data Field Descriptions" section
                        for details.





Chapman, et al               Informational                     [Page 55]

RFC 1841           LAN Extension Interface Protocol       September 1995


   Option-Data Field Descriptions

   The Option-Data field uses the Status field to send the download
   status to the host router. The Status field reports the following
   status information:

      *  1 - Acknowledgment that no errors occurred
      *  3 - Sequence error occurred
      *  6 - Flash write error occurred
      *  7 - Checksum error

12.3 LEX RCMD_NAK/LEX RCMD_REJ - Download Status

   Refer to the "Conditions for Sending PPP-LEX Packets" section earlier
   in this document for information on when the LAN extension interface
   unit sends a Download Status LEX_RCMD_NAK packet and Download Status
   LEX_RCMD_REJ packet.

   The frame format for these two response packets mirror the frame
   format of the Download Status LEX_RCMD_REQUEST packet. Table 23
   summarizes the field values of the Download Status LEX_RCMD_NAK and
   LEX_RCMD_REJ packets.

   Table 23  Field Values for LEX_RCMD_NAK/LEX_RCMD_REJ Packets - Download
   Status

   Field                Value
   Address/Control      0xFF03 (Broadcast address/Unnumbered
                        information)
   Protocol-Type        0x8041 (Control packet)
   Code                 Valid values:
                        * 0x42 (LEX_RCMD_NAK packet)
                        * 0x43 (LEX_RCMD_REJ packet)
   Identifier           The same value as that sent by the
                        LEX_RCMD_REQUEST packet
   Length               12 octets
   Option-Type          0x0A (Download Status)
   Option-Flags         None
   Option-Length        4 octets
   Option-Data          None

13.0 Inventory Request

   The host router sends a LEX_RCMD_REQUEST packet with an Option-Type
   of 0x0B to the LAN extension interface unit to request inventory
   information. The host router may use this remote command option to
   accomplish the following:




Chapman, et al               Informational                     [Page 56]

RFC 1841           LAN Extension Interface Protocol       September 1995


   *  Distinguish between different versions of the LAN extension
      interface unit for determining their capabilities

   *  Determine whether a new version of Flash code should be downloaded

13.1 LEX RCMD_REQUEST - Inventory Request

   Figure 18 shows the frame format for a LEX_RCMD_REQUEST packet with
   an Inventory Request remote command option. The host router transmits
   the fields from left to right.

   Figure 18  LEX_RCMD_REQUEST Packet Frame Format - Inventory Request

                           PPP Header
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|              0xFF03           |          Protocol-Type        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              (2 octets)                         (2)

                LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      Code     |   Identifier  |              Length           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        (1)             (1)                     (2)

            LAN Extension Interface Remote Command Option
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|  Option-Type  |  Option-Flags |        Option-Length          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         (1)            (1)                    (2)

   Summary Field Descriptions

   For a complete description of the fields in the PPP Header, the LAN
   Extension Interface Protocol Header, and the LAN Extension Interface
   Remote Command Option, refer to the "Remote Command Options" section
   earlier in this document. Table 24 provides a summary of these fields
   when sending a LEX_RCMD_REQUEST packet that requests inventory
   information.






Chapman, et al               Informational                     [Page 57]

RFC 1841           LAN Extension Interface Protocol       September 1995


   Table 24  Field Values for LEX_RCMD_REQUEST Packet-Inventory Request

   Field                Value
   Address/Control      0xFF03 (Broadcast address/Unnumbered
                        information)
   Protocol-Type        0x8041 (Control packet)
   Code                 0x40 (LEX_RCMD_REQUEST packet)
   Identifier           Valid values: 0x01-0xFF
   Length               12 octets
   Option-Type          0x0B (Inventory Request)
   Option-Flags         None
   Option-Length        4 octets
   Option-Data          None

13.2 LEX RCMD_ACK - Inventory Request

   When it correctly receives the Inventory Request remote command
   option and retrieves the inventory information, the LAN extension
   interface unit responds with an acknowledgment. This acknowledgment
   contains the requested inventory information in the Option-Data
   field.

   Figure 19 shows the frame format for the Inventory Request
   LEX_RCMD_ACK packet.

      Figure 19 LEX_RCMD_ACK Packet Frame Format - Inventory Request

                            PPP Header
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|              0xFF03           |          Protocol-Type        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              (2 octets)                         (2)

                LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      Code     |   Identifier  |              Length           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        (1)             (1)                     (2)









Chapman, et al               Informational                     [Page 58]

RFC 1841           LAN Extension Interface Protocol       September 1995


            LAN Extension Interface Remote Command Option
<--------------------------------
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|  Option-Type  |  Option-Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         (1)            (1)

                ----------------------------------------------->
                 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
                -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                        Option-Length          |  Option-Data  |
                -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                              (2)

   Where the Option-Data field contains the following fields:

                            (32 bits)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                           Flash Size                          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                         Serial Number                         |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|  HW Version   | PROM Major Ver| PROM Minor Ver|Flash Major Ver|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Flash Minor Ver|     FLAGS     | RAM Major Ver | RAM Minor Ver |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
+   Mac Address (6 octets)      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Summary Field Descriptions

   For a complete description of the fields in the PPP Header, the LAN
   Extension Interface Protocol Header, and the LAN Extension Interface
   Remote Command Option, refer to the "Remote Command Options" section
   earlier in this document. Table 25 provides a summary of these fields
   when acknowledging a LEX_RCMD_REQUEST packet that requests inventory
   information.

    Table 25  Field Values for LEX_RCMD_ACK Packet - Inventory Request

   Field                Value
   Address/Control      0xFF03 (Broadcast address/Unnumbered
                        information)
   Protocol-Type        0x8041 (Control packet)
   Code                 0x41 (LEX_RCMD_ACK packet)



Chapman, et al               Informational                     [Page 59]

RFC 1841           LAN Extension Interface Protocol       September 1995


   Identifier           The same value as that sent by
                        LEX_RCMD_REQUEST packet
   Length               34 octets
   Option-Type          0x0B (Inventory Request)
   Option-Flags         None
   Option-Length        26 octets
   Option-Data          Inventory data. See the following
                        "Option-Data Field Descriptions" section
                        for details.

   Option-Data Field Descriptions

   The Option-Data field of the LEX_RCMD_ACK packet uses the following
   fields to send inventory data to the host router about the LAN
   extension interface unit.

   *  Flash Size

   This field contains the LAN extension interface unit's Flash size in
   bytes.

   *  Serial Number

   This field provides the LAN extension interface unit's serial number.
   This is an unassigned, 32-bit number.

   *  HW Version

   This field contains the version number of the LAN extension interface
   hardware unit.

   *  PROM Major Ver

   This field contains part of the version number of the PROM image.
   "Major" indicates which major software release this revision belongs
   to. For example, if the PROM version number is 1.2, then the major
   version number is 1.

   *  PROM Minor Ver

   This field contains part of the version number of the PROM image.
   "Minor" indicates which minor software release this revision belongs
   to. For example, if the PROM version number is 1.2, then the minor
   version number is 2.







Chapman, et al               Informational                     [Page 60]

RFC 1841           LAN Extension Interface Protocol       September 1995


   *  Flash Major Ver

   This field contains the "major" version number of the Flash image.
   For example, if the Flash image version number is 1.2, then the major
   version number is 1.

   *  Flash Minor Ver

   This field contains the "minor" version number of the Flash image.
   For example, if the Flash image version number is 1.2, then the minor
   version number is 2.

   *  FLAGS

   FLAGS report the boot status of the LAN extension interface unit. The
   flags are as follows:

   - 0x01 - Running PROM image
   - 0x02 - Running Flash image
   - 0x04 - PROM image passed checksum
   - 0x08 - Flash image passed checksum

   *  RAM Major Ver

   This field contains the "major" version number of the running image
   in RAM. For example, if the RAM image version number is 1.2, then the
   major version number is 1.

   *  RAM Minor Ver

   This field contains the "minor" version number of the running image
   in RAM. For example, if the RAM image version number is 1.2, then the
   minor version number is 2.

   *  MAC Address

   The MAC Address is the LAN extension interface unit's burned-in MAC
   address in canonical format. This field is six octets.

13.3 LEX RCMD_NAK/LEX RCMD_REJ - Inventory Request

   Refer to the "Conditions for Sending PPP-LEX Packets" section earlier
   in this document for information on when the LAN extension interface
   unit sends an Inventory Request LEX_RCMD_NAK packet and Inventory
   Request LEX_RCMD_REJ packet.

   The frame format of these two response packets mirrors that of the
   request. Table 26 summarizes the field values for such Inventory



Chapman, et al               Informational                     [Page 61]

RFC 1841           LAN Extension Interface Protocol       September 1995


   Request LEX_RCMD_NAK/LEX_RCMD_REJ packets.

      Table 26  Field Values for LEX_RCMD_NAK/LEX_RCMD_REJ Packets -
                             Inventory Request

   Field                Value
   Address/Control      0xFF03 (Broadcast address/Unnumbered
                        information)
   Protocol-Type        0x8041 (Control packet)
   Code                 Valid values:
                        * 0x42 (LEX_RCMD_NAK packet)
                        * 0x43 (LEX_RCMD_REJ packet)
   Identifier           The same value as that sent by the
                        LEX_RCMD_REQUEST packet
   Length               12 octets
   Option-Type          0x0B (Inventory Request)
   Option-Flags         None
   Option-Length        4 octets
   Option-Data          None

14.0 LAN Extension Interface Protocol Data Packets

   When the PPP-LEX NCP is in an "opened" state, the LAN extension
   interface unit and the host router also exchange PPP-LEX data packets
   (as well as control packets). There is only one type of PPP-LEX data
   packet. This data packet is a subset of the PPP-BCP packet format.

   The format subsetting is such that a PPP-BCP implementation will
   successfully process a LAN extension interface protocol packet. The
   differences are as follows:

      *  LAN ID field will not be present.
      *  LAN FCS field will never be present (that is, the F flag will
         always be off [=0]).
      *  LAN ID flag (I) will always be off.
      *  Pad field for the serial link will never be present, and the
         count field will be 0.

   For detailed information on PPP-BCP packets, refer to the "PPP
   Bridging Control Protocol (BCP)" RFC. (References, [2])

14.1 Frame Format

   Figure 20 shows the frame format for a PPP-LEX data packet. The MAC
   frame is transferred except for the FCS field. The LAN extension
   interface unit computes the FCS for packets transferred to the LAN
   and strips the FCS for packets destined for the host router.




Chapman, et al               Informational                     [Page 62]

RFC 1841           LAN Extension Interface Protocol       September 1995


                Figure 20  PPP-LEX Data Packet Frame Format

    (8 bits)         (8 bits)      (8 bits)         (8 bits)
+-+-+-+-+-+-+-+-+
|   HDLC FLAG   |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|     0xFF      |      0x03     |             0x0041            |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| F|I|Z|0| Pad  |    Mac Type   |    Destination MAC Address    |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                        Destination MAC Address                |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                         Source MAC Address                    |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|       Source MAC Address      |           Length/Type         |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                           LLC Data                            |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                       ...                                     |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|       (Serial) HDLC CRC       |  HDLC FLAG    |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

14.2 Summary Field Descriptions

   HDLC FLAG

   HDLC Frame delimiter.

   0xFF

   This Address field contains the broadcast address.

   0x03

   This Control field contains unnumbered information.

   0x0041

   This field contains the IETF-assigned protocol type value for a
   PPP-LEX data packet. In this case this field will always contain
   0x0041.

   Flags

   The flags F, I, Z, 0 have the following meanings:





Chapman, et al               Informational                     [Page 63]

RFC 1841           LAN Extension Interface Protocol       September 1995


      * F: Set bit F if the LAN FCS field is present. Because PPP-LEX
        data packets do not contain the LAN FCS field, this bit should
        not be set (field=0).

      * I: Set bit I if the LAN ID field is present. Because PPP-LEX
        data packets do not contain the field, this bit should not be
        set (field=0).

      * Z: Set bit Z if IEEE 802.3 Pad must be zero filled to minimum
        size.

      * 0: Reserved, must be zero.

   Pad

   Any PPP frame may have padding inserted in the Optional Data Link
   Layer Padding field. The value tells the receiving system how many
   pad octets to strip off. The LAN extension interface protocol does
   not support the Optional Data Link Layer Padding field, so the
   value of this field should be zero.

   MAC Type

   This field contains the most up-to-date value of the MAC type as
   specified in the most recent "Assigned Numbers" RFC. The current
   value is as follows:

      *  1: IEEE 802.3/Ethernet with canonical addresses

   Destination MAC Address

   This field is 6 octets and contains the MAC address of the
   destination system as defined by IEEE. The MAC Type field defines
   the bit ordering.

   Source MAC Address

   This field is 6 octets and contains the MAC address of the
   destination system as defined by IEEE. The MAC Type field defines
   the bit ordering.

   Length/Type

   This field is any Ethernet protocol type (See RFC 1700 in the
   references "Assigned Numbers").  For IEEE 802.3 frames, this is a
   length field.





Chapman, et al               Informational                     [Page 64]

RFC 1841           LAN Extension Interface Protocol       September 1995


   LLC Data

   This field is the remainder of the MAC frame which is (or would be
   if it were present) protected by the LAN FCS.

   (Serial) HDLC CRC

   This is a 16 bit Cyclic Redundancy Check field.

   For complete information on the above fields and their relationship
   to PPP-BCP packets, refer to the "PPP Bridging Control Protocol
   (BCP)" RFC. (References, [2])

Notes

   1. The LAN extension interface protocol does allow the segmentation
      of individual LAN packets across the serial link. Each LAN
      packet must be transmitted across the serial link as one PPP-LEX
      encapsulation.

   2. MAC addresses in PPP-LEX packets should be in canonical format.

References

   [1] Simpson, W., "The Point-To-Point Protocol (PPP) for the
       Transmission of Multi-protocol Datagrams over Point-To-Point
       Links", RFC 1331, Daydreamer, May 1992.

   [2] Baker, F., and R. Bowen, "PPP Bridging Control Protocol (BCP)",
       RFC 1638, ACC, IBM, June 1994.

   [3] Lloyd, B., and W. Simpson, "PPP Authentication Protocols", RFC
       1334, Lloyd & Associates, Daydreamer, October 1992.

   [4] Reynolds, J., and J. Postel, "Assigned Numbers", STD 2, RFC 1700,
       USC/Information Sciences Institute, October 1994.

   [5] Reynolds, J., and J. Postel, "Standard for the transmission of IP
       datagrams over IEEE 802 networks", RFC 1042, USC/Information
       Sciences Institute, February 1988.











Chapman, et al               Informational                     [Page 65]

RFC 1841           LAN Extension Interface Protocol       September 1995


Security Considerations

   Security issues are not discussed in this memo.

Authors' Addresses

   Joelle Bafile Chapman, Technical Writer
   Cisco Systems, Inc.
   170 West Tasman Drive
   San Jose, CA 95134-1706

   EMail: joelle@cisco.com


   Dave Coli, Software Engineer
   Cisco Systems, Inc.
   170 West Tasman Drive
   San Jose, CA 95134-1706

   EMail: dcoli@cisco.com


   Andy Harvey, Software Engineer
   Cisco Systems, Inc.
   170 West Tasman Drive
   San Jose, CA 95134-1706

   EMail: agh@cisco.com


   Bent Jensen, Engineering Manager
   Cisco Systems, Inc.
   170 West Tasman Drive
   San Jose, CA 95134-1706

   EMail: bent@cisco.com


   Kevin Rowett, Software Engineer
   Cisco Systems, Inc.
   170 West Tasman Drive
   San Jose, CA 95134-1706

   EMail: krowett@cisco.com







Chapman, et al               Informational                     [Page 66]