File: rfc1573.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 (3083 lines) | stat: -rw-r--r-- 123,057 bytes parent folder | download | duplicates (8)
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






Network Working Group                                      K. McCloghrie
Request for Comments: 1573                            Hughes LAN Systems
Obsoletes: 1229                                            F. Kastenholz
Category: Standards Track                                   FTP Software
                                                            January 1994


              Evolution of the Interfaces Group of MIB-II

Status of this Memo

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

Table of Contents

   1. Introduction .............................................    2
   2. The SNMPv2 Network Management Framework ..................    2
   2.1 Object Definitions ......................................    3
   3 Experience with the Interfaces Group ......................    3
   3.1 Areas of Clarification/Revision .........................    3
   3.1.1 Interface Numbering ...................................    4
   3.1.2 Interface Sub-Layers ..................................    4
   3.1.3 Virtual Circuits ......................................    5
   3.1.4 Bit, Character, and Fixed-Length Interfaces ...........    5
   3.1.5 Counter Size ..........................................    5
   3.1.6 Interface Speed .......................................    6
   3.1.7 Multicast/Broadcast Counters ..........................    6
   3.1.8 Addition of New ifType values .........................    6
   3.1.9 ifSpecific ............................................    6
   3.2 Clarifications/Revisions ................................    7
   3.2.1 Interface Numbering ...................................    7
   3.2.2 Interface Sub-Layers ..................................    8
   3.2.3 Guidance on Defining Sub-layers .......................   11
   3.2.4 Virtual Circuits ......................................   12
   3.2.5 Bit, Character, and Fixed-Length Interfaces ...........   12
   3.2.6 Counter Size ..........................................   14
   3.2.7 Interface Speed .......................................   16
   3.2.8 Multicast/Broadcast Counters ..........................   16
   3.2.9 Trap Enable ...........................................   17
   3.2.10 Addition of New ifType values ........................   17
   3.2.11 InterfaceIndex Textual Convention ....................   17
   3.2.12 IfAdminStatus and IfOperStatus .......................   18
   3.2.13 Traps ................................................   19
   3.2.14 ifSpecific ...........................................   20



McCloghrie & Kastenholz                                         [Page 1]

RFC 1573               Interfaces Group Evolution           January 1994


   3.3 Media-Specific MIB Applicability ........................   20
   4. Overview .................................................   21
   5. IANAifType Definition ....................................   22
   6. Interfaces Group Definitions .............................   24
   7. Acknowledgements .........................................   53
   8. References ...............................................   53
   9. Security Considerations ..................................   55
   10. Authors' Addresses.......................................   55

1.  Introduction

   This memo defines a portion of the Management Information Base (MIB)
   for use with network management protocols in the Internet community.
   In particular, it describes managed objects used for managing Network
   Interfaces.

   This memo discusses the 'interfaces' group of MIB-II, especially the
   experience gained from the definition of numerous media-specific MIB
   modules for use in conjunction with the 'interfaces' group for
   managing various sub-layers beneath the internetwork-layer.  It
   proposes clarifications to, and extensions of, the architectural
   issues within the current model used for the 'interfaces' group.

   This memo also includes a MIB module.  As well as including new MIB
   definitions to support the architectural extensions, this MIB module
   also re-specifies the 'interfaces' group of MIB-II in a manner which
   is both compliant to the SNMPv2 SMI and semantically-identical to the
   existing SNMPv1-based definitions.

2.  The SNMPv2 Network Management Framework

   The SNMPv2 Network Management Framework consists of four major
   components.  They are:

      o    RFC 1442 which defines the SMI, the mechanisms used for
           describing and naming objects for the purpose of management.

      o    STD 17, RFC 1213 defines MIB-II, the core set of managed
           objects for the Internet suite of protocols.

      o    RFC 1445 which defines the administrative and other
           architectural aspects of the framework.

      o    RFC 1448 which defines the protocol used for network access
           to managed objects.

   The Framework permits new objects to be defined for the purpose of
   experimentation and evaluation.



McCloghrie & Kastenholz                                         [Page 2]

RFC 1573               Interfaces Group Evolution           January 1994


2.1.  Object Definitions

   Managed objects are accessed via a virtual information store, termed
   the Management Information Base or MIB.  Objects in the MIB are
   defined using the subset of Abstract Syntax Notation One (ASN.1)
   defined in the SMI.  In particular, each object object type is named
   by an OBJECT IDENTIFIER, an administratively assigned name.  The
   object type together with an object instance serves to uniquely
   identify a specific instantiation of the object.  For human
   convenience, we often use a textual string, termed the descriptor, to
   refer to the object type.

3.  Experience with the Interfaces Group

   One of the strengths of internetwork-layer protocols such as IP [6]
   is that they are designed to run over any network interface.  In
   achieving this, IP considers any and all protocols it runs over as a
   single "network interface" layer.  A similar view is taken by other
   internetwork-layer protocols.  This concept is represented in MIB-II
   by the 'interfaces' group which defines a generic set of managed
   objects such that any network interface can be managed in an
   interface-independent manner through these managed objects.  The
   'interfaces' group provides the means for additional managed objects
   specific to particular types of network interface (e.g., a specific
   medium such as Ethernet) to be defined as extensions to the
   'interfaces' group for media-specific management.  Since the
   standardization of MIB-II, many such media-specific MIB modules have
   been defined.

   Experience in defining these media-specific MIB modules has shown
   that the model defined by MIB-II is too simplistic and/or static for
   some types of media-specific management.  As a result, some of these
   media-specific MIB modules have assumed an evolution or loosening of
   the model.  This memo is a proposal to document and standardize the
   evolution of the model and to fill in the gaps caused by that
   evolution.

   A previous effort to extend the interfaces group resulted in the
   publication of RFC 1229 [7].  As part of defining the evolution of
   the interfaces group, this memo applies that evolution to, and
   thereby incorporates, the RFC 1229 extensions.

3.1.  Areas of Clarification/Revision

   There are several areas for which experience indicates that
   clarification, revision, or extension of the model would be helpful.
   The next sections discuss these.




McCloghrie & Kastenholz                                         [Page 3]

RFC 1573               Interfaces Group Evolution           January 1994


3.1.1.  Interface Numbering

   MIB-II defines an object, ifNumber, whose value represents:

     "The number of network interfaces (regardless of their
     current state) present on this system."

   Each interface is identified by a unique value of the ifIndex object,
   and the description of ifIndex constrains its value as follows:

     "Its value ranges between 1 and the value of ifNumber.  The
     value for each interface must remain constant at least from
     one re-initialization of the entity's network management
     system to the next re-initialization."

   This constancy requirement on the value of ifIndex for a particular
   interface is vital for efficient management.  However, an increasing
   number of devices allow for the dynamic addition/removal of network
   interfaces.  One example of this is a dynamic ability to configure
   the use of SLIP/PPP over a character-oriented port.  For such dynamic
   additions/removals, the combination of the constancy requirement and
   the restriction that the value of ifIndex is less than ifNumber is
   problematic.

3.1.2.  Interface Sub-Layers

   Experience in defining media-specific management information has
   shown the need to distinguish between the multiple sub-layers beneath
   the internetwork-layer.  In addition, there is a need to manage these
   sub-layers in devices (e.g., MAC-layer bridges) which are unaware of
   which, if any, internetwork protocols run over these sub-layers.  As
   such, a model of having a single conceptual row in the interfaces
   table (MIB-II's ifTable) represent a whole interface underneath the
   internetwork-layer, and having a single associated media-specific MIB
   module (referenced via the ifType object) is too simplistic.  A
   further problem arises with the value of the ifType object which has
   enumerated values for each type of interface.

   Consider, for example, an interface with PPP running over an HDLC
   link which uses a RS232-like connector.  Each of these sub-layers has
   its own media-specific MIB module.  If all of this is represented by
   a single conceptual row in the ifTable, then an enumerated value for
   ifType is needed for that specific combination which maps to the
   specific combination of media-specific MIBs.  Furthermore, there is
   still a lack of a method to describe the relationship of all the
   sub-layers of the MIB stack.

   An associated problem is that of upward and downward multiplexing of



McCloghrie & Kastenholz                                         [Page 4]

RFC 1573               Interfaces Group Evolution           January 1994


   the sub-layers.  An example of upward multiplexing is MLP (Multi-
   Link-Procedure) which provides load-sharing over several serial lines
   by appearing as a single point-to-point link to the sub-layer(s)
   above.  An example of downward multiplexing would be several
   instances of PPP, each framed within a separate X.25 virtual circuit,
   all of which run over one fractional T1 channel, concurrently with
   other uses of the T1 link.  The current MIB structure does not allow
   for these sorts of relationships to be described.

3.1.3.  Virtual Circuits

   Several of the sub-layers for which media-specific MIB modules have
   been defined are connection oriented (e.g., Frame Relay, X.25).
   Experience has shown that each effort to define such a MIB module
   revisits the question of whether separate conceptual rows in the
   ifTable are needed for each virtual circuit.  Most, if not all, of
   these efforts to date have decided to have all virtual circuits
   reference a single conceptual row in the ifTable.

3.1.4.  Bit, Character, and Fixed-Length Interfaces

   RS-232 is an example of a character-oriented sub-layer over which
   (e.g., through use of PPP) IP datagrams can be sent.  Due to the
   packet-based nature of many of the objects in the ifTable, experience
   has shown that it is not appropriate to have a character-oriented
   sub-layer represented by a (whole) conceptual row in the ifTable.

   Experience has also shown that it is sometimes desirable to have some
   management information for bit-oriented interfaces, which are
   similarly difficult to represent by a (whole) conceptual row in the
   ifTable.  For example, to manage the channels of a DS1 circuit, where
   only some of the channels are carrying packet-based data.

   A further complication is that some subnetwork technologies transmit
   data in fixed length transmission units.  One example of such a
   technology is cell relay, and in particular Asynchronous Transfer
   Mode (ATM), which transmits data in fixed-length cells.  Representing
   such a interface as a packet-based interface produces redundant
   objects if the relationship between the number of packets and the
   number of octets in either direction is fixed by the size of the
   transmission unit (e.g., the size of a cell).

3.1.5.  Counter Size

   As the speed of network media increase, the minimum time in which a
   32 bit counter will wrap decreases.  For example, on an Ethernet, a
   stream of back-to-back, full-size packets will cause ifInOctets to
   wrap in just over 57 minutes.  For a T3 line, the minimum wrap-time



McCloghrie & Kastenholz                                         [Page 5]

RFC 1573               Interfaces Group Evolution           January 1994


   is just over 12 minutes.  For FDDI, it will wrap in 5.7 minutes.  For
   a 1-gigabit medium, the counter might wrap in as little as 34
   seconds.  Requiring that interfaces be polled frequently enough not
   to miss a counter wrap will be increasingly problematic.

3.1.6.  Interface Speed

   Network speeds are increasing.  The range of ifSpeed is limited to
   reporting a maximum speed of (2**31)-1 bits/second, or approximately
   2.2Gbs.  SONET defines an OC-48 interface, which is defined at
   operating at 48 times 51 Mbs, which is a speed in excess of 2.4gbits.
   Thus, ifSpeed will be of diminishing utility over the next several
   years.

3.1.7.  Multicast/Broadcast Counters

   The counters in the ifTable for packets addressed to a multicast or
   the broadcast address, are combined as counters of non-unicast
   packets.  In contrast, the ifExtensions MIB [7] defines one set of
   counters for multicast, and a separate set for broadcast packets.
   With the separate counters, the original combined counters become
   redundant.

3.1.8.  Addition of New ifType values

   Over time new ifType enumerated values have been needed for new
   interface types.  With the syntax of ifType being defined in a MIB,
   this requires the new MIB to be re-issued in order to define the new
   values.  In the past, re-issuing of the MIB has occurred only after
   several years.

3.1.9.  ifSpecific

   The original definition of the OBJECT IDENTIFIER value of ifSpecific
   was not sufficently clear.  As a result, different implementors have
   used it differently, and confusion has resulted.  Some
   implementations have the value of ifSpecific be the OBJECT IDENTIFIER
   that defines the media-specific MIB, i.e., the "foo" of:

          foo OBJECT IDENTIFIER ::= { transmission xxx }

   while others have it be the OBJECT IDENTIFIER of the table or entry
   in the appropriate media-specific MIB (e.g. fooTable or fooEntry),
   while still others have it be the OBJECT IDENTIFIER of the index
   object of the table's row, including instance identifier (e.g.,
   fooIfIndex.ifIndex).  A definition based on the latter would not be
   sufficient unless it also allowed for media-specific MIBs which
   include several tables, where each table has its own, different,



McCloghrie & Kastenholz                                         [Page 6]

RFC 1573               Interfaces Group Evolution           January 1994


   indexing.

3.2.  Clarifications/Revisions

   The following clarifications and/or revisions are proposed.

3.2.1.  Interface Numbering

   One solution to the interface numbering problem would be to redefine
   ifNumber to be the largest value of ifIndex, but the utility of such
   an object is questionable, and such a re-definition would require
   ifNumber to be deprecated.  Thus, an improvement would be to
   deprecate ifNumber and not replace it.  However, the deprecation of
   ifNumber would require a change to that portion of ifIndex's
   definition which refers to ifNumber.  So, since the definition of
   ifIndex must be changed anyway in order to solve the problem, changes
   to ifNumber do not benefit the solution.

   The solution adopted in this memo is to delete the requirement that
   the value of ifIndex must be less than the value of ifNumber, and to
   retain ifNumber with its current definition.  It could be argued that
   this is a change in the semantics of ifIndex; however, all existing
   implementations conform to this new definition, and in the interests
   of not requiring changes in existing implementations and in the many
   existing media-specific MIBs, it is proposed that this change does
   not require ifIndex to be deprecated.

   This solution also results in the possibility of "holes" in the
   ifTable (i.e., the ifIndex values of conceptual rows in the ifTable
   are not necessarily contiguous), but SNMP's GetNext (and SNMPv2's
   GetBulk) operation easily deals with such holes.  The value of
   ifNumber still represents the number of conceptual rows, which
   increases/decreases as new interfaces are dynamically added/removed.
   The vital constancy requirement is met by requiring that after an
   interface is dynamically removed, its ifIndex value is not re-used
   (by a different dynamically added interface) until after the
   following re-initialization of the network management system.  This
   avoids the need for a priori assignment of ifIndex values for all
   possible interfaces which might be added dynamically.

   The exact meaning of a "different" interface is hard to define, and
   there will be gray areas.  One important criterion is that a
   management station, not noticing that an interface has gone away and
   another come into existence, should not be confused when it
   calculates the difference between the counter values retrieved on
   successive polls for a particular ifIndex value.  However, any firm
   definition in this document would likely to turn out to be
   inadequate.  Instead, the following guidelines are offered to allow



McCloghrie & Kastenholz                                         [Page 7]

RFC 1573               Interfaces Group Evolution           January 1994


   implementors to choose what "different" means in their particular
   situation.

   A previously-unused value of ifIndex should be assigned to a
   dynamically added interface if:

      (1)  the assignment of a previously-used ifIndex value to the
           interface could result in a discontinuity in the values of
           ifTable counters for that value of ifIndex; or,

      (2)  an agent has no knowledge of whether the interface is the
           "same" or "different" from a previous interface incarnation.

   Because of the restriction of the value of ifIndex to be less than
   ifNumber, interfaces have been numbered with small integer values.
   This has led to the ability by humans to use the ifIndex values as
   (somewhat) user-friendly names for network interfaces (e.g.,
   "interface number 3").  With the relaxation of the restriction on the
   value of ifIndex, there is now the possibility that ifIndex values
   could be assigned as very large numbers (e.g., memory addresses).
   Such numbers would be much less user-friendly.

   Therefore, this memo recommends that ifIndex values still be assigned
   as (relatively) small integer values starting at 1, even though the
   values in use at any one time are not necessarily contiguous.  (Note
   that this makes remembering which values have been assigned easy for
   agents which dynamically add new interfaces.)

   This proposed change introduces a new problem of its own.
   Previously, there usually was a simple, direct, mapping of interfaces
   to the physical ports on systems.  This mapping would be based on the
   ifIndex value.  However, by removing the previous restrictions on the
   values allowed for ifIndex, along with the interface sub-layer
   concept (see the following section), mapping from interfaces to
   physical ports becomes increasingly problematic.

   To address this issue, a new object, ifName, is added to the MIB.
   This object contains the device's name for the interface of which the
   relevant entry in the ifTable is a component.  For example, if a
   router has an interface named wan1, which is composed of PPP running
   over an RS-232 port, the ifName objects for the corresponding PPP and
   RS-232 entries in the ifTable will contain the string "wan1".

3.2.2.  Interface Sub-Layers

   One possible but not recommended solution to the problem of
   representing multiple sub-layers would be to retain the concept of
   one conceptual row for all the sub-layers of an interface and have



McCloghrie & Kastenholz                                         [Page 8]

RFC 1573               Interfaces Group Evolution           January 1994


   each media-specific MIB module identify its "superior" and
   "subordinate" sub-layers through OBJECT IDENTIFIER "pointers".  The
   drawbacks of this scheme are: 1) the superior/subordinate pointers
   are contained in the media-specific MIB modules, and thus, a manager
   could not learn the structure of an interface, without inspecting
   multiple pointers in different MIB modules; this is overly complex
   and only possible if the manager has knowledge of all the relevant
   media-specific MIB modules; 2) current MIB modules would all need to
   be retrofitted with these new "pointers"; 3) this scheme does not
   adequately address the problem of upward and downward multiplexing;
   and 4) enumerated values of ifType are needed for each combination of
   sub-layers.

   Another possible but not recommended scheme would be to retain the
   concept of one conceptual row for all the sub-layers of an interface
   and have a new separate MIB table to identify the "superior" and
   "subordinate" sub-layers which contain OBJECT IDENTIFIER "pointers"
   to media-specific MIB module(s) for each sub-layer.  Effectively, one
   conceptual row in the ifTable would represent each combination of
   sub-layers between the internetwork-layer and the wire.  While this
   scheme has fewer drawbacks, it does not support downward
   multiplexing, such as PPP over MLP; since MLP makes two (or more)
   serial lines appear to the layers above as a single physical
   interface, PPP over MLP should appear to the internetwork-layer as a
   single interface.  However, this scheme would result in two (or more)
   conceptual rows in the ifTable and the internetwork-layer would run
   over both of them.  This scheme also requires enumerated values of
   ifType for each combination of sub-layers.

   The solution adopted in this memo is to have an individual conceptual
   row in the ifTable to represent each sub-layer and have a new
   separate MIB table (the ifStackTable, see section 5 of this memo) to
   identify the "superior" and "subordinate" sub-layers through INTEGER
   "pointers" to the appropriate conceptual rows in the ifTable.  This
   solution supports both upward and downward multiplexing.  It also
   allows the IANAIfType to Media-Specific MIB mapping to identify the
   media-specific MIB module for each sub- layer.  The new table
   (ifStackTable) need be referenced only to obtain information about
   layering.  Enumerated values for ifType are required for each sub-
   layer only, not for combinations of them.

   However, this solution does require that the descriptions of some
   objects in the ifTable (specifically, ifType, ifPhysAddress,
   ifInUcastPkts, and ifOutUcastPkts) be generalized so as to apply to
   any sub-layer (rather than only to a sub-layer immediately beneath
   the network layer, as at present).  It also requires that some
   objects (specifically, ifSpeed) need to have appropriate values
   identified for use when a generalized definition does not apply to a



McCloghrie & Kastenholz                                         [Page 9]

RFC 1573               Interfaces Group Evolution           January 1994


   particular sub-layer.

   In addition, this adopted solution makes no requirement that a
   device, in which a sub-layer is instrumented by a conceptual row of
   the ifTable, be aware of whether an internetwork protocol runs on top
   of (i.e., at some layer above) that sub-layer.  In fact, the counters
   of packets received on an interface are defined as counting the
   number "delivered to a higher-layer protocol".  This meaning of
   "higher-layer" includes:

      (1)  Delivery to a forwarding module which accepts
           packets/frames/octets and forwards them on at the same
           protocol layer.  For example, for the purposes of this
           definition, the forwarding module of a MAC-layer bridge is
           considered as a "higher-layer" to the MAC-layer of each port
           on the bridge.

      (2)  Delivery to a higher sub-layer within a interface stack.  For
           example, for the purposes of this definition, if a PPP module
           operated directly over a serial interface, the PPP module
           would be considered the higher sub-layer to the serial
           interface.

      (3)  Delivery to a higher protocol layer which does not do packet
           forwarding for sub-layers that are "at the top of" the
           interface stack.  For example, for the purposes of this
           definition, the local IP module would be considered the
           higher layer to a SLIP serial interface.

   Similarly, for output, the counters of packets transmitted out an
   interface are defined as counting the number "that higher-level
   protocols requested to be transmitted".  This meaning of "higher-
   layer" includes:

      (1)  A forwarding module, at the same protocol layer, which
           transmits packets/frames/octets that were received on an
           different interface.  For example, for the purposes of this
           definition, the forwarding module of a MAC-layer bridge is
           considered as a "higher-layer" to the MAC-layer of each port
           on the bridge.

      (2)  The next higher sub-layer within an interface stack.  For
           example, for the purposes of this definition, if a PPP module
           operated directly over a serial interface, the PPP module
           would be a "higher layer" to the serial interface.






McCloghrie & Kastenholz                                        [Page 10]

RFC 1573               Interfaces Group Evolution           January 1994


      (3)  For sub-layers that are "at the top of" the interface stack,
           a higher element in the network protocol stack.  For example,
           for the purposes of this definition, the local IP module
           would be considered the higher layer to an Ethernet
           interface.

3.2.3.  Guidance on Defining Sub-layers

   The designer of a media-specific MIB must decide whether to divide
   the interface into sub-layers, and if so, how to make the divisions.
   The following guidance is offered to assist the media-specific MIB
   designer in these decisions.

   In general, the number of entries in the ifTable should be kept to
   the minimum required for network management.  In particular, a group
   of related interfaces should be treated as a single interface with
   one entry in the ifTable providing that:

      (1)  None of the group of interfaces performs multiplexing for any
           other interface in the agent,

      (2)  There is a meaningful and useful way for all of the ifTable's
           information (e.g., the counters, and the status variables),
           and all of the ifTable's capabilities (e.g., write access to
           ifAdminStatus), to apply to the group of interfaces as a
           whole.

   Under these circumstances, there should be one entry in the ifTable
   for such a group of interfaces, and any internal structure which
   needs to be represented to network management should be captured in a
   MIB module specific to the particular type of interface.

   Note that application of bullet 2 above to the ifTable's ifType
   object requires that there is a meaningful media-specific MIB and a
   meaningful ifType value which apply to the group of interfaces as a
   whole.  For example, it is not appropriate to treat an HDLC sub-layer
   and an RS-232 sub-layer as a single ifTable entry when the media-
   specific MIBs and the ifType values for HDLC and RS-232 are separate
   (rather than combined).

   Note that the sub-layers of an interface on one device will sometimes
   be different to the sub-layers of the interconnected interface of
   another device.  A simple example of this is a frame-relay DTE
   interface which connects to a frameRelayService interface, where the
   DTE interface has a different ifType value and media-specific MIB to
   the DCE interface.

   Also note that a media-specific MIB may mandate that a particular



McCloghrie & Kastenholz                                        [Page 11]

RFC 1573               Interfaces Group Evolution           January 1994


   ifTable counter does not apply and that its value must always be 0,
   signifying that the applicable event can not and does not occur for
   that type of interface; for example, ifInMulticastPkts and
   ifOutMulticastPkts on an interface type which has no multicast
   capability.  In other circumstances, an agent must not always return
   0 for any counter just because its implementation is incapable of
   detecting occurrences of the particular event; instead, it must
   return a noSuchName/noSuchObject error/exception when queried for the
   counter, even if this prevents the implementation from complying with
   the relevant MODULE-COMPLIANCE macro.

   These guidelines are just that - guidelines.  The designer of a
   media-specific MIB is free to lay out the MIB in whatever SMI
   conformant manner is desired.  However, in so doing, the media-
   specific MIB MUST completely specify the sub-layering model used for
   the MIB, and provide the assumptions, reasoning, and rationale used
   to develop that model.

3.2.4.  Virtual Circuits

   This memo strongly recommends that connection-oriented sub-layers do
   not have a conceptual row in the ifTable for each virtual circuit.
   This avoids the proliferation of conceptual rows, especially those
   which have considerable redundant information.  (Note, as a
   comparison, that connection-less sub-layers do not have conceptual
   rows for each remote address.)  There may, however, be circumstances
   under which it is appropriate for a virtual circuit of a connection-
   oriented sub-layer to have its own conceptual row in the ifTable; an
   example of this might be PPP over an X.25 virtual circuit.  The MIB
   in section 6 of this memo supports such circumstances.

   If a media-specific MIB wishes to assign an entry in the ifTable to
   each virtual circuit, the MIB designer must present the rationale for
   this decision in the media-specific MIB's specification.

3.2.5.  Bit, Character, and Fixed-Length Interfaces

   About half the objects in the ifTable are applicable to every type of
   interface: packet-oriented, character-oriented, and bit-oriented.  Of
   the other half, two are applicable to both character-oriented and
   packet-oriented interfaces, and the rest are applicable only to
   packet-oriented interfaces.  Thus, while it is desirable for
   consistency to be able to represent any/all types of interfaces in
   the ifTable, it is not possible to implement the full ifTable for
   bit- and character-oriented sub-layers.

   One possible but not recommended solution to this problem would be to
   split the ifTable into two (or more) new MIB tables, one of which



McCloghrie & Kastenholz                                        [Page 12]

RFC 1573               Interfaces Group Evolution           January 1994


   would contain objects that are relevant only to packet-oriented
   interfaces (e.g., PPP), and another that may be used by all
   interfaces.  This is highly undesirable since it would require
   changes in every agent implementing the ifTable (i.e., just about
   every existing SNMP agent).

   The solution adopted in this memo builds upon the fact that
   compliance statements in SNMPv2 (in contrast to SNMPv1) refer to
   object groups, where object groups are explicitly defined by listing
   the objects they contain.  Thus, in SNMPv2, multiple compliance
   statements can be specified, one for all interfaces and additional
   ones for specific types of interfaces.  The separate compliance
   statements can be based on separate object groups, where the object
   group for all interfaces can contain only those objects from the
   ifTable which are appropriate for every type of interfaces.  Using
   this solution, every sub-layer can have its own conceptual row in the
   ifTable.

   Thus, section 6 of this memo contains definitions of the objects of
   the existing 'interfaces' group of MIB-II, in a manner which is both
   SNMPv2-compliant and semantically-equivalent to the existing MIB-II
   definitions.  With equivalent semantics, and with the BER ("on the
   wire") encodings unchanged, these definitions retain the same OBJECT
   IDENTIFIER values as assigned by MIB-II.  Thus, in general, no
   rewrite of existing agents which conform to MIB-II and the
   ifExtensions MIB is required.

   In addition, this memo defines several object groups for the purposes
   of defining which objects apply to which types of interface:

      (1)  the ifGeneralGroup.  This group contains those objects
           applicable to all types of network interfaces, including
           bit-oriented interfaces.

      (2)  the ifPacketGroup.  This group contains those objects
           applicable to packet-oriented network interfaces.

      (3)  the ifFixedLengthGroup.  This group contains the objects
           applicable not only to character-oriented interfaces, such as
           RS-232, but also to those subnetwork technologies, such as
           cell-relay/ATM, which transmit data in fixed length
           transmission units.  As well as the octet counters, there are
           also a few other counters (e.g., the error counters) which
           are useful for this type of interface, but are currently
           defined as being packet-oriented.  To accommodate this, the
           definitions of these counters are generalized to apply to
           character-oriented interfaces and fixed-length-transmission
           interfaces.



McCloghrie & Kastenholz                                        [Page 13]

RFC 1573               Interfaces Group Evolution           January 1994


   It should be noted that the octet counters in the ifTable aggregate
   octet counts for unicast and non-unicast packets into a single octet
   counter per direction (received/transmitted).  Thus, with the above
   definition of fixed-length-transmission interfaces, where such
   interfaces which support non-unicast packets, separate counts of
   unicast and multicast/broadcast transmissions can only be maintained
   in a media-specific MIB module.

3.2.6.  Counter Size

   Two approaches to addressing the shrinking minimum counter-wrap time
   problem were evaluated.  Counters could be scaled, for example,
   ifInOctets could be changed to count received octets in, e.g., 1024
   byte blocks.  Alternatively, the size of the counter could be
   increased.

   Scaling the counters was rejected.  While it provides acceptable
   performance at high count rates, at low rates it suffers.  If there
   is little traffic on an interface, there might be a significant
   interval before enough counts occur to cause a counter to be
   incremented.  Traffic would then appear to be very bursty, leading to
   incorrect conclusions of the network's performance.

   The alternative, which this memo adopts, is to provide expanded, 64
   bit, counters.  These counters are provided in new "high capacity"
   groups,

   The old, 32-bit, counters have not been deprecated.  The 64-bit
   counters are to be used only when the 32-bit counters do not provide
   enough capacity; that is, the 32 bit counters could wrap too fast.

   For interfaces that operate at 20,000,000 (20 million) bits per
   second or less, 32-bit byte and packet counters MUST be used.  For
   interfaces that operate faster than 20,000,000 bits/second, and
   slower than 650,000,000 bits/second, 32-bit packet counters MUST be
   used and 64-bit octet counters MUST be used.  For interfaces that
   operate at 650,000,000 bits/second or faster, both 64-bit packet
   counters AND 64-bit octet counters MUST be used.

   These speed steps were chosen as reasonable compromises based on the
   following:

      (1)  The cost of maintaining 64-bit counters is relatively high,
           so minimizing the number of agents which must support them is
           desirable.  Common interfaces (such as Ethernet) should not
           require them.





McCloghrie & Kastenholz                                        [Page 14]

RFC 1573               Interfaces Group Evolution           January 1994


      (2)  64-bit counters are a new feature, introduced in SNMPv2.  It
           is reasonable to expect that support for them will be spotty
           for the immediate future.  Thus, we wish to limit them to as
           few systems as possible.  This, in effect, means that 64-bit
           counters should be limited to higher speed interfaces.
           Ethernet (10,000,000 bps) and Token Ring (16,000,000 bps) are
           fairly wide-spread so it seems reasonable to not require 64-
           bit counters for these interfaces.

      (3)  The 32-bit octet counters will wrap in the following times,
           for the following interfaces (when transmitting maximum-sized
           packets back-to-back):

           -   Ethernet: 57 minutes,

           -   16 megabit Token Ring: 36 minutes,

           -   A US T3 line (45 megabits): 12 minutes,

           -   FDDI: 5.7 minutes

      (4)  The 32-bit packet counters wraps in about 57 minutes when
           64-byte packets are transmitted back-to-back on a 650,000,000
           bit/second link.

           As an aside, a 1-terabit (1,000 gigabits) link will cause a
           64 bit octet counter to wrap in just under 5 years.
           Conversely, an 81,000,000 terabit/second link is required to
           cause a 64-bit counter to wrap in 30 minutes.  We believe
           that, while technology rapidly marches forward, this link
           speed will not be achieved for at least several years,
           leaving sufficient time to evaluate the introduction of 96
           bit counters.

   When 64-bit counters are in use, the 32-bit counters MUST still be
   available.  They will report the low 32-bits of the associated 64-bit
   count (e.g., ifInOctets will report the least significant 32 bits of
   ifHCInOctets).  This enhances inter-operability with existing
   implementations at a very minimal cost to agents.

   The new "high capacity" groups are:

      (1)  the ifHCFixedLengthGroup for character-oriented/fixed-length
           interfaces, and the ifHCPacketGroup for packet-based
           interfaces; both of these groups include 64 bit counters for
           octets, and





McCloghrie & Kastenholz                                        [Page 15]

RFC 1573               Interfaces Group Evolution           January 1994


      (2)  the ifVHCPacketGroup for packet-based interfaces; this group
           includes 64 bit counters for octets and packets.

3.2.7.  Interface Speed

   In order to deal with increasing interface speeds, we have added an
   ifHighSpeed object.

   This object reports the speed of the interface in 1,000,000 (1
   million) bits/second units.  Thus, the true speed of the interface
   will be the value reported by this object, plus or minus 500,000
   bits/second.

   Other alternatives considered were:

      (1)  Making the interface speed a 64-bit gauge.  This was rejected
           since the current SMI does not allow such a syntax.

           Furthermore, even if 64-bit gauges were available, their use
           would require additional complexity in agents due to an
           increased requirement for 64-bit operations.

      (2)  We also considered making "high-32 bit" and "low-32-bit"
           objects which, when combined, would be a 64-bit value.  This
           simply seemed overly complex for what we are trying to do.

           Furthermore, a full 64-bits of precision does not seem
           necessary.  The value of ifHighSpeed will be the only report
           of interface speed for interfaces that are faster than
           4,294,967,295 bits per second.  At this speed, the
           granularity of ifHighSpeed will be 1,000,000 bits per second,
           thus the error will be 1/4294, or about 0.02%.  This seems
           reasonable.

      (3)  Adding a "scale" object, which would define the units which
           ifSpeed's value is.

           This would require two additional objects; one for the
           scaling object, and one to replace the current ifSpeed.  This
           later object is required since the semantics of ifSpeed would
           be significantly altered, and manager stations which do not
           understand the new semantics would be confused.

3.2.8.  Multicast/Broadcast Counters

   To avoid the redundancy of counting all non-unicast packets as well
   as having individual multicast and broadcast packet counters, we
   deprecate the use of the non-unicast counters, which can be derived



McCloghrie & Kastenholz                                        [Page 16]

RFC 1573               Interfaces Group Evolution           January 1994


   from the values of the others.

   For the output broadcast and multicast counters defined in RFC 1229,
   their definitions varied slightly from the packet counters in the
   ifTable, in that they did not count errors/discarded packets.  To
   align the definitions better, the old counters are deprecated and
   replaced by new definitions.  Counters with 64 bits of range are also
   needed, as explained above.

3.2.9.  Trap Enable

   In the multi-layer interface model, each sub-layer for which there is
   an entry in the ifTable can generate linkUp/Down Traps.  Since
   interface state changes would tend to propagate through the interface
   (from top to bottom, or bottom to top), it is likely that several
   traps would be generated for each linkUp/Down occurrence.

   It is desirable to provide a mechanism for manager stations to
   control the generation of these traps.  To this end, the
   ifLinkUpDownTrapEnable object has been added.  This object allows
   managers to limit generation of traps to just the sub-layers of
   interest.

   The default setting should limit the number of traps generated to one
   per interface per linkUp/Down event.  Furthermore, it seems that the
   conditions that cause these state changes that are of most interest
   to network managers occur at the lowest level of an interface stack.
   Therefore we specify that by default, only the lowest sub-layer of
   the interface generate traps.

3.2.10.  Addition of New ifType values

   The syntax of ifType is changed to be a textual convention, such that
   the enumerated integer values are now defined in the textual
   convention, IANAifType, which can be re-specified (with additional
   values) without issuing a new version of this document.  The Internet
   Assigned Number Authority (IANA) is responsible for the assignment of
   all Internet numbers, including various SNMP-related numbers, and
   specifically, new ifType values.  Thus, this document defines two MIB
   modules: one to define the MIB for the 'interfaces' group, and a
   second to define the first version of the IANAifType textual
   convention.  The latter will be periodically re-issued by the IANA.

3.2.11.  InterfaceIndex Textual Convention

   A new textual convention, InterfaceIndex, has been defined.  This
   textual convention "contains" all of the semantics of the ifIndex
   object.  This allows other mib modules to easily import the semantics



McCloghrie & Kastenholz                                        [Page 17]

RFC 1573               Interfaces Group Evolution           January 1994


   of ifIndex.

3.2.12.  IfAdminStatus and IfOperStatus

   A new state has been added to ifOperStatus: dormant.  This state
   indicates that the relevant interface is not actually in a condition
   to pass packets (i.e., up) but is in a "pending" state, waiting for
   some external event.  For "on-demand" interfaces, this new state
   identifies the situation where the interface is waiting for events to
   place it in the up state.  Examples of such events might be:

      (1)  having packets to transmit before establishing a connection
           to a remote system.

      (2)  having a remote system establish a connection to the
           interface (e.g., dialing up to a slip-server).

   The down state now has two meanings, depending on the value of
   ifAdminStatus.

      (1)  If ifAdminStatus is not down and ifOperStatus is down, then a
           fault condition is presumed to exist on the interface.

      (2)  If ifAdminStatus is down, then ifOperStatus will normally
           also be down, i.e., there is not (necessarily) a fault
           condition on the interface.

   Note that when ifAdminStatus transitions to down, ifOperStatus will
   normally also transition to down.  In this situation, it is possible
   that ifOperStatus's transition will not occur immediately, but rather
   after a small time lag to complete certain operations before going
   "down"; for example, it might need to finish transmitting a packet.
   If a manager station finds that ifAdminStatus is down and
   ifOperStatus is not down for a particular interface, the manager
   station should wait a short while and check again.  If the condition
   still exists only then should it raise an error indication.
   Naturally, it should also ensure that ifLastChange has not changed
   during this interval.

   Whenever an interface table entry is created (usually as a result of
   system initialization), the relevant instance of ifAdminStatus is set
   to down, and presumably ifOperStatus will also be down.

   An interface may be enabled in two ways: either as a result of
   explicit management action (e.g., setting ifAdminStatus to up) or as
   a result of the managed system's initialization process.  When
   ifAdminStatus changes to the up state, the related ifOperStatus
   should do one of the following:



McCloghrie & Kastenholz                                        [Page 18]

RFC 1573               Interfaces Group Evolution           January 1994


      (1)  Change to the up state if and only if the interface is able
           to send and receive packets.

      (2)  Change to the dormant state if and only if the interface is
           found to be operable, but the interface is waiting for other,
           external, events to occur before it can transmit or receive
           packets.  Presumably when the expected events occur, the
           interface will then transition to the up state.

      (3)  Remain in the down state if an error or other fault condition
           is detected on the interface.

      (4)  Change to the unknown state if, for some reason, the state of
           the interface can not be ascertained.

      (5)  Change to the testing state if some test(s) must be performed
           on the interface.  Presumably after completion of the test,
           the interface's state will change to up, dormant, or down, as
           appropriate.

3.2.13.  Traps

   The exact definition of when linkUp and linkDown traps are generated,
   has been changed to reflect the changes to ifAdminStatus and
   ifOperStatus.

   LinkUp and linkDown traps are generated just after ifOperStatus
   leaves, or just before it enters, the down state, respectively.  The
   wording of the conditions under which a linkDown trap is generated
   was explicitly chosen to allow a node with only one interface to
   transmit the linkDown trap before that interface goes down.

   Operational experience seems to indicate that manager stations are
   most concerned with an interface being in the down state and the fact
   that this state may indicate a failure.  It seemed most useful to
   instrument either transitions into/out of the up state or the down
   state.

   Instrumenting transitions into or out of the up state has the
   drawback that an on-demand interface might have many transitions
   between up and dormant, leading to many linkUp traps and no linkDown
   traps.  Furthermore, if a node's only interface is the on-demand
   interface, then a transition to dormant will entail generation of a
   trap, necessitating bringing the link to the up state (and a linkUp
   trap)!!

   On the other hand, instrumenting transitions into or out of the down
   state has the advantages:



McCloghrie & Kastenholz                                        [Page 19]

RFC 1573               Interfaces Group Evolution           January 1994


      (1)  A transition into the down state will occur when an error is
           detected on an interface.  Error conditions are presumably of
           great interest to network managers.

      (2)  Departing the down state generally indicates that the
           interface is going to either up or dormant, both of which are
           considered "healthy" states.

   Furthermore, it is believed that generarating traps on transitions
   into or out of the down state is generally consistent with current
   usage and interpretation of these traps by manager stations.

   Therefore, this memo defines that it is the transitions into/out of
   the down state which generate traps.

   Obviously, if a failure condition is present on a node with a single
   interface, the linkDown trap will probably not be succesfully
   transmitted since the interface through which it must be transmitted
   has failed.

3.2.14.  ifSpecific

   The current definition of ifSpecific is not explicit enough.  The
   only definition that can both be made explicit and can cover all the
   useful situations (see section 3.1.9) is to have ifSpecific be the
   most general value for the media-specific MIB module (the first
   example given section in 3.1.9).  This effectively makes it redundant
   because it contains no more information than is provided by ifType.
   For this reason, ifSpecific has been deprecated.

3.3.  Media-Specific MIB Applicability

   The exact use and semantics of many objects in this MIB are open to
   some interpretation.  This is a result of the generic nature of this
   MIB.  It is not always possible to come up with specific,
   unambiguous, text that covers all cases and yet preserve the generic
   nature of the MIB.

   Therefore, it is incumbent upon a media-specific MIB designer to,
   wherever necessary, clarify the use of the objects in this MIB with
   respect to the media-specific MIB.

   Specific areas of clarification include:

   Layering Model
        The media-specific MIB designer MUST completely and
        unambiguously specify the layering model used.  Each
        individual sub-layer must be identified.



McCloghrie & Kastenholz                                        [Page 20]

RFC 1573               Interfaces Group Evolution           January 1994


   Virtual Circuits
        The media-specific MIB designer MUST specify whether virtual
        circuits are assigned entries in the ifTable or not.  If they
        are, compelling rationale must be presented.

   ifTestTable
        The media-specific MIB designer MUST specify the
        applicability of the ifTestTable.

   ifRcvAddressTable
        The media-specific MIB designer MUST specify the
        applicability of the ifRcvAddressTable.

   ifType
        For each of the ifType values to which the media-specific MIB
        applies, it must specify the mapping of ifType values to
        media-specific MIB module(s) and instances of MIB objects
        within those modules.

   However, wherever this interface MIB is specific in the semantics,
   DESCRIPTION, or applicability of objects, the media-specific MIB
   designer MUST NOT change said semantics, DESCRIPTION, or
   applicability.

4.  Overview

   This MIB consists of 5 tables:

   ifTable
        This table is the ifTable from MIB-II.

   ifXTable
        This table contains objects that have been added to the
        Interface MIB as a result of the Interface Evolution effort,
        or replacements for objects of the original, MIB-II, ifTable
        that were deprecated because the semantics of said objects
        have significantly changed.  This table also contains objects
        that were previously in the ifExtnsTable.

   ifStackTable
        This table contains objects that define the relationships
        among the sub-layers of an interface.

   ifTestTable
        This table contains objects that are used to perform tests on
        interfaces.  This table is a generic table.  The designers of
        media-specific MIBs must define exactly how this table
        applies to their specific MIB.



McCloghrie & Kastenholz                                        [Page 21]

RFC 1573               Interfaces Group Evolution           January 1994


        This table replaces the interface test table defined in
        RFC1229 [7].  The significant change is the replacement of
        the ifExtnsTestCommunity (and ifExtnsTestContext which would
        also have been required for SNMPv2) and ifExtnsTestRequestId
        objects, by the new ifTestId, ifTestStatus, and ifTestOwner
        objects.

   ifRcvAddressTable
        This table contains objects that are used to define the
        media-level addresses which this interface will receive.
        This table is a generic table.  The designers of media-
        specific MIBs must define exactly how this table applies to
        their specific MIB.

5.  IANAifType Definition

   IANAifType-MIB DEFINITIONS ::= BEGIN

   IMPORTS
       MODULE-IDENTITY, OBJECT-TYPE        FROM SNMPv2-SMI
       TEXTUAL-CONVENTION                  FROM SNMPv2-TC;

   ianaifType MODULE-IDENTITY
       LAST-UPDATED "9311082155Z"
       ORGANIZATION "IANA"
       CONTACT-INFO

                  "        Internet Assigned Numbers Authority

                   Postal: USC/Information Sciences Institute
                           4676 Admiralty Way, Marina del Rey, CA 90292

                   Tel:    +1  310 822 1511
                   E-Mail: iana@isi.edu"
       DESCRIPTION
               "The MIB module which defines the IANAifType textual
               convention, and thus the enumerated values of the
               ifType object defined in MIB-II's ifTable."
       ::= { mib-2 30 }


   IANAifType ::= TEXTUAL-CONVENTION
       STATUS       current
       DESCRIPTION
               "This data type is used as the syntax of the ifType
               object in the (updated) definition of MIB-II's
               ifTable.




McCloghrie & Kastenholz                                        [Page 22]

RFC 1573               Interfaces Group Evolution           January 1994


               The definition of this textual convention with the
               addition of newly assigned values is published
               periodically by the IANA, in either the Assigned
               Numbers RFC, or some derivative of it specific to
               Internet Network Management number assignments.  (The
               latest arrangements can be obtained by contacting the
               IANA.)

               Requests for new values should be made to IANA via
               email (iana@isi.edu).

               The relationship between the assignment of ifType
               values and of OIDs to particular media-specific MIBs
               is solely the purview of IANA and is subject to change
               without notice.  Quite often, a media-specific MIB's
               OID-subtree assignment within MIB-II's 'transmission'
               subtree will be the same as its ifType value.
               However, in some circumstances this will not be the
               case, and implementors must not pre-assume any
               specific relationship between ifType values and
               transmission subtree OIDs."
       SYNTAX  INTEGER {
                   other(1),          -- none of the following
                   regular1822(2),
                   hdh1822(3),
                   ddnX25(4),
                   rfc877x25(5),
                   ethernetCsmacd(6),
                   iso88023Csmacd(7),
                   iso88024TokenBus(8),
                   iso88025TokenRing(9),
                   iso88026Man(10),
                   starLan(11),
                   proteon10Mbit(12),
                   proteon80Mbit(13),
                   hyperchannel(14),
                   fddi(15),
                   lapb(16),
                   sdlc(17),
                   ds1(18),           -- DS1/E1 (RFC 1406)
                   e1(19),            -- obsolete
                   basicISDN(20),
                   primaryISDN(21),
                   propPointToPointSerial(22), -- proprietary serial
                   ppp(23),
                   softwareLoopback(24),
                   eon(25),            -- CLNP over IP (RFC 1070)
                   ethernet3Mbit(26),



McCloghrie & Kastenholz                                        [Page 23]

RFC 1573               Interfaces Group Evolution           January 1994


                   nsip(27),           -- XNS over IP
                   slip(28),           -- generic SLIP
                   ultra(29),          -- ULTRA technologies
                   ds3(30),            -- T-3
                   sip(31),            -- SMDS
                   frameRelay(32),    -- DTE only
                   rs232(33),
                   para(34),           -- parallel-port
                   arcnet(35),         -- arcnet
                   arcnetPlus(36),     -- arcnet plus
                   atm(37),            -- ATM cells
                   miox25(38),
                   sonet(39),          -- SONET or SDH
                   x25ple(40),
                   iso88022llc(41),
                   localTalk(42),
                   smdsDxi(43),
                   frameRelayService(44),  -- Frame relay DCE
                   v35(45),
                   hssi(46),
                   hippi(47),
                   modem(48),          -- Generic modem
                   aal5(49),           -- AAL5 over ATM
                   sonetPath(50),
                   sonetVT(51),
                   smdsIcip(52),       -- SMDS InterCarrier Interface
                   propVirtual(53),    -- proprietary virtual/internal
                   propMultiplexor(54) -- proprietary multiplexing
               }

   END

6.  Interfaces Group Definitions

   IF-MIB DEFINITIONS ::= BEGIN

   IMPORTS
       MODULE-IDENTITY, OBJECT-TYPE, Counter32, Gauge32,
       Integer32, TimeTicks,
       NOTIFICATION-TYPE                        FROM SNMPv2-SMI
       TEXTUAL-CONVENTION, DisplayString,
       PhysAddress, TruthValue, RowStatus,
       AutonomousType, TestAndIncr              FROM SNMPv2-TC
       MODULE-COMPLIANCE, OBJECT-GROUP          FROM SNMPv2-CONF
       IANAifType                               FROM IANAifType-MIB
       interfaces                               FROM RFC-1213;





McCloghrie & Kastenholz                                        [Page 24]

RFC 1573               Interfaces Group Evolution           January 1994


   ifMIB MODULE-IDENTITY
       LAST-UPDATED "9311082155Z"
       ORGANIZATION "IETF Interfaces MIB Working Group"
       CONTACT-INFO

                  "        Keith McCloghrie

                   Postal: Hughes LAN Systems
                           1225 Charleston Road, Mountain View, CA 94043

                   Tel:    +1 415 966 7934
                   E-Mail: kzm@hls.com


                           Frank Kastenholz

                   Postal: FTP Software
                           2 High Street, North Andover, MA 01845

                   Tel:    +1 508 685 4000
                   E-Mail: kasten@ftp.com"
       DESCRIPTION
               "The MIB module to describe generic objects for
               network interface sub-layers.  This MIB is an updated
               version of MIB-II's ifTable, and incorporates the
               extensions defined in RFC 1229."
       ::= { mib-2 31 }

   ifMIBObjects OBJECT IDENTIFIER ::= { ifMIB 1 }

   -- OwnerString has the same semantics as used in RFC 1271

   OwnerString ::= TEXTUAL-CONVENTION
       DISPLAY-HINT "255a"
       STATUS       current
       DESCRIPTION
               "This data type is used to model an administratively
               assigned name of the owner of a resource.  This
               information is taken from the NVT ASCII character set.
               It is suggested that this name contain one or more of
               the following: ASCII form of the manager station's
               transport address, management station name (e.g.,
               domain name), network management personnel's name,
               location, or phone number.  In some cases the agent
               itself will be the owner of an entry.  In these cases,
               this string shall be set to a string starting with
               'agent'."
       SYNTAX       OCTET STRING (SIZE(0..255))



McCloghrie & Kastenholz                                        [Page 25]

RFC 1573               Interfaces Group Evolution           January 1994


   -- InterfaceIndex contains the semantics of ifIndex and
   -- should be used for any objects defined on other mib
   -- modules that need these semantics.

   InterfaceIndex ::= TEXTUAL-CONVENTION
       DISPLAY-HINT "d"
       STATUS       current
       DESCRIPTION
               "A unique value, greater than zero, for each interface
               or interface sub-layer in the managed system.  It is
               recommended that values are assigned contiguously
               starting from 1.  The value for each interface sub-
               layer must remain constant at least from one re-
               initialization of the entity's network management
               system to the next re-initialization."
       SYNTAX       Integer32

   ifNumber  OBJECT-TYPE
       SYNTAX      Integer32
       MAX-ACCESS  read-only
       STATUS      current
       DESCRIPTION
               "The number of network interfaces (regardless of their
               current state) present on this system."
       ::= { interfaces 1 }


   -- the Interfaces table

   -- The Interfaces table contains information on the entity's
   -- interfaces.  Each sub-layer below the internetwork-layer
   -- of a network interface is considered to be an interface.

   ifTable OBJECT-TYPE
       SYNTAX      SEQUENCE OF IfEntry
       MAX-ACCESS  not-accessible
       STATUS      current
       DESCRIPTION
               "A list of interface entries.  The number of entries
               is given by the value of ifNumber."
       ::= { interfaces 2 }

   ifEntry OBJECT-TYPE
       SYNTAX      IfEntry
       MAX-ACCESS  not-accessible
       STATUS      current
       DESCRIPTION
               "An entry containing management information applicable



McCloghrie & Kastenholz                                        [Page 26]

RFC 1573               Interfaces Group Evolution           January 1994


               to a particular interface."
       INDEX   { ifIndex }
       ::= { ifTable 1 }

   IfEntry ::=
       SEQUENCE {
           ifIndex                 InterfaceIndex,
           ifDescr                 DisplayString,
           ifType                  IANAifType,
           ifMtu                   Integer32,
           ifSpeed                 Gauge32,
           ifPhysAddress           PhysAddress,
           ifAdminStatus           INTEGER,
           ifOperStatus            INTEGER,
           ifLastChange            TimeTicks,
           ifInOctets              Counter32,
           ifInUcastPkts           Counter32,
           ifInNUcastPkts          Counter32,  -- deprecated
           ifInDiscards            Counter32,
           ifInErrors              Counter32,
           ifInUnknownProtos       Counter32,
           ifOutOctets             Counter32,
           ifOutUcastPkts          Counter32,
           ifOutNUcastPkts         Counter32,  -- deprecated
           ifOutDiscards           Counter32,
           ifOutErrors             Counter32,
           ifOutQLen               Gauge32,    -- deprecated
           ifSpecific              OBJECT IDENTIFIER -- deprecated
       }


   ifIndex OBJECT-TYPE
       SYNTAX      InterfaceIndex
       MAX-ACCESS  read-only
       STATUS      current
       DESCRIPTION
               "A unique value, greater than zero, for each
               interface.  It is recommended that values are assigned
               contiguously starting from 1.  The value for each
               interface sub-layer must remain constant at least from
               one re-initialization of the entity's network
               management system to the next re-initialization."
       ::= { ifEntry 1 }

   ifDescr OBJECT-TYPE
       SYNTAX      DisplayString (SIZE (0..255))
       MAX-ACCESS  read-only
       STATUS      current



McCloghrie & Kastenholz                                        [Page 27]

RFC 1573               Interfaces Group Evolution           January 1994


       DESCRIPTION
               "A textual string containing information about the
               interface.  This string should include the name of the
               manufacturer, the product name and the version of the
               interface hardware/software."
       ::= { ifEntry 2 }

   ifType OBJECT-TYPE
       SYNTAX      IANAifType
       MAX-ACCESS  read-only
       STATUS      current
       DESCRIPTION
               "The type of interface.  Additional values for ifType
               are assigned by the Internet Assigned Numbers
               Authority (IANA), through updating the syntax of the
               IANAifType textual convention."
       ::= { ifEntry 3 }

   ifMtu OBJECT-TYPE
       SYNTAX      Integer32
       MAX-ACCESS  read-only
       STATUS      current
       DESCRIPTION
               "The size of the largest packet which can be
               sent/received on the interface, specified in octets.
               For interfaces that are used for transmitting network
               datagrams, this is the size of the largest network
               datagram that can be sent on the interface."
       ::= { ifEntry 4 }

   ifSpeed OBJECT-TYPE
       SYNTAX      Gauge32
       MAX-ACCESS  read-only
       STATUS      current
       DESCRIPTION
               "An estimate of the interface's current bandwidth in
               bits per second.  For interfaces which do not vary in
               bandwidth or for those where no accurate estimation
               can be made, this object should contain the nominal
               bandwidth.  If the bandwidth of the interface is
               greater than the maximum value reportable by this
               object then this object should report its maximum
               value (4,294,967,295) and ifHighSpeed must be used to
               report the interace's speed.  For a sub-layer which
               has no concept of bandwidth, this object should be
               zero."
       ::= { ifEntry 5 }




McCloghrie & Kastenholz                                        [Page 28]

RFC 1573               Interfaces Group Evolution           January 1994


   ifPhysAddress OBJECT-TYPE
       SYNTAX      PhysAddress
       MAX-ACCESS  read-only
       STATUS      current
       DESCRIPTION
               "The interface's address at its protocol sub-layer.
               The interface's media-specific MIB must define the bit
               and byte ordering and format of the value contained by
               this object.  For interfaces which do not have such an
               address (e.g., a serial line), this object should
               contain an octet string of zero length."
       ::= { ifEntry 6 }

   ifAdminStatus OBJECT-TYPE
       SYNTAX  INTEGER {
                   up(1),       -- ready to pass packets
                   down(2),
                   testing(3)   -- in some test mode
               }
       MAX-ACCESS  read-write
       STATUS      current
       DESCRIPTION
               "The desired state of the interface.  The testing(3)
               state indicates that no operational packets can be
               passed.  When a managed system initializes, all
               interfaces start with ifAdminStatus in the down(2)
               state.  As a result of either explicit management
               action or per configuration information retained by
               the managed system, ifAdminStatus is then changed to
               either the up(1) or testing(3) states (or remains in
               the down(2) state)."
       ::= { ifEntry 7 }

   ifOperStatus OBJECT-TYPE
       SYNTAX  INTEGER {
                   up(1),       -- ready to pass packets
                   down(2),
                   testing(3),  -- in some test mode
                   unknown(4),  -- status can not be determined
                                -- for some reason.
                   dormant(5)
               }
       MAX-ACCESS  read-only
       STATUS      current
       DESCRIPTION
               "The current operational state of the interface.  The
               testing(3) state indicates that no operational packets
               can be passed.  If ifAdminStatus is down(2) then



McCloghrie & Kastenholz                                        [Page 29]

RFC 1573               Interfaces Group Evolution           January 1994


               ifOperStatus should be down(2).  If ifAdminStatus is
               changed to up(1) then ifOperStatus should change to
               up(1) if the interface is ready to transmit and
               receive network traffic; it should change to
               dormant(5) if the interface is waiting for external
               actions (such as a serial line waiting for an
               incomming connection); it should remain in the down(2)
               state if and only if there is a fault that prevents if
               from going to the up(1) state."
       ::= { ifEntry 8 }

   ifLastChange OBJECT-TYPE
       SYNTAX      TimeTicks
       MAX-ACCESS  read-only
       STATUS      current
       DESCRIPTION
               "The value of sysUpTime at the time the interface
               entered its current operational state.  If the current
               state was entered prior to the last re-initialization
               of the local network management subsystem, then this
               object contains a zero value."
       ::= { ifEntry 9 }

   ifInOctets OBJECT-TYPE
       SYNTAX      Counter32
       MAX-ACCESS  read-only
       STATUS      current
       DESCRIPTION
               "The total number of octets received on the interface,
               including framing characters."
       ::= { ifEntry 10 }

   ifInUcastPkts OBJECT-TYPE
       SYNTAX      Counter32
       MAX-ACCESS  read-only
       STATUS      current
       DESCRIPTION
               "The number of packets, delivered by this sub-layer to
               a higher (sub-)layer, which were not addressed to a
               multicast or broadcast address at this sub-layer."
       ::= { ifEntry 11 }

   ifInNUcastPkts OBJECT-TYPE
       SYNTAX  Counter32
       MAX-ACCESS  read-only
       STATUS      deprecated
       DESCRIPTION
               "The number of packets, delivered by this sub-layer to



McCloghrie & Kastenholz                                        [Page 30]

RFC 1573               Interfaces Group Evolution           January 1994


               a higher (sub-)layer, which were addressed to a
               multicast or broadcast address at this sub-layer.
               This object is deprecated in favour of
               ifInMulticastPkts and ifInBroadcastPkts."
       ::= { ifEntry 12 }

   ifInDiscards OBJECT-TYPE
       SYNTAX      Counter32
       MAX-ACCESS  read-only
       STATUS      current
       DESCRIPTION
               "The number of inbound packets which were chosen to be
               discarded even though no errors had been detected to
               prevent their being deliverable to a higher-layer
               protocol.  One possible reason for discarding such a
               packet could be to free up buffer space."
       ::= { ifEntry 13 }

   ifInErrors OBJECT-TYPE
       SYNTAX      Counter32
       MAX-ACCESS  read-only
       STATUS      current
       DESCRIPTION
               "For packet-oriented interfaces, the number of inbound
               packets that contained errors preventing them from
               being deliverable to a higher-layer protocol.  For
               character-oriented or fixed-length interfaces, the
               number of inbound transmission units that contained
               errors preventing them from being deliverable to a
               higher-layer protocol."
       ::= { ifEntry 14 }

   ifInUnknownProtos OBJECT-TYPE
       SYNTAX      Counter32
       MAX-ACCESS  read-only
       STATUS      current
       DESCRIPTION
               "For packet-oriented interfaces, the number of packets
               received via the interface which were discarded
               because of an unknown or unsupported protocol.  For
               character-oriented or fixed-length interfaces which
               support protocol multiplexing the number of
               transmission units received via the interface which
               were discarded because of an unknown or unsupported
               protocol.  For any interface which does not support
               protocol multiplexing, this counter will always be 0."
       ::= { ifEntry 15 }




McCloghrie & Kastenholz                                        [Page 31]

RFC 1573               Interfaces Group Evolution           January 1994


   ifOutOctets OBJECT-TYPE
       SYNTAX      Counter32
       MAX-ACCESS  read-only
       STATUS      current
       DESCRIPTION
               "The total number of octets transmitted out of the
               interface, including framing characters."
       ::= { ifEntry 16 }

   ifOutUcastPkts OBJECT-TYPE
       SYNTAX      Counter32
       MAX-ACCESS  read-only
       STATUS      current
       DESCRIPTION

               "The total number of packets that higher-level
               protocols requested be transmitted, and which were not
               addressed to a multicast or broadcast address at this
               sub-layer, including those that were discarded or not
               sent."
       ::= { ifEntry 17 }

   ifOutNUcastPkts OBJECT-TYPE
       SYNTAX      Counter32
       MAX-ACCESS  read-only
       STATUS      deprecated
       DESCRIPTION
               "The total number of packets that higher-level
               protocols requested be transmitted, and which were
               addressed to a multicast or broadcast address at this
               sub-layer, including those that were discarded or not
               sent.

               This object is deprecated in favour of
               ifOutMulticastPkts and ifOutBroadcastPkts."
       ::= { ifEntry 18 }

   ifOutDiscards OBJECT-TYPE
       SYNTAX      Counter32
       MAX-ACCESS  read-only
       STATUS      current
       DESCRIPTION
               "The number of outbound packets which were chosen to
               be discarded even though no errors had been detected
               to prevent their being transmitted.  One possible
               reason for discarding such a packet could be to free
               up buffer space."
       ::= { ifEntry 19 }



McCloghrie & Kastenholz                                        [Page 32]

RFC 1573               Interfaces Group Evolution           January 1994


   ifOutErrors OBJECT-TYPE
       SYNTAX      Counter32
       MAX-ACCESS  read-only
       STATUS      current
       DESCRIPTION
               "For packet-oriented interfaces, the number of
               outbound packets that could not be transmitted because
               of errors.  For character-oriented or fixed-length
               interfaces, the number of outbound transmission units
               that could not be transmitted because of errors."
       ::= { ifEntry 20 }

   ifOutQLen OBJECT-TYPE
       SYNTAX      Gauge32
       MAX-ACCESS  read-only
       STATUS      deprecated
       DESCRIPTION
               "The length of the output packet queue (in packets)."
       ::= { ifEntry 21 }

   ifSpecific OBJECT-TYPE
       SYNTAX      OBJECT IDENTIFIER
       MAX-ACCESS  read-only
       STATUS      deprecated
       DESCRIPTION
               "A reference to MIB definitions specific to the
               particular media being used to realize the interface.
               It is recommended that this value point to an instance
               of a MIB object in the media-specific MIB, i.e., that
               this object have the semantics associated with the
               InstancePointer textual convention defined in RFC
               1443.  In fact, it is recommended that the media-
               specific MIB specify what value ifSpecific should/can
               take for values of ifType.  If no MIB definitions
               specific to the particular media are available, the
               value should be set to the OBJECT IDENTIFIER { 0 0 }."
       ::= { ifEntry 22 }


   --
   --   Extension to the interface table
   --
   -- This table replaces the ifExtnsTable table.
   --

   ifXTable        OBJECT-TYPE
       SYNTAX      SEQUENCE OF IfXEntry
       MAX-ACCESS  not-accessible



McCloghrie & Kastenholz                                        [Page 33]

RFC 1573               Interfaces Group Evolution           January 1994


       STATUS      current
       DESCRIPTION
               "A list of interface entries.  The number of entries
               is given by the value of ifNumber.  This table
               contains additional objects for the interface table."
       ::= { ifMIBObjects 1 }

   ifXEntry        OBJECT-TYPE
       SYNTAX      IfXEntry
       MAX-ACCESS  not-accessible
       STATUS      current
       DESCRIPTION
               "An entry containing additional management information
               applicable to a particular interface."
       AUGMENTS    { ifEntry }
       ::= { ifXTable 1 }

   IfXEntry ::=
       SEQUENCE {
           ifName                  DisplayString,
           ifInMulticastPkts       Counter32,
           ifInBroadcastPkts       Counter32,
           ifOutMulticastPkts      Counter32,
           ifOutBroadcastPkts      Counter32,
           ifHCInOctets            Counter64,
           ifHCInUcastPkts         Counter64,
           ifHCInMulticastPkts     Counter64,
           ifHCInBroadcastPkts     Counter64,
           ifHCOutOctets           Counter64,
           ifHCOutUcastPkts        Counter64,
           ifHCOutMulticastPkts    Counter64,
           ifHCOutBroadcastPkts    Counter64,
           ifLinkUpDownTrapEnable  INTEGER,
           ifHighSpeed             Gauge32,
           ifPromiscuousMode       TruthValue,
           ifConnectorPresent      TruthValue
       }


   ifName OBJECT-TYPE
       SYNTAX      DisplayString
       MAX-ACCESS  read-only
       STATUS      current
       DESCRIPTION
               "The textual name of the interface.  The value of this
               object should be the name of the interface as assigned
               by the local device and should be suitable for use in
               commands entered at the device's `console'.  This



McCloghrie & Kastenholz                                        [Page 34]

RFC 1573               Interfaces Group Evolution           January 1994


               might be a text name, such as `le0' or a simple port
               number, such as `1', depending on the interface naming
               syntax of the device.  If several entries in the
               ifTable together represent a single interface as named
               by the device, then each will have the same value of
               ifName.  If there is no local name, or this object is
               otherwise not applicable, then this object contains a
               0-length string."
       ::= { ifXEntry 1 }

   ifInMulticastPkts OBJECT-TYPE
       SYNTAX      Counter32
       MAX-ACCESS  read-only
       STATUS      current
       DESCRIPTION
               "The number of packets, delivered by this sub-layer to
               a higher (sub-)layer, which were addressed to a
               multicast address at this sub-layer.  For a MAC layer
               protocol, this includes both Group and Functional
               addresses."
       ::= { ifXEntry 2 }

   ifInBroadcastPkts OBJECT-TYPE
       SYNTAX      Counter32
       MAX-ACCESS  read-only
       STATUS      current
       DESCRIPTION
               "The number of packets, delivered by this sub-layer to
               a higher (sub-)layer, which were addressed to a
               broadcast address at this sub-layer."
       ::= { ifXEntry 3 }

   ifOutMulticastPkts OBJECT-TYPE
       SYNTAX      Counter32
       MAX-ACCESS  read-only
       STATUS      current
       DESCRIPTION
               "The total number of packets that higher-level
               protocols requested be transmitted, and which were
               addressed to a multicast address at this sub-layer,
               including those that were discarded or not sent.  For
               a MAC layer protocol, this includes both Group and
               Functional addresses."
       ::= { ifXEntry 4 }

   ifOutBroadcastPkts OBJECT-TYPE
       SYNTAX      Counter32
       MAX-ACCESS  read-only



McCloghrie & Kastenholz                                        [Page 35]

RFC 1573               Interfaces Group Evolution           January 1994


       STATUS      current
       DESCRIPTION
               "The total number of packets that higher-level
               protocols requested be transmitted, and which were
               addressed to a broadcast address at this sub-layer,
               including those that were discarded or not sent."
       ::= { ifXEntry 5 }

   --
   -- High Capacity Counter objects.  These objects are all

   -- 64 bit versions of the "basic" ifTable counters.  These
   -- objects all have the same basic semantics as their 32-bit
   -- counterparts, however, their syntax has been extended
   -- to 64 bits.
   --

   ifHCInOctets OBJECT-TYPE
       SYNTAX      Counter64
       MAX-ACCESS  read-only
       STATUS      current
       DESCRIPTION
               "The total number of octets received on the interface,
               including framing characters.  This object is a 64-bit
               version of ifInOctets."
       ::= { ifXEntry 6 }

   ifHCInUcastPkts OBJECT-TYPE
       SYNTAX      Counter64
       MAX-ACCESS  read-only
       STATUS      current
       DESCRIPTION
               "The number of packets, delivered by this sub-layer to
               a higher (sub-)layer, which were not addressed to a
               multicast or broadcast address at this sub-layer.
               This object is a 64-bit version of ifInUcastPkts."
       ::= { ifXEntry 7 }

   ifHCInMulticastPkts OBJECT-TYPE
       SYNTAX      Counter64
       MAX-ACCESS  read-only
       STATUS      current
       DESCRIPTION
               "The number of packets, delivered by this sub-layer to
               a higher (sub-)layer, which were addressed to a
               multicast address at this sub-layer.  For a MAC layer
               protocol, this includes both Group and Functional
               addresses.  This object is a 64-bit version of



McCloghrie & Kastenholz                                        [Page 36]

RFC 1573               Interfaces Group Evolution           January 1994


               ifInMulticastPkts."
       ::= { ifXEntry 8 }

   ifHCInBroadcastPkts OBJECT-TYPE
       SYNTAX      Counter64
       MAX-ACCESS  read-only
       STATUS      current
       DESCRIPTION
               "The number of packets, delivered by this sub-layer to
               a higher (sub-)layer, which were addressed to a
               broadcast address at this sub-layer.  This object is a
               64-bit version of ifInBroadcastPkts."
       ::= { ifXEntry 9 }

   ifHCOutOctets OBJECT-TYPE
       SYNTAX      Counter64
       MAX-ACCESS  read-only
       STATUS      current
       DESCRIPTION
               "The total number of octets transmitted out of the
               interface, including framing characters.  This object
               is a 64-bit version of ifOutOctets."
       ::= { ifXEntry 10 }

   ifHCOutUcastPkts OBJECT-TYPE
       SYNTAX      Counter64
       MAX-ACCESS  read-only
       STATUS      current
       DESCRIPTION
               "The total number of packets that higher-level
               protocols requested be transmitted, and which were not
               addressed to a multicast or broadcast address at this
               sub-layer, including those that were discarded or not
               sent.  This object is a 64-bit version of
               ifOutUcastPkts."
       ::= { ifXEntry 11 }

   ifHCOutMulticastPkts OBJECT-TYPE
       SYNTAX      Counter64
       MAX-ACCESS  read-only
       STATUS      current
       DESCRIPTION
               "The total number of packets that higher-level
               protocols requested be transmitted, and which were
               addressed to a multicast address at this sub-layer,
               including those that were discarded or not sent.  For
               a MAC layer protocol, this includes both Group and
               Functional addresses.  This object is a 64-bit version



McCloghrie & Kastenholz                                        [Page 37]

RFC 1573               Interfaces Group Evolution           January 1994


               of ifOutMulticastPkts."
       ::= { ifXEntry 12 }

   ifHCOutBroadcastPkts OBJECT-TYPE
       SYNTAX      Counter64
       MAX-ACCESS  read-only
       STATUS      current
       DESCRIPTION
               "The total number of packets that higher-level
               protocols requested be transmitted, and which were
               addressed to a broadcast address at this sub-layer,
               including those that were discarded or not sent.  This
               object is a 64-bit version of ifOutBroadcastPkts."
       ::= { ifXEntry 13 }

   ifLinkUpDownTrapEnable  OBJECT-TYPE
       SYNTAX      INTEGER { enabled(1), disabled(2) }
       MAX-ACCESS  read-write
       STATUS      current
       DESCRIPTION
               "Indicates whether linkUp/linkDown traps should be
               generated for this interface.

               By default, this object should have the value
               enabled(1) for interfaces which do not operate on
               'top' of any other interface (as defined in the
               ifStackTable), and disabled(2) otherwise."
       ::= { ifXEntry 14 }

   ifHighSpeed OBJECT-TYPE
       SYNTAX      Gauge32
       MAX-ACCESS  read-only
       STATUS      current
       DESCRIPTION
               "An estimate of the interface's current bandwidth in
               units of 1,000,000 bits per second.  If this object
               reports a value of `n' then the speed of the interface
               is somewhere in the range of `n-500,000' to
               `n+499,999'.  For interfaces which do not vary in
               bandwidth or for those where no accurate estimation
               can be made, this object should contain the nominal
               bandwidth.  For a sub-layer which has no concept of
               bandwidth, this object should be zero."
       ::= { ifXEntry 15 }

   ifPromiscuousMode  OBJECT-TYPE
       SYNTAX      TruthValue
       MAX-ACCESS  read-write



McCloghrie & Kastenholz                                        [Page 38]

RFC 1573               Interfaces Group Evolution           January 1994


       STATUS      current
       DESCRIPTION
               "This object has a value of false(2) if this interface
               only accepts packets/frames that are addressed to this
               station.  This object has a value of true(1) when the
               station accepts all packets/frames transmitted on the
               media.  The value true(1) is only legal on certain
               types of media.  If legal, setting this object to a
               value of true(1) may require the interface to be reset
               before becoming effective.

               The value of ifPromiscuousMode does not affect the
               reception of broadcast and multicast packets/frames by
               the interface."
       ::= { ifXEntry 16 }

   ifConnectorPresent   OBJECT-TYPE
       SYNTAX      TruthValue
       MAX-ACCESS  read-only
       STATUS      current
       DESCRIPTION
               "This object has the value 'true(1)' if the interface
               sublayer has a physical connector and the value
               'false(2)' otherwise."
       ::= { ifXEntry 17 }


   --           The Interface Stack Group
   --
   -- Implementation of this group is mandatory for all systems
   --

   ifStackTable  OBJECT-TYPE
        SYNTAX        SEQUENCE OF IfStackEntry
        MAX-ACCESS    not-accessible
        STATUS        current
        DESCRIPTION
               "The table containing information on the relationships
               between the multiple sub-layers of network interfaces.
               In particular, it contains information on which sub-
               layers run 'on top of' which other sub-layers.  Each
               sub-layer corresponds to a conceptual row in the
               ifTable."
        ::= { ifMIBObjects 2 }


   ifStackEntry  OBJECT-TYPE
        SYNTAX        IfStackEntry



McCloghrie & Kastenholz                                        [Page 39]

RFC 1573               Interfaces Group Evolution           January 1994


        MAX-ACCESS    not-accessible
        STATUS        current
        DESCRIPTION
               "Information on a particular relationship between two
               sub-layers, specifying that one sub-layer runs on
               'top' of the other sub-layer.  Each sub-layer
               corresponds to a conceptual row in the ifTable."
        INDEX { ifStackHigherLayer, ifStackLowerLayer }
        ::= { ifStackTable 1 }


   IfStackEntry ::=
       SEQUENCE {
           ifStackHigherLayer  Integer32,
           ifStackLowerLayer   Integer32,
           ifStackStatus       RowStatus
        }


   ifStackHigherLayer  OBJECT-TYPE
        SYNTAX        Integer32
        MAX-ACCESS    not-accessible
        STATUS        current
        DESCRIPTION
               "The value of ifIndex corresponding to the higher
               sub-layer of the relationship, i.e., the sub-layer
               which runs on 'top' of the sub-layer identified by the
               corresponding instance of ifStackLowerLayer.  If there
               is no higher sub-layer (below the internetwork layer),
               then this object has the value 0."
        ::= { ifStackEntry 1 }


   ifStackLowerLayer  OBJECT-TYPE
        SYNTAX        Integer32
        MAX-ACCESS    not-accessible
        STATUS        current
        DESCRIPTION
               "The value of ifIndex corresponding to the lower sub-
               layer of the relationship, i.e., the sub-layer which
               runs 'below' the sub-layer identified by the
               corresponding instance of ifStackHigherLayer.  If
               there is no lower sub-layer, then this object has the
               value 0."
        ::= { ifStackEntry 2 }


   ifStackStatus  OBJECT-TYPE



McCloghrie & Kastenholz                                        [Page 40]

RFC 1573               Interfaces Group Evolution           January 1994


       SYNTAX         RowStatus
       MAX-ACCESS     read-write
       STATUS         current
       DESCRIPTION
               "The status of the relationship between two sub-
               layers.

               Changing the value of this object from 'active' to
               'notInService' or 'destroy' will likely have
               consequences up and down the interface stack.  Thus,
               write access to this object is likely to be
               inappropriate for some types of interfaces, and many
               implementations will choose not to support write-
               access for any type of interface."
       ::= { ifStackEntry 3 }


   --
   --    The Interface Test Table
   --
   -- This group of objects is optional.  However, a media-specific
   -- MIB may make implementation of this group mandatory.
   --
   -- This table replaces the ifExtnsTestTable
   --

   ifTestTable   OBJECT-TYPE
       SYNTAX      SEQUENCE OF IfTestEntry
       MAX-ACCESS  not-accessible
       STATUS      current
       DESCRIPTION
               "This table contains one entry per interface.  It
               defines objects which allow a network manager to
               instruct an agent to test an interface for various
               faults.  Tests for an interface are defined in the
               media-specific MIB for that interface.  After invoking
               a test, the object ifTestResult can be read to
               determine the outcome.  If an agent can not perform
               the test, ifTestResult is set to so indicate.  The
               object ifTestCode can be used to provide further
               test-specific or interface-specific (or even
               enterprise-specific) information concerning the
               outcome of the test.  Only one test can be in progress
               on each interface at any one time.  If one test is in
               progress when another test is invoked, the second test
               is rejected.  Some agents may reject a test when a
               prior test is active on another interface.




McCloghrie & Kastenholz                                        [Page 41]

RFC 1573               Interfaces Group Evolution           January 1994


               Before starting a test, a manager-station must first
               obtain 'ownership' of the entry in the ifTestTable for
               the interface to be tested.  This is accomplished with
               the ifTestId and ifTestStatus objects as follows:

            try_again:
                get (ifTestId, ifTestStatus)
                while (ifTestStatus != notInUse)
                    /*
                     * Loop while a test is running or some other
                     * manager is configuring a test.
                     */
                    short delay
                    get (ifTestId, ifTestStatus)
                }

                /*
                 * Is not being used right now -- let's compete
                 * to see who gets it.
                 */
                lock_value = ifTestId

                if ( set(ifTestId = lock_value, ifTestStatus = inUse,
                         ifTestOwner = 'my-IP-address') == FAILURE)
                    /*
                     * Another manager got the ifTestEntry -- go
                     * try again
                     */
                    goto try_again;

                /*
                 * I have the lock
                 */
                set up any test parameters.

                /*
                 * This starts the test
                 */
                set(ifTestType = test_to_run);

                wait for test completion by polling ifTestResult

                when test completes, agent sets ifTestResult
                     agent also sets ifTestStatus = 'notInUse'

                retrieve any additional test results, and ifTestId

                if (ifTestId == lock_value+1) results are valid



McCloghrie & Kastenholz                                        [Page 42]

RFC 1573               Interfaces Group Evolution           January 1994


              A manager station first retrieves the value of the
              appropriate ifTestId and ifTestStatus objects,
              periodically repeating the retrieval if necessary,
              until the value of ifTestStatus is 'notInUse'.  The
              manager station then tries to set the same ifTestId
              object to the value it just retrieved, the same
              ifTestStatus object to 'inUse', and the corresponding
              ifTestOwner object to a value indicating itself.  If
              the set operation succeeds then the manager has
              obtained ownership of the ifTestEntry, and the value of
              the ifTestId object is incremented by the agent (per
              the semantics of TestAndIncr).  Failure of the set
              operation indicates that some other manager has
              obtained ownership of the ifTestEntry.

              Once ownership is obtained, any test parameters can be
              setup, and then the test is initiated by setting
              ifTestType.  On completion of the test, the agent sets
              ifTestStatus to 'notInUse'.  Once this occurs, the
              manager can retrieve the results.  In the (rare) event
              that the invocation of tests by two network managers
              were to overlap, then there would be a possibility that
              the first test's results might be overwritten by the
              second test's results prior to the first results being
              read.  This unlikely circumstance can be detected by a
              network manager retrieving ifTestId at the same time as
              retrieving the test results, and ensuring that the
              results are for the desired request.

              If ifTestType is not set within an abnormally long
              period of time after ownership is obtained, the agent
              should time-out the manager, and reset the value of the
              ifTestStatus object back to 'notInUse'.  It is
              suggested that this time-out period be 5 minutes.

              In general, a management station must not retransmit a
              request to invoke a test for which it does not receive
              a response; instead, it properly inspects an agent's
              MIB to determine if the invocation was successful.
              Only if the invocation was unsuccessful, is the
              invocation request retransmitted.

              Some tests may require the interface to be taken off-
              line in order to execute them, or may even require the
              agent to reboot after completion of the test.  In these
              circumstances, communication with the management
              station invoking the test may be lost until after
              completion of the test.  An agent is not required to



McCloghrie & Kastenholz                                        [Page 43]

RFC 1573               Interfaces Group Evolution           January 1994


              support such tests.  However, if such tests are
              supported, then the agent should make every effort to
              transmit a response to the request which invoked the
              test prior to losing communication.  When the agent is
              restored to normal service, the results of the test are
              properly made available in the appropriate objects.
              Note that this requires that the ifIndex value assigned
              to an interface must be unchanged even if the test
              causes a reboot.  An agent must reject any test for
              which it cannot, perhaps due to resource constraints,
              make available at least the minimum amount of
              information after that test completes."
       ::= { ifMIBObjects 3 }

   ifTestEntry OBJECT-TYPE
       SYNTAX       IfTestEntry
       MAX-ACCESS   not-accessible
       STATUS       current
       DESCRIPTION
               "An entry containing objects for invoking tests on an
               interface."
       AUGMENTS  { ifEntry }
       ::= { ifTestTable 1 }

   IfTestEntry ::=
       SEQUENCE {
           ifTestId           TestAndIncr,
           ifTestStatus       INTEGER,
           ifTestType         AutonomousType,
           ifTestResult       INTEGER,
           ifTestCode         OBJECT IDENTIFIER,
           ifTestOwner        OwnerString
       }

   ifTestId         OBJECT-TYPE
       SYNTAX       TestAndIncr
       MAX-ACCESS   read-write
       STATUS       current
       DESCRIPTION
               "This object identifies the current invocation of the
               interface's test."
       ::= { ifTestEntry 1 }

   ifTestStatus     OBJECT-TYPE
       SYNTAX       INTEGER { notInUse(1), inUse(2) }
       MAX-ACCESS   read-write
       STATUS       current
       DESCRIPTION



McCloghrie & Kastenholz                                        [Page 44]

RFC 1573               Interfaces Group Evolution           January 1994


               "This object indicates whether or not some manager
               currently has the necessary 'ownership' required to
               invoke a test on this interface.  A write to this
               object is only successful when it changes its value
               from 'notInUse(1)' to 'inUse(2)'.  After completion of
               a test, the agent resets the value back to
               'notInUse(1)'."
       ::= { ifTestEntry 2 }

   ifTestType       OBJECT-TYPE
       SYNTAX       AutonomousType
       MAX-ACCESS   read-write
       STATUS       current
       DESCRIPTION
               "A control variable used to start and stop operator-
               initiated interface tests.  Most OBJECT IDENTIFIER
               values assigned to tests are defined elsewhere, in
               association with specific types of interface.
               However, this document assigns a value for a full-
               duplex loopback test, and defines the special meanings
               of the subject identifier:

                   noTest  OBJECT IDENTIFIER ::= { 0 0 }

               When the value noTest is written to this object, no
               action is taken unless a test is in progress, in which
               case the test is aborted.  Writing any other value to
               this object is only valid when no test is currently in
               progress, in which case the indicated test is
               initiated.

               When read, this object always returns the most recent
               value that ifTestType was set to.  If it has not been
               set since the last initialization of the network
               management subsystem on the agent, a value of noTest
               is returned."
       ::= { ifTestEntry 3 }

   ifTestResult  OBJECT-TYPE
       SYNTAX       INTEGER {
                        none(1),          -- no test yet requested
                        success(2),
                        inProgress(3),
                        notSupported(4),
                        unAbleToRun(5),   -- due to state of system
                        aborted(6),
                        failed(7)
                    }



McCloghrie & Kastenholz                                        [Page 45]

RFC 1573               Interfaces Group Evolution           January 1994


       MAX-ACCESS   read-only
       STATUS       current
       DESCRIPTION
               "This object contains the result of the most recently
               requested test, or the value none(1) if no tests have
               been requested since the last reset.  Note that this
               facility provides no provision for saving the results
               of one test when starting another, as could be
               required if used by multiple managers concurrently."
       ::= { ifTestEntry 4 }

   ifTestCode  OBJECT-TYPE
       SYNTAX       OBJECT IDENTIFIER
       MAX-ACCESS   read-only
       STATUS       current
       DESCRIPTION
               "This object contains a code which contains more
               specific information on the test result, for example
               an error-code after a failed test.  Error codes and
               other values this object may take are specific to the
               type of interface and/or test.  The value may have the
               semantics of either the AutonomousType or
               InstancePointer textual conventions as defined in RFC
               1443.  The identifier:

                   testCodeUnknown  OBJECT IDENTIFIER ::= { 0 0 }

               is defined for use if no additional result code is
               available."
       ::= { ifTestEntry 5 }

   ifTestOwner      OBJECT-TYPE
       SYNTAX       OwnerString
       MAX-ACCESS   read-write
       STATUS       current
       DESCRIPTION
               "The entity which currently has the 'ownership'
               required to invoke a test on this interface."
       ::= { ifTestEntry 6 }


   --   Generic Receive Address Table
   --
   -- This group of objects is mandatory for all types of
   -- interfaces which can receive packets/frames addressed to
   -- more than one address.
   --
   -- This table replaces the ifExtnsRcvAddr table.  The main



McCloghrie & Kastenholz                                        [Page 46]

RFC 1573               Interfaces Group Evolution           January 1994


   -- difference is that this table makes use of the RowStatus
   -- textual convention, while ifExtnsRcvAddr did not.

   ifRcvAddressTable  OBJECT-TYPE
       SYNTAX      SEQUENCE OF IfRcvAddressEntry
       MAX-ACCESS  not-accessible
       STATUS      current
       DESCRIPTION
               "This table contains an entry for each address
               (broadcast, multicast, or uni-cast) for which the
               system will receive packets/frames on a particular
               interface, except as follows:

               - for an interface operating in promiscuous mode,
               entries are only required for those addresses for
               which the system would receive frames were it not
               operating in promiscuous mode.

               - for 802.5 functional addresses, only one entry is
               required, for the address which has the functional
               address bit ANDed with the bit mask of all functional
               addresses for which the interface will accept frames."
       ::= { ifMIBObjects 4 }

   ifRcvAddressEntry  OBJECT-TYPE
       SYNTAX      IfRcvAddressEntry
       MAX-ACCESS  not-accessible
       STATUS      current
       DESCRIPTION
               "A list of objects identifying an address for which
               the system will accept packets/frames on the
               particular interface identified by the index value
               ifIndex."
       INDEX  { ifIndex, ifRcvAddressAddress }
       ::= { ifRcvAddressTable 1 }

   IfRcvAddressEntry ::=
       SEQUENCE {
           ifRcvAddressAddress   PhysAddress,
           ifRcvAddressStatus    RowStatus,
           ifRcvAddressType      INTEGER
       }

   ifRcvAddressAddress OBJECT-TYPE
       SYNTAX      PhysAddress
       MAX-ACCESS  read-create
       STATUS      current
       DESCRIPTION



McCloghrie & Kastenholz                                        [Page 47]

RFC 1573               Interfaces Group Evolution           January 1994


               "An address for which the system will accept
               packets/frames on this entry's interface."
       ::= { ifRcvAddressEntry 1 }

   ifRcvAddressStatus OBJECT-TYPE
       SYNTAX      RowStatus
       MAX-ACCESS  read-write
       STATUS      current
       DESCRIPTION
               "This object is used to create and delete rows in the
               ifRcvAddressTable."

       ::= { ifRcvAddressEntry 2 }

   ifRcvAddressType OBJECT-TYPE
       SYNTAX      INTEGER {
                       other(1),
                       volatile(2),
                       nonVolatile(3)
                   }

       MAX-ACCESS  read-create
       STATUS      current
       DESCRIPTION
               "This object has the value nonVolatile(3) for those
               entries in the table which are valid and will not be
               deleted by the next restart of the managed system.
               Entries having the value volatile(2) are valid and
               exist, but have not been saved, so that will not exist
               after the next restart of the managed system.  Entries
               having the value other(1) are valid and exist but are
               not classified as to whether they will continue to
               exist after the next restart."

       DEFVAL  { volatile }

       ::= { ifRcvAddressEntry 3 }


   -- definition of interface-related traps.

   linkDown NOTIFICATION-TYPE
       OBJECTS { ifIndex, ifAdminStatus, ifOperStatus }
       STATUS  current
       DESCRIPTION
               "A linkDown trap signifies that the SNMPv2 entity,
               acting in an agent role, has detected that the
               ifOperStatus object for one of its communication links



McCloghrie & Kastenholz                                        [Page 48]

RFC 1573               Interfaces Group Evolution           January 1994


               is about to transition into the down state."
       ::= { snmpTraps 3 }

   linkUp NOTIFICATION-TYPE
       OBJECTS { ifIndex, ifAdminStatus, ifOperStatus }
       STATUS  current
       DESCRIPTION
               "A linkUp trap signifies that the SNMPv2 entity,
               acting in an agent role, has detected that the
               ifOperStatus object for one of its communication links
               has transitioned out of the down state."
       ::= { snmpTraps 4 }


   -- conformance information

   ifConformance OBJECT IDENTIFIER ::= { ifMIB 2 }

   ifGroups      OBJECT IDENTIFIER ::= { ifConformance 1 }
   ifCompliances OBJECT IDENTIFIER ::= { ifConformance 2 }


   -- compliance statements

   ifCompliance MODULE-COMPLIANCE
       STATUS  current
       DESCRIPTION
               "The compliance statement for SNMPv2 entities which
               have network interfaces."

       MODULE  -- this module
           MANDATORY-GROUPS { ifGeneralGroup, ifStackGroup }

           GROUP       ifFixedLengthGroup
           DESCRIPTION
               "This group is mandatory for all network interfaces
               which are character-oriented or transmit data in
               fixed-length transmission units."

           GROUP       ifHCFixedLengthGroup
           DESCRIPTION
               "This group is mandatory only for those network
               interfaces which are character-oriented or transmit
               data in fixed-length transmission units, and for which
               the value of the corresponding instance of ifSpeed is
               greater than 20,000,000 bits/second."

           GROUP       ifPacketGroup



McCloghrie & Kastenholz                                        [Page 49]

RFC 1573               Interfaces Group Evolution           January 1994


           DESCRIPTION
               "This group is mandatory for all network interfaces
               which are packet-oriented."

           GROUP       ifHCPacketGroup
           DESCRIPTION
               "This group is mandatory only for those network
               interfaces which are packet-oriented and for which the
               value of the corresponding instance of ifSpeed is
               greater than 650,000,000 bits/second."
           GROUP       ifTestGroup
           DESCRIPTION
               "This group is optional.  Media-specific MIBs which
               require interface tests are strongly encouraged to use
               this group for invoking tests and reporting results.
               A medium specific MIB which has mandatory tests may
               make implementation of this group mandatory."

           GROUP       ifRcvAddressGroup
           DESCRIPTION
               "The applicability of this group MUST be defined by
               the media-specific MIBs.  Media-specific MIBs must
               define the exact meaning, use, and semantics of the
               addresses in this group."

           OBJECT      ifLinkUpDownTrapEnable
           MIN-ACCESS  read-only
           DESCRIPTION
               "Write access is not required."

           OBJECT      ifPromiscuousMode
           MIN-ACCESS  read-only
           DESCRIPTION
               "Write access is not required."

           OBJECT      ifStackStatus
           SYNTAX      INTEGER { active(1) } -- subset of RowStatus
           MIN-ACCESS  read-only
           DESCRIPTION
               "Write access is not required, and only one of the six
               enumerated values for the RowStatus textual convention
               need be supported, specifically: active(1)."

           OBJECT       ifAdminStatus
           SYNTAX       INTEGER { up(1), down(2) }
           MIN-ACCESS   read-only
           DESCRIPTION
               "Write access is not required, nor is support for the



McCloghrie & Kastenholz                                        [Page 50]

RFC 1573               Interfaces Group Evolution           January 1994


               value testing(3)."
       ::= { ifCompliances 1 }


   -- units of conformance

   ifGeneralGroup    OBJECT-GROUP
       OBJECTS { ifDescr, ifType, ifSpeed, ifPhysAddress,
                 ifAdminStatus, ifOperStatus, ifLastChange,
                 ifLinkUpDownTrapEnable, ifConnectorPresent,
                 ifHighSpeed, ifName }
       STATUS  current
       DESCRIPTION
               "A collection of objects providing information
               applicable to all network interfaces."
       ::= { ifGroups 1 }

   -- the following five groups are mutually exclusive; at most
   -- one of these groups is implemented for any interface

   ifFixedLengthGroup    OBJECT-GROUP
       OBJECTS { ifInOctets, ifOutOctets, ifInUnknownProtos,
                 ifInErrors, ifOutErrors }
       STATUS  current
       DESCRIPTION
               "A collection of objects providing information
               specific to non-high speed, character-oriented or
               fixed-length-transmission network interfaces.  (Non-
               high speed interfaces transmit and receive at speeds
               less than or equal to 20,000,000 bits/second.)"
       ::= { ifGroups 2 }

   ifHCFixedLengthGroup    OBJECT-GROUP
       OBJECTS { ifHCInOctets, ifHCOutOctets,
                 ifInOctets, ifOutOctets, ifInUnknownProtos,
                 ifInErrors, ifOutErrors }
       STATUS  current
       DESCRIPTION
               "A collection of objects providing information
               specific to high speed (greater than 20,000,000
               bits/second) character-oriented or fixed-length-
               transmission network interfaces."
       ::= { ifGroups 3 }

   ifPacketGroup    OBJECT-GROUP
       OBJECTS { ifInOctets, ifOutOctets, ifInUnknownProtos,
                 ifInErrors, ifOutErrors,
                 ifMtu, ifInUcastPkts, ifInMulticastPkts,



McCloghrie & Kastenholz                                        [Page 51]

RFC 1573               Interfaces Group Evolution           January 1994


                 ifInBroadcastPkts, ifInDiscards,
                 ifOutUcastPkts, ifOutMulticastPkts,
                 ifOutBroadcastPkts, ifOutDiscards,
                 ifPromiscuousMode }
       STATUS  current
       DESCRIPTION
               "A collection of objects providing information
               specific to non-high speed, packet-oriented network
               interfaces.  (Non-high speed interfaces transmit and
               receive at speeds less than or equal to 20,000,000
               bits/second.)"
       ::= { ifGroups 4 }

   ifHCPacketGroup    OBJECT-GROUP
       OBJECTS { ifHCInOctets, ifHCOutOctets,
                 ifInOctets, ifOutOctets, ifInUnknownProtos,
                 ifInErrors, ifOutErrors,
                 ifMtu, ifInUcastPkts, ifInMulticastPkts,
                 ifInBroadcastPkts, ifInDiscards,
                 ifOutUcastPkts, ifOutMulticastPkts,
                 ifOutBroadcastPkts, ifOutDiscards,
                 ifPromiscuousMode }
       STATUS  current
       DESCRIPTION
               "A collection of objects providing information
               specific to high speed (greater than 20,000,000
               bits/second but less than or equal to 650,000,000
               bits/second) packet-oriented network interfaces."
       ::= { ifGroups 5 }

   ifVHCPacketGroup    OBJECT-GROUP
       OBJECTS { ifHCInUcastPkts, ifHCInMulticastPkts,
                 ifHCInBroadcastPkts, ifHCOutUcastPkts,
                 ifHCOutMulticastPkts, ifHCOutBroadcastPkts,
                 ifHCInOctets, ifHCOutOctets,
                 ifInOctets, ifOutOctets, ifInUnknownProtos,
                 ifInErrors, ifOutErrors,
                 ifMtu, ifInUcastPkts, ifInMulticastPkts,
                 ifInBroadcastPkts, ifInDiscards,
                 ifOutUcastPkts, ifOutMulticastPkts,
                 ifOutBroadcastPkts, ifOutDiscards,
                 ifPromiscuousMode }
       STATUS  current
       DESCRIPTION
               "A collection of objects providing information
               specific to higher speed (greater than 650,000,000
               bits/second) packet-oriented network interfaces."
       ::= { ifGroups 6 }



McCloghrie & Kastenholz                                        [Page 52]

RFC 1573               Interfaces Group Evolution           January 1994


   ifRcvAddressGroup    OBJECT-GROUP
       OBJECTS { ifRcvAddressStatus, ifRcvAddressType }
       STATUS  current
       DESCRIPTION
               "A collection of objects providing information on the
               multiple addresses which an interface receives."
       ::= { ifGroups 7 }

   ifTestGroup    OBJECT-GROUP
       OBJECTS { ifTestId, ifTestStatus, ifTestType,
                 ifTestResult, ifTestCode, ifTestOwner }
       STATUS  current
       DESCRIPTION
               "A collection of objects providing the ability to
               invoke tests on an interface."
       ::= { ifGroups 8 }

   ifStackGroup    OBJECT-GROUP
       OBJECTS { ifStackStatus }
       STATUS  current
       DESCRIPTION
               "A collection of objects providing information on the
               layering of MIB-II interfaces."
       ::= { ifGroups 9 }

   END

7.  Acknowledgements

   This memo has been produced by the IETF's Interfaces MIB Working
   Group.

   The initial proposal to the working group was the result of
   conversations and discussions with many people, including at least
   the following: Fred Baker, Ted Brunner, Chuck Davin, Jeremy Greene,
   Marshall Rose, Kaj Tesink, and Dean Throop.

8.  References

   [1] Case, J., McCloghrie, K., Rose, M., and S. Waldbusser, "Structure
       of Management Information for version 2 of the Simple Network
       Management Protocol (SNMPv2)", RFC 1442, SNMP Research, Inc.,
       Hughes LAN Systems, Dover Beach Consulting, Inc., Carnegie Mellon
       University, April 1993.

   [2] Galvin, J., and K. McCloghrie, "Administrative Model for version
       2 of the Simple Network Management Protocol (SNMPv2)", RFC 1445,
       Trusted Information Systems, Hughes LAN Systems, April 1993.



McCloghrie & Kastenholz                                        [Page 53]

RFC 1573               Interfaces Group Evolution           January 1994


   [3] Case, J., McCloghrie, K., Rose, M., and S. Waldbusser, "Protocol
       Operations for version 2 of the Simple Network Management
       Protocol (SNMPv2)", RFC 1448, SNMP Research, Inc., Hughes LAN
       Systems, Dover Beach Consulting, Inc., Carnegie Mellon
       University, April 1993.

   [4] McCloghrie, K., and M. Rose, "Management Information Base for
       Network Management of TCP/IP-based internets - MIB-II", STD 17,
       RFC 1213, Hughes LAN Systems, Performance Systems International,
       March 1991.

   [5] Case, J., Fedor, M., Schoffstall, M., and J. Davin, "Simple
       Network Management Protocol", RFC 1157, SNMP Research,
       Performance Systems International, Performance Systems
       International, MIT Laboratory for Computer Science, May 1990.

   [6] Postel, J., "Internet Protocol", STD 5, RFC 791, USC/Information
       Sciences Institute, September 1981.

   [7] McCloghrie, K., "Extensions to the Generic-Interface MIB", RFC
       1229, Hughes LAN Systems, May 1991.

   [8] Case, J., McCloghrie, K., Rose, M., and S. Waldbusser, "Textual
       Conventions for version 2 of the Simple Network Management
       Protocol (SNMPv2)", RFC 1443, SNMP Research, Inc., Hughes LAN
       Systems, Dover Beach Consulting, Inc., Carnegie Mellon
       University, April 1993.
























McCloghrie & Kastenholz                                        [Page 54]

RFC 1573               Interfaces Group Evolution           January 1994


9.  Security Considerations

   Security issues are not discussed in this memo.

10.  Authors' Addresses

   Keith McCloghrie
   Hughes LAN Systems
   1225 Charleston Rd,
   Mountain View, Ca 94043

   Phone: 415-966-7934
   EMail: kzm@hls.com


   Frank Kastenholz
   FTP Software
   2 High Street
   North Andover, Mass. USA 01845

   Phone: (508)685-4000
   EMail: kasten@ftp.com





























McCloghrie & Kastenholz                                        [Page 55]