File: rfc2251.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 (2803 lines) | stat: -rw-r--r-- 114,488 bytes parent folder | download | duplicates (12)
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






Network Working Group                                            M. Wahl
Request for Comments: 2251                           Critical Angle Inc.
Category: Standards Track                                       T. Howes
                                           Netscape Communications Corp.
                                                                S. Kille
                                                           Isode Limited
                                                           December 1997


               Lightweight Directory Access Protocol (v3)

1. Status of this Memo

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

Copyright Notice

   Copyright (C) The Internet Society (1997).  All Rights Reserved.

IESG Note

   This document describes a directory access protocol that provides
   both read and update access.  Update access requires secure
   authentication, but this document does not mandate implementation of
   any satisfactory authentication mechanisms.

   In accordance with RFC 2026, section 4.4.1, this specification is
   being approved by IESG as a Proposed Standard despite this
   limitation, for the following reasons:

   a. to encourage implementation and interoperability testing of
      these protocols (with or without update access) before they
      are deployed, and

   b. to encourage deployment and use of these protocols in read-only
      applications.  (e.g. applications where LDAPv3 is used as
      a query language for directories which are updated by some
      secure mechanism other than LDAP), and

   c. to avoid delaying the advancement and deployment of other Internet
      standards-track protocols which require the ability to query, but
      not update, LDAPv3 directory servers.





Wahl, et. al.               Standards Track                     [Page 1]

RFC 2251                         LDAPv3                    December 1997


   Readers are hereby warned that until mandatory authentication
   mechanisms are standardized, clients and servers written according to
   this specification which make use of update functionality are
   UNLIKELY TO INTEROPERATE, or MAY INTEROPERATE ONLY IF AUTHENTICATION
   IS REDUCED TO AN UNACCEPTABLY WEAK LEVEL.

   Implementors are hereby discouraged from deploying LDAPv3 clients or
   servers which implement the update functionality, until a Proposed
   Standard for mandatory authentication in LDAPv3 has been approved and
   published as an RFC.

Table of Contents

   1.  Status of this Memo ....................................  1
       Copyright Notice .......................................  1
       IESG Note ..............................................  1
   2.  Abstract ...............................................  3
   3.  Models .................................................  4
   3.1. Protocol Model ........................................  4
   3.2. Data Model ............................................  5
   3.2.1. Attributes of Entries ...............................  5
   3.2.2. Subschema Entries and Subentries ....................  7
   3.3. Relationship to X.500 .................................  8
   3.4. Server-specific Data Requirements .....................  8
   4.  Elements of Protocol ...................................  9
   4.1. Common Elements .......................................  9
   4.1.1. Message Envelope ....................................  9
   4.1.1.1. Message ID ........................................ 11
   4.1.2. String Types ........................................ 11
   4.1.3. Distinguished Name and Relative Distinguished Name .. 11
   4.1.4. Attribute Type ...................................... 12
   4.1.5. Attribute Description ............................... 13
   4.1.5.1. Binary Option ..................................... 14
   4.1.6. Attribute Value ..................................... 14
   4.1.7. Attribute Value Assertion ........................... 15
   4.1.8. Attribute ........................................... 15
   4.1.9. Matching Rule Identifier ............................ 15
   4.1.10. Result Message ..................................... 16
   4.1.11. Referral ........................................... 18
   4.1.12. Controls ........................................... 19
   4.2. Bind Operation ........................................ 20
   4.2.1. Sequencing of the Bind Request ...................... 21
   4.2.2. Authentication and Other Security Services .......... 22
   4.2.3. Bind Response ....................................... 23
   4.3. Unbind Operation ...................................... 24
   4.4. Unsolicited Notification .............................. 24
   4.4.1. Notice of Disconnection ............................. 24
   4.5. Search Operation ...................................... 25



Wahl, et. al.               Standards Track                     [Page 2]

RFC 2251                         LDAPv3                    December 1997


   4.5.1. Search Request ...................................... 25
   4.5.2. Search Result ....................................... 29
   4.5.3. Continuation References in the Search Result ........ 31
   4.5.3.1. Example ........................................... 31
   4.6. Modify Operation ...................................... 32
   4.7. Add Operation ......................................... 34
   4.8. Delete Operation ...................................... 35
   4.9. Modify DN Operation ................................... 36
   4.10. Compare Operation .................................... 37
   4.11. Abandon Operation .................................... 38
   4.12. Extended Operation ................................... 38
   5.  Protocol Element Encodings and Transfer ................ 39
   5.1. Mapping Onto BER-based Transport Services ............. 39
   5.2. Transfer Protocols .................................... 40
   5.2.1. Transmission Control Protocol (TCP) ................. 40
   6.  Implementation Guidelines .............................. 40
   6.1. Server Implementations ................................ 40
   6.2. Client Implementations ................................ 40
   7.  Security Considerations ................................ 41
   8.  Acknowledgements ....................................... 41
   9.  Bibliography ........................................... 41
   10. Authors' Addresses ..................................... 42
   Appendix A - Complete ASN.1 Definition ..................... 44
   Full Copyright Statement ................................... 50

2.  Abstract

   The protocol described in this document is designed to provide access
   to directories supporting the X.500 models, while not incurring the
   resource requirements of the X.500 Directory Access Protocol (DAP).
   This protocol is specifically targeted at management applications and
   browser applications that provide read/write interactive access to
   directories. When used with a directory supporting the X.500
   protocols, it is intended to be a complement to the X.500 DAP.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED",  and "MAY" in this document
   are to be interpreted as described in RFC 2119 [10].

   Key aspects of this version of LDAP are:

   - All protocol elements of LDAPv2 (RFC 1777) are supported. The
     protocol is carried directly over TCP or other transport, bypassing
     much of the session/presentation overhead of X.500 DAP.

   - Most protocol data elements can be encoded as ordinary strings
     (e.g., Distinguished Names).




Wahl, et. al.               Standards Track                     [Page 3]

RFC 2251                         LDAPv3                    December 1997


   - Referrals to other servers may be returned.

   - SASL mechanisms may be used with LDAP to provide association
     security services.

   - Attribute values and Distinguished Names have been
     internationalized through the use of the ISO 10646 character set.

   - The protocol can be extended to support new operations, and
     controls may be used to extend existing operations.

   - Schema is published in the directory for use by clients.

3.  Models

   Interest in X.500 [1] directory technologies in the Internet has led
   to efforts to reduce the high cost of entry associated with use of
   these technologies.  This document continues the efforts to define
   directory protocol alternatives, updating the LDAP [2] protocol
   specification.

3.1. Protocol Model

   The general model adopted by this protocol is one of clients
   performing protocol operations against servers. In this model, a
   client transmits a protocol request describing the operation to be
   performed to a server. The server is then responsible for performing
   the necessary operation(s) in the directory. Upon completion of the
   operation(s), the server returns a response containing any results or
   errors to the requesting client.

   In keeping with the goal of easing the costs associated with use of
   the directory, it is an objective of this protocol to minimize the
   complexity of clients so as to facilitate widespread deployment of
   applications capable of using the directory.

   Note that although servers are required to return responses whenever
   such responses are defined in the protocol, there is no requirement
   for synchronous behavior on the part of either clients or servers.
   Requests and responses for multiple operations may be exchanged
   between a client and server in any order, provided the client
   eventually receives a response for every request that requires one.

   In LDAP versions 1 and 2, no provision was made for protocol servers
   returning referrals to clients.  However, for improved performance
   and distribution this version of the protocol permits servers to
   return to clients referrals to other servers.  This allows servers to
   offload the work of contacting other servers to progress operations.



Wahl, et. al.               Standards Track                     [Page 4]

RFC 2251                         LDAPv3                    December 1997


   Note that the core protocol operations defined in this document can
   be mapped to a strict subset of the X.500(1997) directory abstract
   service, so it can be cleanly provided by the DAP.  However there is
   not a one-to-one mapping between LDAP protocol operations and DAP
   operations: server implementations acting as a gateway to X.500
   directories may need to make multiple DAP requests.

3.2. Data Model

   This section provides a brief introduction to the X.500 data model,
   as used by LDAP.

   The LDAP protocol assumes there are one or more servers which jointly
   provide access to a Directory Information Tree (DIT).  The tree is
   made up of entries.  Entries have names: one or more attribute values
   from the entry form its relative distinguished name (RDN), which MUST
   be unique among all its siblings.  The concatenation of the relative
   distinguished names of the sequence of entries from a particular
   entry to an immediate subordinate of the root of the tree forms that
   entry's Distinguished Name (DN), which is unique in the tree.  An
   example of a Distinguished Name is

   CN=Steve Kille, O=Isode Limited, C=GB

   Some servers may hold cache or shadow copies of entries, which can be
   used to answer search and comparison queries, but will return
   referrals or contact other servers if modification operations are
   requested.

   Servers which perform caching or shadowing MUST ensure that they do
   not violate any access control constraints placed on the data by the
   originating server.

   The largest collection of entries, starting at an entry that is
   mastered by a particular server, and including all its subordinates
   and their subordinates, down to the entries which are mastered by
   different servers, is termed a naming context.  The root of the DIT
   is a DSA-specific Entry (DSE) and not part of any naming context:
   each server has different attribute values in the root DSE.  (DSA is
   an X.500 term for the directory server).

3.2.1. Attributes of Entries

   Entries consist of a set of attributes.  An attribute is a type with
   one or more associated values.  The attribute type is identified by a
   short descriptive name and an OID (object identifier). The attribute





Wahl, et. al.               Standards Track                     [Page 5]

RFC 2251                         LDAPv3                    December 1997


   type governs whether there can be more than one value of an attribute
   of that type in an entry, the syntax to which the values must
   conform, the kinds of matching which can be performed on values of
   that attribute, and other functions.

   An example of an attribute is "mail". There may be one or more values
   of this attribute, they must be IA5 (ASCII) strings, and they are
   case insensitive (e.g. "foo@bar.com" will match "FOO@BAR.COM").

   Schema is the collection of attribute type definitions, object class
   definitions and other information which a server uses to determine
   how to match a filter or attribute value assertion (in a compare
   operation) against the attributes of an entry, and whether to permit
   add and modify operations.  The definition of schema for use with
   LDAP is given in [5] and [6].  Additional schema elements may be
   defined in other documents.

   Each entry MUST have an objectClass attribute.  The objectClass
   attribute specifies the object classes of an entry, which along with
   the system and user schema determine the permitted attributes of an
   entry.  Values of this attribute may be modified by clients, but the
   objectClass attribute cannot be removed.  Servers may restrict the
   modifications of this attribute to prevent the basic structural class
   of the entry from being changed (e.g. one cannot change a person into
   a country).  When creating an entry or adding an objectClass value to
   an entry, all superclasses of the named classes are implicitly added
   as well if not already present, and the client must supply values for
   any mandatory attributes of new superclasses.

   Some attributes, termed operational attributes, are used by servers
   for administering the directory system itself.  They are not returned
   in search results unless explicitly requested by name.  Attributes
   which are not operational, such as "mail", will have their schema and
   syntax constraints enforced by servers, but servers will generally
   not make use of their values.

   Servers MUST NOT permit clients to add attributes to an entry unless
   those attributes are permitted by the object class definitions, the
   schema controlling that entry (specified in the subschema - see
   below), or are operational attributes known to that server and used
   for administrative purposes.  Note that there is a particular
   objectClass 'extensibleObject' defined in [5] which permits all user
   attributes to be present in an entry.

   Entries MAY contain, among others, the following operational
   attributes, defined in [5]. These attributes are maintained
   automatically by the server and are not modifiable by clients:




Wahl, et. al.               Standards Track                     [Page 6]

RFC 2251                         LDAPv3                    December 1997


   - creatorsName: the Distinguished Name of the user who added this
     entry to the directory.

   - createTimestamp: the time this entry was added to the directory.

   - modifiersName: the Distinguished Name of the user who last modified
     this entry.

   - modifyTimestamp: the time this entry was last modified.

   - subschemaSubentry:  the Distinguished Name of the subschema entry
     (or subentry) which controls the schema for this entry.

3.2.2. Subschema Entries and Subentries

   Subschema entries are used for administering information about the
   directory schema, in particular the object classes and attribute
   types supported by directory servers.  A single subschema entry
   contains all schema definitions used by entries in a particular part
   of the directory tree.

   Servers which follow X.500(93) models SHOULD implement subschema
   using the X.500 subschema mechanisms, and so these subschemas are not
   ordinary entries.  LDAP clients SHOULD NOT assume that servers
   implement any of the other aspects of X.500 subschema.  A server
   which masters entries and permits clients to modify these entries
   MUST implement and provide access to these subschema entries, so that
   its clients may discover the attributes and object classes which are
   permitted to be present. It is strongly recommended that all other
   servers implement this as well.

   The following four attributes MUST be present in all subschema
   entries:

   - cn: this attribute MUST be used to form the RDN of the subschema
     entry.

   - objectClass: the attribute MUST have at least the values "top" and
     "subschema".

   - objectClasses: each value of this attribute specifies an object
     class known to the server.

   - attributeTypes: each value of this attribute specifies an attribute
     type known to the server.

   These are defined in [5]. Other attributes MAY be present in
   subschema entries, to reflect additional supported capabilities.



Wahl, et. al.               Standards Track                     [Page 7]

RFC 2251                         LDAPv3                    December 1997


   These include matchingRules, matchingRuleUse, dITStructureRules,
   dITContentRules, nameForms and ldapSyntaxes.

   Servers SHOULD provide the attributes createTimestamp and
   modifyTimestamp in subschema entries, in order to allow clients to
   maintain their caches of schema information.

   Clients MUST only retrieve attributes from a subschema entry by
   requesting a base object search of the entry, where the search filter
   is "(objectClass=subschema)". (This will allow LDAPv3 servers which
   gateway to X.500(93) to detect that subentry information is being
   requested.)

3.3. Relationship to X.500

   This document defines LDAP in terms of X.500 as an X.500 access
   mechanism.  An LDAP server MUST act in accordance with the
   X.500(1993) series of ITU recommendations when providing the service.
   However, it is not required that an LDAP server make use of any X.500
   protocols in providing this service, e.g. LDAP can be mapped onto any
   other directory system so long as the X.500 data and service model as
   used in LDAP is not violated in the LDAP interface.

3.4. Server-specific Data Requirements

   An LDAP server MUST provide information about itself and other
   information that is specific to each server.  This is represented as
   a group of attributes located in the root DSE (DSA-Specific Entry),
   which is named with the zero-length LDAPDN.  These attributes are
   retrievable if a client performs a base object search of the root
   with filter "(objectClass=*)", however they are subject to access
   control restrictions.  The root DSE MUST NOT be included if the
   client performs a subtree search starting from the root.

   Servers may allow clients to modify these attributes.

   The following attributes of the root DSE are defined in section 5 of
   [5].  Additional attributes may be defined in other documents.

   - namingContexts: naming contexts held in the server. Naming contexts
     are defined in section 17 of X.501 [6].

   - subschemaSubentry: subschema entries (or subentries) known by this
     server.

   - altServer: alternative servers in case this one is later
     unavailable.




Wahl, et. al.               Standards Track                     [Page 8]

RFC 2251                         LDAPv3                    December 1997


   - supportedExtension: list of supported extended operations.

   - supportedControl: list of supported controls.

   - supportedSASLMechanisms: list of supported SASL security features.

   - supportedLDAPVersion: LDAP versions implemented by the server.

   If the server does not master entries and does not know the locations
   of schema information, the subschemaSubentry attribute is not present
   in the root DSE.  If the server masters directory entries under one
   or more schema rules, there may be any number of values of the
   subschemaSubentry attribute in the root DSE.

4.  Elements of Protocol

   The LDAP protocol is described using Abstract Syntax Notation 1
   (ASN.1) [3], and is typically transferred using a subset of ASN.1
   Basic Encoding Rules [11]. In order to support future extensions to
   this protocol, clients and servers MUST ignore elements of SEQUENCE
   encodings whose tags they do not recognize.

   Note that unlike X.500, each change to the LDAP protocol other than
   through the extension mechanisms will have a different version
   number.  A client will indicate the version it supports as part of
   the bind request, described in section 4.2.  If a client has not sent
   a bind, the server MUST assume that version 3 is supported in the
   client (since version 2 required that the client bind first).

   Clients may determine the protocol version a server supports by
   reading the supportedLDAPVersion attribute from the root DSE. Servers
   which implement version 3 or later versions MUST provide this
   attribute.  Servers which only implement version 2 may not provide
   this attribute.

4.1. Common Elements

   This section describes the LDAPMessage envelope PDU (Protocol Data
   Unit) format, as well as data type definitions which are used in the
   protocol operations.

4.1.1. Message Envelope

   For the purposes of protocol exchanges, all protocol operations are
   encapsulated in a common envelope, the LDAPMessage, which is defined
   as follows:

        LDAPMessage ::= SEQUENCE {



Wahl, et. al.               Standards Track                     [Page 9]

RFC 2251                         LDAPv3                    December 1997


                messageID       MessageID,
                protocolOp      CHOICE {
                        bindRequest     BindRequest,
                        bindResponse    BindResponse,
                        unbindRequest   UnbindRequest,
                        searchRequest   SearchRequest,
                        searchResEntry  SearchResultEntry,
                        searchResDone   SearchResultDone,
                        searchResRef    SearchResultReference,
                        modifyRequest   ModifyRequest,
                        modifyResponse  ModifyResponse,
                        addRequest      AddRequest,
                        addResponse     AddResponse,
                        delRequest      DelRequest,
                        delResponse     DelResponse,
                        modDNRequest    ModifyDNRequest,
                        modDNResponse   ModifyDNResponse,
                        compareRequest  CompareRequest,
                        compareResponse CompareResponse,
                        abandonRequest  AbandonRequest,
                        extendedReq     ExtendedRequest,
                        extendedResp    ExtendedResponse },
                 controls       [0] Controls OPTIONAL }

        MessageID ::= INTEGER (0 .. maxInt)

        maxInt INTEGER ::= 2147483647 -- (2^^31 - 1) --

   The function of the LDAPMessage is to provide an envelope containing
   common fields required in all protocol exchanges. At this time the
   only common fields are the message ID and the controls.

   If the server receives a PDU from the client in which the LDAPMessage
   SEQUENCE tag cannot be recognized, the messageID cannot be parsed,
   the tag of the protocolOp is not recognized as a request, or the
   encoding structures or lengths of data fields are found to be
   incorrect, then the server MUST return the notice of disconnection
   described in section 4.4.1, with resultCode protocolError, and
   immediately close the connection. In other cases that the server
   cannot parse the request received by the client, the server MUST
   return an appropriate response to the request, with the resultCode
   set to protocolError.

   If the client receives a PDU from the server which cannot be parsed,
   the client may discard the PDU, or may abruptly close the connection.

   The ASN.1 type Controls is defined in section 4.1.12.




Wahl, et. al.               Standards Track                    [Page 10]

RFC 2251                         LDAPv3                    December 1997


4.1.1.1. Message ID

   All LDAPMessage envelopes encapsulating responses contain the
   messageID value of the corresponding request LDAPMessage.

   The message ID of a request MUST have a value different from the
   values of any other requests outstanding in the LDAP session of which
   this message is a part.

   A client MUST NOT send a second request with the same message ID as
   an earlier request on the same connection if the client has not
   received the final response from the earlier request.  Otherwise the
   behavior is undefined.  Typical clients increment a counter for each
   request.

   A client MUST NOT reuse the message id of an abandonRequest or of the
   abandoned operation until it has received a response from the server
   for another request invoked subsequent to the abandonRequest, as the
   abandonRequest itself does not have a response.

4.1.2. String Types

   The LDAPString is a notational convenience to indicate that, although
   strings of LDAPString type encode as OCTET STRING types, the ISO
   10646 [13] character set (a superset of Unicode) is used, encoded
   following the UTF-8 algorithm [14]. Note that in the UTF-8 algorithm
   characters which are the same as ASCII (0x0000 through 0x007F) are
   represented as that same ASCII character in a single byte.  The other
   byte values are used to form a variable-length encoding of an
   arbitrary character.

        LDAPString ::= OCTET STRING

   The LDAPOID is a notational convenience to indicate that the
   permitted value of this string is a (UTF-8 encoded) dotted-decimal
   representation of an OBJECT IDENTIFIER.

        LDAPOID ::= OCTET STRING

   For example,

        1.3.6.1.4.1.1466.1.2.3

4.1.3. Distinguished Name and Relative Distinguished Name

   An LDAPDN and a RelativeLDAPDN are respectively defined to be the
   representation of a Distinguished Name and a Relative Distinguished
   Name after encoding according to the specification in [4], such that



Wahl, et. al.               Standards Track                    [Page 11]

RFC 2251                         LDAPv3                    December 1997


        <distinguished-name> ::= <name>

        <relative-distinguished-name> ::= <name-component>

   where <name> and <name-component> are as defined in [4].

        LDAPDN ::= LDAPString

        RelativeLDAPDN ::= LDAPString

   Only Attribute Types can be present in a relative distinguished name
   component; the options of Attribute Descriptions (next section) MUST
   NOT be used in specifying distinguished names.

4.1.4. Attribute Type

   An AttributeType takes on as its value the textual string associated
   with that AttributeType in its specification.

        AttributeType ::= LDAPString

   Each attribute type has a unique OBJECT IDENTIFIER which has been
   assigned to it.  This identifier may be written as decimal digits
   with components separated by periods, e.g. "2.5.4.10".

   A specification may also assign one or more textual names for an
   attribute type.  These names MUST begin with a letter, and only
   contain ASCII letters, digit characters and hyphens.  They are case
   insensitive.  (These ASCII characters are identical to ISO 10646
   characters whose UTF-8 encoding is a single byte between 0x00 and
   0x7F.)

   If the server has a textual name for an attribute type, it MUST use a
   textual name for attributes returned in search results.  The dotted-
   decimal OBJECT IDENTIFIER is only used if there is no textual name
   for an attribute type.

   Attribute type textual names are non-unique, as two different
   specifications (neither in standards track RFCs) may choose the same
   name.

   A server which masters or shadows entries SHOULD list all the
   attribute types it supports in the subschema entries, using the
   attributeTypes attribute.  Servers which support an open-ended set of
   attributes SHOULD include at least the attributeTypes value for the
   'objectClass' attribute. Clients MAY retrieve the attributeTypes
   value from subschema entries in order to obtain the OBJECT IDENTIFIER
   and other information associated with attribute types.



Wahl, et. al.               Standards Track                    [Page 12]

RFC 2251                         LDAPv3                    December 1997


   Some attribute type names which are used in this version of LDAP are
   described in [5].  Servers may implement additional attribute types.

4.1.5. Attribute Description

   An AttributeDescription is a superset of the definition of the
   AttributeType.  It has the same ASN.1 definition, but allows
   additional options to be specified.  They are also case insensitive.

        AttributeDescription ::= LDAPString

   A value of AttributeDescription is based on the following BNF:

        <AttributeDescription> ::= <AttributeType> [ ";" <options> ]

        <options>  ::= <option> | <option> ";" <options>

        <option>   ::= <opt-char> <opt-char>*

        <opt-char> ::=  ASCII-equivalent letters, numbers and hyphen

   Examples of valid AttributeDescription:

        cn
        userCertificate;binary

   One option, "binary", is defined in this document.  Additional
   options may be defined in IETF standards-track and experimental RFCs.
   Options beginning with "x-" are reserved for private experiments.
   Any option could be associated with any AttributeType, although not
   all combinations may be supported by a server.

   An AttributeDescription with one or more options is treated as a
   subtype of the attribute type without any options.  Options present
   in an AttributeDescription are never mutually exclusive.
   Implementations MUST generate the <options> list sorted in ascending
   order, and servers MUST treat any two AttributeDescription with the
   same AttributeType and options as equivalent.  A server will treat an
   AttributeDescription with any options it does not implement as an
   unrecognized attribute type.

   The data type "AttributeDescriptionList" describes a list of 0 or
   more attribute types.  (A list of zero elements has special
   significance in the Search request.)

        AttributeDescriptionList ::= SEQUENCE OF
                AttributeDescription




Wahl, et. al.               Standards Track                    [Page 13]

RFC 2251                         LDAPv3                    December 1997


4.1.5.1. Binary Option

   If the "binary" option is present in an AttributeDescription, it
   overrides any string-based encoding representation defined for that
   attribute in [5]. Instead the attribute is to be transferred as a
   binary value encoded using the Basic Encoding Rules [11].  The syntax
   of the binary value is an ASN.1 data type definition which is
   referenced by the "SYNTAX" part of the attribute type definition.

   The presence or absence of the "binary" option only affects the
   transfer of attribute values in protocol; servers store any
   particular attribute in a single format.  If a client requests that a
   server return an attribute in the binary format, but the server
   cannot generate that format, the server MUST treat this attribute
   type as an unrecognized attribute type.  Similarly, clients MUST NOT
   expect servers to return an attribute in binary format if the client
   requested that attribute by name without the binary option.

   This option is intended to be used with attributes whose syntax is a
   complex ASN.1 data type, and the structure of values of that type is
   needed by clients.  Examples of this kind of syntax are "Certificate"
   and "CertificateList".

4.1.6. Attribute Value

   A field of type AttributeValue takes on as its value either a string
   encoding of a AttributeValue data type, or an OCTET STRING containing
   an encoded binary value, depending on whether the "binary" option is
   present in the companion AttributeDescription to this AttributeValue.

   The definition of string encodings for different syntaxes and types
   may be found in other documents, and in particular [5].

        AttributeValue ::= OCTET STRING

   Note that there is no defined limit on the size of this encoding;
   thus protocol values may include multi-megabyte attributes (e.g.
   photographs).

   Attributes may be defined which have arbitrary and non-printable
   syntax.  Implementations MUST NEITHER simply display nor attempt to
   decode as ASN.1 a value if its syntax is not known.  The
   implementation may attempt to discover the subschema of the source
   entry, and retrieve the values of attributeTypes from it.

   Clients MUST NOT send attribute values in a request which are not
   valid according to the syntax defined for the attributes.




Wahl, et. al.               Standards Track                    [Page 14]

RFC 2251                         LDAPv3                    December 1997


4.1.7. Attribute Value Assertion

   The AttributeValueAssertion type definition is similar to the one in
   the X.500 directory standards.  It contains an attribute description
   and a matching rule assertion value suitable for that type.

        AttributeValueAssertion ::= SEQUENCE {
                attributeDesc   AttributeDescription,
                assertionValue  AssertionValue }

        AssertionValue ::= OCTET STRING

   If the "binary" option is present in attributeDesc, this signals to
   the server that the assertionValue is a binary encoding of the
   assertion value.

   For all the string-valued user attributes described in [5], the
   assertion value syntax is the same as the value syntax.  Clients may
   use attribute values as assertion values in compare requests and
   search filters.

   Note however that the assertion syntax may be different from the
   value syntax for other attributes or for non-equality matching rules.
   These may have an assertion syntax which contains only part of the
   value.  See section 20.2.1.8 of X.501 [6] for examples.

4.1.8. Attribute

   An attribute consists of a type and one or more values of that type.
   (Though attributes MUST have at least one value when stored, due to
   access control restrictions the set may be empty when transferred in
   protocol.  This is described in section 4.5.2, concerning the
   PartialAttributeList type.)

        Attribute ::= SEQUENCE {
                type    AttributeDescription,
                vals    SET OF AttributeValue }

   Each attribute value is distinct in the set (no duplicates).  The
   order of attribute values within the vals set is undefined and
   implementation-dependent, and MUST NOT be relied upon.

4.1.9. Matching Rule Identifier

   A matching rule is a means of expressing how a server should compare
   an AssertionValue received in a search filter with an abstract data
   value.  The matching rule defines the syntax of the assertion value
   and the process to be performed in the server.



Wahl, et. al.               Standards Track                    [Page 15]

RFC 2251                         LDAPv3                    December 1997


   An X.501(1993) Matching Rule is identified in the LDAP protocol by
   the printable representation of its OBJECT IDENTIFIER, either as one
   of the strings given in [5], or as decimal digits with components
   separated by periods, e.g. "caseIgnoreIA5Match" or
   "1.3.6.1.4.1.453.33.33".

        MatchingRuleId ::= LDAPString

   Servers which support matching rules for use in the extensibleMatch
   search filter MUST list the matching rules they implement in
   subschema entries, using the matchingRules attributes.  The server
   SHOULD also list there, using the matchingRuleUse attribute, the
   attribute types with which each matching rule can be used.  More
   information is given in section 4.4 of [5].

4.1.10. Result Message

   The LDAPResult is the construct used in this protocol to return
   success or failure indications from servers to clients. In response
   to various requests servers will return responses containing fields
   of type LDAPResult to indicate the final status of a protocol
   operation request.

        LDAPResult ::= SEQUENCE {
                resultCode      ENUMERATED {
                             success                      (0),
                             operationsError              (1),
                             protocolError                (2),
                             timeLimitExceeded            (3),
                             sizeLimitExceeded            (4),
                             compareFalse                 (5),
                             compareTrue                  (6),

                             authMethodNotSupported       (7),
                             strongAuthRequired           (8),
                                        -- 9 reserved --
                             referral                     (10),  -- new
                             adminLimitExceeded           (11),  -- new
                             unavailableCriticalExtension (12),  -- new
                             confidentialityRequired      (13),  -- new
                             saslBindInProgress           (14),  -- new
                             noSuchAttribute              (16),
                             undefinedAttributeType       (17),
                             inappropriateMatching        (18),
                             constraintViolation          (19),
                             attributeOrValueExists       (20),
                             invalidAttributeSyntax       (21),
                                        -- 22-31 unused --



Wahl, et. al.               Standards Track                    [Page 16]

RFC 2251                         LDAPv3                    December 1997


                             noSuchObject                 (32),
                             aliasProblem                 (33),
                             invalidDNSyntax              (34),
                             -- 35 reserved for undefined isLeaf --
                             aliasDereferencingProblem    (36),
                                        -- 37-47 unused --
                             inappropriateAuthentication  (48),
                             invalidCredentials           (49),
                             insufficientAccessRights     (50),
                             busy                         (51),
                             unavailable                  (52),
                             unwillingToPerform           (53),
                             loopDetect                   (54),
                                        -- 55-63 unused --
                             namingViolation              (64),
                             objectClassViolation         (65),
                             notAllowedOnNonLeaf          (66),
                             notAllowedOnRDN              (67),
                             entryAlreadyExists           (68),
                             objectClassModsProhibited    (69),
                                        -- 70 reserved for CLDAP --
                             affectsMultipleDSAs          (71), -- new
                                        -- 72-79 unused --
                             other                        (80) },
                             -- 81-90 reserved for APIs --
                matchedDN       LDAPDN,
                errorMessage    LDAPString,
                referral        [3] Referral OPTIONAL }

   All the result codes with the exception of success, compareFalse and
   compareTrue are to be treated as meaning the operation could not be
   completed in its entirety.

   Most of the result codes are based on problem indications from X.511
   error data types.  Result codes from 16 to 21 indicate an
   AttributeProblem, codes 32, 33, 34 and 36 indicate a NameProblem,
   codes 48, 49 and 50 indicate a SecurityProblem, codes 51 to 54
   indicate a ServiceProblem, and codes 64 to 69 and 71 indicates an
   UpdateProblem.

   If a client receives a result code which is not listed above, it is
   to be treated as an unknown error condition.

   The errorMessage field of this construct may, at the server's option,
   be used to return a string containing a textual, human-readable
   (terminal control and page formatting characters should be avoided)
   error diagnostic. As this error diagnostic is not standardized,




Wahl, et. al.               Standards Track                    [Page 17]

RFC 2251                         LDAPv3                    December 1997


   implementations MUST NOT rely on the values returned.  If the server
   chooses not to return a textual diagnostic, the errorMessage field of
   the LDAPResult type MUST contain a zero length string.

   For result codes of noSuchObject, aliasProblem, invalidDNSyntax and
   aliasDereferencingProblem, the matchedDN field is set to the name of
   the lowest entry (object or alias) in the directory that was matched.
   If no aliases were dereferenced while attempting to locate the entry,
   this will be a truncated form of the name provided, or if aliases
   were dereferenced, of the resulting name, as defined in section 12.5
   of X.511 [8]. The matchedDN field is to be set to a zero length
   string with all other result codes.

4.1.11. Referral

   The referral error indicates that the contacted server does not hold
   the target entry of the request.  The referral field is present in an
   LDAPResult if the LDAPResult.resultCode field value is referral, and
   absent with all other result codes.  It contains a reference to
   another server (or set of servers) which may be accessed via LDAP or
   other protocols.  Referrals can be returned in response to any
   operation request (except unbind and abandon which do not have
   responses). At least one URL MUST be present in the Referral.

   The referral is not returned for a singleLevel or wholeSubtree search
   in which the search scope spans multiple naming contexts, and several
   different servers would need to be contacted to complete the
   operation. Instead, continuation references, described in section
   4.5.3, are returned.

        Referral ::= SEQUENCE OF LDAPURL  -- one or more

        LDAPURL ::= LDAPString -- limited to characters permitted in URLs

   If the client wishes to progress the operation, it MUST follow the
   referral by contacting any one of servers.  All the URLs MUST be
   equally capable of being used to progress the operation.  (The
   mechanisms for how this is achieved by multiple servers are outside
   the scope of this document.)

   URLs for servers implementing the LDAP protocol are written according
   to [9].  If an alias was dereferenced, the <dn> part of the URL MUST
   be present, with the new target object name.  If the <dn> part is
   present, the client MUST use this name in its next request to
   progress the operation, and if it is not present the client will use
   the same name as in the original request.  Some servers (e.g.
   participating in distributed indexing) may provide a different filter
   in a referral for a search operation.  If the filter part of the URL



Wahl, et. al.               Standards Track                    [Page 18]

RFC 2251                         LDAPv3                    December 1997


   is present in an LDAPURL, the client MUST use this filter in its next
   request to progress this search, and if it is not present the client
   MUST use the same filter as it used for that search.  Other aspects
   of the new request may be the same or different as the request which
   generated the referral.

   Note that UTF-8 characters appearing in a DN or search filter may not
   be legal for URLs (e.g. spaces) and MUST be escaped using the %
   method in RFC 1738 [7].

   Other kinds of URLs may be returned, so long as the operation could
   be performed using that protocol.

4.1.12. Controls

   A control is a way to specify extension information. Controls which
   are sent as part of a request apply only to that request and are not
   saved.

        Controls ::= SEQUENCE OF Control

        Control ::= SEQUENCE {
                controlType             LDAPOID,
                criticality             BOOLEAN DEFAULT FALSE,
                controlValue            OCTET STRING OPTIONAL }

   The controlType field MUST be a UTF-8 encoded dotted-decimal
   representation of an OBJECT IDENTIFIER which uniquely identifies the
   control.  This prevents conflicts between control names.

   The criticality field is either TRUE or FALSE.

   If the server recognizes the control type and it is appropriate for
   the operation, the server will make use of the control when
   performing the operation.

   If the server does not recognize the control type and the criticality
   field is TRUE, the server MUST NOT perform the operation, and MUST
   instead return the resultCode unsupportedCriticalExtension.

   If the control is not appropriate for the operation and criticality
   field is TRUE, the server MUST NOT perform the operation, and MUST
   instead return the resultCode unsupportedCriticalExtension.

   If the control is unrecognized or inappropriate but the criticality
   field is FALSE, the server MUST ignore the control.





Wahl, et. al.               Standards Track                    [Page 19]

RFC 2251                         LDAPv3                    December 1997


   The controlValue contains any information associated with the
   control, and its format is defined for the control.  The server MUST
   be prepared to handle arbitrary contents of the controlValue octet
   string, including zero bytes.  It is absent only if there is no value
   information which is associated with a control of its type.

   This document does not define any controls.  Controls may be defined
   in other documents.  The definition of a control consists of:

     - the OBJECT IDENTIFIER assigned to the control,

     - whether the control is always noncritical, always critical, or
       critical at the client's option,

     - the format of the controlValue contents of the control.

   Servers list the controls which they recognize in the
   supportedControl attribute in the root DSE.

4.2. Bind Operation

   The function of the Bind Operation is to allow authentication
   information to be exchanged between the client and server.

   The Bind Request is defined as follows:

        BindRequest ::= [APPLICATION 0] SEQUENCE {
                version                 INTEGER (1 .. 127),
                name                    LDAPDN,
                authentication          AuthenticationChoice }

        AuthenticationChoice ::= CHOICE {
                simple                  [0] OCTET STRING,
                                         -- 1 and 2 reserved
                sasl                    [3] SaslCredentials }

        SaslCredentials ::= SEQUENCE {
                mechanism               LDAPString,
                credentials             OCTET STRING OPTIONAL }

   Parameters of the Bind Request are:

   - version: A version number indicating the version of the protocol to
     be used in this protocol session.  This document describes version
     3 of the LDAP protocol.  Note that there is no version negotiation,
     and the client just sets this parameter to the version it desires.
     If the client requests protocol version 2, a server that supports
     the version 2 protocol as described in [2] will not return any v3-



Wahl, et. al.               Standards Track                    [Page 20]

RFC 2251                         LDAPv3                    December 1997


     specific protocol fields.  (Note that not all LDAP servers will
     support protocol version 2, since they may be unable to generate
     the attribute syntaxes associated with version 2.)

   - name: The name of the directory object that the client wishes to
     bind as.  This field may take on a null value (a zero length
     string) for the purposes of anonymous binds, when authentication
     has been performed at a lower layer, or when using SASL credentials
     with a mechanism that includes the LDAPDN in the credentials.

   - authentication: information used to authenticate the name, if any,
     provided in the Bind Request.

   Upon receipt of a Bind Request, a protocol server will authenticate
   the requesting client, if necessary.  The server will then return a
   Bind Response to the client indicating the status of the
   authentication.

   Authorization is the use of this authentication information when
   performing operations.  Authorization MAY be affected by factors
   outside of the LDAP Bind request, such as lower layer security
   services.

4.2.1. Sequencing of the Bind Request

   For some SASL authentication mechanisms, it may be necessary for the
   client to invoke the BindRequest multiple times.  If at any stage the
   client wishes to abort the bind process it MAY unbind and then drop
   the underlying connection.  Clients MUST NOT invoke operations
   between two Bind requests made as part of a multi-stage bind.

   A client may abort a SASL bind negotiation by sending a BindRequest
   with a different value in the mechanism field of SaslCredentials, or
   an AuthenticationChoice other than sasl.

   If the client sends a BindRequest with the sasl mechanism field as an
   empty string, the server MUST return a BindResponse with
   authMethodNotSupported as the resultCode.  This will allow clients to
   abort a negotiation if it wishes to try again with the same SASL
   mechanism.

   Unlike LDAP v2, the client need not send a Bind Request in the first
   PDU of the connection.  The client may request any operations and the
   server MUST treat these as unauthenticated. If the server requires
   that the client bind before browsing or modifying the directory, the
   server MAY reject a request other than binding, unbinding or an
   extended request with the "operationsError" result.




Wahl, et. al.               Standards Track                    [Page 21]

RFC 2251                         LDAPv3                    December 1997


   If the client did not bind before sending a request and receives an
   operationsError, it may then send a Bind Request.  If this also fails
   or the client chooses not to bind on the existing connection, it will
   close the connection, reopen it and begin again by first sending a
   PDU with a Bind Request.  This will aid in interoperating with
   servers implementing other versions of LDAP.

   Clients MAY send multiple bind requests on a connection to change
   their credentials.  A subsequent bind process has the effect of
   abandoning all operations outstanding on the connection.  (This
   simplifies server implementation.)  Authentication from earlier binds
   are subsequently ignored, and so if the bind fails, the connection
   will be treated as anonymous. If a SASL transfer encryption or
   integrity mechanism has been negotiated, and that mechanism does not
   support the changing of credentials from one identity to another,
   then the client MUST instead establish a new connection.

4.2.2. Authentication and Other Security Services

   The simple authentication option provides minimal authentication
   facilities, with the contents of the authentication field consisting
   only of a cleartext password.  Note that the use of cleartext
   passwords is not recommended over open networks when there is no
   authentication or encryption being performed by a lower layer; see
   the "Security Considerations" section.

   If no authentication is to be performed, then the simple
   authentication option MUST be chosen, and the password be of zero
   length.  (This is often done by LDAPv2 clients.)  Typically the DN is
   also of zero length.

   The sasl choice allows for any mechanism defined for use with SASL
   [12].  The mechanism field contains the name of the mechanism.  The
   credentials field contains the arbitrary data used for
   authentication, inside an OCTET STRING wrapper.  Note that unlike
   some Internet application protocols where SASL is used, LDAP is not
   text-based, thus no base64 transformations are performed on the
   credentials.

   If any SASL-based integrity or confidentiality services are enabled,
   they take effect following the transmission by the server and
   reception by the client of the final BindResponse with resultCode
   success.

   The client can request that the server use authentication information
   from a lower layer protocol by using the SASL EXTERNAL mechanism.





Wahl, et. al.               Standards Track                    [Page 22]

RFC 2251                         LDAPv3                    December 1997


4.2.3. Bind Response

   The Bind Response is defined as follows.

        BindResponse ::= [APPLICATION 1] SEQUENCE {
             COMPONENTS OF LDAPResult,
             serverSaslCreds    [7] OCTET STRING OPTIONAL }

    BindResponse consists simply of an indication from the server of he
   status of the client's request for authentication.

   f the bind was successful, the resultCode will be success, therwise
   it will be one of:

   - operationsError: server encountered an internal error,

   - protocolError: unrecognized version number or incorrect PDU
     structure,

   - authMethodNotSupported: unrecognized SASL mechanism name,

   - strongAuthRequired: the server requires authentication be
     performed with a SASL mechanism,

   - referral: this server cannot accept this bind and the client
     should try another,

   - saslBindInProgress: the server requires the client to send a
     new bind request, with the same sasl mechanism, to continue the
     authentication process,

   - inappropriateAuthentication: the server requires the client
     which had attempted to bind anonymously or without supplying
     credentials to provide some form of credentials,

   - invalidCredentials: the wrong password was supplied or the SASL
     credentials could not be processed,

   - unavailable: the server is shutting down.

   If the server does not support the client's requested protocol
   version, it MUST set the resultCode to protocolError.

   If the client receives a BindResponse response where the resultCode
   was protocolError, it MUST close the connection as the server will be
   unwilling to accept further operations.  (This is for compatibility
   with earlier versions of LDAP, in which the bind was always the first
   operation, and there was no negotiation.)



Wahl, et. al.               Standards Track                    [Page 23]

RFC 2251                         LDAPv3                    December 1997


   The serverSaslCreds are used as part of a SASL-defined bind mechanism
   to allow the client to authenticate the server to which it is
   communicating, or to perform "challenge-response" authentication. If
   the client bound with the password choice, or the SASL mechanism does
   not require the server to return information to the client, then this
   field is not to be included in the result.

4.3. Unbind Operation

   The function of the Unbind Operation is to terminate a protocol
   session.  The Unbind Operation is defined as follows:

        UnbindRequest ::= [APPLICATION 2] NULL

   The Unbind Operation has no response defined. Upon transmission of an
   UnbindRequest, a protocol client may assume that the protocol session
   is terminated. Upon receipt of an UnbindRequest, a protocol server
   may assume that the requesting client has terminated the session and
   that all outstanding requests may be discarded, and may close the
   connection.

4.4. Unsolicited Notification

   An unsolicited notification is an LDAPMessage sent from the server to
   the client which is not in response to any LDAPMessage received by
   the server. It is used to signal an extraordinary condition in the
   server or in the connection between the client and the server.  The
   notification is of an advisory nature, and the server will not expect
   any response to be returned from the client.

   The unsolicited notification is structured as an LDAPMessage in which
   the messageID is 0 and protocolOp is of the extendedResp form.  The
   responseName field of the ExtendedResponse is present. The LDAPOID
   value MUST be unique for this notification, and not be used in any
   other situation.

   One unsolicited notification is defined in this document.

4.4.1. Notice of Disconnection

   This notification may be used by the server to advise the client that
   the server is about to close the connection due to an error
   condition.  Note that this notification is NOT a response to an
   unbind requested by the client: the server MUST follow the procedures
   of section 4.3. This notification is intended to assist clients in
   distinguishing between an error condition and a transient network





Wahl, et. al.               Standards Track                    [Page 24]

RFC 2251                         LDAPv3                    December 1997


   failure.  As with a connection close due to network failure, the
   client MUST NOT assume that any outstanding requests which modified
   the directory have succeeded or failed.

   The responseName is 1.3.6.1.4.1.1466.20036, the response field is
   absent, and the resultCode is used to indicate the reason for the
   disconnection.

   The following resultCode values are to be used in this notification:

   - protocolError: The server has received data from the client in
   which
     the LDAPMessage structure could not be parsed.

   - strongAuthRequired: The server has detected that an established
     underlying security association protecting communication between
     the client and server has unexpectedly failed or been compromised.

   - unavailable: This server will stop accepting new connections and
     operations on all existing connections, and be unavailable for an
     extended period of time.  The client may make use of an alternative
     server.

   After sending this notice, the server MUST close the connection.
   After receiving this notice, the client MUST NOT transmit any further
   on the connection, and may abruptly close the connection.

4.5. Search Operation

   The Search Operation allows a client to request that a search be
   performed on its behalf by a server.  This can be used to read
   attributes from a single entry, from entries immediately below a
   particular entry, or a whole subtree of entries.

4.5.1. Search Request

   The Search Request is defined as follows:

        SearchRequest ::= [APPLICATION 3] SEQUENCE {
                baseObject      LDAPDN,
                scope           ENUMERATED {
                        baseObject              (0),
                        singleLevel             (1),
                        wholeSubtree            (2) },
                derefAliases    ENUMERATED {
                        neverDerefAliases       (0),
                        derefInSearching        (1),
                        derefFindingBaseObj     (2),



Wahl, et. al.               Standards Track                    [Page 25]

RFC 2251                         LDAPv3                    December 1997


                        derefAlways             (3) },
                sizeLimit       INTEGER (0 .. maxInt),
                timeLimit       INTEGER (0 .. maxInt),
                typesOnly       BOOLEAN,
                filter          Filter,
                attributes      AttributeDescriptionList }

        Filter ::= CHOICE {
                and             [0] SET OF Filter,
                or              [1] SET OF Filter,
                not             [2] Filter,
                equalityMatch   [3] AttributeValueAssertion,
                substrings      [4] SubstringFilter,
                greaterOrEqual  [5] AttributeValueAssertion,
                lessOrEqual     [6] AttributeValueAssertion,
                present         [7] AttributeDescription,
                approxMatch     [8] AttributeValueAssertion,
                extensibleMatch [9] MatchingRuleAssertion }

        SubstringFilter ::= SEQUENCE {
                type            AttributeDescription,
                -- at least one must be present
                substrings      SEQUENCE OF CHOICE {
                        initial [0] LDAPString,
                        any     [1] LDAPString,
                        final   [2] LDAPString } }

        MatchingRuleAssertion ::= SEQUENCE {
                matchingRule    [1] MatchingRuleId OPTIONAL,
                type            [2] AttributeDescription OPTIONAL,
                matchValue      [3] AssertionValue,
                dnAttributes    [4] BOOLEAN DEFAULT FALSE }

   Parameters of the Search Request are:

   - baseObject: An LDAPDN that is the base object entry relative to
     which the search is to be performed.

   - scope: An indicator of the scope of the search to be performed. The
     semantics of the possible values of this field are identical to the
     semantics of the scope field in the X.511 Search Operation.

   - derefAliases: An indicator as to how alias objects (as defined in
     X.501) are to be handled in searching.  The semantics of the
     possible values of this field are:

             neverDerefAliases: do not dereference aliases in searching
             or in locating the base object of the search;



Wahl, et. al.               Standards Track                    [Page 26]

RFC 2251                         LDAPv3                    December 1997


             derefInSearching: dereference aliases in subordinates of
             the base object in searching, but not in locating the
             base object of the search;

             derefFindingBaseObj: dereference aliases in locating
             the base object of the search, but not when searching
             subordinates of the base object;

             derefAlways: dereference aliases both in searching and in
             locating the base object of the search.

   - sizelimit: A sizelimit that restricts the maximum number of entries
     to be returned as a result of the search. A value of 0 in this
     field indicates that no client-requested sizelimit restrictions are
     in effect for the search.  Servers may enforce a maximum number of
     entries to return.

   - timelimit: A timelimit that restricts the maximum time (in seconds)
     allowed for a search. A value of 0 in this field indicates that no
     client-requested timelimit restrictions are in effect for the
     search.

   - typesOnly: An indicator as to whether search results will contain
     both attribute types and values, or just attribute types.  Setting
     this field to TRUE causes only attribute types (no values) to be
     returned.  Setting this field to FALSE causes both attribute types
     and values to be returned.

   - filter: A filter that defines the conditions that must be fulfilled
     in order for the search to match a given entry.

     The 'and', 'or' and 'not' choices can be used to form combinations of
     filters. At least one filter element MUST be present in an 'and' or
     'or' choice.  The others match against individual attribute values of
     entries in the scope of the search.  (Implementor's note: the 'not'
     filter is an example of a tagged choice in an implicitly-tagged
     module.  In BER this is treated as if the tag was explicit.)

     A server MUST evaluate filters according to the three-valued logic
     of X.511(93) section 7.8.1.  In summary, a filter is evaluated to
     either "TRUE", "FALSE" or "Undefined".  If the filter evaluates
     to TRUE for a particular entry, then the attributes of that entry
     are returned as part of the search result (subject to any applicable
     access control restrictions). If the filter evaluates to FALSE or
     Undefined, then the entry is ignored for the search.






Wahl, et. al.               Standards Track                    [Page 27]

RFC 2251                         LDAPv3                    December 1997


     A filter of the "and" choice is TRUE if all the filters in the SET
     OF evaluate to TRUE, FALSE if at least one filter is FALSE, and
     otherwise Undefined.  A filter of the "or" choice is FALSE if all
     of the filters in the SET OF evaluate to FALSE, TRUE if at least
     one filter is TRUE, and Undefined otherwise.  A filter of the "not"
     choice is TRUE if the filter being negated is FALSE, FALSE if it is
     TRUE, and Undefined if it is Undefined.

     The present match evaluates to TRUE where there is an attribute or
     subtype of the specified attribute description present in an entry,
     and FALSE otherwise (including a presence test with an unrecognized
     attribute description.)

     The extensibleMatch is new in this version of LDAP.  If the
     matchingRule field is absent, the type field MUST be present, and
     the equality match is performed for that type.  If the type field is
     absent and matchingRule is present, the matchValue is compared
     against all attributes in an entry which support that matchingRule,
     and the matchingRule determines the syntax for the assertion value
     (the filter item evaluates to TRUE if it matches with at least
     one attribute in the entry, FALSE if it does not match any attribute
     in the entry, and Undefined if the matchingRule is not recognized
     or the assertionValue cannot be parsed.)  If the type field is
     present and matchingRule is present, the matchingRule MUST be one
     permitted for use with that type, otherwise the filter item is
     undefined.  If the dnAttributes field is set to TRUE, the match is
     applied against all the attributes in an entry's distinguished name
     as well, and also evaluates to TRUE if there is at least one
     attribute in the distinguished name for which the filter item
     evaluates to TRUE.  (Editors note: The dnAttributes field is present
     so that there does not need to be multiple versions of generic
     matching rules such as for word matching, one to apply to entries
     and another to apply to entries and dn attributes as well).

     A filter item evaluates to Undefined when the server would not
     be able to determine whether the assertion value matches an
     entry.  If an attribute description in an equalityMatch, substrings,
     greaterOrEqual, lessOrEqual, approxMatch or extensibleMatch
     filter is not recognized by the server, a matching rule id in the
     extensibleMatch is not recognized by the server, the assertion
     value cannot be parsed, or the type of filtering requested is not
     implemented, then the filter is Undefined.  Thus for example if a
     server did not recognize the attribute type shoeSize, a filter of
     (shoeSize=*) would evaluate to FALSE, and the filters (shoeSize=12),
     (shoeSize>=12) and (shoeSize<=12) would evaluate to Undefined.






Wahl, et. al.               Standards Track                    [Page 28]

RFC 2251                         LDAPv3                    December 1997


     Servers MUST NOT return errors if attribute descriptions or matching
     rule ids are not recognized, or assertion values cannot be parsed.
     More details of filter processing are given in section 7.8 of X.511
     [8].

   - attributes: A list of the attributes to be returned from each entry
     which matches the search filter. There are two special values which
     may be used: an empty list with no attributes, and the attribute
     description string "*".  Both of these signify that all user
     attributes are to be returned.  (The "*" allows the client to
     request all user attributes in addition to specific operational
     attributes).

     Attributes MUST be named at most once in the list, and are returned
     at most once in an entry.   If there are attribute descriptions in
     the list which are not recognized, they are ignored by the server.

     If the client does not want any attributes returned, it can specify
     a list containing only the attribute with OID "1.1".  This OID was
     chosen arbitrarily and does not correspond to any attribute in use.

     Client implementors should note that even if all user attributes are
     requested, some attributes of the entry may not be included in
     search results due to access control or other restrictions.
     Furthermore, servers will not return operational attributes, such
     as objectClasses or attributeTypes, unless they are listed by name,
     since there may be extremely large number of values for certain
     operational attributes. (A list of operational attributes for use
     in LDAP is given in [5].)

   Note that an X.500 "list"-like operation can be emulated by the client
   requesting a one-level LDAP search operation with a filter checking
   for the existence of the objectClass attribute, and that an X.500
   "read"-like operation can be emulated by a base object LDAP search
   operation with the same filter.  A server which provides a gateway to
   X.500 is not required to use the Read or List operations, although it
   may choose to do so, and if it does must provide the same semantics
   as the X.500 search operation.

4.5.2. Search Result

   The results of the search attempted by the server upon receipt of a
   Search Request are returned in Search Responses, which are LDAP
   messages containing either SearchResultEntry, SearchResultReference,
   ExtendedResponse or SearchResultDone data types.

        SearchResultEntry ::= [APPLICATION 4] SEQUENCE {
                objectName      LDAPDN,



Wahl, et. al.               Standards Track                    [Page 29]

RFC 2251                         LDAPv3                    December 1997


                attributes      PartialAttributeList }

        PartialAttributeList ::= SEQUENCE OF SEQUENCE {
                type    AttributeDescription,
                vals    SET OF AttributeValue }
        -- implementors should note that the PartialAttributeList may
        -- have zero elements (if none of the attributes of that entry
        -- were requested, or could be returned), and that the vals set
        -- may also have zero elements (if types only was requested, or
        -- all values were excluded from the result.)

        SearchResultReference ::= [APPLICATION 19] SEQUENCE OF LDAPURL
        -- at least one LDAPURL element must be present

        SearchResultDone ::= [APPLICATION 5] LDAPResult

   Upon receipt of a Search Request, a server will perform the necessary
   search of the DIT.

   If the LDAP session is operating over a connection-oriented transport
   such as TCP, the server will return to the client a sequence of
   responses in separate LDAP messages.  There may be zero or more
   responses containing SearchResultEntry, one for each entry found
   during the search.  There may also be zero or more responses
   containing SearchResultReference, one for each area not explored by
   this server during the search.  The SearchResultEntry and
   SearchResultReference PDUs may come in any order. Following all the
   SearchResultReference responses and all SearchResultEntry responses
   to be returned by the server, the server will return a response
   containing the SearchResultDone, which contains an indication of
   success, or detailing any errors that have occurred.

   Each entry returned in a SearchResultEntry will contain all
   attributes, complete with associated values if necessary, as
   specified in the attributes field of the Search Request.  Return of
   attributes is subject to access control and other administrative
   policy.  Some attributes may be returned in binary format (indicated
   by the AttributeDescription in the response having the binary option
   present).

   Some attributes may be constructed by the server and appear in a
   SearchResultEntry attribute list, although they are not stored
   attributes of an entry. Clients MUST NOT assume that all attributes
   can be modified, even if permitted by access control.

   LDAPMessage responses of the ExtendedResponse form are reserved for
   returning information associated with a control requested by the
   client.  These may be defined in future versions of this document.



Wahl, et. al.               Standards Track                    [Page 30]

RFC 2251                         LDAPv3                    December 1997


4.5.3. Continuation References in the Search Result

   If the server was able to locate the entry referred to by the
   baseObject but was unable to search all the entries in the scope at
   and under the baseObject, the server may return one or more
   SearchResultReference, each containing a reference to another set of
   servers for continuing the operation.  A server MUST NOT return any
   SearchResultReference if it has not located the baseObject and
   thus has not searched any entries; in this case it would return a
   SearchResultDone containing a referral resultCode.

   In the absence of indexing information provided to a server from
   servers holding subordinate naming contexts, SearchResultReference
   responses are not affected by search filters and are always returned
   when in scope.

   The SearchResultReference is of the same data type as the Referral.
   URLs for servers implementing the LDAP protocol are written according
   to [9].  The <dn> part MUST be present in the URL, with the new target
   object name.  The client MUST use this name in its next request.
   Some servers (e.g. part of a distributed index exchange system) may
   provide a different filter in the URLs of the SearchResultReference.
   If the filter part of the URL is present in an LDAP URL, the client
   MUST use the new filter in its next request to progress the search,
   and if the filter part is absent the client will use again the same
   filter.  Other aspects of the new search request may be the same or
   different as the search which generated the continuation references.

   Other kinds of URLs may be returned so long as the operation could be
   performed using that protocol.

   The name of an unexplored subtree in a SearchResultReference need not
   be subordinate to the base object.

   In order to complete the search, the client MUST issue a new search
   operation for each SearchResultReference that is returned.  Note that
   the abandon operation described in section 4.11 applies only to a
   particular operation sent on a connection between a client and server,
   and if the client has multiple outstanding search operations to
   different servers, it MUST abandon each operation individually.

4.5.3.1. Example

   For example, suppose the contacted server (hosta) holds the entry
   "O=MNN,C=WW" and the entry "CN=Manager,O=MNN,C=WW".  It knows that
   either LDAP-capable servers (hostb) or (hostc) hold
   "OU=People,O=MNN,C=WW" (one is the master and the other server a




Wahl, et. al.               Standards Track                    [Page 31]

RFC 2251                         LDAPv3                    December 1997


   shadow), and that LDAP-capable server (hostd) holds the subtree
   "OU=Roles,O=MNN,C=WW".  If a subtree search of "O=MNN,C=WW" is
   requested to the contacted server, it may return the following:

     SearchResultEntry for O=MNN,C=WW
     SearchResultEntry for CN=Manager,O=MNN,C=WW
     SearchResultReference {
       ldap://hostb/OU=People,O=MNN,C=WW
       ldap://hostc/OU=People,O=MNN,C=WW
     }
     SearchResultReference {
       ldap://hostd/OU=Roles,O=MNN,C=WW
     }
     SearchResultDone (success)

   Client implementors should note that when following a
   SearchResultReference, additional SearchResultReference may be
   generated.  Continuing the example, if the client contacted the
   server (hostb) and issued the search for the subtree
   "OU=People,O=MNN,C=WW", the server might respond as follows:

     SearchResultEntry for OU=People,O=MNN,C=WW
     SearchResultReference {
      ldap://hoste/OU=Managers,OU=People,O=MNN,C=WW
     }
     SearchResultReference {
      ldap://hostf/OU=Consultants,OU=People,O=MNN,C=WW
     }
     SearchResultDone (success)

   If the contacted server does not hold the base object for the search,
   then it will return a referral to the client.  For example, if the
   client requests a subtree search of "O=XYZ,C=US" to hosta, the server
   may return only a SearchResultDone containing a referral.

     SearchResultDone (referral) {
       ldap://hostg/
     }

4.6. Modify Operation

   The Modify Operation allows a client to request that a modification
   of an entry be performed on its behalf by a server.  The Modify
   Request is defined as follows:

        ModifyRequest ::= [APPLICATION 6] SEQUENCE {
                object          LDAPDN,
                modification    SEQUENCE OF SEQUENCE {



Wahl, et. al.               Standards Track                    [Page 32]

RFC 2251                         LDAPv3                    December 1997


                        operation       ENUMERATED {
                                                add     (0),
                                                delete  (1),
                                                replace (2) },
                        modification    AttributeTypeAndValues } }

        AttributeTypeAndValues ::= SEQUENCE {
                type    AttributeDescription,
                vals    SET OF AttributeValue }

   Parameters of the Modify Request are:

   - object: The object to be modified. The value of this field contains
     the DN of the entry to be modified.  The server will not perform
     any alias dereferencing in determining the object to be modified.

   - modification: A list of modifications to be performed on the entry.
     The entire list of entry modifications MUST be performed
     in the order they are listed, as a single atomic operation.  While
     individual modifications may violate the directory schema, the
     resulting entry after the entire list of modifications is performed
     MUST conform to the requirements of the directory schema. The
     values that may be taken on by the 'operation' field in each
     modification construct have the following semantics respectively:

             add: add values listed to the given attribute, creating
             the attribute if necessary;

             delete: delete values listed from the given attribute,
             removing the entire attribute if no values are listed, or
             if all current values of the attribute are listed for
             deletion;

             replace: replace all existing values of the given attribute
             with the new values listed, creating the attribute if it
             did not already exist.  A replace with no value will delete
             the entire attribute if it exists, and is ignored if the
             attribute does not exist.

   The result of the modify attempted by the server upon receipt of a
   Modify Request is returned in a Modify Response, defined as follows:

        ModifyResponse ::= [APPLICATION 7] LDAPResult

   Upon receipt of a Modify Request, a server will perform the necessary
   modifications to the DIT.





Wahl, et. al.               Standards Track                    [Page 33]

RFC 2251                         LDAPv3                    December 1997


   The server will return to the client a single Modify Response
   indicating either the successful completion of the DIT modification,
   or the reason that the modification failed. Note that due to the
   requirement for atomicity in applying the list of modifications in
   the Modify Request, the client may expect that no modifications of
   the DIT have been performed if the Modify Response received indicates
   any sort of error, and that all requested modifications have been
   performed if the Modify Response indicates successful completion of
   the Modify Operation.  If the connection fails, whether the
   modification occurred or not is indeterminate.

   The Modify Operation cannot be used to remove from an entry any of
   its distinguished values, those values which form the entry's
   relative distinguished name.  An attempt to do so will result in the
   server returning the error notAllowedOnRDN.  The Modify DN Operation
   described in section 4.9 is used to rename an entry.

   If an equality match filter has not been defined for an attribute type,
   clients MUST NOT attempt to delete individual values of that attribute
   from an entry using the "delete" form of a modification, and MUST
   instead use the "replace" form.

   Note that due to the simplifications made in LDAP, there is not a
   direct mapping of the modifications in an LDAP ModifyRequest onto the
   EntryModifications of a DAP ModifyEntry operation, and different
   implementations of LDAP-DAP gateways may use different means of
   representing the change.  If successful, the final effect of the
   operations on the entry MUST be identical.

4.7. Add Operation

   The Add Operation allows a client to request the addition of an entry
   into the directory. The Add Request is defined as follows:

        AddRequest ::= [APPLICATION 8] SEQUENCE {
                entry           LDAPDN,
                attributes      AttributeList }

        AttributeList ::= SEQUENCE OF SEQUENCE {
                type    AttributeDescription,
                vals    SET OF AttributeValue }

   Parameters of the Add Request are:

   - entry: the Distinguished Name of the entry to be added. Note that
     the server will not dereference any aliases in locating the entry
     to be added.




Wahl, et. al.               Standards Track                    [Page 34]

RFC 2251                         LDAPv3                    December 1997


   - attributes: the list of attributes that make up the content of the
     entry being added.  Clients MUST include distinguished values
     (those forming the entry's own RDN) in this list, the objectClass
     attribute, and values of any mandatory attributes of the listed
     object classes.  Clients MUST NOT supply the createTimestamp or
     creatorsName attributes, since these will be generated
     automatically by the server.

   The entry named in the entry field of the AddRequest MUST NOT exist
   for the AddRequest to succeed.  The parent of the entry to be added
   MUST exist.  For example, if the client attempted to add
   "CN=JS,O=Foo,C=US", the "O=Foo,C=US" entry did not exist, and the
   "C=US" entry did exist, then the server would return the error
   noSuchObject with the matchedDN field containing "C=US".  If the
   parent entry exists but is not in a naming context held by the
   server, the server SHOULD return a referral to the server holding the
   parent entry.

   Servers implementations SHOULD NOT restrict where entries can be
   located in the directory.  Some servers MAY allow the administrator
   to restrict the classes of entries which can be added to the
   directory.

   Upon receipt of an Add Request, a server will attempt to perform the
   add requested.  The result of the add attempt will be returned to the
   client in the Add Response, defined as follows:

        AddResponse ::= [APPLICATION 9] LDAPResult

   A response of success indicates that the new entry is present in the
   directory.

4.8. Delete Operation

   The Delete Operation allows a client to request the removal of an
   entry from the directory. The Delete Request is defined as follows:

        DelRequest ::= [APPLICATION 10] LDAPDN

   The Delete Request consists of the Distinguished Name of the entry to
   be deleted. Note that the server will not dereference aliases while
   resolving the name of the target entry to be removed, and that only
   leaf entries (those with no subordinate entries) can be deleted with
   this operation.

   The result of the delete attempted by the server upon receipt of a
   Delete Request is returned in the Delete Response, defined as
   follows:



Wahl, et. al.               Standards Track                    [Page 35]

RFC 2251                         LDAPv3                    December 1997


        DelResponse ::= [APPLICATION 11] LDAPResult

   Upon receipt of a Delete Request, a server will attempt to perform
   the entry removal requested. The result of the delete attempt will be
   returned to the client in the Delete Response.

4.9. Modify DN Operation

   The Modify DN Operation allows a client to change the leftmost (least
   significant) component of the name of an entry in the directory, or
   to move a subtree of entries to a new location in the directory.  The
   Modify DN Request is defined as follows:

        ModifyDNRequest ::= [APPLICATION 12] SEQUENCE {
                entry           LDAPDN,
                newrdn          RelativeLDAPDN,
                deleteoldrdn    BOOLEAN,
                newSuperior     [0] LDAPDN OPTIONAL }

   Parameters of the Modify DN Request are:

   - entry: the Distinguished Name of the entry to be changed.  This
     entry may or may not have subordinate entries.

   - newrdn: the RDN that will form the leftmost component of the new
     name of the entry.

   - deleteoldrdn: a boolean parameter that controls whether the old RDN
     attribute values are to be retained as attributes of the entry, or
     deleted from the entry.

   - newSuperior: if present, this is the Distinguished Name of the entry
     which becomes the immediate superior of the existing entry.

   The result of the name change attempted by the server upon receipt of
   a Modify DN Request is returned in the Modify DN Response, defined
   as follows:

        ModifyDNResponse ::= [APPLICATION 13] LDAPResult

   Upon receipt of a ModifyDNRequest, a server will attempt to
   perform the name change. The result of the name change attempt will
   be returned to the client in the Modify DN Response.

   For example, if the entry named in the "entry" parameter was
   "cn=John Smith,c=US", the newrdn parameter was "cn=John Cougar Smith",
   and the newSuperior parameter was absent, then this operation would




Wahl, et. al.               Standards Track                    [Page 36]

RFC 2251                         LDAPv3                    December 1997


   attempt to rename the entry to be "cn=John Cougar Smith,c=US".  If
   there was already an entry with that name, the operation would fail
   with error code entryAlreadyExists.

   If the deleteoldrdn parameter is TRUE, the values forming the old
   RDN are deleted from the entry.  If the deleteoldrdn parameter is
   FALSE, the values forming the old RDN will be retained as
   non-distinguished attribute values of the entry.  The server may
   not perform the operation and return an error code if the setting of
   the deleteoldrdn parameter would cause a schema inconsistency in the
   entry.

   Note that X.500 restricts the ModifyDN operation to only affect
   entries that are contained within a single server.  If the LDAP
   server is mapped onto DAP, then this restriction will apply, and the
   resultCode affectsMultipleDSAs will be returned if this error
   occurred.  In general clients MUST NOT expect to be able to perform
   arbitrary movements of entries and subtrees between servers.

4.10. Compare Operation

   The Compare Operation allows a client to compare an assertion
   provided with an entry in the directory. The Compare Request is
   defined as follows:

        CompareRequest ::= [APPLICATION 14] SEQUENCE {
                entry           LDAPDN,
                ava             AttributeValueAssertion }

   Parameters of the Compare Request are:

   - entry: the name of the entry to be compared with.

   - ava: the assertion with which an attribute in the entry is to be
     compared.

   The result of the compare attempted by the server upon receipt of a
   Compare Request is returned in the Compare Response, defined as
   follows:

        CompareResponse ::= [APPLICATION 15] LDAPResult

   Upon receipt of a Compare Request, a server will attempt to perform
   the requested comparison. The result of the comparison will be
   returned to the client in the Compare Response. Note that errors and
   the result of comparison are all returned in the same construct.





Wahl, et. al.               Standards Track                    [Page 37]

RFC 2251                         LDAPv3                    December 1997


   Note that some directory systems may establish access controls which
   permit the values of certain attributes (such as userPassword) to be
   compared but not read.  In a search result, it may be that an
   attribute of that type would be returned, but with an empty set of
   values.

4.11. Abandon Operation

   The function of the Abandon Operation is to allow a client to request
   that the server abandon an outstanding operation.  The Abandon
   Request is defined as follows:

        AbandonRequest ::= [APPLICATION 16] MessageID

   The MessageID MUST be that of a an operation which was requested
   earlier in this connection.

   (The abandon request itself has its own message id.  This is distinct
    from the id of the earlier operation being abandoned.)

   There is no response defined in the Abandon Operation. Upon
   transmission of an Abandon Operation, a client may expect that the
   operation identified by the Message ID in the Abandon Request has
   been abandoned. In the event that a server receives an Abandon
   Request on a Search Operation in the midst of transmitting responses
   to the search, that server MUST cease transmitting entry responses to
   the abandoned request immediately, and MUST NOT send the
   SearchResponseDone.  Of course, the server MUST ensure that only
   properly encoded LDAPMessage PDUs are transmitted.

   Clients MUST NOT send abandon requests for the same operation
   multiple times, and MUST also be prepared to receive results from
   operations it has abandoned (since these may have been in transit
   when the abandon was requested).

   Servers MUST discard abandon requests for message IDs they do not
   recognize, for operations which cannot be abandoned, and for
   operations which have already been abandoned.

4.12. Extended Operation

   An extension mechanism has been added in this version of LDAP, in
   order to allow additional operations to be defined for services not
   available elsewhere in this protocol, for instance digitally signed
   operations and results.






Wahl, et. al.               Standards Track                    [Page 38]

RFC 2251                         LDAPv3                    December 1997


   The extended operation allows clients to make requests and receive
   responses with predefined syntaxes and semantics.  These may be
   defined in RFCs or be private to particular implementations.  Each
   request MUST have a unique OBJECT IDENTIFIER assigned to it.

        ExtendedRequest ::= [APPLICATION 23] SEQUENCE {
                requestName      [0] LDAPOID,
                requestValue     [1] OCTET STRING OPTIONAL }

   The requestName is a dotted-decimal representation of the OBJECT
   IDENTIFIER corresponding to the request. The requestValue is
   information in a form defined by that request, encapsulated inside an
   OCTET STRING.

   The server will respond to this with an LDAPMessage containing the
   ExtendedResponse.

        ExtendedResponse ::= [APPLICATION 24] SEQUENCE {
                COMPONENTS OF LDAPResult,
                responseName     [10] LDAPOID OPTIONAL,
                response         [11] OCTET STRING OPTIONAL }

   If the server does not recognize the request name, it MUST return
   only the response fields from LDAPResult, containing the
   protocolError result code.

5.  Protocol Element Encodings and Transfer

   One underlying service is defined here.  Clients and servers SHOULD
   implement the mapping of LDAP over TCP described in 5.2.1.

5.1. Mapping Onto BER-based Transport Services

   The protocol elements of LDAP are encoded for exchange using the
   Basic Encoding Rules (BER) [11] of ASN.1 [3]. However, due to the
   high overhead involved in using certain elements of the BER, the
   following additional restrictions are placed on BER-encodings of LDAP
   protocol elements:

   (1) Only the definite form of length encoding will be used.

   (2) OCTET STRING values will be encoded in the primitive form only.

   (3) If the value of a BOOLEAN type is true, the encoding MUST have
       its contents octets set to hex "FF".






Wahl, et. al.               Standards Track                    [Page 39]

RFC 2251                         LDAPv3                    December 1997


   (4) If a value of a type is its default value, it MUST be absent.
       Only some BOOLEAN and INTEGER types have default values in this
       protocol definition.

   These restrictions do not apply to ASN.1 types encapsulated inside of
   OCTET STRING values, such as attribute values, unless otherwise
   noted.

5.2. Transfer Protocols

   This protocol is designed to run over connection-oriented, reliable
   transports, with all 8 bits in an octet being significant in the data
   stream.

5.2.1. Transmission Control Protocol (TCP)

   The LDAPMessage PDUs are mapped directly onto the TCP bytestream.  It
   is recommended that server implementations running over the TCP MAY
   provide a protocol listener on the assigned port, 389.  Servers may
   instead provide a listener on a different port number. Clients MUST
   support contacting servers on any valid TCP port.

6.  Implementation Guidelines

   This document describes an Internet protocol.

6.1. Server Implementations

   The server MUST be capable of recognizing all the mandatory attribute
   type names and implement the syntaxes specified in [5].  Servers MAY
   also recognize additional attribute type names.

6.2. Client Implementations

   Clients which request referrals MUST ensure that they do not loop
   between servers. They MUST NOT repeatedly contact the same server for
   the same request with the same target entry name, scope and filter.
   Some clients may be using a counter that is incremented each time
   referral handling occurs for an operation, and these kinds of clients
   MUST be able to handle a DIT with at least ten layers of naming
   contexts between the root and a leaf entry.

   In the absence of prior agreements with servers, clients SHOULD NOT
   assume that servers support any particular schemas beyond those
   referenced in section 6.1. Different schemas can have different
   attribute types with the same names.  The client can retrieve the
   subschema entries referenced by the subschemaSubentry attribute in
   the server's root DSE or in entries held by the server.



Wahl, et. al.               Standards Track                    [Page 40]

RFC 2251                         LDAPv3                    December 1997


7.  Security Considerations

   When used with a connection-oriented transport, this version of the
   protocol provides facilities for the LDAP v2 authentication
   mechanism, simple authentication using a cleartext password, as well
   as any SASL mechanism [12].  SASL allows for integrity and privacy
   services to be negotiated.

   It is also permitted that the server can return its credentials to
   the client, if it chooses to do so.

   Use of cleartext password is strongly discouraged where the
   underlying transport service cannot guarantee confidentiality and may
   result in disclosure of the password to unauthorized parties.

   When used with SASL, it should be noted that the name field of the
   BindRequest is not protected against modification.  Thus if the
   distinguished name of the client (an LDAPDN) is agreed through the
   negotiation of the credentials, it takes precedence over any value in
   the unprotected name field.

   Implementations which cache attributes and entries obtained via LDAP
   MUST ensure that access controls are maintained if that information
   is to be provided to multiple clients, since servers may have access
   control policies which prevent the return of entries or attributes in
   search results except to particular authenticated clients.  For
   example, caches could serve result information only to the client
   whose request caused it to be cache.

8.  Acknowledgements

   This document is an update to RFC 1777, by Wengyik Yeong, Tim Howes,
   and Steve Kille.  Design ideas included in this document are based on
   those discussed in ASID and other IETF Working Groups.  The
   contributions of individuals in these working groups is gratefully
   acknowledged.

9.  Bibliography

   [1] ITU-T Rec. X.500, "The Directory: Overview of Concepts, Models
       and Service",  1993.

   [2] Yeong, W., Howes, T., and S. Kille, "Lightweight Directory Access
       Protocol", RFC 1777, March 1995.

   [3] ITU-T Rec. X.680, "Abstract Syntax Notation One (ASN.1) -
       Specification of Basic Notation", 1994.




Wahl, et. al.               Standards Track                    [Page 41]

RFC 2251                         LDAPv3                    December 1997


   [4] Kille, S., Wahl, M., and T. Howes, "Lightweight Directory Access
       Protocol (v3): UTF-8 String Representation of Distinguished
       Names", RFC 2253, December 1997.

   [5] Wahl, M., Coulbeck, A., Howes, T., and S. Kille, "Lightweight
       Directory Access Protocol (v3): Attribute Syntax Definitions",
       RFC 2252, December 1997.

   [6] ITU-T Rec. X.501, "The Directory: Models", 1993.

   [7] Berners-Lee, T., Masinter, L., and M. McCahill, "Uniform
       Resource  Locators (URL)", RFC 1738, December 1994.

   [8] ITU-T Rec. X.511, "The Directory: Abstract Service Definition",
       1993.

   [9] Howes, T., and M. Smith, "The LDAP URL Format", RFC 2255,
       December 1997.

   [10] Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Levels", RFC 2119, March 1997.

   [11] ITU-T Rec. X.690, "Specification of ASN.1 encoding rules: Basic,
        Canonical, and Distinguished Encoding Rules", 1994.

   [12] Meyers, J., "Simple Authentication and Security Layer",
        RFC 2222, October 1997.

   [13] Universal Multiple-Octet Coded Character Set (UCS) -
        Architecture and Basic Multilingual Plane, ISO/IEC 10646-1 :
        1993.

   [14] Yergeau, F., "UTF-8, a transformation format of Unicode and ISO
        10646", RFC 2044, October 1996.

10. Authors' Addresses

   Mark Wahl
   Critical Angle Inc.
   4815 W Braker Lane #502-385
   Austin, TX 78759
   USA

   Phone:  +1 512 372-3160
   EMail:  M.Wahl@critical-angle.com






Wahl, et. al.               Standards Track                    [Page 42]

RFC 2251                         LDAPv3                    December 1997


   Tim Howes
   Netscape Communications Corp.
   501 E. Middlefield Rd., MS MV068
   Mountain View, CA 94043
   USA

   Phone:  +1 650 937-3419
   EMail:   howes@netscape.com

   Steve Kille
   Isode Limited
   The Dome, The Square
   Richmond
   TW9 1DT
   UK

   Phone:  +44-181-332-9091
   EMail:  S.Kille@isode.com

































Wahl, et. al.               Standards Track                    [Page 43]

RFC 2251                         LDAPv3                    December 1997


Appendix A - Complete ASN.1 Definition

        Lightweight-Directory-Access-Protocol-V3 DEFINITIONS
        IMPLICIT TAGS ::=

        BEGIN

        LDAPMessage ::= SEQUENCE {
                messageID       MessageID,
                protocolOp      CHOICE {
                        bindRequest     BindRequest,
                        bindResponse    BindResponse,
                        unbindRequest   UnbindRequest,
                        searchRequest   SearchRequest,
                        searchResEntry  SearchResultEntry,
                        searchResDone   SearchResultDone,
                        searchResRef    SearchResultReference,
                        modifyRequest   ModifyRequest,
                        modifyResponse  ModifyResponse,
                        addRequest      AddRequest,
                        addResponse     AddResponse,
                        delRequest      DelRequest,
                        delResponse     DelResponse,
                        modDNRequest    ModifyDNRequest,
                        modDNResponse   ModifyDNResponse,
                        compareRequest  CompareRequest,
                        compareResponse CompareResponse,
                        abandonRequest  AbandonRequest,
                        extendedReq     ExtendedRequest,
                        extendedResp    ExtendedResponse },
                 controls       [0] Controls OPTIONAL }

        MessageID ::= INTEGER (0 .. maxInt)

        maxInt INTEGER ::= 2147483647 -- (2^^31 - 1) --

        LDAPString ::= OCTET STRING

        LDAPOID ::= OCTET STRING

        LDAPDN ::= LDAPString

        RelativeLDAPDN ::= LDAPString

        AttributeType ::= LDAPString

        AttributeDescription ::= LDAPString




Wahl, et. al.               Standards Track                    [Page 44]

RFC 2251                         LDAPv3                    December 1997


        AttributeDescriptionList ::= SEQUENCE OF
                AttributeDescription

        AttributeValue ::= OCTET STRING

        AttributeValueAssertion ::= SEQUENCE {
                attributeDesc   AttributeDescription,
                assertionValue  AssertionValue }

        AssertionValue ::= OCTET STRING

        Attribute ::= SEQUENCE {
                type    AttributeDescription,
                vals    SET OF AttributeValue }

        MatchingRuleId ::= LDAPString

        LDAPResult ::= SEQUENCE {
                resultCode      ENUMERATED {
                             success                      (0),
                             operationsError              (1),
                             protocolError                (2),
                             timeLimitExceeded            (3),
                             sizeLimitExceeded            (4),
                             compareFalse                 (5),
                             compareTrue                  (6),
                             authMethodNotSupported       (7),
                             strongAuthRequired           (8),
                                        -- 9 reserved --
                             referral                     (10),  -- new
                             adminLimitExceeded           (11),  -- new
                             unavailableCriticalExtension (12),  -- new
                             confidentialityRequired      (13),  -- new
                             saslBindInProgress           (14),  -- new
                             noSuchAttribute              (16),
                             undefinedAttributeType       (17),
                             inappropriateMatching        (18),
                             constraintViolation          (19),
                             attributeOrValueExists       (20),
                             invalidAttributeSyntax       (21),
                                        -- 22-31 unused --
                             noSuchObject                 (32),
                             aliasProblem                 (33),
                             invalidDNSyntax              (34),
                             -- 35 reserved for undefined isLeaf --
                             aliasDereferencingProblem    (36),
                                        -- 37-47 unused --
                             inappropriateAuthentication  (48),



Wahl, et. al.               Standards Track                    [Page 45]

RFC 2251                         LDAPv3                    December 1997


                             invalidCredentials           (49),
                             insufficientAccessRights     (50),
                             busy                         (51),
                             unavailable                  (52),
                             unwillingToPerform           (53),
                             loopDetect                   (54),
                                        -- 55-63 unused --
                             namingViolation              (64),
                             objectClassViolation         (65),
                             notAllowedOnNonLeaf          (66),
                             notAllowedOnRDN              (67),
                             entryAlreadyExists           (68),
                             objectClassModsProhibited    (69),
                                        -- 70 reserved for CLDAP --
                             affectsMultipleDSAs          (71), -- new
                                        -- 72-79 unused --
                             other                        (80) },
                             -- 81-90 reserved for APIs --
                matchedDN       LDAPDN,
                errorMessage    LDAPString,
                referral        [3] Referral OPTIONAL }

        Referral ::= SEQUENCE OF LDAPURL

        LDAPURL ::= LDAPString -- limited to characters permitted in URLs

        Controls ::= SEQUENCE OF Control

        Control ::= SEQUENCE {
                controlType             LDAPOID,
                criticality             BOOLEAN DEFAULT FALSE,
                controlValue            OCTET STRING OPTIONAL }

        BindRequest ::= [APPLICATION 0] SEQUENCE {
                version                 INTEGER (1 .. 127),
                name                    LDAPDN,
                authentication          AuthenticationChoice }

        AuthenticationChoice ::= CHOICE {
                simple                  [0] OCTET STRING,
                                         -- 1 and 2 reserved
                sasl                    [3] SaslCredentials }

        SaslCredentials ::= SEQUENCE {
                mechanism               LDAPString,
                credentials             OCTET STRING OPTIONAL }

        BindResponse ::= [APPLICATION 1] SEQUENCE {



Wahl, et. al.               Standards Track                    [Page 46]

RFC 2251                         LDAPv3                    December 1997


             COMPONENTS OF LDAPResult,
             serverSaslCreds    [7] OCTET STRING OPTIONAL }

        UnbindRequest ::= [APPLICATION 2] NULL

        SearchRequest ::= [APPLICATION 3] SEQUENCE {
                baseObject      LDAPDN,
                scope           ENUMERATED {
                        baseObject              (0),
                        singleLevel             (1),
                        wholeSubtree            (2) },
                derefAliases    ENUMERATED {
                        neverDerefAliases       (0),
                        derefInSearching        (1),
                        derefFindingBaseObj     (2),
                        derefAlways             (3) },
                sizeLimit       INTEGER (0 .. maxInt),
                timeLimit       INTEGER (0 .. maxInt),
                typesOnly       BOOLEAN,
                filter          Filter,
                attributes      AttributeDescriptionList }

        Filter ::= CHOICE {
                and             [0] SET OF Filter,
                or              [1] SET OF Filter,
                not             [2] Filter,
                equalityMatch   [3] AttributeValueAssertion,
                substrings      [4] SubstringFilter,
                greaterOrEqual  [5] AttributeValueAssertion,
                lessOrEqual     [6] AttributeValueAssertion,
                present         [7] AttributeDescription,
                approxMatch     [8] AttributeValueAssertion,
                extensibleMatch [9] MatchingRuleAssertion }

        SubstringFilter ::= SEQUENCE {
                type            AttributeDescription,
                -- at least one must be present
                substrings      SEQUENCE OF CHOICE {
                        initial [0] LDAPString,
                        any     [1] LDAPString,
                        final   [2] LDAPString } }

        MatchingRuleAssertion ::= SEQUENCE {
                matchingRule    [1] MatchingRuleId OPTIONAL,
                type            [2] AttributeDescription OPTIONAL,
                matchValue      [3] AssertionValue,
                dnAttributes    [4] BOOLEAN DEFAULT FALSE }




Wahl, et. al.               Standards Track                    [Page 47]

RFC 2251                         LDAPv3                    December 1997


        SearchResultEntry ::= [APPLICATION 4] SEQUENCE {
                objectName      LDAPDN,
                attributes      PartialAttributeList }

        PartialAttributeList ::= SEQUENCE OF SEQUENCE {
                type    AttributeDescription,
                vals    SET OF AttributeValue }

        SearchResultReference ::= [APPLICATION 19] SEQUENCE OF LDAPURL

        SearchResultDone ::= [APPLICATION 5] LDAPResult

        ModifyRequest ::= [APPLICATION 6] SEQUENCE {
                object          LDAPDN,
                modification    SEQUENCE OF SEQUENCE {
                        operation       ENUMERATED {
                                                add     (0),
                                                delete  (1),
                                                replace (2) },
                        modification    AttributeTypeAndValues } }

        AttributeTypeAndValues ::= SEQUENCE {
                type    AttributeDescription,
                vals    SET OF AttributeValue }

        ModifyResponse ::= [APPLICATION 7] LDAPResult

        AddRequest ::= [APPLICATION 8] SEQUENCE {
                entry           LDAPDN,
                attributes      AttributeList }

        AttributeList ::= SEQUENCE OF SEQUENCE {
                type    AttributeDescription,
                vals    SET OF AttributeValue }

        AddResponse ::= [APPLICATION 9] LDAPResult

        DelRequest ::= [APPLICATION 10] LDAPDN

        DelResponse ::= [APPLICATION 11] LDAPResult

        ModifyDNRequest ::= [APPLICATION 12] SEQUENCE {
                entry           LDAPDN,
                newrdn          RelativeLDAPDN,
                deleteoldrdn    BOOLEAN,
                newSuperior     [0] LDAPDN OPTIONAL }

        ModifyDNResponse ::= [APPLICATION 13] LDAPResult



Wahl, et. al.               Standards Track                    [Page 48]

RFC 2251                         LDAPv3                    December 1997


        CompareRequest ::= [APPLICATION 14] SEQUENCE {
                entry           LDAPDN,
                ava             AttributeValueAssertion }

        CompareResponse ::= [APPLICATION 15] LDAPResult

        AbandonRequest ::= [APPLICATION 16] MessageID

        ExtendedRequest ::= [APPLICATION 23] SEQUENCE {
                requestName      [0] LDAPOID,
                requestValue     [1] OCTET STRING OPTIONAL }

        ExtendedResponse ::= [APPLICATION 24] SEQUENCE {
                COMPONENTS OF LDAPResult,
                responseName     [10] LDAPOID OPTIONAL,
                response         [11] OCTET STRING OPTIONAL }

        END

































Wahl, et. al.               Standards Track                    [Page 49]

RFC 2251                         LDAPv3                    December 1997


Full Copyright Statement

   Copyright (C) The Internet Society (1997).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
























Wahl, et. al.               Standards Track                    [Page 50]