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'10' -- Possible downref: Non-RFC (?) normative reference: ref. '11' -- Possible downref: Non-RFC (?) normative reference: ref. '12' Summary: 12 errors (**), 0 flaws (~~), 5 warnings (==), 13 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Protocol Operations 2 for Version 2 of the 3 Simple Network Management Protocol (SNMPv2) 5 19 March 1995 | 7 draft-ietf-snmpv2-proto-ds-01.txt | 9 Jeffrey D. Case 10 SNMP Research, Inc. 11 case@snmp.com 13 Keith McCloghrie 14 Cisco Systems, Inc. 15 kzm@cisco.com 17 Marshall T. Rose 18 Dover Beach Consulting, Inc. 19 mrose@dbc.mtview.ca.us 21 Steven Waldbusser 22 Carnegie Mellon University 23 waldbusser@cmu.edu 25 Status of this Memo 27 This document is an Internet-Draft. Internet-Drafts are working 28 documents of the Internet Engineering Task Force (IETF), its areas, and 29 its working groups. Note that other groups may also distribute working 30 documents as Internet-Drafts. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet- Drafts as reference material 35 or to cite them other than as ``work in progress.'' 37 To learn the current status of any Internet-Draft, please check the 38 ``1id-abstracts.txt'' listing contained in the Internet- Drafts Shadow 39 Directories on ds.internic.net (US East Coast), nic.nordu.net (Europe), 40 ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific Rim). 42 1. Introduction 44 A management system contains: several (potentially many) nodes, each 45 with a processing entity, termed an agent, which has access to 46 management instrumentation; at least one management station; and, a 47 management protocol, used to convey management information between the 48 agents and management stations. Operations of the protocol are carried 49 out under an administrative framework which defines authentication, 50 authorization, access control, and privacy policies. 52 Management stations execute management applications which monitor and 53 control managed elements. Managed elements are devices such as hosts, 54 routers, terminal servers, etc., which are monitored and controlled via 55 access to their management information. 57 Management information is viewed as a collection of managed objects, 58 residing in a virtual information store, termed the Management 59 Information Base (MIB). Collections of related objects are defined in 60 MIB modules. These modules are written using a subset of OSI's Abstract 61 Syntax Notation One (ASN.1) [1], termed the Structure of Management 62 Information (SMI) [2]. 64 The management protocol, version 2 of the Simple Network Management 65 Protocol, provides for the exchange of messages which convey management 66 information between the agents and the management stations. The form of 67 these messages is a message "wrapper" which encapsulates a Protocol Data 68 Unit (PDU). The form and meaning of the "wrapper" is determined by an 69 administrative framework which defines both authentication and 70 authorization policies. 72 It is the purpose of this document, Protocol Operations for SNMPv2, to 73 define the operations of the protocol with respect to the sending and 74 receiving of the PDUs. 76 1.1. A Note on Terminology 78 For the purpose of exposition, the original Internet-standard Network 79 Management Framework, as described in RFCs 1155, 1157, and 1212, is 80 termed the SNMP version 1 framework (SNMPv1). The current framework is 81 termed the SNMP version 2 framework (SNMPv2). 83 1.2. Change Log 85 For the 19 March version: + 87 - The changes adopted by the SNMPv2 Working Group. + 89 For the 1 November version: 91 - recast RFC 1448 into an Internet-Draft, 93 - fixed typos, 95 - clarified that while there is a theoretical limit on the number of 96 varbinds, the size of a message is in practice not limited by the 97 number of varbinds, 99 - clarified the definition of noSuchInstance, 101 - added text to require snmpStatsSilentDrops to be incremented 102 whenever a message is discarded without sending a Response. 104 2. Overview 106 2.1. Roles of Protocol Entities 108 A SNMPv2 entity may operate in a manager role or an agent role. 110 A SNMPv2 entity acts in an agent role when it performs SNMPv2 management 111 operations in response to received SNMPv2 protocol messages (other than 112 an inform notification) or when it sends trap notifications. 114 A SNMPv2 entity acts in a manager role when it initiates SNMPv2 115 management operations by the generation of SNMPv2 protocol messages or 116 when it performs SNMPv2 management operations in response to received 117 trap or inform notifications. 119 A SNMPv2 entity may support either or both roles, as dictated by its 120 implementation and configuration. Further, a SNMPv2 entity can also act 121 in the role of a proxy agent, in which it appears to be acting in an 122 agent role, but satisfies management requests by acting in a manager 123 role with a remote entity. The use of proxy agents and the transparency 124 principle that defines their behavior is described in [3]. 126 2.2. Management Information 128 The term, variable, refers to an instance of a non-aggregate object type 129 defined according to the conventions set forth in the SMI [2] or the 130 textual conventions based on the SMI [4]. The term, variable binding, 131 normally refers to the pairing of the name of a variable and its 132 associated value. However, if certain kinds of exceptional conditions 133 occur during processing of a retrieval request, a variable binding will 134 pair a name and an indication of that exception. 136 A variable-binding list is a simple list of variable bindings. 138 The name of a variable is an OBJECT IDENTIFIER which is the 139 concatenation of the OBJECT IDENTIFIER of the corresponding object-type 140 together with an OBJECT IDENTIFIER fragment identifying the instance. 141 The OBJECT IDENTIFIER of the corresponding object-type is called the 142 OBJECT IDENTIFIER prefix of the variable. 144 2.3. Access to Management Information 146 Three types of access to management information are provided by the 147 protocol. One type is a request-response interaction, in which a SNMPv2 148 entity, acting in a manager role, sends a request to a SNMPv2 entity, 149 acting in an agent role, and the latter SNMPv2 entity then responds to 150 the request. This type is used to retrieve or modify management 151 information associated with the managed device. 153 A second type is also a request-response interaction, in which a SNMPv2 154 entity, acting in a manager role, sends a request to a SNMPv2 entity, 155 also acting in a manager role, and the latter SNMPv2 entity then 156 responds to the request. This type is used to notify a SNMPv2 entity, 157 acting in a manager role, of management information associated with 158 another SNMPv2 entity, also acting in a manager role. 160 The third type of access is an unconfirmed interaction, in which a 161 SNMPv2 entity, acting in an agent role, sends a unsolicited message, 162 termed a trap, to a SNMPv2 entity, acting in a manager role, and no 163 response is returned. This type is used to notify a SNMPv2 entity, 164 acting in a manager role, of an exceptional situation, which has 165 resulted in changes to management information associated with the 166 managed device. 168 2.4. Retransmission of Requests 170 For all types of request in this protocol, the receiver is required 171 under normal circumstances, to generate and transmit a response to the 172 originator of the request. Whether or not a request should be 173 retransmitted if no corresponding response is received in an appropriate 174 time interval, is at the discretion of the application originating the 175 request. This will normally depend on the urgency of the request. 176 However, such an application needs to act responsibly in respect to the 177 frequency and duration of re-transmissions. 179 2.5. Message Sizes 181 The maximum size of a SNMPv2 message is limited the minimum of: 183 (1) the maximum message size which the destination SNMPv2 entity can 184 accept; and, 186 (2) the maximum message size which the source SNMPv2 entity can 187 generate. 189 The former is indicated by partyMaxMessageSize[5] of the destination 190 party. The latter is imposed by implementation-specific local 191 constraints. 193 Each transport mapping for the SNMPv2 indicates the minimum message size 194 which a SNMPv2 implementation must be able to produce or consume. 195 Although implementations are encouraged to support larger values 196 whenever possible, a conformant implementation must never generate 197 messages larger than allowed by the receiving SNMPv2 entity. 199 One of the aims of the GetBulkRequest-PDU, specified in this protocol, 200 is to minimize the number of protocol exchanges required to retrieve a 201 large amount of management information. As such, this PDU type allows a 202 SNMPv2 entity acting in a manager role to request that the response be 203 as large as possible given the constraints on message sizes. These 204 constraints include the limits on the size of messages which the SNMPv2 205 entity acting in an agent role can generate, and the SNMPv2 entity 206 acting in a manager role can receive. 208 However, it is possible that such maximum sized messages may be larger 209 than the Path MTU of the path across the network traversed by the 210 messages. In this situation, such messages are subject to 211 fragmentation. Fragmentation is generally considered to be harmful [6], 212 since among other problems, it leads to a decrease in the reliability of 213 the transfer of the messages. Thus, a SNMPv2 entity which sends a 214 GetBulkRequest-PDU must take care to set its parameters accordingly, so 215 as to reduce the risk of fragmentation. In particular, under conditions 216 of network stress, only small values should be used for max-repetitions. 218 2.6. Transport Mappings 220 It is important to note that the exchange of SNMPv2 messages requires 221 only an unreliable datagram service, with every message being entirely 222 and independently contained in a single transport datagram. Specific 223 transport mappings and encoding rules are specified elsewhere [7]. 224 However, the preferred mapping is the use of the User Datagram Protocol 225 [8]. 227 3. Definitions 229 SNMPv2-PDU DEFINITIONS ::= BEGIN 231 IMPORTS 232 ObjectName, ObjectSyntax, Integer32 233 FROM SNMPv2-SMI; 235 -- protocol data units 237 PDUs ::= 238 CHOICE { 239 get-request 240 GetRequest-PDU, 242 get-next-request 243 GetNextRequest-PDU, 245 get-bulk-request 246 GetBulkRequest-PDU, 248 response 249 Response-PDU, 251 set-request 252 SetRequest-PDU, 254 inform-request 255 InformRequest-PDU, 257 snmpV2-trap 258 SNMPv2-Trap-PDU 259 } 261 -- PDUs 263 GetRequest-PDU ::= 264 [0] 265 IMPLICIT PDU 267 GetNextRequest-PDU ::= 268 [1] 269 IMPLICIT PDU 271 Response-PDU ::= 272 [2] 273 IMPLICIT PDU 275 SetRequest-PDU ::= 276 [3] 277 IMPLICIT PDU 279 -- [4] is obsolete 281 GetBulkRequest-PDU ::= 282 [5] 283 IMPLICIT BulkPDU 285 InformRequest-PDU ::= 286 [6] 287 IMPLICIT PDU 289 SNMPv2-Trap-PDU ::= 290 [7] 291 IMPLICIT PDU 293 -- defined in reference [3] + 294 -- Report-PDU ::= + 295 -- [8] + 296 -- IMPLICIT PDU + 297 max-bindings 298 INTEGER ::= 2147483647 300 PDU ::= 301 SEQUENCE { 302 request-id 303 Integer32, 305 error-status -- sometimes ignored 306 INTEGER { 307 noError(0), 308 tooBig(1), 309 noSuchName(2), -- for proxy compatibility 310 badValue(3), -- for proxy compatibility 311 readOnly(4), -- for proxy compatibility 312 genErr(5), 313 noAccess(6), 314 wrongType(7), 315 wrongLength(8), 316 wrongEncoding(9), 317 wrongValue(10), 318 noCreation(11), 319 inconsistentValue(12), 320 resourceUnavailable(13), 321 commitFailed(14), 322 undoFailed(15), 323 authorizationError(16), 324 notWritable(17), 325 inconsistentName(18) 326 }, 328 error-index -- sometimes ignored 329 INTEGER (0..max-bindings), 331 variable-bindings -- values are sometimes ignored 332 VarBindList 333 } 335 BulkPDU ::= -- MUST be identical in 336 SEQUENCE { -- structure to PDU 337 request-id 338 Integer32, 340 non-repeaters 341 INTEGER (0..max-bindings), 343 max-repetitions 344 INTEGER (0..max-bindings), 346 variable-bindings -- values are ignored 347 VarBindList 348 } 350 -- variable binding 352 VarBind ::= 353 SEQUENCE { 354 name 355 ObjectName, 357 CHOICE { 358 value 359 ObjectSyntax, 361 unSpecified -- in retrieval requests 362 NULL, 364 -- exceptions in responses 365 noSuchObject[0] 366 IMPLICIT NULL, 368 noSuchInstance[1] 369 IMPLICIT NULL, 371 endOfMibView[2] 372 IMPLICIT NULL 373 } 374 } 376 -- variable-binding list 378 VarBindList ::= 379 SEQUENCE (SIZE (0..max-bindings)) OF 380 VarBind 382 END 384 4. Protocol Specification 386 4.1. Common Constructs 388 The value of the request-id field in a Response-PDU takes the value of 389 the request-id field in the request PDU to which it is a response. By 390 use of the request-id value, a SNMPv2 application can distinguish the 391 (potentially multiple) outstanding requests, and thereby correlate 392 incoming responses with outstanding requests. In cases where an 393 unreliable datagram service is used, the request-id also provides a 394 simple means of identifying messages duplicated by the network. Use of 395 the same request-id on a retransmission of a request allows the response 396 to either the original transmission or the retransmission to satisfy the 397 request. However, in order to calculate the round trip time for 398 transmission and processing of a request-response transaction, the 399 SNMPv2 application needs to use a different request-id value on a 400 retransmitted request. The latter strategy is recommended for use in 401 the majority of situations. 403 A non-zero value of the error-status field in a Response-PDU is used to 404 indicate that an exception occurred to prevent the processing of the 405 request. In these cases, a non-zero value of the Response-PDU's error- 406 index field provides additional information by identifying which 407 variable binding in the list caused the exception. A variable binding 408 is identified by its index value. The first variable binding in a 409 variable-binding list is index one, the second is index two, etc. 411 SNMPv2 limits OBJECT IDENTIFIER values to a maximum of 128 sub- 412 identifiers, where each sub-identifier has a maximum value of 2**32-1. 414 4.2. PDU Processing 416 It is mandatory that all SNMPv2 entities acting in an agent role be able 417 to generate the following PDU types: Response-PDU and SNMPv2-Trap-PDU; 418 further, all such implementations must be able to receive the following 419 PDU types: GetRequest-PDU, GetNextRequest-PDU, GetBulkRequest-PDU, and 420 SetRequest-PDU. 422 It is mandatory that all SNMPv2 entities acting in a manager role be 423 able to generate the following PDU types: GetRequest-PDU, 424 GetNextRequest-PDU, GetBulkRequest-PDU, SetRequest-PDU, InformRequest- 425 PDU, and Response-PDU; further, all such implementations must be able to 426 receive the following PDU types: Response-PDU, SNMPv2-Trap-PDU, 427 InformRequest-PDU; 429 In the elements of procedure below, any field of a PDU which is not 430 referenced by the relevant procedure is ignored by the receiving SNMPv2 431 entity. However, all components of a PDU, including those whose values 432 are ignored by the receiving SNMPv2 entity, must have valid ASN.1 syntax 433 and encoding. For example, some PDUs (e.g., the GetRequest-PDU) are 434 concerned only with the name of a variable and not its value. In this 435 case, the value portion of the variable binding is ignored by the 436 receiving SNMPv2 entity. The unSpecified value is defined for use as 437 the value portion of such bindings. 439 For all generated PDUs, the message "wrapper" to encapsulate the PDU is 440 generated and transmitted as specified in [3]. While the definition of 441 "max-bindings" does impose an upper-bound on the number of variable 442 bindings, in practice, the size of a message is limited only by 443 constraints on the maximum message size, either a local limitation or 444 the limit associated with the message's destination party, i.e., it is 445 not limited by the number of variable bindings. 447 On receiving a management communication, the procedures defined in 448 Section 3.2 of [3] are followed. If these procedures indicate that the 449 PDU contained within the message "wrapper" is to be processed, then the 450 SNMPv2 context associated with the PDU defines the object resources 451 which are visible to the operation. 453 4.2.1. The GetRequest-PDU 455 A GetRequest-PDU is generated and transmitted at the request of a SNMPv2 456 application. 458 Upon receipt of a GetRequest-PDU, the receiving SNMPv2 entity processes 459 each variable binding in the variable-binding list to produce a 460 Response-PDU. All fields of the Response-PDU have the same values as 461 the corresponding fields of the received request except as indicated 462 below. Each variable binding is processed as follows: 464 (1) If the variable binding's name exactly matches the name of a 465 variable accessible by this request, then the variable binding's 466 value field is set to the value of the named variable. 468 (2) Otherwise, if the variable binding's name does not have an OBJECT 469 IDENTIFIER prefix which exactly matches the OBJECT IDENTIFIER 470 prefix of any (potential) variable accessible by this request, then 471 its value field is set to `noSuchObject'. 473 (3) Otherwise, the variable binding's value field is set to to 474 `noSuchInstance'. 476 If the processing of any variable binding fails for a reason other than 477 listed above, then the Response-PDU is re-formatted with the same values 478 in its request-id and variable-bindings fields as the received 479 GetRequest-PDU, with the value of its error-status field set to 480 `genErr', and the value of its error-index field is set to the index of 481 the failed variable binding. 483 Otherwise, the value of the Response-PDU's error-status field is set to 484 `noError', and the value of its error-index field is zero. 486 The generated Response-PDU is then encapsulated into a message. If the 487 size of the resultant message is less than or equal to both a local 488 constraint and the maximum message size of the request's source party, 489 it is transmitted to the originator of the GetRequest-PDU. 491 Otherwise, an alternate Response-PDU is generated. This alternate 492 Response-PDU is formatted with the same value in its request-id field as 493 the received GetRequest-PDU, with the value of its error-status field 494 set to `tooBig', the value of its error-index field set to zero, and an 495 empty variable-bindings field. This alternate Response-PDU is then 496 encapsulated into a message. If the size of the resultant message is 497 less than or equal to both a local constraint and the maximum message 498 size of the request's source party, it is transmitted to the originator 499 of the GetRequest-PDU. Otherwise, the snmpStatsSilentDrops [11] counter 500 is incremented and the resultant message is discarded. 502 4.2.2. The GetNextRequest-PDU 504 A GetNextRequest-PDU is generated and transmitted at the request of a 505 SNMPv2 application. 507 Upon receipt of a GetNextRequest-PDU, the receiving SNMPv2 entity 508 processes each variable binding in the variable-binding list to produce 509 a Response-PDU. All fields of the Response-PDU have the same values as 510 the corresponding fields of the received request except as indicated 511 below. Each variable binding is processed as follows: 513 (1) The variable is located which is in the lexicographically ordered 514 list of the names of all variables which are accessible by this 515 request and whose name is the first lexicographic successor of the 516 variable binding's name in the incoming GetNextRequest-PDU. The 517 corresponding variable binding's name and value fields in the 518 Response-PDU are set to the name and value of the located variable. 520 (2) If the requested variable binding's name does not lexicographically 521 precede the name of any variable accessible by this request, i.e., 522 there is no lexicographic successor, then the corresponding 523 variable binding produced in the Response-PDU has its value field 524 set to `endOfMibView', and its name field set to the variable 525 binding's name in the request. 527 If the processing of any variable binding fails for a reason other than 528 listed above, then the Response-PDU is re-formatted with the same values 529 in its request-id and variable-bindings fields as the received 530 GetNextRequest-PDU, with the value of its error-status field set to 531 `genErr', and the value of its error-index field is set to the index of 532 the failed variable binding. 534 Otherwise, the value of the Response-PDU's error-status field is set to 535 `noError', and the value of its error-index field is zero. 537 The generated Response-PDU is then encapsulated into a message. If the 538 size of the resultant message is less than or equal to both a local 539 constraint and the maximum message size of the request's source party, 540 it is transmitted to the originator of the GetNextRequest-PDU. 542 Otherwise, an alternate Response-PDU is generated. This alternate 543 Response-PDU is formatted with the same values in its request-id field 544 as the received GetNextRequest-PDU, with the value of its error-status 545 field set to `tooBig', the value of its error-index field set to zero, 546 and an empty variable-bindings field. This alternate Response-PDU is 547 then encapsulated into a message. If the size of the resultant message 548 is less than or equal to both a local constraint and the maximum message 549 size of the request's source party, it is transmitted to the originator 550 of the GetNextRequest-PDU. Otherwise, the snmpStatsSilentDrops [11] 551 counter is incremented and the resultant message is discarded. 553 4.2.2.1. Example of Table Traversal 555 An important use of the GetNextRequest-PDU is the traversal of 556 conceptual tables of information within a MIB. The semantics of this 557 type of request, together with the method of identifying individual 558 instances of objects in the MIB, provides access to related objects in 559 the MIB as if they enjoyed a tabular organization. 561 In the protocol exchange sketched below, a SNMPv2 application retrieves 562 the media-dependent physical address and the address-mapping type for 563 each entry in the IP net-to-media Address Translation Table [9] of a 564 particular network element. It also retrieves the value of sysUpTime 565 [11], at which the mappings existed. Suppose that the agent's IP net- 566 to-media table has three entries: 568 Interface-Number Network-Address Physical-Address Type 570 1 10.0.0.51 00:00:10:01:23:45 static 571 1 9.2.3.4 00:00:10:54:32:10 dynamic 572 2 10.0.0.15 00:00:10:98:76:54 dynamic 574 The SNMPv2 entity acting in a manager role begins by sending a 575 GetNextRequest-PDU containing the indicated OBJECT IDENTIFIER values as 576 the requested variable names: 578 GetNextRequest ( sysUpTime, 579 ipNetToMediaPhysAddress, 580 ipNetToMediaType ) 582 The SNMPv2 entity acting in an agent role responds with a Response-PDU: 584 Response (( sysUpTime.0 = "123456" ), 585 ( ipNetToMediaPhysAddress.1.9.2.3.4 = 586 "000010543210" ), 587 ( ipNetToMediaType.1.9.2.3.4 = "dynamic" )) 589 The SNMPv2 entity acting in a manager role continues with: 591 GetNextRequest ( sysUpTime, 592 ipNetToMediaPhysAddress.1.9.2.3.4, 593 ipNetToMediaType.1.9.2.3.4 ) 595 The SNMPv2 entity acting in an agent role responds with: 597 Response (( sysUpTime.0 = "123461" ), 598 ( ipNetToMediaPhysAddress.1.10.0.0.51 = 599 "000010012345" ), 600 ( ipNetToMediaType.1.10.0.0.51 = "static" )) 602 The SNMPv2 entity acting in a manager role continues with: 604 GetNextRequest ( sysUpTime, 605 ipNetToMediaPhysAddress.1.10.0.0.51, 606 ipNetToMediaType.1.10.0.0.51 ) 608 The SNMPv2 entity acting in an agent role responds with: 610 Response (( sysUpTime.0 = "123466" ), 611 ( ipNetToMediaPhysAddress.2.10.0.0.15 = 612 "000010987654" ), 613 ( ipNetToMediaType.2.10.0.0.15 = "dynamic" )) 615 The SNMPv2 entity acting in a manager role continues with: 617 GetNextRequest ( sysUpTime, 618 ipNetToMediaPhysAddress.2.10.0.0.15, 619 ipNetToMediaType.2.10.0.0.15 ) 621 As there are no further entries in the table, the SNMPv2 entity acting 622 in an agent role responds with the variables that are next in the 623 lexicographical ordering of the accessible object names, for example: 625 Response (( sysUpTime.0 = "123471" ), 626 ( ipNetToMediaNetAddress.1.9.2.3.4 = 627 "9.2.3.4" ), 628 ( ipRoutingDiscards.0 = "2" )) 630 This response signals the end of the table to the SNMPv2 entity acting 631 in a manager role. 633 4.2.3. The GetBulkRequest-PDU 635 A GetBulkRequest-PDU is generated and transmitted at the request of a 636 SNMPv2 application. The purpose of the GetBulkRequest-PDU is to request 637 the transfer of a potentially large amount of data, including, but not 638 limited to, the efficient and rapid retrieval of large tables. 640 Upon receipt of a GetBulkRequest-PDU, the receiving SNMPv2 entity 641 processes each variable binding in the variable-binding list to produce 642 a Response-PDU with its request-id field having the same value as in the 643 request. Processing begins by examining the values in the non-repeaters 644 and max-repetitions fields. If the value in the non-repeaters field is 645 less than zero, then the value of the field is set to zero. Similarly, 646 if the value in the max-repetitions field is less than zero, then the 647 value of the field is set to zero. 649 For the GetBulkRequest-PDU type, the successful processing of each 650 variable binding in the request generates zero or more variable bindings 651 in the Response-PDU. That is, the one-to-one mapping between the 652 variable bindings of the GetRequest-PDU, GetNextRequest-PDU, and 653 SetRequest-PDU types and the resultant Response-PDUs does not apply for 654 the mapping between the variable bindings of a GetBulkRequest-PDU and 655 the resultant Response-PDU. 657 The values of the non-repeaters and max-repetitions fields in the 658 request specify the processing requested. One variable binding in the 659 Response-PDU is requested for the first N variable bindings in the 660 request and M variable bindings are requested for each of the R 661 remaining variable bindings in the request. Consequently, the total 662 number of requested variable bindings communicated by the request is 663 given by N + (M * R), where N is the minimum of: a) the value of the 664 non-repeaters field in the request, and b) the number of variable 665 bindings in the request; M is the value of the max-repetitions field in 666 the request; and R is the maximum of: a) number of variable bindings in 667 the request - N, and b) zero. 669 The receiving SNMPv2 entity produces a Response-PDU with up to the total 670 number of requested variable bindings communicated by the request. The 671 request-id shall have the same value as the received GetBulkRequest-PDU. 673 If N is greater than zero, the first through the (N)-th variable 674 bindings of the Response-PDU are each produced as follows: 676 (1) The variable is located which is in the lexicographically ordered 677 list of the names of all variables which are accessible by this 678 request and whose name is the first lexicographic successor of the 679 variable binding's name in the incoming GetBulkRequest-PDU. The 680 corresponding variable binding's name and value fields in the 681 Response-PDU are set to the name and value of the located variable. 683 (2) If the requested variable binding's name does not lexicographically 684 precede the name of any variable accessible by this request, i.e., 685 there is no lexicographic successor, then the corresponding 686 variable binding produced in the Response-PDU has its value field 687 set to `endOfMibView', and its name field set to the variable 688 binding's name in the request. 690 If M and R are non-zero, the (N + 1)-th and subsequent variable bindings 691 of the Response-PDU are each produced in a similar manner. For each 692 iteration i, such that i is greater than zero and less than or equal to 693 M, and for each repeated variable, r, such that r is greater than zero 694 and less than or equal to R, the (N + ( (i-1) * R ) + r)-th variable 695 binding of the Response-PDU is produced as follows: 697 (1) The variable which is in the lexicographically ordered list of the 698 names of all variables which are accessible by this request and 699 whose name is the (i)-th lexicographic successor of the (N + r)-th 700 variable binding's name in the incoming GetBulkRequest-PDU is 701 located and the variable binding's name and value fields are set to 702 the name and value of the located variable. 704 (2) If there is no (i)-th lexicographic successor, then the 705 corresponding variable binding produced in the Response-PDU has its 706 value field set to `endOfMibView', and its name field set to either 707 the last lexicographic successor, or if there are no lexicographic 708 successors, to the (N + r)-th variable binding's name in the 709 request. 711 While the maximum number of variable bindings in the Response-PDU is 712 bounded by N + (M * R), the response may be generated with a lesser 713 number of variable bindings (possibly zero) for either of three reasons. | 715 (1) If the size of the message encapsulating the Response-PDU 716 containing the requested number of variable bindings would be 717 greater than either a local constraint or the maximum message size 718 of the request's source party, then the response is generated with 719 a lesser number of variable bindings. This lesser number is the 720 ordered set of variable bindings with some of the variable bindings 721 at the end of the set removed, such that the size of the message 722 encapsulating the Response-PDU is approximately equal to but no 723 greater than the minimum of the local constraint and the maximum 724 message size of the request's source party. Note that the number 725 of variable bindings removed has no relationship to the values of 726 N, M, or R. 728 (2) The response may also be generated with a lesser number of variable 729 bindings if for some value of iteration i, such that i is greater 730 than zero and less than or equal to M, that all of the generated 731 variable bindings have the value field set to the `endOfMibView'. 732 In this case, the variable bindings may be truncated after the (N + 733 (i * R))-th variable binding. 735 (3) In the event that the processing of a request with many repetitions + 736 requires a significantly greater amount of processing time than a + 737 normal request, then an agent may terminate the request with less + 738 than the full number of repetitions, providing at least one + 739 repetition is completed. + 741 If the processing of any variable binding fails for a reason other than 742 listed above, then the Response-PDU is re-formatted with the same values 743 in its request-id and variable-bindings fields as the received 744 GetBulkRequest-PDU, with the value of its error-status field set to 745 `genErr', and the value of its error-index field is set to the index of 746 the variable binding in the original request which corresponds to the | 747 failed variable binding. | 749 Otherwise, the value of the Response-PDU's error-status field is set to 750 `noError', and the value of its error-index field to zero. 752 The generated Response-PDU (possibly with an empty variable-bindings 753 field) is then encapsulated into a message. If the size of the 754 resultant message is less than or equal to both a local constraint and 755 the maximum message size of the request's source party, it is 756 transmitted to the originator of the GetBulkRequest-PDU. Otherwise, the 757 snmpStatsSilentDrops [11] counter is incremented and the resultant 758 message is discarded. 760 4.2.3.1. Another Example of Table Traversal 762 This example demonstrates how the GetBulkRequest-PDU can be used as an 763 alternative to the GetNextRequest-PDU. The same traversal of the IP 764 net-to-media table as shown in Section 4.2.2.1 is achieved with fewer 765 exchanges. 767 The SNMPv2 entity acting in a manager role begins by sending a 768 GetBulkRequest-PDU with the modest max-repetitions value of 2, and 769 containing the indicated OBJECT IDENTIFIER values as the requested 770 variable names: 772 GetBulkRequest [ non-repeaters = 1, max-repetitions = 2 ] 773 ( sysUpTime, 774 ipNetToMediaPhysAddress, 775 ipNetToMediaType ) 777 The SNMPv2 entity acting in an agent role responds with a Response-PDU: 779 Response (( sysUpTime.0 = "123456" ), 780 ( ipNetToMediaPhysAddress.1.9.2.3.4 = 781 "000010543210" ), 782 ( ipNetToMediaType.1.9.2.3.4 = "dynamic" ), 783 ( ipNetToMediaPhysAddress.1.10.0.0.51 = 784 "000010012345" ), 785 ( ipNetToMediaType.1.10.0.0.51 = "static" )) 787 The SNMPv2 entity acting in a manager role continues with: 789 GetBulkRequest [ non-repeaters = 1, max-repetitions = 2 ] 790 ( sysUpTime, 791 ipNetToMediaPhysAddress.1.10.0.0.51, 792 ipNetToMediaType.1.10.0.0.51 ) 794 The SNMPv2 entity acting in an agent role responds with: 796 Response (( sysUpTime.0 = "123466" ), 797 ( ipNetToMediaPhysAddress.2.10.0.0.15 = 798 "000010987654" ), 799 ( ipNetToMediaType.2.10.0.0.15 = 800 "dynamic" ), 801 ( ipNetToMediaNetAddress.1.9.2.3.4 = 802 "9.2.3.4" ), 803 ( ipRoutingDiscards.0 = "2" )) 805 This response signals the end of the table to the SNMPv2 entity acting 806 in a manager role. 808 4.2.4. The Response-PDU 810 The Response-PDU is generated by a SNMPv2 entity only upon receipt of a 811 GetRequest-PDU, GetNextRequest-PDU, GetBulkRequest-PDU, SetRequest-PDU, 812 or InformRequest-PDU, as described elsewhere in this document. 814 If the error-status field of the Response-PDU is non-zero, the value 815 fields of the variable bindings in the variable binding list are 816 ignored. 818 If both the error-status field and the error-index field of the 819 Response-PDU are non-zero, then the value of the error-index field is 820 the index of the variable binding (in the variable-binding list of the 821 corresponding request) for which the request failed. The first variable 822 binding in a request's variable-binding list is index one, the second is 823 index two, etc. 825 A compliant SNMPv2 entity acting in a manager role must be able to 826 properly receive and handle a Response-PDU with an error-status field 827 equal to `noSuchName', `badValue', or `readOnly'. (See Section 3.1.2 of 828 [10].) 830 Upon receipt of a Response-PDU, the receiving SNMPv2 entity presents its 831 contents to the SNMPv2 application which generated the request with the 832 same request-id value. 834 4.2.5. The SetRequest-PDU 836 A SetRequest-PDU is generated and transmitted at the request of a SNMPv2 837 application. 839 Upon receipt of a SetRequest-PDU, the receiving SNMPv2 entity determines 840 the size of a message encapsulating a Response-PDU having the same | 841 values in its request-id and variable-bindings fields as the received | 842 SetRequest-PDU, and the largest possible sizes of the error-status and | 843 error-index fields. | 844 If the determined message size is greater than either a local constraint 845 or the maximum message size of the request's source party, then an 846 alternate Response-PDU is generated, transmitted to the originator of 847 the SetRequest-PDU, and processing of the SetRequest-PDU terminates 848 immediately thereafter. This alternate Response-PDU is formatted with 849 the same values in its request-id field as the received SetRequest-PDU, 850 with the value of its error-status field set to `tooBig', the value of 851 its error-index field set to zero, and an empty variable-bindings field. 852 This alternate Response-PDU is then encapsulated into a message. If the 853 size of the resultant message is less than or equal to both a local 854 constraint and the maximum message size of the request's source party, 855 it is transmitted to the originator of the SetRequest-PDU. Otherwise, 856 the snmpStatsSilentDrops [11] counter is incremented and the resultant 857 message is discarded. Regardless, processing of the SetRequest-PDU 858 terminates. 860 Otherwise, the receiving SNMPv2 entity processes each variable binding 861 in the variable-binding list to produce a Response-PDU. All fields of 862 the Response-PDU have the same values as the corresponding fields of the 863 received request except as indicated below. 865 The variable bindings are conceptually processed as a two phase 866 operation. In the first phase, each variable binding is validated; if 867 all validations are successful, then each variable is altered in the 868 second phase. Of course, implementors are at liberty to implement 869 either the first, or second, or both, of the these conceptual phases as 870 multiple implementation phases. Indeed, such multiple implementation 871 phases may be necessary in some cases to ensure consistency. 873 The following validations are performed in the first phase on each 874 variable binding until they are all successful, or until one fails: 876 (1) If the variable binding's name specifies an existing or non- | 877 existent variable to which this request is/would be denied access, | 878 then the value of the Response-PDU's error-status field is set to 879 `noAccess', and the value of its error-index field is set to the 880 index of the failed variable binding. 882 (2) - 883 Otherwise, if there are no variables which share the same OBJECT | 884 IDENTIFIER prefix as the variable binding's name, and which are | 885 able to be created or modified no matter what new value is | 886 specified, | 887 then the value of the Response-PDU's error-status field is set to 888 `notWritable', and the value of its error-index field is set to the 889 index of the failed variable binding. 891 (3) Otherwise, if the variable binding's value field specifies, 892 according to the ASN.1 language, a type which is inconsistent with | 893 that required for all variables which share the same OBJECT | 894 IDENTIFIER prefix as the variable binding's name, | 895 then the value of the Response-PDU's error-status field is set to 896 `wrongType', and the value of its error-index field is set to the 897 index of the failed variable binding. 899 (4) Otherwise, if the variable binding's value field specifies, 900 according to the ASN.1 language, a length which is inconsistent | 901 with that required for all variables which share the same OBJECT | 902 IDENTIFIER prefix as the variable binding's name, | 903 then the value of the Response-PDU's error-status field is set to 904 `wrongLength', and the value of its error-index field is set to the 905 index of the failed variable binding. 907 (5) Otherwise, if the variable binding's value field contains an ASN.1 908 encoding which is inconsistent with that field's ASN.1 tag, then 909 the value of the Response-PDU's error-status field is set to 910 `wrongEncoding', and the value of its error-index field is set to 911 the index of the failed variable binding. (Note that not all | 912 implementation strategies will generate this error.) | 914 (6) Otherwise, if the variable binding's value field specifies a value 915 which could under no circumstances be assigned to the variable, 916 then the value of the Response-PDU's error-status field is set to 917 `wrongValue', and the value of its error-index field is set to the 918 index of the failed variable binding. 920 (7) Otherwise, if the variable binding's name specifies a variable + 921 which does not exist and could not ever be created (even though + 922 some variables sharing the same OBJECT IDENTIFIER prefix might + 923 under some circumstances be able to be created), then the value of + 924 the Response-PDU's error-status field is set to `noCreation', and + 925 the value of its error-index field is set to the index of the + 926 failed variable binding. + 928 (8) + 929 Otherwise, if the variable binding's name specifies a variable 930 which does not exist but can not be created under the present 931 circumstances (even though it could be created under other 932 circumstances), then the value of the Response-PDU's error-status 933 field is set to `inconsistentName', and the value of its error- 934 index field is set to the index of the failed variable binding. 936 (9) Otherwise, if the variable binding's value field specifies a value 937 that could under other circumstances be assigned to the variable, 938 but is presently inconsistent, then the value of the Response-PDU's 939 error-status field is set to `inconsistentValue', and the value of 940 its error-index field is set to the index of the failed variable 941 binding. 943 (10) When, during the above steps, the assignment of the value specified | 944 by the | 945 variable binding's value field to the specified variable requires 946 the allocation of a resource which is presently unavailable, then 947 the value of the Response-PDU's error-status field is set to 948 `resourceUnavailable', and the value of its error-index field is 949 set to the index of the failed variable binding. 951 (11) If the processing of the variable binding fails for a reason other 952 than listed above, then the value of the Response-PDU's error- 953 status field is set to `genErr', and the value of its error-index 954 field is set to the index of the failed variable binding. 956 (12) Otherwise, the validation of the variable binding succeeds. 958 At the end of the first phase, if the validation of all variable 959 bindings succeeded, then the value of the Response-PDU's error-status 960 field is set to `noError' and the value of its error-index field is 961 zero, and processing continues as follows. 963 For each variable binding in the request, the named variable is created 964 if necessary, and the specified value is assigned to it. Each of these 965 variable assignments occurs as if simultaneously with respect to all 966 other assignments specified in the same request. However, if the same 967 variable is named more than once in a single request, with different 968 associated values, then the actual assignment made to that variable is 969 implementation-specific. 971 If any of these assignments fail (even after all the previous 972 validations), then all other assignments are undone, and the Response- 973 PDU is modified to have the value of its error-status field set to 974 `commitFailed', and the value of its error-index field set to the index 975 of the failed variable binding. 977 If and only if it is not possible to undo all the assignments, then the 978 Response-PDU is modified to have the value of its error-status field set 979 to `undoFailed', and the value of its error-index field is set to zero. 980 Note that implementations are strongly encouraged to take all possible 981 measures to avoid use of either `commitFailed' or `undoFailed' - these 982 two error-status codes are not to be taken as license to take the easy 983 way out in an implementation. 985 Finally, the generated Response-PDU is encapsulated into a message, and 986 transmitted to the originator of the SetRequest-PDU. 988 4.2.6. The SNMPv2-Trap-PDU 990 A SNMPv2-Trap-PDU is generated and transmitted by a SNMPv2 entity acting 991 in an agent role when an exceptional situation occurs. 993 The destination(s) to which a SNMPv2-Trap-PDU is sent is determined by | 994 consulting the acTable [5] to find all entries satisfying the | 995 following conditions: 997 (1) The value of acTarget refers to the generating SNMPv2 entity. | 998 (2) The value of acPrivileges allows for the SNMPv2-Trap-PDU. | 1000 (3) The value of acContext refers to a SNMPv2 context denoting local | 1001 management information. | 1003 (4) The notification's administratively assigned name is present in | 1004 the corresponding MIB view. (That is, the set of entries in the 1005 viewTable [5] for which the instance of viewIndex has the same | 1006 value as acReadViewIndex, | 1007 define a MIB view which contains the notification's 1008 administratively assigned name.) 1010 (5) If the OBJECTS clause is present in the invocation of the 1011 corresponding NOTIFICATION-TYPE macro, then the correspondent 1012 variables are all present in the MIB view corresponding to | 1013 acReadViewIndex. | 1015 (6) For any additional variables which the generating SNMPv2 entity | 1016 chooses to include within this SNMPv2-Trap-PDU, then these | 1017 variables are all present in the MIB view corresponding to | 1018 acReadViewIndex. | 1020 Then, for each entry satisfying these conditions, a SNMPv2-Trap-PDU is | 1021 sent from acTarget with context acContext to acSubject. The instance of | 1022 snmpTrapNumbers [11] corresponding to acSubject is incremented, | 1023 and is used as the request-id field of the SNMPv2-Trap-PDU. Then, the 1024 variable-bindings field are constructed as: 1026 (1) The first variable is sysUpTime.0 [11]. 1028 (2) The second variable is snmpTrapOID.0 [11], which contains the 1029 administratively assigned name of the notification. 1031 (3) If the OBJECTS clause is present in the invocation of the 1032 corresponding NOTIFICATION-TYPE macro, then each corresponding 1033 variable is copied, in order, to the variable-bindings field. 1035 (4) If any additional variables are being included (at the option of | 1036 the generating SNMPv2 entity), then each is copied to the | 1037 variable-bindings field. | 1039 4.2.7. The InformRequest-PDU 1041 An InformRequest-PDU is generated and transmitted at the request an 1042 application in a SNMPv2 entity acting in a manager role, that wishes to 1043 notify another application (in a SNMPv2 entity also acting in a manager 1044 role) of information in a MIB View local to the sending | 1045 application. 1047 The destination(s) to which an InformRequest-PDU is sent is specified by | 1048 the requesting application. | 1049 The first two variable bindings in the variable binding list of an | 1050 InformRequest-PDU are sysUpTime.0 [11] and snmpTrapOID.0 [11] | 1051 respectively. | 1052 If the OBJECTS clause is present in the invocation of the corresponding 1053 NOTIFICATION-TYPE macro, then each corresponding variable, as 1054 instantiated by this notification, is copied, in order, to the 1055 variable-bindings field. 1057 Upon receipt of an InformRequest-PDU, the receiving SNMPv2 entity 1058 determines the size of a message encapsulating a Response-PDU with the 1059 same values in its request-id, error-status, error-index and variable- 1060 bindings fields as the received InformRequest-PDU. If the determined 1061 message size is greater than either a local constraint or the maximum 1062 message size of the request's source party, then an alternate Response- 1063 PDU is generated, transmitted to the originator of the InformRequest- 1064 PDU, and processing of the InformRequest-PDU terminates immediately 1065 thereafter. This alternate Response-PDU is formatted with the same 1066 values in its request-id field as the received InformRequest-PDU, with 1067 the value of its error-status field set to `tooBig', the value of its 1068 error-index field set to zero, and an empty variable-bindings field. 1069 This alternate Response-PDU is then encapsulated into a message. If the 1070 size of the resultant message is less than or equal to both a local 1071 constraint and the maximum message size of the request's source party, 1072 it is transmitted to the originator of the InformRequest-PDU. 1073 Otherwise, the snmpStatsSilentDrops [11] counter is incremented and the 1074 resultant message is discarded. Regardless, processing of the 1075 InformRequest-PDU terminates. 1077 Otherwise, the receiving SNMPv2 entity: 1079 (1) presents its contents to the appropriate SNMPv2 application; 1081 (2) generates a Response-PDU with the same values in its request-id and 1082 variable-bindings fields as the received InformRequest-PDU, with 1083 the value of its error-status field is set to `noError' and the 1084 value of its error-index field is zero; and 1086 (3) transmits the generated Response-PDU to the originator of the 1087 InformRequest-PDU. 1089 5. Acknowledgements 1091 The authors wish to acknowledge the contributions of the SNMPv2 Working 1092 Group in general. In particular, the following individuals 1094 Dave Arneson (Cabletron), 1095 Uri Blumenthal (IBM), 1096 Doug Book (Chipcom), 1097 Maria Greene (Ascom Timeplex), 1098 Deirdre Kostik (Bellcore), 1099 Dave Harrington (Cabletron), 1100 Jeff Johnson (Cisco Systems), 1101 Brian O'Keefe (Hewlett Packard), 1102 Dave Perkins (Bay Networks), 1103 Randy Presuhn (Peer Networks), 1104 Shawn Routhier (Epilogue), 1105 Bob Stewart (Cisco Systems), 1106 Kaj Tesink (Bellcore). 1108 deserve special thanks for their contributions. 1110 6. References 1112 [1] Information processing systems - Open Systems Interconnection - 1113 Specification of Abstract Syntax Notation One (ASN.1), 1114 International Organization for Standardization. International 1115 Standard 8824, (December, 1987). 1117 [2] Case, J., McCloghrie, K., Rose, M., and Waldbusser, S., "Structure 1118 of Management Information for Version 2 of the Simple Network 1119 Management Protocol (SNMPv2)", Internet Draft, SNMP Research, Inc., 1120 Cisco Systems, Dover Beach Consulting, Inc., Carnegie Mellon 1121 University, March 1995. | 1123 [3] Case, J., Galvin, J., McCloghrie, K., Rose, M., and Waldbusser, S., | 1124 "Administrative Infrastructure for Version 2 of the Simple Network | 1125 Management Protocol (SNMPv2)", | 1126 Internet Draft, SNMP Research, Inc., Trusted Information Systems, | 1127 Cisco Systems, Dover Beach Consulting, Inc., Carnegie Mellon | 1128 University, March 1995. | 1130 [4] Case, J., McCloghrie, K., Rose, M., and Waldbusser, S., "Textual 1131 Conventions for Version 2 of the the Simple Network Management 1132 Protocol (SNMPv2)", Internet Draft, SNMP Research, Inc., Cisco 1133 Systems, Dover Beach Consulting, Inc., Carnegie Mellon University, | 1134 March 1995. | 1136 [5] Case, J., Galvin, J., McCloghrie, K., Rose, M., and Waldbusser, S., | 1137 "Party MIB for Version 2 of the Simple Network Management Protocol 1138 (SNMPv2)", Internet Draft, SNMP Research, Inc., Trusted Information | 1139 Systems, Cisco Systems, Dover Beach Consulting, Inc., Carnegie | 1140 Mellon University, March 1995. | 1142 [6] C. Kent, J. Mogul, Fragmentation Considered Harmful, Proceedings, 1143 ACM SIGCOMM '87, Stowe, VT, (August 1987). 1145 [7] Case, J., McCloghrie, K., Rose, M., and Waldbusser, S., "Transport 1146 Mappings for Version 2 of the Simple Network Management Protocol 1147 (SNMPv2)", Internet Draft, SNMP Research, Inc., Cisco Systems, 1148 Dover Beach Consulting, Inc., Carnegie Mellon University, March | 1149 1995. | 1151 [8] Postel, J., "User Datagram Protocol", STD 6, RFC 768, 1152 USC/Information Sciences Institute, August 1980. 1154 [9] Case, J., McCloghrie, K., Rose, M., and Waldbusser, S., "SNMPv2 1155 Management Information Base for the Internet Protocol", Internet 1156 Draft, SNMP Research, Inc., Cisco Systems, Dover Beach Consulting, 1157 Inc., Carnegie Mellon University, March 1995. | 1159 [10] Case, J., McCloghrie, K., Rose, M., and Waldbusser, S., 1160 "Coexistence between Version 1 and Version 2 of the Internet- 1161 standard Network Management Framework", Internet Draft, SNMP 1162 Research, Inc., Cisco Systems, Dover Beach Consulting, Inc., 1163 Carnegie Mellon University, March 1995. | 1165 [11] Case, J., McCloghrie, K., Rose, M., and Waldbusser, S., "Management 1166 Information Base for Version 2 of the Simple Network Management 1167 Protocol (SNMPv2)", Internet Draft, SNMP Research, Inc., Cisco 1168 Systems, Dover Beach Consulting, Inc., Carnegie Mellon University, | 1169 March 1995. | 1171 [12] Case, J., McCloghrie, K., Rose, M., and Waldbusser, S., "Manager- 1172 to-Manager Management Information Base", Internet Draft, SNMP 1173 Research, Inc., Cisco Systems, Dover Beach Consulting, Inc., 1174 Carnegie Mellon University, March 1995. | 1176 7. Security Considerations 1178 Security issues are not discussed in this memo. 1180 8. Authors' Addresses 1182 Jeffrey D. Case 1183 SNMP Research, Inc. 1184 3001 Kimberlin Heights Rd. 1185 Knoxville, TN 37920-9716 1186 US 1188 Phone: +1 615 573 1434 1189 Email: case@snmp.com 1191 Keith McCloghrie 1192 Cisco Systems, Inc. 1193 170 West Tasman Drive, 1194 San Jose CA 95134-1706. 1196 Phone: +1 408 526 5260 1197 Email: kzm@cisco.com 1199 Marshall T. Rose 1200 Dover Beach Consulting, Inc. 1201 420 Whisman Court 1202 Mountain View, CA 94043-2186 1203 US 1205 Phone: +1 415 968 1052 1206 Email: mrose@dbc.mtview.ca.us 1208 Steven Waldbusser 1209 Carnegie Mellon University 1210 5000 Forbes Ave 1211 Pittsburgh, PA 15213 1212 US 1214 Phone: +1 412 268 6628 1215 Email: waldbusser@cmu.edu 1217 Table of Contents 1219 1 Introduction .................................................... 3 1220 1.1 A Note on Terminology ......................................... 3 1221 1.2 Change Log .................................................... 4 1222 2 Overview ........................................................ 5 1223 2.1 Roles of Protocol Entities .................................... 5 1224 2.2 Management Information ........................................ 5 1225 2.3 Access to Management Information .............................. 6 1226 2.4 Retransmission of Requests .................................... 6 1227 2.5 Message Sizes ................................................. 6 1228 2.6 Transport Mappings ............................................ 7 1229 3 Definitions ..................................................... 8 1230 4 Protocol Specification .......................................... 13 1231 4.1 Common Constructs ............................................. 13 1232 4.2 PDU Processing ................................................ 13 1233 4.2.1 The GetRequest-PDU .......................................... 14 1234 4.2.2 The GetNextRequest-PDU ...................................... 15 1235 4.2.2.1 Example of Table Traversal ................................ 16 1236 4.2.3 The GetBulkRequest-PDU ...................................... 18 1237 4.2.3.1 Another Example of Table Traversal ........................ 21 1238 4.2.4 The Response-PDU ............................................ 22 1239 4.2.5 The SetRequest-PDU .......................................... 23 1240 4.2.6 The SNMPv2-Trap-PDU ......................................... 26 1241 4.2.7 The InformRequest-PDU ....................................... 28 1242 5 Acknowledgements ................................................ 30 1243 6 References ...................................................... 30 1244 7 Security Considerations ......................................... 32 1245 8 Authors' Addresses .............................................. 32