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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 5226 (ref. 'IANA') (Obsoleted by RFC 8126) Summary: 2 errors (**), 0 flaws (~~), 1 warning (==), 4 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group A. Zinin 3 Internet-Draft Alcatel 4 Obsoletes: 4813 (if approved) A. Roy 5 Intended status: Standards Track L. Nguyen 6 Expires: June 20, 2009 Cisco Systems 7 B. Friedman 8 Redback Networks 9 D. Yeung 10 Cisco Systems 11 December 17, 2008 13 OSPF Link-local Signaling 14 draft-ietf-ospf-lls-06.txt 16 Status of this Memo 18 This Internet-Draft is submitted to IETF in full conformance with the 19 provisions of BCP 78 and BCP 79. 21 Internet-Drafts are working documents of the Internet Engineering 22 Task Force (IETF), its areas, and its working groups. Note that 23 other groups may also distribute working documents as Internet- 24 Drafts. 26 Internet-Drafts are draft documents valid for a maximum of six months 27 and may be updated, replaced, or obsoleted by other documents at any 28 time. It is inappropriate to use Internet-Drafts as reference 29 material or to cite them other than as "work in progress." 31 The list of current Internet-Drafts can be accessed at 32 http://www.ietf.org/ietf/1id-abstracts.txt. 34 The list of Internet-Draft Shadow Directories can be accessed at 35 http://www.ietf.org/shadow.html. 37 This Internet-Draft will expire on June 20, 2009. 39 Copyright Notice 41 Copyright (c) 2008 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (http://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. 51 Abstract 53 OSPF is a link-state intra-domain routing protocol. OSPF routers 54 exchange information on a link using packets that follow a well- 55 defined fixed format. The format is not flexible enough to enable 56 new features which need to exchange arbitrary data. This document 57 describes a backward-compatible technique to perform link-local 58 signaling, i.e., exchange arbitrary data on a link. This document 59 replaces the experimental specification published in RFC4813 to bring 60 it on the Standards Track. 62 Table of Contents 64 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 65 1.1. Requirements notation . . . . . . . . . . . . . . . . . . 4 66 2. Proposed solution . . . . . . . . . . . . . . . . . . . . . . 5 67 2.1. Options Field . . . . . . . . . . . . . . . . . . . . . . 6 68 2.2. LLS Data Block . . . . . . . . . . . . . . . . . . . . . . 6 69 2.3. LLS TLVs . . . . . . . . . . . . . . . . . . . . . . . . . 7 70 2.4. Extended Options TLV . . . . . . . . . . . . . . . . . . . 7 71 2.5. Cryptographic Authentication TLV (OSPFv2 ONLY) . . . . . . 8 72 2.6. Private TLVs . . . . . . . . . . . . . . . . . . . . . . . 9 73 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 74 4. Compatibility Issues . . . . . . . . . . . . . . . . . . . . . 11 75 5. Security Considerations . . . . . . . . . . . . . . . . . . . 12 76 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 77 6.1. Normative References . . . . . . . . . . . . . . . . . . . 13 78 6.2. Informative References . . . . . . . . . . . . . . . . . . 13 79 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 14 80 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15 82 1. Introduction 84 This document describes an extension to OSPFv2 [OSPFV2] and OSPFv3 85 [OSPFV3] allowing additional information to be exchanged between 86 routers on the same link. OSPFv2 and OSPFv3 packet formats are fixed 87 and do not allow for extension. This document proposes appending an 88 optional data block composed of Type/Length/Value (TLV) triplets to 89 existing OSPFv2 and OSPFv3 packets to carry this additional 90 information. Throughout this document, OSPF will be used when the 91 specification is applicable to both OSPFv2 and OSPFv3. Similarly, 92 OSPFv2 or OSPFv3 will be used when the text is protocol specific. 94 One potential way of solving this task could be introducing a new 95 packet type. However, that would mean introducing extra packets on 96 the network which may not be desirable and may cause backward 97 compatibility issues. This document describes how to exchange data 98 using standard OSPF packet types. 100 1.1. Requirements notation 102 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 103 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 104 document are to be interpreted as described in [KEY]. 106 2. Proposed solution 108 To perform link-local signaling (LLS), OSPF routers add a special 109 data block to the end of OSPF packets or right after the 110 authentication data block when cryptographic authentication is used. 111 The length of the LLS block is not included into the length of OSPF 112 packet, but is included in the IPv4/IPv6 packet length. Figure 1 113 illustrates how the LLS data block is attached. 115 +---------------------+ -- -- +---------------------+ 116 | IP Header | ^ ^ | IPv6 Header | 117 | Length = HL+X+Y+Z | | Header Length | | Length = HL+X+Y | 118 | | v v | | 119 +---------------------+ -- -- +---------------------+ 120 | OSPF Header | ^ ^ | OSPFv3 Header | 121 | Length = X | | | | Length = X | 122 |.....................| | X | X |.....................| 123 | | | | | | 124 | OSPFv2 Data | | | | OSPFv3 Data | 125 | | v v | | 126 +---------------------+ -- -- +---------------------+ 127 | | ^ ^ | | 128 | Authentication Data | | Y | Y | LLS Data | 129 | | v v | | 130 +---------------------+ -- -- +---------------------+ 131 | | ^ 132 | LLS Data | | Z 133 | | v 134 +---------------------+ -- 136 Figure 1: LLS Data Block in OSPFv2 and OSPFv3 138 The LLS block MAY be attached to OSPF Hello and DD packets. LLS 139 block MUST NOT be attached to any other OSPF packet types on 140 generation and MUST be ignored on reception. 142 The data included in the LLS block attached to a Hello packet MAY be 143 used for dynamic signaling since Hello packets may be sent at any 144 time in time. However, delivery of LLS data in Hello packets is not 145 guaranteed. The data sent with DD packets is guaranteed to be 146 delivered as part of the adjacency forming process. 148 This document does not specify how the data transmitted by the LLS 149 mechanism should be interpreted by OSPF routers. As routers that do 150 not understand LLS may receive these packets, changes made due to LLS 151 block TLV's do not affect the basic routing when interacting with 152 non-LLS routers. 154 2.1. Options Field 156 A new L bit (L stands for LLS) is introduced into the OSPF Options 157 field (see Figure 2a/2b). Routers set the L bit in Hello and DD 158 packets to indicate that the packet contains an LLS data block. In 159 other words, the LLS data block is only examined if the L bit is set. 161 +---+---+---+---+---+---+---+---+ 162 | * | O | DC| L |N/P| MC| E | * | 163 +---+---+---+---+---+---+---+-+-+ 165 Figure 2a: OSPFv2 Options field 167 0 1 2 168 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 169 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--+-+-+--+--+--+--+--+--+ 170 | | | | | | | | | | | | | | |L|AF|*|*|DC| R| N|MC| E|V6| 171 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--+-+-+--+--+--+--+--+--+ 173 Figure 2b: OSPFv3 Options field 175 The L bit MUST NOT be set except in Hello and DD packets that contain 176 LLS block. 178 2.2. LLS Data Block 180 The data block used for link-local signaling is formatted as 181 described below (see Figure 3 for illustration). 183 0 1 2 3 184 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 185 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 186 | Checksum | LLS Data Length | 187 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 188 | | 189 | LLS TLVs | 190 . . 191 . . 192 . . 193 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 195 Figure 3: Format of LLS Data Block 197 The Checksum field contains the standard IP checksum for the entire 198 contents of the LLS block. Before computing the checksum, the 199 checksum field is set to 0. If the checksum is incorrect, LLS block 200 MUST NOT be processed. 202 The 16-bit LLS Data Length field contains the length (in 32-bit 203 words) of the LLS block including the header and payload. 205 Note that if the OSPF packet is cryptographically authenticated, the 206 LLS data block MUST also be cryptographically authenticated. In this 207 case, the regular LLS checksum is not calculated, but is instead set 208 to 0. 210 The rest of the block contains a set of Type/Length/Value (TLV) 211 triplets as described in Section 2.3. All TLVs MUST be 32-bit 212 aligned (with padding if necessary). 214 2.3. LLS TLVs 216 The contents of LLS data block is constructed using TLVs. See Figure 217 4 for the TLV format. 219 The type field contains the TLV ID which is unique for each type of 220 TLV. The Length field contains the length of the Value field (in 221 bytes). The value field is variable and contains arbitrary data. 223 0 1 2 3 224 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 225 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 226 | Type | Length | 227 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 228 | | 229 . . 230 . Value . 231 . . 232 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 234 Figure 4: Format of LLS TLVs 236 Note that TLVs are always padded to 32-bit boundary, but padding 237 bytes are not included in the TLV Length field (though they are 238 included in the LLS Data Length field in the LLS block header). 239 Unrecognized TLV types are ignored. 241 2.4. Extended Options TLV 243 This subsection describes a TLV called the Extended Options (EO) TLV. 244 The format of EO-TLV is shown in Figure 5. 246 Bits in the Value field do not have any semantics from the point of 247 view of the LLS mechanism. This field MAY be used to announce some 248 OSPF capabilities that are link-specific. Also, other OSPF 249 extensions MAY allocate bits in the bit vector to perform boolean 250 link-local signaling. 252 The length of the Value field in the EO-TLV is 4 bytes. 254 The value of the type field in the EO-TLV is 1. 256 The EO-TLV MUST only appear once in the LLS data block. 258 0 1 2 3 259 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 260 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 261 | 1 | 4 | 262 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 263 | Extended Options | 264 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 266 Figure 5: Format of EO TLV 268 Currently, [OOB] and [RESTART] use bits in the Extended Options field 269 of the EO-TLV. 271 The Extended Options bits are defined in Section 3. 273 2.5. Cryptographic Authentication TLV (OSPFv2 ONLY) 275 This document defines a special TLV that is used for cryptographic 276 authentication (CA-TLV) of the LLS data block. This TLV MUST be 277 included in the LLS block when cryptographic authentication is 278 enabled on the corresponding interface. The message digest of the 279 LLS block MUST be calculated using the same key and authentication 280 algorithm as used for the OSPFv2 packet. The cryptographic sequence 281 number is included in the TLV and MUST be the same as the one in the 282 OSPFv2 authentication data for the LLS block to be considered 283 authentic. 285 The TLV is constructed as shown in Figure 6. 287 0 1 2 3 288 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 289 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 290 | 2 | AuthLen | 291 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 292 | Sequence number | 293 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 294 | | 295 . . 296 . AuthData . 297 . . 298 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 300 Figure 6: Format of Cryptographic Authentication TLV 302 The value of the Type field for the CA-TLV is 2. 304 The Length field in the header contains the length of the data 305 portion of the TLV including 4 bytes for Sequence Number and the 306 length of the message digest block for the whole LLS block in bytes. 308 The Sequence Number field contains the cryptographic sequence number 309 that is used to prevent simple replay attacks. For the LLS block to 310 be considered authentic, the Sequence Number in the CA-TLV MUST match 311 the Sequence Number in the OSPFv2 packet header Authentication field. 312 In the event of Sequence Number mismatch or Authentication failure, 313 the whole LLS block MUST be ignored. 315 The AuthData contains the message digest calculated for the LLS data 316 block. 318 The CA-TLV MUST NOT appear more than once in the LLS block. Also, 319 when present, this TLV MUST be the last TLV in the LLS block. If it 320 appears more than once, only the first occurrence is processed and 321 any others MUST be ignored. 323 The CA-TLV is not applicable to OSPFv3 and it MUST NOT be added to 324 any OSPFv3 packet. If found on reception, this TLV MUST be ignored. 326 2.6. Private TLVs 328 LLS type values in the range of 32768-65536 are reserved for private 329 use. The first four octets of the Value field MUST be the private 330 enterprise code [ENTNUM]. This allows multiple vendor private 331 extensions to coexist in a network. 333 3. IANA Considerations 335 IANA is requested to allocate L-bit in "OSPFv2 Options Registry" and 336 "OSPFv3 Options Registry" as per Section 2.1. 338 LLS TLV types are maintained by the IANA. Extensions to OSPF which 339 require a new LLS TLV type MUST be reviewed by an designated expert 340 from the routing area. 342 Following the policies outlined in [IANA], LLS type values in the 343 range of 0-32767 are allocated through an IETF Consensus action and 344 LLS type values in the range of 32768-65536 are reserved for private 345 use. 347 This document assigns the following LLS TLV types in OSPFv2/OSPFv3. 349 TLV Type Name Reference 350 0 Reserved 351 1 Extended Options [RFCNNNN]* 352 2 Cryptographic Authentication+ [RFCNNNN]* 353 3-32767 Reserved for assignment by the IANA 354 32768-65535 Private Use 356 *[RFCNNNN] refers to the RFC number-to-be for this document. 357 + Cryptographic Authentication TLV is only defined for OSPFv2 359 This document also assigns the following bits for the Extended 360 Options bits field in the EO-TLV outlined in Section 2.5: 362 Extended Options Bit Name Reference 363 0x00000001 LSDB Resynchronization (LR) [OOB] 364 0x00000002 Restart Signal (RS-bit) [RESTART] 366 Other Extended Options bits will be allocated through an IETF 367 consensus action. 369 4. Compatibility Issues 371 The modifications to OSPF packet formats are compatible with standard 372 OSPF since OSPF routers not supporting LLS will ignore the LLS data 373 block after the OSPF packet or cryptographic message digest. 375 5. Security Considerations 377 Security Considerations inherited from OSPFv2 are described in 378 [OSPFV2]. This technique provides the same level of security as the 379 basic OSPFv2 protocol by allowing LLS data to be authenticated using 380 the same cryptographic authentication that OSPFv2 uses (see 381 Section 2.5 for more details). 383 Security considerations inherited from OSPFv3 are described in 384 [OSPFV3] and [OSPFV3AUTH]. OSPFv3 utilizes IPSec for authentication 385 and encryption. With IPsec, the AH (Authentication Header), ESP 386 (Encapsulating Security Payload), or both are applied to the entire 387 OSPFv3 payload including the LLS block. 389 6. References 391 6.1. Normative References 393 [IANA] Narten, T. and H. Alvestrand, "Guidelines for Writing an 394 IANA Considerations Section in RFCs", RFC 5226, May 2008. 396 [KEY] Bradner, S., "Key words for use in RFC's to Indicate 397 Requirement Levels", RFC 2119, March 1997. 399 [OSPFV2] Moy, J., "OSPF Version 2", RFC 2328, April 1998. 401 [OSPFV3] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF 402 for IPv6", RFC 5340, July 2008. 404 [OSPFV3AUTH] 405 Gupta, M. and N. Melam, "Authentication/Confidentiality 406 for OSPFv3", RFC 4552, June 2006. 408 6.2. Informative References 410 [ENTNUM] IANA, 411 "http://www.iana.org/assignments/enterprise-numbers". 413 [OOB] Zinin, A., Roy, A., and L. Nguyen, "OSPF Out-of-band LSDB 414 resynchronization", RFC 4811, March 2007. 416 [RESTART] Zinin, A., Roy, A., and L. Nguyen, "OSPF Restart 417 Signaling", RFC 4812, March 2007. 419 Appendix A. Acknowledgements 421 The authors would like to acknowledge Russ White, Acee Lindem and 422 Manral Vishwas for their review of this document. 424 Authors' Addresses 426 Alex Zinin 427 Alcatel 428 Sunnyvale 429 USA 431 Email: zinin@psg.com 433 Abhay Roy 434 Cisco Systems 435 170 West Tasman Drive 436 San Jose, CA 95134 437 USA 439 Email: akr@cisco.com 441 Liem Nguyen 442 Cisco Systems 443 170 West Tasman Drive 444 San Jose, CA 95134 445 USA 447 Email: lhnguyen@cisco.com 449 Barry Friedman 450 Redback Networks 451 100 Headquarters Drive 452 San Jose, CA 95134 453 USA 455 Email: friedman@redback.com 457 Derek Yeung 458 Cisco Systems 459 170 West Tasman Drive 460 San Jose, CA 95134 461 USA 463 Email: myeung@cisco.com