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'BGP-MP') (Obsoleted by RFC 4760) ** Obsolete normative reference: RFC 2842 (ref. 'BGP-CAP') (Obsoleted by RFC 3392) == Outdated reference: A later version (-09) exists of draft-ramachandra-bgp-ext-communities-02 -- Possible downref: Normative reference to a draft: ref. 'BGP-EXT-COMMUNITIES' Summary: 8 errors (**), 0 flaws (~~), 5 warnings (==), 3 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group Enke Chen 3 Internet Draft Redback Networks, Inc. 4 Expiration Date: November 2001 Yakov Rekhter 5 Juniper Networks 7 Cooperative Route Filtering Capability for BGP-4 9 draft-ietf-idr-route-filter-04.txt 11 1. Status of this Memo 13 This document is an Internet-Draft and is in full conformance with 14 all provisions of Section 10 of RFC2026 except that the right to 15 produce derivative works is not granted. 17 Internet-Drafts are working documents of the Internet Engineering 18 Task Force (IETF), its areas, and its working groups. Note that 19 other groups may also distribute working documents as Internet- 20 Drafts. 22 Internet-Drafts are draft documents valid for a maximum of six months 23 and may be updated, replaced, or obsoleted by other documents at any 24 time. It is inappropriate to use Internet-Drafts as reference 25 material or to cite them other than as ``work in progress.'' 27 The list of current Internet-Drafts can be accessed at 28 http://www.ietf.org/ietf/1id-abstracts.txt 30 The list of Internet-Draft Shadow Directories can be accessed at 31 http://www.ietf.org/shadow.html. 33 2. Abstract 35 This document defines a BGP-based mechanism that allows a BGP speaker 36 to send to its BGP peer a set of route filters that the peer would 37 use to constrain/filter its outbound routing updates to the speaker. 39 3. Introduction 41 Currently it is not uncommon for a BGP speaker to receive, and then 42 filter out some unwanted routes from its peers based on its local 43 routing policy. Since the generation and transmission of routing 44 updates by the sender, as well as the processing of routing updates 45 by the receiver consume resources, it may be beneficial if the 46 generation of such unwanted routing updates can be avoided in the 47 first place. 49 This document defines a BGP-based mechanism that allows a BGP speaker 50 to send to its BGP peer a set of Outbound Route Filters (ORFs). The 51 peer would then apply these filters, in addition to its locally 52 configured outbound filters (if any), to constrain/filter its 53 outbound routing updates to the speaker. 55 4. Outbound Route Filter (ORF) 57 Conceptually an ORF entry is a tuple of the form ; an ORF consists of one or more ORF entries 59 that have a common AFI/SAFI and ORF-Type. An ORF is identified by 60 . 62 The "AFI/SAFI" component provides a coarse granularity control by 63 limiting the ORF to only the routes whose NLRI matches the "AFI/SAFI" 64 component of the ORF. 66 The "ORF-Type" component determines the content of the ORF-value. 68 The "Action" component controls handling of the ORF Request by the 69 remote peer. Action can be one of ADD, REMOVE, REMOVE-ALL. ADD adds 70 an ORF entry to the ORF on the remote peer; REMOVE deletes a 71 previously installed ORF entry on the remote peer; REMOVE-ALL deletes 72 the previously installed entries in the specified ORF on the remote 73 peer. 75 The "Match" component can be one of PERMIT or DENY. The semantics of 76 PERMIT is to ask the peer to pass updates for the set of routes that 77 match the ORF entry. The semantics of DENY is to ask the peer not to 78 pass updates for the set of routes that match the ORF entry. 80 4.1. Communities ORF-Type 82 The Community ORF-Type allows to express ORFs in terms of BGP 83 Communities [BGP-COMMUNITIES]. That is, the Communities ORF-Type 84 provides Communities-based route filtering. 86 Conceptually the ORF-value of the Communities ORF-Type consists of 87 . "Scope" indicates the set of routes that must 88 be considered by the remote peer for the given ORF request. Scope can 89 be one of the EXACT or NORMAL. EXACT scope indicates that the remote 90 peer should consider only those routes whose Communities attribute is 91 equal to the Communities list specified in the ORF. NORMAL scope 92 indicates that the remote peer should consider only those routes 93 whose Communities attribute either is equal to the Communities list 94 specified in the ORF, or exhibit a subset relation with the 95 Communities list specified in the ORF. 97 The Communities list is a list of BGP Communities. 99 4.2. Extended Communities ORF-Type 101 The Extended Community ORF-Type allows to express ORFs in terms of 102 BGP Extended Communities [BGP-EXT-COMMUNITIES]. That is, the Extended 103 Communities ORF-Type provides Extended Communities-based route 104 filtering. 106 Conceptually the ORF-value of the Extended Communities ORF-Type 107 consists of . "Scope" indicates the set 108 of routes that must be considered by the remote peer for the given 109 ORF request. Scope can be one of the EXACT or NORMAL. EXACT scope 110 indicates that the remote peer should consider only those routes 111 whose Extended Communities attribute is equal to the Extended 112 Communities list specified in the ORF. NORMAL scope indicates that 113 the remote peer should consider only those routes whose Extended 114 Communities attribute either is equal to the Extended Communities 115 list specified in the ORF, or exhibit a subset relation with the 116 Extended Communities list specified in the ORF. 118 The Extended Communities list is a list of BGP Extended Communities. 120 5. Carrying ORF entries in BGP 122 ORF entries are carried in the BGP ROUTE-REFRESH message [BGP-RR]. A 123 single ROUTE-REFRESH message could carry multiple ORF entries, as 124 long as all these entries share the same AFI/SAFI. 126 From the encoding point of view each ORF entry consists of a common 127 part and type-specific part. 129 The common part consists of , and 130 is encoded as follows: 132 The AFI/SAFI component of an ORF entry is encoded in the AFI/SAFI 133 field of the ROUTE-REFRESH message. 135 Following the AFI/SAFI component is the one-octet When-to-refresh 136 field. The value of this field can be one of IMMEDIATE (0x01) or 137 DEFER (0x02). The semantics of IMMEDIATE is to ask the peer to 138 refresh the routes for the AFI/SAFI carried in the message 139 immediately after processing the message. The semantics of DEFER 140 is to ask the peer to defer refreshing of all the routes until it 141 receives a subsequent ROUTE-REFRESH message for the same AFI/SAFI 142 either without any ORF entries, or with one or more ORF entries 143 and When-to-refresh set to IMMEDIATE. 145 Following the When-to-refresh field is a collection of one or more 146 ORFs, grouped by ORF-Type. 148 The ORF-Type component is encoded as a one-octet field. 150 The Length of ORFs component is a two-octets field that contains 151 the length (in octets) of the ORF entries that follows. 153 +--------------------------------------------------+ 154 | Address Family Identifier (2 octets) | 155 +--------------------------------------------------+ 156 | Reserved (1 octet) | 157 +--------------------------------------------------+ 158 | Subsequent Address Family Identifier (1 octet) | 159 +--------------------------------------------------+ 160 | When-to-refresh (1 octet) | 161 +--------------------------------------------------+ 162 | ORF Type (1 octet) | 163 +--------------------------------------------------+ 164 | Length of ORFs (2 octets) | 165 +--------------------------------------------------+ 166 | First ORF entry (variable) | 167 +--------------------------------------------------+ 168 | Second ORF entry (variable) | 169 +--------------------------------------------------+ 170 ......... 171 +--------------------------------------------------+ 172 | N-th ORF entry (variable) | 173 +--------------------------------------------------+ 174 | ORF Type (1 octet) | 175 +--------------------------------------------------+ 176 | Length of ORFs (2 octets) | 177 +--------------------------------------------------+ 178 | First ORF entry (variable) | 179 +--------------------------------------------------+ 180 | Second ORF entry (variable) | 181 +--------------------------------------------------+ 182 ......... 183 +--------------------------------------------------+ 184 | N-th ORF entry (variable) | 185 +--------------------------------------------------+ 186 ......... 188 Fig 1. Carrying ORF entries in the ROUTE-REFRESH message 190 The rest of the components in the common part are encoded in first 191 octet of each ORF-entry as follows (from the most significant to the 192 least significant bit): 194 Action is a two-bit field. The value of this field is 0 for ADD, 1 195 for REMOVE, and 2 for REMOVE-ALL. 197 Match is a one-bit field. The value of this field is 0 for PERMIT 198 and 1 for DENY. 200 Reserved is a 5-bit field. It is set to 0 on transmit and ignored 201 on receive. 203 +---------------------------------+ 204 | Action (2 bit) | 205 +---------------------------------+ 206 | Match (1 bit) | 207 +---------------------------------+ 208 | Reserved (5 bits) | 209 +---------------------------------+ 210 | Type specific part (variable) | 211 +---------------------------------+ 213 Fig 2. ORF entry encoding 214 When the Action component of an ORF entry specifies REMOVE-ALL, 215 the entry consists of only the common part. 217 5.1. Type specific encoding (Communities ORF-Type) 219 The value of the ORF-Type for the Communities ORF-Type is 2. 221 The type-specific part of Communities ORF-Type consists of , and is encoded as follows: 224 Scope is a one-octet field. The EXACT Scope has the value of 1. 225 The NORMAL Scope has the value of 2. 227 Communities are encoded as a one octet Number of Communities 228 field, followed by one or more Communities, where each Community 229 is encoded as a four-octets field. 231 5.2. Type specific encoding (Extended Communities ORF-Type) 233 The value of the ORF-Type for the Extended Communities ORF-Type is 3. 235 The type-specific part of Extended Communities ORF-Type consists of 236 , and is encoded as follows: 238 Scope is a one-octet field. The EXACT Scope has the value of 1. 239 The NORMAL Scope has the value of 2. 241 Extended Communities are encoded as a one octet Number of Extended 242 Communities field, followed by one or more Extended Communities, 243 where each Extended Community is encoded as a eight-octets field. 245 6. Cooperative Route Filtering Capability 247 A BGP speaker that is willing to receive ORF entries from its peer, 248 or a BGP speaker that would like to send ORF entries to its peer 249 advertises this to the peer by using the Cooperative Route Filtering 250 Capability, as described below. 252 The Cooperative Route Filtering Capability is a new BGP capability 253 [BGP-CAP] defined as follows: 255 Capability code: 3 257 Capability length: variable 258 Capability value: one or more of the following entries: 260 +--------------------------------------------------+ 261 | Address Family Identifier (2 octets) | 262 +--------------------------------------------------+ 263 | Reserved (1 octet) | 264 +--------------------------------------------------+ 265 | Subsequent Address Family Identifier (1 octet) | 266 +--------------------------------------------------+ 267 | Number of ORFs (1 octet) | 268 +--------------------------------------------------+ 269 | ORF Type (1 octet) | 270 +--------------------------------------------------+ 271 | Send/Receive (1 octet) | 272 +--------------------------------------------------+ 273 | ... | 274 +--------------------------------------------------+ 275 | ORF Type (1 octet) | 276 +--------------------------------------------------+ 277 | Send/Receive (1 octet) | 278 +--------------------------------------------------+ 280 Fig 4. Capability encoding 282 The use and meaning of these fields are as follows: 284 Address Family Identifier (AFI): 286 This field carries the identity of the Network Layer protocol 287 associated with the Network Address that follows. Presently 288 defined values for this field are specified in RFC1700 (see the 289 Address Family Numbers section). 291 Subsequent Address Family Identifier (SAFI): 293 This field provides additional information about the type of 294 the Network Layer Reachability Information carried in the 295 attribute. 297 Number of ORF Types: 299 This field contains the number of Filter Types to be listed in 300 the following fields. 302 ORF Type: 304 This field contains the value of an ORF Type. 306 Send/Receive: 308 This field indicates whether the sender is (a) willing to 309 receive ORF entries from its peer (value 1), (b) would like to 310 send ORF entries to its peer (value 2), or (c) both (value 3) 311 for the ORF Type that follows. 313 7. Operation 315 A BGP speaker that is willing to receive ORF entries from its peer, 316 or would like to send ORF entries to its peer should advertise the 317 Cooperative Route Filtering Capability to the peer using BGP 318 Capabilities advertisement [BGP-CAP]. 320 A BGP speaker that implements the Cooperative Route Filtering 321 Capability must support BGP ROUTE-REFRESH message, as defined in 322 [BGP-RR]. A BGP speaker that advertises the Cooperative Route 323 Filtering Capability to a peer using BGP Capabilities advertisement 324 [BGP-CAP] doesn't have to advertise the BGP Route Refresh capability 325 to that peer. 327 Consider a BGP speaker that advertises the Cooperative Route 328 Filtering Capability indicating its willingness to receive a 329 particular set of from its peer, and that 330 receives the Cooperative Route Filtering Capability indicating the 331 desire of the peer to send a particular set to 332 the speaker. If for a given the intersection between 333 these two sets are not-empty, the speaker should not advertise to the 334 peer any routes with that prior to receiving from the 335 peer any ROUTE-REFRESH message carrying that , where the 336 message could be either without any ORF entries, or with one or more 337 ORF entry and When-to-refresh field set to IMMEDIATE. If, on the 338 other hand, for a given the intersection between these 339 two sets is empty, the speaker should follow normal BGP procedures. 341 A BGP speaker may send a ROUTE-REFRESH message with one or more ORF 342 entries to its peer only if the peer advertises to the speaker the 343 Cooperative Route Filtering Capability indicating its willingness to 344 receive ORF entries from the speaker, and the speaker advertises to 345 the peer the Cooperative Route Filtering Capability indicating its 346 desire to send ORF entries to the peer. The message may contain only 347 ORF entries of that the peer is willing to 348 receive, as advertised to the speaker in the Cooperative Route 349 Filtering Capability. 351 When a BGP speaker receives a ROUTE-REFRESH message with one or more 352 ORF entries from its peer, then the speaker performs the following 353 actions. If the carried by the message doesn't 354 match that the speaker is willing to receive 355 from the peer (as advertised to the peer in the Cooperative Route 356 Filtering Capability), the specified ORF is ignored. Otherwise, the 357 speaker modifies the specified ORF, as specified in the ORF entries 358 carried by the message. If any of the fields within an ORF entry 359 contain an unrecognized value, the whole specified ORF is removed. 361 If the Action component of an ORF entry is REMOVE, but the ORF 362 doesn't contain the specified entry, the entry is ignored. 364 ORF entries with either REMOVE or REMOVE-ALL can not remove locally 365 configured outbound route filters. 367 If the When-to-Refresh indicates IMMEDIATE, then after processing all 368 the ORF entries carried in the message the speaker should re- 369 advertise to the peer routes from the Adj-RIB-Out that have the same 370 AFI/SAFI as what is carried in the message, and taking into account 371 all the ORF entries received from the peer. 373 The set of ORF entries that the speaker sends to the peer expresses 374 the speaker's local preference, that the peer may or may not decide 375 to honor. 377 During a single BGP session the speaker may pass multiple ORF entries 378 to the peer. 380 The lifetime of an ORF is the duration of the BGP session during 381 which the ORF is exchanged. 383 An ORF is removed when the last ORF entry is remove (either via 384 REMOVE-ALL, or via a sequence of REMOVE). 386 If a particular route maintained by a BGP speaker doesn't match any 387 of the ORF entries of any of the (non-empty) ORFs associated with a 388 particular peer, then this route should not be advertised to the 389 peer. 391 If a BGP speaker maintains multiple ORFs of different ORF-Types for a 392 particular peer, then the decision by the speaker to advertise a 393 route to the peer is determined by passing the route through each 394 such ORF, and and-ing the results (and-ing of PERMIT and DENY results 395 in DENY). 397 8. IANA Considerations 399 As specified in this document, an ORF enty contains the ORF-Type 400 field. ORF-Type value 0 is reserved. ORF-Type values 1 through 63 401 are to be assigned by IANA using the "IETF Consensus" policy defined 402 in RFC2434. ORF-Type values 64 through 127 are to be assigned by 403 IANA, using the "First Come First Served" policy defined in RFC2434. 404 ORF-Type values 128 through 255 are vendor-specific, and values in 405 this range are not to be assigned by IANA. 407 9. Security Considerations 409 This extension to BGP does not change the underlying security issues. 411 10. Acknowledgements 413 Some of the material in the document is "borrowed" from a proposal 414 for selective updates by Yakov Rekhter, Kannan Varadhan, and Curtis 415 Villamizar. 417 11. References 419 [BGP-4] Rekhter, Y., and T. Li, "A Border Gateway Protocol 4 420 (BGP-4)", RFC 1771, March 1995. 422 [BGP-MP] Bates, T., Chandra, R., Katz, D., and Rekhter, Y., 423 "Multiprotocol Extensions for BGP-4", RFC 2858, June 2000 425 [BGP-CAP] Chandra, R., Scudder, J., "Capabilities Advertisement with 426 BGP-4", RFC2842, May 2000 428 [BGP-COMMUNITIES] Chandra, R., Traina, P., and Li, T., "BGP 429 Communities Attribute", RFC1997, August 1996. 431 [BGP-EXT-COMMUNITIES] Ramachandra, S., Tappan, D., "BGP Extended 432 Communities Attribute", draft-ramachandra-bgp-ext-communities-02.txt 434 [BGP-RR] Chen, E., "Route Refresh Capability for BGP-4", RFC2918, 435 September 2000 436 12. Author Information 438 Enke Chen 439 Redback Networks, Inc. 440 350 Holger Way 441 San Jose, CA 95134 442 e-mail: enke@redback.com 444 Yakov Rekhter 445 Juniper Networks 446 e-mail: yakov@juniper.net