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'BGP-CAP') (Obsoleted by RFC 3392) == Outdated reference: A later version (-09) exists of draft-ramachandra-bgp-ext-communities-02 -- Possible downref: Normative reference to a draft: ref.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: 7 errors (**), 0 flaws (~~), 5 warnings (==), 3 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Network Working Group Enke Chen 2 Internet Draft Redback Networks, Inc. 3 Expiration Date: May 2001 Yakov Rekhter 4 Cisco Systems 6 Cooperative Route Filtering Capability for BGP-4 8 draft-ietf-idr-route-filter-02.txt 10 1. Status of this Memo 12 This document is an Internet-Draft and is in full conformance with 13 all provisions of Section 10 of RFC2026 except that the right to 14 produce derivative works is not granted. 16 Internet-Drafts are working documents of the Internet Engineering 17 Task Force (IETF), its areas, and its working groups. Note that 18 other groups may also distribute working documents as Internet- 19 Drafts. 21 Internet-Drafts are draft documents valid for a maximum of six months 22 and may be updated, replaced, or obsoleted by other documents at any 23 time. It is inappropriate to use Internet-Drafts as reference 24 material or to cite them other than as ``work in progress.'' 26 The list of current Internet-Drafts can be accessed at 27 http://www.ietf.org/ietf/1id-abstracts.txt 29 The list of Internet-Draft Shadow Directories can be accessed at 30 http://www.ietf.org/shadow.html. 32 2. Abstract 34 This document defines a BGP-based mechanism that allows a BGP speaker 35 to send to its BGP peer a set of route filters that the peer would 36 use to constrain/filter its outbound routing updates to the speaker. 38 3. Introduction 40 Currently it is not uncommon for a BGP speaker to receive, and then 41 filter out some unwanted routes from its peers based on its local 42 routing policy. Since the generation and transmission of routing 43 updates by the sender, as well as the processing of routing updates 44 by the receiver consume resources, it may be beneficial if the 45 generation of such unwanted routing updates can be avoided in the 46 first place. 48 This document defines a BGP-based mechanism that allows a BGP speaker 49 to send to its BGP peer a set of Outbound Route Filters (ORFs). The 50 peer would then apply these filters, in addition to its locally 51 configured outbound filters (if any), to constrain/filter its 52 outbound routing updates to the speaker. 54 4. Outbound Route Filter (ORF) 56 Conceptually an ORF entry is a tuple of the form ; an ORF consists of one or more ORF entries 58 that have a common AFI/SAFI and ORF-Type. An ORF is identified by 59 . 61 The "AFI/SAFI" component provides a coarse granularity control by 62 limiting the ORF to only the routes whose NLRI matches the "AFI/SAFI" 63 component of the ORF. 65 The "ORF-Type" component determines the content of the ORF-value. 67 The "Action" component controls handling of the ORF Request by the 68 remote peer. Action can be one of ADD, REMOVE, REMOVE-ALL. ADD adds 69 an ORF entry to the ORF on the remote peer; REMOVE deletes a 70 previously installed ORF entry on the remote peer; REMOVE-ALL deletes 71 the previously installed entries in the specified ORF on the remote 72 peer. 74 The "Match" component can be one of PERMIT or DENY. The semantics of 75 PERMIT is to ask the peer to pass updates for the set of routes that 76 match the ORF entry. The semantics of DENY is to ask the peer not to 77 pass updates for the set of routes that match the ORF entry. 79 4.1. Communities ORF-Type 81 The Community ORF-Type allows to express ORFs in terms of BGP 82 Communities [BGP-COMMUNITIES]. That is, the Communities ORF-Type 83 provides Communities-based route filtering. 85 Conceptually the ORF-value of the Communities ORF-Type consists of 86 . "Scope" indicates the set of routes that 87 must be considered by the remote peer for the given ORF request. 88 Scope can be one of the EXACT or NORMAL. EXACT scope indicates that 89 the remote peer should consider only those routes whose Communities 90 attribute is equal to the Communities list specified in the ORF. 91 NORMAL scope indicates that the remote peer should consider only 92 those routes whose Communities attribute has at least one Community 93 in common with the Communities list specified in the ORF. 95 The Communities list is a list of BGP Communities. 97 4.2. Extended Communities ORF-Type 99 The Extended Community ORF-Type allows to express ORFs in terms of 100 BGP Extended Communities [BGP-EXT-COMMUNITIES]. That is, the Extended 101 Communities ORF-Type provides Extended Communities-based route 102 filtering. 104 Conceptually the ORF-value of the Extended Communities ORF-Type 105 consists of . "Scope" indicates the 106 set of routes that must be considered by the remote peer for the 107 given ORF request. Scope can be one of the EXACT or NORMAL. EXACT 108 scope indicates that the remote peer should consider only those 109 routes whose Extended Communities attribute is equal to the Extended 110 Communities list specified in the ORF. NORMAL scope indicates that 111 the remote peer should consider only those routes whose Extended 112 Communities attribute has at least one Extended Community in common 113 with the Extended Communities list specified in the ORF. 115 The Extended Communities list is a list of BGP Extended Communities. 117 5. Carrying ORF entries in BGP 119 ORF entries are carried in the BGP ROUTE-REFRESH message [BGP-RR]. A 120 single ROUTE-REFRESH message could carry multiple ORF entries, as 121 long as all these entries share the same AFI/SAFI. 123 From the encoding point of view each ORF entry consists of a common 124 part and type-specific part. 126 The common part consists of , and 127 is encoded as follows: 129 The AFI/SAFI component of an ORF entry is encoded in the AFI/SAFI 130 field of the ROUTE-REFRESH message. 132 Following the AFI/SAFI component is the one-octet When-to-refresh 133 field. The value of this field can be one of IMMEDIATE (0x01) or 134 DEFER (0x02). The semantics of IMMEDIATE is to ask the peer to 135 refresh the routes for the AFI/SAFI carried in the message 136 immediately after processing the message. The semantics of DEFER 137 is to ask the peer to defer refreshing of all the routes, 138 including the newly arrived routes, until it receives a subsequent 139 ROUTE-REFRESH message for the same AFI/SAFI either without any ORF 140 entries, or with one or more ORF entries and When-to-refresh set 141 to IMMEDIATE. 143 Following the When-to-refresh field is a collection of one or more 144 ORFs, grouped by ORF-Type. 146 The ORF-Type component is encoded as a one-octet field. 148 The Length of ORFs component is a two-octets field that contains 149 the length (in octets) of the ORF entries that follows. 151 +--------------------------------------------------+ 152 | Address Family Identifier (2 octets) | 153 +--------------------------------------------------+ 154 | Reserved (1 octet) | 155 +--------------------------------------------------+ 156 | Subsequent Address Family Identifier (1 octet) | 157 +--------------------------------------------------+ 158 | When-to-refresh (1 octet) | 159 +--------------------------------------------------+ 160 | ORF Type (1 octet) | 161 +--------------------------------------------------+ 162 | Length of ORFs (2 octets) | 163 +--------------------------------------------------+ 164 | First ORF entry (variable) | 165 +--------------------------------------------------+ 166 | Second ORF entry (variable) | 167 +--------------------------------------------------+ 168 ......... 169 +--------------------------------------------------+ 170 | N-th ORF entry (variable) | 171 +--------------------------------------------------+ 172 | ORF Type (1 octet) | 173 +--------------------------------------------------+ 174 | Length of ORFs (2 octets) | 175 +--------------------------------------------------+ 176 | First ORF entry (variable) | 177 +--------------------------------------------------+ 178 | Second ORF entry (variable) | 179 +--------------------------------------------------+ 180 ......... 181 +--------------------------------------------------+ 182 | N-th ORF entry (variable) | 183 +--------------------------------------------------+ 184 ......... 186 Fig 1. Carrying ORF entries in the ROUTE-REFRESH message 188 The rest of the components in the common part are encoded in first 189 octet of each ORF-entry as follows (from the most significant to the 190 least significant bit): 192 Action is a two-bit field. The value of this field is 0 for ADD, 1 193 for REMOVE, and 2 for REMOVE-ALL. 195 Match is a one-bit field. The value of this field is 0 for PERMIT 196 and 1 for DENY. 198 Reserved is a 5-bit field. It is set to 0 on transmit and ignored 199 on receive. 201 +---------------------------------+ 202 | Action (2 bit) | 203 +---------------------------------+ 204 | Match (1 bit) | 205 +---------------------------------+ 206 | Reserved (5 bits) | 207 +---------------------------------+ 208 | Type specific part (variable) | 209 +---------------------------------+ 210 Fig 2. ORF entry encoding 212 When the Action component of an ORF entry specifies REMOVE-ALL, 213 the entry consists of only the common part. 215 5.1. Type specific encoding (Communities ORF-Type) 217 The value of the ORF-Type for the Communities ORF-Type is 2. 219 The type-specific part of Communities ORF-Type consists of , and is encoded as follows: 222 Scope is a one-octet field. The EXACT Scope has the value of 1. 223 The NORMAL Scope has the value of 2. 225 Communities are encoded as a one octet Number of Communities 226 field, followed by one or more Communities, where each Community 227 is encoded as a four-octets field. 229 5.2. Type specific encoding (Extended Communities ORF-Type) 231 The value of the ORF-Type for the Extended Communities ORF-Type is 3. 233 The type-specific part of Extended Communities ORF-Type consists of 234 , and is encoded as follows: 236 Scope is a one-octet field. The EXACT Scope has the value of 1. 237 The NORMAL Scope has the value of 2. 239 Extended Communities are encoded as a one octet Number of Extended 240 Communities field, followed by one or more Extended Communities, 241 where each Extended Community is encoded as a eight-octets field. 243 6. Cooperative Route Filtering Capability 245 A BGP speaker that is willing to receive ORF entries from its peer, 246 or a BGP speaker that would like to send ORF entries to its peer 247 advertises this to the peer by using the Cooperative Route Filtering 248 Capability, as described below. 250 The Cooperative Route Filtering Capability is a new BGP capability 251 [BGP-CAP] defined as follows: 253 Capability code: 3 255 Capability length: variable 257 Capability value: one or more of the following entries: 259 +--------------------------------------------------+ 260 | Address Family Identifier (2 octets) | 261 +--------------------------------------------------+ 262 | Reserved (1 octet) | 263 +--------------------------------------------------+ 264 | Subsequent Address Family Identifier (1 octet) | 265 +--------------------------------------------------+ 266 | Number of ORFs (1 octet) | 267 +--------------------------------------------------+ 268 | ORF Type (1 octet) | 269 +--------------------------------------------------+ 270 | Send/Receive (1 octet) | 271 +--------------------------------------------------+ 272 | ... | 273 +--------------------------------------------------+ 274 | ORF Type (1 octet) | 275 +--------------------------------------------------+ 276 | Send/Receive (1 octet) | 277 +--------------------------------------------------+ 279 Fig 4. Capability encoding 281 The use and meaning of these fields are as follows: 283 Address Family Identifier (AFI): 285 This field carries the identity of the Network Layer protocol 286 associated with the Network Address that follows. Presently 287 defined values for this field are specified in RFC1700 (see the 288 Address Family Numbers section). 290 Subsequent Address Family Identifier (SAFI): 292 This field provides additional information about the type of 293 the Network Layer Reachability Information carried in the 294 attribute. 296 Number of ORF Types: 298 This field contains the number of Filter Types to be listed in 299 the following fields. 301 ORF Type: 303 This field contains the value of an ORF Type. 305 Send/Receive: 307 This field indicates whether the sender is (a) willing to 308 receive ORF entries from its peer (value 1), (b) would like to 309 send ORF entries to its peer (value 2), or (c) both (value 3) 310 for the ORF Type that follows. 312 7. Operation 314 A BGP speaker that is willing to receive ORF entries from its peer, 315 or would like to send ORF entries to its peer should advertise the 316 Cooperative Route Filtering Capability to the peer using BGP 317 Capabilities advertisement [BGP-CAP]. 319 A BGP speaker that implements the Cooperative Route Filtering 320 Capability must support BGP ROUTE-REFRESH message, as defined in 321 [BGP-RR]. A BGP speaker that advertises the Cooperative Route 322 Filtering Capability to a peer using BGP Capabilities advertisement 323 [BGP-CAP] doesn't have to advertise the BGP Route Refresh capability 324 to that peer. 326 Consider a BGP speaker that advertises the Cooperative Route 327 Filtering Capability indicating its willingness to receive a 328 particular set of from its peer, and that 329 receives the Cooperative Route Filtering Capability indicating the 330 desire of the peer to send a particular set to 331 the speaker. If for a given the intersection between 332 these two sets are not-empty, the speaker should not advertise to the 333 peer any routes with that prior to receiving from the 334 peer any ROUTE-REFRESH message carrying that , where the 335 message could be either without any ORF entries, or with one or more 336 ORF entry and When-to-refresh field set to IMMEDIATE. If, on the 337 other hand, for a given the intersection between these 338 two sets is empty, the speaker should follow normal BGP procedures. 340 A BGP speaker may send a ROUTE-REFRESH message with one or more ORF 341 entries to its peer only if the peer advertises to the speaker the 342 Cooperative Route Filtering Capability indicating its willingness to 343 receive ORF entries from the speaker, and the speaker advertises to 344 the peer the Cooperative Route Filtering Capability indicating its 345 desire to send ORF entries to the peer. The message may contain only 346 ORF entries of that the peer is willing to 347 receive, as advertised to the speaker in the Cooperative Route 348 Filtering Capability. 350 When a BGP speaker receives a ROUTE-REFRESH message with one or more 351 ORF entries from its peer, then the speaker performs the following 352 actions. If the carried by the message doesn't 353 match that the speaker is willing to receive 354 from the peer (as advertised to the peer in the Cooperative Route 355 Filtering Capability), the specified ORF is ignored. Otherwise, the 356 speaker modifies the specified ORF, as specified in the ORF entries 357 carried by the message. If any of the fields within an ORF entry 358 contain an unrecognized value, the whole specified ORF is removed. 360 If the Action component of an ORF entry is REMOVE, but the ORF 361 doesn't contain the specified entry, the entry is ignored. 363 ORF entries with either REMOVE or REMOVE-ALL can not remove locally 364 configured outbound route filters. 366 If the When-to-Refresh indicates IMMEDIATE, then after processing all 367 the ORF entries carried in the message the speaker should re- 368 advertise to the peer routes from the Adj-RIB-Out that have the same 369 AFI/SAFI as what is carried in the message, and taking into account 370 all the ORF entries received from the peer. 372 The set of ORF entries that the speaker sends to the peer expresses 373 the speaker's local preference, that the peer may or may not decide 374 to honor. 376 During a single BGP session the speaker may pass multiple ORF entries 377 to the peer. 379 The lifetime of an ORF is the duration of the BGP session during 380 which the ORF is exchanged. 382 An ORF is removed when the last ORF entry is remove (either via 383 REMOVE-ALL, or via a sequence of REMOVE). 385 If a particular route maintained by a BGP speaker doesn't match any 386 of the ORF entries of any of the (non-empty) ORFs associated with a 387 particular peer, then this route should not be advertised to the 388 peer. 390 If a BGP speaker maintains multiple ORFs of different ORF-Types for a 391 particular peer, then the decision by the speaker to advertise a 392 route to the peer is determined by passing the route through each 393 such ORF, and and-ing the results (and-ing of PERMIT and DENY results 394 in DENY). 396 8. IANA Considerations 398 As specified in this document, an ORF enty contains the ORF-Type 399 field. ORF-Type value 0 is reserved. ORF-Type values 1 through 63 400 are to be assigned by IANA using the "IETF Consensus" policy defined 401 in RFC2434. ORF-Type values 64 through 127 are to be assigned by 402 IANA, using the "First Come First Served" policy defined in RFC2434. 403 ORF-Type values 128 through 255 are vendor-specific, and values in 404 this range are not to be assigned by IANA. 406 9. Security Considerations 408 This extension to BGP does not change the underlying security issues. 410 10. Acknowledgements 412 Some of the material in the document is "borrowed" from a proposal 413 for selective updates by Yakov Rekhter, Kannan Varadhan, and Curtis 414 Villamizar. 416 We express our thanks to John Scudder for his comments. 418 11. References 420 [BGP-4] Rekhter, Y., and T. Li, "A Border Gateway Protocol 4 (BGP- 421 4)", RFC 1771, March 1995. 423 [BGP-MP] Bates, T., Chandra, R., Katz, D., and Rekhter, Y., 424 "Multiprotocol Extensions for BGP-4", RFC 2858, June 2000 426 [BGP-CAP] Chandra, R., Scudder, J., "Capabilities Advertisement with 427 BGP-4", RFC2842, May 2000 429 [BGP-COMMUNITIES] Chandra, R., Traina, P., and Li, T., "BGP 430 Communities Attribute", RFC1997, August 1996. 432 [BGP-EXT-COMMUNITIES] Ramachandra, S., Tappan, D., "BGP Extended 433 Communities Attribute", draft-ramachandra-bgp-ext-communities-02.txt 435 [BGP-RR] Chen, E., "Route Refresh Capability for BGP-4", RFC2918, 436 September 2000 438 12. Author Information 440 Enke Chen 441 Redback Networks, Inc. 442 350 Holger Way 443 San Jose, CA 95134 444 e-mail: enke@redback.com 446 Yakov Rekhter 447 Cisco Systems, Inc. 448 170 West Tasman Drive 449 San Jose, CA 95134 450 e-mail: yakov@cisco.com