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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 'BGP-CAP') (Obsoleted by RFC 3392) == Outdated reference: A later version (-09) exists of draft-ramachandra-bgp-ext-communities-02 -- Possible downref: Normative reference to a draft: ref.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. -------------------------------------------------------------------------------- 1 Network Working Group Enke Chen 2 Internet Draft Redback Networks, Inc. 3 Expiration Date: October 2001 Yakov Rekhter 4 Juniper Networks 6 Cooperative Route Filtering Capability for BGP-4 8 draft-ietf-idr-route-filter-03.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 must 87 be considered by the remote peer for the given ORF request. Scope can 88 be one of the EXACT or NORMAL. EXACT scope indicates that the remote 89 peer should consider only those routes whose Communities attribute is 90 equal to the Communities list specified in the ORF. NORMAL scope 91 indicates that the remote peer should consider only those routes 92 whose Communities attribute either is equal to the Communities list 93 specified in the ORF, or exhibit a subset relation with the 94 Communities list specified in the ORF. 96 The Communities list is a list of BGP Communities. 98 4.2. Extended Communities ORF-Type 100 The Extended Community ORF-Type allows to express ORFs in terms of 101 BGP Extended Communities [BGP-EXT-COMMUNITIES]. That is, the Extended 102 Communities ORF-Type provides Extended Communities-based route 103 filtering. 105 Conceptually the ORF-value of the Extended Communities ORF-Type 106 consists of . "Scope" indicates the set 107 of routes that must be considered by the remote peer for the given 108 ORF request. Scope can be one of the EXACT or NORMAL. EXACT scope 109 indicates that the remote peer should consider only those routes 110 whose Extended Communities attribute is equal to the Extended 111 Communities list specified in the ORF. NORMAL scope indicates that 112 the remote peer should consider only those routes whose Extended 113 Communities attribute either is equal to the Extended Communities 114 list specified in the ORF, or exhibit a subset relation with the 115 Extended Communities list specified in the ORF. 117 The Extended Communities list is a list of BGP Extended Communities. 119 5. Carrying ORF entries in BGP 121 ORF entries are carried in the BGP ROUTE-REFRESH message [BGP-RR]. A 122 single ROUTE-REFRESH message could carry multiple ORF entries, as 123 long as all these entries share the same AFI/SAFI. 125 From the encoding point of view each ORF entry consists of a common 126 part and type-specific part. 128 The common part consists of , and 129 is encoded as follows: 131 The AFI/SAFI component of an ORF entry is encoded in the AFI/SAFI 132 field of the ROUTE-REFRESH message. 134 Following the AFI/SAFI component is the one-octet When-to-refresh 135 field. The value of this field can be one of IMMEDIATE (0x01) or 136 DEFER (0x02). The semantics of IMMEDIATE is to ask the peer to 137 refresh the routes for the AFI/SAFI carried in the message 138 immediately after processing the message. The semantics of DEFER 139 is to ask the peer to defer refreshing of all the routes until it 140 receives a subsequent ROUTE-REFRESH message for the same AFI/SAFI 141 either without any ORF entries, or with one or more ORF entries 142 and When-to-refresh set to IMMEDIATE. 144 Following the When-to-refresh field is a collection of one or more 145 ORFs, grouped by ORF-Type. 147 The ORF-Type component is encoded as a one-octet field. 149 The Length of ORFs component is a two-octets field that contains 150 the length (in octets) of the ORF entries that follows. 152 +--------------------------------------------------+ 153 | Address Family Identifier (2 octets) | 154 +--------------------------------------------------+ 155 | Reserved (1 octet) | 156 +--------------------------------------------------+ 157 | Subsequent Address Family Identifier (1 octet) | 158 +--------------------------------------------------+ 159 | When-to-refresh (1 octet) | 160 +--------------------------------------------------+ 161 | ORF Type (1 octet) | 162 +--------------------------------------------------+ 163 | Length of ORFs (2 octets) | 164 +--------------------------------------------------+ 165 | First ORF entry (variable) | 166 +--------------------------------------------------+ 167 | Second ORF entry (variable) | 168 +--------------------------------------------------+ 169 ......... 170 +--------------------------------------------------+ 171 | N-th ORF entry (variable) | 172 +--------------------------------------------------+ 173 | ORF Type (1 octet) | 174 +--------------------------------------------------+ 175 | Length of ORFs (2 octets) | 176 +--------------------------------------------------+ 177 | First ORF entry (variable) | 178 +--------------------------------------------------+ 179 | Second ORF entry (variable) | 180 +--------------------------------------------------+ 181 ......... 182 +--------------------------------------------------+ 183 | N-th ORF entry (variable) | 184 +--------------------------------------------------+ 185 ......... 187 Fig 1. Carrying ORF entries in the ROUTE-REFRESH message 189 The rest of the components in the common part are encoded in first 190 octet of each ORF-entry as follows (from the most significant to the 191 least significant bit): 193 Action is a two-bit field. The value of this field is 0 for ADD, 1 194 for REMOVE, and 2 for REMOVE-ALL. 196 Match is a one-bit field. The value of this field is 0 for PERMIT 197 and 1 for DENY. 199 Reserved is a 5-bit field. It is set to 0 on transmit and ignored 200 on receive. 202 +---------------------------------+ 203 | Action (2 bit) | 204 +---------------------------------+ 205 | Match (1 bit) | 206 +---------------------------------+ 207 | Reserved (5 bits) | 208 +---------------------------------+ 209 | Type specific part (variable) | 210 +---------------------------------+ 212 Fig 2. ORF entry encoding 213 When the Action component of an ORF entry specifies REMOVE-ALL, 214 the entry consists of only the common part. 216 5.1. Type specific encoding (Communities ORF-Type) 218 The value of the ORF-Type for the Communities ORF-Type is 2. 220 The type-specific part of Communities ORF-Type consists of , and is encoded as follows: 223 Scope is a one-octet field. The EXACT Scope has the value of 1. 224 The NORMAL Scope has the value of 2. 226 Communities are encoded as a one octet Number of Communities 227 field, followed by one or more Communities, where each Community 228 is encoded as a four-octets field. 230 5.2. Type specific encoding (Extended Communities ORF-Type) 232 The value of the ORF-Type for the Extended Communities ORF-Type is 3. 234 The type-specific part of Extended Communities ORF-Type consists of 235 , and is encoded as follows: 237 Scope is a one-octet field. The EXACT Scope has the value of 1. 238 The NORMAL Scope has the value of 2. 240 Extended Communities are encoded as a one octet Number of Extended 241 Communities field, followed by one or more Extended Communities, 242 where each Extended Community is encoded as a eight-octets field. 244 6. Cooperative Route Filtering Capability 246 A BGP speaker that is willing to receive ORF entries from its peer, 247 or a BGP speaker that would like to send ORF entries to its peer 248 advertises this to the peer by using the Cooperative Route Filtering 249 Capability, as described below. 251 The Cooperative Route Filtering Capability is a new BGP capability 252 [BGP-CAP] defined as follows: 254 Capability code: 3 256 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 11. References 418 [BGP-4] Rekhter, Y., and T. Li, "A Border Gateway Protocol 4 419 (BGP-4)", RFC 1771, March 1995. 421 [BGP-MP] Bates, T., Chandra, R., Katz, D., and Rekhter, Y., 422 "Multiprotocol Extensions for BGP-4", RFC 2858, June 2000 424 [BGP-CAP] Chandra, R., Scudder, J., "Capabilities Advertisement with 425 BGP-4", RFC2842, May 2000 427 [BGP-COMMUNITIES] Chandra, R., Traina, P., and Li, T., "BGP 428 Communities Attribute", RFC1997, August 1996. 430 [BGP-EXT-COMMUNITIES] Ramachandra, S., Tappan, D., "BGP Extended 431 Communities Attribute", draft-ramachandra-bgp-ext-communities-02.txt 433 [BGP-RR] Chen, E., "Route Refresh Capability for BGP-4", RFC2918, 434 September 2000 435 12. Author Information 437 Enke Chen 438 Redback Networks, Inc. 439 350 Holger Way 440 San Jose, CA 95134 441 e-mail: enke@redback.com 443 Yakov Rekhter 444 Juniper Networks 445 e-mail: yakov@juniper.net