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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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: draft-ietf-spring-segment-routing has been published as RFC 8402 == Outdated reference: draft-ietf-spring-segment-routing-mpls has been published as RFC 8660 == Outdated reference: draft-ietf-idr-bgp-ls-segment-routing-ext has been published as RFC 9085 == Outdated reference: draft-ietf-idr-bgpls-segment-routing-epe has been published as RFC 9086 == Outdated reference: draft-ietf-spring-segment-routing-msdc has been published as RFC 8670 Summary: 0 errors (**), 0 flaws (~~), 6 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 IDR S. Previdi, Ed. 3 Internet-Draft C. Filsfils 4 Intended status: Standards Track A. Lindem 5 Expires: July 6, 2018 Cisco Systems 6 A. Sreekantiah 8 H. Gredler 9 RtBrick Inc. 10 January 2, 2018 12 Segment Routing Prefix SID extensions for BGP 13 draft-ietf-idr-bgp-prefix-sid-08 15 Abstract 17 Segment Routing (SR) architecture allows a node to steer a packet 18 flow through any topological path and service chain by leveraging 19 source routing. The ingress node prepends a SR header to a packet 20 containing a set of segment identifiers (SID). Each SID represents a 21 topological or a service-based instruction. Per-flow state is 22 maintained only on the ingress node of the SR domain. 24 This document defines an optional, transitive BGP attribute for 25 announcing BGP Prefix Segment Identifiers (BGP Prefix-SID) 26 information. 28 Requirements Language 30 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 31 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 32 document are to be interpreted as described in RFC 2119 [RFC2119] 33 only when they appear in all upper case. They may also appear in 34 lower or mixed case as English words, without any normative meaning. 36 Status of This Memo 38 This Internet-Draft is submitted in full conformance with the 39 provisions of BCP 78 and BCP 79. 41 Internet-Drafts are working documents of the Internet Engineering 42 Task Force (IETF). Note that other groups may also distribute 43 working documents as Internet-Drafts. The list of current Internet- 44 Drafts is at http://datatracker.ietf.org/drafts/current/. 46 Internet-Drafts are draft documents valid for a maximum of six months 47 and may be updated, replaced, or obsoleted by other documents at any 48 time. It is inappropriate to use Internet-Drafts as reference 49 material or to cite them other than as "work in progress." 51 This Internet-Draft will expire on July 6, 2018. 53 Copyright Notice 55 Copyright (c) 2018 IETF Trust and the persons identified as the 56 document authors. All rights reserved. 58 This document is subject to BCP 78 and the IETF Trust's Legal 59 Provisions Relating to IETF Documents 60 (http://trustee.ietf.org/license-info) in effect on the date of 61 publication of this document. Please review these documents 62 carefully, as they describe your rights and restrictions with respect 63 to this document. Code Components extracted from this document must 64 include Simplified BSD License text as described in Section 4.e of 65 the Trust Legal Provisions and are provided without warranty as 66 described in the Simplified BSD License. 68 Table of Contents 70 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 71 2. BGP-Prefix-SID . . . . . . . . . . . . . . . . . . . . . . . 4 72 2.1. MPLS BGP Prefix SID . . . . . . . . . . . . . . . . . . . 4 73 2.2. IPv6 Prefix Segment . . . . . . . . . . . . . . . . . . . 5 74 3. BGP-Prefix-SID Attribute . . . . . . . . . . . . . . . . . . 5 75 3.1. Label-Index TLV . . . . . . . . . . . . . . . . . . . . . 6 76 3.2. IPv6 SID . . . . . . . . . . . . . . . . . . . . . . . . 6 77 3.3. Originator SRGB TLV . . . . . . . . . . . . . . . . . . . 7 78 4. Receiving BGP-Prefix-SID Attribute . . . . . . . . . . . . . 9 79 4.1. MPLS Dataplane: Labeled Unicast . . . . . . . . . . . . . 9 80 4.2. IPv6 Dataplane . . . . . . . . . . . . . . . . . . . . . 10 81 5. Announcing BGP-Prefix-SID Attribute . . . . . . . . . . . . . 10 82 5.1. MPLS Dataplane: Labeled Unicast . . . . . . . . . . . . . 10 83 5.2. IPv6 Dataplane . . . . . . . . . . . . . . . . . . . . . 11 84 6. Error Handling of BGP-Prefix-SID Attribute . . . . . . . . . 11 85 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 86 8. Manageability Considerations . . . . . . . . . . . . . . . . 12 87 9. Security Considerations . . . . . . . . . . . . . . . . . . . 13 88 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 13 89 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13 90 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 91 12.1. Normative References . . . . . . . . . . . . . . . . . . 14 92 12.2. Informative References . . . . . . . . . . . . . . . . . 14 93 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 95 1. Introduction 97 Segment Routing (SR) architecture leverages the source routing 98 paradigm. A group of inter-connected nodes that use SR forms a SR 99 domain. A segment represents either a topological instruction such 100 as "go to prefix P following shortest path" or a service instruction 101 (e.g.: "pass through deep packet inspection"). Other types of 102 segments may be defined in the future. 104 A segment is identified through a Segment Identifier (SID). 105 Typically, the ingress node of the SR domain prepends a SR header 106 containing segments identifiers (SIDs) to an incoming packet. 108 As described in [I-D.ietf-spring-segment-routing], when SR is applied 109 to the MPLS dataplane ([I-D.ietf-spring-segment-routing-mpls]) the 110 SID consists of a label while when SR is applied to the IPv6 111 dataplane the SID consists of an IPv6 address. 113 A BGP-Prefix Segment (and its BGP Prefix-SID), is a BGP segment 114 attached to a BGP prefix. A BGP Prefix-SID is always a global SID 115 ([I-D.ietf-spring-segment-routing]) within the SR/BGP domain (i.e., 116 the set of Autonomous Systems under a common administration and 117 control and where SR is used) and identifies an instruction to 118 forward the packet over the ECMP-aware best-path computed by BGP to 119 the related prefix. The BGP Prefix-SID is the identifier of the BGP 120 prefix segment. In this document, we always refer to the BGP Segment 121 by the BGP Prefix-SID. 123 This document describes the BGP extension to signal the BGP Prefix- 124 SID. Specifically, this document defines a BGP attribute known as 125 the BGP Prefix-SID attribute and specifies the rules to originate, 126 receive, and handle error conditions for the attribute. 128 The BGP Prefix-SID attribute defined in this document can be attached 129 to prefixes from AFI/SAFI: 131 Multiprotocol BGP labeled IPv4/IPv6 Unicast ([RFC8277]). 133 Multiprotocol BGP ([RFC4760]) unlabeled IPv6 Unicast. 135 [I-D.ietf-spring-segment-routing-msdc] describes example use cases 136 where the Prefix-SID is used for the above AFI/SAFI. 138 It should be noted that: 140 o A BGP Prefix-SID MAY be global between domains when the 141 interconnected domains agree on the SID allocation scheme. 142 Alternatively, when interconnecting domains, the ASBRs of each 143 domain will have to handle the advertisement of unique SIDs. The 144 mechanisms for such interconnection are outside the scope of the 145 protocol extensions defined in this document. 147 o A BGP Prefix-SID MAY be attached to a prefix. In addition, each 148 prefix will likely have a different AS_PATH attribute. This 149 implies that each prefix is advertised individually, reducing the 150 ability to pack BGP advertisements (when sharing common 151 attributes). 153 2. BGP-Prefix-SID 155 The BGP Prefix-SID attached to a BGP prefix P represents the 156 instruction "go to Prefix P" along its BGP best path (potentially 157 ECMP-enabled). 159 2.1. MPLS BGP Prefix SID 161 The BGP Prefix-SID is realized on the MPLS dataplane 162 ([I-D.ietf-spring-segment-routing-mpls]) in the following way: 164 The operator assigns a globally unique "index", L_I, to a locally 165 sourced prefix of a BGP speaker N which is advertised to all other 166 BGP speakers in the SR domain. 168 According to [I-D.ietf-spring-segment-routing], each BGP speaker 169 is configured with a label block called the Segment Routing Global 170 Block (SRGB). While [I-D.ietf-spring-segment-routing] recommends 171 to use the same SRGB across all the nodes within the SR domain, 172 the SRGB of a node is a local property and could be different on 173 different speakers. The drawbacks of the use case where BGP 174 speakers have different SRGBs are documented in 175 [I-D.ietf-spring-segment-routing] and 176 [I-D.ietf-spring-segment-routing-msdc]. 178 If traffic-engineering within the SR domain is required, each node 179 may also be required to advertise topological information and 180 Peering SID's for each of its links and peers. This information 181 is required to perform the explicit path computation and to 182 express any explicit path into a list of SIDs. The advertisement 183 of topological information and Peer segments (Peer SIDs) is 184 assumed to be done through 185 [I-D.ietf-idr-bgpls-segment-routing-epe]. 187 If the BGP speakers are not all configured with the same SRGB, and 188 if traffic-engineering within the SR domain is required, each node 189 may be required to advertise its local SRGB in addition to the 190 topological information. 192 This documents assumes that BGP-LS is the preferred method for 193 collecting both topological, peer segments (Peer SIDs) and SRGB 194 information through [RFC7752], 195 [I-D.ietf-idr-bgpls-segment-routing-epe] and 196 [I-D.ietf-idr-bgp-ls-segment-routing-ext]. However, as an 197 optional alternative for the advertisement of the local SRGB 198 without the topology nor the peer SID's, hence without 199 applicability for TE, the Originator SRGB TLV of the prefix-SID 200 attribute, is specified in Section 3.3 of this document. 202 As defined in [I-D.ietf-spring-segment-routing-mpls], the index 203 L_I is an offset in the SRGB. Each BGP speaker derives its local 204 MPLS label, L, by adding L_I to the start value of its own SRGB, 205 and programs L in its MPLS dataplane as its incoming/local label 206 for the prefix. It should be noted that while SRGBs and SIDs are 207 advertised using 32-bit values, the derived label is to be 208 considered as the 20 right-most bits. See Section 4.1 for more 209 details. 211 The outgoing label for the prefix is found in the NLRI of the 212 Multiprotocol BGP labeled IPv4/IPv6 Unicast prefix advertisement. 213 The index L_I is only used as a hint to derive the local/incoming 214 label. 216 Section 3.1 of this document specifies the Label-Index TLV of the 217 BGP Prefix-SID attribute; this TLV can be used to advertise the 218 label index of a given prefix. 220 In order to advertise the label index of a given prefix P and, 221 optionally, the SRGB, an extension to BGP is needed: the BGP Prefix- 222 SID attribute. This extension is described in subsequent sections. 224 2.2. IPv6 Prefix Segment 226 When SR is used over an IPv6 dataplane, the BGP Prefix-SID consists 227 of an IPv6 address assigned to the BGP speaker. 229 3. BGP-Prefix-SID Attribute 231 The BGP Prefix-SID attribute is an optional, transitive BGP path 232 attribute. The attribute type code 40 has been assigned by IANA (see 233 Section 7). 235 The BGP Prefix-SID attribute is defined here to be a set of elements 236 encoded as "Type/Length/Value" (i.e., a set of TLVs). The following 237 TLVs are defined: 239 o Label-Index TLV 240 o IPv6 SID TLV 242 o Originator SRGB TLV 244 Label-Index and Originator SRGB TLVs are used only when SR is applied 245 to the MPLS dataplane. 247 IPv6 SID TLV is used only when SR is applied to the IPv6 dataplane. 249 3.1. Label-Index TLV 251 The Label-Index TLV MUST be present in the Prefix-SID attribute 252 attached to Labeled IPv4/IPv6 unicast prefixes ([RFC8277]) and has 253 the following format: 255 0 1 2 3 256 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 1 257 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 258 | Type | Length | RESERVED | 259 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 260 | Flags | Label Index | 261 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 262 | Label Index | 263 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 265 where: 267 o Type is 1. 269 o Length: is 7, the total length of the value portion of the TLV. 271 o RESERVED: 8-bit field. MUST be clear on transmission and MUST be 272 ignored on reception. 274 o Flags: 16 bits of flags. None are defined by this document. The 275 flag field MUST be clear on transmission and MUST be ignored on 276 reception. 278 o Label Index: 32-bit value representing the index value in the SRGB 279 space. 281 3.2. IPv6 SID 283 The IPv6-SID TLV MAY be present in the Prefix-SID attribute attached 284 to MP-BGP unlabeled IPv6 unicast prefixes ([RFC4760]) and has the 285 following format: 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 | Type | Length | RESERVED | 291 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 292 | RESERVED | | 293 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 294 | | 295 | IPv6 SID (16 octets) | 296 | | 297 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 298 | | 299 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 301 where: 303 o Type is 2. 305 o Length: is 19, the total length of the value portion of the TLV. 307 o RESERVED: 24-bit field for future use. MUST be clear on 308 transmission and MUST be ignored on reception. 310 o IPv6 SID: 16 octets. 312 3.3. Originator SRGB TLV 314 The Originator SRGB TLV is an optional TLV and has the following 315 format: 317 0 1 2 3 318 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 1 319 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 320 | Type | Length | Flags | 321 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 322 | Flags | 323 +-+-+-+-+-+-+-+-+ 325 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 326 | SRGB 1 (6 octets) | 327 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 328 | | 329 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 331 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 332 | SRGB n (6 octets) | 333 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 334 | | 335 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 337 where: 339 o Type is 3. 341 o Length is the total length of the value portion of the TLV: 2 + 342 multiple of 6. 344 o Flags: 16 bits of flags. None are defined in this document. 345 Flags MUST be clear on transmission and MUST be ignored on 346 reception. 348 o SRGB: 3 octets of base followed by 3 octets of range. Note that 349 the SRGB field MAY appear multiple times. If the SRGB field 350 appears multiple times, the SRGB consists of multiple ranges. 352 The Originator SRGB TLV contains the SRGB of the node originating the 353 prefix to which the BGP Prefix-SID is attached. The Originator SRGB 354 TLV MUST NOT be changed during the propagation of the BGP update. 356 The originator SRGB describes the SRGB of the node where the BGP 357 Prefix SID is attached. It is used to build segment routing policies 358 when different SRGBs are used in the fabric, for example 359 ([I-D.ietf-spring-segment-routing-msdc]). 361 The originator SRGB may only appear on Prefix-SID attribute attached 362 to prefixes of SAFI 4 (labeled unicast, [RFC8277]). 364 4. Receiving BGP-Prefix-SID Attribute 366 A BGP speaker receiving a BGP Prefix-SID attribute from an EBGP 367 neighbor residing outside the boundaries of the SR domain, SHOULD 368 discard the attribute unless it is configured to accept the attribute 369 from the EBGP neighbor. A BGP speaker MAY log an error for further 370 analysis when discarding an attribute. 372 4.1. MPLS Dataplane: Labeled Unicast 374 A Multiprotocol BGP labeled IPv4/IPv6 Unicast ([RFC8277]) session 375 type is required. 377 A BGP speaker MAY be locally configured with an SRGB=[SRGB_Start, 378 SRGB_End]. The preferred method for deriving the SRGB is a matter of 379 local node configuration. 381 Given a label_index L_I, we call L = L_I + SRGB_Start as the derived 382 label. A BGP Prefix-SID attribute is designated "unacceptable" for a 383 speaker M if the derived label value L lies outside the SRGB 384 configured on M. Otherwise the Label Index attribute is designated 385 "acceptable" to speaker M. 387 The mechanisms through which a given label_index value is assigned to 388 a given prefix are outside the scope of this document. The label- 389 index value associated with a prefix is locally configured at the BGP 390 node originating the prefix. 392 The Prefix-SID attribute MUST contain the Label-Index TLV and MAY 393 contain the Originator SRGB TLV. A BGP Prefix-SID attribute received 394 without a Label-Index TLV MUST be considered as "unacceptable" by the 395 receiving speaker. 397 If multiple prefixes are received with the same label_index value, 398 all these prefixes MUST have their BGP Prefix-SID attribute 399 considered as "unacceptable" by the receiving speaker. 401 When a BGP speaker receives a path from a neighbor with an acceptable 402 BGP Prefix-SID attribute, it MUST program the derived label as the 403 local label for the prefix in its MPLS dataplane. In case of any 404 error, a BGP speaker MUST follow to the error handling rules 405 specified in Section 6. A BGP speaker MAY log an error for further 406 analysis. 408 When a BGP speaker receives a path from a neighbor with an 409 unacceptable BGP Prefix-SID attribute or when a BGP speaker receives 410 a path from a neighbor with a BGP Prefix-SID attribute but is unable 411 to process it (it does not have the capability or local policy 412 disables the capability), it MUST treat the path as if it came 413 without a Prefix-SID attribute. For the purposes of local label 414 allocation, a BGP speaker MUST assign a local (also called dynamic) 415 label (non-SRGB) for such a prefix as per classic Multiprotocol BGP 416 labeled IPv4/IPv6 Unicast ([RFC8277]) operation. A BGP speaker MAY 417 log an error for further analysis. 419 The outgoing label is always programmed as per classic Multiprotocol 420 BGP labeled IPv4/IPv6 Unicast (RFC8277 [RFC8277]) operation. 422 Specifically, a BGP speaker receiving a prefix with a Prefix-SID 423 attribute and a label NLRI field of implicit-null from a neighbor 424 MUST adhere to standard behavior and program its MPLS dataplane to 425 pop the top label when forwarding traffic to the prefix. The label 426 NLRI defines the outbound label that MUST be used by the receiving 427 node. The Label Index gives the information to the receiving node on 428 which local/incoming label the BGP speaker SHOULD use. 430 4.2. IPv6 Dataplane 432 When an SR IPv6 BGP speaker receives a IPv6 Unicast BGP Update with a 433 prefix having the BGP Prefix-SID attribute attached, it checks 434 whether the IPv6 SID TLV is present. If present, then the receiver 435 assumes that the originator supports SR on the IPv6 dataplane. 437 The Originator SRGB MUST be ignored on reception. 439 A BGP speaker receiving a BGP Prefix-SID attribute from an EBGP 440 neighbor residing outside the boundaries of the SR domain, SHOULD 441 discard the attribute unless it is configured to accept the attribute 442 from the EBGP neighbor. A BGP speaker MAY log an error for further 443 analysis when discarding an attribute. 445 5. Announcing BGP-Prefix-SID Attribute 447 The BGP Prefix-SID attribute MAY be attached to labeled BGP prefixes 448 (IPv4/IPv6) [RFC8277] or to IPv6 prefixes [RFC4760]. In order to 449 prevent distribution of the BGP Prefix-SID attribute beyond its 450 intended scope of applicability, attribute filtering SHOULD be 451 deployed. 453 5.1. MPLS Dataplane: Labeled Unicast 455 A BGP speaker that originates a prefix attaches the Prefix-SID 456 attribute when it advertises the prefix to its neighbors via 457 Multiprotocol BGP labeled IPv4/IPv6 Unicast ([RFC8277]). The value 458 of the Label-Index in the Label-Index TLV is determined by 459 configuration. 461 A BGP speaker that originates a Prefix-SID attribute MAY optionally 462 announce Originator SRGB TLV along with the mandatory Label-Index 463 TLV. The content of the Originator SRGB TLV is determined by the 464 configuration. 466 Since the Label-index value must be unique within an SR domain, by 467 default an implementation SHOULD NOT advertise the BGP Prefix-SID 468 attribute outside an Autonomous System unless it is explicitly 469 configured to do so. 471 A BGP speaker that advertises a path received from one of its 472 neighbors SHOULD advertise the Prefix-SID received with the path 473 without modification, regardless of whether the Prefix-SID was 474 acceptable. If the path did not come with a Prefix-SID attribute, 475 the speaker MAY attach a Prefix-SID to the path if configured to do 476 so. The content of the TLVs present in the Prefix-SID is determined 477 by the configuration. 479 In all cases, the label field of the advertised NLRI ([RFC8277], 480 [RFC4364]) MUST be set to the local/incoming label programmed in the 481 MPLS dataplane for the given advertised prefix. If the prefix is 482 associated with one of the BGP speaker's interfaces, this label is 483 the usual MPLS label (such as the implicit or explicit NULL label). 485 5.2. IPv6 Dataplane 487 A BGP speaker that originates an IPv6 prefix with the Prefix-SID 488 attribute, MAY include the IPv6 SID TLV. 490 A BGP speaker that advertises a path received from one of its 491 neighbors SHOULD advertise the Prefix-SID received with the path 492 without modification, regardless of whether the Prefix-SID was 493 acceptable. If the path did not come with a Prefix-SID attribute, 494 the speaker MAY attach a Prefix-SID to the path if configured to do 495 so. 497 6. Error Handling of BGP-Prefix-SID Attribute 499 When a BGP Speaker receives a BGP Update message containing a 500 malformed BGP Prefix-SID attribute, it MUST ignore the received BGP 501 Prefix-SID attributes and not pass it to other BGP peers. This is 502 equivalent to the "Attribute discard" action specified in [RFC7606]. 503 When discarding an attribute, a BGP speaker MAY log an error for 504 further analysis. 506 If the BGP Prefix-SID attribute appears more than once in an BGP 507 Update message, then, according to [RFC7606], all the occurrences of 508 the attribute other than the first one SHALL be discarded and the BGP 509 Update message SHALL continue to be processed. 511 When a BGP speaker receives an unacceptable Prefix-SID attribute, it 512 MAY log an error for further analysis. 514 7. IANA Considerations 516 This document defines a BGP path attribute known as the BGP Prefix- 517 SID attribute. This document requests IANA to assign an attribute 518 code type (suggested value: 40) for BGP the Prefix-SID attribute from 519 the BGP Path Attributes registry. 521 Currently, IANA temporarily assigned the following: 523 40 BGP Prefix-SID (TEMPORARY - registered 2015-09-30, expires 524 2016-09-30) [draft-ietf-idr-bgp-prefix-sid] 526 This document defines 3 TLVs for BGP Prefix-SID attribute. These 527 TLVs need to be registered with IANA. We request IANA to create a 528 registry for BGP Prefix-SID Attribute TLVs as follows: 530 Under "Border Gateway Protocol (BGP) Parameters" registry, "BGP 531 Prefix-SID attribute Types" Reference: draft-ietf-idr-bgp-prefix-sid 532 Registration Procedure(s): Values 1-254 First Come, First Served, 533 Value 0 and 255 reserved 535 Value Type Reference 536 0 Reserved this document 537 1 Label-Index this document 538 2 IPv6 SID this document 539 3 Originator SRGB this document 540 4-254 Unassigned 541 255 Reserved this document 543 8. Manageability Considerations 545 This document defines a BGP attribute to address use cases such as 546 the one described in [I-D.ietf-spring-segment-routing-msdc]. It is 547 assumed that the BGP Prefix-SID attribute advertisement is controlled 548 by the operator in order to: 550 o Prevent undesired origination/advertisement of the BGP Prefix-SID 551 attribute. By default, a BGP Prefix-SID attribute SHOULD NOT be 552 originated and attached to a prefix. The operator MUST be capable 553 of explicitly enabling BGP Prefix-SID origination. 555 o Prevent any undesired propagation of the BGP Prefix-SID attribute. 556 By default, the BGP Prefix-SID is not advertised outside the 557 boundary of an AS. The propagation to other ASs MUST be 558 explicitly configured. 560 The deployment model described in 561 [I-D.ietf-spring-segment-routing-msdc] assumes multiple Autonomous 562 Systems (AS) under a common administrative domain. For this use 563 case, the BGP Prefix-SID advertisement is applicable to the inter-AS 564 context, i.e., EBGP, while it is confined to a single administrative 565 domain. 567 9. Security Considerations 569 This document introduces a BGP attribute (BGP Prefix-SID) which 570 inherits the security considerations expressed in: [RFC4271] and 571 [RFC8277]. 573 It should be noted, as described in Section 8, that this document 574 refers to a deployment model where all nodes are under the single 575 administrative domain. In this context, we assume that the operator 576 doesn't want to leak outside of the domain any information related to 577 internal prefixes and topology. The internal information includes 578 the BGP Prefix-SID. In order to prevent such leaking, the standard 579 BGP mechanisms (filters) are applied on the boundary of the SR 580 domain. 582 10. Contributors 584 Keyur Patel 585 Arrcus, Inc. 586 US 588 Email: Keyur@arrcus.com 590 Saikat Ray 591 Unaffiliated 592 US 594 Email: raysaikat@gmail.com 596 11. Acknowledgements 598 The authors would like to thanks Satya Mohanty for his contribution 599 to this document. 601 12. References 603 12.1. Normative References 605 [I-D.ietf-spring-segment-routing] 606 Filsfils, C., Previdi, S., Ginsberg, L., Decraene, B., 607 Litkowski, S., and R. Shakir, "Segment Routing 608 Architecture", draft-ietf-spring-segment-routing-14 (work 609 in progress), December 2017. 611 [I-D.ietf-spring-segment-routing-mpls] 612 Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., 613 Litkowski, S., and R. Shakir, "Segment Routing with MPLS 614 data plane", draft-ietf-spring-segment-routing-mpls-11 615 (work in progress), October 2017. 617 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 618 Requirement Levels", BCP 14, RFC 2119, 619 DOI 10.17487/RFC2119, March 1997, . 622 [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A 623 Border Gateway Protocol 4 (BGP-4)", RFC 4271, 624 DOI 10.17487/RFC4271, January 2006, . 627 [RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private 628 Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February 629 2006, . 631 [RFC7606] Chen, E., Ed., Scudder, J., Ed., Mohapatra, P., and K. 632 Patel, "Revised Error Handling for BGP UPDATE Messages", 633 RFC 7606, DOI 10.17487/RFC7606, August 2015, 634 . 636 [RFC8277] Rosen, E., "Using BGP to Bind MPLS Labels to Address 637 Prefixes", RFC 8277, DOI 10.17487/RFC8277, October 2017, 638 . 640 12.2. Informative References 642 [I-D.ietf-idr-bgp-ls-segment-routing-ext] 643 Previdi, S., Psenak, P., Filsfils, C., Gredler, H., and M. 644 Chen, "BGP Link-State extensions for Segment Routing", 645 draft-ietf-idr-bgp-ls-segment-routing-ext-03 (work in 646 progress), July 2017. 648 [I-D.ietf-idr-bgpls-segment-routing-epe] 649 Previdi, S., Filsfils, C., Patel, K., Ray, S., and J. 650 Dong, "BGP-LS extensions for Segment Routing BGP Egress 651 Peer Engineering", draft-ietf-idr-bgpls-segment-routing- 652 epe-14 (work in progress), December 2017. 654 [I-D.ietf-spring-segment-routing-msdc] 655 Filsfils, C., Previdi, S., Mitchell, J., Aries, E., and P. 656 Lapukhov, "BGP-Prefix Segment in large-scale data 657 centers", draft-ietf-spring-segment-routing-msdc-08 (work 658 in progress), December 2017. 660 [RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter, 661 "Multiprotocol Extensions for BGP-4", RFC 4760, 662 DOI 10.17487/RFC4760, January 2007, . 665 [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and 666 S. Ray, "North-Bound Distribution of Link-State and 667 Traffic Engineering (TE) Information Using BGP", RFC 7752, 668 DOI 10.17487/RFC7752, March 2016, . 671 Authors' Addresses 673 Stefano Previdi (editor) 674 Cisco Systems 675 IT 677 Email: stefano@previdi.net 679 Clarence Filsfils 680 Cisco Systems 681 Brussels 682 Belgium 684 Email: cfilsfils@cisco.com 686 Acee Lindem 687 Cisco Systems 688 170 W. Tasman Drive 689 San Jose, CA 95124 95134 690 USA 692 Email: acee@cisco.com 693 Arjun Sreekantiah 695 Email: arjunhrs@gmail.com 697 Hannes Gredler 698 RtBrick Inc. 700 Email: hannes@rtbrick.com