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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 9, 2018 Cisco Systems 6 A. Sreekantiah 8 H. Gredler 9 RtBrick Inc. 10 January 5, 2018 12 Segment Routing Prefix SID extensions for BGP 13 draft-ietf-idr-bgp-prefix-sid-09 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 an 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", "NOT RECOMMENDED", "MAY", and 32 "OPTIONAL" in this document are to be interpreted as described in BCP 33 14 [RFC2119] [RFC8174] when, and only when, they appear in all 34 capitals, as shown here. 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 9, 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 . . . . . . . . . . . . . . . . . . . . . . . . 7 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. Advertising BGP Prefix-SID Attribute . . . . . . . . . . . . 10 82 5.1. MPLS Dataplane: Labeled Unicast . . . . . . . . . . . . . 11 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 . . . . . . . . . . . . . . . . . . . . . . 14 90 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 91 12.1. Normative References . . . . . . . . . . . . . . . . . . 14 92 12.2. Informative References . . . . . . . . . . . . . . . . . 15 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 an 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 an 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 combinations: 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 BGP Prefix-SID is used for the above AFI/SAFI combinations. 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 label index, L_I, to a 165 locally sourced prefix of a BGP speaker N which is advertised to 166 all other 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 SIDs for each of its links and peers. This information is 181 required to perform the explicit path computation and to express 182 an explicit path as a list of SIDs. The advertisement of 183 topological information and Peer segments (Peer SIDs) is done 184 through [I-D.ietf-idr-bgpls-segment-routing-epe]. 186 If the BGP speakers are not all configured with the same SRGB, and 187 if traffic-engineering within the SR domain is required, each node 188 may be required to advertise its local SRGB in addition to the 189 topological information. 191 This documents assumes that BGP-LS is the preferred method for 192 collecting both peer segments (Peer SIDs) and SRGB information 193 through [RFC7752], [I-D.ietf-idr-bgpls-segment-routing-epe], and 194 [I-D.ietf-idr-bgp-ls-segment-routing-ext]. However, as an 195 optional alternative for the advertisement of the local SRGB 196 without the topology nor the peer SIDs, hence without 197 applicability for TE, the Originator SRGB TLV of the prefix-SID 198 attribute is specified in Section 3.3 of this document. 200 As defined in [I-D.ietf-spring-segment-routing], the label index 201 L_I is an offset into the SRGB. Each BGP speaker derives its 202 local MPLS label, L, by adding L_I to the start value of its own 203 SRGB, and programs L in its MPLS dataplane as its incoming/local 204 label for the prefix. It should be noted that while SRGBs and 205 SIDs are advertised using 32-bit values, the derived label is 206 advertised in the 20 right-most bits. See Section 4.1 for more 207 details. 209 The outgoing label for the prefix is found in the NLRI of the 210 Multiprotocol BGP labeled IPv4/IPv6 Unicast prefix advertisement. 211 The label index L_I is only used as a hint to derive the local/ 212 incoming label. 214 Section 3.1 of this document specifies the Label-Index TLV of the 215 BGP Prefix-SID attribute; this TLV can be used to advertise the 216 label index for a given prefix. 218 In order to advertise the label index of a given prefix P and, 219 optionally, the SRGB, an extension to BGP is needed: the BGP Prefix- 220 SID attribute. This extension is described in subsequent sections. 222 2.2. IPv6 Prefix Segment 224 When SR is used over an IPv6 dataplane, the BGP Prefix-SID consists 225 of an IPv6 address assigned to the BGP speaker. 227 3. BGP Prefix-SID Attribute 229 The BGP Prefix-SID attribute is an optional, transitive BGP path 230 attribute. The attribute type code 40 has been assigned by IANA (see 231 Section 7). 233 The BGP Prefix-SID attribute is defined here to be a set of elements 234 encoded as "Type/Length/Value" tuples (i.e., a set of TLVs). The 235 following TLVs are defined: 237 o Label-Index TLV 238 o IPv6 SID TLV 240 o Originator SRGB TLV 242 The Label-Index and Originator SRGB TLVs are used only when SR is 243 applied to the MPLS dataplane. 245 The IPv6 SID TLV is used only when SR is applied to the IPv6 246 dataplane. 248 3.1. Label-Index TLV 250 The Label-Index TLV MUST be present in the BGP Prefix-SID attribute 251 attached to Labeled IPv4/IPv6 unicast prefixes ([RFC8277]). It will 252 be ignored when received for other BGP AFI/SAFI combinations. The 253 Label-Index TLV has 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 in octets of the value portion of 270 the TLV. 272 o RESERVED: 8-bit field. MUST be clear on transmission and MUST be 273 ignored on reception. 275 o Flags: 16 bits of flags. None are defined by this document. The 276 flag field MUST be clear on transmission and MUST be ignored on 277 reception. 279 o Label Index: 32-bit value representing the index value in the SRGB 280 space. 282 3.2. IPv6 SID 284 The IPv6 SID TLV MAY be present in the BGP Prefix-SID attribute 285 attached to MP-BGP unlabeled IPv6 unicast prefixes ([RFC4760]). It 286 will be ignored for other BGP AFI/SAFI combinations. The IPv6 SID 287 TLV has the following format: 289 0 1 2 3 290 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 1 291 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 292 | Type | Length | RESERVED | 293 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 294 | RESERVED | | 295 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 296 | | 297 | IPv6 SID (16 octets) | 298 | | 299 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 300 | | 301 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 303 where: 305 o Type is 2. 307 o Length: is 19, the total length in octets of the value portion of 308 the TLV. 310 o RESERVED: 24-bit field for future use. MUST be clear on 311 transmission and MUST be ignored on reception. 313 o IPv6 SID: 16 octets. 315 3.3. Originator SRGB TLV 317 The Originator SRGB TLV is an optional TLV and has the following 318 format: 320 0 1 2 3 321 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 1 322 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 323 | Type | Length | Flags | 324 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 325 | Flags | 326 +-+-+-+-+-+-+-+-+ 328 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 329 | SRGB 1 (6 octets) | 330 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 331 | | 332 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 334 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 335 | SRGB n (6 octets) | 336 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 337 | | 338 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 340 where: 342 o Type is 3. 344 o Length is the total length in octets of the value portion of the 345 TLV: 2 + multiple of 6. 347 o Flags: 16 bits of flags. None are defined in this document. 348 Flags MUST be clear on transmission and MUST be ignored on 349 reception. 351 o SRGB: 3 octets of base followed by 3 octets of range. Note that 352 the SRGB field MAY appear multiple times. If the SRGB field 353 appears multiple times, the SRGB consists of multiple ranges. 355 The Originator SRGB TLV contains the SRGB of the node originating the 356 prefix to which the BGP Prefix-SID is attached. The Originator SRGB 357 TLV MUST NOT be changed during the propagation of the BGP update. 359 The originator SRGB describes the SRGB of the node where the BGP 360 Prefix SID is attached. It is used to build segment routing policies 361 when different SRGBs are used in the fabric, for example 362 ([I-D.ietf-spring-segment-routing-msdc]). 364 The originator SRGB may only appear in a BGP Prefix-SID attribute 365 attached to Labeled IPv4/IPv6 unicast prefixes ([RFC8277]). It will 366 be ignored when received for other BGP AFI/SAFI combinations. 368 4. Receiving BGP Prefix-SID Attribute 370 A BGP speaker receiving a BGP Prefix-SID attribute from an EBGP 371 neighbor residing outside the boundaries of the SR domain, MUST 372 discard the attribute unless it is configured to accept the attribute 373 from the EBGP neighbor. A BGP speaker MAY log an error for further 374 analysis when discarding an attribute. 376 4.1. MPLS Dataplane: Labeled Unicast 378 A Multiprotocol BGP labeled IPv4/IPv6 Unicast ([RFC8277]) session 379 type is required. 381 A BGP speaker may be locally configured with an SRGB=[SRGB_Start, 382 SRGB_End]. The preferred method for deriving the SRGB is a matter of 383 local node configuration. 385 Given a label index L_I, we call L = L_I + SRGB_Start as the derived 386 label. A BGP Prefix-SID attribute is designated "unacceptable" for a 387 speaker M if the derived label value L lies outside the SRGB 388 configured on M. Otherwise the Label-Index TLV is designated 389 "acceptable" to speaker M. 391 The mechanisms through which a given label index value is assigned to 392 a given prefix are outside the scope of this document. The label- 393 index value associated with a prefix is locally configured at the BGP 394 node originating the prefix. 396 The BGP Prefix-SID attribute MUST contain the Label-Index TLV and MAY 397 contain the Originator SRGB TLV. A BGP Prefix-SID attribute received 398 without a Label-Index TLV MUST be considered as "unacceptable" by the 399 receiving speaker. 401 If multiple prefixes are received with the same label index value, 402 all these prefixes MUST have their BGP Prefix-SID attribute 403 considered as "unacceptable" by the receiving speaker. 405 When a BGP speaker receives a path from a neighbor with an acceptable 406 BGP Prefix-SID attribute, it MUST program the derived label as the 407 local label for the prefix in its MPLS dataplane. In case of an 408 error, a BGP speaker MUST follow to the error handling rules 409 specified in Section 6. A BGP speaker MAY log an error for further 410 analysis. 412 When a BGP speaker receives a path from a neighbor with an 413 unacceptable BGP Prefix-SID attribute or when a BGP speaker receives 414 a path from a neighbor with a BGP Prefix-SID attribute but is unable 415 to process it (it does not have the capability or local policy 416 disables the capability), it MUST treat the path as if it came 417 without a BGP Prefix-SID attribute. For the purposes of local label 418 allocation, a BGP speaker MUST assign a local (also called dynamic) 419 label (non-SRGB) for such a prefix as per classic Multiprotocol BGP 420 labeled IPv4/IPv6 Unicast ([RFC8277]) operation. A BGP speaker MAY 421 log an error for further analysis. 423 The outgoing label is always programmed as per classic Multiprotocol 424 BGP labeled IPv4/IPv6 Unicast ([RFC8277]) operation. 426 Specifically, a BGP speaker receiving a prefix with a BGP Prefix-SID 427 attribute and a label NLRI field of Implicit NULL from a neighbor 428 MUST adhere to standard behavior and program its MPLS dataplane to 429 pop the top label when forwarding traffic to the prefix. The label 430 NLRI defines the outbound label that MUST be used by the receiving 431 node. The label index gives the information to the receiving node on 432 which local/incoming label the BGP speaker SHOULD assign. 434 4.2. IPv6 Dataplane 436 When an SR IPv6 BGP speaker receives an IPv6 Unicast BGP Update with 437 a prefix having the BGP Prefix-SID attribute attached, it checks 438 whether the IPv6 SID TLV is present. If present and the chosen as 439 the best path, the prefix is installed into the Segment Routing IPv6 440 dataplane as described in [I-D.ietf-spring-segment-routing]. 442 The Originator SRGB MUST be ignored on reception. 444 5. Advertising BGP Prefix-SID Attribute 446 The BGP Prefix-SID attribute MAY be attached to labeled BGP prefixes 447 (IPv4/IPv6) [RFC8277] or to IPv6 unicast prefixes [RFC4760]. In 448 order to prevent distribution of the BGP Prefix-SID attribute beyond 449 its intended scope of applicability, attribute filtering SHOULD be 450 deployed. 452 A BGP speaker that advertises a path received from one of its 453 neighbors SHOULD advertise the BGP Prefix-SID received with the path 454 without modification, as long as the BGP Prefix-SID was acceptable. 455 If the path did not come with a BGP Prefix-SID attribute, the speaker 456 MAY attach a BGP Prefix-SID to the path if configured to do so. The 457 content of the TLVs present in the BGP Prefix-SID is determined by 458 the configuration. 460 5.1. MPLS Dataplane: Labeled Unicast 462 A BGP speaker that originates a prefix attaches the BGP Prefix-SID 463 attribute when it advertises the prefix to its neighbors via 464 Multiprotocol BGP labeled IPv4/IPv6 Unicast ([RFC8277]). The value 465 of the label index in the Label-Index TLV is determined by 466 configuration. 468 A BGP speaker that originates a BGP Prefix-SID attribute MAY 469 optionally announce the Originator SRGB TLV along with the mandatory 470 Label-Index TLV. The content of the Originator SRGB TLV is 471 determined by configuration. 473 Since the label index value must be unique within an SR domain, by 474 default an implementation SHOULD NOT advertise the BGP Prefix-SID 475 attribute outside an Autonomous System unless it is explicitly 476 configured to do so. 478 In all cases, the label field of the advertised NLRI ([RFC8277], 479 [RFC4364]) MUST be set to the local/incoming label programmed in the 480 MPLS dataplane for the given advertised prefix. If the prefix is 481 associated with one of the BGP speaker's interfaces, this is the 482 usual MPLS label (such as the Implicit or Explicit NULL label). 484 5.2. IPv6 Dataplane 486 A BGP speaker that originates an IPv6 prefix with the BGP Prefix-SID 487 attribute MAY include the IPv6 SID TLV. 489 6. Error Handling of BGP Prefix-SID Attribute 491 When a BGP Speaker receives a BGP Update message containing a 492 malformed or unacceptable BGP Prefix-SID attribute attached to a 493 Labeled IPv4/IPv6 unicast prefix [RFC8277], it MUST ignore the 494 received BGP Prefix-SID attributes and not advertise it to other BGP 495 peers. This is equivalent to the "Attribute discard" action 496 specified in [RFC7606]. When discarding an attribute, a BGP speaker 497 SHOULD log an error for further analysis. 499 When a BGP Speaker receives a BGP Update message containing a 500 malformed or unacceptable BGP Prefix-SID attribute attached to an 501 unlabeled IPv6 unicast prefix [RFC4760], it MUST treat the 502 advertisement as a withdrawal. This is equivalent to the "Treat-as- 503 withdraw" action specified in [RFC7606]. This action is required 504 since simply ignoring the BGP Prefix-SID attribute would modify the 505 installed path and the "Attribute discard" option is not applicable 506 in this case [RFC7606]. When withdrawing the prefix, a BGP speaker 507 SHOULD log an error for further analysis. 509 Consistent with [RFC7606], only the first occurrence of the BGP 510 Prefix-SID attribute will be considered and subsequent occurrences 511 will be discarded. 513 7. IANA Considerations 515 This document defines a BGP path attribute known as the BGP Prefix- 516 SID attribute. This document requests IANA to assign an attribute 517 code type (suggested value: 40) the BGP Prefix-SID attribute from the 518 BGP Path Attributes registry. 520 Currently, IANA temporarily assigned the following: 522 40 BGP Prefix-SID (TEMPORARY - registered 2015-09-30, expires 523 2016-09-30) [draft-ietf-idr-bgp-prefix-sid] 525 This document defines 3 TLVs for the BGP Prefix-SID attribute. These 526 TLVs need to be registered with IANA. We request IANA to create a 527 registry for BGP Prefix-SID Attribute TLVs as follows: 529 Under "Border Gateway Protocol (BGP) Parameters" registry, "BGP 530 Prefix-SID TLV Types" Reference: draft-ietf-idr-bgp-prefix-sid 531 Registration Procedure(s): Values 1-254 First Come, First Served, 532 Value 0 and 255 reserved 534 Value Type Reference 535 0 Reserved this document 536 1 Label-Index this document 537 2 IPv6 SID this document 538 3 Originator SRGB this document 539 4-254 Unassigned 540 255 Reserved this document 542 This document also creates a registry for the 16 bits of flags in the 543 Label-Index TLV. Initially, the registry will be empty. Flag bits 544 will be allocated First-Come, First Served consistent with the BGP- 545 SID TLV Types registry. 547 Finally, this document creates a registry for the 16 bits of flags in 548 the SRGB Originator TLV. Initially, the registry will be empty. 549 Flag bits will be allocated First-Come, First Served consistent with 550 the BGP-SID TLV Types registry. 552 8. Manageability Considerations 554 This document defines a BGP attribute to address use cases such as 555 the one described in [I-D.ietf-spring-segment-routing-msdc]. It is 556 assumed that advertisement of the BGP Prefix-SID attribute is 557 controlled by the operator in order to: 559 o Prevent undesired origination/advertisement of the BGP Prefix-SID 560 attribute. By default, a BGP Prefix-SID attribute SHOULD NOT be 561 attached to a prefix and advertised. Hence, BGP Prefix-SID 562 advertisement SHOULD require explicit enablement. 564 o Prevent any undesired propagation of the BGP Prefix-SID attribute. 565 By default, the BGP Prefix-SID is not advertised outside the 566 boundary of a single SR/administrative domain which may include 567 one or more ASes. The propagation to other ASes MUST be 568 explicitly configured. 570 The deployment model described in 571 [I-D.ietf-spring-segment-routing-msdc] assumes multiple Autonomous 572 Systems (ASes) under a common administrative domain. For this use 573 case, the BGP Prefix-SID advertisement is applicable to the inter-AS 574 context, i.e., EBGP, while it is confined to a single administrative 575 domain. 577 9. Security Considerations 579 This document introduces a BGP attribute (BGP Prefix-SID) which 580 inherits the security considerations expressed in: [RFC4271], 581 [RFC8277], and [I-D.ietf-spring-segment-routing]. 583 It should be noted that, as described in Section 8, this document 584 refers to a deployment model where all nodes are under the single 585 administrative domain. In this context, we assume that the operator 586 doesn't want to leak any information related to internal prefixes and 587 topology outside of the administrative domain. The internal 588 information includes the BGP Prefix-SID. In order to prevent such 589 leaking, the standard BGP mechanisms (filters) are applied at the 590 boundary of the SR/administrative domain. 592 10. Contributors 594 Keyur Patel 595 Arrcus, Inc. 596 US 598 Email: Keyur@arrcus.com 599 Saikat Ray 600 Unaffiliated 601 US 603 Email: raysaikat@gmail.com 605 11. Acknowledgements 607 The authors would like to thank Satya Mohanty for his contribution to 608 this document. 610 The authors would like to thank Alvaro Retana for substantive 611 comments as part of the Routing AD review. 613 12. References 615 12.1. Normative References 617 [I-D.ietf-spring-segment-routing] 618 Filsfils, C., Previdi, S., Ginsberg, L., Decraene, B., 619 Litkowski, S., and R. Shakir, "Segment Routing 620 Architecture", draft-ietf-spring-segment-routing-14 (work 621 in progress), December 2017. 623 [I-D.ietf-spring-segment-routing-mpls] 624 Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., 625 Litkowski, S., and R. Shakir, "Segment Routing with MPLS 626 data plane", draft-ietf-spring-segment-routing-mpls-11 627 (work in progress), October 2017. 629 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 630 Requirement Levels", BCP 14, RFC 2119, 631 DOI 10.17487/RFC2119, March 1997, . 634 [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A 635 Border Gateway Protocol 4 (BGP-4)", RFC 4271, 636 DOI 10.17487/RFC4271, January 2006, . 639 [RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private 640 Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February 641 2006, . 643 [RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter, 644 "Multiprotocol Extensions for BGP-4", RFC 4760, 645 DOI 10.17487/RFC4760, January 2007, . 648 [RFC7606] Chen, E., Ed., Scudder, J., Ed., Mohapatra, P., and K. 649 Patel, "Revised Error Handling for BGP UPDATE Messages", 650 RFC 7606, DOI 10.17487/RFC7606, August 2015, 651 . 653 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 654 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 655 May 2017, . 657 [RFC8277] Rosen, E., "Using BGP to Bind MPLS Labels to Address 658 Prefixes", RFC 8277, DOI 10.17487/RFC8277, October 2017, 659 . 661 12.2. Informative References 663 [I-D.ietf-idr-bgp-ls-segment-routing-ext] 664 Previdi, S., Psenak, P., Filsfils, C., Gredler, H., and M. 665 Chen, "BGP Link-State extensions for Segment Routing", 666 draft-ietf-idr-bgp-ls-segment-routing-ext-03 (work in 667 progress), July 2017. 669 [I-D.ietf-idr-bgpls-segment-routing-epe] 670 Previdi, S., Filsfils, C., Patel, K., Ray, S., and J. 671 Dong, "BGP-LS extensions for Segment Routing BGP Egress 672 Peer Engineering", draft-ietf-idr-bgpls-segment-routing- 673 epe-14 (work in progress), December 2017. 675 [I-D.ietf-spring-segment-routing-msdc] 676 Filsfils, C., Previdi, S., Mitchell, J., Aries, E., and P. 677 Lapukhov, "BGP-Prefix Segment in large-scale data 678 centers", draft-ietf-spring-segment-routing-msdc-08 (work 679 in progress), December 2017. 681 [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and 682 S. Ray, "North-Bound Distribution of Link-State and 683 Traffic Engineering (TE) Information Using BGP", RFC 7752, 684 DOI 10.17487/RFC7752, March 2016, . 687 Authors' Addresses 689 Stefano Previdi (editor) 690 Cisco Systems 691 IT 693 Email: stefano@previdi.net 694 Clarence Filsfils 695 Cisco Systems 696 Brussels 697 Belgium 699 Email: cfilsfils@cisco.com 701 Acee Lindem 702 Cisco Systems 703 301 Midenhall Way 704 Cary, NC 27513 705 USA 707 Email: acee@cisco.com 709 Arjun Sreekantiah 711 Email: arjunhrs@gmail.com 713 Hannes Gredler 714 RtBrick Inc. 716 Email: hannes@rtbrick.com