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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: October 22, 2017 A. Sreekantiah 6 Cisco Systems 7 H. Gredler 8 RtBrick Inc. 9 April 20, 2017 11 Segment Routing Prefix SID extensions for BGP 12 draft-ietf-idr-bgp-prefix-sid-05 14 Abstract 16 Segment Routing (SR) architecture allows a node to steer a packet 17 flow through any topological path and service chain by leveraging 18 source routing. The ingress node prepends a SR header to a packet 19 containing a set of segment identifiers (SID). Each SID represents a 20 topological or a service-based instruction. Per-flow state is 21 maintained only at the ingress node of the SR domain. 23 This document describes the BGP extension for announcing BGP Prefix 24 Segment Identifier (BGP Prefix-SID) information. 26 Requirements Language 28 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 29 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 30 document are to be interpreted as described in RFC 2119 [RFC2119] 31 only when they appear in all upper case. They may also appear in 32 lower or mixed case as English words, without any normative meaning. 34 Status of This Memo 36 This Internet-Draft is submitted in full conformance with the 37 provisions of BCP 78 and BCP 79. 39 Internet-Drafts are working documents of the Internet Engineering 40 Task Force (IETF). Note that other groups may also distribute 41 working documents as Internet-Drafts. The list of current Internet- 42 Drafts is at http://datatracker.ietf.org/drafts/current/. 44 Internet-Drafts are draft documents valid for a maximum of six months 45 and may be updated, replaced, or obsoleted by other documents at any 46 time. It is inappropriate to use Internet-Drafts as reference 47 material or to cite them other than as "work in progress." 48 This Internet-Draft will expire on October 22, 2017. 50 Copyright Notice 52 Copyright (c) 2017 IETF Trust and the persons identified as the 53 document authors. All rights reserved. 55 This document is subject to BCP 78 and the IETF Trust's Legal 56 Provisions Relating to IETF Documents 57 (http://trustee.ietf.org/license-info) in effect on the date of 58 publication of this document. Please review these documents 59 carefully, as they describe your rights and restrictions with respect 60 to this document. Code Components extracted from this document must 61 include Simplified BSD License text as described in Section 4.e of 62 the Trust Legal Provisions and are provided without warranty as 63 described in the Simplified BSD License. 65 Table of Contents 67 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 68 2. BGP-Prefix-SID . . . . . . . . . . . . . . . . . . . . . . . 4 69 2.1. MPLS BGP Prefix SID . . . . . . . . . . . . . . . . . . . 4 70 2.2. IPv6 Prefix Segment . . . . . . . . . . . . . . . . . . . 5 71 3. BGP-Prefix-SID Attribute . . . . . . . . . . . . . . . . . . 5 72 3.1. Label-Index TLV . . . . . . . . . . . . . . . . . . . . . 6 73 3.2. IPv6 SID . . . . . . . . . . . . . . . . . . . . . . . . 7 74 3.3. Originator SRGB TLV . . . . . . . . . . . . . . . . . . . 7 75 4. Receiving BGP-Prefix-SID Attribute . . . . . . . . . . . . . 9 76 4.1. MPLS Dataplane: Labeled Unicast . . . . . . . . . . . . . 9 77 4.2. IPv6 Dataplane . . . . . . . . . . . . . . . . . . . . . 10 78 5. Announcing BGP-Prefix-SID Attribute . . . . . . . . . . . . . 10 79 5.1. MPLS Dataplane: Labeled Unicast . . . . . . . . . . . . . 10 80 5.2. IPv6 Dataplane . . . . . . . . . . . . . . . . . . . . . 11 81 6. Error Handling of BGP-Prefix-SID Attribute . . . . . . . . . 11 82 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 83 8. Manageability Considerations . . . . . . . . . . . . . . . . 12 84 9. Security Considerations . . . . . . . . . . . . . . . . . . . 13 85 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 13 86 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13 87 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 88 12.1. Normative References . . . . . . . . . . . . . . . . . . 14 89 12.2. Informative References . . . . . . . . . . . . . . . . . 14 90 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 92 1. Introduction 94 Segment Routing (SR) architecture leverages the source routing 95 paradigm. A group of inter-connected nodes that use SR forms a SR 96 domain. A segment represents either a topological instruction such 97 as "go to prefix P following shortest path" or a service instruction 98 (e.g.: "pass through deep packet inspection"). Other types of 99 segments may be defined in the future. 101 A segment is identified through a Segment Identifier (SID). 102 Typically, the ingress node of the SR domain prepends a SR header 103 containing segments identifiers (SIDs) to an incoming packet. 105 As described in [I-D.ietf-spring-segment-routing], when SR is applied 106 to the MPLS dataplane ([I-D.ietf-spring-segment-routing-mpls]) the 107 SID consists of a label while when SR is applied to the IPv6 108 dataplane the SID consists of an IPv6 address. 110 A BGP-Prefix Segment (and its BGP Prefix-SID), is a BGP segment 111 attached to a BGP prefix. A BGP Prefix-SID is always a global SID 112 ([I-D.ietf-spring-segment-routing]) within the SR/BGP domain (i.e., 113 the set of Autonomous Systems under a common administration and 114 control and where SR is used) and identifies an instruction to 115 forward the packet over the ECMP-aware best-path computed by BGP to 116 the related prefix. The BGP Prefix-SID is the identifier of the BGP 117 prefix segment. In this document we always refer to the BGP segment 118 as the BGP Prefix-SID. 120 This document describes the BGP extension to signal the BGP Prefix- 121 SID. Specifically, this document defines a new BGP attribute known 122 as the BGP Prefix-SID attribute and specifies the rules to originate, 123 receive and handle error conditions of the new attribute. 125 As described in [I-D.ietf-spring-segment-routing-msdc], the BGP 126 Prefix-SID attribute defined in this document can be attached to 127 prefixes from AFI/SAFI: 129 Multiprotocol BGP labeled IPv4/IPv6 Unicast ([RFC3107]). 131 Multiprotocol BGP ([RFC4760]) unlabeled IPv6 Unicast. 133 [I-D.ietf-spring-segment-routing-msdc] describes use cases where the 134 Prefix-SID is used for the above AFI/SAFI. 136 It has to be noted that: 138 o A BGP Prefix-SID MAY be global between domains when the 139 interconnected domains agree on the SID allocation scheme. 141 Alternatively, when interconnecting domains, the ASBRs of each 142 domain will have to handle the advertisement of unique SIDs. The 143 mechanisms for such interconnection are outside the scope of the 144 protocol extensions defined in this document. 146 o As described in [I-D.ietf-spring-segment-routing-msdc], a BGP 147 Prefix-SID MAY be attached to a prefix. In addition, each prefix 148 will likely have a different as_path attribute. This implies that 149 each prefix is advertised individually, reducing the ability to 150 pack BGP advertisements (when sharing common attributes). 152 2. BGP-Prefix-SID 154 The BGP Prefix-SID attached to a BGP prefix P represents the 155 instruction "go to Prefix P" along its BGP bestpath (potentially 156 ECMP-enabled). 158 2.1. MPLS BGP Prefix SID 160 The BGP Prefix-SID is realized on the MPLS dataplane 161 ([I-D.ietf-spring-segment-routing-mpls]) in the following way: 163 As described in [I-D.ietf-spring-segment-routing-msdc] the 164 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 in order to perform the explicit path computation and 182 to express any explicit path into a list of SIDs. The 183 advertisement of topological information and Peer segments (Peer 184 SIDs) is 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 has to 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, a new extension to BGP is needed: the BGP 222 Prefix-SID attribute. This extension is described in subsequent 223 sections. 225 2.2. IPv6 Prefix Segment 227 As illustrated in [I-D.ietf-spring-segment-routing-msdc], when SR is 228 used over an IPv6 dataplane, the BGP Prefix-SID consists of an IPv6 229 address assigned to the BGP speaker. 231 3. BGP-Prefix-SID Attribute 233 The BGP Prefix-SID attribute is an optional, transitive BGP path 234 attribute. The attribute type code 40 has been assigned by IANA (see 235 Section 7). 237 The BGP Prefix-SID attribute is defined here to be a set of elements 238 encoded as "Type/Length/Value" (i.e., a set of TLVs). The following 239 TLVs are defined: 241 o Label-Index TLV 243 o IPv6 SID TLV 245 o Originator SRGB TLV 247 Label-Index and Originator SRGB TLVs are used only when SR is applied 248 to the MPLS dataplane. 250 IPv6 SID TLV is used only when SR is applied to the IPv6 dataplane. 252 3.1. Label-Index TLV 254 The Label-Index TLV MUST be present in the Prefix-SID attribute 255 attached to Labeled IPv4/IPv6 unicast prefixes ([RFC3107]) and has 256 the following format: 258 0 1 2 3 259 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 1 260 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 261 | Type | Length | RESERVED | 262 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 263 | Flags | Label Index | 264 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 265 | Label Index | 266 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 268 where: 270 o Type is 1. 272 o Length: is 7, the total length of the value portion of the TLV. 274 o RESERVED: 8 bit field. MUST be clear on transmission an MUST be 275 ignored at reception.. 277 o Flags: 16 bits of flags. None is defined by this document. The 278 flag field MUST be clear on transmission and MUST be ignored at 279 reception. 281 o Label Index: 32 bit value representing the index value in the SRGB 282 space. 284 3.2. IPv6 SID 286 The IPv6-SID TLV MAY be present in the Prefix-SID attribute attached 287 to MP-BGP unlabeled IPv6 unicast prefixes ([RFC4760]) and has the 288 following format: 290 0 1 2 3 291 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 1 292 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 293 | Type | Length | RESERVED | 294 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 295 | RESERVED | | 296 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 297 | | 298 | IPv6 SID (16 octets) | 299 | | 300 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 301 | | 302 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 304 where: 306 o Type is 2. 308 o Length: is 19, the total length of the value portion of the TLV. 310 o RESERVED: 24 bit field for future use. MUST be clear on 311 transmission an MUST be ignored at 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 of the value portion of the TLV: 2 + 345 multiple of 6. 347 o Flags: 16 bits of flags. None is defined in this document. Flags 348 MUST be clear on transmission an MUST be ignored at reception. 350 o SRGB: 3 octets of base followed by 3 octets of range. Note that 351 the SRGB field MAY appear multiple times. If the SRGB field 352 appears multiple times, the SRGB consists of multiple ranges. 354 The Originator SRGB TLV contains the SRGB of the node originating the 355 prefix to which the BGP Prefix-SID is attached and MUST be kept in 356 the Prefix-SID Attribute unchanged during the propagation of the BGP 357 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 SRGB's are used in the fabric 362 ([I-D.ietf-spring-segment-routing-msdc]). 364 The originator SRGB may only appear on Prefix-SID attribute attached 365 to prefixes of SAFI 4 (labeled unicast, [RFC3107]). 367 4. Receiving BGP-Prefix-SID Attribute 369 A BGP speaker receiving a BGP Prefix-SID attribute from an EBGP 370 neighbor residing outside the boundaries of the SR domain, SHOULD 371 discard the attribute unless it is configured to accept the attribute 372 from the EBGP neighbor. A BGP speaker MAY log an error for further 373 analysis when discarding an attribute. 375 4.1. MPLS Dataplane: Labeled Unicast 377 A Multiprotocol BGP labeled IPv4/IPv6 Unicast ([RFC3107]) session 378 type is required. 380 A BGP speaker MAY be locally configured with an SRGB=[SRGB_Start, 381 SRGB_End]. The preferred method for deriving the SRGB is a matter of 382 local node configuration. 384 Given a label_index L_I, we call L = L_I + SRGB_Start as the derived 385 label. A BGP Prefix-SID attribute is called "unacceptable" for a 386 speaker M if the derived label value L lies outside the SRGB 387 configured on M. Otherwise the Label Index attribute is called 388 "acceptable" to speaker M. 390 The mechanisms through which a given label_index value is assigned to 391 a given prefix are outside the scope of this document. The label- 392 index value associated with a prefix is locally configured at the BGP 393 node originating the prefix. 395 The Prefix-SID attribute MUST contain the Label-Index TLV and MAY 396 contain the Originator SRGB TLV. A BGP Prefix-SID attribute received 397 without a Label-Index TLV MUST be considered as "unacceptable" by the 398 receiving speaker. 400 If multiple prefixes are received with the same label_index value, 401 all these prefixes MUST have their BGP Prefix-SID attribute 402 considered as "unacceptable" by the receiving speaker. 404 When a BGP speaker receives a path from a neighbor with an acceptable 405 BGP Prefix-SID attribute, it MUST program the derived label as the 406 local label for the prefix in its MPLS dataplane. In case of any 407 error, a BGP speaker MUST resort to the error handling rules 408 specified in Section 6. A BGP speaker MAY log an error for further 409 analysis. 411 When a BGP speaker receives a path from a neighbor with an 412 unacceptable BGP Prefix-SID attribute or when a BGP speaker receives 413 a path from a neighbor with a BGP Prefix-SID attribute but is unable 414 to process it (it does not have the capability or local policy 415 disables the capability), it MUST treat the path as if it came 416 without a Prefix-SID attribute. For the purposes of local label 417 allocation, a BGP speaker MUST assign a local (also called dynamic) 418 label (non-SRGB) for such a prefix as per classic Multiprotocol BGP 419 labeled IPv4/IPv6 Unicast ([RFC3107]) operation. A BGP speaker MAY 420 log an error for further analysis. 422 The outgoing label is always programmed as per classic Multiprotocol 423 BGP labeled IPv4/IPv6 Unicast (RFC3107 [RFC3107]) operation. 425 Specifically, a BGP speaker receiving a prefix with a Prefix-SID 426 attribute and a label NLRI field of implicit-null from a neighbor 427 MUST adhere to standard behavior and program its MPLS dataplane to 428 pop the top label when forwarding traffic to the prefix. The label 429 NLRI defines the outbound label that MUST be used by the receiving 430 node. The Label Index gives the information to the receiving node on 431 which local/incoming label the BGP speaker SHOULD use. 433 4.2. IPv6 Dataplane 435 When an SR IPv6 BGP speaker receives a IPv6 Unicast BGP Update with a 436 prefix having the BGP Prefix-SID attribute attached, it checks 437 whether the IPv6 SID TLV is present. If present, then the receiver 438 assumes that the originator supports SR on the IPv6 dataplane. 440 The Originator SRGB MUST be ignored on reception. 442 A BGP speaker receiving a BGP Prefix-SID attribute from an EBGP 443 neighbor residing outside the boundaries of the SR domain, SHOULD 444 discard the attribute unless it is configured to accept the attribute 445 from the EBGP neighbor. A BGP speaker MAY log an error for further 446 analysis when discarding an attribute. 448 5. Announcing BGP-Prefix-SID Attribute 450 The BGP Prefix-SID attribute MAY be attached to labeled BGP prefixes 451 (IPv4/IPv6) [RFC3107] or to IPv6 prefixes [RFC4760]. In order to 452 prevent distribution of the BGP Prefix-SID attribute beyond its 453 intended scope of applicability, attribute filtering SHOULD be 454 deployed. 456 5.1. MPLS Dataplane: Labeled Unicast 458 A BGP speaker that originates a prefix attaches the Prefix-SID 459 attribute when it advertises the prefix to its neighbors via 460 Multiprotocol BGP labeled IPv4/IPv6 Unicast ([RFC3107]). The value 461 of the Label-Index in the Label-Index TLV is determined by 462 configuration. 464 A BGP speaker that originates a Prefix-SID attribute MAY optionally 465 announce Originator SRGB TLV along with the mandatory Label-Index 466 TLV. The content of the Originator SRGB TLV is determined by the 467 configuration. 469 Since the Label-index value must be unique within an SR domain, by 470 default an implementation SHOULD NOT advertise the BGP Prefix-SID 471 attribute outside an Autonomous System unless it is explicitly 472 configured to do so. 474 A BGP speaker that advertises a path received from one of its 475 neighbors SHOULD advertise the Prefix-SID received with the path 476 without modification regardless of whether the Prefix-SID was 477 acceptable. If the path did not come with a Prefix-SID attribute, 478 the speaker MAY attach a Prefix-SID to the path if configured to do 479 so. The content of the TLVs present in the Prefix-SID is determined 480 by the configuration. 482 In all cases, the label field of the advertised NLRI ([RFC3107], 483 [RFC4364]) MUST be set to the local/incoming label programmed in the 484 MPLS dataplane for the given advertised prefix. If the prefix is 485 associated with one of the BGP speakers interfaces, this label is the 486 usual MPLS label (such as the implicit or explicit NULL label). 488 5.2. IPv6 Dataplane 490 A BGP speaker that originates an IPv6 prefix with the Prefix-SID 491 attribute, MAY include the IPv6 SID TLV. 493 A BGP speaker that advertises a path received from one of its 494 neighbors SHOULD advertise the Prefix-SID received with the path 495 without modification regardless of whether the Prefix-SID was 496 acceptable. If the path did not come with a Prefix-SID attribute, 497 the speaker MAY attach a Prefix-SID to the path if configured to do 498 so. 500 6. Error Handling of BGP-Prefix-SID Attribute 502 When a BGP Speaker receives a BGP Update message containing a 503 malformed BGP Prefix-SID attribute, it MUST ignore the received BGP 504 Prefix-SID attributes and not pass it to other BGP peers. This is 505 equivalent to the -attribute discard- action specified in [RFC7606]. 506 When discarding an attribute, a BGP speaker MAY log an error for 507 further analysis. 509 If the BGP Prefix-SID attribute appears more than once in an BGP 510 Update message, then, according to [RFC7606], all the occurrences of 511 the attribute other than the first one SHALL be discarded and the BGP 512 Update message SHALL continue to be processed. 514 When a BGP speaker receives an unacceptable Prefix-SID attribute, it 515 MAY log an error for further analysis. 517 7. IANA Considerations 519 This document defines a new BGP path attribute known as the BGP 520 Prefix-SID attribute. This document requests IANA to assign a new 521 attribute code type (suggested value: 40) for BGP the Prefix-SID 522 attribute from the BGP Path Attributes registry. 524 Currently, IANA temporarily assigned the following: 526 40 BGP Prefix-SID (TEMPORARY - registered 2015-09-30, expires 527 2016-09-30) [draft-ietf-idr-bgp-prefix-sid] 529 This document defines 3 new TLVs for BGP Prefix-SID attribute. These 530 TLVs need to be registered with IANA. We request IANA to create a 531 new registry for BGP Prefix-SID Attribute TLVs as follows: 533 Under "Border Gateway Protocol (BGP) Parameters" registry, "BGP 534 Prefix-SID attribute Types" Reference: draft-ietf-idr-bgp-prefix-sid 535 Registration Procedure(s): Values 1-254 First Come, First Served, 536 Value 0 and 255 reserved 538 Value Type Reference 539 0 Reserved this document 540 1 Label-Index this document 541 2 IPv6 SID this document 542 3 Originator SRGB this document 543 4-254 Unassigned 544 255 Reserved this document 546 8. Manageability Considerations 548 This document defines a new BGP attribute in order to address the use 549 case described in [I-D.ietf-spring-segment-routing-msdc]. It i 550 assumed that the new attribute (BGP Prefix-SID) advertisement is 551 controlled by the operator in order to: 553 o prevent undesired origination/advertisement of the BGP Prefix-SID 554 attribute. By default, a BGP Prefix-SID attribute SHOULD NOT be 555 originated and attached to a prefix. The operator MUST be capable 556 of explicitly enabling the BGP Prefix-SID origination. 558 o Prevent any undesired propagation of the BGP Prefix-SID attribute. 559 By default the BGP Prefix-SID is not advertised outside the 560 boundary of an AS. The propagation to other ASs MUST be 561 explicitly configured. 563 The deployment model described in 564 [I-D.ietf-spring-segment-routing-msdc] assumes multiple Autonomous 565 Systems (AS) under a common administration. The BGP Prefix-SID 566 advertisement is therefore applicable to inter-AS context while it is 567 confined within a single SR Domain. 569 9. Security Considerations 571 This document introduces a new BGP attribute (BGP Prefix-SID) which 572 inherits the security considerations expressed in: [RFC4271] and 573 [RFC3107]. 575 The BGP Prefix-SID attribute addresses the requirements introduced in 576 [I-D.ietf-spring-segment-routing-msdc] and It has to be noted, as 577 described in Section 8, that this document refer to a deployment 578 model where all nodes are under the same administration. In this 579 context, we assume that the operator doesn't want to leak outside of 580 the domain any information related to internal prefixes and topology. 581 The internal information includes the BGP Prefix-SID. In order to 582 prevent such leaking, the standard BGP mechanisms (filters) are 583 applied on the boundary of the domain. 585 10. Contributors 587 Keyur Patel 588 Arrcus, Inc. 589 US 591 Email: Keyur@arrcus.com 593 Saikat Ray 594 Unaffiliated 595 US 597 Email: raysaikat@gmail.com 599 11. Acknowledgements 601 The authors would like to thanks Satya Mohanty for his contribution 602 to this document. 604 12. References 606 12.1. Normative References 608 [I-D.ietf-spring-segment-routing] 609 Filsfils, C., Previdi, S., Decraene, B., Litkowski, S., 610 and R. Shakir, "Segment Routing Architecture", draft-ietf- 611 spring-segment-routing-11 (work in progress), February 612 2017. 614 [I-D.ietf-spring-segment-routing-mpls] 615 Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., 616 Litkowski, S., and R. Shakir, "Segment Routing with MPLS 617 data plane", draft-ietf-spring-segment-routing-mpls-08 618 (work in progress), March 2017. 620 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 621 Requirement Levels", BCP 14, RFC 2119, 622 DOI 10.17487/RFC2119, March 1997, 623 . 625 [RFC3107] Rekhter, Y. and E. Rosen, "Carrying Label Information in 626 BGP-4", RFC 3107, DOI 10.17487/RFC3107, May 2001, 627 . 629 [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A 630 Border Gateway Protocol 4 (BGP-4)", RFC 4271, 631 DOI 10.17487/RFC4271, January 2006, 632 . 634 [RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private 635 Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February 636 2006, . 638 [RFC7606] Chen, E., Ed., Scudder, J., Ed., Mohapatra, P., and K. 639 Patel, "Revised Error Handling for BGP UPDATE Messages", 640 RFC 7606, DOI 10.17487/RFC7606, August 2015, 641 . 643 12.2. Informative References 645 [I-D.ietf-idr-bgp-ls-segment-routing-ext] 646 Previdi, S., Psenak, P., Filsfils, C., Gredler, H., Chen, 647 M., and j. jefftant@gmail.com, "BGP Link-State extensions 648 for Segment Routing", draft-ietf-idr-bgp-ls-segment- 649 routing-ext-01 (work in progress), February 2017. 651 [I-D.ietf-idr-bgpls-segment-routing-epe] 652 Previdi, S., Filsfils, C., Patel, K., Ray, S., Dong, J., 653 and M. Chen, "Segment Routing BGP Egress Peer Engineering 654 BGP-LS Extensions", draft-ietf-idr-bgpls-segment-routing- 655 epe-11 (work in progress), March 2017. 657 [I-D.ietf-spring-segment-routing-msdc] 658 Filsfils, C., Previdi, S., Mitchell, J., Aries, E., and P. 659 Lapukhov, "BGP-Prefix Segment in large-scale data 660 centers", draft-ietf-spring-segment-routing-msdc-04 (work 661 in progress), March 2017. 663 [RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter, 664 "Multiprotocol Extensions for BGP-4", RFC 4760, 665 DOI 10.17487/RFC4760, January 2007, 666 . 668 [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and 669 S. Ray, "North-Bound Distribution of Link-State and 670 Traffic Engineering (TE) Information Using BGP", RFC 7752, 671 DOI 10.17487/RFC7752, March 2016, 672 . 674 Authors' Addresses 676 Stefano Previdi (editor) 677 Cisco Systems 678 Via Del Serafico, 200 679 Rome 00142 680 Italy 682 Email: sprevidi@cisco.com 684 Clarence Filsfils 685 Cisco Systems 686 Brussels 687 Belgium 689 Email: cfilsfils@cisco.com 690 Acee Lindem 691 Cisco Systems 692 170 W. Tasman Drive 693 San Jose, CA 95124 95134 694 USA 696 Email: acee@cisco.com 698 Arjun Sreekantiah 699 Cisco Systems 700 170 W. Tasman Drive 701 San Jose, CA 95124 95134 702 USA 704 Email: asreekan@cisco.com 706 Hannes Gredler 707 RtBrick Inc. 709 Email: hannes@rtbrick.com