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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references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 3107 (Obsoleted by RFC 8277) == Outdated reference: A later version (-19) exists of draft-ietf-idr-bgpls-segment-routing-epe-00 == Outdated reference: A later version (-15) exists of draft-ietf-spring-segment-routing-05 == Outdated reference: A later version (-11) exists of draft-ietf-spring-segment-routing-msdc-00 Summary: 1 error (**), 0 flaws (~~), 4 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 IDR S. Previdi 3 Internet-Draft C. Filsfils 4 Intended status: Standards Track A. Lindem 5 Expires: April 16, 2016 K. Patel 6 A. Sreekantiah 7 Cisco Systems 8 S. Ray 9 Unaffiliated 10 H. Gredler 11 Juniper Networks 12 October 14, 2015 14 Segment Routing Prefix SID extensions for BGP 15 draft-ietf-idr-bgp-prefix-sid-01 17 Abstract 19 Segment Routing (SR) architecture allows a node to steer a packet 20 flow through any topological path and service chain by leveraging 21 source routing. The ingress node prepends a SR header to a packet 22 containing a set of "segments". Each segment represents a 23 topological or a service-based instruction. Per-flow state is 24 maintained only at the ingress node of the SR domain. 26 This document describes the BGP extension for announcing BGP Prefix 27 Segment Identifier (BGP Prefix SID) information. 29 Requirements Language 31 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 32 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 33 document are to be interpreted as described in RFC 2119 [RFC2119] 34 only when they appear in all upper case. They may also appear in 35 lower or mixed case as English words, without any normative meaning. 37 Status of This Memo 39 This Internet-Draft is submitted in full conformance with the 40 provisions of BCP 78 and BCP 79. 42 Internet-Drafts are working documents of the Internet Engineering 43 Task Force (IETF). Note that other groups may also distribute 44 working documents as Internet-Drafts. The list of current Internet- 45 Drafts is at http://datatracker.ietf.org/drafts/current/. 47 Internet-Drafts are draft documents valid for a maximum of six months 48 and may be updated, replaced, or obsoleted by other documents at any 49 time. It is inappropriate to use Internet-Drafts as reference 50 material or to cite them other than as "work in progress." 52 This Internet-Draft will expire on April 16, 2016. 54 Copyright Notice 56 Copyright (c) 2015 IETF Trust and the persons identified as the 57 document authors. All rights reserved. 59 This document is subject to BCP 78 and the IETF Trust's Legal 60 Provisions Relating to IETF Documents 61 (http://trustee.ietf.org/license-info) in effect on the date of 62 publication of this document. Please review these documents 63 carefully, as they describe your rights and restrictions with respect 64 to this document. Code Components extracted from this document must 65 include Simplified BSD License text as described in Section 4.e of 66 the Trust Legal Provisions and are provided without warranty as 67 described in the Simplified BSD License. 69 Table of Contents 71 1. Segment Routing Documents . . . . . . . . . . . . . . . . . . 3 72 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 73 3. BGP-Prefix-SID . . . . . . . . . . . . . . . . . . . . . . . 4 74 3.1. MPLS Prefix Segment . . . . . . . . . . . . . . . . . . . 4 75 3.2. IPv6 Prefix Segment . . . . . . . . . . . . . . . . . . . 5 76 4. BGP-Prefix-SID Attribute . . . . . . . . . . . . . . . . . . 5 77 4.1. Label-Index TLV . . . . . . . . . . . . . . . . . . . . . 6 78 4.2. IPv6 SID . . . . . . . . . . . . . . . . . . . . . . . . 7 79 4.3. Originator SRGB TLV . . . . . . . . . . . . . . . . . . . 8 80 5. Receiving BGP-Prefix-SID Attribute . . . . . . . . . . . . . 9 81 5.1. MPLS Dataplane: Labeled Unicast . . . . . . . . . . . . . 9 82 5.2. IPv6 Dataplane . . . . . . . . . . . . . . . . . . . . . 10 83 6. Announcing BGP-Prefix-SID Attribute . . . . . . . . . . . . . 10 84 6.1. MPLS Dataplane: Labeled Unicast . . . . . . . . . . . . . 10 85 6.2. IPv6 Dataplane . . . . . . . . . . . . . . . . . . . . . 11 86 7. Error Handling of BGP-Prefix-SID Attribute . . . . . . . . . 11 87 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 88 9. Security Considerations . . . . . . . . . . . . . . . . . . . 12 89 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12 90 11. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 12 91 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 92 12.1. Normative References . . . . . . . . . . . . . . . . . . 13 93 12.2. Informative References . . . . . . . . . . . . . . . . . 13 94 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14 96 1. Segment Routing Documents 98 The main references for this document are the SR architecture defined 99 in [I-D.ietf-spring-segment-routing] and the related use case 100 illustrated in [I-D.ietf-spring-segment-routing-msdc]. 102 The Segment Routing Egress Peer Engineering architecture is described 103 in [I-D.filsfils-spring-segment-routing-central-epe]. 105 The Segment Routing Egress Peer Engineering BGPLS extensions are 106 described in [I-D.ietf-idr-bgpls-segment-routing-epe]. 108 2. Introduction 110 Segment Routing (SR) architecture leverages the source routing 111 paradigm. A group of inter-connected nodes that use SR forms a SR 112 domain. The ingress node of the SR domain prepends a SR header 113 containing "segments" to an incoming packet. Each segment represents 114 a topological instruction such as "go to prefix P following shortest 115 path" or a service instruction (e.g.: "pass through deep packet 116 inspection"). By inserting the desired sequence of instructions, the 117 ingress node is able to steer a packet via any topological path and/ 118 or service chain; per-flow state is maintained only at the ingress 119 node of the SR domain. 121 Each segment is identified by a Segment Identifier (SID). As 122 described in [I-D.ietf-spring-segment-routing], when SR is applied to 123 the MPLS dataplane the SID consists of a label while when SR is 124 applied to the IPv6 dataplane the SID consists of an IPv6 prefix (see 125 [I-D.previdi-6man-segment-routing-header]). 127 A BGP-Prefix Segment (aka BGP-Prefix-SID), is a BGP segment attached 128 to a BGP prefix. A BGP-Prefix-SID is always global within the SR/BGP 129 domain and identifies an instruction to forward the packet over the 130 ECMP-aware best-path computed by BGP to the related prefix. The BGP- 131 Prefix-SID is the identifier of the BGP prefix segment. 133 This document describes the BGP extension to signal the BGP-Prefix- 134 SID. Specifically, this document defines a new BGP attribute known 135 as the BGP Prefix SID attribute and specifies the rules to originate, 136 receive and handle error conditions of the new attribute. 138 As described in [I-D.ietf-spring-segment-routing-msdc], the newly 139 proposed BGP Prefix-SID attribute can be attached to prefixes from 140 AFI/SAFI: 142 Multiprotocol BGP labeled IPv4/IPv6 Unicast ([RFC3107]). 144 Multiprotocol BGP ([RFC4760]) unlabeled IPv6 Unicast. 146 [I-D.ietf-spring-segment-routing-msdc] describes use cases where the 147 Prefix-SID is used for the above AFI/SAFI. 149 3. BGP-Prefix-SID 151 The BGP-Prefix-SID attached to a BGP prefix P represents the 152 instruction "go to Prefix P" along its BGP bestpath (potentially 153 ECMP-enabled). 155 3.1. MPLS Prefix Segment 157 The BGP Prefix Segment is realized on the MPLS dataplane in the 158 following way: 160 A Multiprotocol BGP labeled IPv4/IPv6 Unicast ([RFC3107]) session 161 type is required. 163 According to [I-D.ietf-spring-segment-routing], each BGP speaker 164 is configured with a label block called the Segment Routing Global 165 Block (SRGB). While it is recommended to use the same SRGB across 166 all the nodes within the SR domain, the SRGB of a node is a local 167 property and could be different on different speakers. The 168 drawbacks of the use case where BGP speakers have different SRGBs 169 are documented in [I-D.ietf-spring-segment-routing]. 171 As described in [I-D.ietf-spring-segment-routing-msdc] the 172 operator assigns a globally unique "index", L_I, to a locally 173 sourced prefix of a BGP speaker N which is advertised to all other 174 BGP speakers in the SR domain. 176 The index L_I is a 32 bit offset in the SRGB. Each BGP speaker 177 derives its local MPLS label, L, by adding L_I to the start value 178 of its own SRGB, and programs L in its MPLS dataplane as its 179 incoming/local label for the prefix. 181 The outgoing label for the prefix is found in the NLRI of the 182 Multiprotocol BGP labeled IPv4/IPv6 Unicast prefix advertisement. 183 The index L_I is only used as a hint to derive the local/incoming 184 label. 186 If the BGP speakers cannot be configured with the same SRGB and 187 traffic-engineering within the SR domain is required, each node 188 MAY be required to advertise its local SRGB. 190 The preferred method leverages 191 [I-D.ietf-idr-bgpls-segment-routing-epe]. 193 Indeed, in order to engineer traffic, it is important to have the 194 internal topology (BGP-LS extensions provide these), the peering 195 topology (BGP-LS-EPE extensions provide these), and the equivalent 196 of adjacency segments for each link in the topology (BGP-LS-EPE 197 extensions provide these through the PeerAdj segments). The first 198 two provide the topology input to the optimization process. The 199 latter provides a deterministic method to engineer a flow through 200 any desired path. 202 In some very-simplified traffic-engineering context, it might not 203 be necessary to have either the topology or the adjacency 204 segments. In such simplified case, the BGP Prefix SID provides an 205 alternative method to distribute the SRGB of each node. 207 If the BGP speakers cannot be configured with the same SRGB, the 208 proposed BGP Prefix-SID attribute allows the advertisement of the 209 SRGB so each node can advertise the SRGB it's configured with. The 210 drawbacks of the use case where BGP speakers have different SRGBs are 211 documented in [I-D.ietf-spring-segment-routing-msdc]. 213 In order to advertise the label index of a given prefix P and, 214 optionally, the SRGB, a new extension to BGP is needed: the BGP 215 Prefix SID attribute. This extension is described in subsequent 216 sections. 218 3.2. IPv6 Prefix Segment 220 As defined in [I-D.previdi-6man-segment-routing-header], and as 221 illustrated in [I-D.ietf-spring-segment-routing-msdc], when SR is 222 used over an IPv6 dataplane, the BGP Prefix Segment is instantiated 223 by an IPv6 prefix originated by the BGP speaker. 225 Each node advertises a globally unique IPv6 address representing 226 itself in the domain. This prefix (e.g.: its loopback interface 227 address) is advertised to all other BGP speakers in the SR domain. 229 Also, each node MUST advertise its support of Segment Routing for 230 IPv6 dataplane. This is realized using the flags contained in the 231 Prefix SID Attribute defined below. 233 4. BGP-Prefix-SID Attribute 235 The BGP Prefix SID attribute is an optional, transitive BGP path 236 attribute. The attribute type code is to be assigned by IANA 237 (suggested value: 40). The value field of the BGP-Prefix-SID 238 attribute has the following format: 240 The value field of the BGP Prefix SID attribute is defined here to be 241 a set of elements encoded as "Type/Length/Value" (i.e., a set of 242 TLVs). Following TLVs are defined: 244 o Label-Index TLV 246 o IPv6 SID TLV 248 o Originator SRGB TLV 250 Label-Index and Originator SRGB TLVs are used only when SR is applied 251 to the MPLS dataplane. 253 IPv6 SID TLV is used only when SR is applied to the IPv6 dataplane. 255 4.1. Label-Index TLV 257 The Label-Index TLV MUST be present in the Prefix-SID attribute 258 attached to Labeled IPv4/IPv6 unicast prefixes ([RFC3107]) and has 259 the following format: 261 0 1 2 3 262 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 1 263 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 264 | Type | Length | RESERVED | 265 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 266 | Flags | Label Index | 267 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 268 | Label Index | 269 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 271 where: 273 o Type is 1. 275 o Length: is 7, the total length of the value portion of the TLV. 277 o RESERVED: 8 bit field. SHOULD be 0 on transmission and MUST be 278 ignored on reception. 280 o Flags: 16 bits of flags. None are defined at this stage of the 281 document. The flag field SHOULD be clear on transmission and MUST 282 be ignored at reception. 284 o Label Index: 32 bit value representing the index value in the SRGB 285 space. 287 4.2. IPv6 SID 289 The IPv6-SID TLV MUST be present in the Prefix-SID attribute attached 290 to MP-BGP unlabeled IPv6 unicast prefixes ([RFC4760]) and has the 291 following format: 293 0 1 2 3 294 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 1 295 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 296 | Type | Length | RESERVED | 297 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 298 | Flags | 299 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 301 where: 303 o Type is 2. 305 o Length: is 3, the total length of the value portion of the TLV. 307 o RESERVED: 8 bit field. SHOULD be 0 on transmission and MUST be 308 ignored on reception. 310 o Flags: 16 bits of flags defined as follow: 312 0 1 313 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 314 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 315 |S| | 316 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 318 where: 320 * S flag: if set then it means that the BGP speaker attaching the 321 Prefix-SID Attribute to a prefix is capable of processing the 322 IPv6 Segment Routing Header (SRH, 323 [I-D.previdi-6man-segment-routing-header]) for the segment 324 corresponding to the originated IPv6 prefix. The use case 325 leveraging the S flag is described in 326 [I-D.ietf-spring-segment-routing-msdc]. 328 The other bits of the flag field SHOULD be clear on transmission 329 an MUST be ignored at reception. 331 4.3. Originator SRGB TLV 333 The Originator SRGB TLV is an optional TLV and has the following 334 format: 336 0 1 2 3 337 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 1 338 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 339 | Type | Length | Flags | 340 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 341 | Flags | 342 +-+-+-+-+-+-+-+-+ 344 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 345 | SRGB 1 (6 octets) | 346 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 347 | | 348 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 350 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 351 | SRGB n (6 octets) | 352 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 353 | | 354 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 356 where: 358 o Type is 3. 360 o Length is the total length of the value portion of the TLV: 2 + 361 multiple of 6. 363 o Flags: 16 bits of flags. None are defined in this document. 364 Flags SHOULD be clear on transmission an MUST be ignored at 365 reception. 367 o SRGB: 3 octets of base followed by 3 octets of range. Note that 368 SRGB field MAY appear multiple times. 370 The Originator SRGB TLV contains the SRGB of the router originating 371 the prefix to which the BGP Prefix SID is attached and MUST be kept 372 in the Prefix-SID Attribute unchanged during the propagation of the 373 BGP update. 375 The originator SRGB describes the SRGB of the node where the BGP 376 Prefix Segment end. It is used to build SRTE policies when different 377 SRGB's are used in the fabric 378 ([I-D.ietf-spring-segment-routing-msdc]). 380 The originator SRGB may only appear on Prefix-SID attribute attached 381 to prefixes of SAFI 4 (labeled unicast, [RFC3107]). 383 5. Receiving BGP-Prefix-SID Attribute 385 A BGP speaker receiving a BGP Prefix-SID attribute from an EBGP 386 neighbor residing outside the boundaries of the SR domain, SHOULD 387 discard the attribute unless it is configured to accept the attribute 388 from the EBGP neighbor. A BGP speaker MAY log an error for further 389 analysis when discarding an attribute. 391 5.1. MPLS Dataplane: Labeled Unicast 393 A Multiprotocol BGP labeled IPv4/IPv6 Unicast ([RFC3107]) session 394 type is required. 396 A BGP speaker may be locally configured with an SRGB=[GB_S, GB_E]. 397 The preferred method for deriving the SRGB is a matter of local 398 router configuration. 400 Given a label index L_I, we call L = L_I + GB_S as the derived label. 401 A BGP Prefix-SID attribute is called "unacceptable" for a speaker M 402 if the derived label value L lies outside the SRGB configured on M. 403 Otherwise the Label Index attribute is called "acceptable" to speaker 404 M. 406 The mechanisms through which a given label_index value is assigned to 407 a given prefix are outside the scope of this document. The label- 408 index value associated with a prefix is locally configured at the BGP 409 router originating the prefix. 411 The Prefix-SID attribute MUST contain the Label-Index TLV and MAY 412 contain the Originator SRGB TLV. A BGP Prefix-SID attribute received 413 without a Label-Index TLV MUST be considered as "unacceptable" by the 414 receiving speaker. 416 When a BGP speaker receives a path from a neighbor with an acceptable 417 BGP Prefix-SID attribute, it MUST program the derived label as the 418 local label for the prefix in its MPLS dataplane. In case of any 419 error, a BGP speaker MUST resort to the error handling rules 420 specified in Section 7. A BGP speaker MAY log an error for further 421 analysis. 423 When a BGP speaker receives a path from a neighbor with an 424 unacceptable BGP Prefix-SID attribute or when a BGP speaker receives 425 a path from a neighbor with a BGP-Prefix-SID attribute but is unable 426 to process it (it does not have the capability or local policy 427 disables the capability), it MUST treat the path as if it came 428 without a Prefix-SID attribute. For the purposes of local label 429 allocation, a BGP speaker MUST assign a local (also called dynamic) 430 label (non-SRGB) for such a prefix as per classic Multiprotocol BGP 431 labeled IPv4/IPv6 Unicast ([RFC3107]) operation. A BGP speaker MAY 432 log an error for further analysis. 434 The outgoing label is always programmed as per classic Multiprotocol 435 BGP labeled IPv4/IPv6 Unicast (RFC3107 [RFC3107]) operation. 437 Specifically, a BGP speaker receiving a prefix with a Prefix-SID 438 attribute and a label NLRI field of implicit-null from a neighbor 439 MUST adhere to standard behavior and program its MPLS dataplane to 440 pop the top label when forwarding traffic to the prefix. The label 441 NLRI defines the outbound label that MUST be used by the receiving 442 node. The Label Index gives a hint to the receiving node on which 443 local/incoming label the BGP speaker SHOULD use. 445 5.2. IPv6 Dataplane 447 When a SR IPv6 BGP speaker receives a IPv6 Unicast BGP Update with a 448 prefix having the BGP Prefix SID attribute attached, it checks 449 whether the IPv6 SID TLV is present and if the S-flag is set. If the 450 IPv6 SID TLV is present and if the S-flag is not set, then the 451 Prefix-SID attribute MUST be considered as "unacceptable" by the 452 receiving speaker. 454 The Originator SRGB MUST be ignored on reception. 456 A BGP speaker receiving a BGP Prefix-SID attribute from an EBGP 457 neighbor residing outside the boundaries of the SR domain, SHOULD 458 discard the attribute unless it is configured to accept the attribute 459 from the EBGP neighbor. A BGP speaker MAY log an error for further 460 analysis when discarding an attribute. 462 6. Announcing BGP-Prefix-SID Attribute 464 The BGP Prefix-SID attribute MAY be attached to labeled BGP prefixes 465 (IPv4/IPv6) [RFC3107]or to IPv6 prefixes [RFC4760]. In order to 466 prevent distribution of the BGP Prefix-SID attribute beyond its 467 intended scope of applicability, attribute filtering MAY be deployed. 469 6.1. MPLS Dataplane: Labeled Unicast 471 A BGP speaker that originates a prefix attaches the Prefix-SID 472 attribute when it advertises the prefix to its neighbors via 473 Multiprotocol BGP labeled IPv4/IPv6 Unicast ([RFC3107])The value of 474 the Label-Index in the Label-Index TLV is determined by 475 configuration. 477 A BGP speaker that originates a Prefix-SID attribute MAY optionally 478 announce Originator SRGB TLV along with the mandatory Label-Index 479 TLV. The content of the Originator SRGB TLV is determined by the 480 configuration. 482 Since the Label-index value must be unique within an SR domain, by 483 default an implementation SHOULD NOT advertise the BGP Prefix-SID 484 attribute outside an Autonomous System unless it is explicitly 485 configured to do so. 487 A BGP speaker that advertises a path received from one of its 488 neighbors SHOULD advertise the Prefix-SID received with the path 489 without modification regardless of whether the Prefix-SID was 490 acceptable. If the path did not come with a Prefix-SID attribute, 491 the speaker MAY attach a Prefix-SID to the path if configured to do 492 so. The content of the TLVs present in the Prefix-SID is determined 493 by the configuration. 495 In all cases, the label field of the advertised NLRI ([RFC3107], 496 [RFC4364]) MUST be set to the local/incoming label programmed in the 497 MPLS dataplane for the given advertised prefix. If the prefix is 498 associated with one of the BGP speakers interfaces, this label is the 499 usual MPLS label (such as the implicit or explicit NULL label). 501 6.2. IPv6 Dataplane 503 A BGP speaker that originates a prefix attaches the Prefix-SID 504 attribute when it advertises the prefix to its neighbors. The IPv6 505 SID TLV MUST be present and the S-flag MUST be set. 507 A BGP speaker that advertises a path received from one of its 508 neighbors SHOULD advertise the Prefix-SID received with the path 509 without modification regardless of whether the Prefix-SID was 510 acceptable. If the path did not come with a Prefix-SID attribute, 511 the speaker MAY attach a Prefix-SID to the path if configured to do 512 so. The IPv6-SID TLV MUST be present in the Prefix-SID and with the 513 S-flag set. 515 7. Error Handling of BGP-Prefix-SID Attribute 517 When a BGP Speaker receives a BGP Update message containing a 518 malformed BGP Prefix-SID attribute, it MUST ignore the received BGP 519 Prefix-SID attributes and not pass it to other BGP peers. This is 520 equivalent to the -attribute discard- action specified in [RFC7606]. 521 When discarding an attribute, a BGP speaker MAY log an error for 522 further analysis. 524 If the BGP Prefix-SID attribute appears more than once in an BGP 525 Update message message, then, according to [RFC7606], all the 526 occurrences of the attribute other than the first one SHALL be 527 discarded and the BGP Update message shall continue to be processed. 529 When a BGP speaker receives an unacceptable Prefix-SID attribute, it 530 MAY log an error for further analysis. 532 8. IANA Considerations 534 This document defines a new BGP path attribute known as the BGP 535 Prefix-SID attribute. This document requests IANA to assign a new 536 attribute code type (suggested value: 40) for BGP the Prefix-SID 537 attribute from the BGP Path Attributes registry. 539 This document defines 3 new TLVs for BGP Prefix-SID attribute. These 540 TLVs need to be registered with IANA. We request IANA to create a 541 new registry for BGP Prefix-SID Attribute TLVs as follows: 543 Under "Border Gateway Protocol (BGP) Parameters" registry, "BGP 544 Prefix SID attribute Types" Reference: draft-ietf-idr-bgp-prefix- 545 sid-00 Registration Procedure(s): Values 1-254 First Come, First 546 Served, Value 0 and 255 reserved 548 Value Type Reference 549 0 Reserved draft-ietf-idr-bgp-prefix-sid-00 550 1 Label-Index draft-ietf-idr-bgp-prefix-sid-00 551 2 IPv6 SID draft-ietf-idr-bgp-prefix-sid-00 552 3 Originator SRGB draft-ietf-idr-bgp-prefix-sid-00 553 4-254 Unassigned 554 255 Reserved draft-ietf-idr-bgp-prefix-sid-00 556 9. Security Considerations 558 This document introduces no new security considerations above and 559 beyond those already specified in [RFC4271] and [RFC3107]. 561 10. Acknowledgements 563 The authors would like to thanks Satya Mohanty and Acee Lindem for 564 their contribution to this document. 566 11. Change Log 568 Initial Version: Sep 21 2014 570 12. References 572 12.1. Normative References 574 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 575 Requirement Levels", BCP 14, RFC 2119, 576 DOI 10.17487/RFC2119, March 1997, 577 . 579 [RFC3107] Rekhter, Y. and E. Rosen, "Carrying Label Information in 580 BGP-4", RFC 3107, DOI 10.17487/RFC3107, May 2001, 581 . 583 [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A 584 Border Gateway Protocol 4 (BGP-4)", RFC 4271, 585 DOI 10.17487/RFC4271, January 2006, 586 . 588 [RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private 589 Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February 590 2006, . 592 [RFC7606] Chen, E., Ed., Scudder, J., Ed., Mohapatra, P., and K. 593 Patel, "Revised Error Handling for BGP UPDATE Messages", 594 RFC 7606, DOI 10.17487/RFC7606, August 2015, 595 . 597 12.2. Informative References 599 [I-D.filsfils-spring-segment-routing-central-epe] 600 Filsfils, C., Previdi, S., Patel, K., Shaw, S., Ginsburg, 601 D., and D. Afanasiev, "Segment Routing Centralized Egress 602 Peer Engineering", draft-filsfils-spring-segment-routing- 603 central-epe-05 (work in progress), August 2015. 605 [I-D.ietf-idr-bgpls-segment-routing-epe] 606 Previdi, S., Filsfils, C., Ray, S., Patel, K., Dong, J., 607 and M. Chen, "Segment Routing Egress Peer Engineering BGP- 608 LS Extensions", draft-ietf-idr-bgpls-segment-routing- 609 epe-00 (work in progress), June 2015. 611 [I-D.ietf-spring-segment-routing] 612 Filsfils, C., Previdi, S., Decraene, B., Litkowski, S., 613 and r. rjs@rob.sh, "Segment Routing Architecture", draft- 614 ietf-spring-segment-routing-05 (work in progress), 615 September 2015. 617 [I-D.ietf-spring-segment-routing-msdc] 618 Filsfils, C., Previdi, S., Mitchell, J., and P. Lapukhov, 619 "BGP-Prefix Segment in large-scale data centers", draft- 620 ietf-spring-segment-routing-msdc-00 (work in progress), 621 October 2015. 623 [I-D.previdi-6man-segment-routing-header] 624 Previdi, S., Filsfils, C., Field, B., Leung, I., Linkova, 625 J., Kosugi, T., Vyncke, E., and D. Lebrun, "IPv6 Segment 626 Routing Header (SRH)", draft-previdi-6man-segment-routing- 627 header-08 (work in progress), October 2015. 629 [RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter, 630 "Multiprotocol Extensions for BGP-4", RFC 4760, 631 DOI 10.17487/RFC4760, January 2007, 632 . 634 Authors' Addresses 636 Stefano Previdi 637 Cisco Systems 638 Via Del Serafico, 200 639 Rome 00142 640 Italy 642 Email: sprevidi@cisco.com 644 Clarence Filsfils 645 Cisco Systems 646 Brussels 647 Belgium 649 Email: cfilsfils@cisco.com 651 Acee Lindem 652 Cisco Systems 653 170 W. Tasman Drive 654 San Jose, CA 95124 95134 655 USA 657 Email: acee@cisco.com 658 Keyur Patel 659 Cisco Systems 660 170 W. Tasman Drive 661 San Jose, CA 95124 95134 662 USA 664 Email: keyupate@cisco.com 666 Arjun Sreekantiah 667 Cisco Systems 668 170 W. Tasman Drive 669 San Jose, CA 95124 95134 670 USA 672 Email: asreekan@cisco.com 674 Saikat Ray 675 Unaffiliated 677 Email: raysaikat@gmail.com 679 Hannes Gredler 680 Juniper Networks 682 Email: hannes@juniper.net