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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Inter-Domain Routing G. Dawra, Ed. 3 Internet-Draft LinkedIn 4 Intended status: Standards Track C. Filsfils 5 Expires: September 7, 2019 K. Talaulikar, Ed. 6 Cisco Systems 7 M. Chen 8 Huawei 9 D. Bernier 10 Bell Canada 11 J. Uttaro 12 AT&T 13 B. Decraene 14 Orange 15 H. Elmalky 16 Ericsson 17 March 6, 2019 19 BGP Link State Extensions for SRv6 20 draft-dawra-idr-bgpls-srv6-ext-05 22 Abstract 24 Segment Routing IPv6 (SRv6) allows for a flexible definition of end- 25 to-end paths within various topologies by encoding paths as sequences 26 of topological or functional sub-paths, called "segments". These 27 segments are advertised by the various protocols such as BGP, ISIS 28 and OSPFv3. 30 BGP Link-state (BGP-LS) address-family solution for SRv6 is similar 31 to BGP-LS for SR for MPLS dataplane. This draft defines extensions 32 to the BGP-LS to advertise SRv6 Segments along with their functions 33 and other attributes via BGP. 35 Requirements Language 37 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 38 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 39 "OPTIONAL" in this document are to be interpreted as described in BCP 40 14 [RFC2119] [RFC8174] when, and only when, they appear in all 41 capitals, as shown here. 43 Status of This Memo 45 This Internet-Draft is submitted in full conformance with the 46 provisions of BCP 78 and BCP 79. 48 Internet-Drafts are working documents of the Internet Engineering 49 Task Force (IETF). Note that other groups may also distribute 50 working documents as Internet-Drafts. The list of current Internet- 51 Drafts is at https://datatracker.ietf.org/drafts/current/. 53 Internet-Drafts are draft documents valid for a maximum of six months 54 and may be updated, replaced, or obsoleted by other documents at any 55 time. It is inappropriate to use Internet-Drafts as reference 56 material or to cite them other than as "work in progress." 58 This Internet-Draft will expire on September 7, 2019. 60 Copyright Notice 62 Copyright (c) 2019 IETF Trust and the persons identified as the 63 document authors. All rights reserved. 65 This document is subject to BCP 78 and the IETF Trust's Legal 66 Provisions Relating to IETF Documents 67 (https://trustee.ietf.org/license-info) in effect on the date of 68 publication of this document. Please review these documents 69 carefully, as they describe your rights and restrictions with respect 70 to this document. Code Components extracted from this document must 71 include Simplified BSD License text as described in Section 4.e of 72 the Trust Legal Provisions and are provided without warranty as 73 described in the Simplified BSD License. 75 Table of Contents 77 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 78 2. BGP-LS Extensions for SRv6 . . . . . . . . . . . . . . . . . 4 79 3. SRv6 Node Attributes . . . . . . . . . . . . . . . . . . . . 5 80 3.1. SRv6 Capabilities TLV . . . . . . . . . . . . . . . . . . 5 81 3.2. SRv6 Node MSD Types . . . . . . . . . . . . . . . . . . . 6 82 4. SRv6 Link Attributes . . . . . . . . . . . . . . . . . . . . 7 83 4.1. SRv6 End.X SID TLV . . . . . . . . . . . . . . . . . . . 7 84 4.2. SRv6 LAN End.X SID TLV . . . . . . . . . . . . . . . . . 9 85 4.3. SRv6 Link MSD Types . . . . . . . . . . . . . . . . . . . 11 86 5. SRv6 Prefix Attributes . . . . . . . . . . . . . . . . . . . 12 87 5.1. SRv6 Locator TLV . . . . . . . . . . . . . . . . . . . . 12 88 6. SRv6 SID NLRI . . . . . . . . . . . . . . . . . . . . . . . . 14 89 6.1. SRv6 SID Information TLV . . . . . . . . . . . . . . . . 15 90 7. SRv6 SID Attributes . . . . . . . . . . . . . . . . . . . . . 16 91 7.1. SRv6 Endpoint Function TLV . . . . . . . . . . . . . . . 16 92 7.2. SRv6 BGP Peer Node SID TLV . . . . . . . . . . . . . . . 17 93 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 94 8.1. BGP-LS NLRI-Types . . . . . . . . . . . . . . . . . . . . 19 95 8.2. BGP-LS TLVs . . . . . . . . . . . . . . . . . . . . . . . 19 97 9. Manageability Considerations . . . . . . . . . . . . . . . . 20 98 10. Operational Considerations . . . . . . . . . . . . . . . . . 20 99 10.1. Operations . . . . . . . . . . . . . . . . . . . . . . . 20 100 11. Security Considerations . . . . . . . . . . . . . . . . . . . 20 101 12. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 20 102 13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 21 103 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 21 104 14.1. Normative References . . . . . . . . . . . . . . . . . . 21 105 14.2. Informative References . . . . . . . . . . . . . . . . . 23 106 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 23 108 1. Introduction 110 SRv6 refers to Segment Routing instantiated on the IPv6 dataplane 111 [RFC8402]. Segment Identifier (SID) is often used as a shorter 112 reference for "SRv6 Segment". 114 The network programming paradigm 115 [I-D.filsfils-spring-srv6-network-programming] is central to SRv6. 116 It describes how different functions can be bound to their SIDs and 117 how a network program can be expressed as a combination of SIDs. 119 An SRv6-capable node N maintains a "My SID Table" (refer 120 [I-D.filsfils-spring-srv6-network-programming]). This table contains 121 all the SRv6 segments explicitly instantiated at node N. 123 The IS-IS [I-D.bashandy-isis-srv6-extensions] and OSPFv3 124 [I-D.li-ospf-ospfv3-srv6-extensions] link-state routing protocols 125 have been extended to advertise some of these SRv6 SIDs and 126 SRv6-related information. BGP ([I-D.dawra-idr-srv6-vpn]) has been 127 extended to advertise some of these SRv6 SIDs for VPN services. 128 Certain other SRv6 SIDs may be instantiated on a node via other 129 mechanisms for topological or service functionalities. 131 The advertisement of SR related information along with the topology 132 for the MPLS dataplane instantiation is specified in 133 [I-D.ietf-idr-bgp-ls-segment-routing-ext] and for the BGP Egress Peer 134 Engineering (EPE) is specified in 135 [I-D.ietf-idr-bgpls-segment-routing-epe]. On the similar lines, 136 introducing the SRv6 related information in BGP-LS allows it's 137 consumer applications that require topological visibility to also 138 receive the "My SID Table" from nodes across a domain or even across 139 Autonomous Systems (AS), as required. This allows applications to 140 leverage the SRv6 capabilities for network programming. 142 The identifying key of each Link-State object, namely a node, link, 143 or prefix, is encoded in the NLRI and the properties of the object 144 are encoded in the BGP-LS Attribute [RFC7752]. 146 This document describes extensions to BGP-LS to advertise the SRv6 147 "My SID Table" and other SRv6 information from all the SRv6 capable 148 nodes in the domain when sourced from link-state routing protocols 149 and directly from individual SRv6 capable nodes when sourced from 150 BGP. 152 2. BGP-LS Extensions for SRv6 154 BGP-LS[RFC7752] defines the BGP Node, Link and Prefix attributes. 155 All non-VPN link, node, and prefix information SHALL be encoded using 156 AFI 16388 / SAFI 71. VPN link, node, and prefix information SHALL be 157 encoded using AFI 16388 / SAFI 72. 159 The SRv6 information pertaining to a node is advertised via the BGP- 160 LS Node NLRI and using the BGP-LS Attribute TLVs as follows: 162 o SRv6 Capabilities of the node is advertised via a new SRv6 163 Capabilities TLV 165 o New MSD types introduced for SRv6 are advertised as new sub-TLVs 166 of the Node MSD TLV specified in 167 [I-D.ietf-idr-bgp-ls-segment-routing-msd]. 169 o Algorithm support for SRv6 is advertised via the existing SR 170 Algorithm TLV specified in 171 [I-D.ietf-idr-bgp-ls-segment-routing-ext]. 173 The SRv6 information pertaining to a link is advertised via the BGP- 174 LS Link NLRI and using the BGP-LS Attribute TLVs as follows: 176 o SRv6 End.X SID of the link state routing adjacency or the BGP EPE 177 Peer Adjacency is advertised via a new SRv6 End.X SID TLV 179 o SRv6 LAN End.X SID of the link state routing adjacency to a non- 180 DR/DIS router is advertised via a new SRv6 LAN End.X SID TLV 182 o New MSD types introduced for SRv6 are advertised as new sub-TLVs 183 of the Link MSD TLV specified in 184 [I-D.ietf-idr-bgp-ls-segment-routing-msd]. 186 The SRv6 Locator information of a node is advertised via the BGP-LS 187 Prefix NLRI using the new SRv6 Locator TLV in the BGP-LS Attribute. 189 The SRv6 SIDs associated with the node from its "My SID Table" are 190 advertised as a newly introduce BGP-LS SRv6 SID NLRI. This enables 191 the BGP-LS encoding to scale to cover a potentially large set of SRv6 192 SIDs instantiated on a node with the granularity of individual SIDs 193 and without affecting the size and scalability of the BGP-LS updates. 195 New BGP-LS Attribute TLVs are introduced for the SRv6 SID NLRI as 196 follows: 198 o The endpoint function of the SRv6 SID is advertised via a new SRv6 199 Endpoint Function TLV 201 o The BGP EPE Peer Node and Peer Set SID context is advertised via a 202 new SRv6 BGP EPE Peer Node SID TLV 204 When the BGP-LS router is advertising topology information that it 205 sources from the underlying link-state routing protocol, then it maps 206 the corresponding SRv6 information from the SRv6 extensions for IS-IS 207 [I-D.bashandy-isis-srv6-extensions] and OSPFv3 208 [I-D.li-ospf-ospfv3-srv6-extensions] protocols to their BGP-LS TLVs/ 209 sub-TLVs for all SRv6 capable nodes in that routing protocol domain. 210 When the BGP-LS router is advertising topology information from the 211 BGP routing protocol [I-D.ietf-idr-bgpls-segment-routing-epe], then 212 it advertises the SRv6 information from the local node alone (e.g. 213 BGP EPE topology information or in the case of a data center network 214 running BGP as the only routing protocol). 216 Subsequent sections of this document specify the encoding of the 217 newly defined extensions. 219 3. SRv6 Node Attributes 221 SRv6 attributes of a node are advertised using the new BGP-LS 222 Attribute TLVs defined in this section and associated with the BGP-LS 223 Node NLRI. 225 3.1. SRv6 Capabilities TLV 227 This BGP-LS Attribute TLV is used to announce the SRv6 capabilities 228 of the node along with the BGP-LS Node NLRI and indicates the SRv6 229 support by the node. A single instance of this TLV MUST be included 230 in the BGP-LS attribute for each SRv6 capable node. This TLV maps to 231 the SRv6 Capabilities sub-TLV and the SRv6 Capabilities TLV of the 232 IS-IS and OSPFv3 protocol SRv6 extensions respectively. 234 0 1 2 3 235 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 1 236 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 237 | Type | Length | 238 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 239 | Flags | Reserved | 240 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 242 Figure 1: SRv6 Capabilities TLV Format 244 Where: 246 o Type: 2 octet field with value TBD, see Section 8. 248 o Length : 2 octet field with value set to 4. 250 o Flags: 2 octet field. The following flags are defined: 252 0 1 253 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 254 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 255 | |O| | 256 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 258 Figure 2: SRv6 Capability TLV Flags Format 260 * O-flag: If set, then router is capable of supporting SRH O-bit 261 Flags, as specified in [I-D.ali-spring-srv6-oam]. 263 o Reserved: 2 octet that SHOULD be set to 0 and MUST be ignored on 264 receipt. 266 3.2. SRv6 Node MSD Types 268 The Node MSD TLV [I-D.ietf-idr-bgp-ls-segment-routing-msd] of the 269 BGP-LS Attribute of the Node NLRI is also used to advertise the 270 limits and the supported Segment Routing Header (SRH) 271 [I-D.ietf-6man-segment-routing-header] operations supported by the 272 SRv6 capable node. The SRv6 MSD Types specified in 273 [I-D.bashandy-isis-srv6-extensions] are also used with the BGP-LS 274 Node MSD TLV as these codepoints are shared between IS-IS, OSPF and 275 BGP-LS protocols. The description and semantics of these new MSD 276 types for BGP-LS are identical as specified 277 [I-D.bashandy-isis-srv6-extensions] and summarized in the table 278 below: 280 +----------+------------------------------+ 281 | MSD Type | Description | 282 +----------+------------------------------+ 283 | TBD | Maximum Segments Left | 284 | TBD | Maximum End Pop | 285 | TBD | Maximum T.Insert | 286 | TBD | Maximum T.Encaps | 287 | TBD | Maximum End D | 288 +----------+------------------------------+ 290 Figure 3: SRv6 Node MSD Types 292 Each MSD type is encoded as a one octet type followed by a one octet 293 value. 295 4. SRv6 Link Attributes 297 SRv6 attributes and SIDs associated with a link or adjacency are 298 advertised using the new BGP-LS Attribute TLVs defined in this 299 section and associated with the BGP-LS Link NLRI. 301 4.1. SRv6 End.X SID TLV 303 The SRv6 End.X SID TLV is used to advertise the SRv6 End.X SIDs that 304 correspond to a point-to-point or point-to-multipoint link or 305 adjacency of the local node for IS-IS and OSPFv3 protocols. This TLV 306 can also be used to advertise the End.X function SRv6 SID 307 corresponding to the underlying layer-2 member links for a layer-3 308 bundle interface using L2 Bundle Member Attribute TLV as specified in 309 [I-D.ietf-idr-bgp-ls-segment-routing-ext] . 311 For the nodes running BGP routing protocol, this TLV is used to 312 advertise the BGP EPE Peer Adjacency SID for SRv6 on the same lines 313 as specified for SR/MPLS in [I-D.ietf-idr-bgpls-segment-routing-epe]. 314 The SRv6 End.X SID for the BGP Peer Adjacency indicates the cross- 315 connect to a specific layer-3 link to the specific BGP session peer 316 (neighbor). 318 The TLV has the following 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 | 324 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 325 | SRv6 Endpoint Function | Flags | Algorithm | 326 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 327 | Weight | Reserved | SID (16 octets) ... 328 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 329 SID (cont ...) 330 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 331 SID (cont ...) 332 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 333 SID (cont ...) 334 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 335 SID (cont ...) | Sub-TLVs (variable) . . . 336 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 338 Figure 4: SRv6 End.X TLV Format 340 Where: 342 Type: 2 octet field with value TBD, see Section 8. 344 Length: 2 octet field with the total length of the value portion 345 of the TLV. 347 Function Code: 2 octet field. The Endpoint Function code point 348 for this SRv6 SID as defined in 349 [I-D.filsfils-spring-srv6-network-programming]. 351 Flags: 1 octet of flags with the following definition: 353 0 1 2 3 4 5 6 7 354 +-+-+-+-+-+-+-+-+ 355 |B|S|P| Rsvd | 356 +-+-+-+-+-+-+-+-+ 358 Figure 5: SRv6 End.X SID TLV Flags Format 360 * B-Flag: Backup Flag. If set, the SID is eligible for 361 protection (e.g. using IPFRR) as described in [RFC8355]. 363 * S-Flag: Set Flag. When set, the S-Flag indicates that the SID 364 refers to a set of adjacencies (and therefore MAY be assigned 365 to other adjacencies as well). 367 * P-Flag: Persistent Flag: When set, the P-Flag indicates that 368 the SID is persistently allocated, i.e., the value remains 369 consistent across router restart and/or interface flap. 371 * Rsvd bits: Reserved for future use and MUST be zero when 372 originated and ignored when received. 374 Algorithm: 1 octet field. Algorithm associated with the SID. 375 Algorithm values are defined in the IGP Algorithm Type registry. 377 Weight: 1 octet field. The value represents the weight of the SID 378 for the purpose of load balancing. The use of the weight is 379 defined in [RFC8402]. 381 Reserved: 1 octet field that SHOULD be set to 0 and MUST be 382 ignored on receipt. 384 SID: 16 octet field. This field encodes the advertised SRv6 SID 385 as 128 bit value. 387 Sub-TLVs : currently none defined. Used to advertise sub-TLVs 388 that provide additional attributes for the given SRv6 End.X SID. 390 4.2. SRv6 LAN End.X SID TLV 392 For a LAN interface, normally a node only announces its adjacency to 393 the IS-IS pseudo-node (or the equivalent OSPF Designated Router). 394 The SRv6 LAN End.X SID TLV allows a node to announce SRv6 SID 395 corresponding to functions like END.X for its adjacencies to all 396 other (i.e. non-DIS or non-DR) nodes attached to the LAN in a single 397 instance of the BGP-LS Link NLRI. Without this TLV, the 398 corresponding BGP-LS link NLRI would need to be originated for each 399 additional adjacency in order to advertise the SRv6 End.X SID TLVs 400 for these neighbor adjacencies. 402 The SRv6 LAN End.X SID TLV has the following format: 404 0 1 2 3 405 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 1 406 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 407 | Type | Length | 408 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 409 | SRv6 Endpoint Function | Flags | Algorithm | 410 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 411 | Weight | Reserved | ISIS System-ID (6 octets) | 412 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 413 | or OSPFv3 Router-ID (4 octets) of the neighbor | 414 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 415 | SID (16 octets) ... 416 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 417 SID (cont ...) 418 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 419 SID (cont ...) 420 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 421 SID (cont ...) | 422 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 423 | Sub-TLVs (variable) . . . 424 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 426 Figure 6: SRv6 LAN End.X SID TLV Format 428 Where: 430 o Type: 2 octet field with value TBD, see Section 8. 432 o Length: 2 octet field with the total length of the value portion 433 of the TLV. 435 o Function Code: 2 octet field. The Endpoint Function code point 436 for this SRv6 SID as defined in 437 [I-D.filsfils-spring-srv6-network-programming]. 439 o Flags: 1 octet of flags with the following definition: 441 0 1 2 3 4 5 6 7 442 +-+-+-+-+-+-+-+-+ 443 |B|S|P| Rsvd | 444 +-+-+-+-+-+-+-+-+ 446 Figure 7: SRv6 LAN End.X SID TLV Flags Format 448 * B-Flag: Backup Flag. If set, the SID is eligible for 449 protection (e.g. using IPFRR) as described in [RFC8355]. 451 * S-Flag: Set Flag. When set, the S-Flag indicates that the SID 452 refers to a set of adjacencies (and therefore MAY be assigned 453 to other adjacencies as well). 455 * P-Flag: Persistent Flag: When set, the P-Flag indicates that 456 the SID is persistently allocated, i.e., the value remains 457 consistent across router restart and/or interface flap. 459 * Rsvd bits: Reserved for future use and MUST be zero when 460 originated and ignored when received. 462 o Algorithm: 1 octet field. Algorithm associated with the SID. 463 Algorithm values are defined in the IGP Algorithm Type registry. 465 o Weight: 1 octet field. The value represents the weight of the SID 466 for the purpose of load balancing. The use of the weight is 467 defined in [RFC8402]. 469 o Reserved: 1 octet field that SHOULD be set to 0 and MUST be 470 ignored on receipt. 472 o Neighbor ID : 6 octets of ISIS System ID of the neighbor when 473 protocol is ISIS or 4 octets of OSPFv3 Router-id of the neighbor 474 when protocol is OSPFv3. The protocol is determined by the 475 Protocol-ID field of the BGP-LS Link NLRI. 477 o SID: 16 octet field. This field encodes the advertised SRv6 SID 478 as 128 bit value. 480 o Sub-TLVs : currently none defined. Used to advertise sub-TLVs 481 that provide additional attributes for the given SRv6 LAN End.X 482 SID. 484 4.3. SRv6 Link MSD Types 486 The Link MSD TLV [I-D.ietf-idr-bgp-ls-segment-routing-msd] of the 487 BGP-LS Attribute of the Link NLRI is also used to advertise the 488 limits and the supported Segment Routing Header (SRH) operations 489 supported on the specific link by the SRv6 capable node. The SRv6 490 MSD Types specified in [I-D.bashandy-isis-srv6-extensions] are also 491 used with the BGP-LS Link MSD TLV as these codepoints are shared 492 between IS-IS, OSPF and BGP-LS protocols. The description and 493 semantics of these new MSD types for BGP-LS are identical as 494 specified [I-D.bashandy-isis-srv6-extensions] and summarized in the 495 table below: 497 +----------+------------------------------+ 498 | MSD Type | Description | 499 +----------+------------------------------+ 500 | TBD | Maximum Segments Left | 501 | TBD | Maximum End Pop | 502 | TBD | Maximum T.Insert | 503 | TBD | Maximum T.Encaps | 504 | TBD | Maximum End D | 505 +----------+------------------------------+ 507 Figure 8: SRv6 Link MSD Types 509 Each MSD type is encoded as a one octet type followed by a one octet 510 value. 512 5. SRv6 Prefix Attributes 514 SRv6 attributes with an IPv6 prefix are advertised using the new BGP- 515 LS Attribute TLVs defined in this section and associated with the 516 BGP-LS Prefix NLRI. 518 5.1. SRv6 Locator TLV 520 As described in [I-D.filsfils-spring-srv6-network-programming], an 521 SRv6 SID is 128 bits and represented as 523 LOC:FUNCT 525 where LOC (the locator portion) is the L most significant bits and 526 FUNCT is the 128-L least significant bits. L is called the locator 527 length and is flexible. A node is provisioned with one or more 528 locators supported by that node. Locators are covering prefixes for 529 the set of SIDs provisioned on that node. These Locators are 530 advertised as BGP-LS Prefix NLRI objects along with the SRv6 Locator 531 TLV in its BGP-LS Attribute. 533 The IPv6 Prefix matching the Locator MAY be also advertised as a 534 prefix reachability by the underlying routing protocol. In this 535 case, the Prefix NLRI would be also associated with the Prefix Metric 536 TLV that carries the routing metric for this prefix. When the 537 Locator prefix is not being advertised as a prefix reachability, then 538 the Prefix NLRI would have the SRv6 Locator TLV associated with it 539 but no Prefix Metric TLV. In the absence of Prefix Metric TLV, the 540 consumer of the BGP-LS topology information MUST NOT interpret the 541 Locator prefix as a prefix reachability routing advertisement. 543 The SRv6 Locator TLV has the following format: 545 0 1 2 3 546 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 1 547 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 548 | Type | Length | 549 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 550 | Flags | Algorithm | Reserved | 551 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 552 | Metric | 553 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 554 | Sub-TLVs (variable) . . . 555 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 557 Figure 9: SRv6 Locator TLV Format 559 Where: 561 Type: 2 octet field with value TBD, see Section 8. 563 Length: 2 octet field with the total length of the value portion 564 of the TLV. 566 Flags: 1 octet of flags with the following definition: 568 0 1 2 3 4 5 6 7 569 +-+-+-+-+-+-+-+-+ 570 |D|A| Reserved | 571 +-+-+-+-+-+-+-+-+ 573 Figure 10: SRv6 Locator TLV Flags Format 575 * D-Flag: Indicates that the locator has been leaked into the IGP 576 domain when set. IS-IS operations for this are discussed in 577 [I-D.bashandy-isis-srv6-extensions]. 579 * A-Flag: When the Locator is associated with anycast 580 destinations, the A flag SHOULD be set. Otherwise, this bit 581 MUST be clear. 583 * Reserved bits: Reserved for future use and MUST be zero when 584 originated and ignored when received. 586 Algorithm: 1 octet field. Algorithm associated with the SID. 587 Algorithm values are defined in the IGP Algorithm Type registry. 589 Reserved: 2 octet field. The value MUST be zero when originated 590 and ignored when received. 592 Metric: 4 octet field. The value of the metric for the Locator. 594 Sub-TLVs : currently none defined. Used to advertise sub-TLVs 595 that provide additional attributes for the given SRv6 Locator. 597 6. SRv6 SID NLRI 599 SRv6 SID information is advertised in BGP UPDATE messages using the 600 MP_REACH_NLRI and MP_UNREACH_NLRI attributes [RFC4760]. The "Link- 601 State NLRI" defined in [RFC7752] is extended to carry the SRv6 SID 602 information. 604 A new "Link-State NLRI Type" is defined for SRv6 SID information as 605 following: 607 o Link-State NLRI Type: SRv6 SID NLRI (value TBD see IANA 608 Considerations Section 8.1). 610 The format of this new NLRI type is as shown in the following figure: 612 0 1 2 3 613 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 1 614 +-+-+-+-+-+-+-+-+ 615 | Protocol-ID | 616 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 617 | Identifier | 618 | (64 bits) | 619 ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+| 620 | Local Node Descriptors (variable) // 621 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 622 | SRv6 SID Descriptors (variable) // 623 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 625 Figure 11: SRv6 SID NLRI Format 627 Where: 629 o Protocol-ID: 1 octet field that specifies the protocol component 630 through which BGP-LS learns the SRv6 SIDs of the node. The 631 following Protocol-IDs apply to the SRv6 SID NLRI: 633 +-------------+----------------------------------+ 634 | Protocol-ID | NLRI information source protocol | 635 +-------------+----------------------------------+ 636 | 1 | IS-IS Level 1 | 637 | 2 | IS-IS Level 2 | 638 | 4 | Direct | 639 | 5 | Static configuration | 640 | 6 | OSPFv3 | 641 | 7 | BGP | 642 +-------------+----------------------------------+ 644 Figure 12: Protocol IDs for SRv6 SID NLRI 646 o Identifier: 8 octet value as defined in [RFC7752]. 648 o Local Node Descriptors TLV: as defined in [RFC7752] for IGPs, 649 local and static configuration and as defined in 650 [I-D.ietf-idr-bgpls-segment-routing-epe] for BGP protocol. 652 o SRv6 SID Descriptors: MUST include the SRv6 SID Information TLV 653 defined in Section 6.1 and optionally MAY include the Multi- 654 Topology Identifier TLV as defined in [RFC7752]. 656 New TLVs carried in the BGP Link State Attribute defined in [RFC7752] 657 are also defined in order to carry the attributes of a SRv6 SID in 658 Section 7. 660 6.1. SRv6 SID Information TLV 662 A SRv6 SID is a 128 bit value 663 [I-D.filsfils-spring-srv6-network-programming] and is encoded using 664 the SRv6 SID Information TLV. 666 The TLV has the following format: 668 0 1 2 3 669 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 1 670 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 671 | Type | Length | 672 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 673 | SID (16 octets) ... 674 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 675 SID (cont ...) 676 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 677 SID (cont ...) 678 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 679 SID (cont ...) | 680 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 682 Figure 13: SRv6 SID Information TLV Format 684 Where: 686 Type: 2 octet field with value TBD, see Section 8. 688 Length: 2 octet field with value set to 16. 690 SID: 16 octet field. This field encodes the advertised SRv6 SID 691 as 128 bit value. 693 7. SRv6 SID Attributes 695 This section specifies the new TLVs to be carried in the BGP Link 696 State Attribute associated with the BGP-LS SRv6 SID NLRI. 698 7.1. SRv6 Endpoint Function TLV 700 Each SRv6 SID instantiated in the "My SID Table" of an SRv6 capable 701 node has a specific instruction bound to it. A set of well-known 702 functions that can be associated with a SID are defined in 703 [I-D.filsfils-spring-srv6-network-programming]. 705 The SRv6 Endpoint Function TLV is a mandatory TLV that MUST be 706 included in the BGP-LS Attribute associated with the BGP-LS SRv6 SID 707 NLRI. The TLV has the following format: 709 0 1 2 3 710 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 1 711 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 712 | Type | Length | 713 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 714 | SRv6 Endpoint Function | Flags | Algorithm | 715 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 717 Figure 14: SRv6 Endpoint Function TLV 719 Where: 721 Type: 2 octet field with value TBD, see Section 8. 723 Length: 2 octet field with the value 4. 725 Function Code: 2 octet field. The Endpoint Function code point 726 for this SRv6 SID as defined in 727 [I-D.filsfils-spring-srv6-network-programming]. 729 Flags: 1 octet of flags with the none defined currently. Reserved 730 for future use and MUST be zero when originated and ignored when 731 received. 733 Algorithm: 1 octet field. Algorithm associated with the SID. 734 Algorithm values are defined in the IGP Algorithm Type registry. 736 7.2. SRv6 BGP Peer Node SID TLV 738 The BGP Peer Node SID and Peer Set SID for SR with MPLS dataplane are 739 specified in [I-D.ietf-idr-bgpls-segment-routing-epe]. The similar 740 Peer Node and Peer Set SID functionality can be realized with SRv6 741 using the END.X SRv6 SID. The SRv6 BGP Peer Node SID TLV is an 742 optional TLV for use in the BGP-LS Attribute for an SRv6 SID NLRI 743 corresponding to BGP protocol. This TLV MUST be included along with 744 SRv6 End.X SID that is associated with the BGP Peer Node or Peer Set 745 functionality. 747 The TLV has the following format: 749 0 1 2 3 750 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 1 751 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 752 | Type | Length | 753 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 754 | Flags | Weight | Reserved | 755 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 756 | Peer AS Number | 757 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 758 | Peer BGP Identifier | 759 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 761 Figure 15: SRv6 BGP Peer Node SID TLV Format 763 Where: 765 o Type: 2 octet field with value TBD, see Section 8. 767 o Length: 2 octet field with the value 12. 769 o Flags: 1 octet of flags with the following definition: 771 0 1 2 3 4 5 6 7 772 +-+-+-+-+-+-+-+-+ 773 |B|S|P| Rsvd | 774 +-+-+-+-+-+-+-+-+ 776 Figure 16: SRv6 BGP Peer End.X SID TLV Flags Format 778 * B-Flag: Backup Flag. If set, the SID is eligible for 779 protection (e.g. using IPFRR) as described in [RFC8355]. 781 * S-Flag: Set Flag. When set, the S-Flag indicates that the SID 782 refers to a set of BGP peering sessions (i.e. BGP Peer Set SID 783 functionality) and therefore MAY be assigned to one or more 784 End.X SIDs associated with BGP peer sessions. 786 * P-Flag: Persistent Flag: When set, the P-Flag indicates that 787 the SID is persistently allocated, i.e., the value remains 788 consistent across router restart and/or session flap. 790 * Rsvd bits: Reserved for future use and MUST be zero when 791 originated and ignored when received. 793 o Weight: 1 octet field. The value represents the weight of the SID 794 for the purpose of load balancing. The use of the weight is 795 defined in [RFC8402]. 797 o Peer AS Number : 4 octets of BGP AS number of the peer router. 799 o Peer BGP Identifier : 4 octets of the BGP Identifier (BGP Router- 800 ID) of the peer router. 802 For a SRv6 BGP EPE Peer Node SID, one instance of this TLV is 803 associated with the SRv6 SID. For SRv6 BGP EPE Peer Set SID, 804 multiple instances of this TLV (one for each peer in the "peer set") 805 are associated with the SRv6 SID and the S (set/group) flag is SET. 807 8. IANA Considerations 809 This document requests assigning code-points from the IANA "Border 810 Gateway Protocol - Link State (BGP-LS) Parameters" registry as 811 described in the sub-sections below. 813 8.1. BGP-LS NLRI-Types 815 The following codepoints is suggested (to be assigned by IANA) from 816 within the sub-registry called "BGP-LS NLRI-Types": 818 +------+----------------------------+---------------+ 819 | Type | NLRI Type | Reference | 820 +------+----------------------------+---------------+ 821 | 6 | SRv6 SID | this document | 822 +------+----------------------------+---------------+ 824 Figure 17: SRv6 SID NLRI Type Codepoint 826 8.2. BGP-LS TLVs 828 The following TLV codepoints are suggested (to be assigned by IANA) 829 from within the sub-registry called "BGP-LS Node Descriptor, Link 830 Descriptor, Prefix Descriptor, and Attribute TLVs": 832 +----------+----------------------------------------+---------------+ 833 | TLV Code | Description | Value defined | 834 | Point | | in | 835 +----------+----------------------------------------+---------------+ 836 | TBD | SRv6 Capabilities TLV | this document | 837 | TBD | SRv6 End.X SID TLV | this document | 838 | TBD | SRv6 LAN End.X SID TLV | this document | 839 | TBD | SRv6 Locator TLV | this document | 840 | TBD | SRv6 SID Information TLV | this document | 841 | TBD | SRv6 Endpoint Function TLV | this document | 842 | TBD | SRv6 BGP Peer Node SID TLV | this document | 843 +----------+----------------------------------------+---------------+ 845 Figure 18: SRv6 BGP-LS Attribute TLV Codepoints 847 9. Manageability Considerations 849 This section is structured as recommended in[RFC5706] 851 10. Operational Considerations 853 10.1. Operations 855 Existing BGP and BGP-LS operational procedures apply. No additional 856 operation procedures are defined in this document. 858 11. Security Considerations 860 Procedures and protocol extensions defined in this document do not 861 affect the BGP security model. See the 'Security Considerations' 862 section of [RFC4271] for a discussion of BGP security. Also refer 863 to[RFC4272] and [RFC6952] for analysis of security issues for BGP. 865 12. Contributors 867 Arjun Sreekantiah 868 Individual 869 US 871 Les Ginsberg 872 Cisco Systems 873 US 874 Email: ginsberg@cisco.com 876 Shunwan Zhuang 877 Huawei 878 China 879 Email: zhuangshunwan@huawei.com 881 13. Acknowledgements 883 The authors would like to thank Peter Psenak and Arun Babu for their 884 review of this document and their comments. 886 14. References 888 14.1. Normative References 890 [I-D.ali-spring-srv6-oam] 891 Ali, Z., Filsfils, C., Kumar, N., Pignataro, C., 892 faiqbal@cisco.com, f., Gandhi, R., Leddy, J., Matsushima, 893 S., Raszuk, R., daniel.voyer@bell.ca, d., Dawra, G., 894 Peirens, B., Chen, M., and G. Naik, "Operations, 895 Administration, and Maintenance (OAM) in Segment Routing 896 Networks with IPv6 Data plane (SRv6)", draft-ali-spring- 897 srv6-oam-02 (work in progress), October 2018. 899 [I-D.bashandy-isis-srv6-extensions] 900 Psenak, P., Filsfils, C., Bashandy, A., Decraene, B., and 901 Z. Hu, "IS-IS Extensions to Support Routing over IPv6 902 Dataplane", draft-bashandy-isis-srv6-extensions-05 (work 903 in progress), March 2019. 905 [I-D.dawra-idr-srv6-vpn] 906 Dawra, G., Filsfils, C., Dukes, D., Brissette, P., 907 Camarillo, P., Leddy, J., daniel.voyer@bell.ca, d., 908 daniel.bernier@bell.ca, d., Steinberg, D., Raszuk, R., 909 Decraene, B., Matsushima, S., and S. Zhuang, "BGP 910 Signaling for SRv6 based Services.", draft-dawra-idr- 911 srv6-vpn-05 (work in progress), October 2018. 913 [I-D.filsfils-spring-srv6-network-programming] 914 Filsfils, C., Camarillo, P., Leddy, J., 915 daniel.voyer@bell.ca, d., Matsushima, S., and Z. Li, "SRv6 916 Network Programming", draft-filsfils-spring-srv6-network- 917 programming-07 (work in progress), February 2019. 919 [I-D.ietf-6man-segment-routing-header] 920 Filsfils, C., Previdi, S., Leddy, J., Matsushima, S., and 921 d. daniel.voyer@bell.ca, "IPv6 Segment Routing Header 922 (SRH)", draft-ietf-6man-segment-routing-header-16 (work in 923 progress), February 2019. 925 [I-D.ietf-idr-bgp-ls-segment-routing-ext] 926 Previdi, S., Talaulikar, K., Filsfils, C., Gredler, H., 927 and M. Chen, "BGP Link-State extensions for Segment 928 Routing", draft-ietf-idr-bgp-ls-segment-routing-ext-11 929 (work in progress), October 2018. 931 [I-D.ietf-idr-bgp-ls-segment-routing-msd] 932 Tantsura, J., Chunduri, U., Mirsky, G., Sivabalan, S., and 933 N. Triantafillis, "Signaling MSD (Maximum SID Depth) using 934 Border Gateway Protocol Link-State", draft-ietf-idr-bgp- 935 ls-segment-routing-msd-04 (work in progress), February 936 2019. 938 [I-D.ietf-idr-bgpls-segment-routing-epe] 939 Previdi, S., Talaulikar, K., Filsfils, C., Patel, K., Ray, 940 S., and J. Dong, "BGP-LS extensions for Segment Routing 941 BGP Egress Peer Engineering", draft-ietf-idr-bgpls- 942 segment-routing-epe-17 (work in progress), October 2018. 944 [I-D.li-ospf-ospfv3-srv6-extensions] 945 Li, Z., Hu, Z., Cheng, D., Talaulikar, K., and P. Psenak, 946 "OSPFv3 Extensions for SRv6", draft-li-ospf- 947 ospfv3-srv6-extensions-02 (work in progress), September 948 2018. 950 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 951 Requirement Levels", BCP 14, RFC 2119, 952 DOI 10.17487/RFC2119, March 1997, 953 . 955 [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and 956 S. Ray, "North-Bound Distribution of Link-State and 957 Traffic Engineering (TE) Information Using BGP", RFC 7752, 958 DOI 10.17487/RFC7752, March 2016, 959 . 961 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 962 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 963 May 2017, . 965 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 966 Decraene, B., Litkowski, S., and R. Shakir, "Segment 967 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 968 July 2018, . 970 14.2. Informative References 972 [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A 973 Border Gateway Protocol 4 (BGP-4)", RFC 4271, 974 DOI 10.17487/RFC4271, January 2006, 975 . 977 [RFC4272] Murphy, S., "BGP Security Vulnerabilities Analysis", 978 RFC 4272, DOI 10.17487/RFC4272, January 2006, 979 . 981 [RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter, 982 "Multiprotocol Extensions for BGP-4", RFC 4760, 983 DOI 10.17487/RFC4760, January 2007, 984 . 986 [RFC5706] Harrington, D., "Guidelines for Considering Operations and 987 Management of New Protocols and Protocol Extensions", 988 RFC 5706, DOI 10.17487/RFC5706, November 2009, 989 . 991 [RFC6952] Jethanandani, M., Patel, K., and L. Zheng, "Analysis of 992 BGP, LDP, PCEP, and MSDP Issues According to the Keying 993 and Authentication for Routing Protocols (KARP) Design 994 Guide", RFC 6952, DOI 10.17487/RFC6952, May 2013, 995 . 997 [RFC8355] Filsfils, C., Ed., Previdi, S., Ed., Decraene, B., and R. 998 Shakir, "Resiliency Use Cases in Source Packet Routing in 999 Networking (SPRING) Networks", RFC 8355, 1000 DOI 10.17487/RFC8355, March 2018, 1001 . 1003 Authors' Addresses 1005 Gaurav Dawra (editor) 1006 LinkedIn 1007 USA 1009 Email: gdawra.ietf@gmail.com 1011 Clarence Filsfils 1012 Cisco Systems 1013 Belgium 1015 Email: cfilsfil@cisco.com 1016 Ketan Talaulikar (editor) 1017 Cisco Systems 1018 India 1020 Email: ketant@cisco.com 1022 Mach Chen 1023 Huawei 1024 China 1026 Email: mach.chen@huawei.com 1028 Daniel Bernier 1029 Bell Canada 1030 Canada 1032 Email: daniel.bernier@bell.ca 1034 Jim Uttaro 1035 AT&T 1036 USA 1038 Email: ju1738@att.com 1040 Bruno Decraene 1041 Orange 1042 France 1044 Email: bruno.decraene@orange.com 1046 Hani Elmalky 1047 Ericsson 1048 USA 1050 Email: hani.elmalky@gmail.com