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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Inter-Domain Routing G. Dawra 3 Internet-Draft LinkedIn 4 Intended status: Standards Track C. Filsfils 5 Expires: May 17, 2021 K. Talaulikar, Ed. 6 Cisco Systems 7 M. Chen 8 Huawei 9 D. Bernier 10 Bell Canada 11 B. Decraene 12 Orange 13 November 13, 2020 15 BGP Link State Extensions for SRv6 16 draft-ietf-idr-bgpls-srv6-ext-05 18 Abstract 20 Segment Routing (SR) over IPv6 (SRv6) allows for a flexible 21 definition of end-to-end paths within various topologies by encoding 22 paths as sequences of topological or functional sub-paths, called 23 "segments". These segments are advertised by the various protocols 24 such as BGP, IS-IS and OSPFv3. 26 BGP Link-state (BGP-LS) address-family solution for SRv6 is similar 27 to BGP-LS for SR for MPLS data-plane. This draft defines extensions 28 to the BGP-LS to advertise SRv6 Segments along with their behaviors 29 and other attributes via BGP. 31 Status of This Memo 33 This Internet-Draft is submitted in full conformance with the 34 provisions of BCP 78 and BCP 79. 36 Internet-Drafts are working documents of the Internet Engineering 37 Task Force (IETF). Note that other groups may also distribute 38 working documents as Internet-Drafts. The list of current Internet- 39 Drafts is at https://datatracker.ietf.org/drafts/current/. 41 Internet-Drafts are draft documents valid for a maximum of six months 42 and may be updated, replaced, or obsoleted by other documents at any 43 time. It is inappropriate to use Internet-Drafts as reference 44 material or to cite them other than as "work in progress." 46 This Internet-Draft will expire on May 17, 2021. 48 Copyright Notice 50 Copyright (c) 2020 IETF Trust and the persons identified as the 51 document authors. All rights reserved. 53 This document is subject to BCP 78 and the IETF Trust's Legal 54 Provisions Relating to IETF Documents 55 (https://trustee.ietf.org/license-info) in effect on the date of 56 publication of this document. Please review these documents 57 carefully, as they describe your rights and restrictions with respect 58 to this document. Code Components extracted from this document must 59 include Simplified BSD License text as described in Section 4.e of 60 the Trust Legal Provisions and are provided without warranty as 61 described in the Simplified BSD License. 63 Table of Contents 65 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 66 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 67 2. BGP-LS Extensions for SRv6 . . . . . . . . . . . . . . . . . 4 68 3. SRv6 Node Attributes . . . . . . . . . . . . . . . . . . . . 5 69 3.1. SRv6 Capabilities TLV . . . . . . . . . . . . . . . . . . 5 70 3.2. SRv6 Node MSD Types . . . . . . . . . . . . . . . . . . . 6 71 4. SRv6 Link Attributes . . . . . . . . . . . . . . . . . . . . 7 72 4.1. SRv6 End.X SID TLV . . . . . . . . . . . . . . . . . . . 7 73 4.2. SRv6 LAN End.X SID TLV . . . . . . . . . . . . . . . . . 9 74 4.3. SRv6 Link MSD Types . . . . . . . . . . . . . . . . . . . 11 75 5. SRv6 Prefix Attributes . . . . . . . . . . . . . . . . . . . 12 76 5.1. SRv6 Locator TLV . . . . . . . . . . . . . . . . . . . . 12 77 6. SRv6 SID NLRI . . . . . . . . . . . . . . . . . . . . . . . . 13 78 6.1. SRv6 SID Information TLV . . . . . . . . . . . . . . . . 14 79 7. SRv6 SID Attributes . . . . . . . . . . . . . . . . . . . . . 15 80 7.1. SRv6 Endpoint Behavior TLV . . . . . . . . . . . . . . . 15 81 7.2. SRv6 BGP Peer Node SID TLV . . . . . . . . . . . . . . . 16 82 8. SRv6 SID Structure TLV . . . . . . . . . . . . . . . . . . . 18 83 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 84 9.1. BGP-LS NLRI-Types . . . . . . . . . . . . . . . . . . . . 19 85 9.2. BGP-LS TLVs . . . . . . . . . . . . . . . . . . . . . . . 19 86 10. Manageability Considerations . . . . . . . . . . . . . . . . 20 87 11. Security Considerations . . . . . . . . . . . . . . . . . . . 21 88 12. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 22 89 13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 22 90 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 23 91 14.1. Normative References . . . . . . . . . . . . . . . . . . 23 92 14.2. Informative References . . . . . . . . . . . . . . . . . 24 93 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 25 95 1. Introduction 97 SRv6 refers to Segment Routing instantiated on the IPv6 data-plane 98 [RFC8402]. A SRv6 Segment is often referred to by its SRv6 Segment 99 Identifier (SID). 101 The network programming paradigm 102 [I-D.ietf-spring-srv6-network-programming] is central to SRv6. It 103 describes how different behaviors can be bound to SIDs and how a 104 network program can be expressed as a combination of SIDs. 106 An SRv6-capable node N maintains all the SRv6 segments explicitly 107 instantiated at node N. 109 The IS-IS [I-D.ietf-lsr-isis-srv6-extensions] and OSPFv3 110 [I-D.ietf-lsr-ospfv3-srv6-extensions] link-state routing protocols 111 have been extended to advertise some of these SRv6 SIDs and 112 SRv6-related information. BGP ([I-D.ietf-bess-srv6-services]) has 113 been extended to advertise some of these SRv6 SIDs for VPN services. 114 Certain other SRv6 SIDs may be instantiated on a node via other 115 mechanisms for topological or service functionalities. 117 The advertisement of SR related information along with the topology 118 for the MPLS data-plane instantiation is specified in 119 [I-D.ietf-idr-bgp-ls-segment-routing-ext] and for the BGP Egress Peer 120 Engineering (EPE) is specified in 121 [I-D.ietf-idr-bgpls-segment-routing-epe]. On the similar lines, 122 introducing the SRv6 related information in BGP-LS allows consumer 123 applications that require topological visibility to also receive the 124 SRv6 SIDs from nodes across a domain or even across Autonomous 125 Systems (AS), as required. This allows applications to leverage the 126 SRv6 capabilities for network programming. 128 The identifying key of each Link-State object, namely a node, link, 129 or prefix, is encoded in the NLRI and the properties of the object 130 are encoded in the BGP-LS Attribute [RFC7752]. 132 This document describes extensions to BGP-LS to advertise the SRv6 133 SIDs and other SRv6 information from all the SRv6 capable nodes in 134 the domain when sourced from link-state routing protocols and 135 directly from individual SRv6 capable nodes (e.g. when sourced from 136 BGP for EPE). 138 1.1. Requirements Language 140 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 141 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 142 "OPTIONAL" in this document are to be interpreted as described in BCP 143 14 [RFC2119] [RFC8174] when, and only when, they appear in all 144 capitals, as shown here. 146 2. BGP-LS Extensions for SRv6 148 BGP-LS [RFC7752] defines the Node, Link and Prefix Link-State Network 149 Layer Reachability Information (NLRI) types and the advertisement of 150 their attributes via BGP. 152 The SRv6 information pertaining to a node is advertised via the BGP- 153 LS Node NLRI and using the BGP-LS Attribute TLVs as follows: 155 o SRv6 Capabilities of the node are advertised via SRv6 Capabilities 156 TLV (Section 3.1) 158 o Maximum SID Depth (MSD) types introduced for SRv6 are advertised 159 (Section 3.2) using the Node MSD TLV specified in [RFC8814] 161 o Algorithm support for SRv6 is advertised via the SR Algorithm TLV 162 specified in [I-D.ietf-idr-bgp-ls-segment-routing-ext]. 164 The SRv6 information pertaining to a link is advertised via the BGP- 165 LS Link NLRI and using the BGP-LS Attribute TLVs as follows: 167 o SRv6 SID of the IGP Adjacency SID or the BGP EPE Peer Adjacency 168 SID [RFC8402] is advertised via SRv6 End.X SID TLV introduced in 169 this document (Section 4.1) 171 o SRv6 SID of the IGP Adjacency SID to a non-Designated Router (DR) 172 or non-Designated Intermediate-System (DIS) [RFC8402] is 173 advertised via SRv6 LAN End.X SID TLV introduced in this document 174 (Section 4.2) 176 o MSD types introduced for SRv6 are advertised (Section 4.3) using 177 the Link MSD TLV specified in [RFC8814]. 179 The SRv6 information pertaining to a prefix is advertised via the 180 BGP-LS Prefix NLRI and using the BGP-LS Attribute TLVs as follows: 182 o SRv6 Locator is advertised via SRv6 Locator TLV introduced in this 183 document (Section 5.1) 185 o The attributes of the SRv6 Locator are advertised via the Prefix 186 Attribute Flags TLV specified in 187 [I-D.ietf-idr-bgp-ls-segment-routing-ext]. 189 The SRv6 SIDs associated with the node are advertised using the BGP- 190 LS SRv6 SID NLRI introduced in this document. This enables the BGP- 191 LS encoding to scale to cover a potentially large set of SRv6 SIDs 192 instantiated on a node with the granularity of individual SIDs and 193 without affecting the size and scalability of the BGP-LS updates. 194 BGP-LS Attribute TLVs for the SRv6 SID NLRI are introduced in this 195 document as follows: 197 o The endpoint behavior of the SRv6 SID is advertised via SRv6 198 Endpoint Behavior TLV (Section 7.1) 200 o The BGP EPE Peer Node and Peer Set context for a Peer Node and 201 Peer Set SID [RFC8402] respectively is advertised via SRv6 BGP EPE 202 Peer Node SID TLV (Section 7.2) 204 When the BGP-LS router is advertising topology information that it 205 sources from the underlying link-state routing protocol (as described 206 in [RFC7752]), then it maps the corresponding SRv6 information from 207 the SRv6 extensions for IS-IS [I-D.ietf-lsr-isis-srv6-extensions] and 208 OSPFv3 [I-D.ietf-lsr-ospfv3-srv6-extensions] protocols to their BGP- 209 LS TLVs/sub-TLVs for all SRv6 capable nodes in that routing protocol 210 domain. When the BGP-LS router is advertising topology information 211 from the BGP routing protocol (e.g. for EPE as described in 212 [I-D.ietf-idr-bgpls-segment-routing-epe]), then it advertises the 213 SRv6 information from the local node alone. 215 Subsequent sections of this document specify the encoding and usage 216 of these extensions. 218 3. SRv6 Node Attributes 220 SRv6 attributes of a node are advertised using the BGP-LS Attribute 221 TLVs defined in this section and associated with the BGP-LS Node 222 NLRI. 224 3.1. SRv6 Capabilities TLV 226 This BGP-LS Attribute TLV is used to announce the SRv6 capabilities 227 of the node along with the BGP-LS Node NLRI and indicates the SRv6 228 support by the node. A single instance of this TLV MUST be included 229 in the BGP-LS attribute for each SRv6 capable node. This TLV maps to 230 the SRv6 Capabilities sub-TLV and the SRv6 Capabilities TLV of the 231 IS-IS and OSPFv3 protocol SRv6 extensions respectively. 233 0 1 2 3 234 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 1 235 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 236 | Type | Length | 237 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 238 | Flags | Reserved | 239 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 241 Figure 1: SRv6 Capabilities TLV Format 243 Where: 245 o Type: 1038 247 o Length : 4. 249 o Flags: 2 octet field. The following flags are defined: 251 0 1 252 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 253 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 254 | |O| | 255 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 257 Figure 2: SRv6 Capability TLV Flags Format 259 * O-flag: If set, then router is capable of supporting SRH O-bit 260 Flags, as specified in [I-D.ietf-6man-spring-srv6-oam]. 262 * The rest of the bits are reserved for future use and MUST be 263 set to 0 and ignored on receipt. 265 o Reserved: 2 octet that MUST be set to 0 and ignored on receipt. 267 3.2. SRv6 Node MSD Types 269 The Node MSD TLV [RFC8814] of the BGP-LS Attribute of the Node NLRI 270 is also used to advertise the limits and the Segment Routing Header 271 (SRH) [RFC8754] operations supported by the SRv6 capable node. The 272 SRv6 MSD Types specified in section 4 of 273 [I-D.ietf-lsr-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 in 277 [I-D.ietf-lsr-isis-srv6-extensions]. 279 Each MSD type is encoded as a one octet type followed by a one octet 280 value as specified in [RFC8814]. 282 4. SRv6 Link Attributes 284 SRv6 attributes and SIDs associated with a link or adjacency are 285 advertised using the BGP-LS Attribute TLVs defined in this section 286 and associated with the BGP-LS Link NLRI. 288 4.1. SRv6 End.X SID TLV 290 The SRv6 End.X SID TLV is used to advertise the SRv6 SIDs associated 291 with an IGP Adjacency SID behavior like the End.X 292 [I-D.ietf-spring-srv6-network-programming] that correspond to a 293 point-to-point or point-to-multipoint link or adjacency of the node 294 running IS-IS and OSPFv3 protocols. This TLV can also be used to 295 advertise the SRv6 SID corresponding to the underlying layer-2 member 296 links for a layer-3 bundle interface as a sub-TLV of the L2 Bundle 297 Member Attribute TLV [I-D.ietf-idr-bgp-ls-segment-routing-ext]. 299 This TLV is also used by BGP to advertise the BGP EPE Peer Adjacency 300 SID for SRv6 on the same lines as specified for SR/MPLS in 301 [I-D.ietf-idr-bgpls-segment-routing-epe]. The SRv6 SID for the BGP 302 Peer Adjacency using and End.X behaviour 303 [I-D.ietf-spring-srv6-network-programming] indicates the cross- 304 connect to a specific layer-3 link to the specific BGP session peer 305 (neighbor). 307 The TLV has the following format: 309 0 1 2 3 310 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 1 311 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 312 | Type | Length | 313 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 314 | Endpoint Behavior | Flags | Algorithm | 315 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 316 | Weight | Reserved | SID (16 octets) ... 317 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 318 SID (cont ...) 319 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 320 SID (cont ...) 321 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 322 SID (cont ...) 323 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 324 SID (cont ...) | Sub-TLVs (variable) . . . 325 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 327 Figure 3: SRv6 End.X TLV Format 329 Where: 331 Type: 1106 333 Length: variable 335 Endpoint Behavior: 2 octet field. The Endpoint Behavior code 336 point for this SRv6 SID as defined in section 9.2 of 337 [I-D.ietf-spring-srv6-network-programming]. 339 Flags: 1 octet of flags with the following definition: 341 0 1 2 3 4 5 6 7 342 +-+-+-+-+-+-+-+-+ 343 |B|S|P| | 344 +-+-+-+-+-+-+-+-+ 346 Figure 4: SRv6 End.X SID TLV Flags Format 348 * B-Flag: Backup Flag. If set, the SID is eligible for 349 protection (e.g. using IPFRR) as described in [RFC8355]. 351 * S-Flag: Set Flag. When set, the S-Flag indicates that the SID 352 refers to a set of adjacencies (and therefore MAY be assigned 353 to other adjacencies as well). 355 * P-Flag: Persistent Flag: When set, the P-Flag indicates that 356 the SID is persistently allocated, i.e., the value remains 357 consistent across router restart and/or interface flap. 359 * The other bits are reserved for future use and MUST be set to 0 360 and ignored on receipt. 362 Algorithm: 1 octet field. Algorithm associated with the SID. 363 Algorithm values are defined in the IANA IGP Algorithm Type 364 registry. 366 Weight: 1 octet field. The value represents the weight of the SID 367 for the purpose of load balancing. The use of the weight is 368 defined in [RFC8402]. 370 Reserved: 1 octet field that MUST be set to 0 and ignored on 371 receipt. 373 SID: 16 octet field. This field encodes the advertised SRv6 SID 374 as 128 bit value. 376 Sub-TLVs : Used to advertise sub-TLVs that provide additional 377 attributes for the specific SRv6 SID. 379 4.2. SRv6 LAN End.X SID TLV 381 For a LAN interface, normally an IGP node only announces its 382 adjacency to the IS-IS pseudo-node (or the equivalent OSPF DR). The 383 SRv6 LAN End.X SID TLV allows a node to announce SRv6 SID 384 corresponding to behaviors like END.X 385 [I-D.ietf-spring-srv6-network-programming] for its adjacencies to all 386 other (i.e. non-DIS or non-DR) nodes attached to the LAN in a single 387 instance of the BGP-LS Link NLRI. Without this TLV, multiple BGP-LS 388 Link NLRI would need to be originated for each additional adjacency 389 in order to advertise the SRv6 End.X SID TLVs for these neighbor 390 adjacencies. 392 The IS-IS and OSPFv3 SRv6 LAN End.X SID TLVs have the following 393 format: 395 0 1 2 3 396 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 1 397 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 398 | Type | Length | 399 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 400 | Endpoint Behavior | Flags | Algorithm | 401 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 402 | Weight | Reserved | Neighbor ID - | 403 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 404 | ISIS System-ID (6 octets) or OSPFv3 Router-ID (4 octets) | 405 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 406 | SID (16 octets) ... 407 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 408 SID (cont ...) 409 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 410 SID (cont ...) 411 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 412 SID (cont ...) | 413 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 414 | Sub-TLVs (variable) . . . 415 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 417 Figure 5: SRv6 LAN End.X SID TLV Format 419 Where: 421 o Type: 1107 in case of IS-IS and 1108 in case of OSPFv3 423 o Length: variable 425 o Endpoint Behavior: 2 octet field. The Endpoint Behavior code 426 point for this SRv6 SID as defined in section 9.2 of 427 [I-D.ietf-spring-srv6-network-programming]. 429 o Flags: 1 octet of flags with the following definition: 431 0 1 2 3 4 5 6 7 432 +-+-+-+-+-+-+-+-+ 433 |B|S|P| | 434 +-+-+-+-+-+-+-+-+ 436 Figure 6: SRv6 LAN End.X SID TLV Flags Format 438 * B-Flag: Backup Flag. If set, the SID is eligible for 439 protection (e.g. using IPFRR) as described in [RFC8355]. 441 * S-Flag: Set Flag. When set, the S-Flag indicates that the SID 442 refers to a set of adjacencies (and therefore MAY be assigned 443 to other adjacencies as well). 445 * P-Flag: Persistent Flag: When set, the P-Flag indicates that 446 the SID is persistently allocated, i.e., the value remains 447 consistent across router restart and/or interface flap. 449 * Other bits are reserved for future use and MUST be set to 0 and 450 ignored on receipt. 452 o Algorithm: 1 octet field. Algorithm associated with the SID. 453 Algorithm values are defined in the IANA IGP Algorithm Type 454 registry. 456 o Weight: 1 octet field. The value represents the weight of the SID 457 for the purpose of load balancing. The use of the weight is 458 defined in [RFC8402]. 460 o Reserved: 1 octet field that MUST be set to 0 and ignored on 461 receipt. 463 o Neighbor ID : 6 octets of ISIS System ID of the neighbor for the 464 ISIS SRv6 LAN End.X SID TLV and 4 octets of OSPFv3 Router-id of 465 the neighbor for the OSPFv3 SRv6 LAN End.X SID TLV. 467 o SID: 16 octet field. This field encodes the advertised SRv6 SID 468 as 128 bit value. 470 o Sub-TLVs : Used to advertise sub-TLVs that provide additional 471 attributes for the specific SRv6 SID. 473 4.3. SRv6 Link MSD Types 475 The Link MSD TLV [RFC8814] of the BGP-LS Attribute of the Link NLRI 476 is also used to advertise the limits and the SRH operations supported 477 on the specific link by the SRv6 capable node. The SRv6 MSD Types 478 specified in section 4 of[I-D.ietf-lsr-isis-srv6-extensions] are also 479 used with the BGP-LS Link MSD TLV as these codepoints are shared 480 between IS-IS, OSPF and BGP-LS protocols. The description and 481 semantics of these new MSD types for BGP-LS are identical as 482 specified in [I-D.ietf-lsr-isis-srv6-extensions]. 484 Each MSD type is encoded as a one octet type followed by a one octet 485 value as specified in [RFC8814]. 487 5. SRv6 Prefix Attributes 489 SRv6 attributes with an IPv6 prefix are advertised using the BGP-LS 490 Attribute TLVs defined in this section and associated with the BGP-LS 491 Prefix NLRI. 493 5.1. SRv6 Locator TLV 495 As specified in [I-D.ietf-spring-srv6-network-programming], an SRv6 496 SID comprises of Locator, Function and Argument parts. 498 A node is provisioned with one or more locators supported by that 499 node. Locators are covering prefixes for the set of SIDs provisioned 500 on that node. These Locators are advertised as BGP-LS Prefix NLRI 501 objects along with the SRv6 Locator TLV in its BGP-LS Attribute. 503 The IPv6 Prefix matching the Locator MAY be also advertised as a 504 prefix reachability by the underlying routing protocol. In this 505 case, the Prefix NLRI would be also associated with the Prefix Metric 506 TLV that carries the routing metric for this prefix. When the 507 Locator prefix is not being advertised as a prefix reachability, then 508 the Prefix NLRI would have the SRv6 Locator TLV associated with it 509 but no Prefix Metric TLV. In the absence of Prefix Metric TLV, the 510 consumer of the BGP-LS topology information MUST NOT interpret the 511 Locator prefix as a prefix reachability routing advertisement in the 512 IGPs default SPF computation. 514 The SRv6 Locator TLV has the following format: 516 0 1 2 3 517 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 1 518 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 519 | Type | Length | 520 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 521 | Flags | Algorithm | Reserved | 522 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 523 | Metric | 524 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 525 | Sub-TLVs (variable) . . . 526 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 528 Figure 7: SRv6 Locator TLV Format 530 Where: 532 Type: 1162 533 Length: variable 535 Flags: 1 octet of flags with the following definition: 537 0 1 2 3 4 5 6 7 538 +-+-+-+-+-+-+-+-+ 539 |D| | 540 +-+-+-+-+-+-+-+-+ 542 Figure 8: SRv6 Locator TLV Flags Format 544 * D-Flag: Indicates that the locator has been leaked into the IGP 545 domain when set. IS-IS operations for this are discussed in 546 [I-D.ietf-lsr-isis-srv6-extensions]. 548 * Other bits are reserved for future use and MUST be set to 0 and 549 ignored on receipt. 551 Algorithm: 1 octet field. Algorithm associated with the SID. 552 Algorithm values are defined in the IANA IGP Algorithm Type 553 registry. 555 Reserved: 2 octet field. The value MUST be set to 0 and ignored 556 on receipt. 558 Metric: 4 octet field. The value of the metric for the Locator. 560 Sub-TLVs : currently none defined. Used to advertise sub-TLVs 561 that provide additional attributes for the given SRv6 Locator. 563 6. SRv6 SID NLRI 565 SRv6 SID information is advertised in BGP UPDATE messages using the 566 MP_REACH_NLRI and MP_UNREACH_NLRI attributes [RFC4760]. The "Link- 567 State NLRI" defined in [RFC7752] is extended to carry the SRv6 SID 568 information. 570 A new "Link-State NLRI Type" is defined for SRv6 SID information as 571 following: 573 o Link-State NLRI Type: SRv6 SID NLRI (value 6). 575 The format of this new NLRI type is as shown in the following figure: 577 0 1 2 3 578 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 1 579 +-+-+-+-+-+-+-+-+ 580 | Protocol-ID | 581 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 582 | Identifier | 583 | (64 bits) | 584 ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+| 585 | Local Node Descriptors (variable) // 586 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 587 | SRv6 SID Descriptors (variable) // 588 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 590 Figure 9: SRv6 SID NLRI Format 592 Where: 594 o Protocol-ID: 1 octet field that specifies the protocol component 595 through which BGP-LS learns the SRv6 SIDs of the node. The 596 Protocol-ID registry was created by [RFC7752] and then extended by 597 other BGP-LS extensions. 599 o Identifier: 8 octet value as defined in [RFC7752]. 601 o Local Node Descriptors TLV: as defined in [RFC7752] for IGPs, 602 local and static configuration and as defined in 603 [I-D.ietf-idr-bgpls-segment-routing-epe] for BGP protocol. 605 o SRv6 SID Descriptors: MUST include a single SRv6 SID Information 606 TLV defined in Section 6.1 and optionally MAY include the Multi- 607 Topology Identifier TLV as defined in [RFC7752]. 609 New TLVs for advertisement within the BGP Link State Attribute 610 [RFC7752] are defined in Section 7 to carry the attributes of an SRv6 611 SID. 613 6.1. SRv6 SID Information TLV 615 An SRv6 SID is encoded using the SRv6 SID Information TLV. 617 The TLV has the following format: 619 0 1 2 3 620 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 1 621 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 622 | Type | Length | 623 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 624 | SID (16 octets) ... 625 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 626 SID (cont ...) 627 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 628 SID (cont ...) 629 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 630 SID (cont ...) | 631 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 633 Figure 10: SRv6 SID Information TLV Format 635 Where: 637 Type: 518 639 Length: 16. 641 SID: 16 octet field. This field encodes the advertised SRv6 SID 642 as 128 bit value. 644 7. SRv6 SID Attributes 646 This section specifies the TLVs to be carried in the BGP Link State 647 Attribute associated with the BGP-LS SRv6 SID NLRI. 649 7.1. SRv6 Endpoint Behavior TLV 651 Each SRv6 SID instantiated on an SRv6 capable node has specific 652 instructions (called behavior) bound to it. 653 [I-D.ietf-spring-srv6-network-programming] describes how behaviors 654 are bound with a SID and also defines the initial set of well-known 655 behaviors. 657 The SRv6 Endpoint Behavior TLV is a mandatory TLV that MUST be 658 included in the BGP-LS Attribute associated with the BGP-LS SRv6 SID 659 NLRI. The TLV has the following format: 661 0 1 2 3 662 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 1 663 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 664 | Type | Length | 665 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 666 | Endpoint Behavior | Flags | Algorithm | 667 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 669 Figure 11: SRv6 Endpoint Behavior TLV 671 Where: 673 Type: 1250 675 Length: 4. 677 Endpoint Behavior: 2 octet field. The Endpoint Behavior code 678 point for this SRv6 SID as defined in section 9.2 of 679 [I-D.ietf-spring-srv6-network-programming]. 681 Flags: 1 octet of flags with the none defined currently. Reserved 682 for future use and MUST be set to 0 and ignored on receipt. 684 Algorithm: 1 octet field. Algorithm associated with the SID. 685 Algorithm values are defined in the IGP Algorithm Type registry. 687 7.2. SRv6 BGP Peer Node SID TLV 689 The BGP Peer Node SID and Peer Set SID for SR with MPLS data-plane 690 are specified in [I-D.ietf-idr-bgpls-segment-routing-epe]. The 691 similar Peer Node and Peer Set functionality can be realized with 692 SRv6 using SIDs with END.X behavior. The SRv6 BGP Peer Node SID TLV 693 is an optional TLV for use in the BGP-LS Attribute for an SRv6 SID 694 NLRI advertised by BGP for the EPE functionality. This TLV MUST be 695 included along with SRv6 SIDs that are associated with the BGP Peer 696 Node or Peer Set functionality. 698 The TLV has the following format: 700 0 1 2 3 701 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 1 702 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 703 | Type | Length | 704 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 705 | Flags | Weight | Reserved | 706 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 707 | Peer AS Number | 708 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 709 | Peer BGP Identifier | 710 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 712 Figure 12: SRv6 BGP Peer Node SID TLV Format 714 Where: 716 o Type: 1251 718 o Length: 12 720 o Flags: 1 octet of flags with the following definition: 722 0 1 2 3 4 5 6 7 723 +-+-+-+-+-+-+-+-+ 724 |B|S|P| | 725 +-+-+-+-+-+-+-+-+ 727 Figure 13: SRv6 BGP Peer End.X SID TLV Flags Format 729 * B-Flag: Backup Flag. If set, the SID is eligible for 730 protection (e.g. using IPFRR) as described in [RFC8355]. 732 * S-Flag: Set Flag. When set, the S-Flag indicates that the SID 733 refers to a set of BGP peering sessions (i.e. BGP Peer Set SID 734 functionality) and therefore MAY be assigned to one or more 735 End.X SIDs associated with BGP peer sessions. 737 * P-Flag: Persistent Flag: When set, the P-Flag indicates that 738 the SID is persistently allocated, i.e., the value remains 739 consistent across router restart and/or session flap. 741 * Other bits are reserved for future use and MUST be set to 0 and 742 ignored on receipt. 744 o Weight: 1 octet field. The value represents the weight of the SID 745 for the purpose of load balancing. The use of the weight is 746 defined in [RFC8402]. 748 o Reserved: 2 octet field. The value MUST be set to 0 and ignored 749 on receipt. 751 o Peer AS Number : 4 octets of BGP AS number of the peer router. 753 o Peer BGP Identifier : 4 octets of the BGP Identifier (BGP Router- 754 ID) of the peer router. 756 For a SRv6 BGP EPE Peer Node SID, one instance of this TLV is 757 associated with the SRv6 SID. For SRv6 BGP EPE Peer Set SID, 758 multiple instances of this TLV (one for each peer in the "peer set") 759 are associated with the SRv6 SID and the S (set/group) flag is SET. 761 8. SRv6 SID Structure TLV 763 SRv6 SID Structure TLV is used to advertise the length of each 764 individual part of the SRv6 SID as defined in 765 [I-D.ietf-spring-srv6-network-programming]. It is an optional TLV 766 for use in the BGP-LS Attribute for an SRv6 SID NLRI and as a sub-TLV 767 of the SRv6 End.X, IS-IS SRv6 LAN End.X and OSPFv3 SRv6 LAN End.X 768 TLVs. The TLV has the following format: 770 0 1 2 3 771 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 1 772 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 773 | Type | Length | 774 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 775 | LB Length | LN Length | Fun. Length | Arg. Length | 776 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 778 Figure 14: SRv6 SID Structure TLV 780 Where: 782 Type: 2 octet field with value 1252 784 Length: 2 octet field with the value 4. 786 Locator Block Length: 1 octet field. SRv6 SID Locator Block 787 length in bits. 789 Locator Node Length: 1 octet field. SRv6 SID Locator Node length 790 in bits. 792 Function Length: 1 octet field. SRv6 SID Function length in bits. 794 Argument Length: 1 octet field. SRv6 SID Argument length in bits. 796 The total of the locator block, locator node, function and argument 797 lengths MUST be less than or equal to 128. 799 9. IANA Considerations 801 This document requests assigning code-points from the IANA "Border 802 Gateway Protocol - Link State (BGP-LS) Parameters" registry as 803 described in the sub-sections below. 805 9.1. BGP-LS NLRI-Types 807 The following codepoints are assigned by IANA via the early 808 allocation process from within the sub-registry called "BGP-LS NLRI- 809 Types": 811 +------+----------------------------+---------------+ 812 | Type | NLRI Type | Reference | 813 +------+----------------------------+---------------+ 814 | 6 | SRv6 SID | this document | 815 +------+----------------------------+---------------+ 817 Figure 15: SRv6 SID NLRI Type Codepoint 819 9.2. BGP-LS TLVs 821 The following TLV codepoints are assigned by IANA via the early 822 allocation process from within the sub-registry called "BGP-LS Node 823 Descriptor, Link Descriptor, Prefix Descriptor, and Attribute TLVs": 825 +----------+----------------------------------------+---------------+ 826 | TLV Code | Description | Value defined | 827 | Point | | in | 828 +----------+----------------------------------------+---------------+ 829 | 1038 | SRv6 Capabilities TLV | this document | 830 | 1106 | SRv6 End.X SID TLV | this document | 831 | 1107 | IS-IS SRv6 LAN End.X SID TLV | this document | 832 | 1108 | OSPFv3 SRv6 LAN End.X SID TLV | this document | 833 | 1162 | SRv6 Locator TLV | this document | 834 | 518 | SRv6 SID Information TLV | this document | 835 | 1250 | SRv6 Endpoint Behavior TLV | this document | 836 | 1251 | SRv6 BGP Peer Node SID TLV | this document | 837 | 1252 | SRv6 SID Structure TLV | this document | 838 +----------+----------------------------------------+---------------+ 840 Figure 16: SRv6 BGP-LS Attribute TLV Codepoints 842 10. Manageability Considerations 844 This section is structured as recommended in [RFC5706]. 846 The new protocol extensions introduced in this document augment the 847 existing IGP topology information that is distributed via [RFC7752]. 848 Procedures and protocol extensions defined in this document do not 849 affect the BGP protocol operations and management other than as 850 discussed in the Manageability Considerations section of [RFC7752]. 851 Specifically, the malformed attribute tests for syntactic checks in 852 the Fault Management section of [RFC7752] now encompass the new BGP- 853 LS extensions defined in this document. The semantic or content 854 checking for the TLVs specified in this document and their 855 association with the BGP-LS NLRI types or their BGP-LS Attribute is 856 left to the consumer of the BGP-LS information (e.g. an application 857 or a controller) and not the BGP protocol. 859 A consumer of the BGP-LS information retrieves this information over 860 a BGP-LS session (refer Section 1 and 2 of [RFC7752]). The handling 861 of semantic or content errors by the consumer would be dictated by 862 the nature of its application usage and hence is beyond the scope of 863 this document. 865 The SR information introduced in BGP-LS by this specification, may be 866 used by BGP-LS consumer applications like a SR path computation 867 engine (PCE) to learn the SRv6 capabilities of the nodes in the 868 topology and the mapping of SRv6 segments to those nodes. This can 869 enable the SR PCE to perform path computations based on SR for 870 traffic engineering use-cases and to steer traffic on paths different 871 from the underlying IGP based distributed best path computation. 872 Errors in the encoding or decoding of the SRv6 information may result 873 in the unavailability of such information to the SR PCE or incorrect 874 information being made available to it. This may result in the SR 875 PCE not being able to perform the desired SR based optimization 876 functionality or to perform it in an unexpected or inconsistent 877 manner. The handling of such errors by applications like SR PCE may 878 be implementation specific and out of scope of this document. 880 The manageability considerations related to BGP EPE functionality are 881 discussed in [I-D.ietf-idr-bgpls-segment-routing-epe] in the context 882 of SR-MPLS and they also apply to this document in the context of 883 SRv6. 885 The extensions, specified in this document, do not introduce any new 886 configuration or monitoring aspects in BGP or BGP-LS other than as 887 discussed in [RFC7752]. The manageability aspects of the underlying 888 SRv6 features are covered by [I-D.ietf-spring-srv6-yang]. 890 11. Security Considerations 892 The new protocol extensions introduced in this document augment the 893 existing IGP topology information that is distributed via [RFC7752]. 894 The advertisement of the SRv6 link-state information defined in this 895 document presents similar risk as associated with the existing set of 896 link-state information as described in [RFC7752]. The Security 897 Considerations section of [RFC7752] also applies to these extensions. 898 The procedures and new TLVs defined in this document, by themselves, 899 do not affect the BGP-LS security model discussed in [RFC7752]. 901 The extensions introduced in this document are used to propagate IGP 902 defined information ([I-D.ietf-lsr-isis-srv6-extensions] and 903 [I-D.ietf-lsr-ospfv3-srv6-extensions]). These extensions represent 904 the advertisement of SRv6 information associated with the IGP node, 905 link and prefix. The IGP instances originating these TLVs are 906 assumed to support all the required security and authentication 907 mechanisms (as described in [I-D.ietf-lsr-isis-srv6-extensions] and 908 [I-D.ietf-lsr-ospfv3-srv6-extensions]) in order to prevent any 909 security issue when propagating the information into BGP-LS. 911 The security considerations related to BGP EPE functionality are 912 discussed in [I-D.ietf-idr-bgpls-segment-routing-epe] in the context 913 of SR-MPLS and they also apply to this document in the context of 914 SRv6. 916 BGP-LS SRv6 extensions enable traffic engineering use-cases within 917 the Segment Routing domain. SR operates within a trusted domain 918 [RFC8402] and its security considerations also apply to BGP-LS 919 sessions when carrying SR information. The SR traffic engineering 920 policies using the SIDs advertised via BGP-LS are expected to be used 921 entirely within this trusted SR domain (e.g. between multiple AS/ 922 domains within a single provider network). Therefore, precaution is 923 necessary to ensure that the link-state information (including SRv6 924 information) advertised via BGP-LS sessions is limited to consumers 925 in a secure manner within this trusted SR domain. BGP peering 926 sessions for address-families other than Link-State may be setup to 927 routers outside the SR domain. The isolation of BGP-LS peering 928 sessions is recommended to ensure that BGP-LS topology information 929 (including the newly added SR information) is not advertised to an 930 external BGP peering session outside the SR domain. 932 12. Contributors 934 James Uttaro 935 AT&T 936 USA 937 Email: ju1738@att.com 939 Hani Elmalky 940 Ericsson 941 USA 942 Email: hani.elmalky@gmail.com 944 Arjun Sreekantiah 945 Individual 946 USA 947 Email: arjunhrs@gmail.com 949 Les Ginsberg 950 Cisco Systems 951 USA 952 Email: ginsberg@cisco.com 954 Shunwan Zhuang 955 Huawei 956 China 957 Email: zhuangshunwan@huawei.com 959 13. Acknowledgements 961 The authors would like to thank Peter Psenak, Arun Babu, Pablo 962 Camarillo, Francois Clad, Peng Shaofu, Cheng Li and Dhruv Dhody for 963 their review of this document and their comments. 965 14. References 967 14.1. Normative References 969 [I-D.ietf-6man-spring-srv6-oam] 970 Ali, Z., Filsfils, C., Matsushima, S., Voyer, D., and M. 971 Chen, "Operations, Administration, and Maintenance (OAM) 972 in Segment Routing Networks with IPv6 Data plane (SRv6)", 973 draft-ietf-6man-spring-srv6-oam-08 (work in progress), 974 October 2020. 976 [I-D.ietf-idr-bgp-ls-segment-routing-ext] 977 Previdi, S., Talaulikar, K., Filsfils, C., Gredler, H., 978 and M. Chen, "BGP Link-State extensions for Segment 979 Routing", draft-ietf-idr-bgp-ls-segment-routing-ext-16 980 (work in progress), June 2019. 982 [I-D.ietf-idr-bgpls-segment-routing-epe] 983 Previdi, S., Talaulikar, K., Filsfils, C., Patel, K., Ray, 984 S., and J. Dong, "BGP-LS extensions for Segment Routing 985 BGP Egress Peer Engineering", draft-ietf-idr-bgpls- 986 segment-routing-epe-19 (work in progress), May 2019. 988 [I-D.ietf-lsr-isis-srv6-extensions] 989 Psenak, P., Filsfils, C., Bashandy, A., Decraene, B., and 990 Z. Hu, "IS-IS Extension to Support Segment Routing over 991 IPv6 Dataplane", draft-ietf-lsr-isis-srv6-extensions-11 992 (work in progress), October 2020. 994 [I-D.ietf-lsr-ospfv3-srv6-extensions] 995 Li, Z., Hu, Z., Cheng, D., Talaulikar, K., and P. Psenak, 996 "OSPFv3 Extensions for SRv6", draft-ietf-lsr- 997 ospfv3-srv6-extensions-01 (work in progress), August 2020. 999 [I-D.ietf-spring-srv6-network-programming] 1000 Filsfils, C., Camarillo, P., Leddy, J., Voyer, D., 1001 Matsushima, S., and Z. Li, "SRv6 Network Programming", 1002 draft-ietf-spring-srv6-network-programming-24 (work in 1003 progress), October 2020. 1005 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1006 Requirement Levels", BCP 14, RFC 2119, 1007 DOI 10.17487/RFC2119, March 1997, 1008 . 1010 [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and 1011 S. Ray, "North-Bound Distribution of Link-State and 1012 Traffic Engineering (TE) Information Using BGP", RFC 7752, 1013 DOI 10.17487/RFC7752, March 2016, 1014 . 1016 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 1017 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 1018 May 2017, . 1020 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 1021 Decraene, B., Litkowski, S., and R. Shakir, "Segment 1022 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 1023 July 2018, . 1025 [RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J., 1026 Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header 1027 (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020, 1028 . 1030 [RFC8814] Tantsura, J., Chunduri, U., Talaulikar, K., Mirsky, G., 1031 and N. Triantafillis, "Signaling Maximum SID Depth (MSD) 1032 Using the Border Gateway Protocol - Link State", RFC 8814, 1033 DOI 10.17487/RFC8814, August 2020, 1034 . 1036 14.2. Informative References 1038 [I-D.ietf-bess-srv6-services] 1039 Dawra, G., Filsfils, C., Talaulikar, K., Raszuk, R., 1040 Decraene, B., Zhuang, S., and J. Rabadan, "SRv6 BGP based 1041 Overlay services", draft-ietf-bess-srv6-services-05 (work 1042 in progress), November 2020. 1044 [I-D.ietf-spring-srv6-yang] 1045 Raza, K., Agarwal, S., Liu, X., Hu, Z., Hussain, I., Shah, 1046 H., Voyer, D., Matsushima, S., Horiba, K., Abdelsalam, A., 1047 and J. Rajamanickam, "YANG Data Model for SRv6 Base and 1048 Static", draft-ietf-spring-srv6-yang-00 (work in 1049 progress), September 2020. 1051 [RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter, 1052 "Multiprotocol Extensions for BGP-4", RFC 4760, 1053 DOI 10.17487/RFC4760, January 2007, 1054 . 1056 [RFC5706] Harrington, D., "Guidelines for Considering Operations and 1057 Management of New Protocols and Protocol Extensions", 1058 RFC 5706, DOI 10.17487/RFC5706, November 2009, 1059 . 1061 [RFC8355] Filsfils, C., Ed., Previdi, S., Ed., Decraene, B., and R. 1062 Shakir, "Resiliency Use Cases in Source Packet Routing in 1063 Networking (SPRING) Networks", RFC 8355, 1064 DOI 10.17487/RFC8355, March 2018, 1065 . 1067 Authors' Addresses 1069 Gaurav Dawra 1070 LinkedIn 1071 USA 1073 Email: gdawra.ietf@gmail.com 1075 Clarence Filsfils 1076 Cisco Systems 1077 Belgium 1079 Email: cfilsfil@cisco.com 1081 Ketan Talaulikar (editor) 1082 Cisco Systems 1083 India 1085 Email: ketant@cisco.com 1087 Mach Chen 1088 Huawei 1089 China 1091 Email: mach.chen@huawei.com 1093 Daniel Bernier 1094 Bell Canada 1095 Canada 1097 Email: daniel.bernier@bell.ca 1098 Bruno Decraene 1099 Orange 1100 France 1102 Email: bruno.decraene@orange.com