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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Inter-Domain Routing S. Previdi 3 Internet-Draft Huawei Technologies 4 Intended status: Standards Track K. Talaulikar, Ed. 5 Expires: October 20, 2019 C. Filsfils 6 Cisco Systems, Inc. 7 H. Gredler 8 RtBrick Inc. 9 M. Chen 10 Huawei Technologies 11 April 18, 2019 13 BGP Link-State extensions for Segment Routing 14 draft-ietf-idr-bgp-ls-segment-routing-ext-13 16 Abstract 18 Segment Routing (SR) allows for a flexible definition of end-to-end 19 paths by encoding paths as sequences of topological sub-paths, called 20 "segments". These segments are advertised by routing protocols e.g. 21 by the link state routing protocols (IS-IS, OSPFv2 and OSPFv3) within 22 IGP topologies. 24 This draft defines extensions to the BGP Link-state address-family in 25 order to carry segment routing information via BGP. 27 Requirements Language 29 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 30 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 31 "OPTIONAL" in this document are to be interpreted as described in BCP 32 14 [RFC2119] [RFC8174] when, and only when, they appear in all 33 capitals, as shown here. 35 Status of This Memo 37 This Internet-Draft is submitted in full conformance with the 38 provisions of BCP 78 and BCP 79. 40 Internet-Drafts are working documents of the Internet Engineering 41 Task Force (IETF). Note that other groups may also distribute 42 working documents as Internet-Drafts. The list of current Internet- 43 Drafts is at https://datatracker.ietf.org/drafts/current/. 45 Internet-Drafts are draft documents valid for a maximum of six months 46 and may be updated, replaced, or obsoleted by other documents at any 47 time. It is inappropriate to use Internet-Drafts as reference 48 material or to cite them other than as "work in progress." 49 This Internet-Draft will expire on October 20, 2019. 51 Copyright Notice 53 Copyright (c) 2019 IETF Trust and the persons identified as the 54 document authors. All rights reserved. 56 This document is subject to BCP 78 and the IETF Trust's Legal 57 Provisions Relating to IETF Documents 58 (https://trustee.ietf.org/license-info) in effect on the date of 59 publication of this document. Please review these documents 60 carefully, as they describe your rights and restrictions with respect 61 to this document. Code Components extracted from this document must 62 include Simplified BSD License text as described in Section 4.e of 63 the Trust Legal Provisions and are provided without warranty as 64 described in the Simplified BSD License. 66 Table of Contents 68 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 69 2. BGP-LS Extensions for Segment Routing . . . . . . . . . . . . 4 70 2.1. Node Attributes TLVs . . . . . . . . . . . . . . . . . . 5 71 2.1.1. SID/Label Sub-TLV . . . . . . . . . . . . . . . . . . 5 72 2.1.2. SR Capabilities TLV . . . . . . . . . . . . . . . . . 6 73 2.1.3. SR Algorithm TLV . . . . . . . . . . . . . . . . . . 7 74 2.1.4. SR Local Block TLV . . . . . . . . . . . . . . . . . 8 75 2.1.5. SRMS Preference TLV . . . . . . . . . . . . . . . . . 9 76 2.2. Link Attribute TLVs . . . . . . . . . . . . . . . . . . . 10 77 2.2.1. Adjacency SID TLV . . . . . . . . . . . . . . . . . . 10 78 2.2.2. LAN Adjacency SID TLV . . . . . . . . . . . . . . . . 12 79 2.2.3. L2 Bundle Member Attribute TLV . . . . . . . . . . . 14 80 2.3. Prefix Attribute TLVs . . . . . . . . . . . . . . . . . . 15 81 2.3.1. Prefix SID TLV . . . . . . . . . . . . . . . . . . . 16 82 2.3.2. Prefix Attribute Flags TLV . . . . . . . . . . . . . 17 83 2.3.3. Source Router Identifier (Source Router-ID) TLV . . . 18 84 2.3.4. Range TLV . . . . . . . . . . . . . . . . . . . . . . 18 85 2.4. Equivalent IS-IS Segment Routing TLVs/Sub-TLVs . . . . . 20 86 2.5. Equivalent OSPFv2/OSPFv3 Segment Routing TLVs/Sub-TLVs . 21 87 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23 88 3.1. TLV/Sub-TLV Code Points Summary . . . . . . . . . . . . . 23 89 4. Manageability Considerations . . . . . . . . . . . . . . . . 24 90 5. Security Considerations . . . . . . . . . . . . . . . . . . . 25 91 6. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 26 92 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 26 93 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 27 94 8.1. Normative References . . . . . . . . . . . . . . . . . . 27 95 8.2. Informative References . . . . . . . . . . . . . . . . . 28 96 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 29 98 1. Introduction 100 Segment Routing (SR) allows for a flexible definition of end-to-end 101 paths by combining sub-paths called "segments". A segment can 102 represent any instruction, topological or service-based. A segment 103 can have a local semantic to an SR node or global within a domain. 104 Within IGP topologies an SR path is encoded as a sequence of 105 topological sub-paths, called "IGP segments". These segments are 106 advertised by the link-state routing protocols (IS-IS, OSPFv2 and 107 OSPFv3). 109 [RFC8402] defines the Link-State IGP segments - Prefix, Node, Anycast 110 and Adjacency segments. Prefix segments, by default, represent an 111 ECMP-aware shortest-path to a prefix, as per the state of the IGP 112 topology. Adjacency segments represent a hop over a specific 113 adjacency between two nodes in the IGP. A prefix segment is 114 typically a multi-hop path while an adjacency segment, in most of the 115 cases, is a one-hop path. Node and Anycast Segments are variations 116 of the Prefix Segment with their specific characteristics. 118 When Segment Routing is enabled in an IGP domain, segments are 119 advertised in the form of Segment Identifiers (SIDs). The IGP link- 120 state routing protocols have been extended to advertise SIDs and 121 other SR-related information. IGP extensions are described in: IS-IS 122 [I-D.ietf-isis-segment-routing-extensions], OSPFv2 123 [I-D.ietf-ospf-segment-routing-extensions] and OSPFv3 124 [I-D.ietf-ospf-ospfv3-segment-routing-extensions]. Using these 125 extensions, Segment Routing can be enabled within an IGP domain. 127 Segment Routing (SR) allows advertisement of single or multi-hop 128 paths. The flooding scope for the IGP extensions for Segment routing 129 is IGP area-wide. Consequently, the contents of a Link State 130 Database (LSDB) or a Traffic Engineering Database (TED) has the scope 131 of an IGP area and therefore, by using the IGP alone it is not enough 132 to construct segments across multiple IGP Area or AS boundaries. 134 In order to address the need for applications that require 135 topological visibility across IGP areas, or even across Autonomous 136 Systems (AS), the BGP-LS address-family/sub-address-family have been 137 defined to allow BGP to carry Link-State information. The BGP 138 Network Layer Reachability Information (NLRI) encoding format for 139 BGP-LS and a new BGP Path Attribute called the BGP-LS attribute are 140 defined in [RFC7752]. The identifying key of each Link-State object, 141 namely a node, link, or prefix, is encoded in the NLRI and the 142 properties of the object are encoded in the BGP-LS attribute. 144 +------------+ 145 | Consumer | 146 +------------+ 147 ^ 148 | 149 v 150 +-------------------+ 151 | BGP Speaker | +-----------+ 152 | (Route-Reflector) | | Consumer | 153 +-------------------+ +-----------+ 154 ^ ^ ^ ^ 155 | | | | 156 +---------------+ | +-------------------+ | 157 | | | | 158 v v v v 159 +-----------+ +-----------+ +-----------+ 160 | BGP | | BGP | | BGP | 161 | Speaker | | Speaker | . . . | Speaker | 162 +-----------+ +-----------+ +-----------+ 163 ^ ^ ^ 164 | | | 165 IGP IGP IGP 167 Figure 1: Link State info collection 169 Figure 1 describes a typical deployment scenario. In each IGP area, 170 one or more nodes are configured with BGP-LS. These BGP speakers 171 form an IBGP mesh by connecting to one or more route-reflectors. 172 This way, all BGP speakers (specifically the route-reflectors) obtain 173 Link-State information from all IGP areas (and from other ASes from 174 EBGP peers). An external component connects to the route-reflector 175 to obtain this information (perhaps moderated by a policy regarding 176 what information is or isn't advertised to the external component) as 177 described in [RFC7752]. 179 This document describes extensions to BGP-LS to advertise the SR 180 information. An external component (e.g., a controller) then can 181 collect SR information from across an SR domain (as described in 182 [RFC8402]) and construct the end-to-end path (with its associated 183 SIDs) that need to be applied to an incoming packet to achieve the 184 desired end-to-end forwarding. The SR domain may be comprised of a 185 single AS or multiple ASes. 187 2. BGP-LS Extensions for Segment Routing 189 This document defines SR extensions to BGP-LS and specifies the TLVs 190 and sub-TLVs for advertising SR information within the BGP-LS 191 Attribute. Section 2.4 and Section 2.5 lists the equivalent TLVs and 192 sub-TLVs in IS-IS, OSPFv2 and OSPFv3 protocols. 194 BGP-LS [RFC7752] defines the BGP-LS NLRI that can be a Node NLRI, a 195 Link NLRI or a Prefix NLRI. BGP-LS [RFC7752] defines the TLVs that 196 map link-state information to BGP-LS NLRI within the BGP-LS 197 Attribute. This document adds additional BGP-LS Attribute TLVs in 198 order to encode SR information. It does not introduce any changes to 199 the encoding of the BGP-LS NLRIs. 201 2.1. Node Attributes TLVs 203 The following Node Attribute TLVs are defined: 205 +------+-----------------+---------------+ 206 | Type | Description | Section | 207 +------+-----------------+---------------+ 208 | 1161 | SID/Label | Section 2.1.1 | 209 | 1034 | SR Capabilities | Section 2.1.2 | 210 | 1035 | SR Algorithm | Section 2.1.3 | 211 | 1036 | SR Local Block | Section 2.1.4 | 212 | 1037 | SRMS Preference | Section 2.1.5 | 213 +------+-----------------+---------------+ 215 Table 1: Node Attribute TLVs 217 These TLVs should only be added to the BGP-LS Attribute associated 218 with the Node NLRI describing the IGP node that is originating the 219 corresponding IGP TLV/sub-TLV described below. 221 2.1.1. SID/Label Sub-TLV 223 The SID/Label TLV is used as a sub-TLV by the SR Capabilities 224 (Section 2.1.2) and Segment Routing Local Block (SRLB) 225 (Section 2.1.4) TLVs and has the following format: 227 0 1 2 3 228 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 1 229 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 230 | Type | Length | 231 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 232 | SID/Label (variable) | 233 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 235 Figure 2: SID/Label sub-TLV Format 237 Where: 239 Type: 1161 241 Length: Either 3 or 4 depending whether the value is encoded as a 242 label or an index/SID. 244 SID/Label: If length is set to 3, then the 20 rightmost bits 245 represent a label (the total TLV size is 7). If length is set to 246 4, then the value represents a 32 bit SID (the total TLV size is 247 8). 249 2.1.2. SR Capabilities TLV 251 The SR Capabilities TLV is used in order to advertise the node's SR 252 Capabilities including its Segment Routing Global Base (SRGB) 253 range(s). In the case of IS-IS, the capabilities also include the 254 IPv4 and IPv6 support for the SR-MPLS forwarding plane. This 255 information is derived from the protocol specific advertisements. 257 o IS-IS, as defined by the SR Capabilities sub-TLV in 258 [I-D.ietf-isis-segment-routing-extensions]. 260 o OSPFv2/OSPFv3, as defined by the SID/Label Range TLV in 261 [I-D.ietf-ospf-segment-routing-extensions] and 262 [I-D.ietf-ospf-ospfv3-segment-routing-extensions]. 264 The SR Capabilities TLV has the following format: 266 0 1 2 3 267 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 1 268 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 269 | Type | Length | 270 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 271 | Flags | Reserved | 272 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 274 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 275 | Range Size | 276 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 277 // SID/Label sub-TLV (variable) // 278 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 280 Figure 3: SR Capabilities TLV Format 282 Where: 284 Type: 1034 285 Length: Variable. Minimum length is 12. 287 Flags: 1 octet of flags as defined in 288 [I-D.ietf-isis-segment-routing-extensions] for IS-IS. The flags 289 are not currently defined for OSPFv2 and OSPFv3 and SHOULD be set 290 to 0 and MUST be ignored on receipt. 292 Reserved: 1 octet that SHOULD be set to 0 and MUST be ignored on 293 receipt. 295 One or more entries, each of which have the following format: 297 Range Size: 3 octet with a non-zero value indicating the number 298 of labels in the range. 300 SID/Label sub-TLV (as defined in Section 2.1.1) which encodes 301 the first label in the range. Since the SID/Label sub-TLV is 302 used to indicate the first label of the SRGB range, only label 303 encoding is valid under the SR Capabilities TLV. 305 2.1.3. SR Algorithm TLV 307 The SR Algorithm TLV is used in order to advertise the SR Algorithms 308 supported by the node. This information is derived from the protocol 309 specific advertisements. 311 o IS-IS, as defined by the SR Algorithm sub-TLV in 312 [I-D.ietf-isis-segment-routing-extensions]. 314 o OSPFv2/OSPFv3, as defined by the SR Algorithm TLV in 315 [I-D.ietf-ospf-segment-routing-extensions] and 316 [I-D.ietf-ospf-ospfv3-segment-routing-extensions]. 318 The SR Algorithm 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 | Algorithm 1 | Algorithm... | Algorithm N | | 326 +- -+ 327 | | 328 + + 330 Figure 4: SR Algorithm TLV Format 332 Where: 334 Type: 1035 336 Length: Variable. Minimum length is 1 and maximum can be 256. 338 Algorithm: 1 octet identifying the algorithm. 340 2.1.4. SR Local Block TLV 342 The SR Local Block (SRLB) TLV contains the range(s) of labels the 343 node has reserved for local SIDs. Local SIDs are used, e.g., in IGP 344 (IS-IS, OSPF) for Adjacency-SIDs, and may also be allocated by 345 components other than IGP protocols. As an example, an application 346 or a controller may instruct a node to allocate a specific local SID. 347 Therefore, in order for such applications or controllers to know the 348 range of local SIDs available, it is required that the node 349 advertises its SRLB. 351 This information is derived from the protocol specific 352 advertisements. 354 o IS-IS, as defined by the SR Local Block sub-TLV in 355 [I-D.ietf-isis-segment-routing-extensions]. 357 o OSPFv2/OSPFv3, as defined by the SR Local Block TLV in 358 [I-D.ietf-ospf-segment-routing-extensions] and 359 [I-D.ietf-ospf-ospfv3-segment-routing-extensions]. 361 The SRLB TLV has the following format: 363 0 1 2 3 364 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 1 365 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 366 | Type | Length | 367 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 368 | Flags | Reserved | 369 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 371 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 372 | Range Size | 373 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 374 // SID/Label sub-TLV (variable) // 375 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 377 Figure 5: SRLB TLV Format 379 Where: 381 Type: 1036 383 Length: Variable. Minimum length is 12. 385 Flags: 1 octet of flags. None are defined at this stage. 387 Reserved: 1 octet that SHOULD be set to 0 and MUST be ignored on 388 receipt. 390 One or more entries, each of which have the following format: 392 Range Size: 3 octet value indicating the number of labels in 393 the range. 395 SID/Label sub-TLV (as defined in Section 2.1.1) which encodes 396 the first label in the range. Since the SID/Label sub-TLV is 397 used to indicate the first label of the SRLB range, only label 398 encoding is valid under the SR Local Block TLV. 400 2.1.5. SRMS Preference TLV 402 The Segment Routing Mapping Server (SRMS) Preference TLV is used in 403 order to associate a preference with SRMS advertisements from a 404 particular source. [I-D.ietf-spring-segment-routing-ldp-interop] 405 specifies the SRMS functionality along with SRMS preference of the 406 node advertising the SRMS Prefix-to-SID Mapping ranges. 408 This information is derived from the protocol specific 409 advertisements. 411 o IS-IS, as defined by the SRMS Preference sub-TLV in 412 [I-D.ietf-isis-segment-routing-extensions]. 414 o OSPFv2/OSPFv3, as defined by the SRMS Preference TLV in 415 [I-D.ietf-ospf-segment-routing-extensions] and 416 [I-D.ietf-ospf-ospfv3-segment-routing-extensions]. 418 The SRMS Preference TLV has the following format: 420 0 1 2 3 421 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 1 422 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 423 | Type | Length | 424 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 425 | Preference | 426 +-+-+-+-+-+-+-+-+ 428 Figure 6: SRMS Preference TLV Format 430 Where: 432 Type: 1037 434 Length: 1. 436 Preference: 1 octet. Unsigned 8 bit SRMS preference. 438 The use of the SRMS Preference TLV is defined in 439 [I-D.ietf-isis-segment-routing-extensions], 440 [I-D.ietf-ospf-segment-routing-extensions] and 441 [I-D.ietf-ospf-ospfv3-segment-routing-extensions]. 443 2.2. Link Attribute TLVs 445 The following Link Attribute TLVs are are defined: 447 +------+-----------------------+---------------+ 448 | Type | Description | Section | 449 +------+-----------------------+---------------+ 450 | 1099 | Adjacency SID TLV | Section 2.2.1 | 451 | 1100 | LAN Adjacency SID TLV | Section 2.2.2 | 452 | 1172 | L2 Bundle Member TLV | Section 2.2.3 | 453 +------+-----------------------+---------------+ 455 Table 2: Link Attribute TLVs 457 These TLVs should only be added to the BGP-LS Attribute associated 458 with the Link NLRI describing the link of the IGP node that is 459 originating the corresponding IGP TLV/sub-TLV described below. 461 2.2.1. Adjacency SID TLV 463 The Adjacency SID TLV is used in order to advertise information 464 related to an Adjacency SID. This information is originated as in 465 Adj-SID sub-TLV of IS-IS [I-D.ietf-isis-segment-routing-extensions], 466 OSPFv2 [I-D.ietf-ospf-segment-routing-extensions] and OSPFv3 467 [I-D.ietf-ospf-ospfv3-segment-routing-extensions]. 469 The Adjacency SID TLV has the following format: 471 0 1 2 3 472 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 1 473 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 474 | Type | Length | 475 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 476 | Flags | Weight | Reserved | 477 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 478 | SID/Label/Index (variable) | 479 +---------------------------------------------------------------+ 481 Figure 7: Adjacency SID TLV Format 483 Where: 485 Type: 1099 487 Length: Variable, 7 or 8 depending on Label or Index encoding of 488 the SID 490 Flags. 1 octet value which sould be parsed as: 492 * IS-IS Adj-SID flags are defined in 493 [I-D.ietf-isis-segment-routing-extensions] section 2.2.1. 495 * OSPFv2 Adj-SID flags are defined in 496 [I-D.ietf-ospf-segment-routing-extensions] section 6.1. 498 * OSPFv3 Adj-SID flags are defined in 499 [I-D.ietf-ospf-segment-routing-extensions] section 7.1. 501 Weight: Weight used for load-balancing purposes. 503 Reserved: 2 octets that SHOULD be set to 0 and MUST be ignored on 504 receipt. 506 SID/Index/Label: 508 * IS-IS: Label or index value as defined in 509 [I-D.ietf-isis-segment-routing-extensions], 511 * OSPFv2: Label or index value as defined in 512 [I-D.ietf-ospf-segment-routing-extensions], 514 * OSPFv3: Label or index value as defined in 515 [I-D.ietf-ospf-ospfv3-segment-routing-extensions], 517 The Flags and, as an extension, the SID/Index/Label fields of this 518 TLV need to be interpreted accordingly to the respective underlying 519 IS-IS, OSPFv2 or OSPFv3 protocol. The Protocol-ID of the BGP-LS Link 520 NLRI should be used to determine the underlying protocol 521 specification for parsing these fields. 523 2.2.2. LAN Adjacency SID TLV 525 For a LAN, normally a node only announces its adjacency to the IS-IS 526 pseudo-node (or the equivalent OSPF Designated and Backup Designated 527 Routers). The LAN Adjacency Segment TLV allows a node to announce 528 adjacencies to all other nodes attached to the LAN in a single 529 instance of the BGP-LS Link NLRI. Without this TLV, the 530 corresponding BGP-LS link NLRI would need to be originated for each 531 additional adjacency in order to advertise the SR TLVs for these 532 neighbor adjacencies. 534 This information is originated as in LAN Adj-SID sub-TLV of IS-IS 535 [I-D.ietf-isis-segment-routing-extensions], OSPFv2 536 [I-D.ietf-ospf-segment-routing-extensions] and OSPFv3 537 [I-D.ietf-ospf-ospfv3-segment-routing-extensions]. 539 The LAN Adjacency SID TLV has the following format: 541 0 1 2 3 542 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 1 543 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 544 | Type | Length | 545 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 546 | Flags | Weight | Reserved | 547 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 549 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 550 | OSPF Neighbor ID / IS-IS System-ID | 551 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 552 | | 553 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 555 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 556 | SID/Label/Index (variable) | 557 +---------------------------------------------------------------+ 559 Figure 8: LAN Adjacency SID TLV Format 561 Where: 563 Type: 1100 565 Length: Variable. For IS-IS it would be 13 or 14 depending on 566 Label or Index encoding of the SID. For OSPF it would be 11 or 12 567 depending on Label or Index encoding of the SID. 569 Flags. 1 octet value which sould be parsed as: 571 * IS-IS LAN Adj-SID flags are defined in 572 [I-D.ietf-isis-segment-routing-extensions] section 2.2.2. 574 * OSPFv2 LAN Adj-SID flags are defined in 575 [I-D.ietf-ospf-segment-routing-extensions] section 6.2. 577 * OSPFv3 LAN Adj-SID flags are defined in 578 [I-D.ietf-ospf-segment-routing-extensions] section 7.3. 580 Weight: Weight used for load-balancing purposes. 582 Reserved: 2 octets that SHOULD be set to 0 and MUST be ignored on 583 receipt. 585 Neighbor ID: 6 octets for IS-IS for the System-ID and 4 octets for 586 OSPF for the OSPF Router-ID of the neighbor. 588 SID/Index/Label: 590 * IS-IS: Label or index value as defined in 591 [I-D.ietf-isis-segment-routing-extensions], 593 * OSPFv2: Label or index value as defined in 594 [I-D.ietf-ospf-segment-routing-extensions], 596 * OSPFv3: Label or index value as defined in 597 [I-D.ietf-ospf-ospfv3-segment-routing-extensions], 599 The Neighbor ID, Flags and, as an extension, the SID/Index/Label 600 fields of this TLV need to be interpreted accordingly to the 601 respective underlying IS-IS, OSPFv2 or OSPFv3 protocol. The 602 Protocol-ID of the BGP-LS Link NLRI should be used to determine the 603 underlying protocol specification for parsing these fields. 605 2.2.3. L2 Bundle Member Attribute TLV 607 The L2 Bundle Member Attribute TLV identifies an L2 Bundle Member 608 link which in turn is associated with a parent L3 link. The L3 link 609 is described by the Link NLRI defined in [RFC7752] and the L2 Bundle 610 Member Attribute TLV is associated with the Link NLRI. The TLV MAY 611 include sub-TLVs which describe attributes associated with the bundle 612 member. The identified bundle member represents a unidirectional 613 path from the originating router to the neighbor specified in the 614 parent L3 Link. Multiple L2 Bundle Member Attribute TLVs MAY be 615 associated with a Link NLRI. 617 This information is originated as in L2 Bundle Member Attributes TLV 618 of IS-IS [I-D.ietf-isis-l2bundles]. The equivalent functionality has 619 not been specified as yet for OSPF. 621 The L2 Bundle Member Attribute TLV has the following format: 623 0 1 2 3 624 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 1 625 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 626 | Type | Length | 627 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 629 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 630 | L2 Bundle Member Descriptor | 631 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 632 // Link attribute sub-TLVs(variable) // 633 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 635 Figure 9: L2 Bundle Member Attributes TLV Format 637 Where: 639 Type: 1172 641 Length: Variable. 643 L2 Bundle Member Descriptor: A Link Local Identifier as defined in 644 [RFC4202]. 646 Link attributes for L2 Bundle Member Links are advertised as sub-TLVs 647 of the L2 Bundle Member Attribute TLV. The sub-TLVs are identical to 648 existing BGP-LS TLVs as identified in the table below. 650 +-------------+------------------------------------+----------------+ 651 | TLV Code | Description | Reference | 652 | Point | | Document | 653 +-------------+------------------------------------+----------------+ 654 | 1088 | Administrative group (color) | [RFC7752] | 655 | 1089 | Maximum link bandwidth | [RFC7752] | 656 | 1090 | Max. reservable link bandwidth | [RFC7752] | 657 | 1091 | Unreserved bandwidth | [RFC7752] | 658 | 1092 | TE default metric | [RFC7752] | 659 | 1093 | Link protection type | [RFC7752] | 660 | 1099 | Adjacency Segment Identifier (Adj- | Section 2.2.1 | 661 | | SID) TLV | | 662 | 1100 | LAN Adjacency Segment Identifier | Section 2.2.2 | 663 | | (Adj-SID) TLV | | 664 | 1114 | Unidirectional link delay | [RFC8571] | 665 | 1115 | Min/Max Unidirectional link delay | [RFC8571] | 666 | 1116 | Unidirectional Delay Variation | [RFC8571] | 667 | 1117 | Unidirectional packet loss | [RFC8571] | 668 | 1118 | Unidirectional residual bandwidth | [RFC8571] | 669 | 1119 | Unidirectional available bandwidth | [RFC8571] | 670 | 1120 | Unidirectional bandwidth | [RFC8571] | 671 | | utilization | | 672 +-------------+------------------------------------+----------------+ 674 Table 3: BGP-LS Attribute TLVs also used as sub-TLVs of L2 Bundle 675 Member Attribute TLV 677 2.3. Prefix Attribute TLVs 679 The following Prefix Attribute TLVs are defined: 681 +------+------------------------+---------------+ 682 | Type | Description | Section | 683 +------+------------------------+---------------+ 684 | 1158 | Prefix SID | Section 2.3.1 | 685 | 1159 | Range | Section 2.3.4 | 686 | 1170 | Prefix Attribute Flags | Section 2.3.2 | 687 | 1171 | Source Router-ID | Section 2.3.3 | 688 +------+------------------------+---------------+ 690 Table 4: Prefix Attribute TLVs 692 These TLVs should only be added to the BGP-LS Attribute associated 693 with the Prefix NLRI describing the prefix of the IGP node that is 694 originating the corresponding IGP TLV/sub-TLV described below. 696 2.3.1. Prefix SID TLV 698 The Prefix SID TLV is used in order to advertise information related 699 to a Prefix SID. This information is originated as in Prefix-SID 700 sub-TLV of IS-IS [I-D.ietf-isis-segment-routing-extensions], OSPFv2 701 [I-D.ietf-ospf-segment-routing-extensions] and OSPFv3 702 [I-D.ietf-ospf-ospfv3-segment-routing-extensions]. 704 The Prefix SID TLV has the following format: 706 0 1 2 3 707 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 1 708 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 709 | Type | Length | 710 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 711 | Flags | Algorithm | Reserved | 712 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 713 | SID/Index/Label (variable) | 714 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 716 Figure 10: Prefix SID TLV Format 718 Where: 720 Type: 1158 722 Length: Variable, 7 or 8 depending on Label or Index encoding of 723 the SID 725 Flags: 1 octet value which sould be parsed as: 727 * IS-IS Prefix SID flags are defined in 728 [I-D.ietf-isis-segment-routing-extensions] section 2.1. 730 * OSPFv2 Prefix SID flags are defined in 731 [I-D.ietf-ospf-segment-routing-extensions] section 5. 733 * OSPFv3 Prefix SID flags are defined in 734 [I-D.ietf-ospf-segment-routing-extensions] section 5. 736 Algorithm: 1 octet value identify the algorithm. 738 Reserved: 2 octets that SHOULD be set to 0 and MUST be ignored on 739 receipt. 741 SID/Index/Label: 743 * IS-IS: Label or index value as defined in 744 [I-D.ietf-isis-segment-routing-extensions], 746 * OSPFv2: Label or index value as defined in 747 [I-D.ietf-ospf-segment-routing-extensions], 749 * OSPFv3: Label or index value as defined in 750 [I-D.ietf-ospf-ospfv3-segment-routing-extensions], 752 The Flags and, as an extension, the SID/Index/Label fields of this 753 TLV need to be interpreted accordingly to the respective underlying 754 IS-IS, OSPFv2 or OSPFv3 protocol. The Protocol-ID of the BGP-LS 755 Prefix NLRI should be used to determine the underlying protocol 756 specification for parsing these fields. 758 2.3.2. Prefix Attribute Flags TLV 760 The Prefix Attribute Flags TLV carries IPv4/IPv6 prefix attribute 761 flags information. These flags are defined for OSPFv2 in [RFC7684], 762 for OSPFv3 in [RFC5340] and for IS-IS in [RFC7794]. 764 The Prefix Attribute Flags TLV has the following format: 766 0 1 2 3 767 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 1 768 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 769 | Type | Length | 770 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 771 // Flags (variable) // 772 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 774 Figure 11: Prefix Attribute Flags TLV Format 776 Where: 778 Type: 1170 780 Length: variable. 782 Flags: a variable length flag field (according to the length 783 field). Flags are routing protocol specific and are to be parsed 784 as below: 786 * IS-IS flags correspond to the IPv4/IPv6 Extended Reachability 787 Attribute Flags defined in [RFC7794] 789 * OSPFv2 flags correspond to the Flags field of the OSPFv2 790 Extended Prefix TLV defined in [RFC7684] 792 * OSPFv3 flags map to the Prefix Options field defined in 793 [RFC5340] and extended via [RFC8362] 795 The Flags field of this TLV need to be interpreted accordingly to the 796 respective underlying IS-IS, OSPFv2 or OSPFv3 protocol. The 797 Protocol-ID of the BGP-LS Prefix NLRI should be used to determine the 798 underlying protocol specification for parsing these fields. 800 2.3.3. Source Router Identifier (Source Router-ID) TLV 802 The Source Router-ID TLV contains the IPv4 or IPv6 Router-ID of the 803 originator of the Prefix. For IS-IS protocol this is as defined in 804 [RFC7794] IPv4 or IPv6 Router-ID of the originating router. For OSPF 805 protocol, this is as defined in [I-D.ietf-lsr-ospf-prefix-originator] 806 and is a 32 bit OSPF Router-ID of the originating router.. 808 The Source Router-ID TLV has the following format: 810 0 1 2 3 811 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 1 812 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 813 | Type | Length | 814 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 815 // 4 or 6 octet Router-ID // 816 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 818 Figure 12: Source Router-ID TLV Format 820 Where: 822 Type: 1171 824 Length: 4 or 16 in case of IS-IS and 4 in case of OSPF. 826 Router-ID: the IPv4 or IPv6 Router-ID in case of IS-IS and the 827 OSPF Router-ID in the case of OSPF. 829 2.3.4. Range TLV 831 The range TLV is used in order to advertise a range of prefix-to-SID 832 mappings as part of the Segment Routing Mapping Server (SRMS) 833 functionality [I-D.ietf-spring-segment-routing-ldp-interop], as 834 defined in the respective underlying IGP SR extensions 835 [I-D.ietf-ospf-segment-routing-extensions], 837 [I-D.ietf-ospf-ospfv3-segment-routing-extensions] and 838 [I-D.ietf-isis-segment-routing-extensions]. 840 A Prefix NLRI, that been advertised with a Range TLV, is considered 841 as a normal routing prefix (i.e. prefix reachability) unless there is 842 also an IGP metric TLV (TLV 1095) attached to it. 844 The format of the Range TLV is as follows: 846 0 1 2 3 847 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 1 848 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 849 | Type | Length | 850 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 851 | Flags | Reserved | Range Size | 852 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 853 // sub-TLVs // 854 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 856 Figure 13: Range TLV Format 858 Where: 860 Type: 1159 862 Length: Variable, 11 or 12 depending on Label or Index encoding of 863 the SID 865 Flags: as defined in [I-D.ietf-ospf-segment-routing-extensions], 866 [I-D.ietf-ospf-ospfv3-segment-routing-extensions] and 867 [I-D.ietf-isis-segment-routing-extensions]. 869 Reserved: 1 octet that SHOULD be set to 0 and MUST be ignored on 870 receipt. 872 Range Size: 2 octets as defined in 873 [I-D.ietf-ospf-segment-routing-extensions]. 875 The Flags field of this TLV need to be interpreted accordingly to the 876 respective underlying IS-IS, OSPFv2 or OSPFv3 protocol. The consumer 877 of the BGP-LS interested in this TLV information MUST check the 878 Protocol-ID of the BGP-LS Prefix NLRI and refer to the underlying 879 protocol specification in order to parse this field. 881 Within the Range TLV, the prefix-to-SID mappings are advertised using 882 sub-TLVs as below: 884 Range TLV 885 Prefix-SID TLV (used as a sub-TLV in this context) 887 Where: 889 o The Range TLV is defined in Section 2.3.4. 891 o The Prefix-SID TLV (used as sub-TLV in this context) is defined in 892 Section 2.3.1. 894 The following sub-sections describe the procedures for mapping of 895 information from the underlying IGP protocols into the Range TLV. 897 2.3.4.1. Advertisement Procedure for OSPF 899 The OSPFv2/OSPFv3 Extended Prefix Range TLV is encoded in the Range 900 TLV. The flags of the Range TLV have the semantic mapped to the 901 definition in [I-D.ietf-ospf-segment-routing-extensions] section 4 or 902 [I-D.ietf-ospf-ospfv3-segment-routing-extensions] section 4. 904 Then the prefix-to-SID mapping from the OSPF Prefix SID sub-TLV is 905 encoded using the BGP-LS Prefix-SID TLV as defined in Section 2.3.1 906 with the flags set according to the definition in 907 [I-D.ietf-ospf-segment-routing-extensions] section 5 or 908 [I-D.ietf-ospf-ospfv3-segment-routing-extensions] section 5. 910 2.3.4.2. Advertisement Procedure for IS-IS 912 The IS-IS SID/Label Binding TLV, when used to signal mapping server 913 label bindings, is encoded in the Range TLV. The flags of the Range 914 TLV have the sematic mapped to the definition in 915 [I-D.ietf-isis-segment-routing-extensions] section 2.4.1. 917 Then the prefix-to-SID mappings from the IS-IS Prefix SID sub-TLV is 918 encoded using the BGP-LS Prefix-SID TLV as defined in Section 2.3.1 919 with the flags set according to the definition in 920 [I-D.ietf-isis-segment-routing-extensions] section 2.4.4.1. 922 2.4. Equivalent IS-IS Segment Routing TLVs/Sub-TLVs 924 This section illustrate the IS-IS Segment Routing Extensions TLVs and 925 sub-TLVs mapped to the ones defined in this document. 927 The following table, illustrates for each BGP-LS TLV, its equivalence 928 in IS-IS. 930 +------------+------------+-----------------------------------------+ 931 | Descriptio | IS-IS TLV | Reference | 932 | n | /sub-TLV | | 933 +------------+------------+-----------------------------------------+ 934 | SR Capabil | 2 | draft-ietf-isis-segment-routing- | 935 | ities | | extensions section-3.1 | 936 | SR | 19 | draft-ietf-isis-segment-routing- | 937 | Algorithm | | extensions section-3.2 | 938 | SR Local | 22 | draft-ietf-isis-segment-routing- | 939 | Block | | extensions section-3.3 | 940 | SRMS | 19 | draft-ietf-isis-segment-routing- | 941 | Preference | | extensions section-3.2 | 942 | Adjacency | 31 | draft-ietf-isis-segment-routing- | 943 | SID | | extensions section-2.2.1 | 944 | LAN | 32 | draft-ietf-isis-segment-routing- | 945 | Adjacency | | extensions section-2.2.2 | 946 | SID | | | 947 | Prefix SID | 3 | draft-ietf-isis-segment-routing- | 948 | | | extensions section-2.1 | 949 | Range | 149 | draft-ietf-isis-segment-routing- | 950 | | | extensions section-2.4 | 951 | SID/Label | 1 | draft-ietf-isis-segment-routing- | 952 | | | extensions section-2.3 | 953 | Prefix | 4 | RFC7794 section-2.1 | 954 | Attribute | | | 955 | Flags | | | 956 | Source | 11/12 | RFC7794 section-2.2 | 957 | Router-ID | | | 958 | L2 Bundle | 25 | draft-ietf-isis-l2bundles section-2 | 959 | Member | | | 960 | Attributes | | | 961 +------------+------------+-----------------------------------------+ 963 Table 5: IS-IS Segment Routing Extensions TLVs/Sub-TLVs 965 2.5. Equivalent OSPFv2/OSPFv3 Segment Routing TLVs/Sub-TLVs 967 This section illustrate the OSPFv2 and OSPFv3 Segment Routing 968 Extensions TLVs and sub-TLVs mapped to the ones defined in this 969 document. 971 The following table, illustrates for each BGP-LS TLV, its equivalence 972 in OSPFv2 and OSPFv3. 974 +------------+------------+-----------------------------------------+ 975 | Descriptio | OSPFv2 TLV | Reference | 976 | n | /sub-TLV | | 977 +------------+------------+-----------------------------------------+ 978 | SR Capabil | 9 | draft-ietf-ospf-segment-routing- | 979 | ities | | extensions section-3.2 | 980 | SR | 8 | draft-ietf-ospf-segment-routing- | 981 | Algorithm | | extensions section-3.1 | 982 | SR Local | 14 | draft-ietf-ospf-segment-routing- | 983 | Block | | extensions section-3.3 | 984 | SRMS | 15 | draft-ietf-ospf-segment-routing- | 985 | Preference | | extensions section-3.4 | 986 | Adjacency | 2 | draft-ietf-ospf-segment-routing- | 987 | SID | | extensions section-6.1 | 988 | LAN | 3 | draft-ietf-ospf-segment-routing- | 989 | Adjacency | | extensions section-6.2 | 990 | SID | | | 991 | Prefix SID | 2 | draft-ietf-ospf-segment-routing- | 992 | | | extensions section-5 | 993 | Range | 2 | draft-ietf-ospf-segment-routing- | 994 | | | extensions section-4 | 995 | SID/Label | 1 | draft-ietf-ospf-segment-routing- | 996 | | | extensions section-2.1 | 997 | Prefix | 4 | RFC7684 section-2.1 | 998 | Attribute | | | 999 | Flags | | | 1000 | Source | TBD | draft-ietf-lsr-ospf-prefix-originator | 1001 | Router-ID | | section-4 | 1002 +------------+------------+-----------------------------------------+ 1004 Table 6: OSPFv2 Segment Routing Extensions TLVs/Sub-TLVs 1006 +-----------+------------+------------------------------------------+ 1007 | Descripti | OSPFv3 TLV | Reference | 1008 | on | /sub-TLV | | 1009 +-----------+------------+------------------------------------------+ 1010 | SR Capabi | 9 | draft-ietf-ospf-ospfv3-segment-routing- | 1011 | lities | | extensions section-3.2 | 1012 | SR | 8 | draft-ietf-ospf-ospfv3-segment-routing- | 1013 | Algorithm | | extensions section-3.1 | 1014 | SR Local | 14 | draft-ietf-ospf-ospfv3-segment-routing- | 1015 | Block | | extensions section-3.3 | 1016 | SRMS Pref | 15 | draft-ietf-ospf-ospfv3-segment-routing- | 1017 | erence | | extensions section-3.4 | 1018 | Adjacency | 5 | draft-ietf-ospf-ospfv3-segment-routing- | 1019 | SID | | extensions section-6.1 | 1020 | LAN | 6 | draft-ietf-ospf-ospfv3-segment-routing- | 1021 | Adjacency | | extensions section-6.2 | 1022 | SID | | | 1023 | Prefix | 4 | draft-ietf-ospf-ospfv3-segment-routing- | 1024 | SID | | extensions section-5 | 1025 | Range | 9 | draft-ietf-ospf-ospfv3-segment-routing- | 1026 | | | extensions section-4 | 1027 | SID/Label | 7 | draft-ietf-ospf-ospfv3-segment-routing- | 1028 | | | extensions section-2.1 | 1029 | Prefix | 4 | RFC8362 section-3.1 | 1030 | Attribute | | | 1031 | Flags | | | 1032 | Source | TBD | draft-ietf-lsr-ospf-prefix-originator | 1033 | Router-ID | | section-4 | 1034 +-----------+------------+------------------------------------------+ 1036 Table 7: OSPFv3 Segment Routing Extensions TLVs/Sub-TLVs 1038 3. IANA Considerations 1040 Early allocation of codepoints has been done by IANA for this 1041 document from the registry "BGP-LS Node Descriptor, Link Descriptor, 1042 Prefix Descriptor, and Attribute TLVs" based on Table 8. The column 1043 "IS-IS TLV/Sub-TLV" defined in the registry does not require any 1044 value and should be left empty. 1046 3.1. TLV/Sub-TLV Code Points Summary 1048 This section contains the global table of all TLVs/sub-TLVs defined 1049 in this document. 1051 +----------------+-----------------------------+---------------+ 1052 | TLV Code Point | Description | Reference | 1053 +----------------+-----------------------------+---------------+ 1054 | 1034 | SR Capabilities | Section 2.1.2 | 1055 | 1035 | SR Algorithm | Section 2.1.3 | 1056 | 1036 | SR Local Block | Section 2.1.4 | 1057 | 1037 | SRMS Preference | Section 2.1.5 | 1058 | 1099 | Adjacency SID | Section 2.2.1 | 1059 | 1100 | LAN Adjacency SID | Section 2.2.2 | 1060 | 1158 | Prefix SID | Section 2.3.1 | 1061 | 1159 | Range | Section 2.3.4 | 1062 | 1161 | SID/Label | Section 2.1.1 | 1063 | 1170 | Prefix Attribute Flags | Section 2.3.2 | 1064 | 1171 | Source Router-ID | Section 2.3.3 | 1065 | 1172 | L2 Bundle Member Attributes | Section 2.2.3 | 1066 +----------------+-----------------------------+---------------+ 1068 Table 8: Summary Table of TLV/Sub-TLV Codepoints 1070 4. Manageability Considerations 1072 This section is structured as recommended in [RFC5706]. 1074 The new protocol extensions introduced in this document augment the 1075 existing IGP topology information that is distributed via [RFC7752]. 1076 Procedures and protocol extensions defined in this document do not 1077 affect the BGP protocol operations and management other than as 1078 discussed in the Manageability Considerations section of [RFC7752]. 1079 Specifically, the malformed attribute tests for syntactic checks in 1080 the Fault Management section of [RFC7752] now encompass the new BGP- 1081 LS Attribute TLVs defined in this document. The semantic or content 1082 checking for the TLVs specified in this document and their 1083 association with the BGP-LS NLRI types or their BGP-LS Attribute is 1084 left to the consumer of the BGP-LS information (e.g. an application 1085 or a controller) and not the BGP protocol. 1087 A consumer of the BGP-LS information retrieves this information over 1088 a BGP-LS session (refer Section 1 and 2 of [RFC7752]). The handling 1089 of semantic or content errors by the consumer would be dictated by 1090 the nature of its application usage and hence is beyond the scope of 1091 this document. 1093 This document only introduces new Attribute TLVs and any syntactic 1094 error in them would result in only that specific attribute being 1095 discarded with an error log. The SR information introduced in BGP-LS 1096 by this specification, may be used by BGP-LS consumer applications 1097 like a SR path computation engine (PCE) to learn the SR capabilities 1098 of the nodes in the topology and the mapping of SR segments to those 1099 nodes. This can enable the SR PCE to perform path computations based 1100 on SR for traffic engineering use-cases and to steer traffic on paths 1101 different from the underlying IGP based distributed best path 1102 computation. Errors in the encoding or decoding of the SR 1103 information may result in the unavailability of such information to 1104 the SR PCE or incorrect information being made available to it. This 1105 may result in the SR PCE not being able to perform the desired SR 1106 based optimization functionality or to perform it in an unexpected or 1107 inconsistent manner. The handling of such errors by applications 1108 like SR PCE may be implementation specific and out of scope of this 1109 document. 1111 The extensions, specified in this document, do not introduce any new 1112 configuration or monitoring aspects in BGP or BGP-LS other than as 1113 discussed in [RFC7752]. The manageability aspects of the underlying 1114 SR features are covered by [I-D.ietf-spring-sr-yang], 1115 [I-D.ietf-isis-sr-yang] and [I-D.ietf-ospf-sr-yang]. 1117 5. Security Considerations 1119 The new protocol extensions introduced in this document augment the 1120 existing IGP topology information that is distributed via [RFC7752]. 1121 The Security Considerations section of [RFC7752] also applies to 1122 these extensions. The procedures and new TLVs defined in this 1123 document, by themselves, do not affect the BGP-LS security model 1124 discussed in [RFC7752]. 1126 The TLVs introduced in this document are used to propagate IGP 1127 defined information ([I-D.ietf-isis-segment-routing-extensions], 1128 [I-D.ietf-ospf-segment-routing-extensions] and 1129 [I-D.ietf-ospf-ospfv3-segment-routing-extensions]). These TLVs 1130 represent the SR information associated with the IGP node, link and 1131 prefix. The IGP instances originating these TLVs are assumed to 1132 support all the required security and authentication mechanisms (as 1133 described in [I-D.ietf-isis-segment-routing-extensions], 1134 [I-D.ietf-ospf-segment-routing-extensions] and 1135 [I-D.ietf-ospf-ospfv3-segment-routing-extensions]) in order to 1136 prevent any security issue when propagating the TLVs into BGP-LS. 1137 The advertisement of the link attribute information defined in this 1138 document presents no additional risk beyond that associated with the 1139 existing set of link attribute information already supported in 1140 [RFC7752]. 1142 BGP-LS SR extensions enable traffic engineering use-cases within the 1143 Segment Routing domain. SR operates within a trusted domain 1144 [RFC8402] and its security considerations also apply to BGP-LS 1145 sessions when carrying SR information. The SR traffic engineering 1146 policies using the SIDs advertised via BGP-LS are expected to be used 1147 entirely within this trusted SR domain (e.g. between multiple AS/ 1148 domains within a single provider network). Therefore, precaution is 1149 necessary to ensure that the SR information collected via BGP-LS is 1150 limited to specific consumers in a secure manner within this SR 1151 domain. 1153 The isolation of BGP-LS peering sessions is also required to ensure 1154 that BGP-LS topology information (including the newly added SR 1155 information) is not advertised to an external BGP peering session 1156 outside an administrative domain. 1158 6. Contributors 1160 The following people have substantially contributed to the editing of 1161 this document: 1163 Peter Psenak 1164 Cisco Systems 1165 Email: ppsenak@cisco.com 1167 Les Ginsberg 1168 Cisco Systems 1169 Email: ginsberg@cisco.com 1171 Acee Lindem 1172 Cisco Systems 1173 Email: acee@cisco.com 1175 Saikat Ray 1176 Individual 1177 Email: raysaikat@gmail.com 1179 Jeff Tantsura 1180 Apstra Inc. 1181 Email: jefftant.ietf@gmail.com 1183 7. Acknowledgements 1185 The authors would like to thank Jeffrey Haas, Aijun Wang, Robert 1186 Raszuk and Susan Hares for their review of this document and their 1187 comments. The authors would also like to thank Alvaro Retana for his 1188 extensive review and comments which helped correct issues and improve 1189 the document. 1191 8. References 1193 8.1. Normative References 1195 [I-D.ietf-isis-l2bundles] 1196 Ginsberg, L., Bashandy, A., Filsfils, C., Nanduri, M., and 1197 E. Aries, "Advertising L2 Bundle Member Link Attributes in 1198 IS-IS", draft-ietf-isis-l2bundles-07 (work in progress), 1199 May 2017. 1201 [I-D.ietf-isis-segment-routing-extensions] 1202 Previdi, S., Ginsberg, L., Filsfils, C., Bashandy, A., 1203 Gredler, H., and B. Decraene, "IS-IS Extensions for 1204 Segment Routing", draft-ietf-isis-segment-routing- 1205 extensions-24 (work in progress), April 2019. 1207 [I-D.ietf-lsr-ospf-prefix-originator] 1208 Wang, A., Lindem, A., Dong, J., Talaulikar, K., and P. 1209 Psenak, "OSPF Extension for Prefix Originator", draft- 1210 ietf-lsr-ospf-prefix-originator-00 (work in progress), 1211 February 2019. 1213 [I-D.ietf-ospf-ospfv3-segment-routing-extensions] 1214 Psenak, P. and S. Previdi, "OSPFv3 Extensions for Segment 1215 Routing", draft-ietf-ospf-ospfv3-segment-routing- 1216 extensions-23 (work in progress), January 2019. 1218 [I-D.ietf-ospf-segment-routing-extensions] 1219 Psenak, P., Previdi, S., Filsfils, C., Gredler, H., 1220 Shakir, R., Henderickx, W., and J. Tantsura, "OSPF 1221 Extensions for Segment Routing", draft-ietf-ospf-segment- 1222 routing-extensions-27 (work in progress), December 2018. 1224 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1225 Requirement Levels", BCP 14, RFC 2119, 1226 DOI 10.17487/RFC2119, March 1997, 1227 . 1229 [RFC4202] Kompella, K., Ed. and Y. Rekhter, Ed., "Routing Extensions 1230 in Support of Generalized Multi-Protocol Label Switching 1231 (GMPLS)", RFC 4202, DOI 10.17487/RFC4202, October 2005, 1232 . 1234 [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF 1235 for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008, 1236 . 1238 [RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., 1239 Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute 1240 Advertisement", RFC 7684, DOI 10.17487/RFC7684, November 1241 2015, . 1243 [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and 1244 S. Ray, "North-Bound Distribution of Link-State and 1245 Traffic Engineering (TE) Information Using BGP", RFC 7752, 1246 DOI 10.17487/RFC7752, March 2016, 1247 . 1249 [RFC7794] Ginsberg, L., Ed., Decraene, B., Previdi, S., Xu, X., and 1250 U. Chunduri, "IS-IS Prefix Attributes for Extended IPv4 1251 and IPv6 Reachability", RFC 7794, DOI 10.17487/RFC7794, 1252 March 2016, . 1254 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 1255 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 1256 May 2017, . 1258 [RFC8362] Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and 1259 F. Baker, "OSPFv3 Link State Advertisement (LSA) 1260 Extensibility", RFC 8362, DOI 10.17487/RFC8362, April 1261 2018, . 1263 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 1264 Decraene, B., Litkowski, S., and R. Shakir, "Segment 1265 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 1266 July 2018, . 1268 [RFC8571] Ginsberg, L., Ed., Previdi, S., Wu, Q., Tantsura, J., and 1269 C. Filsfils, "BGP - Link State (BGP-LS) Advertisement of 1270 IGP Traffic Engineering Performance Metric Extensions", 1271 RFC 8571, DOI 10.17487/RFC8571, March 2019, 1272 . 1274 8.2. Informative References 1276 [I-D.ietf-isis-sr-yang] 1277 Litkowski, S., Qu, Y., Sarkar, P., Chen, I., and J. 1278 Tantsura, "YANG Data Model for IS-IS Segment Routing", 1279 draft-ietf-isis-sr-yang-05 (work in progress), March 2019. 1281 [I-D.ietf-ospf-sr-yang] 1282 Yeung, D., Qu, Y., Zhang, Z., Chen, I., and A. Lindem, 1283 "YANG Data Model for OSPF SR (Segment Routing) Protocol", 1284 draft-ietf-ospf-sr-yang-07 (work in progress), March 2019. 1286 [I-D.ietf-spring-segment-routing-ldp-interop] 1287 Bashandy, A., Filsfils, C., Previdi, S., Decraene, B., and 1288 S. Litkowski, "Segment Routing interworking with LDP", 1289 draft-ietf-spring-segment-routing-ldp-interop-15 (work in 1290 progress), September 2018. 1292 [I-D.ietf-spring-sr-yang] 1293 Litkowski, S., Qu, Y., Lindem, A., Sarkar, P., and J. 1294 Tantsura, "YANG Data Model for Segment Routing", draft- 1295 ietf-spring-sr-yang-12 (work in progress), February 2019. 1297 [RFC5706] Harrington, D., "Guidelines for Considering Operations and 1298 Management of New Protocols and Protocol Extensions", 1299 RFC 5706, DOI 10.17487/RFC5706, November 2009, 1300 . 1302 Authors' Addresses 1304 Stefano Previdi 1305 Huawei Technologies 1306 Rome 1307 Italy 1309 Email: stefano@previdi.net 1311 Ketan Talaulikar (editor) 1312 Cisco Systems, Inc. 1313 India 1315 Email: ketant@cisco.com 1317 Clarence Filsfils 1318 Cisco Systems, Inc. 1319 Brussels 1320 Belgium 1322 Email: cfilsfil@cisco.com 1324 Hannes Gredler 1325 RtBrick Inc. 1327 Email: hannes@rtbrick.com 1328 Mach(Guoyi) Chen 1329 Huawei Technologies 1330 Huawei Building, No. 156 Beiqing Rd. 1331 Beijing 100095 1332 China 1334 Email: mach.chen@huawei.com