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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Open Shortest Path First IGP P. Psenak, Ed. 3 Internet-Draft Cisco Systems, Inc. 4 Intended status: Standards Track S. Previdi, Ed. 5 Expires: April 24, 2019 Individual 6 October 21, 2018 8 OSPFv3 Extensions for Segment Routing 9 draft-ietf-ospf-ospfv3-segment-routing-extensions-16 11 Abstract 13 Segment Routing (SR) allows a flexible definition of end-to-end paths 14 within IGP topologies by encoding paths as sequences of topological 15 sub-paths, called "segments". These segments are advertised by the 16 link-state routing protocols (IS-IS and OSPF). 18 This draft describes the OSPFv3 extensions required for Segment 19 Routing. 21 Requirements Language 23 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 24 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 25 document are to be interpreted as described in [RFC2119]. 27 Status of This Memo 29 This Internet-Draft is submitted in full conformance with the 30 provisions of BCP 78 and BCP 79. 32 Internet-Drafts are working documents of the Internet Engineering 33 Task Force (IETF). Note that other groups may also distribute 34 working documents as Internet-Drafts. The list of current Internet- 35 Drafts is at https://datatracker.ietf.org/drafts/current/. 37 Internet-Drafts are draft documents valid for a maximum of six months 38 and may be updated, replaced, or obsoleted by other documents at any 39 time. It is inappropriate to use Internet-Drafts as reference 40 material or to cite them other than as "work in progress." 42 This Internet-Draft will expire on April 24, 2019. 44 Copyright Notice 46 Copyright (c) 2018 IETF Trust and the persons identified as the 47 document authors. All rights reserved. 49 This document is subject to BCP 78 and the IETF Trust's Legal 50 Provisions Relating to IETF Documents 51 (https://trustee.ietf.org/license-info) in effect on the date of 52 publication of this document. Please review these documents 53 carefully, as they describe your rights and restrictions with respect 54 to this document. Code Components extracted from this document must 55 include Simplified BSD License text as described in Section 4.e of 56 the Trust Legal Provisions and are provided without warranty as 57 described in the Simplified BSD License. 59 Table of Contents 61 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 62 2. Segment Routing Identifiers . . . . . . . . . . . . . . . . . 3 63 2.1. SID/Label Sub-TLV . . . . . . . . . . . . . . . . . . . . 3 64 3. Segment Routing Capabilities . . . . . . . . . . . . . . . . 4 65 3.1. SR-Algorithm TLV . . . . . . . . . . . . . . . . . . . . 4 66 3.2. SID/Label Range TLV . . . . . . . . . . . . . . . . . . . 5 67 3.3. SR Local Block TLV . . . . . . . . . . . . . . . . . . . 7 68 3.4. SRMS Preference TLV . . . . . . . . . . . . . . . . . . . 9 69 4. OSPFv3 Extended Prefix Range TLV . . . . . . . . . . . . . . 10 70 5. Prefix SID Sub-TLV . . . . . . . . . . . . . . . . . . . . . 13 71 6. Adjacency Segment Identifier (Adj-SID) . . . . . . . . . . . 16 72 6.1. Adj-SID Sub-TLV . . . . . . . . . . . . . . . . . . . . . 17 73 6.2. LAN Adj-SID Sub-TLV . . . . . . . . . . . . . . . . . . . 18 74 7. Elements of Procedure . . . . . . . . . . . . . . . . . . . . 19 75 7.1. Intra-area Segment routing in OSPFv3 . . . . . . . . . . 19 76 7.2. Inter-area Segment routing in OSPFv3 . . . . . . . . . . 20 77 7.3. Segment Routing for External Prefixes . . . . . . . . . . 21 78 7.4. Advertisement of Adj-SID . . . . . . . . . . . . . . . . 22 79 7.4.1. Advertisement of Adj-SID on Point-to-Point Links . . 22 80 7.4.2. Adjacency SID on Broadcast or NBMA Interfaces . . . . 22 81 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22 82 8.1. OSPFv3 Extended-LSA TLV Registry . . . . . . . . . . . . 22 83 8.2. OSPFv3 Extended-LSA Sub-TLV registry . . . . . . . . . . 23 84 9. Security Considerations . . . . . . . . . . . . . . . . . . . 23 85 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 23 86 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 24 87 11.1. Normative References . . . . . . . . . . . . . . . . . . 24 88 11.2. Informative References . . . . . . . . . . . . . . . . . 26 89 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26 91 1. Introduction 93 Segment Routing (SR) allows a flexible definition of end-to-end paths 94 within IGP topologies by encoding paths as sequences of topological 95 sub-paths, called "segments". These segments are advertised by the 96 link-state routing protocols (IS-IS and OSPF). Prefix segments 97 represent an ECMP-aware shortest-path to a prefix (or a node), as per 98 the state of the IGP topology. Adjacency segments represent a hop 99 over a specific adjacency between two nodes in the IGP. A prefix 100 segment is typically a multi-hop path while an adjacency segment, in 101 most cases, is a one-hop path. SR's control-plane can be applied to 102 both IPv6 and MPLS data-planes, and does not require any additional 103 signalling (other than IGP extensions). The IPv6 data plane is out 104 of the scope of this specification - OSPFv3 extension for SR with 105 IPv6 data plane will be specified in a separate document. When used 106 in MPLS networks, SR paths do not require any LDP or RSVP-TE 107 signalling. However, SR can interoperate in the presence of LSPs 108 established with RSVP or LDP. 110 There are additional segment types, e.g., Binding SID defined in 111 [RFC8402]. 113 This draft describes the OSPFv3 extensions required for Segment 114 Routing with MPLS data plane. 116 Segment Routing architecture is described in [RFC8402]. 118 Segment Routing use cases are described in [RFC7855]. 120 2. Segment Routing Identifiers 122 Segment Routing defines various types of Segment Identifiers (SIDs): 123 Prefix-SID, Adjacency-SID, LAN Adjacency SID, and Binding SID. 125 2.1. SID/Label Sub-TLV 127 The SID/Label Sub-TLV appears in multiple TLVs or Sub-TLVs defined 128 later in this document. It is used to advertise the SID or label 129 associated with a prefix or adjacency. The SID/Label Sub-TLV has 130 following format: 132 0 1 2 3 133 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 1 134 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 135 | Type | Length | 136 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 137 | SID/Label (variable) | 138 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 140 where: 142 Type: 7 144 Length: Variable, 3 or 4 octets 145 SID/Label: If length is set to 3, then the 20 rightmost bits 146 represent a label. If length is set to 4, then the value 147 represents a 32-bit SID. 149 The receiving router MUST ignore the SID/Label Sub-TLV if the 150 length is other then 3 or 4. 152 3. Segment Routing Capabilities 154 Segment Routing requires some additional router capabilities to be 155 advertised to other routers in the area. 157 These SR capabilities are advertised in the OSPFv3 Router Information 158 Opaque LSA (defined in [RFC7770]). 160 3.1. SR-Algorithm TLV 162 The SR-Algorithm TLV is a top-level TLV of the OSPFv3 Router 163 Information Opaque LSA (defined in [RFC7770]). 165 The SR-Algorithm TLV is optional. It SHOULD only be advertised once 166 in the OSPFv3 Router Information Opaque LSA. If the SR-Algorithm TLV 167 is not advertised by the node, such node is considered as not being 168 segment routing capable. 170 An SR router can use various algorithms when calculating reachability 171 to OSPFv3 routers or prefixes in an OSPFv3 area. Examples of these 172 algorithms are metric-based Shortest Path First (SPF), various 173 flavors of Constrained SPF, etc. The SR-Algorithm TLV allows a 174 router to advertise the algorithms currently used by the router to 175 other routers in an OSPFv3 area. The SR-Algorithm TLV has following 176 format: 178 0 1 2 3 179 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 1 180 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 181 | Type | Length | 182 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 183 | Algorithm 1 | Algorithm... | Algorithm n | | 184 +- -+ 185 | | 186 + + 188 where: 190 Type: 8 191 Length: Variable, in octets, dependent on number of algorithms 192 advertised. 194 Algorithm: Single octet identifying the algorithm. Algorithms are 195 defined in "IGP Algorithm Type" registry under "Interior Gateway 196 Protocol (IGP) Parameters", defined in 197 [I-D.ietf-ospf-segment-routing-extensions]. 199 When multiple SR-Algorithm TLVs are received from a given router, the 200 receiver MUST use the first occurrence of the TLV in the OSPFv3 201 Router Information Opaque LSA. If the SR-Algorithm TLV appears in 202 multiple OSPFv3 Router Information Opaque LSAs that have different 203 flooding scopes, the SR-Algorithm TLV in the OSPFv3 Router 204 Information Opaque LSA with the area-scoped flooding scope MUST be 205 used. If the SR-Algorithm TLV appears in multiple OSPFv3 Router 206 Information Opaque LSAs that have the same flooding scope, the SR- 207 Algorithm TLV in the OSPFv3 Router Information Opaque LSA with the 208 numerically smallest Instance ID MUST be used and subsequent 209 instances of the SR-Algorithm TLV MUST be ignored. 211 The OSPFv3 Router Information Opaque LSA can be advertised at any of 212 the defined opaque flooding scopes (link, area, or Autonomous System 213 (AS)). For the purpose of SR-Algorithm TLV advertisement, area- 214 scoped flooding is REQUIRED. 216 3.2. SID/Label Range TLV 218 Prefix SIDs MAY be advertised in a form of an index as described in 219 Section 5. Such index defines the offset in the SID/Label space 220 advertised by the router. The SID/Label Range TLV is used to 221 advertise such SID/Label space. 223 The SID/Label Range TLV is a top-level TLV of the OSPFv3 Router 224 Information Opaque LSA (defined in [RFC7770]). 226 The SID/Label Range TLV MAY appear multiple times and has the 227 following format: 229 0 1 2 3 230 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 1 231 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 232 | Type | Length | 233 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 234 | Range Size | Reserved | 235 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 236 | Sub-TLVs (variable) | 237 +- -+ 238 | | 239 + + 241 where: 243 Type: 9 245 Length: Variable, in octets, dependent on Sub-TLVs. 247 Range Size: 3-octet SID/label range size (i.e., the number of SIDs 248 or labels in the range including the first SID/label). It MUST be 249 greater than 0. 251 Reserved: SHOULD be set to 0 on transmission and MUST be ignored 252 on reception. 254 Initially, the only supported Sub-TLV is the SID/Label Sub-TLV as 255 defined in Section 2.1. The SID/Label Sub-TLV MUST be included in 256 the SID/Label Range TLV. The SID/Label advertised in the SID/Label 257 Sub-TLV represents the first SID/Label in the advertised range. 259 Only a single SID/Label Sub-TLV MAY be advertised in SID/Label Range 260 TLV. If more then one SID/Label Sub-TLVs are present, the SID/Label 261 Range TLV MUST be ignored. 263 Multiple occurrences of the SID/Label Range TLV MAY be advertised, in 264 order to advertise multiple ranges. In such case: 266 o The originating router MUST encode each range into a different 267 SID/Label Range TLV. 269 o The originating router decides the order in which the set of SID/ 270 Label Range TLVs are advertised inside the Router Information 271 Opaque LSA. The originating router MUST ensure the order is the 272 same after a graceful restart (using checkpointing, non-volatile 273 storage, or any other mechanism) in order to assure the SID/label 274 range and SID index correspondence is preserved across graceful 275 restarts. 277 o The receiving router MUST adhere to the order in which the ranges 278 are advertised when calculating a SID/label from a SID index. 280 o The originating router MUST NOT advertise overlapping ranges. 282 o When a router receives multiple overlapping ranges, it MUST 283 conform to the procedures defined in 284 [I-D.ietf-spring-segment-routing-mpls]. 286 The following example illustrates the advertisement of multiple 287 ranges: 289 The originating router advertises the following ranges: 291 Range 1: Range Size: 100 SID/Label Sub-TLV: 100 292 Range 1: Range Size: 100 SID/Label Sub-TLV: 1000 293 Range 1: Range Size: 100 SID/Label Sub-TLV: 500 295 The receiving routers concatenate the ranges and build the Segment 296 Routing Global Block (SRGB) as follows: 298 SRGB = [100, 199] 299 [1000, 1099] 300 [500, 599] 302 The indexes span multiple ranges: 304 index=0 means label 100 305 ... 306 index 99 means label 199 307 index 100 means label 1000 308 index 199 means label 1099 309 ... 310 index 200 means label 500 311 ... 313 The OSPFv3 Router Information Opaque LSA can be advertised at any of 314 the defined flooding scopes (link, area, or autonomous system (AS)). 315 For the purpose of SID/Label Range TLV advertisement, area-scoped 316 flooding is REQUIRED. 318 3.3. SR Local Block TLV 320 The SR Local Block TLV (SRLB TLV) contains the range of labels the 321 node has reserved for local SIDs. SIDs from the SRLB MAY be used for 322 Adjacency-SIDs, but also by components other than the OSPFv3 323 protocol. As an example, an application or a controller can instruct 324 the router to allocate a specific local SID. Some controllers or 325 applications can use the control plane to discover the available set 326 of local SIDs on a particular router. In such cases, the SRLB is 327 advertised in the control plane. The requirement to advertise the 328 SRLB is further described in [I-D.ietf-spring-segment-routing-mpls]. 329 The SRLB TLV is used to advertise the SRLB. 331 The SRLB TLV is a top-level TLV of the OSPFv3 Router Information 332 Opaque LSA (defined in [RFC7770]). 334 The SRLB TLV MAY appear multiple times in the OSPFv3 Router 335 Information Opaque LSA and has the following format: 337 0 1 2 3 338 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 1 339 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 340 | Type | Length | 341 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 342 | Range Size | Reserved | 343 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 344 | Sub-TLVs (variable) | 345 +- -+ 346 | | 347 + + 349 where: 351 Type: 14 353 Length: Variable, in octets, dependent on Sub-TLVs. 355 Range Size: 3-octet SID/label range size (i.e., the number of SIDs 356 or labels in the range including the first SID/label). It MUST be 357 greater than 0. 359 Reserved: SHOULD be set to 0 on transmission and MUST be ignored 360 on reception. 362 Initially, the only supported Sub-TLV is the SID/Label Sub-TLV as 363 defined in Section 2.1. The SID/Label Sub-TLV MUST be included in 364 the SRLB TLV. The SID/Label advertised in the SID/Label Sub-TLV 365 represents the first SID/Label in the advertised range. 367 Only a single SID/Label Sub-TLV MAY be advertised in the SRLB TLV. 368 If more then one SID/Label Sub-TLVs are present, the SRLB TLV MUST be 369 ignored. 371 The originating router MUST NOT advertise overlapping ranges. 373 Each time a SID from the SRLB is allocated, it SHOULD also be 374 reported to all components (e.g., controller or applications) in 375 order for these components to have an up-to-date view of the current 376 SRLB allocation. This is required to avoid collisions between 377 allocation instructions. 379 Within the context of OSPFv3, the reporting of local SIDs is done 380 through OSPFv3 Sub-TLVs such as the Adjacency-SID (Section 6). 381 However, the reporting of allocated local SIDs can also be done 382 through other means and protocols which are outside the scope of this 383 document. 385 A router advertising the SRLB TLV MAY also have other label ranges, 386 outside of the SRLB, used for its local allocation purposes which are 387 not advertised in the SRLB TLV. For example, it is possible that an 388 Adjacency-SID is allocated using a local label that is not part of 389 the SRLB. 391 The OSPFv3 Router Information Opaque LSA can be advertised at any of 392 the defined flooding scopes (link, area, or autonomous system (AS)). 393 For the purpose of SRLB TLV advertisement, area-scoped flooding is 394 REQUIRED. 396 3.4. SRMS Preference TLV 398 The Segment Routing Mapping Server Preference TLV (SRMS Preference 399 TLV) is used to advertise a preference associated with a node that 400 acts as an SR Mapping Server. The role of an SRMS is described in 401 [I-D.ietf-spring-segment-routing-ldp-interop]. SRMS preference is 402 defined in [I-D.ietf-spring-segment-routing-ldp-interop]. 404 The SRMS Preference TLV is a top-level TLV of the OSPFv3 Router 405 Information Opaque LSA (defined in [RFC7770]). 407 The SRMS Preference TLV MAY only be advertised once in the OSPFv3 408 Router Information Opaque LSA and has the following format: 410 0 1 2 3 411 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 1 412 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 413 | Type | Length | 414 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 415 | Preference | Reserved | 416 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 418 where: 420 Type: 15 421 Length: 4 octets 423 Preference: 1 octet. SRMS preference value from 0 to 255. 425 Reserved: SHOULD be set to 0 on transmission and MUST be ignored 426 on reception. 428 When multiple SRMS Preference TLVs are received from a given router, 429 the receiver MUST use the first occurrence of the TLV in the OSPFv3 430 Router Information Opaque LSA. If the SRMS Preference TLV appears in 431 multiple OSPFv3 Router Information Opaque LSAs that have different 432 flooding scopes, the SRMS Preference TLV in the OSPFv3 Router 433 Information Opaque LSA with the narrowest flooding scope MUST be 434 used. If the SRMS Preference TLV appears in multiple OSPFv3 Router 435 Information Opaque LSAs that have the same flooding scope, the SRMS 436 Preference TLV in the OSPFv3 Router Information Opaque LSA with the 437 numerically smallest Instance ID MUST be used and subsequent 438 instances of the SRMS Preference TLV MUST be ignored. 440 The OSPFv3 Router Information Opaque LSA can be advertised at any of 441 the defined flooding scopes (link, area, or autonomous system (AS)). 442 For the purpose of the SRMS Preference TLV advertisement, AS-scoped 443 flooding SHOULD be used. This is because SRMS servers can be located 444 in different areas than consumers of the SRMS advertisements. If 445 SRMS advertisements from an SRMS server are only used inside the SRMS 446 server's area, area-scoped flooding MAY be used. 448 4. OSPFv3 Extended Prefix Range TLV 450 In some cases it is useful to advertise attributes for a range of 451 prefixes. The Segment Routing Mapping Server, which is described in 452 [I-D.ietf-spring-segment-routing-ldp-interop], is an example of where 453 we need a single advertisement to advertise SIDs for multiple 454 prefixes from a contiguous address range. 456 The OSPFv3 Extended Prefix Range TLV is defined for this purpose. 458 The OSPFv3 Extended Prefix Range TLV is a top-level TLV of the 459 following LSAs defined in [RFC8362]: 461 E-Intra-Area-Prefix-LSA 463 E-Inter-Area-Prefix-LSA 465 E-AS-External-LSA 467 E-Type-7-LSA 469 Multiple OSPFv3 Extended Prefix Range TLVs MAY be advertised in each 470 LSA mentioned above. The OSPFv3 Extended Prefix Range TLV has the 471 following format: 473 0 1 2 3 474 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 1 475 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 476 | Type | Length | 477 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 478 | Prefix Length | AF | Range Size | 479 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 480 | Flags | Reserved | 481 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 482 | Address Prefix (variable) | 483 | ... | 484 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 485 | Sub-TLVs (variable) | 486 +- -+ 487 | | 489 where: 491 Type: 9 493 Length: Variable, in octets, dependent on Sub-TLVs. 495 Prefix length: Length of prefix in bits. 497 AF: Address family for the prefix. 499 AF: 0 - IPv4 unicast 501 AF: 1 - IPv6 unicast 503 Range size: Represents the number of prefixes that are covered by 504 the advertisement. The Range Size MUST NOT exceed the number of 505 prefixes that could be satisfied by the prefix length without 506 including: 508 Addresses from the IPv4 multicast address range (224.0.0.0/3), 509 if the AF is IPv4 unicast 511 Addresses other than the IPv6 unicast addresses, if the AF is 512 IPv6 unicast 514 Flags: Single octet field. The following flags are defined: 516 0 1 2 3 4 5 6 7 517 +--+--+--+--+--+--+--+--+ 518 |IA| | | | | | | | 519 +--+--+--+--+--+--+--+--+ 521 where: 523 IA-Flag: Inter-Area flag. If set, advertisement is of inter- 524 area type. An Are Border Router (ABR) that is advertising the 525 OSPFv3 Extended Prefix Range TLV between areas MUST set this 526 bit. 528 This bit is used to prevent redundant flooding of Prefix Range 529 TLVs between areas as follows: 531 An ABR only propagates an inter-area Prefix Range 532 advertisement from the backbone area to connected non- 533 backbone areas if the advertisement is considered to be the 534 best one. The following rules are used to select the best 535 range from the set of advertisements for the same Prefix 536 Range: 538 An ABR always prefers intra-area Prefix Range 539 advertisements over inter-area advertisements. 541 An ABR does not consider inter-area Prefix Range 542 advertisements coming from non-backbone areas. 544 Reserved: SHOULD be set to 0 on transmission and MUST be ignored 545 on reception. 547 Address Prefix: 549 For the address family IPv4 unicast, the prefix itself is 550 encoded as a 32-bit value. The default route is represented by 551 a prefix of length 0. 553 For the address family IPv6 unicast, the prefix, encoded as an 554 even multiple of 32-bit words, padded with zeroed bits as 555 necessary. This encoding consumes ((PrefixLength + 31) / 32) 556 32-bit words. 558 Prefix encoding for other address families is beyond the scope 559 of this specification. 561 If the OSPFv3 Extended Prefix Range TLVs advertising the exact same 562 range appears in multiple LSAs of the same type, originated by the 563 same OSPFv3 router, the LSA with the numerically smallest Instance ID 564 MUST be used and subsequent instances of the OSPFv3 Extended Prefix 565 Range TLVs MUST be ignored. 567 5. Prefix SID Sub-TLV 569 The Prefix SID Sub-TLV is a Sub-TLV of the following OSPFv3 TLVs as 570 defined in [RFC8362] and in Section 4: 572 Intra-Area Prefix TLV 574 Inter-Area Prefix TLV 576 External Prefix TLV 578 OSPFv3 Extended Prefix Range TLV 580 It MAY appear more than once in the parent TLV and has the following 581 format: 583 0 1 2 3 584 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 1 585 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 586 | Type | Length | 587 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 588 | Flags | Algorithm | Reserved | 589 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 590 | SID/Index/Label (variable) | 591 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 592 where: 594 Type: 4 596 Length: 7 or 8 octets, dependent on the V-flag 598 Flags: Single octet field. The following flags are defined: 600 0 1 2 3 4 5 6 7 601 +--+--+--+--+--+--+--+--+ 602 | |NP|M |E |V |L | | | 603 +--+--+--+--+--+--+--+--+ 604 where: 606 NP-Flag: No-PHP flag. If set, then the penultimate hop MUST 607 NOT pop the Prefix-SID before delivering packets to the node 608 that advertised the Prefix-SID. 610 M-Flag: Mapping Server Flag. If set, the SID was advertised by 611 a Segment Routing Mapping Server as described in 612 [I-D.ietf-spring-segment-routing-ldp-interop]. 614 E-Flag: Explicit-Null Flag. If set, any upstream neighbor of 615 the Prefix-SID originator MUST replace the Prefix-SID with the 616 Explicit-NULL label (0 for IPv4, 2 for IPv6) before forwarding 617 the packet. 619 V-Flag: Value/Index Flag. If set, then the Prefix-SID carries 620 an absolute value. If not set, then the Prefix-SID carries an 621 index. 623 L-Flag: Local/Global Flag. If set, then the value/index 624 carried by the Prefix-SID has local significance. If not set, 625 then the value/index carried by this Sub-TLV has global 626 significance. 628 Other bits: Reserved. These MUST be zero when sent and are 629 ignored when received. 631 Reserved: SHOULD be set to 0 on transmission and MUST be ignored 632 on reception. 634 Algorithm: Single octet identifying the algorithm the Prefix-SID 635 is associated with as defined in Section 3.1. 637 A router receiving a Prefix-SID from a remote node and with an 638 algorithm value that such remote node has not advertised in the 639 SR-Algorithm Sub-TLV (Section 3.1) MUST ignore the Prefix-SID Sub- 640 TLV. 642 SID/Index/Label: According to the V and L flags, it contains 643 either: 645 A 32-bit index defining the offset in the SID/Label space 646 advertised by this router. 648 A 24-bit label where the 20 rightmost bits are used for 649 encoding the label value. 651 If an OSPFv3 router advertises multiple Prefix-SIDs for the same 652 prefix, topology, and algorithm, all of them MUST be ignored. 654 When calculating the outgoing label for the prefix, the router MUST 655 take into account, as described below, the E, NP, and M flags 656 advertised by the next-hop router if that router advertised the SID 657 for the prefix. This MUST be done regardless of whether the next-hop 658 router contributes to the best path to the prefix. 660 The NP-Flag (No-PHP) MUST be set and the E-flag MUST be clear for 661 Prefix-SIDs allocated to prefixes that are propagated between areas 662 by an ABR based on intra-area or inter-area reachability, unless the 663 advertised prefix is directly attached to such ABR. 665 The NP-Flag (No-PHP) MUST be set and the E-flag MUST be clear for 666 Prefix-SIDs allocated to redistributed prefixes, unless the 667 redistributed prefix is directly attached to the advertising 668 Autonomous System Boundary Router (ASBR). 670 If the NP-Flag is not set, then any upstream neighbor of the Prefix- 671 SID originator MUST pop the Prefix-SID. This is equivalent to the 672 penultimate hop popping mechanism used in the MPLS dataplane. If the 673 NP-flag is not set, then the received E-flag is ignored. 675 If the NP-flag is set then: 677 If the E-flag is not set, then any upstream neighbor of the 678 Prefix-SID originator MUST keep the Prefix-SID on top of the 679 stack. This is useful when the originator of the Prefix-SID needs 680 to stitch the incoming packet into a continuing MPLS LSP to the 681 final destination. This could occur at an Area Border Router 682 (prefix propagation from one area to another) or at an AS Boundary 683 Router (prefix propagation from one domain to another). 685 If the E-flag is set, then any upstream neighbor of the Prefix-SID 686 originator MUST replace the Prefix-SID with an Explicit-NULL 687 label. This is useful, e.g., when the originator of the Prefix- 688 SID is the final destination for the related prefix and the 689 originator wishes to receive the packet with the original EXP 690 bits. 692 When the M-Flag is set, the NP-flag and the E-flag MUST be ignored on 693 reception. 695 As the Mapping Server does not specify the originator of a prefix 696 advertisement, it is not possible to determine PHP behavior solely 697 based on the Mapping Server advertisement. However, PHP behavior 698 SHOULD be done in following cases: 700 The Prefix is intra-area type and the downstream neighbor is the 701 originator of the prefix. 703 The Prefix is inter-area type and the downstream neighbor is an 704 ABR, which is advertising prefix reachability and is setting the 705 LA-bit in the Prefix Options as described in [RFC8362]. 707 The Prefix is external type and the downstream neighbor is an 708 ASBR, which is advertising prefix reachability and is setting the 709 LA-bit in the Prefix Options as described in [RFC8362]. 711 When a Prefix-SID is advertised in the OSPFv3 Extended Prefix Range 712 TLV, then the value advertised in the Prefix SID Sub-TLV is 713 interpreted as a starting SID/Label value. 715 Example 1: If the following router addresses (loopback addresses) 716 need to be mapped into the corresponding Prefix SID indexes: 718 Router-A: 2001:DB8::1/128, Prefix-SID: Index 1 719 Router-B: 2001:DB8::2/128, Prefix-SID: Index 2 720 Router-C: 2001:DB8::3/128, Prefix-SID: Index 3 721 Router-D: 2001:DB8::4/128, Prefix-SID: Index 4 723 then the Address Prefix field in the OSPFv3 Extended Prefix Range TLV 724 would be set to 2001:DB8::1, the Prefix Length would be set to 128, 725 the Range Size would be set to 4, and the Index value in the Prefix- 726 SID Sub-TLV would be set to 1. 728 Example 2: If the following prefixes need to be mapped into the 729 corresponding Prefix-SID indexes: 731 2001:DB8:1::0/120, Prefix-SID: Index 51 732 2001:DB8:1::100/120, Prefix-SID: Index 52 733 2001:DB8:1::200/120, Prefix-SID: Index 53 734 2001:DB8:1::300/120, Prefix-SID: Index 54 735 2001:DB8:1::400/120, Prefix-SID: Index 55 736 2001:DB8:1::500/120, Prefix-SID: Index 56 737 2001:DB8:1::600/120, Prefix-SID: Index 57 739 then the Prefix field in the OSPFv3 Extended Prefix Range TLV would 740 be set to 2001:DB8:1::0, the Prefix Length would be set to 120, the 741 Range Size would be set to 7, and the Index value in the Prefix-SID 742 Sub-TLV would be set to 51. 744 6. Adjacency Segment Identifier (Adj-SID) 746 An Adjacency Segment Identifier (Adj-SID) represents a router 747 adjacency in Segment Routing. 749 6.1. Adj-SID Sub-TLV 751 The Adj-SID Sub-TLV is an optional Sub-TLV of the Router-Link TLV as 752 defined in [RFC8362]. It MAY appear multiple times in the Router- 753 Link TLV. The Adj-SID Sub-TLV has the following format: 755 0 1 2 3 756 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 1 757 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 758 | Type | Length | 759 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 760 | Flags | Weight | Reserved | 761 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 762 | SID/Label/Index (variable) | 763 +---------------------------------------------------------------+ 765 where: 767 Type: 5 769 Length: 7 or 8 octets, dependent on the V flag. 771 Flags: Single octet field containing the following flags: 773 0 1 2 3 4 5 6 7 774 +-+-+-+-+-+-+-+-+ 775 |B|V|L|G|P| | 776 +-+-+-+-+-+-+-+-+ 778 where: 780 B-Flag: Backup Flag. If set, the Adj-SID refers to an 781 adjacency that is eligible for protection (e.g., using IPFRR or 782 MPLS-FRR) as described in section 3.5 of [RFC8402]. 784 The V-Flag: Value/Index Flag. If set, then the Adj-SID carries 785 an absolute value. If not set, then the Adj-SID carries an 786 index. 788 The L-Flag: Local/Global Flag. If set, then the value/index 789 carried by the Adj-SID has local significance. If not set, 790 then the value/index carried by this Sub-TLV has global 791 significance. 793 The G-Flag: Group Flag. When set, the G-Flag indicates that 794 the Adj-SID refers to a group of adjacencies (and therefore MAY 795 be assigned to other adjacencies as well). 797 P-Flag. Persistent flag. When set, the P-Flag indicates that 798 the Adj-SID is persistently allocated, i.e., the Adj-SID value 799 remains the same across router restart and/or interface flap. 801 Other bits: Reserved. These MUST be zero when sent and are 802 ignored when received. 804 Reserved: SHOULD be set to 0 on transmission and MUST be ignored 805 on reception. 807 Weight: Weight used for load-balancing purposes. The use of the 808 weight is defined in [RFC8402]. 810 SID/Index/Label: According to the V and L flags, it contains 811 either: 813 A 32-bit index defining the offset in the SID/Label space 814 advertised by this router. 816 A 24-bit label where the 20 rightmost bits are used for 817 encoding the label value. 819 An SR-capable router MAY allocate an Adj-SID for each of its 820 adjacencies and set the B-Flag when the adjacency is eligible for 821 protection by an FRR mechanism (IP or MPLS) as described in 822 [RFC8402]. 824 An SR-capable router MAY allocate more than one Adj-SID to an 825 adjacency. 827 An SR-capable router MAY allocate the same Adj-SID to different 828 adjacencies. 830 When the P-flag is not set, the Adj-SID MAY be persistent. When the 831 P-flag is set, the Adj-SID MUST be persistent. 833 6.2. LAN Adj-SID Sub-TLV 835 The LAN Adj-SID Sub-TLV is an optional Sub-TLV of the Router-Link 836 TLV. It MAY appear multiple times in the Router-Link TLV. It is 837 used to advertise a SID/Label for an adjacency to a non-DR router on 838 a broadcast, NBMA, or hybrid [RFC6845] network. 840 0 1 2 3 841 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 1 842 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 843 | Type | Length | 844 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 845 | Flags | Weight | Reserved | 846 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 847 | Neighbor ID | 848 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 849 | SID/Label/Index (variable) | 850 +---------------------------------------------------------------+ 852 where: 854 Type: 6 856 Length: 11 or 12 octets, dependent on V-flag. 858 Flags: same as in Section 6.1 860 Weight: Weight used for load-balancing purposes. The use of the 861 weight is defined in [RFC8402]. 863 Reserved: SHOULD be set to 0 on transmission and MUST be ignored 864 on reception. 866 Neighbor ID: The Router ID of the neighbor for which the LAN-Adj- 867 SID is advertised. 869 SID/Index/Label: According to the V and L flags, it contains 870 either: 872 A 32-bit index defining the offset in the SID/Label space 873 advertised by this router. 875 A 24-bit label where the 20 rightmost bits are used for 876 encoding the label value. 878 When the P-flag is not set, the Adj-SID MAY be persistent. When 879 the P-flag is set, the Adj-SID MUST be persistent. 881 7. Elements of Procedure 883 7.1. Intra-area Segment routing in OSPFv3 885 An OSPFv3 router that supports segment routing MAY advertise Prefix- 886 SIDs for any prefix to which it is advertising reachability (e.g., a 887 loopback IP address as described in Section 5). 889 A Prefix-SID can also be advertised by SR Mapping Servers (as 890 described in [I-D.ietf-spring-segment-routing-ldp-interop]). A 891 Mapping Server advertises Prefix-SIDs for remote prefixes that exist 892 in the OSPFv3 routing domain. Multiple Mapping Servers can advertise 893 Prefix-SIDs for the same prefix, in which case the same Prefix-SID 894 MUST be advertised by all of them. The SR Mapping Server could use 895 either area flooding scope or autonomous system flooding scope when 896 advertising Prefix SIDs for prefixes, based on the configuration of 897 the SR Mapping Server. Depending on the flooding scope used, the SR 898 Mapping Server chooses the OSPFv3 LSA type that will be used. If the 899 area flooding scope is needed, an E-Intra-Area-Prefix-LSA [RFC8362] 900 is used. If autonomous system flooding scope is needed, an E-AS- 901 External-LSA [RFC8362] is used. 903 When a Prefix-SID is advertised by the Mapping Server, which is 904 indicated by the M-flag in the Prefix-SID Sub-TLV (Section 5), the 905 route type as implied by the LSA type is ignored and the Prefix-SID 906 is bound to the corresponding prefix independent of the route type. 908 Advertisement of the Prefix-SID by the Mapping Server using an Inter- 909 Area Prefix TLV, External-Prefix TLV, or Intra-Area-Prefix TLV 910 [RFC8362] does not itself contribute to the prefix reachability. The 911 NU-bit MUST be set in the PrefixOptions field of the LSA which is 912 used by the Mapping Server to advertise SID or SID Range, which 913 prevents the advertisement from contributing to prefix reachability. 915 An SR Mapping Server MUST use the OSPFv3 Extended Prefix Range TLVs 916 when advertising SIDs for prefixes. Prefixes of different route- 917 types can be combined in a single OSPFv3 Extended Prefix Range TLV 918 advertised by an SR Mapping Server. 920 Area-scoped OSPFv3 Extended Prefix Range TLVs are propagated between 921 areas. Similar to propagation of prefixes between areas, an ABR only 922 propagates the OSPFv3 Extended Prefix Range TLV that it considers to 923 be the best from the set it received. The rules used to pick the 924 best OSPFv3 Extended Prefix Range TLV are described in Section 4. 926 When propagating an OSPFv3 Extended Prefix Range TLV between areas, 927 ABRs MUST set the IA-Flag, that is used to prevent redundant flooding 928 of the OSPFv3 Extended Prefix Range TLV between areas as described in 929 Section 4. 931 7.2. Inter-area Segment routing in OSPFv3 933 In order to support SR in a multi-area environment, OSPFv3 MUST 934 propagate Prefix-SID information between areas. The following 935 procedure is used to propagate Prefix SIDs between areas. 937 When an OSPFv3 ABR advertises an Inter-Area-Prefix-LSA from an intra- 938 area prefix to all its connected areas, it will also include the 939 Prefix-SID Sub-TLV, as described in Section 5. The Prefix-SID value 940 will be set as follows: 942 The ABR will look at its best path to the prefix in the source 943 area and find the advertising router associated with the best path 944 to that prefix. 946 The ABR will then determine if such router advertised a Prefix-SID 947 for the prefix and use it when advertising the Prefix-SID to other 948 connected areas. 950 If no Prefix-SID was advertised for the prefix in the source area 951 by the router that contributes to the best path to the prefix, the 952 originating ABR will use the Prefix-SID advertised by any other 953 router when propagating the Prefix-SID for the prefix to other 954 areas. 956 When an OSPFv3 ABR advertises Inter-Area-Prefix-LSA LSAs from an 957 inter-area route to all its connected areas, it will also include the 958 Prefix-SID Sub-TLV, as described in Section 5. The Prefix-SID value 959 will be set as follows: 961 The ABR will look at its best path to the prefix in the backbone 962 area and find the advertising router associated with the best path 963 to that prefix. 965 The ABR will then determine if such router advertised a Prefix-SID 966 for the prefix and use it when advertising the Prefix-SID to other 967 connected areas. 969 If no Prefix-SID was advertised for the prefix in the backbone 970 area by the ABR that contributes to the best path to the prefix, 971 the originating ABR will use the Prefix-SID advertised by any 972 other router when propagating the Prefix-SID for the prefix to 973 other areas. 975 7.3. Segment Routing for External Prefixes 977 AS-External-LSAs are flooded domain wide. When an ASBR, which 978 supports SR, originates an E-AS-External-LSA, it SHOULD also include 979 a Prefix-SID Sub-TLV, as described in Section 5. The Prefix-SID 980 value will be set to the SID that has been reserved for that prefix. 982 When an NSSA [RFC3101] ABR translates an E-NSSA-LSA into an E-AS- 983 External-LSA, it SHOULD also advertise the Prefix-SID for the prefix. 984 The NSSA ABR determines its best path to the prefix advertised in the 985 translated E-NSSA-LSA and finds the advertising router associated 986 with that path. If the advertising router has advertised a Prefix- 987 SID for the prefix, then the NSSA ABR uses it when advertising the 988 Prefix-SID for the E-AS-External-LSA. Otherwise, the Prefix-SID 989 advertised by any other router will be used. 991 7.4. Advertisement of Adj-SID 993 The Adjacency Segment Routing Identifier (Adj-SID) is advertised 994 using the Adj-SID Sub-TLV as described in Section 6. 996 7.4.1. Advertisement of Adj-SID on Point-to-Point Links 998 An Adj-SID MAY be advertised for any adjacency on a P2P link that is 999 in neighbor state 2-Way or higher. If the adjacency on a P2P link 1000 transitions from the FULL state, then the Adj-SID for that adjacency 1001 MAY be removed from the area. If the adjacency transitions to a 1002 state lower then 2-Way, then the Adj-SID advertisement MUST be 1003 withdrawn from the area. 1005 7.4.2. Adjacency SID on Broadcast or NBMA Interfaces 1007 Broadcast, NBMA, or hybrid [RFC6845] networks in OSPFv3 are 1008 represented by a star topology where the Designated Router (DR) is 1009 the central point to which all other routers on the broadcast, NBMA, 1010 or hybrid network connect. As a result, routers on the broadcast, 1011 NBMA, or hybrid network advertise only their adjacency to the DR. 1012 Routers that do not act as DR do not form or advertise adjacencies 1013 with each other. They do, however, maintain 2-Way adjacency state 1014 with each other and are directly reachable. 1016 When Segment Routing is used, each router on the broadcast, NBMA, or 1017 hybrid network MAY advertise the Adj-SID for its adjacency to the DR 1018 using the Adj-SID Sub-TLV as described in Section 6.1. 1020 SR-capable routers MAY also advertise a LAN-Adj-SID for other 1021 neighbors (e.g., BDR, DR-OTHER) on the broadcast, NBMA, or hybrid 1022 network using the LAN-Adj-SID Sub-TLV as described in Section 6.2. 1024 8. IANA Considerations 1026 This specification updates several existing OSPFv3 registries. 1028 8.1. OSPFv3 Extended-LSA TLV Registry 1030 Following values are allocated: 1032 o 9 - OSPFv3 Extended Prefix Range TLV 1034 8.2. OSPFv3 Extended-LSA Sub-TLV registry 1036 o 4 - Prefix SID Sub-TLV 1038 o 5 - Adj-SID Sub-TLV 1040 o 6 - LAN Adj-SID Sub-TLV 1042 o 7 - SID/Label Sub-TLV 1044 9. Security Considerations 1046 With the OSPFv3 segment routing extensions defined herein, OSPFv3 1047 will now program the MPLS data plane [RFC3031]. Previously, LDP 1048 [RFC5036] or another label distribution mechanism was required to 1049 advertise MPLS labels and program the MPLS data plane. 1051 In general, the same types of attacks that can be carried out on the 1052 IP control plane can be carried out on the MPLS control plane 1053 resulting in traffic being misrouted in the respective data planes. 1054 However, the latter can be more difficult to detect and isolate. 1056 Existing security extensions as described in [RFC5340] and [RFC8362] 1057 apply to these segment routing extensions. While OSPFv3 is under a 1058 single administrative domain, there can be deployments where 1059 potential attackers have access to one or more networks in the OSPFv3 1060 routing domain. In these deployments, stronger authentication 1061 mechanisms such as those specified in [RFC4552] or [RFC7166] SHOULD 1062 be used. 1064 Implementations MUST assure that malformed TLV and Sub-TLV defined in 1065 this document are detected and do not provide a vulnerability for 1066 attackers to crash the OSPFv3 router or routing process. Reception 1067 of a malformed TLV or Sub-TLV SHOULD be counted and/or logged for 1068 further analysis. Logging of malformed TLVs and Sub-TLVs SHOULD be 1069 rate-limited to prevent a Denial of Service (DoS) attack (distributed 1070 or otherwise) from overloading the OSPFv3 control plane. 1072 10. Contributors 1074 The following people gave a substantial contribution to the content 1075 of this document and should be considered as co-authors: 1077 Clarence Filsfils 1078 Cisco Systems, Inc. 1079 Brussels 1080 Belgium 1082 Email: cfilsfil@cisco.com 1084 Hannes Gredler 1085 RtBrick Inc. 1086 Austria 1088 Email: hannes@rtbrick.com 1090 Rob Shakir 1091 Google, Inc. 1092 1600 Amphitheatre Parkway 1093 Mountain View, CA 94043 1094 US 1096 Email: robjs@google.com 1098 Wim Henderickx 1099 Nokia 1100 Copernicuslaan 50 1101 Antwerp 2018 1102 BE 1104 Email: wim.henderickx@nokia.com 1106 Jeff Tantsura 1107 Nuage Networks 1108 US 1110 Email: jefftant.ietf@gmail.com 1112 Thanks to Acee Lindem for his substantial contribution to the content 1113 of this document. 1115 We would like to thank Anton Smirnov for his contribution as well. 1117 11. References 1119 11.1. Normative References 1121 [I-D.ietf-ospf-segment-routing-extensions] 1122 Psenak, P., Previdi, S., Filsfils, C., Gredler, H., 1123 Shakir, R., Henderickx, W., and J. Tantsura, "OSPF 1124 Extensions for Segment Routing", draft-ietf-ospf-segment- 1125 routing-extensions-25 (work in progress), April 2018. 1127 [I-D.ietf-spring-segment-routing-ldp-interop] 1128 Bashandy, A., Filsfils, C., Previdi, S., Decraene, B., and 1129 S. Litkowski, "Segment Routing interworking with LDP", 1130 draft-ietf-spring-segment-routing-ldp-interop-15 (work in 1131 progress), September 2018. 1133 [I-D.ietf-spring-segment-routing-mpls] 1134 Bashandy, A., Filsfils, C., Previdi, S., Decraene, B., 1135 Litkowski, S., and R. Shakir, "Segment Routing with MPLS 1136 data plane", draft-ietf-spring-segment-routing-mpls-14 1137 (work in progress), June 2018. 1139 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1140 Requirement Levels", BCP 14, RFC 2119, 1141 DOI 10.17487/RFC2119, March 1997, 1142 . 1144 [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol 1145 Label Switching Architecture", RFC 3031, 1146 DOI 10.17487/RFC3031, January 2001, 1147 . 1149 [RFC3101] Murphy, P., "The OSPF Not-So-Stubby Area (NSSA) Option", 1150 RFC 3101, DOI 10.17487/RFC3101, January 2003, 1151 . 1153 [RFC5036] Andersson, L., Ed., Minei, I., Ed., and B. Thomas, Ed., 1154 "LDP Specification", RFC 5036, DOI 10.17487/RFC5036, 1155 October 2007, . 1157 [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF 1158 for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008, 1159 . 1161 [RFC6845] Sheth, N., Wang, L., and J. Zhang, "OSPF Hybrid Broadcast 1162 and Point-to-Multipoint Interface Type", RFC 6845, 1163 DOI 10.17487/RFC6845, January 2013, 1164 . 1166 [RFC7770] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and 1167 S. Shaffer, "Extensions to OSPF for Advertising Optional 1168 Router Capabilities", RFC 7770, DOI 10.17487/RFC7770, 1169 February 2016, . 1171 [RFC8362] Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and 1172 F. Baker, "OSPFv3 Link State Advertisement (LSA) 1173 Extensibility", RFC 8362, DOI 10.17487/RFC8362, April 1174 2018, . 1176 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 1177 Decraene, B., Litkowski, S., and R. Shakir, "Segment 1178 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 1179 July 2018, . 1181 11.2. Informative References 1183 [RFC4552] Gupta, M. and N. Melam, "Authentication/Confidentiality 1184 for OSPFv3", RFC 4552, DOI 10.17487/RFC4552, June 2006, 1185 . 1187 [RFC7166] Bhatia, M., Manral, V., and A. Lindem, "Supporting 1188 Authentication Trailer for OSPFv3", RFC 7166, 1189 DOI 10.17487/RFC7166, March 2014, 1190 . 1192 [RFC7855] Previdi, S., Ed., Filsfils, C., Ed., Decraene, B., 1193 Litkowski, S., Horneffer, M., and R. Shakir, "Source 1194 Packet Routing in Networking (SPRING) Problem Statement 1195 and Requirements", RFC 7855, DOI 10.17487/RFC7855, May 1196 2016, . 1198 Authors' Addresses 1200 Peter Psenak (editor) 1201 Cisco Systems, Inc. 1202 Eurovea Centre, Central 3 1203 Pribinova Street 10 1204 Bratislava 81109 1205 Slovakia 1207 Email: ppsenak@cisco.com 1209 Stefano Previdi (editor) 1210 Individual 1212 Email: stefano.previdi@net