idnits 2.17.1 draft-ietf-lsr-isis-srv6-extensions-14.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- ** There is 1 instance of too long lines in the document, the longest one being 1 character in excess of 72. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (April 22, 2021) is 1099 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-13) exists of draft-ietf-6man-spring-srv6-oam-08 == Outdated reference: A later version (-26) exists of draft-ietf-lsr-flex-algo-13 -- Possible downref: Non-RFC (?) normative reference: ref. 'ISO10589' Summary: 1 error (**), 0 flaws (~~), 3 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Networking Working Group P. Psenak, Ed. 3 Internet-Draft C. Filsfils 4 Updates: 7370 (if approved) Cisco Systems 5 Intended status: Standards Track A. Bashandy 6 Expires: October 24, 2021 Individual 7 B. Decraene 8 Orange 9 Z. Hu 10 Huawei Technologies 11 April 22, 2021 13 IS-IS Extension to Support Segment Routing over IPv6 Dataplane 14 draft-ietf-lsr-isis-srv6-extensions-14 16 Abstract 18 The Segment Routing (SR) allows for a flexible definition of end-to- 19 end paths by encoding paths as sequences of topological sub-paths, 20 called "segments". Segment routing architecture can be implemented 21 over an MPLS data plane as well as an IPv6 data plane. This document 22 describes the IS-IS extensions required to support Segment Routing 23 over an IPv6 data plane. 25 This documents updates RFC 7370 by modifying an existing registry. 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 24, 2021. 51 Copyright Notice 53 Copyright (c) 2021 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. SRv6 Capabilities sub-TLV . . . . . . . . . . . . . . . . . . 4 70 3. Advertising Supported Algorithms . . . . . . . . . . . . . . 4 71 4. Advertising Maximum SRv6 SID Depths . . . . . . . . . . . . . 4 72 4.1. Maximum Segments Left MSD Type . . . . . . . . . . . . . 5 73 4.2. Maximum End Pop MSD Type . . . . . . . . . . . . . . . . 5 74 4.3. Maximum H.Encaps MSD Type . . . . . . . . . . . . . . . . 5 75 4.4. Maximum End D MSD Type . . . . . . . . . . . . . . . . . 6 76 5. SRv6 SIDs and Reachability . . . . . . . . . . . . . . . . . 6 77 6. Advertising Anycast Property . . . . . . . . . . . . . . . . 7 78 7. Advertising Locators and End SIDs . . . . . . . . . . . . . . 8 79 7.1. SRv6 Locator TLV Format . . . . . . . . . . . . . . . . . 9 80 7.2. SRv6 End SID sub-TLV . . . . . . . . . . . . . . . . . . 10 81 8. Advertising SRv6 Adjacency SIDs . . . . . . . . . . . . . . . 12 82 8.1. SRv6 End.X SID sub-TLV . . . . . . . . . . . . . . . . . 12 83 8.2. SRv6 LAN End.X SID sub-TLV . . . . . . . . . . . . . . . 14 84 9. SRv6 SID Structure Sub-Sub-TLV . . . . . . . . . . . . . . . 16 85 10. Advertising Endpoint Behaviors . . . . . . . . . . . . . . . 17 86 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 87 11.1. SRv6 Locator TLV . . . . . . . . . . . . . . . . . . . . 17 88 11.1.1. SRv6 End SID sub-TLV . . . . . . . . . . . . . . . . 18 89 11.1.2. Revised sub-TLV table . . . . . . . . . . . . . . . 18 90 11.2. SRv6 Capabilities sub-TLV . . . . . . . . . . . . . . . 19 91 11.3. SRv6 End.X SID and SRv6 LAN End.X SID sub-TLVs . . . . . 19 92 11.4. MSD Types . . . . . . . . . . . . . . . . . . . . . . . 20 93 11.5. Sub-Sub-TLVs for SID Sub-TLVs . . . . . . . . . . . . . 20 94 11.6. Prefix Attribute Flags Sub-TLV . . . . . . . . . . . . . 21 95 11.7. ISIS SRv6 Capabilities sub-TLV Flags Registry . . . . . 21 96 11.8. ISIS SRv6 Locator TLV Flags Registry . . . . . . . . . . 21 97 11.9. ISIS SRv6 End SID sub-TLV Flags Registry . . . . . . . . 22 98 11.10. ISIS SRv6 End.X SID and LAN End.X SID sub-TLVs Flags 99 Registry . . . . . . . . . . . . . . . . . . . . . . . . 22 100 12. Security Considerations . . . . . . . . . . . . . . . . . . . 23 101 13. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 23 102 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 24 103 14.1. Normative References . . . . . . . . . . . . . . . . . . 24 104 14.2. Informative References . . . . . . . . . . . . . . . . . 27 105 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27 107 1. Introduction 109 With Segment Routing (SR) [RFC8402], a node steers a packet through 110 an ordered list of instructions, called segments. 112 Segments are identified through Segment Identifiers (SIDs). 114 Segment Routing can be directly instantiated on the IPv6 data plane 115 through the use of the Segment Routing Header defined in [RFC8754]. 116 SRv6 refers to this SR instantiation on the IPv6 dataplane. 118 The network programming paradigm [RFC8986] is central to SRv6. It 119 describes how any behavior can be bound to a SID and how any network 120 program can be expressed as a combination of SIDs. 122 This document specifies IS-IS extensions that allow the IS-IS 123 protocol to encode some of these SIDs and their behaviors. 125 Familiarity with the network programming paradigm [RFC8986] is 126 necessary to understand the extensions specified in this document. 128 The new SRv6 Locator top level TLV announces SRv6 locators - a form 129 of summary address for the set of topology/algorithm specific SIDs 130 instantiated at the node. 132 The SRv6 Capabilities sub-TLV announces the ability to support SRv6. 134 Several new sub-TLVs are defined to advertise various SRv6 Maximum 135 SID Depths. 137 The SRv6 End SID sub-TLV, the SRv6 End.X SID sub-TLV, and the SRv6 138 LAN End.X SID sub-TLV are used to advertise which SIDs are 139 instantiated at a node and what Endpoint behavior is bound to each 140 instantiated SID. 142 This documents updates [RFC7370] by modifying an existing registry 143 (Section 11.1.2). 145 2. SRv6 Capabilities sub-TLV 147 A node indicates that it supports the SR Segment Endpoint Node 148 functionality as specified in [RFC8754] by advertising a new SRv6 149 Capabilities sub-TLV of the router capabilities TLV [RFC7981]. 151 The SRv6 Capabilities sub-TLV may contain optional sub-sub-TLVs. No 152 sub-sub-TLVs are currently defined. 154 The SRv6 Capabilities sub-TLV has the following format: 156 0 1 2 3 157 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 1 158 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 159 | Type | Length | Flags | 160 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 161 | optional sub-sub-TLVs... 163 Type: 25 165 Length: 2 + length of sub-sub-TLVs 167 Flags: 2 octets The following flags are defined: 169 0 1 170 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 171 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 172 | |O| | 173 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 175 where: 177 O-flag: If set, the router supports use of the O-bit 178 in the Segment Routing Header (SRH) as defined in 179 [I-D.ietf-6man-spring-srv6-oam]. 181 3. Advertising Supported Algorithms 183 An SRv6 capable router indicates supported algorithm(s) by 184 advertising the SR Algorithm sub-TLV as defined in [RFC8667]. 186 4. Advertising Maximum SRv6 SID Depths 188 [RFC8491] defines the means to advertise node/link specific values 189 for Maximum SID Depths (MSD) of various types. Node MSDs are 190 advertised in a sub-TLV of the Router Capabilities TLV [RFC7981]. 192 Link MSDs are advertised in a sub-TLV of TLVs 22, 23, 141, 222, and 193 223. 195 This document defines the relevant SRv6 MSDs and requests MSD type 196 assignments in the MSD Types registry created by [RFC8491]. 198 4.1. Maximum Segments Left MSD Type 200 The Maximum Segments Left MSD Type signals the maximum value of the 201 "Segments Left" field [RFC8754] in the SRH of a received packet 202 before applying the Endpoint behavior associated with a SID. 204 SRH Max Segments Left Type: 41 206 If no value is advertised the supported value is 0. 208 4.2. Maximum End Pop MSD Type 210 The Maximum End Pop MSD Type signals the maximum number of SIDs in 211 the SRH to which the router can apply "Penultimate Segment Pop of the 212 SRH" or "Ultimate Segment Pop of the SRH" behavior, as defined in 213 [RFC8986] flavors. 215 SRH Max End Pop Type: 42 217 If the advertised value is zero or no value is advertised 218 then the router cannot apply PSP or USP flavors. 220 4.3. Maximum H.Encaps MSD Type 222 The Maximum H.Encaps MSD Type signals the maximum number of SIDs that 223 can be added as part of the "H.Encaps" behavior as defined in 224 [RFC8986]. 226 SRH Max H.encaps Type: 44 228 If the advertised value is zero or no value is advertised then the 229 headend can apply an SR Policy that only contains one segment, without 230 inserting any SRH header. 232 A non-zero SRH Max H.encaps MSD indicates that the headend can insert 233 an SRH up to the advertised value. 235 4.4. Maximum End D MSD Type 237 The Maximum End D MSD Type specifies the maximum number of SIDs 238 present in an SRH when performing decapsulation. These includes, but 239 not limited to, End.DX6, End.DT4, End.DT46, End with USD, End.X with 240 USD as defined in [RFC8986]. 242 SRH Max End D Type: 45 244 If the advertised value is zero or no value is advertised 245 then the router cannot apply any behavior that results in 246 decapsulation and forwarding of the inner packet if the 247 other IPv6 header contains an SRH. 249 5. SRv6 SIDs and Reachability 251 As discussed in [RFC8986], an SRv6 Segment Identifier (SID) is 128 252 bits and consists of Locator, Function and Argument parts. 254 A node is provisioned with topology/algorithm specific locators for 255 each of the topology/algorithm pairs supported by that node. Each 256 locator is a covering prefix for all SIDs provisioned on that node 257 which have the matching topology/algorithm. 259 Locators MUST be advertised in the SRv6 Locator TLV (see 260 Section 7.1). Forwarding entries for the locators advertised in the 261 SRv6 Locator TLV MUST be installed in the forwarding plane of 262 receiving SRv6 capable routers when the associated topology/algorithm 263 is supported by the receiving node. The processing of the prefix 264 advertised in the SRv6 Locator TLV, the calculation of its 265 reachability and the installation in the forwarding plane follows the 266 process defined for the Prefix Reachability TLV 236 [RFC5308], or TLV 267 237 [RFC5120]. 269 Locators associated with algorithm 0 and 1 (for all supported 270 topologies) SHOULD be advertised in a Prefix Reachability TLV (236 or 271 237) so that legacy routers (i.e., routers which do not support SRv6) 272 will install a forwarding entry for algorithm 0 and 1 SRv6 traffic. 274 In cases where a locator advertisement is received in both a Prefix 275 Reachability TLV and an SRv6 Locator TLV - (e.g. prefix, prefix- 276 length, MTID all being equal and Algorithm being 0 in Locator TLV), 277 In case where the same prefix, with the same prefix-length, MTID, and 278 algorithm is received in both a Prefix Reachability TLV and an SRv6 279 Locator TLV, the Prefix Reachability advertisement MUST be preferred 280 when installing entries in the forwarding plane. This is to prevent 281 inconsistent forwarding entries between SRv6 capable and SRv6 282 incapable routers. Such preference of Prefix Reachability 283 advertisement does not have any impact on the rest of the data 284 advertised in the SRv6 Locator TLV. 286 Locators associated with Flexible Algorithms (see Section 4 of 287 [I-D.ietf-lsr-flex-algo]) SHOULD NOT be advertised in Prefix 288 Reachability TLVs (236 or 237). Advertising the Flexible Algorithm 289 locator in regular Prefix Reachability TLV (236 or 237) would make 290 the forwarding for it to follow algo 0 path. 292 SRv6 SIDs are advertised as sub-TLVs in the SRv6 Locator TLV except 293 for SRv6 SIDs which are associated with a specific Neighbor/Link and 294 are therefore advertised as sub-TLVs in TLVs 22, 23, 222, 223, and 295 141. 297 SRv6 SIDs received from other nodes are not directly routable and 298 MUST NOT be installed in the forwarding plane. Reachability to SRv6 299 SIDs depends upon the existence of a covering locator. 301 Adherence to the rules defined in this section will assure that SRv6 302 SIDs associated with a supported topology/algorithm pair will be 303 forwarded correctly, while SRv6 SIDs associated with an unsupported 304 topology/algorithm pair will be dropped. NOTE: The drop behavior 305 depends on the absence of a default/summary route covering a given 306 locator. 308 In order for forwarding to work correctly, the locator associated 309 with SRv6 SID advertisements must be the longest match prefix 310 installed in the forwarding plane for those SIDs. In order to ensure 311 correct forwarding, network operators should take steps to make sure 312 that this requirement is not compromised. For example, the following 313 situations should be avoided: 315 o Another locator associated with a different topology/algorithm is 316 the longest match 318 o Another prefix advertisement (i.e., from TLV 236 or 237) is the 319 longest match 321 6. Advertising Anycast Property 323 Both prefixes and SRv6 Locators may be configured as anycast and as 324 such the same value can be advertised by multiple routers. It is 325 useful for other routers to know that the advertisement is for an 326 anycast identifier. 328 A new flag in Prefix Attribute Flags Sub-TLV [RFC7794] is defined to 329 advertise the anycast property: 331 Bit #: 4 332 Name: Anycast Flag (A-flag) 334 When the prefix/SRv6 locator is configured as anycast, the A-flag 335 SHOULD be set. Otherwise, this flag MUST be clear. 337 The A-flag MUST be preserved when the advertisement is leaked between 338 levels. 340 The A-flag and the N-flag MUST NOT both be set. If both N-flag and 341 A-flag are set in the prefix/SRv6 Locator advertisement, the 342 receiving routers MUST ignore the N-flag. 344 The same prefix/SRv6 Locator can be advertised by multiple routers. 345 If at least one of them sets the A-Flag in its advertisement, the 346 prefix/SRv6 Locator SHOULD be considered as anycast. 348 A prefix/SRv6 Locator that is advertised by a single node and without 349 an A-Flag is considered node specific. 351 All the nodes advertising the same anycast locator MUST instantiate 352 the exact same set of SIDs under such anycast locator. Failure to do 353 so may result in traffic being black-holed or mis-routed. 355 The Prefix Attribute Flags Sub-TLV can be carried in the SRv6 Locator 356 TLV as well as the Prefix Reachability TLVs. When a router 357 originates both the Prefix Reachability TLV and the SRv6 Locator TLV 358 for a given prefix, and the router is originating the Prefix 359 Attribute Flags Sub-TLV in one of the TLVs, the router SHOULD 360 advertise the same flags in the Prefix Attribute Flags Sub-TLV in 361 both TLVs. However, unlike TLVs 236 [RFC5308] and 237 [RFC5120] the 362 X-flag in the Prefix Attributes Flags sub-TLV is valid when sent in 363 the SRv6 Locator TLV. The state of the X-flag in the Prefix 364 Attributes Flags sub-TLV when included in the Locator TLV MUST match 365 the setting of the embedded "X-bit" in any advertisement of the same 366 prefix in TLVs 236 [RFC5308] and 237 [RFC5120]. In case of any 367 inconsistency between the Prefix Attribute Flags advertised in the 368 Locator TLV and in the Prefix Reachability TLV, the ones advertised 369 in Prefix Reachability TLV MUST be preferred. 371 7. Advertising Locators and End SIDs 373 The SRv6 Locator TLV is introduced to advertise SRv6 Locators and End 374 SIDs associated with each locator. 376 This new TLV shares the sub-TLV space defined for TLVs 135, 235, 236 377 and 237. 379 7.1. SRv6 Locator TLV Format 381 The SRv6 Locator TLV has the following format: 383 0 1 2 3 384 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 1 385 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 386 | Type | Length |R|R|R|R| MT ID | 387 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 389 Type: 27 391 Length: variable. 393 R bits: reserved for future use. They MUST be 394 set to zero on transmission and MUST be ignored on receipt. 396 MT ID: Multitopology Identifier as defined in [RFC5120]. 397 Note that the value 0 is legal. 399 Followed by one or more locator entries of the form: 401 0 1 2 3 402 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 1 403 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 404 | Metric | 405 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 406 | Flags | Algorithm | 407 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 408 | Loc Size | Locator (variable)... 409 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 410 | Sub-TLV-len | Sub-TLVs (variable) . . . | 411 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 413 Metric: 4 octets. As described in [RFC5305]. 415 Flags: 1 octet. The following flags are defined 417 0 418 0 1 2 3 4 5 6 7 419 +-+-+-+-+-+-+-+-+ 420 |D| Reserved | 421 +-+-+-+-+-+-+-+-+ 423 where: 424 D-flag: Same as described in section 4.1. of [RFC5305]. 426 The remaining bits are reserved for future use. They MUST be 427 set to zero on transmission and MUST be ignored on receipt. 429 Algorithm: 1 octet. As defined in [RFC8665]. 431 Loc-Size: 1 octet. Number of bits in the SRv6 Locator field. 432 MUST be from the range (1 - 128). The TLV MUST be ignored if 433 the Loc-Size is outside of this range. 435 Locator: 1-16 octets. This field encodes the advertised SRv6 436 Locator. The Locator is encoded in the minimal number of 437 octets for the given number of bits. Trailing bits MUST be set 438 to zero and ignored when received. 440 Sub-TLV-length: 1 octet. Number of octets used by sub-TLVs 442 Optional sub-TLVs: Sub-TLVs 1, 2, 4, 5, 11, 12 are allowed. 443 Any other Sub-TLVs MUST be ignored. 445 7.2. SRv6 End SID sub-TLV 447 The SRv6 End SID sub-TLV is introduced to advertise SRv6 Segment 448 Identifiers (SID) with Endpoint behaviors which do not require a 449 particular neighbor in order to be correctly applied. SRv6 SIDs 450 associated with a neighbor are advertised using the sub-TLVs defined 451 in Section 8. 453 Supported behavior values together with parent TLVs in which they 454 area advertised are specified in Section 10 of this document. Please 455 note that not all behaviors defined in [RFC8986] are defined in this 456 document, e.g. END.T is not. 458 This new sub-TLV is advertised in the SRv6 Locator TLV defined in the 459 previous section. SRv6 End SIDs inherit the topology/algorithm from 460 the parent locator. 462 The SRv6 End SID sub-TLV has the following format: 464 0 1 2 3 465 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 1 466 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 467 | Type | Length | 468 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 469 | Flags | Endpoint Behavior | 470 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 471 | SID (128 bits) . . . | 472 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 473 | SID (cont . . .) | 474 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 475 | SID (cont . . .) | 476 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 477 | SID (cont . . .) | 478 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 479 |Sub-sub-TLV-len| Sub-sub-TLVs (variable) . . . | 480 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 482 Type: 5. 484 Length: variable. 486 Flags: 1 octet. No flags are currently defined. 488 Endpoint Behavior: 2 octets, as defined in [RFC8986]. Supported 489 behavior values for this sub-TLV are defined in Section 10 of this 490 document. Unsupported or unrecognized behavior values are ignored 491 by the receiver. 493 SID: 16 octets. This field encodes the advertised SRv6 SID. 495 Sub-sub-TLV-length: 1 octet. Number of octets used by sub-sub- 496 TLVs. 498 Optional Sub-sub-TLVs. 500 The SRv6 End SID MUST be a subnet of the associated Locator. SRv6 501 End SIDs which are not a subnet of the associated locator MUST be 502 ignored. 504 Multiple SRv6 End SIDs MAY be associated with the same locator. In 505 cases where the number of SRv6 End SID sub-TLVs exceeds the capacity 506 of a single TLV, multiple Locator TLVs for the same locator MAY be 507 advertised. For a given MTID/Locator the algorithm MUST be the same 508 in all TLVs. If this restriction is not met all TLVs for that MTID/ 509 Locator MUST be ignored. 511 8. Advertising SRv6 Adjacency SIDs 513 Certain SRv6 Endpoint behaviors [RFC8986] are associated with a 514 particular adjacency. 516 This document defines two new sub-TLVs of TLV 22, 23, 222, 223, and 517 141 - namely "SRv6 End.X SID sub-TLVs" and "SRv6 LAN End.X SID sub- 518 TLVs". 520 IS-IS Neighbor advertisements are topology specific - but not 521 algorithm specific. SIDs advertised in SRv6 End.X SID and SRv6 LAN 522 End.X SID sub-TLVs therefore inherit the topology from the associated 523 neighbor advertisement, but the algorithm is specified in the 524 individual SID. 526 All SIDs advertised in SRv6 End.X SID and SRv6 LAN End.X SID sub-TLVs 527 MUST be a subnet of a Locator with matching topology and algorithm 528 which is advertised by the same node in an SRv6 Locator TLV. SIDs 529 that do not meet this requirement MUST be ignored. This ensures that 530 the node advertising these SIDs is also advertising its corresponding 531 Locator with the algorithm that will be used for computing paths 532 destined to the SID. 534 8.1. SRv6 End.X SID sub-TLV 536 This sub-TLV is used to advertise an SRv6 SID associated with a point 537 to point adjacency. Multiple SRv6 End.X SID sub-TLVs MAY be 538 associated with the same adjacency. 540 The SRv6 End.X SID sub-TLV has the following format: 542 0 1 2 3 543 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 1 544 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 545 | Type | Length | 546 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 547 | Flags | Algorithm | Weight | 548 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 549 | Endpoint Behavior | 550 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 551 | SID (128 bits) . . . | 552 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 553 | SID (cont . . .) | 554 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 555 | SID (cont . . .) | 556 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 557 | SID (cont . . .) | 558 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 559 |Sub-sub-tlv-len| Sub-sub-TLVs (variable) . . . | 560 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 562 Type: 43 564 Length: variable. 566 Flags: 1 octet. 568 0 1 2 3 4 5 6 7 569 +-+-+-+-+-+-+-+-+ 570 |B|S|P|Reserved | 571 +-+-+-+-+-+-+-+-+ 573 where: 575 B-Flag: Backup flag. If set, the SID is eligible for 576 protection (e.g., using IPFRR) as described in [RFC8355]. 578 S-Flag. Set flag. When set, the S-Flag indicates that the SID 579 refers to a set of adjacencies (and therefore MAY be assigned 580 to other adjacencies as well). 582 P-Flag. Persistent flag. When set, the P-Flag indicates that 583 the SID is persistently allocated, i.e., the SID value remains 584 consistent across router restart and/or interface flap. 586 Reserved bits: MUST be zero when originated and ignored when 587 received. 589 Algorithm: 1 octet. As defined in [RFC8665]. 591 Weight: 1 octet. The value represents the weight of the SID for 592 the purpose of load balancing. The use of the weight is defined 593 in [RFC8402]. 595 Endpoint Behavior: 2 octets. As defined in [RFC8986]. Supported 596 behavior values for this sub-TLV are defined in Section 10 of this 597 document. Unsupported or unrecognized behavior values are ignored 598 by the receiver. 600 SID: 16 octets. This field encodes the advertised SRv6 SID. 602 Sub-sub-TLV-length: 1 octet. Number of octets used by sub-sub- 603 TLVs. 605 Note that multiple TLVs for the same neighbor may be required in 606 order to advertise all of the SRv6 SIDs associated with that 607 neighbor. 609 8.2. SRv6 LAN End.X SID sub-TLV 611 This sub-TLV is used to advertise an SRv6 SID associated with a LAN 612 adjacency. Since the parent TLV is advertising an adjacency to the 613 Designated Intermediate System (DIS) for the LAN, it is necessary to 614 include the System ID of the physical neighbor on the LAN with which 615 the SRv6 SID is associated. Given that a large number of neighbors 616 may exist on a given LAN a large number of SRv6 LAN END.X SID sub- 617 TLVs may be associated with the same LAN. Note that multiple TLVs 618 for the same DIS neighbor may be required in order to advertise all 619 of the SRv6 SIDs associated with that neighbor. 621 The SRv6 LAN End.X SID sub-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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 628 | Neighbor System-ID (ID length octets) | 629 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 630 | Flags | Algorithm | Weight | 631 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 632 | Endpoint Behavior | 633 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 634 | SID (128 bits) . . . | 635 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 636 | SID (cont . . .) | 637 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 638 | SID (cont . . .) | 639 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 640 | SID (cont . . .) | 641 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 642 |Sub-sub-TLV-len| sub-sub-TLVs (variable) . . . | 643 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 645 Type: 44 647 Length: variable. 649 Neighbor System-ID: IS-IS System-ID of length "ID Length" as 650 defined in [ISO10589]. 652 Flags: 1 octet. 654 0 1 2 3 4 5 6 7 655 +-+-+-+-+-+-+-+-+ 656 |B|S|P|Reserved | 657 +-+-+-+-+-+-+-+-+ 659 where B,S, and P flags are as described in Section 8.1. 660 Reserved bits MUST be zero when originated and MUST be ignored 661 when received. 663 Algorithm: 1 octet. As defined in [RFC8665]. 665 Weight: 1 octet. The value represents the weight of the SID for 666 the purpose of load balancing. The use of the weight is defined 667 in [RFC8402]. 669 Endpoint Behavior: 2 octets. As defined in [RFC8986]. Supported 670 behavior values for this sub-TLV are defined in Section 10 of this 671 document. Unsupported or unrecognized behavior values are ignored 672 by the receiver. 674 SID: 16 octets. This field encodes the advertised SRv6 SID. 676 Sub-sub-TLV-length: 1 octet. Number of octets used by sub-sub- 677 TLVs. 679 9. SRv6 SID Structure Sub-Sub-TLV 681 SRv6 SID Structure Sub-Sub-TLV is an optional Sub-Sub-TLV of: 683 SRv6 End SID Sub-TLV (Section 7.2) 685 SRv6 End.X SID Sub-TLV (Section 8.1) 687 SRv6 LAN End.X SID Sub-TLV (Section 8.2) 689 SRv6 SID Structure Sub-Sub-TLV is used to advertise the as defined in 690 [RFC8986]. It has the following format: 692 0 1 2 3 693 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 1 694 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 695 | Type | Length | 696 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 697 | LB Length | LN Length | Fun. Length | Arg. Length | 698 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 700 where: 702 Type: 1 704 Length: 4 octets. 706 LB Length: 1 octet. SRv6 SID Locator Block length in bits. 708 LN Length: 1 octet. SRv6 SID Locator Node length in bits. 710 Fun. Length: 1 octet. SRv6 SID Function length in bits. 712 Arg. Length: 1 octet. SRv6 SID Arguments length in bits. 714 ISIS SRv6 SID Structure Sub-Sub-TLV MUST NOT appear more than once in 715 its parent Sub-TLV. If it appears more than once in its parent Sub- 716 TLV, the parent Sub-TLV MUST be ignored by the receiver. 718 The sum of all four sizes advertised in ISIS SRv6 SID Structure Sub- 719 Sub-TLV MUST be lower or equal to 128 bits. If the sum of all four 720 sizes advertised in the ISIS SRv6 SID Structure Sub-Sub-TLV is larger 721 than 128 bits, the parent Sub-TLV MUST be ignored by the receiver. 723 The SRv6 SID Structure Sub-Sub-TLV indicates the structure of the SID 724 associated with it. It's usage is outside of the scope of this 725 document. 727 10. Advertising Endpoint Behaviors 729 Endpoint behaviors are defined in [RFC8986]. The codepoints for the 730 Endpoint behaviors are defined in the "SRv6 Endpoint Behaviors" 731 registry defined in [RFC8986]. If this behavior is advertised it 732 MUST only be advertised in the TLV[s] as indicated by "Y" in the 733 table below, and MUST NOT be advertised in the TLV[s] as indicated by 734 "N" in the table below. 736 Endpoint |Endpoint | End | End.X | Lan End.X | 737 Behavior |Behavior Codepoint| SID | SID | SID | 738 ----------------------|------------------|-----|-------|-----------| 739 End (PSP, USP, USD)| 1-4, 28-31 | Y | N | N | 740 ----------------------|------------------|-----|-------|-----------| 741 End.X (PSP, USP, USD)| 5-8, 32-35 | N | Y | Y | 742 ----------------------|------------------|-----|-------|-----------| 743 End.DX6 | 16 | N | Y | Y | 744 ----------------------|------------------|-----|-------|-----------| 745 End.DX4 | 17 | N | Y | Y | 746 ----------------------|------------------|-----|-------|-----------| 747 End.DT6 | 18 | Y | N | N | 748 ----------------------|------------------|-----|-------|-----------| 749 End.DT4 | 19 | Y | N | N | 750 ----------------------|------------------|-----|-------|-----------| 751 End.DT46 | 20 | Y | N | N | 753 11. IANA Considerations 755 This document requests allocation for the following TLVs, sub-TLVs, 756 and sub-sub-TLVs as well updating the ISIS TLV registry and defining 757 a new registry. 759 11.1. SRv6 Locator TLV 761 This document makes the following registrations in the the IS-IS TLV 762 Codepoints registry. 764 Type Description IIH LSP SNP Purge 765 ---- --------------------- --- --- --- ----- 766 27 SRv6 Locator TLV n y n n 768 11.1.1. SRv6 End SID sub-TLV 770 The SRv6 Locator TLV shares sub-TLV space with TLVs 135, 235, 236 and 771 237. This document updates the "Sub-TLVs for TLVs 135, 235, 236, and 772 237 (Extended IP reachability, MT IP. Reach, IPv6 IP. Reach, and MT 773 IPv6 IP. Reach TLVs)" registry defined in [RFC7370]. IANA is 774 requested to update the name of the "Sub-TLVs for TLVs 135, 235, 236, 775 and 237 (Extended IP reachability, MT IP. Reach, IPv6 IP. Reach, 776 and MT IPv6 IP. Reach TLVs)" registry to "Sub-TLVs for TLVs 27, 135, 777 235, 236, and 237 (SRv6 Locator, Extended IP reachability, MT IP. 778 Reach, IPv6 IP. Reach, and MT IPv6 IP. Reach TLVs)". 780 IANA is asked to add this document as a reference to (renamed) "Sub- 781 TLVs for TLVs 27, 135, 235, 236, and 237 (SRv6 Locator, Extended IP 782 reachability, MT IP. Reach, IPv6 IP. Reach, and MT IPv6 IP. Reach 783 TLVs)" registry. 785 This document makes the following registrations in the (renamed) 786 "Sub-TLVs for TLVs 27, 135, 235, 236, and 237 (SRv6 Locator, Extended 787 IP reachability, MT IP. Reach, IPv6 IP. Reach, and MT IPv6 IP. 788 Reach TLVs)" registry: 790 Type: 5 792 Description: SRv6 End SID sub-TLV. 794 Reference: This document (Section 7.2). 796 11.1.2. Revised sub-TLV table 798 The revised table of sub-TLVs for the (renamed) "Sub-TLVs for TLVs 799 27, 135, 235, 236, and 237 (SRv6 Locator, Extended IP reachability, 800 MT IP. Reach, IPv6 IP. Reach, and MT IPv6 IP. Reach TLVs)" 801 registry is shown below: 803 Type 27 135 235 236 237 805 1 y y y y y 806 2 y y y y y 807 3 n y y y y 808 4 y y y y y 809 5 y n n n n 810 6 n y y y y 811 11 y y y y y 812 12 y y y y y 813 32 n y y y y 815 11.2. SRv6 Capabilities sub-TLV 817 This document makes the following registrations in the "Sub-TLVs for 818 TLV 242 (IS-IS Router CAPABILITY TLV)": 820 Type: 25 822 Description: SRv6 Capabilities sub-TLV. 824 Reference: This document (Section 2). 826 This document requests the creation of a new IANA managed registry, 827 under "IS-IS TLV Codepoints" registry - sub-sub-TLVs of the SRv6 828 Capability sub-TLV. The registration procedure is "Expert Review" as 829 defined in [RFC8126]. Guidance for the Designated Experts is 830 provided in the [RFC7370]. Suggested registry name is "sub-sub-TLVs 831 for SRv6 Capability sub-TLV". No sub-sub-TLVs are defined by this 832 document except for the reserved value. 834 0: Reserved 836 1-255: Unassigned 838 11.3. SRv6 End.X SID and SRv6 LAN End.X SID sub-TLVs 840 This document makes the following registrations in the "Sub-TLVs for 841 TLVs 22, 23, 25, 141, 222, and 223 (Extended IS reachability, IS 842 Neighbor Attribute, L2 Bundle Member Attributes, inter-AS 843 reachability information, MT-ISN, and MT IS Neighbor Attribute TLVs)" 844 registry: 846 Type: 43 848 Description: SRv6 End.X SID sub-TLV. 850 Reference: This document (Section 8.1). 852 Type: 44 854 Description: SRv6 LAN End.X SID sub-TLV. 856 Reference: This document (Section 8.2). 858 Type 22 23 25 141 222 223 860 43 y y y y y y 861 44 y y y y y y 863 11.4. MSD Types 865 This document makes the following registrations in the IGP MSD-Types 866 registry: 868 Value Name Reference 869 ------------------ 870 41 SRH Max SL [This Document] 871 42 SRH Max End Pop [This Document] 872 44 SRH Max H.encaps [This Document] 873 45 SRH Max End D [This Document] 875 11.5. Sub-Sub-TLVs for SID Sub-TLVs 877 This document requests a new IANA registry be created under the IS-IS 878 TLV Codepoints Registry to control the assignment of sub-TLV types 879 for the SID Sub-TLVs specified in this document - Section 7.2, 880 Section 8.1, Section 8.2. The suggested name of the new registry is 881 "sub-sub-TLVs for SRv6 End SID (5) (sub-TLV of TLVs 27, 135, 235, 236 882 and 237) and SRv6 End.X SID (43)/SRv6 LAN End.X SID (44) (Sub-TLVs 883 for TLVs 22, 23, 25, 141, 222, and 223)". The registration procedure 884 is "Expert Review" as defined in [RFC8126]. Guidance for the 885 Designated Experts is provided in [RFC7370]. The following 886 assignments are made by this document: 888 Type Description Encoding 889 Reference 890 --------------------------------------------------------- 891 0 Reserved 892 1 SRv6 SID Structure Sub-Sub-TLV [This Document] 893 2-255 Unassigned 895 Type 5 43 44 897 1 y y y 899 11.6. Prefix Attribute Flags Sub-TLV 901 This document adds a new bit in the "Bit Values for Prefix Attribute 902 Flags Sub-TLV" registry: 904 Bit #: 4 906 Description: Anycast Flag (A-flag) 908 Reference: This document (Section 6). 910 11.7. ISIS SRv6 Capabilities sub-TLV Flags Registry 912 This document requests a new IANA registry be created under the IS-IS 913 TLV Codepoints Registry to control the assignment of bits in the 914 Flags field of the ISIS SRv6 Capabilities sub-TLV specified in this 915 document (Section 2). The suggested name of the new registry is 916 "ISIS SRv6 Capabilities sub-TLV Flags". The registration procedure 917 is "Expert Review" as defined in [RFC8126]. Guidance for the 918 Designated Experts is provided in [RFC7370]. The following 919 assignments are made by this document: 921 Bit #: 1 923 Description: O-flag 925 Reference: This document (Section 2). 927 11.8. ISIS SRv6 Locator TLV Flags Registry 929 This document requests a new IANA registry be created under the IS-IS 930 TLV Codepoints Registry to control the assignment of bits in the 931 Flags field of the ISIS SRv6 SRv6 Locator TLV specified in this 932 document (Section 7.1). The suggested name of the new registry is 933 "ISIS SRv6 Locator TLV Flags". The registration procedure is "Expert 934 Review" as defined in [RFC8126]. Guidance for the Designated Experts 935 is provided in [RFC7370]. The following assignments are made by this 936 document: 938 Bit #: 0 940 Description: D-flag 942 Reference: This document (Section 7.1). 944 11.9. ISIS SRv6 End SID sub-TLV Flags Registry 946 This document requests a new IANA registry be created under the IS-IS 947 TLV Codepoints Registry to control the assignment of bits in the 948 Flags field of the ISIS SRv6 End SID sub-TLV specified in this 949 document (Section 7.2). The suggested name of the new registry is 950 "ISIS SRv6 End SID sub-TLV Flags". The registration procedure is 951 "Expert Review" as defined in [RFC8126]. Guidance for the Designated 952 Experts is provided in [RFC7370]. No assignments are made by this 953 document. 955 11.10. ISIS SRv6 End.X SID and LAN End.X SID sub-TLVs Flags Registry 957 This document requests a new IANA registry be created under the IS-IS 958 TLV Codepoints Registry to control the assignment of bits in the 959 Flags field of the ISIS SRv6 End.X SID and LAN End.X SID sub-TLVs 960 (Section 8.1 and Section 8.2). The suggested name of the new 961 registry is "ISIS SRv6 End.X SID and LAN End.X SID sub-TLVs Flags". 962 The registration procedure is "Expert Review" as defined in 963 [RFC8126]. Guidance for the Designated Experts is provided in 964 [RFC7370]. The following assignments are made by this document: 966 Bit #: 0 968 Description: B-flag 970 Reference: This document (Section 8.1). 972 Bit #: 1 974 Description: S-flag 976 Reference: This document (Section 8.1). 978 Bit #: 2 980 Description: P-flag 981 Reference: This document (Section 8.1). 983 12. Security Considerations 985 Security concerns for IS-IS are addressed in [ISO10589], [RFC5304], 986 and [RFC5310]. While IS-IS is deployed under a single administrative 987 domain, there can be deployments where potential attackers have 988 access to one or more networks in the IS-IS routing domain. In these 989 deployments, the stronger authentication mechanisms defined in the 990 aforementioned documents SHOULD be used. 992 This document describes the IS-IS extensions required to support 993 Segment Routing over an IPv6 data plane. The security considerations 994 for Segment Routing are discussed in [RFC8402]. [RFC8986] defines 995 the SRv6 Network Programming concept and specifies the main Segment 996 Routing behaviors to enable the creation of interoperable overlays; 997 the security considerations from that document apply too. 999 The advertisement of an incorrect MSD value may have negative 1000 consequences, see [RFC8491] for additional considerations. 1002 13. Contributors 1004 The following people gave a substantial contribution to the content 1005 of this document and should be considered as co-authors: 1007 Stefano Previdi 1008 Huawei Technologies 1009 Email: stefano@previdi.net 1011 Paul Wells 1012 Cisco Systems 1013 Saint Paul, 1014 Minnesota 1015 United States 1016 Email: pauwells@cisco.com 1018 Daniel Voyer 1019 Email: daniel.voyer@bell.ca 1021 Satoru Matsushima 1022 Email: satoru.matsushima@g.softbank.co.jp 1024 Bart Peirens 1025 Email: bart.peirens@proximus.com 1027 Hani Elmalky 1028 Email: hani.elmalky@ericsson.com 1030 Prem Jonnalagadda 1031 Email: prem@barefootnetworks.com 1033 Milad Sharif 1034 Email: msharif@barefootnetworks.com> 1036 Robert Hanzl 1037 Cisco Systems 1038 Millenium Plaza Building, V Celnici 10, Prague 1, 1039 Prague, Czech Republic 1040 Email rhanzl@cisco.com 1042 Ketan Talaulikar 1043 Cisco Systems, Inc. 1044 Email: ketant@cisco.com 1046 14. References 1048 14.1. Normative References 1050 [I-D.ietf-6man-spring-srv6-oam] 1051 Ali, Z., Filsfils, C., Matsushima, S., Voyer, D., and M. 1052 Chen, "Operations, Administration, and Maintenance (OAM) 1053 in Segment Routing Networks with IPv6 Data plane (SRv6)", 1054 draft-ietf-6man-spring-srv6-oam-08 (work in progress), 1055 October 2020. 1057 [I-D.ietf-lsr-flex-algo] 1058 Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and 1059 A. Gulko, "IGP Flexible Algorithm", draft-ietf-lsr-flex- 1060 algo-13 (work in progress), October 2020. 1062 [ISO10589] 1063 International Organization for Standardization, 1064 "Intermediate system to Intermediate system intra-domain 1065 routeing information exchange protocol for use in 1066 conjunction with the protocol for providing the 1067 connectionless-mode Network Service (ISO 8473)", Nov 2002. 1069 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1070 Requirement Levels", BCP 14, RFC 2119, 1071 DOI 10.17487/RFC2119, March 1997, 1072 . 1074 [RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi 1075 Topology (MT) Routing in Intermediate System to 1076 Intermediate Systems (IS-ISs)", RFC 5120, 1077 DOI 10.17487/RFC5120, February 2008, 1078 . 1080 [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic 1081 Engineering", RFC 5305, DOI 10.17487/RFC5305, October 1082 2008, . 1084 [RFC5308] Hopps, C., "Routing IPv6 with IS-IS", RFC 5308, 1085 DOI 10.17487/RFC5308, October 2008, 1086 . 1088 [RFC7370] Ginsberg, L., "Updates to the IS-IS TLV Codepoints 1089 Registry", RFC 7370, DOI 10.17487/RFC7370, September 2014, 1090 . 1092 [RFC7794] Ginsberg, L., Ed., Decraene, B., Previdi, S., Xu, X., and 1093 U. Chunduri, "IS-IS Prefix Attributes for Extended IPv4 1094 and IPv6 Reachability", RFC 7794, DOI 10.17487/RFC7794, 1095 March 2016, . 1097 [RFC7981] Ginsberg, L., Previdi, S., and M. Chen, "IS-IS Extensions 1098 for Advertising Router Information", RFC 7981, 1099 DOI 10.17487/RFC7981, October 2016, 1100 . 1102 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 1103 Writing an IANA Considerations Section in RFCs", BCP 26, 1104 RFC 8126, DOI 10.17487/RFC8126, June 2017, 1105 . 1107 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 1108 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 1109 May 2017, . 1111 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 1112 Decraene, B., Litkowski, S., and R. Shakir, "Segment 1113 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 1114 July 2018, . 1116 [RFC8491] Tantsura, J., Chunduri, U., Aldrin, S., and L. Ginsberg, 1117 "Signaling Maximum SID Depth (MSD) Using IS-IS", RFC 8491, 1118 DOI 10.17487/RFC8491, November 2018, 1119 . 1121 [RFC8665] Psenak, P., Ed., Previdi, S., Ed., Filsfils, C., Gredler, 1122 H., Shakir, R., Henderickx, W., and J. Tantsura, "OSPF 1123 Extensions for Segment Routing", RFC 8665, 1124 DOI 10.17487/RFC8665, December 2019, 1125 . 1127 [RFC8667] Previdi, S., Ed., Ginsberg, L., Ed., Filsfils, C., 1128 Bashandy, A., Gredler, H., and B. Decraene, "IS-IS 1129 Extensions for Segment Routing", RFC 8667, 1130 DOI 10.17487/RFC8667, December 2019, 1131 . 1133 [RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J., 1134 Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header 1135 (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020, 1136 . 1138 [RFC8986] Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer, 1139 D., Matsushima, S., and Z. Li, "Segment Routing over IPv6 1140 (SRv6) Network Programming", RFC 8986, 1141 DOI 10.17487/RFC8986, February 2021, 1142 . 1144 14.2. Informative References 1146 [RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic 1147 Authentication", RFC 5304, DOI 10.17487/RFC5304, October 1148 2008, . 1150 [RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R., 1151 and M. Fanto, "IS-IS Generic Cryptographic 1152 Authentication", RFC 5310, DOI 10.17487/RFC5310, February 1153 2009, . 1155 [RFC8355] Filsfils, C., Ed., Previdi, S., Ed., Decraene, B., and R. 1156 Shakir, "Resiliency Use Cases in Source Packet Routing in 1157 Networking (SPRING) Networks", RFC 8355, 1158 DOI 10.17487/RFC8355, March 2018, 1159 . 1161 Authors' Addresses 1163 Peter Psenak (editor) 1164 Cisco Systems 1165 Pribinova Street 10 1166 Bratislava 81109 1167 Slovakia 1169 Email: ppsenak@cisco.com 1171 Clarence Filsfils 1172 Cisco Systems 1173 Brussels 1174 Belgium 1176 Email: cfilsfil@cisco.com 1178 Ahmed Bashandy 1179 Individual 1181 Email: abashandy.ietf@gmail.com 1183 Bruno Decraene 1184 Orange 1185 Issy-les-Moulineaux 1186 France 1188 Email: bruno.decraene@orange.com 1189 Zhibo Hu 1190 Huawei Technologies 1192 Email: huzhibo@huawei.com