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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 Intended status: Standards Track Cisco Systems 5 Expires: April 11, 2021 A. Bashandy 6 Individual 7 B. Decraene 8 Orange 9 Z. Hu 10 Huawei Technologies 11 October 8, 2020 13 IS-IS Extension to Support Segment Routing over IPv6 Dataplane 14 draft-ietf-lsr-isis-srv6-extensions-11 16 Abstract 18 Segment Routing (SR) allows for a flexible definition of end-to-end 19 paths by encoding paths as sequences of topological sub-paths, called 20 "segments". Segment routing architecture can be implemented over an 21 MPLS data plane as well as an IPv6 data plane. This draft describes 22 the IS-IS extensions required to support Segment Routing over an IPv6 23 data plane. 25 Requirements Language 27 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 28 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 29 "OPTIONAL" in this document are to be interpreted as described in BCP 30 14 [RFC2119] [RFC8174] when, and only when, they appear in all 31 capitals, as shown here. 33 Status of This Memo 35 This Internet-Draft is submitted in full conformance with the 36 provisions of BCP 78 and BCP 79. 38 Internet-Drafts are working documents of the Internet Engineering 39 Task Force (IETF). Note that other groups may also distribute 40 working documents as Internet-Drafts. The list of current Internet- 41 Drafts is at https://datatracker.ietf.org/drafts/current/. 43 Internet-Drafts are draft documents valid for a maximum of six months 44 and may be updated, replaced, or obsoleted by other documents at any 45 time. It is inappropriate to use Internet-Drafts as reference 46 material or to cite them other than as "work in progress." 48 This Internet-Draft will expire on April 11, 2021. 50 Copyright Notice 52 Copyright (c) 2020 IETF Trust and the persons identified as the 53 document authors. All rights reserved. 55 This document is subject to BCP 78 and the IETF Trust's Legal 56 Provisions Relating to IETF Documents 57 (https://trustee.ietf.org/license-info) in effect on the date of 58 publication of this document. Please review these documents 59 carefully, as they describe your rights and restrictions with respect 60 to this document. Code Components extracted from this document must 61 include Simplified BSD License text as described in Section 4.e of 62 the Trust Legal Provisions and are provided without warranty as 63 described in the Simplified BSD License. 65 Table of Contents 67 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 68 2. SRv6 Capabilities sub-TLV . . . . . . . . . . . . . . . . . . 4 69 3. Advertising Supported Algorithms . . . . . . . . . . . . . . 4 70 4. Advertising Maximum SRv6 SID Depths . . . . . . . . . . . . . 5 71 4.1. Maximum Segments Left MSD Type . . . . . . . . . . . . . 5 72 4.2. Maximum End Pop MSD Type . . . . . . . . . . . . . . . . 5 73 4.3. Maximum H.Encaps MSD Type . . . . . . . . . . . . . . . . 5 74 4.4. Maximum End D MSD Type . . . . . . . . . . . . . . . . . 6 75 5. SRv6 SIDs and Reachability . . . . . . . . . . . . . . . . . 6 76 6. Advertising Anycast Property . . . . . . . . . . . . . . . . 7 77 7. Advertising Locators and End SIDs . . . . . . . . . . . . . . 8 78 7.1. SRv6 Locator TLV Format . . . . . . . . . . . . . . . . . 8 79 7.2. SRv6 End SID sub-TLV . . . . . . . . . . . . . . . . . . 10 80 8. Advertising SRv6 Adjacency SIDs . . . . . . . . . . . . . . . 11 81 8.1. SRv6 End.X SID sub-TLV . . . . . . . . . . . . . . . . . 12 82 8.2. SRv6 LAN End.X SID sub-TLV . . . . . . . . . . . . . . . 13 83 9. SRv6 SID Structure Sub-Sub-TLV . . . . . . . . . . . . . . . 15 84 10. Advertising Endpoint Behaviors . . . . . . . . . . . . . . . 16 85 11. Implementation Status . . . . . . . . . . . . . . . . . . . . 16 86 11.1. Cisco . . . . . . . . . . . . . . . . . . . . . . . . . 17 87 11.2. Huawei . . . . . . . . . . . . . . . . . . . . . . . . . 17 88 11.3. Juniper . . . . . . . . . . . . . . . . . . . . . . . . 17 89 11.4. Arrcus . . . . . . . . . . . . . . . . . . . . . . . . . 17 90 11.5. Interoperability Testing. . . . . . . . . . . . . . . . 18 91 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 92 12.1. SRv6 Locator TLV . . . . . . . . . . . . . . . . . . . . 18 93 12.1.1. SRv6 End SID sub-TLV . . . . . . . . . . . . . . . . 18 94 12.1.2. Revised sub-TLV table . . . . . . . . . . . . . . . 18 95 12.2. SRv6 Capabilities sub-TLV . . . . . . . . . . . . . . . 19 96 12.3. SRv6 End.X SID and SRv6 LAN End.X SID sub-TLVs . . . . . 19 97 12.4. MSD Types . . . . . . . . . . . . . . . . . . . . . . . 20 98 12.5. Sub-Sub-TLVs for SID Sub-TLVs . . . . . . . . . . . . . 20 99 12.6. Prefix Attribute Flags Sub-TLV . . . . . . . . . . . . . 20 100 13. Security Considerations . . . . . . . . . . . . . . . . . . . 21 101 14. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 21 102 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 22 103 15.1. Normative References . . . . . . . . . . . . . . . . . . 22 104 15.2. Informative References . . . . . . . . . . . . . . . . . 24 105 15.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 25 106 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 25 108 1. Introduction 110 With Segment Routing (SR) [RFC8402], a node steers a packet through 111 an ordered list of instructions, called segments. 113 Segments are identified through Segment Identifiers (SIDs). 115 Segment Routing can be directly instantiated on the IPv6 data plane 116 through the use of the Segment Routing Header defined in [RFC8754]. 117 SRv6 refers to this SR instantiation on the IPv6 dataplane. 119 The network programming paradigm 120 [I-D.ietf-spring-srv6-network-programming] is central to SRv6. It 121 describes how any behavior can be bound to a SID and how any network 122 program can be expressed as a combination of SIDs. 124 This document specifies IS-IS extensions that allow the IS-IS 125 protocol to encode some of these SIDs and their behaviors. 127 Familiarity with the network programming paradigm 128 [I-D.ietf-spring-srv6-network-programming] is necessary to understand 129 the extensions specified in this document. 131 This document defines one new top level IS-IS TLV and several new IS- 132 IS sub-TLVs. 134 The SRv6 Capabilities sub-TLV announces the ability to support SRv6. 136 Several new sub-TLVs are defined to advertise various SRv6 Maximum 137 SID Depths. 139 The new SRv6 Locator top level TLV announces SRv6 locators - a form 140 of summary address for the set of topology/algorithm specific SIDs 141 instantiated at the node. 143 The SRv6 End SID sub-TLV, the SRv6 End.X SID sub-TLV, and the SRv6 144 LAN End.X SID sub-TLV are used to advertise which SIDs are 145 instantiated at a node and what Endpoint behavior is bound to each 146 instantiated SID. 148 2. SRv6 Capabilities sub-TLV 150 A node indicates that it supports the SR Segment Endpoint Node 151 functionality as specified in [RFC8754] by advertising a new SRv6 152 Capabilities sub-TLV of the router capabilities TLV [RFC7981]. 154 The SRv6 Capabilities sub-TLV may contain optional sub-sub-TLVs. No 155 sub-sub-TLVs are currently defined. 157 The SRv6 Capabilities sub-TLV has the following format: 159 0 1 2 3 160 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 1 161 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 162 | Type | Length | Flags | 163 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 164 | optional sub-sub-TLVs... 166 Type: 25 168 Length: 2 + length of sub-sub-TLVs 170 Flags: 2 octets The following flags are defined: 172 0 1 173 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 174 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 175 | |O| | 176 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 178 where: 180 O-flag: If set, the router supports use of the O-bit 181 in the Segment Routing Header(SRH) as defined in 182 [I-D.ietf-6man-spring-srv6-oam]. 184 3. Advertising Supported Algorithms 186 SRv6 capable router indicates supported algorithm(s) by advertising 187 the SR Algorithm TLV as defined in [RFC8667]. 189 4. Advertising Maximum SRv6 SID Depths 191 [RFC8491] defines the means to advertise node/link specific values 192 for Maximum SID Depths (MSD) of various types. Node MSDs are 193 advertised in a sub-TLV of the Router Capabilities TLV [RFC7981]. 194 Link MSDs are advertised in a sub-TLV of TLVs 22, 23, 141, 222, and 195 223. 197 This document defines the relevant SRv6 MSDs and requests MSD type 198 assignments in the MSD Types registry created by [RFC8491]. 200 4.1. Maximum Segments Left MSD Type 202 The Maximum Segments Left MSD Type specifies the maximum value of the 203 "SL" field [RFC8754] in the SRH of a received packet before applying 204 the Endpoint behavior associated with a SID. 206 SRH Max SL Type: 41 208 If no value is advertised the supported value is assumed to be 0. 210 4.2. Maximum End Pop MSD Type 212 The Maximum End Pop MSD Type specifies the maximum number of SIDs in 213 the SRH to which the router can apply "PSP" or USP" behavior, as 214 defined in [I-D.ietf-spring-srv6-network-programming] flavors. 216 SRH Max End Pop Type: 42 218 If the advertised value is zero or no value is advertised 219 then it is assumed that the router cannot apply PSP or USP flavors. 221 4.3. Maximum H.Encaps MSD Type 223 The Maximum H.Encaps MSD Type specifies the maximum number of SIDs 224 that can be included as part of the "H.Encaps" behavior as defined in 225 [I-D.ietf-spring-srv6-network-programming]. 227 SRH Max H.encaps Type: 44 229 If the advertised value is zero or no value is advertised 230 then the router can apply H.Encaps only by encapsulating 231 the incoming packet in another IPv6 header without SRH 232 the same way IPinIP encapsulation is performed. 234 If the advertised value is non-zero then the router supports both 235 IPinIP and SRH encapsulation subject to the SID limitation 236 specified by the advertised value. 238 4.4. Maximum End D MSD Type 240 The Maximum End D MSD Type specifies the maximum number of SIDs in an 241 SRH when performing decapsulation associated with "End.Dx" behaviors 242 (e.g., "End.DX6" and "End.DT6") as defined in 243 [I-D.ietf-spring-srv6-network-programming]. 245 SRH Max End D Type: 45 247 If the advertised value is zero or no value is advertised 248 then it is assumed that the router cannot apply 249 "End.DX6" or "End.DT6" behaviors if the outer IPv6 header 250 contains an SRH. 252 5. SRv6 SIDs and Reachability 254 As discussed in [I-D.ietf-spring-srv6-network-programming], an SRv6 255 Segment Identifier (SID) is 128 bits and consists of Locator, 256 Function and Argument parts. 258 A node is provisioned with topology/algorithm specific locators for 259 each of the topology/algorithm pairs supported by that node. Each 260 locator is a covering prefix for all SIDs provisioned on that node 261 which have the matching topology/algorithm. 263 Locators MUST be advertised in the SRv6 Locator TLV (see 264 Section 7.1). Forwarding entries for the locators advertised in the 265 SRv6 Locator TLV MUST be installed in the forwarding plane of 266 receiving SRv6 capable routers when the associated topology/algorithm 267 is supported by the receiving node. 269 Locators are routable and MAY also be advertised in Prefix 270 Reachability TLVs (236 or 237). 272 Locators associated with Flexible Algorithms [I-D.ietf-lsr-flex-algo] 273 SHOULD NOT be advertised in Prefix Reachability TLVs (236 or 237). 275 Locators associated with algorithm 0 and 1 (for all supported 276 topologies) SHOULD be advertised in a Prefix Reachability TLV (236 or 277 237) so that legacy routers (i.e., routers which do NOT support SRv6) 278 will install a forwarding entry for algorithm 0 and 1 SRv6 traffic. 280 In cases where a locator advertisement is received in both a Prefix 281 Reachability TLV and an SRv6 Locator TLV, the Prefix Reachability 282 advertisement MUST be preferred when installing entries in the 283 forwarding plane. This is to prevent inconsistent forwarding entries 284 between SRv6 capable and SRv6 incapable routers. 286 SRv6 SIDs are advertised as sub-TLVs in the SRv6 Locator TLV except 287 for SRv6 End.X SIDs/LAN End.X SIDs which are associated with a 288 specific Neighbor/Link and are therefore advertised as sub-TLVs in 289 TLVs 22, 23, 222, 223, and 141. 291 SRv6 SIDs are not directly routable and MUST NOT be installed in the 292 forwarding plane. Reachability to SRv6 SIDs depends upon the 293 existence of a covering locator. 295 Adherence to the rules defined in this section will assure that SRv6 296 SIDs associated with a supported topology/algorithm pair will be 297 forwarded correctly, while SRv6 SIDs associated with an unsupported 298 topology/algorithm pair will be dropped. NOTE: The drop behavior 299 depends on the absence of a default/summary route covering a given 300 locator. 302 In order for forwarding to work correctly, the locator associated 303 with SRv6 SID advertisements MUST be the longest match prefix 304 installed in the forwarding plane for those SIDs. There are a number 305 of ways in which this requirement could be compromised. In order to 306 ensure correct forwarding, network operators should take steps to 307 make sure that this requirement is not compromised. 309 o Another locator associated with a different topology/algorithm is 310 the longest match 312 o A prefix advertisement (i.e., from TLV 236 or 237) is the longest 313 match 315 6. Advertising Anycast Property 317 Both prefixes and SRv6 Locators may be configured as anycast and as 318 such the same value can be advertised by multiple routers. It is 319 useful for other routers to know that the advertisement is for an 320 anycast identifier. 322 A new flag in "Bit Values for Prefix Attribute Flags Sub-TLV" 323 registry [RFC7794] is defined to advertise the anycast property: 325 Bit #: 4 326 Name: Anycast Flag (A-flag) 328 When the prefix/SRv6 locator is configured as anycast, the A-flag 329 SHOULD be set. Otherwise, this flag MUST be clear. 331 The A-flag MUST be preserved when leaked between levels. 333 The A-flag and the N-flag MUST NOT both be set. 335 If both N-flag and A-flag are set in the prefix/SRv6 Locator 336 advertisement, the receiving routers MUST ignore the N-flag. 338 The same prefix/SRv6 Locator can be advertised by multiple routers. 339 If at least one of them sets the A-Flag in its advertisement, the 340 prefix/SRv6 Locator SHOULD be considered as anycast. 342 A prefix/SRv6 Locator that is advertised by a single node and without 343 an A-Flag SHOULD be interpreted as a node specific locator. 345 All the nodes advertising the same anycast locator MUST instantiate 346 the exact same set of SIDs under such anycast locator. Failure to do 347 so may result in traffic being black-holed or mis-routed. 349 The Prefix Attribute Flags Sub-TLV can be carried in the SRv6 Locator 350 TLV as well as the Prefix Reachability TLVs. When a router 351 originates both the Prefix Reachability TLV and the SRv6 Locator TLV 352 for a given prefix, and the router is originating the Prefix 353 Attribute Flags Sub-TLV in one of the TLVs, the router SHOULD 354 advertise identical versions of the Prefix Attribute Flags Sub-TLV in 355 both TLVs. 357 7. Advertising Locators and End SIDs 359 The SRv6 Locator TLV is introduced to advertise SRv6 Locators and End 360 SIDs associated with each locator. 362 This new TLV shares the sub-TLV space defined for TLVs 135, 235, 236 363 and 237. 365 7.1. SRv6 Locator TLV Format 367 The SRv6 Locator TLV has the following format: 369 0 1 2 3 370 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 1 371 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 372 | Type | Length |R|R|R|R| MTID | 373 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 375 Type: 27 377 Length: variable. 379 R bits: reserved for future use. They MUST be 380 set to zero on transmission and MUST be ignored on receipt. 382 MTID: Multitopology Identifier as defined in [RFC5120]. 383 Note that the value 0 is legal. 385 Followed by one or more locator entries of the form: 387 0 1 2 3 388 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 1 389 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 390 | Metric | 391 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 392 | Flags | Algorithm | 393 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 394 | Loc Size | Locator (variable)... 395 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 396 | Sub-tlv-len | Sub-TLVs (variable) . . . | 397 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 399 Metric: 4 octets. As described in [RFC5305]. 401 Flags: 1 octet. The following flags are defined 403 0 404 0 1 2 3 4 5 6 7 405 +-+-+-+-+-+-+-+-+ 406 |D| Reserved | 407 +-+-+-+-+-+-+-+-+ 409 where: 410 D bit: When the Locator is leaked from level-2 to level-1, the D 411 bit MUST be set. Otherwise, this bit MUST be clear. Locators 412 with the D bit set MUST NOT be leaked from level-1 to level-2. 413 This is to prevent looping. 415 The remaining bits are reserved for future use. They MUST be 416 set to zero on transmission and MUST be ignored on receipt. 418 Algorithm: 1 octet. Associated algorithm. Algorithm values 419 are defined in the IGP Algorithm Type registry. 421 Loc-Size: 1 octet. Number of bits in the SRv6 Locator field. 422 (1 - 128) 424 Locator: 1-16 octets. This field encodes the advertised SRv6 425 Locator. The Locator is encoded in the minimal number of 426 octets for the given number of bits. Trailing bits MUST be set 427 to zero and ignored when received. 429 Sub-TLV-length: 1 octet. Number of octets used by sub-TLVs 431 Optional sub-TLVs. 433 7.2. SRv6 End SID sub-TLV 435 The SRv6 End SID sub-TLV is introduced to advertise SRv6 Segment 436 Identifiers (SID) with Endpoint behaviors which do not require a 437 particular neighbor in order to be correctly applied 438 [I-D.ietf-spring-srv6-network-programming]. SRv6 SIDs associated 439 with a neighbor are advertised using the sub-TLVs defined in 440 Section 8. 442 This new sub-TLV is advertised in the SRv6 Locator TLV defined in the 443 previous section. SRv6 End SIDs inherit the topology/algorithm from 444 the parent locator. 446 The SRv6 End SID sub-TLV has the following format: 448 0 1 2 3 449 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 1 450 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 451 | Type | Length | 452 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 453 | Flags | Endpoint Behavior | 454 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 455 | SID (128 bits) . . . | 456 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 457 | SID (cont . . .) | 458 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 459 | SID (cont . . .) | 460 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 461 | SID (cont . . .) | 462 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 463 |Sub-sub-tlv-len| sub-sub-TLVs (variable) . . . | 464 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 466 Type: 5. 468 Length: variable. 470 Flags: 1 octet. No flags are currently defined. 472 Endpoint Behavior: 2 octets, as defined in [I-D.ietf-spring-srv6- 473 network-programming]. Legal behavior values for this sub-TLV are 474 defined in Section 10 of this document. 476 SID: 16 octets. This field encodes the advertised SRv6 SID. 478 Sub-sub-TLV-length: 1 octet. Number of octets used by sub-sub- 479 TLVs. 481 Optional sub-sub-TLVs. 483 The SRv6 End SID MUST be a subnet of the associated Locator. SRv6 484 End SIDs which are NOT a subnet of the associated locator MUST be 485 ignored. 487 Multiple SRv6 End SIDs MAY be associated with the same locator. In 488 cases where the number of SRv6 End SID sub-TLVs exceeds the capacity 489 of a single TLV, multiple Locator TLVs for the same locator MAY be 490 advertised. For a given MTID/Locator the algorithm MUST be the same 491 in all TLVs. If this restriction is not met all TLVs for that MTID/ 492 Locator MUST be ignored. 494 8. Advertising SRv6 Adjacency SIDs 496 Certain SRv6 Endpoint behaviors 497 [I-D.ietf-spring-srv6-network-programming] are associated with a 498 particular adjacency. 500 This document defines two new sub-TLVs of TLV 22, 23, 222, 223, and 501 141 - namely "SRv6 End.X SID" and "SRv6 LAN End.X SID". 503 IS-IS Neighbor advertisements are topology specific - but not 504 algorithm specific. End.X SIDs therefore inherit the topology from 505 the associated neighbor advertisement, but the algorithm is specified 506 in the individual SID. 508 All End.X SIDs MUST be a subnet of a Locator with matching topology 509 and algorithm which is advertised by the same node in an SRv6 Locator 510 TLV. End.X SIDs which do not meet this requirement MUST be ignored. 512 All End.X and LAN End.X SIDs MUST be subsumed by the subnet of a 513 Locator with the matching algorithm which is advertised by the same 514 node in an SRv6 Locator TLV. End.X SIDs which do not meet this 515 requirement MUST be ignored. This ensures that the node advertising 516 the End.X or LAN End.X SID is also advertising its corresponding 517 Locator with the algorithm that will be used for computing paths 518 destined to the SID. 520 8.1. SRv6 End.X SID sub-TLV 522 This sub-TLV is used to advertise an SRv6 SID associated with a point 523 to point adjacency. Multiple SRv6 End.X SID sub-TLVs MAY be 524 associated with the same adjacency. 526 The SRv6 End.X SID sub-TLV has the following format: 528 0 1 2 3 529 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 1 530 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 531 | Type | Length | 532 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 533 | Flags | Algorithm | Weight | 534 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 535 | Endpoint Behavior | 536 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 537 | SID (128 bits) . . . | 538 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 539 | SID (cont . . .) | 540 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 541 | SID (cont . . .) | 542 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 543 | SID (cont . . .) | 544 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 545 |Sub-sub-tlv-len| Sub-sub-TLVs (variable) . . . | 546 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 548 Type: 43 550 Length: variable. 552 Flags: 1 octet. 554 0 1 2 3 4 5 6 7 555 +-+-+-+-+-+-+-+-+ 556 |B|S|P|Reserved | 557 +-+-+-+-+-+-+-+-+ 559 where: 561 B-Flag: Backup flag. If set, the End.X SID is eligible for 562 protection (e.g., using IPFRR) as described in [RFC8355]. 564 S-Flag. Set flag. When set, the S-Flag indicates that the 565 End.X SID refers to a set of adjacencies (and therefore MAY be 566 assigned to other adjacencies as well). 568 P-Flag. Persistent flag. When set, the P-Flag indicates that 569 the End.X SID is persistently allocated, i.e., the End.X SID 570 value remains consistent across router restart and/or interface 571 flap. 573 Reserved bits: MUST be zero when originated and ignored when 574 received. 576 Algorithm: 1 octet. Associated algorithm. Algorithm values are 577 defined in the IGP Algorithm Type registry. 579 Weight: 1 octet. The value represents the weight of the End.X SID 580 for the purpose of load balancing. The use of the weight is 581 defined in [RFC8402]. 583 Endpoint Behavior: 2 octets. As defined in [I-D.ietf-spring-srv6- 584 network-programming] Legal behavior values for this sub-TLV are 585 defined in Section 10. 587 SID: 16 octets. This field encodes the advertised SRv6 SID. 589 Sub-sub-TLV-length: 1 octet. Number of octets used by sub-sub- 590 TLVs. 592 Note that multiple TLVs for the same neighbor may be required in 593 order to advertise all of the SRv6 End.X SIDs associated with that 594 neighbor. 596 8.2. SRv6 LAN End.X SID sub-TLV 598 This sub-TLV is used to advertise an SRv6 SID associated with a LAN 599 adjacency. Since the parent TLV is advertising an adjacency to the 600 Designated Intermediate System(DIS) for the LAN, it is necessary to 601 include the System ID of the physical neighbor on the LAN with which 602 the SRv6 SID is associated. Given that a large number of neighbors 603 may exist on a given LAN a large number of SRv6 LAN END.X SID sub- 604 TLVs may be associated with the same LAN. Note that multiple TLVs 605 for the same DIS neighbor may be required in order to advertise all 606 of the SRv6 End.X SIDs associated with that neighbor. 608 The SRv6 LAN End.X SID sub-TLV has the following format: 610 0 1 2 3 611 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 1 612 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 613 | Type | Length | | 614 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 615 | Neighbor System-ID (ID length octets) | 616 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 617 | Flags | Algorithm | Weight | 618 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 619 | Endpoint Behavior | 620 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 621 | SID (128 bits) . . . | 622 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 623 | SID (cont . . .) | 624 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 625 | SID (cont . . .) | 626 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 627 | SID (cont . . .) | 628 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 629 |Sub-sub-tlv-len| sub-sub-TLVs (variable) . . . | 630 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 632 Type: 44 634 Length: variable. 636 Neighbor System-ID: IS-IS System-ID of length "ID Length" as 637 defined in [ISO10589]. 639 Flags: 1 octet. 641 0 1 2 3 4 5 6 7 642 +-+-+-+-+-+-+-+-+ 643 |B|S|P|Reserved | 644 +-+-+-+-+-+-+-+-+ 646 where B,S, and P flags are as described in Section 8.1. 647 Reserved bits MUST be zero when originated and MUST be ignored 648 when received. 650 Algorithm: 1 octet. Associated algorithm. Algorithm values are 651 defined in the IGP Algorithm Type registry. 653 Weight: 1 octet. The value represents the weight of the End.X SID 654 for the purpose of load balancing. The use of the weight is 655 defined in [RFC8402]. 657 Endpoint Behavior: 2 octets. As defined in [I-D.ietf-spring-srv6- 658 network-programming] Legal behavior values for this sub-TLV are 659 defined in Section 10. 661 SID: 16 octets. This field encodes the advertised SRv6 SID. 663 Sub-sub-TLV-length: 1 octet. Number of octets used by sub-sub- 664 TLVs. 666 9. SRv6 SID Structure Sub-Sub-TLV 668 SRv6 SID Structure Sub-Sub-TLV is an optional Sub-Sub-TLV of: 670 SRv6 End SID Sub-TLV (Section 7.2) 672 SRv6 End.X SID Sub-TLV (Section 8.1) 674 SRv6 LAN End.X SID Sub-TLV (Section 8.2) 676 SRv6 SID Structure Sub-Sub-TLV is used to advertise the length of 677 each individual part of the SRv6 SID as defined in 678 [I-D.ietf-spring-srv6-network-programming]. It has the following 679 format: 681 0 1 2 3 682 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 1 683 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 684 | Type | Length | 685 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 686 | LB Length | LN Length | Fun. Length | Arg. Length | 687 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 689 where: 691 Type: 1 693 Length: 4 octets. 695 LB Length: 1 octet. SRv6 SID Locator Block length in bits. 697 LN Length: 1 octet. SRv6 SID Locator Node length in bits. 699 Fun. Length: 1 octet. SRv6 SID Function length in bits. 701 Arg. Length: 1 octet. SRv6 SID Arguments length in bits. 703 ISIS SRv6 SID Structure Sub-Sub-TLV MUST NOT appear more than once in 704 its parent Sub-TLV. If it appears more than once in its parent Sub- 705 TLV, the parent Sub-TLV MUST be ignored by the receiver. 707 The sum of all four sizes advertised in ISIS SRv6 SID Structure Sub- 708 Sub-TLV must be lower or equal to 128 bits. If the sum of all four 709 sizes advertised in the ISIS SRv6 SID Structure Sub-Sub-TLV is larger 710 than 128 bits, the parent Sub-TLV MUST be ignored by the receiver. 712 10. Advertising Endpoint Behaviors 714 Endpoint behaviors are defined in 715 [I-D.ietf-spring-srv6-network-programming]. The codepoints for the 716 Endpoint behaviors are defined in the "SRv6 Endpoint Behaviors" 717 registry defined in [I-D.ietf-spring-srv6-network-programming]. This 718 section lists the Endpoint behaviors which MAY be advertised by ISIS, 719 together with their codepoints. If this behavior is advertised it 720 MUST only be advertised in the TLV[s] as indicated by "Y" in the 721 table below, and MUST NOT be advertised in the TLV[s] as indicated by 722 "N" in the table below. 724 Endpoint |Endpoint | End | End.X | Lan End.X | 725 Behavior |Behavior Codepoint| SID | SID | SID | 726 ----------------------|------------------|-----|-------|-----------| 727 End (PSP, USP, USD)| 1-4, 28-31 | Y | N | N | 728 ----------------------|------------------|-----|-------|-----------| 729 End.X (PSP, USP, USD)| 5-8, 32-35 | N | Y | Y | 730 ----------------------|------------------|-----|-------|-----------| 731 End.DX6 | 16 | N | Y | Y | 732 ----------------------|------------------|-----|-------|-----------| 733 End.DX4 | 17 | N | Y | Y | 734 ----------------------|------------------|-----|-------|-----------| 735 End.DT6 | 18 | Y | N | N | 736 ----------------------|------------------|-----|-------|-----------| 737 End.DT4 | 19 | Y | N | N | 738 ----------------------|------------------|-----|-------|-----------| 739 End.DT64 | 20 | Y | N | N | 741 11. Implementation Status 743 RFC Ed.: Please remove this section prior to publication. 745 This section describes the implementation status of the ISIS SRv6 746 extensions. 748 11.1. Cisco 750 Cisco's ISIS SRv6 implementation supports following functionalities: 752 Types of SID supported: End, End.X, LAN End.X, END.OP 754 Intra/Inter area/level support: Yes 756 Anycast SID support: Yes, including A-flag (Section 6) 758 SID Structure Sub-Sub-TLV: Yes 760 11.2. Huawei 762 Huawei's ISIS SRv6 implementation supports following functionalities: 764 Types of SID supported: End, End.X, LAN End.X 766 Intra/Inter area/level support: Yes 768 Anycast SID support: Yes, no A-flag support (Section 6) 770 SID Structure Sub-Sub-TLV: Yes 772 11.3. Juniper 774 Juniper's ISIS SRv6 implementation supports following 775 functionalities: 777 Types of SID supported: End, End.X, LAN End.X 779 Intra/Inter area/level support: Yes 781 Anycast SID support: Yes, no A-flag support (Section 6) 783 SID Structure Sub-Sub-TLV: No 785 11.4. Arrcus 787 Arrcus's ISIS SRv6 implementation supports following functionalities: 789 Types of SID supported: End, End.X, LAN End.X 791 Intra/Inter area/level support: Yes 793 Anycast SID support: No (Section 6) 795 SID Structure Sub-Sub-TLV: Yes 797 11.5. Interoperability Testing. 799 EANTC interoperability testing has been performed in April 2019. 800 Results can be found at EANTC site [1]. 802 12. IANA Considerations 804 This document requests allocation for the following TLVs, sub-TLVs, 805 and sub-sub-TLVs as well updating the ISIS TLV registry and defining 806 a new registry. 808 12.1. SRv6 Locator TLV 810 This document makes the following registrations in the the IS-IS TLV 811 Codepoints registry: 813 Type: 27 815 Description: SRv6 Locator TLV. 817 Reference: This document (Section 7.1). 819 A Locator TLV shares sub-TLV space with existing "Sub-TLVs for TLVs 820 135, 235, 236 and 237 registry". The name of this registry needs to 821 be changed to "Sub-TLVs for TLVs 27, 135, 235, 236 and 237 registry". 823 12.1.1. SRv6 End SID sub-TLV 825 This document makes the following registrations in the (renamed) 826 "Sub-TLVs for TLVs 27, 135, 235, 236 and 237 registry": 828 Type: 5 830 Description: SRv6 End SID sub-TLV. 832 Reference: This document (Section 7.2). 834 12.1.2. Revised sub-TLV table 836 The revised table of sub-TLVs for the (renamed) "Sub-TLVs for TLVs 837 27, 135, 235, 236 and 237 registry" is shown below: 839 Type 27 135 235 236 237 841 1 y y y y y 842 2 y y y y y 843 3 n y y y y 844 4 y y y y y 845 5 y n n n n 846 6 n y y y y 847 11 y y y y y 848 12 y y y y y 849 32 n y y y y 851 12.2. SRv6 Capabilities sub-TLV 853 This document makes the following registrations in the "Sub- TLVs for 854 TLV 242 registry": 856 Type: 25 858 Description: SRv6 Capabilities sub-TLV. 860 Reference: This document (Section 2). 862 This document requests the creation of a new IANA managed registry 863 for sub-sub-TLVs of the SRv6 Capability sub-TLV. The registration 864 procedure is "Expert Review" as defined in [RFC8126]. Suggested 865 registry name is "sub-sub-TLVs for SRv6 Capability sub-TLV". No sub- 866 sub-TLVs are defined by this document except for the reserved value. 868 0: Reserved 870 1-255: Unassigned 872 12.3. SRv6 End.X SID and SRv6 LAN End.X SID sub-TLVs 874 This document makes the following registrations in the "sub- TLVs for 875 TLV 22, 23, 25, 141, 222 and 223 registry": 877 Type: 43 879 Description: SRv6 End.X SID sub-TLV. 881 Reference: This document (Section 8.1). 883 Type: 44 885 Description: SRv6 LAN End.X SID sub-TLV. 887 Reference: This document (Section 8.2). 889 Type 22 23 25 141 222 223 891 43 y y y y y y 892 44 y y y y y y 894 12.4. MSD Types 896 This document makes the following registrations in the IGP MSD Types 897 registry: 899 Type Description 900 ------------------ 901 41 SRH Max SL 902 42 SRH Max End Pop 903 44 SRH Max H.encaps 904 45 SRH Max End D 906 12.5. Sub-Sub-TLVs for SID Sub-TLVs 908 This document requests a new IANA registry be created under the IS-IS 909 TLV Codepoints Registry to control the assignment of sub-TLV types 910 for the SID Sub-TLVs specified in this document - Section 7.2, 911 Section 8.1, Section 8.2. The suggested name of the new registry is 912 "Sub-Sub-TLVs for SID Sub-TLVs". The registration procedure is 913 "Expert Review" as defined in [RFC8126]. The following assignments 914 are made by this document: 916 0: Reserved 918 1: SRv6 SID Structure Sub-Sub-TLV (Section 9). 920 12.6. Prefix Attribute Flags Sub-TLV 922 This document adds a new bit in the "Bit Values for Prefix Attribute 923 Flags Sub-TLV" registry: 925 Bit #: 4 927 Description: A bit 929 Reference: This document (Section 6). 931 13. Security Considerations 933 Security concerns for IS-IS are addressed in [ISO10589], [RFC5304], 934 and [RFC5310]. 936 14. Contributors 938 The following people gave a substantial contribution to the content 939 of this document and should be considered as co-authors: 941 Stefano Previdi 942 Huawei Technologies 943 Email: stefano@previdi.net 945 Paul Wells 946 Cisco Systems 947 Saint Paul, 948 Minnesota 949 United States 950 Email: pauwells@cisco.com 952 Daniel Voyer 953 Email: daniel.voyer@bell.ca 955 Satoru Matsushima 956 Email: satoru.matsushima@g.softbank.co.jp 958 Bart Peirens 959 Email: bart.peirens@proximus.com 961 Hani Elmalky 962 Email: hani.elmalky@ericsson.com 964 Prem Jonnalagadda 965 Email: prem@barefootnetworks.com 967 Milad Sharif 968 Email: msharif@barefootnetworks.com> 970 Robert Hanzl 971 Cisco Systems 972 Millenium Plaza Building, V Celnici 10, Prague 1, 973 Prague, Czech Republic 974 Email rhanzl@cisco.com 976 Ketan Talaulikar 977 Cisco Systems, Inc. 978 Email: ketant@cisco.com 980 15. References 982 15.1. Normative References 984 [I-D.ietf-6man-spring-srv6-oam] 985 Ali, Z., Filsfils, C., Matsushima, S., Voyer, D., and M. 986 Chen, "Operations, Administration, and Maintenance (OAM) 987 in Segment Routing Networks with IPv6 Data plane (SRv6)", 988 draft-ietf-6man-spring-srv6-oam-07 (work in progress), 989 July 2020. 991 [I-D.ietf-spring-srv6-network-programming] 992 Filsfils, C., Camarillo, P., Leddy, J., Voyer, D., 993 Matsushima, S., and Z. Li, "SRv6 Network Programming", 994 draft-ietf-spring-srv6-network-programming-24 (work in 995 progress), October 2020. 997 [ISO10589] 998 Standardization", I. ". O. F., "Intermediate system to 999 Intermediate system intra-domain routeing information 1000 exchange protocol for use in conjunction with the protocol 1001 for providing the connectionless-mode Network Service (ISO 1002 8473), ISO/IEC 10589:2002, Second Edition.", Nov 2002. 1004 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1005 Requirement Levels", BCP 14, RFC 2119, 1006 DOI 10.17487/RFC2119, March 1997, 1007 . 1009 [RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi 1010 Topology (MT) Routing in Intermediate System to 1011 Intermediate Systems (IS-ISs)", RFC 5120, 1012 DOI 10.17487/RFC5120, February 2008, 1013 . 1015 [RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic 1016 Authentication", RFC 5304, DOI 10.17487/RFC5304, October 1017 2008, . 1019 [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic 1020 Engineering", RFC 5305, DOI 10.17487/RFC5305, October 1021 2008, . 1023 [RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R., 1024 and M. Fanto, "IS-IS Generic Cryptographic 1025 Authentication", RFC 5310, DOI 10.17487/RFC5310, February 1026 2009, . 1028 [RFC7370] Ginsberg, L., "Updates to the IS-IS TLV Codepoints 1029 Registry", RFC 7370, DOI 10.17487/RFC7370, September 2014, 1030 . 1032 [RFC7794] Ginsberg, L., Ed., Decraene, B., Previdi, S., Xu, X., and 1033 U. Chunduri, "IS-IS Prefix Attributes for Extended IPv4 1034 and IPv6 Reachability", RFC 7794, DOI 10.17487/RFC7794, 1035 March 2016, . 1037 [RFC7981] Ginsberg, L., Previdi, S., and M. Chen, "IS-IS Extensions 1038 for Advertising Router Information", RFC 7981, 1039 DOI 10.17487/RFC7981, October 2016, 1040 . 1042 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 1043 Writing an IANA Considerations Section in RFCs", BCP 26, 1044 RFC 8126, DOI 10.17487/RFC8126, June 2017, 1045 . 1047 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 1048 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 1049 May 2017, . 1051 [RFC8491] Tantsura, J., Chunduri, U., Aldrin, S., and L. Ginsberg, 1052 "Signaling Maximum SID Depth (MSD) Using IS-IS", RFC 8491, 1053 DOI 10.17487/RFC8491, November 2018, 1054 . 1056 [RFC8667] Previdi, S., Ed., Ginsberg, L., Ed., Filsfils, C., 1057 Bashandy, A., Gredler, H., and B. Decraene, "IS-IS 1058 Extensions for Segment Routing", RFC 8667, 1059 DOI 10.17487/RFC8667, December 2019, 1060 . 1062 [RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J., 1063 Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header 1064 (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020, 1065 . 1067 15.2. Informative References 1069 [I-D.ietf-lsr-flex-algo] 1070 Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and 1071 A. Gulko, "IGP Flexible Algorithm", draft-ietf-lsr-flex- 1072 algo-12 (work in progress), October 2020. 1074 [RFC8355] Filsfils, C., Ed., Previdi, S., Ed., Decraene, B., and R. 1075 Shakir, "Resiliency Use Cases in Source Packet Routing in 1076 Networking (SPRING) Networks", RFC 8355, 1077 DOI 10.17487/RFC8355, March 2018, 1078 . 1080 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 1081 Decraene, B., Litkowski, S., and R. Shakir, "Segment 1082 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 1083 July 2018, . 1085 15.3. URIs 1087 [1] http://www.eantc.de/fileadmin/eantc/downloads/events/2017- 1088 2020/MPLS2019/Segment_Routing_IPv6__SRv6_.pdf 1090 Authors' Addresses 1092 Peter Psenak (editor) 1093 Cisco Systems 1094 Pribinova Street 10 1095 Bratislava 81109 1096 Slovakia 1098 Email: ppsenak@cisco.com 1100 Clarence Filsfils 1101 Cisco Systems 1102 Brussels 1103 Belgium 1105 Email: cfilsfil@cisco.com 1107 Ahmed Bashandy 1108 Individual 1110 Email: abashandy.ietf@gmail.com 1112 Bruno Decraene 1113 Orange 1114 Issy-les-Moulineaux 1115 France 1117 Email: bruno.decraene@orange.com 1119 Zhibo Hu 1120 Huawei Technologies 1122 Email: huzhibo@huawei.com