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Filsfils 4 Intended status: Standards Track Cisco Systems 5 Expires: September 4, 2020 A. Bashandy 6 Individual 7 B. Decraene 8 Orange 9 Z. Hu 10 Huawei Technologies 11 March 3, 2020 13 IS-IS Extension to Support Segment Routing over IPv6 Dataplane 14 draft-ietf-lsr-isis-srv6-extensions-06.txt 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 September 4, 2020. 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 . . . . . . . . . . . . . . . . . 9 79 7.2. SRv6 End SID sub-TLV . . . . . . . . . . . . . . . . . . 10 80 8. Advertising SRv6 Adjacency SIDs . . . . . . . . . . . . . . . 12 81 8.1. SRv6 End.X SID sub-TLV . . . . . . . . . . . . . . . . . 12 82 8.2. SRv6 LAN End.X SID sub-TLV . . . . . . . . . . . . . . . 14 83 9. SRv6 SID Structure Sub-Sub-TLV . . . . . . . . . . . . . . . 15 84 10. Advertising Endpoint Behaviors . . . . . . . . . . . . . . . 16 85 11. Implementation Status . . . . . . . . . . . . . . . . . . . . 17 86 11.1. Cisco . . . . . . . . . . . . . . . . . . . . . . . . . 17 87 11.2. Huawei . . . . . . . . . . . . . . . . . . . . . . . . . 17 88 11.3. Juniper . . . . . . . . . . . . . . . . . . . . . . . . 18 89 11.4. Interoperability Testing. . . . . . . . . . . . . . . . 18 90 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 91 12.1. SRv6 Locator TLV . . . . . . . . . . . . . . . . . . . . 18 92 12.1.1. SRv6 End SID sub-TLV . . . . . . . . . . . . . . . . 18 93 12.1.2. Revised sub-TLV table . . . . . . . . . . . . . . . 19 94 12.2. SRv6 Capabilities sub-TLV . . . . . . . . . . . . . . . 19 95 12.3. SRv6 End.X SID and SRv6 LAN End.X SID sub-TLVs . . . . . 19 96 12.4. MSD Types . . . . . . . . . . . . . . . . . . . . . . . 20 97 12.5. Sub-Sub-TLVs for SID Sub-TLVs . . . . . . . . . . . . . 20 98 12.6. Prefix Attribute Flags Sub-TLV . . . . . . . . . . . . . 20 99 13. Security Considerations . . . . . . . . . . . . . . . . . . . 21 100 14. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 21 101 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 22 102 15.1. Normative References . . . . . . . . . . . . . . . . . . 22 103 15.2. Informative References . . . . . . . . . . . . . . . . . 24 104 15.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 25 105 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 25 107 1. Introduction 109 With Segment Routing (SR) [I-D.ietf-spring-segment-routing], a node 110 steers a packet through an ordered list of instructions, called 111 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 117 [I-D.ietf-6man-segment-routing-header]. SRv6 refers to this SR 118 instantiation on the IPv6 dataplane. 120 The network programming paradigm 121 [I-D.ietf-spring-srv6-network-programming] is central to SRv6. It 122 describes how any behavior can be bound to a SID and how any network 123 program can be expressed as a combination of SIDs. 125 This document specifies IS-IS extensions that allow the IS-IS 126 protocol to encode some of these SIDs and their behaviors. 128 Familiarity with the network programming paradigm 129 [I-D.ietf-spring-srv6-network-programming] is necessary to understand 130 the extensions specified in this document. 132 This document defines one new top level IS-IS TLV and several new IS- 133 IS sub-TLVs. 135 The SRv6 Capabilities sub-TLV announces the ability to support SRv6. 137 Several new sub-TLVs are defined to advertise various SRv6 Maximum 138 SID Depths. 140 The new SRv6 Locator top level TLV announces SRv6 locators - a form 141 of summary address for the set of topology/algorithm specific SIDs 142 instantiated at the node. 144 The SRv6 End SID sub-TLV, the SRv6 End.X SID sub-TLV, and the SRv6 145 LAN End.X SID sub-TLV are used to advertise which SIDs are 146 instantiated at a node and what Endpoint behavior is bound to each 147 instantiated SID. 149 2. SRv6 Capabilities sub-TLV 151 A node indicates that it supports the SR Segment Endpoint Node 152 functionality as specified in [I-D.ietf-6man-segment-routing-header] 153 by advertising a new SRv6 Capabilities sub-TLV of the router 154 capabilities TLV [RFC7981]. 156 The SRv6 Capabilities sub-TLV may contain optional sub-sub-TLVs. No 157 sub-sub-TLVs are currently defined. 159 The SRv6 Capabilities sub-TLV has the following format: 161 0 1 2 3 162 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 1 163 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 164 | Type | Length | Flags | 165 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 166 | optional sub-sub-TLVs... 168 Type: Suggested value 25, to be assigned by IANA 170 Length: 2 + length of sub-sub-TLVs 172 Flags: 2 octets The following flags are defined: 174 0 1 175 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 176 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 177 | |O| | 178 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 180 where: 182 O-flag: If set, the router supports use of the O-bit 183 in the Segment Routing Header(SRH) as defined in 184 [I-D.ietf-6man-spring-srv6-oam]. 186 3. Advertising Supported Algorithms 188 SRv6 capable router indicates supported algorithm(s) by advertising 189 the SR Algorithm TLV as defined in [RFC8667]. 191 4. Advertising Maximum SRv6 SID Depths 193 [RFC8491] defines the means to advertise node/link specific values 194 for Maximum SID Depths (MSD) of various types. Node MSDs are 195 advertised in a sub-TLV of the Router Capabilities TLV [RFC7981]. 196 Link MSDs are advertised in a sub-TLV of TLVs 22, 23, 141, 222, and 197 223. 199 This document defines the relevant SRv6 MSDs and requests MSD type 200 assignments in the MSD Types registry created by [RFC8491]. 202 4.1. Maximum Segments Left MSD Type 204 The Maximum Segments Left MSD Type specifies the maximum value of the 205 "SL" field [I-D.ietf-6man-segment-routing-header] in the SRH of a 206 received packet before applying the Endpoint behavior associated with 207 a SID. 209 SRH Max SL Type: 41 (Suggested value - to be assigned by IANA) 211 If no value is advertised the supported value is assumed to be 0. 213 4.2. Maximum End Pop MSD Type 215 The Maximum End Pop MSD Type specifies the maximum number of SIDs in 216 the SRH to which the router can apply "PSP" or USP" behavior, as 217 defined in [I-D.ietf-spring-srv6-network-programming] flavors. 219 SRH Max End Pop Type: 42 (Suggested value - to be assigned by IANA) 221 If the advertised value is zero or no value is advertised 222 then it is assumed that the router cannot apply PSP or USP flavors. 224 4.3. Maximum H.Encaps MSD Type 226 The Maximum H.Encaps MSD Type specifies the maximum number of SIDs 227 that can be included as part of the "H.Encaps" behavior as defined in 228 [I-D.ietf-spring-srv6-network-programming] . 230 SRH Max H.encaps Type: 44 (Suggested value - to be assigned by IANA) 232 If the advertised value is zero then the router can apply H.Encaps 233 only by encapsulating the incoming packet in another 234 IPv6 header without SRH the same way IPinIP encapsulation is 235 performed. 237 If the advertised value is non-zero then the router supports both 238 IPinIP and SRH encapsulation subject to the SID limitation 239 specified by the advertised value. 241 4.4. Maximum End D MSD Type 243 The Maximum End D MSD Type specifies the maximum number of SIDs in an 244 SRH when performing decapsulation associated with "End.Dx" behaviors 245 (e.g., "End.DX6" and "End.DT6") as defined in 246 [I-D.ietf-spring-srv6-network-programming]. 248 SRH Max End D Type: 45 (Suggested value - to be assigned by IANA) 250 If the advertised value is zero or no value is advertised 251 then it is assumed that the router cannot apply 252 "End.DX6" or "End.DT6" behaviors if the outer IPv6 header contains an SRH. 254 5. SRv6 SIDs and Reachability 256 As discussed in [I-D.ietf-spring-srv6-network-programming], an SRv6 257 Segment Identifier (SID) is 128 bits and consists of Locator, 258 Function and Argument parts. 260 A node is provisioned with topology/algorithm specific locators for 261 each of the topology/algorithm pairs supported by that node. Each 262 locator is a covering prefix for all SIDs provisioned on that node 263 which have the matching topology/algorithm. 265 Locators MUST be advertised in the SRv6 Locator TLV (see 266 Section 6.1). Forwarding entries for the locators advertised in the 267 SRv6 Locator TLV MUST be installed in the forwarding plane of 268 receiving SRv6 capable routers when the associated topology/algorithm 269 is supported by the receiving node. 271 Locators are routable and MAY also be advertised in Prefix 272 Reachability TLVs (236 or 237). 274 Locators associated with Flexible Algorithms [I-D.ietf-lsr-flex-algo] 275 SHOULD NOT be advertised in Prefix Reachability TLVs (236 or 237). 277 Locators associated with algorithm 0 and 1 (for all supported 278 topologies) SHOULD be advertised in a Prefix Reachability TLV (236 or 279 237) so that legacy routers (i.e., routers which do NOT support SRv6) 280 will install a forwarding entry for algorithm 0 and 1 SRv6 traffic. 282 In cases where a locator advertisement is received in both a Prefix 283 Reachability TLV and an SRv6 Locator TLV, the Prefix Reachability 284 advertisement MUST be preferred when installing entries in the 285 forwarding plane. This is to prevent inconsistent forwarding entries 286 between SRv6 capable and SRv6 incapable routers. 288 SRv6 SIDs are advertised as sub-TLVs in the SRv6 Locator TLV except 289 for SRv6 End.X SIDs/LAN End.X SIDs which are associated with a 290 specific Neighbor/Link and are therefore advertised as sub-TLVs in 291 TLVs 22, 23, 222, 223, and 141. 293 SRv6 SIDs are not directly routable and MUST NOT be installed in the 294 forwarding plane. Reachability to SRv6 SIDs depends upon the 295 existence of a covering locator. 297 Adherence to the rules defined in this section will assure that SRv6 298 SIDs associated with a supported topology/algorithm pair will be 299 forwarded correctly, while SRv6 SIDs associated with an unsupported 300 topology/algorithm pair will be dropped. NOTE: The drop behavior 301 depends on the absence of a default/summary route covering a given 302 locator. 304 In order for forwarding to work correctly, the locator associated 305 with SRv6 SID advertisements MUST be the longest match prefix 306 installed in the forwarding plane for those SIDs. There are a number 307 of ways in which this requirement could be compromised. In order to 308 ensure correct forwarding, network operators should take steps to 309 make sure that this requirement is not compromised. 311 o Another locator associated with a different topology/algorithm is 312 the longest match 314 o A prefix advertisement (i.e., from TLV 236 or 237) is the longest 315 match 317 6. Advertising Anycast Property 319 Both prefixes and SRv6 Locators may be configured as anycast and as 320 such the same value can be advertised by multiple routers. It is 321 useful for other routers to know that the advertisement is for an 322 anycast identifier. 324 A new flag in "Bit Values for Prefix Attribute Flags Sub-TLV" 325 registry [RFC7794] is defined to advertise the anycast property: 327 Bit #: 4 (Suggested - to be assigned by IANA) 328 Name: Anycast Flag (A-flag) 330 When the prefix/SRv6 locator is configured as anycast, the A-flag 331 SHOULD be set. Otherwise, this flag MUST be clear. 333 The A-flag MUST be preserved when leaked between levels. 335 The A-flag and the N-flag MUST NOT both be set. 337 If both N-flag and A-flag are set in the prefix/SRv6 Locator 338 advertisement, the receiving routers MUST ignore the N-flag. 340 The same prefix/SRv6 Locator can be advertised by multiple routers. 341 If at least one of them sets the A-Flag in its advertisement, the 342 prefix/SRv6 Locator SHOULD be considered as anycast. 344 Locator that is advertised by a single node and without an A-Flag 345 SHOULD be interpreted as a node specific locator. 347 All the nodes advertising the same anycast locator MUST instantiate 348 the exact same set of SIDs under such anycast locator. Failure to do 349 so may result in traffic being black-holed or mis-routed. 351 The Prefix Attribute Flags Sub-TLV can be carried in the SRv6 Locator 352 TLV as well as the Prefix Reachability TLVs. When a router 353 originates both the Prefix Reachability TLV and the SRv6 Locator TLV 354 for a given prefix, and the router is originating the Prefix 355 Attribute Flags Sub-TLV in one of the TLVs, the router SHOULD 356 advertise identical versions of the Prefix Attribute Flags Sub-TLV in 357 both TLVs. 359 7. Advertising Locators and End SIDs 361 The SRv6 Locator TLV is introduced to advertise SRv6 Locators and End 362 SIDs associated with each locator. 364 This new TLV shares the sub-TLV space defined for TLVs 135, 235, 236 365 and 237. 367 7.1. SRv6 Locator TLV Format 369 The SRv6 Locator TLV has the following format: 371 0 1 2 3 372 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 1 373 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 374 | Type | Length |R|R|R|R| MTID | 375 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 377 Type: 27 (Suggested value to be assigned by IANA) 379 Length: variable. 381 MTID: Multitopology Identifier as defined in [RFC5120]. 382 Note that the value 0 is legal. 384 Followed by one or more locator entries of the form: 386 0 1 2 3 387 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 1 388 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 389 | Metric | 390 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 391 | Flags | Algorithm | 392 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 393 | Loc Size | Locator (variable)... 394 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 395 | Sub-tlv-len | Sub-TLVs (variable) . . . | 396 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 398 Metric: 4 octets. As described in [RFC5305]. 400 Flags: 1 octet. The following flags are defined 402 0 403 0 1 2 3 4 5 6 7 404 +-+-+-+-+-+-+-+-+ 405 |D| Reserved | 406 +-+-+-+-+-+-+-+-+ 408 where: 409 D bit: When the Locator is leaked from level-2 to level-1, the D 410 bit MUST be set. Otherwise, this bit MUST be clear. Locators 411 with the D bit set MUST NOT be leaked from level-1 to level-2. 412 This is to prevent looping. 414 The remaining bits are reserved for future use. They SHOULD be 415 set to zero on transmission and MUST be ignored on receipt. 417 Algorithm: 1 octet. Associated algorithm. Algorithm values 418 are defined in the IGP Algorithm Type registry. 420 Loc-Size: 1 octet. Number of bits in the SRv6 Locator field. 421 (1 - 128) 423 Locator: 1-16 octets. This field encodes the advertised SRv6 424 Locator. The Locator is encoded in the minimal number of 425 octets for the given number of bits. Trailing bits MUST be set 426 to zero and ignored when received. 428 Sub-TLV-length: 1 octet. Number of octets used by sub-TLVs 430 Optional sub-TLVs. 432 7.2. SRv6 End SID sub-TLV 434 The SRv6 End SID sub-TLV is introduced to advertise SRv6 Segment 435 Identifiers (SID) with Endpoint behaviors which do not require a 436 particular neighbor in order to be correctly applied 437 [I-D.ietf-spring-srv6-network-programming]. SRv6 SIDs associated 438 with a neighbor are advertised using the sub-TLVs defined in 439 Section 6. 441 This new sub-TLV is advertised in the SRv6 Locator TLV defined in the 442 previous section. SRv6 End SIDs inherit the topology/algorithm from 443 the parent locator. 445 The SRv6 End SID sub-TLV has the following format: 447 0 1 2 3 448 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 1 449 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 450 | Type | Length | 451 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 452 | Flags | Endpoint Behavior | 453 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 454 | SID (128 bits) . . . | 455 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 456 | SID (cont . . .) | 457 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 458 | SID (cont . . .) | 459 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 460 | SID (cont . . .) | 461 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 462 |Sub-sub-tlv-len| sub-sub-TLVs (variable) . . . | 463 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 465 Type: 5 (Suggested value to be assigned by IANA) 467 Length: variable. 469 Flags: 1 octet. No flags are currently defined. 471 Endpoint Behavior: 2 octets, as defined in [I-D.ietf-spring-srv6-network-programming]. 472 Legal behavior values for this sub-TLV are defined in Section 9 of this document. 474 SID: 16 octets. This field encodes the advertised SRv6 SID. 476 Sub-sub-TLV-length: 1 octet. Number of octets used by sub-sub-TLVs 478 Optional sub-sub-TLVs 480 The SRv6 End SID MUST be a subnet of the associated Locator. SRv6 481 End SIDs which are NOT a subnet of the associated locator MUST be 482 ignored. 484 Multiple SRv6 End SIDs MAY be associated with the same locator. In 485 cases where the number of SRv6 End SID sub-TLVs exceeds the capacity 486 of a single TLV, multiple Locator TLVs for the same locator MAY be 487 advertised. For a given MTID/Locator the algorithm MUST be the same 488 in all TLVs. If this restriction is not met all TLVs for that MTID/ 489 Locator MUST be ignored. 491 8. Advertising SRv6 Adjacency SIDs 493 Certain SRv6 Endpoint behaviors 494 [I-D.ietf-spring-srv6-network-programming] must be associated with a 495 particular neighbor, and in case of multiple links to the same 496 neighbor, with a particular link in order to be correctly applied. 498 This document defines two new sub-TLVs of TLV 22, 23, 222, 223, and 499 141 - namely "SRv6 End.X SID" and "SRv6 LAN End.X SID". 501 IS-IS Neighbor advertisements are topology specific - but not 502 algorithm specific. End.X SIDs therefore inherit the topology from 503 the associated neighbor advertisement, but the algorithm is specified 504 in the individual SID. 506 All End.X SIDs MUST be a subnet of a Locator with matching topology 507 and algorithm which is advertised by the same node in an SRv6 Locator 508 TLV. End.X SIDs which do not meet this requirement MUST be ignored. 510 All End.X and LAN End.X SIDs MUST be subsumed by the subnet of a 511 Locator with the matching algorithm which is advertised by the same 512 node in an SRv6 Locator TLV. End.X SIDs which do not meet this 513 requirement MUST be ignored. This ensures that the node advertising 514 the End.X or LAN End.X SID is also advertising its corresponding 515 Locator with the algorithm that will be used for computing paths 516 destined to the SID. 518 8.1. SRv6 End.X SID sub-TLV 520 This sub-TLV is used to advertise an SRv6 SID associated with a point 521 to point adjacency. Multiple SRv6 End.X SID sub-TLVs MAY be 522 associated with the same adjacency. 524 The SRv6 End.X SID sub-TLV has the following format: 526 0 1 2 3 527 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 1 528 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 529 | Type | Length | 530 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 531 | Flags | Algorithm | Weight | 532 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 533 | Endpoint Behavior | 534 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 535 | SID (128 bits) . . . | 536 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 537 | SID (cont . . .) | 538 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 539 | SID (cont . . .) | 540 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 541 | SID (cont . . .) | 542 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 543 |Sub-sub-tlv-len| Sub-sub-TLVs (variable) . . . | 544 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 546 Type: 43 (Suggested value to be assigned by IANA) 548 Length: variable. 550 Flags: 1 octet. 552 0 1 2 3 4 5 6 7 553 +-+-+-+-+-+-+-+-+ 554 |B|S|P|Reserved | 555 +-+-+-+-+-+-+-+-+ 557 where: 559 B-Flag: Backup flag. If set, the End.X SID is eligible 560 for protection (e.g., using IPFRR) as described in [RFC8355]. 562 S-Flag. Set flag. When set, the S-Flag indicates that the 563 End.X SID refers to a set of adjacencies (and therefore 564 MAY be assigned to other adjacencies as well). 566 P-Flag. Persistent flag. When set, the P-Flag indicates that 567 the End.X SID is persistently allocated, i.e., the 568 End.X SID value remains consistent across router restart 569 and/or interface flap. 571 Other bits: MUST be zero when originated and ignored when 572 received. 574 Algorithm: 1 octet. Associated algorithm. Algorithm values 575 are defined in the IGP Algorithm Type registry. 577 Weight: 1 octet. The value represents the weight of the 578 End.X SID for the purpose of load balancing. The use 579 of the weight is defined in [I-D.ietf-spring-segment-routing]. 581 Endpoint Behavior: 2 octets. As defined in 582 [I-D.ietf-spring-srv6-network-programming] 583 Legal behavior values for this sub-TLV are defined in Section 9. 585 SID: 16 octets. This field encodes the advertised SRv6 SID. 587 Sub-sub-TLV-length: 1 octet. Number of octets used by sub-sub- 588 TLVs 590 Note that multiple TLVs for the same neighbor may be required in 591 order to advertise all of the SRv6 End.X SIDs associated with that 592 neighbor. 594 8.2. SRv6 LAN End.X SID sub-TLV 596 This sub-TLV is used to advertise an SRv6 SID associated with a LAN 597 adjacency. Since the parent TLV is advertising an adjacency to the 598 Designated Intermediate System(DIS) for the LAN, it is necessary to 599 include the System ID of the physical neighbor on the LAN with which 600 the SRv6 SID is associated. Given that a large number of neighbors 601 may exist on a given LAN a large number of SRv6 LAN END.X SID sub- 602 TLVs may be associated with the same LAN. Note that multiple TLVs 603 for the same DIS neighbor may be required in order to advertise all 604 of the SRv6 End.X SIDs associated with that neighbor. 606 The SRv6 LAN End.X SID sub-TLV has the following format: 608 0 1 2 3 609 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 1 610 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 611 | Type | Length | System ID (6 octets) | 612 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 613 | | 614 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 615 | Flags | Algorithm | Weight | 616 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 617 | Endpoint Behavior | 618 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 619 | SID (128 bits) . . . | 620 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 621 | SID (cont . . .) | 622 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 623 | SID (cont . . .) | 624 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 625 | SID (cont . . .) | 626 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 627 |Sub-sub-tlv-len| sub-sub-TLVs (variable) . . . | 628 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 630 Type: 44 (Suggested value to be assigned by IANA) 631 Length: variable. 633 System-ID: 6 octets of IS-IS System-ID of length "ID Length" as 634 defined in [ISO10589]. 636 Flags: 1 octet. 638 0 1 2 3 4 5 6 7 639 +-+-+-+-+-+-+-+-+ 640 |B|S|P|Reserved | 641 +-+-+-+-+-+-+-+-+ 643 where B,S, and P flags are as described in Section 8.1. 644 Other bits: MUST be zero when originated and ignored when 645 received. 647 Algorithm: 1 octet. Associated algorithm. Algorithm values 648 are defined in the IGP Algorithm Type registry. 650 Weight: 1 octet. The value represents the weight of the 651 End.X SID for the purpose of load balancing. The use 652 of the weight is defined in [I-D.ietf-spring-segment-routing]. 654 Endpoint Behavior: 2 octets. As defined in 655 [I-D.ietf-spring-srv6-network-programming] 656 Legal behavior values for this sub-TLV are defined in Section 9. 658 SID: 16 octets. This field encodes the advertised SRv6 SID. 660 Sub-sub-TLV-length: 1 octet. Number of octets used by sub-sub- 661 TLVs. 663 9. SRv6 SID Structure Sub-Sub-TLV 665 SRv6 SID Structure Sub-Sub-TLV is an optional Sub-Sub-TLV of: 667 SRv6 End SID Sub-TLV (Section 7.2) 669 SRv6 End.X SID Sub-TLV (Section 8.1) 671 SRv6 LAN End.X SID Sub-TLV (Section 8.2) 673 SRv6 SID Structure Sub-Sub-TLV is used to advertise the length of 674 each individual part of the SRv6 SID as defined in 675 [I-D.ietf-spring-srv6-network-programming]. It has the following 676 format: 678 0 1 2 3 679 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 1 680 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 681 | Type | Length | 682 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 683 | LB Length | LN Length | Fun. Length | Arg. Length | 684 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 686 where: 688 Type: 1 690 Length: 4 octets. 692 LB Length: 1 octet. SRv6 SID Locator Block length in bits. 694 LN Length: 1 octet. SRv6 SID Locator Node length in bits. 696 Fun. Length: 1 octet. SRv6 SID Function length in bits. 698 Arg. Length: 1 octet. SRv6 SID Arguments length in bits. 700 ISIS SRv6 SID Structure Sub-Sub-TLV MUST NOT appear more than once in 701 its parent Sub-TLV. If it appears more than once in its parent Sub- 702 TLV, the parent Sub-TLV MUST be ignored by the receiver. 704 The sum of all four sizes advertised in ISIS SRv6 SID Structure Sub- 705 Sub-TLV must be lower or equal to 128 bits. If the sum of all four 706 sizes advertised in the ISIS SRv6 SID Structure Sub-Sub-TLV is larger 707 than 128 bits, the parent Sub-TLV MUST be ignored by the receiver. 709 10. Advertising Endpoint Behaviors 711 Endpoint behaviors are defined in 712 [I-D.ietf-spring-srv6-network-programming] and 713 [I-D.ietf-6man-spring-srv6-oam]. The codepoints for the Endpoint 714 behaviors are defined in the "SRv6 Endpoint Behaviors" registry 715 defined in [I-D.ietf-spring-srv6-network-programming]. This section 716 lists the Endpoint behaviors and their codepoints, which MAY be 717 advertised by IS-IS and the SID sub-TLVs in which each type MAY 718 appear. 720 Endpoint |Endpoint | End | End.X | Lan End.X | 721 Behavior |Behavior Codepoint | SID | SID | SID | 722 -----------------------|--------------------|-------|-------|-----------| 723 End (PSP, USP, USD) | 1-4, 28-31 | Y | N | N | 724 -----------------------|--------------------|-------|-------|-----------| 725 End.X (PSP, USP, USD) | 5-8, 32-35 | N | Y | Y | 726 -----------------------|--------------------|-------|-------|-----------| 727 End.T (PSP, USP, USD) | 9-12, 36-39 | Y | N | N | 728 -----------------------|--------------------|-------|-------|-----------| 729 End.DX6 | 16 | N | Y | Y | 730 -----------------------|--------------------|-------|-------|-----------| 731 End.DX4 | 17 | N | Y | Y | 732 -----------------------|--------------------|-------|-------|-----------| 733 End.DT6 | 18 | Y | N | N | 734 -----------------------|--------------------|-------|-------|-----------| 735 End.DT4 | 19 | Y | N | N | 736 -----------------------|--------------------|-------|-------|-----------| 737 End.DT64 | 20 | Y | N | N | 738 -----------------------|--------------------|-------|-------|-----------| 739 End.OP | 40 | Y | N | N | 740 -----------------------|--------------------|-------|-------|-----------| 741 End.OTP | 41 | Y | N | N | 743 11. Implementation Status 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 765 Intra/Inter area/level support: Yes 767 Anycast SID support: Yes, no A-flag support (Section 6) 769 SID Structure Sub-Sub-TLV: No 771 11.3. Juniper 773 Juniper's ISIS SRv6 implementation supports following 774 functionalities: 776 Types of SID supported: End, End.X, LAN End.X 778 Intra/Inter area/level support: Yes 780 Anycast SID support: Yes, no A-flag support (Section 6) 782 SID Structure Sub-Sub-TLV: No 784 11.4. Interoperability Testing. 786 EANTC interoperability testing has been performed in April 2019. 787 Results can be found at EANTC site [1]. 789 12. IANA Considerations 791 This document requests allocation for the following TLVs, sub- TLVs, 792 and sub-sub-TLVs as well updating the ISIS TLV registry and defining 793 a new registry. 795 12.1. SRv6 Locator TLV 797 This document adds one new TLV to the IS-IS TLV Codepoints registry. 799 Value: 27 (suggested - to be assigned by IANA) 801 Name: SRv6 Locator 803 This TLV shares sub-TLV space with existing "Sub-TLVs for TLVs 135, 804 235, 236 and 237 registry". The name of this registry needs to be 805 changed to "Sub-TLVs for TLVs 27, 135, 235, 236 and 237 registry". 807 12.1.1. SRv6 End SID sub-TLV 809 This document adds the following new sub-TLV to the (renamed) "Sub- 810 TLVs for TLVs 27, 135, 235, 236 and 237 registry". 812 Value: 5 (suggested - to be assigned by IANA) 813 Name: SRv6 End SID 815 12.1.2. Revised sub-TLV table 817 The revised table of sub-TLVs for the (renamed) "Sub-TLVs for TLVs 818 27, 135, 235, 236 and 237 registry" is shown below: 820 Type 27 135 235 236 237 822 1 n y y y y 823 2 n y y y y 824 3 n y y y y 825 4 y y y y y 826 5 y n n n n 827 11 y y y y y 828 12 y y y y y 830 12.2. SRv6 Capabilities sub-TLV 832 This document adds the definition of a new sub-TLV in the "Sub- TLVs 833 for TLV 242 registry". 835 Type: 25 (Suggested - to be assigned by IANA) 837 Description: SRv6 Capabilities 839 This document requests the creation of a new IANA managed registry 840 for sub-sub-TLVs of the SRv6 Capability sub-TLV. The registration 841 procedure is "Expert Review" as defined in [RFC7370]. Suggested 842 registry name is "sub-sub-TLVs for SRv6 Capability sub-TLV". No sub- 843 sub-TLVs are defined by this document except for the reserved value. 845 0: Reserved 847 1-255: Unassigned 849 12.3. SRv6 End.X SID and SRv6 LAN End.X SID sub-TLVs 851 This document adds the definition of two new sub-TLVs in the "sub- 852 TLVs for TLV 22, 23, 25, 141, 222 and 223 registry". 854 Type: 43 (suggested - to be assigned by IANA) 856 Description: SRv6 End.X SID 858 Type: 44 (suggested - to be assigned by IANA) 860 Description: SRv6 LAN End.X SID 861 Type 22 23 25 141 222 223 863 43 y y y y y y 864 44 y y y y y y 866 12.4. MSD Types 868 This document defines the following new MSD types. These types are 869 to be defined in the IGP MSD Types registry defined in [RFC8491] . 871 All values are suggested values to be assigned by IANA. 873 Type Description 874 ------------------ 875 41 SRH Max SL 876 42 SRH Max End Pop 877 44 SRH Max H.encaps 878 45 SRH Max End D 880 12.5. Sub-Sub-TLVs for SID Sub-TLVs 882 This document creates the following Sub-Sub-TLV Registry within the 883 "IS-IS TLV Codepoints" registry: 885 Registry: Sub-Sub-TLVs for SID Sub-TLVs 887 Registration Procedure: Expert review 889 Reference: This document (Section 7.2, Section 8.1, Section 8.2). 891 This document defines the following Sub-Sub-TLV in the "Sub-Sub-TLVs 892 for SID Sub-TLVs" registry: 894 Type: 1 896 Description: SRv6 SID Structure Sub-Sub-TLV. 898 Reference: This document (Section 9). 900 12.6. Prefix Attribute Flags Sub-TLV 902 This document adds a new bit in the "Bit Values for Prefix Attribute 903 Flags Sub-TLV" registry: 905 Bit #: 4 907 Description: A bit 908 Reference: This document (Section 6). 910 13. Security Considerations 912 Security concerns for IS-IS are addressed in [ISO10589], [RFC5304], 913 and [RFC5310]. 915 14. Contributors 917 The following people gave a substantial contribution to the content 918 of this document and should be considered as co-authors: 920 Stefano Previdi 921 Huawei Technologies 922 Email: stefano@previdi.net 924 Paul Wells 925 Cisco Systems 926 Saint Paul, 927 Minnesota 928 United States 929 Email: pauwells@cisco.com 931 Daniel Voyer 932 Email: daniel.voyer@bell.ca 934 Satoru Matsushima 935 Email: satoru.matsushima@g.softbank.co.jp 937 Bart Peirens 938 Email: bart.peirens@proximus.com 940 Hani Elmalky 941 Email: hani.elmalky@ericsson.com 943 Prem Jonnalagadda 944 Email: prem@barefootnetworks.com 946 Milad Sharif 947 Email: msharif@barefootnetworks.com> 949 Robert Hanzl 950 Cisco Systems 951 Millenium Plaza Building, V Celnici 10, Prague 1, 952 Prague, Czech Republic 953 Email rhanzl@cisco.com 955 Ketan Talaulikar 956 Cisco Systems, Inc. 957 Email: ketant@cisco.com 959 15. References 961 15.1. Normative References 963 [I-D.ietf-6man-segment-routing-header] 964 Filsfils, C., Dukes, D., Previdi, S., Leddy, J., 965 Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header 966 (SRH)", draft-ietf-6man-segment-routing-header-26 (work in 967 progress), October 2019. 969 [I-D.ietf-6man-spring-srv6-oam] 970 Ali, Z., Filsfils, C., Matsushima, S., Voyer, D., and M. 971 Chen, "Operations, Administration, and Maintenance (OAM) 972 in Segment Routing Networks with IPv6 Data plane (SRv6)", 973 draft-ietf-6man-spring-srv6-oam-03 (work in progress), 974 December 2019. 976 [I-D.ietf-spring-srv6-network-programming] 977 Filsfils, C., Camarillo, P., Leddy, J., Voyer, D., 978 Matsushima, S., and Z. Li, "SRv6 Network Programming", 979 draft-ietf-spring-srv6-network-programming-11 (work in 980 progress), March 2020. 982 [ISO10589] 983 Standardization", I. ". O. F., "Intermediate system to 984 Intermediate system intra-domain routeing information 985 exchange protocol for use in conjunction with the protocol 986 for providing the connectionless-mode Network Service (ISO 987 8473), ISO/IEC 10589:2002, Second Edition.", Nov 2002. 989 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 990 Requirement Levels", BCP 14, RFC 2119, 991 DOI 10.17487/RFC2119, March 1997, 992 . 994 [RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi 995 Topology (MT) Routing in Intermediate System to 996 Intermediate Systems (IS-ISs)", RFC 5120, 997 DOI 10.17487/RFC5120, February 2008, 998 . 1000 [RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic 1001 Authentication", RFC 5304, DOI 10.17487/RFC5304, October 1002 2008, . 1004 [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic 1005 Engineering", RFC 5305, DOI 10.17487/RFC5305, October 1006 2008, . 1008 [RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R., 1009 and M. Fanto, "IS-IS Generic Cryptographic 1010 Authentication", RFC 5310, DOI 10.17487/RFC5310, February 1011 2009, . 1013 [RFC7370] Ginsberg, L., "Updates to the IS-IS TLV Codepoints 1014 Registry", RFC 7370, DOI 10.17487/RFC7370, September 2014, 1015 . 1017 [RFC7794] Ginsberg, L., Ed., Decraene, B., Previdi, S., Xu, X., and 1018 U. Chunduri, "IS-IS Prefix Attributes for Extended IPv4 1019 and IPv6 Reachability", RFC 7794, DOI 10.17487/RFC7794, 1020 March 2016, . 1022 [RFC7981] Ginsberg, L., Previdi, S., and M. Chen, "IS-IS Extensions 1023 for Advertising Router Information", RFC 7981, 1024 DOI 10.17487/RFC7981, October 2016, 1025 . 1027 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 1028 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 1029 May 2017, . 1031 [RFC8491] Tantsura, J., Chunduri, U., Aldrin, S., and L. Ginsberg, 1032 "Signaling Maximum SID Depth (MSD) Using IS-IS", RFC 8491, 1033 DOI 10.17487/RFC8491, November 2018, 1034 . 1036 [RFC8667] Previdi, S., Ed., Ginsberg, L., Ed., Filsfils, C., 1037 Bashandy, A., Gredler, H., and B. Decraene, "IS-IS 1038 Extensions for Segment Routing", RFC 8667, 1039 DOI 10.17487/RFC8667, December 2019, 1040 . 1042 15.2. Informative References 1044 [I-D.ietf-lsr-flex-algo] 1045 Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and 1046 A. Gulko, "IGP Flexible Algorithm", draft-ietf-lsr-flex- 1047 algo-06 (work in progress), February 2020. 1049 [I-D.ietf-spring-segment-routing] 1050 Filsfils, C., Previdi, S., Ginsberg, L., Decraene, B., 1051 Litkowski, S., and R. Shakir, "Segment Routing 1052 Architecture", draft-ietf-spring-segment-routing-15 (work 1053 in progress), January 2018. 1055 [RFC8355] Filsfils, C., Ed., Previdi, S., Ed., Decraene, B., and R. 1056 Shakir, "Resiliency Use Cases in Source Packet Routing in 1057 Networking (SPRING) Networks", RFC 8355, 1058 DOI 10.17487/RFC8355, March 2018, 1059 . 1061 15.3. URIs 1063 [1] http://www.eantc.de/fileadmin/eantc/downloads/events/2017- 1064 2020/MPLS2019/Segment_Routing_IPv6__SRv6_.pdf 1066 Authors' Addresses 1068 Peter Psenak (editor) 1069 Cisco Systems 1070 Pribinova Street 10 1071 Bratislava 81109 1072 Slovakia 1074 Email: ppsenak@cisco.com 1076 Clarence Filsfils 1077 Cisco Systems 1078 Brussels 1079 Belgium 1081 Email: cfilsfil@cisco.com 1083 Ahmed Bashandy 1084 Individual 1086 Email: abashandy.ietf@gmail.com 1088 Bruno Decraene 1089 Orange 1090 Issy-les-Moulineaux 1091 France 1093 Email: bruno.decraene@orange.com 1095 Zhibo Hu 1096 Huawei Technologies 1098 Email: huzhibo@huawei.com