idnits 2.17.1 draft-ietf-lsr-isis-srv6-extensions-18.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 are 3 instances of too long lines in the document, the longest one being 14 characters 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 (October 20, 2021) is 919 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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-13) exists of draft-ietf-6man-spring-srv6-oam-11 == Outdated reference: A later version (-26) exists of draft-ietf-lsr-flex-algo-17 -- Possible downref: Non-RFC (?)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: April 23, 2022 Individual 7 B. Decraene 8 Orange 9 Z. Hu 10 Huawei Technologies 11 October 20, 2021 13 IS-IS Extensions to Support Segment Routing over IPv6 Dataplane 14 draft-ietf-lsr-isis-srv6-extensions-18 16 Abstract 18 The Segment Routing (SR) architecture allows flexible definition of 19 the end-to-end path by encoding it as a sequence of topological 20 elements called "segments". It can be implemented over the MPLS or 21 the IPv6 data plane. This document describes the IS-IS extensions 22 required to support Segment Routing over the IPv6 data plane. 24 This document updates RFC 7370 by modifying an existing registry. 26 Requirements Language 28 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 29 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 30 "OPTIONAL" in this document are to be interpreted as described in BCP 31 14 [RFC2119] [RFC8174] when, and only when, they appear in all 32 capitals, as shown here. 34 Status of This Memo 36 This Internet-Draft is submitted in full conformance with the 37 provisions of BCP 78 and BCP 79. 39 Internet-Drafts are working documents of the Internet Engineering 40 Task Force (IETF). Note that other groups may also distribute 41 working documents as Internet-Drafts. The list of current Internet- 42 Drafts is at https://datatracker.ietf.org/drafts/current/. 44 Internet-Drafts are draft documents valid for a maximum of six months 45 and may be updated, replaced, or obsoleted by other documents at any 46 time. It is inappropriate to use Internet-Drafts as reference 47 material or to cite them other than as "work in progress." 48 This Internet-Draft will expire on April 23, 2022. 50 Copyright Notice 52 Copyright (c) 2021 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 . . . . . . . . . . . . . . 5 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 . . . . . . . . . . . . . . . . 8 77 7. Advertising Locators and End SIDs . . . . . . . . . . . . . . 9 78 7.1. SRv6 Locator TLV Format . . . . . . . . . . . . . . . . . 9 79 7.2. SRv6 End SID sub-TLV . . . . . . . . . . . . . . . . . . 11 80 8. Advertising SRv6 Adjacency SIDs . . . . . . . . . . . . . . . 12 81 8.1. SRv6 End.X SID sub-TLV . . . . . . . . . . . . . . . . . 13 82 8.2. SRv6 LAN End.X SID sub-TLV . . . . . . . . . . . . . . . 14 83 9. SRv6 SID Structure Sub-Sub-TLV . . . . . . . . . . . . . . . 16 84 10. Advertising Endpoint Behaviors . . . . . . . . . . . . . . . 17 85 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 86 11.1. SRv6 Locator TLV . . . . . . . . . . . . . . . . . . . . 18 87 11.1.1. SRv6 End SID sub-TLV . . . . . . . . . . . . . . . . 18 88 11.1.2. Revised sub-TLV table . . . . . . . . . . . . . . . 19 89 11.2. SRv6 Capabilities sub-TLV . . . . . . . . . . . . . . . 19 90 11.3. Sub-Sub-TLVs of the SRv6 Capability sub-TLV . . . . . . 20 91 11.4. SRv6 End.X SID and SRv6 LAN End.X SID sub-TLVs . . . . . 20 92 11.5. MSD Types . . . . . . . . . . . . . . . . . . . . . . . 20 93 11.6. Sub-Sub-TLVs for SID Sub-TLVs . . . . . . . . . . . . . 21 94 11.7. Prefix Attribute Flags Sub-TLV . . . . . . . . . . . . . 21 95 11.8. ISIS SRv6 Capabilities sub-TLV Flags Registry . . . . . 21 96 11.9. ISIS SRv6 Locator TLV Flags Registry . . . . . . . . . . 22 97 11.10. ISIS SRv6 End SID sub-TLV Flags Registry . . . . . . . . 22 98 11.11. ISIS SRv6 End.X SID and LAN End.X SID sub-TLVs Flags 99 Registry . . . . . . . . . . . . . . . . . . . . . . . . 23 100 12. Security Considerations . . . . . . . . . . . . . . . . . . . 23 101 13. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 24 102 14. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 25 103 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 26 104 15.1. Normative References . . . . . . . . . . . . . . . . . . 26 105 15.2. Informative References . . . . . . . . . . . . . . . . . 28 106 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 28 108 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 [RFC8986] is central to SRv6. It 120 describes how any behavior can be bound to a SID and how any network 121 program can be expressed as a combination of SIDs. 123 This document specifies IS-IS extensions that allow the IS-IS 124 protocol to encode some of these SIDs and their behaviors. 126 Familiarity with the network programming paradigm [RFC8986] is 127 necessary to understand the extensions specified in this document. 129 The new SRv6 Locator top level TLV announces SRv6 locators - a form 130 of summary address for the set of topology/algorithm-specific SIDs 131 instantiated at the node. 133 The SRv6 Capabilities sub-TLV announces the ability to support SRv6. 135 Several new sub-TLVs are defined to advertise various SRv6 Maximum 136 SID Depths. 138 The SRv6 End SID sub-TLV, the SRv6 End.X SID sub-TLV, and the SRv6 139 LAN End.X SID sub-TLV are used to advertise which SIDs are 140 instantiated at a node and what Endpoint behavior is bound to each 141 instantiated SID. 143 This document updates [RFC7370] by modifying an existing registry 144 (Section 11.1.2). 146 2. SRv6 Capabilities sub-TLV 148 A node indicates that it supports the SR Segment Endpoint Node 149 functionality as specified in [RFC8754] by advertising a new SRv6 150 Capabilities sub-TLV of the router capabilities TLV [RFC7981]. 152 The SRv6 Capabilities sub-TLV may contain optional sub-sub-TLVs. No 153 sub-sub-TLVs are currently defined. 155 The SRv6 Capabilities sub-TLV has the following format: 157 0 1 2 3 158 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 1 159 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 160 | Type | Length | Flags | 161 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 162 | optional sub-sub-TLVs... 164 Type: 25. Single octet as defined in section 9 of [ISO10589]. 166 Length: Single octet as defined in section 9 of [ISO10589]. The length value is 167 2 + length of sub-sub-TLVs. 169 Flags: 2 octets The following flags are defined: 171 0 1 172 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 173 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 174 | |O| Reserved | 175 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 177 where: 179 O-flag: If set, the router supports use of the O-bit 180 in the Segment Routing Header (SRH) as defined in 181 [I-D.ietf-6man-spring-srv6-oam]. 183 The remaining bits, including bit 0, are reserved for future use. They MUST be 184 set to zero on transmission and MUST be ignored on receipt. 186 3. Advertising Supported Algorithms 188 An SRv6 capable router indicates supported algorithm(s) by 189 advertising the Segment Routing Algorithm sub-TLV as defined in 190 [RFC8667]. 192 4. Advertising Maximum SRv6 SID Depths 194 [RFC8491] defines the means to advertise node/link specific values 195 for Maximum SID Depths (MSD) of various types. Node MSDs are 196 advertised in a sub-TLV of the Router Capabilities TLV [RFC7981]. 197 Link MSDs are advertised in a sub-TLV of TLVs 22, 23, 25, 141, 222, 198 and 223. 200 This document defines the relevant SRv6 MSDs and requests MSD type 201 assignments in the MSD Types registry created by [RFC8491]. 203 4.1. Maximum Segments Left MSD Type 205 The Maximum Segments Left MSD Type signals the maximum value of the 206 "Segments Left" field [RFC8754] in the SRH of a received packet 207 before applying the Endpoint behavior associated with a SID. 209 SRH Max Segments Left Type: 41 211 If no value is advertised, the supported value is 0. 213 4.2. Maximum End Pop MSD Type 215 The Maximum End Pop MSD Type signals the maximum number of SIDs in 216 the SRH to which the router can apply "Penultimate Segment Pop of the 217 SRH" or "Ultimate Segment Pop of the SRH" behavior, as defined in 218 [RFC8986] flavors. 220 SRH Max End Pop Type: 42 222 If the advertised value is zero or no value is advertised, 223 then the router cannot apply PSP or USP flavors. 225 4.3. Maximum H.Encaps MSD Type 227 The Maximum H.Encaps MSD Type signals the maximum number of SIDs that 228 can be added to the Segment List of an SRH as part of the "H.Encaps" 229 behavior as defined in [RFC8986]. 231 SRH Max H.encaps Type: 44 233 If the advertised value is zero or no value is advertised, then the 234 headend can apply an SR Policy that only contains one segment, without 235 inserting any SRH header. 237 A non-zero SRH Max H.encaps MSD indicates that the headend can insert 238 an SRH up to the advertised number of SIDs. 240 4.4. Maximum End D MSD Type 242 The Maximum End D MSD Type specifies the maximum number of SIDs 243 present in an SRH when performing decapsulation. As specified in 244 [RFC8986] the permitted SID types include, but are not limited to 245 End.DX6, End.DT4, End.DT46, End with USD, End.X with USD. 247 SRH Max End D Type: 45 249 If the advertised value is zero or no value is advertised 250 then the router cannot apply any behavior that results in 251 decapsulation and forwarding of the inner packet if the 252 outer IPv6 header contains an SRH. 254 5. SRv6 SIDs and Reachability 256 As discussed in [RFC8986], an SRv6 Segment Identifier (SID) is 128 257 bits and consists of Locator, Function and Argument parts. 259 A node is provisioned with topology/algorithm specific locators for 260 each of the topology/algorithm pairs supported by that node. Each 261 locator is a covering prefix for all SIDs provisioned on that node 262 which have the matching topology/algorithm. 264 Locators MUST be advertised in the SRv6 Locator TLV (see 265 Section 7.1). Forwarding entries for the locators advertised in the 266 SRv6 Locator TLV MUST be installed in the forwarding plane of 267 receiving SRv6 capable routers when the associated topology/algorithm 268 is supported by the receiving node. The processing of the prefix 269 advertised in the SRv6 Locator TLV, the calculation of its 270 reachability and the installation in the forwarding plane follows the 271 process defined for the Prefix Reachability TLV 236 [RFC5308], or TLV 272 237 [RFC5120]. 274 Locators associated with algorithm 0 and 1 (for all supported 275 topologies) SHOULD be advertised in a Prefix Reachability TLV (236 or 276 237) so that legacy routers (i.e., routers which do not support SRv6) 277 will install a forwarding entry for algorithm 0 and 1 SRv6 traffic. 279 In cases where the same prefix, with the same prefix-length, Multi 280 Topology ID (MT ID), and algorithm 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. Such preference of 285 Prefix Reachability advertisement does not have any impact on the 286 rest of the data advertised in the SRv6 Locator TLV. 288 Locators associated with Flexible Algorithms (see Section 4 of 289 [I-D.ietf-lsr-flex-algo]) SHOULD NOT be advertised in Prefix 290 Reachability TLVs (236 or 237). Advertising the Flexible Algorithm 291 locator in regular Prefix Reachability TLV (236 or 237) would make 292 the forwarding for it to follow algo 0 path. 294 SRv6 SIDs are advertised as sub-TLVs in the SRv6 Locator TLV except 295 for SRv6 SIDs which are associated with a specific Neighbor/Link and 296 are therefore advertised as sub-TLVs in TLVs 22, 23, 25, 141, 222, 297 and 223. 299 SRv6 SIDs received from other nodes are not directly routable and 300 MUST NOT be installed in the forwarding plane. Reachability to SRv6 301 SIDs depends upon the existence of a covering locator. 303 Adherence to the rules defined in this section will assure that SRv6 304 SIDs associated with a supported topology/algorithm pair will be 305 forwarded correctly, while SRv6 SIDs associated with an unsupported 306 topology/algorithm pair will be dropped. NOTE: The drop behavior 307 depends on the absence of a default/summary route covering a given 308 locator. 310 In order for forwarding to work correctly, the locator associated 311 with SRv6 SID advertisements must be the longest match prefix 312 installed in the forwarding plane for those SIDs. In order to ensure 313 correct forwarding, network operators should take steps to make sure 314 that this requirement is not compromised. For example, the following 315 situations should be avoided: 317 o Another locator associated with a different topology/algorithm is 318 the longest match 320 o Another prefix advertisement (i.e., from TLV 236 or 237) is the 321 longest match 323 6. Advertising Anycast Property 325 Both prefixes and SRv6 Locators may be configured as anycast and as 326 such the same value can be advertised by multiple routers. It is 327 useful for other routers to know that the advertisement is for an 328 anycast identifier. 330 A new flag in Prefix Attribute Flags Sub-TLV [RFC7794] is defined to 331 advertise the anycast property: 333 Bit #: 4 334 Name: Anycast Flag (A-flag) 336 When the prefix/SRv6 locator is configured as anycast, the A-flag 337 SHOULD be set. Otherwise, this flag MUST be clear. 339 The A-flag MUST be preserved when the advertisement is leaked between 340 levels. 342 The A-flag and the N-flag MUST NOT both be set. If both N-flag and 343 A-flag are set in the prefix/SRv6 Locator advertisement, the 344 receiving routers MUST ignore the N-flag. 346 The same prefix/SRv6 Locator can be advertised by multiple routers. 347 If at least one of them sets the A-Flag in its advertisement, the 348 prefix/SRv6 Locator SHOULD be considered as anycast. 350 A prefix/SRv6 Locator that is advertised by a single node and without 351 an A-Flag is considered node specific. 353 All the nodes advertising the same anycast locator MUST instantiate 354 the exact same set of SIDs under that anycast locator. Failure to do 355 so may result in traffic being black-holed or mis-routed. 357 The Prefix Attribute Flags Sub-TLV can be carried in the SRv6 Locator 358 TLV as well as the Prefix Reachability TLVs. When a router 359 originates both the Prefix Reachability TLV and the SRv6 Locator TLV 360 for a given prefix, and the router is originating the Prefix 361 Attribute Flags Sub-TLV in one of the TLVs, the router SHOULD 362 advertise the same flags in the Prefix Attribute Flags Sub-TLV in 363 both TLVs. However, unlike TLVs 236 [RFC5308] and 237 [RFC5120] the 364 X-flag in the Prefix Attributes Flags sub-TLV is valid when sent in 365 the SRv6 Locator TLV. The state of the X-flag in the Prefix 366 Attributes Flags sub-TLV when included in the Locator TLV MUST match 367 the setting of the embedded "X-bit" in any advertisement for the same 368 prefix in TLVs 236 [RFC5308] and 237 [RFC5120]. In case of any 369 inconsistency between the Prefix Attribute Flags advertised in the 370 Locator TLV and in the Prefix Reachability TLV, the ones advertised 371 in Prefix Reachability TLV MUST be preferred. 373 7. Advertising Locators and End SIDs 375 The SRv6 Locator TLV is introduced to advertise SRv6 Locators and End 376 SIDs associated with each locator. 378 This new TLV shares the sub-TLV space defined for TLVs 135, 235, 236 379 and 237. 381 7.1. SRv6 Locator TLV Format 383 The SRv6 Locator TLV has the following format: 385 0 1 2 3 386 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 1 387 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 388 | Type | Length |R|R|R|R| MT ID | 389 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 390 | Locator Entries . . . | 392 Type: 27. Single octet as defined in section 9 of [ISO10589]. 394 Length: Single octet as defined in section 9 of [ISO10589]. The 395 length value is variable. 397 R bits: reserved for future use. They MUST be set to zero on 398 transmission and MUST be ignored on receipt. 400 MT ID: Multitopology Identifier as defined in [RFC5120]. Note 401 that the value 0 is legal. 403 Followed by one or more locator entries of the form: 405 0 1 2 3 406 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 1 407 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 408 | Metric | 409 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 410 | Flags | Algorithm | Loc Size | 411 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 413 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 414 // Locator (continued, variable) // 415 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 416 | Sub-TLV-len | Sub-TLVs (variable) . . . | 417 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 418 Metric: 4 octets. As described in Section 4 of [RFC5305]. 420 Flags: 1 octet. The following flags are defined: 422 0 423 0 1 2 3 4 5 6 7 424 +-+-+-+-+-+-+-+-+ 425 |D| Reserved | 426 +-+-+-+-+-+-+-+-+ 428 D-flag: Same as described in section 4.1. of [RFC5305]. 430 The remaining bits are reserved for future use. They MUST be 431 set to zero on transmission and MUST be ignored on receipt. 433 Algorithm: 1 octet. As defined in IGP Algorithm Types registry 434 [RFC8665]. 436 Loc-Size: 1 octet. Number of bits in the SRv6 Locator field. 437 MUST be from the range (1 - 128). The TLV MUST be ignored if the 438 Loc-Size is outside this range. 440 Locator: 1-16 octets. This field encodes the advertised SRv6 441 Locator. The Locator is encoded in the minimal number of octets 442 for the given number of bits. Trailing bits MUST be set to zero 443 and ignored when received. 445 Sub-TLV-length: 1 octet. Number of octets used by sub-TLVs. 447 Optional sub-TLVs: Supported sub-TLVs are specified in 448 Section 11.1.2. Any Sub-TLV that is not allowed in the SRv6 449 Locator TLV MUST be ignored. 451 Prefix Attribute Flags Sub-TLV [RFC7794] SHOULD be included in the 452 Locator TLV. 454 Prefix Attribute Flags Sub-TLV MUST be included in the the Locator 455 TLV when it is leaked upwards in the hierarchy or originated as a 456 result of the redistribution from another protocol or another ISIS 457 instance. If the Prefix Attribute Flags Sub-TLV is not included in 458 these cases, receivers will be unable to determine the correct source 459 of the advertisement. The receivers will be unable to detect the 460 violation. 462 7.2. SRv6 End SID sub-TLV 464 The SRv6 End SID sub-TLV is introduced to advertise SRv6 Segment 465 Identifiers (SID) with Endpoint behaviors which do not require a 466 particular neighbor in order to be correctly applied. SRv6 SIDs 467 associated with a neighbor are advertised using the sub-TLVs defined 468 in Section 8. 470 Supported behavior values, together with parent TLVs in which they 471 are advertised, are specified in Section 10 of this document. Please 472 note that not all behaviors defined in [RFC8986] are defined in this 473 document, e.g. END.T is not. 475 This new sub-TLV is advertised in the SRv6 Locator TLV defined in the 476 previous section. SRv6 End SIDs inherit the topology/algorithm from 477 the parent locator. 479 The SRv6 End SID sub-TLV has the following format: 481 0 1 2 3 482 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 1 483 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 484 | Type | Length | Flags | 485 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 487 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 488 | Endpoint Behavior | 489 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 490 | SID (128 bits) . . . | 491 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 492 | SID (cont . . .) | 493 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 494 | SID (cont . . .) | 495 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 496 | SID (cont . . .) | 497 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 498 |Sub-sub-TLV-len| Sub-sub-TLVs (variable) . . . | 499 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 501 Type: 5. Single octet as defined in section 9 of [ISO10589]. 503 Length: Single octet as defined in section 9 of [ISO10589]. The 504 length value is variable. 506 Flags: 1 octet. No flags are currently defined. All bits are 507 reserved for future use. They MUST be set to zero on transmission 508 and MUST be ignored on receipt. 510 Endpoint Behavior: 2 octets, as defined in [RFC8986]. Supported 511 behavior values for this sub-TLV are defined in Section 10 of this 512 document. Unsupported or unrecognized behavior values are ignored 513 by the receiver. 515 SID: 16 octets. This field encodes the advertised SRv6 SID. 517 Sub-sub-TLV-length: 1 octet. Number of octets used by sub-sub- 518 TLVs. 520 Optional Sub-sub-TLVs: Supported Sub-sub-TLVs are specified in 521 Section 11.6. Any Sub-sub-TLV that is not allowed in SRv6 End SID 522 sub-TLV MUST be ignored. 524 The SRv6 End SID MUST be allocated from its associated locator. SRv6 525 End SIDs that are not allocated from the associated locator MUST be 526 ignored. 528 Multiple SRv6 End SIDs MAY be associated with the same locator. In 529 cases where the number of SRv6 End SID sub-TLVs exceeds the capacity 530 of a single TLV, multiple Locator TLVs for the same locator MAY be 531 advertised. For a given MTID/Locator the algorithm MUST be the same 532 in all TLVs. If this restriction is not met all TLVs for that MTID/ 533 Locator MUST be ignored. 535 8. Advertising SRv6 Adjacency SIDs 537 Certain SRv6 Endpoint behaviors [RFC8986] are associated with a 538 particular adjacency. 540 This document defines two new sub-TLVs of TLV 22, 23, 25, 141, 222, 541 and 223 - namely "SRv6 End.X SID sub-TLVs" and "SRv6 LAN End.X SID 542 sub-TLVs". 544 IS-IS Neighbor advertisements are topology specific - but not 545 algorithm specific. SIDs advertised in SRv6 End.X SID and SRv6 LAN 546 End.X SID sub-TLVs therefore inherit the topology from the associated 547 neighbor advertisement, but the algorithm is specified in the 548 individual SID. 550 All SIDs advertised in SRv6 End.X SID and SRv6 LAN End.X SID sub-TLVs 551 MUST be a subnet of a Locator with matching topology and algorithm 552 which is advertised by the same node in an SRv6 Locator TLV. SIDs 553 that do not meet this requirement MUST be ignored. This ensures that 554 the node advertising these SIDs is also advertising its corresponding 555 Locator with the algorithm that will be used for computing paths 556 destined to the SID. 558 8.1. SRv6 End.X SID sub-TLV 560 This sub-TLV is used to advertise an SRv6 SID associated with a point 561 to point adjacency. Multiple SRv6 End.X SID sub-TLVs MAY be 562 associated with the same adjacency. 564 The SRv6 End.X SID sub-TLV has the following format: 566 0 1 2 3 567 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 1 568 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 569 | Type | Length | Flags | Algorithm | 570 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 571 | Weight | Endpoint Behavior | 572 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 574 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 575 | SID (128 bits) . . . | 576 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 577 | SID (cont . . .) | 578 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 579 | SID (cont . . .) | 580 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 581 | SID (cont . . .) | 582 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 583 |Sub-sub-tlv-len| Sub-sub-TLVs (variable) . . . | 584 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 586 Type: 43. Single octet as defined in section 9 of [ISO10589]. 588 Length: Single octet as defined in section 9 of [ISO10589]. The 589 length value is variable. 591 Flags: 1 octet. 593 0 1 2 3 4 5 6 7 594 +-+-+-+-+-+-+-+-+ 595 |B|S|P|Reserved | 596 +-+-+-+-+-+-+-+-+ 598 where: 600 B-Flag: Backup flag. If set, the SID is eligible for 601 protection, e.g., using IP Fast Re-route (IPFRR) [RFC5286], as 602 described in [RFC8355]. 604 S-Flag. Set flag. When set, the S-Flag indicates that the SID 605 refers to a set of adjacencies (and therefore MAY be assigned 606 to other adjacencies as well). 608 P-Flag. Persistent flag. When set, the P-Flag indicates that 609 the SID is persistently allocated, i.e., the SID value remains 610 consistent across router restart and/or interface flap. 612 Reserved bits: MUST be zero when originated and MUST be ignored 613 when received. 615 Algorithm: 1 octet. As defined in IGP Algorithm Types registry 616 [RFC8665]. 618 Weight: 1 octet. The value represents the weight of the SID for 619 the purpose of load balancing. The use of the weight is defined 620 in [RFC8402]. 622 Endpoint Behavior: 2 octets. As defined in [RFC8986]. Supported 623 behavior values for this sub-TLV are defined in Section 10 of this 624 document. Unsupported or unrecognized behavior values are ignored 625 by the receiver. 627 SID: 16 octets. This field encodes the advertised SRv6 SID. 629 Sub-sub-TLV-length: 1 octet. Number of octets used by sub-sub- 630 TLVs. 632 Optional Sub-sub-TLVs: Supported Sub-sub-TLVs are specified in 633 Section 11.6. Any Sub-sub-TLV that is not allowed in SRv6 End.X 634 SID sub-TLV MUST be ignored. 636 Note that multiple TLVs for the same neighbor may be required in 637 order to advertise all the SRv6 SIDs associated with that neighbor. 639 8.2. SRv6 LAN End.X SID sub-TLV 641 This sub-TLV is used to advertise an SRv6 SID associated with a LAN 642 adjacency. Since the parent TLV is advertising an adjacency to the 643 Designated Intermediate System (DIS) for the LAN, it is necessary to 644 include the System ID of the physical neighbor on the LAN with which 645 the SRv6 SID is associated. Given that many neighbors may exist on a 646 given LAN, multiple SRv6 LAN END.X SID sub-TLVs may be associated 647 with the same LAN. Note that multiple TLVs for the same DIS neighbor 648 may be required in order to advertise all the SRv6 SIDs associated 649 with that neighbor. 651 The SRv6 LAN End.X SID sub-TLV has the following format: 653 0 1 2 3 654 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 1 655 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 656 | Type | Length | | 657 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 658 | Neighbor System-ID (ID length octets) | 659 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 660 | Flags | Algorithm | Weight | 661 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 663 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 664 | Endpoint Behavior | 665 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 666 | SID (128 bits) . . . | 667 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 668 | SID (cont . . .) | 669 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 670 | SID (cont . . .) | 671 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 672 | SID (cont . . .) | 673 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 674 |Sub-sub-TLV-len| sub-sub-TLVs (variable) . . . | 675 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 677 Type: 44. Single octet as defined in section 9 of [ISO10589]. 679 Length: Single octet as defined in section 9 of [ISO10589]. The 680 length value is variable. 682 Neighbor System-ID: IS-IS System-ID of length "ID Length" as 683 defined in [ISO10589]. 685 Flags: 1 octet. 687 0 1 2 3 4 5 6 7 688 +-+-+-+-+-+-+-+-+ 689 |B|S|P|Reserved | 690 +-+-+-+-+-+-+-+-+ 692 where B,S, and P flags are as described in Section 8.1. 693 Reserved bits MUST be zero when originated and MUST be ignored 694 when received. 696 Algorithm: 1 octet. As defined in IGP Algorithm Types registry 697 [RFC8665]. 699 Weight: 1 octet. The value represents the weight of the SID for 700 the purpose of load balancing. The use of the weight is defined 701 in [RFC8402]. 703 Endpoint Behavior: 2 octets. As defined in [RFC8986]. Supported 704 behavior values for this sub-TLV are defined in Section 10 of this 705 document. Unsupported or unrecognized behavior values are ignored 706 by the receiver. 708 SID: 16 octets. This field encodes the advertised SRv6 SID. 710 Sub-sub-TLV-length: 1 octet. Number of octets used by sub-sub- 711 TLVs. 713 Optional Sub-sub-TLVs: Supported Sub-sub-TLVs are specified in 714 Section 11.6. Any Sub-sub-TLV that is not allowed in SRv6 LAN 715 End.X SID sub-TLV MUST be ignored. 717 Note that multiple TLVs for the same neighbor, on the same LAN, may 718 be required in order to advertise all the SRv6 SIDs associated with 719 that neighbor. 721 9. SRv6 SID Structure Sub-Sub-TLV 723 SRv6 SID Structure Sub-Sub-TLV is an optional Sub-Sub-TLV of: 725 SRv6 End SID Sub-TLV (Section 7.2) 727 SRv6 End.X SID Sub-TLV (Section 8.1) 729 SRv6 LAN End.X SID Sub-TLV (Section 8.2) 731 SRv6 SID Structure Sub-Sub-TLV is used to advertise the structure of 732 the SRv6 SID as defined in [RFC8986]. It has the following format: 734 0 1 2 3 735 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 1 736 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 737 | Type | Length | 738 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 739 | LB Length | LN Length | Fun. Length | Arg. Length | 740 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 742 where: 744 Type: 1. Single octet as defined in section 9 of [ISO10589]. 746 Length: Single octet as defined in section 9 of [ISO10589]. The 747 length value is 4 octets. 749 LB Length: 1 octet. SRv6 SID Locator Block length in bits. 751 LN Length: 1 octet. SRv6 SID Locator Node length in bits. 753 Fun. Length: 1 octet. SRv6 SID Function length in bits. 755 Arg. Length: 1 octet. SRv6 SID Arguments length in bits. 757 ISIS SRv6 SID Structure Sub-Sub-TLV MUST NOT appear more than once in 758 its parent Sub-TLV. If it appears more than once in its parent Sub- 759 TLV, the parent Sub-TLV MUST be ignored by the receiver. 761 The sum of all four sizes advertised in ISIS SRv6 SID Structure Sub- 762 Sub-TLV MUST be less than or equal to 128 bits. If the sum of all 763 four sizes advertised in the ISIS SRv6 SID Structure Sub-Sub-TLV is 764 larger than 128 bits, the parent Sub-TLV MUST be ignored by the 765 receiver. 767 The SRv6 SID Structure Sub-Sub-TLV is intended for informational use 768 by the control and management planes. It MUST NOT be used at a 769 transit node (as defined in [RFC8754]) for forwarding packets. As an 770 example, this information could be used for: 772 o validation of SRv6 SIDs being instantiated in the network and 773 advertised via ISIS. These can be learnt by controllers via BGP- 774 LS and then be monitored for conformance to the SRv6 SID 775 allocation scheme chosen by the operator as described in 776 Section 3.2 of [RFC8986]. 778 o verification and the automation for securing the SRv6 domain by 779 provisioning filtering rules at SR domain boundaries as described 780 in Section 5 of [RFC8754]. 782 The details of these potential applications are outside the scope of 783 this document. 785 10. Advertising Endpoint Behaviors 787 Endpoint behaviors are defined in [RFC8986]. The codepoints for the 788 Endpoint behaviors are defined in the "SRv6 Endpoint Behaviors" 789 registry defined in [RFC8986]. If a behavior is advertised it MUST 790 only be advertised in the TLV[s] marked with "Y" in the table below, 791 and MUST NOT be advertised in the TLV[s] marked with "N" in the table 792 below. 794 Endpoint |Endpoint | End | End.X | Lan End.X | 795 Behavior |Behavior Codepoint| SID | SID | SID | 796 ----------------------|------------------|-----|-------|-----------| 797 End (PSP, USP, USD)| 1-4, 28-31 | Y | N | N | 798 ----------------------|------------------|-----|-------|-----------| 799 End.X (PSP, USP, USD)| 5-8, 32-35 | N | Y | Y | 800 ----------------------|------------------|-----|-------|-----------| 801 End.DX6 | 16 | N | Y | Y | 802 ----------------------|------------------|-----|-------|-----------| 803 End.DX4 | 17 | N | Y | Y | 804 ----------------------|------------------|-----|-------|-----------| 805 End.DT6 | 18 | Y | N | N | 806 ----------------------|------------------|-----|-------|-----------| 807 End.DT4 | 19 | Y | N | N | 808 ----------------------|------------------|-----|-------|-----------| 809 End.DT46 | 20 | Y | N | N | 811 11. IANA Considerations 813 This document requests allocation for the following TLVs, sub-TLVs, 814 and sub-sub-TLVs as well as updating the ISIS TLV registry and 815 defining new registries. 817 11.1. SRv6 Locator TLV 819 This document makes the following registrations in the IS-IS TLV 820 Codepoints registry. 822 Type Description IIH LSP SNP Purge 823 ---- --------------------- --- --- --- ----- 824 27 SRv6 Locator TLV n y n n 826 11.1.1. SRv6 End SID sub-TLV 828 The SRv6 Locator TLV shares sub-TLV space with TLVs 135, 235, 236 and 829 237. This document updates the "Sub-TLVs for TLVs 135, 235, 236, and 830 237 (Extended IP reachability, MT IP. Reach, IPv6 IP. Reach, and MT 831 IPv6 IP. Reach TLVs)" registry defined in [RFC7370]. IANA is 832 requested to update the name of the "Sub-TLVs for TLVs 135, 235, 236, 833 and 237 (Extended IP reachability, MT IP. Reach, IPv6 IP. Reach, 834 and MT IPv6 IP. Reach TLVs)" registry to "Sub-TLVs for TLVs 27, 135, 835 235, 236, and 237 (SRv6 Locator, Extended IP reachability, MT IP. 836 Reach, IPv6 IP. Reach, and MT IPv6 IP. Reach TLVs)". 838 IANA is asked to add this document as a reference to (renamed) "Sub- 839 TLVs for TLVs 27, 135, 235, 236, and 237 (SRv6 Locator, Extended IP 840 reachability, MT IP. Reach, IPv6 IP. Reach, and MT IPv6 IP. Reach 841 TLVs)" registry. 843 This document makes the following registrations in the (renamed) 844 "Sub-TLVs for TLVs 27, 135, 235, 236, and 237 (SRv6 Locator, Extended 845 IP reachability, MT IP. Reach, IPv6 IP. Reach, and MT IPv6 IP. 846 Reach TLVs)" registry: 848 Type: 5 850 Description: SRv6 End SID sub-TLV. 852 Reference: This document (Section 7.2). 854 11.1.2. Revised sub-TLV table 856 The revised table of sub-TLVs for the (renamed) "Sub-TLVs for TLVs 857 27, 135, 235, 236, and 237 (SRv6 Locator, Extended IP reachability, 858 MT IP. Reach, IPv6 IP. Reach, and MT IPv6 IP. Reach TLVs)" 859 registry is shown below: 861 Type 27 135 235 236 237 863 1 y y y y y 864 2 y y y y y 865 3 n y y y y 866 4 y y y y y 867 5 y n n n n 868 6 n y y y y 869 11 y y y y y 870 12 y y y y y 871 32 n y y y y 873 11.2. SRv6 Capabilities sub-TLV 875 This document makes the following registrations in the "Sub-TLVs for 876 TLV 242 (IS-IS Router CAPABILITY TLV)": 878 Type: 25 880 Description: SRv6 Capabilities sub-TLV. 882 Reference: This document (Section 2). 884 11.3. Sub-Sub-TLVs of the SRv6 Capability sub-TLV 886 This document requests a new IANA registry be created under the IS-IS 887 TLV Codepoints Registry to control the assignment of sub-TLV types 888 for the SRv6 Capability sub-TLV specified in this document - 889 Section 2. The suggested name of the new registry is "sub-sub-TLVs 890 of the SRv6 Capability sub-TLV". The registration procedure is 891 "Expert Review" as defined in [RFC8126]. Guidance for the Designated 892 Experts is provided in the [RFC7370]. No sub-sub-TLVs are defined by 893 this document except for the reserved type 0. 895 Type Description Encoding 896 Reference 897 --------------------------------------------------------- 898 0 Reserved 899 1-255 Unassigned 901 11.4. SRv6 End.X SID and SRv6 LAN End.X SID sub-TLVs 903 This document makes the following registrations in the "Sub-TLVs for 904 TLVs 22, 23, 25, 141, 222, and 223 (Extended IS reachability, IS 905 Neighbor Attribute, L2 Bundle Member Attributes, inter-AS 906 reachability information, MT-ISN, and MT IS Neighbor Attribute TLVs)" 907 registry: 909 Type: 43 911 Description: SRv6 End.X SID sub-TLV. 913 Reference: This document (Section 8.1). 915 Type: 44 917 Description: SRv6 LAN End.X SID sub-TLV. 919 Reference: This document (Section 8.2). 921 Type 22 23 25 141 222 223 923 43 y y y y y y 924 44 y y y y y y 926 11.5. MSD Types 928 This document makes the following registrations in the IGP MSD-Types 929 registry: 931 Value Name Reference 932 ------------------ 933 41 SRH Max SL [This Document] 934 42 SRH Max End Pop [This Document] 935 44 SRH Max H.encaps [This Document] 936 45 SRH Max End D [This Document] 938 11.6. Sub-Sub-TLVs for SID Sub-TLVs 940 This document requests a new IANA registry be created under the IS-IS 941 TLV Codepoints Registry to control the assignment of sub-TLV types 942 for the SID Sub-TLVs specified in this document - Section 7.2, 943 Section 8.1, Section 8.2. The suggested name of the new registry is 944 "sub-sub-TLVs for SRv6 End SID and SRv6 End.X SID". The registration 945 procedure is "Expert Review" as defined in [RFC8126]. Guidance for 946 the Designated Experts is provided in [RFC7370]. The following 947 assignments are made by this document: 949 Type Description Encoding 950 Reference 951 --------------------------------------------------------- 952 0 Reserved 953 1 SRv6 SID Structure Sub-Sub-TLV [This Document] 954 2-255 Unassigned 956 Type 5 43 44 958 1 y y y 960 11.7. Prefix Attribute Flags Sub-TLV 962 This document adds a new bit in the "Bit Values for Prefix Attribute 963 Flags Sub-TLV" registry: 965 Bit #: 4 967 Description: Anycast Flag (A-flag) 969 Reference: This document (Section 6). 971 11.8. ISIS SRv6 Capabilities sub-TLV Flags Registry 973 This document requests a new IANA registry be created under the IS-IS 974 TLV Codepoints Registry to control the assignment of bits 0 to 15 in 975 the Flags field of the ISIS SRv6 Capabilities sub-TLV specified in 976 this document (Section 2). The suggested name of the new registry is 977 "ISIS SRv6 Capabilities sub-TLV Flags". The registration procedure 978 is "Expert Review" as defined in [RFC8126]. Guidance for the 979 Designated Experts is provided in [RFC7370]. The following 980 assignments are made by this document: 982 Bit #: 1 984 Description: O-flag 986 Reference: This document (Section 2). 988 Bit #: 0, 2-7 990 Description: Unassigned 992 11.9. ISIS SRv6 Locator TLV Flags Registry 994 This document requests a new IANA registry be created under the IS-IS 995 TLV Codepoints Registry to control the assignment of bits 0 to 7 in 996 the Flags field of the ISIS SRv6 Locator TLV specified in this 997 document (Section 7.1). The suggested name of the new registry is 998 "ISIS SRv6 Locator TLV Flags". The registration procedure is "Expert 999 Review" as defined in [RFC8126]. Guidance for the Designated Experts 1000 is provided in [RFC7370]. The following assignments are made by this 1001 document: 1003 Bit #: 0 1005 Description: D-flag 1007 Reference: This document (Section 7.1). 1009 Bit #: 1-7 1011 Description: Unassigned 1013 11.10. ISIS SRv6 End SID sub-TLV Flags Registry 1015 This document requests a new IANA registry be created under the IS-IS 1016 TLV Codepoints Registry to control the assignment of bits 0 to 7 in 1017 the Flags field of the ISIS SRv6 End SID sub-TLV specified in this 1018 document (Section 7.2). The suggested name of the new registry is 1019 "ISIS SRv6 End SID sub-TLV Flags". The registration procedure is 1020 "Expert Review" as defined in [RFC8126]. Guidance for the Designated 1021 Experts is provided in [RFC7370]. No assignments are made by this 1022 document. 1024 Bit #: 0-7 1025 Description: Unassigned 1027 11.11. ISIS SRv6 End.X SID and LAN End.X SID sub-TLVs Flags Registry 1029 This document requests a new IANA registry be created under the IS-IS 1030 TLV Codepoints Registry to control the assignment of bits 0 to 7 in 1031 the Flags field of the ISIS SRv6 End.X SID and LAN End.X SID sub-TLVs 1032 (Section 8.1 and Section 8.2). The suggested name of the new 1033 registry is "ISIS SRv6 End.X SID and LAN End.X SID sub-TLVs Flags". 1034 The registration procedure is "Expert Review" as defined in 1035 [RFC8126]. Guidance for the Designated Experts is provided in 1036 [RFC7370]. The following assignments are made by this document: 1038 Bit #: 0 1040 Description: B-flag 1042 Reference: This document (Section 8.1). 1044 Bit #: 1 1046 Description: S-flag 1048 Reference: This document (Section 8.1). 1050 Bit #: 2 1052 Description: P-flag 1054 Reference: This document (Section 8.1). 1056 Bit #: 3-7 1058 Description: Unassigned 1060 12. Security Considerations 1062 Security concerns for IS-IS are addressed in [ISO10589], [RFC5304], 1063 and [RFC5310]. While IS-IS is deployed under a single administrative 1064 domain, there can be deployments where potential attackers have 1065 access to one or more networks in the IS-IS routing domain. In these 1066 deployments, the stronger authentication mechanisms defined in the 1067 aforementioned documents SHOULD be used. 1069 This document describes the IS-IS extensions required to support 1070 Segment Routing over an IPv6 data plane. The security considerations 1071 for Segment Routing are discussed in [RFC8402]. [RFC8986] defines 1072 the SRv6 Network Programming concept and specifies the main Segment 1073 Routing behaviors to enable the creation of interoperable overlays; 1074 the security considerations from that document apply too. 1076 The advertisement for an incorrect MSD value may have negative 1077 consequences, see [RFC8491] for additional considerations. 1079 Security concerns associated with the setting of the O-flag are 1080 described in [I-D.ietf-6man-spring-srv6-oam]. 1082 Security concerns associated with the usage of Flex-Algorithms are 1083 described in [I-D.ietf-lsr-flex-algo]). 1085 13. Contributors 1087 The following people gave a substantial contribution to the content 1088 of this document and should be considered as co-authors: 1090 Stefano Previdi 1091 Huawei Technologies 1092 Email: stefano@previdi.net 1094 Paul Wells 1095 Cisco Systems 1096 Saint Paul, 1097 Minnesota 1098 United States 1099 Email: pauwells@cisco.com 1101 Daniel Voyer 1102 Email: daniel.voyer@bell.ca 1104 Satoru Matsushima 1105 Email: satoru.matsushima@g.softbank.co.jp 1107 Bart Peirens 1108 Email: bart.peirens@proximus.com 1110 Hani Elmalky 1111 Email: hani.elmalky@ericsson.com 1113 Prem Jonnalagadda 1114 Email: prem@barefootnetworks.com 1116 Milad Sharif 1117 Email: msharif@barefootnetworks.com> 1119 Robert Hanzl 1120 Cisco Systems 1121 Millenium Plaza Building, V Celnici 10, Prague 1, 1122 Prague, Czech Republic 1123 Email rhanzl@cisco.com 1125 Ketan Talaulikar 1126 Cisco Systems, Inc. 1127 Email: ketant@cisco.com 1129 14. Acknowledgments 1131 Thanks to Christian Hopps for his review comments and shepherd work. 1133 Thanks to Alvaro Retana and John Scudder for AD review and comments. 1135 15. References 1137 15.1. Normative References 1139 [I-D.ietf-6man-spring-srv6-oam] 1140 Ali, Z., Filsfils, C., Matsushima, S., Voyer, D., and M. 1141 Chen, "Operations, Administration, and Maintenance (OAM) 1142 in Segment Routing Networks with IPv6 Data plane (SRv6)", 1143 draft-ietf-6man-spring-srv6-oam-11 (work in progress), 1144 June 2021. 1146 [I-D.ietf-lsr-flex-algo] 1147 Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and 1148 A. Gulko, "IGP Flexible Algorithm", draft-ietf-lsr-flex- 1149 algo-17 (work in progress), July 2021. 1151 [ISO10589] 1152 International Organization for Standardization, 1153 "Intermediate system to Intermediate system intra-domain 1154 routeing information exchange protocol for use in 1155 conjunction with the protocol for providing the 1156 connectionless-mode Network Service (ISO 8473)", Nov 2002. 1158 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1159 Requirement Levels", BCP 14, RFC 2119, 1160 DOI 10.17487/RFC2119, March 1997, 1161 . 1163 [RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi 1164 Topology (MT) Routing in Intermediate System to 1165 Intermediate Systems (IS-ISs)", RFC 5120, 1166 DOI 10.17487/RFC5120, February 2008, 1167 . 1169 [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic 1170 Engineering", RFC 5305, DOI 10.17487/RFC5305, October 1171 2008, . 1173 [RFC5308] Hopps, C., "Routing IPv6 with IS-IS", RFC 5308, 1174 DOI 10.17487/RFC5308, October 2008, 1175 . 1177 [RFC7370] Ginsberg, L., "Updates to the IS-IS TLV Codepoints 1178 Registry", RFC 7370, DOI 10.17487/RFC7370, September 2014, 1179 . 1181 [RFC7794] Ginsberg, L., Ed., Decraene, B., Previdi, S., Xu, X., and 1182 U. Chunduri, "IS-IS Prefix Attributes for Extended IPv4 1183 and IPv6 Reachability", RFC 7794, DOI 10.17487/RFC7794, 1184 March 2016, . 1186 [RFC7981] Ginsberg, L., Previdi, S., and M. Chen, "IS-IS Extensions 1187 for Advertising Router Information", RFC 7981, 1188 DOI 10.17487/RFC7981, October 2016, 1189 . 1191 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 1192 Writing an IANA Considerations Section in RFCs", BCP 26, 1193 RFC 8126, DOI 10.17487/RFC8126, June 2017, 1194 . 1196 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 1197 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 1198 May 2017, . 1200 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 1201 Decraene, B., Litkowski, S., and R. Shakir, "Segment 1202 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 1203 July 2018, . 1205 [RFC8491] Tantsura, J., Chunduri, U., Aldrin, S., and L. Ginsberg, 1206 "Signaling Maximum SID Depth (MSD) Using IS-IS", RFC 8491, 1207 DOI 10.17487/RFC8491, November 2018, 1208 . 1210 [RFC8665] Psenak, P., Ed., Previdi, S., Ed., Filsfils, C., Gredler, 1211 H., Shakir, R., Henderickx, W., and J. Tantsura, "OSPF 1212 Extensions for Segment Routing", RFC 8665, 1213 DOI 10.17487/RFC8665, December 2019, 1214 . 1216 [RFC8667] Previdi, S., Ed., Ginsberg, L., Ed., Filsfils, C., 1217 Bashandy, A., Gredler, H., and B. Decraene, "IS-IS 1218 Extensions for Segment Routing", RFC 8667, 1219 DOI 10.17487/RFC8667, December 2019, 1220 . 1222 [RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J., 1223 Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header 1224 (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020, 1225 . 1227 [RFC8986] Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer, 1228 D., Matsushima, S., and Z. Li, "Segment Routing over IPv6 1229 (SRv6) Network Programming", RFC 8986, 1230 DOI 10.17487/RFC8986, February 2021, 1231 . 1233 15.2. Informative References 1235 [RFC5286] Atlas, A., Ed. and A. Zinin, Ed., "Basic Specification for 1236 IP Fast Reroute: Loop-Free Alternates", RFC 5286, 1237 DOI 10.17487/RFC5286, September 2008, 1238 . 1240 [RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic 1241 Authentication", RFC 5304, DOI 10.17487/RFC5304, October 1242 2008, . 1244 [RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R., 1245 and M. Fanto, "IS-IS Generic Cryptographic 1246 Authentication", RFC 5310, DOI 10.17487/RFC5310, February 1247 2009, . 1249 [RFC8355] Filsfils, C., Ed., Previdi, S., Ed., Decraene, B., and R. 1250 Shakir, "Resiliency Use Cases in Source Packet Routing in 1251 Networking (SPRING) Networks", RFC 8355, 1252 DOI 10.17487/RFC8355, March 2018, 1253 . 1255 Authors' Addresses 1257 Peter Psenak (editor) 1258 Cisco Systems 1259 Pribinova Street 10 1260 Bratislava 81109 1261 Slovakia 1263 Email: ppsenak@cisco.com 1265 Clarence Filsfils 1266 Cisco Systems 1267 Brussels 1268 Belgium 1270 Email: cfilsfil@cisco.com 1271 Ahmed Bashandy 1272 Individual 1274 Email: abashandy.ietf@gmail.com 1276 Bruno Decraene 1277 Orange 1278 Issy-les-Moulineaux 1279 France 1281 Email: bruno.decraene@orange.com 1283 Zhibo Hu 1284 Huawei Technologies 1286 Email: huzhibo@huawei.com