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'ISO10589' == Outdated reference: A later version (-26) exists of draft-ietf-6man-segment-routing-header-02 == Outdated reference: A later version (-12) exists of draft-ietf-spring-resiliency-use-cases-08 -- Obsolete informational reference (is this intentional?): RFC 5316 (Obsoleted by RFC 9346) Summary: 0 errors (**), 0 flaws (~~), 5 warnings (==), 10 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 IS-IS for IP Internets S. Previdi, Ed. 3 Internet-Draft C. Filsfils 4 Intended status: Standards Track A. Bashandy 5 Expires: May 3, 2017 Cisco Systems, Inc. 6 H. Gredler 7 RtBrick Inc. 8 S. Litkowski 9 B. Decraene 10 Orange 11 J. Tantsura 12 Individual 13 October 30, 2016 15 IS-IS Extensions for Segment Routing 16 draft-ietf-isis-segment-routing-extensions-09 18 Abstract 20 Segment Routing (SR) allows for a flexible definition of end-to-end 21 paths within IGP topologies by encoding paths as sequences of 22 topological sub-paths, called "segments". These segments are 23 advertised by the link-state routing protocols (IS-IS and OSPF). 25 This draft describes the necessary IS-IS extensions that need to be 26 introduced for Segment Routing. 28 Requirements Language 30 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 31 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 32 document are to be interpreted as described in RFC 2119 [RFC2119]. 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 http://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 May 3, 2017. 50 Copyright Notice 52 Copyright (c) 2016 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 (http://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. Segment Routing Identifiers . . . . . . . . . . . . . . . . . 4 69 2.1. Prefix Segment Identifier (Prefix-SID Sub-TLV) . . . . . 4 70 2.1.1. Flags . . . . . . . . . . . . . . . . . . . . . . . . 6 71 2.1.2. Prefix-SID Propagation . . . . . . . . . . . . . . . 8 72 2.2. Adjacency Segment Identifier . . . . . . . . . . . . . . 8 73 2.2.1. Adjacency Segment Identifier (Adj-SID) Sub-TLV . . . 9 74 2.2.2. Adjacency Segment Identifiers in LANs . . . . . . . . 11 75 2.3. SID/Label Sub-TLV . . . . . . . . . . . . . . . . . . . . 13 76 2.4. SID/Label Binding TLV . . . . . . . . . . . . . . . . . . 13 77 2.4.1. Flags . . . . . . . . . . . . . . . . . . . . . . . . 15 78 2.4.2. Weight . . . . . . . . . . . . . . . . . . . . . . . 16 79 2.4.3. Range . . . . . . . . . . . . . . . . . . . . . . . . 16 80 2.4.4. Prefix Length, Prefix . . . . . . . . . . . . . . . . 18 81 2.4.5. Mapping Server Prefix-SID . . . . . . . . . . . . . . 18 82 2.4.6. SID/Label Sub-TLV . . . . . . . . . . . . . . . . . . 19 83 2.4.7. ERO Metric sub-TLV . . . . . . . . . . . . . . . . . 19 84 2.4.8. IPv4 ERO subTLV . . . . . . . . . . . . . . . . . . . 20 85 2.4.9. IPv6 ERO subTLV . . . . . . . . . . . . . . . . . . . 20 86 2.4.10. Unnumbered Interface ID ERO subTLV . . . . . . . . . 21 87 2.4.11. IPv4 Backup ERO subTLV . . . . . . . . . . . . . . . 22 88 2.4.12. IPv6 Backup ERO subTLV . . . . . . . . . . . . . . . 22 89 2.4.13. Unnumbered Interface ID Backup ERO subTLV . . . . . . 23 90 2.4.14. Prefix ERO and Prefix Backup ERO subTLV path 91 semantics . . . . . . . . . . . . . . . . . . . . . . 24 92 2.5. Multi-Topology SID/Label Binding TLV . . . . . . . . . . 24 93 3. Router Capabilities . . . . . . . . . . . . . . . . . . . . . 25 94 3.1. SR-Capabilities Sub-TLV . . . . . . . . . . . . . . . . . 25 95 3.2. SR-Algorithm Sub-TLV . . . . . . . . . . . . . . . . . . 28 96 3.3. SR Local Block Sub-TLV . . . . . . . . . . . . . . . . . 29 97 3.4. SRMS Preference Sub-TLV . . . . . . . . . . . . . . . . . 31 98 4. Non backward compatible changes with prior versions of this 99 document . . . . . . . . . . . . . . . . . . . . . . . . . . 31 100 4.1. Encoding of Multiple SRGBs . . . . . . . . . . . . . . . 31 101 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 32 102 5.1. Sub TLVs for Type 22,23,222 and 223 . . . . . . . . . . . 32 103 5.2. Sub TLVs for Type 135,235,236 and 237 . . . . . . . . . . 33 104 5.3. Sub TLVs for Type 242 . . . . . . . . . . . . . . . . . . 33 105 5.4. New TLV Codepoint and Sub-TLV registry . . . . . . . . . 34 106 6. Manageability Considerations . . . . . . . . . . . . . . . . 36 107 7. Security Considerations . . . . . . . . . . . . . . . . . . . 36 108 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 36 109 9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 36 110 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 38 111 10.1. Normative References . . . . . . . . . . . . . . . . . . 38 112 10.2. Informative References . . . . . . . . . . . . . . . . . 39 113 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 40 115 1. Introduction 117 Segment Routing (SR) allows for a flexible definition of end-to-end 118 paths within IGP topologies by encoding paths as sequences of 119 topological sub-paths, called "segments". These segments are 120 advertised by the link-state routing protocols (IS-IS and OSPF). Two 121 types of segments are defined, Prefix segments and Adjacency 122 segments. Prefix segments represent an ecmp-aware shortest-path to a 123 prefix, as per the state of the IGP topology. Adjacency segments 124 represent a hop over a specific adjacency between two nodes in the 125 IGP. A prefix segment is typically a multi-hop path while an 126 adjacency segment, in most of the cases, is a one-hop path. SR's 127 control-plane can be applied to both IPv6 and MPLS data-planes, and 128 do not require any additional signaling (other than the regular IGP). 129 For example, when used in MPLS networks, SR paths do not require any 130 LDP or RSVP-TE signaling. Still, SR can interoperate in the presence 131 of LSPs established with RSVP or LDP. 133 This draft describes the necessary IS-IS extensions that need to be 134 introduced for Segment Routing. 136 Segment Routing architecture is described in 137 [I-D.ietf-spring-segment-routing]. 139 Segment Routing use cases are described in [RFC7855]. 141 2. Segment Routing Identifiers 143 Segment Routing architecture ([I-D.ietf-spring-segment-routing]) 144 defines different types of Segment Identifiers (SID). This document 145 defines the IS-IS encodings for the IGP-Prefix-SID, the IGP- 146 Adjacency-SID, the IGP-LAN-Adjacency-SID and the Binding-SID. 148 2.1. Prefix Segment Identifier (Prefix-SID Sub-TLV) 150 A new IS-IS sub-TLV is defined: the Prefix Segment Identifier sub-TLV 151 (Prefix-SID sub-TLV). 153 The Prefix-SID sub-TLV carries the Segment Routing IGP-Prefix-SID as 154 defined in [I-D.ietf-spring-segment-routing]. The 'Prefix SID' MUST 155 be unique within a given IGP domain (when the L-flag is not set). 156 The 'Prefix SID' MUST carry an index (when the V-flag is not set) 157 that determines the actual SID/label value inside the set of all 158 advertised SID/label ranges of a given router. A receiving router 159 uses the index to determine the actual SID/label value in order to 160 construct forwarding state to a particular destination router. 162 In many use-cases a 'stable transport' IP Address is overloaded as an 163 identifier of a given node. Because the IP Prefixes may be re- 164 advertised into other levels there may be some ambiguity (e.g. 165 Originating router vs. L1L2 router) for which node a particular IP 166 prefix serves as identifier. The Prefix-SID sub-TLV contains the 167 necessary flags to disambiguate IP Prefix to node mappings. 168 Furthermore if a given node has several 'stable transport' IP 169 addresses there are flags to differentiate those among other IP 170 Prefixes advertised from a given node. 172 A Prefix-SID sub-TLV is associated to a prefix advertised by a node 173 and MAY be present in any of the following TLVs: 175 TLV-135 (IPv4) defined in [RFC5305]. 177 TLV-235 (MT-IPv4) defined in [RFC5120]. 179 TLV-236 (IPv6) defined in [RFC5308]. 181 TLV-237 (MT-IPv6) defined in [RFC5120]. 183 Binding-TLV defined in Section 2.4. 185 When the IP Reachability TLV is propagated across level boundaries, 186 the Prefix-SID sub-TLV SHOULD be kept. 188 The Prefix-SID sub-TLV has the following format: 190 0 1 2 3 191 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 1 192 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 193 | Type | Length | Flags | Algorithm | 194 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 195 | SID/Index/Label (variable) | 196 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 198 where: 200 Type: TBD, suggested value 3 202 Length: variable. 204 Flags: 1 octet field of following flags: 206 0 1 2 3 4 5 6 7 207 +-+-+-+-+-+-+-+-+ 208 |R|N|P|E|V|L| | 209 +-+-+-+-+-+-+-+-+ 211 where: 213 R-Flag: Re-advertisement flag. If set, then the prefix to 214 which this Prefix-SID is attached, has been propagated by the 215 router either from another level (i.e., from level-1 to level-2 216 or the opposite) or from redistribution (e.g.: from another 217 protocol). 219 N-Flag: Node-SID flag. If set, then the Prefix-SID refers to 220 the router identified by the prefix. Typically, the N-Flag is 221 set on Prefix-SIDs attached to a router loopback address. The 222 N-Flag is set when the Prefix-SID is a Node-SID as described in 223 [I-D.ietf-spring-segment-routing]. 225 P-Flag: no-PHP flag. If set, then the penultimate hop MUST NOT 226 pop the Prefix-SID before delivering the packet to the node 227 that advertised the Prefix-SID. 229 E-Flag: Explicit-Null Flag. If set, any upstream neighbor of 230 the Prefix-SID originator MUST replace the Prefix-SID with a 231 Prefix-SID having an Explicit-NULL value (0 for IPv4 and 2 for 232 IPv6) before forwarding the packet. 234 V-Flag: Value flag. If set, then the Prefix-SID carries a 235 value (instead of an index). By default the flag is UNSET. 237 L-Flag: Local Flag. If set, then the value/index carried by 238 the Prefix-SID has local significance. By default the flag is 239 UNSET. 241 Other bits: MUST be zero when originated and ignored when 242 received. 244 Algorithm: the router may use various algorithms when calculating 245 reachability to other nodes or to prefixes attached to these 246 nodes. Algorithms identifiers are defined in Section 3.2. 247 Examples of these algorithms are metric based Shortest Path First 248 (SPF), various sorts of Constrained SPF, etc. The algorithm field 249 of the Prefix-SID contains the identifier of the algorithm the 250 router has used in order to compute the reachability of the prefix 251 the Prefix-SID is associated to. 253 At origination, the Prefix-SID algorithm field MUST be set to 0 on 254 all Prefix-SID of prefixes computed using SPF algorithm (Shortest 255 Path First). On reception of the Prefix-SID sub-TLV, any non-zero 256 algorithm value MUST match what advertised in the SR-Algorithm 257 sub-TLV (Section 3.2). 259 A router receiving a Prefix-SID from a remote node and with an 260 algorithm value that such remote node has not advertised in the 261 SR-Algorithm sub-TLV (Section 3.2) MUST ignore the Prefix-SID sub- 262 TLV. 264 SID/Index/Label: according to the V and L flags, it contains 265 either: 267 * A 4 octet index defining the offset in the SID/Label space 268 advertised by this router using the encodings defined in 269 Section 3.1. In this case the V and L flags MUST be unset. 271 * A 3 octet local label where the 20 rightmost bits are used for 272 encoding the label value. In this case the V and L flags MUST 273 be set. 275 2.1.1. Flags 277 2.1.1.1. R and N Flags 279 The R-Flag MUST be set for prefixes that are not local to the router 280 and either: 282 advertised because of propagation (Level-1 into Level-2); 284 advertised because of leaking (Level-2 into Level-1); 285 advertised because of redistribution (e.g.: from another 286 protocol). 288 In the case where a Level-1-2 router has local interface addresses 289 configured in one level, it may also propagate these addresses into 290 the other level. In such case, the Level-1-2 router MUST NOT set the 291 R bit. The R-bit MUST be set only for prefixes that are not local to 292 the router and advertised by the router because of propagation and/or 293 leaking. 295 The N-Flag is used in order to define a Node-SID. A router MAY set 296 the N-Flag only if all of the following conditions are met: 298 The prefix to which the Prefix-SID is attached is local to the 299 router (i.e., the prefix is configured on one of the local 300 interfaces, e.g., a 'stable transport' loopback). 302 The prefix to which the Prefix-SID is attached MUST have a Prefix 303 length of either /32 (IPv4) or /128 (IPv6). 305 The router MUST ignore the N-Flag on a received Prefix-SID if the 306 prefix has a Prefix length different than /32 (IPv4) or /128 (IPv6). 308 [RFC7794] also defines the N and R flags and with the same semantics 309 of the equivalent flags defined in this document. There will be a 310 transition period where both sets of flags will be used and 311 eventually only the flags of the Prefix Attributes will remain. 312 During the transition period implementations supporting the N and R 313 flags defined in this document and the N and R flags defined in 314 [RFC7794] MUST advertise and parse all flags. In case the received 315 flags have different values, the value of the flags defined in 316 [RFC7794] prevails. 318 2.1.1.2. E and P Flags 320 When calculating the outgoing label for the prefix, the router MUST 321 take into account E and P flags advertised by the next-hop router, if 322 next-hop router advertised the SID for the prefix. This MUST be done 323 regardless of next-hop router contributing to the best path to the 324 prefix or not. 326 When propagating (either from Level-1 to Level-2 or vice versa) a 327 reachability advertisement originated by another IS-IS speaker, the 328 router MUST set the P-flag and MUST clear the E-flag of the related 329 Prefix-SIDs. 331 The following behavior is associated with the settings of the E and P 332 flags: 334 o If the P-flag is not set then any upstream neighbor of the Prefix- 335 SID originator MUST pop the Prefix-SID. This is equivalent to the 336 penultimate hop popping mechanism used in the MPLS dataplane which 337 improves performance of the ultimate hop. MPLS EXP bits of the 338 Prefix-SID are not preserved to the ultimate hop (the Prefix-SID 339 being removed). If the P-flag is unset the received E-flag is 340 ignored. 342 o If the P-flag is set then: 344 * If the E-flag is not set then any upstream neighbor of the 345 Prefix-SID originator MUST keep the Prefix-SID on top of the 346 stack. This is useful when, e.g., the originator of the 347 Prefix-SID must stitch the incoming packet into a continuing 348 MPLS LSP to the final destination. This could occur at an 349 inter-area border router (prefix propagation from one area to 350 another) or at an inter-domain border router (prefix 351 propagation from one domain to another). 353 * If the E-flag is set then any upstream neighbor of the Prefix- 354 SID originator MUST replace the PrefixSID with a Prefix-SID 355 having an Explicit-NULL value. This is useful, e.g., when the 356 originator of the Prefix-SID is the final destination for the 357 related prefix and the originator wishes to receive the packet 358 with the original EXP bits. 360 2.1.2. Prefix-SID Propagation 362 The Prefix-SID sub-TLV MUST be preserved when the IP Reachability TLV 363 gets propagated across level boundaries. 365 The level-1-2 router that propagates the Prefix-SID sub-TLV between 366 levels MUST set the R-flag. 368 If the Prefix-SID contains a global index (L and V flags unset) and 369 it is propagated as such (with L and V flags unset), the value of the 370 index MUST be preserved when propagated between levels. 372 The level-1-2 router that propagates the Prefix-SID sub-TLV between 373 levels MAY change the setting of the L and V flags in case a local 374 label value is encoded in the Prefix-SID instead of the received 375 value. 377 2.2. Adjacency Segment Identifier 379 A new IS-IS sub-TLV is defined: the Adjacency Segment Identifier sub- 380 TLV (Adj-SID sub-TLV). 382 The Adj-SID sub-TLV is an optional sub-TLV carrying the Segment 383 Routing IGP-Adjacency-SID as defined in 384 [I-D.ietf-spring-segment-routing] with flags and fields that may be 385 used, in future extensions of Segment Routing, for carrying other 386 types of SIDs. 388 IS-IS adjacencies are advertised using one of the IS-Neighbor TLVs 389 below: 391 TLV-22 [RFC5305] 393 TLV-222 [RFC5120] 395 TLV-23 [RFC5311] 397 TLV-223 [RFC5311] 399 TLV-141 [RFC5316] 401 Multiple Adj-SID sub-TLVs MAY be associated with a single IS- 402 neighbor. 404 2.2.1. Adjacency Segment Identifier (Adj-SID) Sub-TLV 406 The following format is defined for the Adj-SID sub-TLV: 408 0 1 2 3 409 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 1 410 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 411 | Type | Length | Flags | Weight | 412 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 413 | SID/Label/Index (variable) | 414 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 416 where: 418 Type: TBD, suggested value 31 420 Length: variable. 422 Flags: 1 octet field of following flags: 424 0 1 2 3 4 5 6 7 425 +-+-+-+-+-+-+-+-+ 426 |F|B|V|L|S| | 427 +-+-+-+-+-+-+-+-+ 429 where: 431 F-Flag: Address-Family flag. If unset, then the Adj-SID refers 432 to an adjacency with outgoing IPv4 encapsulation. If set then 433 the Adj-SID refers to an adjacency with outgoing IPv6 434 encapsulation. 436 B-Flag: Backup flag. If set, the Adj-SID is eligible for 437 protection (e.g.: using IPFRR or MPLS-FRR) as described in 438 [I-D.ietf-spring-resiliency-use-cases]. 440 V-Flag: Value flag. If set, then the Adj-SID carries a value. 441 By default the flag is SET. 443 L-Flag: Local Flag. If set, then the value/index carried by 444 the Adj-SID has local significance. By default the flag is 445 SET. 447 S-Flag. Set Flag. When set, the S-Flag indicates that the 448 Adj-SID refers to a set of adjacencies (and therefore MAY be 449 assigned to other adjacencies as well). 451 Other bits: MUST be zero when originated and ignored when 452 received. 454 Weight: 1 octet. The value represents the weight of the Adj-SID 455 for the purpose of load balancing. The use of the weight is 456 defined in [I-D.ietf-spring-segment-routing]. 458 SID/Index/Label: according to the V and L flags, it contains 459 either: 461 * A 3 octet local label where the 20 rightmost bits are used for 462 encoding the label value. In this case the V and L flags MUST 463 be set. 465 * A 4 octet index defining the offset in the SID/Label space 466 advertised by this router using the encodings defined in 467 Section 3.1. In this case V and L flags MUST be unset. 469 * A 16 octet IPv6 address. In this case the V flag MUST be set. 470 The L flag MUST be unset if the IPv6 address is globally 471 unique. 473 An SR capable router MAY allocate an Adj-SID for each of its 474 adjacencies and SHOULD set the B-Flag when the adjacency is 475 eligible for protection (IP or MPLS). 477 An SR capable router MAY allocate more than one Adj-SID to an 478 adjacency. 480 An SR capable router MAY allocate the same Adj-SID to different 481 adjacencies. 483 Examples of use of the Adj-SID sub-TLV are described in 484 [I-D.ietf-spring-segment-routing]. and 485 [I-D.ietf-6man-segment-routing-header]. 487 The F-flag is used in order for the router to advertise the 488 outgoing encapsulation of the adjacency the Adj-SID is attached 489 to. 491 2.2.2. Adjacency Segment Identifiers in LANs 493 In LAN subnetworks, the Designated Intermediate System (DIS) is 494 elected and originates the Pseudonode-LSP (PN-LSP) including all 495 neighbors of the DIS. 497 When Segment Routing is used, each router in the LAN MAY advertise 498 the Adj-SID of each of its neighbors. Since, on LANs, each router 499 only advertises one adjacency to the DIS (and doesn't advertise any 500 other adjacency), each router advertises the set of Adj-SIDs (for 501 each of its neighbors) inside a newly defined sub-TLV part of the TLV 502 advertising the adjacency to the DIS (e.g.: TLV-22). 504 The following new sub-TLV is defined: LAN-Adj-SID (Type: TBD, 505 suggested value 32) containing the set of Adj-SIDs the router 506 assigned to each of its LAN neighbors. 508 The format of the LAN-Adj-SID sub-TLV is as follows: 510 0 1 2 3 511 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 1 512 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 513 | Type | Length | Flags | Weight | 514 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 516 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 517 | System-ID (6 octets) | 518 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 519 | | 520 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 522 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 523 | SID/Label/Index (variable) | 524 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 526 where: 528 Type: TBD, suggested value 32 530 Length: variable. 532 Flags: 1 octet field of following flags: 534 0 1 2 3 4 5 6 7 535 +-+-+-+-+-+-+-+-+ 536 |F|B|V|L|S| | 537 +-+-+-+-+-+-+-+-+ 539 where F, B, V, L and S flags are defined in Section 2.2.1. Other 540 bits: MUST be zero when originated and ignored when received. 542 Weight: 1 octet. The value represents the weight of the Adj-SID 543 for the purpose of load balancing. The use of the weight is 544 defined in [I-D.ietf-spring-segment-routing]. 546 System-ID: 6 octets of IS-IS System-ID of length "ID Length" as 547 defined in [ISO10589]. 549 SID/Index/Label: according to the V and L flags, it contains 550 either: 552 * A 3 octet local label where the 20 rightmost bits are used for 553 encoding the label value. In this case the V and L flags MUST 554 be set. 556 * A 4 octet index defining the offset in the SID/Label space 557 advertised by this router using the encodings defined in 558 Section 3.1. In this case V and L flags MUST be unset. 560 * A 16 octet IPv6 address. In this case the V flag MUST be set. 561 The L flag MUST be unset if the IPv6 address is globally 562 unique. 564 Multiple LAN-Adj-SID sub-TLVs MAY be encoded. 566 In case one TLV-22/23/222/223 (reporting the adjacency to the DIS) 567 can't contain the whole set of LAN-Adj-SID sub-TLVs, multiple 568 advertisements of the adjacency to the DIS MUST be used and all 569 advertisements MUST have the same metric. 571 Each router within the level, by receiving the DIS PN LSP as well as 572 the non-PN LSP of each router in the LAN, is capable of 573 reconstructing the LAN topology as well as the set of Adj-SID each 574 router uses for each of its neighbors. 576 A label is encoded in 3 octets (in the 20 rightmost bits). 578 An index is encoded in 4 octets. 580 An ipv6 address SID is encoded in 16 octets (IPv6 Adj-SID is defined 581 in [I-D.ietf-6man-segment-routing-header]). 583 2.3. SID/Label Sub-TLV 585 The SID/Label sub-TLV is present in the following sub-TLVs defined in 586 this document: 588 Binding TLV Section 2.4. 590 SR Capability sub-TLV Section 3.1. 592 The SID/Label sub-TLV contains a SID or a MPLS Label. The SID/Label 593 sub-TLV has the following format: 595 0 1 2 3 596 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 1 597 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 598 | Type | Length | 599 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 600 | SID/Label (variable) | 601 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 603 where: 605 Type: TBD, suggested value 1 607 Length: variable 609 SID/Label: if length is set to 3 then the 20 rightmost bits 610 represent a MPLS label. 612 2.4. SID/Label Binding TLV 614 The SID/Label Binding TLV MAY be originated by any router in an IS-IS 615 domain. There are multiple uses of the SID/Label Binding TLV: 617 o The router may advertise a SID/Label binding to a FEC along with 618 at least a single 'nexthop style' anchor. The protocol supports 619 more than one 'nexthop style' anchor to be attached to a SID/Label 620 binding, which results into a simple path description language. 621 In analogy to RSVP the terminology for this is called an 'Explicit 622 Route Object' (ERO). Since ERO style path notation allows to 623 anchor SID/label bindings to both link and node IP addresses any 624 label switched path, can be described. Furthermore also SID/Label 625 Bindings from external protocols can get easily re-advertised. 627 o The SID/Label Binding TLV may be used for advertising SID/Label 628 Bindings and their associated Primary and Backup paths. In one 629 single TLV either a primary ERO Path, a backup ERO Path or both 630 are advertised. If a router wants to advertise multiple parallel 631 paths then it can generate several TLVs for the same Prefix/FEC. 632 Each occurrence of a Binding TLV with respect with a given FEC 633 Prefix has accumulating and not canceling semantics. Due the 634 space constraints in the 8-Bit IS-IS TLVs an originating router 635 MAY encode a primary ERO path in one SID/Label Binding TLV and the 636 backup ERO path in a second SID/Label Binding TLV. Note that the 637 FEC Prefix and SID/Label sub-TLV MUST be identical in both TLVs. 639 o The SID/Label Binding TLV may also be used in order to advertise 640 prefixes to SID/Label mappings. This functionality is called the 641 'Mapping Server' and it's used when, in a heterogeneous network, 642 not all nodes are capable of advertising their own SIDs/Labels. 643 When the SID/Label Binding TLV is used by the Mapping Server in 644 order to advertise prefix to SID/label mappings, the index/label 645 MUST include the Prefix-SID SubTLV (Section 2.1). 647 The SID/Label Binding TLV has Type TBD (suggested value 149), and has 648 the following format: 650 0 1 2 3 651 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 1 652 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 653 | Type | Length | Flags | Weight | 654 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 655 | Range | Prefix Length | FEC Prefix | 656 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 657 // FEC Prefix (continued, variable) // 658 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 659 | SubTLVs (variable) | 660 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 662 Figure 1: SID/Label Binding TLV format 664 o Type: TBD, suggested value 149 666 o Length: variable. 668 o 1 octet of flags 670 o 1 octet of Weight 671 o 2 octets of Range 673 o 1 octet of Prefix Length 675 o 0-16 octets of FEC Prefix 677 o sub-TLVs, where each sub-TLV consists of a sequence of: 679 * 1 octet of sub-TLV type 681 * 1 octet of length of the value field of the sub-TLV 683 * 0-243 octets of value 685 2.4.1. Flags 687 Flags: 1 octet field of following flags: 689 0 1 2 3 4 5 6 7 690 +-+-+-+-+-+-+-+-+ 691 |F|M|S|D|A| | 692 +-+-+-+-+-+-+-+-+ 694 where: 696 F-Flag: Address Family flag. If unset, then the Prefix FEC 697 carries an IPv4 Prefix. If set then the Prefix FEC carries an 698 IPv6 Prefix. 700 M-Flag: Mirror Context flag. Set if the advertised SID/path 701 corresponds to a mirrored context. The use of the M flag is 702 described in [I-D.ietf-spring-segment-routing]. 704 S-Flag: If set, the SID/Label Binding TLV SHOULD be flooded across 705 the entire routing domain. If the S flag is not set, the SID/ 706 Label Binding TLV MUST NOT be leaked between levels. This bit 707 MUST NOT be altered during the TLV leaking. 709 D-Flag: when the SID/Label Binding TLV is leaked from level-2 to 710 level-1, the D bit MUST be set. Otherwise, this bit MUST be 711 clear. SID/Label Binding TLVs with the D bit set MUST NOT be 712 leaked from level-1 to level-2. This is to prevent TLV looping 713 across levels. 715 A-Flag: Attached flag. The originator of the SID/Label Binding 716 TLV MAY set the A bit in order to signal that the prefixes and 717 SIDs advertised in the SID/Label Binding TLV are directly 718 connected to their originators. The mechanisms through which the 719 originator of the SID/Label Binding TLV can figure out if a prefix 720 is attached or not are outside the scope of this document (e.g.: 721 through explicit configuration). If the Binding TLV is leaked to 722 other areas/levels the A-flag MUST be cleared. 724 An implementation MAY decide not to honor the S-flag in order not 725 to leak Binding TLV's between levels (for policy reasons). In all 726 cases, the D flag MUST always be set by any router leaking the 727 Binding TLV from level-2 into level-1 and MUST be checked when 728 propagating the Binding TLV from level-1 into level-2. If the D 729 flag is set, the Binding TLV MUST NOT be propagated into level-2. 731 Other bits: MUST be zero when originated and ignored when 732 received. 734 2.4.2. Weight 736 Weight: 1 octet: The value represents the weight of the path for the 737 purpose of load balancing. The use of the weight is defined in 738 [I-D.ietf-spring-segment-routing]. 740 2.4.3. Range 742 The 'Range' field provides the ability to specify a range of 743 addresses and their associated Prefix SIDs. This functionality is 744 called "Mapping Server". It is essentially a compression scheme to 745 distribute a continuous Prefix and their continuous, corresponding 746 SID/Label Block. If a single SID is advertised then the range field 747 MUST be set to one. For range advertisements > 1, the number of 748 addresses that need to be mapped into a Prefix-SID and the starting 749 value of the Prefix-SID range. 751 Example 1: if the following router addresses (loopback addresses) 752 need to be mapped into the corresponding Prefix SID indexes. 754 Router-A: 192.0.2.1/32, Prefix-SID: Index 1 755 Router-B: 192.0.2.2/32, Prefix-SID: Index 2 756 Router-C: 192.0.2.3/32, Prefix-SID: Index 3 757 Router-D: 192.0.2.4/32, Prefix-SID: Index 4 758 0 1 2 3 759 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 1 760 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 761 | Type | Length |0|0| | Weight | 762 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 763 | Range = 4 | /32 | 192 | 764 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 765 | .0 | .2 | .1 |Prefix-SID Type| 766 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 767 | sub-TLV Length| Flags | Algorithm | | 768 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 769 | 1 | 770 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 772 Example-2: If the following prefixes need to be mapped into the 773 corresponding Prefix-SID indexes: 775 10.1.1/24, Prefix-SID: Index 51 776 10.1.2/24, Prefix-SID: Index 52 777 10.1.3/24, Prefix-SID: Index 53 778 10.1.4/24, Prefix-SID: Index 54 779 10.1.5/24, Prefix-SID: Index 55 780 10.1.6/24, Prefix-SID: Index 56 781 10.1.7/24, Prefix-SID: Index 57 783 0 1 2 3 784 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 1 785 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 786 | Type | Length |0|0| | Weight | 787 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 788 | Range = 7 | /24 | 10 | 789 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 790 | .1 | .1 |Prefix-SID Type| sub-TLV Length| 791 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 792 | Flags | Algorithm | | 793 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 794 | 51 | 795 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 797 It is not expected that a network operator will be able to keep fully 798 continuous FEC Prefix / SID/Index mappings. In order to support 799 noncontinuous mapping ranges an implementation MAY generate several 800 instances of Binding TLVs. 802 For example if a router wants to advertise the following ranges: 804 Range 16: { 192.0.2.1-15, Index 1-15 } 805 Range 6: { 192.0.2.22-27, Index 22-27 } 807 Range 41: { 192.0.2.44-84, Index 80-120 } 809 A router would need to advertise three instances of the Binding TLV. 811 2.4.4. Prefix Length, Prefix 813 The 'FEC Prefix' represents the Forwarding equivalence class at the 814 tail-end of the advertised path. The 'FEC Prefix' does not need to 815 correspond to a routable prefix of the originating node. 817 The 'Prefix Length' field contains the length of the prefix in bits. 818 Only the most significant octets of the Prefix FEC are encoded. 819 (i.e., 1 octet for FEC prefix length 1 up to 8, 2 octets for FEC 820 prefix length 9 to 16, 3 octets for FEC prefix length 17 up to 24 and 821 4 octets for FEC prefix length 25 up to 32, ...., 16 octets for FEC 822 prefix length 113 up to 128). 824 2.4.5. Mapping Server Prefix-SID 826 The Prefix-SID sub-TLV (suggested value 3) is defined in Section 2.1 827 and contains the SID/index/label value associated with the prefix and 828 range. The Prefix-SID SubTLV MUST be used when the SID/Label Binding 829 TLV is used by the Mapping Server (i.e., advertising one or a range 830 of prefixes and their associated SIDs/Labels). 832 A node receiving a MS entry for a prefix MUST check the existence of 833 such prefix in its link-state database prior to consider and use the 834 associated SID. 836 2.4.5.1. Prefix-SID Flags 838 The Prefix-SID flags are defined in Section 2.1. The Mapping Server 839 MAY advertise a mapping with the N flag set when the prefix being 840 mapped is known in the link-state topology with a mask length of 32 841 (IPv4) or 128 (IPv6) and when the prefix represents a node. The 842 mechanisms through which the operator defines that a prefix 843 represents a node are outside the scope of this document (typically 844 it will be through configuration). 846 The other flags defined in Section 2.1 are not used by the Mapping 847 Server and MUST be ignored at reception. 849 2.4.5.2. PHP Behavior when using Mapping Server Advertisements 851 As the mapping server does not specify the originator of a prefix 852 advertisement it is not possible to determine PHP behavior solely 853 based on the Mapping Server Advertisement. However, if additional 854 information is available PHP behavior may safely be done. The 855 required information consists of: 857 o A prefix reachability advertisement for the prefix has been 858 received which includes the Extended Reachability Attribute Flags 859 sub-TLV ([RFC7794]). 861 o X and R flags are both set to 0 in the Extended Reachability 862 Attribute Flags sub-TLV. 864 In the absence of an Extended Reachability Attribute Flags sub-TLV 865 ([RFC7794]) the A flag in the binding TLV indicates that the 866 originator of a prefix reachability advertisement is directly 867 connected to the prefix and thus PHP MUST be done by the neighbors of 868 the router originating the prefix reachability advertisement. Note 869 that A-flag is only valid in the original area in which the Binding 870 TLV is advertised. 872 2.4.5.3. Prefix-SID Algorithm 874 The algorithm field contains the identifier of the algorithm the 875 router MUST use in order to compute reachability to the range of 876 prefixes. Use of the algorithm field is described in Section 2.1. 878 2.4.6. SID/Label Sub-TLV 880 The SID/Label sub-TLV (Type: TBD, suggested value 1) contains the 881 SID/Label value as defined in Section 2.3. It MAY be present in the 882 SID/Label Binding TLV. 884 2.4.7. ERO Metric sub-TLV 886 ERO Metric sub-TLV (Type: TBD, suggested value 10) is a sub-TLV of 887 the SID/Label Binding TLV. 889 The ERO Metric sub-TLV carries the cost of an ERO path. It is used 890 to compare the cost of a given source/destination path. A router MAY 891 advertise the ERO Metric sub-TLV. The cost of the ERO Metric sub-TLV 892 SHOULD be set to the cumulative IGP or TE path cost of the advertised 893 ERO. Since manipulation of the Metric field may attract or distract 894 traffic from and to the advertised segment it MAY be manually 895 overridden. 897 0 1 2 3 898 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 1 899 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 900 | Type | Length | Metric | 901 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 902 | Metric (continued) | 903 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 905 ERO Metric sub-TLV format 907 where: 909 Type: TBD, suggested value 10 911 Length: 4 913 Metric: 4 bytes 915 2.4.8. IPv4 ERO subTLV 917 The IPv4 ERO subTLV (Type: TBD, suggested value 11) describes a path 918 segment using IPv4 address style of encoding. Its semantics have 919 been borrowed from [RFC3209]. 921 The 'L' bit in the Flags is a one-bit attribute. If the L bit is 922 set, then the value of the attribute is 'loose.' Otherwise, the 923 value of the attribute is 'strict.' 925 0 1 2 3 926 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 1 927 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 928 | Type | Length |L| Reserved | IPv4 address | 929 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 930 | IPv4 address (continued) | 931 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 933 Figure 2: IPv4 ERO subTLV format 935 2.4.9. IPv6 ERO subTLV 937 The IPv6 ERO subTLV (Type: TBD, suggested value 12) describes a path 938 segment using IPv6 Address style of encoding. Its semantics have 939 been borrowed from [RFC3209]. 941 The 'L' bit in the Flags is a one-bit attribute. If the L bit is 942 set, then the value of the attribute is 'loose.' Otherwise, the 943 value of the attribute is 'strict.' 944 0 1 2 3 945 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 1 946 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 947 | Type | Length |L| Reserved | IPv6 address | 948 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 949 | IPv6 Address (continued) | 950 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 951 | IPv6 Address (continued) | 952 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 953 | IPv6 Address (continued) | 954 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 955 | IPv6 Address (continued) | 956 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 958 Figure 3: IPv6 ERO subTLV format 960 2.4.10. Unnumbered Interface ID ERO subTLV 962 The appearance and semantics of the 'Unnumbered Interface ID' have 963 been borrowed from Section 4 [RFC3477]. 965 The Unnumbered Interface-ID ERO subTLV (Type: TBD, suggested value 966 13) describes a path segment that spans over an unnumbered interface. 967 Unnumbered interfaces are referenced using the interface index. 968 Interface indices are assigned local to the router and therefore not 969 unique within a domain. All elements in an ERO path need to be 970 unique within a domain and hence need to be disambiguated using a 971 domain unique Router-ID. 973 The 'Router-ID' field contains the router ID of the router which has 974 assigned the 'Interface ID' field. Its purpose is to disambiguate 975 the 'Interface ID' field from other routers in the domain. 977 IS-IS supports two Router-ID formats: 979 o (TLV 134, 32-Bit format) [RFC5305] 981 o (TLV 140, 128-Bit format) [RFC6119] 983 The actual Router-ID format gets derived from the 'Length' field. 985 o For 32-Bit Router-ID width the subTLV length is set to 8 octets. 987 o For 128-Bit Router-ID width the subTLV length is set to 20 octets. 989 The 'Interface ID' is the identifier assigned to the link by the 990 router specified by the router ID. 992 The 'L' bit in the Flags is a one-bit attribute. If the L bit is 993 set, then the value of the attribute is 'loose.' Otherwise, the 994 value of the attribute is 'strict.' 996 0 1 2 3 997 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 1 998 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 999 | Type | Length |L| Reserved | 1000 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1001 // Router ID (32 or 128 bits) // 1002 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1003 | Interface ID (32 bits) | 1004 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1006 Figure 4: Unnumbered Interface ID ERO subTLV format 1008 2.4.11. IPv4 Backup ERO subTLV 1010 The IPv4 Backup ERO subTLV (Type: TBD, suggested value 14) describes 1011 a Backup path segment using IPv4 Address style of encoding. Its 1012 appearance and semantics have been borrowed from [RFC3209]. 1014 The 'L' bit in the Flags is a one-bit attribute. If the L bit is 1015 set, then the value of the attribute is 'loose.' Otherwise, the 1016 value of the attribute is 'strict.' 1018 0 1 2 3 1019 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 1020 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1021 | Type | Length |L| Reserved | IPv4 address | 1022 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1023 | IPv4 address (continued) | 1024 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1026 Figure 5: IPv4 Backup ERO subTLV format 1028 2.4.12. IPv6 Backup ERO subTLV 1030 The IPv6 Backup ERO subTLV (Type: TBD, suggested value 15) describes 1031 a Backup path segment using IPv6 Address style of encoding. Its 1032 appearance and semantics have been borrowed from [RFC3209]. 1034 The 'L' bit in the Flags is a one-bit attribute. If the L bit is 1035 set, then the value of the attribute is 'loose.' Otherwise, the 1036 value of the attribute is 'strict.' 1037 0 1 2 3 1038 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 1039 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1040 | Type | Length |L| Reserved | IPv6 address | 1041 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1042 | IPv6 Address (continued) | 1043 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1044 | IPv6 Address (continued) | 1045 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1046 | IPv6 Address (continued) | 1047 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1048 | IPv6 Address (continued) | 1049 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1051 Figure 6: IPv6 Backup ERO subTLV format 1053 2.4.13. Unnumbered Interface ID Backup ERO subTLV 1055 The appearance and semantics of the 'Unnumbered Interface ID' have 1056 been borrowed from Section 4 [RFC3477]. 1058 The Unnumbered Interface-ID Backup ERO subTLV (Type: TBD, suggested 1059 value 16) describes a Backup LSP path segment that spans over an 1060 unnumbered interface. Unnumbered interfaces are referenced using the 1061 interface index. Interface indices are assigned local to the router 1062 and therefore not unique within a domain. All elements in an ERO 1063 path need to be unique within a domain and hence need to be 1064 disambiguated using a domain unique Router-ID. 1066 The 'Router-ID' field contains the router ID of the router which has 1067 assigned the 'Interface ID' field. Its purpose is to disambiguate 1068 the 'Interface ID' field from other routers in the domain. 1070 IS-IS supports two Router-ID formats: 1072 o (TLV 134, 32-Bit format) [RFC5305] 1074 o (TLV 140, 128-Bit format) [RFC6119] 1076 The actual Router-ID format gets derived from the 'Length' field. 1078 o For 32-Bit Router-ID width the subTLV length is set to 8 octets. 1080 o For 128-Bit Router-ID width the subTLV length is set to 20 octets. 1082 The 'Interface ID' is the identifier assigned to the link by the 1083 router specified by the router ID. 1085 The 'L' bit in the Flags is a one-bit attribute. If the L bit is 1086 set, then the value of the attribute is 'loose.' Otherwise, the 1087 value of the attribute is 'strict.' 1089 0 1 2 3 1090 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 1091 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1092 | Type | Length |L| Reserved | 1093 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1094 // Router ID (32 or 128 bits) // 1095 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1096 | Interface ID (32 bits) | 1097 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1099 Figure 7: Unnumbered Interface ID Backup ERO subTLV format 1101 2.4.14. Prefix ERO and Prefix Backup ERO subTLV path semantics 1103 All 'ERO' and 'Backup ERO' information represents an ordered set 1104 which describes the segments of a path. The last ERO subTLV 1105 describes the segment closest to the egress point of the path. 1106 Contrary the first ERO subTLV describes the first segment of a path. 1107 If a router extends or stitches a label switched path it MUST prepend 1108 the new segments path information to the ERO list. The same ordering 1109 applies for the Backup ERO labels. An implementation SHOULD first 1110 encode all primary path EROs followed by the bypass EROs. 1112 2.5. Multi-Topology SID/Label Binding TLV 1114 The Multi-Topology SID/Label Binding TLV allows the support of M-ISIS 1115 as defined in [RFC5120]. The Multi-Topology SID/Label Binding TLV 1116 has the same format as the SID/Label Binding TLV defined in 1117 Section 2.4 with the difference consisting of a Multitopology 1118 Identifier (MTID) as defined here below: 1120 0 1 2 3 1121 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 1122 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1123 | Type | Length | MTID | 1124 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1125 | Flags | Weight | Range | 1126 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1127 | Prefix Length | FEC Prefix | FEC Prefix (variable) | 1128 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1129 | SubTLVs (variable) | 1130 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1132 Figure 8: Multi-Topology SID/Label Binding TLV format 1134 where: 1136 Type: TBD, suggested value 150 1138 Length: variable 1140 MTID is the multitopology identifier defined as: 1142 0 1 1143 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 1144 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1145 | RESVD | MTID | 1146 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1148 RESVD: reserved bits. MUST be reset on transmission and 1149 ignored on receive. 1151 MTID: a 12-bit field containing the non-zero ID of the topology 1152 being announced. The TLV MUST be ignored if the ID is zero. 1153 This is to ensure the consistent view of the standard unicast 1154 topology. 1156 The other fields and SubTLVs are defined in Section 2.4. 1158 3. Router Capabilities 1160 3.1. SR-Capabilities Sub-TLV 1162 Segment Routing requires each router to advertise its SR data-plane 1163 capability and the range of MPLS label values it uses for Segment 1164 Routing in the case where global SIDs are allocated (i.e., global 1165 indexes). Data-plane capabilities and label ranges are advertised 1166 using the newly defined SR-Capabilities sub-TLV inserted into the IS- 1167 IS Router Capability TLV-242 that is defined in [RFC7981]. 1169 The Router Capability TLV specifies flags that control its 1170 advertisement. The SR Capabilities sub-TLV MUST be propagated 1171 throughout the level and SHOULD NOT be advertised across level 1172 boundaries. Therefore Router Capability TLV distribution flags 1173 SHOULD be set accordingly, i.e., the S flag in the Router Capability 1174 TLV ([RFC7981]) MUST be unset. 1176 The SR Capabilities sub-TLV has following format: 1178 0 1 2 3 1179 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 1180 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1181 | Type | Length | Flags | 1182 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1184 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1185 | Range | 1186 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1187 // SID/Label Sub-TLV (variable) // 1188 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1190 Type: TBD, suggested value 2 1192 Length: variable. 1194 Flags: 1 octet of flags. The following are defined: 1196 0 1 2 3 4 5 6 7 1197 +-+-+-+-+-+-+-+-+ 1198 |I|V|H| | 1199 +-+-+-+-+-+-+-+-+ 1201 where: 1203 I-Flag: MPLS IPv4 flag. If set, then the router is capable of 1204 processing SR MPLS encapsulated IPv4 packets on all interfaces. 1206 V-Flag: MPLS IPv6 flag. If set, then the router is capable of 1207 processing SR MPLS encapsulated IPv6 packets on all interfaces. 1209 H-Flag: SR-IPv6 flag. If set, then the router is capable of 1210 processing the IPv6 Segment Routing Header on all interfaces as 1211 defined in [I-D.ietf-6man-segment-routing-header]. 1213 One or more SRGB Descriptor entries, each of which have the 1214 following format: 1216 Range: 3 octets. 1218 SID/Label sub-TLV (as defined in Section 2.3). 1220 SID/Label sub-TLV contains the first value of the SRGB while the 1221 range contains the number of SRGB elements. The range value MUST be 1222 higher than 0. 1224 The SR-Capabilities sub-TLV MAY be advertised in an LSP of any number 1225 but a router MUST NOT advertise more than one SR-Capabilities sub- 1226 TLV. A router receiving multiple SR-Capabilities sub-TLVs, from the 1227 same originator, SHOULD select the first advertisement in the lowest 1228 numbered LSP. 1230 When multiple SRGB Descriptors are advertised the entries define an 1231 ordered set of ranges on which a SID index is to be applied. For 1232 this reason changing the order in which the descriptors are 1233 advertised will have a disruptive effect on forwarding. 1235 When a router adds a new SRGB Descriptor to an existing SR- 1236 Capabilities sub-TLV the new Descriptor SHOULD add the newly 1237 configured block at the end of the sub-TLV and SHOULD NOT change the 1238 order of previously advertised blocks. Changing the order of the 1239 advertised descriptors will create label churn in the FIB and 1240 blackhole / misdirect some traffic during the IGP convergence. In 1241 particular, if a range which is not the last is extended it's 1242 preferable to add a new range rather than extending the previously 1243 advertised range. 1245 The originating router MUST ensure the order is same after a graceful 1246 restart (using checkpointing, non-volatile storage or any other 1247 mechanism) in order to guarantee the same order before and after GR. 1249 The originating router MUST NOT advertise overlapping ranges. 1251 When a router receives multiple overlapping ranges, it MUST conform 1252 to the procedures defined in [I-D.ietf-spring-conflict-resolution]. 1254 Here follows an example of advertisement of multiple ranges: 1256 The originating router advertises following ranges: 1257 SR-Cap: range: 100, SID value: 100 1258 SR-Cap: range: 100, SID value: 1000 1259 SR-Cap: range: 100, SID value: 500 1261 The receiving routers concatenate the ranges in the received 1262 order and build the SRGB as follows: 1264 SRGB = [100, 199] 1265 [1000, 1099] 1266 [500, 599] 1268 The indexes span multiple ranges: 1270 index=0 means label 100 1271 ... 1272 index 99 means label 199 1273 index 100 means label 1000 1274 index 199 means label 1099 1275 ... 1276 index 200 means label 500 1277 ... 1279 3.2. SR-Algorithm Sub-TLV 1281 The router may use various algorithms when calculating reachability 1282 to other nodes or to prefixes attached to these nodes. Examples of 1283 these algorithms are metric based Shortest Path First (SPF), various 1284 sorts of Constrained SPF, etc. The SR-Algorithm sub-TLV (Type: TBD, 1285 suggested value 19) allows the router to advertise the algorithms 1286 that the router is currently using. The following value has been 1287 defined: 1289 0: Shortest Path First (SPF) algorithm based on link metric. This 1290 is the well-known shortest path algorithm as computed by the IS-IS 1291 Decision process. Consistent with the deployed practice for link- 1292 state protocols, algorithm 0 permits any node to overwrite the SPF 1293 path with a different path based on local policy. 1295 1: Strict Shortest Path First (SPF) algorithm based on link 1296 metric. The algorithm is identical to algorithm 0 but algorithm 1 1297 requires that all nodes along the path will honor the SPF routing 1298 decision. Local policy MUST NOT alter the forwarding decision 1299 computed by algorithm 1 at the node claiming to support algorithm 1300 1. 1302 The SR-Algorithm sub-TLV is inserted into the IS-IS Router Capability 1303 TLV-242 that is defined in [RFC7981]. 1305 The Router Capability TLV specifies flags that control its 1306 advertisement. The SR-Algorithm MUST be propagated throughout the 1307 level and need not to be advertised across level boundaries. 1308 Therefore Router Capability TLV distribution flags MUST be set 1309 accordingly, i.e., the S flag MUST be unset. 1311 The SR-Algorithm sub-TLV is optional, it MAY only appear a single 1312 time inside the Router Capability TLV. 1314 When the originating router does not advertise the SR-Algorithm sub- 1315 TLV, then all the Prefix-SID advertised by the router MUST have 1316 algorithm field set to 0. Any receiving router MUST assume SPF 1317 algorithm (i.e., Shortest Path First). 1319 When the originating router does advertise the SR-Algorithm sub-TLV, 1320 then algorithm 0 MUST be present while algorithm 1 MAY be present. 1322 The SR-Algorithm sub-TLV has following format: 1324 0 1 2 3 1325 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 1326 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1327 | Type | Length | 1328 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1329 | Algorithm 1 | Algorithm 2 | Algorithm ... | Algorithm n | 1330 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1332 where: 1334 Type: TBD, suggested value 19 1336 Length: variable. 1338 Algorithm: 1 octet of algorithm Section 2.1 1340 3.3. SR Local Block Sub-TLV 1342 The SR Local Block (SRLB) Sub-TLV contains the range of labels the 1343 node has reserved for local SIDs. Local SIDs are used, e.g., for 1344 Adjacency-SIDs, and may also be allocated by other components than 1345 IS-IS protocol. As an example, an application or a controller may 1346 instruct the router to allocate a specific local SID. Therefore, in 1347 order for such applications or controllers to know what are the local 1348 SIDs available in the router, it is required that the router 1349 advertises its SRLB. 1351 The SRLB Sub-TLV is used for that purpose and has following format: 1353 0 1 2 3 1354 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 1355 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1356 | Type | Length | Flags | 1357 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1359 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1360 | Range | 1361 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1362 // SID/Label Sub-TLV (variable) // 1363 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1365 Type: TBD, suggested value 22. 1367 Length: variable. 1369 Flags: 1 octet of flags. None are defined at this stage. 1371 One or more SRLB Descriptor entries, each of which have the 1372 following format: 1374 Range: 3 octets. 1376 SID/Label sub-TLV (as defined in Section 2.3). 1378 SID/Label sub-TLV contains the first value of the SRLB while the 1379 range contains the number of SRLB elements. The range value MUST be 1380 higher than 0. 1382 The SRLB sub-TLV MAY be advertised in an LSP of any number but a 1383 router MUST NOT advertise more than one SRLB sub-TLV. A router 1384 receiving multiple SRLB sub-TLVs, from the same originator, SHOULD 1385 select the first advertisement in the lowest numbered LSP. 1387 The originating router MUST NOT advertise overlapping ranges. 1389 It is important to note that each time a SID from the SRLB is 1390 allocated, it SHOULD also be reported to all components (e.g.: 1391 controller or applications) in order for these components to have an 1392 up-to-date view of the current SRLB allocation and in order to avoid 1393 collision between allocation instructions. 1395 Within the context of IS-IS, the reporting of local SIDs is done 1396 through IS-IS Sub-TLVs such as the Adjacency-SID. However, the 1397 reporting of allocated local SIDs may also be done through other 1398 means and protocols which mechanisms are outside the scope of this 1399 document. 1401 A router advertising the SRLB TLV may also have other label ranges, 1402 outside the SRLB, for its local allocation purposes which are NOT 1403 advertised in the SRLB. For example, it is possible that an 1404 Adjacency-SID is allocated using a local label not part of the SRLB. 1406 3.4. SRMS Preference Sub-TLV 1408 The Segment Routing Mapping Server (SRMS) Preference sub-TLV is used 1409 in order to associate a preference with SRMS advertisements from a 1410 particular source. 1412 The SRMS Preference sub-TLV has following format: 1414 0 1 2 3 1415 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 1416 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1417 | Type | Length | Preference | 1418 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1420 Type: TBD, suggested value 23. 1422 Length: 1. 1424 Preference: 1 octet. Unsigned 8 bit SRMS preference. 1426 The SRMS Preference sub-TLV MAY be advertised in an LSP of any number 1427 but a router MUST NOT advertise more than one SRMS Preference sub- 1428 TLV. A router receiving multiple SRMS Preference sub-TLVs, from the 1429 same originator, SHOULD select the first advertisement in the lowest 1430 numbered LSP. 1432 The use of the SRMS Preference during the SID selection process is 1433 described in [I-D.ietf-spring-conflict-resolution]. 1435 4. Non backward compatible changes with prior versions of this document 1437 This section describes the changes that have been applied to this 1438 document that are not backward compatible with previous versions. 1440 4.1. Encoding of Multiple SRGBs 1442 Version -04 of this document introduced a change in Section 3.1 1443 regarding the encoding method for multiple SRGBs in the SR-Cap SubTLV 1444 and made the support of multiple SRGBs REQUIRED. 1446 The modified method consists of having a single SR-Cap Sub-TLV where 1447 all SRGBs are encoded. In previous versions (prior to version -04) 1448 of this document it was allowed to have multiple occurrences of the 1449 SR-Cap Sub-TLV. 1451 At the time of writing this document, no existing implementations are 1452 affected by the change since no implementations actually (i.e., at 1453 the time of updating this document) encode multiple SRGBs anyway. 1455 5. IANA Considerations 1457 This documents request allocation for the following TLVs and subTLVs. 1459 5.1. Sub TLVs for Type 22,23,222 and 223 1461 This document makes the following registrations in the "sub-TLVs for 1462 TLV 22, 23, 222 and 223" registry. 1464 Type: TBD (suggested value 31) 1466 Description: Adjacency Segment Identifier 1468 TLV 22: yes 1470 TLV 23: yes 1472 TLV 222: yes 1474 TLV 223: yes 1476 Reference: This document (Section 2.2.1) 1478 Type: TBD (suggested value 32) 1480 Description: LAN Adjacency Segment Identifier 1482 TLV 22: yes 1484 TLV 23: yes 1486 TLV 222: yes 1488 TLV 223: yes 1490 Reference: This document (Section 2.2.2) 1492 5.2. Sub TLVs for Type 135,235,236 and 237 1494 This document makes the following registrations in the "sub-TLVs for 1495 TLV 135,235,236 and 237" registry. 1497 Type: TBD (suggested value 3) 1499 Description: Prefix Segment Identifier 1501 TLV 135: yes 1503 TLV 235: yes 1505 TLV 236: yes 1507 TLV 237: yes 1509 Reference: This document (Section 2.1) 1511 5.3. Sub TLVs for Type 242 1513 This document makes the following registrations in the "sub-TLVs for 1514 TLV 242" registry. 1516 Type: TBD (suggested value 2) 1518 Description: Segment Routing Capability 1520 Reference: This document (Section 3.1) 1522 Type: TBD (suggested value 19) 1524 Description: Segment Routing Algorithm 1526 Reference: This document (Section 3.2) 1528 Type: TBD (suggested value 22) 1530 Description: Segment Routing Local Base (SRLB) 1532 Reference: This document (Section 3.3) 1533 Type: TBD (suggested value 23) 1535 Description: Segment Routing Mapping Server Preference (SRMS 1536 Preference) 1538 Reference: This document (Section 3.4) 1540 5.4. New TLV Codepoint and Sub-TLV registry 1542 This document registers the following TLV: 1544 Type: TBD (suggested value 149) 1546 name: Segment Identifier / Label Binding 1548 IIH: no 1550 LSP: yes 1552 SNP: no 1554 Purge: no 1556 Reference: This document (Section 2.4) 1558 Type: TBD (suggested value 150) 1560 name: Multi-Topology Segment Identifier / Label Binding 1562 IIH: no 1564 LSP: yes 1566 SNP: no 1568 Purge: no 1570 Reference: This document (Section 2.5) 1572 This document creates the following sub-TLV Registry: 1574 Registry: sub-TLVs for TLV 149 and 150 1576 Registration Procedure: Expert review 1578 Reference: This document (Section 2.4) 1579 Type: TBD, suggested value 1 1581 Description: SID/Label 1583 Reference: This document (Section 2.3) 1585 Type: TBD, suggested value 3 1587 Description: Prefix-SID 1589 Reference: This document (Section 2.1) 1591 Type: TBD, suggested value 10 1593 Description: ERO Metric 1595 Reference: This document (Section 2.4.7) 1597 Type: TBD, suggested value 11 1599 Description: IPv4 ERO 1601 Reference: This document (Section 2.4.8) 1603 Type: TBD, suggested value 12 1605 Description: IPv6 ERO 1607 Reference: This document (Section 2.4.9) 1609 Type: TBD, suggested value 13 1611 Description: Unnumbered Interface-ID ERO 1613 Reference: This document (Section 2.4.10) 1615 Type: TBD, suggested value 14 1616 Description: IPv4 Backup ERO 1618 Reference: This document (Section 2.4.11) 1620 Type: TBD, suggested value 15 1622 Description: IPv6 Backup ERO 1624 Reference: This document (Section 2.4.12) 1626 Type: TBD, suggested value 16 1628 Description: Unnumbered Interface-ID Backup ERO 1630 Reference: This document (Section 2.4.13) 1632 6. Manageability Considerations 1634 TBD 1636 7. Security Considerations 1638 TBD 1640 8. Acknowledgements 1642 We would like to thank Dave Ward, Dan Frost, Stewart Bryant, Pierre 1643 Francois and Jesper Skrivers for their contribution to the content of 1644 this document. 1646 Many thanks to Yakov Rekhter and Ina Minei for their contribution on 1647 earlier definition of the "Binding / MPLS Label TLV". 1649 9. Contributors 1651 The following people gave a substantial contribution to the content 1652 of this document and should be considered as co-authors: 1654 Les Ginsberg 1655 Cisco Systems Inc. 1656 US 1658 Email: ginsberg@cisco.com 1659 Martin Horneffer 1660 Deutsche Telekom 1661 DE 1663 Email: Martin.Horneffer@telekom.de 1665 Wim Henderickx 1666 Alcatel-Lucent 1667 BE 1669 Email: wim.henderickx@alcatel-lucent.com 1671 Edward Crabbe 1672 Individual 1673 US 1675 Email: edward.crabbe@gmail.com 1677 Rob Shakir 1678 Individual 1679 UK 1681 Email: rjs@rob.sh 1683 Igor Milojevic 1684 Individual 1685 RS 1687 Email: milojevicigor@gmail.com 1689 Saku Ytti 1690 TDC 1691 FI 1693 Email: saku@ytti.fi 1695 Steven Luong 1696 Cisco Systems Inc. 1697 US 1699 Email: sluong@cisco.com 1701 10. References 1703 10.1. Normative References 1705 [I-D.ietf-spring-conflict-resolution] 1706 Ginsberg, L., Psenak, P., Previdi, S., and M. Pilka, 1707 "Segment Routing Conflict Resolution", draft-ietf-spring- 1708 conflict-resolution-02 (work in progress), October 2016. 1710 [I-D.ietf-spring-segment-routing] 1711 Filsfils, C., Previdi, S., Decraene, B., Litkowski, S., 1712 and R. Shakir, "Segment Routing Architecture", draft-ietf- 1713 spring-segment-routing-09 (work in progress), July 2016. 1715 [ISO10589] 1716 International Organization for Standardization, 1717 "Intermediate system to Intermediate system intra-domain 1718 routeing information exchange protocol for use in 1719 conjunction with the protocol for providing the 1720 connectionless-mode Network Service (ISO 8473)", ISO/ 1721 IEC 10589:2002, Second Edition, Nov 2002. 1723 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1724 Requirement Levels", BCP 14, RFC 2119, 1725 DOI 10.17487/RFC2119, March 1997, 1726 . 1728 [RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi 1729 Topology (MT) Routing in Intermediate System to 1730 Intermediate Systems (IS-ISs)", RFC 5120, 1731 DOI 10.17487/RFC5120, February 2008, 1732 . 1734 [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic 1735 Engineering", RFC 5305, DOI 10.17487/RFC5305, October 1736 2008, . 1738 [RFC5308] Hopps, C., "Routing IPv6 with IS-IS", RFC 5308, 1739 DOI 10.17487/RFC5308, October 2008, 1740 . 1742 [RFC6119] Harrison, J., Berger, J., and M. Bartlett, "IPv6 Traffic 1743 Engineering in IS-IS", RFC 6119, DOI 10.17487/RFC6119, 1744 February 2011, . 1746 [RFC7794] Ginsberg, L., Ed., Decraene, B., Previdi, S., Xu, X., and 1747 U. Chunduri, "IS-IS Prefix Attributes for Extended IPv4 1748 and IPv6 Reachability", RFC 7794, DOI 10.17487/RFC7794, 1749 March 2016, . 1751 [RFC7981] Ginsberg, L., Previdi, S., and M. Chen, "IS-IS Extensions 1752 for Advertising Router Information", RFC 7981, 1753 DOI 10.17487/RFC7981, October 2016, 1754 . 1756 10.2. Informative References 1758 [I-D.ietf-6man-segment-routing-header] 1759 Previdi, S., Filsfils, C., Field, B., Leung, I., Linkova, 1760 J., Aries, E., Kosugi, T., Vyncke, E., and D. Lebrun, 1761 "IPv6 Segment Routing Header (SRH)", draft-ietf-6man- 1762 segment-routing-header-02 (work in progress), September 1763 2016. 1765 [I-D.ietf-spring-resiliency-use-cases] 1766 Filsfils, C., Previdi, S., Decraene, B., and R. Shakir, 1767 "Resiliency use cases in SPRING networks", draft-ietf- 1768 spring-resiliency-use-cases-08 (work in progress), October 1769 2016. 1771 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 1772 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 1773 Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001, 1774 . 1776 [RFC3477] Kompella, K. and Y. Rekhter, "Signalling Unnumbered Links 1777 in Resource ReSerVation Protocol - Traffic Engineering 1778 (RSVP-TE)", RFC 3477, DOI 10.17487/RFC3477, January 2003, 1779 . 1781 [RFC5311] McPherson, D., Ed., Ginsberg, L., Previdi, S., and M. 1782 Shand, "Simplified Extension of Link State PDU (LSP) Space 1783 for IS-IS", RFC 5311, DOI 10.17487/RFC5311, February 2009, 1784 . 1786 [RFC5316] Chen, M., Zhang, R., and X. Duan, "ISIS Extensions in 1787 Support of Inter-Autonomous System (AS) MPLS and GMPLS 1788 Traffic Engineering", RFC 5316, DOI 10.17487/RFC5316, 1789 December 2008, . 1791 [RFC7855] Previdi, S., Ed., Filsfils, C., Ed., Decraene, B., 1792 Litkowski, S., Horneffer, M., and R. Shakir, "Source 1793 Packet Routing in Networking (SPRING) Problem Statement 1794 and Requirements", RFC 7855, DOI 10.17487/RFC7855, May 1795 2016, . 1797 Authors' Addresses 1799 Stefano Previdi (editor) 1800 Cisco Systems, Inc. 1801 Via Del Serafico, 200 1802 Rome 00142 1803 Italy 1805 Email: sprevidi@cisco.com 1807 Clarence Filsfils 1808 Cisco Systems, Inc. 1809 Brussels 1810 BE 1812 Email: cfilsfil@cisco.com 1814 Ahmed Bashandy 1815 Cisco Systems, Inc. 1816 170, West Tasman Drive 1817 San Jose, CA 95134 1818 US 1820 Email: bashandy@cisco.com 1822 Hannes Gredler 1823 RtBrick Inc. 1825 Email: hannes@rtbrick.com 1827 Stephane Litkowski 1828 Orange 1829 FR 1831 Email: stephane.litkowski@orange.com 1832 Bruno Decraene 1833 Orange 1834 FR 1836 Email: bruno.decraene@orange.com 1838 Jeff Tantsura 1839 Individual 1841 Email: jefftant@gmail.com