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'ISO10589' ** Obsolete normative reference: RFC 4971 (Obsoleted by RFC 7981) == Outdated reference: draft-ietf-6man-segment-routing-header has been published as RFC 8754 == Outdated reference: draft-ietf-spring-resiliency-use-cases has been published as RFC 8355 Summary: 1 error (**), 0 flaws (~~), 6 warnings (==), 9 comments (--).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: December 15, 2016 Cisco Systems, Inc. 6 H. Gredler 7 Individual 8 S. Litkowski 9 B. Decraene 10 Orange 11 J. Tantsura 12 Ericsson 13 June 13, 2016 15 IS-IS Extensions for Segment Routing 16 draft-ietf-isis-segment-routing-extensions-07 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 December 15, 2016. 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 . . . . . . . . . . . . . . . . . 3 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 . . . . . . . . . . . . . . 9 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 . . . . . . . . . . . . . . . . . . 14 77 2.4.1. Flags . . . . . . . . . . . . . . . . . . . . . . . . 15 78 2.4.2. Weight . . . . . . . . . . . . . . . . . . . . . . . 16 79 2.4.3. Range . . . . . . . . . . . . . . . . . . . . . . . . 17 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 . . . . . . . . . . . . . . . . . . 20 83 2.4.7. ERO Metric sub-TLV . . . . . . . . . . . . . . . . . 20 84 2.4.8. IPv4 ERO subTLV . . . . . . . . . . . . . . . . . . . 20 85 2.4.9. IPv6 ERO subTLV . . . . . . . . . . . . . . . . . . . 21 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 . . . . . . . . . . . . . . . 23 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 . . . . . . . . . . 25 93 3. Router Capabilities . . . . . . . . . . . . . . . . . . . . . 26 94 3.1. SR-Capabilities Sub-TLV . . . . . . . . . . . . . . . . . 26 95 3.2. SR-Algorithm Sub-TLV . . . . . . . . . . . . . . . . . . 28 97 4. Non backward compatible changes with prior versions of this 98 document . . . . . . . . . . . . . . . . . . . . . . . . . . 29 99 4.1. Encoding of Multiple SRGBs . . . . . . . . . . . . . . . 29 100 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 30 101 5.1. Sub TLVs for Type 22,23,222 and 223 . . . . . . . . . . . 30 102 5.2. Sub TLVs for Type 135,235,236 and 237 . . . . . . . . . . 31 103 5.3. Sub TLVs for Type 242 . . . . . . . . . . . . . . . . . . 31 104 5.4. New TLV Codepoint and Sub-TLV registry . . . . . . . . . 31 105 6. Manageability Considerations . . . . . . . . . . . . . . . . 34 106 7. Security Considerations . . . . . . . . . . . . . . . . . . . 34 107 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 34 108 9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 34 109 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 35 110 10.1. Normative References . . . . . . . . . . . . . . . . . . 35 111 10.2. Informative References . . . . . . . . . . . . . . . . . 36 112 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 37 114 1. Introduction 116 Segment Routing (SR) allows for a flexible definition of end-to-end 117 paths within IGP topologies by encoding paths as sequences of 118 topological sub-paths, called "segments". These segments are 119 advertised by the link-state routing protocols (IS-IS and OSPF). Two 120 types of segments are defined, Prefix segments and Adjacency 121 segments. Prefix segments represent an ecmp-aware shortest-path to a 122 prefix, as per the state of the IGP topology. Adjacency segments 123 represent a hop over a specific adjacency between two nodes in the 124 IGP. A prefix segment is typically a multi-hop path while an 125 adjacency segment, in most of the cases, is a one-hop path. SR's 126 control-plane can be applied to both IPv6 and MPLS data-planes, and 127 do not require any additional signaling (other than the regular IGP). 128 For example, when used in MPLS networks, SR paths do not require any 129 LDP or RSVP-TE signaling. Still, SR can interoperate in the presence 130 of LSPs established with RSVP or LDP. 132 This draft describes the necessary IS-IS extensions that need to be 133 introduced for Segment Routing. 135 Segment Routing architecture is described in 136 [I-D.ietf-spring-segment-routing]. 138 Segment Routing use cases are described in [RFC7855]. 140 2. Segment Routing Identifiers 142 Segment Routing architecture ([I-D.ietf-spring-segment-routing]) 143 defines different types of Segment Identifiers (SID). This document 144 defines the IS-IS encodings for the IGP-Prefix-SID, the IGP- 145 Adjacency-SID, the IGP-LAN-Adjacency-SID and the Binding-SID. 147 2.1. Prefix Segment Identifier (Prefix-SID Sub-TLV) 149 A new IS-IS sub-TLV is defined: the Prefix Segment Identifier sub-TLV 150 (Prefix-SID sub-TLV). 152 The Prefix-SID sub-TLV carries the Segment Routing IGP-Prefix-SID as 153 defined in [I-D.ietf-spring-segment-routing]. The 'Prefix SID' MUST 154 be unique within a given IGP domain (when the L-flag is not set). 155 The 'Prefix SID' MUST carry an index (when the V-flag is not set) 156 that determines the actual SID/label value inside the set of all 157 advertised SID/label ranges of a given router. A receiving router 158 uses the index to determine the actual SID/label value in order to 159 construct forwarding state to a particular destination router. 161 In many use-cases a 'stable transport' IP Address is overloaded as an 162 identifier of a given node. Because the IP Prefixes may be re- 163 advertised into other levels there may be some ambiguity (e.g. 164 Originating router vs. L1L2 router) for which node a particular IP 165 prefix serves as identifier. The Prefix-SID sub-TLV contains the 166 necessary flags to disambiguate IP Prefix to node mappings. 167 Furthermore if a given node has several 'stable transport' IP 168 addresses there are flags to differentiate those among other IP 169 Prefixes advertised from a given node. 171 A Prefix-SID sub-TLV is associated to a prefix advertised by a node 172 and MAY be present in any of the following TLVs: 174 TLV-135 (IPv4) defined in [RFC5305]. 176 TLV-235 (MT-IPv4) defined in [RFC5120]. 178 TLV-236 (IPv6) defined in [RFC5308]. 180 TLV-237 (MT-IPv6) defined in [RFC5120]. 182 Binding-TLV defined in Section 2.4. 184 When the IP Reachability TLV is propagated across level boundaries, 185 the Prefix-SID sub-TLV SHOULD be kept. 187 The Prefix-SID sub-TLV has the following format: 189 0 1 2 3 190 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 1 191 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 192 | Type | Length | Flags | Algorithm | 193 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 194 | SID/Index/Label (variable) | 195 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 197 where: 199 Type: TBD, suggested value 3 201 Length: variable. 203 Flags: 1 octet field of following flags: 205 0 1 2 3 4 5 6 7 206 +-+-+-+-+-+-+-+-+ 207 |R|N|P|E|V|L| | 208 +-+-+-+-+-+-+-+-+ 210 where: 212 R-Flag: Re-advertisement flag. If set, then the prefix to 213 which this Prefix-SID is attached, has been propagated by the 214 router either from another level (i.e.: from level-1 to level-2 215 or the opposite) or from redistribution (e.g.: from another 216 protocol). 218 N-Flag: Node-SID flag. If set, then the Prefix-SID refers to 219 the router identified by the prefix. Typically, the N-Flag is 220 set on Prefix-SIDs attached to a router loopback address. The 221 N-Flag is set when the Prefix-SID is a Node-SID as described in 222 [I-D.ietf-spring-segment-routing]. 224 P-Flag: no-PHP flag. If set, then the penultimate hop MUST NOT 225 pop the Prefix-SID before delivering the packet to the node 226 that advertised the Prefix-SID. 228 E-Flag: Explicit-Null Flag. If set, any upstream neighbor of 229 the Prefix-SID originator MUST replace the Prefix-SID with a 230 Prefix-SID having an Explicit-NULL value (0 for IPv4 and 2 for 231 IPv6) before forwarding the packet. 233 V-Flag: Value flag. If set, then the Prefix-SID carries a 234 value (instead of an index). By default the flag is UNSET. 236 L-Flag: Local Flag. If set, then the value/index carried by 237 the Prefix-SID has local significance. By default the flag is 238 UNSET. 240 Other bits: MUST be zero when originated and ignored when 241 received. 243 Algorithm: the router may use various algorithms when calculating 244 reachability to other nodes or to prefixes attached to these 245 nodes. Algorithms identifiers are defined in Section 3.2. 246 Examples of these algorithms are metric based Shortest Path First 247 (SPF), various sorts of Constrained SPF, etc. The algorithm field 248 of the Prefix-SID contains the identifier of the algorithm the 249 router has used in order to compute the reachability of the prefix 250 the Prefix-SID is associated to. 252 At origination, the Prefix-SID algorithm field MUST be set to 0 on 253 all Prefix-SID of prefixes computed using SPF algorithm (Shortest 254 Path First). On reception of the Prefix-SID sub-TLV, any non-zero 255 algorithm value MUST match what advertised in the SR-Algorithm 256 sub-TLV (Section 3.2). 258 A router receiving a Prefix-SID from a remote node and with an 259 algorithm value that such remote node has not advertised in the 260 SR-Algorithm sub-TLV (Section 3.2) MUST ignore the Prefix-SID sub- 261 TLV. 263 SID/Index/Label: according to the V and L flags, it contains 264 either: 266 * A 4 octet index defining the offset in the SID/Label space 267 advertised by this router using the encodings defined in 268 Section 3.1. In this case the V and L flags MUST be unset. 270 * A 3 octet local label where the 20 rightmost bits are used for 271 encoding the label value. In this case the V and L flags MUST 272 be set. 274 2.1.1. Flags 276 2.1.1.1. R and N Flags 278 The R-Flag MUST be set for prefixes that are not local to the router 279 and either: 281 advertised because of propagation (Level-1 into Level-2); 283 advertised because of leaking (Level-2 into Level-1); 284 advertised because of redistribution (e.g.: from another 285 protocol). 287 In the case where a Level-1-2 router has local interface addresses 288 configured in one level, it may also propagate these addresses into 289 the other level. In such case, the Level-1-2 router MUST NOT set the 290 R bit. The R-bit MUST be set only for prefixes that are not local to 291 the router and advertised by the router because of propagation and/or 292 leaking. 294 The N-Flag is used in order to define a Node-SID. A router MAY set 295 the N-Flag only if all of the following conditions are met: 297 The prefix to which the Prefix-SID is attached is local to the 298 router. I.e.: the prefix is configured on one of the local 299 interfaces. (e.g.: 'stable transport' loopback). 301 The prefix to which the Prefix-SID is attached MUST have a Prefix 302 length of either /32 (IPv4) or /128 (IPv6). 304 The router MUST ignore the N-Flag on a received Prefix-SID if the 305 prefix has a Prefix length different than /32 (IPv4) or /128 (IPv6). 307 [I-D.ietf-isis-prefix-attributes] also defines the N and R flags and 308 with the same semantics of the equivalent flags defined in this 309 document. There will be a transition period where both sets of flags 310 will be used and eventually only the flags of the Prefix Attributes 311 will remain. During the transition period implementations supporting 312 the N and R flags defined in this document and the N and R flags 313 defined in [I-D.ietf-isis-prefix-attributes] MUST advertise and parse 314 all flags. In case the received flags have different values, the 315 value of the flags defined in [I-D.ietf-isis-prefix-attributes] 316 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 672 o 2 octets of Range 674 o 1 octet of Prefix Length 676 o 0-16 octets of FEC Prefix 678 o sub-TLVs, where each sub-TLV consists of a sequence of: 680 * 1 octet of sub-TLV type 682 * 1 octet of length of the value field of the sub-TLV 684 * 0-243 octets of value 686 2.4.1. Flags 688 Flags: 1 octet field of following flags: 690 0 1 2 3 4 5 6 7 691 +-+-+-+-+-+-+-+-+ 692 |F|M|S|D|A| | 693 +-+-+-+-+-+-+-+-+ 695 where: 697 F-Flag: Address Family flag. If unset, then the Prefix FEC 698 carries an IPv4 Prefix. If set then the Prefix FEC carries an 699 IPv6 Prefix. 701 M-Flag: Mirror Context flag. Set if the advertised SID/path 702 corresponds to a mirrored context. The use of the M flag is 703 described in [I-D.ietf-spring-segment-routing]. 705 S-Flag: If set, the SID/Label Binding TLV SHOULD be flooded across 706 the entire routing domain. If the S flag is not set, the SID/ 707 Label Binding TLV MUST NOT be leaked between levels. This bit 708 MUST NOT be altered during the TLV leaking. 710 D-Flag: when the SID/Label Binding TLV is leaked from level-2 to 711 level-1, the D bit MUST be set. Otherwise, this bit MUST be 712 clear. SID/Label Binding TLVs with the D bit set MUST NOT be 713 leaked from level-1 to level-2. This is to prevent TLV looping 714 across levels. 716 A-Flag: Attached flag. The originator of the SID/Label Binding 717 TLV MAY set the A bit in order to signal that the prefixes and 718 SIDs advertised in the SID/Label Binding TLV are directly 719 connected to their originators. The mechanisms through which the 720 originator of the SID/Label Binding TLV can figure out if a prefix 721 is attached or not are outside the scope of this document (e.g.: 722 through explicit configuration). If the Binding TLV is leaked to 723 other areas/levels the A-flag MUST be cleared. 725 An implementation MAY decide not to honor the S-flag in order not 726 to leak Binding TLV's between levels (for policy reasons). In all 727 cases, the D flag MUST always be set by any router leaking the 728 Binding TLV from level-2 into level-1 and MUST be checked when 729 propagating the Binding TLV from level-1 into level-2. If the D 730 flag is set, the Binding TLV MUST NOT be propagated into level-2. 732 Other bits: MUST be zero when originated and ignored when 733 received. 735 2.4.2. Weight 737 Weight: 1 octet: The value represents the weight of the path for the 738 purpose of load balancing. The use of the weight is defined in 739 [I-D.ietf-spring-segment-routing]. 741 2.4.3. Range 743 The 'Range' field provides the ability to specify a range of 744 addresses and their associated Prefix SIDs. This functionality is 745 called "Mapping Server". It is essentially a compression scheme to 746 distribute a continuous Prefix and their continuous, corresponding 747 SID/Label Block. If a single SID is advertised then the range field 748 MUST be set to one. For range advertisements > 1, the number of 749 addresses that need to be mapped into a Prefix-SID and the starting 750 value of the Prefix-SID range. 752 Example 1: if the following router addresses (loopback addresses) 753 need to be mapped into the corresponding Prefix SID indexes. 755 Router-A: 192.0.2.1/32, Prefix-SID: Index 1 756 Router-B: 192.0.2.2/32, Prefix-SID: Index 2 757 Router-C: 192.0.2.3/32, Prefix-SID: Index 3 758 Router-D: 192.0.2.4/32, Prefix-SID: Index 4 760 0 1 2 3 761 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 1 762 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 763 | Type | Length |0|0| | Weight | 764 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 765 | Range = 4 | /32 | 192 | 766 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 767 | .0 | .2 | .1 |Prefix-SID Type| 768 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 769 | sub-TLV Length| Flags | Algorithm | | 770 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 771 | 1 | 772 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 774 Example-2: If the following prefixes need to be mapped into the 775 corresponding Prefix-SID indexes: 777 10.1.1/24, Prefix-SID: Index 51 778 10.1.2/24, Prefix-SID: Index 52 779 10.1.3/24, Prefix-SID: Index 53 780 10.1.4/24, Prefix-SID: Index 54 781 10.1.5/24, Prefix-SID: Index 55 782 10.1.6/24, Prefix-SID: Index 56 783 10.1.7/24, Prefix-SID: Index 57 784 0 1 2 3 785 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 1 786 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 787 | Type | Length |0|0| | Weight | 788 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 789 | Range = 7 | /24 | 10 | 790 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 791 | .1 | .1 |Prefix-SID Type| sub-TLV Length| 792 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 793 | Flags | Algorithm | | 794 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 795 | 51 | 796 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 798 It is not expected that a network operator will be able to keep fully 799 continuous FEC Prefix / SID/Index mappings. In order to support 800 noncontinuous mapping ranges an implementation MAY generate several 801 instances of Binding TLVs. 803 For example if a router wants to advertise the following ranges: 805 Range 16: { 192.0.2.1-15, Index 1-15 } 807 Range 6: { 192.0.2.22-27, Index 22-27 } 809 Range 41: { 192.0.2.44-84, Index 80-120 } 811 A router would need to advertise three instances of the Binding TLV. 813 2.4.4. Prefix Length, Prefix 815 The 'FEC Prefix' represents the Forwarding equivalence class at the 816 tail-end of the advertised path. The 'FEC Prefix' does not need to 817 correspond to a routable prefix of the originating node. 819 The 'Prefix Length' field contains the length of the prefix in bits. 820 Only the most significant octets of the Prefix FEC are encoded. I.e. 821 1 octet for FEC prefix length 1 up to 8, 2 octets for FEC prefix 822 length 9 to 16, 3 octets for FEC prefix length 17 up to 24 and 4 823 octets for FEC prefix length 25 up to 32, ...., 16 octets for FEC 824 prefix length 113 up to 128. 826 2.4.5. Mapping Server Prefix-SID 828 The Prefix-SID sub-TLV (suggested value 3) is defined in Section 2.1 829 and contains the SID/index/label value associated with the prefix and 830 range. The Prefix-SID SubTLV MUST be used when the SID/Label Binding 831 TLV is used by the Mapping Server (i.e.: advertising one or a range 832 of prefixes and their associated SIDs/Labels). 834 A node receiving a MS entry for a prefix MUST check the existence of 835 such prefix in its link-state database prior to consider and use the 836 associated SID. 838 For a given prefix, if both a MS entry with its Prefix-SID Sub-TLV 839 and a Prefix TLV (e.g.: TLV135) with its Prefix-SID are received, the 840 Prefix-SID advertised within the Prefix TLV MUST be preferred while 841 the MS entry MUST be ignored. 843 2.4.5.1. Prefix-SID Flags 845 The Prefix-SID flags are defined in Section 2.1. The Mapping Server 846 MAY advertise a mapping with the N flag set when the prefix being 847 mapped is known in the link-state topology with a mask length of 32 848 (IPv4) or 128 (IPv6) and when the prefix represents a node. The 849 mechanisms through which the operator defines that a prefix 850 represents a node are outside the scope of this document (typically 851 it will be through configuration). 853 The other flags defined in Section 2.1 are not used by the Mapping 854 Server and MUST be ignored at reception. 856 2.4.5.2. PHP Behavior when using Mapping Server Advertisements 858 As the mapping server does not specify the originator of a prefix 859 advertisement it is not possible to determine PHP behavior solely 860 based on the Mapping Server Advertisement. However, if additional 861 information is available PHP behavior may safely be done. The 862 required information consists of: 864 o A prefix reachability advertisement for the prefix has been 865 received which includes the Extended Reachability Attribute Flags 866 sub-TLV ([I-D.ietf-isis-prefix-attributes]). 868 o X and R flags are both set to 0 in the Extended Reachability 869 Attribute Flags sub-TLV. 871 In the absence of an Extended Reachability Attribute Flags sub-TLV 872 ([I-D.ietf-isis-prefix-attributes]) the A flag in the binding TLV 873 indicates that the originator of a prefix reachability advertisement 874 is directly connected to the prefix and thus PHP MUST be done by the 875 neighbors of the router originating the prefix reachability 876 advertisement. Note that A-flag is only valid in the original area 877 in which the Binding TLV is advertised. 879 2.4.5.3. Prefix-SID Algorithm 881 The algorithm field contains the identifier of the algorithm the 882 router MUST use in order to compute reachability to the range of 883 prefixes. Use of the algorithm field is described in Section 2.1. 885 2.4.6. SID/Label Sub-TLV 887 The SID/Label sub-TLV (Type: TBD, suggested value 1) contains the 888 SID/Label value as defined in Section 2.3. It MAY be present in the 889 SID/Label Binding TLV. 891 2.4.7. ERO Metric sub-TLV 893 ERO Metric sub-TLV (Type: TBD, suggested value 10) is a sub-TLV of 894 the SID/Label Binding TLV. 896 The ERO Metric sub-TLV carries the cost of an ERO path. It is used 897 to compare the cost of a given source/destination path. A router MAY 898 advertise the ERO Metric sub-TLV. The cost of the ERO Metric sub-TLV 899 SHOULD be set to the cumulative IGP or TE path cost of the advertised 900 ERO. Since manipulation of the Metric field may attract or distract 901 traffic from and to the advertised segment it MAY be manually 902 overridden. 904 0 1 2 3 905 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 1 906 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 907 | Type | Length | Metric | 908 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 909 | Metric (continued) | 910 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 912 ERO Metric sub-TLV format 914 where: 916 Type: TBD, suggested value 10 918 Length: 4 920 Metric: 4 bytes 922 2.4.8. IPv4 ERO subTLV 924 The IPv4 ERO subTLV (Type: TBD, suggested value 11) describes a path 925 segment using IPv4 address style of encoding. Its semantics have 926 been borrowed from [RFC3209]. 928 The 'L' bit in the Flags is a one-bit attribute. If the L bit is 929 set, then the value of the attribute is 'loose.' Otherwise, the 930 value of the attribute is 'strict.' 932 0 1 2 3 933 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 1 934 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 935 | Type | Length |L| Reserved | IPv4 address | 936 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 937 | IPv4 address (continued) | 938 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 940 Figure 2: IPv4 ERO subTLV format 942 2.4.9. IPv6 ERO subTLV 944 The IPv6 ERO subTLV (Type: TBD, suggested value 12) describes a path 945 segment using IPv6 Address style of encoding. Its semantics have 946 been borrowed from [RFC3209]. 948 The 'L' bit in the Flags is a one-bit attribute. If the L bit is 949 set, then the value of the attribute is 'loose.' Otherwise, the 950 value of the attribute is 'strict.' 952 0 1 2 3 953 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 1 954 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 955 | Type | Length |L| Reserved | IPv6 address | 956 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 957 | IPv6 Address (continued) | 958 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 959 | IPv6 Address (continued) | 960 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 961 | IPv6 Address (continued) | 962 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 963 | IPv6 Address (continued) | 964 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 966 Figure 3: IPv6 ERO subTLV format 968 2.4.10. Unnumbered Interface ID ERO subTLV 970 The appearance and semantics of the 'Unnumbered Interface ID' have 971 been borrowed from Section 4 [RFC3477]. 973 The Unnumbered Interface-ID ERO subTLV (Type: TBD, suggested value 974 13) describes a path segment that spans over an unnumbered interface. 975 Unnumbered interfaces are referenced using the interface index. 977 Interface indices are assigned local to the router and therefore not 978 unique within a domain. All elements in an ERO path need to be 979 unique within a domain and hence need to be disambiguated using a 980 domain unique Router-ID. 982 The 'Router-ID' field contains the router ID of the router which has 983 assigned the 'Interface ID' field. Its purpose is to disambiguate 984 the 'Interface ID' field from other routers in the domain. 986 IS-IS supports two Router-ID formats: 988 o (TLV 134, 32-Bit format) [RFC5305] 990 o (TLV 140, 128-Bit format) [RFC6119] 992 The actual Router-ID format gets derived from the 'Length' field. 994 o For 32-Bit Router-ID width the subTLV length is set to 8 octets. 996 o For 128-Bit Router-ID width the subTLV length is set to 20 octets. 998 The 'Interface ID' is the identifier assigned to the link by the 999 router specified by the router ID. 1001 The 'L' bit in the Flags is a one-bit attribute. If the L bit is 1002 set, then the value of the attribute is 'loose.' Otherwise, the 1003 value of the attribute is 'strict.' 1005 0 1 2 3 1006 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 1007 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1008 | Type | Length |L| Reserved | 1009 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1010 // Router ID (32 or 128 bits) // 1011 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1012 | Interface ID (32 bits) | 1013 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1015 Figure 4: Unnumbered Interface ID ERO subTLV format 1017 2.4.11. IPv4 Backup ERO subTLV 1019 The IPv4 Backup ERO subTLV (Type: TBD, suggested value 14) describes 1020 a Backup path segment using IPv4 Address style of encoding. Its 1021 appearance and semantics have been borrowed from [RFC3209]. 1023 The 'L' bit in the Flags is a one-bit attribute. If the L bit is 1024 set, then the value of the attribute is 'loose.' Otherwise, the 1025 value of the attribute is 'strict.' 1027 0 1 2 3 1028 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 1029 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1030 | Type | Length |L| Reserved | IPv4 address | 1031 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1032 | IPv4 address (continued) | 1033 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1035 Figure 5: IPv4 Backup ERO subTLV format 1037 2.4.12. IPv6 Backup ERO subTLV 1039 The IPv6 Backup ERO subTLV (Type: TBD, suggested value 15) describes 1040 a Backup path segment using IPv6 Address style of encoding. Its 1041 appearance and semantics have been borrowed from [RFC3209]. 1043 The 'L' bit in the Flags is a one-bit attribute. If the L bit is 1044 set, then the value of the attribute is 'loose.' Otherwise, the 1045 value of the attribute is 'strict.' 1047 0 1 2 3 1048 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 1049 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1050 | Type | Length |L| Reserved | IPv6 address | 1051 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1052 | IPv6 Address (continued) | 1053 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1054 | IPv6 Address (continued) | 1055 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1056 | IPv6 Address (continued) | 1057 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1058 | IPv6 Address (continued) | 1059 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1061 Figure 6: IPv6 Backup ERO subTLV format 1063 2.4.13. Unnumbered Interface ID Backup ERO subTLV 1065 The appearance and semantics of the 'Unnumbered Interface ID' have 1066 been borrowed from Section 4 [RFC3477]. 1068 The Unnumbered Interface-ID Backup ERO subTLV (Type: TBD, suggested 1069 value 16) describes a Backup LSP path segment that spans over an 1070 unnumbered interface. Unnumbered interfaces are referenced using the 1071 interface index. Interface indices are assigned local to the router 1072 and therefore not unique within a domain. All elements in an ERO 1073 path need to be unique within a domain and hence need to be 1074 disambiguated using a domain unique Router-ID. 1076 The 'Router-ID' field contains the router ID of the router which has 1077 assigned the 'Interface ID' field. Its purpose is to disambiguate 1078 the 'Interface ID' field from other routers in the domain. 1080 IS-IS supports two Router-ID formats: 1082 o (TLV 134, 32-Bit format) [RFC5305] 1084 o (TLV 140, 128-Bit format) [RFC6119] 1086 The actual Router-ID format gets derived from the 'Length' field. 1088 o For 32-Bit Router-ID width the subTLV length is set to 8 octets. 1090 o For 128-Bit Router-ID width the subTLV length is set to 20 octets. 1092 The 'Interface ID' is the identifier assigned to the link by the 1093 router specified by the router ID. 1095 The 'L' bit in the Flags is a one-bit attribute. If the L bit is 1096 set, then the value of the attribute is 'loose.' Otherwise, the 1097 value of the attribute is 'strict.' 1099 0 1 2 3 1100 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 1101 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1102 | Type | Length |L| Reserved | 1103 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1104 // Router ID (32 or 128 bits) // 1105 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1106 | Interface ID (32 bits) | 1107 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1109 Figure 7: Unnumbered Interface ID Backup ERO subTLV format 1111 2.4.14. Prefix ERO and Prefix Backup ERO subTLV path semantics 1113 All 'ERO' and 'Backup ERO' information represents an ordered set 1114 which describes the segments of a path. The last ERO subTLV 1115 describes the segment closest to the egress point of the path. 1116 Contrary the first ERO subTLV describes the first segment of a path. 1117 If a router extends or stitches a label switched path it MUST prepend 1118 the new segments path information to the ERO list. The same ordering 1119 applies for the Backup ERO labels. An implementation SHOULD first 1120 encode all primary path EROs followed by the bypass EROs. 1122 2.5. Multi-Topology SID/Label Binding TLV 1124 The Multi-Topology SID/Label Binding TLV allows the support of M-ISIS 1125 as defined in [RFC5120]. The Multi-Topology SID/Label Binding TLV 1126 has the same format as the SID/Label Binding TLV defined in 1127 Section 2.4 with the difference consisting of a Multitopology 1128 Identifier (MTID) as defined here below: 1130 0 1 2 3 1131 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 1132 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1133 | Type | Length | MTID | 1134 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1135 | Flags | Weight | Range | 1136 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1137 | Prefix Length | FEC Prefix | FEC Prefix (variable) | 1138 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1139 | SubTLVs (variable) | 1140 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1142 Figure 8: Multi-Topology SID/Label Binding TLV format 1144 where: 1146 Type: TBD, suggested value 150 1148 Length: variable 1150 MTID is the multitopology identifier defined as: 1152 0 1 1153 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 1154 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1155 | RESVD | MTID | 1156 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1158 RESVD: reserved bits. MUST be reset on transmission and 1159 ignored on receive. 1161 MTID: a 12-bit field containing the non-zero ID of the topology 1162 being announced. The TLV MUST be ignored if the ID is zero. 1163 This is to ensure the consistent view of the standard unicast 1164 topology. 1166 The other fields and SubTLVs are defined in Section 2.4. 1168 3. Router Capabilities 1170 3.1. SR-Capabilities Sub-TLV 1172 Segment Routing requires each router to advertise its SR data-plane 1173 capability and the range of MPLS label values it uses for Segment 1174 Routing in the case where global SIDs are allocated (i.e.: global 1175 indexes). Data-plane capabilities and label ranges are advertised 1176 using the newly defined SR-Capabilities sub-TLV inserted into the IS- 1177 IS Router Capability TLV-242 that is defined in [RFC4971]. 1179 The Router Capability TLV specifies flags that control its 1180 advertisement. The SR Capabilities sub-TLV MUST be propagated 1181 throughout the level and SHOULD NOT be advertised across level 1182 boundaries. Therefore Router Capability TLV distribution flags 1183 SHOULD be set accordingly, i.e.: the S flag in the Router Capability 1184 TLV ([RFC4971]) MUST be unset. 1186 The SR Capabilities sub-TLV has following format: 1188 0 1 2 3 1189 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 1190 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1191 | Type | Length | Flags | 1192 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1194 Type: TBD, suggested value 2 1196 Length: variable. 1198 Flags: 1 octet of flags. The following are defined: 1200 0 1 2 3 4 5 6 7 1201 +-+-+-+-+-+-+-+-+ 1202 |I|V|H| | 1203 +-+-+-+-+-+-+-+-+ 1205 where: 1207 I-Flag: MPLS IPv4 flag. If set, then the router is capable of 1208 processing SR MPLS encapsulated IPv4 packets on all interfaces. 1210 V-Flag: MPLS IPv6 flag. If set, then the router is capable of 1211 processing SR MPLS encapsulated IPv6 packets on all interfaces. 1213 H-Flag: SR-IPv6 flag. If set, then the router is capable of 1214 processing the IPv6 Segment Routing Header on all interfaces as 1215 defined in [I-D.ietf-6man-segment-routing-header]. 1217 One or more SRGB Descriptor entries, each of which have the 1218 following format: 1220 Range: 3 octets. 1222 SID/Label sub-TLV (as defined in Section 2.3). 1224 SID/Label sub-TLV contains the first value of the SRGB while the 1225 range contains the number of SRGB elements. The range value MUST be 1226 higher than 0. 1228 The SR-Capabilities sub-TLV MAY be advertised in an LSP of any number 1229 but a router MUST NOT advertise more than one SR-Capabilities sub- 1230 TLV. When multiple SR-Capabilities sub-TLVs are received from a 1231 given router the behavior of the receiving system is undefined. 1233 When multiple SRGB Descriptors are advertised the entries define an 1234 ordered set of ranges on which a SID index is to be applied. For 1235 this reason changing the order in which the descriptors are 1236 advertised will have a disruptive effect on forwarding. 1238 When a router adds a new SRGB Descriptor to an existing SR- 1239 Capabilities sub-TLV the new Descriptor SHOULD add the newly 1240 configured block at the end of the sub-TLV and SHOULD NOT change the 1241 order of previously advertised blocks. Changing the order of the 1242 advertised descriptors will create label churn in the FIB and 1243 blackhole / misdirect some traffic during the IGP convergence. In 1244 particular, if a range which is not the last is extended it's 1245 preferable to add a new range rather than extending the previously 1246 advertised range. 1248 The originating router MUST ensure the order is same after a graceful 1249 restart (using checkpointing, non-volatile storage or any other 1250 mechanism) in order to guarantee the same order before and after GR. 1252 The originating router MUST NOT advertise overlapping ranges. 1254 When a router receives multiple overlapping ranges, it MUST conform 1255 to the procedures defined in [I-D.ietf-spring-conflict-resolution]. 1257 Here follows an example of advertisement of multiple ranges: 1259 The originating router advertises following ranges: 1260 SR-Cap: range: 100, SID value: 100 1261 SR-Cap: range: 100, SID value: 1000 1262 SR-Cap: range: 100, SID value: 500 1264 The receiving routers concatenate the ranges in the received 1265 order and build the SRGB as follows: 1267 SRGB = [100, 199] 1268 [1000, 1099] 1269 [500, 599] 1271 The indexes span multiple ranges: 1273 index=0 means label 100 1274 ... 1275 index 99 means label 199 1276 index 100 means label 1000 1277 index 199 means label 1099 1278 ... 1279 index 200 means label 500 1280 ... 1282 3.2. SR-Algorithm Sub-TLV 1284 The router may use various algorithms when calculating reachability 1285 to other nodes or to prefixes attached to these nodes. Examples of 1286 these algorithms are metric based Shortest Path First (SPF), various 1287 sorts of Constrained SPF, etc. The SR-Algorithm sub-TLV (Type: TBD, 1288 suggested value 19) allows the router to advertise the algorithms 1289 that the router is currently using. The following value has been 1290 defined: 1292 0: Shortest Path First (SPF) algorithm based on link metric. This 1293 is the well-known shortest path algorithm as computed by the IS-IS 1294 Decision process. Consistent with the deployed practice for link- 1295 state protocols, algorithm 0 permits any node to overwrite the SPF 1296 path with a different path based on local policy. 1298 1: Strict Shortest Path First (SPF) algorithm based on link 1299 metric. The algorithm is identical to algorithm 0 but algorithm 1 1300 requires that all nodes along the path will honor the SPF routing 1301 decision. Local policy MUST NOT alter the forwarding decision 1302 computed by algorithm 1 at the node claiming to support algorithm 1303 1. 1305 The SR-Algorithm sub-TLV is inserted into the IS-IS Router Capability 1306 TLV-242 that is defined in [RFC4971]. 1308 The Router Capability TLV specifies flags that control its 1309 advertisement. The SR-Algorithm MUST be propagated throughout the 1310 level and need not to be advertised across level boundaries. 1311 Therefore Router Capability TLV distribution flags MUST be set 1312 accordingly, i.e.: the S flag MUST be unset. 1314 The SR-Algorithm sub-TLV is optional, it MAY only appear a single 1315 time inside the Router Capability TLV. 1317 When the originating router does not advertise the SR-Algorithm sub- 1318 TLV, then all the Prefix-SID advertised by the router MUST have 1319 algorithm field set to 0. Any receiving router MUST assume SPF 1320 algorithm (i.e.: Shortest Path First). 1322 When the originating router does advertise the SR-Algorithm sub-TLV, 1323 then algorithm 0 MUST be present while algorithm 1 MAY be present. 1325 The SR-Algorithm sub-TLV has following format: 1327 0 1 2 3 1328 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 1329 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1330 | Type | Length | 1331 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1332 | Algorithm 1 | Algorithm 2 | Algorithm ... | Algorithm n | 1333 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1335 where: 1337 Type: TBD, suggested value 19 1339 Length: variable. 1341 Algorithm: 1 octet of algorithm Section 2.1 1343 4. Non backward compatible changes with prior versions of this document 1345 This section describes the changes that have been applied to this 1346 document that are not backward compatible with previous versions. 1348 4.1. Encoding of Multiple SRGBs 1350 Version -04 of this document introduced a change in Section 3.1 1351 regarding the encoding method for multiple SRGBs in the SR-Cap SubTLV 1352 and made the support of multiple SRGBs REQUIRED. 1354 The modified method consists of having a single SR-Cap Sub-TLV where 1355 all SRGBs are encoded. In previous versions (prior to version -04) 1356 of this document it was allowed to have multiple occurrences of the 1357 SR-Cap Sub-TLV. 1359 At the time of writing this document, no existing implementations are 1360 affected by the change since no implementations actually (i.e.: at 1361 the time of updating this document) encode multiple SRGBs anyway. 1363 5. IANA Considerations 1365 This documents request allocation for the following TLVs and subTLVs. 1367 5.1. Sub TLVs for Type 22,23,222 and 223 1369 This document makes the following registrations in the "sub-TLVs for 1370 TLV 22, 23, 222 and 223" registry. 1372 Type: TBD (suggested value 31) 1374 Description: Adjacency Segment Identifier 1376 TLV 22: yes 1378 TLV 23: yes 1380 TLV 222: yes 1382 TLV 223: yes 1384 Reference: This document (Section 2.2.1) 1386 Type: TBD (suggested value 32) 1388 Description: LAN Adjacency Segment Identifier 1390 TLV 22: yes 1392 TLV 23: yes 1394 TLV 222: yes 1396 TLV 223: yes 1398 Reference: This document (Section 2.2.2) 1400 5.2. Sub TLVs for Type 135,235,236 and 237 1402 This document makes the following registrations in the "sub-TLVs for 1403 TLV 135,235,236 and 237" registry. 1405 Type: TBD (suggested value 3) 1407 Description: Prefix Segment Identifier 1409 TLV 135: yes 1411 TLV 235: yes 1413 TLV 236: yes 1415 TLV 237: yes 1417 Reference: This document (Section 2.1) 1419 5.3. Sub TLVs for Type 242 1421 This document makes the following registrations in the "sub-TLVs for 1422 TLV 242" registry. 1424 Type: TBD (suggested value 2) 1426 Description: Segment Routing Capability 1428 Reference: This document (Section 3.1) 1430 Type: TBD (suggested value 19) 1432 Description: Segment Routing Algorithm 1434 Reference: This document (Section 3.2) 1436 5.4. New TLV Codepoint and Sub-TLV registry 1438 This document registers the following TLV: 1440 Type: TBD (suggested value 149) 1442 name: Segment Identifier / Label Binding 1443 IIH: no 1445 LSP: yes 1447 SNP: no 1449 Purge: no 1451 Reference: This document (Section 2.4) 1453 Type: TBD (suggested value 150) 1455 name: Multi-Topology Segment Identifier / Label Binding 1457 IIH: no 1459 LSP: yes 1461 SNP: no 1463 Purge: no 1465 Reference: This document (Section 2.5) 1467 This document creates the following sub-TLV Registry: 1469 Registry: sub-TLVs for TLV 149 and 150 1471 Registration Procedure: Expert review 1473 Reference: This document (Section 2.4) 1475 Type: TBD, suggested value 1 1477 Description: SID/Label 1479 Reference: This document (Section 2.3) 1481 Type: TBD, suggested value 3 1483 Description: Prefix-SID 1485 Reference: This document (Section 2.1) 1486 Type: TBD, suggested value 10 1488 Description: ERO Metric 1490 Reference: This document (Section 2.4.7) 1492 Type: TBD, suggested value 11 1494 Description: IPv4 ERO 1496 Reference: This document (Section 2.4.8) 1498 Type: TBD, suggested value 12 1500 Description: IPv6 ERO 1502 Reference: This document (Section 2.4.9) 1504 Type: TBD, suggested value 13 1506 Description: Unnumbered Interface-ID ERO 1508 Reference: This document (Section 2.4.10) 1510 Type: TBD, suggested value 14 1512 Description: IPv4 Backup ERO 1514 Reference: This document (Section 2.4.11) 1516 Type: TBD, suggested value 15 1518 Description: IPv6 Backup ERO 1520 Reference: This document (Section 2.4.12) 1521 Type: TBD, suggested value 16 1523 Description: Unnumbered Interface-ID Backup ERO 1525 Reference: This document (Section 2.4.13) 1527 6. Manageability Considerations 1529 TBD 1531 7. Security Considerations 1533 TBD 1535 8. Acknowledgements 1537 We would like to thank Dave Ward, Dan Frost, Stewart Bryant, Pierre 1538 Francois and Jesper Skrivers for their contribution to the content of 1539 this document. 1541 Many thanks to Yakov Rekhter and Ina Minei for their contribution on 1542 earlier definition of the "Binding / MPLS Label TLV". 1544 9. Contributors 1546 The following people gave a substantial contribution to the content 1547 of this document and should be considered as co-authors: 1549 Les Ginsberg 1550 Cisco Systems Inc. 1551 US 1553 Email: ginsberg@cisco.com 1555 Martin Horneffer 1556 Deutsche Telekom 1557 DE 1559 Email: Martin.Horneffer@telekom.de 1561 Wim Henderickx 1562 Alcatel-Lucent 1563 BE 1565 Email: wim.henderickx@alcatel-lucent.com 1566 Edward Crabbe 1567 Individual 1568 US 1570 Email: edward.crabbe@gmail.com 1572 Rob Shakir 1573 Individual 1574 UK 1576 Email: rjs@rob.sh 1578 Igor Milojevic 1579 Individual 1580 RS 1582 Email: milojevicigor@gmail.com 1584 Saku Ytti 1585 TDC 1586 FI 1588 Email: saku@ytti.fi 1590 Steven Luong 1591 Cisco Systems Inc. 1592 US 1594 Email: sluong@cisco.com 1596 10. References 1598 10.1. Normative References 1600 [I-D.ietf-isis-prefix-attributes] 1601 Ginsberg, L., Decraene, B., Previdi, S., Xu, X., and U. 1602 Chunduri, "IS-IS Prefix Attributes for Extended IP and 1603 IPv6 Reachability", draft-ietf-isis-prefix-attributes-04 1604 (work in progress), January 2016. 1606 [I-D.ietf-spring-conflict-resolution] 1607 Ginsberg, L., Psenak, P., Previdi, S., and M. Pilka, 1608 "Segment Routing Conflict Resolution", draft-ietf-spring- 1609 conflict-resolution-00 (work in progress), May 2016. 1611 [I-D.ietf-spring-segment-routing] 1612 Filsfils, C., Previdi, S., Decraene, B., Litkowski, S., 1613 and R. Shakir, "Segment Routing Architecture", draft-ietf- 1614 spring-segment-routing-08 (work in progress), May 2016. 1616 [ISO10589] 1617 International Organization for Standardization, 1618 "Intermediate system to Intermediate system intra-domain 1619 routeing information exchange protocol for use in 1620 conjunction with the protocol for providing the 1621 connectionless-mode Network Service (ISO 8473)", ISO/ 1622 IEC 10589:2002, Second Edition, Nov 2002. 1624 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1625 Requirement Levels", BCP 14, RFC 2119, 1626 DOI 10.17487/RFC2119, March 1997, 1627 . 1629 [RFC4971] Vasseur, JP., Ed., Shen, N., Ed., and R. Aggarwal, Ed., 1630 "Intermediate System to Intermediate System (IS-IS) 1631 Extensions for Advertising Router Information", RFC 4971, 1632 DOI 10.17487/RFC4971, July 2007, 1633 . 1635 [RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi 1636 Topology (MT) Routing in Intermediate System to 1637 Intermediate Systems (IS-ISs)", RFC 5120, 1638 DOI 10.17487/RFC5120, February 2008, 1639 . 1641 [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic 1642 Engineering", RFC 5305, DOI 10.17487/RFC5305, October 1643 2008, . 1645 [RFC5308] Hopps, C., "Routing IPv6 with IS-IS", RFC 5308, 1646 DOI 10.17487/RFC5308, October 2008, 1647 . 1649 [RFC6119] Harrison, J., Berger, J., and M. Bartlett, "IPv6 Traffic 1650 Engineering in IS-IS", RFC 6119, DOI 10.17487/RFC6119, 1651 February 2011, . 1653 10.2. Informative References 1655 [I-D.ietf-6man-segment-routing-header] 1656 Previdi, S., Filsfils, C., Field, B., Leung, I., Linkova, 1657 J., Kosugi, T., Vyncke, E., and D. Lebrun, "IPv6 Segment 1658 Routing Header (SRH)", draft-ietf-6man-segment-routing- 1659 header-01 (work in progress), March 2016. 1661 [I-D.ietf-spring-resiliency-use-cases] 1662 Francois, P., Filsfils, C., Decraene, B., and R. Shakir, 1663 "Use-cases for Resiliency in SPRING", draft-ietf-spring- 1664 resiliency-use-cases-03 (work in progress), April 2016. 1666 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 1667 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 1668 Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001, 1669 . 1671 [RFC3477] Kompella, K. and Y. Rekhter, "Signalling Unnumbered Links 1672 in Resource ReSerVation Protocol - Traffic Engineering 1673 (RSVP-TE)", RFC 3477, DOI 10.17487/RFC3477, January 2003, 1674 . 1676 [RFC5311] McPherson, D., Ed., Ginsberg, L., Previdi, S., and M. 1677 Shand, "Simplified Extension of Link State PDU (LSP) Space 1678 for IS-IS", RFC 5311, DOI 10.17487/RFC5311, February 2009, 1679 . 1681 [RFC5316] Chen, M., Zhang, R., and X. Duan, "ISIS Extensions in 1682 Support of Inter-Autonomous System (AS) MPLS and GMPLS 1683 Traffic Engineering", RFC 5316, DOI 10.17487/RFC5316, 1684 December 2008, . 1686 [RFC7855] Previdi, S., Ed., Filsfils, C., Ed., Decraene, B., 1687 Litkowski, S., Horneffer, M., and R. Shakir, "Source 1688 Packet Routing in Networking (SPRING) Problem Statement 1689 and Requirements", RFC 7855, DOI 10.17487/RFC7855, May 1690 2016, . 1692 Authors' Addresses 1694 Stefano Previdi (editor) 1695 Cisco Systems, Inc. 1696 Via Del Serafico, 200 1697 Rome 00142 1698 Italy 1700 Email: sprevidi@cisco.com 1701 Clarence Filsfils 1702 Cisco Systems, Inc. 1703 Brussels 1704 BE 1706 Email: cfilsfil@cisco.com 1708 Ahmed Bashandy 1709 Cisco Systems, Inc. 1710 170, West Tasman Drive 1711 San Jose, CA 95134 1712 US 1714 Email: bashandy@cisco.com 1716 Hannes Gredler 1717 Individual 1719 Email: hannes@gredler.at 1721 Stephane Litkowski 1722 Orange 1723 FR 1725 Email: stephane.litkowski@orange.com 1727 Bruno Decraene 1728 Orange 1729 FR 1731 Email: bruno.decraene@orange.com 1733 Jeff Tantsura 1734 Ericsson 1735 300 Holger Way 1736 San Jose, CA 95134 1737 US 1739 Email: Jeff.Tantsura@ericsson.com