idnits 2.17.1 draft-ietf-isis-segment-routing-extensions-12.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- -- The document has examples using IPv4 documentation addresses according to RFC6890, but does not use any IPv6 documentation addresses. Maybe there should be IPv6 examples, too? Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (April 27, 2017) is 2554 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- Looks like a reference, but probably isn't: '100' on line 1260 -- Looks like a reference, but probably isn't: '199' on line 1260 -- Looks like a reference, but probably isn't: '1000' on line 1261 -- Looks like a reference, but probably isn't: '1099' on line 1261 -- Looks like a reference, but probably isn't: '500' on line 1262 -- Looks like a reference, but probably isn't: '599' on line 1262 == Outdated reference: A later version (-05) exists of draft-ietf-spring-conflict-resolution-02 == Outdated reference: A later version (-15) exists of draft-ietf-spring-segment-routing-11 -- Possible downref: Non-RFC (?) normative reference: ref. 'ISO10589' == Outdated reference: A later version (-12) exists of draft-ietf-spring-resiliency-use-cases-08 -- Obsolete informational reference (is this intentional?): RFC 5316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 (~~), 4 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: October 29, 2017 Cisco Systems, Inc. 6 H. Gredler 7 RtBrick Inc. 8 S. Litkowski 9 B. Decraene 10 Orange 11 J. Tantsura 12 Individual 13 April 27, 2017 15 IS-IS Extensions for Segment Routing 16 draft-ietf-isis-segment-routing-extensions-12 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 operating on an MPLS data-plane. 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 October 29, 2017. 50 Copyright Notice 52 Copyright (c) 2017 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 . . . . . . . . . . . . . . . . . . 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 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 operating on an MPLS data-plane. 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 (Extended IPv4 reachability) defined in [RFC5305]. 177 TLV-235 (Multitopology IPv4 Reachability) defined in [RFC5120]. 179 TLV-236 (IPv6 IP Reachability) defined in [RFC5308]. 181 TLV-237 (Multitopology IPv6 IP Reachability) 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 (Extended IS reachability)[RFC5305] 393 TLV-222 (Multitopology IS)[RFC5120] 395 TLV-23 (IS Neighbor Attribute)[RFC5311] 397 TLV-223 (Multitopology IS Neighbor Attribute)[RFC5311] 399 TLV-141 (inter-AS reachability information)[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|P| | 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 P-Flag. Persistent flag. When set, the P-Flag indicates that 452 the Adj-SID is persistently allocated, i.e., the Adj-SID value 453 remains consistent across router restart and/or interface flap. 455 Other bits: MUST be zero when originated and ignored when 456 received. 458 Weight: 1 octet. The value represents the weight of the Adj-SID 459 for the purpose of load balancing. The use of the weight is 460 defined in [I-D.ietf-spring-segment-routing]. 462 SID/Index/Label: according to the V and L flags, it contains 463 either: 465 * A 3 octet local label where the 20 rightmost bits are used for 466 encoding the label value. In this case the V and L flags MUST 467 be set. 469 * A 4 octet index defining the offset in the SID/Label space 470 advertised by this router using the encodings defined in 471 Section 3.1. In this case V and L flags MUST be unset. 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 When the P-flag is not set, the Adj-SID MAY be persistent. When 484 the P-flag is set, the Adj-SID MUST be persistent. 486 Examples of use of the Adj-SID sub-TLV are described in 487 [I-D.ietf-spring-segment-routing]. 489 The F-flag is used in order for the router to advertise the 490 outgoing encapsulation of the adjacency the Adj-SID is attached 491 to. 493 2.2.2. Adjacency Segment Identifiers in LANs 495 In LAN subnetworks, the Designated Intermediate System (DIS) is 496 elected and originates the Pseudonode-LSP (PN-LSP) including all 497 neighbors of the DIS. 499 When Segment Routing is used, each router in the LAN MAY advertise 500 the Adj-SID of each of its neighbors. Since, on LANs, each router 501 only advertises one adjacency to the DIS (and doesn't advertise any 502 other adjacency), each router advertises the set of Adj-SIDs (for 503 each of its neighbors) inside a newly defined sub-TLV part of the TLV 504 advertising the adjacency to the DIS (e.g.: TLV-22). 506 The following new sub-TLV is defined: LAN-Adj-SID (Type: TBD, 507 suggested value 32) containing the set of Adj-SIDs the router 508 assigned to each of its LAN neighbors. 510 The format of the LAN-Adj-SID sub-TLV is as follows: 512 0 1 2 3 513 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 1 514 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 515 | Type | Length | Flags | Weight | 516 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 518 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 519 | System-ID (6 octets) | 520 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 521 | | 522 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 524 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 525 | SID/Label/Index (variable) | 526 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 528 where: 530 Type: TBD, suggested value 32 532 Length: variable. 534 Flags: 1 octet field of following flags: 536 0 1 2 3 4 5 6 7 537 +-+-+-+-+-+-+-+-+ 538 |F|B|V|L|S|P| | 539 +-+-+-+-+-+-+-+-+ 541 where F, B, V, L, S and P flags are defined in Section 2.2.1. 542 Other bits: MUST be zero when originated and ignored when 543 received. 545 Weight: 1 octet. The value represents the weight of the Adj-SID 546 for the purpose of load balancing. The use of the weight is 547 defined in [I-D.ietf-spring-segment-routing]. 549 System-ID: 6 octets of IS-IS System-ID of length "ID Length" as 550 defined in [ISO10589]. 552 SID/Index/Label: according to the V and L flags, it contains 553 either: 555 * A 3 octet local label where the 20 rightmost bits are used for 556 encoding the label value. In this case the V and L flags MUST 557 be set. 559 * A 4 octet index defining the offset in the SID/Label space 560 advertised by this router using the encodings defined in 561 Section 3.1. In this case V and L flags MUST be unset. 563 Multiple LAN-Adj-SID sub-TLVs MAY be encoded. 565 When the P-flag is not set, the LAN-Adj-SID MAY be persistent. When 566 the P-flag is set, the LAN-Adj-SID MUST be persistent. 568 In case one TLV-22/23/222/223 (reporting the adjacency to the DIS) 569 can't contain the whole set of LAN-Adj-SID sub-TLVs, multiple 570 advertisements of the adjacency to the DIS MUST be used and all 571 advertisements MUST have the same metric. 573 Each router within the level, by receiving the DIS PN LSP as well as 574 the non-PN LSP of each router in the LAN, is capable of 575 reconstructing the LAN topology as well as the set of Adj-SID each 576 router uses for each of its neighbors. 578 A label is encoded in 3 octets (in the 20 rightmost bits). 580 An index is encoded in 4 octets. 582 2.3. SID/Label Sub-TLV 584 The SID/Label sub-TLV is present in the following sub-TLVs defined in 585 this document: 587 Binding TLV Section 2.4. 589 SR Capability sub-TLV Section 3.1. 591 The SID/Label sub-TLV contains a SID or a MPLS Label. The SID/Label 592 sub-TLV has the following format: 594 0 1 2 3 595 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 1 596 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 597 | Type | Length | 598 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 599 | SID/Label (variable) | 600 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 602 where: 604 Type: TBD, suggested value 1 606 Length: variable 607 SID/Label: if length is set to 3 then the 20 rightmost bits 608 represent a MPLS label. 610 2.4. SID/Label Binding TLV 612 The SID/Label Binding TLV MAY be originated by any router in an IS-IS 613 domain. There are multiple uses of the SID/Label Binding TLV: 615 o The router may advertise a SID/Label binding to a FEC along with 616 at least a single 'nexthop style' anchor. The protocol supports 617 more than one 'nexthop style' anchor to be attached to a SID/Label 618 binding, which results into a simple path description language. 619 In analogy to RSVP the terminology for this is called an 'Explicit 620 Route Object' (ERO). Since ERO style path notation allows to 621 anchor SID/label bindings to both link and node IP addresses any 622 label switched path, can be described. Furthermore also SID/Label 623 Bindings from external protocols can get easily re-advertised. 625 o The SID/Label Binding TLV may be used for advertising SID/Label 626 Bindings and their associated Primary and Backup paths. In one 627 single TLV either a primary ERO Path, a backup ERO Path or both 628 are advertised. If a router wants to advertise multiple parallel 629 paths then it can generate several TLVs for the same Prefix/FEC. 630 Each occurrence of a Binding TLV with respect with a given FEC 631 Prefix has accumulating and not canceling semantics. Due the 632 space constraints in the 8-Bit IS-IS TLVs an originating router 633 MAY encode a primary ERO path in one SID/Label Binding TLV and the 634 backup ERO path in a second SID/Label Binding TLV. Note that the 635 FEC Prefix and SID/Label sub-TLV MUST be identical in both TLVs. 637 o The SID/Label Binding TLV may also be used in order to advertise 638 prefixes to SID/Label mappings. This functionality is called the 639 'Mapping Server' and it's used when, in a heterogeneous network, 640 not all nodes are capable of advertising their own SIDs/Labels. 641 When the SID/Label Binding TLV is used by the Mapping Server in 642 order to advertise prefix to SID/label mappings, the index/label 643 MUST include the Prefix-SID SubTLV (Section 2.1). 645 The SID/Label Binding TLV has Type TBD (suggested value 149), and has 646 the following format: 648 0 1 2 3 649 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 1 650 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 651 | Type | Length | Flags | Weight | 652 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 653 | Range | Prefix Length | FEC Prefix | 654 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 655 // FEC Prefix (continued, variable) // 656 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 657 | SubTLVs (variable) | 658 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 660 Figure 1: SID/Label Binding TLV format 662 o Type: TBD, suggested value 149 664 o Length: variable. 666 o 1 octet of flags 668 o 1 octet of Weight 670 o 2 octets of Range 672 o 1 octet of Prefix Length 674 o 0-16 octets of FEC Prefix 676 o sub-TLVs, where each sub-TLV consists of a sequence of: 678 * 1 octet of sub-TLV type 680 * 1 octet of length of the value field of the sub-TLV 682 * 0-243 octets of value 684 2.4.1. Flags 686 Flags: 1 octet field of following flags: 688 0 1 2 3 4 5 6 7 689 +-+-+-+-+-+-+-+-+ 690 |F|M|S|D|A| | 691 +-+-+-+-+-+-+-+-+ 693 where: 695 F-Flag: Address Family flag. If unset, then the Prefix FEC 696 carries an IPv4 Prefix. If set then the Prefix FEC carries an 697 IPv6 Prefix. 699 M-Flag: Mirror Context flag. Set if the advertised SID/path 700 corresponds to a mirrored context. The use of the M flag is 701 described in [I-D.ietf-spring-segment-routing]. 703 S-Flag: If set, the SID/Label Binding TLV SHOULD be flooded across 704 the entire routing domain. If the S flag is not set, the SID/ 705 Label Binding TLV MUST NOT be leaked between levels. This bit 706 MUST NOT be altered during the TLV leaking. 708 D-Flag: when the SID/Label Binding TLV is leaked from level-2 to 709 level-1, the D bit MUST be set. Otherwise, this bit MUST be 710 clear. SID/Label Binding TLVs with the D bit set MUST NOT be 711 leaked from level-1 to level-2. This is to prevent TLV looping 712 across levels. 714 A-Flag: Attached flag. The originator of the SID/Label Binding 715 TLV MAY set the A bit in order to signal that the prefixes and 716 SIDs advertised in the SID/Label Binding TLV are directly 717 connected to their originators. The mechanisms through which the 718 originator of the SID/Label Binding TLV can figure out if a prefix 719 is attached or not are outside the scope of this document (e.g.: 720 through explicit configuration). If the Binding TLV is leaked to 721 other areas/levels the A-flag MUST be cleared. 723 An implementation MAY decide not to honor the S-flag in order not 724 to leak Binding TLV's between levels (for policy reasons). In all 725 cases, the D flag MUST always be set by any router leaking the 726 Binding TLV from level-2 into level-1 and MUST be checked when 727 propagating the Binding TLV from level-1 into level-2. If the D 728 flag is set, the Binding TLV MUST NOT be propagated into level-2. 730 Other bits: MUST be zero when originated and ignored when 731 received. 733 2.4.2. Weight 735 Weight: 1 octet: The value represents the weight of the path for the 736 purpose of load balancing. The use of the weight is defined in 737 [I-D.ietf-spring-segment-routing]. 739 2.4.3. Range 741 The 'Range' field provides the ability to specify a range of 742 addresses and their associated Prefix SIDs. This functionality is 743 called "Mapping Server". It is essentially a compression scheme to 744 distribute a continuous Prefix and their continuous, corresponding 745 SID/Label Block. If a single SID is advertised then the range field 746 MUST be set to one. For range advertisements > 1, the number of 747 addresses that need to be mapped into a Prefix-SID and the starting 748 value of the Prefix-SID range. 750 Example 1: if the following router addresses (loopback addresses) 751 need to be mapped into the corresponding Prefix SID indexes. 753 Router-A: 192.0.2.1/32, Prefix-SID: Index 1 754 Router-B: 192.0.2.2/32, Prefix-SID: Index 2 755 Router-C: 192.0.2.3/32, Prefix-SID: Index 3 756 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 57 782 0 1 2 3 783 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 1 784 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 785 | Type | Length |0|0| | Weight | 786 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 787 | Range = 7 | /24 | 10 | 788 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 789 | .1 | .1 |Prefix-SID Type| sub-TLV Length| 790 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 791 | Flags | Algorithm | | 792 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 793 | 51 | 794 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 796 It is not expected that a network operator will be able to keep fully 797 continuous FEC Prefix / SID/Index mappings. In order to support 798 noncontinuous mapping ranges an implementation MAY generate several 799 instances of Binding TLVs. 801 For example if a router wants to advertise the following ranges: 803 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.' 924 0 1 2 3 925 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 1 926 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 927 | Type | Length |L| Reserved | IPv4 address | 928 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 929 | IPv4 address (continued) | 930 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 932 Figure 2: IPv4 ERO subTLV format 934 2.4.9. IPv6 ERO subTLV 936 The IPv6 ERO subTLV (Type: TBD, suggested value 12) describes a path 937 segment using IPv6 Address style of encoding. Its semantics have 938 been borrowed from [RFC3209]. 940 The 'L' bit in the Flags is a one-bit attribute. If the L bit is 941 set, then the value of the attribute is 'loose.' Otherwise, the 942 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 9 octets. 987 o For 128-Bit Router-ID width the subTLV length is set to 21 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.' 1017 0 1 2 3 1018 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 1019 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1020 | Type | Length |L| Reserved | IPv4 address | 1021 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1022 | IPv4 address (continued) | 1023 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1025 Figure 5: IPv4 Backup ERO subTLV format 1027 2.4.12. IPv6 Backup ERO subTLV 1029 The IPv6 Backup ERO subTLV (Type: TBD, suggested value 15) describes 1030 a Backup path segment using IPv6 Address style of encoding. Its 1031 appearance and semantics have been borrowed from [RFC3209]. 1033 The 'L' bit in the Flags is a one-bit attribute. If the L bit is 1034 set, then the value of the attribute is 'loose.' Otherwise, the 1035 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 9 octets. 1080 o For 128-Bit Router-ID width the subTLV length is set to 21 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| | 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 One or more SRGB Descriptor entries, each of which have the 1210 following format: 1212 Range: 3 octets. 1214 SID/Label sub-TLV (as defined in Section 2.3). 1216 SID/Label sub-TLV contains the first value of the SRGB while the 1217 range contains the number of SRGB elements. The range value MUST be 1218 higher than 0. 1220 The SR-Capabilities sub-TLV MAY be advertised in an LSP of any number 1221 but a router MUST NOT advertise more than one SR-Capabilities sub- 1222 TLV. A router receiving multiple SR-Capabilities sub-TLVs, from the 1223 same originator, SHOULD select the first advertisement in the lowest 1224 numbered LSP. 1226 When multiple SRGB Descriptors are advertised the entries define an 1227 ordered set of ranges on which a SID index is to be applied. For 1228 this reason changing the order in which the descriptors are 1229 advertised will have a disruptive effect on forwarding. 1231 When a router adds a new SRGB Descriptor to an existing SR- 1232 Capabilities sub-TLV the new Descriptor SHOULD add the newly 1233 configured block at the end of the sub-TLV and SHOULD NOT change the 1234 order of previously advertised blocks. Changing the order of the 1235 advertised descriptors will create label churn in the FIB and 1236 blackhole / misdirect some traffic during the IGP convergence. In 1237 particular, if a range which is not the last is extended it's 1238 preferable to add a new range rather than extending the previously 1239 advertised range. 1241 The originating router MUST ensure the order is same after a graceful 1242 restart (using checkpointing, non-volatile storage or any other 1243 mechanism) in order to guarantee the same order before and after GR. 1245 The originating router MUST NOT advertise overlapping ranges. 1247 When a router receives multiple overlapping ranges, it MUST conform 1248 to the procedures defined in [I-D.ietf-spring-conflict-resolution]. 1250 Here follows an example of advertisement of multiple ranges: 1252 The originating router advertises following ranges: 1253 SR-Cap: range: 100, SID value: 100 1254 SR-Cap: range: 100, SID value: 1000 1255 SR-Cap: range: 100, SID value: 500 1257 The receiving routers concatenate the ranges in the received 1258 order and build the SRGB as follows: 1260 SRGB = [100, 199] 1261 [1000, 1099] 1262 [500, 599] 1264 The indexes span multiple ranges: 1266 index=0 means label 100 1267 ... 1268 index 99 means label 199 1269 index 100 means label 1000 1270 index 199 means label 1099 1271 ... 1272 index 200 means label 500 1273 ... 1275 3.2. SR-Algorithm Sub-TLV 1277 The router may use various algorithms when calculating reachability 1278 to other nodes or to prefixes attached to these nodes. Examples of 1279 these algorithms are metric based Shortest Path First (SPF), various 1280 sorts of Constrained SPF, etc. The SR-Algorithm sub-TLV (Type: TBD, 1281 suggested value 19) allows the router to advertise the algorithms 1282 that the router is currently using. The following value has been 1283 defined: 1285 0: Shortest Path First (SPF) algorithm based on link metric. This 1286 is the well-known shortest path algorithm as computed by the IS-IS 1287 Decision process. Consistent with the deployed practice for link- 1288 state protocols, algorithm 0 permits any node to overwrite the SPF 1289 path with a different path based on local policy. 1291 1: Strict Shortest Path First (SPF) algorithm based on link 1292 metric. The algorithm is identical to algorithm 0 but algorithm 1 1293 requires that all nodes along the path will honor the SPF routing 1294 decision. Local policy MUST NOT alter the forwarding decision 1295 computed by algorithm 1 at the node claiming to support algorithm 1296 1. 1298 The SR-Algorithm sub-TLV is inserted into the IS-IS Router Capability 1299 TLV-242 that is defined in [RFC7981]. 1301 The Router Capability TLV specifies flags that control its 1302 advertisement. The SR-Algorithm MUST be propagated throughout the 1303 level and need not to be advertised across level boundaries. 1304 Therefore Router Capability TLV distribution flags MUST be set 1305 accordingly, i.e., the S flag MUST be unset. 1307 The SR-Algorithm sub-TLV is optional, it MAY only appear a single 1308 time inside the Router Capability TLV. 1310 When the originating router does not advertise the SR-Algorithm sub- 1311 TLV, then all the Prefix-SID advertised by the router MUST have 1312 algorithm field set to 0. Any receiving router MUST assume SPF 1313 algorithm (i.e., Shortest Path First). 1315 When the originating router does advertise the SR-Algorithm sub-TLV, 1316 then algorithm 0 MUST be present while algorithm 1 MAY be present. 1318 The SR-Algorithm sub-TLV has following format: 1320 0 1 2 3 1321 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 1322 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1323 | Type | Length | 1324 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1325 | Algorithm 1 | Algorithm 2 | Algorithm ... | Algorithm n | 1326 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1328 where: 1330 Type: TBD, suggested value 19 1332 Length: variable. 1334 Algorithm: 1 octet of algorithm Section 2.1 1336 3.3. SR Local Block Sub-TLV 1338 The SR Local Block (SRLB) Sub-TLV contains the range of labels the 1339 node has reserved for local SIDs. Local SIDs are used, e.g., for 1340 Adjacency-SIDs, and may also be allocated by other components than 1341 IS-IS protocol. As an example, an application or a controller may 1342 instruct the router to allocate a specific local SID. Therefore, in 1343 order for such applications or controllers to know what are the local 1344 SIDs available in the router, it is required that the router 1345 advertises its SRLB. 1347 The SRLB Sub-TLV is used for that purpose and has following format: 1349 0 1 2 3 1350 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 1351 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1352 | Type | Length | Flags | 1353 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1355 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1356 | Range | 1357 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1358 // SID/Label Sub-TLV (variable) // 1359 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1361 Type: TBD, suggested value 22. 1363 Length: variable. 1365 Flags: 1 octet of flags. None are defined at this stage. 1367 One or more SRLB Descriptor entries, each of which have the 1368 following format: 1370 Range: 3 octets. 1372 SID/Label sub-TLV (as defined in Section 2.3). 1374 SID/Label sub-TLV contains the first value of the SRLB while the 1375 range contains the number of SRLB elements. The range value MUST be 1376 higher than 0. 1378 The SRLB sub-TLV MAY be advertised in an LSP of any number but a 1379 router MUST NOT advertise more than one SRLB sub-TLV. A router 1380 receiving multiple SRLB sub-TLVs, from the same originator, SHOULD 1381 select the first advertisement in the lowest numbered LSP. 1383 The originating router MUST NOT advertise overlapping ranges. 1385 It is important to note that each time a SID from the SRLB is 1386 allocated, it SHOULD also be reported to all components (e.g.: 1387 controller or applications) in order for these components to have an 1388 up-to-date view of the current SRLB allocation and in order to avoid 1389 collision between allocation instructions. 1391 Within the context of IS-IS, the reporting of local SIDs is done 1392 through IS-IS Sub-TLVs such as the Adjacency-SID. However, the 1393 reporting of allocated local SIDs may also be done through other 1394 means and protocols which mechanisms are outside the scope of this 1395 document. 1397 A router advertising the SRLB TLV may also have other label ranges, 1398 outside the SRLB, for its local allocation purposes which are NOT 1399 advertised in the SRLB. For example, it is possible that an 1400 Adjacency-SID is allocated using a local label not part of the SRLB. 1402 3.4. SRMS Preference Sub-TLV 1404 The Segment Routing Mapping Server (SRMS) Preference sub-TLV is used 1405 in order to associate a preference with SRMS advertisements from a 1406 particular source. 1408 The SRMS Preference sub-TLV has following format: 1410 0 1 2 3 1411 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 1412 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1413 | Type | Length | Preference | 1414 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1416 Type: TBD, suggested value 23. 1418 Length: 1. 1420 Preference: 1 octet. Unsigned 8 bit SRMS preference. 1422 The SRMS Preference sub-TLV MAY be advertised in an LSP of any number 1423 but a router MUST NOT advertise more than one SRMS Preference sub- 1424 TLV. A router receiving multiple SRMS Preference sub-TLVs, from the 1425 same originator, SHOULD select the first advertisement in the lowest 1426 numbered LSP. 1428 The use of the SRMS Preference during the SID selection process is 1429 described in [I-D.ietf-spring-conflict-resolution]. 1431 4. Non backward compatible changes with prior versions of this document 1433 This section describes the changes that have been applied to this 1434 document that are not backward compatible with previous versions. 1436 4.1. Encoding of Multiple SRGBs 1438 Version -04 of this document introduced a change in Section 3.1 1439 regarding the encoding method for multiple SRGBs in the SR-Cap SubTLV 1440 and made the support of multiple SRGBs REQUIRED. 1442 The modified method consists of having a single SR-Cap Sub-TLV where 1443 all SRGBs are encoded. In previous versions (prior to version -04) 1444 of this document it was allowed to have multiple occurrences of the 1445 SR-Cap Sub-TLV. 1447 At the time of writing this document, no existing implementations are 1448 affected by the change since no implementations actually (i.e., at 1449 the time of updating this document) encode multiple SRGBs anyway. 1451 5. IANA Considerations 1453 This documents request allocation for the following TLVs and subTLVs. 1455 5.1. Sub TLVs for Type 22,23,222 and 223 1457 This document makes the following registrations in the "sub-TLVs for 1458 TLV 22, 23, 222 and 223" registry. 1460 Type: TBD (suggested value 31) 1462 Description: Adjacency Segment Identifier 1464 TLV 22: yes 1466 TLV 23: yes 1468 TLV 222: yes 1470 TLV 223: yes 1472 Reference: This document (Section 2.2.1) 1474 Type: TBD (suggested value 32) 1476 Description: LAN Adjacency Segment Identifier 1478 TLV 22: yes 1480 TLV 23: yes 1482 TLV 222: yes 1484 TLV 223: yes 1486 Reference: This document (Section 2.2.2) 1488 5.2. Sub TLVs for Type 135,235,236 and 237 1490 This document makes the following registrations in the "sub-TLVs for 1491 TLV 135,235,236 and 237" registry. 1493 Type: TBD (suggested value 3) 1495 Description: Prefix Segment Identifier 1497 TLV 135: yes 1499 TLV 235: yes 1501 TLV 236: yes 1503 TLV 237: yes 1505 Reference: This document (Section 2.1) 1507 5.3. Sub TLVs for Type 242 1509 This document makes the following registrations in the "sub-TLVs for 1510 TLV 242" registry. 1512 Type: TBD (suggested value 2) 1514 Description: Segment Routing Capability 1516 Reference: This document (Section 3.1) 1518 Type: TBD (suggested value 19) 1520 Description: Segment Routing Algorithm 1522 Reference: This document (Section 3.2) 1524 Type: TBD (suggested value 22) 1526 Description: Segment Routing Local Base (SRLB) 1528 Reference: This document (Section 3.3) 1529 Type: TBD (suggested value 23) 1531 Description: Segment Routing Mapping Server Preference (SRMS 1532 Preference) 1534 Reference: This document (Section 3.4) 1536 5.4. New TLV Codepoint and Sub-TLV registry 1538 This document registers the following TLV: 1540 Type: TBD (suggested value 149) 1542 name: Segment Identifier / Label Binding 1544 IIH: no 1546 LSP: yes 1548 SNP: no 1550 Purge: no 1552 Reference: This document (Section 2.4) 1554 Type: TBD (suggested value 150) 1556 name: Multi-Topology Segment Identifier / Label Binding 1558 IIH: no 1560 LSP: yes 1562 SNP: no 1564 Purge: no 1566 Reference: This document (Section 2.5) 1568 This document creates the following sub-TLV Registry: 1570 Registry: sub-TLVs for TLV 149 and 150 1572 Registration Procedure: Expert review 1574 Reference: This document (Section 2.4) 1575 Type: TBD, suggested value 1 1577 Description: SID/Label 1579 Reference: This document (Section 2.3) 1581 Type: TBD, suggested value 3 1583 Description: Prefix-SID 1585 Reference: This document (Section 2.1) 1587 Type: TBD, suggested value 10 1589 Description: ERO Metric 1591 Reference: This document (Section 2.4.7) 1593 Type: TBD, suggested value 11 1595 Description: IPv4 ERO 1597 Reference: This document (Section 2.4.8) 1599 Type: TBD, suggested value 12 1601 Description: IPv6 ERO 1603 Reference: This document (Section 2.4.9) 1605 Type: TBD, suggested value 13 1607 Description: Unnumbered Interface-ID ERO 1609 Reference: This document (Section 2.4.10) 1611 Type: TBD, suggested value 14 1612 Description: IPv4 Backup ERO 1614 Reference: This document (Section 2.4.11) 1616 Type: TBD, suggested value 15 1618 Description: IPv6 Backup ERO 1620 Reference: This document (Section 2.4.12) 1622 Type: TBD, suggested value 16 1624 Description: Unnumbered Interface-ID Backup ERO 1626 Reference: This document (Section 2.4.13) 1628 6. Manageability Considerations 1630 TBD 1632 7. Security Considerations 1634 TBD 1636 8. Acknowledgements 1638 We would like to thank Dave Ward, Dan Frost, Stewart Bryant, Pierre 1639 Francois and Jesper Skrivers for their contribution to the content of 1640 this document. 1642 Many thanks to Yakov Rekhter and Ina Minei for their contribution on 1643 earlier definition of the "Binding / MPLS Label TLV". 1645 9. Contributors 1647 The following people gave a substantial contribution to the content 1648 of this document and should be considered as co-authors: 1650 Les Ginsberg 1651 Cisco Systems Inc. 1652 US 1654 Email: ginsberg@cisco.com 1655 Peter Psenak 1656 Cisco Systems Inc. 1657 US 1659 Email: ppsenak@cisco.com 1661 Martin Horneffer 1662 Deutsche Telekom 1663 DE 1665 Email: Martin.Horneffer@telekom.de 1667 Wim Henderickx 1668 Nokia 1669 BE 1671 Email: wim.henderickx@nokia.com 1673 Edward Crabbe 1674 Individual 1675 US 1677 Email: edward.crabbe@gmail.com 1679 Rob Shakir 1680 Google 1681 UK 1683 Email: robjs@google.com 1685 Igor Milojevic 1686 Individual 1687 RS 1689 Email: milojevicigor@gmail.com 1691 Saku Ytti 1692 TDC 1693 FI 1695 Email: saku@ytti.fi 1697 Steven Luong 1698 Cisco Systems Inc. 1699 US 1701 Email: sluong@cisco.com 1703 10. References 1705 10.1. Normative References 1707 [I-D.ietf-spring-conflict-resolution] 1708 Ginsberg, L., Psenak, P., Previdi, S., and M. Pilka, 1709 "Segment Routing Conflict Resolution", draft-ietf-spring- 1710 conflict-resolution-02 (work in progress), October 2016. 1712 [I-D.ietf-spring-segment-routing] 1713 Filsfils, C., Previdi, S., Decraene, B., Litkowski, S., 1714 and R. Shakir, "Segment Routing Architecture", draft-ietf- 1715 spring-segment-routing-11 (work in progress), February 1716 2017. 1718 [ISO10589] 1719 International Organization for Standardization, 1720 "Intermediate system to Intermediate system intra-domain 1721 routeing information exchange protocol for use in 1722 conjunction with the protocol for providing the 1723 connectionless-mode Network Service (ISO 8473)", ISO/ 1724 IEC 10589:2002, Second Edition, Nov 2002. 1726 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1727 Requirement Levels", BCP 14, RFC 2119, 1728 DOI 10.17487/RFC2119, March 1997, 1729 . 1731 [RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi 1732 Topology (MT) Routing in Intermediate System to 1733 Intermediate Systems (IS-ISs)", RFC 5120, 1734 DOI 10.17487/RFC5120, February 2008, 1735 . 1737 [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic 1738 Engineering", RFC 5305, DOI 10.17487/RFC5305, October 1739 2008, . 1741 [RFC5308] Hopps, C., "Routing IPv6 with IS-IS", RFC 5308, 1742 DOI 10.17487/RFC5308, October 2008, 1743 . 1745 [RFC6119] Harrison, J., Berger, J., and M. Bartlett, "IPv6 Traffic 1746 Engineering in IS-IS", RFC 6119, DOI 10.17487/RFC6119, 1747 February 2011, . 1749 [RFC7794] Ginsberg, L., Ed., Decraene, B., Previdi, S., Xu, X., and 1750 U. Chunduri, "IS-IS Prefix Attributes for Extended IPv4 1751 and IPv6 Reachability", RFC 7794, DOI 10.17487/RFC7794, 1752 March 2016, . 1754 [RFC7981] Ginsberg, L., Previdi, S., and M. Chen, "IS-IS Extensions 1755 for Advertising Router Information", RFC 7981, 1756 DOI 10.17487/RFC7981, October 2016, 1757 . 1759 10.2. Informative References 1761 [I-D.ietf-spring-resiliency-use-cases] 1762 Filsfils, C., Previdi, S., Decraene, B., and R. Shakir, 1763 "Resiliency use cases in SPRING networks", draft-ietf- 1764 spring-resiliency-use-cases-08 (work in progress), October 1765 2016. 1767 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 1768 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 1769 Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001, 1770 . 1772 [RFC3477] Kompella, K. and Y. Rekhter, "Signalling Unnumbered Links 1773 in Resource ReSerVation Protocol - Traffic Engineering 1774 (RSVP-TE)", RFC 3477, DOI 10.17487/RFC3477, January 2003, 1775 . 1777 [RFC5311] McPherson, D., Ed., Ginsberg, L., Previdi, S., and M. 1778 Shand, "Simplified Extension of Link State PDU (LSP) Space 1779 for IS-IS", RFC 5311, DOI 10.17487/RFC5311, February 2009, 1780 . 1782 [RFC5316] Chen, M., Zhang, R., and X. Duan, "ISIS Extensions in 1783 Support of Inter-Autonomous System (AS) MPLS and GMPLS 1784 Traffic Engineering", RFC 5316, DOI 10.17487/RFC5316, 1785 December 2008, . 1787 [RFC7855] Previdi, S., Ed., Filsfils, C., Ed., Decraene, B., 1788 Litkowski, S., Horneffer, M., and R. Shakir, "Source 1789 Packet Routing in Networking (SPRING) Problem Statement 1790 and Requirements", RFC 7855, DOI 10.17487/RFC7855, May 1791 2016, . 1793 Authors' Addresses 1795 Stefano Previdi (editor) 1796 Cisco Systems, Inc. 1797 Via Del Serafico, 200 1798 Rome 00142 1799 Italy 1801 Email: sprevidi@cisco.com 1803 Clarence Filsfils 1804 Cisco Systems, Inc. 1805 Brussels 1806 BE 1808 Email: cfilsfil@cisco.com 1810 Ahmed Bashandy 1811 Cisco Systems, Inc. 1812 170, West Tasman Drive 1813 San Jose, CA 95134 1814 US 1816 Email: bashandy@cisco.com 1818 Hannes Gredler 1819 RtBrick Inc. 1821 Email: hannes@rtbrick.com 1823 Stephane Litkowski 1824 Orange 1825 FR 1827 Email: stephane.litkowski@orange.com 1829 Bruno Decraene 1830 Orange 1831 FR 1833 Email: bruno.decraene@orange.com 1834 Jeff Tantsura 1835 Individual 1837 Email: jefftant@gmail.com