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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Unused Reference: 'RFC4206' is defined on line 838, but no explicit reference was found in the text -- Obsolete informational reference (is this intentional?): RFC 3567 (Obsoleted by RFC 5304) -- Obsolete informational reference (is this intentional?): RFC 4971 (Obsoleted by RFC 7981) -- Obsolete informational reference (is this intentional?): RFC 5316 (Obsoleted by RFC 9346) Summary: 2 errors (**), 0 flaws (~~), 4 warnings (==), 5 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Internet Engineering Task Force M. Chen 3 Internet-Draft Huawei 4 Intended status: Standards Track L. Ginsberg 5 Expires: July 8, 2017 S. Previdi 6 Cisco Systems 7 D. Xiaodong 8 China Mobile 9 January 4, 2017 11 ISIS Extensions in Support of Inter-Autonomous System (AS) MPLS and 12 GMPLS Traffic Engineering 13 draft-chen-isis-rfc5316bis-02 15 Abstract 17 This document describes extensions to the ISIS (ISIS) protocol to 18 support Multiprotocol Label Switching (MPLS) and Generalized MPLS 19 (GMPLS) Traffic Engineering (TE) for multiple Autonomous Systems 20 (ASes). It defines ISIS-TE extensions for the flooding of TE 21 information about inter-AS links, which can be used to perform inter- 22 AS TE path computation. 24 No support for flooding information from within one AS to another AS 25 is proposed or defined in this document. 27 This document obsoletes [RFC5316] 29 Requirements Language 31 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 32 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 33 document are to be interpreted as described in RFC 2119 [RFC2119]. 35 Status of This Memo 37 This Internet-Draft is submitted in full conformance with the 38 provisions of BCP 78 and BCP 79. 40 Internet-Drafts are working documents of the Internet Engineering 41 Task Force (IETF). Note that other groups may also distribute 42 working documents as Internet-Drafts. The list of current Internet- 43 Drafts is at http://datatracker.ietf.org/drafts/current/. 45 Internet-Drafts are draft documents valid for a maximum of six months 46 and may be updated, replaced, or obsoleted by other documents at any 47 time. It is inappropriate to use Internet-Drafts as reference 48 material or to cite them other than as "work in progress." 49 This Internet-Draft will expire on July 8, 2017. 51 Copyright Notice 53 Copyright (c) 2017 IETF Trust and the persons identified as the 54 document authors. All rights reserved. 56 This document is subject to BCP 78 and the IETF Trust's Legal 57 Provisions Relating to IETF Documents 58 (http://trustee.ietf.org/license-info) in effect on the date of 59 publication of this document. Please review these documents 60 carefully, as they describe your rights and restrictions with respect 61 to this document. Code Components extracted from this document must 62 include Simplified BSD License text as described in Section 4.e of 63 the Trust Legal Provisions and are provided without warranty as 64 described in the Simplified BSD License. 66 Table of Contents 68 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 69 2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 4 70 2.1. A Note on Non-Objectives . . . . . . . . . . . . . . . . 4 71 2.2. Per-Domain Path Determination . . . . . . . . . . . . . . 4 72 2.3. Backward Recursive Path Computation . . . . . . . . . . . 6 73 3. Extensions to ISIS-TE . . . . . . . . . . . . . . . . . . . . 7 74 3.1. Inter-AS Reachability TLV . . . . . . . . . . . . . . . . 8 75 3.2. TE Router ID . . . . . . . . . . . . . . . . . . . . . . 9 76 3.3. Sub-TLVs for Inter-AS Reachability TLV . . . . . . . . . 10 77 3.3.1. Remote AS Number Sub-TLV . . . . . . . . . . . . . . 10 78 3.3.2. IPv4 Remote ASBR ID Sub-TLV . . . . . . . . . . . . . 10 79 3.3.3. IPv6 Remote ASBR ID Sub-TLV . . . . . . . . . . . . . 11 80 3.3.4. IPv6 Router ID sub-TLV . . . . . . . . . . . . . . . 12 81 3.4. Sub-TLVs for IS-IS Router Capability TLV . . . . . . . . 13 82 3.4.1. IPv4 TE Router ID sub-TLV . . . . . . . . . . . . . . 13 83 3.4.2. IPv6 TE Router ID sub-TLV . . . . . . . . . . . . . . 13 84 4. Procedure for Inter-AS TE Links . . . . . . . . . . . . . . . 14 85 4.1. Origin of Proxied TE Information . . . . . . . . . . . . 15 86 5. Security Considerations . . . . . . . . . . . . . . . . . . . 15 87 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 88 6.1. Inter-AS Reachability TLV . . . . . . . . . . . . . . . . 16 89 6.2. Sub-TLVs for the Inter-AS Reachability TLV . . . . . . . 17 90 6.3. Sub-TLVs for the IS-IS Router Capability TLV . . . . . . 17 91 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 18 92 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 18 93 8.1. Normative References . . . . . . . . . . . . . . . . . . 18 94 8.2. Informative References . . . . . . . . . . . . . . . . . 18 95 Appendix A. Changes to RFC 5316 . . . . . . . . . . . . . . . . 20 96 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20 98 1. Introduction 100 [RFC5305] defines extensions to the ISIS protocol [RFC1195] to 101 support intra-area Traffic Engineering (TE). The extensions provide 102 a way of encoding the TE information for TE-enabled links within the 103 network (TE links) and flooding this information within an area. The 104 extended IS reachability TLV and traffic engineering router ID TLV, 105 which are defined in [RFC5305], are used to carry such TE 106 information. The extended IS reachability TLV has several nested 107 sub-TLVs that describe the TE attributes for a TE link. 109 [RFC6119] and [RFC5307] define similar extensions to ISIS in support 110 of IPv6 and Generalized Multiprotocol Label Switching (GMPLS) TE 111 respectively. 113 Requirements for establishing Multiprotocol Label Switching (MPLS) TE 114 Label Switched Paths (LSPs) that cross multiple Autonomous Systems 115 (ASes) are described in [RFC4216]. As described in [RFC4216], a 116 method SHOULD provide the ability to compute a path spanning multiple 117 ASes. So a path computation entity that may be the head-end Label 118 Switching Router (LSR), an AS Border Router (ASBR), or a Path 119 Computation Element (PCE) [RFC4655] needs to know the TE information 120 not only of the links within an AS, but also of the links that 121 connect to other ASes. 123 In this document, a new TLV, which is referred to as the inter-AS 124 reachability TLV, is defined to advertise inter-AS TE information, 125 three new sub-TLVs are defined for inclusion in the inter-AS 126 reachability TLV to carry the information about the remote AS number 127 and remote ASBR ID. The sub-TLVs defined in [RFC5305][RFC6119] and 128 other documents for inclusion in the extended IS reachability TLV for 129 describing the TE properties of a TE link are applicable to be 130 included in the Inter-AS Reachability TLV for describing the TE 131 properties of an inter-AS TE link as well. Also, two more new sub- 132 TLVs are defined for inclusion in the IS-IS router capability TLV to 133 carry the TE Router ID when the TE Router ID needs to reach all 134 routers within an entire ISIS routing domain. The extensions are 135 equally applicable to IPv4 and IPv6 as identical extensions to 136 [RFC5305] and [RFC6119]. Detailed definitions and procedures are 137 discussed in the following sections. 139 This document does not propose or define any mechanisms to advertise 140 any other extra-AS TE information within ISIS. See Section 2.1 for a 141 full list of non-objectives for this work. 143 2. Problem Statement 145 As described in [RFC4216], in the case of establishing an inter-AS TE 146 LSP that traverses multiple ASes, the Path message [RFC3209] may 147 include the following elements in the Explicit Route Object (ERO) in 148 order to describe the path of the LSP: 150 o a set of AS numbers as loose hops; and/or 152 o a set of LSRs including ASBRs as loose hops. 154 Two methods for determining inter-AS paths are currently being 155 discussed. The per-domain method [RFC5152] determines the path one 156 domain at a time. The backward recursive method [RFC5441] uses 157 cooperation between PCEs to determine an optimum inter-domain path. 158 The sections that follow examine how inter-AS TE link information 159 could be useful in both cases. 161 2.1. A Note on Non-Objectives 163 It is important to note that this document does not make any change 164 to the confidentiality and scaling assumptions surrounding the use of 165 ASes in the Internet. In particular, this document is conformant to 166 the requirements set out in [RFC4216]. 168 The following features are explicitly excluded: 170 o There is no attempt to distribute TE information from within one 171 AS to another AS. 173 o There is no mechanism proposed to distribute any form of TE 174 reachability information for destinations outside the AS. 176 o There is no proposed change to the PCE architecture or usage. 178 o TE aggregation is not supported or recommended. 180 o There is no exchange of private information between ASes. 182 o No ISIS adjacencies are formed on the inter-AS link. 184 2.2. Per-Domain Path Determination 186 In the per-domain method of determining an inter-AS path for an MPLS- 187 TE LSP, when an LSR that is an entry-point to an AS receives a Path 188 message from an upstream AS with an ERO containing a next hop that is 189 an AS number, it needs to find which LSRs (ASBRs) within the local AS 190 are connected to the downstream AS. That way, it can compute a TE 191 LSP segment across the local AS to one of those LSRs and forward the 192 Path message to that LSR and hence into the next AS. See Figure 1 193 for an example. 195 R1------R3----R5-----R7------R9-----R11 196 | | \ | / | 197 | | \ | ---- | 198 | | \ | / | 199 R2------R4----R6 --R8------R10----R12 200 : : 201 <-- AS1 -->:<---- AS2 --->:<--- AS3 ---> 203 Figure 1: Inter-AS Reference Model 205 The figure shows three ASes (AS1, AS2, and AS3) and twelve LSRs (R1 206 through R12). R3 and R4 are ASBRs in AS1. R5, R6, R7, and R8 are 207 ASBRs in AS2. R9 and R10 are ASBRs in AS3. 209 If an inter-AS TE LSP is planned to be established from R1 to R12, 210 the AS sequence will be: AS1, AS2, AS3. 212 Suppose that the Path message enters AS2 from R3. The next hop in 213 the ERO shows AS3, and R5 must determine a path segment across AS2 to 214 reach AS3. It has a choice of three exit points from AS2 (R6, R7, 215 and R8), and it needs to know which of these provide TE connectivity 216 to AS3, and whether the TE connectivity (for example, available 217 bandwidth) is adequate for the requested LSP. 219 Alternatively, if the next hop in the ERO is the entry ASBR for AS3 220 (say R9), R5 needs to know which of its exit ASBRs has a TE link that 221 connects to R9. Since there may be multiple ASBRs that are connected 222 to R9 (both R7 and R8 in this example), R5 also needs to know the TE 223 properties of the inter-AS TE links so that it can select the correct 224 exit ASBR. 226 Once the Path message reaches the exit ASBR, any choice of inter-AS 227 TE link can be made by the ASBR if not already made by the entry ASBR 228 that computed the segment. 230 More details can be found in Section 4 of [RFC5152], which clearly 231 points out why advertising of inter-AS links is desired. 233 To enable R5 to make the correct choice of exit ASBR, the following 234 information is needed: 236 o List of all inter-AS TE links for the local AS. 238 o TE properties of each inter-AS TE link. 240 o AS number of the neighboring AS connected to by each inter-AS TE 241 link. 243 o Identity (TE Router ID) of the neighboring ASBR connected to by 244 each inter-AS TE link. 246 In GMPLS networks, further information may also be required to select 247 the correct TE links as defined in [RFC5307]. 249 The example above shows how this information is needed at the entry- 250 point ASBRs for each AS (or the PCEs that provide computation 251 services for the ASBRs). However, this information is also needed 252 throughout the local AS if path computation functionality is fully 253 distributed among LSRs in the local AS, for example to support LSPs 254 that have start points (ingress nodes) within the AS. 256 2.3. Backward Recursive Path Computation 258 Another scenario using PCE techniques has the same problem. 259 [RFC5441] defines a PCE-based TE LSP computation method (called 260 Backward Recursive Path Computation) to compute optimal inter-domain 261 constrained MPLS-TE or GMPLS LSPs. In this path computation method, 262 a specific set of traversed domains (ASes) are assumed to be selected 263 before computation starts. Each downstream PCE in domain(i) returns 264 to its upstream neighbor PCE in domain(i-1) a multipoint-to-point 265 tree of potential paths. Each tree consists of the set of paths from 266 all boundary nodes located in domain(i) to the destination where each 267 path satisfies the set of required constraints for the TE LSP 268 (bandwidth, affinities, etc.). 270 So a PCE needs to select boundary nodes (that is, ASBRs) that provide 271 connectivity from the upstream AS. In order for the tree of paths 272 provided by one PCE to its neighbor to be correlated, the identities 273 of the ASBRs for each path need to be referenced. Thus, the PCE must 274 know the identities of the ASBRs in the remote AS that are reached by 275 any inter-AS TE link, and, in order to provide only suitable paths in 276 the tree, the PCE must know the TE properties of the inter-AS TE 277 links. See the following figure as an example. 279 PCE1<------>PCE2<-------->PCE3 280 / : : 281 / : : 282 R1------R3----R5-----R7------R9-----R11 283 | | \ | / | 284 | | \ | ---- | 285 | | \ | / | 286 R2------R4----R6 --R8------R10----R12 287 : : 288 <-- AS1 -->:<---- AS2 --->:<--- AS3 ---> 290 Figure 2: BRPC for Inter-AS Reference Model 292 The figure shows three ASes (AS1, AS2, and AS3), three PCEs (PCE1, 293 PCE2, and PCE3), and twelve LSRs (R1 through R12). R3 and R4 are 294 ASBRs in AS1. R5, R6, R7, and R8 are ASBRs in AS2. R9 and R10 are 295 ASBRs in AS3. PCE1, PCE2, and PCE3 cooperate to perform inter-AS 296 path computation and are responsible for path segment computation 297 within their own domain(s). 299 If an inter-AS TE LSP is planned to be established from R1 to R12, 300 the traversed domains are assumed to be selected: AS1->AS2->AS3, and 301 the PCE chain is: PCE1->PCE2->PCE3. First, the path computation 302 request originated from the PCC (R1) is relayed by PCE1 and PCE2 303 along the PCE chain to PCE3. Then, PCE3 begins to compute the path 304 segments from the entry boundary nodes that provide connection from 305 AS2 to the destination (R12). But, to provide suitable path 306 segments, PCE3 must determine which entry boundary nodes provide 307 connectivity to its upstream neighbor AS (identified by its AS 308 number), and must know the TE properties of the inter-AS TE links. 309 In the same way, PCE2 also needs to determine the entry boundary 310 nodes according to its upstream neighbor AS and the inter-AS TE link 311 capabilities. 313 Thus, to support Backward Recursive Path Computation, the same 314 information listed in Section 2.2 is required. The AS number of the 315 neighboring AS connected to by each inter-AS TE link is particularly 316 important. 318 3. Extensions to ISIS-TE 320 Note that this document does not define mechanisms for distribution 321 of TE information from one AS to another, does not distribute any 322 form of TE reachability information for destinations outside the AS, 323 does not change the PCE architecture or usage, does not suggest or 324 recommend any form of TE aggregation, and does not feed private 325 information between ASes. See Section 2.1. 327 In this document, for the advertisement of inter-AS TE links, a new 328 TLV, which is referred to as the inter-AS reachability TLV, is 329 defined. Three new sub-TLVs are also defined for inclusion in the 330 inter-AS reachability TLV to carry the information about the 331 neighboring AS number and the remote ASBR ID of an inter-AS link. 332 The sub-TLVs defined in [RFC5305], [RFC6119], and other documents for 333 inclusion in the extended IS reachability TLV are applicable to be 334 included in the inter-AS reachability TLV for inter-AS TE links 335 advertisement. Also, two other new sub-TLVs are defined for 336 inclusion in the IS-IS router capability TLV to carry the TE Router 337 ID when the TE Router ID is needed to reach all routers within an 338 entire ISIS routing domain. 340 While some of the TE information of an inter-AS TE link may be 341 available within the AS from other protocols, in order to avoid any 342 dependency on where such protocols are processed, this mechanism 343 carries all the information needed for the required TE operations. 345 3.1. Inter-AS Reachability TLV 347 The inter-AS reachability TLV has type 141 (see Section 6.1) and 348 contains a data structure consisting of: 350 4 octets of Router ID 351 3 octets of default metric 352 1 octet of control information, consisting of: 353 1 bit of flooding-scope information (S bit) 354 1 bit of up/down information (D bit) 355 6 bits reserved 356 1 octet of length of sub-TLVs 357 0-246 octets of sub-TLVs, where each sub-TLV consists of a sequence of: 358 1 octet of sub-type 359 1 octet of length of the value field of the sub-TLV 360 0-244 octets of value 362 Compared to the extended reachability TLV which is defined in 363 [RFC5305], the inter-AS reachability TLV replaces the "7 octets of 364 System ID and Pseudonode Number" field with a "4 octets of Router ID" 365 field and introduces an extra "control information" field, which 366 consists of a flooding-scope bit (S bit), an up/down bit (D bit), and 367 6 reserved bits. 369 The Router ID field of the inter-AS reachability TLV is 4 octets in 370 length, which contains the IPv4 Router ID of the router who generates 371 the inter-AS reachability TLV. The Router ID SHOULD be identical to 372 the value advertised in the Traffic Engineering Router ID TLV 373 [RFC5305]. If no Traffic Engineering Router ID is assigned, the 374 Router ID SHOULD be identical to an IP Interface Address [RFC1195] 375 advertised by the originating IS. If the originating node does not 376 support IPv4, then the reserved value 0.0.0.0 MUST be used in the 377 Router ID field and the IPv6 Router ID sub-TLV MUST be present in the 378 inter-AS reachability TLV. The Router ID could be used to indicate 379 the source of the inter-AS reachability TLV. 381 The flooding procedures for inter-AS reachability TLV are identical 382 to the flooding procedures for the GENINFO TLV, which are defined in 383 Section 4 of [RFC6823]. These procedures have been previously 384 discussed in [RFC4971]. The flooding-scope bit (S bit) SHOULD be set 385 to 0 if the flooding scope is to be limited to within the single IGP 386 area to which the ASBR belongs. It MAY be set to 1 if the 387 information is intended to reach all routers (including area border 388 routers, ASBRs, and PCEs) in the entire ISIS routing domain. The 389 choice between the use of 0 or 1 is an AS-wide policy choice, and 390 configuration control SHOULD be provided in ASBR implementations that 391 support the advertisement of inter-AS TE links. 393 The sub-TLVs defined in [RFC5305], [RFC6119], and other documents for 394 describing the TE properties of a TE link are also applicable to the 395 inter-AS reachability TLV for describing the TE properties of an 396 Inter-AS TE link. Apart from these sub-TLVs, four new sub-TLVs are 397 defined for inclusion in the inter-AS reachability TLV defined in 398 this document: 400 Sub-TLV type Length Name 401 ------------ ------ --------------------------- 402 24 4 remote AS number 403 25 4 IPv4 remote ASBR identifier 404 26 16 IPv6 remote ASBR identifier 405 TBD1 16 IPv6 Router ID 407 Detailed definitions of the three new sub-TLVs are described in 408 Section 3.3.1, 3.3.2, 3.3.3, and 3.3.4. 410 3.2. TE Router ID 412 The IPv4 TE Router ID TLV and IPv6 TE Router ID TLV, which are 413 defined in [RFC5305] and [RFC6119] respectively, only have area 414 flooding-scope. When performing inter-AS TE, the TE Router ID MAY be 415 needed to reach all routers within an entire ISIS routing domain and 416 it MUST have the same flooding scope as the Inter-AS Reachability TLV 417 does. 419 [RFC4971] defines a generic advertisement mechanism for ISIS which 420 allows a router to advertise its capabilities within an ISIS area or 421 an entire ISIS routing domain. [RFC4971] also points out that the TE 422 Router ID is a candidate to be carried in the IS-IS router capability 423 TLV when performing inter-area TE. 425 This document uses such mechanism for TE Router ID advertisement when 426 the TE Router ID is needed to reach all routers within an entire ISIS 427 Routing domain. Two new sub-TLVs are defined for inclusion in the 428 IS-IS Router Capability TLV to carry the TE Router IDs. 430 Sub-TLV type Length Name 431 ------------ ------ ----------------- 432 11 4 IPv4 TE Router ID 433 12 16 IPv6 TE Router ID 435 Detailed definitions of the new sub-TLV are described in 436 Section 3.4.1 and 3.4.2. 438 3.3. Sub-TLVs for Inter-AS Reachability TLV 440 3.3.1. Remote AS Number Sub-TLV 442 A new sub-TLV, the remote AS number sub-TLV, is defined for inclusion 443 in the inter-AS reachability TLV when advertising inter-AS links. 444 The remote AS number sub-TLV specifies the AS number of the 445 neighboring AS to which the advertised link connects. 447 The remote AS number sub-TLV is TLV type 24 (see Section 6.2) and is 448 4 octets in length. The format is as follows: 450 0 1 2 3 451 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 1 452 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 453 | Type | Length | 454 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 455 | Remote AS Number | 456 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 458 The remote AS number field has 4 octets. When only 2 octets are used 459 for the AS number, as in current deployments, the left (high-order) 2 460 octets MUST be set to 0. The remote AS number sub-TLV MUST be 461 included when a router advertises an inter-AS TE link. 463 3.3.2. IPv4 Remote ASBR ID Sub-TLV 465 A new sub-TLV, which is referred to as the IPv4 remote ASBR ID sub- 466 TLV, is defined for inclusion in the inter-AS reachability TLV when 467 advertising inter-AS links. The IPv4 remote ASBR ID sub-TLV 468 specifies the IPv4 identifier of the remote ASBR to which the 469 advertised inter-AS link connects. This could be any stable and 470 routable IPv4 address of the remote ASBR. Use of the TE Router ID as 471 specified in the Traffic Engineering router ID TLV [RFC5305] is 472 RECOMMENDED. 474 The IPv4 remote ASBR ID sub-TLV is TLV type 25 (see Section 6.2) and 475 is 4 octets in length. The format of the IPv4 remote ASBR ID sub-TLV 476 is as follows: 478 0 1 2 3 479 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 1 480 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 481 | Type | Length | 482 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 483 | Remote ASBR ID | 484 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 486 The IPv4 remote ASBR ID sub-TLV MUST be included if the neighboring 487 ASBR has an IPv4 address. If the neighboring ASBR does not have an 488 IPv4 address (not even an IPv4 TE Router ID), the IPv6 remote ASBR ID 489 sub-TLV MUST be included instead. An IPv4 remote ASBR ID sub-TLV and 490 IPv6 remote ASBR ID sub-TLV MAY both be present in an extended IS 491 reachability TLV. 493 3.3.3. IPv6 Remote ASBR ID Sub-TLV 495 A new sub-TLV, which is referred to as the IPv6 remote ASBR ID sub- 496 TLV, is defined for inclusion in the inter-AS reachability TLV when 497 advertising inter-AS links. The IPv6 remote ASBR ID sub-TLV 498 specifies the IPv6 identifier of the remote ASBR to which the 499 advertised inter-AS link connects. This could be any stable and 500 routable IPv6 address of the remote ASBR. Use of the TE Router ID as 501 specified in the IPv6 Traffic Engineering router ID TLV [RFC6119] is 502 RECOMMENDED. 504 The IPv6 remote ASBR ID sub-TLV is TLV type 26 (see Section 6.2) and 505 is 16 octets in length. The format of the IPv6 remote ASBR ID sub- 506 TLV is as follows: 508 0 1 2 3 509 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 1 510 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 511 | Type | Length | 512 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 513 | Remote ASBR ID | 514 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 515 | Remote ASBR ID (continued) | 516 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 517 | Remote ASBR ID (continued) | 518 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 519 | Remote ASBR ID (continued) | 520 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 522 The IPv6 remote ASBR ID sub-TLV MUST be included if the neighboring 523 ASBR has an IPv6 address. If the neighboring ASBR does not have an 524 IPv6 address, the IPv4 remote ASBR ID sub-TLV MUST be included 525 instead. An IPv4 remote ASBR ID sub-TLV and IPv6 remote ASBR ID sub- 526 TLV MAY both be present in an extended IS reachability TLV. 528 3.3.4. IPv6 Router ID sub-TLV 530 The IPv6 Router ID sub-TLV is TLV type TBD1 (see Section 6.3) and is 531 16 octets in length. The format of the IPv6 Router ID sub-TLV is as 532 follows: 534 0 1 2 3 535 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 1 536 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 537 | Type | Length | 538 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 539 | IPv6 Router ID | 540 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 541 | IPv6 Router ID (continued) | 542 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 543 | IPv6 Router ID (continued) | 544 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 545 | IPv6 Router ID (continued) | 546 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 548 The IPv6 TE Router ID SHOULD be identical to the value advertised in 549 the IPv6 Traffic Engineering Router ID TLV [RFC6119]. 551 If the originating node does not support IPv4, the IPv6 Router ID 552 sub-TLV MUST be present in the inter-AS reachability TLV. Inter-AS 553 reachability TLVs which have a Router ID of 0.0.0.0 and do NOT have 554 the IPv6 Router ID sub-TLV present MUST be ignored. 556 3.4. Sub-TLVs for IS-IS Router Capability TLV 558 3.4.1. IPv4 TE Router ID sub-TLV 560 The IPv4 TE Router ID sub-TLV is TLV type 11 (see Section 6.3) and is 561 4 octets in length. The format of the IPv4 TE Router ID sub-TLV is 562 as follows: 564 0 1 2 3 565 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 1 566 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 567 | Type | Length | 568 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 569 | TE Router ID | 570 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 572 The IPv4 TE Router ID SHOULD be identical to the value advertised in 573 the IPv4 Traffic Engineering Router ID TLV [RFC5305]. 575 When the TE Router ID is needed to reach all routers within an entire 576 ISIS routing domain, the IS-IS Router capability TLV MUST be included 577 in its LSP. If an ASBR supports Traffic Engineering for IPv4 and if 578 the ASBR has an IPv4 TE Router ID, the IPv4 TE Router ID sub-TLV MUST 579 be included. If the ASBR does not have an IPv4 TE Router ID, the 580 IPv6 TE Router sub-TLV MUST be included instead. An IPv4 TE Router 581 ID sub-TLV and IPv6 TE Router ID sub-TLV MAY both be present in an 582 IS-IS router capability TLV. 584 3.4.2. IPv6 TE Router ID sub-TLV 586 The IPv6 TE Router ID sub-TLV is TLV type 12 (see Section 6.3) and is 587 16 octets in length. The format of the IPv6 TE Router ID sub-TLV is 588 as follows: 590 0 1 2 3 591 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 1 592 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 593 | Type | Length | 594 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 595 | TE Router ID | 596 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 597 | TE Router ID (continued) | 598 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 599 | TE Router ID (continued) | 600 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 601 | TE Router ID (continued) | 602 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 603 The IPv6 TE Router ID SHOULD be identical to the value advertised in 604 the IPv6 Traffic Engineering Router ID TLV [RFC6119]. 606 When the TE Router ID is needed to reach all routers within an entire 607 ISIS routing domain, the IS-IS router capability TLV MUST be included 608 in its LSP. If an ASBR supports Traffic Engineering for IPv6 and if 609 the ASBR has an IPv6 TE Router ID, the IPv6 TE Router ID sub-TLV MUST 610 be included. If the ASBR does not have an IPv6 TE Router ID, the 611 IPv4 TE Router sub-TLV MUST be included instead. An IPv4 TE Router 612 ID sub-TLV and IPv6 TE Router ID sub-TLV MAY both be present in an 613 IS-IS router capability TLV. 615 4. Procedure for Inter-AS TE Links 617 When TE is enabled on an inter-AS link and the link is up, the ASBR 618 SHOULD advertise this link using the normal procedures for [RFC5305]. 619 When either the link is down or TE is disabled on the link, the ASBR 620 SHOULD withdraw the advertisement. When there are changes to the TE 621 parameters for the link (for example, when the available bandwidth 622 changes), the ASBR SHOULD re-advertise the link but MUST take 623 precautions against excessive re-advertisements. 625 Hellos MUST NOT be exchanged over the inter-AS link, and 626 consequently, an ISIS adjacency MUST NOT be formed. 628 The information advertised comes from the ASBR's knowledge of the TE 629 capabilities of the link, the ASBR's knowledge of the current status 630 and usage of the link, and configuration at the ASBR of the remote AS 631 number and remote ASBR TE Router ID. 633 Legacy routers receiving an advertisement for an inter-AS TE link are 634 able to ignore it because they do not know the new TLV and sub-TLVs 635 that are defined in Section 3 of this document. They will continue 636 to flood the LSP, but will not attempt to use the information 637 received. 639 In the current operation of ISIS TE, the LSRs at each end of a TE 640 link emit LSPs describing the link. The databases in the LSRs then 641 have two entries (one locally generated, the other from the peer) 642 that describe the different 'directions' of the link. This enables 643 Constrained Shortest Path First (CSPF) to do a two-way check on the 644 link when performing path computation and eliminate it from 645 consideration unless both directions of the link satisfy the required 646 constraints. 648 In the case we are considering here (i.e., of a TE link to another 649 AS), there is, by definition, no IGP peering and hence no 650 bidirectional TE link information. In order for the CSPF route 651 computation entity to include the link as a candidate path, we have 652 to find a way to get LSPs describing its (bidirectional) TE 653 properties into the TE database. 655 This is achieved by the ASBR advertising, internally to its AS, 656 information about both directions of the TE link to the next AS. The 657 ASBR will normally generate a LSP describing its own side of a link; 658 here we have it 'proxy' for the ASBR at the edge of the other AS and 659 generate an additional LSP that describes that device's 'view' of the 660 link. 662 Only some essential TE information for the link needs to be 663 advertised; i.e., the Interface Address, the remote AS number, and 664 the remote ASBR ID of an inter-AS TE link. 666 Routers or PCEs that are capable of processing advertisements of 667 inter-AS TE links SHOULD NOT use such links to compute paths that 668 exit an AS to a remote ASBR and then immediately re-enter the AS 669 through another TE link. Such paths would constitute extremely rare 670 occurrences and SHOULD NOT be allowed except as the result of 671 specific policy configurations at the router or PCE computing the 672 path. 674 4.1. Origin of Proxied TE Information 676 Section 4 describes how an ASBR advertises TE link information as a 677 proxy for its neighbor ASBR, but does not describe where this 678 information comes from. 680 Although the source of this information is outside the scope of this 681 document, it is possible that it will be a configuration requirement 682 at the ASBR, as are other local properties of the TE link. Further, 683 where BGP is used to exchange IP routing information between the 684 ASBRs, a certain amount of additional local configuration about the 685 link and the remote ASBR is likely to be available. 687 We note further that it is possible, and may be operationally 688 advantageous, to obtain some of the required configuration 689 information from BGP. Whether and how to utilize these possibilities 690 is an implementation matter. 692 5. Security Considerations 694 The protocol extensions defined in this document are relatively minor 695 and can be secured within the AS in which they are used by the 696 existing ISIS security mechanisms (e.g., using the cleartext 697 passwords or Hashed Message Authentication Codes - Message Digest 5 698 (HMAC-MD5) algorithm, which are defined in [RFC1195] and [RFC3567] 699 separately). 701 There is no exchange of information between ASes, and no change to 702 the ISIS security relationship between the ASes. In particular, 703 since no ISIS adjacency is formed on the inter-AS links, there is no 704 requirement for ISIS security between the ASes. 706 Some of the information included in these new advertisements (e.g., 707 the remote AS number and the remote ASBR ID) is obtained manually 708 from a neighboring administration as part of a commercial 709 relationship. The source and content of this information should be 710 carefully checked before it is entered as configuration information 711 at the ASBR responsible for advertising the inter-AS TE links. 713 It is worth noting that in the scenario we are considering, a Border 714 Gateway Protocol (BGP) peering may exist between the two ASBRs and 715 that this could be used to detect inconsistencies in configuration 716 (e.g., the administration that originally supplied the information 717 may be lying, or some manual mis-configurations or mistakes may be 718 made by the operators). For example, if a different remote AS number 719 is received in a BGP OPEN [RFC4271] from that locally configured to 720 ISIS-TE, as we describe here, then local policy SHOULD be applied to 721 determine whether to alert the operator to a potential mis- 722 configuration or to suppress the ISIS advertisement of the inter-AS 723 TE link. Note further that if BGP is used to exchange TE information 724 as described in Section 4.1, the inter-AS BGP session SHOULD be 725 secured using mechanisms as described in [RFC4271] to provide 726 authentication and integrity checks. 728 For a discussion of general security considerations for IS-IS, see 729 [RFC5304]. 731 6. IANA Considerations 733 IANA is requested to make the following allocations from registries 734 under its control. 736 6.1. Inter-AS Reachability TLV 738 This document defines the following new ISIS TLV type, described in 739 Section 3.1, which has been registered in the ISIS TLV codepoint 740 registry: 742 Type Description IIH LSP SNP 743 ---- ---------------------- --- --- --- 744 141 inter-AS reachability n y n 745 information 747 6.2. Sub-TLVs for the Inter-AS Reachability TLV 749 This document defines the following new sub-TLV types (described in 750 Sections 3.3.1, 3.3.2, 3.3.3, and, 3.3.4) of top-level TLV 141 (see 751 Section 6.1 above), which have been registered in the ISIS sub-TLV 752 registry for TLV 141. Note that these four new sub-TLVs SHOULD NOT 753 appear in TLV 22 (or TLV 23, TLV 222, TLV223) and MUST be ignored in 754 TLV 22 (or TLV 23, TLV 222, TLV223): 756 Type Description 757 ---- ------------------------------ 758 24 remote AS number 759 25 IPv4 remote ASBR identifier 760 26 IPv6 remote ASBR identifier 761 TBD1 IPv6 Router ID 763 As described above in Section 3.1, the sub-TLVs which are defined in 764 [RFC5305], [RFC6119] and other documents for describing the TE 765 properties of an TE link are applicable to describe an inter-AS TE 766 link and MAY be included in the inter-AS reachability TLV when 767 adverting inter-AS TE links. 769 IANA has created the following sub-TLVs registries in "Sub-TLVs for 770 TLVs 22, 23, 141, 222, and 223" registry. 772 TLV TLV TLV TLV TLV 773 Type Description 22 23 141 222 223 Reference 774 ----- --------------------------- --- --- --- --- --- --------- 775 24 remote AS number n n y n n [This.I-D] 776 25 IPv4 remote ASBR identifier n n y n n [This.I-D] 777 26 IPv6 remote ASBR identifier n n y n n [This.I-D] 779 IANA is requested to create a new sub-TLV registry in "Sub-TLVs for 780 TLVs 22, 23, 141, 222, and 223" registry. 782 TLV TLV TLV TLV TLV 783 Type Description 22 23 141 222 223 Reference 784 ----- --------------------------- --- --- --- --- --- --------- 785 TBD1 IPv6 Router ID n n y n n [This.I-D] 787 6.3. Sub-TLVs for the IS-IS Router Capability TLV 789 This document defines the following new sub-TLV types, described in 790 Sections 3.4.1 and 3.4.2, of top-level TLV 242 (which is defined in 791 [RFC4971]) that have been registered in the ISIS sub-TLV registry for 792 TLV 242: 794 Type Description Length 795 ---- ------------------------------ -------- 796 11 IPv4 TE Router ID 4 797 12 IPv6 TE Router ID 16 799 7. Acknowledgements 801 For the original version of [RFC5316] the authors would like to thank 802 Adrian Farrel, Jean-Louis Le Roux, Christian Hopps, Les Ginsberg, and 803 Hannes Gredler for their review and comments on this document. 805 8. References 807 8.1. Normative References 809 [RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and 810 dual environments", RFC 1195, DOI 10.17487/RFC1195, 811 December 1990, . 813 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 814 Requirement Levels", BCP 14, RFC 2119, 815 DOI 10.17487/RFC2119, March 1997, 816 . 818 [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic 819 Engineering", RFC 5305, DOI 10.17487/RFC5305, October 820 2008, . 822 [RFC6119] Harrison, J., Berger, J., and M. Bartlett, "IPv6 Traffic 823 Engineering in IS-IS", RFC 6119, DOI 10.17487/RFC6119, 824 February 2011, . 826 8.2. Informative References 828 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 829 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 830 Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001, 831 . 833 [RFC3567] Li, T. and R. Atkinson, "Intermediate System to 834 Intermediate System (IS-IS) Cryptographic Authentication", 835 RFC 3567, DOI 10.17487/RFC3567, July 2003, 836 . 838 [RFC4206] Kompella, K. and Y. Rekhter, "Label Switched Paths (LSP) 839 Hierarchy with Generalized Multi-Protocol Label Switching 840 (GMPLS) Traffic Engineering (TE)", RFC 4206, 841 DOI 10.17487/RFC4206, October 2005, 842 . 844 [RFC4216] Zhang, R., Ed. and J. Vasseur, Ed., "MPLS Inter-Autonomous 845 System (AS) Traffic Engineering (TE) Requirements", 846 RFC 4216, DOI 10.17487/RFC4216, November 2005, 847 . 849 [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A 850 Border Gateway Protocol 4 (BGP-4)", RFC 4271, 851 DOI 10.17487/RFC4271, January 2006, 852 . 854 [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation 855 Element (PCE)-Based Architecture", RFC 4655, 856 DOI 10.17487/RFC4655, August 2006, 857 . 859 [RFC4971] Vasseur, JP., Ed., Shen, N., Ed., and R. Aggarwal, Ed., 860 "Intermediate System to Intermediate System (IS-IS) 861 Extensions for Advertising Router Information", RFC 4971, 862 DOI 10.17487/RFC4971, July 2007, 863 . 865 [RFC5152] Vasseur, JP., Ed., Ayyangar, A., Ed., and R. Zhang, "A 866 Per-Domain Path Computation Method for Establishing Inter- 867 Domain Traffic Engineering (TE) Label Switched Paths 868 (LSPs)", RFC 5152, DOI 10.17487/RFC5152, February 2008, 869 . 871 [RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic 872 Authentication", RFC 5304, DOI 10.17487/RFC5304, October 873 2008, . 875 [RFC5307] Kompella, K., Ed. and Y. Rekhter, Ed., "IS-IS Extensions 876 in Support of Generalized Multi-Protocol Label Switching 877 (GMPLS)", RFC 5307, DOI 10.17487/RFC5307, October 2008, 878 . 880 [RFC5316] Chen, M., Zhang, R., and X. Duan, "ISIS Extensions in 881 Support of Inter-Autonomous System (AS) MPLS and GMPLS 882 Traffic Engineering", RFC 5316, DOI 10.17487/RFC5316, 883 December 2008, . 885 [RFC5441] Vasseur, JP., Ed., Zhang, R., Bitar, N., and JL. Le Roux, 886 "A Backward-Recursive PCE-Based Computation (BRPC) 887 Procedure to Compute Shortest Constrained Inter-Domain 888 Traffic Engineering Label Switched Paths", RFC 5441, 889 DOI 10.17487/RFC5441, April 2009, 890 . 892 [RFC6823] Ginsberg, L., Previdi, S., and M. Shand, "Advertising 893 Generic Information in IS-IS", RFC 6823, 894 DOI 10.17487/RFC6823, December 2012, 895 . 897 Appendix A. Changes to RFC 5316 899 This document makes the following changes to RFC 5316. 901 RFC 5316 only allowed a 32 bit Router ID in the fixed header of TLV 902 141. This is problematic in an IPv6-only deployment where an IPv4 903 address may not be available. This document specifies: 905 1. The Router ID SHOULD be identical to the value advertised in the 906 Traffic Engineering Router ID TLV (134) if available. 908 2. If no Traffic Engineering Router ID is assigned the Router ID 909 SHOULD be identical to an IP Interface Address [RFC1195] advertised 910 by the originating IS. 912 3. If the originating node does not support IPv4, then the reserved 913 value 0.0.0.0 MUST be used in the Router ID field and the IPv6 TE 914 Router ID sub-TLV MUST be present in the TLV. 916 Authors' Addresses 918 Mach(Guoyi) Chen 919 Huawei 921 Email: mach.chen@huawei.com 923 Les Ginsberg 924 Cisco Systems 926 Email: ginsberg@cisco.com 927 Stefano Previdi 928 Cisco Systems 930 Email: sprevidi@cisco.com 932 Xiaodong Duan 933 China Mobile 935 Email: duanxiaodong@chinamobile.com