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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 833, 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: 1 error (**), 0 flaws (~~), 4 warnings (==), 4 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: April 16, 2016 S. Previdi 6 Cisco Systems 7 October 14, 2015 9 ISIS Extensions in Support of Inter-Autonomous System (AS) MPLS and 10 GMPLS Traffic Engineering 11 draft-chen-teas-rfc5316bis-00 13 Abstract 15 This document describes extensions to the ISIS (ISIS) protocol to 16 support Multiprotocol Label Switching (MPLS) and Generalized MPLS 17 (GMPLS) Traffic Engineering (TE) for multiple Autonomous Systems 18 (ASes). It defines ISIS-TE extensions for the flooding of TE 19 information about inter-AS links, which can be used to perform inter- 20 AS TE path computation. 22 No support for flooding information from within one AS to another AS 23 is proposed or defined in this document. 25 Requirements Language 27 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 28 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 29 document are to be interpreted as described in RFC 2119 [RFC2119]. 31 Status of This Memo 33 This Internet-Draft is submitted in full conformance with the 34 provisions of BCP 78 and BCP 79. 36 Internet-Drafts are working documents of the Internet Engineering 37 Task Force (IETF). Note that other groups may also distribute 38 working documents as Internet-Drafts. The list of current Internet- 39 Drafts is at http://datatracker.ietf.org/drafts/current/. 41 Internet-Drafts are draft documents valid for a maximum of six months 42 and may be updated, replaced, or obsoleted by other documents at any 43 time. It is inappropriate to use Internet-Drafts as reference 44 material or to cite them other than as "work in progress." 46 This Internet-Draft will expire on April 16, 2016. 48 Copyright Notice 50 Copyright (c) 2015 IETF Trust and the persons identified as the 51 document authors. All rights reserved. 53 This document is subject to BCP 78 and the IETF Trust's Legal 54 Provisions Relating to IETF Documents 55 (http://trustee.ietf.org/license-info) in effect on the date of 56 publication of this document. Please review these documents 57 carefully, as they describe your rights and restrictions with respect 58 to this document. Code Components extracted from this document must 59 include Simplified BSD License text as described in Section 4.e of 60 the Trust Legal Provisions and are provided without warranty as 61 described in the Simplified BSD License. 63 Table of Contents 65 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 66 2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 4 67 2.1. A Note on Non-Objectives . . . . . . . . . . . . . . . . 4 68 2.2. Per-Domain Path Determination . . . . . . . . . . . . . . 4 69 2.3. Backward Recursive Path Computation . . . . . . . . . . . 6 70 3. Extensions to ISIS-TE . . . . . . . . . . . . . . . . . . . . 7 71 3.1. Inter-AS Reachability TLV . . . . . . . . . . . . . . . . 8 72 3.2. TE Router ID . . . . . . . . . . . . . . . . . . . . . . 9 73 3.3. Sub-TLVs for Inter-AS Reachability TLV . . . . . . . . . 10 74 3.3.1. Remote AS Number Sub-TLV . . . . . . . . . . . . . . 10 75 3.3.2. IPv4 Remote ASBR ID Sub-TLV . . . . . . . . . . . . . 10 76 3.3.3. IPv6 Remote ASBR ID Sub-TLV . . . . . . . . . . . . . 11 77 3.3.4. IPv6 Router ID sub-TLV . . . . . . . . . . . . . . . 12 78 3.4. Sub-TLVs for IS-IS Router Capability TLV . . . . . . . . 12 79 3.4.1. IPv4 TE Router ID sub-TLV . . . . . . . . . . . . . . 12 80 3.4.2. IPv6 TE Router ID sub-TLV . . . . . . . . . . . . . . 13 81 4. Procedure for Inter-AS TE Links . . . . . . . . . . . . . . . 14 82 4.1. Origin of Proxied TE Information . . . . . . . . . . . . 15 83 5. Security Considerations . . . . . . . . . . . . . . . . . . . 15 84 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 85 6.1. Inter-AS Reachability TLV . . . . . . . . . . . . . . . . 16 86 6.2. Sub-TLVs for the Inter-AS Reachability TLV . . . . . . . 16 87 6.3. Sub-TLVs for the IS-IS Router Capability TLV . . . . . . 17 88 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 18 89 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 18 90 8.1. Normative References . . . . . . . . . . . . . . . . . . 18 91 8.2. Informative References . . . . . . . . . . . . . . . . . 18 92 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20 94 1. Introduction 96 [RFC5305] defines extensions to the ISIS protocol [RFC1195] to 97 support intra-area Traffic Engineering (TE). The extensions provide 98 a way of encoding the TE information for TE-enabled links within the 99 network (TE links) and flooding this information within an area. The 100 extended IS reachability TLV and traffic engineering router ID TLV, 101 which are defined in [RFC5305], are used to carry such TE 102 information. The extended IS reachability TLV has several nested 103 sub-TLVs that describe the TE attributes for a TE link. 105 [RFC6119] and [RFC5307] define similar extensions to ISIS in support 106 of IPv6 and Generalized Multiprotocol Label Switching (GMPLS) TE 107 respectively. 109 Requirements for establishing Multiprotocol Label Switching (MPLS) TE 110 Label Switched Paths (LSPs) that cross multiple Autonomous Systems 111 (ASes) are described in [RFC4216]. As described in [RFC4216], a 112 method SHOULD provide the ability to compute a path spanning multiple 113 ASes. So a path computation entity that may be the head-end Label 114 Switching Router (LSR), an AS Border Router (ASBR), or a Path 115 Computation Element (PCE) [RFC4655] needs to know the TE information 116 not only of the links within an AS, but also of the links that 117 connect to other ASes. 119 In this document, a new TLV, which is referred to as the inter-AS 120 reachability TLV, is defined to advertise inter-AS TE information, 121 three new sub-TLVs are defined for inclusion in the inter-AS 122 reachability TLV to carry the information about the remote AS number 123 and remote ASBR ID. The sub-TLVs defined in [RFC5305][RFC6119] and 124 other documents for inclusion in the extended IS reachability TLV for 125 describing the TE properties of a TE link are applicable to be 126 included in the Inter-AS Reachability TLV for describing the TE 127 properties of an inter-AS TE link as well. Also, two more new sub- 128 TLVs are defined for inclusion in the IS-IS router capability TLV to 129 carry the TE Router ID when the TE Router ID needs to reach all 130 routers within an entire ISIS routing domain. The extensions are 131 equally applicable to IPv4 and IPv6 as identical extensions to 132 [RFC5305] and [RFC6119]. Detailed definitions and procedures are 133 discussed in the following sections. 135 This document does not propose or define any mechanisms to advertise 136 any other extra-AS TE information within ISIS. See Section 2.1 for a 137 full list of non-objectives for this work. 139 2. Problem Statement 141 As described in [RFC4216], in the case of establishing an inter-AS TE 142 LSP that traverses multiple ASes, the Path message [RFC3209] may 143 include the following elements in the Explicit Route Object (ERO) in 144 order to describe the path of the LSP: 146 o a set of AS numbers as loose hops; and/or 148 o a set of LSRs including ASBRs as loose hops. 150 Two methods for determining inter-AS paths are currently being 151 discussed. The per-domain method [RFC5152] determines the path one 152 domain at a time. The backward recursive method [RFC5441] uses 153 cooperation between PCEs to determine an optimum inter-domain path. 154 The sections that follow examine how inter-AS TE link information 155 could be useful in both cases. 157 2.1. A Note on Non-Objectives 159 It is important to note that this document does not make any change 160 to the confidentiality and scaling assumptions surrounding the use of 161 ASes in the Internet. In particular, this document is conformant to 162 the requirements set out in [RFC4216]. 164 The following features are explicitly excluded: 166 o There is no attempt to distribute TE information from within one 167 AS to another AS. 169 o There is no mechanism proposed to distribute any form of TE 170 reachability information for destinations outside the AS. 172 o There is no proposed change to the PCE architecture or usage. 174 o TE aggregation is not supported or recommended. 176 o There is no exchange of private information between ASes. 178 o No ISIS adjacencies are formed on the inter-AS link. 180 2.2. Per-Domain Path Determination 182 In the per-domain method of determining an inter-AS path for an MPLS- 183 TE LSP, when an LSR that is an entry-point to an AS receives a Path 184 message from an upstream AS with an ERO containing a next hop that is 185 an AS number, it needs to find which LSRs (ASBRs) within the local AS 186 are connected to the downstream AS. That way, it can compute a TE 187 LSP segment across the local AS to one of those LSRs and forward the 188 Path message to that LSR and hence into the next AS. See Figure 1 189 for an example. 191 R1------R3----R5-----R7------R9-----R11 192 | | \ | / | 193 | | \ | ---- | 194 | | \ | / | 195 R2------R4----R6 --R8------R10----R12 196 : : 197 <-- AS1 -->:<---- AS2 --->:<--- AS3 ---> 199 Figure 1: Inter-AS Reference Model 201 The figure shows three ASes (AS1, AS2, and AS3) and twelve LSRs (R1 202 through R12). R3 and R4 are ASBRs in AS1. R5, R6, R7, and R8 are 203 ASBRs in AS2. R9 and R10 are ASBRs in AS3. 205 If an inter-AS TE LSP is planned to be established from R1 to R12, 206 the AS sequence will be: AS1, AS2, AS3. 208 Suppose that the Path message enters AS2 from R3. The next hop in 209 the ERO shows AS3, and R5 must determine a path segment across AS2 to 210 reach AS3. It has a choice of three exit points from AS2 (R6, R7, 211 and R8), and it needs to know which of these provide TE connectivity 212 to AS3, and whether the TE connectivity (for example, available 213 bandwidth) is adequate for the requested LSP. 215 Alternatively, if the next hop in the ERO is the entry ASBR for AS3 216 (say R9), R5 needs to know which of its exit ASBRs has a TE link that 217 connects to R9. Since there may be multiple ASBRs that are connected 218 to R9 (both R7 and R8 in this example), R5 also needs to know the TE 219 properties of the inter-AS TE links so that it can select the correct 220 exit ASBR. 222 Once the Path message reaches the exit ASBR, any choice of inter-AS 223 TE link can be made by the ASBR if not already made by the entry ASBR 224 that computed the segment. 226 More details can be found in Section 4 of [RFC5152], which clearly 227 points out why advertising of inter-AS links is desired. 229 To enable R5 to make the correct choice of exit ASBR, the following 230 information is needed: 232 o List of all inter-AS TE links for the local AS. 234 o TE properties of each inter-AS TE link. 236 o AS number of the neighboring AS connected to by each inter-AS TE 237 link. 239 o Identity (TE Router ID) of the neighboring ASBR connected to by 240 each inter-AS TE link. 242 In GMPLS networks, further information may also be required to select 243 the correct TE links as defined in [RFC5307]. 245 The example above shows how this information is needed at the entry- 246 point ASBRs for each AS (or the PCEs that provide computation 247 services for the ASBRs). However, this information is also needed 248 throughout the local AS if path computation functionality is fully 249 distributed among LSRs in the local AS, for example to support LSPs 250 that have start points (ingress nodes) within the AS. 252 2.3. Backward Recursive Path Computation 254 Another scenario using PCE techniques has the same problem. 255 [RFC5441] defines a PCE-based TE LSP computation method (called 256 Backward Recursive Path Computation) to compute optimal inter-domain 257 constrained MPLS-TE or GMPLS LSPs. In this path computation method, 258 a specific set of traversed domains (ASes) are assumed to be selected 259 before computation starts. Each downstream PCE in domain(i) returns 260 to its upstream neighbor PCE in domain(i-1) a multipoint-to-point 261 tree of potential paths. Each tree consists of the set of paths from 262 all boundary nodes located in domain(i) to the destination where each 263 path satisfies the set of required constraints for the TE LSP 264 (bandwidth, affinities, etc.). 266 So a PCE needs to select boundary nodes (that is, ASBRs) that provide 267 connectivity from the upstream AS. In order for the tree of paths 268 provided by one PCE to its neighbor to be correlated, the identities 269 of the ASBRs for each path need to be referenced. Thus, the PCE must 270 know the identities of the ASBRs in the remote AS that are reached by 271 any inter-AS TE link, and, in order to provide only suitable paths in 272 the tree, the PCE must know the TE properties of the inter-AS TE 273 links. See the following figure as an example. 275 PCE1<------>PCE2<-------->PCE3 276 / : : 277 / : : 278 R1------R3----R5-----R7------R9-----R11 279 | | \ | / | 280 | | \ | ---- | 281 | | \ | / | 282 R2------R4----R6 --R8------R10----R12 283 : : 284 <-- AS1 -->:<---- AS2 --->:<--- AS3 ---> 286 Figure 2: BRPC for Inter-AS Reference Model 288 The figure shows three ASes (AS1, AS2, and AS3), three PCEs (PCE1, 289 PCE2, and PCE3), and twelve LSRs (R1 through R12). R3 and R4 are 290 ASBRs in AS1. R5, R6, R7, and R8 are ASBRs in AS2. R9 and R10 are 291 ASBRs in AS3. PCE1, PCE2, and PCE3 cooperate to perform inter-AS 292 path computation and are responsible for path segment computation 293 within their own domain(s). 295 If an inter-AS TE LSP is planned to be established from R1 to R12, 296 the traversed domains are assumed to be selected: AS1->AS2->AS3, and 297 the PCE chain is: PCE1->PCE2->PCE3. First, the path computation 298 request originated from the PCC (R1) is relayed by PCE1 and PCE2 299 along the PCE chain to PCE3. Then, PCE3 begins to compute the path 300 segments from the entry boundary nodes that provide connection from 301 AS2 to the destination (R12). But, to provide suitable path 302 segments, PCE3 must determine which entry boundary nodes provide 303 connectivity to its upstream neighbor AS (identified by its AS 304 number), and must know the TE properties of the inter-AS TE links. 305 In the same way, PCE2 also needs to determine the entry boundary 306 nodes according to its upstream neighbor AS and the inter-AS TE link 307 capabilities. 309 Thus, to support Backward Recursive Path Computation, the same 310 information listed in Section 2.2 is required. The AS number of the 311 neighboring AS connected to by each inter-AS TE link is particularly 312 important. 314 3. Extensions to ISIS-TE 316 Note that this document does not define mechanisms for distribution 317 of TE information from one AS to another, does not distribute any 318 form of TE reachability information for destinations outside the AS, 319 does not change the PCE architecture or usage, does not suggest or 320 recommend any form of TE aggregation, and does not feed private 321 information between ASes. See Section 2.1. 323 In this document, for the advertisement of inter-AS TE links, a new 324 TLV, which is referred to as the inter-AS reachability TLV, is 325 defined. Three new sub-TLVs are also defined for inclusion in the 326 inter-AS reachability TLV to carry the information about the 327 neighboring AS number and the remote ASBR ID of an inter-AS link. 328 The sub-TLVs defined in [RFC5305], [RFC6119], and other documents for 329 inclusion in the extended IS reachability TLV are applicable to be 330 included in the inter-AS reachability TLV for inter-AS TE links 331 advertisement. Also, two other new sub-TLVs are defined for 332 inclusion in the IS-IS router capability TLV to carry the TE Router 333 ID when the TE Router ID is needed to reach all routers within an 334 entire ISIS routing domain. 336 While some of the TE information of an inter-AS TE link may be 337 available within the AS from other protocols, in order to avoid any 338 dependency on where such protocols are processed, this mechanism 339 carries all the information needed for the required TE operations. 341 3.1. Inter-AS Reachability TLV 343 The inter-AS reachability TLV has type 141 (see Section 6.1) and 344 contains a data structure consisting of: 346 4 octets of Router ID 347 3 octets of default metric 348 1 octet of control information, consisting of: 349 1 bit of flooding-scope information (S bit) 350 1 bit of up/down information (D bit) 351 6 bits reserved 352 1 octet of length of sub-TLVs 353 0-246 octets of sub-TLVs, where each sub-TLV consists of a sequence of: 354 1 octet of sub-type 355 1 octet of length of the value field of the sub-TLV 356 0-244 octets of value 358 Compared to the extended reachability TLV which is defined in 359 [RFC5305], the inter-AS reachability TLV replaces the "7 octets of 360 System ID and Pseudonode Number" field with a "4 octets of Router ID" 361 field and introduces an extra "control information" field, which 362 consists of a flooding-scope bit (S bit), an up/down bit (D bit), and 363 6 reserved bits. 365 The Router ID field of the inter-AS reachability TLV is 4 octets in 366 length, which contains the IPv4 Router ID of the router who generates 367 the inter-AS reachability TLV. The Router ID SHOULD be identical to 368 the value advertised in the Traffic Engineering Router ID TLV 369 [RFC5305]. If no Traffic Engineering Router ID is assigned, the 370 Router ID SHOULD be identical to an IP Interface Address [RFC1195] 371 advertised by the originating IS. If the originating node does not 372 support IPv4, then the reserved value 0.0.0.0 MUST be used in the 373 Router ID field and the IPv6 Router ID sub-TLV MUST be present in the 374 inter-AS reachability TLV. 376 The flooding procedures for inter-AS reachability TLV are identical 377 to the flooding procedures for the GENINFO TLV, which are defined in 378 Section 4 of [RFC6823]. These procedures have been previously 379 discussed in [RFC4971]. The flooding-scope bit (S bit) SHOULD be set 380 to 0 if the flooding scope is to be limited to within the single IGP 381 area to which the ASBR belongs. It MAY be set to 1 if the 382 information is intended to reach all routers (including area border 383 routers, ASBRs, and PCEs) in the entire ISIS routing domain. The 384 choice between the use of 0 or 1 is an AS-wide policy choice, and 385 configuration control SHOULD be provided in ASBR implementations that 386 support the advertisement of inter-AS TE links. 388 The sub-TLVs defined in [RFC5305], [RFC6119], and other documents for 389 describing the TE properties of a TE link are also applicable to the 390 inter-AS reachability TLV for describing the TE properties of an 391 Inter-AS TE link. Apart from these sub-TLVs, four new sub-TLVs are 392 defined for inclusion in the inter-AS reachability TLV defined in 393 this document: 395 Sub-TLV type Length Name 396 ------------ ------ --------------------------- 397 24 4 remote AS number 398 25 4 IPv4 remote ASBR identifier 399 26 16 IPv6 remote ASBR identifier 400 TBD1 16 IPv6 Router ID 402 Detailed definitions of the three new sub-TLVs are described in 403 Section 3.3.1, 3.3.2, 3.3.3, and 3.3.4. 405 3.2. TE Router ID 407 The IPv4 TE Router ID TLV and IPv6 TE Router ID TLV, which are 408 defined in [RFC5305] and [RFC6119] respectively, only have area 409 flooding-scope. When performing inter-AS TE, the TE Router ID MAY be 410 needed to reach all routers within an entire ISIS routing domain and 411 it MUST have the same flooding scope as the Inter-AS Reachability TLV 412 does. 414 [RFC4971] defines a generic advertisement mechanism for ISIS which 415 allows a router to advertise its capabilities within an ISIS area or 416 an entire ISIS routing domain. [RFC4971] also points out that the TE 417 Router ID is a candidate to be carried in the IS-IS router capability 418 TLV when performing inter-area TE. 420 This document uses such mechanism for TE Router ID advertisement when 421 the TE Router ID is needed to reach all routers within an entire ISIS 422 Routing domain. Two new sub-TLVs are defined for inclusion in the 423 IS-IS Router Capability TLV to carry the TE Router IDs. 425 Sub-TLV type Length Name 426 ------------ ------ ----------------- 427 11 4 IPv4 TE Router ID 428 12 16 IPv6 TE Router ID 430 Detailed definitions of the new sub-TLV are described in 431 Section 3.4.1 and 3.4.2. 433 3.3. Sub-TLVs for Inter-AS Reachability TLV 435 3.3.1. Remote AS Number Sub-TLV 437 A new sub-TLV, the remote AS number sub-TLV, is defined for inclusion 438 in the inter-AS reachability TLV when advertising inter-AS links. 439 The remote AS number sub-TLV specifies the AS number of the 440 neighboring AS to which the advertised link connects. 442 The remote AS number sub-TLV is TLV type 24 (see Section 6.2) and is 443 4 octets in length. The format is as follows: 445 0 1 2 3 446 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 1 447 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 448 | Type | Length | 449 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 450 | Remote AS Number | 451 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 453 The remote AS number field has 4 octets. When only 2 octets are used 454 for the AS number, as in current deployments, the left (high-order) 2 455 octets MUST be set to 0. The remote AS number sub-TLV MUST be 456 included when a router advertises an inter-AS TE link. 458 3.3.2. IPv4 Remote ASBR ID Sub-TLV 460 A new sub-TLV, which is referred to as the IPv4 remote ASBR ID sub- 461 TLV, is defined for inclusion in the inter-AS reachability TLV when 462 advertising inter-AS links. The IPv4 remote ASBR ID sub-TLV 463 specifies the IPv4 identifier of the remote ASBR to which the 464 advertised inter-AS link connects. This could be any stable and 465 routable IPv4 address of the remote ASBR. Use of the TE Router ID as 466 specified in the Traffic Engineering router ID TLV [RFC5305] is 467 RECOMMENDED. 469 The IPv4 remote ASBR ID sub-TLV is TLV type 25 (see Section 6.2) and 470 is 4 octets in length. The format of the IPv4 remote ASBR ID sub-TLV 471 is as follows: 473 0 1 2 3 474 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 1 475 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 476 | Type | Length | 477 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 478 | Remote ASBR ID | 479 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 481 The IPv4 remote ASBR ID sub-TLV MUST be included if the neighboring 482 ASBR has an IPv4 address. If the neighboring ASBR does not have an 483 IPv4 address (not even an IPv4 TE Router ID), the IPv6 remote ASBR ID 484 sub-TLV MUST be included instead. An IPv4 remote ASBR ID sub-TLV and 485 IPv6 remote ASBR ID sub-TLV MAY both be present in an extended IS 486 reachability TLV. 488 3.3.3. IPv6 Remote ASBR ID Sub-TLV 490 A new sub-TLV, which is referred to as the IPv6 remote ASBR ID sub- 491 TLV, is defined for inclusion in the inter-AS reachability TLV when 492 advertising inter-AS links. The IPv6 remote ASBR ID sub-TLV 493 specifies the IPv6 identifier of the remote ASBR to which the 494 advertised inter-AS link connects. This could be any stable and 495 routable IPv6 address of the remote ASBR. Use of the TE Router ID as 496 specified in the IPv6 Traffic Engineering router ID TLV [RFC6119] is 497 RECOMMENDED. 499 The IPv6 remote ASBR ID sub-TLV is TLV type 26 (see Section 6.2) and 500 is 16 octets in length. The format of the IPv6 remote ASBR ID sub- 501 TLV is as follows: 503 0 1 2 3 504 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 1 505 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 506 | Type | Length | 507 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 508 | Remote ASBR ID | 509 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 510 | Remote ASBR ID (continued) | 511 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 512 | Remote ASBR ID (continued) | 513 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 514 | Remote ASBR ID (continued) | 515 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 516 The IPv6 remote ASBR ID sub-TLV MUST be included if the neighboring 517 ASBR has an IPv6 address. If the neighboring ASBR does not have an 518 IPv6 address, the IPv4 remote ASBR ID sub-TLV MUST be included 519 instead. An IPv4 remote ASBR ID sub-TLV and IPv6 remote ASBR ID sub- 520 TLV MAY both be present in an extended IS reachability TLV. 522 3.3.4. IPv6 Router ID sub-TLV 524 The IPv6 Router ID sub-TLV is TLV type TBD1 (see Section 6.3) and is 525 16 octets in length. The format of the IPv6 Router ID sub-TLV is as 526 follows: 528 0 1 2 3 529 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 1 530 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 531 | Type | Length | 532 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 533 | IPv6 Router ID | 534 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 535 | IPv6 Router ID (continued) | 536 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 537 | IPv6 Router ID (continued) | 538 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 539 | IPv6 Router ID (continued) | 540 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 542 The IPv6 TE Router ID SHOULD be identical to the value advertised in 543 the IPv6 Traffic Engineering Router ID TLV [RFC6119]. 545 If the originating node does not support IPv4, the IPv6 Router ID 546 sub-TLV MUST be present in the inter-AS reachability TLV. Inter-AS 547 reachability TLVs which have a Router ID of 0.0.0.0 and do NOT have 548 the IPv6 Router ID sub-TLV present MUST be ignored. 550 3.4. Sub-TLVs for IS-IS Router Capability TLV 552 3.4.1. IPv4 TE Router ID sub-TLV 554 The IPv4 TE Router ID sub-TLV is TLV type 11 (see Section 6.3) and is 555 4 octets in length. The format of the IPv4 TE Router ID sub-TLV is 556 as follows: 558 0 1 2 3 559 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 1 560 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 561 | Type | Length | 562 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 563 | TE Router ID | 564 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 566 The IPv4 TE Router ID SHOULD be identical to the value advertised in 567 the IPv4 Traffic Engineering Router ID TLV [RFC5305]. 569 When the TE Router ID is needed to reach all routers within an entire 570 ISIS routing domain, the IS-IS Router capability TLV MUST be included 571 in its LSP. If an ASBR supports Traffic Engineering for IPv4 and if 572 the ASBR has an IPv4 TE Router ID, the IPv4 TE Router ID sub-TLV MUST 573 be included. If the ASBR does not have an IPv4 TE Router ID, the 574 IPv6 TE Router sub-TLV MUST be included instead. An IPv4 TE Router 575 ID sub-TLV and IPv6 TE Router ID sub-TLV MAY both be present in an 576 IS-IS router capability TLV. 578 3.4.2. IPv6 TE Router ID sub-TLV 580 The IPv6 TE Router ID sub-TLV is TLV type 12 (see Section 6.3) and is 581 16 octets in length. The format of the IPv6 TE Router ID sub-TLV is 582 as follows: 584 0 1 2 3 585 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 1 586 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 587 | Type | Length | 588 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 589 | TE Router ID | 590 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 591 | TE Router ID (continued) | 592 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 593 | TE Router ID (continued) | 594 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 595 | TE Router ID (continued) | 596 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 598 The IPv6 TE Router ID SHOULD be identical to the value advertised in 599 the IPv6 Traffic Engineering Router ID TLV [RFC6119]. 601 When the TE Router ID is needed to reach all routers within an entire 602 ISIS routing domain, the IS-IS router capability TLV MUST be included 603 in its LSP. If an ASBR supports Traffic Engineering for IPv6 and if 604 the ASBR has an IPv6 TE Router ID, the IPv6 TE Router ID sub-TLV MUST 605 be included. If the ASBR does not have an IPv6 TE Router ID, the 606 IPv4 TE Router sub-TLV MUST be included instead. An IPv4 TE Router 607 ID sub-TLV and IPv6 TE Router ID sub-TLV MAY both be present in an 608 IS-IS router capability TLV. 610 4. Procedure for Inter-AS TE Links 612 When TE is enabled on an inter-AS link and the link is up, the ASBR 613 SHOULD advertise this link using the normal procedures for [RFC5305]. 614 When either the link is down or TE is disabled on the link, the ASBR 615 SHOULD withdraw the advertisement. When there are changes to the TE 616 parameters for the link (for example, when the available bandwidth 617 changes), the ASBR SHOULD re-advertise the link but MUST take 618 precautions against excessive re-advertisements. 620 Hellos MUST NOT be exchanged over the inter-AS link, and 621 consequently, an ISIS adjacency MUST NOT be formed. 623 The information advertised comes from the ASBR's knowledge of the TE 624 capabilities of the link, the ASBR's knowledge of the current status 625 and usage of the link, and configuration at the ASBR of the remote AS 626 number and remote ASBR TE Router ID. 628 Legacy routers receiving an advertisement for an inter-AS TE link are 629 able to ignore it because they do not know the new TLV and sub-TLVs 630 that are defined in Section 3 of this document. They will continue 631 to flood the LSP, but will not attempt to use the information 632 received. 634 In the current operation of ISIS TE, the LSRs at each end of a TE 635 link emit LSPs describing the link. The databases in the LSRs then 636 have two entries (one locally generated, the other from the peer) 637 that describe the different 'directions' of the link. This enables 638 Constrained Shortest Path First (CSPF) to do a two-way check on the 639 link when performing path computation and eliminate it from 640 consideration unless both directions of the link satisfy the required 641 constraints. 643 In the case we are considering here (i.e., of a TE link to another 644 AS), there is, by definition, no IGP peering and hence no 645 bidirectional TE link information. In order for the CSPF route 646 computation entity to include the link as a candidate path, we have 647 to find a way to get LSPs describing its (bidirectional) TE 648 properties into the TE database. 650 This is achieved by the ASBR advertising, internally to its AS, 651 information about both directions of the TE link to the next AS. The 652 ASBR will normally generate a LSP describing its own side of a link; 653 here we have it 'proxy' for the ASBR at the edge of the other AS and 654 generate an additional LSP that describes that device's 'view' of the 655 link. 657 Only some essential TE information for the link needs to be 658 advertised; i.e., the Interface Address, the remote AS number, and 659 the remote ASBR ID of an inter-AS TE link. 661 Routers or PCEs that are capable of processing advertisements of 662 inter-AS TE links SHOULD NOT use such links to compute paths that 663 exit an AS to a remote ASBR and then immediately re-enter the AS 664 through another TE link. Such paths would constitute extremely rare 665 occurrences and SHOULD NOT be allowed except as the result of 666 specific policy configurations at the router or PCE computing the 667 path. 669 4.1. Origin of Proxied TE Information 671 Section 4 describes how an ASBR advertises TE link information as a 672 proxy for its neighbor ASBR, but does not describe where this 673 information comes from. 675 Although the source of this information is outside the scope of this 676 document, it is possible that it will be a configuration requirement 677 at the ASBR, as are other local properties of the TE link. Further, 678 where BGP is used to exchange IP routing information between the 679 ASBRs, a certain amount of additional local configuration about the 680 link and the remote ASBR is likely to be available. 682 We note further that it is possible, and may be operationally 683 advantageous, to obtain some of the required configuration 684 information from BGP. Whether and how to utilize these possibilities 685 is an implementation matter. 687 5. Security Considerations 689 The protocol extensions defined in this document are relatively minor 690 and can be secured within the AS in which they are used by the 691 existing ISIS security mechanisms (e.g., using the cleartext 692 passwords or Hashed Message Authentication Codes - Message Digest 5 693 (HMAC-MD5) algorithm, which are defined in [RFC1195] and [RFC3567] 694 separately). 696 There is no exchange of information between ASes, and no change to 697 the ISIS security relationship between the ASes. In particular, 698 since no ISIS adjacency is formed on the inter-AS links, there is no 699 requirement for ISIS security between the ASes. 701 Some of the information included in these new advertisements (e.g., 702 the remote AS number and the remote ASBR ID) is obtained manually 703 from a neighboring administration as part of a commercial 704 relationship. The source and content of this information should be 705 carefully checked before it is entered as configuration information 706 at the ASBR responsible for advertising the inter-AS TE links. 708 It is worth noting that in the scenario we are considering, a Border 709 Gateway Protocol (BGP) peering may exist between the two ASBRs and 710 that this could be used to detect inconsistencies in configuration 711 (e.g., the administration that originally supplied the information 712 may be lying, or some manual mis-configurations or mistakes may be 713 made by the operators). For example, if a different remote AS number 714 is received in a BGP OPEN [RFC4271] from that locally configured to 715 ISIS-TE, as we describe here, then local policy SHOULD be applied to 716 determine whether to alert the operator to a potential mis- 717 configuration or to suppress the ISIS advertisement of the inter-AS 718 TE link. Note further that if BGP is used to exchange TE information 719 as described in Section 4.1, the inter-AS BGP session SHOULD be 720 secured using mechanisms as described in [RFC4271] to provide 721 authentication and integrity checks. 723 For a discussion of general security considerations for IS-IS, see 724 [RFC5304]. 726 6. IANA Considerations 728 IANA is requested to make the following allocations from registries 729 under its control. 731 6.1. Inter-AS Reachability TLV 733 This document defines the following new ISIS TLV type, described in 734 Section 3.1, which has been registered in the ISIS TLV codepoint 735 registry: 737 Type Description IIH LSP SNP 738 ---- ---------------------- --- --- --- 739 141 inter-AS reachability n y n 740 information 742 6.2. Sub-TLVs for the Inter-AS Reachability TLV 744 This document defines the following new sub-TLV types (described in 745 Sections 3.3.1, 3.3.2, 3.3.3, and, 3.3.4) of top-level TLV 141 (see 746 Section 6.1 above), which have been registered in the ISIS sub-TLV 747 registry for TLV 141. Note that these four new sub-TLVs SHOULD NOT 748 appear in TLV 22 (or TLV 23, TLV 222, TLV223) and MUST be ignored in 749 TLV 22 (or TLV 23, TLV 222, TLV223): 751 Type Description 752 ---- ------------------------------ 753 24 remote AS number 754 25 IPv4 remote ASBR identifier 755 26 IPv6 remote ASBR identifier 756 TBD1 IPv6 Router ID 758 As described above in Section 3.1, the sub-TLVs which are defined in 759 [RFC5305], [RFC6119] and other documents for describing the TE 760 properties of an TE link are applicable to describe an inter-AS TE 761 link and MAY be included in the inter-AS reachability TLV when 762 adverting inter-AS TE links. 764 IANA has created the following sub-TLVs registries in "Sub-TLVs for 765 TLVs 22, 23, 141, 222, and 223" registry. 767 TLV TLV TLV TLV TLV 768 Type Description 22 23 141 222 223 Reference 769 ----- --------------------------- --- --- --- --- --- --------- 770 24 remote AS number n n y n n [This.I-D] 771 25 IPv4 remote ASBR identifier n n y n n [This.I-D] 772 26 IPv6 remote ASBR identifier n n y n n [This.I-D] 774 IANA is requested to create a new sub-TLV registry in "Sub-TLVs for 775 TLVs 22, 23, 141, 222, and 223" registry. 777 TLV TLV TLV TLV TLV 778 Type Description 22 23 141 222 223 Reference 779 ----- --------------------------- --- --- --- --- --- --------- 780 TBD1 IPv6 Router ID n n y n n [This.I-D] 782 6.3. Sub-TLVs for the IS-IS Router Capability TLV 784 This document defines the following new sub-TLV types, described in 785 Sections 3.4.1 and 3.4.2, of top-level TLV 242 (which is defined in 786 [RFC4971]) that have been registered in the ISIS sub-TLV registry for 787 TLV 242: 789 Type Description Length 790 ---- ------------------------------ -------- 791 11 IPv4 TE Router ID 4 792 12 IPv6 TE Router ID 16 794 7. Acknowledgements 796 For the original version of [RFC5316] the authors would like to thank 797 Adrian Farrel, Jean-Louis Le Roux, Christian Hopps, Les Ginsberg, and 798 Hannes Gredler for their review and comments on this document. 800 8. References 802 8.1. Normative References 804 [RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and 805 dual environments", RFC 1195, DOI 10.17487/RFC1195, 806 December 1990, . 808 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 809 Requirement Levels", BCP 14, RFC 2119, 810 DOI 10.17487/RFC2119, March 1997, 811 . 813 [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic 814 Engineering", RFC 5305, DOI 10.17487/RFC5305, October 815 2008, . 817 [RFC6119] Harrison, J., Berger, J., and M. Bartlett, "IPv6 Traffic 818 Engineering in IS-IS", RFC 6119, DOI 10.17487/RFC6119, 819 February 2011, . 821 8.2. Informative References 823 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 824 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 825 Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001, 826 . 828 [RFC3567] Li, T. and R. Atkinson, "Intermediate System to 829 Intermediate System (IS-IS) Cryptographic Authentication", 830 RFC 3567, DOI 10.17487/RFC3567, July 2003, 831 . 833 [RFC4206] Kompella, K. and Y. Rekhter, "Label Switched Paths (LSP) 834 Hierarchy with Generalized Multi-Protocol Label Switching 835 (GMPLS) Traffic Engineering (TE)", RFC 4206, 836 DOI 10.17487/RFC4206, October 2005, 837 . 839 [RFC4216] Zhang, R., Ed. and J. Vasseur, Ed., "MPLS Inter-Autonomous 840 System (AS) Traffic Engineering (TE) Requirements", 841 RFC 4216, DOI 10.17487/RFC4216, November 2005, 842 . 844 [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A 845 Border Gateway Protocol 4 (BGP-4)", RFC 4271, 846 DOI 10.17487/RFC4271, January 2006, 847 . 849 [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation 850 Element (PCE)-Based Architecture", RFC 4655, 851 DOI 10.17487/RFC4655, August 2006, 852 . 854 [RFC4971] Vasseur, JP., Ed., Shen, N., Ed., and R. Aggarwal, Ed., 855 "Intermediate System to Intermediate System (IS-IS) 856 Extensions for Advertising Router Information", RFC 4971, 857 DOI 10.17487/RFC4971, July 2007, 858 . 860 [RFC5152] Vasseur, JP., Ed., Ayyangar, A., Ed., and R. Zhang, "A 861 Per-Domain Path Computation Method for Establishing Inter- 862 Domain Traffic Engineering (TE) Label Switched Paths 863 (LSPs)", RFC 5152, DOI 10.17487/RFC5152, February 2008, 864 . 866 [RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic 867 Authentication", RFC 5304, DOI 10.17487/RFC5304, October 868 2008, . 870 [RFC5307] Kompella, K., Ed. and Y. Rekhter, Ed., "IS-IS Extensions 871 in Support of Generalized Multi-Protocol Label Switching 872 (GMPLS)", RFC 5307, DOI 10.17487/RFC5307, October 2008, 873 . 875 [RFC5316] Chen, M., Zhang, R., and X. Duan, "ISIS Extensions in 876 Support of Inter-Autonomous System (AS) MPLS and GMPLS 877 Traffic Engineering", RFC 5316, DOI 10.17487/RFC5316, 878 December 2008, . 880 [RFC5441] Vasseur, JP., Ed., Zhang, R., Bitar, N., and JL. Le Roux, 881 "A Backward-Recursive PCE-Based Computation (BRPC) 882 Procedure to Compute Shortest Constrained Inter-Domain 883 Traffic Engineering Label Switched Paths", RFC 5441, 884 DOI 10.17487/RFC5441, April 2009, 885 . 887 [RFC6823] Ginsberg, L., Previdi, S., and M. Shand, "Advertising 888 Generic Information in IS-IS", RFC 6823, 889 DOI 10.17487/RFC6823, December 2012, 890 . 892 Authors' Addresses 894 Mach(Guoyi) Chen 895 Huawei 897 Email: mach.chen@huawei.com 899 Les Ginsberg 900 Cisco Systems 902 Email: ginsberg@cisco.com 904 Stefano Previdi 905 Cisco Systems 907 Email: sprevidi@cisco.com