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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 837, 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: May 19, 2016 S. Previdi 6 Cisco Systems 7 D. Xiaodong 8 China Mobile 9 November 16, 2015 11 ISIS Extensions in Support of Inter-Autonomous System (AS) MPLS and 12 GMPLS Traffic Engineering 13 draft-chen-isis-rfc5316bis-00 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 May 19, 2016. 51 Copyright Notice 53 Copyright (c) 2015 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 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20 97 1. Introduction 99 [RFC5305] defines extensions to the ISIS protocol [RFC1195] to 100 support intra-area Traffic Engineering (TE). The extensions provide 101 a way of encoding the TE information for TE-enabled links within the 102 network (TE links) and flooding this information within an area. The 103 extended IS reachability TLV and traffic engineering router ID TLV, 104 which are defined in [RFC5305], are used to carry such TE 105 information. The extended IS reachability TLV has several nested 106 sub-TLVs that describe the TE attributes for a TE link. 108 [RFC6119] and [RFC5307] define similar extensions to ISIS in support 109 of IPv6 and Generalized Multiprotocol Label Switching (GMPLS) TE 110 respectively. 112 Requirements for establishing Multiprotocol Label Switching (MPLS) TE 113 Label Switched Paths (LSPs) that cross multiple Autonomous Systems 114 (ASes) are described in [RFC4216]. As described in [RFC4216], a 115 method SHOULD provide the ability to compute a path spanning multiple 116 ASes. So a path computation entity that may be the head-end Label 117 Switching Router (LSR), an AS Border Router (ASBR), or a Path 118 Computation Element (PCE) [RFC4655] needs to know the TE information 119 not only of the links within an AS, but also of the links that 120 connect to other ASes. 122 In this document, a new TLV, which is referred to as the inter-AS 123 reachability TLV, is defined to advertise inter-AS TE information, 124 three new sub-TLVs are defined for inclusion in the inter-AS 125 reachability TLV to carry the information about the remote AS number 126 and remote ASBR ID. The sub-TLVs defined in [RFC5305][RFC6119] and 127 other documents for inclusion in the extended IS reachability TLV for 128 describing the TE properties of a TE link are applicable to be 129 included in the Inter-AS Reachability TLV for describing the TE 130 properties of an inter-AS TE link as well. Also, two more new sub- 131 TLVs are defined for inclusion in the IS-IS router capability TLV to 132 carry the TE Router ID when the TE Router ID needs to reach all 133 routers within an entire ISIS routing domain. The extensions are 134 equally applicable to IPv4 and IPv6 as identical extensions to 135 [RFC5305] and [RFC6119]. Detailed definitions and procedures are 136 discussed in the following sections. 138 This document does not propose or define any mechanisms to advertise 139 any other extra-AS TE information within ISIS. See Section 2.1 for a 140 full list of non-objectives for this work. 142 2. Problem Statement 144 As described in [RFC4216], in the case of establishing an inter-AS TE 145 LSP that traverses multiple ASes, the Path message [RFC3209] may 146 include the following elements in the Explicit Route Object (ERO) in 147 order to describe the path of the LSP: 149 o a set of AS numbers as loose hops; and/or 151 o a set of LSRs including ASBRs as loose hops. 153 Two methods for determining inter-AS paths are currently being 154 discussed. The per-domain method [RFC5152] determines the path one 155 domain at a time. The backward recursive method [RFC5441] uses 156 cooperation between PCEs to determine an optimum inter-domain path. 157 The sections that follow examine how inter-AS TE link information 158 could be useful in both cases. 160 2.1. A Note on Non-Objectives 162 It is important to note that this document does not make any change 163 to the confidentiality and scaling assumptions surrounding the use of 164 ASes in the Internet. In particular, this document is conformant to 165 the requirements set out in [RFC4216]. 167 The following features are explicitly excluded: 169 o There is no attempt to distribute TE information from within one 170 AS to another AS. 172 o There is no mechanism proposed to distribute any form of TE 173 reachability information for destinations outside the AS. 175 o There is no proposed change to the PCE architecture or usage. 177 o TE aggregation is not supported or recommended. 179 o There is no exchange of private information between ASes. 181 o No ISIS adjacencies are formed on the inter-AS link. 183 2.2. Per-Domain Path Determination 185 In the per-domain method of determining an inter-AS path for an MPLS- 186 TE LSP, when an LSR that is an entry-point to an AS receives a Path 187 message from an upstream AS with an ERO containing a next hop that is 188 an AS number, it needs to find which LSRs (ASBRs) within the local AS 189 are connected to the downstream AS. That way, it can compute a TE 190 LSP segment across the local AS to one of those LSRs and forward the 191 Path message to that LSR and hence into the next AS. See Figure 1 192 for an example. 194 R1------R3----R5-----R7------R9-----R11 195 | | \ | / | 196 | | \ | ---- | 197 | | \ | / | 198 R2------R4----R6 --R8------R10----R12 199 : : 200 <-- AS1 -->:<---- AS2 --->:<--- AS3 ---> 202 Figure 1: Inter-AS Reference Model 204 The figure shows three ASes (AS1, AS2, and AS3) and twelve LSRs (R1 205 through R12). R3 and R4 are ASBRs in AS1. R5, R6, R7, and R8 are 206 ASBRs in AS2. R9 and R10 are ASBRs in AS3. 208 If an inter-AS TE LSP is planned to be established from R1 to R12, 209 the AS sequence will be: AS1, AS2, AS3. 211 Suppose that the Path message enters AS2 from R3. The next hop in 212 the ERO shows AS3, and R5 must determine a path segment across AS2 to 213 reach AS3. It has a choice of three exit points from AS2 (R6, R7, 214 and R8), and it needs to know which of these provide TE connectivity 215 to AS3, and whether the TE connectivity (for example, available 216 bandwidth) is adequate for the requested LSP. 218 Alternatively, if the next hop in the ERO is the entry ASBR for AS3 219 (say R9), R5 needs to know which of its exit ASBRs has a TE link that 220 connects to R9. Since there may be multiple ASBRs that are connected 221 to R9 (both R7 and R8 in this example), R5 also needs to know the TE 222 properties of the inter-AS TE links so that it can select the correct 223 exit ASBR. 225 Once the Path message reaches the exit ASBR, any choice of inter-AS 226 TE link can be made by the ASBR if not already made by the entry ASBR 227 that computed the segment. 229 More details can be found in Section 4 of [RFC5152], which clearly 230 points out why advertising of inter-AS links is desired. 232 To enable R5 to make the correct choice of exit ASBR, the following 233 information is needed: 235 o List of all inter-AS TE links for the local AS. 237 o TE properties of each inter-AS TE link. 239 o AS number of the neighboring AS connected to by each inter-AS TE 240 link. 242 o Identity (TE Router ID) of the neighboring ASBR connected to by 243 each inter-AS TE link. 245 In GMPLS networks, further information may also be required to select 246 the correct TE links as defined in [RFC5307]. 248 The example above shows how this information is needed at the entry- 249 point ASBRs for each AS (or the PCEs that provide computation 250 services for the ASBRs). However, this information is also needed 251 throughout the local AS if path computation functionality is fully 252 distributed among LSRs in the local AS, for example to support LSPs 253 that have start points (ingress nodes) within the AS. 255 2.3. Backward Recursive Path Computation 257 Another scenario using PCE techniques has the same problem. 258 [RFC5441] defines a PCE-based TE LSP computation method (called 259 Backward Recursive Path Computation) to compute optimal inter-domain 260 constrained MPLS-TE or GMPLS LSPs. In this path computation method, 261 a specific set of traversed domains (ASes) are assumed to be selected 262 before computation starts. Each downstream PCE in domain(i) returns 263 to its upstream neighbor PCE in domain(i-1) a multipoint-to-point 264 tree of potential paths. Each tree consists of the set of paths from 265 all boundary nodes located in domain(i) to the destination where each 266 path satisfies the set of required constraints for the TE LSP 267 (bandwidth, affinities, etc.). 269 So a PCE needs to select boundary nodes (that is, ASBRs) that provide 270 connectivity from the upstream AS. In order for the tree of paths 271 provided by one PCE to its neighbor to be correlated, the identities 272 of the ASBRs for each path need to be referenced. Thus, the PCE must 273 know the identities of the ASBRs in the remote AS that are reached by 274 any inter-AS TE link, and, in order to provide only suitable paths in 275 the tree, the PCE must know the TE properties of the inter-AS TE 276 links. See the following figure as an example. 278 PCE1<------>PCE2<-------->PCE3 279 / : : 280 / : : 281 R1------R3----R5-----R7------R9-----R11 282 | | \ | / | 283 | | \ | ---- | 284 | | \ | / | 285 R2------R4----R6 --R8------R10----R12 286 : : 287 <-- AS1 -->:<---- AS2 --->:<--- AS3 ---> 289 Figure 2: BRPC for Inter-AS Reference Model 291 The figure shows three ASes (AS1, AS2, and AS3), three PCEs (PCE1, 292 PCE2, and PCE3), and twelve LSRs (R1 through R12). R3 and R4 are 293 ASBRs in AS1. R5, R6, R7, and R8 are ASBRs in AS2. R9 and R10 are 294 ASBRs in AS3. PCE1, PCE2, and PCE3 cooperate to perform inter-AS 295 path computation and are responsible for path segment computation 296 within their own domain(s). 298 If an inter-AS TE LSP is planned to be established from R1 to R12, 299 the traversed domains are assumed to be selected: AS1->AS2->AS3, and 300 the PCE chain is: PCE1->PCE2->PCE3. First, the path computation 301 request originated from the PCC (R1) is relayed by PCE1 and PCE2 302 along the PCE chain to PCE3. Then, PCE3 begins to compute the path 303 segments from the entry boundary nodes that provide connection from 304 AS2 to the destination (R12). But, to provide suitable path 305 segments, PCE3 must determine which entry boundary nodes provide 306 connectivity to its upstream neighbor AS (identified by its AS 307 number), and must know the TE properties of the inter-AS TE links. 308 In the same way, PCE2 also needs to determine the entry boundary 309 nodes according to its upstream neighbor AS and the inter-AS TE link 310 capabilities. 312 Thus, to support Backward Recursive Path Computation, the same 313 information listed in Section 2.2 is required. The AS number of the 314 neighboring AS connected to by each inter-AS TE link is particularly 315 important. 317 3. Extensions to ISIS-TE 319 Note that this document does not define mechanisms for distribution 320 of TE information from one AS to another, does not distribute any 321 form of TE reachability information for destinations outside the AS, 322 does not change the PCE architecture or usage, does not suggest or 323 recommend any form of TE aggregation, and does not feed private 324 information between ASes. See Section 2.1. 326 In this document, for the advertisement of inter-AS TE links, a new 327 TLV, which is referred to as the inter-AS reachability TLV, is 328 defined. Three new sub-TLVs are also defined for inclusion in the 329 inter-AS reachability TLV to carry the information about the 330 neighboring AS number and the remote ASBR ID of an inter-AS link. 331 The sub-TLVs defined in [RFC5305], [RFC6119], and other documents for 332 inclusion in the extended IS reachability TLV are applicable to be 333 included in the inter-AS reachability TLV for inter-AS TE links 334 advertisement. Also, two other new sub-TLVs are defined for 335 inclusion in the IS-IS router capability TLV to carry the TE Router 336 ID when the TE Router ID is needed to reach all routers within an 337 entire ISIS routing domain. 339 While some of the TE information of an inter-AS TE link may be 340 available within the AS from other protocols, in order to avoid any 341 dependency on where such protocols are processed, this mechanism 342 carries all the information needed for the required TE operations. 344 3.1. Inter-AS Reachability TLV 346 The inter-AS reachability TLV has type 141 (see Section 6.1) and 347 contains a data structure consisting of: 349 4 octets of Router ID 350 3 octets of default metric 351 1 octet of control information, consisting of: 352 1 bit of flooding-scope information (S bit) 353 1 bit of up/down information (D bit) 354 6 bits reserved 355 1 octet of length of sub-TLVs 356 0-246 octets of sub-TLVs, where each sub-TLV consists of a sequence of: 357 1 octet of sub-type 358 1 octet of length of the value field of the sub-TLV 359 0-244 octets of value 361 Compared to the extended reachability TLV which is defined in 362 [RFC5305], the inter-AS reachability TLV replaces the "7 octets of 363 System ID and Pseudonode Number" field with a "4 octets of Router ID" 364 field and introduces an extra "control information" field, which 365 consists of a flooding-scope bit (S bit), an up/down bit (D bit), and 366 6 reserved bits. 368 The Router ID field of the inter-AS reachability TLV is 4 octets in 369 length, which contains the IPv4 Router ID of the router who generates 370 the inter-AS reachability TLV. The Router ID SHOULD be identical to 371 the value advertised in the Traffic Engineering Router ID TLV 372 [RFC5305]. If no Traffic Engineering Router ID is assigned, the 373 Router ID SHOULD be identical to an IP Interface Address [RFC1195] 374 advertised by the originating IS. If the originating node does not 375 support IPv4, then the reserved value 0.0.0.0 MUST be used in the 376 Router ID field and the IPv6 Router ID sub-TLV MUST be present in the 377 inter-AS reachability TLV. The Router ID could be used to indicate 378 the source of the inter-AS reachability TLV. 380 The flooding procedures for inter-AS reachability TLV are identical 381 to the flooding procedures for the GENINFO TLV, which are defined in 382 Section 4 of [RFC6823]. These procedures have been previously 383 discussed in [RFC4971]. The flooding-scope bit (S bit) SHOULD be set 384 to 0 if the flooding scope is to be limited to within the single IGP 385 area to which the ASBR belongs. It MAY be set to 1 if the 386 information is intended to reach all routers (including area border 387 routers, ASBRs, and PCEs) in the entire ISIS routing domain. The 388 choice between the use of 0 or 1 is an AS-wide policy choice, and 389 configuration control SHOULD be provided in ASBR implementations that 390 support the advertisement of inter-AS TE links. 392 The sub-TLVs defined in [RFC5305], [RFC6119], and other documents for 393 describing the TE properties of a TE link are also applicable to the 394 inter-AS reachability TLV for describing the TE properties of an 395 Inter-AS TE link. Apart from these sub-TLVs, four new sub-TLVs are 396 defined for inclusion in the inter-AS reachability TLV defined in 397 this document: 399 Sub-TLV type Length Name 400 ------------ ------ --------------------------- 401 24 4 remote AS number 402 25 4 IPv4 remote ASBR identifier 403 26 16 IPv6 remote ASBR identifier 404 TBD1 16 IPv6 Router ID 406 Detailed definitions of the three new sub-TLVs are described in 407 Section 3.3.1, 3.3.2, 3.3.3, and 3.3.4. 409 3.2. TE Router ID 411 The IPv4 TE Router ID TLV and IPv6 TE Router ID TLV, which are 412 defined in [RFC5305] and [RFC6119] respectively, only have area 413 flooding-scope. When performing inter-AS TE, the TE Router ID MAY be 414 needed to reach all routers within an entire ISIS routing domain and 415 it MUST have the same flooding scope as the Inter-AS Reachability TLV 416 does. 418 [RFC4971] defines a generic advertisement mechanism for ISIS which 419 allows a router to advertise its capabilities within an ISIS area or 420 an entire ISIS routing domain. [RFC4971] also points out that the TE 421 Router ID is a candidate to be carried in the IS-IS router capability 422 TLV when performing inter-area TE. 424 This document uses such mechanism for TE Router ID advertisement when 425 the TE Router ID is needed to reach all routers within an entire ISIS 426 Routing domain. Two new sub-TLVs are defined for inclusion in the 427 IS-IS Router Capability TLV to carry the TE Router IDs. 429 Sub-TLV type Length Name 430 ------------ ------ ----------------- 431 11 4 IPv4 TE Router ID 432 12 16 IPv6 TE Router ID 434 Detailed definitions of the new sub-TLV are described in 435 Section 3.4.1 and 3.4.2. 437 3.3. Sub-TLVs for Inter-AS Reachability TLV 439 3.3.1. Remote AS Number Sub-TLV 441 A new sub-TLV, the remote AS number sub-TLV, is defined for inclusion 442 in the inter-AS reachability TLV when advertising inter-AS links. 443 The remote AS number sub-TLV specifies the AS number of the 444 neighboring AS to which the advertised link connects. 446 The remote AS number sub-TLV is TLV type 24 (see Section 6.2) and is 447 4 octets in length. The format is as follows: 449 0 1 2 3 450 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 1 451 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 452 | Type | Length | 453 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 454 | Remote AS Number | 455 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 457 The remote AS number field has 4 octets. When only 2 octets are used 458 for the AS number, as in current deployments, the left (high-order) 2 459 octets MUST be set to 0. The remote AS number sub-TLV MUST be 460 included when a router advertises an inter-AS TE link. 462 3.3.2. IPv4 Remote ASBR ID Sub-TLV 464 A new sub-TLV, which is referred to as the IPv4 remote ASBR ID sub- 465 TLV, is defined for inclusion in the inter-AS reachability TLV when 466 advertising inter-AS links. The IPv4 remote ASBR ID sub-TLV 467 specifies the IPv4 identifier of the remote ASBR to which the 468 advertised inter-AS link connects. This could be any stable and 469 routable IPv4 address of the remote ASBR. Use of the TE Router ID as 470 specified in the Traffic Engineering router ID TLV [RFC5305] is 471 RECOMMENDED. 473 The IPv4 remote ASBR ID sub-TLV is TLV type 25 (see Section 6.2) and 474 is 4 octets in length. The format of the IPv4 remote ASBR ID sub-TLV 475 is as follows: 477 0 1 2 3 478 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 1 479 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 480 | Type | Length | 481 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 482 | Remote ASBR ID | 483 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 485 The IPv4 remote ASBR ID sub-TLV MUST be included if the neighboring 486 ASBR has an IPv4 address. If the neighboring ASBR does not have an 487 IPv4 address (not even an IPv4 TE Router ID), the IPv6 remote ASBR ID 488 sub-TLV MUST be included instead. An IPv4 remote ASBR ID sub-TLV and 489 IPv6 remote ASBR ID sub-TLV MAY both be present in an extended IS 490 reachability TLV. 492 3.3.3. IPv6 Remote ASBR ID Sub-TLV 494 A new sub-TLV, which is referred to as the IPv6 remote ASBR ID sub- 495 TLV, is defined for inclusion in the inter-AS reachability TLV when 496 advertising inter-AS links. The IPv6 remote ASBR ID sub-TLV 497 specifies the IPv6 identifier of the remote ASBR to which the 498 advertised inter-AS link connects. This could be any stable and 499 routable IPv6 address of the remote ASBR. Use of the TE Router ID as 500 specified in the IPv6 Traffic Engineering router ID TLV [RFC6119] is 501 RECOMMENDED. 503 The IPv6 remote ASBR ID sub-TLV is TLV type 26 (see Section 6.2) and 504 is 16 octets in length. The format of the IPv6 remote ASBR ID sub- 505 TLV is as follows: 507 0 1 2 3 508 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 1 509 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 510 | Type | Length | 511 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 512 | Remote ASBR ID | 513 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 514 | Remote ASBR ID (continued) | 515 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 516 | Remote ASBR ID (continued) | 517 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 518 | Remote ASBR ID (continued) | 519 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 521 The IPv6 remote ASBR ID sub-TLV MUST be included if the neighboring 522 ASBR has an IPv6 address. If the neighboring ASBR does not have an 523 IPv6 address, the IPv4 remote ASBR ID sub-TLV MUST be included 524 instead. An IPv4 remote ASBR ID sub-TLV and IPv6 remote ASBR ID sub- 525 TLV MAY both be present in an extended IS reachability TLV. 527 3.3.4. IPv6 Router ID sub-TLV 529 The IPv6 Router ID sub-TLV is TLV type TBD1 (see Section 6.3) and is 530 16 octets in length. The format of the IPv6 Router ID sub-TLV is as 531 follows: 533 0 1 2 3 534 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 1 535 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 536 | Type | Length | 537 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 538 | IPv6 Router ID | 539 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 540 | IPv6 Router ID (continued) | 541 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 542 | IPv6 Router ID (continued) | 543 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 544 | IPv6 Router ID (continued) | 545 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 547 The IPv6 TE Router ID SHOULD be identical to the value advertised in 548 the IPv6 Traffic Engineering Router ID TLV [RFC6119]. 550 If the originating node does not support IPv4, the IPv6 Router ID 551 sub-TLV MUST be present in the inter-AS reachability TLV. Inter-AS 552 reachability TLVs which have a Router ID of 0.0.0.0 and do NOT have 553 the IPv6 Router ID sub-TLV present MUST be ignored. 555 3.4. Sub-TLVs for IS-IS Router Capability TLV 557 3.4.1. IPv4 TE Router ID sub-TLV 559 The IPv4 TE Router ID sub-TLV is TLV type 11 (see Section 6.3) and is 560 4 octets in length. The format of the IPv4 TE Router ID sub-TLV is 561 as follows: 563 0 1 2 3 564 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 1 565 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 566 | Type | Length | 567 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 568 | TE Router ID | 569 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 571 The IPv4 TE Router ID SHOULD be identical to the value advertised in 572 the IPv4 Traffic Engineering Router ID TLV [RFC5305]. 574 When the TE Router ID is needed to reach all routers within an entire 575 ISIS routing domain, the IS-IS Router capability TLV MUST be included 576 in its LSP. If an ASBR supports Traffic Engineering for IPv4 and if 577 the ASBR has an IPv4 TE Router ID, the IPv4 TE Router ID sub-TLV MUST 578 be included. If the ASBR does not have an IPv4 TE Router ID, the 579 IPv6 TE Router sub-TLV MUST be included instead. An IPv4 TE Router 580 ID sub-TLV and IPv6 TE Router ID sub-TLV MAY both be present in an 581 IS-IS router capability TLV. 583 3.4.2. IPv6 TE Router ID sub-TLV 585 The IPv6 TE Router ID sub-TLV is TLV type 12 (see Section 6.3) and is 586 16 octets in length. The format of the IPv6 TE Router ID sub-TLV is 587 as follows: 589 0 1 2 3 590 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 1 591 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 592 | Type | Length | 593 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 594 | TE Router ID | 595 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 596 | TE Router ID (continued) | 597 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 598 | TE Router ID (continued) | 599 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 600 | TE Router ID (continued) | 601 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 602 The IPv6 TE Router ID SHOULD be identical to the value advertised in 603 the IPv6 Traffic Engineering Router ID TLV [RFC6119]. 605 When the TE Router ID is needed to reach all routers within an entire 606 ISIS routing domain, the IS-IS router capability TLV MUST be included 607 in its LSP. If an ASBR supports Traffic Engineering for IPv6 and if 608 the ASBR has an IPv6 TE Router ID, the IPv6 TE Router ID sub-TLV MUST 609 be included. If the ASBR does not have an IPv6 TE Router ID, the 610 IPv4 TE Router sub-TLV MUST be included instead. An IPv4 TE Router 611 ID sub-TLV and IPv6 TE Router ID sub-TLV MAY both be present in an 612 IS-IS router capability TLV. 614 4. Procedure for Inter-AS TE Links 616 When TE is enabled on an inter-AS link and the link is up, the ASBR 617 SHOULD advertise this link using the normal procedures for [RFC5305]. 618 When either the link is down or TE is disabled on the link, the ASBR 619 SHOULD withdraw the advertisement. When there are changes to the TE 620 parameters for the link (for example, when the available bandwidth 621 changes), the ASBR SHOULD re-advertise the link but MUST take 622 precautions against excessive re-advertisements. 624 Hellos MUST NOT be exchanged over the inter-AS link, and 625 consequently, an ISIS adjacency MUST NOT be formed. 627 The information advertised comes from the ASBR's knowledge of the TE 628 capabilities of the link, the ASBR's knowledge of the current status 629 and usage of the link, and configuration at the ASBR of the remote AS 630 number and remote ASBR TE Router ID. 632 Legacy routers receiving an advertisement for an inter-AS TE link are 633 able to ignore it because they do not know the new TLV and sub-TLVs 634 that are defined in Section 3 of this document. They will continue 635 to flood the LSP, but will not attempt to use the information 636 received. 638 In the current operation of ISIS TE, the LSRs at each end of a TE 639 link emit LSPs describing the link. The databases in the LSRs then 640 have two entries (one locally generated, the other from the peer) 641 that describe the different 'directions' of the link. This enables 642 Constrained Shortest Path First (CSPF) to do a two-way check on the 643 link when performing path computation and eliminate it from 644 consideration unless both directions of the link satisfy the required 645 constraints. 647 In the case we are considering here (i.e., of a TE link to another 648 AS), there is, by definition, no IGP peering and hence no 649 bidirectional TE link information. In order for the CSPF route 650 computation entity to include the link as a candidate path, we have 651 to find a way to get LSPs describing its (bidirectional) TE 652 properties into the TE database. 654 This is achieved by the ASBR advertising, internally to its AS, 655 information about both directions of the TE link to the next AS. The 656 ASBR will normally generate a LSP describing its own side of a link; 657 here we have it 'proxy' for the ASBR at the edge of the other AS and 658 generate an additional LSP that describes that device's 'view' of the 659 link. 661 Only some essential TE information for the link needs to be 662 advertised; i.e., the Interface Address, the remote AS number, and 663 the remote ASBR ID of an inter-AS TE link. 665 Routers or PCEs that are capable of processing advertisements of 666 inter-AS TE links SHOULD NOT use such links to compute paths that 667 exit an AS to a remote ASBR and then immediately re-enter the AS 668 through another TE link. Such paths would constitute extremely rare 669 occurrences and SHOULD NOT be allowed except as the result of 670 specific policy configurations at the router or PCE computing the 671 path. 673 4.1. Origin of Proxied TE Information 675 Section 4 describes how an ASBR advertises TE link information as a 676 proxy for its neighbor ASBR, but does not describe where this 677 information comes from. 679 Although the source of this information is outside the scope of this 680 document, it is possible that it will be a configuration requirement 681 at the ASBR, as are other local properties of the TE link. Further, 682 where BGP is used to exchange IP routing information between the 683 ASBRs, a certain amount of additional local configuration about the 684 link and the remote ASBR is likely to be available. 686 We note further that it is possible, and may be operationally 687 advantageous, to obtain some of the required configuration 688 information from BGP. Whether and how to utilize these possibilities 689 is an implementation matter. 691 5. Security Considerations 693 The protocol extensions defined in this document are relatively minor 694 and can be secured within the AS in which they are used by the 695 existing ISIS security mechanisms (e.g., using the cleartext 696 passwords or Hashed Message Authentication Codes - Message Digest 5 697 (HMAC-MD5) algorithm, which are defined in [RFC1195] and [RFC3567] 698 separately). 700 There is no exchange of information between ASes, and no change to 701 the ISIS security relationship between the ASes. In particular, 702 since no ISIS adjacency is formed on the inter-AS links, there is no 703 requirement for ISIS security between the ASes. 705 Some of the information included in these new advertisements (e.g., 706 the remote AS number and the remote ASBR ID) is obtained manually 707 from a neighboring administration as part of a commercial 708 relationship. The source and content of this information should be 709 carefully checked before it is entered as configuration information 710 at the ASBR responsible for advertising the inter-AS TE links. 712 It is worth noting that in the scenario we are considering, a Border 713 Gateway Protocol (BGP) peering may exist between the two ASBRs and 714 that this could be used to detect inconsistencies in configuration 715 (e.g., the administration that originally supplied the information 716 may be lying, or some manual mis-configurations or mistakes may be 717 made by the operators). For example, if a different remote AS number 718 is received in a BGP OPEN [RFC4271] from that locally configured to 719 ISIS-TE, as we describe here, then local policy SHOULD be applied to 720 determine whether to alert the operator to a potential mis- 721 configuration or to suppress the ISIS advertisement of the inter-AS 722 TE link. Note further that if BGP is used to exchange TE information 723 as described in Section 4.1, the inter-AS BGP session SHOULD be 724 secured using mechanisms as described in [RFC4271] to provide 725 authentication and integrity checks. 727 For a discussion of general security considerations for IS-IS, see 728 [RFC5304]. 730 6. IANA Considerations 732 IANA is requested to make the following allocations from registries 733 under its control. 735 6.1. Inter-AS Reachability TLV 737 This document defines the following new ISIS TLV type, described in 738 Section 3.1, which has been registered in the ISIS TLV codepoint 739 registry: 741 Type Description IIH LSP SNP 742 ---- ---------------------- --- --- --- 743 141 inter-AS reachability n y n 744 information 746 6.2. Sub-TLVs for the Inter-AS Reachability TLV 748 This document defines the following new sub-TLV types (described in 749 Sections 3.3.1, 3.3.2, 3.3.3, and, 3.3.4) of top-level TLV 141 (see 750 Section 6.1 above), which have been registered in the ISIS sub-TLV 751 registry for TLV 141. Note that these four new sub-TLVs SHOULD NOT 752 appear in TLV 22 (or TLV 23, TLV 222, TLV223) and MUST be ignored in 753 TLV 22 (or TLV 23, TLV 222, TLV223): 755 Type Description 756 ---- ------------------------------ 757 24 remote AS number 758 25 IPv4 remote ASBR identifier 759 26 IPv6 remote ASBR identifier 760 TBD1 IPv6 Router ID 762 As described above in Section 3.1, the sub-TLVs which are defined in 763 [RFC5305], [RFC6119] and other documents for describing the TE 764 properties of an TE link are applicable to describe an inter-AS TE 765 link and MAY be included in the inter-AS reachability TLV when 766 adverting inter-AS TE links. 768 IANA has created the following sub-TLVs registries in "Sub-TLVs for 769 TLVs 22, 23, 141, 222, and 223" registry. 771 TLV TLV TLV TLV TLV 772 Type Description 22 23 141 222 223 Reference 773 ----- --------------------------- --- --- --- --- --- --------- 774 24 remote AS number n n y n n [This.I-D] 775 25 IPv4 remote ASBR identifier n n y n n [This.I-D] 776 26 IPv6 remote ASBR identifier n n y n n [This.I-D] 778 IANA is requested to create a new sub-TLV registry in "Sub-TLVs for 779 TLVs 22, 23, 141, 222, and 223" registry. 781 TLV TLV TLV TLV TLV 782 Type Description 22 23 141 222 223 Reference 783 ----- --------------------------- --- --- --- --- --- --------- 784 TBD1 IPv6 Router ID n n y n n [This.I-D] 786 6.3. Sub-TLVs for the IS-IS Router Capability TLV 788 This document defines the following new sub-TLV types, described in 789 Sections 3.4.1 and 3.4.2, of top-level TLV 242 (which is defined in 790 [RFC4971]) that have been registered in the ISIS sub-TLV registry for 791 TLV 242: 793 Type Description Length 794 ---- ------------------------------ -------- 795 11 IPv4 TE Router ID 4 796 12 IPv6 TE Router ID 16 798 7. Acknowledgements 800 For the original version of [RFC5316] the authors would like to thank 801 Adrian Farrel, Jean-Louis Le Roux, Christian Hopps, Les Ginsberg, and 802 Hannes Gredler for their review and comments on this document. 804 8. References 806 8.1. Normative References 808 [RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and 809 dual environments", RFC 1195, DOI 10.17487/RFC1195, 810 December 1990, . 812 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 813 Requirement Levels", BCP 14, RFC 2119, 814 DOI 10.17487/RFC2119, March 1997, 815 . 817 [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic 818 Engineering", RFC 5305, DOI 10.17487/RFC5305, October 819 2008, . 821 [RFC6119] Harrison, J., Berger, J., and M. Bartlett, "IPv6 Traffic 822 Engineering in IS-IS", RFC 6119, DOI 10.17487/RFC6119, 823 February 2011, . 825 8.2. Informative References 827 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 828 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 829 Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001, 830 . 832 [RFC3567] Li, T. and R. Atkinson, "Intermediate System to 833 Intermediate System (IS-IS) Cryptographic Authentication", 834 RFC 3567, DOI 10.17487/RFC3567, July 2003, 835 . 837 [RFC4206] Kompella, K. and Y. Rekhter, "Label Switched Paths (LSP) 838 Hierarchy with Generalized Multi-Protocol Label Switching 839 (GMPLS) Traffic Engineering (TE)", RFC 4206, 840 DOI 10.17487/RFC4206, October 2005, 841 . 843 [RFC4216] Zhang, R., Ed. and J. Vasseur, Ed., "MPLS Inter-Autonomous 844 System (AS) Traffic Engineering (TE) Requirements", 845 RFC 4216, DOI 10.17487/RFC4216, November 2005, 846 . 848 [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A 849 Border Gateway Protocol 4 (BGP-4)", RFC 4271, 850 DOI 10.17487/RFC4271, January 2006, 851 . 853 [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation 854 Element (PCE)-Based Architecture", RFC 4655, 855 DOI 10.17487/RFC4655, August 2006, 856 . 858 [RFC4971] Vasseur, JP., Ed., Shen, N., Ed., and R. Aggarwal, Ed., 859 "Intermediate System to Intermediate System (IS-IS) 860 Extensions for Advertising Router Information", RFC 4971, 861 DOI 10.17487/RFC4971, July 2007, 862 . 864 [RFC5152] Vasseur, JP., Ed., Ayyangar, A., Ed., and R. Zhang, "A 865 Per-Domain Path Computation Method for Establishing Inter- 866 Domain Traffic Engineering (TE) Label Switched Paths 867 (LSPs)", RFC 5152, DOI 10.17487/RFC5152, February 2008, 868 . 870 [RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic 871 Authentication", RFC 5304, DOI 10.17487/RFC5304, October 872 2008, . 874 [RFC5307] Kompella, K., Ed. and Y. Rekhter, Ed., "IS-IS Extensions 875 in Support of Generalized Multi-Protocol Label Switching 876 (GMPLS)", RFC 5307, DOI 10.17487/RFC5307, October 2008, 877 . 879 [RFC5316] Chen, M., Zhang, R., and X. Duan, "ISIS Extensions in 880 Support of Inter-Autonomous System (AS) MPLS and GMPLS 881 Traffic Engineering", RFC 5316, DOI 10.17487/RFC5316, 882 December 2008, . 884 [RFC5441] Vasseur, JP., Ed., Zhang, R., Bitar, N., and JL. Le Roux, 885 "A Backward-Recursive PCE-Based Computation (BRPC) 886 Procedure to Compute Shortest Constrained Inter-Domain 887 Traffic Engineering Label Switched Paths", RFC 5441, 888 DOI 10.17487/RFC5441, April 2009, 889 . 891 [RFC6823] Ginsberg, L., Previdi, S., and M. Shand, "Advertising 892 Generic Information in IS-IS", RFC 6823, 893 DOI 10.17487/RFC6823, December 2012, 894 . 896 Authors' Addresses 898 Mach(Guoyi) Chen 899 Huawei 901 Email: mach.chen@huawei.com 903 Les Ginsberg 904 Cisco Systems 906 Email: ginsberg@cisco.com 908 Stefano Previdi 909 Cisco Systems 911 Email: sprevidi@cisco.com 913 Xiaodong Duan 914 China Mobile 916 Email: duanxiaodong@chinamobile.com