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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Network work group Mach Chen 2 Internet Draft Renhai Zhang 3 Expires: August 2008 Huawei Technologies Co.,Ltd 4 Category: Standards Track Xiaodong Duan 5 China Mobile 6 February 3, 2008 8 ISIS Extensions in Support of Inter-AS Multiprotocol Label Switching 9 (MPLS) and Generalized MPLS (GMPLS) Traffic Engineering 10 draft-ietf-ccamp-isis-interas-te-extension-00.txt 12 Status of this Memo 14 By submitting this Internet-Draft, each author represents that 15 any applicable patent or other IPR claims of which he or she is 16 aware have been or will be disclosed, and any of which he or she 17 becomes aware will be disclosed, in accordance with Section 6 of 18 BCP 79. 20 Internet-Drafts are working documents of the Internet Engineering 21 Task Force (IETF), its areas, and its working groups. Note that other 22 groups may also distribute working documents as Internet-Drafts. 24 Internet-Drafts are draft documents valid for a maximum of six months 25 and may be updated, replaced, or obsoleted by other documents at any 26 time. It is inappropriate to use Internet-Drafts as reference 27 material or to cite them other than as "work in progress." 29 The list of current Internet-Drafts can be accessed at 30 http://www.ietf.org/ietf/1id-abstracts.txt 32 The list of Internet-Draft Shadow Directories can be accessed at 33 http://www.ietf.org/shadow.html 35 This Internet-Draft will expire on August 3, 2008. 37 Abstract 39 This document describes extensions to the ISIS (ISIS) protocol to 40 support Multiprotocol Label Switching (MPLS) and Generalized MPLS 41 (GMPLS) Traffic Engineering (TE) for multiple Autonomous Systems 42 (ASes). It defines ISIS-TE extensions for the flooding of TE 43 information about inter-AS links which can be used to perform inter- 44 AS TE path computation. 46 No support for flooding TE information from other outside the AS is 47 proposed or defined in this document. 49 Conventions used in this document 51 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 52 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 53 document are to be interpreted as described in RFC-2119 [RFC2119]. 55 Table of Contents 57 1. Introduction.................................................2 58 2. Problem Statement............................................3 59 2.1. A Note on Non-Objectives................................4 60 2.2. Per-Domain Path Determination...........................4 61 2.3. Backward Recursive Path Computation.....................6 62 3. Extensions to ISIS-TE........................................7 63 3.1. Inter-AS Reachability TLV...............................8 64 3.2. TE Router ID............................................9 65 3.3. Sub-TLV Detail.........................................10 66 3.3.1. Remote AS Number Sub-TLV..........................10 67 3.3.2. IPv4 Remote ASBR ID Sub-TLV.......................10 68 3.3.3. IPv6 Remote ASBR ID Sub-TLV.......................11 69 3.3.4. IPv4 TE Router ID sub-TLV.........................12 70 3.3.5. IPv6 TE Router ID sub-TLV.........................12 71 4. Procedure for Inter-AS TE Links.............................13 72 4.1. Origin of Proxied TE Information.......................14 73 5. Security Considerations.....................................14 74 6. IANA Considerations.........................................15 75 6.1. Inter-AS Reachability TLV..............................15 76 6.2. Sub-TLVs for the Inter-AS Reachability TLV.............15 77 6.3. Sub-TLVs for the IS-IS Router Capability TLV...........16 78 7. Acknowledgments.............................................16 79 8. References..................................................16 80 8.1. Normative References...................................16 81 8.2. Informative References.................................17 82 Authors' Addresses.............................................18 83 Intellectual Property Statement................................18 84 Disclaimer of Validity.........................................19 85 Copyright Statement............................................19 87 1. Introduction 89 [ISIS-TE] defines extensions to the ISIS protocol [ISIS] to support 90 intra-area Traffic Engineering (TE). The extensions provide a way of 91 encoding the TE information for TE-enabled links within the network 92 (TE links) and flooding this information within an area. The Extended 93 IS Reachability TLV and Traffic Engineering Router ID TLV, which are 94 defined in [ISIS-TE], are used to carry such TE information. The 95 Extended IS Reachability TLV has several nested sub-TLVs which 96 describe the TE attributes for a TE link. 98 [ISIS-TE-V3] and [GMPLS-TE] define similar extensions to ISIS [ISIS] 99 in support of IPv6 and GMPLS traffic engineering respectively. 101 Requirements for establishing Multiprotocol Label Switching (MPLS) TE 102 Label Switched Paths (LSPs) that cross multiple Autonomous Systems 103 (ASes) are described in [INTER-AS-TE-REQ]. As described in [INTER-AS- 104 TE-REQ], a method SHOULD provide the ability to compute a path 105 spanning multiple ASes. So a path computation entity that may be the 106 head-end Label Switching Router (LSR), an AS Border Router (ASBR), or 107 a Path Computation Element (PCE [PCE]) needs to know the TE 108 information not only of the links within an AS, but also of the links 109 that connect to other ASes. 111 In this document, a new TLV, which is referred to as the Inter-AS 112 Reachability TLV, is defined to advertise inter-AS TE information, 113 three new sub-TLVs are defined for inclusion in the Inter-AS 114 Reachability TLV to carry the information about the remote AS number 115 and remote ASBR ID. The sub-TLVs defined in [ISIS-TE], [ISIS-TE-V3] 116 and other documents for inclusion in the Extended IS Reachability TLV 117 for describing the TE properties of a TE link are applicable to be 118 included in the Inter-AS Reachability TLV for describing the TE 119 properties of an inter-AS TE link as well. And two more new sub-TLVs 120 are defined for inclusion in the IS-IS Router Capability TLV to carry 121 the TE Router ID when TE Router ID needs to reach all routers within 122 an entire ISIS routing domain. The extensions are equally applicable 123 to IPv4 and IPv6 as identical extensions to [ISIS-TE] and [ISIS-TE- 124 V3]. The detailed definitions and procedures are discussed in the 125 following sections. 127 This document does not propose or define any mechanisms to advertise 128 any other extra-AS TE information within ISIS. See Section 2.1 for a 129 full list of non-objectives for this work. 131 2. Problem Statement 133 As described in [INTER-AS-TE-REQ], in the case of establishing an 134 inter-AS TE LSP traversing multiple ASes, the Path message [RFC3209] 135 may include the following elements in the Explicit Route Object (ERO) 136 in order to describe the path of the LSP: 138 - a set of AS numbers as loose hops; and/or 139 - a set of LSRs including ASBRs as loose hops. 141 Two methods for determining inter-AS paths are currently being 142 discussed. The per-domain method [PD-PATH] determines the path one 143 domain at a time. The backward recursive method [BRPC] uses 144 cooperation between PCEs to determine an optimum inter-domain path. 145 The sections that follow examine how inter-AS TE link information 146 could be useful in both cases. 148 2.1. A Note on Non-Objectives 150 It is important to note that this document does not make any change 151 to the confidentiality and scaling assumptions surrounding the use of 152 ASes in the Internet. In particular, this document is conformant to 153 the requirements set out in [INTER-AS-TE-REQ]. 155 The following features are explicitly excluded: 157 o There is no attempt to distribute TE information from within one 158 AS to another AS. 160 o There is no mechanism proposed to distribute any form of TE 161 reachability information for destinations outside the AS. 163 o There is no proposed change to the PCE architecture or usage. 165 o TE aggregation is not supported or recommended. 167 o There is no exchange of private information between ASes. 169 o No ISIS adjacencies are formed on the inter-AS link. 171 2.2. Per-Domain Path Determination 173 In the per-domain method of determining an inter-AS path for an MPLS- 174 TE LSP, when an LSR that is an entry-point to an AS receives a PATH 175 message from an upstream AS with an ERO containing a next hop that is 176 an AS number, it needs to find which LSRs (ASBRs) within the local AS 177 are connected to the downstream AS so that it can compute a TE LSP 178 segment across the AS to one of those LSRs and forward the PATH 179 message to it and hence into the next AS. See Figure 1 for an 180 example : 182 R1------R3----R5-----R7------R9-----R11 183 | | \ | / | 184 | | \ | ---- | 185 | | \ | / | 186 R2------R4----R6 --R8------R10----R12 187 : : 188 <-- AS1 -->:<---- AS2 --->:<--- AS3 ---> 190 Figure 1: Inter-AS Reference Model 192 The figure shows three ASes (AS1, AS2, and AS3) and twelve LSRs (R1 193 through R12). R3 and R4 are ASBRs in AS1. R5, R6, R7, and R8 are 194 ASBRs in AS2. R9 and R10 are ASBRs in AS3. 196 If it is planned to establish an inter-AS TE LSP from R1 to R12, the 197 AS sequence will be: AS1, AS2, AS3. 199 Suppose that the Path message enters AS2 from R3. The next hop in the 200 ERO shows AS3, and R5 must determine a path segment across AS2 to 201 reach AS3. It has a choice of three exit points from AS2 (R6, R7, and 202 R8) and it needs to know which of these provide TE connectivity to 203 AS3, and whether the TE connectivity (for example, available 204 bandwidth) is adequate for the requested LSP. 206 Alternatively, if the next hop in the ERO is the entry ASBR for AS3 207 (say R9), R5 needs to know which of its exit ASBRs has a TE link that 208 connects to R9. Since there may be multiple ASBRs that are connected 209 to R9 (both R7 and R8 in this example), R5 also needs to know the TE 210 properties of the inter-AS TE links so that it can select the correct 211 exit ASBR. 213 Once the path message reaches the exit ASBR, any choice of inter-AS 214 TE link can be made by the ASBR if not already made by entry ASBR 215 that computed the segment. 217 More details can be found in the Section 4.0 of [PD-PATH], which 218 clearly points out why advertising of inter-AS links is desired. 220 To enable R5 to make the correct choice of exit ASBR the following 221 information is needed: 223 o List of all inter-AS TE links for the local AS. 225 o TE properties of each inter-AS TE link. 227 o AS number of the neighboring AS connected to by each inter-AS TE 228 link. 230 o Identity (TE Router ID) of the neighboring ASBR connected to by 231 each inter-AS TE link. 233 In GMPLS networks further information may also be required to select 234 the correct TE links as defined in [GMPLS-TE]. 236 The example above shows how this information is needed at the entry 237 point ASBRs for each AS (or the PCEs that provide computation 238 services for the ASBRs), but this information is also needed 239 throughout the local AS if path computation function is fully 240 distributed among LSRs in the local AS, for example to support LSPs 241 that have start points (ingress nodes) within the AS. 243 2.3. Backward Recursive Path Computation 245 Another scenario using PCE techniques has the same problem. [BRPC] 246 defines a PCE-based TE LSP computation method (called Backward 247 Recursive Path Computation) to compute optimal inter-domain 248 constrained MPLS-TE or GMPLS LSPs. In this path computation method, a 249 specific set of traversed domains (ASes) are assumed to be selected 250 before computation starts. Each downstream PCE in domain(i) returns 251 to its upstream neighbor PCE in domain(i-1) a multipoint-to-point 252 tree of potential paths. Each tree consists of the set of paths from 253 all Boundary Nodes located in domain(i) to the destination where each 254 path satisfies the set of required constraints for the TE LSP 255 (bandwidth, affinities, etc.). 257 So a PCE needs to select Boundary Nodes (that is, ASBRs) that provide 258 connectivity from the upstream AS. In order that the tree of paths 259 provided by one PCE to its neighbor can be correlated, the identities 260 of the ASBRs for each path need to be referenced, so the PCE must 261 know the identities of the ASBRs in the remote AS reached by any 262 inter-AS TE link, and, in order that it provides only suitable paths 263 in the tree, the PCE must know the TE properties of the inter-AS TE 264 links. See the following figure as an example: 266 PCE1<------>PCE2<-------->PCE3 267 / : : 268 / : : 269 R1------R3----R5-----R7------R9-----R11 270 | | \ | / | 271 | | \ | ---- | 272 | | \ | / | 273 R2------R4----R6 --R8------R10----R12 274 : : 275 <-- AS1 -->:<---- AS2 --->:<--- AS3 ---> 277 Figure 2: BRPC for Inter-AS Reference Model 279 The figure shows three ASes (AS1, AS2, and AS3), three PCEs(PCE1, 280 PCE2, and PCE3) and twelve LSRs (R1 through R12). R3 and R4 are ASBRs 281 in AS1. R5, R6, R7, and R8 are ASBRs in AS2. R9 and R10 are ASBRs in 282 AS3. PCE1, PCE2, and PCE3 cooperate to perform inter-AS path 283 computation and are responsible for path segment computation within 284 their own domains. 286 If it is planned to establish an inter-AS TE LSP from R1 to R12, the 287 traversed domains are assumed to be selected: AS1->AS2->AS3, and the 288 PCE chain is: PCE1->PCE2->PCE3. First, the path computation request 289 originated from the PCC (R1) is relayed by PCE1 and PCE2 along the 290 PCE chain to PCE3, then PCE3 begins to compute the path segments from 291 the entry boundary nodes that provide connection from AS2 to the 292 destination (R12). But, to provide suitable path segments, PCE3 must 293 determine which entry boundary nodes provide connectivity to its 294 upstream neighbor AS (identified by its AS number), and must know the 295 TE properties of the inter-AS TE links. In the same way, PCE2 also 296 needs to determine the entry boundary nodes according to its upstream 297 neighbor AS and the inter-AS TE link capabilities. 299 Thus, to support Backward Recursive Path Computation the same 300 information listed in Section 2.2 is required. 302 3. Extensions to ISIS-TE 304 Note that this document does not define mechanisms for distribution 305 of TE information from one AS to another, does not distribute any 306 form of TE reachability information for destinations outside the AS, 307 does not change the PCE architecture or usage, does not suggest or 308 recommend any form of TE aggregation, and does not feed private 309 information between ASes. See Section 2.1. 311 In this document, for the advertisement of inter-AS TE links, a new 312 TLV, which is referred to as the Inter-AS Reachability TLV, is 313 defined and three new sub-TLVs are defined for inclusion in the 314 Inter-AS Reachability TLV to carry the information about the 315 neighboring AS number and the remote ASBR ID of an inter-AS link. The 316 sub-TLVs defined in [ISIS-TE], [ISIS-TE-V3] and other documents for 317 inclusion in the Extended IS Reachability TLV are applicable to be 318 included in the Inter-AS Reachability TLV for inter-AS TE links 319 advertisement. And another two new sub-TLVs are defined for inclusion 320 in the IS-IS Router Capability TLV to carry the TE Router ID when the 321 TE Router ID is needed to reach all routers within an entire ISIS 322 routing domain. 324 3.1. Inter-AS Reachability TLV 326 The Inter-AS Reachability TLV has type 141 (which needs to be 327 confirmed by IANA), it contains a data structure consisting of: 329 7 octets of System ID and Pseudonode Number 330 3 octets of default metric 331 1 octet of control information, consisting of: 332 1 bit of flooding-scope information 333 1 bit of up/down information 334 6 bits reserved 335 1 octet of length of sub-TLVs 336 0-243 octets of sub-TLVs 337 where each sub-TLV consists of a sequence of: 338 1 octet of sub-type 339 1 octet of length of the value field of the sub-TLV 340 0-241 octets of value 342 Compare to the Extended Reachability TLV which is defined in [ISIS- 343 TE], the Inter-AS Reachability TLV introduces an extra "control 344 information" field which is consisted of a flooding-scope bit, a 345 up/down bit and 6 reserved bits. 347 As the S bit defined in [ISIS-CAP], the flooding-scope bit is used to 348 control the flooding scope of the Inter-AS Reachability TLV. When the 349 flooding-scope bit is set to 1, the Inter-AS Reachability TLV MUST be 350 flooded into the entire ISIS routing domain. If the flooding-scope 351 bit is set to 0, the Inter-AS Reachability TLV MUST NOT be leaked 352 between different levels. And this flooding-scope bit MUST NOT be 353 modified during the TLV leaking. The choice between the use of 0 or 1 354 is a network-wide policy choice, and configuration control SHOULD be 355 provided in ASBR implementations that supports the advertisement of 356 inter-AS TE links. 358 The semantics of the up/down bit in the Inter-AS Reachability TLV are 359 identical to the semantics of the up/down bit defined in [ISIS-TE]. 361 It can be used to facilitate the redistribution of inter-AS TE 362 information freely between level 1 and level 2. And the up/down bit 363 MUST be set to 0 when the Inter-AS TE information first injected into 364 ISIS [ISIS], and the up/dawn bit MUST be set to 1 if the Inter-AS TE 365 information needs to be advertised from high level to low level. 367 The sub-TLVs which are defined in [ISIS-TE], [ISIS-TE-V3] and other 368 documents for describing the TE properties of an TE link are also 369 applicable to be carried in the Inter-AS Reachability TLV to describe 370 the TE properties of an Inter-AS TE link. Apart from these sub-TLVs, 371 three new sub-TLVs are defined for inclusion in the Inter-AS 372 Reachability TLV in the document: 374 Sub-TLV type Length Name 375 ------------ ------ --------------------------- 376 23 4 Remote AS number 377 24 4 IPv4 Remote ASBR Identifier 378 25 16 IPv6 Remote ASBR Identifier 380 The detailed definitions of the three new sub-TLVs are described in 381 Section 3.3. 383 3.2. TE Router ID 385 The IPv4 TE Router ID TLV (type 134) and IPv6 TE Router ID TLV (type 386 140), which are defined in [ISIS-TE] and [ISIS-TE-V3] respectively, 387 only have area flooding-scope, when performing inter-AS TE, the TE 388 Router ID MAY be needed to reach all routers within an entire ISIS 389 routing domain, and it MUST have the same flooding scope as the 390 Inter-AS Reachability TLV does. 392 [ISIS-CAP] defines a generic advertisement mechanism for ISIS which 393 allows a router to advertise its capabilities within an ISIS area or 394 an entire ISIS routing domain. And [ISIS-CAP] also points out that TE 395 Router ID is candidate to be carried in the IS-IS Router Capability 396 TLV when performing inter-area TE. 398 This document uses such mechanism for TE Router ID advertisement when 399 the TE Router ID is needed to reach all routers within an entire ISIS 400 Routing domain. Two new sub-TLVs are defined for inclusion in the IS- 401 IS Router Capability TLV to carry the IPv4 and IPv6 TE Router ID 402 respectively: 404 Sub-TLV type Length Name 405 ------------ ------ ----------------- 406 11 4 IPv4 TE Router ID 407 12 16 IPv6 TE Router ID 409 The Detailed definitions of the two new sub-TLVs are described in 410 Section 3.3. 412 3.3. Sub-TLV Detail 414 3.3.1. Remote AS Number Sub-TLV 416 A new sub-TLV, the Remote AS Number sub-TLV is defined for inclusion 417 in the Inter-AS Reachability TLV when advertising inter-AS links. The 418 Remote AS Number sub-TLV specifies the AS number of the neighboring 419 AS to which the advertised link connects. 421 The Remote AS number sub-TLV is TLV type 23 (which needs to be 422 confirmed by IANA), and is four octets in length. The format is as 423 follows: 425 0 1 2 3 426 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 1 427 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 428 | Type | Length | 429 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 430 | Remote AS Number | 431 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 433 The Remote AS number field has 4 octets. When only two octets are 434 used for the AS number, as in current deployments, the left (high- 435 order) two octets MUST be set to zero. The Remote AS Number Sub-TLV 436 MUST be included when a router advertises an inter-AS TE link. 438 3.3.2. IPv4 Remote ASBR ID Sub-TLV 440 A new sub-TLV, which is referred to as the IPv4 Remote ASBR ID sub- 441 TLV, is defined for inclusion in the Inter-AS Reachability TLV when 442 advertising inter-AS links. The IPv4 Remote ASBR ID sub-TLV specifies 443 the IPv4 identifier of the remote ASBR to which the advertised inter- 444 AS link connects. This could be any stable and routable IPv4 address 445 of the remote ASBR. Use of the TE Router ID is RECOMMENDED. 447 The IPv4 Remote ASBR ID sub-TLV is TLV type 24 (which needs to be 448 confirmed by IANA), and is four octets in length. The format of the 449 IPv4 Remote ASBR ID sub-TLV is as follows: 451 0 1 2 3 452 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 1 453 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 454 | Type | Length | 455 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 456 | Remote ASBR ID | 457 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 459 The IPv4 Remote ASBR ID sub-TLV MUST be included if the neighboring 460 ASBR has an IPv4 address. If the neighboring ASBR does not have an 461 IPv4 address (not even an IPv4 TE Router ID), the IPv6 Remote ASBR ID 462 sub-TLV MUST be included instead. An IPv4 Remote ASBR ID sub-TLV and 463 IPv6 Remote ASBR ID sub-TLV MAY both be present in an Extended IS 464 Reachability TLV. 466 3.3.3. IPv6 Remote ASBR ID Sub-TLV 468 A new sub-TLV, which is referred to as the IPv6 Remote ASBR ID sub- 469 TLV, is defined for inclusion in the Inter-AS Reachability TLV when 470 advertising inter-AS links. The IPv6 Remote ASBR ID sub-TLV specifies 471 the IPv6 identifier of the remote ASBR to which the advertised inter- 472 AS link connects. This could be any stable and routable IPv6 address 473 of the remote ASBR. Use of the TE Router ID is RECOMMENDED. 475 The IPv6 Remote ASBR ID sub-TLV is TLV type 25 (which needs to be 476 confirmed by IANA), and is sixteen octets in length. The format of 477 the IPv6 Remote ASBR ID sub-TLV is as follows: 479 0 1 2 3 480 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 1 481 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 482 | Type | Length | 483 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 484 | Remote ASBR ID | 485 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 486 | Remote ASBR ID (continued) | 487 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 488 | Remote ASBR ID (continued) | 489 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 490 | Remote ASBR ID (continued) | 491 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 493 The IPv6 Remote ASBR ID sub-TLV MUST be included if the neighboring 494 ASBR has an IPv6 address. If the neighboring ASBR does not have an 495 IPv6 address, the IPv4 Remote ASBR ID sub-TLV MUST be included 496 instead. An IPv4 Remote ASBR ID sub-TLV and IPv6 Remote ASBR ID sub- 497 TLV MAY both be present in an Extended IS Reachability TLV. 499 3.3.4. IPv4 TE Router ID sub-TLV 501 The IPv4 TE Router ID sub-TLV is TLV type 11 (which needs to be 502 confirmed by IANA), and is four octets in length. The format of the 503 IPv4 TE Router ID sub-TLV is as follows: 505 0 1 2 3 506 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 1 507 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 508 | Type | Length | 509 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 510 | TE Router ID | 511 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 513 When the TE Router ID is needed to reach all routers within an entire 514 ISIS routing domain, the IS-IS Router Capability TLV MUST be included 515 in its LSP. And if an ASBR supports Traffic Engineering for IPv4, the 516 IPv4 TE Router ID sub-TLV MUST be included if the ASBR has an IPv4 TE 517 Router ID. If the ASBR does not have an IPv4 TE Router ID, the IPv6 518 TE Router sub-TLV MUST be included instead. An IPv4 TE Router ID sub- 519 TLV and IPv6 TE Router ID sub-TLV MAY both be present in an IS-IS 520 Router Capability TLV. 522 3.3.5. IPv6 TE Router ID sub-TLV 524 The IPv6 TE Router ID sub-TLV is TLV type 12 (which needs to be 525 confirmed by IANA), and is four octets in length. The format of the 526 IPv6 TE Router ID sub-TLV is as 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 | TE Router ID | 534 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 535 | TE Router ID (continued) | 536 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 537 | TE Router ID (continued) | 538 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 539 | TE Router ID (continued) | 540 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 542 When the TE Router ID is needed to reach all routers within an entire 543 ISIS routing domain, the IS-IS Router Capability TLV MUST be included 544 in its LSP. And if an ASBR supports Traffic Engineering for IPv6, the 545 IPv6 TE Router ID sub-TLV MUST be included if the ASBR has an IPv6 TE 546 Router ID. If the ASBR does not have an IPv6 TE Router ID, the IPv4 547 TE Router sub-TLV MUST be included instead. An IPv4 TE Router ID sub- 548 TLV and IPv6 TE Router ID sub-TLV MAY both be present in an IS-IS 549 Router Capability TLV. 551 4. Procedure for Inter-AS TE Links 553 When TE is enabled on an inter-AS link and the link is up, the ASBR 554 SHOULD advertise this link using the normal procedures for ISIS-TE 555 [ISIS-TE]. When either the link is down or TE is disabled on the link, 556 the ASBR SHOULD withdraw the advertisement. When there are changes to 557 the TE parameters for the link (for example, when the available 558 bandwidth changes) the ASBR SHOULD re-advertise the link, but the 559 ASBR MUST take precautions against excessive re-advertisements. 561 Hellos MUST NOT be exchanged over the inter-AS link, and consequently, 562 an ISIS adjacency MUST NOT be formed. 564 The information advertised comes from the ASBR's knowledge of the TE 565 capabilities of the link, the ASBR's knowledge of the current status 566 and usage of the link, and configuration at the ASBR of the remote AS 567 number and remote ASBR TE Router ID. 569 Legacy routers receiving an advertisement for an inter-AS TE link are 570 able to ignore it because they do not know the new TLV and sub-TLVs 571 that are defined in Section 3 in this document. They will continue to 572 flood the LSP, but will not attempt to use the information received. 574 In the current operation of ISIS TE the LSRs at each end of a TE link 575 emit LSAs describing the link. The databases in the LSRs then have 576 two entries (one locally generated, the other from the peer) that 577 describe the different 'directions' of the link. This enables CSPF 578 to do a two-way check on the link when performing path computation 579 and eliminate it from consideration unless both directions of the 580 link satisfy the required constraints. 582 In the case we are considering here (i.e., of a TE link to another AS) 583 there is, by definition, no IGP peering and hence no bi-directional 584 TE link information. In order for the CSPF route computation entity 585 to include the link as a candidate path, we have to find a way to get 586 LSAs describing its (bidirectional) TE properties into the TE 587 database. 589 This is achieved by the ASBR advertising, internally to its AS, 590 information about both directions of the TE link to the next AS. The 591 ASBR will normally generate a LSA describing its own side of a link; 592 here we have it 'proxy' for the ASBR at the edge of the other AS and 593 generate an additional LSA that describes that devices 'view' of the 594 link. 596 Only some essential TE information for the link needs to be 597 advertised; i.e., the Interface Address, the Remote AS number and the 598 Remote ASBR ID of an inter-AS TE link. 600 Routers or PCEs that are capable of processing advertisements of 601 inter-AS TE links SHOULD NOT use such links to compute paths that 602 exit an AS to a remote ASBR and then immediately re-enter the AS 603 through another TE link. Such paths would constitute extremely rare 604 occurrences and SHOULD NOT be allowed except as the result of 605 specific policy configurations at the router or PCE computing the 606 path. 608 4.1. Origin of Proxied TE Information 610 Section 4 describes how to an ASBR advertises TE link information as 611 a proxy for its neighbor ASBR, but does not describe where this 612 information comes from. 614 Although the source of this information is outside the scope of this 615 document, it is possible that it will be a configuration requirement 616 at the ASBR, as are other, local, properties of the TE link. Further, 617 where BGP is used to exchange IP routing information between the 618 ASBRs, a certain amount of additional local configuration about the 619 link and the remote ASBR is likely to be available. 621 We note further that it is possible, and may be operationally 622 advantageous, to obtain some of the required configuration 623 information from BGP. Whether and how to utilize these possibilities 624 is an implementation matter. 626 5. Security Considerations 628 The protocol extensions defined in this document are relatively minor 629 and can be secured within the AS in which they are used by the 630 existing ISIS security mechanisms. 632 There is no exchange of information between ASes, and no change to 633 the ISIS security relationship between the ASes. In particular, since 634 no ISIS adjacency is formed on the inter-AS links, there is no 635 requirement for ISIS security between the ASes. 637 Some of the information included in these new advertisements (e.g., 638 the remote AS number and the remote ASBR ID) is obtained manually 639 from a neighboring administration as part of commercial relationship. 641 The source and content of this information should be carefully 642 checked before it is entered as configuration information at the ASBR 643 responsible for advertising the inter-AS TE links. 645 It is worth noting that in the scenario we are considering a Border 646 Gateway Protocol (BGP) peering may exist between the two ASBRs and 647 this could be used to detect inconsistencies in configuration. For 648 example, if a different remote AS number is received in a BGP OPEN 649 [BGP] from that locally configured into ISIS-TE, as we describe here, 650 then something is amiss. Note, further, that if BGP is used to 651 exchange TE information as described in Section 4.1, the inter-AS BGP 652 session will need to be fully secured. 654 6. IANA Considerations 656 IANA is requested to make the following allocations from registries 657 under its control. 659 6.1. Inter-AS Reachability TLV 661 This document defines the following new ISIS TLV type, described in 662 Section 3.4, that needs to be registered in the ISIS TLV code-point 663 registry: 665 Type Description IIH LSP SNP 666 ---- ---------------------- --- --- --- 667 141 Inter-AS reachability n y n 668 information 670 6.2. Sub-TLVs for the Inter-AS Reachability TLV 672 This document defines the following new sub-TLV types, described in 673 Sections 3.3.1, 3.3.2 and 3.3.3, of top-level TLV 141 (see section 674 6.1 above) that need to be registered in the ISIS sub-TLV registry 675 for TLV 141: 677 Type Description Length 678 ---- ------------------------------ -------- 679 23 Remote AS number 4 680 24 IPv4 Remote ASBR Identifier 4 681 25 IPv6 Remote ASBR Identifier 16 683 As described above in Section 3.1, the sub-TLVs which are defined in 684 [ISIS-TE], [ISIS-TE-V3] and other documents for describing the TE 685 properties of an TE link are applicable to describe an inter-AS TE 686 link and MAY be included in the Inter-AS Reachability TLV when 687 adverting inter-AS TE links. So, these sub-TLVs need to be registered 688 in the ISIS sub-TLV registry for TLV 141. And in order to simplify 689 the registration, we suggest using the same registry value as they 690 are registered in the ISIS sub-TLV registry for TLV 22. 692 6.3. Sub-TLVs for the IS-IS Router Capability TLV 694 This document defines the following new sub-TLV types, described in 695 Sections 3.3.4 and 3.3.5, of top-level TLV 242 (which is defined in 696 [ISIS-CAP]) that need to be registered in the ISIS sub-TLV registry 697 for TLV 242: 699 Type Description Length 700 ---- ------------------------------ -------- 701 11 IPv4 TE Router ID 4 702 12 IPv6 TE Router ID 16 704 7. Acknowledgments 706 The authors would like to thank Adrian Farrel, Jean-Louis Le Roux, 707 Christian Hopps, and Les Ginsberg for their review and comments on 708 this document. 710 8. References 712 8.1. Normative References 714 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 715 Requirement Levels", BCP 14, RFC 2119, March 1997. 717 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 718 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 719 Tunnels", RFC 3209, December 2001. 721 [ISIS] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and 722 dual environments", RFC 1195, December 1990. 724 [ISIS-TE] Smit, H. and T. Li, "Intermediate System to Intermediate 725 System (IS-IS) Extensions for Traffic Engineering (TE)", 726 draft-ietf-isis-te-bis-00.txt, {work in progress}. 728 [ISIS-TE-V3] Harrison, J., Berger, J., and Bartlett, M., "IPv6 729 Traffic Engineering in IS-IS", draft-ietf-isis-ipv6-te, 730 {work in progress}. 732 [ISIS-CAP] Vasseur, J.P. et al., "IS-IS extensions for advertising 733 router information", RFC 4971, July 2007. 735 8.2. Informative References 737 [INTER-AS-TE-REQ] Zhang and Vasseur, "MPLS Inter-AS Traffic 738 Engineering Requirements", RFC4216, November 2005. 740 [PD-PATH] Ayyangar, A., Vasseur, JP., and Zhang, R., "A Per-domain 741 path computation method for establishing Inter-domain", 742 draft-ietf-ccamp-inter-domain-pd-path-comp, (work in 743 progress). 745 [BRPC] JP. Vasseur, Ed., R. Zhang, N. Bitar, JL. Le Roux, "A Backward 746 Recursive PCE-based Computation (BRPC) procedure to compute 747 shortest inter-domain Traffic Engineering Label Switched 748 Paths ", draft-ietf-pce-brpc, (work in progress) 750 [PCE] Farrel, A., Vasseur, JP., and Ash, J., "A Path Computation 751 Element (PCE)-Based Architecture", RFC4655, August 2006. 753 [GMPLS-TE] K.Kompella and Y.Rekhter, "IS-IS Extensions in Support of 754 Generalized Multi-Protocol Label Switching", RFC 4205, 755 October 2005. 757 [BGP] Rekhter, Li, Hares, "A Border Gateway Protocol 4 (BGP-4)", 758 RFC4271, January 2006 760 Authors' Addresses 762 Mach(Guoyi) Chen 763 Huawei Technologies Co.,Ltd 764 KuiKe Building, No.9 Xinxi Rd., 765 Hai-Dian District 766 Beijing, 100085 767 P.R. China 769 Email: mach@huawei.com 771 Renhai Zhang 772 Huawei Technologies Co.,Ltd 773 KuiKe Building, No.9 Xinxi Rd., 774 Hai-Dian District 775 Beijing, 100085 776 P.R. China 778 Email: zhangrenhai@huawei.com 780 Xiaodong Duan 781 China Mobile 782 53A,Xibianmennei Ave,Xunwu District 783 Beijing, China 785 Email: duanxiaodong@chinamobile.com 787 Intellectual Property Statement 789 The IETF takes no position regarding the validity or scope of any 790 Intellectual Property Rights or other rights that might be claimed to 791 pertain to the implementation or use of the technology described in 792 this document or the extent to which any license under such rights 793 might or might not be available; nor does it represent that it has 794 made any independent effort to identify any such rights. 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