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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Network working group M. Chen 2 Internet Draft Renhai Zhang 3 Expires: October 2008 Huawei Technologies Co.,Ltd 4 Category: Standards Track Xiaodong Duan 5 China Mobile 6 April 10, 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-01.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 October 10, 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 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.........................13 71 4. Procedure for Inter-AS TE Links.............................13 72 4.1. Origin of Proxied TE Information.......................14 73 5. Security Considerations.....................................15 74 6. IANA Considerations.........................................15 75 6.1. Inter-AS Reachability TLV..............................15 76 6.2. Sub-TLVs for the Inter-AS Reachability TLV.............16 77 6.3. Sub-TLVs for the IS-IS Router Capability TLV...........16 78 7. Acknowledgments.............................................16 79 8. References..................................................17 80 8.1. Normative References...................................17 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 OSPF adjacencies are formed on the inter-AS link. 171 Note also that the extensions proposed in this document are used only 172 to advertise information about inter-AS TE links. As such these 173 extensions address an entirely different problem from L1VPN Auto- 174 Discovery [L1VPN-OSPF-AD] which defines how TE information about 175 links between Customer Edge (CE) equipment and Provider Edge (PE) 176 equipment can be advertised in OSPF-TE alongside the auto-discovery 177 information for the CE-PE links. There is no overlap between this 178 document and [L1VPN-OSPF-AD]. 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 so that it can compute a TE LSP 187 segment across the local AS to one of those LSRs and forward the PATH 188 message to it and hence into the next AS. See Figure 1 for an example: 190 R1------R3----R5-----R7------R9-----R11 191 | | \ | / | 192 | | \ | ---- | 193 | | \ | / | 194 R2------R4----R6 --R8------R10----R12 195 : : 196 <-- AS1 -->:<---- AS2 --->:<--- AS3 ---> 198 Figure 1: Inter-AS Reference Model 200 The figure shows three ASes (AS1, AS2, and AS3) and twelve LSRs (R1 201 through R12). R3 and R4 are ASBRs in AS1. R5, R6, R7, and R8 are 202 ASBRs in AS2. R9 and R10 are ASBRs in AS3. 204 If an inter-AS TE LSP is planned to be established from R1 to R12, 205 the AS sequence will be: AS1, AS2, AS3. 207 Suppose that the Path message enters AS2 from R3. The next hop in the 208 ERO shows AS3, and R5 must determine a path segment across AS2 to 209 reach AS3. It has a choice of three exit points from AS2 (R6, R7, and 210 R8) and it needs to know which of these provide TE connectivity to 211 AS3, and whether the TE connectivity (for example, available 212 bandwidth) is adequate for the requested LSP. 214 Alternatively, if the next hop in the ERO is the entry ASBR for AS3 215 (say R9), R5 needs to know which of its exit ASBRs has a TE link that 216 connects to R9. Since there may be multiple ASBRs that are connected 217 to R9 (both R7 and R8 in this example), R5 also needs to know the TE 218 properties of the inter-AS TE links so that it can select the correct 219 exit ASBR. 221 Once the path message reaches the exit ASBR, any choice of inter-AS 222 TE link can be made by the ASBR if not already made by entry ASBR 223 that computed the segment. 225 More details can be found in the Section 4. of [PD-PATH], which 226 clearly points out why advertising of inter-AS links is desired. 228 To enable R5 to make the correct choice of exit ASBR the following 229 information is needed: 231 o List of all inter-AS TE links for the local AS. 233 o TE properties of each inter-AS TE link. 235 o AS number of the neighboring AS connected to by each inter-AS TE 236 link. 238 o Identity (TE Router ID) of the neighboring ASBR connected to by 239 each inter-AS TE link. 241 In GMPLS networks further information may also be required to select 242 the correct TE links as defined in [GMPLS-TE]. 244 The example above shows how this information is needed at the entry 245 point ASBRs for each AS (or the PCEs that provide computation 246 services for the ASBRs), but this information is also needed 247 throughout the local AS if path computation function is fully 248 distributed among LSRs in the local AS, for example to support LSPs 249 that have start points (ingress nodes) within the AS. 251 2.3. Backward Recursive Path Computation 253 Another scenario using PCE techniques has the same problem. [BRPC] 254 defines a PCE-based TE LSP computation method (called Backward 255 Recursive Path Computation) to compute optimal inter-domain 256 constrained MPLS-TE or GMPLS LSPs. In this path computation method, a 257 specific set of traversed domains (ASes) are assumed to be selected 258 before computation starts. Each downstream PCE in domain(i) returns 259 to its upstream neighbor PCE in domain(i-1) a multipoint-to-point 260 tree of potential paths. Each tree consists of the set of paths from 261 all Boundary Nodes located in domain(i) to the destination where each 262 path satisfies the set of required constraints for the TE LSP 263 (bandwidth, affinities, etc.). 265 So a PCE needs to select Boundary Nodes (that is, ASBRs) that provide 266 connectivity from the upstream AS. In order that the tree of paths 267 provided by one PCE to its neighbor can be correlated, the identities 268 of the ASBRs for each path need to be referenced, so the PCE must 269 know the identities of the ASBRs in the remote AS reached by any 270 inter-AS TE link, and, in order that it provides only suitable paths 271 in the tree, the PCE must know the TE properties of the inter-AS TE 272 links. See the following figure as an example: 274 PCE1<------>PCE2<-------->PCE3 275 / : : 276 / : : 277 R1------R3----R5-----R7------R9-----R11 278 | | \ | / | 279 | | \ | ---- | 280 | | \ | / | 281 R2------R4----R6 --R8------R10----R12 282 : : 283 <-- AS1 -->:<---- AS2 --->:<--- AS3 ---> 285 Figure 2: BRPC for Inter-AS Reference Model 287 The figure shows three ASes (AS1, AS2, and AS3), three PCEs (PCE1, 288 PCE2, and PCE3), and twelve LSRs (R1 through R12). R3 and R4 are 289 ASBRs in AS1. R5, R6, R7, and R8 are ASBRs in AS2. R9 and R10 are 290 ASBRs in AS3. PCE1, PCE2, and PCE3 cooperate to perform inter-AS path 291 computation and are responsible for path segment computation within 292 their own domain(s). 294 If an inter-AS TE LSP is planned to be established from R1 to R12, 295 the traversed domains are assumed to be selected: AS1->AS2->AS3, and 296 the PCE chain is: PCE1->PCE2->PCE3. First, the path computation 297 request originated from the PCC (R1) is relayed by PCE1 and PCE2 298 along the PCE chain to PCE3, then PCE3 begins to compute the path 299 segments from the entry boundary nodes that provide connection from 300 AS2 to the destination (R12). But, to provide suitable path segments, 301 PCE3 must determine which entry boundary nodes provide connectivity 302 to its upstream neighbor AS (identified by its AS number), and must 303 know the TE properties of the inter-AS TE links. In the same way, 304 PCE2 also needs to determine the entry boundary nodes according to 305 its upstream neighbor AS and the inter-AS TE link capabilities. 307 Thus, to support Backward Recursive Path Computation the same 308 information listed in Section 2.2 is required. The AS number of the 309 neighboring AS connected to by each inter-AS TE link is particularly 310 important. 312 3. Extensions to ISIS-TE 314 Note that this document does not define mechanisms for distribution 315 of TE information from one AS to another, does not distribute any 316 form of TE reachability information for destinations outside the AS, 317 does not change the PCE architecture or usage, does not suggest or 318 recommend any form of TE aggregation, and does not feed private 319 information between ASes. See Section 2.1. 321 In this document, for the advertisement of inter-AS TE links, a new 322 TLV, which is referred to as the Inter-AS Reachability TLV, is 323 defined and three new sub-TLVs are defined for inclusion in the 324 Inter-AS Reachability TLV to carry the information about the 325 neighboring AS number and the remote ASBR ID of an inter-AS link. The 326 sub-TLVs defined in [ISIS-TE], [ISIS-TE-V3] and other documents for 327 inclusion in the Extended IS Reachability TLV are applicable to be 328 included in the Inter-AS Reachability TLV for inter-AS TE links 329 advertisement. And another two new sub-TLVs are defined for inclusion 330 in the IS-IS Router Capability TLV to carry the TE Router ID when the 331 TE Router ID is needed to reach all routers within an entire ISIS 332 routing domain. 334 3.1. Inter-AS Reachability TLV 336 The Inter-AS Reachability TLV has type 141 (which needs to be 337 confirmed by IANA see Section 6.1), it contains a data structure 338 consisting of: 340 7 octets of System ID and Pseudonode Number 341 3 octets of default metric 342 1 octet of control information, consisting of: 343 1 bit of flooding-scope information 344 1 bit of up/down information 345 6 bits reserved 346 1 octet of length of sub-TLVs 347 0-243 octets of sub-TLVs 348 where each sub-TLV consists of a sequence of: 349 1 octet of sub-type 350 1 octet of length of the value field of the sub-TLV 351 0-241 octets of value 353 Compare to the Extended Reachability TLV which is defined in [ISIS- 354 TE], the Inter-AS Reachability TLV introduces an extra "control 355 information" field which is consisted of a flooding-scope bit, a 356 up/down bit and 6 reserved bits. 358 As the S bit defined in [ISIS-CAP], the flooding-scope bit is used to 359 control the flooding scope of the Inter-AS Reachability TLV. When the 360 flooding-scope bit is set to 1, the Inter-AS Reachability TLV MUST be 361 flooded into the entire ISIS routing domain. If the flooding-scope 362 bit is set to 0, the Inter-AS Reachability TLV MUST NOT be leaked 363 between different levels. And this flooding-scope bit MUST NOT be 364 modified during the TLV leaking. The choice between the use of 0 or 1 365 is a AS-wide policy choice, and configuration control SHOULD be 366 provided in ASBR implementations that supports the advertisement of 367 inter-AS TE links. 369 The semantics of the up/down bit in the Inter-AS Reachability TLV are 370 identical to the semantics of the up/down bit defined in [ISIS-TE]. 371 It can be used to facilitate the redistribution of inter-AS TE 372 information freely between level 1 and level 2. And the up/down bit 373 MUST be set to 0 when the Inter-AS TE information first injected into 374 ISIS [ISIS], and the up/dawn bit MUST be set to 1 if the Inter-AS TE 375 information needs to be advertised from high level to low level. 377 The sub-TLVs which are defined in [ISIS-TE], [ISIS-TE-V3] and other 378 documents for describing the TE properties of an TE link are also 379 applicable to be carried in the Inter-AS Reachability TLV to describe 380 the TE properties of an Inter-AS TE link. Apart from these sub-TLVs, 381 three new sub-TLVs are defined for inclusion in the Inter-AS 382 Reachability TLV in this document: 384 Sub-TLV type Length Name 385 ------------ ------ --------------------------- 386 23 4 Remote AS number 387 24 4 IPv4 Remote ASBR Identifier 388 25 16 IPv6 Remote ASBR Identifier 390 The detailed definitions of the three new sub-TLVs are described in 391 Section 3.3. 393 3.2. TE Router ID 395 The IPv4 TE Router ID TLV (type 134) and IPv6 TE Router ID TLV (type 396 140), which are defined in [ISIS-TE] and [ISIS-TE-V3] respectively, 397 only have area flooding-scope, when performing inter-AS TE, the TE 398 Router ID MAY be needed to reach all routers within an entire ISIS 399 routing domain, and it MUST have the same flooding scope as the 400 Inter-AS Reachability TLV does. 402 [ISIS-CAP] defines a generic advertisement mechanism for ISIS which 403 allows a router to advertise its capabilities within an ISIS area or 404 an entire ISIS routing domain. And [ISIS-CAP] also points out that TE 405 Router ID is candidate to be carried in the IS-IS Router Capability 406 TLV when performing inter-area TE. 408 This document uses such mechanism for TE Router ID advertisement when 409 the TE Router ID is needed to reach all routers within an entire ISIS 410 Routing domain. Two new sub-TLVs are defined for inclusion in the IS- 411 IS Router Capability TLV to carry the IPv4 and IPv6 TE Router ID 412 respectively: 414 Sub-TLV type Length Name 415 ------------ ------ ----------------- 416 11 4 IPv4 TE Router ID 417 12 16 IPv6 TE Router ID 419 The Detailed definitions of the two new sub-TLVs are described in 420 Section 3.3. 422 3.3. Sub-TLV Detail 424 3.3.1. Remote AS Number Sub-TLV 426 A new sub-TLV, the Remote AS Number sub-TLV is defined for inclusion 427 in the Inter-AS Reachability TLV when advertising inter-AS links. The 428 Remote AS Number sub-TLV specifies the AS number of the neighboring 429 AS to which the advertised link connects. 431 The Remote AS number sub-TLV is TLV type 23 (which needs to be 432 confirmed by IANA see Section 6.2), and is four octets in length. The 433 format is as follows: 435 0 1 2 3 436 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 1 437 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 438 | Type | Length | 439 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 440 | Remote AS Number | 441 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 443 The Remote AS number field has 4 octets. When only two octets are 444 used for the AS number, as in current deployments, the left (high- 445 order) two octets MUST be set to zero. The Remote AS Number Sub-TLV 446 MUST be included when a router advertises an inter-AS TE link. 448 3.3.2. IPv4 Remote ASBR ID Sub-TLV 450 A new sub-TLV, which is referred to as the IPv4 Remote ASBR ID sub- 451 TLV, is defined for inclusion in the Inter-AS Reachability TLV when 452 advertising inter-AS links. The IPv4 Remote ASBR ID sub-TLV specifies 453 the IPv4 identifier of the remote ASBR to which the advertised inter- 454 AS link connects. This could be any stable and routable IPv4 address 455 of the remote ASBR. Use of the TE Router ID as specified in the 456 Traffic Engineering Router ID TLV [ISIS-TE] is RECOMMENDED. 458 The IPv4 Remote ASBR ID sub-TLV is TLV type 24 (which needs to be 459 confirmed by IANA see Section 6.2), and is four octets in length. The 460 format of the IPv4 Remote ASBR ID sub-TLV is as follows: 462 0 1 2 3 463 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 1 464 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 465 | Type | Length | 466 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 467 | Remote ASBR ID | 468 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 470 The IPv4 Remote ASBR ID sub-TLV MUST be included if the neighboring 471 ASBR has an IPv4 address. If the neighboring ASBR does not have an 472 IPv4 address (not even an IPv4 TE Router ID), the IPv6 Remote ASBR ID 473 sub-TLV MUST be included instead. An IPv4 Remote ASBR ID sub-TLV and 474 IPv6 Remote ASBR ID sub-TLV MAY both be present in an Extended IS 475 Reachability TLV. 477 3.3.3. IPv6 Remote ASBR ID Sub-TLV 479 A new sub-TLV, which is referred to as the IPv6 Remote ASBR ID sub- 480 TLV, is defined for inclusion in the Inter-AS Reachability TLV when 481 advertising inter-AS links. The IPv6 Remote ASBR ID sub-TLV specifies 482 the IPv6 identifier of the remote ASBR to which the advertised inter- 483 AS link connects. This could be any stable and routable IPv6 address 484 of the remote ASBR. Use of the TE Router ID as specified in the IPv6 485 Traffic Engineering Router ID TLV [ISIS-TE-V3] is RECOMMENDED. 487 The IPv6 Remote ASBR ID sub-TLV is TLV type 25 (which needs to be 488 confirmed by IANA see Section 6.2), and is sixteen octets in length. 489 The format of the IPv6 Remote ASBR ID sub-TLV is as follows: 491 0 1 2 3 492 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 1 493 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 494 | Type | Length | 495 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 496 | Remote ASBR ID | 497 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 498 | Remote ASBR ID (continued) | 499 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 500 | Remote ASBR ID (continued) | 501 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 502 | Remote ASBR ID (continued) | 503 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 505 The IPv6 Remote ASBR ID sub-TLV MUST be included if the neighboring 506 ASBR has an IPv6 address. If the neighboring ASBR does not have an 507 IPv6 address, the IPv4 Remote ASBR ID sub-TLV MUST be included 508 instead. An IPv4 Remote ASBR ID sub-TLV and IPv6 Remote ASBR ID sub- 509 TLV MAY both be present in an Extended IS Reachability TLV. 511 3.3.4. IPv4 TE Router ID sub-TLV 513 The IPv4 TE Router ID sub-TLV is TLV type 11 (which needs to be 514 confirmed by IANA see Section 6.3), and is four octets in length. The 515 format of the IPv4 TE Router ID sub-TLV is as follows: 517 0 1 2 3 518 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 1 519 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 520 | Type | Length | 521 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 522 | TE Router ID | 523 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 525 When the TE Router ID is needed to reach all routers within an entire 526 ISIS routing domain, the IS-IS Router Capability TLV MUST be included 527 in its LSP. And if an ASBR supports Traffic Engineering for IPv4, the 528 IPv4 TE Router ID sub-TLV MUST be included if the ASBR has an IPv4 TE 529 Router ID. If the ASBR does not have an IPv4 TE Router ID, the IPv6 530 TE Router sub-TLV MUST be included instead. An IPv4 TE Router ID sub- 531 TLV and IPv6 TE Router ID sub-TLV MAY both be present in an IS-IS 532 Router Capability TLV. 534 3.3.5. IPv6 TE Router ID sub-TLV 536 The IPv6 TE Router ID sub-TLV is TLV type 12 (which needs to be 537 confirmed by IANA see Section 6.3), and is four octets in length. The 538 format of the IPv6 TE Router ID sub-TLV is as follows: 540 0 1 2 3 541 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 1 542 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 543 | Type | Length | 544 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 545 | TE Router ID | 546 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 547 | TE Router ID (continued) | 548 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 549 | TE Router ID (continued) | 550 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 551 | TE Router ID (continued) | 552 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 554 When the TE Router ID is needed to reach all routers within an entire 555 ISIS routing domain, the IS-IS Router Capability TLV MUST be included 556 in its LSP. And if an ASBR supports Traffic Engineering for IPv6, the 557 IPv6 TE Router ID sub-TLV MUST be included if the ASBR has an IPv6 TE 558 Router ID. If the ASBR does not have an IPv6 TE Router ID, the IPv4 559 TE Router sub-TLV MUST be included instead. An IPv4 TE Router ID sub- 560 TLV and IPv6 TE Router ID sub-TLV MAY both be present in an IS-IS 561 Router Capability TLV. 563 4. Procedure for Inter-AS TE Links 565 When TE is enabled on an inter-AS link and the link is up, the ASBR 566 SHOULD advertise this link using the normal procedures for ISIS-TE 567 [ISIS-TE]. When either the link is down or TE is disabled on the link, 568 the ASBR SHOULD withdraw the advertisement. When there are changes to 569 the TE parameters for the link (for example, when the available 570 bandwidth changes) the ASBR SHOULD re-advertise the link, but the 571 ASBR MUST take precautions against excessive re-advertisements. 573 Hellos MUST NOT be exchanged over the inter-AS link, and consequently, 574 an ISIS adjacency MUST NOT be formed. 576 The information advertised comes from the ASBR's knowledge of the TE 577 capabilities of the link, the ASBR's knowledge of the current status 578 and usage of the link, and configuration at the ASBR of the remote AS 579 number and remote ASBR TE Router ID. 581 Legacy routers receiving an advertisement for an inter-AS TE link are 582 able to ignore it because they do not know the new TLV and sub-TLVs 583 that are defined in Section 3 in this document. They will continue to 584 flood the LSP, but will not attempt to use the information received. 586 In the current operation of ISIS TE the LSRs at each end of a TE link 587 emit LSAs describing the link. The databases in the LSRs then have 588 two entries (one locally generated, the other from the peer) that 589 describe the different 'directions' of the link. This enables CSPF 590 to do a two-way check on the link when performing path computation 591 and eliminate it from consideration unless both directions of the 592 link satisfy the required constraints. 594 In the case we are considering here (i.e., of a TE link to another AS) 595 there is, by definition, no IGP peering and hence no bi-directional 596 TE link information. In order for the CSPF route computation entity 597 to include the link as a candidate path, we have to find a way to get 598 LSAs describing its (bidirectional) TE properties into the TE 599 database. 601 This is achieved by the ASBR advertising, internally to its AS, 602 information about both directions of the TE link to the next AS. The 603 ASBR will normally generate a LSA describing its own side of a link; 604 here we have it 'proxy' for the ASBR at the edge of the other AS and 605 generate an additional LSA that describes that devices 'view' of the 606 link. 608 Only some essential TE information for the link needs to be 609 advertised; i.e., the Interface Address, the Remote AS number and the 610 Remote ASBR ID of an inter-AS TE link. 612 Routers or PCEs that are capable of processing advertisements of 613 inter-AS TE links SHOULD NOT use such links to compute paths that 614 exit an AS to a remote ASBR and then immediately re-enter the AS 615 through another TE link. Such paths would constitute extremely rare 616 occurrences and SHOULD NOT be allowed except as the result of 617 specific policy configurations at the router or PCE computing the 618 path. 620 4.1. Origin of Proxied TE Information 622 Section 4 describes how to an ASBR advertises TE link information as 623 a proxy for its neighbor ASBR, but does not describe where this 624 information comes from. 626 Although the source of this information is outside the scope of this 627 document, it is possible that it will be a configuration requirement 628 at the ASBR, as are other, local, properties of the TE link. Further, 629 where BGP is used to exchange IP routing information between the 630 ASBRs, a certain amount of additional local configuration about the 631 link and the remote ASBR is likely to be available. 633 We note further that it is possible, and may be operationally 634 advantageous, to obtain some of the required configuration 635 information from BGP. Whether and how to utilize these possibilities 636 is an implementation matter. 638 5. Security Considerations 640 The protocol extensions defined in this document are relatively minor 641 and can be secured within the AS in which they are used by the 642 existing ISIS security mechanisms. 644 There is no exchange of information between ASes, and no change to 645 the ISIS security relationship between the ASes. In particular, since 646 no ISIS adjacency is formed on the inter-AS links, there is no 647 requirement for ISIS security between the ASes. 649 Some of the information included in these new advertisements (e.g., 650 the remote AS number and the remote ASBR ID) is obtained manually 651 from a neighboring administration as part of commercial relationship. 652 The source and content of this information should be carefully 653 checked before it is entered as configuration information at the ASBR 654 responsible for advertising the inter-AS TE links. 656 It is worth noting that in the scenario we are considering a Border 657 Gateway Protocol (BGP) peering may exist between the two ASBRs and 658 this could be used to detect inconsistencies in configuration. For 659 example, if a different remote AS number is received in a BGP OPEN 660 [BGP] from that locally configured into ISIS-TE, as we describe here, 661 then something is amiss. Note, further, that if BGP is used to 662 exchange TE information as described in Section 4.1, the inter-AS BGP 663 session will need to be fully secured. 665 6. IANA Considerations 667 IANA is requested to make the following allocations from registries 668 under its control. 670 6.1. Inter-AS Reachability TLV 672 This document defines the following new ISIS TLV type, described in 673 Section 3.4, that needs to be registered in the ISIS TLV code-point 674 registry: 676 Type Description IIH LSP SNP 677 ---- ---------------------- --- --- --- 678 141 Inter-AS reachability n y n 679 information 681 6.2. Sub-TLVs for the Inter-AS Reachability TLV 683 This document defines the following new sub-TLV types, described in 684 Sections 3.3.1, 3.3.2 and 3.3.3, of top-level TLV 141 (see section 685 6.1 above) that need to be registered in the ISIS sub-TLV registry 686 for TLV 141: 688 Type Description Length 689 ---- ------------------------------ -------- 690 23 Remote AS number 4 691 24 IPv4 Remote ASBR Identifier 4 692 25 IPv6 Remote ASBR Identifier 16 694 As described above in Section 3.1, the sub-TLVs which are defined in 695 [ISIS-TE], [ISIS-TE-V3] and other documents for describing the TE 696 properties of an TE link are applicable to describe an inter-AS TE 697 link and MAY be included in the Inter-AS Reachability TLV when 698 adverting inter-AS TE links. So, these sub-TLVs need to be registered 699 in the ISIS sub-TLV registry for TLV 141. And in order to simplify 700 the registration, we suggest using the same registry value as they 701 are registered in the ISIS sub-TLV registry for TLV 22. 703 6.3. Sub-TLVs for the IS-IS Router Capability TLV 705 This document defines the following new sub-TLV types, described in 706 Sections 3.3.4 and 3.3.5, of top-level TLV 242 (which is defined in 707 [ISIS-CAP]) that need to be registered in the ISIS sub-TLV registry 708 for TLV 242: 710 Type Description Length 711 ---- ------------------------------ -------- 712 11 IPv4 TE Router ID 4 713 12 IPv6 TE Router ID 16 715 7. Acknowledgments 717 The authors would like to thank Adrian Farrel, Jean-Louis Le Roux, 718 Christian Hopps, and Les Ginsberg for their review and comments on 719 this document. 721 8. References 723 8.1. Normative References 725 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 726 Requirement Levels", BCP 14, RFC 2119, March 1997. 728 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 729 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 730 Tunnels", RFC 3209, December 2001. 732 [ISIS] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and 733 dual environments", RFC 1195, December 1990. 735 [ISIS-TE-V3] Harrison, J., Berger, J., and Bartlett, M., "IPv6 736 Traffic Engineering in IS-IS", draft-ietf-isis-ipv6-te, 737 {work in progress}. 739 [ISIS-CAP] Vasseur, J.P. et al., "IS-IS extensions for advertising 740 router information", RFC 4971, July 2007. 742 8.2. Informative References 744 [INTER-AS-TE-REQ] Zhang and Vasseur, "MPLS Inter-AS Traffic 745 Engineering Requirements", RFC4216, November 2005. 747 [PD-PATH] Ayyangar, A., Vasseur, JP., and Zhang, R., "A Per-domain 748 path computation method for establishing Inter-domain", RFC 749 5152, February 2008. 751 [BRPC] JP. Vasseur, Ed., R. Zhang, N. Bitar, JL. Le Roux, "A Backward 752 Recursive PCE-based Computation (BRPC) procedure to compute 753 shortest inter-domain Traffic Engineering Label Switched 754 Paths ", draft-ietf-pce-brpc, (work in progress) 756 [PCE] Farrel, A., Vasseur, JP., and Ash, J., "A Path Computation 757 Element (PCE)-Based Architecture", RFC4655, August 2006. 759 [ISIS-TE] Smit, H. and T. Li, "Intermediate System to Intermediate 760 System (IS-IS) Extensions for Traffic Engineering (TE)", 761 RFC 3784, June 2004. 763 [GMPLS-TE] K.Kompella and Y.Rekhter, "IS-IS Extensions in Support of 764 Generalized Multi-Protocol Label Switching", RFC 4205, 765 October 2005. 767 [L1VPN-OSPF-AD] Bryskin, I., and Berger, L., "OSPF Based L1VPN Auto- 768 Discovery", draft-ietf-l1vpn-ospf-auto-discovery, (work in 769 progress). 771 [BGP] Rekhter, Li, Hares, "A Border Gateway Protocol 4 (BGP-4)", 772 RFC4271, January 2006 774 Authors' Addresses 776 Mach(Guoyi) Chen 777 Huawei Technologies Co.,Ltd 778 KuiKe Building, No.9 Xinxi Rd., 779 Hai-Dian District 780 Beijing, 100085 781 P.R. China 783 Email: mach@huawei.com 785 Renhai Zhang 786 Huawei Technologies Co.,Ltd 787 KuiKe Building, No.9 Xinxi Rd., 788 Hai-Dian District 789 Beijing, 100085 790 P.R. China 792 Email: zhangrenhai@huawei.com 794 Xiaodong Duan 795 China Mobile 796 53A,Xibianmennei Ave,Xunwu District 797 Beijing, China 799 Email: duanxiaodong@chinamobile.com 801 Intellectual Property Statement 803 The IETF takes no position regarding the validity or scope of any 804 Intellectual Property Rights or other rights that might be claimed to 805 pertain to the implementation or use of the technology described in 806 this document or the extent to which any license under such rights 807 might or might not be available; nor does it represent that it has 808 made any independent effort to identify any such rights. 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