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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: October 2007 Huawei Technologies Co.,Ltd 4 Category: Standards Track April 2, 2007 6 OSPF Traffic Engineering (OSPF-TE) Extensions in Support of Inter-AS 7 Multiprotocol Label Switching (MPLS) and Generalized MPLS (GMPLS) 8 Traffic Engineering 9 draft-chen-ccamp-ospf-interas-te-extensions-02.txt 11 Status of this Memo 13 By submitting this Internet-Draft, each author represents that 14 any applicable patent or other IPR claims of which he or she is 15 aware have been or will be disclosed, and any of which he or she 16 becomes aware will be disclosed, in accordance with Section 6 of 17 BCP 79. 19 Internet-Drafts are working documents of the Internet Engineering 20 Task Force (IETF), its areas, and its working groups. Note that other 21 groups may also distribute working documents as Internet-Drafts. 23 Internet-Drafts are draft documents valid for a maximum of six months 24 and may be updated, replaced, or obsoleted by other documents at any 25 time. It is inappropriate to use Internet-Drafts as reference 26 material or to cite them other than as "work in progress." 28 The list of current Internet-Drafts can be accessed at 29 http://www.ietf.org/ietf/1id-abstracts.txt 31 The list of Internet-Draft Shadow Directories can be accessed at 32 http://www.ietf.org/shadow.html 34 This Internet-Draft will expire on October 2, 2007. 36 Abstract 38 This document describes extensions to the OSPF Traffic Engineering 39 (OSPF-TE) mechanisms to support Multiprotocol Label Switching (MPLS) 40 and Generalized MPLS (GMPLS) Traffic Engineering (TE) for multiple 41 Autonomous Systems (ASes). It defines OSPF-TE extensions for the 42 flooding of TE information about inter-AS links which can be used to 43 perform inter-AS TE path computation. 45 Conventions used in this document 47 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 48 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 49 document are to be interpreted as described in RFC-2119 [RFC2119]. 51 Table of Contents 53 1. Introduction.................................................2 54 2. Problem statement............................................3 55 2.1. A Note on Non-Objectives................................3 56 2.2. Per-Domain Path Determination...........................4 57 2.3. Backward Recursive Path Computation.....................5 58 3. Extensions to OSPF-TE........................................6 59 3.1. Remote AS Number Sub-TLV................................6 60 3.2. Inter-AS Link Type......................................7 61 3.3. Link ID.................................................7 62 4. Procedure for Inter-AS TE Links..............................7 63 5. Security Considerations......................................8 64 6. IANA Considerations..........................................8 65 6.1. OSPF LSA Sub-TLVs type..................................8 66 6.2. OSPF TE Link Type.......................................9 67 7. Acknowledgments..............................................9 68 8. References...................................................9 69 8.1. Normative References....................................9 70 8.2. Informative References.................................10 71 Author's Addresses.............................................10 72 Intellectual Property Statement................................11 73 Disclaimer of Validity.........................................11 74 Copyright Statement............................................11 75 Acknowledgment.................................................12 77 1. Introduction 79 [OSPF-TE] defines extensions to the OSPF protocol [OSPF] to support 80 intra-area Traffic Engineering (TE). The extensions provide a way of 81 encoding the TE information for TE-enabled links within the network 82 (TE links) and flooding this information within an area. Type 10 83 opaque LSAs [RFC2370] are used to carry such TE information. Two top- 84 level TLVs are defined in [OSPF-TE]: Router Address TLV and Link TLV. 85 The Link TLV has several nested sub-TLVs which describe the TE 86 attributes for a TE link. 88 [OSPF-TE-V3] defines similar extensions to OSPFv3 [OSPFV3]. 90 Requirements for establishing Multiprotocol Label Switching (MPLS) TE 91 Label Switched Paths (LSPs) that cross multiple Autonomous Systems 92 (ASes) are described in [INTER-AS-TE-REQ]. As described in [INTER-AS- 93 TE-REQ], a method SHOULD provide the ability to compute a path 94 spanning multiple ASes. So a path computation entity that may be the 95 head-end Label Switching Router (LSR), an AS Border Router (ASBR), or 96 a Path Computation Element (PCE [PCE]) needs to know the TE 97 information not only of the links within an AS, but also of the links 98 that connect to other ASes. 100 In this document, some extensions to OSPF-TE are defined in support 101 of carrying inter-AS TE link information for inter-AS Traffic 102 Engineering. A new sub-TLV is added to the Link TLV and a new link 103 type is introduced. The extensions are equally applicable to OSPFv2 104 and OSPFv3 as identical extensions to [OSPF-TE] and [OSPF-TE-V3]. The 105 detailed definitions and procedures are discussed in the following 106 sections. 108 2. Problem statement 110 As described in [INTER-AS-TE-REQ], in the case of establishing an 111 inter-AS TE LSP traversing multiple ASes, the Path message [RFC3209] 112 may include the following elements in the Explicit Route Object (ERO) 113 in order to describe the path of the LSP: 115 - a set of AS numbers as loose hops; and/or 117 - a set of LSRs including ASBRs as loose hops. 119 Two methods for determining inter-AS paths are currently discussed. 120 The per-domain method [PD-PATH] determines the path one domain at a 121 time. The backward recursive method [BRPC] uses cooperation between 122 PCEs to determine an optimum inter-domain path. The sections that 123 follow examine how inter-AS TE link information could be useful in 124 both cases. 126 2.1. A Note on Non-Objectives 128 It is important to note that this document does not make any change 129 to the confidentiality and scaling assumptions surrounding the use of 130 ASes in the Internet. In particular, this document is conformant to 131 the requirements set out in [INTER-AS-TE-REQ]. 133 The following lists of features are explicit exclusions. 135 o There is no attempt to distribute TE information from within one 136 AS to another AS. 138 o There is no mechanism proposed to distribute any form of TE 139 reachability information for destinations outside the AS. 141 o There is no proposed change to the PCE architecture or usage. 143 o TE aggregation is not supported or recommended. 145 o There is no exchange of private information between ASes. 147 Note further that the extensions proposed in this document are 148 limited to use for information about inter-AS TE links. L1VPN Auto- 149 Discovery [L1VPN-OSPF-AD] defines how TE information about links 150 between Customer Edge (CE) equipment and Provider Edge (PE) equipment 151 can be advertised in OSPF alongside the auto-discovery information 152 for the CE-PE links. That is separate functionality and does not 153 overlap with the function defined in this document. 155 2.2. Per-Domain Path Determination 157 In the per-domain method of determining an inter-AS path for an MPLS- 158 TE LSP, when an LSR that is an entry-point to an AS receives a PATH 159 message from an upstream AS with an ERO containing a next hop that is 160 an AS number, it needs to find which LSRs within the local AS are 161 connected to the downstream AS so that it can compute a TE LSP 162 segment across the AS to that LSR and forward the PATH message to the 163 LSR and hence into the next AS. See the figure below for an example: 165 R1------R3----R5-----R7------R9-----R11 166 | | \ | / | 167 | | \ | ---- | 168 | | \ | / | 169 R2------R4----R6 --R8------R10----R12 170 : : 171 <-- AS1 -->:<---- AS2 --->:<--- AS3 ---> 173 Figure 1: Inter-AS Reference Model 175 The figure shows three ASes (AS1, AS2, and AS3) and twelve LSRs (R1 176 through R12). R3 and R4 are ASBRs in AS1. R5, R6, R7, and R8 are 177 ASBRs in AS2. R9 and R10 are ASBRs in AS3. 179 If an inter-AS TE LSP is planned to be established from R1 to R12, 180 the AS sequence is limited as: AS1, AS2, AS3. 182 Suppose that the Path message enters AS2 from R3. The next hop in the 183 ERO shows AS3, and R5 must determine a path segment across AS2 to 184 reach AS3. It has a choice of three exit points from AS2 (R6, R7, and 185 R8) and it needs to know which of these provide TE connectivity to 186 AS3, and whether the TE connectivity (for example, available 187 bandwidth) is adequate for the requested LSP. 189 Alternatively, if the next hop in the ERO is the entry ASBR for AS3 190 (say R9), R5 needs to know which of its exit ASBRs has a TE link that 191 connects to R9. Since there may be multiple exist ASBRs that are 192 connected to R9 (both R7 and R8 in this example), R5 also needs to 193 know the TE properties of the inter-AS TE links so that it can select 194 the correct exit ASBR. 196 Once the path message reaches the exit ASBR, any choice of inter-AS 197 TE link can be made by the ASBR if not already made by entry ASBR 198 that computed the segment. 200 More details can be found in the Section 4.0 of [PD-PATH], which 201 clearly points out why advertising of inter-AS links is desired. 203 To enable R5 to make the correct choice of exit ASBR the following 204 information is needed: 206 o List of all inter-AS TE links for the local AS. 208 o TE properties of each inter-AS TE link. 210 o AS number of the neighboring AS connected to by each inter-AS TE link. 212 o Identity (TE Router ID) of the neighboring ASBR connected to by each 213 inter-AS TE link. 215 In GMPLS networks further information may also be required to select 216 the correct TE links as defined in [GMPLS-TE]. 218 The example above shows how this information is needed at the entry 219 point ASBRs for each AS (or the PCEs that provide computation 220 services for the ASBRs), but this information is also needed 221 throughout the local AS if path computation function is fully 222 distributed among LSRs in the local AS, for example to support LSPs 223 that have start points (ingress nodes) within the AS. 225 2.3. Backward Recursive Path Computation 227 Another scenario using PCE techniques has the same problem. [BRPC] 228 defines a PCE-based TE LSP computation method (called Backward 229 Recursive Path Computation) to compute optimal inter-domain 230 constrained MPLS-TE or GMPLS LSPs. In this path computation method, a 231 specific set of traversed domains are assumed to be selected before 232 computation starts. Each downstream PCE in domain(i) returns a 233 multipoint-to-point tree of potential paths to its upstream neighbor 234 PCE in domain(i-1). Each tree consists of the set of paths from all 235 Boundary Nodes located in domain(i) to the destination where each 236 path satisfies the set of required constraints for the TE LSP 237 (bandwidth, affinities, etc.). 239 So a PCE needs to select Boundary Nodes (that is, ASBRs) that provide 240 connectivity from the upstream AS. In order that the tree of paths 241 provided by one PCE to its neighbor can be correlated, the identities 242 of the ASBRs for each path need to be referenced, so the PCE must 243 know the identities of the ASBRs in the remote AS reached by any 244 inter-AS TE link, and, in order that it provides only suitable paths 245 in the tree, the PCE must know the TE properties of the inter-AS TE 246 links. 248 Thus, to support Backward Recursive Path Computation the same 249 information as listed in Section 2.2 is required. 251 3. Extensions to OSPF-TE 253 Note that this document does not define mechanisms for distribution 254 of TE information from one AS to another, does not distribute any 255 form of TE reachability information for destinations outside the AS, 256 does not change the PCE architecture or usage, does not suggest or 257 recommend any form of TE aggregation, and does not feed private 258 information between ASes. See section 2.1. 260 The extensions defined in this document allow an inter-AS TE link 261 advertisement to be easily identified as such by the use of a new 262 link type. A new sub-TLV to the Link TLV is defined to carry the 263 information about the neighboring AS. The extensions are equally 264 applicable to TE distribution using OSPFv2 and OSPFv3. 266 3.1. Remote AS Number Sub-TLV 268 As described in [OSPF-TE], the Link TLV describes a single link and 269 consists of a set of sub-TLVs. A new sub-TLV, the Remote AS Number 270 sub-TLV is added to the Link TLV when advertising inter-AS links. The 271 Remote AS Number sub-TLV specifies the AS number of the neighboring 272 AS to which the advertised link connects. 274 The Remote AS number sub-TLV is TLV type 21 (which needs to be 275 confirmed by IANA), and is four octets in length. The format is as 276 follows: 278 0 1 2 3 279 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 1 280 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 281 | Type | Length | 282 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 283 | Remote AS Number | 284 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 286 The Remote AS number field has 4 octets. When two octets are used for 287 the AS number, as in current deployments, the left (high-order) two 288 octets MUST be set to zero. 290 3.2. Inter-AS Link Type 292 To identify a link as an inter-AS link and allow easy identification 293 of these new advertisements, a new Link Type value is defined for use 294 in the Link Type sub-TLV. The value of the Link Type for an inter-AS 295 point-to-point link is 3 (which needs to be confirmed by IANA). The 296 use of multi-access inter-AS TE links is for future study. 298 3.3. Link ID 300 For an inter-AS link, the Link ID carried in the Link ID sub-TLV is 301 the TE Router ID of the remote ASBR reached through this inter-AS 302 link. 304 4. Procedure for Inter-AS TE Links 306 When TE is enabled on an inter-AS link and the link is up, the ASBR 307 SHOULD advertise this link using the normal procedures for OSPF-TE 308 [OSPF-TE]. When either the link is down or TE is disabled on the link, 309 the ASBR SHOULD withdraw the advertisement. When there are changes to 310 the TE parameters for the link (for example, when the available 311 bandwidth changes) the ASBR SHOULD re-advertise the link, but the 312 ASBR MUST take precautions against excessive re-advertisements as 313 described in [OSPF-TE]. 315 The information advertised comes from the ASBR's knowledge of the TE 316 capabilities of the link, the ASBR's knowledge of the current status 317 and usage of the link, and configuration at the ASBR of the remote AS 318 number and remote ASBR TE Router ID. 320 The TE link advertisement SHOULD be carried in a Type 10 Opaque LSA 321 if the flooding scope is to be limited to within the single IGP area 322 to which the ASBR belongs, or MAY be carried in a Type 11 Opaque LSA 323 if the information should reach all routers (including area border 324 routers, ASBRs, and PCEs) in the AS. 326 Legacy routers receiving an advertisement for an inter-AS TE link are 327 able to ignore it because the Link Type carries an unknown value. 328 They will continue to flood the LSA, but will not attempt to use the 329 information received as if the link were an intra-AS TE link. 331 Routers or PCEs that are capable of processing advertisements of 332 inter-AS TE links SHOULD NOT use such links to compute paths that 333 exit an AS to a remote ASBR and then immediately re-enter the AS 334 through another TE link. Such paths would constitute extremely rare 335 occurrences and SHOULD NOT be allowed except as the result of 336 specific policy configurations at the router or PCE computing the 337 path. 339 5. Security Considerations 341 The protocol extensions defined in this document are relatively minor 342 and can be secured within the AS in which they are used by the 343 existing OSPF security mechanisms. 345 It should be noted, however, that some of the information included in 346 these new advertisements(the remote AS number and the remote ASBR ID) 347 are obtained from a neighboring administration and cannot be verified 348 in anyway. Since the means of delivery of this information is likely 349 to be part of a commercial relationship, the source of the 350 information should be carefully checked before it is entered as 351 configuration information at the ASBR responsible for advertising the 352 inter-AS TE links. 354 6. IANA Considerations 356 IANA is requested to make the following allocations from registries 357 under its control. 359 6.1. OSPF LSA Sub-TLVs type 361 IANA maintains the "Open Shortest Path First (OSPF) Traffic 362 Engineering TLVs" registry with sub-registry "Types for sub-TLVs in a 363 TE Link TLV". IANA is requested to assign a new sub-TLV as follows. 364 The number 21 is suggested. 366 Value Meaning 368 21 Remote AS Number sub-TLV. 370 6.2. OSPF TE Link Type 372 IANA is requested to create a new sub-registry "TE Link Types" of the 373 registry "Open Shortest Path First (OSPF) Traffic Engineering TLVs" 374 to track TE Link Types. 376 The sub-registry should read as follows: 378 [OSPF-TE] defines the Link Type sub-TLV of the Link TLV. The 379 following values are defined. 381 Value Meaning Reference 383 1 Point-to-point link [OSPF-TE] 385 2 Multi-access link [OSPF-TE] 387 3 Inter-AS link [this document] 389 New allocations from this registry are by IETF Standards Action. 391 7. Acknowledgments 393 The authors would like to thank Adrian Farrel, Acee Lindem, JP 394 Vasseur, and Dean Cheng for their review and comments to this 395 document. 397 8. References 399 8.1. Normative References 401 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 402 Requirement Levels", BCP 14, RFC 2119, March 1997. 404 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 405 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 406 Tunnels", RFC 3209, December 2001. 408 [RFC2370] R. Coltun, "The OSPF Opaque LSA Option", RFC2370, July 409 1998. 411 [OSPF] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998. 413 [OSPF-TE] Katz, D., Kompella, K., and Yeung, D., "Traffic Engineering 414 (TE) Extensions to OSPF Version 2", RFC 3630, September 415 2003. 417 [GMPLS-TE] Rekhter, Y., and Kompella, K., "OSPF Extensions in Support 418 of Generalized Multi-Protocol Label Switching (GMPLS)", RFC 419 4203, October 2005. 421 8.2. Informative References 423 [INTER-AS-TE-REQ] Zhang and Vasseur, "MPLS Inter-AS Traffic 424 Engineering Requirements", RFC4216, November 2005. 426 [PD-PATH] Ayyangar, A., Vasseur, JP., and Zhang, R., "A Per-domain 427 path computation method for establishing Inter-domain", 428 draft-ietf-ccamp-inter-domain-pd-path-comp, (work in 429 progress). 431 [BRPC] JP. Vasseur, Ed., R. Zhang, N. Bitar, JL. Le Roux, "A Backward 432 Recursive PCE-based Computation (BRPC) procedure to compute 433 shortest inter-domain Traffic Engineering Label Switched 434 Paths ", draft-ietf-pce-brpc, (work in progress) 436 [PCE] Farrel, A., Vasseur, JP., and Ash, J., "A Path Computation 437 Element (PCE)-Based Architecture", RFC4655, August 2006. 439 [OSPF-TE-V3] Ishiguro K., Manral V., Davey A., and Lindem A. "Traffic 440 Engineering Extensions to OSPF version 3", draft-ietf-ospf- 441 ospfv3-traffic, {work in progress}. 443 [OSPFV3] Coltun, R., Ferguson, D., and J. Moy, "OSPF for IPv6", RFC 444 2740, April 1998. 446 [L1VPN-OSPF-AD] Bryskin, I., and Berger, L., "OSPF Based L1VPN Auto- 447 Discovery", draft-ietf-l1vpn-ospf-auto-discovery-02.txt, 448 (work in progress). 450 Author's Addresses 452 Mach Chen 453 Huawei Technologies Co.,Ltd 454 KuiKe Building, No.9 Xinxi Rd., 455 Hai-Dian District 456 Beijing, 100085 457 P.R. China 459 Email: mach@huawei.com 460 Renhai Zhang 461 Huawei Technologies Co.,Ltd 462 KuiKe Building, No.9 Xinxi Rd., 463 Hai-Dian District 464 Beijing, 100085 465 P.R. China 467 Email: zhangrenhai@huawei.com 469 Intellectual Property Statement 471 The IETF takes no position regarding the validity or scope of any 472 Intellectual Property Rights or other rights that might be claimed to 473 pertain to the implementation or use of the technology described in 474 this document or the extent to which any license under such rights 475 might or might not be available; nor does it represent that it has 476 made any independent effort to identify any such rights. 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Please address the information to the IETF at 491 ietf-ipr@ietf.org. 493 Disclaimer of Validity 495 This document and the information contained herein are provided on an 496 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 497 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 498 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 499 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 500 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 501 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 503 Copyright Statement 505 Copyright (C) The IETF Trust (2007). 507 This document is subject to the rights, licenses and restrictions 508 contained in BCP 78, and except as set forth therein, the authors 509 retain all their rights. 511 Acknowledgment