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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Internet Engineering Task Force H. Chen 3 Internet-Draft Huawei Technologies 4 Intended status: Standards Track February 25, 2013 5 Expires: August 29, 2013 7 Extensions to the Path Computation Element Communication Protocol (PCEP) 8 for Backup Egress of a Traffic Engineering Label Switched Path 9 draft-chen-pce-compute-backup-egress-05.txt 11 Abstract 13 This document presents extensions to the Path Computation Element 14 Communication Protocol (PCEP) for a PCC to send a request for 15 computing a backup egress for an MPLS TE P2MP LSP or an MPLS TE P2P 16 LSP to a PCE and for a PCE to compute the backup egress and reply to 17 the PCC with a computation result for the backup egress. 19 Status of this Memo 21 This Internet-Draft is submitted to IETF in full conformance with the 22 provisions of BCP 78 and BCP 79. 24 Internet-Drafts are working documents of the Internet Engineering 25 Task Force (IETF). Note that other groups may also distribute 26 working documents as Internet-Drafts. The list of current Internet- 27 Drafts is at http://datatracker.ietf.org/drafts/current/. 29 Internet-Drafts are draft documents valid for a maximum of six months 30 and may be updated, replaced, or obsoleted by other documents at any 31 time. It is inappropriate to use Internet-Drafts as reference 32 material or to cite them other than as "work in progress." 34 This Internet-Draft will expire on August 29, 2013. 36 Copyright Notice 38 Copyright (c) 2013 IETF Trust and the persons identified as the 39 document authors. All rights reserved. 41 This document is subject to BCP 78 and the IETF Trust's Legal 42 Provisions Relating to IETF Documents 43 (http://trustee.ietf.org/license-info) in effect on the date of 44 publication of this document. Please review these documents 45 carefully, as they describe your rights and restrictions with respect 46 to this document. Code Components extracted from this document must 47 include Simplified BSD License text as described in Section 4.e of 48 the Trust Legal Provisions and are provided without warranty as 49 described in the Simplified BSD License. 51 Table of Contents 53 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 54 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 55 3. Conventions Used in This Document . . . . . . . . . . . . . . 3 56 4. Extensions to PCEP . . . . . . . . . . . . . . . . . . . . . . 3 57 4.1. Backup Egress Capability Advertisement . . . . . . . . . . 4 58 4.1.1. Capability TLV in Existing PCE Discovery Protocol . . 4 59 4.1.2. Open Message Extension . . . . . . . . . . . . . . . . 5 60 4.2. Request and Reply Message Extension . . . . . . . . . . . 6 61 4.2.1. RP Object Extension . . . . . . . . . . . . . . . . . 6 62 4.2.2. External Destination Nodes . . . . . . . . . . . . . . 6 63 4.2.3. Constraints between Egress and Backup Egress . . . . . 11 64 4.2.4. Constraints for Backup Path . . . . . . . . . . . . . 11 65 4.2.5. Backup Egress Node . . . . . . . . . . . . . . . . . . 12 66 4.2.6. Backup Egress PCEP Error Objects and Types . . . . . . 12 67 4.2.7. Request Message Format . . . . . . . . . . . . . . . . 12 68 4.2.8. Reply Message Format . . . . . . . . . . . . . . . . . 13 69 5. Security Considerations . . . . . . . . . . . . . . . . . . . 14 70 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 71 6.1. Backup Egress Capability Flag . . . . . . . . . . . . . . 14 72 6.2. Backup Egress Capability TLV . . . . . . . . . . . . . . . 15 73 6.3. Request Parameter Bit Flags . . . . . . . . . . . . . . . 15 74 6.4. PCEP Objects . . . . . . . . . . . . . . . . . . . . . . . 15 75 7. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 16 76 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16 77 8.1. Normative References . . . . . . . . . . . . . . . . . . . 16 78 8.2. Informative References . . . . . . . . . . . . . . . . . . 16 79 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 16 81 1. Introduction 83 RFC 4655 "A Path Computation Element-(PCE) Based Architecture" 84 describes a set of building blocks for constructing solutions to 85 compute Point-to-Point (P2P) Traffic Engineering (TE) label switched 86 paths across multiple areas or Autonomous System (AS) domains. A 87 typical PCE-based system comprises one or more path computation 88 servers, traffic engineering databases (TED), and a number of path 89 computation clients (PCC). A routing protocol is used to exchange 90 traffic engineering information from which the TED is constructed. A 91 PCC sends a Point-to-Point traffic engineering Label Switched Path 92 (LSP) computation request to the path computation server, which uses 93 the TED to compute the path and responses to the PCC with the 94 computed path. A path computation server is named as a PCE. The 95 communications between a PCE and a PCC for Point-to-Point label 96 switched path computations follow the PCE communication protocol 97 (PCEP). 99 RFC6006 "Extensions to PCEP for Point-to-Multipoint Traffic 100 Engineering Label Switched Paths" describes extensions to PCEP to 101 handle requests and responses for the computation of paths for P2MP 102 TE LSPs. 104 This document defines extensions to the Path Computation Element 105 Communication Protocol (PCEP) for a PCC to send a request for 106 computing a backup egress node for an MPLS TE P2MP LSP or an MPLS TE 107 P2P LSP to a PCE and for a PCE to compute the backup egress node and 108 reply to the PCC with a computation result for the backup egress 109 node. 111 2. Terminology 113 This document uses terminologies defined in RFC5440, and RFC4875. 115 3. Conventions Used in This Document 117 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 118 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 119 document are to be interpreted as described in RFC 2119. 121 4. Extensions to PCEP 123 This section describes the extensions to PCEP for computing a backup 124 egress of an MPLS TE P2MP LSP and an MPLS TE P2P LSP. 126 4.1. Backup Egress Capability Advertisement 128 4.1.1. Capability TLV in Existing PCE Discovery Protocol 130 An option for advertising a PCE capability for computing a backup 131 egress for an MPLS TE P2MP LSP or an MPLS TE P2P LSP is to define two 132 new flags. One new flag in the OSPF and IS-IS PCE Capability Flags 133 indicates the capability that a PCE is capable to compute a backup 134 egress for an MPLS TE P2MP LSP; and another new flag in the OSPF and 135 IS-IS PCE Capability Flags indicates the capability that a PCE is 136 capable to compute a backup egress for an MPLS TE P2P LSP.. 138 The format of the PCE-CAP-FLAGS sub-TLV is as follows: 140 0 1 2 3 141 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 1 142 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 143 | Type = 5 | Length | 144 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 145 | | 146 // PCE Capability Flags // 147 | | 148 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 150 Type: 5 151 Length: Multiple of 4 octets 152 Value: This contains an array of units of 32-bit flags 153 numbered from the most significant as bit zero, where 154 each bit represents one PCE capability. 156 The following capability bits have been assigned by IANA: 158 Bit Capabilities 160 0 Path computation with GMPLS link constraints 161 1 Bidirectional path computation 162 2 Diverse path computation 163 3 Load-balanced path computation 164 4 Synchronized path computation 165 5 Support for multiple objective functions 166 6 Support for additive path constraints 167 (max hop count, etc.) 168 7 Support for request prioritization 169 8 Support for multiple requests per message 170 9 Global Concurrent Optimization (GCO) 171 10 P2MP path computation 172 11-31 Reserved for future assignments by IANA. 174 Reserved bits SHOULD be set to zero on transmission and MUST be 175 ignored on receipt. 177 For the backup egress capabilities, one bit such as bit 13 may be 178 assigned to indicate that a PCE is capable to compute a backup egress 179 for an MPLS TE P2MP LSP and another bit such as bit 14 may be 180 assigned to indicate that a PCE is capable to compute a backup egress 181 for an MPLS TE P2P LSP as follows. 183 Bit Capabilities 185 13 Backup egress computation for P2MP LSP 186 14 Backup egress computation for P2P LSP 188 15-31 Reserved for future assignments by IANA. 190 4.1.2. Open Message Extension 192 If a PCE does not advertise its backup egress compution capability 193 during discovery, PCEP should be used to allow a PCC to discover, 194 during the Open Message Exchange, which PCEs are capable of 195 supporting backup egress computation. 197 To achieve this, we extend the PCEP OPEN object by defining a new 198 optional TLV to indicate the PCE's capability to perform backup 199 egress computation for an MPLS TE P2MP LSP and an MPLS TE P2P LSP. 201 We request IANA to allocate a value such as 8 from the "PCEP TLV Type 202 Indicators" subregistry, as documented in Section below ("Backup 203 Egress Capability TLV"). The description is "backup egress capable", 204 and the length value is 2 bytes. The value field is set to indicate 205 the capability of a PCE for backup egress computation for an MPLS TE 206 LSP in details. 208 We can use flag bits in the value field in the same way as the PCE 209 Capability Flags described in the previous section. 211 The inclusion of this TLV in an OPEN object indicates that the sender 212 can perform backup egress computation for an MPLS TE P2MP LSP or an 213 MPLS TE P2P LSP. 215 The capability TLV is meaningful only for a PCE, so it will typically 216 appear only in one of the two Open messages during PCE session 217 establishment. However, in case of PCE cooperation (e.g., inter- 218 domain), when a PCE behaving as a PCC initiates a PCE session it 219 SHOULD also indicate its path computation capabilities. 221 4.2. Request and Reply Message Extension 223 This section describes extensions to the existing RP (Request 224 Parameters) object to allow a PCC to request a PCE for computing a 225 backup egress of an MPLS TE P2MP LSP or an MPLS TE P2P LSP when the 226 PCE receives the PCEP request. 228 4.2.1. RP Object Extension 230 The following flags are added into the RP Object: 232 The T bit is added in the flag bits field of the RP object to tell 233 the receiver of the message that the request/reply is for computing a 234 bcakup egress of an MPLS TE P2MP LSP and an MPLS TE P2P LSP. 236 o T ( Backup Egress bit - 1 bit): 238 0: This indicates that this is not PCReq/PCRep 239 for backup egress. 241 1: This indicates that this is PCReq or PCRep message 242 for backup egress. 244 The IANA request is referenced in Section below (Request Parameter 245 Bit Flags) of this document. 247 This T bit with the N bit defined in RFC 6006 can indicate whether a 248 request/reply is for a bcakup egress of an MPLS TE P2MP LSP or an 249 MPLS TE P2P LSP. 251 o T = 1 and N = 1: This indicates that this is a PCReq/PCRep 252 message for backup egress of an MPLS TE 253 P2MP LSP. 255 o T = 1 and N = 0: This indicates that this is a PCReq/PCRep 256 message for backup egress of an MPLS TE 257 P2P LSP. 259 4.2.2. External Destination Nodes 261 In addition to the information about the path that an MPLS TE P2MP 262 LSP or an MPLS TE P2P LSP traverses, a request message may comprise 263 other information that may be used for computing the backup egress 264 for the P2MP LSP or P2P LSP. For example, the information about an 265 external destination node, to which data traffic is delivered from an 266 egress node of the P2MP LSP or P2P LSP, is useful for computing a 267 backup egress node. 269 4.2.2.1. External Destination Nodes Object 271 The PCC can specify an external destination nodes (EDN) Object. In 272 order to represent the external destination nodes efficiently, we 273 define two types of encodes for the external destination nodes in the 274 object. 276 One encode indicates that the EDN object contains an external 277 destination node for every egress node of an MPLS TE P2MP LSP or an 278 MPLS TE P2P LSP. The order of the external destination nodes in the 279 object is the same as the egress node(s) of the P2MP LSP or P2P LSP 280 contained in the PCE messages. 282 Another encode indicates that the EDN object contains a list of 283 egress node and external destination node pairs. For an egress node 284 and external destination node pair, the data traffic is delivered to 285 the external destination node from the egress node of the LSP. 287 The format of the external destination nodes (EDN) object boby for 288 IPv4 with the first type of encodes is illustrated as follows: 290 0 1 2 3 291 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 1 292 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 293 | Encode of External Destination Nodes (1) | 294 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 295 | External Destination IPv4 address | 296 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 297 | External Destination IPv4 address | 298 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 299 ~ ... ~ 300 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 301 | External Destination IPv4 address | 302 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 304 Figure 1: Format of EDN Object with one Encode for IPv4 306 The format of the external destination nodes (EDN) object boby for 307 IPv4 with the second type of encodes is illustrated below: 309 0 1 2 3 310 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 1 311 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 312 | Encode of External Destination Nodes (2) | 313 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 314 | Egress IPv4 address | 315 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 316 | External Destination IPv4 address | 317 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 318 | Egress IPv4 address | 319 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 320 | External Destination IPv4 address | 321 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 322 ~ ... ~ 323 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 324 | Egress IPv4 address | 325 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 326 | External Destination IPv4 address | 327 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 329 Figure 2: Format of EDN Object with another Encode for IPv4 331 The format of the external destination nodes (EDN) object boby for 332 IPv6 with the first type of encodes is illustrated as follows: 334 0 1 2 3 335 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 1 336 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 337 | Encode of External Destination Nodes (1) | 338 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 339 | | 340 | External Destination IPv6 address (16 bytes) | 341 | | 342 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 343 | | 344 | External Destination IPv6 address (16 bytes) | 345 | | 346 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 347 ~ ... ~ 348 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 349 | | 350 | External Destination IPv6 address (16 bytes) | 351 | | 352 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 354 Figure 3: Format of EDN Object with one Encode for IPv6 356 The format of the external destination nodes (EDN) object boby for 357 IPv6 with the second type of encodes is illustrated below: 359 0 1 2 3 360 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 1 361 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 362 | Encode of External Destination Nodes (2) | 363 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 364 | | 365 | Egress IPv6 address | 366 | | 367 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 368 | | 369 | External Destination IPv6 address (16 bytes) | 370 | | 371 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 372 | | 373 | Egress IPv6 address | 374 | | 375 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 376 | | 377 | External Destination IPv6 address (16 bytes) | 378 | | 379 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 380 ~ ... ~ 381 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 382 | | 383 | Egress IPv6 address | 384 | | 385 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 386 | | 387 | External Destination IPv6 address (16 bytes) | 388 | | 389 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 391 Figure 4: Format of EDN Object with another Encode for IPv6 393 The object can only be carried in a PCReq message. A Path Request 394 may carry at most one external destination nodes Object. 396 The Object-Class and Object-types will need to be allocated by IANA. 397 The IANA request is documented in Section below (PCEP Objects). 399 4.2.2.2. New Type of END-POINTS Objects 401 Alternatively, we may use END-POINTS to represent external 402 destination nodes in a request message for computing backup egress 403 nodes of MPLS LSP. 405 The format of the external destination nodes (EDN) END-POINTS object 406 boby for IPv4 with the first type of encodes is illustrated as 407 follows: 409 0 1 2 3 410 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 1 411 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 412 | Compact External Destination Nodes Type (12) | 413 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 414 | External Destination IPv4 address | 415 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 416 | External Destination IPv4 address | 417 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 418 ~ ... ~ 419 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 420 | External Destination IPv4 address | 421 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 423 Figure 5: EDN END-POINTS Body with one Encode for IPv4 425 The new type of END-POINTS is Compact External Destination Nodes Type 426 (12). The final value for the type will be assigned by IANA. The 427 EDN END-POINTS object of type 12 contains an external destination 428 node for every egress node of an MPLS TE P2MP LSP or an MPLS TE P2P 429 LSP. The order of the external destination nodes in the object is 430 the same as the egress node(s) of the P2MP LSP or P2P LSP contained 431 in the PCE messages. 433 The format of the external destination nodes END-POINTS object boby 434 for IPv4 with the second type of encodes is illustrated below: 436 0 1 2 3 437 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 1 438 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 439 | External Destination Nodes Type (13) | 440 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 441 | Egress IPv4 address | 442 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 443 | External Destination IPv4 address | 444 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 445 | Egress IPv4 address | 446 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 447 | External Destination IPv4 address | 448 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 449 ~ ... ~ 450 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 451 | Egress IPv4 address | 452 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 453 | External Destination IPv4 address | 454 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 456 Figure 6: EDN END-POINTS Body with another Encode for IPv4 458 The new type of END-POINTS is External Destination Nodes Type (13). 459 The final value for the type will be assigned by IANA. The EDN END- 460 POINTS object of type 13 contains a list of egress node and external 461 destination node pairs. For an egress node and external destination 462 node pair, the data traffic is delivered to the external destination 463 node from the egress node of the LSP. 465 4.2.3. Constraints between Egress and Backup Egress 467 A request message sent to a PCE from a PCC for computing a backup 468 egress of an MPLS TE P2MP LSP or an MPLS TE P2P LSP may comprise a 469 constraint indicating that there must be a path from the backup 470 egress node to be computed to the egress node of the P2MP LSP or P2P 471 LSP and that the length of the path is within a given hop limit such 472 as one hop. 474 This constraint can be considered as default by a PCE or explicitly 475 sent to the PCE by a PCC [TBD]. 477 4.2.4. Constraints for Backup Path 479 A request message sent to a PCE from a PCC for computing a backup 480 egress of a P2MP LSP or P2P LSP may comprise a constraint indicating 481 that the backup egress node to be computed may not be a node on the 482 P2MP LSP or P2P LSP. In addition, the request message may comprise a 483 list of nodes, each of which is a candidate for the backup egress 484 node. 486 A request message sent to a PCE from a PCC for computing a backup 487 egress of a P2MP LSP or P2P LSP may comprise a constraint indicating 488 that there must be a path from the previous hop node of the egress 489 node of the P2MP LSP or P2P LSP to the backup egress node to be 490 computed and that there is not an internal node of the path from the 491 previous hop node of the egress node of the P2MP LSP or P2P LSP to 492 the backup egress that is on the path of the P2MP LSP or P2P LSP. 494 Most of these constraints for the backup path can be considered as 495 default by a PCE. The constraints for the backup path may be 496 explicitly sent to the PCE by a PCC [TBD]. 498 4.2.5. Backup Egress Node 500 The PCE may send a reply message to the PCC in return to the request 501 message for computing a new backup egress node or a number of backup 502 egress nodes. The reply message may comprise information about the 503 computed backup egress node(s), which is contained in the path(s) 504 from the previous-hop node of the egress node of the P2MP LSP or P2P 505 LSP to the backup egress node(s) computed. 507 4.2.6. Backup Egress PCEP Error Objects and Types 509 In some cases, the PCE may not complete the backup egress computation 510 as requested, for example based on a set of constraints. As such, 511 the PCE may send a reply message to the PCC that indicates an 512 unsuccessful backup egress computation attempt. The reply message 513 may comprise a PCEP-error object, which may comprise an error-value, 514 error-type and some detail information. 516 4.2.7. Request Message Format 518 The PCReq message is encoded as follows using RBNF as defined in 519 [RFC5511]. 521 Below is the message format for a request message: 523 ::= 524 [] 525 526 ::= 527 528 [] 529 [] 530 [] 531 [] 532 [] 533 [] 534 [] 535 where: 536 is an external destination nodes object. 538 Figure 7: The Format for a Request Message 540 The definitions for svec-list, RP, end-point-rro-pair-list, OF, LSPA, 541 BANDWIDTH, metric-list, IRO, and LOAD-BALANCING are described in 542 RFC5440 and RFC6006. 544 4.2.8. Reply Message Format 546 The PCRep message is encoded as follows using RBNF as defined in 547 [RFC5511]. 549 Below is the message format for a reply message: 551 ::= 552 553 ::= 554 555 [] 556 [] 557 where: 559 ::= 560 [][] 562 ::= (|) [] 564 ::= [] 565 [] 566 [] 567 [] 568 [] 570 Figure 8: The Format for a Reply Message 572 The definitions for RP, NO-PATH, END-POINTS, OF, LSPA, BANDWIDTH, 573 metric-list, IRO, and SERO are described in RFC5440, RFC6006 and 574 RFC4875. 576 5. Security Considerations 578 The mechanism described in this document does not raise any new 579 security issues for the PCEP, OSPF or IS-IS protocols. 581 6. IANA Considerations 583 This section specifies requests for IANA allocation. 585 6.1. Backup Egress Capability Flag 587 Two new OSPF Capability Flags are defined in this document to 588 indicate the capabilities for computing a backup egress for an MPLS 589 TE P2MP LSP and an MPLS TE P2P LSP. IANA is requested to make the 590 assignment from the "OSPF Parameters Path Computation Element (PCE) 591 Capability Flags" registry: 593 Bit Description Reference 595 13 Backup egress for P2MP LSP This I-D 596 14 Backup egress for P2P LSP This I-D 598 6.2. Backup Egress Capability TLV 600 A new backup egress capability TLV is defined in this document to 601 allow a PCE to advertize its backup egress computation capability. 602 IANA is requested to make the following allocation from the "PCEP TLV 603 Type Indicators" sub-registry. 605 Value Description Reference 607 8 Backup egress capable This I-D 609 6.3. Request Parameter Bit Flags 611 A new RP Object Flag has been defined in this document. IANA is 612 requested to make the following allocation from the "PCEP RP Object 613 Flag Field" Sub-Registry: 615 Bit Description Reference 617 15 Backup egress (T-bit) This I-D 619 6.4. PCEP Objects 621 An External Destination Nodes Object-Type is defined in this 622 document. IANA is requested to make the following Object-Type 623 allocation from the "PCEP Objects" sub-registry: 625 Object-Class Value 34 626 Name External Destination Nodes 627 Object-Type 1: IPv4 628 2: IPv6 629 3-15: Unassigned 630 Reference This I-D 632 7. Acknowledgement 634 The author would like to thank Ramon Casellas, Dhruv Dhody and 635 Quintin Zhao for their valuable comments on this draft. 637 8. References 639 8.1. Normative References 641 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 642 Requirement Levels", BCP 14, RFC 2119, March 1997. 644 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 645 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 646 Tunnels", RFC 3209, December 2001. 648 [RFC4090] Pan, P., Swallow, G., and A. Atlas, "Fast Reroute 649 Extensions to RSVP-TE for LSP Tunnels", RFC 4090, 650 May 2005. 652 [RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation Element 653 (PCE) Communication Protocol (PCEP)", RFC 5440, 654 March 2009. 656 [RFC4875] Aggarwal, R., Papadimitriou, D., and S. Yasukawa, 657 "Extensions to Resource Reservation Protocol - Traffic 658 Engineering (RSVP-TE) for Point-to-Multipoint TE Label 659 Switched Paths (LSPs)", RFC 4875, May 2007. 661 [RFC6006] Zhao, Q., King, D., Verhaeghe, F., Takeda, T., Ali, Z., 662 and J. Meuric, "Extensions to the Path Computation Element 663 Communication Protocol (PCEP) for Point-to-Multipoint 664 Traffic Engineering Label Switched Paths", RFC 6006, 665 September 2010. 667 8.2. Informative References 669 [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation 670 Element (PCE)-Based Architecture", RFC 4655, August 2006. 672 [RFC5862] Yasukawa, S. and A. Farrel, "Path Computation Clients 673 (PCC) - Path Computation Element (PCE) Requirements for 674 Point-to-Multipoint MPLS-TE", RFC 5862, June 2010. 676 Author's Address 678 Huaimo Chen 679 Huawei Technologies 680 Boston, MA 681 USA 683 Email: Huaimochen@huawei.com