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Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (July 14, 2013) is 3931 days in the past. Is this intentional? Checking references for intended status: Experimental ---------------------------------------------------------------------------- No issues found here. Summary: 1 error (**), 0 flaws (~~), 1 warning (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Network Working Group F. Zhang, Ed. 2 Internet-Draft Q. Zhao 3 Intended status: Experimental Huawei 4 Expires: January 14, 2014 O. Gonzalez de Dios, Ed. 5 Telefonica I+D 6 R. Casellas 7 CTTC 8 D. King 9 Old Dog Consulting 10 July 14, 2013 12 Extensions to Path Computation Element Communication Protocol (PCEP) for 13 Hierarchical Path Computation Elements (PCE) 14 draft-zhang-pce-hierarchy-extensions-04 16 Abstract 18 The Hierarchical Path Computation Element (H-PCE) architecture, 19 defined in the companion framework document [RFC6805], provides a 20 mechanism to allow the optimum sequence of domains to be selected, 21 and the optimum end-to-end path to be derived through the use of a 22 hierarchical relationship between domains. 24 This document defines the Path Computation Element Protocol (PCEP) 25 extensions for the purpose of implementing Hierarchical PCE 26 procedures which are described in the aforementioned document. These 27 extensions are experimental and published for examination, 28 discussion, implementation, and evaluation. 30 Status of this Memo 32 This Internet-Draft is submitted in full conformance with the 33 provisions of BCP 78 and BCP 79. 35 Internet-Drafts are working documents of the Internet Engineering 36 Task Force (IETF). Note that other groups may also distribute 37 working documents as Internet-Drafts. The list of current Internet- 38 Drafts is at http://datatracker.ietf.org/drafts/current/. 40 Internet-Drafts are draft documents valid for a maximum of six months 41 and may be updated, replaced, or obsoleted by other documents at any 42 time. It is inappropriate to use Internet-Drafts as reference 43 material or to cite them other than as "work in progress." 45 This Internet-Draft will expire on January 14, 2014. 47 Copyright Notice 49 Copyright (c) 2013 IETF Trust and the persons identified as the 50 document authors. All rights reserved. 52 This document is subject to BCP 78 and the IETF Trust's Legal 53 Provisions Relating to IETF Documents 54 (http://trustee.ietf.org/license-info) in effect on the date of 55 publication of this document. Please review these documents 56 carefully, as they describe your rights and restrictions with respect 57 to this document. Code Components extracted from this document must 58 include Simplified BSD License text as described in Section 4.e of 59 the Trust Legal Provisions and are provided without warranty as 60 described in the Simplified BSD License. 62 Table of Contents 64 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 65 1.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 3 66 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 67 1.3. Requirements Language . . . . . . . . . . . . . . . . . . 4 68 2. Requirements for H-PCE . . . . . . . . . . . . . . . . . . . . 4 69 2.1. PCEP Requests . . . . . . . . . . . . . . . . . . . . . . 4 70 2.1.1. Qualification of PCEP Requests . . . . . . . . . . . . 4 71 2.1.2. Multi-domain Objective Functions . . . . . . . . . . . 5 72 2.1.3. Multi-domain Metrics . . . . . . . . . . . . . . . . . 6 73 2.2. Parent PCE Capability Discovery . . . . . . . . . . . . . 6 74 2.3. PCE Domain and PCE ID Discovery . . . . . . . . . . . . . 6 75 3. PCEP Extensions (Encoding) . . . . . . . . . . . . . . . . . . 6 76 3.1. OPEN Object . . . . . . . . . . . . . . . . . . . . . . . 6 77 3.1.1. OF Codes . . . . . . . . . . . . . . . . . . . . . . . 6 78 3.1.2. OPEN Object Flags . . . . . . . . . . . . . . . . . . 7 79 3.1.3. Domain-ID TLV . . . . . . . . . . . . . . . . . . . . 7 80 3.1.4. PCE-ID TLV . . . . . . . . . . . . . . . . . . . . . . 9 81 3.2. RP object . . . . . . . . . . . . . . . . . . . . . . . . 9 82 3.2.1. RP Object Flags . . . . . . . . . . . . . . . . . . . 9 83 3.2.2. Domain-ID TLV . . . . . . . . . . . . . . . . . . . . 9 84 3.3. Metric Object . . . . . . . . . . . . . . . . . . . . . .10 85 3.4. PCEP-ERROR Object . . . . . . . . . . . . . . . . . . . .10 86 3.4.1. Hierarchy PCE Error-Type . . . . . . . . . . . . . . .10 87 3.5. NO-PATH Object . . . . . . . . . . . . . . . . . . . . . .10 88 4. H-PCE Procedures . . . . . . . . . . . . . . . . . . . . . . .10 89 4.1. OPEN Procedure between Child PCE and Parent PCE . . . . .11 90 4.2. Procedure to Obtain Domain Sequence . . . . . . . . . . .11 91 5. Error Handling . . . . . . . . . . . . . . . . . . . . . . . .11 92 6. Manageability Considerations . . . . . . . . . . . . . . . . .12 93 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . .12 94 8. Security Considerations . . . . . . . . . . . . . . . . . . .12 95 9. Contributing Authors . . . . . . . . . . . . . . . . . . . . .12 96 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .12 97 11. Normative References . . . . . . . . . . . . . . . . . . . . .13 98 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .13 100 1. Introduction 102 [RFC6805] describes a Hierarchical PCE (H-PCE) architecture which can 103 be used for computing end-to-end paths for inter-domain MPLS Traffic 104 Engineering (TE) and GMPLS Label Switched Paths (LSPs). 106 Within the hierarchical PCE architecture, the parent PCE is used to 107 compute a multi-domain path based on the domain connectivity 108 information. A child PCE may be responsible for a single domain or 109 multiple domains, it is used to compute the intra-domain path based 110 on its domain topology information. 112 The H-PCE end-to-end domain path computation procedure is described 113 below: 115 o A path computation client (PCC) sends the inter-domain path 116 computation requests to the child PCE responsible for its domain; 118 o The child PCE forwards the request to the parent PCE; 120 o The parent PCE computes the likely domain paths from the ingress 121 domain to the egress domain; 123 o The parent PCE sends the intra-domain path computation requests 124 (between the domain border nodes) to the child PCEs which are 125 responsible for the domains along the domain path; 127 o The child PCEs return the intra-domain paths to the parent PCE; 129 o The parent PCE constructs the end-to-end inter-domain path based 130 on the intra-domain paths; 132 o The parent PCE returns the inter-domain path to the child PCE; 134 o The child PCE forwards the inter-domain path to the PCC. 136 In addition, the parent PCE may be requested to provide only the 137 sequence of domains to a child PCE so that alternative inter-domain 138 path computation procedures, including Per Domain (PD) [RFC5152] and 139 Backwards Recursive Path Computation (BRPC) [RFC5441] may be used. 141 This document defines the PCEP extensions for the purpose of 142 implementing Hierarchical PCE procedures, which are described in 143 [RFC6805]. 145 1.1. Scope 146 The following functions are out of scope of this document. 148 o Finding end point addresses; 150 o Parent Traffic Engineering Database (TED) methods; 152 o Domain connectivity; 154 The document also uses a number of [editor notes] to describe options 155 and alternative solutions. These options and notes will be removed 156 before publication once agreement is reached. 158 1.2. Terminology 160 This document uses the terminology defined in [RFC4655], [RFC5440] 161 and the additional terms defined in section 1.4 of [RFC6805]. 163 1.3. Requirements Language 165 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 166 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 167 document are to be interpreted as described in [RFC2119]. 169 2. Requirements for H-PCE 171 This section compiles the set of requirements of the PCEP protocol to 172 support the H-PCE architecture and procedures. 174 [RFC6805] identifies high-level requirements of PCEP extensions 175 required to support the hierarchical PCE model. 177 2.1. PCEP Requests 179 The PCReq messages are used by a PCC or PCE to make a path 180 computation request to a PCE. In order to achieve the full 181 functionality of the H-PCE procedures, the PCReq message needs to 182 include: 184 o Qualification of PCE Requests. 186 o Multi-domain Objective Functions (OF). 188 o Multi-domain Metrics. 190 2.1.1. Qualification of PCEP Requests 192 As described in section 4.8.1 of [RFC6805], the H-PCE architecture 193 introduces new request qualifications, which are: 195 o It MUST be possible for a child PCE to indicate that a request it 196 sends to a parent PCE should be satisfied by a domain sequence 197 only, that is, not by a full end-to-end path. This allows the 198 child PCE to initiate a per-domain (PD) [RFC5152] or a backward 199 recursive path computation (BRPC) [RFC5441]. 201 o As stated in [RFC6805], section 4.5, if a PCC knows the egress 202 domain, it can supply this information as the path computation 203 request. It SHOULD be possible to specify the destination domain 204 information in a PCEP request, if it is known. 206 2.1.2. Multi-domain Objective Functions 208 For inter-domain path computation, there are two new objective 209 functions which are defined in section 1.3.1 and 4.1 of [RFC6805]: 211 o Minimize the number of domains crossed. A domain can be either an 212 Autonomous System (AS) or an Internal Gateway Protocol (IGP) area 213 depending on the type of multi-domain network hierarchical PCE is 214 applied to. 216 o Disallow domain re-entry.[Editor's note: Disallow domain re-entry 217 may not be an objective function, but an option in the request]. 219 During the PCEP session establishment procedure, the parent PCE needs 220 to be capable of indicating the Objective Functions (OF) capability 221 in the Open message. This capability information may then be 222 announced by child PCEs, and used for selecting the PCE when a PCC 223 wants a path that satisfies one or multiple inter-domain objective 224 functions. 226 When a PCC requests a PCE to compute an inter-domain path, the PCC 227 needs also to be capable of indicating the new objective functions 228 for inter-domain path. Note that a given child PCE may also act as a 229 parent PCE. 231 For the reasons described previously, new OF codes need to be defined 232 for the new inter-domain objective functions. Then the PCE can 233 notify its new inter-domain objective functions to the PCC by 234 carrying them in the OF-list TLV which is carried in the OPEN object. 235 The PCC can specify which objective function code to use, which is 236 carried in the OF object when requesting a PCE to compute an inter- 237 domain path. 239 The proposed solution may need to differentiate between the OF code 240 that is requested at the parent level, and the OF code that is 241 requested at the intra-domain (child domain). 243 A parent PCE MUST be capable of ensuring homogeneity, across domains, 244 when applying OF codes for strict OF intra-domain requests. 246 2.1.3. Multi-domain Metrics 248 For inter-domain path computation, there are several path metrics of 249 interest [Editor's note: Current framework only mentions metric 250 objectives. The metric itself should be also defined]: 252 o Domain count (number of domains crossed). 254 o Border Node count. 256 A PCC may be able to limit the number of domains crossed by applying 257 a limit on these metrics. 259 2.2. Parent PCE Capability Discovery 261 Parent and child PCE relationships are likely to be configured. 262 However, as mentioned in [RFC6805], it would assist network operators 263 if the child and parent PCE could indicate their H-PCE capabilities. 265 During the PCEP session establishment procedure, the child PCE needs 266 to be capable of indicating to the parent PCE whether it requests the 267 parent PCE capability or not. Also, during the PCEP session 268 establishment procedure, the parent PCE needs to be capable of 269 indicating whether its parent capability can be provided or not. 271 2.3. PCE Domain and PCE ID Discovery 273 A PCE domain is a single domain with an associated PCE. Although it 274 is possible for a PCE to manage multiple domains. The PCE domain may 275 be an IGP area or AS. 277 The PCE ID is an IPv4 and/or IPv6 address that is used to reach the 278 parent/child PCE. It is RECOMMENDED to use an address that is always 279 reachable if there is any connectivity to the PCE. 281 The PCE ID information and PCE domain identifiers may be provided 282 during the PCEP session establishment procedure or the domain 283 connectivity information collection procedure. 285 3. PCEP Extensions (Encoding) 287 3.1. OPEN object 289 3.1.1. OF Codes 290 This H-PCE experiment will be carried out using the following OF 291 codes: 293 o MTD 295 * Name: Minimize the number of Transit Domains. 297 * Objective Function Code. 299 * Description: Find a path P such that it passes through the 300 lnumber of transit domains. 302 o MBN 304 * Name: Minimize the number of border nodes. 306 * Objective Function Code. 308 * Description: Find a path P such that it passes through the 309 least number of border nodes. 311 o DDR 313 * Name: Disallow Domain Re-entry (DDR) 315 * Objective Function Code. 317 * Description: Find a path P such that does not entry a domain 318 more than once. 320 3.1.2. OPEN Object Flags 322 This H-PCE experiment will also require two OPEN object flags: 324 o Parent PCE Request bit (to be assigned by IANA, recommended bit 325 0): if set, it would signal that the child PCE wishes to use the 326 peer PCE as a parent PCE. 328 o Parent PCE Indication bit (to be assigned by IANA, recommended bit 329 1): if set, it would signal that the PCE can be used as a parent 330 PCE by the peer PCE. 332 3.1.3. Domain-ID TLV 334 The Domain-ID TLV for this H-PCE experiment is defined below: 336 0 1 2 3 337 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 1 338 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 339 | Domain Type | Reserved | 340 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 341 | Domain ID | 342 // // 343 | | 344 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 346 Figure 1: Domain-ID TLV 348 Domain Type (8 bits): Indicates the domain type. Two types of domain 349 are currently defined: 351 o Type=1: the Domain ID field carries an IGP Area ID. 353 o Type=2: the Domain ID field carries an AS number. 355 Domain ID (variable): Indicates an IGP Area ID or AS number. It can 356 be 2 bytes, 4 bytes or 8 bytes long depending on the domain 357 identifier used. 359 [Editor's note: draft-dhody-pce-pcep-domain-sequence, section 3.2 360 deals with the encoding of domain sequences, using ERO-subobjects. 361 Work is ongoing to define domain identifiers for OSPF-TE areas, IS-IS 362 area (which are variable sized), 2-byte and 4-byte AS number, and any 363 other domain that may be defined in the future. It uses RSVP-TE 364 subobject discriminators, rather than new type 1/ type 2. A domain 365 sequence may be encoded as a route object. The "VALUE" part of the 366 TLV could follow common RSVP-TE subobject format: 368 0 1 2 3 369 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 1 370 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 371 |0| Type | Length | Reserved | 372 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 373 | AS Id (4 bytes) | 374 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 376 0 1 2 3 377 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 1 378 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 379 |0| Type | Length | AS Id (2 bytes) | 380 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 382 Figure 2: Alternative Domain-ID TLV 384 3.1.4. PCE-ID TLV 386 The type of PCE-ID TLV for this H-PCE experiment is defined below: 388 0 1 2 3 389 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 1 390 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 391 | Address Type | Reserved | 392 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 393 | | 394 // PCE IP Address // 395 | | 396 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 398 Figure 3: PCE-ID TLV 400 Address Type (16 bits): Indicates the address type of PCE IP Address. 401 1 means IPv4 address type, 2 means IPv6 address type. 403 PCE IP Address: Indicates the reachable address of a PCE. 405 [Editor's note: [RFC5886] already defines the PCE-ID object. If a 406 semantically equivalent PCE-ID TLV is needed (to avoid modifying 407 message grammars to include the object), it can align with the PCEP 408 object: in any case, the length (4 / 16 bytes) can be used to know 409 whether it is an IPv4 or an IPv6 PCE, the address type is not 410 needed.] 412 3.2. RP object 414 3.2.1. RP Object Flags 416 The following RP object flags are defined for this H-PCE experiment: 418 o Domain Path Request bit: if set, it means the child PCE wishes to 419 get the domain sequence. 421 o Destination Domain Query bit: if set, it means the parent PCE 422 wishes to get the destination domain ID. 424 3.2.2. Domain-ID TLV 426 The format of this TLV is defined in Section 3.1.3. This TLV can be 427 carried in an OPEN object to indicate a (list of) managed domains, or 428 carried in a RP object to indicate the destination domain ID when a 429 child PCE responds to the parent PCE's destination domain query by a 430 PCRep message. 432 [Editors note. In some cases, the Parent PCE may need to allocate a 433 node which is not necessarily the destination node.] 435 3.3. Metric Object 437 There are two new metrics defined in this document for H-PCE: 439 o Domain count (number of domains crossed). 441 o Border Node Count (number of border nodes crossed). 443 3.4. PCEP-ERROR object 445 3.4.1. Hierarchy PCE Error-Type 447 A new PCEP Error-Type is used for this H-PCE experiment and is 448 defined below: 450 +------------+------------------------------------------------------+ 451 | Error-Type | Meaning | 452 +------------+------------------------------------------------------+ 453 | 19 | H-PCE error Error-value=1: parent PCE capability | 454 | | cannot be provided | 455 +------------+------------------------------------------------------+ 457 H-PCE error table 459 3.5. NO-PATH Object 461 To communicate the reason(s) for not being able to find a multi- 462 domain path or domain sequence, the NO-PATH object can be used in the 463 PCRep message. [RFC5440] defines the format of the NO-PATH object. 464 The object may contain a NO-PATH-VECTOR TLV to provide additional 465 information about why a (domain) path computation has failed. 467 Three new bit flags are defined to be carried in the Flags field in 468 the NO-PATH-VECTOR TLV carried in the NO-PATH Object. 470 o Bit 23: When set, the parent PCE indicates that destination domain 471 unknown; 473 o Bit 22: When set, the parent PCE indicates unresponsive child 474 PCE(s); 476 o Bit 21: When set, the parent PCE indicates no available resource 477 available in one or more domain(s). 479 4. H-PCE Procedures 480 4.1. OPEN Procedure between Child PCE and Parent PCE 482 If a child PCE wants to use the peer PCE as a parent, it can set the 483 parent PCE request bit in the OPEN object carried in the Open message 484 during the PCEP session creation procedure. If the peer PCE does not 485 want to provide the parent function to the child PCE, it must send a 486 PCErr message to the child PCE and clear the parent PCE indication 487 bit in the OPEN object. 489 If the parent PCE can provide the parent function to the peer PCE, it 490 may set the parent PCE indication bit in the OPEN object carried in 491 the Open message during the PCEP session creation procedure. 493 The PCE may also report its PCE ID and list of domain ID to the peer 494 PCE by specifying them in the PCE-ID TLV and List of Domain-ID TLVs 495 in the OPEN object carried in the Open message during the PCEP 496 session creation procedure. 498 The OF codes defined in this document can be carried in the OF-list 499 TLV of the OPEN object. If the OF-list TLV carries the OF codes, it 500 means that the PCE is capable of implementing the corresponding 501 objective functions. This information can be used for selecting a 502 proper parent PCE when a child PCE wants to get a path that satisfies 503 a certain objective function. 505 When a specific child PCE sends a PCReq to a peer PCE that requires 506 parental activity and the peer PCE does not want to act as the parent 507 for it, the peer PCE should send a PCErr message to the child PCE and 508 specify the error-type (IANA) and error-value (1) in the PCEP-ERROR 509 object. 511 4.2. Procedure to obtain Domain Sequence 513 If a child PCE only wants to get the domain sequence for a multi- 514 domain path computation from a parent PCE, it can set the Domain Path 515 Request bit in the RP object carried in a PCReq message. The parent 516 PCE which receives the PCReq message tries to compute a domain 517 sequence for it. If the domain path computation succeeds the parent 518 PCE sends a PCRep message which carries the domain sequence in the 519 ERO to the child PCE. The domain sequence is specified as AS or AREA 520 ERO sub-objects (type 32 for AS [RFC3209] or a to-be-defined IGP area 521 type). Otherwise it sends a PCReq message which carries the NO-PATH 522 object to the child PCE. 524 5. Error Handling 526 A PCE that is capable of acting as a parent PCE might not be 527 configured or willing to act as the parent for a specific child PCE. 529 This fact could be determined when the child sends a PCReq that 530 requires parental activity (such as querying other child PCEs), and 531 could result in a negative response in a PCEP Error (PCErr) message 532 and indicate the hierarchy PCE error types. 534 Additionally, the parent PCE may fail to find the multi-domain path 535 or domain sequence due to one or more of the following reasons: 537 o A child PCE cannot find a suitable path to the egress; 539 o The parent PCE do not hear from a child PCE for a specified time; 541 o The objective functions specified in the path request cannot be 542 met. 544 In this case, the parent PCE MAY need to send a negative path 545 computation reply specifying the reason. This can be achieved by 546 including NO-PATH object in the PCRep message. Extension to NO-PATH 547 object is needed to include the aforementioned reasons. 549 6. Manageability Considerations 551 TBD. 553 7. IANA Considerations 555 Due to the experimental nature of this draft no IANA requests are 556 made. 558 8. Security Considerations 560 To be added. 562 9. Contributing Authors 564 Xian Zhang 565 Huawei 566 zhang.xian@huawei.com 568 10. Acknowledgments 570 To be added. 572 11. Normative References 574 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 575 Requirement Levels", BCP 14, RFC 2119, March 1997. 577 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 578 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 579 Tunnels", RFC 3209, December 2001. 581 [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation 582 Element (PCE)-Based Architecture", RFC 4655, August 2006. 584 [RFC5152] Vasseur, JP., Ayyangar, A., and R. Zhang, "A Per-Domain 585 Path Computation Method for Establishing Inter-Domain 586 Traffic Engineering (TE) Label Switched Paths (LSPs)", 587 RFC 5152, February 2008. 589 [RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation Element 590 (PCE) Communication Protocol (PCEP)", RFC 5440, 591 March 2009. 593 [RFC5441] Vasseur, JP., Zhang, R., Bitar, N., and JL. Le Roux, "A 594 Backward-Recursive PCE-Based Computation (BRPC) Procedure 595 to Compute Shortest Constrained Inter-Domain Traffic 596 Engineering Label Switched Paths", RFC 5441, April 2009. 598 [RFC5886] Vasseur, JP., Le Roux, JL., and Y. Ikejiri, "A Set of 599 Monitoring Tools for Path Computation Element (PCE)-Based 600 Architecture", RFC 5886, June 2010. 602 [RFC6805] King, D. and A. Farrel, "The Application of the Path 603 Computation Element Architecture to the Determination of a 604 Sequence of Domains in MPLS and GMPLS", RFC 6805, 605 November 2012. 607 Authors' Addresses 609 Fatai Zhang (editor) 610 Huawei 611 Huawei Base, Bantian, Longgang District 612 Shenzhen, 518129 613 China 615 Phone: +86-755-28972912 616 Email: zhangfatai@huawei.com 617 Quintin Zhao 618 Huawei 619 125 Nagog Technology Park 620 Acton, MA 01719 621 US 623 Phone: 624 Email: qzhao@huawei.com 626 Oscar Gonzalez de Dios (editor) 627 Telefonica I+D 628 Don Ramon de la Cruz 82-84 629 Madrid, 28045 630 Spain 632 Phone: +34913128832 633 Email: ogondio@tid.es 635 Ramon Casellas 636 CTTC 637 Av. Carl Friedrich Gauss n.7 638 Castelldefels, Barcelona 639 Spain 641 Phone: +34 93 645 29 00 642 Email: ramon.casellas@cttc.es 644 Daniel King 645 Old Dog Consulting 646 UK 648 Phone: 649 Email: daniel@olddog.co.uk