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Checking references for intended status: Experimental ---------------------------------------------------------------------------- No issues found here. Summary: 0 errors (**), 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: August, 2014 O. Gonzalez de Dios, Ed. 5 Telefonica I+D 6 R. Casellas 7 CTTC 8 D. King 9 Old Dog Consulting 10 February 14, 2014 12 Extensions to Path Computation Element Communication Protocol (PCEP) for 13 Hierarchical Path Computation Elements (PCE) 14 draft-ietf-pce-hierarchy-extensions-01 16 Abstract 18 The Hierarchical Path Computation Element (H-PCE) architecture, 19 provides a mechanism to allow the optimum sequence of domains to be 20 selected,and the optimum end-to-end path to be derived through the 21 use of a hierarchical relationship between domains. 23 This document defines the Path Computation Element Protocol (PCEP) 24 extensions for the purpose of implementing Hierarchical PCE 25 procedures which are described in the aforementioned document. These 26 extensions are experimental and published for examination, 27 discussion, implementation, and evaluation. 29 Status of this Memo 31 This Internet-Draft is submitted in full conformance with the 32 provisions of BCP 78 and BCP 79. 34 Internet-Drafts are working documents of the Internet Engineering 35 Task Force (IETF). Note that other groups may also distribute 36 working documents as Internet-Drafts. The list of current Internet- 37 Drafts is at http://datatracker.ietf.org/drafts/current/. 39 Internet-Drafts are draft documents valid for a maximum of six months 40 and may be updated, replaced, or obsoleted by other documents at any 41 time. It is inappropriate to use Internet-Drafts as reference 42 material or to cite them other than as "work in progress." 44 This Internet-Draft will expire in August, 2014. 46 Copyright Notice 48 Copyright (c) 2014 IETF Trust and the persons identified as the 49 document authors. All rights reserved. 51 This document is subject to BCP 78 and the IETF Trust's Legal 52 Provisions Relating to IETF Documents 53 (http://trustee.ietf.org/license-info) in effect on the date of 54 publication of this document. Please review these documents 55 carefully, as they describe your rights and restrictions with respect 56 to this document. Code Components extracted from this document must 57 include Simplified BSD License text as described in Section 4.e of 58 the Trust Legal Provisions and are provided without warranty as 59 described in the Simplified BSD License. 61 Table of Contents 63 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 64 1.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 3 65 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 66 1.3. Requirements Language . . . . . . . . . . . . . . . . . . 4 67 2. Requirements for H-PCE . . . . . . . . . . . . . . . . . . . . 4 68 2.1. PCEP Requests . . . . . . . . . . . . . . . . . . . . . . 4 69 2.1.1. Qualification of PCEP Requests . . . . . . . . . . . . 4 70 2.1.2. Multi-domain Objective Functions . . . . . . . . . . . 5 71 2.1.3. Multi-domain Metrics . . . . . . . . . . . . . . . . . 6 72 2.2. Parent PCE Capability Discovery . . . . . . . . . . . . . 6 73 2.3. PCE Domain and PCE ID Discovery . . . . . . . . . . . . . 6 74 3. PCEP Extensions (Encoding) . . . . . . . . . . . . . . . . . . 6 75 3.1. OPEN Object . . . . . . . . . . . . . . . . . . . . . . . 6 76 3.1.1. OF Codes . . . . . . . . . . . . . . . . . . . . . . . 6 77 3.1.2. OPEN Object Flags . . . . . . . . . . . . . . . . . . 7 78 3.1.3. Domain-ID TLV . . . . . . . . . . . . . . . . . . . . 7 79 3.1.4. PCE-ID TLV . . . . . . . . . . . . . . . . . . . . . . 9 80 3.2. RP object . . . . . . . . . . . . . . . . . . . . . . . . 9 81 3.2.1. RP Object Flags . . . . . . . . . . . . . . . . . . . 9 82 3.2.2. Domain-ID TLV . . . . . . . . . . . . . . . . . . . . 9 83 3.3. Metric Object . . . . . . . . . . . . . . . . . . . . . .10 84 3.4. PCEP-ERROR Object . . . . . . . . . . . . . . . . . . . .10 85 3.4.1. Hierarchy PCE Error-Type . . . . . . . . . . . . . . .10 86 3.5. NO-PATH Object . . . . . . . . . . . . . . . . . . . . . .10 87 4. H-PCE Procedures . . . . . . . . . . . . . . . . . . . . . . .10 88 4.1. OPEN Procedure between Child PCE and Parent PCE . . . . .11 89 4.2. Procedure to Obtain Domain Sequence . . . . . . . . . . .11 90 5. Error Handling . . . . . . . . . . . . . . . . . . . . . . . .11 91 6. Manageability Considerations . . . . . . . . . . . . . . . . .12 92 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . .12 93 8. Security Considerations . . . . . . . . . . . . . . . . . . .12 94 9. Contributing Authors . . . . . . . . . . . . . . . . . . . . .12 95 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .12 96 11. Normative References . . . . . . . . . . . . . . . . . . . . .13 97 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .13 99 1. Introduction 101 [RFC6805] describes a Hierarchical PCE (H-PCE) architecture which can 102 be used for computing end-to-end paths for inter-domain MPLS Traffic 103 Engineering (TE) and GMPLS Label Switched Paths (LSPs). 105 Within the hierarchical PCE architecture, the parent PCE is used to 106 compute a multi-domain path based on the domain connectivity 107 information. A child PCE may be responsible for a single domain or 108 multiple domains, it is used to compute the intra-domain path based 109 on its domain topology information. 111 The H-PCE end-to-end domain path computation procedure is described 112 below: 114 o A path computation client (PCC) sends the inter-domain path 115 computation requests to the child PCE responsible for its domain; 117 o The child PCE forwards the request to the parent PCE; 119 o The parent PCE computes the likely domain paths from the ingress 120 domain to the egress domain; 122 o The parent PCE sends the intra-domain path computation requests 123 (between the domain border nodes) to the child PCEs which are 124 responsible for the domains along the domain path; 126 o The child PCEs return the intra-domain paths to the parent PCE; 128 o The parent PCE constructs the end-to-end inter-domain path based 129 on the intra-domain paths; 131 o The parent PCE returns the inter-domain path to the child PCE; 133 o The child PCE forwards the inter-domain path to the PCC. 135 In addition, the parent PCE may be requested to provide only the 136 sequence of domains to a child PCE so that alternative inter-domain 137 path computation procedures, including Per Domain (PD) [RFC5152] and 138 Backwards Recursive Path Computation (BRPC) [RFC5441] may be used. 140 This document defines the PCEP extensions for the purpose of 141 implementing Hierarchical PCE procedures, which are described in 142 [RFC6805]. 144 1.1. Scope 145 The following functions are out of scope of this document. 147 o Finding end point addresses; 149 o Parent Traffic Engineering Database (TED) methods; 151 o Domain connectivity; 153 The document also uses a number of [editor notes] to describe options 154 and alternative solutions. These options and notes will be removed 155 before publication once agreement is reached. 157 1.2. Terminology 159 This document uses the terminology defined in [RFC4655], [RFC5440] 160 and the additional terms defined in section 1.4 of [RFC6805]. 162 1.3. Requirements Language 164 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 165 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 166 document are to be interpreted as described in [RFC2119]. 168 2. Requirements for H-PCE 170 This section compiles the set of requirements of the PCEP protocol to 171 support the H-PCE architecture and procedures. 173 [RFC6805] identifies high-level requirements of PCEP extensions 174 required to support the hierarchical PCE model. 176 2.1. PCEP Requests 178 The PCReq messages are used by a PCC or PCE to make a path 179 computation request to a PCE. In order to achieve the full 180 functionality of the H-PCE procedures, the PCReq message needs to 181 include: 183 o Qualification of PCE Requests. 185 o Multi-domain Objective Functions (OF). 187 o Multi-domain Metrics. 189 2.1.1. Qualification of PCEP Requests 191 As described in section 4.8.1 of [RFC6805], the H-PCE architecture 192 introduces new request qualifications, which are: 194 o It MUST be possible for a child PCE to indicate that a request it 195 sends to a parent PCE should be satisfied by a domain sequence 196 only, that is, not by a full end-to-end path. This allows the 197 child PCE to initiate a per-domain (PD) [RFC5152] or a backward 198 recursive path computation (BRPC) [RFC5441]. 200 o As stated in [RFC6805], section 4.5, if a PCC knows the egress 201 domain, it can supply this information as the path computation 202 request. It SHOULD be possible to specify the destination domain 203 information in a PCEP request, if it is known. 205 2.1.2. Multi-domain Objective Functions 207 For inter-domain path computation, there are two new objective 208 functions which are defined in section 1.3.1 and 4.1 of [RFC6805]: 210 o Minimize the number of domains crossed. A domain can be either an 211 Autonomous System (AS) or an Internal Gateway Protocol (IGP) area 212 depending on the type of multi-domain network hierarchical PCE is 213 applied to. 215 o Disallow domain re-entry.[Editor's note: Disallow domain re-entry 216 may not be an objective function, but an option in the request]. 218 During the PCEP session establishment procedure, the parent PCE needs 219 to be capable of indicating the Objective Functions (OF) capability 220 in the Open message. This capability information may then be 221 announced by child PCEs, and used for selecting the PCE when a PCC 222 wants a path that satisfies one or multiple inter-domain objective 223 functions. 225 When a PCC requests a PCE to compute an inter-domain path, the PCC 226 needs also to be capable of indicating the new objective functions 227 for inter-domain path. Note that a given child PCE may also act as a 228 parent PCE. 230 For the reasons described previously, new OF codes need to be defined 231 for the new inter-domain objective functions. Then the PCE can 232 notify its new inter-domain objective functions to the PCC by 233 carrying them in the OF-list TLV which is carried in the OPEN object. 234 The PCC can specify which objective function code to use, which is 235 carried in the OF object when requesting a PCE to compute an inter- 236 domain path. 238 The proposed solution may need to differentiate between the OF code 239 that is requested at the parent level, and the OF code that is 240 requested at the intra-domain (child domain). 242 A parent PCE MUST be capable of ensuring homogeneity, across domains, 243 when applying OF codes for strict OF intra-domain requests. 245 2.1.3. Multi-domain Metrics 247 For inter-domain path computation, there are several path metrics of 248 interest [Editor's note: Current framework only mentions metric 249 objectives. The metric itself should be also defined]: 251 o Domain count (number of domains crossed). 253 o Border Node count. 255 A PCC may be able to limit the number of domains crossed by applying 256 a limit on these metrics. 258 2.2. Parent PCE Capability Discovery 260 Parent and child PCE relationships are likely to be configured. 261 However, as mentioned in [RFC6805], it would assist network operators 262 if the child and parent PCE could indicate their H-PCE capabilities. 264 During the PCEP session establishment procedure, the child PCE needs 265 to be capable of indicating to the parent PCE whether it requests the 266 parent PCE capability or not. Also, during the PCEP session 267 establishment procedure, the parent PCE needs to be capable of 268 indicating whether its parent capability can be provided or not. 270 2.3. PCE Domain and PCE ID Discovery 272 A PCE domain is a single domain with an associated PCE. Although it 273 is possible for a PCE to manage multiple domains. The PCE domain may 274 be an IGP area or AS. 276 The PCE ID is an IPv4 and/or IPv6 address that is used to reach the 277 parent/child PCE. It is RECOMMENDED to use an address that is always 278 reachable if there is any connectivity to the PCE. 280 The PCE ID information and PCE domain identifiers may be provided 281 during the PCEP session establishment procedure or the domain 282 connectivity information collection procedure. 284 3. PCEP Extensions (Encoding) 286 3.1. OPEN object 288 3.1.1. OF Codes 289 This H-PCE experiment will be carried out using the following OF 290 codes: 292 o MTD 294 * Name: Minimize the number of Transit Domains. 296 * Objective Function Code. 298 * Description: Find a path P such that it passes through the 299 lnumber of transit domains. 301 o MBN 303 * Name: Minimize the number of border nodes. 305 * Objective Function Code. 307 * Description: Find a path P such that it passes through the 308 least number of border nodes. 310 o DDR 312 * Name: Disallow Domain Re-entry (DDR) 314 * Objective Function Code. 316 * Description: Find a path P such that does not entry a domain 317 more than once. 319 3.1.2. OPEN Object Flags 321 This H-PCE experiment will also require two OPEN object flags: 323 o Parent PCE Request bit (to be assigned by IANA, recommended bit 324 0): if set, it would signal that the child PCE wishes to use the 325 peer PCE as a parent PCE. 327 o Parent PCE Indication bit (to be assigned by IANA, recommended bit 328 1): if set, it would signal that the PCE can be used as a parent 329 PCE by the peer PCE. 331 3.1.3. Domain-ID TLV 333 The Domain-ID TLV for this H-PCE experiment is defined below: 335 0 1 2 3 336 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 1 337 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 338 | Domain Type | Reserved | 339 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 340 | Domain ID | 341 // // 342 | | 343 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 345 Figure 1: Domain-ID TLV 347 Domain Type (8 bits): Indicates the domain type. Two types of domain 348 are currently defined: 350 o Type=1: the Domain ID field carries an IGP Area ID. 352 o Type=2: the Domain ID field carries an AS number. 354 Domain ID (variable): Indicates an IGP Area ID or AS number. It can 355 be 2 bytes, 4 bytes or 8 bytes long depending on the domain 356 identifier used. 358 [Editor's note: draft-dhody-pce-pcep-domain-sequence, section 3.2 359 deals with the encoding of domain sequences, using ERO-subobjects. 360 Work is ongoing to define domain identifiers for OSPF-TE areas, IS-IS 361 area (which are variable sized), 2-byte and 4-byte AS number, and any 362 other domain that may be defined in the future. It uses RSVP-TE 363 subobject discriminators, rather than new type 1/ type 2. A domain 364 sequence may be encoded as a route object. The "VALUE" part of the 365 TLV could follow common RSVP-TE subobject format: 367 0 1 2 3 368 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 1 369 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 370 |0| Type | Length | Reserved | 371 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 372 | AS Id (4 bytes) | 373 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 375 0 1 2 3 376 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 1 377 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 378 |0| Type | Length | AS Id (2 bytes) | 379 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 381 Figure 2: Alternative Domain-ID TLV 383 3.1.4. PCE-ID TLV 385 The type of PCE-ID TLV for this H-PCE experiment is defined below: 387 0 1 2 3 388 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 1 389 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 390 | Address Type | Reserved | 391 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 392 | | 393 // PCE IP Address // 394 | | 395 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 397 Figure 3: PCE-ID TLV 399 Address Type (16 bits): Indicates the address type of PCE IP Address. 400 1 means IPv4 address type, 2 means IPv6 address type. 402 PCE IP Address: Indicates the reachable address of a PCE. 404 [Editor's note: [RFC5886] already defines the PCE-ID object. If a 405 semantically equivalent PCE-ID TLV is needed (to avoid modifying 406 message grammars to include the object), it can align with the PCEP 407 object: in any case, the length (4 / 16 bytes) can be used to know 408 whether it is an IPv4 or an IPv6 PCE, the address type is not 409 needed.] 411 3.2. RP object 413 3.2.1. RP Object Flags 415 The following RP object flags are defined for this H-PCE experiment: 417 o Domain Path Request bit: if set, it means the child PCE wishes to 418 get the domain sequence. 420 o Destination Domain Query bit: if set, it means the parent PCE 421 wishes to get the destination domain ID. 423 3.2.2. Domain-ID TLV 425 The format of this TLV is defined in Section 3.1.3. This TLV can be 426 carried in an OPEN object to indicate a (list of) managed domains, or 427 carried in a RP object to indicate the destination domain ID when a 428 child PCE responds to the parent PCE's destination domain query by a 429 PCRep message. 431 [Editors note. In some cases, the Parent PCE may need to allocate a 432 node which is not necessarily the destination node.] 434 3.3. Metric Object 436 There are two new metrics defined in this document for H-PCE: 438 o Domain count (number of domains crossed). 440 o Border Node Count (number of border nodes crossed). 442 3.4. PCEP-ERROR object 444 3.4.1. Hierarchy PCE Error-Type 446 A new PCEP Error-Type is used for this H-PCE experiment and is 447 defined below: 449 +------------+------------------------------------------------------+ 450 | Error-Type | Meaning | 451 +------------+------------------------------------------------------+ 452 | 19 | H-PCE error Error-value=1: parent PCE capability | 453 | | cannot be provided | 454 +------------+------------------------------------------------------+ 456 H-PCE error table 458 3.5. NO-PATH Object 460 To communicate the reason(s) for not being able to find a multi- 461 domain path or domain sequence, the NO-PATH object can be used in the 462 PCRep message. [RFC5440] defines the format of the NO-PATH object. 463 The object may contain a NO-PATH-VECTOR TLV to provide additional 464 information about why a (domain) path computation has failed. 466 Three new bit flags are defined to be carried in the Flags field in 467 the NO-PATH-VECTOR TLV carried in the NO-PATH Object. 469 o Bit 23: When set, the parent PCE indicates that destination domain 470 unknown; 472 o Bit 22: When set, the parent PCE indicates unresponsive child 473 PCE(s); 475 o Bit 21: When set, the parent PCE indicates no available resource 476 available in one or more domain(s). 478 4. H-PCE Procedures 479 4.1. OPEN Procedure between Child PCE and Parent PCE 481 If a child PCE wants to use the peer PCE as a parent, it can set the 482 parent PCE request bit in the OPEN object carried in the Open message 483 during the PCEP session creation procedure. If the peer PCE does not 484 want to provide the parent function to the child PCE, it must send a 485 PCErr message to the child PCE and clear the parent PCE indication 486 bit in the OPEN object. 488 If the parent PCE can provide the parent function to the peer PCE, it 489 may set the parent PCE indication bit in the OPEN object carried in 490 the Open message during the PCEP session creation procedure. 492 The PCE may also report its PCE ID and list of domain ID to the peer 493 PCE by specifying them in the PCE-ID TLV and List of Domain-ID TLVs 494 in the OPEN object carried in the Open message during the PCEP 495 session creation procedure. 497 The OF codes defined in this document can be carried in the OF-list 498 TLV of the OPEN object. If the OF-list TLV carries the OF codes, it 499 means that the PCE is capable of implementing the corresponding 500 objective functions. This information can be used for selecting a 501 proper parent PCE when a child PCE wants to get a path that satisfies 502 a certain objective function. 504 When a specific child PCE sends a PCReq to a peer PCE that requires 505 parental activity and the peer PCE does not want to act as the parent 506 for it, the peer PCE should send a PCErr message to the child PCE and 507 specify the error-type (IANA) and error-value (1) in the PCEP-ERROR 508 object. 510 4.2. Procedure to obtain Domain Sequence 512 If a child PCE only wants to get the domain sequence for a multi- 513 domain path computation from a parent PCE, it can set the Domain Path 514 Request bit in the RP object carried in a PCReq message. The parent 515 PCE which receives the PCReq message tries to compute a domain 516 sequence for it. If the domain path computation succeeds the parent 517 PCE sends a PCRep message which carries the domain sequence in the 518 ERO to the child PCE. The domain sequence is specified as AS or AREA 519 ERO sub-objects (type 32 for AS [RFC3209] or a to-be-defined IGP area 520 type). Otherwise it sends a PCReq message which carries the NO-PATH 521 object to the child PCE. 523 5. Error Handling 525 A PCE that is capable of acting as a parent PCE might not be 526 configured or willing to act as the parent for a specific child PCE. 528 This fact could be determined when the child sends a PCReq that 529 requires parental activity (such as querying other child PCEs), and 530 could result in a negative response in a PCEP Error (PCErr) message 531 and indicate the hierarchy PCE error types. 533 Additionally, the parent PCE may fail to find the multi-domain path 534 or domain sequence due to one or more of the following reasons: 536 o A child PCE cannot find a suitable path to the egress; 538 o The parent PCE do not hear from a child PCE for a specified time; 540 o The objective functions specified in the path request cannot be 541 met. 543 In this case, the parent PCE MAY need to send a negative path 544 computation reply specifying the reason. This can be achieved by 545 including NO-PATH object in the PCRep message. Extension to NO-PATH 546 object is needed to include the aforementioned reasons. 548 6. Manageability Considerations 550 TBD. 552 7. IANA Considerations 554 Due to the experimental nature of this draft no IANA requests are 555 made. 557 8. Security Considerations 559 To be added. 561 9. Contributing Authors 563 Xian Zhang 564 Huawei 565 zhang.xian@huawei.com 567 10. Acknowledgments 569 To be added. 571 11. Normative References 573 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 574 Requirement Levels", BCP 14, RFC 2119, March 1997. 576 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 577 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 578 Tunnels", RFC 3209, December 2001. 580 [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation 581 Element (PCE)-Based Architecture", RFC 4655, August 2006. 583 [RFC5152] Vasseur, JP., Ayyangar, A., and R. Zhang, "A Per-Domain 584 Path Computation Method for Establishing Inter-Domain 585 Traffic Engineering (TE) Label Switched Paths (LSPs)", 586 RFC 5152, February 2008. 588 [RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation Element 589 (PCE) Communication Protocol (PCEP)", RFC 5440, 590 March 2009. 592 [RFC5441] Vasseur, JP., Zhang, R., Bitar, N., and JL. Le Roux, "A 593 Backward-Recursive PCE-Based Computation (BRPC) Procedure 594 to Compute Shortest Constrained Inter-Domain Traffic 595 Engineering Label Switched Paths", RFC 5441, April 2009. 597 [RFC5886] Vasseur, JP., Le Roux, JL., and Y. Ikejiri, "A Set of 598 Monitoring Tools for Path Computation Element (PCE)-Based 599 Architecture", RFC 5886, June 2010. 601 [RFC6805] King, D. and A. Farrel, "The Application of the Path 602 Computation Element Architecture to the Determination of a 603 Sequence of Domains in MPLS and GMPLS", RFC 6805, 604 November 2012. 606 Authors' Addresses 608 Fatai Zhang (editor) 609 Huawei 610 Huawei Base, Bantian, Longgang District 611 Shenzhen, 518129 612 China 614 Phone: +86-755-28972912 615 Email: zhangfatai@huawei.com 616 Quintin Zhao 617 Huawei 618 125 Nagog Technology Park 619 Acton, MA 01719 620 US 622 Phone: 623 Email: qzhao@huawei.com 625 Oscar Gonzalez de Dios (editor) 626 Telefonica I+D 627 Don Ramon de la Cruz 82-84 628 Madrid, 28045 629 Spain 631 Phone: +34913128832 632 Email: ogondio@tid.es 634 Ramon Casellas 635 CTTC 636 Av. Carl Friedrich Gauss n.7 637 Castelldefels, Barcelona 638 Spain 640 Phone: +34 93 645 29 00 641 Email: ramon.casellas@cttc.es 643 Daniel King 644 Old Dog Consulting 645 UK 647 Phone: 648 Email: daniel@olddog.co.uk