idnits 2.17.1 draft-ietf-pce-hierarchy-extensions-03.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (July 7, 2016) is 2849 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- Obsolete informational reference (is this intentional?): RFC 5226 (Obsoleted by RFC 8126) -- Obsolete informational reference (is this intentional?): RFC 7752 (Obsoleted by RFC 9552) Summary: 0 errors (**), 0 flaws (~~), 1 warning (==), 3 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Network Working Group F. Zhang 2 Internet-Draft Q. Zhao 3 Intended status: Standards Track Huawei 4 Expires: January 8, 2017 O. Gonzalez de Dios 5 Telefonica I+D 6 R. Casellas 7 CTTC 8 D. King 9 Old Dog Consulting 10 July 7, 2016 12 Extensions to Path Computation Element Communication Protocol (PCEP) for 13 Hierarchical Path Computation Elements (PCE) 14 draft-ietf-pce-hierarchy-extensions-03 16 Abstract 18 The Hierarchical Path Computation Element (H-PCE) architecture (RFC 19 6805), provides a mechanism to allow the optimum sequence of domains 20 to be selected, and the optimum end-to-end path to be derived through 21 the use of a hierarchical relationship between domains. 23 This document defines the Path Computation Element Protocol (PCEP) 24 extensions for the purpose of implementing necessary Hierarchical PCE 25 procedures and protocol extensions. 27 Status of this Memo 29 This Internet-Draft is submitted in full conformance with the 30 provisions of BCP 78 and BCP 79. 32 Internet-Drafts are working documents of the Internet Engineering 33 Task Force (IETF). Note that other groups may also distribute 34 working documents as Internet-Drafts. The list of current Internet- 35 Drafts is at http://datatracker.ietf.org/drafts/current/. 37 Internet-Drafts are draft documents valid for a maximum of six months 38 and may be updated, replaced, or obsoleted by other documents at any 39 time. It is inappropriate to use Internet-Drafts as reference 40 material or to cite them other than as "work in progress." 42 This Internet-Draft will expire in January 8, 2017. 44 Copyright Notice 46 Copyright (c) 2016 IETF Trust and the persons identified as the 47 document authors. All rights reserved. 49 This document is subject to BCP 78 and the IETF Trust's Legal 50 Provisions Relating to IETF Documents 51 (http://trustee.ietf.org/license-info) in effect on the date of 52 publication of this document. Please review these documents 53 carefully, as they describe your rights and restrictions with respect 54 to this document. Code Components extracted from this document must 55 include Simplified BSD License text as described in Section 4.e of 56 the Trust Legal Provisions and are provided without warranty as 57 described in the Simplified BSD License. 59 Table of Contents 61 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . .3 62 1.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . .4 63 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . .4 64 1.3. Requirements Language . . . . . . . . . . . . . . . . . .4 65 2. Requirements for H-PCE . . . . . . . . . . . . . . . . . . . .4 66 2.1. PCEP Requests . . . . . . . . . . . . . . . . . . . . . .5 67 2.1.1. Qualification of PCEP Requests . . . . . . . . . . . .5 68 2.1.2. Multi-domain Objective Functions . . . . . . . . . . .5 69 2.1.3. Multi-domain Metrics . . . . . . . . . . . . . . . . .6 70 2.2. Parent PCE Capability Discovery . . . . . . . . . . . . .6 71 2.3. PCE Domain and PCE ID Discovery . . . . . . . . . . . . .6 72 3. PCEP Extensions (Encoding) . . . . . . . . . . . . . . . . . .6 73 3.1. OPEN Object . . . . . . . . . . . . . . . . . . . . . . .7 74 3.1.1. H-PCE capability TLV . . . . . . . . . . . . . . . . .7 75 3.1.2. Domain-ID TLV . . . . . . . . . . . . . . . . . . . .8 76 3.2. RP object . . . . . . . . . . . . . . . . . . . . . . . . .9 77 3.2.1. H-PCE-FLAG TLV . . . . . . . . . . . . . . . . . . . .9 78 3.2.2. Domain-ID TLV . . . . . . . . . . . . . . . . . . . .9 79 3.3. Objective Function . . . . . . . . . . . . . . . . . . . .10 80 3.3.1. OF Codes . . . . . . . . . . . . . . . . . . . . . . .10 81 3.3.2. OF Object . . . . . . . . . . . . . . . . . . . . . .11 82 3.4. Metric Object . . . . . . . . . . . . . . . . . . . . . .11 83 3.5. PCEP-ERROR Object . . . . . . . . . . . . . . . . . . . .12 84 3.5.1. Hierarchy PCE Error-Type . . . . . . . . . . . . . . .12 85 3.6. NO-PATH Object . . . . . . . . . . . . . . . . . . . . . .12 86 4. H-PCE Procedures . . . . . . . . . . . . . . . . . . . . . . .13 87 4.1. OPEN Procedure between Child PCE and Parent PCE . . . . .13 88 4.2. Procedure to Obtain Domain Sequence . . . . . . . . . . .13 89 5. Error Handling . . . . . . . . . . . . . . . . . . . . . . . .14 90 6. Manageability Considerations . . . . . . . . . . . . . . . . .14 91 6.1. Control of Function and Policy . . . . . . . . . . . . . .15 92 6.1.1. Child PCE . . . . . . . . . . . . . . . . . . . . . .15 93 6.1.2. Parent PCE . . . . . . . . . . . . . . . . . . . . . .15 94 6.1.3. Policy Control . . . . . . . . . . . . . . . . . . . .15 95 6.2. Information and Data Models . . . . . . . . . . . . . . .15 96 6.3. Liveness Detection and Monitoring . . . . . . . . . . . .16 97 6.4. Verifying Correct Operation . . . . . . . . . . . . . . .16 98 6.5. Impact on Network Operation . . . . . . . . . . . . . . .16 99 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . .16 100 7.1. PCEP TLV . . . . . . . . . . . . . . . . . . . . . . . . .16 101 7.2. H-PCE-CAPABILITY TLV Flags . . . . . . . . . . . . . . . .17 102 7.3. Domain-ID TLV Domain Type . . . . . . . . . . . . . . . .17 103 7.4. H-PCE-FLAG TLV Flags . . . . . . . . . . . . . . . . . . .17 104 7.5. OF Codes . . . . . . . . . . . . . . . . . . . . . . . . .18 105 7.6. METRIC Types . . . . . . . . . . . . . . . . . . . . . . .18 106 7.7. New PCEP Error-Types and Values . . . . . . . . . . . . .19 107 7.8. New NO-PATH-VECTOR TLV Bit Flag . . . . . . . . . . . . .19 108 8. Security Considerations . . . . . . . . . . . . . . . . . . . 20 109 9. Implementation Status . . . . . . . . . . . . . . . . . . . .20 110 9.1. Inter-layer traffic engineering with H-PCE. . . . . . . . .21 111 9.2. Telefonica Netphony (Open Source PCE) . . . . . . . . . . .21 112 9.3. H-PCE Proof of Concept developed by Huawei. . . . . . . . .23 113 10. Contributing Authors . . . . . . . . . . . . . . . . . . . .23 114 11. Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . 23 115 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 23 116 12.1. Normative References. . . . . . . . . . . . . . . . . . . 23 117 12.2. Informative References. . . . . . . . . . . . . . . . . . 24 119 1. Introduction 121 [RFC6805] describes a Hierarchical PCE (H-PCE) architecture which can 122 be used for computing end-to-end paths for inter-domain MPLS Traffic 123 Engineering (TE) and GMPLS Label Switched Paths (LSPs). 125 Within the hierarchical PCE architecture, the parent PCE is used to 126 compute a multi-domain path based on the domain connectivity 127 information . A child PCE may be responsible for a single domain or 128 multiple domains, it is used to compute the intra-domain path based 129 on its own domain topology information. 130 The H-PCE end-to-end domain path computation procedure is described 131 below: 133 o A path computation client (PCC) sends the inter-domain path 134 computation requests to the child PCE responsible for its domain; 136 o The child PCE forwards the request to the parent PCE; 138 o The parent PCE computes the likely domain paths from the ingress 139 domain to the egress domain; 141 o The parent PCE sends the intra-domain path computation requests 142 (between the domain border nodes) to the child PCEs which are 143 responsible for the domains along the domain path; 145 o The child PCEs return the intra-domain paths to the parent PCE; 146 o The parent PCE constructs the end-to-end inter-domain path based 147 on the intra-domain paths; 149 o The parent PCE returns the inter-domain path to the child PCE; 151 o The child PCE forwards the inter-domain path to the PCC. 153 In addition, the parent PCE may be requested to provide only the 154 sequence of domains to a child PCE so that alternative inter-domain 155 path computation procedures, including Per Domain (PD) [RFC5152] and 156 Backwards Recursive Path Computation (BRPC) [RFC5441] may be used. 158 This document defines the PCEP extensions for the purpose of 159 implementing Hierarchical PCE procedures, which are described in 160 [RFC6805]. 162 1.1. Scope 164 The following functions are out of scope of this document. 166 o Determination of Destination Domain (section 4.5 of [RFC6805]) 168 - via collection of reachability information from child domain; 170 - via requests to the child PCEs to discover if they contain the 171 destination node; 173 - or any other methods. 175 o Parent Traffic Engineering Database (TED) methods (section 4.4 of 176 [RFC6805]) 178 o Learning of Domain connectivity and boundary nodes (BN) addresses. 180 1.2. Terminology 182 This document uses the terminology defined in [RFC4655], [RFC5440] 183 and the additional terms defined in section 1.4 of [RFC6805]. 185 1.3. Requirements Language 187 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 188 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 189 document are to be interpreted as described in [RFC2119]. 191 2. Requirements for H-PCE 193 This section compiles the set of requirements of the PCEP protocol to 194 support the H-PCE architecture and procedures. 196 [RFC6805] identifies high-level requirements of PCEP extensions 197 required to support the hierarchical PCE model. 199 2.1. Path Computation Request 201 The Path Computation Request (PCReq) messages are used by a PCC or 202 PCE to make a path computation request to a PCE. In order to achieve 203 the full functionality of the H-PCE procedures, the PCReq message 204 needs to include: 206 o Qualification of PCE Requests; 208 o Multi-domain Objective Functions (OF); 210 o Multi-domain Metrics. 212 2.1.1. Qualification of PCEP Requests 214 As described in section 4.8.1 of [RFC6805], the H-PCE architecture 215 introduces new request qualifications, which are: 217 o It MUST be possible for a child PCE to indicate that a request it 218 sends to a parent PCE should be satisfied by a domain sequence 219 only, that is, not by a full end-to-end path. This allows the 220 child PCE to initiate a per-domain (PD) [RFC5152] or a backward 221 recursive path computation (BRPC) [RFC5441]. 223 o As stated in [RFC6805], section 4.5, if a PCC knows the egress 224 domain, it can supply this information as the path computation 225 request. It SHOULD be possible to specify the destination domain 226 information in a PCEP request, if it is known. 228 o It MAY be possible to indicate that the inter domain path computed 229 by parent PCE should disallow domain re-entry. 231 2.1.2. Multi-domain Objective Functions 233 For inter-domain path computation, there is one new objective 234 Function which is defined in section 1.3.1 and 4.1 of [RFC6805]: 236 o Minimize the number of domains crossed. A domain can be either an 237 Autonomous System (AS) or an Internal Gateway Protocol (IGP) area 238 depending on the type of multi-domain network hierarchical PCE is 239 applied to. 241 During the PCEP session establishment procedure, the parent PCE needs 242 to be capable of indicating the Objective Functions (OF) [RFC5541] 243 capability in the Open message. This capability information may then 244 be announced by child PCEs, and used for selecting the PCE when a PCC 245 wants a path that satisfies one or multiple inter-domain objective 246 functions. 248 When a PCC requests a PCE to compute an inter-domain path, the PCC 249 needs also to be capable of indicating the new objective functions 250 for inter-domain path. Note that a given child PCE may also act as a 251 parent PCE. 253 For the reasons described previously, new OF codes need to be defined 254 for the new inter-domain objective functions. Then the PCE can 255 notify its new inter-domain objective functions to the PCC by 256 carrying them in the OF-list TLV which is carried in the OPEN object. 257 The PCC can specify which objective function code to use, which is 258 carried in the OF object when requesting a PCE to compute an inter- 259 domain path. 261 A parent PCE MUST be capable of ensuring homogeneity, across domains, 262 when applying OF codes for strict OF intra-domain requests . 264 2.1.3. Multi-domain Metrics 266 For inter-domain path computation, there are several path metrics of 267 Interest. 269 o Domain count (number of domains crossed); 271 o Border Node count. 273 A PCC may be able to limit the number of domains crossed by applying 274 a limit on these metrics. Details in section 3.3. 276 2.2. Parent PCE Capability Advertisement 278 Parent and child PCE relationships are likely to be configured. 279 However, as mentioned in [RFC6805], it would assist network operators 280 if the child and parent PCEs could indicate their H-PCE capabilities. 282 During the PCEP session establishment procedure, the child PCE needs 283 to be capable of indicating to the parent PCE whether it requests the 284 parent PCE capability or not. Also, during the PCEP session 285 establishment procedure, the parent PCE needs to be capable of 286 indicating whether its parent capability can be provided or not. 288 A PCEP Speaker (Parent PCE or Child PCE or PCC) includes the "H-PCE 289 Capability" TLV, described in Section 3.1.1, in the OPEN Object to 290 advertise its support for PCEP extensions for H-PCE Capability. 292 2.3. PCE Domain Discovery 293 A PCE domain is a single domain with an associated PCE. Although it 294 is possible for a PCE to manage multiple domains. The PCE domain may 295 be an IGP area or AS. 297 The PCE domain identifiers may be provided during the PCEP session 298 establishment procedure. 300 3. PCEP Extensions 302 This section defines PCEP extensions to ([RFC5440]) so as to 303 support the H-PCE procedures. 305 3.1. OPEN object 307 Two new TLVs are defined in this document to be carried within an 308 OPEN object. This way, during PCEP session establishment, the H-PCE 309 capability and Domain information can be advertised. 311 3.1.1. H-PCE capability TLV 313 The H-PCE-CAPABILITY TLV is an optional TLV associated with the OPEN 314 Object [RFC5440] to exchange H-PCE capability of PCEP speakers. 316 Its format is shown in the following figure: 318 0 1 2 3 319 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 1 320 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 321 | Type= TBD1 | Length=4 | 322 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 323 | Flags |I|R| 324 +---------------------------------------------------------------+ 325 Figure 1: H-PCE-CAPABILITY TLV format 327 The type of the TLV is TBD1 (to be assigned by IANA) and it has a 328 fixed length of 4 octets. 330 The value comprises a single field - Flags (32 bits): 332 R (Parent PCE Request bit): if set, will signal that the child 333 PCE wishes to use the peer PCE as a parent PCE. 335 I (Parent PCE Indication bit): if set, will signal that the PCE can 336 be used as a parent PCE by the peer PCE. 338 The inclusion of this TLV in an OPEN object indicate that the H-PCE 339 extensions are supported by the PCEP speaker. The PCC MAY include 340 this TLV to indicate that it understands the H-PCE extensions. The 341 Child PCE MUST include this TLV and set the R flag (and unset the I 342 flag) on the PCEP session towards the Parent PCE. The Parent PCE MUST 343 include this TLV and set the I flag and unset the R flag on the 344 PCEP session towards the child PCE. The parent-child PCEP session is 345 set to be established only when this capability is advertised. 347 If such capability is not exchanged and the parent PCE receive a "H- 348 PCE path computation request", it MUST send a PCErr message with 349 Error-Type=TBD8 (H-PCE error) and Error-Value=1 (Parent PCE 350 Capability not advertised). 352 3.1.2. Domain-ID TLV 354 The Domain-ID TLV when used in OPEN object identify the domain(s) 355 served by the PCE. The child PCE uses this mechanism to inform the 356 domain information to the parent PCE. 358 The Domain-ID TLV is defined below: 360 0 1 2 3 361 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 1 362 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 363 | Type= TBD2 | Length | 364 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 365 | Domain Type | Reserved | 366 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 367 | Domain ID | 368 // // 369 | | 370 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 372 Figure 2: Domain-ID TLV format 374 The type of the TLV is TBD2 (to be assigned by IANA) and it has a 375 variable Length of the value portion. The value part comprises of - 377 Domain Type (8 bits): Indicates the domain type. Four types of 378 domain are currently defined: 380 o Type=1: the Domain ID field carries a 2-byte AS number. Padded 381 with trailing zeroes to a 4-byte boundary. 383 o Type=2: the Domain ID field carries a 4-byte AS number. 385 o Type=3: the Domain ID field carries an 4-byte OSPF area ID. 387 o Type=4: the Domain ID field carries <2-byte Area-Len, variable 388 length IS-IS area ID>. Padded with trailing zeroes to a 4-byte 389 boundary. 391 Reserved: Zero at transmission; ignored at receipt. 393 Domain ID (variable): Indicates an IGP Area ID or AS number. It can 394 be 2 bytes, 4 bytes or variable length depending on the domain 395 identifier used. It is padded with trailing zeroes to a 4-byte 396 boundary . 398 In case a PCE serves more than one domain, multiple Domain-ID TLV is 399 included for each domain it serves. 401 3.2. RP object 403 3.2.1. H-PCE-FLAG TLV 405 The H-PCE-FLAG TLV is an optional TLV associated with the RP Object 406 [RFC5440] to indicate the H-PCE path computation request and 407 options.. 409 Its format is shown in the following figure: 411 0 1 2 3 412 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 1 413 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 414 | Type= TBD3 | Length=4 | 415 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 416 | Flags |D|S| 417 +---------------------------------------------------------------+ 418 Figure 3: H-PCE-FLAG TLV format 420 The type of the TLV is TBD3 (to be assigned by IANA) and it has a 421 fixed length of 4 octets. 423 The value comprises a single field - Flags (32 bits): 425 S (Domain Sequence bit): if set, will signal that the child PCE 426 wishes to get only the domain sequence in the path computation reply. 428 D (Disallow Domain Re-entry bit): if set, will signal that the 429 computed path does not enter a domain more than once. 431 3.2.2. Domain-ID TLV 433 The usage of Domain-ID TLV carried in an OPEN object is used to 434 indicate a (list of) managed domains and is described in section 435 3.1.2. This TLV when carried in a RP object, indicates the 436 destination domain ID. If a PCC knows the egress domain, it can 437 supply this information in the PCReq message. The format of this 438 TLV is defined in Section 3.1.2. 440 3.3. Objective Functions 442 3.3.1. OF Codes 444 [RFC5541] defines a mechanism to specify an objective function that 445 is used by a PCE when it computes a path. Two new objective functions 446 are defined for the H-PCE experiment. 448 o MTD 450 * Name: Minimize the number of Transit Domains (MTD) 452 * Objective Function Code - TBD4 (to be assigned by IANA) 454 * Description: Find a path P such that it passes through the 455 least number of transit domains. 457 Objective functions are formulated using the following terminology: 459 - A network comprises a set of N domains {Di, (i=1...N)}. 461 - A path P passes through K domains {Dpi,(i=1...K)}. 463 Find a path P such that the value of K is minimized. 465 o MBN 467 * Name: Minimize the number of border nodes. 469 * Objective Function Code - TBD5 (to be assigned by IANA) 471 * Description: Find a path P such that it passes through the 472 least number of border nodes. 474 Objective functions are formulated using the following 475 terminology: 477 - A network comprises a set of N nodes {Ni, (i=1...N)}. 479 - A path P is a list of K nodes {Npi,(i=1...K)}. 481 - B(N) if a function that determine if the node is a border node. 482 B(Ni) = 1 if Ni is border node; B(Nk) = 0 if Nk is not a border 483 node. 485 - The number of border node in a path P is denoted by B(P), where 486 B(P) = sum{B(Npi),(i=1...K)}. 488 Find a path P such that B(P) is minimized. 490 3.3.2. OF Object 491 The OF (Objective Function) object [RFC5541] is carried within a 492 PCReq message so as to indicate the desired/required objective 493 function to be applied by the PCE during path computation. As per 494 section 3.2 of [RFC5541] a single OF object may be included in 495 a path computation request. 497 The new OF code described in section 3.3.1 are applicable at the 498 inter-domain level (parent), it is also necessary to specify the OF 499 code that may be applied at the intra-domain (child) path computation 500 level. To accommodate this, the OF-List TLV (described in section 501 2.1. of [RFC5541]) is included in the OF object as an optional TLV. 503 OF-List TLV allow encoding of multiple OF codes. When this TLV is 504 included inside the OF object, only the first OF-code in the OF-LIST 505 TLV is considered. The parent PCE would use this OF code in the OF 506 object when sending the intra domain path computation request to the 507 child PCE . 509 If the objective functions defined in this document are unknown/ 510 unsupported by a PCE, then the procedure as defined in [RFC5541] is 511 followed. 513 3.4. Metric Object 515 The METRIC object is defined in section 7.8 of [RFC5440], comprising 516 metric-value, metric-type (T field) and flags. This document defines 517 the following types for the METRIC object for H-PCE: 519 o T=TBD6: Domain count metric (number of domains crossed); 521 o T=TBD7: Border Node count metric (number of border nodes crossed). 523 The domain count metric type of the METRIC object encodes the number 524 of domain crossed in the path. The border node count metric type of 525 the METRIC object encodes the number of border nodes in the path. 527 A PCC or child PCE MAY use these metric in PCReq message an inter- 528 domain path meeting the number of domain or border nodes requirement. 529 In this case, the B bit MUST be set to suggest a bound (a maximum) 530 for the metric that must not be exceeded for the PCC to consider the 531 computed path as acceptable. 533 A PCC or child PCE MAY also use this metric to ask the PCE to 534 optimize the metric during inter-domain path computation. In this 535 case, the B flag MUST be cleared. 537 The Parent PCE MAY use these metric in a PCRep message along with a 538 NO-PATH object in the case where the PCE cannot compute a path 539 meeting this constraint. A PCE MAY also use this metric to send the 540 computed end to end metric in a reply message. 542 3.5. PCEP-ERROR object 544 3.5.1. Hierarchy PCE Error-Type 546 A new PCEP Error-Type is used for this H-PCE experiment and is 547 defined below: 549 +------------+------------------------------------------------------+ 550 | Error-Type | Meaning | 551 +------------+------------------------------------------------------+ 552 | TBD8 | H-PCE error | 553 | | Error-value=1: parent PCE capability | 554 | | was not advertised | 555 | | Error-value=2: parent PCE capability | 556 | | cannot be provided | 557 +------------+------------------------------------------------------+ 559 Figure 4: H-PCE error 561 3.6. NO-PATH Object 563 To communicate the reason(s) for not being able to find a multi- 564 domain path or domain sequence, the NO-PATH object can be used in the 565 PCRep message. [RFC5440] defines the format of the NO-PATH object. 566 The object may contain a NO-PATH-VECTOR TLV to provide additional 567 information about why a path computation has failed. 569 Three new bit flags are defined to be carried in the Flags field in 570 the NO-PATH-VECTOR TLV carried in the NO-PATH Object. 572 o Bit number TBD9: When set, the parent PCE indicates that 573 destination domain unknown; 575 o Bit number TBD10: When set, the parent PCE indicates unresponsive 576 child PCE(s); 578 o Bit number TBD11: When set, the parent PCE indicates no available 579 resource available in one or more domain(s). 581 4. H-PCE Procedures 583 4.1. OPEN Procedure between Child PCE and Parent PCE 585 If a child PCE wants to use the peer PCE as a parent, it can set the 586 R (parent PCE request flag) in the H-PCE-CAPABILITY TLV inside the 587 OPEN object carried in the Open message 588 during the PCEP session creation procedure. 590 If the parent PCE can provide the parent function to the peer PCE, it 591 may set the I (parent PCE indication flag) in the H-PCE-CAPABILITY 592 TLV inside the OPEN object carried in 593 the Open message during the PCEP session creation procedure. 595 The PCE may also report its list of domain IDs to the peer 596 PCE by specifying them in the Domain-ID TLVs in the OPEN object 597 carried in the Open message during the PCEP session creation 598 procedure. 600 The OF codes defined in this document can be carried in the OF-list 601 TLV of the OPEN object. If the OF-list TLV carries the OF codes, it 602 means that the PCE is capable of implementing the corresponding 603 objective functions. This information can be used for selecting a 604 proper parent PCE when a child PCE wants to get a path that satisfies 605 a certain objective function. 607 When a specific child PCE sends a PCReq to a peer PCE that requires 608 parental activity and H-PCE capability flags were not set in the 609 session establishment procedure as described above, the peer PCE 610 should send a PCErr message to the child PCE and 611 specify the error-type=TBD (H-PCE error) and error-value=1 (parent 612 PCE capability was not advertised) in the PCEP-ERROR object. 614 When a specific child PCE sends a PCReq to a peer PCE that requires 615 parental activity and the peer PCE does not want to act as the parent 616 for it, the peer PCE should send a PCErr message to the child PCE and 617 specify the error-type=TBD (H-PCE error) and error-value=2 (parent 618 PCE capability cannot be provided) in the PCEP-ERROR object. 620 4.2. Procedure to obtain Domain Sequence 622 If a child PCE only wants to get the domain sequence for a multi- 623 domain path computation from a parent PCE, it can set the Domain Path 624 Request bit in the H-PCE FlagH-PCE-FLAG TLV in the RP object carried 625 in a PCReq message. The parent PCE which receives the PCReq message 626 tries to compute a domain sequence for it. If the domain path 627 computation succeeds the parent PCE sends a PCRep message which 628 carries the domain sequence in the ERO to the child PCE. Refer 629 [RFC7897] for more details about domain sub-objects in the ERO. 631 Otherwise it sends a PCReq message which carries the NO-PATH object 632 to the child PCE. 634 5. Error Handling 636 A PCE that is capable of acting as a parent PCE might not be 637 configured or willing to act as the parent for a specific child PCE. 639 This fact could be determined when the child sends a PCReq that 640 requires parental activity, and could result in a negative response 641 in a PCEP Error (PCErr) message and indicate the hierarchy PCE error- 642 type=TBD8 (H-PCE error) and suitable error-value. (section 3.5.1) 644 Additionally, the parent PCE may fail to find the multi-domain path 645 or domain sequence due to one or more of the following reasons: 647 o A child PCE cannot find a suitable path to the egress; 649 o The parent PCE do not hear from a child PCE for a specified time; 651 o The objective functions specified in the path request cannot be 652 met. 654 In this case, the parent PCE MAY need to send a negative path 655 computation reply specifying the reason. This can be achieved by 656 including NO-PATH object in the PCRep message. Extension to NO-PATH 657 object is needed to include the aforementioned reasons described in 658 section 3.6. 660 6. Manageability Considerations 662 General PCE and PCEP management considerations are discussed in 663 [RFC4655] and [RFC5440]. There are additional management 664 considerations for H-PCE which are described in [RFC6805], and 665 repeated in this section. 667 The administrative entity responsible for the management of the 668 parent PCEs must be determined for the following cases: 670 o multi-domains (e.g., IGP areas or multiple ASes) within a single 671 service provider network, the management responsibility for the 672 parent PCE would most likely be handled by the service provider, 674 o multiple ASes within different service provider networks, it may 675 be necessary for a third party to manage the parent PCEs according 676 to commercial and policy agreements from each of the participating 677 service providers. 679 6.1. Control of Function and Policy 681 Control and function will need to be carefully managed in a H-PCE 682 network. A child PCE will need to be configured with the 683 address of its parent PCE. It is expected that there will only be 684 one or two parents of any child. 686 The parent PCE also needs to be aware of the child PCEs for all child 687 domains that it can see. This information is most likely to be 688 configured (as part of the administrative definition of each domain). 690 Discovery of the relationships between parent PCEs and child PCEs 691 does not form part of the hierarchical PCE architecture. Mechanisms 692 that rely on advertising or querying PCE locations across domain or 693 provider boundaries are undesirable for security, scaling, 694 commercial, and confidentiality reasons. 695 Specific behavior of the child and parent PCE are described in the 696 following sub-sections. 698 6.1.1. Child PCE 700 Support of the hierarchical procedure will be controlled by the 701 management organization responsible for each child PCE. A child 702 PCE must be configured with the address of its parent PCE in order 703 for it to interact with its parent PCE. The child PCE must also 704 be authorized to peer with the parent PCE. 706 6.1.2. Parent PCE 708 The parent PCE must only accept path computation requests from 709 authorized child PCEs. If a parent PCE receives requests from an 710 unauthorized child PCE, the request should be dropped. This means 711 that a parent PCE must be configured with the identities and 712 security credentials of all of its child PCEs, or there must be 713 some form of shared secret that allows an unknown child PCE to be 714 authorized by the parent PCE. 716 6.1.3. Policy Control 718 It may be necessary to maintain a policy module on the parent PCE 719 [RFC5394]. This would allow the parent PCE to apply commercially 720 relevant constraints such as SLAs, security, peering preferences, and 721 monetary costs. 723 It may also be necessary for the parent PCE to limit end-to-end path 724 selection by including or excluding specific domains based on 725 commercial relationships, security implications, and reliability. 727 6.2. Information and Data Models 728 A MIB module for PCEP was published as RFC 7420 [RFC7420] that 729 describes managed objects for modeling of PCEP communication. A 730 YANG module for PCEP has also been proposed [I-D.pkd-pce-pcep-yang]. 732 A H-PCE MIB module, or additional data model, will be required to 733 report parent PCE and child PCE information, including: 735 o parent PCE configuration and status, 737 o child PCE configuration and information, 739 o notifications to indicate session changes between parent PCEs and 740 child PCEs, and 742 o notification of parent PCE TED updates and changes. 744 6.3. Liveness Detection and Monitoring 746 The hierarchical procedure requires interaction with multiple PCEs. 747 Once a child PCE requests an end-to-end path, a sequence of events 748 occurs that requires interaction between the parent PCE and each 749 child PCE. If a child PCE is not operational, and an alternate 750 transit domain is not available, then a failure must be reported. 752 6.4. Verifying Correct Operation 754 Verifying the correct operation of a parent PCE can be performed by 755 monitoring a set of parameters. The parent PCE implementation should 756 provide the following parameters monitored by the parent PCE: 758 o number of child PCE requests, 760 o number of successful hierarchical PCE procedures completions on a 761 per-PCE-peer basis, 763 o number of hierarchical PCE procedure completion failures on a per- 764 PCE-peer basis, and 766 o number of hierarchical PCE procedure requests from unauthorized 767 child PCEs. 769 6.5. Impact on Network Operation 771 The hierarchical PCE procedure is a multiple-PCE path computation 772 scheme. Subsequent requests to and from the child and parent PCEs do 773 not differ from other path computation requests and should not have 774 any significant impact on network operations. 776 7. IANA Considerations 778 7.1. PCEP TLV 779 IANA Manages the PCEP TLV code point registry (see [RFC5440]). This 780 is maintained as the "PCEP TLV Type Indicators" sub-registry of the 781 "Path Computation Element Protocol (PCEP) Numbers" registry. 783 This document defines three new PCEP TLVs. IANA is requested to make 784 the following allocation: 786 Type TLV name References 787 ----------------------------------------------- 788 TBD1 H-PCE-CAPABILITY TLV This I-D 789 TBD2 Domain-ID TLV This I-D 790 TBD3 H-PCE-FLAG TLV This I-D 792 7.2. H-PCE-CAPABILITY TLV Flags 794 This document requests that a new sub-registry, named " H-PCE- 795 CAPABILITY TLV Flag Field", is created within the "Path Computation 796 Element Protocol (PCEP) Numbers" registry to manage the Flag field in 797 the H-PCE-CAPABILITY TLV of the PCEP OPEN object (class = 1). 799 New values are to be assigned by Standards Action [RFC5226]. Each 800 bit should be tracked with the following qualities: 802 o Bit number (counting from bit 0 as the most significant bit) 804 o Capability description 806 o Defining RFC 808 The following values are defined in this document: 810 Bit Description Reference 811 -------------------------------------------------- 812 31 R (Parent PCE Request bit) This I.D. 813 30 I (Parent PCE Indication bit) This I.D. 815 7.3. Domain-ID TLV Domain type 817 This document requests that a new sub-registry, named " Domain-ID TLV 818 Domain type", is created within the "Path Computation Element 819 Protocol (PCEP) Numbers" registry to manage the Domain-Type 820 field of the Domain-ID TLV. 822 Value Meaning 823 ----------------------------------------------- 824 1 2-byte AS number 825 2 4-byte AS number 826 3 4-byte OSPF area ID 827 4 Variable length IS-IS area ID 829 7.4. H-PCE-FLAG TLV Flags 830 This document requests that a new sub-registry, named "H-PCE-FLAGS 832 TLV Flag Field", is created within the "Path Computation Element 833 Protocol (PCEP) Numbers" registry to manage the Flag field in 834 the H-PCE-FLAGS TLV of the PCEP OPEN object (class = 1). New values 835 are to be assigned by Standards Action [RFC5226]. Each bit should be 836 tracked with the following qualities: 838 o Bit number (counting from bit 0 as the most significant bit) 840 o Capability description 842 o Defining RFC 844 The following values are defined in this document: 846 Bit Description Reference 847 ----------------------------------------------- 848 31 S (Domain This I.D. 849 Sequence bit) 850 30 D (Disallow Domain This I.D. 851 Re-entry bit) 853 7.5. OF Codes 855 IANA maintains registry of Objective Function (described in 856 [RFC5541]) at the sub-registry "Objective Function". Two new 857 Objective Functions have been defined in this document. 859 IANA is requested to make the following allocations: 861 Code 862 Point Name Reference 863 ------------------------------------------------------ 864 TBD4 Minimum number of Transit This I.D. 865 Domains (MTD) 866 TBD5 Minimize number of Border This I.D. 867 Nodes (MBN) 869 7.6. METRIC Types 871 IANA maintains one sub-registry for "METRIC object T field". Two new 872 metric types are defined in this document for the METRIC object 873 (specified in [RFC5440]). 875 IANA is requested to make the following allocations: 877 Value Description Reference 878 ---------------------------------------------------------- 879 TBD6 Domain Count metric This I.D. 880 TBD7 Border Node Count metric This I.D. 882 7.7. New PCEP Error-Types and Values 884 IANA maintains a registry of Error-Types and Error-values for use in 885 PCEP messages. This is maintained as the "PCEP-ERROR Object Error 886 Types and Values" sub-registry of the "Path Computation Element 887 Protocol (PCEP) Numbers" registry. 889 IANA is requested to make the following allocations: 891 Error-Type Meaning and error values Reference 892 ------------------------------------------------------ 893 TBD8 H-PCE Error This I.D. 895 Error-value=1 Parent PCE 896 Capability not advertised 898 Error-value=2 Parent PCE 899 Capability not supported 901 7.8. New NO-PATH-VECTOR TLV Bit Flag 903 IANA maintains a registry of bit flags carried in the PCEP NO-PATH- 904 VECTOR TLV in the PCEP NO-PATH object as defined in [RFC5440]. IANA 905 Is requested to assign three new bit flag as follows: 907 Bit Number Name Flag Reference 908 ------------------------------------------------------ 909 TBD9 Destination Domain unknown This I.D. 910 TBD10 Unresponsive child PCE(s) This I.D. 911 TBD11 No available resource in This I.D. 912 one or more domain 914 8. Security Considerations 916 The hierarchical PCE procedure relies on PCEP and inherits the 917 security requirements defined in [RFC5440]. As PCEP operates 918 over TCP, it may also make use of TCP security mechanisms, such as 919 TCP-AO or [I-D.ietf-pce-pceps]. 921 H-PCE operation also relies on information used to build the TED. 922 Attacks on a parent or child PCE may be achieved by falsifying 923 or impeding this flow of information. If the child PCE listens to 924 the IGP or BGP-LS for populating the TED, then normal IGP or BGP-LS 925 security measures may be applied, and it should be noted that an IGP 926 routing system is generally assumed to be a trusted domain such that 927 router subversion is not a risk. The parent PCE TED is constructed as 928 described in this document and may involve: 930 o multiple parent-child relationships using PCEP 932 o the parent PCE listening to child domain IGPs (with the same 933 security features as a child PCE listening to its IGP) 935 o an external mechanism (such as [RFC7752]), which will need to be 936 authorized and secured. 938 Any multi-domain operation necessarily involves the exchange of 939 information across domain boundaries. This is bound to represent a 940 significant security and confidentiality risk especially when the 941 child domains are controlled by different commercial concerns. PCEP 942 allows individual PCEs to maintain confidentiality of their domain 943 path information using path-keys [RFC5520], and the H-PCE 944 architecture is specifically designed to enable as much isolation of 945 domain topology and capabilities information as is possible. 947 For further considerations of the security issues related to inter-AS 948 path computation, see [RFC5376]. 950 9. Implementation Status 952 The H-PCE architecture and protocol procedures describe in this I-D 953 were implemented and tested for a variety of optical research 954 applications. 956 9.1 Inter-layer traffic engineering with H-PCE 958 This work was led by: 960 o Ramon Casellas 961 o Centre Tecnologic de Telecomunicacions de Catalunya (CTTC) 963 The H-PCE instances (parent and child) were multi-threaded 964 asynchronous processes. Implemented in C++11, using C++ Boost 965 Libraries. The targeted system used to deploy and run H-PCE 966 applications was a POSIX system (Debian GNU/Linux operating 967 system). 969 Some parts of the software may require a Linux Kernel, the 970 availability of a Routing Controller running collocated in the same 971 host and the usage of libnetfilter / libipq and GNU/Linux 972 firewalling capabilities. Most of the functionality, including 973 algorithms is done by means of plugins (e.g., as shared libraries 974 or .so files in Unix systems). 976 The CTTC PCE supports the H-PCE architecture, but also supports 977 stateful PCE with active capabilities, as an OpenFlow controller, 978 and has dedicated plugins to support monitoring, BRPC, P2MP, path 979 keys, back end PCEs. Management of the H-PCE entities was supported 980 via HTTP and CLI via Telnet. 982 Further details of the H-PCE prototyping and experimentation can be 983 found in the following scientific papers: 985 R. Casellas, R. Martinez, R. Munoz, L. Liu, T. Tsuritani, I. 987 Morita, "Inter-layer traffic engineering with hierarchical-PCE in 988 MPLS-TP over wavelength switched optical networks" , Optics 989 Express, Vol. 20, No. 28, December 2012. 991 R. Casellas, R. Martinez, R. Munoz, L. Liu, T. Tsuritani, I. Morita, 992 M. Msurusawa, "Dynamic virtual link mesh topology aggregation in 993 multi-domain translucent WSON with hierarchical-PCE", Optics Express 994 Journal, Vol. 19, No. 26, December 2011. 996 R. Casellas, R. Munoz, R. Martinez, R. Vilalta, L. Liu, T. Tsuritani, 997 I. Morita, V. Lopez, O. Gonzalez de Dios, J. P. Fernandez-Palacios, 998 "SDN based Provisioning Orchestration of OpenFlow/GMPLS Flexi-grid 999 Networks with a Stateful Hierarchical PCE", in Proceedings of Optical 1000 Fiber Communication Conference and Exposition (OFC), 9-13 March, 1001 2014, San Francisco (EEUU). Extended Version to appear in Journal 1002 Of Optical Communications and Networking January 2015 1004 F. Paolucci, O. Gonzalez de Dios, R. Casellas, S. Duhovnikov, P. 1005 Castoldi, R. Munoz, R. Martinez, "Experimenting Hierarchical PCE 1006 Architecture in a Distributed Multi-Platform Control Plane Testbed" , 1007 in Proceedings of Optical Fiber Communication Conference and 1008 Exposition (OFC) and The National Fiber Optic Engineers Conference 1009 (NFOEC), 4-8 March, 2012, Los Angeles, California (USA). 1011 R. Casellas, R. Martinez, R. Munoz, L. Liu, T. Tsuritani, I. Morita, 1012 M. Tsurusawa, "Dynamic Virtual Link Mesh Topology Aggregation in 1013 Multi-Domain Translucent WSON with Hierarchical-PCE", in 1014 Proceedings of 37th European Conference and Exhibition on Optical 1015 Communication (ECOC 2011), 18-22 September 2011, Geneve ( 1016 Switzerland). 1018 R. Casellas, R. Munoz, R. Martinez, "Lab Trial of Multi-Domain Path 1019 Computation in GMPLS Controlled WSON Using a Hierarchical PCE", in 1020 Proceedings of OFC/NFOEC Conference (OFC2011), 10 March 2011, Los 1021 Angeles (USA). 1023 9.2 Telefonica Netphony (Open Source PCE) 1025 The Telefonica Netphony PCE is an open source Java-based 1026 implementation of a Path Computation Element, with several flavours, 1027 and a Path Computation Client. The PCE follows a modular architecture 1028 and allows to add customized algorithms. The PCE has also stateful 1029 and remote initiation capabilities. In current version, three 1030 components can be built, a domain PCE (aka child PCE), a parent PCE 1031 (ready for the H-PCE architecture) and a PCC (path computation 1032 client). 1034 This work was led by: 1036 o Oscar Gonzalez de Dios 1037 o Victor Lopez Alvarez 1038 o Telefonica I+D, Madrid, Spain 1040 The PCE code is publicly available in a GitHub repository: 1041 * https://github.com/telefonicaid/netphony-pce 1043 The PCEP protocol encodings are located in the following repository: 1044 * https://github.com/telefonicaid/netphony-network protocols 1046 The traffic engineering database and a BGP-LS speaker to fill the 1047 database is located in: 1048 * https://github.com/telefonicaid/netphony-topology 1050 The parent and child PCE are multi-threaded java applications. The 1051 path computation uses the jgrapht free Java class library (0.9.1) 1052 that provides mathematical graph-theory objects and algorithms. 1053 Current version of netphony PCE runs on java 1.7 and 1.8, and has 1054 been tested in GNU/Linux, Mac OS-X and Windows environments. The 1055 management of the parent and domain PCEs is supported though CLI via 1056 Telnet, and configured via XML files . 1058 Further details of the netphony H-PCE prototyping and experimentation 1059 can be found in the following research papers: 1061 O. Gonzalez de Dios, R. Casellas, F. Paolucci, A. Napoli, L. Gifre, 1062 A. Dupas, E, Hugues-Salas, R. Morro, S. Belotti, G. Meloni, T. 1063 Rahman, V.P Lopez, R. Martinez, F. Fresi, M. Bohn, S. Yan, L. 1064 Velasco, . Layec and J. P. Fernandez-Palacios: Experimental 1065 Demonstration of Multivendor and Multidomain EON With Data and 1066 Control Interoperability Over a Pan-European Test Bed, in Journal of 1067 Lightwave Technology, Dec. 2016, Vol. 34, Issue 7, pp. 1610-1617. 1069 O. Gonzalez de Dios, R. Casellas, R. Morro, F. Paolucci, V. Lopez, 1070 R. Martinez, R. Munoz, R. Villalta, P. Castoldi: "Multi-partner 1071 Demonstration of BGP-LS enabled multi-domain EON, in Journal of 1072 Optical Communications and Networking, Dec. 2015, Vol. 7, Issue 12, 1073 pp. B153-B162. 1075 F. Paolucci, O. Gonzalez de Dios, R. Casellas, S. Duhovnikov, P. 1076 Castoldi, R. Munoz, R. Martinez, "Experimenting Hierarchical PCE 1077 Architecture in a Distributed Multi-Platform Control Plane Testbed" , 1078 in Proceedings of Optical Fiber Communication Conference and 1079 Exposition (OFC) and The National Fiber Optic Engineers Conference 1080 (NFOEC), 4-8 March, 2012, Los Angeles, California (USA). 1082 9.3 Implementation 3: H-PCE Proof of Concept developed by Huawei 1084 Huawei developed this H-PCE on the Huawei Versatile Routing Platform 1085 (VRP) to experiment with the hierarchy of PCE. Both end to end path 1086 computation as well as computation for domain-sequence are supported. 1088 This work was led by: 1090 o Udayasree Pallee 1091 o Dhruv Dhody 1092 o Huawei Technologies, Bangalore, India 1094 Further work on stateful H-PCE is being carried out on ONOS. 1096 10. Contributing Authors 1098 Xian Zhang 1099 Huawei 1100 zhang.xian@huawei.com 1102 Dhruv Dhody 1103 Huawei Technologies 1104 Divyashree Techno Park, Whitefield 1105 Bangalore, Karnataka 560066 1106 India 1108 EMail: dhruv.ietf@gmail.com 1110 11. Acknowledgments 1112 12. References 1114 12.1 Normative References 1116 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1117 Requirement Levels", BCP 14, RFC 2119, March 1997. 1119 [RFC5152] Vasseur, JP., Ayyangar, A., and R. Zhang, "A Per-Domain 1120 Path Computation Method for Establishing Inter-Domain 1121 Traffic Engineering (TE) Label Switched Paths (LSPs)", 1122 RFC 5152, February 2008. 1124 [RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation Element 1125 (PCE) Communication Protocol (PCEP)", RFC 5440, 1126 March 2009. 1128 [RFC5441] Vasseur, JP., Zhang, R., Bitar, N., and JL. Le Roux, "A 1129 Backward-Recursive PCE-Based Computation (BRPC) Procedure 1130 to Compute Shortest Constrained Inter-Domain Traffic 1131 Engineering Label Switched Paths", RFC 5441, April 2009. 1133 [RFC5541] Le Roux, JL., Vasseur, JP., and Y. Lee, "Encoding of 1134 Objective Functions in the Path Computation Element 1135 Communication Protocol (PCEP)", RFC 5541, June 2009. 1137 12.2 Informative References 1139 [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation 1140 Element (PCE)-Based Architecture", RFC 4655, August 2006. 1142 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 1143 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 1144 DOI 10.17487/RFC5226, May 2008, 1146 [RFC5376] Bitar, N., Zhang, R., and K. Kumaki, "Inter-AS 1147 Requirements for the Path Computation Element 1148 Communication Protocol (PCECP)", RFC 5376, November 1149 2008. 1151 [RFC5394] Bryskin, I., Papadimitriou, D., Berger, L., and J. Ash, 1152 "Policy-Enabled Path Computation Framework", RFC 5394, 1153 December 2008. 1155 [RFC5520] Bradford, R., Ed., Vasseur, JP., and A. Farrel, 1156 "Preserving Topology Confidentiality in Inter-Domain 1157 Path Computation Using a Path-Key-Based Mechanism", 1158 RFC 5520, April 2009. 1160 [RFC6805] King, D. and A. Farrel, "The Application of the Path 1161 Computation Element Architecture to the Determination of a 1162 Sequence of Domains in MPLS and GMPLS", RFC 6805, 1163 November 2012. 1165 [RFC7420] Koushik, A., Stephan, E., Zhao, Q., King, D., Hardwick, 1166 J., "Path Computation Element Communication Protocol 1167 (PCEP) Management Information Base (MIB) Module", RFC 1168 7420, December 2014. 1170 [RFC7752] Gredler, H., Medved, J., Previdi, S., Farrel, A., and 1171 S. Ray, "North-Bound Distribution of Link-State and TE 1172 Information using BGP", Work in Progress, RFC 7752, 1173 March, 2016. 1175 [RFC7897] Dhody, D., Palle, U., and R. Casellas, "Domain Subobjects 1176 for the Path Computation Element Communication Protocol 1177 (PCEP)", RFC 7897, DOI 10.17487/RFC7897, June 2016. 1179 [I-D.ietf-pce-pceps] 1180 Lopez, D., Dios, O., Wu, W., and D. Dhody, "Secure 1181 Transport for PCEP", draft-ietf-pce-pceps (work in 1182 progress), March 2016. 1184 [I-D.pkd-pce-pcep-yang] 1185 Dhody, D., Hardwick, J., Beeram, V., and J. Tantsura, "A 1186 YANG Data Model for Path Computation Element 1187 Communications Protocol (PCEP)", draft-pkd-pce-pcep- 1188 yang (work in progress), January 2016. 1190 Authors' Addresses 1192 Fatai Zhang 1193 Huawei 1194 Huawei Base, Bantian, Longgang District 1195 Shenzhen, 518129 1196 China 1198 Phone: +86-755-28972912 1199 Email: zhangfatai@huawei.com 1201 Quintin Zhao 1202 Huawei 1203 125 Nagog Technology Park 1204 Acton, MA 01719 1205 US 1207 Phone: 1208 Email: qzhao@huawei.com 1210 Oscar Gonzalez de Dios 1211 Telefonica I+D 1212 Don Ramon de la Cruz 82-84 1213 Madrid, 28045 1214 Spain 1216 Phone: +34913128832 1217 Email: ogondio@tid.es 1219 Ramon Casellas 1220 CTTC 1221 Av. Carl Friedrich Gauss n.7 1222 Castelldefels, Barcelona 1223 Spain 1225 Phone: +34 93 645 29 00 1226 Email: ramon.casellas@cttc.es 1228 Daniel King 1229 Old Dog Consulting 1230 UK 1232 Phone: 1233 Email: daniel@olddog.co.uk