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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 PCE Working Group F. Zhang 3 Internet-Draft Q. Zhao 4 Intended status: Standards Track Huawei 5 Expires: September 6, 2018 O. Gonzalez de Dios 6 Telefonica I+D 7 R. Casellas 8 CTTC 9 D. King 10 Old Dog Consulting 11 March 5, 2018 13 Extensions to Path Computation Element Communication Protocol (PCEP) for 14 Hierarchical Path Computation Elements (PCE) 15 draft-ietf-pce-hierarchy-extensions-04 17 Abstract 19 The Hierarchical Path Computation Element (H-PCE) architecture RFC 20 6805, provides a mechanism to allow the optimum sequence of domains 21 to be selected, and the optimum end-to-end path to be derived through 22 the use of a hierarchical relationship between domains. 24 This document defines the Path Computation Element Protocol (PCEP) 25 extensions for the purpose of implementing necessary Hierarchical PCE 26 procedures and protocol extensions. 28 Status of This Memo 30 This Internet-Draft is submitted in full conformance with the 31 provisions of BCP 78 and BCP 79. 33 Internet-Drafts are working documents of the Internet Engineering 34 Task Force (IETF). Note that other groups may also distribute 35 working documents as Internet-Drafts. The list of current Internet- 36 Drafts is at https://datatracker.ietf.org/drafts/current/. 38 Internet-Drafts are draft documents valid for a maximum of six months 39 and may be updated, replaced, or obsoleted by other documents at any 40 time. It is inappropriate to use Internet-Drafts as reference 41 material or to cite them other than as "work in progress." 43 This Internet-Draft will expire on September 6, 2018. 45 Copyright Notice 47 Copyright (c) 2018 IETF Trust and the persons identified as the 48 document authors. All rights reserved. 50 This document is subject to BCP 78 and the IETF Trust's Legal 51 Provisions Relating to IETF Documents 52 (https://trustee.ietf.org/license-info) in effect on the date of 53 publication of this document. Please review these documents 54 carefully, as they describe your rights and restrictions with respect 55 to this document. Code Components extracted from this document must 56 include Simplified BSD License text as described in Section 4.e of 57 the Trust Legal Provisions and are provided without warranty as 58 described in the Simplified BSD License. 60 Table of Contents 62 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 63 1.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 4 64 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5 65 1.3. Requirements Language . . . . . . . . . . . . . . . . . . 5 66 2. Requirements for H-PCE . . . . . . . . . . . . . . . . . . . 5 67 2.1. Path Computation Request . . . . . . . . . . . . . . . . 5 68 2.1.1. Qualification of PCEP Requests . . . . . . . . . . . 5 69 2.1.2. Multi-domain Objective Functions . . . . . . . . . . 6 70 2.1.3. Multi-domain Metrics . . . . . . . . . . . . . . . . 6 71 2.2. Parent PCE Capability Advertisement . . . . . . . . . . . 7 72 2.3. PCE Domain Discovery . . . . . . . . . . . . . . . . . . 7 73 2.4. Domain Diversity . . . . . . . . . . . . . . . . . . . . 7 74 3. PCEP Extensions . . . . . . . . . . . . . . . . . . . . . . . 8 75 3.1. OPEN object . . . . . . . . . . . . . . . . . . . . . . . 8 76 3.1.1. H-PCE capability TLV . . . . . . . . . . . . . . . . 8 77 3.1.2. Domain-ID TLV . . . . . . . . . . . . . . . . . . . . 9 78 3.2. RP object . . . . . . . . . . . . . . . . . . . . . . . . 10 79 3.2.1. H-PCE-FLAG TLV . . . . . . . . . . . . . . . . . . . 10 80 3.2.2. Domain-ID TLV . . . . . . . . . . . . . . . . . . . . 10 81 3.3. Objective Functions . . . . . . . . . . . . . . . . . . . 11 82 3.3.1. OF Codes . . . . . . . . . . . . . . . . . . . . . . 11 83 3.3.2. OF Object . . . . . . . . . . . . . . . . . . . . . . 12 84 3.4. Metric Object . . . . . . . . . . . . . . . . . . . . . . 12 85 3.5. SVEC Object . . . . . . . . . . . . . . . . . . . . . . . 13 86 3.6. PCEP-ERROR object . . . . . . . . . . . . . . . . . . . . 13 87 3.6.1. Hierarchy PCE Error-Type . . . . . . . . . . . . . . 13 88 3.7. NO-PATH Object . . . . . . . . . . . . . . . . . . . . . 14 89 4. H-PCE Procedures . . . . . . . . . . . . . . . . . . . . . . 14 90 4.1. OPEN Procedure between Child PCE and Parent PCE . . . . . 14 91 4.2. Procedure to obtain Domain Sequence . . . . . . . . . . . 15 92 5. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 15 93 6. Manageability Considerations . . . . . . . . . . . . . . . . 16 94 6.1. Control of Function and Policy . . . . . . . . . . . . . 16 95 6.1.1. Child PCE . . . . . . . . . . . . . . . . . . . . . . 17 96 6.1.2. Parent PCE . . . . . . . . . . . . . . . . . . . . . 17 97 6.1.3. Policy Control . . . . . . . . . . . . . . . . . . . 17 98 6.2. Information and Data Models . . . . . . . . . . . . . . . 17 99 6.3. Liveness Detection and Monitoring . . . . . . . . . . . . 18 100 6.4. Verify Correct Operations . . . . . . . . . . . . . . . . 18 101 6.5. Requirements On Other Protocols . . . . . . . . . . . . . 18 102 6.6. Impact On Network Operations . . . . . . . . . . . . . . 18 103 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 104 7.1. PCEP TLV Type Indicators . . . . . . . . . . . . . . . . 19 105 7.2. H-PCE-CAPABILITY TLV Flags . . . . . . . . . . . . . . . 19 106 7.3. Domain-ID TLV Domain type . . . . . . . . . . . . . . . . 19 107 7.4. H-PCE-FLAG TLV Flags . . . . . . . . . . . . . . . . . . 20 108 7.5. OF Codes . . . . . . . . . . . . . . . . . . . . . . . . 20 109 7.6. METRIC Types . . . . . . . . . . . . . . . . . . . . . . 21 110 7.7. New PCEP Error-Types and Values . . . . . . . . . . . . . 21 111 7.8. New NO-PATH-VECTOR TLV Bit Flag . . . . . . . . . . . . . 22 112 7.9. SVEC Flag . . . . . . . . . . . . . . . . . . . . . . . . 22 113 8. Security Considerations . . . . . . . . . . . . . . . . . . . 22 114 9. Implementation Status . . . . . . . . . . . . . . . . . . . . 23 115 9.1. Inter-layer traffic engineering with H-PCE . . . . . . . 23 116 9.2. Telefonica Netphony (Open Source PCE) . . . . . . . . . . 24 117 9.3. Implementation 3: H-PCE Proof of Concept developed by 118 Huawei . . . . . . . . . . . . . . . . . . . . . . . . . 26 119 10. Contributing Authors . . . . . . . . . . . . . . . . . . . . 26 120 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 26 121 11.1. Normative References . . . . . . . . . . . . . . . . . . 27 122 11.2. Informative References . . . . . . . . . . . . . . . . . 27 123 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 29 125 1. Introduction 127 [RFC6805] describes a Hierarchical PCE (H-PCE) architecture which can 128 be used for computing end-to-end paths for inter-domain MPLS Traffic 129 Engineering (TE) and GMPLS Label Switched Paths (LSPs). 131 Within the hierarchical PCE architecture, the parent PCE is used to 132 compute a multi-domain path based on the domain connectivity 133 information . A child PCE may be responsible for a single domain or 134 multiple domains, it is used to compute the intra-domain path based 135 on its own domain topology information. 137 The H-PCE end-to-end domain path computation procedure is described 138 below: 140 o A path computation client (PCC) sends the inter-domain path 141 computation requests to the child PCE responsible for its domain; 143 o The child PCE forwards the request to the parent PCE; 145 o The parent PCE computes the likely domain paths from the ingress 146 domain to the egress domain; 148 o The parent PCE sends the intra-domain path computation requests 149 (between the domain border nodes) to the child PCEs which are 150 responsible for the domains along the domain path; 152 o The child PCEs return the intra-domain paths to the parent PCE; 154 o The parent PCE constructs the end-to-end inter-domain path based 155 on the intra-domain paths; 157 o The parent PCE returns the inter-domain path to the child PCE; 159 o The child PCE forwards the inter-domain path to the PCC. 161 In addition, the parent PCE may be requested to provide only the 162 sequence of domains to a child PCE so that alternative inter-domain 163 path computation procedures, including Per Domain (PD) [RFC5152] and 164 Backwards Recursive Path Computation (BRPC) [RFC5441] may be used. 166 This document defines the PCEP extensions for the purpose of 167 implementing Hierarchical PCE procedures, which are described in 168 [RFC6805]. 170 1.1. Scope 172 The following functions are out of scope of this document. 174 o Determination of Destination Domain (section 4.5 of [RFC6805]) 176 * via collection of reachability information from child domain; 178 * via requests to the child PCEs to discover if they contain the 179 destination node; 181 * or any other methods. 183 o Parent Traffic Engineering Database (TED) methods (section 4.4 of 184 [RFC6805]) 186 o Learning of Domain connectivity and boundary nodes (BN) addresses. 188 1.2. Terminology 190 This document uses the terminology defined in [RFC4655], [RFC5440] 191 and the additional terms defined in section 1.4 of [RFC6805]. 193 1.3. Requirements Language 195 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 196 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 197 "OPTIONAL" in this document are to be interpreted as described in BCP 198 14 [RFC2119] [RFC8174] when, and only when, they appear in all 199 capitals, as shown here. 201 2. Requirements for H-PCE 203 This section compiles the set of requirements of the PCEP protocol to 204 support the H-PCE architecture and procedures. 206 [RFC6805] identifies high-level requirements of PCEP extensions 207 required to support the hierarchical PCE model. 209 2.1. Path Computation Request 211 The Path Computation Request (PCReq) messages are used by a PCC or 212 PCE to make a path computation request to a PCE. In order to achieve 213 the full functionality of the H-PCE procedures, the PCReq message 214 needs to include: 216 o Qualification of PCE Requests; 218 o Multi-domain Objective Functions (OF); 220 o Multi-domain Metrics. 222 2.1.1. Qualification of PCEP Requests 224 As described in section 4.8.1 of [RFC6805], the H-PCE architecture 225 introduces new request qualifications, which are: 227 o It MUST be possible for a child PCE to indicate that a request it 228 sends to a parent PCE should be satisfied by a domain sequence 229 only, that is, not by a full end-to-end path. This allows the 230 child PCE to initiate a per-domain (PD) [RFC5152] or a backward 231 recursive path computation (BRPC) [RFC5441]. 233 o As stated in [RFC6805], section 4.5, if a PCC knows the egress 234 domain, it can supply this information as the path computation 235 request. It SHOULD be possible to specify the destination domain 236 information in a PCEP request, if it is known. 238 o It MAY be possible to indicate that the inter domain path computed 239 by parent PCE should disallow domain re-entry. 241 2.1.2. Multi-domain Objective Functions 243 For inter-domain path computation, there is one new objective 244 Function which is defined in section 1.3.1 and 4.1 of [RFC6805]: 246 o Minimize the number of domains crossed. A domain can be either an 247 Autonomous System (AS) or an Internal Gateway Protocol (IGP) area 248 depending on the type of multi-domain network hierarchical PCE is 249 applied to. 251 Another objective Function to minimize the number of border nodes is 252 also defined in this document. 254 During the PCEP session establishment procedure, the parent PCE needs 255 to be capable of indicating the Objective Functions (OF) [RFC5541] 256 capability in the Open message. This capability information may then 257 be announced by child PCEs, and used for selecting the PCE when a PCC 258 wants a path that satisfies one or multiple inter-domain objective 259 functions. 261 When a PCC requests a PCE to compute an inter-domain path, the PCC 262 needs also to be capable of indicating the new objective functions 263 for inter-domain path. Note that a given child PCE may also act as a 264 parent PCE. 266 For the reasons described previously, new OF codes need to be defined 267 for the new inter-domain objective functions. Then the PCE can 268 notify its new inter-domain objective functions to the PCC by 269 carrying them in the OF-list TLV which is carried in the OPEN object. 270 The PCC can specify which objective function code to use, which is 271 carried in the OF object when requesting a PCE to compute an inter- 272 domain path. 274 A parent PCE MUST be capable of ensuring homogeneity, across domains, 275 when applying OF codes for strict OF intra-domain requests. 277 2.1.3. Multi-domain Metrics 279 For inter-domain path computation, there are several path metrics of 280 interest. 282 o Domain count (number of domains crossed); 283 o Border Node count. 285 A PCC may be able to limit the number of domains crossed by applying 286 a limit on these metrics. Details in section 3.3. 288 2.2. Parent PCE Capability Advertisement 290 Parent and child PCE relationships are likely to be configured. 291 However, as mentioned in [RFC6805], it would assist network operators 292 if the child and parent PCEs could indicate their H-PCE capabilities. 294 During the PCEP session establishment procedure, the child PCE needs 295 to be capable of indicating to the parent PCE whether it requests the 296 parent PCE capability or not. Also, during the PCEP session 297 establishment procedure, the parent PCE needs to be capable of 298 indicating whether its parent capability can be provided or not. 300 A PCEP Speaker (Parent PCE or Child PCE or PCC) includes the "H-PCE 301 Capability" TLV, described in Section 3.1.1, in the OPEN Object to 302 advertise its support for PCEP extensions for H-PCE Capability. 304 2.3. PCE Domain Discovery 306 A PCE domain is a single domain with an associated PCE. Although it 307 is possible for a PCE to manage multiple domains. The PCE domain may 308 be an IGP area or AS. 310 The PCE domain identifiers may be provided during the PCEP session 311 establishment procedure. 313 2.4. Domain Diversity 315 In a multi-domain environment, Domain Diversity is defined in 316 [RFC6805]. A pair of paths are domain-diverse if they do not 317 traverse any of the same transit domains. Domain diversity may be 318 maximized for a pair of paths by selecting paths that have the 319 smallest number of shared domains. Path computation should 320 facilitate the selection of domain diverse paths as a way to reduce 321 the risk of shared failure and automatically helps to ensure path 322 diversity for most of the route of a pair of LSPs. 324 The main motivation behind domain diversity is to avoid fate sharing, 325 but it can also be because of some geo-political reasons and 326 commercial relationships that would require domain diversity. for 327 example, a pair of paths should choose different transit Autonomous 328 System (AS) because of some policy considerations. 330 In case when full domain diversity could not be achieved, it is 331 helpful to minimize the common shared domains. Also it is 332 interesting to note that other scope of diversity (node, link, SRLG 333 etc) can still be applied inside the common shared domains. 335 3. PCEP Extensions 337 This section defines PCEP extensions to ([RFC5440]) so as to support 338 the H-PCE procedures. 340 3.1. OPEN object 342 Two new TLVs are defined in this document to be carried within an 343 OPEN object. This way, during PCEP session establishment, the H-PCE 344 capability and Domain information can be advertised. 346 3.1.1. H-PCE capability TLV 348 The H-PCE-CAPABILITY TLV is an optional TLV associated with the OPEN 349 Object [RFC5440] to exchange H-PCE capability of PCEP speakers. 351 Its format is shown in the following figure: 353 0 1 2 3 354 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 1 355 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 356 | Type= TBD1 | Length=4 | 357 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 358 | Flags |I|R| 359 +---------------------------------------------------------------+ 361 Figure 1: H-PCE-CAPABILITY TLV format 363 The type of the TLV is TBD1 (to be assigned by IANA) and it has a 364 fixed length of 4 octets. 366 The value comprises a single field - Flags (32 bits): 368 R (Parent PCE Request bit): if set, will signal that the child PCE 369 wishes to use the peer PCE as a parent PCE. 371 I (Parent PCE Indication bit): if set, will signal that the PCE 372 can be used as a parent PCE by the peer PCE. 374 The inclusion of this TLV in an OPEN object indicate that the H-PCE 375 extensions are supported by the PCEP speaker. The PCC MAY include 376 this TLV to indicate that it understands the H-PCE extensions. The 377 Child PCE MUST include this TLV and set the R flag (and unset the I 378 flag) on the PCEP session towards the Parent PCE. The Parent PCE 379 MUST include this TLV and set the I flag and unset the R flag on the 380 PCEP session towards the child PCE. The parent-child PCEP session is 381 set to be established only when this capability is advertised. 383 If such capability is not exchanged and the parent PCE receive a "H- 384 PCE path computation request", it MUST send a PCErr message with 385 Error-Type=TBD8 (H-PCE error) and Error-Value=1 (Parent PCE 386 Capability not advertised). 388 3.1.2. Domain-ID TLV 390 The Domain-ID TLV when used in OPEN object identify the domain(s) 391 served by the PCE. The child PCE uses this mechanism to inform the 392 domain information to the parent PCE. 394 The Domain-ID TLV is defined below: 396 0 1 2 3 397 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 1 398 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 399 | Type= TBD2 | Length | 400 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 401 | Domain Type | Reserved | 402 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 403 | Domain ID | 404 // // 405 | | 406 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 408 Figure 2: Domain-ID TLV format 410 The type of the TLV is TBD2 (to be assigned by IANA) and it has a 411 variable Length of the value portion. The value part comprises of - 413 Domain Type (8 bits): Indicates the domain type. Four types of 414 domain are currently defined: 416 * Type=1: the Domain ID field carries a 2-byte AS number. Padded 417 with trailing zeroes to a 4-byte boundary. 419 * Type=2: the Domain ID field carries a 4-byte AS number. 421 * Type=3: the Domain ID field carries an 4-byte OSPF area ID. 423 * Type=4: the Domain ID field carries [2-byte Area-Len, variable 424 length IS-IS area ID]. Padded with trailing zeroes to a 4-byte 425 boundary. 427 Reserved: Zero at transmission; ignored at receipt. 429 Domain ID (variable): Indicates an IGP Area ID or AS number. It 430 can be 2 bytes, 4 bytes or variable length depending on the domain 431 identifier used. It is padded with trailing zeroes to a 4-byte 432 boundary. 434 In case a PCE serves more than one domain, multiple Domain-ID TLV is 435 included for each domain it serves. 437 3.2. RP object 439 3.2.1. H-PCE-FLAG TLV 441 The H-PCE-FLAG TLV is an optional TLV associated with the RP Object 442 [RFC5440] to indicate the H-PCE path computation request and options. 444 Its format is shown in the following figure: 446 0 1 2 3 447 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 1 448 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 449 | Type= TBD3 | Length=4 | 450 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 451 | Flags |D|S| 452 +---------------------------------------------------------------+ 454 Figure 3: H-PCE-FLAG TLV format 456 The type of the TLV is TBD3 (to be assigned by IANA) and it has a 457 fixed length of 4 octets. 459 The value comprises a single field - Flags (32 bits): 461 S (Domain Sequence bit): if set, will signal that the child PCE 462 wishes to get only the domain sequence in the path computation 463 reply. Refer section 3.7 of [RFC7897] for details. 465 D (Disallow Domain Re-entry bit): if set, will signal that the 466 computed path does not enter a domain more than once. 468 3.2.2. Domain-ID TLV 470 The usage of Domain-ID TLV carried in an OPEN object is used to 471 indicate a (list of) managed domains and is described in section 472 3.1.2. This TLV when carried in a RP object, indicates the 473 destination domain ID. If a PCC knows the egress domain, it can 474 supply this information in the PCReq message. The format of this TLV 475 is defined in Section 3.1.2. 477 3.3. Objective Functions 479 3.3.1. OF Codes 481 [RFC5541] defines a mechanism to specify an objective function that 482 is used by a PCE when it computes a path. Two new objective 483 functions are defined for the H-PCE experiment. 485 o MTD 487 * Name: Minimize the number of Transit Domains (MTD) 489 * Objective Function Code - TBD4 (to be assigned by IANA) 491 * Description: Find a path P such that it passes through the 492 least number of transit domains. 494 * Objective functions are formulated using the following 495 terminology: 497 + A network comprises a set of N domains {Di, (i=1...N)}. 499 + A path P passes through K domains {Dpi,(i=1...K)}. 501 + Find a path P such that the value of K is minimized. 503 o MBN 505 * Name: Minimize the number of border nodes. 507 * Objective Function Code - TBD5 (to be assigned by IANA) 509 * Description: Find a path P such that it passes through the 510 least number of border nodes. 512 * Objective functions are formulated using the following 513 terminology: 515 + A network comprises a set of N nodes {Ni, (i=1...N)}. 517 + A path P is a list of K nodes {Npi,(i=1...K)}. 519 + B(N) if a function that determine if the node is a border 520 node. B(Ni) = 1 if Ni is border node; B(Nk) = 0 if Nk is 521 not a border node. 523 + The number of border node in a path P is denoted by B(P), 524 where B(P) = sum{B(Npi),(i=1...K)}. 526 + Find a path P such that B(P) is minimized. 528 MCTD 530 o Name: Minimize the number of Common Transit Domains. 532 o Objective Function Code: TBD13 534 o Description: Find a set of paths such that it passes through the 535 least number of common transit domains. 537 3.3.2. OF Object 539 The OF (Objective Function) object [RFC5541] is carried within a 540 PCReq message so as to indicate the desired/required objective 541 function to be applied by the PCE during path computation. As per 542 section 3.2 of [RFC5541] a single OF object may be included in a path 543 computation request. 545 The new OF code described in section 3.3.1 are applicable at the 546 inter-domain level (parent), it is also necessary to specify the OF 547 code that may be applied at the intra-domain (child) path computation 548 level. To accommodate this, the OF-List TLV (described in section 549 2.1. of [RFC5541]) is included in the OF object as an optional TLV. 551 OF-List TLV allow encoding of multiple OF codes. When this TLV is 552 included inside the OF object, only the first OF-code in the OF-LIST 553 TLV is considered. The parent PCE would use this OF code in the OF 554 object when sending the intra domain path computation request to the 555 child PCE. 557 If the objective functions defined in this document are unknown/ 558 unsupported by a PCE, then the procedure as defined in [RFC5541] is 559 followed. 561 3.4. Metric Object 563 The METRIC object is defined in section 7.8 of [RFC5440], comprising 564 metric-value, metric-type (T field) and flags. This document defines 565 the following types for the METRIC object for H-PCE: 567 o T=TBD6: Domain count metric (number of domains crossed); 569 o T=TBD7: Border Node count metric (number of border nodes crossed). 571 The domain count metric type of the METRIC object encodes the number 572 of domain crossed in the path. The border node count metric type of 573 the METRIC object encodes the number of border nodes in the path. 575 A PCC or child PCE MAY use these metric in PCReq message an inter- 576 domain path meeting the number of domain or border nodes requirement. 577 In this case, the B bit MUST be set to suggest a bound (a maximum) 578 for the metric that must not be exceeded for the PCC to consider the 579 computed path as acceptable. 581 A PCC or child PCE MAY also use this metric to ask the PCE to 582 optimize the metric during inter-domain path computation. In this 583 case, the B flag MUST be cleared. 585 The Parent PCE MAY use these metric in a PCRep message along with a 586 NO-PATH object in the case where the PCE cannot compute a path 587 meeting this constraint. A PCE MAY also use this metric to send the 588 computed end to end metric in a reply message. 590 3.5. SVEC Object 592 [RFC5440] defines SVEC object which includes flags for the potential 593 dependency between the set of path computation requests (Link, Node 594 and SRLG diverse). This document proposes a new flag O for domain 595 diversity. 597 Following new bit is added in the Flags field: 599 o O (Domain diverse) bit - TBD12 : when set, this indicates that the 600 computed paths corresponding to the requests specified by the 601 following RP objects MUST NOT have any transit domain(s) in 602 common. 604 The Domain Diverse O-bit can be used in Hierarchical PCE path 605 computation to compute synchronized domain diverse end to end path or 606 diverse domain sequences. 608 When domain diverse O bit is set, it is applied to the transit 609 domains. The other bit in SVEC object (N, L, S etc) is set, SHOULD 610 still be applied in the ingress and egress shared domain. 612 3.6. PCEP-ERROR object 614 3.6.1. Hierarchy PCE Error-Type 616 A new PCEP Error-Type is used for this H-PCE experiment and is 617 defined below: 619 +------------+------------------------------------------------------+ 620 | Error-Type | Meaning | 621 +------------+------------------------------------------------------+ 622 | TBD8 | H-PCE error | 623 | | Error-value=1: parent PCE capability | 624 | | was not advertised | 625 | | Error-value=2: parent PCE capability | 626 | | cannot be provided | 627 +------------+------------------------------------------------------+ 629 Figure 4: H-PCE error 631 3.7. NO-PATH Object 633 To communicate the reason(s) for not being able to find a multi- 634 domain path or domain sequence, the NO-PATH object can be used in the 635 PCRep message. [RFC5440] defines the format of the NO-PATH object. 636 The object may contain a NO-PATH-VECTOR TLV to provide additional 637 information about why a path computation has failed. 639 Three new bit flags are defined to be carried in the Flags field in 640 the NO-PATH-VECTOR TLV carried in the NO-PATH Object. 642 o Bit number TBD9: When set, the parent PCE indicates that 643 destination domain unknown; 645 o Bit number TBD10: When set, the parent PCE indicates unresponsive 646 child PCE(s); 648 o Bit number TBD11: When set, the parent PCE indicates no available 649 resource available in one or more domain(s). 651 4. H-PCE Procedures 653 4.1. OPEN Procedure between Child PCE and Parent PCE 655 If a child PCE wants to use the peer PCE as a parent, it can set the 656 R (parent PCE request flag) in the H-PCE-CAPABILITY TLV inside the 657 OPEN object carried in the Open message during the PCEP session 658 creation procedure. 660 If the parent PCE can provide the parent function to the peer PCE, it 661 may set the I (parent PCE indication flag) in the H-PCE-CAPABILITY 662 TLV inside the OPEN object carried in the Open message during the 663 PCEP session creation procedure. 665 The PCE may also report its list of domain IDs to the peer PCE by 666 specifying them in the Domain-ID TLVs in the OPEN object carried in 667 the Open message during the PCEP session creation procedure. 669 The OF codes defined in this document can be carried in the OF-list 670 TLV of the OPEN object. If the OF-list TLV carries the OF codes, it 671 means that the PCE is capable of implementing the corresponding 672 objective functions. This information can be used for selecting a 673 proper parent PCE when a child PCE wants to get a path that satisfies 674 a certain objective function. 676 When a specific child PCE sends a PCReq to a peer PCE that requires 677 parental activity and H-PCE capability flags were not set in the 678 session establishment procedure as described above, the peer PCE 679 should send a PCErr message to the child PCE and specify the error- 680 type=TBD (H-PCE error) and error-value=1 (parent PCE capability was 681 not advertised) in the PCEP-ERROR object. 683 When a specific child PCE sends a PCReq to a peer PCE that requires 684 parental activity and the peer PCE does not want to act as the parent 685 for it, the peer PCE should send a PCErr message to the child PCE and 686 specify the error-type=TBD (H-PCE error) and error-value=2 (parent 687 PCE capability cannot be provided) in the PCEP-ERROR object. 689 4.2. Procedure to obtain Domain Sequence 691 If a child PCE only wants to get the domain sequence for a multi- 692 domain path computation from a parent PCE, it can set the Domain Path 693 Request bit in the H-PCE-FLAG TLV in the RP object carried in a PCReq 694 message. The parent PCE which receives the PCReq message tries to 695 compute a domain sequence for it (instead for E2E path). If the 696 domain path computation succeeds the parent PCE sends a PCRep message 697 which carries the domain sequence in the ERO to the child PCE. Refer 698 [RFC7897] for more details about domain sub-objects in the ERO. 699 Otherwise it sends a PCReq message which carries the NO-PATH object 700 to the child PCE. 702 5. Error Handling 704 A PCE that is capable of acting as a parent PCE might not be 705 configured or willing to act as the parent for a specific child PCE. 707 This fact could be determined when the child sends a PCReq that 708 requires parental activity, and could result in a negative response 709 in a PCEP Error (PCErr) message and indicate the hierarchy PCE error- 710 type=TBD8 (H-PCE error) and suitable error-value. (section 3.5.1) 711 Additionally, the parent PCE may fail to find the multi-domain path 712 or domain sequence due to one or more of the following reasons: 714 o A child PCE cannot find a suitable path to the egress; 716 o The parent PCE do not hear from a child PCE for a specified time; 718 o The objective functions specified in the path request cannot be 719 met. 721 In this case, the parent PCE MAY need to send a negative path 722 computation reply specifying the reason. This can be achieved by 723 including NO-PATH object in the PCRep message. Extension to NO-PATH 724 object is needed to include the aforementioned reasons described in 725 section 3.6. 727 6. Manageability Considerations 729 General PCE and PCEP management considerations are discussed in 730 [RFC4655] and [RFC5440]. There are additional management 731 considerations for H-PCE which are described in [RFC6805], and 732 repeated in this section. 734 The administrative entity responsible for the management of the 735 parent PCEs must be determined for the following cases: 737 o multi-domains (e.g., IGP areas or multiple ASes) within a single 738 service provider network, the management responsibility for the 739 parent PCE would most likely be handled by the service provider, 741 o multiple ASes within different service provider networks, it may 742 be necessary for a third party to manage the parent PCEs according 743 to commercial and policy agreements from each of the participating 744 service providers. 746 6.1. Control of Function and Policy 748 Control and function will need to be carefully managed in a H-PCE 749 network. A child PCE will need to be configured with the address of 750 its parent PCE. It is expected that there will only be one or two 751 parents of any child. 753 The parent PCE also needs to be aware of the child PCEs for all child 754 domains that it can see. This information is most likely to be 755 configured (as part of the administrative definition of each domain). 757 Discovery of the relationships between parent PCEs and child PCEs 758 does not form part of the hierarchical PCE architecture. Mechanisms 759 that rely on advertising or querying PCE locations across domain or 760 provider boundaries are undesirable for security, scaling, 761 commercial, and confidentiality reasons. Specific behavior of the 762 child and parent PCE are described in the following sub-sections. 764 6.1.1. Child PCE 766 Support of the hierarchical procedure will be controlled by the 767 management organization responsible for each child PCE. A child PCE 768 must be configured with the address of its parent PCE in order for it 769 to interact with its parent PCE. The child PCE must also be 770 authorized to peer with the parent PCE. 772 6.1.2. Parent PCE 774 The parent PCE must only accept path computation requests from 775 authorized child PCEs. If a parent PCE receives requests from an 776 unauthorized child PCE, the request should be dropped. This means 777 that a parent PCE must be configured with the identities and security 778 credentials of all of its child PCEs, or there must be some form of 779 shared secret that allows an unknown child PCE to be authorized by 780 the parent PCE. 782 6.1.3. Policy Control 784 It may be necessary to maintain a policy module on the parent PCE 785 [RFC5394]. This would allow the parent PCE to apply commercially 786 relevant constraints such as SLAs, security, peering preferences, and 787 monetary costs. 789 It may also be necessary for the parent PCE to limit end-to-end path 790 selection by including or excluding specific domains based on 791 commercial relationships, security implications, and reliability. 793 6.2. Information and Data Models 795 A MIB module for PCEP was published as RFC 7420 [RFC7420] that 796 describes managed objects for modeling of PCEP communication. A YANG 797 module for PCEP has also been proposed [I-D.ietf-pce-pcep-yang]. 799 A H-PCE MIB module, or additional data model, will be required to 800 report parent PCE and child PCE information, including: 802 o parent PCE configuration and status, 804 o child PCE configuration and information, 805 o notifications to indicate session changes between parent PCEs and 806 child PCEs, and 808 o notification of parent PCE TED updates and changes. 810 6.3. Liveness Detection and Monitoring 812 The hierarchical procedure requires interaction with multiple PCEs. 813 Once a child PCE requests an end-to-end path, a sequence of events 814 occurs that requires interaction between the parent PCE and each 815 child PCE. If a child PCE is not operational, and an alternate 816 transit domain is not available, then a failure must be reported. 818 6.4. Verify Correct Operations 820 Verifying the correct operation of a parent PCE can be performed by 821 monitoring a set of parameters. The parent PCE implementation should 822 provide the following parameters monitored by the parent PCE: 824 o number of child PCE requests, 826 o number of successful hierarchical PCE procedures completions on a 827 per-PCE-peer basis, 829 o number of hierarchical PCE procedure completion failures on a per- 830 PCE-peer basis, and 832 o number of hierarchical PCE procedure requests from unauthorized 833 child PCEs. 835 6.5. Requirements On Other Protocols 837 Mechanisms defined in this document do not imply any new requirements 838 on other protocols. 840 6.6. Impact On Network Operations 842 The hierarchical PCE procedure is a multiple-PCE path computation 843 scheme. Subsequent requests to and from the child and parent PCEs do 844 not differ from other path computation requests and should not have 845 any significant impact on network operations. 847 7. IANA Considerations 848 7.1. PCEP TLV Type Indicators 850 IANA Manages the PCEP TLV code point registry (see [RFC5440]). This 851 is maintained as the "PCEP TLV Type Indicators" sub-registry of the 852 "Path Computation Element Protocol (PCEP) Numbers" registry. 854 This document defines three new PCEP TLVs. IANA is requested to make 855 the following allocation: 857 Type TLV name References 858 ----------------------------------------------- 859 TBD1 H-PCE-CAPABILITY TLV This I-D 860 TBD2 Domain-ID TLV This I-D 861 TBD3 H-PCE-FLAG TLV This I-D 863 7.2. H-PCE-CAPABILITY TLV Flags 865 This document requests that a new sub-registry, named " H-PCE- 866 CAPABILITY TLV Flag Field", is created within the "Path Computation 867 Element Protocol (PCEP) Numbers" registry to manage the Flag field in 868 the H-PCE-CAPABILITY TLV of the PCEP OPEN object (class = 1). 870 New values are to be assigned by Standards Action [RFC5226]. Each 871 bit should be tracked with the following qualities: 873 o Bit number (counting from bit 0 as the most significant bit) 875 o Capability description 877 o Defining RFC 879 The following values are defined in this document: 881 Bit Description Reference 882 -------------------------------------------------- 883 31 R (Parent PCE Request bit) This I.D. 884 30 I (Parent PCE Indication bit) This I.D. 886 7.3. Domain-ID TLV Domain type 888 This document requests that a new sub-registry, named " Domain-ID TLV 889 Domain type", is created within the "Path Computation Element 890 Protocol (PCEP) Numbers" registry to manage the Domain-Type field of 891 the Domain-ID TLV. 893 Value Meaning 894 ----------------------------------------------- 895 1 2-byte AS number 896 2 4-byte AS number 897 3 4-byte OSPF area ID 898 4 Variable length IS-IS area ID 900 7.4. H-PCE-FLAG TLV Flags 902 This document requests that a new sub-registry, named "H-PCE-FLAGS 903 TLV Flag Field", is created within the "Path Computation Element 904 Protocol (PCEP) Numbers" registry to manage the Flag field in the H- 905 PCE-FLAGS TLV of the PCEP OPEN object (class = 1). New values are to 906 be assigned by Standards Action [RFC5226]. Each bit should be 907 tracked with the following qualities: 909 o Bit number (counting from bit 0 as the most significant bit) 911 o Capability description 913 o Defining RFC 915 The following values are defined in this document: 917 Bit Description Reference 918 ----------------------------------------------- 919 31 S (Domain This I.D. 920 Sequence bit) 921 30 D (Disallow Domain This I.D. 922 Re-entry bit) 924 7.5. OF Codes 926 IANA maintains registry of Objective Function (described in 927 [RFC5541]) at the sub-registry "Objective Function". Two new 928 Objective Functions have been defined in this document. 930 IANA is requested to make the following allocations: 932 Code 933 Point Name Reference 934 ------------------------------------------------------ 935 TBD4 Minimum number of Transit This I.D. 936 Domains (MTD) 937 TBD5 Minimize number of Border This I.D. 938 Nodes (MBN) 939 TBD13 Minimize the number of This I.D. 940 Common Transit Domains. 941 (MCTD) 943 7.6. METRIC Types 945 IANA maintains one sub-registry for "METRIC object T field". Two new 946 metric types are defined in this document for the METRIC object 947 (specified in [RFC5440]). 949 IANA is requested to make the following allocations: 951 Value Description Reference 952 ---------------------------------------------------------- 953 TBD6 Domain Count metric This I.D. 954 TBD7 Border Node Count metric This I.D. 956 7.7. New PCEP Error-Types and Values 958 IANA maintains a registry of Error-Types and Error-values for use in 959 PCEP messages. This is maintained as the "PCEP-ERROR Object Error 960 Types and Values" sub-registry of the "Path Computation Element 961 Protocol (PCEP) Numbers" registry. 963 IANA is requested to make the following allocations: 965 Error-Type Meaning and error values Reference 966 ------------------------------------------------------ 967 TBD8 H-PCE Error This I.D. 969 Error-value=1 Parent PCE 970 Capability not advertised 972 Error-value=2 Parent PCE 973 Capability not supported 975 7.8. New NO-PATH-VECTOR TLV Bit Flag 977 IANA maintains a registry of bit flags carried in the PCEP NO-PATH- 978 VECTOR TLV in the PCEP NO-PATH object as defined in [RFC5440]. IANA 979 Is requested to assign three new bit flag as follows: 981 Bit Number Name Flag Reference 982 ------------------------------------------------------ 983 TBD9 Destination Domain unknown This I.D. 984 TBD10 Unresponsive child PCE(s) This I.D. 985 TBD11 No available resource in This I.D. 986 one or more domain 988 7.9. SVEC Flag 990 IANA maintains a registry of bit flags carried in the PCEP SVEC 991 object as defined in [RFC5440]. IANA Is requested to assign one new 992 bit flag as follows: 994 Bit Number Name Flag Reference 995 ------------------------------------------------------ 996 TBD13 Domain Diverse This I.D. 998 8. Security Considerations 1000 The hierarchical PCE procedure relies on PCEP and inherits the 1001 security requirements defined in [RFC5440]. As PCEP operates over 1002 TCP, it may also make use of TCP security mechanisms, such as TCP-AO 1003 or [RFC8253]. 1005 H-PCE operation also relies on information used to build the TED. 1006 Attacks on a parent or child PCE may be achieved by falsifying or 1007 impeding this flow of information. If the child PCE listens to the 1008 IGP or BGP-LS for populating the TED, then normal IGP or BGP-LS 1009 security measures may be applied, and it should be noted that an IGP 1010 routing system is generally assumed to be a trusted domain such that 1011 router subversion is not a risk. The parent PCE TED is constructed 1012 as described in this document and may involve: 1014 o multiple parent-child relationships using PCEP 1016 o the parent PCE listening to child domain IGPs (with the same 1017 security features as a child PCE listening to its IGP) 1019 o an external mechanism (such as [RFC7752]), which will need to be 1020 authorized and secured. 1022 Any multi-domain operation necessarily involves the exchange of 1023 information across domain boundaries. This is bound to represent a 1024 significant security and confidentiality risk especially when the 1025 child domains are controlled by different commercial concerns. PCEP 1026 allows individual PCEs to maintain confidentiality of their domain 1027 path information using path-keys [RFC5520], and the H-PCE 1028 architecture is specifically designed to enable as much isolation of 1029 domain topology and capabilities information as is possible. 1031 For further considerations of the security issues related to inter-AS 1032 path computation, see [RFC5376]. 1034 9. Implementation Status 1036 The H-PCE architecture and protocol procedures describe in this I-D 1037 were implemented and tested for a variety of optical research 1038 applications. 1040 9.1. Inter-layer traffic engineering with H-PCE 1042 This work was led by: 1044 o Ramon Casellas [ramon.casellas@cttc.es] 1046 o Centre Tecnologic de Telecomunicacions de Catalunya (CTTC) 1048 The H-PCE instances (parent and child) were multi-threaded 1049 asynchronous processes. Implemented in C++11, using C++ Boost 1050 Libraries. The targeted system used to deploy and run H-PCE 1051 applications was a POSIX system (Debian GNU/Linux operating system). 1053 Some parts of the software may require a Linux Kernel, the 1054 availability of a Routing Controller running collocated in the same 1055 host and the usage of libnetfilter / libipq and GNU/Linux firewalling 1056 capabilities. Most of the functionality, including algorithms is 1057 done by means of plugins (e.g., as shared libraries or .so files in 1058 Unix systems). 1060 The CTTC PCE supports the H-PCE architecture, but also supports 1061 stateful PCE with active capabilities, as an OpenFlow controller, and 1062 has dedicated plugins to support monitoring, BRPC, P2MP, path keys, 1063 back end PCEs. Management of the H-PCE entities was supported via 1064 HTTP and CLI via Telnet. 1066 Further details of the H-PCE prototyping and experimentation can be 1067 found in the following scientific papers: 1069 R. Casellas, R. Martinez, R. Munoz, L. Liu, T. Tsuritani, I. 1070 Morita, "Inter-layer traffic engineering with hierarchical-PCE in 1071 MPLS-TP over wavelength switched optical networks" , Optics 1072 Express, Vol. 20, No. 28, December 2012. 1074 R. Casellas, R. Martinez, R. Munoz, L. Liu, T. Tsuritani, I. 1075 Morita, M. Msurusawa, "Dynamic virtual link mesh topology 1076 aggregation in multi-domain translucent WSON with hierarchical- 1077 PCE", Optics Express Journal, Vol. 19, No. 26, December 2011. 1079 R. Casellas, R. Munoz, R. Martinez, R. Vilalta, L. Liu, T. 1080 Tsuritani, I. Morita, V. Lopez, O. Gonzalez de Dios, J. P. 1081 Fernandez-Palacios, "SDN based Provisioning Orchestration of 1082 OpenFlow/GMPLS Flexi-grid Networks with a Stateful Hierarchical 1083 PCE", in Proceedings of Optical Fiber Communication Conference and 1084 Exposition (OFC), 9-13 March, 2014, San Francisco (EEUU). 1085 Extended Version to appear in Journal Of Optical Communications 1086 and Networking January 2015 1088 F. Paolucci, O. Gonzalez de Dios, R. Casellas, S. Duhovnikov, 1089 P. Castoldi, R. Munoz, R. Martinez, "Experimenting Hierarchical 1090 PCE Architecture in a Distributed Multi-Platform Control Plane 1091 Testbed" , in Proceedings of Optical Fiber Communication 1092 Conference and Exposition (OFC) and The National Fiber Optic 1093 Engineers Conference (NFOEC), 4-8 March, 2012, Los Angeles, 1094 California (USA). 1096 R. Casellas, R. Martinez, R. Munoz, L. Liu, T. Tsuritani, I. 1097 Morita, M. Tsurusawa, "Dynamic Virtual Link Mesh Topology 1098 Aggregation in Multi-Domain Translucent WSON with Hierarchical- 1099 PCE", in Proceedings of 37th European Conference and Exhibition on 1100 Optical Communication (ECOC 2011), 18-22 September 2011, Geneve ( 1101 Switzerland). 1103 R. Casellas, R. Munoz, R. Martinez, "Lab Trial of Multi-Domain 1104 Path Computation in GMPLS Controlled WSON Using a Hierarchical 1105 PCE", in Proceedings of OFC/NFOEC Conference (OFC2011), 10 March 1106 2011, Los Angeles (USA). 1108 9.2. Telefonica Netphony (Open Source PCE) 1110 The Telefonica Netphony PCE is an open source Java-based 1111 implementation of a Path Computation Element, with several flavours, 1112 and a Path Computation Client. The PCE follows a modular 1113 architecture and allows to add customized algorithms. The PCE has 1114 also stateful and remote initiation capabilities. In current 1115 version, three components can be built, a domain PCE (aka child PCE), 1116 a parent PCE (ready for the H-PCE architecture) and a PCC (path 1117 computation client). 1119 This work was led by: 1121 o Oscar Gonzalez de Dios [oscar.gonzalezdedios@telefonica.com] 1123 o Victor Lopez Alvarez [victor.lopezalvarez@telefonica.com] 1125 o Telefonica I+D, Madrid, Spain 1127 The PCE code is publicly available in a GitHub repository: 1129 o https://github.com/telefonicaid/netphony-pce 1131 The PCEP protocol encodings are located in the following repository: 1133 o https://github.com/telefonicaid/netphony-network protocols 1135 The traffic engineering database and a BGP-LS speaker to fill the 1136 database is located in: 1138 o https://github.com/telefonicaid/netphony-topology 1140 The parent and child PCE are multi-threaded java applications. The 1141 path computation uses the jgrapht free Java class library (0.9.1) 1142 that provides mathematical graph-theory objects and algorithms. 1143 Current version of netphony PCE runs on java 1.7 and 1.8, and has 1144 been tested in GNU/Linux, Mac OS-X and Windows environments. The 1145 management of the parent and domain PCEs is supported though CLI via 1146 Telnet, and configured via XML files. 1148 Further details of the netphony H-PCE prototyping and experimentation 1149 can be found in the following research papers: 1151 o O. Gonzalez de Dios, R. Casellas, F. Paolucci, A. Napoli, L. 1152 Gifre, A. Dupas, E, Hugues-Salas, R. Morro, S. Belotti, G. 1153 Meloni, T. Rahman, V.P Lopez, R. Martinez, F. Fresi, M. Bohn, 1154 S. Yan, L. Velasco, . Layec and J. P. Fernandez-Palacios: 1155 Experimental Demonstration of Multivendor and Multidomain EON With 1156 Data and Control Interoperability Over a Pan-European Test Bed, in 1157 Journal of Lightwave Technology, Dec. 2016, Vol. 34, Issue 7, pp. 1158 1610-1617. 1160 o O. Gonzalez de Dios, R. Casellas, R. Morro, F. Paolucci, V. 1161 Lopez, R. Martinez, R. Munoz, R. Villalta, P. Castoldi: 1162 "Multi-partner Demonstration of BGP-LS enabled multi-domain EON, 1163 in Journal of Optical Communications and Networking, Dec. 2015, 1164 Vol. 7, Issue 12, pp. B153-B162. 1166 o F. Paolucci, O. Gonzalez de Dios, R. Casellas, S. Duhovnikov, 1167 P. Castoldi, R. Munoz, R. Martinez, "Experimenting Hierarchical 1168 PCE Architecture in a Distributed Multi-Platform Control Plane 1169 Testbed" , in Proceedings of Optical Fiber Communication 1170 Conference and Exposition (OFC) and The National Fiber Optic 1171 Engineers Conference (NFOEC), 4-8 March, 2012, Los Angeles, 1172 California (USA). 1174 9.3. Implementation 3: H-PCE Proof of Concept developed by Huawei 1176 Huawei developed this H-PCE on the Huawei Versatile Routing Platform 1177 (VRP) to experiment with the hierarchy of PCE. Both end to end path 1178 computation as well as computation for domain-sequence are supported. 1180 This work was led by: 1182 o Udayasree Pallee [udayasreereddy@gmail.com] 1184 o Dhruv Dhody [dhruv.ietf@gmail.com] 1186 o Huawei Technologies, Bangalore, India 1188 Further work on stateful H-PCE [I-D.ietf-pce-stateful-hpce] is being 1189 carried out on ONOS. 1191 10. Contributing Authors 1193 Xian Zhang 1194 Huawei 1195 EMail: zhang.xian@huawei.com 1197 Dhruv Dhody 1198 Huawei Technologies 1199 Divyashree Techno Park, Whitefield 1200 Bangalore, Karnataka 560066 1201 India 1203 EMail: dhruv.ietf@gmail.com 1205 11. References 1206 11.1. Normative References 1208 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1209 Requirement Levels", BCP 14, RFC 2119, 1210 DOI 10.17487/RFC2119, March 1997, 1211 . 1213 [RFC5152] Vasseur, JP., Ed., Ayyangar, A., Ed., and R. Zhang, "A 1214 Per-Domain Path Computation Method for Establishing Inter- 1215 Domain Traffic Engineering (TE) Label Switched Paths 1216 (LSPs)", RFC 5152, DOI 10.17487/RFC5152, February 2008, 1217 . 1219 [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation 1220 Element (PCE) Communication Protocol (PCEP)", RFC 5440, 1221 DOI 10.17487/RFC5440, March 2009, 1222 . 1224 [RFC5541] Le Roux, JL., Vasseur, JP., and Y. Lee, "Encoding of 1225 Objective Functions in the Path Computation Element 1226 Communication Protocol (PCEP)", RFC 5541, 1227 DOI 10.17487/RFC5541, June 2009, 1228 . 1230 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 1231 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 1232 May 2017, . 1234 11.2. Informative References 1236 [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation 1237 Element (PCE)-Based Architecture", RFC 4655, 1238 DOI 10.17487/RFC4655, August 2006, 1239 . 1241 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 1242 IANA Considerations Section in RFCs", RFC 5226, 1243 DOI 10.17487/RFC5226, May 2008, 1244 . 1246 [RFC5376] Bitar, N., Zhang, R., and K. Kumaki, "Inter-AS 1247 Requirements for the Path Computation Element 1248 Communication Protocol (PCECP)", RFC 5376, 1249 DOI 10.17487/RFC5376, November 2008, 1250 . 1252 [RFC5394] Bryskin, I., Papadimitriou, D., Berger, L., and J. Ash, 1253 "Policy-Enabled Path Computation Framework", RFC 5394, 1254 DOI 10.17487/RFC5394, December 2008, 1255 . 1257 [RFC5520] Bradford, R., Ed., Vasseur, JP., and A. Farrel, 1258 "Preserving Topology Confidentiality in Inter-Domain Path 1259 Computation Using a Path-Key-Based Mechanism", RFC 5520, 1260 DOI 10.17487/RFC5520, April 2009, 1261 . 1263 [RFC5441] Vasseur, JP., Ed., Zhang, R., Bitar, N., and JL. Le Roux, 1264 "A Backward-Recursive PCE-Based Computation (BRPC) 1265 Procedure to Compute Shortest Constrained Inter-Domain 1266 Traffic Engineering Label Switched Paths", RFC 5441, 1267 DOI 10.17487/RFC5441, April 2009, 1268 . 1270 [RFC6805] King, D., Ed. and A. Farrel, Ed., "The Application of the 1271 Path Computation Element Architecture to the Determination 1272 of a Sequence of Domains in MPLS and GMPLS", RFC 6805, 1273 DOI 10.17487/RFC6805, November 2012, 1274 . 1276 [RFC7470] Zhang, F. and A. Farrel, "Conveying Vendor-Specific 1277 Constraints in the Path Computation Element Communication 1278 Protocol", RFC 7470, DOI 10.17487/RFC7470, March 2015, 1279 . 1281 [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and 1282 S. Ray, "North-Bound Distribution of Link-State and 1283 Traffic Engineering (TE) Information Using BGP", RFC 7752, 1284 DOI 10.17487/RFC7752, March 2016, 1285 . 1287 [RFC7897] Dhody, D., Palle, U., and R. Casellas, "Domain Subobjects 1288 for the Path Computation Element Communication Protocol 1289 (PCEP)", RFC 7897, DOI 10.17487/RFC7897, June 2016, 1290 . 1292 [RFC8253] Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody, 1293 "PCEPS: Usage of TLS to Provide a Secure Transport for the 1294 Path Computation Element Communication Protocol (PCEP)", 1295 RFC 8253, DOI 10.17487/RFC8253, October 2017, 1296 . 1298 [I-D.ietf-pce-pcep-yang] 1299 Dhody, D., Hardwick, J., Beeram, V., and J. Tantsura, "A 1300 YANG Data Model for Path Computation Element 1301 Communications Protocol (PCEP)", draft-ietf-pce-pcep- 1302 yang-07 (work in progress), March 2018. 1304 [I-D.ietf-pce-stateful-hpce] 1305 Dhody, D., Lee, Y., Ceccarelli, D., Shin, J., King, D., 1306 and O. Dios, "Hierarchical Stateful Path Computation 1307 Element (PCE).", draft-ietf-pce-stateful-hpce-04 (work in 1308 progress), March 2018. 1310 Authors' Addresses 1312 Fatai Zhang 1313 Huawei 1314 Huawei Base, Bantian, Longgang District 1315 Shenzhen 518129 1316 China 1318 EMail: zhangfatai@huawei.com 1320 Quintin Zhao 1321 Huawei 1322 125 Nagog Technology Park 1323 Acton, MA 01719 1324 USA 1326 EMail: quintin.zhao@huawei.com 1328 Oscar Gonzalez de Dios 1329 Telefonica I+D 1330 Don Ramon de la Cruz 82-84 1331 Madrid 28045 1332 Spain 1334 EMail: ogondio@tid.es 1336 Ramon Casellas 1337 CTTC 1338 Av. Carl Friedrich Gauss n.7 1339 Barcelona, Castelldefels 1340 Spain 1342 EMail: ramon.casellas@cttc.es 1343 Daniel King 1344 Old Dog Consulting 1345 UK 1347 EMail: daniel@olddog.co.uk