idnits 2.17.1 draft-ietf-pce-hierarchy-extensions-05.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 15, 2018) is 2111 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(Obsoleted by RFC 8126) -- Obsolete informational reference (is this intentional?): RFC 7752 (Obsoleted by RFC 9552) == Outdated reference: A later version (-23) exists of draft-ietf-pce-pcep-yang-08 == Outdated reference: A later version (-15) exists of draft-ietf-pce-stateful-hpce-05 Summary: 0 errors (**), 0 flaws (~~), 3 warnings (==), 3 comments (--). 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: January 16, 2019 O. Gonzalez de Dios 6 Telefonica I+D 7 R. Casellas 8 CTTC 9 D. King 10 Old Dog Consulting 11 July 15, 2018 13 Extensions to Path Computation Element Communication Protocol (PCEP) for 14 Hierarchical Path Computation Elements (PCE) 15 draft-ietf-pce-hierarchy-extensions-05 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 January 16, 2019. 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 . . . . . . . . . . . 6 69 2.1.2. Multi-domain Objective Functions . . . . . . . . . . 6 70 2.1.3. Multi-domain Metrics . . . . . . . . . . . . . . . . 7 71 2.2. Parent PCE Capability Advertisement . . . . . . . . . . . 7 72 2.3. PCE Domain Discovery . . . . . . . . . . . . . . . . . . 7 73 2.4. Domain Diversity . . . . . . . . . . . . . . . . . . . . 8 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 . . . . . . . . . . . . . . . . . . . . 11 81 3.3. Objective Functions . . . . . . . . . . . . . . . . . . . 11 82 3.3.1. OF Codes . . . . . . . . . . . . . . . . . . . . . . 11 83 3.3.2. OF Object . . . . . . . . . . . . . . . . . . . . . . 13 84 3.4. Metric Object . . . . . . . . . . . . . . . . . . . . . . 13 85 3.5. SVEC Object . . . . . . . . . . . . . . . . . . . . . . . 14 86 3.6. PCEP-ERROR object . . . . . . . . . . . . . . . . . . . . 14 87 3.6.1. Hierarchy PCE Error-Type . . . . . . . . . . . . . . 14 88 3.7. NO-PATH Object . . . . . . . . . . . . . . . . . . . . . 15 89 4. H-PCE Procedures . . . . . . . . . . . . . . . . . . . . . . 15 90 4.1. OPEN Procedure between Child PCE and Parent PCE . . . . . 15 91 4.2. Procedure to obtain Domain Sequence . . . . . . . . . . . 16 92 5. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 16 93 6. Manageability Considerations . . . . . . . . . . . . . . . . 17 94 6.1. Control of Function and Policy . . . . . . . . . . . . . 17 95 6.1.1. Child PCE . . . . . . . . . . . . . . . . . . . . . . 17 96 6.1.2. Parent PCE . . . . . . . . . . . . . . . . . . . . . 18 97 6.1.3. Policy Control . . . . . . . . . . . . . . . . . . . 18 98 6.2. Information and Data Models . . . . . . . . . . . . . . . 18 99 6.3. Liveness Detection and Monitoring . . . . . . . . . . . . 18 100 6.4. Verify Correct Operations . . . . . . . . . . . . . . . . 19 101 6.5. Requirements On Other Protocols . . . . . . . . . . . . . 19 102 6.6. Impact On Network Operations . . . . . . . . . . . . . . 19 103 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 104 7.1. PCEP TLV Type Indicators . . . . . . . . . . . . . . . . 19 105 7.2. H-PCE-CAPABILITY TLV Flags . . . . . . . . . . . . . . . 20 106 7.3. Domain-ID TLV Domain type . . . . . . . . . . . . . . . . 20 107 7.4. H-PCE-FLAG TLV Flags . . . . . . . . . . . . . . . . . . 20 108 7.5. OF Codes . . . . . . . . . . . . . . . . . . . . . . . . 21 109 7.6. METRIC Types . . . . . . . . . . . . . . . . . . . . . . 21 110 7.7. New PCEP Error-Types and Values . . . . . . . . . . . . . 22 111 7.8. New NO-PATH-VECTOR TLV Bit Flag . . . . . . . . . . . . . 22 112 7.9. SVEC Flag . . . . . . . . . . . . . . . . . . . . . . . . 22 113 8. Security Considerations . . . . . . . . . . . . . . . . . . . 23 114 9. Implementation Status . . . . . . . . . . . . . . . . . . . . 23 115 9.1. Inter-layer traffic engineering with H-PCE . . . . . . . 23 116 9.2. Telefonica Netphony (Open Source PCE) . . . . . . . . . . 25 117 9.3. Implementation 3: H-PCE Proof of Concept developed by 118 Huawei . . . . . . . . . . . . . . . . . . . . . . . . . 26 119 10. Contributing Authors . . . . . . . . . . . . . . . . . . . . 27 120 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 27 121 11.1. Normative References . . . . . . . . . . . . . . . . . . 27 122 11.2. Informative References . . . . . . . . . . . . . . . . . 28 123 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 30 125 1. Introduction 127 The Path Computation Element communication Protocol (PCEP) provides 128 mechanisms for Path Computation Elements (PCEs) to perform path 129 computations in response to Path Computation Clients' (PCCs) 130 requests. 132 The capability to compute the routes of end-to-end inter-domain MPLS 133 Traffic Engineering (MPLS-TE) and GMPLS Label Switched Paths (LSPs) 134 is expressed as requirements in [RFC4105] and [RFC4216]. This 135 capability may be realized by a PCE [RFC4655]. The methods for 136 establishing and controlling inter-domain MPLS-TE and GMPLS LSPs are 137 documented in [RFC4726]. 139 [RFC6805] describes a Hierarchical PCE (H-PCE) architecture which can 140 be used for computing end-to-end paths for inter-domain MPLS Traffic 141 Engineering (TE) and GMPLS Label Switched Paths (LSPs). 143 Within the hierarchical PCE architecture, the parent PCE is used to 144 compute a multi-domain path based on the domain connectivity 145 information . A child PCE may be responsible for a single domain or 146 multiple domains, it is used to compute the intra-domain path based 147 on its own domain topology information. 149 The H-PCE end-to-end domain path computation procedure is described 150 below: 152 o A path computation client (PCC) sends the inter-domain path 153 computation requests to the child PCE responsible for its domain; 155 o The child PCE forwards the request to the parent PCE; 157 o The parent PCE computes the likely domain paths from the ingress 158 domain to the egress domain; 160 o The parent PCE sends the intra-domain path computation requests 161 (between the domain border nodes) to the child PCEs which are 162 responsible for the domains along the domain path; 164 o The child PCEs return the intra-domain paths to the parent PCE; 166 o The parent PCE constructs the end-to-end inter-domain path based 167 on the intra-domain paths; 169 o The parent PCE returns the inter-domain path to the child PCE; 171 o The child PCE forwards the inter-domain path to the PCC. 173 In addition, the parent PCE may be requested to provide only the 174 sequence of domains to a child PCE so that alternative inter-domain 175 path computation procedures, including Per Domain (PD) [RFC5152] and 176 Backwards Recursive Path Computation (BRPC) [RFC5441] may be used. 178 This document defines the PCEP extensions for the purpose of 179 implementing Hierarchical PCE procedures, which are described in 180 [RFC6805]. 182 1.1. Scope 184 The following functions are out of scope of this document. 186 o Determination of Destination Domain (section 4.5 of [RFC6805]) 187 * via collection of reachability information from child domain; 189 * via requests to the child PCEs to discover if they contain the 190 destination node; 192 * or any other methods. 194 o Parent Traffic Engineering Database (TED) methods (section 4.4 of 195 [RFC6805]) 197 o Learning of Domain connectivity and boundary nodes (BN) addresses. 199 o Stateful PCE Operations. (Refer [I-D.ietf-pce-stateful-hpce]) 201 1.2. Terminology 203 This document uses the terminology defined in [RFC4655], [RFC5440] 204 and the additional terms defined in section 1.4 of [RFC6805]. 206 1.3. Requirements Language 208 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 209 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 210 "OPTIONAL" in this document are to be interpreted as described in BCP 211 14 [RFC2119] [RFC8174] when, and only when, they appear in all 212 capitals, as shown here. 214 2. Requirements for H-PCE 216 This section compiles the set of requirements of the PCEP protocol to 217 support the H-PCE architecture and procedures. 219 [RFC6805] identifies high-level requirements of PCEP extensions 220 required to support the hierarchical PCE model. 222 2.1. Path Computation Request 224 The Path Computation Request (PCReq) messages are used by a PCC or 225 PCE to make a path computation request to a PCE. In order to achieve 226 the full functionality of the H-PCE procedures, the PCReq message 227 needs to include: 229 o Qualification of PCE Requests; 231 o Multi-domain Objective Functions (OF); 233 o Multi-domain Metrics. 235 2.1.1. Qualification of PCEP Requests 237 As described in section 4.8.1 of [RFC6805], the H-PCE architecture 238 introduces new request qualifications, which are: 240 o It MUST be possible for a child PCE to indicate that a path 241 computation request sent to a parent PCE should be satisfied by a 242 domain sequence only, that is, not by a full end-to-end path. 243 This allows the child PCE to initiate a per-domain (PD) [RFC5152] 244 or a backward recursive path computation (BRPC) [RFC5441]. 246 o As stated in [RFC6805], section 4.5, if a PCC knows the egress 247 domain, it can supply this information as the path computation 248 request. It SHOULD be possible to specify the destination domain 249 information in a PCEP request, if it is known. 251 o It MAY be possible to indicate that the inter domain path computed 252 by parent PCE should disallow domain re-entry. 254 2.1.2. Multi-domain Objective Functions 256 For inter-domain path computation, there is one new objective 257 Function which is defined in section 1.3.1 and 4.1 of [RFC6805]: 259 o Minimize the number of domains crossed. A domain can be either an 260 Autonomous System (AS) or an Internal Gateway Protocol (IGP) area 261 depending on the type of multi-domain network hierarchical PCE is 262 applied to. 264 Another objective Function to minimize the number of border nodes is 265 also defined in this document. 267 During the PCEP session establishment procedure, the parent PCE needs 268 to be capable of indicating the Objective Functions (OF) [RFC5541] 269 capability in the Open message. This capability information may then 270 be announced by child PCEs, and used for selecting the PCE when a PCC 271 wants a path that satisfies one or multiple inter-domain objective 272 functions. 274 When a PCC requests a PCE to compute an inter-domain path, the PCC 275 needs to be capable of indicating the new objective functions for 276 inter-domain path. Note that a given child PCE may also act as a 277 parent PCE (for some other child PCE). 279 For the reasons described previously, new OF codes need to be defined 280 for the new inter-domain objective functions. Then the PCE can 281 notify its new inter-domain objective functions to the PCC by 282 carrying them in the OF-list TLV which is carried in the OPEN object. 284 The PCC can specify which objective function code to use, which is 285 carried in the OF object when requesting a PCE to compute an inter- 286 domain path. 288 A parent PCE MUST be capable of ensuring homogeneity, across domains, 289 when applying OF codes for strict OF intra-domain requests. 291 2.1.3. Multi-domain Metrics 293 For inter-domain path computation, there are several path metrics of 294 interest. 296 o Domain count (number of domains crossed); 298 o Border Node count. 300 A PCC may be able to limit the number of domains crossed by applying 301 a limit on these metrics. Details in Section 3.4. 303 2.2. Parent PCE Capability Advertisement 305 Parent and child PCE relationships are likely to be configured. 306 However, as mentioned in [RFC6805], it would assist network operators 307 if the child and parent PCEs could indicate their H-PCE capabilities. 309 During the PCEP session establishment procedure, the child PCE needs 310 to be capable of indicating to the parent PCE whether it requests the 311 parent PCE capability or not. Also, during the PCEP session 312 establishment procedure, the parent PCE needs to be capable of 313 indicating whether its parent capability can be provided or not. 315 A PCEP Speaker (Parent PCE or Child PCE or PCC) includes the "H-PCE 316 Capability" TLV, described in Section 3.1.1, in the OPEN Object to 317 advertise its support for PCEP extensions for H-PCE Capability. 319 2.3. PCE Domain Discovery 321 A PCE domain is a single domain with an associated PCE. Although it 322 is possible for a PCE to manage multiple domains simultaneously. The 323 PCE domain could be an IGP area or AS. 325 The PCE domain identifiers MAY be provided during the PCEP session 326 establishment procedure. 328 2.4. Domain Diversity 330 In a multi-domain environment, Domain Diversity is defined in 331 [RFC6805]. A pair of paths are domain-diverse if they do not 332 traverse any of the same transit domains. Domain diversity may be 333 maximized for a pair of paths by selecting paths that have the 334 smallest number of shared domains. Path computation should 335 facilitate the selection of domain diverse paths as a way to reduce 336 the risk of shared failure and automatically helps to ensure path 337 diversity for most of the route of a pair of LSPs. 339 The main motivation behind domain diversity is to avoid fate sharing, 340 but it can also be because of some geo-political reasons and 341 commercial relationships that would require domain diversity. for 342 example, a pair of paths should choose different transit Autonomous 343 System (AS) because of some policy considerations. 345 In case when full domain diversity could not be achieved, it is 346 helpful to minimize the common shared domains. Also it is 347 interesting to note that other scope of diversity (node, link, SRLG 348 etc) can still be applied inside the common shared domains. 350 3. PCEP Extensions 352 This section defines PCEP extensions to ([RFC5440]) so as to support 353 the H-PCE procedures. 355 3.1. OPEN object 357 Two new TLVs are defined in this document to be carried within an 358 OPEN object. This way, during PCEP session establishment, the H-PCE 359 capability and Domain information can be advertised. 361 3.1.1. H-PCE capability TLV 363 The H-PCE-CAPABILITY TLV is an optional TLV associated with the OPEN 364 Object [RFC5440] to exchange H-PCE capability of PCEP speakers. 366 Its format is shown in the following figure: 368 0 1 2 3 369 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 370 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 371 | Type= TBD1 | Length=4 | 372 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 373 | Flags |I|R| 374 +---------------------------------------------------------------+ 376 Figure 1: H-PCE-CAPABILITY TLV format 378 The type of the TLV is TBD1 (to be assigned by IANA) and it has a 379 fixed length of 4 octets. 381 The value comprises a single field - Flags (32 bits): 383 R (Parent PCE Request bit): if set, will signal that the child PCE 384 wishes to use the peer PCE as a parent PCE. 386 I (Parent PCE Indication bit): if set, will signal that the PCE 387 can be used as a parent PCE by the peer PCE. 389 The inclusion of this TLV in an OPEN object indicate that the H-PCE 390 extensions are supported by the PCEP speaker. The PCC MAY include 391 this TLV to indicate that it understands the H-PCE extensions. The 392 Child PCE MUST include this TLV and set the R flag (and unset the I 393 flag) on the PCEP session towards the Parent PCE. The Parent PCE 394 MUST include this TLV and set the I flag and unset the R flag on the 395 PCEP session towards the child PCE. The parent-child PCEP session is 396 set to be established only when this capability is advertised. 398 If such capability is not exchanged and the parent PCE receive a "H- 399 PCE path computation request", it MUST send a PCErr message with 400 Error-Type=TBD8 (H-PCE error) and Error-Value=1 (Parent PCE 401 Capability not advertised). 403 3.1.2. Domain-ID TLV 405 The Domain-ID TLV when used in OPEN object identify the domain(s) 406 served by the PCE. The child PCE uses this mechanism to inform the 407 domain information to the parent PCE. 409 The Domain-ID TLV is defined below: 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= TBD2 | Length | 415 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 416 | Domain Type | Reserved | 417 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 418 | Domain ID | 419 // // 420 | | 421 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 423 Figure 2: Domain-ID TLV format 425 The type of the TLV is TBD2 (to be assigned by IANA) and it has a 426 variable Length of the value portion. The value part comprises of - 428 Domain Type (8 bits): Indicates the domain type. Four types of 429 domain are currently defined: 431 * Type=1: the Domain ID field carries a 2-byte AS number. Padded 432 with trailing zeros to a 4-byte boundary. 434 * Type=2: the Domain ID field carries a 4-byte AS number. 436 * Type=3: the Domain ID field carries an 4-byte OSPF area ID. 438 * Type=4: the Domain ID field carries (2-byte Area-Len, variable 439 length IS-IS area ID). Padded with trailing zeros to a 4-byte 440 boundary. 442 Reserved: Zero at transmission; ignored at receipt. 444 Domain ID (variable): Indicates an IGP Area ID or AS number. It 445 can be 2 bytes, 4 bytes or variable length depending on the domain 446 identifier used. It is padded with trailing zeros to a 4-byte 447 boundary. 449 In case a PCE serves more than one domain, multiple Domain-ID TLV is 450 included for each domain it serves. 452 3.2. RP object 454 3.2.1. H-PCE-FLAG TLV 456 The H-PCE-FLAG TLV is an optional TLV associated with the RP Object 457 [RFC5440] to indicate the H-PCE path computation request and options. 459 Its format is shown in the following figure: 461 0 1 2 3 462 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 1 463 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 464 | Type= TBD3 | Length=4 | 465 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 466 | Flags |D|S| 467 +---------------------------------------------------------------+ 469 Figure 3: H-PCE-FLAG TLV format 471 The type of the TLV is TBD3 (to be assigned by IANA) and it has a 472 fixed length of 4 octets. 474 The value comprises a single field - Flags (32 bits): 476 S (Domain Sequence bit): if set, will signal that the child PCE 477 wishes to get only the domain sequence in the path computation 478 reply. Refer section 3.7 of [RFC7897] for details. 480 D (Disallow Domain Re-entry bit): if set, will signal that the 481 computed path does not enter a domain more than once. 483 3.2.2. Domain-ID TLV 485 The usage of Domain-ID TLV carried in an OPEN object is used to 486 indicate a (list of) managed domains and is described in 487 Section 3.1.2. This TLV when carried in a RP object, indicates the 488 destination domain ID. If a PCC knows the egress domain, it can 489 supply this information in the PCReq message. The format and 490 procedure of this TLV is defined in Section 3.1.2. 492 3.3. Objective Functions 494 3.3.1. OF Codes 496 [RFC5541] defines a mechanism to specify an objective function that 497 is used by a PCE when it computes a path. Two new objective 498 functions are defined for the H-PCE experiment. 500 o MTD 502 * Name: Minimize the number of Transit Domains (MTD) 504 * Objective Function Code - TBD4 (to be assigned by IANA) 505 * Description: Find a path P such that it passes through the 506 least number of transit domains. 508 * Objective functions are formulated using the following 509 terminology: 511 + A network comprises a set of N domains {Di, (i=1...N)}. 513 + A path P passes through K domains {Dpi,(i=1...K)}. 515 + Find a path P such that the value of K is minimized. 517 o MBN 519 * Name: Minimize the number of border nodes. 521 * Objective Function Code - TBD5 (to be assigned by IANA) 523 * Description: Find a path P such that it passes through the 524 least number of border nodes. 526 * Objective functions are formulated using the following 527 terminology: 529 + A network comprises a set of N nodes {Ni, (i=1...N)}. 531 + A path P is a list of K nodes {Npi,(i=1...K)}. 533 + B(N) if a function that determine if the node is a border 534 node. B(Ni) = 1 if Ni is border node; B(Nk) = 0 if Nk is 535 not a border node. 537 + The number of border node in a path P is denoted by B(P), 538 where B(P) = sum{B(Npi),(i=1...K)}. 540 + Find a path P such that B(P) is minimized. 542 MCTD 544 o Name: Minimize the number of Common Transit Domains. 546 o Objective Function Code: TBD13 548 o Description: Find a set of paths such that it passes through the 549 least number of common transit domains. 551 3.3.2. OF Object 553 The OF (Objective Function) object [RFC5541] is carried within a 554 PCReq message so as to indicate the desired/required objective 555 function to be applied by the PCE during path computation. As per 556 section 3.2 of [RFC5541] a single OF object may be included in a path 557 computation request. 559 The new OF code described in Section 3.3.1 are applicable at the 560 inter-domain level (parent), it is also necessary to specify the OF 561 code that may be applied at the intra-domain (child) path computation 562 level. To accommodate this, the OF-List TLV (described in section 563 2.1. of [RFC5541]) is included in the OF object as an optional TLV. 565 OF-List TLV allow encoding of multiple OF codes. When this TLV is 566 included inside the OF object, only the first OF-code in the OF-LIST 567 TLV is considered. The parent PCE MUST use this OF code in the OF 568 object when sending the intra domain path computation request to the 569 child PCE. 571 If the objective functions defined in this document are unknown/ 572 unsupported by a PCE, then the procedure as defined in [RFC5541] is 573 followed. 575 3.4. Metric Object 577 The METRIC object is defined in section 7.8 of [RFC5440], comprising 578 metric-value, metric-type (T field) and flags. This document defines 579 the following types for the METRIC object for H-PCE: 581 o T=TBD6: Domain count metric (number of domains crossed); 583 o T=TBD7: Border Node count metric (number of border nodes crossed). 585 The domain count metric type of the METRIC object encodes the number 586 of domain crossed in the path. The border node count metric type of 587 the METRIC object encodes the number of border nodes in the path. 589 A PCC or child PCE MAY use these metric in PCReq message an inter- 590 domain path meeting the number of domain or border nodes requirement. 591 As per [RFC5440], in this case, the B bit is set to suggest a bound 592 (a maximum) for the metric that must not be exceeded for the PCC to 593 consider the computed path as acceptable. 595 A PCC or child PCE MAY also use this metric to ask the PCE to 596 optimize the metric during inter-domain path computation. In this 597 case, the B flag is cleared. 599 The Parent PCE MAY use these metric in a PCRep message along with a 600 NO-PATH object in the case where the PCE cannot compute a path 601 meeting this constraint. A PCE MAY also use this metric to send the 602 computed end to end metric in a reply message. 604 3.5. SVEC Object 606 [RFC5440] defines SVEC object which includes flags for the potential 607 dependency between the set of path computation requests (Link, Node 608 and SRLG diverse). This document proposes a new flag O for domain 609 diversity. 611 Following new bit is added in the Flags field: 613 o O (Domain diverse) bit - TBD12 : when set, this indicates that the 614 computed paths corresponding to the requests specified by the 615 following RP objects MUST NOT have any transit domain(s) in 616 common. 618 The Domain Diverse O-bit can be used in Hierarchical PCE path 619 computation to compute synchronized domain diverse end to end path or 620 diverse domain sequences. 622 When domain diverse O bit is set, it is applied to the transit 623 domains. The other bit in SVEC object (N, L, S etc) MAY be set and 624 MUST still be applied in the ingress and egress shared domain. 626 3.6. PCEP-ERROR object 628 3.6.1. Hierarchy PCE Error-Type 630 A new PCEP Error-Type [RFC5440] is used for the H-PCE extension as 631 defined below: 633 +------------+-----------------------------------------+ 634 | Error-Type | Meaning | 635 +------------+-----------------------------------------+ 636 | TBD8 | H-PCE error | 637 | | Error-value=1: parent PCE capability | 638 | | was not advertised | 639 | | Error-value=2: parent PCE capability | 640 | | cannot be provided | 641 +------------+-----------------------------------------+ 643 Figure 4: H-PCE error 645 3.7. NO-PATH Object 647 To communicate the reason(s) for not being able to find a multi- 648 domain path or domain sequence, the NO-PATH object can be used in the 649 PCRep message. [RFC5440] defines the format of the NO-PATH object. 650 The object may contain a NO-PATH-VECTOR TLV to provide additional 651 information about why a path computation has failed. 653 Three new bit flags are defined to be carried in the Flags field in 654 the NO-PATH-VECTOR TLV carried in the NO-PATH Object. 656 o Bit number TBD9: When set, the parent PCE indicates that 657 destination domain unknown; 659 o Bit number TBD10: When set, the parent PCE indicates unresponsive 660 child PCE(s); 662 o Bit number TBD11: When set, the parent PCE indicates no available 663 resource available in one or more domain(s). 665 4. H-PCE Procedures 667 4.1. OPEN Procedure between Child PCE and Parent PCE 669 If a child PCE wants to use the peer PCE as a parent, it MUST set the 670 R (parent PCE request flag) in the H-PCE-CAPABILITY TLV inside the 671 OPEN object carried in the Open message during the PCEP session 672 initialization procedure. 674 If the parent PCE can provide the parent function to the peer PCE, it 675 MUST set the I (parent PCE indication flag) in the H-PCE-CAPABILITY 676 TLV inside the OPEN object carried in the Open message during the 677 PCEP session creation procedure. 679 The child PCE MAY also report its list of domain IDs to the parent 680 PCE by specifying them in the Domain-ID TLVs in the OPEN object 681 carried in the Open message during the PCEP session initialization 682 procedure. 684 The OF codes defined in this document can be carried in the OF-list 685 TLV of the OPEN object. If the OF-list TLV carries the OF codes, it 686 means that the PCE is capable of implementing the corresponding 687 objective functions. This information can be used for selecting a 688 proper parent PCE when a child PCE wants to get a path that satisfies 689 a certain objective function. 691 When a specific child PCE sends a PCReq to a peer PCE that requires 692 parental activity and H-PCE capability flags were not set in the 693 session establishment procedure as described above, the peer PCE 694 should send a PCErr message to the child PCE and specify the error- 695 type=TBD (H-PCE error) and error-value=1 (parent PCE capability was 696 not advertised) in the PCEP-ERROR object. 698 When a specific child PCE sends a PCReq to a peer PCE that requires 699 parental activity and the peer PCE does not want to act as the parent 700 for it, the peer PCE should send a PCErr message to the child PCE and 701 specify the error-type=TBD (H-PCE error) and error-value=2 (parent 702 PCE capability cannot be provided) in the PCEP-ERROR object. 704 4.2. Procedure to obtain Domain Sequence 706 If a child PCE only wants to get the domain sequence for a multi- 707 domain path computation from a parent PCE, it can set the Domain Path 708 Request bit in the H-PCE-FLAG TLV in the RP object carried in a PCReq 709 message. The parent PCE which receives the PCReq message tries to 710 compute a domain sequence for it (instead for E2E path). If the 711 domain path computation succeeds the parent PCE sends a PCRep message 712 which carries the domain sequence in the ERO to the child PCE. Refer 713 [RFC7897] for more details about domain sub-objects in the ERO. 714 Otherwise it sends a PCReq message which carries the NO-PATH object 715 to the child PCE. 717 5. Error Handling 719 A PCE that is capable of acting as a parent PCE might not be 720 configured or willing to act as the parent for a specific child PCE. 721 This fact could be determined when the child sends a PCReq that 722 requires parental activity, and could result in a negative response 723 in a PCEP Error (PCErr) message and indicate the hierarchy PCE error- 724 type=TBD8 (H-PCE error) and suitable error-value. (Section 3.6) 726 Additionally, the parent PCE may fail to find the multi-domain path 727 or domain sequence due to one or more of the following reasons: 729 o A child PCE cannot find a suitable path to the egress; 731 o The parent PCE do not hear from a child PCE for a specified time; 733 o The objective functions specified in the path request cannot be 734 met. 736 In this case, the parent PCE MAY need to send a negative path 737 computation reply specifying the reason. This can be achieved by 738 including NO-PATH object in the PCRep message. Extension to NO-PATH 739 object is needed to include the aforementioned reasons described in 740 Section 3.7. 742 6. Manageability Considerations 744 General PCE and PCEP management considerations are discussed in 745 [RFC4655] and [RFC5440]. There are additional management 746 considerations for H-PCE which are described in [RFC6805], and 747 repeated in this section. 749 The administrative entity responsible for the management of the 750 parent PCEs must be determined for the following cases: 752 o multi-domains (e.g., IGP areas or multiple ASes) within a single 753 service provider network, the management responsibility for the 754 parent PCE would most likely be handled by the service provider, 756 o multiple ASes within different service provider networks, it may 757 be necessary for a third party to manage the parent PCEs according 758 to commercial and policy agreements from each of the participating 759 service providers. 761 6.1. Control of Function and Policy 763 Control and function will need to be carefully managed in a H-PCE 764 network. A child PCE will need to be configured with the address of 765 its parent PCE. It is expected that there will only be one or two 766 parents of any child. 768 The parent PCE also needs to be aware of the child PCEs for all child 769 domains that it can see. This information is most likely to be 770 configured (as part of the administrative definition of each domain). 772 Discovery of the relationships between parent PCEs and child PCEs 773 does not form part of the hierarchical PCE architecture. Mechanisms 774 that rely on advertising or querying PCE locations across domain or 775 provider boundaries are undesirable for security, scaling, 776 commercial, and confidentiality reasons. Specific behavior of the 777 child and parent PCE are described in the following sub-sections. 779 6.1.1. Child PCE 781 Support of the hierarchical procedure will be controlled by the 782 management organization responsible for each child PCE. A child PCE 783 must be configured with the address of its parent PCE in order for it 784 to interact with its parent PCE. The child PCE must also be 785 authorized to peer with the parent PCE. 787 6.1.2. Parent PCE 789 The parent PCE must only accept path computation requests from 790 authorized child PCEs. If a parent PCE receives requests from an 791 unauthorized child PCE, the request should be dropped. This means 792 that a parent PCE must be configured with the identities and security 793 credentials of all of its child PCEs, or there must be some form of 794 shared secret that allows an unknown child PCE to be authorized by 795 the parent PCE. 797 6.1.3. Policy Control 799 It may be necessary to maintain a policy module on the parent PCE 800 [RFC5394]. This would allow the parent PCE to apply commercially 801 relevant constraints such as SLAs, security, peering preferences, and 802 monetary costs. 804 It may also be necessary for the parent PCE to limit end-to-end path 805 selection by including or excluding specific domains based on 806 commercial relationships, security implications, and reliability. 808 6.2. Information and Data Models 810 A MIB module for PCEP was published as RFC 7420 [RFC7420] that 811 describes managed objects for modeling of PCEP communication. A YANG 812 module for PCEP has also been proposed [I-D.ietf-pce-pcep-yang]. 814 A H-PCE MIB module, or additional data model, will be required to 815 report parent PCE and child PCE information, including: 817 o parent PCE configuration and status, 819 o child PCE configuration and information, 821 o notifications to indicate session changes between parent PCEs and 822 child PCEs, and 824 o notification of parent PCE TED updates and changes. 826 6.3. Liveness Detection and Monitoring 828 The hierarchical procedure requires interaction with multiple PCEs. 829 Once a child PCE requests an end-to-end path, a sequence of events 830 occurs that requires interaction between the parent PCE and each 831 child PCE. If a child PCE is not operational, and an alternate 832 transit domain is not available, then a failure must be reported. 834 6.4. Verify Correct Operations 836 Verifying the correct operation of a parent PCE can be performed by 837 monitoring a set of parameters. The parent PCE implementation should 838 provide the following parameters monitored by the parent PCE: 840 o number of child PCE requests, 842 o number of successful hierarchical PCE procedures completions on a 843 per-PCE-peer basis, 845 o number of hierarchical PCE procedure completion failures on a per- 846 PCE-peer basis, and 848 o number of hierarchical PCE procedure requests from unauthorized 849 child PCEs. 851 6.5. Requirements On Other Protocols 853 Mechanisms defined in this document do not imply any new requirements 854 on other protocols. 856 6.6. Impact On Network Operations 858 The hierarchical PCE procedure is a multiple-PCE path computation 859 scheme. Subsequent requests to and from the child and parent PCEs do 860 not differ from other path computation requests and should not have 861 any significant impact on network operations. 863 7. IANA Considerations 865 7.1. PCEP TLV Type Indicators 867 IANA Manages the PCEP TLV code point registry (see [RFC5440]). This 868 is maintained as the "PCEP TLV Type Indicators" sub-registry of the 869 "Path Computation Element Protocol (PCEP) Numbers" registry. 871 This document defines three new PCEP TLVs. IANA is requested to make 872 the following allocation: 874 Type TLV name References 875 ----------------------------------------------- 876 TBD1 H-PCE-CAPABILITY TLV This I-D 877 TBD2 Domain-ID TLV This I-D 878 TBD3 H-PCE-FLAG TLV This I-D 880 7.2. H-PCE-CAPABILITY TLV Flags 882 This document requests that a new sub-registry, named " H-PCE- 883 CAPABILITY TLV Flag Field", is created within the "Path Computation 884 Element Protocol (PCEP) Numbers" registry to manage the Flag field in 885 the H-PCE-CAPABILITY TLV of the PCEP OPEN object. 887 New values are to be assigned by Standards Action [RFC5226]. Each 888 bit should be tracked with the following qualities: 890 o Bit number (counting from bit 0 as the most significant bit) 892 o Capability description 894 o Defining RFC 896 The following values are defined in this document: 898 Bit Description Reference 899 -------------------------------------------------- 900 31 R (Parent PCE Request bit) This I.D. 901 30 I (Parent PCE Indication bit) This I.D. 903 7.3. Domain-ID TLV Domain type 905 This document requests that a new sub-registry, named " Domain-ID TLV 906 Domain type", is created within the "Path Computation Element 907 Protocol (PCEP) Numbers" registry to manage the Domain-Type field of 908 the Domain-ID TLV. 910 Value Meaning 911 ----------------------------------------------- 912 1 2-byte AS number 913 2 4-byte AS number 914 3 4-byte OSPF area ID 915 4 Variable length IS-IS area ID 917 7.4. H-PCE-FLAG TLV Flags 919 This document requests that a new sub-registry, named "H-PCE-FLAGS 920 TLV Flag Field", is created within the "Path Computation Element 921 Protocol (PCEP) Numbers" registry to manage the Flag field in the H- 922 PCE-FLAGS TLV of the PCEP RP object. New values are to be assigned 923 by Standards Action [RFC5226]. Each bit should be tracked with the 924 following qualities: 926 o Bit number (counting from bit 0 as the most significant bit) 927 o Capability description 929 o Defining RFC 931 The following values are defined in this document: 933 Bit Description Reference 934 ----------------------------------------------- 935 31 S (Domain This I.D. 936 Sequence bit) 937 30 D (Disallow Domain This I.D. 938 Re-entry bit) 940 7.5. OF Codes 942 IANA maintains registry of Objective Function (described in 943 [RFC5541]) at the sub-registry "Objective Function". Two new 944 Objective Functions have been defined in this document. 946 IANA is requested to make the following allocations: 948 Code 949 Point Name Reference 950 ------------------------------------------------------ 951 TBD4 Minimum number of Transit This I.D. 952 Domains (MTD) 953 TBD5 Minimize number of Border This I.D. 954 Nodes (MBN) 955 TBD13 Minimize the number of This I.D. 956 Common Transit Domains. 957 (MCTD) 959 7.6. METRIC Types 961 IANA maintains one sub-registry for "METRIC object T field". Two new 962 metric types are defined in this document for the METRIC object 963 (specified in [RFC5440]). 965 IANA is requested to make the following allocations: 967 Value Description Reference 968 ---------------------------------------------------------- 969 TBD6 Domain Count metric This I.D. 970 TBD7 Border Node Count metric This I.D. 972 7.7. New PCEP Error-Types and Values 974 IANA maintains a registry of Error-Types and Error-values for use in 975 PCEP messages. This is maintained as the "PCEP-ERROR Object Error 976 Types and Values" sub-registry of the "Path Computation Element 977 Protocol (PCEP) Numbers" registry. 979 IANA is requested to make the following allocations: 981 Error-Type Meaning and error values Reference 982 ------------------------------------------------------ 983 TBD8 H-PCE Error This I.D. 985 Error-value=1 Parent PCE 986 Capability not advertised 988 Error-value=2 Parent PCE 989 Capability not supported 991 7.8. New NO-PATH-VECTOR TLV Bit Flag 993 IANA maintains a registry of bit flags carried in the PCEP NO-PATH- 994 VECTOR TLV in the PCEP NO-PATH object as defined in [RFC5440]. IANA 995 Is requested to assign three new bit flag as follows: 997 Bit Number Name Flag Reference 998 ------------------------------------------------------ 999 TBD9 Destination Domain unknown This I.D. 1000 TBD10 Unresponsive child PCE(s) This I.D. 1001 TBD11 No available resource in This I.D. 1002 one or more domain 1004 7.9. SVEC Flag 1006 IANA maintains a registry of bit flags carried in the PCEP SVEC 1007 object as defined in [RFC5440]. IANA Is requested to assign one new 1008 bit flag as follows: 1010 Bit Number Name Flag Reference 1011 ------------------------------------------------------ 1012 TBD13 Domain Diverse This I.D. 1014 8. Security Considerations 1016 The hierarchical PCE procedure relies on PCEP and inherits the 1017 security requirements defined in [RFC5440]. As PCEP operates over 1018 TCP, it may also make use of TCP security mechanisms, such as TCP-AO 1019 or [RFC8253]. 1021 H-PCE operation also relies on information used to build the TED. 1022 Attacks on a parent or child PCE may be achieved by falsifying or 1023 impeding this flow of information. If the child PCE listens to the 1024 IGP or BGP-LS for populating the TED, then normal IGP or BGP-LS 1025 security measures may be applied, and it should be noted that an IGP 1026 routing system is generally assumed to be a trusted domain such that 1027 router subversion is not a risk. The parent PCE TED is constructed 1028 as described in this document and may involve: 1030 o multiple parent-child relationships using PCEP 1032 o the parent PCE listening to child domain IGPs (with the same 1033 security features as a child PCE listening to its IGP) 1035 o an external mechanism (such as [RFC7752]), which will need to be 1036 authorized and secured. 1038 Any multi-domain operation necessarily involves the exchange of 1039 information across domain boundaries. This is bound to represent a 1040 significant security and confidentiality risk especially when the 1041 child domains are controlled by different commercial concerns. PCEP 1042 allows individual PCEs to maintain confidentiality of their domain 1043 path information using path-keys [RFC5520], and the H-PCE 1044 architecture is specifically designed to enable as much isolation of 1045 domain topology and capabilities information as is possible. 1047 For further considerations of the security issues related to inter-AS 1048 path computation, see [RFC5376]. 1050 9. Implementation Status 1052 The H-PCE architecture and protocol procedures describe in this I-D 1053 were implemented and tested for a variety of optical research 1054 applications. 1056 9.1. Inter-layer traffic engineering with H-PCE 1058 This work was led by: 1060 o Ramon Casellas [ramon.casellas@cttc.es] 1061 o Centre Tecnologic de Telecomunicacions de Catalunya (CTTC) 1063 The H-PCE instances (parent and child) were multi-threaded 1064 asynchronous processes. Implemented in C++11, using C++ Boost 1065 Libraries. The targeted system used to deploy and run H-PCE 1066 applications was a POSIX system (Debian GNU/Linux operating system). 1068 Some parts of the software may require a Linux Kernel, the 1069 availability of a Routing Controller running collocated in the same 1070 host and the usage of libnetfilter / libipq and GNU/Linux firewalling 1071 capabilities. Most of the functionality, including algorithms is 1072 done by means of plugins (e.g., as shared libraries or .so files in 1073 Unix systems). 1075 The CTTC PCE supports the H-PCE architecture, but also supports 1076 stateful PCE with active capabilities, as an OpenFlow controller, and 1077 has dedicated plugins to support monitoring, BRPC, P2MP, path keys, 1078 back end PCEs. Management of the H-PCE entities was supported via 1079 HTTP and CLI via Telnet. 1081 Further details of the H-PCE prototyping and experimentation can be 1082 found in the following scientific papers: 1084 R. Casellas, R. Martinez, R. Munoz, L. Liu, T. Tsuritani, I. 1085 Morita, "Inter-layer traffic engineering with hierarchical-PCE in 1086 MPLS-TP over wavelength switched optical networks" , Optics 1087 Express, Vol. 20, No. 28, December 2012. 1089 R. Casellas, R. Martinez, R. Munoz, L. Liu, T. Tsuritani, I. 1090 Morita, M. Msurusawa, "Dynamic virtual link mesh topology 1091 aggregation in multi-domain translucent WSON with hierarchical- 1092 PCE", Optics Express Journal, Vol. 19, No. 26, December 2011. 1094 R. Casellas, R. Munoz, R. Martinez, R. Vilalta, L. Liu, T. 1095 Tsuritani, I. Morita, V. Lopez, O. Gonzalez de Dios, J. P. 1096 Fernandez-Palacios, "SDN based Provisioning Orchestration of 1097 OpenFlow/GMPLS Flexi-grid Networks with a Stateful Hierarchical 1098 PCE", in Proceedings of Optical Fiber Communication Conference and 1099 Exposition (OFC), 9-13 March, 2014, San Francisco (EEUU). 1100 Extended Version to appear in Journal Of Optical Communications 1101 and Networking January 2015 1103 F. Paolucci, O. Gonzalez de Dios, R. Casellas, S. Duhovnikov, 1104 P. Castoldi, R. Munoz, R. Martinez, "Experimenting Hierarchical 1105 PCE Architecture in a Distributed Multi-Platform Control Plane 1106 Testbed" , in Proceedings of Optical Fiber Communication 1107 Conference and Exposition (OFC) and The National Fiber Optic 1108 Engineers Conference (NFOEC), 4-8 March, 2012, Los Angeles, 1109 California (USA). 1111 R. Casellas, R. Martinez, R. Munoz, L. Liu, T. Tsuritani, I. 1112 Morita, M. Tsurusawa, "Dynamic Virtual Link Mesh Topology 1113 Aggregation in Multi-Domain Translucent WSON with Hierarchical- 1114 PCE", in Proceedings of 37th European Conference and Exhibition on 1115 Optical Communication (ECOC 2011), 18-22 September 2011, Geneve ( 1116 Switzerland). 1118 R. Casellas, R. Munoz, R. Martinez, "Lab Trial of Multi-Domain 1119 Path Computation in GMPLS Controlled WSON Using a Hierarchical 1120 PCE", in Proceedings of OFC/NFOEC Conference (OFC2011), 10 March 1121 2011, Los Angeles (USA). 1123 9.2. Telefonica Netphony (Open Source PCE) 1125 The Telefonica Netphony PCE is an open source Java-based 1126 implementation of a Path Computation Element, with several flavours, 1127 and a Path Computation Client. The PCE follows a modular 1128 architecture and allows to add customized algorithms. The PCE has 1129 also stateful and remote initiation capabilities. In current 1130 version, three components can be built, a domain PCE (aka child PCE), 1131 a parent PCE (ready for the H-PCE architecture) and a PCC (path 1132 computation client). 1134 This work was led by: 1136 o Oscar Gonzalez de Dios [oscar.gonzalezdedios@telefonica.com] 1138 o Victor Lopez Alvarez [victor.lopezalvarez@telefonica.com] 1140 o Telefonica I+D, Madrid, Spain 1142 The PCE code is publicly available in a GitHub repository: 1144 o https://github.com/telefonicaid/netphony-pce 1146 The PCEP protocol encodings are located in the following repository: 1148 o https://github.com/telefonicaid/netphony-network protocols 1150 The traffic engineering database and a BGP-LS speaker to fill the 1151 database is located in: 1153 o https://github.com/telefonicaid/netphony-topology 1154 The parent and child PCE are multi-threaded java applications. The 1155 path computation uses the jgrapht free Java class library (0.9.1) 1156 that provides mathematical graph-theory objects and algorithms. 1157 Current version of netphony PCE runs on java 1.7 and 1.8, and has 1158 been tested in GNU/Linux, Mac OS-X and Windows environments. The 1159 management of the parent and domain PCEs is supported though CLI via 1160 Telnet, and configured via XML files. 1162 Further details of the netphony H-PCE prototyping and experimentation 1163 can be found in the following research papers: 1165 o O. Gonzalez de Dios, R. Casellas, F. Paolucci, A. Napoli, L. 1166 Gifre, A. Dupas, E, Hugues-Salas, R. Morro, S. Belotti, G. 1167 Meloni, T. Rahman, V.P Lopez, R. Martinez, F. Fresi, M. Bohn, 1168 S. Yan, L. Velasco, . Layec and J. P. Fernandez-Palacios: 1169 Experimental Demonstration of Multivendor and Multidomain EON With 1170 Data and Control Interoperability Over a Pan-European Test Bed, in 1171 Journal of Lightwave Technology, Dec. 2016, Vol. 34, Issue 7, pp. 1172 1610-1617. 1174 o O. Gonzalez de Dios, R. Casellas, R. Morro, F. Paolucci, V. 1175 Lopez, R. Martinez, R. Munoz, R. Villalta, P. Castoldi: 1176 "Multi-partner Demonstration of BGP-LS enabled multi-domain EON, 1177 in Journal of Optical Communications and Networking, Dec. 2015, 1178 Vol. 7, Issue 12, pp. B153-B162. 1180 o F. Paolucci, O. Gonzalez de Dios, R. Casellas, S. Duhovnikov, 1181 P. Castoldi, R. Munoz, R. Martinez, "Experimenting Hierarchical 1182 PCE Architecture in a Distributed Multi-Platform Control Plane 1183 Testbed" , in Proceedings of Optical Fiber Communication 1184 Conference and Exposition (OFC) and The National Fiber Optic 1185 Engineers Conference (NFOEC), 4-8 March, 2012, Los Angeles, 1186 California (USA). 1188 9.3. Implementation 3: H-PCE Proof of Concept developed by Huawei 1190 Huawei developed this H-PCE on the Huawei Versatile Routing Platform 1191 (VRP) to experiment with the hierarchy of PCE. Both end to end path 1192 computation as well as computation for domain-sequence are supported. 1194 This work was led by: 1196 o Udayasree Pallee [udayasreereddy@gmail.com] 1198 o Dhruv Dhody [dhruv.ietf@gmail.com] 1200 o Huawei Technologies, Bangalore, India 1201 Further work on stateful H-PCE [I-D.ietf-pce-stateful-hpce] is being 1202 carried out on ONOS. 1204 10. Contributing Authors 1206 Xian Zhang 1207 Huawei 1208 EMail: zhang.xian@huawei.com 1210 Dhruv Dhody 1211 Huawei Technologies 1212 Divyashree Techno Park, Whitefield 1213 Bangalore, Karnataka 560066 1214 India 1216 EMail: dhruv.ietf@gmail.com 1218 11. References 1220 11.1. Normative References 1222 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1223 Requirement Levels", BCP 14, RFC 2119, 1224 DOI 10.17487/RFC2119, March 1997, 1225 . 1227 [RFC5152] Vasseur, JP., Ed., Ayyangar, A., Ed., and R. Zhang, "A 1228 Per-Domain Path Computation Method for Establishing Inter- 1229 Domain Traffic Engineering (TE) Label Switched Paths 1230 (LSPs)", RFC 5152, DOI 10.17487/RFC5152, February 2008, 1231 . 1233 [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation 1234 Element (PCE) Communication Protocol (PCEP)", RFC 5440, 1235 DOI 10.17487/RFC5440, March 2009, 1236 . 1238 [RFC5541] Le Roux, JL., Vasseur, JP., and Y. Lee, "Encoding of 1239 Objective Functions in the Path Computation Element 1240 Communication Protocol (PCEP)", RFC 5541, 1241 DOI 10.17487/RFC5541, June 2009, 1242 . 1244 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 1245 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 1246 May 2017, . 1248 11.2. Informative References 1250 [RFC4105] Le Roux, J., Ed., Vasseur, J., Ed., and J. Boyle, Ed., 1251 "Requirements for Inter-Area MPLS Traffic Engineering", 1252 RFC 4105, DOI 10.17487/RFC4105, June 2005, 1253 . 1255 [RFC4216] Zhang, R., Ed. and J. Vasseur, Ed., "MPLS Inter-Autonomous 1256 System (AS) Traffic Engineering (TE) Requirements", 1257 RFC 4216, DOI 10.17487/RFC4216, November 2005, 1258 . 1260 [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation 1261 Element (PCE)-Based Architecture", RFC 4655, 1262 DOI 10.17487/RFC4655, August 2006, 1263 . 1265 [RFC4726] Farrel, A., Vasseur, J., and A. Ayyangar, "A Framework for 1266 Inter-Domain Multiprotocol Label Switching Traffic 1267 Engineering", RFC 4726, DOI 10.17487/RFC4726, November 1268 2006, . 1270 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 1271 IANA Considerations Section in RFCs", RFC 5226, 1272 DOI 10.17487/RFC5226, May 2008, 1273 . 1275 [RFC5376] Bitar, N., Zhang, R., and K. Kumaki, "Inter-AS 1276 Requirements for the Path Computation Element 1277 Communication Protocol (PCECP)", RFC 5376, 1278 DOI 10.17487/RFC5376, November 2008, 1279 . 1281 [RFC5394] Bryskin, I., Papadimitriou, D., Berger, L., and J. Ash, 1282 "Policy-Enabled Path Computation Framework", RFC 5394, 1283 DOI 10.17487/RFC5394, December 2008, 1284 . 1286 [RFC5520] Bradford, R., Ed., Vasseur, JP., and A. Farrel, 1287 "Preserving Topology Confidentiality in Inter-Domain Path 1288 Computation Using a Path-Key-Based Mechanism", RFC 5520, 1289 DOI 10.17487/RFC5520, April 2009, 1290 . 1292 [RFC5441] Vasseur, JP., Ed., Zhang, R., Bitar, N., and JL. Le Roux, 1293 "A Backward-Recursive PCE-Based Computation (BRPC) 1294 Procedure to Compute Shortest Constrained Inter-Domain 1295 Traffic Engineering Label Switched Paths", RFC 5441, 1296 DOI 10.17487/RFC5441, April 2009, 1297 . 1299 [RFC6805] King, D., Ed. and A. Farrel, Ed., "The Application of the 1300 Path Computation Element Architecture to the Determination 1301 of a Sequence of Domains in MPLS and GMPLS", RFC 6805, 1302 DOI 10.17487/RFC6805, November 2012, 1303 . 1305 [RFC7420] Koushik, A., Stephan, E., Zhao, Q., King, D., and J. 1306 Hardwick, "Path Computation Element Communication Protocol 1307 (PCEP) Management Information Base (MIB) Module", 1308 RFC 7420, DOI 10.17487/RFC7420, December 2014, 1309 . 1311 [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and 1312 S. Ray, "North-Bound Distribution of Link-State and 1313 Traffic Engineering (TE) Information Using BGP", RFC 7752, 1314 DOI 10.17487/RFC7752, March 2016, 1315 . 1317 [RFC7897] Dhody, D., Palle, U., and R. Casellas, "Domain Subobjects 1318 for the Path Computation Element Communication Protocol 1319 (PCEP)", RFC 7897, DOI 10.17487/RFC7897, June 2016, 1320 . 1322 [RFC8253] Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody, 1323 "PCEPS: Usage of TLS to Provide a Secure Transport for the 1324 Path Computation Element Communication Protocol (PCEP)", 1325 RFC 8253, DOI 10.17487/RFC8253, October 2017, 1326 . 1328 [I-D.ietf-pce-pcep-yang] 1329 Dhody, D., Hardwick, J., Beeram, V., and J. Tantsura, "A 1330 YANG Data Model for Path Computation Element 1331 Communications Protocol (PCEP)", draft-ietf-pce-pcep- 1332 yang-08 (work in progress), June 2018. 1334 [I-D.ietf-pce-stateful-hpce] 1335 Dhody, D., Lee, Y., Ceccarelli, D., Shin, J., King, D., 1336 and O. Dios, "Hierarchical Stateful Path Computation 1337 Element (PCE).", draft-ietf-pce-stateful-hpce-05 (work in 1338 progress), June 2018. 1340 Authors' Addresses 1342 Fatai Zhang 1343 Huawei 1344 Huawei Base, Bantian, Longgang District 1345 Shenzhen 518129 1346 China 1348 EMail: zhangfatai@huawei.com 1350 Quintin Zhao 1351 Huawei 1352 125 Nagog Technology Park 1353 Acton, MA 01719 1354 USA 1356 EMail: quintin.zhao@huawei.com 1358 Oscar Gonzalez de Dios 1359 Telefonica I+D 1360 Don Ramon de la Cruz 82-84 1361 Madrid 28045 1362 Spain 1364 EMail: ogondio@tid.es 1366 Ramon Casellas 1367 CTTC 1368 Av. Carl Friedrich Gauss n.7 1369 Barcelona, Castelldefels 1370 Spain 1372 EMail: ramon.casellas@cttc.es 1374 Daniel King 1375 Old Dog Consulting 1376 UK 1378 EMail: daniel@olddog.co.uk