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Checking references for intended status: Informational ---------------------------------------------------------------------------- == Outdated reference: A later version (-11) exists of draft-ietf-pce-pce-initiated-lsp-10 == Outdated reference: A later version (-15) exists of draft-ietf-teas-actn-framework-06 == Outdated reference: A later version (-12) exists of draft-ietf-pce-applicability-actn-00 == Outdated reference: A later version (-10) exists of draft-litkowski-pce-state-sync-01 == Outdated reference: A later version (-11) exists of draft-ietf-pce-hierarchy-extensions-03 == Outdated reference: A later version (-18) exists of draft-ietf-pce-pceps-14 Summary: 0 errors (**), 0 flaws (~~), 7 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 PCE Working Group D. Dhody 3 Internet-Draft Y. Lee 4 Intended status: Informational Huawei Technologies 5 Expires: December 31, 2017 D. Ceccarelli 6 Ericsson 7 J. Shin 8 SK Telecom 9 D. King 10 Lancaster University 11 O. Gonzalez de Dios 12 Telefonica I+D 13 June 29, 2017 15 Hierarchical Stateful Path Computation Element (PCE). 16 draft-ietf-pce-stateful-hpce-01 18 Abstract 20 A Stateful Path Computation Element (PCE) maintains information on 21 the current network state, including: computed Label Switched Path 22 (LSPs), reserved resources within the network, and pending path 23 computation requests. This information may then be considered when 24 computing new traffic engineered LSPs, and for associated 25 and dependent LSPs, received from Path Computation Clients (PCCs). 27 The Hierarchical Path Computation Element (H-PCE) architecture, 28 provides an architecture to allow the optimum sequence of 29 inter-connected domains to be selected, and network policy to be 30 applied if applicable, via the use of a hierarchical relationship 31 between PCEs. 33 Combining the capabilities of Stateful PCE and the Hierarchical PCE 34 would be advantageous. This document describes general considerations 35 and use cases for the deployment of Stateful PCE(s) using the 36 Hierarchical PCE architecture. 38 Status of This Memo 40 This Internet-Draft is submitted in full conformance with the 41 provisions of BCP 78 and BCP 79. 43 Internet-Drafts are working documents of the Internet Engineering 44 Task Force (IETF). Note that other groups may also distribute 45 working documents as Internet-Drafts. The list of current Internet- 46 Drafts is at http://datatracker.ietf.org/drafts/current/. 48 Internet-Drafts are draft documents valid for a maximum of six months 49 and may be updated, replaced, or obsoleted by other documents at any 50 time. It is inappropriate to use Internet-Drafts as reference 51 material or to cite them other than as "work in progress." 53 Copyright Notice 55 Copyright (c) 2017 IETF Trust and the persons identified as the 56 document authors. All rights reserved. 58 This document is subject to BCP 78 and the IETF Trust's Legal 59 Provisions Relating to IETF Documents 60 (http://trustee.ietf.org/license-info) in effect on the date of 61 publication of this document. Please review these documents 62 carefully, as they describe your rights and restrictions with respect 63 to this document. Code Components extracted from this document must 64 include Simplified BSD License text as described in Section 4.e of 65 the Trust Legal Provisions and are provided without warranty as 66 described in the Simplified BSD License. 68 Table of Contents 70 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 71 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 72 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 73 3. Hierarchical Stateful PCE . . . . . . . . . . . . . . . . . . 4 74 3.1. Passive Operations . . . . . . . . . . . . . . . . . . . 4 75 3.2. Active Operations . . . . . . . . . . . . . . . . . . . . 7 76 3.3. PCE Initiation Operation . . . . . . . . . . . . . . . . 8 77 3.3.1. Per Domain Stitched LSP . . . . . . . . . . . . . . . 8 78 4. Other Considerations . . . . . . . . . . . . . . . . . . . . 10 79 4.1. Applicability to Inter-Layer . . . . . . . . . . . . . . 10 80 4.2. Applicability to ACTN . . . . . . . . . . . . . . . . . . 11 81 5. Security Considerations . . . . . . . . . . . . . . . . . . . 12 82 6. Manageability Considerations . . . . . . . . . . . . . . . . 12 83 6.1. Control of Function and Policy . . . . . . . . . . . . . 12 84 6.2. Information and Data Models . . . . . . . . . . . . . . . 12 85 6.3. Liveness Detection and Monitoring . . . . . . . . . . . . 12 86 6.4. Verify Correct Operations . . . . . . . . . . . . . . . . 12 87 6.5. Requirements On Other Protocols . . . . . . . . . . . . . 12 88 6.6. Impact On Network Operations . . . . . . . . . . . . . . 12 89 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 90 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12 91 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 92 9.1. Normative References . . . . . . . . . . . . . . . . . . 12 93 9.2. Informative References . . . . . . . . . . . . . . . . . 13 94 Appendix A. Contributor Addresses . . . . . . . . . . . . . . . 14 95 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14 97 1. Introduction 99 The Path Computation Element communication Protocol (PCEP) provides 100 mechanisms for Path Computation Elements (PCEs) to perform path 101 computations in response to Path Computation Clients' (PCCs) 102 requests. 104 A stateful PCE is capable of considering, for the purposes of 105 path computation, not only the network state in terms of links and 106 nodes (referred to as the Traffic Engineering Database or TED) but 107 also the status of active services (previously computed paths, 108 and currently reserved resources, stored in the Label Switched 109 Paths Database (LSPDB). 111 [RFC8051] describes general considerations for a stateful PCE 112 deployment and examines its applicability and benefits, as well as 113 its challenges and limitations through a number of use cases. 115 [I-D.ietf-pce-stateful-pce] describes a set of extensions to PCEP to 116 provide stateful control. A stateful PCE has access to not only the 117 information carried by the network's Interior Gateway Protocol (IGP), 118 but also the set of active paths and their reserved resources for its 119 computations. The additional state allows the PCE to compute 120 constrained paths while considering individual LSPs and their 121 interactions. [I-D.ietf-pce-pce-initiated-lsp] describes the setup, 122 maintenance and teardown of PCE-initiated LSPs under the stateful PCE 123 model. 125 [I-D.ietf-pce-stateful-pce] also describes the active stateful PCE. 126 The active PCE functionality allows a PCE to reroute an existing 127 LSP or make changes to the attributes of an existing LSP, or delegate 128 control of specific LSPs to a new PCE. 130 The ability to compute shortest constrained TE LSPs in Multiprotocol 131 Label Switching (MPLS) and Generalized MPLS (GMPLS) networks across 132 multiple domains has been identified as a key motivation for PCE 133 development. [RFC6805] describes a Hierarchical PCE (H-PCE) 134 architecture which can be used for computing end-to-end paths for 135 inter-domain MPLS Traffic Engineering (TE) and GMPLS Label Switched 136 Paths (LSPs). Within the Hierarchical PCE (H-PCE) architecture 137 [RFC6805], the Parent PCE (P-PCE) is used to compute a multi-domain 138 path based on the domain connectivity information. A Child PCE 139 (C-PCE) may be responsible for a single domain or multiple domains, 140 it is used to compute the intra-domain path based on its domain 141 topology information. 143 This document presents general considerations for stateful PCE(s) in 144 hierarchical PCE architecture. In particular, the behavior changes 145 and additions to the existing stateful PCE mechanisms (including PCE- 146 initiated LSP setup and active PCE usage) in the context of networks 147 using the H-PCE architecture. 149 1.1. Requirements Language 151 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 152 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 153 document are to be interpreted as described in [RFC2119]. 155 2. Terminology 157 The terminology is as per [RFC4655], [RFC5440], [RFC6805], and 158 [I-D.ietf-pce-stateful-pce]. 160 3. Hierarchical Stateful PCE 162 As described in [RFC6805], in the hierarchical PCE architecture, a 163 P-PCE maintains a domain topology map that contains the child domains 164 (seen as vertices in the topology) and their interconnections (links 165 in the topology). The P-PCE has no information about the content of 166 the child domains. Each child domain has at least one PCE capable of 167 computing paths across the domain. These PCEs are known as C-PCEs 168 and have a direct relationship with the P-PCE. The P-PCE builds the 169 domain topology map either via direct configuration (allowing network 170 policy to also be applied) or from learned information received from 171 each C-PCE. 173 [I-D.ietf-pce-stateful-pce] specifies new functions to support a 174 stateful PCE. It also specifies that a function can be initiated 175 either from a PCC towards a PCE (C-E) or from a PCE towards a PCC 176 (E-C). 178 This document extends these functions to support H-PCE Architecture 179 from a C-PCE towards a P-PCE (CE-PE) or from a P-PCE 180 towards a C-PCE (PE-CE). All PCE types herein (i.e., PE or CE) 181 are assumed to be 'stateful PCE'. 183 A number of interactions are expected in the Hierarchical Stateful 184 PCE architecture, these include: 186 LSP State Report (CE-PE): a child stateful PCE sends an LSP state 187 report to a Parent Stateful PCE whenever the state of a LSP 188 changes. 190 LSP State Synchronization (CE-PE): after the session between the 191 Child and Parent stateful PCEs is initialized, the P-PCE must 192 learn the state of C-PCE's TE LSPs. 194 LSP Control Delegation (CE-PE,PE-CE): a C-PCE grants to the 195 P-PCE the right to update LSP attributes on one or more LSPs; 196 the C-PCE may withdraw the delegation or the P-PCE may 197 give up the delegation at any time. 199 LSP Update Request (PE-CE): a stateful P-PCE requests 200 modification of attributes on a C-PCE's TE LSP. 202 PCE LSP Initiation Request (PE-CE): a stateful P-PCE requests 203 C-PCE to initiate a TE LSP. 205 Note that this hierarchy is recursive and thus a LSR could delegate 206 the control to a PCE, which may delegate to its parent, which may 207 further delegate it to its parent (if it exist or needed). Similarly 208 update operations could also be applied recursively. 210 [I-D.ietf-pce-hierarchy-extensions] defines the H-PCE capability TLV 211 that should be used in the OPEN message to advertise the H-PCE 212 capability. [I-D.ietf-pce-stateful-pce] defines the stateful PCE 213 capability TLV. The presence of both TLVs represent the support for 214 stateful H-PCE operations as described in this document. 216 [I-D.litkowski-pce-state-sync] describes the procedures to allow a 217 stateful communication between PCEs for various use-cases. The 218 procedures and extensions as described in Section 3 of 219 [I-D.litkowski-pce-state-sync] are also applicable to Child and 220 Parent PCE communication. 222 3.1. Passive Operations 224 Procedures as described in [RFC6805] are applied, where the ingress 225 C-PCE sends a request to the P-PCE. The P-PCE selects a set of 226 candidate domain paths based on the domain topology and the state of 227 the inter-domain links. It then sends computation requests to the C- 228 PCEs responsible for each of the domains on the candidate domain 229 paths. Each C-PCE computes a set of candidate path segments across 230 its domain and sends the results to the P-PCE. The P-PCE uses this 231 information to select path segments and concatenate them to derive 232 the optimal end-to-end inter-domain path. The end-to-end path is 233 then sent to the C-PCE that received the initial path request, and 234 this C-PCE passes the path on to the PCC that issued the original 235 request. 237 As per [I-D.ietf-pce-stateful-pce], PCC sends an LSP State Report 238 carried on a PCRpt message to the C-PCE, indicating the LSP's status. 239 The C-PCE MAY further propagate the State Report to the P-PCE. A 240 local policy at C-PCE MAY dictate which LSPs to be reported to the P- 241 PCE. The PCRpt message is sent from C-PCE to P-PCE. 243 State synchronization mechanism as described in 244 [I-D.ietf-pce-stateful-pce] and 245 [I-D.ietf-pce-stateful-sync-optimizations] are applicable to PCEP 246 session between C-PCE and P-PCE as well. 248 Taking the sample hierarchical domain topology example from [RFC6805] 249 as the reference topology for the entirety of this document. 251 ----------------------------------------------------------------- 252 | Domain 5 | 253 | ----- | 254 | |PCE 5| | 255 | ----- | 256 | | 257 | ---------------- ---------------- ---------------- | 258 | | Domain 1 | | Domain 2 | | Domain 3 | | 259 | | | | | | | | 260 | | ----- | | ----- | | ----- | | 261 | | |PCE 1| | | |PCE 2| | | |PCE 3| | | 262 | | ----- | | ----- | | ----- | | 263 | | | | | | | | 264 | | ----| |---- ----| |---- | | 265 | | |BN11+---+BN21| |BN23+---+BN31| | | 266 | | - ----| |---- ----| |---- - | | 267 | | |S| | | | | |D| | | 268 | | - ----| |---- ----| |---- - | | 269 | | |BN12+---+BN22| |BN24+---+BN32| | | 270 | | ----| |---- ----| |---- | | 271 | | | | | | | | 272 | | ---- | | | | ---- | | 273 | | |BN13| | | | | |BN33| | | 274 | -----------+---- ---------------- ----+----------- | 275 | \ / | 276 | \ ---------------- / | 277 | \ | | / | 278 | \ |---- ----| / | 279 | ----+BN41| |BN42+---- | 280 | |---- ----| | 281 | | | | 282 | | ----- | | 283 | | |PCE 4| | | 284 | | ----- | | 285 | | | | 286 | | Domain 4 | | 287 | ---------------- | 288 | | 289 ----------------------------------------------------------------- 291 Figure 1: Sample Hierarchical Domain Topology 293 Steps 1 to 11 are exactly as described in section 4.6.2 (Hierarchical 294 PCE End-to-End Path Computation Procedure) of [RFC6805], the 295 following additional steps are added for stateful PCE: 297 (1) The Ingress LSR initiates the setup of the LSP as per the path 298 and reports to the PCE1 the LSP status ("GOING-UP"). 300 (2) The PCE1 further reports the status of the LSP to the P-PCE 301 (PCE5). 303 (3) The Ingress LSR notifies the LSP state to PCE1 when the state is 304 "UP". 306 (4) The PCE1 further reports the status of the LSP to the P-PCE 307 (PCE5). 309 3.2. Active Operations 311 [I-D.ietf-pce-stateful-pce] describes the case of active stateful 312 PCE. The active PCE functionality uses two specific PCEP messages: 314 o Update Request (PCUpd) 315 o State Report (PCRpt) 317 The first is sent by the PCE to a Path Computation Client (PCC) for 318 modifying LSP attributes. The PCC sends back a PCRpt to acknowledge 319 the requested operation or report any change in LSP's state. 321 As per [RFC8051], Delegation is an operation to 322 grant a PCE, temporary rights to modify a subset of LSP parameters on 323 one or more PCC's LSPs. The C-PCE may further choose to delegate 324 to P-PCE based on a local policy. The PCRpt message with "D" 325 (delegate) flag is sent from C-PCE to P-PCE. 327 To update an LSP, a PCE send to the PCC, an LSP Update Request using 328 a PCUpd message. For LSP delegated to the P-PCE via the child 329 PCE, the P-PCE can use the same PCUpd message to request change 330 to the C-PCE (the Ingress domain PCE), the PCE further propagates 331 the update request to the PCC. 333 The P-PCE uses the same mechanism described in Section 3.1 to compute 334 the end to end path using PCReq and PCRep messages. 336 The following additional steps are also initially performed, 337 for active operations, again using the reference architecture 338 described in Figure 1 (Sample Hierarchical Domain Topology). 340 (1) The Ingress LSR delegates the LSP to the PCE1 via PCRpt message 341 with D flag set. 343 (2) The PCE1 further delegates the LSP to the P-PCE (PCE5). 345 Steps 4 to 10 of section 4.6.2 of [RFC6805] are executed to determine 346 the end to end path. 348 (3) The P-PCE (PCE5) sends the update request to the C-PCE 349 (PCE1) via PCUpd message. 351 (4) The PCE1 further updates the LSP to the Ingress LSR (PCC). 353 (5) The Ingress LSR initiates the setup of the LSP as per the path 354 and reports to the PCE1 the LSP status ("GOING-UP"). 356 (6) The PCE1 further reports the status of the LSP to the P-PCE 357 (PCE5). 359 (7) The Ingress LSR notifies the LSP state to PCE1 when the state is 360 "UP". 362 (8) The PCE1 further reports the status of the LSP to the P-PCE 363 (PCE5). 365 3.3. PCE Initiation Operation 367 [I-D.ietf-pce-pce-initiated-lsp] describes the setup, maintenance and 368 teardown of PCE-initiated LSPs under the stateful PCE model, without 369 the need for local configuration on the PCC, thus allowing for a 370 dynamic network that is centrally controlled and deployed. To 371 instantiate or delete an LSP, the PCE sends the Path Computation LSP 372 Initiate Request (PCInitiate) message to the PCC. In case of inter- 373 domain LSP in Hierarchical PCE architecture, the initiation 374 operations can be carried out at the P-PCE. In which case after 375 P-PCE finishes the E2E path computation, it can send the 376 PCInitiate message to the C-PCE (the Ingress domain PCE), the PCE 377 further propagates the initiate request to the PCC. 379 The following additional steps are also initially performed, 380 for PCE initiated operations, again using the reference 381 architecture described in Figure 1 (Sample Hierarchical Domain 382 Topology): 384 (1) The P-PCE (PCE5) is requested to initiate a LSP. 386 Steps 4 to 10 of section 4.6.2 of [RFC6805] are executed to determine 387 the end to end path. 389 (2) The P-PCE (PCE5) sends the initiate request to the child 390 PCE (PCE1) via PCInitiate message. 392 (3) The PCE1 further propagates the initiate message to the Ingress 393 LSR (PCC). 395 (4) The Ingress LSR initiates the setup of the LSP as per the path 396 and reports to the PCE1 the LSP status ("GOING-UP"). 398 (5) The PCE1 further reports the status of the LSP to the P-PCE 399 (PCE5). 401 (6) The Ingress LSR notifies the LSP state to PCE1 when the state is 402 "UP". 404 (7) The PCE1 further reports the status of the LSP to the P-PCE 405 (PCE5). 407 3.3.1. Per Domain Stitched LSP 409 The hierarchical PCE architecture as per [RFC6805] is primarily used 410 for E2E LSP. With PCE-Initiated capability, another mode of 411 operation is possible, where multiple intra-domain LSPs are initiated 412 in each domain which are further stitched to form an E2E LSP. The 413 P-PCE sends PCInitiate message to each C-PCE separately to 414 initiate individual LSP segments along the domain path. These 415 individual per domain LSP are stitched together by some mechanism, 416 which is out of scope of this document. The P-PCE may also send 417 the PCInitiate message to the ingress C-PCE to initiate the E2E 418 LSP separately. 420 The following additional steps are also initially performed, 421 for the Per Domain stiched LSP operation, again using the reference 422 architecture described in Figure 1 (Sample Hierarchical Domain 423 Topology): 425 (1) The P-PCE (PCE5) is requested to initiate a LSP. 427 Steps 4 to 10 of section 4.6.2 of [RFC6805] are executed to determine 428 the end to end path, which are broken into per-domain LSPs say - 430 o S-BN41 432 o BN41-BN33 434 o BN33-D 436 It should be noted that the P-PCE MAY use other mechanisms to 437 determine the suitable per-domain LSPs (apart from [RFC6805]). 439 For LSP (BN33-D) 441 (2) The P-PCE (PCE5) sends the initiate request to the child 442 PCE (PCE3) via PCInitiate message for LSP (BN33-D). 444 (3) The PCE3 further propagates the initiate message to BN33. 446 (4) BN33 initiates the setup of the LSP as per the path and reports 447 to the PCE3 the LSP status ("GOING-UP"). 449 (5) The PCE3 further reports the status of the LSP to the P-PCE 450 (PCE5). 452 (6) The node BN33 notifies the LSP state to PCE3 when the state is 453 "UP". 455 (7) The PCE3 further reports the status of the LSP to the P-PCE 456 (PCE5). 458 For LSP (BN41-BN33) 460 (8) The P-PCE (PCE5) sends the initiate request to the child PCE 461 (PCE4) via PCInitiate message for LSP (BN41-BN33). 463 (9) The PCE4 further propagates the initiate message to BN41. 465 (10) BN41 initiates the setup of the LSP as per the path and reports 466 to the PCE4 the LSP status ("GOING-UP"). 468 (11) The PCE4 further reports the status of the LSP to the P-PCE 469 (PCE5). 471 (l2) The node BN41 notifies the LSP state to PCE4 when the state is 472 "UP". 474 (13) The PCE4 further reports the status of the LSP to the P-PCE 475 (PCE5). 477 For LSP (S-BN41) 479 (14) The P-PCE (PCE5) sends the initiate request to the child 480 PCE (PCE1) via PCInitiate message for LSP (S-BN41). 482 (15) The PCE1 further propagates the initiate message to node S. 484 (16) S initiates the setup of the LSP as per the path and reports to 485 the PCE1 the LSP status ("GOING-UP"). 487 (17) The PCE1 further reports the status of the LSP to the P-PCE 488 (PCE5). 490 (18) The node S notifies the LSP state to PCE1 when the state is 491 "UP". 493 (19) The PCE1 further reports the status of the LSP to the P-PCE 494 (PCE5). 496 Additionally: 498 (20) Once P-PCE receives report of each per-domain LSP, it 499 should use some stitching mechanism, which is out of scope of 500 this document. In this step, P-PCE (PCE5) could also initiate 501 an E2E LSP (S-D) by sending the PCInitiate message to Ingress 502 C-PCE (PCE1). 504 A suitable stitching mechanism would be used to stitch these per 505 domain LSPs. One such mechanism is described in [I-D.lee-pce-lsp- 506 stitching-hpce], where PCEP is extended to support stitching in 507 stateful H-PCE context. Section 2.1 of [I-D.lee-pce-lsp-stitching- 508 hpce] updates the procedure described in this section to handle the 509 stitching via PCEP stateful H-PCE extension for Stitching Label. 511 4. Other Considerations 513 4.1. Applicability to Inter-Layer 515 [RFC5623] describes a framework for applying the PCE-based 516 architecture to inter-layer (G)MPLS traffic engineering. The H-PCE 517 Stateful architecture with stateful P-PCE coordinating with the 518 stateful C-PCEs of higher and lower layer is shown in the figure 519 below. 521 +----------+ 522 /| Parent | 523 / | PCE | 524 / +----------+ 525 / / Stateful 526 / / 527 / / 528 / / 529 Stateful +---+/ / 530 Child + PCE + / 531 PCE Hi + Hi + / 532 +---+ / 533 +---+ +---+ / +---+ +---+ 534 + LSR +--+ LSR +........................+ LSR +--+ LSR + 535 + H1 + + H2 + / + H3 + + H4 + 536 +---+ +---+\ +---+/ /+---+ +---+ 537 \ + PCE + / 538 \ + Lo + / 539 Stateful \ +---+ / 540 C-PCE \ / 541 Lo \+---+ +---+/ 542 + LSR +--+ LSR + 543 + L1 + + L2 + 544 +---+ +---+ 546 Figure 2: Sample Inter-Layer Topology 548 All procedures described in Section 3 are applicable to inter-layer 549 path setup as well. 551 4.2. Applicability to ACTN 553 [I-D.ietf-teas-actn-framework] describes framework for 554 Abstraction and Control of TE Networks (ACTN), where each Physical 555 Network Controller (PNC) is equivalent to C-PCE and P-PCE is 556 the Multi-Domain Service Coordinator (MDSC). The Per domain stitched 557 LSP as per the Hierarchical PCE architecture described in 558 Section 3.3.1 and Section 4.1 is well suited for ACTN. 560 [I-D.ietf-pce-applicability-actn] examines the applicability of PCE 561 to the ACTN framework. To support the function of multi domain 562 coordination via hierarchy, the stateful hierarchy of PCEs plays a 563 crucial role. 565 In ACTN framework, Customer Network Controller (CNC) can request the 566 MDSC to check if there is a possibility to meet Virtual Network (VN) 567 requirements (before requesting for VN provision). The H-PCE 568 architecture as described in [RFC6805] can supports via the use of 569 PCReq and PCRep messages between the P-PCE and C-PCEs. 571 5. Scalability Considerations 573 It should be noted that if all the C-PCEs would report all the LSPs 574 in their domain, it could lead to scalability issues for the P-PCE. 575 Thus it is recommended to only report the LSPs which are involved in 576 H-PCE, i.e. the LSPs which are either delegated to the P-PCE or 577 initiated by the P-PCE. Scalability considerations for PCEP as per 578 [I-D.ietf-pce-stateful-pce] continue to apply for the PCEP session 579 between child and parent PCE. 581 6. Security Considerations 583 The security considerations listed in [I-D.ietf-pce-stateful- 584 pce],[RFC6805] and [RFC5440] apply to this document as well. As per 585 [RFC6805], it is expected that the parent PCE will require all child 586 PCEs to use full security when communicating with the parent. 588 Any multi-domain operation necessarily involves the exchange of 589 information across domain boundaries. This is bound to represent a 590 significant security and confidentiality risk especially when the 591 child domains are controlled by different commercial concerns. PCEP 592 allows individual PCEs to maintain confidentiality of their domain 593 path information using path-keys [RFC5520], and the hierarchical PCE 594 architecture is specifically designed to enable as much isolation of 595 domain topology and capabilities information as is possible. The LSP 596 state in the PCRpt message SHOULD continue to use this. 598 The security consideration for PCE-Initiated LSP as per 599 [I-D.ietf-pce-pce-initiated-lsp] is also applicable from P-PCE to C- 600 PCE. 602 Thus securing the PCEP session (between the P-PCE and the C-PCE) 603 using mechanism like TCP Authentication Option (TCP-AO) [RFC5925] or 604 Transport Layer Security (TLS) [I-D.ietf-pce-pceps] is RECOMMENDED. 606 7. Manageability Considerations 608 All manageability requirements and considerations listed in 609 [RFC5440], [RFC6805], [I-D.ietf-pce-stateful-pce], and 610 [I-D.ietf-pce-pce-initiated-lsp] apply to Stateful H-PCE defined in 611 this document. In addition, requirements and considerations listed 612 in this section apply. 614 7.1. Control of Function and Policy 616 Support of the hierarchical procedure will be controlled by the 617 management organization responsible for each child PCE. The parent 618 PCE must only accept path computation requests from authorized child 619 PCEs. If a parent PCE receives report from an unauthorized child 620 PCE, the report should be dropped. All mechanism as described in [I- 621 D.ietf-pce-stateful-pce] and [I-D.ietf-pce-pce-initiated-lsp] 622 continue to apply. 624 7.2. Information and Data Models 626 An implementation SHOULD allow the operator to view the stateful and 627 H-PCE capabilities advertised by each peer. The PCEP YANG module [I- 628 D.ietf-pce-pcep-yang] can be extended to include details stateful H- 629 PCE. 631 7.3. Liveness Detection and Monitoring 633 Mechanisms defined in this document do not imply any new liveness 634 detection and monitoring requirements in addition to those already 635 listed in [RFC5440]. 637 7.4. Verify Correct Operations 639 Mechanisms defined in this document do not imply any new operation 640 verification requirements in addition to those already listed in 641 [RFC5440] and [I-D.ietf-pce-stateful-pce]. 643 7.5. Requirements On Other Protocols 645 Mechanisms defined in this document do not imply any new requirements 646 on other protocols. 648 7.6. Impact On Network Operations 650 Mechanisms defined in [RFC5440] and [I-D.ietf-pce-stateful-pce] also 651 apply to PCEP extensions defined in this document. 653 The stateful H-PCE technique brings the applicability of stateful PCE 654 as described in [RFC8051], for the LSP traversing multiple domains. 656 8. IANA Considerations 658 There are no IANA considerations. 660 9. Acknowledgments 662 Thanks to Manuela Scarella, Haomian Zheng, Sergio Marmo, Stefano 663 Parodi, Giacomo Agostini, Jeff Tantsura and Rajan Rao for 664 suggestions. 666 10. References 668 10.1. Normative References 670 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 671 Requirement Levels", BCP 14, RFC 2119, 672 DOI 10.17487/RFC2119, March 1997, 673 . 675 [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation 676 Element (PCE) Communication Protocol (PCEP)", RFC 5440, 677 DOI 10.17487/RFC5440, March 2009, 678 . 680 [RFC6805] King, D., Ed. and A. Farrel, Ed., "The Application of the 681 Path Computation Element Architecture to the Determination 682 of a Sequence of Domains in MPLS and GMPLS", RFC 6805, DOI 683 10.17487/RFC6805, November 2012, 684 . 686 [I-D.ietf-pce-stateful-pce] 687 Crabbe, E., Minei, I., Medved, J., and R. Varga, "PCEP 688 Extensions for Stateful PCE", draft-ietf-pce-stateful- 689 pce-21 (work in progress), June 2017. 691 [I-D.ietf-pce-pce-initiated-lsp] 692 Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "PCEP 693 Extensions for PCE-initiated LSP Setup in a Stateful PCE 694 Model", draft-ietf-pce-pce-initiated-lsp-10 (work in 695 progress), June 2017. 697 10.2. Informative References 699 [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation 700 Element (PCE)-Based Architecture", RFC 4655, 701 DOI 10.17487/RFC4655, August 2006, 702 . 704 [RFC5520] Bradford, R., Ed., Vasseur, JP., and A. Farrel, 705 "Preserving Topology Confidentiality in Inter-Domain Path 706 Computation Using a Path-Key-Based Mechanism", RFC 5520, 707 DOI 10.17487/RFC5520, April 2009, 708 . 710 [RFC5623] Oki, E., Takeda, T., Le Roux, JL., and A. Farrel, 711 "Framework for PCE-Based Inter-Layer MPLS and GMPLS 712 Traffic Engineering", RFC 5623, DOI 10.17487/RFC5623, 713 September 2009, . 715 [RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP 716 Authentication Option", RFC 5925, DOI 10.17487/RFC5925, 717 June 2010, . 719 [RFC8051] Zhang, X., Ed. and I. Minei, Ed., "Applicability of a 720 Stateful Path Computation Element (PCE)", RFC 8051, 721 DOI 10.17487/RFC8051, January 2017, 722 . 724 [I-D.ietf-pce-stateful-sync-optimizations] 725 Crabbe, E., Minei, I., Medved, J., Varga, R., Zhang, X., 726 and D. Dhody, "Optimizations of Label Switched Path State 727 Synchronization Procedures for a Stateful PCE", draft- 728 ietf-pce-stateful-sync-optimizations-10 (work in 729 progress), March 2017. 731 [I-D.ietf-teas-actn-framework] 732 Ceccarelli D. and Y. Lee, "Framework for Abstraction and 733 Control of Transport Networks", draft-ietf-teas- 734 actn-framework-06 (work in progress), June 2017. 736 [I-D.ietf-pce-applicability-actn] 737 Dhody, D., Lee, Y., and D. Ceccarelli, "Applicability of 738 Path Computation Element (PCE) for Abstraction and 739 Control of TE Networks (ACTN)", draft-ietf-pce- 740 applicability-actn-00 (work in progress), June 2017. 742 [I-D.litkowski-pce-state-sync] 743 Litkowski, S., Sivabalan, S., and D. Dhody, "Inter 744 Stateful Path Computation Element communication 745 procedures", draft-litkowski-pce-state-sync-01 (work in 746 progress), February 2017. 748 [I-D.ietf-pce-hierarchy-extensions] 749 Zhang, F., Zhao, Q., Dios, O., Casellas, R., and D. King, 750 "Extensions to Path Computation Element Communication 751 Protocol (PCEP) for Hierarchical Path Computation Elements 752 (PCE)", draft-ietf-pce-hierarchy-extensions-03 (work in 753 progress), July 2016. 755 [I-D.ietf-pce-pceps] 756 Lopez, D., Dios, O., Wu, W., and D. Dhody, "Secure 757 Transport for PCEP", draft-ietf-pce-pceps-14 (work in 758 progress), May 2017. 760 Appendix A. Contributor Addresses 762 Avantika 763 Huawei Technologies 764 Divyashree Techno Park, Whitefield 765 Bangalore, Karnataka 560066 766 India 768 EMail: s.avantika.avantika@gmail.com 770 Xian Zhang 771 Huawei Technologies 772 Bantian, Longgang District 773 Shenzhen, Guangdong 518129 774 P.R.China 776 EMail: zhang.xian@huawei.com 778 Udayasree Palle 779 Huawei Technologies 780 Divyashree Techno Park, Whitefield 781 Bangalore, Karnataka 560066 782 India 784 EMail: udayasreereddy@gmail.com 786 Authors' Addresses 788 Dhruv Dhody 789 Huawei Technologies 790 Divyashree Techno Park, Whitefield 791 Bangalore, Karnataka 560066 792 India 794 EMail: dhruv.ietf@gmail.com 796 Young Lee 797 Huawei Technologies 798 5340 Legacy Drive, Building 3 799 Plano, TX 75023 800 USA 802 EMail: leeyoung@huawei.com 804 Daniele Ceccarelli 805 Ericsson 806 Torshamnsgatan,48 807 Stockholm 808 Sweden 810 EMail: daniele.ceccarelli@ericsson.com 812 Jongyoon Shin 813 SK Telecom 814 6 Hwangsaeul-ro, 258 beon-gil, Bundang-gu, Seongnam-si, 815 Gyeonggi-do 463-784 816 Republic of Korea 818 EMail: jongyoon.shin@sk.com 820 Daniel King 821 Lancaster University 822 UK 824 EMail: d.king@lancaster.ac.uk 826 Oscar Gonzalez de Dios 827 Telefonica I+D 828 Don Ramon de la Cruz 82-84 829 Madrid, 28045 830 Spain 832 Phone: +34913128832 833 Email: ogondio@tid.es