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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 PCE Working Group Xian Zhang 2 Internet Draft Haomian Zheng 3 Category: Standards track Huawei Technologies 4 Oscar Gonzales de Dios 5 Victor Lopez 6 Telefonica I+D 7 Yunbin Xu 8 CAICT 10 Expires: October 21, 2020 April 21, 2020 12 Extensions to the Path Computation Element Protocol (PCEP) to Support 13 Resource Sharing-based Path Computation 15 draft-zhang-pce-resource-sharing-12 17 Abstract 19 Resource sharing in a network means two or more Label Switched Paths 20 (LSPs) use common pieces of resource along their paths. This can 21 help save network resources and is useful in scenarios such as LSP 22 recovery or when two LSPs do not need to be active at the same time. 23 A Path Computation Element (PCE) is responsible for path computation 24 with such requirement. 26 Existing extensions to the Path Computation Element Protocol (PCEP) 27 allow one path computation request for an LSP to be associated with 28 other (existing) LSPs through the use of the PCEP Association 29 Object. 31 This document extends PCEP in order to support resource-sharing- 32 based path computation as another use of the Association Object to 33 enable better efficiency in the computation and in the resultant 34 paths and network resource usage. 36 Status of this Memo 38 This Internet-Draft is submitted to IETF in full conformance with 39 the provisions of BCP 78 and BCP 79. 41 Internet-Drafts are working documents of the Internet Engineering 42 Task Force (IETF), its areas, and its working groups. Note that 43 other groups may also distribute working documents as Internet- 44 Drafts. 46 Internet-Drafts are draft documents valid for a maximum of six 47 months and may be updated, replaced, or obsoleted by other documents 48 at any time. It is inappropriate to use Internet-Drafts as 49 reference material or to cite them other than as "work in progress." 51 The list of current Internet-Drafts can be accessed at 52 http://www.ietf.org/ietf/1id-abstracts.txt. 54 The list of Internet-Draft Shadow Directories can be accessed at 55 http://www.ietf.org/shadow.html. 57 This Internet-Draft will expire on October 21, 2020. 59 Copyright Notice 61 Copyright (c) 2020 IETF Trust and the persons identified as the 62 document authors. All rights reserved. 64 This document is subject to BCP 78 and the IETF Trust's Legal 65 Provisions Relating to IETF Documents 66 (http://trustee.ietf.org/license-info) in effect on the date of 67 publication of this document. Please review these documents 68 carefully, as they describe your rights and restrictions with 69 respect to this document. Code Components extracted from this 70 document must include Simplified BSD License text as described in 71 Section 4.e of the Trust Legal Provisions and are provided without 72 warranty as described in the Simplified BSD License. 74 Table of Contents 76 1. Introduction and Motivation .................................. 3 77 1.1. Requirements Language ................................... 4 78 2. Motivation ................................................... 5 79 2.1. Single Domain Use Case .................................. 5 80 2.2. Multiple Layers/Domains Use Case ........................ 6 81 2.3. Bulk Path Computation Use Case .......................... 8 82 3. Extensions to PCEP ........................................... 9 83 3.1. Association Group and Type .............................. 9 84 3.2. Resource Sharing TLV ................................... 10 85 3.3. Processing Rules ....................................... 11 86 4. Implementation Status ....................................... 12 87 5. Manageability Considerations ................................ 12 88 5.1. Control of Function and Policy ......................... 12 89 5.2. Information and Data Models ............................ 12 90 5.3. Liveness Detection and Monitoring ...................... 13 91 5.4. Verify Correct Operations .............................. 13 92 5.5. Requirements on Other Protocols ........................ 13 93 5.6. Impact on Network Operations ........................... 13 94 6. Security Considerations ..................................... 13 95 7. IANA Considerations ......................................... 14 96 7.1. Association Object Type Indicators ..................... 14 97 7.2. PCEP TLV Definitions ................................... 14 98 8. References .................................................. 15 99 8.1. Normative References ................................... 15 100 8.2. Informative References ................................. 15 101 9. Acknowledgements ............................................ 16 102 10. Contributor's Address ...................................... 16 103 11. Authors' Addresses ......................................... 17 105 1. Introduction and Motivation 107 A Path Computation Element (PCE) is a way to provide path 108 computation function, and it is especially useful in the scenarios 109 where complex constraints and/or a demanding amount of computation 110 resource are required [RFC4655]. The development of PCE 111 standardization has evolved from stateless to stateful. A stateful 112 PCE has access to the LSP database information of the networks it 113 serves as a computation engine [RFC8231]. Unless specified, this 114 document assumes a PCE mentioned is a stateful PCE. 116 Resource sharing denotes that two or more Label Switched Paths 117 (LSPs) share common pieces of resource, (such as a common time slot 118 of a link in an Optical Transport Network (OTN)). This is usually 119 useful in the scenario where only one of the LSPs is active and the 120 benefit is to save network resources. A simple example of this is 121 dynamically calculating a recovery LSP for an existing LSP 122 undergoing a link failure. Note that resource sharing can be worked 123 out using a stateless PCE, but the mechanism may be complex and is 124 out the scope of this document. 126 This document considers the requirement that a new LSP may request 127 for resource sharing with one or multiple existing LSPs. Furthermore, 128 if there is resource sharing between a new LSP and existing an LSP, 129 the two LSPs cannot be used to carry traffic simultaneously, the new 130 LSP will take over the traffic from the existing LSP. 132 In a single domain, this is a common requirement in the recovery 133 cases especially in order to increase traffic resilience against 134 failure while reducing the amount of network resource used for 135 recovery purposes [RFC4428]. 137 The current protocol supporting the communication between a PCE and 138 a Path Computation Client (PCC), i.e. PCE Protocol (PCEP), allows 139 for re-optimization of an existing LSP [RFC5440]. This is achieved 140 by setting the R bit in the Request Parameter (RP) object, together 141 with some additional information if applicable, in the Path 142 Computation Request (PCReq) message sent from a PCC to the PCE. To 143 support this type of resource sharing, a PCC needs to ask a PCE to 144 compute a new path with the constraints of sharing resource with one 145 or multiple existing LSPs. It is worth noting the "resource sharing" 146 in this draft not only means one LSP re-using the same links of 147 another LSP, but also the same slice of bandwidth in the network. 148 This may occur when an LSP is required for re-routing, or online re- 149 optimization. Current PCEP specifications do not provide such 150 function. More specifically, this document describes the resource 151 sharing issue during the procedure when a new LSP is required to 152 replace an existing LSP for use together with Make-before-break 153 (MBB) described in [RFC3209]. 155 As mentioned in [RFC8231], the PLSP-ID provides a unique identifier 156 for an LSP during a PCEP session between PCC and PCE. Such 157 identification is helpful in supporting the resource sharing 158 requirement for stateful PCEs because it greatly simplifies the 159 operation of a PCC. Instead of the PCC determining all the resources 160 to be shared, the PCC can request that the PCE share the resources 161 of a specific LSP: the stateful PCE is able to determine those 162 resource itself. 164 Resource sharing can also be required in an inter-layer PCEP 165 session. This is similar to the previous requirement. However, it is 166 more complex and therefore deserves a more detailed explanation 167 here. 169 In a multi-layer network, LSPs in a lower layer are used to carry 170 higher-layer LSPs across the lower-layer network [RFC5623]. 171 Therefore, the resource sharing constraints in the higher layer 172 might actually relate to resource sharing in the lower layer. Thus, 173 it is useful to consider how this can be achieved and whether 174 additional extensions are needed using the models defined in 175 [RFC5623]. 177 In the next sections, use cases are provided to show what 178 information needs to be exchanged to fulfill these requirements. 179 This memo then provides extensions to PCEP to enable this function. 181 1.1. Requirements Language 183 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 184 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 185 "OPTIONAL" in this document are to be interpreted as described in 186 BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all 187 capitals, as shown here. 189 2. Motivation 191 2.1. Single Domain Use Case 193 There are two potential cases that request resource to be shared: 194 restoration and re-optimization. Figure 1 shows a single domain 195 network with a stateful PCE, and is used as an example for the 196 resource sharing application. 198 +--------------+ 199 | | 200 | Stateful PCE | 201 | | 202 +--------------+ 204 +------+ +------+ +------+ 205 | N1 +----------+ N2 +-----X---+ N3 | 206 +--+---+ +---+--+ +---+--+ 207 | | | 208 | +---------+ | 209 | | | 210 | +------+ +------+ | 211 +-----+ N5 +----------+ N4 +-----+ 212 +------+ +------+ 214 Figure 1: A Single Domain Example 216 LSP0 (existing): N1-N2-N3 217 LSP1 (restoration): N1-N2-N4-N3 218 LSP2 (re-optimization): N1-N5-N4-N3 220 For the failure restoration, we can assume a working LSP (LSP0) 221 exists in the network. When there is failure on the link N2-N3, it 222 is desired to set up a restoration path for this working LSP. 223 Suppose N1 serves as the PCC and sends a request to the stateful PCE 224 for such an LSP. Before sending the request, N1 may need to check 225 what policy should be applied for the restoration. For example, it 226 might value resource sharing and prefer to share as much resource 227 with the working LSP as possible and specify this policy in the 228 PCReq message. Given such policy, a probable outcome from the path 229 computation would be LSP1, which shares the link 'N1-N2' with the 230 existing LSP. 232 Re-optimization does not usually result from a specific failure in 233 the network, but takes place on a stable network when more optimal 234 paths may have become available. Thus switching from the existing 235 LSP to the new LSP happens with live traffic. An example can be 236 found in Figure 1 without failure on the link N2-N3. Instead, an 237 online re-optimization is needed for the working LSP (LSP0) from the 238 stateful PCE. In such cases, the best choice is to set up a backup 239 LSP for the working LSP with totally separate routing (for example, 240 LSP2), and move the traffic to that backup LSP. After that, the 241 working LSP can be torn down, which will not result in any 242 interruption during the optimization procedure. This can actually be 243 implemented with existing PCEP mechanisms. However, if there is no 244 such separate path, existing PCEP mechanisms will return an error. A 245 secondary option for this case is to set up an LSP and complete re- 246 optimization with resource sharing, even if some interruption is 247 introduced. 249 In the example from Figure 1 it is assumed that the restored LSP or 250 re-optimized LSP have the same source and destination nodes. But in 251 some applications there is no restriction for this assumption, i.e., 252 after an LSP is failed, it can be restored as a new LSP with 253 different source/destination. 255 In the use cases above it is also assumed that the characteristics 256 of the restored LSP or re-optimized LSP are unchanged. However, it 257 is possible to have parameter changes during the resource sharing 258 computation. For example, the bandwidth of the request LSP may be 259 different from the existing LSP, while resource sharing is still 260 preferred by the PCC. The PCE should consider the sharing request 261 together with the policy and available resources in the network. 262 Details can be found in Section 3.3. 264 Conversely to resource sharing, it may also be required to apply a 265 disjoint constraint for the path computation. [ietf-pce-association- 266 diversity] discusses the solution under such a scenario, which is a 267 companion work to this document. 269 2.2. Multiple Layers/Domains Use Case 271 As Discussed in Section 3 of [RFC5623], there are three models for 272 inter-layer path computation. They are single PCE computation, 273 multiple PCE with inter-PCE communication, and multiple PCE without 274 inter-PCE communication. For the single PCE computation, the process 275 would be similar to that of the use case in Section 2.1. 277 An inter-layer path computation example is shown in Figure 2. Assume 278 an LSP (LSP1: H2-H3) has been established already, visible as H2-H3 279 from the view of the higher-layer PCE, and as H2-L1-L2-H3 from the 280 global view (or from the view of the lower-layer PCE). A new request 281 is received by H2 to establish a new LSP (LSP2: from H2 to H5), 282 given the constraint that it can share resources with LSP1. This 283 requirement is possible if only one of the LSPs needs to be active 284 and resource sharing is the target. 286 ----- 287 .................................| LSR | 288 .: | H5 | 289 .: /----- 290 .: / | 291 ----- -----.: ----- -----/ | 292 | LSR |--| LSR |.......................| LSR |--| LSR | / 293 | H1 | | H2 | | H3 | | H4 | / 294 ----- -----\ /----- ----- / 295 \ / / 296 \ / / 297 \ / / 298 \ / / 299 \----- -----/ / 300 | LSR |-| LSR | / 301 | L1 | | L2 | / 302 ----- -----\ / 303 | \ / 304 | \ / 305 | \ / 306 ----- \-----/ 307 | LSR |-----------| LSR | 308 | L3 | | L4 | 309 ----- ----- 310 Figure 2: A Two-layer Network Example 312 If the model of multiple PCEs with inter-PCE communication is 313 employed, the path computation request sent by H2 to higher-layer 314 PCE will be forwarded to lower-layer PCE since there is no resource 315 readily available in the higher layer. So it leaves the lower-layer 316 PCE to compute a path in the lower layer in order to support the 317 higher layer request. In this case, the lower-layer PCE is required 318 to compute a path between H2 and H5 under the constraint that it can 319 share the resource with that of LSP1. At this moment the lower-layer 320 PCE has knowledge of the explicit route of LSP1 (H2-L1-L2-H3), and 321 therefore can map the lower layer LSP with the higher-layer one. So 322 when the lower-layer PCE computes the path for LSP2, it can consider 323 the resource used by LSP1 as available with higher priority. For 324 example, the lower-layer PCE may choose H2-L1-L2-L4-H5 as the 325 computation result. On the other hand, if the path computation 326 policy is to have a separate path with LSP1, the lower-layer PCE may 327 choose H2-L1-L3-L4-H5. 329 During this procedure the higher-layer PCE can only use information 330 about LSP1 (such as its five-tuple LSP information). An issue to 331 solve is how the lower-layer PCE can resolve this information to the 332 actual resource usage in its own layer, i.e. the lower layer. This 333 could be solved by the edge LSR (L1) reporting this higher-lower LSP 334 correlation to the lower-layer PCE as part of the LSP information 335 during the LSP state synchronization process. If needed, it can be 336 updated later when there is a change in this information. 337 Alternatively, the lower-layer PCE can get this information from 338 other sources, such as a network management system, where this 339 information should be stored. 341 If the model of multiple PCEs without inter-PCE communication is 342 employed, the path computation request in the lower layer will be 343 initiated by the border LSR node, i.e., L1. The process would be 344 similar to that of the previous scenario. A point worth noting is 345 that the border LSR node may be able to resolve the higher layer LSP 346 information itself, such as by mapping it to the corresponding LSP 347 in the lower layer, in this way the lower-layer PCE does not need to 348 perform this function. Otherwise, the mapping method mentioned above 349 can still be used. 351 2.3. Bulk Path Computation Use Case 353 There is a potential need for resource sharing during bulk path 354 computation, especially the processing of the "sticky resources" in 355 [RFC7399]. It would be useful to specify the resources that can be 356 shared among different paths, i.e., the bandwidth information. 358 Considering the H-PCE architecture in [RFC8751], when the parent PCE 359 asks for a single path across a few domains, such a request may 360 become a bulk path computation to a certain child PCE. Figure 3 361 shows an example of 3 domains. The parent PCE will select one of 362 these path for establishment. 364 +-------+ 365 /| P-PCE |\ 366 / +---+---+ \ 367 / | \ 368 / | \ 370 / | \ 371 / | \ 372 / | \ 373 / | \ 374 +-----/+ +---+---+ +\------+ 375 |C-PCE1| |C-PCE2 | |C-PCE3 | 376 +------+ +-------+ +-------+ 377 / | \ 378 --------------- ----------------------- ------------- 379 / \ / \ / \ 380 | +---+ +---+ | | +---+ +---+ +---+ | | +---+ +---+ | 381 | | A +-----+ B +-+--+--+ D +---+ E +---+ H +-+--+-+ J +----+ L | | 382 | +-\-+ +---+ | | +---+ +---+ +--\+ | | +---+ +-/-+ | 383 | \ | | / \ | | / | 384 | \ | | / \| | / | 385 | \ +---+ | | +---+ / |\\| +---+/ | 386 | \+ C +-+--+--+ G +/ | |----| K | | 387 \ +---+/ \ +---+ / \ +---+ / 388 ---------------- ----------------------- -------------- 389 Figure 3: Bulk Request example with Hierarchical PCEs 391 A 3-domain example is shown in Figure 3, with the hierarchical PCE 392 architecture. In this example nodes A/B/C belong to domain 1, nodes 393 D/E/G/H belong to domain 2, and nodes J/K/L belong to domain 3. 394 Inter-domain links are B-D/C-G between domains 1 and 2, and H-J/H-K 395 between domains 2 and 3. Given a path computation request from A to 396 L, a bulk request from P-PCE would be helpful to understand whether 397 it is possible to have different combinations on the inter-domain 398 links. However, the resources on some specific links become 'sticky' 399 and have to be indicated as 'sharing allowed' to avoid unnecessary 400 resource competition. For example, both the route A-B-D-E-H-J-L and 401 A-C-G-E-H-K-L are qualified, but these routes are competing for the 402 resource on the link E-H and cannot be established simultaneously, 403 so there must be one route failed to be reported to P-PCE. Given the 404 indication of allowing resource sharing on the link E-H, both of 405 these routes can be reported for P-PCE's decision, and there will 406 not be any competition as the P-PCE understands that only one path 407 needs to be set up. 409 3. Extensions to PCEP 411 3.1. Association Group and Type 413 According to the definition in [RFC8697], the association group is 414 used to associate multiple LSPs into one group for further path 415 computation considerations, such as disjointness and resource 416 sharing. An association ID will be used to identify the resource 417 sharing group. An association type that described disjointness has 418 been defined in [ietf-pce-association-diversity]. In this document, 419 a new association type is defined as follows: 421 Association type = TBD1 ("Sharing Association Type"). 423 A sharing group should have multiple LSPs. The number of LSPs and 424 the criteria for how LSPs share among each other are dependent on 425 local policy. 427 3.2. Resource Sharing TLV 429 The PCEP Resource Sharing group MAY carry the following TLV. It MAY 430 be carried within a PCReq message from the network element (or other 431 PCCs) so as to indicate the desired resource sharing requirements to 432 be applied by the stateful PCE during path computation. 434 0 1 2 3 436 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 1 438 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 440 | Type = [TBD2] | Length | 442 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 444 | Flags |B|S|N|L| 446 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 448 | Optional TLVs | 450 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 452 The following flags are defined: 454 * L (Link share) bit: when set, this flag indicates that the PCE 455 should prioritize the links shared by existing LSPs within the 456 sharing group for path computation. 458 * N (Node share) bit: when set, this flag indicates that the PCE 459 should prioritize the nodes shared by existing LSPs within the 460 sharing group for path computation. 462 * S (SRLG share) bit: when set, this flag indicates that the PCE 463 should set the SRLG (Shared Risk Link Group) of the computed LSP to 464 the same as existing LSPs within the sharing group for path 465 computation. 467 * B (Bandwidth share) bit: when set, this flag indicates that the 468 PCE should prioritize the bandwidth to be shared by LSPs within the 469 sharing group for bulk path computation. 471 It is worth noting that there can be multiple flags set which may 472 conflict with each. In this scenario, the result for path 473 computation will be dependent on the policy of PCE. 475 Optional TLVs may be needed to indicate the LSPs with which the 476 resource is shared. If multiple LSPs are required, the PCE may need 477 to consider different sharing policies, which is implementation 478 dependent and may result in a different computing result. The 479 selection policy among multiple computation result is out of the 480 scope of this document. 482 3.3. Processing Rules 484 To request a path allowing resource sharing with one or multiple 485 existing LSPs, a PCC includes a Resource Sharing TLV in the 486 Association Group Object in any kind of path computation request 487 message, such as the PCReq, PCUpd, or PCInitiate messages specified 488 in [RFC8231] and [RFC8281]. 490 On receipt of a PCEP message with a Resource Sharing TLV, a stateful 491 PCE MUST proceed as follows: 493 - If the Resource Sharing TLV is unknown/unsupported, the PCE will 494 follow procedures defined in [RFC5440]. That is, the PCE sends a 495 PCErr message with error type 26 (Association Error) and error 496 value 6 (Association Information Mismatch), and the related path 497 computation request is discarded. 499 - If the Resource Sharing TLV is extracted correctly, the PCE MUST 500 apply the requested resource sharing requirement. 502 The procedure of setting flags follows the rules defined in Section 503 3.1. The flags in the Resource Sharing TLV may be locally configured 504 on the requesting nodes via external entities, such as a network 505 management system or the entity that imposes the resource sharing 506 requirement. 508 It is worth noting that the Resource Sharing TLV can be used 509 together with other path indication objects like the IRO/XRO, with 510 different objectives. The first difference is, the use of the 511 Resource Sharing TLV is to set up an alternative path, instead a new 512 path. It is also dependent on the knowledge held be the PCC, e.g., 513 if the PCC has full knowledge of the path information and has a 514 strong preference on the route, it may send the request message with 515 an IRO to specify the route. On the other hand, if the PCC does not 516 know how the path should go but just wants to set up a new LSP to 517 replace the old one, it may use the Resource Sharing TLV instead of 518 an IRO. The second difference is that the Resource Sharing TLV is a 519 loose requirement. For example, if the constraint specified in an 520 IRO/XRO in an A-Z path computation request cannot be satisfied, the 521 reply message from PCE to PCC would be unsuccessful. However it is 522 still possible to have a path from the A-Z. If the target 523 node/link/SRLG/Bandwidth is set in the Resource Sharing TLV rather 524 than an IRO, the PCE may feedback a path from A-Z that does not 525 share the target specified in the Resource Sharing TLV. 527 4. Implementation Status 529 [Note to the RFC Editor - remove this section before publication, as 530 well as remove the reference to [RFC7942]. 532 Currently the authors are not aware of any implementations. 534 5. Manageability Considerations 536 All manageability requirements and considerations listed in 537 [RFC5440] and [RFC8231] apply to the PCEP protocol extensions 538 defined in this document. In addition, requirements and 539 considerations listed in this section apply. 541 5.1. Control of Function and Policy 543 A PCE or PCC implementation MUST allow operator-configured 544 associations and SHOULD allow setting of the resource sharing TLV 545 (Section 3.4) as described in this document. 547 5.2. Information and Data Models 549 An implementation SHOULD allow the operator to view the resource 550 sharing configured or created dynamically. Further implementation 551 SHOULD allow to view resource sharing associations reported by each 552 peer, and the current set of LSPs in the association. The PCEP YANG 553 module [ietf-pce-pcep-yang] includes association groups information. 555 5.3. Liveness Detection and Monitoring 557 Mechanisms defined in this document do not imply any new liveness 558 detection and monitoring requirements in addition to those already 559 listed in [RFC5440]. 561 5.4. Verify Correct Operations 563 Mechanisms defined in this document do not imply any new operation 564 verification requirements in addition to those already listed in 565 [RFC5440] and [RFC8231]. 567 5.5. Requirements on Other Protocols 569 Mechanisms defined in this document do not imply any new 570 requirements on other protocols. The configuration on local policy 571 may be accomplished by other protocols, such as Netconf. 573 5.6. Impact on Network Operations 575 Mechanisms defined in [RFC5440] and [RFC8231] also apply to PCEP 576 extensions defined in this document. 578 6. Security Considerations 580 Security of PCEP is discussed in [RFC5440] and [RFC6952]. The 581 extensions in this document do not change the fundamentals of 582 security for PCEP. 584 However, the introduction of the Resource Sharing TLV in the 585 Association Group Object provides a vector that may be used to probe 586 for information from a network. For example, a PCC that wants to 587 discover the path of an LSP with which it is not involved can issue 588 a request message with a Resource Sharing TLV and may be able to get 589 back quite a lot of information about the path of the LSP through 590 issuing multiple such requests for different endpoints and analyzing 591 the received results. To protect against this, a PCE SHOULD be 592 configured with access and authorization controls such that only 593 authorized PCCs (for example, those within the network) can make 594 computation requests, only specifically authorized PCCs can make 595 requests for resource sharing, and such requests relating to 596 specific LSPs are further limited to a select few PCCs. How such 597 access controls and authorization is managed is outside the scope of 598 this document, but it will at the least include Access Control 599 Lists. 601 Furthermore, a PCC must be aware that setting up an LSP that shares 602 resources with another LSP may be a way of attacking the other LSP, 603 for example by depriving it of the resources it needs to operate 604 correctly. Thus it is important that, both in PCEP and the 605 associated signaling protocols, only authorized resource sharing is 606 allowed. 608 7. IANA Considerations 610 7.1. Association Object Type Indicators 612 IANA maintains a registry called the "Path Computation Element 613 Protocol (PCEP) Numbers" registry with a subregistry called the 614 "Association Type Field" subregistry. IANA is requested to make an 615 assignment from that subregistry as follows: 617 Object Name Object Reference 618 Class Type 619 ------------------------------------------------------------ 621 TBD1 Sharing-group Association Type [this document] 623 7.2. PCEP TLV Definitions 625 This document defines the following TLVs to support the resource 626 sharing scenario: 628 Value Name Reference 629 ------------------------------------------------------------ 631 TBD2 Resource-sharing TLV [this document] 633 IANA is requested to allocate the following bit numbers in the flag 634 spaces of Resource-sharing TLV: 636 Bit Flag name Reference 638 31 Link Share [this document] 640 30 Node Share [this document] 642 29 SRLG Share [this document] 644 28 Bandwidth Share [this document] 646 8. References 648 8.1. Normative References 650 [RFC2119] Bradner, S., "Key words for use in RFCs to indicate 651 requirements levels", RFC 2119, March 1997. 652 . 654 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 655 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 656 Tunnels", RFC 3209, December 2001. . 659 [RFC5440] Vasseur, J.-P., and Le Roux, JL., "Path Computation 660 Element (PCE) Communication Protocol (PCEP)", RFC 5440, 661 March 2009. . 663 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 664 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 665 May 2017, . 667 [RFC8231] Crabbe, E., Medved, J., Minei, I., and R. Varga, "PCEP 668 Extensions for Stateful PCE", RFC8231, June 2017. 669 . 671 [RFC8281] Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "PCEP 672 Extensions for PCE-initiated LSP Setup in a Stateful PCE 673 Model", RFC 8281, October 2017. . 676 [RFC8697] Minei, I., Crabbe E., Sivabalan S., Ananthakrishnan H., 677 Dhody D., Tanaka Y., "PCEP Extensions for Establishing 678 Relationships Between Sets of LSPs", RFC8697, January 679 2020. . 681 [ietf-pce-association-diversity] Litkowski, S., Sivabalan, S., 682 Barth, C., Dhody, D., "Path Computation Element 683 communication Protocol extension for signaling LSP 684 diversity constraint", work in progress. 686 8.2. Informative References 688 [RFC4428] Papadimitriou, D., Mannie., E., "Analysis of Generalized 689 Multi-Protocol Label Switching (GMPLS)-based Recovery 690 Mechanisms (including Protection and Restoration)", 691 RFC4428, March 2006. . 694 [RFC4655] Farrel, A., Vasseur, J.-P., and Ash, J., "A Path 695 Computation Element (PCE)-Based Architecture", RFC 4655, 696 August 2006. . 698 [RFC5623] Oki., E., Takeda, T., Le Roux, JL., Farrel, A., "Framework 699 for PCE-Based Inter-Layer MPLS and GMPLS Traffic 700 Engineering", RFC5623, September 2009. . 703 [RFC6952] Jethanandani, M., Patel, K., Zheng, L., "Analysis of BGP, 704 LDP, PCEP, and MSDP Issues According to the Keying and 705 Authentication for Routing Protocols (KARP) Design Guide", 706 RFC6952, May 2013. . 709 [RFC7399] Farrel, A., King, D., "Unanswered Questions in the Path 710 Computation Element Architecture", RFC7399, October 2014. 711 . 713 [RFC7942] Sheffer, Y., Farrel, A., "Improving Awareness of Running 714 Code: The Implementation Status Section", RFC7942, July 715 2016. . 717 [RFC8751] Dhody, D., Lee, Y., Ceccarelli, D., Shin, J., King, D., 718 Gonzalez de Dios, O., "Hierarchical Stateful Path 719 Computation Element (PCE)", RFC8751, March 2020. 720 . 722 [ietf-pce-pcep-yang] Dhody, D., Hardwick, J., Beeram, V., Tantsura, 723 J., "A YANG Data Model for Path Computation Element 724 Communications Protocol(PCEP)", work in progress. 726 9. Acknowledgements 728 The authors would like to thank Adrian Farrel for his review and 729 valuable comments. 731 10. Contributor's Address 733 Dhruv Dhody 734 Huawei Technologies 735 Email: dhruv.dhody@huawei.com 737 Igor Bryskin 738 Huawei Technologies 739 Email: Igor.Bryskin@huawei.com 741 11. Authors' Addresses 743 Xian Zhang 744 Huawei Technologies 745 Email: zhang.xian@huawei.com 747 Haomian Zheng 748 Huawei Technologies 749 Email: zhenghaomian@huawei.com 751 Oscar Gonzalez de Dios 752 Telefonica I+D/gCTIO 753 Distrito Telefonica 754 E-28050 Madrid, Spain 755 EMail: oscar.gonzalezdedios@telefonica.com 757 Victor Lopez 758 Telefonica I+D/gCTIO 759 Distrito Telefonica 760 E-28050 Madrid, Spain 761 EMail: victor.lopezalvarez@telefonica.com 763 Yunbin Xu 764 CAICT 765 xuyunbin@caict.ac.cn