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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-18) exists of draft-ietf-pce-pcep-yang-12 Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 PCE Working Group A. Raghuram 3 Internet-Draft A. Goddard 4 Intended status: Standards Track AT&T 5 Expires: April 15, 2020 J. Karthik 6 S. Sivabalan 7 Cisco Systems, Inc. 8 M. Negi 9 Huawei Technologies 10 October 13, 2019 12 Ability for a Stateful Path Computation Element (PCE) to request and 13 obtain control of a Label Switched Path (LSP) 14 draft-ietf-pce-lsp-control-request-11 16 Abstract 18 A Stateful Path Computation Element (PCE) retains information about 19 the placement of Multiprotocol Label Switching (MPLS) Traffic 20 Engineering Label Switched Paths (TE LSPs). When a PCE has stateful 21 control over LSPs it may send indications to LSP head-ends to modify 22 the attributes (especially the paths) of the LSPs. A Path 23 Computation Client (PCC) that has set up LSPs under local 24 configuration may delegate control of those LSPs to a stateful PCE. 26 There are use-cases in which a stateful PCE may wish to obtain 27 control of locally configured LSPs of which it is aware but that have 28 not been delegated to the PCE. 30 This document describes an extension to the Path Computation Element 31 communication Protocol (PCEP) to enable a PCE to make requests for 32 such control. 34 Status of This Memo 36 This Internet-Draft is submitted in full conformance with the 37 provisions of BCP 78 and BCP 79. 39 Internet-Drafts are working documents of the Internet Engineering 40 Task Force (IETF). Note that other groups may also distribute 41 working documents as Internet-Drafts. The list of current Internet- 42 Drafts is at https://datatracker.ietf.org/drafts/current/. 44 Internet-Drafts are draft documents valid for a maximum of six months 45 and may be updated, replaced, or obsoleted by other documents at any 46 time. It is inappropriate to use Internet-Drafts as reference 47 material or to cite them other than as "work in progress." 48 This Internet-Draft will expire on April 15, 2020. 50 Copyright Notice 52 Copyright (c) 2019 IETF Trust and the persons identified as the 53 document authors. All rights reserved. 55 This document is subject to BCP 78 and the IETF Trust's Legal 56 Provisions Relating to IETF Documents 57 (https://trustee.ietf.org/license-info) in effect on the date of 58 publication of this document. Please review these documents 59 carefully, as they describe your rights and restrictions with respect 60 to this document. Code Components extracted from this document must 61 include Simplified BSD License text as described in Section 4.e of 62 the Trust Legal Provisions and are provided without warranty as 63 described in the Simplified BSD License. 65 Table of Contents 67 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 68 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 69 2.1. Requirements Language . . . . . . . . . . . . . . . . . . 4 70 3. LSP Control Request Flag . . . . . . . . . . . . . . . . . . 4 71 4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 5 72 5. Implementation Status . . . . . . . . . . . . . . . . . . . . 6 73 5.1. Huawei's Proof of Concept based on ONOS . . . . . . . . . 6 74 6. Security Considerations . . . . . . . . . . . . . . . . . . . 7 75 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 76 7.1. SRP Object Flags . . . . . . . . . . . . . . . . . . . . 8 77 8. Manageability Considerations . . . . . . . . . . . . . . . . 8 78 8.1. Control of Function and Policy . . . . . . . . . . . . . 8 79 8.2. Information and Data Models . . . . . . . . . . . . . . . 8 80 8.3. Liveness Detection and Monitoring . . . . . . . . . . . . 8 81 8.4. Verify Correct Operations . . . . . . . . . . . . . . . . 8 82 8.5. Requirements On Other Protocols . . . . . . . . . . . . . 9 83 8.6. Impact On Network Operations . . . . . . . . . . . . . . 9 84 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 85 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 86 10.1. Normative References . . . . . . . . . . . . . . . . . . 9 87 10.2. Informative References . . . . . . . . . . . . . . . . . 10 88 Appendix A. Contributor Addresses . . . . . . . . . . . . . . . 11 89 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 91 1. Introduction 93 Stateful Path Computation Element (PCE) communication Protocol (PCEP) 94 extensions [RFC8231] specifies a set of extensions to PCEP [RFC5440] 95 to enable stateful control of Traffic Engineering Label Switched 96 Paths (TE LSPs) between and across PCEP sessions in compliance with 97 [RFC4657]. It includes mechanisms to synchronize LSP state between 98 Path Computation Clients (PCCs) and PCEs, delegate control of LSPs to 99 PCE, and PCE-control of timing and sequence of path computations 100 within and across PCEP sessions. The stateful PCEP defines the 101 following two useful network operations: 103 o Delegation: As per [RFC8051], an operation to grant a PCE 104 temporary rights to modify a subset of LSP parameters on one or 105 more LSPs of a PCC. LSPs are delegated from a PCC to a PCE and 106 are referred to as "delegated" LSPs. 108 o Revocation: As per [RFC8231], an operation performed by a PCC on a 109 previously delegated LSP. Revocation revokes the rights granted 110 to the PCE in the delegation operation. 112 For Redundant Stateful PCEs (section 5.7.4. of [RFC8231]), during a 113 PCE failure, one of the redundant PCE might want to request to take 114 control over an LSP. The redundant PCEs may use a local policy or a 115 proprietary election mechanism to decide which PCE would take 116 control. In this case, a mechanism is needed for a stateful PCE to 117 request control of one or more LSPs from a PCC, so that a newly 118 elected primary PCE can request to take over control. 120 In case of virtualized PCEs (vPCEs) running in virtual network 121 function (VNF) mode, as the computation load in the network 122 increases, a new instance of vPCE could be instantiated to balance 123 the current load. The PCEs could use a proprietary algorithm to 124 decide which LSPs to be assigned to the new vPCE. Thus, having a 125 mechanism for the PCE to request control of some LSPs is needed. 127 In some deployments, the operator would like to use stateful PCE for 128 global optimization algorithms but would still like to keep the 129 control of the LSP at the PCC. In such cases, a stateful PCE could 130 request to take control during the global optimization and return the 131 delegation once done. 133 Note that [RFC8231] specifies a mechanism for a PCC to delegate an 134 orphaned LSP to another PCE. The mechanism defined in this document 135 can be used in conjunction to [RFC8231]. Ultimately, it is the PCC 136 that decides which PCE to delegate the orphaned LSP to. 138 This specification provides a simple extension: by using it a PCE can 139 request control of one or more LSPs from any PCC over the stateful 140 PCEP session. The procedures for granting and relinquishing control 141 of the LSPs are specified in accordance with the specification 142 [RFC8231] unless explicitly set aside in this document. 144 2. Terminology 146 This document uses the following terms defined in [RFC5440]: 148 PCC: Path Computation Client. 150 PCE: Path Computation Element. 152 PCEP: Path Computation Element communication Protocol. 154 This document uses the following terms defined in [RFC8231]: 156 PCRpt: Path Computation State Report message. 158 PCUpd: Path Computation Update Request message. 160 PLSP-ID: A PCEP-specific identifier for the LSP. 162 SRP: Stateful PCE Request Parameters. 164 Readers of this document are expected to have some familiarity with 165 [RFC8231]. 167 2.1. Requirements Language 169 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 170 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 171 "OPTIONAL" in this document are to be interpreted as described in BCP 172 14 [RFC2119] [RFC8174] when, and only when, they appear in all 173 capitals, as shown here. 175 3. LSP Control Request Flag 177 The Stateful PCE Request Parameters (SRP) object is defined in 178 Section 7.2 of [RFC8231] and it includes a Flags field. 180 A new flag, the "LSP-Control Request Flag" (C) - TBD, is introduced 181 in the SRP object. On a PCUpd message, a PCE sets the C Flag to 1 to 182 indicate that it wishes to gain control of LSPs. The LSPs are 183 identified by the PLSP-ID in the LSP object following the SRP object. 184 A PLSP-ID of value other than 0 and 0xFFFFF is used to identify the 185 LSP for which the PCE requests control. The PLSP-ID value of 0 186 indicates that the PCE is requesting control of all LSPs originating 187 from the PCC that it wishes to delegate. The C Flag has no meaning 188 in other PCEP messages that carry SRP objects and for which the C 189 flag MUST be set to 0 on transmission and MUST be ignored on receipt. 191 4. Operation 193 During normal operation, a PCC that wishes to delegate the control of 194 an LSP sets the D Flag (delegate, Section 7.3 of [RFC8231]) to 1 in 195 all PCRpt messages pertaining to the LSP. The PCE confirms the 196 delegation by setting D Flag to 1 in all PCUpd messages pertaining to 197 the LSP. The PCC revokes the control of the LSP from the PCE by 198 setting D Flag to 0 in PCRpt messages pertaining to the LSP. If the 199 PCE wishes to relinquish the control of the LSP, it sets D Flag to 0 200 in all PCUpd messages pertaining to the LSP. 202 If a PCE wishes to gain control over an LSP, it sends a PCUpd message 203 with C Flag set to 1 in SRP object. The LSP for which the PCE 204 requests control is identified by the PLSP-ID in the associated LSP 205 object. The PLSP-ID of 0 indicates that the PCE wants control over 206 all LSPs originating from the PCC. An implementation of this feature 207 needs to make sure to check for the LSP control feature (C flag set 208 to 1) before any check for PLSP-ID (as prescribed in [RFC8231]). The 209 D Flag and C Flag are mutually exclusive in a PCUpd message. The PCE 210 MUST NOT send a control request for the LSP which is already 211 delegated to the PCE, i.e. if the D Flag is set in the PCUpd message, 212 then the C Flag MUST NOT be set. If a PCC receives a PCUpd message 213 with D Flag set in the LSP object (i.e. LSP is already delegated) 214 and the C Flag is also set (i.e. PCE is making a control request), 215 the PCC MUST ignore the C Flag. A PCC can decide to delegate the 216 control of the LSP at its own discretion. If the PCC grants or 217 denies the control, it sends a PCRpt message with D Flag set to 1 and 218 0 respectively in accordance with stateful PCEP [RFC8231]. If the 219 PCC does not grant the control, it MAY choose to not respond, and the 220 PCE MAY choose to retry requesting the control preferably using 221 exponentially increasing timer. Note that, if the PCUpd message with 222 C Flag set is received for a currently non-delegated LSP (for which 223 the PCE is requesting delegation), this MUST NOT trigger the error 224 handling as specified in [RFC8231] (a PCErr with Error-type=19 225 (Invalid Operation) and error-value 1 (Attempted LSP Update Request 226 for a non-delegated LSP)). 228 As per [RFC8231], a PCC cannot delegate an LSP to more than one PCE 229 at any time. If a PCE requests control of an LSP that has already 230 been delegated by the PCC to another PCE, the PCC MAY ignore the 231 request, or MAY revoke the delegation to the first PCE before 232 delegating it to the second. This choice is a matter of local 233 policy. 235 It should be noted that a legacy implementation of PCC that does not 236 support this extension would receive an LSP control request: PCUpd 237 message with C flag set and D flag (delegate) unset, it would ignore 238 the C flag and trigger the error condition for the D flag as 239 specified in [RFC8231] (a PCErr with Error-type=19 (Invalid 240 Operation) and error-value 1 (Attempted LSP Update Request for a non- 241 delegated LSP)). Further, in case of PLSP-ID of 0, the error 242 condition as specified in [RFC8231] (a PCErr with Error-type=19 243 (Invalid Operation) and error-value 3 (Attempted LSP Update Request 244 for an LSP identified by an unknown PSP-ID)) would be triggered. 246 [RFC8281] describes the setup, maintenance and teardown of PCE- 247 initiated LSPs under the stateful PCE model. It also specifies how a 248 PCE may obtain control over an orphaned LSP that was PCE-initiated. 249 A PCE implementation can apply the mechanism described in this 250 document in conjunction with those in [RFC8281]. 252 5. Implementation Status 254 [Note to the RFC Editor - remove this section before publication, as 255 well as remove the reference to RFC 7942.] 257 This section records the status of known implementations of the 258 protocol defined by this specification at the time of posting of this 259 Internet-Draft, and is based on a proposal described in [RFC7942]. 260 The description of implementations in this section is intended to 261 assist the IETF in its decision processes in progressing drafts to 262 RFCs. Please note that the listing of any individual implementation 263 here does not imply endorsement by the IETF. Furthermore, no effort 264 has been spent to verify the information presented here that was 265 supplied by IETF contributors. This is not intended as, and must not 266 be construed to be, a catalog of available implementations or their 267 features. Readers are advised to note that other implementations may 268 exist. 270 According to [RFC7942], "this will allow reviewers and working groups 271 to assign due consideration to documents that have the benefit of 272 running code, which may serve as evidence of valuable experimentation 273 and feedback that have made the implemented protocols more mature. 274 It is up to the individual working groups to use this information as 275 they see fit". 277 5.1. Huawei's Proof of Concept based on ONOS 279 The PCE function was developed in the ONOS open source platform. 280 This extension was implemented on a private version as a proof of 281 concept to enable multi-instance support. 283 o Organization: Huawei 285 o Implementation: Huawei's PoC based on ONOS 286 o Description: PCEP as a southbound plugin was added to ONOS. To 287 support multi-instance ONOS deployment in a cluster, this 288 extension in PCEP is used. Refer 289 https://wiki.onosproject.org/display/ONOS/PCEP+Protocol 291 o Maturity Level: Prototype 293 o Coverage: Full 295 o Contact: satishk@huawei.com 297 6. Security Considerations 299 The security considerations listed in [RFC8231] and [RFC8281] apply 300 to this document as well. However, this document also introduces a 301 new attack vector. An attacker may flood the PCC with request to 302 delegate all of its LSPs at a rate which exceeds the PCC's ability to 303 process them, either by spoofing messages or by compromising the PCE 304 itself. The PCC SHOULD be configured with a threshold rate for the 305 delegation requests received from the PCE. If the threshold is 306 reached, it is RECOMMENDED to log the issue. 308 A PCC is the ultimate arbiter of delegation. As per [RFC8231], a 309 local policy at PCC is used to influence the delegation. A PCC can 310 also revoke the delegation at any time. A PCC need not blindly trust 311 the control requests and SHOULD take local policy and other factors 312 into consideration before honoring the request. 314 Note that, a PCE may not be sure if a PCC supports this feature. A 315 PCE would try sending a control request to a 'legacy' PCC, which 316 would in turn respond with an error as described in Section 4. So a 317 PCE would learn this fact only when it wants to take control over an 318 LSP. A PCE might also be susceptible to a downgrade attacks by 319 falsifying the error condition. 321 As per [RFC8231], it is RECOMMENDED that these PCEP extensions only 322 be activated on authenticated and encrypted sessions across PCEs and 323 PCCs belonging to the same administrative authority, using Transport 324 Layer Security (TLS) [RFC8253], as per the recommendations and best 325 current practices in BCP 195 [RFC7525] (unless explicitly excluded in 326 [RFC8253]). 328 7. IANA Considerations 329 7.1. SRP Object Flags 331 IANA maintains a registry called the "Path Computation Element 332 Protocol (PCEP) Numbers" registry. It contains a subregistry called 333 the "SRP Object Flag Field" registry. This document requests IANA to 334 allocate following code point in the "SRP Object Flag Field" 335 subregistry. 337 Bit Description Reference 338 TBD LSP-Control Request Flag This document 340 8. Manageability Considerations 342 All manageability requirements and considerations listed in [RFC5440] 343 and [RFC8231] apply to PCEP protocol extensions defined in this 344 document. In addition, requirements and considerations listed in 345 this section apply. 347 8.1. Control of Function and Policy 349 A PCC implementation SHOULD allow the operator to configure the 350 policy based on which it honors the request to control the LSPs. 351 This includes the handling of the case where an LSP control request 352 is received for an LSP that is currently delegated to some other PCE. 353 A PCC implementation SHOULD also allow the operator to configure the 354 threshold rate based on which it accepts the delegation requests from 355 the PCE. Further, the operator MAY be allowed to trigger the LSP 356 control request for a particular LSP at the PCE. A PCE 357 implementation SHOULD also allow the operator to configure an 358 exponentially increasing timer to retry the control requests for 359 which the PCE did not get a response. 361 8.2. Information and Data Models 363 The PCEP YANG module [I-D.ietf-pce-pcep-yang] could be extended to 364 include mechanism to trigger the LSP control request. 366 8.3. Liveness Detection and Monitoring 368 Mechanisms defined in this document do not imply any new liveness 369 detection and monitoring requirements in addition to those already 370 listed in [RFC5440]. 372 8.4. Verify Correct Operations 374 Mechanisms defined in this document do not imply any new operation 375 verification requirements in addition to those already listed in 376 [RFC5440] and [RFC8231]. 378 8.5. Requirements On Other Protocols 380 Mechanisms defined in this document do not imply any new requirements 381 on other protocols. 383 8.6. Impact On Network Operations 385 Mechanisms defined in [RFC5440] and [RFC8231] also apply to PCEP 386 extensions defined in this document. Further, the mechanism 387 described in this document can help the operator to request control 388 of the LSPs at a particular PCE. 390 9. Acknowledgements 392 Thanks to Jonathan Hardwick to remind the authors to not use 393 suggested values in IANA section. 395 Thanks to Adrian Farrel, Haomian Zheng and Tomonori Takeda for their 396 valuable comments. 398 Thanks to Shawn M. Emery for security directorate's review. 400 Thanks to Francesca Palombini for GENART review. 402 Thanks to Benjamin Kaduk, Martin Vigoureux, Alvaro Retana, and Barry 403 Leiba for IESG reviews. 405 10. References 407 10.1. Normative References 409 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 410 Requirement Levels", BCP 14, RFC 2119, 411 DOI 10.17487/RFC2119, March 1997, 412 . 414 [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation 415 Element (PCE) Communication Protocol (PCEP)", RFC 5440, 416 DOI 10.17487/RFC5440, March 2009, 417 . 419 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 420 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 421 May 2017, . 423 [RFC8231] Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path 424 Computation Element Communication Protocol (PCEP) 425 Extensions for Stateful PCE", RFC 8231, 426 DOI 10.17487/RFC8231, September 2017, 427 . 429 [RFC8281] Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path 430 Computation Element Communication Protocol (PCEP) 431 Extensions for PCE-Initiated LSP Setup in a Stateful PCE 432 Model", RFC 8281, DOI 10.17487/RFC8281, December 2017, 433 . 435 10.2. Informative References 437 [RFC4657] Ash, J., Ed. and J. Le Roux, Ed., "Path Computation 438 Element (PCE) Communication Protocol Generic 439 Requirements", RFC 4657, DOI 10.17487/RFC4657, September 440 2006, . 442 [RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre, 443 "Recommendations for Secure Use of Transport Layer 444 Security (TLS) and Datagram Transport Layer Security 445 (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May 446 2015, . 448 [RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running 449 Code: The Implementation Status Section", BCP 205, 450 RFC 7942, DOI 10.17487/RFC7942, July 2016, 451 . 453 [RFC8051] Zhang, X., Ed. and I. Minei, Ed., "Applicability of a 454 Stateful Path Computation Element (PCE)", RFC 8051, 455 DOI 10.17487/RFC8051, January 2017, 456 . 458 [RFC8253] Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody, 459 "PCEPS: Usage of TLS to Provide a Secure Transport for the 460 Path Computation Element Communication Protocol (PCEP)", 461 RFC 8253, DOI 10.17487/RFC8253, October 2017, 462 . 464 [I-D.ietf-pce-pcep-yang] 465 Dhody, D., Hardwick, J., Beeram, V., and J. Tantsura, "A 466 YANG Data Model for Path Computation Element 467 Communications Protocol (PCEP)", draft-ietf-pce-pcep- 468 yang-12 (work in progress), July 2019. 470 Appendix A. Contributor Addresses 472 Dhruv Dhody 473 Huawei Technologies 474 Divyashree Techno Park, Whitefield 475 Bangalore, Karnataka 560066 476 India 478 EMail: dhruv.ietf@gmail.com 480 Jon Parker 481 Cisco Systems, Inc. 482 2000 Innovation Drive 483 Kanata, Ontario K2K 3E8 484 Canada 486 EMail: jdparker@cisco.com 488 Chaitanya Yadlapalli 489 AT&T 490 200 S Laurel Aevenue 491 Middletown NJ 07748 492 USA 494 EMail: cy098d@att.com 496 Authors' Addresses 498 Aswatnarayan Raghuram 499 AT&T 500 200 S Laurel Aevenue 501 Middletown, NJ 07748 502 USA 504 EMail: ar2521@att.com 506 Al Goddard 507 AT&T 508 200 S Laurel Aevenue 509 Middletown, NJ 07748 510 USA 512 EMail: ag6941@att.com 513 Jay Karthik 514 Cisco Systems, Inc. 515 125 High Street 516 Boston, Massachusetts 02110 517 USA 519 EMail: jakarthi@cisco.com 521 Siva Sivabalan 522 Cisco Systems, Inc. 523 2000 Innovation Drive 524 Kanata, Ontario K2K 3E8 525 Canada 527 EMail: msiva@cisco.com 529 Mahendra Singh Negi 530 Huawei Technologies 531 Divyashree Techno Park, Whitefield 532 Bangalore, Karnataka 560066 533 India 535 EMail: mahend.ietf@gmail.com