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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documents in RFCs) -- Obsolete informational reference (is this intentional?): RFC 7525 (Obsoleted by RFC 9325) == Outdated reference: A later version (-23) exists of draft-ietf-pce-pcep-yang-11 Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 2 comments (--). 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: December 23, 2019 J. Karthik 6 S. Sivabalan 7 Cisco Systems, Inc. 8 M. Negi 9 Huawei Technologies 10 June 21, 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-05 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) has set up LSPs under local configuration 24 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 such requests. 33 Status of This Memo 35 This Internet-Draft is submitted in full conformance with the 36 provisions of BCP 78 and BCP 79. 38 Internet-Drafts are working documents of the Internet Engineering 39 Task Force (IETF). Note that other groups may also distribute 40 working documents as Internet-Drafts. The list of current Internet- 41 Drafts is at https://datatracker.ietf.org/drafts/current/. 43 Internet-Drafts are draft documents valid for a maximum of six months 44 and may be updated, replaced, or obsoleted by other documents at any 45 time. It is inappropriate to use Internet-Drafts as reference 46 material or to cite them other than as "work in progress." 48 This Internet-Draft will expire on December 23, 2019. 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 . . . . . . . . . . . . . . . . . . . . . . . . . . 4 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 . . . . . . . . . . . . . . . . . . . . 7 77 8. Manageability Considerations . . . . . . . . . . . . . . . . 7 78 8.1. Control of Function and Policy . . . . . . . . . . . . . 7 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 . . . . . . . . . . . . . 8 83 8.6. Impact On Network Operations . . . . . . . . . . . . . . 8 84 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8 85 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 86 10.1. Normative References . . . . . . . . . . . . . . . . . . 8 87 10.2. Informative References . . . . . . . . . . . . . . . . . 9 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 effect LSP state 98 synchronization between Path Computation Clients (PCCs) and PCEs, 99 delegation of control of LSPs to PCE, and PCE control of timing and 100 sequence of path computations within and across PCEP sessions. The 101 stateful PCEP defines the 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 could request to take control 114 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 (vPCE) running as virtual network 121 function (VNF), as the computation load in the network increases, a 122 new instance of vPCE could be instantiated to balance the current 123 load. The PCEs could use proprietary algorithm to decide which LSPs 124 to be assigned to the new vPCE. Thus having a mechanism for the PCE 125 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] specify 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. 138 This specification provides a simple extension, by using this a PCE 139 can request control of one or more LSPs from any PCC over the 140 stateful PCEP session. The procedures for granting and relinquishing 141 control of the LSPs are specified in accordance with the 142 specification [RFC8231]. 144 2. Terminology 146 The following terminologies are used in this document: 148 PCC: Path Computation Client. 150 PCE: Path Computation Element 152 PCEP: Path Computation Element communication Protocol. 154 PCRpt: Path Computation State Report message. 156 PCUpd: Path Computation Update Request message. 158 PLSP-ID: A PCEP-specific identifier for the LSP. 160 2.1. Requirements Language 162 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 163 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 164 "OPTIONAL" in this document are to be interpreted as described in BCP 165 14 [RFC2119] [RFC8174] when, and only when, they appear in all 166 capitals, as shown here. 168 3. LSP Control Request Flag 170 The Stateful PCE Request Parameters (SRP) object is defined in 171 [RFC8231], it includes a Flags field. 173 A new flag, the "LSP-Control Request Flag" (C), is introduced in the 174 SRP object. On a PCUpd message, a PCE sets the C Flag to 1 to 175 indicate that, it wishes to gain control of LSPs. The LSPs are 176 identified by the LSP object. A PLSP-ID of value other than 0 and 177 0xFFFFF is used to identify the LSP for which the PCE requests 178 control. The PLSP-ID value of 0 indicates that the PCE is requesting 179 control of all LSPs originating from the PCC that it wishes to 180 delegate. The C flag has no meaning in the PCRpt and PCInitiate 181 message and MUST be set to 0 on transmission and MUST be ignored on 182 receipt. 184 4. Operation 186 During normal operation, a PCC that wishes to delegate the control of 187 an LSP sets the D Flag (delegate) to 1 in all PCRpt messages 188 pertaining to the LSP. The PCE confirms the delegation by setting D 189 Flag to 1 in all PCUpd messages pertaining to the LSP. The PCC 190 revokes the control of the LSP from the PCE by setting D Flag to 0 in 191 PCRpt messages pertaining to the LSP. If the PCE wishes to 192 relinquish the control of the LSP, it sets D Flag to 0 in all PCUpd 193 messages pertaining to the LSP. 195 If a PCE wishes to gain control over an LSP, it sends a PCUpd message 196 with C Flag set to 1 in SRP object. The LSP for which the PCE 197 requests control is identified by the PLSP-ID. The PLSP-ID of 0 198 indicates that the PCE wants control over all LSPs originating from 199 the PCC. A PCC that receives a PCUpd message with C Flag set to 1 200 and PLSP-ID of 0 MUST NOT trigger the error condition for unknown 201 PLSP-ID in an LSP update request as per [RFC8231]. The PCE SHOULD 202 NOT send control request for LSP which is already delegated to the 203 PCE, i.e. if the D flag is set in the PCUpd message, then C flag 204 SHOULD NOT be set. If a PCC receives a PCUpd message with D flag set 205 in the LSP object (i.e. LSP is already delegated) and the C flag is 206 also set (i.e. PCE is making a control request), the PCC MUST ignore 207 the C Flag. A PCC can decide to delegate the control of the LSP at 208 its own discretion. If the PCC grants or denies the control, it 209 sends PCRpt message with D Flag set to 1 and 0 respectively in 210 accordance with stateful PCEP [RFC8231]. If the PCC does not grant 211 the control, it MAY choose to not respond, and the PCE MAY choose to 212 retry requesting the control preferably using exponentially 213 increasing timer. A PCE ignores the C Flag on the PCRpt message. 214 Note that, the PCUpd message with C flag set is received for a 215 currently non-delegated LSP (for which the PCE is requesting 216 delegation), this MUST NOT trigger the error handling as specified in 217 [RFC8231] (a PCErr with Error-type=19 (Invalid Operation) and error- 218 value 1 (Attempted LSP Update Request for a non-delegated LSP)). 220 As per [RFC8231], a PCC cannot delegate an LSP to more than one PCE 221 at any time. If a PCE requests control of an LSP that has already 222 been delegated by the PCC to another PCE, the PCC MAY ignore the 223 request, or MAY revoke the delegation to the first PCE before 224 delegating it to the second. This choice is a matter of local 225 policy. 227 It should be noted that a legacy implementation of PCC, that does not 228 support this extension would trigger the error condition as specified 229 in [RFC8231] (a PCErr with Error-type=19 (Invalid Operation) and 230 error-value 1 (Attempted LSP Update Request for a non-delegated LSP)) 231 as the D flag would be unset in this update request. Further, in 232 case of PLSP-ID of 0, the error condition as specified in [RFC8231] 233 (a PCErr with Error-type=19 (Invalid Operation) and error-value 3 234 (Attempted LSP Update Request for an LSP identified by an unknown 235 PSP-ID)) would be triggered. 237 [RFC8281] describes the setup, maintenance and teardown of PCE- 238 initiated LSPs under the stateful PCE model. It also specify how a 239 PCE MAY obtain control over an orphaned LSP that was PCE-initiated. 241 A PCE implementation can apply the mechanism described in this 242 document in conjunction with those in [RFC8281]. 244 5. Implementation Status 246 [Note to the RFC Editor - remove this section before publication, as 247 well as remove the reference to RFC 7942.] 249 This section records the status of known implementations of the 250 protocol defined by this specification at the time of posting of this 251 Internet-Draft, and is based on a proposal described in [RFC7942]. 252 The description of implementations in this section is intended to 253 assist the IETF in its decision processes in progressing drafts to 254 RFCs. Please note that the listing of any individual implementation 255 here does not imply endorsement by the IETF. Furthermore, no effort 256 has been spent to verify the information presented here that was 257 supplied by IETF contributors. This is not intended as, and must not 258 be construed to be, a catalog of available implementations or their 259 features. Readers are advised to note that other implementations may 260 exist. 262 According to [RFC7942], "this will allow reviewers and working groups 263 to assign due consideration to documents that have the benefit of 264 running code, which may serve as evidence of valuable experimentation 265 and feedback that have made the implemented protocols more mature. 266 It is up to the individual working groups to use this information as 267 they see fit". 269 5.1. Huawei's Proof of Concept based on ONOS 271 The PCE function was developed in the ONOS open source platform. 272 This extension was implemented on a private version as a proof of 273 concept to enable multi-instance support. 275 o Organization: Huawei 277 o Implementation: Huawei's PoC based on ONOS 279 o Description: PCEP as a southbound plugin was added to ONOS. To 280 support multi-instance ONOS deployment in a cluster, this 281 extension in PCEP is used. Refer 282 https://wiki.onosproject.org/display/ONOS/PCEP+Protocol 284 o Maturity Level: Prototype 286 o Coverage: Full 288 o Contact: satishk@huawei.com 290 6. Security Considerations 292 The security considerations listed in [RFC8231] and [RFC8281] apply 293 to this document as well. However, this document also introduces a 294 new attack vector. An attacker may flood the PCC with request to 295 delegate all its LSPs at a rate which exceeds the PCC's ability to 296 process them, either by spoofing messages or by compromising the PCE 297 itself. The PCC SHOULD be configured with a threshold rate for the 298 delegation requests received from the PCE. If threshold is reached, 299 it is RECOMMENDED to log the issue. 301 As per [RFC8231], it is RECOMMENDED that these PCEP extensions only 302 be activated on authenticated and encrypted sessions across PCEs and 303 PCCs belonging to the same administrative authority, using Transport 304 Layer Security (TLS) [RFC8253], as per the recommendations and best 305 current practices in [RFC7525] (unless explicitly set aside in 306 [RFC8253]). 308 7. IANA Considerations 310 7.1. SRP Object Flags 312 IANA maintains a registry called the "Path Computation Element 313 Protocol (PCEP) Numbers" registry. It contains a subregistry called 314 the "SRP Object Flag Field" registry. This document requests IANA to 315 allocate following code point in the "SRP Object Flag Field" 316 subregistry. 318 Bit Description Reference 319 TBD LSP-Control This document 321 8. Manageability Considerations 323 All manageability requirements and considerations listed in [RFC5440] 324 and [RFC8231] apply to PCEP protocol extensions defined in this 325 document. In addition, requirements and considerations listed in 326 this section apply. 328 8.1. Control of Function and Policy 330 A PCC implementation SHOULD allow the operator to configure the 331 policy based on which it honors the request to control the LSPs. 332 This includes the handling of the case where an LSP control request 333 is received for an LSP that is currently delegated to some other PCE. 334 Further, the operator MAY be to be allowed to trigger the LSP control 335 request for a particular LSP at the PCE. A PCE implementation SHOULD 336 also allow the operator to configure an exponentially increasing 337 timer to retry the control requests for which the PCE did not get a 338 response. 340 8.2. Information and Data Models 342 The PCEP YANG module [I-D.ietf-pce-pcep-yang] could be extended to 343 include mechanism to trigger the LSP control request. 345 8.3. Liveness Detection and Monitoring 347 Mechanisms defined in this document do not imply any new liveness 348 detection and monitoring requirements in addition to those already 349 listed in [RFC5440]. 351 8.4. Verify Correct Operations 353 Mechanisms defined in this document do not imply any new operation 354 verification requirements in addition to those already listed in 355 [RFC5440] and [RFC8231]. 357 8.5. Requirements On Other Protocols 359 Mechanisms defined in this document do not imply any new requirements 360 on other protocols. 362 8.6. Impact On Network Operations 364 Mechanisms defined in [RFC5440] and [RFC8231] also apply to PCEP 365 extensions defined in this document. Further, the mechanism 366 described in this document can help the operator to request control 367 of the LSPs at a particular PCE. 369 9. Acknowledgements 371 Thanks to Jonathan Hardwick to remind the authors to not use 372 suggested values in IANA section. 374 Thanks to Adrian Farrel and Haomian Zheng for the review comments. 376 10. References 378 10.1. Normative References 380 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 381 Requirement Levels", BCP 14, RFC 2119, 382 DOI 10.17487/RFC2119, March 1997, 383 . 385 [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation 386 Element (PCE) Communication Protocol (PCEP)", RFC 5440, 387 DOI 10.17487/RFC5440, March 2009, 388 . 390 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 391 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 392 May 2017, . 394 [RFC8231] Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path 395 Computation Element Communication Protocol (PCEP) 396 Extensions for Stateful PCE", RFC 8231, 397 DOI 10.17487/RFC8231, September 2017, 398 . 400 [RFC8281] Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path 401 Computation Element Communication Protocol (PCEP) 402 Extensions for PCE-Initiated LSP Setup in a Stateful PCE 403 Model", RFC 8281, DOI 10.17487/RFC8281, December 2017, 404 . 406 10.2. Informative References 408 [RFC4657] Ash, J., Ed. and J. Le Roux, Ed., "Path Computation 409 Element (PCE) Communication Protocol Generic 410 Requirements", RFC 4657, DOI 10.17487/RFC4657, September 411 2006, . 413 [RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre, 414 "Recommendations for Secure Use of Transport Layer 415 Security (TLS) and Datagram Transport Layer Security 416 (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May 417 2015, . 419 [RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running 420 Code: The Implementation Status Section", BCP 205, 421 RFC 7942, DOI 10.17487/RFC7942, July 2016, 422 . 424 [RFC8051] Zhang, X., Ed. and I. Minei, Ed., "Applicability of a 425 Stateful Path Computation Element (PCE)", RFC 8051, 426 DOI 10.17487/RFC8051, January 2017, 427 . 429 [RFC8253] Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody, 430 "PCEPS: Usage of TLS to Provide a Secure Transport for the 431 Path Computation Element Communication Protocol (PCEP)", 432 RFC 8253, DOI 10.17487/RFC8253, October 2017, 433 . 435 [I-D.ietf-pce-pcep-yang] 436 Dhody, D., Hardwick, J., Beeram, V., and J. Tantsura, "A 437 YANG Data Model for Path Computation Element 438 Communications Protocol (PCEP)", draft-ietf-pce-pcep- 439 yang-11 (work in progress), March 2019. 441 Appendix A. Contributor Addresses 443 Dhruv Dhody 444 Huawei Technologies 445 Divyashree Techno Park, Whitefield 446 Bangalore, Karnataka 560066 447 India 449 EMail: dhruv.ietf@gmail.com 451 Jon Parker 452 Cisco Systems, Inc. 453 2000 Innovation Drive 454 Kanata, Ontario K2K 3E8 455 Canada 457 EMail: jdparker@cisco.com 459 Chaitanya Yadlapalli 460 AT&T 461 200 S Laurel Aevenue 462 Middletown NJ 07748 463 USA 465 EMail: cy098d@att.com 467 Authors' Addresses 469 Aswatnarayan Raghuram 470 AT&T 471 200 S Laurel Aevenue 472 Middletown, NJ 07748 473 USA 475 EMail: ar2521@att.com 477 Al Goddard 478 AT&T 479 200 S Laurel Aevenue 480 Middletown, NJ 07748 481 USA 483 EMail: ag6941@att.com 484 Jay Karthik 485 Cisco Systems, Inc. 486 125 High Street 487 Boston, Massachusetts 02110 488 USA 490 EMail: jakarthi@cisco.com 492 Siva Sivabalan 493 Cisco Systems, Inc. 494 2000 Innovation Drive 495 Kanata, Ontario K2K 3E8 496 Canada 498 EMail: msiva@cisco.com 500 Mahendra Singh Negi 501 Huawei Technologies 502 Divyashree Techno Park, Whitefield 503 Bangalore, Karnataka 560066 504 India 506 EMail: mahendrasingh@huawei.com