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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documents in RFCs) -- Obsolete informational reference (is this intentional?): RFC 7525 (Obsoleted by RFC 9325) == Outdated reference: A later version (-23) exists of draft-ietf-pce-pcep-yang-12 Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 2 comments (--).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: March 16, 2020 J. Karthik 6 S. Sivabalan 7 Cisco Systems, Inc. 8 M. Negi 9 Huawei Technologies 10 September 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-09 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 March 16, 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 . . . . . . . . . . . . . . . . . . . . 7 77 8. Manageability Considerations . . . . . . . . . . . . . . . . 7 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 . . . . . . . . . . . . . 8 83 8.6. Impact On Network Operations . . . . . . . . . . . . . . 8 84 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8 85 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 86 10.1. Normative References . . . . . . . . . . . . . . . . . . 9 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] 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. 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 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], it includes a Flags field. 180 A new flag, the "LSP-Control Request Flag" (C), is introduced in the 181 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 LSP object. A PLSP-ID of value other than 0 and 184 0xFFFFF is used to identify the LSP for which the PCE requests 185 control. The PLSP-ID value of 0 indicates that the PCE is requesting 186 control of all LSPs originating from the PCC that it wishes to 187 delegate. The C Flag has no meaning in other PCEP messages that 188 carry SRP object and the flag MUST be set to 0 on transmission and 189 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. The PLSP-ID of 0 205 indicates that the PCE wants control over all LSPs originating from 206 the PCC. A PCC that receives a PCUpd message with C Flag set to 1 207 and PLSP-ID of 0 MUST NOT trigger the error condition for unknown 208 PLSP-ID in an LSP update request as per [RFC8231]. The D Flag and C 209 Flag are mutually exclusive in PCUpd message. The PCE SHOULD NOT 210 send control request for LSP which is already delegated to the PCE, 211 i.e. if the D Flag is set in the PCUpd message, then C Flag SHOULD 212 NOT be set. If a PCC receives a PCUpd message with D Flag set in the 213 LSP object (i.e. LSP is already delegated) and the C Flag is also 214 set (i.e. PCE is making a control request), the PCC MUST ignore the 215 C Flag. A PCC can decide to delegate the control of the LSP at its 216 own discretion. If the PCC grants or denies the control, it sends a 217 PCRpt message with D Flag set to 1 and 0 respectively in accordance 218 with stateful PCEP [RFC8231]. If the PCC does not grant the control, 219 it MAY choose to not respond, and the PCE MAY choose to retry 220 requesting the control preferably using exponentially increasing 221 timer. A PCE ignores the C Flag on the PCRpt message. Note that, if 222 the PCUpd message with C Flag set is received for a currently non- 223 delegated LSP (for which the PCE is requesting delegation), this MUST 224 NOT trigger the error handling as specified in [RFC8231] (a PCErr 225 with Error-type=19 (Invalid Operation) and error-value 1 (Attempted 226 LSP Update Request 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 trigger the error condition as specified 237 in [RFC8231] (a PCErr with Error-type=19 (Invalid Operation) and 238 error-value 1 (Attempted LSP Update Request for a non-delegated LSP)) 239 as the D Flag would be unset in this update request. Further, in 240 case of PLSP-ID of 0, the error condition as specified in [RFC8231] 241 (a PCErr with Error-type=19 (Invalid Operation) and error-value 3 242 (Attempted LSP Update Request for an LSP identified by an unknown 243 PSP-ID)) would be triggered. 245 [RFC8281] describes the setup, maintenance and teardown of PCE- 246 initiated LSPs under the stateful PCE model. It also specifies how a 247 PCE MAY obtain control over an orphaned LSP that was PCE-initiated. 248 A PCE implementation can apply the mechanism described in this 249 document in conjunction with those in [RFC8281]. 251 5. Implementation Status 253 [Note to the RFC Editor - remove this section before publication, as 254 well as remove the reference to RFC 7942.] 256 This section records the status of known implementations of the 257 protocol defined by this specification at the time of posting of this 258 Internet-Draft, and is based on a proposal described in [RFC7942]. 259 The description of implementations in this section is intended to 260 assist the IETF in its decision processes in progressing drafts to 261 RFCs. Please note that the listing of any individual implementation 262 here does not imply endorsement by the IETF. Furthermore, no effort 263 has been spent to verify the information presented here that was 264 supplied by IETF contributors. This is not intended as, and must not 265 be construed to be, a catalog of available implementations or their 266 features. Readers are advised to note that other implementations may 267 exist. 269 According to [RFC7942], "this will allow reviewers and working groups 270 to assign due consideration to documents that have the benefit of 271 running code, which may serve as evidence of valuable experimentation 272 and feedback that have made the implemented protocols more mature. 273 It is up to the individual working groups to use this information as 274 they see fit". 276 5.1. Huawei's Proof of Concept based on ONOS 278 The PCE function was developed in the ONOS open source platform. 279 This extension was implemented on a private version as a proof of 280 concept to enable multi-instance support. 282 o Organization: Huawei 284 o Implementation: Huawei's PoC based on ONOS 285 o Description: PCEP as a southbound plugin was added to ONOS. To 286 support multi-instance ONOS deployment in a cluster, this 287 extension in PCEP is used. Refer 288 https://wiki.onosproject.org/display/ONOS/PCEP+Protocol 290 o Maturity Level: Prototype 292 o Coverage: Full 294 o Contact: satishk@huawei.com 296 6. Security Considerations 298 The security considerations listed in [RFC8231] and [RFC8281] apply 299 to this document as well. However, this document also introduces a 300 new attack vector. An attacker may flood the PCC with request to 301 delegate all of its LSPs at a rate which exceeds the PCC's ability to 302 process them, either by spoofing messages or by compromising the PCE 303 itself. The PCC SHOULD be configured with a threshold rate for the 304 delegation requests received from the PCE. If the threshold is 305 reached, it is RECOMMENDED to log the issue. 307 As per [RFC8231], it is RECOMMENDED that these PCEP extensions only 308 be activated on authenticated and encrypted sessions across PCEs and 309 PCCs belonging to the same administrative authority, using Transport 310 Layer Security (TLS) [RFC8253], as per the recommendations and best 311 current practices in [RFC7525] (unless explicitly excluded in 312 [RFC8253]). 314 7. IANA Considerations 316 7.1. SRP Object Flags 318 IANA maintains a registry called the "Path Computation Element 319 Protocol (PCEP) Numbers" registry. It contains a subregistry called 320 the "SRP Object Flag Field" registry. This document requests IANA to 321 allocate following code point in the "SRP Object Flag Field" 322 subregistry. 324 Bit Description Reference 325 TBD LSP-Control This document 327 8. Manageability Considerations 329 All manageability requirements and considerations listed in [RFC5440] 330 and [RFC8231] apply to PCEP protocol extensions defined in this 331 document. In addition, requirements and considerations listed in 332 this section apply. 334 8.1. Control of Function and Policy 336 A PCC implementation SHOULD allow the operator to configure the 337 policy based on which it honors the request to control the LSPs. 338 This includes the handling of the case where an LSP control request 339 is received for an LSP that is currently delegated to some other PCE. 340 A PCC implementation SHOULD also allow the operator to configure the 341 threshold rate based on which it accepts the delegation requests from 342 the PCE. Further, the operator MAY be allowed to trigger the LSP 343 control request for a particular LSP at the PCE. A PCE 344 implementation SHOULD also allow the operator to configure an 345 exponentially increasing timer to retry the control requests for 346 which the PCE did not get a response. 348 8.2. Information and Data Models 350 The PCEP YANG module [I-D.ietf-pce-pcep-yang] could be extended to 351 include mechanism to trigger the LSP control request. 353 8.3. Liveness Detection and Monitoring 355 Mechanisms defined in this document do not imply any new liveness 356 detection and monitoring requirements in addition to those already 357 listed in [RFC5440]. 359 8.4. Verify Correct Operations 361 Mechanisms defined in this document do not imply any new operation 362 verification requirements in addition to those already listed in 363 [RFC5440] and [RFC8231]. 365 8.5. Requirements On Other Protocols 367 Mechanisms defined in this document do not imply any new requirements 368 on other protocols. 370 8.6. Impact On Network Operations 372 Mechanisms defined in [RFC5440] and [RFC8231] also apply to PCEP 373 extensions defined in this document. Further, the mechanism 374 described in this document can help the operator to request control 375 of the LSPs at a particular PCE. 377 9. Acknowledgements 379 Thanks to Jonathan Hardwick to remind the authors to not use 380 suggested values in IANA section. 382 Thanks to Adrian Farrel, Haomian Zheng and Tomonori Takeda for their 383 valuable comments. 385 Thanks to Shawn M. Emery for security directorate's review. 387 Thanks to Francesca Palombini for GENART review. 389 10. References 391 10.1. Normative References 393 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 394 Requirement Levels", BCP 14, RFC 2119, 395 DOI 10.17487/RFC2119, March 1997, 396 . 398 [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation 399 Element (PCE) Communication Protocol (PCEP)", RFC 5440, 400 DOI 10.17487/RFC5440, March 2009, 401 . 403 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 404 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 405 May 2017, . 407 [RFC8231] Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path 408 Computation Element Communication Protocol (PCEP) 409 Extensions for Stateful PCE", RFC 8231, 410 DOI 10.17487/RFC8231, September 2017, 411 . 413 [RFC8281] Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path 414 Computation Element Communication Protocol (PCEP) 415 Extensions for PCE-Initiated LSP Setup in a Stateful PCE 416 Model", RFC 8281, DOI 10.17487/RFC8281, December 2017, 417 . 419 10.2. Informative References 421 [RFC4657] Ash, J., Ed. and J. Le Roux, Ed., "Path Computation 422 Element (PCE) Communication Protocol Generic 423 Requirements", RFC 4657, DOI 10.17487/RFC4657, September 424 2006, . 426 [RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre, 427 "Recommendations for Secure Use of Transport Layer 428 Security (TLS) and Datagram Transport Layer Security 429 (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May 430 2015, . 432 [RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running 433 Code: The Implementation Status Section", BCP 205, 434 RFC 7942, DOI 10.17487/RFC7942, July 2016, 435 . 437 [RFC8051] Zhang, X., Ed. and I. Minei, Ed., "Applicability of a 438 Stateful Path Computation Element (PCE)", RFC 8051, 439 DOI 10.17487/RFC8051, January 2017, 440 . 442 [RFC8253] Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody, 443 "PCEPS: Usage of TLS to Provide a Secure Transport for the 444 Path Computation Element Communication Protocol (PCEP)", 445 RFC 8253, DOI 10.17487/RFC8253, October 2017, 446 . 448 [I-D.ietf-pce-pcep-yang] 449 Dhody, D., Hardwick, J., Beeram, V., and J. Tantsura, "A 450 YANG Data Model for Path Computation Element 451 Communications Protocol (PCEP)", draft-ietf-pce-pcep- 452 yang-12 (work in progress), July 2019. 454 Appendix A. Contributor Addresses 456 Dhruv Dhody 457 Huawei Technologies 458 Divyashree Techno Park, Whitefield 459 Bangalore, Karnataka 560066 460 India 462 EMail: dhruv.ietf@gmail.com 464 Jon Parker 465 Cisco Systems, Inc. 466 2000 Innovation Drive 467 Kanata, Ontario K2K 3E8 468 Canada 470 EMail: jdparker@cisco.com 472 Chaitanya Yadlapalli 473 AT&T 474 200 S Laurel Aevenue 475 Middletown NJ 07748 476 USA 478 EMail: cy098d@att.com 480 Authors' Addresses 482 Aswatnarayan Raghuram 483 AT&T 484 200 S Laurel Aevenue 485 Middletown, NJ 07748 486 USA 488 EMail: ar2521@att.com 490 Al Goddard 491 AT&T 492 200 S Laurel Aevenue 493 Middletown, NJ 07748 494 USA 496 EMail: ag6941@att.com 497 Jay Karthik 498 Cisco Systems, Inc. 499 125 High Street 500 Boston, Massachusetts 02110 501 USA 503 EMail: jakarthi@cisco.com 505 Siva Sivabalan 506 Cisco Systems, Inc. 507 2000 Innovation Drive 508 Kanata, Ontario K2K 3E8 509 Canada 511 EMail: msiva@cisco.com 513 Mahendra Singh Negi 514 Huawei Technologies 515 Divyashree Techno Park, Whitefield 516 Bangalore, Karnataka 560066 517 India 519 EMail: mahend.ietf@gmail.com