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Chen 3 Internet-Draft Futurewei 4 Intended status: Standards Track July 7, 2019 5 Expires: January 8, 2020 7 Extensions to Path Computation Element Communication Protocol (PCEP) for 8 Backup Ingress of a Traffic Engineering Label Switched Path 9 draft-chen-pce-compute-backup-ingress-14.txt 11 Abstract 13 This document presents extensions to the Path Computation Element 14 Communication Protocol (PCEP) for a PCC to send a request for 15 computing a backup ingress for an MPLS TE P2MP LSP or an MPLS TE P2P 16 LSP to a PCE and for a PCE to compute the backup ingress and reply to 17 the PCC with a computation result for the backup ingress. 19 Status of This Memo 21 This Internet-Draft is submitted to IETF in full conformance with the 22 provisions of BCP 78 and BCP 79. 24 Internet-Drafts are working documents of the Internet Engineering 25 Task Force (IETF). Note that other groups may also distribute 26 working documents as Internet-Drafts. The list of current Internet- 27 Drafts is at https://datatracker.ietf.org/drafts/current/. 29 Internet-Drafts are draft documents valid for a maximum of six months 30 and may be updated, replaced, or obsoleted by other documents at any 31 time. It is inappropriate to use Internet-Drafts as reference 32 material or to cite them other than as "work in progress." 34 This Internet-Draft will expire on January 8, 2020. 36 Copyright Notice 38 Copyright (c) 2019 IETF Trust and the persons identified as the 39 document authors. All rights reserved. 41 This document is subject to BCP 78 and the IETF Trust's Legal 42 Provisions Relating to IETF Documents 43 (https://trustee.ietf.org/license-info) in effect on the date of 44 publication of this document. Please review these documents 45 carefully, as they describe your rights and restrictions with respect 46 to this document. 48 Table of Contents 50 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 51 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 52 3. Conventions Used in This Document . . . . . . . . . . . . . . 3 53 4. Extensions to PCEP . . . . . . . . . . . . . . . . . . . . . 3 54 4.1. Backup Ingress Capability Advertisement . . . . . . . . . 4 55 4.1.1. Capability TLV in Existing PCE Discovery Protocol . . 4 56 4.1.2. Open Message Extension . . . . . . . . . . . . . . . 6 57 4.2. Request and Reply Message Extension . . . . . . . . . . . 6 58 4.2.1. RP Object Extension . . . . . . . . . . . . . . . . . 6 59 4.2.2. External Source Node . . . . . . . . . . . . . . . . 7 60 4.2.3. Constraints between Ingress and Backup Ingress . . . 8 61 4.2.4. Constraints for Backup Path . . . . . . . . . . . . . 8 62 4.2.5. Backup Ingress Node . . . . . . . . . . . . . . . . . 9 63 4.2.6. Backup Ingress PCEP Error Objects and Types . . . . . 9 64 4.2.7. Request Message Format . . . . . . . . . . . . . . . 9 65 4.2.8. Reply Message Format . . . . . . . . . . . . . . . . 10 66 5. Security Considerations . . . . . . . . . . . . . . . . . . 10 67 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 68 6.1. Backup Ingress Capability Flag . . . . . . . . . . . . . 10 69 6.2. Backup Ingress Capability TLV . . . . . . . . . . . . . . 11 70 6.3. Request Parameter Bit Flags . . . . . . . . . . . . . . . 11 71 6.4. PCEP Objects . . . . . . . . . . . . . . . . . . . . . . 11 72 7. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 11 73 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 74 8.1. Normative References . . . . . . . . . . . . . . . . . . 12 75 8.2. Informative References . . . . . . . . . . . . . . . . . 12 76 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 13 78 1. Introduction 80 RFC4090 "Fast Reroute Extensions to RSVP-TE for LSP Tunnels" 81 describes two methods to protect P2P LSP tunnels or paths at local 82 repair points. The local repair points may comprise a number of 83 intermediate nodes between an ingress node and an egress node along 84 the path. The first method is a one-to-one backup method, where a 85 detour backup P2P LSP for each protected P2P LSP is created at each 86 potential point of local repair. The second method is a facility 87 bypass backup protection method, where a bypass backup P2P LSP tunnel 88 is created using MPLS label stacking to protect a potential failure 89 point for a set of P2P LSP tunnels. The bypass backup tunnel can 90 protect a set of P2P LSPs that have similar backup constraints. 92 RFC4875 "Extensions to RSVP-TE for P2MP TE LSPs" describes how to use 93 the one-to-one backup method and facility bypass backup method to 94 protect a link or intermediate node failure on the path of a P2MP 95 LSP. 97 However, there is no mention of locally protecting an ingress node 98 failure in a protected P2MP LSP or P2P LSP. 100 The methods for protecting an ingress node of a P2MP LSP or P2P LSP 101 may be classified into two categories. 103 A first category uses a backup P2MP LSP that is from a backup ingress 104 node to the number of destination nodes for the P2MP LSP, and a 105 backup P2P LSP that is from a backup ingress node to the destination 106 node for the P2P LSP. The disadvantages of this class of methods 107 include more network resource such as computer power and link 108 bandwidth consumption since the backup P2MP LSP or P2P LSP is from 109 the backup ingress node to the number of destination nodes or the 110 destination respectively. 112 A second category uses a local P2MP LSP or P2P LSP for protecting the 113 ingress of a P2MP LSP or P2P LSP locally. The local P2MP LSP is from 114 a backup ingress node to the next hop nodes of the ingress of the 115 P2MP LSP. The local P2P LSP is from a backup ingress node to the 116 next hop node of the ingress of the P2P LSP. It is desirable to let 117 PCE compute these backup ingress nodes. 119 This document defines extensions to the Path Computation Element 120 Communication Protocol (PCEP) for a PCC to send a request for 121 computing a backup ingress node for an MPLS TE P2MP LSP or an MPLS TE 122 P2P LSP to a PCE and for a PCE to compute the backup ingress node and 123 reply to the PCC with a computation result for the backup ingress 124 node. 126 2. Terminology 128 This document uses terminologies defined in RFC5440, RFC4090, and 129 RFC4875. 131 3. Conventions Used in This Document 133 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 134 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 135 document are to be interpreted as described in RFC2119. 137 4. Extensions to PCEP 139 This section describes the extensions to PCEP for computing a backup 140 ingress of an MPLS TE P2MP LSP and an MPLS TE P2P LSP. 142 4.1. Backup Ingress Capability Advertisement 144 4.1.1. Capability TLV in Existing PCE Discovery Protocol 146 There are a couple of options for advertising a PCE capability for 147 computing a backup ingress for an MPLS TE P2MP LSP or an MPLS TE P2P 148 LSP. 150 The first option is to define a new flag in the OSPF and ISIS PCE 151 Capability Flags to indicate the capability that a PCE is capable to 152 compute both a backup ingress for an MPLS TE P2MP LSP and a backup 153 ingress for an MPLS TE P2P LSP. 155 The second option is to define two new flags. One new flag in the 156 OSPF and ISIS PCE Capability Flags indicates the capability that a 157 PCE is capable to compute a backup ingress for an MPLS TE P2MP LSP; 158 and another new flag in the OSPF and ISIS PCE Capability Flags 159 indicates the capability that a PCE is capable to compute a backup 160 ingress for an MPLS TE P2P LSP. 162 This second option is preferred now. 164 The format of the PCE-CAP-FLAGS sub-TLV is as follows: 166 0 1 2 3 167 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 1 168 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 169 | Type = 5 | Length | 170 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 171 | | 172 ~ PCE Capability Flags ~ 173 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 175 Type: 5 176 Length: Multiple of 4 octets 177 Value: This contains an array of units of 32-bit flags 178 numbered from the most significant as bit zero, where 179 each bit represents one PCE capability. 181 The following capability bits have been assigned by IANA: 183 Bit Capabilities 184 0 Path computation with GMPLS link constraints 185 1 Bidirectional path computation 186 2 Diverse path computation 187 3 Load-balanced path computation 188 4 Synchronized path computation 189 5 Support for multiple objective functions 190 6 Support for additive path constraints 191 (max hop count, etc.) 192 7 Support for request prioritization 193 8 Support for multiple requests per message 194 9 Global Concurrent Optimization (GCO) 195 10 P2MP path computation 196 11-31 Reserved for future assignments by IANA. 198 Reserved bits SHOULD be set to zero on transmission and MUST be 199 ignored on receipt. 201 For the second option, one bit such as bit 11 may be assigned to 202 indicate that a PCE is capable to compute a backup ingress for an 203 MPLS TE P2MP LSP and another bit such as bit 12 may be assigned to 204 indicate that a PCE is capable to compute a backup ingress for an 205 MPLS TE P2P LSP. 207 Bit Capabilities 208 11 Backup ingress computation for P2MP LSP 209 12 Backup ingress computation for P2P LSP 210 13-31 Reserved for future assignments by IANA. 212 4.1.2. Open Message Extension 214 If a PCE does not advertise its backup ingress compution capability 215 during discovery, PCEP should be used to allow a PCC to discover, 216 during the Open Message Exchange, which PCEs are capable of 217 supporting backup ingress computation. 219 To achieve this, we extend the PCEP OPEN object by defining a new 220 optional TLV to indicate the PCE's capability to perform backup 221 ingress compution for an MPLS TE P2MP LSP and an MPLS TE P2P LSP. 223 We request IANA to allocate a value such as 8 from the "PCEP TLV Type 224 Indicators" subregistry, as documented in Section below ("Backup 225 Ingress Capability TLV"). The description is "backup ingress 226 capable", and the length value is 2 bytes. The value field is set to 227 indicate the capability of a PCE for backup ingress compution for an 228 MPLS TE LSP in details. 230 We can use flag bits in the value field in the same way as the PCE 231 Capability Flags described in the previous section. 233 The inclusion of this TLV in an OPEN object indicates that the sender 234 can perform backup ingress compution for an MPLS TE P2MP LSP or an 235 MPLS TE P2P LSP. 237 The capability TLV is meaningful only for a PCE, so it will typically 238 appear only in one of the two Open messages during PCE session 239 establishment. However, in case of PCE cooperation (e.g., inter- 240 domain), when a PCE behaving as a PCC initiates a PCE session it 241 SHOULD also indicate its path computation capabilities. 243 4.2. Request and Reply Message Extension 245 This section describes extensions to the existing RP (Request 246 Parameters) object to allow a PCC to request a PCE for computing a 247 backup ingress of an MPLS TE P2MP LSP or an MPLS TE P2P LSP when the 248 PCE receives the PCEP request. 250 4.2.1. RP Object Extension 252 The following flags are added into the RP Object: 254 The I bit is added in the flag bits field of the RP object to tell 255 the receiver of the message that the request/reply is for computing a 256 bcakup ingress of an MPLS TE P2MP LSP and an MPLS TE P2P LSP. 258 o I ( Backup Ingress bit - 1 bit): 259 0: This indicates that this is not PCReq/PCRep 260 for backup ingress. 261 1: This indicates that this is PCReq or PCRep message 262 for backup ingress. 264 The IANA request is referenced in Section below (Request Parameter 265 Bit Flags) of this document. 267 This I bit with the N bit defined in RFC6006 can indicate whether the 268 request/reply is for a bcakup ingress of an MPLS TE P2MP LSP or an 269 MPLS TE P2P LSP. 271 o I = 1 and N = 1: This indicates that this is a PCReq/PCRep 272 message for backup ingress of an MPLS TE 273 P2MP LSP. 274 o I = 1 and N = 0: This indicates that this is a PCReq/PCRep 275 message for backup ingress of an MPLS TE 276 P2P LSP. 278 4.2.2. External Source Node 280 In addition to the information about the path that an MPLS TE P2MP 281 LSP or an MPLS TE P2P LSP traverses, a request message may comprise 282 other information that may be used for computing the backup ingress 283 for the P2MP LSP or P2P LSP. For example, the information about an 284 external source node, from which data traffic is delivered to the 285 ingress node of the P2MP LSP or P2P LSP and transported to the egress 286 node(s) via the P2MP LSP or P2P LSP, is useful for computing a backup 287 ingress node. 289 The PCC can specify an external source node (ESN) Object. The ESN 290 Object has the same format as the IRO object defined in [RFC5440] 291 except that it only supports IPv4 and IPv6 prefix sub-objects. 293 The object can only be carried in a PCReq message. A Path Request 294 may carry at most one external source node Object. 296 The Object-Class and Object-types will need to be allocated by IANA. 297 The IANA request is documented in Section below. (PCEP Objects). 299 Alternatively, we may use END-POINTS to represent an external source 300 node in a request message for computing a backup ingress node of MPLS 301 LSP. 303 To represent an external source node efficiently, we define a new 304 type of END-POINTS objects for computing a backup ingress node of 305 MPLS LSP. The format of the new END-POINTS object body for IPv4 306 (Object-Type 3) is as follows: 308 0 1 2 3 309 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 1 310 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 311 | External Source Type (11) | 312 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 313 | External Source IPv4 address | 314 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 316 The new type of END-POINTS is External Source Node Type (11). The 317 final value for the type will be assigned by IANA. This new type of 318 END-POINTS object contains an external source node IPv4 address. 320 4.2.3. Constraints between Ingress and Backup Ingress 322 A request message sent to a PCE from a PCC for computing a backup 323 ingress of an MPLS TE P2MP LSP or an MPLS TE P2P LSP may comprise a 324 constraint indicating that there must be a path from the backup 325 ingress node to be computed to the ingress node of the P2MP LSP or 326 P2P LSP and that the length of the path is within a given hop limit 327 such as one hop. 329 This constraint can be considered as default by a PCE or explicitly 330 sent to the PCE by a PCC [TBD]. 332 4.2.4. Constraints for Backup Path 334 A request message sent to a PCE from a PCC for computing a backup 335 ingress of a P2MP LSP or P2P LSP may comprise a constraint indicating 336 that the backup ingress node to be computed may not be a node on the 337 P2MP LSP or P2P LSP. In addition, the request message may comprise a 338 list of nodes, each of which is a candidate for the backup ingress 339 node. 341 A request message sent to a PCE from a PCC for computing a backup 342 ingress of a P2MP LSP or P2P LSP may comprise a constraint indicating 343 that there must be a path from the backup ingress node to be computed 344 to the next-hop nodes of the ingress node of the P2MP LSP or P2P LSP 345 and that there is not an internal node of the path from the backup 346 ingress to the next-hop nodes on the P2MP LSP or P2P LSP . 348 Most of these constraints for the backup path can be considered as 349 default by a PCE. The constraints for the backup path may be 350 explicitly sent to the PCE by a PCC [TBD]. 352 4.2.5. Backup Ingress Node 354 The PCE may send a reply message to the PCC in return to the request 355 message for computing a new backup ingress node. The reply message 356 may comprise information about the computed backup ingress node, 357 which is contained in the path from the backup ingress computed to 358 the next-hop node(s) of the ingress node of the P2MP LSP or P2P LSP. 360 The backup ingress node is the root or head node of the backup path 361 computed. 363 4.2.6. Backup Ingress PCEP Error Objects and Types 365 In some cases, the PCE may not complete the backup ingress 366 computation as requested, for example based on a set of constraints. 367 As such, the PCE may send a reply message to the PCC that indicates 368 an unsuccessful backup ingress computation attempt. The reply 369 message may comprise a PCEP-error object, which may comprise an 370 error-value, error-type and some detail information. 372 4.2.7. Request Message Format 374 The PCReq message is encoded as follows using RBNF as defined in 375 [RFC5511]. 377 Below is the message format for a request message: 379 ::= 380 [] 381 382 ::= [] 383 [] [] [] 384 [] 385 [] 386 [] 387 where: 388 is an external source node object. 390 The definitions for svec-list, RP, end-point-rro-pair-list, OF, LSPA, 391 BANDWIDTH, metric-list, IRO, and LOAD-BALANCING are described in 392 RFC5440 and RFC6006. 394 4.2.8. Reply Message Format 396 The PCRep message is encoded as follows using RBNF as defined in 397 [RFC5511]. 399 Below is the message format for a reply message: 401 ::= 402 403 ::= 404 [] 405 [] 406 where: 407 ::= 408 [][] 410 ::= (|) [] 412 ::= [] [] [] 413 [] [] 415 The definitions for RP, NO-PATH, END-POINTS, OF, LSPA, BANDWIDTH, 416 metric-list, IRO, and SERO are described in RFC5440, RFC6006 and 417 RFC4875. 419 5. Security Considerations 421 The mechanism described in this document does not raise any new 422 security issues for the PCEP, OSPF and IS-IS protocols. 424 6. IANA Considerations 426 This section specifies requests for IANA allocation. 428 6.1. Backup Ingress Capability Flag 430 Two new OSPF Capability Flags are defined in this document to 431 indicate the capabilities for computing a backup ingress for an MPLS 432 TE P2MP LSP and an MPLS TE P2P LSP. IANA is requested to make the 433 assignment from the "OSPF Parameters Path Computation Element (PCE) 434 Capability Flags" registry: 436 Bit Description Reference 437 11 Backup ingress for P2MP LSP This I-D 438 12 Backup ingress for P2P LSP This I-D 440 6.2. Backup Ingress Capability TLV 442 A new backup ingress capability TLV is defined in this document to 443 allow a PCE to advertize its backup ingress computation capability. 444 IANA is requested to make the following allocation from the "PCEP TLV 445 Type Indicators" sub-registry. 447 Value Description Reference 448 8 Backup ingress capable This I-D 450 6.3. Request Parameter Bit Flags 452 A new RP Object Flag has been defined in this document. IANA is 453 requested to make the following allocation from the "PCEP RP Object 454 Flag Field" Sub-Registry: 456 Bit Description Reference 457 16 Backup ingress (I-bit) This I-D 459 6.4. PCEP Objects 461 An External Source Node Object-Type is defined in this document. 462 IANA is requested to make the following Object-Type allocation from 463 the "PCEP Objects" sub-registry: 465 Object-Class Value 33 466 Name External Source Node 467 Object-Type 1: IPv4 468 2: IPv6 469 3-15: Unassigned 470 Reference This I-D 472 7. Acknowledgement 474 The author would like to thank Cyril Margaria, Ramon Casellas, Dhruv 475 Dhody and Quintin Zhao for their valuable comments and suggestions on 476 this draft. 478 8. References 480 8.1. Normative References 482 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 483 Requirement Levels", BCP 14, RFC 2119, 484 DOI 10.17487/RFC2119, March 1997, 485 . 487 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 488 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 489 Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001, 490 . 492 [RFC4090] Pan, P., Ed., Swallow, G., Ed., and A. Atlas, Ed., "Fast 493 Reroute Extensions to RSVP-TE for LSP Tunnels", RFC 4090, 494 DOI 10.17487/RFC4090, May 2005, 495 . 497 [RFC4875] Aggarwal, R., Ed., Papadimitriou, D., Ed., and S. 498 Yasukawa, Ed., "Extensions to Resource Reservation 499 Protocol - Traffic Engineering (RSVP-TE) for Point-to- 500 Multipoint TE Label Switched Paths (LSPs)", RFC 4875, 501 DOI 10.17487/RFC4875, May 2007, 502 . 504 [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation 505 Element (PCE) Communication Protocol (PCEP)", RFC 5440, 506 DOI 10.17487/RFC5440, March 2009, 507 . 509 [RFC6006] Zhao, Q., Ed., King, D., Ed., Verhaeghe, F., Takeda, T., 510 Ali, Z., and J. Meuric, "Extensions to the Path 511 Computation Element Communication Protocol (PCEP) for 512 Point-to-Multipoint Traffic Engineering Label Switched 513 Paths", RFC 6006, DOI 10.17487/RFC6006, September 2010, 514 . 516 8.2. Informative References 518 [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation 519 Element (PCE)-Based Architecture", RFC 4655, 520 DOI 10.17487/RFC4655, August 2006, 521 . 523 [RFC5862] Yasukawa, S. and A. Farrel, "Path Computation Clients 524 (PCC) - Path Computation Element (PCE) Requirements for 525 Point-to-Multipoint MPLS-TE", RFC 5862, 526 DOI 10.17487/RFC5862, June 2010, 527 . 529 Author's Address 531 Huaimo Chen 532 Futurewei 533 Boston, MA 534 USA 536 Email: Huaimo.chen@futurewei.com