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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group Chandra Ramachandran 3 Internet Draft Juniper Networks 4 Intended status: Standards Track Ina Minei 5 Google, Inc 6 Dante Pacella 7 Verizon 8 Tarek Saad 9 Cisco Systems Inc. 11 Expires: February 11, 2018 August 11, 2017 13 Refresh Interval Independent FRR Facility Protection 14 draft-ietf-mpls-ri-rsvp-frr-02 16 Status of this Memo 18 This Internet-Draft is submitted in full conformance with the 19 provisions of BCP 78 and BCP 79. 21 Internet-Drafts are working documents of the Internet Engineering 22 Task Force (IETF), its areas, and its working groups. Note that 23 other groups may also distribute working documents as Internet- 24 Drafts. 26 Internet-Drafts are draft documents valid for a maximum of six 27 months and may be updated, replaced, or obsoleted by other documents 28 at any time. It is inappropriate to use Internet-Drafts as 29 reference material or to cite them other than as "work in progress." 31 The list of current Internet-Drafts can be accessed at 32 http://www.ietf.org/ietf/1id-abstracts.txt 34 The list of Internet-Draft Shadow Directories can be accessed at 35 http://www.ietf.org/shadow.html 37 This Internet-Draft will expire on August 12, 2017. 39 Copyright Notice 41 Copyright (c) 2016 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (http://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with 49 respect to this document. Code Components extracted from this 50 document must include Simplified BSD License text as described in 51 Section 4.e of the Trust Legal Provisions and are provided without 52 warranty as described in the Simplified BSD License. 54 Abstract 56 RSVP-TE relies on periodic refresh of RSVP messages to synchronize 57 and maintain the LSP related states along the reserved path. In the 58 absence of refresh messages, the LSP related states are 59 automatically deleted. Reliance on periodic refreshes and refresh 60 timeouts are problematic from the scalability point of view. The 61 number of RSVP-TE LSPs that a router needs to maintain has been 62 growing in service provider networks and the implementations should 63 be capable of handling increase in LSP scale. 65 RFC 2961 specifies mechanisms to eliminate the reliance on periodic 66 refresh and refresh timeout of RSVP messages, and enables a router 67 to increase the message refresh interval to values much longer than 68 the default 30 seconds defined in RFC 2205. However, the protocol 69 extensions defined in RFC 4090 for supporting fast reroute (FRR) 70 using bypass tunnels implicitly rely on short refresh timeouts to 71 cleanup stale states. 73 In order to eliminate the reliance on refresh timeouts, the routers 74 should unambiguously determine when a particular LSP state should be 75 deleted. Coupling LSP state with the corresponding RSVP-TE signaling 76 adjacencies as recommended in RSVP-TE Scaling Recommendations 77 (draft-ietf-teas-rsvp-te-scaling-rec) will apply in scenarios other 78 than RFC 4090 FRR using bypass tunnels. In scenarios involving RFC 79 4090 FRR using bypass tunnels, additional explicit tear down 80 messages are necessary. Refresh-interval Independent RSVP FRR (RI- 81 RSVP-FRR) extensions specified in this document consists of 82 procedures to enable LSP state cleanup that are essential in 83 scenarios not covered by procedures defined in RSVP-TE Scaling 84 Recommendations. 86 Requirements Language 88 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 89 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 90 document are to be interpreted as described in RFC-2119 [RFC2119]. 92 Table of Contents 94 1. Introduction...................................................4 95 1.1. Motivation................................................4 96 2. Terminology....................................................5 97 3. Problem Description............................................5 98 4. Solution Aspects...............................................8 99 4.1. Signaling Handshake between PLR and MP....................8 100 4.1.1. PLR Behavior.........................................8 101 4.1.2. Remote Signaling Adjacency..........................10 102 4.1.3. MP Behavior.........................................10 103 4.1.4. "Remote" state on MP................................11 104 4.2. Impact of Failures on LSP State..........................12 105 4.2.1. Non-MP Behavior.....................................12 106 4.2.2. LP-MP Behavior......................................12 107 4.2.3. NP-MP Behavior......................................12 108 4.2.4. Behavior of a Router that is both LP-MP and NP-MP...14 109 4.3. Conditional Path Tear....................................14 110 4.3.1. Sending Conditional Path Tear.......................15 111 4.3.2. Processing Conditional Path Tear....................15 112 4.3.3. CONDITIONS object...................................15 113 4.4. Remote State Teardown....................................16 114 4.4.1. PLR Behavior on Local Repair Failure................17 115 4.4.2. PLR Behavior on Resv RRO Change.....................17 116 4.4.3. LSP Preemption during Local Repair..................18 117 4.4.3.1. Preemption on LP-MP after Phop Link failure....18 118 4.4.3.2. Preemption on NP-MP after Phop Link failure....18 119 4.5. Backward Compatibility Procedures........................19 120 4.5.1. Detecting Support for Refresh interval Independent FRR 121 ...........................................................19 122 4.5.2. Procedures for backward compatibility...............20 123 4.5.2.1. Lack of support on Downstream Node.............20 124 4.5.2.2. Lack of support on Upstream Node...............20 125 4.5.2.3. Incremental Deployment.........................21 126 5. Security Considerations.......................................22 127 6. IANA Considerations...........................................22 128 6.1. New Object - CONDITIONS..................................22 129 7. Normative References..........................................22 130 8. Informative References........................................23 131 9. Acknowledgments...............................................23 132 10. Contributors.................................................24 133 11. Authors' Addresses...........................................24 135 1. Introduction 137 RSVP-TE Fast Reroute [RFC4090] defines two local repair techniques 138 to reroute label switched path (LSP) traffic over pre-established 139 backup tunnel. Facility backup method allows one or more LSPs 140 traversing a connected link or node to be protected using a bypass 141 tunnel. The many-to-one nature of local repair technique is 142 attractive from scalability point of view. This document enumerates 143 facility backup procedures in RFC 4090 that rely on refresh timeout 144 and hence make facility backup method refresh-interval dependent. 145 The RSVP-TE extensions defined in this document will enhance the 146 facility backup protection mechanism by making the corresponding 147 procedures refresh-interval independent. 149 1.1. Motivation 151 Standard RSVP [RFC2205] maintains state via the generation of RSVP 152 Path/Resv refresh messages. Refresh messages are used to both 153 synchronize state between RSVP neighbors and to recover from lost 154 RSVP messages. The use of Refresh messages to cover many possible 155 failures has resulted in a number of operational problems. 157 - One problem relates to RSVP control plane scaling due to periodic 158 refreshes of Path and Resv messages, another relates to the 159 reliability and latency of RSVP signaling. 161 - An additional problem is the time to clean up the stale state 162 after a tear message is lost. For more on these problems see 163 Section 1 of RSVP Refresh Overhead Reduction Extensions 164 [RFC2961]. 166 The problems listed above adversely affect RSVP control plane 167 scalability and RSVP-TE [RFC3209] inherited these problems from 168 standard RSVP. Procedures specified in [RFC2961] address the above 169 mentioned problems by eliminating dependency on refreshes for state 170 synchronization and for recovering from lost RSVP messages, and by 171 eliminating dependency on refresh timeout for stale state cleanup. 172 Implementing these procedures allows implementations to improve 173 RSVP-TE control plane scalability. For more details on eliminating 174 dependency on refresh timeout for stale state cleanup, refer to 175 "Refresh Interval Independent RSVP" section in [TE-SCALE-REC]. 177 However, the procedures specified in [RFC2961] do not fully address 178 stale state cleanup for facility backup protection [RFC4090], as 179 facility backup protection still depends on refresh timeouts for 180 stale state cleanup. Thus [RFC2961] is insufficient to address the 181 problem of stale state cleanup when facility backup protection is 182 used. 184 The procedures specified in this document, in combination with 185 [RFC2961], eliminate facility backup protection dependency on 186 refresh timeouts for stale state cleanup. These procedures, in 187 combination with [RFC2961], fully address the above mentioned 188 problem of RSVP-TE stale state cleanup, including the cleanup for 189 facility backup protection. 191 The procedures specified in this document assume reliable delivery 192 of RSVP messages, as specified in [RFC2961]. Therefore this document 193 makes support for [RFC2961] a pre-requisite. 195 2. Terminology 197 The reader is assumed to be familiar with the terminology in 198 [RFC2205], [RFC3209], [RFC4090] and [RFC4558]. 200 Phop node: Previous-hop router along the label switched path 202 PPhop node: Previous-Previous-hop router along the LSP 204 LP-MP node: Merge Point router at the tail of Link-protecting bypass 205 tunnel 207 NP-MP node: Merger Point router at the tail of Node-protecting 208 bypass tunnel 210 TED: Traffic Engineering Database 212 LSP state: The combination of "path state" maintained as Path State 213 Block (PSB) and "reservation state" maintained as Reservation State 214 Block (RSB) forms an individual LSP state on an RSVP-TE speaker 216 Conditional PathTear: PathTear message containing a suggestion to a 217 receiving downstream router to retain Path state if the receiving 218 router is NP-MP 220 Remote PathTear: PathTear message sent from Point of Local Repair 221 (PLR) to MP to delete LSP state on MP if PLR had not reliably sent 222 backup Path state before 224 3. Problem Description 225 E 226 / \ 227 / \ 228 / \ 229 / \ 230 / \ 231 / \ 232 A ----- B ----- C ----- D 233 \ / 234 \ / 235 \ / 236 \ / 237 \ / 238 \ / 239 F 240 Figure 1: Example Topology 242 In the topology in Figure 1, consider a large number of LSPs from A 243 to D transiting B and C. Assume that refresh interval has been 244 configured to be long of the order of minutes and refresh reduction 245 extensions are enabled on all routers. 247 Also assume that node protection has been configured for the LSPs 248 and the LSPs are protected by each router in the following way 250 - A has made node protection available using bypass LSP A -> E -> 251 C; A is the Point of Local Repair (PLR) and C is Node Protecting 252 Merge Point (NP-MP) 254 - B has made node protection available using bypass LSP B -> F -> 255 D; B is the PLR and D is the NP-MP 257 - C has made link protection available using bypass LSP C -> B -> F 258 -> D; C is the PLR and D is the Link Protecting Merge Point (LP- 259 MP) 261 In the above condition, assume that B-C link fails. The following is 262 the sequence of events that is expected to occur for all protected 263 LSPs under normal conditions. 265 1. B performs local repair and re-directs LSP traffic over the bypass 266 LSP B -> F -> D. 267 2. B also creates backup state for the LSP and triggers sending of 268 backup LSP state to D over the bypass LSP B -> F -> D. 269 3. D receives backup LSP states and merges the backups with the 270 protected LSPs. 271 4. As the link on C, over which the LSP states are refreshed has 272 failed, C will no longer receive state refreshes. Consequently the 273 protected LSP states on C will time out and C will send tear down 274 message for all LSPs. As each router should consider itself as a 275 Merge Point, C will time out the state only after waiting for an 276 additional duration equal to refresh timeout. 277 While the above sequence of events has been described in [RFC4090], 278 there are a few problems for which no mechanism has been specified 279 explicitly. 281 - If the protected LSP on C times out before D receives signaling 282 for the backup LSP, then D would receive PathTear from C prior to 283 receiving signaling for the backup LSP, thus resulting in deleting 284 the LSP state. This would be possible at scale even with default 285 refresh time. 287 - If upon the link failure C is to keep state until its timeout, 288 then with long refresh interval this may result in a large amount 289 of stale state on C. Alternatively, if upon the link failure C is 290 to delete the state and send PathTear to D, this would result in 291 deleting the state on D, thus deleting the LSP. D needs a reliable 292 mechanism to determine whether it is MP or not to overcome this 293 problem. 295 - If head-end A attempts to tear down LSP after step 1 but before 296 step 2 of the above sequence, then B may receive the tear down 297 message before step 2 and delete the LSP state from its state 298 database. If B deletes its state without informing D, with long 299 refresh interval this could cause (large) buildup of stale state 300 on D. 302 - If B fails to perform local repair in step 1, then B will delete 303 the LSP state from its state database without informing D. As B 304 deletes its state without informing D, with long refresh interval 305 this could cause (large) buildup of stale state on D. 307 The purpose of this document is to provide solutions to the above 308 problems which will then make it practical to scale up to a large 309 number of protected LSPs in the network. 311 4. Solution Aspects 313 The solution consists of five parts. 315 - Utilize MP determination mechanism specified in [SUMMARY-FRR] 316 that enables the PLR to signal the availability of local 317 protection to the MP. In addition, introduce PLR and MP procedures 318 to establish Node-ID based hello session between the PLR and the 319 MP to detect router failures and to determine capability. See 320 section 4.1 for more details. This part of the solution re-uses 321 some of the extensions defined in [SUMMARY-FRR] and [TE-SCALE- 322 REC], and the subsequent sub-sections will list the extensions in 323 these drafts that are utilized in this document. 325 - Handle upstream link or node failures by cleaning up LSP states 326 if the node has not found itself as MP through the MP 327 determination mechanism. See section 4.2 for more details. 329 - Introduce extensions to enable a router to send tear down message 330 to the downstream router that enables the receiving router to 331 conditionally delete its local LSP state. See section 4.3 for more 332 details. 334 - Enhance facility protection by allowing a PLR to directly send 335 tear down message to MP without requiring the PLR to either have a 336 working bypass LSP or have already signaled backup LSP state. See 337 section 4.4 for more details. 339 - Introduce extensions to enable the above procedures to be 340 backward compatible with routers along the LSP path running 341 implementation that do not support these procedures. See section 342 4.5 for more details. 344 4.1. Signaling Handshake between PLR and MP 346 4.1.1. PLR Behavior 348 As per the procedures specified in RFC 4090, when a protected LSP 349 comes up and if the "local protection desired" flag is set in the 350 SESSION_ATTRIBUTE object, each node along the LSP path attempts to 351 make local protection available for the LSP. 353 - If the "node protection desired" flag is set, then the node 354 tries to become a PLR by attempting to create a NP-bypass LSP to 355 the NNhop node avoiding the Nhop node on protected LSP path. In 356 case node protection could not be made available, the node 357 attempts to create a LP-bypass LSP to Nhop node avoiding only the 358 link that protected LSP takes to reach Nhop 360 - If the "node protection desired" flag is not set, then the PLR 361 attempts to create a LP-bypass LSP to Nhop node avoiding the link 362 that the protected LSP takes to reach Nhop 364 With regard to the PLR procedures described above and that are 365 specified in RFC 4090, this document specifies the following 366 additional procedures. 368 - While selecting the destination address of the bypass LSP, the 369 PLR SHOULD attempt to select the router ID of the NNhop or Nhop 370 node. If the PLR and the MP are in same area, then the PLR may 371 utilize the TED to determine the router ID from the interface 372 address in RRO (if NodeID is not included in RRO). If the PLR and 373 the MP are in different IGP areas, then the PLR SHOULD use the 374 NodeID address of NNhop MP if included in the RRO of RESV. If the 375 NP-MP in a different area has not included NodeID in RRO, then the 376 PLR SHOULD use NP-MP's interface address present in the RRO. The 377 PLR SHOULD use its router ID as the source address of the bypass 378 LSP. 380 - The PLR SHOULD also include its router ID in a NodeID sub-object 381 in PATH RRO unless configured explicitly not to include NodeID. 382 While including its router ID in the NodeID sub-object carried in 383 the outgoing Path message, the PLR MUST include the NodeID sub- 384 object after including its IPv4/IPv6 address or unnumbered 385 interface ID sub-object. 387 - In parallel to the attempt made to create NP-bypass or LP-bypass, 388 the PLR SHOULD initiate a Node-ID based Hello session to the NNhop 389 or Nhop node respectively to establish the RSVP-TE signaling 390 adjacency. This Hello session is used to detect MP node failure as 391 well as determine the capability of the MP node. If the MP sets I- 392 bit in CAPABILITY object [TE-SCALE-REC] carried in Hello message 393 corresponding to NodeID based Hello session, then the PLR SHOULD 394 conclude that the MP supports refresh-interval independent FRR 395 procedures defined in this document. 397 - If the bypass LSP comes up, then the PLR SHOULD include Bypass 398 Summary FRR Extended (B-SFRR) Association object and triggers a 399 PATH message to be sent. If a B-SFRR Extended Association object 400 is included in the PATH message, then the encoding and ordering 401 rules for the B-SFRR Extended Association object specified in 402 [SUMMARY-FRR] MUST be followed. 404 4.1.2. Remote Signaling Adjacency 406 A NodeID based RSVP-TE Hello session is one in which NodeID is used 407 in source and destination address fields in RSVP Hello. [RFC4558] 408 formalizes NodeID based Hello messages between two routers. This 409 document extends NodeID based RSVP Hello session to track the state 410 of any RSVP-TE neighbor that is not directly connected by at least 411 one interface. In order to apply NodeID based RSVP-TE Hello session 412 between any two routers that are not immediate neighbors, the router 413 that supports the extensions defined in the document SHOULD set TTL 414 to 255 in the NodeID based Hello messages exchanged between PLR and 415 MP. The default hello interval for this NodeID hello session SHOULD 416 be set to the default specified in [TE-SCALE-REC]. 418 In the rest of the document the term "signaling adjacency", or 419 "remote signaling adjacency" refers specifically to the RSVP-TE 420 signaling adjacency. 422 4.1.3. MP Behavior 424 When the NNhop or the Nhop node receives the triggered PATH with a 425 "matching" Bypass Summary FRR Extended Association object, the node 426 should consider itself as the MP for the PLR IP address 427 "corresponding" to the Bypass Summary FRR Extended Association 428 object. The matching and ordering rules for Bypass Summary FRR 429 Extended Association specified in [SUMMARY-FRR] MUST be followed by 430 implementations supporting this document. 432 In addition to the above procedures, the node SHOULD check the 433 presence of remote signaling adjacency with PLR. If a matching 434 Bypass Summary FRR Extended Association object is found in the PATH 435 and if the RSVP-TE signaling adjacency is also present, then the 436 node concludes that the PLR will undertake refresh-interval 437 independent FRR procedures specified in this document. If the PLR 438 has included NodeID sub-object in PATH RRO, then that NodeID is the 439 remote neighbor address. Otherwise, the PLR's interface address in 440 PATH RRO will be the remote neighbor address. 442 - If a matching Bypass Summary FRR Extended Association object is 443 included by the PPhop node and if a corresponding Node-ID 444 signaling adjacency exists with the PPhop node, then the router 445 SHOULD conclude it is NP-MP. 447 - If a matching Bypass Summary FRR Extended Association object is 448 included by Phop node and if a corresponding Node-ID signaling 449 adjacency exists with the Phop node, then the router SHOULD 450 conclude it is LP-MP. 452 4.1.4. "Remote" state on MP 454 Once a router concludes it is the MP for a PLR running refresh- 455 interval independent FRR procedures, it SHOULD create a remote path 456 state for the LSP. The "remote" state is identical to the protected 457 LSP path state except for the difference in RSVP_HOP object. The 458 thatRSVP_HOP object in "remote" Path state contains the address that 459 the PLR uses to send NodeID hello messages to MP. 461 The MP SHOULD consider the "remote" path state automatically deleted 462 if: 464 - MP later receives a PATH with no matching B-SFRR Extended 465 Association object corresponding to the PLR's IP address contained 466 in PATH RRO, or 468 - Node signaling adjacency with PLR goes down, or 470 - MP receives backup LSP signaling from PLR or 472 - MP receives PathTear, or 474 - MP deletes the LSP state on local policy or exception event 476 Unlike the normal path state that is either locally generated on the 477 Ingress or created from a PATH message from the Phop node, the 478 "remote" path state is not signaled explicitly from PLR. The purpose 479 of "remote" path state is to enable the PLR to explicitly tear down 480 path and reservation states corresponding to the LSP by sending tear 481 message for the "remote" path state. Such message tearing down 482 "remote" path state is called "Remote PathTear. 484 The scenarios in which "Remote" PathTear is applied are described in 485 Section 4.4 - Remote State Teardown. 487 4.2. Impact of Failures on LSP State 489 This section describes the procedures for routers on the LSP path 490 for different kinds of failures. The procedures described on 491 detecting RSVP control plane adjacency failures do not impact the 492 RSVP-TE graceful restart mechanisms ([RFC3473], [RFC5063]). If the 493 router executing these procedures act as helper for neighboring 494 router, then the control plane adjacency will be declared as having 495 failed after taking into account the grace period extended for 496 neighbor by the helper. 498 Immediate node failures are detected from the state of NodeID hello 499 sessions established with immediate neighbors. [TE-SCALE-REC] 500 recommends each router to establish NodeID hello sessions with all 501 its immediate neighbors. PLR or MP node failure is detected from the 502 state of remote signaling adjacency established according to Section 503 4.1.2 of this document. 505 4.2.1. Non-MP Behavior 507 When a router detects Phop link or Phop node failure and the router 508 is not an MP for the LSP, then it SHOULD send Conditional PathTear 509 (refer to Section "Conditional PathTear" below) and delete PSB and 510 RSB states corresponding to the LSP. 512 4.2.2. LP-MP Behavior 514 When the Phop link for an LSP fails on a router that is LP-MP for 515 the LSP, the LP-MP SHOULD retain PSB and RSB states corresponding to 516 the LSP till the occurrence of any of the following events. 518 - Node-ID signaling adjacency with Phop PLR goes down, or 520 - MP receives normal or "Remote" PathTear for PSB, or 522 - MP receives ResvTear RSB. 524 When a router that is LP-MP for an LSP detects Phop node failure 525 from Node-ID signaling adjacency state, the LP-MP SHOULD send normal 526 PathTear and delete PSB and RSB states corresponding to the LSP. 528 4.2.3. NP-MP Behavior 530 When a router that is NP-MP for an LSP detects Phop link failure, or 531 Phop node failure from Node-ID signaling adjacency, the router 532 SHOULD retain PSB and RSB states corresponding to the LSP till the 533 occurrence of any of the following events. 535 - Remote Node-ID signaling adjacency with PPhop PLR goes down, or 537 - MP receives normal or "Remote" PathTear for PSB, or 539 - MP receives ResvTear for RSB. 541 When a router that is NP-MP does not detect Phop link or node 542 failure, but receives Conditional PathTear from the Phop node, then 543 the router SHOULD retain PSB and RSB states corresponding to the LSP 544 till the occurrence of any of the following events. 546 - Remote Node-ID signaling adjacency with PPhop PLR goes down, or 548 - MP receives normal or "Remote" PathTear for PSB, or 550 - MP receives ResvTear for RSB. 552 Receiving Conditional PathTear from the Phop node will not impact 553 the "remote" state from the PPhop PLR. Note that Phop node would 554 send Conditional PathTear if it was not an MP. 556 In the example topology in Figure 1, assume C & D are NP-MP for PLRs 557 A & B respectively. Now when A-B link fails, as B is not MP and its 558 Phop link has failed, B will delete LSP state (this behavior is 559 required for unprotected LSPs - Section 4.2.1). In the data plane, 560 that would require B to delete the label forwarding entry 561 corresponding to the LSP. So if B's downstream nodes C and D 562 continue to retain state, it would not be correct for D to continue 563 to assume itself as NP-MP for PLR B. 565 The mechanism that enables D to stop considering itself as the NP-MP 566 for B and delete the corresponding "remote" path state is given 567 below. 569 1. When C receives Conditional PathTear from B, it decides to 570 retain LSP state as it is NP-MP of PLR A. C also SHOULD check 571 whether Phop B had previously signaled availability of node 572 protection. As B had previously signaled NP availability by 573 including B-SFRR Extended Association object, C SHOULD remove 574 the B-SFRR Extended Association object containing Association 575 Source set to B from the PATH message and trigger PATH to D. 577 2. When D receives triggered PATH, it realizes that it is no 578 longer the NP-MP for B and so it deletes the corresponding 579 "remote" path state. D does not propagate PATH further down 580 because the only change is that the B-SFRR Extended Association 581 object corresponding to Association Source B is no longer 582 present in the PATH message. 583 4.2.4. Behavior of a Router that is both LP-MP and NP-MP 585 A router may be both LP-MP as well as NP-MP at the same time for 586 Phop and PPhop nodes respectively of an LSP. If Phop link fails on 587 such node, the node SHOULD retain PSB and RSB states corresponding 588 to the LSP till the occurrence of any of the following events. 590 - Both Node-ID signaling adjacencies with Phop and PPhop nodes go 591 down, or 593 - MP receives normal or "Remote" PathTear for PSB, or 595 - MP receives ResvTear for RSB. 597 If a router that is both LP-MP and NP-MP detects Phop node failure, 598 then the node SHOULD retain PSB and RSB states corresponding to the 599 LSP till the occurrence of any of the following events. 601 - Remote Node-ID signaling adjacency with PPhop PLR goes down, or 603 - MP receives normal or "Remote" PathTear for PSB, or 605 - MP receives ResvTear for RSB. 607 4.3. Conditional Path Tear 609 In the example provided in the Section 4.2.5 "NP-MP Behavior on PLR 610 link failure", B deletes PSB and RSB states corresponding to the LSP 611 once B detects its link to Phop went down as B is not MP. If B were 612 to send PathTear normally, then C would delete LSP state 613 immediately. In order to avoid this, there should be some mechanism 614 by which B can indicate to C that B does not require the receiving 615 node to unconditionally delete the LSP state immediately. For this, 616 B SHOULD add a new optional object called CONDITIONS object in 617 PathTear. The new optional object is defined in Section 4.3.3. If 618 node C also understands the new object, then C SHOULD delete LSP 619 state only if it is not an NP-MP - in other words C SHOULD delete 620 LSP state if there is no "remote" PLR path state on C. 622 4.3.1. Sending Conditional Path Tear 624 A router that is not an MP for an LSP SHOULD delete PSB and RSB 625 states corresponding to the LSP if Phop link or Phop Node-ID 626 signaling adjacency goes down (Section 4.2.1). The router SHOULD 627 send Conditional PathTear if the following are also true. 629 - Ingress has requested node protection for the LSP, and 631 - PathTear is not received from the upstream node 633 4.3.2. Processing Conditional Path Tear 635 When a router that is not an NP-MP receives Conditional PathTear, 636 the node SHOULD delete PSB and RSB states corresponding to the LSP, 637 and process Conditional PathTear by considering it as normal 638 PathTear. Specifically, the node SHOULD NOT propagate Conditional 639 PathTear downstream but remove the optional object and send normal 640 PathTear downstream. 642 When a node that is an NP-MP receives Conditional PathTear, it 643 SHOULD NOT delete LSP state. The node SHOULD check whether the Phop 644 node had previously included B-SFRR Extended Association object in 645 PATH. If the object had been included previously by the Phop, then 646 the node processing Conditional PathTear from the Phop SHOULD remove 647 the corresponding object and trigger PATH downstream. 649 If Conditional PathTear is received from a neighbor that has not 650 advertised support (refer to Section 4.5) for the new procedures 651 defined in this document, then the node SHOULD consider the message 652 as normal PathTear. The node SHOULD propagate normal PathTear 653 downstream and delete the LSP state. 655 4.3.3. CONDITIONS object 657 As any implementation that does not support Conditional PathTear 658 SHOULD ignore the new object but process the message as normal 659 PathTear without generating any error, the Class-Num of the new 660 object SHOULD be 10bbbbbb where 'b' represents a bit (from Section 661 3.10 of [RFC2205]). 663 The new object is called as "CONDITIONS" object that will specify 664 the conditions under which default processing rules of the RSVP-TE 665 message SHOULD be invoked. 667 The object has the following format: 669 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 670 | Length | Class | C-type | 671 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 672 | Reserved |M| 673 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 675 Length 677 This contains the size of the object in bytes and should be set to 678 eight. 680 Class 682 To be assigned 684 C-type 686 1 688 M bit 690 If M-bit is set to 1, then the PathTear message SHOULD be processed 691 based on the condition if the receiver router is a Merge Point or 692 not. 694 If M-bit is set to 0, then the PathTear message SHOULD be processed 695 as normal PathTear message. 697 4.4. Remote State Teardown 699 If the Ingress wants to tear down the LSP because of a management 700 event while the LSP is being locally repaired at a transit PLR, it 701 would not be desirable to wait till the completion of backup LSP 702 signaling to perform state cleanup. To enable LSP state cleanup when 703 the LSP is being locally repaired, the PLR SHOULD send "remote" 704 PathTear message instructing the MP to delete PSB and RSB states 705 corresponding to the LSP. The TTL in "remote" PathTear message 706 SHOULD be set to 255. 708 Consider node C in example topology (Figure 1) has gone down and B 709 locally repairs the LSP. 711 1. Ingress A receives a management event to tear down the LSP. 712 2. A sends normal PathTear to B. 713 3. Assume B has not initiated backup signaling for the LSR. To enable 714 LSP state cleanup, B SHOULD send "remote" PathTear with 715 destination IP address set to that of D used in Node-ID signaling 716 adjacency with D, and RSVP_HOP object containing local address 717 used in Node-ID signaling adjacency. 718 4. B then deletes PSB and RSB states corresponding to the LSP. 719 5. On D there would be a remote signaling adjacency with B and so D 720 SHOULD accept the remote PathTear and delete PSB and RSB states 721 corresponding to the LSP. 722 4.4.1. PLR Behavior on Local Repair Failure 724 If local repair fails on the PLR after a failure, then this should 725 be considered as a case for cleaning up LSP state from PLR to the 726 Egress. PLR would achieve this using "remote" PathTear to clean up 727 state from MP. If MP has retained state, then it would propagate 728 PathTear downstream thereby achieving state cleanup. Note that in 729 the case of link protection, the PathTear would be directed to LP-MP 730 node IP address rather than the Nhop interface address. 732 4.4.2. PLR Behavior on Resv RRO Change 734 When a router that has already made NP available detects a change in 735 the RRO carried in RESV message, and if the RRO change indicates 736 that the router's former NP-MP is no longer present in the LSP path, 737 then the router SHOULD send "Remote" PathTear directly to its former 738 NP-MP. 740 In the example topology in Figure 1, assume A has made node 741 protection available and C has concluded it is the NP-MP for A. When 742 the B-C link fails then C, implementing the procedure specified in 743 Section 4.2.4 of this document, will retain state till: remote 744 NodeID signaling adjacency with A goes down, or PathTear or ResvTear 745 is received for PSB or RSB respectively. If B also has made node 746 protection available, B will eventually complete backup LSP 747 signaling with its NP-MP D and trigger RESV to A with RRO changed. 748 The new RRO of the LSP carried in RESV will not contain C. When A 749 processes the RESV with a new RRO not containing C - its former NP- 750 MP, A SHOULD send "Remote" PathTear to C. When C receives a "Remote" 751 PathTear for its PSB state, C will send normal PathTear downstream 752 to D and delete both PSB and RSB states corresponding to the LSP. As 753 D has already received backup LSP signaling from B, D will retain 754 control plane and forwarding states corresponding to the LSP. 756 4.4.3. LSP Preemption during Local Repair 758 4.4.3.1. Preemption on LP-MP after Phop Link failure 760 If an LSP is preempted on LP-MP after its Phop or incoming link has 761 already failed but the backup LSP has not been signaled yet, then 762 the node SHOULD send normal PathTear and delete both PSB and RSB 763 states corresponding to the LSP. As the LP-MP has retained LSP state 764 expecting the PLR to perform backup LSP signaling, preemption would 765 bring down the LSP and the node would not be LP-MP any more 766 requiring the node to clean up LSP state. 768 4.4.3.2. Preemption on NP-MP after Phop Link failure 770 If an LSP is preempted on NP-MP after its Phop link has already 771 failed but the backup LSP has not been signaled yet, then the node 772 SHOULD send normal PathTear and delete PSB and RSB states 773 corresponding to the LSP. As the NP-MP has retained LSP state 774 expecting the PLR to perform backup LSP signaling, preemption would 775 bring down the LSP and the node would not be NP-MP any more 776 requiring the node to clean up LSP state. 778 Consider B-C link goes down on the same example topology (Figure 1). 779 As C is NP-MP for PLR A, C will retain LSP state. 781 1. The LSP is preempted on C. 782 2. C will delete RSB state corresponding to the LSP. But C cannot 783 send PathErr or ResvTear to PLR A because backup LSP has not 784 been signaled yet. 785 3. As the only reason for C having retained state after Phop node 786 failure was that it was NP-MP, C SHOULD send normal PathTear to 787 D and delete PSB state also. D would also delete PSB and RSB 788 states on receiving PathTear from C. 789 4. B starts backup LSP signaling to D. But as D does not have the 790 LSP state, it will reject backup LSP PATH and send PathErr to B. 791 5. B will delete its reservation and send ResvTear to A. 793 4.5. Backward Compatibility Procedures 795 The "Refresh interval Independent FRR" or RI-RSVP-FRR referred below 796 in this section refers to the changes that have been proposed in 797 previous sections. Any implementation that does not support them has 798 been termed as "non-RI-RSVP-FRR implementation". The extensions 799 proposed in [SUMMARY-FRR] are applicable to implementations that do 800 not support RI-RSVP-FRR. On the other hand, changes proposed 801 relating to LSP state cleanup namely Conditional and remote PathTear 802 require support from one-hop and two-hop neighboring nodes along the 803 LSP path. So procedures that fall under LSP state cleanup category 804 SHOULD be turned on only if all nodes involved in the node 805 protection FRR i.e. PLR, MP and intermediate node in the case of NP, 806 support the extensions. Note that for LSPs requesting only link 807 protection, the PLR and the LP-MP should support the extensions. 809 4.5.1. Detecting Support for Refresh interval Independent FRR 811 An implementation supporting the extensions specified in previous 812 sections (called RI-RSVP-FRR here after) SHOULD set the flag 813 "Refresh interval Independent RSVP" or RI-RSVP in CAPABILITY object 814 carried in Hello messages. The RI-RSVP flag is specified in [TE- 815 SCALE-REC]. 817 - As nodes supporting the extensions SHOULD initiate Node Hellos 818 with adjacent nodes, a node on the path of protected LSP can 819 determine whether its Phop or Nhop neighbor supports RI-RSVP-FRR 820 enhancements from the Hello messages sent by the neighbor. 822 - If a node attempts to make node protection available, then the 823 PLR SHOULD initiate remote Node-ID signaling adjacency with NNhop. 824 If the NNhop (a) does not reply to remote node Hello message or 825 (b) does not set RI-RSVP flag in CAPABILITY object carried in its 826 Node-ID Hello messages, then the PLR can conclude that NNhop does 827 not support RI-RSVP-FRR extensions. 829 - If node protection is requested for an LSP and if (a) PPhop node 830 has not included a matching B-SFRR Extended Association object in 831 PATH or (b) PPhop node has not initiated remote node Hello 832 messages or (c) PPhop node does not set RI-RSVP flag in CAPABILITY 833 object carried in its Node-ID Hello messages, then the node SHOULD 834 conclude that the PLR does not support RI-RSVP-FRR extensions. The 835 details are described in the "Procedures for backward 836 compatibility" section below. 838 4.5.2. Procedures for backward compatibility 840 The procedures defined hereafter are performed on a subset of LSPs 841 that traverse a node, rather than on all LSPs that traverse a node. 842 This behavior is required to support backward compatibility for a 843 subset of LSPs traversing nodes running non-RI-RSVP-FRR 844 implementations. 846 4.5.2.1. Lack of support on Downstream Node 848 - If the Nhop does not support the RI-RSVP-FRR extensions, then the 849 node SHOULD reduce the "refresh period" in TIME_VALUES object 850 carried in PATH to default short refresh default value. 852 - If node protection is requested and the NNhop node does not 853 support the enhancements, then the node SHOULD reduce the "refresh 854 period" in TIME_VALUES object carried in PATH to a short refresh 855 default value. 857 If the node reduces the refresh time from the above procedures, it 858 SHOULD also not send remote PathTear or Conditional PathTear 859 messages. 861 Consider the example topology in Figure 1. If C does not support the 862 RI-RSVP-FRR extensions, then: 864 - A and B SHOULD reduce the refresh time to default value of 30 865 seconds and trigger PATH 867 - If B is not an MP and if Phop link of B fails, B cannot send 868 Conditional PathTear to C but SHOULD time out PSB state from A 869 normally. This would be accomplished if A would also reduce the 870 refresh time to default value. So if C does not support the RI- 871 RSVP-FRR extensions, then Phop B and PPhop A SHOULD reduce refresh 872 time to a small default value. 874 4.5.2.2. Lack of support on Upstream Node 876 - If Phop node does not support the RI-RSVP-FRR extensions, then 877 the node SHOULD reduce the "refresh period" in TIME_VALUES object 878 carried in RESV to default short refresh time value. 880 - If node protection is requested and the Phop node does not 881 support the RI-RSVP-FRR extensions, then the node SHOULD reduce 882 the "refresh period" in TIME_VALUES object carried in PATH to 883 default value. 885 - If node protection is requested and PPhop node does not support 886 the RI-RSVP-FRR extensions, then the node SHOULD reduce the 887 "refresh period" in TIME_VALUES object carried in RESV to default 888 value. 890 - If the node reduces the refresh time from the above procedures, 891 it SHOULD also not execute MP procedures specified in Section 4.2 892 of this document. 894 4.5.2.3. Incremental Deployment 896 The backward compatibility procedures described in the previous sub- 897 sections imply that a router supporting the RI-RSVP-FRR extensions 898 specified in this document can apply the procedures specified in the 899 document either in the downstream or upstream direction of an LSP, 900 depending on the capability of the routers downstream or upstream in 901 the LSP path. 903 - RI-RSVP-FRR extensions and procedures are enabled for downstream 904 Path, PathTear and ResvErr messages corresponding to an LSP if 905 link protection is requested for the LSP and the Nhop node 906 supports the extensions 908 - RI-RSVP-FRR extensions and procedures are enabled for downstream 909 Path, PathTear and ResvErr messages corresponding to an LSP if 910 node protection is requested for the LSP and both Nhop & NNhop 911 nodes support the extensions 913 - RI-RSVP-FRR extensions and procedures are enabled for upstream 914 PathErr, Resv and ResvTear messages corresponding to an LSP if 915 link protection is requested for the LSP and the Phop node 916 supports the extensions 918 - RI-RSVP-FRR extensions and procedures are enabled for upstream 919 PathErr, Resv and ResvTear messages corresponding to an LSP if 920 node protection is requested for the LSP and both Phop and PPhop 921 nodes support the extensions 923 For example, if an implementation supporting the RI-RSVP-FRR 924 extensions specified in this document is deployed on all routers in 925 particular region of the network and if all the LSPs in the network 926 request node protection, then the FRR extensions will only be 927 applied for the LSP segments that traverse the particular region. 928 This will aid incremental deployment of these extensions and also 929 allow reaping the benefits of the extensions in portions of the 930 network where it is supported. 932 5. Security Considerations 934 This security considerations pertaining to [RFC2205], [RFC3209] and 935 [RFC5920] remain relevant. 937 This document extends the applicability of Node-ID based Hello 938 session between immediate neighbors. The Node-ID based Hello session 939 between PLR and NP-MP may require the two routers to exchange Hello 940 messages with non-immediate neighbor. So, the implementations SHOULD 941 provide the option to configure Node-ID neighbor specific or global 942 authentication key to authentication messages received from Node-ID 943 neighbors. The network administrator MAY utilize this option to 944 enable RSVP-TE routers to authenticate Node-ID Hello messages 945 received with TTL greater than 1. Implementations SHOULD also 946 provide the option to specify a limit on the number of Node-ID based 947 Hello sessions that can be established on a router supporting the 948 extensions defined in this document. 950 6. IANA Considerations 952 6.1. New Object - CONDITIONS 954 RSVP Change Guidelines [RFC3936] defines the Class-Number name space 955 for RSVP objects. The name space is managed by IANA. 957 IANA registry: RSVP Parameters 958 Subsection: Class Names, Class Numbers, and Class Types 960 A new RSVP object using a Class-Number from 128-183 range called the 961 "CONDITIONS" object is defined in Section 4.3 of this document. The 962 Class-Number from 128-183 range will be allocated by IANA. 964 7. Normative References 966 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 967 Requirement Levels", BCP 14, RFC 2119, March 1997. 969 [RFC3209] Awduche, D., "RSVP-TE: Extensions to RSVP for LSP 970 Tunnels", RFC 3209, December 2001. 972 [RFC4090] Pan, P., "Fast Reroute Extensions to RSVP-TE for LSP 973 Tunnels", RFC 4090, May 2005. 975 [RFC2961] Berger, L., "RSVP Refresh Overhead Reduction Extensions", 976 RFC 2961, April 2001. 978 [RFC2205] Braden, R., "Resource Reservation Protocol (RSVP)", RFC 979 2205, September 1997. 981 [RFC4558] Ali, Z., "Node-ID Based Resource Reservation (RSVP) Hello: 982 A Clarification Statement", RFC 4558, June 2006. 984 [RFC3473] Berger, L., "Generalized Multi-Protocol Label Switching 985 Signaling Resource Reservation Protocol-Traffic Engineering 986 Extensions", RFC 3473, January 2003. 988 [RFC5063] Satyanarayana, A., "Extensions to GMPLS Resource 989 Reservation Protocol Graceful Restart", RFC5063, October 990 2007. 992 [RFC3936] Kompella, K. and J. Lang, "Procedures for Modifying the 993 Resource reSerVation Protocol (RSVP)", BCP 96, RFC 3936, 994 October 2004. 996 [TE-SCALE-REC] Vishnu Pavan Beeram et. al, "Implementation 997 Recommendations to improve scalability of RSVP-TE 998 Deployments", draft-ietf-teas-rsvp-te-scaling-rec (work in 999 progress) 1001 [SUMMARY-FRR] Mike Tallion et. al, "RSVP-TE Summary Fast Reroute 1002 Extensions for LSP Tunnels", draft-mtaillon-mpls-summary- 1003 frr-rsvpte (work in progress) 1005 8. Informative References 1007 [RFC5439] Yasukawa, S., "An Analysis of Scaling Issues in MPLS-TE 1008 Core Networks", RFC 5439, February 2009. 1010 [RFC5920] Fang, L., "Security Framework for MPLS and GMPLS 1011 Networks", RFC 5920, July 2010. 1013 9. Acknowledgments 1015 We are very grateful to Yakov Rekhter for his contributions to the 1016 development of the idea and thorough review of content of the draft. 1017 Thanks to Raveendra Torvi and Yimin Shen for their comments and 1018 inputs. 1020 10. Contributors 1022 Markus Jork 1023 Juniper Networks 1024 Email: mjork@juniper.net 1026 Harish Sitaraman 1027 Juniper Networks 1028 Email: hsitaraman@juniper.net 1030 Vishnu Pavan Beeram 1031 Juniper Networks 1032 Email: vbeeram@juniper.net 1034 Ebben Aries 1035 Juniper Networks 1036 Email: exa@juniper.net 1038 Mike Tallion 1039 Cisco Systems Inc. 1040 Email: mtallion@cisco.com 1042 11. Authors' Addresses 1044 Chandra Ramachandran 1045 Juniper Networks 1046 Email: csekar@juniper.net 1048 Ina Minei 1049 Google, Inc 1050 inaminei@google.com 1052 Dante Pacella 1053 Verizon 1054 Email: dante.j.pacella@verizon.com 1056 Tarek Saad 1057 Cisco Systems Inc. 1058 Email: tsaad@cisco.com