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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Internet Engineering Task Force J. Uttaro 3 Internet-Draft AT&T 4 Updates: 6368 (if approved) E. Chen 5 Intended status: Standards Track Cisco Systems 6 Expires: November 24, 2019 B. Decraene 7 Orange 8 J. Scudder 9 Juniper Networks 10 May 23, 2019 12 Support for Long-lived BGP Graceful Restart 13 draft-uttaro-idr-bgp-persistence-05 15 Abstract 17 In this document we introduce a new BGP capability termed "Long-lived 18 Graceful Restart Capability" so that stale routes can be retained for 19 a longer time upon session failure. A well-known BGP community 20 "LLGR_STALE" is introduced for marking stale routes retained for a 21 longer time. A second well-known BGP community, "NO_LLGR", is 22 introduced to mark routes for which these procedures should not be 23 applied. We also specify that such long-lived stale routes be 24 treated as the least-preferred, and their advertisements be limited 25 to BGP speakers that have advertised the new capability. Use of this 26 extension is not advisable in all cases, and we provide guidelines to 27 help determine if it is. 29 We update RFC 6368 by specifying that the LLGR_STALE community must 30 be propagated into, or out of, the path attributes exchanged between 31 PE and CE. 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 November 24, 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 . . . . . . . . . . . . . . . . . . . . . . . . 3 68 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4 69 2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 4 70 3. Protocol Extensions . . . . . . . . . . . . . . . . . . . . . 5 71 3.1. Long-lived Graceful Restart Capability . . . . . . . . . 5 72 3.2. LLGR_STALE Community . . . . . . . . . . . . . . . . . . 6 73 3.3. NO_LLGR Community . . . . . . . . . . . . . . . . . . . . 7 74 4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 7 75 4.1. Use of Graceful Restart Capability . . . . . . . . . . . 7 76 4.2. Session Resets . . . . . . . . . . . . . . . . . . . . . 8 77 4.3. Processing LLGR_STALE Routes . . . . . . . . . . . . . . 10 78 4.4. Route Selection . . . . . . . . . . . . . . . . . . . . . 10 79 4.5. Multicast VPN . . . . . . . . . . . . . . . . . . . . . . 10 80 4.6. Errors . . . . . . . . . . . . . . . . . . . . . . . . . 13 81 4.7. Optional Partial Deployment Procedure . . . . . . . . . . 13 82 4.8. Procedures when BGP is the PE-CE Protocol in a VPN . . . 13 83 4.8.1. Procedures when EBGP is the PE-CE Protocol in a VPN . 13 84 4.8.2. Procedures when IBGP is the PE-CE Protocol in a VPN . 14 85 5. Deployment Considerations . . . . . . . . . . . . . . . . . . 15 86 5.1. When BGP is the PE-CE Protocol in a VPN . . . . . . . . . 17 87 5.2. Risks of Depreferencing Routes . . . . . . . . . . . . . 17 88 6. Security Considerations . . . . . . . . . . . . . . . . . . . 18 89 7. Examples of Operation . . . . . . . . . . . . . . . . . . . . 19 90 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 21 91 9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 22 92 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22 93 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 23 94 11.1. Normative References . . . . . . . . . . . . . . . . . . 23 95 11.2. Informative References . . . . . . . . . . . . . . . . . 24 96 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 24 98 1. Introduction 100 Historically, routing protocols in general and BGP in particular have 101 been designed with a focus on correctness, where a key part of 102 "correctness" is for each network element's forwarding state to 103 converge toward the current state of the network as quickly as 104 possible. For this reason, the protocol was designed to remove state 105 advertised by routers which went down (from a BGP perspective) as 106 quickly as possible. Over time, this has been relaxed somewhat, 107 notably by BGP Graceful Restart [RFC4724]; however, the paradigm has 108 remained one of attempting to rapidly remove "stale" state from the 109 network. 111 Over time, two phenomena have arisen that call into question the 112 underlying assumptions of this paradigm. The first is the widespread 113 adoption of tunneled forwarding infrastructures, for example MPLS. 114 Such infrastructures eliminate the risk of some types of forwarding 115 loops that can arise in hop-by-hop forwarding, and thus reduce one of 116 the motivations for strong consistency between forwarding elements. 117 The second is the increasing use of BGP as a transport for data less 118 closely associated with packet forwarding than was originally the 119 case. Examples include the use of BGP for autodiscovery (VPLS 120 [RFC4761]) and filter programming (FLOWSPEC [RFC5575]). In these 121 cases, BGP data takes on a character more akin to configuration than 122 to traditional routing. 124 The observations above motivate a desire to offer network operators 125 the ability to choose to retain BGP data for a longer period than has 126 hitherto been possible when the BGP control plane fails for some 127 reason. Although the semantics of BGP Graceful Restart [RFC4724] are 128 close to those desired, several gaps exist, most notably in maximum 129 time for which "stale" information can be retained -- Graceful 130 Restart imposes a 4095 second upper bound. 132 In this document we introduce a new BGP capability termed "Long-lived 133 Graceful Restart Capability" so that stale information can be 134 retained for a longer time across a session reset. We also introduce 135 two new BGP well-known communities, "LLGR_STALE", to mark such 136 information, and "NO_LLGR", to indicate that these procedures should 137 not be applied to the marked route. Long-lived stale information is 138 to be treated as least-preferred, and its advertisement limited to 139 BGP speakers that support the new capability. Where possible, we 140 reference the semantics of BGP Graceful Restart [RFC4724] rather than 141 specifying similar semantics in this document. 143 The expected deployment model for this extension is that it will only 144 be invoked for certain address families. This is discussed in more 145 detail in the Deployment Considerations section (Section 5). When 146 used, its use may be combined with that of traditional Graceful 147 Restart, in which case it is invoked only after the traditional 148 Graceful Restart interval has elapsed, or it may be invoked 149 immediately. Apart from the potential to greatly extend the timer, 150 the most obvious difference between Long-Lived and traditional 151 Graceful Restart is that in the Long-Lived version, routes are 152 "depreferenced", that is, treated as least-preferred, whereas in the 153 traditional version, route preference is not affected. The design 154 choice to treat Long-Lived Stale routes as least-preferred was 155 informed by the expectation that they might be retained for a 156 (potentially) almost unbounded period of time, whereas in the 157 traditional Graceful Restart case, stale routes are retained for only 158 a brief interval. In the GR case, the tradeoff between advertising 159 new route status (at the cost of routing churn) and not advertising 160 it (at the cost of suboptimal or incorrect route selection) is 161 resolved in favor of not advertising, and in the LLGR case, it is 162 resolved in favor of advertising new state. 164 1.1. Requirements Language 166 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 167 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 168 document are to be interpreted as described in RFC 2119 [RFC2119]. 170 2. Definitions 172 Depreference, Depreferenced: A route is said to be depreferenced if 173 it has its route selection preference reduced in reaction to some 174 event. 176 GR: Abbreviation for "Graceful Restart" [RFC4724], also sometimes 177 referred to herein as "conventional Graceful Restart" or 178 "conventional GR" to distinguish it from the "Long-lived Graceful 179 Restart" defined by this document. 181 Helper: Or "helper router". During Graceful Restart or Long-lived 182 Graceful Restart, the router that detects a session failure and 183 applies the listed procedures. [RFC4724] refers to this as the 184 "receiving speaker". 186 LLGR: Abbreviation for "Long-lived Graceful Restart". 188 LLST: Abbreviation for "Long-lived Stale Time". 190 Route: We use "route" to mean any information encoded as a BGP NLRI 191 and set of path attributes. As discussed above, the connection 192 between such routes and installation of forwarding state may be 193 quite remote. 195 3. Protocol Extensions 197 A new BGP capability and two new BGP communities are introduced. 199 3.1. Long-lived Graceful Restart Capability 201 The "Long-lived Graceful Restart Capability", or "LLGR Capability" 202 (value: 71) is a new BGP capability [RFC5492] that can be used by a 203 BGP speaker to indicate its ability to preserve its state according 204 to the procedures of this document. This capability MUST be 205 advertised in conjunction with the Graceful Restart capability 206 [RFC4724], see the "Use of Graceful Restart Capability" section 207 (Section 4.1). 209 The capability value consists of zero or more tuples as follows: 212 +--------------------------------------------------+ 213 | Address Family Identifier (16 bits) | 214 +--------------------------------------------------+ 215 | Subsequent Address Family Identifier (8 bits) | 216 +--------------------------------------------------+ 217 | Flags for Address Family (8 bits) | 218 +--------------------------------------------------+ 219 | Long-lived Stale Time (24 bits) | 220 +--------------------------------------------------+ 221 | ... | 222 +--------------------------------------------------+ 223 | Address Family Identifier (16 bits) | 224 +--------------------------------------------------+ 225 | Subsequent Address Family Identifier (8 bits) | 226 +--------------------------------------------------+ 227 | Flags for Address Family (8 bits) | 228 +--------------------------------------------------+ 229 | Long-lived Stale Time (24 bits) | 230 +--------------------------------------------------+ 232 The meaning of the fields are as follows: 234 Address Family Identifier (AFI), Subsequent Address Family 235 Identifier (SAFI): 237 The AFI and SAFI, taken in combination, indicate that the BGP 238 speaker has the ability to preserve its forwarding state for 239 the address family during a subsequent BGP restart. Routes may 240 be explicitly associated with a particular AFI and SAFI using 241 the encoding of [RFC4760] or implicitly associated with 242 if using the encoding of [RFC4271]. 244 Flags for Address Family: 246 This field contains bit flags relating to routes that were 247 advertised with the given AFI and SAFI. 249 0 1 2 3 4 5 6 7 250 +-+-+-+-+-+-+-+-+ 251 |F| Reserved | 252 +-+-+-+-+-+-+-+-+ 254 The most significant bit is used to indicate whether the state 255 for routes that were advertised with the given AFI and SAFI has 256 indeed been preserved during the previous BGP restart. When 257 set (value 1), the bit indicates that the state has been 258 preserved. This bit is called the "F bit" since it was 259 historically used to indicate preservation of Forwarding State. 260 Use of the F bit is detailed in the Session Resets section 261 (Section 4.2). 263 The remaining bits are reserved and MUST be set to zero by the 264 sender and ignored by the receiver. 266 Long-lived Stale Time: 268 This time (in seconds) specifies how long stale information 269 (for the AFI/SAFI) may be retained (possibly in conjunction 270 with the period specified by the "Restart Time" in the Graceful 271 Restart Capability, if present). 273 3.2. LLGR_STALE Community 275 We introduce a well-known BGP community [RFC1997] "LLGR_STALE" 276 (value: 0xFFFF0006). It can be used to mark stale routes retained 277 for a longer period of time. Such long-lived stale routes are to be 278 handled according to the procedures specified in the Operation 279 section (Section 4). 281 An implementation MAY allow users to configure policies that accept, 282 reject, or modify routes based on the presence or absence of this 283 community. 285 3.3. NO_LLGR Community 287 We introduce a well-known BGP community "NO_LLGR" (value: 288 0xFFFF0007). It can be used to mark routes which a BGP speaker does 289 not want treated according to these procedures, as detailed in the 290 Operation section (Section 4). 292 An implementation MAY allow users to configure policies that accept, 293 reject, or modify routes based on the presence or absence of this 294 community. 296 4. Operation 298 A BGP speaker MAY use BGP Capabilities Advertisement [RFC5492] to 299 advertise the "Long-lived Graceful Restart Capability" to indicate 300 its ability to retain state and perform related procedures specified 301 in this document. The setting of the parameters for an AFI/SAFI 302 depends on the properties of the BGP speaker, network scale, and 303 local configuration. 305 In the presence of the "Long-lived Graceful Restart Capability", the 306 procedures specified in [RFC4724] and [RFC8538] continue to apply 307 unless explicitly revised by this document. 309 4.1. Use of Graceful Restart Capability 311 The Graceful Restart capability MUST be advertised in conjunction 312 with the LLGR capability. If it is not so advertised, the LLGR 313 capability MUST be disregarded. The purpose for mandating that both 314 be used in conjunction is to enable reuse of certain base mechanisms 315 that are common to both "flavors", notably origination, collection 316 and processing of EoR, as well as the finite state machine 317 modifications and connection reset logic introduced by GR. 319 We observe that if support for conventional Graceful Restart is not 320 desired for the session, the conventional GR phase can be skipped by 321 omitting all AFI/SAFI from the GR capability, advertising a Restart 322 Time of zero, or both. The Session Resets section (Section 4.2) 323 discusses the interaction of conventional and long-lived GR. 325 4.2. Session Resets 327 BGP Graceful Restart [RFC4724], updated by [RFC8538], defines 328 conditions under which a BGP session can reset and have its 329 associated routes retained. If such a reset occurs for a session for 330 which the LLGR Capability has also been exchanged, the following 331 procedures apply. 333 If the Graceful Restart Capability that was received does not list 334 all AFI/SAFI supported by the session, then for those non-listed AFI/ 335 SAFI the GR "Restart Time" shall be deemed zero. Similarly, if the 336 received LLGR Capability does not list all AFI/SAFI supported by the 337 session, then for those non-listed AFI/SAFI the "Long-lived Stale 338 Time" shall be deemed zero. 340 The following text in Section 4.2 of the GR specification [RFC4724] 341 no longer applies: 343 If the session does not get re-established within the "Restart 344 Time" that the peer advertised previously, the Receiving Speaker 345 MUST delete all the stale routes from the peer that it is 346 retaining. 348 and the following procedures are specified instead: 350 After the session goes down and before the session is re-established, 351 the stale routes for an AFI/SAFI MUST be retained. The interval for 352 which they are retained is limited by the sum of the "Restart Time" 353 in the received Graceful Restart Capability and the "Long-lived Stale 354 Time" in the received Long-lived Graceful Restart Capability. These 355 timers MAY be modified by local configuration. 357 If the value of the "Restart Time" or the "Long-lived Stale Time" is 358 zero, the duration of the corresponding period would be zero seconds. 359 So, for example, if the "Restart Time" is zero and the "Long-lived 360 Stale Time" is nonzero, only the procedures particular to LLGR would 361 apply. Conversely, if the "Long-lived Stale Time" is zero and the 362 "Restart Time" is nonzero, only the procedures of GR would apply. If 363 both are zero, none of these procedures would apply, only those of 364 the base BGP specification (although EoR would still be used as 365 detailed in [RFC4724]). And finally, if both are nonzero, then the 366 procedures would be applied serially -- first those of GR, then those 367 of LLGR. We observe that during the first interval, while the 368 procedures of GR are in effect, route preference would not be 369 affected, while during the second interval, while LLGR procedures are 370 in effect, routes would be treated as least-preferred as specified 371 elsewhere in this document. 373 Once the "Restart Time" period ends (including the case that the 374 "Restart Time" is zero), the LLGR period is said to have begun and 375 the following procedures MUST be performed: 377 o The helper router MUST start a timer for the "Long-lived Stale 378 Time". If the timer for the "Long-lived Stale Time" expires 379 before the session is re-established, the helper MUST delete all 380 the stale routes from the neighbor that it is retaining. 382 o The helper router MUST attach the LLGR_STALE community for the 383 stale routes being retained. Note that this requirement implies 384 that the routes would need to be readvertised, to disseminate the 385 modified community. 387 o If any of the routes from the peer have been marked with the 388 NO_LLGR community, either as sent by the peer, or as the result of 389 a configured policy, they MUST NOT be retained, but MUST be 390 removed as per the normal operation of [RFC4271]. 392 o The helper router MUST perform the procedures listed under 393 Section 4.3. 395 Once the session is re-established, the procedures specified in 396 [RFC4724] apply for the stale routes irrespective of whether the 397 stale routes are retained during the "Restart Time" period or the 398 "Long-lived Stale Time" period. However, in the case of consecutive 399 restarts (i.e, the session goes down before the EoR is received) the 400 previously marked stale routes MUST NOT be deleted before the timer 401 for the "Long-lived Stale Time" expires. 403 Similarly to [RFC4724], once the session is re-established, if the F 404 bit for a specific address family is not set in the newly received 405 LLGR Capability, or if a specific address family is not included in 406 the newly received LLGR Capability, or if the LLGR and accompanying 407 GR Capability are not received in the re-established session at all, 408 then the Helper MUST immediately remove all the stale routes from the 409 peer that it is retaining for that address family. 411 If a "Long-lived Stale Time" timer is running for a peer, it MUST NOT 412 be updated (other than by manual operator intervention) until the 413 peer has established and synchronized a new session. The session is 414 termed "synchronized" once the EoR has been received from the peer. 416 The value of the "Long-lived Stale Time" in the capability received 417 from a neighbor MAY be reduced by local configuration. 419 While the session is down, the expiration of the "Long-lived Stale 420 Time" timer is treated analogously to the expiration of the "Restart 421 Time" timer in Graceful Restart. However, the timer continues to run 422 once the session has re-established. The timer is not stopped, nor 423 updated, until EoR is received from the peer. If the timer expires 424 during synchronization with the peer, any stale routes that the peer 425 has not refreshed, are removed. If the session subsequently resets 426 prior to becoming synchronized, any remaining routes should be 427 removed immediately. 429 4.3. Processing LLGR_STALE Routes 431 A BGP speaker that has advertised the "Long-lived Graceful Restart 432 Capability" to a neighbor MUST perform the following upon receiving a 433 route from that neighbor with the "LLGR_STALE" community, or upon 434 attaching the "LLGR_STALE" community itself per Section 4.2: 436 o Treat the route as the least-preferred in route selection (see 437 below). See the Risks of Depreferencing Routes section 438 (Section 5.2) for a discussion of potential risks inherent in 439 doing this. 441 o The route SHOULD NOT be advertised to any neighbor from which the 442 Long-lived Graceful Restart Capability has not been received. The 443 exception is described in the Optional Partial Deployment 444 Procedure section (Section 4.7). Note that this requirement 445 implies that such routes should be withdrawn from any such 446 neighbor. 448 o The "LLGR_STALE" community MUST NOT be removed when the route is 449 further advertised. 451 4.4. Route Selection 453 In this document, when we refer to treating a route as least- 454 preferred, this means the route MUST be treated as less preferred 455 than any other route that is not so treated. When performing route 456 selection between two routes both of which are least-preferred, 457 normal tie-breaking applies. Note that this would only be expected 458 to happen if the only routes available for selection were least- 459 preferred -- in all other cases, such routes would have been 460 eliminated from consideration. 462 4.5. Multicast VPN 464 If LLGR is being used in a network that carries Multicast VPN (MVPN) 465 traffic ([RFC6513],[RFC6514]), special considerations apply. 467 [RFC6513] defines the notion of the "Upstream PE" and the "Upstream 468 Multicast Hop" (UMH) for a particular multicast flow. To determine 469 the Upstream PE and/or the UMH for a particular flow, a particular 470 set of comparable BGP routes (the "UMH-eligible" routes for that 471 flow, as defined in [RFC6513]) is considered, and the "best" one 472 (according to the BGP bestpath selection algorithm) is chosen. The 473 UMH-eligible routes are routes with AFI/SAFI 1/1, 1/2, 2/1, or 2/2. 474 When a router detects a change in the Upstream PE or UMH for a given 475 flow, the router may modify its data plane state for that flow. For 476 example, the router may begin to discard any packets of the flow that 477 it believes have arrived from the previously chosen Upstream PE or 478 UMH. The assumption is that the newly chosen Upstream PE and/or UMH 479 will make the corresponding changes, if necessary, to their own data 480 plane states. In addition, if a router detects a change in the 481 Uptream PE or UMH for a given flow, it may originate or readvertise 482 (with different attributes) certain of the BGP MCAST-VPN routes 483 (routes with SAFI 5) that are defined in [RFC6514]. The assumption 484 is that the MCAST-VPN routes will be properly distributed by BGP to 485 other routers that have data plane states for the given flow, i.e., 486 that BGP will converge so that all routers handle the flow in a 487 consistent manner. 489 However, if detection of a change to the Upstream PE or UMH is based 490 entirely on stale routes, one cannot assume that BGP will converge; 491 rather one must assume that the UMH-eligible routes and the MCAST-VPN 492 routes are not being properly distributed. Since the purpose of the 493 LLGR procedures is to try to keep the data flowing (by "freezing" the 494 data plane states) when the control plane updates are not being 495 properly distributed, it does not seem appropriate to react to 496 changes that are based entirely on stale routes. Therefore, the 497 following rules MUST be applied when a router is computing or 498 recomputing the Upstream PE and/or the UMH for a given multicast 499 flow: 501 o STALE routes (i.e., UMH-eligible routes with the LLGR_STALE 502 attribute) are less preferable than non-STALE routes. 504 o If all the UMH-eligible routes for a given flow are STALE, then 505 the Upstream PE and/or UMH for that flow is considered to be 506 "stale". 508 o If the Upstream PE or UMH for a given multicast flow has already 509 been determined, and the result of a new computation yields a new 510 Upstream PE or UMH, but the Upstream PE or UMH is "stale" (as 511 defined just above), then the Upstream PE and/or UMH for that flow 512 MUST be left unchanged. 514 o If the Upstream PE or UMH for a given multicast flow has not 515 already been determined, but is now determined to be STALE, the 516 multicast flow is considered to have no reachable Upstream PE and/ 517 or UMH. 519 [RFC6514] also defines a set of route types with SAFI 5 ("MCAST-VPN" 520 routes). LLGR can be applied to MCAST-VPN routes. However, the 521 following MCAST-VPN route types require special procedures, as 522 specified in this section: 524 o Leaf A-D routes 525 o C-multicast Shared Tree Join routes 526 o C-multicast Source Tree Join routes 528 Routes of these three types are always "targeted" to a particular 529 upstream router. Depending on the situation, the targeted router may 530 be the Upstream PE for a given flow or the UMH for a given flow. 531 Alternatively, the targeted router may be determined by choosing the 532 "best" route (according to the BGP bestpath algorithm) from among a 533 set of comparable Intra-AS I-PMSI A-D routes, or from among a set of 534 comparable Inter-AS I-PMSI A-D routes, or from among a set of 535 comparable S-PMSI A-D routes. (See [RFC6513], [RFC6514], [RFC6625], 536 and [RFC7524] for details.) Once the target is chosen, it is 537 identified in an IPv4-address-specific Route Target (RT) or an IPv6- 538 address-specific RT that is attached to the route before the route is 539 advertised. If the target for one of these routes changes, the value 540 of the attached RT will also change. This in turn may cause the 541 route to be advertised, readvertised, or withdrawn on specific BGP 542 sessions. 544 For cases where the targeted router is the Upstream PE or the UMH for 545 a particular flow, the rules given previously in this section apply. 546 For example, if a Leaf A-D route is targeted to a flow's UMH, and all 547 the relevant UMH-eligible routes are stale, the UMH is left 548 unchanged. Thus the Leaf A-D route is not readvertised with a new 549 RT. 551 In those cases where the targeted router for a given Leaf A-D route 552 is selected by comparing a set of S-PMSI A-D routes, or where the 553 targeted router for a given C-multicast Shared or Source Tree Join 554 route is selected by comparing a set of Inter-AS I-PMSI A-D routes, 555 the following rules MUST be applied: 557 o STALE routes (i.e., "I/S-PMSI A-D routes" with the LLGR_STALE 558 attribute) are less preferable than non-STALE routes. 560 o If all the routes being considered are STALE, then the targeted 561 router of the Leaf A-D route or C-multicast Shared or Source Tree 562 Join route MUST NOT be changed. 564 This prevents a Leaf A-D route or C-multicast route from being 565 targeted to a particular router if the relevant I/S-PMSI A-D routes 566 from that router are stale. Since those routes are stale, it is 567 likely that the Leaf A-D route or C-multicast route would not make it 568 to the targeted router, in which case it is better to maintain the 569 existing data plane states than to make changes that presuppose that 570 the MCAST-VPN routes will be properly distributed. 572 4.6. Errors 574 If the LLGR capability is received without an accompanying GR 575 capability, the LLGR capability MUST be ignored, that is, the 576 implementation MUST behave as though no LLGR capability had been 577 received. 579 4.7. Optional Partial Deployment Procedure 581 Ideally, all routers in an Autonomous System would support this 582 specification before it was enabled. However, to facilitate 583 incremental deployment, stale routes MAY be advertised to neighbors 584 that have not advertised the Long-lived Graceful Restart Capability 585 under the following conditions: 587 o The neighbors MUST be internal (IBGP or Confederation) neighbors. 589 o The NO_EXPORT community [RFC1997] MUST be attached to the stale 590 routes. 592 o The stale routes MUST have their LOCAL_PREF set to zero. See the 593 Risks of Depreferencing Routes section (Section 5.2) for a 594 discussion of potential risks inherent in doing this. 596 If this strategy for partial deployment is used, the network operator 597 should set LOCAL_PREF to zero for all LLGR routes throughout the 598 Autonomous System. This trades off a small reduction in flexibility 599 (ordering may not be preserved between competing LLGR routes) for 600 consistency between routers which do, and do not, support this 601 specification. Since consistency of route selection can be important 602 for preventing forwarding loops, the latter consideration dominates. 604 4.8. Procedures when BGP is the PE-CE Protocol in a VPN 606 4.8.1. Procedures when EBGP is the PE-CE Protocol in a VPN 608 In VPN deployments, for example [RFC4364], EBGP is often used as a 609 PE-CE protocol. It may be a practical necessity in such deployments 610 to accommodate interoperation with peer routers that cannot easily be 611 upgraded to support specifications such as this one. This leads to a 612 problem: in this specification, we take pains to ensure that "stale" 613 routing information will not leak beyond the perimeter of routers 614 that support these procedures, so that it can be depreferenced as 615 expected, and we provide a workaround (Section 4.7) for the case 616 where one or more IBGP routers are not upgraded. However, in the VPN 617 PE-CE case, the protocol in use is EBGP, and our workaround does not 618 work since it relies on the use of LOCAL_PREF, an IBGP-only path 619 attribute. 621 We observe that the principal motivation for restricting the 622 propagation of "stale" routing information is the desire to prevent 623 it from spreading without limit once it exits the "safe" perimeter. 624 We further observe that VPN deployments are typically topologically 625 constrained, making this concern moot. For this reason, an 626 implementation MAY advertise stale routes over a PE-CE session, when 627 explicitly configured to do so. That is, the second rule listed in 628 Section 4.3 MAY be disregarded in such cases. All other rules 629 continue to apply. Finally, if this exception is used, the 630 implementation SHOULD by default attach the NO_EXPORT community to 631 the routes in question, as an additional protection against stale 632 routes spreading without limit. Attachment of the NO_EXPORT 633 community MAY be disabled by explicit configuration, to accommodate 634 exceptional cases. 636 See further discussion of using explicitly configured policy to 637 mitigate this issue in Section 5.1. 639 4.8.2. Procedures when IBGP is the PE-CE Protocol in a VPN 641 If IBGP is used as the PE-CE protocol, following the procedures of 642 [RFC6368], then when a PE router imports a VPN route that contains 643 the ATTR_SET attribute into a destination VRF and subsequently 644 advertises that route to a CE router, 646 o If the CE router does support the procedures of this document (in 647 other words, if the CE router has advertised the LLGR Capability): 648 In addition to including in the advertised route the path 649 attributes derived from the ATTR_SET as per [RFC6368], the PE 650 router MUST also include the LLGR_STALE community if it is present 651 in the path attributes of the imported route, even if it is not 652 present in the ATTR_SET attribute. 654 o If the CE router does not support the procedures of this document, 655 then the optional procedures of Section 4.7 MAY be followed, 656 attaching the NO_EXPORT community and setting the value of 657 LOCAL_PREF to zero, overriding the value found in the ATTR_SET. 659 Similarly, when a PE router receives a route from a CE into its VRF 660 and subsequently exports that route to a VPN address family, 662 o If the PE router does support the procedures of this document (in 663 other words, if the PE router has advertised the LLGR Capability): 664 In addition to including in the VPN route the ATTR_SET derived 665 from the path attributes as per [RFC6368], the PE router MUST also 666 include the LLGR_STALE community in the VPN route if it is present 667 in the path attributes of the route as received from the CE. 669 o If the PE router does not support the procedures of this document, 670 there exists no ideal solution. The CE could advertise a route 671 with LLGR_STALE, with the understanding that the LLGR_STALE 672 marking will only be honored by the provider network if 673 appropriate policy configuration exists on the PE (see 674 Section 5.1). It is at least guaranteed that LLGR_STALE will be 675 propagated when the route is propagated beyond the provider 676 network. Or, the CE could refrain from advertising the LLGR_STALE 677 route to the incapable PE. 679 5. Deployment Considerations 681 The deployment considerations discussed in [RFC4724] apply to this 682 document. In addition, network operators are cautioned to carefully 683 consider the potential disadvantages of deploying these procedures 684 for a given AFI/SAFI. Most notably, if used for an AFI/SAFI that 685 conveys traditional reachability information, use of a long-lived 686 stale route could result in a loss of connectivity for the covered 687 prefix. This specification takes pains to mitigate this risk where 688 possible, by making such routes least-preferred and by restricting 689 the scope of such routes to routers that support these procedures 690 (or, optionally, a single Autonomous System, see "Optional Partial 691 Deployment Procedure", above). However, according to the normal 692 rules of IP forwarding a stale more-specific route, that has no non- 693 stale alternate paths available, will still be used instead of a non- 694 stale less-specific route. Networks in which the deployment of these 695 procedures would be especially concerning include those which do not 696 use "tunneled" forwarding (in other words, those using traditional 697 hop-by-hop forwarding). 699 Implementations MUST NOT enable these procedures by default. They 700 MUST require affirmative configuration per AFI/SAFI in order to 701 enable them. 703 The procedures of this document do not alter the route resolvability 704 requirement of [RFC4271] Section 9.1.2.1.. Because of this, it will 705 commonly be the case that "stale" IBGP routes will only continue to 706 be used if the router depicted in the next hop remains resolvable, 707 even if its BGP component is down. Details of IGP fault-tolerance 708 strategies are beyond the scope of this document. In addition to the 709 foregoing, it may be advisable to check the viability of the next hop 710 through other means, see for example 711 [I-D.ietf-idr-bgp-bestpath-selection-criteria]. This may be 712 especially useful in cases where the next hop is known directly at 713 the network layer, notably EBGP. 715 As discussed in this document, after a BGP session goes down and 716 before the session is re-established, stale routes may be retained 717 for up to two consecutive periods, controlled by the "Restart Time" 718 and the "Long-lived Stale Time", respectively. During the first 719 period routing churn would be prevented but with potential 720 blackholing of traffic. During the second period potential 721 blackholing of traffic may be reduced but routing churn would be 722 visible throughout the network. The setting of the relevant 723 parameters for a particular application should take into account the 724 tradeoffs, the network dynamics and potential failure scenarios. If 725 needed, the first period can be bypassed either by local 726 configuration or by setting the "Restart Time" in the Graceful 727 Restart Capability to zero and/or not listing the AFI/SAFI in that 728 Capability. 730 The setting of the F bit (and the "Forwarding State" bit of the 731 accompanying GR capability) depends in part on deployment 732 considerations. The F bit can be understood as an indication that 733 the Helper should flush associated routes (if the bit is left clear). 734 As discussed in the Introduction, an important use case for LLGR is 735 for routes that are more akin to configuration than to traditional 736 routing. For such routes, it may make sense to always set the F bit, 737 regardless of other considerations. Likewise, for control-plane-only 738 entities such as dedicated route reflectors, that do not participate 739 in the forwarding plane, it makes sense to always set the F bit. 740 Overall, the rule of thumb is that if loss of state on the restarting 741 router can reasonably be expected to cause a forwarding loop or black 742 hole, the F bit should be set scrupulously according to whether state 743 has been retained. Specifics of when the F bit is, and is not, set 744 are implementation-dependent and may also be controlled by 745 configuration. Also, for every AFI/SAFI represented in the LLGR 746 capability that is also represented in the GR capability, there will 747 be two corresponding F bits -- the LLGR F bit and the GR F bit. If 748 the LLGR F bit is set, the corresponding GR F bit should also be set, 749 since to do otherwise would cause the state to be cleared on the 750 Receiving Router per the normal rules of GR, violating the intent of 751 the set LLGR bit. 753 5.1. When BGP is the PE-CE Protocol in a VPN 755 As discussed in Section 4.8, it may be necessary for a PE (or CE, in 756 the symmetric case) to advertise stale routes to a CE (or PE) in some 757 VPN deployments, even if the CE (PE) does not support this 758 specification. In that case, the operator configuring their PE (CE) 759 to advertise such routes should notify the operator of the CE (PE) 760 receiving the routes, and the CE (PE) should be configured to 761 depreference the routes. Typical BGP implementations will be able to 762 do this by matching on the LLGR_STALE community, and setting the 763 LOCAL_PREF for matching routes to zero, similar to the procedure 764 described in Section 4.7. 766 5.2. Risks of Depreferencing Routes 768 Depreferencing EBGP routes is considered safe, no different from the 769 common practice of applying a routing policy to an EBGP session. 770 However, the same is not always true of IBGP. 772 Consistent route selection is a fundamental tenet of IBGP correctness 773 and safe operation in hop-by-hop routed networks. When routers 774 within an AS apply different criteria in selecting routes, they can 775 arrive at inconsistent route selections, potentially with the 776 consequence of forming forwarding loops unless some form of tunneled 777 forwarding is used to prevent "core" routers from making a 778 (potentially inconsistent) forwarding decision based on the IP 779 header. 781 This specification uses the state of a peering session as an input to 782 the selection criteria, depreferencing routes that are associated 783 with a session that has gone down but have not yet aged out. Since 784 different routers within an AS might have different notions as to 785 whether their respective sessions with a given peer are up or down, 786 they might apply different selection criteria to routes from that 787 peer. This could result in a forwarding loop forming between such 788 routers. 790 For an example of such a forwarding loop, consider the following 791 simple topology: 793 A ---- B ---- C ------------------------- D 794 ^ ^ 795 | | 796 R1 R2 798 In this example, A - D are routers with a full mesh of IBGP sessions 799 between them. The short links have unit cost, the long link has cost 800 5. Routers A and D are AS border routers, each advertising some 801 route, R, into the AS -- these are denoted R1 and R2 in the diagram. 802 In ordinary operation, it can be seen that routers B and C will 803 select R1 for forwarding, and will forward toward A. 805 Suppose that the session between A and B goes down for some reason, 806 and stays down long enough for LLGR processing to be invoked on B. 807 Then on B, route R1 will be depreferenced, leading to the selection 808 of R2 by B. However, C will continue to prefer R1. It can be seen 809 that in this case, a forwarding loop for packets destined to R would 810 form between B and C. (We note that other forwarding loop scenarios 811 can be constructed for traditional GR, but are generally considered 812 less severe since GR can remain in effect for a much more limited 813 interval.) 815 The potential benefits of this specification can outweigh the risks 816 discussed above, as long as care is exercised in deployment. The 817 cardinal rule to be followed is, if a given set of routes are being 818 used within an AS for hop-by-hop forwarding, it is not recommended to 819 enable LLGR procedures. If tunneled forwarding (such as MPLS) is 820 used within the AS, or if routes are being used for purposes other 821 than hop-by-hop forwarding, less caution is needed, though the 822 operator should still carefully consider the consequences of enabling 823 LLGR. 825 6. Security Considerations 827 The security implications of the LLGR mechanism defined within in 828 this document are akin to those incurred by the maintenance of stale 829 routing information within a network. This is particularly relevant 830 when considering the maintenance of routing information that is 831 utilised for service segregation - such as MPLS label entries. 833 For MPLS VPN services, the effectiveness of the traffic isolation 834 between VPNs relies on the correctness of the MPLS labels between 835 ingress and egress PEs. In particular, when an egress PE withdraws a 836 label L1 allocated to a VPN1 route, this label MUST NOT be assigned 837 to a VPN route of a different VPN until all ingress PEs stop using 838 the old VPN1 route using L1. 840 Such a corner case may happen today, if the propagation of VPN routes 841 by BGP messages between PEs takes more time than the label re- 842 allocation delay on a PE. Given that we can generally bound worst 843 case BGP propagation time to a few minutes (for example 2-5), the 844 security breach will not occur if PEs are designed to not reallocate 845 a previous used and withdrawn label before a few minutes. 847 The problem is made worse with BGP GR between PEs as VPN routes can 848 be stalled for a longer period of time (for example 20 minutes). 850 This is further aggravated by the BGP LLGR extension proposed in this 851 document as VPN routes can be stalled for a much longer period of 852 time (for example 2 hours, 1 day). 854 Therefore, to avoid VPN breach, before enabling BGP LLGR, SPs need to 855 check how fast a given label can be reused by a PE, taking into 856 account: 858 o The load of the BGP route churn on a PE (in term of number of VPN 859 label advertised and churn rate). 861 o The label allocation policy on the PE (possibly depending upon the 862 size of pool of the VPN labels (which can be restricted by 863 hardware consideration or others MPLS usages), the label 864 allocation scheme (for example per route or per VRF/CE), the re- 865 allocation policy (for example least recently used label...) 867 Note that [RFC4781] which defines Graceful Restart Mechanism for BGP 868 with MPLS is also applicable to BGP LLGR. 870 In addition to these considerations, the LLGR mechanism described 871 within this document is considered to be complex to exploit 872 maliciously - in order to inject packets into a topology, there is a 873 requirement to engineer a specific LLGR state between two PE devices, 874 whilst engineering label reallocation to occur in a manner that 875 results in the two topologies overlapping. Such allocation is 876 particularly difficult to engineer (since it is typically an internal 877 mechanism of an LSR). 879 7. Examples of Operation 881 For illustrative purposes, we present a few examples of how this 882 specification might be used in practice. These examples are neither 883 exhaustive nor normative. 885 Consider the following scenario: A border router, ASBR1, has an IBGP 886 peering with a route reflector, RR1, from which it learns routes. It 887 has an EBGP peering with an external peer, EXT, to which it 888 advertises those routes. The external peer has advertised the GR and 889 LLGR Capabilities to ASBR1. ASBR1 is configured to support GR and 890 LLGR on its session with RR1 and EXT. RR1 advertises a GR Restart 891 Time of 1 (second) and a LLST of 3600 (seconds): 893 +----------+--------------------------------------------------------+ 894 | Time | Event | 895 +----------+--------------------------------------------------------+ 896 | t | ASBR1's IBGP session with RR fails. ASBR1 retains RR's | 897 | | routes according to the rules of GR [RFC4724] | 898 | | | 899 | t+1 | GR Restart Time expires. ASBR1 transitions RR's routes | 900 | | to long-lived stale by attaching the LLGR_STALE | 901 | | community and depreferencing them. However, since it | 902 | | has no backup routes, it continues to make use of | 903 | | them. It re-announces them to EXT with the LLGR_STALE | 904 | | community attached. | 905 | | | 906 | t+1+3600 | LLST expires. ASBR1 removes RR's stale routes from its | 907 | | own RIB and sends BGP updates to withdraw them from | 908 | | EXT. | 909 +----------+--------------------------------------------------------+ 911 Next, imagine the same scenario but suppose RR1 advertised a GR 912 Restart Time of zero, effectively disabling GR. Equally, ASBR1 could 913 have used local configuration to override RR1's offered Restart Time, 914 setting it to a locally-configured value of zero: 916 +----------+--------------------------------------------------------+ 917 | Time | Event | 918 +----------+--------------------------------------------------------+ 919 | t | ASBR1's IBGP session with RR fails. ASBR1 transitions | 920 | | RR's routes to long-lived stale by attaching the | 921 | | LLGR_STALE community and depreferencing them. However, | 922 | | since it has no backup routes, it continues to make | 923 | | use of them. It re-announces them to EXT with the | 924 | | LLGR_STALE community attached. | 925 | | | 926 | t+0+3600 | LLST expires. ASBR1 removes RR's stale routes from its | 927 | | own RIB and sends BGP updates to withdraw them from | 928 | | EXT. | 929 +----------+--------------------------------------------------------+ 931 Next, imagine the original scenario, but consider that the ASBR1-RR1 932 session comes back up and becomes synchronized 180 seconds after the 933 failure was detected: 935 +---------+---------------------------------------------------------+ 936 | Time | Event | 937 +---------+---------------------------------------------------------+ 938 | t | ASBR1's IBGP session with RR fails. ASBR1 retains RR's | 939 | | routes according to the rules of GR [RFC4724] | 940 | | | 941 | t+1 | GR Restart Time expires. ASBR1 transitions RR's routes | 942 | | to long-lived stale by attaching the LLGR_STALE | 943 | | community and depreferencing them. However, since it | 944 | | has no backup routes, it continues to make use of them. | 945 | | It re-announces them to EXT with the LLGR_STALE | 946 | | community attached. | 947 | | | 948 | t+1+179 | Session is reestablished and resynchronized. ASBR1 | 949 | | removes the LLGR_STALE community from RR1's routes and | 950 | | re-announces them to EXT with the LLGR_STALE community | 951 | | removed. | 952 +---------+---------------------------------------------------------+ 954 Finally, imagine the original scenario, but consider that EXT has not 955 advertised the LLGR Capability to ASBR1: 957 +----------+--------------------------------------------------------+ 958 | Time | Event | 959 +----------+--------------------------------------------------------+ 960 | t | ASBR1's IBGP session with RR fails. ASBR1 retains RR's | 961 | | routes according to the rules of GR [RFC4724] | 962 | | | 963 | t+1 | GR Restart Time expires. ASBR1 transitions RR's routes | 964 | | to long-lived stale by attaching the LLGR_STALE | 965 | | community and depreferencing them. However, since it | 966 | | has no backup routes, it continues to make use of | 967 | | them. It withdraws them from EXT. | 968 | | | 969 | t+1+3600 | LLST expires. ASBR1 removes RR's stale routes from its | 970 | | own RIB. | 971 +----------+--------------------------------------------------------+ 973 8. Acknowledgements 975 We would like to thank Nabil Bitar, Martin Djernaes, Roberto 976 Fragassi, Jeffrey Haas, Nicolai Leymann, Paul Mattes, John Medamana, 977 Pranav Mehta, Han Nguyen, Saikat Ray and Eric Rosen for their 978 valuable input and contributions to the discussion and solution. 980 9. Contributors 982 Clarence Filsfils 983 Cisco Systems 984 Brussels 1000 985 Belgium 987 Email: cf@cisco.com 989 Pradosh Mohapatra 990 Cumulus Networks 992 Email: pmohapat@cumulusnetworks.com 994 Yakov Rekhter 995 Juniper Networks 997 Email: yakov@juniper.net 999 Eric Rosen 1000 Cisco Systems 1002 Email: erosen@cisco.com 1004 Rob Shakir 1005 BT 1007 Email: rob.shakir@bt.com 1009 Adam Simpson 1010 Alcatel-Lucent 1011 600 March Road 1012 Ottawa, Ontario K2K 2E6 1013 Canada 1015 Email: adam.simpson@alcatel-lucent.com 1017 10. IANA Considerations 1019 This document defines a new BGP capability - Long-lived Graceful 1020 Restart Capability. IANA has assigned a Capability Code of 71. 1022 This document introduces a new BGP community "LLGR_STALE" for marking 1023 the long-lived stale routes, and another community "NO_LLGR" to 1024 indicate that stale routes should not be retained. IANA has assigned 1025 these well-known community values 0xFFFF0006 and 0xFFFF0007, 1026 respectively. 1028 11. References 1030 11.1. Normative References 1032 [RFC1997] Chandra, R., Traina, P., and T. Li, "BGP Communities 1033 Attribute", RFC 1997, DOI 10.17487/RFC1997, August 1996, 1034 . 1036 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1037 Requirement Levels", BCP 14, RFC 2119, 1038 DOI 10.17487/RFC2119, March 1997, 1039 . 1041 [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A 1042 Border Gateway Protocol 4 (BGP-4)", RFC 4271, 1043 DOI 10.17487/RFC4271, January 2006, 1044 . 1046 [RFC4724] Sangli, S., Chen, E., Fernando, R., Scudder, J., and Y. 1047 Rekhter, "Graceful Restart Mechanism for BGP", RFC 4724, 1048 DOI 10.17487/RFC4724, January 2007, 1049 . 1051 [RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter, 1052 "Multiprotocol Extensions for BGP-4", RFC 4760, 1053 DOI 10.17487/RFC4760, January 2007, 1054 . 1056 [RFC5492] Scudder, J. and R. Chandra, "Capabilities Advertisement 1057 with BGP-4", RFC 5492, DOI 10.17487/RFC5492, February 1058 2009, . 1060 [RFC6513] Rosen, E., Ed. and R. Aggarwal, Ed., "Multicast in MPLS/ 1061 BGP IP VPNs", RFC 6513, DOI 10.17487/RFC6513, February 1062 2012, . 1064 [RFC6514] Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP 1065 Encodings and Procedures for Multicast in MPLS/BGP IP 1066 VPNs", RFC 6514, DOI 10.17487/RFC6514, February 2012, 1067 . 1069 [RFC6625] Rosen, E., Ed., Rekhter, Y., Ed., Hendrickx, W., and R. 1070 Qiu, "Wildcards in Multicast VPN Auto-Discovery Routes", 1071 RFC 6625, DOI 10.17487/RFC6625, May 2012, 1072 . 1074 [RFC8538] Patel, K., Fernando, R., Scudder, J., and J. Haas, 1075 "Notification Message Support for BGP Graceful Restart", 1076 RFC 8538, DOI 10.17487/RFC8538, March 2019, 1077 . 1079 11.2. Informative References 1081 [I-D.ietf-idr-bgp-bestpath-selection-criteria] 1082 Asati, R., "BGP Bestpath Selection Criteria Enhancement", 1083 draft-ietf-idr-bgp-bestpath-selection-criteria-10 (work in 1084 progress), December 2018. 1086 [RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private 1087 Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February 1088 2006, . 1090 [RFC4761] Kompella, K., Ed. and Y. Rekhter, Ed., "Virtual Private 1091 LAN Service (VPLS) Using BGP for Auto-Discovery and 1092 Signaling", RFC 4761, DOI 10.17487/RFC4761, January 2007, 1093 . 1095 [RFC4781] Rekhter, Y. and R. Aggarwal, "Graceful Restart Mechanism 1096 for BGP with MPLS", RFC 4781, DOI 10.17487/RFC4781, 1097 January 2007, . 1099 [RFC5575] Marques, P., Sheth, N., Raszuk, R., Greene, B., Mauch, J., 1100 and D. McPherson, "Dissemination of Flow Specification 1101 Rules", RFC 5575, DOI 10.17487/RFC5575, August 2009, 1102 . 1104 [RFC6368] Marques, P., Raszuk, R., Patel, K., Kumaki, K., and T. 1105 Yamagata, "Internal BGP as the Provider/Customer Edge 1106 Protocol for BGP/MPLS IP Virtual Private Networks (VPNs)", 1107 RFC 6368, DOI 10.17487/RFC6368, September 2011, 1108 . 1110 [RFC7524] Rekhter, Y., Rosen, E., Aggarwal, R., Morin, T., 1111 Grosclaude, I., Leymann, N., and S. Saad, "Inter-Area 1112 Point-to-Multipoint (P2MP) Segmented Label Switched Paths 1113 (LSPs)", RFC 7524, DOI 10.17487/RFC7524, May 2015, 1114 . 1116 Authors' Addresses 1117 James Uttaro 1118 AT&T 1119 200 S. Laurel Avenue 1120 Middletown, NJ 07748 1121 USA 1123 Email: ju1738@att.com 1125 Enke Chen 1126 Cisco Systems 1127 170 W. Tasman Drive 1128 San Jose, CA 95134 1129 USA 1131 Email: enkechen@cisco.com 1133 Bruno Decraene 1134 Orange 1135 38-40 Rue de General Leclerc 1136 92794 Issy Moulineaux cedex 9 1137 France 1139 Email: bruno.decraene@orange.com 1141 John G. Scudder 1142 Juniper Networks 1143 1194 N. Mathilda Ave 1144 Sunnyvale, CA 94089 1145 USA 1147 Email: jgs@juniper.net