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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group Y. Rekhter 3 Internet Draft Juniper Networks 4 Expiration Date: October 2013 5 R. Aggarwal 7 T. Morin 8 France Telecom 10 I. Grosclaude 11 France Telecom 13 N. Leymann 14 Deutsche Telekom AG 16 S. Saad 17 AT&T 19 May 14 2013 21 Inter-Area P2MP Segmented LSPs 23 draft-ietf-mpls-seamless-mcast-07.txt 25 Status of this Memo 27 This Internet-Draft is submitted to IETF in full conformance with the 28 provisions of BCP 78 and BCP 79. 30 Internet-Drafts are working documents of the Internet Engineering 31 Task Force (IETF), its areas, and its working groups. Note that other 32 groups may also distribute working documents as Internet-Drafts. 34 Internet-Drafts are draft documents valid for a maximum of six months 35 and may be updated, replaced, or obsoleted by other documents at any 36 time. It is inappropriate to use Internet-Drafts as reference 37 material or to cite them other than as "work in progress." 39 The list of current Internet-Drafts can be accessed at 40 http://www.ietf.org/ietf/1id-abstracts.txt. 42 The list of Internet-Draft Shadow Directories can be accessed at 43 http://www.ietf.org/shadow.html. 45 Copyright and License Notice 47 Copyright (c) 2011 IETF Trust and the persons identified as the 48 document authors. All rights reserved. 50 This document is subject to BCP 78 and the IETF Trust's Legal 51 Provisions Relating to IETF Documents 52 (http://trustee.ietf.org/license-info) in effect on the date of 53 publication of this document. Please review these documents 54 carefully, as they describe your rights and restrictions with respect 55 to this document. Code Components extracted from this document must 56 include Simplified BSD License text as described in Section 4.e of 57 the Trust Legal Provisions and are provided without warranty as 58 described in the Simplified BSD License. 60 This document may contain material from IETF Documents or IETF 61 Contributions published or made publicly available before November 62 10, 2008. The person(s) controlling the copyright in some of this 63 material may not have granted the IETF Trust the right to allow 64 modifications of such material outside the IETF Standards Process. 65 Without obtaining an adequate license from the person(s) controlling 66 the copyright in such materials, this document may not be modified 67 outside the IETF Standards Process, and derivative works of it may 68 not be created outside the IETF Standards Process, except to format 69 it for publication as an RFC or to translate it into languages other 70 than English. 72 Abstract 74 This document describes procedures for building inter-area point-to- 75 multipoint (P2MP) segmented service LSPs by partitioning such LSPs 76 into intra-area segments and using BGP as the inter-area routing and 77 label distribution protocol. Within each IGP area the intra-area 78 segments are either carried over intra-area P2MP LSPs, using P2MP LSP 79 hierarchy, or instantiated using ingress replication. The intra-area 80 P2MP LSPs may be signaled using P2MP RSVP-TE or P2MP mLDP. If ingress 81 replication is used within an IGP area, then MP2P LDP LSPs or P2P 82 RSVP-TE LSPs may be used in the IGP area. The applications/services 83 that use such inter-area service LSPs may be BGP MVPN, VPLS 84 multicast, or global table multicast over MPLS. 86 Table of Contents 88 1 Specification of requirements ......................... 4 89 2 Introduction .......................................... 4 90 3 General Assumptions and Terminology ................... 5 91 4 Inter-area P2MP Segmented Next-Hop Extended Community . 7 92 5 Discovering P2MP FEC of Inter-Area P2MP Service LSP ... 7 93 5.1 BGP MVPN .............................................. 8 94 5.2 BGP VPLS or LDP VPLS with BGP auto-discovery .......... 9 95 5.3 Global Table Multicast over MPLS ...................... 11 96 6 Egress PE/ASBR Procedures ............................. 11 97 6.1 Determining the Upstream ABR/PE/ASBR (Upstream Node) .. 12 98 6.1.1 Upstream Node for MVPN or VPLS ........................ 12 99 6.1.2 Upstream Node for Global Table Multicast .............. 12 100 6.2 Originating a Leaf A-D Route .......................... 13 101 6.2.1 Leaf A-D Route for MVPN and VPLS ...................... 13 102 6.2.2 Leaf A-D Route for Global Table Multicast ............. 14 103 6.2.3 Constructing the Rest of the Leaf A-D Route ........... 16 104 6.3 PIM-SM in ASM mode for Global Table Multicast ......... 16 105 6.3.1 Option 1 .............................................. 16 106 6.3.1.1 Originating Source Active A-D Routes .................. 17 107 6.3.1.2 Receiving BGP Source Active A-D Route by PE ........... 17 108 6.3.1.3 Handling (S, G, RPTbit) state ......................... 18 109 6.3.2 Option 2 .............................................. 18 110 6.3.2.1 Originating Source Active A-D Routes .................. 18 111 6.3.2.2 Receiving BGP Source Active A-D Route ................. 19 112 6.3.2.3 Pruning Sources off the Shared Tree ................... 19 113 6.3.2.4 More on handling (S, G, RPTbit) state ................. 20 114 7 Egress ABR Procedures ................................. 20 115 7.1 Handling Leaf A-D route on Egress ABR ................. 20 116 7.2 P2MP LSP as the Intra-Area LSP in the Egress Area ..... 22 117 7.2.1 Received Leaf A-D route is for MVPN or VPLS ........... 22 118 7.2.2 Received Leaf A-D route is for global table multicast . 23 119 7.2.2.1 Global Table Multicast and S-PMSI A-D Routes .......... 23 120 7.2.2.2 Global Table Multicast and Wildcard S-PMSI A-D Routes . 24 121 7.2.3 Global Table Multicast and the Expected Upstream Node . 24 122 7.2.4 P2MP LDP LSP as the Intra-Area P2MP LSP ............... 25 123 7.2.5 P2MP RSVP-TE LSP as the Intra-Area P2MP LSP ........... 25 124 7.3 Ingress Replication in the Egress Area ................ 25 125 8 Ingress ABR Procedures ................................ 26 126 8.1 P2MP LSP as the Intra-Area LSP in the Backbone Area ... 26 127 8.2 Ingress Replication in the Backbone Area .............. 26 128 9 Ingress PE/ASBR Procedures ............................ 27 129 9.1 P2MP LSP as the Intra-Area LSP in the Ingress Area .... 28 130 9.2 Ingress Replication in the Ingress Area ............... 28 131 10 Common Tunnel Type in the Ingress and Egress Areas .... 29 132 11 Placement of Ingress and Egress PEs ................... 30 133 12 MVPN with Virtual Hub-and-Spoke ....................... 30 134 13 Data Plane ............................................ 31 135 13.1 Data Plane Procedures on ABRs ......................... 31 136 13.2 Data Plane Procedures on Egress PEs ................... 31 137 13.3 Data Plane Procedures on Ingress PEs .................. 32 138 13.4 Data Plane Procedures on Transit Routers .............. 33 139 14 Support for Inter-Area Transport LSPs ................. 33 140 14.1 Transport Tunnel Tunnel Type .......................... 33 141 14.2 Discovering Leaves of the Inter-Area P2MP Service LSP . 33 142 14.3 Discovering P2MP FEC of P2MP Transport LSP ............ 34 143 14.4 Egress PE Procedures for P2MP Transport LSP ........... 34 144 14.5 Egress/Ingress ABR, Ingress PE procedures for P2MP Transport LSP 35 145 14.6 Discussion ............................................ 36 146 15 IANA Considerations ................................... 38 147 16 Security Considerations ............................... 38 148 17 Acknowledgements ...................................... 38 149 18 References ............................................ 38 150 18.1 Normative References .................................. 38 151 18.2 Informative References ................................ 39 152 19 Author's Address ...................................... 40 154 1. Specification of requirements 156 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 157 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 158 document are to be interpreted as described in [RFC2119]. 160 2. Introduction 162 This document describes procedures for building inter-area point-to- 163 multipoint (P2MP) segmented service LSPs by partitioning such LSPs 164 into intra-area segments and using BGP as the inter-area routing and 165 label distribution protocol. Within each IGP area the intra-area 166 segments are either carried over intra-area P2MP LSPs, potentially 167 using P2MP LSP hierarchy, or instantiated using ingress replication. 168 The intra-area P2MP LSPs may be signaled using P2MP RSVP-TE or P2MP 169 mLDP. If ingress replication is used in an IGP area then MP2P LDP or 170 P2P RSVP-TE LSPs may be used within the IGP area. The 171 applications/services that use such inter-area service LSPs may be 172 BGP MVPN, VPLS multicast, or global table multicast over MPLS. 174 The primary use case of such segmented P2MP service LSPs is when the 175 PEs are in different areas but in the same AS and thousands or more 176 of PEs require P2MP connectivity. For instance this may be the case 177 when MPLS is pushed further to the metro edge and the metros are in 178 different IGP areas. This may also be the case when a Service 179 Provider's network comprises multiple IGP areas in a single 180 Autonomous System, with a large number of PEs. Seamless MPLS is the 181 industry term to address this case [SEAMLESS-MPLS]. Thus one of the 182 applicabilities of this document is that it describes the multicast 183 procedures for seamless MPLS. 185 It is to be noted that [RFC6514], [VPLS-P2MP] already specify 186 procedures for building segmented inter-AS P2MP service LSPs. This 187 document complements those procedures, as it extends the segmented 188 P2MP LSP model such that it is applicable to inter-area P2MP service 189 LSPs as well. Infact an inter-AS deployment could use inter-AS 190 segmented P2MP LSPs as specified in [RFC6514, VPLS-P2MP] where each 191 intra-AS segment is constructed using inter-area segmented P2MP LSPs 192 as specified in this document. 194 3. General Assumptions and Terminology 196 This document allows ABRs, acting as Route Reflectors, to follow the 197 procedures specified in [SEAMLESS-MPLS] when handling BGP Next-Hop of 198 the routes to the PEs. Specifically, when reflecting such routes from 199 the non-backbone areas into the backbone area, the ABRs MUST set BGP 200 Next-Hop to their own loopback addresses (next-hop-self), while when 201 reflecting such routes from the backbone area into the non-backbone 202 areas, the ABRs SHOULD NOT change the BGP Next-Hop addresses (next- 203 hop-unchanged). 205 While this document allows ABRs to follow the procedures specified in 206 [SEAMLESS-MPLS], procedures specified in this document are applicable 207 even when ABRs do not follow the procedures specified in [SEAMLESS- 208 MPLS]. 210 One possible way to support the global table multicast service is by 211 relying on the MVPN procedures, as specified in [RFC6514], in which 212 case the MVPN procedures specified in this document would be used to 213 support the global table multicast service. This document specifies 214 an alternative approach to support the global table multicast 215 service. This document refers to this approach as "global table 216 multicast" (although this by no means imply that this alternative 217 approach is the only way to support the global table multicast 218 service). 220 This document assumes that in the context of global table multicast 221 ABRs do not carry routes to the destinations external to their own 222 AS. Furthermore, in the context of global table multicast this 223 document assumes that an ASBR, when re-advertising into IBGP routes 224 received from an external speaker (received via EBGP) may not change 225 BGP Next-Hop to self. 227 Within an AS a P2MP service LSP is partitioned into 3 segments: 228 ingress area segment, backbone area segment, and egress area segment. 229 Within each area a segment is carried over an intra-area P2MP LSP or 230 instantiated using ingress replication. 232 When intra-area P2MP LSPs are used to instantiate the intra-area 233 segments there could be either 1:1 or n:1 mapping between intra-area 234 segments of the inter-area P2MP service LSP and a given intra-area 235 P2MP LSP. The latter is realized using P2MP LSP hierarchy with 236 upstream-assigned labels [RFC5331]. For simplicity of presentation we 237 assume that P2MP LSP hierarchy is used even with 1:1 mapping, in 238 which case the upstream-assigned label SHOULD be an Implicit NULL. 240 When intra-area segments of the inter-area P2MP service LSP are 241 instantiated using ingress replication, then multiple such segments 242 may be carried in the same P2P RSVP-TE or MP2P LDP LSP. This can be 243 achieved using downstream-assigned labels alone. 245 The ingress area segment of a P2MP service LSP is rooted at a PE (or 246 at an ASBR in the case where the P2MP service LSP spans multiple 247 ASes). The leaves of this segment are other PEs/ASBRs and ABRs in the 248 same area as the root PE. 250 The backbone area segment is rooted at an ABR that is connected to 251 the ingress area (ingress ABR), or at an ASBR if the ASBR is present 252 in the backbone area, or at a PE if the PE is present in the backbone 253 area. The backbone area segment has as its leaves ABRs that are 254 connected to the egress area(s) or PEs in the backbone area, or ASBRs 255 in the backbone area. 257 The egress area segment is rooted at an ABR in the egress area 258 (egress ABR), and has as its leaves PEs and ASBR in that egress area 259 (the latter covers the case where the P2MP service LSP spans multiple 260 ASes). Note that for a given P2MP service LSP there may be more than 261 one backbone segment, each rooted at its own ingress ABR, and more 262 than one egress area segment, each rooted at its own egress ABR. 264 This document uses the term "A-D routes" for "auto-discovery routes". 266 An implementation that supports this document MUST implement the 267 procedures described in the following sections to support inter-area 268 point-to-multipoint (P2MP) segmented service LSPs. 270 4. Inter-area P2MP Segmented Next-Hop Extended Community 272 This document defines a new BGP Extended Community "Inter-area P2MP 273 Next-Hop" Extended Community. This is an IP-address specific Extended 274 Community of an extended type and is transitive across AS boundaries 275 [RFC4360]. 277 A PE or an ABR or an ASBR constructs the Inter-area P2MP Segmented 278 Next-Hop Extended Community as follows: 280 - The Global Administrator field MUST be set to an IP address of 281 the PE or ASBR or ABR that originates or advertises the route, 282 which carries the P2MP Next-Hop Extended Community. For example 283 this address may be the loopback address or the PE, ASBR or ABR 284 that advertises the route. 286 - The Local Administrator field MUST be set to 0. 288 The detailed usage of this Extended Community is described in the 289 following sections. 291 5. Discovering P2MP FEC of Inter-Area P2MP Service LSP 293 Each inter-area P2MP service LSP has associated with it P2MP FEC. 294 The egress PEs need to learn this P2MP FEC in order to initiate the 295 creation of the egress area segment of the P2MP inter-area service 296 LSP. 298 The P2MP FEC of the inter-area P2MP LSP is learned by the egress PEs 299 either by configuration, or based on the application-specific 300 procedures (e.g., MVPN-specific procedures, VPLS-specific 301 procedures). 303 5.1. BGP MVPN 305 Egress PEs and/or ASBRs discover the P2MP FEC of the service LSPs 306 used by BGP MVPN using the I-PMSI or S-PMSI A-D routes that are 307 originated by the ingress PEs or ASBRs following the procedures of 308 [RFC6514], along with modifications as described in this document. 309 The NLRI of such routes encodes the P2MP FEC. The procedures in this 310 document require that at least one ABR in a given IGP area act as 311 Route Reflector for MVPN A-D routes. 313 The "Leaf Information Required" flag MUST be set in the P-Tunnel 314 attribute carried in such routes, when originated by the ingress PEs 315 or ASBRs, except for the case where (a) as a matter of policy 316 (provisioned on the ingress PEs or ASBRs) there is no aggregation of 317 ingress area segments of the service LSPs, and (b) mLDP is used as 318 the protocol to establish intra-area transport LSPs in the ingress 319 area. Before any Leaf A-D route is advertised by a PE or ABR in the 320 same area, as described in the following sections, an I-PMSI/S-PMSI 321 A-D route is advertised either with an explicit Tunnel Type and 322 Tunnel Identifier in the PMSI Tunnel Attribute, if the Tunnel 323 Identifier has already been assigned, or with a special Tunnel Type 324 of "No tunnel information present" otherwise. 326 When the I-PMSI/S-PMSI A-D routes are re-advertised by an ingress 327 ABR, the "Leaf Information Required" flag MUST be set in the P-Tunnel 328 attribute present in the routes, except for the case where (a) as a 329 matter of policy (provisioned on the ingress ABR) there is no 330 aggregation of backbone area segments of the service LSPs, and (b) 331 mLDP is used as the protocol to establish intra-area transport LSPs 332 in the backbone area. Likewise, when the I-PMSI/S-PMSI A-D routes are 333 re-advertised by an egress ABR, the "Leaf Information Required" flag 334 MUST be set in the P-Tunnel attribute present in the routes, except 335 for the case where (a) as a matter of policy (provisioned on the 336 egress ABR) there is no aggregation of egress area segments of the 337 service LSPs, and (b) mLDP is used as the protocol to establish 338 intra-area transport LSPs in the egress area. 340 Note that the procedures in the above paragraph apply when intra-area 341 segments are realized by either intra-area P2MP LSPs or by ingress 342 replication. 344 When BGP MVPN I-PMSI or S-PMSI A-D routes are advertised or 345 propagated to signal Inter-area P2MP service LSPs, to indicate that 346 these LSPs should be segmented using the procedures specified in this 347 document, these routes MUST carry the Inter-area P2MP Segmented Next- 348 Hop Extended Community. This Extended Community MUST be included in 349 the I-PMSI/S-PMSI A-D route by the PE that originates such a route, 350 or an ASBR that re-advertises such a route into its own AS. The 351 Global Administrator field in this Extended Community MUST be set to 352 the advertising PE or ASBR's IP address. This Extended Community MUST 353 also be included by ABRs as they re-advertise such routes. An ABR 354 MUST set the Global Administrator field of the P2MP Segmented Next- 355 Hop Extended Community to its own IP address. Presence of this 356 community in the I-PMSI/S-PMSI A-D routes indicates to ABRs and 357 PEs/ASBRs that they have to follow the procedures in this document 358 when these procedures differ from those in [RFC6514]. 360 If an ASBR receives from an IBGP peer an I-PMSI or S-PMSI A-D route 361 that carries the Inter-area P2MP Segmented Next-Hop Extended 362 Community, then before re-advertising this route to an EBGP peer the 363 ASBR SHOULD remove this Community from the route. 365 If an ASBR receives an I-PMSI/S-PMSI A-D route from an EBGP peer, and 366 this route does carry the Inter-area P2MP Segmented Next- Hop 367 Extended Community, if the inter-area P2MP service LSP signalled by 368 this route should not be segmented, then before re-advertising this 369 route to its IBGP peers the ASBR MUST remove this community from the 370 route. 372 To avoid requiring ABRs to participate in the propagation of C- 373 multicast routes, this document requires ABRs NOT to modify BGP Next 374 Hop when re-advertising Inter-AS I-PMSI A-D routes. For consistency 375 this document requires ABRs to NOT modify BGP Next-Hop when re- 376 advertising both Intra-AS and Inter-AS I-PMSI/S-PMSI A-D routes. The 377 egress PEs may advertise the C-multicast routes to RRs that are 378 different than the ABRs. However ABRs still can be configured to be 379 the Route Reflectors for C-multicast routes, in which case they will 380 participate in the propagation of C-multicast routes. 382 5.2. BGP VPLS or LDP VPLS with BGP auto-discovery 384 Egress PEs discover the P2MP FEC of the service LSPs used by VPLS, 385 using the VPLS A-D routes that are originated by the ingress PEs 386 [RFC4761, RFC6074], or VPLS S-PMSI A-D routes that are originated by 387 the ingress PEs [VPLS-P2MP]. The NLRI of such routes encodes the P2MP 388 FEC. 390 The "Leaf Information Required" flag MUST be set in the P-Tunnel 391 attribute carried in such routes, when originated by the ingress PEs 392 or ASBRs, except for the case where (a) as a matter of policy 393 (provisioned on the ingress PEs or ASBRs) there is no aggregation of 394 ingress area segments of the service LSPs, and (b) mLDP is used as 395 the protocol to establish intra-area transport LSPs in the ingress 396 area. Before any Leaf A-D route is advertised by a PE or ABR in the 397 same area, as described in the following sections, an VPLS/S-PMSI A-D 398 route is advertised either with an explicit Tunnel Type and Tunnel 399 Identifier in the PMSI Tunnel Attribute, if the Tunnel Identifier has 400 already been assigned, or with a special Tunnel Type of "No tunnel 401 information present" otherwise. 403 When the VPLS/S-PMSI A-D routes are re-advertised by an ingress ABR, 404 the "Leaf Information Required" flag MUST be set in the P-Tunnel 405 attribute present in the routes, except for the case where (a) as a 406 matter of policy (provisioned on the ingress ABR) there is no 407 aggregation of backbone area segments of the service LSPs, and (b) 408 mLDP is used as the protocol to establish intra-area transport LSPs 409 in the backbone area. Likewise, when the VPLS/S-PMSI A-D routes are 410 re-advertised by an egress ABR, the "Leaf Information Required" flag 411 MUST be set in the P-Tunnel attribute present in the routes, except 412 for the case where (a) as a matter of policy (provisioned on the 413 egress ABR) there is no aggregation of egress area segments of the 414 service LSPs, and (b) mLDP is used as the protocol to establish 415 intra-area transport LSPs in the egress area. 417 When VPLS A-D routes or S-PMSI A-D routes are advertised or 418 propagated to signal Inter-area P2MP service LSPs, to indicate that 419 these LSPs should be segmented using the procedures specified in this 420 document, these routes MUST carry the Inter-area P2MP Segmented Next- 421 Hop Extended Community. This Extended Community MUST be included in 422 the A-D route by the PE or ASBR that originates such a route and the 423 Global Administrator field MUST be set to the advertising PE or 424 ASBR's IP address. This Extended Community MUST also be included by 425 ABRs as they re-advertise such routes. An ABR MUST set the Global 426 Administrator field of the P2MP Segmented Next-Hop Extended Community 427 to its own IP address. Presence of this community in the I-PMSI/S- 428 PMSI A-D routes indicates to ABRs and PEs/ASBRs that they have to 429 follow the procedures in this document when these procedures differ 430 from those in [VPLS-P2MP]. 432 Note that the procedures in the above paragraph apply when intra-area 433 segments are realized by either intra-area P2MP LSPs or by ingress 434 replication. 436 The procedures in this document require that at least one ABR in a 437 given area act as Route Reflector for VPLS A-D routes. These ABRs/RRs 438 MUST NOT modify BGP Next Hop when re-advertising these A-D routes. 440 5.3. Global Table Multicast over MPLS 442 This section describes how the egress PEs discover the P2MP FEC when 443 the application is global table multicast over an MPLS-capable 444 infrastructure. In the rest of the document we will refer to this 445 application as "global table multicast". 447 When PIM-SM is used for non-bidirectional ASM ("Any Source 448 Multicast") group addresses, this document refers to this as "PIM-SM 449 in ASM mode". 451 In the case where global table multicast uses PIM-SM in ASM mode the 452 following assumes that an inter-area P2MP service LSP could be used 453 to either carry traffic on a shared (*,G), or a source (S,G) tree. 455 An egress PE learns the (S/*, G) of a multicast stream as a result of 456 receiving IGMP or PIM messages on one of its IP multicast interfaces. 457 This (S/*, G) forms the P2MP FEC of the inter-area P2MP service LSP. 458 For each such P2MP FEC there MAY exist a distinct inter-area P2MP 459 service LSP, or multiple such FECs MAY be carried over a single P2MP 460 service LSP using a wildcard (*, *) S-PMSI [RFC6625]. 462 Note that this document does not require the use of (*, G) Inter-area 463 P2MP service LSPs when global table multicast uses PIM-SM in ASM 464 mode. In fact, PIM-SM in ASM mode may be supported entirely by using 465 only (S, G) inter-area P2MP service LSPs. 467 6. Egress PE/ASBR Procedures 469 This section describes egress PE/ASBR procedures for constructing 470 segmented inter-area P2MP LSP. The procedures in this section apply 471 irrespective of whether the egress PE/ASBR is in a leaf IGP area, or 472 the backbone area, or even in the same IGP area as the ingress 473 PE/ASBR. 475 An egress PE/ASBR applies procedures specified in this section to 476 MVPN I-PMSI or S-PMSI A-D routes only if these routes carry the 477 Inter-area P2MP Segmented Next-Hop Extended Community. An egress PE 478 applies procedures specified in this section to VPLS A-D routes or 479 VPLS S-PMSI A-D routes only if these routes carry the Inter-area P2MP 480 Segmented Next-Hop Extended Community. 482 In order to support global table multicast an egress PE MUST auto- 483 configure an import AS-specific Route Target Extended Community 484 ([RFC4360]) with the Global Administrator field set to the AS of the 485 PE and the Local Administrator field set to 0. 487 Once an egress PE/ASBR discovers the P2MP FEC of an inter-area 488 segmented P2MP service LSP, it MUST propagate this P2MP FEC in BGP in 489 order to construct the segmented inter-area P2MP service LSP. This 490 propagation uses BGP Leaf A-D routes. 492 6.1. Determining the Upstream ABR/PE/ASBR (Upstream Node) 494 An egress PE/ASBR discovers the P2MP FEC of an inter-area P2MP 495 Segmented Service LSP as described in section 5 ("Discovering P2MP 496 FEC of the Inter-Area P2MP Service LSP"). Once the egress PE/ASBR 497 discovers this P2MP FEC, it MUST determine the upstream node to reach 498 such a FEC. If the egress PE/ASBR and the ingress PE/ASBR are not in 499 the same area, and the egress PE/ASBR is not in the backbone IGP 500 area, then this upstream node would be an egress ABR. If the egress 501 PE/ASBR is in the backbone area and the ingress PE/ASBR is not in the 502 backbone area, then this upstream node would be an ingress ABR. If 503 the egress PE/ASBR is in the same area as the ingress PE/ASBR, then 504 this upstream node would be the ingress PE/ASBR. 506 6.1.1. Upstream Node for MVPN or VPLS 508 If the application is MVPN or VPLS, then the upstream node's IP 509 address is the IP address determined from the Global Administrator 510 field of the Inter-area P2MP Segmented Next-hop Extended Community. 511 As described in section 5 ("Discovering P2MP FEC of the Inter-Area 512 P2MP Service LSP"), this Extended Community MUST be carried in the 513 MVPN or VPLS A-D route from which the P2MP FEC of the inter-area P2MP 514 Segmented Service LSP is determined. 516 6.1.2. Upstream Node for Global Table Multicast 518 If the application is global table multicast, then the unicast routes 519 to multicast sources/RPs SHOULD carry the VRF Route Import Extended 520 Community [RFC6514] where the IP address in the Global Administrator 521 field is set to the IP address of the PE or ASBR advertising the 522 unicast route. The Local Administrator field of this community MUST 523 be set to 0 (note, that this is in contrast to the case of MVPN, 524 where the Global Administrator field carries a non-zero value that 525 identifies a particular VRF on a PE that originates VPN-IP routes). 526 If it is not desirable to advertise the VRF Route Import Extended 527 Community in unicast routes, then unicast routes to multicast 528 sources/RPs MUST be advertised using the multicast SAFI i.e. SAFI 2, 529 and such routes MUST carry the VRF Route Import Extended Community. 531 Further, if the application is global table multicast, then the BGP 532 unicast routes that advertise the routes to the IP addresses of 533 PEs/ASBRs/ABRs SHOULD carry the Inter-area P2MP Segmented Next-Hop 534 Extended Community. The IP address in the Global Administrator field 535 of this community MUST be set to the IP address of the PE or ASBR or 536 ABR advertising the unicast route. The Local Administrator field of 537 this community MUST be set to 0. If it is not desirable to advertise 538 the P2MP Segmented Next-Hop Extended Community in BGP unicast routes, 539 then the BGP unicast routes to the IP addresses of PEs/ASBRs/ABRs 540 MUST be advertised using the multicast SAFI i.e. SAFI 2, and such 541 routes MUST carry the Inter-area P2MP Segmented Next-hop Extended 542 Community. The procedures for handling the BGP Next-Hop attribute of 543 SAFI 2 routes are the same as those of handling regular Unicast 544 routes and MAY follow [SEAMLESS-MPLS]. 546 If the application is global table multicast, then in order to 547 determine the upstream node address the egress PE first determines 548 the ingress PE. In order to determine the ingress PE, the egress PE 549 determines the best route to reach S/RP. The ingress PE address is 550 the IP address determined from the Global Administrator field of the 551 VRF Route Import Extended Community that is carried in this route. 552 The egress PE then finds the best unicast route to reach the ingress 553 PE. The upstream node address is the IP address determined from the 554 Global Administrator field of the Inter-area P2MP Segmented Next-Hop 555 Extended Community that is carried in this route. 557 6.2. Originating a Leaf A-D Route 559 If the P2MP FEC was derived from a MVPN or VPLS A-D route then the 560 egress PE MUST originate a Leaf A-D route if the MVPN or VPLS A-D 561 route carries a P-Tunnel Attribute with the "Leaf Information 562 Required" flag set. 564 If the P2MP FEC was derived from a global table multicast (S/*, G), 565 and the upstream node's address is not the same as the egress PE, 566 then the egress PE MUST originate a Leaf A-D route. 568 6.2.1. Leaf A-D Route for MVPN and VPLS 570 If the P2MP FEC was derived from MVPN or VPLS A-D routes then the 571 Route Key field of the Leaf A-D route contains the NLRI of the A-D 572 route from which the P2MP FEC was derived. This follows procedures 573 for constructing Leaf A-D routes described in [RFC6514, VPLS-P2MP]. 575 6.2.2. Leaf A-D Route for Global Table Multicast 577 If the application is global table multicast, then the MCAST-VPN NLRI 578 of the Leaf A-D route is constructed as follows: 580 The Route Key field of MCAST-VPN NLRI has the following format: 582 +-----------------------------------+ 583 | RD (8 octets) | 584 +-----------------------------------+ 585 | Multicast Source Length (1 octet) | 586 +-----------------------------------+ 587 | Multicast Source (Variable) | 588 +-----------------------------------+ 589 | Multicast Group Length (1 octet) | 590 +-----------------------------------+ 591 | Multicast Group (Variable) | 592 +-----------------------------------+ 593 | Ingress PE's IP address | 594 +-----------------------------------+ 596 RD is set to 0 for (S,G) state and all 1s for (*,G) state, Multicast 597 Source is set to S for (S,G) state or RP for (*,G) state, Multicast 598 Group is set to G, Multicast Source Length and Multicast Group Length 599 is set to either 4 or 16 (depending on whether S/RP and G are IPv4 or 600 IPv6 addresses). 602 The Ingress PE's IP address is determined as described in the section 603 6.1 ("Determining the Upstream ABR/PE/ASBR (Upstream Node)"). 605 The Originating Router's IP address field of MCAST-VPN NLRI is set to 606 the address of the local PE (PE that originates the route). 608 Thus the entire MCAST-VPN NLRI of the route has the following format: 610 +-----------------------------------+ 611 | Route Type = 4 (1 octet) | 612 +-----------------------------------+ 613 | Length (1 octet) | 614 +-----------------------------------+ 615 | RD (8 octets) | 616 +-----------------------------------+ 617 | Multicast Source Length (1 octet) | 618 +-----------------------------------+ 619 | Multicast Source (Variable) | 620 +-----------------------------------+ 621 | Multicast Group Length (1 octet) | 622 +-----------------------------------+ 623 | Multicast Group (Variable) | 624 +-----------------------------------+ 625 | Ingress PE's IP address | 626 +-----------------------------------+ 627 | Originating Router's IP address | 628 +-----------------------------------+ 630 Note that the encoding of MCAST-VPN NLRI for the Leaf A-D routes used 631 for global table multicast is different from the encoding used by the 632 Leaf A-D routes originated in response to S-PMSI or I-PMSI A-D 633 routes. A router that receives a Leaf A-D route can distinguish 634 between these two cases by examining the third octet of the MCAST-VPN 635 NLRI of the route. If the value of this octet is 0x01 or 0x02, or 636 0x03 then this Leaf A-D route was originated in response to an S-PMSI 637 or I-PMSI A-D route. If the value of this octet is either 0x00 or 638 0xff, and octets 3 through 10 contain either all 0x00, or all 0xff 639 then this is a Leaf A-D route used for global table multicast. 641 When the PE deletes (S,G)/(*,G) state that was created as a result of 642 receiving PIM or IGMP messages on one of its IP multicast interfaces, 643 if the PE previously originated a Leaf A-D route for that state, then 644 the PE SHOULD withdraw that route. 646 An Autonomous System with an IPv4 network may provide global table 647 multicast service for customers that use IPv6, and an Autonomous 648 System with an IPv6 network may provide global table multicast 649 service for customers that use IPv4. Therefore the address family of 650 the Ingress PE's IP address and Originating Router's IP address in 651 the Leaf A-D routes used for global table multicast MUST NOT be 652 inferred from the AFI field of the associated 653 MP_REACH_NLRI/MP_UNREACH_NLRI attribute of these routes. The address 654 family is determined from the length of the address (a length of 4 655 octets for IPv4 addresses, a length of 16 octets for IPv6 addresses). 657 For example if an Autonomous System with an IPv4 network is providing 658 IPv6 multicast service to a customer, the Ingress PE's IP address and 659 Originating Router's IP address in the Leaf A-D routes used for IPv6 660 global table multicast will be a four-octet IPv4 address, even though 661 the AFI of those routes will have the value 2. 663 Note that the Ingress PE's IP address and the Originating Router's IP 664 address must be either both IPv4 or both IPv6 addresses, and thus 665 must be of the same length. Since the two variable length fields 666 (Multicast Source and Multicast Group) in the Leaf A-D routes used 667 for global table multicast have their own length field, from these 668 two length fields, and the Length field of the MCAST-VPN NLRI, one 669 can compute length of the Ingress PE's IP address and the Originating 670 Router's IP address fields. If the computed length of these fields is 671 neither 4 nor 16, the MP_REACH_NLRI attribute MUST be considered to 672 be "incorrect", and MUST be handled as specified in section 7 of 673 [RFC4760]. 675 6.2.3. Constructing the Rest of the Leaf A-D Route 677 The Next Hop field of the MP_REACH_NLRI attribute of the route SHOULD 678 be set to the same IP address as the one carried in the Originating 679 Router's IP Address field of the route. 681 When Ingress Replication is used to instantiate the egress area 682 segment then the Leaf A-D route MUST carry a downstream assigned 683 label in the P-Tunnel Attribute where the P-Tunnel type is set to 684 Ingress Replication. A PE MUST assign a distinct MPLS label for each 685 Leaf A-D route originated by the PE. 687 To constrain distribution of this route, the originating PE 688 constructs an IP-based Route Target community by placing the IP 689 address of the upstream node in the Global Administrator field of the 690 community, with the Local Administrator field of this community set 691 to 0. The originating PE then adds this Route Target Extended 692 Community to this Leaf A-D route. The upstream node's address is as 693 determined in section 6.1 ("Determining the Upstream ABR/PE/ASBR 694 (Upstream Node)"). 696 The PE then advertises this route to the upstream node. 698 6.3. PIM-SM in ASM mode for Global Table Multicast 700 This specification allows two options for supporting global table 701 multicast with PIM-SM in ASM mode. The first option does not transit 702 IP multicast shared trees over the MPLS network. The second option 703 does transit shared trees over the MPLS network and relies on shared 704 tree to source tree switchover. 706 6.3.1. Option 1 708 This option does not transit IP multicast shared trees over the MPLS 709 network. Therefore, when an (egress) PE creates (*, G) state (as a 710 result of receiving PIM or IGMP messages on one of its IP multicast 711 interfaces), the PE does not propagate this state using Leaf A-D 712 routes. 714 6.3.1.1. Originating Source Active A-D Routes 716 Whenever as a result of receiving PIM Register or MSDP messages an RP 717 that is co-located with a PE discovers a new multicast source, the 718 RP/PE SHOULD originate a BGP Source Active A-D route. Similarly 719 whenever as a result of receiving MSDP messages a PE, that is not 720 configured as a RP, discovers a new multicast source the PE SHOULD 721 originate a BGP Source Active A-D route. The BGP Source Active A-D 722 route carries a single MCAST-VPN NLRI constructed as follows: 724 + The RD in this NLRI is set to 0. 726 + The Multicast Source field MUST be set to S. The Multicast 727 Source Length field is set appropriately to reflect this. 729 + The Multicast Group field MUST be set to G. The Multicast Group 730 Length field is set appropriately to reflect this. 732 The Route Target of this Source Active A-D route is an AS-specific 733 Route Target Extended Community with the Global Administrator field 734 set to the AS of the advertising RP/PE, and the Local Administrator 735 field is set to 0. 737 To constrain distribution of the Source Active A-D route to the AS of 738 the advertising RP this route SHOULD carry the NO_EXPORT Community 739 ([RFC1997]). 741 Using the normal BGP procedures the Source Active A-D route is 742 propagated to all other PEs within the AS. 744 Whenever the RP/PE discovers that the source is no longer active, the 745 RP MUST withdraw the Source Active A-D route, if such a route was 746 previously advertised by the RP. 748 6.3.1.2. Receiving BGP Source Active A-D Route by PE 750 When as a result of receiving PIM or IGMP messages on one of its IP 751 multicast interfaces an (egress) PE creates in its Tree Information 752 Base (TIB) a new (*, G) entry with a non-empty outgoing interface 753 list that contains one or more IP multicast interfaces, the PE MUST 754 check if it has any Source Active A-D routes for that G. If there is 755 such a route, S of that route is reachable via an MPLS interface, and 756 the PE does not have (S, G) state in its TIB for (S, G) carried in 757 the route, then the PE originates a Leaf A-D route carrying that (S, 758 G), as specified in section 6.2.2 ("Leaf A-D Route for Global Table 759 Multicast"). 761 When an (egress) PE receives a new Source Active A-D route, the PE 762 MUST check if its TIB contains an (*, G) entry with the same G as 763 carried in the Source Active A-D route. If such an entry is found, S 764 is reachable via an MPLS interface, and the PE does not have (S, G) 765 state in its TIB for (S, G) carried in the route, then the PE 766 originates a Leaf A-D route carrying that (S, G), as specified in 767 section 6.2.2 ("Leaf A-D Route for Global Table Multicast"). 769 6.3.1.3. Handling (S, G, RPTbit) state 771 Creation and deletion of (S, G, RPTbit) state on a PE that resulted 772 from receiving PIM messages on one of its IP multicast interfaces 773 does not result in any BGP actions by the PE. 775 6.3.2. Option 2 777 This option does transit IP multicast shared trees over the MPLS 778 network. Therefore, when an (egress) PE creates (*, G) state (as a 779 result of receiving PIM or IGMP messages on one of its IP multicast 780 interfaces), the PE does propagate this state using Leaf A-D routes. 782 6.3.2.1. Originating Source Active A-D Routes 784 Whenever a PE creates an (S, G) state as a result of receiving Leaf 785 A-D routes associated with the global table multicast service, if S 786 is reachable via one of the IP multicast capable interfaces, and the 787 PE determines that G is in the PIM-SM in ASM mode range, the PE MUST 788 originate a BGP Source Active A-D route. The route carries a single 789 MCAST-VPN NLRI constructed as follows: 791 + The RD in this NLRI is set to 0. 793 + The Multicast Source field MUST be set to S. The Multicast 794 Source Length field is set appropriately to reflect this. 796 + The Multicast Group field MUST be set to G. The Multicast Group 797 Length field is set appropriately to reflect this. 799 The Route Target of this Source Active A-D route is an AS-specific 800 Route Target Extended Community with the Global Administrator field 801 set to the AS of the advertising PE, and the Local Administrator 802 field is set to 0. 804 To constrain distribution of the Source Active A-D route to the AS of 805 the advertising PE this route SHOULD carry the NO_EXPORT Community 806 ([RFC1997]). 808 Using the normal BGP procedures the Source Active A-D route is 809 propagated to all other PEs within the AS. 811 Whenever the PE deletes the (S, G) state that was previously created 812 as a result of receiving a Leaf A-D route for (S, G), the PE that 813 deletes the state MUST also withdraw the Source Active A-D route, if 814 such a route was advertised when the state was created. 816 6.3.2.2. Receiving BGP Source Active A-D Route 818 Procedures for receiving BGP Source Active A-D routes are the same as 819 with Option 1. 821 6.3.2.3. Pruning Sources off the Shared Tree 823 If after receiving a new Source Active A-D route for (S,G) a PE 824 determines that (a) it has the (*, G) entry in its TIB, (b) the 825 incoming interface list (iif) for that entry contains one of the IP 826 interfaces, (c) a MPLS LSP is in the outgoing interface list (oif) 827 for that entry, and (d) the PE does not originate a Leaf A-D route 828 for (S,G), then the PE MUST transition the (S,G,rpt) downstream state 829 to the Prune state. [Conceptually the PIM state machine on the PE 830 will act "as if" it had received Prune(S,G,Rpt) from some other PE, 831 without actually having received one.] Depending on the (S,G,rpt) 832 state on the iifs, this may result in the PE using PIM procedures to 833 prune S off the Shared (*,G) tree. 835 Transitioning the state machine to the Prune state SHOULD be done 836 after a delay that is controlled by a timer. The value of the timer 837 MUST be configurable. The purpose of this timer is to ensure that S 838 is not pruned off the shared tree until all PEs have had time to 839 receive the Source Active A-D route for (S,G). 841 The PE MUST keep the (S,G,rpt) downstream state machine in the Prune 842 state for as long as (a) the outgoing interface list (oif) for (*, G) 843 contains a MPLS LSP, and (b) the PE has at least one Source Active A- 844 D route for (S,G), and (c) the PE does not originate the Leaf A-D 845 route for (S,G). Once either of these conditions become no longer 846 valid, the PE MUST transition the (S,G,rpt) downstream state machine 847 to the NoInfo state. 849 Note that except for the scenario described in the first paragraph of 850 this section, in all other scenarios relying solely on PIM procedures 851 on the PE is sufficient to ensure the correct behavior when pruning 852 sources off the shared tree. 854 6.3.2.4. More on handling (S, G, RPTbit) state 856 Creation and deletion of (S, G, RPTbit) state on a PE that resulted 857 from receiving PIM messages on one of its IP multicast interfaces 858 does not result in any BGP actions by the PE. 860 7. Egress ABR Procedures 862 This section describes Egress ABR Procedures for constructing 863 segmented inter-area P2MP LSP. 865 7.1. Handling Leaf A-D route on Egress ABR 867 When an egress ABR receives a Leaf A-D route and the Route Target 868 Extended Community carried by the route contains the IP address of 869 this ABR, then the following procedures will be executed. 871 If the value of the third octet of the MCAST-VPN NLRI of the received 872 Leaf A-D route is either 0x01, or 0x02, or 0x03, this indicates that 873 the Leaf A-D route was originated in response to an S-PMSI or I-PMSI 874 A-D route (see section "Leaf A-D Route for Global Table Multicast"). 875 In this case the egress ABR MUST find a S-PMSI or I-PMSI route whose 876 NLRI has the same value as the Route Key field of the received Leaf 877 A-D route. If such a matching route is found then the Leaf A-D route 878 MUST be accepted, else it MUST be discarded. If the Leaf A-D route 879 is accepted and if it is the first Leaf A-D route update for the 880 Route Key field in the route, or the withdrawl of the last Leaf A-D 881 route for the Route Key field then the following procedures will be 882 executed. 884 If the RD of the received Leaf A-D route is set to all 0s or all 1s 885 then the received Leaf A-D route is for the global table multicast 886 service. 888 If the received Leaf A-D route is the first Leaf A-D route update for 889 the Route Key field carried in the route, then the egress ABR 890 originates a Leaf A-D route, whose MCAST-VPN NLRI is constructed as 891 follows. 893 The Route Key field of MCAST-VPN NLRI is the same as the Route Key 894 field of MCAST-VPN NLRI of the received Leaf A-D route. The 895 Originating Router's IP address field of MCAST-VPN NLRI is set to the 896 address of the local ABR (the ABR that originates the route). 898 The Next Hop field of the MP_REACH_NLRI attribute of the route SHOULD 899 be set to the same IP address as the one carried in the Originating 900 Router's IP Address field of the route. 902 To constrain distribution of this route the originating egress ABR 903 constructs an IP-based Route Target Extended Community by placing the 904 IP address of the upstream node in the Global Administrator field of 905 the community, with the Local Administrator field of this community 906 set to 0, and sets the Extended Communities attribute of this Leaf A- 907 D route to that community. 909 The upstream node's IP address is the IP address determined from the 910 Global Administrator field of the Inter-area P2MP Segmented Next-hop 911 Extended Community, where this Extended Community is obtained as 912 follows. When the Leaf A-D route is for MVPN or VPLS, then this 913 Extended Community is the one carried in the I-PMSI/S-PMSI A-D route 914 that matches the Leaf A-D route. When the Leaf A-D route is for 915 global table multicast, then this Extended Community is the one 916 carried in the best unicast route to the Ingress PE. The Ingress PE 917 address is determined from the received Leaf A-D route. The best 918 unicast route MUST first be determined from multicast SAFI i.e., SAFI 919 2 routes, if present. 921 The ABR then advertises this Leaf A-D route to the upstream node in 922 the backbone area. 924 Mechanisms specific in [RFC4684] for constrained BGP route 925 distribution can be used along with this specification to ensure that 926 only the needed PE/ABR will have to process a said Leaf A-D route. 928 When Ingress Replication is used to instantiate the backbone area 929 segment then the Leaf A-D route originated by the egress ABR MUST 930 carry a downstream assigned label in the P-Tunnel Attribute where the 931 P-Tunnel type is set to Ingress Replication. The ABR MUST assign a 932 distinct MPLS label for each Leaf A-D route that it originates. 934 In order to support global table multicast an egress ABR MUST auto- 935 configure an import AS-based Route Target Extended Community with the 936 Global Administrator field set to the AS of the ABR and the Local 937 Administrator field set to 0. 939 If the received Leaf A-D route is the withdrawl of the last Leaf A-D 940 route for the Route Key carried in the route, then the egress ABR 941 must withdraw the Leaf A-D route associated with that Route Key that 942 has been previously advertised by the egress ABR in the backbone 943 area. 945 7.2. P2MP LSP as the Intra-Area LSP in the Egress Area 947 This section describes procedures for using intra-area P2MP LSPs in 948 the egress area. The procedures that are common to both P2MP RSVP-TE 949 and P2MP LDP are described first, followed by procedures that are 950 specific to the signaling protocol. 952 When P2MP LSPs are used as the intra-area LSPs, note that an existing 953 intra-area P2MP LSP may be used solely for a particular inter-area 954 P2MP service LSP, or for other inter-area P2MP service LSPs as well. 955 The choice between the two options is purely local to the egress ABR. 956 The first option provides one-to-one mapping between inter-area P2MP 957 service LSPs and intra-area P2MP LSPs; the second option provides 958 many-to-one mapping, thus allowing to aggregate forwarding state. 960 7.2.1. Received Leaf A-D route is for MVPN or VPLS 962 If the value of the third octet of the MCAST-VPN NLRI of the received 963 Leaf A-D route is either 0x01, or 0x02, or 0x03, this indicates that 964 the Leaf A-D route was originated in response to an MVPN or VPLS S- 965 PMSI or I-PMSI A-D route (see section "Leaf A-D Route for Global 966 Table Multicast"). In this case the ABR MUST re-advertise in the 967 egress area the MVPN/VPLS A-D route that matches the Leaf A-D route 968 to signal the binding of the intra-area P2MP LSP to the inter-area 969 P2MP service LSP. This must be done ONLY if (a) such a binding hasn't 970 already been advertised, or (b) the binding has changed. The re- 971 advertised route MUST carry the Inter-area P2MP Segmented Next-Hop 972 Extended Community. 974 The PMSI Tunnel attribute of the re-advertised route specifies either 975 an intra-area P2MP RSVP-TE LSP or an intra-area P2MP LDP LSP rooted 976 at the ABR and MUST also carry an upstream assigned MPLS label. The 977 upstream-assigned MPLS label MUST be set to implicit NULL if the 978 mapping between the inter-area P2MP service LSP and the intra-area 979 P2MP LSP is one-to-one. If the mapping is many-to-one the intra-area 980 segment of the inter-area P2MP service LSP (referred to as the 981 "inner" P2MP LSP) is constructed by nesting the inter-area P2MP 982 service LSP in an intra-area P2MP LSP (referred to as the "outer" 983 intra-area P2MP LSP), by using P2MP LSP hierarchy based on upstream- 984 assigned MPLS labels [RFC 5332]. 986 If segments of multiple MVPN or VPLS S-PMSI service LSPs are carried 987 over a given intra-area P2MP LSP, each of these segments MUST carry a 988 distinct upstream-assigned label, even if all these service LSPs are 989 for (C-S/*, C-G/*)s from the same MVPN/VPLS. Therefore, an ABR 990 maintains an LFIB state for each of the (C-S/*, C-G/*)s carried over 991 S-PMSIs traversing this ABR (that applies to both the ingress and the 992 egress ABRs). 994 7.2.2. Received Leaf A-D route is for global table multicast 996 When the RD of the received Leaf A-D route is set to all 0s or all 997 1s, then this is the case of inter-area P2MP service LSP being 998 associated with the global table multicast service. The procedures 999 for this are described below. 1001 7.2.2.1. Global Table Multicast and S-PMSI A-D Routes 1003 This section applies only if it is desirable to send a particular (S, 1004 G) or (*, G) global table multicast flow only to those egress PEs 1005 that have receivers for that multicast flow. 1007 If the egress ABR have not previousely received (and re-advertised) 1008 an S-PMSI A-D route for (S, G) or (*, G) that has been originated by 1009 an ingress PE/ASBR (see section "P2MP LSP as the Intra-Area LSP in 1010 the Ingress Area"), then the egress ABR MUST originate a S-PMSI A-D 1011 route. The PMSI Tunnel attribute of the route MUST contain the 1012 identity of the intra-area P2MP LSP and an upstream assigned MPLS 1013 label (although this label may be an Implicit NULL - see section 1014 "General Assumptions and Terminology"). The RD, Multicast Source 1015 Length, Multicast Source, Multicast Group Length (1 octet), and 1016 Multicast Group fields of the NLRI of this route are the same as of 1017 the received Leaf A-D route. The Originating Router's IP address 1018 field in the S-PMSI A-D route is the same as the Ingress PE's IP 1019 address field in the received Leaf A-D route. The Route Target of 1020 this route is an AS-specific Route Target Extended Community with the 1021 Global Administrator field set to the AS of the advertising ABR, and 1022 the Local Administrator field is set to 0. The route MUST carry the 1023 Inter-area P2MP Segmented Next-Hop Extended Community. This 1024 community is constructed following the procedures in section 4 1025 ("Inter-area P2MP Segmented Next-Hop Extended Community"). 1027 The egress ABR MUST advertise this route into the egress area. PEs in 1028 the egress area that participate in the global table multicast will 1029 import this route. 1031 A PE in the egress area that originated the Leaf A-D route SHOULD 1032 join the P2MP LSP advertised in the PMSI Tunnel attribute of the S- 1033 PMSI A-D route. 1035 7.2.2.2. Global Table Multicast and Wildcard S-PMSI A-D Routes 1037 It may be desirable for an ingress PE to carry multiple multicast 1038 flows associated with the global table multicast over the same inter- 1039 area P2MP service LSP. This can be achieved using wildcard, i.e., 1040 (*,*) S-PMSI A-D routes [RFC6625]. An ingress PE MAY advertise a 1041 wildcard S-PMSI A-D route as described in section 9 ("Ingress PE/ASBR 1042 Procedures"). 1044 If the ingress PE originates a wildcard S-PMSI A-D route, and the 1045 egress ABR receives this route from the ingress ABR, then the egress 1046 ABR either (a) MUST re-advertise this route into the egress area with 1047 the PMSI Tunnel Attribute containing the identifier of the intra-area 1048 P2MP LSP in the egress area and an upstream assigned label (note that 1049 this label may be an Implicit NULL - see section "General Assumptions 1050 and Terminology") assigned to the inter-area wildcard S-PMSI, or (b) 1051 MUST be able to disaggregate traffic carried over the wildcard S-PMSI 1052 onto the egress area (S, G) or (*, G) S-PMSIs. The procedures for 1053 such disaggregation require IP processing on the egress ABRs. 1055 If the egress ABR advertises a wildcard S-PMSI A-D route into the 1056 egress area, this route MUST carry AS-specific Route Target Extended 1057 Community with the Global Administrator field set to the AS of the 1058 advertising ABR, and the Local Administrator field set to 0. PEs in 1059 the egress area that participate in the global table multicast will 1060 import this route. 1062 A PE in the egress area SHOULD join the P2MP LSP advertised in the 1063 PMSI Tunnel attribute of the wildcard S-PMSI A-D route if (a) the 1064 Originating Router's IP Address field in the S-PMSI A-D route has the 1065 same value as the Ingress PE's IP address in at least one of the Leaf 1066 A-D routes for global table multicast originated by the PE, and (b) 1067 the upstream ABR for the Ingress PE's IP address in that Leaf A-D 1068 route is the (egress) ABR that advertises the wildcard S-PMSI A-D 1069 route. 1071 7.2.3. Global Table Multicast and the Expected Upstream Node 1073 If the mapping between the inter-area P2MP service LSP for global 1074 table multicast service and the intra-area P2MP LSP is many-to-one 1075 then an egress PE must be able to determine whether a given multicast 1076 packet for a particular (S, G) is received from the "expected" 1077 upstream node. The expected node is the node towards which the Leaf 1078 A-D route is sent by the egress PE. Packets received from another 1079 upstream node for that (S, G) MUST be dropped. To allow the egress PE 1080 to determine the sender upstream node, the intra-area P2MP LSP must 1081 be signaled with no PHP, when the mapping between the inter-area P2MP 1082 service LSP for global table multicast service and the intra-area 1083 P2MP LSP is many-to-one. 1085 Further the egress ABR MUST first push onto the label stack the 1086 upstream assigned label advertised in the S-PMSI A-D route, if the 1087 label is not the Implicit NULL. 1089 7.2.4. P2MP LDP LSP as the Intra-Area P2MP LSP 1091 The above procedures are sufficient if P2MP LDP LSPs are used as the 1092 Intra-area P2MP LSP in the Egress area. 1094 7.2.5. P2MP RSVP-TE LSP as the Intra-Area P2MP LSP 1096 If P2MP RSVP-TE LSP is used as the the intra-area LSP in the egress 1097 area, then the egress ABR can either (a) graft the leaf (whose IP 1098 address is specified in the received Leaf A-D route) into an existing 1099 P2MP LSP rooted at the egress ABR, and use that LSP for carrying 1100 traffic for the inter-area segmented P2MP service LSP, or (b) 1101 originate a new P2MP LSP to be used for carrying (S,G). 1103 When the RD of the received Leaf A-D route is all 0s or all 1s, then 1104 the procedures are as described in section "Received Leaf A-D route 1105 is for global table multicast". 1107 Note also that the SESSION object that the egress ABR would use for 1108 the intra-area P2MP LSP need not encode the P2MP FEC from the 1109 received Leaf A-D route. 1111 7.3. Ingress Replication in the Egress Area 1113 When Ingress Replication is used to instantiate the egress area 1114 segment then the Leaf A-D route advertised by the egress PE MUST 1115 carry a downstream assigned label in the P-Tunnel Attribute where the 1116 P-Tunnel type is set to Ingress Replication. We will call this label 1117 the egress PE downstream assigned label. 1119 The egress ABR MUST forward packets received from the backbone area 1120 intra-area segment, for a particular inter-area P2MP LSP, to all the 1121 egress PEs from which the egress ABR has imported a Leaf A-D route 1122 for the inter-area P2MP LSP. A packet to a particular egress PE is 1123 encapsulated, by the egress ABR, using a MPLS label stack the bottom 1124 label of which is the egress PE downstream assigned label. The top 1125 label is the P2P RSVP-TE or the MP2P LDP label to reach the egress 1126 PE. 1128 Note that these procedures ensures that an egress PE always receives 1129 packets only from the upstream node expected by the egress PE. 1131 8. Ingress ABR Procedures 1133 When an ingress ABR receives a Leaf A-D route and the Route Target 1134 Extended Community carried by the route contains the IP address of 1135 this ABR, then the ingress ABR follows the same procedures as in 1136 section 7 ("Egress ABR Procedures"), with egress ABR replaced by 1137 ingress ABR, backbone area replaced by ingress area, and backbone 1138 area segment replaced by ingress area segment. 1140 In order to support global table multicast the ingress ABR MUST be 1141 auto-configured with an import AS-based Route Target Extended 1142 Community whose Global Administrator field is set to the AS of the 1143 ABR and the Local Administrator field is set to 0. 1145 8.1. P2MP LSP as the Intra-Area LSP in the Backbone Area 1147 The procedures for binding the backbone area segment of an inter-area 1148 P2MP LSP to the intra-area P2MP LSP in the backbone area are the same 1149 as in section "Egress ABR Procedures" and sub-section "P2MP LSP as 1150 the Intra-Area LSP in the Egress Area", with egress PE being replace 1151 by egress ABR, egress ABR being replaced by ingress ABR, and egress 1152 area being replaced by backbone area. This applies to the inter-area 1153 P2MP LSPs associated with either MVPN, or VPLS, or global table 1154 multicast. 1156 It is to be noted that in the case of global table multicast, if the 1157 backbone area uses wildcard S-PMSI, then the egress area also SHOULD 1158 use wildcard S-PMSI for global table multicast, or the egress ABRs 1159 MUST be able to disaggregate traffic carried over the wildcard S-PMSI 1160 onto the egress area (S, G) or (*, G) S-PMSIs. The procedures for 1161 such disaggregation require IP processing on the egress ABRs. 1163 8.2. Ingress Replication in the Backbone Area 1165 When Ingress Replication is used to instantiate the backbone area 1166 segment then the Leaf A-D route advertised by the egress ABR MUST 1167 carry a downstream assigned label in the P-Tunnel Attribute where the 1168 P-Tunnel type is set to Ingress Replication. We will call this the 1169 egress ABR downstream assigned label. The egress ABR MUST assign a 1170 distinct MPLS label for each Leaf A-D route originated by the ABR. 1172 The ingress ABR MUST forward packets received from the ingress area 1173 intra-area segment, for a particular inter-area P2MP LSP, to all the 1174 egress ABRs from which the ingress ABR has imported a Leaf A-D route 1175 for the inter-area P2MP LSP. A packet to a particular egress ABR is 1176 encapsulated, by the ingress ABR, using a MPLS label stack the bottom 1177 label of which is the egress ABR downstream assigned label. The top 1178 label is the P2P RSVP-TE or the MP2P LDP label to reach the egress 1179 ABR. 1181 9. Ingress PE/ASBR Procedures 1183 This section describes Ingress PE/ASBR procedures for constructing 1184 segmented inter-area P2MP LSP. 1186 When an ingress PE/ASBR receives a Leaf A-D route and the Route 1187 Target Extended Community carried by the route contains the IP 1188 address of this PE/ASBR, then the following procedures will be 1189 executed. 1191 If the value of the third octet of the MCAST-VPN NLRI of the received 1192 Leaf A-D route is either 0x01, or 0x02, or 0x03, this indicates that 1193 the Leaf A-D route was originated in response to an S-PMSI or I-PMSI 1194 A-D route (see section "Leaf A-D Route for Global Table Multicast"). 1195 In this case the ingress PE/ASBR MUST find a S-PMSI or I-PMSI route 1196 whose NLRI has the same value as the Route Key field of the received 1197 Leaf A-D route. If such a matching route is found then the Leaf A-D 1198 route MUST be accepted else it MUST be discarded. If the Leaf A-D 1199 route is accepted then it MUST be processed as per MVPN or VPLS 1200 procedures. 1202 If the RD of the received A-D route is set to all 0s or all 1s, then 1203 the received Leaf A-D route is for the global table multicast 1204 service. If this is the first Leaf A-D route for the Route Key 1205 carried in the route, the PIM implementation MUST set its upstream 1206 (S/RP,G) state machine to Joined state for the (S/RP, G) received via 1207 a Leaf A-D route update. Likewise, if this is the withdrawal of the 1208 last Leaf A-D route whose Route Key matches a particular (S/RP, G) 1209 state, the PIM implementation MUST set its upstream (S/RP, G) state 1210 machine to Pruned state for the (S/RP, G). 1212 9.1. P2MP LSP as the Intra-Area LSP in the Ingress Area 1214 If the value of the third octet of the MCAST-VPN NLRI of the received 1215 Leaf A-D route is either 0x01, or 0x02, or 0x03 (which indicates that 1216 the Leaf A-D route was originated in response to an S-PMSI or I-PMSI 1217 A-D route), and P2MP LSP is used as the the intra-area LSP in the 1218 ingress area, then the procedures for binding the ingress area 1219 segment of the inter-area P2MP LSP to the intra-area P2MP LSP in the 1220 ingress area, are the same as in section "Egress ABR Procedures" and 1221 sub-section "P2MP LSP as the Intra-Area LSP in the Egress Area". 1223 When the RD of the received Leaf A-D route is all 0s or all 1s, as is 1224 the case where the inter-area service P2MP LSP is associated with the 1225 global table multicast service, then the ingress PE MAY originate a 1226 S-PMSI A-D route with the RD, multicast source, multicast group 1227 fields being the same as those in the received Leaf A-D route. 1229 Further in the case of global table multicast an ingress PE MAY 1230 originate a wildcard S-PMSI A-D route as per the procedures in 1231 [RFC6625] with the RD set to 0. This route may be originated by the 1232 ingress PE based on configuration or based on the import of a Leaf A- 1233 D route with RD set to 0. If an ingress PE originates such a route, 1234 then the ingress PE MAY decide not to originate (S, G) or (*, G) S- 1235 PMSI A-D routes. 1237 The wildcard S-PMSI A-D route MUST carry the Inter-area P2MP 1238 Segmented Next-Hop Extended Community. This community is constructed 1239 following the procedures in section 4 ("Inter-area P2MP Segmented 1240 Next-Hop Extended Community"). 1242 It is to be noted that in the case of global table multicast, if the 1243 ingress area uses wildcard S-PMSI, then the backbone area also SHOULD 1244 use wildcard S-PMSI for global table multicast, or the ingress ABRs 1245 MUST be able to disaggregate traffic carried over the wildcard S-PMSI 1246 onto the backbone area (S, G) or (*, G) S-PMSIs. The procedures for 1247 such disaggregation require IP processing on the ingress ABRs. 1249 9.2. Ingress Replication in the Ingress Area 1251 When Ingress Replication is used to instantiate the ingress area 1252 segment then the Leaf A-D route advertised by the ingress ABR MUST 1253 carry a downstream assigned label in the P-Tunnel Attribute where the 1254 P-Tunnel type is set to Ingress Replication. We will call this the 1255 ingress ABR downstream assigned label. The ingress ABR MUST assign a 1256 distinct MPLS label for each Leaf A-D route originated by the ABR. 1258 The ingress PE/ASBR MUST forward packets received from the CE, for a 1259 particular inter-area P2MP LSP, to all the ingress ABRs from which 1260 the ingress PE/ASBR has imported a Leaf A-D route for the inter-area 1261 P2MP LSP. A packet to a particular ingress ABR is encapsulated, by 1262 the ingress PE/ASBR, using a MPLS label stack the bottom label of 1263 which is the ingress ABR downstream assigned label. The top label is 1264 the P2P RSVP-TE or the MP2P LDP label to reach the ingress ABR. 1266 10. Common Tunnel Type in the Ingress and Egress Areas 1268 For a given inter-area service P2MP LSP, the PE/ASBR that is the root 1269 of that LSP controls the tunnel type of the intra-area P-tunnel that 1270 carries the ingress area segment of that LSP. However, the tunnel 1271 type of the intra-area P-tunnel that carries the backbone area 1272 segment of that LSP may be different from the tunnel type of the 1273 intra-area P-tunnels that carry the ingress area segment and the 1274 egress area segment of that LSP. In that situation if for a given 1275 inter-area P2MP LSP it is desirable/necessary to use the same tunnel 1276 type for the intra-area P-tunnels that carry the ingress area segment 1277 and the egress area segment of that LSP, then the following 1278 procedures on the ingress ABR and egress ABR provide this 1279 functionality. 1281 When an ingress ABR re-advertises into the backbone area a BGP MVPN 1282 I-PMSI, or S-PMSI A-D route, or VPLS A-D route, the ingress ABR 1283 places the PMSI Tunnel attribute of this route into the ATTR_SET BGP 1284 Attribute [RFC6368], adds this attribute to the re-advertised route, 1285 and then replaces the original PMSI Tunnel attribute with a new one 1286 (note, that the Tunnel type of the new attribute may be different 1287 from the Tunnel type of the original attribute). 1289 When an egress ABR re-advertises into the egress area a BGP MVPN I- 1290 PMSI or S-PMSI A-D route, or VPLS A-D route, if the route carries the 1291 ATTR_SET BGP attribute [RFC6368], then the ABR sets the Tunnel type 1292 of the PMSI Tunnel attribute in the re-advertised route to the Tunnel 1293 type of the PMSI Tunnel attribute carried in the ATTR_SET BGP 1294 attribute, and removes the ATTR_SET from the route. 1296 11. Placement of Ingress and Egress PEs 1298 As described in the earlier sections, procedures in this document 1299 allow the placement of ingress and egress PEs in the backbone area. 1300 They also allow the placement of egress PEs in the ingress area or 1301 the placement of ingress PEs in the egress area. 1303 For instance, ABRs in the backbone area may act as ingress and egress 1304 PEs for global table multicast, as per the ingress and egress PE 1305 definition in this document. This may be the case if the service is 1306 global table multicast and relies on global table multicast in the 1307 ingress and egress areas and its desirable to carry global table 1308 multicast over MPLS in the backbone area. This may also be the case 1309 if the service is MVPN and the P-tunnel technology in the ingress and 1310 egress areas uses PIM based IP/GRE P-tunnels. As far as the ABRs are 1311 concerned PIM signaling for such P-Tunnels is handled as per the 1312 ingress/egress PE global table multicast procedures specified in this 1313 document. To facilitate this the ABRs may advertise their loopback 1314 addresses in BGP using multicast-SAFI i.e., SAFI 2, if non-congruence 1315 between unicast and multicast is desired. 1317 12. MVPN with Virtual Hub-and-Spoke 1319 Procedures described in this document could be used in conjunction 1320 with the Virtual Hub-and-Spoke procedures [virtual-hub-and-spoke]. 1322 This document does not place any restrictions on the placement of 1323 Virtual Hubs and Virtual Spokes. 1325 In addition to I-PMSI/S-PMSI A-D routes, the procedures described in 1326 this document are applicable to Associated-V-spoke-only I-PMSI A-D 1327 routes. 1329 In the scenario where a V-hub, as a result of importing an S-PMSI A-D 1330 route in its VRF, originates an S-PMSI A-D route targeted to its V- 1331 spokes (as specified in section "Case 2" of [virtual-hub-and-spoke]), 1332 the V-hub SHOULD be able to control via configuration whether the 1333 Inter-area P2MP Segmented Next-Hop Extended Community, if present in 1334 the received S-PMSI A-D route, be also carried in the originated S- 1335 PMSI A-D route. By default if the received S-PMSI A-D route carries 1336 the Inter-area P2MP Segmented Next-Hop Extended Community, then the 1337 originated S-PMSI A-D route SHOULD also carry this community. 1339 13. Data Plane 1341 This section describes the data plane procedures on the ABRs, ingress 1342 PEs, egress PEs and transit routers. 1344 13.1. Data Plane Procedures on ABRs 1346 When procedures in this document are followed to signal inter-area 1347 P2MP Segmented LSPs, then ABRs are required to perform only MPLS 1348 switching. When an ABR receives a MPLS packet from an "incoming" 1349 intra-area segment of the inter-area P2MP Segmented LSP, it forwards 1350 the packet, based on MPLS switching, onto another "outgoing" intra- 1351 area segment of the inter-area P2MP Segmented LSP. 1353 If the outgoing intra-area segment is instantiated using a P2MP LSP, 1354 and if there is a one-to-one mapping between the outgoing intra-area 1355 segment and the P2MP LSP, then the ABR MUST pop the incoming 1356 segment's label stack and push the label stack of the outgoing P2MP 1357 LSP. If there is a many-to-one mapping between outgoing intra-area 1358 segments and the P2MP LSP then the ABR MUST pop the incoming 1359 segment's label stack and first push the upstream assigned label 1360 corresponding to the outgoing intra-area segment, if such a label has 1361 been assigned, and then push the label stack of the outgoing P2MP 1362 LSP. 1364 If the outgoing intra-area segment is instantiated using ingress 1365 replication then the ABR must pop the incoming segment's label stack 1366 and replicate the packet once to each leaf ABR or PE of the outgoing 1367 intra-area segment. The label stack of the packet sent to each such 1368 leaf MUST first include a downstream assigned label assigned by the 1369 leaf to the segment, followed by the label stack of the P2P or MP2P 1370 LSP to the leaf. 1372 13.2. Data Plane Procedures on Egress PEs 1374 An egress PE must first identify the inter-area P2MP segmented LSP 1375 based on the incoming label stack. After this identification the 1376 egress PE must forward the packet using the application that is bound 1377 to the inter-area P2MP segmented LSP. 1379 Note that the application specific forwarding for MVPN service may 1380 require the egress PE to determine whether the packets were received 1381 from the expected sender PE. When the application is MVPN then the 1382 FEC of an inter-area P2MP Segmented LSP is at the granularity of the 1383 sender PE. Note that MVPN intra-AS I-PMSI A-D routes and S-PMSI A-D 1384 routes both carry the Originating Router IP Address. Thus an egress 1385 PE could associate the data arriving on P-tunnels advertised by these 1386 routes with the Originating Router IP Address carried by these routes 1387 which is the same as the ingress PE. Since a unique label stack is 1388 associated with each such FEC, the egress PE can determine the sender 1389 PE from the label stack. 1391 Likewise for VPLS service for the purposes of MAC learning the egress 1392 PE must be able to determine the "VE-ID" from which the packets have 1393 been received. The FEC of the VPLS A-D routes carries the VE-ID. Thus 1394 an egress PE could associate the data arriving on P-tunnels 1395 advertised by these routes with the VE-ID carried by these routes. 1396 Since a unique label stack is associated with each such FEC, the 1397 egress PE can perform MAC learning for packets received from a given 1398 VE-ID. 1400 When the application is global table multicast it is sufficient for 1401 the label stack to include identification of the sender upstream 1402 node. When P2MP LSPs are used this requires that PHP MUST be turned 1403 off. When Ingress Replication is used the egress PE knows the 1404 incoming downstream assigned label to which it has bound a particular 1405 (S/*, G) and must accept packets with only that label for that (S/*, 1406 G). 1408 13.3. Data Plane Procedures on Ingress PEs 1410 An Ingress PE must perform application specific forwarding procedures 1411 to identify the outgoing inta-area segment of an incoming packet. 1413 If the outgoing intra-area segment is instantiated using a P2MP LSP, 1414 and if there is a one-to-one mapping between the outgoing intra-area 1415 segment and the P2MP LSP, then the ingress PE MUST encapsulate the 1416 packet in the label stack of the outgoing P2MP LSP. If there is a 1417 many-to-one mapping between outgoing intra-area segments and the P2MP 1418 LSP then the PE MUST first push the upstream assigned label 1419 corresponding to the outgoing intra-area segment, if such a label has 1420 been assigned, and then push the label stack of the outgoing P2MP 1421 LSP. 1423 If the outgoing intra-area segment is instantiated using ingress 1424 replication then the PE must replicate the packet once to each leaf 1425 ABR or PE of the outgoing intra-area segment. The label stack of the 1426 packet sent to each such leaf MUST first include a downstream 1427 assigned label assigned by the leaf to the segment, followed by the 1428 label stack of the P2P or MP2P LSP to the leaf. 1430 13.4. Data Plane Procedures on Transit Routers 1432 When procedures in this document are followed to signal inter-area 1433 P2MP Segmented LSPs then transit routers in each area perform only 1434 MPLS switching. 1436 14. Support for Inter-Area Transport LSPs 1438 This section describes OPTIONAL procedures that allow to aggregate 1439 multiple (inter-area) P2MP service LSPs into a single inter-area P2MP 1440 transport LSP, and then apply the segmentation procedures, as 1441 specified in this document, to these inter-area P2MP transport LSPs 1442 (rather than applying these procedures directly to the inter-area 1443 P2MP service LSPs). 1445 14.1. Transport Tunnel Tunnel Type 1447 For the PMSI Tunnel Attribute we define a new Tunnel type, called 1448 "Transport Tunnel", whose Tunnel Identifier is a tuple . This Tunnel type is assigned a value of 8. 1450 The Source PE Address is the address of the PE that originates the 1451 (service) A-D route that carries this attribute, and the Local Number 1452 is a number that is unique to the Source PE. The length of the Local 1453 Number part is the same as the length of the Source PE Address. Thus 1454 if the Source PE Address is an IPv4 address, then the Local Number 1455 part is 4 octets, and if the Source PE Address is an IPv6 address, 1456 then the Local Number part is 16 octets. 1458 14.2. Discovering Leaves of the Inter-Area P2MP Service LSP 1460 When aggregating multiple P2MP LSPs using P2MP LSP hierarchy, 1461 determining the leaf nodes of the LSPs being aggregated is essential 1462 for being able to tradeoff the overhead due to the P2MP LSPs vs 1463 suboptimal use of bandwidth due to the partial congruency of the LSPs 1464 being aggregated. 1466 Therefore, if a PE that is a root of a given service P2MP LSP wants 1467 to aggregate this LSP with other (service) P2MP LSPs rooted at the 1468 same PE into an inter-area P2MP transport LSP, the PE should first 1469 determine all the leaf nodes of that service LSP, as well as those of 1470 the other service LSPs being aggregated). 1472 To accomplish this the PE sets the PMSI Tunnel attribute of the 1473 service A-D route (an I-PMSI or S-PMSI A-D route for MVPN or VPLS 1474 service) associated with that LSP as follows. The Tunnel Type is set 1475 to "No tunnel information present", Leaf Information Required flag is 1476 set to 1, the route MUST NOT carry the P2MP Segmented Next-Hop 1477 Extended Community. In contrast to the procedures for the MVPN and 1478 VPLS A-D routes described so far, the Route Reflectors that 1479 participate in the distribution of this route need not be ABRs. 1481 14.3. Discovering P2MP FEC of P2MP Transport LSP 1483 Once the ingress PE determines all the leaves of a given P2MP service 1484 LSP, the PE (using some local to the PE criteria) selects a 1485 particular inter-area transport P2MP LSP to be used for carrying the 1486 (inter-area) service P2MP LSP. 1488 Once the PE selects the transport P2MP LSP, the PE (re)originates the 1489 service A-D route. The PMSI Tunnel attribute of this route now 1490 carries the Tunnel Identifier of the selected transport LSP, with the 1491 Tunnel Type set to "Transport Tunnel". If the transport LSP carries 1492 multiple P2MP service LSPs, then the MPLS Label field in the 1493 attribute carries an upstream-assigned label assigned by the PE that 1494 is bound to the P2MP FEC of the inter-area P2MP service LSP. 1495 Otherwise, this field is set to Implicit NULL. 1497 Just as described earlier, this service A-D route MUST NOT carry the 1498 P2MP Segmented Next-Hop Extended Community. Just as described 1499 earlier, the Route Reflectors that participate in the distribution of 1500 this route need not be ABRs. 1502 14.4. Egress PE Procedures for P2MP Transport LSP 1504 When an egress PE receives and accepts an MVPN or VPLS service A-D 1505 route, if the Leaf Information Required flag in the PMSI Tunnel 1506 attribute of the received A-D route is set to 1, and the route does 1507 not carry the P2MP Segmented Next-Hop Extended Community, then the 1508 egress PE, following the "regular" MVPN or VPLS procedures associated 1509 with the received A-D route (as specified in [RFC6514] and [VPLS- 1510 P2MP]), originates a Leaf A-D route. 1512 In addition, if the Tunnel Type in the PMSI Tunnel attribute of the 1513 received service A-D route is set to "Transport Tunnel", the egress 1514 PE originates yet another Leaf A-D route. 1516 The format of the Route Key field of MCAST-VPN NLRI of this 1517 additional Leaf A-D route is the same as defined in section 6.2.2 1518 ("Leaf A-D Route for Global Table Multicast"). The Route Key field of 1519 MCAST-VPN NLRI of this route is constructed as follows: 1521 RD (8 octets) - set to 0 1523 Multicast Source Length, Multicast Source - constructed from 1524 the Source PE address part of the Tunnel Identifier carried 1525 in the PMSI Tunnel attribute of the received service S-PMSI 1526 A-D route. 1528 Multicast Group Length, Multicast Group - constructed from 1529 Local Number part of the Tunnel Identifier carried in the 1530 PMSI Tunnel attribute of the received service S-PMSI A-D 1531 route. 1533 Ingress PE IP Address is set to the Source PE address part 1534 of the Tunnel Identifier carried in the PMSI Tunnel attribute 1535 of the received service S-PMSI A-D route. 1537 The egress PE, when determining the upstream ABR, follows the 1538 procedures specified in section 6.1 ("Determining the Upstream 1539 ABR/PE/ASBR (Upstream Node)") for global table multicast. 1541 The egress PE constructs the rest of the Leaf A-D route following the 1542 procedures specified in section 6.2.3 ("Constructing the Rest of the 1543 Leaf A-D Route"). 1545 From that point on we follow the procedures used for the Leaf A-D 1546 routes for global table multicast, as outlined below. 1548 14.5. Egress/Ingress ABR, Ingress PE procedures for P2MP Transport LSP 1550 When an egress ABR receives the Leaf A-D route, and P2MP LSP is used 1551 to instantiate the egress area segment of the inter-area transport 1552 LSP, the egress ABR will advertise into the egress area an S-PMSI A-D 1553 route. This route is constructed following the procedures in section 1554 "Global Table Multicast and S-PMSI A-D Routes". The egress PE(s) will 1555 import this route. 1557 The egress ABR will also propagate, with appropriate modifications, 1558 the received Leaf A-D route into the backbone area. This is 1559 irrespective of whether the egress area segment is instantiated using 1560 P2MP LSP or ingress replication. 1562 If P2MP LSP is used to instantiate the backbone area segment of the 1563 inter-area transport LSP, then an ingress ABR will advertise into the 1564 backbone area an S-PMSI A-D route. This route is constructed 1565 following the procedures in section 7.1.2.1 ("Global Table Multicast 1566 and S-PMSI A-D Routes"). The egress ABR(s) will import this route. 1568 The ingress ABR will also propagate, with appropriate modifications, 1569 the received Leaf A-D route into the ingress area towards the 1570 ingress/root PE. This is irrespective of whether the backbone area 1571 segment is instantiated using P2MP LSP or ingress replication. 1573 Finally, if P2MP LSP is used to instantiate the ingress area segment, 1574 the ingress PE will advertise into the ingress area an S-PMSI A-D 1575 route with the RD, multicast source, and multicast group fields being 1576 the same as those in the received Leaf A-D route. The PMSI Tunnel 1577 attribute of this route contains the identity of the intra-area P2MP 1578 LSP used to instantiate the ingress area segment, and an upstream- 1579 assigned MPLS label. The ingress ABR(s) and other PE(s) in the 1580 ingress area, if any, will import this route. The ingress PE will use 1581 the (intra-area) P2MP LSP advertised in this route for carrying 1582 traffic associated with the original service A-D route advertised by 1583 the PE. 1585 14.6. Discussion 1587 Use of inter-area transport P2MP LSPs, as described in this section, 1588 creates a level of indirection between (inter-area) P2MP service 1589 LSPs, and intra-area transport LSPs that carry the service LSPs. 1590 Rather than segmenting (inter-area) service P2MP LSPs, and then 1591 aggregating (intra-area) segments of these service LSPs into intra- 1592 area transport LSPs, this approach first aggregates multiple (inter- 1593 area) service P2MP LSPs into a single inter-area transport P2MP LSP, 1594 then segments such inter-area transport P2MP LSPs, and then 1595 aggregates (intra-area) segments of these inter-area transport LSPs 1596 into intra-area transport LSPs. 1598 On one hand this approach could result in reducing the state (and the 1599 overhead associated with maintaining the state) on ABRs. This is 1600 because instead of requiring ABRs to maintain state for individual 1601 P2MP service LSPs, ABRs would need to maintain state only for the 1602 inter-area P2MP transport LSPs. Note however, that this reduction is 1603 possible only if a single inter-area P2MP transport LSP aggregates 1604 more than one (inter-area) service LSP. In the absence of such 1605 aggregation, use of inter-area transport LSPs provides no benefits, 1606 yet results in extra overhead. And while such aggregation does allow 1607 to reduce state on ABRs, it comes at a price, as described below. 1609 As we mentioned before, aggregating multiple P2MP service LSPs into a 1610 single inter-area P2MP transport LSP requires the PE rooted at these 1611 LSPs to determine all the leaf nodes of the service LSPs to be 1612 aggregated. This means that the root PE has to track all the leaf PEs 1613 of these LSPs. In contrast, when one applies segmentation procedures 1614 directly to the P2MP service LSPs, the root PE has to track only the 1615 leaf PEs in its own IGP area, plus the ingress ABR(s). Likewise, an 1616 ingress ABR has to track only the egress ABRs. Finally, an egress ABR 1617 has to track only the leaf PEs in its own area. Therefore, while the 1618 total overhead of leaf tracking due to the P2MP service LSPs is about 1619 the same in both approaches, the distribution of this overhead is 1620 different. Specifically, when one uses inter-area P2MP transport 1621 LSPs, this overhead is concentrated on the ingress PE. When one 1622 applies segmentation procedures directly to the P2MP service LSPs, 1623 this overhead is distributed among ingress PE and ABRs. 1625 Moreover, when one uses inter-area P2MP transport LSPs, ABRs have to 1626 bear the overhead of leaf tracking for inter-area P2MP transport 1627 LSPs. In contrast, when one applies segmentation procedures directly 1628 to the P2MP service LSPs, there is no such overhead (as there are no 1629 inter-area P2MP transport LSPs). 1631 Use of inter-area P2MP transport LSPs may also result in more 1632 bandwidth inefficiency, as compared to applying segmentation 1633 procedures directly to the P2MP service LSPs. This is because with 1634 inter-area P2MP transport LSPs the ABRs aggregate segments of inter- 1635 area P2MP transport LSPs, rather than segments of (inter-area) P2MP 1636 service LSPs. To illustrate this consider the following example. 1638 Assume PE1 in Area 1 is an ingress PE, with two multicast streams, 1639 (C-S1, C-G1) and (C-S2, C-G2), originated by an MVPN site connected 1640 to PE1. Assume that PE2 in Area 2 has an MVPN site with receivers for 1641 (C-S1, C-G1), PE3 and PE4 in Area 3 have an MVPN site with receivers 1642 both for (C-S1, C-G1) and for (C-S2, C-G2). Finally, assume that PE5 1643 in Area 4 has an MVPN site with receivers for (C-S2, C-G2). 1645 When segmentation applies directly to the P2MP service LSPs then Area 1646 2 would have just one intra-area transport LSP which would carry the 1647 egress area segment of the P2MP service LSP for (C-S1, C-G1); Area 3 1648 would have just one intra-area transport LSP which would carry the 1649 egress area segments of both the P2MP service LSP for (C-S1, C-G1) 1650 and the P2MP service LSP for (C-S2, C-G2); Area 4 would have just one 1651 intra-area transport LSP which would carry the egress area segment of 1652 the P2MP service LSP for (C-S2, C-G2). Note that there is no 1653 bandwidth inefficiency in this case at all. 1655 When using inter-area P2MP transport LSPs, to achieve the same state 1656 overhead on the routers within each of the egress areas (except for 1657 egress ABRs), PE1 would need to aggregate the P2MP service LSP for 1658 (C-S1, C-G1) and the P2MP service LSP for (C-S2, C-G2) into the same 1659 inter-area P2MP transport LSP. While such aggregation would reduce 1660 state on ABRs, it would also result in bandwidth inefficiency, as (C- 1661 S1, C-G1) will be delivered not just to PE2, PE3, and PE4, but also 1662 to PE5, which has no receivers for this stream. Likewise, (C-S2, C- 1663 G2) will be delivered not just to PE3, PE4, and PE5, but also to PE2, 1664 which has no receivers for this stream. 1666 15. IANA Considerations 1668 This document defines a new BGP Extended Community called "Inter-area 1669 P2MP Segmented Next-Hop" (see section "Inter-area P2MP Segmented 1670 Next-Hop Extended Community"). This community is IP Address Specific, 1671 of an extended type, and is transitive. A codepoint for this 1672 community should be assigned both from the IPv4 Address Specific 1673 Extended Community registry, and from the IPv6 Address Specific 1674 Extended Community registry. The same code point should be assigned 1675 from both registries. 1677 This document also assigns a new Tunnel Type in the PMSI Tunnel 1678 Attribute, called the "Transport Tunnel" (see section "Transport 1679 Tunnel Type"). This Tunnel Type is assigned a value of 8. 1681 16. Security Considerations 1683 These will be spelled out in a future revision. 1685 17. Acknowledgements 1687 We would like to thank Eric Rosen for his comments. 1689 18. References 1691 18.1. Normative References 1693 [RFC1997] "BGP Communities Attribute", Ravi Chandra, et al., RFC1997, 1694 August 1996 1696 [RFC2119] "Key words for use in RFCs to Indicate Requirement 1697 Levels.", Bradner, March 1997 1699 [RFC4360] S. Sangle et. al., "BGP Extended Communities Attribute", 1700 RFC4360, February 2006 1702 [RFC4684] P. Marques et. al., "Constrained Route Distribution for 1703 Border Gateway Protocol/MultiProtocol Label Switching (BGP/MPLS) 1704 Internet Protocol (IP) Virtual Private Networks (VPNs)", RFC 4684, 1705 November 2006 1707 [RFC4760] Bates, T., Rekhter, Y., Chandra, R., and D. Katz, 1708 "Multiprotocol Extensions for BGP-4", RFC 4760, January 2007. 1710 [RFC4761] Kompella, K., Rekhter, Y., "Virtual Private LAN Service 1711 (VPLS) Using BGP for Auto-Discovery and Signaling", RFC 4761, January 1712 2007 1714 [RFC6368] "Internal BGP as PE-CE protocol", Pedro Marques, et al., 1715 RFC6368, September 2011 1717 [RFC5331] "MPLS Upstream Label Assignment and Context-Specific Label 1718 Space", Rahul Aggarwal, et al., RFC5331, August 2008 1720 [RFC5332] "MPLS Multicast Encapsulations", T. Eckert, E. Rosen, R. 1721 Aggarwal, Y. Rekhter, RFC5332, August 2008 1723 [RFC6514] "BGP Encodings and Procedures for Multicast in MPLS/BGP IP 1724 VPNs", R. Aggarwal, E. Rosen, T. Morin, Y. Rekhter, RFC6514, February 1725 2012 1727 [RFC6074] "Provisioning, Auto-Discovery, and Signaling in Layer 2 1728 Virtual Private Networks (L2VPNs)", E. Rosen, B. Davie, V. Radoaca, 1729 W. Luo, RFC6074, January 2011 1731 [RFC6625] "Wildcards in Multicast VPN Auto-Discovery Routes", Eric 1732 Rosen, et al., RFC6625, May 2012 1734 [VPLS-P2MP] "Multicast in VPLS", R. Aggarwal, Y. Kamite, L. Fang, 1735 draft-ietf-l2vpn-vpls-mcast, work in progress 1737 18.2. Informative References 1739 [SEAMLESS-MPLS] "Seamless MPLS Architecture", N. Leymann et. al., 1740 draft-ietf-mpls-seamless-mpls, work in progress 1742 [virtual-hub-and-spoke] "Virtual Hub-and-Spoke in BGP/MPLS VPNs", 1743 Huajin Jeng et. al., draft-ietf-l3vpn-virtual-hub, work in progress 1745 19. Author's Address 1747 Yakov Rekhter 1748 Juniper Networks 1749 1194 North Mathilda Ave. 1750 Sunnyvale, CA 94089 1751 Email: yakov@juniper.net 1753 Rahul Aggarwal 1754 Email: raggarwa_1@yahoo.com 1756 Thomas Morin 1757 France Telecom R & D 1758 2, avenue Pierre-Marzin 1759 22307 Lannion Cedex 1760 France 1761 Email: thomas.morin@orange-ftgroup.com 1763 Irene Grosclaude 1764 France Telecom R & D 1765 2, avenue Pierre-Marzin 1766 22307 Lannion Cedex 1767 France 1768 Email: irene.grosclaude@orange-ftgroup.com 1770 Nicolai Leymann 1771 Deutsche Telekom AG 1772 Winterfeldtstrasse 21 1773 Berlin 10781 1774 DE 1775 Email: n.leymann@telekom.de 1777 Samir Saad 1778 AT&T 1779 Email: ss2539@att.com