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Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year == Using lowercase 'not' together with uppercase 'MUST', 'SHALL', 'SHOULD', or 'RECOMMENDED' is not an accepted usage according to RFC 2119. Please use uppercase 'NOT' together with RFC 2119 keywords (if that is what you mean). Found 'SHOULD not' in this paragraph: [RFC4875], the status of the corresponding P-Tunnel SHOULD be re-evaluated. If the P-Tunnel transitions from up to down state, the upstream PE, that is the ingress of the P-Tunnel, SHOULD not be considered a valid UMH. -- The document seems to lack a disclaimer for pre-RFC5378 work, but may have content which was first submitted before 10 November 2008. If you have contacted all the original authors and they are all willing to grant the BCP78 rights to the IETF Trust, then this is fine, and you can ignore this comment. If not, you may need to add the pre-RFC5378 disclaimer. (See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (March 8, 2010) is 5155 days in the past. Is this intentional? Checking references for intended status: Experimental ---------------------------------------------------------------------------- == Outdated reference: A later version (-02) exists of draft-karan-mofrr-00 Summary: 1 error (**), 0 flaws (~~), 3 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group T. Morin 3 Internet-Draft France Telecom - Orange Labs 4 Intended status: Experimental Y. Rekhter 5 Expires: September 9, 2010 R. Aggarwal 6 Juniper Networks 7 W. Henderickx 8 P. Muley 9 Alcatel-Lucent 10 R. Qiu 11 Huawei 12 March 8, 2010 14 Multicast VPN fast upstream failover 15 draft-morin-l3vpn-mvpn-fast-failover-04 17 Abstract 19 This document defines multicast VPN extensions and procedures that 20 allow fast failover for upstream failures, by allowing downstream PEs 21 to take into account the status of Provider-Tunnels (P-tunnels) when 22 selecting the upstream PE for a VPN multicast flow, and extending BGP 23 MVPN routing so that a C-multicast route can be advertised toward a 24 standby upstream PE. 26 Requirements Language 28 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 29 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 30 document are to be interpreted as described in RFC 2119 [RFC2119]. 32 Status of this Memo 34 This Internet-Draft is submitted to IETF in full conformance with the 35 provisions of BCP 78 and BCP 79. 37 Internet-Drafts are working documents of the Internet Engineering 38 Task Force (IETF), its areas, and its working groups. Note that 39 other groups may also distribute working documents as Internet- 40 Drafts. 42 Internet-Drafts are draft documents valid for a maximum of six months 43 and may be updated, replaced, or obsoleted by other documents at any 44 time. It is inappropriate to use Internet-Drafts as reference 45 material or to cite them other than as "work in progress." 47 The list of current Internet-Drafts can be accessed at 48 http://www.ietf.org/ietf/1id-abstracts.txt. 50 The list of Internet-Draft Shadow Directories can be accessed at 51 http://www.ietf.org/shadow.html. 53 This Internet-Draft will expire on September 9, 2010. 55 Copyright Notice 57 Copyright (c) 2010 IETF Trust and the persons identified as the 58 document authors. All rights reserved. 60 This document is subject to BCP 78 and the IETF Trust's Legal 61 Provisions Relating to IETF Documents 62 (http://trustee.ietf.org/license-info) in effect on the date of 63 publication of this document. Please review these documents 64 carefully, as they describe your rights and restrictions with respect 65 to this document. Code Components extracted from this document must 66 include Simplified BSD License text as described in Section 4.e of 67 the Trust Legal Provisions and are provided without warranty as 68 described in the BSD License. 70 Table of Contents 72 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 73 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 74 3. UMH Selection based on tunnel status . . . . . . . . . . . . . 4 75 3.1. Determining the status of a tunnel . . . . . . . . . . . . 5 76 3.1.1. mVPN tunnel root tracking . . . . . . . . . . . . . . 6 77 3.1.2. PE-P Upstream link status . . . . . . . . . . . . . . 6 78 3.1.3. P2MP RSVP-TE tunnels . . . . . . . . . . . . . . . . . 6 79 3.1.4. Leaf-initiated P-tunnels . . . . . . . . . . . . . . . 7 80 3.1.5. P2MP LSP OAM . . . . . . . . . . . . . . . . . . . . . 7 81 3.1.6. (S,G) counter information . . . . . . . . . . . . . . 7 82 4. Standby C-multicast route . . . . . . . . . . . . . . . . . . 8 83 4.1. Downstream PE behavior . . . . . . . . . . . . . . . . . . 8 84 4.2. Upstream PE behavior . . . . . . . . . . . . . . . . . . . 9 85 4.3. Reachability determination . . . . . . . . . . . . . . . . 10 86 4.4. Inter-AS . . . . . . . . . . . . . . . . . . . . . . . . . 11 87 4.4.1. Inter-AS procedures for downstream PEs, ASBR fast 88 failover . . . . . . . . . . . . . . . . . . . . . . . 11 89 4.4.2. Inter-AS procedures for ASBRs . . . . . . . . . . . . 11 90 5. Hot leaf standby . . . . . . . . . . . . . . . . . . . . . . . 12 91 6. Duplicate packets . . . . . . . . . . . . . . . . . . . . . . 13 92 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 93 8. Security Considerations . . . . . . . . . . . . . . . . . . . 13 94 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13 95 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 96 10.1. Normative References . . . . . . . . . . . . . . . . . . . 13 97 10.2. Informative References . . . . . . . . . . . . . . . . . . 14 98 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14 100 1. Introduction 102 In the context of multicast in BGP/MPLS VPNs, it is desirable to 103 provide mechanisms allowing fast recovery of connectivity on 104 different types of failures. This document addresses failures of 105 elements in the provider network that are upstream of PEs connected 106 to VPN sites with receivers. 108 The sections 3 and 4 describe two independent mechanisms, allowing 109 different levels of resiliency, and providing different failure 110 coverage: 112 o Section 3 describes local procedures allowing an egress PE (a PE 113 connected to a receiver site) to take into account the status of 114 P-Tunnels to determine the Upstream Multicast Hop (UMH) for a 115 given (C-S, C-G). 117 o Section 4 describes protocol extensions that can speed up failover 118 by not requiring any multicast VPN routing message exchange at 119 recovery time. 121 Moreover, section 5 describes a "hot leaf standby" mechanism, that 122 uses a combination of these two mechanisms. This approach has 123 similarities with the solution described in [I-D.karan-mofrr] to 124 improve failover times when PIM routing is used in a network given 125 some topology and metric constraints. 127 2. Terminology 129 The terminology used in this document is the terminology defined in 130 [I-D.ietf-l3vpn-2547bis-mcast] and 131 [I-D.ietf-l3vpn-2547bis-mcast-bgp]. 133 3. UMH Selection based on tunnel status 135 Current multicast VPN specifications [I-D.ietf-l3vpn-2547bis-mcast], 136 section 5.1, describe the procedures used by a multicast VPN 137 downstream PE to determine what the upstream multicast hop (UMH) is 138 for a said (C-S,C-G). 140 The procedure described here is an OPTIONAL procedure that consist in 141 having a downstream PE take into account the status of P-tunnels 142 rooted at each possible upstream PEs, for including or not including 143 each said PE in the list of candidate UMHs for a said (C-S,C-G) 144 state. The result is that, if a P-tunnel is "down" (see 145 Section 3.1), the PE that is the root of the P-Tunnel will not be 146 considered for UMH selection, which will result in the downstream PE 147 to failover to the upstream PE which is next in the list of 148 candidates. 150 More precisely, UMH determination for a said (C-S,C-G) will consider 151 the UMH candidates in the following order: 153 o first, the UMH candidates that either (a) advertise a PMSI bound 154 to a tunnel that is "up", or (b) do not advertise any I- or S- 155 PMSI applicable to the said (C-S,C-G) but have associated a VRF 156 Route Import BGP attribute to the unicast VPN route for S (this is 157 necessary to avoid considering invalid some UMH PEs that use a a 158 policy where no I-PMSI is advertized for a said VRF and where only 159 S-PMSI are used, the S-PMSI advertisement being possibly done only 160 after the upstream PE receives a C-multicast route for (C-S, 161 C-G)/(C-*, C-G) to be carried over the advertised S-PMSI) 163 o second, the UMH candidates that advertise a PMSI bound to a tunnel 164 that is "down" -- these will thus be used as a last resort to 165 ensure a graceful fallback to the basic MVPN UMH selection 166 procedures in the hypothetical case where a false negative would 167 occur when determining the status of all tunnels 169 For a said downstream PE and a said VRF, the P-tunnel corresponding 170 to a said upstream PE for a said (C-S,C-G) state is the S-PMSI tunnel 171 advertized by that upstream PE for this (C-S,C-G) and imported into 172 that VRF, or if there isn't any such S-PMSI, the I-PMSI tunnel 173 advertized by that PE and imported into that VRF. 175 Note that this documents assumes that if a site of a given MVPN that 176 contains C-S is dual-homed to two PEs, then all the other sites of 177 that MVPN would have two unicast VPN routes (VPN-IPv4 or VPN-IPv6) 178 routes to C-S, each with its own RD. 180 3.1. Determining the status of a tunnel 182 Different factors can be considered to determine the "status" of a 183 P-tunnel and are described in the following sub-sections. The 184 procedure proposed here also allows that all downstream PEs don't 185 apply the same rules to define what the status of a P-tunnel is 186 (please see Section 6), and some of them will produce a result that 187 may be different for different downstream PEs. Thus what is called 188 the "status" of a P-tunnel in this section, is not a characteristic 189 of the tunnel in itself, but is the status of the tunnel, *as seen 190 from a particular downstream PE*. 192 Depending on the criteria used to determine the status of a P-tunnel, 193 there may be an interaction with other resiliency mechanism used for 194 the P-tunnel itself, and the UMH update may happen immediately or may 195 need to be delayed. Each particular case is covered in each separate 196 sub-section below. 198 3.1.1. mVPN tunnel root tracking 200 A condition to consider that the status of a P-tunnel is up is that 201 the root of the tunnel, as determined in the PMSI tunnel attribute, 202 is reachable through unicast routing tables. In this case the 203 downstream PE can immediately update its UMH when the reachability 204 condition changes. 206 This is similar to BGP next-hop tracking for VPN routes, except that 207 the address considered is not the BGP next-hop address, but the root 208 address in the PMSI tunnel attribute. 210 If BGP next-hop tracking is done for VPN routes, and the root address 211 of a said tunnel happens to be the same as the next-hop address in 212 the BGP autodiscovery route advertising the tunnel, then this 213 mechanisms may be omitted for this tunnel, as it will not bring any 214 specific benefit. 216 3.1.2. PE-P Upstream link status 218 A condition to consider a tunnel status as up can be that the last- 219 hop link of the P-tunnel is up. 221 In that case, if the PE can determine that there is no fast 222 restoration mechanism (such as MPLS FRR [RFC4090]) in place for the 223 P-tunnel, it can update the UMH immediately. Else, it should wait 224 before updating the UMH, to let the P-tunnel restoration mechanims 225 happen. A configurable timer MUST be provided for this purpose, and 226 it is recommended to provide a reasonable default value for this 227 timer. 229 3.1.3. P2MP RSVP-TE tunnels 231 For P-Tunnels of type P2MP MPLS-TE, the status of the P-Tunnel is 232 considered up if one or more of the P2MP RSVP-TE LSPs, identified by 233 the P-Tunnel Attribute, are in up state. The determination of 234 whether a P2MP RSVP-TE LSP is in up state requires Path and Resv 235 state for the LSP and is based on procedures in [RFC4875]. In this 236 case the downstream PE can immediately update its UMH when the 237 reachability condition changes. 239 When signaling state for a P2MP TE LSP is removed (e.g. if the 240 ingress of the P2MP TE LSP sends a PathTear message) or the P2MP TE 241 LSP changes state from up to down as determined by procedures in 243 [RFC4875], the status of the corresponding P-Tunnel SHOULD be re- 244 evaluated. If the P-Tunnel transitions from up to down state, the 245 upstream PE, that is the ingress of the P-Tunnel, SHOULD not be 246 considered a valid UMH. 248 3.1.4. Leaf-initiated P-tunnels 250 A PE can be removed from the UMH candidate list for a said (S,G) if 251 the P-tunnel for this S,G (I or S , depending) is leaf triggered 252 (PIM, mLDP), but for some reason internal to the protocol the 253 upstream one-hop branch of the tunnel from P to PE cannot be built. 254 In this case the downstream PE can immediately update its UMH when 255 the reachability condition changes. 257 3.1.5. P2MP LSP OAM 259 When a P2MP connectivity verification mechanism such as 260 [I-D.katz-ward-bfd-multipoint] used in conjunction with bootstraping 261 mechanisms described in [I-D.ietf-mpls-mcast-cv] has been setup for a 262 tunnel, the result of the connectivity verification can be used to 263 define the status of the tree. 265 If a MultipointHead session has been established on a P2MP MPLS LSP 266 so that BFD packets are periodically sent from the root toward 267 leaves, a condition to consider the status of corresponding tunnel as 268 up is that the BFD SessionState is Up. 270 When such a procedure is used, in context where fast restoration 271 mechanisms are used for the P-tunnels, downstream PEs should be 272 configured to wait before updating the UMH, to let the P-tunnel 273 restoration mechanims happen. A configurable timer MUST be provided 274 for this purpose, and it is recommended to provide a reasonable 275 default value for this timer. 277 3.1.6. (S,G) counter information 279 In cases, where the downstream node can be configured so that the 280 maximum inter-packet time is known for all the multicast flows mapped 281 on a P-tunnel, the local per-(C-S,C-G) traffic counter information 282 for traffic received on this P-tunnel can be used to determine the 283 status of the P-tunnel. 285 When such a procedure is used, in context where fast restoration 286 mechanisms are used for the P-tunnels, downstream PEs should be 287 configured to wait before updating the UMH, to let the P-tunnel 288 restoration mechanims happen. A configurable timer MUST be provided 289 for this purpose, and it is recommended to provide a reasonable 290 default value for this timer. 292 This method can be applicable for instance when a (S,G) flow is 293 mapped on an S-PMSI. 295 In cases where this mechanism is used in conjunction with Hot leaf 296 standby, then no prior knowledge of the rate of the multicast streams 297 is required ; downstream PEs can compare reception on the two 298 P-tunnels to determine when one of them is down. 300 4. Standby C-multicast route 302 The procedures described below are limited to the case where the site 303 that contains C-S is connected to exactly two PEs. The procedures 304 require all the PEs of that MVPN to follow the single forwarder PE 305 selection, as specified in [I-D.ietf-l3vpn-2547bis-mcast]. The 306 procedures assume that if a site of a given MVPN that contains C-S is 307 dual-homed to two PEs, then all the other sites of that MVPN would 308 have two unicast VPN routes (VPN-IPv4 or VPN-IPv6) routes to C-S, 309 each with its own RD. 311 As long as C-S is reachable via both PEs, a said downstream PE will 312 select one of the PEs connected to C-S as its Upstream PE with 313 respect to C-S. We will refer to the other PE connected to C-S as 314 the "Standby Upstream PE". Note that if the connectivity to C-S 315 through the Primary Upstream PE becomes unavailable, then the PE will 316 select the Standby Upstream PE as its Upstream PE with respect to 317 C-S. 319 For readability, in the following sub-sections, the procedures are 320 described for BGP C-multicast Source Tree Join routes, but they apply 321 equally to BGP C-multicast Shared Tree Join routes failover for the 322 case where the customer RP is dual-homed (substitute "C-RP" to 323 "C-S"). 325 4.1. Downstream PE behavior 327 When a (downstream) PE connected to some site of an MVPN needs to 328 send a C-multicast route (C-S, C-G), then following the procedures 329 specified in Section "Originating C-multicast routes by a PE" of 330 [I-D.ietf-l3vpn-2547bis-mcast-bgp] the PE sends the C-multicast route 331 with RT that identifies the Upstream PE selected by the PE 332 originating the route. As long as C-S is reachable via the Primary 333 Upstream PE, the Upstream PE is the Primary Upstream PE. If C-S is 334 reachable only via the Standby Upstream PE, then the Upstream PE is 335 the Standby Upstream PE. 337 If C-S is reachable via both the Primary and the Standby Upstream PE, 338 then in addition to sending the C-multicast route with an RT that 339 identifies the Primary Upstream PE, the PE also originates and sends 340 a C-multicast route with an RT that identifies the Standby Upstream 341 PE. This route, that has the semantic of being a 'standby' 342 C-multicast route, is further called a "Standby BGP C-multicast 343 route", and is constructed as follows: 345 o the NLRI is constructed as the original C-multicast route, except 346 that the RD is the same as if the C-multicast route was built 347 using the standby PE as the UMH (it will carry the RD associated 348 to the unicast VPN route advertised by the standby PE for S) 350 o MUST carry the "Standby PE" BGP Community (this is a new BGP 351 Community, see Section 7) 353 The normal and the standby C-multicast routes must have their Local 354 Preference attribute adjusted so that, if two C-multicast routes with 355 same NLRI are received by a BGP peer, one carrying the "Standby PE" 356 attribute and the other one *not* carrying the "Standby PE" 357 community, then preference is given to the one *not* carrying the 358 "Standby PE" attribute. Such a situation can happen when, for 359 instance due to transient unicast routing inconistencies, two 360 different downstream PEs consider different upstream PEs to be the 361 primary one ; in that case, without any precaution taken, both 362 upstream PEs would process a standby C-multicast route and possibly 363 stop forwarding at the same time. For this purpose a Standby BGP 364 C-multicast route MUST have the LOCAL_PREF attribute set to zero. 366 Note that, when a PE advertizes such a Standby C-multicast join for 367 an (S,G) it must join the corresponding P-tunnel. 369 If at some later point the local PE determines that C-S is no longer 370 reachable through the Primary Upstream PE, the Standby Upstream PE 371 becomes the Upstream PE, and the local PE re-sends the C-multicast 372 route with RT that identifies the Standby Upstream PE, except that 373 now the route does not carry the Standby PE BGP Community (which 374 results in replacing the old route with a new route, with the only 375 difference between these routes being the presence/absence of the 376 Standby PE BGP Community). 378 4.2. Upstream PE behavior 380 When a PE receives a C-multicast route for a particular (C-S, C-G), 381 and the RT carried in the route results in importing the route into a 382 particular VRF on the PE, if the route carries the Standby PE BGP 383 Community, then the PE performs as follows: 385 when the PE determines that C-S is not reachable through some 386 other PE, the PE SHOULD install VRF PIM state corresponding to 387 this Standby BGP C-multicast route (the result will be that a PIM 388 Join message will be sent to the CE towards C-S, and that the PE 389 will receive (C-S,C-G) traffic), and the PE SHOULD forward (C-S, 390 C-G) traffic received by the PE to other PEs through a P-tunnel 391 rooted at the PE. 393 Furthermore, irrespective of whether C-S carried in that route is 394 reachable through some other PE: 396 a) based on local policy, as soon as the PE receives this Standby BGP 397 C-multicast route, the PE MAY install VRF PIM state corresponding 398 to this BGP Source Tree Join route (the result will be that Join 399 messages will be sent to the CE toward C-S, and that the PE will 400 receive (C-S,C-G) traffic) 402 b) based on local policy, as soon as the PE receives this Standby BGP 403 C-multicast route, the PE MAY forward (C-S, C-G) traffic to other 404 PEs through a P-tunnel independently of the reachability of C-S 405 through some other PE. [note that this implies also doing (a)] 407 Doing neither (a), nor (b) for a said (C-S,C-G) is called "cold root 408 standby". 410 Doing (a) but not (b) for a said (C-S,C-G) is called "warm root 411 standby". 413 Doing (b) (which implies also doing (a)) for a said (C-S,C-G) is 414 called "hot root standby". 416 Note that, if an upstream PE uses an S-PMSI only policy, it shall 417 advertise an S-PMSI for an (S,G) as soon as it receives a C-multicast 418 route for (S,G), normal or Standby ; i.e. it shall not wait for 419 receiving a non-Standby C-multicast route before advertising the 420 corresponding S-PMSI. 422 4.3. Reachability determination 424 The standby PE can use the following information to determine that 425 C-S can or cannot be reached through the primary PE: 427 o presence/absence of a unicast VPN route toward C-S 429 o supposing that the standby PE is an egress of the tunnel rooted at 430 the Primary PE, the standby PE can determine the reachability of 431 C-S through the Primary PE based on the status of this tunnel, 432 determined thanks to the same criteria as the ones described in 433 Section 3.1 (without using the UMH selection procedures of 434 Section 3) 436 o other mechanisms MAY be used 438 4.4. Inter-AS 440 If the non-segmented inter-AS approach is used, the procedures in 441 section 4 can be applied. 443 When multicast VPNs are used in a inter-AS context with the segmented 444 inter-AS approach described in section 8.2 of 445 [I-D.ietf-l3vpn-2547bis-mcast-bgp], the procedures in this section 446 can be applied. 448 A pre-requisite for the procedures described below to be applied for 449 a source of a said MVPN is: 451 o that any PE of this MVPN receives two Inter-AS I-PMSI auto- 452 discovery routes advertized by the AS of the source (or more) 454 o that these Inter-AS I-PMSI autodiscovery routes have distinct 455 Route Distinguishers (as described in item "(2)" of section 9.2 of 456 [I-D.ietf-l3vpn-2547bis-mcast-bgp]). 458 As an example, these conditions will be satisfied when the source is 459 dual homed to an AS that connects to the receiver AS through two ASBR 460 using auto-configured RDs. 462 4.4.1. Inter-AS procedures for downstream PEs, ASBR fast failover 464 The following procedure is applied by downstream PEs of an AS, for a 465 source S in a remote AS. 467 Additionaly to choosing an Inter-AS I-PMSI autodiscovery route 468 advertized from the AS of the source to construct a C-multicast 469 route, as described in section 11.1.3 470 [I-D.ietf-l3vpn-2547bis-mcast-bgp] a downstream PE will choose a 471 second Inter-AS I-PMSI autodiscovery route advertized from the AS of 472 the source and use this route to construct and advertise a Standby 473 C-multicast route (C-multicast route carrying the Standby extended 474 community) as described in Section 4.1. 476 4.4.2. Inter-AS procedures for ASBRs 478 When an upstream ASBR receives a C-multicast route, and at least one 479 of the RTs of the route matches one of the ASBR Import RT, the ASBR 480 locates an Inter-AS I-PMSI A-D route whose RD and Source AS matches 481 the RD and Source AS carried in the C-multicast route. If the match 482 is found, and C-multicast route carries the Standby PE BGP Community, 483 then the ASBR performs as follows: 485 o if the route was received over iBGP ; the route is expected to 486 have a LOCAL_PREF attribute set to zero and it should be re- 487 advertized in eBGP with a MED attribute (MULTI_EXIT_DISC) set to 488 the highest possible value (0xffff) 490 o if the route was received over eBGP ; the route is expected to 491 have a MED attribute set of 0xffff and should be re-advertised in 492 iBGP with a LOCAL_PREF attribute set to zero 494 Other ASBR procedures are applied without modification. 496 5. Hot leaf standby 498 The mechanisms defined in sections Section 4 and Section 3 can be 499 used together as follows. 501 The principle is that, for a said VRF (or possibly only for a said 502 C-S,C-G): 504 o downstream PEs advertise a Standby BGP C-multicast route (based on 505 Section 4) 507 o upstream PEs use the "hot standby" optional behavior and thus will 508 forward traffic for a said multicast state as soon as they have 509 whether a (primary) BGP C-multicast route or a Standby BGP 510 C-multicast route for that state (or both) 512 o downstream PEs accept traffic from the primary or standby tunnel, 513 based on the status of the tunnel (based on Section 3) 515 Other combinations of the mechanisms proposed in Section 4) and 516 Section 3 are for further study. 518 Note that the same level of protection would be achievable with a 519 simple C-multicast Source Tree Join route advertised to both the 520 primary and secondary upstream PEs (carrying as Route Target extended 521 communities, the values of the VRF Route Import attribute of each VPN 522 route from each upstream PEs). The advantage of using the Standby 523 semantic for is that, supposing that downstream PEs always advertise 524 a Standby C-multicast route to the secondary upstream PE, it allows 525 to choose the protection level through a change of configuration on 526 the secondary upstream PE, without requiring any reconfiguration of 527 all the downstream PEs. 529 6. Duplicate packets 531 Multicast VPN specifications [I-D.ietf-l3vpn-2547bis-mcast] impose 532 that a PE only forwards to CEs the packets coming from the expected 533 usptream PE (Section 9.1). 535 We highlight the reader's attention to the fact that the respect of 536 this part of multicast VPN specifications is especially important 537 when two distinct upstream PEs are succeptible to forward the same 538 traffic on P-tunnels at the same time in steady state. This will be 539 the case when "hot root standby" mode is used (Section 4), and which 540 can also be the case if procedures of Section 3 are used and (a) the 541 rules determining the status of a tree are not the same on two 542 distinct downstream PEs or (b) the rule determining the status of a 543 tree depend on conditions local to a PE (e.g. the PE-P upstream link 544 being up). 546 7. IANA Considerations 548 Allocation is expected from IANA for the BGP "Standby PE" community. 549 (TBC) 551 [Note to RFC Editor: this section may be removed on publication as an 552 RFC.] 554 8. Security Considerations 556 9. Acknowledgements 558 The authors want to thank Greg Reaume for its review and useful 559 feedback. 561 10. References 563 10.1. Normative References 565 [I-D.ietf-l3vpn-2547bis-mcast] 566 Aggarwal, R., Bandi, S., Cai, Y., Morin, T., Rekhter, Y., 567 Rosen, E., Wijnands, I., and S. Yasukawa, "Multicast in 568 MPLS/BGP IP VPNs", draft-ietf-l3vpn-2547bis-mcast-10 (work 569 in progress), January 2010. 571 [I-D.ietf-l3vpn-2547bis-mcast-bgp] 572 Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP 573 Encodings and Procedures for Multicast in MPLS/BGP IP 574 VPNs", draft-ietf-l3vpn-2547bis-mcast-bgp-08 (work in 575 progress), September 2009. 577 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 578 Requirement Levels", BCP 14, RFC 2119, March 1997. 580 [RFC4875] Aggarwal, R., Papadimitriou, D., and S. Yasukawa, 581 "Extensions to Resource Reservation Protocol - Traffic 582 Engineering (RSVP-TE) for Point-to-Multipoint TE Label 583 Switched Paths (LSPs)", RFC 4875, May 2007. 585 10.2. Informative References 587 [I-D.ietf-mpls-mcast-cv] 588 Swallow, G., "Connectivity Verification for Multicast 589 Label Switched Paths", draft-ietf-mpls-mcast-cv-00 (work 590 in progress), April 2007. 592 [I-D.karan-mofrr] 593 Karan, A., Filsfils, C., and D. Farinacci, "Multicast only 594 Fast Re-Route", draft-karan-mofrr-00 (work in progress), 595 March 2009. 597 [I-D.katz-ward-bfd-multipoint] 598 Katz, D. and D. Ward, "BFD for Multipoint Networks", 599 draft-katz-ward-bfd-multipoint-02 (work in progress), 600 February 2009. 602 [RFC4090] Pan, P., Swallow, G., and A. Atlas, "Fast Reroute 603 Extensions to RSVP-TE for LSP Tunnels", RFC 4090, 604 May 2005. 606 Authors' Addresses 608 Thomas Morin 609 France Telecom - Orange Labs 610 2, avenue Pierre Marzin 611 Lannion 22307 612 France 614 Email: thomas.morin@orange-ftgroup.com 615 Yakov Rekhter 616 Juniper Networks 617 1194 North Mathilda Ave. 618 Sunnyvale, CA 94089 619 U.S.A. 621 Email: yakov@juniper.net 623 Rahul Aggarwal 624 Juniper Networks 625 1194 North Mathilda Ave. 626 Sunnyvale, CA 94089 627 U.S.A. 629 Email: rahul@juniper.net 631 Wim Henderickx 632 Alcatel-Lucent 633 Copernicuslaan 50 634 Antwerp 2018 635 Belgium 637 Email: wim.henderickx@alcatel-lucent.com 639 Praveen Muley 640 Alcatel-Lucent 641 701 East Middlefield Rd 642 Mountain View, CA 94043 643 U.S.A. 645 Email: praveen.muley@alcatel-lucent.com 647 Ray (Lei) Qiu 648 Huawei 649 2330 Central Expressway 650 Santa Clara, CA 95050 651 U.S.A. 653 Email: rayq@huawei.com