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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 4601 (Obsoleted by RFC 7761) == Outdated reference: A later version (-05) exists of draft-ietf-bess-ir-02 Summary: 1 error (**), 0 flaws (~~), 2 warnings (==), 3 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 BESS Working Group Y. Rekhter, Ed. 3 Internet-Draft E. Rosen, Ed. 4 Updates: 6513,6514,6625 (if approved) Juniper Networks, Inc. 5 Intended status: Standards Track R. Aggarwal 6 Expires: May 20, 2016 Arktan 7 Y. Cai 8 Microsoft 9 T. Morin 10 Orange 11 November 17, 2015 13 Extranet Multicast in BGP/IP MPLS VPNs 14 draft-ietf-bess-mvpn-extranet-04 16 Abstract 18 Previous RFCs specify the procedures necessary to allow IP multicast 19 traffic to travel from one site to another within a BGP/MPLS IP VPN 20 (Virtual Private Network). However, it is sometimes desirable to 21 allow multicast traffic whose source is in one VPN to be received by 22 systems that are in another VPN. This is known as a "Multicast VPN 23 (MVPN) extranet". This document updates RFCs 6513, 6514, and 6625 by 24 specifying the procedures that are necessary in order to provide MVPN 25 extranet service. 27 Status of This Memo 29 This Internet-Draft is submitted in full conformance with the 30 provisions of BCP 78 and BCP 79. 32 Internet-Drafts are working documents of the Internet Engineering 33 Task Force (IETF). Note that other groups may also distribute 34 working documents as Internet-Drafts. The list of current Internet- 35 Drafts is at http://datatracker.ietf.org/drafts/current/. 37 Internet-Drafts are draft documents valid for a maximum of six months 38 and may be updated, replaced, or obsoleted by other documents at any 39 time. It is inappropriate to use Internet-Drafts as reference 40 material or to cite them other than as "work in progress." 42 This Internet-Draft will expire on May 20, 2016. 44 Copyright Notice 46 Copyright (c) 2015 IETF Trust and the persons identified as the 47 document authors. All rights reserved. 49 This document is subject to BCP 78 and the IETF Trust's Legal 50 Provisions Relating to IETF Documents 51 (http://trustee.ietf.org/license-info) in effect on the date of 52 publication of this document. Please review these documents 53 carefully, as they describe your rights and restrictions with respect 54 to this document. Code Components extracted from this document must 55 include Simplified BSD License text as described in Section 4.e of 56 the Trust Legal Provisions and are provided without warranty as 57 described in the Simplified BSD License. 59 Table of Contents 61 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 62 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 63 1.2. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 7 64 1.2.1. Customer Multicast Control 65 Protocols . . . . . . . . . . . . . . . . . . . . . . 7 66 1.2.2. Provider Multicast Control 67 Protocols . . . . . . . . . . . . . . . . . . . . . . 7 68 1.3. Clarification on Use of Route 69 Distinguishers . . . . . . . . . . . . . . . . . . . . . 7 70 1.4. Overview . . . . . . . . . . . . . . . . . . . . . . . . 9 71 2. Extranets and Overlapping Address 72 Spaces . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 73 2.1. Ambiguity: P-tunnel with 74 Extranet/Non-Extranet Flows . . . . . . . . . . . . . . . 13 75 2.2. Ambiguity: P-tunnel with Multiple 76 Extranet Flows . . . . . . . . . . . . . . . . . . . . . 15 77 2.3. Preventing Misdelivery in These 78 Scenarios . . . . . . . . . . . . . . . . . . . . . . . . 17 79 2.3.1. Do Not Deliver Packets from the 'Wrong' P-tunnel . . 17 80 2.3.2. Policies to Prevent Ambiguity on a P-tunnel . . . . . 19 81 3. Extranet Transmission Models . . . . . . . . . . . . . . . . 20 82 3.1. Transmitting an Extranet C-flow on a Single PMSI . . . . 20 83 3.1.1. Without Extranet Separation . . . . . . . . . . . . . 21 84 3.1.2. With Extranet Separation . . . . . . . . . . . . . . 21 85 3.2. Transmitting an Extranet C-flow over Multiple PMSIs . . . 21 86 4. Distribution of Routes that Match 87 C-S/C-RP Addresses . . . . . . . . . . . . . . . . . . . . . 22 88 4.1. UMH-Eligible Routes . . . . . . . . . . . . . . . . . . . 22 89 4.1.1. Extranet Separation . . . . . . . . . . . . . . . . . 23 90 4.2. Distribution of Unicast Routes 91 Matching C-RPs and DRs . . . . . . . . . . . . . . . . . 23 92 4.3. Route Targets and Ambiguous 93 UMH-Eligible Routes . . . . . . . . . . . . . . . . . . . 24 94 4.4. Dynamically Marking Extranet 95 Routes . . . . . . . . . . . . . . . . . . . . . . . . . 26 96 4.4.1. The Extranet Source Extended 97 Community . . . . . . . . . . . . . . . . . . . . . . 26 98 4.4.2. Distribution of Extranet Source Extended 99 Community . . . . . . . . . . . . . . . . . . . . . . 27 100 4.5. The 'Extranet Separation' Extended Community . . . . . . 28 101 5. Origination and Distribution of BGP A-D Routes . . . . . . . 28 102 5.1. Route Targets of UMH-eligible Routes and A-D 103 Routes . . . . . . . . . . . . . . . . . . . . . . . . . 28 104 5.2. Considerations for Particular Inclusive Tunnel 105 Types . . . . . . . . . . . . . . . . . . . . . . . . . . 31 106 5.2.1. RSVP-TE P2MP or Ingress 107 Replication . . . . . . . . . . . . . . . . . . . . . 31 108 5.2.2. Ingress Replication . . . . . . . . . . . . . . . . . 31 109 6. When PIM is the PE-PE C-multicast Control Plane . . . . . . . 33 110 6.1. Provisioning VRFs with RTs . . . . . . . . . . . . . . . 34 111 6.1.1. Incoming and Outgoing Extranet RTs . . . . . . . . . 34 112 6.1.2. UMH-eligible Routes and RTs . . . . . . . . . . . . . 35 113 6.1.3. PIM C-Instance Reverse Path Forwarding 114 Determination . . . . . . . . . . . . . . . . . . . . 35 115 6.2. Single PMSI per C-flow Model . . . . . . . . . . . . . . 35 116 6.2.1. Forming the MI-PMSIs . . . . . . . . . . . . . . . . 35 117 6.2.2. S-PMSIs . . . . . . . . . . . . . . . . . . . . . . . 38 118 6.2.3. Sending PIM Control Packets . . . . . . . . . . . . . 40 119 6.2.4. Receiving PIM Control Packets . . . . . . . . . . . . 40 120 6.2.5. Sending and Receiving Data Packets . . . . . . . . . 40 121 6.3. Multiple PMSIs per C-flow Model . . . . . . . . . . . . . 41 122 6.3.1. Forming the MI-PMSIs . . . . . . . . . . . . . . . . 41 123 7. When BGP is the PE-PE C-multicast Control Plane . . . . . . . 43 124 7.1. Originating C-multicast Routes . . . . . . . . . . . . . 43 125 7.2. Originating A-D Routes Without Extranet 126 Separation . . . . . . . . . . . . . . . . . . . . . . . 44 127 7.2.1. Intra-AS I-PMSI A-D Routes . . . . . . . . . . . . . 44 128 7.2.2. S-PMSI A-D Routes . . . . . . . . . . . . . . . . . . 45 129 7.2.3. Source Active A-D Routes . . . . . . . . . . . . . . 45 130 7.2.3.1. When Inter-Site Shared Trees Are Used . . . . . . 45 131 7.2.3.2. When Inter-Site Shared Trees Are Not Used . . . . 46 132 7.3. Originating A-D Routes With Extranet Separation . . . . . 46 133 7.3.1. Intra-AS I-PMSI A-D Routes . . . . . . . . . . . . . 46 134 7.3.2. S-PMSI A-D Routes . . . . . . . . . . . . . . . . . . 47 135 7.3.3. Source Active A-D Routes . . . . . . . . . . . . . . 49 136 7.4. Determining the Expected P-tunnel for a C-flow . . . . . 49 137 7.4.1. (C-S,C-G) S-PMSI A-D Routes . . . . . . . . . . . . . 51 138 7.4.2. (C-S,C-*) S-PMSI A-D Routes . . . . . . . . . . . . . 51 139 7.4.3. (C-*,C-G) S-PMSI A-D Routes . . . . . . . . . . . . . 51 140 7.4.4. (C-*,C-*) S-PMSI A-D Routes . . . . . . . . . . . . . 53 141 7.4.5. I-PMSI A-D Routes . . . . . . . . . . . . . . . . . . 53 142 7.5. Packets Arriving from the Wrong P-tunnel . . . . . . . . 54 143 8. Multiple Extranet VRFs on the same 144 PE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 146 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 55 147 10. Security Considerations . . . . . . . . . . . . . . . . . . . 55 148 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 57 149 12. Contributor Addresses . . . . . . . . . . . . . . . . . . . . 57 150 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 58 151 13.1. Normative References . . . . . . . . . . . . . . . . . . 58 152 13.2. Informative References . . . . . . . . . . . . . . . . . 59 153 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 60 155 1. Introduction 157 Previous RFCs ([RFC6513], [RFC6514]) specify the procedures necessary 158 to allow IP multicast traffic to travel from one site to another 159 within a BGP/MPLS IP VPN (Virtual Private Network). However, it is 160 sometimes desirable to allow multicast traffic whose source is in one 161 VPN to be received by systems that are in another VPN. This is known 162 as an "extranet MVPN". This document specifies the procedures that 163 are necessary in order to provide Extranet MVPN functionality. 165 1.1. Terminology 167 This document uses terminology from [RFC6513], and in particular uses 168 the prefixes "C-" and "P-" as specified in Section 3.1 of [RFC6513], 169 and "A-D routes" for "auto-discovery routes". 171 The term "Upstream Multicast Hop" (UMH) is used as defined in 172 [RFC6513]. 174 The term "UMH-eligible route" is used to mean "route eligible for UMH 175 determination", as defined in Section 5.1.1 of [RFC6513]. We will 176 say that a given UMH-eligible route or unicast route "matches" a 177 given IP address, in the context of a given Virtual Routing and 178 Forwarding Table (VRF), if the address prefix of the given route is 179 the longest match in that VRF for the given IP address. We will 180 sometimes say that a route "matches" a particular host if the route 181 matches an IP address of the host. 183 We follow the terminology of Section 3.2 of [RFC6625] when talking of 184 a "Selective Provider Multicast Service Interface" (S-PMSI) A-D route 185 being "installed". That is, we say that an S-PMSI A-D route is 186 "installed" (in a given VRF) if it has been selected by the BGP 187 decision process as the preferred route for its NLRI. We also follow 188 the terminology of Section 3.2 of [RFC6625] when saying that an 189 S-PMSI A-D route has been "originated by a given PE"; this means that 190 the given PE's IP address is contained in the "Originating Router's 191 IP Address" field in the NLRI of the route. 193 We use the following additional terminology and notation: 195 o Extranet C-source: a multicast source, in a given VPN, that is 196 allowed by policy to send multicast traffic to receivers that are 197 in other VPNs. 199 o Extranet C-receiver: a multicast receiver, in a given VPN, that is 200 allowed by policy to receive multicast traffic from extranet 201 C-sources that are in other VPNs. 203 o Extranet C-flow: a multicast flow (with a specified C-source 204 address and C-group address) whose source is an extranet C-source, 205 and which is allowed by policy to have extranet C-receivers. 207 o Extranet C-group: a multicast group address that is in the "Any 208 Source Multicast" (ASM) group address range, and that is allowed 209 by policy to have Extranet C-sources and Extranet C-receivers that 210 are not all in the same VPN. Note that we will sometimes refer to 211 "Source-Specific Multicast" (SSM) C-group addresses" (i.e., to 212 C-group addresses in the SSM group address range), but will never 213 call them "extranet C-groups". 215 N.B.: Any source of traffic for an extranet C-group is considered 216 to be an extranet C-source, and any receiver of traffic addressed 217 to an extranet C-group is considered to be an extranet C-receiver. 219 o Extranet C-RP: a multicast Rendezvous Point (RP) for an extranet 220 C-group; it is allowed by policy to receive PIM register messages 221 [RFC4601] from outside its VPN, and to send multicast data packets 222 to extranet C-receivers outside its VPN. 224 o Host(C-S,A): the host (or if C-S is an "anycast address", the set 225 of hosts) denoted by the address C-S in the context of VPN-A. For 226 example, if a particular C-source in VPN A has address C-S, then 227 Host(C-S,A) refers to that C-source. 229 o SAFI-n route: a BGP route whose Address Family Identifier (AFI) is 230 either 1 (IPv4) or 2 (IPv6), and whose Subsequent Address Family 231 Identifier (SAFI) is "n". 233 Note that a given extranet C-source is not necessarily allowed to 234 transmit to every extranet C-receiver; policy determines which 235 extranet C-sources are allowed to transmit to which extranet 236 C-receivers. However, in the case of an extranet (ASM) C-group, all 237 transmitters to the group are allowed to transmit to all the 238 receivers of the group, and all the receivers of the group are 239 allowed to receive from all transmitters to the group. 241 We say that a given VRF "contains" or "has" a multicast C-source (or 242 that the C-source is "in" the VRF), if that C-source is in a site 243 connected to that VRF, and the VRF originates a UMH-eligible route 244 (see Section 4) that matches the address of the C-source. 246 We say that a given VRF "contains" or "has" a multicast C-receiver 247 (or that the C-receiver is "in" the VRF), if that C-receiver is in a 248 site connected to that VRF. 250 We say that a given VRF "contains" or "has" the C-RP for a given ASM 251 group (or that the C-RP is "in" the VRF) if that C-RP is in a site 252 connected to that VRF, and the VRF originates a unicast route and a 253 (possibly different, possibly the same) UMH-eligible route (see 254 Section 4) whose respective address prefixes match the C-RP address. 256 [RFC6513] allows a set of "Provider tunnels" (P-tunnels) to be 257 aggregated together and transported via an outer P-tunnel, i.e., it 258 allows for the use of hierarchical Label Switched Paths (LSPs) as 259 P-tunnels. A two-level hierarchical LSP, for example, can be thought 260 of as a set of "inner tunnels" aggregated into an outer tunnel. In 261 this document, when we speak of a P-tunnel, we are always speaking of 262 the innermost P-tunnel, i.e., of a P-tunnel at the lowest level of 263 hierarchy. P-tunnels are identified in the Provider Multicast 264 Service Interface (PMSI) Tunnel Attributes (PTAs) [RFC6514] of BGP 265 Auto-Discovery (A-D) routes. Two PTAs that have the same Tunnel Type 266 and Tunnel Identifier fields, but different MPLS label fields, are 267 thus considered to identify two different P-tunnels. (I.e., for the 268 purposes of this document, the MPLS label included in the PTA, if 269 any, is considered to be part of the tunnel identifier.) 271 We say that the NLRI of a BGP S-PMSI A-D route or Source Active A-D 272 route contains (C-S,C-G) if its "Multicast Source" field contains C-S 273 and its "Multicast Group" field contains C-G. If either or both of 274 these fields is encoded as a wildcard, we will say that the NLRI 275 contains (C-*,C-*) (both fields encoded as wildcard), or (C-*,C-G) 276 (multicast source field encoded as wildcard) or (C-S,C-*) (multicast 277 group field encoded as wildcard). 279 We use the term "VPN security violation" to refer to any situation in 280 which a packet is delivered to a particular VPN, even though, by 281 policy, it should not be delivered to that VPN. 283 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 284 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 285 "OPTIONAL" in this document are to be interpreted as described in 286 [RFC2119]. 288 1.2. Scope 290 1.2.1. Customer Multicast Control Protocols 292 This document presumes that the VPN customer is using "PIM Sparse 293 Mode", operating in either "Source-Specific Mode" (SSM) or "Any 294 Source Mode" (ASM), as the multicast control protocol at the customer 295 sites. Support for other customer IP multicast control protocols 296 (e.g., [RFC5015], PIM "Dense Mode") is outside the scope of this 297 document. Support for the customer use of MPLS multicast control 298 protocols (e.g., [RFC6388], [RFC4875]) is also outside the scope of 299 this document. 301 When a VPN customer uses ASM, the customer routers need to be able to 302 map from a C-group address to a C-RP address. These mappings can be 303 provisioned in each router, or can be discovered dynamically through 304 protocols such as BSR [RFC5059]. However, it cannot be assumed that 305 such protocols will automatically work in the context of an extranet. 306 Discussion of the use of such protocols in an extranet is outside the 307 scope of this document. 309 1.2.2. Provider Multicast Control Protocols 311 [RFC6513] allows either PIM or BGP to be used as the protocol for 312 distributing customer multicast routing information. Except where 313 otherwise specified, such as in Sections 6 and 7, the procedures of 314 this document cover both cases. 316 1.3. Clarification on Use of Route Distinguishers 318 [RFC4364] requires that every VRF be associated with one or more 319 Route Distinguishers (RD). Each VPN-IPv4 or VPN-IPv6 route that is 320 exported from a particular VRF contains, in its NLRI, an RD that is 321 associated with that VRF. 323 [RFC4364] allows a given RD to be associated with more than one VRF, 324 as long as all the VRFs associated with that RD belong to the same 325 VPN. However, in the most common deployment model, each RD is 326 associated with one and only one VRF. [RFC6513] and [RFC6514] 327 presuppose this deployment model. That is, [RFC6513] and [RFC6514] 328 presuppose that every RD is associated with one and only one VRF. We 329 will call this the "unique VRF per RD" condition. 331 [RFC6514] defines the MCAST-VPN address family, which has a number of 332 route types. Each Intra-AS "Inclusive Provider Multicast Service 333 Interface" (I-PMSI) A-D route, S-PMSI A-D route, and Source Active 334 A-D route, when exported from a given VRF, contains, in its NLRI, an 335 RD that is associated with the VRF. [RFC6513] and [RFC6514] also 336 discuss a class of routes known as "UMH-eligible" routes; when a UMH- 337 eligible route is exported from a given VRF, its NLRI contains an RD 338 of the VRF. 340 [RFC6514] also defines MCAST-VPN routes whose NLRIs do not contain an 341 RD of the VRF from which they are exported: the C-multicast Join 342 routes and the Leaf A-D routes. 344 Those route types that, when exported from a given VRF, contain (in 345 their NLRIs) an RD of the VRF, will be known in this document as 346 "local-RD routes". 348 Given the "unique VRF per RD condition", if one sees that two local- 349 RD routes have the same RD, one can infer that the two routes 350 originated from the same VRF. This inference can be drawn even if 351 the two routes do not have the same SAFI, as long as the two routes 352 are both local-RD routes. 354 This document builds upon [RFC6513] and [RFC6514]; therefore the 355 "unique VRF per RD" condition is REQUIRED. 357 [RFC6514] presupposes a further requirement on the use of RDs in the 358 local-RD routes exported from a given VRF. Suppose a given VRF 359 exports a Source Active A-D route containing (C-S,C-G). That VRF 360 will also export a UMH-eligible route matching C-S. [RFC6514] 361 presupposes that the UMH-eligible route and the Source Active A-D 362 route have the same RD. 364 In most cases, not only is a given RD associated with only a single 365 VRF, but a given VRF is associated with only a single RD. We will 366 call this the "unique RD per VRF" condition. When this condition 367 holds, all the local-RD routes exported from a given VRF will have 368 the same RD. This ensures that the presupposition of the previous 369 paragraph will hold, i.e., that the RD in a Source Active A-D route 370 exported from a given VRF will have the same RD as the corresponding 371 UMH-eligible route exported from the same VRF. 373 Section 7.3 of this document describes a procedure known as "Extranet 374 Separation". When Extranet Separation is NOT being used, it is 375 REQUIRED by this document that the "unique RD per VRF" condition 376 hold. This ensures that all the local-RD routes exported from a 377 given VRF will have the same RD. 379 When Extranet Separation is used, a VRF that contains both extranet 380 sources and non-extranet sources MUST be configured with two RDs. 381 One of these RDs is known as the "default RD", and the other is known 382 as the "extranet RD". It MUST be known by configuration which RD is 383 the default RD and which is the extranet RD. 385 When a VRF is configured with only one RD, we will refer to that RD 386 as the "default RD". 388 In general, local-RD routes exported from a given VRF will contain 389 the default RD. However, when Extranet Separation is used, some of 390 the local-RD routes exported from the VRF will contain the extranet 391 RD. Details concerning the exported routes that contain the extranet 392 RD can be found in Sections 4.1 and 7.3. 394 Note that the "unique VRF per RD" condition applies to the extranet 395 RD as well as to the default RD. That is, a given extranet RD is 396 associated with a unique VRF. 398 1.4. Overview 400 Consider two VPNs, VPN-S and VPN-R, each of which supports MVPN 401 functionality as specified in [RFC6513] and/or [RFC6514]. In the 402 simplest configuration, VPN-S is a collection of VRFs, each of which 403 is configured with a particular Route Target (RT) value (call it "RT- 404 S") as its import RT and as its export RT. Similarly, VPN-R is a 405 collection of VRFs, each of which is configured with a particular RT 406 value (call it "RT-R") as its import RT and as its export RT. 408 In this configuration, multicast C-receivers contained in a VPN-R VRF 409 cannot receive multicast data traffic from multicast C-sources 410 contained in a VPN-S VRF. If it is desired to allow this, one needs 411 to create an MVPN "extranet". Creating an extranet requires 412 procedures in addition to those specified in [RFC6513], [RFC6514], 413 and [RFC6625]; this document specifies these additional procedures. 415 In the example above, the additional procedures will allow a selected 416 set of routes exported from the VPN-S VRFs (i.e., from the VRFs 417 containing extranet C-sources) to be imported into the VPN-R VRFs 418 (i.e., into the VRFs containing extranet C-receivers). These routes 419 include the routes that are to be eligible for use as UMH routes (see 420 Section 5.1 of [RFC6513]) in the extranet, as well as a selected set 421 of BGP A-D routes (Intra-AS I-PMSI A-D routes, S-PMSI A-D routes, 422 Source Active A-D routes). Importing these routes into the VPN-R 423 VRFs makes it possible to determine, in the context of a VPN-R VRF, 424 that a particular C-multicast Join needs to be delivered to a 425 particular VPN-S VRF. It also makes it possible to determine, in the 426 context of a VPN-R VRF, the P-tunnel through which the aforementioned 427 VPN-S VRF sends a particular C-flow. 429 Depending on the type of P-tunnel used, it may also be necessary for 430 Leaf A-D routes to be exported by one or more VPN-R VRFs and imported 431 into a VPN-S VRF. 433 There are no extranet-specific procedures governing the use and 434 distribution of BGP C-Multicast routes. 436 If PIM is used as the PE-PE protocol for distributing C-multicast 437 routing information, additional BGP A-D routes must be exported from 438 the VPN-R VRFs and imported into the VPN-S VRFS, so that the VPN-S 439 VRFs can join the P-tunnels that the VPN-R VRFs use for sending PIM 440 control messages. Details can be found in Section 6. 442 The simple example above describes an extranet created from two 443 MVPNs, one of which contains extranet C-sources and one of which 444 contains extranet C-receivers. However, the procedures described in 445 this document allow for much more complicated scenarios. 447 For instance, an extranet may contain extranet C-sources and/or 448 extranet C-receivers from an arbitrary number of VPNs, not just from 449 two VPNs. An extranet C-receiver in VPN-R may be allowed to receive 450 multicast traffic from extranet C-sources in VPN-A, VPN-B, and VPN-C. 451 Similarly, extranet C-sources in VPN-S may be allowed to send 452 multicast traffic to multicast C-receivers that are in VPN-A, VPN-B, 453 VPN-C, etc. 455 A given VPN customer may desire that only some of its multicast 456 C-sources be treated as extranet C-sources. This can be accomplished 457 by appropriate provisioning of the import and export RTs of that 458 customer's VRFs (as well as the VRFs of other VPNs that contain 459 extranet C-receivers for extranet C-flows of the given customer.) 461 A given VPN customer may desire that some of its extranet C-sources 462 can transmit only to a certain set of VPNs, while other of its 463 extranet C-sources can transmit only to a different set of VPNs. 464 This can be accomplished by provisioning the VRFs to export different 465 routes with different RTs. 467 In all these cases, the VPN customers set the policies, and the 468 Service Provider (SP) implements the policies by the way it 469 provisions the import and export RTs of the VRFs. It is assumed that 470 the customer communicates to the SP the set of extranet C-source 471 addresses, and the set of VPNs to which each C-source can transmit. 472 (Recall that every C-source that can transmit to an extranet C-group 473 is an extranet C-source, and must be able transmit to any VPN that 474 has receivers for that group. This must be taken into account when 475 the provisioning is done.) This customer/SP communication is part of 476 the service provisioning process, and outside the scope of this 477 document. 479 It is possible that an extranet C-source will transmit both extranet 480 C-flows and non-extranet C-flows. However, if extranet C-receiver 481 C-R can receive extranet C-flows from extranet C-source C-S, the 482 procedures of this document do not prevent C-R from requesting and 483 receiving the non-extranet flows that are transmitted by C-S. 484 Therefore it is NOT RECOMMENDED to allow an extranet C-source to 485 transmit non-extranet C-flows. However, the Service Provider (SP) 486 has no control over the set of C-flows transmitted by a given 487 C-source, and can do no more than communicate this recommendation to 488 its customers. (Alternatively, the customer and SP may coordinate on 489 setting up filters to prevent unauthorized flows from being sent to a 490 customer site; such a procedure is outside the scope of this 491 document.) See the "Security Considerations" section (Section 10) 492 for additional discussion of this issue. 494 2. Extranets and Overlapping Address Spaces 496 As specified in [RFC4364], the address space of one VPN may overlap 497 with the address space of another. A given address may be 498 "ambiguous", in that it denotes one system within VPN-A and a 499 different system within VPN-B. In the notation of Section 1.1, if an 500 address C-S is ambiguous between VPNs A and B, then Host(C-S,A) != 501 Host(C-S,B). However, any given address C-S MUST be unambiguous 502 (i.e., MUST denote a single system) in the context of a given VPN. 504 When a set of VRFs belonging to different VPNs are combined into an 505 extranet, it is no longer sufficient for an address to be unambiguous 506 only within the context of a single VPN: 508 1. Suppose C-S is the address of a given extranet C-source contained 509 in VPN-A. Now consider the set of VPNs {VPN-B, VPN-C, ...} 510 containing extranet C-receivers that are allowed by policy to 511 receive extranet C-flows from VPN-A's C-S. The address C-S MUST 512 be unambiguous among this entire set of VPNs (VPN-A, VPN-B, VPN- 513 C, etc.); i.e., Host(C-S,A) == Host(C-S,B) == Host(C-S,C). 515 The implication is that C-S in VPN-A is not necessarily an 516 extranet C-source for all VPNs that contain extranet C-receivers; 517 policy MUST be used to ensure that C-S is an extranet C-source 518 for a given VPN, say VPN-B, only if C-S is unambiguous between 519 VPN-A and VPN-B. 521 2. If a given VRF contains extranet C-receivers for a given extranet 522 C-source, then the address of this C-source MUST be unambiguous 523 among all the extranet C-sources for which there are C-receivers 524 in the VRF. This is true whether or not C-sources are in VRFs 525 that belong to the same or to different VPNs. 527 The implication is that if C-S in VRF-X is ambiguous with C-S in 528 VRF-Y, then there MUST NOT be any VRF, say VRF-Z, containing 529 C-receivers that are allowed by policy to receive extranet 530 C-flows from both C-S in VRF-X and C-S in VRF-Y. 532 Note: A VPN customer may be using "anycast" addresses. An anycast 533 address is intentionally ambiguous, as it denotes a set of systems 534 rather than a single system. In this document, we will consider an 535 anycast address to be unambiguous in a given context as long as it 536 denotes the same set of systems whenever it occurs in that context. 538 A multicast C-group address, say C-G, may also be ambiguous, in that 539 it may be used for one multicast group in VPN-A and for an entirely 540 different multicast group in VPN-B. If a set of MVPNs are combined 541 into an extranet, and C-G is an extranet C-group, it is necessary to 542 ensure that C-G is unambiguous among the entire set of VPNs whose 543 VRFs contain extranet C-sources, C-RPs, and/or extranet C-receivers 544 for that C-group. This may require, as part of the provisioning 545 process, customer/SP communication that is outside the scope of this 546 document. 548 Subject to these restrictions, the SP has complete control over the 549 distribution of routes in an MVPN. This control is exerted either by 550 provisioning the export RTs on the VRFs that originate the routes 551 (i.e., on the VRFs that contain the extranet C-sources), or by 552 provisioning the import RTs on the VRFs that receive the routes 553 (i.e., on the VRFs that contain the extranet C-receivers), or both. 555 Some of the rules and restrictions on provisioning the RTs are 556 applicable to all extranets; these are specified in Section 4. 557 Sections 6 and 7 add additional rules and restrictions that are 558 applicable only to particular extranet scenarios. 560 Even if all the RTs are provisioned according to the above rules and 561 restrictions, it is still possible for a single P-tunnel to contain 562 multicast data packets whose source and/or group addresses are 563 ambiguous in the context of the set of PEs that receive data from the 564 P-tunnel. That is, the above rules and restrictions are necessary, 565 but not sufficient, to prevent address ambiguity from causing 566 misdelivery of traffic. To prevent such misdelivery, additional 567 procedures or policies must be used. 569 Sections 2.1 and 2.2 describe scenarios in which a given P-tunnel may 570 carry data packets with ambiguous addresses. The additional 571 procedures and policies needed to prevent misdelivery of data in 572 those scenarios are outlined in Section 2.3. (The detailed 573 procedures described in Sections 6 and 7 incorporate the 574 considerations of Section 2.3.) 576 2.1. Ambiguity: P-tunnel with Extranet/Non-Extranet Flows 578 In the following, we will use the notation "VRF A-n" to mean "VRF n 579 of VPN-A". 581 If VPN-A and VPN-B have overlapping address spaces, and are part of 582 the same extranet, then the following problem may exist, as 583 illustrated in Figure 1. 585 C-S2(A) C-S1 Join(C-S2(A),G) 586 \ / / 587 \ / / 588 +-------+---+ P1: (C-S1,G), (C-S2(A),G) +---+--------+ 589 |VRF A-1| |---------------------------------| |VRF A-2 | 590 +-------+PE1| |PE2+--------+ 591 |VRF B-1| |---------------------------------| |VRF B-2 | 592 +-------+---+ P2: (C-S2(B),G) +---+--------+ 593 / / \ 594 / / \ 595 C-S2(B) Join(C-S2(B),G) Join(C-S1,G) 597 Figure 1: Ambiguity of Extranet and Non-Extranet Source Address 599 Suppose: 601 o C-G is an SSM C-group used in VPNs A and B. 603 o VRF A-1, on PE1, contains an extranet C-source, whose IP address 604 is C-S1, that is allowed to have receivers in VPN B. VRF A-1 thus 605 exports to VPN B a UMH-eligible route matching C-S1. 607 o VRF A-1 also contains a non-extranet C-source, whose IP address is 608 C-S2. VRF A-1 exports a UMH-eligible route matching C-S2 to other 609 VPN A VRFs, but NOT to VPN B. 611 o VRF B-1, also on PE1, contains a non-extranet C-source whose IP 612 address is C-S2. A UMH-eligible route matching C-S2 is thus 613 exported from VRF B-1 to other VRFs in VPN B. 615 o Host(C-S2,A) != Host(C-S2,B). That is, C-S2 is an ambiguous 616 address in any extranet that contains both VPN-A VRFs and VPN-B 617 VRFs. 619 o VRF B-2, on some other PE, say PE2, requests to receive the 620 multicast flow (C-S1,C-G). In the context of VRF B-2, C-S1 621 matches the route exported from VRF A-1. Thus B-2's request to 622 receive the (C-S1,C-G) flow is transmitted to VRF A-1. 624 o VRF A-1 responds to VRF B-2's request for (C-S1,C-G) traffic by 625 transmitting that traffic on P-tunnel P1. 627 o VRF B-2 joins P-tunnel P1, in order to receive the (C-S1,C-G) 628 traffic. 630 o VRF A-2, on PE2, requests to receive the (non-extranet) multicast 631 flow (C-S2,C-G). In the context of VRF A-2, C-S2 matches the 632 route exported from VRF A-1. Thus A-2's request to receive the 633 (C-S2,C-G) traffic is transmitted to VRF A-1. 635 o VRF A-1 responds to VRF A-2's request for (C-S2,C-G) traffic by 636 transmitting that traffic on P-tunnel P1. 638 o VRF A-2 joins P-tunnel P1, in order to receive the (C-S2,C-G) 639 traffic. 641 o VRF B-2 requests to receive the (non-extranet) multicast flow 642 (C-S2,C-G). In the context of VRF B-2, C-S2 matches the route 643 exported from VRF B-1. Thus B-2's request to receive the 644 (C-S2,C-G) flow is transmitted to VRF B-1. 646 o VRF B-1 responds to VRF B-2's request for (C-S2,C-G) traffic by 647 transmitting that traffic on P-tunnel P2. 649 o VRF B-2 joins P-tunnel P2. 651 Since VRF B-2 has joined P-tunnel P1 and P-tunnel P2, it will receive 652 (C-S2,C-G) traffic on both P-tunnels. The (C-S2,C-G) traffic that 653 VRF B-2 needs to receive is traveling on P-tunnel P2; this (C-S2,C-G) 654 traffic must be forwarded by B-2 to any attached customer sites that 655 have C-receivers for it. But B-2 MUST discard the (C-S2,C-G) traffic 656 that it receives on P1, as this is not the traffic that it has 657 requested. If the (C-S2,C-G) traffic arriving on P1 were forwarded 658 to B-2's customer sites, the C-receivers would not be able to 659 distinguish the two flows, and the result would be a corrupted data 660 stream. 662 Note that the procedures of [RFC6513] Section 9.1.1 ("Discarding 663 Packets from the Wrong PE") will not cause VRF B-2 to discard the 664 (C-S2,C-G) that arrives on tunnel P1, because P1 and P2 have the same 665 upstream PE. 667 Therefore, it is necessary EITHER to prevent the above scenario from 668 occurring, OR ELSE to ensure that multicast data packets will be 669 discarded if they arrive on the "wrong" P-tunnel (even if they arrive 670 from the expected PE). See Section 2.3 for further discussion of 671 this issue. 673 2.2. Ambiguity: P-tunnel with Multiple Extranet Flows 675 Here is another example in which overlapping address spaces may cause 676 a problem. This example is illustrated in Figure 2. 678 C-S2(A2D) C-S1(A2C) Join(C-S2(A2D),G) 679 \ / / 680 \ / / 681 +-------+---+ P1: (C-S1(A2C),G), (C-S2(A2D),G)+---+--------+ 682 |VRF A-1| |---------------------------------| |VRF D-1 | 683 +-------+PE1| |PE2+--------+ 684 |VRF B-1| |---------------------------------| |VRF C-1 | 685 +-------+---+ P2: (C-S2(B2C),G) +---+--------+ 686 / / \ 687 / / \ 688 C-S2(B2C) / \ 689 Join Join 690 (C-S2(B2C),G) (C-S1(A2C),G) 692 Figure 2: Ambiguity of Extranet Source Addresses 694 Suppose: 696 o C-G is an SSM C-group address that is used in VPNs A, B, C, and D. 698 o VRF A-1, on PE1, contains an extranet C-source whose IP address is 699 C-S1, and that is allowed by policy to have C-receivers in VPN C 700 (but not in VPN D). VRF A-1 thus exports a UMH-eligible route 701 matching C-S1 to VPN C. 703 o VRF A-1 also contains an extranet C-source whose IP address is 704 C-S2, and that is allowed by policy to have C-receivers in VPN D 705 (but not in VPN C). VRF A-1 thus exports a UMH-eligible route 706 matching C-S2 to VPN D. 708 o VRF B-1, also on PE1, contains an extranet C-source whose IP 709 address is C-S2, and that is allowed by policy to have C-receivers 710 in VPN C (but not in VPN D). VRF B-1 thus exports a UMH-eligible 711 route matching C-S2 to VPN C. 713 o Host(C-S2,A) != Host (C-S2,B). That is, C-S2 is an ambiguous 714 address in any extranet that contains both VPN-A VRFs and VPN-B 715 VRFs. 717 o VRF C-1, on some other PE, say PE2, requests to receive the 718 extranet multicast flow (C-S1,C-G). In the context of VRF C-1, 719 C-S1 matches the route exported from VRF A-1. Thus C-1's request 720 to receive the (C-S1,C-G) flow is transmitted to VRF A-1. 722 o VRF A-1 responds to VRF C-1's request for (C-S1,C-G) traffic by 723 transmitting that traffic on P-tunnel P1, 725 o VRF C-1 joins P-tunnel P1, in order to receive the (C-S1,C-G) 726 traffic. 728 o VRF C-1 requests to receive the extranet multicast flow 729 (C-S2,C-G). In the context of VRF C-1, C-S2 matches the route 730 exported from VRF B-1. Thus C-1's request to receive the 731 (C-S2,C-G) flow is transmitted to VRF B-1. 733 o VRF B-1 responds by transmitting its (C-S2,C-G) traffic on 734 P-tunnel P2. 736 o VRF C-1 joins P-tunnel P2 in order to receive the (C-S2,C-G) 737 traffic. 739 o VRF D-1, on PE2, requests to receive the extranet multicast flow 740 (C-S2,C-G). In the context of VRF D-1, C-S2 matches the route 741 exported from VRF A-1. Thus D-1's request to receive the 742 (C-S2,C-G) flow is transmitted to VRF A-1. 744 o VRF A-1 responds by transmitting its (C-S2,C-G) traffic on 745 P-tunnel P1. 747 o VRF D-1 joins P-tunnel P1 in order to receive the (C-S2,C-G) 748 traffic. 750 In this example, VRF A-1 has chosen to use the same P-tunnel, P1, to 751 carry both its (C-S2,C-G) traffic and the (C-S1,C-G) traffic. VRF 752 C-1 has joined tunnel P1 in order to receive the (C-S1,C-G) traffic 753 from VRF A-1, which means that VRF C-1 will also receive the unwanted 754 (C-S2,C-G) traffic from P1. VRF C-1 is also expecting (C-S2,C-G) 755 traffic from VRF B-1; this traffic will be received from P2. Thus 756 VRF C-1 is receiving (C-S2,C-G) traffic on both tunnels, and both 757 C-flows arrive from the expected PE, PE1. 759 Therefore, it is necessary EITHER to prevent the above scenario from 760 occurring, OR ELSE to ensure that VRF C-1 discards any (C-S,C-G) 761 traffic that arrives from the "wrong" P-tunnel. See Section 2.3 for 762 further discussion of this issue. 764 Note that the ambiguity described in this section (Section 2.2) would 765 not occur if C-G were an (ASM) extranet C-group. In that case, the 766 scenario would violate the rule, given previously in Section 2, 767 requiring that all sources sending to a particular ASM extranet 768 C-group must have addresses that are unambiguous over all the MVPNs 769 receiving traffic for that C-group. 771 2.3. Preventing Misdelivery in These Scenarios 773 There are two ways to prevent the scenarios of Section 2.1 and 774 Section 2.2 from resulting in misdelivery of data. These two ways 775 are discussed respectively in Section 2.3.1 and Section 2.3.2. 777 2.3.1. Do Not Deliver Packets from the 'Wrong' P-tunnel 779 Consider a particular C-flow that has receivers in a particular VRF. 780 Sections 6 and 7 describe a set of procedures that enable an egress 781 PE to determine the "expected P-tunnel" for that C-flow in the 782 context of that VRF. If a PE receives packets of the C-flow (as 783 determined by the IP source and/or destination address of the 784 packet), it checks to see if the packet was received on the expected 785 P-tunnel for that VRF. If so, the packet is delivered to the VRF 786 (and thus to the C-flow's receivers in that VRF). If not, the packet 787 is not delivered to the VRF. 789 Note that at a given egress PE, the "wrong" P-tunnel for one VRF may 790 be the right P-tunnel for another. 792 These procedures, if applied at every PE that joins a given P-tunnel, 793 are sufficient to prevent misdelivery of traffic in the scenarios of 794 Sections 2.1 and 2.2. 796 IF these procedures cannot be applied by every PE that is attached to 797 a given extranet, then the policies of Section 2.3.2 MUST be applied 798 at every VRF containing C-sources for that extranet. 800 In some cases, however, it may be safe to deliver packets that arrive 801 from other than the expected P-tunnel. Suppose it is known that 802 every packet gets transmitted on only a single P-tunnel. (This will 803 be the case if the "single PMSI per C-flow" transmission model, 804 discussed in Section 3.1, is being used.) Suppose further that it is 805 known that T1 and T2 carry only packets that arrived at the same 806 ingress PE, over one or more VRF interfaces that are associated with 807 the same VRF. (I.e., that there is a particular VRF that is the 808 ingress VRF for ALL the packets carried by T1 or T2.) In this case, 809 if T1 is the expected P-tunnel for a given (C-S,C-G) , it is NOT 810 necessary to discard (S,G) packets that arrive over T2. 812 It is not always possible to determine whether two P-tunnels are 813 carrying packets from the same ingress VRF. However, in some cases, 814 this can be determined by examination of the A-D routes in which the 815 tunnels have been advertised. 817 Consider the following example: 819 o Tunnel T1 is a P2MP mLDP or RSVP-TE P-tunnel advertised in an 820 Intra-AS I-PMSI A-D route, call it R1. 822 o Tunnel T2 is a P2MP mLDP or RSVP-TE P-tunnel advertised in an 823 S-PMSI A-D route, call it R2. 825 o The respective NLRIs of R1 and R2 contain the same RD value. 827 o The MPLS Label field of R1's PMSI Tunnel attribute is zero, and 828 the MPLS label value of R2's PMSI Tunnel attribute is zero. 830 In this example, it can be concluded that T1 and T2 are carrying 831 packets from the same ingress VRF. Thus if T1 is the expected 832 P-tunnel for a (C-S,C-G) flow, (S,G) packets from T2 can be safely 833 delivered to the egress VRF; they do not need to be discarded. 834 Similarly, if T2 is the expected P-tunnel for a (C-S,C-G) flow, (S,G) 835 packets from T1 can be safely delivered to the egress VRF. 837 Another example is the following: 839 o Tunnel T3 is a P2MP mLDP or RSVP-TE P-tunnel advertised in a 840 (C-*,C-*) S-PMSI A-D route, call it R3. 842 o Tunnel T4 is a P2MP mLDP or RSVP-TE P-tunnel advertised in a 843 (C-S,C-G) S-PMSI A-D route, call it R4. 845 o The respective NLRIs of R3 and R4 contain the same RD value. 847 o The MPLS Label field of R3's PMSI Tunnel attribute is zero, and 848 the MPLS label value of R4's PMSI Tunnel attribute is zero. 850 In this example, it can be concluded that T3 and T4 are carrying 851 packets from the same ingress VRF. Thus if T3 is the expected 852 P-tunnel for a (C-S,C-G) flow, (S,G) packets from T4 can be safely 853 delivered to the egress VRF; they do not need to be discarded. 854 Similarly, if T4 is the expected P-tunnel for a (C-S,C-G) flow, (S,G) 855 packets from T3 can be safely delivered to the egress VRF. 857 When Ingress Replication (IR) P-tunnels are being used, please see 858 [MVPN-IR], especially Section 6 ("The PTA's MPLS Label Field") for a 859 discussion of how to determine when packets from other than the 860 expected P-tunnel must be discarded. 862 2.3.2. Policies to Prevent Ambiguity on a P-tunnel 864 For P-tunnels that are advertised in S-PMSI A-D routes whose NLRI 865 contains (C-S,C-G) or (C-S,C-*), the ambiguities described in 866 Sections 2.1 and 2.2 can be prevented by provisioning a policy that 867 assigns, to such P-tunnels, only flows from the same C-source. 869 However, it is not always possible to determine, through inspection 870 of the control messages, whether this policy has been deployed. For 871 instance, suppose a given VRF has imported a set of S-PMSI A-D 872 routes, that each route in the set has bound only a single 873 (C-S1,C-G1) to a single P-tunnel, and that each route in the set 874 identifies a different P-tunnel in its PTA than is identified by the 875 PTA of any other route in the set. One cannot infer from this that 876 there is no ambiguity, as the same P-tunnel may also have been 877 advertised in an S-PMSI A-D route that is not imported by the given 878 VRF, and that S-PMSI A-D route may have bound (C-S2,C-G2) to the 879 P-tunnel, where C-S1 != C-S2. 881 Therefore, in order to determine that a given P-tunnel (advertised in 882 a (C-S,C-G) or (C-S,C-*) S-PMSI A-D route) carries only C-flows from 883 a single C-source, a PE must have a priori knowledge (through 884 provisioning) that this policy has been deployed. In the remainder 885 of this document, we will refer to this policy as the "Single 886 C-source per (C-S,C-G) or (C-S,C-*) P-tunnel" policy. Note that this 887 policy is only applicable to P-tunnels that are advertised only in 888 (C-S,C-G) or (C-S,C-*) S-PMSI A-D routes. 890 Of course, if a P-tunnel is advertised in (a) an I-PMSI A-D route, or 891 (b) an S-PMSI A-D route whose NLRI contains (C-*,C-*), or (c) an 892 S-PMSI A-D route whose NLRI contains (C-*,C-G), then it is always 893 possible for the P-tunnel to contain traffic from multiple C-sources; 894 there is no policy that can prevent that. 896 However, if a P-tunnel advertised in a (C-*,C-G) S-PMSI A-D route 897 contains only traffic addressed to a single C-G, the address 898 uniqueness rules of Section 2 prevent the C-source addresses from 899 being ambiguous; the set of C-sources transmitting to a particular 900 extranet C-group address must be unambiguous over the set of MVPNs 901 that have receivers for that C-group. So for P-tunnels that are 902 advertised in (C-*,C-G) S-PMSI A-D routes, the ambiguities described 903 Section 2.1 and Section 2.2 can be prevented by provisioning a policy 904 that assigns, to such P-tunnels, only flows to the same extranet 905 C-group. We will refer to this policy as the "Single C-group per 906 (C-*,C-G) P-tunnel" policy. 908 These considerations can be summarized as follows. IF the procedures 909 referenced in Section 2.3.1 cannot be applied, then the PEs MUST be 910 provisioned so that the all of the following conditions hold true of 911 the VRFs that contain extranet C-sources: 913 o the "Single C-source per (C-S,C-G) or (C-S,C-*) P-tunnel" policy 914 is provisioned, and 916 o either no (C-*,C-G) S-PMSI A-D routes are advertised, or else the 917 "Single C-group per (C-*,C-G) P-tunnel" policy is provisioned, and 919 o no P-tunnels are advertised in I-PMSI A-D routes, and 921 o no (C-*,C-*) S-PMSI A-D routes are advertised. 923 Section 3 of this document describes a procedure known as "extranet 924 separation". When extranet separation is used, the ambiguity of 925 Section 2.1 is prevented. However, the ambiguity of Section 2.2 is 926 not prevented by extranet separation. Therefore, the use of extranet 927 separation is not a sufficient condition for avoiding the procedures 928 referenced in Section 2.3.1. Extranet separation is, however, 929 implied by the policies discussed in this section (Section 2.3.2). 931 3. Extranet Transmission Models 933 This document specifies several "extranet transmission models". A 934 given VRF, containing extranet C-sources or C-receivers, MUST use 935 only one of these models. Further if VRF S contains extranet 936 C-sources, VRF R contains extranet C-receivers, and it is allowed by 937 policy for an extranet C-receiver in VRF R to receive a C-flow from 938 an extranet C-source in VRF S, then VRFs S and R MUST use the same 939 extranet transmission model. The model used by a given VRF is 940 determined by provisioning. 942 3.1. Transmitting an Extranet C-flow on a Single PMSI 944 In one extranet transmission model, which we call the "transmitting 945 an extranet C-flow on a single PMSI" model, or more simply, the 946 "single PMSI per C-flow model", a PE transmitting a packet of an 947 extranet C-flow transmits it on only a single PMSI. If the PMSI is 948 instantiated by a multicast P-tunnel, this means that the PE 949 transmits the packet on a single P-tunnel. Of course, if the PE is a 950 replication point for that multicast P-tunnel, the packet is 951 transmitted more than once by the PE. Similarly, if the PMSI is 952 instantiated by a set of unicast tunnels (i.e., via Ingress 953 Replication), each packet may be transmitted multiple times. It is 954 still the case though that the packet is transmitted only on one 955 PMSI. 957 This document provides procedures for supporting this transmission 958 model using either BGP or PIM as the PE-PE C-multicast control 959 protocol. 961 There are two variants of this transmission model: "without extranet 962 separation" and "with extranet separation". 964 3.1.1. Without Extranet Separation 966 In this variant, multicast data traffic from extranet C-sources and 967 from non-extranet C-sources may be carried in the same P-tunnel. 969 This document provides procedures for supporting this variant using 970 either BGP or PIM as the PE-PE C-multicast control protocol. 972 3.1.2. With Extranet Separation 974 In this variant, multicast data traffic from extranet C-sources and 975 from non-extranet C-sources are never carried in the same P-tunnel. 976 Under certain circumstances, this can reduce the amount of multicast 977 data traffic that is delivered unnecessarily to certain PE routers. 978 It also eliminates the ambiguity discussed in Section 2.1. 980 By definition, when extranet separation is used, the following rule 981 MUST be applied: 983 Traffic from extranet C-sources MUST NOT be carried in the same 984 P-tunnel as traffic from non-extranet C-sources. 986 This rule does not impact those VRFs that contain only non-extranet 987 C-sources, nor does it impact those VRFs that contain only extranet 988 C-sources. However, if a particular VRF contains both kinds of 989 C-source, it will need to advertise some P-tunnels that are used for 990 carrying only extranet C-flows, and some that are used only for 991 carrying non-extranet C-flows. 993 This document provides procedures for supporting extranet separation 994 when BGP is used as the PE-PE C-multicast control protocol. Support 995 for extranet separation using PIM as the PE-PE C-multicast control 996 protocol is outside the scope of this document. 998 3.2. Transmitting an Extranet C-flow over Multiple PMSIs 1000 The second extranet transmission model is called the "transmitting an 1001 extranet C-flow over multiple PMSIs" model, or more simply, the 1002 "multiple PMSIs per C-flow model". In this model, a PE may transmit 1003 the packets of an extranet C-flow on several different PMSIs. 1005 Support for extranet separation with this model is outside the scope 1006 of this document. 1008 This document provides procedures for supporting this transmission 1009 model when PIM as the PE-PE C-multicast control protocol. Support 1010 for this transmission model when BGP is used as the PE-PE C-multicast 1011 control protocol is outside the scope of this document. 1013 4. Distribution of Routes that Match C-S/C-RP Addresses 1015 4.1. UMH-Eligible Routes 1017 As described in Section 5.1 of [RFC6513], in order for a C-flow 1018 (C-S,C-G) to be carried across the SP backbone, a VRF that has 1019 multicast receivers for that C-flow must import a route that matches 1020 C-S, and this route must be "eligible for UMH selection". In this 1021 document, we will refer to these routes as "UMH-eligible extranet 1022 C-source routes". 1024 The UMH-eligible extranet C-source routes do not necessarily have to 1025 be unicast routes; they MAY be SAFI-129 routes (see Section 5.1.1 of 1026 [RFC6513]). For example, suppose one wants a VPN-R C-receiver to be 1027 able to receive extranet C-flows from C-sources in VPN-S, but one 1028 does not want any VPN-R system to be able to send unicast traffic to 1029 those C-sources. One can achieve this by using SAFI-129 routes as 1030 the UMH-eligible routes exported from VPN-S and imported by VPN-R. 1031 Since SAFI-129 routes are used only for UMH determination, but not 1032 for unicast routing, this allows the multicast traffic to be 1033 forwarded properly, but does not create unicast routes to the 1034 C-sources. 1036 If a customer is using PIM-SM in ASM mode, and one or more customer 1037 sites have C-receivers that are allowed by policy to join a (C-*,C-G) 1038 tree, where C-G is an extranet C-group, then any VRF with C-receivers 1039 for that group MUST import a UMH-eligible route that matches C-RP, 1040 where C-RP is the Rendezvous Point (RP) address for C-G. 1042 The UMH-eligible extranet C-source and C-RP routes do not have to be 1043 "host routes." That is, they can be routes whose IPv4 address 1044 prefixes are not 32 bits in length, or whose IPv6 address prefixes 1045 are not 128 bits in length. So it is possible for a UMH-eligible 1046 extranet C-source route to match the address of an extranet C-source 1047 and to also match the address of a non-extranet C-source. However, 1048 if such a route is exported from a VPN-S VRF and imported by a VPN-R 1049 VRF, VPN-R receivers will be able to receive C-flows from any non- 1050 extranet C-sources whose addresses match that route. To prevent 1051 this, the VPN-S VRF SHOULD be provisioned such that it will NOT 1052 export a UMH-eligible route that matches (in the context of the VPN-R 1053 VRF) both extranet C-sources and non-extranet C-sources. Failure to 1054 follow this rule may result in a VPN security violation. (See 1055 Section 10.) 1057 In general, one does not want ALL the routes from the VPN-S VRFs to 1058 be exported to all the VPN-R VRFs, as only a subset of the routes in 1059 the VPN-S VRFs will be UMH-eligible extranet C-source routes. Route 1060 distribution is, as always in a BGP/MPLS IP VPN [RFC4364], controlled 1061 by Route Targets (RTs). A variety of route distribution policies can 1062 be created by appropriately provisioning the import and export RTs of 1063 the various VRFs. 1065 For example, the VPN-S VRFs that contain extranet C-sources could be 1066 configured to apply an export RT whose value is "RT-A-extranet" to 1067 the routes that match the extranet C-sources. The VPN-R VRFs that 1068 contain extranet C-receivers allowed to receive extranet C-flows from 1069 VPN-S extranet C-sources could then be configured with "RT- 1070 A-extranet" as an import RT. 1072 Arbitrarily complex policies can be created by suitable manipulation 1073 of the import and export RTs. 1075 4.1.1. Extranet Separation 1077 If Extranet Separation is being used, and if a given VRF is exporting 1078 UMH-eligible routes both for extranet C-sources for non-extranet 1079 C-sources, then the VRF MUST be configured not only with its "default 1080 RD", but also with an "extranet RD". The exported UMH-eligible 1081 routes MUST contain the extranet RD in their NLRIs. 1083 4.2. Distribution of Unicast Routes Matching C-RPs and DRs 1085 Consider a C-source, C-S, that may transmit to a particular extranet 1086 C-group, C-G. 1088 In order to follow the procedures of [RFC4601], 1090 o the "first hop designated router" (DR) of C-S needs to be able to 1091 unicast "PIM Register Messages" to a C-RP that services C-G; 1093 o the C-RPs servicing C-G need to be able to unicast "PIM Register- 1094 Stop Messages" to the DR of C-S. 1096 It follows that if a VRF contains C-S, but does not contain a C-RP 1097 for C-G, then the VRF MUST import a unicast route matching a C-RP for 1098 C-G. Note that the unicast route matching the C-RP is needed whether 1099 or not the VRF has also imported a SAFI-129 route matching the C-RP. 1100 (If the VRF also contains receivers for C-G, and if UMH determination 1101 is being done using SAFI-129 routes, both a unicast route and a 1102 SAFI-129 matching C-RP route are needed.) 1104 Similarly, if a VRF contains a C-RP for C-G, but does not contain 1105 C-S, the VRF MUST import a unicast route matching the DR for C-S. 1106 Note that the unicast route matching the DR for C-S is needed even if 1107 UMH determination is being done using SAFI-129 routes; in that case, 1108 if the VRF also contains receivers for C-G, it needs to import a 1109 SAFI-129 route matching C-S and a unicast route matching the DR for 1110 C-S. 1112 If, for a particular extranet C-group, C-G, the customer is using 1113 "anycast-RP"([RFC3446], [RFC4610]) or MSDP [RFC3618], then all the 1114 C-RPs serving C-G need to send unicast messages to each other. Thus 1115 any VRF that contains a C-RP for C-G needs to import unicast routes 1116 matching ALL the other C-RPs that serve C-G. 1118 The need to distribute these unicast routes is usually not a problem 1119 as long as all the C-sources and C-RPs for C-G are in the same MVPN. 1120 If, however, the C-sources are not all in the same MVPN, great care 1121 must be taken to ensure that the unicast routes mentioned above are 1122 properly distributed. 1124 There may be scenarios in which all the C-sources for C-G are in the 1125 same MVPN, but there are receivers in different VPNs, and some or all 1126 of the VPNs with receivers have their own C-RPs for C-G. In this 1127 case, care must be taken to ensure that the C-RPs can all unicast to 1128 each other. 1130 4.3. Route Targets and Ambiguous UMH-Eligible Routes 1132 This section imposes constraints on the way RTs are assigned to (a) 1133 UMH-eligible routes and to (b) the BGP A-D routes that advertise 1134 P-tunnels (i.e., to BGP A-D routes that contain a PTA). The 1135 constraints specified here apply to any extranet for which the 1136 ambiguity of Section 2.2 is possible. (The conditions under which 1137 such ambiguity is possible are described in Section 2.2.) 1139 We want to ensure that, in any given VRF, the UMH-eligible route 1140 matching a given extranet C-source has an RT in common with every BGP 1141 A-D route that advertises a P-tunnel that may be used to carry 1142 extranet multicast traffic from that C-source. We also want to 1143 ensure that the UMH-eligible route matching a given extranet C-source 1144 does not have any RT in common with any BGP A-D route that advertises 1145 a P-tunnel that may be used to carry any multicast traffic from a 1146 different C-source that has the same IP address. This enables us to 1147 determine whether traffic that appears to be from the given C-source 1148 is really arriving on the "wrong tunnel", and hence is really from a 1149 different C-source with the same IP address. 1151 Suppose an IP address C-S is used in VPN-A as the address of one 1152 system, and is used in VPN-B as the address of a different system. 1153 In this case, one or more VPN-A VRFs may export a VPN-IP route whose 1154 NLRI is , and one or more VPN-B VRFs may export a VPN-IP route 1155 whose NLRI is , where RD1 != RD2. Consider two routes, R1 and 1156 R2, for which the following conditions all hold: 1158 o R1 and R2 are UMH-eligible extranet C-source or C-RP routes, or 1159 are unicast routes matching a C-RP 1161 o R1 is exported from a VRF of VPN-A, while R2 is exported from a 1162 VRF of a different VPN, say VPN-B 1164 o R1's NLRI specifies IP address prefix S/n 1166 o R2's NLRI specifies IP address prefix S/m 1168 o m >= n, (S/m is either the same as or more specific than S/n) 1170 o There is some host address H such that: 1172 * H denotes a different system in VPN-A than in VPN-B, 1174 * H/m == S/m (so either S/m or S/n might be a longest match for H 1175 in some VRF). 1177 We impose the following constraint: RTs MUST be assigned in such a 1178 way that R1 and R2 do not have any RT in common. 1180 (This constraint is not as onerous at it may seem. Typically R1 and 1181 R2 would not have an RT in common, as that might result in their 1182 being imported into the same VRF, making the address H ambiguous in 1183 that VRF.) 1185 Sections 6 and 7 specify procedures for determining if a received 1186 C-flow has been received over the expected P-tunnel. Those 1187 procedures will not work if this constraint is violated. (The 1188 constraint described in this section is necessary but not sufficient 1189 for the procedures of those sections to work; additional constraints, 1190 covering the assignment of RTs to BGP A-D routes, are given in 1191 subsequent sections.) 1193 4.4. Dynamically Marking Extranet Routes 1195 4.4.1. The Extranet Source Extended Community 1197 Sections 4.1, 4.2, and 4.3 place specific requirements on the way in 1198 which certain VPN-IP routes are distributed. In order to ensure that 1199 these requirements are met, a VPN customer must tell its SP which 1200 routes are the matching routes for extranet C-sources and C-RPs. 1201 This may be done as part of the provisioning process. Note that this 1202 does not necessarily require customer/provider interaction every time 1203 the customer adds a new extranet C-source or C-RP, but only when the 1204 IP address of the new C-source or C-RP does not match an existing 1205 route that is already being distributed as a VPN-IP extranet route. 1206 Nevertheless, it seems worthwhile to support an OPTIONAL mechanism 1207 that allows a customer to dynamically mark certain routes as being 1208 extranet routes. 1210 To facilitate this, we define a new Transitive Opaque Extended 1211 Community, the "Extranet Source" Extended Community. When a CE 1212 router advertises (via BGP) a route to a PE router, and the AFI/SAFI 1213 of the route is 1/1, 1/2, 1/4, 2/1, 2/2, or 2/4, the Extranet Source 1214 Extended Community MAY be attached to the route. The value field of 1215 the Extended Community MUST be set to zero. By placing this Extended 1216 Community on a particular route, a CE router indicates to a PE router 1217 that the procedures of Sections 4.1, 4.2, and 4.3 are to be applied 1218 to that route. That is, the CE router may use this Extended 1219 Community to indicate to the PE router that a particular route is to 1220 be treated as a route that matches the address of an extranet source, 1221 and exported accordingly to other VPNs. 1223 Whether a CE router uses the Extranet Source Extended Community is 1224 determined by the configuration of the CE router. If used, the set 1225 of routes to which the Extended Community is attached is also 1226 determined by configuration of the CE. Note that a particular PE 1227 router may or may not support the use of the Extranet Source Extended 1228 Community by a particular CE router; this is determined by the 1229 service agreement between the SP and its customer. 1231 If a CE is advertising SAFI-2 routes to the PE as the UMH-eligible 1232 extranet C-source and C-RP routes, and if the CE is using the 1233 Extranet Source Extended Community, it is important that the CE 1234 attach that Extended Community to the SAFI-2 routes, rather than just 1235 to the corresponding SAFI-1 routes. Otherwise extranet receivers may 1236 not be able to join the (C-S,C-G) or (C-*,C-G) multicast trees. 1238 However, if the C-sources and the C-RPs for a given extranet C-group 1239 are not all in the same VPN, the Extended Community would also have 1240 to be attached to the SAFI-1 routes that match the C-RP addresses and 1241 to the SAFI-1 routes that match the addresses of the first hop 1242 designated routers for all the C-sources. Otherwise, the first hop 1243 routers might not be able to send PIM Register messages to the C-RPs, 1244 and the C-RPs might not be able to send PIM Register-Stop messages to 1245 the first hop routers. 1247 While this Extended Community allows a customer to inform the SP 1248 dynamically that certain routes are "extranet routes", it does not 1249 allow a customer to control the set of RTs that the route will carry 1250 when it is redistributed as a VPN-IP route. Thus it is only useful 1251 when all the extranet routes from a given VRF are exported with 1252 exactly the same set of RTs. (Cf. Section 4.3.1 of [RFC4364], which 1253 does provide a mechanism that, if properly supported by the SP, 1254 allows the customer to determine the set of RTs carried by a VPN-IP 1255 route.) A CE SHOULD NOT attach the Extranet Source Extended 1256 Community to any route for which it uses another method of specifying 1257 the RTs to be carried by that route. A CE SHOULD NOT attach the 1258 Extranet Source Extended Community to a route unless all the extranet 1259 routes from the CE's VPN are intended to carry the same set of RTs. 1261 A PE SHOULD ignore the Extranet Source Extended Community if it 1262 appears on a route that the CE should not have put it on. A PE that 1263 ignores the Extranet Source Extended Community SHOULD NOT follow the 1264 procedures of Section 4.4.2. 1266 Note that misconfiguration on the CE router can result in the 1267 Extranet Source Extended Community being mistakenly attached to a 1268 route that is not intended to be exported as an extranet route. This 1269 could result in a VPN security violation. 1271 4.4.2. Distribution of Extranet Source Extended Community 1273 Suppose a PE receives from a CE a route, call it R, with the Extranet 1274 Source Extended Community. The PE must determine (via the 1275 considerations of Section 4.4.1) whether it should ignore that 1276 Extended Community on route R. If so, the procedures of the current 1277 Section are not followed. 1279 Otherwise, when the PE originates a VPN-IP route corresponding to 1280 route R, the PE MUST attach this Extended Community to that route. 1282 A Route Reflector MUST NOT add/remove the Extranet Source Extended 1283 Community from the VPN-IP routes reflected by the Route Reflector, 1284 including the case where VPN-IP routes received via IBGP are 1285 reflected to EBGP peers (inter-AS option (c), see [RFC6513] 1286 Section 10). 1288 When re-advertising VPN-IP routes, ASBRs MUST NOT add/remove the 1289 Extranet Source Extended Community from these routes. This includes 1290 inter-AS options (a) and (b) (see [RFC6513] Section 10). 1292 When a PE advertises (via BGP) IP routes to a CE, these routes MUST 1293 NOT carry the Extranet Source Extended Community, unless the PE-CE 1294 connection is actually an inter-AS option (a) connection (see 1295 [RFC6513] Section 10). When the PE-CE connection is not an inter-AS 1296 option (a) connection, a CE that receives an IP route with the 1297 Extranet Source Extended Community MUST remove it from the route 1298 before readvertising the route. 1300 4.5. The 'Extranet Separation' Extended Community 1302 We define a new Transitive Opaque Extended Community, the "Extranet 1303 Separation" Extended Community. This Extended Community is used only 1304 when extranet separation is being used. Its value field MUST be set 1305 to zero upon origination, MUST be ignored upon reception, and MUST be 1306 passed unchanged by intermediate routers. 1308 If a VRF has been provisioned to use extranet separation, and if that 1309 VRF has been provisioned to transmit any extranet C-flows on a 1310 P-tunnel that it advertises in an I-PMSI A-D route or a (C-*,C-*) 1311 S-PMSI A-D route, then any UMH-eligible routes that are exported from 1312 that VRF following the procedures of Sections 4.1, 4.2, and 4.3 MUST 1313 carry the Extranet Separation Extended Community. In addition, if an 1314 I-PMSI A-D route and/or (C-*,C-*) S-PMSI A-D route, exported from 1315 that VRF, is used to carry extranet traffic, that A-D route MUST also 1316 carry the Extranet Separation Extended Community. Further details 1317 may be found in Sections 7.3, 7.4.4, and 7.4.5. 1319 5. Origination and Distribution of BGP A-D Routes 1321 Except where otherwise specified, this section describes procedures 1322 and restrictions that are independent of the PE-PE C-multicast 1323 control protocol. 1325 5.1. Route Targets of UMH-eligible Routes and A-D Routes 1327 Suppose there is an extranet C-flow such that: 1329 o The extranet C-source of that C-flow is in VRF A-1. 1331 o One or more extranet C-receivers of that C-flow are in VRF B-1. 1333 In this case VRF A-1 MUST export a UMH-eligible route that matches 1334 the extranet C-source address, and VRF B-1 MUST import that route. 1335 In addition, VRF A-1 MUST export an Intra-AS I-PMSI A-D route or an 1336 S-PMSI A-D route specifying the P-tunnel through which it will send 1337 the data traffic of the given extranet C-flow, and VRF B-1 MUST 1338 import that route. If BGP is the PE-PE C-multicast control protocol, 1339 then under certain conditions (as specified in [RFC6514]), VRF A-1 1340 may also need to export a Source Active A-D route specifying that it 1341 contains a source of the given C-flow, and VRF B-1 must import that 1342 Source Active A-D route. That is, in order for VRF B-1 to receive a 1343 C-flow from, a given extranet C-source contained in VRF A-1, VRF A-1 1344 MUST export a set of A-D routes that are "about" that source, and VRF 1345 B-1 MUST import them. 1347 One way to ensure this is to provision an RT that is carried by all 1348 the routes exported from VRF A-1 that are "about" a given extranet 1349 C-source, and to provision this RT as an import RT at any VRF (such 1350 as VRF B-1) that is allowed to receive extranet flows from source. 1352 If the "single PMSI per C-flow" transmission model is being used 1353 (with or without extranet separation), there is a an additional 1354 requirement, stated below, on the way RTs are provisioned, as the RTs 1355 carried by a UMH-eligible route that matches a given extranet 1356 C-source may need to be used to identify the A-D routes that are 1357 "about" that source. 1359 Consider the following scenario: 1361 o IP address S is the address of one system in VPN-A, and of a 1362 different system in VPN-B. 1364 o VRF A-1 on PE1 exports UMH-eligible route R1, which is a matching 1365 route for S. 1367 o VRF A-1 on PE1 exports an A-D route P1 whose PTA identifies a 1368 P-tunnel through which VRF A-1 may send traffic whose C-source is 1369 S, where one of the following conditions holds: 1371 * P1 is an I-PMSI A-D route, OR 1373 * P1 is an S-PMSI A-D route whose NLRI contains (C-*,C-*) or 1374 (C-*,C-G), OR 1376 * P1 is an S-PMSI A-D route whose NLRI contains (C-S,C-G) or 1377 (C-S,C-*), BUT the "single C-source per (C-S,C-G) or (C-S,C-*) 1378 P-tunnel" policy is not provisioned. 1380 * P1 is a Source Active A-D route whose NLRI contains (C-S,C-G). 1382 o VRF B-1 on PE1 exports a UMH-eligible route R2, which is a 1383 matching route for S. 1385 o VRF B-1 on PE1 exports an A-D route P2 whose PTA identifies a 1386 P-tunnel on which VRF B-1 may send traffic whose C-source is S, 1387 where one of the following conditions holds: 1389 * P2 is an I-PMSI A-D route, OR 1391 * P2 is an S-PMSI A-D route whose NLRI specifies (C-*,C-*) or 1392 (C-*,C-G), OR 1394 * P2 is an S-PMSI A-D whose NLRI specifies (C-S,C-G) or 1395 (C-S,C-*), BUT the "single C-source per (C-S,C-G) or (C-S,C-*) 1396 P-tunnel" policy is not provisioned. 1398 * P2 is a Source Active A-D route whose NLRI contains (C-S,C-G) 1400 As already specified in Section 4.1, there MUST NOT be any RT that is 1401 common to both R1 and R2. In addition, the following set of rules 1402 for RT assignment MUST be followed when extranets are supported. 1403 This set of rules supports all the extranet transmission models 1404 described in this specification: 1406 o There MUST NOT be any RT that is carried by both P1 and P2. 1408 o The intersection of the set of RTs carried by P1 and the set of 1409 RTs carried by R1 MUST be non-null, and any VRF that imports both 1410 P1 and R1 MUST be configured with an import RT from this 1411 intersection. 1413 o The intersection of the set of RTs carried by P2 and the set of 1414 RTs carried by R2 MUST be non-null, and any VRF that imports both 1415 P2 and R2 MUST be configured with an import RT from this 1416 intersection. 1418 Suppose VRF C-1 on PE2 imports P1 and R1 from VRF A-1, while also 1419 importing P2 from VRF B-1. Since: 1421 o R1 is VRF C-1's route to S, and 1423 o R1 has an RT in common with P1, and 1425 o R1 has no RT in common with P2 1427 it can be concluded that VRF C-1 should expect that multicast traffic 1428 from S will arrive on the P-tunnel specified in P1. See Section 6 1429 and Section 7 for more details on determining the expected P-tunnel 1430 for a given extranet C-flow. 1432 While the assignment of import and export RTs to routes is a 1433 deployment and provisioning issue rather than a protocol issue, it 1434 should be understood that failure to follow these rules is likely to 1435 result in VPN security violations. 1437 5.2. Considerations for Particular Inclusive Tunnel Types 1439 An Inclusive Tunnel (sometimes referred to as an "Inclusive Tree", 1440 see Section 2.1.1 of [RFC6513]) is a tunnel that, by default, carries 1441 all the multicast traffic of a given MVPN that enters the backbone 1442 network via a particular PE. An Inclusive Tunnel is advertised in 1443 the PTA of an I-PMSI A-D route. 1445 5.2.1. RSVP-TE P2MP or Ingress Replication 1447 This section applies when Inclusive Tunnels are created using either 1448 RSVP-TE P2MP or Ingress Replication. 1450 Suppose a VRF, VRF-S, contains a given extranet C-source C-S, and 1451 that VRF-S advertises in its Intra-AS I-PMSI A-D route either a P2MP 1452 RSVP-TE P-tunnel or an Ingress Replication P-tunnel to carry extranet 1453 traffic. 1455 In order for VRF-S to set up the P2MP RSVP-TE or Ingress Replication 1456 P-tunnel, it must know all the PEs that are leaf nodes of the 1457 P-tunnel, and to learn this it must import an Intra-AS I-PMSI A-D 1458 route from every VRF that needs to receive data through that tunnel. 1460 Therefore if VRF-R contains an extranet C-receiver that is allowed by 1461 policy to receive extranet flows from C-S, the RT(s) carried by the 1462 Intra-AS I-PMSI A-D routes originated by VRF-R MUST be such that 1463 those Intra-AS I-PMSI A-D routes will be imported into VRF-S. 1465 In the case of Ingress Replication, this has the following 1466 consequence. If an egress PE has n VRFs with receivers for a flow 1467 that VRF-S transmits on its I-PMSI, that egress PE will receive n 1468 copies of the same packet, one for each of the n VRFs. 1470 Note that Section 9.1.1 of [RFC6514] prohibits the Leaf Information 1471 Required flag from being set in the PTA of an Intra-AS I-PMSI A-D 1472 route. If this prohibition is ever removed, the requirement of this 1473 section will apply only if VRF-S does not set that flag. 1475 5.2.2. Ingress Replication 1477 This section applies only when Inclusive Tunnels are created via 1478 Ingress Replication. 1480 [RFC6513] and [RFC6514] specify procedures that allow I-PMSIs to be 1481 instantiated by Ingress Replication. The concept of an IR P-tunnel, 1482 and the procedures for supporting IR P-tunnels, are explained more 1483 fully in [MVPN-IR]. An IR P-tunnel can be thought of as a P2MP tree 1484 in which a packet is transmitted from one node on the tree to another 1485 by being encapsulated and sent through a unicast tunnel. 1487 As discussed in Section 2, when I-PMSIs are used to support 1488 extranets, egress PEs MUST have the ability to discard customer 1489 multicast data packets that arrive on the wrong P-tunnel. When 1490 I-PMSIs are instantiated by IR, this implies that the following two 1491 procedures MUST be followed: 1493 1. One of the following three procedures MUST be followed: 1495 a. the "Single Forwarder Selection" procedures of [RFC6513] 1496 Section 9.1.2, 1498 b. the "Native PIM Methods" procedures of [RFC6513] 1499 Section 9.1.3 1501 c. the unicast encapsulation used to transmit packets along the 1502 IR P-tunnel is such as to enable the receiving node to 1503 identify the transmitting node (note that this would not be 1504 the case if, e.g., the unicast tunnels were MP2P LSPs); 1506 and 1508 2. If a PE assigns an MPLS label value in the PMSI Tunnel attribute 1509 of an Intra-AS or Inter-AS I-PMSI A-D route that it originates, 1510 that label value MUST NOT appear in the PMSI Tunnel attribute of 1511 any other I-PMSI or S-PMSI A-D route originated by the same PE. 1513 Failure to follow these procedures would make it impossible to 1514 discard packets that arrive on the wrong P-tunnel, and thus could 1515 lead to duplication of data. 1517 If it is desired to support extranet while also using IR to 1518 instantiate the PMSIs, an alternative is to use (C-*,C-*) S-PMSIs 1519 instead of I-PMSIs. (See [RFC6625], as well as Sections 7.2.2, 1520 7.3.2, and 7.4.4 of this document.) This has much the same effect in 1521 the data plane, and there are no restrictions on the type of unicast 1522 tunnel that can be used for instantiating S-PMSIs. 1524 Section 6.4.5 of [RFC6513] describes a way to support VPNs using 1525 I-PMSIs that are instantiated by IR, using no S-PMSIs, but using 1526 "explicit tracking" to ensure that a C-flow goes only to egress PEs 1527 that have receivers for it. This document does not provide 1528 procedures to support extranet using that model. 1530 6. When PIM is the PE-PE C-multicast Control Plane 1532 As specified in [RFC6513], when PIM is used as the PE-PE C-multicast 1533 control plane for a particular MVPN, there is a "Multidirectional 1534 Inclusive Provider Multicast Serivce Interface" (MI-PMSI) for that 1535 MVPN, and all the PEs of that MVPN must be able to send and receive 1536 on that MI-PMSI. Associated with each VRF of the MVPN is a PIM 1537 C-instance, and the PIM C-instance treats the MI-PMSI as if it were a 1538 LAN interface. That is, the "ordinary" PIM procedures run over the 1539 MI-PMSI just as they would over a real LAN interface, except that the 1540 data plane and control plane "RPF checks" need to be modified. 1541 Section 5.2 of [RFC6513] specifies the RPF check modifications for 1542 non-extranet MVPN service. 1544 For example, suppose that there are two VPNs, VPN-S and VPN-R. In 1545 the absence of extranet support, all the VRFs of VPN-S are connected 1546 via one MI-PMSI (call it "the VPN-S MI-PMSI"), and all the VRFs of 1547 VPN-R are connected via another ("the VPN-R MI-PMSI"). If we want to 1548 provide extranet service in which the extranet C-sources are attached 1549 to some set of VPN-S VRFs, while the extranet C-receivers are 1550 attached to some set of VPN-R VRFs, then we have two choices: 1552 1. either the VPN-R VRFs need to join the VPN-S MI-PMSI, or 1554 2. the VPN-S VRFs need to join the VPN-R MI-PMSI. 1556 The first choice is used to support the "single PMSI per C-flow" 1557 transmission model. The second choice is used to support the 1558 "multiple PMSIs per C-flow" transmission model. 1560 Procedures for both models are described below. 1562 To support these models, it must be possible to determine which 1563 I-PMSI A-D routes are associated with the VPN-S I-PMSI, and which are 1564 associated with the VPN-R I-PMSI. Procedures are given for assigning 1565 RTs to these routes in a way that makes this determination possible. 1567 Both models allow the use of S-PMSIs to carry multicast data traffic. 1568 If a VRF containing receivers can receive from multiple MI-PMSIs, 1569 each S-PMSI must be uniquely associated with a particular MI-PMSI. 1570 Procedures are given for assigning RTs to these routes in a way that 1571 makes this determination possible. 1573 All the procedures specified in Sections 3, 4, and 5 still apply. 1575 Note that there are no special extranet procedures for Inter-AS 1576 I-PMSI A-D routes or for Leaf A-D routes. Source Active A-D routes 1577 are not used when PIM is the PE-PE C-multicast protocol. 1579 6.1. Provisioning VRFs with RTs 1581 6.1.1. Incoming and Outgoing Extranet RTs 1583 In the absence of extranet service, suppose that each VRF of a given 1584 VPN, call it VPN-S, is configured with RT-S as its import and export 1585 RT, and that each VRF of a second VPN, call it VPN-R, is configured 1586 with RT-R as its import and export RT. We will refer to RT-S and 1587 RT-R as "non-extranet RTs". 1589 Now suppose that VPN-S contains some extranet C-sources, and VPN-R 1590 contains some extranet C-receivers that are allowed by policy to 1591 receive extranet C-flows from the VPN-S extranet C-sources. 1593 To set up this S-to-R extranet, it is REQUIRED to provision an 1594 additional RT, call it RT-S-to-R, whose value is, in general, 1595 distinct from RT-S and RT-R. 1597 A VPN-S VRF that contains extranet C-sources allowed to transmit to 1598 VPN-R MUST be configured with RT-S-to-R as an "Outgoing Extranet RT". 1600 A VPN-R VRF that contains extranet C-receivers allowed to received 1601 from VPN-S MUST be configured with RT-S-to-R as an "Incoming Extranet 1602 RT". 1604 Note that the terms "Incoming" and "Outgoing" in this context refer 1605 to the direction of multicast data packets relative to the VRF. 1607 The Incoming Extranet RTs and Outgoing Extranet RTs that are 1608 configured for a given VRF serve as import RTs for that VRF. They 1609 also serve as export RTs, but only for specific routes as specified 1610 in Section 6.1.2 below. 1612 Note that any VRF that contains both extranet C-sources and extranet 1613 C-receivers MUST be configured with both Outgoing and Incoming 1614 Extranet RTs. 1616 A VRF MAY be configured with more than one Incoming and/or Outgoing 1617 Extranet RT. 1619 If it happens to be the case that all C-sources in VPN-S are extranet 1620 C-sources allowed to transmit to VPN-R, then VPN-S VRFs MAY be 1621 configured such that RT-S is both a non-extranet RT and an Outgoing 1622 Extranet RT, and VPN-R VRFs MAY be configured such that RT-S is an 1623 Incoming Extranet RT. 1625 6.1.2. UMH-eligible Routes and RTs 1627 Suppose R1 is a route, exported from a VPN-S VRF, matching an 1628 extranet C-source that is allowed by policy to transmit to VPN-R. 1629 Then R1 MUST carry the Outgoing Extranet RT used for the S-to-R 1630 extranet. This will cause the route to be imported into the VPN-R 1631 VRFs that have extranet C-receivers that are allowed by policy to 1632 receive from VPN-S. 1634 The rules of Section 4 regarding route targets and ambiguous 1635 addresses still apply. 1637 6.1.3. PIM C-Instance Reverse Path Forwarding Determination 1639 Suppose a PIM control message, call it M, is received by a given VRF 1640 V, from a particular P-tunnel T. In order to process control message 1641 M, the PIM C-instance associated with VRF V may need to do an "RPF 1642 determination" (see Section 5.2.2 of RFC 6513) for a particular IP 1643 prefix S. RPF determination is based upon the rules for UMH 1644 selection as specified in Section 5.1 of RFC 6513. 1646 This document adds an additional constraint on the UMH selection 1647 procedure. When doing RPF determination for a PIM control message 1648 received over a P-tunnel, a route matching prefix S is not considered 1649 to be eligible for UMH selection unless there is an RT, call it RT1, 1650 configured as one of V's Outgoing Extranet RTs, such that the 1651 following two conditions both hold: 1653 1. The route matching S is exported from VRF V carrying RT1, and 1655 2. An I-PMSI A-D route advertising P-tunnel T (in its PTA) has been 1656 imported into VRF V, and that I-PMSI A-D route carries RT1. 1658 6.2. Single PMSI per C-flow Model 1660 In this model, if a VPN-S VRF has extranet multicast C-sources, and a 1661 VPN-R VRF has extranet multicast C-receivers allowed by policy to 1662 receive from the C-sources in the VPN-S VRF, then the VPN-R VRF joins 1663 the MI-PMSI that VPN-S uses for its non-extranet traffic. 1665 6.2.1. Forming the MI-PMSIs 1667 Consider a VPN-S VRF that has extranet C-sources. Per [RFC6513], 1668 each VPN-S VRF must originate an Intra-AS I-PMSI A-D route containing 1669 a PMSI Tunnel Attribute (PTA) specifying the P-tunnel to be used as 1670 part of the VPN-S MI-PMSI. In the absence of extranet service, this 1671 route carries the VRF's non-extranet RT, RT-S. When extranet service 1672 is provided (using the "single PMSI per C-flow" model), this route 1673 MUST also carry each of the VRF's Outgoing Extranet RTs. 1675 Consider a VPN-R VRF that has extranet C-receivers. Per [RFC6513], 1676 each VPN-R VRF must originate an Intra-AS I-PMSI A-D route containing 1677 a PTA specifying the P-tunnel to be used as part of the VPN-R MI- 1678 PMSI. This route carries the VRF's non-extranet RT RT-R. When 1679 extranet service is provided (using the "single PMSI per C-flow" 1680 model), the VPN-R VRF MUST also originate one or more additional 1681 Intra-AS I-PMSI A-D routes. It MUST originate one additional Intra- 1682 AS I-PMSI A-D route for each Incoming Extranet RT with which it has 1683 been configured; each such route will carry exactly one of the 1684 configured Incoming Extranet RTs. 1686 Note that when a VRF originates more than one Intra-AS I-PMSI A-D 1687 route, each of them MUST contain a different RD in its NLRI. In 1688 addition, we add the requirement that any pair of such routes MUST 1689 NOT contain an RT in common. 1691 A VRF with extranet C-sources MUST join the P-tunnels advertised in 1692 the imported I-PMSI A-D routes that carry its non-extranet RT or any 1693 of its Outgoing Extranet RTs. This set of P-tunnels will be treated 1694 as instantiating a single MI-PMSI, and the associated PIM C-instance 1695 will treat that MI-PMSI as a single LAN, and will run PIM procedures 1696 on that LAN, as specified in [RFC6513]. The fact that the MI-PMSI 1697 attaches to VRFs of different VPNs is not known to the PIM C-instance 1698 of the VRF containing the sources. 1700 A VRF with extranet C-receivers MUST join the P-tunnels advertised in 1701 all the imported I-PMSI A-D routes. The set of P-tunnels advertised 1702 in the I-PMSI A-D routes that carry a particular Incoming Extranet RT 1703 are treated as instantiating a particular MI-PMSI. So a VRF with 1704 C-receivers will "see" several MI-PMSIs, one corresponding to the 1705 non-extranet, and as many as one for each configured Incoming 1706 Extranet RT. The PIM C-instance associated with the VRF will treat 1707 each of these MI-PMSIs as a separate LAN interface. 1709 As an example, suppose: 1711 o All VPN-R VRFs are configured with RT-R as a non-extranet import 1712 and export RT, 1714 o VPN-R VRFs with extranet receivers are configured with RT-S-to-R 1715 as an Incoming Extranet RT, 1717 o VPN-S VRFs with extranet transmitters are configured: 1719 * with RT-S as a non-extranet import and export RT 1721 * with a list of IP addresses that are the addresses of the 1722 extranet sources 1724 * with RT-S-to-R as an Outgoing Extranet RT 1726 Then VPN-S VRFs will export UMH-eligible routes matching extranet 1727 C-sources, and these routes will carry both RT-S and RT-S-to-R. Each 1728 VPN-S VRF will also export an Intra-AS I-PMSI A-D route that carries 1729 both RT-S and RT-S-to-R. 1731 VPN-R VRFs will originate and export two Intra-AS I-PMSI A-D routes: 1732 one carrying RT-R, and one carrying RT-S-to-R. The Intra-AS I-PMSI 1733 A-D route with RT-S-to-R will be imported into the VPN-S VRFs. 1735 VPN-R will regard all the I-PMSI A-D routes it has exported or 1736 imported with RT-S-to-R as part of a single MI-PMSI. VPN-R will 1737 regard all the I-PMSI A-D routes it has exported or imported with 1738 RT-R as part of a second MI-PMSI. The PIM C-instance associated with 1739 a VPN-R VRF will treat the two MI-PMSIs as two separate LAN 1740 interfaces. However, the VPN-S VRFs will regard all the I-PMSI A-D 1741 routes imported with RT-S or RT-S-to-R as establishing only a single 1742 MI-PMSI. One can think of this as follows: the VPN-R VRFs have 1743 joined the VPN-S MI-PMSI, as well as the VPN-R MI-PMSI. 1745 Extranets consisting of more than two VPNs are easily supported as 1746 follows. Suppose there are three VPNs, VPN-A, VPN-B, and VPN-C. 1747 VPN-A and VPN-B have extranet C-sources, and VPN-C contains receivers 1748 for both VPN-A extranet C-sources and VPN-B extranet C-sources. In 1749 this case, the VPN-C VRFs that have receivers for both VPN-A and 1750 VPN-B sources may be provisioned as follows. These VPN-C VRFs may be 1751 provisioned with RT-C as a non-extranet RT, and with RT-A-to-C and 1752 RT-B-to-C as Incoming Extranet RTs. In this case, the VPN-C VRFs 1753 that are so provisioned will originate three Intra-AS I-PMSI A-D 1754 routes (each with a different RD in its NLRI), each of which carries 1755 exactly one of the three RTs just mentioned. The VPN-B VRFs with 1756 extranet C-sources will be provisioned with RT-B-to-C as an Outgoing 1757 Extranet RT, and the VPN-A VRFs are provisioned with RT-A-to-C as an 1758 Outgoing Extranet RT. The result will be that the PIM C-instance 1759 associated with a VPN-C VRF will see three LAN interfaces: one for 1760 the non-extranet, one for each of the two extranets. This 1761 generalizes easily to the case where there are VPN-C receivers in n 1762 different extranets (i.e., receiving extranet flows whose sources are 1763 in n different VPNs). 1765 Suppose again that there are there are three VPNs, VPN-A, VPN-B, and 1766 VPN-C. But in this example, VPN-A is the only one with extranet 1767 sources, while VPN-B and VPN-C both have receivers for the VPN-A 1768 extranet sources. This can be provisioned as either one extranet or 1769 as two. 1771 To provision it as one extranet, the VPN-A VRFs are configured with 1772 one Outgoing Extranet RT, call it "RT-A-extranet". The VPN-B and 1773 VPN-C VRFs with extranet receivers will be provisioned with RT- 1774 A-extranet as Incoming Extranet RT. Thus the VPN-B and VPN-C VRFs 1775 will each originate two Intra-AS I-PMSI A-D routes, one for non- 1776 extranet, and one for the extranet. The Intra-AS I-PMSI A-D route, 1777 from a given VRF, for the extranet will carry RT-A-extranet, but will 1778 not share any RT with the non-extranet A-D routes exported from the 1779 same VRF. 1781 The result is that the VPN-B and VPN-C VRFs each belong to two MI- 1782 PMSIs, one for the extranet and one for the intranet. The MI-PMSI 1783 for the extranet attaches VPN-A VRFs, VPN-B VRFs, and VPN-C VRFs. 1785 Alternatively, one could provision the VPN-A VRFs so that some UMH- 1786 eligible extranet source routes carry an RT which we will call "RT-A- 1787 to-B", and some carry an RT which we will call "RT-A-to-C". The 1788 VPN-A VRFs would be configured with both of these as Outgoing 1789 Extranet RTs. To allow an extranet flow from a VPN-A source to have 1790 both VPN-B and VPN-C receivers, the UMH-eligible route for that 1791 source would carry both RTs. VPN-B VRFs (but not VPN-C VRFs) would 1792 be provisioned with RT-A-to-B as an Incoming Extranet RT. VPN-C VRFs 1793 (but not VPN-B VRFs) would be provisioned with RT-A-to-C as an an 1794 Incoming Extranet RT. 1796 Following the rules above, if any VPN-A extranet source is to have 1797 both VPN-B and VPN-C receivers, the VPN-B and VPN-C VRFs will each 1798 originate two I-PMSI A-D routes, one for extranet and one for non- 1799 extranet. The single Intra-AS I-PMSI A-D route originated by the 1800 VPN-A VRFs will have both RT-A-to-B and RT-A-to-C among its RTs (as 1801 well as VPN-A's non-extranet RT). The extranet I-PMSI A-D route 1802 originated from a VPN-B VRF would have RT-A-to-B, and the extranet 1803 I-PMSI A-D route originated from a VPN-C VRF would have RT-A-to-C. 1805 If a given VRF contains both extranet C-receivers and extranet 1806 C-sources, the procedures described above still work, as the VRF will 1807 be configured with both Incoming Extranet RTs and Outgoing Extranet 1808 RTs; the VRF functions both as a VPN-S VRF and as a VPN-R VRF. 1810 6.2.2. S-PMSIs 1812 When PIM is used as the PE-PE C-multicast control plane, every S-PMSI 1813 is considered to be part of the "emulated LAN" that "corresponds" to 1814 a particular MI-PMSI. 1816 When the bindings of C-flows to particular S-PMSIs are announced via 1817 S-PMSI Join Messages ([RFC6513], Section 7) sent on the MI-PMSI, the 1818 S-PMSI is considered to be part of the same LAN interface as the 1819 corresponding MI-PMSI. 1821 When the bindings of C-flows to particular S-PMSIs are announced via 1822 S-PMSI A-D routes, then any S-PMSI A-D route exported from that VRF 1823 MUST have an RT in common with exactly one of the Intra-AS A-D routes 1824 exported from that VRF, and this MUST be one of the VRF's Outgoing 1825 Extranet RTs. Further, the S-PMSI A-D route MUST NOT have an RT in 1826 common with any other Intra-AS A-D route exported from a VRF on the 1827 same PE. A given S-PMSI A-D route will be considered to "correspond" 1828 to the MI-PMSI of the Intra-AS I-PMSI A-D route (originated from the 1829 same PE) with which it shares an RT. 1831 The MI-PMSI that corresponds to a given S-PMSI is determined as 1832 follows: 1834 o If there is an Intra-AS I-PMSI A-D route originated by the same PE 1835 that originated the S-PMSI A-D route, and if the those two routes 1836 have an RT in common, and if that RT is one of the VRF's Incoming 1837 Extranet RTs, then the S-PMSI corresponds to the I-PMSI associated 1838 with that Intra-AS I-PMSI A-D route. 1840 o Otherwise, if there is an Inter-AS I-PMSI A-D route originated in 1841 the same AS as the S-PMSI A-D route, and if the those two routes 1842 have an RT in common, and if that RT is one of the VRF's Incoming 1843 Extranet RTs, then the S-PMSI corresponds to the I-PMSI associated 1844 with that Inter-AS I-PMSI A-D route. 1846 o Otherwise, there must be a configuration error (a violation of the 1847 requirements of Sections 3, 4, and 5 of this document). 1849 When wildcard S-PMSIs are used, the rules given in [RFC6625] for 1850 determining whether a given S-PMSI A-D route is a "match for 1851 reception" to a given (C-S,C-G) or (C-*,C-G) are modified as follows: 1853 A given S-PMSI A-D route MUST NOT be considered to be a "match for 1854 reception" for a given (C-S,C-G) or (C-*,C-G) state UNLESS that 1855 S-PMSI A-D route "corresponds" (as defined above) to the MI-PMSI 1856 that is the incoming interface for the given state. 1858 The rules given in [RFC6625] for determining whether a given S-PMSI 1859 A-D route is a "match for transmission" are unchanged. 1861 6.2.3. Sending PIM Control Packets 1863 Suppose a PE, say PE1, receives a PIM Join(S,G) from a CE, over a VRF 1864 interface that is associated with a VPN-R VRF. The PE does the RPF 1865 check for S by looking up S in the VPN-R VRF. The PIM C-instance 1866 associated with that VRF must determine the correct P-tunnel over 1867 which to send a PIM Join(S,G) to other PEs. 1869 To do this, PE1 finds, in the VRF associated with the interface over 1870 which the Join was received, the selected UMH route for S, following 1871 the procedures of Section 5.1 of [RFC6513]. PE1 determines the set 1872 of RTs carried by that route. PE1 then checks to see if there is an 1873 Intra-AS I-PMSI A-D route, currently originated by PE1, that has an 1874 RT in common with the selected UMH route for S. 1876 If the rules of Sections 3, 4, and 5 have been followed, each of 1877 PE1's selected UMH routes will share an RT with a single one of PE1's 1878 currently originated Intra-AS I-PMSI A-D routes. If this is so, the 1879 Join is sent on the P-tunnel advertised in the PTA of that route. 1880 Otherwise, the Join MUST NOT be sent. 1882 In essence, this procedure makes the RPF check for C-S resolve to the 1883 MI-PMSI that is serving as the next hop "interface" to C-S. 1885 If a PE receives a PIM Join(*,G) from a CE, the procedure for doing 1886 the RPF check is the same, except that the selected UMH route will be 1887 a route to the C-RP associated with the C-G group. 1889 6.2.4. Receiving PIM Control Packets 1891 When a PIM C-instance receives a PIM control message from a P-tunnel, 1892 it needs to identify the message's "incoming interface". This 1893 incoming interface is the MI-PMSI of which the P-tunnel is a part. 1895 6.2.5. Sending and Receiving Data Packets 1897 The rules for choosing the PMSI on which to send a multicast data 1898 packet are as specified in [RFC6513] and [RFC6625], with one new 1899 restriction: a VPN-S VRF always transmits a multicast data packet 1900 either on the VPN-S MI-PMSI or on an S-PMSI that corresponds to the 1901 VPN-S MI-PMSI. From the perspective of the PIM C-instance, there is 1902 only one outgoing interface. 1904 When a PIM C-instance receives a multicast data packet from a given 1905 P-tunnel, and that P-tunnel is being used to instantiate an MI-PMSI, 1906 the MI-PMSI of which the P-tunnel is a part (see Sections 6.2.1 and 1907 6.2.2) is considered to be the packet's "incoming interface". If the 1908 packet is received on a P-tunnel that was advertised in an S-PMSI A-D 1909 route, the packet's "incoming interface" is the MI-PMSI to which that 1910 S-PMSI route corresponds, as defined in Section 6.2.2. Ordinary PIM 1911 rules for data plane RPF check apply. 1913 Following ordinary PIM procedures, packets arriving from an 1914 unexpected incoming interface are discarded. This eliminates any 1915 problems due to the ambiguities described in Sections 2.1 and 2.2. 1917 6.3. Multiple PMSIs per C-flow Model 1919 In this model, if a VPN-S VRF has extranet multicast C-sources, and a 1920 VPN-R VRF has extranet multicast C-receivers allowed by policy to 1921 receive from the C-sources in the VPN-S VRF, then the VPN-S VRF joins 1922 the MI-PMSI that VPN-R uses for its non-extranet traffic. 1924 In the "single PMSI per C-flow" transmission model (as described in 1925 Section 6.2), a PE that needs to transmit a multicast data packet to 1926 a set of other PEs transmits the packet on a single PMSI. This means 1927 that if a packet needs to be transmitted from a VPN-A VRF and 1928 received at a VPN-B VRF and a VPN-C VRF, there must be some P-tunnel 1929 from which the VPN-B and VPN-C VRFs can both receive packets. 1931 In the "multiple PMSIs per C-flow" transmission model, a PE that 1932 needs to transmit a multicast data packet to a set of other PEs may 1933 transmit the packet on several different PMSIs. (Of course, any 1934 given packet is transmitted only once on a given P-tunnel.) For 1935 example, if a C-flow (C-S,C-G) has a VPN-A C-source, a VPN-B 1936 receiver, and a VPN-C receiver, there could be one PMSI that the 1937 VPN-A VRF uses to transmit the packet to the VPN-B VRFs, and another 1938 PMSI that the VPN-A VRF uses to transmit the packet to the VPN-C 1939 VRFs. 1941 6.3.1. Forming the MI-PMSIs 1943 Consider a VPN-R VRF that has extranet C-receivers. Per [RFC6513], 1944 each VPN-R VRF must originate an Intra-AS I-PMSI A-D route containing 1945 a PMSI Tunnel Attribute (PTA) specifying the P-tunnel to be used as 1946 part of the VPN-R MI-PMSI. In the absence of extranet service, this 1947 route carries the VRF's non-extranet RT, RT-R. When extranet service 1948 is provided (using the "single PMSI per C-flow" model), this route 1949 MUST also carry each of the VRF's Incoming Extranet RTs. 1951 Consider a VPN-S VRF that has extranet C-sources. Per [RFC6513], 1952 each VPN-S VRF must originate an Intra-AS I-PMSI A-D route containing 1953 a PTA specifying the P-tunnel to be used as part of the VPN-S MI- 1954 PMSI. This route carries the VRF's non-extranet RT RT-S. When 1955 extranet service is provided using the "multiple PMSI per C-flow" 1956 model, the VPN-S VRF MUST also originate one or more additional 1957 Intra-AS I-PMSI A-D routes. It MUST originate one additional Intra- 1958 AS I-PMSI A-D route for each outgoing extranet RT with which it has 1959 been configured; each such route will have a distinct RD, and will 1960 carry exactly one of the configured Outgoing Extranet RTs. 1962 As with the "single PMSI per C-flow" transmission model, VRFs 1963 containing extranet C-receivers need to import UMH-eligible extranet 1964 C-source routes from VRFs containing C-sources. This is ensured by 1965 the rules of 3, 4, and 5. 1967 However, in the "multiple PMSIs per C-flow model", a VRF containing 1968 only C-receivers originates only a single Intra-AS I-PMSI A-D route, 1969 carrying the non-extranet RT and all the Incoming Extranet RTs. 1971 When a VRF containing C-receivers imports Intra-AS I-PMSI A-D routes 1972 that carry the non-extranet RT or one of the Incoming Extranet RTs, 1973 the P-tunnels specified in the PTA of all such routes are considered 1974 to be part of the same MI-PMSI. I.e., the associated PIM C-instance 1975 will treat them as part of a single interface. 1977 In this model, it is the VRF containing extranet C-sources that MUST 1978 originate multiple Intra-AS I-PMSI A-D routes. Each such route MUST 1979 have a distinct RD, and the set of RTs carried by any one of these 1980 routes MUST be disjoint from the set carried by any other. There 1981 MUST be one such route for each of the VRF's Outgoing Extranet RTs, 1982 and each such route MUST carry exactly one of the VRF's Outgoing 1983 Extranet RTs. The VRFs containing extranet C-sources MUST also 1984 import all the A-D routes originated by the VRFs containing extranet 1985 C-receivers. If a set of originated and/or imported Intra-AS I-PMSI 1986 A-D routes have an RT in common, and that RT is one of the VRF's 1987 Outgoing Export RTs, then those routes are considered to be "about" 1988 the same MI-PMSI. The PIM C-instance of the VRF treats each MI-PMSI 1989 as a LAN Interface. 1991 In effect, if VPN-S has only extranet C-sources and VPN-R has only 1992 extranet C-receivers, this model has the VPN-S VRFs join the VPN-R 1993 MI-PMSI. The VPN-S VRFs will thus be attached to multiple MI-PMSIs, 1994 while the VPN-R VRFs are attached to only one. The fact that the 1995 VPN-R MI-PMSI is attached to VPN-S VRFs is not known to the PIM 1996 C-instance at the VPN-R VRFs. 1998 If a VPN-A VRF has extranet C-sources allowed to send to C-receivers 1999 in a VPN-B VRF, and the VPN-B VRF has C-sources allowed to send to 2000 C-receivers in the VPN-A VRF, the above procedures still work as 2001 specified. 2003 Following normal PIM procedures, when the PIM C-instance at a VRF 2004 with extranet C-sources receives a Join(C-S,C-G) or a Join(C-*,C-G) 2005 over an MI-PMSI, it may create (C-S,C-G) or (C-*,C-G) state, and the 2006 MI-PMSI over which the Join was received may be added to the set of 2007 outgoing interfaces for that multicast state. If n MI-PMSIs are 2008 added to the outgoing interface list for a particular multicast 2009 state, a multicast data packet may need to be replicated n times, and 2010 transmitted once on each of the n MI-PMSIs. 2012 Since the all multicast data packets received from another PE are 2013 received over a single emulated LAN, it is not necessary to have any 2014 special procedures to determine a packet's "incoming interface". The 2015 ambiguities described in Section 2.1 and Section 2.2 do not occur, 2016 because a VPN-R VRF can only receive multicast data traffic that has 2017 been requested by a VPN-R VRF. 2019 7. When BGP is the PE-PE C-multicast Control Plane 2021 This document assumes that if BGP is used as the PE-PE C-multicast 2022 control plane, the "Single PMSI per C-flow" model is used. 2023 Procedures for providing the "Multiple PMSIs per C-flow" model with 2024 BGP C-multicast are outside the scope of this document. 2026 When BGP is used as the C-multicast control plane, the Single PMSI 2027 per C-flow model may be used either with or without "extranet 2028 separation". (Recall that "extranet separation" means that no 2029 P-tunnel can carry both traffic from extranet sources and traffic 2030 from non-extranet sources.) In either case, the data traffic may be 2031 carried on inclusive tunnels only, or on selective tunnels only 2032 (known as the "S-PMSI only" model), or on a combination of inclusive 2033 and selective tunnels. This is determined by provisioning. The 2034 procedures specified below support all three choices. 2036 Note that there are no special extranet procedures for Inter-AS 2037 I-PMSI A-D routes or for Leaf A-D routes. 2039 7.1. Originating C-multicast Routes 2041 This section applies whether extranet separation is used or not. 2043 When it is necessary to originate a C-multicast Source Tree Join for 2044 (C-S,C-G), a PE must follow the procedures of Section 11.1.3 2045 ("Constructing the rest of the C-multicast route") of [RFC6514] to 2046 find the selected UMH route for C-S. When it is necessary to 2047 originate a C-multicast Shared Tree Join for (C-*,C-G),where C-G is 2048 an ASM group, a PE must follow the procedures of that section to find 2049 the selected UMH route for C-G's C-RP. 2051 Section 11.1.3 of [RFC6514] specifies how information from the 2052 selected UMH route is used to find an Intra-AS I-PMSI A-D route or an 2053 Inter-AS I-PMSI A-D route. Information from that I-PMSI A-D route is 2054 then used to construct part of the C-multicast route. 2056 For extranet, this specification modifies the procedures of 2057 Section 11.1.3 of [RFC6514] as follows. The rules given in 2058 Section 7.4.5 ("I-PMSI A-D Routes") of this document are used to find 2059 the Inter-AS I-PMSI A-D route or an Intra-AS I-PMSI A-D route that 2060 "corresponds to" the selected UMH route. (That is, the rules of 2061 Section 7.4.5 of this document replace the rules given in 2062 Section 11.1.3 of [RFC6514] for finding the Inter-AS or Intra-AS 2063 I-PMSI A-D route.) 2065 Information from this I-PMSI A-D route is then used, as specified in 2066 Section 11.1.3 of [RFC6514], to construct the C-multicast route. 2068 7.2. Originating A-D Routes Without Extranet Separation 2070 7.2.1. Intra-AS I-PMSI A-D Routes 2072 Consider a VRF, call it VRF-S, that contains extranet C-sources, and 2073 that exports UMH-eligible routes matching those C-sources. The VRF 2074 may also originate and export an Intra-AS I-PMSI A-D route. 2076 As specified in [RFC6514], if exactly one Intra-AS I-PMSI A-D route 2077 is originated by and exported from VRF-S, the RTs carried by that 2078 route MUST be chosen such that every VRF that imports a UMH-eligible 2079 route from VRF-S also imports this Intra-AS I-PMSI A-D route. 2081 If inclusive P-tunnels are being used to carry extranet C-flows, 2082 there are additional requirements on the way the RTs carried by the 2083 Intra-AS I-PMSI A-D routes must be chosen, as specified in the 2084 following paragraph. 2086 If VRF-S is using inclusive P-tunnels, but is not using extranet 2087 separation, there is one inclusive P-tunnel rooted at VRF-S, and this 2088 tunnel carries both extranet and non-extranet C-flows. This 2089 inclusive tunnel is identified in the PMSI Tunnel Attribute (PTA) of 2090 the Intra-AS I-PMSI A-D route originated from VRF-S. The set of RTs 2091 carried by this Intra-AS I-PMSI A-D route MUST be chosen so as to 2092 ensure that every VRF that imports a UMH-eligible route from this 2093 VRF-S also imports this Intra-AS I-PMSI A-D route. Further, the set 2094 of RTs carried by this Intra-AS I-PMSI A-D route MUST be chosen such 2095 that it has at least one RT in common with every UMH-eligible route 2096 that is exported from the VRF. 2098 7.2.2. S-PMSI A-D Routes 2100 Let R-SP be an S-PMSI A-D route that is exported from VRF-S. Suppose 2101 that R-SP is used to bind some or all of the extranet C-flows from a 2102 given extranet C-source to a given selective P-tunnel. Let R-UMH be 2103 a UMH-eligible route that is exported from VRF-S and that matches the 2104 given extranet C-source. Then R-SP and R-UMH MUST have at least one 2105 RT in common. Further, the RTs carried by these two routes MUST be 2106 such that every VRF that imports R-UMH also imports R-SP. These 2107 rules apply whether or not R-SP uses wildcards [RFC6625]. 2109 An implementation MUST allow the set of RTs carried by the S-PMSI A-D 2110 routes to be specified by configuration. In the absence of such 2111 configuration, an S-PMSI A-D route originated by a given VRF X MUST 2112 carry a default set of RTs, as specified by the following rules: 2114 1. By default an S-PMSI A-D route originated by VRF X for a given 2115 (C-S,C-G) or (C-S,C-*) carries the same RT(s) as the UMH-eligible 2116 route originated by VRF X that matches C-S. 2118 2. By default an S-PMSI A-D route originated by VRF X for a given 2119 (C-*,C-G) carries as its RTs a set union of all RT(s) of the UMH- 2120 eligible route(s) matching the multicast C-sources contained in 2121 VRF X that could originate traffic for that C-G. Moreover, if 2122 the VRF contains (as defined in Section 1.1) the C-RP of C-G, 2123 then this set union also includes the RT(s) of the UMH-eligible 2124 route matching C-RP, and of the unicast VPN-IP route matching 2125 C-RP. 2127 3. By default, if a (C-*,C-*) S-PMSI A-D route originated by VRF X 2128 is to be used for both extranet and non-extranet traffic, it 2129 carries the same RTs that would be carried (as specified in 2130 Section 7.2.1) by an I-PMSI A-D route originated by VRF X if that 2131 I-PMSI A-D route were advertising an inclusive P-tunnel for 2132 carrying both extranet and non-extranet traffic. In general, a 2133 given VRF would not originate both (a) an S-PMSI A-D route 2134 advertising a (C-*,C-*) selective P-tunnel for both extranet and 2135 non-extranet traffic and (b) an I-PMSI A-D route advertising an 2136 inclusive P-tunnel for both extranet and non-extranet traffic, as 2137 the inclusive P-tunnel would not get used in that case. 2139 7.2.3. Source Active A-D Routes 2141 7.2.3.1. When Inter-Site Shared Trees Are Used 2143 This section applies when Inter-Site Shared Trees are used, as 2144 specified in [RFC6514] Section 13. 2146 If VRF-S exports a Source Active A-D route that contains C-S in the 2147 Multicast Source field of its NLRI, and if that VRF also exports a 2148 UMH-eligible route matching C-S, the Source Active A-D route MUST 2149 carry at least one RT in common with the UMH-eligible route. The RT 2150 MUST be chosen such that the following condition holds: if VRF-R 2151 contains an extranet C-receiver allowed by policy to receive extranet 2152 traffic from C-S, then VRF-R imports both the UMH-eligible route and 2153 the Source Active A-D route. 2155 By default, a Source Active A-D route for a given (C-S,C-G), exported 2156 by a given VRF, carries the same set of RTs as the UMH-eligible route 2157 matching C-S that is exported from that VRF. 2159 7.2.3.2. When Inter-Site Shared Trees Are Not Used 2161 This section applies when Inter-Site Shared Trees are not used, as 2162 specified in [RFC6514] Section 14. 2164 Suppose a VRF, say VRF-X, contains the C-RP for a given extranet 2165 C-group, say C-G. If C-S is an active source for C-G, then following 2166 the procedures of Section 14.1 of [RFC6514], VRF-X may export a 2167 Source Active A-D route that contains C-S in the Multicast Source 2168 field of its NLRI. This document replaces the rule for constructing 2169 the RT(s) carried by such a route, specified in Section 14.1 of 2170 [RFC6514], with the following. VRF-X MUST be configured such that 2171 the Source Active A-D route for (C-S,C-G) carries the same set of RTs 2172 as the UMH-eligible route matching C-S that is exported from the 2173 VRF(s) containing C-S. This way, if a VRF, say VRF-R, contains an 2174 extranet C-receiver allowed by policy to receive extranet traffic 2175 from C-S, then VRF-R imports both the UMH-eligible route and the 2176 Source Active A-D route. 2178 7.3. Originating A-D Routes With Extranet Separation 2180 If a VRF contains both extranet C-sources and non-extranet C-sources, 2181 it MUST be configured with both a "default RD" and an "extranet RD" 2182 (see Section 1.3). The use of these RDs is explained in the 2183 following sub-sections. 2185 7.3.1. Intra-AS I-PMSI A-D Routes 2187 This section applies when VRF-S is using extranet separation, AND 2188 when VRF-S is using an inclusive P-tunnel to carry some or all of the 2189 extranet C-flows that it needs to transmit to other VRFs. 2191 If VRF-S contains both extranet C-sources and non-extranet C-sources, 2192 and if inclusive P-tunnels are used to carry both extranet C-flows 2193 and non-extranet C-flows, then there MUST be two inclusive tunnels 2194 from VRF-S, one of which is to be used only to carry extranet C-flows 2195 (the "extranet inclusive P-tunnel"), and one of which is to be used 2196 only to carry non-extranet C-flows (the "non-extranet inclusive 2197 P-tunnel"). 2199 In this case, the VRF MUST originate two Intra-AS I-PMSI A-D routes. 2200 Their respective NLRIs MUST of course have different RDs. One of the 2201 Intra-AS I-PMSI A-D routes identifies the extranet inclusive P-tunnel 2202 in its PTA. This route MUST have the VRF's "extranet RD" in its 2203 NLRI. The other route identifies the non-extranet inclusive P-tunnel 2204 in its PTA. This route MUST have the VRF's "default RD" in its PTA. 2206 If VRF-S uses an inclusive P-tunnel for carrying extranet traffic, 2207 but does not use an inclusive P-tunnel for carrying non-extranet 2208 traffic, then of course only a single Intra-AS I-PMSI A-D route need 2209 be originated. The PTA of this route identifies the "extranet 2210 inclusive P-tunnel". The NLRI of that route MUST contain the VRF's 2211 extranet RD. 2213 An Intra-AS I-PMSI A-D route whose PTA identifies an extranet 2214 inclusive P-tunnel MUST carry the Extranet Separation Extended 2215 Community defined in Section 4.5. 2217 The RTs carried by an Intra-AS I-PMSI A-D route whose PTA identifies 2218 the "extranet inclusive P-tunnel" MUST be chosen such that the 2219 following condition holds: if a VRF (call it VRF-R) imports a UMH- 2220 eligible route from VRF-S, and if that route matches an extranet 2221 C-source, then VRF-R also imports that Intra-AS I-PMSI A-D route. 2223 Note that when extranet separation is used, it is possible to use an 2224 inclusive P-tunnel for non-extranet traffic while using only 2225 selective P-tunnels for extranet traffic. It is also possible to use 2226 an inclusive P-tunnel for extranet traffic while using only selective 2227 P-tunnels for non-extranet traffic. 2229 7.3.2. S-PMSI A-D Routes 2231 Let R-SP be an S-PMSI A-D route that is exported from VRF-S. Suppose 2232 that R-SP is used to bind some or all of the extranet C-flows from a 2233 given extranet C-source to a given selective P-tunnel. Let R-UMH be 2234 a UMH-eligible route that is exported from VRF-S and that matches the 2235 given extranet C-source. Then R-SP and R-UMH MUST have at least one 2236 RT in common. Further, the RTs carried by these two routes MUST be 2237 such that every VRF that imports R-UMH also imports R-SP. These 2238 rules apply whether or not R-SP uses wildcards [RFC6625]. 2240 The following rules, specific to the use of extranet separation, 2241 apply: 2243 o A selective P-tunnel MUST NOT carry C-flows from both extranet and 2244 non-extranet C-sources, 2246 o If it is desired to use a (C-*,C-*) S-PMSI to carry extranet 2247 traffic and also to use a (C-*,C-*) S-PMSI to carry non-extranet 2248 traffic, then two (C-*,C-*) S-PMSI A-D routes MUST be originated. 2249 These two routes MUST have different RDs in their respective NLRI 2250 fields, and their respective PTAs MUST identify different 2251 P-tunnels. If the route advertises a P-tunnel that carries only 2252 non-extranet traffic, the route's NLRI MUST contain the VRF's 2253 default RD. If the route advertises a P-tunnel that carries only 2254 extranet traffic, the route's NLRI MUST contain the VRF's extranet 2255 RD. 2257 o In the following cases, an S-PMSI A-D route exported from the VRF 2258 MUST have the VRF's extranet RD in its NLRI: 2260 * The S-PMSI A-D route is a (C-S,C-G) or a (C-S,C-*) S-PMSI A-D 2261 route, and C-S is an extranet C-source. 2263 * The S-PMSI A-D route is a (C-*,C-G) S-PMSI A-D route, and C-G 2264 is an extranet C-group. 2266 In all other cases, a (C-S,C-G), (C-S,C-*), or (C-*,C-G) S-PMSI 2267 A-D route MUST have the VRF's default RD in its NLRI. 2269 o A (C-*,C-*) S-PMSI A-D route advertising a P-tunnel that is used 2270 to carry extranet traffic MUST carry the Extranet Separation 2271 Extended Community defined in Section 4.5. 2273 An implementation MUST allow the set of RTs carried by the S-PMSI A-D 2274 routes to be specified by configuration. In the absence of such 2275 configuration, an S-PMSI A-D route originated by a given VRF X MUST 2276 carry a default set of RTs, as specified by the following rules: 2278 1. Rule 1 of Section 7.2.2 applies. 2280 2. By default, if C-G is an extranet C-group, rule 2 of 2281 Section 7.2.2 applies. 2283 3. By default, if a (C-*,C-*) S-PMSI A-D route originated by VRF X 2284 is to be used for extranet traffic, it carries the same RTs that 2285 would be carried (as specified in Section 7.3.1) by an I-PMSI A-D 2286 route originated by VRF X if that I-PMSI A-D route were 2287 advertising an inclusive P-tunnel for carrying extranet traffic. 2288 In general, a given VRF would not originate both an S-PMSI A-D 2289 route advertising a (C-*,C-*) selective P-tunnel for extranet 2290 traffic and an I-PMSI A-D route advertising an inclusive P-tunnel 2291 for extranet traffic, as the inclusive P-tunnel would not get 2292 used in that case. 2294 7.3.3. Source Active A-D Routes 2296 The procedures of Section 7.2.3 apply. 2298 However, if a Source Active A-D route is exported from a given VRF, 2299 and the route contains C-S, where C-S is an extranet C-source, then 2300 the RD of the route's NLRI MUST be the extranet RD of the VRF. 2301 Otherwise the RD is the default RD of the VRF. 2303 7.4. Determining the Expected P-tunnel for a C-flow 2305 This section applies whether extranet separation is used or not. 2307 In the context of a VRF with receivers for a particular C-flow, a PE 2308 must determine the P-tunnel over which packets of that C-flow are 2309 expected to arrive. This is done by finding an I-PMSI or S-PMSI A-D 2310 route that "matches" the flow. The matching A-D route will contain a 2311 PTA that specifies the P-tunnel being used to carry the traffic of 2312 that C-flow. We will refer to this P-tunnel as the "expected 2313 P-tunnel" for the C-flow. (Note that, per [MVPN-IR], if the PTA 2314 specifies an tunnel of type "Ingress Replication" (IR), the 2315 identifier of the P-tunnel is actually the NLRI of the I-PMSI or 2316 S-PMSI A-D route. If the PTA specifies a tunnel type other than IR, 2317 the identifier of the P-tunnel is found in the "tunnel identifier" 2318 field of the PTA.) 2320 A PE that needs to receive a given (C-S,C-G) or (C-*,C-G) C-flow MUST 2321 join the expected P-tunnel for that C-flow, and the PE MUST remain 2322 joined to the P-tunnel as long as the PE continues to need to receive 2323 the given C-flow, and the P-tunnel continues to remain the expected 2324 P-tunnel for that C-flow. Procedures for joining and leaving a 2325 tunnel depend, of course, on the tunnel type. 2327 If a PTA specifies a non-zero MPLS label for a tunnel that is not an 2328 IR tunnel, then the PE originating the A-D route containing that PTA 2329 is advertising an aggregate P-tunnel. The aggregate P-tunnel can be 2330 thought of as an outer P-tunnel multiplexing some number of inner 2331 P-tunnels. The inner P-tunnels are demultiplexed by means of the 2332 MPLS label in the PTA. In this document, when we talk of the 2333 "expected P-tunnel" in the context of an aggregate P-tunnel, we refer 2334 to a particular inner P-tunnel, not to the outer P-tunnel. It is 2335 this "inner P-tunnel" that is the expected P-tunnel for a given 2336 C-flow. 2338 In order to find the expected P-tunnel for a given C-flow, the 2339 upstream PE of the C-flow is first determined. Then the S-PMSI A-D 2340 routes originated by that PE are examined, and their NLRIs compared 2341 to the (C-S/C-RP,C-G) of the flow, to see if there is a "match for 2342 reception". (If there is no S-PMSI A-D route that matches a given 2343 C-flow, the expected P-tunnel for that C-flow may have been 2344 advertised in an I-PMSI A-D route; see Section 7.4.5.) 2346 The rules for determining, in non-extranet cases, whether a given 2347 C-flow is a "match for reception" for a given S-PMSI A-D route are 2348 given in [RFC6625] Section 3.2. Note that we use the terms 2349 "installed" and "originated" as they are defined in [RFC6625] 2350 Section 3.2. (See also Section 1.1 of this document.) 2352 This specification adds additional rules for determining whether a 2353 given S-PMSI A-D route is a "match for reception" for a given (C-S/ 2354 C-RP,C-G). Note that these rules all assume the context of a 2355 particular VRF into which the A-D route has been imported. 2357 The rules given in [RFC6625] for determining whether a given S-PMSI 2358 A-D route is a "match for transmission" remain unchanged. 2360 Suppose a PE has originated a C-multicast Shared Tree Join for 2361 (C-*,C-G), has not originated a C-multicast Source Tree Join for 2362 (C-S,C-G), but has received and installed a Source Active A-D route 2363 for (C-S,C-G). As described in Section 13.2 of [RFC6514], the PE 2364 must receive the (C-S,C-G) traffic from the tunnel the originator of 2365 the installed Source Active A-D route uses for sending (C-S,C-G). 2367 The originator of the installed Source Active A-D route is determined 2368 as follows: 2370 1. Look at the "UMH Route Candidate Set" for C-S, as defined in 2371 [RFC6513] Section 5.1.3. 2373 2. From that set select a subset of UMH routes to C-S, such that 2374 each route in the subset has at least one RT in common with the 2375 Source Active A-D route, and at least one of the RTs in common is 2376 an import RT of the VRF. 2378 3. From that subset, find the route whose RD is the same as the RD 2379 from the NLRI of the Source Active A-D route. 2381 4. The Upstream PE is the PE identified in the VRF Route Import 2382 Extended Community of that route. 2384 5. The Upstream AS is the AS identified in the Source AS Extended 2385 Community of that route. 2387 If the result of step 2 is an empty set, or if step 3 fails to find a 2388 route, then the Upstream PE of the Source Active A-D route cannot be 2389 determined, and it is necessary to act as if the Source Active A-D 2390 route had not been installed. (A subsequent change to the UMH Route 2391 Candidate Set for C-S may require that a new attempt be made to 2392 determine the Upstream PE.) 2394 Once the upstream PE is determined, the P-tunnel over which the flow 2395 is expected is determined according to the procedures already 2396 described in this section. 2398 7.4.1. (C-S,C-G) S-PMSI A-D Routes 2400 When extranet functionality is being provided, an S-PMSI A-D route 2401 whose NLRI contains (C-S,C-G) is NOT considered to be a "match for 2402 reception" for a given C-flow (C-S,C-G) unless one of the following 2403 conditions holds (in addition to the conditions specified in 2404 [RFC6625]): 2406 o the "single C-source per (C-S,C-G) or (C-S,C-*) P-tunnel" is 2407 provisioned, or 2409 o the selected UMH route for C-S has at least one RT in common with 2410 the S-PMSI A-D route, and at least one of the common RTs is an 2411 import RT of the VRF. 2413 7.4.2. (C-S,C-*) S-PMSI A-D Routes 2415 When extranet functionality is being provided, an S-PMSI A-D route 2416 whose NLRI contains (C-S,C-*) is NOT considered to be a "match for 2417 reception" for a given C-flow (C-S,C-G) unless one of the following 2418 conditions holds, in addition to the conditions specified in 2419 [RFC6625]: 2421 o the "single C-source per (C-S,C-G) or (C-S,C-*) P-tunnel" is 2422 provisioned, or 2424 o the selected UMH route for C-S has at least one RT in common with 2425 the S-PMSI A-D route, and at least one of the common RTs is an 2426 import RT of the VRF. 2428 7.4.3. (C-*,C-G) S-PMSI A-D Routes 2430 When extranet functionality is being provided, an S-PMSI A-D route 2431 whose NLRI contains (C-*,C-G) is NOT considered to be a "match for 2432 reception" for a given C-flow (C-S,C-G) in a given VRF unless either 2433 condition 1 or condition 2 below holds, in addition to the conditions 2434 specified in [RFC6625]: 2436 1. The given VRF has currently originated a C-multicast Shared Tree 2437 Join route for (C-*,C-G), and 2439 a. (C-*,C-G) matches an installed (C-*,C-G) S-PMSI A-D route 2440 (according to [RFC6625]) in the given VRF, and 2442 b. either 2444 i. the "Single C-group per (C-*,C-G) P-tunnel" policy has 2445 been provisioned, or 2447 ii. the RTs of that S-PMSI A-D route form a non-empty 2448 intersection with the RTs carried in the VRF's 2449 selected UMH route for C-RP of that C-G, or 2451 iii. installed in the VRF is at least one (C-S,C-G) Source 2452 Active A-D route that was originated by the same PE as 2453 the (C-*,C-G) S-PMSI A-D route. 2455 2. The given VRF does not have a currently originated C-multicast 2456 Shared Tree Join for (C-*,C-G), but 2458 a. there are one or more values for C-S for which the VRF has a 2459 currently originated Source Tree Join C-multicast route for 2460 (C-S,C-G), and 2462 b. the (C-* C-G) S-PMSI A-D route matches (according to 2463 [RFC6625]) each such (C-S,C-G), and 2465 c. either 2467 i. the "Single C-group per (C-*,C-G) P-tunnel" policy has 2468 been provisioned, or 2470 ii. the RTs of that S-PMSI A-D route form a non-empty 2471 intersection with the RTs carried in the VRF's selected 2472 UMH routes for each such C-S 2474 If a VRF has an installed (C-*,C-G) S-PMSI A-D route, but does 2475 not have a (C-S,C-G) or (C-*,C-G) multicast state that matches 2476 that route for reception, the procedures of Section 12.3 2477 ("Receiving S-PMSI A-D Routes by PEs") of [RFC6514] are not 2478 invoked for that route. If those multicast states are created at 2479 some later time when the route is still installed, the procedures 2480 of Section 12.3 of [RFC6514] are invoked at that time. 2482 7.4.4. (C-*,C-*) S-PMSI A-D Routes 2484 A (C-*,C-*) S-PMSI A-D Route (call it "R-AD") is NOT considered to be 2485 a match for reception for a given C-flow (C-S,C-G) or (C-*,C-G) 2486 unless the following conditions hold (in addition to the conditions 2487 specified in [RFC6625]: 2489 o the selected UMH route (call it "R-UMH") for C-S or for C-G's C-RP 2490 respectively has at least one RT in common with R-AD, and at least 2491 one of the common RTs is an import RT of the VRF. 2493 o either R-AD and R-UMH both carry the Extranet Separation Extended 2494 Community, or neither carries the Extranet Separation Extended 2495 Community. 2497 7.4.5. I-PMSI A-D Routes 2499 If a particular egress VRF in a particular egress PE contains no 2500 matching S-PMSI A-D routes for a particulalr C-flow, then the C-flow 2501 is expected to arrive (at that egress VRF) on an inclusive P-tunnel. 2503 Suppose that an egress PE has originated a (C-S,C-G) C-Multicast 2504 Source Tree Join. Let R-UMH be the selected UMH route (in the given 2505 egress VRF) or C-S. As specified in [RFC6514], the selected upstream 2506 PE for (C-S,C-G) is determined from the VRF Route Import RT of R-UMH, 2507 and the "selected upstream AS" for the flow is determined from the 2508 Source AS Extended Community of R-UMH. 2510 Suppose that an egress PE has originated a (C-*,C-G) C-Multicast 2511 Shared Tree Join, but has not originated a (C-S,C-G) C-Multicast 2512 Source Tree Join. If the egress VRF does not have a (C-S,C-G) Source 2513 Active A-D route installed, the selected upstream PE is determined 2514 from the VRF Route Import EC of the installed UMH-eligible route 2515 matching C-RP, where C-RP is the RP for the group C-G. The selected 2516 upstream AS for the flow is determined from the Source AS EC of that 2517 route. If the egress VRF does have a (C-S,C-G) Source Active A-D 2518 route installed, the selected upstream PE and upstream AS are 2519 determined as specified in Section 7.4. In either case, let R-UMH be 2520 the installed UMH-eligible route matching C-S. 2522 The inclusive P-tunnel that is expected to be carrying a particular 2523 C-flow is found as follows: 2525 o If the selected upstream AS is the local AS, or if segmented 2526 Inter-AS P-tunnels are not being used to instantiate I-PMSIs, then 2527 look in the VRF for an installed Intra-AS I-PMSI A-D route, R-AD, 2528 such that (a) R-AD originated by the selected upstream PE, (b) 2529 R-AD has at least one an RT in common with R-UMH, (c) at least one 2530 of the common RTs is an import RT of the local VRF, and (d) either 2531 R-AD and R-UMH both carry the Extranet Separation Extended 2532 Community, or neither carries the Extranet Separation Extended 2533 Community. 2535 The PTA of R-AD specifies the P-tunnel over which traffic of the 2536 given C-flow is expected. 2538 o If the selected upstream AS is not the local AS, and if segmented 2539 Inter-AS P-tunnels are being used to instantiate I-PMSIs, then 2540 look in the VRF for an installed Inter-AS I-PMSI A-D route, R-AD, 2541 such that (a) the Source AS field of R-AD's NLRI contains the AS 2542 number of the selected upstream AS, (b) R-AD has at least one RT 2543 in common with R-UMH, (c) at least one of the common RTs is an 2544 import RT of the local VRF, and (d) either R-AD and R-UMH both 2545 carry the Extranet Separation Extended Community, or neither 2546 carries the Extranet Separation Extended Community. 2548 The PTA of R-AD specifies the P-tunnel over which traffic of the 2549 given C-flow is expected. 2551 7.5. Packets Arriving from the Wrong P-tunnel 2553 Any packets that arrive on a P-tunnel other than the expected 2554 P-tunnel (as defined in Section 7.4) MUST be discarded, unless it is 2555 know that all the packets carried by both P-tunnels are from the same 2556 ingress VRF. (See Section 2.3.1 for a more detailed discussion of 2557 when to discard packets from other than the expected P-tunnel.) Note 2558 that packets arriving on the wrong P-tunnel are to be discarded even 2559 if they are arriving from the expected PE. 2561 8. Multiple Extranet VRFs on the same PE 2563 When multiple VRFs that contain extranet receivers for a given 2564 extranet source are present on the same PE, this PE becomes a single 2565 leaf of the P-tunnel used for sending (multicast) traffic from that 2566 source to these extranet receivers. The PE MUST be able to replicate 2567 this traffic to the multiple VRFs. Specific procedures for doing so 2568 are local to the PE, and outside the scope of this document. 2570 Two or more VRFs on the same PE may import the same S-PMSI A-D route. 2571 If this S-PMSI A-D route contains a PTA that has its "Leaf Info 2572 Required" bit set, it may be necessary for the PE to originate a Leaf 2573 A-D route whose NLRI is computed from the NLRI of the S-PMSI A-D 2574 route. (Details are in [RFC6514].) Note that for a given S-PMSI A-D 2575 route, the PE can originate only one corresponding Leaf A-D route, 2576 even if the S-PMSI A-D route is imported into multiple VRFs. This 2577 Leaf A-D route can thus be thought of as originating from several 2578 VRFs. It MUST NOT be withdrawn by the PE until there are no longer 2579 any VRFs originating it. 2581 [RFC6514] specifies conditions under which a PE originates a 2582 C-Multicast Source Tree Join or a C-Multicast Shared Tree Join, based 2583 on the (*,G) and (S,G) states associated with a given VRF. It also 2584 specifies the procedure for computing the NLRI of each such route. 2585 While a given PE may contain two or more VRFs that have (extranet) 2586 receivers for the same extranet C-flow, the PE cannot originate more 2587 than one BGP route with a given NLRI. If there are multiple VRFs, 2588 each of which has state that is sufficient to cause a given 2589 C-multicast route to be originated, the route can be thought of as 2590 originating from several VRFs. It MUST NOT be withdrawn by the PE 2591 until there is no longer any VRF with multicast state sufficient to 2592 cause the route to be originated. 2594 For a given extranet the site(s) that contain the extranet source(s) 2595 and the site(s) that contain the extranet receiver(s) may be 2596 connected to the same PE. In this scenario, the procedures by which 2597 (multicast) traffic from these sources is delivered to these 2598 receivers is a local matter to the PE, and outside the scope of this 2599 document. 2601 An implementation MUST support multiple extranet VRFs on a PE. 2603 9. IANA Considerations 2605 IANA is requested to allocate two new codepoints from the "First 2606 Come, First Served" range of the "Transitive Opaque Extended 2607 Community Sub-Types" Registry (under the top-level registry: "Border 2608 Gateway Protocol (BGP) Extended Communities"). [TO BE REMOVED: This 2609 registration should take place at the following location: 2610 http://www.iana.org/assignments/bgp-extended-communities/bgp- 2611 extended-communities.xhtml#trans-opaque] 2613 o A codepoint for "Extranet Source Extended Community" 2615 o A codepoint for "Extranet Separation Extended Community" 2617 10. Security Considerations 2619 The security considerations of [RFC6513] and [RFC6514] are 2620 applicable. 2622 As is the case with any application of technology based upon 2623 [RFC4364], misconfiguration of the RTs may result in VPN security 2624 violations (i.e., may result in a packet being delivered to a VPN 2625 where, according to policy, it is not supposed to go). 2627 In general, different VPNs are allowed to have overlapping IP address 2628 spaces, i.e., a host in one VPN may have the same IP address as a 2629 host in another. This is safe because the customer routes from a 2630 given VPN do not pass into other VPNs. Even if there is overlapping 2631 address space among VPNs, the routes that are known at any given VPN 2632 site are unambiguous, as long as the address space of that VPN is 2633 unambiguous. However, this is not necessarily true when extranet 2634 service is provided. If an extranet C-receiver in VPN-R is to be 2635 able to receive multicast traffic from an extranet C-source in VPN-S, 2636 then the address of the VPN-S extranet C-source must be imported into 2637 one or more VPN-R VRFs. If that address is also the address of a 2638 VPN-R non-extranet C-source, then a system attempting to receive an 2639 extranet C-flow from the VPN-R extranet C-source may instead receive 2640 a non-extranet C-flow from the VPN-S C-source. This would result in 2641 a VPN security violation. 2643 To avoid this, this document specifies that if a route is imported 2644 into a given VRF, all addresses that match that route must be 2645 unambiguous in the context of that VRF. Improper provisioning of the 2646 RTs may cause this rule to be violated, and hence result in a VPN 2647 security violation. 2649 It is possible that a given multicast C-source is the source of 2650 multiple flows, some of which are intended to be extranet C-flows, 2651 and some of which are intended to be non-extranet flows. However, 2652 the procedures of this document will allow any C-receiver that is 2653 able to receive the extranet C-flows from a given C-source to also 2654 receive the non-extranet C-flows from that source. As a result, VPN 2655 security violations may result if any system is a C-source for both 2656 extranet and non-extranet C-flows. However, the set of C-flows 2657 transmitted by a given C-source is not under the control of the SP. 2658 SPs who offer the extranet MVPN service must make sure that this 2659 potential for VPN security violations is clearly understood by the 2660 customers who administer the C-sources. 2662 This specification does not require that UMH-eligible routes be "host 2663 routes"; they may be less specific routes. So it is possible for the 2664 NLRI of a UMH-eligible route to contain an address prefix that 2665 matches the address of both an extranet C-source and a non-extranet 2666 C-source. If such a route is exported from a VPN-S VRF and imported 2667 by a VPN-R VRF, C-receivers contained in VPN-R will be able to 2668 receive C-flows from the non-extranet C-sources whose addresses match 2669 that route. This may result in VPN security violations. Service 2670 providers who offer the extranet MVPN service must make sure that 2671 this is clearly understood by the customers who administer the 2672 distribution of routes from CE to PE routers. 2674 If the address ambiguities described in Sections 2.1 and 2.2 are not 2675 prohibited by policy, VRFs must be able to discard traffic that 2676 arrives on the wrong P-tunnel; otherwise VPN security violations may 2677 occur. 2679 Section 4.4 specifies the optional use of a new Extended Community, 2680 the Extranet Source Extended Community. Security considerations 2681 regarding the use and distribution of that Extended Community are 2682 discussed in that section. 2684 11. Acknowledgments 2686 The authors wish to thank DP Ayyadevara, Robert Kebler, Padmini 2687 Misra, Rayen Mohanty, Maria Napierala, Karthik Subramanian, and Kurt 2688 Windisch for their contributions to this work. 2690 We also wish to thank Lizhong Jin and Rishabh Parekh for their 2691 reviews and comments. 2693 Special thanks to Jeffrey (Zhaohui) Zhang for his careful review and 2694 for providing the ascii art appearing in Section 2. 2696 12. Contributor Addresses 2698 Below is a list of other contributing authors in alphabetical order: 2700 Wim Henderickx 2701 Alcatel-Lucent 2702 Copernicuslaan 50 2703 Antwerp 2018 2704 Belgium 2706 Email: wim.henderickx@alcatel-lucent.com 2708 Praveen Muley 2709 Alcatel-Lucent 2711 Email: Praveen.Muley@alcatel-lucent.com 2713 Ray Qiu 2714 Juniper Networks, Inc. 2715 1194 North Mathilda Avenue 2716 Sunnyvale, CA 94089 2717 United States 2719 Email: rqiu@juniper.net 2721 IJsbrand Wijnands 2722 Cisco Systems, Inc. 2723 De Kleetlaan 6a 2724 Diegem 1831 2725 Belgium 2727 Email: ice@cisco.com 2729 13. References 2731 13.1. Normative References 2733 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 2734 Requirement Levels", BCP 14, RFC 2119, 2735 DOI 10.17487/RFC2119, March 1997, 2736 . 2738 [RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private 2739 Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February 2740 2006, . 2742 [RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas, 2743 "Protocol Independent Multicast - Sparse Mode (PIM-SM): 2744 Protocol Specification (Revised)", RFC 4601, 2745 DOI 10.17487/RFC4601, August 2006, 2746 . 2748 [RFC6513] Rosen, E., Ed. and R. Aggarwal, Ed., "Multicast in MPLS/ 2749 BGP IP VPNs", RFC 6513, DOI 10.17487/RFC6513, February 2750 2012, . 2752 [RFC6514] Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP 2753 Encodings and Procedures for Multicast in MPLS/BGP IP 2754 VPNs", RFC 6514, DOI 10.17487/RFC6514, February 2012, 2755 . 2757 [RFC6625] Rosen, E., Ed., Rekhter, Y., Ed., Hendrickx, W., and R. 2758 Qiu, "Wildcards in Multicast VPN Auto-Discovery Routes", 2759 RFC 6625, DOI 10.17487/RFC6625, May 2012, 2760 . 2762 13.2. Informative References 2764 [MVPN-IR] Rosen, E., Subramanian, K., and Z. Zhang, "Ingress 2765 Replication Tunnels in Multicast VPN", internet-draft 2766 draft-ietf-bess-ir-02, October 2015. 2768 [RFC3446] Kim, D., Meyer, D., Kilmer, H., and D. Farinacci, "Anycast 2769 Rendevous Point (RP) mechanism using Protocol Independent 2770 Multicast (PIM) and Multicast Source Discovery Protocol 2771 (MSDP)", RFC 3446, DOI 10.17487/RFC3446, January 2003, 2772 . 2774 [RFC3618] Fenner, B., Ed. and D. Meyer, Ed., "Multicast Source 2775 Discovery Protocol (MSDP)", RFC 3618, 2776 DOI 10.17487/RFC3618, October 2003, 2777 . 2779 [RFC4610] Farinacci, D. and Y. Cai, "Anycast-RP Using Protocol 2780 Independent Multicast (PIM)", RFC 4610, 2781 DOI 10.17487/RFC4610, August 2006, 2782 . 2784 [RFC4875] Aggarwal, R., Ed., Papadimitriou, D., Ed., and S. 2785 Yasukawa, Ed., "Extensions to Resource Reservation 2786 Protocol - Traffic Engineering (RSVP-TE) for Point-to- 2787 Multipoint TE Label Switched Paths (LSPs)", RFC 4875, 2788 DOI 10.17487/RFC4875, May 2007, 2789 . 2791 [RFC5015] Handley, M., Kouvelas, I., Speakman, T., and L. Vicisano, 2792 "Bidirectional Protocol Independent Multicast (BIDIR- 2793 PIM)", RFC 5015, DOI 10.17487/RFC5015, October 2007, 2794 . 2796 [RFC5059] Bhaskar, N., Gall, A., Lingard, J., and S. Venaas, 2797 "Bootstrap Router (BSR) Mechanism for Protocol Independent 2798 Multicast (PIM)", RFC 5059, DOI 10.17487/RFC5059, January 2799 2008, . 2801 [RFC6388] Wijnands, IJ., Ed., Minei, I., Ed., Kompella, K., and B. 2802 Thomas, "Label Distribution Protocol Extensions for Point- 2803 to-Multipoint and Multipoint-to-Multipoint Label Switched 2804 Paths", RFC 6388, DOI 10.17487/RFC6388, November 2011, 2805 . 2807 Authors' Addresses 2809 Yakov Rekhter (editor) 2810 Juniper Networks, Inc. 2811 1194 North Mathilda Avenue 2812 Sunnyvale, CA 94089 2813 United States 2815 Eric C. Rosen (editor) 2816 Juniper Networks, Inc. 2817 10 Technology Park Drive 2818 Westford, Massachusetts 01886 2819 United States 2821 Email: erosen@juniper.net 2823 Rahul Aggarwal 2824 Arktan 2826 Email: raggarwa_1@yahoo.com 2828 Yiqun Cai 2829 Microsoft 2830 1065 La Avenida 2831 Mountain View, CA 94043 2832 United States 2834 Email: yiqunc@microsoft.com 2835 Thomas Morin 2836 Orange 2837 2 Avenue Pierre-Marzin 2838 22307 Lannion Cedex 2839 France 2841 Email: thomas.morin@orange.com