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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references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 4601 (Obsoleted by RFC 7761) == Outdated reference: A later version (-05) exists of draft-ietf-bess-ir-02 Summary: 1 error (**), 0 flaws (~~), 2 warnings (==), 3 comments (--).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: July 15, 2016 Arktan 7 Y. Cai 8 Microsoft 9 T. Morin 10 Orange 11 January 12, 2016 13 Extranet Multicast in BGP/IP MPLS VPNs 14 draft-ietf-bess-mvpn-extranet-06 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 July 15, 2016. 44 Copyright Notice 46 Copyright (c) 2016 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 . . . . . . . 29 102 5.1. Route Targets of UMH-eligible Routes and A-D 103 Routes . . . . . . . . . . . . . . . . . . . . . . . . . 29 104 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 . . . . . . . . . . . . . . . . . 32 109 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 . . . . . . . . . . . . . . 36 116 6.2.1. Forming the MI-PMSIs . . . . . . . . . . . . . . . . 36 117 6.2.2. S-PMSIs . . . . . . . . . . . . . . . . . . . . . . . 39 118 6.2.3. Sending PIM Control Packets . . . . . . . . . . . . . 40 119 6.2.4. Receiving PIM Control Packets . . . . . . . . . . . . 41 120 6.2.5. Sending and Receiving Data Packets . . . . . . . . . 41 121 6.3. Multiple PMSIs per C-flow Model . . . . . . . . . . . . . 41 122 6.3.1. Forming the MI-PMSIs . . . . . . . . . . . . . . . . 42 123 7. When BGP is the PE-PE C-multicast Control Plane . . . . . . . 43 124 7.1. Originating C-multicast Routes . . . . . . . . . . . . . 44 125 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 . . . . . . . . . . . . . . 46 130 7.2.3.1. When Inter-Site Shared Trees Are Used . . . . . . 46 131 7.2.3.2. When Inter-Site Shared Trees Are Not Used . . . . 46 132 7.3. Originating A-D Routes With Extranet Separation . . . . . 47 133 7.3.1. Intra-AS I-PMSI A-D Routes . . . . . . . . . . . . . 47 134 7.3.2. S-PMSI A-D Routes . . . . . . . . . . . . . . . . . . 48 135 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 . . . . . . . . . . . . . 52 139 7.4.3. (C-*,C-G) S-PMSI A-D Routes . . . . . . . . . . . . . 52 140 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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 146 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 56 147 10. Security Considerations . . . . . . . . . . . . . . . . . . . 56 148 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 57 149 12. Contributor Addresses . . . . . . . . . . . . . . . . . . . . 58 150 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 o PTA: PMSI Tunnel attribute [RFC6514]. 235 Note that a given extranet C-source is not necessarily allowed to 236 transmit to every extranet C-receiver; policy determines which 237 extranet C-sources are allowed to transmit to which extranet 238 C-receivers. However, in the case of an extranet (ASM) C-group, all 239 transmitters to the group are allowed to transmit to all the 240 receivers of the group, and all the receivers of the group are 241 allowed to receive from all transmitters to the group. 243 We say that a given VRF "contains" or "has" a multicast C-source (or 244 that the C-source is "in" the VRF), if that C-source is in a site 245 connected to that VRF, and the VRF originates a UMH-eligible route 246 (see Section 4) that matches the address of the C-source. 248 We say that a given VRF "contains" or "has" a multicast C-receiver 249 (or that the C-receiver is "in" the VRF), if that C-receiver is in a 250 site connected to that VRF. 252 We say that a given VRF "contains" or "has" the C-RP for a given ASM 253 group (or that the C-RP is "in" the VRF) if that C-RP is in a site 254 connected to that VRF, and the VRF originates a unicast route and a 255 (possibly different, possibly the same) UMH-eligible route (see 256 Section 4) whose respective address prefixes match the C-RP address. 258 [RFC6513] allows a set of "Provider tunnels" (P-tunnels) to be 259 aggregated together and transported via an outer P-tunnel, i.e., it 260 allows for the use of hierarchical Label Switched Paths (LSPs) as 261 P-tunnels. A two-level hierarchical LSP, for example, can be thought 262 of as a set of "inner tunnels" aggregated into an outer tunnel. In 263 this document, when we speak of a P-tunnel, we are always speaking of 264 the innermost P-tunnel, i.e., of a P-tunnel at the lowest level of 265 hierarchy. P-tunnels are identified in the Provider Multicast 266 Service Interface (PMSI) Tunnel Attributes (PTAs) [RFC6514] of BGP 267 Auto-Discovery (A-D) routes. Two PTAs that have the same Tunnel Type 268 and Tunnel Identifier fields, but different MPLS label fields, are 269 thus considered to identify two different P-tunnels. (I.e., for the 270 purposes of this document, the MPLS label included in the PTA, if 271 any, is considered to be part of the tunnel identifier.) 273 We say that the NLRI of a BGP S-PMSI A-D route or Source Active A-D 274 route contains (C-S,C-G) if its "Multicast Source" field contains C-S 275 and its "Multicast Group" field contains C-G. If either or both of 276 these fields is encoded as a wildcard, we will say that the NLRI 277 contains (C-*,C-*) (both fields encoded as wildcard), or (C-*,C-G) 278 (multicast source field encoded as wildcard) or (C-S,C-*) (multicast 279 group field encoded as wildcard). 281 We use the term "VPN security violation" to refer to any situation in 282 which a packet is delivered to a particular VPN, even though, by 283 policy, it should not be delivered to that VPN. 285 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 286 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 287 "OPTIONAL" in this document are to be interpreted as described in 288 [RFC2119]. 290 1.2. Scope 292 1.2.1. Customer Multicast Control Protocols 294 This document presumes that the VPN customer is using "PIM Sparse 295 Mode", operating in either "Source-Specific Mode" (SSM) or "Any 296 Source Mode" (ASM), as the multicast control protocol at the customer 297 sites. Support for other customer IP multicast control protocols 298 (e.g., [RFC5015], PIM "Dense Mode") is outside the scope of this 299 document. Support for the customer use of MPLS multicast control 300 protocols (e.g., [RFC6388], [RFC4875]) is also outside the scope of 301 this document. 303 When a VPN customer uses ASM, the customer routers need to be able to 304 map from a C-group address to a C-RP address. These mappings can be 305 provisioned in each router, or can be discovered dynamically through 306 protocols such as BSR [RFC5059]. However, it cannot be assumed that 307 such protocols will automatically work in the context of an extranet. 308 Discussion of the use of such protocols in an extranet is outside the 309 scope of this document. 311 1.2.2. Provider Multicast Control Protocols 313 [RFC6513] allows either PIM or BGP to be used as the protocol for 314 distributing customer multicast routing information. Except where 315 otherwise specified, such as in Sections 6 and 7, the procedures of 316 this document cover both cases. 318 1.3. Clarification on Use of Route Distinguishers 320 [RFC4364] requires that every VRF be associated with one or more 321 Route Distinguishers (RD). Each VPN-IPv4 or VPN-IPv6 route that is 322 exported from a particular VRF contains, in its NLRI, an RD that is 323 associated with that VRF. 325 [RFC4364] allows a given RD to be associated with more than one VRF, 326 as long as all the VRFs associated with that RD belong to the same 327 VPN. However, in the most common deployment model, each RD is 328 associated with one and only one VRF. [RFC6513] and [RFC6514] 329 presuppose this deployment model. That is, [RFC6513] and [RFC6514] 330 presuppose that every RD is associated with one and only one VRF. We 331 will call this the "unique VRF per RD" condition. 333 [RFC6514] defines the MCAST-VPN address family, which has a number of 334 route types. Each Intra-AS "Inclusive Provider Multicast Service 335 Interface" (I-PMSI) A-D route, S-PMSI A-D route, and Source Active 336 A-D route, when exported from a given VRF, contains, in its NLRI, an 337 RD that is associated with the VRF. [RFC6513] and [RFC6514] also 338 discuss a class of routes known as "UMH-eligible" routes; when a UMH- 339 eligible route is exported from a given VRF, its NLRI contains an RD 340 of the VRF. 342 [RFC6514] also defines MCAST-VPN routes whose NLRIs do not contain an 343 RD of the VRF from which they are exported: the C-multicast Join 344 routes and the Leaf A-D routes. 346 Those route types that, when exported from a given VRF, contain (in 347 their NLRIs) an RD of the VRF, will be known in this document as 348 "local-RD routes". 350 Given the "unique VRF per RD condition", if one sees that two local- 351 RD routes have the same RD, one can infer that the two routes 352 originated from the same VRF. This inference can be drawn even if 353 the two routes do not have the same SAFI, as long as the two routes 354 are both local-RD routes. 356 This document builds upon [RFC6513] and [RFC6514]; therefore the 357 "unique VRF per RD" condition is REQUIRED. 359 [RFC6514] presupposes a further requirement on the use of RDs in the 360 local-RD routes exported from a given VRF. Suppose a given VRF 361 exports a Source Active A-D route containing (C-S,C-G). That VRF 362 will also export a UMH-eligible route matching C-S. [RFC6514] 363 presupposes that the UMH-eligible route and the Source Active A-D 364 route have the same RD. 366 In most cases, not only is a given RD associated with only a single 367 VRF, but a given VRF is associated with only a single RD. We will 368 call this the "unique RD per VRF" condition. When this condition 369 holds, all the local-RD routes exported from a given VRF will have 370 the same RD. This ensures that the presupposition of the previous 371 paragraph will hold, i.e., that the RD in a Source Active A-D route 372 exported from a given VRF will have the same RD as the corresponding 373 UMH-eligible route exported from the same VRF. 375 Section 7.3 of this document describes a procedure known as "Extranet 376 Separation". When Extranet Separation is NOT being used, it is 377 REQUIRED by this document that the "unique RD per VRF" condition 378 hold. This ensures that all the local-RD routes exported from a 379 given VRF will have the same RD. 381 When Extranet Separation is used, a VRF that contains both extranet 382 sources and non-extranet sources MUST be configured with two RDs. 383 One of these RDs is known as the "default RD", and the other is known 384 as the "extranet RD". It MUST be known by configuration which RD is 385 the default RD and which is the extranet RD. 387 When a VRF is configured with only one RD, we will refer to that RD 388 as the "default RD". 390 In general, local-RD routes exported from a given VRF will contain 391 the default RD. However, when Extranet Separation is used, some of 392 the local-RD routes exported from the VRF will contain the extranet 393 RD. Details concerning the exported routes that contain the extranet 394 RD can be found in Sections 4.1 and 7.3. 396 Note that the "unique VRF per RD" condition applies to the extranet 397 RD as well as to the default RD. That is, a given extranet RD is 398 associated with a unique VRF. 400 1.4. Overview 402 Consider two VPNs, VPN-S and VPN-R, each of which supports MVPN 403 functionality as specified in [RFC6513] and/or [RFC6514]. In the 404 simplest configuration, VPN-S is a collection of VRFs, each of which 405 is configured with a particular Route Target (RT) value (call it "RT- 406 S") as its import RT and as its export RT. Similarly, VPN-R is a 407 collection of VRFs, each of which is configured with a particular RT 408 value (call it "RT-R") as its import RT and as its export RT. 410 In this configuration, multicast C-receivers contained in a VPN-R VRF 411 cannot receive multicast data traffic from multicast C-sources 412 contained in a VPN-S VRF. If it is desired to allow this, one needs 413 to create an MVPN "extranet". Creating an extranet requires 414 procedures in addition to those specified in [RFC6513], [RFC6514], 415 and [RFC6625]; this document specifies these additional procedures. 417 In the example above, the additional procedures will allow a selected 418 set of routes exported from the VPN-S VRFs (i.e., from the VRFs 419 containing extranet C-sources) to be imported into the VPN-R VRFs 420 (i.e., into the VRFs containing extranet C-receivers). These routes 421 include the routes that are to be eligible for use as UMH routes (see 422 Section 5.1 of [RFC6513]) in the extranet, as well as a selected set 423 of BGP A-D routes (Intra-AS I-PMSI A-D routes, S-PMSI A-D routes, 424 Source Active A-D routes). Importing these routes into the VPN-R 425 VRFs makes it possible to determine, in the context of a VPN-R VRF, 426 that a particular C-multicast Join needs to be delivered to a 427 particular VPN-S VRF. It also makes it possible to determine, in the 428 context of a VPN-R VRF, the P-tunnel through which the aforementioned 429 VPN-S VRF sends a particular C-flow. 431 Depending on the type of P-tunnel used, it may also be necessary for 432 Leaf A-D routes to be exported by one or more VPN-R VRFs and imported 433 into a VPN-S VRF. 435 There are no extranet-specific procedures governing the use and 436 distribution of BGP C-Multicast routes. 438 If PIM is used as the PE-PE protocol for distributing C-multicast 439 routing information, additional BGP A-D routes must be exported from 440 the VPN-R VRFs and imported into the VPN-S VRFs, so that the VPN-S 441 VRFs can join the P-tunnels that the VPN-R VRFs use for sending PIM 442 control messages. Details can be found in Section 6. 444 The simple example above describes an extranet created from two 445 MVPNs, one of which contains extranet C-sources and one of which 446 contains extranet C-receivers. However, the procedures described in 447 this document allow for much more complicated scenarios. 449 For instance, an extranet may contain extranet C-sources and/or 450 extranet C-receivers from an arbitrary number of VPNs, not just from 451 two VPNs. An extranet C-receiver in VPN-R may be allowed to receive 452 multicast traffic from extranet C-sources in VPN-A, VPN-B, and VPN-C. 453 Similarly, extranet C-sources in VPN-S may be allowed to send 454 multicast traffic to multicast C-receivers that are in VPN-A, VPN-B, 455 VPN-C, etc. 457 A given VPN customer may desire that only some of its multicast 458 C-sources be treated as extranet C-sources. This can be accomplished 459 by appropriate provisioning of the import and export RTs of that 460 customer's VRFs (as well as the VRFs of other VPNs that contain 461 extranet C-receivers for extranet C-flows of the given customer.) 463 A given VPN customer may desire that some of its extranet C-sources 464 can transmit only to a certain set of VPNs, while other of its 465 extranet C-sources can transmit only to a different set of VPNs. 466 This can be accomplished by provisioning the VRFs to export different 467 routes with different RTs. 469 In all these cases, the VPN customers set the policies, and the 470 Service Provider (SP) implements the policies by the way it 471 provisions the import and export RTs of the VRFs. It is assumed that 472 the customer communicates to the SP the set of extranet C-source 473 addresses, and the set of VPNs to which each C-source can transmit. 474 (Recall that every C-source that can transmit to an extranet C-group 475 is an extranet C-source, and must be able transmit to any VPN that 476 has receivers for that group. This must be taken into account when 477 the provisioning is done.) This customer/SP communication is part of 478 the service provisioning process, and outside the scope of this 479 document. 481 It is possible that an extranet C-source will transmit both extranet 482 C-flows and non-extranet C-flows. However, if extranet C-receiver 483 C-R can receive extranet C-flows from extranet C-source C-S, the 484 procedures of this document do not prevent C-R from requesting and 485 receiving the non-extranet flows that are transmitted by C-S. 486 Therefore it is NOT RECOMMENDED to allow an extranet C-source to 487 transmit non-extranet C-flows. However, the Service Provider (SP) 488 has no control over the set of C-flows transmitted by a given 489 C-source, and can do no more than communicate this recommendation to 490 its customers. (Alternatively, the customer and SP may coordinate on 491 setting up filters to prevent unauthorized flows from being sent to a 492 customer site; such a procedure is outside the scope of this 493 document.) See the "Security Considerations" section (Section 10) 494 for additional discussion of this issue. 496 2. Extranets and Overlapping Address Spaces 498 As specified in [RFC4364], the address space of one VPN may overlap 499 with the address space of another. A given address may be 500 "ambiguous", in that it denotes one system within VPN-A and a 501 different system within VPN-B. In the notation of Section 1.1, if an 502 address C-S is ambiguous between VPNs A and B, then Host(C-S,A) != 503 Host(C-S,B). However, any given address C-S MUST be unambiguous 504 (i.e., MUST denote a single system) in the context of a given VPN. 506 When a set of VRFs belonging to different VPNs are combined into an 507 extranet, it is no longer sufficient for an address to be unambiguous 508 only within the context of a single VPN: 510 1. Suppose C-S is the address of a given extranet C-source contained 511 in VPN-A. Now consider the set of VPNs {VPN-B, VPN-C, ...} 512 containing extranet C-receivers that are allowed by policy to 513 receive extranet C-flows from VPN-A's C-S. The address C-S MUST 514 be unambiguous among this entire set of VPNs (VPN-A, VPN-B, VPN- 515 C, etc.); i.e., Host(C-S,A) == Host(C-S,B) == Host(C-S,C). 517 The implication is that C-S in VPN-A is not necessarily an 518 extranet C-source for all VPNs that contain extranet C-receivers; 519 policy MUST be used to ensure that C-S is an extranet C-source 520 for a given VPN, say VPN-B, only if C-S is unambiguous between 521 VPN-A and VPN-B. 523 2. If a given VRF contains extranet C-receivers for a given extranet 524 C-source, then the address of this C-source MUST be unambiguous 525 among all the extranet C-sources for which there are C-receivers 526 in the VRF. This is true whether or not C-sources are in VRFs 527 that belong to the same or to different VPNs. 529 The implication is that if C-S in VRF-X is ambiguous with C-S in 530 VRF-Y, then there MUST NOT be any VRF, say VRF-Z, containing 531 C-receivers that are allowed by policy to receive extranet 532 C-flows from both C-S in VRF-X and C-S in VRF-Y. 534 Note: A VPN customer may be using "anycast" addresses. An anycast 535 address is intentionally ambiguous, as it denotes a set of systems 536 rather than a single system. In this document, we will consider an 537 anycast address to be unambiguous in a given context as long as it 538 denotes the same set of systems whenever it occurs in that context. 540 A multicast C-group address, say C-G, may also be ambiguous, in that 541 it may be used for one multicast group in VPN-A and for an entirely 542 different multicast group in VPN-B. If a set of MVPNs are combined 543 into an extranet, and C-G is an extranet C-group, it is necessary to 544 ensure that C-G is unambiguous among the entire set of VPNs whose 545 VRFs contain extranet C-sources, C-RPs, and/or extranet C-receivers 546 for that C-group. This may require, as part of the provisioning 547 process, customer/SP communication that is outside the scope of this 548 document. 550 Subject to these restrictions, the SP has complete control over the 551 distribution of routes in an MVPN. This control is exerted either by 552 provisioning the export RTs on the VRFs that originate the routes 553 (i.e., on the VRFs that contain the extranet C-sources), or by 554 provisioning the import RTs on the VRFs that receive the routes 555 (i.e., on the VRFs that contain the extranet C-receivers), or both. 557 Some of the rules and restrictions on provisioning the RTs are 558 applicable to all extranets; these are specified in Section 4. 559 Sections 6 and 7 add additional rules and restrictions that are 560 applicable only to particular extranet scenarios. 562 Even if all the RTs are provisioned according to the above rules and 563 restrictions, it is still possible for a single P-tunnel to contain 564 multicast data packets whose source and/or group addresses are 565 ambiguous in the context of the set of PEs that receive data from the 566 P-tunnel. That is, the above rules and restrictions are necessary, 567 but not sufficient, to prevent address ambiguity from causing 568 misdelivery of traffic. To prevent such misdelivery, additional 569 procedures or policies must be used. 571 Sections 2.1 and 2.2 describe scenarios in which a given P-tunnel may 572 carry data packets with ambiguous addresses. The additional 573 procedures and policies needed to prevent misdelivery of data in 574 those scenarios are outlined in Section 2.3. (The detailed 575 procedures described in Sections 6 and 7 incorporate the 576 considerations of Section 2.3.) 578 2.1. Ambiguity: P-tunnel with Extranet/Non-Extranet Flows 580 In the following, we will use the notation "VRF A-n" to mean "VRF n 581 of VPN-A". 583 If VPN-A and VPN-B have overlapping address spaces, and are part of 584 the same extranet, then the following problem may exist, as 585 illustrated in Figure 1. 587 C-S2(A) C-S1 Join(C-S2(A),G) 588 \ / / 589 \ / / 590 +-------+---+ P1: (C-S1,G), (C-S2(A),G) +---+--------+ 591 |VRF A-1| |---------------------------------| |VRF A-2 | 592 +-------+PE1| |PE2+--------+ 593 |VRF B-1| |---------------------------------| |VRF B-2 | 594 +-------+---+ P2: (C-S2(B),G) +---+--------+ 595 / / \ 596 / / \ 597 C-S2(B) Join(C-S2(B),G) Join(C-S1,G) 599 Figure 1: Ambiguity of Extranet and Non-Extranet Source Address 601 Suppose: 603 o C-G is an SSM C-group used in VPNs A and B. 605 o VRF A-1, on PE1, contains an extranet C-source, whose IP address 606 is C-S1, that is allowed to have receivers in VPN B. VRF A-1 thus 607 exports to VPN B a UMH-eligible route matching C-S1. 609 o VRF A-1 also contains a non-extranet C-source, whose IP address is 610 C-S2. VRF A-1 exports a UMH-eligible route matching C-S2 to other 611 VPN A VRFs, but NOT to VPN B. 613 o VRF B-1, also on PE1, contains a non-extranet C-source whose IP 614 address is C-S2. A UMH-eligible route matching C-S2 is thus 615 exported from VRF B-1 to other VRFs in VPN B. 617 o Host(C-S2,A) != Host(C-S2,B). That is, C-S2 is an ambiguous 618 address in any extranet that contains both VPN-A VRFs and VPN-B 619 VRFs. 621 o VRF B-2, on some other PE, say PE2, requests to receive the 622 multicast flow (C-S1,C-G). In the context of VRF B-2, C-S1 623 matches the route exported from VRF A-1. Thus B-2's request to 624 receive the (C-S1,C-G) flow is transmitted to VRF A-1. 626 o VRF A-1 responds to VRF B-2's request for (C-S1,C-G) traffic by 627 transmitting that traffic on P-tunnel P1. 629 o VRF B-2 joins P-tunnel P1, in order to receive the (C-S1,C-G) 630 traffic. 632 o VRF A-2, on PE2, requests to receive the (non-extranet) multicast 633 flow (C-S2,C-G). In the context of VRF A-2, C-S2 matches the 634 route exported from VRF A-1. Thus A-2's request to receive the 635 (C-S2,C-G) traffic is transmitted to VRF A-1. 637 o VRF A-1 responds to VRF A-2's request for (C-S2,C-G) traffic by 638 transmitting that traffic on P-tunnel P1. 640 o VRF A-2 joins P-tunnel P1, in order to receive the (C-S2,C-G) 641 traffic. 643 o VRF B-2 requests to receive the (non-extranet) multicast flow 644 (C-S2,C-G). In the context of VRF B-2, C-S2 matches the route 645 exported from VRF B-1. Thus B-2's request to receive the 646 (C-S2,C-G) flow is transmitted to VRF B-1. 648 o VRF B-1 responds to VRF B-2's request for (C-S2,C-G) traffic by 649 transmitting that traffic on P-tunnel P2. 651 o VRF B-2 joins P-tunnel P2. 653 Since VRF B-2 has joined P-tunnel P1 and P-tunnel P2, it will receive 654 (C-S2,C-G) traffic on both P-tunnels. The (C-S2,C-G) traffic that 655 VRF B-2 needs to receive is traveling on P-tunnel P2; this (C-S2,C-G) 656 traffic must be forwarded by B-2 to any attached customer sites that 657 have C-receivers for it. But B-2 MUST discard the (C-S2,C-G) traffic 658 that it receives on P1, as this is not the traffic that it has 659 requested. If the (C-S2,C-G) traffic arriving on P1 were forwarded 660 to B-2's customer sites, the C-receivers would not be able to 661 distinguish the two flows, and the result would be a corrupted data 662 stream. 664 Note that the procedures of [RFC6513] Section 9.1.1 ("Discarding 665 Packets from the Wrong PE") will not cause VRF B-2 to discard the 666 (C-S2,C-G) that arrives on tunnel P1, because P1 and P2 have the same 667 upstream PE. 669 Therefore, it is necessary EITHER to prevent the above scenario from 670 occurring, OR ELSE to ensure that multicast data packets will be 671 discarded if they arrive on the "wrong" P-tunnel (even if they arrive 672 from the expected PE). See Section 2.3 for further discussion of 673 this issue. 675 2.2. Ambiguity: P-tunnel with Multiple Extranet Flows 677 Here is another example in which overlapping address spaces may cause 678 a problem. This example is illustrated in Figure 2. 680 C-S2(A2D) C-S1(A2C) Join(C-S2(A2D),G) 681 \ / / 682 \ / / 683 +-------+---+ P1: (C-S1(A2C),G), (C-S2(A2D),G)+---+--------+ 684 |VRF A-1| |---------------------------------| |VRF D-1 | 685 +-------+PE1| |PE2+--------+ 686 |VRF B-1| |---------------------------------| |VRF C-1 | 687 +-------+---+ P2: (C-S2(B2C),G) +---+--------+ 688 / / \ 689 / / \ 690 C-S2(B2C) / \ 691 Join Join 692 (C-S2(B2C),G) (C-S1(A2C),G) 694 Figure 2: Ambiguity of Extranet Source Addresses 696 Suppose: 698 o C-G is an SSM C-group address that is used in VPNs A, B, C, and D. 700 o VRF A-1, on PE1, contains an extranet C-source whose IP address is 701 C-S1, and that is allowed by policy to have C-receivers in VPN C 702 (but not in VPN D). VRF A-1 thus exports a UMH-eligible route 703 matching C-S1 to VPN C. 705 o VRF A-1 also contains an extranet C-source whose IP address is 706 C-S2, and that is allowed by policy to have C-receivers in VPN D 707 (but not in VPN C). VRF A-1 thus exports a UMH-eligible route 708 matching C-S2 to VPN D. 710 o VRF B-1, also on PE1, contains an extranet C-source whose IP 711 address is C-S2, and that is allowed by policy to have C-receivers 712 in VPN C (but not in VPN D). VRF B-1 thus exports a UMH-eligible 713 route matching C-S2 to VPN C. 715 o Host(C-S2,A) != Host (C-S2,B). That is, C-S2 is an ambiguous 716 address in any extranet that contains both VPN-A VRFs and VPN-B 717 VRFs. 719 o VRF C-1, on some other PE, say PE2, requests to receive the 720 extranet multicast flow (C-S1,C-G). In the context of VRF C-1, 721 C-S1 matches the route exported from VRF A-1. Thus C-1's request 722 to receive the (C-S1,C-G) flow is transmitted to VRF A-1. 724 o VRF A-1 responds to VRF C-1's request for (C-S1,C-G) traffic by 725 transmitting that traffic on P-tunnel P1, 727 o VRF C-1 joins P-tunnel P1, in order to receive the (C-S1,C-G) 728 traffic. 730 o VRF C-1 requests to receive the extranet multicast flow 731 (C-S2,C-G). In the context of VRF C-1, C-S2 matches the route 732 exported from VRF B-1. Thus C-1's request to receive the 733 (C-S2,C-G) flow is transmitted to VRF B-1. 735 o VRF B-1 responds by transmitting its (C-S2,C-G) traffic on 736 P-tunnel P2. 738 o VRF C-1 joins P-tunnel P2 in order to receive the (C-S2,C-G) 739 traffic. 741 o VRF D-1, on PE2, requests to receive the extranet multicast flow 742 (C-S2,C-G). In the context of VRF D-1, C-S2 matches the route 743 exported from VRF A-1. Thus D-1's request to receive the 744 (C-S2,C-G) flow is transmitted to VRF A-1. 746 o VRF A-1 responds by transmitting its (C-S2,C-G) traffic on 747 P-tunnel P1. 749 o VRF D-1 joins P-tunnel P1 in order to receive the (C-S2,C-G) 750 traffic. 752 In this example, VRF A-1 has chosen to use the same P-tunnel, P1, to 753 carry both its (C-S2,C-G) traffic and the (C-S1,C-G) traffic. VRF 754 C-1 has joined tunnel P1 in order to receive the (C-S1,C-G) traffic 755 from VRF A-1, which means that VRF C-1 will also receive the unwanted 756 (C-S2,C-G) traffic from P1. VRF C-1 is also expecting (C-S2,C-G) 757 traffic from VRF B-1; this traffic will be received from P2. Thus 758 VRF C-1 is receiving (C-S2,C-G) traffic on both tunnels, and both 759 C-flows arrive from the expected PE, PE1. 761 Therefore, it is necessary EITHER to prevent the above scenario from 762 occurring, OR ELSE to ensure that VRF C-1 discards any (C-S,C-G) 763 traffic that arrives from the "wrong" P-tunnel. See Section 2.3 for 764 further discussion of this issue. 766 Note that the ambiguity described in this section (Section 2.2) would 767 not occur if C-G were an (ASM) extranet C-group. In that case, the 768 scenario would violate the rule, given previously in Section 2, 769 requiring that all sources sending to a particular ASM extranet 770 C-group must have addresses that are unambiguous over all the MVPNs 771 receiving traffic for that C-group. 773 2.3. Preventing Misdelivery in These Scenarios 775 There are two ways to prevent the scenarios of Section 2.1 and 776 Section 2.2 from resulting in misdelivery of data. These two ways 777 are discussed respectively in Section 2.3.1 and Section 2.3.2. 779 2.3.1. Do Not Deliver Packets from the 'Wrong' P-tunnel 781 Consider a particular C-flow that has receivers in a particular VRF. 782 Sections 6 and 7 describe a set of procedures that enable an egress 783 PE to determine the "expected P-tunnel" for that C-flow in the 784 context of that VRF. If a PE receives packets of the C-flow (as 785 determined by the IP source and/or destination address of the 786 packet), it checks to see if the packet was received on the expected 787 P-tunnel for that VRF. If so, the packet is delivered to the VRF 788 (and thus to the C-flow's receivers in that VRF). If not, the packet 789 is not delivered to the VRF. 791 Note that at a given egress PE, the "wrong" P-tunnel for one VRF may 792 be the right P-tunnel for another. 794 These procedures, if applied at every PE that joins a given P-tunnel, 795 are sufficient to prevent misdelivery of traffic in the scenarios of 796 Sections 2.1 and 2.2. 798 IF these procedures cannot be applied by every PE that is attached to 799 a given extranet, then the policies of Section 2.3.2 MUST be applied 800 at every VRF containing C-sources for that extranet. 802 In some cases, however, it may be safe to deliver packets that arrive 803 from other than the expected P-tunnel. Suppose it is known that 804 every packet gets transmitted on only a single P-tunnel. (This will 805 be the case if the "single PMSI per C-flow" transmission model, 806 discussed in Section 3.1, is being used.) Suppose further that it is 807 known that T1 and T2 carry only packets that arrived at the same 808 ingress PE, over one or more VRF interfaces that are associated with 809 the same VRF. (I.e., that there is a particular VRF that is the 810 ingress VRF for ALL the packets carried by T1 or T2.) In this case, 811 if T1 is the expected P-tunnel for a given (C-S,C-G) , it is NOT 812 necessary to discard (S,G) packets that arrive over T2. 814 It is not always possible to determine whether two P-tunnels are 815 carrying packets from the same ingress VRF. However, in some cases, 816 this can be determined by examination of the A-D routes in which the 817 tunnels have been advertised. 819 Consider the following example: 821 o Tunnel T1 is a P2MP mLDP or RSVP-TE P-tunnel advertised in an 822 Intra-AS I-PMSI A-D route, call it R1. 824 o Tunnel T2 is a P2MP mLDP or RSVP-TE P-tunnel advertised in an 825 S-PMSI A-D route, call it R2. 827 o The respective NLRIs of R1 and R2 contain the same RD value. 829 o The MPLS Label field of R1's PMSI Tunnel attribute is zero, and 830 the MPLS label value of R2's PMSI Tunnel attribute is zero. 832 In this example, it can be concluded that T1 and T2 are carrying 833 packets from the same ingress VRF. Thus if T1 is the expected 834 P-tunnel for a (C-S,C-G) flow, (S,G) packets from T2 can be safely 835 delivered to the egress VRF; they do not need to be discarded. 836 Similarly, if T2 is the expected P-tunnel for a (C-S,C-G) flow, (S,G) 837 packets from T1 can be safely delivered to the egress VRF. 839 Another example is the following: 841 o Tunnel T3 is a P2MP mLDP or RSVP-TE P-tunnel advertised in a 842 (C-*,C-*) S-PMSI A-D route, call it R3. 844 o Tunnel T4 is a P2MP mLDP or RSVP-TE P-tunnel advertised in a 845 (C-S,C-G) S-PMSI A-D route, call it R4. 847 o The respective NLRIs of R3 and R4 contain the same RD value. 849 o The MPLS Label field of R3's PMSI Tunnel attribute is zero, and 850 the MPLS label value of R4's PMSI Tunnel attribute is zero. 852 In this example, it can be concluded that T3 and T4 are carrying 853 packets from the same ingress VRF. Thus if T3 is the expected 854 P-tunnel for a (C-S,C-G) flow, (S,G) packets from T4 can be safely 855 delivered to the egress VRF; they do not need to be discarded. 856 Similarly, if T4 is the expected P-tunnel for a (C-S,C-G) flow, (S,G) 857 packets from T3 can be safely delivered to the egress VRF. 859 When Ingress Replication (IR) P-tunnels are being used, please see 860 [MVPN-IR], especially Section 6 ("The PTA's MPLS Label Field") for a 861 discussion of how to determine when packets from other than the 862 expected P-tunnel must be discarded. 864 2.3.2. Policies to Prevent Ambiguity on a P-tunnel 866 For P-tunnels that are advertised in S-PMSI A-D routes whose NLRI 867 contains (C-S,C-G) or (C-S,C-*), the ambiguities described in 868 Sections 2.1 and 2.2 can be prevented by provisioning a policy that 869 assigns, to such P-tunnels, only flows from the same C-source. 871 However, it is not always possible to determine, through inspection 872 of the control messages, whether this policy has been deployed. For 873 instance, suppose a given VRF has imported a set of S-PMSI A-D 874 routes, that each route in the set has bound only a single 875 (C-S1,C-G1) to a single P-tunnel, and that each route in the set 876 identifies a different P-tunnel in its PTA than is identified by the 877 PTA of any other route in the set. One cannot infer from this that 878 there is no ambiguity, as the same P-tunnel may also have been 879 advertised in an S-PMSI A-D route that is not imported by the given 880 VRF, and that S-PMSI A-D route may have bound (C-S2,C-G2) to the 881 P-tunnel, where C-S1 != C-S2. 883 Therefore, in order to determine that a given P-tunnel (advertised in 884 a (C-S,C-G) or (C-S,C-*) S-PMSI A-D route) carries only C-flows from 885 a single C-source, a PE must have a priori knowledge (through 886 provisioning) that this policy has been deployed. In the remainder 887 of this document, we will refer to this policy as the "Single 888 C-source per (C-S,C-G) or (C-S,C-*) P-tunnel" policy. Note that this 889 policy is only applicable to P-tunnels that are advertised only in 890 (C-S,C-G) or (C-S,C-*) S-PMSI A-D routes. 892 Of course, if a P-tunnel is advertised in (a) an I-PMSI A-D route, or 893 (b) an S-PMSI A-D route whose NLRI contains (C-*,C-*), or (c) an 894 S-PMSI A-D route whose NLRI contains (C-*,C-G), then it is always 895 possible for the P-tunnel to contain traffic from multiple C-sources; 896 there is no policy that can prevent that. 898 However, if a P-tunnel advertised in a (C-*,C-G) S-PMSI A-D route 899 contains only traffic addressed to a single C-G, the address 900 uniqueness rules of Section 2 prevent the C-source addresses from 901 being ambiguous; the set of C-sources transmitting to a particular 902 extranet C-group address must be unambiguous over the set of MVPNs 903 that have receivers for that C-group. So for P-tunnels that are 904 advertised in (C-*,C-G) S-PMSI A-D routes, the ambiguities described 905 Section 2.1 and Section 2.2 can be prevented by provisioning a policy 906 that assigns, to such P-tunnels, only flows to the same extranet 907 C-group. We will refer to this policy as the "Single C-group per 908 (C-*,C-G) P-tunnel" policy. 910 These considerations can be summarized as follows. IF the procedures 911 referenced in Section 2.3.1 cannot be applied, then the PEs MUST be 912 provisioned so that the all of the following conditions hold true of 913 the VRFs that contain extranet C-sources: 915 o the "Single C-source per (C-S,C-G) or (C-S,C-*) P-tunnel" policy 916 is provisioned, and 918 o either no (C-*,C-G) S-PMSI A-D routes are advertised, or else the 919 "Single C-group per (C-*,C-G) P-tunnel" policy is provisioned, and 921 o no P-tunnels are advertised in I-PMSI A-D routes, and 923 o no (C-*,C-*) S-PMSI A-D routes are advertised. 925 Section 3 of this document describes a procedure known as "extranet 926 separation". When extranet separation is used, the ambiguity of 927 Section 2.1 is prevented. However, the ambiguity of Section 2.2 is 928 not prevented by extranet separation. Therefore, the use of extranet 929 separation is not a sufficient condition for avoiding the procedures 930 referenced in Section 2.3.1. Extranet separation is, however, 931 implied by the policies discussed in this section (Section 2.3.2). 933 3. Extranet Transmission Models 935 This document specifies several "extranet transmission models". A 936 given VRF, containing extranet C-sources or C-receivers, MUST use 937 only one of these models. Further if VRF S contains extranet 938 C-sources, VRF R contains extranet C-receivers, and it is allowed by 939 policy for an extranet C-receiver in VRF R to receive a C-flow from 940 an extranet C-source in VRF S, then VRFs S and R MUST use the same 941 extranet transmission model. The model used by a given VRF is 942 determined by provisioning. 944 3.1. Transmitting an Extranet C-flow on a Single PMSI 946 In one extranet transmission model, which we call the "transmitting 947 an extranet C-flow on a single PMSI" model, or more simply, the 948 "single PMSI per C-flow model", a PE transmitting a packet of an 949 extranet C-flow transmits it on only a single PMSI. If the PMSI is 950 instantiated by a multicast P-tunnel, this means that the PE 951 transmits the packet on a single P-tunnel. Of course, if the PE is a 952 replication point for that multicast P-tunnel, the packet is 953 transmitted more than once by the PE. Similarly, if the PMSI is 954 instantiated by a set of unicast tunnels (i.e., via Ingress 955 Replication), each packet may be transmitted multiple times. It is 956 still the case though that the packet is transmitted only on one 957 PMSI. 959 This document provides procedures for supporting this transmission 960 model using either BGP or PIM as the PE-PE C-multicast control 961 protocol. 963 There are two variants of this transmission model: "without extranet 964 separation" and "with extranet separation". 966 3.1.1. Without Extranet Separation 968 In this variant, multicast data traffic from extranet C-sources and 969 from non-extranet C-sources may be carried in the same P-tunnel. 971 This document provides procedures for supporting this variant using 972 either BGP or PIM as the PE-PE C-multicast control protocol. 974 3.1.2. With Extranet Separation 976 In this variant, multicast data traffic from extranet C-sources and 977 from non-extranet C-sources are never carried in the same P-tunnel. 978 Under certain circumstances, this can reduce the amount of multicast 979 data traffic that is delivered unnecessarily to certain PE routers. 980 It also eliminates the ambiguity discussed in Section 2.1. 982 By definition, when extranet separation is used, the following rule 983 MUST be applied: 985 Traffic from extranet C-sources MUST NOT be carried in the same 986 P-tunnel as traffic from non-extranet C-sources. 988 This rule does not impact those VRFs that contain only non-extranet 989 C-sources, nor does it impact those VRFs that contain only extranet 990 C-sources. However, if a particular VRF contains both kinds of 991 C-source, it will need to advertise some P-tunnels that are used for 992 carrying only extranet C-flows, and some that are used only for 993 carrying non-extranet C-flows. 995 This document provides procedures for supporting extranet separation 996 when BGP is used as the PE-PE C-multicast control protocol. Support 997 for extranet separation using PIM as the PE-PE C-multicast control 998 protocol is outside the scope of this document. 1000 3.2. Transmitting an Extranet C-flow over Multiple PMSIs 1002 The second extranet transmission model is called the "transmitting an 1003 extranet C-flow over multiple PMSIs" model, or more simply, the 1004 "multiple PMSIs per C-flow model". In this model, a PE may transmit 1005 the packets of an extranet C-flow on several different PMSIs. 1007 Support for extranet separation with this model is outside the scope 1008 of this document. 1010 This document provides procedures for supporting this transmission 1011 model when PIM as the PE-PE C-multicast control protocol. Support 1012 for this transmission model when BGP is used as the PE-PE C-multicast 1013 control protocol is outside the scope of this document. 1015 4. Distribution of Routes that Match C-S/C-RP Addresses 1017 4.1. UMH-Eligible Routes 1019 As described in Section 5.1 of [RFC6513], in order for a C-flow 1020 (C-S,C-G) to be carried across the SP backbone, a VRF that has 1021 multicast receivers for that C-flow must import a route that matches 1022 C-S, and this route must be "eligible for UMH selection". In this 1023 document, we will refer to these routes as "UMH-eligible extranet 1024 C-source routes". 1026 The UMH-eligible extranet C-source routes do not necessarily have to 1027 be unicast routes; they MAY be SAFI-129 routes (see Section 5.1.1 of 1028 [RFC6513]). For example, suppose one wants a VPN-R C-receiver to be 1029 able to receive extranet C-flows from C-sources in VPN-S, but one 1030 does not want any VPN-R system to be able to send unicast traffic to 1031 those C-sources. One can achieve this by using SAFI-129 routes as 1032 the UMH-eligible routes exported from VPN-S and imported by VPN-R. 1033 Since SAFI-129 routes are used only for UMH determination, but not 1034 for unicast routing, this allows the multicast traffic to be 1035 forwarded properly, but does not create unicast routes to the 1036 C-sources. 1038 If a customer is using PIM-SM in ASM mode, and one or more customer 1039 sites have C-receivers that are allowed by policy to join a (C-*,C-G) 1040 tree, where C-G is an extranet C-group, then any VRF with C-receivers 1041 for that group MUST import a UMH-eligible route that matches C-RP, 1042 where C-RP is the Rendezvous Point (RP) address for C-G. 1044 The UMH-eligible extranet C-source and C-RP routes do not have to be 1045 "host routes." That is, they can be routes whose IPv4 address 1046 prefixes are not 32 bits in length, or whose IPv6 address prefixes 1047 are not 128 bits in length. So it is possible for a UMH-eligible 1048 extranet C-source route to match the address of an extranet C-source 1049 and to also match the address of a non-extranet C-source. However, 1050 if such a route is exported from a VPN-S VRF and imported by a VPN-R 1051 VRF, VPN-R receivers will be able to receive C-flows from any non- 1052 extranet C-sources whose addresses match that route. To prevent 1053 this, the VPN-S VRF SHOULD be provisioned such that it will NOT 1054 export a UMH-eligible route that matches (in the context of the VPN-R 1055 VRF) both extranet C-sources and non-extranet C-sources. Failure to 1056 follow this rule may result in a VPN security violation. (See 1057 Section 10.) 1059 In general, one does not want ALL the routes from the VPN-S VRFs to 1060 be exported to all the VPN-R VRFs, as only a subset of the routes in 1061 the VPN-S VRFs will be UMH-eligible extranet C-source routes. Route 1062 distribution is, as always in a BGP/MPLS IP VPN [RFC4364], controlled 1063 by Route Targets (RTs). A variety of route distribution policies can 1064 be created by appropriately provisioning the import and export RTs of 1065 the various VRFs. 1067 For example, the VPN-S VRFs that contain extranet C-sources could be 1068 configured to apply an export RT whose value is "RT-A-extranet" to 1069 the routes that match the extranet C-sources. The VPN-R VRFs that 1070 contain extranet C-receivers allowed to receive extranet C-flows from 1071 VPN-S extranet C-sources could then be configured with "RT- 1072 A-extranet" as an import RT. 1074 Arbitrarily complex policies can be created by suitable manipulation 1075 of the import and export RTs. 1077 4.1.1. Extranet Separation 1079 If Extranet Separation is being used, and if a given VRF is exporting 1080 UMH-eligible routes both for extranet C-sources for non-extranet 1081 C-sources, then the VRF MUST be configured not only with its "default 1082 RD", but also with an "extranet RD". The exported UMH-eligible 1083 routes MUST contain the extranet RD in their NLRIs. 1085 4.2. Distribution of Unicast Routes Matching C-RPs and DRs 1087 Consider a C-source, C-S, that may transmit to a particular extranet 1088 C-group, C-G. 1090 In order to follow the procedures of [RFC4601], 1092 o the "first hop designated router" (DR) of C-S needs to be able to 1093 unicast "PIM Register Messages" to a C-RP that services C-G; 1095 o the C-RPs servicing C-G need to be able to unicast "PIM Register- 1096 Stop Messages" to the DR of C-S. 1098 It follows that if a VRF contains C-S, but does not contain a C-RP 1099 for C-G, then the VRF MUST import a unicast route matching a C-RP for 1100 C-G. Note that the unicast route matching the C-RP is needed whether 1101 or not the VRF has also imported a SAFI-129 route matching the C-RP. 1102 (If the VRF also contains receivers for C-G, and if UMH determination 1103 is being done using SAFI-129 routes, both a unicast route and a 1104 SAFI-129 matching C-RP route are needed.) 1106 Similarly, if a VRF contains a C-RP for C-G, but does not contain 1107 C-S, the VRF MUST import a unicast route matching the DR for C-S. 1108 Note that the unicast route matching the DR for C-S is needed even if 1109 UMH determination is being done using SAFI-129 routes; in that case, 1110 if the VRF also contains receivers for C-G, it needs to import a 1111 SAFI-129 route matching C-S and a unicast route matching the DR for 1112 C-S. 1114 If, for a particular extranet C-group, C-G, the customer is using 1115 "anycast-RP"([RFC3446], [RFC4610]) or MSDP [RFC3618], then all the 1116 C-RPs serving C-G need to send unicast messages to each other. Thus 1117 any VRF that contains a C-RP for C-G needs to import unicast routes 1118 matching ALL the other C-RPs that serve C-G. 1120 The need to distribute these unicast routes is usually not a problem 1121 as long as all the C-sources and C-RPs for C-G are in the same MVPN. 1122 If, however, the C-sources are not all in the same MVPN, great care 1123 must be taken to ensure that the unicast routes mentioned above are 1124 properly distributed. 1126 There may be scenarios in which all the C-sources for C-G are in the 1127 same MVPN, but there are receivers in different VPNs, and some or all 1128 of the VPNs with receivers have their own C-RPs for C-G. In this 1129 case, care must be taken to ensure that the C-RPs can all unicast to 1130 each other. 1132 4.3. Route Targets and Ambiguous UMH-Eligible Routes 1134 This section imposes constraints on the way RTs are assigned to (a) 1135 UMH-eligible routes and to (b) the BGP A-D routes that advertise 1136 P-tunnels (i.e., to BGP A-D routes that contain a PTA). The 1137 constraints specified here apply to any extranet for which the 1138 ambiguity of Section 2.2 is possible. (The conditions under which 1139 such ambiguity is possible are described in Section 2.2.) 1141 We want to ensure that, in any given VRF, the UMH-eligible route 1142 matching a given extranet C-source has an RT in common with every BGP 1143 A-D route that advertises a P-tunnel that may be used to carry 1144 extranet multicast traffic from that C-source. We also want to 1145 ensure that the UMH-eligible route matching a given extranet C-source 1146 does not have any RT in common with any BGP A-D route that advertises 1147 a P-tunnel that may be used to carry any multicast traffic from a 1148 different C-source that has the same IP address. This enables us to 1149 determine whether traffic that appears to be from the given C-source 1150 is really arriving on the "wrong tunnel", and hence is really from a 1151 different C-source with the same IP address. 1153 Suppose an IP address C-S is used in VPN-A as the address of one 1154 system, and is used in VPN-B as the address of a different system. 1155 In this case, one or more VPN-A VRFs may export a VPN-IP route whose 1156 NLRI is , and one or more VPN-B VRFs may export a VPN-IP route 1157 whose NLRI is , where RD1 != RD2. Consider two routes, R1 and 1158 R2, for which the following conditions all hold: 1160 o R1 and R2 are UMH-eligible extranet C-source or C-RP routes, or 1161 are unicast routes matching a C-RP 1163 o R1 is exported from a VRF of VPN-A, while R2 is exported from a 1164 VRF of a different VPN, say VPN-B 1166 o R1's NLRI specifies IP address prefix S/n 1168 o R2's NLRI specifies IP address prefix S/m 1170 o m >= n, (S/m is either the same as or more specific than S/n) 1172 o There is some host address H such that: 1174 * H denotes a different system in VPN-A than in VPN-B, 1176 * H/m == S/m (so either S/m or S/n might be a longest match for H 1177 in some VRF). 1179 We impose the following constraint: RTs MUST be assigned in such a 1180 way that R1 and R2 do not have any RT in common. 1182 (This constraint is not as onerous at it may seem. Typically R1 and 1183 R2 would not have an RT in common, as that might result in their 1184 being imported into the same VRF, making the address H ambiguous in 1185 that VRF.) 1187 Sections 6 and 7 specify procedures for determining if a received 1188 C-flow has been received over the expected P-tunnel. Those 1189 procedures will not work if this constraint is violated. (The 1190 constraint described in this section is necessary but not sufficient 1191 for the procedures of those sections to work; additional constraints, 1192 covering the assignment of RTs to BGP A-D routes, are given in 1193 subsequent sections.) 1195 4.4. Dynamically Marking Extranet Routes 1197 4.4.1. The Extranet Source Extended Community 1199 Sections 4.1, 4.2, and 4.3 place specific requirements on the way in 1200 which certain VPN-IP routes are distributed. In order to ensure that 1201 these requirements are met, a VPN customer must tell its SP which 1202 routes are the matching routes for extranet C-sources and C-RPs. 1203 This may be done as part of the provisioning process. Note that this 1204 does not necessarily require customer/provider interaction every time 1205 the customer adds a new extranet C-source or C-RP, but only when the 1206 IP address of the new C-source or C-RP does not match an existing 1207 route that is already being distributed as a VPN-IP extranet route. 1208 Nevertheless, it seems worthwhile to support an OPTIONAL mechanism 1209 that allows a customer to dynamically mark certain routes as being 1210 extranet routes. 1212 To facilitate this, we define a new Transitive Opaque Extended 1213 Community (see [RFC4360], [RFC7153], and Section 9 of this document) 1214 the "Extranet Source" Extended Community. When a CE router 1215 advertises (via BGP) a route to a PE router, and the AFI/SAFI of the 1216 route is 1/1, 1/2, 1/4, 2/1, 2/2, or 2/4, the Extranet Source 1217 Extended Community MAY be attached to the route. The value field of 1218 the Extended Community MUST be set to zero. By placing this Extended 1219 Community on a particular route, a CE router indicates to a PE router 1220 that the procedures of Sections 4.1, 4.2, and 4.3 are to be applied 1221 to that route. That is, the CE router may use this Extended 1222 Community to indicate to the PE router that a particular route is to 1223 be treated as a route that matches the address of an extranet source, 1224 and exported accordingly to other VPNs. A PE router that interprets 1225 this Extended Community MUST ignore the contents of the value field. 1227 Whether a CE router uses the Extranet Source Extended Community is 1228 determined by the configuration of the CE router. If used, the set 1229 of routes to which the Extended Community is attached is also 1230 determined by configuration of the CE. Note that a particular PE 1231 router may or may not support the use of the Extranet Source Extended 1232 Community by a particular CE router; this is determined by the 1233 service agreement between the SP and its customer. 1235 If a CE is advertising SAFI-2 routes to the PE as the UMH-eligible 1236 extranet C-source and C-RP routes, and if the CE is using the 1237 Extranet Source Extended Community, it is important that the CE 1238 attach that Extended Community to the SAFI-2 routes, rather than just 1239 to the corresponding SAFI-1 routes. Otherwise extranet receivers may 1240 not be able to join the (C-S,C-G) or (C-*,C-G) multicast trees. 1242 However, if the C-sources and the C-RPs for a given extranet C-group 1243 are not all in the same VPN, the Extended Community would also have 1244 to be attached to the SAFI-1 routes that match the C-RP addresses and 1245 to the SAFI-1 routes that match the addresses of the first hop 1246 designated routers for all the C-sources. Otherwise, the first hop 1247 routers might not be able to send PIM Register messages to the C-RPs, 1248 and the C-RPs might not be able to send PIM Register-Stop messages to 1249 the first hop routers. 1251 While this Extended Community allows a customer to inform the SP 1252 dynamically that certain routes are "extranet routes", it does not 1253 allow a customer to control the set of RTs that the route will carry 1254 when it is redistributed as a VPN-IP route. Thus it is only useful 1255 when all the extranet routes from a given VRF are exported with 1256 exactly the same set of RTs. (Cf. Section 4.3.1 of [RFC4364], which 1257 does provide a mechanism that, if properly supported by the SP, 1258 allows the customer to determine the set of RTs carried by a VPN-IP 1259 route.) A CE SHOULD NOT attach the Extranet Source Extended 1260 Community to any route for which it uses another method of specifying 1261 the RTs to be carried by that route. A CE SHOULD NOT attach the 1262 Extranet Source Extended Community to a route unless all the extranet 1263 routes from the CE's VPN are intended to carry the same set of RTs. 1265 A PE SHOULD ignore the Extranet Source Extended Community if it 1266 appears on a route that the CE should not have put it on. A PE that 1267 ignores the Extranet Source Extended Community SHOULD NOT follow the 1268 procedures of Section 4.4.2. 1270 Note that misconfiguration on the CE router can result in the 1271 Extranet Source Extended Community being mistakenly attached to a 1272 route that is not intended to be exported as an extranet route. This 1273 could result in a VPN security violation. 1275 4.4.2. Distribution of Extranet Source Extended Community 1277 Suppose a PE receives from a CE a route, call it R, with the Extranet 1278 Source Extended Community. The PE must determine (via the 1279 considerations of Section 4.4.1) whether it should ignore that 1280 Extended Community on route R. If so, the procedures of the current 1281 Section are not followed. 1283 Otherwise, when the PE originates a VPN-IP route corresponding to 1284 route R, the PE MUST attach this Extended Community to that route. 1286 A Route Reflector MUST NOT add or remove the Extranet Source Extended 1287 Community from the VPN-IP routes reflected by the Route Reflector, 1288 including the case where VPN-IP routes received via IBGP are 1289 reflected to EBGP peers (inter-AS option (c), see [RFC6513] 1290 Section 10). The value of the Extended Community MUST NOT be changed 1291 by the route reflector. 1293 When re-advertising VPN-IP routes, ASBRs MUST NOT add/remove the 1294 Extranet Source Extended Community from these routes. This includes 1295 inter-AS options (b) and (c) (see [RFC6513] Section 10). The value 1296 of the Extended Community MUST NOT be changed by the ASBRs. 1298 When a PE advertises (via BGP) IP routes to a CE, these routes MUST 1299 NOT carry the Extranet Source Extended Community, unless the PE-CE 1300 connection is actually an inter-AS Option (a) connection (see 1301 [RFC6513] Section 10). When the PE-CE connection is not an inter-AS 1302 Option (a) connection, a CE that receives an IP route with the 1303 Extranet Source Extended Community MUST remove it from the route 1304 before readvertising the route. 1306 The rules for attaching the Extranet Source Extended Community to a 1307 VPN-IP route, and the rules for propagating that Extended Community, 1308 are needed in order to support the scenario in which a VPN contains 1309 an Option (a) interconnect (see Section 10 of [RFC4364]). At the 1310 Option (a) interconnect, the VPN-IP route gets translated back to an 1311 IP route, and the RTs are stripped off before the IP route is 1312 propagated. If the Extranet Source EC has also been stripped off, 1313 there is no way for the router at the other end of the Option (a) 1314 interconnect to know that the route represents an extranet source. 1315 Thus the technique of using the Extranet Source EC to dynamically 1316 signal that a particular route represents an extranet source will not 1317 work correctly across an Option (a) interconnect unless the rules 1318 this section are followed. 1320 4.5. The 'Extranet Separation' Extended Community 1322 We define a new Transitive Opaque Extended Community, the "Extranet 1323 Separation" Extended Community (see [RFC4360], [RFC7153], and 1324 Section 9 of this document). This Extended Community is used only 1325 when extranet separation is being used. Its value field MUST be set 1326 to zero upon origination, MUST be ignored upon reception, and MUST be 1327 passed unchanged by intermediate routers. A Route Reflector MUST NOT 1328 add or remove the Extranet Separation Extended Community from the 1329 routes it reflects, including the case where routes received via IBGP 1330 are reflected to EBGP peers (inter-AS option (c), see [RFC6513] 1331 Section 10). 1333 If a VRF has been provisioned to use extranet separation, and if that 1334 VRF has been provisioned to transmit any extranet C-flows on a 1335 P-tunnel that it advertises in an I-PMSI A-D route or a (C-*,C-*) 1336 S-PMSI A-D route, then any UMH-eligible routes that are exported from 1337 that VRF following the procedures of Sections 4.1, 4.2, and 4.3 MUST 1338 carry the Extranet Separation Extended Community. In addition, if an 1339 I-PMSI A-D route and/or (C-*,C-*) S-PMSI A-D route, exported from 1340 that VRF, is used to carry extranet traffic, that A-D route MUST also 1341 carry the Extranet Separation Extended Community. Further details 1342 may be found in Sections 7.3, 7.4.4, and 7.4.5. 1344 5. Origination and Distribution of BGP A-D Routes 1346 Except where otherwise specified, this section describes procedures 1347 and restrictions that are independent of the PE-PE C-multicast 1348 control protocol. 1350 5.1. Route Targets of UMH-eligible Routes and A-D Routes 1352 Suppose there is an extranet C-flow such that: 1354 o The extranet C-source of that C-flow is in VRF A-1. 1356 o One or more extranet C-receivers of that C-flow are in VRF B-1. 1358 In this case VRF A-1 MUST export a UMH-eligible route that matches 1359 the extranet C-source address, and VRF B-1 MUST import that route. 1360 In addition, VRF A-1 MUST export an Intra-AS I-PMSI A-D route or an 1361 S-PMSI A-D route specifying the P-tunnel through which it will send 1362 the data traffic of the given extranet C-flow, and VRF B-1 MUST 1363 import that route. If BGP is the PE-PE C-multicast control protocol, 1364 then under certain conditions (as specified in [RFC6514]), VRF A-1 1365 may also need to export a Source Active A-D route specifying that it 1366 contains a source of the given C-flow, and VRF B-1 must import that 1367 Source Active A-D route. That is, in order for VRF B-1 to receive a 1368 C-flow from, a given extranet C-source contained in VRF A-1, VRF A-1 1369 MUST export a set of A-D routes that are "about" that source, and VRF 1370 B-1 MUST import them. 1372 One way to ensure this is to provision an RT that is carried by all 1373 the routes exported from VRF A-1 that are "about" a given extranet 1374 C-source, and to provision this RT as an import RT at any VRF (such 1375 as VRF B-1) that is allowed to receive extranet flows from source. 1377 If the "single PMSI per C-flow" transmission model is being used 1378 (with or without extranet separation), there is a an additional 1379 requirement, stated below, on the way RTs are provisioned, as the RTs 1380 carried by a UMH-eligible route that matches a given extranet 1381 C-source may need to be used to identify the A-D routes that are 1382 "about" that source. 1384 Consider the following scenario: 1386 o IP address S is the address of one system in VPN-A, and of a 1387 different system in VPN-B. 1389 o VRF A-1 on PE1 exports UMH-eligible route R1, which is a matching 1390 route for S. 1392 o VRF A-1 on PE1 exports an A-D route P1 whose PTA identifies a 1393 P-tunnel through which VRF A-1 may send traffic whose C-source is 1394 S, where one of the following conditions holds: 1396 * P1 is an I-PMSI A-D route, OR 1398 * P1 is an S-PMSI A-D route whose NLRI contains (C-*,C-*) or 1399 (C-*,C-G), OR 1401 * P1 is an S-PMSI A-D route whose NLRI contains (C-S,C-G) or 1402 (C-S,C-*), BUT the "single C-source per (C-S,C-G) or (C-S,C-*) 1403 P-tunnel" policy is not provisioned. 1405 * P1 is a Source Active A-D route whose NLRI contains (C-S,C-G). 1407 o VRF B-1 on PE1 exports a UMH-eligible route R2, which is a 1408 matching route for S. 1410 o VRF B-1 on PE1 exports an A-D route P2 whose PTA identifies a 1411 P-tunnel on which VRF B-1 may send traffic whose C-source is S, 1412 where one of the following conditions holds: 1414 * P2 is an I-PMSI A-D route, OR 1416 * P2 is an S-PMSI A-D route whose NLRI specifies (C-*,C-*) or 1417 (C-*,C-G), OR 1419 * P2 is an S-PMSI A-D whose NLRI specifies (C-S,C-G) or 1420 (C-S,C-*), BUT the "single C-source per (C-S,C-G) or (C-S,C-*) 1421 P-tunnel" policy is not provisioned. 1423 * P2 is a Source Active A-D route whose NLRI contains (C-S,C-G) 1425 As already specified in Section 4.1, there MUST NOT be any RT that is 1426 common to both R1 and R2. In addition, the following set of rules 1427 for RT assignment MUST be followed when extranets are supported. 1428 This set of rules supports all the extranet transmission models 1429 described in this specification: 1431 o There MUST NOT be any RT that is carried by both P1 and P2. 1433 o The intersection of the set of RTs carried by P1 and the set of 1434 RTs carried by R1 MUST be non-null, and any VRF that imports both 1435 P1 and R1 MUST be configured with an import RT from this 1436 intersection. 1438 o The intersection of the set of RTs carried by P2 and the set of 1439 RTs carried by R2 MUST be non-null, and any VRF that imports both 1440 P2 and R2 MUST be configured with an import RT from this 1441 intersection. 1443 Suppose VRF C-1 on PE2 imports P1 and R1 from VRF A-1, while also 1444 importing P2 from VRF B-1. Since: 1446 o R1 is VRF C-1's route to S, and 1448 o R1 has an RT in common with P1, and 1450 o R1 has no RT in common with P2 1452 it can be concluded that VRF C-1 should expect that multicast traffic 1453 from S will arrive on the P-tunnel specified in P1. See Section 6 1454 and Section 7 for more details on determining the expected P-tunnel 1455 for a given extranet C-flow. 1457 While the assignment of import and export RTs to routes is a 1458 deployment and provisioning issue rather than a protocol issue, it 1459 should be understood that failure to follow these rules is likely to 1460 result in VPN security violations. 1462 5.2. Considerations for Particular Inclusive Tunnel Types 1464 An Inclusive Tunnel (sometimes referred to as an "Inclusive Tree", 1465 see Section 2.1.1 of [RFC6513]) is a tunnel that, by default, carries 1466 all the multicast traffic of a given MVPN that enters the backbone 1467 network via a particular PE. An Inclusive Tunnel is advertised in 1468 the PTA of an I-PMSI A-D route. 1470 5.2.1. RSVP-TE P2MP or Ingress Replication 1472 This section applies when Inclusive Tunnels are created using either 1473 RSVP-TE P2MP or Ingress Replication. 1475 Suppose a VRF, VRF-S, contains a given extranet C-source C-S, and 1476 that VRF-S advertises in its Intra-AS I-PMSI A-D route either a P2MP 1477 RSVP-TE P-tunnel or an Ingress Replication P-tunnel to carry extranet 1478 traffic. 1480 In order for VRF-S to set up the P2MP RSVP-TE or Ingress Replication 1481 P-tunnel, it must know all the PEs that are leaf nodes of the 1482 P-tunnel, and to learn this it must import an Intra-AS I-PMSI A-D 1483 route from every VRF that needs to receive data through that tunnel. 1485 Therefore if VRF-R contains an extranet C-receiver that is allowed by 1486 policy to receive extranet flows from C-S, the RT(s) carried by the 1487 Intra-AS I-PMSI A-D routes originated by VRF-R MUST be such that 1488 those Intra-AS I-PMSI A-D routes will be imported into VRF-S. 1490 In the case of Ingress Replication, this has the following 1491 consequence. If an egress PE has n VRFs with receivers for a flow 1492 that VRF-S transmits on its I-PMSI, that egress PE will receive n 1493 copies of the same packet, one for each of the n VRFs. 1495 Note that Section 9.1.1 of [RFC6514] prohibits the Leaf Information 1496 Required flag from being set in the PTA of an Intra-AS I-PMSI A-D 1497 route. If this prohibition is ever removed, the requirement of this 1498 section will apply only if VRF-S does not set that flag. 1500 5.2.2. Ingress Replication 1502 This section applies only when Inclusive Tunnels are created via 1503 Ingress Replication. 1505 [RFC6513] and [RFC6514] specify procedures that allow I-PMSIs to be 1506 instantiated by Ingress Replication. The concept of an IR P-tunnel, 1507 and the procedures for supporting IR P-tunnels, are explained more 1508 fully in [MVPN-IR]. An IR P-tunnel can be thought of as a P2MP tree 1509 in which a packet is transmitted from one node on the tree to another 1510 by being encapsulated and sent through a unicast tunnel. 1512 As discussed in Section 2, when I-PMSIs are used to support 1513 extranets, egress PEs MUST have the ability to discard customer 1514 multicast data packets that arrive on the wrong P-tunnel. When 1515 I-PMSIs are instantiated by IR, this implies that the following two 1516 procedures MUST be followed: 1518 1. One of the following three procedures MUST be followed: 1520 a. the "Single Forwarder Selection" procedures of [RFC6513] 1521 Section 9.1.2, 1523 b. the "Native PIM Methods" procedures of [RFC6513] 1524 Section 9.1.3 1526 c. the unicast encapsulation used to transmit packets along the 1527 IR P-tunnel is such as to enable the receiving node to 1528 identify the transmitting node (note that this would not be 1529 the case if, e.g., the unicast tunnels were MP2P LSPs); 1531 and 1533 2. If a PE assigns an MPLS label value in the PMSI Tunnel attribute 1534 of an Intra-AS or Inter-AS I-PMSI A-D route that it originates, 1535 that label value MUST NOT appear in the PMSI Tunnel attribute of 1536 any other I-PMSI or S-PMSI A-D route originated by the same PE. 1538 Failure to follow these procedures would make it impossible to 1539 discard packets that arrive on the wrong P-tunnel, and thus could 1540 lead to duplication of data. 1542 If it is desired to support extranet while also using IR to 1543 instantiate the PMSIs, an alternative is to use (C-*,C-*) S-PMSIs 1544 instead of I-PMSIs. (See [RFC6625], as well as Sections 7.2.2, 1545 7.3.2, and 7.4.4 of this document.) This has much the same effect in 1546 the data plane, and there are no restrictions on the type of unicast 1547 tunnel that can be used for instantiating S-PMSIs. 1549 Section 6.4.5 of [RFC6513] describes a way to support VPNs using 1550 I-PMSIs that are instantiated by IR, using no S-PMSIs, but using 1551 "explicit tracking" to ensure that a C-flow goes only to egress PEs 1552 that have receivers for it. This document does not provide 1553 procedures to support extranet using that model. 1555 6. When PIM is the PE-PE C-multicast Control Plane 1557 As specified in [RFC6513], when PIM is used as the PE-PE C-multicast 1558 control plane for a particular MVPN, there is a "Multidirectional 1559 Inclusive Provider Multicast Serivce Interface" (MI-PMSI) for that 1560 MVPN, and all the PEs of that MVPN must be able to send and receive 1561 on that MI-PMSI. Associated with each VRF of the MVPN is a PIM 1562 C-instance, and the PIM C-instance treats the MI-PMSI as if it were a 1563 LAN interface. That is, the "ordinary" PIM procedures run over the 1564 MI-PMSI just as they would over a real LAN interface, except that the 1565 data plane and control plane "RPF checks" need to be modified. 1566 Section 5.2 of [RFC6513] specifies the RPF check modifications for 1567 non-extranet MVPN service. 1569 For example, suppose that there are two VPNs, VPN-S and VPN-R. In 1570 the absence of extranet support, all the VRFs of VPN-S are connected 1571 via one MI-PMSI (call it "the VPN-S MI-PMSI"), and all the VRFs of 1572 VPN-R are connected via another ("the VPN-R MI-PMSI"). If we want to 1573 provide extranet service in which the extranet C-sources are attached 1574 to some set of VPN-S VRFs, while the extranet C-receivers are 1575 attached to some set of VPN-R VRFs, then we have two choices: 1577 1. either the VPN-R VRFs need to join the VPN-S MI-PMSI, or 1579 2. the VPN-S VRFs need to join the VPN-R MI-PMSI. 1581 The first choice is used to support the "single PMSI per C-flow" 1582 transmission model. The second choice is used to support the 1583 "multiple PMSIs per C-flow" transmission model. 1585 Procedures for both models are described below. 1587 To support these models, it must be possible to determine which 1588 I-PMSI A-D routes are associated with the VPN-S I-PMSI, and which are 1589 associated with the VPN-R I-PMSI. Procedures are given for assigning 1590 RTs to these routes in a way that makes this determination possible. 1592 Both models allow the use of S-PMSIs to carry multicast data traffic. 1593 If a VRF containing receivers can receive from multiple MI-PMSIs, 1594 each S-PMSI must be uniquely associated with a particular MI-PMSI. 1595 Procedures are given for assigning RTs to these routes in a way that 1596 makes this determination possible. 1598 All the procedures specified in Sections 3, 4, and 5 still apply. 1600 Note that there are no special extranet procedures for Inter-AS 1601 I-PMSI A-D routes or for Leaf A-D routes. Source Active A-D routes 1602 are not used when PIM is the PE-PE C-multicast protocol. 1604 6.1. Provisioning VRFs with RTs 1606 6.1.1. Incoming and Outgoing Extranet RTs 1608 In the absence of extranet service, suppose that each VRF of a given 1609 VPN, call it VPN-S, is configured with RT-S as its import and export 1610 RT, and that each VRF of a second VPN, call it VPN-R, is configured 1611 with RT-R as its import and export RT. We will refer to RT-S and 1612 RT-R as "non-extranet RTs". 1614 Now suppose that VPN-S contains some extranet C-sources, and VPN-R 1615 contains some extranet C-receivers that are allowed by policy to 1616 receive extranet C-flows from the VPN-S extranet C-sources. 1618 To set up this S-to-R extranet, it is REQUIRED to provision an 1619 additional RT, call it RT-S-to-R, whose value is, in general, 1620 distinct from RT-S and RT-R. 1622 A VPN-S VRF that contains extranet C-sources allowed to transmit to 1623 VPN-R MUST be configured with RT-S-to-R as an "Outgoing Extranet RT". 1625 A VPN-R VRF that contains extranet C-receivers allowed to received 1626 from VPN-S MUST be configured with RT-S-to-R as an "Incoming Extranet 1627 RT". 1629 Note that the terms "Incoming" and "Outgoing" in this context refer 1630 to the direction of multicast data packets relative to the VRF. 1632 The Incoming Extranet RTs and Outgoing Extranet RTs that are 1633 configured for a given VRF serve as import RTs for that VRF. They 1634 also serve as export RTs, but only for specific routes as specified 1635 in Section 6.1.2 below. 1637 Note that any VRF that contains both extranet C-sources and extranet 1638 C-receivers MUST be configured with both Outgoing and Incoming 1639 Extranet RTs. 1641 A VRF MAY be configured with more than one Incoming and/or Outgoing 1642 Extranet RT. 1644 If it happens to be the case that all C-sources in VPN-S are extranet 1645 C-sources allowed to transmit to VPN-R, then VPN-S VRFs MAY be 1646 configured such that RT-S is both a non-extranet RT and an Outgoing 1647 Extranet RT, and VPN-R VRFs MAY be configured such that RT-S is an 1648 Incoming Extranet RT. 1650 6.1.2. UMH-eligible Routes and RTs 1652 Suppose R1 is a route, exported from a VPN-S VRF, matching an 1653 extranet C-source that is allowed by policy to transmit to VPN-R. 1654 Then R1 MUST carry the Outgoing Extranet RT used for the S-to-R 1655 extranet. This will cause the route to be imported into the VPN-R 1656 VRFs that have extranet C-receivers that are allowed by policy to 1657 receive from VPN-S. 1659 The rules of Section 4 regarding route targets and ambiguous 1660 addresses still apply. 1662 6.1.3. PIM C-Instance Reverse Path Forwarding Determination 1664 Suppose a PIM control message, call it M, is received by a given VRF 1665 V, from a particular P-tunnel T. In order to process control message 1666 M, the PIM C-instance associated with VRF V may need to do an "RPF 1667 determination" (see Section 5.2.2 of RFC 6513) for a particular IP 1668 prefix S. RPF determination is based upon the rules for UMH 1669 selection as specified in Section 5.1 of RFC 6513. 1671 This document adds an additional constraint on the UMH selection 1672 procedure. When doing RPF determination for a PIM control message 1673 received over a P-tunnel, a route matching prefix S is not considered 1674 to be eligible for UMH selection unless there is an RT, call it RT1, 1675 configured as one of V's Outgoing Extranet RTs, such that the 1676 following two conditions both hold: 1678 1. The route matching S is exported from VRF V carrying RT1, and 1680 2. An I-PMSI A-D route advertising P-tunnel T (in its PTA) has been 1681 imported into VRF V, and that I-PMSI A-D route carries RT1. 1683 6.2. Single PMSI per C-flow Model 1685 In this model, if a VPN-S VRF has extranet multicast C-sources, and a 1686 VPN-R VRF has extranet multicast C-receivers allowed by policy to 1687 receive from the C-sources in the VPN-S VRF, then the VPN-R VRF joins 1688 the MI-PMSI that VPN-S uses for its non-extranet traffic. 1690 6.2.1. Forming the MI-PMSIs 1692 Consider a VPN-S VRF that has extranet C-sources. Per [RFC6513], 1693 each VPN-S VRF must originate an Intra-AS I-PMSI A-D route containing 1694 a PMSI Tunnel Attribute (PTA) specifying the P-tunnel to be used as 1695 part of the VPN-S MI-PMSI. In the absence of extranet service, this 1696 route carries the VRF's non-extranet RT, RT-S. When extranet service 1697 is provided (using the "single PMSI per C-flow" model), this route 1698 MUST also carry each of the VRF's Outgoing Extranet RTs. 1700 Consider a VPN-R VRF that has extranet C-receivers. Per [RFC6513], 1701 each VPN-R VRF must originate an Intra-AS I-PMSI A-D route containing 1702 a PTA specifying the P-tunnel to be used as part of the VPN-R MI- 1703 PMSI. This route carries the VRF's non-extranet RT RT-R. When 1704 extranet service is provided (using the "single PMSI per C-flow" 1705 model), the VPN-R VRF MUST also originate one or more additional 1706 Intra-AS I-PMSI A-D routes. It MUST originate one additional Intra- 1707 AS I-PMSI A-D route for each Incoming Extranet RT with which it has 1708 been configured; each such route will carry exactly one of the 1709 configured Incoming Extranet RTs. 1711 Note that when a VRF originates more than one Intra-AS I-PMSI A-D 1712 route, each of them MUST contain a different RD in its NLRI. In 1713 addition, we add the requirement that any pair of such routes MUST 1714 NOT contain an RT in common. 1716 A VRF with extranet C-sources MUST join the P-tunnels advertised in 1717 the imported I-PMSI A-D routes that carry its non-extranet RT or any 1718 of its Outgoing Extranet RTs. This set of P-tunnels will be treated 1719 as instantiating a single MI-PMSI, and the associated PIM C-instance 1720 will treat that MI-PMSI as a single LAN, and will run PIM procedures 1721 on that LAN, as specified in [RFC6513]. The fact that the MI-PMSI 1722 attaches to VRFs of different VPNs is not known to the PIM C-instance 1723 of the VRF containing the sources. 1725 A VRF with extranet C-receivers MUST join the P-tunnels advertised in 1726 all the imported I-PMSI A-D routes. The set of P-tunnels advertised 1727 in the I-PMSI A-D routes that carry a particular Incoming Extranet RT 1728 are treated as instantiating a particular MI-PMSI. So a VRF with 1729 C-receivers will "see" several MI-PMSIs, one corresponding to the 1730 non-extranet, and as many as one for each configured Incoming 1731 Extranet RT. The PIM C-instance associated with the VRF will treat 1732 each of these MI-PMSIs as a separate LAN interface. 1734 As an example, suppose: 1736 o All VPN-R VRFs are configured with RT-R as a non-extranet import 1737 and export RT, 1739 o VPN-R VRFs with extranet receivers are configured with RT-S-to-R 1740 as an Incoming Extranet RT, 1742 o VPN-S VRFs with extranet transmitters are configured: 1744 * with RT-S as a non-extranet import and export RT 1746 * with a list of IP addresses that are the addresses of the 1747 extranet sources 1749 * with RT-S-to-R as an Outgoing Extranet RT 1751 Then VPN-S VRFs will export UMH-eligible routes matching extranet 1752 C-sources, and these routes will carry both RT-S and RT-S-to-R. Each 1753 VPN-S VRF will also export an Intra-AS I-PMSI A-D route that carries 1754 both RT-S and RT-S-to-R. 1756 VPN-R VRFs will originate and export two Intra-AS I-PMSI A-D routes: 1757 one carrying RT-R, and one carrying RT-S-to-R. The Intra-AS I-PMSI 1758 A-D route with RT-S-to-R will be imported into the VPN-S VRFs. 1760 VPN-R will regard all the I-PMSI A-D routes it has exported or 1761 imported with RT-S-to-R as part of a single MI-PMSI. VPN-R will 1762 regard all the I-PMSI A-D routes it has exported or imported with 1763 RT-R as part of a second MI-PMSI. The PIM C-instance associated with 1764 a VPN-R VRF will treat the two MI-PMSIs as two separate LAN 1765 interfaces. However, the VPN-S VRFs will regard all the I-PMSI A-D 1766 routes imported with RT-S or RT-S-to-R as establishing only a single 1767 MI-PMSI. One can think of this as follows: the VPN-R VRFs have 1768 joined the VPN-S MI-PMSI, as well as the VPN-R MI-PMSI. 1770 Extranets consisting of more than two VPNs are easily supported as 1771 follows. Suppose there are three VPNs, VPN-A, VPN-B, and VPN-C. 1772 VPN-A and VPN-B have extranet C-sources, and VPN-C contains receivers 1773 for both VPN-A extranet C-sources and VPN-B extranet C-sources. In 1774 this case, the VPN-C VRFs that have receivers for both VPN-A and 1775 VPN-B sources may be provisioned as follows. These VPN-C VRFs may be 1776 provisioned with RT-C as a non-extranet RT, and with RT-A-to-C and 1777 RT-B-to-C as Incoming Extranet RTs. In this case, the VPN-C VRFs 1778 that are so provisioned will originate three Intra-AS I-PMSI A-D 1779 routes (each with a different RD in its NLRI), each of which carries 1780 exactly one of the three RTs just mentioned. The VPN-B VRFs with 1781 extranet C-sources will be provisioned with RT-B-to-C as an Outgoing 1782 Extranet RT, and the VPN-A VRFs are provisioned with RT-A-to-C as an 1783 Outgoing Extranet RT. The result will be that the PIM C-instance 1784 associated with a VPN-C VRF will see three LAN interfaces: one for 1785 the non-extranet, one for each of the two extranets. This 1786 generalizes easily to the case where there are VPN-C receivers in n 1787 different extranets (i.e., receiving extranet flows whose sources are 1788 in n different VPNs). 1790 Suppose again that there are there are three VPNs, VPN-A, VPN-B, and 1791 VPN-C. But in this example, VPN-A is the only one with extranet 1792 sources, while VPN-B and VPN-C both have receivers for the VPN-A 1793 extranet sources. This can be provisioned as either one extranet or 1794 as two. 1796 To provision it as one extranet, the VPN-A VRFs are configured with 1797 one Outgoing Extranet RT, call it "RT-A-extranet". The VPN-B and 1798 VPN-C VRFs with extranet receivers will be provisioned with RT- 1799 A-extranet as Incoming Extranet RT. Thus the VPN-B and VPN-C VRFs 1800 will each originate two Intra-AS I-PMSI A-D routes, one for non- 1801 extranet, and one for the extranet. The Intra-AS I-PMSI A-D route, 1802 from a given VRF, for the extranet will carry RT-A-extranet, but will 1803 not share any RT with the non-extranet A-D routes exported from the 1804 same VRF. 1806 The result is that the VPN-B and VPN-C VRFs each belong to two MI- 1807 PMSIs, one for the extranet and one for the intranet. The MI-PMSI 1808 for the extranet attaches VPN-A VRFs, VPN-B VRFs, and VPN-C VRFs. 1810 Alternatively, one could provision the VPN-A VRFs so that some UMH- 1811 eligible extranet source routes carry an RT which we will call "RT-A- 1812 to-B", and some carry an RT which we will call "RT-A-to-C". The 1813 VPN-A VRFs would be configured with both of these as Outgoing 1814 Extranet RTs. To allow an extranet flow from a VPN-A source to have 1815 both VPN-B and VPN-C receivers, the UMH-eligible route for that 1816 source would carry both RTs. VPN-B VRFs (but not VPN-C VRFs) would 1817 be provisioned with RT-A-to-B as an Incoming Extranet RT. VPN-C VRFs 1818 (but not VPN-B VRFs) would be provisioned with RT-A-to-C as an an 1819 Incoming Extranet RT. 1821 Following the rules above, if any VPN-A extranet source is to have 1822 both VPN-B and VPN-C receivers, the VPN-B and VPN-C VRFs will each 1823 originate two I-PMSI A-D routes, one for extranet and one for non- 1824 extranet. The single Intra-AS I-PMSI A-D route originated by the 1825 VPN-A VRFs will have both RT-A-to-B and RT-A-to-C among its RTs (as 1826 well as VPN-A's non-extranet RT). The extranet I-PMSI A-D route 1827 originated from a VPN-B VRF would have RT-A-to-B, and the extranet 1828 I-PMSI A-D route originated from a VPN-C VRF would have RT-A-to-C. 1830 If a given VRF contains both extranet C-receivers and extranet 1831 C-sources, the procedures described above still work, as the VRF will 1832 be configured with both Incoming Extranet RTs and Outgoing Extranet 1833 RTs; the VRF functions both as a VPN-S VRF and as a VPN-R VRF. 1835 6.2.2. S-PMSIs 1837 When PIM is used as the PE-PE C-multicast control plane, every S-PMSI 1838 is considered to be part of the "emulated LAN" that "corresponds" to 1839 a particular MI-PMSI. 1841 When the bindings of C-flows to particular S-PMSIs are announced via 1842 S-PMSI Join Messages ([RFC6513], Section 7) sent on the MI-PMSI, the 1843 S-PMSI is considered to be part of the same LAN interface as the 1844 corresponding MI-PMSI. 1846 When the bindings of C-flows to particular S-PMSIs are announced via 1847 S-PMSI A-D routes, then any S-PMSI A-D route exported from that VRF 1848 MUST have an RT in common with exactly one of the Intra-AS A-D routes 1849 exported from that VRF, and this MUST be one of the VRF's Outgoing 1850 Extranet RTs. Further, the S-PMSI A-D route MUST NOT have an RT in 1851 common with any other Intra-AS A-D route exported from a VRF on the 1852 same PE. A given S-PMSI A-D route will be considered to "correspond" 1853 to the MI-PMSI of the Intra-AS I-PMSI A-D route (originated from the 1854 same PE) with which it shares an RT. 1856 The MI-PMSI that corresponds to a given S-PMSI is determined as 1857 follows: 1859 o If there is an Intra-AS I-PMSI A-D route originated by the same PE 1860 that originated the S-PMSI A-D route, and if the those two routes 1861 have an RT in common, and if that RT is one of the VRF's Incoming 1862 Extranet RTs, then the S-PMSI corresponds to the I-PMSI associated 1863 with that Intra-AS I-PMSI A-D route. 1865 o Otherwise, if there is an Inter-AS I-PMSI A-D route originated in 1866 the same AS as the S-PMSI A-D route, and if the those two routes 1867 have an RT in common, and if that RT is one of the VRF's Incoming 1868 Extranet RTs, then the S-PMSI corresponds to the I-PMSI associated 1869 with that Inter-AS I-PMSI A-D route. 1871 o Otherwise, there must be a configuration error (a violation of the 1872 requirements of Sections 3, 4, and 5 of this document). 1874 When wildcard S-PMSIs are used, the rules given in [RFC6625] for 1875 determining whether a given S-PMSI A-D route is a "match for 1876 reception" to a given (C-S,C-G) or (C-*,C-G) are modified as follows: 1878 A given S-PMSI A-D route MUST NOT be considered to be a "match for 1879 reception" for a given (C-S,C-G) or (C-*,C-G) state UNLESS that 1880 S-PMSI A-D route "corresponds" (as defined above) to the MI-PMSI 1881 that is the incoming interface for the given state. 1883 The rules given in [RFC6625] for determining whether a given S-PMSI 1884 A-D route is a "match for transmission" are unchanged. 1886 6.2.3. Sending PIM Control Packets 1888 Suppose a PE, say PE1, receives a PIM Join(S,G) from a CE, over a VRF 1889 interface that is associated with a VPN-R VRF. The PE does the RPF 1890 check for S by looking up S in the VPN-R VRF. The PIM C-instance 1891 associated with that VRF must determine the correct P-tunnel over 1892 which to send a PIM Join(S,G) to other PEs. 1894 To do this, PE1 finds, in the VRF associated with the interface over 1895 which the Join was received, the selected UMH route for S, following 1896 the procedures of Section 5.1 of [RFC6513]. PE1 determines the set 1897 of RTs carried by that route. PE1 then checks to see if there is an 1898 Intra-AS I-PMSI A-D route, currently originated by PE1, that has an 1899 RT in common with the selected UMH route for S. 1901 If the rules of Sections 3, 4, and 5 have been followed, each of 1902 PE1's selected UMH routes will share an RT with a single one of PE1's 1903 currently originated Intra-AS I-PMSI A-D routes. If this is so, the 1904 Join is sent on the P-tunnel advertised in the PTA of that route. 1905 Otherwise, the Join MUST NOT be sent. 1907 In essence, this procedure makes the RPF check for C-S resolve to the 1908 MI-PMSI that is serving as the next hop "interface" to C-S. 1910 If a PE receives a PIM Join(*,G) from a CE, the procedure for doing 1911 the RPF check is the same, except that the selected UMH route will be 1912 a route to the C-RP associated with the C-G group. 1914 6.2.4. Receiving PIM Control Packets 1916 When a PIM C-instance receives a PIM control message from a P-tunnel, 1917 it needs to identify the message's "incoming interface". This 1918 incoming interface is the MI-PMSI of which the P-tunnel is a part. 1920 6.2.5. Sending and Receiving Data Packets 1922 The rules for choosing the PMSI on which to send a multicast data 1923 packet are as specified in [RFC6513] and [RFC6625], with one new 1924 restriction: a VPN-S VRF always transmits a multicast data packet 1925 either on the VPN-S MI-PMSI or on an S-PMSI that corresponds to the 1926 VPN-S MI-PMSI. From the perspective of the PIM C-instance, there is 1927 only one outgoing interface. 1929 When a PIM C-instance receives a multicast data packet from a given 1930 P-tunnel, and that P-tunnel is being used to instantiate an MI-PMSI, 1931 the MI-PMSI of which the P-tunnel is a part (see Sections 6.2.1 and 1932 6.2.2) is considered to be the packet's "incoming interface". If the 1933 packet is received on a P-tunnel that was advertised in an S-PMSI A-D 1934 route, the packet's "incoming interface" is the MI-PMSI to which that 1935 S-PMSI route corresponds, as defined in Section 6.2.2. Ordinary PIM 1936 rules for data plane RPF check apply. 1938 Following ordinary PIM procedures, packets arriving from an 1939 unexpected incoming interface are discarded. This eliminates any 1940 problems due to the ambiguities described in Sections 2.1 and 2.2. 1942 6.3. Multiple PMSIs per C-flow Model 1944 In this model, if a VPN-S VRF has extranet multicast C-sources, and a 1945 VPN-R VRF has extranet multicast C-receivers allowed by policy to 1946 receive from the C-sources in the VPN-S VRF, then the VPN-S VRF joins 1947 the MI-PMSI that VPN-R uses for its non-extranet traffic. 1949 In the "single PMSI per C-flow" transmission model (as described in 1950 Section 6.2), a PE that needs to transmit a multicast data packet to 1951 a set of other PEs transmits the packet on a single PMSI. This means 1952 that if a packet needs to be transmitted from a VPN-A VRF and 1953 received at a VPN-B VRF and a VPN-C VRF, there must be some P-tunnel 1954 from which the VPN-B and VPN-C VRFs can both receive packets. 1956 In the "multiple PMSIs per C-flow" transmission model, a PE that 1957 needs to transmit a multicast data packet to a set of other PEs may 1958 transmit the packet on several different PMSIs. (Of course, any 1959 given packet is transmitted only once on a given P-tunnel.) For 1960 example, if a C-flow (C-S,C-G) has a VPN-A C-source, a VPN-B 1961 receiver, and a VPN-C receiver, there could be one PMSI that the 1962 VPN-A VRF uses to transmit the packet to the VPN-B VRFs, and another 1963 PMSI that the VPN-A VRF uses to transmit the packet to the VPN-C 1964 VRFs. 1966 6.3.1. Forming the MI-PMSIs 1968 Consider a VPN-R VRF that has extranet C-receivers. Per [RFC6513], 1969 each VPN-R VRF must originate an Intra-AS I-PMSI A-D route containing 1970 a PMSI Tunnel Attribute (PTA) specifying the P-tunnel to be used as 1971 part of the VPN-R MI-PMSI. In the absence of extranet service, this 1972 route carries the VRF's non-extranet RT, RT-R. When extranet service 1973 is provided (using the "single PMSI per C-flow" model), this route 1974 MUST also carry each of the VRF's Incoming Extranet RTs. 1976 Consider a VPN-S VRF that has extranet C-sources. Per [RFC6513], 1977 each VPN-S VRF must originate an Intra-AS I-PMSI A-D route containing 1978 a PTA specifying the P-tunnel to be used as part of the VPN-S MI- 1979 PMSI. This route carries the VRF's non-extranet RT RT-S. When 1980 extranet service is provided using the "multiple PMSI per C-flow" 1981 model, the VPN-S VRF MUST also originate one or more additional 1982 Intra-AS I-PMSI A-D routes. It MUST originate one additional Intra- 1983 AS I-PMSI A-D route for each outgoing extranet RT with which it has 1984 been configured; each such route will have a distinct RD, and will 1985 carry exactly one of the configured Outgoing Extranet RTs. 1987 As with the "single PMSI per C-flow" transmission model, VRFs 1988 containing extranet C-receivers need to import UMH-eligible extranet 1989 C-source routes from VRFs containing C-sources. This is ensured by 1990 the rules of 3, 4, and 5. 1992 However, in the "multiple PMSIs per C-flow model", a VRF containing 1993 only C-receivers originates only a single Intra-AS I-PMSI A-D route, 1994 carrying the non-extranet RT and all the Incoming Extranet RTs. 1996 When a VRF containing C-receivers imports Intra-AS I-PMSI A-D routes 1997 that carry the non-extranet RT or one of the Incoming Extranet RTs, 1998 the P-tunnels specified in the PTA of all such routes are considered 1999 to be part of the same MI-PMSI. I.e., the associated PIM C-instance 2000 will treat them as part of a single interface. 2002 In this model, it is the VRF containing extranet C-sources that MUST 2003 originate multiple Intra-AS I-PMSI A-D routes. Each such route MUST 2004 have a distinct RD, and the set of RTs carried by any one of these 2005 routes MUST be disjoint from the set carried by any other. There 2006 MUST be one such route for each of the VRF's Outgoing Extranet RTs, 2007 and each such route MUST carry exactly one of the VRF's Outgoing 2008 Extranet RTs. The VRFs containing extranet C-sources MUST also 2009 import all the A-D routes originated by the VRFs containing extranet 2010 C-receivers. If a set of originated and/or imported Intra-AS I-PMSI 2011 A-D routes have an RT in common, and that RT is one of the VRF's 2012 Outgoing Export RTs, then those routes are considered to be "about" 2013 the same MI-PMSI. The PIM C-instance of the VRF treats each MI-PMSI 2014 as a LAN Interface. 2016 In effect, if VPN-S has only extranet C-sources and VPN-R has only 2017 extranet C-receivers, this model has the VPN-S VRFs join the VPN-R 2018 MI-PMSI. The VPN-S VRFs will thus be attached to multiple MI-PMSIs, 2019 while the VPN-R VRFs are attached to only one. The fact that the 2020 VPN-R MI-PMSI is attached to VPN-S VRFs is not known to the PIM 2021 C-instance at the VPN-R VRFs. 2023 If a VPN-A VRF has extranet C-sources allowed to send to C-receivers 2024 in a VPN-B VRF, and the VPN-B VRF has C-sources allowed to send to 2025 C-receivers in the VPN-A VRF, the above procedures still work as 2026 specified. 2028 Following normal PIM procedures, when the PIM C-instance at a VRF 2029 with extranet C-sources receives a Join(C-S,C-G) or a Join(C-*,C-G) 2030 over an MI-PMSI, it may create (C-S,C-G) or (C-*,C-G) state, and the 2031 MI-PMSI over which the Join was received may be added to the set of 2032 outgoing interfaces for that multicast state. If n MI-PMSIs are 2033 added to the outgoing interface list for a particular multicast 2034 state, a multicast data packet may need to be replicated n times, and 2035 transmitted once on each of the n MI-PMSIs. 2037 Since the all multicast data packets received from another PE are 2038 received over a single emulated LAN, it is not necessary to have any 2039 special procedures to determine a packet's "incoming interface". The 2040 ambiguities described in Section 2.1 and Section 2.2 do not occur, 2041 because a VPN-R VRF can only receive multicast data traffic that has 2042 been requested by a VPN-R VRF. 2044 7. When BGP is the PE-PE C-multicast Control Plane 2046 This document assumes that if BGP is used as the PE-PE C-multicast 2047 control plane, the "Single PMSI per C-flow" model is used. 2048 Procedures for providing the "Multiple PMSIs per C-flow" model with 2049 BGP C-multicast are outside the scope of this document. 2051 When BGP is used as the C-multicast control plane, the Single PMSI 2052 per C-flow model may be used either with or without "extranet 2053 separation". (Recall that "extranet separation" means that no 2054 P-tunnel can carry both traffic from extranet sources and traffic 2055 from non-extranet sources.) In either case, the data traffic may be 2056 carried on inclusive tunnels only, or on selective tunnels only 2057 (known as the "S-PMSI only" model), or on a combination of inclusive 2058 and selective tunnels. This is determined by provisioning. The 2059 procedures specified below support all three choices. 2061 Note that there are no special extranet procedures for Inter-AS 2062 I-PMSI A-D routes or for Leaf A-D routes. 2064 7.1. Originating C-multicast Routes 2066 This section applies whether extranet separation is used or not. 2068 When it is necessary to originate a C-multicast Source Tree Join for 2069 (C-S,C-G), a PE must follow the procedures of Section 11.1.3 2070 ("Constructing the rest of the C-multicast route") of [RFC6514] to 2071 find the selected UMH route for C-S. When it is necessary to 2072 originate a C-multicast Shared Tree Join for (C-*,C-G),where C-G is 2073 an ASM group, a PE must follow the procedures of that section to find 2074 the selected UMH route for C-G's C-RP. 2076 Section 11.1.3 of [RFC6514] specifies how information from the 2077 selected UMH route is used to find an Intra-AS I-PMSI A-D route or an 2078 Inter-AS I-PMSI A-D route. Information from that I-PMSI A-D route is 2079 then used to construct part of the C-multicast route. 2081 For extranet, this specification modifies the procedures of 2082 Section 11.1.3 of [RFC6514] as follows. The rules given in 2083 Section 7.4.5 ("I-PMSI A-D Routes") of this document are used to find 2084 the Inter-AS I-PMSI A-D route or an Intra-AS I-PMSI A-D route that 2085 "corresponds to" the selected UMH route. (That is, the rules of 2086 Section 7.4.5 of this document replace the rules given in 2087 Section 11.1.3 of [RFC6514] for finding the Inter-AS or Intra-AS 2088 I-PMSI A-D route.) 2090 Information from this I-PMSI A-D route is then used, as specified in 2091 Section 11.1.3 of [RFC6514], to construct the C-multicast route. 2093 7.2. Originating A-D Routes Without Extranet Separation 2095 7.2.1. Intra-AS I-PMSI A-D Routes 2097 Consider a VRF, call it VRF-S, that contains extranet C-sources, and 2098 that exports UMH-eligible routes matching those C-sources. The VRF 2099 may also originate and export an Intra-AS I-PMSI A-D route. 2101 As specified in [RFC6514], if exactly one Intra-AS I-PMSI A-D route 2102 is originated by and exported from VRF-S, the RTs carried by that 2103 route MUST be chosen such that every VRF that imports a UMH-eligible 2104 route from VRF-S also imports this Intra-AS I-PMSI A-D route. 2106 If inclusive P-tunnels are being used to carry extranet C-flows, 2107 there are additional requirements on the way the RTs carried by the 2108 Intra-AS I-PMSI A-D routes must be chosen, as specified in the 2109 following paragraph. 2111 If VRF-S is using inclusive P-tunnels, but is not using extranet 2112 separation, there is one inclusive P-tunnel rooted at VRF-S, and this 2113 tunnel carries both extranet and non-extranet C-flows. This 2114 inclusive tunnel is identified in the PMSI Tunnel Attribute (PTA) of 2115 the Intra-AS I-PMSI A-D route originated from VRF-S. The set of RTs 2116 carried by this Intra-AS I-PMSI A-D route MUST be chosen so as to 2117 ensure that every VRF that imports a UMH-eligible route from this 2118 VRF-S also imports this Intra-AS I-PMSI A-D route. Further, the set 2119 of RTs carried by this Intra-AS I-PMSI A-D route MUST be chosen such 2120 that it has at least one RT in common with every UMH-eligible route 2121 that is exported from the VRF. 2123 7.2.2. S-PMSI A-D Routes 2125 Let R-SP be an S-PMSI A-D route that is exported from VRF-S. Suppose 2126 that R-SP is used to bind some or all of the extranet C-flows from a 2127 given extranet C-source to a given selective P-tunnel. Let R-UMH be 2128 a UMH-eligible route that is exported from VRF-S and that matches the 2129 given extranet C-source. Then R-SP and R-UMH MUST have at least one 2130 RT in common. Further, the RTs carried by these two routes MUST be 2131 such that every VRF that imports R-UMH also imports R-SP. These 2132 rules apply whether or not R-SP uses wildcards [RFC6625]. 2134 An implementation MUST allow the set of RTs carried by the S-PMSI A-D 2135 routes to be specified by configuration. In the absence of such 2136 configuration, an S-PMSI A-D route originated by a given VRF X MUST 2137 carry a default set of RTs, as specified by the following rules: 2139 1. By default an S-PMSI A-D route originated by VRF X for a given 2140 (C-S,C-G) or (C-S,C-*) carries the same RT(s) as the UMH-eligible 2141 route originated by VRF X that matches C-S. 2143 2. By default an S-PMSI A-D route originated by VRF X for a given 2144 (C-*,C-G) carries as its RTs a set union of all RT(s) of the UMH- 2145 eligible route(s) matching the multicast C-sources contained in 2146 VRF X that could originate traffic for that C-G. Moreover, if 2147 the VRF contains (as defined in Section 1.1) the C-RP of C-G, 2148 then this set union also includes the RT(s) of the UMH-eligible 2149 route matching C-RP, and of the unicast VPN-IP route matching 2150 C-RP. 2152 3. By default, if a (C-*,C-*) S-PMSI A-D route originated by VRF X 2153 is to be used for both extranet and non-extranet traffic, it 2154 carries the same RTs that would be carried (as specified in 2155 Section 7.2.1) by an I-PMSI A-D route originated by VRF X if that 2156 I-PMSI A-D route were advertising an inclusive P-tunnel for 2157 carrying both extranet and non-extranet traffic. In general, a 2158 given VRF would not originate both (a) an S-PMSI A-D route 2159 advertising a (C-*,C-*) selective P-tunnel for both extranet and 2160 non-extranet traffic and (b) an I-PMSI A-D route advertising an 2161 inclusive P-tunnel for both extranet and non-extranet traffic, as 2162 the inclusive P-tunnel would not get used in that case. 2164 7.2.3. Source Active A-D Routes 2166 7.2.3.1. When Inter-Site Shared Trees Are Used 2168 This section applies when Inter-Site Shared Trees are used, as 2169 specified in [RFC6514] Section 13. 2171 If VRF-S exports a Source Active A-D route that contains C-S in the 2172 Multicast Source field of its NLRI, and if that VRF also exports a 2173 UMH-eligible route matching C-S, the Source Active A-D route MUST 2174 carry at least one RT in common with the UMH-eligible route. The RT 2175 MUST be chosen such that the following condition holds: if VRF-R 2176 contains an extranet C-receiver allowed by policy to receive extranet 2177 traffic from C-S, then VRF-R imports both the UMH-eligible route and 2178 the Source Active A-D route. 2180 By default, a Source Active A-D route for a given (C-S,C-G), exported 2181 by a given VRF, carries the same set of RTs as the UMH-eligible route 2182 matching C-S that is exported from that VRF. 2184 7.2.3.2. When Inter-Site Shared Trees Are Not Used 2186 This section applies when Inter-Site Shared Trees are not used, as 2187 specified in [RFC6514] Section 14. 2189 Suppose a VRF, say VRF-X, contains the C-RP for a given extranet 2190 C-group, say C-G. If C-S is an active source for C-G, then following 2191 the procedures of Section 14.1 of [RFC6514], VRF-X may export a 2192 Source Active A-D route that contains C-S in the Multicast Source 2193 field of its NLRI. This document replaces the rule for constructing 2194 the RT(s) carried by such a route, specified in Section 14.1 of 2195 [RFC6514], with the following. VRF-X MUST be configured such that 2196 the Source Active A-D route for (C-S,C-G) carries the same set of RTs 2197 as the UMH-eligible route matching C-S that is exported from the 2198 VRF(s) containing C-S. This way, if a VRF, say VRF-R, contains an 2199 extranet C-receiver allowed by policy to receive extranet traffic 2200 from C-S, then VRF-R imports both the UMH-eligible route and the 2201 Source Active A-D route. 2203 7.3. Originating A-D Routes With Extranet Separation 2205 If a VRF contains both extranet C-sources and non-extranet C-sources, 2206 it MUST be configured with both a "default RD" and an "extranet RD" 2207 (see Section 1.3). The use of these RDs is explained in the 2208 following sub-sections. 2210 7.3.1. Intra-AS I-PMSI A-D Routes 2212 This section applies when VRF-S is using extranet separation, AND 2213 when VRF-S is using an inclusive P-tunnel to carry some or all of the 2214 extranet C-flows that it needs to transmit to other VRFs. 2216 If VRF-S contains both extranet C-sources and non-extranet C-sources, 2217 and if inclusive P-tunnels are used to carry both extranet C-flows 2218 and non-extranet C-flows, then there MUST be two inclusive tunnels 2219 from VRF-S, one of which is to be used only to carry extranet C-flows 2220 (the "extranet inclusive P-tunnel"), and one of which is to be used 2221 only to carry non-extranet C-flows (the "non-extranet inclusive 2222 P-tunnel"). 2224 In this case, the VRF MUST originate two Intra-AS I-PMSI A-D routes. 2225 Their respective NLRIs MUST of course have different RDs. One of the 2226 Intra-AS I-PMSI A-D routes identifies the extranet inclusive P-tunnel 2227 in its PTA. This route MUST have the VRF's "extranet RD" in its 2228 NLRI. The other route identifies the non-extranet inclusive P-tunnel 2229 in its PTA. This route MUST have the VRF's "default RD" in its PTA. 2231 If VRF-S uses an inclusive P-tunnel for carrying extranet traffic, 2232 but does not use an inclusive P-tunnel for carrying non-extranet 2233 traffic, then of course only a single Intra-AS I-PMSI A-D route need 2234 be originated. The PTA of this route identifies the "extranet 2235 inclusive P-tunnel". The NLRI of that route MUST contain the VRF's 2236 extranet RD. 2238 An Intra-AS I-PMSI A-D route whose PTA identifies an extranet 2239 inclusive P-tunnel MUST carry the Extranet Separation Extended 2240 Community defined in Section 4.5. 2242 The RTs carried by an Intra-AS I-PMSI A-D route whose PTA identifies 2243 the "extranet inclusive P-tunnel" MUST be chosen such that the 2244 following condition holds: if a VRF (call it VRF-R) imports a UMH- 2245 eligible route from VRF-S, and if that route matches an extranet 2246 C-source, then VRF-R also imports that Intra-AS I-PMSI A-D route. 2248 Note that when extranet separation is used, it is possible to use an 2249 inclusive P-tunnel for non-extranet traffic while using only 2250 selective P-tunnels for extranet traffic. It is also possible to use 2251 an inclusive P-tunnel for extranet traffic while using only selective 2252 P-tunnels for non-extranet traffic. 2254 7.3.2. S-PMSI A-D Routes 2256 Let R-SP be an S-PMSI A-D route that is exported from VRF-S. Suppose 2257 that R-SP is used to bind some or all of the extranet C-flows from a 2258 given extranet C-source to a given selective P-tunnel. Let R-UMH be 2259 a UMH-eligible route that is exported from VRF-S and that matches the 2260 given extranet C-source. Then R-SP and R-UMH MUST have at least one 2261 RT in common. Further, the RTs carried by these two routes MUST be 2262 such that every VRF that imports R-UMH also imports R-SP. These 2263 rules apply whether or not R-SP uses wildcards [RFC6625]. 2265 The following rules, specific to the use of extranet separation, 2266 apply: 2268 o A selective P-tunnel MUST NOT carry C-flows from both extranet and 2269 non-extranet C-sources, 2271 o If it is desired to use a (C-*,C-*) S-PMSI to carry extranet 2272 traffic and also to use a (C-*,C-*) S-PMSI to carry non-extranet 2273 traffic, then two (C-*,C-*) S-PMSI A-D routes MUST be originated. 2274 These two routes MUST have different RDs in their respective NLRI 2275 fields, and their respective PTAs MUST identify different 2276 P-tunnels. If the route advertises a P-tunnel that carries only 2277 non-extranet traffic, the route's NLRI MUST contain the VRF's 2278 default RD. If the route advertises a P-tunnel that carries only 2279 extranet traffic, the route's NLRI MUST contain the VRF's extranet 2280 RD. 2282 o In the following cases, an S-PMSI A-D route exported from the VRF 2283 MUST have the VRF's extranet RD in its NLRI: 2285 * The S-PMSI A-D route is a (C-S,C-G) or a (C-S,C-*) S-PMSI A-D 2286 route, and C-S is an extranet C-source. 2288 * The S-PMSI A-D route is a (C-*,C-G) S-PMSI A-D route, and C-G 2289 is an extranet C-group. 2291 In all other cases, a (C-S,C-G), (C-S,C-*), or (C-*,C-G) S-PMSI 2292 A-D route MUST have the VRF's default RD in its NLRI. 2294 o A (C-*,C-*) S-PMSI A-D route advertising a P-tunnel that is used 2295 to carry extranet traffic MUST carry the Extranet Separation 2296 Extended Community defined in Section 4.5. 2298 An implementation MUST allow the set of RTs carried by the S-PMSI A-D 2299 routes to be specified by configuration. In the absence of such 2300 configuration, an S-PMSI A-D route originated by a given VRF X MUST 2301 carry a default set of RTs, as specified by the following rules: 2303 1. Rule 1 of Section 7.2.2 applies. 2305 2. By default, if C-G is an extranet C-group, rule 2 of 2306 Section 7.2.2 applies. 2308 3. By default, if a (C-*,C-*) S-PMSI A-D route originated by VRF X 2309 is to be used for extranet traffic, it carries the same RTs that 2310 would be carried (as specified in Section 7.3.1) by an I-PMSI A-D 2311 route originated by VRF X if that I-PMSI A-D route were 2312 advertising an inclusive P-tunnel for carrying extranet traffic. 2313 In general, a given VRF would not originate both an S-PMSI A-D 2314 route advertising a (C-*,C-*) selective P-tunnel for extranet 2315 traffic and an I-PMSI A-D route advertising an inclusive P-tunnel 2316 for extranet traffic, as the inclusive P-tunnel would not get 2317 used in that case. 2319 7.3.3. Source Active A-D Routes 2321 The procedures of Section 7.2.3 apply. 2323 However, if a Source Active A-D route is exported from a given VRF, 2324 and the route contains C-S, where C-S is an extranet C-source, then 2325 the RD of the route's NLRI MUST be the extranet RD of the VRF. 2326 Otherwise the RD is the default RD of the VRF. 2328 7.4. Determining the Expected P-tunnel for a C-flow 2330 This section applies whether extranet separation is used or not. 2332 In the context of a VRF with receivers for a particular C-flow, a PE 2333 must determine the P-tunnel over which packets of that C-flow are 2334 expected to arrive. This is done by finding an I-PMSI or S-PMSI A-D 2335 route that "matches" the flow. The matching A-D route will contain a 2336 PTA that specifies the P-tunnel being used to carry the traffic of 2337 that C-flow. We will refer to this P-tunnel as the "expected 2338 P-tunnel" for the C-flow. (Note that, per [MVPN-IR], if the PTA 2339 specifies an tunnel of type "Ingress Replication" (IR), the 2340 identifier of the P-tunnel is actually the NLRI of the I-PMSI or 2341 S-PMSI A-D route. If the PTA specifies a tunnel type other than IR, 2342 the identifier of the P-tunnel is found in the "tunnel identifier" 2343 field of the PTA.) 2344 A PE that needs to receive a given (C-S,C-G) or (C-*,C-G) C-flow MUST 2345 join the expected P-tunnel for that C-flow, and the PE MUST remain 2346 joined to the P-tunnel as long as the PE continues to need to receive 2347 the given C-flow, and the P-tunnel continues to remain the expected 2348 P-tunnel for that C-flow. Procedures for joining and leaving a 2349 tunnel depend, of course, on the tunnel type. 2351 If a PTA specifies a non-zero MPLS label for a tunnel that is not an 2352 IR tunnel, then the PE originating the A-D route containing that PTA 2353 is advertising an aggregate P-tunnel. The aggregate P-tunnel can be 2354 thought of as an outer P-tunnel multiplexing some number of inner 2355 P-tunnels. The inner P-tunnels are demultiplexed by means of the 2356 MPLS label in the PTA. In this document, when we talk of the 2357 "expected P-tunnel" in the context of an aggregate P-tunnel, we refer 2358 to a particular inner P-tunnel, not to the outer P-tunnel. It is 2359 this "inner P-tunnel" that is the expected P-tunnel for a given 2360 C-flow. 2362 In order to find the expected P-tunnel for a given C-flow, the 2363 upstream PE of the C-flow is first determined. Then the S-PMSI A-D 2364 routes originated by that PE are examined, and their NLRIs compared 2365 to the (C-S/C-RP,C-G) of the flow, to see if there is a "match for 2366 reception". (If there is no S-PMSI A-D route that matches a given 2367 C-flow, the expected P-tunnel for that C-flow may have been 2368 advertised in an I-PMSI A-D route; see Section 7.4.5.) 2370 The rules for determining, in non-extranet cases, whether a given 2371 C-flow is a "match for reception" for a given S-PMSI A-D route are 2372 given in [RFC6625] Section 3.2. Note that we use the terms 2373 "installed" and "originated" as they are defined in [RFC6625] 2374 Section 3.2. (See also Section 1.1 of this document.) 2376 This specification adds additional rules for determining whether a 2377 given S-PMSI A-D route is a "match for reception" for a given (C-S/ 2378 C-RP,C-G). Note that these rules all assume the context of a 2379 particular VRF into which the A-D route has been imported. 2381 The rules given in [RFC6625] for determining whether a given S-PMSI 2382 A-D route is a "match for transmission" remain unchanged. 2384 Suppose a PE has originated a C-multicast Shared Tree Join for 2385 (C-*,C-G), has not originated a C-multicast Source Tree Join for 2386 (C-S,C-G), but has received and installed a Source Active A-D route 2387 for (C-S,C-G). As described in Section 13.2 of [RFC6514], the PE 2388 must receive the (C-S,C-G) traffic from the tunnel the originator of 2389 the installed Source Active A-D route uses for sending (C-S,C-G). 2391 The originator of the installed Source Active A-D route is determined 2392 as follows: 2394 1. Look at the "UMH Route Candidate Set" for C-S, as defined in 2395 [RFC6513] Section 5.1.3. 2397 2. From that set select a subset of UMH routes to C-S, such that 2398 each route in the subset has at least one RT in common with the 2399 Source Active A-D route, and at least one of the RTs in common is 2400 an import RT of the VRF. 2402 3. From that subset, find the route whose RD is the same as the RD 2403 from the NLRI of the Source Active A-D route. 2405 4. The Upstream PE is the PE identified in the VRF Route Import 2406 Extended Community of that route. 2408 5. The Upstream AS is the AS identified in the Source AS Extended 2409 Community of that route. 2411 If the result of step 2 is an empty set, or if step 3 fails to find a 2412 route, then the Upstream PE of the Source Active A-D route cannot be 2413 determined, and it is necessary to act as if the Source Active A-D 2414 route had not been installed. (A subsequent change to the UMH Route 2415 Candidate Set for C-S may require that a new attempt be made to 2416 determine the Upstream PE.) 2418 Once the upstream PE is determined, the P-tunnel over which the flow 2419 is expected is determined according to the procedures already 2420 described in this section. 2422 7.4.1. (C-S,C-G) S-PMSI A-D Routes 2424 When extranet functionality is being provided, an S-PMSI A-D route 2425 whose NLRI contains (C-S,C-G) is NOT considered to be a "match for 2426 reception" for a given C-flow (C-S,C-G) unless one of the following 2427 conditions holds (in addition to the conditions specified in 2428 [RFC6625]): 2430 o the "single C-source per (C-S,C-G) or (C-S,C-*) P-tunnel" is 2431 provisioned, or 2433 o the selected UMH route for C-S has at least one RT in common with 2434 the S-PMSI A-D route, and at least one of the common RTs is an 2435 import RT of the VRF. 2437 7.4.2. (C-S,C-*) S-PMSI A-D Routes 2439 When extranet functionality is being provided, an S-PMSI A-D route 2440 whose NLRI contains (C-S,C-*) is NOT considered to be a "match for 2441 reception" for a given C-flow (C-S,C-G) unless one of the following 2442 conditions holds, in addition to the conditions specified in 2443 [RFC6625]: 2445 o the "single C-source per (C-S,C-G) or (C-S,C-*) P-tunnel" is 2446 provisioned, or 2448 o the selected UMH route for C-S has at least one RT in common with 2449 the S-PMSI A-D route, and at least one of the common RTs is an 2450 import RT of the VRF. 2452 7.4.3. (C-*,C-G) S-PMSI A-D Routes 2454 When extranet functionality is being provided, an S-PMSI A-D route 2455 whose NLRI contains (C-*,C-G) is NOT considered to be a "match for 2456 reception" for a given C-flow (C-S,C-G) in a given VRF unless either 2457 condition 1 or condition 2 below holds, in addition to the conditions 2458 specified in [RFC6625]: 2460 1. The given VRF has currently originated a C-multicast Shared Tree 2461 Join route for (C-*,C-G), and 2463 a. (C-*,C-G) matches an installed (C-*,C-G) S-PMSI A-D route 2464 (according to [RFC6625]) in the given VRF, and 2466 b. either 2468 i. the "Single C-group per (C-*,C-G) P-tunnel" policy has 2469 been provisioned, or 2471 ii. the RTs of that S-PMSI A-D route form a non-empty 2472 intersection with the RTs carried in the VRF's 2473 selected UMH route for C-RP of that C-G, or 2475 iii. installed in the VRF is at least one (C-S,C-G) Source 2476 Active A-D route that was originated by the same PE as 2477 the (C-*,C-G) S-PMSI A-D route. 2479 2. The given VRF does not have a currently originated C-multicast 2480 Shared Tree Join for (C-*,C-G), but 2482 a. there are one or more values for C-S for which the VRF has a 2483 currently originated Source Tree Join C-multicast route for 2484 (C-S,C-G), and 2486 b. the (C-* C-G) S-PMSI A-D route matches (according to 2487 [RFC6625]) each such (C-S,C-G), and 2489 c. either 2491 i. the "Single C-group per (C-*,C-G) P-tunnel" policy has 2492 been provisioned, or 2494 ii. the RTs of that S-PMSI A-D route form a non-empty 2495 intersection with the RTs carried in the VRF's selected 2496 UMH routes for each such C-S 2498 If a VRF has an installed (C-*,C-G) S-PMSI A-D route, but does 2499 not have a (C-S,C-G) or (C-*,C-G) multicast state that matches 2500 that route for reception, the procedures of Section 12.3 2501 ("Receiving S-PMSI A-D Routes by PEs") of [RFC6514] are not 2502 invoked for that route. If those multicast states are created at 2503 some later time when the route is still installed, the procedures 2504 of Section 12.3 of [RFC6514] are invoked at that time. 2506 7.4.4. (C-*,C-*) S-PMSI A-D Routes 2508 A (C-*,C-*) S-PMSI A-D Route (call it "R-AD") is NOT considered to be 2509 a match for reception for a given C-flow (C-S,C-G) or (C-*,C-G) 2510 unless the following conditions hold (in addition to the conditions 2511 specified in [RFC6625]: 2513 o the selected UMH route (call it "R-UMH") for C-S or for C-G's C-RP 2514 respectively has at least one RT in common with R-AD, and at least 2515 one of the common RTs is an import RT of the VRF. 2517 o either R-AD and R-UMH both carry the Extranet Separation Extended 2518 Community, or neither carries the Extranet Separation Extended 2519 Community. 2521 7.4.5. I-PMSI A-D Routes 2523 If a particular egress VRF in a particular egress PE contains no 2524 matching S-PMSI A-D routes for a particulalr C-flow, then the C-flow 2525 is expected to arrive (at that egress VRF) on an inclusive P-tunnel. 2527 Suppose that an egress PE has originated a (C-S,C-G) C-Multicast 2528 Source Tree Join. Let R-UMH be the selected UMH route (in the given 2529 egress VRF) or C-S. As specified in [RFC6514], the selected upstream 2530 PE for (C-S,C-G) is determined from the VRF Route Import Extended 2531 Community of R-UMH, and the "selected upstream AS" for the flow is 2532 determined from the Source AS Extended Community of R-UMH. 2534 Suppose that an egress PE has originated a (C-*,C-G) C-Multicast 2535 Shared Tree Join, but has not originated a (C-S,C-G) C-Multicast 2536 Source Tree Join. If the egress VRF does not have a (C-S,C-G) Source 2537 Active A-D route installed, the selected upstream PE is determined 2538 from the VRF Route Import Extended Community of the installed UMH- 2539 eligible route matching C-RP, where C-RP is the RP for the group C-G. 2540 The selected upstream AS for the flow is determined from the Source 2541 AS Extended Community of that route. If the egress VRF does have a 2542 (C-S,C-G) Source Active A-D route installed, the selected upstream PE 2543 and upstream AS are determined as specified in Section 7.4. In 2544 either case, let R-UMH be the installed UMH-eligible route matching 2545 C-S. 2547 The inclusive P-tunnel that is expected to be carrying a particular 2548 C-flow is found as follows: 2550 o If the selected upstream AS is the local AS, or if segmented 2551 Inter-AS P-tunnels are not being used to instantiate I-PMSIs, then 2552 look in the VRF for an installed Intra-AS I-PMSI A-D route, R-AD, 2553 such that (a) R-AD originated by the selected upstream PE, (b) 2554 R-AD has at least one an RT in common with R-UMH, (c) at least one 2555 of the common RTs is an import RT of the local VRF, and (d) either 2556 R-AD and R-UMH both carry the Extranet Separation Extended 2557 Community, or neither carries the Extranet Separation Extended 2558 Community. 2560 The PTA of R-AD specifies the P-tunnel over which traffic of the 2561 given C-flow is expected. 2563 o If the selected upstream AS is not the local AS, and if segmented 2564 Inter-AS P-tunnels are being used to instantiate I-PMSIs, then 2565 look in the VRF for an installed Inter-AS I-PMSI A-D route, R-AD, 2566 such that (a) the Source AS field of R-AD's NLRI contains the AS 2567 number of the selected upstream AS, (b) R-AD has at least one RT 2568 in common with R-UMH, (c) at least one of the common RTs is an 2569 import RT of the local VRF, and (d) either R-AD and R-UMH both 2570 carry the Extranet Separation Extended Community, or neither 2571 carries the Extranet Separation Extended Community. 2573 The PTA of R-AD specifies the P-tunnel over which traffic of the 2574 given C-flow is expected. 2576 7.5. Packets Arriving from the Wrong P-tunnel 2578 Any packets that arrive on a P-tunnel other than the expected 2579 P-tunnel (as defined in Section 7.4) MUST be discarded, unless it is 2580 know that all the packets carried by both P-tunnels are from the same 2581 ingress VRF. (See Section 2.3.1 for a more detailed discussion of 2582 when to discard packets from other than the expected P-tunnel.) Note 2583 that packets arriving on the wrong P-tunnel are to be discarded even 2584 if they are arriving from the expected PE. 2586 8. Multiple Extranet VRFs on the same PE 2588 When multiple VRFs that contain extranet receivers for a given 2589 extranet source are present on the same PE, this PE becomes a single 2590 leaf of the P-tunnel used for sending (multicast) traffic from that 2591 source to these extranet receivers. The PE MUST be able to replicate 2592 this traffic to the multiple VRFs. Specific procedures for doing so 2593 are local to the PE, and outside the scope of this document. 2595 Two or more VRFs on the same PE may import the same S-PMSI A-D route. 2596 If this S-PMSI A-D route contains a PTA that has its "Leaf Info 2597 Required" bit set, it may be necessary for the PE to originate a Leaf 2598 A-D route whose NLRI is computed from the NLRI of the S-PMSI A-D 2599 route. (Details are in [RFC6514].) Note that for a given S-PMSI A-D 2600 route, the PE can originate only one corresponding Leaf A-D route, 2601 even if the S-PMSI A-D route is imported into multiple VRFs. This 2602 Leaf A-D route can thus be thought of as originating from several 2603 VRFs. It MUST NOT be withdrawn by the PE until there are no longer 2604 any VRFs originating it. 2606 [RFC6514] specifies conditions under which a PE originates a 2607 C-Multicast Source Tree Join or a C-Multicast Shared Tree Join, based 2608 on the (*,G) and (S,G) states associated with a given VRF. It also 2609 specifies the procedure for computing the NLRI of each such route. 2610 While a given PE may contain two or more VRFs that have (extranet) 2611 receivers for the same extranet C-flow, the PE cannot originate more 2612 than one BGP route with a given NLRI. If there are multiple VRFs, 2613 each of which has state that is sufficient to cause a given 2614 C-multicast route to be originated, the route can be thought of as 2615 originating from several VRFs. It MUST NOT be withdrawn by the PE 2616 until there is no longer any VRF with multicast state sufficient to 2617 cause the route to be originated. 2619 For a given extranet the site(s) that contain the extranet source(s) 2620 and the site(s) that contain the extranet receiver(s) may be 2621 connected to the same PE. In this scenario, the procedures by which 2622 (multicast) traffic from these sources is delivered to these 2623 receivers is a local matter to the PE, and outside the scope of this 2624 document. 2626 An implementation MUST support multiple extranet VRFs on a PE. 2628 9. IANA Considerations 2630 IANA is requested to allocate two new codepoints from the "First 2631 Come, First Served" range of the "Transitive Opaque Extended 2632 Community Sub-Types" Registry (under the top-level registry: "Border 2633 Gateway Protocol (BGP) Extended Communities"). [TO BE REMOVED: This 2634 registration should take place at the following location: 2635 http://www.iana.org/assignments/bgp-extended-communities/bgp- 2636 extended-communities.xhtml#trans-opaque] 2638 o A codepoint for "Extranet Source Extended Community" 2640 o A codepoint for "Extranet Separation Extended Community" 2642 10. Security Considerations 2644 The security considerations of [RFC6513] and [RFC6514] are 2645 applicable. 2647 As is the case with any application of technology based upon 2648 [RFC4364], misconfiguration of the RTs may result in VPN security 2649 violations (i.e., may result in a packet being delivered to a VPN 2650 where, according to policy, it is not supposed to go). 2652 The procedures of this document do not provide encryption of the data 2653 flows that are sent across the SP backbone network. Hence these 2654 procedures do not by themselves ensure the privacy or integrity of 2655 the data against attacks on the backbone network. 2657 In general, different VPNs are allowed to have overlapping IP address 2658 spaces, i.e., a host in one VPN may have the same IP address as a 2659 host in another. This is safe because the customer routes from a 2660 given VPN do not pass into other VPNs. Even if there is overlapping 2661 address space among VPNs, the routes that are known at any given VPN 2662 site are unambiguous, as long as the address space of that VPN is 2663 unambiguous. However, this is not necessarily true when extranet 2664 service is provided. If an extranet C-receiver in VPN-R is to be 2665 able to receive multicast traffic from an extranet C-source in VPN-S, 2666 then the address of the VPN-S extranet C-source must be imported into 2667 one or more VPN-R VRFs. If that address is also the address of a 2668 VPN-R non-extranet C-source, then a system attempting to receive an 2669 extranet C-flow from the VPN-R extranet C-source may instead receive 2670 a non-extranet C-flow from the VPN-S C-source. This would result in 2671 a VPN security violation. 2673 To avoid this, this document specifies that if a route is imported 2674 into a given VRF, all addresses that match that route must be 2675 unambiguous in the context of that VRF. Improper provisioning of the 2676 RTs may cause this rule to be violated, and hence result in a VPN 2677 security violation. 2679 It is possible that a given multicast C-source is the source of 2680 multiple flows, some of which are intended to be extranet C-flows, 2681 and some of which are intended to be non-extranet flows. However, 2682 the procedures of this document will allow any C-receiver that is 2683 able to receive the extranet C-flows from a given C-source to also 2684 receive the non-extranet C-flows from that source. As a result, VPN 2685 security violations may result if any system is a C-source for both 2686 extranet and non-extranet C-flows. However, the set of C-flows 2687 transmitted by a given C-source is not under the control of the SP. 2688 SPs who offer the extranet MVPN service must make sure that this 2689 potential for VPN security violations is clearly understood by the 2690 customers who administer the C-sources. 2692 This specification does not require that UMH-eligible routes be "host 2693 routes"; they may be less specific routes. So it is possible for the 2694 NLRI of a UMH-eligible route to contain an address prefix that 2695 matches the address of both an extranet C-source and a non-extranet 2696 C-source. If such a route is exported from a VPN-S VRF and imported 2697 by a VPN-R VRF, C-receivers contained in VPN-R will be able to 2698 receive C-flows from the non-extranet C-sources whose addresses match 2699 that route. This may result in VPN security violations. Service 2700 providers who offer the extranet MVPN service must make sure that 2701 this is clearly understood by the customers who administer the 2702 distribution of routes from CE to PE routers. 2704 If the address ambiguities described in Sections 2.1 and 2.2 are not 2705 prohibited by policy, VRFs must be able to discard traffic that 2706 arrives on the wrong P-tunnel; otherwise VPN security violations may 2707 occur. 2709 Section 4.4 specifies the optional use of a new Extended Community, 2710 the Extranet Source Extended Community. Security considerations 2711 regarding the use and distribution of that Extended Community are 2712 discussed in that section. 2714 11. Acknowledgments 2716 The authors wish to thank DP Ayyadevara, Robert Kebler, Padmini 2717 Misra, Rayen Mohanty, Maria Napierala, Karthik Subramanian, and Kurt 2718 Windisch for their contributions to this work. 2720 We also wish to thank Lizhong Jin and Rishabh Parekh for their 2721 reviews and comments. 2723 Special thanks to Jeffrey (Zhaohui) Zhang for his careful review and 2724 for providing the ascii art appearing in Section 2. 2726 12. Contributor Addresses 2728 Below is a list of other contributing authors in alphabetical order: 2730 Wim Henderickx 2731 Alcatel-Lucent 2732 Copernicuslaan 50 2733 Antwerp 2018 2734 Belgium 2736 Email: wim.henderickx@alcatel-lucent.com 2738 Praveen Muley 2739 Alcatel-Lucent 2741 Email: Praveen.Muley@alcatel-lucent.com 2743 Ray Qiu 2744 Juniper Networks, Inc. 2745 1194 North Mathilda Avenue 2746 Sunnyvale, CA 94089 2747 United States 2749 Email: rqiu@juniper.net 2751 IJsbrand Wijnands 2752 Cisco Systems, Inc. 2753 De Kleetlaan 6a 2754 Diegem 1831 2755 Belgium 2757 Email: ice@cisco.com 2759 13. References 2761 13.1. Normative References 2763 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 2764 Requirement Levels", BCP 14, RFC 2119, 2765 DOI 10.17487/RFC2119, March 1997, 2766 . 2768 [RFC4360] Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended 2769 Communities Attribute", RFC 4360, DOI 10.17487/RFC4360, 2770 February 2006, . 2772 [RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private 2773 Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February 2774 2006, . 2776 [RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas, 2777 "Protocol Independent Multicast - Sparse Mode (PIM-SM): 2778 Protocol Specification (Revised)", RFC 4601, 2779 DOI 10.17487/RFC4601, August 2006, 2780 . 2782 [RFC6513] Rosen, E., Ed. and R. Aggarwal, Ed., "Multicast in MPLS/ 2783 BGP IP VPNs", RFC 6513, DOI 10.17487/RFC6513, February 2784 2012, . 2786 [RFC6514] Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP 2787 Encodings and Procedures for Multicast in MPLS/BGP IP 2788 VPNs", RFC 6514, DOI 10.17487/RFC6514, February 2012, 2789 . 2791 [RFC6625] Rosen, E., Ed., Rekhter, Y., Ed., Hendrickx, W., and R. 2792 Qiu, "Wildcards in Multicast VPN Auto-Discovery Routes", 2793 RFC 6625, DOI 10.17487/RFC6625, May 2012, 2794 . 2796 [RFC7153] Rosen, E. and Y. Rekhter, "IANA Registries for BGP 2797 Extended Communities", RFC 7153, DOI 10.17487/RFC7153, 2798 March 2014, . 2800 13.2. Informative References 2802 [MVPN-IR] Rosen, E., Subramanian, K., and Z. Zhang, "Ingress 2803 Replication Tunnels in Multicast VPN", internet-draft 2804 draft-ietf-bess-ir-02, October 2015. 2806 [RFC3446] Kim, D., Meyer, D., Kilmer, H., and D. Farinacci, "Anycast 2807 Rendevous Point (RP) mechanism using Protocol Independent 2808 Multicast (PIM) and Multicast Source Discovery Protocol 2809 (MSDP)", RFC 3446, DOI 10.17487/RFC3446, January 2003, 2810 . 2812 [RFC3618] Fenner, B., Ed. and D. Meyer, Ed., "Multicast Source 2813 Discovery Protocol (MSDP)", RFC 3618, 2814 DOI 10.17487/RFC3618, October 2003, 2815 . 2817 [RFC4610] Farinacci, D. and Y. Cai, "Anycast-RP Using Protocol 2818 Independent Multicast (PIM)", RFC 4610, 2819 DOI 10.17487/RFC4610, August 2006, 2820 . 2822 [RFC4875] Aggarwal, R., Ed., Papadimitriou, D., Ed., and S. 2823 Yasukawa, Ed., "Extensions to Resource Reservation 2824 Protocol - Traffic Engineering (RSVP-TE) for Point-to- 2825 Multipoint TE Label Switched Paths (LSPs)", RFC 4875, 2826 DOI 10.17487/RFC4875, May 2007, 2827 . 2829 [RFC5015] Handley, M., Kouvelas, I., Speakman, T., and L. Vicisano, 2830 "Bidirectional Protocol Independent Multicast (BIDIR- 2831 PIM)", RFC 5015, DOI 10.17487/RFC5015, October 2007, 2832 . 2834 [RFC5059] Bhaskar, N., Gall, A., Lingard, J., and S. Venaas, 2835 "Bootstrap Router (BSR) Mechanism for Protocol Independent 2836 Multicast (PIM)", RFC 5059, DOI 10.17487/RFC5059, January 2837 2008, . 2839 [RFC6388] Wijnands, IJ., Ed., Minei, I., Ed., Kompella, K., and B. 2840 Thomas, "Label Distribution Protocol Extensions for Point- 2841 to-Multipoint and Multipoint-to-Multipoint Label Switched 2842 Paths", RFC 6388, DOI 10.17487/RFC6388, November 2011, 2843 . 2845 Authors' Addresses 2847 Yakov Rekhter (editor) 2848 Juniper Networks, Inc. 2849 1194 North Mathilda Avenue 2850 Sunnyvale, CA 94089 2851 United States 2853 Eric C. Rosen (editor) 2854 Juniper Networks, Inc. 2855 10 Technology Park Drive 2856 Westford, Massachusetts 01886 2857 United States 2859 Email: erosen@juniper.net 2860 Rahul Aggarwal 2861 Arktan 2863 Email: raggarwa_1@yahoo.com 2865 Yiqun Cai 2866 Microsoft 2867 1065 La Avenida 2868 Mountain View, CA 94043 2869 United States 2871 Email: yiqunc@microsoft.com 2873 Thomas Morin 2874 Orange 2875 2 Avenue Pierre-Marzin 2876 22307 Lannion Cedex 2877 France 2879 Email: thomas.morin@orange.com