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Checking references for intended status: Experimental ---------------------------------------------------------------------------- No issues found here. Summary: 0 errors (**), 0 flaws (~~), 1 warning (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Internet Engineering Task Force E. Rosen, Ed. 3 Internet-Draft Juniper Networks, Inc. 4 Intended status: Experimental M. Sivakumar 5 Expires: January 27, 2018 Cisco Systems, Inc. 6 S. Aldrin 7 Google, Inc. 8 A. Dolganow 9 Nokia 10 T. Przygienda 11 Juniper Networks, Inc. 12 July 26, 2017 14 Multicast VPN Using BIER 15 draft-ietf-bier-mvpn-07 17 Abstract 19 The Multicast Virtual Private Network (MVPN) specifications require 20 the use of multicast tunnels ("P-tunnels") that traverse a Service 21 Provider's backbone network. The P-tunnels are used for carrying 22 multicast traffic across the backbone. A variety of P-tunnel types 23 are supported. Bit Index Explicit Replication (BIER) is a new 24 architecture that provides optimal multicast forwarding through a 25 "multicast domain", without requiring intermediate routers to 26 maintain any per-flow state or to engage in an explicit tree-building 27 protocol. This document specifies the protocol and procedures that 28 allow MVPN to use BIER as the method of carrying multicast traffic 29 over an SP backbone network. 31 Status of This Memo 33 This Internet-Draft is submitted in full conformance with the 34 provisions of BCP 78 and BCP 79. 36 Internet-Drafts are working documents of the Internet Engineering 37 Task Force (IETF). Note that other groups may also distribute 38 working documents as Internet-Drafts. The list of current Internet- 39 Drafts is at http://datatracker.ietf.org/drafts/current/. 41 Internet-Drafts are draft documents valid for a maximum of six months 42 and may be updated, replaced, or obsoleted by other documents at any 43 time. It is inappropriate to use Internet-Drafts as reference 44 material or to cite them other than as "work in progress." 46 This Internet-Draft will expire on January 27, 2018. 48 Copyright Notice 50 Copyright (c) 2017 IETF Trust and the persons identified as the 51 document authors. All rights reserved. 53 This document is subject to BCP 78 and the IETF Trust's Legal 54 Provisions Relating to IETF Documents 55 (http://trustee.ietf.org/license-info) in effect on the date of 56 publication of this document. Please review these documents 57 carefully, as they describe your rights and restrictions with respect 58 to this document. Code Components extracted from this document must 59 include Simplified BSD License text as described in Section 4.e of 60 the Trust Legal Provisions and are provided without warranty as 61 described in the Simplified BSD License. 63 Table of Contents 65 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 66 2. Use of the PMSI Tunnel Attribute in x-PMSI A-D Routes . . . . 5 67 2.1. MPLS Label . . . . . . . . . . . . . . . . . . . . . . . 6 68 2.2. Explicit Tracking . . . . . . . . . . . . . . . . . . . . 8 69 2.2.1. Using the LIR Flag . . . . . . . . . . . . . . . . . 9 70 2.2.2. Using the LIR-pF Flag . . . . . . . . . . . . . . . . 9 71 3. Use of the PMSI Tunnel Attribute in Leaf A-D routes . . . . . 10 72 4. Data Plane . . . . . . . . . . . . . . . . . . . . . . . . . 11 73 4.1. Encapsulation and Transmission . . . . . . . . . . . . . 11 74 4.2. Disposition . . . . . . . . . . . . . . . . . . . . . . . 12 75 4.2.1. At a BFER that is an Egress PE . . . . . . . . . . . 13 76 4.2.2. At a BFER that is a P-tunnel Segmentation Boundary . 13 77 5. Contributor Addresses . . . . . . . . . . . . . . . . . . . . 13 78 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14 79 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 80 8. Security Considerations . . . . . . . . . . . . . . . . . . . 14 81 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 82 9.1. Normative References . . . . . . . . . . . . . . . . . . 14 83 9.2. Informative References . . . . . . . . . . . . . . . . . 15 84 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 86 1. Introduction 88 [RFC6513] and [RFC6514] specify the protocols and procedures that a 89 Service Provider (SP) can use to provide Multicast Virtual Private 90 Network (MVPN) service to its customers. Multicast tunnels are 91 created through an SP's backbone network; these are known as 92 "P-tunnels". The P-tunnels are used for carrying multicast traffic 93 across the backbone. The MVPN specifications allow the use of 94 several different kinds of P-tunnel technology. 96 Bit Index Explicit Replication (BIER) ([BIER_ARCH]) is an 97 architecture that provides optimal multicast forwarding through a 98 "multicast domain", without requiring intermediate routers to 99 maintain any per-flow state or to engage in an explicit tree-building 100 protocol. The purpose of the current document is to specify the 101 protocols and procedures needed in order to provide MVPN service 102 using BIER to transport the multicast traffic over the backbone. 104 Although BIER does not explicitly build and maintain multicast 105 tunnels, one can think of BIER as using a number of implicitly 106 created tunnels through a "BIER domain". In particular, one can 107 think of there as being one Point-to-Multipoint (P2MP) tunnel from 108 each "Bit Forwarding Ingress Router" (BFIR) to all the "Bit 109 Forwarding Egress Routers" (BFERs) in the BIER domain, where a BIER 110 domain is generally co-extensive with an IGP network. These 111 "tunnels" are not specific to any particular VPN. However, the MVPN 112 architecture provides protocols and procedures that allow the traffic 113 of multiple MVPNs to be aggregated on a single P-tunnel. In this 114 document, we specify how to use these multi-VPN aggregation 115 procedures to enable BIER to transport traffic from multiple MVPNs. 117 MVPN traffic must sometimes traverse more than one IGP domain, 118 whereas BIER only carries multicast traffic within a single IGP 119 domain. However, the MVPN specifications allow P-tunnels to be 120 "segmented", where the segmentation points may either be Autonomous 121 System Border Routers (ASBRs), as described in [RFC6514], or Area 122 Border Routers (ABRs), as described in [RFC7524]. As long as the 123 segmentation points are capable of acting as BFIRs and BFERs, BIER 124 can be used to provide some or all of the segments of a P-tunnel. 126 Procedures to support MVPN customers who are using BIDIR-PIM are 127 outside the scope of this document. 129 This document uses the following terminology from [BIER_ARCH]: 131 o BFR: Bit-Forwarding Router. 133 o BFIR: Bit-Forwarding Ingress Router. 135 o BFER: Bit-Forwarding Egress Router. 137 This document uses the following terminology from [RFC6513]: 139 o MVPN: Multicast Virtual Private Network -- a VPN [RFC4364] in 140 which multicast service is offered. 142 o P-tunnel. A multicast tunnel through the network of one or more 143 SPs. P-tunnels are used to transport MVPN multicast data 145 o PMSI: Provider Multicast Service Interface. PMSI is an 146 abstraction that represents a multicast service for carrying 147 packets. A PMSI is instantiated via one or more P-tunnels. 149 o C-S: A multicast source address, identifying a multicast source 150 located at a VPN customer site. 152 o C-G: A multicast group address used by a VPN customer. 154 o C-flow: A customer multicast flow. Each C-flow is identified by 155 the ordered pair (source address, group address), where each 156 address is in the customer's address space. The identifier of a 157 particular C-flow is usually written as (C-S,C-G). 159 Sets of C-flows can be identified by the use of the "C-*" wildcard 160 (see [RFC6625]), e.g., (C-*,C-G). 162 o I-PMSI A-D Route: Inclusive PMSI Auto-Discovery route. Carried in 163 BGP Update messages, these routes are used to advertise the 164 "default" P-tunnel for a particular MVPN. 166 o S-PMSI A-D route: Selective PMSI Auto-Discovery route. Carried in 167 BGP Update messages, these routes are used to advertise the fact 168 that particular C-flows are bound to (i.e., are traveling through) 169 particular P-tunnels. 171 o x-PMSI A-D route: a route that is either an I-PMSI A-D route or an 172 S-PMSI A-D route. 174 o Leaf A-D route: a route that a multicast egress node sends in 175 order to join a particular P-tunnel. 177 o PMSI Tunnel attribute (PTA). In an x-PMSI A-D route, the NLRI of 178 the route identifies a PMSI. The BGP attribute known as the PMSI 179 Tunnel attribute is attached to such a route in order to identify 180 a particular P-tunnel that is associated with the PMSI. When 181 C-flows of multiple VPNs are carried in a single P-tunnel, this 182 attribute also carries the information needed to multiplex and 183 demultiplex the C-flows. A PTA can also be carried by a Leaf A-D 184 root. In this case, it contains information that is needed in 185 order for the originator of the route to join the specified 186 P-tunnel. 188 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 189 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 190 document are to be interpreted as described in RFC 2119 [RFC2119]. 192 2. Use of the PMSI Tunnel Attribute in x-PMSI A-D Routes 194 As defined in [RFC6514], the PMSI Tunnel attribute (PTA) carried by 195 an x-PMSI A-D route identifies the P-tunnel that is used to 196 instantiate a particular PMSI. If a PMSI is to be instantiated by 197 BIER, the PTA is constructed by a BFIR. 199 If segmented P-tunnels are not being used, the PTA attached to a 200 given x-PMSI A-D route is constructed by the router that originated 201 the route (typically by the ingress PE), and the PTA is not changed 202 as the route is propagated. 204 If segmented P-tunnels are being used, the PTA attached to a given 205 x-PMSI A-D route by the route's originator may replaced, at a 206 segmentation point (a BFER), by a PTA identifying the next segment of 207 the P-tunnel. If the next segment of the P-tunnel is instantiated by 208 BIER, the segmentation point serves as the BFIR for that next 209 segment. 211 In either case, a PTA is constructed by a BFIR as follows: 213 The PTA contains the following fields: 215 o "Tunnel Type". IANA is requested to assign a new tunnel type 216 codepoint for "BIER" from the "P-Multicast Service Interface 217 Tunnel (PMSI Tunnel) Tunnel Types" registry. This codepoint will 218 be used to indicate that the PMSI is instantiated by BIER. 220 Although BIER does not actually create tunnels, the MVPN 221 procedures treat BIER as if it were a type of tunnel. 223 o "Tunnel Identifier". When the "tunnel type" is "BIER", this field 224 contains two subfields: 226 1. The first subfield is a single octet, containing a BIER 227 sub-domain-id. (See [BIER_ARCH].) This indicates that 228 packets sent on the PMSI will be sent on the specified BIER 229 sub-domain. How that sub-domain is chosen is outside the 230 scope of this document. 232 2. The second subfield is the BFR-Prefix (see [BIER_ARCH]) of the 233 router (a BFIR) that is constructing the PTA. This must be 234 the BFIR's BFR-prefix in the specified sub-domain. The 235 BFR-Prefix will either be a /32 IPv4 address or a /128 IPv6 236 address. Whether the address is IPv4 or IPv6 can be inferred 237 from the total length of the PTA. 239 The BFR-Prefix need not be the same IP address that is carried 240 in any other field of the x-PMSI A-D route, even if the BFIR 241 is the originating router of the x-PMSI A-D route. 243 Failure to properly set the Tunnel Identifier field cannot be 244 detected by the protocol, and will result in improper delivery of 245 the data packets sent on the PMSI. 247 o "MPLS label". This field MUST contain an upstream-assigned non- 248 zero MPLS label. It is assigned by the router (a BFIR) that 249 constructs the PTA. Constraints on the way in which a BFIR 250 selects this label are discussed in Section 2.1. 252 Failure to follow the constraints on label assignment cannot be 253 detected by the protocol, and may result in improper handling of 254 data packets by the egress PE routers. 256 o "Flags". When the tunnel type is BIER, two of the flags in the 257 PTA Flags field are meaningful. Details about the use of these 258 flags can be found in Section 2.2. 260 * "Leaf Info Required per Flow (LIR-pF)". This flag is 261 introduced in [EXPLICIT_TRACKING]. A BFIR SHOULD NOT set this 262 flag UNLESS it knows that all the BFERs in the BIER domain (or 263 at least all the BFERs to which it needs to transmit) support 264 this flag. (How this is known is outside the scope of this 265 document.) Procedures for the use of this flag are given in 266 Section 2.2.2. Support for this flag is OPTIONAL. 268 * "Leaf Info Required Bit". See Section 2.2.1. 270 If a PTA specifying tunnel type "BIER" is attached to an x-PMSI A-D 271 route, the route MUST NOT be distributed beyond the boundaries of a 272 BIER domain. That is, any routers that receive the route must be in 273 the same BIER domain as the originator of the route. If the 274 originator is in more than one BIER domain, the route must be 275 distributed only within the BIER domain in which the BFR-Prefix in 276 the PTA uniquely identifies the originator. As with all MVPN routes, 277 distribution of these routes is controlled by the provisioning of 278 Route Targets. Thus the requirement expressed in this paragraph is 279 really a requirement on the way the Route Targets are provisioned. 281 2.1. MPLS Label 283 Suppose a BFIR attaches a PTA to each of two x-PMSI A-D routes, and 284 both PTAs specify a tunnel type of "BIER". 286 o If the two routes do not carry the same set of Route Targets 287 (RTs), then their respective PTAs MUST contain different MPLS 288 label values. 290 o If the two routes do not have the same Address Family Identifier 291 (AFI) value, then their respective PTAs MUST contain different 292 MPLS label values. This ensures that when an egress PE receives a 293 data packet with the given label, the egress PE can infer from the 294 label whether the payload is an IPv4 packet or an IPv6 packet. 296 o If the BFIR is an ingress PE supporting MVPN extranet ([RFC7900]) 297 functionality, and if the two routes originate from different VRFs 298 on this ingress PE, then the respective PTAs of the two routes 299 MUST contain different MPLS label values. 301 o If the BFIR is an ingress PE supporting the "Extranet Separation" 302 feature of MVPN extranet (see Section 7.3 of [RFC7900]), and if 303 one of the routes carries the "Extranet Separation" extended 304 community but the other does not, then the respective PTAs of the 305 two routes MUST contain different MPLS label values. 307 o If segmented P-tunnels are being used, then the respective PTAs of 308 the two routes MUST contain different MPLS label values whenever 309 the respective NLRIs of the two routes are not identical. The 310 MPLS label can then be used at the next segmentation point to 311 switch packets from one P-tunnel segment directly to the next, 312 without requiring the segmentation points to contain any other 313 multicast forwarding state. This is explained further below. See 314 also Section 4. 316 When segmented P-tunnels are being used, a segmentation point, call 317 it "B1", may receive, from within a given BIER domain, an x-PMSI A-D 318 route whose PTA specifies "BIER". This means that BIER is being used 319 for the previous segment of a segmented P-tunnel. If the next 320 segment is also of type "BIER", B1 will be the BFIR for the next 321 segment. That is, B1 is a BFER of one BIER domain (corresponding to 322 the previous segment), and a BFIR of another BIER domain 323 (corresponding to the next segment). B1 needs to replace the PTA of 324 the x-PMSI A-D route with a new PTA, specifying its own BFR-Prefix, 325 and specifying an upstream-assigned label assigned by B1 itself. 327 Suppose B1 has received two x-PMSI A-D routes, R1 and R2, where: 329 o R1 and R2 each have a PTA specifying BIER, 331 o R1's PTA specifies BFR-Prefix B2 and Label L2. 333 o R2's PTA specifies BFR-Prefix B3 and Label L3. 335 Suppose B1 decides to propagate both R1 and R2, replacing each PTA 336 with a new PTA specifying BIER. Suppose these new PTAs specify 337 labels L4 and L5 respectively. Then L4 and L5 MUST be different 338 (upstream-assigned) label values, UNLESS both of the following 339 conditions hold: 341 o R1 and R2 have the same value in the "originating router" field of 342 their respective NLRIs, and 344 o B2 is equal to B3, and 346 o L2 is equal to L3. 348 The segmentation point (B1 in this example) MUST also program its 349 dataplane appropriately. For example, when: 351 o B1 receives a BIER packet for which it is a BFER, and 353 o the BIER header specifies the BFIR-id that corresponds to B2,and 355 o the BIER payload is an MPLS packet with upstream-assigned label, 356 and 358 o the top label value is L2, 360 then the dataplane must be programmed to replace L2 with L4, and to 361 reencapsulate the packet in a BIER header, with B1's BFIR-id in the 362 BFIR-id field. The BitString of the new BIER header is determined by 363 the MVPN explicit tracking procedures (see Section 2.2 in the BIER 364 domain of the next segment. 366 2.2. Explicit Tracking 368 When using BIER to transport an MVPN data packet through a BIER 369 domain, an ingress PE functions as a BFIR (see [BIER_ARCH]). The 370 BFIR must determine the set of BFERs to which the packet needs to be 371 delivered. This can be done in either of two ways: 373 1. Using the explicit tracking mechanism based on the "Leaf Info 374 Required" flag specified in [RFC6513] and [RFC6514]. This method 375 is further described in Section 2.2.1. 377 2. Using the OPTIONAL explicit tracking mechanism based on the 378 LIR-pF flag specified in [EXPLICIT_TRACKING]. This method, 379 further described in Section 2.2.2, may be used if (and only if) 380 segmented P-tunnels are not being used. 382 2.2.1. Using the LIR Flag 384 To determine the set of BFERs to which the packets of a given C-flow 385 must be sent, a BFIR MUST originate a (C-S,C-G) S-PMSI A-D route for 386 the given C-flow. It MUST attach a PTA to that route, and MUST set 387 the LIR flag in the PTA. Per [RFC6514], the BFERs that need to 388 receive that C-flow will respond with (C-S,C-G) Leaf A-D routes. By 389 matching the received Leaf A-D routes to the originated S-PMSI A-D 390 routes, the originator of the S-PMSI A-D route determines the set of 391 BFERs that need to receive the multicast data flow that is identified 392 in the NLRI of S-PMSI A-D route. 394 Suppose an ingress PE has originated an I-PMSI A-D route or a 395 wildcard S-PMSI A-D route [RFC6625] with a PTA specifying a tunnel 396 type of BIER. Now suppose the ingress PE originates an S-PMSI A-D 397 route specifying (C-S, C-G), where (C-S, C-G) "matches" (according to 398 the rules of [RFC6625]) the wildcard S-PMSI A-D route or the I-PMSI 399 A-D route. Instead of attaching to the (C-S, C-G) route a PTA 400 specifying BIER, the ingress PE MAY attach a PTA specifying a tunnel 401 type of "no tunnel information". This is equivalent to attaching the 402 same PTA attached to the matching "less specific" route. 404 2.2.2. Using the LIR-pF Flag 406 If segmented P-tunnels are not being used, the BFIR can determine the 407 set of BFERs that need to receive the packets of a given (C-S,C-G) 408 C-flow as follows. The BFIR MUST originate a wildcard S-PMSI A-D 409 route (either (C-*,C-*), (C-*,C-G), or (C-S,C-G)) and the PTA of that 410 route MUST the following settings: 412 o The LIR-pF flag MUST be set; 414 o The tunnel type MUST be set to "BIER"; 416 o A non-zero MPLS label MUST be specified. 418 Per [EXPLICIT_TRACKING], a BFER that needs to receive (C-S,C-G) 419 traffic from the BFIR will respond with a Leaf A-D route. 421 A BFIR MUST NOT use this method of finding the set of BFERs needing 422 to receive a given C-flow unless it knows that all those BFERs 423 support the LIR-pF flag. How this is known is outside the scope of 424 this document. 426 This method greatly reduces the number of S-PMSI A-D routes that a 427 BFIR needs to originate; it can now originate as few as one such 428 route (a (C-*,C-*) S-PMSI A-D route), rather than one for each 429 C-flow. However, the method does not provide a way for the BFIR to 430 assign a distinct label to each C-flow. Therefore it cannot be used 431 when segmented P-tunnels are in use (see Section 4 for an 432 explanation). 434 Note: if a BFIR originates a (C-*,C-*) S-PMSI A-D route with the 435 LIR-pF flag set, but also originates a more specific wildcard route 436 that matches a particular (C-S,C-G), the BFERs will not originate 437 Leaf A-D routes for that (C-S,C-G) unless the LIR-pF flag is also set 438 in the more specific wildcard route. If the BFIR also originates a 439 (C-S,C-G) S-PMSI A-D route without the LIR flag set, the BFERs will 440 not originate Leaf A-D routes for that (C-S,C-G) unless the LIR flag 441 is also set in that route. 443 3. Use of the PMSI Tunnel Attribute in Leaf A-D routes 445 Before an egress PE can receive a (C-S,C-G) flow from a given ingress 446 PE via BIER, the egress PE must have received one of the following 447 x-PMSI A-D routes from the ingress PE: 449 o A (C-S,C-G) S-PMSI A-D route (i.e., an S-PMSI A-D route whose NLRI 450 encodes (C-S,C-G) and whose PTA specifies a tunnel type of "BIER". 451 If such a route is found, we refer to it as the "matching x-PMSI 452 A-D route." 454 o A "less specific" x-PMSI A-D route (one specifying (C-*,C-*), 455 (C-*,C-G), or (C-S,C-G)) whose PTA specifies a tunnel type of 456 "BIER", and that is the egress PE's "match for reception" of 457 (C-S,C-G). 459 The rules for determining which x-PMSI A-D route is the match for 460 reception are given in [RFC6625]. However, these rules are 461 modified here to exclude any x-PMSI A-D route that does not have a 462 PTA, or whose PTA specifies "no tunnel type". 464 If such a route is found, we refer to it as the "matching x-PMSI 465 A-D route." 467 If no matching x-PMSI A-D route for (C-S,C-G) is found, the egress PE 468 cannot receive the (C-S,C-G) flow from the ingress PE via BIER until 469 such time as a matching route is received. 471 When an egress PE determines that it needs to receive a (C-S,C-) flow 472 from a particular ingress PE via BIER, it originates a Leaf A-D 473 route. Construction of the Leaf A-D route generally follows the 474 procedures specified in [RFC6514], or optionally, the procedures 475 specified in [EXPLICIT_TRACKING]. However, when BIER is being used, 476 the Leaf A-D route MUST carry a PTA that is constructed as follows: 478 1. The tunnel type MUST be set to "BIER". 480 2. The MPLS label field SHOULD be set to zero. 482 3. The sub-domain-id field of the Tunnel Identifier field (as 483 defined in Section 2) MUST be set to the corresponding value from 484 the PTA of the matching x-PMSI A-D route. 486 4. The BFR-Prefix field of the Tunnel Identifier field (as defined 487 in Section 2) MUST be set to the egress PE's BFR-Prefix in the 488 sub-domain identifiers in the PTA of the matching x-PMSI A-D 489 route. 491 The BFR-Prefix need not be the same IP address that is carried in 492 any other field of the Leaf A-D route. 494 When an ingress PE receives such a Leaf A-D route, it learns the 495 BFR-Prefix of the egress PE from the PTA. The ingress PE does not 496 make any use the value of the PTA's MPLS label field. 498 Failure to properly construct the PTA cannot always be detected by 499 the protocol, and will cause improper delivery of the data packets. 501 4. Data Plane 503 The MVPN application plays the role of the "multicast flow overlay" 504 as described in [BIER_ARCH]. 506 4.1. Encapsulation and Transmission 508 To transmit an MVPN data packet, an ingress PE follows the rules of 509 [RFC6625] to find the x-PMSI A-D route that is a "match for 510 transmission" for that packet. (In applying the rules of [RFC6625], 511 any S-PMSI A-D route with a PTA specifying "no tunnel information" is 512 ignored.) If the matching route has a PTA specifying "BIER", the 513 (upstream-assigned) MPLS label from that PTA is pushed on the 514 packet's label stack. Then the packet is encapsulated in a BIER 515 header. That is, the ingress PE functions as a BFIR. The BIER sub- 516 domain used for transmitting the packet is specified in the PTA of 517 the abovementioned x-PMSI A-D route. 519 In order to create the proper BIER header for a given packet, the 520 BFIR must know all the BFERs that need to receive that packet. It 521 determines this by finding all the Leaf A-D routes that correspond to 522 the S-PMSI A-D route that is the packet's match for transmission. 523 There are two different cases to consider: 525 1. The S-PMSI A-D route that is the match for transmission carries a 526 PTA that has the LIR flag set but does not have the LIR-pF flag 527 set. 529 In this case, the corresponding Leaf A-D routes are those whose 530 "route key" field is identical to the NLRI of the S-PMSI A-D 531 route. 533 2. The S-PMSI A-D route that is the match for transmission carries a 534 PTA that has the LIR-pF flag. 536 In this case, the corresponding Leaf A-D routes are those whose 537 "route key" field is derived from the NLRI of the S-PMSI A-D 538 route according to the procedures described in Section 5.2 of 539 [EXPLICIT_TRACKING]. 541 The Leaf A-D route from a given BFER will contain a PTA that 542 specifies the BFER's BFR-Prefix. With this information, the BFIR can 543 construct the BIER BitString. 545 However, if the PTA of the Leaf A-D route from a given BFER specifies 546 a sub-domain other than the one being used for transmitting the 547 packet, the bit for that BFER cannot be determined, and that BFER 548 will not receive the packet. 550 The BIER-encapsulated packet is then forwarded, according to the 551 procedures of [BIER_ARCH] and [BIER_ENCAPS]. (See especially 552 Section 4, "Imposing and Processing the BIER Encapsulation", of 553 [BIER_ENCAPS].) 555 4.2. Disposition 557 When a BFER receives an MVPN multicast data packet that has been 558 BIER-encapsulated, the BIER layer passes the following information to 559 the multicast flow overlay: 561 o The BFR-prefix corresponding to the sub-domain-id and BFIR-id in 562 the BIER header. 564 o The "payload", which is an MPLS packet whose top label is an 565 upstream-assigned label. The BFR-prefix provides the "context" in 566 which the upstream-assigned label is interpreted. 568 Note that per [RFC5331], the context for an upstream-assigned 569 label is the IP address of the label assigner, which in this case 570 is the BFR-prefix of the BFIR. 572 By looking up the upstream-assigned label in the appropriate context, 573 the multicast flow overlay determines whether the BFER is an egress 574 PE for the packet. 576 Note that if segmented P-tunnels are in use, a BFER might be a 577 P-tunnel segmentation border router rather than an egress PE, or a 578 BFER might be both an egress PE and a P-tunnel segmentation border 579 router. Depending upon the role of the BFER for given packet, it may 580 need to follow the procedures of Section 4.2.1, the procedures of 581 Section 4.2.2, or both. 583 4.2.1. At a BFER that is an Egress PE 585 From looking up the packet's upstream-assigned label in the context 586 of the packet's BFIR-prefix, the egress PE determines the egress VRF 587 for the packet. From the IP header of the payload, the multicast 588 states of the VRF, the upstream-assigned label, and the BFR-prefix, 589 the egress PE can determine whether the packet needs to be forwarded 590 out one or more VRF interfaces. 592 4.2.2. At a BFER that is a P-tunnel Segmentation Boundary 594 When segmented P-tunnels are being used, a BFER that receives a BIER- 595 encapsulated MVPN multicast data packet may need to be forwarded on 596 its next P-tunnel segment. The choice of the next P-tunnel segment 597 for the packet depends upon the C-flow to which the packet belongs. 598 As long as the BFIR has assigned the MPLS label according to the 599 constraints specified in Section 2.1, the BFIR will have assigned 600 distinct upstream-assigned MPLS labels to distinct C-flows. The BFER 601 can thus select the proper "next P-tunnel segment" for a given packet 602 simply by looking up the upstream-assigned label that immediately 603 follows the BIER header. 605 5. Contributor Addresses 607 Below is a list of other contributing authors in alphabetical order: 609 IJsbrand Wijnands 610 Cisco Systems, Inc. 611 De Kleetlaan 6a 612 Diegem 1831 613 Belgium 615 Email: ice@cisco.com 617 6. Acknowledgments 619 The authors wish to thank Jeffrey Zhang for his ideas and 620 contributions to this work. We also thank Stig Venaas for his review 621 and comments. 623 7. IANA Considerations 625 IANA is requested to assign a value for "BIER" from the "P-Multicast 626 Service Interface Tunnel (PMSI Tunnel) Tunnel Types" registry. The 627 reference should be this document. 629 8. Security Considerations 631 The security considerations of [BIER_ARCH], [BIER_ENCAPS], [RFC6513] 632 and [RFC6514] are applicable. 634 9. References 636 9.1. Normative References 638 [BIER_ARCH] 639 Wijnands, IJ., Rosen, E., Dolganow, A., Przygienda, T., 640 and S. Aldrin, "Multicast using Bit Index Explicit 641 Replication", internet-draft draft-ietf-bier-architecture- 642 07, June 2017. 644 [BIER_ENCAPS] 645 Wijnands, IJ., Rosen, E., Dolganow, A., Tantsura, J., and 646 S. Aldrin, "Encapsulation for Bit Index Explicit 647 Replication in MPLS Networks", internet-draft draft-ietf- 648 bier-mpls-encapsulation-07.txt, June 2017. 650 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 651 Requirement Levels", BCP 14, RFC 2119, 652 DOI 10.17487/RFC2119, March 1997, 653 . 655 [RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private 656 Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February 657 2006, . 659 [RFC5331] Aggarwal, R., Rekhter, Y., and E. Rosen, "MPLS Upstream 660 Label Assignment and Context-Specific Label Space", 661 RFC 5331, DOI 10.17487/RFC5331, August 2008, 662 . 664 [RFC6513] Rosen, E., Ed. and R. Aggarwal, Ed., "Multicast in MPLS/ 665 BGP IP VPNs", RFC 6513, DOI 10.17487/RFC6513, February 666 2012, . 668 [RFC6514] Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP 669 Encodings and Procedures for Multicast in MPLS/BGP IP 670 VPNs", RFC 6514, DOI 10.17487/RFC6514, February 2012, 671 . 673 [RFC6625] Rosen, E., Ed., Rekhter, Y., Ed., Hendrickx, W., and R. 674 Qiu, "Wildcards in Multicast VPN Auto-Discovery Routes", 675 RFC 6625, DOI 10.17487/RFC6625, May 2012, 676 . 678 9.2. Informative References 680 [EXPLICIT_TRACKING] 681 Dolganow, A., Kotalwar, J., Rosen, E., and Z. Zhang, 682 "Explicit Tracking with Wild Card Routes in Multicast 683 VPN", internet-draft draft-ietf-bess-mvpn-expl-track-02, 684 June 2017. 686 [RFC7524] Rekhter, Y., Rosen, E., Aggarwal, R., Morin, T., 687 Grosclaude, I., Leymann, N., and S. Saad, "Inter-Area 688 Point-to-Multipoint (P2MP) Segmented Label Switched Paths 689 (LSPs)", RFC 7524, DOI 10.17487/RFC7524, May 2015, 690 . 692 [RFC7900] Rekhter, Y., Ed., Rosen, E., Ed., Aggarwal, R., Cai, Y., 693 and T. Morin, "Extranet Multicast in BGP/IP MPLS VPNs", 694 RFC 7900, DOI 10.17487/RFC7900, June 2016, 695 . 697 Authors' Addresses 699 Eric C. Rosen (editor) 700 Juniper Networks, Inc. 701 10 Technology Park Drive 702 Westford, Massachusetts 01886 703 United States 705 Email: erosen@juniper.net 706 Mahesh Sivakumar 707 Cisco Systems, Inc. 708 510 McCarthy Blvd 709 Milpitas, California 95035 710 United States 712 Email: masivaku@cisco.com 714 Sam K Aldrin 715 Google, Inc. 716 1600 Amphitheatre Parkway 717 Mountain View, California 718 United States 720 Email: aldrin.ietf@gmail.com 722 Andrew Dolganow 723 Nokia 724 600 March Rd. 725 Ottawa, Ontario K2K 2E6 726 Canada 728 Email: andrew.dolganow@nokia.com 730 Tony Przygienda 731 Juniper Networks, Inc. 732 1137 Innovation Way 733 San Jose, California 94089 734 United States 736 Email: prz@juniper.net