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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: April 19, 2018 Cisco Systems, Inc. 6 S. Aldrin 7 Google, Inc. 8 A. Dolganow 9 Nokia 10 T. Przygienda 11 Juniper Networks, Inc. 12 October 16, 2017 14 Multicast VPN Using BIER 15 draft-ietf-bier-mvpn-08 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 https://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 April 19, 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 (https://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 . . . . . . . . . . . . . . . . . . . . . . . 7 68 2.2. Explicit Tracking . . . . . . . . . . . . . . . . . . . . 9 69 2.2.1. Using the LIR Flag . . . . . . . . . . . . . . . . . 9 70 2.2.2. Using the LIR-pF Flag . . . . . . . . . . . . . . . . 10 71 3. Use of the PMSI Tunnel Attribute in Leaf A-D routes . . . . . 11 72 4. Data Plane . . . . . . . . . . . . . . . . . . . . . . . . . 12 73 4.1. Encapsulation and Transmission . . . . . . . . . . . . . 12 74 4.2. Disposition . . . . . . . . . . . . . . . . . . . . . . . 13 75 4.2.1. At a BFER that is an Egress PE . . . . . . . . . . . 14 76 4.2.2. At a BFER that is a P-tunnel Segmentation Boundary . 14 77 5. Contributor Addresses . . . . . . . . . . . . . . . . . . . . 14 78 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14 79 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 80 8. Security Considerations . . . . . . . . . . . . . . . . . . . 15 81 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 15 82 9.1. Normative References . . . . . . . . . . . . . . . . . . 15 83 9.2. Informative References . . . . . . . . . . . . . . . . . 16 84 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16 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 (see 212 Figure 1): 214 The PTA contains the following fields: 216 o "Tunnel Type". IANA has assigned 0x0B as the tunnel type 217 codepoint for "BIER" in the "P-Multicast Service Interface Tunnel 218 (PMSI Tunnel) Tunnel Types" registry. This codepoint is used to 219 indicate that the PMSI is instantiated by BIER. 221 Although BIER does not actually create tunnels, the MVPN 222 procedures treat BIER as if it were a type of tunnel. 224 o "Tunnel Identifier". When the "tunnel type" is "BIER", this field 225 contains three subfields: 227 1. The first subfield is a single octet, containing a BIER 228 sub-domain-id. (See [BIER_ARCH].) This indicates that 229 packets sent on the PMSI will be sent on the specified BIER 230 sub-domain. How that sub-domain is chosen is outside the 231 scope of this document. 233 2. The second subfield is a two-octet field containing the 234 BFR-id, in the sub-domain identified in the first subfield, of 235 the router that is constructing the PTA. 237 3. The third subfield is the BFR-Prefix (see [BIER_ARCH]) of the 238 router (a BFIR) that is constructing the PTA. The BFR-Prefix 239 will either be a /32 IPv4 address or a /128 IPv6 address. 241 Whether the address is IPv4 or IPv6 can be inferred from the 242 total length of the PTA. 244 The BFR-Prefix need not be the same IP address that is carried 245 in any other field of the x-PMSI A-D route, even if the BFIR 246 is the originating router of the x-PMSI A-D route. 248 Failure to properly set the Tunnel Identifier field cannot be 249 detected by the protocol, and will result in improper delivery of 250 the data packets sent on the PMSI. 252 o "MPLS Label". This field MUST contain an upstream-assigned non- 253 zero MPLS label. It is assigned by the router (a BFIR) that 254 constructs the PTA. Constraints on the way in which a BFIR 255 selects this label are discussed in Section 2.1. 257 Failure to follow the constraints on label assignment cannot be 258 detected by the protocol, and may result in improper handling of 259 data packets by the egress PE routers. 261 o "Flags". When the tunnel type is BIER, two of the flags in the 262 PTA Flags field are meaningful. Details about the use of these 263 flags can be found in Section 2.2. 265 * "Leaf Info Required per Flow (LIR-pF)". This flag is 266 introduced in [EXPLICIT_TRACKING]. A BFIR SHOULD NOT set this 267 flag UNLESS it knows that all the BFERs in the BIER domain (or 268 at least all the BFERs to which it needs to transmit) support 269 this flag. (How this is known is outside the scope of this 270 document.) Procedures for the use of this flag are given in 271 Section 2.2.2. Support for this flag is OPTIONAL. 273 * "Leaf Info Required Bit". See Section 2.2.1. 275 +---------------------------------+ 276 | Flags (1 octet) | 277 +---------------------------------+ 278 | Tunnel Type = 0x0B (1 octet) | 279 +---------------------------------+ 280 | MPLS Label (3 octets) | 281 +---------------------------------+ 282 | Sub-domain-id (1 octet) | <--- 283 +---------------------------------+ | 284 | BFIR-id (2 octets) | |-- Tunnel 285 +---------------------------------+ | Identifier 286 | BFIR-Prefix (4 or 16 octets) | <--- 287 +---------------------------------+ 289 Figure 1: PMSI Tunnel Attribute for BIER 291 If a PTA specifying tunnel type "BIER" is attached to an x-PMSI A-D 292 route, the route MUST NOT be distributed beyond the boundaries of a 293 BIER domain. That is, any routers that receive the route must be in 294 the same BIER domain as the originator of the route. If the 295 originator is in more than one BIER domain, the route must be 296 distributed only within the BIER domain in which the BFR-Prefix in 297 the PTA uniquely identifies the originator. As with all MVPN routes, 298 distribution of these routes is controlled by the provisioning of 299 Route Targets. Thus the requirement expressed in this paragraph is 300 really a requirement on the way the Route Targets are provisioned. 302 2.1. MPLS Label 304 The MPLS Label carried in the PTA is an upstream-assigned label. 306 If two PTAs contain the same BFR-prefix in their respective Tunnel 307 Identifier fields, then the labels carried in those PTAs MUST come 308 from the same label space. (See section 7 of [RFC5331].) An 309 implementation may choose to use this fact when setting up the tables 310 it uses to interpret the upstream-assigned labels. 312 Suppose a BFIR attaches a PTA to each of two x-PMSI A-D routes, and 313 both PTAs specify a tunnel type of "BIER". 315 o If the two routes do not carry the same set of Route Targets 316 (RTs), then their respective PTAs MUST contain different MPLS 317 label values. 319 o If the two routes do not have the same Address Family Identifier 320 (AFI) value, then their respective PTAs MUST contain different 321 MPLS label values. This ensures that when an egress PE receives a 322 data packet with the given label, the egress PE can infer from the 323 label whether the payload is an IPv4 packet or an IPv6 packet. 325 o If the BFIR is an ingress PE supporting MVPN extranet ([RFC7900]) 326 functionality, and if the two routes originate from different VRFs 327 on this ingress PE, then the respective PTAs of the two routes 328 MUST contain different MPLS label values. 330 o If the BFIR is an ingress PE supporting the "Extranet Separation" 331 feature of MVPN extranet (see Section 7.3 of [RFC7900]), and if 332 one of the routes carries the "Extranet Separation" extended 333 community but the other does not, then the respective PTAs of the 334 two routes MUST contain different MPLS label values. 336 o If segmented P-tunnels are being used, then the respective PTAs of 337 the two routes MUST contain different MPLS label values whenever 338 the respective NLRIs of the two routes are not identical. The 339 MPLS label can then be used at the next segmentation point to 340 switch packets from one P-tunnel segment directly to the next, 341 without requiring the segmentation points to contain any other 342 multicast forwarding state. This is explained further below. See 343 also Section 4. 345 When segmented P-tunnels are being used, a segmentation point, call 346 it "B1", may receive, from within a given BIER domain, an x-PMSI A-D 347 route whose PTA specifies "BIER". This means that BIER is being used 348 for the previous segment of a segmented P-tunnel. If the next 349 segment is also of type "BIER", B1 will be the BFIR for the next 350 segment. That is, B1 is a BFER of one BIER domain (corresponding to 351 the previous segment), and a BFIR of another BIER domain 352 (corresponding to the next segment). B1 needs to replace the PTA of 353 the x-PMSI A-D route with a new PTA, specifying its own BFR-Prefix, 354 and specifying an upstream-assigned label assigned by B1 itself. 356 Suppose B1 has received two x-PMSI A-D routes, R1 and R2, where: 358 o R1 and R2 each have a PTA specifying BIER, 360 o R1's PTA specifies BFR-Prefix B2 and Label L2. 362 o R2's PTA specifies BFR-Prefix B3 and Label L3. 364 Suppose B1 decides to propagate both R1 and R2, replacing each PTA 365 with a new PTA specifying BIER. Suppose these new PTAs specify 366 labels L4 and L5 respectively. Then L4 and L5 MUST be different 367 (upstream-assigned) label values, UNLESS both of the following 368 conditions hold: 370 o R1 and R2 have the same value in the Originating Router field of 371 their respective NLRIs, and 373 o B2 is equal to B3, and 375 o L2 is equal to L3. 377 The segmentation point (B1 in this example) MUST also program its 378 dataplane appropriately. For example, when: 380 o B1 receives a BIER packet for which it is a BFER, and 382 o the BIER header specifies the BFIR-id that corresponds to B2,and 384 o the BIER payload is an MPLS packet with upstream-assigned label, 385 and 387 o the top label value is L2, 389 then the dataplane must be programmed to replace L2 with L4, and to 390 reencapsulate the packet in a BIER header, with B1's BFIR-id in the 391 BFIR-id field. The BitString of the new BIER header is determined by 392 the MVPN explicit tracking procedures (see Section 2.2 in the BIER 393 domain of the next segment. 395 2.2. Explicit Tracking 397 When using BIER to transport an MVPN data packet through a BIER 398 domain, an ingress PE functions as a BFIR (see [BIER_ARCH]). The 399 BFIR must determine the set of BFERs to which the packet needs to be 400 delivered. This can be done in either of two ways: 402 1. Using the explicit tracking mechanism based on the "Leaf Info 403 Required" flag specified in [RFC6513] and [RFC6514]. This method 404 is further described in Section 2.2.1. 406 2. Using the OPTIONAL explicit tracking mechanism based on the 407 LIR-pF flag specified in [EXPLICIT_TRACKING]. This method, 408 further described in Section 2.2.2, may be used if (and only if) 409 segmented P-tunnels are not being used. 411 2.2.1. Using the LIR Flag 413 To determine the set of BFERs to which the packets of a given C-flow 414 must be sent, a BFIR MUST originate a (C-S,C-G) S-PMSI A-D route for 415 the given C-flow. It MUST attach a PTA to that route, and MUST set 416 the LIR flag in the PTA. Per [RFC6514], the BFERs that need to 417 receive that C-flow will respond with (C-S,C-G) Leaf A-D routes. By 418 matching the received Leaf A-D routes to the originated S-PMSI A-D 419 routes, the originator of the S-PMSI A-D route determines the set of 420 BFERs that need to receive the multicast data flow that is identified 421 in the NLRI of S-PMSI A-D route. 423 Suppose an ingress PE has originated an I-PMSI A-D route or a 424 wildcard S-PMSI A-D route [RFC6625] with a PTA specifying a tunnel 425 type of BIER. Now suppose the ingress PE originates an S-PMSI A-D 426 route specifying (C-S, C-G), where (C-S, C-G) "matches" (according to 427 the rules of [RFC6625]) the wildcard S-PMSI A-D route or the I-PMSI 428 A-D route. Instead of attaching to the (C-S, C-G) route a PTA 429 specifying BIER, the ingress PE MAY attach a PTA specifying a tunnel 430 type of "no tunnel information". This is equivalent to attaching the 431 same PTA attached to the matching "less specific" route. 433 2.2.2. Using the LIR-pF Flag 435 If segmented P-tunnels are not being used, the BFIR can determine the 436 set of BFERs that need to receive the packets of a given (C-S,C-G) 437 C-flow as follows. The BFIR MUST originate a wildcard S-PMSI A-D 438 route (either (C-*,C-*), (C-*,C-G), or (C-S,C-G)) and the PTA of that 439 route MUST the following settings: 441 o The LIR-pF flag MUST be set; 443 o The tunnel type MUST be set to "BIER"; 445 o A non-zero MPLS label MUST be specified. 447 Per [EXPLICIT_TRACKING], a BFER that needs to receive (C-S,C-G) 448 traffic from the BFIR will respond with a Leaf A-D route. 450 A BFIR MUST NOT use this method of finding the set of BFERs needing 451 to receive a given C-flow unless it knows that all those BFERs 452 support the LIR-pF flag. How this is known is outside the scope of 453 this document. 455 This method greatly reduces the number of S-PMSI A-D routes that a 456 BFIR needs to originate; it can now originate as few as one such 457 route (a (C-*,C-*) S-PMSI A-D route), rather than one for each 458 C-flow. However, the method does not provide a way for the BFIR to 459 assign a distinct label to each C-flow. Therefore it cannot be used 460 when segmented P-tunnels are in use (see Section 4 for an 461 explanation). 463 Note: if a BFIR originates a (C-*,C-*) S-PMSI A-D route with the 464 LIR-pF flag set, but also originates a more specific wildcard route 465 that matches a particular (C-S,C-G), the BFERs will not originate 466 Leaf A-D routes for that (C-S,C-G) unless the LIR-pF flag is also set 467 in the more specific wildcard route. If the BFIR also originates a 468 (C-S,C-G) S-PMSI A-D route without the LIR flag set, the BFERs will 469 not originate Leaf A-D routes for that (C-S,C-G) unless the LIR flag 470 is also set in that route. 472 3. Use of the PMSI Tunnel Attribute in Leaf A-D routes 474 Before an egress PE can receive a (C-S,C-G) flow from a given ingress 475 PE via BIER, the egress PE must have received one of the following 476 x-PMSI A-D routes from the ingress PE: 478 o A (C-S,C-G) S-PMSI A-D route (i.e., an S-PMSI A-D route whose NLRI 479 encodes (C-S,C-G) and whose PTA specifies a tunnel type of "BIER". 480 If such a route is found, we refer to it as the "matching x-PMSI 481 A-D route." 483 o A "less specific" x-PMSI A-D route (one specifying (C-*,C-*), 484 (C-*,C-G), or (C-S,C-G)) whose PTA specifies a tunnel type of 485 "BIER", and that is the egress PE's "match for reception" of 486 (C-S,C-G). 488 The rules for determining which x-PMSI A-D route is the match for 489 reception are given in [RFC6625]. However, these rules are 490 modified here to exclude any x-PMSI A-D route that does not have a 491 PTA, or whose PTA specifies "no tunnel type". 493 If such a route is found, we refer to it as the "matching x-PMSI 494 A-D route." 496 If no matching x-PMSI A-D route for (C-S,C-G) is found, the egress PE 497 cannot receive the (C-S,C-G) flow from the ingress PE via BIER until 498 such time as a matching route is received. 500 When an egress PE determines that it needs to receive a (C-S,C-G) 501 flow from a particular ingress PE via BIER, it originates a Leaf A-D 502 route. Construction of the Leaf A-D route generally follows the 503 procedures specified in [RFC6514], or optionally, the procedures 504 specified in [EXPLICIT_TRACKING]. However, when BIER is being used, 505 the Leaf A-D route MUST carry a PTA that is constructed as follows: 507 1. The tunnel type MUST be set to "BIER". 509 2. The MPLS Label field SHOULD be set to zero. 511 3. The Sub-domain-id subfield of the Tunnel Identifier field (as 512 defined in Section 2) MUST be set to the corresponding value from 513 the PTA of the matching x-PMSI A-D route. 515 4. The BFR-id subfield of the Tunnel Identifier field MUST be set to 516 the BFR-id, in the sub-domain identified by the sub-domain-id 517 subfield, of the egress PE. 519 5. The BFR-Prefix field of the Tunnel Identifier field (as defined 520 in Section 2) MUST be set to the egress PE's BFR-Prefix. 522 The BFR-Prefix need not be the same IP address that is carried in 523 any other field of the Leaf A-D route. 525 When an ingress PE receives such a Leaf A-D route, it learns the 526 BFR-Prefix of the egress PE from the PTA. The ingress PE does not 527 make any use the value of the PTA's MPLS label field. 529 Failure to properly construct the PTA cannot always be detected by 530 the protocol, and will cause improper delivery of the data packets. 532 4. Data Plane 534 The MVPN application plays the role of the "multicast flow overlay" 535 as described in [BIER_ARCH]. 537 4.1. Encapsulation and Transmission 539 To transmit an MVPN data packet, an ingress PE follows the rules of 540 [RFC6625] to find the x-PMSI A-D route that is a "match for 541 transmission" for that packet. (In applying the rules of [RFC6625], 542 any S-PMSI A-D route with a PTA specifying "no tunnel information" is 543 ignored.) If the matching route has a PTA specifying "BIER", the 544 (upstream-assigned) MPLS label from that PTA is pushed on the 545 packet's label stack. Then the packet is encapsulated in a BIER 546 header. That is, the ingress PE functions as a BFIR. The BIER sub- 547 domain used for transmitting the packet is specified in the PTA of 548 the abovementioned x-PMSI A-D route. 550 In order to create the proper BIER header for a given packet, the 551 BFIR must know all the BFERs that need to receive that packet. It 552 determines this by finding all the Leaf A-D routes that correspond to 553 the S-PMSI A-D route that is the packet's match for transmission. 554 There are two different cases to consider: 556 1. The S-PMSI A-D route that is the match for transmission carries a 557 PTA that has the LIR flag set but does not have the LIR-pF flag 558 set. 560 In this case, the corresponding Leaf A-D routes are those whose 561 "route key" field is identical to the NLRI of the S-PMSI A-D 562 route. 564 2. The S-PMSI A-D route that is the match for transmission carries a 565 PTA that has the LIR-pF flag. 567 In this case, the corresponding Leaf A-D routes are those whose 568 "route key" field is derived from the NLRI of the S-PMSI A-D 569 route according to the procedures described in Section 5.2 of 570 [EXPLICIT_TRACKING]. 572 The Leaf A-D route from a given BFER will contain a PTA that 573 specifies the BFER's BFR-Prefix. With this information, the BFIR can 574 construct the BIER BitString. 576 However, if the PTA of the Leaf A-D route from a given BFER specifies 577 a sub-domain other than the one being used for transmitting the 578 packet, the bit for that BFER cannot be determined, and that BFER 579 will not receive the packet. 581 The BIER-encapsulated packet is then forwarded, according to the 582 procedures of [BIER_ARCH] and [BIER_ENCAPS]. (See especially 583 Section 4, "Imposing and Processing the BIER Encapsulation", of 584 [BIER_ENCAPS].) 586 4.2. Disposition 588 When a BFER receives an MVPN multicast data packet that has been 589 BIER-encapsulated, the BIER layer passes the following information to 590 the multicast flow overlay: 592 o The sub-domain-id and the BFIR-id from the BIER header. (As the 593 sub-domain-id is inferred from the BIFT-id field of the BIER 594 header, an implementation might choose to pass the BIFT-id rather 595 than the sub-domain-id; this is an implementation matter.) 597 o The "payload", which is an MPLS packet whose top label is an 598 upstream-assigned label. In the dataplane, the BFIR-id and the 599 sub-domain-id provide the context in which the upstream-assigned 600 label is interpreted. 602 By looking up the upstream-assigned label in the appropriate context, 603 the multicast flow overlay determines whether the BFER is an egress 604 PE for the packet. 606 Note that if segmented P-tunnels are in use, a BFER might be a 607 P-tunnel segmentation border router rather than an egress PE, or a 608 BFER might be both an egress PE and a P-tunnel segmentation border 609 router. Depending upon the role of the BFER for given packet, it may 610 need to follow the procedures of Section 4.2.1, the procedures of 611 Section 4.2.2, or both. 613 4.2.1. At a BFER that is an Egress PE 615 From looking up the packet's upstream-assigned label in the context 616 of the packet's BFIR-prefix, the egress PE determines the egress VRF 617 for the packet. From the IP header of the payload, the multicast 618 states of the VRF, the upstream-assigned label, and the BFR-prefix, 619 the egress PE can determine whether the packet needs to be forwarded 620 out one or more VRF interfaces. 622 4.2.2. At a BFER that is a P-tunnel Segmentation Boundary 624 When segmented P-tunnels are being used, a BFER that receives a BIER- 625 encapsulated MVPN multicast data packet may need to be forwarded on 626 its next P-tunnel segment. The choice of the next P-tunnel segment 627 for the packet depends upon the C-flow to which the packet belongs. 628 As long as the BFIR has assigned the MPLS label according to the 629 constraints specified in Section 2.1, the BFIR will have assigned 630 distinct upstream-assigned MPLS labels to distinct C-flows. The BFER 631 can thus select the proper "next P-tunnel segment" for a given packet 632 simply by looking up the upstream-assigned label that immediately 633 follows the BIER header. 635 5. Contributor Addresses 637 Below is a list of other contributing authors in alphabetical order: 639 IJsbrand Wijnands 640 Cisco Systems, Inc. 641 De Kleetlaan 6a 642 Diegem 1831 643 Belgium 645 Email: ice@cisco.com 647 6. Acknowledgments 649 The authors wish to thank Jeffrey Zhang for his ideas and 650 contributions to this work. We also thank Stig Venaas for his review 651 and comments. 653 7. IANA Considerations 655 IANA has assigned the codepoint 0x0B to "BIER" in the "P-Multicast 656 Service Interface Tunnel (PMSI Tunnel) Tunnel Types" registry. 658 8. Security Considerations 660 The security considerations of [BIER_ARCH], [BIER_ENCAPS], [RFC6513] 661 and [RFC6514] are applicable. 663 9. References 665 9.1. Normative References 667 [BIER_ARCH] 668 Wijnands, IJ., Rosen, E., Dolganow, A., Przygienda, T., 669 and S. Aldrin, "Multicast using Bit Index Explicit 670 Replication", internet-draft draft-ietf-bier-architecture- 671 07, June 2017. 673 [BIER_ENCAPS] 674 Wijnands, IJ., Rosen, E., Dolganow, A., Tantsura, J., and 675 S. Aldrin, "Encapsulation for Bit Index Explicit 676 Replication in MPLS Networks", internet-draft draft-ietf- 677 bier-mpls-encapsulation-07.txt, June 2017. 679 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 680 Requirement Levels", BCP 14, RFC 2119, 681 DOI 10.17487/RFC2119, March 1997, 682 . 684 [RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private 685 Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February 686 2006, . 688 [RFC5331] Aggarwal, R., Rekhter, Y., and E. Rosen, "MPLS Upstream 689 Label Assignment and Context-Specific Label Space", 690 RFC 5331, DOI 10.17487/RFC5331, August 2008, 691 . 693 [RFC6513] Rosen, E., Ed. and R. Aggarwal, Ed., "Multicast in MPLS/ 694 BGP IP VPNs", RFC 6513, DOI 10.17487/RFC6513, February 695 2012, . 697 [RFC6514] Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP 698 Encodings and Procedures for Multicast in MPLS/BGP IP 699 VPNs", RFC 6514, DOI 10.17487/RFC6514, February 2012, 700 . 702 [RFC6625] Rosen, E., Ed., Rekhter, Y., Ed., Hendrickx, W., and R. 703 Qiu, "Wildcards in Multicast VPN Auto-Discovery Routes", 704 RFC 6625, DOI 10.17487/RFC6625, May 2012, 705 . 707 9.2. Informative References 709 [EXPLICIT_TRACKING] 710 Dolganow, A., Kotalwar, J., Rosen, E., and Z. Zhang, 711 "Explicit Tracking with Wild Card Routes in Multicast 712 VPN", internet-draft draft-ietf-bess-mvpn-expl-track-02, 713 June 2017. 715 [RFC7524] Rekhter, Y., Rosen, E., Aggarwal, R., Morin, T., 716 Grosclaude, I., Leymann, N., and S. Saad, "Inter-Area 717 Point-to-Multipoint (P2MP) Segmented Label Switched Paths 718 (LSPs)", RFC 7524, DOI 10.17487/RFC7524, May 2015, 719 . 721 [RFC7900] Rekhter, Y., Ed., Rosen, E., Ed., Aggarwal, R., Cai, Y., 722 and T. Morin, "Extranet Multicast in BGP/IP MPLS VPNs", 723 RFC 7900, DOI 10.17487/RFC7900, June 2016, 724 . 726 Authors' Addresses 728 Eric C. Rosen (editor) 729 Juniper Networks, Inc. 730 10 Technology Park Drive 731 Westford, Massachusetts 01886 732 United States 734 Email: erosen@juniper.net 736 Mahesh Sivakumar 737 Cisco Systems, Inc. 738 510 McCarthy Blvd 739 Milpitas, California 95035 740 United States 742 Email: masivaku@cisco.com 744 Sam K Aldrin 745 Google, Inc. 746 1600 Amphitheatre Parkway 747 Mountain View, California 748 United States 750 Email: aldrin.ietf@gmail.com 751 Andrew Dolganow 752 Nokia 753 438B Alexandra Rd #08-07/10 754 Alexandra Technopark 755 Singapore 119968 757 Email: andrew.dolganow@nokia.com 759 Tony Przygienda 760 Juniper Networks, Inc. 761 1137 Innovation Way 762 San Jose, California 94089 763 United States 765 Email: prz@juniper.net