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Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year == Using lowercase 'not' together with uppercase 'MUST', 'SHALL', 'SHOULD', or 'RECOMMENDED' is not an accepted usage according to RFC 2119. Please use uppercase 'NOT' together with RFC 2119 keywords (if that is what you mean). Found 'MUST not' in this paragraph: o The MPLS Label field in the BIER PTA of the BGP-MVPN x-PMSI A-D route MUST be ignored and MUST not be used for the identification of the VRF. -- The document date (July 1, 2019) is 1733 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Missing Reference: 'RFC4364' is mentioned on line 105, but not defined == Missing Reference: 'RFC8114' is mentioned on line 326, but not defined == Outdated reference: A later version (-02) exists of draft-dawra-bess-srv6-services-00 == Outdated reference: A later version (-28) exists of draft-ietf-spring-srv6-network-programming-00 == Outdated reference: A later version (-10) exists of draft-xie-bier-ipv6-encapsulation-01 Summary: 1 error (**), 0 flaws (~~), 7 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group J. Xie 3 Internet-Draft Huawei Technologies 4 Intended status: Standards Track M. McBride 5 Expires: January 2, 2020 Futurewei 6 S. Dhanaraj 7 Huawei Technologies 8 L. Geng 9 China Mobile 10 July 1, 2019 12 Use of BIER IPv6 Encapsulation (BIERv6) for Multicast VPN in IPv6 13 networks 14 draft-xie-bier-ipv6-mvpn-01 16 Abstract 18 This draft defines the procedures and messages for using Bit Index 19 Explicit Replication (BIER) for Multicast VPN Services in IPv6 20 networks using the BIER IPv6 encapsulation. It provides a migration 21 path for Multicast VPN service using BIER MPLS encapsulation in MPLS 22 networks to multicast VPN service using BIER IPv6 encapsulation 23 (BIERv6) in IPv6 networks. 25 Requirements Language 27 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 28 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 29 document are to be interpreted as described in [RFC2119] and 30 [RFC8174]. 32 Status of This Memo 34 This Internet-Draft is submitted in full conformance with the 35 provisions of BCP 78 and BCP 79. 37 Internet-Drafts are working documents of the Internet Engineering 38 Task Force (IETF). Note that other groups may also distribute 39 working documents as Internet-Drafts. The list of current Internet- 40 Drafts is at https://datatracker.ietf.org/drafts/current/. 42 Internet-Drafts are draft documents valid for a maximum of six months 43 and may be updated, replaced, or obsoleted by other documents at any 44 time. It is inappropriate to use Internet-Drafts as reference 45 material or to cite them other than as "work in progress." 47 This Internet-Draft will expire on January 2, 2020. 49 Copyright Notice 51 Copyright (c) 2019 IETF Trust and the persons identified as the 52 document authors. All rights reserved. 54 This document is subject to BCP 78 and the IETF Trust's Legal 55 Provisions Relating to IETF Documents 56 (https://trustee.ietf.org/license-info) in effect on the date of 57 publication of this document. Please review these documents 58 carefully, as they describe your rights and restrictions with respect 59 to this document. Code Components extracted from this document must 60 include Simplified BSD License text as described in Section 4.e of 61 the Trust Legal Provisions and are provided without warranty as 62 described in the Simplified BSD License. 64 Table of Contents 66 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 67 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 68 3. Use of PTA and Prefix-SID Attribute in x-PMSI A-D Routes . . 4 69 4. MVPN over BIERv6 Core . . . . . . . . . . . . . . . . . . . . 4 70 5. GTM over BIERv6 Core . . . . . . . . . . . . . . . . . . . . 7 71 6. Data Plane . . . . . . . . . . . . . . . . . . . . . . . . . 7 72 6.1. Encapsulation of Multicast Traffic . . . . . . . . . . . 8 73 6.2. MTU . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 74 6.3. TTL . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 75 7. Security Considerations . . . . . . . . . . . . . . . . . . . 9 76 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 77 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10 78 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 79 10.1. Normative References . . . . . . . . . . . . . . . . . . 10 80 10.2. Informative References . . . . . . . . . . . . . . . . . 11 81 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 83 1. Introduction 85 Bit Index Explicit Replication (BIER) [RFC8279] is an architecture 86 that provides optimal multicast forwarding without requiring 87 intermediate routers to maintain any per-flow state by using a 88 multicast-specific BIER header. BIERv6 refers to the deployment of 89 BIER in IPv6 networks using the BIER IPv6 encapsulation format 90 defined in [I-D.xie-bier-ipv6-encapsulation]. 92 [I-D.ietf-spring-srv6-network-programming] introduces the Network 93 programming concepts in SRv6 networks and explains how the 128-bit 94 IPv6 address can be used as SRv6 SID in the format LOC:FUNCT, where 95 LOC part of the SID is routable, while FUNCT part of the SID is an 96 opaque identification of a local function bound to the SID. It has 97 also defined some well known standard functions like End.DT4 - 98 Endpoint with decaps and IPv4 table lookup for L3VPN (equivalent to 99 per-VRF VPN label). 101 [I-D.dawra-bess-srv6-services] defines the TLVs to associate a 102 function like End.DT4 with the L3VPN Unicast routes advertised via 103 BGP. It also details how the functions of End.DT4, End.DT6, End.DT46 104 (End.DTx) can be used to identify a L3VPN/EVPN instead of using a VPN 105 Label in MPLS-VPN [RFC4364] of the received data packet and thereby 106 realize the L3VPN Services in the SRv6 Networks. However, it covers 107 unicast services exclusively. 109 This document describes a method to realize MVPN services using BIER 110 as a P-tunnel in the IPv6 Networks (BIERv6 Networks). It defines a 111 method to use an SRv6 Service SID, called Src.DTx in this document, 112 as source address of an IPv6 header, to identify the MVPN instance at 113 the Egress PE. The LOC part and FUNCT part of this SRv6 Service SID 114 represent the context and the upstream-assigned VPN Label 115 respectively in MVPN scenario's as defined in [RFC8556]. 117 In particular, MVPN deployment in IPv6 networks relies on L3VPN 118 deployment on IPv6 networks firstly, thus the c-multicast routing 119 procedure like UMH Selection can be done. The L3VPN deployment in 120 IPv6 networks can be referred to [I-D.dawra-bess-srv6-services]. 122 GTM defined in [RFC7716] is also covered in this document, as GTM 123 shares the same BGP-MVPN signaling, while providing an approach of 124 Non-VPN multicast over a service provider core with various P-tunnel 125 type. For the same reason of UMH selection, and the requirement of 126 basic operation like ping (e.g, to the multicast source address), the 127 Global IPv4/IPv6 over SRv6 Core as described in 128 [I-D.dawra-bess-srv6-services] is also required. 130 2. Terminology 132 Readers of this document are assumed to be familiar with the 133 terminology and concepts of the documents listed as Normative 134 References. Additionally the following terms are used through out 135 the document. 137 o BIERv6 - BIER in IPv6 networks using the BIERv6 encapsulation 138 format defined in [I-D.xie-bier-ipv6-encapsulation]. 140 o SRv6 - Segment Routing instantiated on the IPv6 dataplane as 141 defined in [I-D.ietf-spring-srv6-network-programming]. 143 o SRv6 SID - SRv6 Segment Identifier as defined in 144 [I-D.ietf-spring-srv6-network-programming]. 146 o End.DTx - Refers to the functions End.DT6, End.DT4, End.DT46 147 defined in [I-D.ietf-spring-srv6-network-programming]. 149 o Src.DTx - Refers to the functions Src.DT4, Src.DT6, Src.DT46 150 defind in this document. 152 o SRv6 L3 Service - L3VPN/Global-L3 service in SRv6 networks defined 153 in [I-D.dawra-bess-srv6-services], or MVPN/GTM service in BIERv6 154 networks defined in this document. 156 3. Use of PTA and Prefix-SID Attribute in x-PMSI A-D Routes 158 The BGP-MVPN I-PMSI A-D (Type 1) or S-PMSI A-D (Type 3) route (called 159 x-PMSI A-D route in this document), advertised by Ingress PE carries 160 the BIER (Type 11) PTA as specified in [RFC8556]. The BIER PTA 161 carried in the x-PMSI A-D route is used for explicitly tracking the 162 receiver-site PEs which are interested in a specific multicast flow. 163 It includes three BIER-specific fields, Sub-domain-id, BFR-id, and 164 BFR-prefix. For BIER P-tunnel using the BIERv6 encapsulation in IPv6 165 networks, the BFR-prefix field in the PTA MUST be set to the BFIR 166 IPv6 prefix and the MPLS Label field in the PTA MUST set to 0. For 167 MVPN over BIERv6, the Src.DTx IPv6 address of the BFIR is used to 168 identify the VRF instead of an MPLS Label. The Src.DTx IPv6 Address 169 (Src.DT6 or Src.DT4 or Src.DT46) MUST be carried within an SRv6 L3 170 Service TLV [I-D.dawra-bess-srv6-services] of BGP Prefix-SID 171 attribute in the x-PMSI A-D route. 173 The Ingress PE encapsulates the c-multicast IP packet with BIERv6 174 header and the source address in the outer IPv6 header will be set to 175 the Src.DTx IPv6 address advertised in the BGP-MVPN x-PMSI A-D 176 routes. See section 3 of [I-D.xie-bier-ipv6-encapsulation] for the 177 detailed packet format. 179 Egress PE (BFER) receiving the x-PMSI A-D routes with BIER PTA and 180 SRv6 L3 Service TLV learns the Src.DTx IPv6 address and uses it to 181 identify the VRF of the c-multicast packet. 183 When Egress PE receives a BIERv6 packet and the self bfr-id is set in 184 the bit-string field of the BIERv6 header, it retrieves the Src.DTx 185 IPv6 address from the source address of the IPv6 header to determine 186 the VRF and the Address Family (AF) of the c-multicast data packet, 187 and performs the MFIB lookup in the corresponding table. 189 4. MVPN over BIERv6 Core 191 [RFC8556] specifies the protocol and procedures to be followed by the 192 Ingress and Egress PEs to use BIER as a P-tunnel for MVPN in MPLS 193 networks. This section specifies the required changes and procedures 194 in addition to support BIER as a P-tunnel in IPv6 networks using 195 BIERv6. 197 In a IPv6 service provider network, many of the IP address fields 198 used in the BGP-MVPN routes are IPv6 address as specified in 199 [RFC6515]. These are listed below. 201 o "Originating Router's IP Address" in the NLRI of Type 1 or Type 3 202 BGP-MVPN route is an IPv6 address. 204 o "Network Address of Next Hop" field in the MP_REACH_NLRI attribute 205 is an IPv6 address. 207 o Route Targets Extended Community (EC) used in C-multicast join 208 (Type 6 or 7) route or Leaf A-D (Type 5) route is an IPv6 Address 209 Specific Extended Community, where the Global Administrator field 210 will be an IPv6 address identifies the Upstream PE or the UMH. 212 o "VRF Route Import Extended Community (EC)" carried by unicast VPN- 213 IPv4 or VPN-IPv6 routes as [RFC6515] specifies, or SAFI 1, 2, or 4 214 unicast routes, or MVPN (SAFI 5) Source-Active routes as [RFC7716] 215 specifies. 217 On the Ingress PE (BFIR), the BGP-MVPN x-PMSI A-D route is 218 constructed as per the procedures specified in [RFC8556] and with the 219 following specifications. 221 o MPLS Label field in the BIER PTA MUST be set to Zero. 223 o BFR-prefix field in the BIER PTA MUST be set to the Ingress PEs 224 (BFIR) IPv6 BFR-Prefix Address. It does not need to be the same 225 as the other IPv6 address of the x-PMSI AD route. 227 o Route MUST also carry an BGP Prefix SID attribute with an SRv6 L3 228 Service TLV carrying an Src.DTx IPv6 address uniquely identifying 229 the MVPN instance. 231 If the MVPN is IPv4 MVPN, the Src.DTx can be either Src.DT4 or 232 Src.DT46. If the MVPN is IPv6 MVPN, the Src.DTx can be either 233 Src.DT6 or Src.DT46. The distribution of the x-PMSI A-D routes uses 234 the Src.DTx according to the local configuration, and is independent 235 to the use of End.DTx in VPN-IP unicast routes of this VPN. For 236 example, one can use End.DT46 for VPNv4 and VPNv6 unicast routes, but 237 use Src.DT4 for the MVPN routes for the same VPN. Another example, 238 one can use End.DX for VPNv4 unicast routes, but use Src.DT46 for the 239 MVPN routes for the same VPN. 241 BFIR MAY carry the BGP Prefix-SID attribute only in I-PMSI A-D route 242 when I-PMSI A-D route is used, while other S-PMSI A-D routes do not 243 carry the BGP Prefix-SID attribute. 245 BFIR MAY carry the BGP Prefix-SID attribute only in wildcard S-PMSI 246 A-D routes when the "S-PMSI Only" mode as described in [RFC6625] is 247 used, while other S-PMSI A-D routes do not carry the BGP Prefix-SID 248 attribute. 250 On the Egress PE (BFER), the BGP-MVPN x-PMSI A-D route is processed 251 as per the procedures specified in [RFC8556] and with the following 252 specifications: 254 o The MPLS Label field in the BIER PTA of the BGP-MVPN x-PMSI A-D 255 route MUST be ignored and MUST not be used for the identification 256 of the VRF. 258 o The BGP-MVPN x-PMSI A-D route MUST be dropped if the BFR-prefix 259 field in the BIER PTA is not an IPv6 address. 261 o The BGP-MVPN x-PMSI A-D route MUST be dropped if it does not carry 262 a Src.DTx IPv6 address in the SRv6 L3 Service TLV in BGP Prefix 263 SID attribute. 265 o Leaf A-D route originated by the Egress PE (BFER) MUST carry the 266 BIER PTA with the BFR-prefix field set to the BFER IPv6 BFR- 267 prefix. 269 Valid BGP-MVPN x-PMSI A-D route received by an Egress PE (BFER) is 270 stored locally, and the Src.DTx IPv6 Address carried in the SRv6 L3 271 service TLV is used to identify the VRF of a c-multicast data packet. 272 This may be populated into forwarding table only when there is 273 c-multicast flow state with UMH of the specific BFIR this Src.DTx 274 located in. 276 If more than one x-PMSI A-D routes belonging to the same VRF has 277 different Src.DTx value, the processing is determined by the local 278 policy of the BFER. 280 If more than one x-PMSI A-D routes belonging to different VRF has the 281 same Src.DTx value, the BFER must log an error, and a BIERv6 packet 282 with this Src.DTx as the IPv6 source address MUST be dropped. 284 The BGP Prefix-SID attribute (which may include the Src.DTx in SRv6 285 L3 Service TLV) MUST NOT be carried in Leaf A-D route upon sending, 286 and MUST be ignored upon reception. 288 5. GTM over BIERv6 Core 290 As specified in [RFC7716], Global Table Multicast (GTM) uses the same 291 Subsequent Address Family Identifier (SAFI) value, the same Network 292 Layer Reachability Information (NLRI) format, and the same procedures 293 of MVPN with only a few adaptions. It support for both IPv4 and IPv6 294 multicast flows over either an IPv4 or IPv6 SP infrastructure. GTM 295 over BIERv6 core is obviously a case of IPv4/IPv6 multicast over an 296 IPv6 SP infrastructure with BIERv6 data-plane. 298 The BIER (Type 11) PTA attribute and the BGP Prefix-SID attribute are 299 carried in the x-PMSI A-D route in GTM cases. When the a BGP-MVPN 300 x-PMSI A-D route is received by Egress PE, it is stored locally, and 301 the Src.DTx IPv6 Address of the Ingress PE in the route is used to 302 determine the VRF of a packet, which is the 'public' VRF in the case 303 of GTM. 305 There are some other attributes listed below for GTM over a BIERv6 306 core: 308 o Route Distinguishers - the RD field of a BGP-MVPN route's NLRI 309 MUST be set to zero (i.e., to 64 bits of zero) to represent a Non- 310 VPN GTM. See section 2.2 of [RFC7716]. 312 o Route Targets Extended Community (EC) - The RT EC carried by the 313 BGP-MVPN C-multicast (Type 6 or 7) route or Leaf A-D (Type 4) 314 route MUST be an IPv6-address-specific Extended Community (EC). 315 The Global Administrator field identifies the Upstream PE or the 316 UMH, and the Local Administrator field MUST always be set to zero 317 in GTM case. 319 o VRF Route Import Extended Community (EC) - The VRF Route Import EC 320 used in BIERv6 core MUST be an IPv6-address-specific EC if used, 321 either used in UMH-eligible unicast routes having a SAFI of 1, 2, 322 or 4, or used in the MVPN (SAFI of 5) Source Active A-D route. 324 GTM IPv4 multicast over an BIERv6 core may be considered an 325 alternative to support IPv4 IPTV content delivery during transition 326 to IPv6 period comparing to [RFC8114]. They both use IPv4-in-IPv6 327 encapsulation, while BIERv6 uses an additional BIER header within an 328 IPv6 Extension header to support stateless core. 330 6. Data Plane 331 6.1. Encapsulation of Multicast Traffic 333 BIER IPv6 encapsulation (BIERv6) [I-D.xie-bier-ipv6-encapsulation] is 334 used for forwarding the c-multicast traffic through an IPv6 core. 335 The following diagram shows the progression of an MVPN c-multicast 336 packet as it enters and leaves the intra-AS service-provider network. 338 +---------------+ +---------------+ 339 | P-IPv6 Header | | P-IPv6 Header | 340 | (SA=Src.DTx | | (SA=Src.DTx | 341 | DA=End.BIER) | | DA=End.BIER) | 342 +---------------+ +---------------+ 343 | P-IPv6 ExtHdr | | P-IPv6 ExtHdr | 344 | (BIER header) | | (BIER header) | 345 ++=========++ ++=============++ ++=============++ ++=========++ 346 ||C-IP Hdr || || C-IP Hdr || || C-IP Hdr || ||C-IP Hdr || 347 ++=========++ >> ++=============++ >> ++=============++ >> ++=========++ 348 ||C-Payload|| || C-Payload || || C-Payload || ||C-Payload|| 349 ++=========++ ++=============++ ++=============++ ++=========++ 350 CE1-----------PE1------------------P2------------------PE2-----------CE2 352 Figure 1: BIERv6 MVPN/GTM Intra-AS 354 In case of inter-AS scenario, BIERv6 packets may travel through 355 unicast to a Boarder Router (BR), and then replicate in a single 356 intra-AS BIERv6 domain. How such non-segmented BIERv6 scenario can 357 be supported is outside the scope of this document. 359 How segmented MVPN, for example, between BIERv6 and BIERv6, or 360 between BIERv6 and Ingress Replication(IR) in Non-MPLS IPv6 networks, 361 is outside the scope of this document. 363 The Src.DTx SHOULD support as destination address of an ICMPv6 364 packet. The following is an example pseudo-code of the Src.DTx 365 function as destination address: 367 1. IF Last_NH = ICMPv6 ;;Ref1 368 2. Send to CPU. 369 3. ELSE 370 4. Drop the packet. 372 Ref1: ICMPv6 packet using Src.DT4, Src.DT6 or Src.DT46 as destination 373 address. 375 6.2. MTU 377 Each BFIR is expected to know the Maximum Transmission Unit (MTU) of 378 the BIER domain. This may be known by provisioning, or by method 379 specified in [draft-ietf-bier-mtud]. The section 3 of [RFC8296] 380 applies. 382 6.3. TTL 384 The ingress PE (BFIR) should not copy the Time to Live (TTL) field 385 from the payload IP header received from a CE router to the delivery 386 IP header. Setting the TTL of the delivery IP header is determined 387 by the local policy of the ingress PE (BFIR) router per section 3 of 388 [RFC8296]. 390 7. Security Considerations 392 The security considerations SEC-1, SEC-2, SEC-3 defined in 393 [I-D.ietf-spring-srv6-network-programming] apply equally to this 394 document. 396 8. IANA Considerations 398 Allocation is expected from IANA for the following Src.DTx functions 399 codepoints from the "SRv6 Endpoint Behaviors" sub-registry. 401 Values 68, 69, 70 is suggested for Src.DT6, Src.DT4, Src.DT46 402 respectively. 404 +-------+--------+--------------------------+------------+ 405 | Value | Hex | Endpoint function | Reference | 406 +-------+--------+--------------------------+------------+ 407 | TBD | TBD | Src.DT6 | This draft | 408 +-------+--------+--------------------------+------------+ 409 | TBD | TBD | Src.DT4 | This draft | 410 +-------+--------+--------------------------+------------+ 411 | TBD | TBD | Src.DT46 | This draft | 412 +-------+--------+--------------------------+------------+ 414 Src.DT6 Source address indicating decapsulation and IPv6 table lookup 415 e.g. IPv6-MVPN (equivalent to per-VRF VPN label in RFC8556) 416 Src.DT4 Source address indicating decapsulation and IPv4 table lookup 417 e.g. IPv4-MVPN (equivalent to per-VRF VPN label in RFC8556) 418 Src.DT46 Source address indicating decapsulation and IP table lookup 419 e.g. IP-MVPN (equivalent to per-VRF VPN label) 421 9. Acknowledgements 423 TBD. 425 10. References 427 10.1. Normative References 429 [I-D.dawra-bess-srv6-services] 430 Dawra, G., Filsfils, C., Dukes, D., Brissette, P., 431 Sethuram, S., Camarillo, P., Leddy, J., 432 daniel.voyer@bell.ca, d., daniel.bernier@bell.ca, d., 433 Steinberg, D., Raszuk, R., Decraene, B., Matsushima, S., 434 and S. Zhuang, "SRv6 BGP based Overlay services", draft- 435 dawra-bess-srv6-services-00 (work in progress), March 436 2019. 438 [I-D.ietf-spring-srv6-network-programming] 439 Filsfils, C., Camarillo, P., Leddy, J., 440 daniel.voyer@bell.ca, d., Matsushima, S., and Z. Li, "SRv6 441 Network Programming", draft-ietf-spring-srv6-network- 442 programming-00 (work in progress), April 2019. 444 [I-D.xie-bier-ipv6-encapsulation] 445 Xie, J., Geng, L., McBride, M., Dhanaraj, S., Yan, G., and 446 Y. Xia, "Encapsulation for BIER in Non-MPLS IPv6 447 Networks", draft-xie-bier-ipv6-encapsulation-01 (work in 448 progress), June 2019. 450 [RFC6515] Aggarwal, R. and E. Rosen, "IPv4 and IPv6 Infrastructure 451 Addresses in BGP Updates for Multicast VPN", RFC 6515, 452 DOI 10.17487/RFC6515, February 2012, 453 . 455 [RFC6625] Rosen, E., Ed., Rekhter, Y., Ed., Hendrickx, W., and R. 456 Qiu, "Wildcards in Multicast VPN Auto-Discovery Routes", 457 RFC 6625, DOI 10.17487/RFC6625, May 2012, 458 . 460 [RFC7716] Zhang, J., Giuliano, L., Rosen, E., Ed., Subramanian, K., 461 and D. Pacella, "Global Table Multicast with BGP Multicast 462 VPN (BGP-MVPN) Procedures", RFC 7716, 463 DOI 10.17487/RFC7716, December 2015, 464 . 466 [RFC8279] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., 467 Przygienda, T., and S. Aldrin, "Multicast Using Bit Index 468 Explicit Replication (BIER)", RFC 8279, 469 DOI 10.17487/RFC8279, November 2017, 470 . 472 [RFC8296] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., 473 Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation 474 for Bit Index Explicit Replication (BIER) in MPLS and Non- 475 MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January 476 2018, . 478 [RFC8556] Rosen, E., Ed., Sivakumar, M., Przygienda, T., Aldrin, S., 479 and A. Dolganow, "Multicast VPN Using Bit Index Explicit 480 Replication (BIER)", RFC 8556, DOI 10.17487/RFC8556, April 481 2019, . 483 10.2. Informative References 485 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 486 Requirement Levels", BCP 14, RFC 2119, 487 DOI 10.17487/RFC2119, March 1997, 488 . 490 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 491 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 492 May 2017, . 494 Authors' Addresses 496 Jingrong Xie 497 Huawei Technologies 499 Email: xiejingrong@huawei.com 501 Mike McBride 502 Futurewei 504 Email: mmcbride7@gmail.com 506 Senthil Dhanaraj 507 Huawei Technologies 509 Email: senthil.dhanaraj@huawei.com 510 Liang Geng 511 China Mobile 513 Email: gengliang@chinamobile.com