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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 L. Geng 5 Expires: December 21, 2019 China Mobile 6 M. McBride 7 Futurewei 8 S. Dhanaraj 9 G. Yan 10 Y. Xia 11 Huawei 12 June 19, 2019 14 Encapsulation for BIER in Non-MPLS IPv6 Networks 15 draft-xie-bier-ipv6-encapsulation-01 17 Abstract 19 This document proposes a BIER IPv6 (BIERv6) encapsulation for Non- 20 MPLS IPv6 Networks using the IPv6 Destination Option extension 21 header. 23 Requirements Language 25 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 26 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 27 document are to be interpreted as described in [RFC2119] and 28 [RFC8174]. 30 Status of This Memo 32 This Internet-Draft is submitted in full conformance with the 33 provisions of BCP 78 and BCP 79. 35 Internet-Drafts are working documents of the Internet Engineering 36 Task Force (IETF). Note that other groups may also distribute 37 working documents as Internet-Drafts. The list of current Internet- 38 Drafts is at https://datatracker.ietf.org/drafts/current/. 40 Internet-Drafts are draft documents valid for a maximum of six months 41 and may be updated, replaced, or obsoleted by other documents at any 42 time. It is inappropriate to use Internet-Drafts as reference 43 material or to cite them other than as "work in progress." 45 This Internet-Draft will expire on December 21, 2019. 47 Copyright Notice 49 Copyright (c) 2019 IETF Trust and the persons identified as the 50 document authors. All rights reserved. 52 This document is subject to BCP 78 and the IETF Trust's Legal 53 Provisions Relating to IETF Documents 54 (https://trustee.ietf.org/license-info) in effect on the date of 55 publication of this document. Please review these documents 56 carefully, as they describe your rights and restrictions with respect 57 to this document. Code Components extracted from this document must 58 include Simplified BSD License text as described in Section 4.e of 59 the Trust Legal Provisions and are provided without warranty as 60 described in the Simplified BSD License. 62 Table of Contents 64 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 65 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 66 3. BIER IPv6 Encapsulation . . . . . . . . . . . . . . . . . . . 3 67 3.1. BIER Option in IPv6 Destination Options Header . . . . . 3 68 3.2. Multicast and Unicast Destination Address . . . . . . . . 6 69 3.3. BIERv6 Packet Format . . . . . . . . . . . . . . . . . . 7 70 4. BIERv6 Packet Processing . . . . . . . . . . . . . . . . . . 8 71 5. Security Considerations . . . . . . . . . . . . . . . . . . . 10 72 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 73 6.1. BIER Option Type . . . . . . . . . . . . . . . . . . . . 10 74 6.2. BIER Multicast Address . . . . . . . . . . . . . . . . . 11 75 6.3. End.BIER Function . . . . . . . . . . . . . . . . . . . . 11 76 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11 77 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 78 8.1. Normative References . . . . . . . . . . . . . . . . . . 11 79 8.2. Informative References . . . . . . . . . . . . . . . . . 12 80 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12 82 1. Introduction 84 Bit Index Explicit Replication (BIER) [RFC8279] is an architecture 85 that provides optimal multicast forwarding without requiring 86 intermediate routers to maintain any per-flow state by using a 87 multicast-specific BIER header. 89 [RFC8296] defines a common BIER Header format for MPLS and Non-MPLS 90 networks. It has defined two types of encapsulation methods using 91 the common BIER Header, (1) BIER encapsulation in MPLS networks, 92 here-in after referred as MPLS BIER Header in this document and (2) 93 BIER encapsulation in Non-MPLS networks, here-in after referred as 94 Non-MPLS BIER Header in this document. [RFC8296] also assigned 95 Ethertype=0xAB37 for Non-MPLS BIER Header packets to be directly 96 carried over the Ethernet links. 98 This document proposes a BIER IPv6 encapsulation for Non-MPLS IPv6 99 Networks, defining a method to carry the standard Non-MPLS BIER 100 header (as defined in [RFC8296]) in the native IPv6 header. A new 101 IPv6 Option type - BIER Option is defined to encode the standard Non- 102 MPLS BIER header and this newly defined BIER Option is carried under 103 the Destination Options header of the native IPv6 Header [RFC8200]. 105 This document details one of the proposed solutions for transporting 106 BIER packets in an IPv6 network. To better understand the overall 107 BIER IPv6 problem space, use cases and proposed solutions, refer to 108 [I-D.ietf-bier-ipv6-requirements]. 110 2. Terminology 112 Readers of this document are assumed to be familiar with the 113 terminology and concepts of the documents listed as Normative 114 References. 116 The following new terms are used throughout this document: 118 o BIERv6 - BIER IPv6. 120 o BIER Option - An Option type carried in IPv6 Destination Options 121 Header which includes the standard Non-MPLS BIER Header. 123 o BIERv6 Header - An IPv6 Header with BIER Option. 125 o BIERv6 Packet - An IPv6 packet with BIERv6 Header. Such an IPv6 126 packet typically carries the user multicast payload and is 127 forwarded by BFRs in the BIERv6 network towards the multicast 128 receivers. 130 o BIER Multicast Address - A well-known multicast address used as a 131 Destination Address in the BIERv6 Header to forward the packets to 132 other BFRs in BIERv6 network. 134 3. BIER IPv6 Encapsulation 136 3.1. BIER Option in IPv6 Destination Options Header 138 Destination Options Header and the Options that can be carried under 139 this extension header is defined in [RFC8200]. This document defines 140 a new Option type - BIER Option, to encode the Non-MPLS BIER header. 141 As specified in Section 4.2 [RFC8200], the BIER Option follows type- 142 length-value (TLV) encoding format and the standard Non-MPLS BIER 143 header [RFC8296] is encoded in the value portion of the BIER Option 144 TLV. 146 This BIER Option MUST be carried only inside the IPv6 Destination 147 Options header and MUST NOT be carried under the Hop-by-Hop Options 148 header. 150 Co-existence of Destination Options Header with BIER option TLV and 151 other IPv6 extension headers MUST confirm to the general requirements 152 defined in [RFC8200]. In addition to the requirements defined in 153 [RFC8200], this document requires that the Destination Options Header 154 with a BIER Option TLV MUST appear only after the Routing Header if 155 the Routing Header is present in the IPv6 Header. 157 The BIER Option is encoded in type-length-value (TLV) format as 158 follows: 160 0 1 2 3 161 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 162 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 163 | Next Header | Hdr Ext Len | Option Type | Option Length | 164 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 165 | | 166 ~ Non-MPLS BIER Header (defined in RFC8296) ~ 167 | | 168 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 170 Next Header 8-bit selector. Identifies the type of header 171 immediately following the Destination Options header. 173 Hdr Ext Len 8-bit unsigned integer. Length of the Destination 174 Options header in 8-octet units, not including the first 8 octets. 176 Option Type To be allocated by IANA. See section 6. 178 Option Length 8-bit unsigned integer. Length of the option, in 179 octets, excluding the Option Type and Option Length fields. 181 Non-MPLS BIER Header The Non-MPLS BIER Header defined in RFC8296. 182 Fields in the Non-MPLS BIER Header MUST be encoded as below. 184 BIFT-id: The BIFT-id is a domain-wide unique value in Non-MPLS 185 IPv6 encapsulation. See Section 2.2 of RFC 8296. 187 TC: SHOULD be set to binary value 000 upon transmission and MUST 188 be ignored upon. See Section 2.2 of RFC 8296. 190 S bit: SHOULD be set to 1 upon transmission, and MUST be ignored 191 upon reception. See Section 2.2 of RFC 8296. 193 TTL: MUST be set to 0 upon transmission, and MUST be ignored 194 upon reception. The function of TTL is replaced by the Hop 195 Limit field in IPv6 header. 197 Nibble: SHOULD be set to 0000 upon transmission, and MUST be 198 ignored upon reception. See Section 2.2 of RFC 8296. 200 Ver: MUST be set to 0 upon transmission, and MUST be discarded 201 when it is not 0 upon reception. See Section 2.2 of RFC 8296. 203 BSL: See Section 2.1.2 of RFC 8296. 205 Entropy: See Section 2.1.2 of RFC 8296. 207 OAM: See Section 2.1.2 of RFC 8296. 209 Rsv: See Section 2.1.2 of RFC 8296. 211 DSCP: SHOULD be set to binary value 000000 upon transmission and 212 MUST be ignored upon reception. In IPv6 BIER encapsulation, 213 uses highest 6-bit of Traffic Class field of IPv6 header to hold 214 a Differentiated Services Codepoint [RFC2474]. 216 Proto: SHOULD be set to 0 upon transmission and MUST be ignored 217 upon reception. In IPv6 BIER encapsulation, the functionality 218 of this 6-bit Proto field is replaced by the Next Header field 219 in Destination Options header, which is the last IPv6 extension 220 header, to indicate the BIER payload, which is also IPv6 221 payload. 223 For BIER Proto 1, indicating a Downstream-assigned MPLS 224 payload, use Next Header value 137. 226 For BIER Proto 2, indicating an Upstream-assigned MPLS 227 payload, there is no Next Header code currently. An 228 upstream-assigned MPLS label within the context of special 229 BFIR router, which in turn is represented by the BFIR-id and 230 the Sub-domain indirectly indicated by the BIFT-id in a BIER- 231 MPLS or BIER-ETH packet, can be replaced by an IPv6 source 232 address in a BIER IPv6 encapsulation packet in a direct 233 manner. In this case, use Next Header value 4 for IPv4 234 payload, or value 41 for IPv6 payload. 236 For BIER Proto 3, indicating an Ethernet payload, use Next 237 Header value 97. 239 For BIER Proto 4, indicating an IPv4 payload, use Next Header 240 value 4. 242 For BIER Proto 5, indicating a BIER-OAM payload, use Next 243 Header value 58. How the BIER-PING is supported with BIER 244 IPv6 encapsulation is outside the scope of this document. 246 For BIER Proto 6, indicating an IPv6 payload, use Next Header 247 value 41. 249 BFIR-id: See Section 2.1.2 of RFC 8296. 251 BitString: See Section 2.1.2 of RFC 8296. 253 3.2. Multicast and Unicast Destination Address 255 BIER is generally a hop-by-hop and one-to-many architecture, and thus 256 the IPv6 Destination Address (DA) being a Multicast Address is a 257 proper approach for both the two paradigms in BIERv6 encapsulation. 259 This document proposes to use multicast address FF0X::AB37 (to be 260 allocated and reserved by IANA - See Section 6.2) as the IPv6 261 destination address for the BIERv6 packets to be forwarded in the 262 BIER domain. 264 All the interfaces of the BFRs supporting the BIERv6 encapsulation 265 defined in this document MUST subscribe and listen to BIER multicast 266 address FF0X::AB37 belong to scopes [1, 2, 3, 4, 5, E] defined in 267 [RFC7346]. However it is RECOMMENDED to use Realm-Local scope (scope 268 value 3), that is FF03:AB37 as a destination address while forwarding 269 the BIERv6 packet, as this scope zone is exactly the BIERv6 Domain. 270 The use of other scopes is outside the scope of this document. 272 Use of a Unicast Address as a IPv6 Destination Address is permissible 273 and useful in certain cases. 275 1. Tunneling a BIERv6 packet over a non-BIER capable router. 277 2. Fast rerouting a BIERv6 packet using a unicast by-pass tunnel. 279 3. Forwarding a BIERv6 packet to one of the many BFR neighbors 280 connected on a LAN. 282 4. Connecting BIER domains, for example Data Center domains, in an 283 overlay manner. 285 The unicast address used in BIERv6 packet targeting a BFR SHOULD be 286 the IPv6 BFR-Prefix advertised from this BFR. When a BFR advertises 287 the BIER information with BIERv6 encapsulation capability, the IPv6 288 BFR-prefix of this BFR MUST be selected specifically for BIERv6 289 packet forwarding. Locally this "BIER Specific" IPv6 address is 290 initialized in FIB with a flag of "BIER specific handling", 291 represented as End.BIER function. For convenience, the indication in 292 FIB share the same space as SRv6 Endpoints Behaviors defined in 293 [I-D.ietf-spring-srv6-network-programming]. Apart from this sharing 294 of code space, there is nothing dependent on SRv6. The co-existance 295 of BIERv6 and SRv6 is outside the scope of this document. 297 BFR Prefix is used only in control plane in BIER MPLS encapsulation 298 but not used in data plane. While in BIERv6, BFR prefix is used in 299 both control plane and data plane. The "BIER Specific" IPv6 address 300 can be used for BIER MPLS in control plane too. So it is RECOMMENDED 301 to use a "BIER specific" IPv6 address as BFR prefix when deploying 302 BIER in IPv6 network from the scratch. One should be careful not use 303 the IPv6 address selected as BFR prefix for other purpose like BGP 304 session until the "BIER specific handling" can do more general 305 process. 307 The following is an example of configuring a BIER specific IPv6 308 address and using this address as BFR prefix: 310 # Config a BIER specific IPv6 address with 128-bit mask on loopback0. 311 interface loopback0 312 ipv6 address 2019::AB37 128 End.BIER 314 # Config the BIER-specific IPv6 address on loopback0 as BFR Prefix. 315 bier sub-domain 6 ipv6-underlay 316 bfr-prefix interface loopback0 318 3.3. BIERv6 Packet Format 320 As a multicast packet enters the BIER domain in a Non-MPLS IPv6 321 network, the multicast packet will be encapsulated with BIERv6 322 Header. 324 Typically a BIERv6 header would contain the Destination Options 325 Header as the only Extensions Header besides IPv6 Header. However, 326 it is allowed and possible for other extension headers to appear 327 along with the Destination Options Header as long as the requirements 328 listed in section 3.1 of this document is met. 330 Format of the multicast packet with BIERv6 encapsulation carrying 331 only the Destination Options header is depicted in the below figure. 333 +---------------+--------------+------------ 334 | IPv6 header | Dest Options | X type of 335 | | Header with | multicast 336 | | BIER Option | packet 337 | | | 338 | Next Hdr = 60 | Nxt Hdr = X | 339 +---------------+--------------+------------ 341 Format of the multicast packet with BIERv6 encapsulation carrying 342 other extension headers along with Destination Options extension 343 header is required to follow general recommendations of [RFC8200] and 344 examples in other RFCs. [RFC6275] introduces how the order should be 345 when other extension headers carries along with Home address option 346 in a destination options header. Similar to this example, this 347 document requires the Destination Options Header carrying the BIER 348 option MUST be placed as follows: 350 o After the routing header, if that header is present 352 o Before the Fragment Header, if that header is present 354 o Before the AH Header or ESP Header, if either one of those headers 355 is present 357 Source Address field in the IPv6 header MUST be a routable IPv6 358 unicast address of the BFIR in any case. 360 BFIR encodes the Non-MPLS BIER header in the above mentioned 361 encapsulation format and forwards the BIERv6 packet to the nexthop 362 BFR following the local BIFT table. 364 BFRs in the IPv6 network, processes and replicates the packets 365 towards the BFERs using the local BIFT table. The bit-string field 366 in the Non-MPLS BIER header may be changed by the BFRs as they 367 replicate the packet. BFRs MUST follow the procedures defined in 368 section 3.1 as they modify the other fields in the Non-MPLS BIER 369 header. The source address in the IPv6 header MUST NOT be modified 370 by the BFRs. 372 4. BIERv6 Packet Processing 374 There is no BIER-specific processing, and all the 8 steps in section 375 6.5 of RFC8279 apply to BIERv6 packet processing. However, there are 376 some IPv6-specific processing procedures due to the base and general 377 procedures of IPv6. 379 On the overlay layer, when a multicast packet enters the BIER domain 380 in a Non-MPLS IPv6 network, the Ingress BFR (BFIR) encapsulates the 381 multicast packet with a BIERv6 Header, transforming it to a BIERv6 382 packet. The BIERv6 header includes an IPv6 header and IPv6 383 Destination Options Header within a standard Non-MPLS BIER header. 384 Source Address field in the IPv6 header MUST be set to a routable 385 IPv6 unicast address of the BFIR. Destination Address field in the 386 IPv6 header is set to a BIER multicast address, FF0X::AB37, if the 387 next-hop BFR is directly connected, or MAY be set to a unicast 388 address in case of the scenarios discussed in section 3.2. 390 On the BIER layer, upon receiving an BIERv6 packet, the BFR processes 391 the IPv6 header first. This is the general procedure of IPv6. 393 If the IPv6 Destination address is the BIER multicast address, a 394 'BIER Specific Handling' indication will be obtained by the preceding 395 Multicast DA lookup (MFIB lookup). The BIER option, if exists, will 396 be checked to decide which neighbor(s) to replicate the BIERv6 packet 397 to. 399 If the IPv6 Destination address is an IPv6 BFR-Prefix unicast address 400 of this BFR, a 'BIER Specific Handling' indication will be obtained 401 by the preceding Unicast DA lookup (FIB lookup). The BIER option, if 402 exists, will be checked to decide which neighbor(s) to replicate the 403 BIERv6 packet to. 405 It is a local behavior to handle the combination of extension 406 headers, options and the BIER option(s) in destination options header 407 when a 'BIER Specific Handling' indication is got by the preceding 408 MFIB or FIB lookup. Early deployment of BIERv6 may require there is 409 only one BIER option TLV in the destination options header followed 410 the IPv6 header. How other extension headers or more BIER option 411 TLVs in a BIERv6 packet is handled is outside the scope of this 412 document. 414 A packet having a 'BIER Specific Handling' indication but not having 415 a BIER option MAY be processed normally as normal multicast or 416 unicast forwarding procedures do, or MAY be dropped. 418 A packet not having a 'BIER Specific Handling' indication but having 419 a BIER option SHOULD be processed normally as normal multicast or 420 unicast forwarding procedures, which may be a behavior of drop, or 421 send to CPU, or other behaviors in existing implementations. 423 The Destination Address field in the IPv6 Header MUST change to the 424 nexthop BFR's BFR Prefix if Unicast address is used in BIERv6. 426 The Hop Limit field of IPv6 header MUST decrease by 1 when sending 427 packets to a BFR neighbor, while the TTL in the BIER header MUST be 428 unchanged. 430 The BitString in the BIER header in the Destination Options Header 431 may change when sending packets to a neighbor. Such change of 432 BitString MUST be aligned with the procedure defined in RFC8279. 433 Because of the requirement to change the content of the option when 434 forwarding BIERv6 packet, the BIER option type should have chg flag 1 435 per section 4.2 of RFC8200. 437 The procedures applies normally if a bit corresponding to the self 438 bfr-id is set in the bit-string field of the Non-MPLS BIER header of 439 the BIERv6 packet. The node is considered to be an Egress BFR (BFER) 440 in this case. The BFER removes the BIERv6 header, including the IPv6 441 header and the Destination Options header, and copies the packet to 442 the multicast flow overlay. The egress VRF of a packet may be 443 determined by a single MFIB lookup on the BFER using both the IPv6 SA 444 and IPv6 DA. 446 5. Security Considerations 448 A BIERv6 packet with a special IPv6 Destination Address, either 449 multicast or unicast, would be processed by BIER forwarding procedure 450 only when the 'BIER valid' flag has been obtained ahead of time in 451 the normal MFIB or FIB lookup of the IPv6 header. Otherwise the 452 packet with an IPv6 BIER Option will be dropped, as if the Option is 453 not recognize by the node. 455 An IPv6 packet with BIER multicast address FF0X::AB37 as destination 456 address, but does not carry IPv6 BIER Option will be dropped. 458 6. IANA Considerations 460 6.1. BIER Option Type 462 Allocation is expected from IANA for a BIER Option Type codepoint 463 from the "Destination Options and Hop-by-Hop Options" sub-registry of 464 the "Internet Protocol Version 6 (IPv6) Parameters" registry. The 465 value 0x70 is suggested. 467 +-----------+-----+-----+-------+-------------+------------+ 468 | Hex Value | act | chg | rest | Description | Reference | 469 +-----------+-----+-----+-------+-------------+------------+ 470 | 0x70 | 01 | 1 | 10000 | BIER Option | This draft | 471 +-----------+-----+-----+-------+-------------+------------+ 473 Figure 1: IPv6 Option Type Suggested 475 6.2. BIER Multicast Address 477 Allocation is expected from IANA for a BIER Multicast Address from 478 the "Variable Scope Multicast Addresses" sub-registry of the "IPv6 479 Multicast Address Space Registry" registry. The address 'FF0X::AB37' 480 is suggested. 482 +-----------------------+---------------------+------------+ 483 | Address(es) | Description | Reference | 484 | | | | 485 +-----------------------+---------------------+------------+ 486 | FF0X:0:0:0:0:0:0:AB37 | ALL_BIER_FORWARDERS | This draft | 487 +-----------------------+---------------------+------------+ 489 Figure 2: Multicast Address Suggested 491 6.3. End.BIER Function 493 Allocation is expected from IANA for an End.BIER function codepoint 494 from the "SRv6 Endpoint Behaviors" sub-registry. The value 60 is 495 suggested. 497 +-------+--------+--------------------------+------------+ 498 | Value | Hex | Endpoint function | Reference | 499 +-------+--------+--------------------------+------------+ 500 | TBD | TBD | End.BIER | This draft | 501 +-------+--------+--------------------------+------------+ 503 Figure 3: End.BIER Function 505 7. Acknowledgements 507 The authors would like to thank Stig Venaas for his valuable 508 comments. 510 8. References 512 8.1. Normative References 514 [RFC6275] Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility 515 Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July 516 2011, . 518 [RFC7346] Droms, R., "IPv6 Multicast Address Scopes", RFC 7346, 519 DOI 10.17487/RFC7346, August 2014, 520 . 522 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 523 (IPv6) Specification", STD 86, RFC 8200, 524 DOI 10.17487/RFC8200, July 2017, 525 . 527 [RFC8279] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., 528 Przygienda, T., and S. Aldrin, "Multicast Using Bit Index 529 Explicit Replication (BIER)", RFC 8279, 530 DOI 10.17487/RFC8279, November 2017, 531 . 533 [RFC8296] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., 534 Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation 535 for Bit Index Explicit Replication (BIER) in MPLS and Non- 536 MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January 537 2018, . 539 8.2. Informative References 541 [I-D.ietf-bier-ipv6-requirements] 542 McBride, M., Xie, J., Dhanaraj, S., and R. Asati, "BIER 543 IPv6 Requirements", draft-ietf-bier-ipv6-requirements-00 544 (work in progress), May 2019. 546 [I-D.ietf-spring-srv6-network-programming] 547 Filsfils, C., Camarillo, P., Leddy, J., 548 daniel.voyer@bell.ca, d., Matsushima, S., and Z. Li, "SRv6 549 Network Programming", draft-ietf-spring-srv6-network- 550 programming-00 (work in progress), April 2019. 552 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 553 Requirement Levels", BCP 14, RFC 2119, 554 DOI 10.17487/RFC2119, March 1997, 555 . 557 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 558 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 559 May 2017, . 561 Authors' Addresses 563 Jingrong Xie 564 Huawei Technologies 566 Email: xiejingrong@huawei.com 567 Liang Geng 568 China Mobile 569 Beijing 10053 571 Email: gengliang@chinamobile.com 573 Mike McBride 574 Futurewei 576 Email: mmcbride7@gmail.com 578 Senthil Dhanaraj 579 Huawei 581 Email: senthil.dhanaraj@huawei.com 583 Gang Yan 584 Huawei 586 Email: yangang@huawei.com 588 Yang Xia 589 Huawei 591 Email: yolanda.xia@huawei.com