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Venaas 5 Intended status: Standards Track Cisco 6 Expires: January 5, 2015 July 04, 2014 8 Updates to the IPv6 Multicast Addressing Architecture 9 draft-ietf-6man-multicast-addr-arch-update-06 11 Abstract 13 This document updates the IPv6 multicast addressing architecture by 14 re-defining the reserved bits as generic flag bits. The document 15 provides also some clarifications related to the use of these flag 16 bits. 18 This document updates RFC 3956, RFC 3306 and RFC 4291. 20 Requirements Language 22 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 23 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 24 document are to be interpreted as described in RFC 2119 [RFC2119]. 26 Status of This Memo 28 This Internet-Draft is submitted in full conformance with the 29 provisions of BCP 78 and BCP 79. 31 Internet-Drafts are working documents of the Internet Engineering 32 Task Force (IETF). Note that other groups may also distribute 33 working documents as Internet-Drafts. The list of current Internet- 34 Drafts is at http://datatracker.ietf.org/drafts/current/. 36 Internet-Drafts are draft documents valid for a maximum of six months 37 and may be updated, replaced, or obsoleted by other documents at any 38 time. It is inappropriate to use Internet-Drafts as reference 39 material or to cite them other than as "work in progress." 41 This Internet-Draft will expire on January 5, 2015. 43 Copyright Notice 45 Copyright (c) 2014 IETF Trust and the persons identified as the 46 document authors. All rights reserved. 48 This document is subject to BCP 78 and the IETF Trust's Legal 49 Provisions Relating to IETF Documents 50 (http://trustee.ietf.org/license-info) in effect on the date of 51 publication of this document. Please review these documents 52 carefully, as they describe your rights and restrictions with respect 53 to this document. Code Components extracted from this document must 54 include Simplified BSD License text as described in Section 4.e of 55 the Trust Legal Provisions and are provided without warranty as 56 described in the Simplified BSD License. 58 Table of Contents 60 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 61 2. Addressing Architecture Update . . . . . . . . . . . . . . . 3 62 3. Flag Bits: A Recommendation . . . . . . . . . . . . . . . . . 3 63 4. RFC Updates . . . . . . . . . . . . . . . . . . . . . . . . . 4 64 4.1. RFC 3306 . . . . . . . . . . . . . . . . . . . . . . . . 4 65 4.1.1. Update #1 . . . . . . . . . . . . . . . . . . . . . . 4 66 4.1.2. Update #2 . . . . . . . . . . . . . . . . . . . . . . 5 67 4.2. RFC 3956 . . . . . . . . . . . . . . . . . . . . . . . . 6 68 4.2.1. Update #1 . . . . . . . . . . . . . . . . . . . . . . 6 69 4.2.2. Update #2 . . . . . . . . . . . . . . . . . . . . . . 6 70 4.2.3. Update #3 . . . . . . . . . . . . . . . . . . . . . . 8 71 4.2.4. Update #4 . . . . . . . . . . . . . . . . . . . . . . 8 72 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 73 6. Security Considerations . . . . . . . . . . . . . . . . . . . 8 74 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8 75 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 76 8.1. Normative References . . . . . . . . . . . . . . . . . . 9 77 8.2. Informative References . . . . . . . . . . . . . . . . . 9 78 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 80 1. Introduction 82 This document updates the IPv6 addressing architecture [RFC4291] by 83 re-defining reserved bits as generic flag bits (Section 2). The 84 document provides also some clarifications related to the use of 85 these flag bits (Section 3). 87 This document updates [RFC3956], [RFC3306], and [RFC4291]. These 88 updates are logical consequences of the recommendation on the flag 89 bits (Section 3). 91 Textual representation of IPv6 addresses included in the RFC updates 92 follows the recommendation in [RFC5952]. 94 2. Addressing Architecture Update 96 Bits 17-20 of a multicast address, where bit 1 is the most 97 significant bit, are defined in [RFC3956] and [RFC3306] as reserved 98 bits. This document defines these bits as generic flag bits so that 99 they apply to any multicast address. These bits are referred to as 100 ff2 (flag field 2) while the flgs bits in [RFC4291][RFC3956] are 101 renamed to ff1 (flag field 1). 103 Within this document, flag bits denote both ff1 and ff2. 105 Defining the bits 17-20 as flags for all IPv6 multicast addresses 106 allows addresses to be treated in a more uniform and generic way, and 107 allows for these bits to be defined in the future for different 108 purposes, irrespective of the specific type of multicast address. 109 For the record, this design choice was initially triggered by 110 specification in [I-D.ietf-mboned-64-multicast-address-format] which 111 proposed for associating a meaning with one of the reserved bits. 112 Moreover, [I-D.ietf-mboned-64-multicast-address-format] considered 113 also the use of the last remaining flag in ff1 but that approach was 114 abandoned because it is not clear at this stage whether there is 115 other usage scenarios of the flag. 117 Section 4 specifies the updated structure of the addressing 118 architecture. 120 Further specification documents may define a meaning for these flag 121 bits. 123 3. Flag Bits: A Recommendation 125 Some implementations and specification documents do not treat the 126 flag bits as separate bits but tend to use their combined value as a 127 4-bit integer. This practice is a hurdle for assigning a meaning to 128 the remaining flag bits. Below are listed some examples for 129 illustration purposes: 131 o the reading of [RFC3306] may lead to conclude that ff3x::/32 is 132 the only allowed Source Specific Multicast (SSM) IPv6 prefix 133 block. 135 o [RFC3956] states only ff70::/12 applies to Embedded-RP. 136 Particularly, implementations should not treat the fff0::/12 range 137 as Embedded-RP. 139 To avoid such confusion and to unambiguously associate a meaning with 140 the remaining flags, the following requirement is made: 142 Implementations MUST treat flag bits as separate bits. 144 4. RFC Updates 146 4.1. RFC 3306 148 4.1.1. Update #1 150 This document changes Section 4 of [RFC3306] as follows: 152 OLD: 154 | 8 | 4 | 4 | 8 | 8 | 64 | 32 | 155 +--------+----+----+--------+--------+----------------+----------+ 156 |11111111|flgs|scop|reserved| plen | network prefix | group ID | 157 +--------+----+----+--------+--------+----------------+----------+ 159 +-+-+-+-+ 160 flgs is a set of 4 flags: |0|0|P|T| 161 +-+-+-+-+ 163 o P = 0 indicates a multicast address that is not assigned 164 based on the network prefix. This indicates a multicast 165 address as defined in [ADDRARCH]. 167 o P = 1 indicates a multicast address that is assigned based 168 on the network prefix. 170 o If P = 1, T MUST be set to 1, otherwise the setting of the T 171 bit is defined in Section 2.7 of [ADDRARCH]. 173 The reserved field MUST be zero. 175 Note: [ADDRARCH] is a reference listed in [RFC3306]. [ADDRARCH] 176 has been since obsoleted by [RFC4291]. 178 NEW: 180 | 8 | 4 | 4 | 4 | 4 | 8 | 64 | 32 | 181 +--------+----+----+----+----+--------+----------------+----------+ 182 |11111111|ff1 |scop|ff2 |rsvd| plen | network prefix | group ID | 183 +--------+----+----+----+----+--------+----------------+----------+ 185 +-+-+-+-+ 186 ff1 (flag field 1) is a set of 4 flags: |X|Y|P|T| 187 +-+-+-+-+ 189 X and Y may each be set to 0 or 1. 191 o P = 0 indicates a multicast address that is not assigned 192 based on the network prefix. This indicates a multicast 193 address as defined in [RFC4291]. 195 o P = 1 indicates a multicast address that is assigned based 196 on the network prefix. 198 o If P = 1, T MUST be set to 1, otherwise the setting of the T 199 bit is defined in Section 2.7 of [RFC4291]. 201 +-+-+-+-+ 202 ff2 (flag field 2) is a set of 4 flags: |r|r|r|r| 203 +-+-+-+-+ 205 where "rrrr" are for future assignment as additional flag bits. 206 r bits MUST each be set to 0. 208 Flag bits denote both ff1 and ff2. 210 4.1.2. Update #2 212 This document changes Section 6 of [RFC3306] as follows: 214 OLD: 216 These settings create an SSM range of FF3x::/32 (where 'x' is any 217 valid scope value). The source address field in the IPv6 header 218 identifies the owner of the multicast address. 220 NEW: 222 If the flag bits in ff1 are set to 0011, these settings create an 223 SSM range of ff3x::/32 (where 'x' is any valid scope value). The 224 source address field in the IPv6 header identifies the owner of 225 the multicast address. ff3x::/32 is not the only allowed SSM 226 prefix range. For example if the most significant flag bit in ff1 227 is set, then we would get the SSM range ffbx::/32. 229 4.2. RFC 3956 231 4.2.1. Update #1 233 This document changes Section 2 of [RFC3956] as follows: 235 OLD: 237 As described in [RFC3306], the multicast address format is as 238 follows: 240 | 8 | 4 | 4 | 8 | 8 | 64 | 32 | 241 +--------+----+----+--------+----+----------------+----------+ 242 |11111111|flgs|scop|reserved|plen| network prefix | group ID | 243 +--------+----+----+--------+----+----------------+----------+ 245 Where flgs are "0011". (The first two bits are as yet undefined, 246 sent as zero and ignored on receipt.) 248 NEW: 250 The multicast address format is as 251 follows: 253 | 8 | 4 | 4 | 4 | 4 | 8 | 64 | 32 | 254 +--------+----+----+----+----+----+----------------+----------+ 255 |11111111|ff1 |scop|ff2 |rsvd|plen| network prefix | group ID | 256 +--------+----+----+----+----+----+----------------+----------+ 258 +-+-+-+-+ 259 ff1 (flag field 1) is a set of four flags: |X|R|P|T| 260 +-+-+-+-+ 261 X may be set to 0 or 1. 263 +-+-+-+-+ 264 ff2 (flag field 2) is a set of 4 flags: |r|r|r|r| 265 +-+-+-+-+ 266 where "rrrr" are for future assignment as additional flag bits. 267 r bits MUST each be set to 0. 269 Flag bits denote both ff1 and ff2. 271 4.2.2. Update #2 273 This document changes Section 3 of [RFC3956] as follows: 275 OLD: 277 | 8 | 4 | 4 | 4 | 4 | 8 | 64 | 32 | 278 +--------+----+----+----+----+----+----------------+----------+ 279 |11111111|flgs|scop|rsvd|RIID|plen| network prefix | group ID | 280 +--------+----+----+----+----+----+----------------+----------+ 281 +-+-+-+-+ 282 flgs is a set of four flags: |0|R|P|T| 283 +-+-+-+-+ 285 When the highest-order bit is 0, R = 1 indicates a multicast address 286 that embeds the address on the RP. Then P MUST be set to 1, and 287 consequently T MUST be set to 1, as specified in [RFC3306]. In 288 effect, this implies the prefix FF70::/12. In this case, the last 4 289 bits of the previously reserved field are interpreted as embedding 290 the RP interface ID, as specified in this memo. 292 The behavior is unspecified if P or T is not set to 1, as then the 293 prefix would not be FF70::/12. Likewise, the encoding and the 294 protocol mode used when the two high-order bits in "flgs" are set to 295 11 ("FFF0::/12") is intentionally unspecified until such time that 296 the highest-order bit is defined. Without further IETF 297 specification, implementations SHOULD NOT treat the FFF0::/12 range 298 as Embedded-RP. 300 NEW: 302 | 8 | 4 | 4 | 4 | 4 | 8 | 64 | 32 | 303 +--------+----+----+----+----+----+----------------+----------+ 304 |11111111|ff1 |scop|ff2 |RIID|plen| network prefix | group ID | 305 +--------+----+----+----+----+----+----------------+----------+ 306 +-+-+-+-+ 307 ff1 is a set of four flags: |X|R|P|T| 308 +-+-+-+-+ 309 X may be set to 0 or 1. 311 R = 1 indicates a multicast address that embeds the address of the 312 RP. Then P MUST be set to 1, and consequently T MUST be set to 1, 313 according to [RFC3306], as this is a special case of unicast-prefix 314 based addresses. This implies that, for instance, prefixes ff70::/12 315 and fff0::/12 are embedded RP prefixes. The behavior is unspecified 316 if P or T is not set to 1. When the R-bit is set, the last 4 bits of 317 the field that were reserved in [RFC3306] are interpreted as 318 embedding the RP interface ID, as specified in this memo. 320 4.2.3. Update #3 322 This document changes Section 4 of [RFC3956] as follows: 324 OLD: 326 It MUST be a multicast address with "flgs" set to 0111, that is, 327 to be of the prefix FF70::/12, 329 NEW: 331 It MUST be a multicast address with R-bit set to 1. 333 It MUST have P-bit and T-bit both set to 1 when using the 334 embedding in this document as it is a prefix-based address. 336 4.2.4. Update #4 338 This document changes Section 7.1 of [RFC3956] as follows: 340 OLD: 342 To avoid loops and inconsistencies, for addresses in the range 343 FF70::/12, the Embedded-RP mapping MUST be considered the longest 344 possible match and higher priority than any other mechanism. 346 NEW: 348 To avoid loops and inconsistencies, for addresses with R-bit set 349 to 1, the Embedded-RP mapping MUST be considered the longest 350 possible match and higher priority than any other mechanism. 352 5. IANA Considerations 354 This document does not require any action from IANA. 356 6. Security Considerations 358 The same security considerations as those discussed in [RFC3956], 359 [RFC3306] and [RFC4291] are to be taken into account. 361 7. Acknowledgements 363 Special thanks to Brian Haberman for the discussions prior to the 364 publication of this document. 366 Many thanks to Jouni Korhonen, Tatuya Jinmei, Charlie Kaufman, and 367 Ben Campbell for their review. 369 8. References 371 8.1. Normative References 373 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 374 Requirement Levels", BCP 14, RFC 2119, March 1997. 376 [RFC3306] Haberman, B. and D. Thaler, "Unicast-Prefix-based IPv6 377 Multicast Addresses", RFC 3306, August 2002. 379 [RFC3956] Savola, P. and B. Haberman, "Embedding the Rendezvous 380 Point (RP) Address in an IPv6 Multicast Address", RFC 381 3956, November 2004. 383 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 384 Architecture", RFC 4291, February 2006. 386 [RFC5952] Kawamura, S. and M. Kawashima, "A Recommendation for IPv6 387 Address Text Representation", RFC 5952, August 2010. 389 8.2. Informative References 391 [I-D.ietf-mboned-64-multicast-address-format] 392 Boucadair, M., Qin, J., Lee, Y., Venaas, S., Li, X., and 393 M. Xu, "IPv6 Multicast Address With Embedded IPv4 394 Multicast Address", draft-ietf-mboned-64-multicast- 395 address-format-05 (work in progress), April 2013. 397 Authors' Addresses 399 Mohamed Boucadair 400 France Telecom 401 Rennes 35000 402 France 404 Email: mohamed.boucadair@orange.com 406 Stig Venaas 407 Cisco 408 USA 410 Email: stig@cisco.com