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Venaas 5 Intended status: Standards Track Cisco 6 Expires: December 20, 2014 June 18, 2014 8 Updates to the IPv6 Multicast Addressing Architecture 9 draft-ietf-6man-multicast-addr-arch-update-05 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 December 20, 2014. 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 . . . . . . . . . . . . . . . 2 62 3. Flag Bits: A Recommendation . . . . . . . . . . . . . . . . . 3 63 4. RFC Updates . . . . . . . . . . . . . . . . . . . . . . . . . 3 64 4.1. RFC 3306 . . . . . . . . . . . . . . . . . . . . . . . . 3 65 4.2. RFC 3956 . . . . . . . . . . . . . . . . . . . . . . . . 6 66 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 67 6. Security Considerations . . . . . . . . . . . . . . . . . . . 8 68 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8 69 8. Normative References . . . . . . . . . . . . . . . . . . . . 8 70 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 72 1. Introduction 74 This document updates the IPv6 addressing architecture [RFC4291] by 75 re-defining reserved bits as generic flag bits (Section 2). The 76 document provides also some clarifications related to the use of 77 these flag bits (Section 3). 79 This document updates [RFC3956], [RFC3306], and [RFC4291]. These 80 updates are logical consequences of the recommendation on the flag 81 bits (Section 3). 83 Textual representation of IPv6 addresses included in the RFC updates 84 follows the recommendation in [RFC5952]. 86 2. Addressing Architecture Update 88 Bits 17-20 of a multicast address, where bit 1 is the most 89 significant bit, are defined in [RFC3956] and [RFC3306] as reserved 90 bits. This document defines these bits as generic flag bits so that 91 they apply to any multicast address. These bits are referred to as 92 ff2 (flag field 2) while the flgs bits in [RFC4291][RFC3956] are 93 renamed to ff1 (flag field 1). 95 Within this document, flag bits denote both ff1 and ff2. 97 Defining the bits 17-20 as flags for all IPv6 multicast addresses 98 allows addresses to be treated in a more uniform and generic way, and 99 allows for these bits to be defined in the future for different 100 purposes, irrespective of the specific type of multicast address. 102 Section 4 specifies the updated structure of the addressing 103 architecture. 105 Further specification documents may define a meaning for these flag 106 bits. 108 3. Flag Bits: A Recommendation 110 Some implementations and specification documents do not treat the 111 flag bits as separate bits but tend to use their combined value as a 112 4-bit integer. This practice is a hurdle for assigning a meaning to 113 the remaining flag bits. Below are listed some examples for 114 illustration purposes: 116 o the reading of [RFC3306] may lead to conclude that ff3x::/32 is 117 the only allowed SSM IPv6 prefix block. 119 o [RFC3956] states only ff70::/12 applies to Embedded-RP. 120 Particularly, implementations should not treat the fff0::/12 range 121 as Embedded-RP. 123 To avoid such confusion and to unambiguously associate a meaning with 124 the remaining flags, the following requirement is made: 126 Implementations MUST treat flag bits as separate bits. 128 4. RFC Updates 130 4.1. RFC 3306 132 This document changes Section 4 of [RFC3306] as follows: 134 OLD: 136 | 8 | 4 | 4 | 8 | 8 | 64 | 32 | 137 +--------+----+----+--------+--------+----------------+----------+ 138 |11111111|flgs|scop|reserved| plen | network prefix | group ID | 139 +--------+----+----+--------+--------+----------------+----------+ 141 +-+-+-+-+ 142 flgs is a set of 4 flags: |0|0|P|T| 143 +-+-+-+-+ 145 o P = 0 indicates a multicast address that is not assigned 146 based on the network prefix. This indicates a multicast 147 address as defined in [ADDRARCH]. 149 o P = 1 indicates a multicast address that is assigned based 150 on the network prefix. 152 o If P = 1, T MUST be set to 1, otherwise the setting of the T 153 bit is defined in Section 2.7 of [ADDRARCH]. 155 The reserved field MUST be zero. 157 NEW: 159 | 8 | 4 | 4 | 4 | 4 | 8 | 64 | 32 | 160 +--------+----+----+----+----+--------+----------------+----------+ 161 |11111111|ff1 |scop|ff2 |rsvd| plen | network prefix | group ID | 162 +--------+----+----+----+----+--------+----------------+----------+ 164 +-+-+-+-+ 165 ff1 (flag field 1) is a set of 4 flags: |X|Y|P|T| 166 +-+-+-+-+ 168 X and Y may each be set to 0 or 1. 170 o P = 0 indicates a multicast address that is not assigned 171 based on the network prefix. This indicates a multicast 172 address as defined in [RFC4291]. 174 o P = 1 indicates a multicast address that is assigned based 175 on the network prefix. 177 o If P = 1, T MUST be set to 1, otherwise the setting of the T 178 bit is defined in Section 2.7 of [RFC4291]. 180 +-+-+-+-+ 181 ff2 (flag field 2) is a set of 4 flags: |r|r|r|r| 182 +-+-+-+-+ 184 where "rrrr" are for future assignment as additional flag bits. 186 Flag bits denote both ff1 and ff2. 188 This document changes Section 6 of [RFC3306] as follows: 190 OLD: 192 These settings create an SSM range of FF3x::/32 (where 'x' is any 193 valid scope value). The source address field in the IPv6 header 194 identifies the owner of the multicast address. 196 NEW: 198 If the flag bits in ff1 are set to 0011, these settings create an 199 SSM range of ff3x::/32 (where 'x' is any valid scope value). The 200 source address field in the IPv6 header identifies the owner of 201 the multicast address. ff3x::/32 is not the only allowed SSM 202 prefix range. For example if the most significant flag bit in ff1 203 is set, then we would get the SSM range ffbx::/32. 205 4.2. RFC 3956 207 This document changes Section 2 of [RFC3956] as follows: 209 OLD: 211 As described in [RFC3306], the multicast address format is as 212 follows: 214 | 8 | 4 | 4 | 8 | 8 | 64 | 32 | 215 +--------+----+----+--------+----+----------------+----------+ 216 |11111111|flgs|scop|reserved|plen| network prefix | group ID | 217 +--------+----+----+--------+----+----------------+----------+ 219 Where flgs are "0011". (The first two bits are as yet undefined, 220 sent as zero and ignored on receipt.) 222 NEW: 224 The multicast address format is as 225 follows: 227 | 8 | 4 | 4 | 4 | 4 | 8 | 64 | 32 | 228 +--------+----+----+----+----+----+----------------+----------+ 229 |11111111|ff1 |scop|ff2 |rsvd|plen| network prefix | group ID | 230 +--------+----+----+----+----+----+----------------+----------+ 232 +-+-+-+-+ 233 ff1 (flag field 1) is a set of four flags: |X|R|P|T| 234 +-+-+-+-+ 235 X may be set to 0 or 1. 237 +-+-+-+-+ 238 ff2 (flag field 2) is a set of 4 flags: |r|r|r|r| 239 +-+-+-+-+ 240 where "rrrr" are for future assignment as additional flag bits. 242 Flag bits denote both ff1 and ff2. 244 This document changes Section 3 of [RFC3956] as follows: 246 OLD: 248 | 8 | 4 | 4 | 4 | 4 | 8 | 64 | 32 | 249 +--------+----+----+----+----+----+----------------+----------+ 250 |11111111|flgs|scop|rsvd|RIID|plen| network prefix | group ID | 251 +--------+----+----+----+----+----+----------------+----------+ 252 +-+-+-+-+ 253 flgs is a set of four flags: |0|R|P|T| 254 +-+-+-+-+ 256 When the highest-order bit is 0, R = 1 indicates a multicast address 257 that embeds the address on the RP. Then P MUST be set to 1, and 258 consequently T MUST be set to 1, as specified in [RFC3306]. In 259 effect, this implies the prefix FF70::/12. In this case, the last 4 260 bits of the previously reserved field are interpreted as embedding 261 the RP interface ID, as specified in this memo. 263 The behavior is unspecified if P or T is not set to 1, as then the 264 prefix would not be FF70::/12. Likewise, the encoding and the 265 protocol mode used when the two high-order bits in "flgs" are set to 266 11 ("FFF0::/12") is intentionally unspecified until such time that 267 the highest-order bit is defined. Without further IETF 268 specification, implementations SHOULD NOT treat the FFF0::/12 range 269 as Embedded-RP. 271 NEW: 273 | 8 | 4 | 4 | 4 | 4 | 8 | 64 | 32 | 274 +--------+----+----+----+----+----+----------------+----------+ 275 |11111111|ff1 |scop|ff2 |RIID|plen| network prefix | group ID | 276 +--------+----+----+----+----+----+----------------+----------+ 277 +-+-+-+-+ 278 ff1 is a set of four flags: |X|R|P|T| 279 +-+-+-+-+ 280 X may be set to 0 or 1. 282 R = 1 indicates a multicast address that embeds the address of the 283 RP. P MUST be set to 1, and consequently T MUST be set to 1, 284 according to [RFC3306], as this is a special case of unicast-prefix 285 based addresses. This implies that for instance prefixes ff70::/12 286 and fff0::/12 are embedded RP prefixes. The behavior is unspecified 287 if P or T is not set to 1. When the R-bit is set, the last 4 bits of 288 the field that were reserved in [RFC3306] are interpreted as 289 embedding the RP interface ID, as specified in this memo. 291 This document changes Section 4 of [RFC3956] as follows: 293 OLD: 295 It MUST be a multicast address with "flgs" set to 0111, that is, 296 to be of the prefix FF70::/12, 298 NEW: 300 It MUST be a multicast address with R-bit set to 1. 302 It MUST have P-bit and T-bit both set to 1 when using the 303 embedding in this document as it is a prefix-based address. 305 This document changes Section 7.1 of [RFC3956] as follows: 307 OLD: 309 To avoid loops and inconsistencies, for addresses in the range 310 FF70::/12, the Embedded-RP mapping MUST be considered the longest 311 possible match and higher priority than any other mechanism. 313 NEW: 315 To avoid loops and inconsistencies, for addresses with R-bit set 316 to 1, the Embedded-RP mapping MUST be considered the longest 317 possible match and higher priority than any other mechanism. 319 5. IANA Considerations 321 This document does not require any action from IANA. 323 6. Security Considerations 325 Security considerations discussed in [RFC3956], [RFC3306] and 326 [RFC4291] MUST be taken into account. 328 7. Acknowledgements 330 Special thanks to Brian Haberman for the discussions prior to the 331 publication of this document. 333 Many thanks to Jouni Korhonen and Tatuya Jinmei their review. 335 8. Normative References 337 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 338 Requirement Levels", BCP 14, RFC 2119, March 1997. 340 [RFC3306] Haberman, B. and D. Thaler, "Unicast-Prefix-based IPv6 341 Multicast Addresses", RFC 3306, August 2002. 343 [RFC3956] Savola, P. and B. Haberman, "Embedding the Rendezvous 344 Point (RP) Address in an IPv6 Multicast Address", RFC 345 3956, November 2004. 347 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 348 Architecture", RFC 4291, February 2006. 350 [RFC5952] Kawamura, S. and M. Kawashima, "A Recommendation for IPv6 351 Address Text Representation", RFC 5952, August 2010. 353 Authors' Addresses 355 Mohamed Boucadair 356 France Telecom 357 Rennes 35000 358 France 360 Email: mohamed.boucadair@orange.com 362 Stig Venaas 363 Cisco 364 USA 366 Email: stig@cisco.com