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Venaas 5 Intended status: Standards Track Cisco 6 Expires: September 13, 2014 March 12, 2014 8 Updates to the IPv6 Multicast Addressing Architecture 9 draft-ietf-6man-multicast-addr-arch-update-04 11 Abstract 13 This document updates the IPv6 multicast addressing architecture by 14 defining the 17-20 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 September 13, 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 . . . . . . . . . . . . . . . . . . . . . . . . . 4 64 4.1. RFC 3306 . . . . . . . . . . . . . . . . . . . . . . . . 4 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 multicast addressing architecture 75 [RFC4291] by defining the 17-20 reserved bits as generic flag bits 76 (Section 2). The document provides also some clarifications related 77 to the use of 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 are defined in [RFC3956] and 89 [RFC3306] as reserved bits. This document defines these bits as 90 generic flag bits so that they apply to any multicast address. 91 Figure 1 and Figure 2 show the updated structure of the addressing 92 architecture. The first diagram shows the update of the base IPv6 93 addressing architecture, and the second shows the update of so-called 94 Embedded-RP. 96 OLD: 97 | 8 | 4 | 4 | 112 bits | 98 +--------+----+----+----------------------------------------------+ 99 |11111111|flgs|scop| group ID | 100 +--------+----+----+----------------------------------------------+ 102 NEW: 103 | 8 | 4 | 4 | 4 | 108 bits | 104 +--------+----+----+----------------------------------------------+ 105 |11111111|ff1 |scop|ff2 | group ID | 106 +--------+----+----+----+-----------------------------------------+ 108 * ff1 refers to "flag field 1" 109 * ff2 refers to "flag field 2" 110 * flag bits denote both ff1 and ff2. 112 Figure 1: Updated IPv6 Multicast Addressing Architecture 114 OLD (RFC 3956): 115 | 8 | 4 | 4 | 4 | 4 | 8 | 64 | 32 | 116 +--------+----+----+----+----+--------+----------------+----------+ 117 |11111111|flgs|scop|rsvd|RIID| plen | network prefix | group ID | 118 +--------+----+----+----+----+--------+----------------+----------+ 120 NEW: 121 | 8 | 4 | 4 | 4 | 4 | 8 | 64 | 32 | 122 +--------+----+----+----+----+--------+----------------+----------+ 123 |11111111|ff1 |scop|ff2 |RIID| plen | network prefix | group ID | 124 +--------+----+----+----+----+--------+----------------+----------+ 126 Figure 2: Embedded-RP with Updated IPv6 Multicast Address Arch. 128 Further specification documents may define a meaning for these flag 129 bits. Defining the bits 17-20 as flags for all IPv6 multicast 130 addresses allows addresses to be treated in a more uniform and 131 generic way, and allows for these bits to be defined in the future 132 for different purposes, irrespective of the specific type of 133 multicast address. 135 3. Flag Bits: A Recommendation 137 Some implementations and specification documents do not treat the 138 flag bits as separate bits but tend to use their combined value as a 139 4-bit integer. This practice is a hurdle for assigning a meaning to 140 the remaining flag bits. Below are listed some examples for 141 illustration purposes: 143 o the reading of [RFC3306] may lead to conclude that ff3x::/32 is 144 the only allowed SSM IPv6 prefix block. 146 o [RFC3956] states only ff70::/12 applies to Embedded-RP. 147 Particularly, implementations should not treat the fff0::/12 range 148 as Embedded-RP. 150 To avoid such confusion and to unambiguously associate a meaning with 151 the remaining flags, the following requirement is made 153 Implementations MUST treat flag bits as separate bits. 155 4. RFC Updates 157 4.1. RFC 3306 159 This document changes Section 4 of [RFC3306] as follows: 161 OLD: 163 | 8 | 4 | 4 | 8 | 8 | 64 | 32 | 164 +--------+----+----+--------+--------+----------------+----------+ 165 |11111111|flgs|scop|reserved| plen | network prefix | group ID | 166 +--------+----+----+--------+--------+----------------+----------+ 168 +-+-+-+-+ 169 flgs is a set of 4 flags: |0|0|P|T| 170 +-+-+-+-+ 172 o P = 0 indicates a multicast address that is not assigned 173 based on the network prefix. This indicates a multicast 174 address as defined in [ADDRARCH]. 176 o P = 1 indicates a multicast address that is assigned based 177 on the network prefix. 179 o If P = 1, T MUST be set to 1, otherwise the setting of the T 180 bit is defined in Section 2.7 of [ADDRARCH]. 182 The reserved field MUST be zero. 184 NEW: 186 | 8 | 4 | 4 | 4 | 4 | 8 | 64 | 32 | 187 +--------+----+----+----+----+--------+----------------+----------+ 188 |11111111|ff1 |scop|ff2 |rsvd| plen | network prefix | group ID | 189 +--------+----+----+----+----+--------+----------------+----------+ 191 +-+-+-+-+ 192 ff1 (flag field 1) is a set of 4 flags: |X|Y|P|T| 193 +-+-+-+-+ 195 X and Y may each be set to 0 or 1. 197 o P = 0 indicates a multicast address that is not assigned 198 based on the network prefix. This indicates a multicast 199 address as defined in [RFC4291]. 201 o P = 1 indicates a multicast address that is assigned based 202 on the network prefix. 204 o If P = 1, T MUST be set to 1, otherwise the setting of the T 205 bit is defined in Section 2.7 of [RFC4291]. 207 +-+-+-+-+ 208 ff2 (flag field 2) is a set of 4 flags: |r|r|r|r| 209 +-+-+-+-+ 211 where "rrrr" are for future assignment as additional flag bits. 213 Flag bits denote both ff1 and ff2. 215 This document changes Section 6 of [RFC3306] as follows: 217 OLD: 219 These settings create an SSM range of FF3x::/32 (where 'x' is any 220 valid scope value). The source address field in the IPv6 header 221 identifies the owner of the multicast address. 223 NEW: 225 If the flag bits in ff1 are set to 0011, these settings create an 226 SSM range of ff3x::/32 (where 'x' is any valid scope value). The 227 source address field in the IPv6 header identifies the owner of 228 the multicast address. ff3x::/32 is not the only allowed SSM 229 prefix range. For example if the most significant flag bit in ff1 230 is set, then we would get the SSM range ffbx::/32. 232 4.2. RFC 3956 234 This document changes Section 2 of [RFC3956] as follows: 236 OLD: 238 As described in [RFC3306], the multicast address format is as 239 follows: 241 | 8 | 4 | 4 | 8 | 8 | 64 | 32 | 242 +--------+----+----+--------+----+----------------+----------+ 243 |11111111|flgs|scop|reserved|plen| network prefix | group ID | 244 +--------+----+----+--------+----+----------------+----------+ 246 Where flgs are "0011". (The first two bits are as yet undefined, 247 sent as zero and ignored on receipt.) 249 NEW: 251 The multicast address format is as 252 follows: 254 | 8 | 4 | 4 | 4 | 4 | 8 | 64 | 32 | 255 +--------+----+----+----+----+----+----------------+----------+ 256 |11111111|ff1 |scop|ff2 |rsvd|plen| network prefix | group ID | 257 +--------+----+----+----+----+----+----------------+----------+ 259 +-+-+-+-+ 260 ff1 (flag field 1) is a set of four flags: |X|R|P|T| 261 +-+-+-+-+ 262 X may be set to 0 or 1. 264 +-+-+-+-+ 265 ff2 (flag field 2) is a set of 4 flags: |r|r|r|r| 266 +-+-+-+-+ 267 where "rrrr" are for future assignment as additional flag bits. 269 Flag bits denote both ff1 and ff2. 271 This document changes Section 3 of [RFC3956] as follows: 273 OLD: 275 | 8 | 4 | 4 | 4 | 4 | 8 | 64 | 32 | 276 +--------+----+----+----+----+----+----------------+----------+ 277 |11111111|flgs|scop|rsvd|RIID|plen| network prefix | group ID | 278 +--------+----+----+----+----+----+----------------+----------+ 279 +-+-+-+-+ 280 flgs is a set of four flags: |0|R|P|T| 281 +-+-+-+-+ 283 When the highest-order bit is 0, R = 1 indicates a multicast address 284 that embeds the address on the RP. Then P MUST be set to 1, and 285 consequently T MUST be set to 1, as specified in [RFC3306]. In 286 effect, this implies the prefix FF70::/12. In this case, the last 4 287 bits of the previously reserved field are interpreted as embedding 288 the RP interface ID, as specified in this memo. 290 The behavior is unspecified if P or T is not set to 1, as then the 291 prefix would not be FF70::/12. Likewise, the encoding and the 292 protocol mode used when the two high-order bits in "flgs" are set to 293 11 ("FFF0::/12") is intentionally unspecified until such time that 294 the highest-order bit is defined. Without further IETF 295 specification, implementations SHOULD NOT treat the FFF0::/12 range 296 as Embedded-RP. 298 NEW: 300 | 8 | 4 | 4 | 4 | 4 | 8 | 64 | 32 | 301 +--------+----+----+----+----+----+----------------+----------+ 302 |11111111|ff1 |scop|ff2 |RIID|plen| network prefix | group ID | 303 +--------+----+----+----+----+----+----------------+----------+ 304 +-+-+-+-+ 305 ff1 is a set of four flags: |X|R|P|T| 306 +-+-+-+-+ 307 X may be set to 0 or 1. 309 R = 1 indicates a multicast address that embeds the address of the 310 RP. P MUST be set to 1, and consequently T MUST be set to 1, 311 according to [RFC3306], as this is a special case of unicast-prefix 312 based addresses. This implies that for instance prefixes ff70::/12 313 and fff0::/12 are embedded RP prefixes. The behavior is unspecified 314 if P or T is not set to 1. When the R-bit is set, the last 4 bits of 315 the field that were reserved in [RFC3306] are interpreted as 316 embedding the RP interface ID, as specified in this memo. 318 This document changes Section 4 of [RFC3956] as follows: 320 OLD: 322 It MUST be a multicast address with "flgs" set to 0111, that is, 323 to be of the prefix FF70::/12, 325 NEW: 327 It MUST be a multicast address with R-bit set to 1. 329 It MUST have P-bit and T-bit both set to 1 when using the 330 embedding in this document as it is a prefix-based address. 332 This document changes Section 7.1 of [RFC3956] as follows: 334 OLD: 336 To avoid loops and inconsistencies, for addresses in the range 337 FF70::/12, the Embedded-RP mapping MUST be considered the longest 338 possible match and higher priority than any other mechanism. 340 NEW: 342 To avoid loops and inconsistencies, for addresses with R-bit set 343 to 1, the Embedded-RP mapping MUST be considered the longest 344 possible match and higher priority than any other mechanism. 346 5. IANA Considerations 348 This document does not require any action from IANA. 350 6. Security Considerations 352 Security considerations discussed in [RFC3956], [RFC3306] and 353 [RFC4291] MUST be taken into account. 355 7. Acknowledgements 357 Special thanks to B. Haberman for the discussions prior to the 358 publication of this document. 360 Many thanks to J. Korhonen and T. Jinmei their comments. 362 8. Normative References 364 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 365 Requirement Levels", BCP 14, RFC 2119, March 1997. 367 [RFC3306] Haberman, B. and D. Thaler, "Unicast-Prefix-based IPv6 368 Multicast Addresses", RFC 3306, August 2002. 370 [RFC3956] Savola, P. and B. Haberman, "Embedding the Rendezvous 371 Point (RP) Address in an IPv6 Multicast Address", RFC 372 3956, November 2004. 374 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 375 Architecture", RFC 4291, February 2006. 377 [RFC5952] Kawamura, S. and M. Kawashima, "A Recommendation for IPv6 378 Address Text Representation", RFC 5952, August 2010. 380 Authors' Addresses 382 Mohamed Boucadair 383 France Telecom 384 Rennes 35000 385 France 387 Email: mohamed.boucadair@orange.com 389 Stig Venaas 390 Cisco 391 USA 393 Email: stig@cisco.com