idnits 2.17.1 draft-ietf-6man-ra-pref64-04.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- == There are 1 instance of lines with private range IPv4 addresses in the document. If these are generic example addresses, they should be changed to use any of the ranges defined in RFC 6890 (or successor): 192.0.2.x, 198.51.100.x or 203.0.113.x. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year == Line 225 has weird spacing: '...96 bits prefi...' == Line 230 has weird spacing: '...bits of prefi...' == Line 235 has weird spacing: '... Length the ...' -- The document date (August 11, 2019) is 1718 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) -- Looks like a reference, but probably isn't: '1' on line 441 == Unused Reference: 'I-D.ietf-intarea-provisioning-domains' is defined on line 383, but no explicit reference was found in the text == Unused Reference: 'RFC4033' is defined on line 389, but no explicit reference was found in the text == Outdated reference: A later version (-11) exists of draft-ietf-intarea-provisioning-domains-05 Summary: 0 errors (**), 0 flaws (~~), 8 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 IPv6 Maintenance L. Colitti 3 Internet-Draft J. Linkova 4 Intended status: Standards Track Google 5 Expires: February 12, 2020 August 11, 2019 7 Discovering PREF64 in Router Advertisements 8 draft-ietf-6man-ra-pref64-04 10 Abstract 12 This document specifies a Router Advertisement option to communicate 13 NAT64 prefixes to clients. 15 Status of This Memo 17 This Internet-Draft is submitted in full conformance with the 18 provisions of BCP 78 and BCP 79. 20 Internet-Drafts are working documents of the Internet Engineering 21 Task Force (IETF). Note that other groups may also distribute 22 working documents as Internet-Drafts. The list of current Internet- 23 Drafts is at https://datatracker.ietf.org/drafts/current/. 25 Internet-Drafts are draft documents valid for a maximum of six months 26 and may be updated, replaced, or obsoleted by other documents at any 27 time. It is inappropriate to use Internet-Drafts as reference 28 material or to cite them other than as "work in progress." 30 This Internet-Draft will expire on February 12, 2020. 32 Copyright Notice 34 Copyright (c) 2019 IETF Trust and the persons identified as the 35 document authors. All rights reserved. 37 This document is subject to BCP 78 and the IETF Trust's Legal 38 Provisions Relating to IETF Documents 39 (https://trustee.ietf.org/license-info) in effect on the date of 40 publication of this document. Please review these documents 41 carefully, as they describe your rights and restrictions with respect 42 to this document. Code Components extracted from this document must 43 include Simplified BSD License text as described in Section 4.e of 44 the Trust Legal Provisions and are provided without warranty as 45 described in the Simplified BSD License. 47 Table of Contents 49 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 50 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2 51 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 2 52 2. Use cases for communicating the NAT64 prefix to hosts . . . . 3 53 3. Why include the NAT64 prefix in Router Advertisements . . . . 3 54 4. Semantics . . . . . . . . . . . . . . . . . . . . . . . . . . 4 55 5. Option format . . . . . . . . . . . . . . . . . . . . . . . . 4 56 6. Handling Multiple NAT64 Prefixes . . . . . . . . . . . . . . 6 57 7. Multihoming . . . . . . . . . . . . . . . . . . . . . . . . . 7 58 8. Pref64 Consistency . . . . . . . . . . . . . . . . . . . . . 8 59 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 60 10. Security Considerations . . . . . . . . . . . . . . . . . . . 8 61 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 62 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 63 12.1. Normative References . . . . . . . . . . . . . . . . . . 9 64 12.2. Informative References . . . . . . . . . . . . . . . . . 9 65 12.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 11 66 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 68 1. Introduction 70 NAT64 [RFC6146] with DNS64 [RFC6147] is a widely-deployed mechanism 71 to provide IPv4 access on IPv6-only networks. In various scenarios, 72 the host must be aware of the NAT64 prefix in use by the network. 73 This document specifies a Router Advertisement [RFC4861] option to 74 communicate the NAT64 prefix to hosts. 76 1.1. Requirements Language 78 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 79 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 80 document are to be interpreted as described in RFC 2119 [RFC2119]. 82 1.2. Terminology 84 Pref64 (or NAT64 prefix): an IPv6 prefix used for IPv6 address 85 synthesis [RFC6146]; 87 NAT64: Network Address and Protocol Translation from IPv6 Clients to 88 IPv4 Servers ([RFC6146]); 90 RA: Router Advertisement, a message used by IPv6 routers to advertise 91 their presence together with various link and Internet parameters 92 ([RFC4861]); 93 DNS64: a mechanism for synthesizing AAAA records from A records 94 ([RFC6147]); 96 2. Use cases for communicating the NAT64 prefix to hosts 98 On networks employing NAT64, it is useful for hosts to know the NAT64 99 prefix for several reasons, including the following: 101 o Local DNSSEC validation. As discussed in [RFC6147] section 2, the 102 stub resolver in the host "will try to obtain (real) AAAA RRs, and 103 in case they are not available, the DNS64 function will synthesize 104 AAAA RRs for internal usage." This is required in order to use 105 DNSSEC on a NAT64 network. 107 o IPv4 address literals on an IPv6-only host. As described in 108 [RFC8305] section 7.1, IPv6-only hosts connecting to IPv4 address 109 literals can resolve the IPv4 literal to an IPv6 address. 111 o 464XLAT [RFC6877]. 464XLAT is widely deployed and requires that 112 the host be aware of the NAT64 prefix. 114 o Trusted DNS server. AAAA synthesis is required for the host to be 115 able to use a DNS server not provided by the network (e.g., a DNS- 116 over-TLS server ([RFC7858]) with which the host has an existing 117 trust relationship). 119 o Networks with no DNS64 server. Hosts that support AAAA synthesis 120 and that are aware of the NAT64 prefix in use do not need the 121 network to perform the DNS64 function at all. 123 3. Why include the NAT64 prefix in Router Advertisements 125 Fate sharing: NAT64 requires a routing to be configured. IPv6 126 routing configuration requires receiving an IPv6 Router Advertisement 127 [RFC4861]. Compared to currently-deployed NAT64 prefix discovery 128 methods such as [RFC7050], including the NAT64 prefix in the Router 129 Advertisement minimizes the number of packets required to configure a 130 host. This speeds up the process of connecting to a network that 131 supports NAT64/DNS64, and simplifies host implementation by removing 132 the possibility that the host can have an incomplete layer 3 133 configuration (e.g., IPv6 addresses and prefixes, but no NAT64 134 prefix). 136 Updatability: it is possible to change the NAT64 prefix at any time, 137 because when it changes, it is possible to notify hosts by sending a 138 new Router Advertisement. 140 Deployability: all IPv6 hosts and networks are required to support 141 [RFC4861]. Other options such as [RFC7225] require implementing 142 other protocols. 144 4. Semantics 146 To support prefix lengths defined in ([RFC6052]) this option contains 147 the prefix length field. However as /96 prefix is considered to be 148 the most common use case, the prefix length field is optional and 149 only presents for non-/96 prefixes. It allows to keep the option 150 length to a minimum (16 bytes) for the most common case and increase 151 it to 20 bytes for non-/96 prefixes only (see Section 5 below for 152 more details). 154 This option specifies exactly one NAT64 prefix for all IPv4 155 destinations. If the network operator desires to route different 156 parts of the IPv4 address space to different NAT64 devices, this can 157 be accomplished by routing more specifics of the NAT64 prefix to 158 those devices. For example, if the operator would like to route 159 10.0.0.0/8 through NAT64 device A and the rest of the IPv4 space 160 through NAT64 device B, and the operator's NAT64 prefix is 161 2001:db8:a:b::/96, then the operator can route 162 2001:db8:a:b::a00:0/104 to NAT64 A and 2001:db8:a:b::/64 to NAT64 B. 164 This option may appear more than once in a Router Advertisement (e.g. 165 in case of graceful renumbering the network from one NAT64 prefix to 166 another). Host behaviour with regards to synthesizing IPv6 addresses 167 from IPv4 addresses SHOULD follow the recommendations given in 168 Section 3 of [RFC7050], limited to the NAT64 prefixes that have non- 169 zero lifetime. 171 In a network (or a provisioning domain) that provides both IPv4 and 172 NAT64, it may be desirable for certain IPv4 addresses not to be 173 translated. An example might be private address ranges that are 174 local to the network/provisioning domain and should not be reached 175 through the NAT64. This type of configuration cannot be conveyed to 176 hosts using this option, or through other NAT64 prefix provisioning 177 mechanisms such as [RFC7050] or [RFC7225]. This problem does not 178 apply in IPv6-only networks, because in such networks, the host does 179 not have an IPv4 address and cannot reach any IPv4 destinations 180 without the NAT64. The multihoming and multiple provisioning domains 181 scenarios are discussed in Section 7. 183 5. Option format 184 0 1 2 3 185 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 1 186 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 187 | Type | Length | Lifetime | 188 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 189 | | 190 + + 191 | Highest 96 bits of the Prefix | 192 + + 193 | | 194 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 195 | Lowest bits (96-127) of the prefix (optional, if Length > 2) | 196 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 197 | Prefix Length | Reserved | 198 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 200 Figure 1: NAT64 Prefix Option Format 202 Fields: 204 Type 8-bit identifier of the Pref64 option type as assigned by 205 IANA: TBD 206 Length 8-bit unsigned integer. The length of the option (including 207 the Type and Length fields) is in units of 8 octets. If the 208 prefix length is 96 bits the sender MUST set the Length to 2 209 and include the 96 bits of the prefix in the option. If the 210 prefix length is not 96 bits then the sender MUST set the 211 length to 3 and include all 128 bits of the prefix in the 212 Prefix field and set the Prefix Length field to the prefix 213 length. The receiver MUST ignore the Pref64 option if the 214 length field value is 1. If the Length field value exceeds 215 3, the receiver MUST utilize the first 21 octets and ignore 216 the rest of the option. 218 Lifetime 16-bit unsigned integer. The maximum time in seconds over 219 which this NAT64 prefix MAY be used. The value of Lifetime 220 SHOULD by default be set to lesser of 3 x MaxRtrAdvInterval 221 or 65535 seconds. A value of zero means that the prefix 222 MUST no longer be used. 224 Highest 96-bit unsigned integer. Contains bits 0 - 95 of the NAT64 225 96 bits prefix. 226 of the 227 prefix 229 Lowest 32-bit unsigned integer. Contains bits 96 - 127 of the NAT64 230 bits of prefix. This field is optional and presents only if the 231 the prefix length is not 96 bits. 232 prefix 234 Prefix 8-bit unsigned integer. Optional field which present only if 235 Length the prefix length is not 96 bits. The sender MUST set it 236 only to one of the following values: 32, 40, 48, 56, 64 237 ([RFC6052]. The receiver MUST ignore the Pref64 option if 238 the prefix length value is not set to one of those numbers. 240 Reserved A 3-byte unused field. If present it MUST be initialized to 241 zero by the sender and MUST be ignored by the receiver. This 242 field is optional and presents only if the prefix length is 243 not 96 bits. 245 6. Handling Multiple NAT64 Prefixes 247 In some cases a host may receive multiple NAT64 prefixes from 248 different sources. Possible scenarios include (but are not limited 249 to): 251 o the host is using multiple mechanisms to discover Pref64 prefixes 252 (e.g. by using PCP ([RFC7225]) and/or by resolving IPv4-only fully 253 qualified domain name ([RFC7050]) in addition to receiving the 254 Pref64 RA option); 256 o The pref64 option presents in a single RA more than once; 258 o the host receives multiple RAs with different Pref64 prefixes on 259 one or multiple interfaces. 261 When multiple Pref64 were discovered via RA Pref64 Option (the Option 262 presents more than once in a single RA or multiple RAs were 263 received), host behaviour with regards to synthesizing IPv6 addresses 264 from IPv4 addresses SHOULD follow the recommendations given in 265 Section 3 of [RFC7050], limited to the NAT64 prefixes that have non- 266 zero lifetime.. 268 When different Pref64 are discovered by using multiple mechanisms, 269 hosts SHOULD select one source of information only. The RECOMMENDED 270 order is: 272 o PCP-discovered prefixes ([RFC7225]), if supported; 274 o Pref64 discovered via RA Option; 276 o Pref64 resolving IPv4-only fully qualified domain name ([RFC7050]) 278 Note that if the network provides Pref64 both via this RA option and 279 [RFC7225], hosts that receive the Pref64 via RA option may choose to 280 use it immediately before waiting for PCP to complete, and therefore 281 some traffic may not reflect any more detailed configuration provided 282 by PCP. 284 7. Multihoming 286 Like most IPv6 configuration information, the Pref64 option is 287 specific to the network on which it is received. For example, a 288 Pref64 option received on a particular wireless network may not be 289 usable unless the traffic is also sourced on that network. 290 Similarly, a host connected to a cellular network that provides NAT64 291 generally cannot use that NAT64 for destinations reached through a 292 VPN tunnel that terminates outside that network. 294 Thus, correct use of this option on a multihomed host generally 295 requires the host to support the concept of multiple Provisioning 296 Domains (PvD, a set of configuration information associated with a 297 network, [RFC7556]) and to be able to use these PvDs. 299 This issue is not specific to the Pref64 RA option and, for example, 300 is quite typical for DNS resolving on multihomed hosts (e.g. a host 301 might resolve a destination name by using the corporate DNS server 302 via the VPN tunnel but then send the traffic via its Internet-facing 303 interface). 305 8. Pref64 Consistency 307 Section 6.2.7 of [RFC4861] recommends that routers inspect RAs sent 308 by other routers to ensure that all routers onlink advertise the 309 consistent information. Routers SHOULD inspect valid Pref64 options 310 received on a given link and verify the consistency. Detected 311 inconsistencies indicate that one or more routers might be 312 misconfigured. Routers SHOULD log such cases to system or network 313 management. Routers SHOULD check and compare the following 314 information: 316 o set of Pref64 with non-zero lifetime; 318 o set of Pref64 with zero lifetime. 320 PvD-aware routers MUST only compare information scoped to the same 321 implicit or explicit PvD. 323 9. IANA Considerations 325 The IANA is requested to assign a new IPv6 Neighbor Discovery Option 326 type for the PREF64 option defined in this document. 328 +---------------+-------+ 329 | Option Name | Type | 330 +---------------+-------+ 331 | PREF64 option | (TBD) | 332 +---------------+-------+ 334 Table 1 336 The IANA registry for these options is: 338 https://www.iana.org/assignments/icmpv6-parameters [1] 340 10. Security Considerations 342 Because Router Advertisements are required in all IPv6 configuration 343 scenarios, on IPv6-only networks, Router Advertisements must already 344 be secured, e.g., by deploying RA guard [RFC6105]. Providing all 345 configuration in Router Advertisements increases security by ensuring 346 that no other protocols can be abused by malicious attackers to 347 provide hosts with invalid configuration. 349 The security measures that must already be in place to ensure that 350 Router Advertisements are only received from legitimate sources 351 eliminate the problem of NAT64 prefix validation described in section 352 3.1 of [RFC7050]. 354 11. Acknowledgements 356 Thanks to the following people (in alphabetical order) for their 357 review and feedback: Mikael Abrahamsson, Mark Andrews, Brian E 358 Carpenter, David Farmer, Nick Heatley, Martin Hunek, Tatuya Jinmei, 359 Erik Kline, David Lamparter, Jordi Palet Martinez, Tommy Pauly, 360 Michael Richardson, David Schinazi. 362 12. References 364 12.1. Normative References 366 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 367 Requirement Levels", BCP 14, RFC 2119, 368 DOI 10.17487/RFC2119, March 1997, 369 . 371 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 372 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 373 DOI 10.17487/RFC4861, September 2007, 374 . 376 [RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X. 377 Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052, 378 DOI 10.17487/RFC6052, October 2010, 379 . 381 12.2. Informative References 383 [I-D.ietf-intarea-provisioning-domains] 384 Pfister, P., Vyncke, E., Pauly, T., Schinazi, D., and W. 385 Shao, "Discovering Provisioning Domain Names and Data", 386 draft-ietf-intarea-provisioning-domains-05 (work in 387 progress), June 2019. 389 [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. 390 Rose, "DNS Security Introduction and Requirements", 391 RFC 4033, DOI 10.17487/RFC4033, March 2005, 392 . 394 [RFC6105] Levy-Abegnoli, E., Van de Velde, G., Popoviciu, C., and J. 395 Mohacsi, "IPv6 Router Advertisement Guard", RFC 6105, 396 DOI 10.17487/RFC6105, February 2011, 397 . 399 [RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful 400 NAT64: Network Address and Protocol Translation from IPv6 401 Clients to IPv4 Servers", RFC 6146, DOI 10.17487/RFC6146, 402 April 2011, . 404 [RFC6147] Bagnulo, M., Sullivan, A., Matthews, P., and I. van 405 Beijnum, "DNS64: DNS Extensions for Network Address 406 Translation from IPv6 Clients to IPv4 Servers", RFC 6147, 407 DOI 10.17487/RFC6147, April 2011, 408 . 410 [RFC6877] Mawatari, M., Kawashima, M., and C. Byrne, "464XLAT: 411 Combination of Stateful and Stateless Translation", 412 RFC 6877, DOI 10.17487/RFC6877, April 2013, 413 . 415 [RFC7050] Savolainen, T., Korhonen, J., and D. Wing, "Discovery of 416 the IPv6 Prefix Used for IPv6 Address Synthesis", 417 RFC 7050, DOI 10.17487/RFC7050, November 2013, 418 . 420 [RFC7225] Boucadair, M., "Discovering NAT64 IPv6 Prefixes Using the 421 Port Control Protocol (PCP)", RFC 7225, 422 DOI 10.17487/RFC7225, May 2014, 423 . 425 [RFC7556] Anipko, D., Ed., "Multiple Provisioning Domain 426 Architecture", RFC 7556, DOI 10.17487/RFC7556, June 2015, 427 . 429 [RFC7858] Hu, Z., Zhu, L., Heidemann, J., Mankin, A., Wessels, D., 430 and P. Hoffman, "Specification for DNS over Transport 431 Layer Security (TLS)", RFC 7858, DOI 10.17487/RFC7858, May 432 2016, . 434 [RFC8305] Schinazi, D. and T. Pauly, "Happy Eyeballs Version 2: 435 Better Connectivity Using Concurrency", RFC 8305, 436 DOI 10.17487/RFC8305, December 2017, 437 . 439 12.3. URIs 441 [1] https://www.iana.org/assignments/icmpv6-parameters 443 Authors' Addresses 445 Lorenzo Colitti 446 Google 447 Roppongi 6-10-1 448 Minato, Tokyo 106-6126 449 JP 451 Email: lorenzo@google.com 453 Jen Linkova 454 Google 455 1 Darling Island Rd 456 Pyrmont, NSW 2009 457 AU 459 Email: furry@google.com