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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 IPv6 Maintenance L. Colitti 3 Internet-Draft E. Kline 4 Intended status: Standards Track J. Linkova 5 Expires: April 4, 2019 Google 6 October 1, 2018 8 Discovering PREF64 in Router Advertisements 9 draft-pref64folks-6man-ra-pref64-02 11 Abstract 13 This document specifies a Router Advertisement option to communicate 14 NAT64 prefixes to clients. 16 Status of This Memo 18 This Internet-Draft is submitted in full conformance with the 19 provisions of BCP 78 and BCP 79. 21 Internet-Drafts are working documents of the Internet Engineering 22 Task Force (IETF). Note that other groups may also distribute 23 working documents as Internet-Drafts. The list of current Internet- 24 Drafts is at https://datatracker.ietf.org/drafts/current/. 26 Internet-Drafts are draft documents valid for a maximum of six months 27 and may be updated, replaced, or obsoleted by other documents at any 28 time. It is inappropriate to use Internet-Drafts as reference 29 material or to cite them other than as "work in progress." 31 This Internet-Draft will expire on April 4, 2019. 33 Copyright Notice 35 Copyright (c) 2018 IETF Trust and the persons identified as the 36 document authors. All rights reserved. 38 This document is subject to BCP 78 and the IETF Trust's Legal 39 Provisions Relating to IETF Documents 40 (https://trustee.ietf.org/license-info) in effect on the date of 41 publication of this document. Please review these documents 42 carefully, as they describe your rights and restrictions with respect 43 to this document. Code Components extracted from this document must 44 include Simplified BSD License text as described in Section 4.e of 45 the Trust Legal Provisions and are provided without warranty as 46 described in the Simplified BSD License. 48 Table of Contents 50 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 51 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2 52 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 2 53 2. Why include the NAT64 prefix in Router Advertisements . . . . 3 54 3. Semantics . . . . . . . . . . . . . . . . . . . . . . . . . . 3 55 4. Option format . . . . . . . . . . . . . . . . . . . . . . . . 4 56 5. Handling Multiple NAT64 Prefixes . . . . . . . . . . . . . . 4 57 6. Multihoming . . . . . . . . . . . . . . . . . . . . . . . . . 5 58 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 59 8. Security Considerations . . . . . . . . . . . . . . . . . . . 6 60 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 61 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 62 10.1. Normative References . . . . . . . . . . . . . . . . . . 6 63 10.2. Informative References . . . . . . . . . . . . . . . . . 7 64 10.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 8 65 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 67 1. Introduction 69 NAT64 [RFC6146] with DNS64 [RFC6147] is a widely-deployed mechanism 70 to provide IPv4 access on IPv6-only networks. In order to support 71 functions such as local validation of DNSSEC [RFC4033] responses, 72 464xlat [RFC6877], and local IPv4 address synthesis [RFC8305], the 73 host must be aware of the NAT64 prefix in use by the network. This 74 document specifies a Router Advertisement [RFC4861] option to 75 communicate the NAT64 prefix to hosts. 77 1.1. Requirements Language 79 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 80 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 81 document are to be interpreted as described in RFC 2119 [RFC2119]. 83 1.2. Terminology 85 Pref64: an IPv6 prefix used for IPv6 address synthesis [RFC6146]; 87 RA Router Advertisement, a message used by IPv6 routers to advertise 88 their presence together with various link and Internet parameters 89 ([RFC4861]); 91 PvD-aware host A host that supports the association of network 92 configuration information into PvDs and the use of these PvDs. Also 93 named PvD-aware node in [RFC7556]. 95 2. Why include the NAT64 prefix in Router Advertisements 97 Fate sharing: NAT64 requires a routing to be configured. IPv6 98 routing configuration requires receiving an IPv6 Router Advertisement 99 [RFC4861]. Compared to currently-deployed NAT64 prefix discovery 100 methods such as [RFC7050], including the NAT64 prefix in the Router 101 Advertisement minimizes the number of packets required to configure a 102 host. This speeds up the process of connecting to a network that 103 supports NAT64/DNS64, and simplifies host implementation by removing 104 the possibility that the host can have an incomplete layer 3 105 configuration (e.g., IPv6 addresses and prefixes, but no NAT64 106 prefix). 108 Deployability: all IPv6 hosts and networks are required to support 109 [RFC4861]. Other options such as [RFC7225] require implementing 110 other protocols. 112 3. Semantics 114 For simplicity, this option only supports a NAT64 prefix length of 96 115 bits, as this is by the most common configuration used by hosts. 116 Networks using one of the other prefix lengths supported in 117 ([RFC6052]) can use other mechanisms such as [RFC7050] or [RFC7225]. 118 If different prefix lengths become common, another RA option can be 119 created to configure them. 121 This option may appear more than once in a Router Advertisement. 122 Host behaviour with regards to synthesizing IPv6 addresses from IPv4 123 addresses SHOULD follow the recommendations given in Section 3 of 124 [RFC7050], limited to the NAT64 prefixes that have non-zero lifetime. 126 This option specifies exactly one NAT64 prefix for all IPv4 127 destinations. If the network operator desires to route different 128 parts of the IPv4 address space to different NAT64 devices, this can 129 be accomplished by routing more specifics of the NAT64 prefix to 130 those devices. For example, if the operator would like to route 131 10.0.0.0/8 through NAT64 device A and the rest of the IPv4 space 132 through NAT64 device B, and the operator's NAT64 prefix is 133 2001:db8:a:b::/96, then the operator can route 134 2001:db8:a:b::a00:0/104 to NAT64 A and 2001:db8:a:b::/64 to NAT64 B. 136 In a network that provides both IPv4 and NAT64, it may be desirable 137 for certain IPv4 addresses not to be translated. An example might be 138 private address ranges that are local to the network and should not 139 be reached through the NAT64. This type of configuration cannot be 140 conveyed to hosts using this option, or through other NAT64 prefix 141 provisioning mechanisms such as [RFC7050] or [RFC7225]. This problem 142 does not apply in IPv6-only networks, because in such networks, the 143 host does not have an IPv4 address and cannot reach any IPv4 144 destinations without the NAT64. 146 4. Option format 148 0 1 2 3 149 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 1 150 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 151 | Type | Length | Lifetime | 152 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 153 | | 154 + Prefix + 155 | | 156 + + 157 | | 158 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 160 Figure 1: NAT64 Prefix Option Format 162 Fields: 164 Type 8-bit identifier of the RDNSS option type as assigned by 165 IANA: TBD 166 Length 8-bit unsigned integer. The length of the option (including 167 the Type and Length fields) is in units of 8 octets. The 168 sender MUST set the Length to 2. A host MUST ignore the 169 NAT64 prefix option if the length field value is 1. If the 170 Length field value exceeds 2, the host MUST utilize the 171 first 16 octets and ignore the rest of the option. 172 Lifetime 16-bit unsigned integer. The maximum time in seconds over 173 which this NAT64 prefix MAY be used. The value of Lifetime 174 SHOULD by default be set to lesser of 3 x MaxRtrAdvInterval 175 or 65535 seconds. A value of zero means that the prefix 176 MUST no longer be used. 177 Prefix The 96-bit NAT64 prefix. 179 5. Handling Multiple NAT64 Prefixes 181 In some cases a host may receive multiple NAT64 prefixes from 182 different sources. Possible scenarios include (but are not limited 183 to): 185 o the host is using multiple mechanisms to discover Pref64 prefixes 186 (e.g. by using PCP ([RFC7225]) and/or by resolving IPv4-only fully 187 qualified domain name ([RFC7050]) in addition to receiving the 188 Pref64 RA option); 190 o The pref64 option presents in a single RA more than once; 192 o the host receives multiple RAs with different Pref64 prefixes on 193 one or multiple interfaces. 195 When multiple Pref64 were discovered via RA Pref64 Option (the Option 196 presents more than once in a singe RA or multiple RAs were received), 197 host behaviour with regards to synthesizing IPv6 addresses from IPv4 198 addresses SHOULD follow the recommendations given in Section 3 of 199 [RFC7050], limited to the NAT64 prefixes that have non-zero 200 lifetime.. 202 When different Pref64 are discovered by using multiple mechanisms, 203 hosts SHOULD select one source of infromation only. The RECOMMENDED 204 order is: 206 o PCP-discovered prefixes ([RFC7225]), if supported; 208 o Pref64 discovered via RA Option; 210 o Pref64 resolving IPv4-only fully qualified domain name ([RFC7050]) 212 Note that if the network provides Pref64 both via this RA option and 213 [RFC7225], hosts that receive the Pref64 via RA option may choose to 214 use it imediately before waiting for PCP to complete, and therefore 215 some traffic may not reflect any more detailed configuration provided 216 by PCP. 218 6. Multihoming 220 Like most IPv6 configuration information, the Pref64 option is 221 specific to the network on which it is received. For example, a 222 Pref64 option received on a particular wireless network may not be 223 usable unless the traffic is also sourced on that network. 224 Similarly, a host connected to a cellular network that povides NAT64 225 generally cannot use that NAT64 for destinations reached through a 226 VPN tunnel that terminates outside that network. 228 Thus, correct use of this option on a multihomed host generally 229 requires the host to be PVD-aware. 231 This issue is not specific to the Pref64 RA option and, for example, 232 is quite typical for DNS resolving on multihomed hosts (e.g. a host 233 might resolve a destination name by using the corporate DNS server 234 via the VPN tunnel but then send the traffic via its Internet-facing 235 interface). 237 7. IANA Considerations 239 The IANA is requested to assign a new IPv6 Neighbor Discovery Option 240 type for the PREF64 option defined in this document. 242 +---------------+-------+ 243 | Option Name | Type | 244 +---------------+-------+ 245 | PREF64 option | (TBD) | 246 +---------------+-------+ 248 Table 1 250 The IANA registry for these options is: 252 https://www.iana.org/assignments/icmpv6-parameters [1] 254 8. Security Considerations 256 Because Router Advertisements are required in all IPv6 configuration 257 scenarios, on IPv6-only networks, Router Advertisements must already 258 be secured, e.g., by deploying RA guard [RFC6105]. Providing all 259 configuration in Router Advertisements increases security by ensuring 260 that no other protocols can be abused by malicious attackers to 261 provide hosts with invalid configuration. 263 The security measures that must already be in place to ensure that 264 Router Advertisements are only received from legitimate sources 265 eliminate the problem of NAT64 prefix validation described in section 266 3.1 of [RFC7050]. 268 9. Acknowledgements 270 Thanks to the following people (in alphabetical order) for their 271 review and feedback: Brian E Carpenter, Nick Heatley, David Schinazi. 273 10. References 275 10.1. Normative References 277 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 278 Requirement Levels", BCP 14, RFC 2119, 279 DOI 10.17487/RFC2119, March 1997, 280 . 282 [RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X. 283 Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052, 284 DOI 10.17487/RFC6052, October 2010, 285 . 287 10.2. Informative References 289 [I-D.ietf-intarea-provisioning-domains] 290 Pfister, P., Vyncke, E., Pauly, T., Schinazi, D., and W. 291 Shao, "Discovering Provisioning Domain Names and Data", 292 draft-ietf-intarea-provisioning-domains-02 (work in 293 progress), June 2018. 295 [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. 296 Rose, "DNS Security Introduction and Requirements", 297 RFC 4033, DOI 10.17487/RFC4033, March 2005, 298 . 300 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 301 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 302 DOI 10.17487/RFC4861, September 2007, 303 . 305 [RFC6105] Levy-Abegnoli, E., Van de Velde, G., Popoviciu, C., and J. 306 Mohacsi, "IPv6 Router Advertisement Guard", RFC 6105, 307 DOI 10.17487/RFC6105, February 2011, 308 . 310 [RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful 311 NAT64: Network Address and Protocol Translation from IPv6 312 Clients to IPv4 Servers", RFC 6146, DOI 10.17487/RFC6146, 313 April 2011, . 315 [RFC6147] Bagnulo, M., Sullivan, A., Matthews, P., and I. van 316 Beijnum, "DNS64: DNS Extensions for Network Address 317 Translation from IPv6 Clients to IPv4 Servers", RFC 6147, 318 DOI 10.17487/RFC6147, April 2011, 319 . 321 [RFC6877] Mawatari, M., Kawashima, M., and C. Byrne, "464XLAT: 322 Combination of Stateful and Stateless Translation", 323 RFC 6877, DOI 10.17487/RFC6877, April 2013, 324 . 326 [RFC7050] Savolainen, T., Korhonen, J., and D. Wing, "Discovery of 327 the IPv6 Prefix Used for IPv6 Address Synthesis", 328 RFC 7050, DOI 10.17487/RFC7050, November 2013, 329 . 331 [RFC7225] Boucadair, M., "Discovering NAT64 IPv6 Prefixes Using the 332 Port Control Protocol (PCP)", RFC 7225, 333 DOI 10.17487/RFC7225, May 2014, 334 . 336 [RFC7556] Anipko, D., Ed., "Multiple Provisioning Domain 337 Architecture", RFC 7556, DOI 10.17487/RFC7556, June 2015, 338 . 340 [RFC8305] Schinazi, D. and T. Pauly, "Happy Eyeballs Version 2: 341 Better Connectivity Using Concurrency", RFC 8305, 342 DOI 10.17487/RFC8305, December 2017, 343 . 345 10.3. URIs 347 [1] https://www.iana.org/assignments/icmpv6-parameters 349 Authors' Addresses 351 Lorenzo Colitti 352 Google 353 Roppongi 6-10-1 354 Minato, Tokyo 106-6126 355 JP 357 Email: lorenzo@google.com 359 Erik Kline 360 Google 361 Roppongi 6-10-1 362 Minato, Tokyo 106-6126 363 JP 365 Email: ek@google.com 367 Jen Linkova 368 Google 369 1 Darling Island Rd 370 Pyrmont, NSW 2009 371 AU 373 Email: furry@google.com