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Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (February 15, 2011) is 4812 days in the past. Is this intentional? Checking references for intended status: Informational ---------------------------------------------------------------------------- No issues found here. Summary: 0 errors (**), 0 flaws (~~), 3 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Behave WG T. Savolainen 3 Internet-Draft Nokia 4 Intended status: Informational J. Korhonen 5 Expires: August 19, 2011 Nokia Siemens Networks 6 February 15, 2011 8 Discovery of a Network-Specific NAT64 Prefix using a Well-Known Name 9 draft-savolainen-heuristic-nat64-discovery-01.txt 11 Abstract 13 This document describes a method for detecting presence of DNS64 and 14 for learning IPv6 prefix used for protocol translation on an access 15 network without explicit support from the access network. The method 16 depends on existence of a known IPv4-only domain name. The 17 information learned enables applications and hosts to perform local 18 IPv6 address synthesis and on dual-stack accesses avoid traversal 19 through NAT64. 21 Status of this Memo 23 This Internet-Draft is submitted in full conformance with the 24 provisions of BCP 78 and BCP 79. 26 Internet-Drafts are working documents of the Internet Engineering 27 Task Force (IETF). Note that other groups may also distribute 28 working documents as Internet-Drafts. The list of current Internet- 29 Drafts is at http://datatracker.ietf.org/drafts/current/. 31 Internet-Drafts are draft documents valid for a maximum of six months 32 and may be updated, replaced, or obsoleted by other documents at any 33 time. It is inappropriate to use Internet-Drafts as reference 34 material or to cite them other than as "work in progress." 36 This Internet-Draft will expire on August 19, 2011. 38 Copyright Notice 40 Copyright (c) 2011 IETF Trust and the persons identified as the 41 document authors. All rights reserved. 43 This document is subject to BCP 78 and the IETF Trust's Legal 44 Provisions Relating to IETF Documents 45 (http://trustee.ietf.org/license-info) in effect on the date of 46 publication of this document. Please review these documents 47 carefully, as they describe your rights and restrictions with respect 48 to this document. Code Components extracted from this document must 49 include Simplified BSD License text as described in Section 4.e of 50 the Trust Legal Provisions and are provided without warranty as 51 described in the Simplified BSD License. 53 Table of Contents 55 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 56 2. Requirements and Terminology . . . . . . . . . . . . . . . . . 3 57 2.1. Requirements . . . . . . . . . . . . . . . . . . . . . . . 3 58 2.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 4 59 3. Host behavior . . . . . . . . . . . . . . . . . . . . . . . . . 4 60 3.1. Connectivity test . . . . . . . . . . . . . . . . . . . . . 5 61 3.2. IPv4 addresses of the known name . . . . . . . . . . . . . 5 62 3.3. Non-standard IPv6 address formats . . . . . . . . . . . . . 6 63 4. Hosting of an IPv4-only name(s) . . . . . . . . . . . . . . . . 6 64 5. Required IPv4 addresses . . . . . . . . . . . . . . . . . . . . 6 65 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 66 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 67 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7 68 9. Normative References . . . . . . . . . . . . . . . . . . . . . 7 69 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7 71 1. Introduction 73 As part of the transition to IPv6 NAT64 74 [I-D.ietf-behave-v6v4-xlate-stateful] and DNS64 75 [I-D.ietf-behave-dns64] technologies will be utilized by some access 76 networks to provide IPv4 connectivity for IPv6-only hosts. The DNS64 77 utilizes IPv6 address synthesis to create local IPv6 presentations of 78 peers having only IPv4 addresses, hence allowing DNS-using IPv6-only 79 hosts to communicate with IPv4-only peers. 81 However, DNS64 cannot serve applications not using DNS, such as those 82 receiving IPv4 address literals as referrals. Such applications 83 could nevertheless be able to work through NAT64, provided they are 84 able to create locally valid IPv6 presentations of peers' IPv4 85 addresses. 87 Additionally, DNS64 is not able to do IPv6 address synthesis for 88 hosts running validating DNSSEC enabled resolvers, but instead the 89 synthetization must be done by the hosts. In order to perform IPv6 90 synthesis hosts have to learn the IPv6 prefix(es) used on the access 91 network for protocol translation. 93 This document describes a best effort method for advanced 94 applications and hosts to learn the information required to perform 95 local IPv6 address synthesis. An example application is a browser 96 encountering an IPv4 address literal in an IPv6-only access network. 97 Another example is a host running validating security aware DNS 98 resolver. 100 The knowledge of IPv6 address synthetization taking place may also be 101 useful if DNS64 and NAT64 are present in dual-stack enabled access 102 network. In such cases hosts may choose to prefer IPv4 in order to 103 avoid traversal through protocol translators. 105 The described method is intented for the scenarios where network 106 assisted NAT64 and prefix discovery solutions are not available. 108 2. Requirements and Terminology 110 2.1. Requirements 112 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 113 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 114 document are to be interpreted as described in [RFC2119]. 116 2.2. Terminology 118 Known Name: a fully qualified domain name known by the implementation 119 to have only an A record. Implementation knows it by hard-coding or 120 e.g. via some provisioning technology. The name is not known by 121 everybody. 123 Well-Known IPv4-only Name: a fully qualified domain name well-known 124 to have only A record. 126 3. Host behavior 128 A host requiring information about presence of NAT64 and the IPv6 129 prefix used for protocol translation shall send a DNS query for AAAA 130 records of a known IPv4-only fully qualified domain name. This may 131 happen, for example, at the moment the host is configured an IPv6 132 address of a DNS server. This may also happen at the time when first 133 DNS query for AAAA record is initiated. The host may perform this 134 check in both IPv6-only and dual-stack access networks. 136 When sending AAAA query for the known name a host MUST set "Checking 137 Disabled (CD)" bit to zero, as otherwise the DNS64 will not perform 138 IPv6 address synthesis hence does not reveal the IPv6 prefix(es) used 139 for protocol translation. 141 A DNS reply with one or more non-empty AAAA records indicates that 142 the access network is utilizing IPv6 address synthesis. A host MUST 143 look through all of the received AAAA records to collect all 144 available prefixes. The prefixes may include Well-Known Prefix or 145 one or more Network-Specific Prefixes. In the case of NSPs the host 146 SHALL search for the IPv4 address inside of the received IPv6 147 addresses to determine used address format. 149 An IPv4 address inside synthesized IPv6 address should be found at 150 some of the locations described in [RFC6052]. If the searched IPv4 151 address is not found on any of the standard locations the network 152 must be using different formatting. In such case the host may try to 153 find out the IPv4 address at some other location. 155 The host should ensure a 32-bit IPv4 address value is present only 156 once in an IPv6 address. In case another instance of the value is 157 found inside the IPv6, the host shall repeat the search with another 158 IPv4 address. 160 In the case only one IPv6 prefix was present in the DNS response: a 161 host shall use that IPv6 prefix for both local synthetization and for 162 detecting synthesis done by the DNS64 entity on the network. 164 In the case multiple IPv6 prefixes were present in the DNS response: 165 a host SHOULD use all received prefixes when determining whether 166 other received IPv6 addresses are synthetic. However, for selecting 167 prefix for the local IPv6 address synthesis host MUST use the 168 following prioritization order, of which purpose is to avoid use of 169 prefixes containing suffixes reserved for the future [RFC6052]: 171 1. Use NSP having /96 prefix 173 2. Use WKP prefix 175 3. Use longest available NSP prefix 177 In the case of NXDOMAIN or empty AAAA reply: the DNS64 is not 178 available on the access network, network filtered the well-known AAAA 179 query on purpose, or something went wrong in the DNS resolution. All 180 unsuccesful cases result in unavailability of a host to perform local 181 IPv6 address synthesis. The host MAY periodically resend AAAA query 182 to check if DNS64 has become available or temporary problem cleared. 183 The host MAY also continue monitoring DNS replies with IPv6 addresses 184 constructed from WKP, in which case the host MAY use the WKP as if it 185 were learned during the query for well-known name. 187 3.1. Connectivity test 189 After the host has obtained a candidate prefix and format for the 190 IPv6 address synthesis it may locally synthesize an IPv6 address, by 191 using a publicly routable IPv4 address, and test connectivity with 192 the resulting IPv6 address. The connectivity test may be conducted 193 e.g. with ICMPv6 or with a transport layer protocol. The used public 194 IPv4 address may be learned via separate A query. 196 This connectivity test ensures local address synthetization results 197 in functional and protocol translatable IPv6 addresses. 199 3.2. IPv4 addresses of the known name 201 The IPv4 addresses of the known name should be such that they are 202 unlikely to appear more than once within an IPv6 address and also as 203 easy as possible to find from within the synthetic IPv6 address. 204 Good addresses might be 127.127.127.127 as a primary and 205 192.168.127.254 as a secondary. The secondary address is needed in 206 the case multiple instaces of primary address are present in a 207 synthetic IPv6 address. The IPv4 addresses can, however, be publicly 208 routable especially if also used for the connectivity test. 210 3.3. Non-standard IPv6 address formats 212 A node may need to perform more complex heuristics to cope with 213 networks possibly using non-standard IPv6 address formats. Non- 214 standard approaches might include for example: 216 1. Non-standard location: IPv4 address in one piece at non-standard 217 location. Can be found by pattern matching. 219 2. Fragmented: IPv4 address in multiple pieces around the IPv6 220 address. May be found by pattern matching. 222 3. Obfuscated address: IPv4 address is obfuscated, for example 223 xorred. May potentially be found especially if standard addess 224 format is used, but as this is an indication of access network's 225 unwillingness to support host based synthetization the host 226 should not try to decipher the IPv6 prefix. 228 4. Hosting of an IPv4-only name(s) 230 The required IPv4-only name has to be hosted by someone. While 231 IANA(?) might host one (?), it may be safest for device, operating 232 system, and/or application vendors to host IPv4-only names for their 233 own uses. The name should have two A records in order to manage in 234 situations where the first IPv4 address appears more than once within 235 synthetic IPv6 address. Another name may be needed for connectivity 236 test purposes. 238 5. Required IPv4 addresses 240 A prefix detection without connectivity test does not require any 241 routable IPv4 addresses. The connectivity test requires a routable 242 IPv4 address on the server side. 244 6. Security Considerations 246 No security considerations have been identified. 248 7. IANA Considerations 250 IANA(?) should define a name and an IPv4 address for a Well-Known 251 IPv4-only Name. 253 8. Acknowledgements 255 Authors would like to thank Dan Wing, Washam Fan, Cameron Byrne, and 256 Christian Huitema for improvement ideas and comments. 258 9. Normative References 260 [I-D.ietf-behave-dns64] 261 Bagnulo, M., Sullivan, A., Matthews, P., and I. Beijnum, 262 "DNS64: DNS extensions for Network Address Translation 263 from IPv6 Clients to IPv4 Servers", 264 draft-ietf-behave-dns64-11 (work in progress), 265 October 2010. 267 [I-D.ietf-behave-v6v4-xlate-stateful] 268 Bagnulo, M., Matthews, P., and I. Beijnum, "Stateful 269 NAT64: Network Address and Protocol Translation from IPv6 270 Clients to IPv4 Servers", 271 draft-ietf-behave-v6v4-xlate-stateful-12 (work in 272 progress), July 2010. 274 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 275 Requirement Levels", BCP 14, RFC 2119, March 1997. 277 [RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X. 278 Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052, 279 October 2010. 281 Authors' Addresses 283 Teemu Savolainen 284 Nokia 285 Hermiankatu 12 D 286 FI-33720 Tampere 287 Finland 289 Email: teemu.savolainen@nokia.com 290 Jouni Korhonen 291 Nokia Siemens Networks 292 Linnoitustie 6 293 FI-02600 Espoo 294 Finland 296 Email: jouni.nospam@gmail.com