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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Unused Reference: '3' is defined on line 181, but no explicit reference was found in the text ** Obsolete normative reference: RFC 2434 (ref. '4') (Obsoleted by RFC 5226) ** Obsolete normative reference: RFC 2460 (ref. '5') (Obsoleted by RFC 8200) ** Obsolete normative reference: RFC 3513 (ref. '6') (Obsoleted by RFC 4291) Summary: 5 errors (**), 0 flaws (~~), 6 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Internet Engineering Task Force A.Durand 2 INTERNET-DRAFT SUN Microsystems,inc. 3 March, 25, 2004 J. Ihren 4 Expires September 24, 2004 Autonomica 6 DNS IPv6 transport operational guidelines 7 9 Status of this Memo 11 This document is an Internet-Draft and is in full conformance with 12 all provisions of Section 10 of RFC2026. 14 Internet-Drafts are working documents of the Internet Engineering 15 Task Force (IETF), its areas, and its working groups. Note that other 16 groups may also distribute working documents as Internet-Drafts. 18 Internet-Drafts are draft documents valid for a maximum of six months 19 and may be updated, replaced, or obsoleted by other documents at any 20 time. It is inappropriate to use Internet-Drafts as reference 21 material or to cite them other than as "work in progress." 23 The list of current Internet-Drafts can be accessed at http:// 24 www.ietf.org/ietf/1id-abstracts.txt. 26 The list of Internet-Draft Shadow Directories can be accessed at 27 http://www.ietf.org/shadow.html. 29 This Internet-Draft will expire on September 24, 2004. 31 Copyright Notice 33 Copyright (C) The Internet Society (2004). All Rights Reserved. 35 Abstract 37 This memo provides guidelines and Best Current Practice for operating 38 DNS in a world where queries and responses are carried in a mixed 39 environment of IPv4 and IPv6 networks. 41 Acknowledgment 43 This document is the result of many conversations that happened in 44 the DNS community at IETF and elsewhere since 2001. During that 45 period of time, a number of Internet drafts have been published to 46 clarify various aspects of the issues at stake. This document focuses 47 on the conclusion of those discussions. 49 The authors would like to acknowledge the role of Pekka Savola in his 50 thorough review of the document. 52 1. Terminology 54 The phrase "IPv4 name server" indicates a name server available over 55 IPv4 transport. It does not imply anything about what DNS [1,2] data 56 is served. Likewise, "IPv6 [5,6,7] name server" indicates a name 57 server available over IPv6 transport. The phrase "dual-stack name 58 server" indicates a name server that is actually configured to run 59 both protocols, IPv4 and IPv6, and not merely a server running on a 60 system capable of running both but actually configured to run only 61 one. 63 2. Introduction to the Problem of Name Space Fragmentation: 64 following the referral chain 66 A resolver that tries to look up a name starts out at the root, and 67 follows referrals until it is referred to a name server that is 68 authoritative for the name. If somewhere down the chain of referrals 69 it is referred to a name server that is only accessible over a 70 transport which the resolver cannot use, the resolver is unable to 71 finish the task. 73 When the Internet moves from IPv4 to a mixture of IPv4 and IPv6 it is 74 only a matter of time until this starts to happen. The complete DNS 75 hierarchy then starts to fragment into a graph where authoritative 76 name servers for certain nodes are only accessible over a certain 77 transport. The concern is that a resolver using only a particular 78 version of IP, querying information about another node using the same 79 version of IP can not do it because, somewhere in the chain of 80 servers accessed during the resolution process, one or more of them 81 will only be accessible with the other version of IP. 83 With all DNS data only available over IPv4 transport everything is 84 simple. IPv4 resolvers can use the intended mechanism of following 85 referrals from the root and down while IPv6 resolvers have to work 86 through a "translator", i.e. they have to use a recursive name server 87 on a so-called "dual stack" host as a "forwarder" since they cannot 88 access the DNS data directly. 90 With all DNS data only available over IPv6 transport everything would 91 be equally simple, with the exception of IPv4 recursive name servers 92 having to switch to a forwarding configuration. 94 However, the second situation will not arise in the foreseeable 95 future. Instead, the transition will be from IPv4 only to a mixture 96 of IPv4 and IPv6, with three categories of DNS data depending on 97 whether the information is available only over IPv4 transport, only 98 over IPv6 or both. 100 Having DNS data available on both transports is the best situation. 101 The major question is how to ensure that it as quickly as possible 102 becomes the norm. However, while it is obvious that some DNS data 103 will only be available over v4 transport for a long time it is also 104 obvious that it is important to avoid fragmenting the name space 105 available to IPv4 only hosts. I.e. during transition it is not 106 acceptable to break the name space that we presently have available 107 for IPv4-only hosts. 109 3. Policy Based Avoidance of Name Space Fragmentation 111 Today there are only a few DNS "zones" on the public Internet that 112 are available over IPv6 transport, and most of them can be regarded 113 as "experimental". However, as soon as the root and top level domains 114 are available over IPv6 transport, it is reasonable to expect that it 115 will become more common to have zones served by IPv6 servers. 117 Having those zones served only by IPv6-only name server would not be 118 a good development, since this will fragment the previously 119 unfragmented IPv4 name space and there are strong reasons to find a 120 mechanism to avoid it. 122 The recommended approach to maintain name space continuity is to use 123 administrative policies, as described in the next section. 125 4. DNS IPv6 Transport recommended Guidelines 127 In order to preserve name space continuity, the following 128 administrative policies are recommended: 130 - every recursive name server SHOULD be either IPv4-only or dual 131 stack, 133 This rules out IPv6-only recursive servers. However, one might 134 well design configurations where a chain of IPv6-only name 135 server forward queries to a set of dual stack recursive name 136 server actually performing those recursive queries. 138 - every DNS zone SHOULD be served by at least one IPv4-reachable 139 authoritative name server. 141 This rules out DNS zones served only by IPv6-only authoritative 142 name servers. 144 Note: zone validation processes SHOULD ensure that there is at least 145 one IPv4 address record available for the name servers of any child 146 delegations within the zone. 148 5. Security Considerations 150 The guidelines described in this memo introduce no new security 151 considerations into the DNS protocol or associated operational 152 scenarios. 154 6. IANA considerations 156 This memo creates no new requirements on IANA namespaces [4]. 158 7. Authors Addresses 160 Alain Durand 161 SUN Microsystems, Inc 162 17 Network circle UMPK17-202 163 Menlo Park, CA, 94025 164 USA 165 Mail: Alain.Durand@sun.com 167 Johan Ihren 168 Autonomica 169 Bellmansgatan 30 170 SE-118 47 Stockholm, Sweden 171 Mail: johani@autonomica.se 173 8. Normative References 175 [1] Mockapetris, P., "Domain Names - Concepts and Facilities", STD 176 13, RFC 1034, November 1987. 178 [2] Mockapetris, P., "Domain Names - Implementation and 179 Specification", STD 13, RFC 1035, November 1987. 181 [3] The Internet Standards Process, S. Bradner, RFC2026, 182 October 1996. 184 [4] Guidelines for Writing an IANA Considerations Section in RFCs, 185 T. Narten, H. Alvestrand, RFC2434, October 1998. 187 [5] Internet Protocol, Version 6 (IPv6) Specification. S. Deering, 188 R. Hinden, RFC2460, December 1998. 190 [6] Hinden, R. and S. Deering, "Internet Protocol Version 6 (IPv6) 191 Addressing Architecture", RFC 3513, April 2003. 193 [7] DNS Extensions to Support IP Version 6. S. Thomson, C. Huitema, 194 V. Ksinant, M. Souissi, RFC3596, October 2003. 196 9. Full Copyright Statement 198 Intellectual Property Statement 200 The IETF takes no position regarding the validity or scope of any 201 intellectual property or other rights that might be claimed to 202 pertain to the implementation or use of the technology described in 203 this document or the extent to which any license under such rights 204 might or might not be available; neither does it represent that it 205 has made any effort to identify any such rights. Information on the 206 IETF's procedures with respect to rights in standards-track and 207 standards-related documentation can be found in BCP-11. 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All Rights Reserved. 224 This document and translations of it may be copied and furnished to 225 others, and derivative works that comment on or otherwise explain it 226 or assist in its implementation may be prepared, copied, published 227 and distributed, in whole or in part, without restriction of any 228 kind, provided that the above copyright notice and this paragraph are 229 included on all such copies and derivative works. However, this 230 document itself may not be modified in any way, such as by removing 231 the copyright notice or references to the Internet Society or other 232 Internet organizations, except as needed for the purpose of 233 developing Internet standards in which case the procedures for 234 copyrights defined in the Internet Standards process must be 235 followed, or as required to translate it into languages other than 236 English. 238 The limited permissions granted above are perpetual and will not be 239 revoked by the Internet Society or its successors or assignees. 241 This document and the information contained herein is provided on an 242 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING 243 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING 244 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION 245 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF 246 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 248 Acknowledgment 250 Funding for the RFC Editor function is currently provided by the 251 Internet Society.