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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 DNSEXT Working Group Randy Bush (ed.) 2 Alain Durand (ed.) 3 Bob Fink (ed.) 4 Olafur Gudmundsson (ed.) 5 Tony Hain (ed.) 6 INTERNET-DRAFT September 2001 8 10 Updates: RFC 1886, RFC 2673, RFC 2874 12 Representing IPv6 addresses in DNS. 14 Status of this Memo 16 This document is an Internet-Draft and is in full conformance with 17 all provisions of Section 10 of RFC 2026. 19 Internet-Drafts are working documents of the Internet Engineering 20 Task Force (IETF), its areas, and its working groups. Note that 21 other groups may also distribute working documents as Internet- 22 Drafts. 24 Internet-Drafts are draft documents valid for a maximum of six months 25 and may be updated, replaced, or obsoleted by other documents at any 26 time. It is inappropriate to use Internet-Drafts as reference 27 material or to cite them other than as ``work in progress.'' 29 The list of current Internet-Drafts can be accessed at 30 http://www.ietf.org/ietf/1id-abstracts.txt 32 The list of Internet-Draft Shadow Directories can be accessed at 33 http://www.ietf.org/shadow.html 35 Comments should be sent to the authors or the DNSEXT WG mailing list 36 namedroppers@ops.ietf.org 38 This draft expires on March 25, 2002. 40 Copyright Notice 42 Copyright (C) The Internet Society (2001). All rights reserved. 44 Abstract 46 This document clarifies and updates the standards status of RFCs that 47 define direct and reverse map of IPv6 addresses in DNS. This document 48 moves the A6 and Bit label specifications to experimental status. 50 1 - Introduction 52 The IETF had begun the process of standardizing two different address 53 formats for IPv6 addresses AAAA[RFC1886] and A6[RFC2874] and both are 54 at proposed standard. This had led to confusion and conflicts on 55 which one to deploy. It is important for deployment that any 56 confusion in this area be cleared up, as there is a feeling in the 57 community that having more than one choice will lead to delays in the 58 deployment of IPv6. The goal of this document is to clarify the 59 situation. 61 This document is based on extensive technical discussion on various 62 relevant working groups mailing lists and a joint DNSEXT and NGTRANS 63 meeting at the 51st IETF in August 2001. This document attempts to 64 capture the sense of the discussions and reflect them in this 65 document to represent the consensus of the community. 67 The main arguments and the issues are covered in a separate 68 document[Tradeoff] that reflects the current understanding of the 69 issues. This document summarizes the outcome of these discussions. 71 The issue of the root of reverse IPv6 address map is outside the 72 scope of this document and is covered in a different 73 document[RFC3152]. 75 1.1 Standards action taken 77 This document changes the status of RFCs 2673 and 2874 from Proposed 78 Standard to Experimental. 80 2 - IPv6 addresses: AAAA RR vs A6 RR 82 Working group consensus as perceived by the chairs of the DNSEXT and 83 NGTRANS working groups is that: 85 a) AAAA records are preferable at the moment for production 86 deployment of IPv6, and 88 b) that A6 records have interesting properties that need to be 89 better understood before deployment. 91 c) It is not known if the benefits of A6 outweigh the costs and 92 risks. 94 2.1 Rationale 96 There are several potential issues with A6 RRs that stem directly 97 from the feature that makes them different from AAAA RRs: the ability 98 to build up addresses via chaining. 100 Resolving a chain of A6 RRs involves resolving a series of what are 101 nearly-independent queries. Each of these sub-queries takes some 102 non-zero amount of time, unless the answer happens to be in the 103 resolver's local cache already. Other things being equal, we expect 104 that the time it takes to resolve an N-link chain of A6 RRs will be 105 roughly proportional to N. What data we have suggests that users are 106 already impatient with the length of time it takes to resolve A RRs 107 in the IPv4 Internet, which suggests that users are not likely to be 108 patient with significantly longer delays in the IPv6 Internet, but 109 terminating queries prematurely is both a waste of resources and 110 another source of user frustration. Thus, we are forced to conclude 111 that indiscriminate use of long A6 chains is likely to lead to 112 increased user frustration. 114 The probability of failure during the process of resolving an N-link 115 A6 chain also appears to be roughly proportional to N, since each of 116 the queries involved in resolving an A6 chain has roughly the same 117 probability of failure as a single AAAA query. 119 Last, several of the most interesting potential applications for A6 120 RRs involve situations where the prefix name field in the A6 RR 121 points to a target that is not only outside the DNS zone containing 122 the A6 RR, but is administered by a different organization entirely. 123 While pointers out of zone are not a problem per se, experience both 124 with glue RRs and with PTR RRs in the IN-ADDR.ARPA tree suggests that 125 pointers to other organizations are often not maintained properly, 126 perhaps because they're less susceptible to automation than pointers 127 within a single organization would be. 129 2.2 Recommended standard action 131 Based on the perceived consensus, this document recommend that RFC 132 1886 stay on standards track and be advanced, while moving RFC 2874 133 to Experimental status. 135 3 - Bitlabels in the reverse DNS tree 137 RFC 2673 defines a new DNS label type. This was the first new type 138 defined since RFC 1035[RFC1035]. Since the development of 2673 it has 139 been learned that deployment of a new type is difficult since DNS 140 servers that do not support bitlabels reject queries containing bit 141 labels as being malformed. The community has also indicated that this 142 new label type is not needed for mapping reverse addresses. 144 3.1 Rationale 146 The hexadecimal text representation of IPv6 addresses appears to be 147 capable of expressing all of the delegation schemes that we expect to 148 be used in the DNS reverse tree, since we do not ever expect to see 149 delegation in the least significant possible hexadecimal label. That 150 is, we do not ever expect to see an IPv6 address architecture that 151 advocates address delegation in the least significant four bits of an 152 IPv6 address. 154 3.2 Recommended standard action 156 RFC 2673 standard status is to be changed from Proposed to 157 Experimental. Future standardization of these documents is to be done 158 by the DNSEXT working group or its successor. 160 4 DNAME in IPv6 reverse tree 162 The issues for DNAME chaining in the reverse tree are substantially 163 identical to the issues for A6 chaining in the forward tree. 164 Therefore, in moving RFC 2874 to experimental, the intent of this 165 document is that use of DNAME RRs in the reverse tree be deprecated. 167 5 Acknowledgments 169 This document is based on input from many members of the various IETF 170 working groups involved in this issues. Special thanks go to the 171 people that prepared reading material for the joint DNSEXT and 172 NGTRANS working group meeting at the 51st IETF in London, Rob 173 Austein, Dan Bernstein, Matt Crawford, Jun-ichiro itojun Hagino, 174 Christian Huitema. Number of other people have made number of 175 comments on mailing lists about this issue including Robert Elz , 176 Johan Ihren , Bill Manning 178 6 - Security Considerations: 180 As this document specifies a course of action, there are no direct 181 security considerations. There is an indirect security impact of the 182 choice, in that the relationship between A6 and DNSSEC is not well 183 understood throughout the community, while the choice of AAAA does 184 leads to a model for use of DNSSEC in IPv6 networks which parallels 185 current IPv4 practice. 187 7 - IANA Considerations: 189 None. 191 References: 193 [RFC1035] P. Mockapetris, ``Domain Names - Implementation and 194 Specification'' STD 13, RFC 1035, November 1987. 196 [RFC1886] S. Thompson, C. Huitema, ``DNS Extensions to support IP 197 version 6'', RFC 1886, December 1995. 199 [RFC2673] M. Crawford ``Binary Labels in the Domain Name System``, RFC 200 2673, August 1999. 202 [RFC2874] M. Crawford, C. Huitema, ``DNS Extensions to Support IPv6 203 Address Aggregation and Renumbering'', RFC 2874, July 2000. 205 [RFC3152] R. Bush, ``Delegation of IP6.ARPA'', RFC 3152 also BCP0049, 206 August 2001, 208 [Tradeoff] R. Austein, ``Tradeoffs in DNS support for IPv6'', Work in 209 progress, draft-ietf-dnsext-ipv6-dns-tradeoffs-xx.txt, July 210 2001. 212 Editors Address 214 Randy Bush 215 Alain Durand 216 Bob Fink 217 Olafur Gudmundsson 218 Tony Hain 220 Full Copyright Statement 222 Copyright (C) The Internet Society (2001). 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 assigns. 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."