Operational Considerations and Issues with IPv6 DNS
RFC 4472

Network Working Group                                          A. Durand
Request for Comments: 4472                                       Comcast
Category: Informational                                         J. Ihren
                                                              Autonomica
                                                               P. Savola
                                                               CSC/FUNET
                                                              April 2006

          Operational Considerations and Issues with IPv6 DNS

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   This memo presents operational considerations and issues with IPv6
   Domain Name System (DNS), including a summary of special IPv6
   addresses, documentation of known DNS implementation misbehavior,
   recommendations and considerations on how to perform DNS naming for
   service provisioning and for DNS resolver IPv6 support,
   considerations for DNS updates for both the forward and reverse
   trees, and miscellaneous issues.  This memo is aimed to include a
   summary of information about IPv6 DNS considerations for those who
   have experience with IPv4 DNS.

Table of Contents

   1. Introduction ....................................................3
      1.1. Representing IPv6 Addresses in DNS Records .................3
      1.2. Independence of DNS Transport and DNS Records ..............4
      1.3. Avoiding IPv4/IPv6 Name Space Fragmentation ................4
      1.4. Query Type '*' and A/AAAA Records ..........................4
   2. DNS Considerations about Special IPv6 Addresses .................5
      2.1. Limited-Scope Addresses ....................................5
      2.2. Temporary Addresses ........................................5
      2.3. 6to4 Addresses .............................................5
      2.4. Other Transition Mechanisms ................................5
   3. Observed DNS Implementation Misbehavior .........................6
      3.1. Misbehavior of DNS Servers and Load-balancers ..............6
      3.2. Misbehavior of DNS Resolvers ...............................6

Durand, et al.               Informational                      [Page 1]
RFC 4472              Considerations with IPv6 DNS            April 2006

   4. Recommendations for Service Provisioning Using DNS ..............7
      4.1. Use of Service Names instead of Node Names .................7
      4.2. Separate vs. the Same Service Names for IPv4 and IPv6 ......8
      4.3. Adding the Records Only When Fully IPv6-enabled ............8
      4.4. The Use of TTL for IPv4 and IPv6 RRs .......................9
           4.4.1. TTL with Courtesy Additional Data ...................9
           4.4.2. TTL with Critical Additional Data ..................10
      4.5. IPv6 Transport Guidelines for DNS Servers .................10
   5. Recommendations for DNS Resolver IPv6 Support ..................10
      5.1. DNS Lookups May Query IPv6 Records Prematurely ............10
      5.2. Obtaining a List of DNS Recursive Resolvers ...............12
      5.3. IPv6 Transport Guidelines for Resolvers ...................12
   6. Considerations about Forward DNS Updating ......................13
      6.1. Manual or Custom DNS Updates ..............................13
      6.2. Dynamic DNS ...............................................13
   7. Considerations about Reverse DNS Updating ......................14
      7.1. Applicability of Reverse DNS ..............................14
      7.2. Manual or Custom DNS Updates ..............................15
      7.3. DDNS with Stateless Address Autoconfiguration .............16
      7.4. DDNS with DHCP ............................................17
      7.5. DDNS with Dynamic Prefix Delegation .......................17
   8. Miscellaneous DNS Considerations ...............................18
      8.1. NAT-PT with DNS-ALG .......................................18
      8.2. Renumbering Procedures and Applications' Use of DNS .......18
   9. Acknowledgements ...............................................19
   10. Security Considerations .......................................19
   11. References ....................................................20
      11.1. Normative References .....................................20
      11.2. Informative References ...................................22
   Appendix A. Unique Local Addressing Considerations for DNS ........24
   Appendix B. Behavior of Additional Data in IPv4/IPv6
               Environments ..........................................24