Network Working Group A. Durand Request for Comments: 3901 SUN Microsystems, Inc. BCP: 91 J. Ihren Category: Best Current Practice Autonomica September 2004 DNS IPv6 Transport Operational Guidelines Status of this Memo This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. Distribution of this memo is unlimited. Copyright Notice Copyright (C) The Internet Society (2004).
AbstractThis memo provides guidelines and Best Current Practice for operating DNS in a world where queries and responses are carried in a mixed environment of IPv4 and IPv6 networks.
through a "translator", i.e., they have to use a recursive name server on a so-called "dual stack" host as a "forwarder" since they cannot access the DNS data directly. With all DNS data only available over IPv6 transport everything would be equally simple, with the exception of IPv4 recursive name servers having to switch to a forwarding configuration. However, the second situation will not arise in the foreseeable future. Instead, the transition will be from IPv4 only to a mixture of IPv4 and IPv6, with three categories of DNS data depending on whether the information is available only over IPv4 transport, only over IPv6 or both. Having DNS data available on both transports is the best situation. The major question is how to ensure that it becomes the norm as quickly as possible. However, while it is obvious that some DNS data will only be available over v4 transport for a long time it is also obvious that it is important to avoid fragmenting the name space available to IPv4 only hosts. For example, during transition it is not acceptable to break the name space that we presently have available for IPv4-only hosts. 1,2] data is served. Likewise, "IPv6 [4,5,6] name server" indicates a name server available over IPv6 transport. The phrase "dual-stack name server" indicates a name server that is actually configured to run both protocols, IPv4 and IPv6, and not merely a server running on a system capable of running both but actually configured to run only one.
The recommended approach to maintain name space continuity is to use administrative policies, as described in the next section.
 Mockapetris, P., "Domain names - concepts and facilities", STD 13, RFC 1034, November 1987.  Mockapetris, P., "Domain names - implementation and specification", STD 13, RFC 1035, November 1987.  Bradner, S., "The Internet Standards Process -- Revision 3", BCP 9, RFC 2026, October 1996.  Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", RFC 2460, December 1998.  Hinden, R. and S. Deering, "Internet Protocol Version 6 (IPv6) Addressing Architecture", RFC 3513, April 2003.  Thomson, S., Huitema, C., Ksinant, V., and M. Souissi, "DNS Extensions to Support IP Version 6", RFC 3596, October 2003.
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