DNS IPv6 Transport Operational Guidelines (RFC3901)
Original Publication Date: 2004-Sep-01
Included in the Prior Art Database: 2004-Sep-23
Internet Society Requests For Comment (RFCs)
A. Durand: AUTHOR [+1]
This 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.
Network Working Group A. Durand
Request for Comments: 3901 SUN Microsystems, Inc.
BCP: 91 J. Ihren
Category: Best Current Practice Autonomica
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 (C) The Internet Society (2004).
This 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.
1. Introduction to the Problem of Name Space Fragmentation:
following the referral chain
A resolver that tries to look up a name starts out at the root, and
follows referrals until it is referred to a name server that is
authoritative for the name. If somewhere down the chain of referrals
it is referred to a name server that is only accessible over a
transport which the resolver cannot use, the resolver is unable to
finish the task.
When the Internet moves from IPv4 to a mixture of IPv4 and IPv6 it is
only a matter of time until this starts to happen. The complete DNS
hierarchy then starts to fragment into a graph where authoritative
name servers for certain nodes are only accessible over a certain
transport. The concern is that a resolver using only a particular
version of IP and querying information about another node using the
same version of IP can not do it because somewhere in the chain of
servers accessed during the resolution process, one or more of them
will only be accessible with the other version of IP.
With all DNS data only available over IPv4 transport everything is
simple. IPv4 resolvers can use the intended mechanism of following
referrals from the root and down while IPv6 resolvers have to work
Durand & Ihren Best Current Practice [Page 1]
RFC 3901 DNS IPv6 Transport Guidelines September 2004
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