draft-ietf-dnsop-ipv6-transport-guidelines-01.txt   draft-ietf-dnsop-ipv6-transport-guidelines-02.txt 
Internet Engineering Task Force A.Durand Internet Engineering Task Force A.Durand
INTERNET-DRAFT SUN Microsystems,inc. INTERNET-DRAFT SUN Microsystems,inc.
November, 24, 2003 J. Ihren March, 25, 2004 J. Ihren
Expires May 25, 2004 Autonomica Expires September 24, 2004 Autonomica
DNS IPv6 transport operational guidelines DNS IPv6 transport operational guidelines
<draft-ietf-dnsop-ipv6-transport-guidelines-01.txt> <draft-ietf-dnsop-ipv6-transport-guidelines-02.txt>
Status of this Memo Status of this Memo
This memo provides information to the Internet community. It does not This document is an Internet-Draft and is in full conformance with
specify an Internet standard of any kind. This memo is in full all provisions of Section 10 of RFC2026.
conformance with all provisions of Section 10 of RFC2026
Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on September 24, 2004.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved. Copyright (C) The Internet Society (2004). All Rights Reserved.
Abstract Abstract
This memo provides guidelines and Best Current Practice to operate This memo provides guidelines and Best Current Practice for operating
DNS in a world where queries and responses are carried in a mixed DNS in a world where queries and responses are carried in a mixed
environment of IPv4 and IPv6 networks. environment of IPv4 and IPv6 networks.
Acknowledgment Acknowledgment
This document is the result of many conversations that happened in This document is the result of many conversations that happened in
the DNS community at IETF and elsewhere since 2001. During that the DNS community at IETF and elsewhere since 2001. During that
period of time, a number of Internet drafts have been published to period of time, a number of Internet drafts have been published to
clarify various aspects of the issues at stake. This document focuses clarify various aspects of the issues at stake. This document focuses
on the conclusion of those discussions. on the conclusion of those discussions.
The authors would like to acknowledge the role of Pekka Savola in his The authors would like to acknowledge the role of Pekka Savola in his
thorough review of the document. thorough review of the document.
1. Terminology 1. Terminology
The phrase "IPv4 name server" indicates a name server available over The phrase "IPv4 name server" indicates a name server available over
IPv4 transport. It does not imply anything about what DNS data is IPv4 transport. It does not imply anything about what DNS [1,2] data
served. Likewise, "IPv6 name server" indicates a name server is served. Likewise, "IPv6 [5,6,7] name server" indicates a name
available over IPv6 transport. The phrase "dual-stack DNS server" server available over IPv6 transport. The phrase "dual-stack name
indicates a DNS server that is actually configured to run both server" indicates a name server that is actually configured to run
protocols, IPv4 and IPv6, and not merely a server running on a system both protocols, IPv4 and IPv6, and not merely a server running on a
capable of running both but actually configured to run only one. system capable of running both but actually configured to run only
one.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [2119].
2. Introduction to the Problem of Name Space Fragmentation: 2. Introduction to the Problem of Name Space Fragmentation:
following the referral chain following the referral chain
The caching resolver that tries to look up a name starts out at the A resolver that tries to look up a name starts out at the root, and
root, and follows referrals until it is referred to a nameserver that follows referrals until it is referred to a name server that is
is authoritative for the name. If somewhere down the chain of authoritative for the name. If somewhere down the chain of referrals
referrals it is referred to a nameserver that is only accessible over it is referred to a name server that is only accessible over a
an unavailable type of transport, a traditional nameserver is unable transport which the resolver cannot use, the resolver is unable to
to finish the task. finish the task.
When the Internet moves from IPv4 to a mixture of IPv4 and IPv6 it is 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 only a matter of time until this starts to happen. The complete DNS
hierarchy then starts to fragment into a graph where authoritative hierarchy then starts to fragment into a graph where authoritative
nameservers for certain nodes are only accessible over a certain nameservers for certain nodes are only accessible over a certain
transport. What is feared is that a node using only a particular transport. The concern is that a resolver using only a particular
version of IP, querying information about another node using the same version of IP, querying information about another node using the same
version of IP can not do it because, somewhere in the chain of version of IP can not do it because, somewhere in the chain of
servers accessed during the resolution process, one or more of them servers accessed during the resolution process, one or more of them
will only be accessible with the other version of IP. will only be accessible with the other version of IP.
With all DNS data only available over IPv4 transport everything is With all DNS data only available over IPv4 transport everything is
simple. IPv4 resolvers can use the intended mechanism of following simple. IPv4 resolvers can use the intended mechanism of following
referrals from the root and down while IPv6 resolvers have to work referrals from the root and down while IPv6 resolvers have to work
through a "translator", i.e. they have to use a second name server on through a "translator", i.e. they have to use a recursive name server
a so-called "dual stack" host as a "forwarder" since they cannot on a so-called "dual stack" host as a "forwarder" since they cannot
access the DNS data directly. access the DNS data directly.
With all DNS data only available over IPv6 transport everything would With all DNS data only available over IPv6 transport everything would
be equally simple, with the exception of old legacy IPv4 name servers be equally simple, with the exception of IPv4 recursive name servers
having to switch to a forwarding configuration. having to switch to a forwarding configuration.
However, the second situation will not arise in a foreseeable time. However, the second situation will not arise in the foreseeable
Instead, it is expected that the transition will be from IPv4 only to future. Instead, the transition will be from IPv4 only to a mixture
a mixture of IPv4 and IPv6, with DNS data of theoretically three of IPv4 and IPv6, with three categories of DNS data depending on
categories depending on whether it is available only over IPv4 whether the information is available only over IPv4 transport, only
transport, only over IPv6 or both. over IPv6 or both.
Having DNS data available on both transports is the best situation. Having DNS data available on both transports is the best situation.
The major question is how to ensure that it as quickly as possible The major question is how to ensure that it as quickly as possible
becomes the norm. However, while it is obvious that some DNS data becomes the norm. However, while it is obvious that some DNS data
will only be available over v4 transport for a long time it is also 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 obvious that it is important to avoid fragmenting the name space
available to IPv4 only hosts. I.e. during transition it is not available to IPv4 only hosts. I.e. during transition it is not
acceptable to break the name space that we presently have available acceptable to break the name space that we presently have available
for IPv4-only hosts. for IPv4-only hosts.
skipping to change at line 120 skipping to change at line 123
are available over IPv6 transport, and most of them can be regarded are available over IPv6 transport, and most of them can be regarded
as "experimental". However, as soon as the root and top level domains as "experimental". However, as soon as the root and top level domains
are available over IPv6 transport, it is reasonable to expect that it are available over IPv6 transport, it is reasonable to expect that it
will become more common to have zones served by IPv6 servers. will become more common to have zones served by IPv6 servers.
Having those zones served only by IPv6-only name server would not be Having those zones served only by IPv6-only name server would not be
a good development, since this will fragment the previously a good development, since this will fragment the previously
unfragmented IPv4 name space and there are strong reasons to find a unfragmented IPv4 name space and there are strong reasons to find a
mechanism to avoid it. mechanism to avoid it.
The RECOMMENDED approach to maintain name space continuity is to use The recommended approach to maintain name space continuity is to use
administrative policies, as described in the next section. administrative policies, as described in the next section.
4. DNS IPv6 Transport RECOMMENDED Guidelines 4. DNS IPv6 Transport recommended Guidelines
In order to preserve name space continuity, the following administrative In order to preserve name space continuity, the following
policies are RECOMMENDED: administrative policies are recommended:
- every recursive DNS server SHOULD be either IPv4-only or dual
- every recursive name server SHOULD be either IPv4-only or dual
stack, stack,
- every single DNS zone SHOULD be served by at least one IPv4
reachable DNS server.
This rules out IPv6-only DNS servers performing full recursion and This rules out IPv6-only recursive servers. However, one might
DNS zones served only by IPv6-only DNS servers. However, one could well design configurations where a chain of IPv6-only name
very well design a configuration where a chain of IPv6 only DNS server forward queries to a set of dual stack recursive name
servers forward queries to a set of dual stack DNS servers actually server actually performing those recursive queries.
performing those recursive queries. This approach could be revisited
if/when translation techniques between IPv4 and IPv6 were to be
widely deployed.
In order to help enforcing the second point, the optional operational - every DNS zone SHOULD be served by at least one IPv4-reachable
zone validation processes SHOULD ensure that there is at least one authoritative name server.
IPv4 address record available for the name servers of any child
This rules out DNS zones served only by IPv6-only authoritative
name servers.
Note: zone validation processes SHOULD ensure that there is at least
one IPv4 address record available for the name servers of any child
delegations within the zone. delegations within the zone.
5. Security Considerations 5. Security Considerations
Being a critical piece of the Internet infrastructure, the DNS is a The guidelines described in this memo introduce no new security
potential value target and thus should be protected. Great care considerations into the DNS protocol or associated operational
should be taken not to weaken the security of DNS while introducing scenarios.
IPv6 operation.
Keeping the DNS name space from fragmenting is a critical thing for 6. IANA considerations
the availability and the operation of the Internet; this memo
addresses this issue by clear and simple operational guidelines.
The RECOMMENDED guidelines are compatible with the operation of This memo creates no new requirements on IANA namespaces [4].
DNSSEC and do not introduce any new security issues.
6. Author Addresses 7. Authors Addresses
Alain Durand Alain Durand
SUN Microsystems, Inc SUN Microsystems, Inc
17 Network circle UMPK17-202 17 Network circle UMPK17-202
Menlo Park, CA, 94025 Menlo Park, CA, 94025
USA USA
Mail: Alain.Durand@sun.com Mail: Alain.Durand@sun.com
Johan Ihren Johan Ihren
Autonomica Autonomica
Bellmansgatan 30 Bellmansgatan 30
SE-118 47 Stockholm, Sweden SE-118 47 Stockholm, Sweden
Mail: johani@autonomica.se Mail: johani@autonomica.se
7. Normative References 8. Normative References
[2119] Bradner, S., "Key Words for Use in RFCs to Indicate [1] Mockapetris, P., "Domain Names - Concepts and Facilities", STD
Requirement Levels", BCP 14, RFC 2119, March 1997. 13, RFC 1034, November 1987.
8. Full Copyright Statement [2] Mockapetris, P., "Domain Names - Implementation and
Specification", STD 13, RFC 1035, November 1987.
"Copyright (C) The Internet Society (2003). All Rights Reserved. [3] The Internet Standards Process, S. Bradner, RFC2026,
October 1996.
[4] Guidelines for Writing an IANA Considerations Section in RFCs,
T. Narten, H. Alvestrand, RFC2434, October 1998.
[5] Internet Protocol, Version 6 (IPv6) Specification. S. Deering,
R. Hinden, RFC2460, December 1998.
[6] Hinden, R. and S. Deering, "Internet Protocol Version 6 (IPv6)
Addressing Architecture", RFC 3513, April 2003.
[7] DNS Extensions to Support IP Version 6. S. Thomson, C. Huitema,
V. Ksinant, M. Souissi, RFC3596, October 2003.
9. Full Copyright Statement
Intellectual Property Statement
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The IETF invites any interested party to bring to its attention any
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Full Copyright Statement
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Acknowledgement Acknowledgment
Funding for the RFC Editor function is currently provided by the Funding for the RFC Editor function is currently provided by the
Internet Society. Internet Society.
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