draft-ietf-dnsop-ipv6-transport-guidelines-00.txt   draft-ietf-dnsop-ipv6-transport-guidelines-01.txt 
Internet Engineering Task Force Alain Durand Internet Engineering Task Force A.Durand
INTERNET-DRAFT SUN Microsystems,inc. INTERNET-DRAFT SUN Microsystems,inc.
June, 17, 2003 Johan Ihren November, 24, 2003 J. Ihren
Expires December 18, 2003 Autonomica Expires May 25, 2004 Autonomica
DNS IPv6 transport operational guidelines DNS IPv6 transport operational guidelines
<draft-ietf-dnsop-ipv6-transport-guidelines-00.txt> <draft-ietf-dnsop-ipv6-transport-guidelines-01.txt>
Status of this memo Status of this Memo
This memo provides information to the Internet community. It does not This memo provides information to the Internet community. It does not
specify an Internet standard of any kind. This memo is in full specify an Internet standard of any kind. This memo is in full
conformance with all provisions of Section 10 of RFC2026 conformance with all provisions of Section 10 of RFC2026
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet- Drafts as reference time. It is inappropriate to use Internet- Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/1id-abstracts.html http://www.ietf.org/1id-abstracts.html
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html http://www.ietf.org/shadow.html
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", Copyright Notice
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [2119]. Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract Abstract
This memo provides guidelines and best common practice to operate DNS This memo provides guidelines and Best Current Practice to operate
in a mixed world of IPv4 and IPv6 transport. DNS in a world where queries and responses are carried in a mixed
environment of IPv4 and IPv6 networks.
Acknowledgment
This document is the result of many conversations that happened in
the DNS community at IETF and elsewhere since 2001. During that
period of time, a number of Internet drafts have been published to
clarify various aspects of the issues at stake. This document focuses
on the conclusion of those discussions.
The authors would like to acknowledge the role of Pekka Savola in his
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 data is
served. Likewise, "IPv6 name server" indicates a name server served. Likewise, "IPv6 name server" indicates a name server
available over IPv6 transport. available over IPv6 transport. The phrase "dual-stack DNS server"
indicates a DNS 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.
2. Introduction to the problem of name space fragmentation: 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:
following the referral chain following the referral chain
The caching resolver that tries to lookup a name starts out at the The caching resolver that tries to lookup a name starts out at the
root, and follows referrals until it is referred to a nameserver that root, and follows referrals until it is referred to a nameserver that
is authoritative for the name. If somewhere down the chain of is authoritative for the name. If somewhere down the chain of
referrals it is referred to a nameserver that is only accessible over referrals it is referred to a nameserver that is only accessible over
a type of transport that is unavailable, a traditional nameserver is an unavailable type of transport, a traditional nameserver is unable
unable to finish the task. to 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 and the complete only a matter of time until this starts to happen. The complete DNS
DNS hierarchy 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. What is feared is that a node 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
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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 old legacy IPv4 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 a foreseeable time.
Instead, it is expected that the transition will be from IPv4 only to Instead, it is expected that the transition will be from IPv4 only to
a mixture of IPv4 and IPv6, with DNS data of theoretically three a mixture of IPv4 and IPv6, with DNS data of theoretically three
categories depending on whether it is available only over IPv4 categories depending on whether it is available only over IPv4
transport, only over IPv6 or both. transport, only over IPv6 or both.
The latter is the best situation, and a major question is how to Having DNS data available on both transports is the best situation.
ensure that it as quickly as possible becomes the norm. However, The major question is how to ensure that it as quickly as possible
while it is obvious that some DNS data will only be available over v4 becomes the norm. However, while it is obvious that some DNS data
transport for a long time it is also obvious that it is important to will only be available over v4 transport for a long time it is also
avoid fragmenting the name space available to IPv4 only hosts. I.e. obvious that it is important to avoid fragmenting the name space
during transition it is not acceptable to break the name space that available to IPv4 only hosts. I.e. during transition it is not
we presently have available for IPv4-only hosts. acceptable to break the name space that we presently have available
for IPv4-only hosts.
3. Policy based avoidance of name space fragmentation. 3. Policy Based Avoidance of Name Space Fragmentation
Today there are only a few DNS "zones" on the public Internet that Today there are only a few DNS "zones" on the public Internet that
are available over IPv6 transport, and they can mostly be regarded are available over IPv6 transport, and most of them can be regarded
as "experimental". However, as soon as there is a root name server as "experimental". However, as soon as the root and top level domains
available over IPv6 transport it is reasonable to expect that it will are available over IPv6 transport, it is reasonable to expect that it
become more common to have zones served by IPv6 servers over time. 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. 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 administrative
policies are RECOMMENDED: policies are RECOMMENDED:
- every recursive DNS server SHOULD be either IPv4-only or dual - every recursive DNS server SHOULD be either IPv4-only or dual
stack, stack,
- every single DNS zone SHOULD be served by at least one IPv4 - every single DNS zone SHOULD be served by at least one IPv4
reachable DNS server. reachable DNS server.
This rules out IPv6-only DNS servers performing full recursion and This rules out IPv6-only DNS servers performing full recursion and
DNS zones served only by IPv6-only DNS servers. This approach could DNS zones served only by IPv6-only DNS servers. However, one could
be revisited if/when translation techniques between IPv4 and IPv6 very well design a configuration where a chain of IPv6 only DNS
were to be widely deployed. servers forward queries to a set of dual stack DNS servers actually
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 enforce the second point, the zone validation process In order to help enforcing the second point, the optional operational
SHOULD ensure that there is at least one IPv4 address record zone validation processes SHOULD ensure that there is at least one
available for the name servers of any child delegations within the IPv4 address record available for the name servers of any child
zone. delegations within the zone.
5. Security considerations 5. Security Considerations
Being a critical piece of the Internet infrastructure, the DNS is a Being a critical piece of the Internet infrastructure, the DNS is a
potential value target and thus should be protected. Great care potential value target and thus should be protected. Great care
should be taken not to weaken the security of DNS while introducing should be taken not to weaken the security of DNS while introducing
IPv6 operation. IPv6 operation.
Keeping the DNS name space from fragmenting is a critical thing for
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 The RECOMMENDED guidelines are compatible with the operation of
DNSsec and do not introduce any new security issues. DNSSEC and do not introduce any new security issues.
6. Author addresses 6. Author 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. References 7. Normative References
[2119] Bradner, S., "Key Words for Use in RFCs to Indicate [2119] Bradner, S., "Key Words for Use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
8. Full Copyright Statement 8. Full Copyright Statement
"Copyright (C) The Internet Society (2001). All Rights Reserved. "Copyright (C) The Internet Society (2003). All Rights Reserved.
This document and translations of it may be copied and furnished to This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of Internet organizations, except as needed for the purpose of
skipping to change at line 179 skipping to change at line 206
The limited permissions granted above are perpetual and will not be The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns. revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
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