Network Working Group M. Andrews
Internet-Draft ISC
Expires: October 17, 2014 April 15, 2014
EDNS Version 1
draft-andrews-edns1-00.txt
Abstract
It is impracticable to deploy new EDNS options, with EDNS version 0,
on a global scale due to inconsistent server behaviour in deployed
servers when a EDNS option is present in the query. Most existing
EDNS option deployment has been small scale between essentially
consenting implementations.
When EDNS options were added to every outgoing recursive query made
it became clear that trial and error to discover the level of EDNS
version 0 support was not practicable.
This document request that EDNS version 1 be assigned so that
consistent well defined behaviour can be seen when a EDNS option is
present.
Status of this Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. EDNS Version 1 . . . . . . . . . . . . . . . . . . . . . . . . 3
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 3
4. Security Considerations . . . . . . . . . . . . . . . . . . . . 3
5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5.1. Normative References . . . . . . . . . . . . . . . . . . . 4
5.2. Informative References . . . . . . . . . . . . . . . . . . 4
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 4
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1. Introduction
Extended DNS (EDNS) supports adding EDNS options to the request.
Unfortunately it was not clear in the original specification [RFC
2671] that unknown EDNS options should be ignored. The updated EDNS
specification [RFC 6891] makes ignoring unknown EDNS options a
explicit requirement but failed to bump the EDNS version number.
Currently there are EDNS version 0 servers that ignore unknown EDNS
options. Those that return FORMERR when unknown EDNS options are
present. Those that return BADVERS when unknown EDNS options are
present. Those that return REFUSED when unknown EDNS options are
present and presumably those that return NOTIMP (though the author
has not seen one).
FORMERR, REFUSED and NOTIMP are all returned from servers that do not
support EDNS. It is impracticable for clients to have yet more
overloading of these error codes and more trial and error to workout
what is and is not supported when there is a clear method available
to resolve the differences.
This document requests EDNS version 1 be assigned and that the EDNS
behaviour be that of [RFC 6891] with the exception of the version
being 1 rather than 0. EDNS version 1 clients then will have well
defined behaviour when sending unknown EDNS options (they should be
ignored) to EDNS version 1 servers. BADVERS to EDNS version 0
servers and FORMERR, REFUSED, NOTIMP to servers that do not support
EDNS and return a error code.
This is effectively a protocol reset for EDNS.
2. EDNS Version 1
EDNS version one behaviour is identical to that described in [RFC
6891] with the exception to that the EDNS version is assigned to 1.
3. IANA Considerations
This document be the reference document for EDNS version 1.
4. Security Considerations
The document does not introduce any security issues that are not
addressed in [RFC 6891].
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5. References
5.1. Normative References
[RFC 6891]
Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms
for DNS (EDNS(0))", STD 75, RFC 6891, April 2013.
5.2. Informative References
[RFC 2671]
Vixie, P., "Extension Mechanisms for DNS (EDNS0)",
RFC 1999, August 1999.
Author's Address
M. Andrews
Internet Systems Consortium
950 Charter Street
Redwood City, CA 94063
US
Email: marka@isc.org
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