Internet DRAFT - draft-andrews-edns1
draft-andrews-edns1
Network Working Group M. Andrews
Internet-Draft ISC
Expires: October 18, 2014 April 16, 2014
EDNS Version 1 (EDNS(1))
draft-andrews-edns1-01.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
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on October 18, 2014.
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Removing Ambiguity . . . . . . . . . . . . . . . . . . . . . . 3
3. EDNS Version 1 . . . . . . . . . . . . . . . . . . . . . . . . 4
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 4
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 4
6.1. Normative References . . . . . . . . . . . . . . . . . . . 4
6.2. Informative References . . . . . . . . . . . . . . . . . . 4
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 5
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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.
There has also been observed ambiguity when responding query types
that are not supported by a server resulting NOTIMP, FORMERR,
SERVFAIL and REFUSED answers from servers rather than the expected
result codes SUCCESS (no data exist) or NAME ERROR responses
depending apon whether the names exists or not which is implictly
implied by [RFC 1034], Section 4.3.2 and further by [RFC 3597].
EDNS version 1 makes returning SUCCESS (no data exist) or NAME ERROR
when a type is not supported by the server a explict requirement
rather than NOTIMP, FORMERR, SERVFAIL REFUSED or any other error
code.
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 DNS and EDNS.
2. Removing Ambiguity
Removing ambiguity in responses in important as it allows a client to
cleanly decide based on error codes what to do, rather than doing
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trial and error to discover the server's behaviour.
EDNS version 1 addresses two observed sources of ambiguity, EDNS
version 0 with unknown options and unknown query type response
handling.
3. 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.
4. IANA Considerations
This document be the reference document for EDNS version 1.
5. Security Considerations
The document does not introduce any security issues that are not
addressed in [RFC 6891].
6. References
6.1. Normative References
[RFC 1034]
Mockapetris, P., "DOMAIN NAMES - CONCEPTS AND FACILITIES",
STD 13, RFC 1034, November 1987.
[RFC 3597]
Gustafsson, A., "Handling of Unknown DNS Resource Record
(RR) Types", RFC 3597, September 2003.
[RFC 6891]
Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms
for DNS (EDNS(0))", STD 75, RFC 6891, April 2013.
6.2. Informative References
[RFC 2671]
Vixie, P., "Extension Mechanisms for DNS (EDNS0)",
RFC 1999, August 1999.
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Author's Address
M. Andrews
Internet Systems Consortium
950 Charter Street
Redwood City, CA 94063
US
Email: marka@isc.org
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