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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   (http://trustee.ietf.org/license-info) in effect on the date of
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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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