Extended DNS Errors
RFC 8914

Document Type RFC - Proposed Standard (October 2020; No errata)
Authors Warren Kumari  , Evan Hunt  , Roy Arends  , Wes Hardaker  , David Lawrence 
Last updated 2020-10-23
Replaces draft-wkumari-dnsop-extended-error
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Stream WG state Submitted to IESG for Publication
Document shepherd Tim Wicinski
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Internet Engineering Task Force (IETF)                         W. Kumari
Request for Comments: 8914                                        Google
Category: Standards Track                                        E. Hunt
ISSN: 2070-1721                                                      ISC
                                                               R. Arends
                                                             W. Hardaker
                                                             D. Lawrence
                                                            October 2020

                          Extended DNS Errors


   This document defines an extensible method to return additional
   information about the cause of DNS errors.  Though created primarily
   to extend SERVFAIL to provide additional information about the cause
   of DNS and DNSSEC failures, the Extended DNS Errors option defined in
   this document allows all response types to contain extended error
   information.  Extended DNS Error information does not change the
   processing of RCODEs.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at

Copyright Notice

   Copyright (c) 2020 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
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction and Background
     1.1.  Requirements Notation
   2.  Extended DNS Error EDNS0 Option Format
   3.  Extended DNS Error Processing
   4.  Defined Extended DNS Errors
     4.1.  Extended DNS Error Code 0 - Other
     4.2.  Extended DNS Error Code 1 - Unsupported DNSKEY Algorithm
     4.3.  Extended DNS Error Code 2 - Unsupported DS Digest Type
     4.4.  Extended DNS Error Code 3 - Stale Answer
     4.5.  Extended DNS Error Code 4 - Forged Answer
     4.6.  Extended DNS Error Code 5 - DNSSEC Indeterminate
     4.7.  Extended DNS Error Code 6 - DNSSEC Bogus
     4.8.  Extended DNS Error Code 7 - Signature Expired
     4.9.  Extended DNS Error Code 8 - Signature Not Yet Valid
     4.10. Extended DNS Error Code 9 - DNSKEY Missing
     4.11. Extended DNS Error Code 10 - RRSIGs Missing
     4.12. Extended DNS Error Code 11 - No Zone Key Bit Set
     4.13. Extended DNS Error Code 12 - NSEC Missing
     4.14. Extended DNS Error Code 13 - Cached Error
     4.15. Extended DNS Error Code 14 - Not Ready
     4.16. Extended DNS Error Code 15 - Blocked
     4.17. Extended DNS Error Code 16 - Censored
     4.18. Extended DNS Error Code 17 - Filtered
     4.19. Extended DNS Error Code 18 - Prohibited
     4.20. Extended DNS Error Code 19 - Stale NXDOMAIN Answer
     4.21. Extended DNS Error Code 20 - Not Authoritative
     4.22. Extended DNS Error Code 21 - Not Supported
     4.23. Extended DNS Error Code 22 - No Reachable Authority
     4.24. Extended DNS Error Code 23 - Network Error
     4.25. Extended DNS Error Code 24 - Invalid Data
   5.  IANA Considerations
     5.1.  A New Extended DNS Error Code EDNS Option
     5.2.  New Registry for Extended DNS Error Codes
   6.  Security Considerations
   7.  References
     7.1.  Normative References
     7.2.  Informative References
   Authors' Addresses

1.  Introduction and Background

   There are many reasons that a DNS query may fail -- some of them
   transient, some permanent; some can be resolved by querying another
   server, some are likely best handled by stopping resolution.
   Unfortunately, the error signals that a DNS server can return are
   very limited and are not very expressive.  This means that
   applications and resolvers often have to "guess" at what the issue
   is, e.g., was the answer marked REFUSED because of a lame delegation
   or because the nameserver is still starting up and loading zones?  Is
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