xNAME RCODE and Status Bits Clarification
RFC 6604

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Internet Engineering Task Force (IETF)                   D. Eastlake 3rd
Request for Comments: 6604                                        Huawei
Updates: 1035, 2308, 2672                                     April 2012
Category: Standards Track
ISSN: 2070-1721

               xNAME RCODE and Status Bits Clarification

Abstract

   The Domain Name System (DNS) has long provided means, such as the
   CNAME (Canonical Name), whereby a DNS query can be redirected to a
   different name.  A DNS response header has an RCODE (Response Code)
   field, used for indicating errors, and response status bits.  This
   document clarifies, in the case of such redirected queries, how the
   RCODE and status bits correspond to the initial query cycle (where
   the CNAME or the like was detected) and subsequent or final query
   cycles.

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 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6604.

Copyright Notice

   Copyright (c) 2012 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
   (http://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.

Eastlake                     Standards Track                    [Page 1]
RFC 6604                xNAME RCODE Clarification             April 2012

Table of Contents

   1. Introduction ....................................................2
      1.1. Conventions Used in This Document ..........................3
   2. Restatement of Status Bits and What They Mean ...................3
      2.1. The Authoritative Answer Bit ...............................3
      2.2. The Authentic Data Bit .....................................3
   3. RCODE Clarification .............................................3
   4. Security Considerations .........................................4
   5. References ......................................................4
      5.1. Normative References .......................................4
      5.2. Informative References .....................................5

1.  Introduction

   The Domain Name System (DNS) has long provided means, such as the
   CNAME (Canonical Name [RFC1035]) and DNAME [RFC2672] RRs (Resource
   Records), whereby a DNS query can be redirected to a different name.
   In particular, CNAME normally causes a query to its owner name to be
   redirected, while DNAME normally causes a query to any lower-level
   name to be redirected.  There has been a proposal for another
   redirection RR.  In addition, as specified in [RFC2672], redirection
   through a DNAME also results in the synthesis of a CNAME RR in the
   response.  In this document, we will refer to all RRs causing such
   redirection as xNAME RRs.

   xNAME RRs can be explicitly retrieved by querying for the xNAME type.
   When a different type is queried and an xNAME RR is encountered, the
   xNAME RR (and possibly a synthesized CNAME) is added to the answer in
   the response, DNS Security Extensions (DNSSEC) [RFC4035] RRs
   applicable to the xNAME RR may be added to the response, and the
   query is restarted with the name to which it was redirected.

   An xNAME may redirect a query to a name at which there is another
   xNAME and so on.  In this document, we use "xNAME chain" to refer to
   a series of one or more xNAMEs each of which refers to another xNAME
   except the last, which refers to a non-xNAME or results in an error.

   A DNS response header has an RCODE (Response Code) field, used for
   indicating errors, and status bits that indicate whether an answer is
   authoritative and/or authentic.  This document clarifies, in the case
   of such redirected queries, how the RCODE and status bits correspond
   to the initial query cycle (where the (first) xNAME was detected) and
   subsequent or final query cycles.

Eastlake                     Standards Track                    [Page 2]
RFC 6604                xNAME RCODE Clarification             April 2012

1.1.  Conventions Used in This Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",