Address-specific DNS aliases (ANAME)

The information below is for an old version of the document
Document Type Active Internet-Draft (dnsop WG)
Authors Tony Finch  , Evan Hunt  , Peter van Dijk  , Anthony Eden  , Matthijs Mekking 
Last updated 2019-04-15 (latest revision 2018-10-19)
Replaces draft-hunt-dnsop-aname
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DNS Operations                                                  T. Finch
Internet-Draft                                   University of Cambridge
Intended status: Standards Track                                 E. Hunt
Expires: October 17, 2019                                            ISC
                                                             P. van Dijk
                                                                 A. Eden
                                                              W. Mekking
                                                          April 15, 2019

                  Address-specific DNS aliases (ANAME)


   This document defines the "ANAME" DNS RR type, to provide similar
   functionality to CNAME, but only for type A and AAAA queries.  Unlike
   CNAME, an ANAME can coexist with other record types.  The ANAME RR
   allows zone owners to make an apex domain name into an alias in a
   standards compliant manner.

Status of This Memo

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   This Internet-Draft will expire on October 17, 2019.

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Table of Contents

   1.  Introduction
     1.1.  Overview
     1.2.  Terminology
   2.  The ANAME resource record
     2.1.  Presentation and wire format
     2.2.  Coexistence with other types
   3.  Additional section processing
     3.1.  Address queries
     3.2.  ANAME queries
   4.  Substituting ANAME sibling address records
   5.  ANAME processing by primary masters
     5.1.  Zone transfers
     5.2.  DNSSEC
     5.3.  TTLs
   6.  ANAME processing by resolvers
   7.  IANA considerations
   8.  Security considerations
   9.  Acknowledgments
   10. Changes since the last revision
     10.1.  Version -03
     10.2.  Version -02
   11. References
     11.1.  Normative References
     11.2.  Informative References
     11.3.  URIs
   Appendix A.  Implementation status
   Appendix B.  Historical note
   Appendix C.  On preserving TTLs
     C.1.  Query bunching
     C.2.  Upstream caches
     C.3.  ANAME chains
     C.4.  TTLs and zone transfers
   Appendix D.  Answer vs Additional sections
   Appendix E.  Alternative setups
   Authors' Addresses

1.  Introduction

   It can be desirable to provide web sites (and other services) at a
   bare domain name (such as "") as well as a service-
   specific subdomain ("").

   If the web site is hosted by a third-party provider, the ideal way to
   provision its name in the DNS is using a CNAME record, so that the
   third party provider retains control over the mapping from names to
   IP address(es).  It is now common for name-to-address mappings to be
   highly dynamic, dependent on client location, server load, etc.

   However, CNAME records cannot coexist with other records with the
   same owner name.  (The reason why is explored in Appendix B).  This
   restriction means they cannot appear at a zone apex (such as
   "") because of the SOA, NS, and other records that have to
   be present there.  CNAME records can also conflict at subdomains, for
   example, if "" has separately hosted mail and
   web servers.

   Redirecting website lookups to an alternate domain name via SRV or
   URI resource records would be an effective solution from the DNS
   point of view, but to date, browser vendors have not accepted this

   As a result, the only widely supported and standards-compliant way to
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