Address-specific DNS aliases (ANAME)
draft-ietf-dnsop-aname-04

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DNS Operations                                                  T. Finch
Internet-Draft                                   University of Cambridge
Intended status: Standards Track                                 E. Hunt
Expires: January 9, 2020                                             ISC
                                                             P. van Dijk
                                                                PowerDNS
                                                                 A. Eden
                                                                DNSimple
                                                              W. Mekking
                                                                     ISC
                                                            July 8, 2019

                  Address-specific DNS aliases (ANAME)
                       draft-ietf-dnsop-aname-04

Abstract

   This document defines the "ANAME" DNS RR type, to provide similar
   functionality to CNAME, but only for address 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

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on January 9, 2020.

Copyright Notice

   Copyright (c) 2019 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
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   described in the Simplified BSD License.

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.  Substituting ANAME sibling address records
   4.  ANAME processing by primary masters
     4.1.  Zone transfers
     4.2.  DNSSEC
     4.3.  TTLs
   5.  ANAME processing by resolvers
   6.  Query processing
     6.1.  Authoritative servers
       6.1.1.  Address queries
       6.1.2.  ANAME queries
     6.2.  Resolvers
       6.2.1.  Address queries
       6.2.2.  ANAME queries
   7.  IANA considerations
   8.  Security considerations
   9.  Acknowledgments
   10. Changes since the last revision
     10.1.  Version -04
     10.2.  Version -03
     10.3.  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.  ANAME substitution inside the name server
     C.5.  TTLs and zone transfers
   Appendix D.  Alternative setups
     D.1.  Reducing query volume
     D.2.  Zone transfer scalability
     D.3.  Tailored responses
   Appendix E.  ANAME loops
   Authors' Addresses

1.  Introduction

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

   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
   "example.com") because of the SOA, NS, and other records that have to
   be present there.  CNAME records can also conflict at subdomains, for
   example, if "department.example.edu" has separately hosted mail and
   web servers.

   Redirecting website lookups to an alternate domain name via SRV or