Architectural Considerations on Application Features in the DNS
RFC 6950

Document Type RFC - Informational (October 2013; No errata)
Last updated 2013-10-09
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Internet Architecture Board (IAB)                            J. Peterson
Request for Comments: 6950                                 NeuStar, Inc.
Category: Informational                                       O. Kolkman
ISSN: 2070-1721                                               NLnet Labs
                                                           H. Tschofenig
                                                  Nokia Siemens Networks
                                                                B. Aboba
                                                                   Skype
                                                            October 2013

    Architectural Considerations on Application Features in the DNS

Abstract

   A number of Internet applications rely on the Domain Name System
   (DNS) to support their operations.  Many applications use the DNS to
   locate services for a domain; some, for example, transform
   identifiers other than domain names into formats that the DNS can
   process, and then fetch application data or service location data
   from the DNS.  Proposals incorporating sophisticated application
   behavior using DNS as a substrate have raised questions about the
   role of the DNS as an application platform.  This document explores
   the architectural consequences of using the DNS to implement certain
   application features, and it provides guidance to future application
   designers as to the limitations of the DNS as a substrate and the
   situations in which alternative designs should be considered.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Architecture Board (IAB)
   and represents information that the IAB has deemed valuable to
   provide for permanent record.  It represents the consensus of the
   Internet Architecture Board (IAB).  Documents approved for
   publication by the IAB are not a candidate for any level of Internet
   Standard; see 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/rfc6950.

Peterson, et al.              Informational                     [Page 1]
RFC 6950               Application Features in DNS          October 2013

Copyright Notice

   Copyright (c) 2013 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.

Table of Contents

   1. Motivation ......................................................2
   2. Overview of DNS Application Usages ..............................4
      2.1. Locating Services in a Domain ..............................5
      2.2. NAPTR and DDDS .............................................6
      2.3. Arbitrary Data in the DNS ..................................8
   3. Challenges for the DNS .........................................10
      3.1. Compound Queries ..........................................10
           3.1.1. Responses Tailored to the Originator ...............12
      3.2. Using DNS as a Generic Database ...........................14
           3.2.1. Large Data in the DNS ..............................14
      3.3. Administrative Structures Misaligned with the DNS .........16
           3.3.1. Metadata about Tree Structure ......................18
      3.4. Domain Redirection ........................................20
   4. Private DNS and Split Horizon ..................................21
   5. Principles and Guidance ........................................23
   6. Security Considerations ........................................25
   7. IAB Members at the Time of Approval ............................26
   8. Acknowledgements ...............................................26
   9. Informative References .........................................27

1.  Motivation

   The Domain Name System (DNS) has long provided a general means of
   translating domain names into Internet Protocol addresses, which
   makes the Internet easier to use by providing a valuable layer of
   indirection between names and lower-layer protocol elements.
   [RFC0974] documented a further use of the DNS: to locate an
   application service operating in a domain, via the Mail Exchange (MX)
   Resource Record; these records help email addressed to the domain to
   find a mail service for the domain sanctioned by the zone
   administrator.

Peterson, et al.              Informational                     [Page 2]
RFC 6950               Application Features in DNS          October 2013
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