DNS Transport over TCP - Operational Requirements
draft-kristoff-dnsop-dns-tcp-requirements-00

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Last updated 2016-03-11
Replaced by draft-ietf-dnsop-dns-tcp-requirements
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Domain Name System Operations                                J. Kristoff
Internet-Draft                                                Team Cymru
Intended status: Best Current Practice                    March 11, 2016
Expires: September 12, 2016

           DNS Transport over TCP - Operational Requirements
              draft-kristoff-dnsop-dns-tcp-requirements-00

Abstract

   This document encourages the practice of permitting DNS messages to
   be carried over TCP on the Internet.  It also describes some of the
   consequences of this behavior and the potential operational issues
   that can arise when this best common practice is not applied.

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 http://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 September 12, 2016.

Copyright Notice

   Copyright (c) 2016 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.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   2
   2.  Background  . . . . . . . . . . . . . . . . . . . . . . . . .   2
     2.1.  Uneven Transport Usage and Preference . . . . . . . . . .   2
     2.2.  Waiting for Large Messages and Reliability  . . . . . . .   3
     2.3.  EDNS0 . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  DNS over TCP Requirements . . . . . . . . . . . . . . . . . .   4
   4.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   DNS messages may be delivered using UDP or TCP communications.  While
   most DNS transactions are carried over UDP, some operators have been
   led to believe that any DNS over TCP traffic is unwanted or
   unnecessary for general DNS operation.  As DNS usage has evolved, DNS
   over TCP has become increasingly important for correct and safe
   operation of the Internet DNS.  Reflecting modern usage, the DNS
   standards were recently updated to declare support for TCP is now a
   required part of the DNS implementation specifications in [RFC7766].
   This document is the formal requirements equivalent for the
   operational community, encouraging operators to ensure DNS over TCP
   communications support in on par with DNS over UDP communications.

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

2.  Background

2.1.  Uneven Transport Usage and Preference

   In the original suite of DNS specifications, [RFC1034] and [RFC1035]
   clearly specified that DNS messages could be carried in either UDP or
   TCP, but they also made clear a preference for UDP as the transport
   for queries in the general case.  As stated in [RFC1035]:

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      "While virtual circuits can be used for any DNS activity,
      datagrams are preferred for queries due to their lower overhead
      and better performance."

   Another early, important and influential document, [RFC1123],
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