CHAIN Query Requests in DNS
RFC 7901

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Internet Engineering Task Force (IETF)                        P. Wouters
Request for Comments: 7901                                       Red Hat
Category: Experimental                                         June 2016
ISSN: 2070-1721

                      CHAIN Query Requests in DNS

Abstract

   This document defines an EDNS0 extension that can be used by a
   security-aware validating resolver configured to use a forwarding
   resolver to send a single query, requesting a complete validation
   path along with the regular query answer.  The reduction in queries
   potentially lowers the latency and reduces the need to send multiple
   queries at once.  This extension mandates the use of source-IP-
   verified transport such as TCP or UDP with EDNS-COOKIE, so it cannot
   be abused in amplification attacks.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for examination, experimental implementation, and
   evaluation.

   This document defines an Experimental Protocol for the Internet
   community.  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).  Not
   all documents approved by the IESG are a candidate for any level of
   Internet Standard; see Section 2 of RFC 7841.

   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/rfc7901.

Wouters                       Experimental                      [Page 1]
RFC 7901               CHAIN Query Requests in DNS             June 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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Requirements Notation . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Option Format . . . . . . . . . . . . . . . . . . . . . . . .   5
   5.  Protocol Description  . . . . . . . . . . . . . . . . . . . .   6
     5.1.  Discovery of Support  . . . . . . . . . . . . . . . . . .   6
     5.2.  Generate a Query  . . . . . . . . . . . . . . . . . . . .   6
     5.3.  Send the Option . . . . . . . . . . . . . . . . . . . . .   6
     5.4.  Generate a Response . . . . . . . . . . . . . . . . . . .   7
   6.  Protocol Considerations . . . . . . . . . . . . . . . . . . .   8
     6.1.  DNSSEC Considerations . . . . . . . . . . . . . . . . . .   8
     6.2.  NS Record Considerations  . . . . . . . . . . . . . . . .   8
     6.3.  Session Management  . . . . . . . . . . . . . . . . . . .   9
     6.4.  Negative Trust Anchors  . . . . . . . . . . . . . . . . .   9
     6.5.  Anycast Considerations  . . . . . . . . . . . . . . . . .   9
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
     7.1.  Additional Work and Bandwidth . . . . . . . . . . . . . .  10
     7.2.  Amplification Attacks . . . . . . . . . . . . . . . . . .  10
     7.3.  Privacy Considerations  . . . . . . . . . . . . . . . . .  10
   8.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .  10
     8.1.  CHAIN Query for "www.example.com" . . . . . . . . . . . .  10
     8.2.  Out-of-Path Query for "example.com" . . . . . . . . . . .  12
     8.3.  Nonexistent Data  . . . . . . . . . . . . . . . . . . . .  13
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  14
     9.1.  EDNS0 Option Code for CHAIN . . . . . . . . . . . . . . .  14
   10. Normative References  . . . . . . . . . . . . . . . . . . . .  14
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  16
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  16

Wouters                       Experimental                      [Page 2]
RFC 7901               CHAIN Query Requests in DNS             June 2016

1.  Introduction

   Traditionally, a DNS client operates in stub mode.  For each DNS
   question the DNS client needs to resolve, it sends a single query to
   an upstream recursive resolver to obtain a single DNS answer.  When