Client Subnet in DNS Queries
RFC 7871

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Internet Engineering Task Force (IETF)                     C. Contavalli
Request for Comments: 7871                              W. van der Gaast
Category: Informational                                           Google
ISSN: 2070-1721                                              D. Lawrence
                                                     Akamai Technologies
                                                               W. Kumari
                                                                  Google
                                                                May 2016

                      Client Subnet in DNS Queries

Abstract

   This document describes an Extension Mechanisms for DNS (EDNS0)
   option that is in active use to carry information about the network
   that originated a DNS query and the network for which the subsequent
   response can be cached.  Since it has some known operational and
   privacy shortcomings, a revision will be worked through the IETF for
   improvement.

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 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 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/rfc7871.

Contavalli, et al.            Informational                     [Page 1]
RFC 7871              Client Subnet in DNS Queries              May 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.

Contavalli, et al.            Informational                     [Page 2]
RFC 7871              Client Subnet in DNS Queries              May 2016

Table of Contents
   1. Introduction ....................................................4
   2. Privacy Note ....................................................5
   3. Requirements Notation ...........................................5
   4. Terminology .....................................................6
   5. Overview ........................................................7
   6. Option Format ...................................................8
   7. Protocol Description ............................................9
      7.1. Originating the Option .....................................9
           7.1.1. Recursive Resolvers .................................9
           7.1.2. Stub Resolvers .....................................10
           7.1.3. Forwarding Resolvers ...............................11
      7.2. Generating a Response .....................................11
           7.2.1. Authoritative Nameserver ...........................11
           7.2.2. Intermediate Nameserver ............................13
      7.3. Handling ECS Responses and Caching ........................14
           7.3.1. Caching the Response ...............................15
           7.3.2. Answering from Cache ...............................16
      7.4. Delegations and Negative Answers ..........................17
      7.5. Transitivity ..............................................18
   8. IANA Considerations ............................................18
   9. DNSSEC Considerations ..........................................19
   10. NAT Considerations ............................................19
   11. Security Considerations .......................................20
      11.1. Privacy ..................................................20
      11.2. Birthday Attacks .........................................21
      11.3. Cache Pollution ..........................................22
   12. Sending the Option ............................................23
      12.1. Probing ..................................................23
      12.2. Whitelist ................................................24
   13. Example .......................................................24
   14. References ....................................................26