ATR: Additional Truncation Response for Large DNS Response
draft-song-atr-large-resp-02

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Last updated 2018-08-02
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Internet Engineering Task Force                                  L. Song
Internet-Draft                                Beijing Internet Institute
Intended status: Experimental                             August 2, 2018
Expires: February 3, 2019

       ATR: Additional Truncation Response for Large DNS Response
                      draft-song-atr-large-resp-02

Abstract

   As the increasing use of DNSSEC and IPv6, there are more public
   evidence and concerns on IPv6 fragmentation issues due to larger DNS
   payloads over IPv6.  This memo introduces an simple improvement on
   DNS server by replying an additional truncated response just after
   the normal fragmented response.  It can be used to relieve users
   suffering on DNS latency and failures due to large DNS response.  An
   ATR Experiment was done to show how well it works and some
   operational issues are discussed in this memo as well.

Status of This Memo

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   This Internet-Draft will expire on February 3, 2019.

Copyright Notice

   Copyright (c) 2018 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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Song                    Expires February 3, 2019                [Page 1]
Internet-DrafATR: Additional Truncation Response for Large D August 2018

   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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  The ATR mechanism . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Experiment on how well ATR works  . . . . . . . . . . . . . .   5
   4.  Operational considerations  . . . . . . . . . . . . . . . . .   6
     4.1.  ATR timer . . . . . . . . . . . . . . . . . . . . . . . .   6
     4.2.  ATR payload size  . . . . . . . . . . . . . . . . . . . .   7
     4.3.  Less aggressiveness of ATR  . . . . . . . . . . . . . . .   8
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   6.  IANA considerations . . . . . . . . . . . . . . . . . . . . .   8
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   8
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
   Appendix A.  Considerations on Resolver awareness of ATR  . . . .  10
   Appendix B.  Revision history of this document  . . . . . . . . .  11
     B.1.  draft-song-atr-large-resp-01  . . . . . . . . . . . . . .  11
     B.2.  draft-song-atr-large-resp-02  . . . . . . . . . . . . . .  12
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

   Large DNS response is identified as a issue for a long time.  There
   is an inherent mechanism defined in [RFC1035] to handle large DNS
   response (larger than 512 octets) by indicating (set TrunCation bit)
   the resolver to fall back to query via TCP.  Due to the fear of cost
   of TCP, EDNS(0) [RFC6891] was proposed which encourages server to
   response larger response instead of falling back to TCP.  However, as
   the increasing use of DNSSEC and IPv6, there are more public evidence
   and concerns on user's suffering due to packets dropping caused by
   IPv6 fragmentation in DNS due to large DNS response.

   It is observed that some IPv6 network devices like firewalls
   intentionally choose to drop the IPv6 packets with fragmentation
   Headers[I-D.taylor-v6ops-fragdrop].  [RFC7872] reported more than 30%
   drop rates for sending fragmented packets.  Regarding IPv6
   fragmentation issue due to larger DNS payloads in response, one
   measurement [IPv6-frag-DNS] reported 35% of endpoints using
   IPv6-capable DNS resolver can not receive a fragmented IPv6 response
   over UDP.  Moreover, most of the underlying issues with fragments are
   unrevealed due to good redundancy and resilience of DNS.  It is hard
   for DNS client and server operators to trace and locate the issue
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