Stretching DNS TTLs
draft-wkumari-dnsop-ttl-stretching-00

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Last updated 2016-11-13
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Network Working Group                                          W. Kumari
Internet-Draft                                                    Google
Intended status: Informational                         November 14, 2016
Expires: May 18, 2017

                          Stretching DNS TTLs
                 draft-wkumari-dnsop-ttl-stretching-00

Abstract

   The TTL of a DNS Resource Record expresses how long a record may be
   cached before it should be discarded.  This document discusses the
   possibility of "stretching TTLS" (using them past their expiration)
   if they cannot be refreshed.  This works on the assumption that stale
   data may be better than no data.

   PLEASE NOTE: This document is a strawman to drive discussion.  It may
   or may not be a good idea; this document documents the idea so that
   there is something concrete to throw tomatoes at.

   [ Ed note: Text inside square brackets ([]) is additional background
   information, answers to frequently asked questions, general musings,
   etc.  They will be removed before publication.  This document is
   being collaborated on in Github at: https://github.com/wkumari/draft-
   wkumari-dnsop-ttl-stretching.  The most recent version of the
   document, open issues, etc should all be available here.  The authors
   (gratefully) accept pull requests ]

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 May 18, 2017.

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Internet-Draft                TTL Stretchng                November 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  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements notation . . . . . . . . . . . . . . . . . .   3
   2.  Proposal  . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   3
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   3
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   3
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   3
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   4
   Appendix A.  Changes / Author Notes.  . . . . . . . . . . . . . .   4
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   4

1.  Introduction

   DNS Resource Records (RR) have an associated TTL.  This is how long
   the record may be cached before it should be expired and new
   information fetched.  This is based upon the assumption that the
   authoritative servers will be reachable when they are needed, and
   that records expire and are immediately evicted from the cache.

   There are a number of reasons why an authoritative server may become
   unreachable, including, unfortunately, Denial of Service (DoS)
   attacks.  Recent proposals, for example "Highly Automated Method for
   Maintaining Expiring Records" ([I-D.wkumari-dnsop-hammer]) propose
   refreshing records in the cache before they expire and are evicted.
   This means that the recursive server still has information in its
   cache when it attempts to contact the authoritative server.

   This document suggests that, if the recursive server is unable to
   contact the authoritative server, it simply extends the existing

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