Serving Stale Data to Improve DNS Resiliency
draft-ietf-dnsop-serve-stale-07

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DNSOP Working Group                                          D. Lawrence
Internet-Draft                                                    Oracle
Updates: 1034, 1035, 2181 (if approved)                        W. Kumari
Intended status: Standards Track                                 P. Sood
Expires: March 2, 2020                                            Google
                                                         August 30, 2019

              Serving Stale Data to Improve DNS Resiliency
                    draft-ietf-dnsop-serve-stale-07

Abstract

   This draft defines a method (serve-stale) for recursive resolvers to
   use stale DNS data to avoid outages when authoritative nameservers
   cannot be reached to refresh expired data.  One of the motivations
   for serve-stale is to make the DNS more resilient to DoS attacks, and
   thereby make them less attractive as an attack vector.  This document
   updates the definitions of TTL from RFC 1034 and RFC 1035 so that
   data can be kept in the cache beyond the TTL expiry, and also updates
   RFC 2181 by interpreting values with the high order bit set as being
   positive, rather than 0, and also suggests a cap of 7 days.

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
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   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
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   time.  It is inappropriate to use Internet-Drafts as reference
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   This Internet-Draft will expire on March 2, 2020.

Copyright Notice

   Copyright (c) 2019 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
   (https://trustee.ietf.org/license-info) in effect on the date of

Lawrence, et al.          Expires March 2, 2020                 [Page 1]
Internet-Draft               DNS Serve Stale                 August 2019

   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Background  . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Standards Action  . . . . . . . . . . . . . . . . . . . . . .   4
   5.  Example Method  . . . . . . . . . . . . . . . . . . . . . . .   4
   6.  Implementation Considerations . . . . . . . . . . . . . . . .   6
   7.  Implementation Caveats  . . . . . . . . . . . . . . . . . . .   8
   8.  Implementation Status . . . . . . . . . . . . . . . . . . . .   9
   9.  EDNS Option . . . . . . . . . . . . . . . . . . . . . . . . .   9
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  10
   11. Privacy Considerations  . . . . . . . . . . . . . . . . . . .  10
   12. NAT Considerations  . . . . . . . . . . . . . . . . . . . . .  10
   13. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   14. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  10
   15. References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     15.1.  Normative References . . . . . . . . . . . . . . . . . .  11
     15.2.  Informative References . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

   Traditionally the Time To Live (TTL) of a DNS resource record has
   been understood to represent the maximum number of seconds that a
   record can be used before it must be discarded, based on its
   description and usage in [RFC1035] and clarifications in [RFC2181].

   This document proposes that the definition of the TTL be explicitly
   expanded to allow for expired data to be used in the exceptional
   circumstance that a recursive resolver is unable to refresh the
   information.  It is predicated on the observation that authoritative
   answer unavailability can cause outages even when the underlying data
   those servers would return is typically unchanged.

   We describe a method below for this use of stale data, balancing the
   competing needs of resiliency and freshness.

   This document updates the definitions of TTL from [RFC1034] and
   [RFC1035] so that data can be kept in the cache beyond the TTL