The DNS thundering herd problem
draft-muks-dnsop-dns-thundering-herd-00

Document Type Active Internet-Draft (individual)
Authors Mukund Sivaraman  , Cricket Liu 
Last updated 2020-06-25
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Internet Engineering Task Force                             M. Sivaraman
Internet-Draft                             Akira Systems Private Limited
Intended status: Experimental                                        Liu
Expires: December 27, 2020                                      Infoblox
                                                           June 25, 2020

                    The DNS thundering herd problem
                draft-muks-dnsop-dns-thundering-herd-00

Abstract

   This document describes an observed regular pattern of spikes in
   queries that affects caching resolvers, and recommends software
   mitigations for it.

Status of This Memo

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   This Internet-Draft will expire on December 27, 2020.

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Table of Contents

   1.  Problem Description . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements Notation . . . . . . . . . . . . . . . . . . . .   4
   3.  Mitigations . . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  Combine identical queries to upstream nameservers . . . .   4
     3.2.  Include noise in response TTLs from caching resolvers . .   4
     3.3.  Other mitigations . . . . . . . . . . . . . . . . . . . .   4
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   5.  IANA considerations . . . . . . . . . . . . . . . . . . . . .   5
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     7.1.  Normative references  . . . . . . . . . . . . . . . . . .   5
     7.2.  Informative references  . . . . . . . . . . . . . . . . .   5
   Appendix A.  Change history (to be removed before publication)  .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Problem Description

   Typically, DNS caching resolvers prepare answers for multiple clients
   from a single cached RRset [RFC1034].  Depending on when in time the
   clients make their queries, caching resolvers reply with lower and
   lower valued TTLs, before the cached RRset from which answers are
   prepared expires.  Clients themselves may cache and use their copies
   of RRsets until the TTL that the resolver replied with expires.  A
   key property is that all these copies of answers, and the cached
   answer from which they are prepared, expire at the same absolute
   time.

   As an example, consider the following query sequence received by a
   resolver from 10 clients all querying for a popular
   www.example.org./A RRset.  We use this example to illustrate two
   kinds of spikes in queries.

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   +--------+------------+--------+------------------------------------+
   | Client | Query time | Answer | Notes                              |
   |        | (seconds   | RRset  |                                    |
   |        | since      | TTL    |                                    |
   |        | epoch)     |        |                                    |
   +--------+------------+--------+------------------------------------+
   | C1     | 1591441620 | 600    | Answer was not found in cache.     |
   |        |            |        | Resolver performs a resolution     |
   |        |            |        | and caches authoritative answer    |
   |        |            |        | with TTL=600.                      |
   | C2     | 1591441626 | 594    | Answered from cache.               |
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