RFC 2308 (rfc2308) - Page 1 of 19
Negative Caching of DNS Queries (DNS NCACHE)
Alternative Format: Original Text Document
Network Working Group M. Andrews
Request for Comments: 2308 CSIRO
Updates: 1034, 1035 March 1998
Category: Standards Track
Negative Caching of DNS Queries (DNS NCACHE)
Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (1998). All Rights Reserved.
Abstract
[RFC 1034] provided a description of how to cache negative responses.
It however had a fundamental flaw in that it did not allow a name
server to hand out those cached responses to other resolvers, thereby
greatly reducing the effect of the caching. This document addresses
issues raise in the light of experience and replaces [RFC 1034 Section
4.3.4].
Negative caching was an optional part of the DNS specification and
deals with the caching of the non-existence of an RRset [RFC 2181] or
domain name.
Negative caching is useful as it reduces the response time for
negative answers. It also reduces the number of messages that have
to be sent between resolvers and name servers hence overall network
traffic. A large proportion of DNS traffic on the Internet could be
eliminated if all resolvers implemented negative caching. With this
in mind negative caching should no longer be seen as an optional part
of a DNS resolver.
Andrews Standards Track