negative response cache (qti)

[Mark.Andrews at nominum.com]

> 
> On Tue, 15 Aug 2000 Mark.Andrews at nominum.com wrote:
> 
> | Date: Tue, 15 Aug 2000 11:33:58 +1000
> | From: Mark.Andrews at nominum.com
> | To: Frank Liu <liug at mama.indstate.edu>
> | Cc: comp-protocols-dns-bind at uunet.uu.net
> | Subject: Re: negative response cache (qti) 
> | 
> | 
> | > 
> | > 
> | > I understand that the negative response from my dns server (such
> | > as non exist host) will be cached on the customers' dns servers.
> | > This means even after I add the host to my dns, the users
> | > out there on the Internet may still get "no such host".
> | > my question is what I can do to make this cache as short (time)
> | > as possible. which ttl controls that?
> | > thanks! frank
> | 
> | 	SOA minimum field.  See RFC 2308.
> | 
> | 	Not that this is generally a problem w/ NXDOMAIN.  Generally
> | 	people do not ask names they do not know about so nothing
> | 	is cached in the first place.  It only becomes a problem
> | 	when you advertise a machine *before* it exists in the DNS,
> | 	or your secondaries are not keeping up to date.
> 
> Also note that this behaviour depends on the version of the remote caching na
> meserver.
> If the remote NS is running BIND <=8.1.2, they will use a compiled in default
> negative caching TTL, and not what you configured into the minimum field.

	10 minutes max.

> 
> Inversely, if the primary is running BIND <=8.1.2 , using the minimum field
> for default TTL, this will be interpreted by caches running BIND >=8.2
> as negative caching TTL. Some zones with minimum to 1D or longer
> (as default TTL) may therefore have longer negative caching on some
> remote cached than desired...
> 
	And unless the defaults have been changed in the caching server
	it will be treated as 1 hour.  This is not as bad as you would
	make it appear.

	Mark

> | 
> | 	Mark
> | --
> | Mark Andrews, Nominum Inc.
> | 1 Seymour St., Dundas Valley, NSW 2117, Australia
> | PHONE: +61 2 9871 4742                 INTERNET: Mark.Andrews at nominum.com
> | 
> 
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> 
--
Mark Andrews, Nominum Inc.
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: Mark.Andrews at nominum.com