negative response cache (qti)

[Mathias Koerber]

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 nameserver.
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.

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...

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

Mathias Koerber	  | Tel: +65 / 471 9820    |   mathias at staff.singnet.com.sg
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