Serial numbers

[David Botham]

> -----Original Message-----
> From: bind-users-bounce at isc.org [mailto:bind-users-bounce at isc.org] On
> Behalf Of Brad
> Sent: Monday, February 17, 2003 9:15 PM
> To: comp-protocols-dns-bind at isc.org
> Subject: Serial numbers
> 
> Hi
> 
> I just want to verify something...
> 
> I am of the understanding that serial numbers are only important
between
> authoritive servers and have no real meaning for other dns servers?
> 
> lets say we ahve auth1 and auth2 and remotecache1
> auth1 and 2 are authoritive for a given domain, where remotecache1 is
just
> a
> dns server out in the wilderness somewhere....
> 
> Does remotecache1 look up and compare serial numbers from auth1 or
auth2
> when the TTL expires and it needs to refresh its information? Does
> remotecache1 care at all about the serial number? I would think that
it
> doesnt care what serial number is in the zone.

Brad,

Serial numbers and TTL values are *not* related.

Serial numbers are used by slave servers to determine if the version of
the zone they have loaded is synchronized with the version on the
master.


TTL values are used by caches to determine if the RR they have in cache
is still valid.  Upon expiration of a TTL, the cached data must me
removed from the cache, therefore, subsequent queries for that data must
be obtained from an authoritative source.

Dave...


> 
> Lets say that the given domain was re-delegated to newauth1 and
newauth2.
> They specify a serial number that is lower than the old auth DNS
servers
> had
> in their zone. When the TTL expires, remotecache1 should not care that
the
> new auth DNS servers have a ower serial, and should still update from
the
> newauth1 and 2by going  through the root servers and find the new auth
> nameserverss and query them for the correct information???
> 
> Any input appreciated..
> 
> Brad
> 
> 
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