Re: DNS Server That Constantly Refreshes Cache?

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DNS Server That Constantly Refreshes Cache?
\ Will (21 Feb 2008)
. \ Joshua Smith (21 Feb 2008)
. \ Matus UHLAR - fantomas (21 Feb 2008)
. . \ Kevin Darcy (21 Feb 2008)
. \ Barry Margolin (22 Feb 2008)

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Subject:	Re: DNS Server That Constantly Refreshes Cache?
Group:	Bind-users
From:	Barry Margolin
Date:	22 Feb 2008

In article <fpktfi$13nj$1>, Kevin Darcy <kcd>
wrote:

> Matus UHLAR - fantomas wrote:
> > On 18.02.08 17:52, Will wrote:
> >
> >> I'm looking for a DNS server that will proactively go out after a cache
> >> record expires and refresh its cache on its own. The result would be a
> >> server with an enormous memory cache of prefetched records, which should
> >> always have up to date records in its cache, even when the domain has not
> >> been used internally for weeks or months. Note, I'm NOT referring to a
> >> standard DNS server with a large cache setting. I'm looking for a
> >> proactive server behavior to prefetch records whose DNS cache is reaching
> >> expiration.
> >>
> >> Does such a product exist for Windows or Unix?
> >>
> >
> > this way you will end up having all dns records on the net in the cache and
> > still refresing them even if you don't need them.
> >
> What an anti-social thing to do.
>
> If I set the TTL of one of my RRsets to 60 seconds, it doesn't mean I
> expect you (and everyone like you) to query it *every* 60 seconds
> *forever*. The 60-second TTL is only for peak usage times, where
> load-balancing/sharing is necessary. I expect the query traffic to fall
> off during non-peak times, in parallel with the dropoff of actual
> production volume.

If this were done adaptively it could work well.

The caching server could keep track of which records it's received
frequent requests for. If a record has been accessed numerous times
since it was last cached, it would be a good idea to prefetch it. But
if lookups have dropped off, it shouldn't bother.

The idea is similar to disk prefetching in filesystem and virtual memory
systems.

--
Barry Margolin, barmar
Arlington, MA
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