Cache Entries
Robert Spangler
lazydog at zoominternet.net
Wed Apr 18 20:43:41 UTC 2007
On Tue April 17 2007 20:55, Kevin Darcy wrote:
> Robert Spangler wrote:
> > Hello,
> >
> > A question has been raised about TTL and cached entries. After the
> > first request do the following request reset the cache TTL or does the
> > entry continue to count down until it expires and once it reaches zero
> > the cache is is cleared until the next request which starts the process
> > all over again?
>
> Once an answer is cached, you answer from the cache until the TTL
> expires, at which point you go and fetch a fresh set of records. The
> only way I could see the TTL being "reset" is if the same data was seen
> in a response to some other query (e.g. part of a CNAME chain) that is
> of equal or higher credibility/trustworthiness/rank (a la RFC 2181).
> Then maybe the new data would "refresh" the old cache TTLs. But I
> haven't actually tested this in practice. Modern BINDs have a lot of
> protection against cache poisoning, so it's possible that such
> "refreshes" will no longer occur.
Thnx. This was my thinking just wanted to make sure that I was thinking along
the correct lines. I will admit that I never thought of the CNAME idea you
listed above.
--
Regards
Robert
Smile... it increases your face value!
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