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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