Limiting memory usage

[phn at icke-reklam.ipsec.nu]

bert hubert <ahu at ds9a.nl> wrote:
> In article <aa9f60$b09 at pub3.rc.vix.com>, phn at icke-reklam.ipsec.nu wrote:
>> 
>> bert hubert <ahu at ds9a.nl> wrote:
>>> In article <aa5n2v$1hj at pub3.rc.vix.com>, phn at icke-reklam.ipsec.nu wrote:
>> 
>>>> I don't think you can (in a reasonable way) limit a nameservers
>>>> memory hunger. It's a function of the clients usage and TTL values
>>>> set in the RR.  Trying to enforce lower TTL will break the
>>>> original RR-publishers suggestion.
>> 
>>> DJBDNS dnscache does this just fine. You tell it how much memory it should
>>> use and it uses exactly that, dropping old entries to store new ones.
>> 
>> 
>> A nameserver is _supposed_ to cache data up to the time given
>> in the original TTL. By silently truncationg the cache it breaks
>> the function it's supposed to do.

> It will answer your question just fine. It has to go out on the net to do
> so. So you are claiming that only a nameserver with infinite memory is rfc
> compliant.. boy.

The DNS design builds upon caching as a vehicle to speed up accesses.
Time to cache is set by the publisher of data. Now this may lead to
a conflict where a nameserver is "too busy" for it's avaliable memory/TTL.
This is an admin error. Any nameserver that is correct configured
will meat a balance where old entries times out in teh same pace as
new ones is stored.

Trying to limit memory usage is trying to fix the problem in the wrong end.
Aggree that one has to, in order to keep services up in the short run.
The solution is to BMM.

There is no _demands_ that any nameserver always must be able to keep
it's cache intact, shure. But a nameserver that randomly drops whatever
it feels for is no good solution.

How would you like a car that drops a passanger whenever the loading 
on the engine goes above 90% ?

Caching is in the design for a reason. Systematically overriding it _is_
breaking standards.


> Regards,

> bert> 


> -- 
> http://www.PowerDNS.com/pdns  Try our new database driven nameserver! 
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-- 
Peter Håkanson         
        IPSec  Sverige      (At the Riverside of Gothenburg, home of Volvo)
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