Re: help with BIND SRV
On Thursday 07 October 2004 22:23, Nate Duehr wrote:
> - They don't understand that there might be multiple DNS servers between
> their top-level and the machine they're servicing (3X and 4X TTL)
Let's say that I have my local (desktop if you prefer) resolver (which I'll
call A is pointed to a caching nameserver B.
Caching nameserver B forwards all of it's DNS requests to their ISP's larger
caching server C.
Caching server C makes queries to the appropriate authoritative server D.
So the DNS query goes:
A->B->C->D
D replies to C with a record having TTL of 3600. C forwards request to B, B
gives answer to A ... TTL 3600.
In 1800 seconds the only server in the above loop that would serve a TTL of
3600 is D (since it is authoritative). B and C will both have decremented
their TTL by 1800 seconds and will respond with a TTL of 1800 seconds. A
should have decremented the TTL in it's resolver cache as well though some
applications and/or operating systems are buggy in this regard.
I have never seen behaviour that you are suggesting can happen nor can I
imagine any way in which it can happen.
We had a similar discussion not too long ago starting at
http://www.mail-archive.com/debian-isp%40lists.debian.org/msg11986.html
... I never really followed up on that one, but I still believe you're
wrong ;-)
BTW, forwarding (to an appropriate server) is an excellent way to speed up DNS
resolution, I use it frequently.
--
Fraser Campbell <fraser@wehave.net> http://www.wehave.net/
Georgetown, Ontario, Canada Debian GNU/Linux
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