On Mon, Sep 01, 2003 at 01:49:12PM +0000, Shane Hollis wrote:
> sigh ... i didn't explain myself fully enough ... my concern is not with
> lookups but with changes in caches. I have had a number of situations where
> caching has resulted in DNS changes being a pain in the neck and not
> propogating correctly. This is especially true when working with overseas
> clients.
>
> To sit on the backbone in the USA gives me a quicker dissemination of changes
> to DNS entries. The lookups are heirarchical .. this I know, as you have
> mentioned you look up the closes and work outwards until you find it but
> caching sometimes mucks this up and so to make changes it is easier to start
> with the main servers and work down to the smaller servers, not the other way
> around.
>
> I am working with clients at a corporate level, closer to the main backbone of
> the naming structure, not small sites here. when a change happens it can
> ripple effects back to main servers in the USA. to start the ripple from a
> central position makes more sense if I am trying to get caches changed. DNS
> lookups can be cached, I have had it happen and trying to change those caches
> can be a right pain in the lookup....
I'm afraid I'm with both Nick and David again...
I think you've got yourself all confused, since location has no bearing
whatsoever on how fast or slow DNS changes take effect...
I can change DNS entries for my domain, and they'll be in effect globally,
after the TTL period has expired. this is set to 1 day, for my domain.
therefore, I can guarantee that any changes I make, will be correctly
queried after 24 hours.
I could shorten this if I wanted, and I do, when I am scheduling a change. I
usually drop the TTL back to 12 hours, then 24 hours later, back to about
4 hours. 12 hours later, back to 1 hour, 4 hours later... etc. back to about
1 minute. then I can make a change, wait a few minutes, then set the TTL
back to 24 hours. (this is a recommended practise for high load domains...
I'm not a high load, but it makes sense to know how to do it)
FWIW, DNS has no 'central position'.
"DNS lookups can be cached," - No, DNS lookups *ARE* cached.
As for recursive lookups, how does caching muck this up? How do you define
'main servers' and 'smaller servers' ? there's usually only the
authoritative servers for a domain...
Again, I'll point out, that sitting on a backbone in the US, and sitting
behind a wet piece of string like I do here, has no bearing whatsoever on
how fast or slow DNS changes can be made. DNS is not reliant on bandwidth,
or location....
These comments and questions are not meant to be flamebait... Just an
attempt at getting a clarified look, to perhaps help repair your
understanding..
Mike.
--
Mike Beattie <[EMAIL PROTECTED]> ZL4TXK, IRLP Node 6184
"This isnt Mission Difficult Mr Hunt, this is Mission Impossible.
Difficult should be a walk in the park for you." -- MI:2
