Les Mikesell <lesmikesell@xxxxxxxxx> wrote:
> Web browsers (IE at least) tend to be very good about
> handling failures if you give out multiple IP addresses for
> a name and one or more locations does not respond.
Er, um, er, it's still a little arbitrary and not exactly
correct. Furthermore, default NT5.x (2000+) operation is to
"hold down" DNS names for a default of 2 mintues, even ones
that are round-robin, if just 1 doesn't resolve. It's a
really messy default in the Windows client that causes a lot
of issues.
I think you might be thinking of ADS name resolution, which
is a little different than DNS (even though Microsoft says
it's DNS ;-). I could be wrong though, but that's what my
experience suggests.
> There are expensive commercial DNS servers like F5's
> 3dns that will test for service availability and modify
> the response if a location is down. Some free variations
> may also be available.
But that still doesn't solve the propogation issue. The most
you could hope for is to find a partner who can seed the
major caching servers of the major providers. But there's
still the downstream issue.
> However, most applications cache the DNS response
internally
> regardless of the TTL and won't automatically pick up a
change
> unless you exit the app and restart it.
Exactomundo, let alone if the OS/resolver or whatever "cached
value" at the "non-authority" honors the TTL in the first
place.
Again, the repeat theme here is that it must be solved at the
layer-3/IP level. You can't hope to solve it at the
application levels, like with DNS.
--
Bryan J. Smith Professional, Technical Annoyance b.j.smith@xxxxxxxx http://thebs413.blogspot.com
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*** Speed doesn't kill, difference in speed does ***
