Les Mikesell <lesmikesell at gmail.com> 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 at ieee.org http://thebs413.blogspot.com ---------------------------------------------------- *** Speed doesn't kill, difference in speed does ***