Les Mikesell lesmikesell@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.