Les Mikesell <lesmikesell at gmail.com> wrote: > The versions of IE I've tried have been very good at this > although it doesn't work for other stock windows apps. You > may need to make sure that ICMP 'unreachable' packets are not > firewalled so down hosts are detected quickly. Okay, now you're getting somewhere. Before, all you were talking about was some arbitrary logic. If MS IE expects an ICMP unreachable to be returned before it attempts to use another host, then that would be doable. But even in that case, there is a lot of space between you and the end. And the terms in which a router or other device sends back that ICMP packet is a matter for yet further discussion. In other words, it's still "arbitrary" compared to the absoluteness of a service at an IP. ;-> > You can test it easily by setting up a dummy DNS name with a > bunch of A records where some point to working servers and > some don't. That isn't a "real test" until you are connecting across many ISPs, through many layers of firewalls, routers, etc... As I said, much of this can be done when you control many aspects. You define the timeouts, authority, etc... But for the arbitrary Internet, the terms in which even some ICMP messages are being returned are getting mighty arbitrary. -- Bryan J. Smith Professional, Technical Annoyance b.j.smith at ieee.org http://thebs413.blogspot.com ---------------------------------------------------- *** Speed doesn't kill, difference in speed does ***