> How it compares is that it actually works when WAN links go down. For an > explanation as to why google for multicast dns. http://support.microsoft.com/default.aspx?kbid=263558 Default IE version 4+ DNS cache timeout is set to 30 minutes as indicated in the above KBA, though it does not mention IE7. So further testing or research would be needed to determine IE7 default values. Apparently someone even wrote a little app to modify this and related settings. http://technize.com/2007/07/11/how-to-change-internet-explorer-dns-cache-kee palive-and-server-info-timeouts/ Obviously that is not a viable solution when you don't control the end users systems. For web applications using web based failover (with or without round robin load balancing) you can something like those fancy appliances that come with Foundry Server Irons, F5 Big IP, Citrix has one, and others but they do not do anything remarkable as already indicated. All they do is modify DNS packets on the fly, with a low TTL of like 5 seconds, usually based on frequent health checks to said application. For maximum reliability you have more than one of these appliances, at least one at two different geographic hosted sites and you point the NS records for the (sub)domain in question to these appliances. This type of service is commonly called Global Server Load Balancing (GSLB). I have written a script to mimic this type of behavior. It runs an HTTP health check and looks for a particularly defined response. If it fails to receive the desired response it modifies the DNS record(s) to use the "failover" address(es). On a later health check that does receive the desired response it modifies the DNS record(s) to use the "primary" address(es). If you do a google search for GSLB you will also find this page. http://www.tenereillo.com/GSLBPageOfShame.htm If DNS SRV records were even to become fully utilized and integrated into all/most internet applications that would be really awesome and remove the need for many of these failover/loadbalancer applications and appliances. The likelihood of this happening is pretty negligible I think. I would bet on IPv6 becoming mainstream long before DNS SRV records.