Here is a scenario... Our Architecture consists of 3 tiers, Web tier (Apache 2.2 version) - 2 Webservers, Apptier (weblogic 10 MP1 Clustered environment - 4 app servers on 4 physical machines ), sql server 2000 - DB. We were asked to assign the Messaging from Multicast to Unicast. When we change the cluster from Multicast to Unicast, the conosle - out logs gives the output as changed. But apache error logs says PROTOCOL ERROR - Backend server not responding. " As we did not bounce the servers after changing, As according the console after activating the change it did not ask for a restart. I dont know what happened, as we did not see the issue while doing the same work on Pre-PROD. Help is appreciated ..