It's unclear from the documentation why you should use Unicast rather than Multicast in a WebLogic cluster. Anyone have experience using either and the benefits of moving to Unicast?
The main difference between Unicast and Multicast is as follows
Say you have three servers (MS-1,MS-2,MS-3) in a cluster. If they have to communicate with each other, then they have to ping (i.e. heartbeats ) the cluster master for informing it that they are alive.
If MS-1 is the master then MS-2 and MS-3 would send the ping to MS-1
In Multicast, there is no cluster master. Instead each server has to ping each other to inform everyone that they are alive.
So MS-1 would send the ping to MS-2 & MS-3 and at the same time MS-2 would send the ping to MS-1 & MS-3 and MS-3 would ping MS-1 & MS-3.
Thus, in multicast there are more pings sent which makes the congestion in sending the pings much heavier compared to unicast. Because of this, WLS recommends using Unicast instead for less congestion in the network: Oracle Docs: Communications In a Cluster