Network issue in vsat

In my server-client architecture, I **multicast** 100 MB files to many clients from server via satellite link. Network traversal is through 5 hops. I have the 10Mbps ( i.e. 1250 Kilo Byte per second ) bandwidth link. When I multicast the first file to many client, first hop get the incoming speed is of ~9.0 mbps but the receiver end get the speed of only ~4.2 mbps. All clients are 10mb half duplex. I can see, there is low network usage; But I don't know where exactly. If server is sending at the speed of ~9.0 mbps, then client should got the same speed. I am using the reliable UDP for multicasting. Is there any way to find out, what is the incoming and outgoing bandwidth usage of each hop (for a particular port.) ? Is there exist any tool/utility/application who can serve the purpose. All the hops are at remote location, so that going over there is not possible.