"help"

Dear Sirs,
	I am a software devolper working in streaming area. I have devoloped
a mpeg 2 streaming server using rtp which sends mpeg 2 program stream data
on to network. For each unicast user that gets connected to server i create
3 new threads. I have used 4 mbps files for streaming.
	I was able to connect three simultaneous clients with out Qos
problem. But twhen the fourth client just comes in the play back becomes
jerky.
	Can you please tell me what are the things which decides the maximum
number of clients that can be connected to a streaming server.
	What are the optimizations that can be done to make the server more
efficient
	All the commercial servers available claims to support 3000 and
above simultaneous clients ??