multicast video streaming server?

i have 8 ip cameras on a wan each on a 6mb connection.

i have a problem when more than5 users try to connect to the camera there is a huge slowdown on the network.

i need to come up with a multicast solution at the main site that collects all these streams and then speads them from a single location. does anyone have any experience with this?

I have done a bit on this. I found the best way to do it was to use 1fps, it was only for basic CCTV use though. 20 30fps just kills the bandwith in a big way.

im going to have 30+ users connection to the one camera, is there any way to centralise it a bit more, id say 1fps could still eat it up.