Every application which has registered to receive messages sent to this group sees the message - contrast with unicast and broadcast .
Servers have to figure out which caches to peer with.
Do without proxy servers altogether, or augment proxy server model by adding indidividual browsers' caches. Finding target server Dealing with communication between the proxy server and the server actually making the resource available. Requires cooperation from server authors and Web server maintainers. Might want to multicast if other sites readily reached, e.g. ac.uk case, or want to peer with other local machines. Might want to peer with other ISPs or other local machines, e.g. LINX case.