A system and method for probing a plurality of clients for a rate appropriate for multicasting is described. In one implementation, test data is sent by a server to a plurality of clients. A rate, R.sub.i, based at least in part on a rate at which test data was received, is sent by at least some of the plurality of clients to the server. A rate, R.sub.0, at which an image is to be sent to the plurality of clients, is then calculated as a function of at least some of the R.sub.i.