1. A method of class network routing in a network to allow a compute processor in a network of compute processors located at nodes of the network to multicast a message to a plurality of other compute processors in the network comprising: dividing a message into one or more message packets which pass through the network; adding a class value to a message packet; at each switch in the network, using the class value as an index to at least one table whose stored values, or as an input to an algorithm whose generated values, determine actions performed by the switch on the message packet.