1. In a computer network having a plurality of communicatively interconnected nodes, a method of preparing a group distribution graph for multicast transmission of packet to a group of nodes in the plurality of nodes, comprising: (a) preparing a spanning tree that includes every node in the plurality of nodes; and (b) preparing a group distribution graph patterned after the spanning tree by evaluating a node in the group distribution graph to determine whether the node is included in the group of nodes and if the node is not included in the group of nodes, and (i) if the node has exactly one neighboring node in the group distribution graph, then removing the node from the group distribution graph; or (ii) if the node has exactly two neighboring nodes in the group distribution graph, then removing the node from the group distribution graph by prescribing direct communication between the neighboring nodes using a communication path that does not include the node being removed.