a data structure is stored in a memory of a router , the router located along a path between a source end station and a plurality of destination end stations in a multicast distribution tree . in response to receipt of trace packets containing a listing of network devices in the multicast distribution tree , the data structure is updated . when the source end station desires to send a multicast packet , it transmits a packet to the router . the router then writes the path information stored in the data structure into the packet . such path information may include a tree list that specifies the arrangement of network devices along the multicast distribution tree and an address list that specifies the internet protocol addresses of these network devices along the multicast distribution tree . by storing the complete description of the network devices of the multicast distribution tree in the packet , routing demands on the devices along the multicast path are minimized .