A software system to study network algorithms was implemented on UNIX. Each part of a network algorithm is written as a single C program which becomes a virtual node in the network. During a simulation, all virtualized nodes run as separate processes on a single PDP 11/40. Inter-node communication is carried out with procedures local to each node, to send and receive inter-node messages to and from a message queuing process, Communication between nodes is effected by use of virtual links which are specified in the simulated network's topology. The links are implemented on inter-process pipes between the message queuing process and the node processes
