Optimum schedule problems in store and forward networks

Store and forward networks are a convenient model to represent problems in the areas of message communication and traffic control. The goal of a typical scheduling problem is to devise an optimal strategy to send messages from their source sites into their sink ones following paths in the network. In this paper the computational complexity of such a problem is analyzed in the cases of fixed and dynamically variable paths. Unfortunately, it turns out that both of the versions of the considered problem are NP-complete even under very restrictive hypothesis. Moreover, they are not approximable, that is, they can be solved only by polynomial-time heuristic algorithms such that the distance between the exact and the approximate solution is not bounded by any fixed value