The impact of local policies on the quality of packet routing in paths, trees, and rings

International audienceWe consider the packet routing problem in store-and-forward networks whose topologies are either paths, trees, or rings. We are interested by the quality of the solution produced, with respect to a global optimal solution, if each link uses a (fixed) local policy to schedule the packets which go through it. The quality of the derived solutions is measured using the worst case analysis for two global optimality criteria, namely the maximum arrival date of a packet at its destination (or makespan) and the average arrival date of the packets at their destinations. We consider the setting where n packets, each one having a size (or length) and a destination, are released from the same source. In the case of rings, there exist two paths between the source and a destination. Each packet is owned by a user which chooses a path to its destination. We assume that users are rational: knowing the local policy used by the links and the state of the network, a user chooses the path which minimizes the arrival date of its packet at its destination. We are then interested by the quality of the Nash equilibria obtained