A Characterization of universal stability in the adversarial queuing model

We study universal stability of directed and undirected graphs in the adversarial queueing model for static packet routing. In this setting, packets are injected in some edge and have to traverse a predefined path before leaving the system. Restrictions on the allowed packet trajectory provide a way to analyze stability under different packet trajectories. We consider five packet trajectories, two for directed graphs and three for undirected graphs, and provide polynomial time algorithms for testing universal stability when considering each of them. In each case we obtain a different characterization of the universal stability property in terms of a set of forbidden subgraphs. Thus we show that variations of the allowed packet trajectory lead to non-equivalent characterizations. Using those characterizations we are able to provide also polynomial time algorithmsfor testing stability under the ntg-lis protocol