QoS routing for anycast communications: motivation and an architecture for DiffServ networks

Much research in QoS routing has focused on the unicast communication paradigm. However, another communication paradigm - anycasting - has grown in importance. In the anycast paradigm, one endpoint is specified and the other is selected from a set of "equivalent" endpoints. An anycast service in a QoS-based network requires selection of both an endpoint and a path that satisfies a QoS constraint. This article provides background material on anycasting in both best-effort networks and QoS-based networks. We then focus on the differentiated services QoS model, and present the design of a QoS-based anycasting architecture consistent with that model. Via simulations, we explore the design options implied by the architecture, including signaling protocols, server selection/sorting algorithms, and resource reservation granularity. We conclude by highlighting open problems in the emerging area of QoS-based anycasting