On the Formation of Multi-Layer Hierarchies

The application of hierarchy in large and dynamic networks improves scalability, survivability and robustness of these networks. Protocol designers have thus introduced mechanisms to automatically create and maintain hierarchical network structures. Existing work, however, is limited to forming only 2-layer structures, even though more than two layers are becoming increasingly necessary for larger networks. Furthermore, the majority of approaches focus on providing robustness in dynamic environments, and largely ignore the quality of the hierarchy formed. Such a design philosophy may result in hierarchy that actually degrades network performance. In this paper we present a general framework for the formation of multilayer hierarchies subject to network performance and hierarchy design requirements. We show the benefits of multilayer hierarchy in the automatic creation of more than two level routing domains. Furthermore, we show that our hierarchy framework can generate very good multilayer routing hierarchies that can minimize routing overhead.