Let us build system-friendly networks-build them hierarchically

Hierarchical systems address many hardware and software problems encountered by designers of large communication and computing systems; hence, interest in this field continues to grow. A diversity of hierarchical networks have been proposed in the literature. This paper introduces a framework for classifying hierarchical topologies. Using the framework, we survey existing topologies in an organized fashion and identify the major design choices. We show how new hierarchical networks can be generated by varying architectural parameters in the framework. The performance evaluation of the numerous topologies remains a non-trivial task; we describe some preliminary efforts in that direction.