Flow control and deadlock avoidance on the partial optical hypergraph

The optical hypergraph is a distributed network in which each edge of the hypergraph is a multiple-access broadcast medium constructed as a passive optical star coupler. The partial optical hypergraph can be also viewed as a centralized switching network. The nodes with two ports (switch nodes) are centered in one location, and the nodes with one port (external nodes) are distributed within an area of 0-20 km around the switching nodes. The main result of this work is a flow control protocol for an arbitrary traffic pattern, which includes algorithms for preventing overflows, while maintaining the maximum switching capability of the switch nodes. Overflow prevention may cause deadlocks, so an algorithm for avoiding deadlocks is shown. These algorithms are realized at the network interface and, therefore, can operate in realtime at a traffic rate of over 1 Gbit/s per link. This network architecture demonstrates a close relationship between centralized and distributed systems. Potential applications of the partial optical hypergraph are varied and include large distributed databases, metropolitan area networks, factory automation, fault tolerant and realtime networks. © 1990.