Lookahead routing for ring networks with random extra links

We study the performance of ring topology networks enhanced with additional, randomly assigned links. In particular, we consider unidirectional and bidirectional rings where each node has an extra link to another node chosen randomly. Scalable routing algorithms with various degrees of lookahead are proposed, and it is shown that a small increase in lookahead can significantly improve the performance (such as the number of hops, delay and throughput) compared to the simplest greedy routing algorithm. It is also shown that with such routing, the ring networks with random assignment of extra links can outperform (with respect to both throughput and delay) the networks where the distance between pairs of nodes connected by an extra link is constant. The results of our study also show that the average number of hops in a large ring network with random extra links is close to a theoretical lower bound when the shortest path routing is used.