Routing algorithms based on shortest paths

This talk is an overview of adaptive quasistatic routing algorithms for communication network that are based on shortest path computations. We first consider single path algorithms such as the one currently operating on the ARPANET and highlights their advantages and inherent limitations. We then focus on an algorithm that allows multipath routing. During the algorithm each node maintains a list of paths along which it sends traffic to each destination together with a list of fractions of total traffic that are sent along these paths. At each iteration a minimum marginal delay path to each destination is computed and added to the current list if not already there. Simultaneously the corresponding fractions are updated in a way that reduces average delay per message. The algorithm is capable of employing second derivates of link delay functions thereby providing automatic scaling with respect to traffic input level. It can be implemented in both a distributed and centralized manner, and it can be shown to converge to an optimal routing at a linear rate.