Wiretap: an experimental multiple-path routing algorithm
David L. Mills · ACM SIGCOMM Computer Communication Review · 1989
This paper introduces Wiretap, an experimental routing algorithm which computes maximum-likelihood diversity routes for packet-radio stations sharing a common broadcast channel, but with some stations hidden from others. The wiretapper observes the paths (source routes) used by other stations sending traffic on the channel and, using a heuristic set of factors and weights, constructs speculative paths for its own traffic. The algorithm is presented as an example of maximum-likelihood routing and database management techniques useful for richly connected networks of mobile stations. Of particular interest are the mechanisms to compute, select, rank and cache a potentially large number of speculative routes when only limited computational resources are available.A prototype implementation has been constructed and tested for the AX.25 packet-radio channel now in widespread use in the amateur-radio community. Its design is similar in many respects to the SPF algorithm used in the ARPANET and NSFNET backbone networks, and is in fact a variation of the Viterbi algorithm, which constructs maximum-likelihood paths on a graph according to a weighted sum of factors assigned to the nodes and edges.