On Distributed Communications Series

III. Determination of Path-Lengths in a Distributed Network

Summary

Results of investigations into the behavior of distributed communications networks under various loading conditions are reported. A mathematical model and a deterministic equation for predicting the distribution of message path-lengths are derived and evaluated. A SCAT-encoded[1] simulation program that corrects deficiencies of earlier simulations is described.

An "input-choking" doctrine, together with a short, purposeful delay of messages passing through each station (when necessary), proved to be a powerful device in preventing loss of messages within networks operating at high loading ratios. The decrease in delay and in message-flow rate caused by the doctrine was negligible.

For the networks studied, a policy of dropping messages that have traversed paths greater than twice the longest possible path between the extremities of the network, resulted in a message dropout rate of less than one in 100,000,000 when the networks were operating at normal, and even higher than normal, loadings. At low loadings there were even fewer messages dropped.


[1] Ibid.


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