On Distributed Communications Series

I. Introduction to Distributed Communications Networks


This Memorandum briefly reviews the distributed communications network concept and compares it to the hierarchical or more centralized systems. The payoff in terms of survivability for a distributed configuration in the cases of enemy attacks directed against nodes, links, or combinations of nodes and links is demonstrated.

The requirements for a future all-digital-data distributed network which provides common user service for a wide range of users having different requirements is considered. The use of a standard format message block permits building relatively simple switching mechanisms using an adaptive store-and-forward routing policy to handle all forms of digital data including "real-time" voice. This network rapidly responds to changes in the network status. Recent history of measured network traffic is used to modify path selection. Simulation results are shown to indicate that highly efficient routing can be performed by local control without the necessity for any central--and therefore vulnerable--control point.

A comparison is made between "diversity of assignment" and "perfect switching" in distributed networks. The high degree of connectivity afforded allows the use of low-cost links so unreliable as to be unusable in present type networks.