Application of learning automata theory to telephone traffic routing and control is described. Improved network performance is demonstrated through the comparative simulation of learning automata routing and the existing fixed rule alternate routing in simple telephone networks. Learning automata routing results in significantly lower blocking probability when selected overload conditions prevail and additional capacity exists elsewhere in the network.

Application of Learning Automata to Telephone Traffic Routing and Control

Dispersity routing distributes the data between a source and destination over several paths through the network, rather than concentrating it on a single path. Non-redundant and redundant dispersity routing techniques are described. By using dispersity routing on virtual circuits, that operate similar to the TASI circuits used in voice networks, long, bursty data sources can share channels without buffering in the network or resequencing packets. This sharing ability is demonstrated by an example that has characteristics and requirements similar to those in medical image transmission. Dispersity routing is better able to deal with unexpected network loads than conventional, single channel systems. This ability is demonstrated by allowing a rogue source to upset the expected statistical utilization of the network.

Dispersity routing in high-speed networks

Computer communication networks is a subject of increasing interest. Although a variety of surveys have appeared which describe network alternatives and explain far-reaching technological possibilities achievable with networking, effectwe network utilization requires an understanding of network functional components and thmr interactions. Describing these issues is the objective of this paper. To do this, the three basic network sharing alternatives are first identified. For those two which involve host/host communication, the basic traffic types are discussed. The communications alternatives are then detailed and a hypothesis is advanced that the "packet-switched" networks provide the most appropriate technology for supporting multimodal traffic between hosts. Consequently, a careful examination of the functional components of the packet switch is provided This provides a basis for describing factors which must be considered in implementing a packet-switched subnetwork. Additional issues which should be considered when several hosts and, perhaps, the communications subnetwork are under the control of a single administrative organization are then discussed. The paper concludes with a description of three networking examples and an identification of areas for future research.

Computer Communication Networks: Approaches, Objectives, and Performance Considerations

The routing and flow control techniques developed for wide-area, local-area, and metropolitan-area networks are surveyed. A classification that shows the characteristics that are desirable for high-speed wide-area networks is developed. On the basis of the classification, techniques that should and should not be considered for future high-speed networks are identified. In particular, an attempt is made to determine the effect of increasing transmission rates on the routing and flow control algorithms that are used in packet-switched networks. >

Routing and flow control in high-speed wide-area networks

This paper deals with a distributed adaptive routing strategy which is very simple and effective, and is free of a ping-pong-type looping in the presence of network failures. Using the number of time intervals required for a node to recover from a network failure as the measure of network's adaptability, performance of this strategy and the ARPANET's previous routing strategy (APRS) is comparatively analyzed without resorting to simulation. Formulas of the exact number of time intervals required for failure recovery under both strategies are also derived. We show that i)the performance of the strategy is always better than, or at least as good as, that of APRS, and ii) network topology has significant effects on the performance of both strategies.

Performance Analysis of Distributed Routing Strategies Free of Ping-Pong-Type Looping

The concept of a netted or distributed communications system is significant because it offers a major advantage over conventional communications systems, i.e., a better chance of providing surviving lines of communication after an attack on the system. During and after an attack, however, an effective adaptive routing technique is necessary to adjust the routing tables of the message-switching control system to the changing situation. Previously investigated adaptive routing techniques are shown to be insufficient for the task, and a number of promising alternatives are formulated and investigated such as some stochastic techniques, which use information on messages passing through the network to adjust the tables, and some deterministic techniques, which use dynamic programming or graph-theoretic algorithms to recalculate changes in the tables from observed changes in the network. Each alternative has operational advantages, which make it good for certain types of communications systems, and certain disadvantages if applied to others. Regions of applicability and inapplicability, with respect to the above system parameters, are given for the various techniques. Recommended techniques are specified for two currently proposed applications of distributed communications systems. A number of research areas are pointed out in which further efforts in the analysis and simulation of adaptive routing techniques will have useful payoffs in the design of future distributed communications systems.

R. Mobley

Papers

Adaptive Routing Techniques for Distributed Communications Systems