A polling model is a system of multiple queues accessed by a single server in cyclic order. Polling models provide performance evaluation criteria for a variety of demand-based, multiple-access schemes in computer and communication systems. This paper presents an overview of the state of the art of polling model analysis, as well as an extensive list of references. In particular, single-buffer systems and infinite-buffer systems with exhaustive, gated, and limited service disciplines are treated. There is also some discussion of systems with a noncyclic order of service and systems with priority. Applications to computer networks are illustrated, and future research topics are suggested.

Queuing analysis of polling models

A variation on the carrier-sense, multiple-access/collision-detection (CSMA/CD) protocol for local-area, random-access broadcast networks is presented. The new protocol supports any mix of voice and data traffic, and has an upper bound on the delay of periodic traffic. In conventional CSMA/CD systems, statistical fluctuations in the transmission delay may cause disruptions in reconstructed voice waveforms. This does not occur with the new protocol. With this protocol, data sources use conventional CSMA/CD techniques to access the channel, while voice sources use a subset of these protocols, and appear to acquire a time-division multiplexed (TDM) slot. As in TDM systems, the entire system capacity can be used by the periodic sources. Unlike TDM systems, periodic slots are repositioned when other transmissions interfere with them, timing discrepancies between sources can be tolerated, and a centralized controller is not required to assign slots. Simulations are used to compare the delays in this system with those in conventional CSMA/CD systems. It is shown that at link utilizations of 0.9, voice sources can operate in a time-assignment, speech-interpolation mode. The effect of periodic traffic on conventional CSMA/CD protocols is also determined.

A variation on CSMA/CD that yields movable TDM slots in integrated voice/data local networks

Symmetric queues served in cyclic order

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 discusses several important performance problems in the design of local-area networks. The questions discussed relate to various aspects of architecture, design, and implementation: (1) the delaythroughput characteristics of the medium access protocols, (2) the performance of local-area networks on which a file server provides file storage and retrieval services to intelligent workstations, and (3) timing problems in local-area network adapters. Since the paper does not primarily addressth e performance analyst, it is descriptive in nature; analytic details are omitted in favor of a more intuitive explanation of the relevant effects.

J. Hayes

Papers

Local distribution in computer communications