A Performance Model of the OSI Communication Architecture

The analytical model proposed in this paper aims at predicting the performance of software implementations which would be built according to the OSI basic reference model, The model uses the peer protocol standard of a layer as the reference description of an implementation of that layer. The model is basically a closed multiclass multichain queueing network with a processor-sharing center modeling process contention at the processor and a delay center modeling times spent waiting for responses from the corresponding peer processes. Each individual transition of the protocol constitutes a different class and each layer of the architecture forms a closed chain. Performance statistics include queue lengths and response times at the processor as a function of processor speed and the number of open connections. It is shown how to reduce the model should the protocol state space become very large. Finally, numerical results based upon the derived formulas are given.