Two-layer modeling for local area networks

A two-layer performance model of a local-area network (LAN), consisting of a media-access control (MAC) layer submodel and transport layer submodels, is presented. A multiple-queue cyclic-service model of the token-passing MAC layer is used along with a closed-queueing network model for the transport layer. To deal with acknowledgement traffic with priority over data messages, a mean-value analysis (MVA) priority approximation is devised for the case where the priority can change at each queue. An iterative solution algorithm is proposed for this two-layer performance model. The method is applied to five models of communication systems: a symmetric-load, piggybacked acknowledgement model: a symmetric-load, explicit-acknowledgement model; full-duplex communication models (without and with priorities); and a client/server model. System performances measures such as throughput and mean-message delay, computed from the analysis, are compared to the simulation results over a wide range of parameters. In most numerical examples, the approximate analysis is shown to be within 90% confidence intervals in the mean-message delay, and within a few percent error in the throughput