Two-Layer Modeling for Local Area Networks

We built a two-layer performance model of LAN (local area network). Our performance model consists of a MAC (media access control) layer submodel and transport layer submodels. We employ a multiple-queue, cyclic-service model for the token passing MAC layer, and a closed queueing network model for the transport layer. To deal with acknowledgment traffic with priority over data messages, we have devised an MVA priority approximation for the case where the priority can change at each queue. We propose an iterative solution algorithm for this two-layer performance model. Our method is applied to five models of communication systems: a symmetric-load, piggybacked acknowledgment model, a symmetric-load, explicit acknowledgment model, full-duplex communication models (without and with priorities), and a client/ server model. System performance measures such as throughput and mean message delay computed from our analysis are compared to the simulation results over a wide range of parameters. In most numerical examples, our approximate analysis is shown to be within 90 percent confidence intervals in the mean message delay and within a few percent error in the throughput. © 1988 IEEE