Comparative Performance Evaluation of Different Data Link and Network Protocol Combinations in Local Area Networks

George Pavlou

University College London

This report describes a protocol performance evaluation study using simulation. A simulator has been designed and implemented, simulating the functionality and operation of the Link and Network Layer protocols of a communications environment. The developed simulator has then been used to obtain and analyse data on protocol performance. The protocols considered in this study were the Link Layer Logical Link Control (LLC) protocol of the Local Area Network (LAN) reference model and the Network Layer CCITT X.25 packet-level protocol. LLC supports two different types of link layer services: connectionless (CL) and connection-oriented (CO). The simulator's operation reflects these two basic protocol strategies. The X.25 network (packet) layer protocol operation was assumed to cause least system overhead so that the obtained data reflect mainly the two types of the LLC provided services. Conclusions concerning the LLC protocol operation are presented and the way these influence CL and CO services in a LAN environment is also outlined.

Thesis submitted for the degree of Master of Science, University College London, September 1986.