Asynchronous Transfer Mode (ATM) has been recommended and has been accepted by industry as the transfer mode for Broadband network. Currently, large scale effort has been undertaken both in the industry and academic environment to design and build high speed ATM networks for corporate bodies. These networks are meant to support both real-time and non-real time applications with different quality of service (QoS) requirements. The resources to support the applications QOS requirements are typically limited and therefore the need to dynamically allocate resource in a fair manner becomes inevitable. In this work, an evaluation is carried out on the performance of enterprise-wide network that its backbone is based on leased trunk. The performance of the leased trunk was evaluated when loaded with homogeneous and heterogeneous traffic. The evaluation was carried out in order to determine the exact effect of traffic overload on resources-trunk transmission capacity and buffer. The aim is to define the optimum loading level and the associated QoS parameter values. A typical network was adopted, modeled and simulated in MATLAB environment using Simulink tool and results obtained were analyzed using Microsoft Excel.

The fundamental purpose of a communication system is to exchange information between two or more devices. Telecommunication has witnessed unprecedented and explosive growth overthe years in the area of services delivered and technology. The key parameters of telecommunication service cannot be easily identified, owing to the very different nature of the various services that can be envisioned. This is basically the reason for the rapidly change in the technological environment. In fact, a person living in the sixties, who faced the only provision of the basic telephone service and the first low-speed data services, could rather easily classify the basic parameters of these two services.