Acknowledgment This assignment couldn’t have been completed without the assistance and effort of many people. All the support and contribution that was provided is very much valued and appreciated by our group. The completion and finishing of the assignment couldn’t have been possible without the big role played by the guidance and encouragement given to us. Our group would love to express its deepest appreciation and recognition to everyone who made this assignment reach the highest levels of success. We would love to take this chance to show our huge appreciation to Mr Mansoor for the role he played in providing the required support and assistance to us and for showing willingness to use his free time to provide us with feedback. We would also like to thank all the lab staff in PC Lab 2 for letting us use the lab when its free. We would also want to express our deepest gratitude to our classmates, relatives, and all family members for the moral support they have provided us with. Abstract In this assignment, a critical evaluation and analysis will be carried out based on the Quality of Service (QoS) of a Wide Area Network (WAN) with the help of the simulation software Riverbed Modeler. to study the network parameters, a network model should be developed first. When the network model is created, an analysis of the network will be done through comparing and contrasting different simulation outputs. After that, the network will be further improved to minimize the delay as well as errors and to improve the traffic handling. In Addition, different scenarios will be created to ensure having a network that is able to handle traffic with no delay at the lowest cost possible. Each scenario will have different capabilities and parameters, therefore each scenario will be critically evaluated, studied and analysed. Finally, an understandable comparison between scenarios will be carried out in the results followed by a well delivered conclusion. Chapter1 Introduction The Aim of the assignment is to determine the quality of service performance and evaluation of WAN of Al Shifa L.L.C pharmaceutical Destitution Company in Oman operating in Muscat , Dubai and Salalah . The head quarter in Muscat and a branch in Sur by integrating the concepts learned in the modeling and simulation methodology. The objectives of the assignment are: · Study the parameters by developing conceptual model of complex computer network. · The network model will be created by the simulation tools. · The output is based on analysis and configuration of the network model. · Analysis the result that will be carried out · Documentation of the whole work · Drawing the conclusion from the result · Recommendation to prevent the problems The approach to determine the quality of service performance and evaluation of WAN of Al Shifa pharmaceutical Destitution Company broken down into five steps starting with: i. Formulation of the problem Al Shifa pharmaceutical Des.