The Internet has historically offered a single level of service, namely, 'best-effort service'. However, the need for a consistent and differentiated service quality is increasing than ever.
This thesis describes the concept and definition of Quality of Services (QoS), and then, explains the fundamental components of QoS and how they can be supported through various mechanisms based on such network engineering tools such as queueing disciplines, traffic shaping and admission control.
Compared in this thesis are the Integrated Services and Differentiated Services. The latter is proposed as a QoS effort by the Internet Engineering Task Force (IETF). The overall architecture of Differentiated Services are introduced in detail.
Also discussed in this thesis are the reasons why the network performance evaluation and the network simulation are necessary while Differentiated Services is deployed and used in Internet. Finally, a framework for evaluating network performance by simulation is presented from the viewpoint of Industrial Engineering.
