I. INTRODUCTION
Differentiated Services (DiffServ) architecture is proposed to meet the demand for different levels of quality of service (QoS) for various types of clients and network applications. To receive different treatments in the network core (routers), a packet's Differentiated Services code points (DSCP) can be set at a network administrative boundary. The routers perform different forwarding operations, “per-hop behaviors”, to the marked packet. Two general strategies for differentiated services have been proposed. One is absolute differentiated services model that aims to provide an end-to-end service with guaranteed bandwidth, low loss, and low latency. The other one is relative differentiated services model that quantifies the relative quality spacing among classes of traffic. In relative differentiated services model, the traffic is divided into classes with ordered levels of services, such that class receives better (or at least no worse) treatment than class where , with respect to local (per-hop) metrics for the queueing delays and packet losses [3]. Furthermore, relative DiffServ with respect to delay is sufficient for soft real-time applications like e-Commerce transactions.