“…Instead, class-based QoS differentiation is a relatively new concept and many studies have been devoted to this area in recent years. Examples include packet scheduling and dropping for DiffServ in the network core Ramanathan (1999, 2000;Liao and Campbell, 2004;Wang et al, 2004), multicasting in DiffServ domains (Li and Mohapatra, 2003), controltheoretical approaches for relative QoS differentiation (Abdelzaher et al, 2002;Lu et al, 2005), QoS differentiation in Web servers (Chen and Mohapatra, 2002;Zhang et al, 2003), resource management for QoS differentiation in cluster-based Internet servers and Grids (Shen et al, 2002;Yeow and Tham, 2004;Zhu et al, 2001), OS and middleware support for QoS isolation (Shenoy et al, 2002;Sundaram et al, 2000). Though many significant research results exist, however, there is no survey paper in the QoS differentiation context.…”