Abstract: The arguments on the necessary for quantized evaluation toward quality of services (QoS) of multicast in Overlay networks are given. The concept of twodegree homeomorphism reduction multicast tree is introduced, extend Bowman’s method for evaluating QoS of unicast dataflow by using stochastic process algebra (SPA) is promoted, a modeling scheme is proposed for quantized evaluating QoS of concrete multicast instances in Overlay networks with simulation tool PEPA workbench. Simulation suggests that the jitter of IP multicast is lighter than the jitter of Overlay multicast, and the latter is further lighter than the jitter of multicast by using unicast technique.

Key words: stochastic process algebras, overlay, quality of services