Delay Variation Based Endpoint Admission Control in DiffServ

摘要

A novel Endpoint Admission Control scheme (EAC) in IP networks is proposed in this paper. EAC mechanisms are driven by independent measurements taken by the edge nodes on flow of packets injected in the network to probe the source-todestination path. We dig into the intrinsic relations among accepted load, QoS achieved and the delay variation statistics, and deduced a few theorems which guide throughout the whole admission control study. Our scheme is characterized by two fundamental features. First, it does not rely on any additional procedure in internal network routers other than the capability to apply different service priorities to probing and data packets. Second, the connection admission decision is based on the analysis of the probing flow delay variation statistics. With only two priority levels used, which different from stateful centralized solutions, this scheme can only provide a single level of QoS. To overcome this limitation, it can be used to perform admission control within a DiffServ class to provide different QoS performance for hetero traffic. NS2 simulation results, which focus on IP telephony scenario, show that, despite the lack of corerouters cooperation, toll-quality performance figures (99th delay percentiles not greater than few ms per router) can be obtained even in severe overload conditions. Finally, a comparison with an EAC scheme driven by probe losses only, shows that the use of delay variation statistics as endpoint decision criterion is a key factor for EAC effectiveness.