Models and Analysis of TCC/AQM Schemes over DiffServ Networks

QoS-enabled networks consist of major functions: one is a TCP congestion control (TCC) mechanism at a source/sink node and the other is an active queue management (AQM) scheme at an intermediate node. In this paper, we introduce the major TCC mechanisms and AQM schemes, and provide analytical models and simulation-based comparisons of these TCC/AQM schemes for the purpose of identifying the reciprocal relationship between TCC mechanisms and AQM schemes in QoS-enabled networks. The results show that the equilibrium and dynamics of the underlying network depends on the harmony between the TCC/AQM pairs. The NewReno/PI pair, a feedback-based mechanism encompassing both network and end-systems, can enhance the performance of packet loss and delay sensitive applications. In our opinion, an appropriate combination of active queue management from the network and TCP source reaction would provide an effective solution to the instantaneous network fluctuation which occurs on the Internet.