This paper presents major quality of service problems in IEEE 802.11 networks. It analyzes unfairness in bandwidth sharing and TCP instability in MAC 802.11. Moreover, differentiation techniques for providing medium access priority are evaluated. Simulation results show that the ad hoc routing protocol has a great influence on unfairness and on the TCP throughput instability due to succeeding routing failures originated by the MAC sublayer. Differentiation mechanism results show that DIFS-based schemes can provide a fine-grained throughput differentiation compared to backoff-based ones. Nevertheless, backoff-based schemes are more effective in providing latency differentiation, which is important for real-time traffic.

This paper proposes a service for multicast video distribution based on the active network paradigm. Active nodes can provide soft-state and perform customized computations on a per-user or per-application basis. These functionalities allow the deployment of an efficient and flexible service that can dynamically adjusts itself to the bandwidth availability. The source learns about the best transmission rate of the video by receiving feedback messages from receivers.A fusion mechanism is used to prevent feedback-message implosion.Simulation results show that a capsule filtering level of 96% can be achieved by using the fusion mechanism.