Fair admission control in QoS capable networks

Current admission controls that seek to optimise network utilisation create a bias against large-bandwidth calls. A buffer without preemption model is proposed that holds a call in a buffer rather than directly rejecting it when the residual bandwidth is insufficient. No other call can be admitted until this queued call is served. Such a mechanism increases the throughput since the buffer can temporarily hold a call. It also reduces the bias for large-bandwidth calls since all calls are rejected when the buffer is not empty, even when the residual bandwidth is sufficient for small-bandwidth calls. The proposed approach is compared with two alternative models, namely no buffer and buffer with preemption models and the performance of the models is analysed by solving a multi-dimensional Markov chain. Analytical and numerical results indicate that the proposed model achieves perfect fairness. A modified model, in which a waiting threshold is added to prevent an overlong wait for the queued call is also presented. Also, different thresholds for various bandwidth calls are set to maintain the optimal fairness. Analytical and numerical results demonstrate that this latter model actually achieves optimal fairness, even when perfect fairness cannot be achieved.