A dynamic approach to reduce preemption in book-ahead reservation in QoS-enabled networks

Increasing demand for multimedia and distributed applications in recent years has drawn renewed attention to book-ahead (BA) reservation. BA reservation has proved itself as an effective technique for time sensitive applications that require high amount of bandwidth with guaranteed QoS. However, BA reservation causes preemption of on-going instantaneous request (IR) calls when resource scarcity arises. Preemption disrupts service continuity for the preempted calls, specially in high speed large networks where rerouting is costly and often disabled because of high bandwidth-delay product and buffer capacity constraint. Recent studies on QoS definition has identified service continuity as one of the most important issues perceived by the users. Minimization of service disruption is crucial for effective implementation of BA reservation. Earlier models proposed to reduce IR call preemption use constant look-ahead time. This paper proposes a new model to calculate look-ahead time dynamically taking traffic parameters and network state into consideration. Simulation results show that the proposed model outperforms earlier model in terms of preemption probability, network utilization, and wasted throughput. The proposed model offers the flexibility of achieving a set level of preemption rate by appropriate selection of a single parameter value. Two techniques to estimate an appropriate value of this parameter are also presented.