An Efficient Call Admission Control for Hard Real Time Communication in Differentiated Services Network

In this paper we study hard real time (HRT) communication over a differentiated service network. Differentiated Services was proposed by IETF as a scalable QoS architecture [1]. Diffserv service providers can provide delay and bandwidth guaranteed service (as per service level agreement (SLA)) by implementing diffserv services with a fair packet scheduling algorithm like WFQ. But this QoS is provided at an aggregate traffic level. Since HRT application require per flow level delay guarantee, simply deploying HRT application over Diffserv network is not adequate. Additional mechanism is needed to provide per flow level QoS over diffserv network. We have devised a method for calculating end-to-end delay of a connection through a diffserv network based on the theory of Latency Rate (LR) server [2]. Our delay analysis considers actual total incoming traffic to the diffserv network rather than SLA level aggregate traffic. Hence it results in better resource utilization. We propose an efficient call admission control (CAC) based on our delay analysis. Through simulation we show that our method performs better than the traditional SLA level aggregate traffic based approach.