An Improved Random Retreat CAC Algorithm for Interactive Real-time Applications

Traditional CAC methods all make decision as soon as possible on the arrival of a flow. However, the accessing delay is not required that strictly to some interactive real-time applications such as videoconference and IP telephone. In that case CAC should use this delay to find the appropriate moment for the flow to access network. Hence, in this paper we propose an improved CAC algorithm, namely Random Retreat CAC (RRCAC), based on an existing CAC framework. RRCAC refers the main idea of a carrier sense protocol--CSMA. If a flow cannot access the network due to the heavy load at the moment, RRCAC randomly assigns a retreat time to the flow until it is admitted or the delay exceeds a reasonable upper bound. The theoretic analysis and computer simulation show that the RRCAC algorithm significantly enhances the utilization of network and guarantees the QoS requirements in terms of probability.