Research Of Service Quality Assurance Mechanisms For VoIP System

The P2P technology enhances VoIP system performance, but also brings some problems. P2P overlay network is openness and extensible, but also great differences and dynamics. The characteristic makes P2P networks unable to meet the needs for VoIP system which is a kind of real-time application. When the two nodes communicate in this network, the system often has quality of service problems.The VoIP service quality assurance mechanisms focus on solving those kinds of problems, when network environment changes, how to ensure quality of service in whole system. Our system constructs a Peer-to-Peer Session Initiation Protocol (P2P SIP) overlay. The entire network consists of SN-C, UE, Bootstrap, RN-S and RN. The main idea of the solution is that find some backup links and successor nodes before making a call,when the network environment changes, the system is able to dynamically switch the call link to the backup link automatically. In this way, the VoIP system can provide preferable service quality.The whole proposition includes relay overlay algorithm, dynamic relay algorithm and dynamic selection algorithm based on SIP.The algorithms run on a separate overlay.The innovation of this proposition is that backup SIP messages to ensure the reliability of signaling transaction. At the same time, when the VoIP system makes the call with a relay node, it can dynamically switch the relay node which can provide better service. The callee automatically detects the voice quality and sends RE-INVITE request then staying on the phone with the caller,in the case of poor voice quality.Finally, we have done the functional test to ensure the feasibility of our solutions. in respect of system performance, exhaustive simulations based on NS2 (Network Simulation Version 2) are performed to evaluate the performance of the algorithms.The results show that the average re-hit rate of relay node is 0.7 to 0.9, when system switch relay node, the latency remains in 150ms. The results also show that the systemarchitecture is feasible and scalable.