Policy-based QoS Mechanism On VoIP Network

With the development of IP technology, various services and applications have emerged, of which, VoIP turns out to be one of the most promising technology. However, the original intension of IP is just to supply a kind of"Best Effort"service without guarantee of the reliability and time delay of the IP passage. It is suitable for those data operation that demands accuracy, but not time delay; while for those real-time operation, such as voice and video, the quality of the service can not be guaranteed. This weakness of traditional IP network has been shown, thus, QoS mechanism becomes the most important and complicated problem faced by IP network nowadays.This paper introduced VoIP technology and the mechanism of QoS in details first, and then analyzed the implementation method and the characteristics of the three models (Inter-Serve, Diff-Serv, and MPLS), which is used to the achieve QoS mechanism. This is followed by the analysis of a kind of end-to-end mixed QoS model, which applies the systematic structure combining MPLS with Diff-Serv in its core network and Int-Serv model in its marginal network. Based on that, the paper adopts the idea of Diff-Serve, leads Policy service into marginal network, and combines Int-Serv to achieve the guarantee of QoS in VoIP network.In traditional network, there is no harmony amon each network equipments, but a uniform control of all the network equipments can be achieved by using policy-based QoS technology. This paper designs a specific QoS control system on the basis of policy-based QoS technology, marks out the module structure for the policy server, discuss the functional framework of each module, and expatiates at length the implementation of directory service and policy service, which are two of the most important modules.To make sure the implementation of strategy on specific equipment, the paper presents a further discussion on the mapping from the QoS mechanism onto the equipment; and simulates a strategy-based QoS control system in Opnet. The simulation results show that the performance of the system is improved by using the policy controller to control the network.