Mechanism And Protocol Of Path QoS Capability Estimation For Overlay Network

IP Multimedia Subsystem,IMS for short, introduced by3GPP in Release5at first, is a multimedia communication system, which is most likely to become the architecture of next generation telecommunication technology. The transmission technology in bearer network lags behind the need of service network development, which has become a serious constraint of application development and service innovation.In IMS overlay networks, real-time media multipath transmission constructed based on application layer relay, is a kind of upgrading method of IMS media transmission technology. In order to achieve quality of service (QoS) guarantee in multi-path transmission, not only path selection in the session establishment process, but also dynamic load allocation in the media transmission process, both rely on path QoS measurement and evaluation.There is no perfect technical solution of relay path QoS measurement and evaluation for path selection in overlay network. In real-time transmission, path QoS could be evaluated by statistical analysis using RTCP, such as delay, jitter, bandwidth,packet loss and so on. But the evaluation is only for single-path and end-to-end path, which could not be effectively applied to multi-path transmission control. Combining with application requirements, four significant issues about multipath real-time QoS estimation are mainly analyzed in the thesis:how to describe the transmission path, what parameters to use for path QoS evaluation, how to measure and evaluate QoS for segment path, how to measure for end-to-end transmission path.The main research contents and obtained achievements in the thesis are as follows. Firstly, two methods which could be used in path description are proposed:description using nodes, description using path ID, which laid the foundation for path QoS evaluation. Secondly, the thesis clears the evaluation parameters, including not only delay and available bandwidth, but also path stability for consideration on relay node type and path intersection degree. Thirdly, an effective method is proposed for measuring path delay and available bandwidth between relay nodes, which is cooperated with relay service controller. The thesis designs the related interactive message format and presents the complete measuring process. Fourthly, end-to-end path QoS evaluation method is proposed, which is called multiple relay path-RTCP to implement end-to-end real-time multipath QoS evaluation. In addition, the thesis also considers the compatibility with OpenPath protocol, and proposes a comprehensive evaluation method of QoS parameters by analyzing the relationship between section path and end-to-end path.Finally, the results of simulation and test show that the solution proposed in the thesis is rational and available, which could be used in multi-path QoS estimation based on application layer relay in the overlay network.