Research On Multicast Routing Protocols And Algorithms In Overlay Network

With the development of computer network, Internet has been becoming an important part of the mean streaming of human being. People hope Internet could provide all kinds of network services the applications need. Especially, the emergence of many new multimedia group applications, such as video conferencing, video-on-demand and distance learning, require multicast communication service imminently.Based on the concept of overlay network, in overlay multicast, end systems perform all multicast communication functionalities instead of IP routers. Compared with IP multicast, the greatest advantage of overlay multicast is it needn't change the lower network infrastructure, and can be deployed easily. Overlay multicast embodies the trend that the emphasis of network service research is shifting from network to application layer in the next generation Internet, and its core problem is how to build overlay multicast routing satisfied by applications.In this thesis, overlay multicast routing protocols and algorithms with other related problems are studied, where the QoS requirements of multimedia application and heterogeneity of network are focused. Firstly, a general overlay multicast network model is proposed, and the routing optimal problems in overlay multicast are classified, then some recent important overlay multicast routing protocols and algorithms are fully analyzed and discussed. These construct the theory framework and point out the study direction of this thesis. Based on the above work, our research on overlay multicast is performed in the following aspects, which include centralized routing algorithms, distributed routing protocols and system prototype.In the study of centralized routing algorithms, based on both degree constraints-delay integration and application layer topology optimum strategies, a new minimum delay overlay multicast tree building algorithm called Degree-Delay Compact Tree (DDCT) is proposed to improve the routing performance; To settle the heterogeneity of bandwidth required by real-time multimedia application, adopting the strategy of layered bandwidth allocation, a heuristic routing algorithm called Layered Compact Tree (LCT) is proposed to build a minimum delay overlay multicast tree in heterogeneous condition. The LCT could reduce both hops and network resource usage of the tree effectively.In the study of distributed routing protocols, a new distributed tree-first overlay multicast protocol called BowCast is proposed. Adopting a simple and flexible one-way delay probe method, BowCast can adapt the asymmetric link delay environment well; To support heterogeneous QoS requirements of real-time multimedia multicast applications, a new QoS overlay multicast routing protocol called QoS-aware Overlay Multicast Tree Protocol (QOMTP) is proposed, and its local optimum algorithm is studied, too. QOMTP can reduce the network resource usage of members on the tree as well as achieve a higher admission rate of members.In prototype, a new proxy-based overlay multicast system called Service Customizable Overlay Multicast System (SCOMS) is studied and implemented. Combining DHT-based P2P and tree-first overlay multicast routing protocols, SCOMS can not only keep high scalability, but also provide efficient QoS overlay multicast routing and flexible capability of service customization.The research conclusions of this thesis could not only provide new theoretical method and idea to study overlay multicast routing protocols and algorithms, but also be applied in practical overlay multicast system, therefore, have high theoretical value and wide applied foreground.