Research Of Overlay Routing Technology Based On Quality Of Service

With the rapid development and comprehensive deployment of Internet, more and more multimedia applications have been appearing, which has special request for QoS (jitter, delay, reliability and etc), such as VoIP, video meeting, streaming audio\video, VOD and so on. However, the present Internet can only offer the transmission service based on "Best Effort" mechanism, it can not satisfy the QoS requests of the upper applications, since it has lots of disadvantages, such as less fault-tolerance, imperfect QoS mechanism and so on.Therefore, the overlay network emerges. Different from the physical substrate, the overlay is virtual network that is composed of overlay relay nodes, distributing in the current network, and logic links among nodes. The overlay is capable to offer QoS support for upper applications and satisfy their QoS request, without massive modification on the current network structure due to its flexibility, simplicity and scalability.The overlay routing, which is the key component of overlay network, is a routing pattern based on overlay network. This paper focuses on the overlay network routing technology on the basis of QoS, including:1) Selection and deployment of overlay relay nodes:the overlay topology depends on the selection of overlay relay nodes, and the features of topology have influence on the overlay routing performance. Hence, the node deployment problem is important;2) The optimization of overlay routing performance:with the overlay applications widely used, the scale and range of overlay network is expanding, and its influence keeps going strong. Consequently, the related research on overlay routing performance becomes more and more important;3) Design and realization of overlay broker:the overlay is composed of relay nodes and logic links among them. These nodes, called overlay brokers that are foundation of services offered for upper applications, can provide many functions, such as data transmission, network state monitoring, network resource allocation and so on. Therefore, the corresponding research of overlay broker is also significant. The realization of traditional IP routing is called as Hop-by-Hop Destination-based Unicast Routing. Along with development of technology and growth of Internet, the scheme reveals its limitations.1) The hop-by-hop look-up strategy is based on IP destination;2) The destination look-up is totally depending on unicast address;3) All the packets have the same transmission path to the same destination;4) All the routers must store the complete routing selection information for reliable packet transmission.Compared to the conventional IP routing, the overlay routing has better flexibility. The overlay nodes, as "smart proxy", can choose the next hop not only by the "source, destination", but also the data content, even combining with other requests. Hence, the research of overlay routing has become a hot topic, attracting more and more attentions.On the one hand, this paper focuses on the overlay routing and related problem, according to the Internet laying scheme, and proposes the node deployment algorithms based on the complex network topology characteristic and the neighbor node selection algorithm based on ACO (Ant Colony Optimization). On the other hand, taking advantage of the flow label in IPv6 main header, combining the overlay routing with the NGI QoS technology, this paper presents the design of overlay smart node relying on the identification feature of flow label, and provides the corresponding QoS routing algorithm. The main contributions and innovations are as follow:1) This paper proposes an overlay node deployment algorithm, NCB (Node-Coreness Based), according to node-coreness, which can enhance the routing stability and reliability on the basis of the path diversity satisfaction. When network topology changing, the scheme is able to guarantee the data and service availability and prevent the severe QoS variation. Besides that, this algorithm has clustering function based on nodes location, it can achieve the uniform node distribution, avoiding the excessively compact node deployment. The algorithm is divided into three parts:coreness calculation phase; clustering phase; relay node generation phase. This placement method is suitable for stable network environment, such as the node deployment in big scale network, since it needs static overall topology information.2) This paper proposes another overlay node deployment algorithm, PDB (Path-Diversity-Based), according to path diversity coefficient. All the potential overlay nodes are clustered based on the correlation of path diversity coefficient, which means the proximity of path difference caused by two different nodes, and the overlay node is selected randomly from each cluster. In this way, by means of reasonable overlay node selection, expanding the difference between overlay routing and IP routing, and overlay routing themselves can improve the overlay routing performance and fault detouring ability. This placement method is suitable for stable network environment, such as the node deployment in big scale network, since it needs static overall topology information.3) This paper proposes an overlay neighbor selection algorithm based on ACO to handle neighborhood set maintenance:the neighborhood set is formed in the progress of ant crawling, which is determined according to the quality evaluation function in order to control the size of set and the influence, caused by neighborhood set, on the network cover extent and overlay routing reliability. The main idea is to reduce the negative influence, caused by increasing network scale, to system working efficiency, for the sake of improving the routing scalability, without network reliability dropping.4) In order to overcome the limitations of traditional IP routing, improve the network performance and satisfy the E2E QoS request, this paper proposes an overlay network, called SQRON (Sensitive QoS Routing Overlay Network). It offers QoS support for upper applications by means of overlay brokers, which provide network performance measurement, QoS class mapping, QoS routing and network performance monitoring. Besides that, taking advantage of the flow label in IPv6 main header, combining the overlay routing with the NGI QoS technology, this paper presents the design of overlay smart node relying on the identification feature of flow label, and provides the corresponding QoS routing algorithm.