Admission Control In SDN-based Media Delivery Network

With the development of the computer network technology, as well as the improvement of network bandwidth, the demand for video media services is continually increasing, and the network video services business is in a stage of rapid development. At present, the streaming media technology is widely used in network video services, due to its high sensibility to transmission delay and services bandwidth, the video service providers have established their own media delivery networks in order to improve business responsiveness, and provide flexible and efficient content transmission for video applications. However, in the traditional network, as network layer applies the best-effort service, unstable network status and link congestion will cause great impact on the video transmission quality and QoS. In such a situation, as a new kind of network architecture to resolve the current network problems such as scalability and mentioned drawbacks, SDN has got the continuous attention from academia and industry. And some researches about media delivery network using SDN system architecture have been proposed, using SDN controller to realize the path selection and optimization control of streaming video on network layer. In a media delivery network, admission control is an important component to improve system resource utilization and provide QoS assurance under limited resources. Thus, studying the admission control problems of SDN-based media delivery network has significant value in both theory and practical applications.The main achievements of this dissertation include the following aspects:1. Focused on the admission control problems of SDN-based media delivery network, an admission control scheme of comprehensively optimizing the service performance of service nodes and transmission links is proposed. Differ with the traditional admission control scheme, the proposed scheme uses SDN controller’s abilities of directly controlling routers and perception of entire network, which can get resource allocation and service status information of service nodes, and the resource consumption situation of the data transmission links as well (e.g. available bandwidth). Then by finding the optimal strategy to jointly optimize the service performance of the service nodes on the application layer and the transmission links between the service nodes and the users on the network layer, the influences of link congestion to data transmission and quality of service are also reduced.2. On the basis of analyzing the structure and characteristics of the media delivery network in SDN, the system admission control process is described by Partially Observable Markov Decision Process (POMDP), and the performance optimization of service nodes as well as transmission links is comprehensively considered in the system modeling. After completion of the model constructing, the observation-based randomized policy is used as the admission control policy of the system. Finally, the policy-gradient algorithm is used to optimize the admission control policy, and the optimal policy of the model can be obtained.3. On the basis of the theoretical analysis and study above, we design a simulation experiment, and by analyzing the simulation results to verify the efficiency of the model and method. The simulation results show that comparing with the best effort service policy the POMDP-based optimal admission control policy can effectively improve system performance, and enhance the system operation capability.