Research On Transport Control Protocol Technologies For Content Delivery Network

Aiming to improve the quality of network content service,Content Delivery Network has been widely used in the world.Usually,Content Delivery Network consists of center cluster nodes and edge nodes.Center cluster nodes storage website and multimedia data,while edge nodes collect end-user requests and transmit data.Center cluster with high bandwidth,low latency and low packet loss rate is quite similar to Data Center.However edge nodes communicated with end-user using complex network,which random packet loss rate and packet reordering rate is high.TCP,as known as transmission control protocol,is an important transport layer protocol,which is widely used in modern Internet.As most of the data in Content Delivery Network are transmitted using TCP protocol,it is important to improve the performance of TCP protocol to promote transmission efficiency of Content Delivery Network.The research content of this dissertation is to propose several TCP variants for these networks to enhance the network transmission performance.The main contribution of this dissertation is:? A delay-based TCP congestion control algorithm,named TCP-FITDC,is proposed for data center network enabling switch marking method.TCP-FITDC uses markings as an indicator of network buffer occupancy as well as round trip delay changes for an estimate of the variations in the available bandwidth.Combining explicit congestion notification markings and queueing delay,TCPFITDC can react to congestion states more accurately,thereby improving the TCP performance in data center networks.? A Ratio estimation tcp congestion control algorithm is proposed for data center which switch marking scheme is disabled.Without modifying switch and receiver,RETCP uses the trend of throughput and round-trip delay variation as calculation parameters to propose a congestion estimating method.RETCP uses dynamic and static method to adjust the congestion window to ensure data transmission smoothly,reduce the occupancy of the buffer queue.? A hybrid TCP variant based on both packet loss and queueing delay named TCPACC is proposed for complex network.First it integrates a real-time reorder metric for calculating the probabilities of unnecessary Fast Retransmissions and Timeouts.Second,an improved round trip delay estimation algorithm is used to give more weights to packets that are sent(as opposed to received)more recently,and third an improved congestion control mechanism based on packet loss and reorder rate measurements.Theoretical analysis demonstrates the equilibrium throughput of TCP-ACC is much higher than traditional TCP,while maintaining good fairness with other TCP algorithms.Extensive experimental results show that the algorithm achieves significant throughput improvement in complex networks as compared with other state-of-the-art algorithms.