Research On End-to-End Bidirectional Resource Allocation Mechanism Based On Decoupling

Nowadays the Transmission Control Protocol(TCP)is the most widely used transport layer protocol.More than 90%data streams are transmitted based on TCP statistically.Since TCP is a reliable transmission protocol based on the acknowledgment mechanism,its performance is determined by the bidirectional state of the path.Therefore,the TCP performance becomes worse in the asymmetric network.Existing methods of solving network asymmetry are concentrating on reducing acknowledgement utilizing traditional TCP.However,it only brings limited perforamce improvement.In order to enable the emerging unidirectional link to support TCP services,binding link at the link layer is expensive and inflexible.With the prevalence of multi-homed devices,it provides new possibilities to solve the reliable transmission of asymmetric and unidirectional links at the transport layer.Selecting a better uplink and downlink network interface to establish a bidirectional reliable connection,the effect of asymmetry on transmission performance can be eliminated and unidirectional link resources can be fully used.Based on the above observation,decoupled TCP is proposed to handle the problems in this paper.Furthermore,we provide a multipath decoupled TCP based on decoupled TCP,in order to make full use of the multi-homed devices resources.Decoupled TCP breaks the bidirectional path which is the basic unit of the traditional TCP,and utilizes two unidirectional paths to form a bidirectional connection for reliable data transmission,under fine-grainedly,flexibly and efficiently using network resources.The designed principles of the decoupled TCP and multipath decoupled TCP are shown as follows.Firstly,it should be transparent to the application layer,which means the service data based on the TCP can be transmitted by the unidirectional link without modifying the existing application.Secondly,the intermediate network equipments need not to be modified.Thirdly,the proposed design should obtain the same performance as the traditional TCP even in the worst condition.Last,it should be TCP-friendly to ensure the fairness of the competition at bottleneck link.The main research contents of this paper include two parts:decoupled TCP and multipath decoupled TCP.We design and implement the decoupled TCP,and verify the correctness and effectiveness in the visible light communication unidirectional link scenario.After decoupling,the traditional TCP congestion control algorithms are applicable.However the resources are allocated in a finer-grained manner,there are more unidirectional path combinations than traditional TCP.Therefore,an uplink-downlink selection algorithm is proposed for decoupled TCP.The simulation results show that the decoupled TCP has better performance compared with the traditional TCP.Furthermore,we design and implement the multipath decoupled TCP,and verify the correctness of the protoco l implementation through the visible light communication platform.Since multipath decoupled TCP is based on unidirectional subflow,we propose an uplink-downlink generated algorithm and pairing algorithm for multipath decoupled TCP,which aims at eliminating the impact of asymmetry on performance and finer granularity of resource allocation.The performance gains of multipath decoupled TCP are verified by simulations.