Research On Link-state Aware File Transfer Mechanism In Space Network

Compared to the traditional terrestrial network,space network has the features of long propagation delay,high bit error rate,bandwidth asymmetry and intermittent connection.Therefore,existing transmission mechanisms can hardly meet the requirements for efficient transmission in space network.In this paper,we propose an appropriate file transfer mechanism for space network through combining the ability of perceiving link states with the mechanism of negative acknowledgment retransmission.The main work includes the following aspects:Firstly,we analyze the characteristics of space network and the shortcomings of traditional transmission mechanisms applied in space network in depth,and then make a comprehensive understanding of the solutions for space network already proposed by domestic or foreign institutions and scholars.In particular,we summarize the advantages and disadvantages of SCPS protocol suite,CFDP protocol and Saratoga protocol.Secondly,we do researches in proposing appropriate transmission mechanisms for space network.The characteristics of space network have caused the low performance of acknowledgment retransmission mechanism of TCP,thus the mechanism of negative acknowledgment has become an important solution strategy.Combining the ability of perceiving link states with the mechanism of negative acknowledgment retransmission can help improve the efficiency of utilization of link resources in space network,which is supposed to have great prospects.Thirdly,we design and implement the Link-state Aware File Transfer Protocol(LA-FTP).Through the approach of modular design,we divided LA-FTP into four modules: user interaction module,transfer core module,network interface module and file interface module and then implement LA-FTP using C programming language and Linux Socket.Lastly,we test and evaluate the performance of LA-FTP through emulating space network environment.Common Open Research Emulator(CORE)can provide the ability for setting a variety of link parameters and controlling through script,supposed to be a good tool for emulating link characteristics of space network.In the last part pf this paper,we test and evaluate the performance of LA-FTP through using CORE to emulate space network environment.