The IPv6 Implementation Of DTN And Research Of Cache Mechanism In Space Network

Because of the high delay and high disruption link rate status of space networks environments,The TCP/IP protocol framework,which is widely used in terrestrial networks,is not very useful in space networks.So the Delay Tolerant Network(DTN)was designed to deal with this complex communication problems in space networks environments.Delay Tolerant Network is a network protocol framework designed to communicate effectively in complex network environments.It could guarantee communication qualities for users in the heterogeneous networks.The most used DTN implementation now is the ION(Interplanetary Overlay Network),which was proposed by the NASA Jet Propulsion Laboratory(JPL)in the United States.Though ION implemented the DTN protocol framework from the software level,ION didn't support the IPv6 when it was written and there was a problem of repeated transmission of the same data when it transmitted so that it was not making full use of space limited link resources in the space networks.This paper was supported by The National 863 Project:Key Technologies and Demonstrations of Future Integrated Network(NO.2015AA015702).In this paper,the ION software was optimized to support the IPv4/IPv6 dual stack network transmission.At the same time,the protocol translation gateway was designed and implemented so that the data of the terrestrial domain and the space domain could be interconnected in the integrated network.On this basis,this paper studied the caching mechanism in the space network environments.This paper first analyzed the DTN architecture,and introduced serveral major convergence layer protocols:Licklider Transmission Protocol(LTP),TCP Convergence-Layer Protocol(TCPCL),and UDP Convergence-Layer Protocol(UDPCL).Then it analyzed the architecture of ION.In terms of the source code of ION,this paper explained how to optimize the ION and apply it in the IPv6 scenes.Based on the requirements of the integrated network connecting space networks and terrestrial networks,the protocol tranlation gateway was designed to convert the DTN packets in the space domain and the UDP data packet in the terrestrial domain.Next,a simple experimental scene was designed to verify the integrity of several major convergence layer protocols' messages when the modified ION was used.For the integrated network transmission experiments,a joint transmission of the space and the terrestrial domain scene was designed to verify the function of ION and the protocol translation gateway.Afterwards,this paper described and compared some of the most commonly used cache replacement algorithms in today's Internet,LRU,LFU,and ARC algorithms.The effectiveness of a cache replacement algorithm was analyzed in terms of the cost point of view.Next,in view of the link characteristics of the space network environments,some optimization was carried out based on the ARC algorithm to make use of the transmission of space networks more effectively.Based on the synthesis of ION and current Internet cache replacement algorithms,a cache server suitable for space satellite networks was designed in this paper.The caching server was divided into three modules.The data transmission module which was based on the previous IONv6 design was responsible for the data transmission in the space networks.The business processing module which was responsible for processing,forwarding,and caching of file requests used a thread model and memory management model optimized for multithreading.The tunnel forwarding module was designed based on Linux Tun/Tap device,which was mainly used to communicate between the two previous modules.At last,in order to analyzing and verifying the effectiveness of the space network cache server,this paper built a simulation scenario based on the "Global Star" satellite system on the future integrated network simulation platform.Then this paper tested the performance of the space network cache server.The experiment shows that the space network cache server has a certain performance advantage compared with the original ION in data transmission.