DTN仿真系统的设计与实现

发布时间：2018-04-05 03:09

本文选题：空间信息网络　切入点：DTN　出处：《山东大学》2017年硕士论文

【摘要】：DTN(Delay/Disruption Tolerant Network)是容延容断网络的简称,具有延时长、链路连接频繁中断、网络拓扑结构多变、数据传输率低并且上下行不对称、节点资源受限等特点,空间通信网络就是DTN的一个典型代表。与陆地通信环境相比,空间通信环境非常恶劣,不能满足传统互联网对通信环境的要求,因此急需研究和发展更适合于空间通信的网络体系。此外,中国作为航天大国,研究和发展DTN网络有助于推动深空探测的进行,对中国的航天事业具有重要意义。本文先对DTN体系结构及其相关协议进行分析。该体系结构的核心就是bundle层,通过在应用层和传输层之间增加覆盖层,将异构网络连接在一起。并且,为了避免覆盖层与传输层之间出现数据格式的不匹配,在这两层之间加入汇聚层来充当接口。Bundle协议和LTP协议是DTN协议栈中两个重要协议。Bundle协议以bundle为基本数据单元,为适应链路的频繁中断,采用存储-转发的方式进行数据传输。托管传递是基于存储转发的可选择的服务机制,能够使bundle的传输更加可靠。LTP协议是一种汇聚层协议,位于bundle层与传输层之间,通过红色数据和绿色数据之分,能够提供可靠传输与不可靠传输。并且在链路断开时中止数据传输,连接恢复后重传之前未成功发送的数据。在分析DTN核心协议的基础上,进行bundle协议和LTP协议的设计与实现工作。在结构上将Bundle协议分为应用代理部分、bundle协议代理部分和汇聚层适配器部分,并对bundle协议代理部分进行了功能的划分,并介绍了各个功能模块的具体实现,画出对应的程序流程图。在结构上将LTP协议划分为存储部分、LTP协议部分与管理信息库部分,并划分了LTP协议部分的功能,并画出流程图。最后对各协议之间的接口进行设计。本文还用三台电脑搭建了 DTN网络仿真系统的网络实验平台,通过本仿真系统发送三幅图片进行传输性能的测试。本系统中可以设置bundle尺寸、LTP数据段尺寸、延时、连接周期、连通时间等参数,能够实现bundle数据的分段封装与重组、托管传输等功能,LTP数据的分段封装重组、可靠传输、中断重传功能。并且,能够通过设置延时参数来模拟空间通信中的延迟时间,通过设置连接周期和连通时间来模拟空间通信中,两节点之间的周期性连接与断开。测试完成后,展示不同参数设置下的运行结果。通过测试,证明了系统可稳定运行,也验证了bundle协议和LTP协议的可行性。
[Abstract]:DTN(Delay/Disruption Tolerant Network is the abbreviation of capacitive capacitive network, which has the characteristics of long delay, frequent interruption of link connection, changeable network topology, low data transmission rate and asymmetry of upstream and downstream, limited node resources, etc.Space communication network is a typical representative of DTN.Compared with the terrestrial communication environment, the space communication environment is very bad and can not meet the requirements of the traditional Internet communication environment. Therefore, it is urgent to study and develop a more suitable network system for space communication.In addition, as a large spaceflight country, the research and development of DTN network is helpful to promote the deep space exploration, which is of great significance to China's space industry.This paper first analyzes the architecture of DTN and its related protocols.The core of the architecture is the bundle layer, which connects heterogeneous networks together by adding overlay between the application layer and the transport layer.In order to avoid the mismatch of data format between the overlay and the transport layer, the convergence layer is added between the two layers to act as the interface .Bundle protocol and the LTP protocol are two important protocols in the DTN protocol stack. Bundle is the basic data unit of the protocol stack.In order to adapt to the frequent interruption of the link, the storage-forward method is used for data transmission.Managed delivery is an optional service mechanism based on storage and forwarding. It can make the transmission of bundle more reliable. It is a convergent layer protocol, located between the bundle layer and the transport layer, through the red data and green data.Can provide reliable transmission and unreliable transmission.The data transmission is stopped when the link is disconnected, and the data that was not successfully transmitted before is retransmitted after the connection is restored.Based on the analysis of DTN core protocols, the design and implementation of bundle and LTP protocols are carried out.In structure, the Bundle protocol is divided into the application agent part and the aggregation layer adapter part, and the function of the bundle protocol proxy part is divided, and the implementation of each function module is introduced.Draw the corresponding program flow chart.In structure, the LTP protocol is divided into storage part and management information base part, and the function of LTP protocol part is divided, and the flow chart is drawn.Finally, the interface between the protocols is designed.In this paper, the network experiment platform of DTN network simulation system is built with three computers, and the transmission performance is tested by sending three pictures through the simulation system.This system can set the parameters of bundle data segment size, delay, connection period, connection time, and so on. It can realize the partition encapsulation and recombination of bundle data, the managed transmission and so on functions, such as segment encapsulation and recombination of bundle data, reliable transmission, etc.Interrupt retransmission function.Furthermore, the delay time in space communication can be simulated by setting delay parameters, and the periodic connection and disconnection between two nodes in space communication can be simulated by setting connection period and connection time.When the test is complete, show the running results under different parameter settings.It is proved that the system can run stably and the feasibility of bundle protocol and LTP protocol is verified by test.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN927;TP391.9

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