本文選題：空間信息網(wǎng)絡(luò)　切入點(diǎn)：DTN　出處：《山東大學(xué)》2017年碩士論文

【摘要】：DTN(Delay/Disruption Tolerant Network)是容延容斷網(wǎng)絡(luò)的簡稱,具有延時(shí)長、鏈路連接頻繁中斷、網(wǎng)絡(luò)拓?fù)浣Y(jié)構(gòu)多變、數(shù)據(jù)傳輸率低并且上下行不對稱、節(jié)點(diǎn)資源受限等特點(diǎn),空間通信網(wǎng)絡(luò)就是DTN的一個(gè)典型代表。與陸地通信環(huán)境相比,空間通信環(huán)境非常惡劣,不能滿足傳統(tǒng)互聯(lián)網(wǎng)對通信環(huán)境的要求,因此急需研究和發(fā)展更適合于空間通信的網(wǎng)絡(luò)體系。此外,中國作為航天大國,研究和發(fā)展DTN網(wǎng)絡(luò)有助于推動深空探測的進(jìn)行,對中國的航天事業(yè)具有重要意義。本文先對DTN體系結(jié)構(gòu)及其相關(guān)協(xié)議進(jìn)行分析。該體系結(jié)構(gòu)的核心就是bundle層,通過在應(yīng)用層和傳輸層之間增加覆蓋層,將異構(gòu)網(wǎng)絡(luò)連接在一起。并且,為了避免覆蓋層與傳輸層之間出現(xiàn)數(shù)據(jù)格式的不匹配,在這兩層之間加入?yún)R聚層來充當(dāng)接口。Bundle協(xié)議和LTP協(xié)議是DTN協(xié)議棧中兩個(gè)重要協(xié)議。Bundle協(xié)議以bundle為基本數(shù)據(jù)單元,為適應(yīng)鏈路的頻繁中斷,采用存儲-轉(zhuǎn)發(fā)的方式進(jìn)行數(shù)據(jù)傳輸。托管傳遞是基于存儲轉(zhuǎn)發(fā)的可選擇的服務(wù)機(jī)制,能夠使bundle的傳輸更加可靠。LTP協(xié)議是一種匯聚層協(xié)議,位于bundle層與傳輸層之間,通過紅色數(shù)據(jù)和綠色數(shù)據(jù)之分,能夠提供可靠傳輸與不可靠傳輸。并且在鏈路斷開時(shí)中止數(shù)據(jù)傳輸,連接恢復(fù)后重傳之前未成功發(fā)送的數(shù)據(jù)。在分析DTN核心協(xié)議的基礎(chǔ)上,進(jìn)行bundle協(xié)議和LTP協(xié)議的設(shè)計(jì)與實(shí)現(xiàn)工作。在結(jié)構(gòu)上將Bundle協(xié)議分為應(yīng)用代理部分、bundle協(xié)議代理部分和匯聚層適配器部分,并對bundle協(xié)議代理部分進(jìn)行了功能的劃分,并介紹了各個(gè)功能模塊的具體實(shí)現(xiàn),畫出對應(yīng)的程序流程圖。在結(jié)構(gòu)上將LTP協(xié)議劃分為存儲部分、LTP協(xié)議部分與管理信息庫部分,并劃分了LTP協(xié)議部分的功能,并畫出流程圖。最后對各協(xié)議之間的接口進(jìn)行設(shè)計(jì)。本文還用三臺電腦搭建了 DTN網(wǎng)絡(luò)仿真系統(tǒng)的網(wǎng)絡(luò)實(shí)驗(yàn)平臺,通過本仿真系統(tǒng)發(fā)送三幅圖片進(jìn)行傳輸性能的測試。本系統(tǒng)中可以設(shè)置bundle尺寸、LTP數(shù)據(jù)段尺寸、延時(shí)、連接周期、連通時(shí)間等參數(shù),能夠?qū)崿F(xiàn)bundle數(shù)據(jù)的分段封裝與重組、托管傳輸?shù)裙δ?LTP數(shù)據(jù)的分段封裝重組、可靠傳輸、中斷重傳功能。并且,能夠通過設(shè)置延時(shí)參數(shù)來模擬空間通信中的延遲時(shí)間,通過設(shè)置連接周期和連通時(shí)間來模擬空間通信中,兩節(jié)點(diǎn)之間的周期性連接與斷開。測試完成后,展示不同參數(shù)設(shè)置下的運(yùn)行結(jié)果。通過測試,證明了系統(tǒng)可穩(wěn)定運(yùn)行,也驗(yàn)證了bundle協(xié)議和LTP協(xié)議的可行性。
[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.
【學(xué)位授予單位】：山東大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TN927;TP391.9

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