計算機網(wǎng)絡畢業(yè)論文中英文資料外文翻譯文獻

中英文資料中英文資料外文翻譯文獻計算機網(wǎng)絡計算機網(wǎng)絡，通常簡單的被稱作是一種網(wǎng)絡，是一家集電腦和設備為一體的溝通渠道，便于用戶之間的溝通交流和資源共享。網(wǎng)絡可以根據(jù)其多種特點來分類。計算機網(wǎng)絡允許資源和信息在互聯(lián)設備中共享。目錄1．歷史2．目的3．網(wǎng)絡分類3.1連接方式3.2有線技術3.3無線技術3.4規(guī)模3.5功能關系(網(wǎng)絡體系結構)3.6網(wǎng)絡拓撲結構4.基于物理范圍的各種類型的網(wǎng)絡4.1局域網(wǎng)4.1.1個人區(qū)域網(wǎng)4.1.2家中大面積網(wǎng)絡4.2廣闊的地區(qū)網(wǎng)絡4.2.1校園網(wǎng)絡4.3大都會區(qū)域網(wǎng)4.3.1企業(yè)專用的網(wǎng)絡4.3.2虛擬專用網(wǎng)絡4.3.3網(wǎng)際網(wǎng)絡4.4骨干網(wǎng)4.4.1全球區(qū)域網(wǎng)4.4.2互聯(lián)網(wǎng)4．4.3內部網(wǎng)和外部網(wǎng)4.4.4覆蓋網(wǎng)絡5．參考文獻一．歷史早期的計算機網(wǎng)絡通信始于20世紀50年代末，包括軍事雷達系統(tǒng)、半自動地面防空系統(tǒng)及其相關的商業(yè)航空訂票系統(tǒng)、半自動商業(yè)研究環(huán)境。1957年俄羅斯向太空發(fā)射人造衛(wèi)星。十八個月后，美國開始設立高級研究計劃局(ARPA)并第一次發(fā)射人造衛(wèi)星。然后用阿帕網(wǎng)上的另外一臺計算機分享了這個信息。這一切的負責者是美國博士萊德里爾克。阿帕網(wǎng)于來于自印度，1969年印度將其名字改為因特網(wǎng)。上世紀60年代，高級研究計劃局(ARPA)開始為美國國防部資助并設計高級研究計劃局網(wǎng)(阿帕網(wǎng))。因特網(wǎng)的發(fā)展始于1969年，20世紀60年代起開始在此基礎上設計開發(fā)，由此，阿帕網(wǎng)演變成現(xiàn)代互聯(lián)網(wǎng)。二．目的計算機網(wǎng)絡可以被用于各種用途:為通信提供便利:使用網(wǎng)絡，人們很容易通過電子郵件、即時信息、聊天室、電話、視頻電話和視頻會議來進行溝通和交流。共享硬件:在網(wǎng)絡環(huán)境下，每臺計算機可以獲取和使用網(wǎng)絡硬件資源，例如打印一份文件可以通過網(wǎng)絡打印機。共享文件：數(shù)據(jù)和信息:在網(wǎng)絡環(huán)境中，授權用戶可以訪問存儲在其他計算機上的網(wǎng)絡數(shù)據(jù)和信息。提供進入數(shù)據(jù)和信息共享存儲設備的能力是許多網(wǎng)絡的一個重要特征。共享軟件:用戶可以連接到遠程計算機的網(wǎng)絡應用程序。信息保存。安全保證。三．網(wǎng)絡分類下面的列表顯示用于網(wǎng)絡分類：3．1連接方式計算機網(wǎng)絡可以據(jù)硬件和軟件技術分為用來連接個人設備的網(wǎng)絡，如：光纖、局域網(wǎng)、無線局域網(wǎng)、家用網(wǎng)絡設備、電纜通訊和G.hn（有線家庭網(wǎng)絡標準）等等。以太網(wǎng)的定義，它是由IEEE802標準，并利用各種媒介，使設備之間進行通信的網(wǎng)絡。經(jīng)常部署的設備包括網(wǎng)絡集線器、交換機、網(wǎng)橋、路由器。無線局域網(wǎng)技術是使用無線設備進行連接的。這些設備使用無線電波或紅外信號作為一種傳輸媒介。ITU-T（電信標準部門）的G.hn技術使用現(xiàn)有的家庭布線（同軸電纜，電話線和電源線）創(chuàng)建一個高速（可達1Gb/S）局域網(wǎng)。3.2有線技術雙絞線是目前應用最廣泛的通訊媒介。它由銅線扭曲配對而成。普通電話線由兩個絕緣銅導線配對扭成。計算機網(wǎng)絡布線由四對銅電纜構成，可以進行語音結構和數(shù)據(jù)傳輸。使用雙絞線電纜可以減少交調失真，電磁感應。它的傳輸速度的范圍很廣，從200萬b/s至1億b/s。雙絞線電纜有兩種類型非屏蔽雙絞線(UTP)和屏蔽雙絞線(STP)，它們被用在不同的場合。同軸電纜廣泛用于有線電視系統(tǒng)、寫字樓、和其他工作區(qū)域的局域網(wǎng)。該電纜通常由銅或鋁合金絲用帶有高介電常數(shù)的靈活性材料絕的緣層包裹，所有這一切都被導電層環(huán)繞。絕緣層幫助減少干擾和變形。傳播速度的范圍從2億b/s到超過5億多b/s。光纖，是由一個或多個細絲狀的玻璃纖維包裹在保護層中。光纖不受電磁輻射。它透過光線延續(xù)的傳播速度可以達到上萬億b/s。光纖的傳輸速度比同軸電纜的傳輸速度快幾百倍，比雙絞線的速度快上千倍。3.3無線技術地面微波——使用地面上的微波發(fā)射器和接收器。設備看起來像衛(wèi)星接受器。地面微波使用的是頻率在千兆赫范圍以內的波，這限制了所有通信線路出現(xiàn)在我們的視線中。中繼站之間的距離大約為30英里。微波天線通常放在建筑物的頂上，例如：塔、丘陵或者山峰的峰頂。通信衛(wèi)星——衛(wèi)星廣播使用微波通信，而微波傳輸不會因地球大氣層而產生偏轉。衛(wèi)星安置在太空中，一般在赤道上22000英里(對于同步衛(wèi)星來說)的高空。這些繞地衛(wèi)星系統(tǒng)能接收和轉播語音、數(shù)據(jù)、電視信號。蜂窩技術和個人通信服務系統(tǒng)，使用幾種無線電通訊技術。這類系統(tǒng)被分布到不同的地理區(qū)域。每個區(qū)域都有低功率發(fā)射器或無線電中繼天線裝置來把電話通信從一個地區(qū)傳遞到下一個地區(qū)。無線LAN,即無線局域網(wǎng)使用高頻無線電技術，類似數(shù)字蜂窩和低頻無線電技術。無線局域網(wǎng)使用擴頻技術來實現(xiàn)有限區(qū)域內多個設備之間的通信。一個開放式標準的無線電波技術的例子就是IEEE。紅外通信，它能在設備之間進行短距離的不超過10米的點對點(面對面)的信號傳輸，傳輸線路之間不能有障礙。3.4規(guī)模網(wǎng)絡通常分為局域網(wǎng)(LAN)、廣域網(wǎng)(WAN)、城域網(wǎng)(MAN)、個人區(qū)域網(wǎng)絡(PAN)、虛擬專用網(wǎng)(VPN)、校園局域網(wǎng)(CAN)、存儲區(qū)域網(wǎng)絡(SAN)。而其它一些國家，則根據(jù)其規(guī)模、范圍和目的分類。例如，控制器局域網(wǎng)(CAN)的使用，信任水平和進入權利之間同這些類型的網(wǎng)絡大有不同。局域網(wǎng)往往是專為內部使用的一種組織內部系統(tǒng)和員工個人物理位置的網(wǎng)絡，比如建筑，而廣域網(wǎng)路可以連接物理上獨立的部分，而且可能包括連接一個組織給第三方。3.5功能關系(網(wǎng)絡體系結構)計算機網(wǎng)絡的功能關系可以根據(jù)元素中存在的網(wǎng)絡進行分類。如，主動網(wǎng)絡、客戶端—服務器、無線自組網(wǎng)絡和點對點(工作組)建筑。3.6網(wǎng)絡拓撲結構計算機網(wǎng)絡分類是根據(jù)網(wǎng)絡拓撲結構建立的，如總線網(wǎng)絡，星型網(wǎng)絡，環(huán)網(wǎng)，網(wǎng)格。網(wǎng)絡拓撲的協(xié)調基于他們在網(wǎng)絡設備上邏輯關系的排列，彼此獨立于物理的安排。即使網(wǎng)絡計算機放置在一個線性安排和被連接到一個集線器，網(wǎng)絡仍是星型拓樸結構，而不是總線網(wǎng)的結構。一個網(wǎng)絡在這方面的視覺和操作特性是不同的。網(wǎng)絡可以基于數(shù)據(jù)分類的方法以用于傳遞數(shù)據(jù)，包括數(shù)字和模擬網(wǎng)絡。4.基于物理范圍的各種類型的網(wǎng)絡常見的可以確定其規(guī)模的計算機網(wǎng)絡類型。4.1局域網(wǎng)局域網(wǎng)(LAN)是一個連接在有限地區(qū)的電腦網(wǎng)絡或設備。如家庭、學校、計算機實驗室、辦公樓、或接近的建筑物。每臺計算機或設備，對網(wǎng)絡是一個節(jié)點。新的標準ITU-TG.hn也提供一種方法即使用現(xiàn)有的家庭電線（同軸電纜，電話線和電源線）來創(chuàng)建一個有線局域網(wǎng)。典型的圖書館網(wǎng)絡，在一個分支樹拓撲結構和控制對資源的訪問所有相互關聯(lián)的設備必須了解網(wǎng)絡層(第三層)，因為他們要處理多個子網(wǎng)(不同的顏色)的。圖書館里面只有10/100Mbit/s的以太網(wǎng)連接到用戶設備和千兆以太網(wǎng)連接到中央路由器，可以稱為“第3層交換機”，因為他們只有從以太網(wǎng)接口才能了解IP。這將是更正確的稱呼他們的接入路由器，在頂部的路由器是一個通訊路由器，它是學生連接到互聯(lián)網(wǎng)和學院網(wǎng)絡的接入路由器。局域網(wǎng)的界定特征，和廣域網(wǎng)絡(廣域網(wǎng)的關系)相比較而言，局域網(wǎng)有更高的數(shù)據(jù)轉移率、小地理范圍,并且不需要租賃電信線路。當前的局域網(wǎng)或其他電氣與電子工程協(xié)會802.3局域網(wǎng)技術操作的速度達10千兆比特/秒。這是數(shù)據(jù)傳輸速率。IEEE已經(jīng)計劃審查的標準是40到100千兆比特/秒。4.1.1個人區(qū)域網(wǎng)個人區(qū)域網(wǎng)絡(盤)是用于一個人周圍的計算機和使用不同信息技術的設備之間進行交流的網(wǎng)絡。在個人區(qū)域網(wǎng)中使用的設備有個人電腦、打印機、傳真機、電話、PDA、掃描儀甚至是視頻游戲機。一個個人區(qū)域網(wǎng)可能包括有線和無線設備。個人區(qū)域網(wǎng)的范圍通常延伸到10米。個人有線區(qū)域網(wǎng)通常采用USB數(shù)據(jù)線及高速的序列文件連接來構建,而藍牙通信技術與紅外通信技術則形成了典型的個人無線區(qū)域網(wǎng)。4.1.2家庭區(qū)域網(wǎng)絡一個家庭區(qū)域網(wǎng)絡(HAN)是一個住宅局域網(wǎng)，一般可用于部署在家里的數(shù)字設備之間的通信，如少量的個人電腦及配件，打印機和移動計算設備。它的一種重要功能是是通過有線電視或數(shù)字用戶線（DSL）提供的寬帶服務來共享上網(wǎng)，它也可以被稱為一個辦公區(qū)域網(wǎng)絡(OAN)。4.2廣域網(wǎng)廣域網(wǎng)(WAN)是覆蓋了一個城市，國家一個很大地理區(qū)域的計算機網(wǎng)絡,如城市、國家或跨洲際距離,使用的通信信道是有多種媒體如電話線、電纜和無線電波相結合的信道。廣域網(wǎng)使用的傳輸設備通常是有公共電信運營商提供的，如電話公司。廣域網(wǎng)技術的一般功能體現(xiàn)在開放式系統(tǒng)互連（OSI）參考模型較低的三層:物理層,數(shù)據(jù)鏈路層和網(wǎng)絡層。4.2.1校園網(wǎng)校園網(wǎng)是一個在有限的地理區(qū)域連接成的局域網(wǎng)(LAN)計算機網(wǎng)絡。網(wǎng)絡設備(交換機、路由器)和傳輸媒體(光纖、銅廠、Cat5布線等)是幾乎完全屬于(校園承租人/所有者的:企業(yè)、學校、政府等)。就大學校園的校園網(wǎng)絡建設來說，網(wǎng)絡是將各種各樣的校園建筑，如，學術部門，大學圖書館和學生學員公寓等連在一起的。4.3城域網(wǎng)一個大城市的網(wǎng)絡是一個大型計算機網(wǎng)絡，通?？缭匠鞘谢蛞粋€大的校園EPN幀中繼廣域網(wǎng)的連接和遠程撥號訪問。VPN用來連接3個辦公室和遠程用戶4.3.1企業(yè)專用網(wǎng)企業(yè)網(wǎng)是由企業(yè)建設用來互聯(lián)公司各個部門的網(wǎng)絡，如生產基地、總部、遠程辦公室、商店等為了共享電腦資源而設立的。4.3.2虛擬專用網(wǎng)虛擬專用網(wǎng)絡（VPN）是一種特殊的計算機網(wǎng)絡，其中某些節(jié)點之間的聯(lián)系通過公開式電路連接或通過一些較大的網(wǎng)絡（例如，互聯(lián)網(wǎng)）中的虛擬鏈路，而不是通過物理線路。這種通過大型網(wǎng)絡的虛擬專用網(wǎng)使用的數(shù)據(jù)鏈路層協(xié)議被稱為隧道。安全通信是公用因特網(wǎng)中一個常見的應用，但VPN不需要這種明確的安全性能，如認證或者內容加密。例如，VPN可以被用來分離不同用戶在擁有強大安全特性的底層網(wǎng)絡進行通訊時的流量。VPN可能有盡力而為的特性或在VPN客戶端和VPN服務提供者之間有固定的服務等級協(xié)定(SLA)。一般來說，VPN拓撲比點對點要復雜的多。4.3.3互聯(lián)網(wǎng)絡一個網(wǎng)際網(wǎng)路使用路由器通過一種常見的路由技術(OSI第三層)連接兩個或更多的私人計算機?；ヂ?lián)網(wǎng)是許多互聯(lián)網(wǎng)絡的一個集合，因此被縮短稱為互聯(lián)網(wǎng)。4.4骨干網(wǎng)骨干網(wǎng)絡(BBN)，骨干網(wǎng)絡或網(wǎng)絡骨干是計算機網(wǎng)絡基礎設施的一部分，它連接了不同種類的網(wǎng)絡，并且它提供了不同局域網(wǎng)和不同子網(wǎng)之間進行通信的路徑。骨干網(wǎng)可以將在同一座樓里、不同的建筑物中、校園環(huán)境中或國外的不同網(wǎng)絡連接起來。通常，骨干網(wǎng)絡的承載能力大于連接到它上面的網(wǎng)絡。在一家擁有分布在不同區(qū)域子公司的大公司里，可能有骨干網(wǎng)將不同的區(qū)域連接在一起，例如，如果一個服務器集群系統(tǒng)需要被公司內坐落于各種不同的地理位置的部門訪問。將不同部門連接在一起的那部分網(wǎng)絡(例如:局域網(wǎng)，無線網(wǎng))經(jīng)常被稱作網(wǎng)絡骨干。在骨干網(wǎng)絡的設計中經(jīng)常會考慮到網(wǎng)絡擁塞的問題。不應將骨干網(wǎng)絡和因特網(wǎng)骨干混同。4.4.1全球區(qū)域網(wǎng)絡全球區(qū)域網(wǎng)絡(GAN)是一個用于支持通過任意數(shù)量的無線局域網(wǎng)、衛(wèi)星覆蓋區(qū)域等進行移動通信的網(wǎng)絡。移動通信的主要挑戰(zhàn)是處理從一個覆蓋地區(qū)轉到另一個地區(qū)的用戶通信。電氣與電子工程協(xié)會802項目涉及一系列地面無線局域網(wǎng)。4.4.2互聯(lián)網(wǎng)互聯(lián)網(wǎng)是一個全球性的聯(lián)結政府、學術、公司、公共領域和私人計算機系統(tǒng)的網(wǎng)絡。它基于互聯(lián)網(wǎng)的網(wǎng)絡技術協(xié)議組件。這繼承了由美國國防部開發(fā)研制的高等研究計劃署網(wǎng)絡(阿帕網(wǎng))?；ヂ?lián)網(wǎng)也是萬維網(wǎng)(WWW)的通信主干。4.4.3內部網(wǎng)和外部網(wǎng)內部網(wǎng)和外部網(wǎng)是一個計算機網(wǎng)絡的延伸部分，它通常是一個局域網(wǎng)。內部網(wǎng)是一系列網(wǎng)絡的集合，它使用網(wǎng)際協(xié)議和基于網(wǎng)際協(xié)議的工具，如瀏覽器和文件傳輸應用程序，他們由單一管理實體進行管理。管理實體只對授權的用戶開放內聯(lián)網(wǎng)。通常內部網(wǎng)是一個機構的內部網(wǎng)絡。一個大的內聯(lián)網(wǎng)一般會有至少一個網(wǎng)絡服務器，為用戶提供組織過的信息。外部網(wǎng)被限制在單一的組織或實體的范圍內，通常它也會被限制連接到一個或多個組織或實體。但不一定是受信任的組織或實體，例如公司的客戶可能獲得企業(yè)內部網(wǎng)的訪問權限，同時從安全的觀點來講客戶可能不會被認為是可信賴的。從技術上講，外部網(wǎng)也被分類為CAN、MAN、WAN或者其他類型的網(wǎng)絡。盡管外聯(lián)網(wǎng)不能只包括單一的一個局域網(wǎng)，它必須擁有至少一個與外部網(wǎng)絡的連接。4.4.4覆蓋網(wǎng)絡覆蓋網(wǎng)絡是一個建立在另一個計算機上面網(wǎng)絡上面的虛擬網(wǎng)絡。覆蓋網(wǎng)絡中的每個節(jié)點通過虛擬的或者邏輯上的鏈接相連，每個節(jié)點都對應一條路徑，或者在底層網(wǎng)絡通過許多物理鏈接來連接網(wǎng)絡。覆蓋網(wǎng)絡的樣本:在SONET光纖上的IPComputernetworkFromWikipedia,thefreeencyclopedia"Computernetworks"redirectshere.Fortheperiodical,seeComputerNetworks(journal).Acomputernetwork,oftensimplyreferredtoasanetwork,isacollectionofcomputersanddevicesinterconnectedbycommunicationschannelsthatfacilitatecommunicationsamongusersandallowsuserstoshareresources.Networksmaybeclassifiedaccordingtoawidevarietyofcharacteristics.Acomputernetworkallowssharingofresourcesandinformationamonginterconnecteddevices.Contents1History2Purpose3Networkclassification3.1Connectionmethod3.2Wiredtechnologies3.3Wirelesstechnologies3.4Scale3.5Functionalrelationship(networkarchitecture)3.6Networktopology4Typesofnetworksbasedonphysicalscope4.1Localareanetwork4.1.1Personalareanetwork4.1.2Homeareanetwork4.2Wideareanetwork4.2.1Campusnetwork4.3Metropolitanareanetwork4.3.1Enterpriseprivatenetwork4.3.2Virtualprivatenetwork4.3.3Internetwork4.4Backbonenetwork4.4.1Globalareanetwork4.4.2Internet4.4.3Intranetsandextranets4.4.4Overlaynetwork5ReferencesHistoryEarlynetworksofcommunicatingcomputersincludedthemilitaryradarsystemSemi-AutomaticGroundEnvironment(SAGE)anditsrelativethecommercialairlinereservationsystemSemi-AutomaticBusinessResearchEnvironment(SABRE),startedinthelate1950s.[1][2]WhenRussialaunchedHisSPUTNIKSatelliteinSpaceIn1957.TheAmericanStartedAgencyNamesADVANCERESEARCHPROJECTAGENCY(ARPA)&launchedHis1stSatelliteWithin18MonthAfterEstablishment.ThenSharingOfTheInformationInAnotherComputerTheyUseARPANET.AndThisAllResponsibilityOnAmerica'sDr.LIEDLIEDER.Thenin1969,ARPANETComesinINDIAAndINDIANSwitchedThisNameToNETWORK.Inthe1960s,theAdvancedResearchProjectsAgency(ARPA)startedfundingthedesignoftheAdvancedResearchProjectsAgencyNetwork(ARPANET)fortheUnitedStatesDepartmentofDefense.Developmentofthenetworkbeganin1969,basedondesignsdevelopedduringthe1960s.[3]TheARPANETevolvedintothemodernInternet.PurposeComputernetworkscanbeusedforavarietyofpurposes:Facilitatingcommunications.Usinganetwork,peoplecancommunicateefficientlyandeasilyviaemail,instantmessaging,chatrooms,telephone,videotelephonecalls,andvideoconferencing.Sharinghardware.Inanetworkedenvironment,eachcomputeronanetworkmayaccessandusehardwareresourcesonthenetwork,suchasprintingadocumentonasharednetworkprinter.Sharingfiles,data,andinformation.Inanetworkenvironment,authorizedusermayaccessdataandinformationstoredonothercomputersonthenetwork.Thecapabilityofprovidingaccesstodataandinformationonsharedstoragedevicesisanimportantfeatureofmanynetworks.Sharingsoftware.Usersconnectedtoanetworkmayrunapplicationprogramsonremotecomputers.Informationpreservation.Security.NetworkclassificationThefollowinglistpresentscategoriesusedforclassifyingnetworks.ConnectionmethodComputernetworkscanbeclassifiedaccordingtothehardwareandsoftwaretechnologythatisusedtointerconnecttheindividualdevicesinthenetwork,suchasopticalfiber,Ethernet,wirelessLAN,HomePNA,powerlinecommunicationorG.hn.EthernetasitisdefinedbyIEEE802utilizesvariousstandardsandmediumsthatenablecommunicationbetweendevices.Frequentlydeployeddevicesincludehubs,switches,bridges,orrouters.WirelessLANtechnologyisdesignedtoconnectdeviceswithoutwiring.Thesedevicesuseradiowavesorinfraredsignalsasatransmissionmedium.ITU-TG.hntechnologyusesexistinghomewiring(coaxialcable,phonelinesandpowerlines)tocreateahigh-speed(upto1Gigabit/s)localareanetwork.WiredtechnologiesTwistedpairwireisthemostwidelyusedmediumfortelecommunication.Twisted-paircablingconsistofcopperwiresthataretwistedintopairs.Ordinarytelephonewiresconsistoftwoinsulatedcopperwirestwistedintopairs.Computernetworkingcablingconsistof4pairsofcoppercablingthatcanbeutilizedforbothvoiceanddatatransmission.Theuseoftwowirestwistedtogetherhelpstoreducecrosstalkandelectromagneticinduction.Thetransmissionspeedrangesfrom2millionbitspersecondto100millionbitspersecond.TwistedpaircablingcomesintwoformswhichareUnshieldedTwistedPair(UTP)andShieldedtwisted-pair(STP)whichareratedincategorieswhicharemanufacturedindifferentincrementsforvariousscenarios.Coaxialcableiswidelyusedforcabletelevisionsystems,officebuildings,andotherwork-sitesforlocalareanetworks.Thecablesconsistofcopperoraluminumwirewrappedwithinsulatinglayertypicallyofaflexiblematerialwithahighdielectricconstant,allofwhicharesurroundedbyaconductivelayer.Thelayersofinsulationhelpminimizeinterferenceanddistortion.Transmissionspeedrangefrom200milliontomorethan500millionbitspersecond.Opticalfibercableconsistsofoneormorefilamentsofglassfiberwrappedinprotectivelayers.Ittransmitslightwhichcantraveloverextendeddistances.Fiber-opticcablesarenotaffectedbyelectromagneticradiation.Transmissionspeedmayreachtrillionsofbitspersecond.Thetransmissionspeedoffiberopticsishundredsoftimesfasterthanforcoaxialcablesandthousandsoftimesfasterthanatwisted-pairwire.[citationneeded]WirelesstechnologiesTerrestrialmicrowave–TerrestrialmicrowavesuseEarth-basedtransmitterandreceiver.Theequipmentlookssimilartosatellitedishes.Terrestrialmicrowavesuselow-gigahertzrange,whichlimitsallcommunicationstoline-of-sight.Pathbetweenrelaystationsspacedapprox,30milesapart.Microwaveantennasareusuallyplacedontopofbuildings,towers,hills,andmountainpeaks.Communicationssatellites–ThesatellitesusemicrowaveradioastheirtelecommunicationsmediumwhicharenotdeflectedbytheEarth'satmosphere.Thesatellitesarestationedinspace,typically22,000miles(forgeosynchronoussatellites)abovetheequator.TheseEarth-orbitingsystemsarecapableofreceivingandrelayingvoice,data,andTVsignals.CellularandPCSsystems–Useseveralradiocommunicationstechnologies.Thesystemsaredividedtodifferentgeographicareas.Eachareahasalow-powertransmitterorradiorelayantennadevicetorelaycallsfromoneareatothenextarea.WirelessLANs–Wirelesslocalareanetworkuseahigh-frequencyradiotechnologysimilartodigitalcellularandalow-frequencyradiotechnology.WirelessLANsusespreadspectrumtechnologytoenablecommunicationbetweenmultipledevicesinalimitedarea.Anexampleofopen-standardswirelessradio-wavetechnologyisIEEE.Infraredcommunication,whichcantransmitsignalsbetweendeviceswithinsmalldistancesnotmorethan10meterspeertopeeror(facetoface)withoutanybodyinthelineoftransmitting.ScaleNetworksareoftenclassifiedaslocalareanetwork(LAN),wideareanetwork(WAN),metropolitanareanetwork(MAN),personalareanetwork(PAN),virtualprivatenetwork(VPN),campusareanetwork(CAN),storageareanetwork(SAN),andothers,dependingontheirscale,scopeandpurpose,e.g.,controllerareanetwork(CAN)usage,trustlevel,andaccessrightoftendifferbetweenthesetypesofnetworks.LANstendtobedesignedforinternalusebyanorganization'sinternalsystemsandemployeesinindividualphysicallocations,suchasabuilding,whileWANsmayconnectphysicallyseparatepartsofanorganizationandmayincludeconnectionstothirdparties.Functionalrelationship(networkarchitecture)Computernetworksmaybeclassifiedaccordingtothefunctionalrelationshipswhichexistamongtheelementsofthenetwork,e.g.,activenetworking,client–server,Wirelessadhocnetworkandpeer-to-peer(workgroup)architecture.NetworktopologyMainarticle:NetworktopologyComputernetworksmaybeclassifiedaccordingtothenetworktopologyuponwhichthenetworkisbased,suchasbusnetwork,starnetwork,ringnetwork,meshnetwork.Networktopologyisthecoordinationbywhichdevicesinthenetworkarearrangedintheirlogicalrelationstooneanother,independentofphysicalarrangement.Evenifnetworkedcomputersarephysicallyplacedinalineararrangementandareconnectedtoahub,thenetworkhasastartopology,ratherthanabustopology.Inthisregardthevisualandoperationalcharacteristicsofanetworkaredistinct.Networksmaybeclassifiedbasedonthemethodofdatausedtoconveythedata,theseincludedigitalandanalognetworks.TypesofnetworksbasedonphysicalscopeCommontypesofcomputernetworksmaybeidentifiedbytheirscale.LocalareanetworkAlocalareanetwork(LAN)isanetworkthatconnectscomputersanddevicesinalimitedgeographicalareasuchashome,school,computerlaboratory,officebuilding,orcloselypositionedgroupofbuildings.Eachcomputerordeviceonthenetworkisanode.CurrentwiredLANsaremostlikelytobebasedonEthernettechnology,althoughnewstandardslikeITU-TG.hnalsoprovideawaytocreateawiredLANusingexistinghomewires(coaxialcables,phonelinesandpowerlines).[4]Typicallibrarynetwork,inabranchingtreetopologyandcontrolledaccesstoresourcesAllinterconnecteddevicesmustunderstandthenetworklayer(layer3),becausetheyarehandlingmultiplesubnets(thedifferentcolors).Thoseinsidethelibrary,whichhaveonly10/100Mbit/sEthernetconnectionstotheuserdeviceandaGigabitEthernetconnectiontothecentralrouter,couldbecalled"layer3switches"becausetheyonlyhaveEthernetinterfacesandmustunderstandIP.Itwouldbemorecorrecttocallthemaccessrouters,wheretherouteratthetopisadistributionrouterthatconnectstotheInternetandacademicnetworks'customeraccessrouters.ThedefiningcharacteristicsofLANs,incontrasttoWANs(WideAreaNetworks),includetheirhigherdatatransferrates,smallergeographicrange,andnoneedforleasedtelecommunicationlines.CurrentEthernetorotherIEEE802.3LANtechnologiesoperateatspeedsupto10Gbit/s.Thisisthedatatransferrate.IEEEhasprojectsinvestigatingthestandardizationof40and100Gbit/s.[5]PersonalareanetworkApersonalareanetwork(PAN)isacomputernetworkusedforcommunicationamongcomputeranddifferentinformationtechnologicaldevicesclosetooneperson.SomeexamplesofdevicesthatareusedinaPANarepersonalcomputers,printers,faxmachines,telephones,PDAs,scanners,andevenvideogameconsoles.APANmayincludewiredandwirelessdevices.ThereachofaPANtypicallyextendsto10meters.[6]AwiredPANisusuallyconstructedwithUSBandFirewireconnectionswhiletechnologiessuchasBluetoothandinfraredcommunicationtypicallyformawirelessPAN.HomeareanetworkAhomeareanetwork(HAN)isaresidentialLANwhichisusedforcommunicationbetweendigitaldevicestypicallydeployedinthehome,usuallyasmallnumberofpersonalcomputersandaccessories,suchasprintersandmobilecomputingdevices.AnimportantfunctionisthesharingofInternetaccess,oftenabroadbandservicethroughaCATVorDigitalSubscriberLine(DSL)provider.Itcanalsobereferredtoasanofficeareanetwork(OAN).WideareanetworkAwideareanetwork(WAN)isacomputernetworkthatcoversalargegeographicareasuchasacity,country,orspansevenintercontinentaldistances,usingacommunicationschannelthatcombinesmanytypesofmediasuchastelephonelines,cables,andairwaves.AWANoftenusestransmissionfacilitiesprovidedbycommoncarriers,suchastelephonecompanies.WANtechnologiesgenerallyfunctionatthelowerthreelayersoftheOSIreferencemodel:thephysicallayer,thedatalinklayer,andthenetworklayer.CampusnetworkAcampusnetworkisacomputernetworkmadeupofaninterconnectionoflocalareanetworks(LAN's)withinalimitedgeographicalarea.Thenetworkingequipments(switches,routers)andtransmissionmedia(opticalfiber,copperplant,Cat5cablingetc.)arealmostentirelyowned(bythecampustenant/owner:anenterprise,university,governmentetc.).Inthecaseofauniversitycampus-basedcampusnetwork,thenetworkislikelytolinkavarietyofcampusbuildingsincluding;academicdepartments,theuniversitylibraryandstudentresidencehalls.MetropolitanareanetworkAMetropolitanareanetworkisalargecomputernetworkthatusuallyspansacityoralargecampus.SampleEPNmadeofFramerelayWANconnectionsanddialupremoteaccess.SampleVPNusedtointerconnect3officesandremoteusersEnterpriseprivatenetworkAnenterpriseprivatenetworkisanetworkbuildbyanenterprisetointerconnectvariouscompanysites,e.g.,productionsites,headoffices,remoteoffices,shops,inordertosharecomputerresources.VirtualprivatenetworkAvirtualprivatenetwork(VPN)isacomputernetworkinwhichsomeofthelinksbetweennodesarecarriedbyopenconnectionsorvirtualcircuitsinsomelargernetwork(e.g.,theInternet)insteadofbyphysicalwires.Thedatalinklayerprotocolsofthevirtualnetworkaresaidtobetunneledthroughthelargernetworkwhenthisisthecase.OnecommonapplicationissecurecommunicationsthroughthepublicInternet,butaVPNneednothaveexplicitsecurityfeatures,suchasauthenticationorcontentencryption.VPNs,forexample,canbeusedtoseparatethetrafficofdifferentusercommunitiesoveranunderlyingnetworkwithstrongsecurityfeatures.VPNmayhavebest-effortperformance,ormayhaveadefinedservicelevelagreement(SLA)betweentheVPNcustomerandtheVPNserviceprovider.Generally,aVPNhasatopologymorecomplexthanpoint-to-point.InternetworkAninternetworkistheconnectionoftwoormoreprivatecomputernetworksviaacommonroutingtechnology(OSILayer3)usingrouters.TheInternetisanaggregationofmanyinternetworks,henceitsnamewasshortenedtoInternet.BackbonenetworkABackbonenetwork(BBN)Abackbonenetworkornetworkbackboneispartofacomputernetworkinfrastructurethatinterconnectsvariouspiecesofnetwork,providingapathfortheexchangeofinformationbetweendifferentLANsorsubnetworks.[1][2]Abackbonecantietogetherdiversenetworksinthesamebuilding,indifferentbuildingsinacampusenvironment,oroverwideareas.Normally,thebackbone'scapacityisgreaterthanthenetworksconnectedtoit.Alargecorporationthathasmanylocationsmayhaveabackbonenetworkthattiesallofthelocationstogether,forexample,ifaserverclusterneedstobeaccessedbydifferentdepartmentsofacompanythatarelocatedatdifferentgeographicallocations.Thepiecesofthenetworkconnections(forexample:ethernet,wireless)thatbringthesedepartmentstogetherisoftenmentionedasnetworkbackbone.Networkcongestionisoftentakenintoconsiderationwhiledesigningbackbones.BackbonenetworksshouldnotbeconfusedwiththeInternetbackbone.GlobalareanetworkAglobalareanetwork(GAN)isanetworkusedforsupportingmobilecommunicationsacrossanarbitrarynumberofwirelessLANs,satellitecoverageareas,etc.Thekeychallengeinmobilecommunicationsishandingofftheusercommunicationsfromonelocalcoverageareatothenext.InIEEEProject802,thisinvolvesasuccessionofterrestrialwirelessLANs.[7]InternetTheInternetisaglobalsystemofinterconnectedgovernmental,academic,corporate,public,andprivatecomputernetworks.ItisbasedonthenetworkingtechnologiesoftheInternetProtocolSuite.ItisthesuccessoroftheAdvancedResearchProjectsAgencyNetwork(ARPANET)developedbyDARPAoftheUnitedStatesDepartmentofDefense.TheInternetisalsothecommunicationsbackboneunderlyingtheWorldWideWeb(WWW).IntranetsandextranetsIntranetsandextranetsarepartsorextensionsofacomputernetwork,usuallyalocalareanetwork.Anintranetisasetofnetworks,usingtheInternetProtocolandIP-basedtoolssuchaswebbrowsersandfiletransferapplications,thatisunderthecontrolofasingleadministrativeentity.Thatadministrativeentityclosestheintranettoallbutspecific,authorizedusers.Mostcommonly,anintranetistheinternalnetworkofanorganization.Alargeintranetwilltypicallyhaveatleastonewebservertoprovideuserswithorganizationalinformation.Anextranetisanetworkthatislimitedinscopetoasingleorganizationorentityandalsohaslimitedconnectionstothenetworksofoneormoreotherusually,butnotnecessarily,trustedorganizationsorentities—acompany'scustomersmaybegivenaccesstosomepartofitsintranet—whileatthesametimethecustomersmaynotbeconsideredtrustedfromasecuritystandpoint.Technically,anextranetmayalsobecategorizedasaCAN,MAN,WAN,orothertypeofnetwork,althoughanextranetcannotconsistofasingleLAN;itmusthaveatleastoneconnectionwithanexternalnetwork.OverlaynetworkAnoverlaynetworkisavirtualcomputernetworkthatisbuiltontopofanothernetwork.Nodesintheoverlayareconnectedbyvirtualorlogicallinks,eachofwhichcorrespondstoapath,perhapsthroughmanyphysicallinks,intheunderlyingnetwork.Asampleoverlaynetwork:IPoverSONEToverOptical

References1.MichaelA.Banks(2008).Onthewaytotheweb:thesecrethistoryoftheinternetanditsfounders.Apress.p.1.ISBN9781430208693./books?id=P9wbSjO9WMMC&pg=PA1.2.ChristosJ.P.Moschovitis(1998).HistoryoftheInternet:achronology,1843tothepresent.ABC-CLIO.p.36.ISBN9781576071182./books?ei=3isZTfzQMIaasAPHrrioAg&ct=result&id=Hu5SAAAAMAAJ&dq=intitle%3A%22history+of+the+internet%22+sage+sabre&q=sage+sabre%27s#search_anchor.3.ChrisSutton."InternetBegan35YearsAgoatUCLAwithFirstMessageEverSentBetweenTwoComputers".UCLA.Archivedfromtheoriginalon2008-03-08./web/20080308120314//stories/2004/Internet35.htm.4.Newglobalstandardforfullynetworkedhome,ITU-TPressRelease5.IEEEP802.3ba40Gb/sand100Gb/sEthernetTaskForce6."personalareanetwork(PAN)"./sDefinition/0,,sid40_gci546288,00.html.Retrieved2011-01-29.7.MobileBroadbandWirelessconnections(MBWA)8.D.Andersen,H.Balakrishnan,M.Kaashoek,andR.Morris.ResilientOverlayNetworks.InProc.ACMSOSP,Oct.2001.9."Defineswitch."../TERM/s/switch.html.Retrieved2008-04-08.10."BasicComponentsofaLocalAreaNetwork(LAN)".NetworkB./lan-components/local-area-network-lan-basic-components/.Retrieved2008-04-08.基于C8051F單片機直流電動機反饋控制系統(tǒng)的設計與研究基于單片機的嵌入式Web服務器的研究MOTOROLA單片機MC68HC（8）05PV8/A內嵌EEPROM的工藝和制程方法及對良率的影響研究基于模糊控制的電阻釬焊單片機溫度控制系統(tǒng)的研制基于MCS-51系列單片機的通用控制模塊的研究基于單片機實現(xiàn)的供暖系統(tǒng)最佳啟停自校正（STR）調節(jié)器單片機控制的二級倒立擺系統(tǒng)的研究基于增強型51系列單片機的TCP/IP協(xié)議棧的實現(xiàn)基于單片機的蓄電池自動監(jiān)測系統(tǒng)基于32位嵌入式單片機系統(tǒng)的圖像采集與處理技術的研究基于單片機的作物營養(yǎng)診斷專家系統(tǒng)的研究基于單片機的交流伺服電機運動控制系統(tǒng)研究與開發(fā)基于單片機的泵管內壁硬度測試