ComputerEnglishUnit8ComputerNetwork計(jì)算機(jī)英語第八單元計(jì)算機(jī)網(wǎng)絡(luò)知識(shí)分享

1、Good is good, but better carries it.精益求精，善益求善。ComputerEnglishUnit8ComputerNetwork計(jì)算機(jī)英語第八單元計(jì)算機(jī)網(wǎng)絡(luò)-Unit8ComputerNetwork第八單元：計(jì)算機(jī)網(wǎng)絡(luò)SectionANetworkFundamentals課文A：網(wǎng)絡(luò)基本原理Theneedtoshareinformationandresourcesamongdifferentcomputershasledtolinkedcomputersystems,callednetworks,inwhichcomputersareconnectedsoth

2、atdatacanbetransferredfrommachinetomachine.在不同計(jì)算機(jī)之間共享信息和資源的需要，導(dǎo)致了相互連接的計(jì)算機(jī)系統(tǒng)的產(chǎn)生。這種相互連接的計(jì)算機(jī)系統(tǒng)被稱為網(wǎng)絡(luò)。在網(wǎng)絡(luò)中，計(jì)算機(jī)連接在一起，從而數(shù)據(jù)可以從一臺(tái)計(jì)算機(jī)傳輸?shù)搅硪慌_(tái)計(jì)算機(jī)。Inthesenetworks,computeruserscanexchangemessagesandshareresources-suchasprintingcapabilities,softwarepackages,anddatastoragefacilities-thatarescatteredthroughoutthesys

3、tem.在網(wǎng)絡(luò)中，計(jì)算機(jī)用戶可以交換信息，并共享分散在整個(gè)網(wǎng)絡(luò)系統(tǒng)的資源，如打印能力、軟件包以及數(shù)據(jù)存儲(chǔ)設(shè)備。Theunderlyingsoftwarerequiredtosupportsuchapplicationshasgrownfromsimpleutilitypackagesintoanexpandingsystemofnetworksoftwarethatprovidesasophisticatednetworkwideinfrastructure.支持這類應(yīng)用所需的基本軟件，已經(jīng)從簡單的實(shí)用軟件包發(fā)展成一個(gè)不斷擴(kuò)展的網(wǎng)絡(luò)軟件系統(tǒng)，該系統(tǒng)提供了一個(gè)復(fù)雜的網(wǎng)絡(luò)范圍的基礎(chǔ)結(jié)構(gòu)。Inase

4、nse,networksoftwareisevolvingintoanetworkwideoperatingsystem.從某種意義上說，網(wǎng)絡(luò)軟件正在演變成一個(gè)網(wǎng)絡(luò)范圍的操作系統(tǒng)。NetworkClassifications一、網(wǎng)絡(luò)分類Acomputernetworkisoftenclassifiedasbeingeitheralocalareanetwork(LAN),ametropolitanareanetwork(MAN),orawideareanetwork(WAN).計(jì)算機(jī)網(wǎng)絡(luò)常常劃分為局域網(wǎng)、城域網(wǎng)和廣域網(wǎng)。ALANnormallyconsistsofacollectionofco

5、mputersinasinglebuildingorbuildingcomplex.局域網(wǎng)通常由一幢建筑物或一個(gè)建筑群中的若干計(jì)算機(jī)組成。Forexample,thecomputersonauniversitycampusorthoseinamanufacturingplantmightbeconnectedbyaLAN.例如，大學(xué)校園里的計(jì)算機(jī)或制造工廠中的計(jì)算機(jī)可以用局域網(wǎng)連接。AMANisanetworkofintermediatesize,suchasonespanningalocalcommunity.城域網(wǎng)屬于中型網(wǎng)絡(luò)，如一個(gè)覆蓋某一社區(qū)的網(wǎng)絡(luò)。AWANlinksmachineso

6、veragreaterdistance-perhapsinneighboringcitiesoronoppositesidesoftheworld.廣域網(wǎng)連接地理范圍更廣的計(jì)算機(jī)，這些計(jì)算機(jī)或許在相鄰的城市，或許在地球相反的兩面。Anothermeansofclassifyingnetworksisbasedonwhetherthenetworksinternaloperationisbasedondesignsthatareinthepublicdomainoroninnovationsownedandcontrolledbyaparticularentitysuchasanindividu

7、aloracorporation.網(wǎng)絡(luò)分類的另一種方式是根據(jù)網(wǎng)絡(luò)的內(nèi)部運(yùn)行是基于無專利權(quán)保護(hù)的設(shè)計(jì)還是基于特定實(shí)體（如個(gè)人或公司）所擁有和控制的革新。Anetworkoftheformertypeiscalledanopennetwork;anetworkofthelattertypeiscalledaclosed,orsometimesaproprietary,network.前一種類型的網(wǎng)絡(luò)稱為開放式網(wǎng)絡(luò)，后一種類型的網(wǎng)絡(luò)稱為封閉式網(wǎng)絡(luò)，有時(shí)也稱為專有網(wǎng)絡(luò)。TheInternetisanopensystem.因特網(wǎng)屬于開放式系統(tǒng)。Inparticular,communicationthro

8、ughouttheInternetisgovernedbyanopencollectionofstandardsknownastheTCP/IPprotocolsuite.尤其是，整個(gè)因特網(wǎng)的通信是由一組稱為TCP/IP協(xié)議組的開放標(biāo)準(zhǔn)來控制的。Anyoneisfreetousethesestandardswithoutpayingfeesorsigninglicenseagreements.任何人都可以自由地使用這些標(biāo)準(zhǔn)，而不需要付費(fèi)或簽署許可協(xié)議。Incontrast,acompanysuchasNovellInc.mightdevelopsystemsforwhichitchoosest

9、omaintainownershiprights,allowingthecompanytodrawincomefromsellingorleasingtheseproducts.相反，像Novell股份有限公司這樣的公司可能選擇為其開發(fā)的系統(tǒng)保留所有權(quán)，通過出售或出租這些產(chǎn)品獲得收入。Networksbasedonsuchsystemsareexamplesofclosednetworks.基于這類系統(tǒng)的網(wǎng)絡(luò)屬于封閉式網(wǎng)絡(luò)的例子。Stillanotherwayofclassifyingnetworksisbasedonthetopologyofthenetwork,whichreferstot

10、hepatterninwhichthemachinesareconnected.還有一種網(wǎng)絡(luò)分類方法，它基于網(wǎng)絡(luò)的拓?fù)浣Y(jié)構(gòu)，即計(jì)算機(jī)相互連接的模式。Thebustopology,ringtopology,andstartopologyarethreepopulartopologies.總線拓?fù)浣Y(jié)構(gòu)、環(huán)形拓?fù)浣Y(jié)構(gòu)和星形拓?fù)浣Y(jié)構(gòu)是3種流行的拓?fù)浣Y(jié)構(gòu)。Ofthese,thestarnetworkisperhapstheoldest,havingevolvedfromtheparadigmofalargecentralcomputerservingmanyusers.其中，星形網(wǎng)絡(luò)或許是最古老的，這種

11、網(wǎng)絡(luò)由一臺(tái)大型中央計(jì)算機(jī)服務(wù)許多用戶的范式演變而來。Asthesimpleterminalsemployedbytheseusersgrewintosmallcomputersthemselves,astarnetworkemerged.隨著這些用戶所使用的簡單終端本身發(fā)展成小型計(jì)算機(jī)，星形網(wǎng)絡(luò)也就出現(xiàn)了。Apointtoemphasizeisthattheconnectionsbetweenmachinesinanetworkdonotneedtobephysical.需要強(qiáng)調(diào)的一點(diǎn)是，在一個(gè)網(wǎng)絡(luò)中，計(jì)算機(jī)之間的連接并不一定是物理連接。Wirelessnetworks,usingradiob

12、roadcasttechnology,arebecomingquitecommon.使用無線廣播技術(shù)的無線網(wǎng)絡(luò)正在變得相當(dāng)常見。Protocols二、協(xié)議Foranetworktofunctionreliably,itisimportanttoestablishrulesbywhichnetworkactivitiesareconducted.為了網(wǎng)絡(luò)可靠運(yùn)行，確立進(jìn)行網(wǎng)絡(luò)活動(dòng)所遵循的規(guī)則很重要。Suchrulesarecalledprotocols.這類規(guī)則稱為協(xié)議。Bydevelopingandadoptingprotocolstandards,vendersareabletobuildp

13、roductsfornetworkapplicationsthatarecompatiblewithproductsfromothervenders.通過開發(fā)和采用協(xié)議標(biāo)準(zhǔn)，不同廠商制造的網(wǎng)絡(luò)應(yīng)用產(chǎn)品能夠相互兼容。Thus,thedevelopmentofprotocolstandardsisanindispensableprocessinthedevelopmentofnetworkingtechnologies.因此，在聯(lián)網(wǎng)技術(shù)的開發(fā)中，協(xié)議標(biāo)準(zhǔn)的開發(fā)是一個(gè)必不可少的過程。Asanintroductiontotheprotocolconcept,letusconsidertheproble

14、mofcoordinatingthetransmissionofmessagesamongcomputersinanetwork.作為對協(xié)議概念的介紹，讓我們考慮在一個(gè)網(wǎng)絡(luò)的計(jì)算機(jī)之間協(xié)調(diào)報(bào)文傳輸?shù)膯栴}。Withoutrulesgoverningthiscommunication,allthecomputersmightinsistontransmittingmessagesatthesametimeormightfailtorelaymessageswhenthatassistanceisrequired.如果沒有控制這種通信的規(guī)則，所有的計(jì)算機(jī)就可能堅(jiān)持同時(shí)傳輸報(bào)文，或者在需要傳遞報(bào)文時(shí)而

15、未能傳遞。Oneapproachtosolvingthisproblemisthetokenringprotocol,whichwasdevelopedbyIBMinthe1970sandcontinuestobeapopularprotocolinnetworksbasedontheringtopology.解決這個(gè)問題的一種方法是令牌環(huán)協(xié)議，該協(xié)議由IBM公司20世紀(jì)70年代開發(fā)，今天在基于環(huán)形拓?fù)浣Y(jié)構(gòu)的網(wǎng)絡(luò)中依然是一種很流行的協(xié)議。Inthisprotocol,allthemachinesinthenetworktransmitmessagesinonlyonecommondirecti

16、on(Figure8A-1),meaningthatallmessagessentoverthenetworkmovearoundtheringinthesamedirectionbybeingforwardedfromcomputertocomputer.在這個(gè)協(xié)議里，網(wǎng)絡(luò)中的所有計(jì)算機(jī)都只沿一個(gè)共同的方向傳輸報(bào)文（圖8A-1）。也就是說，通過網(wǎng)絡(luò)發(fā)送的所有報(bào)文都沿一個(gè)相同的方向繞環(huán)形網(wǎng)絡(luò)移動(dòng)，依次經(jīng)由各個(gè)計(jì)算機(jī)轉(zhuǎn)發(fā)。Whenamessagereachesitsdestination,thedestinationmachinekeepsacopyofitandforwardsacopyona

17、roundthering.一份報(bào)文到達(dá)目的地后，目的地的計(jì)算機(jī)保留一個(gè)副本并繞環(huán)形網(wǎng)絡(luò)轉(zhuǎn)發(fā)一個(gè)副本。Whentheforwardedcopyreachestheoriginatingcomputer,thatmachineknowsthatthemessagemusthavereacheditsdestinationandremovesthemessagefromthering.當(dāng)轉(zhuǎn)發(fā)的副本到達(dá)始發(fā)計(jì)算機(jī)時(shí)，該計(jì)算機(jī)知道報(bào)文一定到達(dá)了目的地，并將其移出環(huán)形網(wǎng)絡(luò)。Ofcourse,thissystemdependsoninter-machinecooperation.當(dāng)然，這種系統(tǒng)的運(yùn)行依靠計(jì)算

18、機(jī)之間的合作。Ifamachineinsistsonconstantlytransmittingmessagesofitsownratherthanforwardingthoseoftheothermachines,nothingwillbeaccomplished.如果一臺(tái)計(jì)算機(jī)堅(jiān)持不斷地傳輸自己的報(bào)文，而不轉(zhuǎn)發(fā)其他計(jì)算機(jī)的報(bào)文，那么這個(gè)系統(tǒng)就什么也執(zhí)行不了。Tosolvethisproblem,auniquebitpattern,calledatoken,ispassedaroundthering.為了解決這個(gè)問題，在環(huán)形網(wǎng)絡(luò)中傳遞一個(gè)稱為令牌的獨(dú)特位模式。Possessionofthis

19、tokengivesamachinetheauthoritytotransmititsownmessage;withoutthetoken,amachineisonlyallowedtoforwardmessages.擁有令牌的計(jì)算機(jī)得到權(quán)利傳輸自己的報(bào)文，而沒有令牌的計(jì)算機(jī)則只允許轉(zhuǎn)發(fā)報(bào)文。Normally,eachmachinemerelyrelaysthetokeninthesamemannerinwhichitrelaysmessages.一般來說，每臺(tái)計(jì)算機(jī)只是像傳遞報(bào)文那樣傳遞令牌。If,however,themachinereceivingthetokenhasmessageso

20、fitsowntointroducetothenetwork,ittransmitsonemessagewhileholdingthetoken.Whenthismessagehascompleteditscyclearoundthering,themachineforwardsthetokentothenextmachineinthering.然而，如果收到令牌的計(jì)算機(jī)有自己的報(bào)文需要通過網(wǎng)絡(luò)傳輸，它就會(huì)保存令牌，同時(shí)傳輸一份報(bào)文。這份報(bào)文在環(huán)形網(wǎng)絡(luò)中環(huán)繞一周后，該計(jì)算機(jī)就將令牌傳遞給環(huán)形網(wǎng)絡(luò)中的下一臺(tái)計(jì)算機(jī)。Likewise,whenthenextmachinereceivesthetok

21、en,itcaneitherforwardthetokenimmediatelyortransmititsownnewmessagebeforesendingthetokenontothenextmachine.同樣，當(dāng)下一臺(tái)計(jì)算機(jī)收到令牌時(shí)，它既可以立即傳遞令牌，也可以先傳輸自己的新報(bào)文，然后將令牌傳遞給下一臺(tái)計(jì)算機(jī)。Inthismanner,eachmachineinthenetworkhasequalopportunitytointroducemessagesofitsownasthetokencirclesaroundthering.這樣，隨著令牌繞著環(huán)形網(wǎng)絡(luò)傳遞，網(wǎng)絡(luò)中的每臺(tái)計(jì)算機(jī)都

22、有同等的機(jī)會(huì)傳輸自己的報(bào)文。AnotherprotocolforcoordinatingmessagetransmissionisusedinbustopologynetworksthatarebasedontheEthernetprotocolcollection.協(xié)調(diào)報(bào)文傳輸?shù)牧硗庖环N協(xié)議用于基于以太網(wǎng)協(xié)議集的總線拓?fù)渚W(wǎng)絡(luò)。InanEthernetsystem,therighttotransmitmessagesiscontrolledbytheprotocolknownasCarrierSenseMultipleAccesswithCollisionDetection(CSMA/CD).

23、在以太網(wǎng)系統(tǒng)中，傳輸報(bào)文的權(quán)利由稱為帶有沖突檢測的載波偵聽多路訪問（CSMA/CD）的協(xié)議控制。Thisprotocoldictatesthateachmessagebebroadcasttoallthemachinesonthebus(Figure8A-2).該協(xié)議規(guī)定，每一份報(bào)文必須向總線上的所有計(jì)算機(jī)廣播（圖8A-2）。Eachmachinemonitorsallthemessagesbutkeepsonlythoseaddressedtoitself.每臺(tái)計(jì)算機(jī)監(jiān)控所有的報(bào)文，但只保留發(fā)送給自己的那些報(bào)文。Totransmitamessage,amachinewaitsuntilthe

24、busissilent,andatthistimeitbeginstransmittingwhilecontinuingtomonitorthebus.一臺(tái)計(jì)算機(jī)要等到總線靜默時(shí)才可以傳輸報(bào)文。這時(shí)，它開始傳輸報(bào)文，同時(shí)繼續(xù)監(jiān)控總線。Ifanothermachinealsobeginstransmitting,bothmachinesdetecttheclashandpauseforabriefrandomperiodoftimebeforetryingtotransmitagain.如果另一臺(tái)計(jì)算機(jī)也開始傳輸報(bào)文，這兩臺(tái)計(jì)算機(jī)都會(huì)檢測到?jīng)_突，并暫停短暫而隨機(jī)的一段時(shí)間，然后再嘗試傳輸。The

25、resultisasystemsimilartothatusedbyasmallgroupofpeopleinaconversation.結(jié)果是形成一種體制，這種體制類似于一小群人對話時(shí)所采用的。Iftwopeoplestarttotalkatonce,theybothstop.如果兩個(gè)人同時(shí)開始說話，他們都會(huì)停下來。Thedifferenceisthatpeoplemightgothroughaseriessuchas,“Imsorry,whatwereyougoingtosay?”,“No,no.不同的是，人們隨后可能進(jìn)行這樣的對話：“抱歉，您想說什么？”，“不，不，您先說?！盰ougof

26、irst,”whereasundertheCSMA/CDprotocoleachmachinemerelytriesagain.而根據(jù)CSMA/CD協(xié)議，每臺(tái)計(jì)算機(jī)只是重新進(jìn)行嘗試。InterprocessCommunication三、進(jìn)程間通信Thevariousactivities(orprocesses)executingonthedifferentcomputerswithinanetwork(orevenexecutingonthesamemachineviatimesharing)mustoftencommunicatewitheachothertocoordinatetheira

27、ctionsandtoperformtheirdesignatedtasks.在一個(gè)網(wǎng)絡(luò)內(nèi)不同計(jì)算機(jī)上（甚至使用分時(shí)方法在同一臺(tái)計(jì)算機(jī)上）執(zhí)行的各種活動(dòng)（或進(jìn)程）必須經(jīng)常互相通信，以便協(xié)調(diào)行動(dòng)，并完成指定的任務(wù)。Suchcommunicationbetweenprocessesiscalledinterprocesscommunication.這種進(jìn)程之間的通信稱為進(jìn)程間通信。Apopularconventionusedforinterprocesscommunicationistheclient/servermodel.進(jìn)程間通信使用的一種流行規(guī)約是客戶機(jī)/服務(wù)器模型。Thismodelde

28、finesthebasicrolesplayedbytheprocessesaseitheraclient,whichmakesrequestsofotherprocesses,oraserver,whichsatisfiestherequestsmadebyclients.這種模型將進(jìn)程扮演的基本角色或定義為向其他進(jìn)程提出請求的客戶機(jī)，或定義為滿足客戶機(jī)所提請求的服務(wù)器。Anearlyapplicationoftheclient/servermodelappearedinnetworksconnectingallthecomputersinaclusterofoffices.客戶機(jī)/服務(wù)器模

29、型的一種早期應(yīng)用，出現(xiàn)在將一組辦公室里的所有計(jì)算機(jī)都連接起來的網(wǎng)絡(luò)中。Inthissituation,asingle,high-qualityprinterwasattachedtothenetworkwhereitwasavailabletoallthemachinesinthenetwork.在這種應(yīng)用中，一臺(tái)高質(zhì)量的打印機(jī)被連接到網(wǎng)絡(luò)上，供其中的所有計(jì)算機(jī)使用。Inthiscasetheprinterplayedtheroleofaserver(oftencalledaprintserver),andtheothermachineswereprogrammedtoplaytheroleo

30、fclientsthatsentprintrequeststotheprintserver.在這種情況下，打印機(jī)扮演了服務(wù)器（常稱為打印服務(wù)器）的角色，而其他計(jì)算機(jī)則通過程序設(shè)計(jì)而扮演了向打印服務(wù)器發(fā)送打印請求的客戶機(jī)角色。Anotherearlyapplicationoftheclient/servermodelwasusedtoreducethecostofdiskstoragewhilealsoremovingtheneedforduplicatecopiesofrecords.客戶機(jī)/服務(wù)器模型的另外一種早期應(yīng)用是為了降低磁盤存儲(chǔ)費(fèi)用，同時(shí)消除復(fù)制記錄的需要。Hereonemachin

31、einanetworkwasequippedwithahigh-capacitymassstoragesystem(usuallyamagneticdisk)thatcontainedallofanorganizationsrecords.在這種情況下，網(wǎng)絡(luò)中的某一臺(tái)計(jì)算機(jī)配備了大容量存儲(chǔ)系統(tǒng)（通常是磁盤），存儲(chǔ)一個(gè)機(jī)構(gòu)的所有記錄。Othermachinesonthenetworkthenrequestedaccesstotherecordsastheyneededthem.這樣，網(wǎng)絡(luò)中的其他計(jì)算機(jī)可根據(jù)需要請求訪問這些記錄。Thusthemachinethatactuallycontaine

32、dtherecordsplayedtheroleofaserver(calledafileserver),andtheothermachinesplayedtheroleofclientsthatrequestedaccesstothefilesthatwerestoredatthefileserver.因此，實(shí)際含有記錄的計(jì)算機(jī)扮演了服務(wù)器（稱為文件服務(wù)器）的角色，而其他計(jì)算機(jī)則扮演了請求訪問文件服務(wù)器上存儲(chǔ)的文件的客戶機(jī)角色。Todaytheclient/servermodelisusedextensivelyinnetworkapplications.今天，客戶機(jī)/服務(wù)器模型在網(wǎng)絡(luò)中廣泛

33、應(yīng)用。However,theclient/servermodelisnottheonlymeansofinterprocesscommunication.不過，客戶機(jī)/服務(wù)器模型并非進(jìn)程間通信的唯一方式。Anothermodelisthepeer-to-peer(oftenabbreviatedP2P)model,whosepropertiesprovideinsightfulcontraststotheclient/servermodel.另外一種模型是對等（peer-to-peer，?？s寫為P2P）模型，其特性與客戶機(jī)/服務(wù)器模型的特性形成鮮明對照。Whereastheclient/ser

34、vermodelinvolvesoneprocess(theserver)communicatingwithnumerousothers(clients),thepeer-to-peermodelinvolvestwoprocessescommunicatingasequals(Figure8A-3).客戶機(jī)/服務(wù)器模型涉及一個(gè)進(jìn)程（服務(wù)器）與許多其他進(jìn)程（客戶機(jī)）通信，而對等模型則涉及兩個(gè)進(jìn)程進(jìn)行對等通信（圖8A-3）。Moreover,whereasaservermustexecutecontinuouslysothatitispreparedtoserveitsclientsatanyt

35、ime,thepeer-to-peermodelusuallyinvolvestwoprocessesthatexecuteonatemporarybasis.而且，服務(wù)器必須持續(xù)運(yùn)行，以準(zhǔn)備好隨時(shí)服務(wù)于客戶機(jī)，而對等模型則通常涉及兩個(gè)進(jìn)程臨時(shí)運(yùn)行。Forexample,applicationofthepeer-to-peermodelincludeinstantmessaginginwhichtwopeoplecarryonawrittenconversationovertheInternetaswellassituationsinwhichpeopleplaygamessuchasches

36、sorcheckers.例如，對等模型的應(yīng)用包括兩個(gè)人通過因特網(wǎng)進(jìn)行書面對話的即時(shí)通信，以及人們參與下國際象棋或西洋跳棋等游戲的情況。Thepeer-to-peermodelisalsoapopularmeansofsharingfilessuchasmusicrecordingsandmotionpicturesviatheInternet(sometimeswithquestionablelegality).對等模型還是通過因特網(wǎng)共享音樂錄音、影片等文件的一種流行方法（其合法性有時(shí)值得懷疑）。Inthiscase,individualswhoareseekingparticularitem

37、sbroadcasttheirdesireovertheInternetandarecontactedbythosewhoowntheitemsofinterest.在這種情況下，尋求特定項(xiàng)目的個(gè)人在因特網(wǎng)上發(fā)布其需求，而擁有他所感興趣項(xiàng)目的人則會(huì)與他取得聯(lián)系。Then,theitemsaretransferredbetweenthetwopartiesusingthepeer-to-peermodel.然后，雙方之間就可以使用對等模型傳輸這些項(xiàng)目。Thisisincontrasttoearlierapproachesthatappliedtheclient/servermodelbyesta

38、blishingacentral“distributioncenter”(theserver)fromwhichclientsdownloadedmusicrecordings(oratleastfoundsourcesforthoseitems).這與應(yīng)用客戶機(jī)/服務(wù)器模型的較早期方法截然不同，這些方法要建立一個(gè)“分發(fā)中心”（服務(wù)器），供客戶機(jī)下載音樂錄音（或者至少找到可以提供這些項(xiàng)目的地方）。Thecentralserver,however,provedtobeafocalpointatwhichthemusicindustrycouldenforcecopyrightlaws,leadi

39、ngtotheeventualdismantlingofthesemusicdistributioncenters.然而，中心服務(wù)器證明是音樂行業(yè)可以運(yùn)用版權(quán)法的一個(gè)焦點(diǎn)對象，結(jié)果最終導(dǎo)致這些音樂分發(fā)中心的解體。Incontrast,thelackofacentralizedbaseofoperationobtainedviathepeer-to-peermodelmakeslegaleffortstoenforcecopyrightlawsmoredifficult.與此形成對照的是，對等模型缺乏一個(gè)操作中心，這使得運(yùn)用版權(quán)法的努力難度增加。Youmightoftenreadorhearth

40、etermpeer-to-peernetwork,whichisanexampleofhowmisuseofterminologycanevolvewhentechnicaltermsareadoptedbythenontechnicalcommunity.你或許經(jīng)常讀到或聽到“對等網(wǎng)絡(luò)”這個(gè)說法，這是當(dāng)技術(shù)術(shù)語被非科技界采用時(shí)可能發(fā)生術(shù)語誤用的一個(gè)例子。Thetermpeer-to-peerreferstoasystembywhichtwoprocessescommunicateoveranetwork(orInternet).Itisnotapropertyofthenetwork(ori

41、nternet).“對等”指的是兩個(gè)進(jìn)程通過網(wǎng)絡(luò)（或互聯(lián)網(wǎng)）進(jìn)行通信的一種體制，并不是網(wǎng)絡(luò)（或互聯(lián)網(wǎng)）的一種特性。Aprocessmightusethepeer-to-peermodeltocommunicatewithanotherprocessandlaterusetheclient/servermodeltocommunicatewithanotherprocessoverthesamenetwork.一個(gè)進(jìn)程可以通過同一個(gè)網(wǎng)絡(luò)先是使用對等模型與另一個(gè)進(jìn)程通信，然后又使用客戶機(jī)/服務(wù)器模型與另一個(gè)進(jìn)程通信。Thus,itwouldbemoreaccuratetospeakofcommun

42、icatingbymeansofthepeer-to-peermodelratherthancommunicatingoverapeer-to-peernetwork.因此，比較準(zhǔn)確的說法是，使用對等模型通信，而不是通過對等網(wǎng)絡(luò)通信。I.Fillintheblankswiththeinformationgiveninthetext:1.MAN2.open;closed3.bus4.token5.Ethernet6.client/server7.equals;workII.TranslatethefollowingtermsorphrasesfromEnglishintoChineseandvi

43、ceversa:1.fileserver文件服務(wù)器2.carriersense載波檢測，載波監(jiān)聽3.protocolsuite協(xié)議組，協(xié)議集4.peer-to-peermodel對等模型5.bustopologynetwork總線拓?fù)渚W(wǎng)絡(luò)6.inter-machinecooperation機(jī)器間合作，計(jì)算機(jī)間合作7.Ethernetprotocolcollection以太網(wǎng)協(xié)議集8.proprietarynetwork專有網(wǎng)絡(luò)9.utilitypackage實(shí)用軟件包，公用程序包10.starnetwork星形網(wǎng)絡(luò)11.局域網(wǎng)localareanetwork(LAN)12.令牌環(huán)tokenring13.無線網(wǎng)絡(luò)wirelessnetwork14.封閉式網(wǎng)絡(luò)closednetwork15.環(huán)形拓?fù)浣Y(jié)構(gòu)ringtopology16.客戶機(jī)/服務(wù)器模型client/serve