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1、ComputerNetworksNWCopyright(C)1991,1992,1993,1994,1995bytheComputationalScienceEducationProjectThiselectronicbookiscopyrighted,andprotectedbythecopyrightlawsoftheUnitedStates.This(andallassociateddocumentsinthesystem)mustcontaintheabovecopyrightnotice.Ifthiselectronicbookisusedanywhereotherthan
2、theproject'soriginalsystem,CSEPmustbenoti edinwriting(emailisacceptable)andthecopyrightnoticemustremainintact.1IntroductionComputernetworksareanindispensablepartofeveryresearchorganization.Localnetworkstietogethermachineswithinalaboroveranentirecampus,allowinguserswithcommongoalsandintereststos
3、hareresourcessuchasdisks,printers,orsupercomputers.WideareanetworksoperatedbytheNSF,theDepartmentofEnergy,andotherfundingagenciesaremainlyusedtoexchangeinformationbutarealsoincreasinglyusedtoaccessremoteresources.Thischapterisanintroductiontocomputernetworkingforcomputationalscientists.Theempha
4、sisisonhowscientistsarelikelytouselocalandwideareanetworks.Wewilldescribethetypesofresourcesthatareavailableovernetworksandhowtousecommonnetworkingtoolstotakeadvantageoftheresources.Theemphasiswillbeontheuser'sviewofnetworking,withonlyenoughofadescriptionofthehardwareandsoftwaretogivereadersase
5、nseofwhynetworksevolvedthewaytheyhaveandwheretheyareheadedinthenearfuture.Thereareseveralgoodbooksoncomputernetworksforthosereaderswhowanttolearnmore.TwotextbooksonnetworkconceptsandlocalareanetworkimplementationarebyComer[3]andPerlman[6].Aninformal,easy-to-readdescriptionoftheInternet(theloose
6、lyorganizedcollectionofwideareanetworksthatwillbedescribedinSection3)isTheWholeInternetCatalog,byKrol[4].Thisbookishighlyrecommendedforanyonewhowillbemorethanacasualuserofnetworkresources.22LocalAreaNetworksComputerswithinadepartmentorcampusoftencommunicateoveralocalareanetwork,orLAN(seeFigure1
7、).Thesenetworksarefairlysmall,intermsofphysicaldistances,usuallylimitedtoasinglebuilding.Thethreebasiccategoriesofequipmentthatarefoundinalocalnetworkareworkstations,servers,andgateways.Usersaccessnetworksthroughterminalsandworkst
