资源描述:
《Computer Networks Problem Solutions (4th Ed 2.pdf》由会员上传分享,免费在线阅读,更多相关内容在学术论文-天天文库。
1、COMPUTERNETWORKSFOURTHEDITIONPROBLEMSOLUTIONSANDREWS.TANENBAUMVrijeUniversiteitAmsterdam,TheNetherlandsPRENTICEHALLPTRUPPERSADDLERIVER,NJ07458©2003PearsonEducation,Inc.PublishingasPrenticeHallPTRUpperSaddleRiver,NewJersey07458Allrightsreserved.Nopartofthisbookmay
2、bereproduced,inanyformorbyanymeans,withoutpermissioninwritingfromthepublisher.PrintedintheUnitedStatesofAmerica10987654321ISBN0-13-046002-8PearsonEducationLTD.PearsonEducationAustraliaPTY,LimitedPearsonEducationSingapore,Pte.Ltd.PearsonEducationNorthAsiaLtd.Pears
3、onEducationCanada,Ltd.PearsonEducacióndeMexico,S.A.deC.V.PearsonEducation—JapanPearsonEducationMalaysia,Pte.Ltd.PROBLEMSOLUTIONS1SOLUTIONSTOCHAPTER1PROBLEMS1.Thedogcancarry21gigabytes,or168gigabits.Aspeedof18km/hourequals0.005km/sec.Thetimetotraveldistancexkmisx/
4、0.005=200xsec,yieldingadatarateof168/200xGbpsor840/xMbps.Forx<5.6km,thedoghasahigherratethanthecommunicationline.2.TheLANmodelcanbegrownincrementally.IftheLANisjustalongcable.itcannotbebroughtdownbyasinglefailure(iftheserversarereplicated)Itisprobablycheaper.Itpr
5、ovidesmorecomputingpowerandbetterinteractiveinterfaces.3.Atranscontinentalfiberlinkmighthavemanygigabits/secofbandwidth,butthelatencywillalsobehighduetothespeedoflightpropagationoverthousandsofkilometers.Incontrast,a56-kbpsmodemcallingacomputerinthesamebuildinghas
6、lowbandwidthandlowlatency.4.Auniformdeliverytimeisneededforvoice,sotheamountofjitterinthenet-workisimportant.Thiscouldbeexpressedasthestandarddeviationofthedeliverytime.Havingshortdelaybutlargevariabilityisactuallyworsethanasomewhatlongerdelayandlowvariability.5.
7、No.Thespeedofpropagationis200,000km/secor200meters/µsec.In10µsecthesignaltravels2km.Thus,eachswitchaddstheequivalentof2kmofextracable.Iftheclientandserverareseparatedby5000km,traversingeven50switchesaddsonly100kmtothetotalpath,whichisonly2%.Thus,switchingdelayisn
8、otamajorfactorunderthesecircumstances.6.Therequesthastogoupanddown,andtheresponsehastogoupanddown.Thetotalpathlengthtraversedisthus160,000km.Thespeedoflightina