0415年网工英语真题.docx

0415年网工英语真题.docx

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0415年网工英语真题

（2015-11）

The Dynamic Host Configuration Protocol provides configuration parameters to Intemet（71）.DHCP consists of two components:

 a（72）fordelivering host-specific 

conguration parameters from a DHCP server to a host and a mechanism for allocation of network addresses to hosts. DHCPis built on a client-server model, where designated DHCP

server hosts allocatenetwork addressesanddeliver（73）parameters to dynamically

configured hosts. DHCP supportsthree mechanismsforIP address allocation,

In “automatic allocation “,DHCP assigns a（74）parameters todynamicallymechanisms

for IP address allocation. In "automatic D address to a client. In "dynamic allocation", DHCP assigns an address to a client for a limited period of time.In "manual allocation", a client's IP address is assigned by the network（75）, and DHCP isusedsimply to

convey the assigned address to the 

client. 

（71）A.switch      B.terminal     C.hosts       D.users 

（72）A.router      B.protocol     C.host        D.mechanism

（73）A.control     B.broadcast    C.configuration  D.transmission   

（74）A.permanent  B.dynamic    C.connection   D.administrator   

（75）A.controller   B.user       C.host        D.administrator

（2015-05）

Traditionalnetworklayerpacketforwardingreliesontheinformationprovidedbynetworklayer（71）protocols,orstaticrouting,tomakeanindependentforwardingdecisionateach（72）withinthenetwork.Theforwardingdecisionisbasedsolelyonthedestination（73）IPaddress.Allpacketsforthesamedestinationfollowthesamepathacrossthenetwork ifnootherequal-cost（74）exist.Wheneverarouterhastwoequal-costpathstowardadestination,thepacketstowardthedestinationmighttakeoneorbothofthem,resultinginsomedegreeofloadsharing.EnhancedInteriorGatewayRoutingProtocol（EIGRP）alsosupportsnon-equal-cost（75）sharingalthoughthedefaultbehaviorofthisprotocolisequal-cost.YoumustconfigureEIGRPvariancefornon-equal-costloadbalancing.

（71）A.switching  B.signaling      Crouting           D.session

（72）A.switch       B.hop          C.host             D.customer

（73）Aconnection   B.transmission   C.broadcast         D.customer

（74）A.paths        B.distance       C.broadcast         D.session

（75）A.loan         B.Load          C.content          D.constant

（2014-05）

Thetraditionalwayofallocatingasinglechannelamongmultiplecompetingusersistochopupits（71）byusingoneofthemultiplexingschemessuchasFDM（FrequencyDivisionMultiplexing）.IfthereareNusers,thebandwidthisdividedintoNequal-sizedportions,witheachuserbeingassignedoneportion.Sinceeachuserhasaprivatefrequency（72）,thereisnointerferenceamongusers.Whenthereisonlyasmallandconstantnumberofusers,eachofwhichhasasteadystreamoraheavyloadof（73）,thisdivisionisasimpleandefficientallocationmechanism.AwirelessexampleisFMradiostations.EachstationgetsaportionoftheFMbandandusesitmostofthetimetobroadcastitssignal.However,whenthenumberofsendersislargeandvaryingorthetrafficis（74）,FDMpresentssomeproblems.IfthespectrumiscutupintoNregionswhilefewerthanNusersarecurrentlyinterestedincommunicating,alargepieceofvaluablespectrumwillbewasted.

IfmorethanNuserswanttocommunicate,someofthemwillbedenied（75）forlackofbandwidth.……

（71）A.capabilityB.capacity C.ability D.power

（72）A.band B.range C.domain D.assignment 

（73）A.traffic B.date C.bursty D.flow

（74）A.continuous B.steady  C.bursty D.flow

（75）A.allowance B.connectionC.percussionD.percussion 

（2013-11）

ThedefactostandardApplicationProgramInterface（API）forTCP/IPapplicationsisthe“sockets”interface.AlthoughthisAPIwasdevelopedfor（71）intheearly1960sithasalsobeenimplementedonawidevarietyofno-Unixsystems.TCP/IP（72）WrittenusingthesocketsAPIhaveinthepastenjoyedahighdegreeofportabilityandwewouldlikethesame（73）withIPv6applications.ButchangesarerequiredtothesocketsAPItosupportIPv6andthismemodescribesthesechanges.TheseincludeanewsocketaddressstructuretocarryIPv6（74）,newaddressconversionfunctions,andsomenewsocketoptions.TheseextensionsaredesignedtoprovideaccesstothebasicIPv6featuresrequitedbyTCPandUDPapplications,includingmulticasting,whileintroducingaminimumsofchangeintothesystemandprovidingcomplete（75）forexistingIPv4applications.

（71）A．WindowsB．LinuxC．UnixD．DOS

（72）A．applicationsB．networksC．protocolsD．systems

（73）A．portabilityB．availabilityC．capabilityD．reliability

（74）A．connectionsB．protocolsC．networksD．address

（75）A．availabilityB．compatibilityC．capabilityD．reliability

（2013-05）

TraditionalIPpacketforwardinganalyzesthe（71）IPaddresscontainedinthennetworklayeeheaderofeachpacketasthepacketrravelsfromitssoursetoitsfinaldestination.ArouteranalyzesthedestinationIPaddressindependentlyateachhopinthenetwork.Dynamic（72）protocolsorstaiticconfigurationbuildsthedatabaseneededtoanalyzethedestinationIPaddress（theroutingtable）.TheprocessofimplementingtraditionalIProutingalsoiscalledhop-by-hopdestination-based（73）routing.Althoughsuccessful,andobviouslywidelydeployed,certainrestrictions,whichhavebeenrealizedforsometime,existforthismethodofpacketforwardingthatdiminishits（74）.NewtechniquesarethereforerequiredtoaddressandexpandthefunctionalityofanIP-basednetworkinfrastructure.Thisfirstchapterconcertratesonidenfifyingtheserestrictions.andpresentsanewarchitecture,knownasmultiprotocol（75）switching,thatprovidessolutionstosomeofthisrestrictions.

（71）.A.datagramB.destinationC.connectionD.service

（72）.A.routingB.forwardingC.transmissionD.managerment

（73）.A.anycastB.multicastC.broadcastD.unicast

（74）.A.reliabilityB.flexibilityC.stabilityD.capability

（75）.A.costB.castC.markD.label

（2012-11）

Letusnowseehowrandomizationisdonewhenacollisionoccurs.Aftera（71）,timeisdividedintodiscreteslotswhoselengthisequaltotheworst-caseround-trippropagationtimeonether.ToaccommodatethelongestpathallowedbyEthernet,theslottimehasbeensetto512bittimes,or51.2us.Afterthefirstcollision,eachstationwaitseither0or1（72）timesbeforetryingagain.Iftwostationscollideandeachonepicksthesamerandomnumber,theywillcollideagain.Afterthesecondcollision,eachonepickseither0,1,2or3atrandomandwaitsthatnumberofslottimes.Ifathirdcollisionoccurs（theprobabilityofthishappeningis0.25）,thenthenexttimethenumberofslotstowaitischosenat（73）fromtheinterval0to23-1.Ingeneral,afterIcollisions,arandomnumberbetween0and2i-1ischosen,andthatnumberofslotsisskipped.However,aftertencollisionshavebeenreached,therandomization（74）isfrozenatamaximumof1023slots.After16collisions,thecontrollerthrowsinthetowelandreportsfailurebacktothecomputer.Furtherrecoveriesupto（75）layers.

（71）A·datagramB·collisionC·connectionD·service

（72）A·slotB·switchC·processD·fire

（73）A·restB·randomC·onceD·odds

（74）A·unicastB·multicastC·broadcastD·interval

（75）A·localB·nextC·higherD·lower

（2012-05）

TheTCPprotocolisa（71）layerprotocol.EachconnectionconnectstwoTCPsthatmaybejustonephysicalnetworkapartorlocatedonoppositesidesoftheglobe.Inotherwords,eachconnectioncreatesa（72）withalengththatmaybetotallydifferentfromanotherpathcreatedbyanotherconnection.ThismeansthatTCPcannotusethesameretransmissiontimeforallconnections.Selectingafixedretransnussiontimeforallconnectionscanresultinseriousconsequences.Iftheretransmissiontimedoesnotallowenoughtimefora（73）toreachthedestinationandanacknowledgmenttoreachthesource,itcanresultinretransmissionofsegmentsthatarestillontheway.Conversely,iftheretransnussiontimeislongerthannecessaryforashortpath,itmayresultindelayfortheapplicationprograms.Evenforonesingleconnection,theretransmissiontimeshouldnotbefixed.Aconnectionmaybeabletosendsegmentsandreceive（74）fasterduringnontrafficperiodthanduringcongestedperiods.TCPusesthedynamicretransmissiontime,atransmissiontimeisdifferentforeachconnectionandwhichmaybechangedduringthesameconnection.Retransmissiontimecanbemade（75）bybasingitontheround-triptime（RTT）.Severalformulasareusedforthispurpose.

（71）A.physicalB.networkC.transpor   D.application

（72）A.path   B.windowC.response   D.process

（73）A.processB.segmentC.program   D.user

（74）A.connectionsB.requestsC.acknowledgments   D.datagrams

（75）A.long   B.short   C.fixed      D.dynamic

（2011-11）

Atransportlayerprotocolusuallyhasseveralresponsibilities．Oneistocreateaprocess-to-processcommunication;UDPuses（71）numberstoaccomplishthis．AnotherResponsibilityistoprovidecontrolmechanismsatthetransptlevel．UDPdoesthistaskataveryminimallevel．ThereisnoflowcontrolmechanismandthereIsno（72）forreceivedpacket．UDP,however,doesprovideerrorcontroltosomeextent．IfUDPdetectsanerrorinthereceivedpacket,itwillsilentlydropit．Thetransportlayeralsoprovidesaconnectionmechanismfortheprocesses．The（73）mustbeabletosendstreamsofdatatothetransportlayer．Itistheresponsibilityofthetransportlayerat（74））stationtomaketheconnectionwiththereceiver．chopthestreamintotransportableunits,numberthem,andsendthemonebyone．Itistheresponsibilityofthtransorortlayeratthereceivingendtowaituntilallthe