Network bandwidth

honggarae 16/12/2021 920

Digitalinformation

Thebasicunitofdigitalinformationflowisbit(bit),andthebasicunitoftimeiss(second),sobit/s(bit/second)describesbandwidthUnit,1bit/sisthebasicunitofbandwidth.Itisnotdifficulttoimaginehowslowitistocommunicateatarateof1bit/s.Fortunately,wecanuseequipmentwithaveryfastcommunicationrate.The56KmodemusesthetelephonelinetodialuptheInternet,anditsbandwidthis56000bit/s(1K=1000bit/s).ThetelecomADSLbroadbandInternetaccessisbetween512Kbit/sand10Mbit/s,whileThenetisupto10Mbit/sormore(1Mbit/s=1000*1000bit/s=10^6bit/s).

Meaning

Bandwidthisaveryusefulconcept,anditspositioninnetworkcommunicationisveryimportant.Theactualmeaningofbandwidthisthemaximumnumberofdatabitsthatcanflowthroughaspecificareaatagiventimeandotherconditions.Althoughitsconceptisabitabstract,metaphorscanbeusedtohelpunderstandthemeaningofbandwidth.Thinkofthecity’sroadsasanetwork.Therearetwo-lane,four-lane,oreight-laneroads.Peopledrivingfromthestartingpointtothedestinationmaypassthroughthetwo-lane,four-lane,orsingle-laneontheway.Here,thenumberoflanesislikebandwidth,andthenumberofvehiclesisliketheamountofinformationtransmittedinthenetwork.Let'susethecity'swatersupplynetworkasananalogy.Thediameterofthewatersupplypipecanmeasurethecapacityofwatertransportation.Thediameterofthemainwaterpipemaybe2m,whilethediameterofthemainwaterpipemaybeonly2cm.Inthisanalogy,thediameterofawaterpipeislikethebandwidth,andwaterisliketheamountofinformation.Usingathickertubemeanshavingawiderbandwidth,thatis,agreatercapacityforinformationtransmission.

Calculationmethod

IncomputernetworksandIDCcomputerrooms,theunitofnetworktransmissionrateisb/s(bitspersecond)(orbit/s,sometimesalsowrittenasbps,Thatisbitpersecond)said.

Inthefieldofcommunicationsandcomputer,specialattentionshouldbepaidtothenumericalvaluesrepresentedbytheEnglishabbreviationssuchas"thousand","million"and"Gee".Theunitofquantityinacomputerusesbytesastheunitofmeasurement.The"thousand"of"kilobyte"isrepresentedbyacapitalK,whichisequalto2¹⁰,whichis1024,not1000.

Inactualnetworkapplications,whendownloadingsoftware,weoftenseethewordssuchasthedownloadspeeddisplayedas176KB/s,103KB/sandotherbroadbandspeeds,becausetheunitofthelinebandwidthprovidedbytheISPisbit(bit),andthegeneraldownloadsoftwaredisplaysthebyte(Byte)(1Byte=8bit),sotheactualvaluecanbeobtainedthroughconversion.Let’stake1Mbroadbandasanexample,andconvertitaccordingtotheconversionformula:

1Mb/s=1024Kb/s=1024/8KB/s=128KB/s

Network bandwidth

Theoretically:2M(ie2Mb/s)Thetheoreticalbroadbandrateis:256KB/s,theactualrateisabout150~240KB/s;(Thereasonisthatitisaffectedbytheuser’scomputerperformance,networkequipmentquality,resourceusage,networkpeakperiod,websiteservicecapacity,andlinefailure.Powerconsumption,signalattenuationandotherfactors).Thetheoreticalbroadbandrateof4M(ie4Mb/s)is:512KB/s,andtheactualrateisabout200~440KB/s.Theuplinkratereferstothedatatransmissionratewhentheusercomputersendsinformationtothenetwork,andthedownlinkratereferstothetransmissionratewhenthenetworksendsinformationtotheusercomputer.Forexample,usingFTPtouploadfilestotheInternet,the"uplinkrate"thataffectstheuploadspeed;whiledownloadingfilesfromtheInternet,the"downlinkrate"affectsthedownloadspeed.Ofcourse,intheactualdownloadingprocess,thequalityoftheline,equipment(includingcomputersandotherequipment),etc.willalsohaveamoreorlessimpactonthespeed.

Throughput

Ifyourworkhasinstalledbroadbandservice,orthebroadbandoftheresidentialareahasbeenconnectedtoyourhome,youaregoingtodownloadaprogram,awebpageoramovie.Maybeyouthinkthatyouareusingallthebandwidthclaimedbytheserviceprovider,butthisisnotthecase,whichhastoinvolveanotherconcept-throughput.

Throughputreferstothebandwidthvalueactuallyobtainedwhendownloadingfilesunderthepremiseofthespecifiedtime,space,andpath(networkpath)takenbythedatainthenetwork.Duetovariousreasons,thethroughputisactuallymuchsmallerthanthenominalmaximumbandwidthofthetransmissionmedium.

Influencingfactors

Themainfactorsaffectingbandwidthandthroughputinthenetworkare:1)Networkequipment(switches,routers,hubs);

2)TopologyStructure(ienetworkstructureshape,suchasstarandring);

3)Datatype;

4)Numberofusers;

5)CustomersComputerandserver(suchassystembus,diskperformance,networkadapter,hardwarefirewall);

6)Failureratecausedbypowersystemandnaturaldisasters.

Whendesigninganetwork,youshouldfocusonthetheoreticalvalueofbandwidth,thatis,thetheoreticalmaximumnumberofdatatransmissionbitsthatcanbetheoreticallyavailableundergivenconditions.Thespeedofthedesignednetworkshouldbeequaltothespeedallowedbythemedium.Whenusersusethenetwork,theyshouldconsiderthethroughput,thatis,whethertheuserissatisfiedwiththebandwidthvalueactuallyobtained.Theimportantfactorthatshouldbeconsideredwhenbuildinganetworkisthechoiceofmedia,whichisinturnrelatedtotheamountoffiledownloadsusersneed.Thelargerthefile,themoretimeittakes.Thereisaformula:estimateddownloadtime=transferfilesize/bandwidth.Regardlessofthevariousfactorsthataffectbandwidth,thisformulacanroughlyestimatethetimerequiredfortheselectedmediumtotransmitfiles.

Summary

Innetworkcommunication,individualsororganizationsalwayshopethatthebandwidthwillbewiderandwiderwhenusingthenetwork,especiallytheuseoftheInternet,therequirementsfordatatransmissionareexplodingAsaresult,thedemandforbandwidthisalsoincreasingdaybyday.Nowadays,therapidincreaseintheamountofinformationinanewgenerationofmultimedia,imagetransmission,databases,andInternetTVhasmadebandwidthaseriousbottleneck,forcingEthernettodevelopathigherspeeds.Varioustechnologiesfordevelopingopticalfibernetworkbandwidtharebeingresearchedandused.Therefore,understandingtheroleofbandwidthwillundoubtedlysavealotofmoney.Asanetworkdesigner,bandwidthisthemaindesignpoint.Asanetworkprofessional,bandwidthandthroughputareessentialforanalyzingnetworkoperation.

TheInternetisbecomingstrongerandstronger,andthenumberofnetizenscontinuestoincrease,accompaniedbytheadventoftheeraofInternetpublicization.People'sdemandfortheInternetisnolongersimplytobrowsethewebandviewnews,buttoputforwardavarietyofapplicationrequirements.Althoughtheemergenceofonlinegames,onlinefilmandtelevision,remoteoffice,andInternetTVhavegreatlyenrichedpeople'slives,theyhavealsoplacedhigherrequirementsonthebandwidthoftheInternet.