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NetworkingQuickReference

1second=1,000milliseconds(msec)1second=1,000,000microseconds(sec)1second=1,000,000,000nanoseconds(nsec)1bps=1bitpersecond1Kbps=1,000bitspersecond1Mbps=1,000,000bitspersecond1Hz=1cyclepersecond1KHz=1,000Hz1MHz=1,000,000HZSpeedoflight(c)invacuum:3x108meters/secincopperwire:2.3x108meters/secinopticalfiber:2x108meters/secWellknownPorts7echo20FTPdataconnection21FTPconnectioncontrol23telnet25SMTP53DNS79finger80HTTPdaemon110POP3143IMAPWellKnownPortsrange:01023RegisteredPortsrange:102449151Dynamicand/orPrivatePortsrange:4915265535IEEENetworkStandards802.3UsesLengthfieldinsteadofTypeEthernet(DIXEthernetorEthernetII)usesTypefieldinsteadofLength802.5TokenRing802.11Wireless802.11aUsesOFDM802.11bUsesHRDSS802.11gEnhanced802.11busingOFDM802.15Bluetooth(physicalanddatalinklayers)802.16WirelessMANOSIReferenceModelApplicationPresentationSessionTransport(segments,datagrams)Network(packets)Datalink(frames)Physical

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NetworkingEquationsPropagationdelay=distancetraveled/propagationspeedTransmissiondelay=#ofbytestotransfer/transmissionspeed(orbandwidth)Signaltonoiseratio(dB)=10log10(S/N)

Attenuationindecibels=10log10(Transmittedpower/receivedpower)

NyquistTheorem:Maximumdatarate=2Hlog2Vbits/secwhereHisinHzandVis#oflevels

ShannonsResult:Maximumnumberofbits/sec=Hlog2(1+S/N)whereHisinHz

PureALOHAthroughputT=Ge2GMaxthroughputoccursatG=0.5

T=throughputperframetimee=2.718G=attemptsperpackettimeThroughputinbitspersec=TxtransmissionspeedVulnerableperiod=2xframetransmissiontime

SlottedALOHAthroughputT=GeGMaxthroughputoccursatG=1

TCProundtriptime

RTT=RTTOLD+M(1)RTTOLD=previouslyobservedroundtriptime=smoothingfactorM=observedroundtriptime(actualtimetoreceiveanACK)

D=DOLD+(1)|RTTM|DOLD=previouslyobservedstandarddeviation

=smoothingfactor(maybe)

TCPTimeout=RTT+4DEthernet/IEEE802.3(p.280)

Channelefficiency=t/(t+2/A)t=avetimetotransmitaframe=endtoendpropagationtime(timeforframetotraverseentireEthernetnetwork)2=durationofeachtimeslot

A=probabilitythatsomestationacquireschannelinaparticularcontentionslot=kP(1P)k1k=#ofstationsreadytotransmit

P=probabilitythateachstationtransmitsduringacontentionslot

Channelefficiency=1/(1+2BLe/cF)B=networkbandwidthc=signalpropagationspeedL=cablelengthF=framelength

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e=contentionslotsperframe(2.718)Maximumthroughput=channelefficiencyxtransmissionspeedMinimumframelength=2xpropagationdelayxtransmissionspeed(datarate)*802.3minimumframelength=64bytes

ARQProtocolChannelUtilizationWindowSizeWs(Sender)WR(Receiver)

StopandWait 11Maximumchannelutilizationwithnoerrors:

GoBackN ifWs> 2m11

ifWs 2m12m1

ifWs