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LanScaper
TM
NIC
Polarity
Straight-ThroughCable
Switch
T568A/B
UPLINK
=NetworkInterfaceCard-TypicallyanoptioncardpluggedintoaPCcardslotthatprovides
anEthernetinterfaceforthatPC.LanScaper™usesthetermNICtodefinetheconnectorpinout
thatallowsfordirectconnectiontoaHUBdeviceusingastraight-throughcable.
-Ethernettransmitandreceivedriverchipsusedifferentialvoltagestoimprovenoise
immunity.Thuseachdirectionoftransmissionusesapairofwires,oneforthepositive(+)side
andtheotherforthenegative(-)side.EarlyEthernetinterfacechipswerenotdesignedto
recognizeandcompensateforreversedcablepair
s,soacrossed(+)and(-)paircouldcause
problems.ModernEthernetchipscancompensate,sothewiringisnotcritical,butthe
LanScaper™candeterminethedifference,andwillreportit.IntheJackIDmodethepolarityis
reportedasNRMorREV.
-AnEthernet(CAT5)cablewhichconnectsall4pairsinthecable
straightthroughtothecorrespondingpairsinthefarendconnector.ThisallowsaNICdeviceto
connectdirectlytoaHUBdevice.
-SimilartoaHUB,aswitchisamultipleportEthernetconnectiondevicethatallowsfor
multipleEthernetdevicestocommunicatebetweeneachother.Unl
ikeaHUB,aswitchhasinternal
logicthatdetermineswhichportaspecificMACaddressisfoundon,andonceithasdetermined
that,itonlyforwardstrafficdestinedforthataddresstothatport.Thisallowsforfewercollisions
ontheLANbynotre-transmittingeverypacketoneveryport.Multiplesimultaneouspoint-point
communicationscanpassthroughaswitchatthesametime,aslongaseachendpointisona
differentportontheswitch.
LikeaHUB,aswitch(initsprimarymode)hasnoIPorMACaddressofit'sown.Alsolikea
HUB,aswitchusesHUBpinoutonitsconnectorstoallowdirectcon
nectionstoNICinterfaces.
SwitchesaremoremoderndevicesthanHUBSandareusuallycapableof100Mbit/sec(100Base-
Tx)operation.
AsaresultoftherequirementofIEEEEthernetspecsrequiringdownwardcompatibility,all100
Mbitinterfacesmustalsosupportlegacy10Mbitcommunications.Thisresultsinarequiringa
switchtohavememorytostorepacketsreceivedat100Mbitsforretransmissionat10Mbits(Store
andForward).
-TheEIA/TIAstructuredwiringstandardsfortelecommunicationswiring.AandB
versionsareelectricallyidenticalandcannotbedistinguishedwitha
wiringtest.Thecolorcodes
andpairnumberingisdifferent,however,andcaremustbetakentouseoneversionwithina
network.AcablewiredtoAononeendandBontheotherresultsinacross-overcable.
-Aspecialconnector,oramechanicalswitch,thatchangesthepinoutofoneconnector
onaHUBorswitchtoNICpinout.Thisallowsastraight-throughcabletobeusedtoconnectone
HUB(orswitch)toanotherwhilebuildingaLAN.