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AppendixA:GlossaryofNetworkingTerms
10Base-T
100Base-Tx
Cross-OverCable
HUB
MAC
MDI/MDI-X
-TheearliestdefinitionofEthernetwasfor10MillionBitspersecond,10Mbps.The
Ethernetspecificationdefinedseveraldifferentcablingschemes,includingT568A/B(4-pairsof
wire)andcoaxwiring.The10in10Base-Tdefines10MbpsandtheBase-TdefinesT568A/B,
CAT3cabling.10Base-2defines10Mbpsovercoax.NotethattheLanScaper™PINGmode
worksin10Base-T.Itreliesonthelegacycompatibilitybuiltintoall100Base-Txequipmentto
communicate.TheLanScaper™reportsthisinJackIDmodeas10Base-T.
-AnewerEthernetspecificationdefines100Mbpsdatarateasanupgradeforhigher
networkbandwidth.Severaldifferentcableschemesaredefinedfor100Mbps.The100in100
Base-Txdefinesthedatarateas100MillionBitspersecond.TheBase-Txdefinesthecable
schemeas2-pairsofwiresinaT568A/B,CAT5cable.NotethattheLanScaper™PINGmode
worksin10Base-T.Itreliesonthelegacycompatibilitybuiltintoall100Base-Txequipmentto
communicate.
OneothercableschemedefinedasBase-T4uses4pairsofwiresinT568A/B,CAT3orCAT5
cable. VeryfewEthernetdevicesusethisscheme,asthe2-pair(-Tx)schemedominatesthemarket.
TheLanScaper™canr
ecognizeandreportthiscapabilityintheJackIDmode,butitdoesnot
operateinthismode.TheLanScaper™reportsthisinJackIDmodeas100Base-T4.
-AnEthernetT568A/Bcablewhichconnectsthe1-2pairononeendtothe3-6
pairontheother.ThisallowsaNICdevicetoconnectdirectlytoanotherNICdevice,orHUBtoa
HUB.TheseareoftenusedtoconnectoneHUB(orswitch)toanotherHUB(orswitch)toenable
LANexpansion.NotethatifoneoftheHUBshasan"UPLINK"connector,thatconnectorcanbe
usedwithastraightthroughcabletoconnectanormalHUBporttothe"UPLINK"port.
-Ethernetphysicalwiringisdoneonapoint-pointmechanism,butanEthernetnetworkisa
starnetwork,whereanydevicecancommunicatedirectlywithanyotherdeviceonthatnetwork.A
HUBisphysicaldevicethathasmultipleEthernetconnectors(ports)onit.Inside,theHUB
receivesincomingdatafromanyofitsportsandthentransmitswhatitreceivesbackoutonallits
ports.Thus,allcommunicationsbetweenalldevicesisvisibletoallotherdevicesonthatLAN.
TheHUBhasnoIPorMACaddressofit'sown.Itisthus,a"transparent"devicethatmerely
enablesmultipleEthernetdevicestocommunic
atebetweenthemselves.
HUBsaretypicallyolderEthernetdevicesthatare10BaseT.Most10/100HUBlikedevicesare
nowswitches(seedefinition).LanScaper™usesHUBasadefinitionforaspecificEthernet
connectionpinassignmentthatallowsittoconnectdirectlytoaNICdeviceusingastraightthrough
cable.
=MediaAccessControl-Protocoldefinedforaddressingnetwork-interfacesonaunique
basis.EachmanufacturerofelectronicdevicesthatinterfacetoaMAC-controlledmechanism(like
Ethernet)mustregisterwiththeIEEEandgetasetofuniqueaddresses.Eachdevicetha
t
manufacturerbuildsisassignedasingleaddressfromthatmanufacturer'ssetofaddresses.Ethernet
willnotworkproperlyifmorethanonedeviceontheLANhasthesameMACaddress.
=MediumDependentInterface,XforCrossover-Thephysicalcableinterface
definedinIEEE802.3iscalledMDIononeendandMDI-Xontheotherend.TheLanScaper™
referstotheseconnectorsasNICandHUBrespectively.ArecentdevelopmentinEthernetdevices
istheabilitytodeterminewhattypeofdeviceisconnectedontheotherendofthecableandadjust
itselftocommunicateproperly.HPinventedthisan
dcallsit“AutoMDI/MDI-X”.The
LanScaper™willrecognizeandreportthistypeofdeviceasanAUTOdeviceinJackIDmode.