outfortheFourRepeaterRulefor10MbpsEthernet,alsoknownasthe5-4-3Rule,whenextendingLANsegments.Thisrulestatesthatyoucanconnectfivenetworksegmentsend-to-endusingfourrepeatersbutonlythreesegmentscanhavehosts(computers)onthem.Thetermrepeatertraditionallymeantasingleport“in”andasingleport“out”device.Butincommonterminologytodaythetermmultiportrepeaterisoftenusedaswell.RepeatersareclassifiedasLayer1devicesintheOSImodel,becausetheyactonlyonthebitlevelandlookatnootherinformation.Thesymbolforrepeatersisnotstandardized.Thepurposeofahubistoregenerateandretimenetworksignals.Thisisdoneatthebitleveltoalargenumberofhosts(e.g.4,8,oreven24)usingaprocessknownasconcentration.Youwillnoticethatthisdefinitionisverysimilartotherepeater’s,whichiswhyahubisalsoknownasamulti-portrepeater.Thedifferenceisthenumberofcablesthatconnecttothedevice.Tworeasonsforusinghubsaretocreateacentralconnectionpointforthewiringmedia,andincreasethereliabilityofthenetwork.Thereliabilityofthenetworkisincreasedbyallowinganysinglecabletofailwithoutdisruptingtheentirenetwork.Thisdiffersfromthebustopologywherehavingonecablefailwilldisrupttheentirenetwork.HubsareconsideredLayer1devicesbecausetheyonlyregeneratethesignalandbroadcastitoutalloftheirports(networkconnections).E-commerce(ElectronicCommerce,isabbreviatedasE-commerce)employsthewayo