User's Manual

RLX2 Industrial Hotspot Series
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ProSoftTechnology,Inc. Page91of208
February5,2015
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standard,IHradiosworkinconjunctionwithwiredEthernetswitchestoforma
redundantnetwork. 
EachRSTPdevice(RLX2radioorEthernetswitch)communicateswithotherRSTP
devicesinthenetworkviapacketscalledBridge ProtocolDataUnits(BPDUs).BPDUs
aresentouteachofthedevicesports.Inawiredsw
itch,thiswouldbefromeachofthe
Ethernetports.InanRLX2Radio,inadditiontotheEthernetport,eachwirelesslinkis
consideredaport.TheseBPDUsarethecommunicationsmeanstoalloweachRSTP
deviceinthenetworktomakesurethattheproperconnectionsstil
lexist.
Inthefollowingillustration,theRLX2Radiohas4RSTP"ports":
 Ethernetport(1)
 Aportforitsparentconnection(2)
 Aportforeachofitstwochildconnections(11and12).
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BPDUsaresentouttheportataratecalledthe"He
lloTime".Theacceptedstandard
valueforthisis2seconds.Ifaradio(oranyotherRSTPdevice)doesnotgetaBPDUfor
2HelloTimes,itassumestheRSTPdevicethathadbeenthereisnolongeravailable.It
canthenopenanalternatepathifoneisavailable.Th
isprocessismuchliketheSTP
process.Ifotherdevicesonthenetworkarenotoperatinginrapidspanningtreemode,
theradiowillreverttonormalspanningtreeoperationonaper‐portbasis.
RSTPprovidesaperformanceenhancementoverSTPoperation.Bycomparison,the
radiousingth
eSTPalgorithmwouldrevertitsporttothelisteningstate,andthentothe
learningstate,beforereturningtotheforwardingstate.Eachofthesestatestakesat
least15seconds,duringwhichtheSTPdevicesarelisteningforBPDUstore‐negotiate
thenetworktopology.TheadvantageofusingtheRS
TPfunctionalityisthatisuses