User's Manual
GuardianManual001‐5006‐000Rev0 18|Page
2.2.2 POINT‐TO‐MULTIPOINT
APoint‐to‐MultipointnetworkisacommonnetworktypeusedinSCADAorotherpollingsystems.Thesingle
pollingmasterstationcommunicateswithanynumberofremotesandcontrolsthenetworkbyissuingpollsand
waitingforremoteresponses.IndividualPLC/RTUremotesmanageaddressingandrespondwhentheirindividual
addresses
arequeried.PLC/RTUunitaddressesaremaintainedinascanningliststoredinthehostprogramor
masterterminaldeviceattheSCADAhostsite.Communicationsequipmentistransparentanddoesnotinteract
withspecificremotes;alldataiscoupledtothehostonasingledataline(sucha
networkiscommonlyusedwith
synchronousradiomodemsandasynchronousradiomodems).
Figure2.2–PointtoMultipointNetwork
2.2.3 MULTIPLEPOINT‐TO‐POINT
Amultiplepoint‐to‐pointissimilartothepoint‐to‐multipointsystemexcepttheSCADAhosthasmultipleserial
portsthataredirectedtodifferentgeographicareasintheSCADAsystem.
2.2.4 PEER‐TO‐PEER
APeer‐to‐Peernetworkisgenerallyusedfordevicetodevicecommunicationsamonganumberofstations.This
networkrequiresfulladdressingcapabilityonthepartofthedataequipment(DTE).Ifthedistancesinvolvedfor
anylinkorlinksaretoogreatforasingleradiohop,theycan
beextendedbymeansofrepeaterswithoutaffecting
thebasicnetworkdesign.
2.2.5 STOREANDFORWARD
StoreandForwardisacommontechniquewhereadatatransmissionissentfromonedevicetoareceivingdevice
butfirstpassesthrougharelayingdevice.ThedeviceistypicallyanRTUorPLCusedbythemessageserviceto
storethereceivedmessagethenittransmitsthemessageto
theintendedrecipient.