JBL VT4880ADP User Manual - page 35
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JBL Professional
Priority
AhigherConductorPriorityover-ridesalowerpriority.IfanoperatingConductorisremovedfromthenet-
workforanyreason(e.g.powerturnedoff),theremainingdevicesagainarbitrateandselectanewConduc-
tor.AllCobraNetdeviceshavethecapacitytoserveastheConductor.
TheConductorperiodicallybroadcastsawell-definedmessagetoallCobraNet™devices.Thisallowseach
CobraNetdevicetorecoverthemasterclocktiminginformationneededforhighqualityaudiodelivery.
TheConductoralsorecognizeseachCobraNetdeviceonthenetworkandassumestheresponsibilityto
assigntransmitterpositionsandprioritiesforeachBundleofeachCobraNetdevice.Likeaconductorofan
orchestra,theConductorsignalsthebeginningofasynchronoustransmissioncycle,andtheneachdevice
sendsitsBundle(s)inlockstep.
PrimaryandSecondaryNetworkPorts(Dualink)
SomeCobraNetdevicesimplementtwonetworkconnections.Thisprovidesforaddedreliabilityintheevent
ofproblemswithnetworkhardwareorcabling.Iftheprimaryconnectionislost,thesecondaryconnection
canbeenabledusinganentirelyseparatenetworkhardwarepathinlessthanafewseconds.
RepeaterNetworks
CobraNetcanoperateonsimplerepeater-basednetworksandmorecomplexswitch-basednetworks.
Repeaternetworksuselow-costEthernethubs.Onarepeater-basednetwork,allpacketsarebroadcastto
allconnectednodes.CobraNetmulti-castandunicastBundlescanbeassignedbutbecauseofthesimpler
repeater-typehubs,evenunicasttransmissionsarebroadcasttoallnodes.Therefore,amaximumof8full-
loadedBundles(6audiochannels)areallowedontheentirenetwork.MoreBundlesmaybeallowedifthey
areloadedwithlessthanthefulleightaudiochannels.Thereisnolimittothenumberofactivereceiverson
arepeaternetwork.Generally,arepeaterbasedCobraNetnetworkmustbededicatedtoCobraNettraffic
onlytoguaranteereliabletransmissionofaudiopackets.
SeeTestedEthernetProductsonthePeakAudiowebsiteforalistofrecommendedEthernetrepeaters.
http://www.peakaudio.com/CobraNet/tested_Ethernet.html
SwitchedNetworks
LargerCobraNetnetworkscanbebuiltusingEthernetswitches.Ethernetswitchingtechnologyismoreso-
phisticatedthanhubs.Switchesdonotsimplybroadcasteachandeverypackettoallnodes.Instead,they
examinethedestinationaddressofeachpacketreceivedoneachport,andthen“switch”thatdatatothe
identifiedrecipient.CobraNetunicastBundlesexploitthisfeaturetoallowmoreoverallnetworktraffic.Inef-
fecteachporthas100MBofbandwidthandtheoverallnetworkcanbeaslargeas100MBtimesthenumber
ofportsonthenetwork.MulticastBundlesareallowedonaswitchednetwork,buttheymustbeusedwith
care.PeakrecommendsthatnotmorethanfourmulticastBundlesbeusedinaswitchedCobraNetnet-
work.
AnotherenhancementavailablewithmostnewEthernetswitchesis“full-duplex”links.Afull-duplexlinkal-
lowssimultaneoussendandreceiveoverthesameEthernetconnection.ThisenablesaCobraNetdeviceto
simultaneouslysendandreceiveupto6channelspernodeforatotalof18channels.
Thecombinationofswitchingandfull-duplextechnologiesinswitchedCobraNetnetworksallowsupto18
channelsper100MbitEthernetlinkandgreaterthan000individualaudiochannels.Thereisnolimittothe
numberofactivereceiversonaswitchedCobraNetnetwork.Switchednetworksalsoeliminatethepotential
forEthernetcollisions.ThisallowsgeneralPCnetworktrafficandCobraNettraffictocoexistonthesame
network.SeeTestedEthernetProductsonthePeakAudiowebsiteforalistofrecommendedEthernet
switches.http://www.peakaudio.com/CobraNet/tested_Ethernet.html