Home Техника Токен пръстен

Токен пръстен



Introduction

Thesmalldata(aspecialframeof3bytes)transmittedonthetokenringiscalledatoken,andwhoeverhasthetokenhasthetransmissionauthority.Ifastationontheringreceivesthetokenandhasinformationtosend,itchangesonebitinthetoken(thisoperationturnsthetokenintoaframestartsequence),addstheinformationitwantstotransmit,andthensendstheentireinformationGotothenextstationinthering.Whenthisinformationframeistransmittedonthering,thereisnotokeninthenetwork,whichmeansthatotherworkstationsmustwaittotransmitdata.Therefore,thereisnotransmissionconflictinthetokenringnetwork.

Theinformationframeistransmittedalongtheringuntilitreachesthedestination,andthedestinationcreatesacopyforfurtherprocessing.Theinformationframecontinuestotravelalongtheringuntilitreachesthesendingstationandcanbedeleted.Thesendingstationcancheckthereturnframetoseeiftheframeisreceivedandcopiedbythereceivingstation.

UnliketheEthernetCSMA/CDnetwork,thetokenpassingnetworkisdeterministic,whichmeansthatanyterminalstationcancalculatethemaximumwaitingtimebeforeitcantransmit.Thisfeature,combinedwithotherreliabilityfeatures,makesthetokenringnetworksuitableforapplicationsthatneedtobeabletopredictdelaysandsituationsthatrequirereliablenetworkoperation.

ThetokenringnetworkwasdevelopedbyIBMin1984.IthasbeenIBM'snetworkstandardforalongtimeandissupportedbyallIBMcomputers.TokenRingcanconnecttoothernetworkswithabridgeorrouter.Thetokenringnetworkisindeeda"ring"networkinpracticalapplications,butbecauseoftheuseofso-calledmulti-stationaccessunitequipment,star-shapedwiringcanberealized.Suchadevicehasacertaindegreeofintelligence,andwillloopupunusedportstomakethetokenunblocked.TheIEEE802.5standardismainlybasedonIBM'stokenringnetwork,buttherearesomesubtledifferences.

Token ring

Принципът на работа на токенринга

(1) Първо, инициализирайте теринга (установете логически пръстен) и след това генерирайте празен токен, за да тече по ринга.

(2)Станцията, желаеща да изпрати рамка, трябва да чака, докато не открие пристигащия празен токен.

(3)Afterthestationthatwantstosendgetsanemptytoken,itfirstputsitinabusystate,andthestationsendsadataframetothebackofthetoken.

(4)Когато токенът е зает, тъй като в мрежата няма празен токен, всички станции, които искат да изпратят рамки с данни, трябва да изчакат.

(5)Eachstationringinterfacethatthedatapassesthroughcomparesthedestinationaddressoftheframewiththeaddressofthestation.Iftheaddressesmatch,theframeisputintothereceivingbufferandthensenttothestation.Atthesametime,theframewillcontinuetoflowonthering;iftheaddressdoesnotmatch,theringinterfacewillonlyforwardthedataframe.

(6)Thesentframecirculatesaroundtheringandthenreturnstothesendingstation.Thesendingstationremovestheframefromtheringandreleasesthetokenatthesametime(changeitsstatusto"idle")Sendtothenextstation.

TokenRingNetwork

TokenRingNetworkisakindoflocalareanetworkdevelopedonthebasisofringnetworktopology.Althoughitcanalsobeconnectedinastarstructureintermsofphysicalcomposition,itstillworksinaringmannerlogically.Thecommunicationtransmissionmediumcanbeunshieldedtwistedpair,shieldedtwistedpairandopticalfiber.

Transmissionmethod

Whentransmittingdata,thecomputerthathasthetokenwillsendthedatafirst.Thecomputerreceivingthedatawillchecktheframeheader,andprocessitifitissenttoitself.Regardlessofwhetheritisgiventoyourself,itwillbepassedonagain,andafteraroundoftransmission,checkwhetherthedataisthesametomakesurethatthedatahasnotransmissionerrors.Aftersendingthedata,youcanadjustthepriorityofthetokenasneeded(changeittobelowerthanyourownpriority),andthenpassthetokentothenextcomputer.Ifyoureceivethetokenbutthepriorityishigherthanyourown,youhavetopassthetokentothenextcomputer.

В допълнение, протоколът за предаване на токени се използва във Fiber Distributed Data Interface (FDDI).

This article is from the network, does not represent the position of this station. Please indicate the origin of reprint
TOP