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1、IEEE802.3ah協(xié)議學(xué)習(xí)（3）——MPCP多點(diǎn)控制協(xié)議64.3Multi-PointControlProtocol(MPCP)?AsdepictedinFigure64–3,theMulti-pointMACControlfunctionalblockcomprisesthefollowingfunctions:a)DiscoveryProcessing.Thisblockmanagesthediscoveryprocess,throughwhichanONUisdiscoveredandregisteredwiththenetworkwhilecompensatingfo
2、rRTT.b)ReportProcessing.Thisblockmanagesthegenerationandcollectionofreportmessages,throughwhichbandwidthrequirementsaresentupstreamfromtheONUtotheOLT.c)GateProcessing.Thisblockmanagesthegenerationandcollectionofgatemessages,throughwhichmultiplexingofmultipletransmittersisachieved.?多點(diǎn)MAC控制功能模塊
3、包括以下功能：a)發(fā)現(xiàn)處理(DiscoveryProcessing)：該模塊管理發(fā)現(xiàn)流程，通過該進(jìn)程發(fā)現(xiàn)ONU并使其注冊到網(wǎng)絡(luò)中，同時(shí)對其RTT進(jìn)行補(bǔ)償。b)報(bào)告處理(ReportProcessing)：該模塊管理報(bào)告消息的產(chǎn)生和搜集，ONU通過該模塊在上行方向向OLT發(fā)送帶寬請求。c)選通處理(GateProcessing)：該模塊管理GATE消息的產(chǎn)生和搜集，通過該模塊實(shí)現(xiàn)多個(gè)發(fā)送端的復(fù)用。?AsdepictedinFigure64–3,thelayeredsystemmayinstantiatemultipleMACentities,usingasinglephysical
4、layer.EachinstantiatedMACcommunicateswithaninstanceoftheopcodespecificfunctionalblocksthroughtheMulti-pointMACControl.Inadditionsomeglobalvariablesaresharedacrossthemultipleinstances.CommonstatecontrolisusedtosynchronizethemultipleMACsusingMPCPprocedures.Operationofthecommonstatecontrolisgene
5、rallyconsideredoutsidethescopeofthisdocument.如圖64-3所示，分層的系統(tǒng)可以實(shí)例化多個(gè)MAC實(shí)體，而只使用一個(gè)物理層。每個(gè)實(shí)例化的MAC通過MPCP和與操作碼(opcode)相關(guān)的功能模塊的實(shí)例進(jìn)行通信。此外，多個(gè)實(shí)例共享一些全局變量。通過MPCP使用公共狀態(tài)控制來同步多個(gè)MAC。有關(guān)公共狀態(tài)控制的操作不在本標(biāo)準(zhǔn)規(guī)范的范圍內(nèi)。?64.3.1PrinciplesofMulti-PointControlProtocol?Multi-pointMACControlenablesaMACClienttoparticipateinapoint-
6、to-multi-pointopticalnetworkbyallowingittotransmitandreceiveframesasifitwasconnectedtoadedicatedlink.Indoingso,itemploysthefollowingprinciplesandconcepts:多點(diǎn)MAC控制通過控制MAC客戶端的接收和發(fā)送使其工作在點(diǎn)對多點(diǎn)光網(wǎng)絡(luò)中，而對MAC客戶端來說就好象連接到一個(gè)獨(dú)享的鏈路上。為了達(dá)到此目的，多點(diǎn)MAC控制協(xié)議遵循以下原則：?a)AMACclienttransmitsandreceivesframesthroughtheMult
7、i-pointMACControlsublayer.b)TheMulti-pointMACControldecideswhentoallowaframetobetransmittedusingtheclientinterfaceControlMultiplexer.c)Givenatransmissionopportunity,theMACControlmaygeneratecontrolframesthatwouldbetransmittedinadvanceoftheMACC
