Introduction
Inthese20years,Ethernethasdevelopedfromtheoriginal10Base510Mthickcablebusto10Base210Mthincable,followedbyashortretreat:1Base51MEthernet,AndthentheEthernettechnologydevelopedintothefamiliarstar-shapedtwistedpair10BaseT.Withtheincreaseinbandwidthrequirementsandtheenhancementofdevicecapabilities,fastEthernethasemerged:100BaseTXforCategory5cabletransmission,100BaseT4forCategory3cabletransmission,and100BaseFXforopticalfibertransmission.Withthefurtherincreaseinbandwidth,GigabitEthernetinterfacesareonthescene:includingshort-wavelengthopticaltransmission1000Base-SX,long-wavelengthopticaltransmission1000Base-LX,andCategory5linetransmission1000BaseT.OnJuly18,2002,IEEEpassed802.3ae:10Gbit/sEthernet,alsoknownas10GigabitEthernet.
10GigabitEthernetdoesnotsimplyincreasethespeedofGigabitEthernetby10times.Therearemanytechnicalproblemstobesolvedhere.
InEthernettechnology,100BaseTisamilestone,establishingthedominanceofEthernettechnologyonthedesktop.GigabitEthernetandthesubsequent10GigabitEthernetstandardsaretwomoreimportantstandards.Throughthesetwostandards,EthernettechnologyextendsfromdesktopLANtechnologytocampusnetworksandtheconvergenceandbackboneofmetropolitanareanetworks.
TheevolutionofEthernetfrom10Mb/sto10Gb/sprovesthatEthernetis:
1.Scalable(from10Mb/sto10Gb/s).
2.Flexible(multiplemedia,full/halfduplex,sharing/switching).
3.Easytoinstall.
4.Goodrobustness.
Foundingbackground
Ethernetisdominantinlocalareanetworks.Butforalongperiodoftime,peoplegenerallybelievedthatEthernetcouldnotbeusedinmetropolitanareanetworks,especiallytheconvergencelayerandbackbonelayer.ThemainreasonisthatthebandwidthofEthernetusedasthebackboneofthemetropolitanareanetworkistoolow(intheeraof10Mand100MfastEthernet),andthetransmissiondistanceistooshort.Atthattime,themostpromisingmetropolitanareanetworktechnologieswereFDDIandDQDB.Inthefollowingyears,ATMtechnologyhasbecomeahotspot.AlmosteveryonebelievesthatATMwillbecometheonlytechnologythatunifieslocalareanetworks,metropolitanareanetworks,andwideareanetworks.However,duetovariousreasons,onlyATMtechnologyamongtheabove-mentionedthreetechnologiesinChinahasbecomeanalternativesolutionfortheconvergencelayerandbackbonelayerofthemetropolitanareanetwork.
ThemostcommonEthernetis10MEthernetand100MEthernet(FastEthernet).100MFastEthernetisobviouslynotenoughasametropolitanareabackbonenetwork.EvenifmultiplefastEthernetlinksareusedincombination,theystillhavemorethanenoughcapacityformultimediaservices.WiththestandardizationofGigabitEthernetanditswideapplicationinproductionpractice,Ethernettechnologyhasgraduallyextendedtotheconvergencelayerofthemetropolitanareanetwork.GigabitEthernetisusuallyusedtoconvergecommunityuserstometropolitanPOPpoints,ortoconnectconvergencelayerequipmenttothebackbonelayer.However,inthecurrentenvironmentof10MEthernettotheuser,GigabitEthernetlinkisalsoreluctantasanaggregation,anditisbeyondreachasabackbone.AlthoughEthernetmulti-linkaggregationtechnologyhasbeenstandardizedandmulti-vendorinteroperabilityisjustaroundthecorner,multiplegigabitlinkscanbebundledandused.However,consideringfiberresourcesandwavelengthresources,linkbundlingisgenerallyonlyusedinPOPpointsorshort-distanceapplicationenvironments.
TransmissiondistanceusedtobeamajorobstaclethatEthernetcannotbeusedasalinktechnologyatthebackbonelayerofthemetropolitanareadatanetwork.Whetheritis10M,100MorGigabitEthernet,thetransmissiondistanceofCategory5linesis100mduetothesignal-to-noiseratio,collisiondetection,andavailablebandwidth.Whenusingopticalfibertransmission,thedistancelimitisrestrictedbythemaster-slavesynchronizationmechanismusedbyEthernet.802.3stipulatesthatthe1000Base-SXinterfaceusesa62.5μmcoremultimodefiberwithalongesttransmissiondistanceof275manda50μmcoremultimodefiberwithalongesttransmissiondistanceof550m;1000Base-LXinterfaceusesa62.5μmcoremultimodefiberwiththelongesttransmissiondistance.Thetransmissiondistanceis550m,thelongesttransmissiondistanceis550mwhenusingamultimodefiberwithacoreof50μm,andthelongesttransmissiondistanceis5000mwhenusingasingle-modefiberwithacoreof10μm.Thelongesttransmissiondistanceof5kmGigabitEthernetlinkisfarfromenoughinthemetropolitanarea.AlthoughtheGigabitinterfaceimplementationbasedonthemanufacturercanreachatransmissiondistanceof80km,andsomemanufacturershavecompletedinteroperabilitytests,itisanon-standardimplementationafterallandcannotguaranteetheinteroperabilityofthistypeofinterfacefromallmanufacturers.
Tosumup,themainreasonwhyEthernettechnologyisnotsuitableforuseinthebackbone/aggregationlayerofthemetropolitanareanetworkisbandwidthandtransmissiondistance.Withtheemergenceof10GigabitEthernettechnology,theabovetwoproblemshavebasicallybeenresolved.
Technicalintroduction
EthernetusestheCSMA/CDmechanism,thatis,carriersensemultipleaccesswithcollisiondetection.GigabitEthernetinterfacesarebasicallyusedinpoint-to-pointlines,andnolongersharebandwidth.Collisiondetection,carriersenseandmultipleaccessarenolongerimportant.ThebiggestsimilaritybetweenGigabitEthernetandtraditionallow-speedEthernetisthatitusesthesameEthernetframestructure.10GigabitEthernettechnologyissimilartoGigabitEthernet,butstillretainstheEthernetframestructure.Provide10Gbit/stransmissionspeedthroughdifferentencodingmethodsorwavelengthdivisionmultiplexing.Soinitsessence,10GEthernetisstillatypeofEthernet.
10GEthernetwaspassedinIEEEinJuly2002.10GEthernetincludes10GBASE-X,10GBASE-R,10GBASE-W,and10GBASE-Tbasedoncoppercables(approvedin2006).10GBASE-Xusesaverycompactpackage,containing1simplerWDMdevice,4receiversand4lasersworkingaroundthe1300nmwavelengthatapproximately25nmintervals,eachpairoftransmitter/receiveroperatingat3.125Gbit/sspeed(dataflowspeedis2.5Gbit/s).10GBASE-Risaserialinterfacethatuses64B/66Bencoding(notthe8B/10BusedinGigabitEthernet).Thedatastreamis10.000Gbit/s,andtheresultingclockrateis10.3Gbit/s.10GBASE-Wisawideareanetworkinterface,compatiblewithSONETOC-192,itsclockis9.953Gbit/sandthedatastreamis9.585Gbit/s.
10Gserialphysicalmedialayer
Theopticalfiber10GigabitEthernetspecificationsforlocalareanetworksare:10GBase-SR,10GBase-LRand10GBase-ER.
1,10GBase-SR
The"SR"in10GBase-SRistheabbreviationof"shortrange",whichmeansthatitisonlyusedforshort-distanceconnections.Thisspecificationsupportsshort-wave(850nmwavelength)multimodefiber(MMF)withacodingmethodof64B/66B,withaneffectivetransmissiondistanceof2metersto300meters.
2,10GBase-LR
The"LR"in10GBase-LRistheabbreviationof"LongRange",whichmeansthatitismainlyusedforlong-distanceconnections.Thespecificationsupportslong-wave(1310nm)single-modefiber(SMF)withacodingmethodof64B/66B,withaneffectivetransmissiondistanceof2metersto10kilometers.
4,10GBase-ER
The"ER"in10GBase-ERistheabbreviationof"ExtendedRange",whichmeansthattheconnectiondistancecanbeverylong.Thisspecificationsupportsultra-longwave(1550nm)single-modefiber(SMF)withacodingmethodof64B/66B,withaneffectivetransmissiondistanceof2metersto40kilometers.
PMDsublayerfunction
ThefunctionofthePMDsublayeristosupporttheexchangeofserializedsymbolcodebitsbetweenthePMAsublayerandthemedium.ThePMDsublayerconvertstheseelectricalsignalsintoaformsuitablefortransmissiononaspecificmedium.PMDisthelowestsublayerofthephysicallayer.Thestandardspecifiesthatthephysicallayerisresponsibleforsendingandreceivingsignalsfromthemedium.
PMAsublayerfunction
ThePMAsublayerprovidesaserializedserviceinterfacebetweenthePCSandPMDlayers.TheconnectionwiththePCSsublayeriscalledthePMAserviceinterface.Inaddition,thePMAsublayeralsoseparatesthesymboltimingclockusedforcorrectsymbolalignment(delimitation)ofthereceiveddatafromthereceivedbitstream.
WISsublayerfunction
TheWISsublayerisanoptionalphysicalsublayer,whichcanbeusedbetweenPMAandPCStoproduceadaptationsdefinedbyANSISONETSTS-192ctransmissionformatorITUdefinesSDHVC-4-64ccontainerrateEthernetdatastream.Thisratedatastreamcanbedirectlymappedtothetransportlayerwithouthigh-levelprocessing.
PCSsublayerfunction
ThePCSsublayerislocatedbetweenthecoordinationsublayer(viaGMII)andthephysicalmediumaccesslayer(PMA)sublayer.ThePCSsublayercompletesthemappingofthewell-definedEthernetMACfunctiontotheexistingcodingandphysicallayersignalsystemfunctions.TheinterfacebetweenthePCSsublayerandtheupperlayerRS/MACisprovidedbyXGMII,andthelowerlayerPMAinterfaceusesthePMAserviceinterface.
RS(coordinationsublayer)andXGMII
ThefunctionofthecoordinationsublayeristomaptheXGMIIchanneldataandrelatedcontrolsignalstotheoriginalPLSserviceinterfaceDefinethe(MAC/PLS)interface.TheXGMIIinterfaceprovidesalogicalinterfacebetweenthe10Gbit/sMACandthephysicallayer.XGMIIandthecoordinationsublayerenableMACtoconnecttodifferenttypesofphysicalmedia.
Because10GEthernetisessentiallyahigh-speedEthernet,inordertobecompatiblewithtraditionalEthernet,theframeformatoftraditionalEthernetmustbeusedtocarryservices.Inordertoachieveahighrateof10Gbit/s,theOC-192cframeformatcanbeusedfortransmission.ThisneedstorealizethemappingfunctionfromEthernetframetoOC-192cframeformatinthephysicalsublayer.Atthesametime,becausetheoriginaldesignofEthernetisforlocalareanetwork,thenetworkmanagementfunctionisweak,thetransmissiondistanceisshort,anditsphysicallinedoesnothaveanyprotectivemeasures.WhenEthernetisusedasawideareanetworkforlong-distance,high-speedtransmission,itwillinevitablycausegreaterjitterinthefrequencyandphaseofthelinesignal,andthetransmissionofEthernetisasynchronous,anditisdifficulttoachievesignalsynchronizationatthereceivingend.Therefore,iftheEthernetframeistobetransmittedinthewideareanetwork,theformatoftheEthernetframeneedstobemodified.
Ethernetgenerallyusesaspecial10B(Byte)codeinthephysicallayertoachieveframedelimitation.WhentheMAClayerhasdatatosend,thePCSsublayerencodesthedatain8B/10B.Whenitfindstheframeheaderandframeend,itautomaticallyaddsthespecialcodegroupSFD(startofframedelimiter)andEFD(endofframe)Delimiter);whenthePCSsublayerreceives10Bcodeddatafromthebottomlayer,itcaneasilyfindthestartandendoftheframeaccordingtoSFDandEFDtocompletetheframedelimitation.However,theGigabitEthernetframedelimitationcarriedinSDHisdifferentfromthestandardGigabitEthernetframedelimitation,becausethemultiplexeddatahasbeenrestoredtoan8Bcodegroup,withSFDandEFDremoved.Ifonlythepreambleandthestartofframedelimiter(SFD)oftheGigabitEthernetareusedforframedelimitation,becausetheprobabilityofthesamecodegroupasthepreambleandthestartofframedelimiterintheinformationdataishigher,useSuchaframedelimitationstrategymaycausethereceivingendtobeunabletoperformcorrectEthernetframedelimitationallthetime.Inordertoavoidtheabove-mentionedsituation,10GEthernetadoptstheHECstrategy.
TheIEEE802.3HSSGgroupproposedtomodifytheGigabitEthernetframeformat,addingthelengthfieldandtheHECfieldtotheEthernetframe.Inordertofindthepositionofthenextframeconvenientlyduringtheframingprocess,andsincethemaximumframelengthis1518bytes,atleast11bits(=2048)arerequired,sotwobytesareusedtoreplacethepreambleintheprocessofmultiplexingMACframesThefirsttwobytesareusedasthelengthfield,andthentheCRC-16checkisperformedonthese8bytes,andthelasttwobytesobtainedareinsertedaftertheSFDastheHEC.
The10GWANphysicallayerdoesnotsimplyuseOC-192ctocarryEthernetMACframes.Althoughtheblockframestructure,pointer,mapping,andlayeredoverheadofOC-192careusedforreference,alotofsimplificationshavebeenmadeonthebasisofSDHframestructure,whichmakesthemodifiedEthernetinsensitivetojitterandrequiresclocks.nottall.Specificperformance:Manyoverheadbytesarereduced,onlyframepositioningbytesA1andA2,segmentlayererrormonitoringB1,tracebyteJ0,synchronizationstatusbyteS1,protectionswitchingbytesK1andK2,andsparebytesareusedZ0,fill00000000forundefinedorunusedbytes.Itreducesalotofunnecessaryoverhead,simplifiestheSDHframestructure,andenhancesthenetworkmanagementandmaintenanceofthephysicallayercomparedwithGigabitEthernet,andcanrealizeprotectionswitchingonthephysicalline.Secondly,cumbersomesynchronousmultiplexingisavoided.Thesignalisnotmultiplexedfromalowratetoahighratestream,butdirectlymappedtotheOC-192cpayload.
Therateofthephysicallayerof10GEthernetLANand10GEthernetWAN(usingOC-192c)isdifferent.Thedatarateof10GEthernetLANis10Gbit/s,whilethedatarateof10GEthernetWANis9.58464Gbit/s(SDHOC-192cistheunencodedrateofthePCSlayer),butthephysicallayersofthetworatesshareaMAClayer,andtheworkingrateoftheMAClayeris10Gbit/s.Whatkindofadjustmentstrategyisadoptedtoreducethe10Gbit/stransmissionrateofthe10GMIIinterfacetomatchthephysicallayertransmissionrateof9.58464Gbit/sisaproblemthatthe10GEthernetWANneedstosolve.TherearethreeadjustmentstrategiesfortheOC-192cthatadaptsthe10Gbit/srateto9.58464Gbit/s:
SendtheHOLDsignalattheGMIIinterface,andtheMAClayerstopssendinginoneclockcycle;
Using"Busyidle",thephysicallayersends"Busyidle"totheMAClayerduringIPG.Afterreceivingit,theMAClayersuspendssendingdata.Thephysicallayersends"Normalidle"totheMAClayerduringIPG,andafterreceivingit,theMAClayerresendsthedata;
AdoptstheIPGextensionmechanism:MACframesaretransmittedoneframeatatime,dynamicallybasedontheaveragedatarateAdjusttheIPGinterval.
Technicalclassification
TherearemanyGigabitEthernetstandardsandspecifications.Intermsofstandards,thereareIEEE 802.3aein2002,IEEE 802.3akin2004,andIEEEin2006.802.3an,IEEE 802.3aqandIEEE 802.3apin2007.Intermsofspecifications,thereareatotalofmorethan10,whichcanbedividedintothreecategories:oneistheLAN10GigabitEthernetspecificationbasedonopticalfiber,thesecondistheLAN10GigabitEthernetspecificationbasedontwistedpair(orcopperwire),andthethirdisOpticalfiber-basedWAN10GigabitEthernetspecification.
TechnologyOutlook
Atthebeginningofthedesignof10GigabitEthernet,therequirementsofthemetrobackbonenetworkwereconsidered.Firstofall,thebandwidthof10Gissufficienttomeetthebandwidthrequirementsofthemetrobackbonenetworkatthisstageandforaperiodoftimeinthefuture(thebackbonebandwidthofmostmetrobackbonenetworksatthisstagedoesnotexceed2.5G).Secondly,themaximumtransmissiondistanceof10GigabitEthernetcanreach40kilometers,anditcanbeusedwith10Gtransmissionchannels,whichisenoughtomeetthecoverageofmosturbanmetropolitanareanetworks.Using10GigabitEthernetasthebackboneofthemetropolitanareanetworkcanomitthePOSorATMlinkofthebackbonenetworkequipment.Firstofall,itcansavecosts:thepriceoftheEthernetportismuchlowerthanthecorrespondingPOSportorATMport.Secondly,itispossibletouseEthernetframesend-to-end:ontheonehand,theVLANinformationandpriorityinformationofthelinklayercanbeusedend-to-end,andontheotherhand,multiplelinklayerencapsulationanddecapsulationonthedatadevicecanbeomitted.Possiblefragmentationofdatapacketstosimplifynetworkequipment.Theuseof10GigabitEthernetlinksatthebackbonelayerofthemetropolitanareanetworkcanimprovethecost-effectivenessofthenetworkandsimplifythenetwork.
Wecanclearlyseethat10GEthernetcanbeappliedtocampusnetworks,metropolitanareanetworks,andcorporatenetworks.However,becausethecurrentbroadbandservicesarenotwidelydeveloped,peopledonothaveanurgentneedforthebandwidthofasingle-port10Gbackbonenetwork.Therefore,10GEthernettechnologyisnotasgoodasotheralternativelinklayertechnologies(suchas2.5GPOS,bundledGigabitEthernet).Thereisnoobviousadvantage.CiscoandJUNIPERhaveintroduced10GEthernetinterfaces(implementedaccordingtothe802.3aedraft),buttheyhavealmostnoapplicationsinChina.Theproblemwiththemetropolitanareanetworkisnotthelackofbandwidth,buttheKillerApplication,whichconsumesalargeamountofbandwidth.Howtobuildthemetropolitanareanetworkintoamanageable,operableandprofitablenetwork.Sotheapplicationof10GEthernettechnologywilldependonthedevelopmentofbroadbandservices.Onlytheextensivedevelopmentofbroadbandservices,suchasvideomulticast,high-definitionTVandreal-timegames,canpromotethewidespreadapplicationof10GEthernettechnologyandpromotethehealthyandorderlydevelopmentofthenetwork.
Technicalfeatures
10GigabitEthernettechnologyprovidesricherbandwidthandprocessingcapabilities,whichcaneffectivelysaveusers’investmentinlinksandmaintainEthernetcompatibility.,Simpletouseandeasytoupgrade.However,wealsoseethatbecause10GigabitEthernetisstillintheearlystagesofdevelopment,therearestillsomeproblemsandshortcomings:First,intermsofprice,thepriceofa10GEportisabout100timesthatofaGEport,especiallywhenthebandwidthisnotavailable.Inthecaseoffullutilization,itwillcauseagreatwasteofinvestment;secondly,10GigabitEthernetinheritstheusualweakQoScharacteristicsofEthernet,andtheproblemofhowtoguaranteethedifferentiatedservicebearerremainsunsolved.FeaturessuchasRPR,MPLS,etc.Thesupportofthesystemisstillimmature;furthermore,10GErequiresequipmenttohavepowerfulprocessingcapabilities,andthe10GEportsintroducedbysomemanufacturersintheindustrycannotachievetruewire-speedprocessing,andthebandwidthadvantageisgreatlyreduced.
Inviewoftheabove-mentionedproblemsandthecurrentsituationwherethedemandfornetworkbandwidthisnoturgent,itisrecommendedthatthenetworkconstructionfocusonbusinessandcostperformance,andthenetworkcorestilladopts2.5GPOSinterfaceorGETrunkmode.When10GigabitEthernetisintermsoftechnologyandcostAftermajorprogresshasbeenmade,itwillbesmoothlyupgradedto10G.
Technicaladvantages
Oneoftheadvantagesof10GigabitEthernetisthatitcanusethesameformfactorinterfaceasGigabitEthernettoobtaintentimesthebandwidth.Thisappliestoswitchportsandhostadapterports.Forexample,onahostserver,ifyouneedeightGigabitEthernetnetworkcardinterfaces,youcanusetwofour-portnetworkcards,fourdual-portnetworkcards,oreightsingle-portnetworkcards.Thiscantakeuptwo,four,oreightserverI/Oslotsandresultineightcablescomingoutoftheserver.Thiscanbedoneinsomecases,butnotallservershavesomanyslots.SomeserverI/Oslotsneedtobeusedforotherpurposes,suchasRAIDcontrollers,FibreChannelhostbusadapters(HBAcards),PCIExpress(PCIe)SSDandsoon.Ifyouusea10GigabitEthernetport,withadual-port10GigabitEthernetcard,oneportcanprovideuptoeightGigabitEthernetinterfaces,whiletheremainingoneisusedforfailoverorothermanagementpurposes.ThiswillonlyoccupyoneI/Oslot,freeuptheI/Oslot,andreducepowerconsumptionatthesametime.Andnomorethantwocablesareneeded.Inaddition,thesamedual-port10GigabitEthernetcardcanbeinstalledonasmallerserver,suchasa1Userverwithonlytwoslots,andstillprovidesufficientnetworkbandwidth.
Developmenthistory
Amongdomesticnetworkmanufacturers,HuaweihastakentheleadinlaunchingtheQuidwayS8500(8505/8512),ahigh-endrouterandswitchsupporting10Gigabit,whichispositionedasacarrier-classoperatingcorenetworkThecoreoftheconvergencelayer,campusnetwork,andenterprisenetwork.QuidwayS8510Gigabitmulti-layercoreswitchhasthecharacteristicsoflargecapacity,richserviceinterfacefeatures,andcompleteprotocolsupport.Thebackplanecapacityis1.2T,theswitchingcapacityis480Gbps,andtheEthernetinterfaceprovidesamaximumof1210GigabitEthernetinterfaces.VPNsupportabilityandperfectQoSability.TheQuidwayNetEngine5000series10Gigabitcorerouterslaunchedatthesametimearehigh-endnetworkproductsforcarrier-classoperatingcorenetworks.Theyadoptathree-dimensionalswitchingnetworkdistributedarchitecture.Eachinterfacemodulehasitsowndistributedswitchingnetwork,whichcanbeeasilystackedandexpanded.Providesamaximumof560interfacemodules,thewholemachineprovides11.2Tbpsswitchingcapacity,themaximumportcapacityis5.6T,supports10GPOS,10GELAN,10GEWANinterfaceIP/MPLSwire-speedforwarding,andsupportssmoothexpansiontohigher-speedinterfaces.TheQuidwayNetEngine50Gigabitcorerouteradoptsathree-dimensionalarchitecture,whichhasadvantagesinscalability,loadbalancing,multi-pathbackup,andnon-blocking.Italsohasincrementalscalabilityandcanincreaseswitchingcapacityasneededwithouthavingtodoitallatonce.Thehighgroundisequippedwithacentralizedswitchingnetworktomeetthecharacteristicsandneedsoffuturecorenetworkdevelopment.
Inaddition,Huawei'sfifth-generationhigh-endcorerouterQuidwayNetEngine80/40alsohastheabilitytosmoothlyupgradeto10G.ThelaunchoftheQuidwayseriesof10Gigabitroutersandswitchesmarksthatthedesigntechnologyofmycountry'slarge-capacitycoreroutersandEthernetswitcheshasenteredtheinternationaladvancedlevel.Thisisnotonlyamajorbreakthroughinthedevelopmentofmycountry'scorenetworkcommunicationtechnology,butalsomycountry'sdatacommunicationindustry.Amajorbreakthroughtowardsinternationalization,andwillprovideastrongerdevelopmentimpetusforthefurtherdevelopmentofmycountry'sinformatization.