Definition
Alinkisaphysicallinefromanodetoanadjacentnodewithoutanyotherswitchingnodesinthemiddle.
Indatacommunication,thepathbetweentwocomputersisoftenformedbyaseriesofmanylinks.
Composition
Alinkiscomposedofnodesatbothendsandcommunicationlinesbetweenthenodes.
Difference
Theconceptoflink(physicallink)isdifferentfromthatofdatalink.Inadditiontophysicallines,datalinksmustalsohaveacommunicationprotocoltocontrolthetransmissionofthesedata.Itisthedatalinkthataddsthehardwareandsoftwarethatimplementtheseprotocolstothelink.Datalinkisalsocalledlogicallink.
Classification
Accordingtotheconnectionmethodofthecommunicationlink,thecommunicationlinkcanbedividedintothefollowingtwocategories:
Point-to-pointconnectioncommunicationLink,thelinkatthistimeonlyconnectstwonodes.
Multipointconnectionlinkreferstohowmany(n>2)nodesareconnectedbyonelink.
Accordingtodifferentcommunicationmethods,linkscanbedividedintothefollowingtwocategories:
One-waycommunicationlink
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Two-waycommunicationlink
Accordingtothedifferentcapacity,thelinkisdividedintothefollowingtwocategories:
Communicationlinkwithoutcapacity
Communicationlinkwithcapacity
EthernetlinkAggregation
LinkaggregationistheaggregationofmultiplephysicalEthernetportstogethertoformalogicalaggregationgroup.Theupperlayerentitythatusesthelinkaggregationservicecombinesmultiplephysicallinksinthesameaggregationgroup.Thinkofitasalogicallink.
Linkaggregationcanrealizetheloadsharingofinbound/outboundloadamongthememberportsintheaggregationgrouptoincreasebandwidth.Atthesametime,eachmemberportofthesameaggregationgroupdynamicallybacksupeachother,whichimprovesconnectionreliability.
Device AandDevice BareconnectedthroughthreephysicalEthernetlinks,andthesethreelinksarebundledtogethertobecomealogicallinkLink aggregation 1,thebandwidthofthislogicallinkItisequaltothesumofthebandwidthoftheoriginalthreeEthernetphysicallinks,thusachievingthepurposeofincreasingthelinkbandwidth;atthesametime,thesethreeEthernetphysicallinksbackupeachother,whicheffectivelyimprovesthereliabilityofthelink.