ATM logical connections
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logical connections in ATM are referred to as virtual channel connections(VCC). a VCC is analogous to a virtual circuit in X.25 ora data link connection in frame relay; itis basic unit of switching in an ATM network.A VCC is set upbetween two end users through the network and a variable-rate ,full duplex flow of fixed size cellsis exchanged over connection.
the virtual path concept was developed inresponse to a trend in high speed networking in which the control costofthe network is becomng an increasinglyhigher proportion of the overall network cost.some of the adavantagesof virtual path are as follow:
. simplified network architecture :netwrok transport functions can be separated into those relatedto an individuallogical connection(virtual channel)and those related to a group of logical connections(virtual path)
.increased network performance and relaibility:the network deals with fewer aggregated entities.
reduced processing andshort connectionsetup time:
much of the workis done when the virtual path is setup.by reserving capacity on a virtual oath connection in anticipation of later call arrivals,new virtual channel connections can be established by executing simple control functionsat the end-points of the virtual path connection: no call processing is required at transit nodes.thus .the addition of new virtual channels to an existing virtual path involves minimum processing . >enhanced network services :the virtual path is used internal to the network but is also available to the enduser.as a result ,the user may define closed usergroups orclosed networks of virtual-channel bundles.
Wednesday, January 21, 2009
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