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VCI: A Virtual Channel Identifier is a virtual channel that is identified bya unique
numerical tag that is defined bya 16-bit field in the ATM cell header.The purpose of the
virtual channel is to identifywhere the cell should travel. The VCI fieldspecifies this 16 bit
numerical tag that determines the destination.
Range: 0-65535 Default: 35
Service Category: This field allows you to select from the following service categories.
l UBR (default): When configured as UBR (Unspecified Bit Rate), trafficis
delivered with best efforts but with no guarantee. This allows for fluctuation in
times oftemporaryincrease ofavailable bandwidth. For example, ifa PVC with
CBR is temporarilyinactive, the PVC(s) with UBR will utilizethat bandwidth while it
is available. UBR is intended for applicationsthat do not require anymaximum
bound on the transfer delay.
l CBR: When a PVC is specified as a CBR (Constant Bit Rate), that PVC is
guaranteed a certain bandwidth, characterized bythe PeakCell Rate (PCR). The
CBR does not have to transmit with a peak cell rate, and when it does, it is only
when the bandwidth specified bythe PCR is guaranteed.
l VBR-nrt: An PVC enabled with VBR-nrt (Variable Bit Rate - non realtime) can
transmit acell only ifthe PVC has atoken available. The PVC accumulates tokens
at the rate of the Sustainable Cell Rate, and the PVC can onlyaccumulate a
maximum of the value specified byMaximum Burst Size tokens.
When a PVC has a token available, it can transmit cells at the rate ofPCR. After a cell is
transmitted, the PVC loses the token it has accumulated.
In the case of multiple PVCs, CBR specified PVCs will have higher priority than
PVCs with UBR. For example, the CBR PVCs will take their bandwidth and the
remaining bandwidth will be split among the UBR PVCs. In the case oftotal PVC CBR
bandwidth exceeding ADSLupstream, the total upstream bandwidth will be shared
proportionallyto the bandwidth allocated for each CBR PVC.
Peak Cell Rate: This value specifies the maximum, and in some cases guaranteed, cell
rate for CBR and VBR-nrt. Peak Cell Rates are typicallymeasured in Cells/Second,
however, the user entered value is in kbpsand is then converted bythe firmware.
Range: 0-32767 Default: 0
Sustainable Cell Rate: It is the sustained rate at which a PVC enabled with VBR-nrt can
transmit ATM cells. Sustainable Cell Rate (SCR) can be considered as the true reserved
bandwidth for a PVC.
Range: 0-32767 Default: 0
Max Burst Size: It is the number of cells a PVC enabled with VBR-nrt can transmit
continuouslyat peak cell rate (PCR).
Range: 0-32767 Default: 0