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3.4.1.1 ATM VC
ATM settings are used to connect to your ISP. Your ISP provides VPI, VCI, settings to
you. In this Device, you can totally setup 8 PVCs on different encapsulations if you
apply 8 different virtual circuits from your ISP. You need to activate the VC to take
effect. For PVCs management, you can use ATM QOS to setup each PVC traffic line's
priority.
Virtual Circuit: Select the VC number you want to setup.
VPI: Virtual Path Identifier. The valid range for the VPI is 0 to 255.
VCI: Virtual Channel Identifier. The valid range for the VCI is 32 to 65635 (0 to 31 is
reserved for local management of ATM traffic).
3.4.1.2 ATM QoS
ATM QoS: Select the Quality of Service types for this Virtual Circuit. The ATM QoS
types include CBR (Constant Bit Rate), UBR (Unspecified Bit Rate). These QoS types
are all controlled by the parameters specified below, including PCR, SCR, and MBS.
PCR: Peak Cell Rate (PCR) is the maximum rate at which the sender can send cells.
This parameter may be lower (but not higher) than the maximum line speed. 1 ATM
cell is 53 bytes (424 bits), so a maximum speed of 832 Kbps gives a maximum PCR of
1962 cells/sec. This rate is not guaranteed because it is dependent on the line speed.
SCR: Sustained Cell Rate (SCR) is the mean cell rate of a bursty, on-off traffic source
that can be sent at the peak rate, and a parameter for burst-type traffic. SCR may not be
greater than the PCR; the system default is 0 cells/sec.
MBS: Maximum Burst Size (MBS) is the maximum number of cells that can be sent at
the PCR. After MBS is reached, cell rates fall below SCR until cell rate averages to the
SCR again. At this time, more cells (up to the MBS) can be sent at the PCR again.
The following figure illustrates the relationship between PCR, SCR and MBS.
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