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Configuring ATM VBR

By default, ATM interfaces use UBR; that is, bandwidth utilization is unlimited. For ATM1 and ATM2 IQ interfaces, you can configure non-real-time VBR, which supports variable bit rate data traffic with average and peak traffic parameters. Compared to RTVBR, non-real-time VBR is scheduled with a lower priority and with a larger SCR limit, allowing it to recover bandwidth if it falls behind. Non-real-time VBR is suitable for packet data transfers.

To define VBR on ATM1 and ATM2 IQ interfaces, include the vbr statement:




vbr peak rate sustained rate burst length;

For a list of hierarchy levels at which you can include this statement, see vbr.

When configuring VBR, you can define the following shaping properties:

Peak rate—Top rate at which traffic can burst.
Sustained rate—Normal traffic rate averaged over time.
Burst length—Maximum number of cells that a burst of traffic can contain. It can be a value from 1 through 4000 cells.

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