A-21/19/05 ATM Services Configuration Guide for CBX 3500, CBX 500, GX 550, and B-STDX 9000
Adjusting the CAC
Beta Draft Confidential
In either of the customizable implementations, you can control the amount of
bandwidth reserved based on either the physical port type or the configurable range of
sustainable cell rate (SCR) values, or both. With the two customized implementations
you can also control circuit establishment based on the configurable range of
maximum burst size (MBS) values.
When you adjust the CAC function, choose only one of these options. Whether you
are tuning the Lucent CAC or configuring a customized CAC, the adjustments you
make apply only to the VBR-RT, VBR-NRT, and ABR traffic types.
Note – QoS for VBR-RT and VBR-NRT is not guaranteed when you use the
“customize VBR-RT, VBR-NRT, and ABR” CAC implementation. Also, the QoS
for VBR-NRT is not guaranteed when you use the “customize VBR-NRT and
ABR” CAC implementation.
Note – Before tuning the Lucent CAC or configuring a customized CAC, you
should closely monitor your network to achieve a good understanding of the
network’s traffic profile. Be conservative when you adjust the CAC to ensure QoS.
After you make adjustments, monitor the network closely to determine the effect of
these adjustments, making sure you have not adversely impacted the QoS on the
network.
Note – The CBX 3500 ULC (Universal Line Card) modules have more buffers than
the legacy IOM1 modules. Lucent CAC's Effective Bandwidth Calculation takes
into account these buffers and certain card dependent parameters. Because of this,
effective bandwidth calculated by a ULC module for a given circuit may be lower
by a small amount than the effective bandwidth calculated on a legacy IOM1 for the
same traffic parameters. This difference in effective bandwidth can be observed in
circuits of type rt VBR, nrt VBR QoS type.
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