Cisco Explorer Series Staging Manual page 49

Recommendations to Improve Your Data Carousel Rate
VPI / VCI Pairing
Note: This discussion of VPI/VCI pairing pertains only to sites that use a BFS BIG
and does not pertain to sites that use an ASI/HMUX card. The Direct ASI
implementation does not use ATM.
We recommend that you map at least 20 VPI/VCI pairs in your Asynchronous
Transfer Mode (ATM) switch for inband data when initially configuring the system.
The DNCS port on the ATM switch uses VPI/VCI permanent virtual circuits (PVCs)
0/256 through 0/275. These PVCs must be mapped to VPI/VCI pairs x/256 through
x/275 respectively, (where x represents any available VPI) on the Broadband
Integrated Gateway (BIG) port of the ATM switch. There is one VPI/VCI PVC for
each inband data carousel for up to 20 inband carousels.
If you plan to support more than 20 inband data carousels, you need additional
PVCs on the ATM switch. Begin configuring your additional PVCs at 0/276.
The BIG ATM module has no awareness of the VPI. Hence, the ATM switch can map
the incoming DNCS PVCs to any VPI on the outgoing BIG PVCs. For simplicity, we
recommend that you use VPI of 0.
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