ABR RM Closed-loop Flow Control
ATM Services Configuration Guide for CBX 3500, CBX 500, GX 550, and B-STDX 9000 1/19/055-13
Beta Draft Confidential
ABR RM Closed-loop Flow Control
ABR RM closed-loop flow control is an additional flow-control loop for switches that
generate ABR RM cells. Because the ABR RM flow-control loop is an end-to-end
loop, the CBX 500 does not generate or terminate ABR RM cells. The FCP forwards
the ABR RM cells through the network transparently.
Cell Rate Adjustment
The ATM FCP performs cell rate adjustments on each circuit that it manages by
distributing the available bandwidth fairly among the managed circuits. A circuit is
initially granted an ICR; its rate is then adjusted continuously. The rate at any given
time is referred to as the ACR.
ICR and ICR Constant
When a VC initially becomes active, its ACR is set to its ICR. The ICR for a VC is
determined by its PCR, MCR, and ICR Constant.
The ICR Constant is configurable through Navis EMS-CBGX. The default value is
zero (0). The following formula shows how to calculate the ICR:
See Table 6-1 on page 6-4 for information on configuring the ICR Constant.
ICR = MCR + PCR-MCR
2
ICR CONSTANT
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