5-101/19/05 ATM Services Configuration Guide for CBX 3500, CBX 500, GX 550, and B-STDX 9000
BCM Closed-loop Flow Control
Beta Draft Confidential
BCM Closed-loop Flow Control
The FCP can also use a BCM closed-loop, flow control algorithm. Unlike CCRM
cells, BCM cells only indicate cell rate decreases. BCM cells are sent at periodic
intervals only when congestion exists.
BCM Closed-loop Flow Control on a Trunk
Figure 5-4 shows an example of BCM closed-loop flow control between two CBX
500 switches.
Figure 5-4. BCM Closed-loop Flow Control
On Switch B, the FCP in IOM 2 generates RM cells to control the rate of data
transmitted by IOM 2 on Switch A. IOM 2 on Switch B also determines the type of
RM cell to generate by looking at the logical port setting on IOM 1 on Switch B.
ATM FCP
CBX 500 SWITCH A
ATM FCP
CBX 500 SWITCH B
Data Flow
Trunk Line
Feedback Flow
Configured to terminate
BCM cells on the logical port
Configured to generate
BCM cells on the logical port
CBX 500
IOM 2
CBX 500
IOM 1
CBX 500
IOM 2
CBX 500
IOM 1
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