BCM Closed-loop Flow Control
ATM Services Configuration Guide for CBX 3500, CBX 500, GX 550, and B-STDX 9000 1/19/055-11
Beta Draft Confidential
BCM Closed-loop Flow Control on a UNI
You can configure an output UNI logical port to allow FCP-managed VCs using that 
logical port to adjust their cell rates to use the available non-real time bandwidth. This 
is done by setting the RM termination type on that logical port to BCM, as shown in 
Figure 5-5.
Figure 5-5. Output UNI Logical Port RM Termination
Because the logical port does not receive any BCM cells from the customer premise 
equipment (CPE), the ACR of the VCs keeps increasing until the logical port becomes 
congested. The ACR will increase fairly, corresponding to the RIF and peak cell rate 
(PCR) values of the VCs. See Table 6-2 on page 6-11 for information on setting the 
RM Cell Termination attribute.
BCM Cell Generation
You can configure any port on an IOM to generate BCM cells. If you select the 
BCM generation option when configuring the ATM FCP, BCM cells are only 
generated when the port is congested. See “Enabling the FCP” on page 6-2 for 
information on configuring the BCM generation option.
ATM FCP
CBX 500
CBX 500 SWITCH
IOM
CBX 500
IOM
Data Flow
UNI
Configured to terminate
BCM cells on the LPort
Output Port
CPE