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ATM Services Configuration Guide for CBX 3500, CBX 500, GX 550, and B-STDX 9000
Frequently Asked Questions About the FCP
Beta Draft Confidential
Default Configuration — The FCP allocates a default amount of 2K cell buffer
memory per T1 port. Maximum available is 512K cells allocated per 3-Port DS3/1
Enhanced IMA module. Each logical port can have either a distinct T1 channel or an
IMA group containing up to eight T1 channels.
Is the CI bit set when BCM cells are generated?
Since BCM cells are generated only when network congestion occurs, it is assumed
that downstream congestion is present when a CBX 500 switch receives BCM cells.
Accordingly, the CBX 500 switch reduces the rate of excess data into the network,
regardless of the CI bit setting. Therefore, since the switch does not check the status of
the CI bit when it receives BCM cells, it is unnecessary to change the CI bit setting
from zero (0) to 1 for BCM cells.
Why are RM cells not generated even though I am using
the Auto RM Generation option?
The VC Manager establishes all circuits. During circuit setup, the VC Manager looks
at the adjacent upstream switch to find an FCP-enabled IOM in the circuit path. If the
VC Manager detects an FCP-enabled IOM, the FCP determines whether or not to
generate RM cells on that circuit, according to congestion status.
The VC Manager prevents backward RM cells from being sent to upstream devices
that may be unable to process RM cells. When the VC Manager does not detect an
FCP-enabled interface, the system overrides the RM cell generation functionality.
The Auto RM Generation field on the ATM FCP Tab (
provides the following two options for RM cell generation:
•
To set RM cells to be generated automatically, select the default option, Allow.
•
To set RM cells to be generated even if no upstream FCP-enabled IOM is
detected, select the Override option.
“Setting Logical Port FCP Attributes” on page 6-10
for more information on these
options.
Summary of Contents for CBX 3500
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