5-61/19/05 ATM Services Configuration Guide for CBX 3500, CBX 500, GX 550, and B-STDX 9000
Closed-loop Flow Control
Beta Draft Confidential
RM Cell Generation
Any port on an IOM can generate CCRM and BCM cells and can be configured to not
generate RM-type cells (the No Loop option). These types of cells let you configure
different closed-loop, flow control algorithms on the same IOM.
In general, RM-type cells can be generated at 30 to 250 millisecond (msec) intervals
per VC. The default value for this parameter is 100 msec.
RM Cell Termination
RM cells generated by other vendors are passed through Lucent switches
transparently. Other vendors may have implementations of the ATM Forum Traffic
Management 4.0 standard that can conflict with Lucent’s implementation of this
standard. Other vendors can set the Protocol ID to any number between 1-255.
RM cells are terminated by Lucent switches under the following conditions:
• If the RM cell received is a backward RM cell, has a Protocol ID of 5, and is
transversing a Virtual Circuit (VC), then it is designated as a BCM cell and may
be terminated.
• If the RM cell received is a backward RM cell, has a Protocol ID of 6, and is
transversing a Virtual Circuit (VC), then it is designated as a CCRM cell and may
be terminated.
• For RM cells that are traversing a Virtual Path (VP), the above conditions apply if
the VCI of the RM cell is 6.
If any of the above conditions are not met, the RM cell will be passed through the
network transparently.
Note – Because RM cells are generated in the backward direction, the type of RM
cells generated depends on the configuration of the logical port through which they are
transmitted.
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