COMSPHERE 3600 Series Data Service Units
D-30 March 1999 3610-A2-GB41-60
MCMP Backup Using FEP Port Sharing
This configuration provides backup of two to three
channels (Figure D-14). When the remote DBM dials into
the control DBM-Vs, the remote DBM automatically
reverts to TDM mode and adjusts its port speeds when the
dial backup speed is less than the MCMP aggregate speed
(Figure D-15). Port speeds are adjusted using the DBM
port speed options.
The assumed configuration for this scenario is as
follows:
•Network is a 2-drop DDS multipoint nondisruptive
circuit operating at 56 kbps.
•Two control DBMs with TDM are dedicated to the
control DSU.
•The MCMP is configured for three channels: one
7.2 kbps, one 4.8 kbps, and one 2.4 kbps.
•The DBM’s are configured for 14.4 kbps. Excess
bandwidth must be reserved on the backup
configuration so that framing and diagnostic data
does not reduce the port speeds. Therefore, the
DBM port speeds are configured to support the 4.8
and 7.2 kbps applications. The 2.4 kbps application
is not supported during backup. DBM speeds must
be the same or set to zero.
•The tributary DBMs are configured for switched
carrier operation on a per-port basis, no fallback,
and password security.
•When the failure occurs, the control DSU reports a
Threshold exceeded alarm, while tributaries are
reported as having No Response alarms. These
alarms will continue to be reported until the DDS
facility is restored.
•There will be a subnetwork No Response alarm at
the control MCMP for each tributary DSU that is
out of service. That happens even when the
tributary is in Backup mode.
Figure D-14. MCMP FEP Port-Sharing Configuration – Dial Backup

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