Issue 4 May 2002 6-1555-233-123
6
Reliability Systems: A Maintenance
Aid
General
A High or Critical Reliability system provides highly-available call processing
because single points-of-failure in the system that result in loss of call processing
are minimized. Such a system
■ Uses existing duplicated TDM buses
■ Duplicates the SPE, translation card, and Tone-Clock circuit pack
■ Packet bus redundancy
Each of these components are single points of failure in a standard reliability
system.
Duplicated SPE
The two SPEs are mounted in separate carriers and powered by different carrier
power supplies. As a result, a high or critical reliability system has two control
carriers: the A control cabinet and the B control cabinet.
Since the circuit packs in the two SPEs are the same, the SPEs have identical
capabilities. Either SPE can act as the active SPE. However, only one of the SPEs
can be the active SPE at any given time. The active SPE performs the same
operations that the single SPE performs in a standard system; that is, all call
processing, administration, and maintenance activities being performed by the
switch. All memory writes performed on the active SPE are copied to the other
SPE. The other SPE is known as the standby SPE. Its role is to take over as the
active SPE if the current active SPE fails. If the active SPE (or a component of the
active SPE) fails, the system automatically switches to the standby SPE.
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