Polycom RealPresence DMA 7000 System Operation Manual page 150

● When calls to a specific MCU fail, the RealPresence DMA system reduces the MCU's reliability score,
causing it to be selected less frequently than other MCUs.
An MCU's reliability depends on the number of consecutive failed calls. As that number increases,
the RealPresence DMA system treats a growing percentage of the MCU's ports as if they were in use.
Since the RealPresence DMA system selects the least used of the capable MCUs in its pool, the
likelihood that an MCU with failures will be chosen for the next call declines rapidly (depending on the
number of consecutive failed calls and the remaining capacity in the MCU pool).
Consecutive Percentage of Ports
Failed Calls Assumed To Be in Use
1
2
3
4
5
6
7
8
9
Every 30 minutes, the reliability score of the MCU is increased so that it won't be permanently removed from
the pool due to failures in the distant past. To avoid trying the MCU every 30 minutes, monitor the
RealPresence DMA system and administratively take the MCU out of service.
By increasing the number of MCUs in the pool or increasing their capacity, you can decrease the usage of
the working MCUs during a failover scenario. So, for example, if you want to avoid routing any more calls
to an MCU after two consecutive failed calls, provide enough excess capacity that the remaining MCUs
never all reach 43% port usage during a failure.
Polycom, Inc.
24%
43%
56%
67%
74%
80%
84%
88%
90%
MCU Management
150