User guide

Appendix F - Automatic Switching F-9
Load switching
Determining Need-for-Change
The following process is used to determine if bandwidth utilization warrants a
need-for-change.
The user defines both a Step Up and Step Down threshold in terms of percent
utilization, a bandwidth margin value, and a latency or averaging period. Once
per second, the CDM router software determines the current percent utilization
by dividing the bits transmitted by the current transmit data rate.
If the percent utilization exceeds the step up threshold or is less than the step
down threshold for the entire latency period, then an ASR (Automatic Switch
Request) is sent to the VMS. The bandwidth requirement for the ASR is
computed by taking the average percent utilization over the latency period and
multiplying that by the current data rate to determine the actual data rate used
over the measured interval. This number is multiplied by the margin value and
rounded up to the nearest 8K to determine the requested bandwidth.