VOSS now supports the ability to check port utilization from the command line:
monitor ports statistics interface utilization
The in/out octet counters show cumulative values over a long time or since you last cleared the port stats.
The % util columns are calculated based on increases of the in/out octets over the last monitor interval period.
The % util may show 0 which is an indication that there is not enough traffic to produce a calculation of 1% or greater. Use a traffic generator to generate at line rate and you should see 100%.
To clear port statistics use the command:
clear-stats port
The monitor-statistics command supports options to select the monitor time duration and the monitor time interval under global configuration mode.