Histogram
Port histogram commands that deal with configuration of data collection and retrieval of samples from a port.
The histogram command names all have the form PD_<xxx> and require both a module index id and a port index id, as well as a sub-index identifying a particular histogram.
A histogram has a number of buckets and counts the packets transmitted or received on a port, possibly limited to those with a particular test payload id. The packet length, inter-frame gap preceding it, or its latency is measured, and the bucket whose range contains this value is incremented.
While a histogram is actively collecting samples its parameters cannot be changed.