An entry describes cumulative and aggregate IP CBR metrics for
a single traffic flow.
The devices creates a row in the cfmIpCbrMetricsTable when a
flow monitor starts monitoring a traffic flow and has been
configured to compute IP CBR metrics for the same traffic flow.
Likewise, the device destroys a row in the
cfmIpCbrMetricsMetricsTable when the corresponding flow monitor
has ceased monitoring the traffic flow (e.g., when a traffic
flow has timed out).