This object indicates the traffic class of the corresponding
traffic flow.
If version 4 of the IP carries the traffic flow, then the value
of this column corresponds to the 'Type of Service' field of the
IP header contained by packets in the traffic flow.
If version 6 of the IP carries the traffic flow, then the value
of this column corresponds to the '' field of the IP header
contained by packets in the traffic flow.
The value of this column is valid only if the 'trafficClass'
bit of the corresponding instance of cfmFlowIpValid is '1'.