Specifies a value that can be translated to the numeric value of
the traffic class to be used as either the congesting or monitored
queue. The absolute value of the enumerated value is the value of
the traffic class plus 1. A value of 0 indicates the traffic class
is not participating in congestion isolation. For example, the
enumerated value congesting-queue-tc-5 specifies that traffic class
4 is used as the congesting queue.