The value of the object tmnxL2tpTuProtStatsType indicates
the instance identifier of the statistics
contained in this conceptual row.
For example: if the value of the object tmnxL2tpTuProtStatsType is equal
to 'outgoingMsgType', the value of tmnxL2tpTuProtStatsInstance is
a message identifier,
e.g. instance '2' refers to '(SCCRP) Start-Control-Connection-Reply',
and the value of tmnxL2tpTuProtStatsVal indicates the number of SCCRP
messages transmitted for this tunnel.
Unknown protocol messages are counted with instance zero.