The number of frames that have been transmitted by this port to its segment. Note that a frame transmitted on the interface corresponding to this port is only counted by this object if and only if it is for a protocol being processed by the local bridging function, including bridge management frames. Discontinuities in the value of the counter can occur at re-initialization of the management system, and at other times as indicated by the value of ifCounterDiscontinuityTime object of the associated interface (if any).