Reports how many data buffers are currently queued for transmission out through this tunnel but not yet sent, per the object's description. Admins watch this to spot outbound congestion or a slow or unresponsive tunnel peer, since a persistently high count suggests the tunnel can't keep up with the data being fed into it. A tunnelInfoTransmitQueueSize that stays elevated across multiple polling intervals would suggest the far end is not acknowledging or receiving data quickly enough, warranting a check of the tunnel's link quality.