This read-only Counter tallies the number of frames discarded on egress specifically due to a physical layer failure. An administrator uses this counter to distinguish loss caused by an actual physical transmission problem, such as a bad line or interface, from congestion-related or protocol-related discards on the same channel. For example, a sudden burst of xmtFramesDiscPhyLayerFail coinciding with a line-alarm event on the physical interface would confirm a physical-layer fault, rather than queue depth or CRC issues, is responsible for the egress loss.