This counter tallies frames discarded on ingress because the HDLC controller's FIFO overran, and the MIB notes it does not apply to MGX Release 1.x. A rising value tells an administrator that incoming data is arriving faster than the HDLC hardware can drain it, pointing to a hardware or clocking bottleneck rather than a wiring fault. For example, an engineer seeing frame loss on a high-speed port during traffic bursts would check this counter to see whether FIFO overrun, rather than line errors, is the source.