This is the number of packets received with an illegal Ethernet packet length on this VC, defined as greater than the advertised maximum MTU supported or shorter than the allowed Ethernet packet size. A rising count here points to an MTU mismatch or a malformed-frame problem on the remote end or across the PSN transport, since it specifically counts frames violating either the negotiated maximum MTU for this pseudowire or the Ethernet minimum frame size, either of which would otherwise be silently dropped. For example, this counter climbing after a remote PE's access-side MTU was increased without updating the negotiated interface MTU on this pseudowire would reveal oversized frames now being rejected that previously fit within the older, smaller MTU.