If not equal to zero, this value is sent as the optional IfMtu object in the maintenance protocol, representing the locally supported MTU size over the interface, or virtual interface, associated with the VC. Leaving it at 0 specifically suppresses sending that optional MTU element at all rather than advertising an MTU of zero, so an admin troubleshooting oversized-frame drops on a pseudowire should check whether this was ever actually populated and matches the true interface MTU. For example, setting this to 1500 on a standard Ethernet-access pseudowire tells the remote PE this VC supports frames up to that size, and a mismatch against the true physical MTU here would explain oversized-frame drops that the cpwVcEnetStatsIllegalLength counter would later report.