The Maximum Transmission Unit (MTU) this interface is permitted to
transmit.
At creation, if a value for this object is not specified, a default will
be chosen that is suitable for the type of lower interface on which this
interface is stacked.
This setting plus 2 bytes for HDLC address/control plus the length
in bytes of the HDLC CRC cannot exceed 65535. The maximum value for
this object reflects the largest possible value when no CRC is used;
technology constraints of a particular implementation may further
limit the upper bound value.