The number of octets of multicast packets that have arrived
on the interface, including framing characters. This object
is similar to ifInOctets in the Interfaces MIB, except that
only multicast packets are counted.
Discontinuities in the value of this counter can occur at
re-initialization of the management system, and at other
times as indicated by the value of
hwIpMcastInterfaceDiscontinuityTime.