A read-only counter tracking the byte volume of frames successfully transmitted on this interface whose destination address had the multicast bit set. This lets an admin see how much of the interface's outbound traffic is multicast, useful for capacity planning on multicast-heavy applications like video distribution; these bytes are also included in the standard ifOutOctets total. An interface distributing a multicast video stream would show a correspondingly large etherMulticastBytesOut value relative to its total outbound traffic.