The number of octets contained in IP datagrams which this
router has received from these sources and addressed to this
multicast group address, which were dropped because the TTL
(IPv4) or Hop Limit (IPv6) was decremented to zero, or to a
value less than hwIpMcastInterfaceTtl for all next hops.
Discontinuities in this monotonically increasing value
occur at re-initialization of the management system.
Discontinuities can also occur as a result of routes being
removed and replaced, which can be detected by observing
the value of hwIpMcastRouteTimeStamp.