The number of octets contained in IP datagrams which were
received from these sources and addressed to this multicast
group address, and which were forwarded by this router.
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.