This object is used to indicate the number of seconds,
in the particular 15 minute or 24 hour interval, for which the
optical performance data is not accounted for.
In the receive direction, the performance data could be
unavailable during these periods for multiple reasons
like the interface being administratively down or if there
is a Loss of Light alarm on the interface. In the transmit
direction, performance data could be unavailable when
the laser is shutdown.