HDSL 24-hour performance table. This table provides the
accumulated counts of errored seconds (ES) and unavailable
seconds (UAS) for the HDSL line including the local, remote
units and any doublers in between during a 24-hour period
for the last 7 days.
The table is indexed by the non-empty slot in the device and
the 24-hour history slot within the last 7 days period.