Scheduled Network Software Maintenance

--------------------------------------

    As explained in RFC 381, we believe that we can minimize
the disruption caused by the release of new IMP software systems by
doing them on a regularly scheduled basis.  In the past we have
reserved the one hour period from 7am until 8am every Tuesday morning
for our IMP system scheduled software maintenance period.  As the size
of the network has grown to about forty IMPs, we find we can no longer
complete a system release to all IMPs in the one hour scheduled.
Therefore, we are extending our scheduled software maintenance period
to two hours from 7am until 9am eastern time every Tuesday
morning. The extended period will take effect as of the first Tuesday
in February.  As we said in RFC 381, we will not always use the
Tuesday morning period, but we always reserve it.  On Tuesday mornings
when we _do_ use the scheduled software maintenance period, a type 2 IMP
to Host message* will be sent to all Hosts about an hour in advance of
the period.

    We understand that the software maintenance period cannot
continue to grow linearly with the number of IMPs, and we will find a
way around this problem before software releases start taking 168
hours a week.

*An IMP-GOING-DOWN-FOR-SCHEDULED-SOFTWARE-MAINTENANCE message.

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