RFC 308 (rfc308) - Page 2 of 4

ARPANET host availability data

Below you will find a summary of the information gathered to
date.  It must be remembered that the SURVEY program can only run when
MIT-DMCG ITS Time-Sharing System is in normal operation and the MIT
IMP is operational.  Thus the current figure of 94% for MIT-DMCG is
inaccurate. (It should actually be closer to 66%.)

     There are, in addition, two other shortcomings of which we are
aware.  The first is that SURVEY is on a 24-hour basis and does _not_
consider advertised up time.  For example, MIT-DMCG will never be
better than 67% on a Tuesday since the machine is always unavailable
from 4 p.m. to midnight.  The second shortcoming is the fact that the
Lincoln Lab's TX-2 shows as "never available".  This reflects an as
yet undiagnosed problem currently under investigation.

     To get availability information from DMCG, you must first follow
the scenario in RFC 254.  Once in NETWRK, the DMCG user-TELNET, there
are seven available commands which pertain to SURVEY data:

     SUMMARY.OF.SURVEYS - summarizes most recent information.

     HISTORY.OF.  - gives a detailed recent history
                    of the given host.  This generates a lot
                    of output, so use it sparingly.

     ACTIVE.HOSTS - lists those hosts who accepted a connection
                    at least once during the last 24 hours.

     BEST.SURVEY - lists the best of the recent surveys.

     LONGTERM SUMMARY.OF.SURVEYS - summarizes all past
                    information.  This was used to generate
                    the table on the next page.


     LONGTERM HISTORY.OF  - gives a summary of
                    past history of the given host.  It
                    does not generate as much output as the
                    HISTORY command.

     LONGTERM ACTIVE.HOSTS - lists those hosts who accepted a
                    connection at least once since December 13,
                    1971.