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+Network Working Group                   Marc Seriff
+Request for Comments 308                MIT-DMCG
+NIC 9259                                13 MARCH 1972
+References: RFC 254
+
+                     ARPANET HOST AVAILABILITY DATA
+
+     Several months ago a SURVEY program was implemented on the
+MIT-DMCG ITS PDP-10 system to aid in gathering information on the
+availability of various HOSTS on the ARPANET.  The purpose of this
+Request for Comments is threefold:
+
+     1. to inform the Network Working Group of the
+        existence of this information gathering service
+        and about getting access to it,
+
+     2. to present the results of SURVEY for its first
+        few months, and
+
+     3. to correct errors in our data or collection methods.
+
+     Briefly, the SURVEY program works as follows: At 15-minute
+intervals whenever the MIT-DMCG ITS Time-Sharing system is in normal
+operation, a SURVEY is started.  The SURVEY program attempts to
+establish a connection to the LOGGER (socket 1) of each HOST listed in
+its table.  The results of each connection attempt are recorded for
+future reference.  The Initial Connection Protocol is aborted prior to
+reading the transmitted socket number so as to cause the minimum
+amount of processing at SURVEYed HOSTS.  If the LOGGER connection
+succeeds, the average request-for connection response time (in
+seconds) for the HOST is updated.  This information can later be
+viewed in several formats using the MIT-DMCG server TELNET "NETWRK" as
+described below.
+
+     Each test results in the assignment of one of the following
+five statuses:
+
+     1.  LOGGER available - connection completed.
+
+     2.  LOGGER not responding - RFC sent (HOST-HOST OK), but
+         no response (20 seconds allowed).
+
+     3.  LOGGER rejecting - CLOSE returned by NCP.
+
+     4.  NCP not responding - RESET timed out (15 seconds allowed).
+
+     5.  HOST dead - host-dead status returned by IMP.
+
+
+
+
+                                                                [Page 1]
+
+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. <host name> - 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 <host name> - 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.
+
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+                                                                [Page 2]
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+For the above seven commands, "recent" is define as "within the
+last 24 hours or less".
+
+     For help in accessing SURVEY data and comments on improving the
+admittedly limited SURVEY service, please contact:
+
+          Marc Seriff
+          M.I.T. - Project MAC
+          545 Main Street
+          Cambridge, Mass. 02139
+          (617) 864-6900 ext. 1458
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+                                                                [Page 3]
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+6528 Surveys from 09:55:18 on 12/13/71 to 08:50:41 on 03/20/72
+--HOST-- -#- -%-UP- -RESP- *
+ucla-nmc 001  064%   00.93
+sri-arc  002  064%   02.96
+ucsb-75  003  048%   00.53
+utah-10  004  057%   03.23
+bbn-ncc  005  000%   00.00
+multics  006  047%   05.60
+rand-rcc 007  000%   00.13
+sdcadept 010  000%   02.60
+harv-10  011  022%   00.23
+ll-67    012  021%   03.70
+su-sail  013  000%   00.00
+ill-11   014  000%   00.06
+case-10  015  000%   00.00
+cmu-10   016  034%   00.23
+burr     017  000%   00.00
+ames-67  020  000%   00.00
+radc-645 022  000%   00.00 **
+nbs-11   023  000%   00.00 **
+tink-418 025  000%   00.00 **
+usc-44   027  000%   01.13 **
+ncar7600 031  000%   00.00 **
+ucla-ccn 101  070%   00.30
+sri-ai   102  000%   02.26
+tenex    105  060%   02.40
+mit-dmcg 106  093%   01.10 ***
+rand-csg 107  013%   02.96 **
+harv-1   111  000%   00.23
+ll-tx2   112  000%   01.76
+ill-6500 114  000%   00.00
+burrtest 117  000%   00.00 **
+tenexb   205  018%   02.93
+mit-ai   206  000%   00.00
+harv-11  211  000%   00.00
+
+* Remember that "UP is defined as "Logger Accepting connections."
+** Surveyed only since February 18, 1972.
+*** MIT-DMCG is actually up about 66% of the time.
+
+
+       [ This RFC was put into machine readable form for entry ]
+       [ into the online RFC archives by BBN Corp. under the   ]
+       [ direction of Alex McKenzie.                   12/96   ]
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+                                                                [Page 4]
+