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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.
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- [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]
-
- 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]
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