Network host status
Daily status of ARPANET hosts from October 26 to November 5, 1971
Westheimer, E., "Network host status", RFC 266, DOI 10.17487/RFC0266, November 1971, <https://www.rfc-editor.org/info/rfc266>.
@misc{rfc266,
series = {Request for Comments},
number = 266,
howpublished = {RFC 266},
publisher = {RFC Editor},
doi = {10.17487/RFC0266},
url = {https://www.rfc-editor.org/info/rfc266},
author = {E. Westheimer},
title = {{Network host status}},
pagetotal = 2,
year = 1971,
month = nov,
} RFC text
Network Working Group Ellen Westheimer RFC #266 Bolt Beranek and Newman Inc. NIC #7814 8 November 1971 Categories: F, G, 3 Updates: RFC 255 Obsoletes: None NETWORK HOST STATUS This RFC reports on the status of most.Network Hosts from October 26 to November 5. (Massachusetts celebrated Armistice day on Monday, October 25.) During these two weeks the general status of these hosts remained as it had been previously. The table on the following page summarizes the daily information on host status for this period. NETWORK ADDRESS SITE COMPUTER DAY, DATE AND TIME (EASTERN) ------- ---- -------- ---------------------------- T W Th F M T W Th F 10/26 10/27 10/28 10/29 11/1 11/2 11/3 11/4 11/5 1430 1200 1300 1300 1630 1330 1330 1330 1330 1 UCLA SIGMA-7 O O O T O T O O O *65 UCLA IBM-360/91 O D O O O O O O O 2 SRI(NIC) PDP-10 O O O O D O D O O 66 SRI(AI) PDP-10 D D D D D D D D D 3 UCSB IBM-360/75 D O O O O D D O O 4 UTAH PDP-10 T T T D D D D D T 69 BBN(TENEX) PDP-10 D O D D O O O O O 6 MIT(MULTICS) H-645 O D D O O O O T O 70 MIT(DM) PDP-10 D H T O O O O O T 8 SDC IBM-360/67 D D D D D D D D D 9 HARVARD PDP-10 D D T D D D D D D 10 LINCOLN IBM-360/67 H D H T T H H D H where D= Dead (Destination Host either dead or inaccessible [due to network partitioning or local IMP failure] from the BBN Terminal IMP.) R= Refused (Destination Host returned a CLS to the initial RFC.) T= Timed out (Destination Host did not respond in any way to the initial RFC, although not dead.) H= 1/2 Open (Destination Host opened a connection but then either immediately closed it, or did not respond any further.) O= Open (Destination Host opened a connection and was accessible to users.) * The UCLA IBM-360/91 currently has Remote Job Service (NETRJS), but has not implemented a full server Telnet System. The BBN Terminal IMP is not equipped to test NETRJS; however, we are assuming that receipt of the UCLA explanatory message indicates that NETRJS is also functioning. [ 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 ]
AI ELI5
On this page
§1Network Status Report
RFC 266 is a status report from BBN (Bolt Beranek and Newman) dated November 8, 1971, covering the two-week period from October 26 to November 5. It shows which ARPANET hosts were operational each day during that period.
The report tests most network hosts at regular intervals by attempting to reach them from the BBN Terminal IMP (Interface Message Processor), the central testing point for host connectivity.
This is a report card for computers on the network. It shows which ones were working on each day.
§2Host Status Codes
Each host receives one of five status codes for each test:
- D (Dead): The destination host is dead or inaccessible, either due to network partitioning or local IMP failure.
- R (Refused): The destination host returned a CLS (close) to the initial RFC.
- T (Timed out): The destination host did not respond to the initial RFC within the timeout period.
- H (1/2 Open): The destination host opened a connection but then immediately closed it or did not respond further.
- O (Open): The destination host opened a connection and was accessible to users.
A special note indicates that UCLA's IBM-360/91 runs NETRJS (Remote Job Service) but not a full Telnet server, so tests assume NETRJS is functioning when the BBN IMP receives its response.
D means the computer was dead. T means it didn't answer. H means it started to open but then closed. O means it worked. R means it said no.
§3Testing and Results
The report includes a table showing daily test results across the two-week period. Tests were conducted at a consistent time each day (typically around 1:00 PM to 1:30 PM Eastern Time). The results show the variability in host availability during this period, with most hosts experiencing at least some downtime.
This regular monitoring practice became a standard operational procedure for the ARPANET, helping operators understand network health and diagnose problems across the growing number of connected sites.
Every day at the same time, they checked each computer to see if it was working. The report shows what they found.