Traffic Statistics (September 1972)
Monthly statistics on ARPANET packet traffic.
McKenzie, A.M., "Traffic Statistics (September 1972)", RFC 400, DOI 10.17487/RFC0400, October 1972, <https://www.rfc-editor.org/info/rfc400>.
@misc{rfc400,
series = {Request for Comments},
number = 400,
howpublished = {RFC 400},
publisher = {RFC Editor},
doi = {10.17487/RFC0400},
url = {https://www.rfc-editor.org/info/rfc400},
author = {A.M. McKenzie},
title = {{Traffic Statistics (September 1972)}},
pagetotal = 3,
year = 1972,
month = oct,
} RFC text
Network Working Group A. McKenzie
Request for Comments: 400 BBN
Updates: 391 18 October 1972
NIC: 11922
TRAFFIC STATISTICS (September 1972)
Attached are the network traffic statistics for the month of September
1972.
AAM/jm
Attach.
HOST THROUGHPUT SUMMARY
(PACKET OUTPUT)
SEPTEMBER 1972
INTER- INTRA- AVG. DAILY
NODE NODE TOTAL INTERNODE DAYS
UCLA HOST 1 232650 32005 264655
UCLA HOST 2 1264597 25042 1289639
UCLA HOST 3 431011 10235 441246
------- ----- -------
1928258 67282 1995540 64275 30
SRI HOST 1 1801046 24363 1825409
SRI HOST 2 16168 1327 17495
------- ----- -------
1817214 25690 1842904 60574 30
UCSB HOST 1 428498 922768 1351366 14283 30
BBN HOST 2 3816667 1180948 4997615
BBN HOST 3 12899 1589244 1602143
BBN HOST 4 90831 2276 93107
------- ------- -------
3920397 2772468 6692865 130680 30
MIT HOST 1 61014 37330 98344
MIT HOST 2 588706 414366 1003072
MIT HOST 3 473483 804424 1277907
MIT HOST 4 326086 532129 858215
------- ------- -------
1449289 1788249 3237538 48310 30
RAND HOST 1 243220 18854 262074
RAND HOST 2 1810611 147138 1957749
------- ------ -------
2053831 165992 2219823 68461 30
SDC HOST 1 10995 2925 13920 366 30
HARV HOST 1 214735 23394 238129
HARV HOST 2 1 6424 6425
------ ----- ------
214736 29818 244554 7158 30
LINC HOST 1 29528 31479 61007
LINC HOST 2 25622 320359 345981
LINC HOST 3 2746 12070 14816
----- ------ ------
57896 363908 421804 1930 30
STAN HOST 1 736633 28870 765503 24554 30
ILL HOST 1 364525 431 364956 12151 30
CASE HOST 1 90546 13488 104034 3018 30
CARN HOST 1 391976 96110 488086
CARN HOST 2 83550 63458 147008
------ ----- ------
475526 159568 635094 15851 30
AMES2 HOST 1 1860607 11378 1871985 62020 30
AMES1 HOST 1 182187 42997 225184
AMES1 HOST 3 3425989 40589 3466578
------- ----- -------
3608176 83586 3691762 120273 30
MITRE HOST 3 905330 24 905354 30178 30
ROME HOST 3 524012 27 524039 17467 30
NBS HOST 1 969 31 1000
NBS HOST 3 797536 35 797571
------ ------ -------
798505 66 798571 26617 30
ETAC HOST 3 302263 129 320392 10675 30
TINK HAD NO TRAFFIC 30
MC CL HAD NO TRAFFIC 30
USC HOST 1 1196 2296 4292
USC HOST 3 526148 13224 539372
------- ------ ------
528144 15520 543664 17605 30
GWC HOST 3 61277 63 61340 2043 30
NOAA HOST 3 8764 14 8778 292 30
SAAC HOST 3 196371 1530 197901 6546 30
BELV HAD NO TRAFFIC 30
ARPA HOST 1 2 574341 574343
ARPA HOST 3 73057 154027 227084
------ ------ -------
73059 728368 801427 2435 30
ABER HOST 1 741 0 741 148 5
BBN T HOST 3 633173 209199 842372 21106 30
ICCC HOST 3 1017365 5524 1022889 33912 30
-------------------------------------
TOTAL 24867510 7589632
DAILY AVERAGE 828917 252988
AVERAGE PER 27478 8386
NODE-DAY
PACKETS/MESSAGES (INTERNODE) 1.07
[This RFC was put into machine readable form for entry]
[into the online RFC archives by Helene Morin, Via Genie 12/99]
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§1The Traffic Report
RFC 400, authored by Alex McKenzie at BBN, publishes traffic statistics for September 1972. BBN operated the ARPANET IMPs and had been collecting these statistics monthly for the Department of Defense. This is the first RFC sharing this operational data with the network community, marking a shift toward transparency in network usage.
The report shows packet activity across the 18 host sites connected to the ARPANET at the time. Traffic is broken down into inter-node packets (sent to other hosts) and intra-node packets (sent to other hosts at the same site), allowing analysis of both network-wide communication patterns and local cluster activity.
Someone from BBN wrote down how many packets went through each computer in one month, and shared the numbers so everyone could see what was happening on the network.
§2Traffic Patterns
The September 1972 data shows significant variation in network usage. BBN's hosts handled the highest traffic, with Host 2 generating over 3.9 million inter-node packets and Host 3 handling 1.6 million intra-node packets—indicating heavy local and remote usage. MIT's hosts collectively sent over 1.4 million inter-node packets. UCLA, SRI, and other major computing centers also show substantial traffic.
The report includes average daily inter-node rates per host and a summary showing that across the month, the network carried about 24.8 million inter-node packets and 7.5 million intra-node packets. The average per-host-day was 27,478 inter-node packets and 8,386 intra-node packets. The ratio of packets to messages (1.07) indicates that most messages fit within a single packet.
BBN was the busiest, but UCLA, SRI, MIT and others all sent millions of packets. The whole network together sent billions of packets in a month.
§3Significance of Data Sharing
Publishing these statistics made the ARPANET community visible to itself. Network operators and researchers could see where traffic was concentrated, which sites were active, and how the network was growing. This transparency helped inform capacity planning, protocol development, and resource allocation decisions across the network.
These monthly reports became a standard part of ARPANET operations, with BBN continuing to publish traffic statistics. The data revealed the changing patterns of network usage as new services and protocols became available and more hosts joined the network.
By sharing these numbers, everyone could see which computers were talking most and how busy the network was, helping them plan for the future.