Tenex bandwidth
A TENEX test of network throughput and the CPU used for transfers.
Murray, H., "Tenex bandwidth", RFC 415, DOI 10.17487/RFC0415, November 1972, <https://www.rfc-editor.org/info/rfc415>.
@misc{rfc415,
series = {Request for Comments},
number = 415,
howpublished = {RFC 415},
publisher = {RFC Editor},
doi = {10.17487/RFC0415},
url = {https://www.rfc-editor.org/info/rfc415},
author = {H. Murray},
title = {{Tenex bandwidth}},
pagetotal = 2,
year = 1972,
month = nov,
} RFC text
Network Working Group H. Murray
Request for Comments: 415 Stanford Research Institute
NIC: 392 29 November 1972
TENEX BANDWIDTH
NIC 11584 (RFC 392) BY G. HICKS AND B. WESSLER AT UTAH RECENTLY
DISCUSSED THE COST OF USING THE NETWORK.
I WOULD LIKE TO TAKE THESE SAME TYPES OF NUMBERS AND LOOK AT THEM
FROM ANOTHER POINT OF VIEW. WITHOUT CALCULATING COSTS, LET US
CONSIDER ULTIMATE PERFORMANCE OF THE HOSTS. I WROTE A SIMPLE TENEX
PROGRAM THAT SENT ITSELF STRINGS OVER THE NET. IT USED BIN/BOUT AND
THE BUFFERED SEND MODE. IT COUNTED THINGS, BUT DID NOT PROCESS THE
STRING. WITH SAMPLES OF A MILLION BITS, THE FOLLOWING RESULTS WERE
OBTAINED.
BYTES/SIZE REAL BAUD CPU BAUD CPU NEEDED
50/36 48.8K 291K 16%
100/36 46.5K 309K 15%
200/36 52.7K 322K 16%
400/36 59.3K 267K 22%
800/36 61.1K 279K 21%
50/8 22.0K 70K 31%
100/8 26.7K 76K 35%
200/8 29.0K 79K 36%
400/8 30.0K 81K 37%
800/8 31.9K 78K 40%
1600/8 38.1K 64K 59%
3200/8 41.8K 59K 70%
THE FOLLOWING WERE OBTAINED BY USING SIN/SOUT WITHOUT THE BUFFERED
MODE.
BYTES/SIZE REAL BAUD CPU BAUD CPU NEEDED
50/36 36K 95K 38%
100/36 44K 95K 45%
200/36 49K 92K 53%
400/36 54K 90K 60%
50/8 12K 22K 57%
100/8 16K 21K 75%
200/8 18K 20K 92%
400/8 20K 20K 99%
THESE TESTS WERE RUN WITH NO OTHER LOAD ON OUR SYSTEM, AN EARLY
VERSION OF 1.29. THE INPUT AND OUTPUT HALVES OF THE TRANSMISSION
HAVE BEEN AVERAGED TOGETHER. I.E. THE ABOVE BAUD RATES WERE
CALCULATED USING 2 MILLION BITS SINCE THE STRINGS WENT OUT AND IN.
OTHER PIECES OF DATA:
OUR TTY'S AND LPT HAVE ULTIMATE CPU BANDWIDTHS NEAR 15-20 KB. AT
2400 BAUD, A TTY TAKES 15% OF THE CPU. TELNETS NESTED THREE DEEP ARE
ALMOST COMPUTE LIMITED WHEN JUST TYPING THINGS OUT ON A 2400 BAUD
TERMINAL.
AS A ROUGH CALCULATION, THE BANDWIDTH OF THE TIP TAPE TRANSMISSION
FEATURE - USING STEVE BUTTERFIELD'S (OF BBN) NETMAG PROGRAM - IS
ABOUT 7 KILOBITS/SEC. ONE TAPE OF ABOUT 6,000 TENEX PAGES TOOK ABOUT
4 HOURS TO TRANSMIT. THIS WAS A FULL TAPE FROM ETAC TO CCA LATE ONE
NIGHT WITH NOTHING ELSE RUNNING ON OUR SYSTEM. ABOUT 30% OF THE CPU
IS NEEDED TO MAINTAIN THIS BANDWIDTH. AGAIN THIS IS ONLY ABOUT 20KB
PER CPU SEC.
[This RFC was put into machine readable form for entry]
[into the online RFC archives by Helene Morin, Via Genie 12/99]
ISO Plain Language
On this page
§1Test Setup
The author describes a simple TENEX program that sent strings over the network to itself, using BIN/BOUT and buffered send mode. It counted data but did not process the strings. Samples contained one million bits.
The tests ran with no other load on the system, using an early version of TENEX 1.29. Input and output halves were averaged together, so reported baud rates used two million bits of combined traffic.
The test program sent data out and received it back without processing the contents. The reported rates combine the outgoing and returning data.
§2Buffered Transfer Results
With buffered send mode and 36-bit sizes, the table reports real baud rates from 46.5K to 61.1K and CPU baud rates from 267K to 322K. CPU needed ranges from 15% to 22% for those entries.
With buffered send mode and 8-bit sizes, real baud rates range from 22.0K to 41.8K, while CPU needed ranges from 31% to 70%. The table lists each tested byte size separately.
The buffered tests report different speeds and CPU use for different byte sizes. The values are measurements under the stated test conditions, not a guarantee for other systems.
§3Unbuffered Transfers and Other Comparisons
The second table uses SIN/SOUT without buffered mode. For 36-bit sizes, its real baud rates range from 36K to 54K and CPU needed ranges from 38% to 60%. For 8-bit sizes, real baud rates range from 12K to 20K and CPU needed ranges from 57% to 99%.
The RFC also reports that TTYs and line printers have ultimate CPU bandwidths near 15-20 KB, and that a TIP tape transmission using NETMAG was about 7 kilobits per second and used about 30% of the CPU.
The unbuffered table reports its own speeds and CPU use for each size. The RFC also gives comparison figures for local terminals, printers and a tape transfer.