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This is a modified version of the Internet RFC suitable for machine-translating. Original version is available here: RFC415




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.

Murray [Page 1]


RFC 415                     TENEX BANDWIDTH                November 1972

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.


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Murray [Page 2]


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