Network Working Group H. Murray Request for Comments: 415 Stanford Research Institute NIC: 392 29 November 1972
TENEX BANDWIDTH
NIC 11584 (RFC392) 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.
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.
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