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Network Working Group                                          H. MurrayRequest for Comments: 415                    Stanford Research InstituteNIC: 392                                                29 November 1972TENEX 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%Murray                                                          [Page 1]

RFC 415                     TENEX BANDWIDTH                November 1972   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]Murray                                                          [Page 2]