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rfc: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%

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]

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