RFC 392 (rfc392) - Page 3 of 6


Measurement of host costs for transmitting network data



Alternative Format: Original Text Document



RFC 392        Measurement for Transmitting Network Data  September 1972


   Column 5 was calculated by the formula:
   us/bit = (chargeable runtime)*1000/((number of bytes)*8)

   Column 6 is the 5 minute load average. (See TENEX documentation for
   details.)

   Using these figures we can conclude that for a million bits of
   information -- programs to be executed or data -- it would take 75 to
   85 cpu seconds to transmit.  At a cost of $474.60 per cpu hour on
   TENEX's[5], this millionbits would cost $9.90 to 11.20 to transfer
   from the originating host and potentially the same for the foreign
   host to receive.  This is about 33 to 37 times higher than the
   predicted network transmission costs[4].

   It is to be noticed that, in some cases, for programs to be
   transmitted over the network, the cost incurred by transmitting them
   was greater than the cost of executing these programs at the foreign
   host!

III.  Analysis

   There may be numerous ways to reduce the cost of the network to the
   host:

      (a) Treat the network not as a file device but as an interprocess
          communications device[6].

      (b) Create an 'intelligent' network input/output device.  This
          would, of course, be customized for individual types of
          operating systems and hardware configurations.  For TENEX
          systems this could be implemented as the ability to do mapping
          operations from the users virtual memory 'directly' onto the
          network.  In any case, this intelligent network device would
          be required to handle the various protocols for the host.
          Some changes may be required in the NCP protocols.

   A way to reduce the cost of the RJS program (the one measured in
   tables 1 and 2) would be to change the RJS-UCLA protocol.  One
   possible change is to allow hosts the option of using 32 bit bytes
   (because it may be more efficient!) instead of the 8 bit bytes now
   required by the protocol.

   Basically, it is our belief, that, in order to make the network as
   viable economically as was anticipated by the authors of
   reference[4], much work is needed on host machines and network
   protocols rather than on further refinements of the communication
   devices involved.




Hicks & Wessler