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