RFC 392 (rfc392) - Page 3 of 6
Measurement of host costs for transmitting network data
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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
