computing network loads


Tait Cyrus (hi!cyrus@hc.dspo.gov)
1 Apr 88 20:29:04 GMT


   I am looking for an equation that roughly computes the theoretical
load on a network given only the following information:
        1) time over which the load is to be computed,
        2) the number of packets seen in that time,
        3) the number of bytes seen in that time.

   Currently I am using something like:
        num_bytes / (MBYTES_PER_SEC * time)

where I have arbitrarally picked MBYTES_PER_SEC to be 1 MegaBytes / sec.
Given a 10MBit (1.25 MByte) channel, subtracting overhead for preambles,
CRC bytes, collisions & the minimum time between packets, I came up
with the VERY approximate # of 1 MByte/sec.

   I know that 1 Meg is a VERY magic number because there are many
different media that the data can be traveling across which will
effect this magic number.

   So, back to the question. Is this a good approximation? What
values for MBYTES_PER_SEC should be used for the various medias,
i.e. think wire, thin wire, broadband, fiber, etc.?
   I don't want to worry about distances between stations and the
media between them, just a rough approximation.

   I have looked at the Blue Book to try to find a "nice" method
for computing network loads, but I am having a hard time trying
to come up with a better equation. Any help anyone could supply
me (as far a clarification of what the Blue Book is saying and
how to use that information) would be greatly appreciated.

Thanks,

--
    @__________@    W. Tait Cyrus   (505) 277-0806
   /|	      /|    University of New Mexico
  / |	     / |    Dept of Electrical & Computer Engineering
 @__|_______@  |       Parallel	Processing Research Group (PPRG)
 |  |	    |  |       UNM/LANL	Hypercube Project
 |  |  hc   |  |    Albuquerque, New Mexico 87131
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 @/_________@/	      cyrus@hc.dspo.gov



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