Re: Testing Bandwidth performance

["David G. Andersen" <dga () lcs mit edu>]

On Wed, Jun 26, 2002 at 06:18:00AM -0700, todd glassey mooed:
> Oh and use something like a SNIFFER to generate the traffic. Most of what we
> know of as commercial computer's cannot generate more than 70% to 80%
> capacity on whatever network they are on because of driver overhead and OS
> latency etc etc etc. It was funny, but I remember testing FDDI on a UnixWARE
> based platform and watching the driver suck 79% of the system into the
> floor.

  Btw, if you've got a bit of time on your hands, the Click router
components have some extremely-low-overhead drivers (for specific
ethernet cards under Linux).  They can generate traffic at pretty
impressive rates.  They used them for testing DOS traffic for a while.

  http://pdos.lcs.mit.edu/click/

  (Most of the driver overhead you see is interrupt latency;  click
uses an optimized polling style to really cram things through).  Also,
the new FreeBSD polling patches should make it so you can get more
throughput from your drivers when doing tests.  I understand there are
similar things for Linux.

  -Dave

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