We present a customizable simulator called netsim for
high-performance point-to-point workstation networks that is accurate
enough to be used for application-level performance analysis yet is
easy enough to customize for multiple architectures and software
configurations. Customization is accomplished without using any
proprietary information, using only publicly available hardware
specifications and information that can be readily determined using a
suite of test programs. We customized netsim for two platforms: a
16-node IBM SP-2 with a multistage network and a 10-node DEC Alpha
Farm with an ATM switch. We show that netsim successfully models these
two architectures with a 2-6% error on the SP-2 and a 10% error on the
Alpha Farm for most test cases. It achieves this accuracy at the cost
of a 7-36 fold simulation slowdown with respect to the SP-2 and a 3-8
fold slowdown with respect to the Alpha Farm. In addition, we show
that the cross-traffic congestion for today's high-speed
point-to-point networks has little, if any, effect on
application-level performance and that modeling end-point congestion
is sufficient for a reasonably accurate simulation.
(Also cross-referenced as UMIACS-TR-96-68