Re: [RE] Comparing graphical analysis and analytical
From a worst-case perspective, CBR traffic with a
hickup at the wrong time
(traffic stops momentarily) gives much worse latency
Have you thought about how this could be included in
Its at first counter-intuitive: transients that reduce
the loading actually
can make the worst case latencies
If this effect could be included in your model, then I
would feel more
confident that we are addressing the true "worst case"
I've looked through the David's
charts and figures in the effort to synchronize our results on the worst-case
latency figures. Few observations:
1) Graphical analysis is considering both input-queue and output-queue
routers. My work exclusively deals with the output-queue routers.
2) In graphical analysis of traffic patterns
I couldn't find an explicit value for bandwidth shaping period under
consideration. This definitely has an effect on the outcome. For the 3 port
output queue analysis it seemed that 125 mks shaping period was used.
3) For the output-port router graphical
analysis for 3 ports, figures are actually in a very good agreement with the
analytical formula for the shaping period of 125 mks and 75% link utilization.
In fact when I graphed latency values from the David's paper they where almost
linear and also fit tightly with the graphs produced analytically. On the
attached graph, analytical curve is black, while curve from the values in the
table F.3 on the page 10) is blue.
All this leads me to believe that there no drastic
disagreement in results at all!