Hi Alan, On Sep 22, 2014, at 15:09 , Alan Goodman wrote: > Hello all once again, > > I tried running the attached ping sweeper yesterday evening as is and didnt get particularly plausible looking results. I concur, that does not look like ATM. I somehow like how I hedged my estimate of the ATM quantization by reporting it likely if the residuals of the stair fit is smaller than the residuals of the linear fit ;) But that clearly is not an ATM carrier... > I therefore decided to increase the upper limit of the size of ping packets sent and let the script run over night while the connection was quiet. I guess not a bad idea, but in this case the simplistic heuristic of just comparing cumulative residuals is just not good enough. (Note though that I do not have sufficient data sets to find a better statistic test) > > Here is a screen shot of the resulting graph which does appear to have a stepped appearance, but perhaps not as expected? > http://imgur.com/RjmT8Qh No, that is not the result to expect from an ATM carrier. Attached you will find example plots from a real ATM quantized link (2558 Kbps upload, 16402 Kbps download), notice how well the red line follows the green stair function in f2? Your example basically shows no stair function in the data, but for FTTC or VDLS2 that is to be expected as they finally got rid of the ATM carrier (which had overstayed its well come once the telco backbones switched away from ATM as well...)