North American Network Operators Group|
Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical
Re: Phantom packet loss is being shown when using pathping in connectionwith asynchronous routing - although there is no real loss.
> The only part that I don't get is that you can mtr to him without > packetloss. Although the path in-between may be different, the final hop > packetloss should exactly equal what he sees when mtring you. A round-trip > is a round-trip, and results should be identical regardless of who > originates. I can't think of any way this would be different unless echo > and echo-reply were being rate limited independently. If the time was different then the packet loss would be different. Perhaps the customer runs the tests during his busy period when he is concerned about making sure there is no delay. Then, later in the day, after his busy period is over he takes the time to contact his ISP. The ISP then runs some tests which show there is no packet loss at all. To be sure this is not happening, synchronize the tests and run simultaneously. Try tcptraceroute because this more accurately reflects the traffic that is flowing. http://michael.toren.net/code/tcptraceroute/ http://tracetcp.sourceforge.net/ is a windows tool that is similar. The open source tool LFT can be built to run on Windows under cygwin http://pwhois.org/lft/ but they have this warning on their page: Many people have complained about various problems on the Windows platform. Both LFT and the WhoB client compile and run well under Cygwin environments on Windows. Unfortunately, Microsoft's changes to the Windows IP stack (as of XP Service Pack 2) reduced their raw socket functionality significantly as part of their security bolstering process. These changes have effectively stopped LFT from working properly while using TCP. LFT's UDP tracing and other advanced features still work properly. For more information on Windows raw sockets, consult www.microsoft.com/technet/prodtechnol/winxppro/maintain/sp2netwk.mspx#EIAA This may have nothing to do with your MTR issue but it does make one wonder whether a Windows machine is safe to do performance testing. In any case, the LFT people think that their non-TCP features still work properly on Windows and this is a tool that you can also run on your end. Worth a try? --Michael Dillon