Hi Nik, On Mon, 24 Oct 2011, Nik Mitev wrote:
> When I added same probe to two more hosts, jitter and delay appeared > (3-4ms) on all hosts for the 20ms probe. Thinking that it is an issue > where FPing handles the load badly, I added one more graph to a fourth > host and expected an increase in jitter, but it went away completely and > returned to the original state for all four hosts. I am able to > reproduce that. At the same time I had a parallel probe running which > only differed in the offset - it was completely unaffected and flat at > all times. I think this is a bug with FPing. Smokeping relies on fping to do the actual pinging in the default configuration, although you can choose a different pinger. I remember trying to debug fping to solve a different bug and finding it trying, but if you program C or you can reproduce the problem on the fping command line, then it's possible to report upstream or investigate further. > 2. Separate scaling issue follows from FPing being limited to sending > pings at 1ms interval as its highest speed. For the purposes of VoIP, > jitter needs to be measured on packets sent at 20ms intervals, which > limits the number of hosts we can monitor to 20 at a particular offset > and to 200 if we only monitor 10% of the time and split the hosts in 10 > groups. Those numbers are the theoretical maximum and are likely to > actually be lower. It's theoretically possible to make fping send any number of pings per 1ms interval, although further skewing the time-distribution of pings may exaggerate the effects of any network boundaries beyond what you'd experience in a real call. Also beware that if you monitor continuously at this rate, your monitoring is going to have a major impact on network bandwidth use and thus negatively affect call quality. Cheers, Chris. -- Aptivate | http://www.aptivate.org | Phone: +44 1223 760887 The Humanitarian Centre, Fenner's, Gresham Road, Cambridge CB1 2ES Aptivate is a not-for-profit company registered in England and Wales with company number 04980791. _______________________________________________ smokeping-users mailing list [email protected] https://lists.oetiker.ch/cgi-bin/listinfo/smokeping-users
