Date: Wed, 13 Nov 2013 19:40:54 -0800 From: Julian Elischer <julian@freebsd.org> To: Lee Dilkie <lee@dilkie.com>, Ahmed Hamza <ahmed.hmz@gmail.com>, freebsd-ipfw@freebsd.org Subject: Re: Bursty data transfer with Dummynet Message-ID: <52844646.2020802@freebsd.org> In-Reply-To: <5283FBBA.8090702@dilkie.com> References: <CAL_s3F5Hx0XJ8Nct=urWGN72hrGQ2LT2nJfG3OxgWT5oxtjW9Q@mail.gmail.com> <52830502.30809@freebsd.org> <CAL_s3F7GhrENW4d22h01wYF%2Bf2Kd6b=BomoZ6TP5jR1HQWAQ6g@mail.gmail.com> <52830C51.6020403@freebsd.org> <CAL_s3F6fnsnogJnUmGJFLP9_-n2hX0u87uQA2tAC4euP9kz3Zg@mail.gmail.com> <5283FBBA.8090702@dilkie.com>
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On 11/13/13, 2:22 PM, Lee Dilkie wrote: > seriously? > > you expect that kind of precise timing running in a VM? the fact that it is in a vm only just came out... still I'd expect better than "several seconds".. > > -lee > > On 11/13/2013 16:29, Ahmed Hamza wrote: >> I'm not sure if this would explain anything. But I am running DummyNet >> on a VirtualBox VM on an Ubuntu host. I have also experienced the same >> behaviour with both Frenzy (a FreeBSD based LiveCD) and Ubuntu guests. >> In the case of Frenzy, the tick was set to 1000Hz. But the host tick >> was 250Hz since it is an Ubuntu machine. Also, the delay between >> bursts is in order of seconds! My assumption about DummyNet is that >> while the queue is being drained new packets will be queued (i.e. >> there is no waiting to fill the queues before transmitting them using >> the specified bandwidth). >> >> On Tue, Nov 12, 2013 at 9:21 PM, Julian Elischer<julian@freebsd.org> wrote: >>> On 11/12/13, 9:06 PM, Ahmed Hamza wrote: >>>> On Tue, Nov 12, 2013 at 8:50 PM, Julian Elischer<julian@freebsd.org> >>>> wrote: >>>>> On 11/12/13, 6:35 PM, Ahmed Hamza wrote: >>>>>> Hi All, >>>>>> >>>>>> I'm trying to use Dummynet to test the behaviour of my video streaming >>>>>> application in various network conditions. Dummynet was compiled and >>>>>> installed on an Ubuntu 12.04 box with a 2.6 Linux kernel. I'm >>>>>> experiencing a strange behaviour when I reduce the bandwidth of the >>>>>> link/path. >>>>>> >>>>>> For some reason, instead of having a slow download speed. It seems as >>>>>> if the download is happening in bursts! A portion of the data is >>>>>> downloaded at a high speed, then the data transfer stops for a period >>>>>> of time and then resumes again (and so on). Does anyone have an idea >>>>>> what could be the cause? Or is this even an expected behaviour? If so, >>>>>> why? >>>>> I can't really speak for dummynet on Linux but the granularity of the >>>>> queues >>>>> is dependent on the timer granularity of the kernel you have and to some >>>>> extent will rely on the correct integration of dummynet into the timer >>>>> facility of the kernel you are running it in. On freeBSD with a 1kHz >>>>> 'tick' >>>>> I'd' expect to see packets being release from the queue each mSec or so. >>>>> if you are getting second sized chunks then it probably is a bug. Either >>>>> dummynet is not compatible with that kind of kernel, something else has >>>>> gone >>>>> wrong. It COULD also be that you are catching the wrong packets.. I've >>>>> seen >>>>> similar behaviour when I was accidentally queuing all the acks instead of >>>>> all the data going in the other direction, but I presume you have already >>>>> checked to see what you are queuing. >>>>> >>>> Thanks Julian and Matthew for your replies. To clarify my settings, >>>> below are the outputs from 'ipfw show' and 'ipfw pipe show'. I should >>>> also mention that it seems the by default the Ubuntu kernel is >>>> configured for 250Hz, not 1000Hz. >>> I would expect that that would give a queue kick every 4 mSec or so so you >>> should get a burst every 4mSec or so. >>> but your queue is only doing 500kbit/sec or 1/2kbit /msec, or about >>> 2kbit/4mSec or 250bytes per tick which is less than a packet. I'm afraid >>> you'll have to talk to Luigi to know what happens in such a case.. >>> >>> >>>> root@vm1:~/# ipfw pipe 1 config bw 500Kbit/s queue 500Kbyte >>>> >>>> root@nsl-vm1:~/# ipfw show >>>> 00100 202247 105063701 pipe 1 ip from 192.168.56.4 to any >>>> 65535 2245577 2648958386 allow ip from any to any >>>> >>>> root@nsl-vm1:~/# ipfw pipe show >>>> 00001: 500.000 Kbit/s 0 ms 500 KB 1 queues (1 buckets) droptail >>>> mask: 0x00 0x00000000/0x0000 -> 0x00000000/0x0000 >>>> BKT Prot ___Source IP/port____ ____Dest. IP/port____ Tot_pkt/bytes >>>> Pkt/Byte Drp >>>> 0 tcp 192.168.56.1/33547 192.168.56.4/80 238083 134515909 >>>> 0 0 623 >>>> >> _______________________________________________ >> freebsd-ipfw@freebsd.org mailing list >> http://lists.freebsd.org/mailman/listinfo/freebsd-ipfw >> To unsubscribe, send any mail to"freebsd-ipfw-unsubscribe@freebsd.org" >help
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