Re: traffic shapping problem with fragmented packets

From: Wael Ashmawi (washmawi@ee.upenn.edu)
Date: Fri Sep 22 2000 - 20:14:15 EDT

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    Thanks andi for the response but I have some comment to tell.
    1- The TBF does not drop packets asI have made the "limit" value to big
    (1MB).. Also I have checked that using the -s option in TC where I found no
    packets are dropped. Finally I can see the packets released after a while
    (using tcpdump) so that means that no drooping is happennig.

    2- The application can not be fixed as it is commercial MS product.

    3- Setteing the burst size to one full big datagram will make the traffic
    nonconforment to the EF statndard and it will be dropped in the next
    policing piont.

    Thanks
    Wael

    ----- Original Message -----
    From: "Andi Kleen" <ak@suse.de>
    To: "Wael Ashmawi" <washmawi@ee.upenn.edu>
    Cc: <linux-kernel@vger.kernel.org>
    Sent: Friday, September 22, 2000 5:16 PM
    Subject: Re: traffic shapping problem with fragmented packets

    > On Fri, Sep 22, 2000 at 04:56:55PM -0400, Wael Ashmawi wrote:
    > > I have tried several ways of doing that the script shown below does the
    > > shaping ok but for packet less than the Ethernet MTU. if I start to have
    > > fragments everything is missed up. I tried it with pings givinig
    > > different packet size in the command line.
    >
    > The problem is not really solvable unless you fix the application to send
    > smaller packets. The only way to shape traffic in IP is to drop packets,
    and
    > with these big fragments a single packet drop the whole fragment is lost.
    TBF
    > doesn't know anything about fragments so it'll just arbitarily drop a rate
    > which results in at least one fragment dropped from every application
    datagram,
    > which results in no data transfered. You could try to set the burst size
    > >= application datagram size, but even that will only work properly with a
    > single stream.
    >
    >
    >
    > -Andi
    >

    -
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