Date: Mon, 27 Jul 2009 14:08:22 +0100 From: Mark Sandford <j.m.sandford@hotmail.co.uk> To: <freebsd-ipfw@freebsd.org> Subject: Using dummynet to restrict bandwidth with more than 2 active pipes / queues Message-ID: <COL110-W10D341161C0B631FE5239892140@phx.gbl>
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Hi all=2C =20 I've been using dummynet for a while to perform degraded network testing wh= ich has been really useful. =20 Recently=2C we wanted to measure the performance limits of it on our hardware. To do this we setup a machine with 8 interfaces paired into 4 ethernet bridges. =20 We are having throughput issues when more than 2 pipes are being used simultaneously. These issues appear to be independent of the bandwidths specified. For example: We set two traffic generators transmitting at 30Mbps across two of the brid= ges (pipes)=2C sending 1000 byte UDP packets (1042 bytes on the wire) for a= 20 second period. These are passed through dummynet pipes set up to restrict the bandwidth to= 20Mbps at the bridge and we can see from the ipfw counters that all the pa= ckets hit the right rules and only the right rules. We the capture on the far end and can see that bandwidth has been restricte= d to 20Mbps as specified. All good! :o) The problem comes when we add any extra flows. The above example is repeated but with two extra traffic generators transmi= tting at just one packet per second each across a further two pipes. Again we can see from the counters that the packets all arrive at ipfw=2C h= owever we only get 10Mbps at the receiving end (and we get a number of pack= et_drops logged at dummynet). We feel we must have missed something obvious but after over a week of read= ing / testing we're running out of ideas. Is anyone able / willing to help? ~~~~~~~~~~~~~~~~~~~~~~~~ Mark Sandford email: j.m.sandford@hotmail.co.uk mob: 07990 565976 ~~~~~~~~~~~~~~~~~~~~~~~~ _________________________________________________________________ Celebrate a decade of Messenger with free winks=2C emoticons=2C display pic= s=2C and more. http://clk.atdmt.com/UKM/go/157562755/direct/01/=
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