Date: Mon, 27 Nov 2006 15:56:41 -0400 From: "D G Teed" <donald.teed@gmail.com> To: freebsd-ipfw@freebsd.org Subject: how to go about diagnosing cause of packet loss Message-ID: <dd4da0390611271156g1f0ee1f5yea9c35f65664053d@mail.gmail.com>
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Howdy, Lately we have been seeing increased packet loss on our firewall. Running a ping plotter outside of the firewall shows the hops are running clean. >From on or behind the firewall, we have 20 to 50% packet loss to each hop, reaching several popular test destinations. e.g.: $ mtr -c 100 -r www.cnn.com HOST: Loss% Snt Last Avg Best Wrst StDev 1. vlan-136.acadiau.ca 0.0% 100 0.4 6.1 0.4 179.9 26.5 2. silverhorde.acadiau.ca 4.0% 100 0.6 0.9 0.3 7.8 1.0 3. wfvlnsauh05-fe-0-0.aliant.ne 17.0% 100 3.4 6.3 2.6 55.0 8.8 4. hlfxns01h29-ge-4-0.aliant.ne 27.0% 100 3.6 3.8 2.5 12.4 1.4 5. rtp629049rts 15.0% 100 4.2 4.0 2.6 9.1 1.2 6. core1-halifax_POS5-0.net.bel 22.0% 100 6.2 3.7 2.6 6.2 0.9 7. core3-montrealak_pos1-1.net. 4.0% 100 24.2 26.8 20.3 126.2 19.2 8. core1-newyork83_pos_5_0_0.ne 19.0% 100 26.1 26.9 26.0 34.1 1.2 9. bx4-newyork83_pos_2_0_0.net. 31.0% 100 27.7 28.1 27.1 30.1 0.8 10. pop1-nye-P8-1.atdn.net 9.0% 100 26.2 45.2 26.2 227.4 48.0 11. bb2-nye-P0-0.atdn.net 16.0% 100 29.0 31.1 26.3 178.2 19.4 12. bb2-vie-P12-0.atdn.net 14.0% 100 33.0 46.3 32.3 206.4 37.6 13. bb2-atm-P3-0.atdn.net 18.0% 100 42.9 44.9 42.5 106.6 9.7 14. ??? 100.0 100 0.0 0.0 0.0 0.0 0.0 We suspect something in FreeBSD or ipfw has a flaw, but cannot find it. Running mtr from the firewall itself produces slightly different packet loss points than one hop behind the firewall running mtr. A reboot initially cleared up the problem, but 10 minutes later we saw the packet loss again, so I wonder if we are seeing some sort of saturation. Does anyone have suggestions no how to troubleshoot/resolve this problem? --Donald
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