Date: Wed, 6 Jul 2011 09:27:45 -1000 From: Kevin Oberman <kob6558@gmail.com> To: Chuck Swiger <cswiger@mac.com> Cc: freebsd-net@freebsd.org, Charles Sprickman <spork@bway.net> Subject: Re: bce packet loss Message-ID: <CAN6yY1u6%2Bh3qcM6KmASMBQqGE8H7GuCoPYt-5U_aLS=BHz313Q@mail.gmail.com> In-Reply-To: <BE3848B9-96C4-4F67-9565-60382DA7D6DB@mac.com> References: <alpine.OSX.2.00.1107042113000.2407@freemac> <BE3848B9-96C4-4F67-9565-60382DA7D6DB@mac.com>
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On Jul 5, 2011 4:49 PM, "Chuck Swiger" <cswiger@mac.com> wrote: > > On Jul 4, 2011, at 6:32 PM, Charles Sprickman wrote: > > We're running a few 8.1-R servers with Broadcom bce interfaces (Dell R510) and I'm seeing occasional packet loss on them (enough that it trips nagios now and then). Cabling seems fine as neither the switch nor the sysctl info for the device show any errors/collisions/etc, however there is one odd one, which is "dev.bce.1.stat_IfHCInBadOctets: 539369". See [1] below for full sysctl output. The switch shows no errors but for "Dropped packets 683868". > > A quick check of the #'s is showing an error rate of 8.6e-6, or about one byte out of 100,000. That's much better than what TCP/IP and ethernet were designed for. At a guess, your box or the switch occasionally gets busy enough that it drops a few packets now and again. > > Regards, > -- > -Chuck > 1 in 10**6? That is totally excessive. The Ethernet spec requires no worse than 10**13 and that is far worse than should ever be seen in the real world. At one in a million, any remotely high volume transfer will crawl, especially over a long path. If dropped packets ate being reported, the most common cause is fan-in. If two input ports are both trying to talk a line rate to a single output port, the buffer will fill an packets will be dropped. Most switches do tail drop, so queue management is terrible, compounding the effects. R. Kevin Oberman, Network Engineer Retired kob6558@gmail.com
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