Date: Wed, 06 Jul 2011 13:04:59 -0700 From: Chuck Swiger <cswiger@mac.com> To: Kevin Oberman <kob6558@gmail.com> Cc: freebsd-net@freebsd.org, Charles Sprickman <spork@bway.net> Subject: Re: bce packet loss Message-ID: <7575C8FD-4E99-4A27-833F-312230078E9E@mac.com> In-Reply-To: <CAN6yY1u6%2Bh3qcM6KmASMBQqGE8H7GuCoPYt-5U_aLS=BHz313Q@mail.gmail.com> References: <alpine.OSX.2.00.1107042113000.2407@freemac> <BE3848B9-96C4-4F67-9565-60382DA7D6DB@mac.com> <CAN6yY1u6%2Bh3qcM6KmASMBQqGE8H7GuCoPYt-5U_aLS=BHz313Q@mail.gmail.com>
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On Jul 6, 2011, at 12:27 PM, Kevin Oberman wrote: > 1 in 10**6? That is totally excessive. It's high for a switched LAN, but I'd imagine you remember collision rates on hubs, which might well exceed 1% of the packets when the network is under load. > 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. 10 Gigabit ethernet wants cabling spec'ed to a BER of 10e-13; standard gigabit ethernet cabling (Cat 5e) supposedly is rated for 10e-10. However, the BER of the cabling doesn't translate directly into octet error count per the NIC statistics, since a bad bit anywhere in a packet causes the entire packet to be dropped with a failed checksum. > 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. Yes, I agree with this as a likely cause. Regards, -- -Chuck
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