Date: Tue, 1 Feb 2000 22:58:22 -0700 From: "Kenneth D. Merry" <ken@kdm.org> To: freebsd-net@FreeBSD.ORG Subject: Re: anyone know about 802.3x flow control? Message-ID: <20000201225822.A39005@panzer.kdm.org> In-Reply-To: <20000201224859.A38780@panzer.kdm.org>; from ken@kdm.org on Tue, Feb 01, 2000 at 10:48:59PM -0700 References: <20000201224859.A38780@panzer.kdm.org>
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On Tue, Feb 01, 2000 at 22:48:59 -0700, Kenneth D. Merry wrote: [ ... ] > Everything works fine, but I noticed something odd on the machine with > the Intel ethernet board tonight. It was getting tons of packets every > second (several screens full) from the switch. > > The packets looked like this in tcpdump: > > 22:15:53.313742 0:0:0:0:0:10 1:80:c2:0:0:1 8808 60: > 0001 0000 0000 8808 0001 0000 0000 8808 > 0001 0000 0000 8808 0001 0000 0000 8808 > 0001 0000 0000 8808 0001 0000 0000 > 22:15:53.355673 0:0:0:0:0:10 1:80:c2:0:0:1 8808 60: > 0001 0000 0000 8808 0001 0000 0000 8808 > 0001 0000 0000 8808 0001 0000 0000 8808 > 0001 0000 0000 8808 0001 0000 0000 > > The last octet of the source hardware address changes based on what port in > the switch I'm plugged into. (It's in port 10 now. If I plug it into say > port 11, it'll be 0x20, 12, 0x30, and so on.) > > I ran tcpdump on the other two FreeBSD boxes (with the SMC and DEC cards), > and didn't notice any packets like that. So my guess was that it must be > some autonegotiated parameter between the switch and the card that caused > that to happen. > > So I went into the switch configuration menu (via the serial port) and > disabled flow control on port 10. The packets above stopped. Now, > occasionally (once every minute or two, maybe?) I get packets like this: [ ... ] One other note on this -- when I disable flow control, throughput with netperf (ports/benchmarks/netperf) is horrible. With the default sysctl parameters (16K socket buffers, no rfc1323), I can normally get 65Mbps or so between the Pentium box with the 21140A and the Pentium Pro with the i82559. Without flow control, however, I only get at most 1.5Mbps. Ken -- Kenneth Merry ken@kdm.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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