From owner-freebsd-net@FreeBSD.ORG Wed Jul 6 20:05:01 2011 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id CF446106566C for ; Wed, 6 Jul 2011 20:05:01 +0000 (UTC) (envelope-from cswiger@mac.com) Received: from asmtpout026.mac.com (asmtpout026.mac.com [17.148.16.101]) by mx1.freebsd.org (Postfix) with ESMTP id B59D98FC12 for ; Wed, 6 Jul 2011 20:05:01 +0000 (UTC) MIME-version: 1.0 Content-transfer-encoding: 7BIT Content-type: text/plain; CHARSET=US-ASCII Received: from cswiger1.apple.com ([17.209.4.71]) by asmtp026.mac.com (Oracle Communications Messaging Exchange Server 7u4-20.01 64bit (built Nov 21 2010)) with ESMTPSA id <0LNX00860H4BKB90@asmtp026.mac.com> for freebsd-net@freebsd.org; Wed, 06 Jul 2011 13:05:01 -0700 (PDT) X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:5.4.6813,1.0.211,0.0.0000 definitions=2011-07-06_06:2011-07-06, 2011-07-06, 1970-01-01 signatures=0 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 ipscore=0 suspectscore=0 phishscore=0 bulkscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx engine=6.0.2-1012030000 definitions=main-1107060145 From: Chuck Swiger In-reply-to: Date: Wed, 06 Jul 2011 13:04:59 -0700 Message-id: <7575C8FD-4E99-4A27-833F-312230078E9E@mac.com> References: To: Kevin Oberman X-Mailer: Apple Mail (2.1084) Cc: freebsd-net@freebsd.org, Charles Sprickman Subject: Re: bce packet loss X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 06 Jul 2011 20:05:01 -0000 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