From owner-freebsd-hackers  Wed Jun 13 23:10:53 2001
Delivered-To: freebsd-hackers@freebsd.org
Received: from johnson.mail.mindspring.net (johnson.mail.mindspring.net [207.69.200.177])
	by hub.freebsd.org (Postfix) with ESMTP
	id 096EF37B40C; Wed, 13 Jun 2001 23:10:45 -0700 (PDT)
	(envelope-from tlambert2@mindspring.com)
Received: from mindspring.com (dialup-209.247.142.175.Dial1.SanJose1.Level3.net [209.247.142.175])
	by johnson.mail.mindspring.net (8.9.3/8.8.5) with ESMTP id CAA18652;
	Thu, 14 Jun 2001 02:10:42 -0400 (EDT)
Message-ID: <3B285581.4CFBBEF3@mindspring.com>
Date: Wed, 13 Jun 2001 23:11:13 -0700
From: Terry Lambert <tlambert2@mindspring.com>
Reply-To: tlambert2@mindspring.com
X-Mailer: Mozilla 4.7 [en]C-CCK-MCD {Sony}  (Win98; U)
X-Accept-Language: en
MIME-Version: 1.0
To: "Louis A. Mamakos" <louie@TransSys.COM>
Cc: Mike Smith <msmith@FreeBSD.ORG>, Bsdguru@aol.com,
	freebsd-hackers@FreeBSD.ORG
Subject: Re: How to disable software TCP checksumming?
References: <200106092135.f59LZW701229@mass.dis.org> <200106110103.f5B13HI87819@whizzo.transsys.com>
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Sender: owner-freebsd-hackers@FreeBSD.ORG
Precedence: bulk
List-ID: <freebsd-hackers.FreeBSD.ORG>
List-Archive: <http://docs.freebsd.org/mail/> (Web Archive)
List-Help: <mailto:majordomo?subject=help> (List Instructions)
List-Subscribe: <mailto:majordomo?subject=subscribe%20freebsd-hackers>
List-Unsubscribe: <mailto:majordomo?subject=unsubscribe%20freebsd-hackers>
X-Loop: FreeBSD.ORG

"Louis A. Mamakos" wrote:
> 
> Setting aside the degree to which you choose to be paranoid about
> where data can be corrupted, and the likelyhood thereof-- there
> is an architectural issue here, which is that the CRC provided
> by your friendly neighborhood Ethernet NIC card only protects the
> data over one Ethernet subnetwork.  The TCP checksum, and TCP in
> general, provides end-to-end semantics, independent of the
> concatenation of physical links the TCP segments might transit from
> the source to the destination.  If you have an end-to-end protocol,
> with end-to-end semantics, then you need and end-to-end mechanism.

I think you need to read the Tigon II driver in the
/sys/pci directory, and come back when you realize
that it supports offloading the TCP checksum.

FWIW: The Intel Gigabit, Tigon III, and several other
Gigabit cards support this, as well.

-- Terry

To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-hackers" in the body of the message