Date: Thu, 24 May 2007 14:12:25 -0600 From: "Andrew Falanga" <af300wsm@gmail.com> To: "Andrew Falanga" <af300wsm@gmail.com>, freebsd-questions <freebsd-questions@freebsd.org> Subject: Re: How does FreeBSD handle tcp checksum offloading Message-ID: <340a29540705241312s1eeae222u626fce3b025c7eaf@mail.gmail.com> In-Reply-To: <20070524193327.GA58657@owl.midgard.homeip.net> References: <340a29540705241210qa6895bem9d4aa1a5d2dd05a0@mail.gmail.com> <20070524193327.GA58657@owl.midgard.homeip.net>
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On 5/24/07, Erik Trulsson <ertr1013@student.uu.se> wrote: > > Checksum offloading is usually enabled by default for hardware that supports > it (assuming that the driver for that hardware also supports it of course.) > > To see if a particular interface uses checksum offloading you can look at > the output of 'ifconfig -m'. > The "options" line in the output refers to those features that are enabled, > while the "capabilities" line refers to those features that are available. > (Checksum offloading for receive and transmit show up as RXCSUM and TXCSUM > respectively.) > Ifconfig can also be used to enable/disable the offloading - see the > ifconfig(8) manpage for details and syntax. > > It can sometimes be desirable to turn of checksum offloading if one suspects > that the hardware has some bugs in it that can cause the checksum to be > wrong. (For those cases were the hardware has known bugs in this area, the > driver normally disable checksum offloading by default.) > > > Most hardware supported by the fxp(4) driver do not have support for > checksum offloading, but some do. > (The fairly commonly used 82559 chip does not support checksum while the > less common 82550 chip does, for example.) > > > Thanks for the info. This is cool. My Intel NIC is the 82550. That explains a few things. Thanks again for the info on how these are used FreeBSD. Andy
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