PE2950 - Linux TCP Offload Engine (TOE) configuration

[Matt Domsch]

> > [root at dfgsrv1 ~]# ethtool -k eth0
> > Offload parameters for eth0:
> > Cannot get device udp large send offload settings: Operation not
> > supported
> > Cannot get device generic segmentation offload settings: Operation not
> > supported
> > rx-checksumming: on
> > tx-checksumming: on
> > scatter-gather: on
> > tcp segmentation offload: on
> > udp fragmentation offload: off
> > generic segmentation offload: off
> > 
> > This suggests to me that TOE is on ???

> On Tue, 2007-12-18 at 12:18 -0500, Hall, James F CTR USAF ASC/ASC/HP
> > As I understand it TSO is separate from TOE. So that is normal for it to
> > be on. 


On Tue, Dec 18, 2007 at 05:25:31PM +0000, Gary Mansell wrote:
> but what about the rx-checksumming?


TOE typically means "Stateful TCP Offload" - meaning the whole TCP
processing is shifted from the OS to the card.  This is what is
considered verboten in Linux.

rx-checksumming etc are "stateless offloads" - meaning the connection
state is maintained by the OS, but some of the underlying feature
implementations, such as checksumming, is handed to the hardware to
perform (because it essentially can do the checksum as it copies the
packet from the wire and into host memory at no additional cost
anyhow).  Such stateless offloads can be disabled (as you see), and
not all cards offer all stateless offload options.

Thanks,
Matt

-- 
Matt Domsch
Linux Technology Strategist, Dell Office of the CTO
linux.dell.com & www.dell.com/linux