Re: Why is my gigabit ethernet so slow?

[Matthias Scheler <tron%zhadum.org.uk@localhost>]

On Fri, Jan 29, 2010 at 03:57:51PM +0200, Andreas Gustafsson wrote:
> > In theory, one should never have to disable it explicitly; its use
> > is negotiated.  But there's no particular harm to using if if both
> > sides support it; it's just that it's not likely to help much.
> 
> In my experience, on NetBSD, SACK does cause harm, by breaking
> TCP Fast Retransmit.  See the discussion on tech-net in 2008:
> 
>   http://mail-index.netbsd.org/tech-net/2008/01/28/msg000168.html

Are you using hardware checksum offload on that "re0" interface?
If you do please try to disable it and reenable SACK.

        Kind regards

-- 
Matthias Scheler                                  http://zhadum.org.uk/