Re: Why is my gigabit ethernet so slow?

[gson%gson.org@localhost (Andreas Gustafsson)]

Steven Bellovin wrote:
> > I wonder if it would make sense for the kernel to keep a list of
> > networks to disable SACK on, or look at TTL values to determine that.
> 
> 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

-- 
Andreas Gustafsson, gson%gson.org@localhost