On Tue, Jul 28, 1998 11:40 AM, Frederick Bruckman
<mailto:fredb@fb.sa.enteract.com> wrote:
> On 27 Jul 1998, Bruce Anderson wrote:
> 
> > Then add the line:
> > sysctl -w net.inet.tcp.rfc1323=0
> > to your /etc/netstart.local
> 
> What does that do?

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>From  netbsd-help@netbsd.org 

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> From alex@vsys.com  Wed Jul  8 19:04:41 1998
> Message-ID: <01BDAA60.F4AE7C20.alex@vsys.com>
> From: Alex Barclay <alex@vsys.com>
> To: "'NetBSD'" <netbsd@hgb-leipzig.de>
> Subject: RE: Slow connection between NetBSD and Sun Solaris
> Date: Wed, 8 Jul 1998 11:10:01 -0600
> Organization: Vsys
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> 
> On Wednesday, July 08, 1998 6:38 AM, NetBSD [SMTP:netbsd@hgb-leipzig.de]
wrote:
> > > Can you also try changing the sysctl variable:
> > >
> > >         net.inet.tcp.mss_ifmtu
> > >
> > > to 1?
> > I tried, but nothing changed.
> >
> >
> > > I guess a tcpdump (or two from both ends) wouldn't hurt.

> 
> I've had a quick look an it seems that there is some retransmission
occuring.
> 
> There are 2 cases in which I have seen this... Both when there is a ppp
link 
> involved..
In this case, there is a PPP link (2xNovell ISDN router) involved.
> 
> (I guess that ISDN may not help here)
> 
> OK here we go
> 
> 1) The MSS negotiation gets screwed up. This is because the mtu of the 
> interface
>     is larger than the mtu of the ppp link. You'll notice the Don't
Fragment 
> being set
>     on the TCP stream. Se here are some suggestions if it is this
> 
>     On the netbsd side
> 
>     sysctl -w net.inet.ip.mtudisc = 0
> 
>     and
> 
>     sysctl -w net.inet.tcp.mssdflt = 128 # A bit small but should be way
less 
> than the ISDN bit!
Nothing changed.
> 
> 2) If Van-Jacobson header compression is in use then packets using the
rfc1323 
> extensions to tcp can
>     become corrupted. rfc1323 is designed to improve performance on high 
> bandwidth x delay networks.
>     So try to turn it off (I don't even know if Sun supports this?)
> 
>     On the netbsd side
> 
>     sysctl -w net.inet.tcp.rfc1323 = 0
> 
Applying sysctl -w net.inet.tcp.rfc1323=0 solved the problem completely.

Thank to all answered me.

Best regards
Uwe