From owner-freebsd-hackers  Sat Sep 26 20:03:33 1998
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Date: Sat, 26 Sep 1998 20:03:10 -0700
From: Ulf Zimmermann <ulf@Alameda.net>
To: Ben Black <black@cypher.net>, dg@root.com, Tony Jones <tony@rtd.com>
Cc: hackers@FreeBSD.ORG
Subject: Re: TCP (http) problem
Reply-To: ulf@Alameda.net
References: <199809270000.RAA00288@zebedee.local> <199809270033.RAA17588@implode.root.com> <19980926204630.A20043@cypher.net>
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In-Reply-To: <19980926204630.A20043@cypher.net>; from Ben Black on Sat, Sep 26, 1998 at 08:46:30PM -0400
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On Sat, Sep 26, 1998 at 08:46:30PM -0400, Ben Black wrote:
> actually, this may be a bug in IIS4.  i have seen a problem exactly as you
> describe (can't get to certain sites, those running IIS4, but everything else
> works fine) when the path MTU is not the same as the MTU on the IIS4 server's
> LAN.
> 
> since the smaller MTU hop was under my control, i increased the MTU and 
> everything worked.  whether anyone upstream was blocking icmp messages used
> in path MTU discovery, i don't know.

But I doubt that altavista runs any IIS 4.x

> 
> 
> ben
> 
> On Sat, Sep 26, 1998 at 05:33:40PM -0700, David Greenman had most eloquently written:
> > >Eventually the http connection will time out.
> > >
> > >I've upgraded -stable, the Linux version of Netscape to v4.06, tried my old
> > >BSD Netscape 3.0 all with the same results. The BSD Netscape _used_ to work
> > >fine, as did the Linux versions.
> > >
> > >I posted to -stable and someone suggested I disable TCP extensions (I'd already
> > >tried this) and also to try sending large ICMP packets (1472) to see if it was 
> > >a fragmentation problem. The pings worked fine.
> > 
> >    It sounds like a problem with Path MTU Discovery. Your ISP is probably
> > blocking outbound "ICMP_UNREACH_NEEDFRAG" messages. You might try setting
> > a smaller MTU/MRU on your PPP connection (I suggest 552).
> > 
> > -DG
> > 
> > David Greenman
> > Co-founder/Principal Architect, The FreeBSD Project
> > 
> > 
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> 
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-- 
Regards, Ulf.

---------------------------------------------------------------------
Ulf Zimmermann, 1525 Pacific Ave., Alameda, CA-94501, #: 510-769-2936
Alameda Networks, Inc. | http://www.Alameda.net  | Fax#: 510-521-5073

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