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Date: Wed, 2 Oct 1996 20:06:32 +1000 (EST)
From: Rowan Crowe <rowan@ozramp.net.au>
To: Peter Wemm <peter@spinner.DIALix.COM>
cc: David Greenman <dg@root.com>, bugs@FreeBSD.ORG
Subject: Re: Possible low level TCP bug 
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On Wed, 2 Oct 1996, Peter Wemm wrote:

> > > >The behaviour is this: seemingly small amounts of complete data (ie: a 
> > > >line on IRC) are split into two packets, and are sent about a second 
> > > >apart. The trace from my current router (not a FreeBSD box) shows this 
> > > >behaviour. Note the first packet has the PSH attribute.
> > > 
> > >    What kind of ethernet card are you using? ...or is this with PPP or SLIP
>     ?

> > Don't laugh: I use 3c501 ethernet cards. The capture I sent to you was 
> > carried over the ethernet from my FreeBSD box. However, I doubt that's 
> > the problem, as I've observed inbound data (via serial/PPP) with this 
> > same quirk.
> 
> Hmm, I wonder if we're running into the (pre-pathmtu) 576 default tcp mss 
> somewhere with the extra tcp headers?

Doubtful, the data in the packet was about 100 bytes, and the IP length is 
only 140 bytes. Other packets with 500+ bytes of data go through fine, 
most of the time. This quirk is only noticed *occasionally*. :-)

I will see if I can reproduce this with some other software, so far it's 
been IRCII (client) and whatever aussie.oz.org uses (IRCD?). Perhaps 
there's a shared library or common routine which is causing this problem.

Cheers.