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From: guido@gvr.win.tue.nl (Guido van Rooij)
Message-Id: <199602262046.VAA05875@gvr.win.tue.nl>
Subject: Re: invalid option in TCP header
To: pmac@til_cad1.kasten.on.ca (Peter MacKenzie)
Date: Mon, 26 Feb 1996 21:46:44 +0100 (MET)
Cc: questions@freebsd.org
In-Reply-To: <199602261727.JAA02503@freefall.freebsd.org> from "Peter MacKenzie" at Feb 26, 96 12:30:15 pm
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Peter MacKenzie wrote:
> 
> Is there an invalid option in the option list of the TCP header with
> FreeBSD 2.1.0?
> 
> When I open a telnet session the first packet has the SYN control bit
> correctly set.  The first four bytes of the TCP options correctly refer
> to the maximum segment size however the next byte is a no operation option
> (01, should this be an end of option list) and the next one is (as far
> as I am aware) an invalid option (03).  Does BSD expect that this should
> be ignored or is there a new option that I am not aware of?

This is the window scale factor. Thta has been around for a long time.
There are others as well. See rfc1323 (window scale and timestamp)
and rfc1644 (T/TCP).

-Guido