Date: Tue, 10 Jul 2001 09:44:23 -0700 From: "Crist Clark" <crist.clark@globalstar.com> To: Darren Reed <avalon@coombs.anu.edu.au> Cc: freebsd-security@FreeBSD.ORG Subject: Re: FW: Small TCP packets == very large overhead == DoS? Message-ID: <3B4B30E7.28607AEE@globalstar.com> References: <200107100938.TAA13064@caligula.anu.edu.au>
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Darren Reed wrote:
>
> In some mail from Crist Clark, sie said:
> >
> > The TCP segment is everything in the IP payload. An SYN segment is a
> > TCP segment, but it carries no data and has a segment length of one (whee!).
> > I can see that clearly in the RFC, and I think we all cab agree on that.
> > However, I think that a SYN segment, which is all header, has a size greater
> > than one. It looks more like 24-or-so bytes typically... or maybe it does not.
> > I am looking for where (if anywhere) the specification comes out and says
> > that segment "size" is the same as "length." Why isn't the MSS called the MSL
> > after the RFC has gone to such pains to define "length?"
>
> Why can't a SYN segment be a TCP segment of length 0 ?
> (with one phantom byte)
For it is written,
segment length
The amount of sequence number space occupied by a segment,
including any controls which occupy sequence space.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
SYN
A control bit in the incoming segment, occupying one sequence
^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^^^^^
number, used at the initiation of a connection, to indicate
^^^^^^
where the sequence numbering will start.
--
Crist J. Clark Network Security Engineer
crist.clark@globalstar.com Globalstar, L.P.
(408) 933-4387 FAX: (408) 933-4926
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