Re: Source of T/TCP traffic

[Knut Bjornstad <kbjo () interpost no>]

On Tue, Sep 09, 2003 at 02:22:58PM +0200, Volker Tanger wrote:
> Greetings!
>
> On Tue, 9 Sep 2003 Knut Bjornstad <kbjo () interpost no> wrote:
>
> > Our IDS are seeing a lot of peculiar T/TCP traffic - the alerts on
> > this is no problem in itself - I can easily disable them. But when I
> > try to analyze the traffic, it seems like ordinary web traffic from
> > various MS IE sources. 
>
> Do you see T/TCP, TAO or the braindead MS-IE/IIS speedup hack? Usually
> newer IE try to send the HTTP request already in the SYN packet (or was
> it first sending an ACK packet with the request?) ignoring the usual
> need for a SYN - SYN/ACK - ACK handshake for a proper TCP connection. 
>
> While the IIS answers directly other servers respond with a RST, upon
> which the IIS starts anew with the standard 3-way handshake. This way 
> a MS-IE/MS-IIS pair has a small speed advantage over standard clients
> or servers. It's called improving industry standards, I fear.
>
> If this is the traffic you see, you can safely ignore it (as MS-IE
> does).
What I see is not - I repeat not - the cheating MS-IE/IIS speedup hack.
(For this see: http://www.cs.wits.ac.za/~jon/help/email/slash.html )
I see SYN packets with proper CC.NEW TCP options. They come from a
handful of Scandinavian providers serving solid customers. We dont get
anything more of the T/TCP TAO because we have no T/TCP ourselves, and
then what is sending this falls back to ordinary TCP in accordance with
the protocol. Further there is quite clear indications of NAT source
adresses - the browser field in our weblogs vary with the same source among
other things. I am pretty sure this is one or several different devices
inserting T/TCP by rewriting the header - but I lack proof.

So what is this?
-- 
--Knut Bjornstad -- ErgoIntegration AS ---Oslo, Norway-------
--kbjo () interpost no -- t:47 23 14 53 36 -- mob: 901 15 917 --
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