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Re: [tcpm] [tcpinc] TCP Stealth - possible interest to the WG

Joe Touch <touch@isi.edu> Thu, 21 August 2014 04:16 UTC

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Date: Wed, 20 Aug 2014 21:16:01 -0700
From: Joe Touch <touch@isi.edu>
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To: "Scheffenegger, Richard" <rs@netapp.com>, "alfiej@fastmail.fm" <alfiej@fastmail.fm>, Jacob Appelbaum <jacob@appelbaum.net>
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Cc: Christian Grothoff <christian@grothoff.org>, "tcpinc@ietf.org" <tcpinc@ietf.org>, "tcpm (tcpm@ietf.org)" <tcpm@ietf.org>
Subject: Re: [tcpm] [tcpinc] TCP Stealth - possible interest to the WG
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On 8/18/2014 3:07 PM, Scheffenegger, Richard wrote:
> Hi Alfie,
>
> my concern is with the use of a static ISN for each 4-tuple; this
> significantly increases the chance of a collision between sessions (ie.
> when the sender terminates a sluggish earlier session, some segments of
> that last session will very likely be in-window for a session that was
> started a short time later).

+1, and I haven't seen a satisfactory answer to this yet.

FWIW, the doc refers to TCP MD5, which has been deprecated and replaced 
by TCP-AO. TCP-AO has an experimental extension to support NAT traversal.

Additionally, responding with a TCP RST isn't the best response if 
you're trying to hide from port knocking. Silence is best in that case.

Joe

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