RE: [tcpm] TCP zero window timeout?

"Caitlin Bestler" <caitlinb@broadcom.com> Mon, 28 August 2006 23:51 UTC

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Subject: RE: [tcpm] TCP zero window timeout?
Date: Mon, 28 Aug 2006 16:50:49 -0700
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From: "Caitlin Bestler" <caitlinb@broadcom.com>
To: "MURALI BASHYAM" <murali_bashyam@yahoo.com>, "Fernando Gont" <fernando@gont.com.ar>, "Mahesh Jethanandani" <mahesh@cisco.com>, "Mahdavi, Jamshid" <jamshid.mahdavi@bluecoat.com>
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MURALI BASHYAM wrote:
> Fernando
> 
> Today there is nothing that prevents a client side
> application from simply stopping to read the TCP receive
> socket buffer and causing the offered window to go down to 0,
> and thus causing the sender to hold a large send queue worth
> of data and probe forever. If this is done by a large number
> of clients against the same server, u have a distributed DOS
> attack on that server. We have seen this in practice.
> 
> To answer an earlier question u had raised, the application
> cannot timeout on this connection because it does not know
> when the connection enters and leaves the persist state, only
> TCP knows that. The application can definitely decide the
> timeout value, but TCP needs to implement the timer because
> only it is aware of the state of the peer.
> 

True, but why does TCP need any wire protocol modifications to
implement such a timeout locally?


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