Subject: Re: [tcpm] New version of tcp-secure draft

From: "Agarwal, Anil" <[email-masked]>
Date: Tue, 25 Sep 2007 10:26:12 -0400

Ananth,
 
Here are some (late) comments on draft-ietf-tcpm-tcpsecure-08 -
 
1. Section 1.1 states - 
"Most modern operating systems have a default window size 
which usually is applied to most connections.  Some applications 
however may change the window size to better suit the needs
of the application". 

Would be useful to mention that some modern operating 
systems (Linux) dynamically adapt the receive window size. 
This somewhat reduces the vulnerability of these attacks.

2. In the first two mitigation techniques, if an attacker 
injects 3 quick successive RST or SYN packets, it may result
in the receiver generating 3 identical ACKs,
which in turn may cause the transmitter to perform
fast retransmission and reduce cwnd. 
This is not as bad as a connection reset, but nevertheless
it can be quite disruptive, especially for LFNs.
Do we need a mechanism to prevent this?
An ACK throttling value of 2 per second would be one way
to address this
 
Anil

Anil Agarwal
ViaSat Inc.
20511 Seneca Meadows Parkway, Suite 200
Germantown, MD 20876
[email-masked] <mailto:[email-masked]> 
ViaSat Brings your Network to Life

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