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[tcpm] ECN+SYN

Stefanos Harhalakis <v13@v13.gr> Tue, 19 February 2008 23:18 UTC

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From: Stefanos Harhalakis <v13@v13.gr>
To: akuzma@northwestern.edu
Date: Wed, 20 Feb 2008 01:16:26 +0200
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Cc: tcpm@ietf.org
Subject: [tcpm] ECN+SYN
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Hello there,

  I've just read the proposal regarding ECN and SYN/ACK packets and I cannot 
understand why not to allow ECN in SYN packets too. Let me elaborate a bit 
further:

  In paragraph 4, page 10 you mention two reasons which I find incorrect:

*  First reason claims that there is no guarantee that the other TCP endpoint 
is ECN-capable. AFAICT this is exactly the case as in ECN in SYN/ACK packets. 
I fail to see why there is a difference when "the connection" looses the SYN 
instead of the SYN/ACK packet.

*  Next paragraph says that SYN packets can be missused. IMHO, this is already 
possible. A malicious host can send IP packets with the ECT codepoint set 
that include non-ECN TCP SYN packets, or even SYN/ECN+ECT packets. There is 
no guarantee that an endpoint will drop SYN/ECN+ECT packets and I believe 
there is no valid reason for having an ECN capable endpoint drop SYN/ECN 
packets (as being malicious).

  Because of my limited experience I believe that I'm not able to comment on 
reason (3) of page 22 (appendix A). 

Best regards,
Harhalakis Stefanos

p.s. Please excuse me if I'm wrong. I'm new in this area.
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