Subject: [tcpm] Alternative to Eifel response

From: Yogesh Prem Swami <[email-masked]>
Date: Mon, 08 Aug 2005 13:03:52 -0500

Hi,

I was going through the TCPM audio archive from IETF63, and I guess
there was a question (I believe from Jon) if there is an alternative to
Eifel response.

I have an old draft called DCLOR [1] which tries to address the problem
of Spurious timeout (STO). There is a Nokia IPR disclosure [2] which I
believe says that you are free to implement it as you want (I too am not
a lawyer, so please direct your IPR questions to the contact person on
the IPR disclosure page :-)).

Coming back to technical issues, I believe that spurious timeouts are
extremely rare in the absence of mobility, where eifel response is
applicable. In the presence of mobility, there is a need for a broader
solution than just spurious timeouts. In fact, eifel response could
*potentially* be dangerous for spurious timeouts after subnet change
because it simply restores the congestion window without much regard to
properties of the new path.

(I saw Kazunori Yamamoto slides from IETF63. The authors don't make the
distinction whether the STOs were caused due to mobility or due to bit
errors. They do, however, point out (slide 5) that STOs occur more often
at higher speed, suggesting that mobility is the main cause of spurious
timeout. This is in line with my observation from EGPRS field data.)

In fact, I don't think that STO is really a TCP problem, so whether you
use eifel or DCLOR or what have you, it doesn't really matter. Spurious
timeout occur mainly because of poor link design, and changing TCP for
that is not the most effective solution. So I would be okay if the TCP
roadmap draft doesn't have a standards track solution for spurious
timeouts.

Thanks
Yogesh

[1] http://www.ietf.org/internet-drafts/draft-swami-tsvwg-tcp-dclor-05.txt

[2] http://www.ietf.org/ietf/IPR/NOKIA-DCLOR.txt

-- 
http://people.nokia.net/~yogesh
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