Subject: [tcpm] new NCR draft

From: Ted Faber <[email-masked]>
Date: Tue, 13 Sep 2005 09:42:28 -0700

As I'm sure you all have noticed, Allman et al. have posted a new NCR
draft for the group's approval.

From what I've seen so far, this spec has received generally good
support and review, though there were a few people with questions.  The
authors and I think this is about ready to consider for a WGLC.

The draft is intended to become an experimental RFC.

If you've been critical of this draft, please have a look at the current
state and see if your concerns have been addressed reasonably for
experimental.  If you've read the draft before, please have a look at it
and see if the current version is ready for WGLC.

I'm not interested in a full WGLC pass right now, just trying to see if
there's consensus that the document is ready for one.  If you have an
opinion, pro or con, I need to hear it to gauge interest and consensus.

Thanks.

-- 
Ted Faber
http://www.isi.edu/~faber           PGP: http://www.isi.edu/~faber/pubkeys.asc
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From: "Armando L. Caro, Jr." <[email-masked]>
Date: Thu, 22 Sep 2005 11:16:13 -0400

> draft for the group's approval.
<snip>
> opinion, pro or con, I need to hear it to gauge interest and consensus.

I have just read over the draft for the first time. I think it is well
written and in good state, but I have one concern in reference to the
"Careful Limited Transmit" algorithm. This algorithm effectively halves
the cwnd when dupacks are received, and reinstates the full cwnd if the
sender determines that reordering caused the dupacks. The problem is
that if/when the cwnd is reinstated, the sender may generate a burst of
packets. I think a max burst limit should be applied in this case, and I
think the initial cwnd is a good limit to use.

-- 
Armando
www.armandocaro.net

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From: Ethan Blanton <[email-masked]>
Date: Thu, 22 Sep 2005 10:31:16 -0500

> think the initial cwnd is a good limit to use.

This precise scenario is considered in section 3.2:

    Upon the termination of Extended Limited Transmit, and especially
    when using the Careful variant, TCP-NCR may be in a situation where
    the entire cwnd is not being utilized and therefore TCP-NCR will be
    prone to transmitting a burst of segments into the network.

The draft goes on to specify that cwnd is capped to (roughly) the
currently outstanding data, and ssthresh and slow start are used to
inflate the window to its previous value without bursting.  (Details
elided as they are a few dozen lines.)

Ethan

-- 
The laws that forbid the carrying of arms are laws [that have no remedy
for evils].  They disarm only those who are neither inclined nor
determined to commit crimes.
		-- Cesare Beccaria, "On Crimes and Punishments", 1764
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From: "Armando L. Caro, Jr." <[email-masked]>
Date: Thu, 22 Sep 2005 11:43:31 -0400

Oops... I guess I read through the draft too fast. I can't believe I
missed that. Sorry about that.

-Armando