Subject: Re: Re draft-ietf-pilc-2.5g3g-00.txt...

From: Mark Allman <[email-masked]>
Date: Mon, 23 Apr 2001 04:49:05 -0400

[Catching up on email -- insomnia and all...]

> I don't see the case for recommending time stamps with a large
> window either.  The need for time stamps over very low
> latency paths, or/and with very high transmission SPEED is
> well understood. (See also earlier mail from Mark Allman on this).
> 
> However, I suggest at moderate rates, there appears to be little
> advantage. I wonder if it may be wise to either include text
> describing the reasoning behind this recommendation, or that you
> rethink what you with to recommend?

I don't think we need to recommend timestamps here.

> You identified "larger initial cwnd" (>4) as a potential solution
> in section 4 (Open Issues).  Although you say this is based on
> experimental data, I would encourage you to look at the conditions
> under which the recommendation is true - in general such
> recommendations need to be very carefully expressed, especially
> when the network may in the future provide connectivity for large
> numbers of down-stream users...

We're (privately) considering 2414.bis at the moment.  One of the
things that 2414 does not say anything about is the impact of a
larger initial window on the RTO.  The idea is that the RTT measured
for the 3WHS does not accuratly enough predict the RTO needed to
avoid a spurious RTO if we're using a large initial window (due to
the increased serialization times of the larger packets).  So,
larger initial windows on slow links may guarantee an RTO unless
some other fix is enabled.  

I'm not saying the recommendation should or should not be in the
document.  I have not yet formed a strong opinion.  But, rather I am
just giving another data point to cogitate on.

allman

---
Mark Allman -- NASA GRC/BBN -- http://roland.grc.nasa.gov/~mallman/