[Codel] Fwd: [aqm] An independent implementation of CoDel in FreeBSD/ipfw/dummynet

Dave Taht dave.taht at gmail.com
Wed Dec 16 07:01:54 EST 2015

---------- Forwarded message ----------
From: Rasool Al-Saadi <ralsaadi at swin.edu.au>
Date: Wed, Dec 16, 2015 at 12:35 PM
Subject: [aqm] An independent implementation of CoDel in FreeBSD/ipfw/dummynet
To: "aqm at ietf.org" <aqm at ietf.org>

Hello all,

I am Rasool Al-Saadi, a PhD student at Centre for Advanced Internet
Architectures - Swinburne University of Technology. I and my
supervisor Grenville Armitage are implementing CoDel (and eventually
PIE, FQ_CoDel and FQ_PIE) in FreeBSD targeting ipfw/dummynet framework
as a small project funded by Comcast Corporation, USA.

We used CoDel I-D
(https://datatracker.ietf.org/doc/draft-ietf-aqm-codel/) as the main
source to implement CoDel and we believe that the information in the
latest draft (draft-ietf-aqm-codel-02) sufficient and the pseudo-code
is straightforward to create functional CoDel code. However, we have
some questions/confusion regarding CoDel I-D:

1- There is little confusion in the text. In section 3.3, the text
says "... the initial drop spacing SHOULD be set to the estimator's
interval plus twice the target (i.e., initial drop spacing = 1.1 *
interval) ...", while in section 4.1, the text says "As discussed in
section 3.3, the initial next drop spacing is intended to be long
enough to give the endpoints time to react to the single drop so
SHOULD be set to a value of 1.0 to 1.1 times the interval."

2- In section 3.2 and 4.4, the text says the ideal setpoint is 5-10%
of the interval (connection RTT). So, should we allow the user to
specify the target value as a percentage of the interval or an
absolute value?


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