Re: [tsvwg] ecn-encap-guidelines reframing section

Jonathan Morton <chromatix99@gmail.com> Wed, 24 March 2021 10:38 UTC

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From: Jonathan Morton <chromatix99@gmail.com>
In-Reply-To: <6b9f2527-ccbd-af2a-caa3-8a0b7c234aa6@bobbriscoe.net>
Date: Wed, 24 Mar 2021 12:38:39 +0200
Cc: "Black, David" <David.Black@dell.com>, Markku Kojo <kojo@cs.helsinki.fi>, Joe Touch <touch@strayalpha.com>, Markku Kojo <kojo=40cs.helsinki.fi@dmarc.ietf.org>, "tsvwg-chairs@ietf.org" <tsvwg-chairs@ietf.org>, "tsvwg@ietf.org" <tsvwg@ietf.org>
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To: Bob Briscoe <ietf@bobbriscoe.net>
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Subject: Re: [tsvwg] ecn-encap-guidelines reframing section
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A quick aside:

> On 24 Mar, 2021, at 11:48 am, Bob Briscoe <ietf@bobbriscoe.net> wrote:
> 
> {Note 1} For instance, the average proportion of marked packets is 'p' in the well known Reno formula,
>     cwnd_avg = sqrt(3/2p)

This assumes that "p" is a uniform probability; that the likelihood that one packet is marked is independent of whether its neighbours are marked.  A mechanism that refers specifically to marking consecutive packets breaks that assumption.

Reno's actual behaviour depends more accurately on the relationship between the interval between RTTs containing at least one mark, and the actual RTT.

 - Jonathan Morton