Re: [tcpPrague] [Bloat] DualPI2 qdisc implementation available for Linux

Stephen Hemminger <> Tue, 25 October 2016 05:12 UTC

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From: Stephen Hemminger <>
Date: Mon, 24 Oct 2016 22:12:00 -0700
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To: "De Schepper, Koen (Nokia - BE)" <>
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Cc: TCP Prague List <>, bloat <>
Subject: Re: [tcpPrague] [Bloat] DualPI2 qdisc implementation available for Linux
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Why not submit it upstream where it can get more review and will get picked
up by more users?

On Fri, Jul 29, 2016 at 2:08 AM, De Schepper, Koen (Nokia - BE) <> wrote:

> Hi all,
> For those who missed the L4S BoF, the PI2 AQM with DualQ option is
> available on the following git:
> PI2 (PI Improved with a Square) is a simplification of PIE (PI Enhanced)
> with the advantage of also supporting L4S congestion controls (like DCTCP).
> PI2 controls by default a single queue, with a common target (default
> 20ms). To get the most out of the L4S traffic you need a second L4S queue
> and a coupled AQM. PI2 supports this by specifying the "dualq" option. The
> L4S queue is having an immediate step ECN marker at 1ms, while the classic
> queue still has the 20ms target (with mark/drop coupled back to both L4S
> and Classic).
> Note that PI2 supports DCTCP, but DCTCP is not the target to be used on
> the internet. The TCP-Prague requirements (
> draft-briscoe-tsvwg-aqm-tcpm-rmcat-l4s-problem-02#appendix-A) defines
> what is needed to have an end-system CC implementation which behaves
> similar to what FQ-X achieves in the network. FQ-X is a way the network can
> correct the behavior of classic TCP CCs, TCP-Prague is the end-system
> alternative that keeps the network simple and transport layer independent.
> Feel free to try it out, and join in developing a TCP CC that meets the
> TCP-Prague requirements.
> Regards,
> Koen.
> _______________________________________________
> Bloat mailing list