Re: [aqm] [tsvwg] Immediate ECN: Autotuning AQM for RTT

[Greg White <[e-mail]>]

This is very interesting work.  There are a lot of unanswered questions
about ecn / no-ecn coexistence and differential treatment in an AQM, and
this could provide some answers.

To those who groaned that ECN was not included in DOCSIS 3.1, read these
slides (and Naeem Khademi's).

Bob, CoDel uses "interval" both as a hold-off for the first packet drop
and as the numerator in the invsqrt drop scheduling.  Setting interval = 0
would result in ECN being signaled on *every* ECN capable packet when the
sojourn time is above threshold.    This jibes with some of your charts
for RED, but others show a ramp up in mark probability rather than a step
function. Could you clarify?

Setting max_burst = 0 in PIE would not result in the step function
behavior.

-Greg


On 11/7/13, 1:03 PM, "Bob Briscoe" <[e-mail]> wrote:

>Folks,
>
>"Immediate ECN" slides:
><http://bobbriscoe.net/presents/1311ietf/1311tsvarea-iecn.pptx>
><http://bobbriscoe.net/presents/1311ietf/1311tsvarea-iecn.pdf>
>
>PS. This talk fell off the end of the TSVAREA agenda. It's mostly
>relevant to AQM, but I didn't originally bring it to AQM, because it
>affects 3 wgs: tsvwg, aqm & tcpm.
>
>In the AQM wg, there was dismay about CableLabs not including
>anything about ECN in DOCSIS3.1. This talk is about AQM dynamics; and
>how ECN can take out the 100ms of delay that CoDel and PIE introduce
>- it's essentially about auto-tuning for RTT.
>
>It gives an interim recommendation for hardware designers that there
>should be a second instance of the AQM algo for ECN packets so that
>it can be configured with different parameters (think of WRED instead of
>RED).
>
>Specifically, for ECN packets:
>interval = 0 (for CoDel)
>max_burst = 0 (for PIE)
>
>
>Bob
>
>PS. We have a paper under submission, which we can supply on request.
>We plan to document this in the IETF too.
>
>
>
>
>________________________________________________________________
>Bob Briscoe,                                                  BT