[Bloat] pie aqm finally landed in Linux

Dave Taht dave.taht at gmail.com
Mon Jan 20 10:46:24 EST 2014


Hat off to vijay and the pie folk at cisco who shepherded the code
through 5 releases to get it upstream!

PIE is now mandated in DOCSIS3.1 cablemodems and the ECO for DOCSIS
3.0 went out a while ago.

I think the mandate differs from the Linux implementation. I don't
know the size of the recomended cablelabs target nor the size of the
estimation window (?)).

So that will improve going-upstream buffering problems dramatically.

The linux implementation supports ECN, the DOCSIS standard does not.
The ECN work in pie has some minor problems that fq_codel doesn't
have, we hope to discuss at ietf...

I will fold the v5 implementation of pie into cerowrt in the next release and
see what happens.


The biggest problem remaining in cable is fixing excessive downstream
buffering. Surely something can be done to remove the 1.6 seconds of
buffering I observed yesterday (at some level without needing to AQM?
Some workaround that operators can use?). Some benchmarks I ran last
night (not against pie):


I sure hope the gpon, lte, and wifi folk are paying attention.

Dave Täht

Fixing bufferbloat with cerowrt: http://www.teklibre.com/cerowrt/subscribe.html

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