[Bloat] Fwd: [aqm] Follow-up: PIE performance in cable modem environments

[Dave Taht]

The pie work now has a nice paper on it out, for those of you not on
the aqm list.... and source is promised for next week. Rumor has it
there is also a fq_pie implementation....


---------- Forwarded message ----------
From: Preethi Natarajan <preethi.cis at gmail.com>
Date: Tue, Apr 23, 2013 at 4:18 PM
Subject: [aqm] Follow-up: PIE performance in cable modem environments
To: iccrg at irtf.org, tsvwg at ietf.org, aqm at ietf.org
Cc: "Rong Pan (ropan)" <ropan at cisco.com>, "Bill Ver Steeg (versteb)"
<versteb at cisco.com>, "Chiara Piglione (cpiglion)"
<cpiglion at cisco.com>, "Mythili Suryanarayana Prabhu (mysuryan)"
<mysuryan at cisco.com>, "Fred Baker (fred)" <fred at cisco.com>


Hello,

This is a follow-up to Greg White's (from Cable Labs) talk at the
recent ICCRG meeting on PIE's performance in cable modem environments.

Post the meeting, Greg was kind to share his ns-2 DOCSIS model with
us. We investigated PIE's performance using this model. The key items
from this investigation:

Bug in PIE code: The previous PIE release (that Greg used for
evaluations) was missing a line of code. This missing line brings down
drop probability under certain conditions and turns out to be critical
for the cable modem scenario. Without this line of code, the drop
probability remains high and takes longer to come down even when the
queue delay has remained lower than the reference. The updated ns-2
PIE code can be found here — ftp://ftpeng.cisco.com/pie/.
Bug in ns-2 TCP/Linux: Greg's cable modem simulations used the TCP
Cubic variant. We discovered a serious bug in ns-2 TCP/Linux Agent
(confirmed by Dr. Injong Rhee's team) that makes TCP/Cubic senders
very aggressive and unresponsive to packet drops/notifications, pretty
much like UDP traffic. Please find more details about the bug here --
http://sourceforge.net/tracker/?func=detail&aid=3608750&group_id=149743&atid=775392.

We are working with Cable Labs to verify the cable modem results,
they'll soon be available on our FTP site along with the PIE code.

A technical paper about PIE was recently accepted at the IEEE
Conference on High Performance Switching and Routing 2013. A copy of
the paper is attached here.

The Linux PIE implementation is expected to be ready by next week and
we'll follow-up on that as well.

Many thanks,
Preethi on behalf of PIE team.

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-- 
Dave Täht

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