[Bloat] AQM and PPP on Linux

[Stefan Alfredsson]

* Quoting Dave Taht <dave.taht at gmail.com> [28 Jul-15 16:44]:
> On Tue, Jul 28, 2015 at 3:09 PM, Juliusz Chroboczek
> <jch at pps.univ-paris-diderot.fr> wrote:
> > I'm currently away from home, and using a 3G modem for Internet access.
> > I've found out that both NetworkManager and wvdial/pppd setup the
> > interface to use pfifo_fast (with a qlen of a mere 3 packets!).  Setting
> > fq_codel manually appears to work fine, but needs to be redone every time
> > the modem has a hiccup.
> 
> However, the netusb-related drivers, and the 3g devices themselves,
> contain oft-huge buffers that reduce the effectiveness of any aqm or
> fq system, sometimes to immeasurability.
> 
> I would be very interested in flent benchmarks of your 3g device with
> the 3 packet txqueue and with fq_codel, for the tcp_upload, rrul, and
> rrul_be tests.


I have a station with mobile broadband USB modems (4xHuawei E392),
directly connected to a Linux box running kernel 3.16.3, with
a (non-public) netperf server (same kernel) hosted on the well-connected
Swedish university network.

I also have a 3 packet txqueue, and ran the flent tcp_upload, rrul, rrul_be
for 3.5G (HSPA+) and 4G (LTE) networks for one of the operators/modems.
For comparison, I ran both pfifo_fast and fq_codel.

The execution script, output and flent result files are available at
https://www.dropbox.com/s/n5tc1dhtu9jdplz/bloatlist-ppp-150729.zip

>From flent --gui inspections, I'd say there is about a factor 10 increase
from base to load latency (from around 40-50 ms to around 400-500 ms),
for both pfifo_fast and fq_codel, for both link types,
with some transients above 1000 ms.


Juliusz: Regarding data usage, the 4G measurements consumed 1.4 Gbyte
download and 357 Mbyte upload - but it all depends on the network
throughput as the experiments are time bound (by default 60 seconds).
For 3.5G 100 Mbyte data was sent, and guesstimately 500 Mbyte received
(sorry, didn't capture the amount; but it can probably be found in
the trace files if necessary. However it all depends on your link 
throughput which will be different from mine anyway).


Cheers,
 Stefan

-- 
Stefan Alfredsson, PhD         Tel: +46 (0) 54 700 1668
Datavetenskap                  Kontor: 21E-414 (Hus Vanern)
Karlstads universitet          PGP 0xB19B4B16
SE-651 88 Karlstad             http://www.cs.kau.se/stefalfr/