BBR performance on LTE

[Azin Neishaboori]

Dear all
I know I have already asked a question recently. But I hope you consider
reading this question:

Consider the following setup: I have a laptop connected on 100Mbps Ehternet
to a router equipped with an LTE SIM and antennas. I run flent tests on an
Ubuntu VM on my laptop.I am trying to assess/compare performance of
different algorithms on bufferbloat mitigation on LTE links. FQ_Codel when
applied, was applied on the router box itself directly.

The results for TCP BBR in any combination seem really underwhelming. I
turned BBR on on my VM manually, by going to /etc/sysctl.conf and adding
net.ipv4.tcp_congestion_control=bbr and net.core.default_qdisc=fq. Then I
issue a sysctl -p to refresh.

I ran flent rrul test, and also in some tests used netem to induce packet
loss. With or without induced loss, BBR still underperformed. Attached
please see the graphs. Is this expected? Has anyone seen something like
this? I would really appreciate any insight you might have into this.

Thanks a lot
Best
Azin
[image: image.png]

Here is with induced loss (1%, 2% and 4%):
[image: image.png]
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