[Bloat] BBR implementations, knobs to turn?

[erik.taraldsen at telenor.com]

I'm in the process of replacing a throughput test server.  The old server is running a 1Gbit Ethernet card on a 1Gbit link and ubuntu.  The new a 10Gbit card on a 40Gbit link and centos.  Both have low load and Xenon processors.


The purpose is for field installers to verify the bandwidth sold to the customers using known clients against known servers.  (4G and 5G fixed installations mainly).


What I'm finding is that the new server is consistently delivering slightly lower throughput than the old server.  The old server allows for more re-transmits and has a slightly higher congestion window than the new server.


Is there any way to tune bbr to allow for more re-transmits (which seems to be the limiting factor)?  Or other suggestions?



(Frankly I think the old server is to aggressive for general purpose use.  It seems to starve out other tcp sessions more than the new server.  So for delivering regular content to users the new implementation seems more balanced, but that is not the target here.  We want to stress test the radio link.)


Regards Erik
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