A couple questions: - I guess this is Linux TCP BBRv1 ("bbr" module)? What's the OS distribution and exact kernel version ("uname -r")?
- What do you mean when you say "The old server allows for more re-transmits"? - If BBRv1 is suffering throughput problems due to high retransmit rates, then usually the retransmit rate is around 15% or higher. If the retransmit rate is that high on a radio link that is being tested, then that radio link may be having issues that should be investigated separately? - Would you be able to take a tcpdump trace of the well-behaved and problematic traffic and share the pcap or a plot? https://github.com/google/bbr/blob/master/Documentation/bbr-faq.md#how-can-i-visualize-the-behavior-of-linux-tcp-bbr-connections - Would you be able to share the output of "ss -tin" from a recently built "ss" binary, near the end of a long-lived test flow, for the well-behaved and problematic cases? https://github.com/google/bbr/blob/master/Documentation/bbr-faq.md#how-can-i-monitor-linux-tcp-bbr-connections best, neal On Mon, Nov 16, 2020 at 10:25 AM <erik.tarald...@telenor.com> wrote: > 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 > _______________________________________________ > Bloat mailing list > Bloat@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/bloat >
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