Subject: Re: TCP and BBR: reproducibly low cwnd and bandwidth

From: Oleksandr Natalenko <[email-masked]>
Date: Sat, 17 Feb 2018 00:06:23 +0100

On pátek 16. února 2018 23:50:35 CET Eric Dumazet wrote:
> /* snip */
> If you use
> 
> tcptrace -R test_s2c.pcap
> xplot.org d2c_rtt.xpl
> 
> Then you'll see plenty of suspect 40ms rtt samples.

That's odd. Even the way how they look uniformly.

> It looks like receiver misses wakeups for some reason,
> and only the TCP delayed ACK timer is helping.
> 
> So it does not look like a sender side issue to me.

To make things even more complicated, I've disabled sg on the server, leaving 
it enabled on the client:

client to server flow: 935 Mbits/sec
server to client flow: 72.5 Mbits/sec

So still, to me it looks like a sender issue. No?