I have got some issue in TCP performance depended on delay.
My lab schema:
Code:
CPE --- (p1) Router (p2) --- Server
The CPE connects to the Server by OpenVPN using TCP. I know about TCP-over-TCP but TCP proto is mandatory! Next I do series of network benchmarks by iperf3 through the OpenVPN tunnel.
Series:
- WITHOUT artificial delay.
- WITH artificial delay of 30 ms (RTT) made on a Router's p1 and p2.
- WITH artificial delay of 60 ms.
So the series results:
- "to Server": 40 mbps, "from Server": 50 mbps
- "to Server": 34 mbps, "from Server": 38 mbps
- "to Server": 20 mbps, "from Server": 10 mbps
Rate limit in test 1 due to CPU on CPE. It's normal. But why third test with delay 60ms reduces performance "from Server" multiple 5 times while "to Server" only 2 times?
P.S.
CPE is an OpenWRT on a Banana PI R2 board. Server is a Ubuntu server, Router is a Ubuntu server too. All devices connect via Ethernet. CPE intefrace is 100M. Others — 1G.
TCP congestion control for both (CPE and Server) is BBR:
Code:
net.ipv4.tcp_congestion_control = bbr
net.core.default_qdisc = fq
Benchmark commands on a CPE:
Code:
"to Server": iperf3 -c ovpn_server_ip
"from Server": iperf3 -c ovpn_server_ip -R
Commands for artificial delay on a Router:
test 2:
Code:
p1: sudo tc qdisc add dev ens224 root handle 1: netem delay 15ms
p2: sudo tc qdisc add dev ens256 root handle 1: netem delay 15ms
test 3:
Code:
p1: sudo tc qdisc add dev ens224 root handle 1: netem delay 30ms
p2: sudo tc qdisc add dev ens256 root handle 1: netem delay 30ms
