qwerty123:
Right. Wonder if your router does TCP MSS clamping, but sets very small MSS and causes excessive fragmentation of TCP packets. You can try either capturing traffic with tcpdump/wireshark or run iperf3 test to some public iperf3 server via udp and see if UDP speeds are higher, like
iperf3 -u -b 10M -p 5201 -c ping.online.net
Connecting to host ping.online.net, port 5201
[ 6] local x.x.x.x port 54308 connected to 62.210.18.40 port 5201
[ ID] Interval Transfer Bandwidth Jitter Lost/Total Datagrams
[ 6] 0.00-10.00 sec 11.8 MBytes 9.91 Mbits/sec 8.423 ms 0/1513 (0%)
[ 6] Sent 1513 datagrams
This is the output I got:
iperf3 -u -b 10M -p 5201 -c ping.online.net
Connecting to host ping.online.net, port 5201
[ 4] local 1.2.3.4 port 59680 connected to 62.210.18.40 port 5201
[ ID] Interval Transfer Bandwidth Total Datagrams
[ 4] 0.00-1.00 sec 1.09 MBytes 9.14 Mbits/sec 140
[ 4] 1.00-2.01 sec 1.20 MBytes 10.0 Mbits/sec 153
[ 4] 2.01-3.01 sec 1.20 MBytes 10.0 Mbits/sec 153
[ 4] 3.01-4.01 sec 1.20 MBytes 9.97 Mbits/sec 153
[ 4] 4.01-5.02 sec 1.20 MBytes 10.0 Mbits/sec 153
[ 4] 5.02-6.00 sec 1.19 MBytes 10.1 Mbits/sec 152
[ 4] 6.00-7.01 sec 1.19 MBytes 9.86 Mbits/sec 152
[ 4] 7.01-8.01 sec 1.20 MBytes 10.0 Mbits/sec 153
[ 4] 8.01-9.01 sec 1.20 MBytes 9.99 Mbits/sec 153
[ 4] 9.01-10.01 sec 1.19 MBytes 10.0 Mbits/sec 152
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bandwidth Jitter Lost/Total Datagrams
[ 4] 0.00-10.01 sec 11.8 MBytes 9.91 Mbits/sec 112.517 ms 0/5 (0%)
[ 4] Sent 5 datagrams
iperf Done.