Hi,
Making experiments with two tp-link tl-wr802n, I found a "weird" issue.
The experiment is the following:
- #1 is hosting an access point;
- #2 is connecting to this access point;
I put a iperf server on #1 and #2, and test from the other one, using first UDP (-u flag):
root@OpenWrt:~# iperf3 -u -b20M -c 192.168.1.1 -p 5200
Connecting to host 192.168.1.1, port 5200
[ 5] local 192.168.1.223 port 51980 connected to 192.168.1.1 port 5200
[ ID] Interval Transfer Bitrate Total Datagrams
[ 5] 0.00-1.00 sec 2.38 MBytes 20.0 Mbits/sec 1726
[ 5] 1.00-2.00 sec 2.38 MBytes 20.0 Mbits/sec 1727
[ 5] 2.00-3.00 sec 2.38 MBytes 20.0 Mbits/sec 1726
[ 5] 3.00-4.00 sec 2.38 MBytes 20.0 Mbits/sec 1726
[ 5] 4.00-5.00 sec 2.38 MBytes 20.0 Mbits/sec 1727
[ 5] 5.00-6.00 sec 2.38 MBytes 20.0 Mbits/sec 1727
[ 5] 6.00-7.00 sec 2.38 MBytes 20.0 Mbits/sec 1726
[ 5] 7.00-8.00 sec 2.38 MBytes 20.0 Mbits/sec 1727
[ 5] 8.00-9.00 sec 2.38 MBytes 20.0 Mbits/sec 1726
[ 5] 9.00-10.00 sec 2.36 MBytes 19.8 Mbits/sec 1707
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-10.00 sec 23.8 MBytes 20.0 Mbits/sec 0.000 ms 0/17245 (0%) sender
[ 5] 0.00-10.05 sec 23.8 MBytes 19.9 Mbits/sec 1.481 ms 8/17244 (0.046%) receiver
iperf Done.
The other way around:
root@OpenWrt:~# iperf3 -u -b20M -c 192.168.1.223 -p 5201
Connecting to host 192.168.1.223, port 5201
[ 5] local 192.168.1.1 port 54542 connected to 192.168.1.223 port 5201
[ ID] Interval Transfer Bitrate Total Datagrams
[ 5] 0.00-1.00 sec 2.38 MBytes 20.0 Mbits/sec 1726
[ 5] 1.00-2.00 sec 2.38 MBytes 20.0 Mbits/sec 1726
[ 5] 2.00-3.00 sec 2.38 MBytes 20.0 Mbits/sec 1727
[ 5] 3.00-4.00 sec 2.38 MBytes 20.0 Mbits/sec 1727
[ 5] 4.00-5.00 sec 2.38 MBytes 20.0 Mbits/sec 1726
[ 5] 5.00-6.00 sec 2.38 MBytes 20.0 Mbits/sec 1727
[ 5] 6.00-7.00 sec 2.38 MBytes 20.0 Mbits/sec 1726
[ 5] 7.00-8.00 sec 2.38 MBytes 20.0 Mbits/sec 1727
[ 5] 8.00-9.00 sec 2.38 MBytes 20.0 Mbits/sec 1726
[ 5] 9.00-10.00 sec 2.38 MBytes 20.0 Mbits/sec 1727
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-10.00 sec 23.8 MBytes 20.0 Mbits/sec 0.000 ms 0/17265 (0%) sender
[ 5] 0.00-10.04 sec 23.8 MBytes 19.9 Mbits/sec 0.315 ms 0/17262 (0%) receiver
iperf Done.
root@OpenWrt:~#
Now, comes the interesting thing: as soon as I remove the -u flag, using therefore TCP, the connection immediatly drops:
-----------------------------------------------------------
Server listening on 5201
-----------------------------------------------------------
Accepted connection from 192.168.1.1, port 44530
[ 5] local 192.168.1.223 port 5201 connected to 192.168.1.1 port 44532
[ ID] Interval Transfer Bitrate
[ 5] 0.00-1.00 sec 21.2 KBytes 174 Kbits/sec
[ 5] 1.00-2.00 sec 0.00 Bytes 0.00 bits/sec
[ 5] 2.00-3.00 sec 0.00 Bytes 0.00 bits/sec
[ 5] 3.00-4.00 sec 0.00 Bytes 0.00 bits/sec
[ 5] 4.00-5.00 sec 0.00 Bytes 0.00 bits/sec
[ 5] 5.00-6.00 sec 0.00 Bytes 0.00 bits/sec
[ 5] 6.00-7.00 sec 0.00 Bytes 0.00 bits/sec
[ 5] 7.00-8.00 sec 0.00 Bytes 0.00 bits/sec
[ 5] 8.00-9.00 sec 0.00 Bytes 0.00 bits/sec
[ 5] 9.00-10.00 sec 0.00 Bytes 0.00 bits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate
[ 5] 0.00-10.03 sec 21.2 KBytes 17.3 Kbits/sec receiver
It "works" (well, it doesn't work in facts) both way: from #1 to #2 or to #2 from #1, as soon as I drop the -u flag it breaks.
In the wpa_supplicant log, I can see many wlan0: CTRL-EVENT-BEACON-LOSS when using TCP with iperf3, but not with UDP.
So, what could be the problem? I mean, even with an abyssal rate (0.1Mbit/s), it breaks, so surely there is a problem somewhere. What would be the next steps to debug this problem?
I'm using a LEDE/OpenWrt snapshot, r5705-88a2cff, from Support for TP-LINK TL-WR802N V4
Thanks,
Rémy
edit: removing the "-b" from the TCP tests changes nothing (the -b is not used when using TCP)