Asymmetric WLAN<->LAN connection

[reddy]

Hello,

I'm fighting for the whole day with a strange phenomena in my network, and I'm out of ideas what may be wrong. I'm testing 5GHz connection between one WLAN server and one client connected to LAN (1Gbps). I have decent speeds one way but almost 10x slower the other way:

root@nas:/home/reddy# iperf -c 192.168.1.4 -i1 -r
------------------------------------------------------------
Server listening on TCP port 5001
TCP window size: 85.3 KByte (default)
------------------------------------------------------------
------------------------------------------------------------
Client connecting to 192.168.1.4, TCP port 5001
TCP window size: 93.5 KByte (default)
------------------------------------------------------------
[  5] local 192.168.1.200 port 52251 connected with 192.168.1.4 port 5001
[ ID] Interval       Transfer     Bandwidth
[  5]  0.0- 1.0 sec  3.50 MBytes  29.4 Mbits/sec
[  5]  1.0- 2.0 sec  3.38 MBytes  28.3 Mbits/sec
[  5]  2.0- 3.0 sec  3.38 MBytes  28.3 Mbits/sec
[  5]  3.0- 4.0 sec  3.38 MBytes  28.3 Mbits/sec
[  5]  4.0- 5.0 sec  3.50 MBytes  29.4 Mbits/sec
[  5]  5.0- 6.0 sec  3.50 MBytes  29.4 Mbits/sec
[  5]  6.0- 7.0 sec  3.38 MBytes  28.3 Mbits/sec
[  5]  7.0- 8.0 sec  3.50 MBytes  29.4 Mbits/sec
[  5]  8.0- 9.0 sec  3.50 MBytes  29.4 Mbits/sec
[  5]  9.0-10.0 sec  3.38 MBytes  28.3 Mbits/sec
[  5]  0.0-10.1 sec  34.5 MBytes  28.8 Mbits/sec
[  4] local 192.168.1.200 port 5001 connected with 192.168.1.4 port 60554
[  4]  0.0- 1.0 sec  23.9 MBytes   201 Mbits/sec
[  4]  1.0- 2.0 sec  26.6 MBytes   223 Mbits/sec
[  4]  2.0- 3.0 sec  26.3 MBytes   220 Mbits/sec
[  4]  3.0- 4.0 sec  25.8 MBytes   217 Mbits/sec
[  4]  4.0- 5.0 sec  25.8 MBytes   216 Mbits/sec
[  4]  5.0- 6.0 sec  26.1 MBytes   219 Mbits/sec
[  4]  6.0- 7.0 sec  26.2 MBytes   220 Mbits/sec
[  4]  7.0- 8.0 sec  26.0 MBytes   218 Mbits/sec
[  4]  8.0- 9.0 sec  26.2 MBytes   220 Mbits/sec
[  4]  9.0-10.0 sec  25.8 MBytes   216 Mbits/sec
[  4]  0.0-10.1 sec   261 MBytes   217 Mbits/sec

My setup:
- Merlin 376.48_3 firmware
- firewall disabled
- channel bandwidth 20/40MHz
- control and extension channels set to Auto (running on channels 36+40)
- WLAN client is 3x3 Intel Ultimate N6300
- both client and server running Linux

Can anyone give me some hints, please?

BTW, how to enable high channels? I'm in Europe (Sweden) and I can't switch to the high ones in the GUI. Settings seem to be ok:

admin@RT-N66U-76D0:/tmp/home/root# nvram get pci/1/1/ccode
EU
admin@RT-N66U-76D0:/tmp/home/root# nvram get pci/2/1/ccode
EU
admin@RT-N66U-76D0:/tmp/home/root# nvram get wl0_country_code
EU
admin@RT-N66U-76D0:/tmp/home/root# nvram get wl1_country_code
EU
admin@RT-N66U-76D0:/tmp/home/root# nvram get regulation_domain
EU
admin@RT-N66U-76D0:/tmp/home/root# nvram get regulation_domain_5G
EU

Thanks in advance for any help!

 

[Nullity]

I would think it was a client problem (power-save enabled, low tx-power, outdated drivers/firmware), rather than an AP problem.

Linux is a crap-shoot with wireless.

 

[reddy]

I would think it was a client problem (power-save enabled, low tx-power, outdated drivers/firmware), rather than an AP problem.

Linux is a crap-shoot with wireless.

Thanks for your reply!
It could be the case, I'll try to investigate it more in the evening. IIRC from iwconfig, I had power saving disabled and maximum TX power. Link quality was 67/70 - 69/70, so pretty much perfect. System is the fresh Debian wheezy 64bit (actually, it's OpenMediaVault: http://www.openmediavault.org/about.html based on wheezy). I can't say about the drivers now (I'm not at home) but I assume it's whatever Intel included in wheezy's kernel version 3.2.

It's weird it works fast one way but not the other... Power saving should not kick in during iperf transfer. I'm really confused

 

[Nullity]

Thanks for your reply!
It could be the case, I'll try to investigate it more in the evening. IIRC from iwconfig, I had power saving disabled and maximum TX power. Link quality was 67/70 - 69/70, so pretty much perfect. System is the fresh Debian wheezy 64bit (actually, it's OpenMediaVault: http://www.openmediavault.org/about.html based on wheezy). I can't say about the drivers now (I'm not at home) but I assume it's whatever Intel included in wheezy's kernel version 3.2.

It's weird it works fast one way but not the other... Power saving should not kick in during iperf transfer. I'm really confused

Did iwconfig show a large increase in errors after running iperf?
Does Debian support the "iw" command? It can be useful too. (Debian may be too outdated for 'iw' support.)

I have experienced asymmetrical and crappy wifi speeds with only my Debian (and maybe Ubuntu 12 LTS) installation. Archlinux, Linux Mint 17, and Fedora 20 have all achieved ~100mbit. Debian-stable is pretty outdated for modern wireless support iirc. You may need to install the 'nonfree' firmware if the included opensource firmware is buggy.

Forums/wikis dedicated to linux troubleshooting would probably be a better place to start, but I will help as much as I can.

and yeah, power-saving shouldn't do lots of things, but sometimes it does. It is a common thing to disable when trouble-shooting most anything with computers.

 

[reddy]

Thanks for your hints, you were perfectly right. The problem was on linux client which simply interferenced itself while sending... All I needed to do is enable transmission antenna aggregation in /etc/modprobe.d/iwlwifi.conf:

options iwlwifi 11n_disable=8

Now after a quick checks I have a stable 100+Mbps both ways. I wonder why it was disabled by default anyway I spent two days heavy debugging on this

So we can close this thread, and no point in moving it to other forum.

Thanks again!

 

[Nullity]

Thanks for your hints, you were perfectly right. The problem was on linux client which simply interferenced itself while sending... All I needed to do is enable transmission antenna aggregation in /etc/modprobe.d/iwlwifi.conf:

options iwlwifi 11n_disable=8

Now after a quick checks I have a stable 100+Mbps both ways. I wonder why it was disabled by default anyway I spent two days heavy debugging on this

So we can close this thread, and no point in moving it to other forum.

Thanks again!

I need to try your fix on my Debian install. Thanks for sharing your findings.

 

[reddy]

You're welcome. In case that doesn't help in your case you may also try the following:

• disable Bluetooth on the adapter, if it's there

  options iwlwifi bt_coex_active=0

• switch to software encryption of the traffic

  options iwlwifi swcrypto=1

• disable 802.11n completely (but that will limit your max speed anyway, I think)

  options iwlwifi 11n_disable=1

Those are the most interesting hints I found while debugging my problems. Good luck!