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[SOLVED]Too slow speed - 8Mbps instead of 22Mbps on 802.11g
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subox
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Joined: 20 Nov 2006
Posts: 33
Location: Bytów/Szczecin

PostPosted: Fri Feb 03, 2012 5:44 pm    Post subject: [SOLVED]Too slow speed - 8Mbps instead of 22Mbps on 802.11g Reply with quote

Hi,

I have internet connection 15mb/s. On linux in every speed test the result is 7,5-8mb/s but using my girlfriend's notebook speed test is always 14,5-15mb/s.
I can't figure out what is wrong with my configuration.

Router params:
Code:
wpa2-psk
aes
channel6
54Mbps( 802.11g )


And my linux configs:
Code:
suboxComp ~ # iwconfig wlan0
wlan0     IEEE 802.11abgn  ESSID:"test1" 
          Mode:Managed  Frequency:2.437 GHz  Access Point: 00:23:CD:FF:8D:90   
          Bit Rate=54 Mb/s   Tx-Power=15 dBm   
          Retry  long limit:7   RTS thr:off   Fragment thr:off
          Encryption key:off
          Power Management:off
          Link Quality=59/70  Signal level=-51 dBm 
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:0  Invalid misc:24   Missed beacon:0


Code:
lspci | grep -i 'network cont'
03:00.0 Network controller: Intel Corporation Centrino Advanced-N 6200 (rev 35)


Code:
suboxComp ~ # lsmod |grep -i iwl
iwlagn                166074  0
mac80211              162488  1 iwlagn
cfg80211              140298  2 iwlagn,mac80211


Code:
suboxComp ~ # grep -r -i iwl /etc/conf.d/
/etc/conf.d/modules:modules_2_6="${modules_2_6} iwlagn"
/etc/conf.d/modules:#modules_2_6="${modules_2_6} iwlagn"
/etc/conf.d/modules:#module_iwlagn_args_2_6="11n_disable=0"


Code:
eix iwl6000
[I] net-wireless/iwl6000-ucode
     Available versions:  (~)9.221.4.1
     Installed versions:  9.221.4.1(13:33:41 27.12.2011)
     Homepage:            http://intellinuxwireless.org/?p=iwlwifi
     Description:         Intel (R) Wireless WiFi Advanced N 6000 ucode


Code:
suboxComp ~ # dmesg | grep -i iwl
[    7.426384] iwlagn: Intel(R) Wireless WiFi Link AGN driver for Linux, in-tree:
[    7.426387] iwlagn: Copyright(c) 2003-2011 Intel Corporation
[    7.426494] iwlagn 0000:03:00.0: PCI INT A -> GSI 17 (level, low) -> IRQ 17
[    7.426524] iwlagn 0000:03:00.0: setting latency timer to 64
[    7.426605] iwlagn 0000:03:00.0: Detected Intel(R) Centrino(R) Advanced-N 6200 AGN, REV=0x74
[    7.443370] iwlagn 0000:03:00.0: device EEPROM VER=0x436, CALIB=0x6
[    7.443374] iwlagn 0000:03:00.0: Device SKU: 0Xb
[    7.443397] iwlagn 0000:03:00.0: Tunable channels: 13 802.11bg, 24 802.11a channels
[    7.443545] iwlagn 0000:03:00.0: irq 43 for MSI/MSI-X
[    7.970832] iwlagn 0000:03:00.0: loaded firmware version 9.221.4.1 build 25532
[    7.971232] ieee80211 phy0: Selected rate control algorithm 'iwl-agn-rs'


Code:
suboxComp ~ # cat /etc/wpa_supplicant/wpa_supplicant.conf
ctrl_interface=/var/run/wpa_supplicant
ctrl_interface_group=users
update_config=1

network={
   ssid="test1"
   psk="test"
   proto=RSN
   key_mgmt=WPA-PSK
   pairwise=CCMP
   auth_alg=OPEN
}


Last edited by subox on Sun Feb 05, 2012 11:44 am; edited 2 times in total
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NeddySeagoon
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Joined: 05 Jul 2003
Posts: 46751
Location: 56N 3W

PostPosted: Fri Feb 03, 2012 9:16 pm    Post subject: Reply with quote

subox,

54Mbps( 802.11g ) means 54 Mbs half duplex so you can't even get close to 54 Mbis in practice.

It gets worse too. 802.11g suses 2.5 channels up and down from the channel you select for 'spread spectrum' every time your network collides with another, you both lose packats and you don't even need to be on the same channel for this packet loss to occur.

Is your gf notebook measuring speed in the same way ?
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.
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subox
n00b
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Joined: 20 Nov 2006
Posts: 33
Location: Bytów/Szczecin

PostPosted: Fri Feb 03, 2012 11:12 pm    Post subject: Reply with quote

Yes, I know that i can get max speed about 22Mbps from 802.11g but not 8 in 1 meter from router without any other networks interference.

My gf notebook measures speed in the same two ways. It must be something with my linux config or driver?


-----------------------------------
UPDATE:
Problem solved. I had wrong mtu for wlan0.

If someone will have same problem, use following command:
Code:
ifconfig wlan0 mtu 1500
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Simba7
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Joined: 22 Jan 2007
Posts: 705
Location: Billings, MT, USA

PostPosted: Tue Feb 07, 2012 8:15 pm    Post subject: Reply with quote

subox wrote:
Problem solved. I had wrong mtu for wlan0.

If someone will have same problem, use following command:
Code:
ifconfig wlan0 mtu 1500

That bit me with one of my ISPs. Optimum set my MTU to 576. I had to have my router ignore their value and use the cards' value, which solved several issues.
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subox
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Joined: 20 Nov 2006
Posts: 33
Location: Bytów/Szczecin

PostPosted: Wed Feb 08, 2012 6:17 am    Post subject: Reply with quote

Unfortunately my router doesn't have possibility to change MTU.
I commented "option interface_mtu" option in /etc/dhcpcd.conf to ignore MTU from router.
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NeddySeagoon
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Posts: 46751
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PostPosted: Wed Feb 08, 2012 5:58 pm    Post subject: Reply with quote

subox,

You have to set the mtu at the source of the packets, not on the router, unless of course the router is also the source of the packets.
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NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.
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subox
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Joined: 20 Nov 2006
Posts: 33
Location: Bytów/Szczecin

PostPosted: Wed Feb 08, 2012 6:02 pm    Post subject: Reply with quote

Ok :), thanks for the explanation.
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