# [SOLVED]Too slow speed - 8Mbps instead of 22Mbps on 802.11g

## subox

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:

```
wpa2-psk

aes

channel6

54Mbps( 802.11g )
```

And my linux configs:

```
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
```

```
lspci | grep -i 'network cont'

03:00.0 Network controller: Intel Corporation Centrino Advanced-N 6200 (rev 35)

```

```
suboxComp ~ # lsmod |grep -i iwl 

iwlagn                166074  0 

mac80211              162488  1 iwlagn

cfg80211              140298  2 iwlagn,mac80211
```

```
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"

```

```
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
```

```
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'
```

```
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

----------

## NeddySeagoon

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 ?

----------

## subox

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:

```
ifconfig wlan0 mtu 1500
```

----------

## Simba7

 *subox wrote:*   

> Problem solved. I had wrong mtu for wlan0.
> 
> If someone will have same problem, use following command:
> 
> ```
> ...

 

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.

----------

## subox

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.

----------

## NeddySeagoon

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.

----------

## subox

Ok  :Smile: , thanks for the explanation.

----------

