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Posted by:Dutch
Subject:Max rates other than 11 and 54 Mbps?
Date:15:22:08 07/02/2008

> Kismet shows that most of the access points in my neighbourhood have a 'max rate' of either 11.0 Mbps or 54 Mbps. However, there are also a few that are listed as 18.0 Mbps or 36.0 Mbps.
>
> I understand that Kismet only displays whatever the AP advertises, but does anyone know why these APs do not advertise the full 54 Mbps? Is it that certain chipsets are suboptimal? Or perhaps those APs are 'underclocked' on purpose?
>
> Signal strength cannot be a factor because one of those APs is mine and it is rated at 18.0 Mbps, even at a distance of 10 cm. Incidentally, it is a Fonera from Fon.com. These are known to run a bit hot (although I haven't noticed) and most broadband users have an Internet connection well under 20 Mbps, so that's why I was wondering if they are underclocking the device.
>
> Thanks,
>
> Jack

It's dependant on the chipset, the OS, and the manufacturers implementation on the AP. The Fonera uses linux as an OS, and an Atheros chipset, running with Madwifi in one of its incarnations. Madwifi used to exhibit a behaviour where the default rate in AP mode would be 36 megabits/s iso the maximum rate of 54 megabits/s pr. the 802.11g standard. So if the AP announces that the max rate it is cabable of is 36 mbps, then that is the info kismet receives and therefore displays. If you can telnet into the device, and use the device equivalent of the iwconfig tool to set the rate properly, then you should see the right rate in kismet.

It's not a kismet problem per se. Kismet displays what the packet header contains in the 802.11 defined fields, and if the hardware transmitting or receiving that header contains wrong information kismet can't do anything about it.


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