network link speed

Hello, does anyone know how the link speed is determined by Windows when
attached to a wireless network? I know Windows queries the Ndis driver using
OID_GEN_LINK_SPEED, which is supposed to return the max Tx rate. In a
wireless network, the max rate is determined by the Service Set. Therefore,
I would assume that when associating with a particular Access Point, I should
always get the same link speed. However, I've seen cases where the link
speed changes between 1, 2, 5.5 & 11Mbps - even though I'm still connected
(i.e. no disassociation/reassociation occurs). My service set consists of a
single Access Point, which is configured to use all 4 rates (i.e. they're all
marked Mandatory in the beacon parameter set).

Thx,
Rick Farrington

Pavel
Mon Aug 16 19:32:48 CDT 2004

The link speed is the *currently active* value - not max. It can change dynamically
as the Tx rate changes due to various conditions.
Exact reasons why the WLAN adapter/driver decides to change the rate, are known
only to the developers of the device.
--PA

"RickFarrington" <RickFarrington@discussions.microsoft.com> wrote in message
news:463ECDDB-37E2-4663-A01E-1E621C09D6B5@microsoft.com...
> Hello, does anyone know how the link speed is determined by Windows when
> attached to a wireless network? I know Windows queries the Ndis driver using
> OID_GEN_LINK_SPEED, which is supposed to return the max Tx rate. In a
> wireless network, the max rate is determined by the Service Set. Therefore,
> I would assume that when associating with a particular Access Point, I should
> always get the same link speed. However, I've seen cases where the link
> speed changes between 1, 2, 5.5 & 11Mbps - even though I'm still connected
> (i.e. no disassociation/reassociation occurs). My service set consists of a
> single Access Point, which is configured to use all 4 rates (i.e. they're all
> marked Mandatory in the beacon parameter set).
>
> Thx,
> Rick Farrington
>