WPA compatibility between manufacturers.

2 Mar 2005 10:42 AM

Stuart Robinson

If I have a WAP set up for WPA PSK, is it reasonable to expect different
manufacturers of Wireless LAN cards to be fully compatible with that WAP ?

I ask the question because I have been trying out one of the Edimax WAPs,
and yes I realise they are cheap.

A couple of Notebooks equipped with Intel Pro Wireless Mini PCI cards
connect OK and seem stable.

If I use Edimax own Wireless cards including latest drivers (I have tried
PCI and USB cards) then either they initially connect but drop after
20mins or so, or they wont connect at all. If everything is set for WEP
they are OK.

Anyone seen anything similar ?

Is it likely that the WAP that may not be implementing WPA PSK correctly
or is the problem more likely to be the drivers for the wireless cards ?

Stuart.

2 Mar 2005 2:34 PM

William P.N. Smith

sr***@cix.co.uk (Stuart Robinson) wrote:

>If I have a WAP set up for WPA PSK, is it reasonable to expect different
>manufacturers of Wireless LAN cards to be fully compatible with that WAP ?

Yes, that's the whole point of standards.

>A couple of Notebooks equipped with Intel Pro Wireless Mini PCI cards
>connect OK and seem stable.
>
>If I use Edimax own Wireless cards including latest drivers (I have tried
>PCI and USB cards) then either they initially connect but drop after
>20mins or so, or they wont connect at all. If everything is set for WEP
>they are OK.

I've found builtin cards to have much better antennas than the PCMCIA
cards, so they'll typically have better coverage and stability.

I'm not sure what's _supposed_ to happen when WPA-PSK does a keychange
in a noisy environment, but I've seen switching back to WEP solve
problems like you are experiencing, so I suspect that's one of the
areas that no-one's spending a lot of time on...

2 Mar 2005 7:19 PM

Stuart Robinson

> I'm not sure what's _supposed_ to happen when WPA-PSK does a keychange
> in a noisy environment, but I've seen switching back to WEP solve
> problems like you are experiencing, so I suspect that's one of the
> areas that no-one's spending a lot of time on...

How often is the key change ?

In this case its not signal strength thats the problem, WAP and
Wireless cards are close together.

Whats weird is that when the problem starts happening it affects two
different PCs equipped with Edimax cards at the same time, the connection
goes up and down at the same time, and the Intel equipped notebook is
completely unaffected.

Now that suggests a problem with WPA coming from the WAP that the Edimax
cards are sensitive too but the Intel cards are not.

Stuart.

2 Mar 2005 11:47 PM

William P.N. Smith

Stuartr@nospam.please (Stuart Robinson) wrote:

>> I'm not sure what's _supposed_ to happen when WPA-PSK does a keychange
>> in a noisy environment

>How often is the key change ?

Usually every 300 seconds (5 minutes), though it's usually
configurable.

>In this case its not signal strength thats the problem, WAP and
>Wireless cards are close together.

Yeah, but a noise burst from a microwave, airport radar, or other
source at _just_ the right time during the keychange handshake could
very well cause a non-recoverable error, and you'd have to start the
whole authentication thing all over again.

Of course, it could be a driver issue with the cards...