Maximum number of APs in use on WZC service?

27 Jan 2009 8:14 PM

Richard

Hi All

In a wifi network using numerous access points all set up with the same
SSID, is there a limit on how many of them the zero-config service will
associate with or even use when roaming?

I've been having troubles lately on a site that uses 7 APs, all configured
with WPA and using the same SSID. Roaming works great as you walk around the
site, but the last AP encountered during the walkaround is one that the
machines just won't associate with. Using netsh I can see that it knows about
it in the list of available APs, but when you're standing next to it, the
laptop would rather use a remote AP that gives a pathetic network speed
rather than use the close AP. If I replace the AP with another one, the same
thing happens, so it's not a faulty AP.

I took the 'stubborn' AP to another site and tried connecting to it, first
with my laptop (that had already refused to do so on the first site), and
second with another laptop that had never seen it. My laptop wouldn't get an
IP address; the other laptop did so without hitch.

So it almost seems like the WZC service maintains a list of all BSSIDs and
for whatever reason, it has placed this one in the 'bad' list or doesn't use
it or something.

Can anyone shed some light on this?

Thanks
Richard

27 Jan 2009 8:24 PM

Richard

I should probably add that I'm getting this problem on WinXP, Vista and the
beta of Windows 7.

27 Jan 2009 10:54 PM

Pavel A.

Richard wrote:

> I should probably add that I'm getting this problem on WinXP, Vista and the
> beta of Windows 7.

Roaming depends not only on the APs, but also on your netcard.
If you already have the latest updated drivers, maybe contacting the
netcard vendor is the way to go - unless you can debug the roaming
process with a sniffer :)

-- pa

27 Jan 2009 11:57 PM

Richard

"Pavel A." wrote:

> Richard wrote:
> > I should probably add that I'm getting this problem on WinXP, Vista and the
> > beta of Windows 7.
>
> Roaming depends not only on the APs, but also on your netcard.
> If you already have the latest updated drivers, maybe contacting the
> netcard vendor is the way to go - unless you can debug the roaming
> process with a sniffer :)

What's a good sniffer to use? I would have thought that something like
Wireshark would only show layer 2 frames and nothing down at roaming level.

28 Jan 2009 12:14 AM

Pavel A.

Richard wrote:

>
> "Pavel A." wrote:
>
>> Richard wrote:
>>> I should probably add that I'm getting this problem on WinXP, Vista and the
>>> beta of Windows 7.
>> Roaming depends not only on the APs, but also on your netcard.
>> If you already have the latest updated drivers, maybe contacting the
>> netcard vendor is the way to go - unless you can debug the roaming
>> process with a sniffer :)
>
> What's a good sniffer to use? I would have thought that something like
> Wireshark would only show layer 2 frames and nothing down at roaming level.

We've used WildPackets Omnipeek and MS Netmon 3 with some in-house
developed protocol decoders.

--pa

27 Jan 2009 10:39 PM

Jack (MVP-Networking).

Hi
I do not know which APs you are using but most APs (especially the Entry
Level one) do not provide clean seamless roaming.
It is a combo of all component involved and that the way it works.
You probably better off trying to solve the issue from the Access Point
perspective.
Jack (MS, MVP-Networking)

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"Richard" <Rich***@discussions.microsoft.com> wrote in message
news:6AC540F0-5767-4971-8674-5B3C14D79C9D@microsoft.com...
> Hi All
>
> In a wifi network using numerous access points all set up with the same
> SSID, is there a limit on how many of them the zero-config service will
> associate with or even use when roaming?
>
> I've been having troubles lately on a site that uses 7 APs, all configured
> with WPA and using the same SSID. Roaming works great as you walk around
> the
> site, but the last AP encountered during the walkaround is one that the
> machines just won't associate with. Using netsh I can see that it knows
> about
> it in the list of available APs, but when you're standing next to it, the
> laptop would rather use a remote AP that gives a pathetic network speed
> rather than use the close AP. If I replace the AP with another one, the
> same
> thing happens, so it's not a faulty AP.
>
> I took the 'stubborn' AP to another site and tried connecting to it, first
> with my laptop (that had already refused to do so on the first site), and
> second with another laptop that had never seen it. My laptop wouldn't get
> an
> IP address; the other laptop did so without hitch.
>
> So it almost seems like the WZC service maintains a list of all BSSIDs and
> for whatever reason, it has placed this one in the 'bad' list or doesn't
> use
> it or something.
>
> Can anyone shed some light on this?
>
> Thanks
> Richard