Building a Visual Studio Release wpa_supplicant.exe 0.5.4 (for Windows)

Jouni Malinen jkmaline
Sat Jul 29 18:12:57 PDT 2006

On Fri, Jul 28, 2006 at 06:44:54AM -0700, George S. Lockwood wrote:

> I'd like to open a thread on Roaming.  How do I do that?

I'm not sure I understood what you mean.. If this is refering to threads
on the mailing list, that would be done by just sending another message
to the list without replying to an existing message. Just make sure that
you are sending it from the address that you used when subscribing to
the list.

> I see the term "roaming" about 3 times in the wpa_supplicant literature;
> either in the list of features or the todo list.  And I'm not really sure
> whether this great product presently can handle a roaming wifi unit as is
> today or if it needs enhancement or if roaming is out of the scope of the
> product.

It depends on your needs and the driver you are using..

> Scenario:  a user uses a wifi client app based upon wpa_supplicant
> (7-22-2006) to make the initial connection and authenticate to a network.
> That network has many SSIDs covering a geographic area.  Every SSID has the
> same name, but of course a unique MAC address.  the User then roams.  As
> they move the signal strength of the original SSID they connected to weakens
> in comparison to the other SSIDs of the network.

This paragraph is somewhat confusing.. This seems to talk about SSIDs in
plural, but I think that you are actually talking about just one SSID
and multiple BSSes, i.e., multiple access points sharing the same SSID.

> In my view the strongest signal should (always) be used by the users wifi.
> So some sort of hand-off must take place.

Well, with some hysteresis added to avoid jumping between the APs too
frequently, I would agree with this.

> How would this take place? Must there be a SSID disconnect and then
> re-connect (to that SSID with the best signal -that the wifi client software
> peforms?

If you are talking about Windows NDIS drivers, the most common way of
doing this would be to allow the driver take care of AP selection. In
case of wpa_supplicant, that would mean using ap_scan=2 mode. In this
mode, wpa_supplicant is only configuring the SSID for the driver and the
driver will decide when to roam to another AP based on its internal
implementation. All re-associations are signaled to wpa_supplicant as
new connections, but there is no disconnection assuming the client
remains in the coverage area of at least one AP all the time.

Jouni Malinen                                            PGP id EFC895FA

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