Re: Which AP is chosen when several are found for the same SSID?

[Dan Williams <dcbw redhat com>]

On Fri, 2008-10-03 at 11:42 -0400, Jose Aliste wrote:
> Thanks for the info ... I just have one more question, see inline. 
> 
> On Thu, Oct 2, 2008 at 3:18 PM, Dan Williams <dcbw redhat com> wrote:
>         On Wed, 2008-10-01 at 19:14 -0400, Jose Aliste wrote:
>         
>         > Hi all,
>         >
>         > I want to ask the question in the subject:
>         > Which AP is chosen when several are found for the same SSID?
>         > I ask this because I see three AP from mi wireless network
>         at my
>         > office. Two of them are "802.11G" AP are the other one is
>         only
>         > "802.11B" the signal for the slow one is better(it is
>         nearer) and NM
>         > always connects to it. However, I would like to NM to
>         connect to one
>         > of the others because even with less signal the connection
>         is
>         > better( 33mb/s against the 11mb/s of  a b connection!).
>         
>         
>         At this moment, this is left up to the driver and the
>         supplicant.  The
>         supplicant will apparently choose the AP with the best signal
>         strength
>         (since the scan results for the same SSID are sorted by signal
>         strength), but the driver can also choose to roam from AP to
>         AP based on
>         other criteria.
>         
>          
>         
>         > So, how can I tell NM to use the AP I need ?
>         
>         
>         You can try to set the BSSID in the connection editor to lock
>         it onto
>         one of the APs, but the driver has the discretion to ignore
>         that and
>         roam to an AP it thinks is better.  We don't yet have the
>         facility to
>         lock to 802.11g at _any_ level of the stack, not just
>         NetworkManager.
> 
> I am using NM 0.6 in Hardy and If I do as you or aaron said(keeping in
> th bssid only the address of the ap I want), but it does not work. 
> However, If I go with manual config and I set the  AP by using the
> wireless-ap option in the /etc/network/interfaces  then everything
> works... Would I be more lucky in NM 0.7, I mean does NM 0.7 try to
> force the AP? Btw wpa_supplicant is used even if I am not using WPA? 

NM 0.6 doesn't have the capability to lock to a particular AP.  NM 0.7
has the capability, but is still subject to driver behavior.  Give NM
0.7 a shot and let us know if locking to your AP's BSSID works.

Dan

> Thanks
> 
> José
> 
>  
> 
>         You could try setting the data rate, but that doesn't always
>         do what you
>         want since you can only set it to one value, and the card
>         would be
>         unable to rate-scale based on signal quality of the locked AP.
>         
>         In short, can't really be done, but this is only partly NM's
>         fault.
>         There's a lot more work in the stack from drivers, to WEXT, to
>         wpa_supplicant to make sure this works the way you want it.
>         
>         Dan
>         
>         
> 
>