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

Finally I tried at office with nm0.7 packages from launchpad ppa and it works! Just added the desired AP address to the BSSID and nm connected without problems. Some last questions:
- Is wpa_supplicant used even if the wireless network is totally open?
- If nm0.7 can lock the AP why not trying to do something like chosing the AP that would be beter in terms of rate and then connecting. I understand the driver is free to roam to another AP but then one just trusts the driver because if not we would have some nasty bugs like in Mac (having the AP changed every two seconds!)

just one last piece of info. In the iwlist scanning the fastest ap( in terms of signal quality / type of router) in my network appear the first. Nevertheless, nm tries to connect to the slow one(which is the best in terms of signal quality) if I don't lock the AP by hand in the connection editor. 

Keep up the good work!


On Fri, Oct 3, 2008 at 4:08 PM, Dan Williams <dcbw redhat com> wrote:
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.


> 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

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