Re: Change wireless interface "sens" value how?

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On Mon, Feb 14, 2011 at 04:30:09PM +0000, mike cloaked wrote:
> On Mon, Feb 14, 2011 at 4:12 PM, John W. Linville <[email protected]> wrote:
> > Neither -- the driver (like all mac80211-based drivers) simply does
> > not support that setting.  mac80211-based drivers are simple, and
> > they don't do roaming by themselves.  Instead they rely on a userland
> > component (e.g. wpa_supplicant) to take care of roaming for them.
> >
> > Unfortunately, I don't know of any roaming "knobs" to turn for
> > wpa_supplicant (or NetworkManager) -- maybe it would be nice to
> > have one.  Even if it were there, I suspect that control of that
> > "knob" would have to flow through NetworkManager if you are using it.
> >
> > John
> Yes I eventually homed in on the reality that you just described.  I
> was able to get an ipw2200 based laptop to roam nicely as the driver
> did support the sens parameter - and it did switch over to another AP
> when the signal from the first went near non-existent - which was what
> I was after.  However it seems that using my netbook with an ath5k
> driver based wireless internal simply won't be able to do it whatever
> I do - is there anyone working to make mac80211 drivers more
> sophisticated in the future?  Maybe roaming is not high on most user's
> agenda?

Obviously wireless users like to be able to roam.  I certainly do it
around the house, etc.  Are you saying that your ath5k device somehow
refuses to disconnect even after you are out of range of the old AP?
That would be rather strange.

> But the main, and separate, issue I have is with initial
> selection of a weak AP signal when a strong one (with same ssid) seems
> more logical - and I don't know if this is something that is within
> the realm of the driver, the NM code or wpa_supplicant?

Yes, I remember that thread.  I'm still not sure I understand why
you care which AP you connect to, so long as the connection works.
In any case, if you are using NetworkManager then the decision for
which AP to use will lie somewhere between NM and wpa_supplicant.
I'm sorry, but I don't know the details to go beyond that.

> I am not sufficiently knowledgeable to know what is possible here.
> I would certainly appreciate knowing what is possible, and what
> provides the limitations?

The driver will only make an association when directed to do so from
userland.  If you are using very basic tools (like iwconfig) then there
is some minimal suppot in the kernel for scanning and finding an AP.
If you use wpa_supplicant, it will control the scanning for APs and
choosing one as it sees fit.  NetworkManager uses wpa_supplicant,
but NM exerts some control over the wpa_supplicant configuration and
I'm not fluent on those details.

If a connection is lost, the kernel will make no effort to reconnect
by itself.  If you are using iwconfig, you will need to trigger the
reconnection manually.  wpa_supplicant will reconnect automatically,
possibly to a new AP if the old one is no longer available.


John W. Linville		The truth will set you free, but first it will
[email protected]			make you miserable. -- James A. Garfield
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