Re: applet and wireless scan

[Dan Williams <dcbw redhat com>]

On Wed, 2007-03-07 at 22:01 +0100, yelo_3 wrote:
> Thank you Dan for your information!!
> I will do some tries and let you know if there are
> problems with the refresh of the list.
> 
> I was complaining about the presence of ghost APs
> because a user thinks that he can connect to it even
> if he is not in range (6 minutes is still a lot. why
> so much?)... anyway he has to wait for at least 1

We can possibly tweak this, since drivers are better these days than
they used to be.  The 6 minute interval was chosen a fairly long time
ago.

> minute to see that he cannot connect (then connection
> timeout si tooooooo long :D even if it is immediately
> visible that the connection can't be done because
> there send-circle does not become green and stays
> grey) and then the AP should be removed from the list.
> 
> Another scan problem is how nm handles the signal
> level. in iwlist eth1 scan there are two values: one
> misured in % and the other in dB. in my case if the
> level is less than -80dB I cannot connect, even if the
> other value is not so low (such as 25/100). which
> problem do you think it can be? a driver issue?
> nm-applet only shows the % value so it is possible
> that the connection cannot be estabilished because the
> other value is less than -80dB, but from nm this is
> not visible...

Scanned signal strength reported from drivers is still not reliable, but
is getting a lot better.  NM cannot rely on signal strength for doing
stuff like switching access points or roaming yet.

Drivers should report signal _quality_ in a 0 - 100% range, they are
free to do whatever they wish with the RSSI/dBm.

> As reguards the scan from console I didn't know that
> in some cases it takes up to 10 seconds.. it is
> instant with ipw2200! (and so it should be instant
> with nm, shouldn't it? or is it introduces a sleep of
> 20 seconds independently?)

Yes, but since NM has to deal with cards _other_ than ipw2200 too.

Dan


> --- Dan Williams <dcbw redhat com> ha scritto:
> 
> > On Wed, 2007-03-07 at 20:25 +0100, yelo_3 wrote:
> > > you told me that I should wait 10 seconds before
> > > having an updated list. for me it is a great
> > thing! is
> > > the list updated even if it is open or should I
> > close
> > > and reopen it? is this feature in 0.7 or already
> > in
> > > 0.6.x?
> > 
> > NM scans every 20 seconds, and backs off to 2
> > minutes.  If you pull down
> > the menu, NM starts at 20 seconds again and backs
> > off from there.
> > 
> > > why iwlist eth1 scan is so quick? is it
> > inaccurate?
> > 
> > Because it blocks waiting for the scan results.  It
> > is also highly
> > driver dependent.  Some drivers take up to 10
> > seconds to scan.
> > 
> > > and definitely I cannot understand why ghost APs
> > are
> > > kept for 6 minutes... this is quite confusing!
> > 
> > Because a single wireless scan, even with an
> > ipw2200, will never give
> > you a _complete_ picture of the wireless
> > environment.  Radio is
> > inherently unreliable.  Your card may fail to
> > receive the beacon for an
> > AP correctly, it may have collided with other
> > traffic, etc.  The only
> > reliable way to get a more complete picture of your
> > radio environment is
> > to do multiple scans and compile the results.
> > 
> > > especially in my case they are not purged if
> > wireless
> > > is off
> > 
> > rfkill isn't well supported under linux at the
> > moment, and it's not
> > reported to NetworkManager right now.  That's being
> > worked on.
> > 
> > Dan
> > 
> > 
> > 
> 
> 
> 
> 	
> 
> 	
> 		
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