Re: Fwd: NetworkManager connection priority - same ssid ?


I have been dealing with the AP algorithm selection a few months ago. The one that selects the best connection is NM. If you get the src you can see it in the file nm-device-wifi.c (for the wireless connections).

The way it is implemented in nm 0.7 (which is the one I have been working on) is that NM will go through each favourite connection you have, and comparing them with the ones available from scan results. It does not prioritize on signal strength rather than timestamp. Which means if the one you last connected to is available it will connect to that one.

I have been playing with the code in order to make that selection signal sensitive. In order to do that you need to get signal strength info. The method nm_ap_get_strength(ap) can help get such data. The thing is that not all wireless adapters report well signal strength, but if you trust yours, then you can make this mod.

Hope I could help. If you need I can share the code I used.


Date: Mon, 10 Jan 2011 01:01:37 +0300
From: elnone <elnone gmail com>
To: mike cloaked <mike cloaked gmail com>
Cc: networkmanager-list gnome org
Subject: Re: Fwd: NetworkManager connection priority - same ssid ?
Message-ID: <4D2A3041 2000604 gmail com>
Content-Type: text/plain; charset=UTF-8

09.01.2011 19:12, mike cloaked ?????:
> ---------- Forwarded message ----------
> From: mike cloaked <mike cloaked gmail com>
> Date: 2011/1/9
> Subject: Re: NetworkManager connection priority - same ssid ?
> To: Jos? Queiroz <zekkerj gmail com>
> 2011/1/9 Jos? Queiroz <zekkerj gmail com>:
>> AFAIK, the selection of which AP to connect, in a ESSID, is done by
>> "wpa_supplicant", not by NM.
> OK - accepted but NM is setting up the wpa_supplicant configs from the
> gnome desktop.
>>> What I would like is that in this instance the connection is made to
>>> that AP that is giving the strongest signal at the laptop but it does
>>> not always do this.
>> That's exactly the criterium used by wpa_supplicant to choose which AP to
>> connect: strongest signal.
>> But if there's some problem with the strongest signal (e.g. authentication
>> timeout), it will try the other APs available.
> In my latest test I am using Fedora F14 and set the laptop to connect
> to the home LAN via G wireless with its primary AP using WPA/AES
> encryption, as well as a range extender set to the *same* SSID with
> the same encryption but on a different level in the house.
> The laptop was initially set to use NM with correct authentication to
> the primary AP and was stable.  When moved to the vicinity of the
> wireless range extender as the nearest and strongest signal (in fact 2
> feet from the antenna!) then it connected fine and began showing the
> nearby strong signal for several seconds, and then showed the primary
> signal for a few seconds (now weaker as it was further away but still
> usable) and then kept switching between the two every 5 to 10 seconds.
> The only way I could make it sit in a stable condition was to put in
> the MAC address as an additional constraint (in the NM connection gui)
> for the nearest strong signal (being the range extender), and then
> define a second connection (using NetworkManager) for the original AP
> using its *different* MAC address with the same SSID and encryption
> details.  Then when I asked NM to go to the near strong signal it
> remains stable and does not continuously hunt between the two.
> However moving the laptop to be near the primary means requiring it to
> be manually selected to the new strong signal since it is a second
> previously connected wireless source - this means that this is not
> seamless in moving the laptop between the two APs.
> I guess the intention was that wpa_supplicant was supposed to work in
> a seamless way under these circumstances but my situation shows that
> the system does not behave in the intended manner - which is why I am
> reporting this to this list.
> By the way in this case both signals are virtually noise free,. and
> indeed there are no neighbours using the same channels - (I checked
> over a period doing a wireless site survey both before the test and
> during the test)
> The hunting behaviour seemed to occur when the two signals had
> different ssid as well - but only when I defined the two connections
> with specific MAC did I get stability - that presumably should not be
> necessary?
> I guess many users will not be hooking up to multiple APs using the
> same ssid and encryption but NM and wpa_supplicant should handle this
> in a transparent manner and not need special configuration.
> I would be interested to hear if anyone else has had a similar problem?
> --
> mike c

Could you please describe ther area as I've got - these APs are
standalone? Are not controlled by a.. as example Cisco or Siemens
Wireless Controller VNS Rounted?


PS With network manager on gentoo no such a kind of problem on a really
big area of WiFi under ... see above.


Ing. Franco Miceli
CITS - Plan Ceibal - Investigación & Desarrollo
Av. Italia 6201 - Montevideo, Uruguay
CP: 11500
Tel: (598 2) 601 5773 int.: 2227

[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]