Hello everyone,
I`m running several experiments involving ad hoc networks. I`ve selected some well known-to-be-compatible adapters, such as Edimax (Ralink shipset), Alfa networks (Realtek) and Atheros (madwifi). Atheros is available only as built-in adapter on the equipement or as a PCI board.
So, I'm experiencing some instability regarding the selection of the BSSID used by all the nodes. I start the network with a single node, then another, then another. Now, for a couple of minutes it works, bu then some nodes start losing sight of each and changing their BSSIDs to a different value (and they should always use the same). I'm really running out of explanations of why this is happening, because these nodes are all in-range of each other, and should be "pingable" directly. My main suspect is the driver instability, but then I dont know of any other better alternatives. I've tested the following USB adapters:
- Edimax EW-7318USg (rt73 drivers) - Alfa AWUS036H-11g
And the builtin adapters:
- Atheros chipset AR5007EG
best regards,
Hey Breno,
sounds like the well known ad-hoc cell splitting problem to me. A common workaround is to fixate the BSSID to some pre-defined value:
iwconfig athX ap 02:CA:FF:EE:BA:BE
hopefully all your drivers support this. :)
best regards, Simon
On Wed, Feb 04, 2009 at 03:03:35PM -0300, Breno Jacinto wrote:
Hello everyone,
I`m running several experiments involving ad hoc networks. I`ve selected some well known-to-be-compatible adapters, such as Edimax (Ralink shipset), Alfa networks (Realtek) and Atheros (madwifi). Atheros is available only as built-in adapter on the equipement or as a PCI board.
So, I'm experiencing some instability regarding the selection of the BSSID used by all the nodes. I start the network with a single node, then another, then another. Now, for a couple of minutes it works, bu then some nodes start losing sight of each and changing their BSSIDs to a different value (and they should always use the same). I'm really running out of explanations of why this is happening, because these nodes are all in-range of each other, and should be "pingable" directly. My main suspect is the driver instability, but then I dont know of any other better alternatives. I've tested the following USB adapters:
Edimax EW-7318USg (rt73 drivers)
Alfa AWUS036H-11g
And the builtin adapters:
Atheros chipset AR5007EG
best regards,
--
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Hello Simon,
Thanks, I was searching a bit on google about that. It's harder to solve than I thought.
I still wonder if setting up a static BSSID will stop the BSSID selection algorithm from ocurring. What do you think? Have tested this in practice?
Setting the BSSID manually was only supported by the Atheros chipset, which runs on my laptop. I'm also working with portable devices, such as OpenMoko Freerunner (which is Atheros too, but I havent checked this) and Nokia N810 (which has a prism chipset). Nokia N810 was really buggy... whenever I tried to put one device on the network, it started to split itself from it.
best regards,
Hi,
I still wonder if setting up a static BSSID will stop the BSSIDselection algorithm from ocurring. What do you think? Have tested this in practice?
yes, it will deactivate the selection algorithm. We used this hack to get the Freifunk Berlin network stable. We had a real hardware zoo (Atheros, Broadcom, Ralink, etc) that was impossible to control without setting the BSSID.
Regards, Marek
Hello Marek,
Have you managed to set a static BSSID to all those chipsets - Atheros, Broadcom, Ralink etc? Because up to now, only Atheros made this trick possible.
If I managed to do that with the rt73 chipset that would be enough. But the driver guys seem to have no documentation stating if this is possible or not, and doing an iwconfig rausb0 ap <BSSID MAC> does not change anything :/.
best regards,
2009/2/5 Marek Lindner lindner_marek@yahoo.de:
Hi,
I still wonder if setting up a static BSSID will stop the BSSIDselection algorithm from ocurring. What do you think? Have tested this in practice?
yes, it will deactivate the selection algorithm. We used this hack to get the Freifunk Berlin network stable. We had a real hardware zoo (Atheros, Broadcom, Ralink, etc) that was impossible to control without setting the BSSID.
Regards, Marek
B.A.T.M.A.N mailing list B.A.T.M.A.N@open-mesh.net https://lists.open-mesh.net/mm/listinfo/b.a.t.m.a.n
Hi,
Have you managed to set a static BSSID to all those chipsets - Atheros, Broadcom, Ralink etc? Because up to now, only Atheros made this trick possible.
thanks to Felix from the OpenWRT project the Atheros driver has that feature (as you know). Broadcom is a much harder cases because the drivers a binary only. We mostly use the famous WRT54G and its derivates for our network. Sven- Ola managed to write patch for that binary driver of the WRT. There also is an open source driver project for the broadcom chips but I'm not sure where it stands. I never experimented with Ralink myself, so I can't answer that. I'm sure Elektra could jump in here. :-)
Regards, Marek
Hello Marek,
Thank you for replying. I have one final question about this.
2009/2/6 Marek Lindner lindner_marek@yahoo.de:
thanks to Felix from the OpenWRT project the Atheros driver has that feature (as you know). Broadcom is a much harder cases because the drivers a binary only. We mostly use the famous WRT54G and its derivates for our network. Sven- Ola managed to write patch for that binary driver of the WRT. There also is an open source driver project for the broadcom chips but I'm not sure where it stands.
How about in the laptops / pcs that access the WRT54G, which make the "infrastructure" of the mesh? What kind of adapters do you use on them?
I never experimented with Ralink myself, so I can't answer that. I'm sure Elektra could jump in here. :-)
That would be really helpful - I'm trying to contact the rt73 drivers guys for the last week and got no response from them. If anyone could confirm whether these Edimax dongles could set a static BSSID, that would help us decide which equipment to buy for building our ad hoc network test-bed.
Regards, Marek
best regards,
Hi -
I'm waiting for working drivers (particularly USB) for IBSS mode for long time and was putting my hope on Ralink RT73 as well.
The situation is improving with the mac80211 driver development in the Linux kernel. Recently patches went into compat-wireless that allow to fix the IBSSID with the
iwconfig <interface> ap <cell-id>
command - with some drivers, not all.
However the situation is a little more complex than just fixing the IBSSID, because the drivers/firmware have to be convinced not to perform a IBSS-merge every time the TSF timestamp in a received beacon is a little older. Upon a merge the cards may flush their MAC table - this could happen every few miliseconds - like I have observed with Intel ipw4965 driver. Also TSF clock skews can cause race conditions.
So far ath5k and ath9k seem to work - but the only driver I can really recommend is Madwifi with all patches from Openwrt - vanilla Madwifi is *not* working. The patched Madwifi in Openwrt Kamikaze works perfectly (I'm using mesh with Batman exclusively every day and I can suspend/resume my EEE-PC for weeks and I'm always online ;-)
But Madwifi does not support USB...
Best bet for USB is Zydas, I guess.
cu elektra
Hello Elektra,
Thanks for the information. At least now I have some background to work on - I already have several rt73 USB dongles, some notebooks with Atheros, some OpenMokos (which have atheros chipsets) and a few Nokia N810 tablets (which have a prism chipset). Specially the Nokias are actually messing up the network, when I put them together. They just dont seem to figure out how to syncronize to the same BSSID. These devices are all on the same room, in close range.
I read this http://wiki.villagetelco.org/index.php/Information_about_cell-id_splitting,_...
And they mentioned about some intermediate mode, called Pseudo-IBSS or AHdemo mode, which allows a device to set a static BSSID and it is supported by some drivers. I suppose we are talking about the same thing here, just not giving any names (?).
When you mentioned your EEE PC, which uses an Atheros chipset, did you also had to set a static BSSID to the same used in the mesh network you use?
regards,
Hi,
How about in the laptops / pcs that access the WRT54G, which makethe "infrastructure" of the mesh? What kind of adapters do you use on them?
I think Elektra made clear that the driver situation for mobile devices is much worse. We stopped promoting laptops as part of the network. Next to the driver issues we faced different OSes in different versions, firewalls, $security_software, wrongly configured routing daemons, confused ordinary users, etc. Instead we encouraged people to use the routers for meshing and normal managed networks for the laptops.
Regards, Marek
Hi,
Thanks for the information. At least now I have some backgroundto work on - I already have several rt73 USB dongles, some notebooks with Atheros, some OpenMokos (which have atheros chipsets) and a few Nokia N810 tablets (which have a prism chipset).
although the Openmoko Freerunner has an Atheros chip inside it does not use the madiwifi driver (this is the AR6001 mobile chip, in case you wonder).
And they mentioned about some intermediate mode, calledPseudo-IBSS or AHdemo mode, which allows a device to set a static BSSID and it is supported by some drivers. I suppose we are talking about the same thing here, just not giving any names (?).
AHdemo is not the same as setting the BSSID in ad-hoc mode manually. As mentioned on the page you linked to the AHdemo mode does not send any beacons. Whereas the ad-hoc mode sends beacons with a fixed BSSID. Not sending beacons has certain side effects: - your network will appear being "invisible" (the normal network manager wont show it) - you have to manually configure the connection speed and other stuff as the usual autonegotiation is using the beacons for that - you will have collisions (might lead to decreased performance) - driver compat problems (only a few drivers support this mode)
Nevertheless, it will fix your cell split problem. :-)
When you mentioned your EEE PC, which uses an Atheros chipset,did you also had to set a static BSSID to the same used in the mesh network you use?
I think EEE PC uses the madwifi driver?! If so you can set the BSSID statically.
Regards, Marek
Hi -
some EEE PC models use a Atheros mPCI wireless card (the 701 for example) but my 901 was shipped with a Ralink rt2870 (802.11 abgn) that I replaced with an Atheros abg card ASAP...
Actually I'm using Ahdemo mode in my EEE-PC which works nicely together with other devices with 'normal' IBSS-mode but fixed IBSS-ID - in our local mesh we use Madwifi with OpenWRT patches and Broadcom-based devices (WRT54G/GL/GS, Asus WL500GP) with OpenWRT Whiterussian and Broadcom proprietary driver with fixed IBSS-ID hack (Freifunk Firmware).
Rate adaption with the Ministrel algorithm works well in Ahdemo mode - and you have the possibility to set up a AP VAP on the same interface, too.
Performance is fine. That may be different if you run a Ahdemo-only network in range with other wireless networks - they won't detect collisions, hence performance can suffer.
Cheers, elektra
Hello Marek, Elektra,
Thank you very much for the information.
By the way, I think you guys are involved on that book project about community wireless networks, hosted at WNDW.net. I'm from Brazil, and I have noticed that the only translation available is to the first edition, but the book seems to be on its thrid edition actually.
I'd be interested to cooperate on the translation of the book, as I intend to use them on my classes and also I intend to start some community network projects where I live. Do you know who should I contact in order to help on the translation?
regards,
2009/2/8 elektra onelektra@gmx.net:
Hi -
some EEE PC models use a Atheros mPCI wireless card (the 701 for example) but my 901 was shipped with a Ralink rt2870 (802.11 abgn) that I replaced with an Atheros abg card ASAP...
Actually I'm using Ahdemo mode in my EEE-PC which works nicely together with other devices with 'normal' IBSS-mode but fixed IBSS-ID - in our local mesh we use Madwifi with OpenWRT patches and Broadcom-based devices (WRT54G/GL/GS, Asus WL500GP) with OpenWRT Whiterussian and Broadcom proprietary driver with fixed IBSS-ID hack (Freifunk Firmware).
Rate adaption with the Ministrel algorithm works well in Ahdemo mode - and you have the possibility to set up a AP VAP on the same interface, too.
Performance is fine. That may be different if you run a Ahdemo-only network in range with other wireless networks - they won't detect collisions, hence performance can suffer.
Cheers, elektra
B.A.T.M.A.N mailing list B.A.T.M.A.N@open-mesh.net https://lists.open-mesh.net/mm/listinfo/b.a.t.m.a.n
Hi Breno -
thank you for your interest in supporting WNDW translations. Please keep in mind that this is off-topic for the Batman list. I'd like to redirect you directly to the forums of the WNDW page: http://forums.wndw.net/ The main editor of the English WNDW book and maintainer of the WNDW web site is Rob Flickenger.
Cheers, elektra
b.a.t.m.a.n@lists.open-mesh.org
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Breno Jacinto -
elektra -
Marek Lindner -
Simon Wunderlich