Thread: [Madwifi-devel] Madwifi Soft MAC
Status: Beta
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From: Rodolphe M. <rod...@ua...> - 2009-04-29 17:29:09
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hi all, Can someone help me understand why can't I have more than one STA in the same physical interface? Why can I have more than one ap but I can only have one STA? Would it be possible to implement a soft mac solution were everything was done in kernel space, and the drivers would implement only the basic primitives like tx and rx? Best Regards Rodolphe Marques |
From: Alfred A. <al...@cc...> - 2009-04-30 10:00:40
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Hi, >Can someone help me understand why can't I have more than one STA in the >same physical interface? >Why can I have more than one ap but I can only have one STA? Don't forget you only have one physical radio. A STA's nature is to associate to an AP, on a channel dictated by the AP. If the APs operate on different radio channels, you would have a problem because the radio can only be programmed for one channel. So this could only work reasonably if the the APs the different 'VSTAs' associate to are operating on the same channel, a scenario you typically want to avoid for bandwidth and performance reasons... In my wildest dreams, I could imagine a STA 'switching' the single radio among the channels of its different APs - each time it switches away from a channel, it tells the respective AP that it entered power save mode so the AP buffers incoming traffic until the station comes back. That would however incur a lot of software overhead and anything else but good performance. On the PA side, the scenario is different because the AP dictates the radio channel - so all VAPs (and all the stations associated to the VAPs) simply operate on the same one... Best regards Alfred Arnold -- Alfred Arnold E-Mail: al...@cc... Computer Club at the http://john.ccac.rwth-aachen.de:8000/alf/ Technical University Phone: +49-241-406526 of Aachen Fax: +49-241-406527 |
From: Eric W A. <Eric.Anderson@Colorado.EDU> - 2009-04-30 16:19:14
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A few people have done things pretty close to what you describe: See for example FatVAP (http://nms.lcs.mit.edu/~kandula/projects/fatvap/). Thus spake Alfred Arnold (al...@cc...): > Hi, > > >Can someone help me understand why can't I have more than one STA in the > >same physical interface? > >Why can I have more than one ap but I can only have one STA? > > Don't forget you only have one physical radio. A STA's nature is to > associate to an AP, on a channel dictated by the AP. If the APs > operate on different radio channels, you would have a problem because the > radio can only be programmed for one channel. So this could only work > reasonably if the the APs the different 'VSTAs' associate to are operating > on the same channel, a scenario you typically want to avoid for bandwidth > and performance reasons... > > In my wildest dreams, I could imagine a STA 'switching' the single > radio among the channels of its different APs - each time it switches away > from a channel, it tells the respective AP that it entered power save mode > so the AP buffers incoming traffic until the station comes back. That > would however incur a lot of software overhead and anything else but good > performance. > > On the PA side, the scenario is different because the AP dictates the > radio channel - so all VAPs (and all the stations associated to the > VAPs) simply operate on the same one... > > Best regards > > Alfred Arnold > > -- > Alfred Arnold E-Mail: al...@cc... > Computer Club at the http://john.ccac.rwth-aachen.de:8000/alf/ > Technical University Phone: +49-241-406526 > of Aachen Fax: +49-241-406527 > > > ------------------------------------------------------------------------------ > Register Now & Save for Velocity, the Web Performance & Operations > Conference from O'Reilly Media. Velocity features a full day of > expert-led, hands-on workshops and two days of sessions from industry > leaders in dedicated Performance & Operations tracks. Use code vel09scf > and Save an extra 15% before 5/3. http://p.sf.net/sfu/velocityconf > _______________________________________________ > Madwifi-devel mailing list > Mad...@li... > https://lists.sourceforge.net/lists/listinfo/madwifi-devel -- Eric W. Anderson University of Colorado eri...@co... Dept. of Computer Science phone: +1-720-984-8864 Systems Research Lab - ECCR 1B54 PGP key fingerprints: personal: 1BD4 CFCE 8B59 8D6E EA3E EBD5 4DC9 3E61 656C 462B academic: D3C5 D6FF EDED 9F1F C36D 53A3 74B7 53A6 3C74 5F12 |
From: Rodolphe M. <rod...@ua...> - 2009-04-30 12:19:54
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Alfred thanks for your comments. I know that it would be very difficult to have more than an STA in the same radio if they were using different channels. What I'm trying to do is just a simple prototype were I can have more than one virtual STA in the same radio and in the same channel. I'm working in cross-layer anonymity and I goal is to create to sessions to two different services in the same interface, but it would look like to diferent terminals to the network. That's why I want more than on virtual STA in the same radio (in the same channel to make things simple). If you think this is feasible (two VSTA same channel) and have some sugestions in the driver I should modify (0.9.4 ath5k or ath9k) that would be great. I only have experience with the 0.9.4. Best Regards Rodolphe Marques Alfred Arnold wrote: > Hi, > > >> Can someone help me understand why can't I have more than one STA in the >> same physical interface? >> Why can I have more than one ap but I can only have one STA? >> > > Don't forget you only have one physical radio. A STA's nature is to > associate to an AP, on a channel dictated by the AP. If the APs > operate on different radio channels, you would have a problem because the > radio can only be programmed for one channel. So this could only work > reasonably if the the APs the different 'VSTAs' associate to are operating > on the same channel, a scenario you typically want to avoid for bandwidth > and performance reasons... > > In my wildest dreams, I could imagine a STA 'switching' the single > radio among the channels of its different APs - each time it switches away > from a channel, it tells the respective AP that it entered power save mode > so the AP buffers incoming traffic until the station comes back. That > would however incur a lot of software overhead and anything else but good > performance. > > On the PA side, the scenario is different because the AP dictates the > radio channel - so all VAPs (and all the stations associated to the > VAPs) simply operate on the same one... > > Best regards > > Alfred Arnold > > |
From: Pavel R. <pr...@gn...> - 2009-04-30 16:41:02
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On Thu, 2009-04-30 at 13:19 +0100, Rodolphe Marques wrote: > Alfred thanks for your comments. > > I know that it would be very difficult to have more than an STA in the > same radio if they were using different channels. > What I'm trying to do is just a simple prototype were I can have more > than one virtual STA in the same radio and in the same channel. > I'm working in cross-layer anonymity and I goal is to create to > sessions to two different services in the same interface, but it would > look like to diferent terminals to the network. That's why I want more > than on virtual STA in the same radio (in the same channel to make > things simple). > > If you think this is feasible (two VSTA same channel) and have some > sugestions in the driver I should modify (0.9.4 ath5k or ath9k) that > would be great. I only have experience with the 0.9.4. I suggest that you do it with ath5k or ath9k. Chances are, all or most of the changes will be done in the common mac80211 code, which will make your code usable for other chipsets. -- Regards, Pavel Roskin |