Hi! Community networking initiatives (like Freifunk/Funkfeuer and many others in developing countries like Air Jaldi in India) are running now large scale layer 3 meshes (up to 800 mesh nodes in a single IBSS cell). A problem has always been the stability of the ad-hoc mode in large ad-hoc cells. Typical problems are steady TSF timestamp skews, MAC timer skews and subsequent lockups, failed or endlessly repeating IBSS merges to the same cell and hence IBSS cell-splits. Currently there is only one open-source driver (not entirely open-source because of the binary HAL blob) which is up to the challenge of such networks - Madwifi (Not the vanilla code from madwifi-project.org, but the patched Madwifi from OpenWRT Kamikaze maintained by OpenWRT developer Felix Fietkau). It would be great to have a few drivers in the kernel that are up to the challenge, too. Hence this is a feature request. Let me explain what has been done to Madwifi to cope with the problems. Madwifi can be forced to bypass IBSS merges and stick to a certain IBSS-ID by issuing a command like: iwconfig athX ap 02:CA:FF:EE:BA:BE This was not sufficient to fix stability problems with Madwifi, as TSF time stamp skews were still messing up a hardware timer related to the ATIM window which caused stuck beacons/stuck transmit queues. The workaround for Atheros was to switch the hardware into AP mode so it doesn't try to adjust its hardware timers to TSF time stamps. Hence beacons have to be generated in software which is not precise enough. (IMHO TSF time stamps are pretty much superfluous in adhoc mode because I guess we can savely forget about power saving mechanisms in a large scale mesh cloud anyway, I propose to deliberately let software generated beacons lag behind the TSF time stamps in order to avoid confusing other ad-hoc peers) If someone wants to experiment with Madwifi in this mode, create the adhoc VAP with the "nosbeacon" option. (Example: wlanconfig ath0 create wlandev wifi0 wlanmode adhoc nosbeacon) So these wireless mesh communities have at least one perfectly working solution for wireless interfaces for Atheros SoC/PCI/PCI-E devices( well, almost perfect because of the timer precision issues). It would be great if ath5k and ath9k could be used in the same way, too. We are lacking support for at least one USB chipset as well. Zydas/Atheros 5007UG would be great. USB would open up the opportunity to connect desktop PCs to mesh networks at low cost / build cheap mesh supernodes (routers with more than two wireless interfaces). It would be awesome to use USB devices, because USB dongles could be easily built into the antennas and save the cost and RF losses of expensive pigtails/RF-plugs/RF-cables. Interfaces usually placed in close proximity on one motherboard and thus all interfering with each other could be seperated up to 10 meters away from each other. Antenna/USB-WLAN<--------------5m USB cable -------------> Router <--------------- 5m USB cable -------------> USB-WLAN/Antenna Cheers, Elektra -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
