On Fri, 2007-11-23 at 10:03 +0100, Holger Schurig wrote: > > Orinoco relies on roaming in the firmware > > And wlags_h1_cs/wlags_h2_cs as well. > > libertas_cs has half-baked roaming in firmware and in > kernel-space, doesn't work very well so far. > > Madwifi has code coarse code roaming in the BSD borrowed > ieee80211 code. It roams only when it lost the association to > the current AP. But before doing that, it went with it's rate > down to 1 MBit/s, even when there's a better AP nearby that it > could use with 11 MBit/s or higher. > > There is code in it which is disabled via "if (0 || ...)" that > allows for a much smoother roaming, e.g. to scan when the RSSI > drops below a certain level. Once enabled and after tuning of > some timeout variables, that roaming code works extremely well. > Both in a WEP-mode without wpa_supplicant and in WPA/WPA2 mode > with wpa_supplicant. > > > > wpa_supplicant gives you roaming in the userspace. > > Yeah, I thought in this lines as well. I have no problem putting > wpa_supplicant on my embedded targets. In fact, it's already > there, it's currently just used for WPA, not for WEP. However, > if suddenly NetworkManager would be needed for roaming, then > from an embedded-usage point of view I wouldn't like that. The problem is, roaming and choosing which AP/BSSID to connect to is pretty complicated. It depends on user preferences, scan results, RSSI, and other stuff like that. It depends on having the necessary security information (keys, PIN, EAP certs, etc) available. wpa_supplicant must run as root to be able to drive the wifi device, and many of these settings are user-specific; so there has to be some mechanism to push those settings down to wpa_supplicant. You could potentially use wpa_supplicant to do what you want, based on network block priorities and turning network blocks on/off dynamically through the control interface. Right now, NetworkManager just pushes _one_ network to wpa_supplicant, the network NM wants to association with. I can imagine further down the line pushing more of the decisions onto wpa_supplicant. But wpa_supplicant seems (to me) to still have quite a few assumptions about static configuration, which is traditionally how it's been used. In any case, the trend with NM is pushing more and more of the Wifi stuff down to wpa_supplicant and to make NetworkManager be more of a policy engine that handles many different device types, from wired to wireless to GSM/CDMA broadband cards to Bluetooth DUN. Dan - 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
