On Mon, 2005-01-31 at 10:00 -0500, Dan Williams wrote: > On Sun, 2005-01-30 at 17:11 -0500, Sven wrote: > > NetworkManager does not work well with my mini Atheros abg card. it can > > associate ok, but then roughly every minute it looses the connection and > > the card is scanning/cycling through all channels for about 10 secs or > > so. during that time iwconfig gives "FF:...:FF" as the AP. it cycles > > through the channels 3 times, and the associates with the original AP > > again. > > Sven, > > Ok, I took a look with this card. The behavior you're seeing is pretty > much expected, that's the card running its wireless scan so we can > update our list of access points. The thing you may not be aware of is > that the card supports so many frequencies that it takes a _long_ time > to scan all the channels (somewhere around 10s it seems, from this > card). Obviously, since the card isn't associated during that time, it > cannot send or receive traffic. > > Some observations: > > 1) NetworkManager starts with a 20s scan interval, and if the aggregate > list of access points does not change with each successive scan, it > backs the scan interval back to 60s. If the list changes (an AP drops > off after the 2m "last seen" check, or a new one appears), the scan > interval jumps back to 20s. > IMHO this is a lot of scanning & disconnection from the AP. I forced the card in b-mode only, and it's still scanning and disconnecting for ~4s every 60s.
> 2) Since the card takes so long to scan, and since no traffic can flow > during the scan, it doesn't work very well from a user's perspective. Word! what bothers me most is the "dead time" of disassociation. > 3) I don't mind tuning the scan algorithm. I can figure out how many > channels the card supports, and if its over 14 that means its an a/b/g > card right now. I then know that it will take a while to scan, since > the time that a card must remain on a channel to sense the AP's beacon > does have a lower bound (a couple hundred ms, something like 150ms - > 200ms). Perhaps if the card is an a/b/g card, I should step the scan > interval back 20s rather than 10. whatever works... i'm just a user ;-) > 4) There are smarter ways of doing this. For example, no card will do > well with streaming video/audio when scanning. So perhaps > NetworkManager should monitor the amount of traffic on the card, and if > its above a certain level, then put off the scan. If more than 4 scans > (for example) have been deferred, then force a scan at the next > interval. This would mean far fewer interruptions. I assume the kernel > has some way of relaying traffic statistics to us. not just audio streaming. i ssh a lot, and scanning time means dead time. > There are really just two things to consider. We can't _never_ scan, > and we can't always scan. We need to find some algorithm for NM of > balancing the two, and make that algorithm tunable on-the-fly. We want > to do a few scans on startup of course, to build the initial list. And > perhaps we want to scan more often when the card isn't in use or when > its not associated, for example. it seems to me that if the card is connected to an AP, it should not try to scan that much/often unless the user wants it to. > I think I've got a few ideas on how to do this, but at the moment there > are a few other things that need to get done first... Patches would be > accepted though. If you'd like to file a bug at bugzilla.gnome.org or > bugzilla.redhat.com just to keep me reminded, that would be helpful. > Say something like "RFE: Tuneable scanning algorithm". done. thanks, Sven _______________________________________________ NetworkManager-list mailing list NetworkManager-list@gnome.org http://mail.gnome.org/mailman/listinfo/networkmanager-list