On Sunday, January 29, 2012 03:17:32 Daniel Halperin wrote: > Adaptive RTS/CTS is important to control for interference---RTS/CTS is > there so that other Wi-Fi devices know not to interfere with your > flow. It may well be the case that this is not a major problem in > whatever your scenario you're working, Marek, but it makes a big > difference in a many bad corner cases. I am very well aware of what RTS/CTS is for and I am not against using it. However, having the rate algorithm overriding the user setting for a specific rate is extremely hard to grasp or debug. To give you an understanding where I am coming from: In our networks we experienced extremely variable throughput ranging from 30Mbit/s (single stream) to 0.2 Mbit/s in the next second. As you can imagine we were trying to figure out what was going on. After spending some time and losing hair I noticed that the RTS/CTS implementation of our driver (ath9k) is buggy. Every once in a while the nodes would "battle" each other with RTS/CTS packets. Strange enough for us, sometimes no RTS packets were sent and sometimes they would battle. All attempts to disable RTS/CTS for the mere sake of testing(!) was impossible. First I thought ath9k did not properly implement the "iw rts" setting but that wasn't the case. After losing more hair I realized that minstrel_ht, a rate control algorithm(!), was overriding my rts settings but not always(!). The only way to make RTS shut up was to apply the posted patch. We should make a difference between the idea (using RTS to increase the reliability) and its implementation. No matter from which angle I look, the current implementation gives me much pain. > I'm with Felix: I could see adding an option that means "force never > use RTS/CTS" but I think we're at the right operating point when > interpreting the standard "RTS/CTS threshold" option. Actually, this option exists already. It's just minstrel_ht overriding it: iw phy <phyname> set rts <rts threshold|off> Put special attention towards the "off" at the end. If we let the rate algorithm override our rts settings it should at least be communicated. I found no such mention anywhere. I'd like to further stress the point that no other rate algorithm does this. We create incoherent and hard to debug behavior. Regards, Marek -- 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
