ANI weirdness

[Ulric]

Not sure if this is the right place for this, if not, please move it

Over the past 2 months, I've experimented with ANI on 3 different routers, in a high interference environment, ANI helped all 3, in a low interference environment, ANI caused 2 routers to drop clients, the remaining router had no problems with ANI being enabled.

Turn ANI off, all 3 routers dropped clients when in a high interference environment, but when in a low interference environment, all 3 routers held connections.

Based on my limited testing, I'm starting to think ANI should be enabled when interference is fairly high, but disabled at other times.

The noise floor here is -58dbm, txpower was SNR is 16 throughout the tests (adjusted TX power at client to ensure SNR of 16), with ANI, link quality was 48/70, without ANI, it was only 11/70. I moved the tests down the road a few miles at a friend's house, the noise floor was -80dbm, ANI caused 2 routers to drop connections (maybe ANI is too aggressive with settings on some routers?), while the other showed the same results with or without ANI.

Being the network admin at the apartments, I can change the noise floor a little with the main network by means of setting it's txpower since it has a rubbish amplifier (set it too high = insane noise floor, lower it = barely any noise)

I'd make a patch to dynamically enable/disable ANI on a case by case basis, but I have very little knowledge of the inner workings of wireless drivers.

[Ulric]

After 5 days of capturing packets and messing with different settings on my router and wireless card (Now an atheros card so I can experiment with ANI on both ends), I believe I've discovered the problem: WPA/WPA2 and ANI don't mix... WEP works fine with it (but being already broken, stay away from it!). I think ANI thinks group key renewal is noise. What leas me to believe this is the fact that group key renewal was ALWAYS occuring when ANI triggers. I've tried everything from 5 minutes to 24 hours for group key renewal, the link ONLY drops when the keys get renewed when ANI is enabled. Disable either ANI or encryption (or set encryption to WEP) and the link remains stable.

Tested with a WZR-600DHP running Gargoyle 1.6.1 and 100+ different clients, 2 known:
Intel Centrino Advanced Wireless N 2230
Atheros AR5BHB92 (Chip is AR9280)

The two known clients are actually one laptop, the wireless card was replaced since my Intel card was beginning to have tx power issues (kept dropping to 1dbm, no way to recover for hours at a time). From card replacement, testing occured on both 2.4GHz (CH6) and 5GHz (CH149) to isolate effects of other networks on testing.

20/40HT-/40HT+ does not matter, only ANI + WPA/WPA2 matters.

AP + client with ANI enabled on both sides drops more often than ANI only being enabled on one side as long as WPA/WPA2 is also enabled, open networks/WEP encrypted networks show no signs of wifi drop outs, even with 250GB file transfers over ftp.

As this router is being used an a public wifi hotspot, it is naturally open, and ANI helps with connection speeds considerably (54-108 Mbps average with ANI vs 18-36 Mbps without ANI). Users have also reported that throughput is better at times that ANI was enabled and almost unusable at times it was disabled.

And sorry my post is so scrambled, I'm a bit pressed for time because I'm fixing a few routers for other people and only writing in my waiting time... Hope this sheds some light on the problem for developers to hopefully fix it

[Ulric]

Ok, ANI on STA's side appears to be good, but on AP's side, it appears to be bad. My previous findings with an open network were messed up by NetworkManager on my laptop, when the wifi dropped, it automatically reconnected on a decrypted network, but when encrypted, it never knew it had been dropped.

Anyway, AP with ANI + STA without ANI = dropped wifi when under any load at random intervals

AP with ANI + STA with ANI = dropped wifi, at much shorter intervals

AP without ANI+ STA without ANI = good throughput at close to medium range, bad throughput at long range, pretty stable connection except at far edges of coverage.

AP without ANI + STA with ANI = slightly lower throughput and signal quality at short range, medium to long range throughput and signal quality better (about 30% in my tests)

Conclusion: keep ANI disabled on APs and STAs at short range and enable it on STAs that are at medium to long range.

Will retest when a BB build of gargoyle is released as BB has many ANI patches (said to help fix AP side, but I have not tested them yet)

[Ulric]

Ok, got OpenWRT BB running on my router, it's rock solid stable even in a very noisy wireless environment, the motel where I'm currently staying has an AP, a wireless router, and my router, and 16 different networks from the neighbors, all running on overlapping channels. My router is a client to the AP so I can get internet access, my router also broadcasts my private network as well as a public guest network to help cover the dead spots for the other guests.

Network hardware is as follows:
Main router: Actiontec GT784WNV (Ch 1 HT40-)
Main AP: EnGenius ENS202EXT (Ch 11 HT40-)
My router: Buffalo WZR-600DHP (Ch 11 HT40- / 149 HT40+)
My laptop: Dell Inspiron-5521 with an Atheros AR9280 (AR5BHB92)

Forcing my wireless card to 2.4 GHz, I can still have 12-26 Mbps actual throughput with ANI (the max my wireless card can manage under any conditions, not sure why though), vs 2.5 Mbps maximum throughput without ANI. The wireless drops are completely gone (Transferring 26 GiB of files from my HDD on the router as I type this.) Ping times are very good given the conditions my network is under (98% channel load, 12ms pings to the router).

The main AP, my router, and my laptop all use ANI, throughput is much better now that ANI is working correctly.

Hope this info helps someone

[Ulric]

Just switched back to my Intel Centrino 2230, the ANI problem showed up worse than it ever did on AA now that I'm on BB. When using Atheros based STAs, the problem is fixed, with my Intel STA, it's worse. I should be getting a newer wireless card soon though, I'll post again when I do.

edit: This post is incorrect, I later attempted to use my Intel STA on a different network that is Broadcom based, my STA still dropped the connection. I believe I have a failing card.