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nikolas
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Joined: Mon Apr 27, 2009 5:32 pm

latency on speed over 2Mbps

Fri May 15, 2009 12:28 am

Hello,

I got RB411A with R52H card on 2.4GHz with 8db omni antenna. I got RouterOS v3.23 and current firmware 2.20.

I got 3 AP's in static WDS and 6 clients connecting to my AP and usually the latency is 3-6ms, but the strange thing is when some of the clients starts some downloads and the speed goes over 2Mbps the latency starts to jump over 100ms there is even packet loss. The latency is not just for the client that is downloading but for all wireless clients. 1 client is going over 2Mbps and all wireless clients are effected.

I've tried everything, changing channels, set fragmentation even to 256, dynamic ack, manual ack, enabled/disabled wmm, lowered the power to 17dbm but nothing worked. i can see around 60 AP's when i scan the network most of them are on 1,6,11 so i tried channel 3, 9 and now I'm on 13(only 2AP's using 13) so I think it's not noise from other AP's.

I don't have spectrum analyzer to check if there are some other devices that are making noise. I've found AirMagnet Laptop analyzer but i don't know if it will scan other then wireless devices. The Mikrotik Frequency Usage is showing very low % of usage on the channels I'm using only 2-3 with noise around -100.

I can't activate Nstream because all the clients are not Mikrotiks.

Here are my current wireless settings:

set 0 ack-timeout=dynamic adaptive-noise-immunity=none allow-sharedkey=no antenna-gain=0 antenna-mode=ant-a area="" arp=enabled band=2.4ghz-b/g \
basic-rates-a/g=6Mbps,9Mbps basic-rates-b=1Mbps,2Mbps,5.5Mbps,11Mbps burst-time=disabled comment="" compression=no country=no_country_set \
default-ap-tx-limit=0 default-authentication=yes default-client-tx-limit=0 default-forwarding=no dfs-mode=none disable-running-check=no disabled=no \
disconnect-timeout=1s frame-lifetime=0 frequency=2457 frequency-mode=manual-txpower hide-ssid=yes hw-fragmentation-threshold=disabled hw-protection-mode=\
cts-to-self hw-protection-threshold=0 hw-retries=15 mac-address=00:0C:42:26:81:54 max-station-count=2007 mode=ap-bridge mtu=1500 name=wlan1 \
noise-floor-threshold=default on-fail-retry-time=1s periodic-calibration=disabled periodic-calibration-interval=60 preamble-mode=both \
proprietary-extensions=post-2.9.25 radio-name=000C42268154 rate-set=configured scan-list=default security-profile=default ssid=stress \
station-bridge-clone-mac=00:00:00:00:00:00 supported-rates-a/g=6Mbps,9Mbps,12Mbps,18Mbps,24Mbps,36Mbps,48Mbps,54Mbps supported-rates-b=\
1Mbps,2Mbps,5.5Mbps,11Mbps tx-power=20 tx-power-mode=all-rates-fixed update-stats-interval=disabled wds-cost-range=50-150 wds-default-bridge=bridge1 \
wds-default-cost=100 wds-ignore-ssid=yes wds-mode=static wmm-support=disabled

If anyone has experienced similar problem i would like to now if you have fixed and how.

Regards,
Nikola
 
RK
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Posts: 560
Joined: Tue Nov 21, 2006 11:22 am
Location: Winnipeg, Canada and Central America

Re: latency on speed over 2Mbps

Fri May 15, 2009 1:02 am

Try setting your system to run in b only (instead of b/g).
Also, set output power to default and hw-retries to 4.

However, the real problem is too much noise.
You deal with that by using a more directional antenna and/or frequency (like 5 GHz).
You could try channel 14, if it's legal where you are.
 
nikolas
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Joined: Mon Apr 27, 2009 5:32 pm

Re: latency on speed over 2Mbps

Fri May 15, 2009 2:03 am

Thanks RK for your fast answer. I was thinking noise also because the there are a lot of wifi devices from the local telco here. With the adsl connection they offer they gave wifi routers cheap so everyone is getting them instead of simple router or a modem.

I'll see how B mode only will work but as i can see the CCQ bumped to 95-100 and it was dropping down too much with my previous configuration. I'll see tomorrow when my traffic goes up.

Channel 14 is not legal here and channel 13 has much more traffic. Those 2 AP's that are on that channel ware getting away from other AP's but they make too much traffic. I'll try to find some channel that is not used too much.

My plan is to go on 5GHz because as i wrote above there are too many 2.4GHz devices around.

Sorry one more question. Should i set B only on all devices or just the Mikrotik AP?

Regards,
Nikola
 
RK
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Posts: 560
Joined: Tue Nov 21, 2006 11:22 am
Location: Winnipeg, Canada and Central America

Re: latency on speed over 2Mbps

Fri May 15, 2009 7:04 am

Setting B only on the AP should be enough.

Channel 1, 6, and 11 are the only ones worth trying.
The other channels overlap with the above.
 
marceloru
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Posts: 47
Joined: Tue Jul 08, 2008 12:00 am
Location: Argentina

Re: latency on speed over 2Mbps

Sat May 23, 2009 8:18 pm

say that a customer downloading 2 Mbits generates latency, which is the total traffic at the AP in that time? 2.4 GHz in B-mode gives you a maximum of 3.5 Mbits in AP with 24 stations aprox, 2.4 ghz G can traffic 5 - 15 Mbit to 24 clients (usually)
 
nikolas
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Re: latency on speed over 2Mbps

Mon May 25, 2009 3:06 am

Hello marceloru,

I was getting high latency on all clients when only one client goes over 2Mbps and total wlan traffic is around 2Mbps + some small 20-30Kbps from other clients.

I got too low traffic 3.5-4Mbps when i put my network only in B mode, and now i want to try to support only 6Mbps, 9Mbps and 12Mbps in G mode and lower the client rate to 12Mbps max. i think if i lower the client rates i will get better CCQ am I right?

So this way will I be able to get 5Mbps from client and get over 10Mbps total wlan traffic?

I use to be able to get 12-14Mbps from client supporting all G mode rates, but this was few months ago when there was not that much AP's around.

I'll try this settings for some time and see if i will be able to get good results in G mode as they ware in B mode.

Regards,
Nikola
 
nikolas
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Posts: 12
Joined: Mon Apr 27, 2009 5:32 pm

Re: latency on speed over 2Mbps

Mon May 25, 2009 4:05 pm

And problems are back again. Set my wifi card to B/G mode and the huge latency with packet loss and low CCQ's are back.

So I'm setting my network to B mode for now and and moving over to 5GHz.

I think there is nothing else to do.

Regards,
Nikola
 
titius
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Joined: Mon Oct 17, 2005 11:43 am
Location: Titel Serbia

Re: latency on speed over 2Mbps

Mon May 25, 2009 4:47 pm

say that a customer downloading 2 Mbits generates latency, which is the total traffic at the AP in that time? 2.4 GHz in B-mode gives you a maximum of 3.5 Mbits in AP with 24 stations aprox, 2.4 ghz G can traffic 5 - 15 Mbit to 24 clients (usually)
You say one can run 24 clients at 3.5 Mbps at the same time i B mode?

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