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80211n with just 60 mbit per second

Frank Lindner
Level 1
Level 1

Hello there,

we have a Cisco 2106 WLC with software version 5.1.151.0 and 2 LAP1252.

Everything is enabled for 802.11n, an Intel 4965 client is connecting correctly, shows that 300 mbit per second. But the real throughput (with the iperf-tool) is just 60mbit/s.

The client is working in 802.11a frequency-band and 40 mhz channel bandwidth. all 11n rates are enabled.

now the questions: what's wrong with it? did we forget something?

thanks for your answers.

greetings from germany

Franky

1 Accepted Solution

Accepted Solutions

How are you testing the throughput? You will have different results if you test between a wired client and a wireless client (best in this case) or between two wireless clients.. Also you will have better results if you use UDP or if you open several connections..

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27 Replies 27

dancampb
Level 7
Level 7

Keep in mind that with a 2106 controller you are going through a 10/100 port. The traffic goes from the AP to the controller, is unencapsulated, and put out on the wire. So basically the 10/100 port on the controller will be a bottleneck. You may want to try putting the AP in H-REAP mode and locally switching that WLAN. That way the traffic wouldn't have to got through the controller.

Hi there, thanks for your response.

I allready activated this, so traffic isn't sent to the controller. I checked this also with wireshark and a mirrored port on the switch.

How are you testing the throughput? You will have different results if you test between a wired client and a wireless client (best in this case) or between two wireless clients.. Also you will have better results if you use UDP or if you open several connections..

i use iperf in tcp-mode for testing. from a wireless client to a wired client. the traffic just goes from client to ap, from ap to switch, from switch to a pc.

tcp-mode in iperf puts maximum possible through the network.

your tip with serveral connections i will try this week.

thanks this time.

You'll never get anywhere close to the 300mbps over wireless. The number is sort of a "raw" throughput speed. Wireless protocol overhead will make a significant impact on that. For example, a single 802.11g client with a 54mbps connection to the AP will only show up as about 18 on iperf.

I'm not saying that 802.11n would suffer the same level of performance difference as 802.11g, but 54 raw/18 actual would work out to about 300 raw/100 actual if it were.

You also need to ensure you are operating in a "clean" wireless environment to achieve the best throughput in your tests (the best speed would be achievable only when there is one AP and one wireless client and nothing else using that frequency).

I think you're also losing some throughput due to the fact that you cannot enable 802.11n "Greenfield" mode, which means that the AP is still set to support 802.11a/g clients.

we have a clean environment, i prooved it with a spectrum-analyzer. in g-mode, i get something about 22 mbit/s und in a-mode 22 mbit/s too, sparely up to 23 mbit/s.

i also allready had disabled the datarates 1 to 54, but this doenst cange anything on the troughput. all interfaces, except the 5 ghz, are disabled. all tx and rx antennas are activated.

and i won't get 300 mbit/s. thats true, that this can't be reached. But up to 140mbit/s should be possible.

When I tested this a few weeks ago, I could not disable all the data rates between 1 and 54. One would always remain enabled, which meant my AP remained in "mixed mode" 802.11a/n. I confirmed this behavior with Cisco (I was using a 4402 with 5.2.x.x code).

I also cannot disable all the 1 through 54 data rates on an autonomous 1252.

i could disable all rates. i also updated from 5.1.x.x to 6.2.x.x (the newest version avaible) but also didn't made any changes

had a similar issue with disappointing data rates for 802.11n on a WLC 4404. i was filtering traffic on the WLC using ACLs and as soon as i removed these ACLs the data rates i got for 802.11n rose dramtically.

posted results on forum:

http://forums.cisco.com/eforum/servlet/NetProf?page=netprof&forum=Wireless%20-%20Mobility&topic=Security%20and%20Network%20Management&CommCmd=MB%3Fcmd%3Dpass_through%26location%3Doutline%40%5E1%40%40.2cc26b59/5#selected_message

ended up removing ACLs from WLC and filtering wireless VLANs elsewhere. Cisco responded saying that the ACLs on the WLC shouldn't introduce any latency but i tried this with a number of different software revs

hth

andy

thanks for your response.

if i don't make a misstake, you receive about 50mbit/s (54xxx kbit/s), right?

that is the same as i have in my environment. but i need to get a bit more. something around 100mbit/s. but i will have a look tomorrow on the ACL.

Thanks.

Frank Lindner
Level 1
Level 1

Thanks to everyone who helped me.

I made multiple TCP connections (best results with 8 parallel) and now i receive about 140 Mbit/s! Some peaks go up 153 Mbit/s. That's great and that's what i wanted.

I have a AP1252AG just installed and with ver 12.4. It has a 2.4GHz and a 5GHz module installed. With a single client next to it I get a 54Mbps Max. Could you explain what configuration needs to be done to get to where you said "Everything is enabled for 802.11n."

Thanks

Ken

On non controller based controller they are called MCS-rates 1 to 15. Its on same page on the webinterface, where you can enable and disable the a- or g- rates.

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