Slow file transfert on 2802i but not on 2702i

[franckehret]

Dear all,

I'm a bit stuck with a small environment setup.

My current setup is a single 2702i in autonomous mode.

The productive SSID is in 5GHz only and the security is WPA2 Enterprise with NPS authentication.

My "test" notebook" is a Macbook pro. I'm testing is 2-3 meters away from the AP. I connect at approx 866 Mbp/s stable. When I transfer files to my NAS, I get a stable throughput of approx 250 Mbp/s every single time.

Now, I wanted to extend a little bit the network range and I bought 2x2802i to create an HA controller fail-over and keep my 2702i as a 3rd lightweight AP. I started configuring the first AP to act as the main controller and configured "exactly" the same settings for the wireless (at my level, which means I I'm not a wireless guru). To do my tests, the new 2802i was always used alone and at the same place as the 2702i as I wanted to be sure I can have the same quality of service. Same device, same location, same amount of files and same connection speed :  I can only get 3 times less throughput (max 80 Mbp/s), which is not really meeting the expectations for that hardware.

One thing is : the new AP with integrated controllers have a nice and shiny web interface, but there is way less to configure. I'm not a SSH console fan

There might a subtle setting that could interfere, but until now I wasn't successful finding it as it could be only available in SSH console...

Where should I start to troubleshoot that ? Any help would be highly appreciated !

[franckehret]

PS : None of the builds upgrade solved the issue, so it must be definitively a configuration issue (8.3, 8.4, 8,5 and 8.6 same results)

[Leo Laohoo]

When doing the comparison test, was the 802.11b radio (physical) enabled or disabled?  

What data rates are enabled on the APs? 

How did you check the speed?  Did you use speedtest.net or fast.com? 

Cable link speed status of the 2800 at 1Gbps/Full duplex without any line errors?

[franckehret]

Hi Leo, thank you for your reply.

Here are my answers :

When doing the comparison test, was the 802.11b radio (physical) enabled or disabled?  
Enabled on both APs

What data rates are enabled on the APs? 

I admit I don't know, I didn't change the default settings.

How did you check the speed?  Did you use speedtest.net or fast.com? 

I checked on Macbook's equivalent of task manager. File transfer was flat and stable so I could measure it. But as a matter of facts : my file transfers takes 3X more time at least with the 2802i. I should still measure in on a Windows machine.

Cable link speed status of the 2800 at 1Gbps/Full duplex without any line errors?

1 GB/s full duplex, no error (re-checked the last time with v8.6). The cables themselves are the same : I just unplug one AP and put the other for the test.

[patoberli]

Make sure you have made the channels 80 MHz wide on the 5 GHz interface, for fastest possible speeds. Not sure if this enabled by default on the Mobility Express models. It isn't on the WLC based ones. You could also do 160 MHz channels, but most clients don't support this additional speed, so for the moment you can leave that as it is. There are also way more channel overlapping issues with 160 Mhz.

[Bernhard82]

What is your RSSI /SNR of the connect device?

is there any other devices associated on the 5GHz radio

what is the RF spectrum like in your area, many rogue networks being detect by the Master AP using the same channel or overlapping channels?

[franckehret]

Hi,

So I made further tests :

Make sure you have made the channels 80 MHz wide on the 5 GHz interface, for fastest possible speeds

Yes it was already on 80Mhz. I agree, 160 Mhz is not an option.

What is your RSSI /SNR of the connect device?

is there any other devices associated on the 5GHz radio

what is the RF spectrum like in your area, many rogue networks being detect by the Master AP using the same channel or overlapping channels?

I didn't check the RSSI/SNR yet. Yes there is other devices, during my tests, one Windows and one MAC were connected on it. In the 5Ghz, I don't have rogues & overlapping channels.

On a general basis : the 2702i doesn't have that problem and channels are setup the same.

As an update : I tested same behavior with a Windows machine as well, so it doesn't seems to be platform related : Windows machine was "only connected" at 390 Mbp/s (Compared to the Macbook between 866 and 1300 Mbp/s)  but I could still measure 3X less real file transfer throughput.

Aside, I found this interesting article but I would like to check with you guys if one of you had to change something on his APs : https://supportforums.cisco.com/t5/other-wireless-mobility-subjects/packet-loss-on-2800-ap/td-p/2931989
It concerns maximum packet length and overhead of a controlled AP.

Any thought ? :-)

[Bernhard82]

Your data rata throughput will vary depending on what the other clients are doing on the network, as wireless is half duplex only one device gets access to the medium at time. are all other clients on the other AP? if not this will affect results

[franckehret]

Hi,

I'm doing the tests only with one AP or the other model. Clients location doesn't change for the testing and I do the tests when only these 2 clients are connected. Also, I only start a test file copy on one client at a time, so one can not affect the other.

On 2802i I get only the third of throughput compared to the 2702i.

[patoberli]

Can you check on the switch if the AP is indeed connected with 1 Gbps and that there are no interface errors?



You could also try iperf.fr, that's a really good tool to test the real throughput (use TCP tests).

[pwwiddicombe]

Are you sure the 2802i is getting enough power?  it may be running in a "degraded" mode if you don't have PoE+ capable of supplying a full 30 watts to the AP.  Several generations of Cisco AP will drop features if  you don't have enough...