FlexConnect local switching slower than FlexConnect central switching?

[Mikolaj Moryto]

Hi,

I was wondering if anyone has seen it in their deployments. I have a simple network at home with 2702i AP being connected to the 3560G switch. ESXi server where I have vWLC (8.5.*) is connected to the same switch directly. 

What I observed is that I have slower network (throughput) when using FlexConnect local switching for my WLAN comparing to FlexConnect central switching. I would agree if that was opposite way. I have not run any intensive, detailed performance tests so I base that only on copying files from the file server VM which sits on the same ESXi server where vWLC is installed.

I sit quite close to the AP and Tx rate is 1300 Mbps. The reason why I prefer local switching is because I wanted to use Flex AVC and local switching must be enabled for that. It is quite fast so I do not complain, just wonder if anyone experienced that before.

Central switching:

Local switching:

Thanks,

Mikolaj

[Rasika Nayanajith]

Did you do this test multiple time to see it is similar in every time ? What exact version of 8.5.x you running ?

HTH

Rasika

[Mikolaj Moryto]

Hi Rasika,

It's 8.5.135. Today I took screenshot transferring few times to confirm it's consistent and it was. Also, I observer that couple of weeks ago and it has been like that since when I turned on AVC (I mean before I was using central switching because I did not need AVC so the moment I wanted to have AVC I changed switching to local). Can the AVC downgrade the performance?. It doesn't hurt that much when browsing internet but I am trying to get the maximum throughput for transferring the files on the LAN between PCs and file servers where I would expect local switching to beat central.

Thank you

[Rasika Nayanajith]

Would you be able to upgrade your vWLC to 8.5.151.0 & test it ?

HTH

Rasika

[patoberli]

AVC does take a little bit more CPU power, check if the vWLC is low on free resources.

[Mikolaj Moryto]

Upgraded to 8.5.151.0 and it is the same. At this point I believe it is the AP and its CPU not being fast enough for Flex AVC. 

During file transfer:

Disabling AVC improves the throughput and CPU utilization goes down a bit

[Jurgens L]

For what it's worth the feedback I've received from Cisco is that AVC can impact performance. In my scenario, it was the WLC's even though they are speced to support 6000 AP's we had to limit the capacity to 80%.
By using AVC on flex connect AP's you most likely shifting more CPU requirement for the AP as well. Later gen AP's such as the 2800's you will most likely not see being impacted by this, although I havent personally tested this.

[Rasika Nayanajith]

Even with disabling AVC, did you notice lower throughput for FlexConnect local switching compare to central switching ?

Would you be able to share what values you got in your testing ? Pls try with different type of devices and see if all goes in same pattern 

Rasika

[Mikolaj Moryto]

Hi,

Disabling AVC improves the through for another 20-30% but it's far from reaching the value it gets with central switching. As with local switching more features are offloaded to AP I believe this is the reason for worse performance.

Thanks everyone for their input.

Regards,

Mikolaj

[patoberli]

As you're nearly at 100% CPU load, I'd say yes the impact is large.