AVC performance impact

[T.Igor]

Hi community,

I found in the Best Practice for the WLC C9800, that AVC inspection may have a performance impact of up to 30%.

How can I calculate the impact before the implementation? Is there any relationship between the number of users and the CPU load and the  created traffic.

let imagine that all WLANs in Flex connect local switching and 1000 clients are connected. What does it mean? 

[Scott Fella]

There is no calculation for this, I believe it’s more of what’s the worse case that can happen. AVC is traffic inspection so there would be a difference between 1000 users doing nothing and 1000 users doing heavy traffic. In many cases, you enable the feature after you have had the network in for a while to get some sort of baseline, then enable it. If things don’t seem to break and users don’t see any difference in their day to day, then you know it’s not impacting your wireless. About 5 years ago we got impacted by AVC because of terado packets being generated by each window client in which TAC and the BU suggested to turn off AVC which helped. The wireless network would slow down and stop sending traffic. They did push a fix for this and ever since had no issues with AVC being enabled.
Again, you do your own testing with it not enabled for a while and then with it enabled. Review your testing and see if there was any impact.

[T.Igor]

Hi Scott,

thanks for the clarification. What do think would it cause any issue if we would enable the AVC on the cloud controller 9800-CL.

I mean from my prospective the only limitation of the SW WLC in compassion to HW WLC is the throughput. The 9800-CL can pass through 2 Gps of the traffic only. 

How much traffic per User does an AP generate in the FlexConnect Local Switching mode? I understand that it depends on the user activity. But any way what do you think? Can the throughput limitation in combination with the AVC cause any problem? 

[Scott Fella]

Well remember you will probably do FlexConnect with local switching so the AP’s will do the inspection not the controller.

https://www.cisco.com/c/en/us/td/docs/wireless/controller/technotes/8-8/b_c9800_avc_ios_xe_rel_16_10.html

[p.lan]

Just as a heads up, we did see a large impact with AVC enabled on flex APs with local switching on 9800 platform... brought throughput down to 100mbps on 2700/3700 APs and 200mbps on 2802/3802. Did not test on new catalyst APs in flex mode.

This makes sense since the AP is doing the inspecting, and those only have so much power in their CPU.