06-15-2012 12:38 PM
Many customers have inquired how they can do some level of Capacity planning using AirWave to find out where they have WLAN capacity issues and should be adding potentially more/better APs. How can we find out whether your RF utilization of airtime is getting to a point where it is becoming a bottleneck for your users.
RF Capacity Analysis can be perform in two ways in AirWave - 1) Using number of Clients as a threshold 2) Using Channel Utilization as a threshold.
1) Number of Clients/ AP for Capacity Planning
This is one potential way to understand APs that are running out of capacity. The caveat here is that excessive number of Clients on an AP may not necessarily translate into high Utilization for the AP. Especially in scenarios where the AP is running an Open SSID such as Guest, a number of clients may auto connect to the AP and possibly not generate as much traffic and still be counted.
If you want to use the number of clients as an indicator of your AP utilization, you can extract data from AirWave via one of two ways.
a) Create a Device Summary report and filter it for appropriate folder, Device Type (don't include controllers only APs) and SSID. This report will show you X number of Top APs loaded by the number of Clients.
b) Create a Trigger in AirWave using Device Client Count and specify i) Duration of atleast 30minutes ii) Client count > X.
This will only flag APs that exceed the Client count for certain amount of time - its a much better measure than the Max Client count
2)Channel Utilization measure for Capacity planning
For customers who are on 6.x code and have AMON turned ON. AirWave can report the channel utilization metrics to determine true bottlenecks in WLAN from an RF capacity perspective. This is a much more robust metric which avoids the caveat of above method #1.
There are two ways to extract the information from AirWave pertaining to Channel utilization
a) RF health report has a widget for "Most Utilized by Channel Usage" for both types of Radios. Add this widget in your capacity planning report and how the top 50 APs by Channel Utilization. APs with more than 75% utilization consistently are going to be candidates for replacement.
b) Create System->Trigger for Channel Utilization and setup Duration of 30minutes and Channel Utilization Busy Threshold of 75%. Any Radios that trigger on this condition are going to be prime candidates for adding capacity. You may also want to keep an eye on the breakdown of the Channel Utilization. If there are excessive Interference related utilization then you can possibly investigate if that lost airtime can be recouped by removing the interference source.
09-18-2012 10:23 AM
Great post! This has definitely helped me configure reporting for Channel Utilization correctly
ACDX #420 | ACMP
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