Case Study: Troubleshooting High latency over Wi-Fi

Problem Statement: User facing high latency issue while accessing the Internet through Wi-Fi.

Observations:

• Latency of the ping was about 40+ ms in the using Wi-Fi infrastructure but when connected through wired the Latency was normal (4-5ms).
• A cluster of 10 IAP’s 215
• Signal strength for the clients were good, most of the clients connects to 2.4ghz band.

Configuration Present in the network.

• VLAN assignment for office-Internal SSID (WPA2-PSK) is network assigned – default.
• For 2.4Ghz, channels were assigned with static channels (3,7,10) as shown below

 

• Noticed high interference in the location, most were on 2.4 GHz band.

To check the interference Click on Access Point–> IDS we can view the rouge access points as shown in the below screenshot. The marked one is the rogue access points.

 

• Channel busy was noticed on the AP’s as well.

To check the channel busy:

Click on client –> monitoring –> Utilization ( In RF Dashboard). The output  is shown below. ( the below screenshot is just an example)

 

Troubleshooting Performed to Overcome the issue.

1. Upgraded the IAP to latest version – 4.1.3.1 (user can upgrade the latest version available).
2. Enabled broadcast filtering all
3. Enabled dynamic multicast optimization

Broadcast filtering at the Virtual AP level stops broadcasts and improves performance.

Dynamic Multicast Optimization: The controller keeps a record of the stations in each multicast group, converts the multicast MAC to unicast MAC (destination  IP address remains as multicast), and sends to that station at the unicast rate.

Click on AP –> edit –> show advanced setting (under WLAN setting) –> select all in broadcast filtering,  enable multicast optimization and changed the local probe threshold value to 20dbm as shown below.

 

 

4. Added channels (1,6,11,4,8) in 2.4Ghz

Click RF–> advance option –> valid 2.4 GHz channels and change the  channels accordingly as shown below. ( the below screenshot is just an example)

 

5. Disabled scanning in RF 5ghz.
6. Changed the transmit power to Min-12 & Max-18  as shown below. (in RF tab only).

7. After the changes we monitored the connection in different floors and with different client machines, latency was reduced to an average 13.3ms on 2.4Ghz and 9ms on 5 GHz.

8. Avoid Hotspots and any interfering devices with the wireless network.

Hope it helps !   Cheers !