How and why to implement Wi-Fi QoS

Quality of service on any type of network seeks to achieve the same goals, namely to ensure that latency-sensitive applications have priority over applications that can tolerate delay and congestion. In other words, it's all about the end-user experience.

For example, my voice over Wi-Fi call might be miserable if my network traffic hits momentary delays, but my web browsing likely won't be perceptively affected. This premise holds true for wired and wireless networks alike.

Complete books and book chapters have detailed QoS in networking. But, in this article, let's explore the basics of QoS for wireless networks.

The key ingredients of Wi-Fi QoS

For Wi-Fi QoS to work properly, three things need to support it. The client device, the wireless network itself and the application in question need to be designed to recognize and use QoS underpinnings in their configurations. Generally, Wi-Fi QoS comes from the 802.11e standard, adapted specifically to Wi-Fi through Wi-Fi Multimedia, or WMM, which enhances QoS by prioritizing data packets according to four categories: voice, video, best effort and background.

Wireless LAN (WLAN) vendors can prioritize network traffic in multiple ways. Though the basic constructs are fairly common, the terminology may differ in different product sets.

In the screenshot below, Cisco references QoS profiles as Platinum, Gold, Silver and Bronze. Other vendors simply use voice, video, best effort and background to assign a priority. This configuration assigns a standards-defined priority to a WLAN network by a service set identifier. You may also choose to apply custom bandwidth controls per wireless client or implement application-specific QoS settings if your equipment is capable of identifying specific applications.