Band-steering is a feature that allows an AP to steer dual-band capable clients to the less congested 5GHz frequency, leaving the 2.4GHz frequency for legacy clients. Without band-steering, the AP may have more clients competing for the same channel on the 2.4GHz frequency, resulting in high latency and airtime contention.
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According to the CompTIA Network+ Certification Exam Objectives, one of the topics covered in the exam is "Given a scenario, use appropriate wireless technologies and configurations". One of the subtopics is "Band steering" 1.
According to the PoliFi: Airtime Policy Enforcement for WiFi paper, "Band steering allows the access point to disable the 2.4 GHz band from probing the client device, so it responds only to the 5 GHz band, reducing the congestion on the 2.4 GHz band while taking advantage of the faster 5GHz band to improve user's network experience." 2.
According to the Aruba Air Slice Tech Brief, "Air Slice minimizes airtime contention and efficiently groups Wi-Fi 6 and non-Wi-Fi 6 client devices to guarantee bit rate, and provide bounded latency and jitter simultaneously." 3.