https://support.apple.com/en-us/HT202628
Wi-Fi network roaming with 802.11k, 802.11r, and 802.11v on iOS
Learn how iOS and iPadOS improves client roaming using Wi-Fi network standards.
iOS supports optimized client roaming on enterprise Wi-Fi networks. The 802.11 Working Group standards k, r, and v let clients roam more seamlessly from access point (AP) to AP within the same network.
802.11k
The 802.11k standard helps devices search quickly for nearby APs that are available as roaming targets by creating an optimized list of channels. When the signal strength of the current AP weakens, your device will scan for target APs from this list.
802.11r
When your device roams from one AP to another on the same network, 802.11r uses a feature called Fast Basic Service Set Transition (FT) to authenticate more quickly. FT works with both preshared key (PSK) and 802.1X authentication methods.
iOS 10 and later and iPadOS include support for adaptive 802.11r on Cisco wireless networks. Adaptive 802.11r offers FT without the need to enable 802.11r on the configured Cisco wireless network. To support adaptive 802.11r, the Cisco network must be using controller code version 8.3 or later.
802.11v
iOS and iPadOS support these 802.11v functionalities on certain devices:
- Basic Service Set (BSS) transition management
- Disassociation Imminent
- Directed Multicast Service (DMS)
- BSS Max Idle Service
BSS transition management with Disassociation Imminent allows the network’s control layer to influence client roaming behavior by providing it the load information of nearby access points. The device takes this information into account when deciding among the possible roam targets.
DMS optimizes multicast traffic transmission on wireless networks. The device uses this information to enhance multicast communication and preserve device battery life.
The BSS Max Idle Service helps clients and access points efficiently decide how long to remain associated when no traffic is being transmitted. The device uses this information to preserve device battery life.
When you combine 802.11k and 802.11v’s ability to speed up the search for the best target AP with FT's faster AP association, apps can perform faster and you get a better Wi-Fi experience in iOS and iPadOS.