macOS wireless roaming for enterprise customers
Find out how macOS supports roaming between access points within a wireless network.
For system administrators, macOS roaming helps your Mac stay connected as it moves between different places within your office network.
The trigger threshold is the minimum signal level a client requires to maintain the current connection.
macOS clients monitor and maintain the current BSSID’s connection until the RSSI has crossed the -75 dBm threshold. After RSSI has crossed that threshold, macOS scans for roam candidate BSSIDs for the current ESSID.
Consider this threshold in view of the signal overlap between your wireless cells. macOS maintains a connection up to the -75 dBm threshold, but 5 GHz cells are designed with a -67 dBm overlap. Those clients will remain connected to the current BSSID longer than you may expect.
Also consider how the cell overlap is measured. The antennas on computers vary from model to model, and they see different cell boundaries compared with what may be expected. It's always best to use the target device when you measure cell overlap.
Selection criteria for band, network and roam candidates
macOS always defaults to the 5 GHz band over the 2.4 GHz band. This happens as long as the RSSI for a 5 GHz network is at least -68 dBm and the load on the network is not excessive.
macOS considers information shared by networks about channel utilisation and quantity of associated clients. macOS uses these details along with signal strength measurements (RSSI) to score candidate networks. Higher score networks offer a better Wi-Fi experience.
If multiple 5 GHz SSIDs receive the same score, macOS chooses a network based on these criteria:
802.11ax is preferred over 802.11ac.
802.11ac is preferred over 802.11n or 802.11a.
802.11n is preferred over 802.11a.
80 MHz channel width is preferred over 40 MHz or 20 MHz.
40 MHz channel width is preferred over 20 MHz.
macOS Monterey supports 802.11k on Mac computers with Apple silicon.
Earlier versions of macOS don't support 802.11k but do interoperate with SSIDs that have 802.11k enabled.
macOS selects a target BSSID with a reported RSSI 12 dB or greater than the current BSSID’s RSSI. This is true even if the macOS client is idle or transmitting/receiving data.
Roam performance describes how long a client needs to authenticate to a new BSSID successfully.
Finding a valid network and AP is only part of the process. The client must complete the roam process quickly and without interruption so the user doesn't experience downtime. Roaming involves the client authenticating against the new BSSID and deauthenticating from the current BSSID. The security and authentication method determines how quickly this can happen.
First, 802.1X-based authentication requires the client to complete the entire EAP key exchange. Then it can deauthenticate from the current BSSID. Depending on the environment’s authentication infrastructure, this may take several seconds. End users could experience interrupted service in the form of dead air.
macOS supports static PMKID (Pairwise Master Key identifier) caching to help optimise roaming between BSSIDs in the same ESSID. macOS doesn't support Fast BSS Transition, also known as 802.11r. You don't have to deploy additional SSIDs to support macOS because macOS interoperates with 802.11r.
macOS Monterey supports 802.11r and 802.11v on Mac computers with Apple silicon.
macOS supports static PMKID (Pairwise Master Key identifier) caching to help optimise roaming between BSSIDs in the same ESSID. Earlier versions of macOS don't support Fast BSS Transition, also known as 802.11r. Earlier versions of macOS interoperate with 802.11r so additional SSIDs don't need to be deployed.
Measure Client RSSI
macOS offers a few built-in tools that scan to measure RSSI.
To find out the RSSI for the associated network, hold the Option key while you click the.
To find out the RSSI for networks in the client’s environment, use Wireless Diagnostics. To open Wireless Diagnostics, Option-click on the, then select Open Wireless Diagnostics. In the menu bar, choose Window > Scan to find all nearby wireless networks and measure their RSSI.