Multiple BSSID sets out to aggregate individual beacon frames from an access point to a single beacon frame.
It helps solve the issue of beacon overhead. As it is today, each SSID broadcasts a beacon. The more SSIDs you’re broadcasting, the more the beacons eat up airtime.
Airtime is a precious resource for Wi-Fi devices. Sometimes beacon overhead can take up a large amount of airtime.
Multiple BSSID aims to reduce the airtime by broadcasting less beacon frames for better efficiency and less wasted airtime capacity.
While Multiple BSSID can be found in 802.11-2020, it was first introduced in 802.11v-2011. In the episode, Rowell mentions that it is mandatory in Wi-Fi 6. But we have not seen documented to be mandatory, or maybe we just missed it.
Within Multiple BSSID, you will find a new information element that contains all the active BSSIDs within the Multiple BSSID set. There will be one transmitted BSSID and the others SSIDs will be listed with non-transmitted BSSID profiles.
Be sure to check out the video and the pcap file!
Sections in the 802.11-2020 standards talking about Multiple-BSSID:
- 188.8.131.52 Multiple BSSID capability
- 184.108.40.206 Multiple BSSID element
- 220.127.116.11 Multiple BSSID-Index element
- 10.6.9 Multiple BSSID Rate Selection
- 18.104.22.168 Multiple BSSID procedure