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Extended service set

Extended service set

(also ESS)

Extended service set definition

An extended service set is a group of interconnected wireless access points and stations that form a single logical network. It is one of the main pillars of IEEE 802.11 wireless networking. Extended service sets allow devices to roam seamlessly between access points without losing their network connection.

See also: mobile ad hoc network, IEEE 802, Access Point Name

How extended service sets work

An extended service set connects multiple basic service sets (single access points that manage communications between devices within their coverage area) together. When any device moves out of range of one access point, it can automatically connect to another access point within the extended service set to avoid disruption.

As a result, devices within an extended service set can communicate with each other as if they are in the same network — even if they are associated with different access points. To facilitate this, each basic service set in an extended service set is assigned a unique BSSID (basic service set identifier) — typically the MAC address of their access point.

While the BSSID uniquely identifies each basic service set, the extended service set is identified by its SSID (service set identifier). All access points within the set broadcast the same SSID to let connected devices recognize others as belonging to the same network.

Extended service set use cases

  • Office buildings use extended service sets to let employees conduct meetings and work in multiple locations without losing access to internal resources.
  • Public Wi-Fi hotspots, such as those found in airports, hotels, and hospitals, use extended service sets to allow users to roam around the facility while retaining internet access.

Further reading

Ultimate digital security