Service set identifier (SSID)
A service set identifier (SSID) is a name that identifies a particular 802.11 wireless LAN. A client device receives beacon messages from all access points within range advertising their SSIDs. The client device can then either manually or automatically—based on configuration—select the network with which to associate. The SSID can be up to 32 characters long. As the SSID displays to users, it normally consists of human-readable characters. However, the standard does not require this. The SSID is defined as a sequence of 2–32 octets each of which may take any value.
It is legitimate for multiple access points to share the same SSID if they provide access to the same network as part of an extended service set.
Some wireless access points support broadcasting multiple SSIDs, allowing the creation of virtual access points, partitioning a single physical access point into several virtual access points, each of which can have a different set of security and network settings. This is not yet part of the 802.11 standard.