Wireless devices connected to a network, whether ad hoc or infrastructure-based, require a way to identify that network. Data packets sent to computers within the network must reach their destination, even if several Wi-Fi networks overlap. The terminology here can be a little confusing, especially given the marketing jargon.
The Basic Service Set Identifier (BSSID) defines the simplest infrastructure network—a BSS consisting of a single access point and one or more wireless devices. In such a simple network, there was no need to come up with a new numbering or naming system, so the BSSID was made identical to the MAC address of the access point. In the case of ad hoc networks, where there is no access point, devices within the IBSS randomly generate a 48-bit string of numbers that looks and functions like a MAC address, and this BSSID is used in every data packet.
Theoretically, it is possible to manually find out the MAC address of the access point in the BSS and enter it when configuring a wireless computer, but this would create two problems. First, it is inconvenient for people to remember 48-digit strings, even if they are presented as six hexadecimal octets. Second, how can multiple computers be connected to an IBSS if the BSSID is generated randomly?
To solve this problem, an additional identifier was introduced—the Service Set Identifier (SSID), a standard name assigned to a BSS or IBSS to simplify connection. The SSID, sometimes referred to as a network name, is a 32-bit identifier string that is inserted into the header of each data packet processed by the access point. All Wi-Fi devices on the same network must use the same SSID to communicate successfully.
In more complex networks with multiple access points, an extended network identifier called ESSID (Extended Service Set Identifier) is used to identify the network name at the ESS level. In practice, most Wi-Fi devices only use the term SSID, even when referring to ESSID. When configuring a connection to an ESS, you are actually using the ESSID, but manufacturers simplify the process by leaving only the SSID designation.
It is worth noting that in the CompTIA Network+ exam, the terms SSID and ESSID are used interchangeably, so it is sufficient to focus on these two concepts when preparing for the exam.
