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What is SSID WiFi | Function of SSID in WiFi

This page describes SSID WiFi structure. It mentions function of SSID in WiFi.SSID stands for Service Set Identifier which is 32 characters consisting alphanumeric letters. It acts as password to allow mobile or other computing devices to connect with the wifi network.

Any WiFi network composed of two elements viz. Access Point (AP) and STATIONS or clients. There are two parameters which are essential to configure wifi AP for the first time. The parameters are SSID and frequency or channel number.

SSID are broadcasted periodically by AP over the air. It is carried in a beacon frame broadcasted by AP at regular intervals. Beacon frame interval is about 100ms typically. Beacon frame consists of SSID as well as other useful functionalities and number of IEs. These informations are very useful for client devices to connect with the wifi network (i.e. AP).

SSID message format and function

SSID format

• SSID identifies access point.
• It allows several APs to operate at same location to access different wifi networks except in ESS where in multiple APs work together with same SSID.
• SSID is a text string in human readable form.
• SSID need to be configured in the client device (mobile, tablet, laptop) to select the wifi AP or router when there are multiple wifi APs are found in the locality.
• SSID is known as "network name" in the wifi network.
• Figure-1 above mentions SSID element format. As mentioned SSID element indicates identity of ESS or IBSS.
• The length of SSID field is between 0 and 32 octets. A 0 length field is used within probe request frame which indicates wildcard SSID.

WiFi frame exchange between AP and Client

WiFi message exchange between AP and client

The figure-2 depicts that SSID is broadcasted by Beacon frame and later the same value of SSID is used by wifi client in the Association Request Frame. SSID wifi is very useful parameter in WLAN networks which is very much required to be known by users of the wifi network.


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