WLAN Wireless Network 07-Overview of Wireless LAN Communications

Overview of wireless local area network communication.

Some people like to compare the communication of a wireless local area network to a wired local area network to plug a network cable connected to a computer into a 802.3 network port. I think there are similarities and great differences here.

First of all, let's take a look at the basic communication process of wireless local area network. The 802.11 network, no matter how it is configured, requires the following processes: scanning, authentication, association and communication data exchange.

Scanning: there are two cases here, active scanning and passive scanning

Passive scanning: the client listens to the beacon frame sent by the access point and learns the surrounding network environment through the information it carries.

Active scanning: the client initiatively sends out the probe frame (probe request). After receiving the probe frame, the access point gives the corresponding response (probe response). The client learns the surrounding network environment through the relevant information it carries.

Authentication: it is equivalent to identification, not that any wireless network device can access the network.

802.11 defines two authentication methods: Open System Authentication and Shared Key Authentication.

802.11i defines two other authentication methods: 802.1X/EAP authentication (enterprise level) and Preshared Key (PSK) or Personal (individual level).

These two methods defined by 802.11i are called RSN (robust security network) networks, and you will often see two versions of WPA and WPA2. These four methods will be described in detail later, which will not be discussed too much here.

The client will first issue the association request, and the access point will reply to the success or failure of the client request after receiving the association request.

Association: the client passes the authentication step, and the next step is the association.

Similar to authentication, the association is also divided into two steps. The client sends out the association request, and the access point will reply to agree to the client association or reject the client association according to the appropriate situation.

Data communication: after completing the above three steps, the client can communicate with the access point, such as obtaining the IP address and communicating with other clients.