How a WLAN Works
A WLAN (Wireless Local Area Network) is one of those things that are simply present. People don't think much about this technology until it's unavailable, or they just can't connect. In its simplest form, a WLAN works as follows: An Access Point (AP) provides the WLAN, and a WLAN-enabled device (Client) connects to it. Both devices are referred to as stations, but for clarity, I'll use the terms Access Point and Client.
The Access Point is connected to the local network and communicates in both directions. It can forward the Client's communication to the LAN and also deliver information from the LAN to the Client.
Often, Access Points are combined with a router or switch. These combo devices are common in homes or small businesses. For instance, a typical DSL router found in most households can serve as an Access Point, allowing all the Clients in the house to connect.
With many WLANs around, it's essential to distinguish between different networks. Therefore, each WLAN has a name known as the SSID (Service Set Identifier), which can be read and recognized by both humans and machines. We see the SSID when selecting a WLAN from a list. This identification helps establish a connection to the correct network. A critical point is that the information sent between the Access Point and the Client is encrypted. We'll dive into the different types of encryption later. Most WLANs also use some form of access control, a topic we will also explore in detail.
Theoretically, a WLAN can support up to 254 Clients per Access Point. However, this is a maximum value rarely achieved in practice. Hence, using more than one Access Point can make sense, especially when many Clients need to connect. It's also possible to install multiple WLANs in the same physical area to separate accesses. However, a Client can only connect to one Access Point at a time. If you want a Client to connect to multiple Access Points simultaneously, you need an additional WLAN adapter, which is not recommended.
Let's take a closer look at the Access Point and how it forwards data to Clients. Ideally, an Access Point would direct data to the intended Client, functioning like a switch. Unfortunately, this isn't technically feasible, and Access Points broadcast all data traffic to all connected Clients. Only the Client for whom the data is intended accepts and processes it; the other Clients discard it. This explains why a WLAN slows down as more Clients are added. The network's bandwidth must be shared more, and each device has to process more traffic. Hence, the operation of an Access Point is more like that of a hub. Hubs are no longer used in Ethernet networks, where only switches are employed.
This type of WLAN network structure is called an infrastructure network. An infrastructure network exists whenever Clients connect to an Access Point. Another way to connect over WLAN is the so-called ad-hoc network, often referred to as Wi-Fi Direct. In this case, two devices connect directly without access to the Internet or a local network. An example of an ad-hoc connection is a wireless link to a printer, set up only between a computer and the printer. This can also be called a direct print mode. Ad-hoc technology is also used for file-sharing functions on smartphones and some streaming services. An ad-hoc connection can also be established using other technologies. Whenever exactly two devices connect, ad-hoc is possible, for example, through Bluetooth.
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