Wireless distribution system:-

A Wireless Distribution System (WDS) allows a wireless network to be expanded using multiple access points without the need for a wired backbone to link them. The notable advantage of WDS over other solutions is that it preserves the MAC addresses of client packets across links between access points. An access point can be either a main, relay or remote base station. A main base station is typically connected to the wired Ethernet.

A relay base station relays data between remote base stations, wireless clients or other relay stations to either a main or another relay base station.

A remote base station accepts connections from wireless clients and passes them to relay or main stations. Connections between "clients" are made using MAC addresses rather than by specifying IP assignments. All base stations in a Wireless Distribution System must be configured to use the same radio channel, and share WEP keys or WPA keys if they are used.

They can be configured to different service set identifiers. WDS also requires that every base station be configured to forward to others in the system .WDS may also be referred to as repeater mode because it appears to bridge and accept wireless clients at the same time (unlike traditional bridging).

Wireless LAN operates in three different frequency ranges

1)2.4Ghz(802.11b/g/n)

2)3.6Ghz(802.11y)

3)4.9-5.0Ghz(802.11a/h/j/n)

Each of these frequency ranges are further divided into multiple channels. At any given instant of time a wireless card can operate on a single channel in any of the given frequency range depending upon the hardware capability of the card and allowed frequency in that area. What utmost can be done is we can make it hop between different channels using a time division multiplexing. Each  country has a list of allowed channels, and the specifications of who is allowed to access which channel mode of operation. However we can tweak the card to disregard these policies and make it operate in the channel we wish. But that would be illegal to do in many countries. Make sure you have the permission before you try to do so.

Access point and packet basics:-

An access point provides a medium for the wifi clients to connect to the network. It generally has a wired side and a wireless side. The client connects to the access point through the wireless side and the access point forwards the information through its wired side.

An access point is configured with a name so that it could be identified on the network. That is what is called a SSID or the service set identifier. The SSID is a name given to an access point or to a network consisting of multiple access points. WiFi clients search for the access point or the network using this SSID. When you start the wifi utility on your laptop or any other device you will see a list of available access points or networks. Now, an interesting

point to notice here is how our laptop does or mobile phones come to know about these networks?

What happens here is that the access point keeps broadcasting packets in its RF vicinity to announce its presence, these broadcast packets are known as Beacon frames. These beacon frame makes the access point visible to the wifi client.

 

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