Why does a mobile device associate (register) with an access point?
Incoming frames from the conventional network are relayed to the mobile device by the access point to which the device is associated. By associating with an access point, the device tells the network that the access point should receive any frames addressed to the device.
Why does an 802.11 frame sometimes require four addresses?
The access point acts as a bridge, forwarding messages between the conventional Ethernet and the 802.11 wireless network. Devices on the conventional network must know the address of the access point (the receiver) that will forward the message to the wireless recipient. In bridging situations, it is also sometimes necessary to specify the device that translated the frame for the wireless medium (the transmitter).
Why was WEP2 developed?
Wired Equivalent Privacy (WEP) was devised to provide a level of security for wireless networks that is approximately equivalent to the security of a conventional network. WEP2 was developed to address some of the problems with WEP, including problems with key length and key management.
Why does WAP provide alternatives to the standard TCP/IP protocols at upper layers?
Wireless communication is not as fast or reliable as conventional network transmission. The WAP protocols were optimized for the wireless environment. WAP protocols often contain a scaled-down subset of services. Some WAP protocols are binary for better performance.