In local area networks three type of networks are usually used, hub-based Ethernet, the switched Ethernet and/or wireless Ethernet. The hub based Ethernet uses a central device called a hub, in which all nodes on the network are connected to this device. The hub-based Ethernet has a physical topology of a start. However once you know how it works you would conclude it is a logical bus network. What the hub does is when a node sends out a message it broadcasts the message to all the nodes on the network. It uses a control protocol called Carrier Sense Multiple Access with Collision Detection and as all computer oriented people like to use acronyms the acronym used is CSMA/CD. The collision detection system works as described in the previous post under the Bus topology. The switched Ethernet doesn’t use CSMA/CD because collisions are impossible in its logical topology, a star. The switch, the central device, opens an connection between two nodes providing them with a full duplex connection. Because there is only two nodes collisions are impossible. The wireless Ethernet uses a central device called an access point. It is a wireless hub-based Ethernet. In other words it has a logical topology of a bus .A more in depth reasoning to why it falls underneath a bus topology is mainly because the node broadcasts the message and the access point listens to the message and re-broadcasts it so the intended node can listen. If there was other nodes in the area listening they can still be able to receive the message.   Because wireless Ethernet uses an unguided mean connectivity it is impossible to use CSMA/CD. Thus it uses a protocol called CSMA/CA; the CA stands collision avoidances.