rn sent by a data station to inform the other stations that they must not transmit. 4. One terminal waits 20 milliseconds, and the other waits 50 milliseconds, and then they again attempt to transmit, assuming that their messages won't Chapter 6 Local Area Networking clear" clear" Sending "Collision" "Collision" Sending Figure 6.5 CSMA/CD bump into each other. Because the terminals waited different amounts of time, most likely the messages don't collide and therefore get transmitted. However, if the messages collide again, the terminals repeat the back-off and random-wait procedure up to 16 times before the frames are dropped. In this type of environment, the more devices added and the greater the traffic volumes, the more likely collisions will occur. When collisions start to exceed the available throughput, you need to start segmenting the LAN into smaller clusters, called collision domains in Ethernet parlance, or consider making the move to switched Ethernet LANs. Shared Versus Switched Ethernet With traditional Ethernets, all the hosts compete for the same bandwidth, and for this rea- son they are referred to as shared Ethernets. A switched Ethernet is an Ethernet LAN that uses switches to connect individual hosts or segments; that is, the network is controlled by a switch instead of a shared hub. The switch cross-connects all clients, servers, and net- work devices, giving each sending-receiving pair the full-rated transmission speed. Switched Ethernet, unlike shared Ethernet, provides a private connection between two nodes on a network, speeding up the rate at which data is sent along the network LAN Characteristics and eliminating collisions. Switched connections allow full-duplex, which means net- work nodes can send and receive data at the same time. This doubles the theoretical speed of Ethernet and Fast Ethernet (offering a maximum of 200Mbps for Fast Ether- net). Switched Ethernets have gained in popularity because they provide a dramatic increase in throughput, offering an effective and convenient w