1.1 LAN Switching
1.1.3 Segmentation with LAN switches

A LAN that uses a switched Ethernet topology creates a network that behaves like it only has two nodes - the sending node and the receiving node. These two nodes share the 10Mbps bandwidth between them, which means that nearly all the bandwidth is available for the transmission of data. Because a switched Ethernet LAN uses bandwidth so efficiently it can provide a faster LAN topology than standard Ethernet LANs. In a switched Ethernet implementation the available bandwidth can reach closer to 100%.

The purpose for using LAN switching is to ease bandwidth shortages and network bottlenecks such as between several PCs and a remote file server. A LAN switch is a very high-speed multiport bridge with one port for each node or segment of the LAN. A switch segments a LAN into microsegments creating collision free domains from one larger collision domain.

Switched Ethernet is based on standard Ethernet. Each node is directly connected to one of its ports or a segment that is connected to one of the switch's ports. This creates a 10Mbps bandwidth connection between each node and each segment on the switch. A computer connected directly to an Ethernet switch is its own collision domain and accesses the full 10Mbps.

As a frame enters a switch it is read for the source and/or destination address. The switch then determines which switching action will take place based on what the switch has learned from the information read off the frame. The frame is then switched to its destination.

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