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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