Switches operate in data-link (Layer-2) layer,which has largely replaced the bridge in the modern network, and which replacing routers in many instances as well. A switch is a box with multiple cable jacks in it that looks a lot like a hub. In fact, some manufacturers have hubs and switches of various sizes that are identical in appearance, except for their markings. The difference between a hub and a switch is that while a hub forwards every incoming packet out through all of its ports, a switch forwards each incoming packet only to the port that provides access to the destination system.
Switches essentially convert the LAN from a shared network medium to a dedicated one If you have a small network that uses a switch instead of a hub, each packet takes a dedicated path from the source computer to the destination, forming a separate collision domain for those two computers. Switches still forward broadcast messages to all of their ports, but not unicasts and multicasts. No systems receive packets destined for other systems, and no collisions occur during unicast transmissions because every pair of computers on the network has what amounts to a dedicated cable segment connecting them. Thus, while a bridge reduces unnecessary traffic congestion on the network, a switch all but eliminates it.
Another advantage of switching is that each pair of computers has the full bandwidth of the network dedicated to it. A standard Ethernet LAN using a hub might have 20 or more computers sharing the same I 0 Mbps of bandwidth. Replace the hub with a switch, and every pair of computers has its own dedicated 10 Mbps channel. This can greatly improve the overall performance of the network without the need for any workstation modifications at all. In addition, some switches provide ports that operate in Full-duplex mode, which means that two computers can send traffic in both directions at the same time using separate wire pairs within the cable. Full-duplex operation can effectively double the throughput of a 10 Mbps network to 20 Mbps.
Switches essentially convert the LAN from a shared network medium to a dedicated one If you have a small network that uses a switch instead of a hub, each packet takes a dedicated path from the source computer to the destination, forming a separate collision domain for those two computers. Switches still forward broadcast messages to all of their ports, but not unicasts and multicasts. No systems receive packets destined for other systems, and no collisions occur during unicast transmissions because every pair of computers on the network has what amounts to a dedicated cable segment connecting them. Thus, while a bridge reduces unnecessary traffic congestion on the network, a switch all but eliminates it.
Another advantage of switching is that each pair of computers has the full bandwidth of the network dedicated to it. A standard Ethernet LAN using a hub might have 20 or more computers sharing the same I 0 Mbps of bandwidth. Replace the hub with a switch, and every pair of computers has its own dedicated 10 Mbps channel. This can greatly improve the overall performance of the network without the need for any workstation modifications at all. In addition, some switches provide ports that operate in Full-duplex mode, which means that two computers can send traffic in both directions at the same time using separate wire pairs within the cable. Full-duplex operation can effectively double the throughput of a 10 Mbps network to 20 Mbps.
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