Switching is a technology that alleviates congestion in Ethernet LANs by reducing traffic and increasing bandwidth. Switches often replace shared hubs and work with existing cable infrastructures to ensure they are installed with minimal disruption of existing networks.
Like bridges, switches connect LAN segments, use a table of MAC addresses to determine the segment on which a datagram needs to be transmitted, and reduce traffic. Switches operate at much higher speeds than bridges, and can support new functionality, such as virtual LANs.
An Ethernet switch has many benefits, such as allowing many users to communicate in parallel by virtual circuits and dedicated network segments in a collision-free medium. This maximizes the bandwidth available on the shared medium. Another benefit is that moving to a switched LAN medium is very cost effective because existing hardware and cabling can be reused. Finally, network administrators have great flexibility in managing the network through the power of the switch and the software to configure the LAN.
By dividing large networks into self-contained units, bridges and switches provide several advantages. A bridge or switch diminishes the traffic experienced by devices on all connected segments because only a certain percentage of traffic is forwarded. Both devices act as a firewall for some potentially damaging network errors. They also accommodate communication between a larger numbers of devices than would be supported on any single LAN connected to the bridge. Bridges and switches extend the effective length of a LAN permitting the attachment of distant stations that were not previously permitted.
Although bridges and switches share most relevant attributes, several distinctions still do exist between them. Switches are significantly faster because they switch in hardware, while bridges switch in software and can interconnect LANs of unlike structures. A 10 Mbps Ethernet LAN and a 100 Mbps Ethernet LAN can be connected by using a switch. Switches can support higher port densities than bridges. Some switches support cut-through switching, which reduces latency and delays in the network, while bridges support only store-and-forward traffic switching. Finally, switches reduce collisions and increase bandwidth on network segments because they provide dedicated bandwidth to each network segment.
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