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Introduction
Overview of Switching Technology
The Ethernet switch allows simultaneous transmission of multiple packets using an internal
high–speed data channel. This means that it can partition a network more efficiently than
bridges or routers in most environments. Therefore, the Ethernet switch is recognized as
one of the most important building blocks for today’s networking technology. See
Appendix C for information about the limitations of shared Ethernet.
The learning function in the switch stores the address and corresponding port number of
each incoming and outgoing packet in a routing table. This information is subsequently
used to filter packets whose destination address is on the same segment as the source
address. Network traffic is thereby confined to its respective domain, reducing the overall
load on the network.
The switch scans the destination address from the packet header, searches the routing table
provided for the incoming port, then forwards the packet only if required, often before fully
received. This fast forwarding makes the switch attractive for connecting servers directly to
the network, thereby increasing throughput and availability. However, the switch is most
commonly used to segment existing hubs, which usually improves overall performance. A
switching hub can be easily configured in any Ethernet network to significantly boost
bandwidth using conventional cabling and adapters.