Bridges, routers, hubs and switches

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The lowdown on bridges, routers, hubs and switches in today’s networks


Today’s networks consisting of more than a couple computers often find themselves in need of quicker and easier data transmission and solutions equipped to handle more complex network traffic. Enter bridges, hubs, routers and switches. The Internet, for example, in all its complexity and mystery, consists of thousands of routers that work hard to connect you to this, and other, web sites. Let’s take a look at these four networking hardware devices.


Bridges


Bridges are different than routers, but provide similar services by forwarding datagrams, or packets, by physical address after filtering the data. Bridges examine each network segment and build a table with a physical address (or computer address) for computers on each segment. Simply put, when data is transmitted on the network segment, the bridge will grab it and check its destination address. If the physical address resides on another segment, the bridge will forward that packet of data to that segment, and ultimately to the packet’s correct destination. If the physical address resides on the same segment in which the datagram was originally transmitted, the bridge will release the data back to the originating segment for delivery. If, however, the bridge cannot find the network segment the packet of data was instructed to travel to, the bridge will assume the destination address is not that of datagram origination, and will forward it to all other network segments.


Hubs


Hubs, although providing many connection conveniences, are actually rather simple. Hubs come in many different port capabilities (number of available computer connection outlets). A 4-port hub, for example, will allow 4 different computers to connect to the hub. When the hub receives data from one computer, it will forward that data to all other computers simultaneously connected to the hub. Often a clump of computers, perhaps in a small office building, will connect by the way of a hub. As the office and network grow, a hub can connect with another hub to provide greater connectivity.


Switches


One problem with hubs is each computer on the network is sent data from one single machine, regardless of the intended computer destination. A switch will take a packet of data from one computer and send it only to the computer to which the packet was addressed, without congesting other computers with unsought datagrams.


Routers


Routers are by far the most complex of the four discussed network hardware devices. In the simplest terms, a router uses a logical address, or IP address, to route data. Routers also monitor network traffic, bandwidth, and length to the destination address and chooses the very best access method for the packet of data. If Internet network traffic through Kansas City is congested, the router may choose a route through Chicago, IL to the North or Little Rock, AK to the south.

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