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What's the difference between a Hub, a Switch and a
Router?
In a
word: intelligence.
Hubs, switches and routers are all devices which let you
connect one or more computers to other computers, networked devices or to other
networks. Each has two or more connectors, called ports, into which you plug in
the cables to make the connection. Varying degrees of magic happen inside the
device, and therein lays the difference. I often see the terms misused, so
let's clarify what each one really means.
A hub is typically the least expensive, least
intelligent, and least complicated of the three. Its job is very, very simple:
anything that comes in one port is sent out to the others. That's it. Every
computer connected to the hub "sees" everything that every other
computer on the hub sees. The hub itself is blissfully ignorant of the data
being transmitted. For years, simple hubs have been quick and easy ways to
connect computers in small networks.
A switch does essentially what a hub does, but more
efficiently. By paying attention to the traffic that comes across it, it can
"learn" where particular addresses are. For example, if it sees
traffic from machine A coming in on port 2, it now
knows that machine A is connected to that port, and that traffic to
machine A needs to only be sent to that port and not any of the others. The net
result of using a switch over a hub is that most of the network traffic only
goes where it needs to, rather than to every port. On busy networks, this can
make the network significantly faster.
A router is the smartest, and most complicated of
the bunch. Routers come in all shapes and sizes, from the small four-port
broadband routers that are very popular right now, to the large industrial
strength devices that drive the internet itself. A simple way to think of a
router is as a computer that can be programmed to understand, possibly
manipulate, and route the data it’s being asked to handle. For example,
broadband routers include the ability to "hide" computers behind a
type of firewall, which involves slightly modifying the packets of network
traffic as they traverse the device. All routers include some kind of user
interface for configuring how the router will treat traffic. The really large
routers include the equivalent of a full-blown programming language to describe
how they should operate, as well as the ability to communicate with other
routers to describe or determine the best way to get network traffic from point
A to point B.
A quick note on one other thing that you'll often see mentioned
with these devices, and that's network speed. Most devices now are capable of
both 10mps (10 mega-bits, or million bits, per second) and 100mbs, and will
automatically detect the speed. If the device is labeled with only one speed,
then it will only be able to communicate with devices that also support that
speed. 1000mbs, or "gigabit" devices are
starting to slowly become more common as well. Similarly, many devices now also
include 802.11b or 802.11g wireless transmitters that simply act like additional
ports to the device.