Hubs and Switches – Bits and Bytes of Computer Networking from Grow with Google #5


We’re going to do a rundown of network
devices in this video and the next one. Almost every IT specialist will have to
interact with these sorts of devices on a regular basis. Cables allow you to form
point-to-point networking connections. These are networks where only a single
device at each end of the link exists. Not to knock point-to-point
networking connections, but they’re not super useful in a world
with billions of computers. Luckily, there are network
devices that allow for many computers to
communicate with each other. The most simple of these devices is a hub. A hub is a physical layer
device that allows for connections from many computers at once. All the devices connected to
a hub will end up talking to all other devices at the same time. It’s up to each system connected
to the hub to determine if the incoming data was meant for
them, or to ignore it if it isn’t. This causes a lot of
noise on the network and creates what’s called a collision domain. A collision domain is a network segment where only one device can
communicate at a time. If multiple systems try
sending data at the same time, the electrical pulses sent across
the cable can interfere with each other. This causes these systems
to have to wait for a quiet period before they
try sending their data again. It really slows down
network communications, and is the primary reason
hubs are fairly rare. They’re mostly a historical
artifact today. A much more common way of connecting many
computers is with a more sophisticated device, known as a network switch,
originally known as a switching hub. A switch is very similar to a hub, since
you can connect many devices to it so they can communicate. The difference is that
while a hub is a layer 1 or physical layer device,
a switch is a level 2 or data link device. This means that a switch can actually
inspect the contents of the Ethernet protocol data being sent around
the network, determine which system the data is intended for and then only
send that data to that one system. This reduces or even completely eliminates the size
of collision domains on a network. If you guessed that this will
lead to fewer retransmissions and a higher overall throughput, you’re right.

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