Ethernet Hub

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An Ethernet hub is a very basic, older networking device used to connect multiple computers together so they can talk to each other in a Local Area Network (LAN).
It looks like a small box with several ports (plugs) on the back for internet cables.
Because of the way it works, a hub is often described as a "dumb" device or a multi-port repeater. It ties closely into the previous concept: it takes a signal from one cable and repeats it, but it does so across many cables at once.

Imagine you are in a room with five coworkers, and you want to pass a private message to just one of them, named Sarah.

Instead of walking over and whispering it to Sarah, you grab a megaphone and shout: "HEY EVERYONE, THIS MESSAGE IS FOR SARAH: THE MEETING IS AT 2 PM!" Everyone in the room is forced to hear the message. Bob, John, and Lisa hear it, realize their name isn't Sarah, and ignore it. Sarah hears it, realizes it is for her, and accepts it.

This is exactly how an Ethernet hub operates.

How It Works: Step-by-Step

  1. Receiving the Data

    Computer A wants to send a document to Computer B. It chops the document up into digital envelopes (packets) and sends them down the cable into the hub.

  2. The "Blind" Broadcast

    Unlike a smart mail-sorter, the hub cannot read the destination addresses (the MAC addresses we talked about earlier) on the envelopes. It has no idea which cable leads to Computer B

  3. Copying and Shouting

    Because it doesn't know where the data is supposed to go, the hub simply makes copies of the electrical signal and blasts it out of every single port to every single computer connected to it.

  4. The Computers Decide

    Every computer connected to the hub receives the data. Their network cards check the address on the packets. The computers that are not Computer B simply drop the data and ignore it. Computer B sees its own address, accepts the data, and puts the document back together.

The Big Problem

Network "Traffic Jams"

Because a hub blasts every single message to every single connected device, it creates a lot of unnecessary noise.

If Computer A and Computer C both try to send a message at the exact same time, their signals crash into each other inside the hub. This is called a collision. The data gets scrambled, both computers have to pause, wait a random amount of milliseconds, and try shouting their messages again.

Because of this inefficiency, Ethernet hubs are almost completely obsolete today.

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