Ethernet: Cables That Keep the World Connected

2025-02-17 | By Antonio Velasco

When I was a kid, my father who worked in IT would always try to teach me about the emerging technology that was the internet. I’d set up our home WiFi with him and connect these super-long blue cables to all of the computers in the house. Back then, I simply understood that it was what allowed my old Intel NUC to connect to the internet and display Club Penguin or the news. Without it, there was no connection, and the computer was fundamentally useless.

Fast forward 15 years and I still find myself relying on those blue cables for most internet or communication applications. This workhorse, known as Ethernet, is the fundamental technology that keeps the world connected. In this blog, I’ll talk about what it is, how it's used, and most importantly, how a few twisted pairs keep computers in the loop.

What is Ethernet?

Ethernet simply put is a protocol–a standard that defines the way data is transmitted from computer to computer or network to network. Like how USB cables are a universal standard across computers and other devices, Ethernet serves as the medium for network communication. To first understand this concept, let’s take a look at how the internet works.

Ethernet: Cables That Keep the World Connected

The internet is an amalgamation of computer networks that allow the world to stay connected. In order to interface with the internet, you need to utilize a router–essentially a gateway. Routers allow your local area network (LAN), like your home setup, to communicate with a wide area network (WAN), like the Internet.

The router can connect to switches or servers in your home or office, which provides internet access. To facilitate the connection between all of these components in a LAN (and on a bigger scale, a WAN), there needs to be a universal medium, else it can get extremely complicated. As such, we have ethernet!

How Does Ethernet Transmit Data?

Data that’s transmitted through the internet is done in frames, consisting of a header (with the destination address and source), payload (with the data needing to be sent), and the trailer (with integrity checks or error failsafes). These frames are utilized within a single network and are converted into packets when needing to be sent from a network to a network (like to the internet).

Ethernet: Cables That Keep the World Connected

Computers transmit and receive data in binary (0’s and 1’s). Ethernet cables facilitate this interaction through pairs of twisted copper wires. Computers utilize a network interface card to send or receive data in the form of electrical signals sent through the wires. Routers and switches relay this signal and ensure it’s being sent to the correct destination.

Most ethernet cables contain 4 different pairs of twisted copper wire pairs.

Ethernet: Cables That Keep the World Connected

In a typical cable, one pair is responsible for transmitting data, and the other for receiving data. The reasoning as to why they’re in pairs is to take advantage of differential signaling. One wire carries a positive signal, and the other a negative signal. When a network interface card or router reads this, they’re able to correlate one with the other and check the signal quality. Moreover, this helps to remove noise and improve transmission speed.

The other two pairs can either be used for extra data channels, grounding, or to provide power over ethernet (where two pairs carry data, and two pairs carry power).

So, What’s the Twist?

One of the key functions of ethernet cables is their twisting. Each pair is twisted and wound with the other in order to keep out noise and minimize interference.

Going back to some physics, you might recall that when electricity is sent through a wire, there is a slight electromagnetic field that is induced around the wire. When small amounts of power are being sent through signal wires, this electromagnetic field can easily create noise and interference in your signal, reducing its integrity and causing problems.

By twisting the pairs, we can cancel out this electromagnetic field. You might recall from earlier that a positive signal is sent in one pair, and a negative signal in the other. This has a secondary effect in which the opposite polarities result in electromagnetic fields which cancel out.

Overall, Ethernet is an amazing technology that provides the foundation for the infrastructure of the Internet. It transmits and receives data efficiently while being engineered to provide more than adequate protection against noise and interference. With such crucial applications, signal integrity is paramount, and ethernet cables have evolved to fit the bill for every application.

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