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What is Ethernet?

Updated on October 7, 2015

The Origins of Ethernet

The term ‘Ethernet’ almost sounds like something from science fiction. The reality, however, is that it is a component of computing and networks that is actually very common. Ethernet was originally invented as a way of connecting a computer to a printer but has since evolved into a specific type of cable that most network devices can use to connect to one another. Sometimes the term ‘Ethernet’ is also used to describe the actual communication protocol that is used in this process. Ethernet was created and developed by Robert Metcalfe in 1973 while he was working at the Xerox Research Centre - and it has become effectively the accepted standard for connecting network devices. Very few computers and laptops do not have an Ethernet port (i.e. where you plug in the cable) as the vast majority have them inbuilt as standard. The speed of networks and the internet in particular have increased rapidly in the past decade or so and as a result the speed of Ethernet has also developed and improved, leading to the creation of ‘fast Ethernet’.



In order to understand the concept of Ethernet it can be helpful to know the basics of computer networks. Networks can range from the very small, where two or more computers are connected, to the huge, such as the internet which is one of the biggest global networks. They are basically a way for different computers and devices to communicate with each other and exchange various types of information. There are two main types of network: LANs and WANs. A LAN is a ‘local area network’, this is where a group of computers are connected together in close proximity - in an office or a school. A WAN is a ‘wide area network’ and is made up of several LANs connected together. Unlike a LAN, a WAN can work over long distances - the internet is a huge WAN. So where does Ethernet come into it? Ethernet is what connects a LAN together and creates the network. It is not generally used for WANs because an Ethernet connection can deteriorate over wide distances.


Connecting Devices

In basic terms Ethernet is a way of letting two devices that may speak different ‘languages’ communicate with each other using a shared ‘language’. When two or more devices can communicate with each other using the same communication protocol they can form a network. Because Ethernet has become such a popular way of connecting devices most computers will have a built-in Ethernet adapter or card. This card or adapter lets the device use Ethernet and allows it to send and receive information around a network. The Ethernet adapter is connected to an Ethernet port - this port is what the Ethernet cable is plugged in to and the information is then sent along the cable. When two devices use an Ethernet connection they simply need to be connected by the same Ethernet cable. For a network of more than two computers the cables will be plugged into a router as this can manage the data being sent and ensure that it goes to the right place. Ethernet cables are usually made up of several different wires which means that information can be both sent and received. When a network needs to be connected to the internet the router will be plugged into a modem.



There are several advantages to using Ethernet. With an Ethernet network different devices can easily be added and removed. There is no need to completely reconfigure a network in order to include a new device, the new component simply needs to be ‘plugged in’. This scalability means that Ethernet is often a popular choice in business environments. Using Ethernet can also avoid unnecessary network congestion. When information is sent over a network it is received by all the devices on the network and this means that all devices may try and understand the information - causing lags and congestion. With Ethernet every piece of information that is sent will have both a source address and a destination address, these addresses (known as Ethernet addresses) allow the devices to know exactly where the data has come from and where it needs to go. If the data is not addressed to a specific device on the the network it will disregard it rather than try to understand it. This means that data can be sent quickly to the appropriate device on the network. A broadcast address will be used when the data being sent needs to be received by all the devices on a network.


Data Collisions

Using Ethernet can also be useful for avoiding data collisions. A data collision is where two, or more, devices start transmitting data at the same time and the transmissions ‘collide’ - this can cause the data to become fragmented and the transmissions may become confused. With Ethernet when a device wants to transmit information around the network it will first ‘listen’ to the network to see if any other device is transmitting. If the network is quiet the device will start transmitting. This system is known as ‘carrier-sense multiple access with collision detection’ or CSMA/CD. The risk of collisions is much lower with Ethernet as a collision will only happen if two devices both hear that the network is quiet and both start transmitting at the same time. There is even a process in place for when this happens, if there is a collision the devices will stop their transmissions and will try again after a random amount of time.


Additional Components

An Ethernet network can be simple with two computers connected via an Ethernet cable but can also be much larger and more advanced. The distance an Ethernet network can cover can be increased through the use of a repeater. A repeater will repeat the data transmissions that it picks up which means that the transmissions can be sent much further. A bridge can connect different parts of a network together but can also manage the traffic and the information being sent. It will look at the packets of data being sent and will determine if it needs to be sent to a specific part of the network. Using a bridge means that data does not cause congestion by being sent to the wrong part of the network. An Ethernet network can also use a switch to organise and manage the traffic flow and to increase the diameter of the network. Unlike a bridge, however, an Ethernet switch can direct packets of data to the intended device rather than a part of the network.

The History of Ethernet

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