How Ethernet Works


Ethernet was initially invented as a way of connecting a printer to a computer but today is the name for the cable that allows most network devices to connect to each other. 
The name Ethernet can also refer to the communication protocol that is used by the cable that allows the devices to 'talk' to each other. Ethernet was created and designed by Bob Metcalfe while he was working at the Xerox research centre in 1973. 
Since then his creation has become almost the standard issue way to connect network devices and almost all computers and laptops have an inbuilt Ethernet port. The speed of Ethernet has also been improved since 1973 and we now have what is known as 'Fast Ethernet'. But what is Ethernet and how does it work?
A network allows computers to connect to each other and exchange information; in today's internet based society networks are hugely important. The internet itself is an example of a mammoth global network. There are two main types of network: a Local Area Network (or LAN) and a Wide Area Network (a WAN). 
A LAN is a network made up of a group of computers in close proximity. A WAN is a network that is made up of several major LANs and can cover vast distances - the internet is a WAN. Ethernet, then, is the connection that makes up a LAN. Ethernet can really only be used for LANs as over the long distances needed for a WAN the signal can break down. Ethernet is the basis for creating a LAN but also can be used to connect a computer or network to the internet.
In basic terms Ethernet breaks down communication barriers between different devices. It is a form of communication protocol. This means that devices can communicate with each other in the same 'language' and therefore form a network. 
Most computers nowadays will have an inbuilt Ethernet card or adapter. This adapter will give the device the ability to transmit and receive information across the network using Ethernet. 
The information that the device is sending and receiving is passed along an Ethernet cable that is plugged into the device's Ethernet port. Ethernet cables are usually made up of several wires; these wires allow data to be sent in both directions - to and from the device.
 The cables will connect to a router which will manage and direct the data that is being sent around the network. When the LAN needs to be connected to the internet, the router will connect to a modem (which carries the internet signal).
Using Ethernet has two main advantages. The first advantage is that new devices can easily be added to an existing network without having to reconfigure the whole network and all the devices in it. Networks using Ethernet have high levels of scalability which can be very useful in businesses that are expanding and growing. 
The second main advantage of Ethernet is the part of it known as 'Ethernet addresses'. When a piece of data is sent over a network it is received by all the other devices on the network. Without Ethernet addresses this could cause congestion and slow the network down as every device would try to understand the data it has received.
 With Ethernet every packet of data has a source address and a destination address (much like a letter will have a destination address and a return address). When the devices on the network receive the data they will check to see whether they are the 'addressee', if they are not they will disregard the data. If a device wants all the other devices on the network to pick up a certain piece of data, a broadcast address will be used instead.
In order to avoid data 'collisions', Ethernet uses what is called CSMA/CD or 'carrier-sense multiple access with collision detection'. It can be seen as much like a conversation. The device that wants to transmit data will 'listen' to see if any other device is already transmitting. 
Only if it is quiet will the device start transmitting its data. Collisions may occur if two devices 'hear' that the network is quiet and both start transmitting at the same time. If this happens the devices will stop transmitting and will wait a random amount of time before they try again. Using a different random amount of time each means that the devices are unlikely to collide again.
There are several other, slightly more advanced, components that can be added into an Ethernet network. A repeater can be added into the network and will repeat the data transmissions that it 'hears' - this means that the signal can travel along greater distances. 
An Ethernet 'bridge' can also be added into the network if there are too many devices connected resulting in congestion. A bridge will connect different parts of the network but will also manage the traffic. 
An Ethernet bridge will examine the destination address of the data being sent and will determine whether it needs to be passed on to other parts of the network. The use of a bridge means that data does not clog up the network by being transmitted unnecessarily to different parts of the network. 
An Ethernet switch is fairly similar to a bridge in that it can also expand the network diameter and regulate the traffic. However, with an Ethernet switch the data will only be passed on to the intended recipient device rather than a whole area of the network.

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