Ethernet
What is Ethernet?
Ethernet is a networking protocol, which basically means it is a set of rules which specify how computers talk to each other. Networking protocols are to computers what language is to humans. In order for you to understand another person speaking they need to speak the same language, whether it be English, Dutch, German, etc. Computers can only understand what other computers are saying if they both speak the same language, or protocol.
Ethernet was invented by Bob Metcalfe back in 1973, at Xerox Corporation’s Palo Alto Research Center. He was working on a method to communicate from Xerox’s “Alto” computer to a printer. Metcalfe developed the physical method of cabling that connected devices on the Ethernet as well as the standards that governed communication on the cable. Ethernet was named for the passive substance called “Luminiferous (light-transmitting) Ether” that was once thought to pervade the universe, carrying light throughout. Ethernet was similarly named to describe the way that cabling, also a passive medium, could similarly carry data everywhere throughout the network.
Ethernet is most commonly used in Local Area Networks (LAN). Local, meaning an area of close proximity such as a single building. Typical wired implementations of Ethernet are usually less than a few hundred meters. However, advances in Fiber optic cable technologies have allowed these LAN distances to be increased.
A Basic Hard Wired Network
A basic wired LAN network involves the following components:
- Two different computers which need to communicate with each other (or a computer and printer)
- A Network Interface Card (NIC) in each computer
- A Network Switch or Network Hub which controls the network traffic
- Network Software
- Ethernet cables to connect the equipment together
The NIC’s are installed in the computers and are assigned a unique address (MAC address). The network switch or hub acts as a relay which inspects and passes the data to the correct destination. Networking software is built-in to most modern operating systems so as soon as the cables are connected the other networked devices are electronically visible immediately.
Wireless Ethernet LAN
Wired networks are still the fastest and most reliable medium for Ethernet, but are not always economically feasible. It takes someone with special skills to install network data cables in a home and these skills usually come with a cost. Ethernet can also communicate over radio waves without the need for any wiring. A wireless access point with a small antenna is required to send and receive these signals and route them thru the wired network.
Many advances in wireless networking have been made over the years so that it’s now possible for a basic home network to use nothing but wireless communication. This lowers the price barrier for new customers allowing the spread of home networks to grow.
What’s a Switched Ethernet Network?
An important concept in networking, even home networks, is switching. As mentioned earlier, every network interface card (NIC) connected to the network has a unique address. When a computer wants to communicate with another computer it sends this message (the correct terminology would be discrete packets or frames) out on to the “Ethernet wire” with the address of the computer it is meant for. As the frame travels the wire, each computer inspects the address and if it is the correct address inspects the data further for processing. If the address is incorrect, it simply ignores the message.
An exception to this Ethernet addressing is an implementation called broadcast address. If a frame has a broadcast address then every computer will open and inspect the data.
Many of these message frames pass down the Ethernet wire. At some point the number of messages a computer needs to ignore greatly exceeds those it needs to process at which points it’s spending more resources than needed, along with filling the capacity of the medium or wire to communicate.
The solution to this Ethernet traffic congestion problem is called a network switch. All network devices connect directly to this switching device instead of each other. The switch then becomes responsible for nothing more than inspecting each frame’s address and relaying down the correct port which connects to the proper computer. This has allowed LAN’s to grow in size and capacity.
Ethernet Terminology, Facts and Figures
- Ethernet transfers data at 10 megabits per second. Fast Ethernet transfers data at 100 megabits per second. Gigabit Ethernet transfers data at 1,000 megabits per second.
- Ethernet cables are different than phone cables or coaxial cables. Although phone and Ethernet cables might sometimes look the same, Ethernet cables use a different connector (RJ45) than phone cables (RJ11).
- Each device on an Ethernet network operates independently and equally, eliminating the need for a central controlling device (passive medium).
- Ethernet supports a wide array of protocols, the most common including TCP/IP, UDP, and ICMP (Ping).
- When two or more network devices attempt to send packets at the same time, Ethernet detects these collisions to prevent the loss of data. When this happens, all devices stop transmitting and wait a randomly determined period of time before they attempt to transmit again.
- Ethernet devices attach to a common medium that provides a path along which the electronic signals will travel. In earlier times, this medium was a copper coaxial cable, but today it is more commonly a twisted pair cable or fiber optic cabling.
- A single shared medium (or wire) by more than one network device is called an Ethernet segment (with a switched network the segment is dedicated to the device).
- Devices that attach to a segment are stations or nodes.
- The nodes communicate in short messages called frames, which are variably sized chunks of information.
