Ethernet

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How a local area network using Ethernet might be connected
RJ45 Ethernet connector

Ethernet is a way of connecting computers together in a local area network or LAN. It has been the most widely used method of linking computers together in LANs since the 1990s. The basic idea of its design is that multiple computers have access to it and can send data at any time. This is comparatively easy to engineer.

Collisions are possible if two computers send data at the same time, a fact that disallows its use if real-time requirements are set. A protocol called Carrier sense multiple access with collision detection or CSMA/CD was designed to deal with these problems.


Different cable types[change | edit source]

There are different Ethernet standards. Today, Ethernet looks like connecting cables that look like thick telephone cables to a set of boxes called hubs or switches. Each cable runs from a computer's network interface card (NIC) to such a box. This cable is called 10BaseT or 100BaseT, or 1000BaseT Cable.

All cable types:

  • 10Base2 and 10Base5: The cables look the same as the cables used to connect a TV to a cable TV company or to a satellite dish, but they are a bit thinner. They are also called "thinnet" or "coax". Each computer has a "T" plugged into it, and cables plug into each side of the "T". Sometimes, instead of a "T", a vampire tap is used which goes through the skin of a cable. It supports 10MBits per second transfer speed, and was the first to be adopted.
  • 10BaseT: Cables look like thick phone cables, but with 8 copper wires instead of 2 or 4, and they go from each computer's Network Interface card to a Hub or a Switch. Supported speed is 10 MBit/second.
  • 10BaseF: Same as 10BaseT, but cables transmit light pulses, instead of electrical signals.
  • 100BaseT: Cables look the same as 10BaseT, but can run at up to 100 MBits per second
  • 1000BaseT: Cables look the same as 10BaseT, but can run at up to 1GBit (1000MBit) per second.

Today, the cables for 10BaseT, 100BaseT, and 1000BaseT are the same. They use unshielded twisted pair of Category 5 (UTP-Cat5) or 5e for that. Shielded cable (STP-Cat5 or Cat5e) can be used when there is a lot of electrical noise, and Category 6 (UTP-Cat6 or STP-Cat6) works better with faster signals such as 1GBit or 10GBit.

Different devices[change | edit source]

Other devices, such as the Xbox 360 and the Playstation 3, can also be connected using the same kind of cabling. Certain computer peripherals, for example printers and certain hard disks can be directly connected to the network with such cables.

Different speeds[change | edit source]

Ethernet can go at different speeds. In the beginning, Ethernet was at 10 MBits per second. The Ethernet most often used today is at 100 MBits per second. Most new computers now have the NIC built in, and can go at 1GBit per second. There are also standards for 1GBit per second and 10 GBit per second. 100 MBit can usually talk to 10 MBit, and 1 GBit can talk to 100 MBit and usually to 10 MBit (both full and half duplex).