Ethernet may be a way of connecting computers together during a local area network or LAN. It has been the foremost widely used method of linking computers together in LANs since the 1990s. The basic idea of its design is that multiple computers have access thereto and may send data at any time. This is comparatively easy to engineer.
If two computers send data at an equivalent time, a collision will occur. When this happens, the data sent is not usable. In general, both computers will stop sending, and wait a random amount of time, before they try again. A special protocol was developed to deal with such problems. It is called Carrier sense multiple access with collision detection or CSMA/CD.
There are different Ethernet standards. Today, Ethernet cables look like thick telephone cables. They connect to boxes called hubs or switches. Each cable runs from a computer’s network interface card (NIC) to such a box. This cable is named 10BaseT or 100BaseT, or 1000BaseT Cable.
All cable types:
10Base2 and 10Base5: These coaxial cables are like those used in television, but 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. It supports 10MBits per second transfer speed. It was the first to be adopted and became rare during the 21st century.
10BaseT: Cables look like thick phone cables, but with 8 copper wires instead of 2 or 4, and they go from each computer’ 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 an equivalent as 10BaseT, but can run at up to 1GBit (1000MBit) per second.
RJ45 Ethernet Wiring Color Guides with Ethernet wiring diagram
Recall that there are two standards for the colors in the RJ45 specification: T568a and T568b. The standard being utilized on either side of a Twisted Pair wire is what determines whether the cable is straight-through or crossover.
To make a Straight-through cable, simply order the wires on both sides of the cable to one specification (either both T568a or both T568b):
To make a Crossover cable, simply use one standard on one side, and the other standard on the opposite side:
Note that wire pair 1 and pair 4 aren’t used (the blue and brown wires). You could, theoretically not include the wires in the cable at all, but this would make keeping the remaining wires in the proper order rather difficult.
Moreover, since they are not used, they do not need to be crossed in a crossover cable. However, the Gigabit specification does require using all 8 wires, and often all pairs are crossed for consistency. We will discuss Gigabit Ethernet later during this article.
And lastly, remember that the signal doesn’t really care what color the wire is. As long as the correct pins are connected to each other, communication will work. You could use all green wires, and as long as Pins 1&2 are connected to Pins 3&6 on the other side (and vice versa), you would have a fully functioning cross-over wire. But just because it works, doesn’t mean it is a good idea – such a cable would be a nightmare to maintain.
Orange cables represent a demarcation point for central office termination.
Green cables represent the termination of network connections on the customer side of the demarcation point.
Purple cables are used to specify the termination of cables that originate from common equipment like LANs, PBXs, computers, or multiplexers.
White cables indicate first-level backbone telecommunications media termination within the building containing the most cross-connect.
Grey cables indicate second-level backbone telecommunications media termination in the building containing the main cross-connect.
Blue cables indicate the termination of telecommunications media and are required only at the equipment room end of the cable, not at the telecommunications outlet.
Red cables are used to signify the termination of key telephone systems within an organization.