Ethernet cabling (cable selection)

In order to communicate between two devices Selection of right Ethernet cable is essential. An Ethernet Cable act as communication media for communicating devices.

Overview

In order to design the media you must first know about communication process. Any communication Channel needs a Transmitter and a Receiver. The transmitter sends information/data which at receiver is received and processed

 In Ethernet Technology, Transmitters and receivers are found on the Networking card (called as Network Interface Cards, NIC). These cards have pins and each pin acts either as a receiver or a transmitter. However pin configuration on some cards are different than other like a PC NIC has different pins configuration than that of a switch. Below figure shows pin configuration card of a PC and that of a switch.  

The cable is used to connect one card pins to the other and based on these pins configuration, wire pairs inside Ethernet cable are arranged succeeding the following standard

Ethernet color coding Standard 

TIA/EA 568 A and TIA/EA 568 B are the standards followed for Ethernet color coding. Both standards have the only difference in wires arrangement i.e 568A used white green for pin1 and green for pin2, white orange for pin3 and orange for pin6 whereas 568B uses white orange for pin1, orange for pin2, white green for pin3 and green for pin6.

So far two type of Network cards are found and based on these cards there are two main categories of  Ethernet cable i.e. straight through and cross over.

Straight through cable

A cable is called straight through cable if it has same wiring order at both ends or If you follow 568A standard OR 568B standard on both sides of the wire it results in a straight cable.

In a straight through cable the cable will go to the same pin number on the other end

Usage

A straight through cable is used to connect different devices (devices that have different NIC pins configuration). Devices that are connected through straight through cable.

Why straight through

Since the network cards are different and to full fill the communication rule (transmitter connects to receiver), the Trans pin on one side have the same number as the receive pin on the other side. Thus the cable at pin1 should connect pin1 on other side. Similarly cable of pin2 goes to pin2, pin3 to pin3 and so on up to pin8 resulting a straight through cable.

Cross over cable

A cable in which pin1 and pin 2 of one end goes to pin3 and pin6 of other end. (Simplest way) if 568 A standard is used on one end and 568B standard is used on other end that results into a cross cable.

In a cross over cable pin1 and pin2 are swapped with pin3 and pin6 on other side.

Usage

A cross cable is used to connect same devices (same devices network card have same pin configuration) like connecting a computer to another computer or server or router. Figure shows some same devices

Why cross over

Since cards have same pins configuration so for communication to take place a trans pin must be connect to a receive pin. Therefore pin1 and pin2 of one end goes to pin3 and pin4 (which connects the trans pin to receive pins).