Network cable, lesson 1: Introduction

This series focuses on the cabling used in today's networks. This series will cover most common cables, which include UTP CAT5 straight through and crossover, Coax and a few more.

This series focuses on the cabling used in today's networks. There's a lot of different type of cabling in today's...

networks and I am not going to cover all of them, but I will be talking about the most common cables, which include UTP CAT5 straight through and crossover, coax and a few more.

Cabling is very important if you want a network to work properly with minimum problems and bandwidth losses. There are certain rules which must never be broken when you're trying to design a network -- otherwise you'll have problems when computers try to communicate. I have seen networks that suffer from enormous problems because the initial design of the network was not done properly!

In the near future, cabling will probably be something old and outdated since wireless communication seems to be gaining more ground, day by day. With that in mind, around 95% of companies still rely on cables.

Let's have a quick look at the history of cabling which will allow us to appreciate what we have today!

The beginning

We tend to think of digital communication as a new idea but in 1844 a man called Samuel Morse sent a message 37 miles from Washington D.C. to Baltimore, using his new invention 'The telegraph.' This may seem a far cry from today's computer networks but the principles remain the same.

Morse code is type of binary system which uses dots and dashes in different sequences to represent letters and numbers. Modern data networks use 1s and 0s to achieve the same result. The big difference is that while the telegraph operators of the mid 19th Century could perhaps transmit 4 or 5 dots and dashes per second, computers now communicate at speeds of up to 1 Giga bit, or to put it another way, 1,000,000,000 separate 1s and 0s every second.

Although the telegraph and the teletypewriter were the forerunners of data communications, it has only been in the last 35 years that things have really started to speed up. This was borne out of the necessity for computers to communicate at ever increasing speeds and has driven the development of faster and faster networking equipment, higher and higher specification cables and connecting hardware.

Development of new network technology

Ethernet was developed in the mid 1970's by the Xerox Corporation at its Palo Alto Research Centre (PARC) in California and in 1979 DEC and Intel joined forces with Xerox to standardize the Ethernet system for everyone to use. The first specification by the three companies, called the 'Ethernet Blue Book', was released in 1980, it was also known as the 'DIX standard' after their initials.

It was a 10 Mega bits per second system (10 Mbps = 10 million 1s and 0s per second) and used a large coaxial backbone cable running throughout the building, with smaller coax cables tapped off at 2.5 meter intervals to connect to the workstations. The large coax, which was usually yellow, became known as 'Thick Ethernet' or 10Base5 - the '10' refers to the speed (10 Mbps), the 'Base' because it is a base band system (base band uses all of its bandwidth for each transmission, as opposed to broad band which splits the bandwidth into separate channels to use concurrently) and the '5' is short for the system's maximum cable length, in this case 500 meters.

The Institute of Electrical and Electronic Engineers (IEEE) released the official Ethernet standard in 1983 called the IEEE 802.3 after the name of the working group responsible for its development and, in 1985, version 2 (IEEE 802.3a) was released. This second version is commonly known as 'Thin Ethernet' or 10Base2; in this case the maximum length is 185 meters even though the '2' suggest that it should be 200 meters.

Since 1983, various standard have been introduced because of the increased bandwidth requirements, so far we are up to the Gigabit rate!

Unshielded Twisted Pair

Unshielded Twisted Pair cable is most certainly by far the most popular cable around the world. UTP cable is used not only for networking but also for the traditional telephone (UTP-Cat 1). There are six different types of UTP categories and, depending on what you want to achieve, you would need the appropriate type of cable. UTP-CAT5 is the most popular UTP cable, it came to replace the good old coaxial cable which was not able to keep up with the constant growing need for faster and more reliable networks.


The characteristics of UTP are very good and make it easy to work with, install, expand and troubleshoot and we are going to look at the different wiring schemes available for UTP, how to create a straight through UTP cable, rules for safe operation and a lot of other cool stuff !

So let's have a quick look at each of the UTP categories available today:

UTP categories

Category 1/2/3/4/5/6 – a specification for the type of copper wire (most telephone and network wire is copper) and jacks. The number (1, 3, 5, etc) refers to the revision of the specification and in practical terms refers to the number of twists inside the wire (or the quality of connection in a jack).

CAT1 is typically used for telephone wire. This type of wire is not capable of supporting computer network traffic and is not twisted. It is also used by phone companies who provide ISDN, where the wiring between the customer's site and the phone company's network uses CAT 1 cable.

CAT2, CAT3, CAT4, CAT5 and CAT6 are network wire specifications. This type of wire can support computer network and telephone traffic. CAT2 is used mostly for token ring networks, supporting speeds up to 4 Mbps. For higher network speeds (100 Mbps plus) you must use CAT5 wire, but for 10 Mbps CAT3 will suffice. CAT3, CAT4 and CAT5 cable are actually 4 pairs of twisted copper wires and CAT5 has more twists per inch than CAT3 therefore can run at higher speeds and greater lengths. The "twist" effect of each pair in the cables will cause any interference presented/picked up on one cable to be cancelled out by the cable's partner which twists around the initial cable. CAT3 and CAT4 are both used for Token Ring -- the only difference is CAT3 can be as long as 100 meters while CAT4 can only be 200 meters.

CAT6 wire was originally designed to support gigabit Ethernet (although there are standards that will allow gigabit transmission over CAT5 wire, that's CAT 5e). It is similar to CAT5 wire, but contains a physical separator between the four pairs to further reduce electromagnetic interference.

Part four of our series will show you how UTP cable is wired and the different wiring schemes. It's well worth coming back and reading about.

Network cable, lesson 1, Introduction
Network cable, lesson 2: Straight-through UTP cables
Network cable, lesson 3: CAT5 UTP x-over cable
Network cable, lesson 4: 10Base-T/2/5/F/35 - Ethernet
Network cable, lesson 5: 100Base-(T) TX/T4/FX - Ethernet
Network cable, lesson 6: Fiber 
Network cable, lesson 7: Direct Cable Connection
Network cable, lesson 8: Serial Direct Cable Connection
Network cable, lesson 9: Parallel Direct Cable Connection
Network cable, lesson 10: USB Direct Cable Connection
Testing network cable

This was first published in May 2004

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