Network Cabling Guide

Local Area Networks (LAN) have become the prevalent way of sharing information. As this is probably the fastest moving of cabling media, by the time you have finished reading this, another new product will be on the market !

Network cables very generally fall into one of the following categories:

Token Ring, (a.k.a. IBM Type 1)
Thin Ethernet (a.k.a. 10 base 2)
UTP (a.k.a. Cat 5/ 10 base T/ 100 base Tx /RJ45 ).

There are of course many other systems, but for this purpose we shall concentrate on these systems.

Token Ring (a.k.a. the IBM cabling system)

Most currently available Token ring products come in a variety of cabling media. This includes UTP, STP and Twin-axial. These different media sometimes need to be mixed when a building is "flood wired" with Token Ring style cabling, and new equipment has come into place that does not appear to be compatible.

The IBM data connector is generally found on MSAU's (Multi Station Access Units) or Wall outlets in a Type 1 cable installation. The other connector style associated with Token ring is the D9 connector. This is found on the IBM Token Ring card installed in the PC. A Token ring "drop" or "adapter" cable attaches the computers Token Ring card to a wall point or directly to an MSAU. (D9 Male - Data Connector)

IBM "patch" cables daisy chain MSAU's to each other or are used in a patch panel enabling more points to be added on to the network.

New token ring cards present an RJ45 connector. This enables Token Ring to be run over a UTP structured cabling system. (see UTP) If this is the case an impedance matching device or Balun is required. This matches the W difference in the two different cabling media enabling the system to work.

This presents an IBM data connector and a RJ45 connector.

To slightly add to the confusion, it is possible to run 10 base T over a Token Ring cabling system. Again a Balun is required but it is different from the Balun used to run Token ring (RJ45). Though externally will appear exactly the same.

Thin Ethernet a.k.a. Ten base 2 / IEEE 802.3

Originally designed in the 1970's Ten base 2/IEEE 802.3 has been widely used and is still a low cost network system. The Thin Ethernet system is a "bus" design. PC's can be joined together via the BNC network card to a maximum of 30 users per 185 Mtr segment. Maximum total network length is 925 Mtrs and 1024 users using repeaters.

The minimum distance between computers or "nodes" is 0.5 Mtr.

Due to the nature of the Thin Ethernet network design. If connection is broken, the whole of that particular segment can be at risk and failure. There are available on the market several different styles of self terminating systems that combat this problem. These types of cables and wall outlets make a new connection before breaking the old one. This enables users to easily plug and unplug systems without crashing the system.

A LAN (Local Area Network) is a network of interconnected workstations sharing the resources of a single processor or server within a relatively small geographic area. Typically, this might be within the area of a small office building.

Ethernet is the most widely-installed Local Area Network technology. Originally specified by the standard, IEEE 802.3, Devices are connected to the cable and compete for access using a Carrier Sense Multiple Access with Collision Detection (CSMA/CD) protocol. Ethernet was originally developed by Xerox and then developed further by Xerox, DEC, and Intel. An Ethernet LAN traditionally utilised coaxial cable. However, most modern networks use special grades of twisted pair cable. This is known as CAT 5 cable.

Still utilising the same IEEE 802.3 standard, but introducing new features into the picture, such as Management, Switching, greater Bandwidth and Routing.

Fast Ethernet or 100BASE T provides transmission speeds up to 100 megabits per second and is typically used for LAN backbone systems, supporting workstations with 10BASE-T cards. Gigabit Ethernet provides an even higher level of backbone support at 1000 megabits per second (1 gigabit or 1 billion bits per second).As greater speeds and bandwidth are achieved, it is now often the case that users require 100 Mbps to the desktop. Cards, switches and hubs are widely available. It is important to assess the design of LAN's where 100 BASE T is concerned. For example by replacing cards, hubs and switches like for like from 10 BASE T to 100 BASE T will not necessarily give the user the increased speed and network access initially assumed.

In 100 Mbps (megabits per second) Ethernet (Also known as Fast Ethernet), there are three types of physical wiring that can carry signals:

• 100BASE-T4 (four pairs of CAT 3 twisted pair wire)
• 100BASE-TX (two pairs of CAT 5data grade twisted-pair wire)
• 100BASE-FX (a two-strand fibre optic cable)

100BASE-T4 was designed to enable 100 Mbps transmission over Category 3 cable, which is only rated at 10 Mbps This was achieved by utilising all 8 lines of the cable. Network Hardware for 100BASE T4 is rare. The most commonly used standard is 100 BASE TX. Fast Ethernet hardware generally conforms to this standard.100BASE-FX transmission the signal across fibre optic cable enabling greater distances to be reached.

In response to the growing demand for data applications, cable performance evolved such that there are currently 5 levels, called Categories, of transmission performance for Unshielded Twisted Pair (UTP) cables. These are detailed in the table overleaf. The levels are hierarchical. In other words, a higher category can be substituted for any lower category.