5.2 Structured Cabling

 5.2 Structured Cabling

The building of a network can be an extremely complex task and should be properly planned. One crucial aspect of a network is the cabling and infrastructure where a structured cabling system should be implemented that allows for future growth.

A variety of tools and materials are required for a successful build of structured cabling. Some of these may be needed at the start of the project while some may be required during the project.

The network plan should include:

  • The building and networking materials required
  • Who the suppliers are and what the costs are
  • The tools needed
  • The project completion date

There are also certain recommended standards that should be followed when building a network.

The 100m Rule

The 100 metre rule concerns Cat 5 horizontal cabling and advises the following:

  • 3 metres maximum from workstation to wall plate (telecommunications outlet)
  • 90 metres maximum for the horizontal cable run
  • 6 metres maximum for patch cables.

Although this only adds to 99 metres, it is generally referred to as the 100 metre rule. All things being equal, if this rule is followed then this should cut down on attenuation problems.

The TIA/EIA-568-A standard states that an RJ-45 connection is used with cables connecting to a wall plate/telecommunications outlet and also as the cable that is punched down to the other side of the wall plate. Like the wires in the cable the wall plate contains eight colour-coded slots. The individual Cat 5 wires are punched down using a punchdown tool (or Krone tool) into the appropriate coloured slot. This tool makes a good connection and secures the wire as well as cutting off any excess.

Telecommunications Outlet

The telecommunications outlet/panel in a horizontal cabling system is usually fixed to the wall with places to connect cables from PCs that look similar to telephone connections.

Structured cabling standards allows for two types of wall mount for the outlet/panel: Surface mount and Flush mount

Surface mounting is possibly the most popular choice because there is no need to cut into walls but rather the panels are mounted on the wall making installation much faster and easier. Surface mounting can be achieved by either using a screw-mounted box or an adhesive-backed box. The latter should only be chosen when the installed outlet will never have to be moved.

Flush mounting requires many factors to be taken into account before the installation, eg: the type of wall and the tools required to cut into it.

Quality of Connections

A LANs performance is closely linked to the quality of its connections. When you use RJ-45 jacks at the telecommunications outlet in a horizontal cabling scheme, the wiring sequence is critical to ensure the best possible network performance. Sequencing refers to the process of matching the wires of a cable to the proper terminals on the jack. To understand how this works, examine an RJ-45 jack, closely. Notice that the jack is colour coded. The colours – blue, green, orange, and brown – correspond to the colours of the wires in each of the twisted pairs of CAT 5 UTP.

Whenever you install cable, it is important that you document your actions. You can do this by using a cut sheet as you install the cable. A cut sheet is a rough diagram that shows the locations of the cable runs. It also indicates the numbers of the classrooms, offices, or other rooms, to which the cables have been run. Later you can refer to this cut sheet to place corresponding numbers on all telecommunications outlets and at the patch panel in the wiring closet. You can use a page in your journal to document cable runs. By doing so, you will have an additional layer of documentation for any cable installation.

TIA/EIA-606 specifies that each hardware termination unit have some kind of unique identifier. This identifier must be marked on each termination hardware unit, or on its label. When identifiers are used at the work area, station terminations must have a label on the faceplate, the housing, or the connector itself. All labels must meet legibility, defacement, and adhesion requirements as specified in UL969.