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The Basics of Structured Cabling

A structured cabling system is a complete system of cabling and associated hardware, which provides a comprehensive Digital communications infrastructure. This infrastructure serves a wide range of uses, such as transmit data through a computer network, connect CCTV or provide telephony services. It should not be device dependent.

We further define a structured cabling system in terms of ownership. The structured cabling system begins at the point where the service provider (SP) terminates. This point is the point of demarcation (demarc) or Network Interface Device (NID).

For example, in a telephone system installation, the SP, BT for example furnishes one or more service lines. The SP connects the service lines at the point of demarcation.

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Every structured cabling system is unique

This is due to variations in:

  • The architectural structure of the building, which houses the cabling installation;
  • The cable and connection products;
  • The function of the cabling installation;
  • The types of equipment the cabling installation will support — present and future;
  • The configuration of an already installed system (upgrades and retrofits);
  • Specific customer needs.

Network cabling standards are used internationally and are published by ISO/IEC, CENELEC and the Telecommunications Industry Association (TIA). The UK and most European countries use CENELEC, International Electrotechnical Commission (IEC) or International Organization for Standardization (ISO) standards.

These bodies as the responsible organization for providing and maintaining standards and practices within the profession and have published a series of standards to design, install, and maintain cabling installations. These help to ensure a proper cabling installation.

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Benefits of these standards include

  • Consistency of design and installation;
  • Conformance to physical and transmission line requirements;
  • A basis for examining a proposed system expansion and other changes; and
  • Uniform documentation.

The industry standard term for a network installation that serves a relatively small area (such as a structured cabling installation serving a building) is a local area network (LAN). There are also metropolitan area networks (MANs) and wide area networks (WANs) serving greater areas.

Structured cabling installations typically include: entrance facilities; vertical and horizontal backbone pathways; vertical and horizontal backbone cables; horizontal pathways; horizontal cables; work area outlets; equipment rooms; telecommunications closets; cross-connect facilities; multi-user telecommunications outlet assemblies (MUTOA); transition points; and consolidation points.

The entrance facility includes the cabling components needed to provide a means to connect the outside service facilities to the premises cabling. This can include service entrance pathways, cables, connecting hardware, circuit protection devices, and transition hardware.

An entrance facility houses the transition outside plant cabling to cabling approved for intrabuilding construction. This usually involves a transition to fire-rated cable. The entrance facility is also the network demarc between the SP and customer premises cabling. National and regional electrical codes govern placement of electrical protection devices at this point.

The location of the entrance facility depends on the type of facility, route of the outside plant cabling (e.g. buried or aerial), building architecture, and aesthetic considerations.

The four principal types of entrance facilities include underground, tunnel, buried, and aerial.

The most common is an existing aerial connection where the SP cables provide service to a building via an overhead route. Aerial entrances usually provide the lowest installation cost, and they’re readily accessible for maintenance. However, they’re subject to traffic and pedestrian clearances, can damage a building’s exterior, are susceptible to environmental conditions (such wind and ice), and are usually joint-use installations with the power company, CATV company, and telephone or data service providers.

Backbone cabling

From the entrance facility, the structured cabling network branches out to other buildings, as well as from floor to floor within a building on the backbone cabling system. We use the term backbone to describe the cables handling the major network traffic.

The function of the backbone cabling is to provide interconnections between telecommunications closets, equipment rooms, and entrance facilities in the telecommunications cabling system structure. Backbone cabling consists of the backbone cables, intermediate and main cross-connects, mechanical terminations, and patch cords or jumpers used for backbone-to-backbone cross-connection. Backbone cabling also includes cabling between buildings.

Interbuilding and intrabuilding are two types of backbone cables. Interbuilding backbone cable handles traffic between buildings. Intrabuilding backbone cable handles traffic between closets in a single building.

This standard identifies two levels of backbone cabling. First-level backbone is a cable between a main cross-connect (MC) and intermediate cross-connect (IC) or horizontal cross-connect (HC). Second-level backbone exists between an IC and HC.

The main components of backbone cabling are:

  • Cable pathways: shafts, conduits, raceways, and floor penetrations (such as sleeves or slots) that provide routing space for the cables.
  • The actual cables: optical fibre, twisted-pair copper, coaxial copper, or some combination of these.
  • Connecting hardware: connecting blocks, patch panels, interconnections, cross-connections, or some combination of these components, and
  • Miscellaneous support facilities: cable support hardware, firestopping and grounding hardware. The terms horizontal and backbone (previously called riser) evolved from the orientations typical for functional cables of these types. However, the physical orientation of the cabling has no bearing on classifying the cable as horizontal or backbone.

The useful life of a backbone cabling system consists of several planned growth periods (typically 3 to 10 years). This is shorter than the life expectancy of the premises cabling system.

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Cabling connectors

A connector is a mechanical device you use to interface a cable to a piece of equipment or one cable to another. The role of the connector is to provide a coupling mechanism that keeps data loss to a minimum.

In the case of fibre, it allows light impulses to transfer from one connector to another. For copper, it allows electrical signals to transfer from one connector to another.

A good connection requires aligning the connectors, preventing the connectors from unintentional separation, and efficient transferring of light or electricity from one connector to the other.

A connector demonstrates durability by withstanding hundreds of insertion and withdrawal cycles without failing. We calculate this as mean time between failures (MTBF).

Connectors are as essential to the integrity of the entire network as is the cable itself. Connectors align, attach, and decouple the media to a transmitter, receiver, another media of same or similar type, an active telecommunications device, or a specified passive telecommunications device.

Structured Cabling Overview

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Structured cabling is the design and installation of a cabling system that will support multiple hardware uses and be suitable for today’s needs and those of the future. With a correctly installed system, current and future requirements can be met, and hardware that is added in the future will be supported.

As mentioned above Structured cabling design and installation is governed by a set of standards that specify wiring data centers, offices, and apartment buildings for data or voice communications using various kinds of cable, most commonly category 5e (Cat 5e), category 6 (Cat 6), and fibre optic cabling and modular connectors. These standards define how to lay the cabling in various topologies in order to meet the needs of the customer, typically using a central patch panel (which is normally 19-inch rack-mounted), from where each modular connection can be used as needed. Each outlet is then patched into a network switch (normally also rack-mounted) for network use or into an IP or PBX (private branch exchange) telephone system patch panel.

It is common to colour-code patch panel cables to identify the type of connection, though structured cabling standards do not require it except in the demarcation wall field.

Cabling standards require that all eight conductors in Cat 5e/6/6A cable be connected.

IP phone systems can run the telephone and the computer on the same wires, eliminating the need for separate phone wiring. Regardless of copper cable type (Cat 5e/6/6A), the maximum distance is 90 m for the permanent link installation, plus an allowance for a combined 10 m of patch cords at the ends.

Cat 5e and Cat 6 can both effectively run power over Ethernet (PoE) applications up to 90 m. However, due to greater power dissipation in Cat 5e cable, performance and power efficiency are higher when Cat 6A cabling is used to power and connect to PoE devices.

What Does Structured Cabling Look Like?

To answer that we would use the word “organisation”; structured cabling is an organised approach to a cabling infrastructure. To fully understand this concept, it is easiest to look at what structured cabling isn’t. In many data centres the cabling methodology used is defined as “point to point”. This is running patch cables (or “jumpers”) directly to and from the hardware that needs connectivity.

With that defined, let’s go back to structured cabling. In a structured cabling system, a series of patch panels and trunks are used to create a structure that allows for hardware ports to be connected to a patch panel at the top of the rack. That patch panel is then connected to another patch panel via a trunk (multi-fibre assembly designed for use in conveyance) in the MDA (Main Distribution Area).

The MDA is the key aspect of structured cabling. This is where all the MAC’s (Moves, Adds, and Changes) can be made with short length patch cords.

What Are the Benefits of Structured Cabling?

Once again, organisation is the key word here. With an organised structured cabling system the benefits are:

  • MAC’s are much quicker due to the fact that they are done in the MDA versus running long patch cords from equipment racks.
  • Potential for downtime is reduced as potential for human error is drastically reduced due to this organization.
  • Time savings; cable and port tracing become a much easier job with a structured cabling system.
  • Aesthetics; Never underestimate the looks! A structured cabling system will look much cleaner than a point to point method. Since the changes are done in the MDA versus at the hardware, the hardware can be cabled up and not touched in most instances. This allows the cabling in front of the switch to remain aesthetically pleasing.

Learn more

To understand how a structured cabling infrastructure will benefit your office and network performance contact PTC for an initial on-site consultation.

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