Cabling System Design and Installation

Understanding how to put the components together into a cohesive cabling system design is very important. Each of the components of a cabling system can fit together in many different ways.  Additionally, you must design the cabling system so that each component of that system meets or exceeds the goals of the cabling project.

Identify and understand the elements of a successful cabling installation

Before designing your system, you should understand how the following elements contribute to asuccessful installation:

1. Using proper design

2. Using quality materials

3. Practicing good workmanship

Each of these aspects can drastically affect network performance.

>> Proper Design

A proper cabling system design is paramount to a well-functioning cabling infrastructure. As with any other major project, the key to a successful cabling installation is this word: PLAN. A proper cabling system design is simply a plan for installing the cable runs and their associated devices. So what is a proper design? A proper cabling system design takes into account five primary criteria:

a. Desired standards and performance characteristics

b. Flexibility

c. Longevity

d. Ease of administration

e. Economy

Failure to think about these standards will lead to usability problems and bad network performance.

>> Quality Materials

Another element of a successful cabling installation is the use of quality materials. The quality of the materials used in a cabling installation will directly affect the transmission efficiency of a network. Many times, a vendor will sell many different cabling product lines, each with a different price point. The old adage that you get what you pay for really does apply to cabling supplies.

But that doesn't always mean that low price means low quality. Some providers make low price, high quality cabling supplies. In addition to price, you should check how the product is assembled. Qaulity materials are sturdy and well constructed. Low-quality materials will not be durable and may actually break while you are handling them.

>> Good Workmanship

There is a saying that any job worth doing is worth doing correctly. When installing cabling, this saying is especially true because shoddy workmanship can cause data transmission problems and thus lower the network's effective throughput. If you try to rush a cabling job to meet a deadline, you will usually end up doing some or the entire job over again.

Identify the pros and cons of network topologies

A topology is basically a map of a network. The physical topology of a network describes the layout of the cables and workstations and the location of all network components. Choosing the layout of how computers will be connected in a company’s network is critical. It is one of the first choices you will make during thedesign of the cabling system, and it is an important one because it tells you how the cables are to be run during the installation.

In this article "How To Choose the Correct Cabling" was described the basics of the hierarchical star, bus, and ring topologies. Here, we'll look at some of their advantages and disadvantages.

The advantages of Hierarchical Star Topology as following:

. It can be reconfigured quickly.

. A single cable failure won't bring down the entire network.

. It is relatively easy to troubleshoot.

. It allows the ability to centralize electronics and run fiber to the desk using the centralized cabling option.

. It also allows an end user to run backbone cables to telecommunications enclosures, also called FTTE.

. It is the only recognized topology in the industry standard, ANSI/TIA-568-C.

The disadvantges of Hierarchical Star Topology as following:

. The total installation cost can be higher than that of bus and ring topologies because of the larger number of cables.

. It has a single point of failure: the main hub.

The advantages of bus topology as following:

. It is simple to install.

. It is relatively inexpensive.

. It uses less cable than other topologies.

On the other hand, a bus topology has the following disadvantages:

. It is difficult to move and change.

. The topology has little fault tolerance (a single fault can bring down the entire network).

. It is difficult to troubleshoot.

Ring Topology

The ring topology has a few pros but many more cons, which is why it is seldom used. On thepro side, the ring topology is relatively easy to troubleshoot.

The cons are as follows:

. It is expensive because multiple cables are needed for each workstation.

. It is difficult to reconfigure.

. It is not fault tolerant. A single cable fault can bring down the entire network.

Selecting the Right Topology

From a practical standpoint, which topology to use has been decided for you. Because of its clear-cut advantages, the hierarchical star topology is the only recognized physical layout in ANSI/TIA-568-C. Unless you insist that your installation defy the standard, this will be the topology selected by your cabling system designer.

Understand cable installation procedures

A cabling installation involves five steps:

1. Design the cabling system.

2. Schedule the installation.

3. Install the cables.

4. Terminate the cables.

5. Test the installation.

>> Design the Cabling System

Following proper cabling design procedures will ensure the success of your cabling system installation is very important. Before you pull a single cable, you should have a detailed plan of how the installation will proceed. You should also know the scope of the project. Finally, you should have the design plan available to all people involved with the installation of the cable. Be sure to include anyone who needs to refer to the way the cabling is being installed. At the very least, this information should contain a blueprint of how the cables will be installed.

>> Schedule the Installation

In addition to having a proper cabling design, you should know approximately how long the installation will take and pick the best time to do it. From a planning standpoint, this is approximately the same time in new construction when the electrical cabling is installed.

For a post construction installation, you should schedule it so as to have the least impact on the building’s occupants and on the existing network or existing building infrastructure. It also works to schedule it in phases or sections.

>> Install the Cabling

Once you have a design and a proper schedule, you can proceed with the installation. We'll start with a discussion of the tools you will need.

The cabling tools as following:

. Pen and paper

. Hand tools

. Cable spool racks

. Fish tape

. Pull string

. Cable-pulling lubricant

. Two-way radio

. Labeling materials

. Tennis ball

Cabling system Documentation

Cabling system documentation includes information about what components make up a cabling system, how it is put together, and where to find individual cables. This information is compiled in a set of documents that can be referred to by the network administrator or cabling installer any time moves, additions, or changes need to be made to the cabling system.

The most useful piece of cabling system documentation is the cabling map. Just as its name implies, a cabling map indicates where every cable starts and ends. It also indicates approximately where each cable runs. Additionally, a cabling map can indicate the location of workstations, segments, hubs, routers, closets, and other cabling devices.

>> Terminate the Cable

Terminating the cables involves installing some kind of connector on each end (either a connector or a termination block) so that the cabling system can be accessed by the devices that are going to use it. This is the part of cabling system installation that requires the most painstaking attention to detail, because the quality of the termination greatly affects the quality of the signal being transmitted. Sloppy termination will yield an installation that won’t support higher- speed technologies.

Though many termination methods are used, they can be classified one of two ways: connectorizing or patch panel termination. Patch Panels have many different types, some for copper, some for fiber. Copper cable patch panels for UTP all have a few similar characteristics, for the most part. During termination, the individual conductors in the UTP Cable are pressed between the metal blades to make both the mechanical and electrical connection between the cable and the connector on the front of the patch panel. This type of patch panel is a 110-punch-down block (or 110-block, for short).

Figure 1 shows a sample patch panel

>> Test the Installation

Once you have a cable or cables installed and terminated, your last installation step is to test the connection. Each connection must be tested for proper operation, category rating, and possible connection problems. If the connection has problems, it must either be re-terminated or, in the worst-case scenario, the entire cable must be re-pulled.

Testing individual cables is done most effectively and quickly with a LAN Cable Tester (as shown in Figure 2. Cable testers are available for both copper and fiber optic cables.

Figure 2 shows Network LAN Cable Tester CT-168

You should test the entire cabling installation before installing any other hardware (hubs,PCs, etc.). That way, you avoid having to troubleshoot cabling-related problems later (or at least you minimize possible later problems).

Transmission Media Used To Implement An Ethernet LAN

Early implementations of Ethernet LANs employed thick coaxial cable. In fact, it was a thick yellow coaxial cable - original recipe Ethernet cable. The cable was defined by the 10Base-5 standard. This implementation was called Thicknet. It could deliver a BER of 10-8. It supported a data rate of 10 MBPS. The maximum LAN cable segment length was 500 meters. The segment length is the maximum distance between data terminal equipment. These are attractive features.
The unfortunately, the thick coaxial cable is difficult to work with. As a result, the second wave of the implementation of the Ethernet LAN using thin coaxial cable. The cable was RG58 A/U coaxial cable - sometimes called Cheapernet. This cable is made from 10Base-2 standard. The implementation was called Thinnet. It supported a data rate of 10 MBPS. But, it had a BER somewhat degraded relative to Thicknet. The LAN cable segment length was reduced to the order of 185 meters.
Thinnet ultimately gave way to the replacement of coaxial cable with Unshielded twisted pair (UTP) cable. This is done through an interesting Ethernet LAN architecture combined with another local area network (LAN) flavor called StarLAN, the AT & T.
StarLAN was based on a telecommunications, telephone company, usually do for the enterprise to provide voice communications. The Transmission Medium a Telecom used in a facility for voice communications are shielded twisted pair (STP) cable. It provides voice communication within a facility and the external world connect all telephone, mobile phone, closet, or by telephone wiring closet. The distance from handset to telephone closet is relatively limited, maybe 250 meters. The StarLAN idea is the basic method of voice and use it to a local area network (LAN). The LAN stations would be connected through a closet. The existing UTP cable present in a facility for voice would be used for the LAN data traffic. There would be no need to install a new and separate Transmissioin Medium. Installation costs would be contained. Unfortunately, StarLAN only supported 1 MBPS. It has never left the ground.
However, in 1990 aspects of StarLAN were taken and merged with the Ethernet LAN architecture. This leads to a new Ethernet LAN based on UTP and 10Based-T standard definition. Based on this method, Ethernet UTP really start the market place.
Ethernet under the 10Base-T standard has a hub and spoke architecture. This is illustrated in Figure 1. The various data equipment units, radio, are connected to a central point called multi-point repeater or Hub. The connections are by UTP cable. This architecture does support the Broadcast Channel - Ethernet Bus. This is because all of the data equipment unit can be broadcast to all the other data units through the Hub. Likewise, all data equipment units can listen to the transmissions from all other data equipment units as they are received via the UTP cable connection to the Hub. The Hub takes the place of the telephone closet. The Hub may be strictly passive or it may perform signal restoration functions.

Figure 1: 10Base-T hub-and-spoke architecture
The illustration Figure 2 indicates how the 10Base-T topology may actually look in an office set-up at some facility. The data units are computer equipment here. One serves as the file server. The illustration shows what is usually referred to as a 10Base-T Work Group. It may serve one specific department in a company. By connecting together these work groups Ethernet LANs may be extended. This can be achieved by using local area network (LAN) connection Hub network elements called bridges, routers and switches. Description of their operations is beyond the focus of the present discussion.

Figure 2: Ethernet operating as a 10Base-T work group
But, let us get back to 10Base-T. It supports a data rate of 10 MBPS. It has a BER comparable to Thinnet. However, the LAN segment length is reduced even further. With 10Base-T LAN segment length is only 100m - a short distance, but distance, it is permissible to many data equipment standing in a typical business. However, it may be too short to others. This is a place, fiber optic cable can come to the rescue.
For the LAN market place 10Base-T was far from the last word. It led to the development of 100Base-T - Fast Ethernet. It is also based on using UTP cable for transmission medium. However, it supports a data rate of 100 MBPS over cable segments of 100 meters.Fast Ethernet, itself, is not the end of the road. Suppliers are starting to promote Giga Bit Ethernet which is capable of supporting 1 GBPS. However, we will stop at Fast Ethernet and the problem that both it and 10Base-T have the short cable segment of 100 meters.
It will be worth define two terms before continuing in discussing the characteristics of the Ethernet. These are 1) the network diameter, and 2) slot time.
The Network Diameter is simply the maximum end-to-end distance between data equipment users, stations, in an ethernet network. It is really what has been referred to above as the cable segment. The Network Diameter is the same for both 10Base-T and 100Base-T, 100 meters.
After a BIU has begun the transmission of a packet the Slot Time is the time interval that a BIU listens for the presence of a collision with an interfering packet. The Slot Time cannot be infinite. It is set for both the 10Base-T and 100Base-T Ethernet architectures. It is defined for both standards as the time duration of 512 bits. With a 10Base-T Ethernet network operating at 10 MBPS the Slot Time translates to 51.2msec. With a 100Base-T Ethernet network operating at 100 MBPS the Slot Time translates to 5.12msec.