Sample Data Installations

As long as you follow the ANSI/TIA-568-C standard, most of your communications infrastructure will be pretty similar and will not vary based on whether it is supporting voice or a specific data application. The horizontal cables will all follow the same structure and rules. However, when you start using the cabling for data applications, you'll notice some differences. We will now take a look at a couple of possible scenarios for using a structured cabling system.

The first scenario, shown in Figure 1, shows the typical horizontal cabling terminated to a patch panel. The horizontal cable terminates to the 110-block on the back of the patch panel. When a workstation is connected to the network, it is connected to the network hub by means of a RJ-45 patch cable that connects the appropriate port on the patch panel to a port on the hub.

 
Figure 1: A structured cabling system designed for use with data

The use of a generic patch panel in Figure 2 allows this cabling system to be the most versatile and expandable. Further, the system can also be used for voice applications if the voice system is also terminated to patch panels.

Another scenario involves the use of 110-blocks with 50-pin Telco connectors. These 50-pin Telco connectors are used to connect to phone systems or to hubs that are equipped with the appropriate 50-pin Telco interface. These are less versatile than patch panels because each connection must be terminated directly to a connection that connects to a hub.

In past years, we have worked with these types of connections, and network administrators have reported to us that these are more difficult to work with. Further, these 50-pin Telco connectors may not be interchangeable with equipment you purchase in the future. Figure 3 shows the use of a 110-block connecting to network equipment using a 50-pin Telco connector.

 
Figure 2: A structured cabling system terminated into 110-connecting blocks with 50-pin Telco connectors

A final scenario that is a combination of the patch-panel approach and the 110-block approach is the use of a 110-block and 110-block patch cables. This is almost identical to the patch-panel approach, except that the patch cables used in the telecommunications closet have a 110-block connector on one side and an RJ-45 on the other. This configuration is shown in Figure 3.

 
Figure 3: Structured cabling using 110-blocks and 110-block patch cords

The previous examples are fairly simple and involve only one wiring closet. Any installation that requires more than one telecommunications closet and also one equipment room will require the service of a data backbone. Figure 4 shows an example where data backbone cabling is required. Due to distance limitations on horizontal cable when it is handling data applications, all horizontal cable is terminated to network equipment (hubs) in the telecommunications closet. The hub is then linked to other hubs via the data backbone cable.

 
Figure 4: Structured cabling that includes data backbone cabling

Data Cabling

The Bottom Line

Identify the key industry standards necessary to specify, install, and test network cabling Early cabling systems were unstructured and proprietary, and often worked only with a specific vendor's equipment. Frequently, vendor-specific cabling caused problems due to lack of flexibility. More important, with so many options, it was difficult to utilize a standard approach to the design, installation, and testing of network cabling systems. This often led to poorly planned and poorly implemented cabling systems that did not support the intended application with the appropriate cable type.

Master It In your new position as a product specification specialist, it is your responsibility to review the end users' requirements and specify products that will support them. Since you must ensure that the product is specified per recognized U.S. industry standards, you will be careful to identify that the customer request references the appropriate application and cabling standards. What industry standards body and standards series numbers do you need to reference for Ethernet applications and cabling?

Understand the different types of unshielded twisted-pair (UTP) cabling. Standards evolve with time to support the need for higher bandwidth and networking speeds. As a result, there have been many types of UTP cabling standardized over the years. It is important to know the differences among these cable types in order to ensure that you are using the correct cable for a given speed.

Master It An end user is interested in ensuring that the network cabling they install today for their 1000Base-T network will be able to support future speeds such as 10Gbps to a maximum of 100 meters. They have heard that Category 6 is their best option. Being well versed in the ANSI/TIA-568-C standard, you have a different opinion. What are the different types of Category 6 cable and what should be recommended for this network?

Understand the different types of shielded twisted-pair cabling Shielded twisted-pair cabling is becoming more popular in the United States for situations where shielding the cable from external factors (such as EMI) is critical to the reliability of the network. In reviewing vendor catalogs, you will see many options. It is important to know the differences.

Master It Your customer is installing communications cabling in a factory full of stray EMI. UTP is not an option and a shielded cable is necessary. The customer wants to ensure capability to operate at 10GBase-T. What cable would you recommend to offer the best shielding performance?

Determine the uses of plenum- and riser-rated cabling There are two main types of UTP cable designs: plenum and riser. The cost difference between them is substantial. Therefore, it's critical to understand the differences between the two.

Master It Your customer is building a traditional star network. They plan to route cable for horizontal links through the same space that is used for air circulation and HVAC systems. They plan to run cable vertically from their main equipment room to their telecommunications rooms on each floor of the building. What type of cable would you use for:

1. The horizontal spaces
2. The vertical links

Identify the key test parameters for communications cables As you begin to work with UTP cable installation, you will need to perform a battery of testing to ensure that the cabling system was installed properly and meets the channel requirements for the intended applications and cable grades. If you find faults, you will need to identify the likely culprits and fix it.

Master It Crosstalk is one of the key electrical phenomena that can interfere with the signal. There are various types of crosstalk: NEXT, FEXT, AXT, among others. This amount of crosstalk can be caused in various ways. What would you look for in trying to find fault if you had the following failures:

1. NEXT and FEXT problems in 1Gbps links
2. Difficulty meeting 10Gbps performance requirements

External Interference | Data Cabling

One hindrance to transmitting data at high speed is the possibility that the signals traveling through the cable will be acted upon by some outside force. Although the designer of any cable, whether it's twisted-pair or coaxial, attempts to compensate for this, external forces are beyond the cable designer's control. All electrical devices, including cables with data flowing through them, generate EMI. Low-power devices and cables supporting low-bandwidth applications do not generate enough of an electromagnetic field to make a difference. In addition, some equipment generates radio-frequency interference; you may notice this if you live near a TV or radio antenna and you use a cordless phone.

Devices and cables that use a lot of electricity can generate EMI that can interfere with data transmission. Consequently, cables should be placed in areas away from these devices.

Some common sources of EMI in a typical office environment include the following:

• Motors
• Heating and air-conditioning equipment
• Fluorescent lights
• Laser printers
• Elevators
• Electrical wiring
• Televisions
• Some medical equipment

Note

Talk about electromagnetic interference! An MRI (magnetic resonance imaging) machine, which is used to look inside the body without surgery or x-rays, can erase the magnetic strip on a credit card from 10′ away.

When running cabling in a building, do so a few feet away from these devices. Never install data cabling in the same conduit as electrical wiring.

In some cases, even certain types of businesses and environments have high levels of interference, including airports, hospitals, military installations, and power plants. If you install cabling in such an environment, consider using cables that are properly shielded, or use fiber-optic cable.

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Cabling and Standards

Maximum acceptable values of attenuation, minimum acceptable values of crosstalk, and even cabling design issues—who is responsible for making sure standards are published? The group varies from country to country; in the United States, the predominant standards organization supervising data cabling standards is the Telecommunications Industry Association (TIA). The standard that covers Category 3, 5e, 6, and 6A cabling, for example, is ANSI/TIA-568-C, which is part of the guideline for building structured cabling systems. These standards are not rigid like an Internet RFC but are refined as needed via addendums. The ANSI/TIA-568-C document dictates the performance specifications for cables and connecting hardware.

The Golden Rules of Data Cabling

Listing our own golden rules of data cabling is a great way to start this chapter and the book. If your cabling is not designed and installed properly, you will have problems that you can't even imagine. Using our experience, we've become cabling evangelists, spreading the good news of proper cabling. What follows is our list of rules to consider when planning structured-cabling systems:

• Networks never get smaller or less complicated.
• Build one cabling system that will accommodate voice and data.
• Always install more cabling than you currently require. Those extra outlets will come in handy someday.
• Use structured-cabling standards when building a new cabling system. Avoid anything proprietary!
• Quality counts! Use high-quality cabling and cabling components. Cabling is the foundation of your network; if the cabling fails, nothing else will matter. For a given grade or category of cabling, you'll see a range of pricing, but the highest prices don't necessarily mean the highest quality. Buy based on the manufacturer's reputation and proven performance, not the price.
• Don't scrimp on installation costs. Even quality components and cable must be installed correctly; poor workmanship has trashed more than one cabling installation.
• Plan for higher-speed technologies than are commonly available today. Just because 1000Base-T Ethernet seems unnecessary today does not mean it won't be a requirement in five years.
• Documentation, although dull, is a necessary evil that should be taken care of while you're setting up the cabling system. If you wait, more pressing concerns may cause you to ignore it.