Data Cabling: How to Plan Ahead?

Data cabling is an important channel for enterprise data transmission, not just a cable. Reliable and fast data cabling solutions are essential for the success of an enterprise's business.

Data cables carry electronic information from a source to a destination. Currently, the types of data cables widely used in computer and telecommunication systems are primarily copper and fiber optic.

Golden Rules for Data Cabling

If the enterprise has improper wiring design and installation in practice, many problems that are difficult to predict may arise.

Here are some rules to consider when planning your structured cabling system:

• Network transmission needs will never get smaller or simpler.
• Build a cabling system that can accommodate both voice and data.
• Always install more cables than you currently need. Those extra cables and connectors will come in handy one day.
• Use structured cabling standards when building new cabling systems to avoid anything proprietary!
• Quality matters! Use high-quality cabling and cabling components. Cabling is the foundation of your network, and if it fails, nothing else matters. You will see a range of different pricing for a given grade or category of cabling, but a high price does not necessarily mean the highest quality. Buy based on the manufacturer's reputation and proven performance, not just price.
• Don't skimp on installation. Even premium components and cables must be installed correctly; shoddy construction can ruin more than one wiring installation.
• Plan for higher speed technology than is generally available today. Just because some high bandwidth Ethernet doesn't seem necessary today, doesn't mean it won't be necessary in 5 years.
• Documentation is tedious but necessary when setting up a cabling system.

Always use reliable cabling

It is hard to overemphasize the importance of reliable cabling. Some recent studies show that:

• Data cabling typically accounts for less than 10% of the total cost of network infrastructure.
• The lifespan of a typical cabling system can be over 16 years. Cabling is probably the second longest-lived asset many businesses own (first being the building's structure).
• Nearly 70% of all network-related problems are caused by poor cabling techniques and cable assembly issues.

If the correct category or grade of cable is installed, most cabling problems are usually related to patch cords, connectors, and termination techniques. The permanent link portion of the cable (the portion that goes in the wall) is unlikely to be a problem unless it is damaged during installation.

Of course, these are facts we already know from past experience. Many businesses have spent a great deal of time troubleshooting non-standard, poorly designed, poorly documented and improperly installed cabling systems. We have seen many expenses wasted on installing additional cabling and cabling infrastructure support that should have been part of the original installation.

So no matter how you look at it, cabling is the foundation of your network.

Data cabling and speed

The past few years have seen tremendous advances not only in network technology, but also in the demands placed on it. In the past 30 years, we have seen the emergence of standards such as 10Mb Ethernet, 16Mb Token Ring, 100Mb FDDI (Fiber Distributed Data Interface), 100Mb Ethernet, 155Mb ATM (Asynchronous Transfer Mode), 655Mb ATM, 1Gb Ethernet, 2.5Gb ATM, 10Gb Ethernet, 40Gb Ethernet, and 100Gb Ethernet. Network technology designers are already planning technologies that support data rates up to 400Gbps, and even 800Gbps.

The average number of nodes on a network segment has dropped dramatically, while the number of applications and the amount of data transferred has increased dramatically. Applications have become more complex, and the amount of network bandwidth required by the typical user has also increased. Do you need the bandwidth provided by some of the new ultra-high-speed network applications (such as 10Gb Ethernet) today? Maybe not on the desktop, but the network backbone has already taken advantage of them.

Does the fact that software applications and data are placing ever-increasing demands on networks have anything to do with data cabling? One might think the issue is more about network interface cards, hubs, switches, and routers, but as data rates increase, so does the need for higher levels of performance in cabling.

Type of propagation medium

There are four main types of communications media (cables) used in data networks today:

• Unshielded twisted pair (UTP)
• Shielded or shielded twisted pair (STP or ScTP)
• Coaxial cable
• Fiber Optic (FO)

It is important to distinguish between backbone cables and horizontal cables. Backbone cables connect network devices such as servers, switches, routers, and connect the computer room and the telecommunications room. Horizontal cables extend from the telecommunications room to the wall sockets. For new installations, multi-strand fiber cables are basically universal backbone cables. For horizontal, UTP accounts for 85% of the typical application market. However, newer fiber-based network topologies have more and more advantages over UTP.

Twisted pair cable

In traditional installations, the most economical and widely installed cabling today is twisted pair cabling. Twisted pair cabling is not only cheaper than other media, but it is also simpler to install and the tools required for installation are not as expensive. Unshielded twisted pair (UTP) and shielded twisted pair (STP) are the two main types of twisted pair cabling on the market today. Shielded twisted pair (ScTP) is a variation of STP.

Unshielded twisted pair (UTP)

Although it has been used in telephone systems for many years, unshielded twisted pair (UTP) for LANs first became common in the late 1980s with the advent of Ethernet and the 10Base-T standard over twisted pair. UTP is cost-effective and simple to install, and its bandwidth capabilities continue to improve.

Shielded twisted pair (STP)

Shielded twisted pair (STP) cabling was first popularized by IBM when it introduced a classification of data cabling types. Although more expensive to purchase and install than UTP, STP offers some distinct advantages. The current ANSI/TIA-568-C cabling standard recognizes IBM Type 1A horizontal cable, which supports frequencies up to 300MHz, but does not recommend it for new installations. STP cabling is less susceptible to external electromagnetic interference (EMI) than UTP cabling because all cable pairs are well shielded.

ScTP - Screened Twisted Pair

The recognized cable type in the ANSI/TIA-568-C standard is screened twisted pair (ScTP) cable, which is a hybrid of STP and UTP cables. ScTP cable contains four pairs of unshielded 24 AWG, 100-ohm wires surrounded by a foil shield or wrap wire and a drain wire for grounding purposes.

For this reason, ScTP is sometimes referred to as Foiled Twisted Pair (FTP) because the foil shield surrounds all four conductors. This foil shield is not as large as the braided copper braid jacket used by some STP cabling systems (such as IBM Type 1 and Type 1A). ScTP cable is essentially STP cable without shielding the individual pairs; the shield may also be smaller than some types of STP cabling. In short, ScTP offers a compromise between cost and interference resistance.

Fully shielded twisted pair (S/STP or S/FTP)

S/STP cabling, also known as fully shielded twisted pair (S/FTP), contains four pairs of 24 AWG, 100-ohm individually shielded wires surrounded by an outer metallic shield that covers the entire shielded copper pair group. This type of cabling provides the best protection from interference from outside sources and also eliminates alien crosstalk, providing the greatest potential for higher speeds.

Category 7 and Category 7A are S/STP cables standardized in ISO 11801 Ed2.2. They provide 600 and 1000MHz usable bandwidth respectively. Their intended use is for 10 Gigabit Ethernet, 10GBase-T applications. S/STP cables have four individually shielded conductor pairs.

Fiber Optic Cable

Until 1993, it looked like enterprises would have to install fiber optic cables directly to the desktop to move toward the future of desktop computing. Surprisingly, copper cabling (UTP) continued to outperform expectations.

Single Mode Fiber Optic Cable

Single-mode fiber optic cable is most commonly used by telecommunications companies in transcontinental links and data installations as backbone cables to interconnect buildings. Single-mode fiber optic cable is not used as horizontal cables to connect computers to hubs, nor is it often used as cables to connect telecommunications rooms to main equipment rooms. Light in single-mode fiber optic cable travels directly along the fiber and is not reflected by the surrounding cladding as it travels. Typical single-mode wavelengths are 1310 and 1550 nanometers.

Multimode fiber optic cable

Multimode fiber (MMF) cable is typically fiber optic cable used for networking applications such as 10Base-FL, 100Base-F, FDDI, ATM, Gigabit Ethernet, a10 Gigabit Ethernet, 40 Gigabit Ethernet, and 100 Gigabit Ethernet that require fiber optics for horizontal and backbone cables. Multimode cable allows more than one mode (part of a light pulse) of light to propagate through the cable. Typical wavelengths of light used in multimode cable are 850 and 1,300 nanometers.

Coaxial Cable

At one time, coaxial cable was the most widely used type of cable in the networking business, and the coaxial cable specification is now contained in ANSI/TIA-568-C.4. It is still widely used for CCTV and other video distribution, and is widely used in broadband and cable TV applications. However, it is being phased out in the data networking field. Coaxial cable is difficult to lay and is generally more expensive than twisted pair cable. However, for the protection of coaxial cable, it provides huge bandwidth and is not as susceptible to external interference as UTP. The overall installation cost may also be lower than other cable types because the connectors take less time to install.

Materials used for wire insulation

Currently, there are a variety of insulation materials, including polyolefins (polyethylene and polypropylene), fluorocarbon polymers, and PVC.

Manufacturers select materials based on material cost, flame rating, and desired transmission properties. Materials such as polyolefins are inexpensive and have excellent transmission properties, but they burn easily, so they must be combined with materials that have better flame ratings. It is important to remember this: Don't focus on a specific material. It is the material system that the manufacturer chooses that matters. Manufacturers will select insulation and jacketing materials that work together based on a delicate balance of fire resistance, transmission properties, and economy.

The most common materials used to insulate the wire pairs in Category 5e and higher plenum-rated cables are fluorocarbon polymers. Two fluorocarbon polymers used are fluorinated ethylene-propylene (FEP) and perfluoroalkoxy (PFA).

These polymers were originally developed by DuPont and are sometimes referred to by their trademark Teflon. The most commonly used and desirable of these materials is FEP. Over the past few years, the demand for plenum-rated cables has outstripped the supply of available FEP. During the FEP shortage, Category 5e plenum designs emerged that replace one or more pairs of wires with another material.

Additionally, there have been some instances of marginal performance in the UL-910 burn test for flame-retardant cables. These concerns, coupled with the increased availability of alternatives such as FEP and MFA, have driven the development of these designs.

Insulation Color

The insulation around each wire in a UTP cable is color-coded. The standardized color code helps cable installers ensure that each wire is properly connected to the hardware. For example, in the United States, the color code is based on 10 colors. Five of these are used on the tip conductors and five are used on the ring conductors. Combining the tip color with the ring color creates 25 possible unique pairing combinations. Therefore, for decades, telephone cables have used 25 wire pair groups.

Entanglement

When you cut open a UTP telecommunications cable, you'll notice that the individual conductors within a pair of wires are twisted around each other. At first, you might not realize the significance of these twists.

Did you know that in a Category 5e cable, a pair of wires that are not twisted more than a half inch apart can adversely affect the performance of the entire cable?

Wire Gauge

Copper wire diameter is often measured in units called AWG (American Wire Gauge). Contrary to many other measurement systems, as the AWG number gets smaller, the wire diameter actually gets larger; thus, AWG 24 wire is smaller than AWG 22 wire. Larger wires are useful because they have greater physical strength and lower resistance.

The challenge for cable designers is to use wires with the smallest possible diameter (reducing cost and installation complexity) while maximizing the performance of the wire to support the necessary power levels and frequencies.

Category 5e UTP is always 24 AWG; IBM Type 1A is usually 22 AWG. Patch cords may be 26 AWG, especially Category 3. The development of higher performance cables such as Category 6 and Category 6A has resulted in 23 AWG often being replaced by 24 AWG.

The table below shows 22, 23, 24 and 26 AWG sizes and their corresponding diameters, areas and weights per kilometer.

The sizes in the table above were developed over 100 years ago. Since then, copper's purity and conductive properties have improved due to better copper processing techniques. Specifications covering communications cable design forgo the actual size of the wire. What really matters is not the size of the wire, but how it performs, specifically with respect to resistance (measured in ohms). The AWG standard states that 24 AWG wire is 0.0201" in diameter, but the actual diameter of the wire may be slightly smaller or larger (but will usually be smaller) depending on the properties of the material.

Solid and stranded conductors

UTP cables used as horizontal cables (permanent cables or in-wall cables) have solid conductors, as opposed to cables used for patch cords and short-distance wiring, which typically have stranded conductors. Stranded conductors consist of many smaller conductors interwoven together to form one conductor.

Cable length

The longer the cable, the less likely it is that the signal will be fully delivered to the end of the cable due to noise and signal attenuation. But realize that for LAN systems, the time it takes for the signal to reach its endpoint is also critical.

Cable design engineers are now measuring two additional performance parameters for cables: propagation delay and delay skew. Both parameters are related to the speed of electrons traveling through the cable and the length of the wire pairs in the cable.