Cabling The Complete Guide to Network Wiring pdf pdf
Cabling: The Complete Guide
Library of Congress Card Number: 2003115682 ISBN: 0-7821-4331-8 SYBEX and the SYBEX logo are either registered trademarks or trademarks of SYBEX Inc. TRADEMARKS: SYBEX has attempted throughout this book to distinguish proprietary trademarks from descriptive terms by following the capitalization style used by the manufacturer.
Library of Congress Card Number: 2003115682 ISBN: 0-7821-4331-8 SYBEX and the SYBEX logo are either registered trademarks or trademarks of SYBEX Inc. originally got involved with this book by assisting Jim McBee with the initial writing of the first edition.
I editions. I’m grateful to Jim and everyone at Sybex for providing me with this opportunity
Also, I would like to recognizethe rest of the Sybex staff for all their hard work on this book, including (but not limited to)Judy Fung for her work on the color insert; the proofreaders, Laurie O’Connell and NancyRiddiough; the indexer Ted Laux; and the electronic publishing specialists at HappenstanceType-O-Rama, who spent time and effort making the book look good. 38 Bandwidth, Frequency, and Data Rate 36 Data Communications 101 30 Twists 34Solid Conductors versus Stranded Conductors 27 Wire Insulation 27 Cable Jackets 22 Plenum 24Riser 26General Purpose 1 Chapter 1 Introduction to Data Cabling 11 Cable Design 9 Types of Communications Media 8 Cabling and the Need for Speed 7 Proprietary Cabling Is a Thing of the Past 6 You’ve Come a Long Way, Baby: The Legacy ofProprietary Cabling Systems 6 Is the Cabling to Blame?
However, over the last decade, the information technology world began to understand the importance of a reliable and well-designed structured cabling system. During the research phase of the book, we continually reviewed newsgroups, cabling FAQs, and other Internet resources, besides polling information technology managers, help-deskstaff, network designers, cable installers, and system managers to find out what people want to know about their cabling system.
Who Is This Book For?
The procedures in this book are illustrated and written inEnglish rather than “technospeak.” That’s because we, the authors, designed this book specif- ically to help unlock the mysteries of the wiring closet, cable in the ceiling, wall jacks, and othercomponents of a cabling system. Just asin the worlds of networking, software, and programming, the world of cabling and telecom- munications has its own language.
Introduction to Data Cabling
During the initial conversation, the ● director had a couple of other “insights”:He said that the walls were not even up in the new location, so it was too early to be talking ● about data cabling. (“We can run 100Base-TX on the old cable.”)He said not to worry about the voice cabling and the cabling for the photocopier tracking system; someone else would coordinate that.
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
Cabling is the foundation of your network; if the cabling fails, nothing else will matter. For a given grade or category ofcabling, you’ll see a range of pricing, but the highest prices don’t necessarily mean the highest quality.
The Importance of Reliable Cabling
● If you have installed the proper Category or grade of cable, the majority of cabling problems will usually be related to patch cables, connectors, and termination techniques. The per-manent portion of the cable (the part in the wall) will not likely be a problem unless it was damaged during installation.
The Cost of Poor Cabling
One company that had recently moved into a new office space used the existingcabling, which was supposed to be Category 5 cable. Many cables did not even meet the minimum requirements of a Category 5 installation, and other cabling runs were installed and terminated poorly.
Is the Cabling to Blame?
These reasons usually pertain to substandard components (patch panels, connectors, and You’ve Come a Long Way, Baby: The Legacy of Proprietary Cabling SystemsRobert Metcalfe (inventor of Ethernet, founder of 3Com, columnist for InfoWorld, industry pundit, and Jim’s hero) helped coin the term drop-rate magnification. When data is lost on the wire, the data is transmitted properly but, dueto problems with the cabling, the data never arrives at the destination or it arrives in an incom- plete format.
You’ve Come a Long Way, Baby: The Legacy of Proprietary Cabling Systems
Net-working standards such as 10Base-T were but a twinkle in the IEEE’s (Institute of Electrical andElectronics Engineers) eye, and guidelines such as the ANSI/TIA/EIA-568 series of cabling Stan- dards were not yet formulated (see the next section for more information on TIA/EIA-568-B). Unfortunately, because the cablingwas not even Category 3, once the 10Base-T specification was approved, many of the installed cables would not support 10Base-T cards on most of the network.
Proprietary Cabling Is a Thing of the Past
Even when the cabling did marginally supporthigher speeds of data transfer (10Mbps), the connecting hardware and installation methods were often still stuck in the “voice” age, which meant that connectors, wall plates, and patchpanels were designed to support voice applications only. A consortium of telecommunications vendors and consultants worked in conjunction with the American National Standards Institute (ANSI), Electronic Industries Alliance (EIA), and theTelecommunications Industry Association (TIA) to create a Standard originally known as the Commercial Building Telecommunications Cabling Standard or ANSI/TIA/EIA-568-1991.
Cabling and the Need for Speed
When this firm installs its new cabling system to support the next-generation network applica- tions, you can be sure that it will want to choose the cabling infrastructure and network appli-cation carefully to ensure that its needs for the next 10 to 15 years will be accommodated. Cabling and the Need for SpeedThe average number of nodes on a network segment has decreased dramatically, while the number of applications and the size of the data transferred has increased dramatically.
Types of Communications Media
Although for most of us fiber to the desktop is not yet a practical reality, fiber-optic cable is touted as the ultimate answer to all our voice, video, and data transmission needs and continues● to make inroads in the LAN market. The main hindrance to using fiber optics all the way to the desktop in lieu of UTP or ScTP is that the electronics (workstation network-interface cards and hubs) are still significantly moreexpensive, and the total cost of a full to-the-desktop FO installation is estimated at 50 percent Cabling and the Need for Speed F I G U R E 1 .
Common Abbreviations So that you can better decipher the markings on cables, here is a list of common acronyms and what they mean: NFPA The National Fire Protection Association NEC The National Electrical Code that is published by the NFPA once every three yearsUL The Underwriters Laboratories CSA The Canadian Standards AssociationPCC The Premises Communications Cord standards for physical wire tests defined by the CSAOften, you will see cables marked with UL-910, FT-4, or FT-6. Realize, though, that for LAN systems the time it takes Cable Designparameters are related to the speed at which the electrons can pass through the cable and the length of the wire pairs in cable.
Data Communications 101
Themore cycles per second, the more noise the cable generates and the more susceptible the cable is to signal-level loss. The bit rate is dependent upon the network electronics, not the cable,provided the operating frequency of the network is within the cable’s usable bandwidth.
What a Difference a dB Makes!
It means that: Every 3dB of attenuation translates into 50 percent of the signal power being lost through the ● Every 3dB of return loss translates into 50 percent of the signal power being reflected back to the source. If you take each decibel value and solve for the P1/P2ratio using this formula, you would arrive at the following values: Ratio = 1 / (Inverse log10(dB/20))Media Remaining Signal Allowed to Signal Returned Due to Attenuation Couple (NEXT) (NEXT) Category 5e 6.3% 3.1% 39.8%Category 6 8.6% 1% 31.6%Existing standards allow a transmission to lose 99 percent of its signal to attenuation and still be received properly.
Speed Bumps: What Slows Down Your Data
As the data rates increase, the magic that happens inside a cable becomes increasinglymysterious, and the likelihood that data signals will become corrupt while traveling at those speeds also increases. Designers of both 1000Base-T (Gigabit Ethernet) and the cables that can support frequencies greater than 100Mhz found electrical problems that they did not have to contend with at lowerfrequencies and data rates.
Hindrances to High-Speed Data Transfer
As the frequency on a cable (and consequently the potential data rate)increases, a number of phenomena hinder the signal’s travel through the cable (and conse- quently the transfer of data). The current specifications for Category 5e and 6 cabling outline a number of these phenom- ena and the maximum (or minimum) acceptable values that a cable can meet and still be cer-tified as compliant.
Attenuation (Loss of Signal)
As the bandwidth of the cable increases, the allowed attenuation values get lower (less loss),although the differences between Category 5, 5e, and 6 are negligible at the common fre- quency of 100MHz. If the elec-trons travel a great distance through the wire before being bounced back to the sender, the return loss may not be noticeable because the returning signal may have dissipated (due toattenuation) before reaching the sender.
Noise (Signal Interference)
Everything electrical in the cable that isn’t the signal itself is noise and constitutes a threat to the integrity of the signal. (That’s as opposed to coaxial cable, in which the center conductor provides a very easy path for the signal but the braid and foil shield that make up the other con-ductor is less efficient and therefore a more difficult pathway for the signal.) As signals travel along a pair, an electrical field is created.
Near-End Crosstalk (NEXT)
On the receiving pair of wires in a cable, the signal received at the end of the cable will be the weakest, so the signal there can bemore easily interfered with. The fol- ● lowing six combinations are tested in a four-pair cable: ● Pair 1 to pair 2 ● Pair 1 to pair 3 ● Pair 1 to pair 4 ● Pair 2 to pair 3 ● Pair 2 to pair 4Pair 3 to pair 4 The test is repeated from the opposite end of the cable, resulting in 12 pair-to-pair combinations tested.
The differential between the crosstalk (noise) and the attenuation (loss of signal) is important because it assures that the signal being sent down a wire is stronger at the receiving end thanany interference that may be imposed by crosstalk or other noise. Twisting the conductors of a pair around each other to aid in can- celing crosstalk increases the actual length of the conductors relative to the cable length.
Structured Cabling and Standardization
The TIA (along with the EIA) was instrumental in the development of the ANSI/TIA/ Structured Cabling and Standardization TIA CommitteesIn the United States (and much of the world), the TIA is ultimately responsible for the Standards related to structured cabling as well as many other technological devices used every day. For more information on the RCDD pro- ANSI/TIA/EIA-568-B Cabling Standard Occupational Safety and Health Administration (OSHA) A division of the United States Department of Labor, the Occupational Safety and HealthAdministration (OSHA) was formed in 1970 with the goal of making workplaces in the UnitedStates the safest in the world.
ANSI/TIA/EIA-568-B Cabling Standard
Under the guidance of the TIA TR-41 committee and associated subcommittees, the TIA andEIA in 1991 published the first version of the Commercial Building Telecommunications Cabling Standard, better known as ANSI/TIA/EIA-568 or sometimes simply as TIA/EIA-568. Consequently, five official additions to the ANSI/TIA/EIA-568-A base Standard were written after its publicationin 1995: ANSI/TIA/EIA-568-A-1, the Propagation Delay and Delay Skew Specifications for 100-Ohm Four-Pair Cable Approved in August and published in September 1997, this addendum was created to add additional requirements to those in the base Standard in support of high-performance net-working, such as 100Base-T (100Mbps Ethernet).
ANSI/TIA/EIA-568-B Purpose and Scope
The work area begins at the telecommunications area and includes components such as the following: ● Adapters such as baluns and other devices that modify the signal or impedance of the cable ● (these devices must be external to the information outlet)Station equipment such as computers, telephones, fax machines, data terminals, and modems The work-area wiring should be simple and easy to manipulate. Entrance Facility The location of the entrance facility is usually either on the first floor or in the basement of a building and must take into consideration the requirements of the telecommunications ser-vices required and other utilities (such as CATV, water, and electrical power).
All shielded cables, racks, and other metallic components should be tied ANSI/TIA/EIA-568-B Cabling StandardANSI/TIA/EIA-607 specifies that the minimum ground-wire size must 6 AWG, but, depending on the distance that the ground wire must cover, it may be up to 3/0 AWG (a prettylarge copper wire!). Ground-wire sizing is based on the distance that the ground wire must travel; the farther the distance, the larger the wire must be.
Other TIA/EIA Standards and Bulletins The TIA/EIA alliance published additional specifications and bulletins relating to data and Cabling @ Work: An Example of Poor GroundingOne of the best examples we can think of that illustrates poor grounding practices was a very large building that accidentally had two main grounds installed. ISO/IEC 11801If you want to keep up on the latest TIA/EIA specifications and the work of the various com- mittees, visit the TIA website at www.tiaonline.org/standard/sfg and go to the TR-42 page.
Anixter Levels: Looking Forward
NOTE For a vendor’s cables or components to be categorized as part of the Anixter Levels Pro- gram, Anixter must test the components in its own lab, the manufacturer must use only vir-gin materials, and the manufacturer must be ISO 9000 registered. Further, we recom- mend that you use components from the same manufacturer as the cable you are purchasing,or from a combination of manufacturers whose cable and connecting components are proven to work well together.
Other Cabling Technologies
(That was a poor attempt at humor.) Seriously, when a single company is responsible for the components andinstallation as well as the cable, you can be assured that the cabling infrastructure should func- tion as promised. Some of the more popular vendor● solutions include: ● The IBM Cabling System ● Avaya SYSTIMAX ● Digital Equipment Corporation’s DECconnectNORDX/CDT Integrated Building Distribution System The focus of this book is centered on the ANSI/TIA/EIA-568-B Standards, but the forego- ing specifications deserve mentioning and are briefly discussed in the following pages.
The IBM Cabling System
Type 2A is also shown in Figure 2.8; the difference is that in addition to the shielded twisted pair of Type 1A, four pairs of unshielded twisted-pair cable are outside themain shield. IBM has also used 50/125- and 100/140-micron fiber-optic cable, but because 62.5/125- micron is the de facto standard for FDDI and is included in both the ANSI/TIA/EIA-568-B and ISO/IEC 11801 Standards, it is more desirable.
Avaya SYSTIMAX SCS Cabling System
Calling SYS-TIMAX SCS Cabling System a proprietary solution would be a stretch because the SYSTIMAX is based on the ANSI/TIA/EIA-568 Standards. Because Avaya is providing a single-vendor solution for all components, it is much easier for them to take a holistic approach to cable performance and reliability.
Digital Equipment Corporation DECconnect
7DECconnect Applications and Cable Types Application Cable Type Connector Type Voice Four-pair UTP RJ-45 Low-speed data (terminals) Two-pair UTP Modified, keyed RJ-45Network 50-ohm coax BNC Network 62.5/125-micron fiber ST or SMAVideo 75-ohm coax F-Type One of the downsides of the DECconnect system was the variety of cable types that had to be run. If you had locations that required a terminal, a PC with Ethernet, and a PBX telephone,you would possibly have to run three different types of horizontal cable to a single wall plate.
Choosing the Correct Cabling
Still, it is a good idea to have an understanding of the networking application you are cabling for and how that can affect the use of the cabling system. Further, because cabling that’s relatedto data also connects to various types of network devices, it is a good idea to have an under- standing of the networking hardware used in common installations.
NOTE Whereas topology refers to the physical layout of the wiring and nodes of a network, it also refers to its method of transmitting data and to its logical, or virtual, layout of the nodes. From this point on in the chapter, we will assume you understand that the physical layout of a modern network is a star topology and that when we discuss bus and ring topologies we’rereferring to the logical layout of the network.
To keep the signal from bounc- ing back and forth along the cable, both ends of the cable in a bus topology must be terminated. The terminator absorbs the signal and keeps it from ringing, which is alsoknown as overshoot or resonance; this is referred to as maximum impedance.
Each computer in the ring receives signals (data) from its neighbor, repeats the signal, and passes it along to the next node in the ring. A true ring topology is a pain in the neck to install cable for because the circular nature of the ring makes it difficult to expand a ring over a large physical area.
UTP, Optical Fiber, and Future-Proofing
The first number in an Ethernet designator indicates the speed of the network, the second portion (the base portion) indicates baseband, and the third indicates the maximum distance or the media type. If you’ve got the cabling in place to handle it, it’s hard to say no to 10 times your current bandwidth when the only obsta-cles in the way are inexpensive hubs and NICs (network-interface cards).● Here are some important facts about 10Base-T: The maximum cable length of a 10Base-T segment is 100 meters (328 feet) when usingCategory 3 cabling.