Lesson 1-3: Cabling

Transcript

Unit 1: Internetworking Overview Lesson 1-3: Cabling At a Glance The physical pathway used to connect two or more computers together as a network includes the transmission media. The quality of the network system is dependent on its transmission media. The most common forms of electrical and electronic transmission are solid and composite wire cables. There are several types of cable, including coaxial, unshielded twisted-pair and fiber optic. Each type adheres to standards set by the Institute of Electrical and Electronics Engineers (IEEE). The Telecommunications Industry Association (TIA) and the Electronic Industries Association (EIA) standards govern all aspects of cable installation, such as regulations on cabling distances and connector configurations. In choosing cabling for a network, there are several factors to consider: cost, expansion capabilities, bandwidth, signal attenuation, and EMI (ElectroMagnetic Interference). Each type of cable has different specifications that affect these factors, and each organization has different needs. Considering cable system factors is very important for building a network system that meets an organization’s needs. What You Will Learn After completing this lesson, you will be able to: • Describe three different types of cable and their structural components. • Demonstrate an understanding of specifications and attributes for coaxial, UTP, and fiber optic cable and how these factors guide decision-making in building networks. • Identify and describe Ethernet cable crimping using proper TIA/EIA 568 wiring sequences. • Crimp and test Ethernet Category 5 cable and discuss cabling quality issues. ST0025803A 63 Lesson 1-3: Cabling Tech Talk 64 • BandwidthBandwidth represents how much information can be sent at one time over a specific cable type, or the measure of information capacity of transmission over a cable. Bandwidth is the difference between the highest and lowest frequencies of the transmission, measured in hertz. Bandwidth is a factor used to evaluate cable. • BNCThe “British Naval Connector” is the connector used with coaxial cables. • ExpansionExpansion is the ability to increase the size of a network after the initial installation. It is a factor used to evaluate cable. • Fiber Optic CableFiber optic cable uses light to transmit information across a network. The core of the cable is made of glass, which is protected by a layer of gel or plastic. A plastic cover surrounds the entire cable. • Hertz (Hz)Hertz is the unit of frequency measurement, which is equal to one cycle per second (for example, one waveform per second). Computers and related devices are often measured in kilohertz (kHz=1,000 Hz), megahertz (MHz=1,000 kHz), gigahertz (GHz= 1,000 MHz). • EMI (Electro-Magnetic Interference)The interference of electrical signals across a cable by outside electrical or magnetic devices. It is a factor that is used to evaluate cable. • RJ-11A registered jack 11 is a telephone connector used on modern telephone lines. • RJ-45A registered jack 45 is an eight-wire connector used to connect computers to category 5 unshielded twisted pair cables in a network. • Signal AttenuationSignal attenuation is a factor used to evaluate cable that relates to how long a signal can travel across a cable before the signal becomes too weak to be recognized in a network. • Thin Coaxial CableThin coaxial cable is often referred to as ThinNet. It consists of a copper wire surrounded first by a layer of plastic, then a layer of metal mesh and a final layer of protective plastic. It is used for peer-to-peer networking. ST0025803A Internetworking Fundamentals Unit 1: Internetworking Overview • Transmission MediaTransmission media is the physical pathway used to connect two or more computers together as a network and includes air and space in addition to cable. • Unshielded Twisted-Pair Cable (UTP)UTP is network cable that consists of up to 4 pairs of wires. Each pair is twisted around each other at a different rate and the entire cable is encased in a protective plastic covering. Decision Factors in Choosing Cable for a Network • The bandwidth represents how much information can be transferred over the cable at one time. The greater the cable’s bandwidth the faster the information is passed over the network. • The further information must travel over a cable the more the electrical strength weakens. This is referred to as signal attenuation. Each type of cable can transmit information up to a specific distance without special equipment to help boost the electrical signal. • EMI (Electro-Magnetic Interference) comes from electrical signals emitted by equipment such as photocopiers, fluorescent lights, and electrical wiring that may disrupt the transmission of information across a network. Some cables are better designed to block out EMI (Electro-Magnetic Interference) than others are. • Organizations may not always be able to build the largest network needed, or their office may grow over time and need more computers added to their network. The ease of installation and need for additional equipment affect the expansion capability of the cable. • The cost of the cable used to build a network is very important. Most organizations have limited funds and seek to build the optimum network. Check Your Understanding ♦ List the factors to consider when choosing cable for building a network. ♦ Why are they important? ♦ The amount of information that can be transferred over cable at one time is called? ♦ How does bandwidth affect a network? ♦ What is it called when information being transmitted over cable loses electrical strength? ST0025803A 65 Lesson 1-3: Cabling ♦ What can you do to prevent it? ♦ Why is cost a factor when planning a network? Cables Solid wire and cable are the oldest forms of electronic transmission media. This lesson covers three basic types, still in use in building networks, coaxial, unshielded twisted-pair, and fiber optic. Thin coaxial cable has a core of copper wire and is primarily used for peer-to-peer LANs due to its low bandwidth and problems with EMI (Electro-Magnetic Interference). Unshielded twisted-pair cable has twisted pairs of wires as the core and is divided into five categories, with category 5 used most commonly for building LANs. Fiber optic cable has a core made of glass and uses light pulses to transmit information across a network. Thin Coaxial Cable Early networks used coaxial cable to connect computers together. Many LANs were built with coaxial cable. It is often referred to as ThinNet. Coaxial cable has: 66 • A core of copper wire surrounded by a layer of plastic. • A layer of metal mesh. • An outer protective plastic insulation sheath. ST0025803A Internetworking Fundamentals Unit 1: Internetworking Overview Coaxial cable is terminated with British Naval Connectors (BNC). Terminators used with BNC/thin coaxial cabling must be 50-ohm terminators. Thin Coaxial Cable BNC T-Connector Outer Plastic Layer Metal Mesh Inner Plastic Layer Copper Wire Decision Factor Thin Coaxial Cable Maximum Bandwidth 10 megabits per second. EMI (ElectroMagnetic Interference) Significant problems with neighboring electrical equipment. Signal Attenuation Maximum distance is 185 meters. Expansion Issues Expansion into multiple rooms is difficult since each computer must be connected directly on to the cable in a chain fashion, often referred to as a bus topology. The cable is thicker and less flexible than unshielded twisted-pair cable. This cable is best used for peer-to-peer networking in a small workgroup LAN. Relative Cost Low. ST0025803A 67 Lesson 1-3: Cabling Unshielded Twisted-Pair Cable Unshielded twisted-pair cable is separated into five categories designated by the TIA/EIA 568-A standard. • Category 1 is telephone cable. • Category 2 was used for token ring networks and is not recommended for Ethernet networks. • Categories 3 and 4 can be used with Ethernet networks, but suffer more from EMI than category 5. Category 3 cables typically have two twists per foot. Category 4 cables have more twists per foot, but less than Category 5 cables. The twisting of the wires in cables is to help prevent EMI (ElectroMagnetic Interference). • Category 5 cable is primarily used in LANs. The most typical connector used with UTP is a RJ-45, which resembles a large telephone connector (RJ-11). This cable has a very high twist rate per foot. Unshielded Twisted-Pair Cable Twisted-Pair of Wires Plastic Insulation Sheath 68 ST0025803A Internetworking Fundamentals Unit 1: Internetworking Overview Decision Factor Unshielded Twisted-Pair Cable: Category 5 Maximum Bandwidth 100 megabits per second. EMI (ElectroMagnetic Interference) Each pair is twisted around each other at a different rate, which reduces EMI (ElectroMagnetic Interference)between the pairs and other electrical signals. Signal Attenuation Maximum distance is 100 meters. Expansion Issues The cable is thin and flexible, which makes installation easy. Expansion is easy, but specialized network equipment is needed to boost the signal. This equipment increases the cost of expansion. This cable is used as a standard today in all Ethernet LANs. Relative Cost Least expensive. Within unshielded twisted-pair (UTP) cable there are typically 2 to 8 wires, 1 to 4 pairs. Each pair is twisted around each other at a different rate, which reduces EMI (Electro-Magnetic Interference) between the pairs and other electrical signals. Each pair is color-coded, according to standards, and the entire cable is inside a protective plastic insulation sheath. In Category 5 UTP, there are usually 4 pairs of wires, with one wire of solid color and one of white with the same color stripe in each pair: • 1 orange pair • 1 brown pair • 1 blue pair • 1 green pair ST0025803A 69 Lesson 1-3: Cabling The TIA/EIA 568 standard has two wiring sequences, T568A and T568B. The sequence of the wires dictates how the wires are terminated on the RJ-45 connector. Either sequence may be used to set up a network. Once a wiring sequence has been chosen, using the same sequence throughout the entire network is necessary. Data networks usually use the TIA/EIA 568B standard. The wires must be correctly paired together for the entire length of the cable to ensure signal quality. TIA/EIA 568A Wiring Sequence In both the 568A and 568B sequences, pair 1 is always designated as the blue wires and pair 4 is always the brown wires. Pair 1 is always assigned to pins 4 and 5 in the connector. The solid blue wire connects to pin 4, as a ring (R) wire, R4-8 T4-7 R2-6 T1-5 R1-4 T2-3 R3-2 T3-1 B ro w n W h ite/B ro w n Orange W h ite/B lu e B lu e W h ite/O r a n g e Green W h ite/G r e e n P a ir 4 P a ir 1 P a ir 2 R = Ring, or Recieve T = Tip, or Transmit P a ir 3 and the white wire of the blue pair connects to pin 5, as a tip (T) wire. Pair 4 is always assigned to pins 7 and 8 on the connector. The white wire of the brown pair connects to pin 7, as the tip wire, and the brown wire connects to pin 8, as the ring wire. The terms tip and ring are old telephony terms used to designate the tip (Tipping the telephone handset off the cradle to transmit a signal that a phone number is about to be dialed) and ring (The response heard on the receiving end of the handset once the number is dialed and the phone is ringing on the other end). The blue and brown pairs may not be used if the network system is set to use up to 10 Mbps bandwidth. In this instance, the blue pair may be used for voice transmission (telephone) and the brown pair dedicated to other network functions. The orange and green pairs, pin positions #1, 2, 3, and 6, are used for Ethernet transmitting (pins 1 and 2) and receiving (pins 3 and 6). 70 ST0025803A Internetworking Fundamentals Unit 1: Internetworking Overview TIA/EIA 568B Wiring Sequence R4-8 T4-7 R2-6 T1-5 R1-4 T2-3 R3-2 T3-1 B ro w n W h it e/B ro w n Green W h it e/B lu e B lu e W h it e/G r e e n Orange W h ite/O r a n g e P a ir 4 P a ir 1 P a ir 3 P a ir 2 In the T568A sequence, the green pair is assigned to pins 1 and 2, and the orange pair is split between pin 3 and 6. In the T568B sequence, it is the green pair that is split between pin 3 and 6, and the orange pair that is assigned to pins 1 and 2. Pairs 2 and 3 are Assigned to Different Pins Pair 2 Pair 3 Pair 3 Pair 1 Pair 4 Pair 2 Pair 1 Pair 4 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 T3 R3 T2 R1 T1 R2 T4 R4 T2 R2 T3 R1 T1 R3 T4 R4 T568A T568B ST0025803A 71 Lesson 1-3: Cabling Fiber-Optic Cable Fiber optic cable uses light pulses rather than electrical signals to transmit information across a network. The cable may be used over many miles because there is no electrical EMI (Electro-Magnetic Interference) and the bandwidth is very high. Fiber optic cable is usually used for the backbone of a network. Since glass and plastic cores can be cracked or broken, installation requires care. Special monitoring equipment is required to locate a break in the fiber optic cable. Fiber Optic Cable Plastic sheath Plastic Casing Glass or Plastic Fiber Strength wires The core of the cable may be made of glass or plastic, which is protected by a layer of gel or light reflecting plastic. A plastic insulation sheath then surrounds the entire cable. Fiber Optic transmission speeds of 10Gigabits per second, currently, 1.6 Terabits per second is being tested Decision Factor Fiber Optic Cable Maximum Bandwidth 10 Gigabits per second currently, though 1.6 Terabits per second is being tested. EMI (ElectroMagnetic Interference) No EMI (Electro-Magnetic Interference) occurs between the cable and other equipment. Signal Attenuation This cable may be laid over several miles. Expansion Issues The use of fiber optic cable is typically limited due to the higher cost and difficulty in installation and maintenance. Fiber optic cable is easily broken requiring monitoring equipment to locate a break in the cable. The cable may be used as the backbone or the main cable of LANs, WANs, and MANs in Enterprise networks. Relative Cost 72 Most expensive. ST0025803A Internetworking Fundamentals Unit 1: Internetworking Overview Check Your Understanding ♦ What advantages does UTP have over thin coaxial cable? ♦ With which type of basic networks would you use thin coaxial cable and UTP? Why? ♦ Why is there no EMI (Electro-Magnetic Interference) with fiber optic cable? ST0025803A 73 Lesson 1-3: Cabling Try It Out Crimping Cable In this activity, you will cut, strip, and crimp a piece of category 5 unshielded twisted pair cable and attach it to a RJ-45 connector. Once you complete this task, you will test your cable to see if your connections function properly. Materials Needed • Category 5 Unshielded Twisted Pair (UTP) Cable • Crimping Tool (model 24-4680P, or equivalent) • Two (2) RJ-45 Connectors • Cable Tester (Brand and model in equipment package, or equivalent) Procedure: Keep a record of this activity as an item for your portfolio. As you go through each of the steps, record any problems you encountered, and any observations you think are important. Your ability to discuss problems and issues of network cabling will be of interest to industry employers. 1. Look at the illustration below and compare it with your crimping tool. The illustrated tool has a stripping blade, a cutting blade, an RJ-45 connector insert for eight wire category 5 UTP, and an RJ-11 connector insert used for six wire telephone cable. Your crimping tool may not have all these features. In that case, you may need to use more than one tool, for example, a separate wire stripper and/or cutter. Crimping Tool Cutting Blade Stripping Blade RJ-45 Crimper RJ-11 Crimper 74 ST0025803A Internetworking Fundamentals Unit 1: Internetworking Overview 2. Cut the category 5 UTP cable to a length specified by your instructor. The ends must be cut squarely, not diagonally. To cut the cable, insert it between the cutting blades and squeeze the crimper handles firmly to close the blades. Crimping Tool – Stripping/Cutting Blades Cutting Blade Stripping Blade 3. To strip the sheathing, insert the end of the cable between the stripper blade with the cable end against the backstop. The stop prevents stripping too much insulation from the cable. Squeeze the blades closed with a gentle, continuous pressure. Too much pressure will cut the wires! Rotate the cable to cut the plastic insulation sheath. Remove the cable from the stripper blades and peel off the short section of plastic sheath. 4. Arrange exposed wires in pairs. If you don’t have eight wires (four pairs of two); you may have cut through one or more wires when you stripped off the insulation sheath. Cut off one inch and repeat the stripping if you don’t have eight wires. 5. Closely examine the RJ-45 connector. On one side you will see the plastic locking clip, and on the other, eight metallic pins. You will notice that the pins are raised slightly above the surface. 6. Carefully insert the eight wires into the connector in the order specified by the T568B wire sequence (see the illustration below). ST0025803A 75 Lesson 1-3: Cabling Use the T568B Wiring Sequence Pair 3 Pair 2 Pair 1 Pair 4 1 2 3 4 5 6 7 8 T2 R2 T3 R1 T1 R3 T4 R4 T568B 7. Each wire must fit into one of the eight separate slots beneath the pins. To make this task easier, separate the wires slightly. When you insert the cable, each wire will slide into a separate slot. 8. Push the cable in with a steady firm pressure until all of the wires are fully inserted into the connector. The ends of the wires must make direct contact with the metal pins at the tip of the connector. 9. Insert the connector assembly into the RJ-45 crimping slot. Align the metal connector contacts with the crimper teeth. Squeeze the handles to crimp. Insert the RJ-45 into the Crimper RJ-45 Crimper 76 ST0025803A Internetworking Fundamentals Unit 1: Internetworking Overview 10. Check the metal pins to see if each individual wire is crimped. The way to be sure is to look at the metal pins. You will notice that they are no longer raised as high on the connector. If they remained in the same position, realign the connector and crimp again. If the plastic cracked, make a new cable cut and try again. 11. Record the color sequence of the wires on your portfolio record sheet as shown in the table below. Hold the connector with the metal contact pins facing you and the plastic locking clip facing away. Starting from either side, record the colors of the wires in the table below. It is very important to compare the order you placed the wires to the T568B wiring sequence. Pin 1 Color Pin 2 Color Pin 3 Color Pin 4 Color Pin 5 Color Pin 6 Color Pin 7 Color Pin 8 Color 12. Repeat steps 3 through 11 for the other end of your cable. Pin 1 Color Pin 2 Color Pin 3 Color Pin 4 Color Pin 5 Color Pin 6 Color Pin 7 Color Pin 8 Color 13. Present your cable and your wire color table to your instructor for inspection and clearance for testing with the cable tester. Rubric: Suggested Evaluation Criteria and Weightings Criteria % Participation (Interest and Determination) 50 Complete descriptive entries in portfolio 20 Directions followed and data recorded as specified 20 Successful test of crimped cable (repeat attempts allowed) 10 TOTAL Your Score 100 ST0025803A 77 Lesson 1-3: Cabling Stretch Yourself Cable Research Materials Needed • Internet Connection • Spreadsheet software 1. Using the Internet, research three companies that sell network cables. 2. Write a short description of the companies and list their cable products and prices. 3. Compare the prices and determine which company you would recommend using for the purchase of cable. 4. Defend your choice with facts you have documented. 5. Create a table or spreadsheet to accompany your description that calculates and/or displays the average cost of each cable type for the companies you have researched. 6. List your web site resources including the URL for each site. 7. Present your work within the specified deadline. Rubric: Suggested Evaluation Criteria and Weightings Criteria % On-time delivery of assignment 10 Use of Web resources 15 Organization, table layout, format, spelling, and grammar 25 Analysis and synthesis of information 50 TOTAL 78 Your Score 100 ST0025803A Internetworking Fundamentals Unit 1: Internetworking Overview Network Wizards Troubleshooting Cable Materials Needed • Student-crimped Category 5 UTP Cable with RJ-45 Connectors • Microscanner During the Try It Out activity, you created your own category 5 cable with RJ45 connectors. Some of your first attempts at creating a working cable may not work. Cable making proficiency comes with attention to detail, care, and practice. In this activity, you are going to troubleshoot potential problems with cables using a microscanner. First, you will check existing cables found in your lab and then you will check the patch cable you made. Patch cable is a common term used for the short wire segments used to connect computer devices to the main cable connection. 1. Test existing networking cable. Insert one end of the cable connector of an existing cable (not the one you made) into the “main” port of the microscanner as shown below. The other end of your cable should be connected to the RJ-45 port of a computer workstation. ST0025803A 79 Lesson 1-3: Cabling 2. Turn the microscanner on and press mode until the wiremap screen appears. W I REMAP FAULT 12345678 36145278 ON OF F MODE 3. If there is a fault, the LED screen will show the word “fault” in the upper right hand corner. In addition to the word fault, the numerical wire indicators will blink. Wiremap Fault 12345678 123**6** 4. If the word “short” is displayed, a short in the wire is indicated. Shorted pairs are indicated with a connecting bracket. Wiremap Fault 12345678 Short [ ]345678 80 ST0025803A Internetworking Fundamentals Unit 1: Internetworking Overview If the word “Open” is displayed, it means that the wire does not go to the far end of the connector. Open wires are indicated by blank spaces. Wiremap Fault 12345678 Open 123 678 5. If the connection is problem free, then the screen will display only the two rows of numerals. Wiremap 12345678 12345678 6. Another way to check for problems is to check the color order of the connectors at each end of the cable to see if they are in the correct order. 7. Record results. Are there any problems? Explain how you might use this tool for troubleshooting networks that are having problems. ST0025803A 81 Lesson 1-3: Cabling Now you will test your patch cable for faults, shorts, or opens. 1. Insert one end of the cable in the “main” port of the microscanner and the other end of the cable in the “loopback” port as shown below. 2. Press mode until the wiremap screen is displayed. If there are any miswires, the number of the faulty wire will blink. 3. Did your cable indicate problems?____________________ . If no, give the cable to your instructor for further lab activities. If yes, what problems were indicated? 4. How can you correct the problem? 5. Diagram the cable or cables, indicating where the problems exist. If your cable was problem-free, diagram one of your peer’s cable problems. 6. Write a one-page paper on crimping and cable testing issues and list several steps or precautions that would improve your ability to crimp problem-free cable. 82 ST0025803A Internetworking Fundamentals Unit 1: Internetworking Overview Rubric: Suggested Evaluation Criteria and Weightings Criteria % Individual initiative or active group participation 50 Quality diagram suitable for reproduction 15 Analysis leading to a viable solution to reduce crimping problems 35 TOTAL Your Score 100 Summary In this lesson, you learned the following: • Three different types of cable and their structural components. • Specifications and attributes for coaxial, UTP, and fiber optic cable and how these factors guide decision making in building networks. • Ethernet cable crimping using proper TIA/EIA 568 wiring sequences. • Cable crimping procedure and cable testing issues. ST0025803A 83 Lesson 1-3: Cabling Review Questions Name__________________ Lesson 1-3: Cabling Part A Identify each cable and label the structural components. 1. a.______________________________ Plastic sheath b.______________________________ Plastic Casing Glass or Plastic Fiber c._______________________ _______ Strength wires d. ____________________________ e. ___________________________ Cable Type 2. a. b. c. f. Cable Type 84 d. ____________________ e ST0025803A Internetworking Fundamentals Unit 1: Internetworking Overview Part B In the spaces provided, write the cable type (UTP Cat.5, Thin Coaxial, or Fiber Optic) that matches the specification or network. Cable Specification or Network Type 1. Uses light to transmit information 2. 8 pairs of twisted wire 3. Metal mesh protecting copper core 4. The most expensive cable 5. Standard Ethernet LANs 6. Glass core 7. High EMI (Electro-Magnetic Interference) problems 8. 100 Mbps Bandwidth 9. Least expensive cable 10. Peer-to-peer workgroup LAN 11. 2 Gbps Bandwidth 12. No EMI (Electro-Magnetic Interference) problems 13. 10 Mbps Bandwidth 14. Maximum distance 185 meters 15. Maximum distance 100 meters Part C Describe how to crimp cable and discuss some of the problems you may encounter, including a discussion on the proper wiring sequences. ST0025803A 85 Lesson 1-3: Cabling Scoring Rubric: Suggested Evaluation Criteria and Weightings Criteria % Part A: Identify different cables and their structural components 30 Part B: Match cable types with attributes and specifications 30 Part C: Describe cable crimping and the T568 wiring sequence, and procedural problems. 40 TOTAL 100 Try It Out: Cable crimping procedure 100 Stretch Yourself 100 For Network Wizards: Cable quality issues 100 FINAL TOTAL 400 Your Score Resources Advanced Computer Networks (1998). Networking Solutions Guide. (1998) [Online]. Available: www.compnetworks.com/solution.htm [1999, March 1]. Aschermann, Robert (1998). 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Telecommunications and Networks in Education. Course TOE 648. The University of Southern Mississippi. [Online]. Available: www.dragon.ep.usm.edu/~yuen/teaching/toe648/spr98w13.htm [1999, May 15]. 88 ST0025803A Internetworking Fundamentals