Guide to Networking Essentials, Fifth Edition 3-1 Chapter 3 Networking Media At a Glance Instructor’s Manual Table of Contents Overview Objectives Teaching Tips Quick Quizzes Class Discussion Topics Additional Projects Additional Resources Key Terms Technical Notes for Hands-On Projects Guide to Networking Essentials, Fifth Edition 3-2 Lecture Notes Overview Chapter 3 offers an introduction to networking media. Students learn about different cabling characteristics applied to physical media and about the primary cable types used in networking. They also learn about the components in a structured cabling installation and about wireless transmission techniques used in LANs and WANs. Objectives Identify general cabling characteristics applied to physical media Describe the primary cable types used in networking Identify the components in a structured cabling installation Describe wireless transmission techniques used in LANs and WANs Teaching Tips Network Cabling: Tangible Physical Media 1. Introduce the role of network media. Note that because all media must support the basic tasks of sending and receiving signals, you can view all networking media as doing the same thing; only the methods vary. 2. Explain that each type of media has a unique design and usage, with associated cost, performance, and installation criteria. General Cable Characteristics 1. Briefly describe each of the following characteristics that apply to network cabling: a. Bandwidth rating b. Maximum segment length c. Maximum number of segments per internetwork d. Maximum number of devices per segment e. Interference susceptibility f. Connection hardware g. Cable grade h. Bend radius i. Material costs j. Installation costs Baseband and Broadband Transmission 1. Explain the difference between baseband and broadband transmission. Stress the differences between using repeaters and amplifiers to deal with signal ―attenuation‖. Guide to Networking Essentials, Fifth Edition 3-3 2. Simulation 3-1 helps students learn the difference between baseband and broadband communications. The Importance of Bandwidth 1. Describe the importance of bandwidth in computer networks. Primary Cable Types 1. Explain that all forms of cabling are similar, in that they provide a medium across which network information can travel in the form of a physical signal, whether it’s a type of electrical transmission or some sequence of light pulses. 2. List the three primary cable types available. Coaxial Cable 1. Use Figure 3-1 to describe the components of a coaxial cable. Stress that this type of cable used to be the predominant form of network cable. Stress that coaxial cable in LAN installations is obsolete. The majority of coaxial cable used today is for carrying broadband signals for cable TV or from a home Teaching satellite dish to the satellite receiver. The information in this section about the Tip properties of coax refers to all types of coaxial cabling. Information on the use of coaxial cable for a LAN is offered for historical purposes only. Keep in mind that this type of cabling should not be used in new LAN installations. 2. Note that coaxial cable is less susceptible to interference and attenuation than twisted- pair, but more susceptible than fiber-optic. Teaching For more information on coaxial cable, go to Tip http://en.wikipedia.org/wiki/Coaxial_cable. 3. The Use of Coaxial Cable for Ethernet. Describe the role of thicknet and thinnet in Ethernet networks. Introduce the terms 10Base5 and 10Base2 and explain how to interpret them. 4. Coaxial Cable in Cable Modem Applications. Note that coaxial cable in LANs has become obsolete. Use Figure 3-2 to describe the use of coaxial cable in cable modem applications. 5. Other Coaxial Cable Types. Briefly describe the role of coaxial cable in ARCnet. Guide to Networking Essentials, Fifth Edition 3-4 Twisted-Pair Cable 1. Use Figure 3-3 to introduce twisted-pair and explain the difference between STP and UTP. Don’t forget to introduce the term crosstalk. Teaching For more information on twisted-pair cable, go to Tip http://en.wikipedia.org/wiki/Twisted_pair. 2. Unshielded Twisted Pair. Describe the role of UTP in networking. Explain how to interpret the term 10BaseT. 3. UTP Cabling Categories. Briefly describe the characteristics of UTP Categories 1 through 6. You may introduce the non-standard Category 7 UTP. Note that of these categories of UTP cabling, Categories 5, 5e, and 6 are by far the most popular types. Note that Category 1 UTP is known as voicegrade, whereas Category 4 UTP is known as datagrade. 4. Shielded Twisted Pair (STP). Describe the role of STP in networking. Note that STP enables support of higher bandwidth over longer distances than UTP. Stress that no set of standards for STP corresponds to the ANSI/TIA/EIA 568 Standard, yet it’s not unusual to find STP cables rated according to those standards. Explain that another type of STP cabling is screened twisted pair (ScTP) or foil Teaching twisted pair (FTP). Both use 100 ohm, four-pair cabling, just like UTP. The Tip cabling is wrapped in a metal foil or screen. This type of cabling can be used in place of UTP in electrically noisy environments. 5. Use Figure 3-4 to introduce the RJ-45 and RJ-11 connectors. 6. Note that typically, twisted-pair systems include the following elements, often in a wiring center (briefly describe each): a. Distribution racks and modular shelving b. Modular patch panels (see Figure 3-6) c. Wall plates (see Figure 3-5) d. Jack couplers 7. Use Table 3-1 to summarize the common characteristics of Category 5, 5e, and 6 UTP cabling. 8. Making Twisted Pair Cable Connections. Introduce the term patch cable. Use Figures 3-7 and 3-8 to describe the TIA/EIA 568A and 568B standards. Don’t forget to introduce the term differential signal. Stress that you can use either standard, but you must stick to one throughout your network. Guide to Networking Essentials, Fifth Edition 3-5 Fiber-Optic Cable 1. Explain that fiber-optic cable trades electrical pulses for their optical equivalents, which are pulses of light. Note that because no electrical signals ever pass through the cable, fiber-optic media is as immune to interference as any medium can get. Stress that this characteristic also makes fiber-optic cables highly secure. Don’t forget to introduce the term electronic eavesdropping. Teaching For more information on optical fiber cable, go to Tip http://en.wikipedia.org/wiki/Optical_fiber. 2. Note that today, commercial implementations of fiber-optic cables at 10 Gbps are in use. 3. Use Figure 3-9 to describe the parts of a fiber-optic cable. 4. Explain that in any fiber-optic cable, each light-conducting core can pass signals in only one direction. 5. Use Table 3-2 to describe the fiber-optic cable characteristics. 6. Use Figure 3-10 to briefly describe each of the available fiber-optic connectors. Don’t forget to describe the MIC and SMA connectors (not shown in the picture). 7. Note that installation of fiber-optic networks is somewhat more difficult and time- consuming than copper media installation. Stress that because of the falling costs of fiber and the inherent advantages of this medium in interference immunity, high bandwidth capability, and increased security, fiber-optic cable is being used almost exclusively for all network backbone connections. 8. Briefly describe the difference between single-mode and multimode fiber-optic cables. Cable Selection Criteria 1. Briefly describe each of the following criteria to be considered for a network installation: a. Bandwidth b. Budget c. Capacity d. Environmental considerations e. Placement f. Span g. Local requirement h. Existing cable plant 2. Table 3-3 condenses the most important cabling information for the cable types covered so far in this chapter. Guide to Networking Essentials, Fifth Edition 3-6 Quick Quiz 1 1. What is attenuation? Answer: Each type of (networking) cable can transport data only so far before its signal begins to weaken beyond where it can be read accurately; this phenomenon is called attenuation. 2. Baseband systems—such as Ethernet—can use special devices called ____________________ that receive incoming signals on one cable segment and refresh them before retransmitting them on another cable segment. Answer: repeaters 3. For many years, coaxial cable—often called ―____________________‖ for short—was the predominant form of network cabling. Answer: coax 4. Why are twisted-pair cables twisted? Answer: The most basic form of twisted-pair (TP) wiring consists of one or more pairs of insulated strands of copper wire twisted around one another. These twists are important because they cause the magnetic fields that form around a conducting wire to wrap around one another and improve TP’s resistance to interference. They also limit the influence of signals traveling on one wire over another (called crosstalk). In fact, the more twists per unit length, the better these characteristics become. It’s safe to say, therefore, that more expensive TP wire is usually more twisted than less expensive kinds. Managing and Installing the Cable Plant 1. Explain that the TIA/EIA developed the document ―568 Commercial Building Wiring Standard,‖ which specifies how network media should be installed to maximize performance and efficiency. Note that this standard defines what’s referred to as structured cabling. Structured Cabling 1. Explain the importance of structured cabling. Note that it relies on an extended star physical topology. 2. Stress that structured cabling facilitates troubleshooting as well as network upgrades and expansion. Guide to Networking Essentials, Fifth Edition 3-7 3. Describe each of the six components of a cable plant (according the structured cabling standard): a. Work Area. Don’t forget to mention that the TIA/EIA 568 standard calls for at least one voice and one data outlet on each faceplate in each work area. Explain that the connection between a wall jack and the telecommunications closet is made with horizontal wiring. b. Horizontal Wiring. Stress that acceptable horizontal wiring types include four- pair UTP (Category 5e or 6) or two fiber-optic cables. c. Telecommunications Closet. Explain that the telecommunications closet (TC) provides connectivity to computer equipment in the nearby work area. Note that in small installations, the TC can also serve as the entrance facility. Use Figure 3-11 to describe the relationship and connections between the work area, horizontal wiring, and telecommunications closet. d. Equipment Rooms. Note that the equipment room can be the main cross-connect of backbone cabling for the entire network, or it might serve as the connecting point for backbone cabling between buildings. e. Backbone Cabling. Note that it can also be called ―vertical cabling‖. Stress that it is frequently fiber-optic cable, but can also be UTP. Note that choice of single- mode or multimode fiber depends on the distance involved. f. Entrance Facilities. Note that the entrance facility can also serve as an equipment room and the main cross-connect for all backbone cabling. Explain that here is also where a connection to a WAN is made and the point where corporate LAN equipment ends and a third-party provider’s equipment and cabling begins—also known as the ―demarcation point‖. Guide to Networking Essentials, Fifth Edition 3-8 Quick Quiz 2 1. What is structured cabling? Answer: The TIA/EIA developed the document ―568 Commercial Building Wiring Standard,‖ which specifies how network media should be installed to maximize performance and efficiency. This standard defines what’s often referred to as structured cabling. Structured cabling specifies how cabling should be organized, regardless of the type of media or network architectures. 2. According to the structured cabling standard, the ____________________, as the name suggests, is where computer workstations and other user devices are located—in short, the place where people work. Answer: work area 3. According to the structured cabling standard, ____________________ runs from the work area’s wall jack to the telecommunications closet and is usually terminated at a patch panel. Answer: horizontal wiring 4. According to the structured cabling standard, what is the role of backbone cabling? Answer: Backbone cabling (or vertical cabling) interconnects TCs and equipment rooms. This cabling runs between floors or wings of a building and between buildings to carry network traffic destined for devices outside the work area. Wireless Networking: Intangible Media 1. Describe the current importance of wireless networks. 2. Explain that wireless networks are often used with wired networks to interconnect geographically dispersed LANs or groups of mobile users with stationary servers and resources on a wired LAN. Note that Microsoft calls networks that include both wired and wireless components hybrid networks. The Wireless World 1. Explain why wireless networks are frequently used (i.e., provide different scenarios in which wireless networks are very useful). 2. Describe some common wireless applications. 3. Figure 3-12 shows an example of using wireless in a home network. 4. Students should see Simulation 3-2 to get an idea of how wireless networks operate. Guide to Networking Essentials, Fifth Edition 3-9 Types of Wireless Networks 1. Briefly describe each of the three main categories of wireless networks: LANs, extended LANs, and mobile computing. Teaching For more information on wireless LANs, go to Tip http://en.wikipedia.org/wiki/Wireless_LAN. 2. Explain that an easy way to differentiate among these uses is to distinguish in-house from carrier-based facilities. Introduce the term communications carrier. Wireless LAN Components 1. Describe the role of the different wireless LAN components. Don’t forget to introduce the terms antenna, transceiver, and access point. Wireless LAN Transmission 1. Provide some background on how wireless LAN transmissions occur. In this part, you should talk about ―waves‖, ―electromagnetic spectrum‖, ―Hertz‖, etc. 2. Explain that the frequency of the waves affects the amount and speed of data transmission. 3. Note that commonly used frequencies for wireless data communications are: radio, microwave, and infrared. Briefly describe each of these. 4. Explain that higher-frequency technologies often use tight-beam broadcasts and require a clear line of sight between sender and receiver. 5. Note that wireless LANs make use of four primary technologies for transmitting and receiving data: infrared, laser, narrowband (single-frequency) radio, and spread- spectrum radio. 6. Infrared LAN Technologies. Describe the role of infrared LAN technologies. Explain that there are four main kinds of infrared LANs: line of sight networks, reflective wireless networks, scatter infrared networks, and broadband optical telepoint networks. Don’t forget to introduce the terms virtual docking and IrDA. 7. Laser-Based LAN Technologies. Describe the role of laser-based LAN technologies. Explain that to protect people from injury and avoid excess radiation, laser-based LAN devices are subject to many of the same limitations as infrared, but aren’t as susceptible to interference from visible light sources. Guide to Networking Essentials, Fifth Edition 3-10 8. Narrowband Radio LAN Technologies. Introduce narrowband radio. Note that it is also called ―single-frequency radio‖. Describe the role of the FCC. Use Table 3-4 to describe the characteristics of narrowband wireless LAN technologies. Use Table 3-5 to describe the characteristics of high-powered single-frequency radio networks. 9. Spread-Spectrum LAN Technologies. Briefly explain how spread-spectrum works. Don’t forget to introduce the terms frequency hopping and direct-sequence modulation. Use Table 3-6 to describe the characteristics of spread-spectrum LANs. 802.11 Wireless Networking 1. Provide an introduction to the 802.11 standard. Briefly describe the roles of 802.11b, 802.11g, and 802.11a. For more information on the 802.11 family of standards, go to Teaching http://grouper.ieee.org/groups/802/11/ and Tip http://en.wikipedia.org/wiki/IEEE_802.11. 2. Note that most 802.11 networks incorporate wired Ethernet segments. 3. Introduce the term hot spot. Note that a newer technology, dubbed ―MIMO‖ for multiple-in, multiple-out, is Teaching available in some wireless products. This technology uses multiple antennas that Tip boost transfer rates to 108 Mbps and beyond. As you can see, there’s no end in sight for the speed upgrades of wireless LANs. Teaching For a wealth of information on the 802.11 standards, see www.wi-fiplanet.com. Tip Wireless Extended LAN Technologies 1. Explain that certain kinds of wireless networking equipment extend LANs beyond their normal cable-based distance limitations, or provide connectivity across areas where cables are not allowed (or able) to traverse. Explain that wireless bridges can connect networks up to three miles (4.4 km) apart. 2. Use Table 3-7 to describe the characteristics of wireless extended LAN technologies. Guide to Networking Essentials, Fifth Edition 3-11 Explain that wireless bridges always appear in pairs, and both devices function together as a repeater—whatever comes in on the wired side of one device is transmitted out the wired side of the other. These devices are sometimes called Teaching ―halfrepeaters,‖ a reference to the frequency ranges they use. Therefore, you Tip sometimes hear this equipment called ―optical half-repeaters‖ (for laser or infrared versions) or ―radio half-repeaters‖ for their spread-spectrum counterparts. Wireless MAN: The 802.16 Standard 1. Provide an introduction to the 802.16 (WiMax) standard. For more information on the 802.16 family of standards, visit Teaching www.80216news.com/, http://en.wikipedia.org/wiki/802.16, and Tip http://standards.ieee.org/getieee802/802.16.html. 2. Fixed WiMax: 802.16-2004. Provide an introduction to the 802.16-2004 (fixed WiMax) standard. Note that fixed WiMax can blanket an area up to a mile in radius, compared to just a few hundred feet for 802.11. 3. Mobile WiMax: 802.16e. Provide an introduction to the 802.16e (mobile WiMax) standard. Stress that this technology is not yet widely adopted (as opposed to fixed WiMax). Stress that fixed WiMax is expected to be the dominant technology for the next several years, but mobile WiMax will win out in the end. Microwave Networking Technologies 1. Explain that microwave systems deliver higher transmission rates than radio-based systems do, but because the frequencies are so high, transmitters and receivers must share a common clear line of sight. 2. Use Table 3-8 to describe the characteristics of terrestrial microwave. 3. Use Table 3-9 to describe the characteristics of satellite microwave. Don’t forget to introduce the term geosynchronous. Note that most organizations can’t fund launching satellites, so most satellite microwave systems must lease frequencies on satellites operated by global communications carriers. Guide to Networking Essentials, Fifth Edition 3-12 Explain that geosynchronous satellites orbit 50,000 km (23,000 miles) above Earth. The distances are great enough to incur measurable transmission delays Teaching (called ―propagation delays‖) that vary between 0.5 and 5 seconds, depending on Tip the number of hops (jumps across network segments) between sender and receiver. Quick Quiz 3 1. In a wireless LAN, a(n) ____________________ device includes an antenna and a transmitter to send and receive wireless traffic, but also connects to the wired side of the network. Answer: access point 2. The ____________________ of the wave forms used for communication is measured in cycles per second usually expressed as hertz (Hz). Answer: frequency 3. IrDA stands for ____________________. Answer: Infrared Device Association 4. The 1997 ____________________ Wireless Networking Standard is also referred to as Wireless Fidelity (Wi-Fi). Answer: 802.11 Guide to Networking Essentials, Fifth Edition 3-13 Class Discussion Topics 1. Have any of the students installed a wireless LAN at home? If so, ask them to discuss their experiences in class. 2. How common are wireless networks in your area? Ask students to list businesses and institutions that they know have hot spots set up. Do they know what standard (802.11a, 802.11b or 802.11g) they use? Do they charge for the use of the wireless LAN? If so, how much? Additional Projects 1. The 802.11 family of standards contains other standards besides those mentioned in this book. Ask students to compile a list of the standards in this family, including a brief description of each. 2. There are special considerations that should be taken when installing and manipulating fiber-optic cables. Ask students to do some research to find out what these considerations are. They should summarize their findings in a written report. Additional Resources 1. Coaxial Cable: http://en.wikipedia.org/wiki/Coaxial_cable 2. Twisted Pair: http://en.wikipedia.org/wiki/Twisted_pair 3. Category 5 Cable: http://en.wikipedia.org/wiki/Category_5_cable 4. Category 6 Cable: http://en.wikipedia.org/wiki/Category_6_cable 5. RJ45: http://en.wikipedia.org/wiki/RJ-45 6. Optical Fiber: http://en.wikipedia.org/wiki/Optical_fiber 7. Structured Cabling: http://en.wikipedia.org/wiki/Structured_cabling 8. Welcome to Belkin – Structured Cabling: http://catalog.belkin.com/IWCatSectionView.process?Section_Id=201488 Guide to Networking Essentials, Fifth Edition 3-14 9. Wireless LAN: http://en.wikipedia.org/wiki/Wireless_LAN 10. IEEE 802.11: http://grouper.ieee.org/groups/802/11/ 11. IEEE 802.11: http://en.wikipedia.org/wiki/IEEE_802.11 12. 802.16 News: www.80216news.com/ 13. 802.16: http://en.wikipedia.org/wiki/802.16 14. IEEE 802.16: http://standards.ieee.org/getieee802/802.16.html 15. Wi-Fi Planet: www.wi-fiplanet.com/ Key Terms 10Base2 — A designation for 802.3 Ethernet thin coaxial cable (also called thinnet, thinwire, or cheapernet). The 10 indicates a bandwidth of 10 Mbps, the Base indicates it’s a baseband transmission technology, and the 2 indicates a maximum segment length of 185 meters (originally 200, hence the ―2‖) for this cable type. 10Base5 — A designation for 802.3 Ethernet thick coaxial cable (also called thicknet or thickwire). The 10 indicates a bandwidth of 10 Mbps, the Base indicates it’s a baseband transmission technology, and the 5 indicates a maximum segment length of 500 meters for this cable type. 10BaseT — A designation for 802.3 Ethernet twisted-pair cable. The 10 indicates a bandwidth of 10 Mbps, the Base indicates it’s a baseband transmission technology, and the T indicates that the medium is twisted-pair. (Maximum segment length is around 100 meters, or 328 feet, but the precise measurement depends on the manufacturer’s testing results for the cable.) 802.11Wireless Networking Standard — An IEEE standard for wireless networking. A version of the 802.11 standard appeared late in 1997. access point device — The device that bridges wireless networking components and a wired network. It moves traffic between the wired and wireless sides as needed. American National Standards Institute (ANSI) — The U.S. representative in the International Organization for Standardization (ISO), a worldwide standards-making body. ANSI creates and publishes standards for networking, communications, and programming languages. amplifiers — Hardware devices that increase the power of electrical signals to maintain their original strength when transmitted across a large network. Guide to Networking Essentials, Fifth Edition 3-15 analog—The method of signal transmission used on broadband networks. Creating analog waveforms from computer-based digital data requires a special device called a digital-to-analog (d-to-a) converter; reversing the conversion requires an analog-to- digital (a-to-d) converter. Broadband networking equipment must include both kinds of devices to work. antenna — A tuned electromagnetic device that can send and receive broadcast signals at particular frequencies. In wireless networking devices, an antenna is an important part of a device’s sending and receiving circuitry. attached resource computing network (ARCnet) — A 2.5 Mbps LAN technology created by DataPoint Corporation in the late 1970s. ARCnet uses token-based networking technology and runs over several kinds of coaxial cable, twisted-pair, and fiber-optic cable. attenuation — The weakening of a signal as it travels the length of a medium, which eventually causes the signal to be unreadable. backbone cabling — The part of the cable plant that interconnects telecommunications closets and equipment rooms. Backbone cabling runs between floors or wings of a building and between buildings to carry network traffic destined for devices outside the work area. bandwidth — The range of frequencies that a communications medium can carry. For baseband networking media, the bandwidth also indicates the theoretical maximum amount of data that the medium can transfer. For broadband networking media, the bandwidth is measured by the variations that any single carrier frequency can carry, minus the analog-to-digital conversion overhead. baseband transmission — A technology that uses digital signals sent over a cable without modulation. It sends binary values (0s and 1s) as pulses of different voltage levels. bend radius — For network cabling, the maximum arc that a segment of cable can be bent over some unit length (typically, one foot or one meter) without incurring damage. broadband optical telepoint networks — An implementation of infrared wireless networking that supports broadband services equal to those a cabled network provides. broadband transmission — An analog transmission technique that can use multiple communication channels simultaneously. Each data channel is represented by modulation on a particular frequency band, and sending or receiving equipment must be tuned to that band. cable modem — A special-purpose networking device that permits a computer to send and receive networking signals, primarily for Internet access, by using two data channels on a broadband CATV network (one to send outgoing data, the other to receive incoming data). Cable modems can support bandwidth up to 1.544 Mbps, but upstream traffic (from computer to network) between 100 and 300 Kbps and downstream traffic (from network to computer) between 300 and 600 Kbps are more typical. cable plant — The combination of installed network cables, connectors, patch panels, wall jacks, and other media components. chips — Fixed-sized elements of data broadcast over a single frequency by using direct-sequence modulation. Also see direct-sequence modulation. cladding — A nontransparent layer of plastic or glass material inside fiber-optic cable; cladding surrounds the inner core of glass or plastic fibers. Cladding provides rigidity, strength, and a manageable outer diameter for fiber-optic cables. Guide to Networking Essentials, Fifth Edition 3-16 coaxial cable — A type of cable that uses a center conductor, wrapped by an insulating layer and surrounded by a braided wire mesh and an outer jacket or sheath, to carry high-bandwidth signals, such as network traffic or broadcast television frequencies. ―Coax‖ is often used as a shortened form of ―coaxial cable.‖ communications carrier — A company that provides communications services for other organizations, such as a local phone company and long-distance telephone carriers. Most mobile computing technologies rely on the services of a communications carrier to handle wireless traffic from mobile units to a centralized wired network. conduit — Plastic or metal pipe laid specifically to provide a protected enclosure for cabling of any kind. crosstalk — A phenomenon that occurs when two wires lay against each other in parallel. Signals traveling down one wire can interfere with signals traveling down the other, and vice versa. datagrade — A designation for cabling of any kind; datagrade indicates that cabling is suitable for transporting digital data. When applied to twisted-pair cabling, ―datagrade‖ indicates that the cable is suitable for voice or data traffic. differential signal — The use of two wires to carry a signal, where one wire carries a positive voltage signal and the other carries a negative voltage signal. Differential signals help mitigate the effects of noise and crosstalk. Also see electromagnetic interference (EMI) and crosstalk. direct-sequence modulation — The form of spread-spectrum data transmission that breaks data into fixed-length segments called chips, and transmits the data on multiple frequencies. dual-cable broadband — A broadband technique in which two cables are used; one is for transmitting, and one is for receiving. electromagnetic interference (EMI) — A form of interference, also referred to as ―noise,‖ caused by emissions from external devices, such as transformers or electrical motors, that can disrupt network transmissions over an electrical medium. electronic eavesdropping — The capability to ―listen‖ to signals passing through a communications medium by detecting its emissions. Eavesdropping on many wireless networking technologies is especially easy because they broadcast data into the atmosphere. Electronic Industries Alliance (EIA) — An industry trade group of electronics and networking manufacturers that collaborates on standards for wiring, connectors, and other common components. entrance facility — The location of the cabling and equipment that connects a corporate network to a third-party telecommunications provider. equipment room — An area that serves as a connection point for backbone cabling running between telecommunications closets; also houses servers, routers, switches, and other major network equipment. extended LANs — Microsoft’s name for the networks resulting from certain wireless bridges’ capability to expand the span of a LAN up to 25 miles. Federal Communications Commission (FCC) — Among other responsibilities, the FCC regulates access to broadcast frequencies throughout the electromagnetic spectrum, including those used for mobile computing and microwave transmissions. When these signals cover any distance (more than half a mile) and require exclusive use of a frequency, FCC requires a broadcast license. Many wireless networking technologies make use of unregulated frequencies set aside by the FCC. These frequencies don’t require licensing, but they must be shared with others. Guide to Networking Essentials, Fifth Edition 3-17 fiber-optic — A cabling technology that uses pulses of light sent along a light- conducting fiber at the heart of the cable to transfer information from sender to receiver. Fiber-optic cable can send data in only one direction, so two cables are required to permit network devices to exchange data in both directions. frequency hopping — The type of spread-spectrum data transmission that switches data across a range of frequencies over time. Frequency-hopping transmitters and receivers must be synchronized to hop at the same time to the same frequencies. geosynchronous — An orbital position relative to Earth where a satellite orbits at the same speed as Earth rotates. This orbit permits satellites to maintain a constant fixed position in relation to Earth stations, and represents the positioning technique used for microwave satellites. hertz (Hz) — A measure of broadcast frequencies in cycles per second; named after Heinrich Hertz, one of the inventors of radio communications. horizontal wiring — Network cabling that runs from the work area’s wall jack to the telecommunications closet and is usually terminated at a patch panel. hot spots — A term used in wireless networking for areas in which wireless access to a network or the Internet is possible. Often these areas are in nontraditional locations, such as outside cafes or college campus courtyards. infrared — The portion of the electromagnetic spectrum immediately below visible light. Infrared frequencies are popular for short- to medium-range (10 m to 40 m) point- to-point network connections. insertion loss — The weakening of signals that occurs on a cable segment each time a network device is attached. Necessary restrictions on the maximum number of devices keep the signals that traverse the network clean and strong enough to remain intelligible to all devices. Institute of Electrical and Electronics Engineers (IEEE) — An engineering organization that issues standards for electrical and electronic devices, including network interfaces, cabling, and connectors. IrDA devices — Devices that are compliant with the Infrared Device Association’s specifications for infrared components and devices. jack couplers — The female receptacles into which modular TP cables plug. latency — The amount of time a signal takes to travel from one end of a cable to the other. light-emitting diodes (LEDs) — A lower-powered alternative for emitting data at optical frequencies. LEDs are sometimes used for wireless LANs and for short-haul, fiber-optic based data transmissions. line-of-sight networks — Networks that require an unobstructed view, or clear line of sight, between the transmitter and receiver. Narrowband tight-beam transmitters and receivers must have an unobstructed path between them. locking connection (LC) — A type of fiber-optic connector that pushes on and pulls off using an RJ-45 style latching mechanism. maximum segment length — The longest cable segment that a particular networking technology permits. This limitation helps network designers and installers make sure the entire network can send and receive signals properly. mechanical transfer registered jack (MT-RJ) — A fiber-optic connector that provides a high-density connection using two fiber-optic cables. medium interface connector (MIC) — One of a number of fiber-optic cable connector types. MIC connectors feature a separate physical connector for each cable in a typical fiber-optic cable pair. Guide to Networking Essentials, Fifth Edition 3-18 mid-split broadband — A broadband technique in which two channels on different frequencies are used to transmit and receive signals via a single cable. mobile computing — A form of wireless networking that uses common carrier frequencies to permit networked devices to be moved freely within the broadcast coverage area yet remain connected to the network. narrowband radio — A type of broadcast-based networking technology that uses a single specific radio frequency to send and receive data. Low-powered, narrowband implementations don’t usually require FCC approval, but are limited to a 250-foot or so range; high-powered narrowband implementations do require FCC approval and licensing. Also called ―single-frequency radio.‖ patch cable — A short length (1 to 20 feet) of network cable used to connect a computer’s network interface card to a jack in the work area, or to connect from a patch panel to a hub or switch in the wiring closet. patch panels — Elements of a wiring center in which separate cable runs are brought together. By making connections between any two points on the patch panel, the physical path of wires can be controlled and the sequence of wires managed. plenum-rated — Cable that has been burn-tested to make sure it doesn’t emit toxic fumes or large amounts of smoke when incinerated. Most building and fire codes require this designation for any cable to be run in plenum space. radio frequency interference (RFI) — Any interference caused by signals operating in the radio frequency range. This term has become generic for interference caused by broadcast signals of any kind. reflective wireless networks — An infrared wireless networking technology that uses a central optical transceiver to relay signals between end stations. All network devices must have an unobstructed view of this central transceiver, which explains why they’re usually mounted on the ceiling. registered jack 45 (RJ-45) — The eight-wire modular jack used for TP networking cables and PBX-based telephone systems. repeaters — Networking devices used to strengthen a signal suffering from attenuation. Also see attenuation. RJ-11 — The four-wire modular jack commonly used for home telephone handsets. satellite microwave — A microwave transmission system that uses geosynchronous satellites to send and relay signals between sender and receiver. Most companies that use satellite microwave lease access to the satellites for an exorbitant fee. Also see geosynchronous. scatter infrared networks — An infrared LAN technology that uses flat reflective surfaces, such as walls and ceilings, to bounce wireless transmissions between sender and receiver. Because bouncing introduces delays and attenuation, this variety of wireless LAN is the slowest and supports the narrowest bandwidth of any infrared technology. sheath — The outer layer of coating on a cable; sometimes also called a jacket. shielded twisted-pair (STP) — A variety of TP cable in which a foil wrap encloses each of one or more pairs of wires for additional shielding, and a wire braid or an additional layer of foil might enclose the entire cable for further shielding. shielding — Any layer of material included in cable to mitigate the effects of interference on the signal-carrying cables it encloses. spread-spectrum radio — A form of wireless networking technology that passes data by using multiple frequencies simultaneously. Guide to Networking Essentials, Fifth Edition 3-19 straight connection (SC) — A type of one-piece fiber-optic connector that’s pushed on yet makes a strong and solid contact with emitters and sensors. straight tip (ST) — The most common type of fiber-optic connector used in Ethernet networks with fiber backbones. These connectors come in pairs, one for each fiber-optic cable. structured cabling — A specification for how network media should be installed to maximize performance and efficiency. subminiature type A (SMA) — Another fiber-optic connector that twists on and comes in pairs. telecommunications closet (TC) — A small room or area housing equipment (such as patch panels, hubs, and switches) that provides connectivity to computer equipment in the nearby work area. Telecommunications Industries Association (TIA) — An industry consortium of telephone equipment, cabling, and communications companies that formulates hardware standards for equipment, cabling, and connectors used in phone systems and on networks. terrestrial microwave — A wireless microwave networking technology that uses line- of-sight communications between pairs of Earth-based transmitters and receivers to relay information. The large distances the signals must extend requires positioning microwave transmitters and receivers well above ground level on towers, on mountaintops, or atop tall buildings. This equipment is usually expensive. thicknet — A form of coaxial Ethernet that uses a rigid cable about 0.4 inches in diameter. Because of its common jacket color and its rigidity, this cable is sometimes called ―frozen yellow garden hose.‖ Also known as thickwire and 10Base5. thinnet — A form of coaxial Ethernet that uses a thin, flexible cable about 0.2 inches in diameter. Also known as thinwire, 10Base2, and cheapernet. transceiver — A compound word made from the words ―transmitter‖ and ―receiver‖ to describe a device that combines the functions of a transmitter and a receiver and integrates into a single device the circuitry needed to emit and receive signals on a medium. twisted-pair (TP) — A type of cabling in which two copper wires, each enclosed in some kind of sheath, are wrapped around each other. The twisting permits narrow- gauge wire, otherwise extraordinarily sensitive to crosstalk and interference, to carry higher-bandwidth signals over longer distances than is traditionally possible with straight wires. TP cabling is used for voice telephone circuits as well as networking. unshielded twisted-pair (UTP) — A form of TP cable that includes no additional shielding material in the cable composition. This cable encloses one or more pairs of twisted wires inside an outer jacket. virtual docking — One of numerous point-to-point wireless infrared technologies that enable portable computing devices to exchange data with desktop machines or allow data exchange between a computer and a handheld device or a printer. The ―virtual‖ term is used because this capability replaces a cable between the two devices. voicegrade — A designation for cable (usually TP) that indicates it’s rated to carry only telephone traffic. Voicegrade cable is not recommended for network use. wall plates — A modular plate used to accommodate numerous outlets used for networking and voice applications. wireless — A network connection that depends on transmission at an electromagnetic frequency through the atmosphere to carry data transmissions from one networked device to another. Guide to Networking Essentials, Fifth Edition 3-20 wireless bridges — A pair of devices, typically narrowband and tight beam, that relay network traffic from one location to another. Wireless bridges that use spread-spectrum radio, infrared, and laser technologies are available and can span distances from hundreds of meters up to 25 miles. Wireless Fidelity (Wi-Fi) — A term used to indicate wireless networking, usually using one of the 802.11 wireless networking standards. wiring center — A set of racks with associated equipment that generally includes hubs, patch panels, backbone access units, and other network-management equipment, which brings TP-wired network cables together for routing, management, and control. work area — The space in a facility or office where computer workstations and other user devices are located. Worldwide Interoperability for Microwave Access (WiMax) — A wireless technology designed for wireless metropolitan area networks defined in standards 802.16-2004 and 802.16e. Technical Notes for Hands-On Projects Hands-On Project 3-1: In this project, students analyze each of the following connectors: RJ- 45, BNC, ST, SC, and MT-RJ. Hands-On Project 3-2: This project requires a wire cutter and stripper, an RJ-45 crimp tool, 3 to 4 feet of Category 5/5e or Category 6 cable (per student), two RJ-45 plugs (per student), and a patch cable checker (optional). Hands-On Project 3-2: No special material, files, or software are required. Hands-On Project 3-3: No special material, files, or software are required. Hands-On Project 3-4: No special material, files, or software are required. Hands-On Project 3-5: No special material, files, or software are required. Hands-On Project 3-6: No special material, files, or software are required. Hands-On Project 3-7: No special material, files, or software are required.
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