Chapter 3 Lecture Notes

Network+ Guide to Networks, Third Edition

Instructors Manual Chapter 3

Lecture NotesTransmission BasicsIn data networking, the term transmit means to issue signals to the network medium. Transmission refers to either the process of transmitting or the progress of signals after they have been transmitted.

Analog and Digital Signaling On a data network, information can be transmitted via one of two signaling methods: analog or digital. Both types of signals are generated by electrical current, the pressure of which is measured in volts.

In analog signals, voltage varies continuously and appears as a wavy line when graphed over time, as shown in Figure 3-1 on page 75 of the text. An analog signal, like other waveforms, is characterized by four fundamental properties: amplitude, frequency, wavelength, and phase. A waves amplitude is a measure of its strength at any given point in time.

Whereas amplitude indicates an analog waves strength, frequency is the number of times that a waves amplitude cycles from its starting point, through its highest amplitude and its lowest amplitude, and back to its starting point over a fixed period of time. Frequency is expressed in cycles per second, or hertz (Hz). The distance between corresponding points on a waves cycle is called its wavelength. Wavelength can be expressed in meters or feet. A waves wavelength is inversely proportional to its frequency.

The term phase refers to the progress of a wave over time in relationship to a fixed point. Figure 3-2 on page 76 of the text illustrates waves with identical amplitudes and frequencies whose phases are 90 degrees apart.

One benefit to analog signals is that, because they are more variable than digital signals, they can convey greater subtleties with less energy.

However, because voltage is varied and imprecise in analog signals, analog transmission is more susceptible to transmission flaws such as noise, or any type of interference that may degrade a signal, than digital signals. Now contrast the analog signals pictured in Figure 3-1 through 3-3 to a digital signal, as shown in Figure 3-4 on page 78 of the text.

Digital signals are composed of pulses of precise, positive voltages and zero voltages. A pulse of positive voltage represents a 1. A pulse of zero voltage represents a 0. As in any binary system, these 1s and 0s combine to encode information. Every pulse in the digital signal is called a binary digit, or bit. A bit can have only one of two possible values: 1 or 0. Eight bits together form a byte.Data ModulationData modulation is a technology used to modify analog signals in order to make them suitable for carrying data over a communication path. In modulation, a simple wave, called a carrier wave, is combined with another analog signal to produce a unique signal that gets transmitted from one node to another.

Modulation can be used to make a signal conform to a specific pathway, as in the case of frequency modulation (FM) radio, in which the data must travel along a particular frequency. In frequency modulation, the frequency of the carrier signal is modified by the application of the data signal. In amplitude modulation (AM), the amplitude of the carrier signal is modified by the application of the data signal. Figure 3-5 on page 80 of the text depicts an unaltered carrier wave, a data wave, and the combined wave as modified through frequency modulation.

Transmission Direction Data transmission, whether analog or digital, may also be characterized by the direction in which the signals travel over the media.

Simplex, Half-Duplex, and Duplex

In cases where signals may travel in only one direction, the transmission is considered simplex. In half-duplex transmission signals may travel in both directions over a medium but in only one direction at a time. When signals are free to travel in both directions over a medium simultaneously, the transmission is considered full-duplex. Full-duplex may also be called bi-directional transmission or, sometimes, simply duplex. A channel is a distinct communication path between nodes, much as a lane is a distinct transportation path on a freeway. Figure 3-6 on page 81 of the text compares simplex, half-duplex, and full-duplex transmissions.

Multiplexing A form of transmission that allows multiple signals to travel simultaneously over on medium is known as multiplexing. In order to carry multiple signals, the mediums channel is logically separated into multiple smaller channels, or subchannel. For each type of multiplexing, a device that can combine many signals on a channel, a multiplexer (mux), is required at the sending end of the channel. At the receiving end, a demultiplexer (demux) separates the combined signals and regenerates them in their original form.

Multiplexing is commonly used on networks to increase the amount of data that can be transmitted in a given time span. For example, one type of multiplexing, time division multiplexing (TDM), divides a channel into multiple intervals of time, or time slots. Figure 3-7 on page 82 of the text shows a simple TDM model.

Statistical multiplexing is similar to time division multiplexing, but rather than assigning a separate slot to each node in succession, the transmitter assigns slots to nodes according to priority and need.

Wavelength division multiplexing (WDM) is a technology used with fiber-optic cable. In fiber-optic transmission, data is represented as pulses of light, rather than pulses of electric current. Figure 3-9 on page 83 of the text illustrates WDM transmission.

The form of WDM used on most modern fiber-optic networks is dense wave division multiplexing (DWDM). In DWDM, a single fiber in a fiber-optic cable can carry between 80 and 160 channels.

Relationships Between NodesWhen a data transmission involves only one transmitter and one receiver, it is considered a point-to-point transmission. An office building in Dallas exchanging data with another office in St. Louis over a WAN connection is an example of point-to-point transmission. In this case, the sender only transmits data that is intended to be used by a specific receiver. By contrast, broadcast transmission involves one transmitter and multiple receivers. For example, a TV station indiscriminately transmitting a signal from its tower to thousands of homes with TVs uses broadcast transmission. Another example of network broadcast transmission is sending video signals to multiple viewers on a network. When used over the Web, this type of broadcast transmission is called Webcasting. Figure 3-10 on page 85 of the text contrasts point-to-point and broadcast transmissions.

Throughput and BandwidthThroughput is the measure of how much data is transmitted during a given period of time. It may also be called capacity or bandwidth. Throughput is commonly expressed as a quantity of bits transmitted per second, with prefixes used to designate different throughput amounts. Table 3-1 on page 86 of the text summarizes the terminology and abbreviations used when discussing different throughput amounts.

Often, the term bandwidth is used interchangeably with throughput, and in fact, this may be the case on the Network+ certification exam. Bandwidth and throughput are similar concepts, but strictly speaking, bandwidth is a measure of the difference between the highest and lowest frequencies that a medium can transmit.

Baseband and Broadband

Baseband is a transmission form in which (typically) digital signals are sent through direct current (DC) pulses applied to the wire. This direct current requires exclusive use of the wires capacity. Ethernet is an example of a baseband system found on many LANs. In Ethernet, each device on a network can transmit over the wirebut only one device at a time.

Broadband is a form of transmission in which signals are modulated as radio frequency (RF) analog waves that use different frequency ranges. Unlike baseband, broadband technology does not encode information as digital pulses. Broadband transmission is used to bring cable TV to your home.

Transmission FlawsBoth analog and digital signals are susceptible to degradation between the time they are issued by a transmitter and the time they are received.

Noise A common source of noise is electromagnetic interference (EMI), or waves that emanate from electrical devices or cables carrying electricity. One type of EMI is radiofrequency interference (RFI), or electromagnetic interference caused by radio waves. Another form of noise that hinders data transmission is crosstalk. Crosstalk occurs when a signal traveling on one wire or cable infringes on the signal traveling over an adjacent wire or cable.

AttenuationAnother transmission flaw is attenuation, or the loss of a signals strength as it travels away from its source. To compensate for attenuation, both analog and digital signals are strengthened en route so they can travel farther. However, the technology used to strengthen an analog signal is different from that used to strengthen a digital signal. Analog signals pass through an amplifier.

When digital signals are repeated, they are actually retransmitted in their original form, without the noise they may have accumulated previously. This process is known as regeneration. A device that regenerates a digital signal is called a repeater. Figure 3-12 on page 89 of the text shows a digital signal distorted by noise and then regenerated by a repeater.

LatencyAlthough electrons travel rapidly, they still have to travel, and a brief delay takes place between the moment you press the key and the moment the server accepts the data. This delay is called latency. The most common way to measure latency on data networks is by calculating a packets round trip time (RTT), or the length of time it takes for a packet to go from sender to receiver, then back from receiver to sender. RTT is usually measured in milliseconds.

Media CharacteristicsGenerally speaking, you will consider five characteristics when choosing a data transfer media: throughput, cost, size and scalability, connectors, and noise immunity.

ThroughputPerhaps the most significant factor in choosing a transmission method is its throughput. All media are limited by the laws of physics that prevent signals from traveling faster than the speed of light. Beyond that, throughput is limited by the signaling and multiplexing techniques used in a given transmission method.

Cost The following variables can all influence the final cost of implementing a certain type of media:

Cost of installation Cost of new infrastructure versus reusing existing infrastructure Cost of maintenance and support Cost of a lower transmission rate affecting productivity Cost of obsolescenceSize and ScalabilityThree specifications determine the size and scalability of networking media: maximum nodes per segment, maximum segment length, and maximum network length. Each device added to a network segment causes a slight increase in the signals increase in the signals attenuation and latency.

The maximum segment length depends on attenuation and latency plus the segment type. A network can include two types of segments: populated and unpopulated. A populated segment is a part of a network that contains end nodes. An unpopulated segment, also known as a link segment, is a part of the network that does not contain end nodes, but simply connects two networking devices such as hubs.

ConnectorsConnectors are the pieces of hardware that connect the wire to the network device, be it a file server, workstation, switch, or printer. Every networking medium requires a specific kind of connector.

Noise ImmunityOn most networks, noise is an ever-present threat, so you should take measures to limit its impact on your network. For example, you should install cabling well away from powerful electromagnetic forces. It is also possible to use anti-noise algorithms to protect data from being corrupted by noise. If these measures dont ward off interference, you may need to use a metal conduit, or pipeline, to contain and further protect the cabling.

Coaxial CableCoaxial cable, called coax for short, was the foundation for Ethernet networks in the 1980s and remained a popular transmission medium for many years.Coaxial cable consists of a central copper core surrounded by an insulator, a braided metal shielding, called braiding, and an outer cover, called the sheath or jacket. Figure 3-13 on page 94 of the text depicts a typical coaxial cable.

Coaxial cabling comes in hundreds of specifications, although you are likely to see only two or three types of coax in use on data networks. The significant differences between the cable types lie in the materials used for their center cores, which in turn influence their impedance, throughput, and purpose.

Thicknet (10Base5) Ethernet

Thicknet cabling, also called thickwire Ethernet, is a rigid coaxial cable approximately 1-cm thick that contains a solid copper core. Thicknet was used for the original Ethernet networks. Because it is often covered with a yellow sheath, Thicknet is sometimes called yellow Ethernet or yellow garden hose. IEEE designates Thicknet as 10Base5 Ethernet.

Quick Reference

Discuss the summary of Thicknets characteristics as illustrated on pages 94 through 95 of the text.

In a Thicknet network, a nodes Ethernet interface, a port on the devices NIC, is connected with the drop cable via an AUI connector or an n-series connector. AUI (Attachment Unit Interface) is an Ethernet standard that establishes physical specifications for connecting coaxial cables with transceivers and networked nodes.

A Thicknet network also must abide by the 5-4-3- rule of networking. This rule says that, between two communicating nodes, the network cannot contain more than five network segments connected by four repeating devices, and no more than three of the segments may be populated (up to two may be unpopulated). Figure 3-15 on page 96 of the text illustrates the 5-4-3 rule, which also applies to other 10-Mbps versions of Ethernet running over copper cable.

Thinnet (10Base2) EthernetThinnet, also known as thin Ethernet, was the most popular medium for Ethernet LANs in the 1980s. Like Thicknet, Thinnet is rarely used on modern networks, although you may encounter it on networks installed in the 1980s.

Quick Reference

Discuss the characteristics listed on pages 97 and 98 of Thinnet.

Both Thicknet and Thinnet coaxial cable rely on the bus topology, in which nodes share one uninterrupted channel. Networks using the bus topology must be terminated at both ends. Without terminators, signals on a bus network would travel endlessly between the two ends of the network, a phenomenon known as signal bounce. Figure 3-17 on page 98 of the text depicts a 10Base2 network using a bus topology.

Twisted-Pair CableTwisted-pair cable consists of color-coded pairs of insulated copper wire, each with a diameter of 0.4 to 0.8 mm, or approximately the diameter of a straight pin. Figure 3-18 on page 99 of the text illustrates how the number of pairs in a cable varies, depending on the cable type.

The more twists per inch in a pair of wires, the more resistant the pair will be to all forms of noise. Higher-quality, more expensive twisted-pair cable contains more twists per foot. The number of twists per meter or foot is known as the twist ratio.

Shielded Twisted-Pair (STP)Shielded twisted-pair (STP) cable consists of twisted wire pairs that are not only individually insulated, but also surrounded by a shielding made of a metallic substance such as foil. Figure 3-19 on page 100 of the text depicts an STP cable.

Unshielded Twisted-Pair (UTP)Unshielded twisted-pair (UTP) cabling consists of one or more insulated wire pairs encased in a plastic sheath. As its name implies, UTP does not contain additional shielding for the twisted pairs. Figure 3-20 on page 101 of the text depicts a typical UTP cable.

Quick Reference

Discuss the different categories of cable as listed on pages 101 through 103 of the text.

10BaseT10baseT is a popular Ethernet networking standard that replaced the older 10Base2 and 10Base5 technologies. The 10 represents its maximum throughput of 10 Mbps, the Base indicates that it uses baseband transmission, and the T stands for twisted pair, the medium it uses.

Fault tolerance is the capacity for a component or system to continue functioning despite damage or partial malfunction. Use of the star topology also makes 10BaseT networks easier to troubleshoot, because you can isolate problems more readily when every device has a separate connection to the LAN. 10BaseT, like 10Base2 and 10Base5, also follows the 5-4-3 rule of networking and is subject to a distance limitation. The maximum distance that a 10BaseT segment can traverse is 100 meters. Figure 3-22 on page 104 of the text depicts a 10BaseT Ethernet network with maximum segment lengths.

100BaseT (Fast Ethernet)100BaseT, specified in the IEEE 802.3u standard, enables LANs to run at a 100-Mbps data transfer rate, a tenfold increase from that provided by 10BaseT, without requiring a significant investment in new infrastructure. 100BaseT uses baseband transmission and the same star topology as 100BaseT. It also uses the same RJ-45 modular connectors. Depending on the type of 100BaseT technology used, it may require CAT 3, CAT 5, or higher UTP.

As with 10BaseT, nodes on a 100BaseT network are configured in a star topology. 100BaseT networks do not follow the 5-4-3 rule. Two 100BaseT specifications100BaseT4 and 100BaseTXhave competed for popularity as organizations move to 100-Mbps technology. 100BaseTX is the version you are most likely to encounter. It achieves its speed by sending the signal 10 times faster and condensing the time between digital pulses as well as the time a station must wait and listen for a signal. 100BaseTC requires CAT 5 or higher unshielded twisted-pair cabling.

1000BaseT (Gigabit Ethernet over Copper)Because of increasing volumes of data and numbers of users who need to access this data quickly, even 100 Mbps has not met the throughput demands of some networks. 1000BaseT is a standard for achieving throughputs ten times faster than Fast Ethernet over copper cable. In 1000BaseT,1000 Megabits per second (Mbps), or 1 Gigabit per second (Gbps).

Comparing STP and UTPSTP and UTP share several characteristics. The following list highlights their similarities and differences.

Throughput

( Cost Connector

( Noise immunity Size and scalabilityQuick Quiz

1. A waves ____________ is a measure of its strength at any given point in time.

2. ____________ is a term used by networking professionals to describe the non-data information that must accompany data in order for a signal to properly routed and interpreted by the network.

3. ___________ is the measure of how much data is transmitted during a given period of time.

4. ___________ occurs when a signal traveling on one wire or cable infringes on the signal traveling over and adjacent wire or cable.

5. ___________ may be used for 16 Mbps Token Ring or 10 Mbps Ethernet networks.

Fiber-Optic Cable

Fiber-optic cable, or simply fiber, contains one or several glass or plastic fibers at its center, or core. Data is transmitted via pulsing light sent from a laser or light-emitting diode (LED) through the central fibers. Surrounding the fibers is a layer of glass or plastic called cladding. Figure 3-25 on page 107 of the text shows the different layers of a fiber-optic cable.

Like twisted-pair cable, fiber comes in a number of different types. Fiber cable variations fall into two categories: single-mode and multimode. Single-mode fiber uses a narrow core (less than 10 microns in diameter) through which light generated by a laser travels over one path, reflecting very little. Multimode fiber contains a core with a larger diameter than single-mode fiber (between 50 and 115 microns in diameter; the most common size is 62.5 microns) over which many pulses of light generated by a laser or LED travel at different angles. Figure 3-26 on page 108 of the text graphically depicts the differences between single-mode and multimode fiber.

The most significant drawback to the use of fiber is its relatively high cost. Another disadvantage is that most fiber-optic networks transmit data in uni-directionally over the fiber; therefore, each cable must contain at least two strands one to send data and one to receive it.

100BaseFXThe 100BaseFX standard specifies a network capable of 100-Mbps throughput that uses baseband transmission and fiber-optic cabling. 100BaseFX requires multimode fiber containing at least two strands of fiber. 100BaseFX, like 100BaseT, is also considered Fast Ethernet. Organizations switching, or migrating, from UTP to fiber media can combine 100BaseTX and 100Base FX within one network. In order to do this, transceivers in computers and connectivity devices must have both RJ-45 and SC or ST ports.

1000BaseLX Probably the most common 1-Gigabit Physical layer standard in use today is 1000BaseLX. The 1000 in 1000BaseLX stands for 1000 Mbpsor 1 Gbpsthroughput. Base stands for baseband transmission, and LX represents its reliance on long wavelengths of 1300 nanometers.

1000BaseSX1000BaseSX is similar to 1000BaseLX in that it has a maximum throughput of 1 Gbps. However, it relies on only multimode fiber-optic cable as its medium. Another difference is that 1000BaseSX uses short wavelengths of 850 nanometersthus, the SX, which stands for short.

10-Gigabit Fiber-Optic Standards Now there are standards for 10-Gbps networks that use single-mode fiber. One standard is 10GBaseLR, in which the 10G stands for 10 Gigabits per second, base stands for baseband transmission, and LR stands for long-reach. 10GBaseLR has a maximum segment length of 10,000 meters. A second 10-Gigabit option is 10GBaseER, In which ER stands for extended reach.

Summary of Physical Layer Standards Table 3-2 on page 112 of the text summarizes the characteristics and limitations for Physical layer networking standards including Ethernet networks that use coaxial cable, twisted-pair cable, and fiber-optic cable.

Cable Design and Management Organizations that pay attention to their cable plantthe hardware that makes up the enterprise-wide cabling systemare apt to experience fewer Physical layer network problems, smoother network expansions, and simpler network troubleshooting.

In 1991, TIA/EIA released its joint 568 Commercial Building Wiring Standard, also known as structured cabling, for uniform, enterprise-wide, multi-vendor cabling systems. Structured cabling is based on a hierarchical design that divides cabling into six subsystems, shown in the following list and illustrated in Figure 3-28 on page 113 of the text.

Entrance facilities

( Backbone wiring Equipment room

( Telecommunications closet Horizontal wiring

( Work areaInstalling Cable Many network problems can be traced to poor cable installation techniques. For example, if you dont crimp twisted-pair wires in the correct position in an RJ-45 connector, the cable will fail to transmit or receive data (or bothin which case, the cable will not function at all). Installing the wrong grade of cable can either cause your network to fail or render it more susceptible to damage.

If you terminate the RJ-45 plugs at both ends of a patch cable identically, following one of the TIA/EIA 568 standards, you will create a straight-through cable. A straight-through cable is so named because it allows signals to pass straight through between terminations. However, in some cases you may want to reverse the pin locations of some wiresfor example, when you want to connect two workstations without using a connectivity device or when you want to connect two hubs. This can be accomplished through the use of a crossover cable, a patch cable in which the termination locations of the transmit and receive wires on one end of the cable are reversed, as shown in Figure 3-36 on page 119 of the text.

Quick Reference

Discuss the cable installation tips that will help prevent Physical layer failures listed on page 120 of the text.

Wireless Transmission Networks that transmit signals through the atmosphere are known as wireless networks or wireless LANs (WLANs). Wireless LANs typically use infrared or radiofrequency (RF) signaling.

The Wireless SpectrumAll wireless signals are carried through the air along electromagnetic waves. The wireless spectrum is a continuum of electromagnetic waves used for data and voice communication. On the spectrum, waves are arranged according to their frequencies between 9 KHz and 300 GHz. Figure 3-37 on page 121 of the text shows the wireless spectrum and identifies the major wireless services associated with each range of frequencies.

Characteristics of Wireless TransmissionJust as with wire-bound signals, wireless signals originate from electrical current traveling along a conductor. The electrical signal travels from the transmitter to an antenna, which then emits the signal, as a series of electromagnetic waves, to the atmosphere. The signal propagates through the air until it reaches its destination. At the destination, another antenna accepts the signal, and a receiver converts it back to current. Figure 3-38 on page 122 of the text illustrates this process.

Antennas A services specifications determine the antennas power output, frequency, and radiation pattern. An antennas radiation pattern describes the relative strength over a three-dimensional area of all the electromagnetic energy the antenna sends or receives.

A directional antenna issues wireless signals along a single direction. This type of antenna is used when the source needs to communicate with one destination, as in a point-to-point to link. In contrast, an omni-directional antenna issues and receives wireless signals with equal strength and clarity in all directions. This type of antenna is used when many different receivers must be able to pick up the signal, or when the receivers location is highly mobile.

Signal PropagationIdeally, a wireless signal would travel directly in a straight line from its transmitter to its intended receiver. This type of propagation, known as line-of-sight (LOS), uses the least amount of energy and results in the reception of the clearest possible signal. Reflection in wireless signaling is no different from reflection of other electromagnetic waves, such as light. The wave encounters an obstacle and reflectsor bounces backtoward its source.

In diffraction, a wireless signal splits into secondary waves when it encounters an obstruction. The secondary waves continue to propagate in the direction in which they were split. Scattering is the diffusion, or the reflection in multiple different directions, of a signal. Scattering occurs when a wireless signal encounters an object that has small dimensions compared to the signals wavelength.

Because of reflection, diffraction, and scattering, wireless signals follow a number of different paths to their destination; such signals are known as multi-path signals. Figure 3-39 on page 124 of the text illustrates multi-path signals caused by these three phenomena.

Signal DegradationNo matter what paths wireless signals take, they are bound to run into obstacles. When they do, the original signal issued by the transmitter will experience fading, or a change in signal strength as a result of some of the electromagnetic energy being scattered, reflected, or diffracted after being issued by the transmitter.

Interference can distort and weaken a wireless signal in the same way that noise distorts and weakens a wire-bound signal. However, because wireless signals cannot depend on a conduit or shielding to protect them from extraneous EMI, they are more vulnerable to noise.

Narrowband, Broadband, and Spread Spectrum SignalsIn narrowband, a transmitter concentrates the signal energy at a single frequency or in a very small range of frequencies. In contrast to narrowband, broadband uses a relatively wide band of the wireless spectrum. Broadband technologies, as a result of their wider frequency bands, offer higher throughputs than narrowband technologies. The use of multiple frequencies to transmit a signal is known as spread spectrum technology.

One specific implementation of spread spectrum is frequency hopping spread spectrum (FHSS). In FHSS transmission, a signal jumps between several different frequencies within a band in a synchronization pattern known only to the channels receiver and transmitter. Another type of spread spectrum signaling is called direct sequence spread spectrum (DSSS). In DSSS, a signals bits are distributed over an entire frequency band at once.

Fixed versus MobileEach type of wireless communication falls into one of two categories: fixed or mobile. In fixed wireless systems, the locations of the transmitter and receiver do not move. In mobile wireless, the receiver can be located anywhere within the transmitters range. This allows the receiver to roam from one place to another while continuing to pick up its signal.

Infrared TransmissionInfrared signals are transmitted by frequencies in the 300 GHz to 300,000 GHz range, which is just above the top of the wireless spectrum as it is defined by the FCC. Infrared frequencies approach the range of visible light in the electromagnetic spectrum, and in fact, some can be seen. On computer networks, infrared transmission is most often used for communications between devices in the same room.

Wireless LAN (WLAN) ArchitectureThe most common form of WLAN relies on lower frequencies in the 2.4-2.4835 GHz band (more commonly known as the 2.4 GHz band) to send and receive signals. Because they are not bound by cabling paths between nodes and connectivity devices, wireless networks do not follow the same kind of topologies as wire-bound networks. They have their own, different layouts. Smaller wireless networks, in which a small number of nodes closely positioned need to exchange data, can be arranged in an ad hoc fashion. In an ad hoc WLAN, wireless nodes, or stations, transmit directly to each other via wireless NICs without any intervening connectivity device.

An access point (AP) is a device that accepts wireless signals from multiple nodes and retransmits them to the rest of the network. To cover its intended range, an access point must have sufficient power and be strategically placed so that stations can communicate with it. It is common for a WLAN to include several access points. The number of access points depends on the number of stations a WLAN connects. The maximum number of stations each access point can serve varies from 10 to 100, depending on the wireless technology used.

Choosing the Right Transmission Medium

The following list summarizes the majority of environmental factors you must take into account and suggests appropriate transmission media for the various conditions. Most environments will contain a combination of these factors; you must therefore weigh the significance of each.

Areas of high EMI

( Distance Security

( Existing infrastructure GrowthQuick Quiz

1. Surrounding the fibers is a layer of glass or plastic called ___________.

2. ___________ is the degradation of the light signal after it travels a certain distance away from its source.

3. The ___________ standard does not use fiber-optic cable, but instead uses twinaxial copper wiring.

4. A(n) ___________ is a panel of data receptors into which horizontal cabling from the workstations is inserted.

5. A(n) ___________ is a device that accepts wireless signals from multiple nodes and retransmits them to the rest of the network.

Discussion Questions1. Discuss how transmission flaws can be avoided.

2. How do you choose the right transmission mediums?

Solutions to Exercises can be found at the following link:

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