Understanding Computer-Network Media Interface: Analog-Digital Signals & Wireless - Prof. , Study notes of Introduction to Business Management

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Chapter 3 Networking Media CIS 3260: Dr. Mike Tarn 2 Network Cabling: Tangible Physical Media  The interface between a computer and the medium to which it attaches defines the translation from a computer’s native digital information into the form needed to send outgoing messages  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  You need to know the physical characteristics and limitations of each kind of network media so that you can make the best use of each type • Each has a unique design and usage, with associated cost, performance, and installation criteria 5 The Importance of Bandwidth  The trend in networking is to offer more complex, comprehensive, and powerful services  These require much higher bandwidth  Users demand access to these applications and have increased their use of existing networked applications, consuming still more bandwidth  Technologists find ways to stretch bandwidth limits of existing technologies so that older, difficult-to- replace networking components can remain, yet support higher bandwidth than originally rated 6 Data and Signals  Data are entities that convey meaning within a computer or computer system  Signals are the electric or electromagnetic impulses used to encode and transmit data 7 Type of Signal  Continuous signal: analog signal, signal intensity carries in a smooth fashion over time.  Discrete signal: digital signal, signal intensity maintains a constant level for some period of time and then change to another constant level. Analog vs. Digital (continued) Figure 2-2 The waveform of a symphonic overture with noise wv oo 6 = ° > Time —> 10 11 Analog vs. Digital (continued)  Digital is a discrete or noncontinuous waveform with examples such as computer 1s and 0s  Noise in digital signal  You can still discern a high voltage from a low voltage  Too much noise – you cannot discern a high voltage from a low voltage w Figure 2-3 A simple example of a digital waveform Analog vs. Digital (continued) 12 15 Fundamentals of Signals  All signals have three components:  Amplitude  Frequency  Phase  Amplitude  The height of the wave above or below a given reference point w Fundamentals of Signals (continued) High Amplitude Low Amplitude i v & > Time —> 16 17 Fundamentals of Signals (continued)  Frequency  The number of times a signal makes a complete cycle within a given time frame; frequency is measured in Hertz (Hz), or cycles per second  Spectrum – range of frequencies that a signal spans from minimum to maximum  Bandwidth – absolute value of the difference between the lowest and highest frequencies of a signal  For example, consider an average voice • The average voice has a frequency range of roughly 300 Hz to 3100 Hz • The spectrum would be 300 – 3100 Hz • The bandwidth would be 2800 Hz w Fundamentals of Signals (continued) Figure 2-8 A sine wave showing (a) no phase change, (b) a 180-degree phase hange, and (c) a 90-degree phase hange [\_/\ \J XSF NS (a) No Phase Change Time — y\ 7 Fis NS b) 180° Phase Change : Time —> Voltage —» Voltage —> f" LN TW WT (c) 90° Phase Change ' Time —» @)) y > 2 Voltage —» 21 Loss of Signal Strength  All signals experience loss (attenuation)  Attenuation is denoted as a decibel (dB) loss  Decibel losses (and gains) are additive w 22 Loss of Signal Strength (continued) w 25 Transmitting Digital Data with Analog Signals  Basic types of modulation of analog signals for digital data (Analog encoding of digital data)  Amplitude modulation (Amplitude-shift keying)  Frequency modulation (Frequency-shift keying)  Phase modulation (Phase-shift keying) 26 Amplitude Shift Keying  One amplitude encodes a 0 while another amplitude encodes a 1 (a form of amplitude modulation) w Amplitude Shift Keying (continued) Example of amplitude 1 ' 0 ' 1 ' 0 shift keying ' . | \ ' \ | ' Time — Al Frequency Shift Keying (continued) igure 17 Simple example of frequency shift keying <0) 31 Phase Shift Keying  One phase change encodes a 0 while another phase change encodes a 1 (a form of phase modulation) w Phase Shift Keying) (Continued) An example of simple phase shift keying of a sine wave cy Phase Shift Keying (continued) 2 different phases, hile Figure (b) shows a phase change with Phase Angle 0° (a) Twelve Phase Angles 45° Phase Change 45° Phase Change ' High Amplitude 1 Low Amplitude DAM Away UU Ue ‘ Time —> ' (b) A Phase Change with Two Amplitudes VS (29) OL 36 Summary of the Key Terms  Amplitude: The instantaneous value or strength of the signal at any time  Period: The amount of time the signal takes to repeat  Frequency: The number of periods in a given time (usually one second)  Hz: Hertz, one cycle per second  Phase: A measure of the relative position in time within a single period of a signal  Spectrum: The range of frequencies that the signal contains  Bandwidth: The width of the spectrum 37 Frequency LF 30 - 300 KHz 0.1 -100 bps MF 300 - 3000 KHz 10 - 1000 bps HF 3 - 30 MHz 10 - 3000 bps VHF 30 - 300 MHz T0 100 Kbps UHF 300 - 3000 MHz To 10 Mbps SHF 3 - 30 GHz To 100 Mbps EHF 30 - 300 GHz To 750 Mbps Coaxial Cable (Continued) Insulation Conducting core Braided shielding Figure 3-1 Coaxial cable 40 41 The Use of Coaxial Cable for Ethernet  Ethernet’s beginnings are in coaxial cable  First, it was run on a very thick, rigid cable, usually yellow, referred to as thicknet (10Base5)  Later, a more manageable coaxial cable called thinnet (10Base2) was used  10Base5 is an IEEE designation  10 Mbps  Baseband  Maximum segment length is 500 meters 42 Coaxial Cable in Cable Modem Applications  Coaxial cable in LANs has become obsolete  The standard cable (75 ohm, RG-6; RG stands for “radio grade”) that delivers cable television (CATV) to millions of homes nationwide is also being used for Internet access Twisted-Pair Cable Shielded twisted-pair (STP) — Two twisted pairs 1 Sheath Foil shielding Unshielded twisted-pair (UTP) Sheath Figure 3-3 STP and UTP cable CI — as Oi 46 Unshielded Twisted Pair (UTP)  10BaseT  Maximum length is 100 meters  UTP is now the most popular form of LAN cabling  The UTP cable used for networking usually includes one or more pairs of insulated wires  UTP specifications govern the number of twists per foot (or per meter), depending on the cable’s intended use  UTP is used for telephony, but requirements for networking uses differ from the telephony ones 47 UTP Cabling Categories  UTP cabling is rated according to a number of categories devised by the TIA and EIA; since 1991, ANSI has also endorsed these standards  ANSI/TIA/EIA 568 Commercial Building Wiring Standard for commercial environments includes: • Category 1 (voicegrade) • Category 2: up to 4 Mbps • Category 3: up to 10 Mbps (16 MHz) • Category 4 (datagrade): up to 16 Mbps (20 MHz) • Category 5: up to 100 Mbps (100 MHz) • Category 5e: up to 1000 Mbps (100 MHz) • Category 6: up to 1000 Mbps (200 MHz) 50 Twisted-Pair Cable (continued)  Typically, twisted-pair systems include the following elements, often in a wiring center:  Distribution racks and modular shelving  Modular patch panels  Wall plates  Jack couplers m— Voice a Data Figure 3-6 Patch panel Figure 3-5 A wall plate providing both voice and data connections ‘Ol 52 Twisted-Pair Cable (continued) Making I\wisted-Pair Cable Connections (Continued) Pin#: 12345678 J )} p View of RJ-45 plug from above: | | | UOTE VIVIV 2 1 Pin # Color Pair # White with orange stripe 2 Orange 2 White with green stripe 3 Blue 1 White with blue stripe 1 Green 3 White with brown stripe 4 Brown 4 AN nob WhH a Figure 3-8 TIA/EIA 568B cable pinouts Function Transmit + Transmit - Receive + Unused Unused Receive - Unused Unused 55 Fiber-Optic Cable Figure 3-9 Fiber-optic cable Sheath Kevlar for strength Optical fiber 56 57 Fiber-Optic Cable (continued) 60 Cable Selection Criteria  Criteria to be considered for a network installation  Bandwidth  Budget  Capacity  Environmental considerations  Placement  Span  Local requirement  Existing cable plant 61 Cable Selection Criteria (continued) 62 Managing and Installing the Cable Plant  Important to understand basic methods and terminology of cable management  The TIA/EIA developed the document “568 Commercial Building Wiring Standard,” which specifies how network media should be installed to maximize performance and efficiency  Standard defines “structured cabling” 65 Horizontal Wiring  Horizontal wiring runs from the work area’s wall jack to the telecommunications closet and is usually terminated at a patch panel  Acceptable horizontal wiring types include four-pair UTP (Category 5e or 6) or two fiber-optic cables  Horizontal wiring from the wall jack to the patch panel should be no longer than 90 meters • Patch cables in the work area and in the telecommunications closet can total up to 10 meters Telecommunications Closet To equipment room Switch ( ~F Patch panel Distribution Telecommunications rack closet ¥ Equipment rack Patch cable Horizontal wiring Wall ae Computer jack Figure 3-11 Work area, horizontal wiring, and telecommunications closet 66 67 Equipment Rooms  The equipment room houses servers, routers, switches, and other major network equipment, and serves as a connection point for backbone cabling running between TCs  Can be the main cross-connect of backbone cabling for the network, or it might serve as the connecting point for backbone cabling between buildings  In multibuilding installations, each building often has its own equipment room 70 Wireless Networking: Intangible Media  Wireless technologies continue to play an increasing role in all kinds of networks  Since 1990, the number of wireless options has increased, and the cost continues to decrease  Wireless networks can now be found in most towns and cities in the form of hot spots, and more home users have turned to wireless networks  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  Microsoft calls networks that include both wired and wireless components hybrid networks 71 The Wireless World  Wireless networking can offer the following:  Create temporary connections to existing wired networks  Establish backup or contingency connectivity for existing wired networks  Extend a network’s span beyond the reach of wire- based or fiber-optic cabling, especially in older buildings where rewiring might be too expensive  Enable users to roam with their machines within certain limits (called “mobile networking”) 72 The Wireless World (continued)  Common wireless applications include:  Ready access to data for mobile professionals  Delivery of network access into isolated facilities or disaster-stricken areas  Access in environments where layout and settings change constantly  Improved customer services in busy areas, such as check-in or reception centers  Network connectivity in structures where in-wall wiring would be impossible to install or too expensive  Home networks where the installation of cables is inconvenient 75 Wireless LAN Components  NIC attaches to an antenna and an emitter  At some point on a cabled network, a transmitter/receiver device, called a transceiver or an access point, must be installed to translate between the wired and wireless networks  An access point device includes an antenna and a transmitter to send and receive wireless traffic, but also connects to the wired side of the network  Some wireless LANs use small transceivers, which can be wall mounted or freestanding, to attach computers or devices to a wired network 76 Wireless LAN Transmission  Wireless LANs send/receive signals broadcast through the atmosphere  Waves in the electromagnetic spectrum  Frequency of the wave forms is measured in Hz • Affects the amount and speed of data transmission  Lower-frequency transmissions can carry less data more slowly over longer distances • Commonly used frequencies for wireless data communications  Radio—10 KHz (kilohertz) to 1 GHz (gigahertz)  Microwave—1 GHz to 500 GHz  Infrared—500 GHz to 1 THz (terahertz) 77 Wireless LAN Transmission (continued)  Higher-frequency technologies often use tight-beam broadcasts and require a clear line of sight between sender and receiver  Wireless LANs make use of four primary technologies for transmitting and receiving data  Infrared  Laser  Narrowband (single-frequency) radio  Spread-spectrum radio 80 Narrowband Radio LAN Technologies 81 Narrowband Radio LAN Technologies (continued) 82 Spread-Spectrum LAN Technologies 85 Wireless MAN: The 802.16 Standard  One of the latest wireless standards, 802.16 Worldwide Interoperability for Microwave Access (WiMax), comes in two flavors: 802.16- 2004 (previously named 802.16a), or fixed WiMax, and 802.16e, or mobile WiMax  Promise wireless broadband to outlying and rural areas, where last-mile wired connections are too expensive or impractical because of rough terrain  Delivers up to 70 Mbps of bandwidth at distances up to 30 miles  Operates in a wide frequency range (2 to 66 GHz) 86 Fixed WiMax: 802.16-2004  Besides providing wireless network service to outlying areas, fixed WiMax is being used to deliver wireless Internet access to entire metropolitan areas rather than the limited-area hot spots available with 802.11  Fixed WiMax can blanket an area up to a mile in radius, compared to just a few hundred feet for 802.11  Los Angeles has begun implementing fixed WiMax in an area of downtown that encompasses a 10-mile radius 87 Mobile WiMax: 802.16e  Promises to bring broadband Internet roaming to the public  Promises to allow users to roam from area to area without losing the connection, which offers mobility much like cell phone users enjoy  The mobile WiMax standard was approved on 12/7/2005 http://standards.ieee.org/announcements/pr_p80216.html  Fixed WiMax is expected to be the dominant technology for the next several years, but mobile WiMax will win out in the end