Network Guide to Networks 5th Edition

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Network Guide to Networks5th Edition

• Chapter 3
• Transmission Basics and
• Networking Media

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Objectives

• Explain basic data transmission concepts,
  including full duplexing, attenuation, latency,
  and noise
• Describe the physical characteristics of coaxial
  cable, STP, UTP, and fiber-optic media
• Compare the benefits and limitations of different
  networking media

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Analog Signaling

• In analog data signals, voltage varies
  continuously

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Digital Signaling

• In digital signaling, there are only 2 values
• Yes/On (1)
• Off/No (0)

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Analog vs. Digital Signaling

• Analog signals can convey greater subtleties
  with less energy than digital signals.
• Digital signals are less susceptible to
  interference.
• Computer data (always digital) must sometimes be
  transmitted over an analog connection, such as
  telephone lines. This requires a
  Modulator-Demodulator, or modem.

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Simplex, Half-Duplex, and Duplex
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Multiplexing

• Sending multiple signals simultaneously over one
  medium
• Methods
• Time division
• Statistical
• Frequency division (used by cell phones, DSL)
• Wavelength division
• Dense wavelength division

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Transmission Types

• Point-to-point
• Point-to-multipoint
• Broadcast
• One transmitter and multiple, undefined receivers
• Used on wired and wireless networks
• Nonbroadcast
• One transmitter and multiple, defined receivers

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Throughput and Bandwidth

• Throughput
• Measures amount of data transmitted
• During given time period
• Capacity or bandwidth
• Quantity of bits transmitted per second
• Bandwidth (strict definition)
• Measures difference between highest and lowest
  frequencies medium can transmit
• Range of frequencies
• Measured in hertz (Hz)

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Baseband vs. Broadband

• Baseband transmission
• Digital signals sent through DC voltage pulses
• Requires exclusive use of wires capacity
• Transmit one signal (channel) at a time
• Example Ethernet
• Broadband transmission
• Signals modulated
• Radiofrequency (RF) analog waves
• Uses different frequency ranges
• Does not encode information as digital pulses

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Transmission Flaws

• Noise any undesirable influence degrading or
  distorting signal
• Types of noise
• EMI (electromagnetic interference)
• RFI (radiofrequency interference)
• Cross talk (within a cable)

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Transmission Flaws (contd.)

• Attenuation loss of signals strength as it
  travels away from source
• Latency delay between signal transmission and
  receipt

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Physical Media Characteristics

• Things to consider when selecting your network
  medium
• Throughput
• Cost
• Size and Scalability
• Connectors
• Noise immunity/vulnerability

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Throughput

• Most significant when selecting media
• Can be limited by
• Laws of physics
• Signaling and multiplexing techniques
• Noise
• Devices connected to transmission medium
• Fiber-optic cables allows fastest throughput
  (compared to copper or wireless connections)

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Cost

• Precise cost difficult to pinpoint(Total Cost of
  Ownership)
• Depends on existing hardware, network size,
  labor costs, etc.
• Variables influencing final cost
• Installation cost
• New infrastructure vs. reusing existing cabling
• Maintenance and support costs
• Cost of lower transmission rate affecting
  productivity
• Cost of obsolescence

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Noise Immunity/Vulnerability

• Noise distorts data signals
• Distortion rate dependent upon transmission
  media
• Fiber-optic cabling is least susceptible to
  noise, but most expensive
• To limit impact of noise on your network
• Install Cables far away from powerful
  electromagnetic forces (fans, motors, etc.)
• Select media that protects signals from noise

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Size and Scalability

• Size limitations
• Maximum nodes per segment, impacted by
• Attenuation
• Latency
• Maximum segment length, impacted by
• Attenuation
• Latency
• Type of segment
• Populated (connects end-user devices)
• Unpopulated (aka link segment)
• Maximum network length (5-4-3-2-1 rule)

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Types of Cables

• Coaxial
• Twisted-Pair
• Shielded (STP)
• Unshielded (UTP)
• Fiber-Optic
• Single-Mode
• Multi-Mode

Network Guide to Networks, 5th Edition
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Coaxial Cable

• Central metal core (often copper)
• Surrounded by insulator
• Braided metal shielding (braiding or shield)
• Outer cover (sheath or jacket)

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Coaxial Cable (contd.)

• High noise resistance
• Can carry signals farther unrepeated signals
  further than twisted-pair, but is more expensive
• Hundreds of specifications (RG specs) for
  different shielding and conducting cores

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Twisted Pair Cable

• Color-coded insulated copper wire pairs
• 0.4 to 0.8 mm diameter
• Encased in a plastic sheath

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Twisted Pair Cable (contd.)

• Twist ratio twists per meter or per foot
• High twist ratio
• More resistance to cross talk
• Higher-quality
• More expensive
• Greater attenuation

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STP (Shielded Twisted Pair)

• Individually insulated
• Surrounded by metallic substance shielding (foil)
• Barrier to external electromagnetic forces
• Contains electrical energy of signals inside
• May be grounded

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UTP (Unshielded Twisted Pair)

• One or more insulated wire pairs
• Encased in plastic sheath
• No additional shielding
• Less expensive, less noise resistance

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UTP (Unshielded Twisted Pair)

• EIA/TIA standards
• Cat 3 (Category 3)
• Cat 4 (Category 4)
• Cat 5 (Category 5)
• Cat 5e (Enhanced Category 5)
• Cat 6 (Category 6)
• Cat 6e (Enhanced Category 6)
• Cat 7 (Category 7)

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• Straight-through cable
• Terminate RJ-45 plugs at both ends identically
• Crossover cable
• Transmit and receive wires on one end reversed

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SMF (Single-Mode Fiber)

• Uses narrow core (lt 10 microns in diameter)
• Laser generated light travels over one path
• Little reflection
• Light does not disperse
• Accommodates
• Highest bandwidths, longest distances
• Connects carriers two facilities
• Costs prohibit use in LANs

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SMF (Single-Mode Fiber) (contd.)
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MMF (Multimode Fiber)

• Uses core with larger diameter than single-mode
  fiber (common size 62.5 microns)
• LED generated light pulses travel at different
  angles
• Common uses
• Cables connecting router to a switch
• Cables connecting server on network backbone

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MMF (Multimode Fiber) (contd.)
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MMF (Multimode Fiber) (contd.)

• Benefits
• Extremely high throughput
• Very high resistance to noise
• Excellent security
• Ability to carry signals for much longer
  distances before requiring repeaters than copper
  cable
• Industry standard for high-speed networking
• Drawbacks
• More expensive than twisted pair cable
• Requires special equipment to splice

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MMF (Multimode Fiber) (contd.)

• Can reach 100 gigabits (or 100,000 megabits) per
  second per channel
• Most expensive transmission medium
• Unaffected by EMI
• Segment lengths vary from 150 to 40,000 meters

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Structured Cabling

• Cable plant
• Hardware making up enterprise-wide cabling
  system
• Standard
• TIA/EIA joint 568 Commercial Building Wiring
  Standard

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Structured Cabling
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