EC301 COMPUTER NETWORKING FUNDAMENTALSCHAPTER 3
DATA TRANSMISSION AND NETWORKING MEDIA
PREPARED BY : AMRUL AKIL BIN AHMAD @ HASHIM1
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Define the Basics of Data TransmissionIdentify the common transmission flaws affecting data signals
Appreciate the Basics of Data Transmission
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Data Transmission Basic Concept
In data networking, transmit means to issue signals to the network medium (copper cable, wireless, fibre etc)
Transmission refers to process of transmitting the signal or the progress of signals after they have been
transmitted
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Analog and digital signaling
2 Signaling method available Analog Digital
Signal strength proportional to voltage
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Analog Signal
In analog signals, voltage varies continuously and appears as a wavy line when graphed over time Wave’s amplitude is a measure of its strength Frequency: number of times wave’s amplitude cycles from
starting point, through highest amplitude and lowest amplitude, back to starting point over a fixed period of time
• Measured in Hz Wavelength: distance between corresponding points on a
wave’s cycle Phase: progress of a wave over time in relationship to a
fixed point
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Analog Signal (continued)
Analog signal can convey subtle detail Analog transmission susceptible to
transmission flaws such as noise Their voltage is varied and imprecise
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Digital signals
Digital signals composed of pulses of precise, positive voltages and zero voltages Positive voltage represents 1 Zero voltage represents 0
Binary system: uses 1s and 0s to represent information Easy to convert between binary and decimal
Bit: a single binary signal Byte: 8 bits
Typically represents one piece of information Overhead: describes non-data information that must
accompany data for a signal to be properly routed and interpreted
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Digital signals
Digital signals send and receive only pattern of 1s & 0s Precise pulse not like the voltage variation
of analog Noise affect digital less severe
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Data Modulation
Technology to modify analog signal for carrying data over a communication path
A wave called carrier is combine with another analog signal (the data signal)
The carrier wave is modified by the added signal FM AM
The new signal is transmitted – the receiver will separate the data from the carrier wave.
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Data Modulation
A carrier wave modified through frequency modulation
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Transmission Direction: Simplex, Half-Duplex, and Duplex
Simplex transmission: signals may travel in only one direction
Half-duplex transmission: signals may travel in both directions over a medium Only one direction at a time
Full-duplex or duplex: signals free to travel in both directions over a medium simultaneously Used on data networks Channel: distinct communication path between
nodes May be separated logically or physically
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Point to Point & Broadcast Transmission
Point-to-point versus broadcast transmission
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Throughout and Bandwidth
Throughput: measure of amount of data transmitted during given time period
Bandwidth: difference between highest and lowest frequencies that a medium can transmit
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NoiseAttenuationLatency
Identify the common transmission flaws affecting data signals:
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Transmission Flaws: Noise
electromagnetic interference (EMI): waves emanating from electrical devices or cables
radiofrequency interference (RFI): electromagnetic interference caused by radiowaves
Crosstalk: signal traveling on a wire or cable infringes on signal traveling over adjacent wire or cable
Certain amount of signal noise is unavoidable All forms of noise measured in decibels (dB)
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Attenuation
An analog signal distorted by noise and then amplified
A digital signal distorted by noise and then repeated
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Latency
Delay between transmission and receipt of a signal Many possible causes:
Cable length Intervening connectivity device (e.g., modems and
routers) Round trip time (RTT): Time for packets to go
from sender to receiver and back Cabling rated for maximum number of connected
network segments Transmission methods assigned maximum
segment lengths
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Size and Scalability
Three specifications determine size and scalability of networking media: Maximum nodes per segment
Depends on attenuation and latency Maximum segment length
Depends on attenuation, latency, and segment type
Populated segment contains end nodes Maximum network length
Sum of network’s segment lengths
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physical characteristicsbenefits and limitationsbest practices for cabling buildings and workareas.characteristics of wireless transmission
Understand the Transmission Media in Networks
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Physical Characteristic
Transmission media Coaxial cable STP (Shielded Twisted-Pair) UTP (Unshielded Twisted-Pair) Fiber-Optic Cable
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Coaxial Cable
a central metal core (often copper) surrounded by an insulator(usually Teflon or PVC), a braided metal shielding, called braiding or shield, and an outer cover, called the sheath or jacket.
The sheath PVC Fire resistant plastic
Coaxial cable
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Coaxial Cable
High resistance to noise; expensive – more material
Impedance: resistance that contributes to controlling signal (expressed in ohms)
Ethernet (Thicknet): original Ethernet media 10BASE-5 Ethernet
Thin Ethernet (Thinnet): more flexible and easier to handle and install than Thicknet 10BASE-2 Ethernet
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Coaxial Cable
10Base5
10 MbpsMaximum
length500m
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STP (Shielded Twisted Pair)
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.
Some STP use a braided copper shielding.
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UTP (Unshielded Twisted Pair)
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.
UTP is both less expensive and less resistant to noise than STP.
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Fiber-Optic
contains one or several glass or plastic fibers at its center, or core.
Data is transmitted via pulsing light sent from a laser or LED.
Surrounding the fibers is a layer of glass or plastic called cladding. different density from the glass or plastic in
the strands reflects light back to the core in patterns that
vary depending on the transmission mode.
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Fiber-Optic
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Fiber-Optic
2 type of Fiber-optic SMF (single mode fiber)
Narrow core through which laser-generated light travels over one path, reflecting very little
Accommodates high bandwidths and long distances
Expensive
MMF (Multi mode fiber) a core with a larger diameter Accommodate large number of different light
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Fiber-Optic
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Fiber-Optic
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
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Benefit and limitation
Discussed in terms of Throughput Noise immunity Size and scalability Cost
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Benefit and limitation
Throughput Probably most significant factor in choosing
transmission method Limited by signalling and multiplexing
techniques used in given transmission method Transmission methods using fiber-optic cables
achieve faster throughput than those using copper or wireless connections
Noise and devices connected to transmission medium can limit throughput
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Benefit and limitation
Noise Immunity Some types of media are more
susceptible to noise than others Fiber-optic cable least susceptible
Install cabling away from powerful electromagnetic forces May need to use metal conduit to contain
and protect cabling Possible to use anti-noise algorithms
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Benefit and limitation
Size and Scalability Three specifications determine size and
scalability of networking media: Maximum nodes per segment
Depends on attenuation and latency Maximum segment length
Depends on attenuation, latency, and segment type
Populated segment contains end nodes Maximum network length
Sum of network’s segment lengths
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Benefit and limitation
Cost Many variables can influence final cost of
implementing specific 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 obsolescence
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Structured Cabling
To avoid Physical Layer network problem as much as possible
Cabling must follows standards and best practices
Maximize performance Minimize upkeep Structure Cabling applies to all type of
media or network technology.
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Structured Cabling
TIA/EIA’s 568 - Commercial Building Wiring Standard
Entrance facilities point where building’s internal cabling plant begins Demarcation point: division between
service carrier’s network and internal network
Backbone wiring: interconnection between telecommunications closets, equipment rooms, and entrance facilities
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Structured Cabling
Equipment room: location of significant networking hardware, such as servers and mainframe hosts
Telecommunications closet: contains connectivity for groups of workstations in area, plus cross connections to equipment rooms
Horizontal wiring: wiring connecting workstations to closest telecommunications closet
Work area: encompasses all patch cables and horizontal wiring necessary to connect workstations, printers, and other network devices from NICs to telecommunications closet
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Structured Cabling
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Structured Cabling
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Structured Cabling
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Wireless Transmission
Earth atmosphere – allow intangible means to transport data over network – wireless.
Network that transmit signal via radio frequency (RF) - WLANs (Wireless Local Area Networks).
Wireless transmission can also be achieve by Microwave Satellite links
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The Wireless Spectrum
Signal are carried by electromagnetic waves (EW)
The Wireless Spectrum – the continuum of the EW used for data and voice communication.
Parts of the spectrum is associate with certain with certain type of wireless service.
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The Wireless Spectrum
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Signal Propagation
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Signal Degradation
Fading: change in signal strength resulting from electromagnetic energy being scattered, reflected, or diffracted after being issued by transmitter
Wireless signals experience attenuation May be amplified and repeated
Interference is significant problem for wireless communications Atmosphere saturated with electromagnetic
waves
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Narrowband, Broadband, and Spread Spectrum Signals
Narrowband: transmitter concentrates signal energy at single frequency or in very small range of frequencies
Broadband: uses relatively wide band of wireless spectrum Offers higher throughputs
Spread spectrum: use of multiple frequencies to transmit a signal Frequency hopping spread spectrum (FHSS) Direct sequence spread spectrum (DSSS)
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Fixed versus Mobile
Fixed wireless system: locations of transmitter and receiver do not move Point-to-point link Efficient use of signal energy
Mobile wireless system: receiver can be located anywhere within transmitter’s range More flexible
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Straight UTP CableCross UTP CableNetwork Patch Panel and Wall JackTesting UTP cableFiber optic termination
Understand Network Cabling Preparation
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Straight UTP Cable
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UTP Cable Construction
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Straight UTP Cable
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Network Patch & Wall Jack
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Network Patch & Wall Jack
Front side
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Network Patch & Wall Jack
Back side
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Network Patch & Wall Jack
Network Wall jack
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Network Patch & Wall Jack
Advantage of using network patch and wall jack. Allow cleaner work place Easy to identify cable Efficient & maintainable
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Testing UTP Cable
Test connectivity – pin to pin Many types of tools – basic to advance.
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Fiber Optic Termination
Coming soon…..
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