Chapter 3

EC301 COMPUTER NETWORKING FUNDAMENTALSCHAPTER 3

DATA TRANSMISSION AND NETWORKING MEDIA

PREPARED BY : AMRUL AKIL BIN AHMAD @ HASHIM1

© POLISAS/JKE/AMR/2011/EC301


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


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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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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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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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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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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Front side


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Back side


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Network Wall jack


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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…..