Transcript CPMT 1449 Computer Networking Technology – Lesson 1 Week 1

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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
Explain the principles behind and uses for
serial connector cables
Identify wiring standards and best practices for
cabling buildings and work areas
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Transmit – means to issue a signal
Transmission – means the process of
transmitting or the progress of a signal
after it has been transmitted
The picture below represents basic
transmissions (very basic)
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Generated as voltage that varies
continuously
Characterized by 4 fundamental properties
◦ Amplitude ◦ Frequency – The number of times the wave’s
amplitude cycles from start to highest and
lowest amplitude and back to the starting
position over a fixed period of time
◦ Wavelength ◦ Phase
Amplitude - A measure of the
signal’s strength at any given point
in time
The number of times a wave cycles in a fixed
period of time
Start point
Highest amplitude
Lowest amplitude
Start point
Expressed in Hertz (Hz)
If the frequency is 1 cycle in 1 second 1 Hz, it is
considered an extremely low frequency
◦ The distance between corresponding points on a
wave’s cycle
◦ Expressed in meters or feet
◦ Is the progress of a wave over time in relationship
to a fixed point
◦ Measured in degrees
Composed of precise pulses of positive and zero
voltages
More reliable than analog signaling
Less susceptible to noise
Uses less overhead – Overhead is all the nondata information that must accompany the
signal
A positive voltage represents a 1
A zero voltage represent a 0
The 1’s and 0’s are indicative of the Binary system
Binary describes a numbering scheme in which there are only two
possible values for each digit: 0 and 1
In the digital world, to count in binary, we have to understand the term
bit and byte
Bit – equals a single pulse and is represented by a 1 or a 0
Byte – equals 8 bits, this means that a byte contains 8 place holder
as shown:
128 64 32 16 8 4 2 1, when these numbers
are added together they equal 255
To count in binary, we place the eight bit values in their perspective
place holder position
We add the entire place holder values that have a bit value of 1 and
ignore the bit holder values of 0….see the example.
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Data relies on digital transmissions
For networks that can only send data using analog signals the
signal must be converted from digital to analog and back to
digital this is called modulation and demodulation this is
accomplished using a modulator/demodulator or what is
commonly referred to as a modem
Connecting to the internet is a good example of
modulation/demodulation
In modulation a simple wave called a carrier wave is
combined with the data wave (see next slide)
The carrier wave has preset properties (amplitude, frequency,
wavelength, and phase)
Frequency Modulation (FM) and Amplitude Modulation (AM)
 FM – the frequency of the carrier signal is modified by the
application
 AM – the amplitude of the carrier signal is modified by the
application
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Simplex is one-way communication
Half-Duplex is two-way communication but not
simultaneously
Full-Duplex is two-way communication simultaneously
Modern networks use full-duplex communications when
sending and receiving data
It is important to remember that if the network is using
full-duplex all devices must use full-duplex
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Allows multiple signals to be sent through a single transmission
medium
This requires the use of channels and sub-channels
 Channel – a distinct communication path
 Sub-channel the separation of a channel into multiple channels
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The channels are separated logically using a
multiplexer/demultiplexer (mux/demux)
The multiplexer takes all of the channels that are going to be
multiplexed and combines them to be sent down a single medium.
Once they arrive at the distant end, the channels are separated and
sent to their separate destinations
There are several types of multiplexing
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Time Division Multiplexing (TDM)
Statistical Multiplexing
Frequency Division Multiplexing (FDM)
Wavelength Division Multiplexing (WDM)
Dense Wavelength Division Multiplexing (DWMD)
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Divides the channels into multiple time slots
A time slot is assigned to each node and in that
time slot is that node’s data
If a node has no data the time slot is wasted
Statistical multiplexing eliminates the wasted
time slots
 Senses an empty time slot and assigns the empty
time slot to another node
 The arbitration for the unused time slot is factors
such as use, priority, and other advanced factors
◦ Assigns a unique frequency band to each subchannel
◦ The signals are modulated with different carrier
frequencies
◦ Then multiplexed to travel over a single channel
simultaneously
◦ Two common forms
 Cellular phone transmissions
 DSL internet access
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Enables one fiber-optic connection to carry
multiple light signals simultaneously
One light beam is divided into 40 different carrier
waves each with a different wavelength (color)
Each wavelength is a different separate channel
capable of transmitting up to 10Gbps
Each carrier wave is modulated with a different
data signal
Lasers issue the modulated waves to the
multiplexer that works like a prism, the waves are
combined into a beam of white light
It is then placed on a single strand of fiber by
another laser and demuxed the same way at the
distant end.
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Most common for fiber networks
Can carry between 80 and 160 channels
Provides less separation between carrier
waves
Used on high-bandwidth or extremely long
WAN links
◦ Point-to-Point
 Involves one transmitter and one receiver
 Transmits data intended only for one receiver
 Typically these are WAN links
◦ Point-to-Multipoint
 One transmitter to 2 or more receivers
 Uses Broadcast or Non-broadcast transmissions
 Broadcast – sent to all nodes on that network
 Non-broadcast – sent to only specific nodes on that
network
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Throughput - capacity
 See the throughput chart below
 Is the measure of data transmitted during a
given time period
 Measured in bits per second (bps)
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Bandwidth – this term is normally used
interchangeably with throughput
 Is actually the measure of the highest and
lowest frequencies that a medium can transmit
 Measured in hertz (Hz)
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Baseband
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Broadband
 transmission form where digital signals are sent through
the medium by direct current (DC) pulses
 Requires exclusive use of the wire’s capacity
 When a node transmits all other nodes must wait until
that transmission ends
 Ethernet is an example of baseband communications
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Signal is modulated as radio Frequency (RF) analog waves
Each wave uses different frequency ranges
Does not encode information as digital signals
Has two meanings in networking terms
 Meaning 1 – carries RF signal across multiple channels on coaxial
cable
 Meaning 2 – several different network types that use digital
signaling to transmit at extremely high transmission rates
◦ Transmissions-analog or digital- are susceptible
to degradation between the time they are sent
until they are received
◦ Three major types
 Noise
 Attenuation
 Latency
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Any undesirable influence that is capable of
distorting or degrading a signal
Three major types
 Electromagnetic Interference (EMI)
 Radiofrequency Interface (RFI)
 Cross Talk – interference from a wire medium
that is in close proximity of another wire
medium
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The use of amplifiers and repeater help
combat these three transmission flaws
(Layer 1 devices)
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Amplifiers
◦ Used to amplify analog signal
◦ Does not “clean” the noise out of the signal, but
rather amplifies the signal and the noise
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Repeaters
◦ Used to regenerate digital signals
◦ Since the signal is regenerated the noise is not
repeated
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Attenuation
◦ The loss of the signal’s strength as it travels away
from its source
◦ Attenuation is commonly seen at the wire medium
that carries the signal to the transmission system’s
antenna when using radios as the transmission
systems
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Latency
◦ The delay of the signal or the time it takes to travel
from sender to receiver.
◦ Commonly measured on networks via the round trip
timer (RTT) and is measured in milliseconds (ms)
BNC
Connector
RJ45
Connectors
Connectors connect the cable to the device
Different cabling types use different connectors
F-Type
Connector
RJ11
Connectors
There are 10 different connectors used
with fiber-optic cables. Listed are the
most common
ST
Connector
SC
Connector
LC
Connector
MT-RJ
Connector
Shielded
Twisted Pair
(STP)
Unshielded
Twisted Pair
(UTP)
Coaxial
(coax)
Fiber Optic
(fiber)
There are several types of cabling that can be
used concerning networks. Listed is the most
common found in today’s modern networks
Two standards
3 Types of Twisted Pair Cable
1. Straight-through
2. Crossover
3. Rollover
◦ Contains one or more fiber strands at its core
◦ Data is transmitted using pulsing light sent via
lasers
◦ Each fiber is surrounded by cladding
◦ All is wrapped in Kevlar strands to protect the
fiber core and then wrapped in a plastic sheath
◦ Has 2 types of fiber cable
 Single Mode Fiber (SMF)
 Multimode Fiber (MMF)
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Single Mode Fiber
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Multimode Fiber (create a graphic)
◦ Has a narrow core (>10 microns in diameter)
◦ Has very little reflection
◦ Has the highest bandwidth and can travel the longest
distances
◦ Very expensive
◦ Core has larger diameter (between 50-150 microns in
diameter – normally 62.5 microns)
◦ Because of the core diameter, several pulses of light can be
sent at different angles
◦ Extremely high through put
◦ Resistant to noise
◦ Good security
◦ Industry standard for high-speed networking
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DTE refers to the user side of the cable –
connects to equipment that is the
responsibility of the user
DCE side connects to a multiplexer or
modem – required to provide timing to the
DTE side of the cable
TIA/EIA standard RS 232 (Recommended
Standard 232)
Uses DB-9 or DB-25 (most common)
For more information on this
lesson, See Chapter 3 in the
text book or email the
Professor
**All Slides and graphics were produced by Professor Patrick Hughes**