Telecom related area description in detail

Jimma University
Faculty of Computing and
Informatics.
Jimma, Ethiopia.
Telecom Technology

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Concept of Networking
A network consists of two or more entities or objects sharing resources
and information.
A computer network is a group of computers/devices(Nodes) that use a
set of common communication protocols over digital interconnections for
the purpose of sharing resources located on or provided by the network
nodes.
The nodes of a computer network may include personal computers,
servers, networking hardware, or other specialized or general-purpose
hosts.

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The interconnections between nodes are formed from a broad spectrum
of telecommunication network technologies, based on physically wired,
optical, and wireless technologies.
A communication protocol is a set of rules for exchanging information
over a network.
The network becomes a powerful tool when computers communicate and
share resources with other computers on the same network or entirely
distinct networks.

5
Cont...
Company’s cost of doing business can be reduced as a result of sharing data
(defined as a piece or pieces of information) and resources.
Instead of having individual copies of the data at several locations around the
company, and needing to keep all of them similarly updated, a company using a
network can have just one shared copy of that data and share it, needing to keep
only that one set of data updated.
Furthermore, sharing networked resources (like printers) means that more people
can use a particular resource and a wider variety of resources (like different
printers) can be used by each network user.
Any time a company can do more with less, or buy fewer items to do the same job,
its total costs are reduced, and it is able to make more money per dollar spent.

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A data communications system has five components.
 Sender: The sender is the device that sends the data message.
 Receiver: The receiver is the device that receives the message.
 Message: The message is the information (data) to be communicated.
 Transmission medium: The transmission medium is the physical path
by which a message travels from sender to receiver.
 Protocol: A protocol is a set of rules that govern data communications.

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Communication between two devices can be simplex, half-duplex, or full
duplex.
 Simplex: In simplex mode, the communication is unidirectional, as on
a one way street. Only one of the two devices on a link can transmit;
the other can only receive.
 Half-Duplex: In half-duplex mode, each station can both transmit and
receive, but not at the same time. When one device is sending, the
other can only receive, and vice versa.
 Full-Duplex: In full-duplex (also called duplex), both stations can
transmit and receive simultaneously.

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
Keyboards and traditional monitors are examples of simplex devices.
Walkie-talkies and CB (citizens band) radios are both half-duplex
systems
One common example of full-duplex communication is the telephone
network.

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Cont...
Basis for
Comparison
Simplex Half Duplex Full Duplex
Direction of
Communication
Unidirectional
Two-directional, one at
a time
Two-directional,
simultaneously
Send /Receive
Sender can only
send data
Sender can send and
receive data, but one a
time
Sender can send and
receive data
simultaneously
Performance
Worst performing
mode of
transmission
Better than Simplex
Best performing
mode of
transmission
Example
Keyboard and
monitor
Walkie-talkie Telephone

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Computers on a network can act as a client or a server.
 A client is a computer that requests for resources.
 A server is a computer that controls and provides access to resources.

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Why Network?
 File Management.
 Sharing, transferring include document, multimedia, graphics.
 Application Sharing—access granted to client. It may be control access and
view access.
 Device Sharing.
 Printers, storage devices, modems.
 Workgroup Activities—computer dedicated to a user and that quickly perform
complex, technical tasks such as digital content creation and detailed analysis
 Scheduling, e-mail, conferencing.
 Facilitate centralized management—consists of many different electronic
devices, power distribution systems, and work consoles.
 All of these can be managed from a single control station.

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Classification of Networks
Classification by network geography.
Classification by component roles.

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Classification by network geography.
Local area network (LAN):
Local area networks, generally called LANs, are privately-owned networks
within a single building or campus of up to a few kilometers in size.
It is widely used to connect personal computers and workstations in company
offices and factories to share resources (e.g., printers) and exchange
information.
LANs are distinguished from other kinds of networks by three characteristics:
(1) their size, (2) their transmission technology, and (3) their topology
LANs are inexpensive to install and also provide higher speeds.
Since a LAN covers a small area, noise and error are minimized.

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LANs are restricted in size, which means that the worst-case transmission
time is bounded
LANs may use a transmission technology consisting of a cable to which
all the machines are attached, like the telephone company party lines
once used in rural areas.
Traditional LANs run at speeds of 10 Mbps to 100 Mbps, have low delay
(microseconds or nanoseconds), and make very few errors.
Newer LANs operate at up to 10 Gbps.

MAN’s (Metropolitan Area Networks):
A metropolitan area network, or MAN, covers a city.
A MAN is a computer network that connects computers within a metropolitan
area, which could be a single large city, multiple cities and towns, or any given
large area with multiple buildings.
The best-known example of a MAN is the cable television network available in
many cities.
The cost of installation and operation is higher.
MANs use high-speed connections such as fiber optics to achieve higher speeds.
MAN is made up of interconnected LANs.
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19
Cont...
Because MANs are smaller, they are usually more efficient than WANs,
since data does not have to travel over large distances.
MANs typically combine the networks of multiple organizations, instead
of being managed by a single organization.
Most MANs use fiber optic cables to form connections between LANs.

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WAN’s (Wide Area Networks)
A wide area network, or WAN, spans a large geographical area, often a
country or continent.
 WANs span a larger area than a single city.
These use long distance telecommunication networks for connection,
thereby increasing the cost.
The Internet is a good example of a WAN.

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Classification of Networks
Classification by Component Roles
Networks can also be classified according to the roles that the networked
computers play in the network’s operation.
 Peer-to-peer and
 server-based

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Peer-to-peer:
 In a peer-to-peer network, all computers are considered equal.
 Each computer controls its own information and is capable of
functioning as either a client or a server depending upon the
requirement.
 Peer-to-peer networks are inexpensive and easy to install.
 They are popular as home networks and for use in small
companies.

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Peer-to-peer (continued):
 Most operating systems come with built-in peer-to-peer networking
capability.
 The maximum number of peers that can operate on a peer-to-peer
network is ten.
Each peer shares resources and allows others open access to them.
 Peer-to-peer networks become difficult to manage when more security
is added to resources, since the users control their security by
password-protecting shares.
Shares can be document folders, printers, peripherals, and any other
resource that they control on their computers.

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Peer-to-peer (continued):
Peer-to-peer network

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Server-based:
 A server-based network offers centralized control and is designed
for secure operations.
 In a server-based network, a dedicated server controls the network.
A dedicated server is one that services the network by storing
data, applications, resources, and also provides access to
resources required by the client.
 These servers can also control the network’s security from one
centralized location or share it with other specially configured
servers.

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Server-based:
Server-based network

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Network Terminology
Workstation
Each computer attached to the network.
Node
Each device attached to the network.
Server
A central repository for information.
Topology
The overall configuration of the network.

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The Role of Network Communications Software
Sending data from one node to another
 Recognize the data.
 Divide the data into manageable chunks.
 Add information to each chunk of data to identify the receiver.
 Add timing and error checking information.
 Put the data on the network and send it on its way.

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Cont...
Data Packets
Packets are the basic units of network communications.
 Each packet has three sections:
Header:
• An alert signal
• Source & destination addresses
• Clock information
Data
Trailer – Error checking information

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Cont...
Protocols
Define the rules that govern the communications between two computers
connected to the network.
Roles: addressing and routing of messages, error detection and recovery,
sequence and flow controls etc.
A protocol specification consists of the syntax, which defines the kinds
and formats of the messages exchanged, and the semantic, which
specifies the action taken by each entity when specific events occur.

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Cont...
Protocols
Rules & procedures for communicating.
 Sending Computer.
Breaks the data into packets
Adds addressing information
Prepares the data for transmission
 Receiving Computer.
Takes packets off the cable
Strips the packets of addressing information
Reassembles the data form the packets

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Cont...
Protocols
For two computers to communicate, they must be using the same set
of protocols (rules)
Examples of protocols
 SMTP – Mail transfer protocol— it's an application used by mail
servers to send, receive, and/or relay outgoing mail between email senders
and receivers
 FTP – File transfer protocol—govern how computers transfer files
from one system to another over the internet
 TCP/IP – Internet protocol— suite of communication protocols used to
interconnect network devices on the internet.

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Cont...
Traffic Control
If two computers put data onto the cable at the same time, the packets
will collide and be destroyed
 There must be a way to…
Access the cable without running into other data.
Be accessed by the receiving computer with assurance that it is
intact.
It is the process of managing, controlling or reducing the network
traffic, particularly Internet bandwidth, e.g. by the network scheduler.
 It is used by network administrators, to reduce congestion, latency and
packet loss.

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Summary
A network consists of two or more entities sharing resources and
information.
A computer network consists of two or more computers that are
connected and are able to communicate.
The basic purpose of networks is to enable effective communication,
share resources, and facilitate centralized management of data.
Networks can be classified according to their geographical boundaries or
their component roles.
The role of network communication software.

Overviews of Telecommunication
Technology
Lecture #2

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Communications
The transmission of a signal by way of a medium from a sender to a
receiver.
It is the process of conveying or transferring information from one point
to another.
It is the process of establishing connection or link between two points for
information exchange.

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Introduction
Etymology
The French word télécommunication was coined in 1904 by the French
engineer and novelist Édouard Estaunié.
 The word telecommunication was adapted from the French word
télécommunication.
“Telecommunication” is a combination of two words which are “Tele”
and “Communication”.
 The word “Tele” in Latin means DISTANCE.
Telecommunication is Distance Communication.

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What is Telecommunication ?
Telecommunications are the means of electronic transmission of information over
distances.
 The information may be in the form of voice telephone calls, data, text, images, or
video.
Telecommunication system is collection of nodes and links to enable telecommunication.
The simplest form of telecommunications takes place between two stations.
 However, it is common for multiple transmitting and receiving stations to exchange
data among themselves.
Telecommunications is the merging of voice, data (WAN), video, image, and wireless
communications technologies with PC and microelectronic technologies to facilitate
communications between people or to deliver entertainment, information, and other
services to people.

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Cont...
Telecommunication is deals with the science and technology of sending and
receiving information such as sound, visual images, or computer data over long
distances through the use of electrical, radio, or light signals, using electronic
devices to encode the information as signals and to decode the signals as
information.

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Cont...
Telecommunication is communication at a distance using electronic
signals or electromagnetic waves.
The electronic transmission of signals for communications, including
such means as:
 Telephone system
 Radio broadcasting system
 Television broadcasting
 Computer Network and internets
The exchange of information in any form (voice, data, text, images,
audio, video) over networks

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Telecom Network Components
Terminals – any input/output device that uses telecommunications networks to
transmit or receive data. Eg. Telephone
 These is starting and stopping points of all communication.
Telecommunications Processors – devices that provide control and support
functions.
 Eg. In many system, data needs to be converted from analog to digital and
back.
Telecommunications Channels – media over which data are transmitted and
received.
 These include various types of cables and wireless radio frequencies.
Protocols specify how each type of telecommunication systems handle the
messages.
 Eg. GSM and 3G are the protocols for mobile phone communications and
TCP/IP is the protocol over the internets.

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Telecom Network Components
Telecommunications Control Software – responsible for controlling the
functionality and activities of the network.
Messages represent the actual data that is being transmitted.

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Telecommunications Processors
Modems – convert digital signals from a computer into analog
frequencies that can be transmitted over ordinary telephone lines
Multiplexers – allows a single communications channel to carry
simultaneous data transmissions from many terminals

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Telecommunications channels
Twisted-Pair Wire–copper wire twisted into pairs. e.g. telephone system
(300bps-10Mbps)
Coaxial Cable–copper or aluminum wire wrapped with spacers to
insulate and protect it. e.g. Cable TV.
 Faster data rate (56 Kbps-200 Mbps), larger BW.
Fiber Optics–one or more hair-thin filaments of glass fiber wrapped in a
protective jacket
 Data transmitted using light beams.
 Very high BW; high data transmission rate (500 Kbps- 25Tbps).

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Wireless Technologies
 Terrestrial Microwave—data transmitted with the help of microwaves. Microwaves are
electromagnetic waves with frequency in the range of 30,000 MHz to 3000MHz.
 Its used for radars, radio navigation systems, sensor systems, and radio astronomy.
 Radio Waves—also electromagnetic waves with low frequency range of 3KHz to 30MHz.
 It is used in standard broadcast radio and television, shortwave radio, navigation and
air-traffic control, cellular telephony, and even remote-controlled toys.
 Communications Satellites—high-earth orbit communications satellites placed in
stationary geosynchronous orbits
 It is used for distributing television signals to terrestrial broadcasting stations.

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Cont...
Cellular and PCS Systems—a geographic area divided into cells with one
low-power transmitter device per cell used to relay calls from one cell to
another
Wireless LANs—low-frequency radio technology installed in an office or
building.
 It is a wireless computer network that links two or more devices using
wireless communication to form a local area network within a limited
area such as a home, school, computer laboratory, campus, or office
building.
Wireless Web—wireless, Web-enabled information appliances accessing the
Internet, intranets and extranets.

General Model of a Telecommunication
Channel
Lecture #3

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Communication Channel
Communicating data from one location to another requires some form of
pathway or medium.
These pathways, called communication channels, use two types of media
 Cable (twisted-pair wire, cable, and fiber-optic cable) and
 Wireless /broadcast (microwave, satellite, radio, and infrared).
The channel is central to operation of a communication system:
 Linear (e.g. mobile radio) or nonlinear (e.g. satellite)
 Time invariant (e.g. fiber) or time varying (e.g. mobile radio)
The information-carrying capacity of a communication system is
proportional to the channel bandwidth.

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Communication involves the transfer of information from one point to
another.
 Three basic elements
Transmitter: converts message into a form suitable for transmission
Channel: the physical medium, introduces distortion, noise,
interference
Receiver: reconstruct a recognizable form of the message.

The transmitter modifies the message signal into a form suitable for
transmission over the channel. This modification often involves
modulation
Moving the signal to a high-frequency carrier (up-conversion) and
varying some parameter of the carrier wave.
Analog: AM, FM, PM.
Digital: ASK FSK PSK (SK: shift keying)
The receiver recreates the original message by demodulation
 Recovery is not exact due to noise/distortion.
 The resulting degradation is influenced by the type of modulation.
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Characterized by:
 Signaling transmission method
 Bandwidth: amount of data transmitted in a fixed amount of
time.
 Direction(s) in which signal can flow
 Noise, attenuation, and distortion characteristics
 Medium used.

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Noise in Communications
Noise is one of the basic factors that set limits on communication.
Unavoidable presence of noise in the channel
 Noise refers to unwanted waves that disturb communications
 Signal is contaminated by noise along the path.
External noise: interference from nearby channels, human made noise,
natural noise...
Internal noise: thermal noise, random emission... In electronic devices
A widely used metric is the signal-to-noise (power) ratio (SNR)

Types of communication systems
The Two basic types of communication systems are: Analog and Digital.
Analog Systems: both the information and the carrier are analog signals.
Digital Systems: The digital pulses are transferred between two or more points
in a communication system.
A signal is some form of energy (light, voltage, etc)
 Varies with time (on/off, high/low, etc.).
 It can be continuous or discrete.
 If the signal is specified for every value in time then it is known as the
Continuous-time signal.
 If the signal is specified only for discrete-time instances then it is called
Discrete-time signal. 56

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Comparison of analog and digital signals

Analog Communication System
The modulation systems or techniques in which one of the characteristics of the
carrier is changed in proportion with the instantaneous value of modulating signal
is called analog communication system.
Analog signal: continuous varying waveforms to carry data.
 It refers to information that is continuous that changes over a time period
 It can have an infinite number of value in a range
 Analog signals are represented by rising and falling voltages (waves) such as
light, voice, video signals that are in a continuous form. Example: Human Voice
 Described by Amplitude, Period or Frequency and Phase
Application: audio tape, telephone, radio, microphone, wireless networking,
satellites, microwave communications
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Cont...
Advantages of Analog communications system
 Transmitters and Receivers are simple
 Low bandwidth requirement
Disadvantage of analog communication system:
 Noise affects the signal quality
 It is not possible to separate noise and signal
 Repeaters can‘t be used between transmitters and receivers
 Coding is not possible
 It is not suitable for the transmission of secret information.

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Digital communications system
Digital Modulation is defined as changing the amplitude of the carrier
signal with respect to the binary information or digital signal.
Digital signal: it refers to information that are discontinuous or discrete in binary
form.
 Represented by Square wave [has a finite range i.e. between 0 and 1.]
 Non periodic signals
 Two different values of electrical voltage or current or on/off light source.
 Digital signals can have only limited number of values
 Frequently preferred to use because less susceptible to noise and interference.
 Application: Mobile, Flash, Computer, Digital Clock, Calculator

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Cont...
Advantages of Digital communications
 It has a better noise immunity
 Repeaters can be used between transmitters and receivers.
 It becomes simpler and cheaper as compared to the analog
communication.
Disadvantages of Digital communications
 It requires a larger channel bandwidth
 Delta modulation needs synchronization incase of synchronous
modulation.

Comparison of Analog and Digital Signal
Analog Signal Digital Signal
Signal Continuously variable Discrete signal
Traffic measurement Hz eg .4Hz Bits per second eg. 1bps
Bandwidth Very low(4KHz) Very High bandwidth
Network Capacity Low (only one
conversation per line)
High (Multiplexors are used for
sharing connections)
Network
Manageability
Poor Good
Power Management High (Requires range of
frequencies and
amplitudes)
Low (Two discrete signals—0s
& 1s are transmitted)
Security Poor (Line can be Tap) Good (Encryption is used)
Error Rate High (10–5 bits is
guaranteed to have an
error)
Less (Twisted-pair: 10-7
)
(Satellite: 10-9
) (Fiber: 10-11
)
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Cont...
Different goals between analog and digital communication
systems:
 Analog communication systems: to reproduce the transmitted
waveform accurately. Use signal to noise ratio to assess the
quality of the system.
 Digital communication systems: the transmitted symbol to be
identified correctly by the receiver. Use the probability of error
of the receiver to assess the quality of the system.

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Channel Organization
Point to point channels: It consists of many connections between individual
pairs of machines. It provides dedicated link between two devices.
 Point to point transmission with one sender and one receiver is sometimes
called unicasting.
Simplex: channel passes data in one direction only.
Half-duplex: transmits data one direction at a time (walkie-talkie).
Full-duplex: transmits data in both directions simultaneously (telephone).
Multipoint: broadcasts messages to all connected receivers.
 A multipoint connection is one in which more than two specific devices share
a single link.

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Multiplexing
Multiplexing is a technique by which different analog and digital streams of
transmission can be simultaneously processed over a shared link.
Carrying multiple messages over a channel simultaneously
 TDM (time division multiplexing)
Example: packet switching on the Internet
Use: Digital channels
 FDM (frequency division multiplexing)
Example: Cable TV
Use: Analog channels
Filters separate different data signals at receiving end.

The OSI Reference Model
Lecture #4

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ISO
International Standards Organization adopted seven-level OSI model
to guide development of international standards for networks of
computers.
 Recommends functions to be performed at each of the seven
layers.
 Does not specify detailed standards.

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The OSI Model
Open Systems Interconnection: describes how network hardware and
software work together in a layered fashion.
 Each layer provides some service or action that prepares the data
for delivery over the network.
 Requests are passed from one layer to the next.
 Each layer adds information to the data packet.

How Data Passes Through Layers
Each computer has a layered protocols

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The OSI Seven Layers
Layer 7: Application
 Deals with user application program
 Interface between Software & network protocol on the computer.
 Mainly holds the application programs to send & receive data
 Transferring of files disturbing the results to the user is also done in
this layer.
 Allows user to log on to a remote host using Network Virtual Terminal
 Common Protocols are: FTP, SMTP,
HTTP,
Provides application with access to the
network: Email, Web browser

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Cont...
Layer 6: Presentation
 Presents data in standard formats.
 Defines the syntax used by hosts in the network to communicate.
 Encryption at Sender side & Decryption at receiver side
 Before transmitted, data should be changed to bit streams
 Performs Data Compression to reduce bandwidth of the data
 Managing the Syntax & Semantics of the data is a design issue
 Data is encoded, encrypted & compressed
 Determines format used to exchange data
among networked computers:
Encryption, Compression

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Layer 5: Session
 Establish, manage and terminates sessions between two communication
hosts.
Ex: Client software (used for login)
 Establish the session between the applications
 Session ID is used to identify a session
 Allows 2 computers to communicate in Half-duplex or Full-duplex
 Adds the checkpoints (Synchronization Points) into stream of data
 Token Management is used to avoid the critical operations by 2 computers

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Cont...
Layer 4: Transport
 TCP and UDP are protocols used at this layer.
Protocol for encoding messages
 Includes service point address which is port address.
 Message is divided into segments; each segment contains sequence number
Breaks up the data from the sending host and then reassembles it in the
receiver.
 Functions such as Multiplexing, Segmenting or Splitting on the data are done
Connectionless Transport: Each segment is sent as an independent packet during
delivery
Connection Oriented Transport:
Connection is made before delivering
packets
Insure reliable data transport
across the network

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Layer 3: Network (routers)
 Mechanism for separating multiple messages and Addresses messages to
proper location.
 Translates logical addresses into physical addresses and determines path.
 Packet routing based on IP addressing and Decides by which route data
should take.
 Responsible for establishing paths that are used for the transfer of data
 Acts as a network controller for packet sequence
Manages the Subnet traffic
Traffic direction, Routing &
Packet Switching
 Divides the outgoing messages into
packets

Layer 2: Logical Link (switches: faster; not concerned with IP)
 Responsible for Sending & receiving Frames
 Synchronizes the information which is to be sent
 Ensures data transfer is error free from one node to another
 Sends & expects acknowledgements for frames received and sent
 Assigns an unique id on layer 2 network called MAC address
 Responsible for Error Detection & Error Correction
 Provide reliable transit of data across a physical link.
 Make decision based on physical addresses(usually MAC address)
What decision? Where to send data next.
Divided into: Media Access Control (MAC) & Logical Link Control (LLC)
 MAC: Responsible for moving data packets from one NIC to another
 LLC: Control field is used for flow & error control.
 LLC: Uses CRC (Cyclic Redundancy Check) to check frame errors
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Layer 1: Physical (wires)
 Lowest layer of the OSI Model.
 Transmits raw bits of data over the physical medium
Data is handled in the form of 1s and 0s.
 Activates, maintains and deactivates the physical connection.
 Voltages & data rates needed for transmission is defined in the physical layer.
 Data encoding is also done in this layer.
 Responsible for physical connection between a network medium & your
computer.
 Define physical connection of the network

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OSI Model
Data unit Layer Function
Host
layers
Data
7. Application Network process to application
6. Presentation Data representation, encryption and decryption
5. Session Interhost communication
Segments 4. Transport
End-to-end connections and reliability, Flow
control
Media
layers
Packet 3. Network Path determination and logical addressing
Frame 2. Data Link Physical addressing
Bit 1. Physical Media, signal and binary transmission

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Physical media communication
Physical media refers to the physical materials that are used to store or
transmit information in data communications.
Examples of physical media include twisted-pair copper wire, coaxial
cable, multimode fiber optic cable, terrestrial radio spectrum and satellite
radio spectrum.
Physical media fall into two categories: guided media and unguided
media.

92
Cont...
 With guided media, the waves are guided along a solid medium, such
as a fiber-optic cable, a twisted-pair cooper wire or a coaxial cable.
 With unguided media, the waves propagate in the atmosphere and in
outer space, such as in a digital satellite channel or in a CDPD system.
In wired media, the electromagnetic waves are in the form of electrical
signals.
 These signals travel through a Solid medium or a transmission line
consisting of twisted copper wires, copper coaxial cables, and optical
fibers.
In wireless media, the electromagnetic waves travel through space.

93
Twisted-Pair Cable (TPC)
TPC is the oldest, least expensive, and most commonly used
transmission medium.
Twisted-pair cable consists of one or more twisted-pair wires bundled
together
 Each twisted-pair wire consists of two separate insulated copper wires
that are twisted together.
 The wires are twisted together to reduce noise. Noise is an electrical
disturbance that can degrade communications.
TPC is used in telephone system, and LANs to connect terminals with
the mainframe computer.
The twisting minimizes the crosstalk interference between adjacent pairs
in a multi pair cable.
TPCs are most commonly used transmission media in both analog and
digital communication because they are cost effective and easy to install.

95
Cont...
TPCs are available in two varieties unshielded and shielded
Unshielded Twisted Pair Cable: Any cable with twisted pair of
insulated wires grouped and place in a flexible plastic jacket is known as
unshielded twisted Pair (UTP).
 The most common example of UTP is an ordinary telephone wire.
 Using unshielded cable reduces the cost, size, and installation time
of the cable and connectors.
Shielded Twisted Pair (STP) Cable: A twisted pair of wires covered
by a protective metal shield is called a shielded Twisted Pair.
 STP cables are more expensive and difficult to handle

96
Coaxial Cable
Twisted pair cables are not able to carry signals of high frequency because
these signals lead to higher attenuation (signal at the beginning of the medium is
not the same as the signal at the end of the medium causes of impairment i.e.
attenuation) and loss of data.
Coaxial cable consists of a single copper wire surrounded by at least three layers:
(1) an insulating material, (2) a woven or braided metal, and (3) a plastic outer
coating
Cable television (CATV) network wiring often uses coaxial cable because it can
be cabled over longer distances than twisted-pair cable.
Most of today’s computer networks, however, do not use coaxial cable because
other transmission media such as fiber-optic cable transmit signals at faster rates.

98
Cont...
Coaxial cables are used in a wide range of applications in data communication,
such as cable television networks, long distance telephone networks, and
LANs.
Coaxial cabling has a single copper conductor at its center. A plastic layer
provides insulation between the center conductor and a braided metal shield.
The metal shield helps to block any outside interference from fluorescent lights,
motors, and other computers.
Although coaxial cabling is difficult to install, it is highly resistant to signal
interference.
In addition, it can support greater cable lengths between network devices than
twisted pair cable.

99
Fiber Optical Cables:
Fiber optical cables was developed as a new transmission media to
overcome the limitations of coaxial cables and achieve higher data
transfer rate and bandwidth.
Fiber optic cabling consists of a center glass core surrounded by several
layers of protective materials.
It transmits light rather than electronic signals eliminating the problem of
electrical interference.
 This makes it ideal for certain environments that contain a large amount of
electrical interference.
 It has also made it the standard for connecting networks between buildings,
due to its immunity to the effects of moisture and lighting

100
Cont...
Fiber optic cable has the ability to transmit signals over much longer
distances than coaxial and twisted pair.
 It also has the capability to carry information at vastly greater speeds.
 This capacity broadens communication possibilities to include services such
as video conferencing and interactive services.
The cost of fiber optic cabling is comparable to copper cabling; however, it is
more difficult to install and modify.
The center core of fiber cables is made from glass or plastic fibers a plastic
coating then cushions the fiber center, and Kevlar fibers help to strengthen the
cables and prevent breakage.
The outer insulating jacket made of Teflonor PVC.

101
Wireless media
In previous we learned about transmission media that use a physical cable
to carry the transmitted signals from the source to the destination.
In wireless communications, the signals are transmitted in the form of
electromagnetic waves through space and through water.
 A special device called antenna is used to receive and transmit
wireless communication signals.
Wireless communication has
 Short-Range Coverage and Long-Range Coverage
Short-Range Wireless Communication:
• Infrared Transmission
• Wi-Fi
• Bluetooth
• Ultra wideband
• Wireless USB
• HomeRF
Long-Range Wireless Communication:
• Broadcast Radio
• Microwave System
• Satellite System

Telecom related area description in detail

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