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Telecommunications

and Networks



Telecommunications and

Networks Effective communication is essential to

organizational success.

An unmistakable trend of communicationstechnology is that more people are able to

send and receive all forms of information

over greater distances at a faster rate.

The effective use of telecommunicationsand networks can turn a company into an

agile, powerful, and creative organization,

giving it a long-term competitive advantage.





Communications



Communications

In human speech, the

sender transmits a

signal through the

transmission mediumof the air.

in telecommunication,

the sender transmits

a signal through a

cable or other telecommunication

medium



Communications

Synchronous Communication

In which the receiver gets the message

immediately.

Voice and phone communications areexamples.

Asynchronous Communication

In which the receiver gets the message later

in minutes, hours, or days after it is sent. Sending a letter through the Post Office or E-

mail over the Internet are examples.



Telecommunications devices relay signals between

computer systems and transmission media.

The model starts with a sending unit (1). The sending unit transmits a signal(2) to a telecommunications device (3). The telecommunications device then

sends the signal through a medium (4). The Telecommunication Medium is

anything that carries an electronic signal and interfaces between a sending

device and a receiving device. The signal is received by another

telecommunications device (5). The process can then be reversed and

another message can go back from the receiving unit (6)



Communications

Computer Networks:

The communications media, devices, and

software needed to connect two or more

computer systems and/or devices.



Telecommunications

Media



Basic Communications Channel

Characteristics

Simplex channel

Half-duplex

Full-duplex channel



Bandwidth

The range of frequencies that an

electronic signal occupies on a given

transmission medium.



Broadband

Telecommunications in which a wide

band of frequencies is available to

transmit information, allowing moreinformation to be transmitted in a

given amount of time.



Fundamental Law of Information

Theory

The information carrying capacity of a

channel is directly proportional to its

bandwidth - the broader thebandwidth, the more information that

can be carried.



Types of Media

Twisted-Pair

Coaxial Cable

Fiber-Optic Cable

Microwave Transmission



Twisted-Pair Wire Cable

Shielded Twisted Pair Wire Cable.

If the twisted pair cable contains a layer of foil shielding to reduce

interference, it is known as shielded twisted pair (STP) cable.)

Unshielded Twisted Pair (UTP) Wire Cable.If it does not contain a layer of foil shielding, it is known as unshielded

twisted pair (UTP) cable and is more susceptible to interference.



Coaxial Cable

A coaxial cable consists of an inner

conductor wire surrounded by insulation,

called the dielectric. The dielectric issurrounded by a conductive shield (usually a

layer of foil or metal braiding), which is in turn

covered by a layer of non-conductive

insulation, called the jacket. When used for

data transmission, coaxial cable falls in the

middle of the cabling spectrum in terms of

cost and performance.

A copper core used for transmitting the

signal

A solid layer of nonconductive insulating

material surrounding the core

A layer of braided metal that reduces

interference

An external jacket of lightweight plastic that

covers the internal cable components to

protect them from damage



Fiber Optic Cable

Consisting of many extremely thin

stands of glass or plastic bound

together in a sheathing (a jacket),

transmits signals with light beams.

In a fiber-optic cable, electrical data

signals from network devices are

converted to light pulses before they

are transmitted.

These high-intensity light beams are

generated by lasers and areconducted along the transparent

fibers. These fibers have a thin

coating, called cladding, which

effectively works like a mirror,

preventing the light from leaking out

of the fiber.



Microwave Transmission

Microwave transmissions are

sent through the atmosphere

and space. Microwave is a

high-frequency radio signal

that is sent through the air.

Microwave transmission is

line-of-sight, which means

that the straight line between

the transmitter and receiver

must be unobstructed.

Microwave dishes must be

placed in relatively high

locations such as atop

mountains, towers, and tall

buildings.



Satellite Transmission

Communications satellites are relay stations that

receive signals from one earth station and rebroadcast

them to another.



Cellular Transmission

A Typical Cellular Transmission Scenario

Using a cellular car phone, the caller (1) dials the number. The signal is sentfrom the car¶s antenna to the low-powered cellular antenna located in that cell

(2). The signal is sent to the regional cellular phone switching office, also called

the mobile telephone subscriber office (MTSO) (3). The signal is switched to the

local telephone company switching station located nearest the call destination

(4). Now integrated into the regular phone system, the call is automatically

switched to the number originally dialed (5), all without the need for operator

assistance.





Telecommunications &

Network Navigation De

vices

Network Adapters

Modems

Special-purpose modems

Multiplexers

Router

Gateways Switches and bridges

Repeaters

Hub



Network Adapters

Devices that enable computers tocommunicate on a network

Network interface cards (NICs)

Network adapters perform three critical

functions. Generate network transmission signals

Create data packets

Act as information gatekeepers

Wireless NICs



Modem

Modem

Translating data from digital to analog is called modulation,and translating data from analog to digital is calleddemodulation. Thus, these devices aremodulation/demodulation devices, or Modems.



Multiplexers:A device that allows several telecommunications

signals to be transmitted over a single communications

medium at the same time.



Network Navigation Devices

Bridges

Connection between two or more

networks at the media access

control portion of the data link

layer; the two networks must use

the same communication protocol.

Send data on a specific routethrough the network

Switches

A device that routes or switches

data to its destination. For

example, a gateway may be able

to connect two differentarchitectures, but a switch may be

able to connect several

Bridges send data betweencollision domains

Routers

Send information between two

networks



Network Navigation Devices

Repeaters

Amplify a signal andretransmit it

Extend cable runs

Hubs

Transmit signals; havemultiple ports

Receive a signal from adevice

Reconstruct the signal

Transmit the signal to allports on the hub



Network Interconnectivity

Technology Gateways

Connection that operates at or above the OSI

transport layer and links LANs or networks that

employ different, higher-level protocols and allows

networks with very different architectures and usingdissimilar protocols to communicate.



Carriers and Ser vices

Digital subscriber line (DSL) A communications line that uses existing

phone wires going into homes and

businesses to provide transmission speedsexceeding 500 Kbps at cost for per month.

Integrated Ser vices Digital Network ISDN is a technology that uses existing

common-carrier lines to simultaneouslytransmit voice, video, and image data indigital form.

ISDN also offers high rates of transmission:the digital service has the capacity to send a22-page document in about a second!



Integrated Ser vices Digital

Network (ISDN)

ISDNNetwork

Switching



Networks & Distributed

Processing



Network Concepts and

Considerations

Network topology

Ring network

Bus network Star network

Network types

Local Area Networks

Wide Area Networks

Home and small business networks

Terminal to Host





Network Topology: Bus

network

All nodes are connected insequence on a single cable

Networked computerscommunicate with each other

One computer transmits dataat a time

Becoming obsolete



Network Topology: Star

network

Most widely deployed

client/server layout

Nodes connect to a centralcommunications device

(switch)

A node sends a signal to the

switch, which retransmits it to

the other nodes

A node accepts only

signals addressed to it



Network Types: Client/Ser ver

Data flows efficiently

Servers respond to requests

from clients

Servers perform specifictasks

Scalable

Centralized



Classifications of

Client/Server Networks

LAN

Local areanetwork

Computers

linked over a

small geographic

area



Classifications of

Client/Server Networks

WAN Wide area network

Computers linkedover largegeographic areas

MAN Metropolitan area

network

Computers linkedwithin a city or county



Network Types: Home and

SmallB

usiness Networks

ConnectingComputing Devices using a Home Network



Network Types: Terminal to

Host



Servers

The number and types of servers

depend on network size and workload

Dedicated servers

Perform one specific function

Authentication servers

Keep track of network logins and

services available

File servers

Store and manage files

Print servers

Manage client-requested printing

jobs Create a print queue (prioritize

print jobs)

Application servers

Act as a storage area for application software

Database servers

Provide clients with access todatabase information

E-mail servers

Process and deliver incoming

and outgoinge-mail

Communications servers

Handle communications betweennetworks, including the Internet

Often the only device on thenetwork directly connected to theInternet

Web servers

Host a Web site availablethrough the Internet



Communications

Software and Protocols



Communications Software

Network operating systems (NOS)

That controls the computer system and devices on a

network and allows them to communicate with each

other.

Provide the protocol that controls the communication

among devices on the network

Many modern OSs include NOS client software

If your OS does not include NOS client software, it must be

installed on each client.

Major network operating systems

Windows Server 2008

UNIX /Linux Enterprise

Novell NetWare

Network management software

That enables a manager on a networked desktop to

monitor the use of individual computers and shared

hardware (like printers) and scan for viruses.



Communications Protocols

Protocols are rules that ensurecommunications among computers of different types and from different

manufacturers. Open Systems Interconnection (OSI)

model

Transmission Control Protocol/Internet

Protocol (TCP/IP) Ethernet

Bluetooth



Open Systems Interconnection

(OSI) model

A standard model for network architecture that dividesdata communications functions into seven distinctlayers to promote the development of modular networks that simplify the development operation, andmaintenance of complex telecommunication network.

Application Layer

Presentation Layer

Session Layer

Transport Layer

Network Layer

Data Link Layer

Physical Layer



Application Layer

The application layer provides a

facility for applications tocommunicate with the network (e.g.

save files to the network, print files on

a network printer or receive data from

the network.



Presentation layer

This layer performs transformations on data

to provide a standardized application

interface and to provide commoncommunication services, such as encryption,

text compression and reformatting (e.g.

EBCDIC code to ASCII code). This layer

provides representation of information, suchas formats, codes, transformation and

encryption.



Session layer

The session layer controls the dialogs

(sessions) between computers. It

establishes the session, conducts the

transfer of data, and terminates the

session once the data transfer is

complete. It establishes checkpointing, termination, restart

procedures



Transport Layer

The transport layer provides reliable andtransparent transfer of the data betweenend points, end to end error recovery, and

flow control (windowing) for minimizing anynetwork congestion issues that may occur upon data reaching their destination. Itsduties include the following: breaking downa message into blocks of data calledpackets or segments; addressing thepackets; forwarding them across thenetwork; and acknowledging andresembling them into the original message.



Network layer

The network layer addresses and

delivers packets among networks.

This is done through physical devices,

such as routers, and on the basis of

the logical network address assigned

to each network and the service

address of the destination devicenetwork addresses differentiate one

network from all other networks that

may interconnected.



Data Link Layer

This layer provides for the reliable transfer of dataacross a physical link for either LAN or WANmediums. It sends blocks of data called framesusing a variety of data link LAN/WAN protocols with

the necessary data fields to provide for synchronization, bit error detection/correction error control, and flow control. A unique feature of thedata link layer includes its ability to handle physicaladdressing through media access control (MAC

normally assigned to it at the time of manufacture)addresses for communication with devicesphysically linked together in a network.



Physical Layer

This layer physically transmits and

receives all binary informationnecessary to establish, maintain,

operate and deactivate the physical

link. Bits are sent and received as

either a digital µ1¶ or µ0¶ or in analogform, regardless of what they

represent.



Communications Protocols

TCP/IP (Transmission Control Protocol /Internet Protocol

The primary communications protocol of theinternet.

Ethernet

The most popular communications protocoloften used with local area network. TheEthernet standard is designed for LAN¶s that

use a bus topology; the standard helpsensure compatibility among devices so thatmany people can attach to a common cableto share network facilities and resources.

Bluetooth



Telecommunications

and Applications




Applications

Voice mail

Technology that enables users to leave, receive, and

store verbal messages for and from other people

around the world.

Electronic software distribution

Process that involves installing software on a file

server for users to share by signing onto the network

and requesting that the software be downloaded onto

their computers over a network

T l i ti d




Applications:

VIDEOCONFERENCING

A telecommunication

system that combinesvideo and phone call

capabilities with data or

document conferencing.




Applications: Electronic data

interchange (EDI)

An intercompany,

application-to-applicationcommunication of data in

standard format,

permitting the recipient to

perform the functions of a

standard business

transaction.



Network Security

Firewalls

Prevent access to

the network by

unauthorized users

Composed of software and/or

hardware

Screen and validate

data packets

Bastion host/proxy

server

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