Saturday, October 1, 2022

1.1 Networking &Telecommunications

1.1 Networking &Telecommunications

 

Data Communication  

Data communication is the process of transferring data and information between

computers and other electronic devices.

Eg. E-Mail, Radio and phone calls.

 

There are two types of communication mode:

i) Simplex mode         ii) Duplex mode

 

Simplex mode
Simplex mode is the transmission of data and information that takes place in only one direction.

It is a unidirectional mode of data transmission.
Radio, newspaper, television broadcasting, books etc. are examples of simplex mode.

 

Duplex mode

Duplex is mode of data transmission in which data and information flow in both directions.

It is bi-directional mode of data transmission.

 

The two types of duplex modes are:

i) Half Duplex mode   ii) Full Duplex mode

 

Half duplex mode
Half duplex is the mode of data transmission in which data and information flows in both directions but only one direction at a time.

Walky-talky and wireless handset are examples of half-duplex mode.

 

Full duplex mode [MF 2076]
Full duplex is the mode of data transmission in which data and information flow in both direction simultaneously.

Mobile and landline phones are examples of full duplex mode.

 

Components of Data Communication.
i) Data             ii) Sender        iii) Medium   

iv) Receiver    v) Protocol

 

Transmission medium / Communication Channel 

A channel or path through which data and information are transmitted between connected

devices in a network environment is called communication media.

 

The types of communication medium are: 

1. Guided (Wired/bounded) communication media

2. Unguided (Wireless/unbounded) communication media

 

Guided medium

The media which uses cable or wire to transfer data and information among computers

are called guided communication media.

It is an easy, fast and secure way to transfer data and information from one computer to another.

 

The three types of guided media are:

a. Twisted pair Cable

b. Co-Axial Cable

c. Fiber Optic Cable

 

Features of guided media: 

- Data transmits through the physical cable or fixed path

- Data transmission rate is higher.

 

Twisted pair cable

A set of four pair of wires twisted with each other is known as twisted pair cable.

Wires are twisted with each other so as to reduce crosstalk (A disturbance caused by electromagnetic interference, along a circuit or a cable pair).

RJ-45 connector is the most popular connector used in twisted-pair wire.

Its types are:  

a) Unshielded Twisted Pair (UTP)    

b) Shielded Twisted Pair (STP)

 

Co-axial cable

Coaxial cable is a common type of cable used for transmitting data over long distances.

They are most commonly used to transmit cable TV and Internet signals.

The connectors used with co-axial cables are BNC, T-connectors and terminators in bus topology.

 

Fiber optic cable

Fiber optics cable is one of the costlier cables used in data communication which uses light to carry a data signal through the cable.

The connectors used in fiber optics are Screw Mounted Adaptors (SMA), Spring-loaded Twist (ST), SC and FC.

 

Unguided medium [SEE 2074 U]

The transmission media which transfer data in the form of electromagnetic waves that do not require any cables for transmission is called unguided medium.

E.g.: radio wave, microwave, satellite communication etc.

 

Radio wave transmission

·       The transmission making use of radio waves through air is called radio wave transmission.

·       It provides low bandwidth for data communication.

·       Radio, TV, cellular phones etc. uses radio transmission in one form or another.

·       The radio waves can travel through walls and through an entire building.

·       It does not require line of sight for data transmission

Microwave transmission

·       Microwave is a line-of-sight wireless communication technology that uses high frequency beams of radio waves to provide high speed wireless connections that can send and receive voice, video, and data information.

·       Microwaves do not pass through buildings. So, indoor receivers cannot be used effectively.

·       It provides higher bandwidth for data communication.

·       It requires line of sight for data transmission.

Satellite Communication

·        Satellite Communication is defined as a type of communication where the exchange of information takes place between different stations present on the surface of the earth using artificial satellites in space. 

·        Through satellite communication, data, voice, audio, video signals can be transmitted and received by using communication links between various regions of the earth.

 

Computer network 

Computer network is a group of two or more computers and devices connected to each other through wired or wireless media to exchange data and information and share hardware, software and other resources.

 

Advantages of computer network 

·       It can share hardware devices such as scanner, printer, hard disk, etc.

·       It can communicate and share information all over the world through Internet.

·       It supports centralized administration.

·       It provides the facility of data and software backup system.

 

Disadvantages of computer network

·       Computer network can be route for computer virus and malware transmission.

·       Skilled manpower is required to manage and operate computer network.

·       The initial setup cost is very high to build computer network.

·       Cybercrimes are originated from computer network.

Basic Elements of the Network

Physical parts and devices used to connect computers in the network environment are called hardware components.

The hardware components of computer network are computer set, modem, hub, NIC card, bridge, repeater, etc.

The software elements are NOS, Protocol and Device Driver

 

NIC Card (Network Interface Card)
A Network Interface Card (NIC) is the hardware component through which the computer is connected to the network.

The function of NIC is to control flow of data to and from computers in network environment.

 

Connector
Connector is a device that facilitates the connection of computers and other device to a network.

Examples of connectors are BNC used with coaxial cable, RJ 45 used with UTP cable, ST used with fiber optic cable etc.

 

Hub

Hub is a network connectivity device with multiple ports for connecting different computers on network.

It broadcasts all network data across each connection.

Hub is mostly used in physical star topology.

 

 

 

Switch
Switch is a network connectivity device which joins multiple computers together to share information among them.

The selected computer can get information through switch.

It works faster than hub.

 

Hub Vs Switch

Hub

Switch

It is cheaper than switch.

It is more expensive than hub.

It transmits data slower than switch.

It transmits data faster than hub.

It broadcasts the information packets to

all computer connected network.

It transfers packets to only those selected

computers connected in network.

It has 4 / 12 ports

It has 24 to 48 ports

 

Bridge

Bridge is a network connectivity device that interconnects two computer networks having similar protocol.

It inspects incoming signals and decides whether to forward or discard it.

 

Router
Router is a network connectivity device that joins multiple wired or wireless networks together.

It also inspects and forwards data among different networks having similar protocol like bridge.

It is an intelligent device that has ability to determine the best possible path for data transmission.

Gateway
Gateway is a network connectivity device that interconnects two networks having dissimilar communication protocols.

 

Repeater
Repeater is a network connectivity device that accepts weak signals and regenerates

them and after that sends the message on their way.

It makes possible for long-distance

data transfer. So it boosts the data signals that are received from network.

 

MODEM (Modulator and Demodulator)

MODEM is a device which is used to transfer the data of one computer to another computer using telephone lines.

 

Importance of MODEM [ 2071 S] 2073 U]

MODEM modulates the digital codes of the computer into analog signal, which then can travel through the telephone cable.

At the receiving end the MODEM kept there will demodulate the analog signal to digital codes, which can be then understood and used by the receiving computer.

 

Modulation

The process of translating digital signals of a computer to analog signals, which are then transmitted across the standard telephone lines, is known as modulation.

Demodulation

The process of translating analog signals from a phone line and converts then into digital signals for the computer is known as demodulation.

 

Bandwidth
The amount of data that can be carried from one point to another in a given time period is called bandwidth.

We can measure bandwidth in digital devices by bits per second (bps) and in analogue devices by cycles per second (cps) or Hertz (Hz).

 

Network operating system (NOS)

Network operating system is a software which control and manages computer network.

E.g. Novell Netware, Windows NT, Linux, Unix etc. The main functions of NOS are:

·        It enables users to have access to network resources.

·        It manages and controls all the resources of computer network.

 

Protocol [MFT 2075]
A set of rules followed for interconnection and communication between computers in a network is called a protocol.

Some common protocols are as follows:

·        TCP/IP (Transmission Control Protocol/Internet Protocol) is used in Internet.

·        HTTP (Hypertext Transfer Protocol) is used to transfer HTML documents in

·        WWW.

·        SMTP (Simple Mail Transfer Protocol) is used in sending e-mail.

·        POP (Post Office Protocol) is used to retrieve e-mail from a mail server.

·        FTP (File Transfer Protocol) is used to transmitting files between computers.

Device driver

Device driver is a program that controls the functionality of the hardware device.

Types of Network

a)     LAN (Local Area Network)

b)     MAN (Metropolitan Area Network)

c)     WAN (Wide Area Network)

 

LAN (Local Area Network)

Local Area Network is a network that connects a group of computers in a small geographical area like a room, a building, school, etc.

Computer in LAN can be connected through wireless media and is referred to as WLAN (Wireless Local Area Network).

Computer lab networking and cyber networking are examples of LAN.

 

Features of LAN

·        It can cover up to one kilometre for transferring data and information between the computers.

·        It is normally owned by single organizations.

·        It has high speed data transfer capacity than MAN and WAN.

·        LAN supports a variety of communications transmission medium such as an Ethernet

cable (thin cable, thick cable, and twisted pair), fiber and wireless transmission.

 

MAN (Metropolitan Area Network)

Metropolitan Area Network (MAN) is a network of computer spread over a city or town located in the same geographical area

It is used in medium size organization having various branches within city or valley.

Cable TV network and branches of banks are examples of MAN.

 

 

Features of MAN

·       It can cover up to fifty kilometre for transferring data and information between the computers.

·       It is normally owned by single or multiple organizations.

·       It has high speed data transfer capacity than WAN and is slower than LAN.

·       Fiber optical cable and twisted pair cables are used for connectivity for communication through MAN networks.

 

WAN (Wide Area Network)

A wide area network (WAN) is a computer network that covers a large geographical area comprising a region, a country, a continent or even the whole world

It is the largest computer network.

Internet, 4G Mobile Broadband Systems and satellite communication are the best examples of WAN.

 

Features of WAN (Wide Area Network)

·       It covers the whole world and cannot be restricted to any geographical location.

·       It is normally owned by multiple organizations.

·       They have low data transfer rate and have low communication speed.

·       It uses satellite and microwave communication.

 

 

 

 

Network architecture (Models of Computer Network)

Network architecture can be defined as how the computer communicates and interacts with each other on network.

 Its types are

a)     Centralized computing network

b)     Client / Server Network

c)     Peer to Peer Network

 

Centralized network

 

A centralized network is a network in which a central host computer performs data processing and storage on behalf of clients.

The main computer is known as host or server computer.

Workstation is just used for input/output operations, which has no processing capabilities and are connected to server or host computer. Linux or UNIX operating system is used in

centralized network.

 

Client/server network

 

Client/ server network is a type of network model where at least one computer is designed as a server and other computers on the network called clients or workstations.

It provides central security administration and the network administrator is responsible for data security and other resources management of the network.

 

 

Peer-to-peer network


Peer-to-Peer network is a type of network model where all the computers have equal responsibilities on the network.

It lacks centralized network administration, where the network administrator needs to manage security on each computer.

It provides no reliable security and might put data in higher risks.

 

Server

A server is the main computer that provides services, data and other resources to the other computers in the network environment.

 

Workstation
A computer on a network that uses resources of the network is called workstation.

 

Node
Each computer or device of network is called node.

 

Network topology (LAN topology)
Network topology is the cabling structure of interconnected computers in LAN.

The three basic topologies are bus topology, ring topology and star topology

 

Bus topology
The network topology in which nodes and network devices are connected to a single cable is called bus topology.

 

Advantages of bus topology

a)     It is cost effective and cable required is least compared to other network topology.

b)     It is easy to expand network.

 

Disadvantages of bus topology

a)     Break/Failure in main cable will make the whole network to malfunction (failure).

b)     Heavy network traffic or increase in nodes will degrade performance of network.

 

Diagram of bus topology

 

 

Ring topology [MF 2076]

A ring topology is a network topology where all the nodes on the network are connected to each other in the form of ring or circle without any end points.

The method by which data is transmitted around the ring is called token passing.

 

 

 

Advantages of ring topology

·       Each computer gets equal opportunity to access the network resources.

·       Transmitting network is not affected by high traffic or by adding more nodes.

 

Disadvantages of ring topology

·       Adding or deleting the computers disturbs the network activity.

·       Failure of one computer disturbs the whole network in this topology.

 

Diagram of ring topology

Image result for ring topology

 

Star topology

The network topology which connects all nodes to central device called hub/switch through a cable is called star topology.

 

Advantages of star topology

·       It provides fast performance and low network traffic.

·       The failure of one node does not affect the rest of the nodes.

 

Disadvantages of star topology

·       Hub and more wires are required, so the cost of installation is high.

·       The whole network is stopped when the hub fails.

 

Diagram of star topology

 

Image result for star topology

 

 

Internet (Network of Networks)
The internet is the largest computer network that connects millions of computers around the world.

 

Services of internet

a)     WWW (World Wide Web)

b)     E-mail (Electronic mail)

c)     FTP (File Transfer Protocol)

d)     IRC (internet Relay Chat)

e)     Telnet

f)      Search Engine

g)     Online Banking

h)     E-Commerce

 

 

Advantages of internet  

a)     Greater access to information reduces research time.

b)     Global reach enables one to connect to anyone on the internet.

c)     Selling and buying has become so easy with the use of internet and it has helped millions to sell and buy their goods online.

d)     Easy communication with other people.

 

Disadvantages of internet

a)      Computer viruses get downloaded and spread across machines connected to networks and have harmful effects.

b)     People using too much of internet get disconnected from the real world. 

c)     Pornography can get in the hands of young children too easily.

d)     Cyber frauds may take place involving Credit/Debit card numbers and details.

 

Intranet

An intranet is a private computer network that uses the internet protocol to securely share any part of information of an organization.

It is owned by a single organization or company.

It can only be used by the employees of the owned organization.

 

Extranet

An extranet is a private network that uses internet technology and the public telecommunication system to connect more than one organization.

ISP (Internet Service Provider) 
An Internet service provider (ISP) is an organization that provides services for accessing and using the Internet.

World Link, Mercantile, Classitech, Vianet etc are the ISPs of Nepal.

 

E-mail (Electronic Mail) [SLC 2068 S] [SLC 2069 S] [SEE 2075 S2] [MM 2076] [MFT 2075]
E-mail (Electronic mail) is one of the most popular services provided by the internet sends and receives messages electronically through the Internet.

E.g. xyz@gmail.com

Any four sites that provide e-mail services are:

a)     www.yahoomail.com

b)     www.hotmail.com

c)     www.gmail.com

d)     www.outlook.com

 

Advantages of E-mail

·       It is the cheapest and fastest means of communication.

·       It is more reliable than postal mail.

·       E-mail can be accessed from any part of the world at any time.

·       Information can be shared globally.

·       We can send photos, songs, video clips and other file with e-mail attachments.

·       A single mail can be sent to multiple people at a time.

 

 

Disadvantages of e-mail

·        The recipient needs access to the internet to receive email.

·        Viruses are easily spread though email attachments.

 

Telnet
Telnet is the facility of Internet that allows user to use a remote computer through Internet.

FTP (File Transfer Protocol)
File Transfer Protocol (FTP) is transmission files between computers on the Internet.

File Transfer protocol helps to transfer (download or upload) files from one computer to another computer.

 

Uploading
Ans: Uploading refers to copying files or documents, programs or data from the user’s computer to the internet server.

Downloading
Downloading refers to the copying files or document or program or data from the internet server to the user’s computer.

 

Web browser
Web browser is a computer program that access web pages and displays them on the user’s computer.

Examples of web browsers are Mozilla Firefox, Google chrome, Internet Explorer, opera etc. Browsing/ Surfing means searching information on the internet.

Search engine [SEE 2074 U] [SQE 2075K]
A search engine is a service of internet that helps allows the users to find the information on the World Wide Web using keywords or phrases.

Examples of search engines are Google, Bing, Yahoo etc

 

Full Forms

NCC - National Computer Center

EDP - Electronic Data Processing Center

RJ-45 – Registered Jack 45

UTP - Unshielded Twisted Pair

Mbps - Megabits per second

STP - Shielded Twisted Pair

EMI- Electromagnetic Interference

BNC – British Naval Connector

ISP – Internet Service Provider

ST – Straight Tip Connector

SMA – Screw Mounted Adaptor

SC – Subscriber Connector

FM – Frequency Modulation

AM – Amplitude Modulation

PM – Phase Modulation

NOS – Network Operating System

NIC – Network Interface Card

LAN – Local Area Network

IP – Internet Protocol

MODEM – Modulator and Demodulator

bps – bits per second

NCP – Network Control Protocol

TCP/IP - Transmission Control Protocol/Internet Protocol

HTTP - Hypertext Transfer Protocol

SMTP – Simple Mail Transfer Protocol

POP – Post Office Protocol

FTP – File Transfer Protocol

MAN -Metropolitan Area Network

WAN - Wide Area Network

WLAN - Wireless Local Area Network

IPOS - Input Process Output System

ARPANET - Advanced Research Projects Agency Network

WWW – World Wide Web

URL – Uniform Resource Locator

E-mail – Electronic Mail

IRC – Internet Relay Chat

B2B - Business to Business

B2C - Business to Customer

C2C – Customer to Customer

C2B - Customer to Business

ATM – Automated Teller Machine

E-Commerce – Electronic Commerce

E- fax – Electronic Fax

FAQ – Frequently Asked Questions

SIM - Subscriber Identity Module

eSIM – embedded - Subscriber Identity Module

MDMS – Mobile Device Management System

Wi-Fi – Wireless Fidelity

ADSL - Asymmetric Digital Subscriber Line

CCTV - Closed Circuit Television

CDMA - Code Division Multiple Access

IPX/SPX - Internetwork Packet Exchange/ Sequenced Packet Exchange

DTH - Direct To Home

GSM - Global System for Mobile Communications

Teachers can open the door, but you must enter it yourself.

 

No comments:

Post a Comment