1. Networking and Telecommunication

Unit 1: Networking and telecommunication

Communication and its modes and components

Communication: The process of exchanging message between sender and receiver through any medium using definite rule is called communication. If communication is done on a longer distance, then it is called tele communication.

Data communication: The process of exchanging data and information between several electronic means and media through any medium using definite rule(protocol) is called data communication.

Components/Elements of communication

Sender
Receiver
Medium
Data
Protocol: The set of rules through communication takes place.

Modes of communication:

Simplex: Only sender sends information, receiver only receive the message. It is one way communication. E.g., Television, radio
Half duplex: Sender sends the data while receiver receive the data and vice-versa. It is the two-way communication but one at a time E.g., Walkie-Talkie
Full duplex: It is two-way communication in which sender and receiver both can send and receive information at same time. E.g., mobile communication.

Computer Network and its pros and cons

Computer network: A group of computers interconnected with each other through any medium using definite protocol (rule) for the purpose of sharing data, information, hardware, software and other resources. Services provided by the computer network.

Data sharing
Print service
File service
Database service
Application service

Advantages/merits/pros/benefits/importance of computer network.

It allows several user computers to share data and information.
Expensive hardware like printer, scanner, fax can be shared in a network.
Application programs and software can be shared in a network.
We can easily communicate in real time i.e., faster communication.
Easy to collect data through centrally located server.

Disadvantages/de-merits/cons/limitations of computer network.

Skilled manpower required to install and operate a network.
Expensive to install and operate.
There may be security and privacy issue due to sharing.
Virus and malware may be share in a network.

Transmission media and its types

Communication media/Transmission media/Communication channel

The medium through which data, information is transmitted from on point to another point in the form of signals are called transmission media. There are two types of transmission media.

A) Wired/bounded/guided media: The transmission media in which data are transmitted physically through cables or wire following a specified path.

a. Twisted pair: Wire are twisted with each other to reduce EMI (Electro Magnetic Interference).

UTP (Unshielded Twisted Pair): Inner pair of twisted cable are not covered/unshielded with outer jacket. Hence, it has more EMI.
STP (Shielded Twisted Pair): Inner pair of twisted cable are covered/shielded with outer jacket. Hence, it has less EMI.

b. Co-axial cable: This cable has higher bandwidth so; they are used in television broadcasting.

c. Fibre optics: These types of cable are made up with thin glass like material where data are transmitted in the form of photons(light). They have high data transmission rate.

Media connector:

Twisted pair use RJ-45
Co-axial cable use BNC
Fibre optics cable use ST-connector

B) Wireless/unbounded/unguided media: The transmission media in which data are not restricted to travel in a closed path rather it can travel in open air. There is no any physical connection between communicating device hence, called wireless.

a. Microwave: Sender and receiver station must be in same line of sight (LOS). They cannot penetrate obstacle. Used for longer distance transmission. Satellite use microwave signal to uplink and downlink data from and to earth.

b. Radio wave: Sender and receiver station may not be in same line of sight (LOS). They can penetrate obstacle. Used by FM station and other local communicating stations.

c. Infrared: It use invisible red ray of light of electromagnetic spectrum for communication purpose. E.g., television remotes, AC remote and many more.

Types of Computer network

Types of networks

LAN: It stands for Local Area Network which connect device in smaller locations such as room, building, organization etc. It is suitable of single organization. It generally uses guided media to connect devices.
MAN: It stands for Metropolitan Area Network which can connect devices in larger geographical area such as town, city, village etc. It consists or two or more than two LANs. It uses wired as well as wireless media for connecting devices.
WAN: It stands for Wide Area Network which is set in a larger geographical area across city, nation and even ocean. It is can be used by multiple organization. Internet is the example of WAN, which is a public network across all around the world. They use wireless media for communication.

Network architecture:

Client-server: In this type of architecture the devices in a network are connected to the centrally located main computer of a network called server. User computers are called client. It provides more security and control in a network. Server allows to mobilize all the resources available in the network. Easier to collect data in centrally located servers.

Client Server architecture

Peer-to-peer: In this type there is no presence of main computer in a network, rather every computer in a network has right to control and use resources. Every computer in this case is client as well as server. Hence there will be less safety.

Peer to Peer Architecture

Network Models:

Centralized model: This is a client-server model in which all devices of a network are connected to the centrally located main computer.
Distributed model: This is the collection of several client-server model located at different location, all connected to a centrally located server.

Network topology and its types

Network topology: The physical layout, geographical orientation, connection pattern or arrangement of computer or devices (node) in the network is called network topologies. Types:

1) Bus topology: In this topology, all devices in the network are connected to a main single cable called trunk or backbone. It is easy and cheaper to setup. It requires a smaller number of cables and adding new devices in a network is also easy. Whereas, if there is fault in main cable then whole network will collapse. Fault finding is fairly difficult.

Bus Topology

2) Star topology: In this topology, all devices in the network are connected to the centrally located device called hub which allows us to easily expand the network. Fault finding is very easy in this type. Whole network depends upon the hub so, if it fails network will collapse. It is expensive to setup but is most practical among all topologies.

Star Topology

3) Ring topology: In this topology, devices are connected with each other in circular manner each device having equal rights and responsibilities. Failure in one device will collapse whole network. Expanding network is difficult is not practical.

Ring Topology

4) Tree topology: It is the combination of bus and star topology. Whole network depends on main cable and some part depend on hub so it is less reliable.

Tree Topology

5) Mesh topology: In this topology, networking device are point to point connected with each other creating a mesh. If one device fails to work then it will not affect whole network. It is expensive and difficult to setup.

Some important term to remember

a. Bandwidth: The amount of data that can travel in a given transmission medium in unit time is called its bandwidth. It is generally known as data transmission speed and measured in terms of bps (Bit per second)

b. Protocol: The set of rules that guides the communication in the network. It is the language used by computers and electronic devices to communication with each other. For egg,

TCP/IP: Transmission Control Protocol/Internet Protocol
HTTP: Hyper Text Transfer Protocol
FTP: File Transfer Protocol
SMTP: Simple Mail Transfer Protocol
POP: Post Office Protocol
ARP: Address Resolution Protocol

c. Network operating system (NOS): It is the collection of programs that helps to mobilize and manages resources of the network. For e.g., Windows NT, Linux etc

Inter-networking devices/hardware: Devices that are used to establish and expand network are called inter networking devices.

NIC (Network Interface card): It physically connects computer system with transmission cable.
Router: Intelligent device that connects two or more network. It facilitates finding best route for data transmission to destination.
Repeater: Networking device that regenerates or amplifies the incoming signal.
Hub: It is a multi-port repeater.
Bridge: Networking device that connects similar networks.
Gateway: Network device that connects dissimilar networks.
MODEM: Modulator Demodulator transfer analog signal into digital (Modulation) and vice versa (Demodulation)
Multiplexer: It combines multiples incoming signal into one signal and opposite is called de-multiplexer.

Internet and its services

Define Internet? Explain services provided by the internet.

Internet is a network of networks that connects millions of users and device all around the world together using TCP/IP (Transmission Control Protocol / Internet Protocol) and allows to share data and information in-between.

Services provided by the internet.

Email: The way of exchanging mails i.e., message between sender and receiver over internet using unique address (email address) is called email. Advantage of email: Faster, Cheaper, Reliable, always available, Secured
E-commerce: The process of buying and selling goods and services is called e-commerce. E.g., daraz, amazon, alibaba
Telnet: It allows user to login remotely to another user computer.
IRC: Internet relay chat allows user to communicate in real time.
Video conferencing: It allows user to communicate in real time using video and audio signal.

Define web browser? Give some example

The application program which allows user to browse web site from internet are called web browser. It establishes the communication between user and web-server so that user can access content of the web. It uses HTTP (Hyper Text Transfer Protocol) to communicate. E.g., Google chrome, Mozilla Firefox, Opera, Safari, Microsoft edge (Internet Explorer), Netscape navigator.

Differentiate between E-mail and postal service.

Email	Postal service
It is the modern digital way of exchanging information.	It is traditional way of exchanging information.
Use of computers and internet.	Use of papers, post box and post office
It is faster and reliable	It is slower and non-reliable
Recipient not required	Recipient required.
It is always available 365 days a year.	It may not be always available
Highly secured.	Less secured.

Differentiate between intranet and extranet.

Intranet	Extranet
Private network accessible within the organization.	Private network accessible outside of the organization.
They are limited with in organization.	They are extended among its branch.

Some important terminologies:

ISP: Internet Service Provider
SMTP: Simple Mail Transfer Protocol
POP: Post Office Protocol
URL: Uniform Resource Locator
DARPA: Défense Advance Research Project Agency
FTP: File Transfer Protocol
ADSL: Asymmetric Digital Subscriber Line
CDMA: Code Division Multiple Access
Web server: The storage location where every content of website is store.
Home page: The introductory page or landing page of a website.
Search engine: The web application which allows user to search content in WWW by using keyword. E.g., google, Bing.
Downloading: Transferring data and file from web server to user.
Uploading: Transferring data and file from user to web server.