1. Unit-3: Introduction to computer networks
1. Computer Network:
- It is a collection of interconnected computers and other devices which are
able to communicate with each other and share hardware and software
resources.
Advantages:
1. Resource Sharing
2. Collaborative User Interaction/Communication Medium
3. Cost Saving
4. Time Saving
5. Increased Storage
2. Types of Networks
a. PAN- Personal Area Network
b. LAN- Local Area Network
c. MAN- Metropolitan Area Network
d. WAN- Wide Area Network
2. • PAN
A PAN is a Network of communicating devices (Computer, Phone, MP3 players, etc) in the
proximity of an individual. It can cover an area of a few meters radius
• LAN
A LAN is a network of computing/communicating devices in a room, building, or campus. It can
cover an area of a few meters to few kilometres radius.
A LAN can be set up using wired(UTP cables, Co-axial cables etc..) or Wireless medium (Infrared,
radio waves…).
• MAN
A MAN is a network of computing/communicating devices with in a city. It can cover an area of a
few kilometres to a few hundred kilometres radius
• WAN
A WAN is a network of computing/communicating devices crossing the limits of a city, country, or
continent. It can cover an area of over hundreds of kilometre radius.
6. 1. Network Interface Card (NIC)
-> It is a device that enables a computer to connect to a network and communication.
-> NIC allows both wired and wireless communications.
-> NIC allows communications between computers connected via local area network
(LAN) as well as communications over large-scale network through Internet Protocol
(IP).
-> NIC is both a physical layer and a data link layer device, i.e. it provides the
necessary hardware circuitry so that the physical layer processes and some data link
layer processes can run on it.
• Internal Network Cards
In internal networks cards, motherboard has a slot for the network card where it can be inserted. It
requires network cables to provide network access.
• External Network Cards
In desktops and laptops that do not have an internal NIC, external NICs are used. External network
cards are of two types: Wireless and USB based. Wireless network card needs to be inserted into the
motherboard, however no network cable is required to connect to the network. They are useful while
traveling or accessing a wireless signal.
7. Internal Network Cards
External Network Cards
2. Hub
. A Hub is an electronic device that connects several nodes to form a network and redirects that received
information to all the connected nodes in broadcast mode.
. Hubs usually can supports 8, 12, or 24 ports.
8. 3. Switch
A Switch is a device that is used to segment networks into different subnetworks called subnets or
LAN subnets
The Main difference between Hub and Switch
Hub Replicates what it receives on one port onto all the other ports while switch keeps a record of the
MAC Addresses (media access control address) of the devices attached to it
9. 4. Gateway
A Gateway is a device, which is used to connect different types of networks and perform the
necessary translation so that the connected networks can communicates
10. 4. Repeater
Repeater is a device that is used to regenerate a signal which is on its way through a
communication channel, a network device that amplifies and restores signals for long distance
transmission
5. Bridge
A bridge is device, which is used to connect two LAN or two Segments of same LAN
11. 6. Router
A router is a network device that connects multiple networks irrespective of their protocol.
Difference between Bridge and Router
1. A bridge cannot handle multiple protocols where as router can.
2. A bridge works with MAC Address where as a router works with IP Address.
12. Network Topologies
The Pattern of interconnection of nodes in a network is called topology
facts:
1. Cost
2. Flexibility
3. Reliability
13. • Point to Point Topology
Point-to-Point Topology is a type of topology that works on the functionality of the sender and
receiver. It is the simplest communication between two nodes, in which one is the sender and the
other one is the receiver. Point-to-Point provides high bandwidth.
• Bus/Linear topology
Bus Topology is a network type in which every computer and network device is connected to a
single cable. It is bi-directional. It is a multi-point connection and a non-robust topology because
if the backbone fails the topology crashes
14. • Ring topology
In a Ring Topology, it forms a ring connecting devices with exactly two neighboring devices.
A number of repeaters are used for Ring topology with a large number of nodes, because if
someone wants to send some data to the last node in the ring topology with 100 nodes, then the
data will have to pass through 99 nodes to reach the 100th node. Hence to prevent data loss
repeaters are used in the network.
The data flows in one direction, i.e. it is unidirectional, but it can be made bidirectional by having 2
connections between each Network Node, it is called Dual Ring Topology. In-Ring Topology, the
Token Ring Passing protocol is used by the workstations to transmit the data
Token passing: It is a network access method in which a token is passed from one node to another
node.
Token: It is a frame that circulates around the network.
15. • Star Topology
In Star Topology, all the devices are connected to a single hub through a cable. This hub
is the central node and all other nodes are connected to the central node.
The hub can be passive in nature i.e., not an intelligent hub such as broadcasting devices.
At the same time the hub can be intelligent known as an active hub. Active hubs have
repeaters in them.
16. • Tree Topology
It is combination of bus topology to different topology.
If one network fails the other networks remain connected and working.
17. • Mesh Topology
In a mesh topology, every device is connected to another device via a particular channel.
It is Excellent for long distance networking because it provides extensive back-up,
rerouting as pass-through capabilities.
• Hybrid Topology
This topological technology is the combination of all the various types of topologies
This topology is very flexible.
The size of the network can be easily expanded by adding new devices.
18. INTERNET (INTerconnection NETwork)
• It’s a Network across the world to share information and communication.
• The first computer network is ARPANET (Advanced Research Projects Agency NETwork)
• Protocol: It is common language for the computers attached to the physical network.
1. IP(Internet Protocol)
The Internet Protocol (IP) is a protocol, or set of rules, for routing and addressing packets of data
so that they can travel across networks and arrive at the correct destination. Data traversing the
Internet is divided into smaller pieces, called packets.
2. TCP (Transmission Control Protocol)
It is a communications standard that enables application programs and computing
devices to exchange messages over a network. It is designed to send packets across the
internet and ensure the successful delivery of data and messages over networks.
19. Interspace:
It is a software that allows multiple users in a client-server environment to communicate with each other to
send and receive data of various types such as data files/ audio/video…..
Example:- Teams, Zoom, Google Meet….
Services available in the internet:
E-Mail
Web enabled audio/video
Online conferencing services
Data Transfer
Social networking
Online Shopping
Financial Serices
Etc…
20. • Intranet: It is a small private network with limited users and limited services.
Internet Applications
Web
E-mail
Chat
VoIP(Voice over Internet Protocol)
1. Web
• WWW (World Wide Web) which also know as Web.
• WWW is a collection of websites or webpages stored in webservers and connected to local
computers through internet.
• WWW defined three fundamental technologies that lead to creation of web.
A. HTML (Hypertext markup language)
B. URL (Universal Resource Locator)
C. HTTP (Hypertext transfer protocol)
21. a. HTML
IT is a standard markup language which is used for creating web pages.
This describes the structure of web pages through HTML elements or tags.
b. URL
URL identifies a resource (hardware/software) either by its location or by its name or both.
22. • Protocol/Scheme
This identifies type of protocol and URL.
http stands for Hyper Text Transfer Protocol,
ftp for File Transfer Protocol,
https for security-enhanced version of Hypertext Transfer Protocol (http), Hyper Text
Transfer Protocol Secure.
Ex:- http:// or https:// or ftp://
• Domain Name / Host Address
The host address is where a website can be found.
• Resource name / file path
The file path always begins with a forward slash character.
There are 2 types of URLs
1. Absolute URL
An Absolute URL is the complete address of a resource
example:- https://www.britannica.com/technology/computer
2.Relative URL
A relative URL indicates where the resource is in relation to the current page
example:- http://computer
23. c. http
The Hypertext Transfer Protocol (HTTP) is the foundation of the World Wide Web, and is
used to load webpages using hypertext links.
HTTP is an application layer protocol designed to transfer information between networked
devices and runs on top of other layers of the network protocol stack.
http are 3 basic features
1. http is connectionless
The client/server knows about each other during current request and response only.
2. http is media independent
Any type of data can be sent by http
3. http is stateless
The client/server is aware of each other only during a current request. Later both of them forget each
other.
24. 2. E-Mail (Electronic Mail)
E-mail is used to send or receive the message like text, image, audio, video..
E-mail Domains are :- google (gmail), yahoo (yahoomail),Microsoft (outlook)
example:- xyz@gmail.com, abc@yahoo.com …
here, com:- commercial
Customized business email address ex:- pqr@SCTSmarthahalli.com
3. Chat
Chatting or Instant Message(IM)is a form where multiple people connect to each other, to
discuss their common interests.
Text, audio call, video call… all the chats done by group or one to one.
Example:- Whatsapp, FB, Messenger, google talk, skype,
4. VoIP: Voice over Internet Protocol
a. VoIP allows us to have voice call (telephone service) over the Internet.
b. It is also known as Internet telephony or Broadband Telephony
c. VoIP works on the principle of converting the analog voice signals into digital signals and then
transmitting them over the broadband line.
25. Website:
• A Website is a collection of webpages
• A visitor navigates from one page to other page by clicking on Hyperlinks.
• The common purposes for web sites
1. Selling products and delivering services
2. Posting and finding information on the internet
3. Communicating with each other
4.Entertainment purposes
5. Disseminating contents and software.
• Components of a webpage
a. Content
b. Structure
27. • Structure:
1. Page title
2. Header
3. Body of web page
4. Footer
5. Navigational links.
Website Vs Webpage
28. • Types of Websites
1. Static Website
2. Dynamic Website
Static Website Dynamic Website
Prebuilt content is same every time the
page is loaded
Content is generated quickly and changes
regularly
It uses the HTML code for developing a
website
It uses the server side language such as
PHP (Pre Processor Hypertext), SERVLET,
JSP (Java Server Pages) and ASP, NET for
developing websites
It sends exactly the same response for
every request
It may generate different HTML for each
of the request.
The content is only changed when
someone publishes and updates the file
The Page contain server-side code which
allows the server to generate the unique
content when page is loaded
Flexibility is the main advantage of static
website
Content Management System(CMS) is the
main advantage of dynamic website.
29. Web Server
• A Web Server is used to store and deliver the contents of a website to clients such as a browser
that request it.
• A Web Server can be software or hardware.
• The Server needs to be connected to the Internet so that its contents can be made accessible to
others.
• The Main job of Web Server is to display the website content.
• If a Web Server is not exposed to the public and is used internally , then it is called Intranet
Server.
• A Web Server whether it is a local server or a could server when connected to the Internet is
assigned a unique numeric address on the Internet called IP Address.
30. Web Hosting:
• Web Hosting is a service that allows web server applications (website or web page) on a
computer system through which web browser client can have easy access to electronic content on
the Internet., Storage is depends on host and cost.
• Types of Web hosting services
1. Free Hosting: -
Host is free of cost,
Unlimited time.
2. Virtual or Shared Hosting:-
Host is shared many websites or many clients with licence,
Limited or unlimited time
3. Dedicated Hosting: -
Host is Rented or Sell with licence,
Limited or unlimited time.
4. Co-location Hosting:-
Hosting is place own web server on the premises of a server provider,
unlimited time.
31. Web Browser:
• A browser is a software application that helps us to view the data or information that is retrieved from
various web servers on the Internet.
• The First browser Mosaic used to support HTML documents containing plain text(static Website) only.
• Ex:- Apple Safari, Google, Mozilla Firefox, Opera…etc
1. Browser Setting:
a. Google Chrome settings:
i. Setting the default browser:- Go to settings and click the “Make Google Chrome My Default
Browser” button.
ii. Auto download updates: - The update process happen in the background and don’t require any
action
iii. Block unwanted pop-ups: -Go to settings > Advanced > Content settings.
iv. Do not save passwords:- Go to settings > Passwords and turn off “offer to save password”.
v. JavaScript:- Go to Settings > Advanced > Content Settings > JavaScript and turn on “Allowed”.
vi. Handling cookies:- Go to settings > Advanced > Content settings > Cookies > and turn on
“Allow” to save and read cookie data and block third party cookies.
vii. Make Flash ask for permission:- Go to settings > Advanced > Content Settings > Flash > and
turn on “Ask first”.
viii. Automatic Downloads: - Go to settings > Advanced > Content Settings > Automatic
downloads and turn on “Ask when a site tries to download files after the first file”
32. b. Mozilla Firefox:
i. Homepage, font and color, downloads :- //option/general
ii. Search bar and search engine: - //option/search
iii. Forms, Passwords, history, cookies, security: - //option/privacy and security
iv. Firefox account: - //option/Firefox account
2. Cookies
a. Cookies are small text files stored on a user’s computer and create and used by websites to
remember basic information or to record the user’s browsing activity.
b. Enable are disable cookies through browser settings
c. cookies are usually harmless
d. It is the browser on our computer which stores and manages the cookies.
e. Viruses can also be tricked as cookies and cause harm to a computer.
