This document provides an overview of computer networks, including: 1) How computer networks allow devices to connect and share resources through wired or wireless connections. Data is divided into packets for transmission. 2) The key components that make up a network including hosts, servers, clients, network hardware, software, and services. 3) An overview of the evolution of computer networking from ARPANET to the modern Internet, and different types of networks classified by span and component roles.

1. Network

2. Computer network
● 2+ anonymous computers connected to one another in order to exchange information or share
resources → computer network.
○ Can be wired or wireless.
○ Advantages:
■ Share resources in a cheap manner [resources : software, storage]by using one printer for
many computers.
■ Improves communication.
■ Cost reduction.
● It includes different types of hosts/nodes like server,desktop,laptop,modem,router,switch
● Connects multiple computers in different settings.
●

3. How is data transferred in a network?
● Data is divided into smaller chunks → packets
● Packets →carried over a network

4. What makes a network
● Hosts/nodes
● Servers
● Client
● Network hardware
● Communication channel
● Software
● Network services

5. 1. Hosts
● Computers attached to that network that are seeking to transfer/share resources.
○ Eg: pc, smartphone, laptop
2. Server
● Very important
● Facilitates sharing and communication among hosts
● In small networks, all the data is stored in the server
● There can be more than one server in a network
● In bigger networks, there are servers for specialised tasks
○ Eg: printer server → handles only printing requests
3. Clients
● A computer which access the service made by the server
4. Network hardware
● Hardware devices to carry out various roles → establishing corrections, controlling network traffic
5. Softwares
● Make network possible
● Comprises of protocols,network os etc
○ Protocols → predecides set of rules using which all parties of a network connect and interact
with one-another.
6 network services
● Provide different functionalities over a network.

6. Evolution of Networking

7. ● ARPANET:
○ Advanced research projects agency
network
○ Sponsored by us department of
defense in 1969.
○ Goal → connect computers at
different universities /research
institution and us defense for
scientific collaboration
○ The users of this system were able
to share information and even play
games on it[long distance]
○ Started small but expanded rapidly.
○ Shutdown in 1990
● Nsfnet
○ Created by a federal agency- national
science foundation
○ Allowed only research on its network
and no private things
○ So many other companies came up
with their own thing which were then
interconnected with arpanet and
nesfnet to give INTERNET.
○ Govt stopped funding in 1995
○ ARPANET + NSFnet+ PRIVATE
NETWORKS → INTERNET
HOW IT ALL STARTED

8. internet
● WORLDWIDE network of computer networks.
● Evolved from arpanet
● Allows users connected to one network communicate with the users connected to another.
● To accomplish the above, a set of common rules must be followed →PROTOCO;S [like: TCP/IP]
➢ HOW DOES INTERNET WORK?
○ Most comps arent connected directly to internet, instead
■ Computer →smaller networks → gateways →internet backbone
○ How is a file transported
■ From source computer →another computer [divides file in packets ]-->packets are numbered
→sent to destination computer [in random order]→packet reassembled and obtained [if
lost,demanded again]
● Protocols followed:
○ Tcp:dvides file into packets in source comp AND in destination comp
reassembles packets to file
○ Ip: handles the address of destination computer to make sure each packet is
routed properly.

9. interspace
● Client-server software program
● Allows multiple users to communicate using real time AUDIO, VIDEO and text chat in 3d
environments.
● Vision of what the internet will become

10. Types of networks
Based on network span or geographical spread:
● PAN
○ Personal area network
○ a network formed by connecting a few personal devices like computers, laptops, mobile phones,
smart phones, printers etc.
○ All these devices lie within an approximate range of 10 metres.
○ may be wired or wireless.
●

11. ● LAN
○ Local area network
○ Small computer networks in a localised area [offic,builing]
○ placed at a limited distance -a single room, a floor, an office having one or more buildings in the
same premise, laboratory, a school, college, or university campus
○ Key purpose → helps in resource sharing of users.
○ They can share a printer,data,information,programs ,modems etc
○ The connectivity is done by means of wires, Ethernet cables, fibre optics, or Wi-Fi
○ provide the short range communication with the high speed data transfer rates
○ extended up to 1 km
○ Data transfer in LAN is quite high, and usually varies from 10 Mbps (called Ethernet) to 1000
Mbps (called Gigabit Ethernet), where Mbps
Ethernet is a set of rules that decides
how computers and other devices
connect with each other through cables
in a local area network

12. ● MAN
○ Metropolitan area network
○ Extended form of lan→ covers city/town
○ Data transfer rate in MAN also ranges in Mbps
○ it is considerably less as compared to LAN.
○ Cable TV network or cable based broadband internet services are examples of MAN.
○ This kind of network can be extended up to 30-40 km.
○ Sometimes, many LANs are connected together to form MAN,

13. ● WAN
○ Wide area network
○ which are spread across different geographical locations of a country or in different countries or
continents.
○ A WAN could be formed by connecting a LAN to other LANs (Figure 10.7) via wired/wireless
media.
○ large business, educational and government organisations connect their different branches in
different locations across the world through WAN
○ The Internet is the largest WAN
○ Fast , cost effective
Lan is cheaper
than wan

14. Types of network by component role
● Client-server network [master-slave
network]
○ A bigger network, have centralised
control
○ Clear designation of servers and
clients.
○ The server here only does the work
of a server, hence called dedicated
server.
○ Each resource access or sharing has
each server, they only do their
specific jobs.
○ Client is dependant ont he server to
provide and manage information.
○ Data is backed up int he main server.
● Peer-to-peer
○ The computers a part of the network →
peers
○ P2p network, theres no designated role for
each peer, they can either be servers or
clients
○ They control their own information and play
roles accordingly.
○ These computers are also called → non
dedicated servers [not completely
dedicated to serving]
○ Slower, needs more memory,a smaller
network
○ Typical p2p has about 10 computers.
○ Each computer has to be backed up.

15. Switching technologies (methods to connect)
● Circuit switching
○ First, physical connection is made → data is
transferred
○ All packets follow the same path established
during the connection
○ Property is to set up an end-to-end path between
computers.
● Packet switching
○ each information or message to be transmitted
between sender and receiver is broken down into
smaller pieces, called packets
○ These packets are then transmitted independently
through the network.
○ Only a fixed size of packet can be transmitted
○ All packets are stored int he main memory unlike
message switching.
○ Improves performance as access time is reduced
○ Each packet has two parts — a header containing the
address of the destination and other information, and
the main message part
● message switching
○ the sender and receiver are not directly
connected.
○ There are a number of intermediate
nodes that transfer data and ensure
that the message reaches its
destination.
○ Also called Store and forward
○ No limit on block size
Difference b/w them

16. Measuring Capacity of Communication
Media
the transmission medium is also known as channel. The capacity of a channel is the maximum amount of
signals or traffic that a channel can carry.
measured in terms of bandwidth
Bandwidth
● bandwidth is the difference of maximum and minimum frequency contained in the composite signals.
Bandwidth is measured in Hertz (Hz)
● Higher the bandwidth, higher the data transfer rate.
Speed of transmission of data : bps [bits per second] or baud or Bps [bytes]

17. Transmission Media
● A transmission medium can be anything that can carry signals or data between the source (transmitter)
and destination (receiver).
○ we switch on a ceiling fan or a light bulb, the electric wire is the medium that carries electric
current from switch to the fan or bulb.
● Transmission can be classified as guided or unguided.
○ guided transmission, there is a physical link made of wire/cable through which data in terms of
signals are propagated between the nodes.
■ They are also known as wired media.
○ unguided transmission, data travels in air in terms of electromagnetic waves using an antenna.
They are also known as wireless media.
■ Dish-shaped antennas are used for sending and receiving data at longer distances
■ Waves gradually become weaker and weaker after travelling a certain distance through the
air. Therefore repeaters are installed to regenerate the signals of the same energy