computer chapter for 10th graders

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