This might help the students of Nepal who are or will sit for SLC exam.

1. Networking and Telecommunication

2. Networking and Telecommunication

3. Networking and Telecommunication
Simplex Communication

4. Networking and Telecommunication
• The transferring of information at a far distance is known as
telecommunication.
• Basically, the communication can be two way (Duplex) or one
way (simplex).
• In a half duplex (HDX) transmission, a data packet is sent by
one system and received by the other. Another data packet
cannot be sent until the receiving system sends an
acknowledgement back to the sender.
• In a full duplex (FDX) transmission, both the sending and
receiving systems communicate with each other
simultaneously.
• Simplex is a communications mode in which only one signal is
transmitted.

5. Networking and Telecommunication
• The transmission of data or information using
computers is known as data communication.
• A communication system has Sender, Medium
and Receiver.
• Sender: A device which creates and send
message.
• Medium: which carries the message. (cables,
satellites links)
• Receiver: A device which receivers.

6. • Bits: It’s a contraction of two Binary Digit. It is a
smallest measurement unit in computer system.
It used in measuring the (digital) speed and
storage capacity.
• Bandwidth: The capacity to handle the data in
communication system is known as Bandwidth.
More bandwidth more speed.
• The bandwidth of digital device is measured in bit
or higher unit.
• The bandwidth of analog device is measured in
hertz.

7. Networking and Telecommunication
Bits: Contraction of two words Binary Digits.
It is a measuring unit of speed/storage.
Bandwidth: The capacity of handling data in
communication system is called bandwidth.
The amount of data transmitted per second is
called bandwidth. The bandwidth is measured
in BPS in digital device and in hertz (Hz) or
KHz.

8. Computer Network: What is it?

9. Computer Network:
An interconnection of two or more computers by means of
transmission media like cables or without cables in order to
communicate and share resources is known as computer
network.
In a computer network there may be one or more servers
and client computers.
Server:
A server is a computer that provides services like sharing of
data or information and resources.
Client/Workstation:
A client is a computer that requests for services like sharing
of data or information and resources.

11. Advantages of Computer Network
• Hardware sharing: Printer, scanner, fax-machine, CD-drive, hard disk
– Economical
– Reduction of cost
• Data and software sharing
– Economical
– Reduction of cost
• Access to remote database
– Helpful for banks, offices
• Transferring and communication facilities
– Send or receive messages
• Security and reliability
– Two servers (primary and secondary domain). If it is deleted from one then it
can be obtained from other
• Cost factor
– Reduction of cost

12. • Domain names are used to identify one or more IP addresses. For
example, the domain name microsoft.com represents about a
dozen IP addresses. Domain names are used in URLs to identify
particular Web pages. For example, in the URL
http://www.pcwebopedia.com/index.html, the domain name is
pcwebopedia.com.
• Every domain name has a suffix that indicates which top level
domain (TLD) it belongs to. There are only a limited number of such
domains. For example:
• gov - Government agencies
• edu - Educational institutions
• org - Organizations (nonprofit)
• mil - Militarycom - commercial business
• net - Network organizations
• ca - Canada
• th - Thailand

13. • The primary name (domain) server is the first server
used for information about a domain as well as the
location of resources associated with a domain. The
information stored on the primary and secondary
name servers is exactly the same. The primary server
acts as the master of information control while the
secondary name server periodically copies primary
server information.
• The secondary name (domain) server is like a back up
system to the primary name server in case the primary
server is too busy or is not able to give a response. It
has become common Internet protocol to require 2
name servers for each domain. It's always good to have
a backup!

14. Networking Devices

15. Server

16. Workstation

17. Networking Components
• Basic components required for a simple
network:
A) Server
B) Workstation
C) Network Interface Card (NIC)
D) Communication Channel or Transmission
channel.

18. Server
– A computer that
controls and
provides the
services of
sharing data,
software and
hardware
resources to the
other computers
on the network
is called server

19. • A dedicated server is a single computer in
a network reserved for serving the needs of the
network. For example, some networks require
that one computer be set aside to manage
communications between all the other
computers
• A dedicated server is a server whose only job is to
help workstations access data, software and
hardware. It does not double up as a workstation.
• A non-dedicated server acts as a server as well as
a workstation.

20. • File server: Shares storage devices, determines
their privileges and regulates their storage.
• Print server: Shares printer; executes the task
on First Come First Out (FIFO).
• Modem server: Shares modem, helps to
download requested pages and send or
receives messages.

21. • Workstation/Client
is computer on a
network that
requests for data,
software and
resources from the
server.
• Windows 95, 98,
NT etc are the
operating system

22. Network Adapter
• It is circuit board that connects
computer with a network cable.
• It commonly known as Network
Interface Card (NIC).
• Can be twisted or co-axial cable
• Has a unique address for
identification.
• Node is a network junction or
connecting point. A node can be
terminal, hub, computer or
switch.
• Terminal: An I/O device for a
computer that has a keyboard,
mouse and monitor

23. Transmission Media (Communication Channel)
• The physical path through which data flow on a
network is called transmission media.
• The data is transmitted in the form of
electromagnetic wave.
• It can transmit through cables, air, vacuum
• The data transmitted can be digital or analog.
• The transmission media can be bounded or
unbounded.

24. Bounded Transmission Media
• The transmission media which use cables are
called bounded transmission media.
• A computer network which uses bounded
media is called wired network.
• It has a limited mobility which means it can’t
be moved easily from place to another.
• There three types of cables used in wired
network.

25. Types of cables
• Twisted pair cable (Shielded and Unshielded)
• Co-axial cable
• Fiber optic cable

26. Twisted pair cable
• It consist of pair of insulated (does not conduct
electricity) copper wires.
• It can be in a pair of 1, 2, 4 or more.
• Mostly used in computer network.
• There are two types of twisted pair cable.
• The are:
– Unshielded twisted pair cable
– Shielded twisted pair cable

27. Unshielded Twisted pair cable
• It consist of pair of insulated (does
not conduct electricity) copper wires.
• It has a simple plastic casing
• Similar to telephone wire but has
high transmission of data
• Cheaper than shielded twisted pair
• No good protection from interference
• The data transfer rate is 10 to 100
Mbps (millions of bits per seconds).
• Widely used in LAN.
• Category 5 and 6 of UTP is widely
used

28. Shielded Twisted pair cable
• Similar to UTP but has a metallic
covering underneath the plastic
cover.
• More expensive than UTP
• STP offers better protection from
interference.
• The data transfer rate is 16 to 500
Mbps (millions of bits per seconds).

29. Co-axial cable
• It looks like television cable.
• The inner copper wire is
covered with insulator
• On the top there is a thick
layer of insulator.
• The thick layer of insulator is
surrounded mesh layer.
• Provides high bandwidth.
• Good protection from
interference
• Transfer rate is from 10 mega
bits per seconds or more.
• What does mega mean?

30. Fiber Optic Cable
• It is a very thin glass fibers
surrounded by insulators is
known as fiber optic cable.
• It uses light pulses that means
that the data is transmitted in
the form of light.
• Supports up to 2 billions bits per
second
• Low data error
• Not effected by electromagnetic
interference.
• Used for transmitted data over
long distances.

31. Unbounded/Unguided Transmission Media
• Transmission which uses radio wave, microwave, infrared or
laser for transferring data and information from one computer
to another on the network is known as Unbounded/Unguided
Transmission Media.
• A network that uses Unbounded/Unguided Transmission Media
is known as wireless network.
• It is flexible.
• Commonly uses wireless communication systems are:
– Microwave system
– Infrared transmission
– Laser transmission
– Communication satellite

32. Microwave system
• It is electromagnetic waves.
• It has longer wavelength than infrared
but shorter than radio waves.
• Wavelength is about 30 cm to 1 mm.
• Wavelength is the distance between
identical points.
• It can transmit data from one point to
other without using cable
• It supports data transfer rate up to 16
giga bits per second.
• The signals can’t be bend or pass
obstacles like hills or building so a very
high towers are mounted.
• It uses repeaters at an interval of 30
to 40 km.

34. Infrared Transmission
• It is an optical transmission.
• The data is transmitted as a beam of light.
• It is invisible to human eye.
• It is inexpensive
• Usually used between two adjacent building.
• It is limited to a distance of few 100 feet.
• Not effected natural hazard (lightening, weather conditions) or
interferences
• It is fairly secure

35. Laser light
• It is optical transmission.
• The data is transmitted as a beam of light.
• The is invisible to human eye.
• It is limited to a distance of few 15 miles (24 km or more).
• Can be uses repeaters to transmit the data over a long distance.
• Provides a high security.

36. Communication Satellite
• An artificial satellite position in a
geosynchronous orbit for the
transmission of data.
• An earth station acts transmitter
and receiver.
• A radio wave is transmitted to
satellite and satellite retransmit
them back to the earth.
• Early Bird is the first artificial
commercial satellite launched in
1965 by International Satellite
Consortium, INTELSAT.
• Nepal’s earth station called
Sagarmatha Satellite is located at
Thankot, Kathmandu.

38. Networking Architecture
• The way the computers on the network
interact and communicate with each other.
• There are two networking models. They are:
– Client-Server Model of Networking
– Peer-to -Peer

39. Client Server Model of Networking
• In this type of networking there at least one server and
one or more workstations.
• The data and information are stored in a server.
• The server provides data, information and resources to
workstations.
• Only authorized person can access the computer of the
network.
• The server controls the information and resources.
• It is also known as Domain Model.
• Workstation (frontend) makes request for information
and resources and server (backend) provides.
• It uses Network Operating System such as Windows
2003, Linux, Novell Netware.

40. Advantages Client Server Model of Networking
• High security; only authorized person can access.
• Controls and Manages the workstation
• Reduction of cost.
• Can be expanded to any size.
• It does not slow down.
Disadvantages Client Server Model of Networking
• More expensive the peer to peer network
• Needs a well trained network administrator.

42. Peer to Peer Model of Networking
• A peer-to-peer (P2P) network is created when two or more
PCs are connected and share resources without going through
a separate server computer.
• A P2P network can be an ad hoc (unplanned) connection
• It can be a couple of computers connected via a Universal
Serial Bus to transfer files.
• A P2P network also can be a permanent infrastructure that
links a half-dozen computers in a small office over copper
wires or a P2P network can be a network on a much grander
scale; over the Internet.
• No server computer; all the computer on the network acts as
both server and client.
• No computer to control the other computers on the network.
• User’s computer decides to provide the information and
resources.

43. Advantages Peer to Peer Model of Networking
• Easy to set up.
• Cheaper than client server Model
• Each user can determine the resources
• Administering can be done easily
Disadvantages Peer to Peer Model of
Networking
• Slows down due to heavy load.
• Requires software to be installed
• Network administrator has to repair each
computer.

45. Types of computer network
• There are three types of network. They are:
• Local Area Network (LAN)
• Metropolitan Area Network (MAN)
• Wide Area Network (WAN)

46. Local Area Network (LAN)
• A computer network that connects a large number of
computers, terminals and other peripheral devices of a
room, building or campus is known as Local Area Network.
• Cables are used for this type of network.
• The main objective of LAN is to share information and
resources.
• Wireless technology of LAN (WLAN) is becoming popular.
• WLAN (Wireless Local Area Network) is a wireless
communication channel where the data is transmitted in
the form of radio waves.
• WLAN is used where cabling is difficult.
• Wireless bridges or WLAN Router can be used for WLAN.

47. Features Local Area Network (LAN)
• Covers an small geographic area of few
kilometers.
• The computer and other peripheral devices are
connected by cable or wire.
• WLAN Router or bridges can be used of wireless
LAN
• Provides higher bandwidth.
• Has a speed rate of 10 to 100 Mbps
• The cost of installation is negligible.
• It is not effected by environmental factors.
• It is normally owned by an organization.

48. Metropolitan Area Network (MAN)
• A computer network bigger than LAN and smaller
than WAN is called MAN.
• MAN covers a network of a city or two
neighboring cities
• There may be large LANs in a MAN.
• It is usually used by Banks, Offices, Schools etc.
• The computers in MAN are connected by using
bounded or unbounded media like microwave
system.
• Cable Television (CATV) is an example of MAN.

49. Features Metropolitan Area Network (MAN)
• It covers an area larger than LAN.
• It is owned by single or multiple organization.
• It uses cables or wires for connecting
computer.
• Internet Service Provider (ISP) provides MAN
services.

50. Wide Area Network (WAN)
• It covers very large geography area i.e. whole
word.
• A computer network within a county or
continents is known as Wide Area Network.
• It can consist of many groups of LAN and MAN.
• The transmission media in WAN may be
telephone line, microwave, radio wave or satellite
links.
• The transmission rate is 10 giga bits per second
• Internet and Intranet are the examples of WAN.

51. Features Wide Area Network (WAN)
• It covers a very large are that is whole world.
• It is owned by multiple organization.
• It uses leased lines, telephone lines or wireless
media to connect computers

52. Communication Protocol
• A set of rules for the communication in
between the computers on the network is
called protocol.
• It is a computer program that control and
manages transfer of data or message from one
computer to other.
• Computers can communicate only if they are
using same protocol.
• Interpretation device is used incase of
different protocol.

53. What is Packet?
• A term first coined by Donald Davies in 1965, a packet is a segment
of data sent from one computer or device to another over a network.
A packet contains the source, destination, size, type, data, and other
useful information that helps packet get to its destination and read.
Below is a breakdown of a TCP packet.
• Another name for a packet is a datagram.
• Most data that is transferred over the Internet is sent in one or more
packets. The most common packet sent is the TCP packet, but every
network can be transmitting dozens of other types.
• Because packets are limited in size, most data transmitted over a
network are broken up into multiple packets before being sent out and
then put back together when received.
• As the packet is transmitted over a network,
network routers and switches examine the packet and its source to
help direct it in the proper direction.
• During its transmission, it is possible for a network packet to be
dropped. If the packet is not received or some other error occurs, it is
sent again.

54. What is Packet?
• A term first coined by Donald Davies in 1965, a packet is a segment
of data sent from one computer or device to another over a network.
A packet contains the source, destination, size, type, data, and other
useful information that helps packet get to its destination and read.
Below is a breakdown of a TCP packet.
• Another name for a packet is a datagram.
• Most data that is transferred over the Internet is sent in one or more
packets. The most common packet sent is the TCP packet, but every
network can be transmitting dozens of other types.
• Because packets are limited in size, most data transmitted over a
network are broken up into multiple packets before being sent out and
then put back together when received.
• As the packet is transmitted over a network,
network routers and switches examine the packet and its source to
help direct it in the proper direction.
• During its transmission, it is possible for a network packet to be
dropped. If the packet is not received or some other error occurs, it is
sent again.