The document discusses basics of computer networks. It defines data communication and its key characteristics like delivery, accuracy and timeliness. The basic components of a communication model are identified as the message, protocol, sender, receiver and transmission medium. Different data types like text, numbers, images, audio and video are represented as bit patterns for transmission. Types of networks like personal area network, local area network, wide area network, campus area network and metropolitan area network are classified based on their geographical span, interconnectivity, administration and architecture.

1. Basics of Computer Network
S.P. Siddique Ibrahim
AP/CSE
Kumaraguru College ofTechnology
1Computer Network by Siddique06/28/16

2. Data Communication
• Communicate-sharing the information(local or
Remote)
• Local-usually occurs face to face
• Remote-take place over distance.
• Telecommunication-includes telephone,
telegraphy and television means
communication at a distance.
• The data-refers to information presented in
whatever form is agreed upon by the parties
creating and using the data.
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3. Data Communication
• Are exchange of data between two devices via
some transmission medium such as a wired
cable (or) Wireless.
• To exchange of digital information from two
digital devices is called data communication.
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4. Character tics
• Delivery- the system must deliver to correct
destination.
• Accuracy- Data that have been altered in
transmission and left uncorrected are
unusable.
• Timeliness(Real time transmission)-Late are
useless.
• Jitter-Uneven receive of packet
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5. Communication model(Components)or
Requirement of Data communication
• Two devices
• Message-The message is the information to
be communicated. Popular forms
text,pic,images,video, audio,number.
• Protocol(A-Set of rules that govern data
communication)
• Sender and Receiver(computer,
workstation,mobile)
• Transmission medium- physical path by which
a message travels from sender to receiver. 5Computer Network by Siddique06/28/16

6. 1.6
Figure 1.1 Components of a data communication system
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7. Data RepresentationData Representation
Information today in different forms like
text,number, images, audio and video.
Text:
In data communication, text is represented as a
bit pattern.
Unicode-32bits
ASCII-first 127 characters in Unicode
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8. Number:
Number also represented in bit patterns
ASCII not used to represent Number.
Number directly converted into binary to
simplify mathematical operations.
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9. ImagesImages
Also represented in bit pattern.
Image is composed of matrix of pixels, each
pixel is a small dot.
The size of the images depends on resolution.
(can be divided into 1000 or 10000)
After divide into pixel each will assigned a bit
pattern
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10. Black and white-1-bit pattern is enough.
Not black and white-increase the bit pattern
like 00-black, 01-gray, 11-white.
Audio:
Sound or music-Analog(continuous not
discrete)
Video:
Movie or broadcasting of a picture.
1.
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11. 1.
11
Figure 1.2 Data flow plex, and full-duplex)
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12. What is Network
• A network is a series of points or nodes
interconnected by communication paths.
Networks can interconnect with other
networks and contain subnetworks.
• Networking is the convenient way of making
information accessible to anyone, anytime &
anywhere.
• Set of technologies that connects computers.
Allows communication and collaboration
between users 12Computer Network by Siddique06/28/16

13. A system of interconnected computers
and computerized peripherals such as
printers is called computer network.This
interconnection among computers
facilitates information sharing among
them. Computers may connect to each
other by either wired or wireless media.
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14. What is Network
• A network is a group of two or more computer systems linked
together. There are many types of computer networks, including
the following:
• local-area networks (LANs): The computers are
geographically close together (that is, in the same
building).wide-area networks (WANs): The computers are
farther apart and are connected by telephone lines or radio
waves.campus-area networks (CANs): The computers are
within a limited geographic area, such as a campus or military
base.metropolitan-area networks MANs): A data network
designed for a town or city.home-area networks (HANs): A
network contained within a user's home that connects a person's
digital devices.
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15. BenefitsBenefits
1. Allows File Sharing
2. Provides Convenient Resource sharing
3. Flexible to be used
4. Common control
5. Easy communication
6. Internet
7. Promoted gaming
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16. Social Networking
• the use of dedicated websites and
applications to interact with other users, or to
find people with similar interests to one's
own.
• A social structure made of nodes that are
generally individuals or organizations. A
social network represents relationships and
flows between people, groups, organizations,
animals, computers or other
information/knowledge processing entities. 16Computer Network by Siddique06/28/16

17. Use of Network
• Interact with others to exchange information
and develop professional(Linkedin) or social
contacts(Facebook).
• A group or system of interconnected people or
things.
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18. The Uses of a NetworkThe Uses of a Network
Simultaneous access to data
◦ Data files are shared
 Access can be limited
◦ Shared files stored on a server
◦ Software can be shared
 Site licenses
 Network versions
 Application servers
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19. The Uses of a NetworkThe Uses of a Network
Shared peripheral device
◦ Printers and faxes are common shares
◦ Reduces the cost per user
◦ Devices can be connected to the network
◦ Print servers control network printing
 Manage the print queue
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20. Sharing DataSharing Data
9A-20
File server contains documentsFile server contains documents
used by other computers.used by other computers.
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21. The Uses of a NetworkThe Uses of a Network
Personal communication
◦ Email
 Instantaneous communication
◦ Conferencing
 Tele conferencing
 Videoconferencing
 Audio-conferencing
 Data-conferencing
◦ Voice over IP
 Phone communication over network wires
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22. Voice Over IPVoice Over IP
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23. The Uses of a NetworkThe Uses of a Network
Easier data backup
◦ Backup copies data to removable media
◦ Server data backed up in one step
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24. The Uses of a NetworkThe Uses of a Network
Easier data backup
◦ Backup copies data to removable media
◦ Server data backed up in one step
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25. ChallengesChallenges
1. Security difficulties
2. ComputerViruses and malware
3. Lake of independence
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26.  Type of Connection
◦ Point to Point - single transmitter and receiver
◦ Multipoint - multiple recipients of single transmission
 Physical Topology
◦ Connection of devices
◦ Type of transmission - unicast, mulitcast, broadcast
1.
26
Physical Structures
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27. 1.
27
Figure 1.3 Types of connections: point-to-point and multipoint
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28. Network CriteriaNetwork Criteria
A network must meet a number of
criteria to be considered as effective and
efficient.
They are:
1. Performance
2. Reliability
3. Security
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29. PerformancePerformance
I.Transit time:
It is the amount of time required for a
message to travel from one device to
another device.
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30. II. Response time:II. Response time:
It is the elapsed time between an inquiry and
a response.
The performance can be measured by
number factors are,
i. Number of user –slow response and heavy
traffic load
ii.Type of transition medium
iii. Hardware
iv. Software
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31. ReliabilityReliability
The reliability is measured by frequency
to failure, the time it takes a link to
recover from a failure and the network’s
robustness in a catastrophe.
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32. i. Frequency of Failure:
A network that fails often
ii. Recovery time:
How much time it takes to recover
service after a failure has occurred?
iii. Catastrophe:
Failures due to such reasons are fire,
earthquake, theft…
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33. 3. Security:3. Security:
It refers to protecting data from unauthorized
access and viruses.
i. Unauthorized Access:
Sensitive data must be protected from
unauthorized access. Protection can be done
by user identification and passwords at the
lowest level.At the highest level, encryption
techniques may use.
ii.Viruses:
A virus is an illicitly introduced code that
damages the system.
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34. Classification of ComputerClassification of Computer
NetworksNetworks
Computer networks are classified based
on various factors.They include:
Geographical span
Inter-connectivity
Administration
Architecture
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35. Geographical SpanGeographical Span
 Geographically a network can be seen in one of
the following categories:
 It may be spanned across your table, among Bluetooth
enabled devices, Ranging not more than few meters.
 It may be spanned across a whole building, including
intermediate devices to connect all floors.
 It may be spanned across a whole city.
 It may be spanned across multiple cities or provinces.
 It may be one network covering whole world.
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36. Inter-ConnectivityInter-Connectivity
Components of a network can be connected
to each other differently in some fashion. By
connectedness we mean either logically,
physically, or both ways.
Every single device can be connected to every other
device on network, making the network mesh.
All devices can be connected to a single medium but
geographically disconnected, created bus-like
structure.
Each device is connected to its left and right peers
only, creating linear structure.
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37. All devices connected together with a
single device, creating star-like structure.
All devices connected arbitrarily using all
previous ways to connect each other,
resulting in a hybrid structure.
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38. AdministrationAdministration
From an administrator’s point of view, a
network can be private network which
belongs a single autonomous system and
cannot be accessed outside its physical or
logical domain.A network can be public,
which is accessed by all.
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39. Network ArchitectureNetwork Architecture
 Computer networks can be discriminated into
various types such as Client-Server, peer-to-peer or
hybrid, depending upon its architecture.
 There can be one or more systems acting as Server. Other
being Client, requests the Server to serve requests. Server
takes and processes request on behalf of Clients.
 Two systems can be connected Point-to-Point, or in back-to-
back fashion.They both reside at the same level and called
peers.
 There can be hybrid network which involves network
architecture of both the above types.
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40. Network ApplicationsNetwork Applications
 Resource sharing such as printers and storage devices
 Exchange of information by means of e-Mails and FTP
 Information sharing by using Web or Internet
 Interaction with other users using dynamic web pages
 IP phones
 Video conferences
 Parallel computing
 Instant messaging
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41. How Networks Are StructuredHow Networks Are Structured
Client/Server network
◦ Nodes and servers share data roles
◦ Nodes are called clients
◦ Servers are used to control access
◦ Database software
 Access to data controlled by server
◦ Server is the most important computer
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42. Types of ServerTypes of Server
Centralized
Decentralized
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43. How Networks Are StructuredHow Networks Are Structured
Peer to peer networks (P2PN)
◦ All nodes are equal
◦ Nodes access resources on other nodes
◦ Each node controls its own resources
◦ Most modern OS allow P2PN
◦ Distributing computing is a form
◦ Kazaa
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44. P2PN conceptsP2PN concepts
All are server
Meta data
Chunk file
Server up and down-Remaining will be
continued
Example :torrent and Multiplayer online
games
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45. Types of CN:Personal AreaTypes of CN:Personal Area
NetworkNetwork
 A Personal Area Network (PAN) is smallest network
which is very personal to a user.
 This may include Bluetooth enabled devices or infra-red
enabled devices.
 PAN has connectivity range up to 10 meters.
 PAN may include wireless computer keyboard and
mouse, Bluetooth enabled headphones, wireless
printers, and TV remotes.
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46. 46Computer Network by Siddique06/28/16

47. Common NetworkTypesCommon NetworkTypes
Local Area Network (LAN)
LAN provides a useful way of sharing the
resources between end users.The
resources such as printers, file servers,
scanners, and internet are easily sharable
among computers.
◦ Contains printers, servers and computers
◦ Systems are close to each other
◦ Contained in one office or building
◦ Organizations often have several LANS
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48. LAN(Contd.,)LAN(Contd.,)
Number of systems connected in LAN
may vary from as least as two to as much
as 16 million.
LAN uses either Ethernet or Token-ring
technology. Ethernet is most widely
employed LAN technology and uses Star
topology, while Token-ring is rarely seen.
LAN can be wired, wireless, or in both
forms at once.
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49. 49Computer Network by Siddique06/28/16

50. Common NetworkTypesCommon NetworkTypes
Wide Area Networks (WAN)
◦ Two or more LANs connected
◦ Over a large geographic area
◦ Typically use public or leased lines
 Phone lines
 Satellite
◦ The Internet is a WAN
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51. WANWAN
the Wide Area Network (WAN) covers a
wide area which may span across
provinces and even a whole country.
Generally, telecommunication networks
are Wide Area Network.These networks
provide connectivity to MANs and LANs.
Since they are equipped with very high
speed backbone,WANs use very
expensive network equipment.
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52. 52Computer Network by Siddique06/28/16

53. It can be in the form of Ethernet,Token-
ring,ATM, or Fiber Distributed Data
Interface (FDDI).
Metro Ethernet is a service which is
provided by ISPs.This service enables its
users to expand their Local Area
Networks. For example, MAN can help an
organization to connect all of its offices in
a city.
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54. 54Computer Network by Siddique06/28/16

55. Hybrid NetworkTypesHybrid NetworkTypes
Campus Area Networks (CAN)
◦ A LAN in one large geographic area
◦ Resources related to the same organization
◦ Each department shares the LAN
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56. Hybrid NetworkTypesHybrid NetworkTypes
Metropolitan Area Network (MAN)
◦ Large network that connects different
organizations
◦ Shares regional resources
◦ A network provider sells time
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57. Hybrid NetworkTypesHybrid NetworkTypes
Home Area Network (HAN)
◦ Small scale network
◦ Connects computers and entertainment
appliances
◦ Found mainly in the home
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58. Hybrid NetworkTypesHybrid NetworkTypes
Personal Area Network (PAN)
◦ Very small scale network
◦ Range is less than 2 meters
◦ Cell phones, PDAs, MP3 players
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59.  Internetwork
 A network of networks is called an internetwork, or simply the internet. It
is the largest network in existence on this planet.The internet hugely
connects all WANs and it can have connection to LANs and Home
networks. Internet uses TCP/IP protocol suite and uses IP as its addressing
protocol. Present day, Internet is widely implemented using IPv4. Because
of shortage of address spaces, it is gradually migrating from IPv4 to IPv6.
 Internet enables its users to share and access enormous amount of
information worldwide. It uses WWW, FTP, email services, audio, and video
streaming etc.At huge level, internet works on Client-Server model.
 Internet uses very high speed backbone of fiber optics.To inter-connect
various continents, fibers are laid under sea known to us as submarine
communication cable.
 Internet is widely deployed onWorld Wide Web services using HTML
linked pages and is accessible by client software known as Web Browsers.
When a user requests a page using some web browser located on some
Web Server anywhere in the world, the Web Server responds with the
proper HTML page.The communication delay is very low.
 Internet is serving many proposes and is involved in many aspects of life.
Some of them are:
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60.  Web sites
 E-mail
 Instant Messaging
 Blogging
 Social Media
 Marketing
 Networking
 Resource Sharing
 Audio andVideo Streaming
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61. 1.
61
1-3 THE INTERNET1-3 THE INTERNET
TheThe InternetInternet has revolutionized many aspects of our dailyhas revolutionized many aspects of our daily
lives. It has affected the way we do business as well as thelives. It has affected the way we do business as well as the
way we spend our leisure time. The Internet is away we spend our leisure time. The Internet is a
communication system that has brought a wealth ofcommunication system that has brought a wealth of
information to our fingertips and organized it for our use.information to our fingertips and organized it for our use.
Organization of the Internet
Internet Service Providers (ISPs)
Topics discussed in this section:Topics discussed in this section:
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62. 1.
62
Figure 1.13 Hierarchical organization of the Internet
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63. 1.
63
1-4 PROTOCOLS1-4 PROTOCOLS
A protocol is synonymous with rule. It consists of a set ofA protocol is synonymous with rule. It consists of a set of
rules that govern data communications. It determines whatrules that govern data communications. It determines what
is communicated, how it is communicated and when it isis communicated, how it is communicated and when it is
communicated. The key elements of a protocol are syntax,communicated. The key elements of a protocol are syntax,
semantics and timingsemantics and timing
 Syntax
 Semantics
 Timing
Topics discussed in this section:Topics discussed in this section:
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64.  Syntax
◦ Structure or format of the data
◦ Indicates how to read the bits - field delineation
 Semantics
◦ Interprets the meaning of the bits
◦ Knows which fields define what action
 Timing
◦ When data should be sent and what
◦ Speed at which data should be sent or speed at which it is being
received.
1.
64
Elements of a Protocol
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