Object Oriented System by Er. Manish Aryal

1. Data Communication and Computer Network
(MIE 214, Elective Course)
MANISH ARYAL

2. Objectives
General Objectives
To get acquainted with various conceptual aspects of Data Communication and
Computer Network
Specific Objectives
◦ To get familiar with foundation of data communication and computer network
◦ To understand the OSI and TCP/IP Network Models
◦ To get through understanding of 7 different layers of OSI model
◦ To conceptualize the mechanism and issues of network management
◦ To conceptualize the mechanism and issues of network security
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3. Course Outline
Unit 1: Introduction
Unit 2: Application Layer Functionality and Protocols
Unit 3: Transport Layer
Unit 4: Network layer
Unit 5: Data Link Layer
Unit 6: Physical Layer
Unit 7: Network Management and Security
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4. me?
Manish Aryal
B.E. Computer, 2003
MSc. Information and Communication Engineering, 2005
Associate Professor/ Member, BoD
Sagarmatha Engineering College
Contact no.:
Cell no.: 9841285747
email: manish@sagarmatha.edu.np
linkedin: http://np.linkedin.com/in/aryalmanish
facebook: https://www.facebook.com/aryalmanish
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5. Introduction

6. Data Communication
The word data refers to raw information presented in whatever
form (text, number, audio, video, image, or combination) is
agreed upon by the parties creating and using the data
Data communications are the exchange of data between two
devices via some form of transmission medium such as a wire
cable
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7. Components
Data Communication {Contd..}
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8. Data flow
Data Communication {Contd..}
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9. Networks
A network is a set of devices (often referred to as nodes)
connected by communication links
A node can be a computer, printer, or any other device capable
of sending and/or receiving data generated by other nodes on
the network
A link can be a cable, air, optical fiber, or any medium which
can transport a signal carrying information.
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10. Performance
◦ Depends on Network Elements
◦ Measured in terms of Delay and Throughput
Reliability
◦ Failure rate of network components
◦ Measured in terms of availability/robustness
Security
◦ Data protection against corruption/loss of data due to:
◦ Errors
◦ Malicious users
Criteria
Networks {Contd..}
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11. 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
Physical Structures
Networks {Contd..}
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12. Connections
Networks {Contd..}
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13. Topology
Networks {Contd..}
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14. Topology (mesh topology )
Networks {Contd..}
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15. Topology (Star)
Networks {Contd..}
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16. Topology (Bus)
Networks {Contd..}
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17. Topology (Ring)
Networks {Contd..}
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18. Topology (Hybrid)
Networks {Contd..}
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19. Local Area Networks (LANs)
◦ Short distances
◦ Designed to provide local interconnectivity
Wide Area Networks (WANs)
◦ Long distances
◦ Provide connectivity over large areas
Metropolitan Area Networks (MANs)
◦ Provide connectivity over areas such as a city, a campus
Categories
Networks {Contd..}
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20. Categories (Local Area Networks (LANs))
Networks {Contd..}
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21. Categories (Wide Area Networks (WANs))
Networks {Contd..}
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22. Categories (heterogeneous network)
Networks {Contd..}
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23. Internet
The Internet has revolutionized many aspects of our daily
lives
It has affected the way we do business as well as the way
we spend our leisure time
The Internet is a communication system that has brought a
wealth of information to our fingertips and organized it for
our use.
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24. Hierarchical organization
Internet {Contd..}
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25. Review !!
Internet vs Network ?
Internet vs World Wide Web ?
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26. Protocols
A protocol is synonymous with rule
It consists of a set of rules that govern data communications
It determines what is communicated, how it is communicated
and when it is communicated
The key elements of a protocol are syntax, semantics and
timing
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27. 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.
Elements
Protocols{Contd..}
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28. What Next?
Network Standardization
Trends in Networking
Network Models
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29. Standardization
Ensure that hardware and software produced by different vendors can
work together.
Makes it much easier to develop software and hardware that link
different networks because software and hardware can be developed
one layer at a time.
Normally, the standards used in data communication are called
protocols.

30. Internet Standards
Email related standards
◦ IMAP, POP, X.400, SMTP, CMC, MIME, binhex, uuencode
Web related standards
◦ http, CGI, html/xml/vrml/sgml
Internet directory standards
◦ X.500, LDAP
Application standards
◦ http, FTP, telnet, gopher, wais
Videoconferencing standards
◦ H.320, H.323, Mpeg-1, Mpeg-2

31. The Standards Making Process
Two types of standards:
◦ Formal standards are developed by an official industry or government
body
◦ Defacto standards emerge in the marketplace and supported by
several vendors, but have no official standing

32. The Standards Making Process
Formal standardization process has three stages
1. Specification stage: developing a nomenclature and identifying
the problems to be addressed.
2. Identification of choices stage: those working on the standard
identify the various solutions and choose the optimum solution from
among the alternatives.
3. Acceptance, the most difficult stage: defining the solution and
getting recognized industry leaders to agree on a single, uniform
solution

33. Standards Organizations
International Telecommunication Union (ITU)
◦ United Nations agency that regulates international telecommunications including
radio and TV frequencies, satellite and telephone specifications, and networking
infrastructure
International Telecommunications Union - Telecommunication
Standardization Sector (ITU-TSS)
Technical standard setting organization of the UN ITU. Formerly called the Consultative
Committee on International Telegraph and Telephone (CCITT)
Comprised of representatives of over 150 Postal Telephone and Telegraphs (PTTs), like
AT&T, RBOCs, or common carriers.
ITU-TSS made v-series modem standards.

34. Standards Organizations {Contd..}
International Organization for Standards (ISO)
Member of the ITU, makes technical recommendations about data
communications interfaces.
ISO created Open System Interconnection (OSI) standard.

35. Internet Engineering Task Force (IETF)
A protocol proposed by a vendor
IETF working group study the proposal
IETF issues a request for comment (RFC)
IETF reviews the comments
IETF proposes an improved RFC
The proposed standard becomes a draft
standard if two or more vendors adopt it
The RFC becomes a proposed standard
Standards Organizations {Contd..}

36. More Organizations
◦ American National Standards Institute (ANSI)
◦ Institute of Electrical and Electronics Engineers (IEEE)
◦ Internet Engineering Task Force (IETF)
◦ Electronic Industries Association (EIA)
◦ National Institute of Standards and Technology (NIST)
◦ National Exchange Carriers Association (NECA)
◦ Corporation for Open Systems (COS)
◦ Electronic Data Interchange -(EDI)
Standards Organizations {Contd..}

37. A network is a combination of hardware and software that sends data from one
location
to another
The hardware consists of the physical equipment that carries signals from one
point of the network to another
The software consists of instruction sets that make possible the services that we
expect from a network
This combination is organized as a layered structure analogous to our daily
activities
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Network Models

38. 38
Network Models {Contd..}

39. OSI and 802
Two primary sets of standards
Define rules for:
◦ How network devices communicate
◦ Methods used to determine when to send data
◦ Methods to ensure that data is received correctly
◦ How the network is cabled
◦ How the network maintains the flow of data
◦ How bits of data are represented

40. Open System Interconnection (OSI)
1977-78 International Organization for Standardization (ISO) began
developing specifications for network communications
1984 OSI model was released
International standard
Best known and most widely used guide to understanding network
communications

41. 802 Model
Model published by the Institute for Electrical and Electronic
Engineers, Inc. (IEEE)
Project began in February 1980 (802)
Predates OSI standard but developed in cooperation with OSI
Defines aspects of networking related to physical cabling, connectivity,
error checking, data transmission, encryption, and emerging
technologies

42. The seven-layer OSI model
To help you remember the order of
the layers
◦ All people seem to need data
processing

43. Relationship of OSI Layers
Each layer of the OSI model must communicate with the layer above
and below it
◦ For example, the Presentation layer must communicate with the Application
layer (one above) and the Session layer (one below)
As data passes down through the OSI layers, each layer (except
Physical) adds some information to the data
When data reaches the receiving computer, the information added by
each layer of the OSI model is read and processed by the
corresponding layer on the receiving computer
This is referred to as peer-layer communications

44. Relationships among OSI layers
Computer A Computer B
Virtual
Communication
Application
Presentation
Session
Transport
Network
Data Link
Physical
Application
Presentation
Session
Transport
Network
Data Link
Physical

45. Data Communication between two hosts
Data Data

46. OSI Process Example
Physical Layer
Places bits onto the network media
Data Link Layer
Packages data into frames
Adds FCS; adds physical addresses
passes to Physical layer
Network layer
Add network addresses
passes data to Data Link Layer
Transport layer
Subdivides data
adds sequencing info
passes data to Network layer
Session layer
Adds a control frame to data that
indicates that you have the right to transmit data
passes data to Transport layer
Presentation layer
encyrpts request (if necessary)
adds any codes required to implement formatting
passes request to Session layer
Application level
formulates request
for data and sends
request to Presentation layer
Request for e-mail is received by Physical layer
on receiving computer
Request is passed up the layers of the OSI model
Each layer read, processes and removes info added by cooresponding layer on sending computer
User Requests Mail

47. Physical Layer
Responsible for transmitting bits from one computer to another
Physical topology
Network connection types
◦ Number of pins on the network connector
◦ Passive and active hubs, terminators, cables, repeaters, transceivers, etc.
Defines the electrical details
◦ Bit encoding—what represents 0 and 1
◦ How data will be synchronized
◦ Baseband/broadband transmission

48. Physical Layer{Contd..}

49. Data Link Layer
Accepts packets of data from Network layer and packages the data
into data units called frames
Adds information such as frame type and physical address
Responsible for providing error-free transfer of data frames
◦ Frame Check Sequence—error checking algorithm is added at the end of each
frame so that receiving computer can detect damaged frames and request that
frames be resent
◦ Cyclic Redundancy Check (CRC)—most commonly used algorithm

50. Data Link Layer {Contd..}
Intelligent hubs, bridges, and switches are addressed by the Data Link Layer
Defines how media will be accessed
Consists of two sub layers

51. Logical Link Control
◦ Uses error check algorithm (FCS) to verify that data is received correctly
◦ Ensures that the rate of transmission is appropriate for the receiving computer
◦ Provides the link between the Data Link layer and the Network layer
Media Access Control
◦ Controls the way multiple devices share the same media channel
◦ Defines the method the NAC will use to determine when to send data
◦ Communicates directly with the network adapter card
◦ MAC (physical) address for network adapter cards provide unique identifier for
each NAC
Data Link Layer {Contd..}

52. Data Link Layer {Contd..}

53. Network Layer
Responsible for addressing messages across networks
Translates network logical addresses into physical machine addresses
Breaks large segments into smaller packets
Determines routing across networks
Supports communications between logically separate networks
◦ Routers and gateways (devices that pass data from one network to another)
operate in the Network layer

54. Network Layer{Contd..}

55. Transport Layer
Ensures data is delivered error-free in sequence and without
duplication or loss
Breaks large packets from the Session layer into segments to be sent
to the receiving computer
Adds sequencing information to segments
Reassembles the segments into messages
Sends acknowledgement to sending computer

56. Transport Layer{Contd..}

57. Session Layer
Responsible for establishing and maintaining communications between
two nodes on the network
Allows applications on separate computers to share a connection (called
a session)
Provides data synchronization and checkpointing so that if there is a
network failure only the data sent after the checkpoint must be resent
Provides name recognition and security needed to allow two
applications to communicate

58. Session Layer{Contd..}

59. Presentation Layer
Translates data between the format the network requires
and the format the application expects
Responsible for encrypting data, changing or converting
the character set and interpreting graphic commands
Manages data compression to reduce number of bits to be
transmitted

60. Presentation Layer{Contd..}

61. Application Layer
Provides services to support user applications, such as
file transfer, database access, and e-mail
Not a particular application—but services that are
provided to applications

62. Application Layer{Contd..}

63. OSI Layers Review

64. Network Packets
Small chunks of data and other information
Packet Structure
◦ Header
◦ Source address
◦ Destination address
◦ Instructions that tell the computer how to pass the data along (routing)
◦ Reassemble information
◦ Data
◦ Trailer containing error-check information

65. Destination ID Control CRC
Sender ID Data
Header
Trailer
Network Packets {Contd..}

66. 66
Network Packets {Contd..}

67. TCP/IP Reference model
A highly standardized protocol used widely on the Internet
Standards area available in the form of RFC documents
◦ Request For Comments (RFC)
Standards are overseen by the Internet Engineering Task Force
(IETF)

68. Layers of TCP/IP Reference Model
There are four layers of the TCP/IP reference model (DARPA model
as named by the US Government Agency)
◦ The ISO-OSI reference model is composed of seven layers
The next slide shows the mapping of the ISO/OSI model to the
TCP/IP model
Note that the ISO/OSI model is more widely used and accepted but
the TCP/IP model is easy to comprehend

69. Reference Models Comparison
Application
Application FTP, Telnet, SMTP, HTTP..
Presentation
Session
Transport Host-to-Host TCP, UDP
Network Internet IP, ICMP, IGMP
Data Link
Network Access Ethernet, Token-Ring ...
Physical

70. Layers of TCP/IP Reference Model {Contd..}

71. Addressing
MAC Address—physical address burned onto NIC card
◦ Unique address for each NIC card produced in the world
◦ Consists of a Block ID and a Device ID
◦ Each manufacturer has one or more Block IDs
◦ Added to frame by Data Link Layer—MAC sub-layer

72. Addressing {Contd..}
Network address—logical address assigned to a network device that
identifies the network that a device belongs
◦ Can be assigned automatically when a computer is turned on
◦ DHCP server provides IP (network) addresses to computers
◦ Can be assigned manually so that address remains the same each time
computer is turned on
◦ Addresses for servers and printers are assigned manually so that
other devices can always locate them

73. Recent Trends in Networking
Some of the recent trends in Networking includes but not limited to
following:
◦ IoT
◦ Big Data
◦ SD-WAN
◦ Cloud
◦ 802.11ac
◦ Smart grid
◦ NaaS
◦ Resiliant Network
◦ IPv6 Migration

74. Addressing {Contd..}
Port Address ?
Specific Address ?

75. Recent Trends in Networking {Contd..}
Internet of Things
The internet of things (IoT) is the network of physical objects—devices,
vehicles, buildings and other items—embedded with electronics,
software, sensors, and network connectivity that enables these objects
to collect and exchange data
The IoT allows objects to be sensed and controlled remotely across
existing network infrastructure, creating opportunities for more direct
integration of the physical world into computer-based systems, and
resulting in improved efficiency, accuracy and economic benefit

76. Recent Trends in Networking {Contd..}
Big Data
◦ Big data is a term for data sets that are so large or complex that traditional
data processing applications are inadequate
◦ Challenges include analysis, capture, data curation, search, sharing,
storage, transfer, visualization, querying, updating and information privacy
◦ The term often refers simply to the use of predictive analytics or certain
other advanced methods to extract value from data, and seldom to a
particular size of data set
◦ Accuracy in big data may lead to more confident decision making, and
better decisions can result in greater operational efficiency, cost reduction
and reduced risk

77. Recent Trends in Networking {Contd..}
SD-WAN
◦ Software-defined networking (SDN) is an umbrella term encompassing
several kinds of network technology aimed at making the network as
responsive and flexible as the virtualized server and storage infrastructure
of the modern data center
◦ The goal of SDN is to allow network engineers and administrators to
respond quickly to changing business requirements
◦ In a software-defined network, a network administrator can shape traffic
from a centralized control console without having to touch individual
switches, and can deliver services to wherever they are needed in the
network, without regard to what specific devices a server or other device is
connected to

78. Recent Trends in Networking {Contd..}
Cloud Computing
◦ Also known as on-demand computing, is a kind of Internet-based computing that
provides shared processing resources and data to computers and other devices on
demand
◦ It is a model for enabling ubiquitous, on-demand access to a shared pool of
configurable computing resources (e.g., networks, servers, storage, applications
and services), which can be rapidly provisioned and released with minimal
management effort
◦ Cloud computing and storage solutions provide users and enterprises with
various capabilities to store and process their data in third-party data centers
◦ It relies on sharing of resources to achieve coherence and economy of scale,
similar to a utility over a network

79. Recent Trends in Networking {Contd..}
802.11ac
◦ IEEE 802.11ac is a wireless networking standard in the 802.11 family
(which is marketed under the brand name Wi-Fi), developed in the IEEE
Standards Association process, providing high-throughput wireless local
area networks (WLANs) on the 5 GHz band
◦ The standard was developed from 2011 through 2013 and approved in
January 2014
◦ This specification has expected multi-station WLAN throughput of at least
1 gigabit per second and a single link throughput of at least 500 megabits
per second (500 Mbit/s)
◦ This is accomplished by extending the air interface concepts embraced by
802.11n: wider RF bandwidth, more MIMO, and high-density modulation

80. Recent Trends in Networking
Smart grid
Smart grid is a generic label for the application of computer intelligence and
networking abilities to a dumb electricity distribution system.
Smart grid initiatives seek to improve operations, maintenance and planning
by making sure that each component of the electric grid can both 'talk' and
'listen‘
Another major component of smart grid technology is automation

81. Recent Trends in Networking
NaaS
◦ Often used along with other marketing terms like cloud computing, along with
acronyms such as Infrastructure-as-a-Service (IaaS), Platform-as-a-Service
(PaaS), Software-as-a-Service (SaaS), and Communication-as-a-Service
(CaaS)
◦ NaaS includes the provision of a virtual network service by the owners of the
network infrastructure to a third party
◦ Often this includes network virtualization using a protocol such as OpenFlow
◦ Some service models are:
◦ Virtual Private Network (VPN)
◦ Bandwidth on demand (BoD)

82. Recent Trends in Networking
Resilient Network
◦ Resilience is the ability to provide and maintain an acceptable level of
service in the face of faults and challenges to normal operation
◦ Threats and challenges for services can range from simple
misconfiguration over large scale natural disasters to targeted attacks
◦ As such, network resilience touches a very wide range of topics
◦ In order to increase the resilience, the probable challenges and risks have
to be identified and appropriate resilience metrics have to be defined for
the service to be protected
◦ These services include:
◦ supporting distributed processing, supporting network storage, maintaining service
of communication services such as (video conferencing, instant messaging, online
collaboration), access to applications and data as needed

83. Recent Trends in Networking {Contd..}
IPv6
While increasing the pool of addresses is one of the most often-talked about
benefit of IPv6, there are other important technological changes in IPv6 that
will improve the IP protocol:
- No more NAT (Network Address Translation)
- Auto-configuration
- No more private address collisions
- Better multicast routing
- Simpler header format
- Simplified, more efficient routing
- True quality of service (QoS), also called "flow labeling"
- Built-in authentication and privacy support
- Flexible options and extensions
- Easier administration

84. What Next?
Application Layer Functionality and Protocols
◦Principles of application layer protocols
◦Application layer protocols and services (DNS, mail, file
transfer, WWW)
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85. Thank You.