The document provides an introduction to netcentric computing, covering its history, architecture, client/server paradigms, distributed computing, mobile and wireless computing, and network security. It discusses the foundational elements of networking, including types of networks, protocols, and the role of the internet, as well as the evolution and challenges of mobile computing and ensuring network security. Additionally, it touches on multimedia systems and their technical requirements for content transmission and management.

1. Netcentric Fundamentals
(ITT501)
Chapter 1 -
Introduction

2. Topic Outline
▰ Background and
history of networking
and the internet
▰ Network Architecture
and Protocols
▰ Client/Server
paradigms
▰ Distributed Computing
▰ Mobile and wireless
computing
▰ Network Security
▰ Networked multimedia
system
2

3. Netcentric Computing
▰ CC2001 introduced a Knowledge Area (KA)
entitled “Net-Centric Computing”, which
encompassed a combination of topics including
traditional networking, web development, and
network security.
▰ range of sub-specialities including:
○ computer communication network concepts
and protocols, multimedia systems, Web
standards and technologies, network security,
wireless and mobile computing, and 3

4. Netcentric Principle
▰ Net-Centric Computing (NCC) principle is based
on a distributed environment where multiple
components, possibly across geographical
boundaries, that communicate and coordinate
their actions through message passing. [2]
▰ To an actor outside this system, it appears as if a
single coherent system.
▰ Example : The Internet
4

5. The Internet
5

6. 6
Background and
history of
networking and
the internet

7. 7

8. NETWORK
▰ Computer network is a collection of computing
devices that are connected in various ways in
order to communicate and share resources
▰ Usually, the connections between
computers in a network are made using physical
wires or cables
▰ However, some connections are wireless,
using radio waves or infrared signals
8

9. ▰ Computer networks have opened up
an entire frontier in the world of
computing called the client/server
model
9
NETWORK

10. History of Network
▰ The Advanced Research Projects Agency
Network (ARPANET) is one of the world's first packet
switching networks, the first network to implement TCP/IP,
and was the main progenitor of what was to become the
global Internet. (later DARPA)
▰ ARBA network was initially funded by the Advanced
Research Projects Agency (ARPA, later DARPA) within
the U.S. Department of Defense for use by its projects at
universities and research laboratories in the US.
▰ The packet switching of the ARPANET, together with TCP/IP,
would form the backbone of how the Internet works. 10

11. Network and Internet History
Timeline
▰ https://www.computerhope.com/
history/network.htm
11

12. INTERNET
▰ It is the largest network in the world that connects
hundreds of thousands of individual networks all
over the world.
▰ The popular term for the Internet is the
“information highway”.
▰ Rather than moving through geographical space,
it moves your ideas and information through
cyberspace – the space of electronic movement of
ideas and information
12

13. 13

14. Internet Ownership
▰ No single person or company owns the Internet
or even controls it entirely. As a wide-area
network, it is made up of many smaller
networks. These smaller networks are often
owned and managed by a person or
organization. The Internet, then, is really
defined by how connections can be made
between these networks.
14

15. World Wide Web (WWW)
▰ The Web (World Wide Web) consists of
information organized into Web pages
containing text and graphic images.
▰ It contains hypertext links, or highlighted
keywords and images that lead to related
information.
▰ A collection of linked Web pages that has a
common theme or focus is called a Web site.
15

16. 16

17. 17
Network
Architecture
and Protocols

18. Network Architecture
▰ Understanding of the relationships between
(architectural) components of the network.
▰ Network architecture guides the technical
design of the network, through the
application of high-level design principles to
the network building blocks.
▰ The generic term node or host refers to any
device on a network 18

19. Types of Network
▰ Local-area network (LAN) A network that connects a
relatively small number of machines in a relatively close
geographical area.
▰ Wide-area network (WAN) A network that connects two
or more local-area networks over a potentially large
geographic distance
▰ Metropolitan-area network (MAN) The communication
infrastructures that have been developed in and around large
cities
▰ Wireless Network 19

20. LAN Topologies(Physical)
1) Bus
2) Star
3) Ring
4) Switched
5) Daisy chains
6) Hierarchies
20

21. WAN Topologies
1) Peer-to-peer WANs
2) Ring WANs
3) Star WANs
4) Full-mesh WANs
5) Partial-mesh WANs
6) Two-tiered
7) Three-tiered
8) Hybrids
21

22. Connections
▰ Internet backbone A set of high-speed networks
that carry Internet traffic
▰ Internet service provider (ISP) A company that
provides other companies or individuals with
access to the Internet
22

23. ▰ Internet: LANs, WANs, and individual
devices connected via TCP/IP software
▰ Intranet: private net accessible to
internal users
▰ Extranet: intranet extended to include
some external users
▰ Virtual private network (VPN): uses
public network as if it is private
23

24. Ports and Addresses
24
▰ Ports are destination points within a host
computer.
▰ Processes are attached to the ports, enabling them
to communicate.
▰ Transport layer addresses are composed of
network address of the host computer and a port
number.
▰ In the Internet every host is assigned a unique IP
number which is used in routing.
▰ In an Ethernet each host is responsible for

25. Protocols
25
▰ The term protocol refers to a well-known set of rules and
formats to be used in order to perform a task. For example,
a task of communicating between processes.
▰ Parts of a protocol:
○ A specification of a sequence of messages that must be
exchanged.
○ A specification of the format of the data in the
messages.
▰ Existence of well-known (standard) protocols enables the
separate components of the distributed systems to be
developed independently in different languages and on

26. 26

27. 27
Client/Server
paradigms

28. ▰ A simple definition of
Client/Server is
“ server software accepts
requests for data from
client software and returns
the results to the client”
28

29. ▰ Servers
○ Run all the time (i.e. infinite)
○ Provide service to any client
○ Typically specialize in providing a certain
type of service, e.g. Mail.
○ Listen to a well-known port and passively
open connection.
▰ Clients
○ Run when needed, then terminate (i.e.
finite)
○ Actively Open TCP or UDP connection with
Server’s socket.
29

30. ▰ Client/server architecture has many variations
based on tiers.
▰ tier architectures try to separate the
components into different tiers/layers
○ Tier: physical separation
○ Layer: logical separation
▰ tier architectures have the same components
o Presentation
o Business/Logic
o Data
30

31. Layers
▰ Presentation Layer
○ Static or dynamically generated content rendered by the
browser (front-end)
▰ Logic Layer
○ A dynamic content processing and generation level
application server, e.g., Java EE, ASP.NET, PHP, platform
(middleware)
▰ Data Layer
○ A database, comprising both data sets and the database
management system or RDBMS software that manages
and provides access to the data (back-end) 31

32. 1-Tier Architecture /
Standalone
▰ All 3 layers are on the same machine
o All code and processing kept on a single
machine. sometimes access by dump
terminal
▰ Presentation, Logic, Data layers are tightly
connected
o Scalability: Single processor means hard to
increase volume of processing
o Portability: Moving to a new machine may
mean rewriting everything
o Maintenance: Changing one layer requires
changing other layers 32

33. 2-Tier Architecture
▰ Database runs on Server
o Separated from client
o Easy to switch to a different database
▰ Presentation and logic layers still
tightly connected (coupled)
o Heavy load on server
o Potential congestion on network
o Presentation still tied to business logic
33

34. 3-Tier Architecture
o Each layer can potentially
run on a different machine
o Presentation, logic, data
layers disconnected
o Change in platform
affects only the layer
running on that
particular platform
34

35. Client/Server
Technologies
35

36. Types of servers
▰ Application Servers
▰ Audio/Video Servers
▰ Chat Servers
▰ Fax Servers
▰ FTP Servers
▰ Groupware Servers
▰ IRC Servers
36
▰ List Servers
▰ Mail Servers
▰ News Servers
▰ Proxy Servers
▰ Telnet Servers
▰ Web Servers
▰ Database Servers

37. 37
Distributed
Computing

38. Distributed Computing is a field of
computer science that studied distributed
system
▰ A distributed system is one in which
components located at networked computers
communicate and coordinate their actions
only by passing messages.
38

39. Distributed Systems
39
▰ Distributed systems have autonomous
components
▰ Distributed systems may be built using
heterogeneous technology
▰ Distributed system components may be
used exclusively
▰ Distributed systems are executed in
concurrent processes
▰ Distributed systems have multiple points
of failure

40. Centralized Systems
40
▰ Centralized systems have non-
autonomous components
▰ Centralized systems are often
build using homogeneous
technology
▰ Multiple users share the resources
of a centralized system at all times
▰ Centralized systems have a single
point of control and of failure

41. Every application is part of a business model.
▰ They are
developed using
different
platforms, OS and
programming
languages.
▰ must make them
work together.
41

42. Middleware technologies enables the
components to communicate to coordinate their
activities.
42

43. Advantages of Distributed
Systems
▰ Collaborative
▰ Expandability
▰ Local autonomy
▰ Improved performance
▰ Improved reliability and availability
▰ Potential cost reductions
43

44. ▰ Network reliance
▰ Complexities
▰ Security
44
Disadvantages of Distributed
Systems

45. 45
Mobile and
wireless
computing

46. Mobile Computing
▰ Mobile computing is to describe technologies
that
○ enable people to access network services
anyplace, anytime, and anywhere,
○ with portable and wireless computing and
communication devices.
46

47. ▰ Aspects of mobility
○ User mobility
■ Between different geographical locations
■ Between different networks
■ Between different communication devices
■ Between different applications
○ Device portability
■ Between different geographical locations
■ Between different networks
47

48. Applications of mobile computing
48
▰ Vehicles
○ transmission of news, road condition, weather, music
via DAB
○ personal communication using GSM
○ position via GPS
○ local ad-hoc network with vehicles close-by to prevent
accidents, guidance system, redundancy
○ vehicle data (e.g., from busses, high-speed trains) can
be transmitted in advance for maintenance
▰ Medical
○ Nurses/Doctors in Medical offices are now using
Wireless Tablet PCs/WLAN to collect and share patient
information.

49. 49
▰ Sales
○ Sales representatives are using Tablet PCs with Smart
phones for presentation, transmitting/access
information among office, hotel, and customer
location.
▰ Emergencies
○ Early transmission of patient data to the hospital,
current status, first diagnosis
○ Provide mobile infrastructure in dealing with Natural
Disaster (earthquake, hurricane, fire), terrorist attacks,
war, ...
▰ Smart Environment
○ Smart home, Smart Car, Smart City
Applications of mobile computing

50. Challenges in mobile
computing
50
▰ Mobility means changes
▰ Hardware
○ Lighter, smaller, energy management, user interface
▰ Low bandwidth, high bandwidth variability
○ Kbit/s to Mbit/s, bandwidth fluctuation
▰ Security risk
○ Devices more vulnerable, endpoint authentication
harder
▰ Heterogeneous network
○ Different devices, interfaces and protocols

51. 51
▰ Location awareness
○ Locality adaptation
▰ Higher loss-rates, higher delays, more jitter
○ Connection setup time, hand-off
▰ Restrictive regulations of frequencies
○ Frequencies have to be coordinated
Challenges in mobile
computing

52. Wireless Network
▰ A wireless network allows devices to stay
connected to the network but roam untethered
to any wires.
▰ Access points amplify Wi-Fi signals, so a device
can be far from a router but still be connected to
the network.
52

53. Wireless Network
Elements
53

54. 54
Wireless Network
Elements

55. 55
Wireless Network
Elements

56. 56
Wireless Network
Elements

57. Wireless Ad Hoc Network
57
▰ Wireless Ad Hoc Network (peer to peer)
○ A collection of autonomous nodes that communicate
with each other by forming a multi-hop radio
network in a decentralized manner.
○ No infrastructure, no default router available
○ “every” node needs to be a router
▰ Mobile Ad Hoc Networks (MANET)
○ Host movement frequent
○ Topology change frequent
▰

58. 58
▰ Wireless Ad Hoc Sensor Networks
○ A number of sensors spread across a geographical
area.
○ Limited resources on sensors
Wireless Ad Hoc Network

59. 59
Wireless Ad Hoc Network

60. 60
Network Security

61. Network Security Key Elements
▰ Confidentiality
○ Preserving authorized restrictions on information
access and disclosure, including means for protecting
personal privacy and proprietary information.
▰ Integrity
○ Guarding against information modifications or
destruction, including ensuring information non-
repudiation and authenticity.
▰ Availability
○ Ensuring timely and reliable access to and use of
information 61

62. Security Attacks,
Mechanisms & Services
• Security Attack
– Any action that compromises the security of
information
• Security Mechanism
– A process / device that is designed to detect,
prevent or recover from a security attack.
• Security Service
– A service intended to counter security
attacks, typically by implementing one or
more mechanisms.
62

63. Threats & Attacks
63
… but threat and attack used nearly interchangeably

64. Security Threats / Attacks
64

65. 65

66. Security Attacks classification
▰ passive attacks - eavesdropping on, or monitoring of,
transmissions to:
○ obtain message contents, or
○ monitor traffic flows
▰ active attacks – modification of data stream to:
○ masquerade of one entity as some other: man-in-the-
middle
○ replay previous messages
○ modify messages in transit
○ denial of service
66

67. Causes of network security threats
▰ Technology weaknesses
▰ Configuration weaknesses
▰ Policy weaknesses
▰ Human weaknesses
67

68. 68
Networked
multimedia system

69. Multimedia System
▰ Multimedia system is a computer (machine) that
can transmit and accept information (multiple
media) from the external world.
▰ supports the integrated storage, transmission and
representation of the discrete media types text,
graphics and image and the continuous media
types audio and video on a digital computer.
69

70. Media types
70
Text Hypertext
Images Static & Dynamic
Audio Speech, Music
Video Movies, Documentaries
2D Graphics Vector Graphics
3D Graphics Games

71. Features of Multimedia System
▰ Very high processing power
- In the modern multimedia context, movement and
processing of large amounts of data in real-time are
emphasized.
- Include support hardware such as graphics and video
adapters, digital signal processors and etc.
▰ A file system capable of handling multimedia
information
- File systems should have the capability to deal with
streams of data, such as video and audio. 71

72. Features of Multimedia System
▰ File formats that exploit the inherent properties
of the multimedia information
- The file formats should be easy to handle from the file
system point of view.
▰ Efficient and high I/O rate
- The input and output subsystem should be able to handle
large storage.
- The controller hardware should be able to provide
recording and reading of data from these storages.
72

73. Features of Multimedia System
▰ Storage and memory
- Caches have to be larger and may have to be in a 2 or 3
level hierarchy for efficient management.
▰ Network support
- To apply client-server paradigm in building multimedia
application, high-speed support from the network
subsystem is needed.
- It should be able to stream the data out of the disk
directly, to minimize delay.
73

74. Multimedia Applications
▰ Network application that transmit audio
and video
▰ (“continuous media”)
74
network provides
application with level of
performance needed for
application to function.
QoS

75. Classes of Multimedia
Applications
▰ Streaming Stored Audio and Video
▰ Streaming Live Audio and Video
▰ Real-Time Interactive Audio and Video
75

76. Challenges
▰ TCP/UDP/IP suite provides best-effort, no
guarantees on expectation or variance of packet
delay
▰ Performance deteriorate if links are congested
(transoceanic)
▰ Most router implementations use only First-
Come-First-Serve (FCFS) packet processing and
transmission scheduling
76

77. 77
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