1. Introduction to Computer Networks
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Introduction to
Computer Networks
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2. Tuesday, April 25, 2017
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.
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3. Overview
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4. Where are the data communications? Why data communications?
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DATA COMMUNICATIONS
Where are the data communications?
Why data communications?
Telecommunication: communication at a distance.
Data: information presented in whatever form is agreed upon by the parties creating and using the data.
Data communications: the exchange of data between two devices via some form of transmission medium such as a wire cable.
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5. Four fundamental characteristics:
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DATA COMMUNICATIONS
What do we need?
Hardware
Software
Four fundamental characteristics:
Delivery: correct destination
Accuracy: correct data
Timeliness: fast enough
Jitter: uneven delay
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6. Topics to be covered: Components Data representation Data flow
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7. Components Figure 1.1 Five components of data communication
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Components
Figure 1.1 Five components of data communication
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8. Communication Tasks Transmission system utilization Interfacing
Some of the key tasks that must be performed in data communication system.
Transmission system utilization
Interfacing
Synchronization
Error Detection & Correction
Flow control
Addressing
Routing
Recovery
Message formatting
Security
Network Management
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9. Data Representation Text Numbers Direct conversion Images Audio Video
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Data Representation
Text
, articles, etc
Coding (Unicode, ASCII)
Numbers
Direct conversion
Images
Pixels, resolution, gray scale, RGB.
Audio
Continuous, signal conversion
Video
Movie, continuous/discrete
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10. Data Flow Figure : Data flow (simplex, half-duplex, and full-duplex)
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Data Flow
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Figure : Data flow (simplex, half-duplex, and full-duplex)
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11. Topics to be covered: Distributed Processing Network Criteria
Physical Structures
Network Models
Categories of Networks
Internetwork
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12. Task is divided among multiple computers.
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Task is divided among multiple computers.
Advantages of Distributed processing
Security/Encapsulation
Distributed Database
Faster problem solving
Security through redundancy
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13. NETWORKS Network criteria Performance Transit time, response time.
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NETWORKS
Network criteria
Performance
Transit time, response time.
Throughput, delay.
Reliability
Failure frequency, recovery time
Security
Protection.
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14. Tuesday, April 25, 2017
Type of Connections
1.Spatially shared
2.Time shared
Figure : Types of connections: point-to-point and multipoint
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15. Physical topology Figure : Categories of physical topology
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Physical topology
Figure : Categories of physical topology
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16. Mesh Networks Fully Mesh A B C D E Partial Mesh A B C D E
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Mesh Networks
Fully Mesh A B C D E
Partial Mesh A B C D E
Things to bring out:
How do you get from A to B in the partial mesh?
There is more than one answer. Which is the shortest route and which is the longest route?
Important points –
You need a method of identifying recipient of the information. They might like to know who sent it as well. The intermediate systems might also like to know where the information should go!
In the full mesh there is always a route to everywhere else, even if there is one fault. Can you say the same for the partial mesh shown above?
What about security? A must trust D, E and C or at least some of them to get the message through.
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17. Star Figure : A star topology connecting four stations
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Star
Figure : A star topology connecting four stations
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18. Bus Figure : A bus topology connecting three stations
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Bus
Figure : A bus topology connecting three stations
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19. Ring Figure : A ring topology connecting six stations
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Ring
Figure : A ring topology connecting six stations
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20. Classification of Networks by Size and Community
A city wide network: area inside a town or city; TV cables.
A company or home: covers few km, mbps
A country wide network: long distance transmission

21. Single to Multiple LANs
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22. Tuesday, April 25, 2017
Figure An isolated LAN connecting 12 computers to a hub in a closet
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23. Metropolitan Area Network
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24. Wide Area Network
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25. Internetworking
When two or more networks are connected , they become an internetwork, or internet .
The term internet means interconnection of network
While the Internet is the name of a specific worldwide network.
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26. Tuesday, April 25, 2017
THE 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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27. The Internet Today’s Internet Hierarchical Infrastructure
International/National
ISPs
Connected by NAP –
Network Access Points
(also called peering points
Or Internet eXchanges)
Regional ISP
(Local) ISP
ISP = Internet Service Provider
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28. PROTOCOLS AND STANDARDS
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PROTOCOLS AND STANDARDS
Protocols (rules)
Why do we need protocols?
Key elements of protocols
Syntax
Semantics
Timing
Standards
De facto (by fact) vs. De jure (by law)
Organizations
Internet standards (Internet draft & RFC)
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29. PROTOCOLS AND STANDARDS
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PROTOCOLS AND STANDARDS
Network Standards Organizations
National Standards Organizations
(Generally responsible for standards within a nation and usually participate in that nation’s international activity)
• American National Standards Institute (ANSI)
• British Standards Institute (BSI)
• French Association for Normalization (AFNOR)
• German Institute for Normalization (DIN)
Regional Standards Organizations
(Restrict their activity to a specific geographical region but generally influence standards outside their regions)
• Committee of European Posts and Telegraph (CEPT)
• European Committee for Standardization (CEN)
• European Computer Manufacturers’ Association (ECMA)
International Standards Organizations
(Promote standards for worldwide use)
• International Standards Organization (ISO)
• International Telecommunications Union (ITU)consists of ITU-T, which is responsible for communications, interfaces, and other standards related to telecommunications; and ITU-R, which is responsible for allocating frequency bands in the electromagnetic spectrum for telecommunications, and for making recommendations relating to radio communications. (Note: ITU-T is the former CCITTConsultative Committee for International Telephony and Telegraphy.)
Industry, Trade, and Professional Standards Organizations
(Restrict their activity to member interest areas but generally influence other areas)
• Electronic Industries Association (EIA)
• Telecommunications Industries Association (TIA)
• Institute for Electrical and Electronics Engineers (IEEE)
• Internet Engineering Task Force (IETF)
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30. Summary Data communications Networks The internet
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Summary
Data communications
Networks
The internet
Protocols and standards
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