1. Chapter 1
Introduction
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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2. Topics discussed in this section:
1-1 DATA COMMUNICATIONS
The term telecommunication means communication at a distance.
The word data refers to information presented in whatever form is agreed upon by the parties creating and using the data.
Data communication is the exchange of data between two devices via some form of transmission medium such as a wire cable.
Topics discussed in this section:
Components
Data Representation Data Flow
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3. 1-1 DATA COMMUNICATIONS
For data communication to occur the communication devices must be part of some kind of communication system (hardware & software).
Characteristics of Data Communication system:
Delivery
Accuracy
Timelines
Jitter
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4. Figure 1.1 Five components of data communication
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5. 1-1 Components Message – data to be transferred
Sender – device that sends the message
Receiver – device that receives the message
Transmission Medium – a physical path by which message travels
Protocol – set of rules and guidelines that must be followed during the communication
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6. 1-1 DATA REPRESENTATION
Text
Numbers
Images
Audio
Video
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7. Figure 1.2 Data flow (simplex, half-duplex, and full-duplex)
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8. Data flow (simplex, half-duplex, and full-duplex)
In simplex mode communication is unidirectional, as a one-way street. Only one of the two devices on a link can transmit; the other can only receive.
Examples: keyboards and traditional monitors
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9. Data flow (simplex, half-duplex, and full-duplex)
In half-duplex mode, each station can both transmit and receive, but not at the same time. When one device is sending, the other can only receive, and vice versa.
Examples: Walkie-talkies and CB Radios
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10. Data flow (simplex, half-duplex, and full-duplex)
In full duplex mode, both stations can transmit and receive simultaneously.
It can be achieved by using two physically separate paths, one for sending and one for receiving, or by dividing the capacity of the channel between signals traveling in both directions
Examples: Telephone network
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11. Topics discussed in this section:
1-2 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.
Topics discussed in this section:
Distributed Processing
Network Criteria Physical Structures Network Models Categories of Networks Interconnection of Networks: Internetwork
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12. 1-1 NETWORKS Distributed Processing:
Network tasks are divided among several computers
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13. 1-1 NETOWRKS Network Criteria:
Performance: measured as throughput & delay
Reliability: frequency of failure – the time it takes for the link to recover from failure
Security: protection and breaches recovery
Physical Structures:
Point-to-Point: dedicated link between two devices
Multipoint: more than two devices share a single link
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14. Figure 1.3 Types of connections: point-to-point and multipoint
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15. Figure 1.4 Categories of topology
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16. Figure 1.5 A fully connected mesh topology (five devices)
Each device has a dedicated point-to-point link to every other device
n(n-1)/2
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17. Figure 1.6 A star topology connecting four stations
Each device has a dedicated point-to-point link only to a central controller called hub or switch
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18. Figure 1.7 A bus topology connecting three stations
One long cable acts as a backbone to link all the devices in the network
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19. Figure 1.8 A ring topology connecting six stations
Each device has a dedicated point-to-point connection with only two devices on either side of it.
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20. Figure 1.9 A hybrid topology: a star backbone with three bus networks
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21. Categories of Networks
LAN: Local Area Network
Its usually privately owned and links devices in a single office, building or campus. LAN can be as simple as two PC’s and a printer or it can extend throughout a company.
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22. Figure 1.10 An isolated LAN connecting 12 computers to a hub in a closet
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23. Categories of Networks
MAN: Metropolitan Area Network
Is a network with a size between a LAN and a WAN. It usually covers area within a town or a city.
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24. Categories of Networks
WAN: Wide Area Network
Provides long-distance transmission of data image , audio and video information over large geographic areas that may comprise a country, a continent, or even the whole world
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25. Figure 1.11 WANs: a switched WAN and a point-to-point WAN
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26. Figure 1.12 A mixed network made of four WANs and two LANs
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27. 1-3 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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28. Figure 1.13 Hierarchical organization of the Internet
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29. 1-4 Protocols and Standards
For communication to occur, the communicating computers must agree an some protocol.
Protocol is a set of rules that govern data communications. The protocol, defines what is communicated, how it is communicated and when it is communicated.
Key elements:
Syntax – refers to the structure or format of data, meaning the order in which they are presented.
Semantics – refers to the meaning of each section of bits.
Timing – refers to two characteristics: when data should be sent and how fast should be sent
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