This document provides an introduction and overview of key concepts in data communications and computer networks. It discusses the components of data communication, including transmission media and devices. Different types of data, such as text, numbers, images, audio and video are represented digitally for transmission. The document also examines network topologies like point-to-point, star, bus, ring and hybrid configurations. Local area networks (LANs) and wide area networks (WANs) are categorized. Protocols and standards that govern network communication are introduced. The brief history and current role of the Internet are outlined.

1. Chapter 1
Introduction
1.1

2. 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 communications are the exchange of data
between two devices via some form of transmission
medium such as a wire cable.
1.2

3. Figure 1.1 Five components of data communication
1.3

4. Data Representation
1- Text
represented as a bit pattern ( code)
2- Numbers
3- Images
its composed of a matrix
4- Audio
it is a continuous signal
5- Video
1.4

5. Figure 1.2 Data flow (simplex, half-duplex, and full-duplex)
1.5

6. 1-2 NETWORKS
A network is a set of devices (often referred to as nodes)
connected by communication links(network medium). 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. Nodes use a common
network protocol to share resources with each other.
Topics discussed in this section:
Distributed Processing
Network Criteria
Physical Structures
Network Models
Categories of Networks
Interconnection of Networks: Internetwork
1.6

7. 1-2 NETWORKS
Network criteria :
Performance measured in transit time, response time
Transit time : amount of time required for a message to travel from device to device.
Response time : elapsed time between an inquiry and a response.
performance is evaluated by 2 networking metrics :Throughput and Delay
Reliability : Accuracy of delivery, frequency of failure, the time it takes a link to
recover from failure.
Security :
protecting data from unauthorized access, protecting data from damage
and development
1.7

8. Figure 1.3 Types of connections: point-to-point and multipoint
1.8

9. Figure 1.4 Categories of topology
1.9

10. Figure 1.5 A fully connected mesh topology (five devices)
1.10

11. Figure 1.6 A star topology connecting four stations
1.11

12. Figure 1.7 A bus topology connecting three stations
1.12

13. Figure 1.8 A ring topology connecting six stations
1.13

14. Figure 1.9 A hybrid topology: a star backbone with three bus networks
1.14

15. Categories of Networks
The category into which a network falls is determined by its size
Local Area Network:
-LAN size is limited to a few kilometers
-LAN can be as simple as 2 computers and a printer
-IN addition to size, LAN is distinguished from other types of
networks by transmission media and topology.
- early LAN data flow rates from 4 to 6 Mbps, Now it is from 100
to 1000 Mbps
Wide Area Network:
1.15

16. Figure 1.11 WANs: a switched WAN and a point-to-point WAN
1.16

17. Figure 1.12 A heterogeneous network made of four WANs and two LANs
1.17

18. 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.
Topics discussed in this section:
A Brief History
The Internet Today (ISPs)
1.18

19. Figure 1.13 Hierarchical organization of the Internet
1.19

20. 1-4 PROTOCOLS AND STANDARDS
In this section, we define two widely used terms: protocols
and standards. First, we define protocol, which is
synonymous with rule. Then we discuss standards, which
are agreed-upon rules.
Topics discussed in this section:
Protocols
Standards
Standards Organizations
Internet Standards
1.20