This document discusses data communication and computer networks. It introduces the five components of data communication: data representation, direction of data flow, transmission medium, terminal equipment, and protocols. It also describes different types of network topologies including point-to-point, star, bus, ring, and mesh. Finally, it discusses protocols and standards used in computer networks and the Internet.

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Chapter 1
Introduction

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1.1 Data Communication
Components
Data Representation
Direction of Data Flow

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Figure 1.1 Five components of data communication

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Figure 1.2 Simplex

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Figure 1.3 Half-duplex

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Figure 1.4 Full-duplex

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1.2 Networks
Distributed Processing
Network Criteria
Physical Structures
Categories of Networks

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Figure 1.5 Point-to-point connection

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Figure 1.6 Multipoint connection

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Figure 1.7 Categories of topology

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Figure 1.8 Fully connected mesh topology (for five devices)

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Figure 1.9 Star topology

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Figure 1.10 Bus topology

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Figure 1.11 Ring topology

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Figure 1.12 Categories of networks

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Figure 1.13 LAN

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Figure 1.13 LAN (Continued)

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Figure 1.14 MAN

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Figure 1.15 WAN

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1.3 The Internet1.3 The Internet
A Brief History
The Internet Today

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Figure 1.16 Internet today

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1.4 Protocols and Standards1.4 Protocols and Standards
Protocols
Standards
Standards Organizations
Internet Standards

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4.4 Transmission Mode4.4 Transmission Mode
Parallel Transmission
Serial Transmission

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Figure 4.24 Data transmission

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Figure 4.25 Parallel transmission

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Figure 4.26 Serial transmission

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In asynchronous transmission, weIn asynchronous transmission, we
send 1 start bit (0) at the beginningsend 1 start bit (0) at the beginning
and 1 or more stop bits (1s) at the endand 1 or more stop bits (1s) at the end
of each byte. There may be a gapof each byte. There may be a gap
between each byte.between each byte.
Note:Note:

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Asynchronous here meansAsynchronous here means
“asynchronous at the byte level,” but“asynchronous at the byte level,” but
the bits are still synchronized; theirthe bits are still synchronized; their
durations are the same.durations are the same.
Note:Note:

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Figure 4.27 Asynchronous transmission

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In synchronous transmission,In synchronous transmission,
we send bits one after another withoutwe send bits one after another without
start/stop bits or gaps.start/stop bits or gaps.
It is the responsibility of the receiver toIt is the responsibility of the receiver to
group the bits.group the bits.
Note:Note:

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Figure 4.28 Synchronous transmission