Chapter 1: Introduction to Data Communication and Networks

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Chapter 1
Introduction
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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1-1 DATA COMMUNICATIONS1-1 DATA COMMUNICATIONS
The termThe term telecommunicationtelecommunication means communication at ameans communication at a
distance. The worddistance. The word datadata refers to information presentedrefers to information presented
in whatever form is agreed upon by the parties creatingin whatever form is agreed upon by the parties creating
and using the data.and using the data. Data communicationsData communications are theare the
exchange of data between two devices via some form ofexchange of data between two devices via some form of
transmission medium such as a wire cable.transmission medium such as a wire cable.
Components
Data Representation
Data Flow
Topics discussed in this section:Topics discussed in this section:

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1-1 DATA COMMUNICATIONS1-1 DATA COMMUNICATIONS
Effective Characteristics of Data CommunicationEffective Characteristics of Data Communication
Delivery (intended Reciever )
Accuracy (unchanged data)
Timeliness
Jitter (uneven delay in audio/video streaming)

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Figure 1.1 Five components of data communication

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

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1-2 NETWORKS1-2 NETWORKS
AA networknetwork is a set of devices (often referred to asis a set of devices (often referred to as nodesnodes))
connected by communicationconnected by communication linkslinks. A node can be a. A node can be a
computer, printer, or any other device capable of sendingcomputer, printer, or any other device capable of sending
and/or receiving data generated by other nodes on theand/or receiving data generated by other nodes on the
network.network.
Distributed Processing
Network Criteria
Physical Structures
Network Models
Categories of Networks
Interconnection of Networks: Internetwork

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1-2 NETWORKS1-2 NETWORKS
Network Criteria
Performance:
transit time (device to device)
response time (enquiry to response)
Throughput
delay
Reliability
Security

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Figure 1.3 Types of connections: point-to-point and multipoint
If several devices can use the link simultaneously, it is a spatially shared
connection. If users must take turns, it is a timeshared connection.

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Figure 1.4 Categories of topology

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Figure 1.5 A fully connected mesh topology (five devices)
• High speed, Little network
failure
• Privacy and Security
• Fault isolation
• Fault identification
• No. of links
• No. of I/O ports
• Costing

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Figure 1.6 A star topology connecting four stations
Installation, reconfigure
Fault isolation and identification
Costing, I/O ports
Single point of dependency

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Figure 1.7 A bus topology connecting three stations
Long distance issue
Installation
Number & length of cables
Reconnection, signal reflection

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Figure 1.8 A ring topology connecting six stations
Uni-directional
Installation
Repeaters
Fault isolation
Dual ring

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

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Figure 1.10 An isolated LAN connecting 12 computers to a hub in a closet

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Categories of Networks
LAN
•Privately owned for office, home, buildings etc.
•limited to few kms.
•resource sharing
•generally one type of transmission medium
•speed
•WLAN
WAN
•Long distance transmission
•either complex (Switched WAN) or simple (point to point WAN)
•e.g. X.25 >> Frame Relay >> ATM
•Wireless WAN
MAN
• High speed, DSL, Cable TV network

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Figure 1.11 WANs: a switched WAN and a point-to-point WAN

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

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1-3 THE INTERNET1-3 THE INTERNET
TheThe InternetInternet has revolutionized many aspects of our dailyhas revolutionized many aspects of our daily
lives. It has affected the way we do business as well as thelives. It has affected the way we do business as well as the
way we spend our leisure time. The Internet is away we spend our leisure time. The Internet is a
communication system that has brought a wealth ofcommunication system that has brought a wealth of
information to our fingertips and organized it for our use.information to our fingertips and organized it for our use.
A Brief History
The Internet Today (ISPs)

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Figure 1.13 Hierarchical organization of the Internet

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1-4 PROTOCOLS AND STANDARDS1-4 PROTOCOLS AND STANDARDS
In this section, we define two widely used terms:In this section, we define two widely used terms: protocolsprotocols
andand standardsstandards. First, we define protocol, which is. First, we define protocol, which is
synonymous with rule. Then we discuss standards, whichsynonymous with rule. Then we discuss standards, which
are agreed-upon rules.are agreed-upon rules.
Protocols
Standards
Standards Organizations
Internet Standards

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Protocols (rules)
what to communicate, how to communicate and when to
communicate
Key Elements of Protocols
1.Syntax
Structure of format of data
2.Semantics
Meaning of each section bits
3.Timing
When to send and how fast..

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Standards (agreed upon rules)
Categories of Standards
1.De facto.
By convention or by fact
2.De jure.
By Law or by Government

Chapter 1: Introduction to Data Communication and Networks

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Chapter 1: Introduction to Data Communication and Networks