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

Chapter 1

Introduction

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

Chapter 1: Outline

1.1 1.1 Data CommunicationsData Communications

1.2 1.2 NetworksNetworks

1.3 1.3 Network TypesNetwork Types

1.4 1.4 Internet HistoryInternet History

1.5 1.5 Standards and Administration Standards and Administration

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1-1 DATA COMMUNICATIONS1-1 DATA COMMUNICATIONS

When we communicate, we are sharing information.

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The term telecommunication, which includes telephony, telegraph, and television, means communication at a distance.

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Data communications are the exchange of data between two devices via some form of transmission media.

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1.1.1 Components1.1.1 Components

A data communications system has five components (see Figure 1.1).

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Sender

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SenderReceiver

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SenderReceiverMessage

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SenderReceiverMessageTransmission medium

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SenderReceiverMessageTransmission mediumProtocol

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Figure 1.1: Five components of data communication

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1.1.2 Data Representation1.1.2 Data Representation

Information today comes in different forms such as text, numbers, images, audio, and video.

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1.1.3 Data Flow1.1.3 Data Flow

Communication between two devices can be simplex

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Communication between two devices can be simplex, half-duplex

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Communication between two devices can be simplex, half-duplex, or full-duplex

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Figure 1.2: Data flow

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1-2 NETWORKS1-2 NETWORKS

A network is the interconnection of a set of A network is the interconnection of a set of devices capable of communication. devices capable of communication.

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1.2.1 Network Criteria1.2.1 Network Criteria

According to Forouzan: A network must be able to meet a certain number of criteria. The most important of these are performance,

reliability, and security.

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CIA

Confidentiality (security)Integrity (reliability)Availability (performance)

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1.2.2 Physical Structures1.2.2 Physical Structures

Before discussing networks, we need to define some network attributes.

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1-2 Vacabulary1-2 Vacabulary

• node - host, network hardware device,node - host, network hardware device,printer, server, etcprinter, server, etc

• link - aka segment or edgelink - aka segment or edge• scalability – the relative ease in changingscalability – the relative ease in changing

nodes and links of a network.nodes and links of a network.

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Figure 1.3: Types of connection

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Figure 1.6: A bus topology

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1-2 Bus Topology1-2 Bus Topology

• Simple to wire.Simple to wire.• Difficult to diagnose problemsDifficult to diagnose problems• Low fault toleranceLow fault tolerance• not scalable due to the shared backbone not scalable due to the shared backbone

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Figure 1.7: A ring topology

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1-2 Ring Topology1-2 Ring Topology

• Simple to wire.Simple to wire.• Requires special repeater hardwareRequires special repeater hardware• Not as popular as it once was Not as popular as it once was

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Figure 1.5: A star topology

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1-2 Star Topology1-2 Star Topology

• Simple to wire.Simple to wire.• Scalable to large networksScalable to large networks• Easy to diagnose problemsEasy to diagnose problems• Requires more wireRequires more wire• Single point of failure Single point of failure

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Figure 1.4: A fully-connected mesh topology

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1-2 Mesh Topology1-2 Mesh Topology

• Easy to diagnose problemsEasy to diagnose problems• High fault toleranceHigh fault tolerance•Complex to wire.Complex to wire.• Requires more wireRequires more wire

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Figure 1.12: compound topology

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1-3 NETWORKS TYPES: LANs & WANs1-3 NETWORKS TYPES: LANs & WANs

The criteria of distinguishing one type of The criteria of distinguishing one type of network from another is difficult and network from another is difficult and sometimes confusing. We use a few criteria sometimes confusing. We use a few criteria such as size, geographical coverage, and such as size, geographical coverage, and ownership to make this distinction. ownership to make this distinction.

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1.3.1 Local Area Network1.3.1 Local Area Network

A domain within a well defined address space.

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Figure 1.8: An Isolated LAN in the past and today

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1.3.2 Wide Area Network1.3.2 Wide Area Network

Two or more LANs connected together to form a larger more capable network.

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Figure 1.9: A Point-to-Point WAN

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Figure 1.11: An internetwork made of two LANs and one WAN

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Figure 1.10: A Switched WAN

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Figure 1.12: A heterogeneous network made of WANs and LANs

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1.3.3 Switching (circuit vs packet)1.3.3 Switching (circuit vs packet)

An internet is a switched network in which a switch connects at least two links together. A switch needs to forward data from a network to another network when required.

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1.3.3 Switching (circuit vs packet)1.3.3 Switching (circuit vs packet)

The two most common types of switched networks are circuit-switched and packet-switched networks. We discuss both next.

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Figure 1.13: A circuit-switched network

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Figure 1.14: A packet-switched network

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1.3.4 The Internet1.3.4 The Internet

An internet (note the lowercase i) is two or more networks that can communicate with each other.

The most notable internet is called THE Internet (uppercase I), and is composed of thousands of interconnected networks all over the world.

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Figure 1.15: The Internet today

Peeringpoint Peering

point

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1.3.5 Accessing the Internet1.3.5 Accessing the Internet

The user needs to be physically connected to an ISP.

The physical connection is normally done through a point-to-point WAN.

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Figure 1.16: Maturity levels of an RFC

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Figure 1.17: Internet administration

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