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Chapter 1: Outline 1.1 Data Communications 1.1 Data Communications 1.2 Networks 1.2 Networks 1.3 Network Types 1.3 Network Types 1.4 Internet History 1.4 Internet History 1.5 Standards and Administration 1.5 Standards and Administration

DATA COMMUNICATIONS When we communicate, we are sharing information.

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

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

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

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

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

Components A data communications system has five components (see Figure 1.1). Sender Receiver Message

Components A data communications system has five components (see Figure 1.1). Sender Receiver Message Transmission medium

Components A data communications system has five components (see Figure 1.1). Sender Receiver Message Transmission medium Protocol

1.12 Figure 1.1 : Five components of data communication

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

Data Flow Communication between two devices can be simplex

Data Flow Communication between two devices can be simplex, half-duplex

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

1.17 Figure 1.2 : Data flow

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

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.

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 CIA Confidentiality (security) Integrity (reliability) Availability (performance) 1.20

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

Vacabulary node - host, network hardware device, node - host, network hardware device, printer, server, etc link - aka segment or edge link - aka segment or edge scalability – the relative ease in changing scalability – the relative ease in changing nodes and links of a network.

1.23 Figure 1.3 : Types of connection

1.24 Figure 1.6 : A bus topology

Bus Topology Simple to wire. Simple to wire. Difficult to diagnose problems Difficult to diagnose problems Low fault tolerance Low fault tolerance not scalable due to the shared backbone not scalable due to the shared backbone

1.26 Figure 1.7 : A ring topology

Ring Topology Simple to wire. Simple to wire. Requires special repeater hardware Requires special repeater hardware Not as popular as it once was Not as popular as it once was

1.28 Figure 1.5 : A star topology

Star Topology Simple to wire. Simple to wire. Scalable to large networks Scalable to large networks Easy to diagnose problems Easy to diagnose problems Requires more wire Requires more wire Single point of failure Single point of failure

1.30 Figure 1.4 : A fully-connected mesh topology

Mesh Topology Easy to diagnose problems Easy to diagnose problems High fault tolerance High fault tolerance Complex to wire. Complex to wire. Requires more wire Requires more wire

1.32 Figure 1.12: compound topology

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

Local Area Network A domain within a well defined address space.

1.35 Figure 1.8: An Isolated LAN in the past and today

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

1.37 Figure 1.9: A Point-to-Point WAN

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

1.39 Figure 1.10: A Switched WAN

1.40 Figure 1.12: A heterogeneous network made of WANs and LANs

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.

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

1.43 Figure 1.13: A circuit-switched network

1.44 Figure 1.14: A packet-switched network

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.

1.46 Figure 1.15: The Internet today

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.

1.48 Figure 1.16: Maturity levels of an RFC

1.49 Figure 1.17: Internet administration