INTRODUCTION

T.Najah Al_Subaie

Kingdom of Saudi Arabia

Prince Norah bint Abdul Rahman University

College of Computer Since and Information System

NET331

NET331

Instructor: T.Najah AL-Subaie

Course URL: http://net331.wikispaces.com/

Text Book: • Behrouz A Frouzan ,”Data

Communications and Networking”, McGraw Hill, Fourth Edition.

• Tanebaum, ”Computer Networks “, Prentic-Hall

Course Objectives

Understanding the basics of computer Networks.

Understanding the types of network architectures

Understanding the principles of the layering concepts.

Understanding the importance of networks in different applications.

Grading

2 Quizzes: 10% Reading Summaries: 5% Mid term : 20% Home Works : 10% Presentation: 5% Final exam: 50%

Chapter 1

Data communications. Networks. Protocols and Standard.

DATA COMMUNICATIONS

Telecommunication Means communication at a distance.

Data Refers to information presented in whatever form is

agreed upon by the parties creating and using the data. Data communications

The exchange of data between two devices via some form of transmission medium such as a wire cable.

DATA COMMUNICATIONS

Data communication system has five components: Message Sender Receiver Transmission medium Protocol

Components of Data Communication

Data Representation

Text Numbers Images Audio Video

Data Flow

Communication between two devices can be: Simplex

The communication is unidirectional; only one of the two devices can transmit.

Keyboard , monitor. Half Duplex

Each station can both transmit and receive , but not at the same time.

Walkie-talkies phones. Full Duplex

Both stations can transmit and receive simultaneously.

Data Flow

Network

A network is a set of devices (often referred to as nodes) connected by communication links. 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.

Network

Distributed Processing Task is divided among multiple computers.

Network Criteria Network must meet a number of criteria:

Performance Reliability Security

Network Criteria

Performance Can be measured in many ways:

Transmission time Response time.

Performance metrics: Throughput and delays. Throughput: network throughput is the average rate of

successful message delivery over a communication channel

Reliability Measured by frequency of failure, time required to recover

from a failure and other. Security

Includes protecting data from unauthorized access.

Physical Structures

Type of connection: Point to point.

Provides a dedicated link between two devices. Entire capacity of the link is reserved for

transmission between those two devices. Example: the connection between the remote

control and the television control system. Multipoint.

More than two specific devices share a single link.

Share the capacity of the channel

Types of connections: point-to-point and multipoint

Physical Structures

Physical topology Refers to the way in which a network is laid

out physically. Four basic topologies:

Mesh Star Bus ring

Categories of Topology

Mesh

Every device has a dedicated point to point link to every other device.

For a network with n nodes. The number of physical links is n(n-1)/2

Pros Cons

A fully connected mesh topology (five devices)

Star Topology

Each device has a dedicated point to point link only to a central controller called a hub.

Number of links: Pros. Cons.

A star topology connecting (four stations)

Bus Topology

The devices are connected to one long cable.

Pros. Cons.

A bus topology connecting (three stations)

Ring Topology

Each device has a dedicated point to point connection with only the two devices on either side of it.

Pros. Cons.

A ring topology connecting six stations

A hybrid topology: a star backbone with three bus networks

Network Models

Network models are defined by a standards.

Standards are needed to allow heterogeneous devices to communicate with each other.

Two standards for network models: OSI (Open System Interconnection) Model. Internet Model.

Network Categories

Categories of the networks based on their sizes: Local Area Network

Privately owned and links the devices in a single office, building.

Size : few kilometers. Usually used to share resources between personal computers.

Wide Area Network Provides long distance transmission of information. (e.g.

country) Metropolitan Area Network

A network with a size between a LAN and WAN. (e.g. city) Internet

Two or more connected networks.

Protocols and Standards

Protocols: Set of rules that govern data communications.

Standards: Agreement upon rules.

Homework

Summarizing Chapter 1 in the text book ( Data communication and networking) .