INTRODUCTION T.Najah Al_Subaie Kingdom of Saudi Arabia Prince Norah bint Abdul Rahman University College of Computer Since and Information System NET331

Instructor: T.Najah AL-Subaie Course URL: 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 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).