Unit 0

Introduction to

Computer Communication Networks

[ Prerequisite ]

Motivation to learn this Subject . . . . . . . . . .

Business

Science

Education

Industry

Topics to be covered in this Introductory Chapter

Data Communications

Networks

Internet

Protocols & Standards

1-1 DATA COMMUNICATIONS

Data communications collectively refers to the exchange of data between two devices via some form of transmission medium ( such as a wire cable ).

Data facts and statistics collected together for reference or analysis.

Communication the imparting or exchanging of information by speaking, writing, or

using some other medium.

a) Effectiveness of a Data Communication Systemb) Componentsc) Data Representation d) Data Flow

Topics discussed in this section:

The effectiveness of a data communication system depends on the following four fundamental characteristics :

~ Delivery [ Destination reached should be correct ]

~ Accuracy [ The data should be 100 % same, as it was, when transmitted ]

~ Timeliness [ The delay should be insignificant ]

~ Jitter [ The speed should be uniform for all data packets ]

a) Effectiveness of a Data Communication System

b) Components of Data Communication System

The five important components of Data Communications are :

~ Message [ Message is the information to be communicated ]

~ Sender [ The sender is the device that sends the message ]

~ Receiver [ The receiver is the device that receives the message ]

~ Transmission Medium [ It is the physical path through which a message travels from sender to receiver

]

~ Protocol [ It is a set of rules that govern data communications ]

c) Data Representation

The data can come in different forms such as :

~ Text [ e.g. a, b, c, X, Y , Z . ]

~ Numbers [ e.g. 0,1,2 , . . . . . . . 9 ]

~ Images [ e.g. *.jpeg , *.png files ]

~ Audio [ e.g. *.mp3 files ]

~ Video [ e.g. *.mp4 , *.avi files etc.]

Data Form

Text

Numbers

Images

Audio

Video

d ) Data Flow

1-2 NETWORKS

What do you mean by 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.

* A link is communication pathway that transfers data from one device to another.

a) Distributed Processingb) Network Criteriac) Physical Structuresd) Network Modelse) Categories of Networksf) Interconnection of Networks: Internetwork

Topics discussed in this section:

a) Distributed Processing

Modern day networks use distributed processing, in which a task is divided among multiple computers.

Note : Contrast this with Centralized Processing

b) Network Criteria

~ Performance [ maximum throughput and minimum delay ]

~ Reliability [ the work should continue in spite of any catastrophe ]

~ Security [ Protecting data from manipulation or damage ]

c) Physical Structures

~ Type of Connection [based on type of link]

~ Physical Topology [based on network’s physical

layout ]

Type of Connection

Physical Topology

i) Mesh Topology

ii) Star Topology

iii) Bus Topology

iv) Ring Topology

Hybrid Topology

d) Network Models

~ OSI Model ( 7 - layer model )

~ Internet Model ( 4 - layer model )

e) Categories of Networks

~ Local Area Network ( LAN )

~ Metropolitan Area Network ( MAN )

~ Wide Area Network ( WAN )

i) LAN ( Local Area Network )

ii) MAN ( Metropolitan Area Network )

Typical Cable TV Network[ An example of MAN ]

iii) WAN ( Wide Area Network )

f ) Interconnection of Networks : Internetwork

1-3 THE INTERNET

The Internet is a communication system that has brought a wealth of information to our fingertips and organized it for our use.

The Internet has revolutionized many aspects of our daily lives. It has affected the way we do business as well as the way we spend our leisure time.

Brief History of Internet~ In mid-1960s’, mainframe computers in research organization were stand-alone devices.

~ In 1967, ARPA ( Advanced Research Projects Agency ) presented the idea for ARPANET.

~ By 1969, ARPANET was a reality. [ Four Universities in USA were interconnected ]

~ In 1973, Vint Cerf and Bob Kahn present the landmark paper outlining the foundations for TCP/IP.

Internet Today~ The Internet has come a long way since the 1960s’. It complexity has grown enormously.

~ It is difficult to give an accurate representation of the Internet because it is continually changing.

~ Hierarchy in Internet Usage : IISPs’ ⇋ NISPs’ ⇋ RISPs’ ⇋ LISPs’ ⇋ Users’. Note : ISP stands for Internet Service Provider

Hierarchical organization of the Internet

* ISP stands for Internet Service Provider * NAP stands for Network Access Point

1-4 PROTOCOLS AND STANDARDS

Protocol A protocol is a set of rules that govern data communications

Standards ~ something that is used or accepted as normal or average. ~ something that is used as a measure, norm, or model in

comparative evaluations.

Standards Organization

An Internet Standard is a thoroughly tested specification that is useful to and adhered to by those who work with the Internet. It is a formalized regulation that must be followed.

Internet Standards

Standards are developed through the cooperation of standards creation committees, forums, and government regulatory agencies. A standards organization is one among these. ( e.g. : ISO / ITU-T / ANSI / IEEE / EIA )