introduction to computer networks 1friday, december 04, 2015

Introduction to

Computer Networks

1Tuesday, April 18, 2023

NETWORKSNETWORKS

A A network network is a set of devices (often referred is a set of devices (often referred to as to as nodesnodes) connected by communication ) connected by communication linkslinks. A node can be a computer, printer, or . A node can be a computer, printer, or any other device capable of sending and/or any other device capable of sending and/or receiving data generated by other nodes on receiving data generated by other nodes on the network.the network.


Overview


DATA COMMUNICATIONSDATA COMMUNICATIONS

Where are the data communications?Why data communications?Telecommunication: communication at a distance.Data: information presented in whatever form is agreed upon by the parties creating and using the data.Data communicationsData communications:: the exchange of data the exchange of data between two devices via some form of between two devices via some form of transmission medium such as a wire cable.transmission medium such as a wire cable.


What do we need?HardwareSoftware

Four fundamental characteristics:1. Delivery: correct destination2. Accuracy: correct data3. Timeliness: fast enough4. Jitter: uneven delay

DATA COMMUNICATIONSDATA COMMUNICATIONS


Topics to be covered:

–Components

–Data representation

–Data flow


Figure 1.1 Five components of data communication

Components


Communication Tasks Some of the key tasks that must be performed in data

communication system.

• Transmission system utilization• Interfacing• Synchronization• Error Detection & Correction• Flow control• Addressing• Routing• Recovery• Message formatting• Security• Network Management


Data Representation

TextEmail, articles, etcCoding (Unicode, ASCII)

NumbersDirect conversion

ImagesPixels, resolution, gray scale, RGB.

AudioContinuous, signal conversion

VideoMovie, continuous/discrete


Figure : Data flow (simplex, half-duplex, and full-duplex)

Data Flow


Topics to be covered:

• Distributed Processing• Network Criteria• Physical Structures• Network Models• Categories of Networks• Internetwork


• Task is divided among multiple computers.

Advantages of Distributed processing• Security/Encapsulation• Distributed Database• Faster problem solving• Security through redundancy


Network criteria1. Performance

Transit time, response time. Throughput, delay.

2. ReliabilityFailure frequency, recovery time

3. SecurityProtection.

NETWORKSNETWORKS


Figure : Types of connections: point-to-point and multipoint

Type of Connections

1.Spatially shared

2.Time shared


Figure : Categories of physical topology

Physical topology


Mesh Networks

Partial Mesh

A

B C

D EFully Mesh

A

B C

DE


Star

Figure : A star topology connecting four stations


Bus

Figure : A bus topology connecting three stations


Ring

Figure : A ring topology connecting six stations


Classification of Networks by Size and Community

A company or home:

covers few km, 100-1000 mbps

A city wide network:

area inside a town or city; TV cables.

A country wide

network: long distance

transmission 20

Single to Multiple LANs


Figure 1.10 An isolated LAN connecting 12 computers to a hub in a closet


Metropolitan Area Network


Wide Area Network


McGraw-Hill ©The McGraw-Hill Companies, Inc., 2000

25

Internetworking

• When two or more networks are connected , they become an internetwork, or internet .

• The term internet means interconnection of network

• While the Internet is the name of a specific worldwide network.

Tuesday, April 18, 2023

THE INTERNETTHE INTERNET

The The Internet Internet has revolutionized many aspects has revolutionized many aspects of our daily lives. It has affected the way we of our daily lives. It has affected the way we do business as well as the way we spend our do business as well as the way we spend our leisure time. The Internet is a leisure time. The Internet is a communication system that has brought a communication system that has brought a wealth of information to our fingertips and wealth of information to our fingertips and organized it for our use.organized it for our use.


3

The Internet

Today’s Internet

Hierarchical Infrastructure

International/National ISPs

Connected by NAP –Network Access Points(also called peering pointsOr Internet eXchanges)

Regional ISP

(Local) ISP

ISP = Internet Service Provider


PROTOCOLS AND STANDARDSPROTOCOLS AND STANDARDS

Protocols (rules)1. Why do we need protocols?2. Key elements of protocols

a) Syntaxb) Semanticsc) Timing

Standards1. De facto (by fact) vs. De jure (by law)2. Organizations3. Internet standards (Internet draft & RFC)


PROTOCOLS AND STANDARDSPROTOCOLS AND STANDARDS

Network Standards Organizations

National Standards Organizations (Generally responsible for standards within a nation and usually participate in that nation’s international activity)• American National Standards Institute (ANSI)• British Standards Institute (BSI)• French Association for Normalization (AFNOR)• German Institute for Normalization (DIN)Regional Standards Organizations (Restrict their activity to a specific geographical region but generally influence standards outside their regions)• Committee of European Posts and Telegraph (CEPT)• European Committee for Standardization (CEN)• European Computer Manufacturers’ Association (ECMA)International Standards Organizations (Promote standards for worldwide use)• International Standards Organization (ISO)• International Telecommunications Union (ITU)consists of ITU-T, which is responsible for communications, interfaces, and other standards related to telecommunications; and ITU-R, which is responsible for allocating frequency bands in the electromagnetic spectrum for telecommunications, and for making recommendations relating to radio communications. (Note: ITU-T is the former CCITTConsultative Committee for International Telephony and Telegraphy.) Industry, Trade, and Professional Standards Organizations (Restrict their activity to member interest areas but generally influence other areas)• Electronic Industries Association (EIA)• Telecommunications Industries Association (TIA) • Institute for Electrical and Electronics Engineers (IEEE)• Internet Engineering Task Force (IETF) 29Tuesday, April 18, 202

3

Summary

Data communicationsNetworksThe internetProtocols and standards


introduction to computer networks 1friday, december 04, 2015

Documents

correct data

exchange of data

data communication system

duplex data flow

data flow simplex

networks networks

data representation

computer networks