UNIT-1

BASICS OF COMPUTER

NETWORK

SYLLABUS

1a.List the applications of Computer Network

1b.Differentiate Various Line configuration

1c. Design Computer Network considering

particular topology

1d.Categories Computer Network based on scope

and connection

1e.Explain use of various types of servers.

TOPICS AND SUB-TOPICS

1.1 Definition and history of networks

1.2 Usage of Computer Networks

1.3 Standard Organizations and protocol

1.4 Line Configurations

1.5 Network Topology

1.6 Categories of network based on topology and

based on connection

1.7 Applications and features of different types of

servers : File server ,Print server, Mail

server,Web server,Proxy server

1.1 COMPUTER NETWORKS

Computer network connects two or more autonomous computers.

Introdution to Computer Networks

APPLICATIONS OF NETWORKS

1.Resource Sharing

Hardware (computing resources, disks, printers)

Software (application software)

2.Information Sharing

Easy accessibility from anywhere (files, databases)

Search Capability (WWW)

3.Communication

Email

Message broadcast

4.Remote computing

Introduction to Computer Networks

DATA COMMUNICATION SYSTEM COMPONENTS

1.2 USAGE OF COMPUTER NETWORKS

1.Resource Sharing:

2.High Reliability:

3.Saving Money:

4.Scalability:

5.Access to Remote Information:

6. Person to Person Communication:

7. Interactive Entertainment:

1.3 STANDARD ORGANIZATION AND

PROTOCOLS

1. ORGANIZATIONS FOR

COMMUNICATION STANDARDS

Standards are developed by cooperation among

standards creation committees, forums, and

government regulatory agencies.

Standards Creation Committees

a) International Standards Organization (ISO)

b) International Telecommunications Union (ITU)

c) American National Standards Institute (ANSI)

d) Institute of Electrical and Electronics Engineers (IEEE)

e) Electronic Industries Association (EIA)

f) Internet Engineering Task Force (IETF)

A) INTERNATIONAL STANDARDS

ORGANIZATION (ISO)

A multinational body whose membership is drawn mainly from the standards creation committees of various governments throughout the world

Dedicated to worldwide agreement on international standards in a variety field.

Currently includes 82 memberships industrialized nations.

Aims to facilitate the international exchange of goods and services by providing models for compatibility, improved quality, increased quality, increased productivity and decreased prices.

B) INTERNATIONAL

TELECOMMUNICATIONS UNION (ITU)

Also known as International Telecommunications Union-Telecommunication Standards Sector (ITU-T)

An international standards organization related to the United Nations that develops standards for telecommunications.

Two popular standards developed by ITU-T are:

i) V series – transmission over phone lines

ii) X series – transmission over public digital networks, email and directory services and ISDN.

C) AMERICAN NATIONAL STANDARDS

INSTITUTE (ANSI)

- A non-profit corporation not affiliated with

US government.

- ANSI members include professional

societies, industry associations,

governmental and regulatory bodies, and

consumer groups.

- Discussing the internetwork planning and

engineering, ISDN services, signaling, and

architecture and optical hierarchy.

D) INSTITUTE OF ELECTRICAL AND

ELECTRONICS ENGINEERS (IEEE)

The largest national professional group involved in

developing standards for computing, communication,

electrical engineering, and electronics.

Aims to advance theory, creativity and product quality

in the fields of electrical engineering, electronics and

radio.

It sponsored an important standard for local area

networks called Project 802 (eg. 802.3, 802.4 and 802.5

standards.)

E) ELECTRONIC INDUSTRIES

ASSOCIATION (EIA)

An association of electronics manufacturers in the US.

Provide activities include public awareness education

and lobbying efforts in addition to standards

development.

Responsible for developing the EIA-232-D and EIA-530

standards.

F) INTERNET ENGINEERING TASK FORCE

(IETF)

Concerned with speeding the growth and

evolution of Internet communications.

The standards body for the Internet itself

Reviews internet software and hardware.

1.4 LINE CONFIGURATION

Point-to-Point Line Configuration

Point-to-Point Line Configuration

Point-to-Point Line Configuration

Multipoint Line Configuration

1.5 NETWORK TOPOLOGY

TOPOLOGY

Topology refers to the layout of connected

devices on a network.

Here, some logical layout of topology.

1. Mesh

2. Star

3. Bus

4. Ring

5. Tree and Hybrid

NETWORK TOPOLOGY

MESH TOPOLOGY

Here every device has a point to point link to

every other device.

Node 1 node must be connected with n-1

nodes.

A fully connected mesh can have n(n-1)/2

physical channels to link n devices.

It must have n-1 I/O ports.

MESH TOPOLOGY

Advantages:

1. They use dedicated links so each link

can only carry its own data load. So

traffic problem can be avoided.

2. It is robust. If any one link get damaged

it cannot affect others.

3. It gives privacy and security.(Message

travels along a dedicated link)

4. Fault identification and fault isolation

are easy.

MESH TOPOLOGY

MESH TOPOLOGY

MESH TOPOLOGY

Disadvantages:

1. The amount of cabling and the number of

I/O ports required are very large. Since

every device is connected to each devices

through dedicated links.

2. The sheer bulk of wiring is larger then the

available space.

3. Hardware required to connected each

device is highly expensive.

MESH TOPOLOGY

Applications:

1. Telephone Regional office.

2. WAN.(Wide Area Network).

STAR TOPOLOGY

1. Here each device has a dedicated point-to-

point link to the central controller called

“Hub”(Act as a Exchange). 2. There is no direct traffic between devices.

3. The transmission are occurred only

through the central “hub”. 4. When device 1 wants to send data to

device 2; First sends the data to hub.

Which then relays the data to the other

connected device.

STAR TOPOLOGY

STAR TOPOLOGY

STAR TOPOLOGY

Advantages:

1. Less expensive then mesh since each

device is connected only to the hub.

2. Installation and configuration are easy.

3. Less cabling is need then mesh.

4. Robustness.(if one link fails, only that

links is affected. All other links remain

active)

5. Easy to fault identification & to remove

parts.

6. No distruptions to the network then

connecting(or) removing devices.

STAR TOPOLOGY

Disadvantages:

1. Even it requires less cabling then mesh

when compared with other topologies it

still large.(Ring or bus).

2. Dependency(whole n/w dependent on one

single point(hub). When it goes down. The

whole system is dead.

APPLICATIONS

Star topology used in Local Area

Networks(LANs).

High speed LAN often used STAR.

BUS TOPOLOGY

A bus topology is multipoint.

Here one long cable act as a backbone to link

all the devices are connected to the backbone

by drop lines and taps.

Drop line- is the connection b/w the devices

and the cable.

Tap- is the splitter that cut the main link.

This allows only one device to transmit at a

time.

BUS TOPOLOGY

BUS TOPOLOGY

BUS TOPOLOGY

BUS TOPOLOGY

BUS TOPOLOGY

A device want to communicate with other

device on the n/ws sends a broadcast message

onto the wire all other devices see.

But only the intended devices accepts and

process the message.

BUS TOPOLOGY

Advantages:

1. Ease of installation

2. Less cabling

Disadvantages:

1. Difficult reconfiguration and fault

isolation.

2. Difficult to add new devices.

3. Signal reflection at top can degradation in

quality.

4. If any fault in backbone can stops all

transmission.

BUS TOPOLOGY

Applications:

Most computer motherboard.

RING TOPOLOGY

Here each device has a dedicated connection

with two devices on either side.

The signal is passed in one direction from

device to device until it reaches the

destination and each device have repeater.

When one device received signals instead of

intended another device, its repeater then

regenerates the data and passes them along.

To add or delete a device requires changing

only two connections.

RING TOPOLOGY

RING TOPOLOGY

RING TOPOLOGY

RING TOPOLOGY

Advantages:

Easy to install.

Easy to reconfigure.

Fault identification is easy.

Disadvantages:

Unidirectional traffic.

Break in a single ring can break entire

network.

RING TOPOLOGY

Applications:

Ring topologies are found in some office

buildings or school campuses.

Today high speed LANs made this topology

less popular.

TREE TOPOLOGY

Alternatively referred to as a star bus

topology.

Tree topology is one of the most common

network setups that is similar to a bus

topology and a star topology.

A tree topology connects multiple star

networks to other star networks. Below is a

visual example of a simple computer setup on

a network using the star topology.

TREE TOPOLOGY

HYBRID TOPOLOGY

A network which contain all type of physical

structure and connected under a single

backbone channel.

HYBRID TOPOLOGY

a

CONSIDERATIONS FOR CHOOSING

TOPOLOGY

Money-Bus n/w may be the least expensive way to

install a n/w.

Length-of cable needed- the linear bus n/w uses

shorter lengths of cable.

Future growth-with star topology, expending a n/w is

easily done by adding another devices.

Cable type-most common used cable in commercial

organization is twisted pair. Which often

used with star topologies.

CONTINUE…

Full mesh topology is theoretically the best

since every device is connected to every

other device.(thus maximizing speed and

security. however, it quite expensive to

install)

Next best would be tree topology, which is

basically a connection of star.

1.6 CATEGORIES OF NETWORK

Based on scope

Based on Connection

1.6 TYPES OF NETWORK:

Local Area Network

Wide Area Network

Metropolitan Area Network

57

LOCAL AREA NETWORK:

A local area network (LAN) is a group of

computers and associated devices that share a

common communications line or wireless link.

Typically, connected devices share the resources

of a single processor or server within a small

geographic area .

A local area network may serve as few as two or

three users or as many as thousands of users.

58

59

WIDE AREA NETWORK:

The WAN is a communications network that

makes use of existing technology to connect

local computer networks into a larger

working network that may cover both

national and international locations.

60

61

METROPOLITAN AREA NETWORK

(MAN):

A metropolitan area network (MAN) is a

network that interconnects users with

computer resources in a geographic area or

region larger than that covered by even a

large local area network but smaller than the

area covered by a wide area network (WAN).

It is also used to mean the interconnection of

several local area networks by bridging them

with backbone lines

62

NETWORK TOPOLOGIES

Network Topology – Maps of how the

physical or logical paths of network

devices connect. The three major

topologies are star, ring, and bus.

Star Topology – Most common Ethernet

network topology where each device

connects to a central hub or switch.

Hub – A device used with the Universal

Serial Bus or in a star network topology

that allows multiple device connections.

Switch – In star networks, a Layer 2 central

controlling device.

63

NETWORK TOPOLOGIES

64

HUB/SWITCH

NETWORK TOPOLOGIES

65

STAR TOPOLOGY

NETWORK TOPOLOGIES

66

LOGICAL RING TOPOLOGY

NETWORK TOPOLOGIES

67

Bus Topology

NETWORK TOPOLOGIES

68

DIFFERENTIATE BETWEEN THE THREE

TYPES OF COMPUTER NETWORKS

SIMPLEX

HALF-DUPLEX

FULL-DUPLEX

1.6 CATEGORIES OF NETWORK

BASED ON SCOPE

BASED ON CONNECTION

LAN, MAN & WAN

Network in small geographical Area (Room, Building or a Campus) is called LAN (Local Area Network)

Network in a City is call MAN (Metropolitan Area Network)

Network spread geographically (Country or across Globe) is called WAN (Wide Area Network)

LOCAL AREA NETWORK

LOCAL AREA NETWORK

METROPOLITAN AREA NETWORK

WIDE AREA NETWORK

Figure 2-19

WCB/McGraw-Hill The McGraw-Hill Companies, Inc., 1998

INTERNETWORK

(INTERNET)

NETWORK TOPOLOGY

The network topology defines the way in which computers, printers, and other devices are connected. A network topology describes the layout of the wire and devices as well as the paths used by data transmissions.

Introduction to Comuter Networks

MESH TOPOLOGY The mesh topology connects all devices (nodes) to each other for redundancy and fault tolerance.

It is used in WANs to interconnect LANs and for mission critical networks like those used by banks and financial institutions.

Implementing the mesh topology is expensive and difficult.

Introduction to Computer Networks

MESH TOPOLOGY

MERITS

NO CONGESTION

PROBLEM

NO MAC PROTOCOLS

ARE NEEDED

MORE SECURE

IT IS ROBUST

FAULT IDENTIFICATION

IS EASY

DEMERITS

CABLE LENGTH

IMPRACTICAL FOR

LARGE NETWORKS

STAR & TREE TOPOLOGY

THE STAR TOPOLOGY IS THE MOST COMMONLY USED ARCHITECTURE IN ETHERNET LANS.

WHEN INSTALLED, THE STAR TOPOLOGY RESEMBLES SPOKES IN A BICYCLE WHEEL.

LARGER NETWORKS USE THE EXTENDED STAR TOPOLOGY ALSO CALLED TREE TOPOLOGY. WHEN USED WITH NETWORK DEVICES THAT FILTER FRAMES OR PACKETS, LIKE BRIDGES, SWITCHES, AND ROUTERS, THIS TOPOLOGY SIGNIFICANTLY REDUCES THE TRAFFIC ON THE WIRES BY SENDING PACKETS ONLY TO THE WIRES OF THE DESTINATION HOST.

Itroduction to Computer Networks

STAR & TREE TOPOLOGY

MERITS

CHEAPER THAN MESH TOPOLOGY

RELATIVELY EASIER TO INSTALL, MAINTAIN &

CONFIGURE

DEMERITS

IF HUB GOES DOWN THE ENTIRE NETWORK

BECOMES DEFUNCT

RING TOPOLOGY

A FRAME TRAVELS AROUND THE RING, STOPPING AT EACH NODE. IF A NODE WANTS TO TRANSMIT DATA, IT ADDS THE DATA AS WELL AS THE DESTINATION ADDRESS TO THE FRAME.

THE FRAME THEN CONTINUES AROUND THE RING UNTIL IT FINDS THE DESTINATION NODE, WHICH TAKES THE DATA OUT OF THE FRAME.

Introduction to Computer Networks

RING TOPOLOGY

MERITS

EASY TO RECONFIGURE AND INSTALL.

FAULT ISOLATION IS RELATIVELY EASY IN A

RING.

DEMERITS

IF A NODE IN A SIMPLE RING FAILS, THE WHOLE

RING CAN NOT FUNCTION.

BUS TOPOLOGY

COMMONLY REFERRED TO AS A LINEAR BUS, ALL THE DEVICES ON A BUS TOPOLOGY ARE CONNECTED BY ONE SINGLE CABLE.

BUS TOPOLOGY

MERITS

EASY TO INSTALL

USES LESS CABLE

DEMERITS

RELATIVELY DIFFICULT

TO ADD NEW NODES.

EVEN IF A PORTION OF

THE BUS BREAKS DOWN,

THE WHOLE BUS CAN NOT

FUNCTION.

1.7 FILE SERVER

IN COMPUTING, A FILE SERVER (OR FILESERVER)

IS A COMPUTER ATTACHED TO A NETWORK THAT

HAS THE PRIMARY PURPOSE OF PROVIDING A

LOCATION FOR SHARED DISK ACCESS, I.E.

SHARED STORAGE OF COMPUTER FILES (SUCH AS

DOCUMENTS, SOUND FILES, PHOTOGRAPHS,

MOVIES, IMAGES, DATABASES, ETC.)

IN COMPUTING, A FILE SERVER (OR FILESERVER)

IS A COMPUTER ATTACHED TO A NETWORK THAT

HAS THE PRIMARY PURPOSE OF PROVIDING A

LOCATION FOR SHARED DISK ACCESS, I.E.

SHARED STORAGE OF COMPUTER FILES (SUCH AS

DOCUMENTS, SOUND FILES, PHOTOGRAPHS,

MOVIES, IMAGES, DATABASES, ETC.)

PRINT SERVER

A PRINT SERVER, OR PRINTER SERVER, IS A

DEVICE THAT CONNECTS PRINTERS TO CLIENT

COMPUTERS OVER A NETWORK.

PROXY SERVER

A PROXY SERVER IS A COMPUTER THAT OFFERS

A COMPUTER NETWORK SERVICE TO ALLOW

CLIENTS TO MAKE INDIRECT NETWORK

CONNECTIONS TO OTHER NETWORK SERVICES

WEB SERVER

A WEB SERVER IS AN INFORMATION

TECHNOLOGY THAT PROCESSES REQUESTS VIA

HTTP, THE BASIC NETWORK PROTOCOL USED

TO DISTRIBUTE INFORMATION ON THE WORLD

WIDE WEB.

APPLICATION SERVER

AN APPLICATION SERVER IS A COMPONENT-

BASED PRODUCT THAT RESIDES IN THE MIDDLE-

TIER OF A SERVER CENTRIC ARCHITECTURE.

MAIL SERVER

A MAIL SERVER (ALSO KNOWN AS A MAIL

TRANSFER AGENT OR MTA, A MAIL TRANSPORT

AGENT, A MAIL ROUTER OR AN INTERNET

MAILER) IS AN APPLICATION THAT RECEIVES

INCOMING E-MAIL FROM LOCAL USERS (PEOPLE

WITHIN THE SAME DOMAIN) AND REMOTE

SENDERS AND FORWARDS OUTGOING E-MAIL FOR

DELIVERY.