deepak bhinde pgt computer science k v no. 2, ajmer · address 0.0.0.0, 127 .0.0.1 and 255 .255...

Deepak BhindeDeepak Bhinde

PGT Computer Science

K V No. 2, Ajmer

Agenda � Introduction

� Need for Networking

� Elementary Terminology of Network

Domain Name Resolution� Domain Name Resolution

� Network Topologies

� Types of Network

� Transmission Media

� Network Devices

� Network Security

Deepak Bhinde PGT Computer Science

Computer Networks� What is a Network ?

An interconnected collection of autonomous computer.

� Computer Networks

Computer network


� Computer networkconnects two or moreautonomouscomputers.

� The computers canbe geographicallylocated anywhere.

Need of Networking � Network Goals

1. Resource Sharing

� To make all programs ,data and peripherals available to any oneon the network irrespective of the physical location of theresource and the user.resource and the user.

2. Reliability

� A file can have copies on two or three different machines , so if one of them is unavailable ( hardware crash ) , the other copies could be used.

3. Cost Factor

� PC’s have better price / performance ratio then micro computer.

4. Communication Medium


Application of Network� Resource Sharing

� Hardware (computing resources, disks, printers)� Software (application software)

� Information Sharing� Easy accessibility from anywhere (files, databases)� Easy accessibility from anywhere (files, databases)� Search Capability (WWW)

� Communication� Email� Message broadcast

� Remote computing

� Distributed processing (GRID Computing)


Elementary Terminology of

Network� Nodes (Workstations )

A computer becomes a workstation (or node ) of a network as soon as it is attached to a network.

� Server � Server

A computer that facilitates the sharing of data , softwareand hardware resource ( e.g. printer , modems etc .) onthe network , is termed as a Server.


� Network Interface Unit (NIU) / MAC Address

� A Network Interface unit is an interpreter that helpsestablish communication between the server andworkstation .

� Each network interface that attested to a workstationhas a unique number identifying it which is known asthe node address.

� The NIU is also called Terminal Access Point (TAP).

� Different manufactures have different names for theinterface . The NIU is also called NIC – NetworkInterface Card.


� Network Interface Unit (NIU) / MAC Address

� The NIC manufacture assigns a unique physical address to each NIC Card. This physical address is known as Media Access Control address ( MAC address)

� The MAC address refers to the physical address assigned by NIC Manufacture.assigned by NIC Manufacture.

� A Mac address is a 6- byte address with each byte separated by a colon

� E.g. Each MAC address is unique for each network card.

10 : B5 : 03 : 63 : 2E : FC


Manufacture Id ( This code is assigned to manufacture by IEEE)

Card no ( assigned by the Manufacture )

� IP Address

� IP address is for the INTERFACE of a host. Multipleinterfaces mean multiple IP addresses, i.e., routers.

� 32 bit IP address in dotted-decimal notation for easeof reading, i.e., 193.140.195.66

� Address 0.0.0.0, 127.0.0.1 and 255.255.255.255 carries� Address 0.0.0.0, 127.0.0.1 and 255.255.255.255 carriesspecial meaning.

� IP address is divided into a network number and ahost number.

� Also bits in Network or Host Address cannot be all 0or 1.


� IP Address


� Class A : Address begins with bit 0. It has 8 bitnetwork number (range 0.0.0.0-to-127.255.255.255), 24bit host number.

� Class B : Address begins with bits 10. It has 16 bitnetwork number (range 128.0.0.0-to-191.255.255.255),network number (range 128.0.0.0-to-191.255.255.255),16 bit host number.

� Class C : Address begins with bits 110. It has 24 bitnetwork number (range 192.0.0.0-to-223.255.255.255),8 bit host number.

� Class D : Begins with 1110, multicast addresses(224.0.0.0-to-239.255.255.255)

� Class E : Begins with 11110, unused


� Domain Name

� The domain name is a unique name assigned to a website.

� easy to remember names for computers on the Internet (such as internic.net).

� A domain generally contain following s following parts:

� www

� Name decribing the website’s purpose

� TLD (Top Level Domain ) such as .com, .net , .org ,.edu , .ca , .in , .jp etc.

� Examples

www.amazon.com

www.wayn.com.cn

www.cbse.nic.in


� Domain Name Resolution

� DNR refers to the process of obtaining corresponding IP address from a domain name

� DNS Resolution is the procedure used to resolve a IP

address from a domain name.

� This is very similar to how we get the phone number of � This is very similar to how we get the phone number of

a person we want to contact.

� It is all based on hierarchy.


Domain Names vs. URLs

� A domain name is contained in a URL. See the examples below.

� ftp://ftp.company.com/downloads.report.doc

� http://www.networkclue.com/index.php� http://www.networkclue.com/index.php


Protocol

Resource or File

Hostname Domain Name

Fully Qualified Domain Name (FQDN)

Network Topology

� The network topologydefines the way in whichcomputers, printers, andother devices areconnected. A network

Introduction to Computer Networks

connected. A networktopology describes thelayout of the wire anddevices as well as thepaths used by datatransmissions.

Bus Topology

Commonly referred to as alinear bus, all the deviceson a bus topology areconnected by one singlecable.cable.

Star & Tree Topology

� The star topology is the most commonly used architecture in Ethernet LANs.

� When installed, the star topologyresembles spokes in a bicyclewheel.

� Larger networks use the extendedstar topology also called treetopology. When used with networkdevices that filter frames orpackets, like bridges, switches, androuters, this topology significantlyreduces the traffic on the wires bysending packets only to the wires ofthe destination host.

Ring Topology

� A frame travels around the ring,stopping at each node. If a node wantsto transmit data, it adds the data as wellas the destination address to the frame.

� The frame then continues around thering until it finds the destination node,ring until it finds the destination node,which takes the data out of the frame.

� Single ring – All the devices on thenetwork share a single cable

� Dual ring – The dual ring topologyallows data to be sent in bothdirections.

Mesh Topology

The mesh topologyconnects all devices(nodes) to each otherfor redundancy andfault tolerance.fault tolerance.

It is used in WANs tointerconnect LANs andfor mission criticalnetworks like thoseused by banks andfinancial institutions.

Implementing themesh topology isexpensive and difficult.

Network Security


� Intrusion Problem / Access Attacks

� When an authorized user attempts to gain access toprotected sensitive information , it is known as AccessAttack or Intrusion Problem .

� This type of attack against confidentially of information.

� Some common access attack are :

Snooping refers to unauthorized access of someone else ‘s� Snooping refers to unauthorized access of someone else ‘sdata ,email, computer – activity , or data communication.

� Eavesdropping is the act of secretly listening /interruptingsomeone else’s private communication / data / information.


� Denial of service (DoS) Attacks

� A Denial of Service (DoS) attack is an attack whichattempts to prevent the victim from being able to use allor part of their network connection.

� A denial of service attack may target a user, to preventthem from making outgoing connections on thenetwork. A denial of service may also target an entireorganization, to either prevent outgoing traffic or toorganization, to either prevent outgoing traffic or toprevent incoming traffic to certain network services,such as the organizations web page.

� Denial of service attacks are much easier to accomplishthan remotely gaining administrative access to a targetsystem. Because of this, denial of service attacks havebecome very common on the


� Network Security Measures

� The combination of identification ,authentication andauthorization can control access to a system.

� The combination is very useful especially in networksecurity.

� Various technologies used for Network Security

1. Active Protection1. Active Protection

2. Preventive Measures


� Active Protection

� Authorization

� Asking the user a legal login- id .

� Authentication

� In termed as Password – protection.

� Firewall

A system deigned to prevent unauthorized access to or � A system deigned to prevent unauthorized access to or from a private network is called firewall.

� Intrusion detection

� The art and science of sensing when a system or network is being used inappropriately or without authorization.


� Preventive Measures

� Implement proper security policy for your organization

� Use proper file access permission when sharing files on theinternetinternet

� Disconnect from the Internet when away


deepak bhinde pgt computer science k v no. 2, ajmer · address 0.0.0.0, 127 .0.0.1 and 255 .255...

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