chapter 15 working on internet

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Working on Internet

Chapter 15



Chapter 15 2

Chapter Objectives

Describe Router

Explain Network Address Translation (NAT)

Explain Proxy Servers

Configure TCP/IP Configure Internet Explorer

Configure MS Outlook and Outlook Express

Configuring DHCP,DNS, Host Names, FQDN,

NETBIOS Troubleshoot DHCP and DNS



Chapter 15 3

Recall

Simple Mail Transfer Protocol (SMTP) is an Internetstandard protocol that is used for transferring email from

one computer to another

File Transfer Protocol is used over the Internet to

exchange files Post Office Protocol version 3 (POP3) is an application

layer Internet standard protocol used to retrieve email

from a remote server to a local client over a TCP/IP

connection



Chapter 15 4

Router

An Internetworking device used to link two differentnetworks

Used to connect at least two networks and works at

the Network layer

Forwards data packets across a network through aprocess called routing

Two types:

Static router - Needs to be configured manually

Dynamic routers - Does not require manual

configuration



Chapter 15 5

Use of Router

Can be installed as an Internet gateway

Router is used to connect two networks for example

WAN and LAN

Firewall are also provided by the router Wireless networking is supported by few routers,

which includes features like support for plug-n-play

devices



Chapter 15 6

Network Address Translation (NAT)

Method in which a system’s IP address is changedinto a different IP address before it’s sent out to an

external network (Internet)

Enables the private network (Intranet) to use

addresses that differs from the actual IP address on

the Internet

Allows address hiding, thus it acts as a firewall

Web servers cannot be used as NAT clients Provides a strong protection against unauthorized

users



Chapter 15 7

NAT Advantages and Disadvantages

Advantages:

Hides internal structureof the network andincreases network

security Allows unlimited class

C network address

Helps in maintaining

same internal network’sIP address when acomputer is attached tothe Internet

Disadvantages:

Changes IP addresses,

thus troubleshooting

becomes more complex

Blocks incoming

connections



Chapter 15 8

Static NAT

A private (internal network) IP address is convertedto a public IP address, which is always static (alwaysremains same

An internal network IP address is mapped to aregistered IP address on one-to-one basis



Chapter 15 9

Dynamic NAT

An unregistered IP address is represented to aregistered IP address from a set of registered IP

addresses

A computer with IP address 25.0.18.25 will translate to

first available IP into a particular range for examplefrom 28.35.15.100 to 28.35.15.125



Chapter 15 10

Working of NAT

When packets of information are received from theoutside network, NAT enabled router checksdestination address and destination port on thepacket

Router checks whether packet belongs to that

network in translation table Packet is rejected if it does not find any match in the

translation table

Else router changes destination address to the onesaved in address translation table and sends it tothat computer

Computer receives the packet from the router



Chapter 15 11

Proxy Server

A computer that allows

network users to make an

indirect network connection to

different network services

Used to configure Internet

connection setting

Enhances the security for the

user accessing the Internet

and speeds up the Internetaccess by storing Web pages

on the server



Chapter 15 12

Types of Proxy Servers

Transparent Proxies

Also known as forced proxy involves a combination of

proxy server with NAT

Reverse Proxies A reverse proxy server handles the request on

behalf of the main Web Server

Anonymous Proxy server

Secure the user’s personal information by hiding

the IP address



Chapter 15 13

NAT Vs. Proxy Server

Proxy server provides better performance through

caching, for example caching of regular visited

websites by the user

NAT is simple to configure, it doesn’t requireadditional software application

A proxy server is not transparent

NAT is transparent to the source and destination

computers



Chapter 15 14

TCP/IP Configuration

Transmission Control Protocol/Internet Protocol is

derived from two of the fundamental protocols, TCP

and IP

Is a collection of networking protocols widely usedon the Internet

TCP/IP is default Wide Area Network protocol

TCP/IP allows communication across various

interconnected networks



Chapter 15 15

Basic TCP/IP Configuration

Parameters - I Host name

Made up of letters, hyphen and numbers, begins with a

letter

Not longer than sixty three characters

DHCP Client

DHCP is a TCP/IP service protocol

Offers dynamic leased configuration of host IP

addresses



Chapter 15 16


Parameters - II

IP address

Made of 32-bit binary number

Displays as four octets expressed in decimal and

separated by periods Domain name

A Domain is not a single computer, but a holding

space into which a computer names can be added

A Unique name for example www.xyx.com

Made up of letters, hyphen and numbers



Chapter 15 17


Parameters - III

Broadcast address

An IP address which enables information to be

broadcasted to all computers on a subnet rather than

only to a specific machine

Default router

A default router is the default gateway used by the

device to access hosts on other networks

In a TCP/IP network, the nearest router to a particularhost is known as default router



Chapter 15 18

Configuring Internet Explorer

Microsoft Internet Explorer is a web browser

Web browser enables to access the Internet

Internet Explorer is installed by default with the

Microsoft Windows operating system Internet Explorer settings can be modified to

improve the Web page security and privacy



Chapter 15 19

Internet Explorer Security - I

Internet Explorer stores all the Websites into a singlezone

By default, all the Websites are stored in the Internetzone

Internet

ExplorerZones

Internet

Zone

Local

Intranet

zone

Trusted

Sites zone

Restricted

Sites zone



Chapter 15 20

Internet Explorer Security - II

Internet Zone Consists of all Web sites that can be accessed by the

computer

Local Intranet Zone

Includes all

Websites that reside on the user’s localnetwork

Trusted Sites Zone

Includes the Websites that are safe

Restricted Sites Zone

Contains the Websites that are unsafe



Chapter 15 21

Case Study

The Delhi branch of the MoneyMaker bank has

marketing department which searches for new

clients using different Web sites. The searches wereperformed in multiple ways such as using the

search explorer bar, Web browser, search engine or

address bar.



Chapter 15 22

Problem

The default search action needs to be changed as

per the requirements.



Chapter 15 23

Solution

Change the default search actions.



Chapter 15 24

Configuring and Working with MS

Outlook and Outlook Express

Microsoft Outlook is a software application for

handling and organizing personal information

Microsoft Outlook is a stand-alone application that is

a part of Microsoft Office

Outlook Express is a part of Microsoft’s Windows

operating system

Outlook Express is an e-mail and news client



Chapter 15 25

MS Outlook

Offers e-mail service and comes under the categoryof e-mail client

Allows users to change the e-mail settings as per

the user requirements

Compatible with other programs such as MicrosoftWord



Chapter 15 26

Outlook Express

E-mail account in Outlook Express provides only e-mail and newsgroup functionality

Aimed at providing required services to home users

Exchange server and third party based accounts are

not supported in Outlook Express



Chapter 15 27

Configuring DHCP Client

Configure client computers to receive IP addresses

from the DHCP server

Any computer running a version of the Windows

operating system such as Windows 2000, WindowsXP and Windows NT can become a DHCP client

You can configure the client using the Internet

Protocol (TCP/IP) Properties dialog box.



Chapter 15 28

Configuring DNS Client

DNS works at the application layer and usesTransmission Control Protocol (TCP) and User

Datagram Protocol (UDP) for transporting data over

the network

DNS is configured so that it can resolve othercomputer names and IP addresses

You can configure the DNS client using the Internet

Protocol (TCP/IP) Properties dialog box



Chapter 15 29

Host Names

Unique name by which a computer is known or

recognized on a network

On a local area network, a hostname is commonly a

single word On the Internet, the host name is in the form

"comp.abc.com”

Made up of lowercase letters and numbers



Chapter 15 30

FQDN ( Fully Qualified Domain Name )

A complete DNS name, including the host name and

all of its domains (in order), is called a Fully

Qualified Domain Name (FQDN)

Complete address of a site on the Internet Consists of a host name and domain name,

including top-level domain name

No two machines should have same Fully Qualified

Domain Name



Chapter 15 31

Network Basic Input/Output System

(NETBIOS)

A program that permits applications on different PCs

to communicate within a Local Area Network

NetBIOS protocol is used when a user browses the

network neighbourhood for any data on the network

Does not support a routing mechanism



Chapter 15 32

Troubleshooting DHCP

You can troubleshoot DHCP using:

Automatic Private IP Address (APIPA)

Used by clients, which are unable to access the DHCP

server

A feature of Microsoft Windows Operating system

Always starts with 169.254.*.*

Releasing or Renewing IP address

IPCONFIG

is available with the release and renew options



Chapter 15 33

Troubleshooting DNS

DNS problems occur when there is a problem with

the client system

You can troubleshoot DNS by:

Removing DNS cache – Use Ipconfig/flushdns Name Server Lookup (Nslookup) - Allows querying

DNS servers and obtaining detailed response at the

command prompt



Chapter 15 34

Applications of Internet - I

Internet is basically network of networks

WebPages are viewed in web browser (Internet

Explorer) through Internet

Applications: WWW (World Wide Web)

E-mail (Electronic Mail)

FTP (File Transfer Protocol)

TELNET (TErminaL NETwork)



Chapter 15 35

Applications of Internet - II

WWW (World Wide Web)

Consists of WebPages

Contents of WebPages are links, text and graphics

through which a user can access information fromconnected computer located at any part of the world

E-mail (Electronic Mail)

E-mail is source of information through which

messages are sent and received via computernetworks

E-mail can be sent to any user with a valid e-mail id



Chapter 15 37

Summary - I

Router is an Internetworking device used to link twodifferent networks

NAT is a method in which it translates system’s IP

address to a public IP address before they pass

through larger network or Internet

Proxy server allows network users to make an

indirect network connection to different network

services Internet Explorer (IE) is the most widely used web

browser



Chapter 15 38

Summary - II

MS Outlook is a part of Microsoft Office and acts asa personal information manager

MS Outlook offers e-mail service and comes under

the category of e-mail client

Microsoft Outlook Express is an e-mail and news

client

IP address can be allocated to a PC on boot

process by a method called DHCP DHCP offers dynamic leased configuration of host

IP addresses and allots other configuration

parameters to suitable network clients



Ch 15 39

Summary - III

Individual computer names are called as host names in anetwork. A computer is known on a network by a unique

name know as i.e. hostname

A complete DNS name, including the host name and all

of its domains (in order), is called a fully qualified domainname (FQDN)

Network Basic Input/Output System is a program that

permits applications on different PCs to communicate

within a local area network Internet also supports different format of information in

form of text, graphics, audio, and video files which are

displayed on the Web pages

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