An interconnected network of thousands of networks and millions of computers linking business, educational institutions, government agencies and individuals together.
The largest collection of networks in the world, interconnected to allow them to function as a single virtual network
Early history of Internet
In the 1950s the U.S. Department of Defense
became concerned that a nuclear attack could
disable its computing (and thus planning and
By 1969 the Advanced Research Projects Agency
Network (ARPANet) had been constructed.
The first computers to be connected were ones at
the University of California at Los Angeles, SRI
International, the University of California at
Santa Barbara, and the University of Utah.
A hypertext server is a computer that stores files
written in hypertext markup language (HTML)
and lets other computers connect to it and read
those files. It is now called a Web server .
A hyperlink is a special tag that contains a pointer
to another location in the same or in a different
HTML is based on Standard Generalized Markup
Language (SGML), which organizations have
used for many years to manage large document
Local Area Network (LAN)
A link-up of workstations and peripheral equipment in an office, building, or locality so users may communicate and share equipment and information.
LAN lets you share the resources of other computers
LAN can be further characterized by topology
MAN(Matropolian Area Network)
It is the network which covers a city.
The best example of the MAN is Cable TV network which covers a city
In today’s world High speed wireless internet access is also a good example of MAN.
WAN(Wide Area Network)
A WAN spans a large geographical area such as a country or continent.
It uses Hosts which are connected by communicated subnets.
Topology describe the manner in which various computer nodes are interconnected to each other
In this context there are different topologies:
Consists of nodes connected to a single bus made up of a long cable.
A thick coaxial cable may serve as the bus and all computer nodes are connected to this running coaxial cable
The computer nodes directly receive and inject data from the bus. Data traverses in both direction
One communication channel exists to serve the entire network.
If this channel fails, then the whole network will go out of operation.
Nodes are organized to form a ring structure
The first node is connected to second using link
Second is connected to third and so on
The last node is connected to first using point to point link.
Signals travel internally around the network from one node to other
Each computer node is connected to a central device
Nodes are located at one end of the segment and other end is terminated in a central device, usually a hub or a switch
If one node is down, others on network are not affected.
Multiple number of paths
Because of it reliability of the network improved.
Structure like a tree
Reliable problem exists due to control exercised by topmost node in the tree.
All the host connected to Internet have an officially address.
It is 4 bytes long and written in dotted decimal notation.
For example IP Address
10000001.1000000.00000100.00000101 can be written as 220.127.116.11
Intranet offers companies open communication and information access, just like the internet but with the added advantage of protection from the outside world by passwords, encryption and electronic barriers or firewalls.
An intranet is an internet network that is located inside the organization and not generally accessible by the general public.
To create our own intranet we need,
A TCP/IP network
E-mail client s/w
Growth of Intranets
The spread of networked comp system based on PC.
The availability of TCP/IP on almost every computer platform, large and small.
The wide adoption of open standards such as HTTP and HTML.
The availability of low cost, high power web servers such as the internet information server.
Advantages of Intranet
Web technologies scalable and applied small and medium sized LAN.
Easy to use web browsers are available for virtually all operating system and h/w combinations.
Advances in HTML authoring tools make it much easier to create HTML pages for web servers.
Disadvantages of Intranet
Intranet requires TCP/IP protocol and may not work with your existing choices.
HTML is not a development language, we will have to use CGI or Perl scripts, or even C or java programmes to access database systems.
A network that links selected resources of the intranet of a company with its customers, suppliers and other business partners, using the internet or private networks to link the organizations intranets.
TCP / IP Layers
Network Interface Layer : Responsible for placing packets on and receiving them from the network medium, which could be a local area network (Ethernet) or Token Ring or other network topology.
Internet Layer : This layer is responsible for addressing, packaging, and routing messages on the Internet.
TCP / IP Layers
Transport Layer : Responsible for providing communication with the application by acknowledging and sequencing the packets to and fro from the application.
Application Layer : Provides a wide variety of applications with the ability to access services of the lower layers
Some of the best applications are FTP,SMTP and HTTP
Internet Service Provider
Firm that provides the lowest level of service in the multi-tiered internet architecture by leasing internet access to home owners, small business, and some large institutions.
Client Server Computing
A model of computing in which very powerful personal computer are connected together in a network with one or more servers.
Internet is a giant example of client server computing
CLIENT : A powerful personal computer that is part of a network. That is capable of displaying rich graphics storing large files and processing sound and graphic files.
SERVER : Networked computer dedicated to common functions that the client machines on the network need, such as storing files, software applications, utility programs such as web connections and printers
Hyper Text Transfer Protocol
The set of rules for exchanging files (text, graphic images, sound, video, and other multimedia files) on the World Wide Web.
Runs in the application layer of the TCP/IP model. An HTTP session begins when a client’s browser requests a web page from remote internet server
When the server responds by sending the page requested, the HTTP session for that object ends
SMTP, IMAP, POP
SMTP : Internet protocol used to send mail to server (Simple Mail Transfer Protocol)
POP : Post Office Protocol, a protocol used by the client to receive the mail from an internet server.
IMAP : a more current e-mail protocol that allows users to search, organize, and filter their mail prior to downloading it from the server (Internet Message Access Protocol)
Internet service that allow you to transfer file from one computer to another computer using client/server technology
You run a client program on your computer which connects to a server program on a remote computer
When you copy a file from remote server we say that you are downloading and when you copy a file from your computer to remote one you are uploading the file
In FTP terminology your computer is LOCAL HOST, the other computer is REMOTE HOST
SSL developed by Netscape Communications Company, is a standard that encrypts data between a Web browser and a Web server. SSL does not specify what data is sent or encrypted. In an SSL session, all data sent is encrypted.
It helps secure communications and payments through a variety of techniques such as message encryption and digital signatures.
Telnet is a internet service that allow you to log in to a remote internet computer
To utilize this service, you need a Telnet client on your machine. Client uses internet to connect to the remote computer
Once the connection is made, the client acts as intermediary between remote and your computer
Every thing you type on your machine is passed on to the remote computer
Everything the other computer displays is sent to your computer
Finding People on the Internet. You can find out who is logged on to a remote network by using Telnet to connect to a server and then typing finger at the prompt.
Finger can tell you who is logged in and how long they have been attached and their user name
Testing address. You can ping a host computer to check the connection between your client and server. The Ping will also tell you the time it takes for the server to respond giving some idea of the internet speed at that time (Packet Internet Groper)
Limitations of Internet I
Bandwidth : Slow service and a very limited capacity to handle video and voice traffic.
Quality of Service : Packets take circuitous root to reach destination. This results in latency. With streaming video and synchronous communication, latency is noticeable and user perceives jerkiness in movies and delay in voice communication.
Latency : uneven flow of information packets throughout the network
Limitations of Internet I
Network Architecture : A thousand requests for single music track from a central server will result in a thousand efforts by the server to download the music to each requesting client. This slows down network performance.
Language Development : HTML the language of the web pages is fine for text and simple graphics but poor at defining rich graphic and communicating “rich documents” such as databases, business documents, or graphics.
World Wide WEB WWW
It is a way of formatting pages with embedded links that connects documents to one another, and that also links pages to other objects such as sound, video, or animation files.
When you type a web address in you browser such as http://www.imt.edu , your browser sends an HTTP request to the imt.edu server requesting the home page of imt.edu
HTTP is the first set of letter at the start of every web address followed by the domain name.
Uniform Resource Locator
The directory path and document name are two more pieces of information with the web address that help the browser track down the requested page.
Together the address is called a URL. When typed into a browser, a URL tells exactly where to look for information. For example: http://www.imt.edu/dlp/pgdbm.htm
Mark Up Languages
SGML : Standard Generalized Markup Language. The purpose of SGML was to help very large organizations format and categorize large collection of documents.
It can run independent of any software program, but it is extremely completed and difficult to learn.
An early version of Generalized Markup language
Hypertext Mark-up Language
One of the next generation GML that is relatively easy to use in the web page design.
HTML provides web page designers with a fixed set of markup tags that are used to format a web page.
HTML functions to define the structure and style of a document, including the headings, graphic positioning tables and text formatting
Extensible Markup Language
XML is a new Markup language specification developed by W3C. It is a Markup language like HTML but with a different purpose. XML is designed to describe data and information.
XML can be used to define database records and this will enable organizations to put most of their information processing functions into an Internet processing environment
Web Server and Clients
The Internet and WEB Features
The most used application of the Internet
Uses a series of protocols to enable messages containing text, images, sound and video clips to be transferred from one internet user to another
Attachment : A file inserted with in the e-mail message.
Spam : Unsolicited e-mail.
Identifies web pages that appear to match keywords, also called queries, typed by the user and provides a list of the best matches.
Top search Engines Yahoo, MSN, AOL, Lycos, Go, Netscape, NBCi, Exite, AskJeeves, Alta Vista, Google, LookSmart, GoTo, Iwon, Direct Hit, DogPile
Or Software Robots (bots) are software programs that gather and / or filter information on specific topic and then provide a list of results for the user.
Displays word type on computer almost instantaneously. Recipients then can respond immediately to sender the same way, making the communication more like a live conversation than is possible through e-mail.
Enables user to communicate via computer in real time, that is simultaneously, unlike Instant Messaging chat can occur among several users.
Cookies : are a tool used by web sites to store information about a user. When visitor enters a web site, site sends a small text file to the user’s computer so that information from the site can be loaded more quickly on future visits
Enables music, video and other large files to be sent to users in chunks so that when received and played, the files comes through uninterrupted.
Streamed files must be viewed live, They can not be stored on client hard drive.
RealAudio and RealVideo are the most widely used streaming tools.