Internet And Its Features

Web

• It is an abstraction(concept) and common set of services on top of the Internet.
• It is a set of protocols and tools that let us share information with each other.

World Wide Web

• It is a collection of linked documents, or pages, stored on millions of computers and spread over the entire Internet.
• The term “World Wide Web” comes from the belief that individual nodes of information are linked with hypertext, and this creates a “web” of information.
• The documents on the web are written in HTML-that defines their appearance and layout, and creates the links to other documents. These links are known as hypertext link or hyperlink.
• In 1989, Tim-Berners-Lee of European Particle Physics Lab(CERN) in Switzerland has developed WWW.
• The purpose of WWW is to provides a network of interactive documents and the software to access them.
• It is based on documents called pages that combine text, pictures, forms, sound, animation and hypertext links

Features of WWW

• The ability to easily deliver information in any format, to/from a wide range of computing platforms.
• Simplified access to the Internet.
• The easy availability of extensive information on a wide range of topics.
• The Web is interactive.

Uses of WWW

• Education Tool
• Search Tool
• Business Tool

Web Browser

• Web Browser is an application that uses information stored at locations around the World Wide Web.
• Browser is a piece of software that acts as an interface between the user and the inner-workings of the

Internet.

• It is also referred to as Web clients or universal clients.

- Functions:

• Contact a web server and sends request for information.
• Receives the information and then displays it on the user’s computer.
• Browser fetches the requested page, interprets the text and formatting commands that it contains, and displays the page properly formatted on the screen.
• Voice based browsers are also being developed.
• When given the URL of a document, the browser becomes a client that contacts a Web server on the computer specified in the URL to request the documents.
• Browser consists of set of clients, a set of interpreters and a controller to manage them.
• The controller forms a central piece of browser.
• When a browser interacts with a web server, two programs follow the HTTP.
• HTTP allows a browser to request a specific item, which the server then returns.

How to access the WWW : Web Browsers?

• Graphical
• Text

Web Server

• Computers that are connected to the Internet and that contain files that their owners have made publicly available are called web servers.
• Any computer can be turned into a Web server by installing web server software and connecting the machine to the Internet.

• Ex:
• Apache
• Microsoft IIS (Internet Information Server)
• A server is a member of a class of programs in a modern software architecture called client/server software architecture, in which all applications have two components:
• The client component
• The server component.

Server

• A server is on large Computer
• Server is passive
• Runs continuously waiting for requests
• Runs in background and interfaces only with other software(Clients) and rarely interfaces directly with users.
• Server must runs multiple tasks concurrently
• Responsible for transmitting the document

Client

• A Client is on small computer & runs a multiple instance
• Client is active
• Runs only on-demand
• Client is invoked by a user and takes commands from the user
• A Client usually works for one person and does one thing after another in sequence
• Responsible for displaying document

Web Pages and Web Sites

• Web page is a page containing information and instructions.
• The information can be text, images,audio or video.
• The instructions are specified in HTML.
• A Web site is a collection of related Web Pages(files) stored on a Web Server.
• Web sites are hosted on Web Servers.

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LISTSERVE || NEWSGROUPS || TELNET || GOPHER || VERONICA || WAIS

LISTSERVE

• First electronic mailing list software application, consisting of a set of email addresses for a group in which the sender can send one email and it will reach a variety of people.
• Also called “distribution lists” or “discussion forums”
• Lists of users hold a discussion about a particular subject.
• Distribution lists are free and very satisfactory
• This system is one of those with easiest access via the Internet, since it only requires the ability to send e-mail.
• There are two types of distribution lists:

• Moderated-The lists maintained by a single person, whose active participation is necessary for maintaining the list. This type is sometimes called a mailing list. The owner may edit the message in this type.
• Unmoderated- The lists that do not require the intervention of anybody, to be maintained, since all the messages are managed by software, which does all the work. This type is called Listserve.

Advantages Of Listserve

1. Information exchange
2. Does not require full access to the Internet.
3. Great independence to the user.

There are major four listservers which provides distribution lists:

1. ListServe
2. Listprocessor
3. Majordomo
4. Mailbase

NEWSGROUPS

• Worldwide system for the electronic exchange of news and views on a particular topic.
• Also referred to as Usenet News.
• Usenet is a discussion forum similar to distribution lists.
• On the Usenet the messages are stored on notice board rather than distribution.
• You do not need to subscribe to a newsgroup.
• To participate in global distributed discussion system you must have the following facilities:
• Your Internet provider must offer a “news feed” service
• You must have a client on your computer that can interpret data sent from an NNTP server. This will take the form of a dedicated newsreader, or your web browser if it has been “news enabled

TELNET(TELETYPE NETWORK)

• Telnet is a protocol that is most commonly used to log into a remote computer.
• Telnet act as a terminal emulator.
• Telnet is the protocol that enables one computer to connect to other computer. This process is also referred to as remote login.
• The user’s computer which initiates the connection is referred to as the local computer.
• The machine being connected to which accepts the connection is referred to as remote or host computer.
• Once connected, the user’s computer emulates the remote computer. When the user types in commands, they are executed on the remote computer.
• Telnet environment is based on text, as it does not support the graphical interface.
• To get access via Telnet, you need an access code

#Using Telnet, you can

• Send email
• Download source code from websites
• Send unexpected input to web servers that can give you amazing and illegal results.
• Give arbitrary(random) input to many other services on Internet host computers
• Probe the services offered by servers, routers and even people’s home computers.

#There are two ways of using the Telnet tool:

• The input mode
• Input mode allows you to establish the connection and use the remote computer
• The command mode
• Command mode is used to set the parameters to Telnet

GOPHER

• It is a hierarchical menu-based system for exploring the Internet.
• Gopher is a protocol designed to search, retrieve and display documents from remote sites on the Internet.
• Originally Gopher had text based interface then it has evolved greatly, becoming a tool for obtaining multimedia data.
• You can access Gopher by means of Telnet, although the menu options cannot be selected with the mouse.
• Information accessible via gopher is stored on many coputers all over the Internet. These computers are called gopher servers.
• Servers do not just contain a files, directories and searchable databases, they can also contain references to other servers.
• To retrieve and search this information, you need to run a gopher client application on your computer.
• Information stored on many kinds of non-gopher servers is also available via special gopher servers that act as gateways.
• Gopher was created as a piece of software to utilize some of the services that were becoming available on the Internet.
• It was designed to work with a variety of different Internet stand alone services.

Characteristics

• Ease of use with user interface based on menus
• It offers the possibility of discovering sources of information on the Internet without needing to know their location.
• Gopher server automatically directs the search to the address, where what you want to see is stored.

VERONICA

• Veronica is a tool which simplifies the search for resources in Gopher.
• Veronica comes from “Very Easy Rodent Oriented Networked Index of Computerized Archives”
• Veronica starts the search on the Gopher menus, from which you select “GOPHER-space search” or the name veronica, by keying in a keyword.
• It gives you Gopher addresses with the keyword on their menus.
• You can choose which of these sources in order to enter them.
• While searching following things must be in consideration:
• Search is not case sensitive
• Veronica does not carry out searches in the complete text of the resources available on the Internet.

Types of Search Using VERONICA

• Searching GOPHER space by keywords in titles- This type locates all types of resources that have title containing the keyword.
• Searching GOPHER directories only for keywords in titles- It searches only for directories in which the keyword is contained in the title.
• Simplified Veronica- When you select the option, veronica asks you for the keyword or words you want, together with additional information to control the search:
• Simple search
• Search by more than one keyword
• Search for word roots
• Search by types of Gopher
• Specification of the number of resources analyzed

WAIS(WIDE AREA INFORMATION SERVERS)

• It is a tool designed to search for information on the Internet by means of the keyword and provide as a result a list of the resources related to the keyword, ordering them according to the number of times the keyword appears in the document.
• 
  
• WAIS searches for the keyword , selected by the user in the text of the files stored on the network.
• 
  
• It is a system of searching in the complete text, not just on the menus or in the names of files.
• 
  
• WAIS uses Natural Query Language
• 
  
• The query is put into the system in natural language and WAIS discounts the irrelevant words and starts to search for the keywords

Searching For Documents With WAIS

• You can gain access to WAIS in various ways:
• Using a client program
• Making a connection with quake.think.com and login as wais
• Entering WAIS via WWW .

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Domain Name Service && IP Address

Domain Name Service

• Domain name is a way to identify and locate computers connected to the Internet.
• No two organizations can have the same domain name.
• A domain name always contains two or more components separated by periods, called dots(“.”)
• Once a domain name has been established , ”Sub domains "can be created within the domain.

#The structure for this is:

• Hostname.subdomain.second-leveldomain.top-leveldomain
• DNS as a whole consists of a network of servers that map Internet domain names like www.google.co.in to a local IP addresses.
• DNS enables domain names to stay constant while the underlying network topology and IP address change.
• Each domain name corresponds to numeric IP addresses.
• The Internet uses the numeric IP address to send data.

#For instance,

• You may be connecting to a World Wide Web server with the domain name www.microsoft.com”, but as far as network is concerned, you are connecting to the web server with the IP address associated with that domain name.
  E.g. IP address for www.microsoft.com is 192.11.1.1
• Domain Name System completes the task of matching the domain names to IP addresses.
• Domain names and their corresponding IP addresses, must be unique.
• Domain Name System is a collection of databases that contain information about domain names and their corresponding IP addressing
• Domain Name Servers are computers that translate domain names to IP addresses.
• This system allows the Internet users to deal with the more sensitive domain names, rather than having to remember a series of numbers.
• Domain name space is a hierarchical ,tree structured name space, starting at an unnamed root used  for  all DNS operations.
• In DNS name space, each node and leaf in the domain name space tree represents a named domain.Each domain can have additional child domains.

#There are three components of DNS:

• Resolver
• Name server
• Database of resource records(RRs)

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Internet Concepts

Listening the word Internet Concepts the first Question stuck to the mind is....

What is Internet..?

• Internet is a global network of interconnected computers over world wide web.
• It is a global web of computers that allows individuals to communicate with each other.
• Internet consists of two types of computers:
• Server
  Server is a computer or program that fulfils the request of another computer or program.
• Client
  Client is a computer or program that requests a service of another computer or program.

Applications of Internet

• Communicate with other people
• Sharing information or resources
• Connect to other computer systems

Types of Network

• MILNET    -    Military Network
• DARPA      -    Defense Advanced Research Network
• BITNET     -    Because it’s Time Network
• USENET    -    User Network
• NSFNET    -    National Science Foundation Network.
• ARPANET -   Advanced Research Projects Agency/Administration Network

History of Internet

• In 1969, the Department of Defense (DOD) of the United States (US) started a network using four computers at four separate universities throughout the United States enabling users to share resources and information, which was known as ARPAnet(Advanced Research Projects Administration Network).
• In 1972, there were 37 computers connected to ARPANET. In that year, ARPA’s name was changed to DARPA (Defense ARPA).
• In order to manage the size and complexity of the network were broken into two parts:
• MILNET-for managing Military sites
• ARPANET –for managing non-military sites(Network for research and educative purpose)
• In 1970’s other networks like BITNET and USENET also come into being.
• In 1980’s NSFNET was created. NSFNET allowed universities and research agencies to link up with its super computer.

 # How Internet works...?

• Internet is a global network of computers, each computer connected to the internet must have a unique address. That address is known as IP address.
• Internet includes thousands of host computers(servers) which provides data and services as requested by client system.

1. Message starts
2. Message is divided into small chunks known as packets
3. Each packets are assigned a port number.
4. Each packets receives its destination address.
5. Data conversion from analog to digital and vice versa.
6. The ISPs router examines the destination address in each packet and determines where to send it.

 ISP(Internet Service Provider)

• When you connect your computer to the internet, you are connecting to a special type of server which is provided & operated by your ISP.
• The job of this ISP is to provide the link between your browser & the rest of the internet.
• The single ISP server handles the internet connections of many individual browsers.
• The main component of providing access to the Internet consists of:
  International connectivity, which allows you to connect to the amorphous(unstructured) Internet.
  Domestic connectivity, which allows you to connect to the domestic gateway.
• There are three ways an ISP can connect to the Internet:
• VSNL(Videsh Sanchar Nigam Limited)/DOT(Department of Telecommunications)
• STPI(Software Technology Park India)Private Operators
• VSNL-VSNL is india’s leading provider of international telecommunications and Internet services.
• DOT-DOT is responsible for issuing security clearances.
• STPI- STPI is a semi government organization that has authorized to sell international gateway services to companies involved in developing software
• Private Operators- Private operators are a private independent companies competing directly with the multi-system operators

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Types Of Internet Connections

Connection Types

• Dial-up Access
• ISDN(Integrated Services Digital Network)
• Leased Lines
• Cable Internet

Dial-up Access

• Also known as narrowband
• Least expensive way to get connected with Internet
• Speed is too low.
• Use the Point-to-Point Protocol.
• To use a Dial-up You need a modem.
• Doesn't require any special H/W.
• Only used for Email & light Web Browsing.

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