Thursday, October 16, 2008
It allows network users to share files using file server for providing this kind of services.
File services are network applications that store retrieve and move the data with the help of network file server.
User can read write and manage files with in this server.
Print servers are used to provide that kind of print services
This service also allows multiple and simultaneous printing access facility.
Network software uses printing queues which has special storage area where print jobs are stored and then sent to the printer in organized manner.
Jobs in print queues may be forward in order to receive the print according to the priority.
Printer can be placed anywhere in network and nay network users can use the printer.
The data sent by the user is transfer to the network printer at network speed.
Another print service is fax service it can be used for communication purpose.
In this services user can fax from its own work station to any other fax machine.
A fax machine can also work as sharing device in computer network.
Communication server handles data flow between numbers of networks.
It also handles the incoming and outgoing remote user and internet traffic.
Windows NT domain controller works as communication server.
Security starts with the login procedures to ensure that a user who is accessing the network is using its password so, that only authorized users can log on to the network.
Login restrictions can force the user to login from a specific station and during a specific time.
Administrative tools can be used for security service in network operating system.
Database services are provided by the data server
This service can provide networking with powerful database handling capabilities.
Most database systems are based on client server architecture so that database application can run on separate components.
The client side it provides the interface and handles less intensive functions line data request.
An interconnected computer systems and also peripherals and devices with the purpose of data communication and information exchange are call network.
Connecting one or more than one computer to each other in such a way that they can share their hardware and software resources called network.
Objectives of network:-
• Using network facilities we can share hardware like cd-drive, printer and other memory devices
• Network provides security to data files.
• Faster data communication without using external memory.
Components of network:-
1. NIC [ Network Interface Card ]
• A chip based circuit board used to connect computer to network or server
• A card is activities by installing it’s driver software
• A card is connect to I/O bus in a vacant slot
• The card contains physical interface for connectivity between computer’s internal and external resources
• A network device where the information flow is accumulated and then distributed various groups and users.
• It can be used between users on the same to LAN and the users on different LAN also [local area network].
• It serves as the central point where cables from all nodes come together.
• HUBs are available in different shapes and size it also provides limited management facility
• Dumb Hub (passive hub):- this type of hub only use for the data communication and there is no management facility.
• Intelligent Hub (Active hub);- this type of hub used for communication and also decision making it also has management facility.
• A device that supports LAN to LAN communication is bridge.
• It will remember all the network addresses on both side of LANs and regulate the flow of traffic.
• Router interconnects two or more physical and logical network and work at network layer.
• It distinguishes data packets according to protocol like, TCP/IP, FTP, HTTP etc.
• It will remember matrices to determine the optimal path of workstation in computer network.
• A shared connection between LAN and a larger system such as mainframe computer or a large packet switching network whose communication protocols are different.
• It usually is slower than bridge or a router, it is a communication of hardware or software.
• It has its own processor and memory used to perform protocol conversion.
• A server is an important component of a dedicated server network.
• The server runs on network operating system and offers network services to users at their individual workstation.
• These services include file storage securing, users management, network commands and many things.
• The most common type of server is file server
• When client computer send request to server , server will give respond to that computer.
• When computer connect to a network it becomes a node on the network and is called a work station or client.
• It has its own local operating system e.g. DOS, win 98, win XP.
• Its job is to execute program files retrieved from the network and the server’s job is to deliver those files to the work station.
8. Cabling system
• In network cabling system is a media used to connect server and network station together.
• In case of wireless network that uses radio or infrared technology where cables are not required.
• There is several kind of cables used in networking like twisted pair cable, coaxial cable, fiber optics cable.
Advantages of networking:-
Creation of workgroup using user management facility
Centralized management system.
Provide security in corporate structure.
Ability to use network software.
Ability to use e-mail.
Communication must occur between distinct point but few organization can justify the cost required.
LAN is characterized by high bandwidth and that company controls and maintain all the connectivity of devices as well as the transmission media (wire).
The company could have transmission media like infrared or satellite communication to establish connectivity.
Another possibility is different kind of cables can be used for connectivity
A variety of commercial options are available that enable organization to pay per only the level of service they require.
It has two main types
1. PSTN [PUBLIC SWITCHED TELEPHONE NETWORK]
This commercial network has its own existing infra structure supplied by the Telephone Company or Cable Company.
The feature of PSTN is its low speed, analog nature of transmission, a restricted bandwidth and also wide spread availability.
It is designed for telephone network but if we want it for digital communication than modem is required.
When the link setup is unreliable and can terminate without warning.
At that time PSTN communication medium is advisable.
This connects are easy to get at short notice. This is widely available and covers almost every location where people live and work.
PSTN is mostly useful for occasional users or as a backup to the private services
Fax machines can also operated in this network.
2. PSDN [PUBLIC SEITCHED DIGITAL(DATA) NETWORK]
It covers number of technology available for public telephone network.
The main feature is its high level of reliable and high quality of connection.
They can support both low and high speed at appropriate cost.
It can also use to link computer and system and network of one organization to several other organizations.
Q: what is internet?
The Internet is the largest computer network in the world, connecting millions of computers. A network is a group of two or more computer systems linked together.
Internet is network of networks. it begin in 1969 as an experiment for computers of U.S. defense and they connected their network with the research institute for the purpose of technological weapon those research institutes connect that network to academic centers like university and colleges. Then they connect that network with one more network which is commercial network at that time it became a network which used by government and some specialized people its call ARPANET [advance research project agency network].
Then in 1990 it made available to all the people of world using telephone lines and other networks and all networks of different countries and centers are connected together and became internet [inter-connection of networks].
The network or computer operating in different platform is connected to internet by common protocol known as TCP/IP. Internet is a window to global information super high-way.
It is a worldwide network of independent smaller networks or other connected machines spanning the entire globe.
Around the world each country has at least one backbone network that operates at very high speed and carries the bulk of the traffic.
Internet was established by VSNL in India at 15th august 1995.Internet is providing services like e-mail service, downloading and uploading services, forums, network news, blog , search engine, communication services in form of chatting and voice and video conferencing and shopping carts online, online customer supports etc.
Internet is managed by following organizations:
IAB: Internet Architecture Board
An organization (originally Internet Activities Board) that oversees standards and development for the Internet. This board also administrates, with the help of the IANA (Internet Assigned Numbers Authority), the internet(1) sub tree in the global tree in which all networking knowledge is stored. The IAB has two task forces: IETF (Internet Engineering Task Force) and IRTF (Internet Research Task Force).
IESG: Internet Engineering Steering Group
In the Internet community, the executive committee for the Internet Engineering Task Force (IETF).
IETF: Internet Engineering Task Force.
A committee that operates under the auspices of the Internet Activities Board (IAB) to help establish standards relating to the Internet. The IETF is largely responsible for formulating the Remote Network Monitoring Management Information Base (RMON MIB), which is expected to become the standard for monitoring and reporting network activity in the Internet environment.
IRTF: Internet Research Task Force
A group within the Internet community that works on long-term research projects. These projects may concern any aspect of Internet operations, and some results have led or may lead to major changes in certain aspects of Internet activity.
InterNIC: Internet Network Information Center.
InterNIC is responsible for the assigning and registering IP address.
ICANN: The Internet Corporation for Assigned Names and Numbers (ICANN) is the authority that coordinates the assignment of unique identifiers on the Internet, including domain names, Internet Protocol (IP) addresses, and protocol port and parameter numbers. A globally unified namespace (i.e., a system of names in which there is at most one holder for each possible name) is essential for the Internet to function. ICANN is headquartered in Marina del Rey, California, but is overseen by an international board of directors drawn from across the Internet technical, business, academic, and non-commercial communities. The US government continues to have the primary role in approving changes to the root zone file that lies at the heart of the domain name system. Because the Internet is a distributed network comprising many voluntarily interconnected networks, the Internet, as such, has no governing body. ICANN's role in coordinating the assignment of unique identifiers distinguishes it as perhaps the only central coordinating body on the global Internet, but the scope of its authority extends only to the Internet's systems of domain names, IP addresses, protocol ports and parameter numbers.
Summary of internet
In 1969, the US Department of Defense started a project to allow researchers and military personnel to communicate with each other in an emergency. The project was called ARPAnet and it is the foundation of the Internet.
Throughout the 1970's, what would later become the Internet was developed. While mostly military personnel and scientists used it in its early days, the advent of the World Wide Web in the early 1990's changed all that.
Today, the Internet is not owned or operated by any one entity. This worldwide computer network allows people to communicate and exchange information in new ways.
According to www.commerce.net, in April of 1999, there were 92.2 million Internet users over the age of 16 in the United States and Canada. By 2005, it is predicted 75% of the total US population will be online.
Q: what is intranet?
An intranet is a private computer network that uses Internet protocols and network connectivity to securely share part of an organization's information or operations with its employees. Sometimes the term refers only to the most visible service, the internal website. The same concepts and technologies of the Internet such as clients and servers running on the Internet protocol suite are used to build an intranet. HTTP and other Internet protocols are commonly used as well, such as FTP. There is often an attempt to use Internet technologies to provide new interfaces with corporate "legacy" data and information systems.
Briefly, an intranet can be understood as "a private version of the Internet," or as a version of the Internet confined to an organization. The term first appeared in print on April 19, 1995, in Digital News & Review in an article authored by technical editor Stephen Lawton.
Intranets differ from "Extranets" in that the former are generally restricted to employees of the organization while extranets can generally be accessed by customers, suppliers, or other approved parties.
There does not necessarily have to be any access from the organization's internal network to the Internet itself. When such access is provided it is usually through a gateway with a firewall, along with user authentication, encryption of messages, and often makes use of virtual private networks (VPNs). Through such devices and systems off-site employees can access company information, computing resources and internal communications.
Intranets are also being used as culture change platforms. For example, large numbers of employees discussing key issues in an online forum could lead to new ideas.
Intranet traffic, like public-facing web site traffic, is better understood by using web metrics software to track overall activity, as well as through surveys of users.
Advantages of intranets
- Workforce productivity: Intranets can help users to locate and view information faster and use applications relevant to their roles and responsibilities. With the help of a web browser interface, users can access data held in any database the organization wants to make available, anytime and - subject to security provisions - from anywhere within the company workstations, increasing employees' ability to perform their jobs faster, more accurately, and with confidence that they have the right information. It also helps to improve the services provided to the users.
- Time: With intranets, organizations can make more information available to employees on a "pull" basis (i.e.: employees can link to relevant information at a time which suits them) rather than being deluged indiscriminately by emails.
- Communication: Intranets can serve as powerful tools for communication within an organization, vertically and horizontally. From a communications standpoint, intranets are useful to communicate strategic initiatives that have a global reach throughout the organization. The type of information that can easily be conveyed is the purpose of the initiative and what the initiative is aiming to achieve, who is driving the initiative, results achieved to date, and who to speak to for more information. By providing this information on the intranet, staffs have the opportunity to keep up-to-date with the strategic focus of the organization.
- Web publishing allows 'cumbersome' corporate knowledge to be maintained and easily accessed throughout the company using hypermedia and Web technologies. Examples include: employee manuals, benefits documents, company policies, business standards, newsfeeds, and even training, can be accessed using common Internet standards (Acrobat files, Flash files, CGI applications). Because each business unit can update the online copy of a document, the most recent version is always available to employees using the intranet.
- Business operations and management: Intranets are also being used as a platform for developing and deploying applications to support business operations and decisions across the internetworked enterprise.
- Cost-effective: Users can view information and data via web-browser rather than maintaining physical documents such as procedure manuals, internal phone list and requisition forms.
- Promote common corporate culture: Every user is viewing the same information within the Intranet.
- Enhance Collaboration: With information easily accessible by all authorized users, teamwork is enabled
- Cross-platform Capability: Standards-compliant web browsers are available for Windows, Mac, and UNIX.
INTERNET APPLICATION AND SERVICES
Email [Electronic Mail]:
- Email service is used to communicate with each other by the message we can read or write or send or receive message from any one at any time.
- This service is very easy , speedy and available at minimum cost.
- Mail service is provided by mail server .mail server will store the all messages in to the inbox and for sending message it will use protocols in mail server user can login and manages the emails.
- User can save time and money using mail-client application like, Microsoft outlook express and Netscape mail for transferring emails the mail application use some protocols
- Protocols used in email services are:-
POP & IMAP: [Post Office Protocol And Internet Message Access Protocol]
This protocol will connect mail-client application to mail server and then receive all emails in the mail-client inbox from the mail server.
SMTP:[Simple Mail Transfer Protocols]
This protocol will sent the email from mail server to another mail server this will send text emails only.
MIME:[Multipurpose Internet Mail Extensions]
MIME is a mail handling standard developed by the IETF (Internet Engineering Task Force) to provide support for multimedia and multipart messages. MIME makes it possible to encode and transmit sound, video, and formatted data in a single message, and also to receive and handle (read, see, or hear) the message.
- Chatting is also one type of internet service with the help of this service we can talk with each other via text messages.
- If we can joint or attached web camera then also we can see each other.
- Chatting service is provided by the chat server. This server will manage the text messages traffic in the chat box or chat application.
- With the help of internet we can gather all the information about all the countries.
- Internet news provides all the information and news about while world.
- News server are used to store the news and also information and it will be used NNTP [Network News Transfer Protocol] for the transferring the news.
Voice and Video Conferencing:
- Voice and video conferencing is important service for the internet
- They can provide any voice chatting and video conferencing with the help of this service we can solve any query or question and they give directly answers or responses.
- Uploading: when we are putting information from our system to remote system or web server its call uploading, we can upload site and other files which contain information.
- Downloading: when we are getting information in our system from remote system or web server its call downloading. We can download files and other resources like picture, sound files etc.
- AOL[America On-Line]: AOL offering searching, shopping, channels online services , chatting and mailing services.
- MSN[Microsoft Network]: Microsoft provide search of the web, news, images and its having its own encyclopedia also offers desktop searching via tool bar application. MSN messenger will allow you chat with the other users.
- CompuServe: CompuServe is online service which can provide services to those users who subscribe for the services. Members can also exchange information with CompuServe's other members. It provide consumer information service. It had the largest consumers for their services approximately 2 million.
- Telnet: it allows an internet user to access a remote login after properly connected the remote host user can enter data or running programs from that login.
- Usenet: It is a bulletin board services of internet messages in this network are organized into thousands of topical groups or news groups which cover specific areas of internet.
TYPE OF ACCOUNTS
- TCP/IP account is point to point protocol (PPP) or serial line protocol account (SLIP).
- PPP or SLIP account is an internet amount that uses the PPP or SLIP communication protocol respectively.
- There are most popular account because the most popular browsers. Internet explorer and Netscape navigator designed to work with PPP and SLIP.
- PPP mere contemporary communication protocol then SLIP so choose PPP is if you have a choice when opening an account.
- Compressed SLIP [CSLIP] is a simple efficient version of SLIP but still is not as good as PPP.
- To use a PPP account you need a PPP compatible communication .The programmed dials phone using your modem and connect to the ISP logs in to your account by using your user name and password and then establish a PPP connection.
- While connected you can be use a variety of program to read your emails browse the web and access other information from the internet.
- Before the advent of PPP and SLIP account most internet accounts were text only shell accounts and this account are still available from same ISP.
- You can run a terminal emulation program on your pc to connect and internet host computer.
- Most internet host runs unique operating system which is powerful but frequently confusing system and also we have to type unique commands to use a shell account.
- When you use shell account you don't see graphics or use mouse and you can't easily store information on your own computer.
- Shell account is generally use for file uploading and downloading process because uniqueness of file transfer speed.
ISP [Internet Service Provider]
An ISP is a service provider that provides some way to connect to the Internet. Severe access methods are possible, and a particular ISP may allow any or all of these methods. ISPs (Internet Service Providers) fall along a spectrum with respect to service At one end, ISPs provide only Internet access; at the other end, online service providers have Internet access as only a small part of their business. Most ISPs charge at monthly rate, which allows the subscriber a limited number of hours online additional hours cost extra. Some ISPs will provide unlimited access for a (higher) fee.
ISP is an internet service provider is an organization that provides dial in internet account usually PPP, CSLIP, SLIP accounts and also sometimes unique shell account.
Features of ISP
Local Phone Number: Most of ISP has many phone numbers that your computers having a local phone number you don't need to spend mere on a long distance charges for internet connection.
Price: ISP externally charge for hours or speed they provide so you can select your ISP by calculating your usage or speed required.
Software: some ISP provides a CD-ROM or diskette with software that you can use to connect to use of internet.
Support: you never know when you are going to a problem so your ISP's technical support phone number and e-mail address should be open in 24 hours.
Speed: Some ISP has local access number that work with 28.8 kbps [kilo byte per second],33.6 kbps and 56 kbps modems some also support high speed of connections such as ISDN[Integrated service digital network],ADSL[Asynchronous digital subscriber line] at extra cost.
Accessibility: If the ISP's access numbers are frequently busy. You can have to do redialing until you connect. Ask internet users in your area whether they have trouble getting connected to the ISP.
- An interlinked collected of hypertext document (web pages) residing on web server & other documents, menu and database, available via URLs.
- Web documents are marked for formatting and linking with HTML and web servers use HTTP to deliver web pages.
- WWW is a software application that makes it is and possible for nearly any one to publish and browse hypertext document on the internet.
- The World Wide Web is a collection of millions of file stored on thousands of computer called web servers all over the world.
- WWW is a most common access method of internet resources.
ELEMENTS OF WEB
- Web page is a resource of information that is suitable for the World Wide Web and can be accessed through web browser. This information is usually in HTML or XHTML format, and may provide navigation to other web pages via hypertext links.
- Web pages may be retrieved by local computer from a remote web server the web server may restrict access only to a private network for example corporate intranet.
- You can also publish pages on the world wide web WebPages are requested and served from web servers using HTTP.
- WebPages may consist of files or static text within web server's file system.
- The web server may construct XHTML for each webpage when it is requested by browser for dynamic WebPages.
- The first online website appeared in 1991; on 30th April 1995 the WWW would be free to anyone.
- A website is a collection of WebPages, images, videos or other digital assets that is hosted on the web server and accessible via internet.
- A webpage is documenting typically written in (X) HTML that is almost always accessible via HTTP.A protocol that transfers information from the web server to display in web browser.
- The pages of websites can usually be accessed from a common URL, some websites require a subscription to access some are free accessible.
- A web browser can have graphical user interface like internet explorer, Mozilla fire fox or opera or can be text based browser of lynx.
- Users of fully graphical browsers may still disable the download and viewing images and other media to save time, network bandwidth or just to simplify their browsing experience.
- Users may also prefer not to user the fonts, font sizes, styles and color schemes selected by the web page designer and may apply their own CSS styling to their viewed version of the page.
- The World Wide Web consortium (W3C) and web accessibility initiative (WAI) recommend that all web pages should designed with that criteria.
- A computer that runs program described above is call web server.web servers have also the capability of logging some detailed information about client requests and server responses to log files this allows the webmaster to collect statics by running log analyzers on log files.
- Web server is able to handling static as well as dynamic contents compression of content and transfer.
INTRODUCTION TO WEB LANGUAGES
HTML [Hypertext Markup Language]:-
- HTML stands for hyper text markup language. HTL provide instructions to web browser in order to control how documents are viewed and how they ate related to each other.
- HTML develops a few years ago as a subset of SGML (standard generalized markup language) which is a higher level markup language. That has long been a favorite of the department of defense.
- HTML is language interpreted by browser. Web pages are also called html document. Html is a set of special codes that can be embedded in text to add formatting and linking information.
- HTML is specified as TAGS in html document.HTML allows the individual elements on the web to be brought together and presented as collection of text, images, multimedia and other files can all be packaged together using html. It's basic structure element is <html>,<head>,<title> and <body>.
- Structure of HTML
<TITLE>:: Patel Kelvani Mandal ::</TITLE>
Any thing you write inside this body tag will be displayed on the browser.
DHTML [Dynamic Hypertext Markup Language]:-
- DHTML stands for dynamic hypertext markup language. DHTML is a Microsoft enhancement of HTML version 4.0 , with the help of DHTML you can created special effect such as rotating text and images , creating menus in the web page and give effect to user interface and also put validation on the form.
- Using java script you can create a dialog boxes and message boxes and put validation over each and every element of the form container. Using CSS [cascading style sheet] you can give effect to the text and different elements of web page by set the values of attributes.
VISUAL BASIC SCRIPT:
- VB script is a web scripting language. VBScript is created by Mocrosoft Corporation hence MSIE works with it while Netscape client doesn't support VB script.
- VBScript is embedded into html program in the head tag and body tag portion of the page.
- If it is refer to specific form object it must follows the body tag.
- The main different between VBScript and Java Script are in VBScript code terminates with a colon sign , where java script code terminates with semicolon.
<TITLE>:: Patel Kelvani Mandal ::</TITLE>
Msgbox "patel kelvani mandal college of technology":
Any thing you write inside this body tag will be displayed on the browser.
- Java script is web scripting language. Java script is created by Netscape hence. Java script works best with Netscape client.
- Java script can be embedded into html page that runs immediately on the client machine.
- Java script's first name was "LIVE SCRIPT" but Netscape decide to exchange of java popularity and rename the product as java script , java script is object based language.
- Java script is not a part of java language.
XML [Extended Markup Language]:
- Extended markup language is much like html & is a W3C specification
- XML is powerful medium of data exchange. It allows you to create your own tag to represent data and meta data.
- The power of xml is that it maintains the separation of the user interface from the structured data.
- Html specify how to display data in browser where as XML defines the contain for example, in html you use tag to display data as bold or italic.
- In XML you only use text to describe data such as city name, temperature, zip code etc.
- In XML you only use style sheets such as XSL [extended style sheet language] and CSS [cascading style sheet] to present the data in browser.
- There are many tools available to create XML documents and then to load, read XML documents and then to load, read validate and parse those documents this allows application running on totally different platform to exchange data because everybody understand "text" and XML document it nothing a tagged text document.
- All xml documents are having "*.xml" extension. XML use DTD document type definition to describe the data.
WML [Wireless markup language]:
- WML stands for wireless markup language .WML is formally called HDML [handled devices markup language].
- WML is a language that allows the text portions of web pages to be presented on cellular phone and PDA personal digital assistants via wireless access.
- WML is a part of the WAP [Wireless Application Protocol].
- WAP works on top of standard data link protocols such as global system for mobile communication CDMA [Code Division Multiple Access] and TDMA [Time Division Multiple Access].
- WML is a open language offered royalty free.WML is based on XML, It's pages are known as deck and decks are constructed as set of cards and card is basic unit of WML, WML is case sensitive language.
PHP [Personal Home Page]:
- PHP is also known as preprocessed hypertext its recursive full form of PHP. PHP is server side scripting language.PHP script is executed on the server.
- PHP supported many databases like Oracle, MS-SQL, MY-SQL etc.PHP is open source language and mostly used with open sourced database like MY-SQL.
- PHP file contains php script, HTML tags and Text also.
- It's having reach set of class and function. its object oriented version is PHP5 and up to PHP3 its procedure oriented language.
VRML [Virtual Reality Markup Language]:
- Is an attempt to extend the web into the domain of three dimension graphics VRML "world" can depict realistic or other worldly places which can contain objects that link to other html documents or vrml world on the web site.
- It is used to create virtual reality worlds that you can fly around in to find information although still in its infancy. It will most certainly be a language that dominates the future .web pages will most likely only be used to place in virtual world and accessing a document from a virtual book
- VRML is a simple ASCII text description of geometries that can be hired across various platforms like UNIX, MAC and Windows. It is based on open invent file format .it has been extended to support web oriented capabilities like hyperlinks and elective refinement.
- VRML is a recent invention intended to be a three-dimensional analog to hypertext markup language (HTML).
- VRML is intended to accomplish just that elaborate 3D environments can be designed and the browser allows you to move within the artificial 3D environment, and move from one environment to another by links.
- Latest version of VRML is 2.0 it is having extension "*.WRL" you can not directly run this page on MSIE you need one plug-in to be installed before run any VRML file its name is Microsoft VRML 2.0 viewer.
- Web surfing is typical approach for find information on the web because surfing is unstructured and random browsing.
- Web surfing is starting with particular web page in this approach is to follow links from one page to another.
- A number of tools have been developed that enable to find information very quickly and effectively from the web.
- Finding the information on the web using two independent approaches.
- Browsing through subject trees and hierarchies (using web index)
- Using keyword or phrases you can search (using web search engine).
- A web index is design to assist users with locating information on the web. Web indexes are also sometime referring as a directory.
- A web index collects and organize resources available via the web or www.There are number of web indexes are available on the web.
- Indexes may present information alphabetically. Web index is use hyper text to present of interest and also actually link directly to the resources from the index.
- Due to vast amount of information available via the web number of single index resources.
- Web index can link hundreds, thousands or more resources. Some web index has many resources that provides a searching capability for user to have to find out the resources within the web index.
WEB SEARCH ENGINE
- The ability to search the web for specific sites or files relies on one tiny factor it is existence of searching and indexing sites that you can access to perform the search.
- These sites are often known as web spiders, crawlers or robots because they endlessly and automatically search the web.
- Search site will create huge databases of all the words in all pages they have and you can search those databases simply by entering keywords you want to find.
- Despite the size of this vast store of information it can generally returns a result to the user within second or two.
- Each day search engine going to store lots of information in its serve and then as per the search criteria search engine will return the information.
META SEARCH ENGINE
- A met search engine or all in one search engine performs a search by calling on more than one other search engine to do the actual work. The results are collated. Duplicate retrievals are eliminated and the result are ranked according to how well they match your query. You are then presented with a list of URLs.
- The advantage of a meta search engine is that you can access a number of different search engines with a single query. The disadvantage is that you will often have a high noise-signal ratio that is a lot of "Matches" .that will not be of interest of you this means you will need to spend more time evaluating the results and deciding which hyperlinks to follow.
- For very specific , hard to locate topics , meta search engine can often be a good starting point for example, if you try to locate a topic using your favorite search engine, but fail to turn up anything useful you may want to query a meta search engine.
- There are some examples of meta search engine like
www.metasearch.com, www.metacrawler.com, www.metafind.com,etc.
- Some websites store information in a small text file on your computer this called a cookies.
- Cookies stored information such as personal information like user name , geographical area or personal references like background color, text font size, color or face etc.
- These are several types of cookies and you can choose whether to allow some none or all of them to be saved on your computer.
- A cookie is a file created by an internet site to store information on your computer such as your preferences when visiting that site. For example, If you inquire about flight schedule at an airline's web site, the site might create cookie that contains a records of the pages you looked at within the site you visited, whenever we can see next time it may be speedy.
- Once a cookie is saved on your computer, only the website that created the cookie can read it. A cookie file is easily accessed and modify by the user because it is stored on user system. there are following types of cookie.
- PERSISTENT COOKIE: It is one stored as file on your computer then, it remains there when you close internet explorer. The cookie can be read by the website that created it when you visit that site again.
- TEMPORARY COOKIES: A temporary or session cookie is stored only for your current browsing session, and is deleted from your computer when you close internet explorer.
- UNSATISFACTORY COOKIES: Unsatisfactory cookies are cookies that might allow access to personally identifiable information that could be used for a secondary purpose without your consent.
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- A firewall is dedicated application or software or hardware running on another computer which inspect network traffic passing through it, and denies or permits passage based on a set of rules.
- A firewall's basic tasks is to regulate some of the flow or traffic between computer networks of different trust levels typical examples are the internal network which a zone of higher trust so firewall will work between those zone internet and internal network.
- A firewall used to prevent network disturbance to the private network. Without proper configuration firewall can often became worthless those configuration requires detailed understanding of network application. For example AVG firewall, STGATE firewall, COMODO firewall are software firewalls. Some operating system like windows xp having its own inbuilt firewall.
- A hacker is a person intensely interested in the secret and complex workings of any computer operating system. Hackers are most often programmers. As such, hackers obtain advanced knowledge of operating systems and programming languages. They might discover holes within systems and the reasons for such holes. Hackers constantly seek further knowledge; freely share what they have discovered, and never intentionally damage data.
- Hackers (as opposed to crackers) are basically thrill-seekers who use information technology rather than fast cars or bungee cords. They spend their time learning how systems work at a deep level and exploit this information to roam the information highways seeking out adventure. They have bulletin boards for sharing information, regular meetings. . . .
- Hackers are "thrill-seekers", they learn how computer systems work, and they are adventure-seekers.
- "people who love to explore the hidden depths of computing systems"
- "Hackers are defined as computer enthusiasts who have an enthusiastic interest in learning about computer systems and how to use them in innovative ways."
- "A scatter group of people often called 'hackers' has been characterized as unethical, irresponsible, and a serious danger to society for actions related to breaking into computer systems . . . . Hackers are learns and explorers who want to help rather than cause damage, and who often have very high standards of behavior.
- It is against hacker ethics to alter any data aside from the logs that are needed to clean their tracks. They have no need of desire to destroy data as the malicious crackers. They are there to explore the system and learn more. The hacker has a constant yearning and thirst for knowledge that increases in intensity as their journey progresses.
- A cracker is one who breaks into or otherwise violates the system integrity of remote machines with cruel intent. Having gained unauthorized access, crackers destroy vital data; deny rightful users service, or cause problems for their targets. Crackers can easily be identified because their actions are cruel.
- Additionally, it should be mentioned that there are two major types of crackers. The first is fortunately few and far between. They are the expert crackers who discover new security holes and often write programs that take advantage of them. The second type, the script kiddies, only knows how to get these programs and run them. Script kiddies are more frequent, but much easier to stop and detect.
- A program or piece of code that is loaded onto your computer without your knowledge and runs against your wishes, viruses can also replicate themselves.
- All computer viruses are manmade and simply virus that can make a copy of it over and over again is relatively easy to produce.
- Even such a simple virus is dangerous because it will quickly use all available memory and bring a system to halt. An even more dangerous type of virus is one capable of transmitting itself across network and bypassing security system.
- A worm is special kind or virus that can replicate itself and use memory, but cannot attach itself to other programs and harm data.
- A Trojan horse is full of as much trickery as mythological Trojan horse it was named after the Trojan horse because at first glance it will appear to be useful software but will actually do damage once installed or run on your computer like virus and worms will not reproduce itself.
- Mixture of all those is call blended threat. A blended threat is a sophisticated attack that bundles some of the worst aspects of viruses, worms and Trojan horses and malicious code into one threat.
- Blended threats use server and internet to initiate transmit and spread an attack. This combination of method and techniques means it will spread quickly and cause wide spread damage.
- Cryptography is science of securing data. Cryptography is the process of transforming original information into an unreadable form it may be sent over unsafe communication channel.
- Encryption is the transformation of data into an unreadable form using encryption and decryption key. There is two types of Encryption.
- Symmetric Encryption (Private Key Encryption)
- Symmetric encryption that the same key is used for message encryption and decryption process.
- For example sender would encrypt a message using a key and then send the message to receiver. Sender would separately communicate the key to receiver to allow him decrypt message to maintain security and privacy however sender and receiver both have to ensure that the key remains private to them.
- Symmetric encryption method is very simple but the simplicity of symmetric encryption is also the source of its problem.
- As the number of people increases. The management of the private keys becomes a costly and cumbersome exercise. Some well known example of this type of encryption DES [ data encryption standard] , IDES [international data encryption standard],AES[advanced encryption standard].
- Asymmetric Encryption (Public Key Encryption)
- Asymmetric or public key encryption differs from symmetric encryption by using a pair of keys instead of single key. one of the key is kept private while the second is made public key so that it can be accessed by any one.
- The key pair works in complementary manner information encrypted by one key can only be decrypted using the other. Only the recipient's private key can decrypt the message, As long as the private key remains secure , then the sender can be sure that only the intended recipient can possibly read the message.
- For example sender is sending a message to receiver and sender will creates a message then encrypts it using receiver's public key. When receiver having encrypted message then use secret private key to decrypt that message, As long as receiver's private key has not been compromised then both sender and receiver knows that message is secured.
- Digital Signature
- Digital signature is one type of asymmetric encryption but in digital signature message is encrypt and decrypt two times.
- It works as below figure.
- Before the sender will send plain text message, sender will do first encryption using the sender's private key which work as digital signature then sender will re-encrypt message using the receiver's public key after that process sender will send the encrypted message to receiver.
- When receiver will receive that message and then decrypt that message by using the receiver's private key and then receiver will re-decrypt that message using the sender's public key.
- Let us extend the example by declaring mr.A as a sender and mr.B as receiver.
- A will encrypt the message using his private key (digital signature)
- A will again encrypt the message using public key of mr.B (second encryption)
- A will send that message to B
- B will decrypt the message using his private key.(first decryption)
- B will re-decrypt message using mr.A's public key
- However this method is not efficient because it involves a lot of time and computer resources the encryption and decryption process are double it takes still longer time and more resources.
- A digital certificate is a file that identifies a person or organization. A digital certificate also known as digital signature
- The organization has gone to some certifying authority and gotten a digital signature.
- When organization server wants to convince your browser, it sends its certificate file. Your browser checks that the certifying authority is on the list that the browser manufacturer programmed into it. Then the server and the browser have a short conversation.
- Organization's server proves that it knows the private key that certificate says, your browser then ready to accept that it is dealing.