How To Add Custom Contact Page To Your Blogger Blog Video Tutorial

I guess many of you are interested to add a Contact Page to your Blogger Blog. But how many of us know, how to do so. By adding a separate contact page, where your visitors can directly contact you from your Blog, instead of using any other mailing options.

It was very simple to add a Contact page to your Blogger blog. The contact page can be Created using Google drive and easily install on Blogger blog. Each step is clearly shown in the Video, How to add Custom Contact Page to your Blogger Blog.

Thank you for watching this "How to Add Custom Contact Page to your Blogger Blog" video tutorial. 

I hope this video tutorial gives you a clear idea to create a Custom Contact Page using Google Drive and install it on your blogger blog Contact Page.

For any suggestions or ideas, leave a comment below.


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Earn Extra Bucks With Paid Surveys

Paid surveys are becoming a very popular way to make extra money online. The sites that provide these surveys are owned or contracted by market research companies. These companies value your opinion and are willing to pay you for spending some time filling out surveys about various products.

 New to online surveys? Here are some tips:
 
After you sign up with a survey site you will be asked give some demographic information about yourself, and possibly to take a few unpaid surveys. These are usually called profile surveys. Not all survey sites have profile surveys, but if they are available you should fill them out as soon as possible. Doing so will help you later to qualify for more paid surveys.
Once in a while you will receive a survey invitation in your email. Some sites may send you several invitations per week, while others may send invites once a month or less. If you accept the invitation, you will first be given a screen-er, which is a few short questions to see if you qualify for the full survey. If you qualify, you can expect to spend from 5 to 20 minutes filling out the survey.
 
The amount paid for a survey varies widely - $1-$5 for typical surveys, to as much as $50 or more for highly specialized surveys. Most survey sites do not pay you directly after completing each survey, but instead send you a total payment after you have reached a certain amount. This amount is known as the minimum cash out.

American Consumer Opinion sends several surveys each month. If you qualify for the full survey, you will be paid for every single survey you complete - there is no minimum amount you must reach before you can cash out. Additionally, all members of American Consumer Opinion are entered automatically into a monthly cash drawing without having to do anything extra, which makes it very worth your while to sign up.
 
Choozz is an entertainment survey site specializing in the topics of music, movies, and games. Choozz requires its users to be between 13 and 35 years old. Each survey on Choozz has a different type of incentive - some offer cash rewards, while others offer chances to win prizes or entries into their $25,000 sweepstakes.
 
Ciao! Surveys is an international survey site now owned by Greenfield Online, which is also listed in this section. It is available to ages 14 and up and all over the world, except in the United States and Canada - residents of these two countries should sign up at Greenfield's main site. Ciao has a low minimum cashout of just $5.00, so you will not have to complete many surveys before you can get paid.

ClickIQ features a paid survey panel called e/visor that is available to US residents only. ClickIQ rewards users with "IQPoints" for taking surveys, with 100 points equal to $1.00. Surveys generally offer 150 points for completing, or a smaller number of points if you do not qualify for the full survey. ClickIQ has a relatively high minimum cashout of $25.00. Like many other survey sites, you can also earn entries into sweepstakes for participating.
 
Esearch is one of the highest paying survey sites on average. However, they send a very small number of survey invitations - typically just one or two per month. There are no profile surveys to fill out, so participation is easy, making Esearch a very good site to sign up with alongside other survey sites. Besides cash, Esearch also offers rewards such as gift certificates for completed surveys.

Global Opinion Panels (also known as Synovate) offers points for completed surveys, with 1,000 points equal to $1. Most surveys offer several thousand points or more for completing, and there is a low minimum cashout of just $5.00. Global Opinion Panels also provides the option of having samples of products mailed to you, and then being paid simply for answering a survey about the product. This is entirely optional. Global Opinion Panels is available in the US only.

Global Test Market is a long running site that compensates well for its surveys. Users are rewarded for every single survey with "MarketPoints" which are then turned in for cash, at a rate of 20 MarketPoints = $1.00. Most surveys offer anywhere from 50 to several hundred MarketPoints for completing, and you will receive some points even if you do not qualify for a particular survey. You can also refer your friends via email for more points.
 
Greenfield Online features a large number of surveys for members to take at most times, although not all surveys are for cash. Many of Greenfield's surveys are for entries into their cash drawings, of which there are several per month. If you do not qualify for a paid survey, you will still receive entries into the drawings simply for filling out the screener. Greenfield Online is available in the US and Canada only. If you live elsewhere, you should visit Greenfield's sister site: Ciao Surveys (listed earlier in this section).
 
HCDSurveys is a survey panel by HCD Research that rewards its users with points for every survey they complete. 100 points are equal to $1 and the minimum cash-out is $10. Typical surveys on HCD pay out 100-500 points. HCD seems to send a small amount of surveys per month compared to other sites, but as always the actual number of invites you get will depend a lot on your demographics.
Lightspeed Consumer Panel sends a relatively large number of invites for paid surveys, although compensation is slightly lower on average than some of the other survey sites. Users receive "Lightspeed Points" for completing surveys - these can be redeemed for cash or other prizes if you choose. In addition, you receive an entry into their $5,000 drawing for each survey whether you qualify for the full survey or not. Lightspeed Panel also features a number of mini-polls that you can fill out, which will earn you even more entries into their cash drawing.

MySurvey (previously known as NFO MySurvey) is another survey site that rewards its users with points that can later be redeemed for cash. On MySurvey, 100 points is equivalent to $1.00 and some surveys offer as much as 1,000 points for completing. MySurvey features a number of different sweepstakes as well. There is a daily 10,000 point ($100) drawing for all members of the site - you only need to log on to their site to qualify for the drawing - and an additional $10,000 drawing awarded several times a year. MySurvey is also known to occasionally award bonus points simply for good participation on their site.

Opinion Outpost rewards its users with points for taking surveys, with 10 points being equal to $1. Surveys typically pay between 10 and 100 points if you qualify, and you only need to accumulate 50 points before you can cash out. The site also has an option for you to answer surveys by phone for extra compensation. Note that this option is disabled by default, and you must specifically opt-in if you want to take part, so you should not worry about receiving unwanted phone calls. Available in the US and Canada only.

Planet Pulse is another survey site that uses the familiar system of rewarding its users with points, which are called "Pulses" on their site. 100 Pulses is equal to $1.00 and some surveys offer as much as 5,000 Pulses ($50.00), though those are rare. Typical survey payouts are in line with most of the other paid survey sites, and you also get a small amount of Pulses even if you do not qualify for a full survey after filling out the screener. Planet Pulse also has a referral program that rewards you with more Pulses every time someone you refer completes a survey.

SurveySavvy sends less survey invitations on average than the typical survey site, but compensation for surveys is generally very good. Even if you do not qualify for a particular survey, you are still entered into a monthly cash drawing. SurveySavvy also features a top notch referral program that pays well if you would like to refer others to their site.

SurveySpot is a good place to go if you really enjoy taking surveys. They generally send out multiple survey invitations per day. However, keep in mind that not all of their surveys are paid surveys. The majority of their surveys will earn you entries into their $25,000 sweepstakes. You are also entered into the sweepstakes every time you do not qualify for a paid survey. Also, you can log on to their site and find a small list of surveys to choose from at almost any time each day. Available in the US, Canada, and UK only.

YouGov Panel is a survey site that specializes in political opinion polls. The YouGov Panel is primarily for the UK. However, they provide two additional sites - YouGovAmerica for US members, and YouGovME for those in the Middle East. YouGov Panel pays out around $1-$2 per poll. One drawback is that they have a high minimum cashout of $50.00.

Your2Cents offers a few extra bonuses over typical survey sites. First, they reward you just for filling out your profile surveys - $1 each. They also have a few other types of surveys -text based surveys that you can receive on your cell phone, and telephone based surveys. These offer extra incentives compared to the standard web based surveys. Note that these extra surveys are entirely optional. Your2Cents is available in the US and Canada only.

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TEXT FORMATTING ON AN HTML PAGE

Text formatting, in other words presenting the text on an HTML page in a desired manner, is an important part of creating a web page. Let us understand how we can lay out of text controls its appearance on a page.

Headers

Headers are used to specify the headings of sections or sub-sections in a document. Depending on the desired size of the text, any of six available levels (<H1> to <H6>) of headers can be used. The usage and varying size of the rendered text depending upon the tag used. See the figure below.



<HTML>
<HEAD>
<TITLE> MY FIRST WEB PAGE</TITLE>
</HEAD>
<BODY>
<CENTER>
<H1> Header Level 1</H1>
<H2> Header Level 2</H2>
<H3> Header Level 3</H3>
<H4> Header Level 4</H4>
<H5> Header Level 5</H5>
<H6> Header Level 6</H6>
</CENTER>
</BODY>
</HTML>

 

There is no predefined sequence for using the different levels of the header tags nor any restrictions on which one can be used. So the user has the option of using any level of header tag anywhere in the document. If you want to center text on a page, use the CENTER tag. The text written between <CENTER> and </CENTER> tag gets aligned in the center of the HTML page. As seen in Figure above, the maximum siz of the text is displayed using the <H1> tag. So the size goes in decreasing order with the increasing order of the level (i.e. From <H1> to <H6>).

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BASIC TAGS OF HTML

Let us now look at tags in more detail. A <TAG> tells the browser to do something. An ATTRIBUTE goes inside the <TAG> and tells the browser how to do it. A tag can have several attributes. Tags can also have default attributes. The default value is a value that the browser assumes if you have not told it otherwise. A good example is the font size. The default font size is 3. If you say nothing the size attribute of the font tag will be taken to have the value 3.






Consider the example shown in Fig.1A. Type the code specified in the figure in a text editor such as notepad and save it as “fig1A.html”. To render the file and see your page you can choose one of two ways:

1. Find the icon of the html file you  just made (fig1A.htm) and double click on it. Or,
2. In Internet Explorer, click on File/Open File and point to the file (fig 1A.htm).

Figure 1A. A Simple Web Page

<html> <!- - This is a comment - - > <head> <title> my web </TITLE> </HEAD> <body> This is my first web page. </BODY> </HTML>

HTML Tag

As shown in Figure 1A above, <HTML> is a starting tag. To delimit the text inside, add a closing tag by adding a “/” to the starting tag. Most but not all tags have a closing tag. It is necessary to write the code for an HTML page between <HTML> and </HTML>. Think of tags as talking to the browser or, better still, giving it instructions. What you have just told the browser is 'this is the start of an HTML document' (<HTML>) and 'this is the end of an HTML document' (</HTML>). Now you need to put some matter in between these two markers. Every HTML document is segregated into a HEAD and BODY. The information about the document is kept within <HEAD> tag. The BODY contains the page content.

TITLE Tag

The only thing you have to concern yourselves with in the HEAD tag (for now) is the TITLE tag. The bulk of the page will be within the BODY tag, as shown in Figure.1A.

<HEAD>
<TITLE> MY WEB </TITLE>
</HEAD>

Here the document has been given the title my web. It is a good practice to give a title to the document created. What you have made here is a skeleton HTML document. This is the minimum required information for a web document and all web documents should contain these basic components. Secondly, the document title is what appears at the very top of the browser window.

BODY Tag

If you have a head, you need a body. All the content to be displayed on the web page has to be written within the body tag. So whether text, headlines, text-box, check-box or any other possible content, everything to be displayed must be kept within the BODY tag as shown in Figure 1A. Whenever you make a change to your document, just save it and hit the Reload/Refresh button on your browser. In some instances just hitting the Reload/Refresh button doesn’t quite work. In that case hit Reload/Refresh while holding down the SHIFT key.

The BODY tag has following attributes:

• BGCOLOR: It can be used for changing the background color of the page. By default the background color is white.
• BACKGROUND: It is used for specifying the image to be displayed in the background of the page.
• LINK: It indicates the color of the hyperlinks, which have not been visited or clicked on.
• ALINK: It indicates the color of the active hyperlink. An active link is the one on which the mouse button is pressed.
• VLINK: It indicates the color of the hyperlinks after the mouse is clicked on it.
• TEXT: It is used for specifying the color of the text displayed on the page.

Consider the following example:

Figure 1B. A Page with a Background Color

<html> <title> MY WEB</TITLE> <body BGCOLOUR="#EA728A" TEXT = “#000000”> Welcome to MY WEB </BODY> </HTML>




The values specified for BGCOLOR and TEXT tags indicate the color of the background of the page and that of the text respectively. These are specified in hexadecimal format. The range of allowable values in this format is from “#000000” to “#FFFFFF”. The“#” symbol has to precede the value of the color so as to indicate to the browser that has to be interpreted as a hexadecimal value. In this six digit value, the first two digits specify the concentration of the color red, the next two digits specify the concentration of the color green and the last two digits specify the concentration of the color blue. So the value is a combination of the primary colors red, green and blue and that is why it is called RGB color. If we specify the value “#FF0000”, the color appears to be red.”#000000” gives black and “#FFFFFF” gives the color white. You also have the option of specifying the color by giving its name, like: <BODY TEXT = “WHITE”>. You can also specify a background image instead. (Note that the image should be in the same folder as your HTML file. More on this below).
Try it out with the example HTML below:

Figure 1C. A Page with an Image in the Background

<html> <body BACKGROUND="viniwebworld.png"> Welcome to MY WEB WORLD </BODY> </HTML>

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INTRODUCTION TO HTML

You would by now have been introduced to the Internet and the World Wide Web (often just called the Web) and how it has changed our lives. Today we have access to a wide variety of information through Web sites on the Internet. We can access a Web site if we have a connection to the Internet and a browser on our computer. Popular browsers are Microsoft Internet Explorer, Netscape Navigator and Opera. When you connect to a Web site, your browser is presented with a file in a special format by the Web server on the remote computer. The contents of the file are stored in a special format using Hyper Text Markup Language, often called HTML This format is rendered, or interpreted, by the browser and you then see the page of the web site from your computer. HTML is one language in a class of markup languages, the most general form of which is Standard Generalized Markup Language, or SGML. Since SGML is complex, HTML was invented as a simple way of creating web pages that could be easily accessed by browsers.

HTML is a special case of SGML. HTML consists of tags and data. The tags serve to define what kind of data follows them, thereby enabling the browser to render the data in the appropriate form for the user to see. There are many tags in HTML, of which the few most important ones are introduced in this unit. HTML files usually have the extension “.htm” or “.html”. If you want to create Web pages, you need a tool to write the HTML code for the page.  This can be a simple text editor if you are hand-coding HTML. You also have sophisticated HTML editors available that automate many (though not all) of the tasks of coding HTML. You also need a browser to be able to render your code so that you can see the results.

WHAT IS HTML?

As indicated earlier, HTML stands for Hypertext Markup Language. HTML provides a way of displaying Web pages with text and images or multimedia content. HTML is not a programming language, but a markup language. An HTML file is a text file containing small markup tags. The markup tags tell the Web browser, such as Internet Explorer or Netscape Navigator, how to display the page. An HTML file must have an htm or html file extension. These files are stored on the web server. So if you want to see the web page of a company, you should enter the URL (Uniform Resource Locator), which is the web site address of the company in the address bar of the browser. This sends a request to the web server, which in turn responds by returning the desired web page.  The browser then renders the web page and you see it on your computer.

HTML allows Web page publishers to create complex pages of text and images that can be viewed by anyone on the Web, regardless of what kind of computer or browser is being used. Despite what you might have heard, you don’t need any special software to create an HTML page; all you need is a word processor (such as Microsoft Word) and a working knowledge of HTML. Fortunately, the basics of HTML are easy to master.  However, you can greatly relieve tedium and improve your productivity by using a good tool.  A simple tool is Microsoft FrontPage that reduces the need to remember and type in HTML tags.  Still, there can always be situations where you are forced to hand code certain parts of the web page. HTML is just a series of tags that are integrated into a document that can have text, images or multimedia content. HTML tags are usually English words (such as block quote) or abbreviations (such as p for paragraph), but they are distinguished from the regular text because they are placed in small angle brackets. So the paragraph tag is <p>, and the block quote tag is <blockquote>. Some tags dictate how the page will be formatted (for instance, <p> begins a new paragraph), and others dictate how the words appear (<b> makes text bold). Still others provide information - such as the title - that doesn’t appear on the page itself. The first thing to remember about tags is that they travel in pairs. Most of the time that you use a tag - say <blockquote> - you must also close it with another tag - in this case, </blockquote>. Note the slash - / - before the word “blockquote”; that is what distinguishes a closing tag from an opening tag.

The basic HTML page begins with the tag <html> and ends with </html>. In between, the file has two sections -the header and the body.  The header - enclosed by the <head> and </head> tags -contains information about a page that will not appear on the page itself, such as the title. The body - enclosed by <body> and </body> - is where the action is. Everything that appears on the page is contained within these tags.

HTML pages are of two types:

• Static
• Dynamic

Static Pages

Static pages, as the name indicates, comprise static content (text or images). So you can only see the contents of a web page without being able to have any interaction with it.

Dynamic Pages

Dynamic pages are those where the content of the web page depend on user input. So interaction with the user is required in order to display the web page. For example, consider a web page which requires a number to be entered from the user in order to find out if it is even or odd. When the user enters the number and clicks on the appropriate button, the number is sent to the web server, which in turn returns the result to the user in an HTML page.

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INTERNET TOOLS

In this article, we will look at two software tools available on the Internet.

Search Engines

Search Engines are programs that search the web. Web is a big graph with the pages being the nodes and hyperlinks being the arcs. Search engines collect all the hyperlinks on each page they read, remove all the ones that have already been processed and save the rest. The Web is then searched breadth-first, i.e. each link on page is followed and all the hyperlinks on all the pages pointed to are collected but they are not traced in the order obtained.

Automated search is the service that is provided by Search engines. An automated search service allows an individual to find information that resides on remote computers. Automated search systems use computer programs to find web pages that contain information related to a given topic. It allows to locate:
 

• Web pages associated with a particular company or individual
• Web pages that contain information about a particular product.
• Web pages that contain information about a particular topic.

The results of an automated search can be used immediately or stored in a file on disk to use it later. The results of a search are returned in the form of a web page that has a link to each of the items that was found. Automated search is helpful when a user wants to explore a new topic. The automated search produces a list of candidate pages that may contain information. The user reviews each page in the list to see whether the contents are related to topic or not. If so, the user records the location or if not user moves on to the page in the list. Search mechanisms uses a similar method of search as in the telephone book i.e. before any user invoke the search mechanism a computer program contacts computers on the Internet, gathers a list of available information, sorts the list and then stores the result on a local disk on the computer that runs a search server. When a user invokes a search, the user client program that contacts the server. The client sends a request that contains the name the user entered. When the request arrives at the server, it consults the list of file names on its local disk and provides the result.

Web Browser

A Web browser is software program that allows you to easily display Web pages and navigate the Web. The first graphical browser, Mosaic, was developed in Illinois at the National Center for Supercomputing Applications (NCSA). Each browser displays Web-formatted documents a little differently. As with all commercial software, every program has its own special features.

The two basic categories of Web browser are:

• Text-only browsers: A text-only browser such as Lynx allows you to view Web pages without showing art or page structure. Essentially, you look at ASCII text on a screen. The advantage of a text-only browser is that it displays Web pages very fast. There's no waiting for multimedia downloads.
• Graphical browsers: To enjoy the multimedia aspect of the Web, you must use a graphical browser such as Netscape Navigator or NCSA Mosaic. Graphical browsers can show pictures, play sounds, and even run video clips. The drawback is that multimedia files, particularly graphics, often take a long time to download. Graphical browsers tend to be significantly slower than their text-only counterparts. And this waiting time can be stretched even further with slow connections or heavy online traffic. 

Many different browsers are available for exploring the Internet. The two most popular browsers are Netscape Navigator and Microsoft Internet Explorer. Both of these are graphical browsers, which mean that they can display graphics as well as text.

SUMMARY

I hope now you have an idea in the basic concepts about an Internet. Internet is a network of networks where lot of information is available and is meant to be utilized by you. No one owns the Internet. It consists of a large number of interconnected autonomous networks that connect millions of computers across the world. The unit describes the various tools available on the Internet and the various services provided by the Internet to users. In this unit we have talked about the Electronic mail Usenet and newsgroups, FTP, Telnet and search engines. We also describe the use of frequently asked questions. The unit also describes the importance of Internet addresses. Addresses are essential for virtually everything we do on the Internet. There are many services available on the Internet for document retrieval. For browsing the Internet there are many browsers available such as Gopher and World Wide Web. Both of these browsers are easy to use and most popular browsing mechanisms on the Internet.

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PROTOCOLS AND SERVICES ON INTERNET

To work with Internet and to utilize its facilities we use certain tools. For example,Telnet is a tool, which is utilized for logging on remote computers on the Internet. Let us briefly discuss about some of the important tools and services.

Domain Name System

Domain name is a name given to a network for ease of reference. Domain refers to a group of computers that are known by a single common name. Somebody has to transfer these domain names into IP addresses. It is decided on the physical location of the web server as well as where the domain name is registered. Some generic domain names are:

Domain name	Description
com	Commercial Organization
Edu	Educational Organization
Gov	Government Organization

Thus, humans use domain names when referring to computers on the Internet, whereas computers work only with IP addresses, which are numeric. DNS was developed as a distributed database. The database contains the mappings between the domain names and IP addresses scattered across different computers. This DNS was consulted whenever any message is to be sent to any computer on the Internet. DNS is based on the creation of the hierarchical domain based naming architecture, which is implemented as a distributed database. It is used for mapping host names and email addresses to IP addresses. Each organization operates a domain name server that contains the list of all computers in that organization along with their IP addresses. When an application program needs to translate a computer’s name into the computer’s IP address, the application becomes a client of the DNS. It contacts a domain name server and sends the server an alphabetic computer name then the server returns the correct IP address. The domain name system works like a directory. A given server does not store the names and addresses of all possible computers in the Internet. Each server stores the name of the computers at only one company or enterprise.

SMTP and Electronic Mail

One of the very useful things about Internet is that it allows you almost instantly exchange of electronic message (e-mail) across the worlds. E-mail is a popular way of communication on the electronic frontier. You can E-mail to your friend or a researcher or anybody for getting a copy of a selected paper. Electronic mail system provides services that allowed complex communication and interaction. E-mail provide the following facilities:

• Composing and sending/receiving a message.
• Storing/forwarding/deleting/replying to a message.
• Sending a single message to more than one person.
• Sending text, voice, graphics and video.
• Sending a message that interacts with other computer programs.

Another commonly used Internet service is electronic mail. E-mail uses an application level protocol called Simple Mail Transfer Protocol or SMTP. SMTP is also a text-based protocol, but unlike HTTP, SMTP is connection oriented. SMTP is also more complicated than HTTP.

When you open your mail client to read your e-mail, this is what typically happens:

1. The mail client (Netscape Mail, Lotus Notes, Microsoft Outlook, etc.) opens a connection to it's default mail server. The mail server's IP address or domain name is typically setup when the mail client is installed.
2. The mail server will always transmit the first message to identify itself.
3. The client will send an SMTP HELO command to which the server will respond with a 250 OK message.
4. Depending on whether the client is checking mail, sending mail, etc. the appropriate SMTP commands will be sent to the server, which will respond accordingly.
5. This request/response transaction will continue until the client sends an SMTP QUIT command.The server will then say goodbye and the connection will be closed.

Similarly, when you send an e-mail message your computer sends it to an SMTP server. The server forwards it to the recipients mail server depending on the email address. The received message is stored at the destination mail server until the addressee retrieves it. To receive E-mail a user Internet account includes an electronic mailbox. A message sent for you is received at your Internet host computer, where it is stored in your electronic mailbox. As soon as you login into your Internet account, one of the first things you should do is to check your mailbox.

E-mail system follows the client-server approach to transfer messages across the Internet. When a user sends an E-mail message a program on the sender’s computer becomes a client. It contacts an e-mail server program on the recipient’s computer and transfers a copy of the message. Some of the mail programs those exist on Internet are UCB mail, Elm, Pine etc. However, one thing, which you must emphasize while selecting a mail program, is the user friendliness of that program. Through E-mail on Internet you can be in direct touch of your friend and colleagues.

Mailing lists on Internet

Another exciting aspect about the E-mail is that you can find groups of people who share your interests-whether you are inclined toward research, games or astronomy. E-mail provides a mechanism for groups of people who have shared interests to establish and maintain contact. Such interest groups are referred to as mailing lists (lists for short). After all they are mailing lists of the members e-mail addresses. You can subscribe to any of such lists. You will receive copies of all the mail sent to the list. You can also send mail to al subscribers of the list.

Http and World Wide Web

One of the most commonly used services on the Internet is the World Wide Web (WWW). The application protocol that makes the web work is Hypertext Transfer Protocol or HTTP. Do not confuse this with the Hypertext Markup Language (HTML). HTML is the language used to write web pages. HTTP is the protocol that web browsers and web servers use to communicate with each other over the Internet. It is an application level protocol because it sits on top of the TCP layer in the protocol stack and is used by specific applications to talk to one another. In this case the applications are web browsers and web servers.

HTTP is a connectionless text based protocol. Clients (web browsers) send requests to web servers for web elements such as web pages and images. After the request is serviced by a server, the connection between client and server across the Internet is disconnected. A new connection must be made for each request. Most protocols are connection oriented. This means that the two computers communicating with each other keep the connection open over the Internet. HTTP does not however. Before an HTTP request can be made by a client, a new connection must be made to the server.

When you type a URL into a web browser, this is what happens:

1. If the URL contains a domain name, the browser first connects to a domain name server and retrieves the corresponding IP address for the web server.
2. The web browser connects to the web server and sends an HTTP request (via the protocol stack) for the desired web page.
3. The web server receives the request and checks for the desired page. If the page exists, the web server sends it. If the server cannot find the requested page, it will send an HTTP 404 error message. (404 means 'Page Not Found' as anyone who has surfed the web probably knows.)
4. The web browser receives the page back and the connection is closed. 
5. The browser then parses through the page and looks for other page elements it needs to complete the web page. These usually include images, applets, etc.
6. For each element needed, the browser makes additional connections and HTTP requests to the server for each element.
7. When the browser has finished loading all images, applets, etc. the page will be completely loaded in the browser window.  

Most Internet protocols are specified by Internet documents known as a Request For Comments or RFCs. RFCs may be found at several locations on the Internet.

WWW is an Internet navigation tool that helps you to find and retrieve information links to other WWW pages. The WWW is a distributed hypermedia environment consisting of documents from around the world. The documents are linked using a system known as hypertext, where elements of one document may be linked to specific elements of another document. The documents may be located on any computer connected to the Internet. The word “document” is not limited to text but may include video, graphics, databases and a host of other tools.

The World Wide Web is described as a “wide area hypermedia information initiative among to give universal access to large universe of documents”. World Wide Web provides users on computer networks with a consistent means to access a variety of media in a simplified fashion. A popular software program to search the Web is called Mosaic, the Web project has modified the way people view and create information. It has created the first global hypermedia network.

Once again the WWW provides an integrated view of the Internet using clients and servers. As discussed earlier, clients are programs that help you seek out information while servers are the programs that find information to the clients. WWW servers are placed all around the Internet.

The operations of the Web mainly rely on hypertext as its means of interacting with users. But what is hypertext? Hypertext as such is the same as regular text that is it can be written, read, searched or edited; however, hypertext contains connections within the text to other documents. The hypertext links are called hyperlinks. These hyperlinks can create a complex virtual web of connections.

Hypermedia is an advanced version of hypertext documents as it contains links not only to other pieces of text but also to other forms of media such as sounds, images and movies. Hypermedia combines hypertext and multimedia.

Usenet and Newsgroups

In Internet there exists another way to meet people and share information. One such way is through Usenet newsgroups. These are special groups set up by people who want to share common interests ranging from current topics to cultural heritages. These are currently thousands of Usenet newsgroups.

The Usenet can be considered as another global network of computers and people, which is interwined with the Internet. However, Usenet does not operate interactively like the Internet, instead Usenet machines store the messages sent by users. Unlike mail from mailing lists, the news articles do not automatically fill your electronic mailbox. For accessing the information on newsnet, one needs a special type of program called a newsreader. This program help in retrieving only the news you want from Usenet storage site and display it on your terminal. Usenet is like living thing, New newsgroups gets added, the groups which have too much traffic get broken up into smaller specialized groups, the groups even can dissolve themselves. However, all of this occurs based on some commonly accepted rules and by voting. For Usenet, there is no enforcement body; it entirely depends on the cooperation of its computers owners and users.
The newsgroups are really meant fro interaction of people who share your interests. You can post your own questions as well as your answers to the questions of others, on the Usenet. One thing, which is worth mentioning here, is that when one is interacting wit people on Internet certain mannerism should be adopted. These rules are sometimes called “netiquette”. In a face-to-face conversation you can always see a person’s facial gestures and hand movements and can ascertain whether he is teasing or is being sarcastic or sometimes even lying. However, in on-line interaction one cannot see the person one is interacting with. The rules of netiquette may help to compensate some of these limitations of this on-line environment.

File Transfer Protocol (FTP)

FTP (File Transfer Protocol), a standard Internet protocol, is the simplest way to exchange files between computers on the Internet. Like the Hypertext Transfer Protocol (Hypertext Transfer Protocol), which transfers displayable Web pages and related files, FTP is an application protocol that uses the Internet's TCP/IP protocols. FTP is commonly used to transfer Web page files from their creator to the computer that acts as their server for everyone on the Internet. It's also commonly used to downloading programs and other files to the computer from other servers. However, for such transfer you need an account name on a host and the password. The FTP program will make connection with the remote host, which will help you to browse its directories and mark files for transfer. However, you cannot look at the contents of a file while you are connected via FTP. You have to transfer the copy and then look at it once it is on your own account.

FTP includes many commands but only few are used to retrieve a file. A user needs to understand the three basic commands to connect to remote computer, retrieve a copy of file and exit the FTP program. The commands with their meanings are:

Command	Purpose
Open	connect to a remote computer
get	retrieve a file from the computer
bye	terminate the connection and leave the FTP program

Transferring a file via FTP requires two participants: an FTP client program and FTP server program. The FTP client is the program that we run on our computers. The FTP server is the program that runs on the huge mainframe somewhere and stores tens thousands of files. It is similar to an online library of files. The FTP client can download (receive) or upload (send) files to the FTP server. Using Web browser you can download the files but you can not upload the files. FTP applications will help you to upload the files to the web sites, which you are maintaining.

FTP only understands two basic file formats. It classifies each file either as a text file or a binary file. A text file contains a sequence of characters collected into lines. Although computers used ASCII encoding for text files, FTP includes commands to translate between ASCII and other character encoding. FTP uses the classification binary file for all nontext files. The user must specify binary for any file that contains:

• A computer program
• Audio data
• A graphic or video image
• A spreadsheet
• A document from a word processor
• A compressed file

FTP service compress files to reduce the total amount of disk space the files require. Before transferring a file user must tell FTP that the file contains ASCII text or nontext file. FTP assumes to perform ASCII transfers unless the user enters the binary command.

There are many FTP programs that you can download from the Internet. Windows has its own command line based FTP program. To execute it, select Run from Windows taskbar and type FTP and press enter. By typing open command you can connect to any ftp server. To connect to FTP server you must have a login name and the password. Most of the FTP servers allow anonymous connections. In this case username is anonymous and password is your e-mail address.

Another important FTP program, which is available as a shareware, is WSFTP. Using this window based program it is easier to maintain your web site.

Telnet

TELNET stands for TErminal NETwork. Telnet is both a TCP/IP application and a protocol for connecting a local computer to a remote computer. Telnet is a program that allows an Internet host computer to become a terminal of another host on the Internet. Telnet is the Internet remote login service. Telnet protocol specifies exactly how a remote login interacts. The standard specifies how to client contacts the server and how the server encodes output for transmission to the client. To use the Telnet service, one must invoke the local application program and specify a remote machine. The local program becomes a client, which forms a connection to a server on the remote computer. The client passes keystrokes and mouse movements to the remote machine and displays output from the remote machine on the user’s display screen. Telnet provides direct access to various services on Internet. Some of these services are available on your host, but Telnet is especially useful when these services are not available on your host. For example, if you want to use graphical interfaces designed by other users then Telnet, allows you to access their hosts and use their new interfaces. Similarly, whenever someone creates a useful service on his host, Telnet allows you to access this valuable information resource. This tools Is especially useful for accessing public services such as library card catalogues, the kind of databases available on the machine etc. You can also log into any catalogue service of a library and use it.
The working of TELNET,

• The commands and characters are sent to the operating system on the common server computer.
• The local operating system sends these commands and characters to a TELNET client program, which is located on the same local computer.
• The TELNET client transforms the characters entered by the user to an agreed format known as Network Virtual Terminal (NVT) characters and sends them to the TCP/IP protocol stack of the server computer. NVT is the common device between the client and server.
• The commands and text are first broken into TCP and then IP packets and are sent across the physical medium from the local client computer to the server.
• At the server computer’s end, the TCP/IP software collects all the IP packets, verifies their correctness and reconstructs the original command and handover the commands or text to that computer operating system.
• The operating system of the server computer hands over these commands or text to the TELNET server program, which is executing on that remote computer.
• The TELNET server program on the remote server computer then transforms the commands or text from the NVT format to the format understood by the remote computer.
• The TELNET cannot directly handover the commands or text to the operating system so TELNET hands over the commands/text to the Psuedo-terminal driver.

The Pseudo-terminal driver program then hands over the commands or text to the operating system of the remote computer, which then invokes the application program on the remote server.
 
There are many databases available on the Internet. You can explore these databases using Telnet. There are going to be many Internet services yet to be created. Every year and better means of accessing the treasures of the Internet is appearing in which Telnet is the key for accessing.

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WHAT IS INTERNET INFRASTRUCTURE

I believe, now you know how packets travel from one computer to another over the Internet. But what's in-between? What actually makes up the Internet infrastructure or backbone?

 The Internet backbone is made up of many large networks, which interconnect with each other. These large networks are known as Network Service Providers or NSPs. These networks peer with each other to exchange packet traffic. Each NSP is required to connect to Network Access Points or NAPs. At the NAPs, packet traffic may jump from one NSP's backbone to another NSP's backbone.

Internet Backbone

NSPs also interconnect at Metropolitan Area Exchanges or MAEs. MAEs serve the same purpose as the NAPs but are privately owned. NAPs were the original Internet interconnects points. Both NAPs and MAEs are referred to as Internet Exchange Points or IXs. NSPs also sell bandwidth to smaller networks, such as ISPs and smaller bandwidth providers. Below is a picture showing this hierarchical infrastructure.

This is not a true representation of an actual piece of the Internet. The above figure is only meant to demonstrate how the NSPs could interconnect with each other and smaller ISPs. None of the physical network components are shown in this figure. This is because a single NSP's backbone infrastructure is a complex drawing by itself. Most NSPs publish maps of their network infrastructure on their web sites and can be found easily. To draw an actual map of the Internet would be nearly impossible due to it's size, complexity, and ever changing structure.

The Internet Routing Hierarchy

 So how do packets find their way across the Internet? Does every computer connected to the Internet know where the other computers are? Do packets simply get 'broadcast' to every computer on the Internet? The answer to both the preceding questions is 'no'. No computer knows where any of the other computers are, and packets do not get sent to every computer. The information used to get packets to their destinations is contained in routing tables kept by each router connected to the Internet. 

 

Routers Connecting in Network

Routers are packet switches. A router is usually connected between networks to route packets between them. Each router knows about it's sub-networks and which IP addresses they use. The router usually doesn't know what IP addresses are 'above' it. Examine the figure below. The black boxes connecting the backbones are routers. The larger NSP backbones at the top are connected at a NAP. Under them are several sub-networks, and under them, more sub-networks. At the bottom are two local area networks with computers attached.

When a packet arrives at a router, the router examines the IP address put there by the IP protocol layer on the originating computer. The router checks it's routing table. If the network containing the IP address is found, the packet is sent to that network. If the network containing the IP address is not found, then the router sends the packet on a default route, usually up the backbone hierarchy to the next router. Hopefully the next router will know where to send the packet. If it does not, again the packet is routed upwards until it reaches a NSP backbone. The routers connected to the NSP backbones hold the largest routing tables and here the packet will be routed to the correct backbone, where it will begin its journey 'downward' through smaller and smaller networks until it finds it's destination.

Domain Names and Address Resolution

But what if you don't know the IP address of the computer you want to connect to? What if you need to access a web server referred to as www.anothercomputer.com? How does your web browser know where on the Internet this computer lives? The answer to all these questions is the Domain Name Service or DNS. The DNS is a distributed database, which keeps track of computer's names and their corresponding IP addresses on the Internet.

Many computers connected to the Internet host part of the DNS database and the software that allows others to access it. These computers are known as DNS servers. No DNS server contains the entire database; they only contain a subset of it. If a DNS server does not contain the domain name requested by another computer, the DNS server re-directs the requesting computer to another DNS server.

DNS Hierarchy

The Domain Name Service is structured as a hierarchy similar to the IP routing hierarchy. The computer requesting a name resolution will be re-directed 'up' the hierarchy until a DNS server is found that can resolve the domain name in the request. Figure 6 illustrates a portion of the hierarchy. At the top of the tree are the domain roots. Some of the older, more common domains are seen near the top. What is not shown are the multitude of DNS servers around the world which form the rest of the hierarchy. When an Internet connection is setup (e.g. for a LAN or Dial-Up Networking in Windows), one primary and one or more secondary DNS servers are usually specified as part of the installation. This way, any Internet applications that need domain name resolution will be able to function correctly. For example, when you enter a web address into your web browser, the browser first connects to your primary DNS server. After obtaining the IP address for the domain name you entered, the browser then connects to the target computer and requests the web page you wanted.

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WHAT ARE INTRANET AND EXTRANET

Intranets are basically 'small' Internets. They use the same network facilities that the Internet does, but access is restricted to a limited sphere. For instance, a company can set up an intranet within the confines of the company itself. Access can be tightly controlled and limited to authorized employees and staff. There is no connection to the Internet or any other outside network. Functions like web sites, file uploads and downloads, and e-mail is available on intranets within the confines of the network. Since frivolous sites are no longer available, there is no employee time lost due to accessing them. There is, of course, the limitation of the networking area. The very benefit of restricting access to all of the facilities available on the Internet also restricts communication to other desirable locations. This is where the extranet steps in.


An Extranet is network that connects a number of intranets into a truly mini-Internet Access is extended to all the intranets connected through the extranet, but, again, not to the Internet.  Extranets requires a constant Internet connection and a hypertext transfer protocol (http) server. Extranets can also be used to connect an intranet to the Internet so that remote offsite access can be made into a company’s intranet by an authorized individual. This can facilitate through an extranet.

Basically, it uses passwords and smart cards to log in to a gateway server that checks the requester’s security credentials. If the user checks out, he or she is allowed access into the company’s intranet structure.

A number of URL address are set aside for intranet and extranet use. Essentially because intranets are self-contained networks, the same set of addresses can be used by all intranets without conflict. Extranet addresses are designed to recognize the intranets they connect and correctly preface each intranet address with an identifier. This allows two interconnected intranets to retain the same set of address values and keep them from being mistaken. One class A address, ranging from 10.0.0.0 to 10.255.255.255 is reserved for intranet usage. Again, since an intranet is a self-contained system, it only needs one class A network to designate the main network. Sub networks use reserved class B and class C addresses. There are 16 class B addresses, from 172.16.0.0 ti 172.31.255.255 and 256 class C addresses, which range from 192.168.0.0 to 192.168.255.255.

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HOW DOES THE INTERNET WORK?

As discussed in the previous articles, every computer connected to the Internet has a unique address. Let's say your IP address is 1.2.3.4 and you want to send a message to the computer with the IP address 5.6.7.8. The message you want to send is "Hello computer 5.6.7.8!” Let's say you've dialed into your ISP from home and the message must be transmitted over the phone line. Therefore the message must be translated from alphabetic text into electronic signals, transmitted over the Internet, and then translated back into alphabetic text.


How is this accomplished? Through the use of a protocol stack. Every computer needs one to communicate on the Internet and it is usually built into the computer's operating system (i.e. Windows, UNIX, etc.). The protocol stack used on the Internet is referred to as the TCP/IP protocol stack

If we were to follow the path that the message "Hello computer 5.6.7.8!" took from our computer to the computer with IP address 5.6.7.8, it would happen something like this:

• The message would start at the top of the protocol stack on your computer and work it's way downward.
• If the message to be sent is long, each stack layer that the message passes through may break the message up into smaller chunks of data. This is because data sent over the Internet (and most computer networks) are sent in manageable chunks. On the Internet, these chunks of data are known as packets.
• The packets would go through the Application Layer and continue to the TCP layer. Each packet is assigned a port number, which is used by program on the destination computer to receive the message because it will be listening on a specific port.
• After going through the TCP layer, the packets proceed to the IP layer. This is where each packet receives its destination address, 5.6.7.8.
• Now that our message packets have a port number and an IP address, they are ready to be sent over the Internet. The hardware layer takes care of turning our packets containing the alphabetic text of our message into electronic signals and transmitting them over the phone line.
• On the other end of the phone line your ISP has a direct connection to the Internet. The ISPs router examines the destination address in each packet and determines where to send it. Often, the packet's next stop is another router. More on routers and Internet infrastructure later.
• Eventually, the packets reach computer 5.6.7.8. Here, the packets start at the bottom of the destination computer's TCP/IP stack and work upwards.
• As the packets go upwards through the stack, all routing data that the sending computer's stack added (such as IP address and port number) is stripped from the packets.
• When the data reaches the top of the stack, the packets have been re-assembled into their original form, "Hello computer 5.6.7.8!"

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WHAT IS INTERNET ADDRESS?

Addresses are essential for virtually everything we do on the Internet. The IP in TCP/IP is a mechanism for providing addresses for computers on the Internet. Internet addresses have two forms:

• Person understandable which is expressed as words.
• Machine understandable which is expressed as numbers.

The following can be a typical person understandable address on Internet:

VWW @ ****.com

VWW is an username which in general is the name of the Internet account. This name is same as the one, which you may use when logging into the computer on which you have your Internet account. Logging in is the process of gaining access to your account on a computer, which is shared by several users. Your Internet account is created on it.

@ Connect “who” with where:

“ **** ” is a sub domain (could be several in each could be separated by (dot). Last one is referred to a domain).

.com is a domain top or what part in – It refers to “where” part which is a country code.

Structure of Internet Servers Address

The structure of an Internet server’s address keyed into a client’s software is as follows:

http://www.microsoft.com

Where,

• http is the communication protocol to be used
• www is the notation for World Wide Web
• .Microsoft is the registered domain Name associated with the IP address of an Internet Server.
• .com the server provides commercial services to clients who connect to it.

To help to speed up access, its IP address can be directly represented in form of numbers. 107.56.23.1 instead of the domain name, microsoft.com. In this case no name resolution needs to take place. An Internet address is a unique 32-bit number that is typically expressed as four 8-bit octets, with each octet separated by a period. Each of the octets can take on any number from 0 through 255.

Hosts, Domains and Sub domains

Hosts are in general, individual machines at a particular location. Resources of a host machine are normally shared and can be utilized by any user on Internet. Hosts and local networks are grouped together into domains, which then are grouped together into one larger domain. For an analogy a host computer is considered as an apartment building in a housing complex and your account is just an apartment in it.

Domain may be an apartment complex, a town or even a country. Sub-domains may correspond to organizations such as *****. Computers termed as name servers contain database of Internets host addresses. They translate word addresses or persons understandable into numeric equivalents.

Let us see another example of Internet address,

http://www.*******.ac.in

What does it all mean? Actually to the ISP server, very little. The server wants to see something quite different. It wants to see a 32-bit number as an Internet address. Something like this equivalent decimal grouping:

198.168.45.249

The Internet addresses, known as universal resources locators (URL), are translated from one form to the other using an address resolution protocol. The first address is in the form we are most used to and that user use to access an Internet site. In this example, the address is for a website, identified by the hypertext transfer protocol (http), which controls access to web pages. Following http is a delimiter sequence,://, and identification for the World Wide Web (www).

The domain name, *******.ac follows www and identifies the general site for the web. (dot) edu is one example of a domain top, which is a broad classification of web users. Other common domain tops are:

.com for commerce and businesses .gov for government agencies .mil for military sites .org for all kinds of organizations.

Lastly, in this example is a country code, again preceded by a dot. Here we are using in for the India, which is the default country.

Addresses may be followed by sub domains separated by dots or slashes (/) as needed. These addresses are translated into a 32-bit (4 decimal numeric groups) address shown as for http:// www.*******.ac.in we will further discuss this topic in the next section.

What does it all mean? Actually to the ISP server, very little. The server wants to see something quite different. It wants to see a 32-bit number as an Internet address. Something like this equivalent decimal grouping:

198.168.45.249

The Internet addresses, known as universal resources locators (URL), are translated from one form to the other using an address resolution protocol. The first address is in the form we are most used to and that user use to access an Internet site. In this example, the address is for a website, identified by the hypertext transfer protocol (http), which controls access to web pages. Following http is a delimiter sequence,://, and identification for the World Wide Web (www).

The domain name, ****.ac follows www and identifies the general site for the web.(dot) com is one example of a domain top, which is a broad classification of web users. Other common domain tops are:

.com for commerce and businesses .gov for government agencies .mil for military sites .org for all kinds of organizations.

Lastly, in this example is a country code, again preceded by a dot. Here we are using us for the U.S, which is the default country.

Addresses may be followed by sub domains separated by dots or slashes (/) as needed. These addresses are translated into a 32-bit (4 decimal numeric groups) address shown as for http:// www.google.in we will further discuss this topic in the next ARTICLES.

Address Space

Internet addresses are divided into five different types of classes. The classes were designated A through E. class A address space allows a small number of networks but a large number of machines, while class C allows for a large number of networks but a relatively small number of machines per network. The following figure lists five address classes used in classical network addresses. Regardless of the class of address space assigned, organizations assigned a particular class of address will not utilize the entire address space provided. This is especially in the case of class A and Class B addresses allocation schemes.

Ports

A port is an additional 16-bit number that uniquely identifies the particular service on any given machine on the Internet. Port numbers are 16 bit wide, therefore each computer on the Internet has a maximum number of 216 or 65,536 ports. The particular application is identified by its unique port number in the same way that a specific television station has a unique channel number.

Port numbers are divided into three ranges:

Well-known ports are those from 0 through 1,023.

Registered ports are those from 1,024 through 49,151.

Dynamic and private ports are those from 49,152 through 65,535.

Well-known ports, those ranging from 0 through 1,023 are where most common services on the Internet are residing. These ports are controlled and assigned by the Internet Assigned Number Authority (IANA) and on most systems can be used only by system (root) processes or by programs executed by privileged users.

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WHAT ARE INTERNET PROTOCOLS?

A communication protocol is an agreement that specifies a common language two computers use to exchange messages. For example, a protocol specifies the exact format and meaning of each message that a computer can send. It also specifies the conditions under which a computer should send a given message and how a computer should respond when a message arrives. Different types of protocols are used in Internet such as IP and TCP. 
 
A computer connected to the Internet needs both TCP and IP software. IP provides a way of transferring a packet from its source to destination and TCP handles the lost datagram’s and delivery of datagram’s. Together, they provide a reliable way to send data across the Internet. We discuss about these protocols in brief in the following section.

Internet Protocol (IP)

The Internet protocol specifies the rules that define the details of how computers communicate. It specifies exactly how a packet must be formed and how a router must forward each packet on toward its destination. Internet Protocol (IP) is the protocol by which data is sent from one computer to another on the Internet. Each computer (known as a host) on the Internet has at least one IP address that uniquely identifies it from all other computers on the Internet. When sending or receiving data, the message gets divided into little chunks called packet. Each of these packets contains both the senders Internet address and the receiver’s address. The packet that follows the IP specification is called an IP datagram. The Internet sends an IP datagram across a single network by placing it inside a network packet. For network the entire IP datagram is data. When the network packet arrives at the next computer, the computer opens the packet and extracts the datagram. The receiver examines the destination address on the datagram to determine how to process it. When a router, determines that the datagram must be sent across another network, the router creates a new network packet, encloses the datagram inside the packet and sends the packet across another network toward its destination. When a packet carrying a datagram arrives at its final destination, local software on the machine opens the packet and processes the datagram. Because a message is divided into a number of packets a different route can send each packet across the Internet. Packets can arrive in a different order than the order they were sent in. The Internet Protocol just delivers them. It's up to another protocol, the Transmission Control Protocol to put them back in the right order. IP is a connectionless protocol, which means that there is no established connection between the end points that are communicating. Each packet that travels through the Internet is treated as an independent unit of data without any relation to any other unit of data. In the Open Systems Interconnection (OSI) communication model, IP is in layer 3, the Networking Layer.

Transmission Control Protocol (TCP)

TCP makes the Internet reliable. TCP solves many problems that can occur in a packet switching system. TCP provide the following facilities:

• TCP eliminates duplicate data.
• TCP ensures that the data is reassembled in exactly the order it was sent.
• TCP resends data when a datagram is lost.
• TCP uses acknowledgements and timeouts to handle problem of loss.

The main features of TCP are:

Reliability: TCP ensures that any data sent by a sender arrives at the destination as it was sent. There cannot be any data loss or change in the order of the data. 

Reliability at the TCP has four important aspects:

• Error Control
• Loss control
• Sequence control
• Duplication control 

Connection-oriented: TCP is connection-oriented. Connection-oriented means a connection is established between the source and destination machines before any data is sent i.e. a connection is established and maintained until such time as the message or messages to be exchanged by the application programs at each end have been exchanged. The connections provided by TCP are called Virtual Connections. It means that there is no physical direct connection between the computers.

TCP is used along with the Internet Protocol to send data in the form of message units between computers over the Internet. While IP takes care of handling the actual delivery of the data, TCP takes care of keeping track of the individual units of data (called Packet) that a message is divided into for efficient routing through the Internet. TCP provides for a reliable, connection-oriented data transmission channel between two programs. Reliable means that data sent is guaranteed to reach its destination in the order sent or an error will be returned to the sender.

For example, when an HTML file is sent to someone from a Web server, the Transmission Control Protocol (TCP) program layer in that server divides the file into one or more packets, numbers the packets, and then forwards them individually. Although each packet has the same destination IP address, it may get routed differently through the network. At the other end (the client program in our computer), TCP reassembles the individual packets and waits until they have arrived to forward them as a single file.

TCP is responsible for ensuring that a message is divided into the packets that IP manages and for reassembling the packets back into the complete message at the other end. In the Open Systems Interconnection (OSI) communication model, TCP is in layer 4, the Transport Layer.

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