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WORKING OF WEB SERVER

DEFINATION OF WEB SERVER :
A computer that stores web document and makes them available to the rest of the world. A server may be dedicated, meaning its sole purpose is to be a web server, or non – dedicated, meaning it can be use for basic computing in addition to acting as a server
Introduction of web server:

Have you ever wondered about the mechanisms that delivered this page to you? Chances are you are sitting at a computer right now, viewing this page in a browser. So, when you clicked on the link for this page, or typed in its URL (uniform resource locator), what happened behind the scenes to bring this page onto your screen?
If you've ever been curious about the process, or have ever wanted to know some of the specific mechanisms that allow you to surf the Internet, then read on. In this article, you will learn how Web servers bring pages into your home, school or office. Let's get started!

The BASIC PROCESS:

Let's say that you are sitting at your computer, surfing the Web, and you get a call from a friend who says, "I just read a great article! Type in this URL and check it out. It's at http://computer.howstuffworks.com/web-server.htm." So you type that URL into your browser and press return. And magically, no matter where in the world that URL lives, the page pops up on your screen.

At the most basic level possible, the following diagram shows the steps that brought that page to your screen:


Your browser formed a connection to a Web server, requested a page and received it.
On the next page, we'll dig a bit deeper.

Background Information:
Before we jump into the core of HTTP, lets sit back and look at what a web server is.
Web Server is not just a "big" machine sitting somewhere in the server room with big processing power and memory.
Whole Web Server = Computer Hardware + Operating System + Web Server Software + Info Content
As a software engineer, we will concentrate on all the software, thus, we could alter the definition as:
Web Server = Operating System + Web Server Software + Info Content




The Three Components:
Operating System distinguishes which platform (Windows, UNIX, AS/400, Mainframe) the web server is running on.
The Web Server Software is a continuously looping server waiting for requests by web client (browsers or other) for documents over the network. It will parse the request, classify the request and take the corresponding actions. The actions might be executing a script, returning a document, accessing a remote database, etc.
As you could see, the web server has to understand the request from the clients. We sometimes say that they speak the same language or same protocol. And the protocol used by web server is Hypertext Transfer Protocol (HTTP). As we mentioned in the background information session, Web (with HTTP) is running on top of the TCP/IP internet network protocol. As a result, some of the same terminologies are used in a web server setting as well. The most important one should be TCP port.
A port is analogous to a telephone extension. When a client program connects to the server on the network, it requests the server program's port. This port indicates exactly which server program the originating client wants to connect to. Data then is written to the outgoing port (on the client's computer) arrives at the server program's incoming port, where it is read. Well, you probably will not see people specifically state which port to connect to when, say, going to http://www.openloop.com/. The reason is because Web Server has a default port, if the client does not specific which port to connect to, it will default to port 80. So, the url http://www.openloop.com/ is the same as http://www.openloop.com/. Another word for default port is well known port. Thus, the well known port of web server is 80.
Info Content is the information being served by a web server. It could be data info from a local disk or data from database or remote location transparent to the clients.




Traditional Web Server:
Traditionally, web server understand how to receive and reply to HTTP requests, serve up local file information and execute scripts as necessary. A traditional web server does not understand the content of the documents. In other words, all documents are served, as they are stream of data from the server to the client. In particular, web server does not know about hyper links within the documents, the links are just part of the document from the point of view of a web server. When user clicks on a hyperlink, the browser will request another document from the hyperlink. Thus, the browser "manages" the hyperlink instead of the web server.
Also, the web server does not know about inline images, movie or voice pieces. All these MIME pieces are requested separately from the browser. These requests are just like any other request as far as web server is concerned.
(In a way, we could say that traditional web server does not have the ability to understand what the content of the documents are. We will in a different tutorial with XML to see how XML can help transforming a traditional web server to an truly interactive one and serve up meaningful contents to different clients. In this tutorial, we will concentrate on the basis. Yes, you could not run without knowing how to walk.)

Behind the Scenes:

If you want to get into a bit more detail on the process of getting a Web page onto your computer screen, here are the basic steps that occurred behind the scenes:

· The browser broke the URL into three parts:
1. The protocol ("http")
2. The server name ("www.howstuffworks.com")
3. The file name ("web-server.htm")

· The browser communicated with a name server to translate the server name "www.howstuffworks.com" into an IP Address, which it uses to connect to the server machine.

· The browser then formed a connection to the server at that IP address on port 80. (We'll discuss ports later in this article.)
· Following the HTTP protocol, the browser sent a GET request to the server, asking for the file "http://computer.howstuffworks.com/web-server.htm." (Note that cookies may be sent from browser to server with the GET request -- see How Internet Cookies Work for details.)

· The server then sent the HTML text for the Web page to the browser. (Cookies may also be sent from server to browser in the header for the page.)

· The browser read the HTML tags and formatted the page onto your screen.

If you've never explored this process before, that's a lot of new vocabulary. To understand this whole process in detail, you need to learn about IP addresses, ports, protocols... The following sections will lead you through a complete explanation.

The Internet:

So what is "the Internet"? The Internet is a gigantic collection of millions of computers, all linked together on a computer network. The network allows all of the computers to communicate with one another. A home computer may be linked to the Internet using a phone-line modem, DSL or cable modem that talks to an Internet service provider (ISP). A computer in a business or university will usually have a network interface card (NIC) that directly connects it to a local area network (LAN) inside the business. The business can then connect its LAN to an ISP using a high-speed phone line like a T1 line. A T1 line can handle approximately 1.5 million bits per second, while a normal phone line using a modem can typically handle 30,000 to 50,000 bits per second.


ISPs then connect to larger ISPs, and the largest ISPs maintain fiber-optic "backbones" for an entire nation or region. Backbones around the world are connected through fiber-optic lines, undersea cables or satellite links (see An Atlas of Cyberspaces for some interesting backbone maps). In this way, every computer on the Internet is connected to every other computer on the Internet.

World Wide Web (The Client and Server Pair):
The World Wide Web, often called "WWW" or simply "the Web" is the hottest thing since the invention of TV. It brings millions of people all over the world for communication on the Internet. Users simply use the web browser and "point-and-click" in order to display a wide variety of multimedia information. The web browser can be viewed as a client which hide most of the complexity of the Internet and help users to access the oceans of information on the Internet. On the other side of the story, we have the Web Server which serves information to thousands of web clients.
Standing at the Web server, you do not see the oceans of information but millions of info requests from clients all over the world from different platforms. This tutorial focuses on Web servers instead of Web browsers. We will examine in details how the web server functions with investigation on server architecture, CGI-script, Java applet, interaction with file systems, database as well as performance and security issues.

Clients and Servers:

In general, all of the machines on the Internet can be categorized as two types: servers and clients. Those machines that provide services (like Web servers or FTP servers) to other machines are servers. And the machines that are used to connect to those services are clients. When you connect to Yahoo! at www.yahoo.com to read a page, Yahoo! is providing a machine (probably a cluster of very large machines), for use on the Internet, to service your request. Yahoo! is providing a server. Your machine, on the other hand, is probably providing no services to anyone else on the Internet. Therefore, it is a user machine, also known as a client. It is possible and common for a machine to be both a server and a client, but for our purposes here you can think of most machines as one or the other.

A server machine may provide one or more services on the Internet. For example, a server machine might have software running on it that allows it to act as a Web server, an e-mail server and an FTP server. Clients that come to a server machine do so with a specific intent, so clients direct their requests to a specific software server running on the overall server machine. For example, if you are running a Web browser on your machine, it will most likely want to talk to the Web server on the server machine. Your Telnet application will want to talk to the Telnet server, your e-mail application will talk to the e-mail server, and so on...

IP Addresses:

To keep all of these machines straight, each machine on the Internet is assigned a unique address called an IP address. IP stands for Internet protocol, and these addresses are 32-bit numbers, normally expressed as four "octets" in a "dotted decimal number." A typical IP address looks like this:
216.27.61.137
The four numbers in an IP address are called octets because they can have values between 0 and 255, which is 28 possibilities per octet.
Every machine on the Internet has a unique IP address. A server has a static IP address that does not change very often. A home machine that is dialing up through a modem often has an IP address that is assigned by the ISP when the machine dials in. That IP address is unique for that session -- it may be different the next time the machine dials in. This way, an ISP only needs one IP address for each modem it supports, rather than for each customer.

If you are working on a Windows machine, you can view a lot of the Internet information for your machine, including your current IP address and hostname, with the command WINIPCFG.EXE (IPCONFIG.EXE for Windows 2000/XP). On a UNIX machine, type nslookup at the command prompt, along with a machine name, like www.howstuffworks.com -- e.g. "nslookup www.howstuffworks.com" -- to display the IP address of the machine, and you can use the command hostname to learn the name of your machine. (For more information on IP addresses, see IANA.)

As far as the Internet's machines are concerned, an IP address is all you need to talk to a server. For example, in your browser, you can type the URL http://209.116.69.66 and arrive at the machine that contains the Web server for HowStuffWorks. On some servers, the IP address alone is not sufficient, but on most large servers it is -- keep reading for details.

Domain Names:

Because most people have trouble remembering the strings of numbers that make up IP addresses, and because IP addresses sometimes need to change, all servers on the Internet also have human-readable names, called domain names. For example, www.howstuffworks.com is a permanent, human-readable name. It is easier for most of us to remember www.howstuffworks.com than it is to remember 209.116.69.66.

The name www.howstuffworks.com actually has three parts:
4. The host name ("www")
5. The domain name ("howstuffworks")
6. The top-level domain name ("com")

Domain names within the ".com" domain are managed by the registrar called VeriSign. VeriSign also manages ".net" domain names. Other registrars (like RegistryPro, NeuLevel and Public Interest Registry) manage the other domains (like .pro, .biz and .org). VeriSign creates the top-level domain names and guarantees that all names within a top-level domain are unique. VeriSign also maintains contact information for each site and runs the "whois" database. The host name is created by the company hosting the domain. "www" is a very common host name, but many places now either omit it or replace it with a different host name that indicates a specific area of the site. For example, in encarta.msn.com, the domain name for Microsoft's Encarta encyclopedia, "encarta" is designated as the host name instead of "www."

Domain Name Servers:

A set of servers called domain name servers (DNS) maps the human-readable names to the IP addresses. These servers are simple databases that map names to IP addresses, and they are distributed all over the Internet. Most individual companies, ISPs and universities maintain small name servers to map host names to IP addresses. There are also central name servers that use data supplied by VeriSign to map domain names to IP addresses.

If you type the URL "http://computer.howstuffworks.com/web-server.htm" into your browser, your browser extracts the name www.howstuffworks.com, " passes it to a domain name server, and the domain name server returns the correct IP address for www.howstuffworks.com. A number of name servers may be involved to get the right IP address. For example, in the case of www.howstuffworks.com, the name server for the "com" top-level domain will know the IP address for the name server that knows host names, and a separate query to that name server, operated by the HowStuffWorks ISP, may deliver the actual IP address for the HowStuffWorks server machine.

On a UNIX machine, you can access the same service using the nslookup command. Simply type a name like "www.howstuffworks.com" into the command line, and the command will query the name servers and deliver the corresponding IP address to you.

So here it is: The Internet is made up of millions of machines, each with a unique IP address. Many of these machines are server machines, meaning that they provide services to other machines on the Internet. You have heard of many of these servers: e-mail servers, Web servers, FTP servers, Gopher servers and Telnet servers, to name a few. All of these are provided by server machines.



Ports:

Any server machine makes its services available to the Internet using numbered ports, one for each service that is available on the server. For example, if a server machine is running a Web server and an FTP server, the Web server would typically be available on port 80, and the FTP server would be available on port 21. Clients connect to a service at a specific IP address and on a specific port.

Each of the most well-known services is available at a well-known port number. Here are some common port numbers:

· echo 7
· daytime 13
· qotd 17 (Quote of the Day)
· ftp 21
· telnet 23
· smtp 25 (Simple Mail Transfer, meaning e-mail)
· time 37
· nameserver 53
· nicname 43 (Who Is)
· gopher 70
· finger 79
· WWW 80

If the server machine accepts connections on a port from the outside world, and if a firewall is not protecting the port, you can connect to the port from anywhere on the Internet and use the service. Note that there is nothing that forces, for example, a Web server to be on port 80. If you were to set up your own machine and load Web server software on it, you could put the Web server on port 918, or any other unused port, if you wanted to. Then, if your machine were known as xxx.yyy.com, someone on the Internet could connect to your server with the URL http://xxx.yyy.com:918. The ":918" explicitly specifies the port number, and would have to be included for someone to reach your server. When no port is specified, the browser simply assumes that the server is using the well-known port 80.

Protocols:

Once a client has connected to a service on a particular port, it accesses the service using a specific protocol. The protocol is the pre-defined way that someone who wants to use a service talks with that service. The "someone" could be a person, but more often it is a computer program like a Web browser. Protocols are often text, and simply describe how the client and server will have their conversation.

Perhaps the simplest protocol is the daytime protocol. If you connect to port 13 on a machine that supports a daytime server, the server will send you its impression of the current date and time and then close the connection. The protocol is, "If you connect to me, I will send you the date and time and then disconnect." Most UNIX machines support this server. If you would like to try it out, you can connect to one with the Telnet application. In UNIX, the session would look like this:

%telnet web67.ntx.net 13
Trying 216.27.61.137...
Connected to web67.ntx.net.
Escape character is '^]'.
Sun Oct 25 08:34:06 1998
Connection closed by foreign host.

On a Windows machine, you can access this server by typing "telnet web67.ntx.net 13" at the MSDOS prompt.

In this example, web67.ntx.net is the server's UNIX machine, and 13 is the port number for the daytime service. The Telnet application connects to port 13 (telnet naturally connects to port 23, but you can direct it to connect to any port), then the server sends the date and time and disconnects. Most versions of Telnet allow you to specify a port number, so you can try this using whatever version of Telnet you have available on your machine.

Most protocols are more involved than daytime and are specified in Request for Comment (RFC) documents that are publicly available (see http://sunsite.auc.dk/RFC/ for a nice archive of all RFCs). Every Web server on the Internet conforms to the HTTP protocol, summarized nicely in The Original HTTP as defined in 1991. The most basic form of the protocol understood by an HTTP server involves just one command: GET. If you connect to a server that understands the HTTP protocol and tell it to "GET filename," the server will respond by sending you the contents of the named file and then disconnecting. Here's a typical session:

%telnet www.howstuffworks.com 80
Trying 216.27.61.137...
Connected to howstuffworks.com.
Escape character is '^]'.
GET http://computer.howstuffworks.com/



...


Connection closed by foreign host.

In the original HTTP protocol, all you would have sent was the actual filename, such as "/" or "/web-server.htm." The protocol was later modified to handle the sending of the complete URL. This has allowed companies that host virtual domains, where many domains live on a single machine, to use one IP address for all of the domains they host. It turns out that hundreds of domains are hosted on 209.116.69.66 -- the HowStuffWorks IP address.

Security:

You can see from this description that a Web server can be a pretty simple piece of software. It takes the file name sent in with the GET command, retrieves that file and sends it down the wire to the browser. Even if you take into account all of the code to handle the ports and port connections, you could easily create a C program that implements a simple Web server in less than 500 lines of code. Obviously, a full-blown enterprise-level Web server is more involved, but the basics are very simple.

Most servers add some level of security to the serving process. For example, if you have ever gone to a Web page and had the browser pop up a dialog box asking for your name and password, you have encountered a password-protected page. The server lets the owner of the page maintain a list of names and passwords for those people who are allowed to access the page; the server lets only those people who know the proper password see the page. More advanced servers add further security to allow an encrypted connection between server and browser, so that sensitive information like credit card numbers can be sent on the Internet.

That's really all there is to a Web server that delivers standard, static pages. Static pages are those that do not change unless the creator edits the page.

Data served on the Web:
The Web is decentralized. It uses the Internet to connect the client (the customer) and the server (the provider). The Internet is composed of a wide variety of computers and networks that interoperate so data can be exchanged among them. The Web, which can be viewed as a high level protocol, was built on top of the Internet.
The Web is made possible by the following key technologies:
· The address system, Universal Resource Locators (URLs), allows retrival of different kind of information on the Internet
· The HyperText Transfer Protocol (HTTP) defines the language (protocol) of how web clients and servers should exchange multimedia information
· The HperText Markup Language (HTML) allows users to author multimedia hypertext documents
· TCP/IP serves as the "low" level protocol on the Internet allowing HTTP and other application level protocol running on top of it

Please note that a Web server has very little role in how the information it delivers is displayed or used. (Except with the use of XML + application). Normally, the web server delivers information and the browser has to use it properly.
The web server can also execute programs dynamically to generate information. As we called it server-side processing to produce interactive web pages. (Compared that with JavaScript which create client-side processing interactive web pages). The web server makes it possible to create web applications that use electronic fill-in forms. It also permits the web server to act as a gateway to access resources that are not web server such as local file systems, database, mainframe data, etc. The ability to run scripts and gateways makes the web extremely flexible with a strong array of services. We will look at how basic text-based pages served as well as how script are run.

Existing Web Servers Software
· Java Web Server
· Apache Web Server
· Microsoft Personal Web Server
· Microsoft Frontpage Web Server
· Microsoft Internet Information Server



INTRODUCTION:

Java Web Server 1.0, an Instance of JavaServer Architecture
While developers were wondering about the future of Sun Microsystem's Web server before the beta release on March 4 1997, Sun has been quite busy establishing a framework for implementing Java solutions on the server side. The Java Web Server 1.0, which shipped June 5 1997, takes full advantage of the JavaServer architecture (see below) implemented in Java Web Server 1.0 and the newly shipped JavaServer Toolkit. (The Toolkit is a source code product that is not downloadable over the Internet.)

Java Servlet API;

One of the more welcome aspects of this architecture is the Java Servlet API, available in the Java Servlet Development Kit. While other Web servers have been written in Java, and many have even implemented the Java Servlet API, Java Web Server 1.0 is the first commercial example of a full-fledged Web server written in Java with "native" support for Java Servlets. The beauty of Java Servlets is that they provide a standard approach to extending server functionality without the limitations of CGI-based or server-specific approaches.

Thanks to add-on modules written by the JavaServer team for running Java Servlets with Netscape Enterprise, Microsoft IIS and Apache servers, Java Servlets written to the Java Servlet API can work with those servers as well. This levels the playing field, in a sense, for developers looking to extend server functionality in a uniform way without having to worry about the particular server software or platform being used.



Apache Web ServerApache has been the most popular web server on the Internet since April of 1996. The July 2003 Netcraft Web Server Survey found that 63% of the web sites on the Internet are using Apache, thus making it more widely used than all other web servers combined.



Standard Web Hosting Features Included In All Our PackagesYou can use the menu below to see more details about each web hosting feature included in our low cost web hosting packages:
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Performance of web server:
Measuring a Operational Web Server
- connections per second
- bytes per second
- round-trip time
- monitoring the system
Example: Controlled Experiments
Software
Conclusion
Performance of the Web: Browsers and Networks
Client side and Server side
The Network
- Latency
- Bandwidth
- Congestion
Network Protocols and the Web
- DNS
- TCP/IP and HTTP
Performance Analysis
- Overview
- Executing CGI Scripts and Other Programs
- Data Compression and Encryption
- Accessing Documents

Web security benefits from Windows Server 2003:
After years of downplaying the security offered by Windows Server products and Internet Information Server, I think Microsoft has finally made a solid and secure move in the right direction with Windows Server 2003. Win2K3, first and foremost, is an improved and security-tweaked foundational operating system that also includes a hardened version of Internet Information Server.
Internet Information Server 6.0 on Windows Server 2003 offers one key benefit that no previous Windows server product has offered -- namely that IIS is not installed by default. If you are not specifically planning to use IIS, this is a solid security design.
Obviously, if you are planning on hosting Web sites on Windows Server 2003, IIS 6.0 is your most logical option. The second most beneficial security change for the updated NOS is that IIS 6.0 no longer runs under the security context of the system. Rather, there is a new IIS service account that has limited administrative capabilities and only enough privileges, access and user rights to perform its duties as a Web server. In addition to this, IIS 6.0 is installed initially in a hardened "locked" mode. This initial mode will only serve static resources and not execute scripts of any kind.
If you are serious about using Windows as your platform for hosting Web sites, you owe it to yourself to seriously investigate Windows Server 2003 and Internet Information Server 6.0.

THE WORLD WEB:

The Information that people need is located in documents, or files, those are stored in computers. Almost all documents make reference to other documents that contain related or supporting information. Those documents in turn reference other documents. What if a document could not only reference other documents, but could also provide an easy way to view (link to) those other documents? Equally important, what if it didn’t matter where the documents were located? A document located on a computer in New York could link to a document on a computer in Mumbai as easily as it could link to one down the hall. The concept of a hyperlink was indeed powerful, permitting the creation of a web of related information, therefore the term World Wide Web.

The concept of a World Wide Web Was indeed intriguing, but actually implementing the idea was more involved. Two essential developments were required an agreed format for the documents on the Web, and agreed technique for transmitting the documents over the Internet. These technologies are Hypertext Markup Language (HTML) and Hypertext Transfer Protocol (HTTP).


INTERNET

Internet consists of all the computers connected to it and the connections between them. The Internet is not some separate “thing” to which people connect their computers. Rather, the Internet is what results when all these people connect their computers together. When you log on to your Internet Service Provider (ISP), your computer becomes part of the Internet.
The only thing that might be considered to be the “Center” of the Internet is the specialized hardware used to transmit information from one location to another. The Internet, ranging from simple telephone lines to high-speed fiber-optic cables and satellite links, uses all sorts of communication links. If the communications links are the highways of the Internet, its traffic cops are the routers, specialized computers that direct traffic, settings that each and every packet of information is sent to the proper destination.

q A mechanism for connecting or bridging different network so that two communities can mutually interconnect is called “Internet”.
q The specifications of the Internet technology are publicly available, allowing
Anyone to develop the software needed to communicate over the Internet.


CONNECTING TO INTERNET:

The majority of the people connect to the Internet have either a direct connection or a modem connection. You are most likely to have a direct connection if you are using a computer at the job, school, or library. With a direct connection, your computer is connected to a Local Area Network (LAN) by means of a network adapter card, such as Ethernet or Token Ring. The LAN, in turn, is connected to the Internet
.
If your computer is at home, you are probably using a modem connection .A modem is a device that can send and receive digital data over a standard telephone line. You dial your ISP and establish a modem connection between your computer and the ISP computer. The ISP computer, in turn, is connected directly to the Internet.






HYPERTEXT MARKUP LANGUAGE:
Hypertext Markup Language (HTML) is the language of the World Wide Web. It is the standard that is used to create all Web documents. That’s right, every web page you view is written in HTML.
HTML documents contain only text, that is, the letters, numbers, and symbols you see on your keyboard. The text in an HTML file can be divided into to categories:

q Content is the subject matter of the document, the text that a user sees and reads when the document is displayed.
q Tags are special codes that control how the content is formatted, define hyperlinks, display images, and do the other tasks.

It’s easy to tell hypertext tags from content because tags are always enclosed in angle brackets . Anything inside angle brackets is a tag; everything else in content. It’s also the cases that many, but not all, HTML tags come in pairs. The first tag in the pair turns something on, and the second tag turns it off. For paired tags, the “off” tag is the same as the “on” tag but with a leading slash (/). For example, to display text in boldface, the on tag is and the off tag is .

In addition to controlling the formatting of the content text, HTML tags are used to display images in the document. Images are kept in their own separate disk files and then linked from the HTML document with an IMG tag. Here is an example.



This tag will display the image contained in the file birds.jpg, at the location in the document where the tag is located.

The most important HTML tag is the one that defines a hyperlink. After all, the whole purpose of HTML is to permit users to quickly link, or jump, from one document to another. A link tag has the following form:

href=”destination”>link Text

Here, destination specifies where the; link points to, which could be another document on the Web or a different location within the same document. When specifying a different document, you use its uniform resource locator (URL). Link text is the text displayed as a hyperlink in the document, with some special indication such as underling or a different color to indicate that it is a hyperlink and not just regular text.

BROWSERS:

For any one who wants to make use of the web, a browser is the one essential piece of software. One fundamental job of a browser is to load an HTML tag in the document. The other fundamental task is to enable hyperlinks- in other words, when the user selects a hyperlink, to retrieve the HTML document specified in the hyperlink and displays it onscreen.

q Browser is software required for opening the web page. A browser decodes HTML symbol in web document turning them into richly formatted document with graphics and other media.
q In addition browser also originate messages that locate and retrieve document every time you click hyperlink. Many browser gives user access to other Internet services maintains e-mail, Gopher, FTP, USENET.
q Browser also required an Internet connection either through LAN or via modem and Internet service provider using Slip/PPP. Mosaic was the first Windows based web browser.

UNIFORM RESOURCE LOCATOR
More commonly known as URL, uniform resource locator identifies a specific resource on the Internet or Web. The term resource generally means a file or documents. Here is an example of URL:

A URL has three parts that provide all the information required to locate retrieve the file. Let’s dissect the preceding URL to see what these parts are:

q A URL is the address of the document that is to be retrieved from a network server.
q It contains the identification of the protocol, the server, and the file name of the document.

1. First is the protocol specification, in this case http://. This part of the URL specifies the communication protocol (Hypertext transfer protocol) to be used to retrieve the file.
2. Second is the domain name (www.yahoo.com), which identifies the computer where the file is located.
3. Third is the name of the file (ic40.htm) to be retrieved.


HYPRTEXT MARKUP LANGUAGE (HTTP):

HTTP is the protocol of the World Wide Web. HTTP is the protocol by which HTML documents are moved over the Internet. HTTP is an additional protocol layer that makes use of TCP/IP specifically for transmitting hypertext document. HTTP is a stateless protocol i.e. during an HTTP provides for a simple request/ respond interaction. Suppose you sit down at your computer fire up your browser and connect to the yahoo web site. For the next hour, you browse through various sites and then you quit. That’s an HTTP session, but your computer is not really connected to the yahoo web server during this period. Instead what is happening is that your computer is sending request to the web server and the web server is sending responses back to your computer.

Whenever you request a web page by selecting it from your favorites list or by clicking by the hyper link on other web page this is what exactly happening. Request for that web page is sent, using HTTP to the computer that is specifies in the link. That computer locates the documents on its hard disk and uses HTTP to send it your computer, which received it and displays it in the browser.

FTP:

File transfer protocol can do quite a bit more than its name suggests. It is indeed used to transferring file between computers but by using FTP you can sit at one computer and perform the various tasks on a remote computer connected over the Internet

1) Transfer files between computers in both directions. Computer.
2) Delete move and rename files on the remote computers.
3) Navigate the folder or directory structure on the remote computer.
4) Create and delete new folders on the remote computers.

FTP is a traditional internet application for receiving or downloading file from the internet to a computer or sending or uploading file from a remote computers.

FTP allows a user to connect to a remote computer and download vast quantities of document and software for all types of computer system.

The extent to which you can perform FTP command on a remote computer depends of course on your privileges. Only with full privilege would you be able to perform potentially dangerous actions such as deleting files. for this reason it is always necessary to log in to an FTP server with a username and password. The administrator of the FTP server will decide on the level of access you have. If you have partial access directory listing but not delete or rename files.

Perhaps the most common type of FTP access is called anonymous log on. Typically anonymous log on permits you to download files from the FTP server and nothing more. Anonymous FTP is very useful when you went to make files available to the general public. Most commonly you log on us and anonymous user using anonymous as your user name and your email address as password.

Unlike HTTP and FTP is not a stateless protocol. FTP involves two connection between the local and remote computer and they are maintain the throughout FTP session. One of the connections is called the control connection and it is used to send command and response to commands between the computer .the second connections is the data connection, which is used for the actual file transfers.


Telnet:

The service that allow user to connect to a remote Internet host is called telnet. The telnet protocol is used to log on to a remote computer and use it as if you ware sitting in front of it. An engineer at a small college for ex. Could use telnet to log on to supercomputer at cal tech and use it far calculations. To use telnet you generally need permission from the manager of the remote system. A few system have set up anonymous telnet accounts that permits anyone to log in and use a restricted set of the system capabilities. Telnet allows user to establish a TCP connection to a login server.


Gopher:

Gopher has a certain similarities to the World Wide Web, and with the widespread use of the web, Gopher is rarely used any more. With Gopher you see a client program to locate and view information located on gopher servers across the Internet the difference between the web is in the way the information is organized. The some of all information available via gopher is referred to as gopher space. Gopher is one of whole range information search and retrieval tools.


FTP Working:

An FTP conversion consists of request sent by the client and responses sent by the server. After the client connects, the server sends a response to the client, either accepting or rejecting the connection. This initial response is called the greeting.

If the server accepts the connection, the client sends zero or more request to the server. Each request is handled as follows.

1. The client send the request to the server.

2. The server sends one or more responses to the client. The last response either accepts or rejects the request. Previous responses are marks.

Working OF Web Server:

Whenever the client gives request through the web server the request flow through the Internet backbone to the web server. The web server then search for the web document in the database. If the web page is found then server gives response to the requested browser by sending the HTML code of the requested page.

Whenever the browser receives the tag then again it will make request for the image. So that the images are displayed on the server after some time of the text. Here the Internet backbone is a middle-ware technology consisting of various protocol used for the transmission of data \ request or the response to the server or from the server respectively.

There are various web server such as HTTP, java web server, Apache web server etc.

Function of web server:

Web Hosting:

Thousand of business is taking to the web each day in hopes of reaping the unprecedented online rewards. In order to be effective, ones web site be appealing, dynamic, and of course, quick. That is why we provide efficient hosting solution on our lighting fast Internet connection. A fast server and connection are vital to World Wide Web success. Our servers also accommodate high –volume web traffic, so your site can grow without limitations. Furthermore, CNW provides web site promotion to help your site get noticed!

DOMAIN NAME SERVICES [DNS]

Register your domain name with CNW. We also provide domain parking and domain pointing.

WEB HOSTING PACKAGES

Manage and maintain your web site through our simple, user friendly on line account management interface. All of our hosting packages include;

· Fast internet connectivity
· Periodic full web site backups to tape and disk.
· 24 hours server monitoring and response
· Free limited technical support
· A private CGI Bin
· Access to site under your domain name [www.yourdomain.com.]
· Domain name registration
· Waived setup fee for annual pre-pay

For information on hosting package pricing please.

WEB – BASED E-MAIL

Your company’s e-mail can be accessible from anywhere. CNW provides customizable e-mail services to fit your needs. Our service will work seamlessly with your favorite web browsers and e-mail applications.

SEREVER CO- LOCATION

This option gives you the connectivity and bandwidth you need to have productive web site. Perfect for customers that want to have total control of the services they offer, benefits of this service include;

· No Telco cost
· Secure temperature – controlled environment
· 24 hours monitoring
· No networking equipment cost
· Generator with battery transfer


COMMERCE:

We help our client gain an online commercial presence whether selling business to business or to the consume market place or via a closed intranet or extranet Features includes;

· Online sales –via secure credit card transaction
· Site contents can be changed by you as often as you wish
· Fully integrated back office for you to manage your business on line
· Database integration to make the step on line that much easier

RADIUS / AUTHENTICATION SERVICES

CNW provides radius services fro customer who are looking for Internet authentication. Authentication is the process for determining that a user is indeed who he / she claims to be. CNW will enable you to be sure that the user is authenticated before being granted network privileges.

APPLICATION HOSTING

CNW provides multiple server operating system platform to efficiently run your application on the internet.









SUMMARY

Establing a web server is not a monumental task in itself .the challenge lies in managing and developing it, since the primary purpose of the websites is to enable your organization employee’s to publish information.