The term client/server refers to a networking architecture where the client is the machine that requests and the server is the one processing the request and trying to answer it, they are connected via a Local Area Network (LAN) or Wide Area Network (WAN). The server and the client can be working or not on the same machine .server is the program that starts first, initializes itself then go to sleep waiting for a request to come then it wakes up to process that request. The roles of the client and the server are asymmetric.
In the terms of how the request are processed by the server, servers can be categorized in 2 categories:
A server is said to be iterative when the server process knows in advance how long it takes to handle each request and it handles all the requests itself .this server process is used only when the service time is very small therefore if the service time can be long this would not be a good solution because the iterative process service time is very small therefore a single copy of the server run at all times and a client may have to wait if the server is busy.
Concurrent servers are used when the amount of work required to handle a request is unknown. Whenever a request comes the server starts another process to handle each request meaning that there are as many copies of server as there are requests.
The client/server communication can use the TCP or UDP depending on the requirements. Before a connection can be made there are a few information you need to know. Those are:
-The protocol used
-source IP address
-source port number
-Destination IP address
-Destination port number
Nowadays, almost every computer that is sold comes equipped with at least one Web browser. The most common browser is Microsoft Internet Explorer, which represents over three-quarters of the browsers in use. The second most common browser is Netscape Navigator, which is the browser of choice for slightly less than one-quarter of users. The rest of the browser market is shared between a number of browsers including Opera, Powermarks, and IBrowse.
Web pages are stored on servers and also transmitted by servers. Intranet servers contain Web server software that enables them to provide the same services as internet to their clients. Web servers use a protocol called HTTP, to send Web pages to a browser.
The final component that is required for an intranet is a TCP/IP-enabled network. TCP/IP enables networks to transmit Intranet content between a server and a client. Although it wasn't always the case, today's networks (including the servers and desktop computers) are generally equipped with TCP/IP. You'll know that your network is TCP/IP-enabled if a network administrator indicates that your network is compatible with TCP/IP, if you can access the Web from your networked computer, or if your network uses UNIX servers (UNIX servers use TCP/IP to transmit data).
Delivering Web pages isn't the only thing you'll be able to accomplish over your intranet-there are also many other technologies that use the same group of Internet protocols. The technologies that enable us to do things over the intranet are called Internet applications or Web services. Here are some of the most important of these Web applications.
Email is the application that enables users to send messages from one computer to another. Most browsers include an email client, which is needed to send and receive mail messages. Email uses SMTP (Simple Mail Transfer Protocol) to transfer messages.
Newsgroups are like bulletin boards that contain messages that can be viewed by groups of people. Most browsers include a news reader, which is required for users who want to view newsgroup messages. Newsgroups use NNTP (Net News Transfer Protocol) to transfer newsgroup postings.
File transfer enables users to download or upload files to or from a server. File transfer is often used to put intranet files on the intranet server. File transfer uses FTP (File Transfer Protocol). There are many types of FTP applications.
The Web handles hypertext files, graphics, sound, video, and other file types. The Web application uses HTTP (Hypertext Transfer Protocol). Web files are displayed by a client browser.
PPP is a method of enabling dial-up users to connect to an intranet. PPP stands for Point-to-Point Protocol.
HOW TO BUILD AN INTRANET
If hures want to implement an intranet there are a few simple steps that they will have to follow: installing a Web server, testing it on their network, designing a site plan, developing Web pages, and uploading the site to the server.
Installing and Testing a Web Server
Before they begin creating intranet Web pages, it is better that they install and test a server over their network . They can do it by following these steps:
1. Obtain a Web server that is compatible with their operating system.
2. Install the Web server on a computer that is connected to a TCP/IP-enabled network.
3. If necessary, obtain and install a Web browser on a different computer on the same network.
4. Using the browser, request a Web page from the Web server.
If, like most organizations, hures uses the Microsoft Windows operating system, it will be easy for them to obtain a Web server. If they are running Windows 9x, they can download Personal Web Server from the Microsoft Web site. If they are running Windows NT/2000/XP, they can install Microsoft Internet Information Server (IIS), which is available as part of the NT/2000/XP setup.
Every computer on an network (including the Internet) has a unique name or numeric address that is used to identify it, these addresses are called IP addresses and enable one computer to contact another computer in order to send or receive data. Computers on a normal office network may be given network identification names that enable them to be recognized by other computers on the network. When hures will install a Web server on a computer that is connected to a TCP/IP network, other computers on the network will be able to request Web pages from the server by entering the server computer's network identification name into their browser's address bars ( hoping that the network supports the correct protocols and allows users to send and request HTTP). So if hures's server computer's name is "hures" and a file in your Web server's HTML directory is called HomePage.html, users on that network will be able to request that page by typing http://hures/HomePage.html into their browser's address bar.
When you enter just a computer's name (not a path and file name) into a Web browser's address bar, the queried computer normally responds by sending its default Web page. Most default pages identify the type of server on which they originate. Many Web servers are set up to send pages called index.html or home.htm when a user requests just the host name. To further test the browser (and HTML coding skills) they can create a Web page, save it in the root directory of their Web server (for many Windows computers, this directory will be C:\Inetpub\wwwroot\), and request it from a remote computer's browser.
Of course, they wouldn't want to serve Web pages from one of their desktop machines for too long, because it could use up its system resources-memory and processing power that will be needed to run applications. So most intranets have a special server machine that is dedicated to serving intranet pages. They will probably need to work with their network administrator to set up and configure that machine.
We often view the Internet as a single thing that directly transports information here and there throughout the world. We don't usually think about what happens behind the scenes to enable the Internet to do its magic. Much like the way that we use the postal service, we simply open our mailbox (or our Web browser) and expect to find files and information delivered to us from all over the world.
Physical Structure of the Internet
A primary reason for the Internet's growing popularity among computer users is because of the World Wide Web (WWW). The Web makes it easy for non-technical users to share information throughout the Internet. These days, computer users refer to the Web and the Internet as if they were the same. In fact, the Web is a new addition to the Internet. It has introduced a new way of accessing information over computer networks.
In reality, the Internet is very complex-it's made of thousands of smaller networks with no central point of control. Each of these networks has at least one specially configured computer, called a router or gateway , that examines each packet (chunk) of information that is passed to it, and determines where to send it next.
Essentially the Internet is a big network made of many smaller networks. The Internet's name comes from the word "internetwork" , meaning a network of networks.
To enable the many smaller networks that comprise the Internet to work together, every computer that communicates across those networks must follow certain rules. These rules-called "protocols" -are like a common language. Protocols enable one computer to share data with another computer anywhere on the Internet, just as two people who speak the same language can share information through a conversation. There are many protocols that are used over the internet so that computers can share information over the Internet.
To access the Internet, computers use special software (called by various names, including protocol stacks , network drivers , and network components ). Protocol stacks give computers the ability to know how to access the Internet according to the established Internet protocols. Protocols define the language or rules by which computers communicate, protocol stacks are the software that enables computers to follow the rules, and by doing so to communicate.
Protocol stacks are provided with the operating system as an installation option. The two most important protocols for communicating on the Internet are Transport Control Protocol (TCP) and Internet Protocol (IP) .
The TCP protocol checks how packets are assembled and disassembled, and how they are verified as intact by the receiver.
The computer sending a file breaks it into small chunks, and puts each chunk of data into a packet for transmission across the Internet. To reassemble a file from the packets that it receives, the computer receiving the packets must know how the original file was broken up. It must be able to determine such things as which packets are part of the same file, in what order they need to be assembled, and how to verify that the received packets match those that were sent.
The Internet Protocol (IP) is responsible for getting packets to their correct destination. Just as TCP specifies that header information should be added to packets to control how they are assembled and disassembled, IP specifies that header information should be added to identify things necessary for moving packets from their source to their destination. This includes such things as the sender address, the destination address, and the packet's Time To Live (TTL).
If we were to compare the client/server against the internet or the intranet we would say that the client/server does not stand a chance and that is what we have been seeing in these past years where Many companies are now creating their own intranet. There are many advantages to use intranet in a company some of the advantages are the ease of deployment and also the ease of software updates but we cannot forget that using the client/server has some advantages as well some of them being that the client server applications have a flexibility in interface design and the speed in execution.