Have you ever thought about the mechanisms that delivered this page to you? May be you are viewing this blog page in a browser now. So when you typed its URL (uniform resource locator), what happened behind the scenes to bring this page onto your screen? Let’s see what actually happens…………….
Let's say that you are sitting at your computer, surfing the Web, you type the URL into your browser and press enter. And automatically the page appears 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.
Behind the Scene
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:
- The protocol ("http")
- The server name ("www.google.com")
- The file name ("web-server.htm")
- The browser communicated with a name server to translate the server name "www.google.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. Following the HTTP protocol, the browser sent a GET request to the server, asking for the file "http://www.google.com/web-server.htm."
- The server then sent the HTML text for the Web page to the browser.
- The browser read the HTML tags and formatted the page onto your screen.
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 connects to an Internet service provider (ISP). A computer usually have a network interface card (NIC) that directly connects it to a local area network (LAN). 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. In this way, every computer on the Internet is connected to every other computer on the Internet.
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), 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, A server machine may provide one or more services on the Internet. 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:
216.239.61.104 (for WWW.Google.com)
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..
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.
Go To Start->Run->Type “ cmd ”->Press ENTER
Then for Hostname type “hostname” & press ENTER
For IP address of your machine type “ ipconfig”
For IP address of any website type “ nslookup website name”
Ex : c:\ nslookup www.google.com
Use the commands without quotes.
Domain Names
The name www.google.com actually has three parts:
- The host name ("www")
- The domain name ("Google")
- 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). 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."
In The End...
when you type a URL into a browser, the following steps occur:
- The browser breaks the URL into three parts:
- The protocol ("http")
- The server name ("www.orkut.com")
- The file name ("web-server.htm")
- The browser communicates with a name server to translate the server name, "www.orkut.com," into an IP address, which it uses to connect to that server machine.
- The browser then forms a connection to the Web server at that IP address on port 80.
- Following the HTTP protocol, the browser sends a GET request to the server, asking for the file "http://www.orkut.com/web-server.htm." (Note that cookies may be sent from browser to server with the GET request)
- The server sends 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 reads the HTML tags and formats the page onto your screen.
