0 Introduction To Html

INTERNET BASIC 

BASIC CONCEPTS

                      The internet began in 1969,as an experimental four - computer network called ARPA net, that was designed by the u.s. defence so that research scientists could communicate .In approximately two years , ARPAnet grew to about two - dozen sites and by 1981 , consisted of more than hundred sites . In 1990 ,ARPAnet was officially disbanded and the network , that now consisted of hundred of sites, came to be known as the internet.

After a while,commercial organizations began to recognize the use of such a network that convert the whole world into a global village  and  allowed almost instant access to business or commerce data and a host of other services such as E-Mail , & E-Commerce .The rapid growth of the internet was due to networking giants  like british telecom,hyundai, AT&T and other setting up fast and reliable networks that encircled the globe. The networking giants were very clear about their role . This was to setup and maintain , monitor , and expand existing networks . Hence another layer was formed above this layer called ISP's(internet service providers).The networking giants gave access to the internet via gateways.

ISP's in turn offer clients access to the internet via their gateways as paid for service .An ISP's gateway generally consists of a server with  a permanent connection to the internet .The server connection to the internet is called the internet pipeline . Special hardware is used as the pipeline  to connect an ISP's server to the internet .ISP pipeline  bandwidth of 2GB to 10GB are quite common . Multiple pipelines can be purchased by an ISP from a networking giants and used.

The internet consists of two types of computers servers and clients.

• computer that offer information to be read are called servers.
• computers that read the information  offered are called clients.

COMMUNICATION ON THE INTERNET 

TCP/IP is  the only protocol used to send data all around the internet .TCP/IP is really two individual section ,(TCP) a set of communication protocols and (IP)  a unique address  by which it can be located on the internet . This is called IPaddress of the machine . For the internet to function smoothly , no two machine can have the same IP address .Hence each machine conected to the internet must have a unique IP address , that identifies that machine.

The internet is  a  worldwide network of network . As the internet grew over the years it become increasingly important to have a governing body , that allocated unique IP address to organization linked to the internet . An international body called interNIC , located in the USA, is responsible for registering  and assigning unique IP address to organizations wishing to manage networks , that will be part of the internet . A unique IP address therefore points to an actual computer connected via a gateway  to the internet .This computer is known as a domain i.e a place where information is available .This is a physical domain on the internet. 

Conceptually , a server , that has a permanent IP address (i.e a physical domain), can provide 

• A gateway to other computers to access the internet .
• It can provide information for internet clients to read .
• It can provide a physical location on which several  virtual domain can be HOSTED.

In many cases , when a web site provides internet clients information to read , the site is mounted  as a virtual domain on an internet server , that is its (host) physical domain.

Virtual domains are identified by a name (eg www.yfc .com) .  just like a physical domain needs to have a unique IP address ,so also virtual domain names need to be unique on the internet .All virtual domain name must be registered with the intrNIC . One internet server may host several virtual domains.

Virtual domains can be conceptualized as sub directories on an internet server's hard disk drive .The information that internet clients wish to read would  be files within the sub directory.

When an internet clients connects to an internet server some software running on the internet server must respond to the internet clients requests's for information .The  software that runs on an internet server and responds on an internet client's request for information is called web server software .

An internet web server responds to an internet client's request for information by going to a specific sub  directory on its internet clients requests for information is called webserver software.

Traditionally , this sub directory on the internet server is 'wwwroot' and the file automatically picked up and passed to the internet clients the first time is traditionally called 'index.html'