| Home | Web Technology | Language | How To | FAQ | |About-Us|

Web Technology     

Web Ch2- Introduction to WWW

1.1 Understanding the World Wide Web

The World Wide Web is currently the most talked about publishing medium. Recent statistics indicate that close to 20 million people browse the web (with over 250,000 different web sites) on a regular basis.

What has made the World Wide Web so popular? That, of course, depends on whom you ask. Most will agree that these are the two primary reasons:
  • Ease of use. Publishing information on the web and browsing for information are relatively easy tasks
  • Quantity of content. With hundreds of thousands of web pages to choose from, and thousands more being created each day, there are sites and pages to cater to almost every surfer's tastes.

1.2 The Internet

The networks found in most offices today are Local Area Networks (LANs), which comprise a group of computers in relatively close proximity to each other and linked by special hardware (Hub) and cabling. Some computers are clients (more commonly known as workstations), others are servers. All these computers communicate with each other to share information.

Now imagine a bigger network, one that spans multiple geographical locations. This type of network is typically used by larger companies with offices in multiple locations. Each location has LAN that links local computers together. All these LANs are, in turn, linked together via some communications medium. The linking can be anything from a 28.8 baud modem to high-speed T1 connections and fiber-optic links. The complete group of interconnected LANs is called a WAN (Wide Area Network).

The high speed backbones do exist. Many are owned and operated by the large telecommunications companies.

The local access points, more commonly known as POPs, or Points of Presence, are run by phone companies, online services, and local Internet service providers (known as ISPs).

The common language is IP, the Internet Protocol, except that the term "language" is a misnomer. A protocol is a set of rules governing behavior in certain situation. The protocols ensure that there are no communication breakdowns or serious misunderstandings. Computers need protocols to ensure that they can communicate with each other correctly and to be sure that data is exchanged correctly. IP is the protocol used to communicate across the Internet, so every computer connected to the Internet must be running a copy of IP.

The unique identifiers are IP addresses. Every computer, or host, connected to the Internet has a unique IP address. These addresses are made up of four sets of numbers separated by periods, for example 206.246.150.10. Some hosts have fixed (or static) IP addresses; others have dynamically assigned addresses. Regardless of how an IP address is obtained, no two hosts connected to the Internet may be using the same IP address at any given time.

1.3 Internet Applications

The Internet itself is simply a massive communications network and offers very little to most users, which is why it took 20 years for the Internet to become the phenomenon is it today.

The Internet has been dubbed the"the Information Superhighway," and that analogy is quite accurate. Highways themselves are not nearly as exciting as the places you can get to by traveling them. The same is true of the Internet. What make the Internet so exciting are the applications that run over it and what you can accomplish with them.

The most popular application now is the World Wide Web. It is the web that single-handedly transformed the Internet into a household world. If fact, many people mistakenly think that the World Wide Web is the Internet. This is definitely not the case, and the following table lists some of the more popular Internet-based applications.
Application Description
Email Simple Mail Transfer Protocol (SMTP) is the most popular email delivery mechanism.
FTP File Transfer Protocol is used to transfer files between hosts
Gopher This menu-driven document retrieval system was very popular before the creation of the World Wide Web.
IRC Internet Relay Chat allows real-time, text-based conferencing over the Internet
NFS Network File System is used to share files among different hosts.
Newsgroups Newsgroups are threaded discussion lists, of which there are thousands
Telnet Telnet is used to log in to a host from a remote location
WWW The World Wide Web

All these different applications, and many others, use IP to communicate across the Internet. The information transmitted by these applications is broken into packets, or small blocks of data, which are sent to a destination IP address. The application at the receiving end processes the received information.

1.4 DNS, the Domain Name Service

IP addresses are the only way to uniquely specify a host. When you want to communicate with a host–for example a web server–you need to specify the IP address of the web server you are trying to contact.

DNS provides another way to access a web site without providing the IP address. DNS maps host names to IP addresses. When you specify the destination address of www.puthi.com, your browser sends an address resolution request to a DNS server asking for the IP address of that host. The DNS server returns and actual IP address. Your browser can then use this address to communicate with the host directly.

If the DNS server was not unable to resolve the specified host name, error messages are displayed to tell you that the host could not be found.

DNS servers are special software programs. Often your ISP will host your DNS entries so that you don't need to install and maintain your own DSN server software.

1.5 Intranets and Extranets

The Intranets and Extranets are currently two of the industry's favorit buzzwords. It was not too long ago that most people thought "intranet" was a typo, but, it a very short period of time, intranets and extranets became recognized as a legitimate and powerful new business tools.

An intranet is nothing more than a private Internet. In other word, it is a private network, usually a LAN or WAN, that enables the user of Internet-based applications in a secure and private environment. As on the public Internet, intranets can host web servers, FTP servers, an any other IP-based services.

Extranets are intranet-style networks that link multiple sites or organizations using intranet-related technologies. Many extranets actually use the public Internet as their backbone, and employ encryption techniques to ensure the security of the data being moved over the network.

The two things that distinguish intranets and extranets from the Internet is who can access them and from where they can be accessed. Don't be confused by hype surrounding applications that claim to be "intranet-ready." If an application can be used over the public Internet, it will work on private intranets and extranets too.

    References

    (1) the Cold Fusion Web Application Construction Kit, Second Edition.
KHMERCyber.com ©2008