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The rise of the Internet occasioned a major upheaval in the way systems are used. Prior to the Internet, each system had its own ergonomics and manmachine interface; a user who wanted to use an application or to access data on a particular server had to adopt that system’s approach; using services on several different systems was therefore a burden to the user, since each could be different. With the Internet’s communications and presentation standards (HTTP and HTML), a much greater degree of transparency was achieved between servers and their users; the industry-wide convergence on TCP/IP as the communications protocol of choice was the first step in this simplification.

To be able to accommodate the new uses and users enabled by the Internet, servers had to support these protocols. In other words, with the rise of the Internet, servers adapted to clients, whereas, in the past, the clients had to adapt to the server.

One can characterize the various Internet variants in the following way:

» Internet. Indicates the network upon which applications and information are put available for any public use and with limited security

» Intranet. Indicates a network where private applications and information are limited to a “community” (generally a company) and present a high degree of security. Access by people outside the community is not allowed

» Extranet. Indicates a network of the type Intranet extended to partners in whom a high degree of confidence is placed Access by people outside the partnership is not allowed. A high degree of security is associated such networks

By May 2004, there were about 786 million Internet users world wide (source: InternetWorldStats.com).

We will not differentiate between Internet, Intranet and Extranet in our description of the technologies used, since the differences are differences between users—employee for an Intranet, employee and partners for an extranet, and everyone in the case of the Internet—not technologies. The user differences give rise to differences in administration and security management, but not at the level of server programming.

The first things that the Internet asks of a server are the properties of scalability and high availability. Scalability, because predicting the number of users in advance is difficult; high availability because in the absence of availability, a customer attempting e-commerce with a site and finding it unavailable will simply go and buy elsewhere—the distance between two electronic shops is just a mouse click.

Source of Information : Elsevier Server Architectures 2005