An intranet is a set of Internet services (for example a web server) inside a local network, i.e. only accessible from workstations of a local network, or rather a set of well-defined networks that are invisible (or inaccessible) from the outside. It involves the use of Internet client-server standards (using TCP/IP) protocols such as, for example, the use of Web browsers (HTTP protocol-based client) and Web servers (HTTP protocol), to create an information system inside of an organization or enterprise.
An intranet is generally based on a three-tier architecture, comprising:
In this manner, the client machines handle the graphical interface while the different servers handle the data. The network makes it possible to exchange queries and the responses between clients and servers.
An intranet naturally has several clients (the computers of the local network) and may also comprise several servers. A large enterprise may, for example, have a web server for each service to provide an Intranet comprising a federator web server linking the different servers that are managed for each service.
An intranet within an enterprise makes it easy to make a wide variety of different documents available to employees, which provides centralized and coherent access to the enterprise's knowledge, which is referred to as capitalization of knowledge. In this manner, it is generally necessary to define the access rights of the users of the Intranet to the documents located thereon, and consequently authentication of such access rights to provide them with personalized access to certain documents.
Documents of any kind (text, images, videos, sounds, etc.) can be made available on an Intranet. In addition, an Intranet may provide a very interesting groupware function, i.e. allow groupwork. Here are some of the functions which may be provided by an Intranet:
An Intranet makes it possible to create an information system at a low cost (specifically, the cost of an Intranet may very well be limited to the cost of the material, its maintenance and updating, with client workstations operating with free navigators, a server running under Linux with the Apache web serve, and the database server MySQL).
An Intranet must be designed in accordance with the needs of the enterprise or of the organization (at the level of the services to be implemented). The Intranet must therefore not only be designed by the computer engineers of the enterprise, but within the scope of a project which takes into account the needs of all the parties interacting with the company.
Insofar as physical setup is concerned, it is sufficient to set up a web server (for example a machine running under Linux with the Apache web server and the database server MySQL or rather a server under Windows with the web server Microsoft Internet Information Server). It is then sufficient to configure a domain name for the server (for exampleintranet.votre_entreprise.com. Please note that there are CMS systems (content management systems) which allow management of the publication of pages by a team of editors.
An extranet is an extension of the information system of the company to its partners located outside of the network.
Access to the extranet must be secured to the extent that the same provides access to the information system for persons located outside of the enterprise.
This might involve simple authentication (authentication via user name and password) or strong authentication (authentication via a certificate). It is recommended to use HTTPS for all web pages that are consulted from the outside to secure the transport of HTTP queries and answers and to prevent, in particular, the open transfer of the password on the network.
An extranet is therefore neither an Intranet nor an Internet site. It is rather a supplementary system providing, for example, the clients of an enterprise, its partners or its subsidiaries with privileged access to certain computer resources of the enterprise via a Web interface.