Administering an ISP Installation

Example: Querying a SQL Server

The following procedure shows how a query extracts data from a SQL server database:

The user sends a request through the Internet to the front-end network.
A Web application then queries the SQL server through the back-end network.
The SQL server sends the data back to the Web server through the back end.
The Web application builds the response HTML page dynamically and sends it back to the Internet user through the front-end network.

In this example, the network traffic can be divided in order to save bandwidth.

In summary, here are the steps that were used in planning a sample architecture:

The network segments were split in order to divide network traffic properly and save bandwidth.
An isolation layer was placed between the Internet and the back-end network, where the actual data was stored, thus enforcing the security of the data in the back-end network.

Every component (production Web servers, routers, firewall, switches, and so on) of a cluster can easily be duplicated to offer a greater failover. This way, if one of the components fails, the redundant one starts immediately, thereby reducing the number of off-line services.