The Internet brings many new features to the process control and automation field. The Internet, however, has its limitations when compared to a traditional control system in terms of functionality, performance, security and reliability. Oil refinery industry in Iraq is in evolution toward the modernization of many material and production procedures. This work is about the design and simulation of web based monitoring system for oil refinery industry taking as case study the North Oil Refineries of Baiji (NORB) in northern Iraq. This dissertation addresses three main issues for the future refinery control system based on existing DCS system infrastructures: NORB Company communication network, Internet used as web applications, and data security related to new challenges. Communication network is simulated based on OPNET, which is a network simulator. Real time data communication network with high load File Transfer Protocol (FTP), database access, E-mail, and Voice over IP (VoIP) with Pulse Code Modulation (PCM) quality application will be simulated. Metrics collected from simulations are represented, and evaluated. Data are encrypted with the Secure And Fast Encryption Routing (SAFER+) algorithm to ensure data security with a fixed key size of 16 bytes. In order to assess the control network from the network reliability point of view, reliability calculations showed that the network of the case study is with acceptable reliability.