A personal computer based Integrated Services Digital Network D-channel interface monitor/simulator

This study aims to develop a Personal Computer (PC) based software which can be connected to the SO interface of an Integrated Services Digital Network (ISDN) in order to observe the D-channel frames and depict them visually on the monitor. Furthermore, the system can simulate an ISDN terminal by generating the typical actions of a terminal. It is flexible in that it allows the user to set up a scenario for the terminal actions. The ability of observing the frames and setting up a scenario will make the system a powerful tool for the technical user with which he/she can observe the ISDN connection and trace down a problem. The software consists of the monitor/simulator subsystem, D-channel L2 protocol and D-channel L3 protocol handlers. These handlers support Q.921 and Q.931 recommendations of CCITT, respectively. A multitasking executive, which is the subject of another study, has been used as an extension to the underlying operating system in order to run the modules as concurrent processes