Here, I describe the basic principles and operation of a VoIP system, the current scenario of the implementation site and what necessary changes are to be made to execute the implementation. I have described, in one chapter all the protocols working in a telephone and a VoIP network and I provide an extensive study of security risks, vulnerabilities, threats which are common while communicating over the internet in another chapter. I showed the probable network topology breaking it down separately for each part of the entire system i.e for the PABX telephone network end and for the IP network end and finally the complete topology of the converged VoIP system along with security solution integrated with it for a university campus.