VoIP is increasingly becoming an alternative to the traditional PSTN for Telephony this is as a result of certain advantages and services... Show moreVoIP is increasingly becoming an alternative to the traditional PSTN for Telephony this is as a result of certain advantages and services offered by VoIP. VoIP will be considered able to fully replace PSTN if it can provide same or better Quality of Service and Security guaranty as PSTN. Delivering telephony services over (best-effort and connectionless) IP data network faces two main issues not experienced in PSTN, security and quality of service; security in the sense that telephone calls will be susceptible to attacks that are known in the Internet, quality of service in the sense that voice packets now have to compete with packets of other traffic for a limited bandwidth. Researches are ongoing in these two fields to make experience on VoIP similar to the traditional telephone. The focus of this thesis work is in the security aspect. SIP protocol has become one of the most popular signaling protocols used for VoIP, SIP architecture is an open architecture originally developed for trusted communications among trusted partners, and therefore much thought was not given to security. Adopting SIP as a main protocol used in VoIP in the Internet where there are where there are lots of hostile users calls for more ways to properly secure its use. The thesis work involves setting up of a SIP based VoIP network based on open source SIP telephony platforms to study various security issues in a SIP-Based VoIP network and experiment some proposed detection mechanism. The contribution of this work is to develop a graphical user interface in the UNIX environment using Java that makes the execution of the attack scenarios easy to carry out and observe. M.S. in Electrical Engineering, December 2011 Show less