Exception violations in Voice over IP telephony

Voice over Internet Protocol (VoIP) is getting high on success in communication services at present. There are still more and more providers that offer telephony services based on VoIP. Many producers of telephony solutions and also manufacturers of electronic devices or software applications expand markets in the communication area. The reason the number of VoIP products is increasing is that there are new possibilities in communication services and costs as well. Most widely used protocol for VoIP implementations is Session Initiation Protocol (SIP) which is also most frequently equated with the VoIP term. Like any other systems, SIP-based VoIP systems are vulnerable to general attacks. When vulnerabilities exist, there are serious security implications when such vulnerabilities are exploited. This paper shows possible vulnerabilities of the SIP implementation on VoIP systems, especially SIP servers in generally. And the practical examples were also done on the real SIP server to show possible defects in the SIP implementation.