Technology trends, consumer and business tendencies are to drop single PSTN lines in favor of VoIP technology. The kernel of VoIp technology is its signaling protocol, where the Session Initiation Protocol (SIP) has been considered the most widespread signaling protocol overall. Within this context, and by considering the huge amount of Internet users and communications that take place over VoIP technology, our work focuses on conducting conformance tests of distributed complex scenarios of SIP in a black box environment. Experimental results have been successfully obtained and discussed