A Formally Verified Mechanism for Countering SPIT

Voice over IP (VoIP) is a key technology, which provides new ways of communication. It enables the transmission of telephone calls over the Internet, which delivers economical telephony that can clearly benefit both consumers and businesses, but it also provides a cheap method of mass advertising. Those bulks unsolicited calls are known as SPam over Internet Telephony (SPIT). In this paper we illustrate an anti-SPIT policy-based management (aSPM) mechanism which can handle the SPIT phenomenon. Moreover, we introduce a formal verification as a mean for validating the effectiveness of the aSPM against its intended goals. We provide model checking results that report upper bounds in the duration of call session establishment for the analyzed anti-SPIT policy over the Session Initiation Protocol (SIP) and prove the absence of deadlocks.