ABSTRACT
VoIP usage has increased over the past few years. For example in Europe, and according to the European Telecommunications Operators Organization, the number of VoIP users has increased by more than 600 percent over the past 5 years. In addition to substituting traditional voice minutes, the existence of cheaper VoIP services forces traditional Operators to reduce call charges, causing a decrease
in revenue. Traditional voice calls have decreased significantly in the PSTN domain.
