SIP’s popularity has grown enormously over the past few years. A big boost in support came in November
2000, with the acceptance of SIP by the 3rd Generation Partnership Project (3GPP). 3GPP is composed of standards
organizations in China, Europe, Japan, North America and South Korea, and is dedicated to the proliferation
of a third-generation wireless global standard. More specifically, this organization focuses on the development
of standards for the Universal Mobile Telecommunications System (UMTS). Furthermore, the 3GPP developed
the IMS (IP Multimedia Subsystem), which defines the way VoIP services will be implemented over
General Packet Radio Services (GPRS) and UMTS cellular networks....