The IP Multimedia Subsystem (IMS) reference architecture, as defined within the 3GPP and other international standards bodies, is continually evolving to meet the changing demands of both consumers and service providers, while taking into consideration the capabilities of current technologies and service delivery mechanisms. At the forefront of today’s drive towards IMS deployment are Transitional Network Elements (TNE), platforms which will aid the migration from legacy (AIN/SS7) telephony infrastructures.  These platforms serve to combine specific components of the IMS architecture while simultaneously extending standard reference interfaces to each logical element.  In this way, the TNE will not only migrate and enable critical applications and services without imposing limitations on cross-network feature interaction, integration or billing, but also continue to be a vital IMS network resource once the transition is complete.