1. The International Telecommunication Union (ITU), http://www.itu.int/ITU-T/studygroups/com13/ngn2004/working_definition.html
2. 3GPP TS 23.228: IP multimedia subsystem (IMS). Version 10.2.0, Release 10 (2010)
3. Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M., Schooler, E.: SIP: Session Initiation Protocol. RFC 3261 (2002)
4. Calhoun, P., Loughney, J., Guttman, E., Zorn, G., Arkko, J.: Diameter Base Protocol. RFC 3588 (2003)
5. ITU-T Recommendation Y.2011: General principles and general reference model for next generation network (2004)