1. ITU-T Y.2001 (2004). General overview of NGN.
2. 3GPP TS 23.228 (2005). IP multimedia subsystem (IMS), Stage 2.
3. ETSI ES 283 003, V1.1.1 (2001). Telecommunications and Internet converged services and protocols for advanced networking (TISPAN); IP multimedia call control protocol based on session initiation protocol (SIP) and session description protocol (SDP), Stage 3.
4. Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnson, A., & Peterson, J. (2002). Session initial protocol. IETF RFC3261.
5. ITU-T Y.2111 (2006). Resource and admission control functions in next generation networks.