1. General overview of NGN, ITU-T Recommendation Y.2001, December 2004
2. IP Multimedia Subsystem (IMS); Stage 2 (Release 14), 3GPP TS 23.228 v14.3.0, March 2017
3. Call processing performance for voice service in hybrid IP networks, ITU-T Recommendation Y.1530, November 2007
4. SIP-based call processing performance, ITU-T Recommendation Y.1531, November 2007
5. Kaczmarek, S., Kaszuba, M., Sac, M.: Simulation model of IMS/NGN call processing performance. Gdańsk Univ. Technol. Faculty ETI Ann. 20, 25–36 (2012)