CHECK OUT THE BELOW DOCUMENT which explains NGN Protocol
http://www.tec.gov.in/technology%20updates/NGN%20Protocols.pdf

some abbreviations on NGN protocol
AGW Access media Gateway
IETF Internet Engineering Task Force
IP Internet Protocol
ISDN Integrated Services Digital Network
ITU International Telecommunication Union
ITU-T ITU Telecommunication Sector
IUA ISDN User Adaptation Layer
M2PA MTP2- User Peer-to-Peer Adaptation Layer
M2UA Message Transfer Part User Adaptation Layer 2
M3UA Message Transfer Part User Adaptation Layer 3
MGW Media Gateway
MTU Maximum Transmission Unit
NGN Next Generation Network
PSTN Public Switched Telephone Network
RFC Request For Comments
RTCP Real Time Control Protocol
RTP Real Time Protocol
SCCP Signalling Connection Control Part
SCN Switched Circuit Network
SCTP Simple Control Transmission Protocol
SCTP Stream Control Transport Protocol
SDP Session Description Protocol
SIP Session Initiation Protocol
SS7 Common Channel Signalling No.7
SUA SCCP User Adaptation
TDM Time Division Multiplex
TEC Telecommunication Engineering Centre
TMG Trunk Media Gateway
UDP User Datagram Protocol
V5UA V 5.2 User Adaptation Layer Protocol