This annex describes the Inter-IMS Network to Network Interface which is used to interconnect two IM CN subsystem networks.
Figure K.1 illustrates an high-level architecture diagram showing the Inter-IMS Network to Network Interface (II-NNI) between two IM CN subsystem networks.
The protocols over the two reference points Ici and Izi make up the Inter-IMS Network to Network Interface.
The Ici reference point allows IBCFs to communicate with each other in order to provide the communication and forwarding of SIP signalling messaging between IM CN subsystem networks. The Izi reference point allows TrGWs to forward media streams between IM CN subsystem networks.