IM-AG IMS Access Gateway
In the 3GPP IMS (IP Multimedia Subsystem) architecture, the IM-AG is a network functional entity which is incorporated into the functionality of the IBCF (Interconnection Border Control Function). The role of the IM-AG is to ensure that addressing associated with inbound and outbound media streams is correct, which is essentially a NAT (Network Address Translation) function. The IM-AG is also referred to as the TrGW (Transition Gateway).
