Interconnect Border Control Function (IBCF) offers boundary control between various service provider networks, providing IMS network security in terms of signaling information. This is done by implementing a Topology-Hiding Inter-network Gateway (THIG) sub-function, which performs signaling-based topology hiding, session screening and IPv4-IPv6 translations based on source and destination signaling addresses. When connecting non-SIP or non-IPv6 networks, the IBCF also invokes the Inter-Working Function and performs bandwidth allocation and admission control using local policies or through the interface to PCRF elements. The IBCF may also interact with TrGW for control of the boundary at the transport layer including NAPT, pinhole firewall, and other features.