A system is provided for content delivery across heterogeneous networks. The system may store a database of unified identity codes (UICs) for respective categories of information, and in-network addresses of in-network subscriber nodes subscribed to the respective categories of information. At least one in-network subscriber node may be a gateway node of and between a heterogeneous network and another heterogeneous network that includes an out-of-network subscriber node. The system may receive a query including a UIC for a category of information to which one or more in-network subscriber nodes are subscribed, and in response thereto retrieve from the database using the UIC, one or more in-network addresses for the one or more in-network subscriber nodes. The system may also reply to the query with the one or more in-network addresses for use by the source node to transmit content to the one or more in-network subscriber nodes.