A method of providing interoperability among communications network nodes. Interoperability types, including a basic type of interoperability, are defined. For each interoperability type, a support capability is defined for implementation on a node without modification to the node application layer. On each node is provided at least the basic interoperability type support capability. Each node can use the basic interoperability type support capability to obtain, on an ad-hoc basis, a support capability for another type of interoperability with another node. This method facilitates system-of-systems interoperability while lowering complexity and risk.