"Network Interoperability is the continuous ability to send and receive data among the interconnected networks, providing the quality level expected by the end user. It becomes indispensable in order to achieve end-to-end connectivity. The more diverse networks exist, the greater becomes the need to ensure that they can interoperate. Network interoperability being the ability of two networks to communicate can be achieved in two ways: either by having the two networks confirm to a common protocol standard or by defining a standard interface to which all networks need to adhere, or by providing a gateway that translates between the two protocols."