The AKARI Project, one of clean slate approaches to design New Generation Network (NwGN), is proposing a six-layer network architecture called ZNA (Z Network Architecture). Although there are several proposals of new network architectures that are not based on layered structure, we concluded that layered architecture is most appropriate for NwGN. One of the features of ZNA is that the session layer is inserted between the application layer and the transport layer. The session layer provides the application layer with more sophisticated communication paths: the regular path, the bundled path, the spatially-spliced path, and the temporally-spliced path. This paper shows feasibility of implementing the session layer through the design of the session layer API and protocol. The proposed API follows the conventional socket interface and is easy to understand.