Is it ensure, insure, or assure?
The second highest layer (layer 6) in the OSI seven layer model. Performs functions such as text compression, code or format conversion to try to smooth out differences between hosts. Allows incompatible processes in the application layer to communicate via the session layer.
Documents: ITU Rec. X.226 (ISO 8823), ITU Rec. X.216 (ISO 8822).