This Recommended Standard defines the Forward Frame Cross Support Transfer Service, a service that provides the transfer of fixed-length and variable-length Transfer Frames and Channel Access Data Units to a Provider Cross Support Service System Earth-Space Link Terminal (e.g., a ground station) to be encoded (as needed) and radiated to a Space User Node (e.g., a Mission spacecraft). The supported variable-length Transfer Frames include CCSDS Telecommand Transfer Frames and variable-length CCSDS Unified Space Data Link Protocol (USLP) Transfer Frames. The supported fixed-length Transfer Frames include the CCSDS Advanced Orbiting System Transfer Frames and fixed-length USLP Transfer Frames.