Packets will be identified and routed in the system using the SAPID, DAPID, ST, and SST. Applications shall provide these fields to the JAS Packet Service to create the stream of packets that will be sent across the communication channel. Communication channels and addresses, such as a SpaceWire address, can be mapped to DAPIDs using lookup tables. When the JAS Packet Service receives a set of packets from the communication channel, it will reassemble the command or telemetry message, and forward it to the appropriate application, using the DAPID, ST, and SST. The SAPID can be used in request/response type transactions. For example, the SAPID of a command going to one application can turn around and become the DAPID of the response that gets returned.
"Internal Standards developed by Sandia National Laboratories". Experience Base, Sandia National Laboratories, Albuquerque, NM, 0000.