Communication Protocols

With the plethora of onboard data storage, communication systems, back-end systems and national authorities involved, it has been proven very difficult to establish an end-to-end communication protocol that would be easy to use, efficient and accepted by all parties. The Consultative Committee for Space Data Systems (CCSDS) has recently tried to provide some answer in this direction, in the form of the CCSDS File Delivery Protocol (CFDP standard).

This document defines a CCSDS File Delivery Protocol (CFDP) and associated service for application in the space environment. It is intended for use over the current and envisaged packet delivery services used in the space environment including:

• CCSDS conventional packet telecommand
• CCSDS conventional packet telemetry
• CCSDS Advanced Orbiting Systems (AOS) Path service

In may also operate over a wide variety of ground network services including those specified by the CCSDS for cross-support purposes. The protocol operates in the space-to-ground, ground-to-space, and space-to-space directions of transfer. It may be initiated by the file sending or receiving entity. In the interests of interoperability, protocol elements are included for generalized forms of standard file manipulation operations based on assumptions of a common model for a filestore, or medium used to store files. It is recognized, however, that the precise nature and capabilities of filestore management systems are operating-system dependent and, for that reason, the protocol assumes a virtual filestore and associated services that an implementation must map to the capabilities of the actual filestore used.