CCSDS File Delivery Protocol (CFDP)—Part 1: Introduction and ...

CCSDS REPORT CONCERNING THE CCSDS FILE DELIVERY PROTOCOL (CFDP)
and-forward service is needed from the NCC. The NCC contains a CFDP entity. The
ground station does not contain a CFDP entity and provides only lower layer services. This
configuration is shown in figure 3-9.
The following options could be selected to meet the requirements:
– implementation—extended procedures;
– transaction type—Put;
– quality of service—unreliable.
The anomaly detection system on the spacecraft initiates the transaction by causing a Put
request to be sent to the local spacecraft CFDP entity.
Upon receipt of the Put request, the spacecraft CFDP entity initiates the transaction. It
configures the protocol options (e.g., quality of service) according to the information
contained in the MIB, unless overridden by information in the Put request. The CFDP
entity places the required information in the file metadata and begins the file delivery
operation. Each item that the CFDP entity wishes transmitted is placed in a PDU and
passed to the lower layer network. In this case, the interface is to CCSDS Path Service.
The operation through the Path Service has been described previously (3.2.1.2).
A TCP/IP network service is used between the NCC and the user. Upon receipt of the
complete file, and when the laboratory is online, the NCC forwards it to the user over the
TCP/IP network.
The sequence of events is shown in figure 3-10. Note that since the file size is unbounded
(the data is real-time telemetry), file closing is triggered by an external event, in this
example a trigger from the onboard spacecraft sequencer.
CCSDS 720.1-G-3 Page 3-17 April 2007