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

CCSDS REPORT CONCERNING THE CCSDS FILE DELIVERY PROTOCOL (CFDP)
3.2.3 EXAMPLE CONFIGURATION 3: FILE DELIVERIES VIA ONE
WAYPOINT
3.2.3.1 General
In Example Mission Configuration 3, a file transfer takes place involving three CFDP
entities, one of which acts as a waypoint. In figure 3-9 the CFDP entities are shown
contained in a spacecraft, an NCC, and a remote science laboratory, but they could as easily
be a spacecraft, a communications spacecraft, and a ground station, or any other mix of
facilities. In the figure, a ground station handles frames and routes data between the
spacecraft and an NCC. The ground station does not contain a CFDP entity and, therefore, is
a relay. Within this configuration examples are given for unreliable space-to-ground, reliable
space-to-ground, and reliable ground-to-space file deliveries.
X Laboratory
CFDP Entity
TCP
Network
Control
TCP
Center
X
CFDP Entity
Packet Service
Ground
Station
Frame/CLTU
Service
Spacecraft
X
CFDP Entity
Packet Service
Frame Service
Figure 3-9: Example Mission Configuration 3
3.2.3.2 Unreliable Download via One Waypoint
This example begins with an intelligent spacecraft that, having detected an anomaly in a
science instrument, wishes to deliver telemetry data to a user located in a science facility
(laboratory) remote from an NCC. As this is real-time telemetry data, the file size is
unbounded. Since the telemetry data inherently contains a great deal of information
redundancy, it is not necessary that every bit of it be received by the science facility. The
spacecraft therefore selects unreliable mode. The remote user has a local CFDP entity, but
does not have direct communication with the spacecraft, and thus requires the use of the
NCC as an intermediary. Also, the laboratory does not operate 24 hours per day, so store-
CCSDS 720.1-G-3 Page 3-16 April 2007