ISO 17355:2007

Space data and information transfer systems - CCSDS file delivery protocol

ISO 17355:2007 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. It 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. The scope and field of application are furthermore detailed in subclauses 1.2 and 1.3 of the enclosed CCSDS publication.

Systèmes de transfert des informations et données spatiales — Protocole CCSDS de livraison de fichiers

General Information

• Status: Published
• Publication Date: 06-May-2007
• ICS: 49.140 - Space systems and operations
• Technical Committee: ISO/TC 20/SC 13 - Space data and information transfer systems
• Drafting Committee: ISO/TC 20/SC 13 - Space data and information transfer systems
• Current Stage: 9060 - Close of review
• Completion Date: 02-Sep-2029

Relations

• Revises: ISO 17355:2004 - Space data and information transfer systems - CCSDS file delivery protocol
• Effective Date: 15-Apr-2008

Overview

ISO 17355:2007 - Space data and information transfer systems: CCSDS file delivery protocol (CFDP) - defines a standard file delivery service and protocol for the space environment. Published as the third edition in 2007 (based on CCSDS 727.0-B-3, June 2005), the standard specifies how files are exchanged over CCSDS packet services (conventional telecommand, telemetry and AOS path service) and across a variety of ground network services. CFDP supports space-to-ground, ground-to-space and space-to-space transfers and assumes a virtual filestore model that implementations map to actual onboard or ground file systems to preserve interoperability.

Key Topics and Requirements

• Protocol scope: File transfer service for spacecraft mass memory and related ground systems using CCSDS packet infrastructures.
• Transport environments: CCSDS conventional packet telecommand, conventional packet telemetry, AOS path service, and compatible ground networks.
• Transfer directions: Space-to-ground, ground-to-space, space-to-space; transfers may be initiated by sender or receiver.
• Virtual filestore model: Protocol elements assume a common, abstract filestore; implementations must map virtual filestore semantics to OS-dependent storage.
• Service primitives & PDUs: Defines CFDP service primitives and detailed PDU formats for directive and data exchange (core and extended procedures).
• Operational procedures: Core file delivery procedures plus extended behaviors (e.g., unacknowledged-mode handling updates in Issue 3).
• User operations: Support for proxy operation, directory operations, remote status reporting, remote suspend/resume and other file management interactions.
• Design constraints: Addresses space constraints such as limited computational resources, noisy/limited/asymmetric/interrupted links and long propagation delays; supports early access to partially transferred data where needed.

Applications and Who Uses It

• Satellite and spacecraft system architects and software engineers implementing onboard file transfer and mass memory access.
• Mission operations and ground-segment developers managing payload data delivery, command file uploads, and cross-support between agencies.
• Developers of relay and inter-spacecraft communication systems enabling space-to-space file exchange.
• Integrators building protocols that require guaranteed or best-effort file delivery over CCSDS packet services.
  Practical uses include reliable science-data downloads, commanding via file upload, store-and-forward relay operations, and autonomous file transfer between spacecraft and ground.

Related Standards

• CCSDS 727.0-B-3 (CFDP Recommended Standard - source publication)
• CCSDS documents mapped to ISO standards cited in the ISO text:
  • CCSDS 732.0-B-1 = ISO 22666:2005
  • CCSDS 132.0-B-1 = ISO 22645:2005
  • CCSDS 133.0-B-1 = ISO 22646:2005
  • CCSDS 232.0-B-1 = ISO 22664:2005

Keywords: CCSDS file delivery protocol, CFDP, space file transfer, virtual filestore, spacecraft mass memory, space-to-ground file transfer, AOS path service, CCSDS packet telemetry, telecommand.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 17355
Third edition
2007-05-15
Space data and information transfer
systems — CCSDS file delivery protocol
Systèmes de transfert des informations et données spatiales —
Protocole CCSDS de livraison de fichiers

Reference number
©
ISO 2007
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.

©  ISO 2007
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail [e-mail]
Web www.iso.org
Published in Switzerland
ii © ISO 2007 – All rights reserved

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 17355 was prepared by the Consultative Committee for Space Data Systems (CCSDS) (as
CCSDS 727.0-B-3, June 2005) and was adopted (without modifications except those stated in Clause 2 of this
International Standard) by Technical Committee ISO/TC 20, Aircraft and space vehicles, Subcommittee
SC 13, Space data and information transfer systems.
This third edition cancels and replaces the second edition (ISO 17355:2004), which has been technically
revised.
INTERNATIONAL STANDARD ISO 17355:2007(E)

Space data and information transfer systems — CCSDS file
delivery protocol
1 Scope
This International Standard 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.
It 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.
The scope and field of application are furthermore detailed in subclauses 1.2 and 1.3 of the enclosed CCSDS
publication.
2 Requirements
Requirements are the technical recommendations made in the following publication (reproduced on the
following pages), which is adopted as an International Standard:
CCSDS 727.0-B-3, June 2005, CCSDS file delivery protocol (CFDP).
For the purposes of international standardization, the modifications outlined below shall apply to the specific
clauses and paragraphs of publication CCSDS 727.0-B-3.
Pages i to v
This part is information which is relevant to the CCSDS publication only.
Page 1-5
Add the following information to the reference indicated:
[1] Document CCSDS 732.0-B-1, September 2003, is equivalent to ISO 22666:2005.
[2] Document CCSDS 132.0-B-1, September 2003, is equivalent to ISO 22645:2005.
[3] Document CCSDS 133.0-B-1, September 2003, is equivalent to ISO 22646:2005.
[4] Document CCSDS 232.0-B-1, September 2003, is equivalent to ISO 22664:2005.
3 Revision of publication CCSDS 727.0-B-3
It has been agreed with the Consultative Committee for Space Data Systems that Subcommittee
ISO/TC 20/SC 13 will be consulted in the event of any revision or amendment of publication
CCSDS 727.0-B-3. To this end, NASA will act as a liaison body between CCSDS and ISO.

2 © ISO 2007 – All rights reserved

Recommendation for Space Data System Standards
CCSDS FILE DELIVERY
PROTOCOL (CFDP)
RECOMMENDED STANDARD
CCSDS 727.0-B-3
BLUE BOOK
June 2005
(Blank page)
4 © ISO 2007 – All rights reserved

CCSDS RECOMMENDED STANDARD FOR CCSDS FILE DELIVERY PROTOCOL (CFDP)
AUTHORITY
Issue: Recommended Standard, Issue 3
Date: June 2005
Location: Not Applicable
This document has been approved for publication by the Management Council of the
Consultative Committee for Space Data Systems (CCSDS) and represents the consensus
technical agreement of the participating CCSDS Member Agencies. The procedure for
review and authorization of CCSDS Recommendations is detailed in the reference [A1], and
the record of Agency participation in the authorization of this document can be obtained
from the CCSDS Secretariat at the address below.

This Recommendation is published and maintained by:

CCSDS Secretariat
Office of Space Communication (Code M-3)
National Aeronautics and Space Administration
Washington, DC 20546, USA
CCSDS 727.0-B-3 Page i June 2005
CCSDS RECOMMENDED STANDARD FOR CCSDS FILE DELIVERY PROTOCOL (CFDP)
STATEMENT OF INTENT
The Consultative Committee for Space Data Systems (CCSDS) is an organization officially
established by the management of its members. The Committee meets periodically to address
data systems problems that are common to all participants, and to formulate sound technical
solutions to these problems. Inasmuch as participation in the CCSDS is completely
voluntary, the results of Committee actions are termed Recommended Standards and are
not considered binding on any Agency.
This Recommended Standard is issued by, and represents the consensus of, the CCSDS
members. Endorsement of this Recommendation is entirely voluntary. Endorsement,
however, indicates the following understandings:
o Whenever a member establishes a CCSDS-related standard, this standard will be in
accord with the relevant Recommended Standard. Establishing such a standard
does not preclude other provisions which a member may develop.
o Whenever a member establishes a CCSDS-related standard, that member will
provide other CCSDS members with the following information:
-- The standard itself.
-- The anticipated date of initial operational capability.
-- The anticipated duration of operational service.
o Specific service arrangements shall be made via memoranda of agreement. Neither
this Recommended Standard nor any ensuing standard is a substitute for a
memorandum of agreement.
No later than five years from its date of issuance, this Recommended Standard will be
reviewed by the CCSDS to determine whether it should: (1) remain in effect without change;
(2) be changed to reflect the impact of new technologies, new requirements, or new
directions; or (3) be retired or canceled.
In those instances when a new version of a Recommended Standard is issued, existing
CCSDS-related member standards and implementations are not negated or deemed to be
non-CCSDS compatible. It is the responsibility of each member to determine when such
standards or implementations are to be modified. Each member is, however, strongly
encouraged to direct planning for its new standards and implementations towards the later
version of the Recommended Standard.
CCSDS 727.0-B-3 Page ii June 2005
6 © ISO 2007 – All rights reserved

CCSDS RECOMMENDED STANDARD FOR CCSDS FILE DELIVERY PROTOCOL (CFDP)
FOREWORD
Until relatively recently the typical storage medium for spacecraft has been the tape recorder,
a complex device offering limited data storage and data access. The use of this type of
storage has typically been limited to the recording and subsequent dump to the ground of
telemetry data. Manipulation from the ground has required significant human intervention
and used ad hoc, privately developed protocols.
The introduction of solid state mass memory providing gigabytes of storage with random
access opens up a whole new ethos of spacecraft operation where much of the routine traffic
to and from the spacecraft will be in the form of files. Furthermore, because of the random
access nature of the onboard storage medium, it becomes possible to repeat transmission of
data lost on the link and thus guarantee delivery of critical information.
To exploit the potential advantages of onboard mass memory, protocol support is required to
provide a standard means to move data to and from the onboard storage medium in the form
of files.
While the onboard storage medium has rapidly evolved, the essential constraints of space
missions remain:
– limited systems resources in terms of computational power and memory capacities;
– environmental restrictions including noisy, bandwidth limited, asymmetrical, and
interrupted communications links, some with very long propagation delay;
– varying user needs including a requirement for early access to transferred data
regardless of its quality.
In view of these constraints, it is clear that there is a need for a file delivery service capable
of transferring files to and from mass memory located in the space segment. Such a
capability must not only operate under the constraints associated with space data
communication, but it must also be applicable to the diverse range of mission configurations
ranging from single low earth orbiting spacecraft to complex networks of relays, orbiters,
and landers.
Through the process of normal evolution, it is expected that expansion, deletion, or
modification of this document may occur. This Recommendation is therefore subject to
CCSDS document management and change control procedures which are defined in reference
[A1]. Current versions of CCSDS documents are maintained at the CCSDS Web site:
http://www.ccsds.org/
Questions relating to the contents or status of this document should be addressed to the
CCSDS Secretariat at the address indicated on page i.
CCSDS 727.0-B-3 Page iii June 2005
CCSDS RECOMMENDED STANDARD FOR CCSDS FILE DELIVERY PROTOCOL (CFDP)
At time of publication, the active Member and Observer Agencies of the CCSDS were:

Member Agencies
– Agenzia Spaziale Italiana (ASI)/Italy.
– British National Space Centre (BNSC)/United Kingdom.
– Canadian Space Agency (CSA)/Canada.
– Centre National d’Etudes Spatiales (CNES)/France.
– Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR)/Germany.
– European Space Agency (ESA)/Europe.
– Federal Space Agency (Roskosmos)/Russian Federation.
– Instituto Nacional de Pesquisas Espaciais (INPE)/Brazil.
– Japan Aerospace Exploration Agency (JAXA)/Japan.
– National Aeronautics and Space Administration (NASA)/USA.

Observer Agencies
– Austrian Space Agency (ASA)/Austria.
– Belgian Federal Science Policy Office (BFSPO)/Belgium.
– Central Research Institute of Machine Building (TsNIIMash)/Russian Federation.
– Centro Tecnico Aeroespacial (CTA)/Brazil.
– Chinese Academy of Space Technology (CAST)/China.
– Commonwealth Scientific and Industrial Research Organization (CSIRO)/Australia.
– Danish Space Research Institute (DSRI)/Denmark.
– European Organization for the Exploitation of Meteorological Satellites
(EUMETSAT)/Europe.
– European Telecommunications Satellite Organization (EUTELSAT)/Europe.
– Hellenic National Space Committee (HNSC)/Greece.
– Indian Space Research Organization (ISRO)/India.
– Institute of Space Research (IKI)/Russian Federation.
– KFKI Research Institute for Particle & Nuclear Physics (KFKI)/Hungary.
– Korea Aerospace Research Institute (KARI)/Korea.
– MIKOMTEK: CSIR (CSIR)/Republic of South Africa.
– Ministry of Communications (MOC)/Israel.
– National Institute of Information and Communications Technology (NICT)/Japan.
– National Oceanic & Atmospheric Administration (NOAA)/USA.
– National Space Program Office (NSPO)/Taipei.
– Space and Upper Atmosphere Research Commission (SUPARCO)/Pakistan.
– Swedish Space Corporation (SSC)/Sweden.
– United States Geological Survey (USGS)/USA.

CCSDS 727.0-B-3 Page iv June 2005
8 © ISO 2007 – All rights reserved

CCSDS RECOMMENDED STANDARD FOR CCSDS FILE DELIVERY PROTOCOL (CFDP)
DOCUMENT CONTROL
Document Title Date Status
CCSDS CCSDS File Delivery Protocol, January Original Issue (superseded)
727.0-B-1 Issue 1 2002
CCSDS CCSDS File Delivery Protocol, October Issue 2
727.0-B-2 Issue 2 2002 (superseded)

CCSDS CCSDS File Delivery Protocol, June Current Issue:
727.0-B-3 Issue 3 2005 adds procedures for
unacknowledged-mode
handling of metadata and
file data received after the
arrival of the EOF PDU
for the same transaction.
CCSDS 727.0-B-3 Page v June 2005
CCSDS RECOMMENDED STANDARD FOR CCSDS FILE DELIVERY PROTOCOL (CFDP)
CONTENTS
Section Page
1 INTRODUCTION . 1-1

1.1 PURPOSE AND SCOPE.1-1
1.2 APPLICABILITY.1-1
1.3 CONVENTIONS AND DEFINITIONS. 1-1
1.4 REFERENCES.1-5

2 OVERVIEW. 2-1

2.1 GENERAL.2-1
2.2 ARCHITECTURE ELEMENTS.2-2
2.3 GENERAL CHARACTERISTICS.2-4
2.4 OVERVIEW OF INTERACTIONS.2-8

3 SERVICE DESCRIPTION. 3-1

3.1 SERVICES AT THE USER INTERFACE . 3-1
3.2 SUMMARY OF PRIMITIVES.3-1
3.3 SUMMARY OF PARAMETERS.3-2
3.4 SERVICES REQUIRED OF THE UNDERLYING COMMUNICATION
SYSTEM.3-6
3.5 CFDP SERVICE PRIMITIVES . 3-8

4 PROTOCOL SPECIFICATION. 4-1

4.1 CORE PROCEDURES.4-1
4.2 EXTENDED PROCEDURES.4-22

5 PDU FORMATS . 5-1

5.1 GENERAL.5-1
5.2 FILE DIRECTIVE PDUs.5-4
5.3 FILE DATA PDU.5-12
5.4 TLV PARAMETERS.5-12

6 USER OPERATIONS . 6-1

6.1 RESERVED CFDP MESSAGE FORMAT. 6-1
6.2 PROXY OPERATION.6-3
6.3 DIRECTORY OPERATIONS.6-9
6.4 REMOTE STATUS REPORT OPERATIONS. 6-11
6.5 REMOTE SUSPEND OPERATIONS . 6-14
CCSDS 727.0-B-3 Page vi June 2005
10 © ISO 2007 – All rights reserved

CCSDS RECOMMENDED STANDARD FOR CCSDS FILE DELIVERY PROTOCOL (CFDP)
CONTENTS (continued)
Section Page
6.6 REMOTE RESUME OPERATIONS.6-17
6.7 STORE AND FORWARD OVERLAY OPERATIONS . 6-19

7 CFDP SERVICE CLASSES . 7-1

7.1 DEFINED CLASSES.7-1
7.2 FUNCTIONS OF CLASS 1—UNRELIABLE TRANSFER. 7-2
7.3 FUNCTIONS OF CLASS 2—RELIABLE TRANSFER. 7-5
7.4 FUNCTIONS OF CLASS 3—UNRELIABLE TRANSFER VIA ONE OR
MORE WAYPOINTS IN SERIES. 7-8
7.5 FUNCTIONS OF CLASS 4—RELIABLE TRANSFER VIA ONE OR
MORE WAYPOINTS IN SERIES. 7-12

8 MANAGEMENT INFORMATION BASE. 8-1

8.1 GENERAL.8-1
8.2 LOCAL ENTITY CONFIGURATION INFORMATION. 8-1
8.3 REMOTE ENTITY CONFIGURATION INFORMATION. 8-2

ANNEX A INFORMATIVE REFERENCES. A-1
ANNEX B ACRONYMS. B-1
ANNEX C EXAMPLE OF CHECKSUM CALCULATION. C-1

Figure
1-1 Bit Numbering Convention. 1-2
1-2 Octet Convention . 1-2
2-1 Architectural Elements of the File Delivery Protocol . 2-2
2-2 CFDP Procedures. 2-5
2-3 Copy Operations, Sequence of Events. 2-9
2-4 Put Operations, Sequence of Events. 2-10
2-5 File Custody Transfer Operations, Sequence of Events . 2-10
2-6 Proxy Put Operations, Sequence of Events . 2-11
6-1 SFO Operations . 6-20

CCSDS 727.0-B-3 Page vii June 2005
CCSDS RECOMMENDED STANDARD FOR CCSDS FILE DELIVERY PROTOCOL (CFDP)
CONTENTS (continued)
Table Page
5-1 Fixed PDU Header Fields. 5-1
5-2 LV Object Format. 5-2
5-3 TLV Object Format . 5-3
5-4 File Directive Codes . 5-4
5-5 Condition Codes.5-5
5-6 End-of-File PDU Contents.5-6
5-7 Finished PDU Contents . 5-7
5-8 ACK PDU Contents.5-9
5-9 Metadata PDU Contents.5-10
5-10 NAK PDU Contents.5-11
5-11 Segment Request Form. 5-11
5-12 Prompt PDU Contents . 5-11
5-13 Keep Alive PDU Contents. 5-12
5-14 File Data PDU Contents . 5-12
5-15 Filestore Request TLV Contents . 5-12
5-16 Filestore Request TLV Action Codes. 5-13
5-17 Filestore Response TLV Contents . 5-13
5-18 Filestore Response Status Codes . 5-14
5-19 Fault Handler Override Field Encoding . 5-15
6-1 Reserved CFDP Message Header. 6-1
6-2 Originating Transaction ID Message. 6-2
6-3 Proxy Operations Message Types . 6-3
6-4 Proxy Put Request Message. 6-4
6-5 Proxy Message to User Message . 6-4
6-6 Proxy Filestore Request Message. 6-5
6-7 Proxy Fault Handler Override Message . 6-5
6-8 Proxy Transmission Mode Message. 6-5
6-9 Proxy Flow Label Message . 6-6
6-10 Proxy Segmentation Control Message. 6-6
6-11 Proxy Put Finished Message. 6-7
6-12 Proxy Filestore Response Message . 6-8
6-13 Directory Operations Message Types. 6-9
6-14 Directory Listing Request Message. 6-9
6-15 Directory Listing Response Message . 6-10
6-16 Remote Status Report Operations Message Types. 6-11
6-17 Remote Status Report Request Message . 6-12
6-18 Remote Status Report Response Message. 6-13
6-19 Remote Suspend Operations Message Types . 6-14
6-20 Remote Suspend Request Message . 6-15
6-21 Remote Suspend Response Message . 6-16
6-22 Remote Resume Operations Message Types. 6-17
CCSDS 727.0-B-3 Page viii June 2005
12 © ISO 2007 – All rights reserved

CCSDS RECOMMENDED STANDARD FOR CCSDS FILE DELIVERY PROTOCOL (CFDP)
CONTENTS (continued)
Table Page
6-23 Remote Resume Request Message . 6-18
6-24 Remote Resume Response Message. 6-19
6-25 SFO Message Types.6-21
6-26 SFO Request Message . 6-23
6-27 SFO Message to User Message . 6-24
6-28 SFO Filestore Request Message . 6-24
6-29 SFO Fault Handler Override Message. 6-24
6-30 SFO Flow Label Message. 6-25
6-31 SFO Report Message.6-28
6-32 Proxy Filestore Response Message . 6-29
7-1 Class 1 Source Procedures. 7-2
7-2 Class 1 Destination Procedures . 7-3
7-3 Class 2 Source Procedures. 7-5
7-4 Class 2 Destination Procedures . 7-6
7-5 Class 3 Source Procedures. 7-8
7-6 Class 3 Waypoint Procedures . 7-9
7-7 Class 4 Destination Procedures . 7-10
7-8 Class 4 Source Procedures. 7-12
7-9 Class 4 Waypoint Procedures . 7-13
7-10 Class 4 Destination Procedures . 7-15
8-1 Local Entity Configuration Information. 8-1
8-2 Remote Entity Configuration Information. 8-2

CCSDS 727.0-B-3 Page ix June 2005
(Blank page)
14 © ISO 2007 – All rights reserved

CCSDS RECOMMENDED STANDARD FOR CCSDS FILE DELIVERY PROTOCOL (CFDP)
1 INTRODUCTION
1.1 PURPOSE AND SCOPE
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.
1.2 APPLICABILITY
This Recommendation specifies a protocol and associated services that are applicable to
space missions with continuous duplex contact, intermittent duplex contact, asymmetrical
time-disjunct contact, and simplex contact.
1.3 CONVENTIONS AND DEFINITIONS
1.3.1 BIT NUMBERING CONVENTION AND NOMENCLATURE
In this document, the following convention is used to identify each bit in an N-bit field. The
first bit in the field to be transmitted (i.e., the most left justified when drawing a figure) is
defined to be ‘Bit 0’; the following bit is defined to be ‘Bit 1’ and so on up to ‘Bit N–1’.
When the field is used to express a binary value (such as a counter), the Most Significant Bit
(MSB) shall be the first transmitted bit of the field, i.e., ‘Bit 0’.
CCSDS 727.0-B-3 Page 1-1 June 2005
CCSDS RECOMMENDED STANDARD FOR CCSDS FILE DELIVERY PROTOCOL (CFDP)
BIT 0 BIT N-1
N-BIT DATA FIELD
FIRST BIT TRANSMITTED = MSB
Figure 1-1: Bit Numbering Convention
In accordance with modern data communications practice, spacecraft data fields are often
grouped into 8-bit ‘words’ which conform to the above convention. Throughout this
Recommendation, the following nomenclature is used to describe this grouping:
8-BIT WORD = ‘OCTET’
Figure 1-2: Octet Convention
By CCSDS convention, all ‘spare’ bits shall be permanently set to value ‘zero’.
1.3.2 ORGANIZATION OF THE RECOMMENDATION
This Recommendation is organized as follows:
– Section 2 provides an overview of the protocol, its intended use, and a description of
the main interactions involved in a file transfer.
– Section 3 defines the services provided by the protocol along with the associated
primitives and parameters.
– Section 4 is the main body of the protocol specification.
– Section 5 defines the formats for the PDUs.
– Section 6 defines proxy and directory operations.
– Section 7 defines a number of classes of operation designed to meet the most typical
operating scenarios.
– Section 8 describes the Management Information Base (MIB).
– Annex A provides a list of informative references.
– Annex B provides a list of acronyms and definitions.
– Annex C provides an example of file checksum calculation.
CCSDS 727.0-B-3 Page 1-2 June 2005
16 © ISO 2007 – All rights reserved

CCSDS RECOMMENDED STANDARD FOR CCSDS FILE DELIVERY PROTOCOL (CFDP)
1.3.3 DEFINITIONS
1.3.3.1 Definitions from Open Systems Interconnection (OSI) Basic Reference Model
This Recommendation makes use of a number of terms defined in reference [5]. The use of
those terms in this Recommendation shall be understood in a generic sense, i.e., in the sense
that those terms are generally applicable to any of a variety of technologies that provide for
the exchange of information between real systems. Those terms are:
– entity;
– Protocol Data Unit (PDU);
– service;
– Service Access Point (SAP);
– Service Data Unit (SDU).
1.3.3.2 Definitions from OSI Service Definition Conventions
This Recommendation makes use of a number of terms defined in reference [6]. The use of
those terms in this Recommendation shall be understood in a generic sense, i.e., in the sense
that those terms are generally applicable to any of a variety of technologies that provide for
the exchange of information between real systems. Those terms are:
– Indication;
– Primitive;
– Request;
– Response.
1.3.3.3 Terms Defined in This Recommendation
Within the context of this document the following definitions apply:
A CFDP protocol entity (or CFDP entity) is a functioning instance of an implementation of
the CFDP protocol, roughly analogous to an Internet protocol ‘host’.
The functional concatenation of a file and related metadata transmitted between two CFDP
entities is termed a File Delivery Unit (FDU); in this context the term ‘metadata’ is used to
refer to any data exchanged between CFDP protocol entities in addition to file content,
typically either additional application data (such as a ‘message to user’) or data that aid the
recipient entity in effectively utilizing the file (such as file name). Note that an FDU may
consist of metadata only. Note also that the term ‘file’ is frequently used in this specification
as an abbreviation for ‘file delivery unit’; only when the context clearly indicates that only
CCSDS 727.0-B-3 Page 1-3 June 2005
CCSDS RECOMMENDED STANDARD FOR CCSDS FILE DELIVERY PROTOCOL (CFDP)
actual files are being discussed, for example, in the explanation of the segmentation control
parameter or the source and destination file name parameters of the CFDP Service
Definition, should the term ‘file’ not be read as ‘file delivery unit’.
The individual, bounded, self-identifying items of CFDP data transmitted between CFDP
entities are termed CFDP Protocol Data Units or CFDP PDUs. Unless otherwise noted, in
this document the term ‘PDU’ always means ‘CFDP PDU’. CFDP PDUs are of two general
types: File Data PDUs convey the contents of the files being delivered, while File Directive
PDUs convey only metadata and other non-file information that advances the operation of
the protocol.
A transaction is the end-to-end transmission of a single FDU between two CFDP entities. A
single transaction normally entails the transmission and reception of multiple PDUs. Each
transaction is identified by a unique transaction ID; all elements of any single FDU, both file
content and metadata, are tagged with the same CFDP transaction ID.
Any single end-to-end file transmission task has two associated entities: the entity that has
the file at the beginning of the task (the source) and the entity that has a copy of the file when
the task is completed (the destination).
Each end-to-end file transmission task comprises one or more point-to-point file copy
operations. A file copy operation has two associated entities: the entity that has a copy of
the file at the beginning of the operation (the sender or sending entity) and the entity that has
a copy of the file when the operation is completed (the receiver or receiving entity). In the
simplest case, the only sender of the file is the source and the only receiver is the destination.
In more complex cases (the general case) there are additional ‘waypoint’ entities that receive
and send copies of the file; the source is the first sender and the destination is the last
receiver.
Filestore is a generic term referring to the medium used to store files.
The term offset is used in a familiar way: the offset of a given octet of file data is the number
of data octets that precede this octet in the file.
The file delivery progress represented by a given file data PDU is the sum of the offset of the
PDU’s file data content (the offset of the content’s first octet) and the length of that file data
content.
The transmission progress for a given transaction, delivering some file, is the maximum
progress value over all file data PDUs sent so far in the course of this transaction.
Similarly the reception progress for a given transaction is the maximum progress value over
all file data PDUs received so far in the course of this transaction. If and only if no data are
lost in transmission, reception progress is equal to the number of file data octets received.
The term CFDP user is used to refer to the software task that causes the local entity to
initiate a transaction or the software task that is notified by the local entity of the progress or
CCSDS 727.0-B-3 Page 1-4 June 2005
18 © ISO 2007 – All rights reserved

CCSDS RECOMMENDED STANDARD FOR CCSDS FILE DELIVERY PROTOCOL (CFDP)
completion of a transaction. The CFDP user local to the source entity is referred to as the
source CFDP user. The CFDP user local to the destination entity is referred to as the
destination CFDP user. The CFDP user may be operated by a human or by another software
process. Unless otherwise noted the term user always refers to the CFDP user.
1.4 REFERENCES
The following documents contain provisions which, through reference in this text, constitute
provisions of this Recommendation. At the time of publication, the editions indicated were
valid. All documents are subject to revision, and users of this Recommendation are
encouraged to investigate the possibility of applying the most recent editions of the
documents indicated below. The CCSDS Secretariat maintains a register of currently valid
CCSDS Recommendations.
[1] AOS Space Data Link Protocol. Recommendation for Space Data System Standards,
CCSDS 732.0-B-1. Blue Book. Issue 1. Washington, D.C.: CCSDS, September 2003.
[2] TM Space Data Link Protocol. Recommendation for Space Data System Standards,
CCSDS 132.0-B-1. Blue Book. Issue 1. Washington, D.C.: CCSDS, September 2003.
[3] Space Packet Protocol. Recommendation for Space Data System Standards, CCSDS
133.0-B-1. Blue Book. Issue 1. Washington, D.C.: CCSDS, September 2003.
[4] TC Space Data Link Protocol. Recommendation for Space Data System Standards,
CCSDS 232.0-B-1. Blue Book. Issue 1. Washington, D.C.: CCSDS, September 2003.
[5] Information Technology—Open Systems Interconnection—Basic Reference Model: The
Basic Model. International Standard, ISO/IEC 7498-1:1994. Geneva: ISO, 1994.
[6] Information Technology—Open Systems Interconnection—Basic Reference Model—
Conventions for the Definition of OSI Services. International Standard, ISO/IEC
10731:1994. Geneva: ISO, 1994.
The latest issues of CCSDS documents may be obtained from the CCSDS Secretariat at the
address indicated on page i.
CCSDS 727.0-B-3 Page 1-5 June 2005
(Blank page)
20 © ISO 2007 – All rights reserved

CCSDS RECOMMENDED STANDARD FOR CCSDS FILE DELIVERY PROTOCOL (CFDP)
2 OVERVIEW
2.1 GENERAL
This Recommendation defines a protocol suitable for the transmission of files to and from
spacecraft data storage. In addition to the purely file delivery related functions, the protocol
also includes file management services to allow control over the storage medium.
The protocol is capable of operating in a wide variety of mission configurations, from
relatively simple low earth orbit spacecraft to complex arrangements of orbiters and landers
supported by multiple ground facilities and transmission links. In its simplest form, the
protocol provides a Core file delivery capability operating across a single link. For more
complex mission scenarios, the protocol offers Extended operation providing store-and-
forward functionality across an arbitrary network containing multiple links with disparate
availability.
The protocol is independent of the technology used to implement data storage and requires
only a few fundamental filestore capabilities in order to operate. It assumes two filestores,
one within the spacecraft and one on the ground, and operates by copying data between the
two filestore locations.
The protocol makes no assumptions about the information being transferred and can be
utilized for a wide range of applications involving the loading, dumping, and control of
spacecraft storage.
The protocol has been specifically designed to minimize the resources required for operation.
It is also scaleable, so that only those elements required to fulfill the selected options are
required to be implemented.
Although the protocol can operate over a wide range of underlying communication services,
this Recommendation assumes the use of CCSDS packet services as defined in references [1]
through [4].
CCSDS 727.0-B-3 Page 2-1 June 2005
CCSDS RECOMMENDED STANDARD FOR CCSDS FILE DELIVERY PROTOCOL (CFDP)
2.2 ARCHITECTURE ELEMENTS
2.2.1 GENERAL
The architectural elements involved in the file delivery protocol are depicted in figure 2-1
and described below.
User
Filestore
Protocol Entity MIB
Communication Sy
...