ISO 22663:2007

INTERNATIONAL ISO
STANDARD 22663
Second edition
2007-10-15
Space data and information transfer
systems — Proximity-1 space link
protocol — Data link layer
Systèmes de transfert des informations et données spatiales —
Protocole pour liaisons spatiales de proximité 1 — Couche de liaisons
de données
Reference number
©
ISO 2007
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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 22663 was prepared by Technical Committee ISO/TC 20, Aircraft and space vehicles, Subcommittee
SC 13, Space data and information transfer systems.
This second edition cancels and replaces the first edition (ISO 22663:2006), which has been technically
revised.
ISO 22663 was prepared by the Consultative Committee for Space Data Systems (CCSDS) (as
CCSDS 211.0-B-4, July 2006) 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.

INTERNATIONAL STANDARD ISO 22663:2007(E)

Space data and information transfer systems — Proximity-1
space link protocol — Data link layer
1 Scope
This International Standard defines the Proximity-1 space link protocol data link layer (framing, media access,
data services, and input-output sublayers). It specifies the protocol data units, framing, media access control,
expedited and sequenced controlled data transfer, timing service, i/o control, as well as the procedures for
establishing and terminating a session between a caller and responder. The coding and synchronization
sublayer is defined in ISO 21459. The physical layer is defined in ISO 21460.
This International Standard does not specify
a) individual implementations or products;
b) implementation of service interfaces within real systems;
c) the methods or technologies required to perform the procedures; or
d) the management activities required to configure and control the protocol.
The scope and field of application are furthermore detailed in subclause 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 211.0-B-4, July 2006, Proximity-1 space link protocol — Data link layer.
For the purposes of international standardization, the modifications outlined below shall apply to the specific
clauses and paragraphs of publication CCSDS 211.0-B-4.
Pages i to v
This part is information which is relevant to the CCSDS publication only.
Page 1-6
Add the following information to the reference indicated:
[2] Document CCSDS 232.1-B-1, September 2003, is equivalent to ISO 22667:2005.
[3] Document CCSDS 232.0-B-1, September 2003, is equivalent to ISO 22664:2005.
[4] Document CCSDS 132.0-B-1, September 2003, is equivalent to ISO 22645:2005.
[5] Document CCSDS 131.0-B-1, September 2003, is equivalent to ISO 22641:2005.
Page 1-7
Add the following information to the reference indicated:
[7] Document CCSDS 301.0-B-3, January 2002, is equivalent to ISO 11104:2003.
[8] Document CCSDS 211.2-B-1, April 2003, is equivalent to ISO 21459:2006.
[9] Document CCSDS 211.1-B-3, March 2006, is equivalent to ISO 21460:2007.
3 Revision of publication CCSDS 211.0-B-4
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 211.0-B-4.
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
PROXIMITY-1 SPACE LINK PROTOCOL—
DATA LINK LAYER
RECOMMENDED STANDARD
CCSDS 211.0-B-4
BLUE BOOK
July 2006
Blank page
4 © ISO 2007 – All rights reserved

CCSDS RECOMMENDED STANDARD FOR PROXIMITY-1 SPACE DATA LINK PROTOCOL
AUTHORITY
Issue: Blue Book, Issue 4
Date: July 2006
Location: Washington, DC, USA
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 Procedures Manual for
the Consultative Committee for Space Data Systems, 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 211.0-B-4 Page i July 2006
CCSDS RECOMMENDED STANDARD FOR PROXIMITY-1 SPACE DATA LINK PROTOCOL
STATEMENT OF INTENT
The Consultative Committee for Space Data Systems (CCSDS) is an organization officially
established by the management of member space Agencies. 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
Recommendations and are not considered binding on any Agency.
This Recommendation is issued by, and represents the consensus of, the CCSDS Plenary
body. Agency endorsement of this Recommendation is entirely voluntary. Endorsement,
however, indicates the following understandings:
– Whenever an Agency establishes a CCSDS-related standard, this standard will be
in accord with the relevant Recommendation. Establishing such a standard does
not preclude other provisions which an Agency may develop.
– Whenever an Agency establishes a CCSDS-related standard, the Agency will provide
other CCSDS member Agencies with the following information:
• The standard itself.
• The anticipated date of initial operational capability.
• The anticipated duration of operational service.
– Specific service arrangements are made via memoranda of agreement. Neither this
Recommendation nor any ensuing standard is a substitute for a memorandum of
agreement.
No later than five years from its date of issuance, this Recommendation 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 Recommendation is issued, existing CCSDS-
related Agency standards and implementations are not negated or deemed to be non-CCSDS
compatible. It is the responsibility of each Agency to determine when such standards or
implementations are to be modified. Each Agency is, however, strongly encouraged to direct
planning for its new standards and implementations towards the later version of the
Recommendation.
CCSDS 211.0-B-4 Page ii July 2006
6 © ISO 2007 – All rights reserved

CCSDS RECOMMENDED STANDARD FOR PROXIMITY-1 SPACE DATA LINK PROTOCOL
FOREWORD
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 the
Procedures Manual for the Consultative Committee for Space Data Systems. 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 211.0-B-4 Page iii July 2006
CCSDS RECOMMENDED STANDARD FOR PROXIMITY-1 SPACE DATA LINK PROTOCOL
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 Organization (NSPO)/Taipei.
– Space and Upper Atmosphere Research Commission (SUPARCO)/Pakistan.
– Swedish Space Corporation (SSC)/Sweden.
– United States Geological Survey (USGS)/USA.
CCSDS 211.0-B-4 Page iv July 2006
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CCSDS RECOMMENDED STANDARD FOR PROXIMITY-1 SPACE DATA LINK PROTOCOL
DOCUMENT CONTROL
Document Title and Issue Date Status

CCSDS Proximity-1 Space Link Protocol October Superseded
211.0-B-1 2002
CCSDS Proximity-1 Space Link Protocol— April Superseded
211.0-B-2 Data Link Layer 2003

CCSDS Proximity-1 Space Link Protocol— May Superseded
211.0-B-3 Data Link Layer 2004

CCSDS Proximity-1 Space Link Protocol— July Current Issue:
211.0-B-4 Data Link Layer, Recommended 2006 – modifies rules for
frame selection
Standard, Issue 4
prioritization,
– adds CARRIER ONLY
RECEIVED condition
to state tables and to
annex D Notifications
to Vehicle Controller,
– clarifies some
terminology.
NOTE – Changes from the previous issue are flagged by change bars in the inside margin.

CCSDS 211.0-B-4 Page v July 2006
CCSDS RECOMMENDED STANDARD FOR PROXIMITY-1 SPACE DATA LINK PROTOCOL
CONTENTS
Section Page
1 INTRODUCTION. 1-1

1.1 PURPOSE.1-1
1.2 SCOPE.1-1
1.3 APPLICABILITY.1-1
1.4 RATIONALE.1-2
1.5 CONVENTIONS AND DEFINITIONS.1-2
1.6 REFERENCES.1-6

2 OVERVIEW. 2-1

2.1 CONCEPT OF PROXIMITY-1.2-1
2.2 OVERVIEW OF SERVICES.2-6

3 PROTOCOL DATA UNITS . 3-1

3.1 CONTEXT OF THE VERSION-3 TRANSFER FRAME. 3-1
3.2 VERSION-3 TRANSFER FRAME. 3-1

4 DATA LINK LAYER . 4-1

4.1 FRAME SUBLAYER.4-1
4.2 MEDIUM ACCESS CONTROL (MAC) SUBLAYER. 4-2
4.3 DATA SERVICES SUBLAYER.4-5
4.4 I/O INTERFACE SUBLAYER.4-8

5 PROXIMITY-1 TIMING SERVICES. 5-1

5.1 COUPLED NON-COHERENT PROXIMITY TIMING SERVICE . 5-1
5.2 PROXIMITY TIME CORRELATION.5-1

6 DATA SERVICES OPERATIONS. 6-1

6.1 OVERVIEW.6-1
6.2 PROXIMITY-1 STATE TABLES . 6-1
6.3 ELEMENTS AND EVENTS THAT AFFECT STATE STATUS . 6-13
6.4 STATE TRANSITION TABLES AND DIAGRAMS. 6-18
6.5 SIMPLEX OPERATIONS.6-28
6.6 INTERFACES WITH THE PHYSICAL LAYER . 6-29
6.7 SENDING OPERATIONS.6-29
6.8 RECEIVING OPERATIONS.6-31

CCSDS 211.0-B-4 Page vi July 2006
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CCSDS RECOMMENDED STANDARD FOR PROXIMITY-1 SPACE DATA LINK PROTOCOL
CONTENTS (continued)
Section Page
7 COMMUNICATION OPERATIONS PROCEDURE FOR PROXIMITY LINKS
(COP-P). 7-1

7.1 SENDING PROCEDURES (FOP-P).7-1
7.2 RECEIVING PROCEDURES (FARM-P) . 7-7

8 INPUT/OUTPUT (I/O) SUBLAYER OPERATIONS. 8-1

8.1 SENDING OPERATIONS.8-1
8.2 RECEIVING OPERATIONS.8-2

ANNEX A VARIABLE-LENGTH SUPERVISORY PROTOCOL DATA FIELD
FORMATS (Normative). A-1
ANNEX B MANAGEMENT INFORMATION BASE (MIB) PARAMETERS
(Normative). B-1
ANNEX C NASA MARS SURVEYOR PROJECT 2001 ODYSSEY ORBITER
PROXIMITY SPACE LINK CAPABILITIES (Informative) . C-1
ANNEX D NOTIFICATIONS TO VEHICLE CONTROLLER (Normative) . D-1
ANNEX E ABBREVIATIONS AND ACRONYMS (Informative) . E-1
ANNEX F INFORMATIVE REFERENCES (Informative) .F-1

Figure
1-1 Bit Numbering Convention. 1-6
2-1 Proximity-1 Layered Protocol Model. 2-4
3-1 Proximity-1 Protocol Data Unit Context Diagram . 3-1
3-2 Version-3 Transfer Frame. 3-2
3-3 Transfer Frame Header . 3-3
3-4 Proximity-1 Transfer Frame Data Field Structure. 3-7
3-5 Proximity Link Control Word Fields. 3-12
4-1 COP-P Process. 4-7
5-1 Proximity Time Tagging and Time Correlation . 5-3
5-2 Transferring Time to a Remote Asset. 5-4
6-1 Full Duplex State Transition Diagram. 6-19
6-2 Half Duplex State Transition Diagram . 6-23
6-3 Simplex Operations. 6-28
A-1 Type 1 SPDU Data Field Contents. A-2
A-2 SET TRANSMITTER PARAMETERS Directive. A-3
A-3 SET CONTROL PARAMETERS Directive . A-6
A-4 SET RECEIVER PARAMETERS Directive . A-8
CCSDS 211.0-B-4 Page vii July 2006
CCSDS RECOMMENDED STANDARD FOR PROXIMITY-1 SPACE DATA LINK PROTOCOL
CONTENTS (continued)
Figure Page
A-5 SET V(R) Directive . A-10
A-6 Report Request. A-11
A-7 Proximity Link Control Word . A-13
A-8 SET PL EXTENSIONS. A-15
A-9 Report Source Spacecraft ID . A-19
A-10 Type 2 SPDU Data Field Contents. A-20
C-1 NASA Mars Surveyor Project 2001 Odyssey SET TRANSMITTER
PARAMETERS Directive.C-2
C-2 NASA Mars Surveyor Project 2001 Odyssey SET RECEIVER
PARAMETERS Directive.C-4
C-3 Proximity Link Control Word Fields.C-7

Table
3-1 U-Frame Data Field Construction Rules . 3-4
3-2 Segment Header Sequence Flags. 3-8
3-3 Fixed-Length Supervisory Protocol Data Unit . 3-11
3-4 Variable-Length Supervisory Protocol Data Unit . 3-14
6-1 Proximity-1 Data Services Operations Roadmap . 6-1
6-2 States Independent of the DUPLEX Variable . 6-2
6-3 States When DUPLEX = Full. 6-3
6-4 States When DUPLEX = Half . 6-5
6-5 States When DUPLEX = Simplex (receive or transmit) . 6-6
6-6 Proximity-1 Control Variable Initialization Table. 6-18
6-7 Full Duplex Session Establishment/Data Services State Transition Table. 6-20
6-8 Full Duplex Communication Change State Table . 6-21
6-9 Full Duplex Session Termination State Table . 6-22
6-10 Half Duplex Session Establishment and Data Services. 6-23
6-11 Half Duplex Communication Change State Table . 6-26
6-12 Half Duplex Session Termination State Table . 6-27
6-13 Simplex State Transition Table. 6-28
6-14 Data Source Selection for Output Bit Stream with TRANSMIT = on and
MODULATION = on . 6-30

CCSDS 211.0-B-4 Page viii July 2006
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CCSDS RECOMMENDED STANDARD FOR PROXIMITY-1 SPACE DATA LINK PROTOCOL
1 INTRODUCTION
1.1 PURPOSE
The purpose of this document is to provide a Recommendation for Space Data System
Standards in the area of Proximity space links. Proximity space links are defined to be short-
range, bi-directional, fixed or mobile radio links, generally used to communicate among
probes, landers, rovers, orbiting constellations, and orbiting relays. These links are
characterized by short time delays, moderate (not weak) signals, and short, independent
sessions.
1.2 SCOPE
This Recommendation defines the Data Link layer (framing, media access, data services, and
input-output sublayers). The specifications for the protocol data units, framing, media access
control, expedited and sequenced controlled data transfer, timing service, i/o control as well
as the procedures for establishing and terminating a session between a caller and responder
are defined in this document. The Coding and Synchronization sublayer is defined in the
separate CCSDS recommendation entitled, Proximity-1 Space Link Protocol—Coding and
Synchronization Sublayer; see reference [8]. The Physical layer is defined in the separate
CCSDS recommendation entitled, Proximity-1 Space Link Protocol—Physical Layer; see
reference [9].
This Recommendation does not specify a) individual implementations or products, b)
implementation of service interfaces within real systems, c) the methods or technologies
required to perform the procedures, or d) the management activities required to configure and
control the protocol.
1.3 APPLICABILITY
This Recommendation applies to the creation of Agency standards and to future data
communications over space links between CCSDS Agencies in cross-support situations. It
applies also to internal Agency links where no cross-support is required. It includes
specification of the services and protocols for inter-Agency cross support. It is neither a
specification of, nor a design for, systems that may be implemented for existing or future
missions.
The Recommendation specified in this document is to be invoked through the normal
standards programs of each CCSDS Agency and is applicable to those missions for which
cross support based on capabilities described in this Recommendation is anticipated. Where
mandatory capabilities are clearly indicated in sections of the Recommendation, they must be
implemented when this document is used as a basis for cross support. Where options are
allowed or implied, implementation of these options is subject to specific bilateral cross
support agreements between the Agencies involved.
CCSDS 211.0-B-4 Page 1-1 July 2006
CCSDS RECOMMENDED STANDARD FOR PROXIMITY-1 SPACE DATA LINK PROTOCOL
1.4 RATIONALE
The CCSDS believes it is important to document the rationale underlying the
recommendations chosen, so that future evaluations of proposed changes or improvements
will not lose sight of previous decisions. Concept and rationale behind the decisions that
formed the basis for Proximity-1 will be documented in the CCSDS Proximity-1 Space Link
Green Book, which is under development.
1.5 CONVENTIONS AND DEFINITIONS
1.5.1 DEFINITIONS
1.5.1.1 Definitions from the Open Systems Interconnection (OSI) Basic Reference
Model
This Recommendation makes use of a number of terms defined in reference [1]. 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 as follows:
a) connection;
b) Data Link layer;
c) entity;
d) physical layer;
e) protocol control information;
f) Protocol Data Unit (PDU);
g) real system;
h) segmenting;
i) service;
j) Service Access Point (SAP);
k) SAP address;
l) Service Data Unit (SDU).
1.5.1.2 Terms Defined in This Recommendation
For the purposes of this Recommendation, the following definitions also apply. Many other
terms that pertain to specific items are defined in the appropriate sections.
CCSDS 211.0-B-4 Page 1-2 July 2006
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CCSDS RECOMMENDED STANDARD FOR PROXIMITY-1 SPACE DATA LINK PROTOCOL
asynchronous channel: a data channel where the symbol data are modulated onto the
channel only for the period of the message. The message must be preceded by an
acquisition sequence to achieve symbol synchronization. Bit synchronization must be
reacquired on every message. A hailing channel is an example of an asynchronous
channel.
asynchronous data link: a data link consisting of a sequence of variable-length Proximity
Link Transmission Units (PLTUs), which are not necessarily concatenated. Two
types of asynchronous data links are:
1) Asynchronous Data Link over an Asynchronous Channel
Hailing provides an example of an asynchronous data link over an asynchronous
channel. An important issue is resynchronization between successive hails. Idle
is provided for the reacquisition process.
2) Asynchronous Data Link over a Synchronous Channel
Data service provides an example of an asynchronous data link over a
synchronous channel. Once the link is established via hailing, communication
transitions to a synchronous channel and maintains the link in this configuration
until the session is interrupted or ends. If the physical layer does not receive data
from the data link layer, it provides idle to maintain a synchronous channel.
caller and responder: A caller transceiver is the initiator of the link establishment process
and manager of negotiation (if required) of the session. A responder transceiver
typically receives link establishment parameters from the caller. The caller initiates
communication between itself and a responder on a pre-arranged communications
channel with predefined controlling parameters. As necessary, the caller and
responder may negotiate the controlling parameters for the session (at some level
between fully controlled and completely adaptive).
COP-P: Communication Operations Procedure for Proximity links (COP-P). The COP-P
includes both the FARM-P and FOP-P of the caller and responder unit.
FARM-P: Frame Acceptance and Reporting Mechanism for Proximity links, for Sequence
Controlled service carried out within the receiver in the Proximity-1 link.
FOP-P: Frame Operation Procedure for Proximity links for ordering the output frames for
Sequence Controlled service carried out in the transmitter in the Proximity-1 link.
forward link: that portion of a Proximity space link in which the caller transmits and the
responder receives (typically a command link).
hailing: the persistent activity used to establish a Proximity link by a caller to a responder in
either full or half duplex. It does not apply to simplex operations.
CCSDS 211.0-B-4 Page 1-3 July 2006
CCSDS RECOMMENDED STANDARD FOR PROXIMITY-1 SPACE DATA LINK PROTOCOL
hailing channel: the forward and return frequency pairs that a caller and responder use to
establish physical link communications.
mission phase: a mission period during which specified communications characteristics are
fixed. The transition between two consecutive mission phases may cause an
interruption of the communications services.
PCID: The Physical Channel ID is used to distinguish between Proximity Link Control
Words (PLCWs) received on a single receive channel in support of two independent
transmitting channels.
P-frame: a Version-3 Transfer Frame that contains only self-identified and self-delimited
supervisory protocol data units; compare U-frame.
physical channel: The RF channel upon which the stream of bits is transferred over a space
link in a single direction.
PLCW: Proximity Link Control Word. The PLCW is the protocol data unit for reporting
Sequence Controlled service status via the return link from the responder back to the
caller.
PLTU: The Proximity Link Transmission Unit is the data unit composed of the Attached
Synchronization Marker, the Version-3 Transfer Frame, and the attached Cyclic
Redundancy Check (CRC)-32.
Protocol object: directives, PLCWs, or status reports contained within an SPDU.
Proximity link: short-range, bi-directional, fixed or mobile radio links, generally used to
communicate among probes, landers, rovers, orbiting constellations, and orbiting
relays. These links are characterized by short time delays, moderate (not weak)
signals, and short, independent sessions.
pseudo packet ID: the temporary packet ID assigned by the protocol to a user’s packet
within the segmentation process.
resynchronization (COP-P): process in which sender and receiver nodes readjust their
sequence controlled frame numbers via the SET V(R) activity.
return link: that portion of a Proximity space link in which the responder transmits and the
caller receives (typically a telemetry link).
Routing ID: identifier that uniquely identifies a user’s packet through the segmentation
process. It consists of a PCID, Port ID, and pseudo packet ID.
Sent queue (Sent Frame queue): contains sequence controlled frames that have been sent
but not yet acknowledged by the receiver.
CCSDS 211.0-B-4 Page 1-4 July 2006
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CCSDS RECOMMENDED STANDARD FOR PROXIMITY-1 SPACE DATA LINK PROTOCOL
session: a continuous dialog between two communicating Proximity link transceivers. It
consists of three distinct operational phases: session establishment, data services, and
session termination.
space link: a communications link between transmitting and receiving entities, at least one of
which is in space.
SPDU: Supervisory Protocol Data Unit. Used by the local transceiver to either control or
report status to the remote partnered transceiver. Consists of one or more directives,
reports, or PLCWs.
synchronous channel: a data channel where the symbol data are continuously modulated
onto the channel at a fixed data rate. If the data link fails to provide frames (data or
fill), it is the responsibility of the physical layer to provide the continuous bit stream.
U-frame: a Version-3 Transfer Frame that contains user data information; compare P-frame.
vehicle controller: the entity (e.g., spacecraft control computer) which receives the
notifications defined in annex E and potentially acts upon them.
Version-3 Transfer Frame: a Proximity-1 transfer frame.
1.5.2 NOMENCLATURE
The following conventions apply throughout this Recommendation:
a) the words ‘shall’ and ‘must’ imply a binding and verifiable specification;
b) the word ‘should’ implies an optional, but desirable, specification;
c) the word ‘may’ implies an optional specification;
d) the words ‘is’, ‘are’, and ‘will’ imply statements of fact.
1.5.3 CONVENTIONS
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’, as shown in figure 1-1.
CCSDS 211.0-B-4 Page 1-5 July 2006
CCSDS RECOMMENDED STANDARD FOR PROXIMITY-1 SPACE DATA LINK PROTOCOL
BIT 0 BIT N-1
N-BIT DATA FIELD
FIRST BIT TRANSMITTED = MSB
Figure 1-1: Bit Numbering Convention
In accordance with standard data-communications practice, data fields are often grouped into
8-bit ‘words’ that conform to the above convention. Throughout this Recommendation, such
an 8-bit word is called an ‘octet’.
The numbering for octets within a data structure begins with zero. Octet zero is the first octet
to be transmitted.
By CCSDS convention, all ‘spare’ bits shall be permanently set to value ‘zero’.
Throughout this Recommendation, directive, parameter, variable, and signal names are
presented with all upper-case characters; data-field and MIB-parameter names are presented
with initial capitalization; values and state names are presented with predominantly lower-
case characters, and are italicized.
1.6 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] Information Technology—Open Systems Interconnection—Basic Reference Model:
The Basic Model. International Standard, ISO/IEC 7498-1. 2nd ed. Geneva: ISO,
1994.
[2] Communications Operation Procedure-1. Recommendation for Space Data System
Standards, CCSDS 232.1-B-1. Blue Book. Issue 1. CCSDS, September 2003.
[3] TC Space Data Link Protocol. Recommendation for Space Data Systems Standards,
CCSDS 232.0-B-1. Blue Book. Issue 1. CCSDS, September 2003.
[4] TM Space Data Link Protocol. Recommendation for Space Data System Standards,
CCSDS 132.0-B-1. Blue Book. Issue 1. CCSDS, September 2003.
[5] TM Synchronization and Channel Coding. Recommendation for Space Data System
Standards, CCSDS 131.0-B-1. Blue Book. Issue 1. CCSDS, September 2003.
CCSDS 211.0-B-4 Page 1-6 July 2006
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CCSDS RECOMMENDED STANDARD FOR PROXIMITY-1 SPACE DATA LINK PROTOCOL
[6] CCSDS Global Spacecraft Identification Field Code Assignment Control Procedures.
Recommendation for Space Data System Standards, CCSDS 320.0-B-3. Blue Book.
Issue 3. Washington, D.C.: CCSDS, April 2003.
[7] Time Code Formats. Recommendation for Space Data System Standards, CCSDS
301.0-B-3. Blue Book. Issue 3. Washington, D.C.: CCSDS, January 2002.
[8] Proximity-1 Space Link Protocol: Coding and Synchronization Sublayer.
Recommendation for Space Data System Standards, CCSDS 211.2-B-1. Blue Book.
Issue 1. Washington, D.C.: CCSDS, April 2003.
[9] Proximity-1 Space Link Protocol—Physical Layer. Recommendation for Space Data
System Standards, CCSDS 211.1-B-3. Blue Book. Issue 3. Washington, D.C.:
CCSDS, March 2006.
CCSDS 211.0-B-4 Page 1-7 July 2006
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CCSDS RECOMMENDED STANDARD FOR PROXIMITY-1 SPACE DATA LINK PROTOCOL
2 OVERVIEW
2.1 CONCEPT OF PROXIMITY-1
2.1.1 LAYERED MODEL
Proximity-1 is a bi-directional Space Link layer protocol to be used by space missions. It
consists of a Physical layer (reference [9]), a Coding and Synchronization sublayer (reference
[8]) and a Data Link layer. This protocol has been designed to meet the requirements of
space missions for efficient transfer of space data over various types and characteristics of
Proximity space links. On the send side, the Data Link layer is responsible for providing data
to be transmitted by the Coding and Synchronization sublayer and Physical layer. The
operation of the transmitter is state-driven. On the receive side, the Data Link layer accepts
the serial data output from the receiver and processes the protocol data units received. It
accepts directives both from the local vehicle controller and across the Proximity link to
control its operations. Once the receiver is turned on, its operation is modeless. It accepts
and processes all valid local and remote directives and received service data units.
The layered model consists of two layers (Physical and Data Link) and has five component
sublayers within the Data Link layer:
a) Physical Layer
1) On the send side:
i) provides an Output Bit Clock to the Coding & Synchronization sublayer in
order to receive the Output Bitstream;
ii) provides status i.e., Carrier_Acquired and Bit_In_Lock_Status signals to the
Media Access Control sublayer.
2) On the receive side: Provides the Received Bit Clock/Data to the Coding &
Synchronization sublayer.
b) Coding and Synchronization Sublayer. The C&S sublayer includes PLTU delimiting
and verification procedures. In addition this sublayer performs as follows:
1) On the send side:
i) includes pre-pending Version-3 frames with the required Attached
Synchronization Marker (ASM);
ii) includes addition of CRC-32 to PLTUs.
2) On both the send and receive sides: Captures the value of the clock used for time
correlation process.
CCSDS 211.0-B-4 Page 2-1 July 2006
CCSDS RECOMMENDED STANDARD FOR PROXIMITY-1 SPACE DATA LINK PROTOCOL
c) Frame Sublayer. The Frame sublayer includes frame validation procedures, such as
transfer frame header checks, and supervisory data processing for supervisory frames.
In addition, this sublayer performs as follows:
1) On the send side:
i) encapsulates the Input/Output (I/O) sublayer–provided User Data (SDUs) into
Version-3 frames;
ii) prioritizes and multiplexes the frames for output via the C&S sublayer to the
Physical layer for transmission across the link.
2) On the receive side:
i) accepts delimited and verified frames from the C&S sublayer;
ii) delivers supervisory protocol data units (reports, directives) to the MAC
sublayer;
iii) passes the user data to the Data Services sublayer;
iv) performs a subset of validation checks to ensure that the received data should
be further processed.
d) Medium Access Control Sublayer. The Medium Access Control (MAC) sublayer
defines how a session is established, maintained (and how characteristics are
modified, e.g., data rate changes), and terminated for point-to-point communications
between Proximity entities. This sublayer builds upon the Physical and Data Link
layer functionality. The MAC controls the operational state of the Data Link and
Physical layers. It accepts and processes Supervisory Protocol Data Units (SPDUs)
and provides the various control signals that dictate the operational state. In addition
this sublayer:
1) decodes the directives from the local vehicle’s controller (e.g., spacecraft control
computer);
2) decodes the directives received via the remote transceiver (extracting and
processing SPDUs from the Frame Data Field);
3) stores and distributes the Management Information Base (MIB) parameters
(implementation-specific) and status variables;
4) maintains and distributes the state control variables (MODE, TRANSMIT,
DUPLEX,
...