ISO 10537:2016

Space data and information transfer systems - Encapsulation service

ISO 10537:2016 defines the Encapsulation Service in terms of: a) the service primitives provided to the users of this service; b) the protocol data units employed by the service provider; and c) the procedures performed by the service provider. It does not specify: a) individual implementations or products; b) the 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 service.

Systèmes de transfert des informations et données spatiales — Service d'encapsulation

General Information

• Status: Published
• Publication Date: 02-Nov-2016
• 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: 9093 - International Standard confirmed
• Start Date: 14-Nov-2023
• Completion Date: 13-Dec-2025

Relations

• Consolidated By: ISO 7551:2023 - Dentistry - Endodontic absorbent points
• Effective Date: 06-Jun-2022
• Revises: ISO 10537:2010 - Space data and information transfer systems - Encapsulation service
• Effective Date: 02-Apr-2016
• Revises: ISO 10537:2010/Amd 1:2015 - Space data and information transfer systems - Encapsulation service - Amendment 1
• Effective Date: 02-Apr-2016

Overview

ISO 10537:2016 - Space data and information transfer systems - Encapsulation service specifies the Encapsulation Service used to transfer protocol data units over ground-to-space or space-to-space links when those units are not directly handled by standard Space Data Link Protocols. Developed from CCSDS recommendations, the standard defines the service primitives, the protocol data units (including Encapsulation Packets and the option to use Space Packets), and the procedures that a service provider must perform. It is intended for inter‑Agency cross‑support of space missions and is a recommended (non‑binding) standard.

Key Topics and Requirements

• Service definition: Clear specification of the Encapsulation Service in terms of service primitives for users, protocol data units used by providers, and required provider procedures.
• Protocol data units: Formal description of Encapsulation Packet structure and the option to encapsulate data inside Space Packets for transport over space links.
• Procedures: Sending-end and receiving-end procedures that the service provider must implement to encapsulate, transmit and de‑encapsulate data units.
• Addressing and managed parameters: Definitions of addressing conventions and a set of managed parameters for configuring the service.
• Security considerations: Informative discussion of security background, threats, and potential mitigations relevant to the Encapsulation Service.
• Scope limitations: The standard explicitly does not define specific implementations, interface implementations within real systems, required technologies for procedures, or managerial/configuration processes.

Practical Applications

• Enabling cross‑agency data exchange in multi‑national space missions where payload or protocol data types are not natively supported by standard link protocols.
• Transporting legacy or proprietary protocol data units across modern CCSDS Space Data Link Protocol implementations by encapsulating them into defined packets.
• Use in mission planning and systems architecture to define how non‑link-native data will be carried across ground-to-space and space-to-space links.
• Informing procurement, interoperability testing, and interface agreements for ground stations, spacecraft onboard data handling, and mission operations.

Who should use ISO 10537:2016

• Space agencies and program managers planning cross‑support missions
• Systems engineers and architects designing spacecraft communications and ground stations
• Standards developers and integrators implementing CCSDS‑aligned data links
• Mission operations and ground segment teams defining interface agreements

Related Standards

• CCSDS Space Data Link Protocols (Space Packets and related Blue Books)
• CCSDS recommended standards that define Space Packet structures and link layer behavior

Keywords: ISO 10537:2016, Encapsulation Service, CCSDS, space data, Encapsulation Packet, Space Packet, space communications, cross‑support, protocol data units, space link protocols.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 10537
Second edition
2016-11-15
Space data and information transfer
systems — Encapsulation service
Systèmes de transfert des informations et données spatiales — Service
d’encapsulation
Reference number
©
ISO 2016
© ISO 2016, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. [phone]
Fax [phone]
[e-mail]
www.iso.org
ii © ISO 2016 – All rights reserved

Recommendation for Space Data System Standards
ENCAPSULATION
SERVICE
RECOMMENDED STANDARD
Note:
This current
issue includes
all updates through
CCSDS 133.1-B-2
Technical Corrigendum 2,
dated April 2014
BLUE BOOK
October 2009
CCSDS RECOMMENDED STANDARD FOR ENCAPSULATION SERVICE
AUTHORITY
Issue: Recommended Standard, Issue 2
Date: October 2009
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 documents is detailed in the 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 document is published and maintained by:
CCSDS Secretariat
Space Communications and Navigation Office, 7L70
Space Operations Mission Directorate
NASA Headquarters
Washington, DC 20546-0001, USA
CCSDS 133.1-B-2 Page i October 2009
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CCSDS RECOMMENDED STANDARD FOR ENCAPSULATION SERVICE
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 133.1-B-2 Page ii October 2009
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CCSDS RECOMMENDED STANDARD FOR ENCAPSULATION SERVICE
FOREWORD
This document is a Recommended Standard for use in developing flight and ground
systems for space missions and has been prepared by the Consultative Committee for
Space Data Systems (CCSDS). The Encapsulation Service described herein is intended for
missions that are cross-supported between Agencies of the CCSDS.
This Recommended Standard specifies a communications service to be used by space
missions to transfer protocol data units that are not directly transferred by the Space Data
Link Protocols (references [1]-[4]) over a ground-to-space or space-to-space communications
link. The data units transferred with this service are encapsulated in either Space Packets,
defined in reference [5], or Encapsulation Packets, defined in this document.
This Recommended Standard is developed from the Encapsulation Service that was
defined in the Advanced Orbiting Systems (AOS) Recommended Standard (reference [B2]).
In this Recommended Standard, that service is re-defined so that it can be used with any of
the Space Data Link Protocols (references [1]-[4]). Also, the Encapsulation Packet that was
defined in references [B2]-[B4] is included in this Recommended Standard as an
alternative packet structure for encapsulation.
In order to define all Space Data Link Protocols in a unified way, a few technical
specifications of the Encapsulation Service in reference [B2] have been changed. Also, some
technical terms in references [B2]-[B4] have been changed in order to unify the terminology
used in all the CCSDS Recommended Standards that define space link protocols. These
changes are listed in annex C of this Recommended Standard.
Through the process of normal evolution, it is expected that expansion, deletion or modification
to this document may occur. This Recommended Standard is therefore subject to CCSDS
document management and change control procedures, as defined in reference [B1]. 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 133.1-B-2 Page iii October 2009
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CCSDS RECOMMENDED STANDARD FOR ENCAPSULATION SERVICE
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.
– China National Space Administration (CNSA)/People’s Republic of China.
– Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR)/Germany.
– European Space Agency (ESA)/Europe.
– Russian Federal Space Agency (RFSA)/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 Sciences (CAS)/China.
– Chinese Academy of Space Technology (CAST)/China.
– Commonwealth Scientific and Industrial Research Organization (CSIRO)/Australia.
– CSIR Satellite Applications Centre (CSIR)/Republic of South Africa.
– Danish National Space Center (DNSC)/Denmark.
– European Organization for the Exploitation of Meteorological Satellites
(EUMETSAT)/Europe.
– European Telecommunications Satellite Organization (EUTELSAT)/Europe.
– Geo-Informatics and Space Technology Development Agency (GISTDA)/Thailand.
– 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.
– Ministry of Communications (MOC)/Israel.
– National Institute of Information and Communications Technology (NICT)/Japan.
– National Oceanic and Atmospheric Administration (NOAA)/USA.
– National Space Organization (NSPO)/Chinese Taipei.
– Naval Center for Space Technology (NCST)/USA.
– Scientific and Technological Research Council of Turkey (TUBITAK)/Turkey.
– Space and Upper Atmosphere Research Commission (SUPARCO)/Pakistan.
– Swedish Space Corporation (SSC)/Sweden.
– United States Geological Survey (USGS)/USA.
CCSDS 133.1-B-2 Page iv October 2009
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CCSDS RECOMMENDED STANDARD FOR ENCAPSULATION SERVICE
DOCUMENT CONTROL
Document Title and Issue Date Status
CCSDS Encapsulation Service, June 2006 Original issue, superseded
133.1-B-1 Recommended Standard, Issue 1
CCSDS Encapsulation Service, October Current issue:
133.1-B-2 Recommended Standard, Issue 2 2009 – adds corrections and
clarifications to the
specification
CCSDS Technical Corrigendum 1 September Replaces reference to CCSDS
133.1-B-2 2012 135.0-B-4, Space Link
Cor.1 Identifiers, with reference to
SANA.
CCSDS Technical Corrigendum 2 April 2014 Cor.2:
133.1-B-2 Editorial change 1 – replaces reference to
Cor.2 SANA with direct
EC 1 references to SANA
registries;
– expands range of reserved
Space Packet APIDs to
include CFDP.
EC 1:
– updates superseded
references with current
issues;
– updates obsolescent style
elements.
NOTE – Substantive changes from the previous issue are indicated with change bars in the
inside margin.
CCSDS 133.1-B-2 CCSDS 133.1-B-2 Cor. 2 Page v October 2009 April 2014
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CCSDS RECOMMENDED STANDARD FOR ENCAPSULATION SERVICE
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 DOCUMENT STRUCTURE . 1-2
1.6 CONVENTIONS AND DEFINITIONS. 1-2
1.7 REFERENCES . 1-5
2  OVERVIEW . 2-1
2.1 CONCEPT OF ENCAPSULATION SERVICE . 2-1
2.2 FEATURES OF ENCAPSULATION SERVICE . 2-2
2.3 ADDRESSING . 2-3
2.4 SERVICE DESCRIPTION . 2-3
3  SERVICE DEFINITION . 3-1
3.1 OVERVIEW . 3-1
3.2 SERVICE PARAMETERS . 3-1
3.3 SERVICE PRIMITIVES . 3-2
4  DATA UNITS AND PROCEDURES . 4-1
4.1 SPACE PACKET . 4-1
4.2 ENCAPSULATION PACKET . 4-1
4.3 PROCEDURES AT THE SENDING END . 4-7
4.4 PROTOCOL PROCEDURES AT THE RECEIVING END . 4-8
5  MANAGED PARAMETERS . 5-1
6  SECURITY . 6-1
6.1 SECURITY BACKGROUND . 6-1
6.2 SECURITY CONCERNS . 6-1
6.3 POTENTIAL THREATS AND ATTACK SCENARIOS . 6-1
6.4 CONSEQUENCES OF NOT APPLYING SECURITY . 6-2
ANNEX A ACRONYMS (Informative) . A-1
ANNEX B INFORMATIVE REFERENCES (Informative) .B-1
ANNEX C CHANGES FROM REFERENCES [B2]-[B4] (Informative) . C-1
CCSDS 133.1-B-2 Page vi October 2009
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CCSDS RECOMMENDED STANDARD FOR ENCAPSULATION SERVICE
CONTENTS (continued)
Figure Page
1-1 Bit Numbering Convention . 1-4
2-1 Concept of Encapsulation Service . 2-1
4-1 Encapsulation Packet Structural Components . 4-2
4-2 Packet Header . 4-3
4-3 Internal Organization of Encapsulation Service (Sending End) . 4-7
4-4 Internal Organization of Encapsulation Service (Receiving End) . 4-8
Table
4-1 Interpretation of Length of Length Field . 4-4
4-1 Encapsulation Packet Lengths, Depending on the Length of the Packet Header . 4-6
5-1 Managed Parameters for Encapsulation Service (Space Packet Used) . 5-1
5-2 Managed Parameters for Encapsulation Service (Encapsulation Packet Used) . 5-1
C-1  Terms That Have Been Changed from Reference [B2] .C-2
C-2  Terms That Have Been Changed from Reference [B3] .C-2
C-3  Terms That Have Been Changed from Reference [B4] .C-3
CCSDS 133.1-B-2 Page vii October 2009
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CCSDS RECOMMENDED STANDARD FOR ENCAPSULATION SERVICE
1 INTRODUCTION
1.1 PURPOSE
The purpose of this Recommended Standard is to specify the Encapsulation Service. This
service is to be used by space missions to transfer data units that are not directly transferred
by the Space Data Link Protocols (references [1]-[4]) over a ground-to-space or space-to-
space communications link.
1.2 SCOPE
This Recommended Standard defines the Encapsulation Service in terms of:
a) the service primitives provided to the users of this service;
b) the protocol data units employed by the service provider; and
c) the procedures performed by the service provider.
It does not specify:
a) individual implementations or products;
b) the 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 service.
1.3 APPLICABILITY
This Recommended Standard applies to the creation of Agency standards and to the future
data communications over space links between CCSDS Agencies in cross-support situations.
The Recommended Standard includes comprehensive specification of the service for inter-
Agency cross support. It is neither a specification of, nor a design for, real systems that may
be implemented for existing or future missions.
The Recommended Standard 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 Recommended Standard is anticipated.
Where mandatory capabilities are clearly indicated in sections of the Recommended
Standard, 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.
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CCSDS RECOMMENDED STANDARD FOR ENCAPSULATION SERVICE
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 this Recommended Standard is documented in reference [B5].
1.5 DOCUMENT STRUCTURE
This document is divided into five numbered sections and three annexes:
a) Section 1 presents the purpose, scope, applicability and rationale of this
Recommended Standard and lists the conventions, definitions, and references used
throughout the document;
b) Section 2 provides an overview of the Encapsulation Service;
c) Section 3 defines the service primitives provided for this service;
d) Section 4 specifies the protocol data units and procedures employed by the service
provider;
e) Section 5 lists the managed parameters associated with this service;
f) Section 6 is discussion of security considerations pertinent to the specification;
g) Annex A lists all acronyms used within this document;
h) Annex B provides a list of informative references;
i) Annex C lists the changes from older CCSDS Recommendations [B2]-[B4].
1.6 CONVENTIONS AND DEFINITIONS
1.6.1 DEFINITIONS
1.6.1.1 Definitions from the Open Systems Interconnection (OSI) Basic Reference
Model
This Recommended Standard makes use of a number of terms defined in reference [6]. The
use of those terms in this Recommended Standard 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:
a) blocking;
b) connection;
c) entity;
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CCSDS RECOMMENDED STANDARD FOR ENCAPSULATION SERVICE
d) flow control;
e) protocol data unit;
f) real system;
g) segmenting;
h) service;
i) Service Access Point (SAP);
j) SAP address;
k) service data unit.
1.6.1.2 Definitions from OSI Service Definition Conventions
This Recommended Standard makes use of a number of terms defined in reference [7]. The
use of those terms in this Recommended Standard 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:
a) indication;
b) primitive;
c) request;
d) service provider;
e) service user.
1.6.1.3 Terms Defined in This Recommended Standard
For the purposes of this Recommended Standard, the following definitions also apply. Many
other terms that pertain to specific items are defined in the appropriate sections.
asynchronous: not synchronous (see below).
delimited: having a known (and finite) length; applies to data in the context of data handling.
Physical Channel: a stream of bits transferred over a space link in a single direction.
space link: a communications link between a spacecraft and its associated ground system,
or between two spacecraft. A space link consists of one or more Physical Channels in one or
both directions.
synchronous: of or pertaining to a sequence of events occurring in a fixed time relationship
(within specified tolerance) to another sequence of events.
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CCSDS RECOMMENDED STANDARD FOR ENCAPSULATION SERVICE
1.6.2 NOMENCLATURE
The following conventions apply throughout this Recommended Standard:
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.
1.6.3 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’ (see figure 1-1).
BIT N-1
BIT 0
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’ which conform to the above convention. Throughout this Recommended
Standard, such an 8-bit word is called an ‘octet’.
The numbering for octets within a data structure starts with 0.
By CCSDS convention, all ‘spare’ bits shall be permanently set to value ‘zero’.
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CCSDS RECOMMENDED STANDARD FOR ENCAPSULATION SERVICE
1.7 REFERENCES
The following documents contain provisions which, through reference in this text, constitute
provisions of this Recommended Standard. At the time of publication, the editions indicated
were valid. All documents are subject to revision, and users of this Recommended Standard
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 Recommended Standards.
[1] TM Space Data Link Protocol. Issue 1. Recommendation for Space Data System
Standards (Blue Book), CCSDS 132.0-B-1. Washington, D.C.: CCSDS, September 2003.
[2] TC Space Data Link Protocol. Issue 2. Recommendation for Space Data System
Standards (Blue Book), CCSDS 232.0-B-2. Washington, D.C.: CCSDS, September 2010.
[3] AOS Space Data Link Protocol. Recommendation for Space Data System Standards,
CCSDS 732.0-B-2. Blue Book. Issue 2. Washington, D.C.: CCSDS, July 2006.
[4] Proximity-1 Space Link Protocol—Data Link Layer. Issue 5. Recommendation for
Space Data System Standards (Blue Book), CCSDS 211.0-B-5. Washington, D.C.:
CCSDS, December 2013.
[5] Space Packet Protocol. Issue 1. Recommendation for Space Data System Standards
(Blue Book), CCSDS 133.0-B-1. Washington, D.C.: CCSDS, September 2003.
[6] Information Technology—Open Systems Interconnection—Basic Reference Model: The
Basic Model. 2nd ed. International Standard, ISO/IEC 7498-1:1994. Geneva: ISO,
1994.
[7] Information Technology—Open Systems Interconnection—Basic Reference Model—
Conventions for the Definition of OSI Services. International Standard, ISO/IEC
10731:1994. Geneva: ISO, 1994.
[8] “Space Assigned Number Authority (SANA) Registry: Packet Version Number.”
Space Assigned Numbers Authority. Consultative Committee for Space Data Systems.
http://sanaregistry.org/r/packet_version_number/.
[9] “Space Assigned Number Authority (SANA) Registry: Space Packet Protocol
Application Process Identifier (APID).” Space Assigned Numbers Authority.
Consultative Committee for Space Data Systems.
http://sanaregistry.org/r/space_packet_protocol_application_process_id/.
[10] “Space Assigned Number Authority (SANA) Registry: Protocol Identifier for
Encapsulation Service.” Space Assigned Numbers Authority. Consultative Committee
for Space Data Systems. http://sanaregistry.org/r/protocol_id/.
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Cor. 2
Cor. 2
CCSDS RECOMMENDED STANDARD FOR ENCAPSULATION SERVICE
[11] “Space Assigned Number Authority (SANA) Registry: Extended Protocol Identifiers.”
Space Assigned Numbers Authority. Consultative Committee for Space Data Systems.
http://sanaregistry.org/r/extended_protocol_id/.
NOTE – Informative references are listed in annex B.
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CCSDS RECOMMENDED STANDARD FOR ENCAPSULATION SERVICE
2 OVERVIEW
2.1 CONCEPT OF ENCAPSULATION SERVICE
The Encapsulation Service is a data transfer service to be used by space missions to transfer
data units that are not directly transferred by the Space Data Link Protocols (references [1]-[4])
over a ground-to-space or space-to-space communications link (hereafter called a space link).
Data units that are directly transferred by the Space Data Link Protocols have a Packet
Version Number (PVN) authorized by CCSDS. (A list of the Packet Version Numbers
presently authorized by CCSDS is contained in reference [8].) The main purpose of the
Encapsulation Service is to provide a mechanism to transfer data units without an authorized
PVN over a space link.
The Encapsulation Service is a service provided by the Data Link Layer of the OSI Basic
Reference Model [6] (see figure 2-1). It is an extra service of the Space Data Link Protocols
defined in references [1]-[4], and therefore shall be used together with one of these
references.
OSI LAYERS
NETWORK AND
PROTOCOL X PROTOCOL Y
UPPER LAYERS
ENCAPSULATION
SERVICE
ENCAPSULATION
PACKET SERVICE
DATA LINK LAYER
SPACE DATA LINK
PROTOCOL
SYNCHRONIZATION AND
CHANNEL CODING
PHYSICAL LAYER
Figure 2-1: Concept of Encapsulation Service
Figure 2-1 illustrates the concept of this service. Protocol data units of Protocols X and Y,
which do not have an authorized PVN, are transferred with the Encapsulation Service within
the Data Link Layer. Protocol data units of Protocols X and Y are encapsulated in either
Space Packets defined in reference [5] or Encapsulation Packets defined in subsection 4.2 of
this document, and are transferred using the Packet Service of a Space Data Link Protocol.
When Space Packets are used for encapsulation, some rules on their format (described in
subsection 4.1) shall be applied. Management shall establish which Space Data Link
Protocol is to be used to transfer encapsulated data units.
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CCSDS RECOMMENDED STANDARD FOR ENCAPSULATION SERVICE
2.2 FEATURES OF ENCAPSULATION SERVICE
The Encapsulation Service transfers a sequence of variable-length, delimited, octet-aligned
data units with a Space Data Link Protocol over a space link. A user of this service is a
protocol entity that sends or receives protocol data units that do not have an authorized PVN.
The format and content of data units transferred with this service are unknown to the service
provider.
A data unit supplied by the service user is encapsulated unchanged into a Space Packet or an
Encapsulation Packet and no more than one data unit is encapsulated into a single packet. An
implementation is conformant if it implements either the Space Packet or the Encapsulation
Packet; i.e., both are not required.
The service permits a data unit to be of any length which is an integral number of octets, and
which is subject to the maximum and minimum sizes established by the project organization.
Although the maximum length of a data unit that can be accommodated by an encapsulating
packet is 65,536 octets (if the Space Packet is used) or 4,294,967,287 octets (if the
Encapsulation Packet is used), individual project organizations may establish the maximum
and minimum sizes for the encapsulated data unit.
The point at which an instance of this service is provided to a user is called a Service Access
Point (SAP) (reference [6]). Data units submitted to a SAP are processed in the order of
submission. No processing order is maintained for data units submitted to different SAPs.
NOTE – Implementations may be required to perform flow control at an SAP between the
service user and the service provider. However, CCSDS does not recommend a
scheme for flow control between the user and the provider.
Features of the Encapsulation Service are as follows:
a) Unidirectional (one way) service: one end of a connection can send, but not receive,
data through the space link, while the other end can receive, but not send, data
through the space link.
b) Asynchronous service: There are no timing relationships between the transfer of data
units supplied by the user and any data transmission mechanism within the Data Link
Layer. The user may request data transfer at any time, but there may be restrictions
imposed by the service provider on the data generation rate.
c) Unconfirmed service: the sending user does not receive confirmation from the
receiving end indicating that data has been received.
d) Incomplete service: the service does not guarantee completeness, but the service
provider may signal gaps in the sequence of data units delivered to the receiving user.
e) Sequence preserving service: the sequence of data units supplied by the sending user
is preserved through the transfer over the space link, although there may be gaps in
the sequence of data units delivered to the receiving user.
CCSDS 133.1-B-2 Page 2-2 October 2009
@ ISO 2016 - All right reserverd

CCSDS RECOMMENDED STANDARD FOR ENCAPSULATION SERVICE
2.3 ADDRESSING
A user of the Encapsulation Service is identified by the combination of the following:
a) a Packet Version Number (PVN) that indicates whether Space Packets (PVN=1) or
Encapsulation Packets (PVN=8) are used for encapsulation; and
b) an Encapsulated Protocol Identifier (EPI).
An Encapsulated Protocol Identifier is either:
a) an Application Process Identifier (APID) defined in reference [5] (if Space Packets
are used); or
b) a Protocol ID defined in section 4 of this document (if Encapsulation Packets are
used).
The APIDs used by the Encapsulation Service must be registered as ‘reserved APIDs’ in
reference [9]. The Protocol IDs used by the Encapsulation Service must be registered as
‘defined Protocol IDs’ in reference [10].
A SAP is identified by the combination of a PVN, an EPI, and a Space Data Link Protocol
(SDLP) channel through which the data units supplied by the user are to be transferred.
2.4 SERVICE DESCRIPTION
The Encapsulation Service is described in terms
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