ISO 20618:2015

INTERNATIONAL ISO
STANDARD 20618
First edition
2015-12-15
Space data and information transfer
systems — Spacecraft onboard interface
services — Device enumeration service
Systèmes de transfert des informations et données spatiales —
Services d'interface à bord du vaisseau spatial — Service
d'énumération du dispositif
Reference number
©
ISO 2015
© ISO 2015, Published in Switzerland
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ii © ISO 2015 – 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 20618 was prepared by the Consultative Committee for Space Data Systems (CCSDS) as
CCSDS 871.3-M-1, October 2014 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.

Recommendation for Space Data System Practices
SPACECRAFT ONBOARD
INTERFACE SERVICES—
DEVICE ENUMERATION
SERVICE
RECOMMENDED PRACTICE
CCSDS 871.3-M-1
MAGENTA BOOK
October 2014
CCSDS RECOMMENDED PRACTICE FOR SOIS DEVICE ENUMERATION SERVICE
AUTHORITY
Issue: Recommended Practice, Issue 0
Date: June 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 documents is detailed in Organization and Processes for
the Consultative Committee for Space Data Systems (CCSDS A02.1-Y-4), and the record of
Agency participation in the authorization of this document can be obtained from the CCSDS
Secretariat at the e-mail address below.

This document is published and maintained by:

CCSDS Secretariat
National Aeronautics and Space Administration
Washington, DC, USA
E-mail: secretariat@mailman.ccsds.org
CCSDS 871.3-M-1 Page i October 2014
CCSDS RECOMMENDED PRACTICE FOR SOIS DEVICE ENUMERATION 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 Recommendations and are not in
themselves considered binding on any Agency.
CCSDS Recommendations take two forms: Recommended Standards that are prescriptive
and are the formal vehicles by which CCSDS Agencies create the standards that specify how
elements of their space mission support infrastructure shall operate and interoperate with
others; and Recommended Practices that are more descriptive in nature and are intended to
provide general guidance about how to approach a particular problem associated with space
mission support. This Recommended Practice is issued by, and represents the consensus of,
the CCSDS members. Endorsement of this Recommended Practice is entirely voluntary
and does not imply a commitment by any Agency or organization to implement its
recommendations in a prescriptive sense.
No later than five years from its date of issuance, this Recommended Practice 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 Practice is issued, existing
CCSDS-related member Practices and implementations are not negated or deemed to be non-
CCSDS compatible. It is the responsibility of each member to determine when such Practices
or implementations are to be modified. Each member is, however, strongly encouraged to
direct planning for its new Practices and implementations towards the later version of the
Recommended Practice.
CCSDS 871.3-M-1 Page ii October 2014
CCSDS RECOMMENDED PRACTICE FOR SOIS DEVICE ENUMERATION SERVICE
FOREWORD
Through the process of normal evolution, it is expected that expansion, deletion, or
modification of this document may occur. This Recommended Practice is therefore subject
to CCSDS document management and change control procedures, which are defined in the
Organization and Processes for the Consultative Committee for Space Data Systems
(CCSDS A02.1-Y-4). 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 sent to the CCSDS
Secretariat at the e-mail address indicated on page i.
CCSDS 871.3-M-1 Page iii October 2014
CCSDS RECOMMENDED PRACTICE FOR SOIS DEVICE ENUMERATION SERVICE
At time of publication, the active Member and Observer Agencies of the CCSDS were:
Member Agencies
– Agenzia Spaziale Italiana (ASI)/Italy.
– 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 (DLR)/Germany.
– European Space Agency (ESA)/Europe.
– Federal Space Agency (FSA)/Russian Federation.
– Instituto Nacional de Pesquisas Espaciais (INPE)/Brazil.
– Japan Aerospace Exploration Agency (JAXA)/Japan.
– National Aeronautics and Space Administration (NASA)/USA.
– UK Space Agency/United Kingdom.
Observer Agencies
– Austrian Space Agency (ASA)/Austria.
– Belgian Federal Science Policy Office (BFSPO)/Belgium.
– Central Research Institute of Machine Building (TsNIIMash)/Russian Federation.
– China Satellite Launch and Tracking Control General, Beijing Institute of Tracking
and Telecommunications Technology (CLTC/BITTT)/China.
– Chinese Academy of Sciences (CAS)/China.
– Chinese Academy of Space Technology (CAST)/China.
– Commonwealth Scientific and Industrial Research Organization (CSIRO)/Australia.
– Danish National Space Center (DNSC)/Denmark.
– Departamento de Ciência e Tecnologia Aeroespacial (DCTA)/Brazil.
– 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 Agency of the Republic of Kazakhstan (NSARK)/Kazakhstan.
– National Space Organization (NSPO)/Chinese Taipei.
– Naval Center for Space Technology (NCST)/USA.
– Scientific and Technological Research Council of Turkey (TUBITAK)/Turkey.
– South African National Space Agency (SANSA)/Republic of South Africa.
– Space and Upper Atmosphere Research Commission (SUPARCO)/Pakistan.
– Swedish Space Corporation (SSC)/Sweden.
– Swiss Space Office (SSO)/Switzerland.
– United States Geological Survey (USGS)/USA.
CCSDS 871.3-M-1 Page iv October 2014
CCSDS RECOMMENDED PRACTICE FOR SOIS DEVICE ENUMERATION SERVICE
DOCUMENT CONTROL
Document Title Date Status
CCSDS Spacecraft Onboard Interface October Original issue
871.3-M-1 Services—Device Enumeration 2014
Service, Recommended Practice,
Issue 1
CCSDS 871.3-M-1 Page v October 2014
CCSDS RECOMMENDED PRACTICE FOR SOIS DEVICE ENUMERATION SERVICE
CONTENTS
Section Page
1 INTRODUCTION . 1-1

1.1 PURPOSE AND SCOPE OF THIS DOCUMENT . 1-1
1.2 APPLICABILITY . 1-1
1.3 RATIONALE . 1-1
1.4 DOCUMENT STRUCTURE . 1-1
1.5 DEFINITIONS . 1-2
1.6 NOMENCLATURE . 1-2
1.7 REFERENCES . 1-3

2 OVERVIEW . 2-1

2.1 CONTEXT . 2-1
2.2 DEVICES . 2-3
2.3 PURPOSE AND OPERATION OF THE DEVICE
ENUMERATION SERVICE . 2-7

3 DEVICE ENUMERATION SERVICE . 3-1

3.1 PROVIDED SERVICE . 3-1
3.2 EXPECTED SERVICE FROM UNDERLYING LAYERS . 3-1
3.3 DEVICE ENUMERATION SERVICE PARAMETERS . 3-2
3.4 DEVICE ENUMERATION SERVICE PRIMITIVES . 3-4

ANNEX A DEVICE ENUMERATION SERVICE PROTOCOL
IMPLEMENTATION CONFORMANCE STATEMENT
PROFORMA (NORMATIVE) . A-1
ANNEX B SECURITY CONSIDERATIONS (INFORMATIVE) .B-1
ANNEX C ACRONYMS (INFORMATIVE) . C-1
ANNEX D INFORMATIVE REFERENCES . D-1
Figure
2-1 Device Enumeration Service Context . 2-1
2-2 Relationship between Device Enumeration Service and Other SOIS Services . 2-1
2-3 Identifiers Mapping in SOIS Services . 2-3
2-4 Device Enumeration Service and Redundancy . 2-6

CCSDS 871.3-M-1 Page vi October 2014
CCSDS RECOMMENDED PRACTICE FOR SOIS DEVICE ENUMERATION SERVICE
1 INTRODUCTION
1.1 PURPOSE AND SCOPE OF THIS DOCUMENT
This document is one of a family of documents specifying the Spacecraft Onboard Interface
Services (SOIS)-compliant service to be provided in support of applications.
The purpose of this document is to define services and service interfaces provided by the
SOIS Device Enumeration Service (DES). Its scope is to specify the service only and not to
specify methods of providing the service, although use of the SOIS subnetwork services is
assumed.
This document conforms to the principles set out in the SOIS Green Book (reference [D3])
and is intended to be applied together with it.
1.2 APPLICABILITY
This document applies to any mission or equipment claiming to provide a SOIS-compatible
DES.
1.3 RATIONALE
SOIS provide service interface specifications in order to promote commonality of
functionality amongst systems implementing well-defined services. These interfaces do not
dictate implementation of interfaces or protocols supporting the services.
1.4 DOCUMENT STRUCTURE
This document comprises three sections:
– this section, containing administrative information, definitions, and references;
– section 2 containing general concepts and assumptions;
– section 3 containing the DES specification.
In addition, one normative and three informative annexes are provided:
– annex A, comprising a Protocol Implementation Conformance Proforma;
– annex B, discussing security considerations relating to the specifications of this
document;
– annex C, containing a list of acronyms;
– annex D containing a list of informative references.
CCSDS 871.3-M-1 Page 1-1 October 2014
CCSDS RECOMMENDED PRACTICE FOR SOIS DEVICE ENUMERATION SERVICE
1.5 DEFINITIONS
1.5.1 GENERAL
For the purpose of this document the following definitions apply.
1.5.2 DEFINITIONS FROM THE OPEN SYSTEMS INTERCONNECTION (OSI)
BASIC REFERENCE MODEL
This document is defined using the style established by the Open Systems Interconnection
(OSI) Basic Reference Model (reference [D2]). This model provides a common framework for
the development of standards in the field of systems interconnection.
The following terms used in this Recommended Practice are adapted from definitions given
in reference [D2]:
layer: A subdivision of the architecture, constituted by subsystems of the same rank.
service: A capability of a layer, and the layers beneath it (a service provider), which is provided
to the service-users at the boundary between the service-providers and the service-users.
1.5.3 TERMS DEFINED IN THIS RECOMMENDED PRACTICE
For the purposes of this Recommended Practice, the following definitions also apply.
application: Any component of the onboard software that makes use of the DES. This
includes flight software applications and higher-layer services.
device: A real hardware component of the spacecraft, such as a sensor or actuator, or a single
register within such a component.
notification: A service interface provided by applications that is invoked by a service
implementation to provide a means for the service implementation to deliver a message to a
set of applications.
1.6 NOMENCLATURE
1.6.1 NORMATIVE TEXT
The following conventions apply for the normative specifications in this Recommended
Practice:
a) the words ‘shall’ and ‘must’ imply a binding and verifiable specification;
b) the word ‘should’ implies an optional, but desirable, specification;
CCSDS 871.3-M-1 Page 1-2 October 2014
CCSDS RECOMMENDED PRACTICE FOR SOIS DEVICE ENUMERATION SERVICE
c) the word ‘may’ implies an optional specification;
d) the words ‘is’, ‘are’, and ‘will’ imply statements of fact.
NOTE – These conventions do not imply constraints on diction in text that is clearly
informative in nature.
1.6.2 INFORMATIVE TEXT
In the normative sections of this document, informative text is set off from the normative
specifications either in notes or under one of the following subsection headings:
– Overview;
– Background;
– Rationale;
– Discussion.
1.7 REFERENCES
The following publications contain provisions which, through reference in this text,
constitute provisions of this document. At the time of publication, the editions indicated
were valid. All publications are subject to revision, and users of this document are
encouraged to investigate the possibility of applying the most recent editions of the
publications indicated below. The CCSDS Secretariat maintains a register of currently valid
CCSDS publications.
[1] Spacecraft Onboard Interface Services—Device Access Service. Issue 1.
Recommendation for Space Data System Practices (Magenta Book), CCSDS 871.0-M-1.
Washington, D.C.: CCSDS, March 2013.
[2] Spacecraft Onboard Interface Services—Device Virtualization Service. Issue 1.
Recommendation for Space Data System Practices (Magenta Book), CCSDS 871.2-M-
1. Washington, D.C.: CCSDS, March 2014.
[3] Spacecraft Onboard Interface Services—Subnetwork Device Discovery Service.
Issue 1. Recommendation for Space Data System Practices (Magenta Book), CCSDS
854.0-M-1. Washington, D.C.: CCSDS, December 2009.
[4] Spacecraft Onboard Interface Services—Subnetwork Memory Access Service. Issue 1.
Recommendation for Space Data System Practices (Magenta Book), CCSDS 852.0-M-1.
Washington, D.C.: CCSDS, December 2009.
CCSDS 871.3-M-1 Page 1-3 October 2014
CCSDS RECOMMENDED PRACTICE FOR SOIS DEVICE ENUMERATION SERVICE
[5] Spacecraft Onboard Interface Services—Subnetwork Packet Service. Issue 1.
Recommendation for Space Data System Practices (Magenta Book), CCSDS 851.0-M-1.
Washington, D.C.: CCSDS, December 2009.
NOTE – Informative references are contained in annex D.

CCSDS 871.3-M-1 Page 1-4 October 2014
Communication Management
CCSDS RECOMMENDED PRACTICE FOR SOIS DEVICE ENUMERATION SERVICE
2 OVERVIEW
2.1 CONTEXT
The SOIS DES is defined within the context of the overall SOIS architecture (reference
[D3]) as one of the services of the Application Support Layer, as illustrated in figure 2-1.
Application
Mission
Layer
Specific
Applications
Application
Cmd & Data Time File & Message Device
Support Layer
Acquisition Access Packet Store Transfer Enumeration
Services Service Services Service Service
Transfer
Transport Protocol
Layer
Network Protocol
Subnetwork
Memory Device
Layer Packet Synchronisation Test
Access Discovery
Service
Service Service
Service Service
Datalink Convergence Protocols
Milbus SpaceWire CAN Wireless
Figure 2-1: Device Enumeration Service Context
The relationship of the DES to the other SOIS services is illustrated in figure 2-2.

Figure 2-2: Relationship between Device Enumeration Service and Other SOIS Services
CCSDS 871.3-M-1 Page 2-1 October 2014
CCSDS RECOMMENDED PRACTICE FOR SOIS DEVICE ENUMERATION SERVICE
The DES provides management and user notification of added or removed devices from a
spacecraft. Management of added devices consists of assigning a (system-wide unique)
virtual device identifier and verifying that the functions and configuration of the discovered
device match the ones required by the system. Management of removed devices consists of
revoking the (system-wide unique) virtual device identifier so that the user can no longer
access the functions provided by the device using the other Application Support Services.
The service also provides the capability to enumerate the identifiers associated with the
devices currently added and to perform queries on device metadata such as device serial
number.
The DES main goal is to assist the onboard reconfiguration functions, such as mode
management or fault detection, isolation, and recovery regarding the notification of changes
in the spacecraft configuration, and the execution of the needed operations to adjust the
onboard software to the new configuration. While the reconfiguration strategy is the
responsibility of the user applications, the DES is charged with detecting the addition or
removal of devices and the reconfiguration of the other SOIS services used to access these
devices. In addition the DES also supports the spacecraft integration and test by managing
the verification of the correct configuration of the onboard devices with respect to the
spacecraft desired configuration or by easing the insertion/removal of device simulators in
replacement of the real equipment.
The basic identification information for the devices installed in the system is retrieved by the
subnetwork Device Discovery Service (DDS), reference [3], and used by the DES to assign a
system-wide unique identifier to each device so that each can be accessed by the user
applications using the appropriate functional interface (using the Device Virtualisation
Service [DVS], reference [2]), device access protocol (using the Device Access Service
[DAS], reference [1]), and subnetwork services (namely Memory Access Service [MAS],
reference [4], or Packet Service [PS], reference [5]).
The mapping between the identifiers used by the services and protocols is also illustrated in
figure 2-3.
Command & Data Acquisition Service and protocol parameters as well as device-specific
access algorithms are preinstalled in the onboard software. The use of DES does not imply
any dynamic code generation or compilation at run-time; instead, it allows selection of
predefined service instances already available in the onboard software system.
The interactions within the other SOIS services for what concerns the device IDs and
subnetwork addresses assignments are done via the Communication Management entity;
therefore these operations are not covered by the service interface specified in this document.
CCSDS 871.3-M-1 Page 2-2 October 2014
CCSDS RECOMMENDED PRACTICE FOR SOIS DEVICE ENUMERATION SERVICE
User Application
Device Virtualisation Virtual Device Identifier
Service (system-wide unique)
Device Access Service Physical Device Identifier
Packet or Memory Spacecraft Network Address
Access Service (system-wide unique)
Subnetwork-Specific
Subnework-Specific Address
Protocol
Hardware Device
Figure 2-3: Identifiers Mapping in SOIS Services
2.2 DEVICES
2.2.1 ADDING DEVICES
Two mechanisms are available for adding a device by means of the DES:
a) ‘Bottom-up’. Discovery of added devices is provided by DDSes within the different
subnetworks and notified to the DES (mandatory feature).
b) ‘Top-down’. Service users (higher-level services or applications) notify the DES of
an added device (optional feature).
CCSDS 871.3-M-1 Page 2-3 October 2014
CCSDS RECOMMENDED PRACTICE FOR SOIS DEVICE ENUMERATION SERVICE
In either case, the following information is provided to the DES:
a) Device Serial Number, the unique identifier of the physical device to distinguish
between devices of the same type (e.g., gyro mounted on axis X, gyro mounted on
axis Y, etc.);
b) Device Type, the identifier of the functional interface supported by the device when
accessed using the DVS;
c) Spacecraft Network Address, the identifier of the device in the spacecraft network,
identifying the subnetwork and the device within the subnetwork.
The DES joins information from two sources. One is the DDS (real configuration), which
provides as minimum the Spacecraft Network Address and Device Serial Number. The other
is the spacecraft configuration data provided by the spacecraft designers as a configuration
table (stored inside the DES or made available through an onboard file system) and providing
for each device the association between Device Serial Number, Spacecraft Network Address,
and Device Type, and device location/orientation.
Matching these two sets of information, the DES then reconfigures DVS and DAS (by using
DVS and DAS management interfaces to modify their Management Information Bases
[MIBs]) to enable user access to the service provided by the device. Management consists of:
a) verification that a device with the attributes mentioned above is foreseen by the
spacecraft configuration (if the check is negative an error is reported); otherwise
b) assignment of the Virtual Device Identifier (system-wide unique) to be used in the
DVS primitives;
NOTE – To ease system integration and space operations, it is advised to use a
deterministic algorithm to assign the device identifiers so that a given device
always receives the same identifier every time it is added/discovered.
c) association of the Virtual Device Identifier assigned at b) with the Physical Device
Identifier used by DAS to the added device in the DVS MIB (reference [2]);
d) association of the Physical Device Identifier (system-wide unique) with the
Spacecraft Network Address in the DAS MIB (reference [1]) to, in order to access the
device in its subnetwork.
Finally, the DES notifies any associated application of the added device by means of a
notification. A notification is a service interface provided by applications that is invoked by a
service implementation to provide a means for the service implementation to deliver a
message to a set of applications. The parameters of this DES notification include the device
attributes defined at a), b), c) and d).
NOTE – The mechanism to associate an application with DES notification is
implementation-dependent.
CCSDS 871.3-M-1 Page 2-4 October 2014
CCSDS RECOMMENDED PRACTICE FOR SOIS DEVICE ENUMERATION SERVICE
2.2.2 REMOVING DEVICES
Two mechanisms are available for removing devices by mean of the DES:
a) ‘Bottom-up’. Discovery of removed devices is provided by the DDS within the
different subnetworks and notified to the DES (mandatory feature).
In this case, the following information is provided to the DES:
Spacecraft Network Address associated to the removed device.
The remaining associated device identifiers can be derived from the Spacecraft
Network Address using the MIBs of the DAS and DVS where the associations
between identifiers are maintained.
b) ‘Top-down’. Service users (higher-level services or applications) notify the DES of a
removed device (optional feature).
In this case, the following information is provided to the DES:
Virtual Device Identifier, the system-wide unique identifier for the removed device.
The DES then reconfigures the DAS and DVS to remove user access to the service provided
by the device. Management consists of:
a) invalidation of the Spacecraft Network Address in the DAS MIB;
b) invalidation of the Physical Device Identifier in the DVS MIB;
c) revocation of the Virtual Device Identifier.
Finally, the DES notifies any associated applications of the removed device by means of a
notification. The parameters of this DES notification include the Virtual Device Identifier of
the removed device.
NOTE – The mechanism to associate an application with the DES notification is
implementation-dependent.
2.2.3 MIB CONSIDERATIONS
The DES MIB contains the following information:
– Virtual Device and Value Identifier Resolution Table, being a set of managed
parameters that map logical device and value identifiers onto individual underlying
services and their associated available addressing mechanisms.
– Physical Device and Value Identifier Resolution Table, being a set of managed
parameters that map physical device and value identifiers onto individual underlying
services and their associated available addressing mechanisms.
CCSDS 871.3-M-1 Page 2-5 October 2014
CCSDS RECOMMENDED PRACTICE FOR SOIS DEVICE ENUMERATION SERVICE
As described in 2.2.1 and 2.2.2, so as to assign or revoke the device identifiers and network
addresses in accordance with the detected spacecraft configuration, upon modification of its
MIB, the DES uses a DAS management interface to change the DAS MIB to align it with the
contents of its Virtual Device and Value Identifier Resolution Table and use a DVS
management interface to change the DVS MIB to align it with the contents of the Physical
Device and Value Identifier Resolution Table.
2.2.4 REDUNDANCY CONSIDERATIONS
The DES does not explicitly manage redundancies among devices of the same type. It
however provides the redundancy control function in the Application Layer with the
mechanisms to configure the SOIS services in accordance with the spacecraft’s Fault
Detection, Identification/Isolation and Recovery (FDIR) strategy.
Figure 2-4 shows the relationship between the DES, the redundancy control application and
the regular user applications making use of Command and Data Acquisition Services
configured by the DES.
In the figure it is assumed that the redundancy control gives visibility only of DVS-1 (device
in use) to the rest of the applications and filters out DVS-2 (backup).
Dev-A
User Application Redundancy Control
Virtual
Device Acquire/ Device Added/
In Use Dev Id
Dev Id
Command Removed
Yes Dev-A DVS-1
DVS-1, DVS-2
Device Virtualisation
No Dev-A DVS-2
Service
Device Acquire/
Command
Device Enumeration
Service
DAS-1, DAS-2
Device Access Service
Virtual Physic. S/C Subnet Dev Dev
Added
Dev Id Dev Id Addr Addr Serial Type
Yes DVS-1 DAS-1 X RT1 ABC A
Receive/Send/
Read/Write
Yes DVS-2 DAS-2 Y RT2 DEF A
... ... ... ... ... ... ...
X, RT1, Y, RT2
Underlying Services
No DVS-N DAS-N Z M KJL C
Figure 2-4: Device Enumeration Service and Redundancy
It is out of scope of the DES to actually command the switch on or off of the devices. This
can be achieved by means of the Command and Data Acquisition services.
CCSDS 871.3-M-1 Page 2-6 October 2014
CCSDS RECOMMENDED PRACTICE FOR SOIS DEVICE ENUMERATION SERVICE
2.3 PURPOSE AND OPERATION OF THE DEVICE ENUMERATION SERVICE
Application software uses the DES to manage (and be notified or notify it of) added or removed
devices from a spacecraft, rather than having to discover the added or removed devices itself.
Applications are notified by receiving device found and lost indications from DES, and
applications notify DES by sending device found and lost requests, as described in 3.1. From
the application software perspective, use of the DES will result in applications that are more
portable, that are easier to develop, and that can tolerate changes in the spacecraft hardware
configuration, communications, or physical devices. From the spacecraft platform
implementers’ perspective, use of the DES will make it easier to control the configuration of
the hardware resources.
The DES is part of the SOIS Plug-and-Play architecture; however, it can also be adopted in a
traditional non–plug-and-play software architecture to help the application software in the
configuration management of the devices and Command and Data Acquisition Services.
The DES is operated by service indications passed from the service provider and the service
user, optionally using service requests and associated service indications passed between the
service user and the service provider.

CCSDS 871.3-M-1 Page 2-7 October 2014
CCSDS RECOMMENDED PRACTICE FOR SOIS DEVICE ENUMERATION SERVICE
3 DEVICE ENUMERATION SERVICE
3.1 PROVIDED SERVICE
3.1.1 GENERAL
The DES shall provide management and notification of added or removed devices from a
spacecraft.
3.1.2 MANAGEMENT OF ADDED DEVICES
3.1.2.1 Management of added devices shall consist of assigning virtual and physical device
identifiers and using DAS and DVS management interfaces to update their MIBs to add the
virtual and physical device identifier mappings in order to enable user access to the functions
provided by the physical device via the DVS and DAS services.
3.1.2.2 The detection of added devices or device attributes not originally foreseen by the
spacecraft design shall be flagged as an error (see 3.3.3).
3.1.3 NOTIFICATION OF ADDED DEVICES
Notification of an added device shall consist of an indication to a service user of the device
identifier, together with the device’s type and device’s serial number.
3.1.4 MANAGEMENT OF REMOVED DEVICES
Management of removed devices shall consist of revoking the related virtual and physical
device identifiers and using DAS and DVS management interfaces to update their MIBs to
remove the virtual and physical device identifier mappings in order to disable the user access
to the functions that were provided by the device via the SOIS services.
3.1.5 NOTIFICATION OF REMOVED DEVICES
Notification of a removed device shall consists of an indication to a service user of the device
identifier, together with the device’s class and type.
3.2 EXPECTED SERVICE FROM UNDERLYING LAYERS
3.2.1 The minimum expected service from the underlying layers is a DDS (reference [3])
for each supported subnetwork type.
3.2.2 An interface to provide access to and configuration of the MIB of the DVS
(reference [2]) implementation to assign/revoke identifiers is expected.
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3.2.3 An interface to provide access to and configuration of the MIB of the DAS
(reference [1]) implementation to assign/revoke identifiers is expected.
NOTE – It is expected that in future there may be standardisation of protocols to discover
the services provided by a physical device directly from the physical device
itself. These protocols will have associated expected services from the underlying
layers.
3.3 DEVICE ENUMERATION SERVICE PARAMETERS
3.3.1 GENERAL
The DES shall use the parameters specified in 3.3.2 to 3.3.9.
3.3.2 TRANSACTION IDENTIFIER
3.3.2.1 The Transaction Identifier parameter shall be a value, assigned by the invoking user
entity, which is subsequently used to associate indication primitives with the causal request
primitives.
NOTE – The user entity is thus able to correlate all indications and confirmations with the
originating service request.
3.3.2.2 Transaction Identifier shall be unique within the user application entity.
3.3.2.3 Uniqueness in the service provider shall be achieved by Transaction Identifier.
3.3.3 RESULT METADATA
The Result Metadata parameter shall be used to provide information generated by the DES
provider to the service invoking entity to provide information related to the successful or
failed result of a device enumeration operation.
NOTE – The parameter can also include other information indicating failure conditions,
e.g., that the specified device type does not match the device types supported by
the spacecraft.
3.3.4 VIRTUAL DEVICE IDENTIFIER
The Virtual Device Identifier shall be the system-wide unique device identifier assigned by
the service when the device is successfully added.
NOTE – The identifier is used in the DVS primitive.
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3.3.5 PHYSICAL DEVICE IDENTIFIER
The Physical Device Identifier shall be the device identifier used in the DAS primitive.
3.3.6 DEVICE SERIAL NUMBER
The Device Serial Number shall be the unique identifier of the physical device added.
NOTES
1 The parameter allows distinguishing between devices of the same type installed on
the spacecraft. The device type does not provide complete discrimination of the
functions that devices can provide. For example, there may be three identical reaction
wheels onboard a spacecraft, each spanning a different part of the attitude actuation
space; in order for an attitude control system to use those reaction wheels correctly, it
must know the orientations of the wheels in the vehicle frame. The function that a
device can provide on board a spacecraft typically depends upon the transformation
between device coordinates and vehicle coordinates.
2 This document assumes (without specifying the implementation) that the designers of
a spacecraft have provided a manifest of devices with serial numbers and with the
appropriate transformation for each device. Given the manifest, the device serial
number completely identifies the function that the device may serve on board the
spacecraft.
3.3.7 DEVICE TYPE
The Device Type shall be the identifier of the type of the device added. The parameter shall
identify the functional interface supported by the device itself.
NOTE – The Device Type identifier may be included in the Common Dictionary of Terms
(reference [D5]—standardisation of this is in progress) and thus identify to a
standardised functional interface (standardisation of functional interfaces is
proposed).
3.3.8 SPACECRAFT NETWORK ADDRESS
3.3.8.1 The Spacecraft Network Address shall be the spacecraft network address of the
device added.
3.3.8.2 The Spacecraft Network Address shall identify the subnetwork and the device
within the subnetwork.
3.3.8.3 The Spacecraft Network Address shall be system-wide unique.
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3.3.9 DEVICE QUERY CONSTRAINTS
3.3.9.1 The Device Query Constraints shall be a list of constraints on a device query, which
DES compares to the manifest of the devices in its inventory and optionally to the electronic
datasheets if available onboard.
3.3.9.2 The constraints of the list shall filter the values of attributes in the manifest or in the
electronic data sheets.
3.3.9.3 The conjunction of constraints shall define the set of devices to be returned.
3.3.9.4 Each constraint shall consist of the name of an attribute, a value of the attribute, and
a relation.
3.3.9.5 The relations shall have the following values:
a) The Equal relation shall indicate that the value of a discrete attribute must be equal to
the value in the constraint.
b) The LessThan relation shall indicate that the value of an ordered attribute must be
less than the value in the constraint.
c) The GreaterThan relation shall indicate that the value of an ordered attribute must be
greater than the value in the constraint.
d) The NotEqual relation shall indicate that the value of a discrete attribute must be not
equal to the value in the constraint.
e) The LessThanOrEqual relation shall indicate that the value of an ordered attribute
must be less than or equal to the value in the constraint.
f) The GreaterThanOrEqual relation shall indicate that the value of an ordered attribute
must be greater than or equal to the value in the constraint.
3.3.9.6 The names of a minimal set of attributes shall be:
a) deviceSerialNumber;
b) deviceType;
c) spacecraftNetworkAddress.
NOTE – Other attributes and relations will be defined in the dictionary of terms for
electronic data sheets.
3.4 DEVICE ENUMERATION SERVICE PRIMITIVES
3.4.1 GENERAL
3.4.1.1 The DES interface shall provide the following primitives:
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a) DEVICE_FOUND.indication, as specified in 3.4.4;
b) DEVICE_LOST.indication, as specified in 3.4.7;
c) ENUMERATE_DEVICES.request as specified in 3.4.8;
d) ENUMERATE_DEVICES.indication as specified in 3.4.9.
3.4.1.2 The DES interface may provide the following primitives:
a) ADD_DEVICE.request, as specified in 3.4.2;
b) ADD_DEVICE.indication, as specified in 3.4.3;
c) REMOVE_DEVICE.request, as specified in 3.4.5;
d) REMOVE_DEVICE.indication, as specified in 3.4.6;
e) QUERY_DEVICES.request as specified in 3.4.10;
f) QUERY_DEVICES.indication as specified in 3.4.11.
3.4.2 ADD_DEVICE.REQUEST
3.4.2.1 Function
The ADD_DEVICE.request primitive shall be used to request that a physical device be
assigned virtual and physical device identifiers and user communication with the associated
physical device using DVS and DES be enabled.
3.4.2.2 Semantics
The ADD_DEVICE.request primitive shall use the following semantics, with the meaning
of the parameters specified in 3.3:
ADD_DEVICE.request (Transaction Identifier, Device Serial Number,
Device Type, Spacecraft Network Address)
3.4.2.3 When Generated
The ADD_DEVICE.request primitive shall be passed to the DES provider to request
assignment of the logical and physical device identifiers and to enable user communication
with the associated physical device using the DVS and DES using the addressing specified
by the primitive parameters.
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3.4.2.4 Effect on Receipt
Receipt of the ADD_DEVICE.request primitive shall cause the DES provider to retrieve the
physical device attributes using DDS and to verify that they match with input parameters.
If the match is positive new virtual and physical device identifiers shall be assigned and,
using the DVS and DAS management interfaces used to update their MIBs respectively,
DVS and DAS shall be configured to support the access to the associated physical device.
3.4.3 ADD_DEVICE.INDICATION
3.4.3.1 Function
The ADD_DEVICE.indication shall be used to pass the result of a previous
ADD_DEVICE.request to the user entity.
3.4.3.2 Semantics
The ADD_DEVICE.indication primitive shall use the following semantics, with the
meaning of the parameters specified in 3.3:
ADD_DEVICE.indication (Transaction Identifier, Device Serial Number, Device
Type, Spacecraft Network Address,
Virtual Device Identifier, Physical Device Identifier,
Result Metadata)
3.4.3.3 When Generated
The ADD_DEVICE.indication shall be issued by the service provider to the receiving user
entity on the addition of a device in response to an ADD_DEVICE.request.
3.4.3.4 Effect on Receipt
The response of the user entity to an ADD_DEVICE.indicati
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