07 september 2015 peter mendham sois plug-and-play: use cases and requirements
TRANSCRIPT
CCSDS Fall Meeting: SOIS PnP Use Cases and Requirements2
Agenda
Introduction and backgroundOperational scenariosScenario use casesSynthesising a use caseService level approaches and requirementsSubnetwork level requirementsSubnetwork support requirementsRecommendationsComments to encourage discussion
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Introduction
Asked to review plug-and-play…Use casesDefinitionScopeRequirements
Starting point was the concept paperPlus any other published material available
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Approach
Back to basicsLargely ignore the SOIS architectureIntend to review the architecture as an outcomeScenarios to use cases to requirements to a better defined purpose and scope
Device Virtualisation Service
Device Access Service
Device Enumeration Service
Applications
Packet ServiceMemory Access
ServiceDevice Discovery
Service
Network Management Service
Physical Layer
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Definitions of Plug-and-Play
Generic definition (various sources)
SOIS definition (concept paper)
Plug-and-play encompasses the characteristics of an interface or device specification to facilitate the discovery of a hardware component in the system and the automatic configuration of that component such that it may be used without user intervention.
Plug-and-play encompasses the mechanisms necessary to establish communication services between two data systems in a spacecraft’s onboard (sub-)network, without requiring reconfiguration or manual installation of device drivers by any user (higher-level service or OBSW application).
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Scenarios
Rapid spacecraft developmentAutomated integration and testFDIR assistanceGround segment access
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Rapid Spacecraft Development (1)
Many drivers to reduce spacecraft development time
Commercial drivers: < 2 yearsMilitary drivers (e.g. ORS): < 1 week
Reduce development time throughStandardised componentsStandardised interfacesIncremental qualification/V&V (cf. IMA)Use of in-house/commercial off the shelfRapid integration
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Rapid Spacecraft Development (2)
Plug-and-play enablers:Removal of dependence on subnetwork configurationReuse of applications independently from devicesReuse of devices independently from applicationsIncrease portability of applications
Beneficiaries:System integrators (e.g. primes)Customers (e.g. agencies)Device manufacturersPermits/promotes inter-agency cooperation
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Automated Integration and Test (1)
During integration a number of configurations are necessary for:
SpacecraftEGSE
Each configuration must be validatedUse plug-and-play to permit
Discovery of devicesAutomated configuration of services/applicationsAutomated configuration of EGSE and other test equipment
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Automated Integration and Test (2)
Plug-and-play enablers:Removal of dependence on subnetwork configurationConfiguration of communications independent to applicationsValidate applications independent to communicationsValidate devices independently from applications etc.
Beneficiaries:System integrators (e.g. primes)Customers (e.g. agencies)Device and EGSE manufacturersPermits/promotes inter-agency cooperation
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FDIR Assistance (1)
Fault detectionDetect the disappearance of subnetwork devicesMight indicate a fault
IsolationUse subnetwork features to isolate deviceReconfigure routing/fail over bus
RecoveryIdentify replacement device(s)Reconfigure subnetwork as necessary
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FDIR Assistance (2)
Plug-and-play enablers:Device discovery (addition/removal notification)Device isolation (depending on subnetwork)Transparent subnetwork reconfiguration for identical redundant devices
Beneficiaries:Software developersSystem integrators (e.g. primes)Customers (e.g. agencies)Spacecraft operators (may see more reliable spacecraft)
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Ground Segment Access (1)
Automated adaptation of ground segment interface to accommodate
Different spacecraft configurationsDifferent devices
Adapt telemetry expectedFormat and content
Adapt telecommands issuedTypes available and format
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Ground Segment Access (2)
Plug-and-play enablers:Device discoveryProvide services independently from subnetwork configurationService discovery by ground segment applications
Beneficiaries:Operational stakeholdersOriginal space and ground segment customer(s) (e.g. agencies)System integrators (e.g. primes)Space and ground segment developers
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Use Cases
Use case for each scenarioPresented as a process
Or multiple processes
Will eventually be drawn together into a synthesised use case
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Rapid Spacecraft Development Use Case (1)
Use case for iterative/incremental development and qualification/V&VUse case for integration of devices into spacecraft
Device driven process for subnetwork issuesApplication driven process for service issues
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Rapid Spacecraft Development Use Case (2)
1. Device is physically and logically integrated onto spacecraft network
2. Subnetwork plug-and-play features discover the device
3. Subnetwork plug-and-play network management carries out network configuration and configuration of subnetwork-related device features
4. Subnetwork plug-and-play network management carries out configuration of subnetwork services
5. Subnetwork plug-and-play assists in the discovery of services/capabilities of device
6. Capabilities are exposed through to (potentially standardised) applications via a suitably standardised interface
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Rapid Spacecraft Development Use Case (3)
1. The application is loaded2. The application queries the service interface for
the availability of a specific device or device type
3. If the device is available the application obtains the service interface and binds to it, application features relating to the service are then enabled
4. If the device is not available the application either waits and then returns to step 2 (re-query), or disables the features relating to the service
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Automated Integration and Test Use Case (1)
Many similarities to previous scenarioTwo parts:
Plug-and-play on spacecraft to adapt to integrated devicesPlug-and-play of EGSE attached to spacecraft for integration and test
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Automated Integration and Test Use Case (2)
1. Device is physically and logically integrated onto spacecraft network
2. Subnetwork plug-and-play features discover the device3. Subnetwork plug-and-play network management carries out
network configuration and configuration of subnetwork-related device features
4. Subnetwork plug-and-play network management carries out configuration of subnetwork services
5. Subnetwork plug-and-play assists in the discovery of services/capabilities of device
6. Capabilities are exposed through to (potentially standardised) applications via a suitably standardised interface
7. Applications registered to use the available service interfaces are either loaded or have the appropriate service-related functions enabled (if they are already loaded)
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Automated Integration and Test Use Case (3)
1. EGSE is physically and logically integrated onto spacecraft network
2. EGSE subnetwork plug-and-play features discover the device3. Subnetwork plug-and-play network management detects
current network configuration and configuration of subnetwork-related device features and configures EGSE subnetwork services accordingly
4. Subnetwork plug-and-play assists in the discovery of services/capabilities of device
5. Capabilities are exposed through to (potentially standardised) EGSE applications via a suitably standardised interface
6. Test and/or V&V applications registered to use the available device service interfaces are either loaded or have the appropriate service-related functions enabled (if they are already loaded)
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FDIR Assistance Use Case (1)
FDIR process utilises plug-and-play at four stages:
Initial integrationFault detectionFault IsolationRecovery
Additionally, plug-and-play may be used to accommodate non-duplicate redundancy
Such as 3 of 4 arrangements e.g. tetrahedral gyro arrangements
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FDIR Assistance Use Case (2)
Initial Integration• Subnetwork plug-and-play features discover both
prime and redundant devices• Subnetwork plug-and-play network management
carries out network configuration and configuration of subnetwork-related device features
• Subnetwork plug-and-play network management carries out configuration of subnetwork services;
• Subnetwork plug-and-play assists in the discovery of services/capabilities of device
• Capabilities of both devices are exposed through to (potentially standardised) applications via a suitably standardised interface
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FDIR Assistance Use Case (3)
Fault Detection1. The prime device ceases to be either
physically or logically present on the subnetwork
2. Network discovery determines the absence of the device either through active polling or passive notification
3. Optionally, applications are notified of the absence of the device (and potential failure) and/or the lack of availability of particular services
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FDIR Assistance Use Case (4)
Fault Isolation1. Subnetwork plug-and-play network
management reconfigures the subnetwork to isolate the failed prime device (if possible)
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FDIR Assistance Use Case (5)
Recovery1. Subnetwork plug-and-play network
management carries out network configuration and configuration of subnetwork-related device features for the redundant device
2. Subnetwork plug-and-play network management carries out configuration of subnetwork services to accommodate the redundant device
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FDIR Assistance Use Case (6)
Service Level Adaptation1. Subnetwork plug-and-play assists in the discovery of
services/capabilities of the remaining device(s)2. A uniform service interface is presented to a (potentially
standardised) application though synthesis of the services provided by the available devices
3. Applications query the service interface to determine the availability of replacement services for the ones lost
4. If suitable services are available the application obtains the service interface and binds to it, application features relating to the service are then enabled (this may require adapting the service interface e.g. type conversions, frame rotations)
5. If suitable services are not available the application either waits and then returns to step 2 (re-query), or disables the features relating to the services
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Ground Segment Access Use Case (1)
Splits into two partsOnboard integration and discovery of devicesAccess by ground segment applications
First part is the same as beforeProcess of second part depends access
Device oriented Service oriented
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Ground Segment Access Use Case (2)
Device Oriented1. The ground segment application queries the
spacecraft service interface for the availability of a specific device or device type
2. If the device is available the application obtains the service interface and binds to it, application features relating to the service are then enabled
3. If the device is not available the application either waits and then returns to step 2 (re-query), or disables the features relating to the service
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Ground Segment Access Use Case (3)
Service OrientedGround segment applications query the service interface to the spacecraft to determine the availability of suitable servicesIf suitable services are available the application obtains the service interface and binds to it, application features relating to the service are then enabled (this may require adapting the service interface e.g. type conversions)If suitable services are not available the application either waits and then returns to step 2 (re-query), or disables the features relating to the services
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Synthesising a Use Case
Separate levelsSubnetwork levelService level (device capabilities)
Subnetwork level is relatively easyService level splits into three approaches
Device-driven, device-boundApplication-driven, device-boundApplication-driven, service-bound
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Subnetwork Level Synthesised Use Case
1. A change is made to the devices physically and/or logically integrated onto spacecraft subnetwork
2. Subnetwork plug-and-play features discover the addition or removal of a devices
3. Subnetwork plug-and-play network management carries out network configuration and configuration of subnetwork-related device features
4. Subnetwork plug-and-play network management carries out configuration of subnetwork services
5. Subnetwork plug-and-play assists in the discovery of services/capabilities of device
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Device-Driven, Device-Bound Use Case
1. The subnetwork indicates the availability of a device or device class, potentially via a higher level service
2. Applications registered to use the available device service interfaces are either loaded or have the appropriate service-related functions enabled (if they are already loaded), or are simply informed
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Application-Driven, Device Bound Use Case
1. The application queries the service interface for the availability of a specific device or device type
2. If the device is available the application obtains the service interface and binds to it, application features relating to the service are then enabled
3. If the device is not available the application either waits and then returns to step 1 (re-query), or disables the features relating to the service
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Application-Driven, Service-Bound
1. Applications query the service interface to determine the availability of suitable services on the basis of the service elements they provide;
2. If suitable services are available the application obtains the service interface and binds to it, application features relating to the service are then enabled (this may require adapting the service interface e.g. type conversions)
3. If suitable services are not available the application either waits and then returns to step 1 (re-query), or disables the features relating to the services
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Where Does the Device Interface Come From?
Something has to know how to talk to the device (i.e. a device driver)Independent concern to how interface is exposedInterface can be:
Manually written or auto-codedGenerated online or offline
Making use of an electronic data sheet
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Manually Generated Device Interface
EDS
Manual Coding
Load/Enable Instantiated I/FVID/PIDClass ID
Instance ID
SubnetworkDevice
Application
DeviceI/F
OBC
Ontology
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Auto-Coded Device Interface
EDS
Auto-coding
Load/Enable Instantiated I/FVID/PIDClass ID
Instance ID
SubnetworkDevice
Application
DeviceI/F
OBC
PrimitiveOps
OntologyManual Coding
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Online Generated Device Interface
EDS
Generation Generated I/FVID/PIDClass ID
Instance ID
SubnetworkDevice
Application
OBCPrimitiveOps
Ontology
Manual Coding
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Device Interface Generation Comments
SimilaritiesAll can/must use an EDSAll utilise subnetwork level plug-and-play
ImportantlyAll are completely independent of subnetwork
Except for EDS provision
All are completely independent of service interface approach
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Service Level Requirements
Need device enumerationNeed service virtualisationService interface depends on approach
Virtual device classes with standardised interfacesCould permit device-driven application loading/enablingService interface permitting queries on service elements
e.g. “I need a service which gives me the temperature of this part of the spacecraft”
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Subnetwork Level Requirements
Device discoveryManagement of subnetwork
Subnetwork-specific features of devicesSubnetwork resources
Management of subnetwork addressingReconfiguration of other subnetwork services appropriately
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Subnetwork Requirements
Network discoveryDevice discovery (polled/notified)Topology discovery
Device identificationUnique identificationType/class
Configuration of subnetwork-specific device features
e.g. address, link speed
Configuration of subnetwork resourcese.g. bus controllers, routers
Sourcing of electronic data sheet
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Subnetwork Network Management
Issues of mechanismHow addresses are setSubnetwork specificIndependent of mission
Issues of policyHow addresses should be assignedSubnetwork specificMission or mission class specific
Mechanism and Policy should be separated
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Subnetwork Plug-and-Play Architecture
Applications
Physical Layer
Device Enumeration
Service
Device Virtualisation
Service
Device Access Service
Device Discovery Service
Memory Access Service
Packet Service
Network Management
Service
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Subnetwork Plug-and-Play Architecture
Applications
Physical Layer
Device Enumeration
Service
Device Virtualisation
Service
Device Access Service
Device Discovery Service
Memory Access Service
Packet Service
Network Management
Service
ConfigurationNetwork
Management Service
Policy
Defined Interface?
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Plug-and-Play Scope
Subnetwork and service levels are separableSubnetwork level scope:
Device discoveryDevice identificationSubnetwork configuration and management
Service level scope:Service discoveryStandardised virtual interfaceQuery-able interface?Application binding
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Conclusions and Discussion Points (1)
Plug-and-play is highly beneficialIt would seriously hinder the progress of platforms using SOIS not to have plug-and-play
Requirements for subnetwork level are easily understoodRequirements placed on subnetwork technologies are easily understoodScope of plug-and-play in the subnetwork context is easily definable and constrainedA couple of minor changes necessary to subnetwork architecturePolicy should be separated from mechanismSubnetwork is separable from service level
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Conclusions and Discussion Points (2)
A standard format for electronic data sheets would be useful to help tie subnetwork and service levelsService level plug-and-play is less constrainedDifferent approaches possible
Based on standardised device classes known a prioriBased on a query-able service interface to permit service inspection
Should both be supported?Should subnetwork and service level plug-and-play be separated in the context of SOIS?