time managment service over dds
DESCRIPTION
This presentation was presented in Siso Spring 2013. Know about the use of DDS for HLA time managment service.TRANSCRIPT
2013 Spring SIW
Time managment service over DDS
Presented by Jose R Martinez
2013 Spring SIW
José Ramón Martínez SalioMSc Industrial EngineeringPresales Team DirectorNADS
Speaker
Total time 30 minutes
AGENDA
Time Management overview
DDS and time management
Implementation Questions
2013 Spring SIW
Time managment overview
2013 Spring SIW2013 Spring SIW
Time Management Service: rationale
• It started in HLA for coordinate simulators
• Guarantee delivery of messages in right order
• Make simulations repeatable
The function of time management service is the delivery of messages in order in a way consistent to all the federation
2013 Spring SIW2013 Spring SIW
Time Management Service: Analysis
• Federators in HLA can be:• Time regulating: send messages that must be delivered in
consistent order.• Time constrained: receive messages in consistent order
• The way each federate uses time internally is transparent to the rest
Time management requisites• Has to cope with different time
uses and necessities• Has to guarantee order and
repeatability
2013 Spring SIW2013 Spring SIW
Time Management Service: Analysis
Any Time management service has to implement
• Time stamp order (TSO) message delivery service.• A protocol where federates explicitly request advances
in their federate time, and the RTI guarantee no events will later arrive containing a smaller time stamp.
TIME STAMPED TIME STAMPED
TIME STAMPED
2013 Spring SIW
DDS and time management
2013 Spring SIW2013 Spring SIW
DDS and time management
2013 Spring SIW2013 Spring SIW
The Time Management Service in DDS
• DDS provides mechanisms to guarantee order, repeatability and time management.
• But, is that enough to cover time management service in HLA?
2013 Spring SIW2013 Spring SIW
The Time Managment Service in DDS
DDS “as is” is not enough.– DDS is oriented to real time. All the nodes are in the same
time. Makes “strict” synchronization: all federates are in each moment in the last available time. Uses real time.
– HLA uses “open” synchronization : all time-constrained federates are in every moment before (or can advance their own) the Federation time. Uses logical time.
2013 Spring SIW2013 Spring SIW
The Time Managment Service in DDS
Order and timestamp– DDS allow to receive messages in reception order OR
in timestamp order.– HLA allows receiving messages in reception order AND
in timestamp order.
2013 Spring SIW
Implementation
2013 Spring SIW2013 Spring SIW
LSA Layers Overview
Data-centric Middleware: OMG DDSIOpen Wire protocol
Simulation Services
Arch specific APIs
Simulators; new and existing (included legacy)
Current simulation architectures; HLA, DIS, TENA
Common interface
Gateways
TIME managementSimulators
HLADDS
DISDDS
TENADDS
DDS simulators
2013 Spring SIW2013 Spring SIW
• We are not using DDS communication layer– DDS is not enough– Open discussion: use of DDS in some cases. The standard allows
the use logical times for time stamp. Implementation is not clear.• Time management is here a new layer over communication
layer.
Creating Time Management in SimWare RTI
DDS-based communication layer
Time management layerOther layers
2013 Spring SIW2013 Spring SIW
• We are building two message queues for time:– One for TSO (TimeStamp order)– One for RO (Receive order)
• There is another queue for msg without time
Time stamp order (TSO) message delivery service
TSO queue RO queueDDS DDS
2013 Spring SIW2013 Spring SIW
The lookahead problem in distributed networks– We are not yet fully distributed: use of central
server.– With DDS is possible to distribute.– Open issue on latest version. Working on it.
Coordinating time advance requests
2013 Spring SIW
Questions?
2013 Spring SIW
Please address any questions about this presentation to:
José Ramón Martínez SalioTechnical Presales [email protected]