This presentation was presented in Siso Spring 2013. Know about the use of DDS for HLA time managment service.

1. Time managment service
over DDS
Presented by Jose R Martinez
2013 Spring SIW

2. Speaker
José Ramón Martínez Salio
MSc Industrial Engineering
AGENDA
Presales Team Director
NADS
 Time Management
overview
jrmartinez@nads.es
 DDS and time
management
 Implementation
 Questions
Total time 30 minutes
2013 Spring SIW

3. Time managment overview
2013 Spring SIW

4. 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 SIW

5. Time Management Service: Analysis
Time management requisites
• Has to cope with different time
uses and necessities
• Has to guarantee order and
repeatability
• 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
2013 Spring SIW

6. 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.
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2013 Spring SIW

7. DDS and time management
2013 Spring SIW

8. DDS and time management
2013 Spring SIW

9. 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 SIW

10. 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 SIW

11. 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

12. Implementation
2013 Spring SIW

13. LSA Layers Overview
Simulators; new and existing (included legacy)
Current simulation architectures; HLA, DIS, TENA DDS simulators
Arch specific APIs Gateways
Simulators TIME management
HLA DIS TENA Simulation Services
DDS DDS DDS Common interface
Data-centric Middleware: OMG DDSI
Open Wire protocol
2013 Spring SIW

14. Creating Time Management in SimWare RTI
• 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.
Other layers Time management layer
DDS-based communication layer
2013 Spring SIW

15. Time stamp order (TSO) message delivery service
• 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
DDS DDS
TSO queue RO queue
2013 Spring SIW

16. Coordinating time advance requests
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.
2013 Spring SIW

17. Questions?
2013 Spring SIW

18. Please address any questions about this presentation to:
José Ramón Martínez Salio
Technical Presales Director
jrmartinez@nads.es
2013 Spring SIW