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Bill%20Helfinstine
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Exploration of possible changes in doctrine, organization, training, material, ... its tuning specifically for scalability and its implementation of inset grids ... – PowerPoint PPT presentation
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Title: Bill%20Helfinstine
1
Experiences with DataDistribution Managementin
Large-Scale Federations
Joint Experimentation and how it takes advantage
of DDM and IP Multicasting
- Bill Helfinstine
- Mark Torpey
- Deborah Wilbert
- Wayne Civinskas
- Lockheed Martin Information Systems
2
What is Joint Experimentation and what makes it
difficult?
- Exploration of possible changes in doctrine,
organization, training, material, leadership and
people to improve joint operations - In order to explore jointness in an interesting
way, a large scenario is needed - Large geographic playbox
- Large number of vehicles to populate the playbox
- In order to support operators in the loop,
real-time operation is needed - In order to support large scenarios, large
amounts of hardware and therefore space are
needed - Simulation distributed around the country to
reduce cost
3
What do we mean by Large-scale federations
- Large number of objects (gt 30,000)
- Large number of federates (gt 100)
- Large number of sites around the country (5 or
more) - Simulation synchronized with real-time clock
- Therefore, there is a very large amount of data
in playwhich must be handled quickly and
efficiently
4
How can DDM help?
- DDM provides a means to tell the RTI what the
federate is interested in. - The RTI will do filtering on the data before the
federate needs to get involved - Provides a means to dynamically control the flow
of data to the simulations - The dynamicism of DDM provides a way to adapt to
the changing data requirements of each simulation
as the scenario progresses - In a joint exercise, DM is often not powerful
enough to describe the data requirements fully
5
Example
D
B
C
A
- Geographic interest regions
6
RTI implementations of DDM
- Distribute all subscription region information
around to all federates, and do source filtering - Include publication region information with each
update/interaction and do receiver filtering - Snap publication region to a grid and use the
grid to do coarse filtering using the network
itself - With a gridded implementation of the DDM, IP
multicasting can be employed - IP multicast lets some or all of the filtering be
done by the network hardware and operating
system, to reduce load on the federates process. - Just doing coarse filtering breaks the spec
7
How has DDM helped Joint Experimentation?
- In previous JE events, total object count was
much higher than a single federate could accept.
MaxObjects PerFederate
Object Count
Vehicle Count
Federate Count
Event
400
7000
3600
300
STOW97
5000
40000
20000
100
J9901
20000
160000
100000
150
AO00
8
MC02 challenges for DDM use
- Millennium Challenge 2002 will be run using
RTI-NG, which does perfect filtering on receive,
which interacts poorly with our historical use of
DDM - We have not come up with a solution yet that
gives us the flexibility and scalability we have
enjoyed in the past, due to RTI-s and its tuning
specifically for scalability and its
implementation of inset grids - JSAFs Hyperspace DDM scheme is hard to explain
to other federate developers - Some sort of DDM will probably be necessary due
to the data requirements (gt30,000 objects at gt10
sites) - Gateways to DIS or private protocols make DDM
work very poorly
9
Caveats of using DDM
- The design of the DDM scheme is fairly
scenario-specific - The operational design of the simulation usually
does not take DDM into account - Placement of opfor
- Centralized data collection
- Operational split by service means joint
interaction happens over the WAN - Many federates are designed to require all the
data - It is not easy to implement DDM support in a
federate - IP multicasting is not well supported by quite a
bit of networking hardware
10
Caveats continued
- Loggers and wide-range viewers make DDM
ineffective - Since they need to receive almost everything, DDM
provides no filtering - Clever data collection design can reduce the data
an individual logger receives - Exercise controllers really like map displays
with everything on them - The HLA 1.3 spec has a number of requirements
that we have heretofore ignored, which
significantly reduce flexibility and performance
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