05FSIW026 - PowerPoint PPT Presentation

Title: 05FSIW026


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2005 FALL SIW
A Modest Proposal for Slimming Down HLA and DIS
Heartbeats
Frank Hill SDS International 3420 Norman Berry
Drive Suite 301Atlanta, GA 30354 fhill_at_sdslink.c
om 404.446.3532
2005 Fall SIW 05F-SIW-026
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The Problem

• Heartbeats are the periodic repetition of
  unchanged data.
• Both large-scale HLA exercises with DIS federates
  and all DIS exercises use heartbeats.
• Heartbeats create a heavy data load on the
  network even when data is being metered over the
  heartbeat interval.
• The problem is only going to get worse as more
  entities are present and more data needs to be
  passed in an exercise.

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Why Heartbeats?

• Heartbeats are needed for 2 basic reasons
• To ensure that data is received by all federates
  when reliable communications cannot be assured.
• To allow a federate that joins or rejoins an
  exercise in progress to receive all data in a
  timely manner.

DIS simulations will be participating in
Joint Exercises with an HLA backbone for the
foresee- able future due to funding and other
constraints. They have learned to peacefully
co-exist.
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Why Slim down Heartbeats?

• Heartbeat bandwidth usage is increasing because
• More entities are being generated in support of
  large exercises (40-50,000 up to 100,000)
• Entities are appearing sooner and not leaving the
  exercise when they are destroyed.
• More data is needed per entity to represent them
  realistically.
• Military PC video players will introduce many
  more human entities and realistic interactions.

The Heartbeat Slimdown Plan will reduce
heartbeat bandwidth usage by up to 95.
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A better way

• Simple, straightforward and builds on a proven
  concept used by military tactical data links.
• Add a Message Reference Number (MRN) to PDUs that
  have a heartbeat requirement using 8-bits of
  padding in the PDU Header.
• Add a new Heartbeat PDU.
• Add a new Data Update Request PDU.

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PDUs With Heartbeats

• Entity State
• Entity State Update
• IFF/ATC/NAVAIDS
• Electromag. Emissions
• Designator
• Transmitter
• Receiver
• Data
• Environmental Process
• Gridded Data
• Data-R
• Record-R
• Underwater Acoustics (UA)

• Supplemental Emission/Entity State
• (SEES)
• Aggregate State
• IsGroupOf
• Minefield Data
• (Heartbeat mode)
• Minefield State
• TSPI (LE)
• Appearance (LE)

Those in red are usually the most numerous PDUs
in an exercise.
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The MRN

• The MRN is set and processed as follows for
  entity-related PDUs
• A separate MRN is established for each PDU Type
  for each entity.
• The issuing and receiving federate must save the
  MRN for each entity for each type of PDU.
• Example Entity 48-2-500
• Entity State MRN 001 IFF Data MRN 004
• Emissions MRN 006
• The MRN is incremented each time a PDU is output
  for a specific entity because data has changed.

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The Heartbeat PDU

• At heartbeat time, a Heartbeat PDU is output for
  each PDU type listing all associated entities.
• Originating federate and PDU Type.
• Each Entity ID of entities that have had this PDU
  type sent for them along with the last MRN for
  that entity.
• Continuation Heartbeat PDUs may be sent.
• The receiving federates treat the Heartbeat PDU
  as meeting the Heartbeat requirement for that PDU
  Type for that entity.
• If the MRN does not match the present MRN for
  that entity and PDU Type, a Data Update Request
  is sent.

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Data Update Request PDU

• The Data Update Request PDU is used in two ways
  (concept borrowed from military data links)
• To request one or more PDU Types for an entity
  when it is determined it does not have the latest
  information.
• When it is joining or rejoining an exercise.
• The Data Update Request (DUR) includes
• Originating federate.
• Addressed federate or broadcast to all.
• What PDU types it needs.
• Specific Entity IDs (if appropriate)
• Criteria - geographic, entity domains,
• kinds, etc. (if appropriate)

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How it works
Initial 48-2-500
Federate A
Federate B
ES PDU MRN 1
48-2-500 MRN 1
48-2-500 MRN 1
Change
Federate A
Federate B
ES PDU MRN 2
48-2-500 MRN 1
48-2-500 MRN 2
Heartbeat PDU
48-2-500 ES PDU MRN2
48-2-500 MRN 1
48-2-500 MRN 2
DUR PDU
Federate A
Federate B
IFF PDU Type ES 48-2-5000
48-2-500 MRN 1
48-2-500 MRN 2
Response
ES PDU MRN 2
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48-2-500 MRN 2
48-2-500 MRN 2
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Joining an Exercise
DUR request
Federate A
Federates
Type data needed
DUR replies
Federate A
Federates
Start Status
Requested data
Federate A
Federates
Various PDU Types
DUR Completed
Federate A
Federates
End Status
Starts sending
Data - interactions
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HLA

• The MRN is associated with entity and data types.
  
• When an attribute is sent, an MRN counter is set
  for the class/entity
• Example IFF Data/Entity 48-2-5000.
• IFF Mode 3/0020 sent, then MRN 001
• IFF Mode 3 turned off, MRN 002.
• At each receiving federate, the MRN for the type
  data and entity is incremented by one each time
  an attribute is received.
• If attributes are bundled, they are treated as
  one message as far as incrementing the MRN.
• The Heartbeat and Data Update Requests become
  interactions.

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Implementation

• Obviously, it is not practical to expect
  widespread adoption of a heartbeat reduction
  concept by DIS or HLA federates.
• The Alternatives include
• Add as a new feature to existing government and
  commercial DIS and HLA Gateways.
• Implement for major simulation programs like
  JCATS, JSAF, AWSIM, OneSAF.
• Only implement for Entity State PDUs initially.

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Present Slimdown Efforts

• The Air Force DIS Filter Program and JNTC and
  Navy DIS/HLA Gateways can
• Filter entities to reduce overall traffic placed
  on the network.
• Reduce the entity output rate for changes (e.g.,
  30X a second flight simulator outputs reduced to
  once every 5 seconds.)
• Setting up subnets within an overall network such
  that not all federates receive all entities.

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Other Slimdown Plans

• IEEE 1278.1-2005 Update in progress has proposed
  changes to slim down heartbeats
• Heartbeat timers by entity domain and present
  status (e.g., static ground entities have a
  different heartbeat than moving ground entities.)
• Attribute PDUs not sent if overall system is off
  (e.g., IFF and emissions).
• Attribute PDUs no longer sent if entity is
  destroyed but remains in the exercise.

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Mode 5/S Heartbeats

• The SISO Mode 5/S Study Group preliminary
  estimate is that the IFF PDU and HLA IFF
  inter-actions will double the amount of data sent
  for a transponder that has both Mode 5 and Mode
  S.
• To reduce the additional network loading, the
  study group is evaluating the idea that federates
  with a Mode 5 and Mode S capability must
  implement
• The new layers of the IFF PDU that support Mode 5
  and Mode S data.
• Setting the MRN in the IFF PDU.
• The Heartbeat PDU for the IFF PDU Type.
• The Data Update Request for the IFF PDU Type.

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Conclusion

• The trend is more entities and more
  entity-associated data to support larger and more
  realistic training exercises.
• We need to start developing heartbeat slim down
  solutions now.
• The Heartbeat slim down concept applies to both
  HLA and DIS.
• HLA Hosts, FOMs and DIS/HLA gateways need to
  support the heartbeat slimdown concept.
• Government DIS gateways like DMOCs DIS Filter
  Program should be encouraged to add support for
  the heartbeat slimdown concept.

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Questions?
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