Connectionless Mode and User Defined DDM in RTING V6

1
Connectionless Mode and User Defined DDM in
RTI-NG V6

• Mark Hyett
• mhyett_at_dctd.saic.com
• Roger Wuerfel
• Roger.D.Wuerfel_at_saic.com

2
Overview

• Introduction
• Connectionless Mode
• Need
• Implementation
• Usage
• Experience
• User Defined DDM
• Need
• Implementation
• Usage
• Summary

3
Introduction

• RTI-NG was designed for configurability and
  extensibility to allow its use in a broad range
  of simulation types
• Each simulation type has different requirements
  for
• Performance
• Reliability
• Operational characteristics
• RTI 1.3NGv6 introduced two new features
• Connectionless Mode
• User Defined DDM

4
Need for Connectionless Mode

• RTI-NGs default configuration creates reliable
  connections between all the federates
• Federates that are not IF Spec compliant cause
  problems
• Crashing federates
• Network outages
• Federates in debuggers
• Requires cleanup of broken connections or
  buffering of data
• IF Spec does not address this type of fault
  tolerance

5
Connectionless Mode

• Remove reliable traffic and reliable connections
• Federate data
• RTI administrative traffic
• IF Spec implies some reliable communication so
  some services are not available
• Reliable transportation type for federate data
• Time Management
• Ownership Management
• Save and Restore
• Synchronization
• MOM
• DDM is still available!

6
Connectionless Mode Implementation

• All network traffic is UDP multicast
• Federate handle is random and broadcast out for
  collision detection
• Federation handle is hash of federation name and
  FED file
• Lazy Discovery
• No rtiexec or fedex processes
• rtiConsole replaced with federateList that uses
  best effort broadcast to discover federates

7
Connectionless Mode Usage

• RTI.RTIMode RID file parameter specifies
  Standard or Connectionless
• Standard mode is the default, verifiable mode
• Since object discovery and deletes are best
  effort, federates need to implement heartbeat and
  timeout semantics
• Crashed federates need only wait for objects to
  time out before rejoining

8
Connectionless Mode Experience in MC02

• Federation execution ran for two weeks, 24/7 over
  a WAN connecting 5 sites
• Federation consisted of about 90 federates
  representing 42 simulations
• Federation stayed up for the entire two weeks
  with
• Federates crashing
• Whole sites disappearing
• Network CRC errors occurring

9
Need for User Defined DDM

• DDM is designed to improve network performance by
  providing data segmentation based on federation
  knowledge
• There are many potential implementations of DDM
• One DDM implementation may not be optimal for all
  DDM schemes
• RTI-NG provides 3 different implementations
• MC02 federates were already optimized to use
  inset grids as implemented in the RTI-S DDM
  strategy
• Re-optimization for RTI-NG strategy would have
  lost optimization for RTI-S

10
User Defined DDM Implementation

• Similar to FedTime
• Users implement a defined DDM class and compile
  it as a separate dynamic library
• Swap in the new dynamic library for the one
  supplied with the RTI-NG distribution
• Implementation must map RTIRegion, class,
  and/or attribute instances to a list of RTI-NG
  communication channels
• The RTI-NG will then handle
• Setting up connections
• Sending/receiving data
• Removing connections as needed.

11
User Defined DDM Steps

• Initialize user code
• Ask user code for a list of channels to create
  along with a requested transport protocol to use
• Ask the user code which information it needs in
  order to compute channel mappings
• As needed, ask the user code for channel mappings
  between Regions, Object/Interaction classes,
  Attributes and their associated channels
• Shutdown user code

12
User Defined DDM Usage

• Select User DDM in the RID file
• RTI-NG DDM strategies are still available after
  swapping libraries
• During execution the RTI-NG will periodically ask
  the user DDM code for a mapping between an
  RTIRegion instance and a list of channels

13
Summary

• Connectionless mode allows better fault tolerance
  for non-compliant federates at the expense of
  availability of some HLA services
• User defined DDM gives federation designers the
  flexibility to map RTIRegion instances to
  channels in a federation specific way to
  optimized performance

14
Additional Information

• include ltRTI.hhgt
• include ltvectorgt
• include ltsetgt
• include ltutilitygt
• include ltstringgt
• ifndef _RtiUserDefinedDdmStrategy_h
• define _RtiUserDefinedDdmStrategy_h
• // Setup the windows export macro
• if defined(_WIN32)
• if defined(BUILDING_USERDDM)
• // define the proper qualifiers to import/export
  symbols from/to DLL
• define RTI_EXPORT_USERDDM __declspec(dllexpor
  t)
• else // ! BUILDING USERDDM
• define RTI_EXPORT_USERDDM __declspec(dllimpor
  t)
• endif // BUILDING_USERDDM
• else // !WIN32

15
Additional Information (contd)

• class RTI_EXPORT_USERDDM RtiUserDefinedDdmStrategy
  
• public
• typedef int ChannelId
• typedef stdpairltChannelId,
  RTITransportationHandlegt
• ChannelToTransportationPair
• typedef stdvectorltChannelToTransportationPai
  rgt
• ChannelToTransportationList
• typedef stdsetltChannelIdgt ChannelSet
• public
• // Default ctor will get called when a
  federate joins a federation
• RtiUserDefinedDdmStrategy(stdstring const
  optionsFromRidFile)

16
Additional Information (contd)

• // This method will get called after the ctor
  but before any other
• // methods. This method returns the list of
  channel IDs along with
• // their associated transportation type. The
  RTI will use this
• // information to create the proper
  communication channels. Each
• // channelId must be unique and may not
  change throughout the existance
• // of the RtiUserDefinedDdmStrategy instance.
• virtual ChannelToTransportationList
  getChannelToTransportationList()
• // If the user ddm strategy needs class
  and/or attribute handles
• // to compute channelSets, then the value
  true should be returned from
• // the appropriate method(s). If a class or
  attribute handle is
• // not needed to compute channelSets, then
  false should be returned for
• // the appropriate method(s). Class or
  attribute data will not
• // be passed to the getXXXChannelSet methods
  for each false value and
• // will thus improve performance. These
  methods may only be called
• // once by the RTI and thus the value
  returned should be considered
• // constant throughout the scope of the
  RtiUserDefinedDdmStrategy instance.
• virtual bool needObjectClassToComputeChannels(
  )
• virtual bool needAttributeToComputeChannels()
  

17
Additional Information (contd)

• // These methods may be called many times
  thoughout the execution of the
• // federate. The method returns the list of
  channel IDs to be used for
• // outgoing updates interactions. The list
  must contain unique IDs.
• // Each ID must have been returned previously
  by the
• // getChannelToTransportationList() method.
  The TransportationHandle
• // parameter is always valid and represents
  the requested
• // transportation types of the outgoing
  channel(s).
• // The ObjectClassHandle InteractionClassHan
  dle parameters are invalid
• // if needClassToComputeChannels() previously
  returned false. The
• // AttributeHandle parameter is invalid if
  needAttributeToComputeChannels()
• // previously returned false. The ChannelSet
  returned will be used
• // by the RTI to send data to each of the
  channels listed. In general,
• // these methods are only called whenever
  publications or regions used
• // for publications change but may, in fact,
  be called at any time.
• virtual ChannelSet getOutgoingChannelSet(
• RTITransportationHandle
  desiredTransportationTypeOfChannels,
• const RTIRegion region,
• RTIObjectClassHandle objectClassHandle,
• RTIAttributeHandle attributeHandle)

18
Additional Information (contd)

• // These methods may be called many times
  thoughout the execution of the
• // federate. The method returns the list of
  channel IDs to be used for
• // receiving updates interactions. The
  list must contain unique IDs.
• // Each ID must have been returned previously
  by the
• // getChannelToTransportationList() method.
• // The ObjectClassHandle InteractionClassHan
  dle parameters are invalid
• // if needClassToComputeChannels() previously
  returned false. The
• // AttributeHandle parameter is invalid if
  needAttributeToComputeChannels()
• // previously returned false. The ChannelSet
  returned will be used
• // by the RTI to subscribe to data from each
  of the channels listed.
• // Channels used for both Reliable
  Best_effort traffic should be
• // returned in the ChannelSet.
• // In general, these methods are only called
  whenever subscriptions or
• // regions used for subscriptions change but
  may, in fact, be called at
• // any time.
• virtual ChannelSet getIncomingChannelSet(
• const RTIRegion region,
• RTIObjectClassHandle objectClassHandle,
• RTIAttributeHandle attributeHandle)

19
Additional Information (contd)

• // This method should return the channel ID to
  use for broadcast LRC
• // communication using the specified
  Transportation type.
• // This method will be called when the LRC
  needs to communicate with
• // other LRCs. The method may only be called
  once so values returned
• // should not change throughout the
  execution.
• virtual ChannelId getOutgoingBroadcastAdminist
  rationChannel(
• RTITransportationHandle
  desiredTransportationTypeOfChannel)
• // This method should return the channel ID
  to use for direct LRC to LRC
• // communication using the specified
  Transportation type.
• // This method will be called when the LRC
  needs to communicate
• // directly with another specific LRC. The
  method may only be called
• // once so values returned should not change
  throughout the execution.
• virtual ChannelId getOutgoingPoint2PointAdmini
  strationChannel(
• RTITransportationHandle
  desiredTransportationTypeOfChannel,
• RTIFederateHandle)
• // This method should return the channel ID
  to use for receiving
• // broadcast LRC communication using the
  specified Transportation type.

20
Additional Information (contd)

• // This method should return the channel ID to
  use for receiving
• // direct LRC to LRC communication using the
  specified Transportation type.
• // This method will be called when the LRC
  needs to subscribe to
• // communications directly from other LRCs.
  The method may only be called
• // once so values returned should not change
  throughout the execution.
• virtual ChannelId getIncomingPoint2PointAdmini
  strationChannel(
• RTITransportationHandle
  desiredTransportationTypeOfChannel,
• RTIFederateHandle)
• endif //_RtiUserDefinedDdmStrategy_h