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Information is exchanged across the SIMNET Local Area Network (LAN) and Long-Haul Network (LHN) using a connectionless data transfer service capable of both point-to-point and broadcast delivery. Data transfer occurs via a set of Protocol Data Units (PDUs). The SIMNET protocol does not assume that the network is fully reliable. It is designed to be robust despite occasional transmission errors. Some PDUs require acknowledgement; if none is received, the PDU is retransmitted. Other PDUs represent minor updates of the state of a simulated entity; if one of these PDUs is corrupted or lost, the next update will correct any discrepancy that has occurred.
The primary PDUs are listed below, along with a brief summary of their purpose and what data they contain. It should be noted that the DIS Protocols (IEEE 1278.1), while based on the SIMNET protocols, reorganized and renamed many of the PDUs. The list below uses the original SIMNET terminology. The SIMNET Components page defines the various abbreviations used in these descriptions. Activate Request. Transmitted by the MCC System to initialize a simulator in an exercise. Superseded by the DIS Create Entity PDU. Assigns a unique ID to the simulator and designates the ID of the exercise in which it is participating. This permits multiple simultaneous exercises to take place on the same network.
Activate Response. Transmitted by the designated simulator to confirm receipt of the activate request and to confirm that it is joining the designated exercise. Superseded by the DIS Acknowledge PDU, which combines the functions of responses to management directives.
Deactivate Request. Transmitted by the MCC System to remove an entity from the designated exercise. Superseded by the DIS Remove Entity PDU.
Deactivate Response. Transmitted by the designated entity to confirm receipt of the deactivate request and to confirm that it is leaving the designated exercise. This function is now incorporated in the DIS Acknowledge PDU.
Vehicle Appearance. Transmitted by each simulator to update its state (e.g., its location, appearance, operational status, orientation of all articulated components, etc.) as required by the Dead Reckoning algorithm being used. Superseded by the DIS Entity State PDU.
Radiate. Transmitted by each simulator whenever it is emitting detectable electromagnetic radiation. Superseded by the DIS Electromagnetic Emission PDU.
Fire. Transmitted by each entity to report the firing of projectile, and what type of munition it is. Superseded by the DIS Fire PDU.
Impact. Transmitted by each entity to report the impact of projectile it has fired, the type of munition it is, and the target, if known. Superseded by the DIS Detonation PDU.
Indirect Fire. Transmitted by the firing entity (e.g., artillery) to report impact of indirect fire and the type of munition. Incorporated into the DIS Impact PDU.
Collision. Transmitted by a simulator to report a collision with another simulated entity or with a fixed object in the database. Superseded by the DIS Collision PDU.
Service Request. Transmitted by a simulator to request resupply of fuel or munitions. Superseded by the DIS Service Request PDU.
Resupply Offer. Transmitted by a logistics vehicle simulator (e.g., a HEMTT) offering to resupply fuel or munitions to the requesting simulator. Superseded by the DIS Resupply Offer PDU.
Resupply Received. Transmitted by a simulator to acknowledge receipt of some or all of offered fuel or munitions. Superseded by the DIS Resupply Received PDU.
Resupply Cancel. Transmitted by a simulator to abort transfer of fuel or munitions. Superseded by the DIS Resupply Cancel PDU.
Repair Request. Transmitted by a simulator to request a repair. Incorporated into the DIS Service Request PDU.
Repair Response. Transmitted by a maintenance vehicle (e.g., an M88 recovery vehicle) to report the completion of a repair. Superseded by the DIS Repair Complete PDU.
Minefield. Transmitted by the MCC System to describe the parameters of an emplaced minefield.
Breached Lane. Transmitted by the MCC System to describe a path cleared through a minefield.
Marker. Transmitted by the MCC System to announce the marking of minefield with flags.
The last three PDUs were superseded by the DIS (1998) family of Minefield PDUs. |