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25-689: The RPR FOM provides backwards compatibility with simulations using the Distributed Interactive Simulation (DIS) standard. It is standardized by Simulation Interoperability Standards Organization (SISO) as SISO-STD-001-2015. The standard consists of two parts: When the High Level Architecture was introduced by the US Department of Defense in 1996 the RPR FOM effort was initiated to facilitate

50-433: A packet , irrespective of its payload type. In the context of packet switching data networks, a protocol data unit (PDU) is best understood in relation to a service data unit (SDU). The features or services of the network are implemented in distinct layers . The physical layer sends ones and zeros across a wire or fiber. The data link layer then organizes these ones and zeros into chunks of data and gets them safely to

75-539: A few basic data types, Enumerations Module with enumerations like types of platforms and equipment, Base Module with commonly used data types and generic object classes and Switches Module with runtime switches for the RTI. The RPR FOM is related to a number of other standards. Distributed Interactive Simulation Distributed Interactive Simulation ( DIS ) is an IEEE standard for conducting real-time platform-level wargaming across multiple host computers and

100-476: A halt in 2007, resulting in a widely used draft version 17. The work was restarted in 2012 and finalized with a published standard in 2015. The standard provides FOMs supporting the following HLA versions: 1.3, IEEE 1516-2000 and IEEE 1516-2010 (“HLA Evolved”) in both modular and monolithic formats. Development of this upcoming version was started in 2016 by the SISO DIS and RPR FOM Product Support Group. In 2018,

125-429: A network address to help with routing, a code to identify the type of data in the packet and error-checking information. All this additional information, plus the original service data unit from the higher layer, constitutes the protocol data unit at this layer. The SDU and metadata added by the lower layer can be larger than the maximum size of that layer's PDU (known as the maximum transmission unit ; MTU). When this

150-401: A service data unit to that layer. The addition of addressing and control information (encapsulation) to an SDU to form a PDU and the passing of that PDU to the next lower layer as an SDU repeats until the lowest layer is reached and the data passes over some medium as a physical signal. The above process can be likened to the mail system in which a letter (SDU) is placed in an envelope on which

175-566: A sponsor committee of the IEEE, promulgates improvements in DIS. Major changes occurred in the DIS 7 update to IEEE 1278.1 to make DIS more extensible, efficient and to support the simulation of more real world capabilities. Simulation state information is encoded in formatted messages, known as protocol data units (PDUs) and exchanged between hosts using existing transport layer protocols, including multicast , though broadcast User Datagram Protocol

200-418: Is RPR FOM version 2.0 that corresponds to DIS version 6. Protocol data unit In telecommunications , a protocol data unit ( PDU ) is a single unit of information transmitted among peer entities of a computer network . It is composed of protocol-specific control information and user data . In the layered architectures of communication protocol stacks, each layer implements protocols tailored to

225-666: Is a Federation Object Model (FOM) for the High-Level Architecture designed to organize the PDUs of DIS into an HLA object class and interaction class hierarchy. It has been developed as the SISO standard SISO-STD-001. The purpose is to support transition of legacy DIS systems to the HLA, to enhance a priori interoperability among RPR FOM users and to support newly developed federates with similar requirements. The most recent version

250-411: Is also supported. There are several versions of the DIS application protocol, not only including the formal standards, but also drafts submitted during the standards balloting process. The current version (DIS 7) defines 72 different PDU types, arranged into 13 families. Frequently used PDU types are listed below for each family. PDU and family names shown in italics are found in DIS 7. The RPR FOM

275-499: Is called a cell . A media access control protocol data unit ( MAC PDU or MPDU ) is a message that is exchanged between media access control (MAC) entities in a communication system based on the layered OSI model. In systems where the MPDU may be larger than the MAC service data unit (MSDU), the MPDU may include multiple MSDUs as a result of packet aggregation . In systems where

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300-422: Is labeled with the region to which all the bags are to be sent, making the crate a PDU. When the crate reaches the destination matching its label, it is opened and the bags (SDUs) removed only to become PDUs when someone reads the code of the destination post office. The letters themselves are SDUs when the bags are opened but become PDUs when the address is read for final delivery. When the addressee finally opens

325-475: Is the case, the PDU must be split into multiple payloads of a size suitable for transmission or processing by the lower layer; a process known as IP fragmentation . The significance of this is that the PDU is the structured information that is passed to a matching protocol layer further along on the data's journey that allows the layer to deliver its intended function or service. The matching layer, or "peer", decodes

350-563: Is used worldwide, especially by military organizations but also by other agencies such as those involved in space exploration and medicine . The standard was developed over a series of "DIS Workshops" at the Interactive Networked Simulation for Training symposium, held by the University of Central Florida's Institute for Simulation and Training (IST). The standard itself is very closely patterned after

375-407: Is written an address (addressing and control information) making it a PDU. The sending post office might look only at the postcode and place the letter in a mailbag so that the address on the envelope can no longer be seen, making it now an SDU. The mailbag is labeled with the destination postcode and so becomes a PDU until it is combined with other bags in a crate when it is now an SDU, and the crate

400-763: The US Army Simulator Network (SimNet) program. Funding and research interest for DIS standards development decreased following the proposal and promulgation of its successor, the High Level Architecture (simulation) (HLA) in 1996. HLA was produced by the merger of the DIS protocol with the Aggregate Level Simulation Protocol (ALSP) designed by MITRE . There was a NATO standardisation agreement ( STANAG 4482, Standardised Information Technology Protocols for Distributed Interactive Simulation (DIS) , adopted in 1995) on DIS for modelling and simulation interoperability. This

425-448: The SDU, but the lower layer at the interface does not; moreover, the lower layer treats the SDU as the payload , undertaking to get it to the same interface at the destination. In order to do this, the protocol (lower) layer will add to the SDU certain data it needs to perform its function; which is called encapsulation . For example, it might add a port number to identify the application,

450-451: The data to extract the original service data unit, decide if it is error-free and where to send it next, etc. Unless we have already arrived at the lowest (physical) layer, the PDU is passed to the peer using services of the next lower layer in the protocol "stack". When the PDU passes over the interface from the layer that constructed it to the layer that merely delivers it (and therefore does not understand its internal structure), it becomes

475-508: The development was handed over to a dedicated Product Development Group. The goal of RPR FOM version 3.0 is to support the capabilities of DIS version IEEE 1278.1-2012 (DIS 7). The RPR FOM defines the information exchanged at runtime in a number of FOM modules. As an example, the object classes of the Physical Module are illustrated in the figure below. The modules are: Additional supporting modules include Foundation Module with

500-698: The envelope, the top-level SDU, the letter itself, emerges. Protocol data units of the OSI model are: Given a context pertaining to a specific OSI layer, PDU is sometimes used as a synonym for its representation at that layer. Protocol data units for the Internet protocol suite are: On TCP/IP over Ethernet, the data on the physical layer is carried in Ethernet frames . The data link layer PDU in Asynchronous Transfer Mode (ATM) networks

525-408: The migration from DIS to HLA. This first RPR FOM version was released in 1998. It supports the capabilities of DIS version IEEE 1278.1-1995 (DIS 5). The standard provides a FOM supporting HLA version 1.3. This updated version was released in 2015 as SISO-STD-001. RPR FOM 2.0 supports the capabilities of DIS version IEEE 1278.1a-1998 (DIS 6). The development of RPR FOM 2.0 started in 2000, but came to

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550-565: The original SIMNET distributed interactive simulation protocol, developed by Bolt, Beranek and Newman (BBN) for Defense Advanced Research Project Agency (DARPA) in the early through late 1980s. BBN introduced the concept of dead reckoning to efficiently transmit the state of battle field entities. In the early 1990s, IST was contracted by the United States Defense Advanced Research Project Agency to undertake research in support of

575-400: The right place on the wire. The network layer transmits the organized data over multiple connected networks, and the transport layer delivers the data to the right software application at the destination. Between the layers (and between the application and the top-most layer), the layers pass service data units (SDUs) across interfaces. The higher layer understands the structure of the data in

600-565: The specific type or mode of data exchange. For example, the Transmission Control Protocol (TCP) implements a connection-oriented transfer mode, and the PDU of this protocol is called a segment , while the User Datagram Protocol (UDP) uses datagrams as protocol data units for connectionless communication . A layer lower in the Internet protocol suite , at the Internet layer , the PDU is called

625-673: Was retired in favour of HLA in 1998 and officially cancelled in 2010 by the NATO Standardization Agency (NSA). DIS is defined under IEEE Standard 1278: In addition to the IEEE standards, the Simulation Interoperability Standards Organization (SISO) maintains and publishes an "enumerations and bit encoded fields" document yearly. This document is referenced by the IEEE standards and used by DIS, TENA and HLA federations. Both PDF and XML versions are available. SISO,

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