DIS History
DIS originated from a Defense Advanced Research Agency (DARPA) project in the late 1980’s called SIMNET. At the time TCP/IP and high speed networks were just getting their legs, computers and networks were becoming powerful enough to do the computational operations needed, and 3D graphics was in its infancy.
A screen capture from an early SIMNET application is shown below:
Each participant was in a SIMNET application that controlled a vehicle, such as a tank, and each simulator viewed the shared virtual battlefield. All the vehicles interacted in the same shared environment. If one simulator caused the tank it controlled to move the other participants saw that movement, in real time. This idea was advanced for the late 80's. Even networking was not universal in that era, CPUs were often computationally slow compared to those of a few years later, and graphics were primitive or non-existent. It was implemented on advanced research workstations. It wasn't until the early/mid 1990's that simulations of this sort could begin to be implemented on commercial machines and in the late 1990's commercial PCs had advanced graphics cards and enough CPU to work well at low prices.
The simulators of the era sometimes had displays that replicated a soldier’s view of the battlefield, but the host running the simulation before the SIMNET research were probably not have been networked with other hosts from multiple vendors. Each simulator worked in isolation, and an aircraft simulator done by a particular vendor couldn’t see a tank controlled by another simulator from another vendor. The idea of SIMNET-–quite advanced for the time–-was to create a virtual, shared battlefield in which all participants on multiple computers could see vehicles simulated on other hosts, and interact with each other. SIMNET’s major accomplishment was to serve as the research that allowed DIS to happen. Soon military 3D simulations could run on common office PCs.
DARPA projects were intended to transition out of the incubator research phase and into useful, real implementations. The SIMNET project worked out many of the state information exchange issues that were needed. Once that was done it needed to be standardized and refined outside of DARPA. The organization that would eventually do this was Simulation Interoperability Standards Group (SISO) that took over development of the network protocol portion of the project, which they renamed to DIS. SISO developed DIS in a series of workshops held from 1989 to 1996. Once the protocol was developed they took the relevant documents to the IEEE standards group and achieved DIS standard approval.
At the time of SIMNET the concept of a shared, networked environment was revolutionary. In today’s commercial game world entertainment like “Call of Duty” or “World of Tanks” routinely share environments between hosts. The companies that own these games make a lot of money selling such applications to the public, entertainment that draws in more revenue than movies. Some sources say that gaming currently makes $85 billion/year, the film industry makes $35 billion/year, and the music industry $15 billion/year.
As mentioned, DARPA led to another organization, SISO, and SISO developed documents that were taken to the IEEE for standards approval. These included the documents below.
Be aware that the documents may specify only some advice, and actual applications may use the standards in only a partial manner. For example IEEE-1278.1 specifies the format of dozens of Protocol Data Units (PDUs). Despite the many PDUs, the vast majority of applications use only a subset of message types, and simply ignore or drop any PDU that is not expected. An application that only deals with the movement of tanks might well ignore any electronic warfare, and the PDUs that implement it. As a result the application developers may only handle a half-dozen PDUs for the application. Very often the IEEE-1278.x documents can be regarded as interesting advice, and few or no applications regard the documents as decisive or mandatory to fully implement.
There are several documents approved in addition to the document that approves the structure of messages. An image from the IEEE document of what is trying to be accomplished is below:
This is from a 1998 document.
The IEEE-1278.1 document is the most valuable and useful standard of any of the documents. It contains exact definitions of all the PDUs, and for some sections good descriptions of how to handle the data within.
The first version was approved as DIS version 5, which was relatively early in the DIS program. It was early, but it let developers get to work. It ran to 138 pages.
A better version game out a few years later in 1998. Standards workers came out with a better documented version of DIS; it was now numbered to version 6. The document now ran to 213 pages.
There are two versions of IEEE-1278.2, one dated in 1995 and one in 2015. Interestingly enough multicast network standards for TCP/IP as a whole had not been invented and adopted yet in 1995, so it was not mentioned in the document.