[ih] Internet at Sea

[Jack Haverty]

Sorry, wrong URL.  Volume II of the "ARPA Technical Accomplishments" is 
at https://apps.dtic.mil/sti/tr/pdf/ADA241725.pdf and it contains the 
SIMNET section I mentioned.   There's also a Volume III, at 
https://apps.dtic.mil/sti/tr/pdf/ADA241680.pdf

This 3-volume set contains a lot of historical detail about the ARPA 
"Information Processing Techniques" projects associated with the 
Internet, mixed in with all sorts of other research activities.   It 
doesn't contain much info about the Internet technologies such as the 
RFCs do, but describes a lot of the military needs that the research was 
targetting in the 1970s and 1980s, and the rationale for such work.

/Jack

On 10/4/25 15:23, Jack Haverty via Internet-history wrote:
> Some better search term on discover.dtic.mil found this - the sequel 
> to the report I just mentioned, published a year later:
>
> https://apps.dtic.mil/sti/tr/pdf/ADA239925.pdf
>
> Chapter XVI is titled "SIMNET" which has a special, but likely as yet 
> untold, history with The Internet.
>
> Sometime in late 1982 or early 1983, ARPA asked our "Internet" group 
> at BBN to get involved with a project that might be able to use the 
> emerging Internet for its communications infrastructure. That program 
> was called SIMNET, or SIMulation NETwork, and the concept was to 
> create a video-game type of training tool for use in combat training.  
> The initial use was training M-1 tank crews, but the concept included 
> other participants, such as helicopters. Mike Kraley and I went to a 
> bunch of meetings to brainstorm and flesh out the ideas, as part of 
> our ongoing work on ARPA Internet-related contracts.
>
> It became clear that for such "gaming" applications, network latency 
> was important.  It mattered a lot.  If you fired at the enemy, you 
> should be able to see the results immediately and consistently.  A 
> training system had to be accurate for the things that mattered, but 
> could cut corners to save costs for the things that didn't.
>
> Inside the Internet world, that need was one of the motivations for 
> the introduction of the TOS field (Type Of Service) in the IP header.  
> Our conclusion was that the Internet would have to support at least 
> two different types of behavior.  Possibly more since SIMNET was also 
> envisioned to simulate radio traffic and "chatter" between the crews 
> in the simulation, using packet voice.
>
> Datagrams associated with things like firing weapons or vocal snippets 
> could be small, but had to get delivered quickly. Datagrams associated 
> with things like detailed maps could be delivered at a more leisurely 
> pace.  Terrestrial routes would be good for the former, and 
> geosynchronous satellites appropriate for the latter.  Of course there 
> would also need to be new appropriate routing mechanisms to make it 
> all work as envisioned.
>
> At BBN, we wrote a proposal to start an actual SIMNET project. Shortly 
> thereafter, in July 1983, BBN reorganized and that project was 
> approved and the contract assigned to a part of BBN that had been 
> doing various training systems.  So I never got to drive an M1 tank 
> (which was an ARPA mandated requirement for everyone assigned to the 
> project).
>
> SIMNET ended up being very successful, as detailed in that report. But 
> the implementors discovered that the Internet, which hadn't 
> implemented any mechanisms for TOS, couldn't provide the 
> communications services that SIMNET needed.   They had to build their 
> own private communications system instead.
>
> In retrospect, we probably didn't do enough to lay out that plan for 
> coordinating the SIMNET and Internet evolution.  ARPA reorganized at 
> about the same time, the ICCB became the IAB, the people involved 
> changed, and the plan was lost.  SIMNET was successful, but TOS 
> support in the Internet didn't happen.
>
> /Jack Haverty
>
>

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