[ih] Fwd: Internet at Sea

[Jack Haverty]

Defense Simulation Internet -- that's it, I couldn't remember the name.

Quick search uncovers this MITRE study with some technical info:

https://apps.dtic.mil/sti/tr/pdf/ADA381147.pdf

/Jack


On 10/7/25 12:54, Craig Partridge wrote:
> As I recall it was called the Defense Simulation INternet (DSIN) or 
> something close and was carefully engineered to have enough capacity 
> to link the various simulators.  It made heavy use of UDP.
>
> Couple of quick comments (some of my college classmates were the core 
> of the initial implementation team, but I was not on the team, so some 
> details may be not quite right) about the networking aspects.
>
> Both network bandwidth and the number of messages was at a premium and 
> the team figured this out quite quickly.  They were working initially 
> with the 1983-vintage Internet, with no working congestion control and 
> where effective Ethernet speed was about 1Mbps due to network adapter 
> limitations and Unix kernel limitations.
>
> They had, initially, an n*n comms pattern, every "thing" in the 
> simulated space was tracking what every other "thing" was doing to 
> ensure everyone had a faithful representation of the world.  Each node 
> drove its own graphics displays (and there were multiple per tank).  
> You didn't have to get too many tanks, plus shells and other moving 
> things, and the network saturated if you sent out an update on every 
> action.
>
> So what they did was develop predictive algorithms for each item.  For 
> instance, if a tank was speeding along, the algorithm predicted it 
> would continue along its current path and the tank only sent an update 
> when it deviated from the predicted path.  Each node was, therefore, 
> calculating what it thought each item in the space was doing and 
> looking for occasional updates.  This sharply reduced network traffic 
> and made performance quite good -- and this is the core of the 
> simulation protocols that were developed in the late 1980s and early 
> 1990s.
>
> There were some early hiccoughs.  There's an art to figuring out how 
> often to update and soldiers (who were getting to play the world's 
> best video game in high end tank simulators) were quick to figure out 
> glitches and take advantage.  As I recall, one trick was to drive your 
> tank at maximum speed (something like 60 mph) crosswise in front of 
> your opponent's tank with your gun pointing ahead -- so they think 
> you're an unsuspecting target but also have to line up a shot on a 
> fast moving object.   Then, just before you estimate your opponent has 
> got their shot ready, you stomp on the brakes and turn your turret 
> towards them and fire.  What the opponent would see is your tank 
> magically jump backwards and shoot at them.
>
> Side story: as I understand the politics of simulation, the SIMNET 
> project had a number of challenges getting the various contractors to 
> play nicely.  I think BBN finally ended up buying the specialized 
> graphics display company to reduce friction.  But what made SIMNET a 
> big success was the NATO Tank Competition.  The US Army historically 
> did poorly -- someone (the SIMNET PM?), in a stroke of marketing 
> genius, had SIMNET code the tank course into the simulator and let the 
> Army team practice on it.  The US won the competition....
>
> Craig
>
>
>
> On Tue, Oct 7, 2025 at 1:26 PM Jack Haverty via Internet-history 
> <internet-history at elists.isoc.org> wrote:
>
>     Answering Barbara's questions...
>
>     A few years ago, someone who had worked on SIMNET told me that
>     they had
>     chosen to use a private network approach rather than running over The
>     Internet which was shared with others.   I don't know any of the
>     details
>     though.
>
>     My suspicion is that they built a private clone of the Internet,
>     using
>     TCP/IP routers, and circuits.  Lots of corporations were deploying
>     similar private clones for use within their corporation and possibly
>     some partners.
>
>     For a particular project, a private "intranet" could be carefully
>     managed to meet the needs for gaming, perhaps using the methodology
>     learned from the ARPANET.
>
>     The ARPANET had a team of analysts who looked at traffic
>     statistics and
>     trends, and designed changes to the ARPANET, e.g., to add or remove
>     circuits, order higher bancwith, modify protocols, etc. That same
>     philosophy could be applied to a private Internet, to maintain needed
>     and consistent performance for a specific application.
>
>     In addition, with all of the switches and computers involved in the
>     project under the project's control, customized approaches could be
>     designed and implemented.  Corporations couldn't really do that
>     when all
>     their routers came from Cisco, but a military project such as SIMNET
>     could; perhaps they implemented some TOS functionality, or something
>     else to address the latency requirements.  With a private system,
>     even
>     based on TCP/IP, you could do that.
>
>     Coordinating with the "public" Internet, funding research on general
>     solutions and implementations, and getting new mechanisms into the
>     Standards Process was not needed for the project to be successful. A
>     project-specific solution was sufficient.
>
>     But I don't know any of the actual details about how the SIMNET
>     communications worked.   So the above is just speculation.  I suspect
>     the details are in reports somewhere in DTIC.
>
>     /Jack
>
>     On 10/7/25 10:38, Greg Skinner via Internet-history wrote:
>     > forwarded for Barbara
>     >
>     >> ----- Forwarded Message -----
>     >> From: Barbara Denny <b_a_denny at yahoo.com>
>     >> To: Internet-history <internet-history at elists.isoc.org>
>     >> Sent: Monday, October 6, 2025 at 10:45:00 AM PDT
>     >> Subject: Re: [ih] Internet at Sea
>     >>
>     >> See inline comments below.
>     >>
>     >> On Saturday, October 4, 2025 at 03:31:27 PM PDT, Jack Haverty
>     via Internet-history <internet-history at elists.isoc.org> wrote:
>     >>
>     >>
>     >> Some better search term on discover.dtic.mil
>     <http://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.
>     >>
>     >>> Can you expand on your thoughts here?  I didn't really
>     participate in SIMNET much but I am confused about your words
>     here. I never heard anything about people deciding they needed to
>     build their own private communications system instead.  Do you
>     remember when you heard this? Or was this just a recommendation?
>     Did this ever happen or did the end of the Cold War stop this
>     thinking?
>     >>> A little more background...
>     >>   > In the fall of 1991, I was sent to Germany for
>     demonstrations of packet radio (DARPA effort).   It used the LPR
>     (Low Cost Packet Radio) which as far as I know was the last
>     version of radio hardware and software before that program ended.
>     BBN was also sent there to support this demonstration and they
>     were tasked with the application component.  The demonstrations
>     were  pretty important. The observers were at the Warrior
>     Preparation Center. (FYI, The LPRs were deployed as far away as
>     Rammstein Air Base. I got to ride in a real Humvee as we set up
>     the network!). Later SRI got a letter from DARPA regarding this
>     effort.  The letter said the success of the demonstrations
>     resulted in the military considering using the lpr in support of
>     mobile responders for Reforger '92  and made them feel they they
>     could extend simulation to the battalion commander ( At some point
>     I remember hearing DARPA wanted to combine both real and simulated
>     elements together for training purposes).  The letter a
>     >   lso said DARPA was looking forward to breaking new ground in
>     warfighting simulation technology.   There was no hint of some
>     other communication system.
>     >>> I am also including a link to a BBN report covering simulation
>     of the radio communication environment for SIMNET.  It was
>     interesting to me because they chose SINCGARS for the model.  This
>     report is dated January 1992 and the SRI DARPA letter is dated
>     December 1991.
>     >> https://apps.dtic.mil/sti/tr/pdf/ADA244212.pdf
>     >>
>     >> 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.
>     >>
>     >>> BTW, if you look at the packet radio paper recently cited,
>     there is a flag in the packet radio E2E header that indicates a
>     packet speech type of service.  The definition of what that means
>     for the radio is defined.  I would think that because of the
>     packet speech work in the 70s, the ToS  field in the IP header
>     would have been used.  I haven't seen or heard about this so what
>     happened?   I think there were other motivations for using this
>     field in the IP header beyond SIMNET.
>     >>> barbara
>     >> /Jack Haverty
>     >>
>     >>
>
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