TENA Test and Training Enabling Architecture

TENA TENA is used in range environments, often in the L portion of LVC Slightly different emphasis; small devices, real- time-ish, sometimes embedded, high performance in the sense of low overhead required, multiple unusual platforms Government-owned source built for multiple platforms

Live, Virtual, constructive

TENA Large-ish user support network Available to international militaries with permission (used in Sweden)

Remote Objects There’s a popular concept in computer science called “remote procedure calls” or “distributed objects.” You’ve got a piece of code on one host, and you want to call it from another You can create and send a message from the client to the server to make this call happen, but it’s popular to make it appear as if the object is “really” on the client. This is done via a proxy object

Proxy Objects -doSomething(int i) -doSomethingElse(float f); -doSomething(int i) -doSomethingElse(float f); -doSomething(int i) -doSomethingElse(float f); -doSomething(int i) -doSomethingElse(float f); ProxyReal Object The proxy is a “stand-in” for the real object on another host. Methods are called by a user on the proxy, which does no computation itself. Instead, it passes the request (along with any parameters) to the real object on a server. The server does the computation and passes back the return value

Proxy and Servant The object on the client side is called the proxy, while the “real” object on the server side is called the servant This means the proxy and servant need to agree on how messages are passed back and forth, ports for passing messages over sockets, etc. The good news is that this can be automated by appropriate code, so the user doesn’t have to write any of it Typically you write a interface file in a special language, then the proxy code and servant interface is generated for you The infrastructure can use a variety of technologies for message passing: multicast, tcp, udp, etc.

TENA Description Language The TDL/CORBA IDL below is run through a compiler to generate the proxy objects and to create the server-side connectors. (TDL and IDL are very similar)

TAO CORBA Architecture

Dangers While this is nice, always remember that the proxy object is not the same thing as the real object. Calls are being made across the network, so they’ll be much slower and less reliable than using a “real” object for(int idx = 0; idx < 1000; idx++ { proxy.doSomething(idx); }

TENA Remote Objects Remote objects are the approach that TENA takes Clients have proxies that connect to the servant objects running on other hosts, so we may have a radar object instance running on a device on the range being called from a host in the lab, and the radar object being shown in a DIS application via a gateway

Stateful Distributed Objects TENA adds “stateful distributed objects” to regular distributed objects With distributed objects you need to call a method to discover state With SDOs the state is pushed to subscribed listeners periodically (often at state change points) So for example a Radar object instance might tell listening objects that it has turned on rather than waiting for other objects to ask its state, or having other objects poll its state

TENA So a TENA application can consist of – Objects that that application publishes (for example, a radar or tank) – Objects that that application is listening to (for example, helicopters published by other applications) – Your own application logic TENA has gateways to allow operation with other standards, for example DIS or HLA

TENA TENA uses something called CORBA in the background, specifically the TAO realtime CORBA ORB But all this is hidden from the user, and as a result is never seen directly Multiple language bindings: C++ is primary, C# also, Java in beta

CORBA CORBA provides the infrastructure for many things: – Publishing objects – Handling parameter serialization, object serialization, response serialization – Object lookup – The interface description language (IDL) – Generating proxy and servant interfaces You provide the servant logic, CORBA does most of the rest

Object Serialization What if you pass an object as a parameter to a method on a servant? Eg, Position with attributes of floats (x,y,z). Or what if you want an object returned as a method result? The attributes of the object need to be placed in a format that can be passed in a message to the servant; this is all done automatically, but it needs to be done How to you find published objects?

TENA

TENA App

Cooperating TENA Apps

Overall TENA uses a hidden implementation of CORBA Adds “stateful distributed objects”, which pushes state information to subscribed listeners High performance, hides most network details Gov’t-provided middleware for most architectures (Linux/Windows/IOS/32/64)