In computing, run-time infrastructure (RTI) is a middleware that is required when implementing the High Level Architecture. RTI is the fundamental component of HLA. It provides a set of software services that are necessary to support federates to coordinate their operations and data exchange during a runtime execution. In other sense, it is the implementation of the HLA interface specification but is not itself part of specification. Modern RTI implementations conform to the IEEE 1516 and/or HLA 1.3 API specifications. These specifications do not include a network protocol for RTI. It is up to the implementors of a RTI to create a specification. Due to this, interoperability between RTI products should not be assumed unless the vendor specifies interoperability with other products or versions. 
Known implementations
| Commercial | ||||
|---|---|---|---|---|
| Name | Vendor | Standard | Bindings | License |
| Chronos RTI | Magnetar Games | IEEE 1516 | C++, .NET | Commercial |
| MÄK High Performance RTI | MÄK Technologies | 1.3, IEEE 1516 | C++, Java | Commercial |
| HLA Direct | General Dynamics C4 Systems | 1.3 | ? | Commercial |
| Openskies RTI | Cybernet Systems | 1.3, IEEE 1516 | C++ | Commercial |
| Pitch pRTI | Pitch Technologies | 1.3, IEEE 1516 | C++, Java | Commercial |
| Mitsubishi ERTI | Mitsubishi Electric Corp. and Mitsubishi Space Software Co. Ltd | 1.3 | C++ | Commercial |
| RTI NG Pro | Raytheon Virtual Technology Corporation | 1.3, IEEE 1516 | C++, Java | Commercial |
| Non-commercial | ||||
| Name | Vendor | Standard | Bindings | License |
| BH-RTI | Beijing University of Aeronautics and Astronautics Virtual Reality Laboratory | 1.3, IEEE 1516 | ? | ? |
| CERTI | ONERA | 1.3partial, IEEE 1516 planning | C++ | GPL |
| EODiSP HLA | P&P Software | IEEE 1516partial | Java | GPL |
| GERTICO (German RTI based on COrba) | Fraunhofer IITB | 1.3 | ? | ? |
| The Portico Project(formerly jaRTI) | littlebluefrog labs | 1.3, IEEE 1516 | Java, C++ | CDDL |
| Open HLA | 1.3partial, IEEE 1516partial | Java | Apache License | |
| RTI-S | US JFCOM J9 Directorate | 1.3 partial | C++, Java | US Government |
| Rendezvous RTI (formerly known as Reusable Architecture for Interoperable Universal Simulations Project # 94) | National University of Science and Technology (NUST), Pakistan | 1.3 | C++, Java | NUST |
| Discontinued | ||||
| Name | Vendor | Standard | Bindings | License |
| GMU RTI | George Mason University | 1.1 | C++ | Free software license |
| jaRTI | littlebluefrog labs | 1.3 partial, IEEE 1516 partial | Java, C++ | CDDL |
| RTI NG | DMSO | 1.3 | C++, Java | |
| SXTA | IEEE 1516 | C# | BSD license | |
| XRTI (Extensible Run-Time Infrastructure) | Naval Postgraduate School | IEEE 1516 | C++ | BSD license |
| yaRTI (yet another RTI) | 1.3 | C++, Ada | GPL | |
