The MAK RTI was the first HLA RTI commercially released, and we originally called it the MAK High-Speed RTI because the only other RTI at the time (a GOTS product) was extremely slow, leading people to believe that HLA was inherently slow. We took it upon ourselves to build a free RTI to prove that HLA was viable.

Over the years, the MAK team has helped lead the HLA standard effort through countless meetings and architecture discussions, tackling some truly thorny problems. HLA has grown into an extremely stable way to connect simulators across the world, as well as across the room. This latest version continues the improvements made where IEEE 1516-2010 (HLA Evolved) left off. Sometimes I think it’s amazing how far HLA has come.

When I started at MAK 23 years ago, we were basically an interoperability company. That’s not so much the case anymore. While MAK as a whole has grown into something much bigger, interoperability remains an important cornerstone of MAK ONE. It may not always be the loudest thing we talk about, but it’s one of the most important parts of our infrastructure. It’s like the internet: we wouldn’t be here without it.

Keep reading to learn more about what's new in HLA 4 and MAK RTI 5.0, and stay tuned for more MAK ONE 2025 product release announcements from me over the next couple of months.

What's new in HLA 4 and MAK RTI 5.0:

Fundamentally, HLA 4 is evolutionary, though we shouldn’t use that term too much lest we get confused with the last version—HLA Evolved! Many of the changes in HLA 4 are focused on updates to language interfaces, easier connection in cloud-based environments, and continuing to make connectivity with diverse federates easier.

Here are a few of the more significant changes:

Modern C++ Compatibility

The API is fully compatible with C++14, with deprecated constructs like std::auto_ptr removed and exception handling updated. It’s also confirmed to work with C++23, ensuring long-term developer support.

FOM Attribute and DDM Merging

This is one of the most impactful additions to HLA 4. It allows FOM modules to add attributes to existing classes, significantly simplifying FOM design and extension. Enhancements to DDM also allow FOMs to add new dimensions or extend existing classes. In addition, there is a new option to relax region overlap requirements, so federates can receive updates even if DDM regions don’t technically overlap—particularly useful for fixed-grid DDM implementations. For more on this topic, take a look at this blog post.

Federate Protocol

A new network packet protocol allows federates to communicate with well-defined network messages. MAK is developing lightweight C++ and Python libraries that use this protocol to communicate with the RTI, which opens up new possibilities for secure and inspectable RTI traffic. This is especially useful for bridging and monitoring applications that require visibility into RTI messaging.

Directed Interactions

Interactions can now be sent to specific object instances. Only federates that own attributes of the target object will receive the interaction, adding precision to interaction delivery.

Authorization

RTI 5.0 can now be configured to require federates to supply credentials when connecting, creating, or joining a federation. Federates that provide credentials when the RTI isn’t expecting them will be denied—offering protection against accidental or malicious federation mismatches. The default implementation uses a simple plain-text password, but more advanced setups using certificates can be implemented via a plugin API.

Transport Order Switching

Federates can now change the transport order (reliable or best-effort) at runtime, offering more flexibility and control over communication behavior during execution.

MOM Logging

RTI 5.0 can now direct MOM (Management Object Model) data to be recorded to a file, supporting traceability, auditing, and debugging workflows.

Compatibility and Future Plans

MAK RTI 5.0 includes core HLA 4 features today, with more to be added in future releases. All MAK ONE products going forward will support HLA 4 out of the box, ensuring a smooth transition across our ecosystem.

We also remain committed to backward compatibility. MAK RTI continues to support:

• HLA 1.3
• IEEE 1516-2000 DLC API
• HLA Evolved (1516-2010)

This release is a major milestone for MAK that demonstrates our ongoing commitment to open standards and simulation interoperability. 

For more details about MAK RTI 5.0, read the detailed product release notes.

Questions or comments? Connect with the MAK team anytime at This email address is being protected from spambots. You need JavaScript enabled to view it., or explore MAK Customer Support through our Support Portal and self-help resources.