: If you have an active maintenance contract or valid credentials, you can download various versions, including 17.x and 18.x, from the Riverbed Modeler Support Site . Note that version 16.1 is an older release; newer versions like 18.12.1 are currently available.
For academic research, is the closest spiritual successor to OPNET Modeler, as it offers detailed protocol stack modeling and output analysis tools. download opnet modeler 16.1
If you are installing 16.1, remember it was designed for older OS environments (Windows 7/XP era). If you are running Windows 10/11, you may need to run the installer in Compatibility Mode or use a VM (like VirtualBox) with an older OS image. : If you have an active maintenance contract