The Network License Manager (NLM) enables several Autodesk products on the same computer to share a single license when appropriate. For example, if you launch AutoCAD, the NLM can assign a single AutoCAD license to your computer. Later, if you launch Revit, and there are available licenses for the Building Design Suite (BDS), the NLM can take back the AutoCAD license and upgrade your license to a BDS license that can support AutoCAD, Revit, and other BDS products running concurrently. If you then shut down Revit and other BDS products, so that you are running only AutoCAD, the NLM cannot downgrade your suite license to a single AutoCAD license if the suite license is required by another user. In this situation, AutoCAD is holding onto a suite license that it may not need. The only way to return that license to NLM is to shut down AutoCAD.
License cascading is a process by which network licenses are automatically switched or substituted by the NLM according to a hierarchy of value. It occurs in order to distribute licenses most efficiently among a group of users, subject to the limitation that licenses can be upgraded but not downgraded. The basic principles are that lower-cost licenses are used when possible, and higher-cost licenses are used only when required, such as when a user is running two or more suite products, or when all the lower-cost licenses are in use.
The NLM surveys license usage every two minutes; if possible, it redistributes licenses among users, and takes back licenses that have been unused for longer than the allowed idle time, or timeout period. For more information on license timeout, see Set Up License Timeout.
License cascading is most effective in a large user group when the NLM has a pool of different license types available for distribution. For example, if the pool includes product-specific licenses for several products, some licenses for a standard suite, and some licenses for an ultimate suite, the NLM has many options for efficient license management. It can assign single-product licenses as individual products start up, replace these with a suite license if a user runs multiple products, and upgrade a standard suite license to an ultimate one if a user invokes an advanced operation that requires a product from the ultimate suite.
For more information, see the Services & Support topic Understanding Cascade Licensing for Autodesk Products.