This paper describes Simmcast, a process-based discrete-event simulation framework that helps the design and evaluation of multicast protocols. Simmcast, based on Java, allows simulated protocols to be specified using a multi-threaded, object-oriented framework; building blocks are combined in order to create new protocol simulation experiments. To help validating Simmcast, two reliable multicast protocols used in a well-known analytical study were simulated and the results achieved compared the ones produced by Simmcast. In Simmcast, users are first presented an easy-to-understand, abstract multicast protocol simulation model, and then can gradually increase the level of detail in their simulation. Unlike existing tools, Simmcast provides a flexible simulation model which is dedicated to the design and evaluation of multicast protocols.