Real-time communication of multimedia data over heterogeneous networks that may include constant delay networks, variable delay networks that have a common reckoning of time, and variable delay networks that do not have a common reckoning of time. If there are any variable delay networks in which there is no common reckoning of time in the heterogeneous networks, a common reckoning of time is established in each of those networks. Then, a constant delay network is emulated for each variable delay network using the specific common time reckoning present in each variable delay network.