An integrated battlespace simulation, consisting of an off-board sensor, an airborne (CI)-I-4 platform, and a fighter aircraft, was performed over an ATM OC-3 backbone network interconnecting multiple, disparate processing platforms (i.e., SUN Sparc-20's, DEC Alpha-500/600's, and SGI Onyx-1/Onyx-2), A multicast capability is required to run a realistic battlespace simulation program over ATM network. However, it is not supported by the existing protocols (e.g., classical Internet protocol (TP) over ATM), A simple solution that addresses the ATM classical TP multicast problem is described in this letter. The network and application performance of ATM classical IP is then compared with that of FDDI and LAN emulation.