This article describes the construction of a TCP/IP network for the support of distributed multimedia conferencing on top of an international ATM network, and draws some general conclusions for the design of networks with similar requirements. An excellent tutorial describing the principles of internetworking over ATM WANs may be found in [?]. The network described in this paper was designed to support the second RACE Summer School that was held, during July 94, in a distributed manner among five sites: DIT-UPM (Spain), TID (Spain), CET (Portugal), U. Aveiro (Portugal) and Ascom (Switzerland). The five sites were interconnected by means of an ATM network, terrestrial and satellite, that provided user network interfaces at 155 Mb/s (STM1) and 34 Mb/s (E3). The devices used to access the ATM network included routers with ATM interface, ATM CSU/DSU equipment, and Ethernet IWUs for satellite ATM connections. Both AAL3/4 and AAL5 had to be combined because of compatibility with available equipment. The ISABEL[?] application was used to support the RACE Summer School, requiring the transmission of digital video (M-JPEG compres-