Up to now, messages and e-mail services are mostly text- and ASCII-based. With the availability and high user acceptance of multimedia-based services like WWW, the need for the transport of multimedia objects like audio, video and graphics arises even in message-based applications. For many multimedia applications a mail-only transfer mode is a must.
Request for Comments (RFCs) and standards already propose solutions for these new requirements, however only few implementations exist today.
In the BERKOM enviroment, a big PTT-driven project to implement the communication infrastructure of Berlin, a superset of the X.400 protocol has been chosen (X.400+) to overcome the deficiencies of present X.400 and the handling of large multimedia messages has been defined: they are stored in a global store and only an external reference pointing to the global store is passed through to the recipients of a message. It is their choice afterwards whether they want to fetch it or not.
GMD has been awarded by the DFN association being responsible for major mail components within the BERKOM environment to implement the multimedia mail gateway. The development is based on the ISODE X.400 product PP and was finished in early 1995 in cooperation with the Fraunhofer Gesellschaft in Darmstadt, being responsible for the development of graphic converters, and GMD's FOKUS institute in Berlin, being responsible for the file transfer component of the gateway.
In this presentation the development of MMMGate, the multimedia mail gateway, to enable communication and cooperation among users using OSI protocols (X.400), Internet users (SMTP/ MIME) and BERKOM users (X.400+). is described together with its multimedia functionality.
Major attention is paid to the handling of large multimedia messages with high bandwidth and storage requirements and the management of partial messages. Due to the idea of external references, the gateway has a mail and a file transfer component doing the gatewaying between FTP and a file transfer protocol (RDT) used in the BERKOM environment. It was a problem to keep the gateway's functionality consistent: the results should be independant of the path through the gateway chosen.
The cooperation with a global store is described as well as the integration of grafic converters. At last the experiences with the embedding of the gateway into the national multimedia reference center and into user-driven projects is presented.