Packet switched network in Japan

Research and development of public data networks have been conducted by various countries to cope with recent diverse data communication demands. Nippon Telegraph and Telephone Public Corporation (NTT) has also been advancing developmental projects on a packet switched network and a circuit switched network. Commercial tests on each will be begun in 1979. Public data networks require the use of standard device-independent interfaces between networks and user devices. Especially, standard interfaces used in packet switched networks need to be specified even concerning an information transfer phase. As the fruits of energetic discussions made by CCITT, ISO etc., CCITT Recommendation X.25 for packet-mode terminals has been completed recently. On the other hand, the interface for non-packet-mode terminals will be discussed in CCITT SG VII during this study period 1977--1980. This paper describes NTT's packet switched network, laying emphasis on details of communication protocols for packet-mode and non-packet-mode terminals.