New developments in packet communication

The TELENET packet-switched public network consists of eight major switching centers and a large number of smaller offices which provide dial-in access to the network. The only mode in which the packet-switched communication subnet interacts with the outside is via the CCITT approved X25 interface. All non-X25 terminals require a protocol conversion process. The protocol conversion modules form a ring around the basic X25 subnet. The employed term 'value-added network' is derived from the value the protocol conversion modules add to the basic transport mechanism. Lines leased from the telephone company are used as a communication link. Protocol conversion is performed by a dedicated multiprocessor. Attention is also given to packet communications over satellites, the use of packet radio facilities, local area bus systems, and telemail.