Abstract: The Integrated Services Digital Network ("ISDN") normally uses 64 Kbits/sec channels which are therefore unsuitable for data traffic at higher rate traffic. This can be overcome by assembling ISDN channels to form higher bit rate channels. However, when the bit-rate required changes frequently, the number of channels grouped together must be changed often. To solve this problem, data packets are received from local area networks by a computer and assembled into groups of ISDN channels which are combined to form high bit rate channels or U-channels. The computer assembles data into an ISDN frame using an appropriate number of slots in the frame for each U-channel. The frames are transmitted using conventional ISDN circuits. On reception, ISDN slots in frames are passed to packet assembly buffers, one for each U-channel, before being passed to users. When a new slot is to be added to a U-channel, synchronization signals are sent in the new slot and flags are used to establish when data is to be sent.

Abstract: Communication channels provided by the Integrated services Digital Network (ISDN) usually carry 64 Kbits/sec in each direction and are therefore unsuitable for data traffic at higher rates. This difficulty can be overcome by assembling ISDN channels to form channels having a higher bit rate. However problems arise, for example, in the transmission of data packets where the bit-rate required changes frequently and therefore the number of channels grouped together must be changed often. These problems are tackled as now described. Data from different data streams to be transmitted is read into respective buffers in a RAM. ISDN channels are grouped into channels known as slots and U-channels, respectively, and each U-channel transmits a respective data stream. Data from the buffers are assembled into frames, corresponding to an ISDN frame in a frame store by a microprocessor.