FOREIGN PATENT DOCUMENTS
2196512 4/1988 United Kingdom H04J 3/16
WO 12467 10/1990 WIPO H04L 25/14
WO 14319 9/1991 WIPO H04J 3/16
WO 85/04300—Sep. 26, 1985.
Primary Examiner—Douglas W. Olms
Assistant Examiner—Russell Blum
Attorney, Agent, or Firm—Cushman, Darby & Cushman
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. When the bit-rate of a U-channel is to be reduced by removing a slot, a distinctive closing sequence is sent in that channel which on reception is an indication that no further data will be sent in that slot.