In Structured Data Transfer (SDT), the data is structured in data blocks and segmented for data transfer in the cells. The method uses an 8- byte Constant Bit Rate ( CBR) field in each CBR cell to identify the sequence number. If the cell time varies and the cells do not arrive at the receiver in the correct order, the receiving station can use the sequence number and put the cells in the correct order. However, if the cell arrival time varies too much or if too many cells need to be changed in sequence, cells can be eliminated. In this case, the receiving station uses the sequence number to inform the sending station of the problem.