| 摘要 |
PURPOSE:To detect the non-arrival of intermediate data by subtracting the data lengths of data units that subsequently arrive from a message length before dividing, and deciding whether the value finally goes to zero. CONSTITUTION:Since a header length 4-1, a segment length 4-2, a total length 4-3 are recorded in the leading parts of respective divided data units, the message length before dividing can be obtained by subtracting the header length from the total length. Also, respective data lengths can be obtained by subtracting the header length from the segment length. Accordingly, when the data transmission is normal, the sum value of the data lengths of all the received data units coincides with the message length before dividing. Inversely, by subtracting the data lengths of the received data successively from the message length before dividing, a value zero can be obtained. Therefore, at the time of receiving the final data unit, when the sum-result of data lengths or the subtraction-result does not give a value zero, it can be decided that some intermediate data is missing.
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