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Method of restoring the correct cell sequence, particularly in an ATM exchange, and output unit therefor

  • US 5,173,897 A
  • Filed: 12/19/1990
  • Issued: 12/22/1992
  • Est. Priority Date: 12/23/1989
  • Status: Expired due to Term
First Claim
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1. Method of restoring the correct sequence of data packets or cells in a packet switching system, wherein, during transmission from an input unit to an output unit, related cells belonging to a single data stream from a specified input unit to a specified output unit of the switching system may overtake each other, said method comprising the steps of:

  • prior to transmission form the input unit, adding a respective sequence label to each of the cells to identify the original transmission order of the cells;

    upon reception at the output unit, buffering each cell in an output buffer;

    waiting for at least a predetermined minimum delay time to elapse following the reception of a candidate cell still contained in the buffer;

    comparing the sequence label of said candidate cell with the corresponding sequence labels of other cells in said output buffer;

    outputting said candidate cell if the comparison indicated that the candidate cell was originally transmitted before the other cells in the output buffer; and

    instead of the candidate cell, outputting another cell if the comparison indicated that the other cell was originally transmitted before the candidate cell.

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