Importance

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Abstract

The present invention facilitates the transmission of a file to a computer where the receiving computer has a file (called the old file) that is related to the file being transmitted (called the new file) but where the sending computer does not know the status or content of the old file. As a preliminary step, one of the computers generates a Delimiter Selection Profile Table (DSPT). The DSPT is generated by first determining the number of times each delimiter in a set of delimiters appears in the file and the distance between the locations of the delimiters in the file. Next using the information in the DSPT one of the delimiters is chosen as the delimiter which will be used and this delimiter is transmitted to the computer which did not generate the DSPT. The receiving computer next generates a Segment Profile (SPT) of the old file and the sending computer generates an SPT the new file. The SPT is generated by calculating a hash code (such as a CRC) for each segment which is defined by the selected delimiter. The hash codes from the old file are transmitted to the sending computer. The sending computer then sends to the receiving computers those segments in the new file that do not have a hash code number which matches one of the hash code numbers from the old file. The sending computer also sends an indication of where segments from the old file should be inserted into the new file. The receiving computer then constructs the new file from the segments received from the appropriate old segments.

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First Claim