1. A method for modeling the error characteristics of a communications system, comprising: establishing a number of simulated defect streams comprising a plurality of codewords; for each simulated defect stream: specifying a mean defect separation; and specifying a mean defect size; generating a defect array for each simulated defect stream, comprising storing in the defect array the starting location and the ending location of each defect within a codeword; concatenating the defect arrays generated from each data stream into a new defect array; merging overlapping defects in the new defect array; apportioning the merged defects to the codewords; generating a histogram of the number of codewords processed having k bytes in error, where k=[0. .. m] and m equals a predetermined maximum number; and based upon the number and location of codeword errors and an error correction capability of an error correction code, estimating the probability of a failure in the error correction code.