Richard Hamming It's frustrating to get only 99% of a file from BitTorrent or Usenet. Error correcting codes could help. The basic idea of an ECC is that the file you download is 110% bigger, but if you're missing 5% of the file you can still recover it. PC hard drives, memory, and modems use ECCs: why not file distribution?
A popular Reed-Solomon code is RS(255,223) with 8-bit symbols. Each codeword contains 255 code word bytes, of which 223 bytes are data and 32 bytes are parity. ... errors in up to 16 bytes anywhere in the codeword can be automatically corrected.
RAR archives support ECCs via data recovery blocks, but few people use them. There's momentum behind PArchive, a file format. It seems optimized for transferring large lists of files rather than a single archive. PAR usability is low but QuickPar is OK.
  2003-10-19 18:40 Z