Re: Checksums, CRC's, and NFS


zweig@p.cs.uiuc.edu
4 Apr 88 16:55:00 GMT


        I agree strongly with the point about checksums missing bugaboos
like word-swaps. Especially with all the OSI hassling and with everyone
from Apple to McDonald's (just kidding) brewing up TCP/IP code, the likelihood
that byte-sex induced problems and weird buffer misuse errors will occur
is increased.
        Another big overhead that often gets left out of the computation is
this: how much CPU and man-time does it take to figure out what's going on
and fix bugs (rare though they be) caused by _not_ having CRC's in the right
places (i.e. over noisy asynch lines)?? If important files get bit rot and no-
body notices for a long time, it can take many hours of travail to set things
right -- this is a hidden cost of not using CRC's that needs to be taken into
account when talking about bandwidth. A zillion bits per second won't buy you
a thing if you have to go over the files with a fine-toothed comb to see if
they have been munched.

Johnny Zweig
University of Illinois at Urbana-Champaign
(standard disclaimer about being a grad-student and ignorant, etc., etc.)



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