[e2e] Re: [e2e], [Tsvwg] Really End-to-end or CRC vs everything else?

Michael B Greenwald mbgreen at dsl.cis.upenn.edu
Fri Jun 8 10:23:03 PDT 2001

   Thu, 7 Jun 2001 17:41:36 -0700
   "Douglas Otis" <dotis at sanlight.net>

   The stuck bit tests for the more elaborate two Fletcher-16 sums indicated
   that errors were undetected 1.3% of the time using disk files as test cases
   if a stuck memory bus bit affected only half of the packet.  

Could you send me a pointer to the paper that reports these measurements
and explains your experiments?  1.3% sounds high --- especially if you are
using a 32bit Fletcher checksum (a 16bit sum and a 16bit sum of products).
I'd like to understand this result.

Thanks.  (Incidentally, assuming your summary accurately represents the
paper, then it is still not clear that there's enough data for the
Sheinwald et.al. draft to draw the conclusion it did about this fairly
minor point)

   pathological failure indicates a low level of assurance that data has not
   been corrupted.  The same test using CRC never failed.  This exceeds the
   number of bits assured by CRC, but the random nature of CRC still provides
   n:2^32 protection.  I did not bother with a splice test as the headers
   within SCTP should provide this level of protection unless these segments
   are out of order within the packet.  I had no information on the nature of
   this type of error.

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