Cell Relay Archive

[murray@pa.dec.com (Hal Murray)]

> crc is fundamentally a probability game: you look for circumstances in
> which the probability of taking the wrong answer is small.  for
> instance, take the case given above in which a single bit error and a
> 3 bit error produce the same residual.  if the bit error rate on the
> facility is 10^-7, then the probability of the former is 10^-7 while
> the probability of the latter is 10^-21.

Only if there is no clumping of errors.  Many physical systems
have mechanisims that generate clumps of errors.

4B/5B is an obvious example. Another one is a screwdriver shorting
a copper pair.
-- 
These are my opinions, not necessarily my employers.