Re: Re: How many bytes should a CRC-32 protect?

Matt-

You're assuming a uniform distribution of errors, aren't you?  If you have 
bursty errors (as in most wireless channels), you win with bigger packets 
since errors are concentrated in a smaller number of packets.

--aaron

> The logic behind the calculation seems to be flawed in the following way:
> If you have a large quantity of data to move (say a Peta Byte, 1e+15
> Bytes) then the total undetected error rate is independent of the packet
> size across a huge range of sizes.   This is because changes in
> per-packet exposure to undetected errors are exactly offset by the change
> in the number of packets.
>
> For example if I send 1e+15 bytes over a link that has a raw error rate
> of  1E-12 then I compute:
>
> Using 1000 byte packets:
>  Raw bit error rate: 1.0e-12
>  Per packet error rate: 1.0e-09
>  Undetected packet errors: 2.5e-19
>  Packets per data set: 1.0e+12
>  Total undetected errors per data set: 2.5e-07
>
> Using 10000000 byte packets:
>  Raw bit error rate: 1.0e-12
>  Per packet error rate: 1.0e-05
>  Undetected packet errors: 2.5e-15
>  Packets per data set: 1.0e+08
>  Total undetected errors per data set: 2.5e-07
>


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