Re: The TCP and UDP checksum algorithm may soon need updating

Craig Partridge <craig@tereschau.net> Tue, 09 June 2020 20:25 UTC

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From: Craig Partridge <craig@tereschau.net>
Date: Tue, 9 Jun 2020 14:25:12 -0600
Message-ID: <CAHQj4CeDNYab3TGm3ijx7cR7Tb2CeGjQE_dZq_2v5zW_M63DuQ@mail.gmail.com>
Subject: Re: The TCP and UDP checksum algorithm may soon need updating
To: Nico Williams <nico@cryptonector.com>
Cc: IETF discussion list <ietf@ietf.org>
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On Tue, Jun 9, 2020 at 1:39 PM Nico Williams <nico@cryptonector.com> wrote:

>
>
> > * Some folks have assumed the TCP checksum, at 16 bits, misses an error
> > about 1 in 2^16 times.  That's not correct.  There are classes of errors
> > that TCP catches 100% of the time (e.g. single-bit errors).  There are
> also
> > classes of errors that the TCP checksum misses about 1 in 2^10 times.
> This
> > latter is because the TCP checksum is not terribly good -- a better
> > designed checksum would miss only about 1 in 2^16.
>
> 2-bit errors do happen.
>
>
I'm not sure what the 2-bit errors happen point is.  Lest someone imagine
that bit errors are the issue...

Lots of errors happen.  1 bit, 2-bit, byte, entire packet buffers trashed,
bytes/words/sequences forced to all 0s and all 1s, chunks of packets erased
or duplicated....  Essentially anything that can go wrong in a
middlebox/router showed up -- data line timing errors, bad memory (in
varying sizes), pointers getting trashed such that other random data gets
added/deleted, etc.

Table 3 my 2000 paper with Jonathan Stone lists a huge range of errors in
that error and few of them were bit errors.

Craig

Craig


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