[ih] "how better protocols could solve those problems better"

[Craig Partridge]

On Wed, Sep 30, 2020 at 6:58 PM Joseph Touch <touch at strayalpha.com> wrote:

>
>
> > On Sep 30, 2020, at 4:58 PM, Craig Partridge via Internet-history <
> internet-history at elists.isoc.org> wrote:
> >
> > I've got some NSF funding to figure out what the error patterns are
> > (nobody's capturing them) with the idea we might propose a new checksum
> > and/or add checkpointing into the file transfer protocols.  It is little
> > hard to add something on top of protocols that have a fail/discard model.
>
> We already have TCP-MD5, TCP-AO, TLS, and IPsec.
>
> Why wouldn’t one (any one) of those suffice?
>

Actually no.  These are security checksums, which are different from error
checksums.  The key differences are:

* Security checksums miss an error 1 in 2^x, where x is the width of the
sum in bits.  Error checksums (good ones) are designed to catch 100% of the
most common errors and miss other errors at a rate of 1 in 2^x.  So a
security checksum is inferior in performance (sometimes dramatically) to an
error checksum.

* Security checksums are expensive to compute (because they assume an
adversary) and so people tend to try to skip doing them.  Error checksums
are easy to compute.

Currently the best answer is that for data transmission (e.g. TCP segments)
you need an error checksum.  At a higher level you do the security checksum.

Craig


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