Re: Most energy efficient (home) setup

[Steven Bellovin <smb () cs columbia edu>]

On Apr 19, 2012, at 6:31 43PM, Douglas Otis wrote:

> On 4/18/12 8:09 PM, Steven Bellovin wrote:
> > On Apr 18, 2012, at 5:55 32PM, Douglas Otis wrote:
> > > Dear Jeroen,
> > >
> > > In the work that led up to RFC3309, many of the errors found on the
> > > Internet pertained to single interface bits, and not single data
> > > bits. Working at a large chip manufacturer that removed internal
> > > memory error detection to foolishly save space, cost them dearly in
> > > then needing to do far more exhaustive four corner testing.
> > > Checksums used by TCP and UDP are able to detect single bit data
> > > errors, but may miss as much as 2% of single interface bit errors.
> > > It would be surprising to find memory designs lacking internal
> > > error detection logic.
> >
> > mallet:~ smb$ head -14 doc/ietf/rfc/rfc3309.txt | sed 1,7d | sed
> > 2,5d; date Request for Comments: 3309
> > Stanford September 2002
> >
> > Wed Apr 18 23:07:53 EDT 2012
> >
> > We are not in a static field... (3309 is one of my favorite RFCs --
> > but the specific findings (errors happen more often than you think),
> > as opposed the general lesson (understand your threat model) may be
> > OBE.
> Dear Steve,
>
> You may be right.  However back then most were also only considering random single bit errors as well.  Although 
> there was plentiful evidence for where errors might be occurring, it seems many worked hard to ignore the clues.
>
> Reminiscent of a drunk searching for keys dropped in the dark under a light post, mathematics for random single bit 
> errors offer easier calculations and simpler solutions.  While there are indeed fewer parallel buses today, these 
> structures still exist in memory modules and other networking components.  Manufactures confront increasingly 
> temperamental bit storage elements, where most include internal error correction to minimize manufacturing and 
> testing costs.  Error sources are not easily ascertained with simple checksums when errors are not random.

Yes -- that's precisely why I like that RFC so much.


                --Steve Bellovin, https://www.cs.columbia.edu/~smb