[ih] History of duplicate address tests

[John Shoch]

I've always thought that in networking there is a place for absolutes,
perfection, and "error free."
But a really important part of system engineering is about cost/benefit
tradeoff, probabilities, and error recovery.

When considering going from manual assignment of Experimental Ethernet
addresses to a semi-automatic generation of 48-bit addresses to be blown
into a PROM on a board:
--We thought, "It may not be perfect, but it's certainly more reliable than
trying to scale the manual process!"
--"But what are the odds a bit blown into a PROM will heal, and produce a
duplicate ID?"  "Let's just make sure the odds of that are LESS than the
odds of your machine catching fire or dying from a power surge; or your
building being destroyed by lightning, flood, or earthquake; or someone
typing Delete *.*"
--"Have a backup and recovery plan!"  "And if you don't have a recovery
plan for fire, lightning, flood, earthquake, or fumble-fingers, don't
complain about lower-probability network events....."

John

PS:  In a similar vein, I would sometimes field provocative questions, "Why
don't you have encryption on the Ethernet?"  I would merely observe, "We do
have a project to build a crypto box in front of the Ethernet transceiver,
for serious government customers with Tempest needs.  But do you shred all
your letters and print-outs before they go in the dumpster?   If not, you
have worse problems than your Ethernet....."

On Thu, Dec 1, 2022 at 12:00 PM <internet-history-request at elists.isoc.org>
wrote:

>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Fri, 2 Dec 2022 08:47:19 +1300
> From: Brian E Carpenter <brian.e.carpenter at gmail.com>
> To: Bob Hinden <bob.hinden at gmail.com>, Jack Haverty <jack at 3kitty.org>
> Cc: internet-history at elists.isoc.org
> Subject: Re: [ih] History of duplicate address tests
> Message-ID: <7f330b01-d5be-2f51-c437-ae051dcb0a45 at gmail.com>
> Content-Type: text/plain; charset=UTF-8; format=flowed
>
> On 02-Dec-22 07:55, Bob Hinden via Internet-history wrote:
> > Hi Jack,
> >
> >> On Dec 1, 2022, at 10:03 AM, Jack Haverty via Internet-history <
> internet-history at elists.isoc.org> wrote:
> >>
> >> Hi Grant,
> >>
> >> Thanks for the update.  I remember reporting the issue to IETF back in
> the mid 80s and again in the early 90s.   I guess it still hasn't risen to
> the top of anybody's priority list.
> >
> > As was noted earlier, Duplicate Address Detection (DAD) was included in
> IPv6.    Our thinking at the time was to detect broken hardware NICs (all
> with the same mac address) as we were initially using MAC addresses to form
> Interface IDs.   We have moved away from that, see RFC 8064.   I think DAD
> is still useful to detect misconfigured manually assigned addresses.
>
> And you cannot 100% discount a collision between pseudorandom IIDs. Yes,
> very very unlikely, unless you have lousy random number generators, which
> we'll never have, right?
>
>     Brian
>
>
>
>