[TUHS] Windows roots and Unix influence (was Re: Happy birthday, Ken Thompson!)

George Michaelson ggm at algebras.org
Tue Feb 6 09:52:42 AEST 2018

My understanding is that FAA rated 'ethernet' switches for aircraft
are modified ASICs which do TDM. You program in slot reservations, and
this is used to give bounded-time delivery guarantees for flight
critical stuff. Cheaper to make by modifying existing stuff, the
physical and link layer code is almost identical, its just put into a
timeslot regime. Its fully isochronous for the flight control and its
best effort delivery for the entertainment.

So, when people talk about the entertainment being 'isolated' its not
opto-isolated and its not airgap discrete switch isolated: the TDM
bitfield excludes the customers from talking in the timeslots for the
flight control logic.

I think the imputed hack, was to "see" the flight control sequences
because you can probably fake out read-side, and get passive view of
them if you can make the ports broadcast-receive. I am really
unconvinced anyone succeeded in write-mode into this model. Not that
it couldn't happen and not that I believe I'm smarted than bad people:
I just thing the descriptions have the quality of urban myth right

On Tue, Feb 6, 2018 at 9:36 AM, Arthur Krewat <krewat at kilonet.net> wrote:
> Sorry, Thunderbird strikes again. I highlighted the text to include, and it
> didn't put the correct address on the quote.
> My apologies.
> On 2/5/2018 6:28 PM, Dave Horsfall wrote:
>> On Mon, 5 Feb 2018, Arthur Krewat wrote:
>>> On 2/5/2018 4:57 PM, Ron Natalie wrote:
>>>> There's certainly been demonstrations of vehicles being taken over via
>>>> the entertainment system; why the stereo needs to talk to the engine
>>>> computer I'll never know...  I know, wind up the volume the faster you go
>>>> etc, but surely it ought to be one-way?
>> Umm, I wrote that, not Ron...

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