On May 13, 2010, at 2:24 04PM, Daniel Senie wrote:
> While the equipment may well be affected by an EM pulse, if the gear returns
> to normal after a power cycle, then the equipment vendor didn't do their job
> fully developing the product. A product should be tested to take such pulses
> and should recover provided it has not suffered a catastrophic failure (and
> in fact it should contain sufficient protection to avoid such in most cases).
>
> In working on one particular router in the lab some years ago, I was
> verifying some software functionality and the hardware engineer I was working
> with reached over my shoulder and used a device that delivered a high voltage
> spike (simulated lightning) to a 10BaseT network port. After I peeled myself
> off the ceiling (and he stopped laughing), we set to work figuring out how to
> get the device to self-reset after such a strike. One component, an Ethernet
> hub chip, got into a confused state. I was able to detect this in software,
> so we adjusted the product design so that the software could yank the hub
> chip's reset line.
>
> It's unfortunate that products, both hardware and software, receive minimal
> quality testing these days. Guess it's not a surprise, since buyers seemed to
> prefer products that were quick to market, with lots of bugs, rather than
> reliability and resilience.
>
It's not just a matter of "these days" -- lightning is awfully hard to deal
with, because of how quirky the real-world behavior can be. I had to deal with
this a lot in the 1970s on RS-232 lines -- we could never predict what would
get fried. Of course, there was also a ground strikes very near my apartment,
where the induced current tripped a circuit breaker, blew out a couple of
lightbulbs, and and came in through the cable TV line to fry the cable box, fry
the impedance-matching transformer, and fry the RF input stage on the
television...
--Steve Bellovin, http://www.cs.columbia.edu/~smb
