> Things like NTP and DNS that other good stuff that DHCP can be used to tell hosts about.
Look up RFC 6106 (published 15 years ago). Router advertisements have carried DNS resolver info for a long time now.
Once again, the old adage “IPv6 haters don’t understand IPv6” applies.
As much as I would like hosts to use the local NTP server, most will ignore the NTP server you specify in DHCP anyway, so it’s kind of a moot point.
Edit: RFC 6016 actually supersedes RFC 5006 from 2007. That’s nearly two full decades we have had DNS info in RAs. That’s the year Itanium2 came out (any greybeards here old enough to remember that one?)
> ...the old adage “IPv6 haters don’t understand IPv6” applies.
I'm an IPv6 hater. Sure. [0][1][2]
> ...RFC 6106...
Yes. I'm quite aware of the RDNSS field in RAs. In past experience from ten-ish years ago, [3] I found that it is unreliably recognized... some systems would use the data in it, and others would only ignore it. In contrast, DHCPv6 worked fine on everything I tested it on except for Android. Might this be because RFC 6106 was published in 2010, while RFC 3315 ("stateful" DHCPv6) was published in 2003, and RFC 3736 ("stateless" DHCPv6) was published in 2004? Maybe.
> ...RFC 6016 actually supersedes RFC 5006 from 2007.
An attentive reader notes that RFC 5006 is an experimental RFC. It took another four years for a non-experimental version of the standard to be published.
So, anyway. Yeah, I should have said
Things like NTP and (sometimes) DNS and that other good stuff...
Whoops. But, my point stands... how do you communicate to clients the network's preferred NTP servers or nearly all of the other stuff that DHCPv6 communicates if one choses to use only SLAAC?
[3] Perhaps things have gotten better in the intervening years? Should I find myself bored as hell one evening, I'll see what the state of device/OS support is.
> Was it essentially doing the high-tech equivalent of dangling a rock on a string with some dampening (in a gyroscopic cage to avoid being affected by the airplane's rotation), or something smarter?
Yes, that is essentially how a gyroscopic artificial horizon works.
Consider that the local horizon changes relative to an inertial frame (the stars) as you travel across the surface of a sphere, so even if you could build a perfect gyro that remained stationary in the inertial frame you would need to update the local down as you move. The solution is to slightly weight the gyro cage to bias it to the local down.
Now, consider that, in a properly-coordinated turn, the passengers (and gyro) will feel that gravity points straight to the floor :) So the time-constant of the damping is important.
I assume the constant is usually chosen short enough that the system will "forget" turns quickly, in exchange for becoming useless while turning?
Still, getting this whole thing accurate to probably one minute of arc is insane, especially with the gyro and star tracker linked only via motors and synchros. So the total error is the sum of any deviation of the gyroscope from the actual down direction, the error in measuring the gyro angle, the error in setting the star tracker to that exact angle, and then all other errors the system introduces. Then you need to take multiple separate measurements at different times and compensate for the movement, and a one-degree difference means you're over the wrong city (or in Europe, country) so the end-to-end accuracy must be much better than that.
And sailors supposedly did that with a sextant to something like 0.01° on a moving ship.
> anyone who can succeed in academia almost certainly has the brains and credentials to get a decent non-academic job.
I suspect the way this usually gets started is similar to embezzlement schemes. “Oh I’ll just borrow a few dollars from the till and pay it back tomorrow” is akin to “The manuscript is due tonight so I’ll just touch up this microphotograph to look like the other one that had bad focus.”
That escalates into forging invoices on the one hand and completely fabricated data on the other. By that point they’re in too deep to stop until they get caught.
Cheap may be the point. The Soviets deployed a missle with an imaging seeker in 1984.
But the real question is: does the appearance of good, cheap IR sensors in combat mean that we civilians will finally be allowed to buy thermal IR cameras that don’t suck? Everything is limited to 20 Hz with potato resolution. The ITAR restriction is a joke at this point.
Yes, but they can't do that if every Indian wants one, and they especially can't do that if every Chinese person wants one at the same time.
IPv4 is 32 bits. It has a hard cap of ~4 billion addresses. China and India alone have 2.85 billion people.
Add in the United States and Europe, and now nobody else gets an IP address. South America, Canada, Mexico, Australia, Africa, the middle east, the rest of Southeast Asia, etc. don't get to use the internet. That's 4 billion people who don't get to use the internet.
32 bits seemed practically infinite at the time IPv4 was created, and the whole thing started as a way for the American military-industrial-research complex to communicate with itself anyway. Why would you even want to assign addresses on your defense network to foreign adversaries?
Now that it's a commercial thing, a more equitable distribution would have, with hindsight, been a good thing.
I get the impression that this fact is fundamentally lost on a lot of the people who want a "compatible" IPv6. Like, their mental model does not distinguish between how we as humans write down an IPv4 address in text and how that address is represented in the packet.
So they think "let's just add a couple more dots and numerals and keep everything else the same"
I think you’re right. Honestly, my impression is that a lot of people imagine it like a string field, and others more like a rich text field, analogous to “can’t we just use a smaller font?”
Err... you do realize that the number of humans currently living on planet earth is twice the number of IPv4 addresses... right?
We can't all have an IPv4 address for each of our devices. We can't all even have one IPv4 address, period. But maybe they should just try not being poor, eh?
Look up RFC 6106 (published 15 years ago). Router advertisements have carried DNS resolver info for a long time now.
Once again, the old adage “IPv6 haters don’t understand IPv6” applies.
As much as I would like hosts to use the local NTP server, most will ignore the NTP server you specify in DHCP anyway, so it’s kind of a moot point.
Edit: RFC 6016 actually supersedes RFC 5006 from 2007. That’s nearly two full decades we have had DNS info in RAs. That’s the year Itanium2 came out (any greybeards here old enough to remember that one?)
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