An AD DC can be offline for as long as 60 days (by default, since the actual length of time is covered by AD's tombstone lifetime, which is configurable) and recover just fine, assuming you're not to worried about the intrinsic fact that changes at or affecting that site aren't replicated immediately.
And assuming you plug the site back into the network somehow, under your 60 day limit, AD will largely just keep truckin'. If you've got sites that are offline for more than 60 days at a time due to unforseen circumstances, well, maybe those sites need some other solution.
Spotty connectivity is just fine for AD, though, especially if you're designing things properly.
The myriad problems and factors that assailed practical IDDN adoption in the early days when a working ISDN interface was a genuine wonder not of miracles in configuration but the capability delivered (we ran applications in advertising that had financial trading style requirements for transactions and the fact that advertising copy was delivered via ISDN was the kind of integration that was envisioned originally)
Everyone is confusing me with their apparent over reaction to the connection of cloud to remote sites. This was what CICS was written for fifty years ago. I feel like I'm discussing state secrets every time I mention CICS. Can anyone recall the killer feature of NT3.1? MTS, if you must have it. MTS is why SQLserver was so easily portable to Linux. I suspect about everyone who reads HN might have a ball with some of the desperately not trendy things we are involved in. Like my uncle dusting his suit vests, smiling he only had to wait thirty years for them to return to fashion. This is a universal interval someone who can explain it will deserve a Nobel I'm sure...
BTW B channel is for "Bearer", and D is for "Delta" or maybe "Data". (Wild hypothesis: maybe it was initially for "Data" at a time when B was seldom used for things other than digitized voice possibly with a bit stolen for in-band signaling)
On my side I consider that ATM was pretty sweet at a time when IP&co was complete garbage (and still somewhat is), but I know who won.
As for CICS, well, mainframe are still not dead. I suspect they won't, because why would they? But the model is not the same as the modern "cloud" stuff, at all levels.
That was that. What was your point again in this context?