One thing the PSTN provided, by its very structure - those 5000 CO's and miles
and miles of copper - was failure isolation. Damage from even major natural
disasters (or, if one is concerned about planning for this kind of thing, acts
of war) can't knock out more than a tiny fraction of the network capacity, at
least at the lower levels. As you get to higher levels in what is inherently a
hierarchical system, vulnerabilities naturally increase - as the Hillsdale fire
of (how long ago was it? 30 years by now?) amply demonstrated. Still, local
service - the most important in organizing recovery - is extremely robust by
its very nature.
The new IP designs gain much of their efficiency exactly by discarding so much
of the physical redundancy. I have an AT&T U-verse phone line - but I've
retained a second POTS line, just in case. When Connecticut suffered extensive
damage from a hurricane last fall, the POTS line pretty much survived
unscathed, but the U-verse line was out for days. (Partly, of course, this is
because the U-verse line requires local power - which was out for days beyond
the couple of hours until battery backup for it drained.)
It's unreasonable to expect AT&T, or any private company - much less taxpayer
dollars - to maintain the old PSTN or anything like it just to maintain
survivability in the event of disasters - though *some* of the survivability
didn't come just from the nature of the system, but from expensive design
choices by the old Bell System (think the huge racks of battery backup in CO's
- a feature cell towers lack). But that doesn't mean we can just blindly
ignore the issue either.
I know there have been some government moves in this direction, at all levels,
since it's government agencies that coordinate much of the response to
disasters. But there's a downside to that, too: It puts government in the
position of actually *running* basic infrastructure after a disaster. For
short periods of time, that may be necessary - but as history has shown, power
is difficult to take back from someone who's become used to having it.
-- Jerry
[ My gut feeling is that expectations of a general retirement of
the PSTN in the near future are significantly unrealistic. We
have hardly even scratched the surface of the complex issues
involved, that could make the transition from analog to digital
TV look like child's play by comparison.
-- Lauren Weinstein
NNSquad Moderator ]
_______________________________________________
nnsquad mailing list
http://lists.nnsquad.org/mailman/listinfo/nnsquad
