On 1/4/2010 5:20 PM, Bill Smith wrote:
VoIP is used daily and has been for over five years for
mission-critical applications such major electric and gas utilities
and public safety. VoIP isn't the problem, it's the transport medium.
Or more accurately, lack of a backup/redundant transport medium beyond
the data center. The "last mile" has always been the problem.
"Backhoe fade" affects the PSTN just as much as it affects the IP
network. The PSTN is slowly moving over to IP transport as their "back
office" connectivity as well... but they're paying big bucks for
redundant underground routes, hardware that can handle switching to the
backup routes, people to test that these backups WORK on a regular
basis, and to design it in the first place.
A residential IP connection meets none of the requirements for anything
like that, but it is typically just as vulnerable to backhoe fade as the
POTS line.
Our VoIP strategy for our PBX at work is designed like this:
a) require IP connectivity to control the call via a PC application.
(All agents must open tickets anyway, so if they don't have IP
connectivity, they're done for the day.)
b) Primary voice is via a SIP client on the PC. If quality is bad...
c) Secondary voice is the PBX still has PSTN connectivity at the office,
and can dial out to cell or home POTS lines, so there's two more network
transports.
d) All ACD PBX's are "cross-strapped" via SIP trunks and can dial out
into the PSTN from multiple locations in multiple countries if their
primary routes "out" are dead/not-working.
e) "Personal" desk phone lines are NEVER mixed on the same VoIP PBX as
ACD/customer inbound traffic. That's a completely different and
redundant PBX system.
NONE of this is anywhere NEAR reliable enough for 911 dispatch. If we
hang up on someone by accident in the middle of a call, no one dies. We
just call them back. Dispatcher's kid fires up BitTorrent to download
illegal copies of DVD's/CD's, and jams the upstream connection so that
the VoIP (typically UDP packets) get dropped going back to the dispatch
office, and they drop a call right when someone's giving their address...
Not to mention, how you going to support E911 in that environment?
Nate WY0X
