Experiences with 911 calls and SIP

Wed May 18 17:47:35 UTC 2005

On Wed, 18 May 2005, Dan Lockwood wrote:

> I'm having a discussion with one of my vendors about the 911
> capabilities of their SIP VoIP phone system.  The vendor says that if we
> use an Enhanced 911 service that their phone system will transmit
> location information to the PSAP at the time of the call in addition to
> the ANI.  I was under the impression that this functionality was not
> possible, hence all the problems that Vonage is having.  Can anyone help
> clarify this for me?

The vendor *CAN*, if they are properly connected to the selective routers
and ANI/ALI database, both route the call to the correct PSAP and display
the location of where you *TELL* them the phone is located.

He isn't technically correct that the system transmits location information
to the PSAP at the time of the call.  The system transmits ANI (calling
number) and the PSAP queries a regional database to obtain the location.
It can take several hour sor even days to update the database if you move.

In most cases, telephone service providers *MUST* maintain a toll-free
number available to the PSAP operators 24/7.  In the event of missing or
incorrect location information, the PSAP can call the carrier who *MUST*
answer with a human being[1], not an auto-attendant.  That person can
then tell the PSAP the current location of record.

If you take your Xten laptop to Bangladesh and register your SIP phone
there, don't expect the ambulance to arrive where you *ARE*, only where
you told your carrier the phone was located.

The same issue occurs with off-premise stations to analog PBX systems
and the like.  G.I.G.O.

[1] I suppose that the human being could be in India and give the same
level of service we've all grown to cherish from SBC and AT&T...

--
Jay Hennigan - CCIE #7880 - Network Administration - jay at west.net
WestNet:  Connecting you to the planet.  805 884-6323      WB6RDV
NetLojix Communications, Inc.  -  http://www.netlojix.com/