"If they're land lines, the NPA/NXX will be local to the CO so you won't have out-of-area numbers other than a rare corner case of a very expensive foreign exchange line." This hasn't been a true statement since Local Number Portability. NPA/NXX is nothing more than 'where the number originally was assigned from', and that only for the ones issued BEFORE LNP started; since is anyone's guess. They follow something similiar to what a routed phone call does, but ties into slightly different information that is 'supposed' to associate the end-client address with said LNI that is 'supposed' to be populated with accurate street address information. Similar to what VoIP has had to deal with since, most charge a fee, disclaim any responsibility as to the accuracy of the information that the end user provides. I am sure litigation on/around THAT particular issue is just around the corner. Regards, Jonathan Smith On Wed, Apr 13, 2016 at 11:22 PM, Jay Hennigan <jay@west.net> wrote:

On 4/13/16 8:54 PM, Peter Beckman wrote:

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On Wed, 13 Apr 2016, Jay Hennigan wrote:

When either of those people dial 9-1-1, where does the ambulance show up?

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I suspect your response was sarcastic, but when you dig into what really happens, it's not nearly as sophisticated as one might hope.

If the numbers are land or VoIP lines, and the address associated with the numbers are registered with the Automatic Location Information (ALI) database run by ILECs or 3rd parties to fetch the address keyed on the calling number, and the 911 PSAP is E911 capable, they operator will see the ALI address.

If they're land lines, the NPA/NXX will be local to the CO so you won't have out-of-area numbers other than a rare corner case of a very expensive foreign exchange line. If they're VoIP lines, the address is *supposed* to be so registered, but softphones and even VoIP handsets tend to move around without the user considering 9-1-1.

VoIP was the scenario to which I was referring. A VoIP phone native to 408-land that moves with a remote office worker to Boston without a conscious effort on his company and VoIP provider to track it down and update ALI will reach a PSAP in San Jose or thereabouts. The PSAPs have forwarding capability but generally only to neighboring PSAPs with a single button. How quickly will they be able to get the call routed to Boston, if at all? And as we saw at the beginning of the thread, forget geo-IP. The ambulance goes to the Vogelmans' farm. If a remote office worker, it could be VPN back to the VoIP PBX in 408-land anyway.

So, it isn't just IP addresses that aren't easily geo-referenced. It's also phone numbers. The number may start as a well-referenced PRI going to an IP-PBX after which all bets are off. If the ANI is the company's HQ main number where the PRI and IP-PBX are located, then it's just about impossible to route 9-1-1 from a worker's IP phone in Boston to the right PSAP.

If they are mobile devices, it depends. Basic gives you nothing (all

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phones since 2003 should have GPS, but people hang on to phones a long time..);

Mobile is a separate case where it's expected that the NPA-NXX isn't going to be tied to a location. In California, mobile 9-1-1 goes to the CHP and not the local PSAP based on the cell tower or GPS for that reason. If not a traffic incident, they forward to the appropriate PSAP based on the caller's info or perhaps whatever ALI (or estimate) they get from the cellular provider.

-- Jay Hennigan - CCIE #7880 - Network Engineering - jay@impulse.net Impulse Internet Service - http://www.impulse.net/ Your local telephone and internet company - 805 884-6323 - WB6RDV