[Asterisk-Users] RE:911, networks of * servers, etc. (was: VOIP Dialtone?)

[John Todd]

Yes, I'm familiar with the E911 platforms and their requirements to 
some degree.  The trick is that the people running Asterisk PBX 
systems have no visibility into SS7, and that is an unreasonable 
expectation, so some other out-of-band method for moving caller 
location to the PSAP is required.

As far as geographic location tracking is concerned: that is the 
user's problem.  If they don't have the correct information in their 
device, then they're SOL.  There is _no way_ to develop lat/lon/alt 
coordinates from an IP address, despite what any .com 
flash-in-the-pan company says they can do with their clever 
databases.  Thus, the PBX/switch provider will have to enforce their 
own database of device-to-geographic-coordinates.  (As mentioned, 
maybe a SIP header is a reasonable thing to use for the UA to relay 
this data to the proxy.)  I am not concerned so much about the 
ability of the devices to send their data to the proxy: I am VERY 
concerned about how the proxy then looks up the appropriate PSAP, and 
then relays the data for the call to that PSAP.

JT




>911 through the phone system is tricky business. e911 which is the
>automated process of handing the address to the 911 center uses the SS7
>database to do it's work (the database is created when the LEC runs
>physical lines to locations not by people filling anything out). Cell phone
>service providers have the simuliar problems as VoIP service providers are
>facing are realizing with call forwarding and call following it will get
>worse.. Congress has mandated that the cell phone industry make it possible
>to track a cell phone users within 300yards via cell sites and
>triangulation. By 2005 every cell phone will be required to have a GPS and
>send GPS information to the 911 system when they call 911. If you want more
>information on e911 try http://www.fcc.gov/911/enhanced/ . As the cell
>phone industry grows there will be a need for a national 911 call routing
>center. I bet it won't be free.
>
>
>Original Message:
>-----------------
>From: John Todd jtodd at loligo.com
>Date: Thu, 21 Aug 2003 01:32:24 -0700
>To: asterisk-users at lists.digium.com
>Subject: [Asterisk-Users] 911, networks of * servers, etc. (was: VOIP
>Dialtone?)
>
>
>
>OK, that "VOIP dialtone?" thread was getting really out of hand, so
>I'll condense my answers into one big ugly message:
>
>
>1) 911 service.  Yes, that is one of three reasons to keep your PSTN
>line.  The other two reasons are:   Inbound calls from local callers
>still should work on a POTS line, for now.  You can't find VOIP
>providers in most area codes, so you'll most likely need to have a
>"local" number that finds it's way to you for "local" tasks.
>Secondly, the Internet is not as reliable as the phone system.
>Sorry, folks, it just works that way right now despite what your
>network engineer might tell you.  That's not to say it's unreliable,
>but those last two nines are very expensive... Besides, any good
>network engineer will tell you that you should have multiple paths
>for your IP connectivity.  With few exceptions, most homes do not
>have multipath connectivity.  (note: businesses may in fact have
>better uptime on their IP network than their phone network, if they
>have competent engineers and a reasonable budget.)
>
>1.5) There are reasonable technical solutions to this problem, but
>for the life of me I can't figure out why the 911 centers haven't
>gotten their act together and solved this.  There are two halves to
>this problem: "What PSAP do I call? (and what phone number)"  and
>"How do I get my location data to the PSAP once I call them?"
>C'mon, this is not difficult.  The first question can be answered
>trivially: there _must_ be a database of address-to-PSAP mappings.
>Any PBX administrator (or SIP phone owner, for that matter) should be
>able to figure out their address.  Methods for associating the PSAP
>number with the phone are numerous, and trivially implemented - if
>people don't keep their address information updated, they're SOL
>(though you can remind them in an automated fashion to keep it
>updated - just forbid them from using the service unless they verify
>the address every month or so.)
>
>The second question is more difficult, but certainly possible.  There
>may be kludge ways of doing it, and there should be more elegant ways
>of doing it.  A SIP header with lat/lon/alt data that gets sent from
>the UA only on 911 (or other programmable string) calls might be
>reasonably elegant... maybe.  But that only gets the data to the SIP
>proxy.  That doesn't solve the issue of how you get that data from
>the SIP proxy to the PSAP, which at some point will be almost
>certainly through a PSTN connection... ADSI FSK, maybe?  Ugly, and
>PSAPs would not want to invest in equipment.  A national caller-id to
>location clearinghouse in which your proxy could participate (any 911
>calls would create a temporary mapping)?  Maybe, but probably not.
>Non-standard, and I doubt PSAP operators would want another tool,
>even if it is web-based and so easy a monkey could use it.  I don't
>know.  I guess I'll grill the PSAP people at the panel next month at
>VON.  :-)
>
[snip]