[Asterisk-Users] RE:911, networks of * servers, etc. (was:
VOIP Dialtone?)
John Todd
jtodd at loligo.com
Thu Aug 21 16:34:48 MST 2003
This is excellent data; thank you. I'll review before harrassing the
E911 folks at VON.
However, this only seems to solve problems for local PSAP
connectivity to your * server. Or am I mistaken?
I think a larger and simpler (read: less hardware and no "custom"
circuits) system needs to be developed to hand information to the
PSAP. I know that none of my customers would ever, EVER consider
purchasing a dedicated circuit into the 911 system until they were
forced to by some sort of laws. With VoIP providers all over the
nation, I think this is an unworkable solution. I may be whistling
in the wind, but that's the reality of the situation.
JT
At 7:15 PM -0400 8/21/03, Tom Zimnicki wrote:
>
>Which brings me to an application at hand:
>
>We currently have an * box connected to a SIP Media Gateway which is
>connected to the PSTN via SS7.
>
>We have MF FG-C 911 trunks connected to a DMS and can bring an MF T-1 into
>the * box if we buy a T400P card.
>
>
>The question is how do you support ringback with SIP devices? (i.e. the PSAP
>operator keeps the 'trunk' siezed and forces ringing on the SIP phone that
>is on-hook. It should also generate a 'howler' tone on an off-hook set)
>
>(There was a list for SIP 911 issues, but it appears to be dormant:
>http://lists.cs.columbia.edu/mailman/listinfo/911 )
>
>There was a reference to using re-invites and suspend/resume via RFC 3064
>and that T1.628 - 2000 might have been looking into it. Does anyone have a
>current copy they could check to see if this issue has been addressed?
>
>(Also GR-529
>http://telecom-info.telcordia.com/site-cgi/ido/docs.cgi?ID=159801680D000801&KEYWORDS=529&TITLE=&DOCUMENT=&DATE=&CLASS=&COUNT=1000
>
>&
>
>ANSI T1.628a-2001. http://www-comm.itsi.disa.mil/t1/628.html will probably
>be of interest.)
>
>Does anyone here have the interest or experience to try and make this happen
>on * ?
>
>(And although the world is moving to E911 and there are folks working on SS7
>for *, is anyone interested in getting the Digium cards and * to intereface
>with the Emergency Service Feature Group C trunks that a Nortel 911-DMS
>Tandem uses? )
>
>Regards,
>
>Tom Zimnicki
>
>----- Original Message -----
>From: "Michael Kane" <mkane at to-talk.com>
>To: <asterisk-users at lists.digium.com>
>Sent: August 21, 2003 3:25 PM
>Subject: Re: [Asterisk-Users] RE:911, networks of * servers, etc. (was: VOIP
>Dialtone?)
>
>
>> There are TDM interfaces higher end PBX's use to interconnect to the
>PS/ALI.
>> I beleive it's a CAMA trunk that signals using MF.
>>
>>
>>
>> ----- Original Message -----
>> From: "John Todd" <jtodd at loligo.com>
>> To: <asterisk-users at lists.digium.com>
>> Sent: Thursday, August 21, 2003 3:00 PM
>> Subject: [Asterisk-Users] RE:911, networks of * servers, etc. (was: VOIP
>> Dialtone?)
>>
>>
>> >
>> > 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]
>> > _______________________________________________
>> > Asterisk-Users mailing list
>> > Asterisk-Users at lists.digium.com
>> > http://lists.digium.com/mailman/listinfo/asterisk-users
>> >
>>
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