Subject: RE: [Ecrit] New ID to get emergency dialsting into UA

From: "Winterbottom, James" <[email-masked]>
Date: Thu, 9 Mar 2006 20:17:17 -0600

James,

One thing that I have continually pointed out, and that seems to be
continually ignored here is that any solution that requires location
determination at boot time will be of use to less than 50% of people
that make requests for emergency services. This figure increases to 60%
when we talk valued added services. Mobile is a reality and is the norm,
not the niche that it once was. Any solution therefore that makes a
requirement on location being determined at boot time should be very
carefully considered before it is adopted so as to avoid the necessity
of deprecating it when implementation and deployment occurs.

Cheers
James

> 
> I have another new ID into DHCP on this topic because that technology
is
> tied to the access infrastructure of where a UA is to be able to know
> which
> national emergency dialstrings are appropriate.  The above is the SIP
> version of the DHCP ID here:
> 
>
http://www.ietf.org/internet-drafts/draft-polk-dhc-emergency-dialstring-
> option-00.txt
> 
> 
> I will be presenting the DHCP ID in that WG for now.
> 
> The idea behind the ECRIT Dialstring ID is that this:
> 
> When a device boots, it will learn its location (a fundamental
assumption
> we need to make for a lot of all this to work).  The UA generates a
PIDF-
> LO
> and includes it in a SIP REGISTER Request message, seeking the
appropriate
> dialstring for the UA's location.  This will either be ignored or
> successfully returned in a 200 OK to the REGISTER request.  The UA can
> have
> its digitmap modified based on this response, because it is just as
likely
> a local user will dial for an emergency and not understand the UA is
from
> another country, so the local (or "visited" from the UA's pov) numbers
> will
> have to function as expected.
> 
> In both IDs I allow for just a country code to be downloaded to the
UA.
> 
> Comments to the ECRIT ID are welcome on this list.
> 
> Please direct any DHCP-related comments to the DHC list, thus showing
> interest there.
> 
> _______________________________________________
> Ecrit mailing list
> [email-masked]
> https://www1.ietf.org/mailman/listinfo/ecrit

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---

From: "James M. Polk" <[email-masked]>
Date: Thu, 09 Mar 2006 20:50:01 -0600

James

Location is not conveyed in the DHCP Option ID for a dialstring, so it 
doesn't need to be downloaded at device boot-time to have this DHCP option 
work.

Tell me this, what mobile solution doesn't have a chance of knowing what 
country you're in?

If DHCP isn't available, the UA can learn location any number of ways, 
build a PIDF-LO and transmit that to a SIP Registrar server to determine 
either an emergency dialstring here:

http://www.ietf.org/internet-drafts/draft-polk-ecrit-emergency-dialstring-00.txt

or a PSAP-URI.  That's here:

http://www.ietf.org/internet-drafts/draft-polk-ecrit-mapping-during-registration-00.txt 

If you don't have location, you cannot tell responders how to get to you to 
give you help.

The second ID above also starts discussing how a UA learns about mapping by 
using SIP SUBSCRIBE, HTTP or another fetch protocol.

Little of this is limited to being done at boot time, and none of it is 
mandated to only be at boot time.

I do not believe too many emergency calls will occur within seconds of 
boot-time, so there is time to get the necessary information.

---

From: "Winterbottom, James" <[email-masked]>
Date: Thu, 9 Mar 2006 21:15:22 -0600

James,

I think that you have missed my point entirely.
There is a huge difference between knowing your country, and knowing the
ultimate destination of a call. All I am saying is that performing
mapping at anytime other than call time makes the assumption that you
are static and not mobile (unless all calls always go to the same
address). Making this assumption requires that both are catered for,
which adds complexity and infrastructure cost. Build one that supports
both in exactly the same way. 

Cheers
James

> -----Original Message-----
> From: James M. Polk [mailto:[email-masked]]
> Sent: Friday, 10 March 2006 1:50 PM
> To: Winterbottom, James; [email-masked]
> Subject: RE: [Ecrit] New ID to get emergency dialsting into UA
> 
> James
> 
http://www.ietf.org/internet-drafts/draft-polk-ecrit-emergency-dialstrin
g-
> 00.txt
> If you don't have location, you cannot tell responders how to get to
you
> to
> give you help.
> 
> The second ID above also starts discussing how a UA learns about
mapping
> by
>-----------------------------------------------------------------------
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> -----------------------
>-----------------------------------------------------------------------
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> -----------------------

---

From: "James M. Polk" <[email-masked]>
Date: Thu, 09 Mar 2006 22:25:44 -0600

James

I don't believe obtaining a country's emergency dialstring is that dynamic 
wrt changing locations.  This DHCP Option doesn't include a client's 
location in the message to the client or to the server, so it is really the 
location of the infrastructure the client is attached to that is important 
when determining what the locally significant emergency dialstring is 
returned in to the request.

Enterprise, SMB, DSL and Cable access infrastructures aren't mobile wrt 
UAs, it's UAs that can be mobile.

This particular ID has nothing to do with LoST, BTW.