RE: RE: [Geopriv] Consensus on changes to location-conveyance

At 08:48 PM 7/26/2006 -0500, Winterbottom, James wrote:
>To what do you send the SIP update and for what do you request the
>update?

to the latter first: UPDATE is not requested, it is a request message just 
like INVITE.

If the PSAP wants to subscribe to the caller, that's a separate transaction 
in SIP.

to the former, are you asking what's the destination address the UPDATE 
goes to, or what triggers the UPDATE message?  Your phrasing could be to 
either the way I read it. I'll answer both below as best I can:

To a destination address, if before the UAC receives a 200 OK with a 
Contact header (indicating the PSAP URI), the UPDATE needs to be built just 
like the original INVITE (with the new location) and sent to the 
urn:service:sos and get routed to the PSAP.  If this results in a new PSAP 
due to movement, the INVITE times out and the new INVITE is to the 
urn:service:sos with a new location and the call goes through.  We can't 
build this to the corner case of someone moving that fast, as much as that 
won't make some happy.

If the 200 OK has been received by the UAC, the UPDATE will go at the PSAP 
URI in the Contact header of that 200 OK, and therefore go straight at the 
PSAP, the fastest way there (barring any route headers that are forced into 
the request).

Due to a trigger, this is UAC device specific as it is the device that 
senses a sufficient change in its location to send a new location.  This 
will in all likelihood be after the 200 OK has been received, even after 
the call has been established, and should follow what is in the paragraph 
above this one to the PSAP.

It has been suggested that a reINVITE can be sent with the new location 
*after* the call is eestablished, and that's fine, but not what the SIP WG 
agreed to several IETFs ago, but it would work in either case.



>-----Original Message-----
>From: Andrew Newton [mailto:[email protected]]
>Sent: Thursday, 27 July 2006 11:47 AM
>To: Winterbottom, James
>Cc: Henning Schulzrinne; [email protected]; IETF SIP List
>Subject: Re: [Sip] RE: [Geopriv] Consensus on changes to
>location-conveyance
>
>
>On Jul 26, 2006, at 9:28 PM, Winterbottom, James wrote:
>
> > In the case you mention below the reality is that if the target has
> > moved during the course of routing, the target will either be at
> > place B
> > by the time dispatch occurs, or at point C which may be further away
> > still.
> > At least in the case of a reference you have the possibility of
> > getting
> > the current location, which is not possible through any of the
> > "by-value" means described thus far unless the caller is stationary!
> >
>
>What about a SIP UPDATE?  Section 5.3 of the draft.
>
>-andy
>
>
>
>
>
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