Subject: [Sipping-emergency] The Real Emergency Calling Scenarios To Look At

From: Tom Taylor <[email-masked]>
Date: Fri, 13 Jun 2003 09:36:15 -0400

I dealt too lightly with Henning's remark on the optionality of proxies in my 
previous message.  Obviously I had to follow through and consider the effect on each 
scenario.  This got me thinking about the real variables of interest, which is 
probably the point of the whole exercise.  It seems to me the key variables are these:

(1) Whether the SIP phone is being used in stationary, nomadic, or mobile mode (with 
the latter still being out of scope?).  Stationary usage implies that information on 
location and call-back addressing can be lodged in a network database in advance of 
the emergency call.

(2) Whether there is a proxy in the signalling path, or the SIP phone signals 
directly to a PSTN gateway.  A proxy provides the opportunity for gateway selection 
if location information is available.

(3) Whether the SIP phone can reach a PSTN gateway which in turn can reach the ECC 
in jurisdiction.

(4) Whether there is an opportunity to pull together information about the SIP 
phone's physical location (in the case of Wi-Fi or LAN access) or at least the 
calling number (for dial-up access), correlate it with the caller's contact 
information, and use the results to provide necessary data to the PSTN gateway.

People can think about this list and consider whether I have it right.  My problem 
now is what this does to the scenarios document.  I'll have to think through how 
many independent scenarios we really have taking account of the above variables, and 
whether they are close enough to the ones already in the document.  In any event, a 
list like the one above should appear in a Conclusions section, along with the 
implications for possible solutions.

Tom

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