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List:       sip-implementors
Subject:    [Sip-implementors] Query: How to derive Emergency Call from SIP INVITE Message
From:       "NC Reddy" <ncreddy75 () gmail ! com>
Date:       2008-02-29 21:15:06
Message-ID: 91d266200802291315m33ce8f7brd4c51814959f1c7b () mail ! gmail ! com
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Hi,
    I have the following queries regarding emergency call interpretation at
SIP Application Server (SIP-AS).

scenario:
========
AP-  Access Point
AS - SIP Application server
MGCF - Media Gateway Control Function (Softswitch )
PSAP -  *Public Safety Answering Point

*AP<----SIP--->AS<---SIP----->MGCF<----Non-SIP---->PSAP

Use case1 : When subscriber(AP) makes emergency call to PSAP (AP
------->PSAP)
Use case2 : When PSAP callbacks to subscriber.  (PSAP ------->AP)

Now Questions related the mechanisms for analyzing the emergency calls at
SIP Application Server. By considering the cases of emergency call numbers
are different in different countries and context.

Option 1:  SIP-AS can do the digit analysis from request uri of the userpart
(ex: 911) and figureout the call as emeregncy and handle the call.
Option 2 :  If the AP/MGCF done the digit analysis and add the "priority :
emergency" header, SIP-AS can rely on that header and route the call.

So which option is suitable in context of SIP-AS implementation for
emeregency calls.


Thanks in advance.

Regards
Channa

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