Public Safety Answering Point (PSAP) Callback
draft-ietf-ecrit-psap-callback-07

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Document Type Active Internet-Draft (ecrit WG)
Last updated 2012-12-18
Replaces draft-schulzrinne-ecrit-psap-callback
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ECRIT                                                     H. Schulzrinne
Internet-Draft                                       Columbia University
Intended status: Standards Track                           H. Tschofenig
Expires: June 21, 2013                            Nokia Siemens Networks
                                                             C. Holmberg
                                                                Ericsson
                                                                M. Patel
                                             InterDigital Communications
                                                       December 18, 2012

             Public Safety Answering Point (PSAP) Callback
                 draft-ietf-ecrit-psap-callback-07.txt

Abstract

   After an emergency call is completed (either prematurely terminated
   by the emergency caller or normally by the call taker) it is possible
   that the call taker feels the need for further communication.  For
   example, the call may have been dropped by accident without the call
   taker having sufficient information about the current situation of a
   wounded person.  A call taker may trigger a callback towards the
   emergency caller using the contact information provided with the
   initial emergency call.  This callback could, under certain
   circumstances, be treated like any other call and as a consequence it
   may get blocked by authorization policies or may get forwarded to an
   answering machine.

   The IETF emergency services architecture specification already offers
   a solution approach for allowing PSAP callbacks to bypass
   authorization policies to reach the caller without unnecessary
   delays.  Unfortunately, the specified mechanism only supports limited
   scenarios.  This document discusses shortcomings of the current
   mechanisms and illustrates additional scenarios where better-than-
   normal call treatment behavior would be desirable.

   Note that this version of the document does not yet specify a
   solution due to the lack of the working group participants agreeing
   on the requirements.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-

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   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on June 21, 2013.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  6
   3.  Callback Scenarios . . . . . . . . . . . . . . . . . . . . . .  7
     3.1.  Routing Asymmetry  . . . . . . . . . . . . . . . . . . . .  7
     3.2.  Multi-Stage Routing  . . . . . . . . . . . . . . . . . . .  8
     3.3.  Call Forwarding  . . . . . . . . . . . . . . . . . . . . .  9
     3.4.  Network-based Service URN Resolution . . . . . . . . . . . 11
     3.5.  PSTN Interworking  . . . . . . . . . . . . . . . . . . . . 12
   4.  SIP PSAP Callback Indicator  . . . . . . . . . . . . . . . . . 13
     4.1.  General  . . . . . . . . . . . . . . . . . . . . . . . . . 13
     4.2.  Usage  . . . . . . . . . . . . . . . . . . . . . . . . . . 13
     4.3.  Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . 13
       4.3.1.  General  . . . . . . . . . . . . . . . . . . . . . . . 13
       4.3.2.  ABNF . . . . . . . . . . . . . . . . . . . . . . . . . 13
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 14
     5.1.  Security Threat  . . . . . . . . . . . . . . . . . . . . . 14
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