Internet Engineering Task Force (IETF) H. Schulzrinne
Request for Comments: 7090 Columbia University
Category: Standards Track H. Tschofenig
ISSN: 2070-1721
C. Holmberg
Ericsson
M. Patel
Huawei Technologies (UK) Co., Ltd.
April 2014
Public Safety Answering Point (PSAP) Callback
Abstract
After an emergency call is completed (terminated either prematurely
by the emergency caller or normally by the call taker), the call
taker may feel 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 state of an accident victim.
A call taker may trigger a callback to 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 Public Safety Answering Point (PSAP)
callbacks to bypass authorization policies in order 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. We describe a solution based on a new header field value
for the SIP Priority header field, called "psap-callback", to mark
PSAP callbacks.
Schulzrinne, et al. Standards Track [Page 1]RFC 7090 PSAP Callback April 2014Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7090.
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Copyright (c) 2014 IETF Trust and the persons identified as the
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described in the Simplified BSD License.
Schulzrinne, et al. Standards Track [Page 2]RFC 7090 PSAP Callback April 2014Table of Contents
1. Introduction ....................................................3
2. Terminology .....................................................5
3. Callback Scenarios ..............................................5
3.1. Routing Asymmetry ..........................................5
3.2. Multi-Stage Routing ........................................7
3.3. Call Forwarding ............................................8
3.4. Network-Based Service URN Resolution ......................10
3.5. PSTN Interworking .........................................11
4. SIP PSAP Callback Indicator ....................................12
4.1. General ...................................................12
4.2. Usage .....................................................12
4.3. Syntax ....................................................12
4.3.1. General ............................................12
4.3.2. ABNF ...............................................12
5. Security Considerations ........................................12
5.1. Security Threat ...........................................12
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