draft-ietf-ecrit-psap-callback-11.txt   draft-ietf-ecrit-psap-callback-12.txt 
ECRIT H. Schulzrinne ECRIT H. Schulzrinne
Internet-Draft Columbia University Internet-Draft Columbia University
Intended status: Standards Track H. Tschofenig Intended status: Standards Track H. Tschofenig
Expires: March 30, 2014 Nokia Solutions and Networks Expires: March 31, 2014 Nokia Solutions and Networks
C. Holmberg C. Holmberg
Ericsson Ericsson
M. Patel M. Patel
InterDigital Communications InterDigital Communications
September 26, 2013 September 27, 2013
Public Safety Answering Point (PSAP) Callback Public Safety Answering Point (PSAP) Callback
draft-ietf-ecrit-psap-callback-11.txt draft-ietf-ecrit-psap-callback-12.txt
Abstract Abstract
After an emergency call is completed (either prematurely terminated After an emergency call is completed (either prematurely terminated
by the emergency caller or normally by the call taker) it is possible by the emergency caller or normally by the call taker) it is possible
that the call taker feels the need for further communication. For that the call taker feels the need for further communication. For
example, the call may have been dropped by accident without the call example, the call may have been dropped by accident without the call
taker having sufficient information about the current situation of a taker having sufficient information about the current situation of a
wounded person. A call taker may trigger a callback towards the wounded person. A call taker may trigger a callback towards the
emergency caller using the contact information provided with the emergency caller using the contact information provided with the
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on March 30, 2014. This Internet-Draft will expire on March 31, 2014.
Copyright Notice Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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The PSAP callback functionality described in this document allows The PSAP callback functionality described in this document allows
marked calls to bypass blacklists, ignore call forwarding procedures marked calls to bypass blacklists, ignore call forwarding procedures
and other similar features used to raise the attention of emergency and other similar features used to raise the attention of emergency
callers when attempting to contact them. In the case where the SIP callers when attempting to contact them. In the case where the SIP
Priority header value, 'psap-callback', is supported by the SIP UA, Priority header value, 'psap-callback', is supported by the SIP UA,
it would override user interface configurations, such as vibrate-only it would override user interface configurations, such as vibrate-only
mode, to alert the caller of the incoming call. mode, to alert the caller of the incoming call.
5.2. Security Requirements 5.2. Security Requirements
The requirement is to ensure that the mechanisms described in this The security threat discussed in Section 5.1 leads to the requirement
document can not be used for malicious purposes, including to ensure that the mechanisms described in this document can not be
telemarketing. used for malicious purposes, including telemarketing.
Furthermore, if the newly defined extension is not recognized, not Furthermore, if the newly defined extension is not recognized, not
verified adequately, or not obeyed by SIP intermediaries or SIP verified adequately, or not obeyed by SIP intermediaries or SIP
endpoints then it must not lead to a failure of the call handling endpoints then it must not lead to a failure of the call handling
procedure. Such call must be treated like a call that does not have procedure. Such call must be treated like a call that does not have
any marking attached. any marking attached.
5.3. Security Solution 5.3. Security Solution
The approach for dealing with implementing the security requirements
described in Section 5.2 can be differentiated between the behavior
applied by the UA and by SIP proxies. A UA that has made an
emergency call will keep state information so that it can recognize
and accepted a callback from the PSAP if it occurs within a
reasonable time after an emergency call was placed, as described in
Section 13 of [RFC6443]. Since UA considerations are described
already in [RFC6443] as well as in [RFC6881] the rest of this section
focuses on the behavior of SIP proxies.
Figure 7 shows the architecture that utilizes the identity of the Figure 7 shows the architecture that utilizes the identity of the
PSAP to decide whether a preferential treatment of callbacks should PSAP to decide whether a preferential treatment of callbacks should
be provided. To make this policy decision, the identity of the PSAP be provided. To make this policy decision, the identity of the PSAP
is compared with a white list of valid PSAPs available to the SIP is compared with a white list of valid PSAPs available to the SIP
entity. The identity assurance in SIP can come in different forms, entity. The identity assurance in SIP can come in different forms,
such as SIP Identity [RFC4474] or with P-Asserted-Identity [RFC3325]. such as SIP Identity [RFC4474] or with P-Asserted-Identity [RFC3325].
The former technique relies on a cryptographic assurance and the The former technique relies on a cryptographic assurance and the
latter on a chain of trust. Also the usage of TLS between latter on a chain of trust. Also the usage of TLS between
neighboring SIP entities may provide useful identity information. neighboring SIP entities may provide useful identity information.
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