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Versions: 00                                                            
stir                                                            B. Rosen
Internet-Draft                                             March 9, 2020
Intended status: Standards Track
Expires: September 10, 2020

                    Non-Interactive Emergency Calls


   Emergency calls from citizens to authorities, and call back of such
   emergency calls by authorities to citizens need assurances that
   headers intended to get appropriate priority from the networks they
   traverse, and in some cases, appropriate routing.  Protection of the
   SIP Resource Priority Header and the SIP Priority header is needed
   for such calls.  This document describes the environment for placing
   emergency calls and call backs which motivate the need and use of the
   mechanisms described in other documents

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
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   This Internet-Draft will expire on September 10, 2020.

Copyright Notice

   Copyright (c) 2020 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
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   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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Emergency Calls . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Emergency Call-backs  . . . . . . . . . . . . . . . . . . . .   4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   4
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   [RFC6643] describes how devices use the Internet to place emergency
   calls and how Public Safety Answering Points (PSAPs) handle Internet
   emergency calls.  In traditional telephone networks, emergency calls
   are not afforded any priority in the network.  Emergency calls are
   marked with a Service URN, [RFC5031].

   Sometimes, the emergency services need to call the person that placed
   an emergency call after the original emergency call was terminated.
   This is a case of "call-back".  [RFC7090] discusses using SIP
   Priority to mark a call as a call back.  The Resource Priority
   Header, [RFC4412] defines a way to request the network afford
   priority in resources: The 'Priority' header field describes the
   importance that the SIP request should have for the receiving human
   or its agent.  For example, that header may be factored into
   decisions about call routing to mobile devices and assistants and
   about call acceptance when the call destination is busy.  The
   'Priority' header field does not affect the usage of PSTN gateway or
   proxy resources, for example.  In addition, any User Agent Client
   (UAC) can assert any 'Priority' value, and usage of 'Resource-
   Priority' header field values is subject to authorization.

   This document describes the environment for placing emergency calls
   on the Internet, which has different capabilities than the PSTN, as
   well as call backs across the Internet and describes the requirements
   for protecting them with the "stir" mechanism.

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2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   SIP is the Session Initiation Protocol [RFC3261]

   PSAP is a Public Safety Answering Point, the call center for
   emergency calls.

3.  Emergency Calls

   SIP signaling for emergency calls is defined in [RFC6881].  An
   emergency call is marked with a Service URN [RFC5031] in the Request-
   URI field.  RFC6881 does not have any recommendations for the
   Resource Priority Header.  Emergency calls will make use of the stir
   mechanism to assure the PSAP that the calling party identifier is
   accurate.  There are numerous cases of what is called "swatting"
   where an emergency call with a spoofed identity is placed and the
   caller fraudulently reports serious criminal activity at some
   address, prompting the authorities to respond with significant force
   (SWAT team).  By validating the identity, authorities hope swatting
   will become much less possible.

   It is desirable in some networks to be able to provide some priority
   in the call handling network for emergency calls, even though the
   PSTN does not do that.  [RFC7135] defines the "esnet" namespace, and
   4 priority levels "for local emergency session establishment to a
   public safety answering point (PSAP), between PSAPs, and between a
   PSAP and first responders and their organizations. ".  There is
   presently no recommendation for what priority level to assign to
   emergency calls.  There are other documents [i3] that describe how to
   use the esnet values within an Emergency Services IP Network, which
   is distinct from the originating service provider networks, over
   which emergency calls may be placed.

   This document recommends that emergency calls from outside an
   Emergency Services IP Network be assigned esnet.0.  This document
   makes no recommendations on what originating service provider
   networks actually provide for resource priority other than to note
   the obvious: emergency calls should receive some priority for

   Whatever the network does with the RPH value, it is desirable to
   protect it from manipulation and

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   [I-D.ietf-stir-rph-emergency-services] provides the mechanism to
   accomplish that.

4.  Emergency Call-backs

   After an emergency call is placed, it is sometimes necessary for the
   PSAP, or a responder, to call the caller back.  This call is placed
   by the authorities back to the original caller.  [RFC7090] describes
   the use of the SIP Priority header field, with the value "psap-
   callback" to mark such calls and describes how called networks may
   use that marking.  RFC7090 does not describe any priority, and does
   not mention use of the Resource Priority header field.  There is no
   protection against misuse of the SIP Priority field, and because, as
   RFC7090 illustrates, it may affect routing, it is very desirable to
   protect it from modification.

   This document recommends that emergency calls-backs from authorities
   outside an ESInet contain a Resource Priority header field and be
   assigned esnet.0.  This document makes no recommendations on what
   service provider networks actually provide for resource priority
   other than to note the obvious: emergency calls-backs should receive
   some priority for resources.

   Many countries are starting to adopt the emergency calling paradigms
   promulgated by the IETF.  For example, in North America, the [i3]
   standard defines IP based emergency calling networks, drawing from
   IETF work.  In those systems, a PKI is being created, with a trusted
   root, the "PSAP Credentialing Agency" (PCA).  The PCA provides a root
   of trust that could be used to sign call-backs protecting the SIP
   Priority and Resource Priority header fields.

5.  IANA Considerations

   There are no actions requested of IANA in this document

6.  Security Considerations


7.  Acknowledgments


8.  References

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8.1.  Normative References

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

8.2.  Informative References

   [i3]       NENA, "Detailed Functional and Interface Standards for the
              NENA i3 Solution", September 2016,

   [RFC5031]  Schulzrinne, H., "A Uniform Resource Name (URN) for
              Emergency and Other Well-Known Services", RFC 5031,
              DOI 10.17487/RFC5031, January 2008,

   [RFC4412]  Schulzrinne, H. and J. Polk, "Communications Resource
              Priority for the Session Initiation Protocol (SIP)",
              RFC 4412, DOI 10.17487/RFC4412, February 2006,

   [RFC6643]  Schoenwaelder, J., "Translation of Structure of Management
              Information Version 2 (SMIv2) MIB Modules to YANG
              Modules", RFC 6643, DOI 10.17487/RFC6643, July 2012,

   [RFC7090]  Schulzrinne, H., Tschofenig, H., Holmberg, C., and M.
              Patel, "Public Safety Answering Point (PSAP) Callback",
              RFC 7090, DOI 10.17487/RFC7090, April 2014,

   [RFC7135]  Polk, J., "Registering a SIP Resource Priority Header
              Field Namespace for Local Emergency Communications",
              RFC 7135, DOI 10.17487/RFC7135, May 2014,

   [RFC6881]  Rosen, B. and J. Polk, "Best Current Practice for
              Communications Services in Support of Emergency Calling",
              BCP 181, RFC 6881, DOI 10.17487/RFC6881, March 2013,

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

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   [RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
              A., Peterson, J., Sparks, R., Handley, M., and E.
              Schooler, "SIP: Session Initiation Protocol", RFC 3261,
              DOI 10.17487/RFC3261, June 2002,

              Dolly, M. and C. Wendt, "Assertion Values for a Resource
              Priority Header Claim in Support of Emergency Services
              Networks", draft-ietf-stir-rph-emergency-services-00 (work
              in progress), January 2020.

Author's Address

   Brian Rosen
   470 Conrad Dr
   Mars,  PA   16046

   Email: br@brianrosen.net

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