stir B. Rosen Internet-Draft March 9, 2020 Intended status: Standards Track Expires: September 10, 2020 Non-Interactive Emergency Calls draft-rosen-stir-emergency-calls-00 Abstract 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 Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://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 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 Provisions Relating to IETF Documents (https://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 to this document. Code Components extracted from this document must Rosen Expires September 10, 2020 [Page 1] Internet-Draft Non-Interactive Emergency Calls March 2020 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. Rosen Expires September 10, 2020 [Page 2] Internet-Draft Non-Interactive Emergency Calls March 2020 2. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "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 resources. Whatever the network does with the RPH value, it is desirable to protect it from manipulation and Rosen Expires September 10, 2020 [Page 3] Internet-Draft Non-Interactive Emergency Calls March 2020 [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 TBD 7. Acknowledgments TBD 8. References Rosen Expires September 10, 2020 [Page 4] Internet-Draft Non-Interactive Emergency Calls March 2020 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, . 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, . Rosen Expires September 10, 2020 [Page 5] Internet-Draft Non-Interactive Emergency Calls March 2020 [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, . [I-D.ietf-stir-rph-emergency-services] 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 US Phone: Email: br@brianrosen.net Rosen Expires September 10, 2020 [Page 6]