Requirements for Emergency Context Resolution with Internet Technologies
RFC 5012

Network Working Group                                     H. Schulzrinne
Request for Comments: 5012                                   Columbia U.
Category: Informational                                 R. Marshall, Ed.
                                                                     TCS
                                                            January 2008

           Requirements for Emergency Context Resolution with
                         Internet Technologies

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Abstract

   This document defines terminology and enumerates requirements for the
   context resolution of emergency calls placed by the public using
   voice-over-IP (VoIP) and general Internet multimedia systems, where
   Internet protocols are used end to end.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2
   2.  Requirements Terminology . . . . . . . . . . . . . . . . . . .  3
   3.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
     3.1.  Emergency Services . . . . . . . . . . . . . . . . . . . .  3
     3.2.  Service Providers  . . . . . . . . . . . . . . . . . . . .  3
     3.3.  Actors . . . . . . . . . . . . . . . . . . . . . . . . . .  4
     3.4.  Call Routing Entities  . . . . . . . . . . . . . . . . . .  5
     3.5.  Location . . . . . . . . . . . . . . . . . . . . . . . . .  5
     3.6.  Identifiers, Numbers, and Dial Strings . . . . . . . . . .  6
     3.7.  Mapping  . . . . . . . . . . . . . . . . . . . . . . . . .  7
   4.  Basic Actors . . . . . . . . . . . . . . . . . . . . . . . . .  8
   5.  High-Level Requirements  . . . . . . . . . . . . . . . . . . . 10
   6.  Identifying the Caller's Location  . . . . . . . . . . . . . . 12
   7.  Emergency Service Identifier . . . . . . . . . . . . . . . . . 14
   8.  Mapping Protocol . . . . . . . . . . . . . . . . . . . . . . . 16
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 20
   10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 20
   11. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 21
   12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 21
     12.1. Normative References . . . . . . . . . . . . . . . . . . . 21
     12.2. Informative References . . . . . . . . . . . . . . . . . . 21

Schulzrinne & Marshall       Informational                      [Page 1]
RFC 5012                   ECRIT Requirements               January 2008

1.  Introduction

   Users of both voice-centric (telephone-like) and non-voice services,
   such as text communication for hearing-disabled users (see [RFC3351]
   and [toip]), expect to be able to initiate a request for help in case
   of an emergency.

   Unfortunately, the existing mechanisms to support emergency calls
   that have evolved within the public circuit-switched telephone
   network (PSTN) are not appropriate to handle evolving IP-based voice,
   text, and real-time multimedia communications.  This document
   outlines the key requirements that IP-based end systems and network
   elements, such as Session Initiation Protocol (SIP) [RFC3261]
   proxies, need to satisfy in order to provide emergency call services,
   which at a minimum, offer the same functionality as existing PSTN
   services, with the additional overall goal of making emergency
   calling more robust, less costly to implement, and multimedia-
   capable.

   This document only focuses on end-to-end IP-based calls, i.e., where
   the emergency call originates from an IP end system and terminates in
   an IP-capable public safety answering point (PSAP), conveyed entirely
   over an IP network.

   We first define terminology in Section 3.  The document then outlines
   various functional issues that relate to placing an IP-based
   emergency call, including a description of baseline requirements
   (Section 5), identification of the emergency caller's location
   (Section 6), use of a service identifier to declare a call to be an
   emergency call (Section 7), and finally, the mapping function
   required to route the call to the appropriate PSAP (Section 8).

   The primary purpose of the mapping protocol is to produce a PSAP URI
   drawn from a preferred set of URI schemes such as SIP or SIPS URIs,
   based on both location information [RFC4119] and a service identifier
   in order to facilitate the IP end-to-end completion of an emergency
   call.

   Aside from obtaining a PSAP URI, the mapping protocol is useful for
   obtaining other information as well.  There may be a case, for
   example, where an appropriate emergency number is not known, only the
   location.  The mapping protocol can then return a geographically