| ECRIT | B. Rosen |
| Internet-Draft | NeuStar, Inc. |
| Intended status: Informational | H. Tschofenig |
| Expires: January 14, 2014 | Nokia Siemens Networks |
| R. Gellens | |
| QUALCOMM Incorporated | |
| July 13, 2013 |
Internet Protocol-based In-Vehicle Emergency Call
draft-rosen-ecrit-ecall-09.txt
This document describes how to re-use the emergency services mechanisms specified for the Session Initiation Protocol (SIP) to accomplishing emergency calling support in vehicles. Profiling and simplifications are possible due to the nature of the functionality that is going to be provided in vehicles with the usage of Global Positioning System (GPS).
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Emergency calls made from vehicles can assist with the objective of significantly reducing road deaths and injuries. Unfortunately, drivers often have a poor location-awareness, especially on urban roads (also during night) and abroad. In the most crucial cases, the victim(s) may not be able to call because they have been injured or trapped.
In Europe the European Commission has launched the 'eCall' initiative that may best be described as a user-initiated or automatically triggered system to provide notifications to Public Safety Answering Point's (PSAP), by means of cellular communications, that a vehicle has crashed, and to provide geodetic location information and where possible a voice channel to the PSAP.
This document registers the 'application/emergencyCall.VEDS+xml' MIME content-type, and registers the 'VEDS' entry in the Emergency Call Additional Data registry.
The Vehicle Emergency Data Set (VEDS) is an XML structure defined by the Association of Public-Safety Communications Officials (APCO) and the National Emergency Number Association (NENA). The 'application/emergencyCall.VEDS+xml' MIME content-type is used to identify it. The 'VEDS' entry in the Emergency Call Additional Data registry is used to construct a 'purpose' parameter value for conveying VEDS data in a Call-Info header.
Circuit-switched eCall systems transmit crash data as a defined set, the Minimum Set of Data (MSD) [eCall-MSD]. The MSD for circuit-switched eCall is a binary format defined by CEN, the European Committee for Standardization. It is expected that CEN will choose to define the XML schema for the eCall MSD for use in next-generation systems. Once this done, a MIME content-type (e.g., 'application/emergencyCall.eCall.MSD+xml') and Emergency Call Additional Data entry (e.g., 'eCall.MSD') need to be registered for the MSD. Note that Appendix A explains how the functionality available in IETF specifications maps to the functionality required for the MSD of the mobile circuit switched voice solution.
CEN and/or other entities may define additional sets of data in the same manor: a standardized format, such as XML, is defined, and a MIME content-type and Emergency Call Additional Data entry registered.
An In-Vehicle System (IVS) transmits crash data by encoding it in one of the standardized and registered formats (such as VEDS or eCall.MSD) and attaching it to an INVITE as a data block. The block is identified by its MIME content-type, and pointed to by a CID URL in a Call-Info header with a 'purpose' parameter value corresponding to the block.
Current (circuit-switched or legacy) systems for placing emergency calls from vehicles, including automatic crash notification system, generally use one of three architectural models: Telematics Service Provider (TSP), direct, and paired handset. These three models are illustrated below.
In the TSP model the IVS transmits crash data to the TSP using proprietary means. The TSP operator bridges in the PSAP and communicates location, crash, and other data to the call taker verbally (there is a three-way voice call between the vehicle, the TSP, and the PSAP).
///----\\\ proprietary +------+ 911 trunk +------+ ||| IVS |||-------------->+ TSP +------------------>+ PSAP | \\\----/// crash data +------+ +------+
Figure 1: TSP Model.
In the paired model the IVS uses a Bluetooth link to a previously-paired handset to establish an emergency call with the PSAP and then communicates location data to the PSAP via text-to-speech; crash data is not conveyed.
++
///----\\\ || 911 voice call via handset +------+
||| IVS |||--->|+----------------------------------->+ PSAP |
\\\----/// ++ +------+
Figure 2: Paired Model
In the direct model the IVS communicates crash data to the PSAP via the eCall in-band modem (in the voice call).
///----\\\ 112/911 voice call via IVS +------+ ||| IVS |||---------------------------------------->+ PSAP | \\\----/// crash data via eCall in-band modem +------+
Figure 3: Direct Model
The migration to next-generation (all-IP) would then look like as follows.
In the TSP model The IVS transmits crash data to the TSP using either proprietary or standard means. The TSP bridges in the PSAP and transmits crash and other data to the PSAP using IETF specifications. There is a three-way call between the vehicle, the TSP, and the PSAP.
proprietary
///----\\\ or standard +------+ standard +------+
IVS ------------->+ TSP +------------------->+ PSAP |
\\\----/// crash data +------+ crash + other data +------+
Figure 4: TSP Model
In the paired model, the IVS uses a Bluetooth link to a previously-paired handset to establish an emergency call with the PSAP; it is not clear what facilities are or will be available for transmitting crash data.
++
///----\\\ || IP-based Emergency Call +------+
IVS --->|+----------------------------------->+ PSAP |
\\\----/// ++ +------+
Figure 5: Paired Model
In the direct model the IVS communicates crash data to PSAP using Internet protocols.
///----\\\ IP-based Emergency Call via IVS +------+
IVS ----------------------------------------->+ PSAP |
\\\----/// +------+
Figure 6: Direct Model
This document is focused on the interface to the PSAP, that is, how an emergency call (including location and crash data) is setup and data is transmitted to the PSAP using existing IETF specifications. The goal is to re-use existing specifications rather than to invent new. For the direct model (such as the European eCall), this is the end-to-end description. For the TSP model, this describes the right-hand side, leaving the left-hand side up to the entities involved (e.g., IVS and TSP vendors) who are then free to use the same mechanism as for the right-hand side or not.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].
This document re-uses terminology defined in Section 3 of [RFC5012].
Additionally, we use the following abbreviations:
In the context of emergncy calls placed from a vehicle it is assumed that the car is equipped with a built-in GPS receiver. For this reason only geodetic location information will be sent within an emergency call. The following location shapes MUST be implemented: 2d and 3d Point (see Section 5.2.1 of [RFC5491]), Circle (see Section 5.2.3 of [RFC5491]), and Ellipsoid (see Section 5.2.7 of [RFC5491]). The coordinate reference systems (CRS) specified in [RFC5491] are also mandatory for this document. The <direction> element, as defined in [RFC5962] which indicates the direction of travel of the vehicle, is important for dispatch and hence it MUST be included in the PIDF-LO . The <heading> element specified in [RFC5962] MUST be implemented and MAY be included.
This specification also inherits the ability to utilize test call functionality from Section 15 of [RFC6881].
Figure 7 shows an emergency call placed from a vehicle whereby location information information is directly attached to the SIP INVITE message itself. The call is marked as an emergency call using the 'urn:service:sos.ecall.automatic' service URN and the PSAP of the VoIP provider determines which PSAP to contact based on the provided location information. The emergency call continues towards the PSAP and in this example it hits the ESRP, as the entry point to the PSAP operators emergency services network. Finally, the emergency call will be received by a call taker and first reponders will be dispatched.
+--------+
| LoST |
| Server |
+--------+
^ +-------+
| | PSAP2 |
| +-------+
v
+-------+ +------+ +-------+
Vehicle ------>| Proxy |---->| ESRP |---->| PSAP1 |-----> Call-Taker
+-------+ +------+ +-------+
+-------+
| PSAP3 |
+-------+
Figure 7: Example of In-Vehicular Emergency Call Message Flow
The example, shown in Figure 8, illustrates a SIP INVITE and location information encoded in a PIDF-LO that is being conveyed in such an emergency call.
INVITE urn:service:sos.ecall.automatic SIP/2.0
To: urn:service:sos.ecall.automatic
From: <sip:+13145551111@example.com>;tag=9fxced76sl
Call-ID: 3848276298220188511@atlanta.example.com
Geolocation: <cid:target123@example.com>
Geolocation-Routing: no
Accept: application/sdp, application/pidf+xml
CSeq: 31862 INVITE
Content-Type: multipart/mixed; boundary=boundary1
Content-Length: ...
--boundary1
Content-Type: application/sdp
...Session Description Protocol (SDP) goes here
--boundary1
Content-Type: application/pidf+xml
Content-ID: <target123@atlanta.example.com>
<?xml version="1.0" encoding="UTF-8"?>
<presence
xmlns="urn:ietf:params:xml:ns:pidf"
xmlns:dm="urn:ietf:params:xml:ns:pidf:data-model"
xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
xmlns:dyn="urn:ietf:params:xml:ns:pidf:geopriv10:dynamic"
xmlns:gml="http://www.opengis.net/gml"
xmlns:gs="http://www.opengis.net/pidflo/1.0"
entity="sip:+13145551111@example.com">
<dm:device id="123">
<gp:geopriv>
<gp:location-info>
<gml:Point srsName="urn:ogc:def:crs:EPSG::4326">
<gml:pos>-34.407 150.883</gml:pos>
</gml:Point>
<dyn:Dynamic>
<dyn:heading>278</dyn:heading>
<dyn:direction><dyn:direction>
</dyn:Dynamic>
</gp:location-info>
<gp:usage-rules/>
<method>gps</method>
</gp:geopriv>
<timestamp>2012-04-5T10:18:29Z</timestamp>
<dm:deviceID>1M8GDM9A_KP042788</dm:deviceID>
</dm:device>
</presence>
--boundary1--
Figure 8: SIP INVITE indicating an In-Vehicular Emergency Call
This document does not raise security considerations beyond those described in [RFC5069]. As with emergency service systems with end host provided location information there is the possibility that that location is incorrect, either intentially (in case of an a denial of service attack against the emergency services infrastructure) or due to a malfunctioning devices. The reader is referred to [I-D.ietf-ecrit-trustworthy-location] for a discussion of some of these vulnerabilities.
IANA is requested to register the URN 'urn:service:sos.ecall' under the sub-services 'sos' registry defined in Section 4.2 of [RFC5031].
This service identifier reaches a public safety answering point (PSAP), which in turn dispatches aid appropriate to the emergency related to accidents of vehicles. Two sub-services are registered as well, namely
This specification requests the registration of a new MIME type according to the procedures of RFC 4288 [RFC4288] and guidelines in RFC 3023 [RFC3023].
This specification requests IANA to add the 'VEDS' entry to the Emergency Call Additional Data registry, with a reference to this document. The Emergency Call Additional Data registry has been established with [I-D.ietf-ecrit-additional-data].
We would like to thank Ulrich Dietz for his help with earlier versions of the document.
We would like to thank Michael Montag, Arnoud van Wijk, Ban Al-Bakri, and Gunnar Hellström for their feedback.
| [1] | Schulzrinne, H. and R. Marshall, "Requirements for Emergency Context Resolution with Internet Technologies", RFC 5012, January 2008. |
| [2] | Taylor, T., Tschofenig, H., Schulzrinne, H. and M. Shanmugam, "Security Threats and Requirements for Emergency Call Marking and Mapping", RFC 5069, January 2008. |
| [3] | Tschofenig, H., Schulzrinne, H. and B. Aboba, "Trustworthy Location", Internet-Draft draft-ietf-ecrit-trustworthy-location-05, March 2013. |
| [4] | Schulzrinne, H., "Timed Presence Extensions to the Presence Information Data Format (PIDF) to Indicate Status Information for Past and Future Time Intervals", RFC 4481, July 2006. |
| [5] | CEN, , "Intelligent transport systems - eSafety - eCall minimum set of data (MSD), EN 15722", June 2011. |
[eCall-MSD] outlines a number of data elements that are transmitted in an emergency call triggered by a vehicle. Note that the work on eCall for mobile circuit switched voice is constrained in a number of ways since legacy eCall uses an inband voice modem for backwards compatibility with the already deployed cellular infrastructure to transmit data from a vehicle to a PSAP. Since the functionality in this document is based on the Session Initiation Protocol (SIP) these limitations do not exist. As such, it is not useful to transmit the MSD inband in the voice channel but to rather use the SIP mechanisms standardized for emergency call handling. Any voice, video, or real-text communication will be negotiated using the Session Description Protocol (SDP), as shown in Figure 8, and the actual media stream will then take place in RTP packets. For transmitting location information an XML-based data structure had been defined, the so-called Presence Information Data Format Location Object (PIDF-LO).
The following list compares the eCall minimum set of data with the functionality provided in this document.
While most fields have an equivalent already in the corresponding SIP emergency signaling payloads there are currently no fields defined in the additional data structure [I-D.ietf-ecrit-additional-data] that allow information about the "Vehicle Type Encoding", "Number of Passengers", and "Vehicle Propulsion Storage type" to be conveyed. Extensions for those fields will have to be defined.