draft-ietf-ecrit-requirements-01.txt   draft-ietf-ecrit-requirements-02.txt 
ecrit H. Schulzrinne ecrit H. Schulzrinne
Internet-Draft Columbia U. Internet-Draft Columbia U.
Expires: April 24, 2006 R. Marshall, Ed. Expires: July 3, 2006 R. Marshall, Ed.
TCS TCS
October 21, 2005 December 30, 2005
Requirements for Emergency Context Resolution with Internet Technologies Requirements for Emergency Context Resolution with Internet Technologies
draft-ietf-ecrit-requirements-01.txt draft-ietf-ecrit-requirements-02.txt
Status of this Memo Status of this Memo
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This Internet-Draft will expire on April 24, 2006. This Internet-Draft will expire on July 3, 2006.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2005). Copyright (C) The Internet Society (2005).
Abstract Abstract
This document enumerates requirements for emergency calls placed by This document enumerates requirements for emergency calls placed by
the public using voice-over-IP (VoIP) and general Internet multimedia the public using voice-over-IP (VoIP) and general Internet multimedia
systems, where Internet protocols are used end-to-end. systems, where Internet protocols are used end-to-end.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Basic Actors . . . . . . . . . . . . . . . . . . . . . . . . . 7 3. Basic Actors . . . . . . . . . . . . . . . . . . . . . . . . . 8
4. High-Level Requirements . . . . . . . . . . . . . . . . . . . 10 4. High-Level Requirements . . . . . . . . . . . . . . . . . . . 11
5. Identifying the Caller Location . . . . . . . . . . . . . . . 12 5. Identifying the Caller Location . . . . . . . . . . . . . . . 13
6. Emergency Identifier . . . . . . . . . . . . . . . . . . . . . 14 6. Emergency Identifier . . . . . . . . . . . . . . . . . . . . . 15
7. Mapping Protocol . . . . . . . . . . . . . . . . . . . . . . . 16 7. Mapping Protocol . . . . . . . . . . . . . . . . . . . . . . . 17
8. Security Considerations . . . . . . . . . . . . . . . . . . . 20 8. Security Considerations . . . . . . . . . . . . . . . . . . . 22
9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 21 9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 23
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 22 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 24
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 23 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 25
11.1. Normative References . . . . . . . . . . . . . . . . . . 23 11.1. Normative References . . . . . . . . . . . . . . . . . . 25
11.2. Informative References . . . . . . . . . . . . . . . . . 23 11.2. Informative References . . . . . . . . . . . . . . . . . 25
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 24 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 26
Intellectual Property and Copyright Statements . . . . . . . . . . 25 Intellectual Property and Copyright Statements . . . . . . . . . . 27
1. Introduction 1. Introduction
Users of both voice-centric (telephone-like) and non voice type Users of both voice-centric (telephone-like) and non voice type
services (e.g. text messaging for hearing disabled users, (RFC 3351 services (e.g. text messaging for hearing disabled users, (RFC 3351
[4]) have an expectation to be able to initiate a request for help in [5]) have an expectation to be able to initiate a request for help in
case of an emergency. case of an emergency.
Unfortunately, the existing mechanisms to support emergency calls Unfortunately, the existing mechanisms to support emergency calls
that have evolved within the public circuit-switched telephone that have evolved within the public circuit-switched telephone
network (PSTN), are not appropriate to handle evolving IP-based network (PSTN), are not appropriate to handle evolving IP-based
voice, text and real-time multimedia communications. This document voice, text and real-time multimedia communications. This document
outlines the key requirements that IP-based end systems and network outlines the key requirements that IP-based end systems and network
elements, such as SIP proxies, need to satisfy in order to provide elements, such as SIP proxies, need to satisfy in order to provide
emergency call services, which at a minimum, offer the same emergency call services, which at a minimum, offer the same
functionality as existing PSTN services, with the additional overall functionality as existing PSTN services, with the additional overall
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Identification of the caller, while not incompatible with the Identification of the caller, while not incompatible with the
requirements for messaging outlined within this document, is not requirements for messaging outlined within this document, is not
currently considered within the scope of the ECRIT charter, and is currently considered within the scope of the ECRIT charter, and is
therefore, left for a future draft to describe. therefore, left for a future draft to describe.
Note: Location is required for two separate purposes, first, to route Note: Location is required for two separate purposes, first, to route
the call to the appropriate PSAP and second, to display the caller's the call to the appropriate PSAP and second, to display the caller's
location to the call taker for help in dispatching emergency location to the call taker for help in dispatching emergency
assistance to the correct location. assistance to the correct location.
Ideally, the mapping protocol would yield a URI from a preferred set
of URIs (e.g. sips:uri; sip:uri), which would allow an emergency call
to be completed using IP end-to-end (possibly via the Internet).
Despite this goal, some PSAPs may not immediately have IP based
connectivity, and therefore it is imperative that the URI scheme not
be fixed, in order to ensure support for a less preferred set of
URIs, such as a TEL URI which may be used to Complete a call over the
PSTN.
2. Terminology 2. Terminology
In this document, the key words "MUST", "MUST NOT", "REQUIRED", In this document, the key words "MUST", "MUST NOT", "REQUIRED",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
and "OPTIONAL" are to be interpreted as described in RFC 2119 [1] and and "OPTIONAL" are to be interpreted as described in RFC 2119 [1] and
indicate requirement levels for compliant implementations. indicate requirement levels for compliant implementations.
Since a requirements document does not directly specify a protocol to Since a requirements document does not directly specify a protocol to
implement, these compliance labels should be read as indicating implement, these compliance labels should be read as indicating
requirements for the protocol or architecture, rather than an requirements for the protocol or architecture, rather than an
implementation. implementation.
For lack of a better term, we will use the term "caller" or For lack of a better term, we will use the term "caller" or
"emergency caller" to refer to the person placing an emergency call "emergency caller" to refer to the person placing an emergency call
or sending an emergency IM. or sending an emergency IM.
Application Service Provider (ASP): The organization or entity that Application Service Provider (ASP): The organization or entity that
provides application-layer services, which may include voice (see provides application-layer services, which may include voice (see
term Voice Service Provider). This entity can be a private "Voice Service Provider"). This entity can be a private
individual, an enterprise, a government, or a service provider. individual, an enterprise, a government, or a service provider.
An ASP is defined as something more general than a Voice Service An ASP is defined as something more general than a Voice Service
Provider, since emergency calls are sometimes likely to use other Provider, since emergency calls are sometimes likely to use other
media, including text and video. Note: For a particular user, the media, including text and video. Note: For a particular user, the
ASP may or may not be the same organization as the IAP and/or ISP. ASP may or may not be the same organization as the IAP and/or ISP.
Basic Emergency Service: Basic Emergency Service allows a user to Basic Emergency Service: Basic Emergency Service allows a user to
reach a PSAP serving its current location, but the PSAP may not be reach a PSAP serving its current location, but the PSAP may not be
able to determine the identity or geographic location of the able to determine the identity or geographic location of the
caller (except by having the call taker ask the caller). caller (except by having the call taker ask the caller).
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call taker: A call taker is an agent at the PSAP that accepts calls call taker: A call taker is an agent at the PSAP that accepts calls
and may dispatch emergency help. (Sometimes the functions of call and may dispatch emergency help. (Sometimes the functions of call
taking and dispatching are handled by different groups of people, taking and dispatching are handled by different groups of people,
but these divisions of labor are not generally visible to the but these divisions of labor are not generally visible to the
outside and thus do not concern us here.) outside and thus do not concern us here.)
civic location: A described location based on some defined grid, such civic location: A described location based on some defined grid, such
as a jurisdictional, postal, metropolitan, or rural reference as a jurisdictional, postal, metropolitan, or rural reference
system (e.g. street address). system (e.g. street address).
directory service: A network service which uses a distributed mapping service: A network service which uses a distributed mapping
directory protocol to provide information about the PSAP, or protocol to provide information about the PSAP, or intermediary
intermediary which knows about the PSAP, and is used to assist in which knows about the PSAP, and is used to assist in routing an
routing an emergency call. emergency call.
emergency address: The sip:uri, sips:uri, or tel:uri which represents emergency address: The uri scheme (e.g. sip:uri, sips:uri, xmpp:uri,
the address of the PSAP useful for the completion of an emergency im:uri, etc.) which represents the address of the PSAP useful for
call. the completion of an emergency call.
emergency caller: The user or user device entity which sends his/her emergency caller: The user or user device entity which sends his/her
location to another entity in the network. location to another entity in the network.
emergency identifier: The numerical and/or text identifier which is emergency identifier: The numerical and/or text identifier which is
supplied by a user or a user device, which identifies the call as supplied by a user or a user device, which identifies the call as
an emergency call and is translated into an emergency address for an emergency call and is translated into an emergency address for
call routing and completion. call routing and completion.
enhanced emergency service: Enhanced emergency services add the enhanced emergency service: Enhanced emergency services add the
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an individual.) an individual.)
ESRP (Emergency Services Routing Proxy): An ESRP is a call routing ESRP (Emergency Services Routing Proxy): An ESRP is a call routing
entity that invokes the location-to-URL mapping, which in turn may entity that invokes the location-to-URL mapping, which in turn may
return either the URL for another ESRP or the PSAP. (In a SIP return either the URL for another ESRP or the PSAP. (In a SIP
system, the ESRP would typically be a SIP proxy, but could also be system, the ESRP would typically be a SIP proxy, but could also be
a Back-to-back user agent (B2BUA). a Back-to-back user agent (B2BUA).
geographic location: A reference to a locatable point described by a geographic location: A reference to a locatable point described by a
set of defined coordinates within a geographic coordinate system, set of defined coordinates within a geographic coordinate system,
(e.g. lat/lon within WGS-84 datum) (e.g. lat/lon within the WGS-84 datum)
Internet Attachment Provider (IAP): An organization that provides Internet Attachment Provider (IAP): An organization that provides
physical network connectivity to its customers or users, e.g. physical network connectivity to its customers or users, e.g.
through digital subscriber lines, cable TV plants, Ethernet, through digital subscriber lines, cable TV plants, Ethernet,
leased lines or radio frequencies. This entity may or may not leased lines or radio frequencies. Examples of such organizations
also provide IP routing, IP addresses, or other Internet protocol include telecommunication carriers, municipal utilities, larger
services. Examples of such organizations include
telecommunication carriers, municipal utilities, larger
enterprises with their own network infrastructure, and government enterprises with their own network infrastructure, and government
organizations such as the military. organizations such as the military.
Internet Service Provider (ISP): An organization that provides IP Internet Service Provider (ISP): An organization that provides IP
network-layer services to its customers or users. This entity may network-layer services to its customers or users. This entity may
or may not provide the physical-layer and layer-2 connectivity, or may not provide the physical-layer and layer-2 connectivity,
such as fiber or Ethernet. such as fiber or Ethernet.
Local Emerency Identifier: An emergency identifier which is
recognized from within a geographic or jurisdictional area from
which an emergency request is initiated.
location: A geographic identification assigned to a region or feature location: A geographic identification assigned to a region or feature
based on a specific coordinate system, or by other precise based on a specific coordinate system, or by other precise
information such as a street number and name. In the geocoding information such as a street number and name. In the geocoding
process, the location is defined with an x,y coordinate value process, the location is defined with an x,y coordinate value
according to the distance north or south of the equator and east according to the distance north or south of the equator and east
or west of the prime meridian. or west of the prime meridian.
location validation: A caller location is considered valid if the location validation: A caller location is considered valid if the
civic or geographic location is recognizable within an acceptable civic or geographic location is recognizable within an acceptable
location reference systems (e.g. USPS, WGS-84, etc.), and can be location reference systems (e.g. USPS, WGS-84, etc.), and can be
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PSAP (Public Safety Answering Point): Physical location where PSAP (Public Safety Answering Point): Physical location where
emergency calls are received under the responsibility of a public emergency calls are received under the responsibility of a public
authority. (This terminology is used by both ETSI, in ETSI SR 002 authority. (This terminology is used by both ETSI, in ETSI SR 002
180, and NENA.) In the United Kingdom, PSAPs are called Operator 180, and NENA.) In the United Kingdom, PSAPs are called Operator
Assistance Centres, in New Zealand, Communications Centres. Assistance Centres, in New Zealand, Communications Centres.
Within this document, it is assumed, unless stated otherwise, that Within this document, it is assumed, unless stated otherwise, that
PSAP is that which supports the receipt of emergency calls over PSAP is that which supports the receipt of emergency calls over
IP. It is also assumed that the PSAP is reachable by IP-based IP. It is also assumed that the PSAP is reachable by IP-based
protocols, such as SIP for call signaling and RTP for media. protocols, such as SIP for call signaling and RTP for media.
Universal Identifier: An emergency identifier which is recognized by
any compatible endpoint, from any geographic location as useful
for initiating an emergency request. A general approach to using
universal identifiers is outlined in the service URN draft
(I-D.schulzrinne-sipping-service [4]).
Voice Service Provider (VSP): A specific type of Application Service Voice Service Provider (VSP): A specific type of Application Service
Provider which provides voice related services based on IP, such Provider which provides voice related services based on IP, such
as call routing, a SIP URI, or PSTN termination. as call routing, a SIP URI, or PSTN termination.
3. Basic Actors 3. Basic Actors
In order to support emergency services covering a large physical area In order to support emergency services covering a large physical area
various infrastructure elements are necessary: Internet Attachment various infrastructure elements are necessary: Internet Attachment
Providers, Application/Voice Service Providers, PSAPs as endpoints Providers, Application/Voice Service Providers, PSAPs as endpoints
for emergency calls, directory services or other infrastructure for emergency calls, mapping services or other infrastructure
elements that assist in during the call routing and potentially many elements that assist in during the call routing and potentially many
other entities. other entities.
This section outlines which entities will be considered in the This section outlines which entities will be considered in the
routing scenarios discussed. routing scenarios discussed.
Location Location
Information +-----------------+ Information +-----------------+
|(1) |Internet | +-----------+ |(1) |Internet | +-----------+
v |Attachment | | | v |Attachment | | |
+-----------+ |Provider | | Directory | +-----------+ |Provider | | Mapping |
| | | (3) | | Service | | | | (3) | | Service |
| Emergency |<---+-----------------+-->| | | Emergency |<---+-----------------+-->| |
| Caller | | (2) | +-----------+ | Caller | | (2) | +-----------+
| |<---+-------+ | ^ | |<---+-------+ | ^
+-----------+ | +----|---------+------+ | +-----------+ | +----|---------+------+ |
^ | | Location | | | ^ | | Location | | |
| | | Information<-+ | | | | | Information<-+ | |
| +--+--------------+ |(8) | | (5) | +--+--------------+ |(8) | | (5)
| | +-----------v+ | | | | +-----------v+ | |
| (4) | |Emergency | | | | (4) | |Emergency | | |
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Below, we describe various interactions between the entities shown in Below, we describe various interactions between the entities shown in
Figure 1 are described: Figure 1 are described:
o (1) Location information might be available to the end host itself. o (1) Location information might be available to the end host itself.
o (2) Location information might, however, also be obtained from the o (2) Location information might, however, also be obtained from the
Internet Attachment Provider (e.g., using DHCP or application layer Internet Attachment Provider (e.g., using DHCP or application layer
signaling protocols). signaling protocols).
o (3) The Emergency Caller might need to consult a directory service o (3) The Emergency Caller might need to consult a mapping service to
to determine the PSAP that is appropriate for the physical location determine the PSAP that is appropriate for the physical location of
of the emergency caller (and considering other attributes such as a the emergency caller (and considering other attributes such as a
certain language support by the Emergency Call Takers). certain language support by the Emergency Call Takers).
o (4) The Emergency Caller might get assistance for emergency call o (4) The Emergency Caller might get assistance for emergency call
routing by infrastructure elements (referred as Emergency Call routing by infrastructure elements (referred as Emergency Call
Routing Support entities). In case of SIP these entities are Routing Support entities). In case of SIP these entities are
proxies. proxies.
o (5) Individual Emergency Call Routing Support entities might need o (5) Individual Emergency Call Routing Support entities might need
to consult a directory servic to determine where to route the to consult a mapping service to determine where to route the
emergency call. emergency call.
o (6) The Emergency Call Routing Support entities need to finally o (6) The Emergency Call Routing Support entities need to finally
forward the call, if infrastructure based emergency call routing is forward the call, if infrastructure based emergency call routing is
used. used.
o (7) The emergency caller might interact directly with the PSAP o (7) The emergency caller might interact directly with the PSAP
without any Emergency Call Routing Support entities. without any Emergency Call Routing Support entities.
o (8) Location Information is used by emergency call routing entities
to determine appropriate PSAP mapping.
4. High-Level Requirements 4. High-Level Requirements
Below, we summarize high-level architectural requirements that guide Below, we summarize high-level architectural requirements that guide
some of the component requirements detailed later in the document. some of the component requirements detailed later in the document.
Re1. Application Service Provider: The existence of an Application Re1. Application Service Provider: The existence of an Application
Service Provider (ASP) MUST NOT be assumed. Service Provider (ASP) MUST NOT be assumed.
Motivation: The caller may not have a application/voice service Motivation: The caller may not have a application/voice service
provider. For example, a residence may have its own DNS domain provider. For example, a residence may have its own DNS domain
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other regions or nations. The system cannot assume, for example, other regions or nations. The system cannot assume, for example,
that there is a single global entity issuing certificates for that there is a single global entity issuing certificates for
PSAPs, ASPs, IAPs or other participants. PSAPs, ASPs, IAPs or other participants.
Re4. Multiple Modes: Multiple communication modes, such as audio, Re4. Multiple Modes: Multiple communication modes, such as audio,
video and text messaging MUST be supported. video and text messaging MUST be supported.
Motivation: In PSTN, voice and text telephony (often called TTY or Motivation: In PSTN, voice and text telephony (often called TTY or
textphone in North America ) are the only commonly supported textphone in North America ) are the only commonly supported
media. Emergency calling must support a variety of media. Such media. Emergency calling must support a variety of media. Such
media should include voice, conversational text (RFC 4103 [6]), media should include voice, conversational text (RFC 4103 [7]),
instant messaging and video. instant messaging and video.
Re5. Alternate Mapping Sources: The mapping protocol SHOULD allow Re5. Alternate Mapping Sources: The mapping protocol SHOULD allow
for alternative redundant sources of mapping information, possibly for alternative redundant sources of mapping information, possibly
of different degrees of currency. of different degrees of currency.
Motivation: This provides the possibility of having available Motivation: This provides the possibility of having available
alternative sources of mapping information when the normal source alternative sources of mapping information when the normal source
is unavailable or unreachable, without specifying the means by is unavailable or unreachable, without specifying the means by
which the alternative source is created or updated. which the alternative source is created or updated.
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without special emergency extensions) unless an error is returned. without special emergency extensions) unless an error is returned.
Motivation: The format of the output returned by the mapping Motivation: The format of the output returned by the mapping
protocol is in a standard format for communication protocol. For protocol is in a standard format for communication protocol. For
example, it should return something SIP specific (e.g. URI), that example, it should return something SIP specific (e.g. URI), that
any SIP capable phone would be able to use if used in a SIP any SIP capable phone would be able to use if used in a SIP
context. Special purpose URIs would not be understood by "legacy" context. Special purpose URIs would not be understood by "legacy"
SIP devices since they do not have knowledge about the mapping SIP devices since they do not have knowledge about the mapping
protocol, and therefore are not to be used. protocol, and therefore are not to be used.
Re7. Relay Services: It SHOULD be possible to involve relay Re7. Ubiquiteous Triggering: It MUST be possible to invoke the
services in the call for translation between different modes. mapping protocol at any time, from any location, by any client
which supports the mapping protocol.
Motivation: It should be possible to connect the relay service so Motivation: While end devices are the typical initiators of
that the direct flow of media to the emergency service is mapping service requests, it is also expected that other mapping
maintained. In addition, it should be possible to convey clients, such as relays, 3rd party devices, PSAPs, etc. may also
telemetry data, such as data from automobile crash sensors. trigger a mapping request.
Re8. PSAP Identification: The mapping information MUST be available Re8. PSAP Identification: The mapping information MUST be available
without having to enroll with a service provider. without having to enroll with a service provider.
Motivation: The mapping server may well be operated by a service Motivation: The mapping server may well be operated by a service
provider, but access to the server offering the mapping must not provider, but access to the server offering the mapping must not
require use of a specific ISP or VSP. require use of a specific ISP or VSP.
5. Identifying the Caller Location 5. Identifying the Caller Location
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announcements (LLDP). announcements (LLDP).
UA-referenced: The caller's user agent provides a reference, via a UA-referenced: The caller's user agent provides a reference, via a
permanent or temporary identifier, to the location which is stored permanent or temporary identifier, to the location which is stored
by a location service somewhere else and then retrieved by the by a location service somewhere else and then retrieved by the
PSAP. PSAP.
Proxy-inserted: A proxy along the call path inserts the location or Proxy-inserted: A proxy along the call path inserts the location or
location reference. location reference.
Lo1. Validation of civic location: It MUST be possible to validate Lo1. Validation of Civic Location: It MUST be possible to validate a
an civic location prior to its use in an actual emergency call. civic location prior to its use in an actual emergency call.
Motivation: Location validation provides an opportunity to help Motivation: Location validation provides an opportunity to help
assure ahead of time, whether successful mapping to the assure ahead of time, whether successful mapping to the
appropriate PSAP will likely occur when it is required. appropriate PSAP will likely occur when it is required.
Validation may also help to avoid delays during emergency call Validation may also help to avoid delays during emergency call
setup due to invalid locations. setup due to invalid locations.
Lo2.: Validation of a civic location MUST NOT be required to enable Lo2. Limits to Validation: Validation of a civic location MUST NOT
any feature that is part of the emergency call process. be required to enable any feature that is part of the emergency
call process.
Motivation: In some cases, (based on a variety of factors), a Motivation: In some cases, (based on a variety of factors), a
civic location may not be considered valid. This fact should not civic location may not be considered valid. This fact should not
result in the call being dropped or rejected by any entity along result in the call being dropped or rejected by any entity along
the signaling path to the PSAP. the signaling path to the PSAP.
Lo3. Reference Datum: The mapping server MUST understand WGS-84 Lo3. Reference Datum: The mapping server MUST understand WGS-84
coordinate reference system and may understand other reference coordinate reference system and may understand other reference
systems. systems.
Lo4. Location Provided: An Emergency Services Routing Proxy (ESRP) Lo4. Location Provided: An Emergency Services Routing Proxy (ESRP)
MUST NOT remove location information after performing location MUST NOT remove location information after performing location
based routing. based routing.
Motivation: The ESRP and the PSAP use the same location Motivation: The ESRP and the PSAP use the same location
information object but for a different purpose. Therefore, the information object but for a different purpose. Therefore, the
PSAP still requires the receipt of information which represents PSAP still requires the receipt of information which represents
the end device's location. the end device's location.
Lo5. 3D Sensitive Mapping: The mapping protocol MUST accept either a
2D or 3D mapping request, and return an appropriate result, based
on which type of input is used.
Motivation: It is expected that provisioning systems will accept
both 2D and 3D data. When a 3D request is presented to an area
only defined by 2D data, the mapping result would be the same as
if the height/altitude dimension was omitted on the request."
6. Emergency Identifier 6. Emergency Identifier
Id1. Universal Identifier - Setup: One or more universal emergency Id1. Universal Identifier Setup: One or more universal emergency
identifiers MUST be recognized by any device or network element identifiers MUST be recognized by any device or network element
for call setup purposes for call setup purposes
Motivation: There must be some way for any device or element to Motivation: There must be some way for any device or element to
recognize an emergency call throughout the call setup. This is recognize an emergency call throughout the call setup. This is
regardless of the device location, the application (voice) service regardless of the device location, the application (voice) service
provider used (if any at all), or of any other factor. Examples provider used (if any at all), or of any other factor. Examples
of these might include: 911, 112, and sos.*. of these might include: 911, 112, and sos.*.
Id2. Universal Identifier Resolution: Where multiple emergency Id2. Universal Identifier Resolution: Where multiple emergency
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identifier separately, based on the specific type of emergency identifier separately, based on the specific type of emergency
help requested. help requested.
Motivation: Some jurisdictions may have multiple types of Motivation: Some jurisdictions may have multiple types of
emergency services available at the same level, (e.g. fire, emergency services available at the same level, (e.g. fire,
police, ambulance), in which case it is important that any one police, ambulance), in which case it is important that any one
could be selected directly. could be selected directly.
Id3. Emergency Marking: Any device in the signaling path that Id3. Emergency Marking: Any device in the signaling path that
recognizes by some means that the signaling is associated with an recognizes by some means that the signaling is associated with an
emergency call MUST add the emergency indication called for in A1a emergency call MUST add the emergency indication called for in Id1
to the signaling before forwarding it. This marking mechanism to the signaling before forwarding it. This marking mechanism
must be different than QoS marking. must be different than QoS marking.
Motivation: Marking ensures proper handling as an emergency call Motivation: Marking ensures proper handling as an emergency call
by downstream elements that may not recognize, for example, a by downstream elements that may not recognize, for example, a
local variant of a logical emergency address (see requirement local variant of a logical emergency address.
A4+).
Id4. Emergency Identifier-based Marking: User agents, proxies, and Id4. Emergency Identifier-based Marking: User agents, proxies, and
other network elements that process signaling associated with other network elements that process signaling associated with
emergency calls SHOULD be configured to recognize a reasonable emergency calls SHOULD be configured to recognize a reasonable
selection of logical emergency identifiers (described in selection of logical emergency identifiers as a means to initiate
requirements below) as a means to initiate emergency marking. emergency marking.
Motivation: Since user devices roam, emergency identifiers may Motivation: Since user devices roam, emergency identifiers may
vary from region to region. It is therefore important that a vary from region to region. It is therefore important that a
network entity be able to perform mapping and/or call routing network entity be able to perform mapping and/or call routing
within the context of its own point of origin rather than relying within the context of its own point of origin rather than relying
on non-local logical emergency identifiers as the only basis for on non-local logical emergency identifiers as the only basis for
emergency marking of calls. emergency marking of calls.
Id5. Prevention of Fraud: A call identified as an emergency call or Id5. Prevention of Fraud: A call identified as an emergency call or
marked as such in accordance with the above requirements for marked as such in accordance with the above requirements for
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of an enterprise). of an enterprise).
Motivation: Any signalling protocol requires the use of some Motivation: Any signalling protocol requires the use of some
identifier to indicate the called party, and the user terminal may identifier to indicate the called party, and the user terminal may
lack the capability to determine the actual emergency address lack the capability to determine the actual emergency address
(PSAP uri). The use of local conventions may be required as a (PSAP uri). The use of local conventions may be required as a
transition mechanism. Note: Such use complicates international transition mechanism. Note: Such use complicates international
movement of the user terminal, and evolution to a standardized movement of the user terminal, and evolution to a standardized
universal emergency identifier or set of identifiers is preferred. universal emergency identifier or set of identifiers is preferred.
Id8. Universal Identifier Recognition: Universal identifier(s), MUST
be universally recognizable by any network element which supports
the ECRIT protocol."
Id9. Universal Identifier not Recognized: A call MUST be recognized
as emergency call even if the specific emergency service requested
is not recognized."
"Motivation: In order to have a robust system that supports
incremental Service deployment while still maintaining a fallback
capability."
7. Mapping Protocol 7. Mapping Protocol
Given the requirement from the previous section, that of a single (or Given the requirement from the previous section, that of a single (or
small number of) emergency identifier(s) which are independent of the small number of) emergency identifier(s) which are independent of the
caller's location, and since PSAPs only serve a limited geographic caller's location, and since PSAPs only serve a limited geographic
region, and for reasons of jurisdictional and local knowledge, having region, and for reasons of jurisdictional and local knowledge, having
the call reach the appropriate PSAP based on a mapping protocol, is the call reach the appropriate PSAP based on a mapping protocol, is
crucial. crucial.
There are two basic architectures described for translating an There are two basic architectures described for translating an
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limited caching mechanism should be supported. limited caching mechanism should be supported.
Ma4. Referral: The mapping client MUST be able to contact any server Ma4. Referral: The mapping client MUST be able to contact any server
and be referred to another server that is more qualified to answer and be referred to another server that is more qualified to answer
the query. the query.
Motivation: This requirement alleviates the potential for Motivation: This requirement alleviates the potential for
incorrect configurations to cause calls to fail, particularly for incorrect configurations to cause calls to fail, particularly for
caller-based queries. caller-based queries.
Ma5. The mapping protocol MUST allow a response to carry multiple Ma5. Multiple Response URIs: The mapping protocol response MUST
URIs. allow the return of multiple URIs.
Motivation: In response to a mapping request, a server will Motivation: In response to a mapping request, a server will
normally provide a URI or set of URIs for contacting the normally provide a URI or set of URIs for contacting the
appropriate PSAP. appropriate PSAP.
Ma6. The mapping protocol MUST be able to return a URI or contact Ma6. URI - Alternate Contact: The mapping protocol MUST be able to
method explicitly marked as an alternate contact. return a URI or contact method explicitly marked as an alternate
contact.
Motivation: In response to a mapping request, if an expected URI Motivation: In response to a mapping request, if an expected URI
is unable to be returned, then mapping server may return an is unable to be returned, then mapping server may return an
alternate URI. When and how this would be used will be described alternate URI. When and how this would be used will be described
in an operational document. in an operational document.
Ma7. Multiple PSAP uri's: The mapping protocol MUST be able to Ma7. Multiple PSAP URI's: The mapping protocol MUST be able to
return multiple URLs for different PSAPs that cover the same area. return multiple URIs for different PSAPs that cover the same area.
Ma8. URL properties: The mapping protocol must provide additional Ma8. URL properties: The mapping protocol must provide additional
information that allows the querying entity to determine relevant information that allows the querying entity to determine relevant
properties of the URL. properties of the URL.
Motivation: In some cases, the same geographic area is served by Motivation: In some cases, the same geographic area is served by
several PSAPs, for example, a corporate campus might be served by several PSAPs, for example, a corporate campus might be served by
both a corporate security department and the municipal PSAP. The both a corporate security department and the municipal PSAP. The
mapping protocol should then return URLs for both, with mapping protocol should then return URLs for both, with
information allowing the querying entity to choose one or the information allowing the querying entity to choose one or the
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Ma14. Location Updates: It SHOULD be possible to have updates of Ma14. Location Updates: It SHOULD be possible to have updates of
location. location.
Motivation: Updated location information may have an impact on Motivation: Updated location information may have an impact on
PSAP routing. In some cases it may be possible to redirect that PSAP routing. In some cases it may be possible to redirect that
call to a more appropriate PSAP (some device measurement call to a more appropriate PSAP (some device measurement
techniques provide quick (i.e. early), but imprecise "first fix" techniques provide quick (i.e. early), but imprecise "first fix"
location). location).
Ma15. Extensible Protocol The mapping protocol MUST be extensible to Ma15. Extensible Protocol: The mapping protocol MUST be extensible
allow for the inclusion of new location fields. to allow for the inclusion of new location fields.
Motivation: This is needed, for example, to accommodate future Motivation: This is needed, for example, to accommodate future
extensions to location information that might be included in the extensions to location information that might be included in the
PIDF-LO (I-D.ietf-geopriv-pidf-lo-03 [2]) PIDF-LO (RFC 4119 [2]).
Ma16. Split responsibility: The mapping protocol MUST allow that Ma16. Split responsibility: The mapping protocol MUST allow that
within a single level of the civic location hierarchy, multiple within a single level of the civic location hierarchy, multiple
mapping servers handle subsets of the data elements. mapping servers handle subsets of the data elements.
Motivation: For example, two directories for the same city or Motivation: For example, two directories for the same city or
county may handle different streets within that city or county. county may handle different streets within that city or county.
Ma17. The mapping function MUST be able to be invoked at any time, Ma17. Pervasive Mapping: The mapping function MUST be able to be
including while an emergency call is in process. invoked at any time, including while an emergency call is in
process.
Ma18. Baseline query protocol: A mandatory-to-implement protocol Ma18. Baseline query protocol: A mandatory-to-implement protocol
MUST be specified. MUST be specified.
Motivation: An over-abundance of similarly-capable choices appears Motivation: An over-abundance of similarly-capable choices appears
undesirable for interoperability. undesirable for interoperability.
Ma19. Single URI Scheme: The mapping protocol MAY return multiple
URIs, though it SHOULD return only one URI per scheme, so that
clients are not required to select among different targets for the
same contact protocol.
Motivation: There may be two or more URIs returned when multiple
contact protocols are available (e.g. SIP and SMS). The client
may select among multiple contact protocols based on its
capabilities, preference settings, or availability.
8. Security Considerations 8. Security Considerations
Note: Security Considerations are referenced in the ECRIT security Note: Security Considerations are referenced in the ECRIT security
document [3]. document [3].
9. Contributors 9. Contributors
The information contained in this document is a result of a joint The information contained in this document is a result of a joint
effort based on individual contributions by those involved in the effort based on individual contributions by those involved in the
ECRIT WG. The contributors include Nadine Abbott, Hideki Arai, ECRIT WG. The contributors include Nadine Abbott, Hideki Arai,
skipping to change at page 23, line 13 skipping to change at page 25, line 13
their input. their input.
11. References 11. References
11.1. Normative References 11.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997. Levels", BCP 14, RFC 2119, March 1997.
[2] Peterson, J., "A Presence-based GEOPRIV Location Object Format", [2] Peterson, J., "A Presence-based GEOPRIV Location Object Format",
draft-ietf-geopriv-pidf-lo-03 (work in progress), RFC 4119, December 2005.
September 2004.
[3] Tschofenig, H., "Security Threats and Requirements for Emergency [3] Schulzrinne, H., "Security Threats and Requirements for
Calling", draft-tschofenig-ecrit-security-threats-01 (work in Emergency Calling", draft-taylor-ecrit-security-threats-01 (work
progress), July 2005. in progress), December 2005.
[4] Schulzrinne, H., "A Uniform Resource Name (URN) for Services",
draft-schulzrinne-sipping-service-01 (work in progress),
October 2005.
11.2. Informative References 11.2. Informative References
[4] Charlton, N., Gasson, M., Gybels, G., Spanner, M., and A. van [5] Charlton, N., Gasson, M., Gybels, G., Spanner, M., and A. van
Wijk, "User Requirements for the Session Initiation Protocol Wijk, "User Requirements for the Session Initiation Protocol
(SIP) in Support of Deaf, Hard of Hearing and Speech-impaired (SIP) in Support of Deaf, Hard of Hearing and Speech-impaired
Individuals", RFC 3351, August 2002. Individuals", RFC 3351, August 2002.
[5] Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and J. [6] Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and J.
Polk, "Geopriv Requirements", RFC 3693, February 2004. Polk, "Geopriv Requirements", RFC 3693, February 2004.
[6] Hellstrom, G. and P. Jones, "RTP Payload for Text Conversation", [7] Hellstrom, G. and P. Jones, "RTP Payload for Text Conversation",
RFC 4103, June 2005. RFC 4103, June 2005.
[7] Wijk, A., "Framework of requirements for real-time text [8] Wijk, A., "Framework of requirements for real-time text
conversation using SIP", draft-ietf-sipping-toip-03 (work in conversation using SIP", draft-ietf-sipping-toip-03 (work in
progress), September 2005. progress), September 2005.
Authors' Addresses Authors' Addresses
Henning Schulzrinne Henning Schulzrinne
Columbia University Columbia University
Department of Computer Science Department of Computer Science
450 Computer Science Building 450 Computer Science Building
New York, NY 10027 New York, NY 10027
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