< draft-ietf-ecrit-requirements-12.txt   draft-ietf-ecrit-requirements-13.txt >
ECRIT H. Schulzrinne ECRIT H. Schulzrinne
Internet-Draft Columbia U. Internet-Draft Columbia U.
Expires: February 27, 2007 R. Marshall, Ed. Intended status: Standards Track R. Marshall, Ed.
TCS Expires: September 3, 2007 TCS
August 26, 2006 March 2, 2007
Requirements for Emergency Context Resolution with Internet Requirements for Emergency Context Resolution with Internet
Technologies Technologies
draft-ietf-ecrit-requirements-12 draft-ietf-ecrit-requirements-13
Status of this Memo Status of this Memo
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Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2006). Copyright (C) The IETF Trust (2007).
Abstract Abstract
This document defines terminology and enumerates requirements for the This document defines terminology and enumerates requirements for the
context resolution of emergency calls placed by the public using context resolution of emergency calls placed by the public using
voice-over-IP (VoIP) and general Internet multimedia systems, where voice-over-IP (VoIP) and general Internet multimedia systems, where
Internet protocols are used end-to-end. Internet protocols are used end-to-end.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Terminology . . . . . . . . . . . . . . . . . . 5 2. Requirements Terminology . . . . . . . . . . . . . . . . . . . 5
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 6 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1 Emergency Services . . . . . . . . . . . . . . . . . . . . 6 3.1. Emergency Services . . . . . . . . . . . . . . . . . . . . 6
3.2 Service Providers . . . . . . . . . . . . . . . . . . . . 6 3.2. Service Providers . . . . . . . . . . . . . . . . . . . . 6
3.3 Actors . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.3. Actors . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.4 Call Routing Entities . . . . . . . . . . . . . . . . . . 7 3.4. Call Routing Entities . . . . . . . . . . . . . . . . . . 7
3.5 Location . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.5. Location . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.6 Identifiers, Numbers and Dial Strings . . . . . . . . . . 8 3.6. Identifiers, Numbers and Dial Strings . . . . . . . . . . 8
3.7 Mapping . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.7. Mapping . . . . . . . . . . . . . . . . . . . . . . . . . 9
4. Basic Actors . . . . . . . . . . . . . . . . . . . . . . . . 11 4. Basic Actors . . . . . . . . . . . . . . . . . . . . . . . . . 11
5. High-Level Requirements . . . . . . . . . . . . . . . . . . 13 5. High-Level Requirements . . . . . . . . . . . . . . . . . . . 13
6. Identifying the Caller's Location . . . . . . . . . . . . . 15 6. Identifying the Caller's Location . . . . . . . . . . . . . . 15
7. Emergency Service Identifier . . . . . . . . . . . . . . . . 18 7. Emergency Service Identifier . . . . . . . . . . . . . . . . . 18
8. Mapping Protocol . . . . . . . . . . . . . . . . . . . . . . 21 8. Mapping Protocol . . . . . . . . . . . . . . . . . . . . . . . 21
9. Security Considerations . . . . . . . . . . . . . . . . . . 26 9. Security Considerations . . . . . . . . . . . . . . . . . . . 25
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . 27 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26
11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 28 11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 27
12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 29 12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 28
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 30 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 29
13.1 Normative References . . . . . . . . . . . . . . . . . . 30 13.1. Normative References . . . . . . . . . . . . . . . . . . . 29
13.2 Informative References . . . . . . . . . . . . . . . . . 30 13.2. Informative References . . . . . . . . . . . . . . . . . . 29
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 31 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 31
Intellectual Property and Copyright Statements . . . . . . . 32 Intellectual Property and Copyright Statements . . . . . . . . . . 32
1. Introduction 1. Introduction
Users of both voice-centric (telephone-like) and non-voice services Users of both voice-centric (telephone-like) and non-voice services
such as text communication for hearing disabled users (RFC 3351 [3]) such as text communication for hearing disabled users (RFC 3351
expect to be able to initiate a request for help in case of an [RFC3351]) expect to be able to initiate a request for help in case
emergency. 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 voice, network (PSTN) are not appropriate to handle evolving IP-based voice,
text and real-time multimedia communications. This document outlines text and real-time multimedia communications. This document outlines
the key requirements that IP-based end systems and network elements, the key requirements that IP-based end systems and network elements,
such as Session Initiation Protocol (SIP) [2] proxies, need to such as Session Initiation Protocol (SIP) [RFC3261] proxies, need to
satisfy in order to provide emergency call services, which at a satisfy in order to provide emergency call services, which at a
minimum, offer the same functionality as existing PSTN services, with minimum, offer the same functionality as existing PSTN services, with
the additional overall goal of making emergency calling more robust, the additional overall goal of making emergency calling more robust,
less costly to implement, and multimedia-capable. less costly to implement, and multimedia-capable.
This document only focuses on end-to-end IP-based calls, i.e., where 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 the emergency call originates from an IP end system and terminates in
an IP-capable PSAP, conveyed entirely over an IP network. an IP-capable PSAP, conveyed entirely over an IP network.
We first define terminology in Section 3. The document then outlines We first define terminology in Section 3. The document then outlines
various functional issues which relate to placing an IP-based various functional issues which relate to placing an IP-based
emergency call, including a description of baseline requirements emergency call, including a description of baseline requirements
(Section 5), identification of the emergency caller's location (Section 5), identification of the emergency caller's location
(Section 6), use of a service identifier to declare a call to be an (Section 6), use of a service identifier to declare a call to be an
emergency call (Section 7), and finally, the mapping function emergency call (Section 7), and finally, the mapping function
required to route the call to the appropriate PSAP (Section 8). required to route the call to the appropriate PSAP (Section 8).
The primary purpose of the mapping protocol is to produce a PSAP URI 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, drawn from a preferred set of URI schemes such as SIP or SIPS URIs,
based on both location information [8] and a service identifier in based on both location information [RFC4119] and a service identifier
order to facilitate the IP end-to-end completion of an emergency in order to facilitate the IP end-to-end completion of an emergency
call. call.
Aside from obtaining a PSAP URI, the mapping protocol is useful for Aside from obtaining a PSAP URI, the mapping protocol is useful for
obtaining other information as well. There may be a case, for obtaining other information as well. There may be a case, for
example, where an appropriate emergency number is not known, only example, where an appropriate emergency number is not known, only
location. The mapping protocol can then return a geographically location. The mapping protocol can then return a geographically
appropriate emergency number based on the input. appropriate emergency number based on the input.
Since some PSAPs may not immediately support IP, or because some user Since some PSAPs may not immediately support IP, or because some user
equipment (UE) may not initially support emergency service equipment (UE) may not initially support emergency service
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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 requirements for messaging outlined within this document, is
considered to be outside the scope of this document. considered to be outside the scope of this document.
Location is required for two separate purposes, first, to support the Location is required for two separate purposes, first, to support the
routing of the emergency call to the appropriate PSAP and second, to routing of the emergency call to the appropriate PSAP and second, to
display the caller's location to the call taker to help in display the caller's location to the call taker to help in
dispatching emergency assistance to the appropriate location. dispatching emergency assistance to the appropriate location.
This latter use, the display of location information to the PSAP, is
orthogonal to the mapping protocol, and is outside the scope of this
document.
2. Requirements Terminology 2. Requirements Terminology
In this document, the key words "MUST", "MUST NOT", "REQUIRED", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
and "OPTIONAL" are to be interpreted as described in RFC 2119 [1], document are to be interpreted as described in RFC 2119 [RFC2119],
with the qualification that unless otherwise stated these words apply with the important qualification that, unless otherwise stated, these
to the design of the mapping protocol, not its implementation or terms apply to the design of the mapping protocol, not its
application. implementation or application.
3. Terminology 3. Terminology
3.1 Emergency Services 3.1. Emergency Services
Basic emergency service: Basic emergency service allows a caller to Basic emergency service: Basic emergency service allows a caller 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 the call taker asking the caller. caller, except by the call taker asking the caller.
Enhanced emergency service: In enhanced emergency service, the PSAP Enhanced emergency service: In enhanced emergency service, the PSAP
call taker can determine the caller's current location. call taker can determine the caller's current location.
3.2 Service Providers 3.2. Service Providers
Internet Attachment Provider (IAP): An organization that provides Internet Access Provider (IAP): An organization that provides
physical and data link (layer 2) network connectivity to its physical and data link (layer 2) network connectivity to its
customers or users, e.g., through digital subscriber lines, cable customers or users, e.g., through digital subscriber lines, cable
TV plants, Ethernet, leased lines or radio frequencies. Examples TV plants, Ethernet, leased lines or radio frequencies. Examples
of such organizations include telecommunication carriers, of such organizations include telecommunication carriers,
municipal utilities, larger enterprises with their own network municipal utilities, larger enterprises with their own network
infrastructure, and government organizations such as the military. infrastructure, and government 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 data link (layer-2) or may not provide the physical-layer and data link (layer-2)
connectivity, such as fiber or Ethernet, i.e., it may or may not connectivity, such as fiber or Ethernet, i.e., it may or may not
play the role of an IAP. play the role of an IAP.
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
"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 more general than a Voice Service Provider, since An ASP is more general than a Voice Service Provider, since
emergency calls may use other media beyond voice, including text emergency calls may use other media beyond voice, including text
and video. For a particular user, the ASP may or may not be the and video. For a particular user, the ASP may or may not be the
same organization as his IAP or ISP. same organization as his IAP or ISP.
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. In this as call routing, a SIP URI, or PSTN termination. In this
document, unless noted otherwise, any reference to "Voice Service document, unless noted otherwise, any reference to "Voice Service
Provider" or "VSP" may be used interchangeably with "Application/ Provider" or "VSP" may be used interchangeably with "Application/
Voice Service Provider" or "ASP/VSP". Voice Service Provider" or "ASP/VSP".
3.3 Actors 3.3. Actors
(Emergency) caller: The term "caller" or "emergency caller" refer to (Emergency) caller: The term "caller" or "emergency caller" refer to
the person placing an emergency call or sending an emergency the person placing an emergency call or sending an emergency
instant message (IM). instant message (IM).
User Equipment (UE): User equipment is the device or software User Equipment (UE): User equipment is the device or software
operated by the caller to place an emergency call. A SIP user operated by the caller to place an emergency call. A SIP user
agent (UA) is an example of a UE. agent (UA) is an example of a UE.
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
caller and thus do not concern us here. caller and thus do not concern us here.
3.4 Call Routing Entities 3.4. Call Routing Entities
Emergency Service Routing Proxy (ESRP): An ESRP is an emergency call Emergency Service Routing Proxy (ESRP): An ESRP is an emergency call
routing support entity that invokes the location-to-PSAP URI routing support entity that invokes the location-to-PSAP URI
mapping, to return either the URI for the appropriate PSAP, or the mapping function, to return an appropriate PSAP URI, or the URI
URI for another ESRP. (In a SIP system, the ESRP would typically for another ESRP. Client mapping requests could also be performed
be a SIP proxy, but may also be a back-to-back user agent by a number of entities, including entities that instantiate the
(B2BUA)). SIP proxy role and the SIP user agent client role.
Public Safety Answering Point (PSAP): Physical location where Public Safety Answering Point (PSAP): 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
PSAPs support the receipt of emergency calls over IP, using PSAPs support the receipt of emergency calls over IP, using
appropriate application layer protocols such as SIP for call appropriate application layer protocols such as SIP for call
signaling and RTP for media. signaling and RTP for media.
3.5 Location 3.5. Location
Location: A geographic identification assigned to a region or feature Location: A geographic identification assigned to a region or
based on a specific coordinate system, or by other precise feature based on a specific coordinate system, or by other precise
information such as a street number and name. It can be either a information such as a street number and name. It can be either a
civic or geographic location. civic or geographic location.
Civic location: A described location based on some reference system, Civic location: A described location based on some reference system,
such as jurisdictional region or postal delivery grid. A street such as jurisdictional region or postal delivery grid. A street
address is a common example of a civic location. address is a common example of a civic location.
Geographic location: A reference to a point which is able to be Geographic location: A reference to a point which is able to be
located as described by a set of defined coordinates within a located as described by a set of defined coordinates within a
geographic coordinate system, such as latitude and longitude geographic coordinate system, such as latitude and longitude
within the WGS-84 datum. For example, 2-D geographic location is within the WGS-84 datum. For example, 2-D geographic location is
defined as an (x,y) coordinate value pair according to the defined as an (x,y) coordinate value pair according to the
distance north or south of the equator and east or west of the distance north or south of the equator and east or west of the
prime meridian. 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 system (e.g., United States Postal Address or location reference system (e.g., United States Postal Address or
the WGS-84 datum) and can be mapped to one or more PSAPs. While the WGS-84 datum) and can be mapped to one or more PSAPs. While
it is desirable to determine that a location exists, validation it is desirable to determine that a location exists, validation
may not ensure that such a location exists, but rather may only may not ensure that such a location exists, but rather may only
ensure that the location falls within some range of known values. ensure that the location falls within some range of known values.
Location validation ensures that a location is able to be Location validation ensures that a location is able to be
referenced for mapping, but makes no assumption about the referenced for mapping, but makes no assumption about the
association between the caller and the caller's location. association between the caller and the caller's location.
3.6 Identifiers, Numbers and Dial Strings 3.6. Identifiers, Numbers and Dial Strings
(Emergency) service number: The (emergency) service number is a (Emergency) service number: The (emergency) service number is a
string of digits used to reach the (emergency) service. The string of digits used to reach the (emergency) service. The
emergency service number is often just called the emergency emergency service number is often just called the emergency
number. It is the number typically dialed on devices directly number. It is the number typically dialed on devices directly
connected to the PSTN and the number reserved for emergency calls connected to the PSTN and the number reserved for emergency calls
by national or regional numbering authorities. It only contains by national or regional numbering authorities. It only contains
the digits 0 through 9, # and *. The service number may depend on the digits 0 through 9, # and *. The service number may depend on
the location of the caller. For example, the general emergency the location of the caller. For example, the general emergency
service number in the United States is 911 and the poison control service number in the United States is 911 and the poison control
service number is 18002221222. In most cases, the service number service number is 18002221222. In most cases, the service number
and dial string are the same; they may differ in some private and dial string are the same; they may differ in some private
phone networks. A service number may be carried in tel URLs [6], phone networks. A service number may be carried in tel URLs
along with a context identifier. In the North American numbering [RFC3966], along with a context identifier. In the North American
plan, some service numbers are also three-digit N11 or service numbering plan, some service numbers are also three-digit N11 or
codes, but not all emergency numbers have three digits. A caller service codes, but not all emergency numbers have three digits. A
may have to dial a service dial string (below) that differs from caller may have to dial a service dial string (below) that differs
the service number when using a PBX. from the service number when using a PBX.
(Emergency) service dial string: The service dial string identifies (Emergency) service dial string: The service dial string identifies
the string of digits that a caller must dial to reach a particular the string of digits that a caller must dial to reach a particular
(emergency) service. In devices directly connected to the PSTN, (emergency) service. In devices directly connected to the PSTN,
the service dial string is the same as the service number and may the service dial string is the same as the service number and may
thus depend on the location of the caller. However, in private thus depend on the location of the caller. However, in private
phone networks, such as in PBXs, the service dial string consists phone networks, such as in PBXs, the service dial string consists
of a dialing prefix to reach an outside line, followed by the of a dialing prefix to reach an outside line, followed by the
emergency number. For example, in a hotel, the dial string for emergency number. For example, in a hotel, the dial string for
emergency services in the United States might be 9911. Dial emergency services in the United States might be 9911. Dial
strings may contain indications of pauses or wait-for-secondary- strings may contain indications of pauses or wait-for-secondary-
dial-tone indications. Service dial strings are outside the scope dial-tone indications. Service dial strings are outside the scope
of this document. of this document.
(Emergency) service identifier: The (emergency) service identifier (Emergency) service identifier: The (emergency) service identifier
describes the emergency service, independent of the user interface describes the emergency service, independent of the user interface
mechanism, the signaling protocol that is used to reach the mechanism, the signaling protocol that is used to reach the
service, or the caller's geographic location. It is a protocol service, or the caller's geographic location. It is a protocol
constant and used within the mapping and signaling protocols. An constant and used within the mapping and signaling protocols. An
example is the service URN [11]. example is the service URN [I-D.ietf-ecrit-service-urn].
(Emergency) service URL: The service URL is a protocol-specific (Emergency) service URL: The service URL is a protocol-specific
(e.g., SIP) or protocol-agnostic (e.g., im: [5]) contains the (e.g., SIP) or protocol-agnostic (e.g., im: [RFC3860]) identifier
address of the PSAP or other emergency service. It depends on the which contains the address of the PSAP or other emergency service.
specific signaling or data transport protocol used to reach the It depends on the specific signaling or data transport protocol
emergency service. used to reach the emergency service.
Service URN: A service URN is an implementation of a service Service URN: A service URN is an implementation of a service
identifier, which can be applied to both emergency and non- identifier, which can be applied to both emergency and non-
emergency contexts, e.g., urn:service:sos or emergency contexts, e.g., urn:service:sos or
urn:service:counseling. Within this document, service URNs are urn:service:counseling. Within this document, service URNs are
referred to as 'emergency service URNs' [11]. referred to as 'emergency service URNs'
[I-D.ietf-ecrit-service-urn].
Home emergency number: A home emergency number is the emergency Home emergency number: A home emergency number is the emergency
number valid at the caller's customary home location, e.g., his number valid at the caller's customary home location, e.g., his
permanent residence. The home location may or may not coincide permanent residence. The home location may or may not coincide
with the service area of the caller's VSP. with the service area of the caller's VSP.
Home emergency dial string: A home dial string is the dial string Home emergency dial string: A home dial string is the dial string
valid at the caller's customary home location, e.g., his permanent valid at the caller's customary home location, e.g., his permanent
residence. residence.
Visited emergency number: A visited emergency number is the emergency Visited emergency number: A visited emergency number is the
number valid at the caller's current physical location. We emergency number valid at the caller's current physical location.
distinguish the visited emergency number if the caller is We distinguish the visited emergency number if the caller is
traveling outside his home region. traveling outside his home region.
Visited emergency dial string: A visited emergency dial string is the Visited emergency dial string: A visited emergency dial string is
dial string number valid at the caller's current physical the dial string number valid at the caller's current physical
location. location.
3.7 Mapping 3.7. Mapping
Mapping: Mapping is the process of resolving a location to one or Mapping: Mapping is the process of resolving a location to one or
more PSAP URIs which directly identify a PSAP, or point to an more PSAP URIs which directly identify a PSAP, or point to an
intermediary which knows about a PSAP and that is designated as intermediary which knows about a PSAP and that is designated as
responsible for serving that location. responsible for serving that location.
Mapping client: A mapping client interacts with the mapping server to Mapping client: A mapping client interacts with the mapping server
learn one or more PSAP URIs for a given location. to learn one or more PSAP URIs for a given location.
Mapping protocol: A protocol used to convey the mapping request and Mapping protocol: A protocol used to convey the mapping request and
response. response.
Mapping server: The mapping server holds information about the Mapping server: The mapping server holds information about the
location-to-PSAP URI mapping. location-to-PSAP URI mapping.
Mapping service: A network service which uses a distributed mapping Mapping service: A network service which uses a distributed mapping
protocol to perform a mapping between a location and a PSAP, or protocol to perform a mapping between a location and a PSAP, or
intermediary which knows about the PSAP, and is used to assist in intermediary which knows about the PSAP, and is used to assist in
routing an emergency call. routing an emergency call.
4. Basic Actors 4. Basic Actors
In order to support emergency services covering a large physical In order to support emergency services covering a large physical
area, various infrastructure elements are necessary, including area, various infrastructure elements are necessary, including
Internet Attachment Providers (IAPs), Application/Voice Service Internet Access Providers (IAPs), Application/Voice Service Providers
Providers (ASP/VSPs), Emergency Service Routing Proxy (ESRP) (ASP/VSPs), Emergency Service Routing Proxy (ESRP) providers, mapping
providers, mapping service providers, and PSAPs. service providers, and PSAPs.
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 |Access | | |
+-----------+ |Provider | | Mapping | +-----------+ |Provider | | Mapping |
| | | (3) | | Service | | | | (3) | | Service |
| Emergency |<---+-----------------+-->| | | Emergency |<---+-----------------+-->| |
| Caller | | (2) | +-----------+ | Caller | | (2) | +-----------+
| |<---+-------+ | ^ | |<---+-------+ | ^
+-----------+ | +----|---------+------+ | +-----------+ | +----|---------+------+ |
^ | | Location | | | ^ | | Location | | |
| | | Information<-+ | | | | | Information<-+ | |
| +--+--------------+ |(5) | | (6) | +--+--------------+ |(5) | | (6)
| | | | | | | | | |
skipping to change at page 12, line 5 skipping to change at page 12, line 5
|Service | |Service |
|Provider | |Provider |
+---------------------+ +---------------------+
Figure 1: Framework for emergency call routing Figure 1: Framework for emergency call routing
Figure 1 shows the interaction between the entities involved in the Figure 1 shows the interaction between the entities involved in the
call. There are a number of different deployment choices, as can be call. There are a number of different deployment choices, as can be
easily seen from the figure. easily seen from the figure.
Is the Internet Attachment Provider also the Application/Voice Is the Internet Access Provider also the Application/Voice Service
Service Provider? In the Internet today these roles are typically Provider? In the Internet today these roles are typically provided
provided by different entities. As a consequence, the Application/ by different entities. As a consequence, the Application/Voice
Voice Service Provider is typically not able to directly determine Service Provider is typically not able to directly determine the
the physical location of the emergency caller. physical location of the emergency caller.
The overlapping squares in the figure indicate that some functions The overlapping squares in the figure indicate that some functions
can be collapsed into a single entity. As an example, the can be collapsed into a single entity. As an example, the
Application/Voice Service Provider might be the same entity as the Application/Voice Service Provider might be the same entity as the
Internet Attachment Provider. There is, however, no requirement that Internet Access Provider. There is, however, no requirement that
this must be the case. Additionally, we consider that end systems this must be the case. Additionally, we consider that end systems
might act as their own ASP/VSP, e.g., either for enterprises or for might act as their own ASP/VSP, e.g., either for enterprises or for
residential users. residential users.
Various potential interactions between the entities depicted in Various potential interactions between the entities depicted in
Figure 1 are described below: Figure 1 are described below:
1. Location information might be available to the end host itself. 1. Location information might be available to the end host itself.
2. Location information might, however, also be obtained from the 2. Location information might, however, also be obtained from the
Internet Attachment Provider. Internet Access Provider.
3. The emergency caller might need to consult a mapping service to 3. The emergency caller might need to consult a mapping service to
determine the PSAP (or other relevant information) that is determine the PSAP (or other relevant information) that is
appropriate for the physical location of the emergency caller, appropriate for the physical location of the emergency caller,
possibly considering other attributes such as appropriate possibly considering other attributes such as appropriate
language support by the emergency call taker. language support by the emergency call taker.
4. The emergency caller might get assistance for emergency call 4. The emergency caller might get assistance for emergency call
routing by infrastructure elements that are emergency call routing by infrastructure elements that are emergency call
routing support entities, such as an Emergency Service Routing routing support entities, such as an Emergency Service Routing
skipping to change at page 13, line 10 skipping to change at page 13, line 10
8. The emergency caller may interact directly with the PSAP, where 8. The emergency caller may interact directly with the PSAP, where
the UE invokes mapping, and initiates a connection, without the UE invokes mapping, and initiates a connection, without
relying on any intermediary emergency call routing support relying on any intermediary emergency call routing support
entities. entities.
5. High-Level Requirements 5. 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/Voice service provider existence: The initiation of Re1. Application/Voice service provider existence: The initiation
an IP-based emergency call SHOULD NOT assume the existence of an of an IP-based emergency call SHOULD NOT assume the existence of
Application/Voice Service Provider (ASP/VSP). an Application/Voice Service Provider (ASP/VSP).
Motivation: The caller may not have an application/voice service Motivation: The caller may not have an 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
and run its own SIP proxy server for that domain. On a larger and run its own SIP proxy server for that domain. On a larger
scale, a university might provide voice services to its students scale, a university might provide voice services to its students
and staff, but might not be a telecommunication provider. and staff, but might not be a telecommunication provider.
Re2. International applicability: Regional, political and Re2. International applicability: Regional, political and
organizational aspects MUST be considered during the design of organizational aspects MUST be considered during the design of
protocols and protocol extensions which support IP-based emergency protocols and protocol extensions which support IP-based emergency
calls. calls.
Motivation: It must be possible for a device or software developed Motivation: It must be possible for a device or software developed
or purchased in one country to place emergency calls in another or purchased in one country to place emergency calls in another
country. System components should not be biased towards a country. System components should not be biased towards a
particular set of emergency numbers or languages. Also, different particular set of emergency numbers or languages. Also, different
countries have evolved different ways of organizing emergency countries have evolved different ways of organizing emergency
services, e.g., either centralizing them or having smaller services, e.g., either centralizing them or having smaller
regional subdivisions such as United States counties or regional subdivisions such as United States counties or
municipalities handle emergency calls within their jurisdiction. municipalities handle emergency calls within their jurisdiction.
Re3. Distributed administration: Deployment of IP-based emergency Re3. Distributed administration: Deployment of IP-based emergency
services MUST NOT depend on a single central administrative services MUST NOT depend on a single central administrative
authority. authority.
Motivation: The design of the mapping protocol must make it Motivation: The design of the mapping protocol must make it
possible to deploy and administer emergency calling features on a possible to deploy and administer emergency calling features on a
regional or national basis without requiring coordination with regional or national basis without requiring coordination with
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, ASP/VSPs, IAPs or other participants. PSAPs, ASP/VSPs, IAPs or other participants.
Re4. Multi-mode communication: IP-based emergency calls MUST support Re4. Multi-mode communication: IP-based emergency calls MUST
multiple communication modes, including, for example, audio, video support multiple communication modes, including, for example,
and text. audio, video and text.
Motivation: Within the PSTN, voice and text telephony (often Motivation: Within the PSTN, voice and text telephony (often
called TTY or text-phone in North America) are the only commonly called TTY or text-phone in North America) are the only commonly
supported media. Emergency calling must support a variety of supported media. Emergency calling must support a variety of
media. Such media should include voice, conversational text (RFC media. Such media should include voice, conversational text (RFC
4103 [7]), instant messaging and video. 4103 [RFC4103]), instant messaging and video.
Re5. Mapping result usability: The mapping protocol MUST return one Re5. Mapping result usability: The mapping protocol MUST return one
or more URIs that are usable within a standard signaling protocol or more URIs that are usable within a standard signaling protocol
(i.e., without special emergency extensions). (i.e., without special emergency extensions).
Motivation: For example, a SIP URI which is returned by the Motivation: For example, a SIP URI which is returned by the
mapping protocol needs to be usable by any SIP capable phone mapping protocol needs to be usable by any SIP capable phone
within a SIP initiated emergency call. This is in contrast to a within a SIP initiated emergency call. This is in contrast to a
"special purpose" URI, which may not be recognizable by a legacy "special purpose" URI, which may not be recognizable by a legacy
SIP device. SIP device.
Re6. PSAP URI accessibility: The mapping protocol MUST support Re6. PSAP URI accessibility: The mapping protocol MUST support
interaction between the client and server where no enrollment to a interaction between the client and server where no enrollment to a
mapping service exists or is required. mapping service exists or is required.
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 ASP/VSP. require use of a specific ISP or ASP/VSP.
Re7. Common data structures and formats: The mapping protocol SHOULD Re7. Common data structures and formats: The mapping protocol
support common formats for location data. SHOULD support common formats for location data.
Motivation: Location databases should not need to be transformed Motivation: Location databases should not need to be transformed
or modified in any unusual or unreasonable way in order for the or modified in any unusual or unreasonable way in order for the
mapping protocol to use the data. For example, a database which mapping protocol to use the data. For example, a database which
contains civic addresses used by location servers may be used for contains civic addresses used by location servers may be used for
multiple purposes and applications beyond emergency service multiple purposes and applications beyond emergency service
location-to-PSAP URI mapping. location-to-PSAP URI mapping.
Re8. Anonymous mapping: The mapping protocol MUST NOT require the Re8. Anonymous mapping: The mapping protocol MUST NOT require the
true identity of the target for which the location information is true identity of the target for which the location information is
attributed. attributed.
Motivation: Ideally, no identity information is provided via the Motivation: Ideally, no identity information is provided via the
mapping protocol. Where identity information is provided, it may mapping protocol. Where identity information is provided, it may
be in the form of an unlinked pseudonym (RFC 3693 [4]). be in the form of an unlinked pseudonym (RFC 3693 [RFC3693]).
6. Identifying the Caller's Location 6. Identifying the Caller's Location
Location can either be provided directly (by value), or via a pointer Location can either be provided directly (by value), or via a pointer
(by reference), and represents either a civic location, or a (by reference), and represents either a civic location, or a
geographic location. An important question is how and when to attach geographic location. An important question is how and when to attach
location information to the VoIP emergency signaling messages. In location information to the VoIP emergency signaling messages. In
general, we can distinguish three modes of operation of how a general, we can distinguish three modes of operation of how a
location is associated with an emergency call: location is associated with an emergency call:
UA-inserted: The caller's user agent inserts the location information UA-inserted: The caller's user agent inserts the location
into the call signaling message. information into the call signaling message.
UA-referenced: The caller's user agent provides a pointer (i.e., a UA-referenced: The caller's user agent provides a pointer (i.e., a
location reference), via a permanent or temporary identifier, to location reference), via a permanent or temporary identifier, to
the location information, which is stored by a location server the location information, which is stored by a location server
somewhere else and then retrieved by the PSAP, ESRP, or other somewhere else and then retrieved by the PSAP, ESRP, or other
authorized entity. authorized entity.
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.
The following requirements apply: The following requirements apply:
Lo1. Reference datum: The mapping protocol MUST support the WGS-84 Lo1. Reference datum: The mapping protocol MUST support the WGS-84
coordinate reference system and MAY support other coordinate coordinate reference system and MAY support other coordinate
reference systems. reference systems.
Motivation: Though many different datums exist around the world, Motivation: Though many different datums exist around the world,
this document recommends the WGS-84 datum since it is designed to this document recommends the WGS-84 datum since it is designed to
describe the whole earth, rather than a single continent or other describe the whole earth, rather than a single continent or other
region, and is commonly used to represent Global Positioning region, and is commonly used to represent Global Positioning
System coordinates. System coordinates.
Lo2. Location delivery by-value: The mapping protocol MUST support Lo2. Location delivery by-value: The mapping protocol MUST support
the delivery of location information using a by-value method, the delivery of location information using a by-value method,
though it MAY also support de-referencing a URL that references a though it MAY also support de-referencing a URL that references a
location object. location object.
Motivation: The mapping protocol is not required to support the Motivation: The mapping protocol is not required to support the
ability to de-reference specific location references. ability to de-reference specific location references.
Lo3. Alternate community names: The mapping protocol MUST support Lo3. Alternate community names: The mapping protocol MUST support
both the jurisdictional community name and the postal community both the jurisdictional community name and the postal community
name fields within the PIDF-LO [8] data. name fields within the PIDF-LO [RFC4119] data.
Motivation: The mapping protocol must accept queries with either Motivation: The mapping protocol must accept queries with either a
a postal or jurisdictional community name field, or both, and postal or jurisdictional community name field, or both, and
provide appropriate responses. If a mapping query contains only provide appropriate responses. If a mapping query contains only
one community name and the database contains both jurisdictional one community name and the database contains both jurisdictional
and postal community names, the mapping protocol response SHOULD and postal community names, the mapping protocol response SHOULD
return both community names. return both community names.
Lo4. Validation of civic location: The mapping protocol MUST support Lo4. Validation of civic location: The mapping protocol MUST
location validation for civic locations (street addresses). support location validation for civic locations (street
addresses).
Motivation: Location validation provides an opportunity to help Motivation: Location validation provides an opportunity to help
ascertain ahead of time whether or not a successful mapping to the ascertain ahead of time whether or not a 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 location data. setup due to invalid location data.
Lo5. Validation resolution: The mapping protocol MUST support the Lo5. Information about location data used for mapping: The mapping
ability to provide ancillary information about the resolution of protocol MUST support the ability to provide ancillary information
location data used to retrieve a PSAP URI. about the resolution of location data used to retrieve a PSAP URI.
Motivation: The mapping server may not use all the data elements Motivation: The mapping server may not use all the data elements
in the provided location information to determine a match, or may in the provided location information to determine a match, or may
be able to find a match based on all of the information except for be able to find a match based on all of the information except for
some specific data elements. The uniqueness of this information some specific data elements. The uniqueness of this information
set may be used to differentiate among emergency jurisdictions. set may be used to differentiate among emergency jurisdictions.
Precision or resolution in the context of this requirement might Precision or resolution in the context of this requirement might
mean, for example, explicit identification of the data elements mean, for example, explicit identification of the data elements
that were used successfully in the mapping. that were used successfully in the mapping.
Lo6. Contact for location problems: The mapping protocol MUST Lo6. Contact for location problems: The mapping protocol MUST
support a mechanism to contact an appropriate authority to resolve support a mechanism to contact an appropriate authority to resolve
mapping-related issues for the queried location. For example, the mapping-related issues for the queried location. For example, the
querier may want to report problems with the response values or querier may want to report problems with the response values or
indicate that the mapping database is mistaken on declaring a indicate that the mapping database is mistaken on declaring a
civic location as non-existent. civic location as non-existent.
Motivation: Initially, authorities may provide URLs where a human Motivation: Initially, authorities may provide URLs where a human
user can report problems with an address or location. In user can report problems with an address or location. In
addition, web services may be defined to automate such reporting. addition, web services may be defined to automate such reporting.
For example, the querier may wish to report that the mapping For example, the querier may wish to report that the mapping
database may be missing a newly-built or renamed street or house database may be missing a newly-built or renamed street or house
number. number.
Lo7. Limits to validation: Successful validation of a civic location Lo7. Limits to validation: Successful validation of a civic
MUST NOT be required to place an emergency call. location MUST NOT be required to place an emergency call.
Motivation: In some cases, a civic location may not be considered Motivation: In some cases, a civic location may not be considered
valid. This fact should not result in the call being dropped or valid. This fact should not result in the call being dropped or
rejected by any entity along the call setup signaling path to the rejected by any entity along the call setup signaling path to the
PSAP. PSAP.
Lo8. 3D sensitive mapping: The mapping protocol MUST implement Lo8. 3D sensitive mapping: The mapping protocol MUST implement
support for both 2D and 3D location information, and may accept support for both 2D and 3D location information, and may accept
either a 2D or 3D mapping request as input. either a 2D or 3D mapping request as input.
Motivation: It is expected that queriers may provide either 2D or Motivation: It is expected that queriers may provide either 2D or
3D data. When a 3D request is presented within an area only 3D data. When a 3D request is presented within an area only
defined by 2D data within the mapping server, the mapping result defined by 2D data within the mapping server, the mapping result
would be the same as if the height or altitude coordinate had been would be the same as if the height or altitude coordinate had been
omitted from the mapping request. omitted from the mapping request.
Lo9. Database type indicator: The mapping protocol MAY support a Lo9. Database type indicator: The mapping protocol MAY support a
mechanism which provides an indication describing a specific type mechanism which provides an indication describing a specific type
of location database used. of location database used.
Motivation: It is useful to know the source of the data stored in Motivation: It is useful to know the source of the data stored in
the database used for location validation, either for civic or the database used for location validation, either for civic or
geographic location matching. In the United States, sources of geographic location matching. In the United States, sources of
data could include the United States Postal Service, the Master data could include the United States Postal Service, the Master
Street Address Guide (MSAG) or commercial map data providers. Street Address Guide (MSAG) or commercial map data providers.
7. Emergency Service Identifier 7. Emergency Service Identifier
Emergency service identifiers are protocol constants that allow Emergency service identifiers are protocol constants that allow
protocol entities such as SIP proxy servers to distinguish emergency protocol entities such as SIP proxy servers to distinguish emergency
calls from non-emergency calls and to identify the specific emergency calls from non-emergency calls and to identify the specific emergency
service desired. Emergency service identifiers are a subclass of service desired. Emergency service identifiers are a subclass of
service identifiers that more generally identify services reachable service identifiers that more generally identify services reachable
by callers. An example of a service identifier is the service URN by callers. An example of a service identifier is the service URN
[11], but other identifiers, such as tel URIs [6], may also serve [I-D.ietf-ecrit-service-urn], but other identifiers, such as tel URIs
this role during a transition period. [RFC3966], may also serve this role during a transition period.
Since this document only addresses emergency services, we use the Since this document only addresses emergency services, we use the
terms "emergency service identifier" and "service identifier" terms "emergency service identifier" and "service identifier"
interchangeably. Requirements for these identifiers include: interchangeably. Requirements for these identifiers include:
Id1. Multiple emergency services: The mapping protocol MUST be able Id1. Multiple emergency services: The mapping protocol MUST be able
to distinguish between different emergency services, to distinguish between different emergency services,
differentiated by different service identifiers. differentiated by different service identifiers.
Motivation: Some jurisdictions may offer multiple types of Motivation: Some jurisdictions may offer multiple types of
emergency services that operate independently and can be contacted emergency services that operate independently and can be contacted
directly, for example, fire, police and ambulance services. directly, for example, fire, police and ambulance services.
Id2. Extensible emergency service identifiers: The mapping protocol Id2. Extensible emergency service identifiers: The mapping protocol
MUST support an extensible list of emergency identifiers, though MUST support an extensible list of emergency identifiers, though
it is not required to provide mappings for every possible service. it is not required to provide mappings for every possible service.
Motivation: Extensibility is required since new emergency Motivation: Extensibility is required since new emergency services
services may be introduced over time, either globally or in some may be introduced over time, either globally or in some
jurisdictions. The availability of emergency services depends on jurisdictions. The availability of emergency services depends on
the locations. For example, the Netherlands are unlikely to offer the locations. For example, the Netherlands are unlikely to offer
a mountain rescue service. a mountain rescue service.
Id3. Discovery of emergency number: The mapping protocol MUST be Id3. Discovery of emergency number: The mapping protocol MUST be
able to return the location-dependent emergency number for the able to return the location-dependent emergency number for the
location indicated in the query. location indicated in the query.
Motivation: Users are trained to dial the appropriate emergency Motivation: Users are trained to dial the appropriate emergency
number to reach emergency services. There needs to be a way to number to reach emergency services. There needs to be a way to
figure out the emergency number at the current location of the figure out the emergency number at the current location of the
caller. caller.
Id4. Home emergency number recognition: User equipment MUST be able Id4. Home emergency number recognition: User equipment MUST be able
to translate a home emergency number into an emergency service to translate a home emergency number into an emergency service
identifier. identifier.
Motivation: The UE could be pre-provisioned with the appropriate Motivation: The UE could be pre-provisioned with the appropriate
information in order to perform such a translation or could information in order to perform such a translation or could
discover the emergency number by querying the mapping protocol discover the emergency number by querying the mapping protocol
with its home location. with its home location.
Id5. Emergency number replacement: There SHOULD be support for Id5. Emergency number replacement: There SHOULD be support for
replacement of the emergency number with the appropriate emergency replacement of the emergency number with the appropriate emergency
service identifier for each signaling protocol used for an service identifier for each signaling protocol used for an
emergency call, based on local conventions, regulations, or emergency call, based on local conventions, regulations, or
preference (e.g., as in the case of an enterprise). preference (e.g., as in the case of an enterprise).
Motivation: Any signaling protocol requires the use of some Motivation: Any signaling protocol requires the use of some
identifier to indicate the called party, and the user equipment identifier to indicate the called party, and the user equipment
may lack the capability to determine the actual service URL (PSAP may lack the capability to determine the actual service URL (PSAP
URI). The use of local conventions may be required as a URI). The use of local conventions may be required as a
transition mechanism. Since relying on recognizing local transition mechanism. Since relying on recognizing local
numbering conventions makes it difficult for devices to be used numbering conventions makes it difficult for devices to be used
outside their home context and for external devices to be outside their home context and for external devices to be
introduced into a network, protocols should use standardized introduced into a network, protocols should use standardized
emergency service identifiers. emergency service identifiers.
Id6. Emergency service identifier marking: Signaling protocols MUST Id6. Emergency service identifier marking: Signaling protocols MUST
support emergency service identifiers to mark a call as an support emergency service identifiers to mark a call as an
emergency call. emergency call.
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. This marking local variant of a logical emergency address. This marking
mechanism is related to, but independent of, marking calls for mechanism is related to, but independent of, marking calls for
prioritized call handling [9]. prioritized call handling [RFC4412].
Id7. Handling unrecognized emergency service identifiers: There MUST Id7. Handling unrecognized emergency service identifiers: There
be support for calls which are initiated as emergency calls even MUST be support for calls which are initiated as emergency calls
if the specific emergency service requested is not recognized by even if the specific emergency service requested is not recognized
the ESRP. Such calls will then be routed to a generic emergency by the ESRP. Such calls will then be routed to a generic
service. emergency service.
Motivation: Fallback routing allows new emergency services to be Motivation: Fallback routing allows new emergency services to be
introduced incrementally, while avoiding non-routable emergency introduced incrementally, while avoiding non-routable emergency
calls. For example, a call for marine rescue services would be calls. For example, a call for marine rescue services would be
routed to a general PSAP if the caller's location does not offer routed to a general PSAP if the caller's location does not offer
marine rescue services yet. marine rescue services yet.
Id8. Return fallback service identifier: The mapping protocol must Id8. Return fallback service identifier: The mapping protocol must
be able to report back the actual service mapped if the mapping be able to report back the actual service mapped if the mapping
protocol substitutes another service for the one requested. protocol substitutes another service for the one requested.
Motivation: A mapping server may be configured to automatically Motivation: A mapping server may be configured to automatically
look up the PSAP for another service if the user-requested service look up the PSAP for another service if the user-requested service
is not available for that location. For example, if there is no is not available for that location. For example, if there is no
marine rescue service, the mapping protocol might return the PSAP marine rescue service, the mapping protocol might return the PSAP
URL for general emergencies and include the "urn:service.sos" URL for general emergencies and include the "urn:service.sos"
identifier in the response to alert the querier to that fact. identifier in the response to alert the querier to that fact.
Id9. Discovery of visited emergency numbers: There MUST be a Id9. Discovery of visited emergency numbers: There MUST be a
mechanism to allow the end device to learn visited emergency mechanism to allow the end device to learn visited emergency
numbers. numbers.
Motivation: Travelers visiting a foreign country may observe the Motivation: Travelers visiting a foreign country may observe the
local emergency number, e.g., seeing it painted on the side of a local emergency number, e.g., seeing it painted on the side of a
fire truck, and then rightfully expect to be able to dial that fire truck, and then rightfully expect to be able to dial that
emergency number. Similarly, a local "good Samaritan" may use a emergency number. Similarly, a local "good Samaritan" may use a
tourist's cell phone to summon help. tourist's cell phone to summon help.
8. Mapping Protocol 8. Mapping Protocol
There are two basic approaches to invoke the mapping protocol. We There are two basic approaches to invoke the mapping protocol. We
refer to these as caller-based and mediated. In each case, the refer to these as caller-based and mediated. In each case, the
mapping client initiates a request to a mapping server via a mapping mapping client initiates a request to a mapping server via a mapping
protocol. A proposed mapping protocol, LoST, is outlined in [12]. protocol. A proposed mapping protocol, LoST, is outlined in
[I-D.hardie-ecrit-lost].
For caller-based resolution, the caller's user agent invokes the For caller-based resolution, the caller's user agent invokes the
mapping protocol to determine the appropriate PSAP based on the mapping protocol to determine the appropriate PSAP based on the
location provided. The resolution may take place well before the location provided. The resolution may take place well before the
actual emergency call is placed, or at the time of the call. actual emergency call is placed, or at the time of the call.
For mediated resolution, an emergency call routing support entity, For mediated resolution, an emergency call routing support entity,
such as a SIP (outbound) proxy or redirect server invokes the mapping such as a SIP (outbound) proxy or redirect server invokes the mapping
service. service.
Since servers may be used as outbound proxy servers by clients that Since servers may be used as outbound proxy servers by clients that
are not in the same geographic area as the proxy server, any proxy are not in the same geographic area as the proxy server, any proxy
server has to be able to translate any caller location to the server has to be able to translate any caller location to the
appropriate PSAP. (A traveler may, for example, accidentally or appropriate PSAP. (A traveler may, for example, accidentally or
intentionally configure its home proxy server as its outbound proxy intentionally configure its home proxy server as its outbound proxy
server, even while far away from home.) server, even while far away from home.)
Ma1. Baseline query protocol: A mandatory-to-implement protocol MUST Ma1. Baseline query protocol: A mandatory-to-implement protocol
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.
Ma2. Extensible protocol: The mapping protocol MUST be designed to Ma2. Extensible protocol: The mapping protocol MUST be designed to
support the extensibility of location data elements, both for new support the extensibility of location data elements, both for new
and existing fields. and existing 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 ([8]). PIDF-LO ([RFC4119]).
Ma3. Incrementally deployable: The mapping protocol MUST be designed Ma3. Incrementally deployable: The mapping protocol MUST be
to support its incremental deployment. designed to support its incremental deployment.
Motivation: It must not be necessary, for example, to have a Motivation: It must not be necessary, for example, to have a
global street level database before deploying the system. It is global street level database before deploying the system. It is
acceptable to have some misrouting of calls when the database does acceptable to have some misrouting of calls when the database does
not (yet) contain accurate PSAP service area information. not (yet) contain accurate PSAP service area information.
Ma4. Any time mapping: The mapping protocol MUST support the ability Ma4. Any time mapping: The mapping protocol MUST support the
of the mapping function to be invoked at any time, including while ability of the mapping function to be invoked at any time,
an emergency call is in process and before an emergency call is including while an emergency call is in process and before an
initiated. emergency call is initiated.
Motivation: Used as a fallback mechanism only, if a mapping query Motivation: Used as a fallback mechanism only, if a mapping query
fails at emergency call time, it may be advantageous to have prior fails at emergency call time, it may be advantageous to have prior
knowledge of the PSAP URI. This prior knowledge would be obtained knowledge of the PSAP URI. This prior knowledge would be obtained
by performing a mapping query at any time prior to an emergency by performing a mapping query at any time prior to an emergency
call. call.
Ma5. Anywhere mapping: The mapping protocol MUST support the ability Ma5. Anywhere mapping: The mapping protocol MUST support the
to provide mapping information in response to an individual query ability to provide mapping information in response to an
from any (earthly) location, regardless of where the mapping individual query from any (earthly) location, regardless of where
client is located, either geographically or by network location. the mapping client is located, either geographically or by network
location.
Motivation: The mapping client, such as an ESRP, may not Motivation: The mapping client, such as an ESRP, may not
necessarily be anywhere close to the caller or the appropriate necessarily be anywhere close to the caller or the appropriate
PSAP, but must still be able to obtain mapping information. PSAP, but must still be able to obtain mapping information.
Ma6. Appropriate PSAP: The mapping protocol MUST support the routing Ma6. Appropriate PSAP: The mapping protocol MUST support the
of an emergency call to the PSAP responsible for a particular routing of an emergency call to the PSAP responsible for a
geographic area. particular geographic area.
Motivation: Routing to the wrong PSAP will result in delays in Motivation: Routing to the wrong PSAP will result in delays in
handling emergencies as calls are redirected, and therefore will handling emergencies as calls are redirected, and therefore will
also result in inefficient use of PSAP resources at the initial also result in inefficient use of PSAP resources at the initial
point of contact. It is important that the location determination point of contact. It is important that the location determination
mechanism not be fooled by the location of IP telephony gateways mechanism not be fooled by the location of IP telephony gateways
or dial-in lines into a corporate LAN (and dispatch emergency help or dial-in lines into a corporate LAN (and dispatch emergency help
to the gateway or campus, rather than the caller), multi-site LANs to the gateway or campus, rather than the caller), multi-site LANs
and similar arrangements. and similar arrangements.
Ma7. Multiple PSAP URIs: The mapping protocol MUST support a method Ma7. Multiple PSAP URIs: The mapping protocol MUST support a method
to return multiple PSAP URIs which cover the same geographic area. to return multiple PSAP URIs which cover the same geographic area.
Motivation: Different contact protocols (e.g., PSTN via tel URIs Motivation: Different contact protocols (e.g., PSTN via tel URIs
and IP via SIP URIs) may be routed to different PSAPs. Less and IP via SIP URIs) may be routed to different PSAPs. Less
likely, two PSAPs may overlap in their coverage region. likely, two PSAPs may overlap in their coverage region.
Ma8. Single primary URI per contact protocol: Though the mapping Ma8. Single primary URI per contact protocol: Though the mapping
protocol may be able to include multiple URIs in the response, it protocol may be able to include multiple URIs in the response, it
SHOULD return only one primary URI per contact protocol used, so SHOULD return only one primary URI per contact protocol used, so
that clients are not required to select among different targets that clients are not required to select among different targets
for the same contact protocol. for the same contact protocol.
Motivation: There may be two or more URIs returned when multiple Motivation: There may be two or more URIs returned when multiple
contact protocols are available (e.g., SIP and SMS). The client contact protocols are available (e.g., SIP and SMS). The client
may select among multiple contact protocols based on its may select among multiple contact protocols based on its
capabilities, preference settings, or availability. capabilities, preference settings, or availability.
Ma9. URI alternate contact: In addition to returning a primary Ma9. Non-preferred URI schemes: The mapping protocol MAY support
contact, the mapping protocol MUST support the return of a PSAP the return of a less preferred URI scheme, such as a tel URI.
URI or contact method explicitly marked as an alternate contact
for use when a fallback contact is needed.
Motivation: There may be multiple ways to provide addresses of
backup PSAPs, including the mapping protocol, DNS lookup via NAPTR
and SRV, or call routing by SIP proxies.
Ma10. Non-preferred URI schemes: The mapping protocol MAY support
the return of a less preferred URI scheme, such as a tel URI.
Motivation: In order to provide incremental support to non-IP Motivation: In order to provide incremental support to non-IP
PSAPs it may be necessary to be able to complete an emergency call PSAPs it may be necessary to be able to complete an emergency call
via the PSTN. via the PSTN.
Ma11. URI properties: The mapping protocol MUST support the ability Ma10. URI properties: The mapping protocol MUST support the ability
to provide ancillary information about a contact that allows the to provide ancillary information about a contact that allows the
mapping client to determine relevant properties of the PSAP URI. mapping client to determine relevant properties of the PSAP URI.
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 URIs for both, with mapping protocol should then return URIs for both, with
information allowing the querying entity to choose one or the information allowing the querying entity to choose one or the
other. This determination could be made by either an ESRP, based other. This determination could be made by either an ESRP, based
on local policy, or by direct user choice, in the case of caller- on local policy, or by direct user choice, in the case of caller-
based methods. based methods.
Ma12. Mapping referral: The mapping protocol MUST support a Ma11. Mapping referral: The mapping protocol MUST support a
mechanism for the mapping client to contact any mapping server and mechanism for the mapping client to contact any mapping server and
be referred to another mapping server that is more qualified to be referred to another mapping server that is more qualified to
answer the query. answer the query.
Motivation: Referrals help mitigate the impact of incorrect Motivation: Referrals help mitigate the impact of incorrect
configuration that directs a client to the wrong initial mapping configuration that directs a client to the wrong initial mapping
server. server.
Ma13. Split responsibility: The mapping protocol MUST support the Ma12. Split responsibility: The mapping protocol MUST support the
division of data subset handling between multiple mapping servers division of data subset handling between multiple mapping servers
within a single level of a civic location hierarchy. within a single level of a civic location hierarchy.
Motivation: For example, two mapping servers for the same city or Motivation: For example, two mapping servers 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.
Ma14. URL for error reporting: The mapping protocol MUST support the Ma13. URL for error reporting: The mapping protocol MUST support
ability to return a URL that can be used to report a suspected or the ability to return a URL that can be used to report a suspected
known error within the mapping database. or known error within the mapping database.
Motivation: If an error is returned, for example, there needs to Motivation: If an error is returned, for example, there needs to
be a URL which points to a resource which can explain or be a URL which points to a resource which can explain or
potentially help resolve the error. potentially help resolve the error.
Ma15. Resilience to failure: The mapping protocol MUST support a Ma14. Resilience to mapping server failure: The mapping protocol
mechanism which enables the client to fail over to different MUST support a mechanism which enables the client to fail over to
(replica) mapping server. different (replica) mapping server.
Motivation: The failure of a mapping server should not preclude Motivation: The failure of a mapping server should not preclude
the mapping client from receiving an answer to its query. the mapping client from receiving an answer to its query.
Ma16. Traceable resolution: The mapping protocol SHOULD support the Ma15. Traceable resolution: The mapping protocol SHOULD support the
ability of the mapping client to be able to determine the entity ability of the mapping client to be able to determine the entity
or entities that provided the emergency address resolution or entities that provided the emergency address resolution
information. information.
Motivation: To improve reliability and performance, it is Motivation: To improve reliability and performance, it is
important to be able to trace which servers contributed to the important to be able to trace which servers contributed to the
resolution of a query. resolution of a query.
Ma17. Minimal additional delay: Mapping protocol execution SHOULD Ma16. Minimal additional delay: Mapping protocol execution SHOULD
minimize the amount of delay within the overall call-setup time. minimize the amount of delay within the overall call-setup time.
Motivation: Since outbound proxies will likely be asked to Motivation: Since outbound proxies will likely be asked to resolve
resolve the same geographic coordinates repeatedly, a suitable the same geographic coordinates repeatedly, a suitable time-
time-limited caching mechanism should be supported. limited caching mechanism should be supported.
Ma18. Alternate mapping sources: The mapping protocol MUST implement
a mechanism that allows for the retrieval of mapping information
from different sources.
Motivation: This provides the possibility of having available
alternative sources of mapping information when the normal source
is unavailable or unreachable.
Ma19. Freshness indication: The mapping protocol SHOULD support an Ma17. Freshness indication: The mapping protocol SHOULD support an
indicator describing how current the information provided by the indicator describing how current the information provided by the
mapping source is. mapping source is.
Motivation: This is especially useful when an alternate mapping is Motivation: This is especially useful when an alternate mapping is
requested, and alternative sources of mapping data may not have requested, and alternative sources of mapping data may not have
been created or updated with the same set of information or within been created or updated with the same set of information or within
the same timeframe. Differences in currency between mapping data the same timeframe. Differences in currency between mapping data
contained within mapping sources should be minimized. contained within mapping sources should be minimized.
9. Security Considerations 9. Security Considerations
Threats and security requirements are discussed in a separate Threats and security requirements are discussed in a separate
document [10]. document [I-D.ietf-ecrit-security-threats].
10. IANA Considerations 10. IANA Considerations
This document does not require actions by the IANA. This document does not require actions by the IANA.
11. Contributors 11. Contributors
The information in this document is partially derived from text The information in this document is partially derived from text
written by the following contributors: written by the following contributors:
skipping to change at page 30, line 7 skipping to change at page 29, line 7
Michael Haberler, Michael Hammer, Ted Hardie, Gunnar Hellstrom, Michael Haberler, Michael Hammer, Ted Hardie, Gunnar Hellstrom,
Cullen Jennings, Marc Linsner, Rohan Mahy, Patti McCalmont, Don Cullen Jennings, Marc Linsner, Rohan Mahy, Patti McCalmont, Don
Mitchell, John Morris, Andrew Newton, Steve Norreys, Jon Peterson, Mitchell, John Morris, Andrew Newton, Steve Norreys, Jon Peterson,
James Polk, Benny Rodrig, John Rosenberg, Jonathan Rosenberg, John James Polk, Benny Rodrig, John Rosenberg, Jonathan Rosenberg, John
Schnizlein, Shida Schubert, James Seng, Byron Smith, Barbara Stark, Schnizlein, Shida Schubert, James Seng, Byron Smith, Barbara Stark,
Richard Stastny, Tom Taylor, Hannes Tschofenig, and Nate Wilcox for Richard Stastny, Tom Taylor, Hannes Tschofenig, and Nate Wilcox for
their helpful input. their helpful input.
13. References 13. References
13.1 Normative References 13.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
13.2 Informative References 13.2. Informative References
[2] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., [I-D.hardie-ecrit-lost]
Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP: Hardie, T., "LoST: A Location-to-Service Translation
Session Initiation Protocol", RFC 3261, June 2002. Protocol", draft-hardie-ecrit-lost-00 (work in progress),
March 2006.
[3] Charlton, N., Gasson, M., Gybels, G., Spanner, M., and A. van [I-D.ietf-ecrit-security-threats]
Wijk, "User Requirements for the Session Initiation Protocol Taylor, T., "Security Threats and Requirements for
(SIP) in Support of Deaf, Hard of Hearing and Speech-impaired Emergency Call Marking and Mapping",
Individuals", RFC 3351, August 2002. draft-ietf-ecrit-security-threats-03 (work in progress),
July 2006.
[4] Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and J. [I-D.ietf-ecrit-service-urn]
Polk, "Geopriv Requirements", RFC 3693, February 2004. Schulzrinne, H., "A Uniform Resource Name (URN) for
Services", draft-ietf-ecrit-service-urn-05 (work in
progress), August 2006.
[5] Peterson, J., "Common Profile for Instant Messaging (CPIM)", [I-D.ietf-sipping-toip]
RFC 3860, August 2004. Wijk, A. and G. Gybels, "Framework for real-time text over
IP using the Session Initiation Protocol (SIP)",
draft-ietf-sipping-toip-07 (work in progress),
August 2006.
[6] Schulzrinne, H., "The tel URI for Telephone Numbers", RFC 3966, [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
December 2004. A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261,
June 2002.
[7] Hellstrom, G. and P. Jones, "RTP Payload for Text [RFC3351] Charlton, N., Gasson, M., Gybels, G., Spanner, M., and A.
Conversation", RFC 4103, June 2005. van Wijk, "User Requirements for the Session Initiation
Protocol (SIP) in Support of Deaf, Hard of Hearing and
Speech-impaired Individuals", RFC 3351, August 2002.
[8] Peterson, J., "A Presence-based GEOPRIV Location Object [RFC3693] Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and
Format", RFC 4119, December 2005. J. Polk, "Geopriv Requirements", RFC 3693, February 2004.
[9] Schulzrinne, H. and J. Polk, "Communications Resource Priority [RFC3860] Peterson, J., "Common Profile for Instant Messaging
for the Session Initiation Protocol (SIP)", RFC 4412, (CPIM)", RFC 3860, August 2004.
February 2006.
[10] Taylor, T., "Security Threats and Requirements for Emergency [RFC3966] Schulzrinne, H., "The tel URI for Telephone Numbers",
Call Marking and Mapping", draft-ietf-ecrit-security-threats-03 RFC 3966, December 2004.
(work in progress), July 2006.
[11] Schulzrinne, H., "A Uniform Resource Name (URN) for Services", [RFC4103] Hellstrom, G. and P. Jones, "RTP Payload for Text
draft-ietf-ecrit-service-urn-04 (work in progress), Conversation", RFC 4103, June 2005.
August 2006.
[12] Hardie, T., "LoST: A Location-to-Service Translation Protocol", [RFC4119] Peterson, J., "A Presence-based GEOPRIV Location Object
draft-hardie-ecrit-lost-00 (work in progress), March 2006. Format", RFC 4119, December 2005.
[13] Wijk, A. and G. Gybels, "Framework for real-time text over IP [RFC4412] Schulzrinne, H. and J. Polk, "Communications Resource
using the Session Initiation Protocol (SIP)", Priority for the Session Initiation Protocol (SIP)",
draft-ietf-sipping-toip-06 (work in progress), August 2006. RFC 4412, February 2006.
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
US US
Phone: +1 212 939 7004 Phone: +1 212 939 7004
Email: hgs+ecrit@cs.columbia.edu Email: hgs+ecrit@cs.columbia.edu
URI: http://www.cs.columbia.edu URI: http://www.cs.columbia.edu
Roger Marshall (editor) Roger Marshall (editor)
TeleCommunication Systems TeleCommunication Systems, Inc.
2401 Elliott Avenue 2401 Elliott Avenue
2nd Floor 2nd Floor
Seattle, WA 98121 Seattle, WA 98121
US US
Phone: +1 206 792 2424 Phone: +1 206 792 2424
Email: rmarshall@telecomsys.com Email: rmarshall@telecomsys.com
URI: http://www.telecomsys.com URI: http://www.telecomsys.com
Intellectual Property Statement Full Copyright Statement
Copyright (C) The IETF Trust (2007).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
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WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Intellectual Property
The IETF takes no position regarding the validity or scope of any The IETF takes no position regarding the validity or scope of any
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on the procedures with respect to rights in RFC documents can be on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79. found in BCP 78 and BCP 79.
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This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Copyright Statement
Copyright (C) The Internet Society (2006). This document is subject
to the rights, licenses and restrictions contained in BCP 78, and
except as set forth therein, the authors retain all their rights.
Acknowledgment Acknowledgment
Funding for the RFC Editor function is currently provided by the Funding for the RFC Editor function is provided by the IETF
Internet Society. Administrative Support Activity (IASA).
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