draft-ietf-ecrit-requirements-05.txt   draft-ietf-ecrit-requirements-06.txt 
ECRIT H. Schulzrinne ECRIT H. Schulzrinne
Internet-Draft Columbia U. Internet-Draft Columbia U.
Expires: August 31, 2006 R. Marshall, Ed. Expires: September 7, 2006 R. Marshall, Ed.
TCS TCS
February 27, 2006 March 6, 2006
Requirements for Emergency Context Resolution with Internet Requirements for Emergency Context Resolution with Internet
Technologies Technologies
draft-ietf-ecrit-requirements-05.txt draft-ietf-ecrit-requirements-06.txt
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Copyright Notice Copyright Notice
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Abstract Abstract
This document enumerates requirements for emergency calls placed by This document enumerates requirements for the context resolution of
the public using voice-over-IP (VoIP) and general Internet multimedia emergency calls placed by the public using voice-over-IP (VoIP) and
systems, where Internet protocols are used end-to-end. general Internet multimedia systems, where Internet protocols are
used end-to-end.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Basic Actors . . . . . . . . . . . . . . . . . . . . . . . . . 9 3. Basic Actors . . . . . . . . . . . . . . . . . . . . . . . . . 9
4. High-Level Requirements . . . . . . . . . . . . . . . . . . . 12 4. High-Level Requirements . . . . . . . . . . . . . . . . . . . 12
5. Identifying the Caller Location . . . . . . . . . . . . . . . 14 5. Identifying the Caller's Location . . . . . . . . . . . . . . 14
6. Emergency Identifier . . . . . . . . . . . . . . . . . . . . . 16 6. Emergency Identifier . . . . . . . . . . . . . . . . . . . . . 15
7. Mapping Protocol . . . . . . . . . . . . . . . . . . . . . . . 19 7. Mapping Protocol . . . . . . . . . . . . . . . . . . . . . . . 18
8. Security Considerations . . . . . . . . . . . . . . . . . . . 25 8. Security Considerations . . . . . . . . . . . . . . . . . . . 24
9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 26 9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 25
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 27 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 26
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 28 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 27
11.1. Normative References . . . . . . . . . . . . . . . . . . 28 11.1. Normative References . . . . . . . . . . . . . . . . . . 27
11.2. Informative References . . . . . . . . . . . . . . . . . 28 11.2. Informative References . . . . . . . . . . . . . . . . . 27
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 29 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 28
Intellectual Property and Copyright Statements . . . . . . . . . . 30 Intellectual Property and Copyright Statements . . . . . . . . . . 29
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 communication for hearing disabled users (RFC
[7]) have an expectation to be able to initiate a request for help in 3351 [8]) have an expectation to be able to initiate a request for
case of an emergency. help in 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,
voice, text and real-time multimedia communications. This document text and real-time multimedia communications. This document outlines
outlines the key requirements that IP-based end systems and network the key requirements that IP-based end systems and network elements,
elements, such as SIP proxies, need to satisfy in order to provide such as SIP proxies, need to satisfy in order to provide emergency
emergency call services, which at a minimum, offer the same call services, which at a minimum, offer the same functionality as
functionality as existing PSTN services, with the additional overall existing PSTN services, with the additional overall goal of making
goal of making emergency calling more robust, less-costly to emergency calling more robust, less costly to implement, and
implement, and multimedia-capable. 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, (Internet the emergency call originates from an IP end system and terminates
device), and terminates to an IP-capable PSAP, done entirely over an into an IP-capable PSAP, conveyed entirely over an IP network.
IP network.
This document outlines the various functional issues which relate to This document outlines the various functional issues which relate to
making an IP-based emergency call, including a description of placing an IP-based emergency call, including a description of
baseline requirements, (Section 4), identification of the emergency baseline requirements (Section 4), identification of the emergency
caller's location, (Section 5), use of an emergency identifier to caller's location (Section 5), use of an emergency identifier to
declare a call to be an emergency call, (Section 6), and finally, the declare a call to be an emergency call (Section 6), and finally, the
mapping function required to route the call to the appropriate PSAP, mapping function required to route the call to the appropriate PSAP
(Section 7). (Section 7).
Ideally, the mapping protocol would yield a URI from a preferred set
of URIs (e.g., SIP:URI, SIPS:URI) which would allow an emergency call
to be completed using IP end-to-end. 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 via the PSTN.
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
currently considered within the scope of the ECRIT charter, and is considered to be outside the scope of the ECRIT charter.
therefore, left for a future draft to describe.
Note: Location is required for two separate purposes, first, to route Location is required for two separate purposes, first, to route the
the call to the appropriate PSAP and second, to display the caller's 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 As used in this document, validation of location does not require to
of URIs (e.g. sips:uri; sip:uri), which would allow an emergency call ascertain whether the location actually exists. For example,
to be completed using IP end-to-end (possibly via the Internet). validation might only check that the house number in a civic address
Despite this goal, some PSAPs may not immediately have IP based falls within the assigned range, not whether that building exists at
connectivity, and therefore it is imperative that the URI scheme not that spot. However, such higher precision validation is desirable.
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].
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 Codes: "caller" or "emergency caller" refers to the person placing an
"emergency caller" to refer to the person placing an emergency call emergency call or sending an emergency instant message (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
"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 more general than a Voice Service Provider, since
Provider, since emergency calls are sometimes likely to use other emergency calls may use other media beyond voice, including text
media, including text and video. Note: For a particular user, the and video. For a particular user, the ASP may or may not be the
ASP may or may not be the same organization as the IAP and/or ISP. same organization as his IAP 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.
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).
Emergency address: The uri scheme (e.g. sip:uri, sips:uri, xmpp:uri, Emergency address: The URI (e.g., SIP:URI, SIPS:URI, XMPP:URI, IM:
im:uri, etc.) which represents the address of the PSAP useful for URI, etc.) which represents the address of the PSAP useful for the
the completion of an emergency call. completion of an emergency call.
Emergency call routing support: An intermediary function which
assists in the routing of an emergency call via IP. An ESRP, is
an example of an Emergency call routing support entity.
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, an emergency call. A universal emergency identifier is an example
useful for call routing and completion of the emergency call. of an emergency identifier.
Enhanced emergency service: Enhanced emergency services add the Emergency Service Routing Proxy (ESRP): An ESRP is an emergency call
ability to identify the caller identity and/or caller location to routing support entity that invokes the location-to-URI mapping,
basic emergency services. (Sometimes, only the caller location to return either the URI for the appropriate PSAP, or the URL for
may be known, e.g. from a public access point that is not owned by another ESRP. (In a SIP system, the ESRP would typically be a SIP
an individual.) proxy, but may also be a Back-to-back user agent (B2BUA).
ESRP (Emergency Service Routing Proxy): An ESRP is a call routing Enhanced emergency service: Enhanced emergency services add the
entity that invokes the location-to-URL mapping, which in turn may ability to identify the caller's identity or location to basic
return either the URL for another ESRP or the PSAP. (In a SIP emergency services. (Sometimes, only the caller location may be
system, the ESRP would typically be a SIP proxy, but could also be known, e.g., when a call is placed from a public access point that
a Back-to-back user agent (B2BUA). is not owned by an individual.)
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 the WGS-84 datum) (e.g., lat/lon within the WGS-84 datum). For example, (2-D)
geographic location is defined as an x,y coordinate value pair
according to the distance North or South of the equator and East
or West of the prime meridian.
Home emergency dial-string: A home emergency dial-string (ref. Home emergency dial string: A home emergency dial string represents a
Location-dependent emergency identifier) represents a sequence of (e.g., dialed) sequence of digits, that is used to initiate an
digits that is used to initiate an emergency call within a emergency call within a geographically correct location of a
geographic vicinity considered to be a user's "home" location or caller if it is considered to be a user's "home" location or
vicinity. vicinity.
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 and layer 2 network connectivity to its customers or
through digital subscriber lines, cable TV plants, Ethernet, users, e.g., through digital subscriber lines, cable TV plants,
leased lines or radio frequencies. Examples of such organizations Ethernet, leased lines or radio frequencies. Examples of such
include telecommunication carriers, municipal utilities, larger organizations include telecommunication carriers, municipal
enterprises with their own network infrastructure, and government utilities, larger enterprises with their own network
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 layer-2 connectivity, or may not provide the physical-layer and layer-2 connectivity,
such as fiber or Ethernet. such as fiber or Ethernet, i.e., it may or may not be the role of
an IAP.
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. It can be either a
process, the location is defined with an x,y coordinate value civic or geographic location.
according to the distance north or south of the equator and east
or west of the prime meridian.
Location Context Mapping System (LCMS): A system defined as a set of
mechanisms and services working together to perform a mapping,
(or, direct association), between a location and a PSAP uri
designated as responsibleto to serve that location.
Location-dependent emergency identifier: Location-dependent emergency Location-dependent emergency dial string: Location-dependent
identifiers, also referred to as "emergency dial-strings" within emergency dial strings should be thought of as the digit sequence
this document, should be thought of as the digit sequence that is that is dialed in order to reach emergency services. There are
dialed in order to reach emergency services. There are two dial- two dial strings, namely either a "home emergency dial string", or
strings, namely either a "home emergency dial-string", or a a "visited emergency dial string", and is something separate from
"visited emergency dial-string", and is something separate from a a universal emergency identifier, since each represents specific
universal emergency identifier, since each represents specific emergency dial string key sequences which are recognized within a
emergency identifiers which are recognized within a local local geographic area or jurisdiction.
geographic area or jurisdiction.
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
mapped to one or more PSAPs. While it is desirable to determine mapped to one or more PSAPs. While it is desirable to determine
that a location exists, validation may not ensure that such a that a location exists, validation may not ensure that such a
location exists. Location validation ensures that a location is location exists. Location validation ensures that a location is
able to be referenced for mapping, but makes no assumption about able to be referenced for mapping, but makes no assumption about
the association between the caller and the caller's location. the association between the caller and the caller's location.
Mapping: Process of resolving a location to a URI (or multiple URIs). Mapping: Process of resolving a location to a URI (or multiple URIs)
which identify a PSAP, or intermediary which knows about a PSAP
that is designated as responsible to serve that location.
Mapping client: A Mapping Client interacts with the Mapping Server to Mapping client: A mapping client interacts with the Mapping Server to
learn one or multiple URIs for a given location. learn one or more 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 URI mappings. location-to-URI mappings.
Mapping service: A network service which uses a distributed mapping Mapping service: A network service which uses a distributed mapping
protocol to provide information about the PSAP, or intermediary protocol, to perform a mapping between a location and a PSAP, or
which knows about the PSAP, and is used to assist in routing an intermediary which knows about the PSAP, and is used to assist in
emergency call. routing an emergency call.
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.
PSAP URI: PSAP URI is a general term, used to refer to the output of PSAP URI: PSAP URI is a general term, used to refer to the output of
the mapping protocol, and represents either the actual PSAP IP the mapping protocol, and represents either the actual PSAP IP
address, or the IP address of some other intermediary, e.g. an address, or the IP address of some other intermediary, e.g., an
ESRP, which points to the actual PSAP. ESRP, which points to the actual PSAP.
Universal identifier: An emergency identifier which is recognized by Universal emergency identifier: An emergency identifier which is
any compatible endpoint, from any geographic location as useful recognized by any compatible endpoint, from any geographic
for initiating an emergency request. A general approach to using location. A general approach to using universal emergency
universal identifiers is outlined in the service URN draft identifiers is outlined in the service URN draft (I-D.ietf-ecrit-
(I-D.schulzrinne-sipping-service [5]). service-urn [5]).
Visited emergency dial-string: A visited emergency dial-string (ref. Visited emergency dial string: A visited emergency dial string
Location-dependent emergency identifier) represents a sequence of represents a sequence of digits that is used to initiate an
digits that is used to initiate an emergency call within a emergency call within a geographically correct location of the
geographic vicinity other than a user's "home" location or caller if outside the caller's "home" location or vicinity.
vicinity.
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
various infrastructure elements are necessary: Internet Attachment area, various infrastructure elements are necessary, including:
Providers, Application/Voice Service Providers, PSAPs as endpoints Internet Attachment Providers (IAPs), Application/Voice Service
for emergency calls, mapping services or other infrastructure Providers (ASPs or VSPs), PSAPs as endpoints for emergency calls,
elements that assist in during the call routing and potentially many mapping services or other infrastructure elements that assist during
other entities. the call routing.
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 | | Mapping | +-----------+ |Provider | | Mapping |
| | | (3) | | Service | | | | (3) | | Service |
| Emergency |<---+-----------------+-->| | | Emergency |<---+-----------------+-->| |
| Caller | | (2) | +-----------+ | Caller | | (2) | +-----------+
| |<---+-------+ | ^ | |<---+-------+ | ^
+-----------+ | +----|---------+------+ | +-----------+ | +----|---------+------+ |
^ | | Location | | | ^ | | Location | | |
| | | Information<-+ | | | | | Information<-+ | |
| +--+--------------+ |(8) | | (5) | +--+--------------+ |(5) | | (6)
| | | | |
| | +-----------v+ | | | | +-----------v+ | |
| (4) | |Emergency | | | | (4) | |Emergency | | |
+--------------+--->|Call Routing|<--+---+ +--------------+--->|Call Routing|<--+---+
| | |Support | | | | |Support | |
| | +------------+ | | | +------------+ |
| | ^ | | | ^ |
| | (6) | +----+--+ | | (7) | | +----+--+
| (7) | +------->| | | (8) | +------------>| |
+--------------+--------------->| PSAP | +--------------+----------------------->| PSAP |
| | | | | | |
|Application/ +----+--+ |Application/ | +----+--+
|Voice | |Voice |
|Service | |Service |
|Provider | |Provider |
+---------------------+ +---------------------+
Figure 1: Framework 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 it can call. There are a number of different deployment choices, as can be
be easily seen from the figure. The following deployment choices easily seen from the figure.
need to be highlighted:
o How is location information provided to the end host? It might o How is location information provided to the end host? It might
either be known to the end host itself (due to manual configuration either be known to the end host itself via manual configuration,
or provided via GPS) or available via a third party. Even if provided via GPS, or obtained via a third party method. Even if
location information is known to the network it might be made location information is known to the network it might be made
available to the end host. Alternatively, location information is available to the end host via DHCP (RFC 3825 [2]) or some other
used as part of call routing and inserted by intermediaries. mechanism. Alternatively, location information is used as part of
call routing and inserted by intermediaries.
o Is the Internet Attachment Provider also the Application/Voice o Is the Internet Attachment Provider also the Application/Voice
Service Provider? In the Internet today these roles are typically Service Provider? In the Internet today these roles are typically
provided by different entities. As a consequence, the Application/ provided by different entities. As a consequence, the Application/
Voice Service Provider is typically not able to learn the physical Voice Service Provider is typically not able to learn the physical
location of the emergency caller. location of the emergency caller.
Please note that the overlapping squares aim to indicate that certain The overlapping squares in the figure indicate that some functions
functionality can be collapsed into a single entity. As an example, can be collapsed into a single entity. As an example, the
the Application/Voice Service Provider might be the same entity as Application/Voice Service Provider might be the same entity as the
the Internet Attachment Provider and they might also operate the Internet Attachment Provider. There is, however, no requirement that
PSAP. There is, however, no requirement that this must be the case. this must be the case. Additionally, we consider that end systems
Additionally it is worth pointing out that end systems might be its might act as their own VSP, e.g., either for enterprises or for
own VSP, e.g., for enterprises or residential users. residential users.
Below, we describe various interactions between the entities shown in Various potential interactions between the entities depicted in
Figure 1 are described: Figure 1, are described in the following:
o (1) Location information might be available to the end host itself. (1) Location information might be available to the end host itself.
o (2) Location information might, however, also be obtained from the (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 mapping service to (3) The emergency caller might need to consult a mapping service to
determine the PSAP that is appropriate for the physical location of determine the PSAP that is appropriate for the physical location of
the emergency caller (and considering other attributes such as a the emergency caller, possibly considering other attributes such as
certain language support by the Emergency Call Takers). appropriate language support by the emergency call taker.
o (4) The Emergency Caller might get assistance for emergency call (4) The emergency caller might get assistance for emergency call
routing by infrastructure elements (referred as Emergency Call routing by infrastructure elements that are Emergency Call Routing
Routing Support entities). In case of SIP these entities are Support entities, e.g., an Emergency Service Routing Proxy (ESRP), in
proxies. SIP).
o (5) Individual Emergency Call Routing Support entities might need (5) Location Information is used by emergency call routing entities
to consult a mapping service to determine where to route the to determine the appropriate PSAP.
emergency call.
o (6) The Emergency Call Routing Support entities need to finally (6) Individual emergency call routing support entities might need to
forward the call, if infrastructure based emergency call routing is consult a mapping service to determine where to route the emergency
used. call.
o (7) The emergency caller might interact directly with the PSAP (7) For infrastructure-based emergency call routing (in contrast to
without any Emergency Call Routing Support entities. UE-based emergency call routing), the emergency call routing support
entity needs to forward the call to the PSAP.
o (8) Location Information is used by emergency call routing entities (8) The emergency caller (UE) may interact directly with the PSAP
to determine appropriate PSAP mapping. (e.g., UE invokes mapping, and initiates a connection), without
relying on any intermediary emergency call routing support entities.
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/Voice service provider: The existence of an
Service Provider (ASP) SHOULD NOT be assumed. Application/Voice Service Provider (ASP/VSP) SHOULD NOT be
assumed.
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 not be a telecommunication provider. and staff, but not be a telecommunication provider.
Re2. International: Regional, political and organizational aspects Re2. International: Regional, political and organizational aspects
MUST be considered during the design of protocols and protocol MUST be considered during the design of protocols and protocol
extensions. extensions.
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 regional services, e.g., either centralizing them or having smaller
subdivisions such as United States counties or municipalities regional subdivisions such as United States counties or
handle emergency calls. municipalities handle emergency calls.
Re3. Distributed Administration: Deployment of emergency services Re3. Distributed administration: Deployment of emergency services
MUST NOT depend on a sole central administration authority. MUST NOT depend on a sole central administration authority.
Motivation: Once common standards are established, it must be Motivation: Once common standards are established, it must be
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, 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 (i.e. implemented in video and text MUST be supported (i.e., implemented in the
the protocol, though not necessarily used). protocol, though not necessarily used in all calls).
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 media. 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 [9]), instant should include voice, conversational text (RFC 4103 [10]), instant
messaging and video. messaging and video.
Re5. Alternate Mapping Sources: The mapping protocol SHOULD Re5. Alternate mapping sources: The mapping protocol MUST implement
implement a mechanism that allows for the retrieval of mapping a mechanism that allows for the retrieval of mapping information
information, possibly of different degrees of currency. from different sources.
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.
which the alternative source is created or updated.
Re6. Incremental Deployment: The ECRIT mapping protocol MUST return Re6. Differences of currency in mapping sources: For alternate
URIs that are usable by a standard signaling protocol (i.e., mapping, differences in currency between mapping data contained
without special emergency extensions) unless an error is returned. within mapping sources SHOULD be minimized.
Motivation: The format of the output returned by the mapping Motivation: Alternative sources of mapping data may not have been
protocol is in a standard format for communication protocol. For created or updated with the same set of information within the
example, it should return something SIP specific (e.g. URI), that same timeframe.
any SIP capable phone would be able to use if used in a SIP
context. Special purpose URIs would not be understood by "legacy"
SIP devices since they do not have knowledge about the mapping
protocol, and therefore are not to be used.
Re7. Ubiquitous Triggering: The mapping protocol MUST implement, Re7. Mapping result usability: The ECRIT mapping protocol MUST
(not necessarily use), the ability to be invoked at any time, from return a URI (or URIs) that are usable within a standard signaling
any location, by any client which supports the mapping protocol. protocol (i.e., without special emergency extensions).
Motivation: While end devices are the typical initiators of Motivation: For example, a SIP specific URI returned by the
mapping service requests, it is also expected that other mapping mapping protocol, needs to be usable within any SIP capable phone
clients, such as relays, 3rd party devices, PSAPs, etc. may also in a SIP initiated emergency call. This is in contrast to a
trigger a mapping request. "special purpose" URI, which may not be recognizable by a legacy
SIP device.
Re8. PSAP Identification: The mapping information MUST be available Re8. PSAP accessibility: 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.
Re9. No Modification of Location Databases: The mapping protocol Re9. No modification of location databases: The mapping protocol
SHOULD NOT require that data within location databases be SHOULD NOT require that data within location databases be
transformed or modified in any unusual or unreasonable way in transformed or modified in any unusual or unreasonable way in
order for the mapping protocol to use the data. order for the mapping protocol to use the data.
Motivation: Databases which contain civic addresses (used within Motivation: Databases which contain civic addresses used within
location information servers), may be used for multiple purposes location servers, may be used for multiple purposes and
and applications, (in addition to being used for emergency service applications beyond emergency service mapping.
mapping only).
5. Identifying the Caller Location 5. Identifying the Caller's Location
Location can either be provided directly, or by reference, and Location can either be provided direct, or by reference, and
represents either a civic location, or as a geographic location. How represents either a civic location, or as a geographic location. How
does the location (or location reference) become associated with the does the location (or location reference) become associated with the
call? In general, we can distinguish three modes of operation of how call? In general, we can distinguish three modes of operation of how
a location is associated with an emergency call: a location is associated with an emergency call:
UA-inserted: The caller's user agent inserts the location UA-inserted: The caller's user agent inserts the location information
information, derived from sources such as GPS, DHCP (RFC 3825 [2]) into the call signaling message. The location information is
and I-D.ietf-geopriv-dhcp-civil [6]) or utilizing the Link Layer derived from sources such as GPS, DHCP (RFC 3825 [2]) and
I-D.ietf-geopriv-dhcp-civil [7]) or utilizing the Link Layer
Discovery Protocol (LLDP) [see IEEE8021AB]. Discovery Protocol (LLDP) [see IEEE8021AB].
UA-referenced: The caller's user agent provides a reference, via a UA-referenced: The caller's user agent provides a pointer (i.e., a
permanent or temporary identifier, to the location which is stored location reference), via a permanent or temporary identifier, to
by a location service somewhere else and then retrieved by the the location which is stored by a location service somewhere else
PSAP. and then retrieved by the PSAP, ESRP, or other authorized service
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.
Lo1. Validation of Civic Location: The mapping protocol MUST Lo1. Reference datum: The mapping server MUST implement support for
implement a method that makes it possible for a mappng server to the WGS-84 coordinate reference system and MAY support other
validate a civic location prior to that location's use in an coordinate reference systems.
actual emergency call.
Motivation: Location validation provides an opportunity to help
assure ahead of time, whether successful mapping to the
appropriate PSAP will likely occur when it is required.
Validation may also help to avoid delays during emergency call
setup due to invalid locations.
Lo2. Validation Resolution: The mapping protocol MUST support (i.e.
required to implement, though not required for use) the return of
additional information which can be used to determine the
precision or resolution of the data elements used to determine a
PSAP URI, for example.
Motivation: The mapping server may not use all the data elements
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
some specific data elements. The uniqueness of this information
set may be used to differentiate among emergency jurisdictions.
Precision or resolution in the context of this requirement might
mean, for example, explicit identification of the data elements
that were used successfully in the mapping.
Lo3. Indication of non-existent location: The protocol MUST support
(i.e. must implement in the protocol, though not necessarily use)
a mechanism to indicate that a location or a part of a location is
known to not exist, even if a valid location-to-PSAP uri mapping
can be provided. This mechanism includes a means to identify a
separate mechanism that could be used to resolve the discrepancy.
Motivation: The emergency authority for a given jurisdiction may
provide a means to resolve addressing problems, e.g., a URI for a
web service that can be used to report problems with an address.
The mapping response would allow this service to be identified.
Lo4. Limits to Validation: Successful validation of a civic location
MUST NOT 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
civic location may not be considered valid. This fact should not
result in the call being dropped or rejected by any entity along
the signaling path to the PSAP.
Lo5. Reference Datum: The mapping server MUST implement support for
the WGS-84 coordinate reference system and may implement support
for use of other reference systems.
Lo6. Location Provided: An Emergency Services Routing Proxy (ESRP) Lo2. 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 needs to receive the caller's location.
the end device's location.
Lo7. 3D Sensitive Mapping: The mapping protocol MUST implement
support for both 2D and 3D location information, and may accept
either a 2D or 3D mapping request as input, so to 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 emergency identifier setup: One or more universal
identifiers MUST be recognized by any device or network element emergency identifiers MUST be recognized by any device or network
for call setup purposes element 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. An example of this might be "urn:service:sos".
of these might include: 911, 112, and sos.*.
Id2. Universal Identifier Resolution: Where multiple emergency Id2. Emergency identifier resolution: Where multiple emergency
service types exist, the mapping protocol MUST support (i.e. identifiers exist, there MUST be a mechanism to differentiate each
implement, though not necessarily use) the individual treatment of emergency identifier used, based on the specific type of emergency
each emergency identifier used, based on the specific type of help requested.
emergency 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, (e.g., fire, police, ambulance), in
police, ambulance), in which case it is important that any one which case, it is important that any one could be selected
could be selected directly. directly.
Id3. Emergency Marking: Any device in the signaling path that Id3. Emergency identifier marking: Any device in the signaling path
recognizes by some means that the signaling is associated with an that recognizes by some means that the signaling is associated
emergency call MUST add a specific emergency indication, if it with an emergency call MUST add a specific emergency indication,
doesn't already exist, to the signaling before forwarding it. if it doesn't already exist, to the signaling before forwarding
This marking mechanism must be different than QoS marking. it. This marking mechanism 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. local variant of a logical emergency address.
Id4. Emergency Identifier-based Marking: User agents, proxies, and Id4. Prevention of fraud: A call MUST be routed to a PSAP if it is
other network elements that process signaling associated with identified as an emergency call.
emergency calls SHOULD be configured to recognize a reasonable
selection of logical emergency identifiers as a means to initiate
emergency marking.
Motivation: Since user devices roam, emergency identifiers may
vary from region to region. It is therefore important that a
network entity be able to perform mapping and/or call routing
within the context of its own point of origin rather than relying
on non-local logical emergency identifiers as the only basis for
emergency marking of calls.
Id5. Prevention of Fraud: A call MUST be routed to a PSAP if it is
identified as an emergency call or is marked as such in accordance
with the above emergency marking requirements.
Motivation: this prevents use of the emergency call indication to Motivation: This prevents use of the emergency call indication to
gain access to call features or authentication override for non- gain access to call features or authentication override for non-
emergency purposes. emergency purposes.
Id6. Extensibility of emergency service types: The list of emergency Id5. Extensibility of emergency identifiers: The list of defined
service types MUST be extensible, and it is not necessary to emergency identifiers MUST be extensible, and it is not necessary
provide mapping for every possible service type. to provide mapping for every possible service.
Motivation: The use of a service type is locally determined. Motivation: The use of an emergency identifier is locally
determined.
Id7. Discovery of emergency dial-string: The mapping protocol MUST Id6. Discovery of emergency dial strings: The protocol MUST support
support (i.e. implement, though not necessarily use) a mechanism a mechanism to discover existing location-dependent emergency dial
to discover existing location-dependent emergency identifiers, strings, (e.g., "9-1-1", "1-1-2"), which are contextually
known as emergency dial-strings, (e.g. 9-1-1, 1-1-2), appropriate appropriate for the location of the caller.
for the location of the caller.
Motivation: Users are trained to dial the appropriate emergency Motivation: Users are trained to dial the appropriate emergency
dial-string to reach emergency services. There needs to be a way dial string to reach emergency services. There needs to be a way
to figure out what the dial-string is within the local environment to figure out what the dial string is within the local environment
of the caller. of the caller.
Id8. Local Identifier Translation: The SIP UA SHOULD translate home Id7. Local emergency dial string translation: An end device (i.e.,
emergency dial-strings to universal emergency identifiers. The UA SIP UA), SHOULD translate home emergency dial strings into
would most likely be pre-provisioned with the appropriate universal emergency identifiers. The UA would most likely be pre-
information in order to make such a translation. This assumes provisioned with the appropriate information in order to make such
that a mechanism to provide the user's home emergency dial-strings a translation.
be available.
Id9. Emergency Identifier Replacement: For each signaling protocol Id8. Emergency dial string replacement: For each signaling protocol
that can be used in an emergency call, reserved identifiers SHOULD that can be used in an emergency call, reserved universal
be allowed to replace the original emergency identifier, based on emergency identifiers SHOULD be allowed to replace the original
local conventions, regulations, or preference (e.g. as in the case emergency dial strings, based on local conventions, regulations,
of an enterprise). or 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 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.
Id10. Universal Identifier Recognition: Universal identifier(s), Id9. Universal emergency identifier recognition: A universal
MUST be universally recognizable (as the label suggests), by any emergency identifier MUST be recognized by any network element
network element which supports the (ECRIT) mapping protocol. which supports the mapping protocol.
Id11. Universal Identifier Unrecognized: A call MUST be recognized Id10. Emergency identifier not recognized: A call MUST be recognized
as emergency call even if the specific emergency service requested as an emergency call even if the specific emergency service
is not recognized. requested is not recognized.
"Motivation: In order to have a robust system that supports Motivation: In order to have a robust system that supports
incremental service deployment while still maintaining a fallback incremental service deployment while still maintaining a fallback
capability." capability.
Id12. Translation of emergency dial-strings: The SIP UA SHOULD
translate both home and visited emergency dial-strings into a
universal emergency identifier.
Id13. Detection of visited emergency dial-strings: The mapping Id11. Discovery of visited emergency dial strings: The mapping
protocol MUST support (i.e. implement, though not necessarily protocol MUST support (i.e., implement, though not necessarily
use), a mechanism to allow the end device to learn visited use) a mechanism to allow the end device to learn visited
emergency dial-strings. emergency dial strings.
Motivation: Scenarios exist where a user dials a visited emergency Motivation: Scenarios exist where a user dials a visited emergency
dial-string that is different from the home emergency dial-string: dial string that is different from the home emergency dial string:
If a user of a UA visits a foreign country, observes a fire truck If a user (i.e., UA operator) visits a foreign country, observes a
with 999 on the side, the expectation is to be able to dial that fire truck with 999 on the side, the expectation is one of being
same number to summon a fire truck; Another use case cited is able to dial that same number to summon a fire truck. Another use
where a tourist collapses, and a "good Samaritan" uses the case cited is where a tourist collapses, and a "good Samaritan"
tourist's cell phone to dial a local emergency number. uses the tourist's cell phone to enter a local emergency dial
string.
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, one of having a
small number of) emergency identifier(s) which are independent of the universal emergency identifier that is independent of the caller's
caller's location, and since PSAPs only serve a limited geographic location, and since each PSAP only serves 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 approaches to invoking a mapping service. We
emergency identifier into the appropriate PSAP emergency address. We refer to these as caller-based and mediated. In each case, the
refer to these as caller-based and mediated. mapping client initiates a request to a mapping server via a mapping
protocol. A proposed mapping protocol is outlined in the document
I-D.hardie-ecrit-lost [6].
For caller-based resolution, the caller's user agent consults a For caller-based resolution, the caller's user agent invokes a
mapping service to determine the appropriate PSAP based on the mapping service 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, a call signaling server, such as a SIP For mediated resolution, a call signaling server, such as a SIP
(outbound) proxy or redirect server performs this function (a request (outbound) proxy or redirect server invokes the mapping service.
for mapping) by invoking the mapping protocol.
Note that this case relies on an architecture where the call is
effectively routed to a copy of the database, rather than having some
non-SIP protocol query the database.
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.)
The problem at hand is more difficult to resolve than that for
traditional web or email services. In this case, the emergency
caller only dialed an emergency identifier, and depending on the
location, any one of several thousand PSAPs around the world could be
appropriate PSAP. In addition, there may be a finer resolution of
routing (which the caller isn't aware of), which results in a
particular "accredited" PSAP (i.e. one run by local authorities)
answering to call. (Many PSAPs are run by private entities. For
example, universities and corporations with large campuses often have
their own emergency response centers.)
Ma1. Appropriate PSAP: Calls MUST be routed to the PSAP responsible Ma1. Appropriate PSAP: Calls MUST be routed to the PSAP responsible
for this particular geographic area. In particular, the location for a particular geographic area. In particular, the location
determination should not be fooled by the location of IP telephony determination should not be fooled by the location of IP telephony
gateways or dial-in lines into a corporate LAN (and dispatch gateways or dial-in lines into a corporate LAN (and dispatch
emergency help to the gateway or campus, rather than the caller), emergency help to the gateway or campus, rather than the caller),
multi-site LANs and similar arrangements. multi-site LANs and similar arrangements.
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 result in handling emergencies as calls are redirected, and result in
inefficient use of PSAP resources at the initial point of contact. inefficient use of PSAP resources at the initial point of contact.
Ma2. Mapping redirection: The mapping protocol MUST support (i.e. Ma2. Minimal additional delay: The execution of the mapping protocol
implement for use) redirection functionality, since in some cases,
an initial mapping may provide a single URL for a large geographic
area. Redirection is needed to then re-invokes the mapping
protocol on a different database to obtain another URL for a more
resolute ESRP or PSAP, which covers a smaller area.
Motivation: The more local the mapping output is, the more
favorable (in most cases) the likely outcome will be for the
emergency caller.
Ma3. Minimal additional delay: The execution of the mapping protocol
SHOULD minimize the amount of additional delay to the overall SHOULD minimize the amount of additional delay to the overall
call-setup time. call-setup time.
Motivation: Since outbound proxies will likely be asked to resolve Motivation: Since outbound proxies will likely be asked to resolve
the same geographic coordinates repeatedly, a suitable time- the same geographic coordinates repeatedly, a suitable time-
limited caching mechanism should be supported. limited caching mechanism should be supported.
Ma4. Referral: The mapping protocol MUST support (i.e. Implement Ma3. Referral: The mapping protocol MUST support (i.e., Implement
for use), a mechanism for the mapping client to be able to contact for use), a mechanism for the mapping client to be able to contact
any mapping server and be referred to another server that is more any mapping server and be referred to another server that is more
qualified to answer the query. qualified to answer 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. Multiple Response URIs: The mapping protocol response MUST Ma4. Multiple response URIs: The mapping protocol response MUST
support (i.e. implement, though not necessarily use), the support the inclusion of multiple URIs in the response.
inclusion of multiple URIs in the response.
Motivation: In response to a mapping request, a server will
normally provide a URI or set of URIs for contacting the
appropriate PSAP.
Ma6. URI - Alternate Contact: The mapping protocol MUST support
(i.e. implement, though not necessarily use), the return of a URI
or contact method explicitly marked as an alternate contact.
Motivation: In response to a mapping request, if an expected URI Ma5. URI alternate contact: The mapping protocol MUST support the
is unable to be returned, then mapping server may return an return of a URI or contact method explicitly marked as an
alternate URI. When and how this would be used will be described alternate contact.
in an operational document.
Ma7. Multiple PSAP URIs: The mapping protocol MUST support (i.e. Motivation: In response to a mapping request, the mapping server
implement, though not necessarily use), a method to be able to may return an alternate URI. Implementation details to be
return multiple URIs for different PSAPs that cover the same area. described within an operational document.
Ma8. URL properties: The mapping protocol MUST support (i.e. Ma6. URL properties: The mapping protocol MUST support the ability
implement, though not necessarily use), the ability to provide to provide additional information that allows the mapping client
additional information that allows the querying entity to to determine relevant properties of the URL.
determine relevant 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
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 trigger methods. based methods.
Ma9. Traceable resolution: The mapping protocol SHOULD support the Ma7. 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 which provided the emergency address resolution or entities which provided the emergency address resolution
information. information.
Motivation: To provide operational traceability in case of errors. Motivation: It is important for public safety reasons, that there
is a method to provide operational traceability in case of errors.
Ma10. URI for error reporting: The mapping protocol MUST support Ma8. URI for error reporting: The mapping protocol MUST support
(i.e. implement for use) a mechanism to return a URI that can be (i.e., implement for use) a mechanism to return a URI that can be
used to report a suspected or known error within the mapping used to report a suspected or known error within the mapping
database. database.
Ma11. Resilience against server failure: The mapping protocol MUST Ma9. Resilience against failure: The mapping protocol MUST support
support (i.e. implement for use) a mechanism to enable the mapping (i.e., implement for use) a mechanism to enable the mapping client
client to be able to fail over to another replica of the mapping to be able to fail over to another replica of the mapping server,
server, so that a failure of a server does not endanger the so that a failure of a server does not endanger the ability to
ability to perform the mapping. perform the mapping.
Ma12. Incrementally deployable: The mapping protocol MUST be Ma10. Incrementally deployable: The mapping protocol MUST be
designed in such a way that supports the incremental deployment of designed in such a way that supports the incremental deployment of
mapping services. mapping services.
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 boundary information. not (yet) contain accurate PSAP service area information.
Ma13. Mapping requested from anywhere: The mapping protocol MUST Ma11. Mapping requested from anywhere: The mapping protocol MUST
support (i.e. implement, though not necessarily use) the ability support (i.e., implement, though not necessarily use) the ability
to provide mapping information in response to queries from any to provide mapping information in response to queries from any
(earthly) location, regardless of where the mapping client is (earthly) location, regardless of where the mapping client is
located, either geographically or by network location. located, either geographically or by network location.
Motivation: The mapping client, (such as the 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 a mapping. PSAP, but must still be able to obtain a mapping.
Ma14. Location Updates: The mapping protocol MUST support (i.e. Ma12. Extensible protocol: The mapping protocol MUST be designed to
implement, though not necessarily use) the ability to provide
location updates. Mapping services should implement the
mechanisms to provide updated location.
Motivation: Updated location information may have an impact on
PSAP routing. In some cases it may be possible to redirect that
call to a more appropriate PSAP (some device measurement
techniques provide quick (i.e. early), but imprecise "first fix"
location).
Ma15. 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 (RFC 4119 [3]). PIDF-LO (RFC 4119 [3]).
Ma16. Split responsibility: The mapping protocol MUST support (i.e. Ma13. Split responsibility: The mapping protocol MUST support (i.e.,
implement for use) the division of data subset handling between implement for use) the division of data subset handling between
multiple mapping servers within a single level of a civic location multiple mapping servers within a single level of a civic location
hierarchy. hierarchy.
Motivation: For example, two directories 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.
Ma17. Pervasive Mapping: The mapping protocol MUST support (i.e. Ma14. Any time mapping: The mapping protocol MUST support (i.e.,
implement for use) the ability of the mapping function to be implement for use) the ability of the mapping function to be
invoked at any time, including while an emergency call is in invoked at any time, including while an emergency call is in
process. process and before an emergency call.
Ma18. Baseline query protocol: A mandatory-to-implement protocol Motivation: Used as a fallback mechanism only, if a mapping query
fails at emergency call time, it may be advantageous to have prior
knowledge of the PSAP URI. This prior knowledge would be obtained
by performing a mapping query at any time prior to an emergency
call.
Ma15. 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 Ma16. Multiple PSAP URIs: The mapping protocol MUST support (i.e.,
URIs, though it SHOULD return only one URI per scheme, so that implement, though not necessarily use), a method to be able to
clients are not required to select among different targets for the return multiple URIs for different PSAPs that cover the same area.
same contact protocol.
Ma17. Single URI per contact protocol: Though the mapping protocol
supports the return of multiple URIs, it SHOULD return only one
URI per contact protocol, 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 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.
Ma20. Separation of Identity from mapping: The mapping protocol MUST Ma18. Anonymous mapping: The mapping protocol MUST NOT require the
NOT require the true identity of the target for which the location true identity of the target for which the location information is
information is attributed. Ideally, no identity information is attributed. Ideally, no identity information is provided via the
provided via the mapping protocol. Where identity information is mapping protocol. Where identity information is provided, it may
provided, it may be in the form of an unlinked pseudonym as be in the form of an unlinked pseudonym (RFC 3693 [9]).
defined in RFC 3963.
Ma21. Location delivery by-value: The mapping protocol MUST support Ma19. Location delivery by-value: The mapping protocol MUST support
(i.e. implement, though not necessarily use) the delivery of (i.e., implement, though not necessarily use) the delivery of
location information by-value, though may alternatively support location information using a by-value method, though it MAY also
de-referencing of specific location references. support de-referencing a URL that references a location object.
Motivation: Location by-reference is not one of the evaluation Motivation: The mapping protocol is not required to support the
criteria for a mapping protocol presented here. (i.e. the mapping ability to de-reference specific location references.
protocol is not required to support the ability to de-reference
specific location references.)
Ma22. Alternate community names: The mapping protocol MUST support Ma20. Alternate community names: The mapping protocol MUST support
(i.e. implement, though not necessarily use) both the jurisdiction both the jurisdictional community name and the postal community
community name and the postal community name fields within the name fields within the PIDF-LO data.
PIDF-LO data.
Motivation: A mapping query must be accepted with either or both Motivation: A mapping query must be accepted with either or both
community name fields, and provide appropriate responses. If a community name fields, and provide appropriate responses. If a
mapping query is made with only one field present, given that the mapping query is made with only one field present, and if the
database has both fields populated, the mapping protocol response database contains both jurisdictional and postal, the mapping
should return both available fields. protocol response should return both.
Ma23. Support for alias locations: The mapping protocol MUST support Ma21. Ubiquitous triggering: The mapping protocol MUST implement,
(i.e. implement, though not necessarily use) one or more aliases but not necessarily use, the ability to be invoked at any time,
for a specific location entry. from any location, by any client which supports the mapping
protocol.
Motivation: It should be possible to relate one entry to another Motivation: While end devices are the typical initiators of
and be able to determine which is the "primary" entry and which is mapping service requests, it is also expected that other mapping
the alias. The result of aliasing is always that mapping from the clients, such as relays, 3rd party devices, PSAPs, etc. may also
primary or any of the aliases is the same. trigger a mapping request.
Ma24. Pre-call mapping for fallback: The mapping protocol MUST Ma22. Validation of civic location: The mapping protocol MUST
support (i.e. implement, though not necessarily use) LCMS queries implement a method via a mapping request, that makes it possible
prior to making an emergency call. for a mapping server to validate a civic location prior to that
location's use in an actual emergency call.
Motivation: Used as a fallback mechanism only, if a LCMS query Motivation: Location validation provides an opportunity to help
fails at emergency call time, it may be advantageous to have prior assure ahead of time, whether successful mapping to the
knowledge of the PSAP URI. This prior knowledge would be obtained appropriate PSAP will likely occur when it is required.
by performing an LCMS query at any time prior to an emergency Validation may also help to avoid delays during emergency call
call. setup due to invalid locations.
Ma23. Validation resolution: The mapping protocol MUST support
(i.e., required to implement, but not required for use) the return
of additional information which can be used to determine the
precision or resolution of the data elements used to determine a
PSAP URI.
Motivation: The mapping server may not use all the data elements
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
some specific data elements. The uniqueness of this information
set may be used to differentiate among emergency jurisdictions.
Precision or resolution in the context of this requirement might
mean, for example, explicit identification of the data elements
that were used successfully in the mapping.
Ma24. Indication of non-existent location: The protocol MUST support
a mechanism to indicate that a location or a part of a location is
known to not exist, even if a valid location-to-PSAP URI mapping
can be provided. This includes a way to identify a separate
mechanism to resolve any such discrepancy.
Motivation: The emergency authority for a given jurisdiction may
provide a means to resolve addressing problems, e.g., a URI for a
web service that can be used to report problems with an address.
Ma25. Limits to validation: Successful validation of a civic
location MUST NOT be required to place an emergency call.
Motivation: In some cases, a civic location may not be considered
valid. This fact should not result in the call being dropped or
rejected by any entity along the signaling path to the PSAP.
Ma26. 3D sensitive mapping: The mapping protocol MUST implement
support for both 2D and 3D location information, and may accept
either a 2D or 3D mapping request as input.
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 in the request.
8. Security Considerations 8. Security Considerations
Note: Security Considerations are referenced in the ECRIT security Security considerations are discussed in the ECRIT security document
document [4]. I-D.taylor-ecrit-security-threats [4] .
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,
Martin Dawson, Motoharu Kawanishi, Brian Rosen, Richard Stastny, Martin Dawson, Motoharu Kawanishi, Brian Rosen, Richard Stastny,
Martin Thomson, James Winterbottom. Martin Thomson, James Winterbottom.
The contributors can be reached at: The contributors can be reached at:
skipping to change at page 27, line 8 skipping to change at page 26, line 8
Richard Stastny Richard.Stastny@oefeg.at Richard Stastny Richard.Stastny@oefeg.at
Martin Thomson Martin.Thomson@andrew.com Martin Thomson Martin.Thomson@andrew.com
James Winterbottom James.Winterbottom@andrew.com James Winterbottom James.Winterbottom@andrew.com
10. Acknowledgments 10. Acknowledgments
In addition to thanking those listed above, we would like to also In addition to thanking those listed above, we would like to also
thank Michael Hammer, Ted Hardie, Marc Linsner, Barbara Stark, Clive thank Guy Caron, Barry Dingle, Keith Drage, Tim Dunn, Patrik
D.W. Feather, Keith Drage, Raymond Forbes, Tim Dunn, Steve Norreys, Faeltstroem, Clive D.W. Feather, Raymond Forbes, Randall Gellens,
Patti McCalmont, Rohan Mahy, Nate Wilcox, Michael Haberler, Jonathan Michael Haberler, Michael Hammer, Ted Hardie, Gunnar Hellstrom,
Rosenberg, Shida Schubert, John Schnizlein, Benny Rodrig, John Cullen Jennings, Marc Linsner, Rohan Mahy, Patti McCalmont, Don
Rosenberg, Patrik Faeltstroem, Barry Dingle, Gunnar Hellstrom, James Mitchell, John Morris, Andrew Newton, Steve Norreys, Jon Peterson,
Seng, Byron Smith, Cullen Jennings, Don Mitchell, John Morris, Jon James Polk, Benny Rodrig, John Rosenberg, Jonathan Rosenberg, John
Peterson, Randall Gellens, Guy Caron, Andrew Newton, James Polk, Tom Schnizlein, Shida Schubert, James Seng, Byron Smith, Tom Taylor,
Taylor, and Hannes Tschofenig for their invaluable input. Barbara Stark, Hannes Tschofenig, and Nate Wilcox, for their
invaluable 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] Polk, J., Schnizlein, J., and M. Linsner, "Dynamic Host [2] Polk, J., Schnizlein, J., and M. Linsner, "Dynamic Host
Configuration Protocol Option for Coordinate-based Location Configuration Protocol Option for Coordinate-based Location
Configuration Information", RFC 3825, July 2004. Configuration Information", RFC 3825, July 2004.
[3] Peterson, J., "A Presence-based GEOPRIV Location Object Format", [3] Peterson, J., "A Presence-based GEOPRIV Location Object Format",
RFC 4119, December 2005. RFC 4119, December 2005.
[4] Schulzrinne, H., "Security Threats and Requirements for [4] Schulzrinne, H., "Security Threats and Requirements for
Emergency Calling", draft-taylor-ecrit-security-threats-01 (work Emergency Call Marking and Mapping",
in progress), December 2005. draft-taylor-ecrit-security-threats-03 (work in progress),
March 2006.
[5] Schulzrinne, H., "A Uniform Resource Name (URN) for Services", [5] Schulzrinne, H., "A Uniform Resource Name (URN) for Services",
draft-schulzrinne-sipping-service-01 (work in progress), draft-ietf-ecrit-service-urn-00 (work in progress),
October 2005. February 2006.
[6] Schulzrinne, H., "Dynamic Host Configuration Protocol (DHCPv4 [6] Hardie, T., "LoST: A Location-to-Service Translation Protocol",
draft-hardie-ecrit-lost-00 (work in progress), March 2006.
[7] Schulzrinne, H., "Dynamic Host Configuration Protocol (DHCPv4
and DHCPv6) Option for Civic Addresses Configuration and DHCPv6) Option for Civic Addresses Configuration
Information", draft-ietf-geopriv-dhcp-civil-09 (work in Information", draft-ietf-geopriv-dhcp-civil-09 (work in
progress), January 2006. progress), January 2006.
11.2. Informative References 11.2. Informative References
[7] Charlton, N., Gasson, M., Gybels, G., Spanner, M., and A. van [8] 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.
[8] Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and J. [9] Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and J.
Polk, "Geopriv Requirements", RFC 3693, February 2004. Polk, "Geopriv Requirements", RFC 3693, February 2004.
[9] Hellstrom, G. and P. Jones, "RTP Payload for Text [10] Hellstrom, G. and P. Jones, "RTP Payload for Text
Conversation", RFC 4103, June 2005. Conversation", RFC 4103, June 2005.
[10] Wijk, A., "Framework of requirements for real-time text [11] 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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