WDIFF

draft-ietf-ecrit-requirements-08.txt --> draft-ietf-ecrit-requirements-09.txt

ECRIT H. Schulzrinne
Internet-Draft Columbia U.
Expires: November 3, 18, 2006 R. Marshall, Ed.
TCS
May 2, 17, 2006

Requirements for Emergency Context Resolution with Internet
Technologies
draft-ietf-ecrit-requirements-08.txt
draft-ietf-ecrit-requirements-09.txt

Status of this Memo

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This Internet-Draft will expire on November 3, 18, 2006.

Abstract

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

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Basic Actors . . . . . . . . . . . . . . . . . . . . . . . . . 9
4. High-Level Requirements . . . . . . . . . . . . . . . . . . . 12
5. Identifying the Caller's Location . . . . . . . . . . . . . . 15
6. Emergency Service Identifier . . . . . . . . . . . . . . . . . . . . . 18
7. Mapping Protocol . . . . . . . . . . . . . . . . . . . . . . . 21
8. Security Considerations . . . . . . . . . . . . . . . . . . . 25
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26
10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 26
10. 27
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 27
11. 28
12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 28
11.1. 29
12.1. Normative References . . . . . . . . . . . . . . . . . . 28
11.2. 29
12.2. Informative References . . . . . . . . . . . . . . . . . 28 29
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 29 30
Intellectual Property and Copyright Statements . . . . . . . . . . 30 31

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1. Introduction

Users of both voice-centric (telephone-like) and non voice type
services (e.g., text communication for hearing disabled users (RFC
3351 [8]) [2]) have an expectation to be able to initiate a request for
help in case of an emergency.

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

This document only focuses on end-to-end IP-based calls, i.e., where
the emergency call originates from an IP end system and terminates
into an IP-capable PSAP, conveyed entirely over an IP network.

This

Outlined within this document outlines the are various functional issues which
relate to placing an IP-based emergency call, including a description
of baseline requirements (Section 4), identification of the emergency
caller's location (Section 5), use of an emergency service identifier to
declare a call to be an emergency call (Section 6), and finally, the
mapping function required to route the call to the appropriate PSAP
(Section 7).

Ideally,

The primary intent of the mapping protocol would yield is to produce a PSAP URI from
(from a preferred set of URIs (e.g., URIs, e.g., SIP:URI, SIPS:URI) which would allow based on both
location information [6] and a service identifier in order to
facilitate the IP end-to-end completion of an emergency call
to call. Aside
from obtaining a PSAP URI, the mapping protocol is useful for
obtaining other information as well. There may be completed using IP end-to-end. Despite this goal, a case, for
example, where an appropriate dial string is not known, only
location. The mapping protocol can then return a geographically
appropriate dial string based on the input.

Since some PSAPs may not immediately have IP based connectivity, and therefore it is
imperative that the URI scheme support IP, or because some end
devices (UAs) may not initially support emergency service URNs, it
may be fixed, in order necessary to ensure also support for a emergency service identifiers that
utilize less preferred set of URIs URI schemes, such as, for example, as a TEL tel URI which may be used in order to
complete a an emergency call via the PSTN.

Identification of the caller, while not incompatible with the
requirements for messaging outlined within this document, is

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considered to be outside the scope of the ECRIT charter. this document.

Location is required for two separate purposes, first, to route support the
routing of the emergency call to the appropriate PSAP and second, to
display the caller's location to the call taker for help in
dispatching emergency assistance to the appropriate location.

As used in this document, validation of location does not require

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that we ascertain as to whether or not the location actually exists.
For example, validation might only check that the house number in a
civic address falls within the assigned range, not whether a
building, known by a specific building number, exists at that
location. However, such higher precision validation is desirable.

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2. Terminology

In this document,

2. Terminology

In this document, the key words "MUST", "MUST NOT", "REQUIRED",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
and "OPTIONAL" are to be interpreted as described in RFC 2119 [1],
with the qualification that unless otherwise stated these words apply
to the design of the mapping protocol, not its implementation or
application.

Codes: "caller"

Basic emergency service: Basic Emergency Service allows a user to
reach a PSAP serving its current location, but the PSAP may not be
able to determine the identity or "emergency caller" refers geographic location of the
caller, except by having the call taker ask the caller.

Enhanced emergency service: Enhanced emergency services add the
ability to identify the person placing an caller's identity or location to basic
emergency services. (Sometimes, only the caller location may be
known, e.g., when a call is placed from a public access point that
is not owned by an individual.)

Internet Attachment Provider (IAP): An organization that provides
physical and layer 2 network connectivity to its customers or sending
users, e.g., through digital subscriber lines, cable TV plants,
Ethernet, leased lines or radio frequencies. Examples of such
organizations include telecommunication carriers, municipal
utilities, larger enterprises with their own network
infrastructure, and government organizations such as the military.

Internet Service Provider (ISP): An organization that provides IP
network-layer services to its customers or users. This entity may
or may not provide the physical-layer and layer-2 connectivity,
such as fiber or Ethernet, i.e., it may or may not be the role of
an emergency instant message (IM). IAP.

Application Service Provider (ASP): The organization or entity that
provides application-layer services, which may include voice (see
"Voice Service Provider"). This entity can be a private
individual, an enterprise, a government, or a service provider.
An ASP is more general than a Voice Service Provider, since
emergency calls may use other media beyond voice, including text
and video. For a particular user, the ASP may or may not be the
same organization as his IAP or ISP.

Basic Emergency Service: Basic Emergency

Voice Service allows Provider (VSP): A specific type of Application Service
Provider which provides voice related services based on IP, such
as call routing, a user to
reach a PSAP serving its current location, but the PSAP may not be
able to determine the identity or geographic location of the
caller, except by having the call taker ask the caller.

Call taker: A call taker is an agent at the PSAP that accepts calls
and may dispatch emergency help. Sometimes the functions of call
taking and dispatching are handled by different groups of people,
but these divisions of labor are not generally visible to the
outside and thus do not concern us here.

Civic location: A described location based on some defined grid, such
as a jurisdictional, postal, metropolitan, or rural reference
system, (e.g., street address).

Emergency address: The URI (e.g., SIP:URI, SIPS:URI, XMPP:URI, IM: SIP URI, etc.) which represents the address of the PSAP useful for the
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
location PSTN termination. In this
document, unless noted otherwise, any reference to another entity in the network. "Voice Service
Provider" or "VSP" may be used interchangeably with "Application/

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Emergency identifier: An identifier that marks a call as an emergency
call.

Voice Service Provider" or "ASP/VSP".

Emergency Service Routing Proxy (ESRP): An ESRP is an emergency call
routing support entity that invokes the location-to-PSAP URI
mapping, to return either the URI for the appropriate PSAP, or the
URL for another ESRP. (In a SIP system, the ESRP would typically
be a SIP proxy, but may also be a Back-to-back user agent
(B2BUA)).

Enhanced emergency service: Enhanced emergency services add the
ability to identify

Emergency Call Routing Support (ECRS): An intermediary function which
assists in the caller's identity or location to basic routing of an emergency services. (Sometimes, only the caller location may be
known, e.g., when a call via IP. An ESRP is placed from an
example of an Emergency call routing support entity.

Public Safety Answering Point (PSAP): Physical location where
emergency calls are received under the responsibility of a public access point
authority. (This terminology is used by both ETSI, in ETSI SR 002
180, and NENA.) In the United Kingdom, PSAPs are called Operator
Assistance Centres, in New Zealand, Communications Centres.
Within this document, it is assumed, unless stated otherwise, that
PSAP is not owned that which supports the receipt of emergency calls over
IP. It is also assumed that the PSAP is reachable by an individual.) IP-based
protocols, such as SIP for call signaling and RTP for media.

Location: A geographic identification assigned to a region or feature
based on a specific coordinate system, or by other precise
information such as a street number and name. It can be either a
civic or geographic location.

Civic location: A described location based on some defined grid, such
as a jurisdictional, postal, metropolitan, or rural reference
system, (e.g., street address).

Geographic location: A reference to a locatable point described by a
set of defined coordinates within a geographic coordinate system,
(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:

Location validation: A home emergency dial string represents a
(e.g., dialed) sequence of digits, that caller location is used to initiate an
emergency call considered valid if the
civic or geographic location is recognizable within a geographically correct an acceptable
location of a
caller if reference system (e.g., USPS, WGS-84, etc.), and can be
mapped to one or more PSAPs. While it is considered desirable to be determine
that a user's "home" location or
vicinity.

Internet Attachment Provider (IAP): An organization exists, validation may not ensure that provides
physical and layer 2 network connectivity to its customers or
users, e.g., through digital subscriber lines, cable TV plants,
Ethernet, leased lines or radio frequencies. Examples of such
organizations include telecommunication carriers, municipal
utilities, larger enterprises with their own network
infrastructure, and government organizations such as the military.

Internet Service Provider (ISP): An organization a
location exists. Location validation ensures that provides IP
network-layer services a location is
able to its customers or users. This entity may
or may not provide the physical-layer and layer-2 connectivity,
such as fiber or Ethernet, i.e., it may or may not be referenced for mapping, but makes no assumption about
the role of
an IAP.

Location: A geographic identification assigned to a region or feature
based on a specific coordinate system, or by other precise
information such as a street number association between the caller and name. It can be either a
civic or geographic the caller's location.

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Location-dependent

(Location-dependent) emergency dial string: Location-dependent
emergency dial strings should be thought of as the digit sequence
that is dialed in order to reach emergency services. There are
two dial strings, namely either a "home emergency dial string", or
a "visited emergency dial string", and is something separate from
an emergency service identifier, since each represents specific
emergency dial string key sequences which are recognized within a
local geographic area or jurisdiction.

Location validation:

Home emergency dial string: A caller location is considered valid if the
civic or geographic location is recognizable within an acceptable
location reference system home emergency dial string represents a
(e.g., USPS, WGS-84, etc.), and can be
mapped to one or more PSAPs. While it dialed) sequence of digits, that is desirable used to determine
that a location exists, validation may not ensure that such initiate an
emergency call within a geographically correct location exists. Location validation ensures that of a location
caller if it is
able considered to be referenced for mapping, but makes no assumption about
the association between the caller and the caller's location.

Mapping: The process of resolving a user's "home" location to one or more PSAP URIs
which directly identify a PSAP,
vicinity.

Visited emergency dial string: A visited emergency dial string
represents a sequence of digits that is used to initiate an
emergency call within a geographically correct location of the
caller if outside the caller's "home" location or vicinity.

Service identifier: A general identifier that has applicability to
both emergency and non-emergency contexts (specifically referred
to within this document as "emergency service identifier").

Service URN: An implementation of a service identifier, which has
applicability to both emergency and non-emergency contexts (e.g.,
urn:service:sos, urn:service:info, etc.) Within this document,
service URN is specifically referred to as 'emergency service URN'
[8].

Emergency service identifier (ESI): A specific service identifier
that is used to request a PSAP URI in order to initiate an
emergency call, and may be used to mark any call as an emergency
call. An ESI is a more general term than 'emergency service URN',
since it could also refer to an alternate identifier, such as a
tel URI (Section 6).

Emergency service URN: An emergency-context specific service URN that
is an implementation of an emergency service identifier (e.g.,
urn:service:sos). Is often referred to as, and is equivalent with
'sos service URN'.

PSAP URI: The URI (e.g., SIP:URI, SIPS:URI, XMPP:URI, etc.) at which
the PSAP may be contacted with an emergency call. This contact
could be done directly, or via an intermediary, (e.g., ESRP).

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Mapping: The process of resolving a location to one or more PSAP URIs
which directly identify a PSAP, or point to an intermediary which
knows about a PSAP and that is designated as responsible to serve
that location.

Mapping client: A mapping client interacts with the Mapping Server mapping server to
learn one or more PSAP URIs for a given location.

Mapping protocol: A protocol used to convey the mapping request and
response.

Mapping server: The Mapping Server mapping server holds information about the
location-to-PSAP URI mapping.

Mapping service: A network service which uses a distributed mapping
protocol, to perform a mapping between a location and a PSAP, or
intermediary which knows about the PSAP, and is used to assist in
routing an emergency call.

PSAP (Public Safety Answering Point): Physical location where
emergency calls are received under

(Emergency) caller: The term "caller" or "emergency caller" refer to
the responsibility of a public
authority. (This terminology is used by both ETSI, in ETSI SR 002
180, and NENA.) In the United Kingdom, PSAPs are called Operator
Assistance Centres, in New Zealand, Communications Centres.
Within this document, it is assumed, unless stated otherwise, that
PSAP is that which supports the receipt of person placing an emergency calls over
IP. It is also assumed that the PSAP is reachable by IP-based
protocols, such as SIP for call signaling and RTP for media.

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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
address, or the IP address of some other intermediary, e.g., sending an
ESRP, which points to the actual PSAP.

Visited emergency dial string:
instant message (IM).

Call taker: A visited emergency dial string
represents a sequence of digits that call taker is used to initiate an
emergency call within a geographically correct location of agent at the
caller if outside PSAP that accepts calls
and may dispatch emergency help. Sometimes the caller's "home" location or vicinity.

Voice Service Provider (VSP): A specific type functions of Application Service
Provider which provides voice related services based on IP, such
as call routing, a SIP URI, or PSTN termination. In this
document, unless noted otherwise, any reference
taking and dispatching are handled by different groups of people,
but these divisions of labor are not generally visible to "Voice Service
Provider" or "VSP" may be used interchangeably with "Application/
Voice Service Provider" or "ASP/VSP". the
outside and thus do not concern us here.

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3. Basic Actors

In order to support emergency services covering a large physical
area, various infrastructure elements are necessary, including:
Internet Attachment Providers (IAPs), Application/Voice Service
Providers (ASP/VSPs), PSAPs as endpoints for emergency calls, Emergency Call Routing Support (ECRS)
providers, mapping
services or other infrastructure elements that assist during the call
routing. service providers, and PSAPs.

This section outlines which entities will be considered in the
routing scenarios discussed.

Location
Information +-----------------+
|(1) |Internet | +-----------+
v |Attachment | | |
+-----------+ |Provider | | Mapping |
| | | (3) | | Service |
| Emergency |<---+-----------------+-->| |
| Caller | | (2) | +-----------+
| |<---+-------+ | ^
+-----------+ | +----|---------+------+ |
^ | | Location | | |
| | | Information<-+ | |
| +--+--------------+ |(5) | | (6)
| | | | |
| | +-----------v+ | |
| (4) | |Emergency | | |
+--------------+--->|Call Routing|<--+---+
| | |Support | |
| | +------------+ |
| | ^ |
| | (7) | | +----+--+
| (8) | +------------>| |
+--------------+----------------------->| PSAP |
| | | |
|Application/ | +----+--+
|Voice |
|Service |
|Provider |
+---------------------+

Figure 1: Framework for emergency call routing

Figure 1 shows the interaction between the entities involved in the
call. There are a number of different deployment choices, as can be
easily seen from the figure.

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o How is location information provided to the end host? It might
either be known to the end host itself via manual configuration,
provided via GPS, or obtained via a third party method. Even if
location information is known to the network it might be made available to the end host via DHCP (RFC 3825 [2]) [4]) or some
other
mechanism. mechanisms. Alternatively, location information is used as
part of call routing and inserted by intermediaries.

o Is the Internet Attachment Provider also the Application/Voice
Service Provider? In the Internet today these roles are typically
provided by different entities. As a consequence, the Application/
Voice Service Provider is typically not able to learn the physical
location of the emergency caller.

The overlapping squares in the figure indicate that some functions
can be collapsed into a single entity. As an example, the
Application/Voice Service Provider might be the same entity as the
Internet Attachment Provider. There is, however, no requirement that
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
residential users.

Various potential interactions between the entities depicted in
Figure 1, are described in the following:

(1) Location information might be available to the end host itself.

(2) Location information might, however, also be obtained from the
Internet Attachment Provider (e.g., using DHCP or application layer
signaling protocols).

(3) The emergency caller might need to consult a mapping service to
determine the PSAP (or other relevant information) that is
appropriate for the physical location of the emergency caller,
possibly considering other attributes such as appropriate language
support by the emergency call taker.

(4) The emergency caller might get assistance for emergency call
routing by infrastructure elements that are Emergency Call Routing
Support entities, e.g., an Emergency Service Routing Proxy (ESRP), in
SIP).

(5) Location Information information is used by emergency call routing entities
for subsequent mapping requests.

(6) Emergency call routing support entities might need to consult a
mapping service to determine where to route the emergency call.

(7) For infrastructure-based emergency call routing (in contrast to
UE-based emergency call routing), the emergency call routing support

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UE-based emergency call routing), the emergency call routing support

entity needs to forward the call to the PSAP.

(8) The emergency caller (UE) may interact directly with the PSAP
(e.g., UE invokes mapping, and initiates a connection), without
relying on any intermediary emergency call routing support entities.

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4. High-Level Requirements

Below, we summarize high-level architectural requirements that guide
some of the component requirements detailed later in the document.

Re1. Application/Voice service provider existence: The initiation of
an IP-based emergency call SHOULD NOT assume the existence of an
Application/Voice Service Provider (ASP/VSP).

Motivation: The caller may not have an application/voice service
provider. For example, a residence may have its own DNS domain
and run its own SIP proxy server for that domain. On a larger
scale, a university might provide voice services to its students
and staff, but might not be a telecommunication provider.

Re2. International applicability: Regional, political and
organizational aspects MUST be considered during the design of
protocols and protocol extensions which support IP-based emergency
calls.

Motivation: It must be possible for a device or software developed
or purchased in one country to place emergency calls in another
country. System components should not be biased towards a
particular set of emergency numbers or languages. Also, different
countries have evolved different ways of organizing emergency
services, e.g., either centralizing them or having smaller
regional subdivisions such as United States counties or
municipalities handle emergency calls.

Re3. Distributed administration: Deployment of IP-based emergency
services MUST NOT depend on a sole central administration
authority.

Motivation: The design mapping protocol must make it possible to
deploy and administer emergency calling features on a regional or
national basis without requiring coordination with other regions
or nations. The system cannot assume, for example, that there is
a single global entity issuing certificates for PSAPs, ASP/VSPs,
IAPs or other participants.

Re4. Multi-mode communication: IP-based emergency calls MUST support
multiple communication modes, including, for example, audio, video
and text.

Motivation: In PSTN, voice and text telephony (often called TTY or
text-phone in North America) are the only commonly supported
media. Emergency calling must support a variety of media. Such
media should include voice, conversational text (RFC 4103 [10]), [5]),

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instant messaging and video.

Re5. 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.

Re6. Currency indication: The mapping protocol SHOULD support an
indicator describing how current the information provided by the
mapping source is.

Motivation: This is especially useful when an alternate mapping is
requested, and alternative sources of mapping data may not have
been created or updated with the same set of information or within
the same timeframe. Differences in currency between mapping data
contained within mapping sources should be minimized.

Re7. Mapping result usability: The mapping protocol MUST return one
or more URIs that are usable within a standard signaling protocol
(i.e., without special emergency extensions).

Motivation: For example, a SIP specific URI which is returned by
the mapping protocol needs to be usable by any SIP capable phone
within a SIP initiated emergency call. This is in contrast to a
"special purpose" URI, which may not be recognizable by a legacy
SIP device.

Re8. PSAP URI accessibility: The mapping protocol MUST support
interaction between the client and server where no enrollment to a
mapping service exists or is required.

Motivation: The mapping server may well be operated by a service
provider, but access to the server offering the mapping must not
require use of a specific ISP or ASP/VSP.

Re9. Common data structures and formats: The mapping protocol SHOULD
support common data structures and formats from the mapping
server.

Motivation: Location databases should not need to be transformed
or modified in any unusual or unreasonable way in order for the
mapping protocol to use the data. For example, a database which
contains civic addresses used by location servers may be used for
multiple purposes and applications beyond emergency service
location-to-PSAP URI mapping.

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Re10. Anonymous mapping: The mapping protocol MUST NOT require the
true identity of the target for which the location information is
attributed.

Motivation: Ideally, no identity information is provided via the
mapping protocol. Where identity information is provided, it may
be in the form of an unlinked pseudonym (RFC 3693 [9]). [3]).

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5. Identifying the Caller's Location

Location can either be provided directly, or by reference, and
represents either a civic location, or as a geographic geospatial location. How
does the location (or An
important question is how and when to attach location reference) become associated with information to
the
call? VoIP emergency signaling. In general, we can distinguish three
modes of operation of how a location is associated with an emergency
call:

UA-inserted: The caller's user agent inserts the location information
into the call signaling message. The location information is
derived from sources such as GPS, DHCP (RFC 3825 [2]) (see [4] for geospatial
location information and
I-D.ietf-geopriv-dhcp-civil [7]) [10]) for civic location information or
utilizing the Link Layer Discovery Protocol (LLDP) [see
IEEE8021AB].

UA-referenced: The caller's user agent provides a pointer (i.e., a
location reference), via a permanent or temporary identifier, to
the location which is stored by a location service server somewhere else
and then retrieved by the PSAP, ESRP, or other authorized service
entity.

Proxy-inserted: A proxy along the call path inserts the location or
location reference.

Lo1. Reference datum: The mapping protocol MUST support the WGS-84
coordinate reference system and MAY support other coordinate
reference systems.

Lo2. Location object/info preservation: The mapping protocol MUST
retain any location information which is provided to it, even
after mapping is performed.

Motivation: The ESRP and the PSAP use the same location
information object, but for a different purpose. Therefore, it is
imperative that the mapping protocol does not remove the location
Information
information from the messaging, so that the PSAP it can still receive be provided to the caller
location.
PSAP.

Lo3. Location delivery by-value: The mapping protocol MUST support
the delivery of location information using a by-value method,
though it MAY also support de-referencing a URL that references a
location object.

Motivation: The mapping protocol is not required to support the
ability to de-reference specific location references.

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Lo4. Alternate community names: The mapping protocol MUST support
both the jurisdictional community name and the postal community
name fields within the PIDF-LO data.

Motivation: A mapping query must be accepted with either or both
community name fields, and provide appropriate responses. If a
mapping query is made with only one field present, and if the
database contains both jurisdictional and postal, the mapping
protocol response should return both.

Lo5. Validation of civic location: The mapping protocol MUST support
location validation for civic location (street addresses), prior
to initiating an emergency call. addresses).

Motivation: Location validation provides an opportunity to help
assure ahead of time, whether or not a 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.

Lo6. Validation resolution: The mapping protocol MUST support the
ability to provide ancillary information about the resolution of
location data used to retrieve 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.

Lo7. Indication of non-existent location: The mapping protocol MUST
support a mechanism to indicate and resolve any associated issues
attributed to a location or a part of a location that is known to
not exist, despite the receipt of a successful mapping response.

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.

Lo8. Limits to validation: Successful validation of a civic location
MUST NOT be required to place an emergency call.

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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 call setup signaling path to the
PSAP.

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Lo9. 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 end devices or location servers
will accept
both provide either 2D and or 3D data. When a 3D request is presented to
within an area only defined by 2D data, data within the mapping server,
the mapping result would be the same as if the height/altitude
dimension was omitted in the request.

Lo10. Location validation indicator: The mapping protocol MAY
support a mechanism which indicates whether a civic location does
or does not fall within an existing range of addresses listed
within a referenced address database.

Motivation: It is helpful to get an indication of whether the
validation process worked or not.

Lo11. Matched element indication: The mapping protocol MAY support a
mechanism which returns an indication of specific data elements
which were matched as a result of a validation query.

Motivation: Given a query using "123 Main St. Anytown"
(represented, as A1, A2, A3, A5 in this example) it may be helpful
to receive an indication that the validation process matched only
elements A2, A3, A5 (but not A1).

Lo12. Database type indicator: The mapping protocol MAY support a
mechanism which provides an indication describing a specific
"type" of location database used.

Motivation: It is useful to know the source of the data stored in
the database used for location validation. This is applicable for
either civic or geographic location matching (e.g., USPS, MSAG,
GDT, etc.).

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6. Emergency Service Identifier

Id1. Emergency

The term, service identifier, is a general term that incorporates all
service URNs [8], but which may also refer to other identifiers which
are not service URNs, for example, a tel URI. In protocol exchanges,
any request to invoke an emergency service along with the specific
type of emergency service desired, such as fire department or police,
is indicated by the service URN.

Since this document addresses only emergency service context specific
requirements for mapping, the terms service identifier and service
URN, which have a more general applicability than that of only
emergency services, are replaced by the terms "emergency service
identifier" and "emergency service URN", respectively, throughout
this document. The term "sos service URN" is used interchangeably
with "emergency service URN".

Id1. Emergency service identifier support: The mapping protocol MUST support
be able to return one or more multiple emergency service identifiers for delivery back to mapping
clients in
response to be used for call setup purposes. a query.

Motivation: Since there is a need for any device or network
element to recognize an emergency call throughout the call setup,
there is also a need to have the mapping protocol provide support
for such an identifier. This is regardless of the device location
or the ASP/VSP used. An example of this kind of identifier might
be "urn:service:sos". the emergency service URN, 'urn:service:sos'.

Id2. Emergency service identifier resolution: Where multiple
emergency service identifiers exist, the mapping protocol MUST be
able to differentiate between identifiers ESIs based on the specific type of
emergency help requested.

Motivation: Some jurisdictions may have multiple types of
emergency services available, (e.g., fire, police, ambulance), in
which case, it is important that any one could be selected
directly.

Id3. Emergency identifier marking: The mapping protocol MUST include
an emergency identifier with the signaling, if one does not exist,
for the purpose of marking the call as an emergency call.

Motivation: Marking ensures proper handling as an emergency call
by downstream elements that may not recognize, for example, a
local variant of a logical emergency address, etc. This marking
mechanism is assumed to be different than a QoS marking mechanism.

Id4. Prevention of fraud: If a call is identified as an emergency
call, the mapping protocol MUST support that call being
successfully routed to a PSAP.

Motivation: This prevents use of the emergency call indication to
gain access to call features or authentication override for non-
emergency purposes.

Id5. Extensible emergency service identifiers: The mapping protocol
MUST support an extensible list of emergency identifiers, though
it is not required to provide mapping for every possible service.

Motivation: The use of an emergency service identifier is locally
determined.

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Id6.

Id4. Discovery of emergency dial string: The mapping protocol There MUST be support for a
mechanism to discover an existing location-dependent emergency
dial string, (e.g., "9-1-1", "1-1-2"), which are contextually appropriate
for the location of the caller.

Motivation: Users are trained to dial the appropriate emergency
dial string to reach emergency services. There needs to be a way
to figure out what the dial string is within the local environment
of the caller.

Id7.

Id5. Home emergency dial string translation: The mapping protocol There MUST be support
for end device translation (e.g. SIP UA) of a home emergency dial
string into an emergency service identifier.

Motivation: The UA would most likely be pre-provisioned with the
appropriate information in order to make such a translation. The
mapping protocol would be able to support either type for those
clients which may not support dial string translation.

Id8.

Id6. Emergency dial string replacement: The mapping protocol There SHOULD be support for
replacement of the original dial string with a reserved emergency
service identifier for each signaling protocol used for an
emergency call. This replacement of the original dial string
should be based on local conventions, regulations, or preference
(e.g., as in the case of an enterprise).

Motivation: Any signaling protocol requires the use of some
identifier to indicate the called party, and the user terminal may
lack the capability to determine the actual emergency address
(PSAP URI). The use of local conventions may be required as a
transition mechanism. Note: Such use complicates international
movement of the user terminal. Evolution to a standardized
emergency service identifier or set of identifiers is preferred.

Id9.

Id7. Emergency service identifier marking: There MUST be support for
an emergency service identifier to be used for marking the call as
an emergency call.

Id8. Emergency service identifier not recognized: The mapping protocol There MUST be
support for calls which are initiated as emergency calls even if
the specific emergency service requested is not recognized, based
on the emergency service identifier used.

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Motivation: In order to have a robust system that supports
incremental service deployment while still maintaining a fallback
capability.

Id10.

Id9. Discovery of visited emergency dial strings: The mapping
protocol There MUST be
support for a mechanism to allow the end device to learn visited
emergency dial strings.

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Motivation: Scenarios exist where a user dials a visited emergency
dial string that is different from the home emergency dial string:
If a user (i.e., UA operator) visits a foreign country, observes a
fire truck with 999 on the side, the expectation is one of being
able to dial that same number to summon a fire truck. Another use
case cited is where a tourist collapses, and a "good Samaritan"
uses the tourist's cell phone to enter a home emergency dial
string appropriate for that foreign country.

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7. Mapping Protocol

There are two basic approaches to invoking a invoke the mapping service. protocol. We
refer to these as caller-based and mediated. In each case, the
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]. [9].

For caller-based resolution, the caller's user agent invokes a the
mapping service protocol to determine the appropriate PSAP based on the
location provided. The resolution may take place well before the
actual emergency call is placed, or at the time of the call.

For mediated resolution, a an emergency call signaling server, routing support entity,
such as a SIP (outbound) proxy or redirect server invokes the mapping
service.

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
server has to be able to translate any caller location to the
appropriate PSAP. (A traveler may, for example, accidentally or
intentionally configure its home proxy server as its outbound proxy
server, even while far away from home.)

Ma1. Appropriate PSAP: Baseline query protocol: A mandatory-to-implement protocol MUST
be specified.

Motivation: An over-abundance of similarly-capable choices appears
undesirable for interoperability.

Ma2. Extensible protocol: The mapping protocol MUST be designed to
support the routing extensibility of an emergency call to the PSAP responsible location data elements, both for a particular
geographic area. new
and existing fields.

Motivation: Routing This is needed, for example, to the wrong PSAP will result in delays accommodate future
extensions to location information that might be included in
handling emergencies as calls are redirected, and result the
PIDF-LO (RFC 4119 [6]).

Ma3. Incrementally deployable: The mapping protocol MUST be designed
in
inefficient use of PSAP resources at such a way that supports the initial point incremental deployment of contact. mapping
services.

Motivation: It is important that the location determination mechanism must not be
fooled by the location of IP telephony gateways or dial-in lines
into a corporate LAN (and dispatch emergency help to the gateway
or campus, rather than the caller), multi-site LANs and similar
arrangements.

Ma2. Minimal additional delay: Mapping protocol execution SHOULD
minimize the amount of delay within the overall call-setup time.

Motivation: Since outbound proxies will likely be asked necessary, for example, to resolve
the same geographic coordinates repeatedly, a suitable time-
limited caching mechanism should be supported.

Ma3. Mapping referral: The mapping protocol MUST support have a mechanism
for
global street level database before deploying the mapping client to contact any mapping server and be
referred to another mapping server that system. It is more qualified
acceptable to
answer have some misrouting of calls when the query. database does
not (yet) contain accurate PSAP service area information.

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Motivation: To help avoid the case of relying on incorrect
configuration data which may cause calls to fail, particularly for
caller-based mapping queries.

Ma4. Multiple response URIs: Any time mapping: The mapping protocol MUST support the
possible inclusion ability
of multiple URIs the mapping function to be invoked at any time, including while
an emergency call is in process and before an emergency call.

Motivation: Used as a fallback mechanism only, if a mapping response.

Motivation: Multiple URIs query
fails at emergency call time, it may be available from advantageous to have prior
knowledge of the PSAP URI. This prior knowledge would be obtained
by performing a mapping
server.

Ma5. URI alternate contact: In addition query at any time prior to returning a primary
contact, the an emergency
call.

Ma5. Anywhere mapping: The mapping protocol MUST support the return of a URI or
contact method explicitly marked as an alternate contact.

Motivation: In response ability
to a provide mapping request, information in response to an individual query
from any (earthly) location, regardless of where the mapping server
may return
client is located, either geographically or by network location.

Motivation: The mapping client, such as an alternate URI. Implementation details ESRP, may not
necessarily be anywhere close to the caller or the appropriate
PSAP, but must still be
described within an operational document. able to obtain mapping information.

Ma6. URL properties: Appropriate PSAP: The mapping protocol MUST support the ability routing
of an emergency call to provide ancillary information about a contact or URI that
allows the mapping client PSAP responsible for a particular
geographic area.

Motivation: Routing to determine relevant properties of the
URL.

Motivation: In some cases, wrong PSAP will result in delays in
handling emergencies as calls are redirected, and result in
inefficient use of PSAP resources at the same geographic area initial point of contact.
It is served by
several PSAPs, for example, a corporate campus might important that the location determination mechanism not be served
fooled by
both the location of IP telephony gateways or dial-in lines
into a corporate security department and the municipal PSAP. The
mapping protocol should then return URLs for both, with
information allowing the querying entity LAN (and dispatch emergency help to choose one or the
other. This determination could be made by either an ESRP, based
on local policy, gateway
or by direct user choice, in campus, rather than the case of caller-
based methods. caller), multi-site LANs and similar
arrangements.

Ma7. Traceable resolution: Multiple PSAP URIs: The mapping protocol SHOULD MUST support the
ability of the mapping client to be able a method
to determine the entity
or entities return multiple PSAP URIs which provided cover the emergency address resolution
information. same geographic area.

Motivation: It is important for public safety reasons, that there
is a method to provide operational traceability in case Two different mapping servers may cover the same
geographic area, and therefore have the same set of errors. coverage
information.

Ma8. Single primary URI for error reporting: The per contact protocol: Though the mapping
protocol MUST support the supports multiple URIs being returned, it SHOULD return of a
only one primary URI per contact protocol used, so that can be used clients
are not required to report a suspected or known
error within the mapping database.

Motivation: If an error is returned, select among different targets for example, there needs to
be a URI which points to a resource which can explain or
potentially help resolve the error. same
contact protocol.

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Ma9. Resilience against failure:

Motivation: There may be two or more URIs returned when multiple
contact protocols are available (e.g., SIP and SMS). The client
may select among multiple contact protocols based on its
capabilities, preference settings, or availability.

Ma9. URI alternate contact: In addition to returning a primary
contact, the mapping protocol MUST support the return of a
mechanism which enables fail over to different (replica) mapping
server in order to obtain PSAP
URI or contact method explicitly marked as an alternate contact
for use when a successful mapping.

Motivation: It fallback contact is important that the failure of needed.

Motivation: In response to a single mapping
server does not preclude request, the mapping client's ability server
will also return an alternate URI. Implementation details to receive
mapping from a different mapping server.

Ma10. Incrementally deployable: The mapping protocol MUST be
designed in such a way that supports
described within an operational document.

Ma10. Non-preferred URI schemes: The mapping protocol MAY support
the incremental deployment return of
mapping services. a less preferred URI scheme, (e.g., TEL URI).

Motivation: It must not In order to provide incremental support to non-IP
PSAPs it may be necessary, for example, necessary to have a
global street level database before deploying the system. It is
acceptable be able to have some misrouting of calls when complete an emergency call
via the database does
not (yet) contain accurate PSAP service area information. PSTN.

Ma11. Any time mapping: URI properties: The mapping protocol MUST support the ability of the mapping function
to be invoked at any time,
including while an emergency call is in process and before an
emergency call.

Motivation: Used as a fallback mechanism only, if provide ancillary information about a contact that allows the
mapping query
fails at emergency call time, it may be advantageous client to have prior
knowledge determine relevant properties of the PSAP URI. This prior knowledge would

Motivation: In some cases, the same geographic area is served by
several PSAPs, for example, a corporate campus might be obtained served by performing
both a corporate security department and the municipal PSAP. The
mapping query at any time prior protocol should then return URIs for both, with
information allowing the querying entity to choose one or the
other. This determination could be made by either an emergency
call. ESRP, based
on local policy, or by direct user choice, in the case of caller-
based methods.

Ma12. Anywhere mapping: Mapping referral: The mapping protocol MUST support a
mechanism for the
ability to provide mapping information in response client to an
individual query from contact any (earthly) location, regardless of where
the mapping client is located, either geographically or by network
location.

Motivation: The mapping client, such as an ESRP, may not
necessarily be anywhere close to the caller or the appropriate
PSAP, but must still server and
be able referred to obtain mapping information.

Ma13. Extensible protocol: The another mapping protocol MUST be designed server that is more qualified to
support
answer the extensibility query.

Motivation: To help avoid the case of location relying on incorrect
configuration data elements, both for new
and existing fields.

Motivation: This is needed, for example, to accommodate future
extensions which may cause calls to location information that might be included in the
PIDF-LO (RFC 4119 [3]).

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Ma14. fail, particularly for
caller-based mapping queries.

Ma13. Split responsibility: The mapping protocol MUST support the
division of data subset handling between multiple mapping servers
within a single level of a civic location hierarchy.

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Motivation: For example, two mapping servers for the same city or
county may handle different streets within that city or county.

Ma15. Baseline query protocol: A mandatory-to-implement

Ma14. URL for error reporting: The mapping protocol MUST support the
ability to return a URL that can be specified. used to report a suspected or
known error within the mapping database.

Motivation: An over-abundance of similarly-capable choices appears
undesirable If an error is returned, for interoperability.

Ma16. Multiple PSAP URIs: example, there needs to
be a URL which points to a resource which can explain or
potentially help resolve the error.

Ma15. Resiliance to failure: The mapping protocol MUST support a method
to receive multiple PSAP URIs
mechanism which cover the same geographic
area.

Motivation: Two enables fail over to different (replica) mapping servers may cover the same
geographic area,
server in order to obtain and therefore have return a successful mapping to the same set
mapping client.

Motivation: It is important that the failure of coverage
information.

Ma17. Single URI per contact protocol: Though a single mapping
server does not preclude the mapping client's ability to receive
mapping from a different mapping server.

Ma16. Traceable resolution: The mapping protocol
supports SHOULD support the return
ability of multiple URIs, it SHOULD return only one
URI per contact protocol, so that clients are not required the mapping client to
select among different targets be able to determine the entity
or entities that provided the emergency address resolution
information.

Motivation: It is important for public safety reasons, that there
is a method to provide operational traceability in case of errors.

Ma17. Minimal additional delay: Mapping protocol execution SHOULD
minimize the same contact protocol. amount of delay within the overall call-setup time.

Motivation: There may Since outbound proxies will likely be asked to resolve
the same geographic coordinates repeatedly, a suitable time-
limited caching mechanism should be two or more URIs returned when multiple
contact protocols are available (e.g., SIP and SMS). The client
may select among multiple contact protocols based on its
capabilities, preference settings, or availability. supported.

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8. Security Considerations

Security considerations

Threats and security requirements are discussed in the ECRIT security document a separate
document, see I-D.ietf-ecrit-security-threats [4] [7] .

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9. IANA Considerations

This document does not require actions by the IANA.

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10. Contributors

The information contained in this document is a result of a several
original joint
effort based on individual contributions of text, which was then discussed and
refined by those involved in and many others within the
ECRIT WG. The working group. These
contributors include to the early text include, Nadine Abbott, Hideki Arai,
Martin Dawson, Motoharu Kawanishi, Brian Rosen, Richard Stastny,
Martin Thomson, James Winterbottom.

The contributors can be reached at:

Nadine Abbott nabbott@telcordia.com

Hideki Arai arai859@oki.com

Martin Dawson Martin.Dawson@andrew.com

Motoharu Kawanishi kawanishi381@oki.com

Brian Rosen br@brianrosen.net

Richard Stastny Richard.Stastny@oefeg.at

Martin Thomson Martin.Thomson@andrew.com

James Winterbottom James.Winterbottom@andrew.com

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10.

11. Acknowledgments

In addition to thanking those listed above, we would like to also
thank Guy Caron, Barry Dingle, Keith Drage, Tim Dunn, Patrik
Faeltstroem, Clive D.W. Feather, Raymond Forbes, Randall Gellens,
Michael Haberler, Michael Hammer, Ted Hardie, Gunnar Hellstrom,
Cullen Jennings, Marc Linsner, Rohan Mahy, Patti McCalmont, Don
Mitchell, John Morris, Andrew Newton, Steve Norreys, Jon Peterson,
James Polk, Benny Rodrig, John Rosenberg, Jonathan Rosenberg, John
Schnizlein, Shida Schubert, James Seng, Byron Smith, Tom Taylor,
Barbara Stark, Hannes Tschofenig, and Nate Wilcox, for their
invaluable input.

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11.

12. References

11.1.

12.1. Normative References

[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.

12.2. Informative References

[2] Charlton, N., Gasson, M., Gybels, G., Spanner, M., and A. 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.

[3] Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and J.
Polk, "Geopriv Requirements", RFC 3693, February 2004.

[4] Polk, J., Schnizlein, J., and M. Linsner, "Dynamic Host
Configuration Protocol Option for Coordinate-based Location
Configuration Information", RFC 3825, July 2004.

[3]

[5] Hellstrom, G. and P. Jones, "RTP Payload for Text
Conversation", RFC 4103, June 2005.

[6] Peterson, J., "A Presence-based GEOPRIV Location Object
Format", RFC 4119, December 2005.

[4]

[7] Taylor, T., "Security Threats and Requirements for Emergency
Call Marking and Mapping", draft-ietf-ecrit-security-threats-01
(work in progress), April 2006.

[5]

[8] Schulzrinne, H., "A Uniform Resource Name (URN) for Services",
draft-ietf-ecrit-service-urn-02 (work in progress), April 2006.

[6]

[9] Hardie, T., "LoST: A Location-to-Service Translation Protocol",
draft-hardie-ecrit-lost-00 (work in progress), March 2006.

[7]

[10] Schulzrinne, H., "Dynamic Host Configuration Protocol (DHCPv4
and DHCPv6) Option for Civic Addresses Configuration
Information", draft-ietf-geopriv-dhcp-civil-09 (work in
progress), January 2006.

11.2. Informative References

[8] Charlton, N., Gasson, M., Gybels, G., Spanner, M., and A. 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.

[9] Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and J.
Polk, "Geopriv Requirements", RFC 3693, February 2004.

[10] Hellstrom, G. and P. Jones, "RTP Payload for Text
Conversation", RFC 4103, June 2005.

[11] Wijk, A., "Framework for real-time text over IP using SIP",
draft-ietf-sipping-toip-04 (work in progress), March 2006.

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Authors' Addresses

Henning Schulzrinne
Columbia University
Department of Computer Science
450 Computer Science Building
New York, NY 10027
US

Phone: +1 212 939 7004
Email: hgs+ecrit@cs.columbia.edu
URI: http://www.cs.columbia.edu

Roger Marshall (editor)
TeleCommunication Systems
2401 Elliott Avenue
2nd Floor
Seattle, WA 98121
US

Phone: +1 206 792 2424
Email: rmarshall@telecomsys.com
URI: http://www.telecomsys.com

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