draft-ietf-ecrit-requirements-02.txt   draft-ietf-ecrit-requirements-03.txt 
ecrit H. Schulzrinne ECRIT H. Schulzrinne
Internet-Draft Columbia U. Internet-Draft Columbia U.
Expires: July 3, 2006 R. Marshall, Ed. Expires: August 6, 2006 R. Marshall, Ed.
TCS TCS
December 30, 2005 February 2, 2006
Requirements for Emergency Context Resolution with Internet Technologies Requirements for Emergency Context Resolution with Internet Technologies
draft-ietf-ecrit-requirements-02.txt draft-ietf-ecrit-requirements-03.txt
Status of this Memo Status of this Memo
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This Internet-Draft will expire on July 3, 2006. This Internet-Draft will expire on August 6, 2006.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2005). Copyright (C) The Internet Society (2006).
Abstract Abstract
This document enumerates requirements for emergency calls placed by This document enumerates requirements for emergency calls placed by
the public using voice-over-IP (VoIP) and general Internet multimedia the public using voice-over-IP (VoIP) and general Internet multimedia
systems, where Internet protocols are used end-to-end. systems, where Internet protocols are used end-to-end.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Basic Actors . . . . . . . . . . . . . . . . . . . . . . . . . 8 3. Basic Actors . . . . . . . . . . . . . . . . . . . . . . . . . 9
4. High-Level Requirements . . . . . . . . . . . . . . . . . . . 11 4. High-Level Requirements . . . . . . . . . . . . . . . . . . . 12
5. Identifying the Caller Location . . . . . . . . . . . . . . . 13 5. Identifying the Caller Location . . . . . . . . . . . . . . . 14
6. Emergency Identifier . . . . . . . . . . . . . . . . . . . . . 15 6. Emergency Identifier . . . . . . . . . . . . . . . . . . . . . 16
7. Mapping Protocol . . . . . . . . . . . . . . . . . . . . . . . 17 7. Mapping Protocol . . . . . . . . . . . . . . . . . . . . . . . 19
8. Security Considerations . . . . . . . . . . . . . . . . . . . 22 8. Security Considerations . . . . . . . . . . . . . . . . . . . 25
9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 23 9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 26
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 24 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 27
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 25 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 28
11.1. Normative References . . . . . . . . . . . . . . . . . . 25 11.1. Normative References . . . . . . . . . . . . . . . . . . 28
11.2. Informative References . . . . . . . . . . . . . . . . . 25 11.2. Informative References . . . . . . . . . . . . . . . . . 28
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 26 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 29
Intellectual Property and Copyright Statements . . . . . . . . . . 27 Intellectual Property and Copyright Statements . . . . . . . . . . 30
1. Introduction 1. Introduction
Users of both voice-centric (telephone-like) and non voice type Users of both voice-centric (telephone-like) and non voice type
services (e.g. text messaging for hearing disabled users, (RFC 3351 services (e.g. text messaging for hearing disabled users, (RFC 3351
[5]) have an expectation to be able to initiate a request for help in [7]) have an expectation to be able to initiate a request for help in
case of an emergency. case of an emergency.
Unfortunately, the existing mechanisms to support emergency calls Unfortunately, the existing mechanisms to support emergency calls
that have evolved within the public circuit-switched telephone that have evolved within the public circuit-switched telephone
network (PSTN), are not appropriate to handle evolving IP-based network (PSTN), are not appropriate to handle evolving IP-based
voice, text and real-time multimedia communications. This document voice, text and real-time multimedia communications. This document
outlines the key requirements that IP-based end systems and network outlines the key requirements that IP-based end systems and network
elements, such as SIP proxies, need to satisfy in order to provide elements, such as SIP proxies, need to satisfy in order to provide
emergency call services, which at a minimum, offer the same emergency call services, which at a minimum, offer the same
functionality as existing PSTN services, with the additional overall functionality as existing PSTN services, with the additional overall
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the call to the appropriate PSAP and second, to display the caller's the call to the appropriate PSAP and second, to display the caller's
location to the call taker for help in dispatching emergency location to the call taker for help in dispatching emergency
assistance to the correct location. assistance to the correct location.
Ideally, the mapping protocol would yield a URI from a preferred set Ideally, the mapping protocol would yield a URI from a preferred set
of URIs (e.g. sips:uri; sip:uri), which would allow an emergency call of URIs (e.g. sips:uri; sip:uri), which would allow an emergency call
to be completed using IP end-to-end (possibly via the Internet). to be completed using IP end-to-end (possibly via the Internet).
Despite this goal, some PSAPs may not immediately have IP based Despite this goal, some PSAPs may not immediately have IP based
connectivity, and therefore it is imperative that the URI scheme not connectivity, and therefore it is imperative that the URI scheme not
be fixed, in order to ensure support for a less preferred set of 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 URIs, such as a TEL URI which may be used to complete a call over the
PSTN. PSTN.
2. Terminology 2. Terminology
In this document, the key words "MUST", "MUST NOT", "REQUIRED", In this document, the key words "MUST", "MUST NOT", "REQUIRED",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
and "OPTIONAL" are to be interpreted as described in RFC 2119 [1] and and "OPTIONAL" are to be interpreted as described in RFC 2119 [1] and
indicate requirement levels for compliant implementations. indicate requirement levels for compliant implementations.
Since a requirements document does not directly specify a protocol to Since a requirements document does not directly specify a protocol to
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An ASP is defined as something more general than a Voice Service An ASP is defined as something more general than a Voice Service
Provider, since emergency calls are sometimes likely to use other Provider, since emergency calls are sometimes likely to use other
media, including text and video. Note: For a particular user, the media, including text and video. Note: For a particular user, the
ASP may or may not be the same organization as the IAP and/or ISP. ASP may or may not be the same organization as the IAP and/or ISP.
Basic Emergency Service: Basic Emergency Service allows a user to Basic Emergency Service: Basic Emergency Service allows a user to
reach a PSAP serving its current location, but the PSAP may not be reach a PSAP serving its current location, but the PSAP may not be
able to determine the identity or geographic location of the able to determine the identity or geographic location of the
caller (except by having the call taker ask the caller). caller (except by having the call taker ask the caller).
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).
mapping service: A network service which uses a distributed mapping Emergency address: The uri scheme (e.g. sip:uri, sips:uri, xmpp:uri,
protocol to provide information about the PSAP, or intermediary
which knows about the PSAP, and is used to assist in routing an
emergency call.
emergency address: The uri scheme (e.g. sip:uri, sips:uri, xmpp:uri,
im:uri, etc.) which represents the address of the PSAP useful for im:uri, etc.) which represents the address of the PSAP useful for
the completion of an emergency call. the completion of an emergency call.
emergency caller: The user or user device entity which sends his/her Emergency caller: The user or user device entity which sends his/her
location to another entity in the network. location to another entity in the network.
emergency identifier: The numerical and/or text identifier which is Emergency identifier: The numerical and/or text identifier which is
supplied by a user or a user device, which identifies the call as supplied by a user or a user device, which identifies the call as
an emergency call and is translated into an emergency address for an emergency call and is translated into an emergency address,
call routing and completion. useful for call routing and completion of the emergency call.
enhanced emergency service: Enhanced emergency services add the Enhanced emergency service: Enhanced emergency services add the
ability to identify the caller identity and/or caller location to ability to identify the caller identity and/or caller location to
basic emergency services. (Sometimes, only the caller location basic emergency services. (Sometimes, only the caller location
may be known, e.g. from a public access point that is not owned by may be known, e.g. from a public access point that is not owned by
an individual.) an individual.)
ESRP (Emergency Services Routing Proxy): An ESRP is a call routing ESRP (Emergency Service Routing Proxy): An ESRP is a call routing
entity that invokes the location-to-URL mapping, which in turn may entity that invokes the location-to-URL mapping, which in turn may
return either the URL for another ESRP or the PSAP. (In a SIP return either the URL for another ESRP or the PSAP. (In a SIP
system, the ESRP would typically be a SIP proxy, but could also be system, the ESRP would typically be a SIP proxy, but could also be
a Back-to-back user agent (B2BUA). a Back-to-back user agent (B2BUA).
geographic location: A reference to a locatable point described by a Geographic location: A reference to a locatable point described by a
set of defined coordinates within a geographic coordinate system, set of defined coordinates within a geographic coordinate system,
(e.g. lat/lon within the WGS-84 datum) (e.g. lat/lon within the WGS-84 datum)
Home emergency dial-string: A home emergency dial-string (ref.
Location-dependent emergency identifier) represents a sequence of
digits that is used to initiate an emergency call within a
geographic vicinity considered to be a user's "home" location or
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 network connectivity to its customers or users, e.g.
through digital subscriber lines, cable TV plants, Ethernet, through digital subscriber lines, cable TV plants, Ethernet,
leased lines or radio frequencies. Examples of such organizations leased lines or radio frequencies. Examples of such organizations
include telecommunication carriers, municipal utilities, larger include telecommunication carriers, municipal utilities, larger
enterprises with their own network infrastructure, and government enterprises with their own network infrastructure, and government
organizations such as the military. organizations such as the military.
Internet Service Provider (ISP): An organization that provides IP Internet Service Provider (ISP): An organization that provides IP
network-layer services to its customers or users. This entity may network-layer services to its customers or users. This entity may
or may not provide the physical-layer and layer-2 connectivity, or may not provide the physical-layer and layer-2 connectivity,
such as fiber or Ethernet. such as fiber or Ethernet.
Local Emerency Identifier: An emergency identifier which is Location: A geographic identification assigned to a region or feature
recognized from within a geographic or jurisdictional area from
which an emergency request is initiated.
location: A geographic identification assigned to a region or feature
based on a specific coordinate system, or by other precise based on a specific coordinate system, or by other precise
information such as a street number and name. In the geocoding information such as a street number and name. In the geocoding
process, the location is defined with an x,y coordinate value process, the location is defined with an x,y coordinate value
according to the distance north or south of the equator and east according to the distance north or south of the equator and east
or west of the prime meridian. or west of the prime meridian.
location validation: A caller location is considered valid if the Location-dependent emergency identifier: Location-dependent emergency
identifiers, also referred to as "emergency dial-strings" within
this document, 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 a
universal emergency identifier, since each represents specific
emergency identifiers which are recognized within a local
geographic area or jurisdiction.
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. Location validation ensures that a mapped to one or more PSAPs. While it is desirable to determine
location is able to be referenced for mapping, but makes no that a location exists, validation may not ensure that such a
assumption about the association between the caller and the location exists. Location validation ensures that a location is
caller's location. able to be referenced for mapping, but makes no assumption about
the association between the caller and the caller's location.
Mapping: Process of resolving an location to a URI (or multiple Mapping: Process of resolving a location to a URI (or multiple URIs).
URIs).
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 multiple 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
protocol to provide information about the 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 PSAP (Public Safety Answering Point): Physical location where
emergency calls are received under the responsibility of a public emergency calls are received under the responsibility of a public
authority. (This terminology is used by both ETSI, in ETSI SR 002 authority. (This terminology is used by both ETSI, in ETSI SR 002
180, and NENA.) In the United Kingdom, PSAPs are called Operator 180, and NENA.) In the United Kingdom, PSAPs are called Operator
Assistance Centres, in New Zealand, Communications Centres. Assistance Centres, in New Zealand, Communications Centres.
Within this document, it is assumed, unless stated otherwise, that Within this document, it is assumed, unless stated otherwise, that
PSAP is that which supports the receipt of emergency calls over PSAP is that which supports the receipt of emergency calls over
IP. It is also assumed that the PSAP is reachable by IP-based IP. It is also assumed that the PSAP is reachable by IP-based
protocols, such as SIP for call signaling and RTP for media. protocols, such as SIP for call signaling and RTP for media.
Universal Identifier: An emergency identifier which is recognized by 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 some other intermediary's IP address, which points to
the actual PSAP.
Universal identifier: An emergency identifier which is recognized by
any compatible endpoint, from any geographic location as useful any compatible endpoint, from any geographic location as useful
for initiating an emergency request. A general approach to using for initiating an emergency request. A general approach to using
universal identifiers is outlined in the service URN draft universal identifiers is outlined in the service URN draft
(I-D.schulzrinne-sipping-service [4]). (I-D.schulzrinne-sipping-service [5]).
Visited emergency dial-string: A visited emergency dial-string (ref.
Location-dependent emergency identifier) represents a sequence of
digits that is used to initiate an emergency call within a
geographic vicinity other than a user's "home" location or
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 area
various infrastructure elements are necessary: Internet Attachment various infrastructure elements are necessary: Internet Attachment
Providers, Application/Voice Service Providers, PSAPs as endpoints Providers, Application/Voice Service Providers, PSAPs as endpoints
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to determine appropriate PSAP mapping. to determine appropriate PSAP mapping.
4. High-Level Requirements 4. High-Level Requirements
Below, we summarize high-level architectural requirements that guide Below, we summarize high-level architectural requirements that guide
some of the component requirements detailed later in the document. some of the component requirements detailed later in the document.
Re1. Application Service Provider: The existence of an Application Re1. Application Service Provider: The existence of an Application
Service Provider (ASP) MUST NOT be assumed. Service Provider (ASP) MUST NOT be assumed.
Motivation: The caller may not have a application/voice service Motivation: The caller may not have 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: The protocols and protocol extensions developed Re2. International: The protocols and protocol extensions developed
MUST support regional, political and organizational differences. MUST support regional, political and organizational differences.
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
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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. video and text messaging MUST be supported.
Motivation: In PSTN, voice and text telephony (often called TTY or Motivation: In PSTN, voice and text telephony (often called TTY or
textphone in North America ) are the only commonly supported textphone in North America) are the only commonly supported media.
media. Emergency calling must support a variety of media. Such Emergency calling must support a variety of media. Such media
media should include voice, conversational text (RFC 4103 [7]), should include voice, conversational text (RFC 4103 [9]), instant
instant messaging and video. messaging and video.
Re5. Alternate Mapping Sources: The mapping protocol SHOULD allow Re5. Alternate Mapping Sources: The mapping protocol SHOULD allow
for alternative redundant sources of mapping information, possibly for alternative redundant sources of mapping information, possibly
of different degrees of currency. of different degrees of currency.
Motivation: This provides the possibility of having available Motivation: This provides the possibility of having available
alternative sources of mapping information when the normal source alternative sources of mapping information when the normal source
is unavailable or unreachable, without specifying the means by is unavailable or unreachable, without specifying the means by
which the alternative source is created or updated. which the alternative source is created or updated.
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without special emergency extensions) unless an error is returned. without special emergency extensions) unless an error is returned.
Motivation: The format of the output returned by the mapping Motivation: The format of the output returned by the mapping
protocol is in a standard format for communication protocol. For protocol is in a standard format for communication protocol. For
example, it should return something SIP specific (e.g. URI), that example, it should return something SIP specific (e.g. URI), that
any SIP capable phone would be able to use if used in a SIP any SIP capable phone would be able to use if used in a SIP
context. Special purpose URIs would not be understood by "legacy" context. Special purpose URIs would not be understood by "legacy"
SIP devices since they do not have knowledge about the mapping SIP devices since they do not have knowledge about the mapping
protocol, and therefore are not to be used. protocol, and therefore are not to be used.
Re7. Ubiquiteous Triggering: It MUST be possible to invoke the Re7. Ubiquitous Triggering: It MUST be possible to invoke the
mapping protocol at any time, from any location, by any client mapping protocol at any time, from any location, by any client
which supports the mapping protocol. which supports the mapping protocol.
Motivation: While end devices are the typical initiators of Motivation: While end devices are the typical initiators of
mapping service requests, it is also expected that other mapping mapping service requests, it is also expected that other mapping
clients, such as relays, 3rd party devices, PSAPs, etc. may also clients, such as relays, 3rd party devices, PSAPs, etc. may also
trigger a mapping request. trigger a mapping request.
Re8. PSAP Identification: The mapping information MUST be available Re8. PSAP Identification: The mapping information MUST be available
without having to enroll with a service provider. without having to enroll with a service provider.
Motivation: The mapping server may well be operated by a service Motivation: The mapping server may well be operated by a service
provider, but access to the server offering the mapping must not provider, but access to the server offering the mapping must not
require use of a specific ISP or VSP. require use of a specific ISP or VSP.
Re9X. No Modification of Location Databases: The mapping protocol
SHOULD NOT require that data within location databases be
transformed or modified in any unusual or unreasonable way in
order for the mapping protocol to use the data.
Motivation: Databases which contain civic addresses (used within
location information servers), may be used for multiple purposes
and applications, (in addition to being used for emergency service
mapping only).
5. Identifying the Caller Location 5. Identifying the Caller Location
Location can either be provided directly, or by reference, and Location can either be provided directly, 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, derived from sources such as GPS, DHCP or link-layer information, derived from sources such as GPS, DHCP (RFC 3825 [2])
announcements (LLDP). and I-D.ietf-geopriv-dhcp-civil [6]) or utilizing the Link Layer
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 reference, via a
permanent or temporary identifier, to the location which is stored permanent or temporary identifier, to the location which is stored
by a location service somewhere else and then retrieved by the by a location service somewhere else and then retrieved by the
PSAP. PSAP.
Proxy-inserted: A proxy along the call path inserts the location or Proxy-inserted: A proxy along the call path inserts the location or
location reference. location reference.
Lo1. Validation of Civic Location: It MUST be possible to validate a Lo1. Validation of Civic Location: It MUST be possible to validate a
civic location prior to its use in an actual emergency call. civic location prior to its use in an actual emergency call.
Motivation: Location validation provides an opportunity to help Motivation: Location validation provides an opportunity to help
assure ahead of time, whether successful mapping to the assure ahead of time, whether successful mapping to the
appropriate PSAP will likely occur when it is required. appropriate PSAP will likely occur when it is required.
Validation may also help to avoid delays during emergency call Validation may also help to avoid delays during emergency call
setup due to invalid locations. setup due to invalid locations.
Lo1X. Validation Resolution: The mapping protocol MUST support 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.
Lo1XX. 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.
Lo2. Limits to Validation: Validation of a civic location MUST NOT Lo2. Limits to Validation: Validation of a civic location MUST NOT
be required to enable any feature that is part of the emergency be required to enable any feature that is part of the emergency
call process. call process.
Motivation: In some cases, (based on a variety of factors), a Motivation: In some cases, (based on a variety of factors), a
civic location may not be considered valid. This fact should not civic location may not be considered valid. This fact should not
result in the call being dropped or rejected by any entity along result in the call being dropped or rejected by any entity along
the signaling path to the PSAP. the signaling path to the PSAP.
Lo3. Reference Datum: The mapping server MUST understand WGS-84 Lo3. Reference Datum: The mapping server MUST understand WGS-84
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emergency marking of calls. emergency marking of calls.
Id5. Prevention of Fraud: A call identified as an emergency call or Id5. Prevention of Fraud: A call identified as an emergency call or
marked as such in accordance with the above requirements for marked as such in accordance with the above requirements for
marking MUST be routed to a PSAP. marking MUST be routed to a PSAP.
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. Minimal configuration: Any local emergency identifiers SHOULD Id6. Extensibility of emergency service types: The list of emergency
be configured automatically, without user intervention. service types MUST be extensible, and it is not necessary to
provide mapping for every possible service type.
Motivation: A new UA "unofficially imported" into an organization Motivation: The use of a service type is locally determined.
from elsewhere should have the same emergency capabilities as one
officially installed. Id6X. Discovery of emergency dial-string: The mapping protocol MUST
support a mechanism to discover existing location-dependent
emergency identifiers, known as emergency dial-strings, (e.g.
9-1-1, 1-1-2), 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.
Id6XX. XXX: The SIP UA SHOULD translate home emergency dial-strings
to universal emergency identifiers. The UA is most likely pre-
provisioned with this information to be able to make such a
translation. A mechanism to provide the user's home emergency
dial-strings MUST be available.
Id7. Emergency Identifier Replacement: For each signaling protocol Id7. Emergency Identifier 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 identifiers SHOULD
be allowed to replace the original emergency identifier, based on be allowed to replace the original emergency identifier, based on
local conventions, regulations, or preference (e.g. as in the case local conventions, regulations, or preference (e.g. as in the case
of an enterprise). of an enterprise).
Motivation: Any signalling 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.
Id8. Universal Identifier Recognition: Universal identifier(s), MUST Id8. Universal Identifier Recognition: Universal identifier(s), MUST
be universally recognizable by any network element which supports be universally recognizable by any network element which supports
the ECRIT protocol." the ECRIT protocol."
Id9. Universal Identifier Unrecognized: A call MUST be recognized as
Id9. Universal Identifier not Recognized: A call MUST be recognized emergency call even if the specific emergency service requested is
as emergency call even if the specific emergency service requested not recognized."
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."
Id10X. Translation of emergency dial-strings: The SIP UA SHOULD
translate both home and visited emergency dial-strings into a
universal emergency identifier.
Id11X. Detection of visited emergency dial-strings: The mapping
protocol MUST support a mechanism to allow the end device to learn
visited emergency dial-strings.
Motivation: Scenarios exist where a user dials a visited emergency
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
with 999 on the side, the expectation is to be 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 dial a local emergency number.
7. Mapping Protocol 7. Mapping Protocol
Given the requirement from the previous section, that of a single (or Given the requirement from the previous section, that of a single (or
small number of) emergency identifier(s) which are independent of the small number of) emergency identifier(s) which are independent of the
caller's location, and since PSAPs only serve a limited geographic caller's location, and since PSAPs only serve a limited geographic
region, and for reasons of jurisdictional and local knowledge, having region, and for reasons of jurisdictional and local knowledge, having
the call reach the appropriate PSAP based on a mapping protocol, is the call reach the appropriate PSAP based on a mapping protocol, is
crucial. crucial.
There are two basic architectures described for translating an There are two basic architectures described for translating an
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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 Ma2. Mapping redirection: The mapping protocol MUST support
redirection functionality, since in some cases, an initial mapping redirection functionality, since in some cases, an initial mapping
may provide a single URL for a large geographic area. Redirection may provide a single URL for a large geographic area. Redirection
is needed to then re-invokes the mapping protocol on a different is needed to then re-invokes the mapping protocol on a different
database to obtain another URL for an more resolute ESRP or PSAP, database to obtain another URL for a more resolute ESRP or PSAP,
which covers a smaller area. which covers a smaller area.
Motivation: The more local the mapping output is, the more Motivation: The more local the mapping output is, the more
favourable (in most cases) the likely outcome will be for the favorable (in most cases) the likely outcome will be for the
emergency caller. emergency caller.
Ma3. Minimal additional delay: The execution of the mapping protocol 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.
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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 trigger methods.
Ma9. Traceable resolution: The entity requesting mapping SHOULD be Ma9. Traceable resolution: The entity requesting mapping SHOULD be
able to determine the entity or entities who provided the able to determine the entity or entities which provided the
emergency address resolution information. emergency address resolution information.
Motivation: To provide operational traceability in case of errors. Motivation: To provide operational traceability in case of errors.
Ma9X. URI for error reporting: The mapping protocol MUST have a
mechanism to return a urii that can be used to report a suspected
or known error within the mapping database.
Ma10. Resilience against server failure: A client MUST be able to Ma10. Resilience against server failure: A client MUST be able to
fail over to another replica of the mapping server, so that a fail over to another replica of the mapping server, so that a
failure of a server does not endanger the ability to perform the failure of a server does not endanger the ability to perform the
mapping. mapping.
Ma11. Incrementally deployable: The mapping function MUST be capable Ma11. Incrementally deployable: The mapping function MUST be capable
of being deployed incrementally. of being deployed incrementally.
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 boundary information.
Ma12. Verify mapping support: The mapping protocol SHOULD support Ma12X. URI for error resolution: The mapping protocol MUST have a
the ability for a requesting entity to verify that mapping mechanism to return a reference URI which can be used to report a
services are available for a referenced location. suspected error in the mapping database.
Motivation: It should be possible to make sure ahead of time, that
requests for emergency services will work when needed.
Ma13. Mapping requested from anywhere: The mapping protocol MUST be Ma13. Mapping requested from anywhere: The mapping protocol MUST be
able to provide the mapping regardless of where the mapping client able to provide the mapping regardless of where the mapping client
is located, either geographically or by network location. is located, either geographically or by network location.
Motivation: The mapping client, (such as the ESRP), may not Motivation: The mapping client, (such as the 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: It SHOULD be possible to have updates of Ma14. Location Updates: It SHOULD be possible to have updates of
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PSAP routing. In some cases it may be possible to redirect that PSAP routing. In some cases it may be possible to redirect that
call to a more appropriate PSAP (some device measurement call to a more appropriate PSAP (some device measurement
techniques provide quick (i.e. early), but imprecise "first fix" techniques provide quick (i.e. early), but imprecise "first fix"
location). location).
Ma15. Extensible Protocol: The mapping protocol MUST be extensible Ma15. Extensible Protocol: The mapping protocol MUST be extensible
to allow for the inclusion of new location fields. to allow for the inclusion of new location fields.
Motivation: This is needed, for example, to accommodate future Motivation: This is needed, for example, to accommodate future
extensions to location information that might be included in the extensions to location information that might be included in the
PIDF-LO (RFC 4119 [2]). PIDF-LO (RFC 4119 [3]).
Ma16. Split responsibility: The mapping protocol MUST allow that Ma16. Split responsibility: The mapping protocol MUST allow that
within a single level of the civic location hierarchy, multiple within a single level of the civic location hierarchy, multiple
mapping servers handle subsets of the data elements. mapping servers handle subsets of the data elements.
Motivation: For example, two directories for the same city or Motivation: For example, two directories for the same city or
county may handle different streets within that city or county. county may handle different streets within that city or county.
Ma17. Pervasive Mapping: The mapping function MUST be able to be Ma17. Pervasive Mapping: The mapping function MUST be able to be
invoked at any time, including while an emergency call is in invoked at any time, including while an emergency call is in
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Ma19. Single URI Scheme: The mapping protocol MAY return multiple Ma19. Single URI Scheme: The mapping protocol MAY return multiple
URIs, though it SHOULD return only one URI per scheme, so that URIs, though it SHOULD return only one URI per scheme, so that
clients are not required to select among different targets for the clients are not required to select among different targets for the
same contact protocol. 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.
Ma20X. Separation of Identity from mapping: The mapping function MUST
NOT require the true identity of the target for which the location
information is attributed. Ideally, no identity information is
provided to the mapping function. Where identity information is
provided, it may be in the form of an unlinked pseudonym as
defined in RFC 3963.
Ma21X. Location delivery by-value: The mapping protocol MUST support
the delivery of location information by-value and MAY support de-
referencing of location references. Location by-reference is not
one of the evaluation criteria. The mapping protocol is not
required to support the ability to de-reference location
references.
Ma22X. Alternate community names: The mapping protocol MUST support
both the jurisdiction community name and the postal community name
fields in the PIDF-LO.
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, given that the
database has both fields populated, the mapping protocol response
should return both available fields.
Ma23X. Support for alias locations: The mapping protocol MUST support
one or more aliases for a specific location entry.
Motivation: It should be possible to relate one entry to another
and be able to determine which is the "primary" entry and which is
the alias. The result of aliasing is always that mapping from the
primary or any of the aliases is the same.
Ma24X. Pre-call mapping for fallback: The mapping protocol MUST
support LCMS queries prior to making an emergency call.
Motivation: Used as a fallback mechanism only, if a LCMS 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 an LCMS query at any time prior to an emergency
call.
8. Security Considerations 8. Security Considerations
Note: Security Considerations are referenced in the ECRIT security Note: Security Considerations are referenced in the ECRIT security
document [3]. document [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:
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Andrew Newton, James Polk, Tom Taylor, and Hannes Tschofenig for Andrew Newton, James Polk, Tom Taylor, and Hannes Tschofenig for
their input. their input.
11. References 11. References
11.1. Normative References 11.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997. Levels", BCP 14, RFC 2119, March 1997.
[2] Peterson, J., "A Presence-based GEOPRIV Location Object Format", [2] Polk, J., Schnizlein, J., and M. Linsner, "Dynamic Host
Configuration Protocol Option for Coordinate-based Location
Configuration Information", RFC 3825, July 2004.
[3] Peterson, J., "A Presence-based GEOPRIV Location Object Format",
RFC 4119, December 2005. RFC 4119, December 2005.
[3] 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 Calling", draft-taylor-ecrit-security-threats-01 (work
in progress), December 2005. in progress), December 2005.
[4] 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-schulzrinne-sipping-service-01 (work in progress),
October 2005. October 2005.
[6] 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 11.2. Informative References
[5] Charlton, N., Gasson, M., Gybels, G., Spanner, M., and A. van [7] 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.
[6] Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and J. [8] Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and J.
Polk, "Geopriv Requirements", RFC 3693, February 2004. Polk, "Geopriv Requirements", RFC 3693, February 2004.
[7] Hellstrom, G. and P. Jones, "RTP Payload for Text Conversation", [9] Hellstrom, G. and P. Jones, "RTP Payload for Text
RFC 4103, June 2005. Conversation", RFC 4103, June 2005.
[8] Wijk, A., "Framework of requirements for real-time text [10] 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
skipping to change at page 27, line 41 skipping to change at page 30, line 41
This document and the information contained herein are provided on an This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Copyright Statement Copyright Statement
Copyright (C) The Internet Society (2005). This document is subject Copyright (C) The Internet Society (2006). This document is subject
to the rights, licenses and restrictions contained in BCP 78, and to the rights, licenses and restrictions contained in BCP 78, and
except as set forth therein, the authors retain all their rights. except as set forth therein, the authors retain all their rights.
Acknowledgment Acknowledgment
Funding for the RFC Editor function is currently provided by the Funding for the RFC Editor function is currently provided by the
Internet Society. Internet Society.
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