ecrit H. Schulzrinne Internet-Draft Columbia U. Expires: November 6, 2005 R. Marshall, Ed. TCS May 5, 2005 Requirements for Emergency Context Resolution with Internet Technologies draft-schulzrinne-ecrit-requirements-00 Status of this Memo This document is an Internet-Draft and is subject to all provisions of Section 3 of RFC 3667. By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she become aware will be disclosed, in accordance with RFC 3668. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on November 6, 2005. Copyright Notice Copyright (C) The Internet Society (2005). Abstract This document enumerates requirements for emergency calls placed by the public using voice-over-IP (VoIP) and general Internet multimedia systems, where Internet protocols are used end-to-end. Schulzrinne & Marshall Expires November 6, 2005 [Page 1] Internet-Draft ECRIT requirements May 2005 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 5 3. High-Level Requirements . . . . . . . . . . . . . . . . . . 9 4. Emergency Address . . . . . . . . . . . . . . . . . . . . . 11 5. Identifying the Caller Location . . . . . . . . . . . . . . 14 6. Identifying the Appropriate Emergency Call Center . . . . . 20 7. Emergency Address Directory . . . . . . . . . . . . . . . . 27 8. Identifying the Caller . . . . . . . . . . . . . . . . . . . 29 9. Call Setup and Call Features . . . . . . . . . . . . . . . . 30 10. Supplemental Information . . . . . . . . . . . . . . . . . . 32 11. Security Considerations . . . . . . . . . . . . . . . . . . 33 12. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 34 13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 35 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 36 14.1 Normative References . . . . . . . . . . . . . . . . . . 36 14.2 Informative References . . . . . . . . . . . . . . . . . 36 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 36 Intellectual Property and Copyright Statements . . . . . . . 38 Schulzrinne & Marshall Expires November 6, 2005 [Page 2] Internet-Draft ECRIT requirements May 2005 1. Introduction Users of telephone-like services expect to be able to call for emergency help, such as police, the fire department or an ambulance, regardless of where they are, what (if any) service provider they are using and what kind of device they are using. Unfortunately, the mechanisms for emergency calls that have evolved in the public circuit-switched telephone network (PSTN) are not quite appropriate for evolving IP-based voice, text and real-time multimedia communications. This document outlines the key requirements that end systems and network elements such as SIP proxies need to satisfy in order to provide emergency call services that offer at least the same functionality as existing PSTN services, with the goal of making emergency calling more robust, cheaper to implement and multimedia- capable. In the future, users of other real-time and near real-time services may also expect to be able to summon emergency help. For example, instant messaging (IM) users may want to use such services. IM is particularly helpful for hearing-disabled users (RFC 3351 [3]) and in cases where bandwidth is scarce. This document only focuses on end-to-end IP-based calls, i.e., where the emergency call originates from an IP end system, (Internet device), and terminates to an IP-capable PSAP, done entirely over an IP network. This document identifies functional and security issues for determining the correct emergency identifier, for identifying the appropriate IPSAP (emergency address) and for identifying the caller and its current location. Emergency calls need to be identified (Section 6). Emergency identifiers are used by the emergency caller to declare a call to be an emergency call. The device MUST recognize the emergency identifiers used and convert them to an emergency address to guide the call to a PSAP. The emergency address MUST be a predefined "sip", "sips" or "tel" URI scheme. Emergency calls need to be routed to the appropriate PSAP (ref. Section 6). Several terms are used for causing the call signaling to reach the geographically appropriate PSAP. This has been referred to as call routing, (PSAP) lookup or location mapping, all capturing aspects of the problem. Emergency calls need to identify who placed the call (Section 7). In most jurisdictions, callers do not have a choice as to whether they want to reveal their location or identity; such disclosure is Schulzrinne & Marshall Expires November 6, 2005 [Page 3] Internet-Draft ECRIT requirements May 2005 typically mandated by law. Emergency calls need to identify the location from which the call is initiated (Section 5). The caller location needs to be identified for two purposes, namely to route the call to the appropriate PSAP and to display the caller location to the call taker to simplify dispatching emergency assistance to the correct location. Emergency calls may not be subject to access restrictions placed on non-emergency calls. Also, some call features may interfere with emergency calls, particularly if triggered accidentally (Section 7). Schulzrinne & Marshall Expires November 6, 2005 [Page 4] Internet-Draft ECRIT requirements May 2005 2. Terminology In this document, the key words "MUST", "MUSTNOT", "REQUIRED", "SHALL", "SHALLNOT", "SHOULD", "SHOULDNOT", "RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as described in RFC 2119 [1] and indicate requirement levels for compliant implementations. Since a requirements document does not directly specify an implementable protocols, these compliance labels should be read as indicating requirements for the protocol or architecture, rather than an implementation. For lack of a better term, we will use the term "caller" or "emergency caller" to refer to the person placing an emergency call or sending an emergency IM. Access Infrastructure Provider (AIP): An organization that provides physical network connectivity to its customers or users, e.g., through digital subscriber lines, cable TV plants, Ethernet, leased lines or radio frequencies. This entity may or may not also provide IP routing, IP addresses, or other Internet protocol services. Examples of such organizations include telecommunication carriers, municipal utilities, larger enterprises with their own network infrastructure, and government organizations such as the military. address: A description of a location of a person, organization, or building, most often consisting of numerical and text elements such as street number, street name, and city arranged in a particular format. Application (Voice) Service Provider (ASP, VSP): The organization that provides voice or other application-layer services, such as call routing, a SIP URI or PSTN termination. This organization can be a private individual, an enterprise, a government or a service provider. We avoid the term voice service provider as emergency calls are likely to use other media, including text and video, in the future. For a particular user, the ASP may not be the same organization as the AIP or ISP. 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 geographic location of the caller (except by having the call taker ask the caller). Schulzrinne & Marshall Expires November 6, 2005 [Page 5] Internet-Draft ECRIT requirements May 2005 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). domain: An area or group of services falling with in a specific category or jurisdictional boundary. [Ed. need further clarification for "domain"] domain authentication and validation entity: A node that has authority within a given domain to authenticate and validate user location information. Emergency Control Center (ECC): Facilities used by emergency organizations to accept and handle emergency calls. A PSAP (below) forwards emergency calls to the emergency control center, which dispatches police, fire, rescue and other emergency services. An ECC serves a limited geographic area. A PSAP and ECC can be combined into one facility (ETSI SR 002 180 definition). We assume that the ECC is reachable by IP-based protocols, such as SIP for call signaling and RTP for media. emergency address: The sip:uri, sips:uri, or tel:uri which represents the network address of the IPSAP useful for the completion of a VoIP emergency call. emergency caller: The user or user device entity needing sending his/ her location to another entity in the network. emergency identifier: The numerical and/or text identifier which is supplied by a user or a user device, which identifies the call as an emergency call and is translated into an emergency address for call routing and completion. enhanced emergency service: Enhanced emergency services add the ability to identify the caller identity and/or caller location to basic emergency services. (Sometimes, only the caller location may be known, e.g., from a public access point that is not owned by an individual.) Schulzrinne & Marshall Expires November 6, 2005 [Page 6] Internet-Draft ECRIT requirements May 2005 geocoding: The process of finding the location of a street address on a map. The location can be an x,y coordinate or a feature such as a street segment, postal delivery location, or building. In GIS, geocoding requires a reference dataset that contains address attributes for the geographic features in the area of interest. geographic coordinates: A representation (measurement) of a location on the earth's surface expressed in degrees of latitude and longitude. geographic coordinate system: A reference system that uses latitude and longitude to define the locations of points on the surface of a sphere or spheroid. geographic transformation: A method of converting data between two geographic coordinate systems (datums). geographic location: A reference to a locatable point described by a set of defined coordinates within a gegraphic coordinate system, (e.g. lat/lon within WGS-84 datum) 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. 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 address. In the geocoding process, the location is defined with an x,y coordinate value according to the distance north or south of the equator and east or west of the prime meridian. Location Key (LK): A key identifier used to query a location server in order to retrieve a specific end user or end user device location. location validation: A caller location is considered valid if the civic or geographic location is recognizable within an acceptable location reference systems (e.g. USPS, WGS84, etc.), and can be mapped to one or more PSAPs. Location validation ensures that a location is referencable, but makes no assumption about the association between the caller and the caller's location. PSAP (Public Safety Answering Point): Physical location where emergency calls are received under 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 Schulzrinne & Marshall Expires November 6, 2005 [Page 7] Internet-Draft ECRIT requirements May 2005 Assistance Centres, in New Zealand Communications Centres. IPSAP (IP-PSAP): PSAP which supports the receipt of emergency calls over IP. It is assumed that the PSAP is reachable by IP-based protocols, such as SIP for call signaling and RTP for media. x,y coordinates: A pair of values that represents the distance from an origin (0,0) along two axes, a horizontal axis (x) representing east-west, and a vertical axis (y) representing north-south. On a map, x,y coordinates are used to represent features at the location they are found on the earth's spherical surface. Schulzrinne & Marshall Expires November 6, 2005 [Page 8] Internet-Draft ECRIT requirements May 2005 3. High-Level Requirements Below, we summarize high-level architectural requirements that guide some of the component requirements detailed later in the document. R1. Application Service Provider: The existence of a Application Service Provider (ASP) MUST NOT be assumed. [Ed. Changed from "voice" to "Application" based on stastny comment (email 4/28).] Motivation: The caller may not have a voice service provider, i.e., a corporate entity that provides voice services as a business. 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 not be a telecommunication provider. R2. International: The protocols and protocol extensions developed MUST support regional, political and organizational differences. 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. R3. Distributed Administration: Deployment of emergency services MUST NOT depend on a sole central administration authority. Motivation: Once common standards are established, it must be 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, ASPs, AIPs or other participants. R4. Multiple Modes: Multiple communication modes, including Multimedia data and services SHOULD/MUST be supported. Motivation: Emergency calling must support a variety of media, not just voice and TDD (telecommunication device for the deaf) beyond the capabilities of current limitations. Such additional media should include conversational text, instant messaging and video. In addition, it should be possible to convey telemetry data, such Schulzrinne & Marshall Expires November 6, 2005 [Page 9] Internet-Draft ECRIT requirements May 2005 as data from automobile crash sensors. [Ed. Need to decide whether it's SHOULD or MUST.] R5. Minimum Connectivity: NEED REQUIREMENT HERE Motivation: If there is network connectivity between the emergency caller and the PSAP, and routing information is available, the call should be completed, even if other parts of the network are not reachable. [Ed. Don't understand above statement, request clarification of requirement.] R6. Incremental Deployment Emergency calls from IP-based devices MUST be incrementally supported. Motivation: Any mechanism must be deployable incrementally and work even if not all entities support IP-based emergency calling. For example, User agents conforming to the SIP specification [1], but unaware of this document, must be able to place emergency calls, possibly with restricted functionality. [Ed. changed above paragraph to make non-SIP specific] R7. Middlebox Reliance: For a transient time the device and the UA MAY use the help of servers (e.g. ESRP) to provide the connectivity to ECC, especially for ECC not yet connected to the Internet. Motivation: Emergency calling mechanisms must support existing emergency call centers based on circuit-switched technology as well as future ECCs that are IP-enabled. Schulzrinne & Marshall Expires November 6, 2005 [Page 10] Internet-Draft ECRIT requirements May 2005 4. Emergency Address A1. Universal: Each device and all network elements MUST recognize one or more universal (global) emergency identifiers, regardless of the location of the device, the service provider used (if any) or other factors. Examples of these might include: 911, 112, and sos.* [Ed. The above examples of 911 and 112, per stastny email on 4/13. This changes the definition of Local, A2, below] Motivation: SIP and other call signaling protocols are not specific to one country or service provider and devices are likely to be used across national or service provider boundaries. Since services such as disabling mandatory authentication for emergency calls requires the cooperation of outbound proxies, the outbound proxy has to be able to recognize the emergency address and be assured that it will be routed as an emergency call. Thus, a simple declaration on a random URI that it is an emergency call will likely lead to fraud and possibly attacks on the network infrastructure. A universal address also makes it possible to create user interface elements that are correctly configured without user intervention. UA features could be made to work without such an identifier, but the user interface would then have to provide an unambiguous way to declare a particular call an emergency call. A2. Local: Since many countries have already deployed national emergency identifiers, such as 911 in North America and 112 in large parts of Europe, UAs, proxies and call routers MUST recognize these universal emergency identifiers, but MAY NOT recognize lower level local emergency identifiers, including those such as 999, 122, 133, etc. In addition, these same call routing entities SHOULD recognize emergency identifiers that are used in other jurisdictions [Ed. Changed "emergency numbers" to "emergency identifiers" (see Terminology section)] [Ed. Changed from "found elsewhere" to "used in other jurisdictions".] [Ed. The requirement A2 is really a set of 3 requirements, and needs to have the question answered which is: "what does the term "local" mean?".] Schulzrinne & Marshall Expires November 6, 2005 [Page 11] Internet-Draft ECRIT requirements May 2005 [Ed. Suggest rewriting A2 as follows: "IP-based components, (including UAs, proxies, and call routers) MAY NOT recognize lower level emergency identifiers which are specific to a local geographic area (i.e. non-universal).] Motivation: The latter requirement is meant to help travelers that may not know the local emergency number and instinctively dial the number they are used to from home. However, it is unlikely that all systems could be programmed to recognize any emergency number used anywhere as some of these numbers are used for non-emergency purposes, in particular extensions and service numbers. A3. Recognizable: Emergency calls MUST be recognizable by user agents, proxies and other network elements. To prevent fraud, an address identified as an emergency number for call features or authentication override MUST also cause routing to a PSAP. [Ed. (repeat) Changed "emergency number" to "emergency identifier"] [Ed. Request clarification/rewording as to meaning of statement, "an address identified as an emergency number"] A4. Minimal configuration: Any local emergency identifiers SHOULD be configured automatically, without user intervention. Motivation: A new UA "unofficially imported" into an organization from elsewhere should have the same emergency capabilities as one officially installed. A5. Secure configuration: Devices SHOULD be assured of the correctness of the local emergency numbers that are automatically configured. Motivation: If we assume a fixed, global emergency service identifier that requires no configuration and only configure local "traditional" emergency numbers, users are not likely to suddenly dial some random number if a rogue configuration server introduces this as an additional emergency number. The ability to override all locally configured emergency identifiers is of more concern. [Ed. Changed from "emergency number" to "emergency identifiers" ] A6. Backwards-compatible: Existing devices that predate the specification of emergency call-related protocols and conventions MUST be able reach a PSAP. Schulzrinne & Marshall Expires November 6, 2005 [Page 12] Internet-Draft ECRIT requirements May 2005 A7. Common Identifier: User initiated requests using local initiation methods (e.g. 9-1-1) MUST be supported across non-local domains (e.g. foreign countries). [Ed. Clarification sought on whether 9-1-1 equates to "local" or "universal"] Motivation: While traveling, users must be able to use their familiar "home" emergency identifier. Users should also be able to dial the local emergency number in the country they are visiting. Schulzrinne & Marshall Expires November 6, 2005 [Page 13] Internet-Draft ECRIT requirements May 2005 5. Identifying the Caller Location This section supplements the requirements outlined in RFC 3693 [4]. Thus, the requirements enumerated there are not repeated here. In general, we can distinguish three modes of operation: UA-inserted: The caller's user agent inserts the location information, derived from sources such as GPS, DHCP or link-layer announcements (LLDP). UA-referenced: The caller's user agent provides a reference, via a permanent or temporary identifier, to the location which is stored by a location service somewhere else and then retrieved by the PSAP. Proxy-inserted: A proxy along the call path inserts the location or location reference. L1. Multiple location services: For UA-referenced locations, PSAPs MUST be able to access different location providers. The location provider may be tied to the ASP, AIP or ISP or may be independent of these entities. Motivation: This requirement avoids that all users have to rely on a single location service provider. This requirement is hard to avoid if there are no traditional national application-layer service providers. L2. Civic and Geographic: Where available, both civic (street address) and geographic (longitude/latitude) information SHOULD be provided to the PSAP. Motivation: While geographic coordinate information can usually be translated into civic address location information, some specific information, such as building number and floor, is more easily provided as civic location information since it does not require a detailed surveying operation. For direct location determination, it may also be easier for the user to check civic location information to assure verity. L3. Location source identification: The source of a location data, whether measured, derived (e.g geocoding or reverse geocoding transformation), or manually input, MUST be indicated to the PSAP. (Transformations include coordinate conversions from one datum to another (e.g. NAD83 to WGS84). Schulzrinne & Marshall Expires November 6, 2005 [Page 14] Internet-Draft ECRIT requirements May 2005 Motivation: This allows the PSAP to better judge the reliability and accuracy of the data and track down problems. L4. Certifiable: In some cases, the source and generation time of the location object used for call routing and caller location display MUST be verifiable, e.g., by a digital signature. The security requirements describe this in more detail. [Ed. Clarification sought, e.g. "In some cases... MUST be verifiable..."? (sounds like we're saying MAY rather than MUST) L5. Multiple locations: Multiple locations MAY be associated with the caller Motivation: Multiple locations may occur either because the caller has provided more than one civic or geographic (coordinates) location, supplies both civic and geospatial location information, or because different location determination entities make different assessments of the caller's location." L6. Validation of civic location: It MUST be possible to validate an address prior to its use in an actual emergency call. L7. Provide location: Calls using VoIP or subsequent methods MUST supply location with the call. L8. Accept two location types: PSAPs shall accept location as civic and/or geo specified. [Ed. Suggest deleting above requirement since it doesn't deal with routing] L9. Altitude included with location: All representations of location SHALL include the ability to carry altitude. This requirement does not imply altitude is always used or supplied. L10. Preferred datum: The preferred geographic coordinate system for emergency calls SHALL be WGS-84. L11. Multiple locations: If multiple locations are provided with a call, it SHOULD be possible to identify the most accurate, current, appropriate location information to be used for routing emergency calls and dispatching emergency responders. L12. Location presenter: No assumption SHALL be made that the entity presenting the call to the PSAP has any knowledge of, or control over the provider of location. Schulzrinne & Marshall Expires November 6, 2005 [Page 15] Internet-Draft ECRIT requirements May 2005 Motivation: The location provider may be independent of all other service providers handling the call. L13. Updated location: Location updates MUST be supported Motivation: The ability to update a location is essential for support of mobility use cases. L14. Imprecise location: Imprecise location information MUST be available for emergency call routing and location delivery in cases where precise measurement based location determination mechanisms fail. Motivation: Examples of rough location include coordinates and/or street address of radio tower, wireless access point, manually provisioned, or last known position fix, etc. L15. Default identification: PSAPs MUST be made aware when imprecise location information was used to route a call. [Ed. Changed from "default" to "imprecise", since the term default doesn't adequately represent a lower precision, yet contextually appropriate location.] L16. Location Responsibility: Location determination MUST assume a responsible party. Motivation: The emergency network in most cases today is accessed via the PSTN using either a wireline or a cellular device. In both cases location information is provided by the Carrier and is used directly to route the call. Since the Carrier must route the call to the emergency network, the emergency network holds the carrier responsible for the correct location determination and routing, and this forms the basis of requirement 1. A certain level of authentication and validation around the source of the location is required for the domain in which the information is to be used. L17. Time of Location: Location determination MUST be relevant to time of call. Motivation: The location information MUST be attributed to a specific point in time. That is, the location used for routing and which is reported to the PSAP call taker, must be the actual location of the caller at the time of making the call. This provides call takers with confidence that the Emergency Caller is at the location. This is accomplished today with existing telephony networks either through the use of a calling-number to Schulzrinne & Marshall Expires November 6, 2005 [Page 16] Internet-Draft ECRIT requirements May 2005 address "wire-map" database, or for cellular with more complex triangulation and GPS based techniques where the location is determined by the network and delivered at the time of the call. L18. Location, Emergency Caller: Location provided with call MUST be associated with an Emergency Caller. Motivation: The location information MUST be attributed to a specific emergency caller. That is, for each call initiated, the emergency network requires that the location was determined for that specific caller and is not reused from a location determination applicable to a different Emergency Caller. This information defines when the location was attributed to the Emergency Caller, thereby tying a valid location to a user at a specific point in time. L19. Location Domain Availability: Location domain MUST be obtainable by Emergency Caller. Motivation: Requirement 1 states that a level of authentication and validation for the source of the location is required. This implies the need to for the Emergency Caller to determine the authenticating and validating entity for the emergency services domain in which they reside. That is, it must be possible for an Emergency Caller to discover and utilize an answerable source of location in the access network they are using. [Ed. Request clarification of supporting text.] L20. Location Certification: Location provided MUST be certified. Motivation: The Emergency Caller must be able to establish a session with the access domain authenticating and validating entity to obtain a certified location. The authentication of the location is granted with an expiry time, after which the location within the domain is deemed invalid. L21. Location and Emergency Caller Identity: It MUST NOT be assumed that Emergency Caller identity provided with location is true identity of Emergency Caller. Motivation: The session between the Emergency Caller and the domain authenticating and validating entity SHALL NOT require the true identity of the Emergency Caller. That is, the true identity of the user need never be revealed to the domain authenticating and validating entity, a random unique pseudonym generated within the authenticated domain is sufficient. Schulzrinne & Marshall Expires November 6, 2005 [Page 17] Internet-Draft ECRIT requirements May 2005 L22. Location Acceptability: Location provided by Emergency Caller MUST be considered acceptable as input to authentication and validation entity. Motivation: The domain authenticating and validation entity MUST be able to accept a location provided by an Emergency Caller. On receipt of the Emergency Caller's location the domain authenticating and validation entity SHOULD validate the location as being applicable to that domain that is, it falls within reasonable geographic boundaries for that domain before returning the certified location to the Emergency Caller. L23. Location Sources: It MUST NOT be assumed that location is always provided by Emergency Caller. Motivation: The Emergency Caller may have no means of determining or providing a location, in which case the domain authentication and validation entity MAY provide an estimate of location. L24. Location Query Authorization: The ability to query emergency caller location using a location key MUST be limited to authorized end points. Motivation: Where the Emergency Caller does not desire the transmission of their location in-band with their call setup, they shall have the option of requesting a unique query key such that only authorized end points may query the location directly from the domain. L25. Location Domain Authorization: Location Source entity MUST be authorized within the access domain. Motivation: That the source of the location is considered to be authorized to provide the location within the access domain. L26. Endpoint Location: Location MUST be tied to an endpoint within the access domain at the time of an emergency call. Motivation: The location is tied to an end-point inside the access domain controlled by the source. This binding between location and end-point is correct at the time of the call. L27. Location Sources: Single source of location MUST NOT be assumed. Schulzrinne & Marshall Expires November 6, 2005 [Page 18] Internet-Draft ECRIT requirements May 2005 Motivation: To achieve this, the end user device MUST be able to retrieve its current location from the access provider, from the infrastructure, via GPS, ... or as last resort, from the user itself. L28. Location Provided: Endpoint location SHOULD be provided to ECC. Motivation: Transmission of the current location of the contacting device to the ECC. L29. Provide Endpoint Identification: Identification of endpoint or Emergency Caller SHOULD be provided to ECC, sufficient to allow the PSAP/ECC to re-initiate contact with the emergency caller after the initial call has ended (or cleared). Motivation: Identification of the contacting person or device. L30. Diverse Location Technologies: Emergency Services SHOULD support variety of current and future location determination technologies. Motivation: Emergency call mechanisms should not require a specific technology for determining the location of the caller. Schulzrinne & Marshall Expires November 6, 2005 [Page 19] Internet-Draft ECRIT requirements May 2005 6. Identifying the Appropriate Emergency Call Center From the previous section, we take the requirement of a single (or small number of) emergency addresses which are independent of the caller's location. However, since for reasons of robustness, jurisdiction and local knowledge, PSAPs only serve a limited geographic region, having the call reach the correct PSAP is crucial. While a PSAP may be able to transfer an errant call, any such transfer is likely to add tens of seconds to call setup latency and is prone to errors. (In the United States, there are about 6,100 PSAPs.) There appear to be two basic architectures for translating an emergency identifier into the correct IPSAP's emergency address. We refer to these as caller-based and mediated. In caller-based resolution, the caller's user agent consults a directory and determines the correct IPSAP based on its location. We assume that the user agent can determine its own location, either by knowing it locally or asking some third party for it. A UA could conceivably store a complete list of all PSAPs across the world, but that would require frequent synchronization with a master database as PSAPs merge or jurisdictional boundaries change. For mediated resolution, a call signaling server, such as a SIP (outbound) proxy or redirect server, performs this function. Note that the latter case includes the architecture where the call is effectively routed to a copy of the database, rather than having some non-SIP protocol query the database. Since servers may be used as outbound proxy servers by clients that 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.) Note that the first proxy, the ESRP, doing the translation may not be in the same geographic area as the UA placing the emergency call. The resolution may take place well before the actual emergency call is placed, or at the time of the call. The problem is harder than for traditional web or email services. There, the originator knows which entity it wants to reach, identified by the email address or HTTP URL. However, the emergency caller only dialed an emergency identifier. Depending on the location, any of several ten thousand PSAPs around the world could be valid. In addition, the caller probably does not care which specific PSAP answers the call, but rather that it be an accredited PSAP, Schulzrinne & Marshall Expires November 6, 2005 [Page 20] Internet-Draft ECRIT requirements May 2005 e.g., one run by the local government authorities. (Many PSAPs are run by private entities. For example, universities and corporations with large campuses often have their own emergency response centers.) I1. Correct PSAP: Calls MUST be routed to the correct PSAP based on the location of the caller and the declared service boundary of the PSAP. Motivation: In particular, the location determination should 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. I2. Early routing: In mediated mode, the first proxy server along a request path MUST attempt to route the call to the appropriate IPSAP. Motivation: Proxy servers close to the caller can be expected to have better call routing knowledge, particularly if international boundaries are being crossed. I3. Multi-stage: In multi-stage mode, intermmediate entities MAY be needed for call routing. The user agent or a call routing entity close to the caller may not be able to deliver the call directly to the serving PSAP, but rather to an intermediary that it turn uses caller location information to route the call closer to the appropriate PSAP. I4. Choice of IPSAPs: The emergency caller SHOULD be provided a choice of emergency call centers if more than one exists and is relevant. Motivation: This choice is often, but not always, provided today. The system should offer the emergency caller a choice as to whether he wants to reach a local private emergency response center, e.g., on a corporate campus, or the government-run emergency call center responsible for his current location. For example, in some cases, the local campus emergency center is reachable by a different identifier, or 9-911 reaches the external PSAP, while 911 reaches campus security. I5. Assuring IPSAP identity: The emergency caller SHOULD be able to determine conclusively that he has reached an accredited emergency call center. Schulzrinne & Marshall Expires November 6, 2005 [Page 21] Internet-Draft ECRIT requirements May 2005 Motivation: This requirement is meant to address the threat that a rogue, possibly criminal, entity pretends to accept emergency calls. I6. Warnings for unidentifiable IPSAP. Implementations SHOULD allow callers to proceed, with appropriate warnings or user confirmations, if the identity of the destination IPSAP cannot be verified. Motivation: Verification can fail for any number of reasons, such as lack of a common certificate chain, especially when traveling, call forwarding, or the expiration of certificates. Accreditation, e.g., in the case of corporate or university campuses, may not exist. I7. Traceable resolution: Particularly for mediated resolution, the caller SHOULD be able to definitively and securely determine who provided the emergency address resolution information. I8. Robustness: The resolution mechanism MUST allow systems to be deployed that are robust in the face of partial network and directory server failures. I9. Caching location: Caching of location MAY be used to mitigate temporary unavailability of directories or network connectivity. Motivation: As long as the routing information used has an expiry date/time, and the PSAP is reachable by the caller, a temporary failure of the lookup and routing mechanism should not prevent completion of the emergency call. I10. Incrementally deployable: An Internet-based emergency call system MUST be able to be deployed incrementally. In the initial stages of deployment, an emergency call may not reach the optimal PSAP. If allowed, emergency calls must only be routed to PSAPs that have agreed to accept non-optimally routed calls. [Ed. Can this be merged with R6?] I11. ECC Availability: ECC communication MUST be continuously available. Motivation: From any Internet-connected device it MUST be possible at any time to contact the ECC responsible for the current location with the most appropriate method for communication for the user and the device. Schulzrinne & Marshall Expires November 6, 2005 [Page 22] Internet-Draft ECRIT requirements May 2005 I12. ECC Testability: The solution MUST include mechanisms to test access and availability to the location-appropriate ECC (PSAP), without affecting or interfering with actual emergency call processing or causing an emergency response. Motivation: It is important that there be mechanisms to verify that contact can be made to the proper ECC, that includes whether or not the PSAP is available at all times. I13. Cross-Jurisdiction Device Support: Devices SHOULD support alternate emergency service systems between countries. Motivation: Even as each country is likely to operate their emergency calling infrastructure differently, SIP devices should be able to reach emergency help and, if possible, be located in any country. [Ed. above text needs clarification] I14: Routing MUST be possible on either civic or geo location information. I15: It MUST be possible to route a call based on either a civic or a geo location without requiring conversion from one to the other. This requirement does not prohibit an implementation from converting and using the resulting conversion for routing. I16: It MUST be possible for a designated 9-1-1 authority to a PSAP to approve of any geocoding database(s) used to assist in determining call routing to that PSAP. Mechanisms must be provided for the PSAP designated 9-1-1 authorities to test and certify a geocoding database as suitable for routing calls to the PSAP. The PSAP may choose to NOT avail itself of such a mechanism. I17: It MUST be possible for the designated 9-1-1 authority to supply, maintain, or approve of databases used for civic routing. Mechanisms must be provided for a designated authority for a PSAP to test and certify a civic routing database as suitable for routing calls to that PSAP. I18: It MUST be possible for the PSAP itself (or a contractor it nominates on its behalf) to provide geocode and reverse geocode data and/or conversion services to be used for routing determination. This implies definition of a standard interchange format for geocode data, and protocols to access it. Schulzrinne & Marshall Expires November 6, 2005 [Page 23] Internet-Draft ECRIT requirements May 2005 I19: The PSAP MUST have a mechanism to declare its serving boundaries (in civic and geographic formats) for routing purposes. I20: Boundaries for civic routing MUST be able to be specific to a street address range, a side of a street (even/odd street addresses), a building within a "campus", or any of the location fields available. [Ed. Available from where? Please clarify. I21: It MUST be possible to use various combined components of the location object for determination of routing. Some areas may only require routing to a country level, others to a state/province, others to a county, or to a municipality, and so on. No assumption should be made on the granularity of routing boundaries or about the combination of components used. I22: Boundaries mechanisms for geo routing MUST be able to be specific to a natural political boundary, a natural physical boundary (such as a river), or the boundaries listed in the previous requirement. I23: Any given geographic location SHOULD result in identification of a unique governmentally-authorized PSAP entity for that location? I24: Routing databases using 9-1-1 Valid Addresses or lat/lon/ altitude as keys MUST both be available to all entities needing to route 9-1-1 calls. I25: Carriers, enterprises and other entities that route emergency calls MUST be able to route calls from any location to its appropriate PSAP. I26: It MUST be possible for a given PSAP to decide where its calls should be routed. I27: It is desirable for higher level civic authorities such as a county or state/province to be able to make common routing decisions for all PSAPs within their jurisdiction. For example, a state may wish to have all emergency calls placed within that state directed to a specific URI. This does NOT imply a single answering point; further routing may occur beyond the common URI. I28: Routing MAY change on short notice due to local conditions, traffic, failures, schedule, etc. Schulzrinne & Marshall Expires November 6, 2005 [Page 24] Internet-Draft ECRIT requirements May 2005 I29: Information and mechanisms used to determine routing MUST be extremely reliable and available, which implies redundancy, protocol stability, and resiliency. I30: Routing information MUST be secured against unauthorized modification. PSAPs (or perhaps a higher level civic authority such as a county, state/province or national body) or their designated representative must be the only entities permitted to change routing information. I31: It MUST be possible to supply contingency routing information, for example, an alternate URI or an E.164 to be used when normal routing fails. I32: Multiple types of failures MAY have different contingency routes. I33: It MUST be possible to provide more than one contingency route for the same type of failure. I34: A procedure MUST be specified to handle "default route" capability when no location is available or the location information is corrupted. I35: Default routes MUST be available when location information is not available. [Ed. Suggest consolidation of above 5 req's.] I36: Entities routing emergency calls SHALL retain information used to choose a route for subsequent error resolution. I37: Access Infrastructure providers MUST provide a location object that is as accurate as possible when location measurement or lookup mechanisms fail. I38: Location available at the time that the call is routed MAY not be accurate. Motivation: Updates to location may result in a different route and the system must accommodate this. I39: It SHOULD be possible to have updates of location (which may occur when measuring devices provider early, but imprecise "first fix" location) which can change routing of calls. Schulzrinne & Marshall Expires November 6, 2005 [Page 25] Internet-Draft ECRIT requirements May 2005 [Ed. Suggest combining previous two req's into L13. Updated location.] Schulzrinne & Marshall Expires November 6, 2005 [Page 26] Internet-Draft ECRIT requirements May 2005 7. Emergency Address Directory D1. ECC Identification: Public access to ECC selection information MUST be assumed. Motivation: The capability to locate the responsible ECC must be available in the public Infrastructure without the additional need for a service provider. D2. Assuring directory identity: The query agent (e.g UA or server) MUST be able to assure that it is querying the intended directory. D3. Query response integrity: The query agent MUST be able to be confident that the query or response has not been tampered with. D4. Assurance of Update integrity: Any update mechanism for the directory MUST ensure that only authorized users can change directory information and must keep an audit log of all change transactions. D5. Call setup latency: The directory lookup SHOULD minimize any added delay to the call setup. Motivation: Since outbound proxies will likely be asked to resolve the same geographic coordinates repeatedly, a suitable time-limited caching mechanism should be supported. D6. Multiple directories: A UA or proxy SHOULD be able to use multiple (separate) directories to resolve the emergency identifier. Motivation: A single directory with worldwide or even nationwide coverage is not assumed. This allows competing or regional data sources. D7. Referral: All directories SHOULD refer out-of-area queries to an appropriate default or region-specific directory. Motivation: This requirement alleviates the potential for misconfigurations to cause calls to fail, particularly for caller- based queries. D8. Multiple query protocols: Directories MAY support multiple query protocols. Schulzrinne & Marshall Expires November 6, 2005 [Page 27] Internet-Draft ECRIT requirements May 2005 It may be useful if directories support multiple query protocols, such as SIP (for proxying), IRIS, LDAP, a SOAP-based query and others. It appears likely that the resolution mechanism will be needed by a variety of session protocols and user applications. D9. Baseline query protocol: A mandatory-to-implement protocol MUST be specified. Motivation: An over-abundance of similarly-capable choices appears undesirable for interoperability. Schulzrinne & Marshall Expires November 6, 2005 [Page 28] Internet-Draft ECRIT requirements May 2005 8. Identifying the Caller C1. Identity: The system SHOULD allow (but not force) the identification of both the caller's identity and his or her terminal network address. C2. Privacy override: The end system MUST be able to automatically detect that a call is an emergency call and override any privacy settings that conflict with emergency calling. Motivation: Since emergency calls are often placed by children, by people using somebody else's end system or by people in panic, any configuration should be automated rather than relying on user interaction at the time of the call. Delaying a call until the user discovers that they have to answer some screen prompt or deal with a voice prompt in an unfamiliar language is likely to lead to large call setup delays or call failures. This does not preclude that end systems can allow, on a call-by-call basis, to configure special call parameters, e.g., to enable anonymous tip lines. Whether this override can be configured by the user or is considered a condition of service is considered a legal matter, not a protocol issue. C3. Recontacting Endpoint: The ECC SHOULD have the capability to recontact the initiating endpoint after disconnection. Motivation: Capability to re-contact the contacting device from the ECC in case of disruption or later query for a tbd period of time. This should also be possible from conventional ECC via temporary (virtual) E.164 numbers. Schulzrinne & Marshall Expires November 6, 2005 [Page 29] Internet-Draft ECRIT requirements May 2005 9. Call Setup and Call Features S1. Authentication override: All outbound proxies and other call filtering elements MUST be able to be configured so that they allow unauthenticated emergency calls. In many jurisdictions, emergency calls can be placed by any device, regardless of whether it has subscribed for service. S2. Mid-call features: The end system MUST be able to recognize an emergency call and allow configuration so that certain call features are not triggered accidentally. Motivation: For example, it may be inappropriate to transfer the PSAP or put it on hold. An end system MAY make it more difficult to disconnect an on-going emergency call or accept other incoming calls while in an emergency call. Call transfer initiated by the emergency caller is likely only to be a problem if a PSTN gateway or B2BUa is in the call path. It is not clear how much effort should be expended on preventing intentional, as opposed to accidental, disconnection, since callers can typically find physical-layer means to terminate the call. This feature is not generally available in the PSTN. For example, ANSI T1.628-2001 states that "E9-1-1 Call hold is an optional network feature provided to a PSAP which prevents a caller from disconnecting an ESC. .... However, there is no DSS1 or SS7 support for this capability at this time." S3. Testable: A user SHOULD be able to test whether a particular address reaches the appropriate PSAP, without actually causing emergency help to be dispatched or consuming PSAP call taker resources. Such tests MUST indicate the source of any problems, including the validity and plausibility of civic addresses and geographic coordinates. This requirement also allows address validation. S4. Integrity: Implementations MUST provide mechanisms that ensure the integrity of IP protocol components that are crucial to providing reliable emergency call service. (This requirement implies authentication of the caller to allow integrity protection of the request and authentication of the PSAP to allow integrity protection of responses.) [Ed. changed "SIP protocol component" to "IP protocol components". This requirement is not well understood based on comments received. Further clarification requested.] Schulzrinne & Marshall Expires November 6, 2005 [Page 30] Internet-Draft ECRIT requirements May 2005 S5. Emergency Requests: Requests for emergency services MUST NOT be assumed to be user initiated. Motivation: Communication may be established by user request or by external events. Devices should support alternate methods for initiating emergency requests without the user having to "dial" or type a specific address. [Ed. Question has been raised as follows: "Should there be a requirement for a mechanism to distinguish calls not initiated by the user, as indicated in this requirement?" S6 Tracking and Tracing Facilities for all calls MUST be provided. This includes all routing entities as well as all signaling entities. S7 Each element in the signaling and routing paths solution SHALL maintain call detail records that can be accessed by management systems to develop call statistics in real time. S8 Each element of the signaling and routing paths SHALL provide congestion controls. S9 It SHALL be possible to determine the complete call chain of a call, including the identity of each signaling element in the path, and the reason it received the call (Call History). Schulzrinne & Marshall Expires November 6, 2005 [Page 31] Internet-Draft ECRIT requirements May 2005 10. Supplemental Information SD1 In addition to information sent with the call, additional information may be available, supplemental to the call, which is retrieved from internal or external databases using a key to the information included with the call. This key may also include information to identify/address the database. SD2 Additional information MAY be available to the call taker based on the location of the caller. SD3 Additional information MAY be available to the call taker based on the owner of the structure. SD4 Additional information MAY be available to the call taker based on the tenant of the structure. SD5 Where a vehicle is involved, additional information MAY be available. SD6 Additional information MAY be available based on the Address of Record (AoR) of the caller. In this context, AoR equates to the caller. SD7 Consideration SHOULD be given to permitting users to have domain independent mechanisms to supply information related to the caller, for example, another datum related to user. SD8. Additional Data: Transfer of additional data SHOULD be supported. Motivation: Capabilities to contact ECC by automatic means and for the transfer of additional information (alarm equipment, cars, buses, trucks with dangerous loads, ...) SD9 Mechanism MUST be provided to automatically generate and provide misroute and location error reports. Schulzrinne & Marshall Expires November 6, 2005 [Page 32] Internet-Draft ECRIT requirements May 2005 11. Security Considerations Note: Security Considerations originally described in this section have removed and will be resubmitted to the ECRIT security document. No reference yet available. SEC1. Safeguards from Attacks: Safeguards SHOULD be provided to assure against network system attacks. Motivation: Safeguards to protect the emergency infrastructure and ECC facilities against malicious attacks, especially to prevent DoS attacks. SEC2. Denial of Service attacks: Special consideration SHOULD be given to "Distributed Denial of Service" attacks. SEC3 Protocols MUST NOT facilitate denial-of-service attacks, e.g., by amplifying incoming unauthenticated messages. [Ed. (per hgs, suggested replacement above first two requirements with third requirement.] Schulzrinne & Marshall Expires November 6, 2005 [Page 33] Internet-Draft ECRIT requirements May 2005 12. Contributors The information contained in this document is a result of a joint effort based on individual contributions by those involved in the ECRIT WG. The contributors 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 mdawson@nortelnetworks.com Motoharu Kawanishi kawanishi381@oki.com Brian Rosen br@brianrosen.net Richard Stastny Richard.Stastny@oefeg.at Martin Thomson marthom@nortelnetworks.com James Winterbottom winterb@nortelnetworks.com Schulzrinne & Marshall Expires November 6, 2005 [Page 34] Internet-Draft ECRIT requirements May 2005 13. Acknowledgments Schulzrinne & Marshall Expires November 6, 2005 [Page 35] Internet-Draft ECRIT requirements May 2005 14. References 14.1 Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [2] Polk, J., "Requirements for Session Initiation Protocol Location Conveyance", draft-ietf-sipping-location-requirements-02 (work in progress), October 2004. 14.2 Informative References [3] 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. [4] Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and J. Polk, "Geopriv Requirements", RFC 3693, February 2004. [5] National Emergency Number Assocation, "NENA technical information document on the interface between the E9-1-1 service providers network and the Internet protocol (IP) PSAP", NENA NENA-08-501, February 2003. 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 Schulzrinne & Marshall Expires November 6, 2005 [Page 36] Internet-Draft ECRIT requirements May 2005 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 Schulzrinne & Marshall Expires November 6, 2005 [Page 37] Internet-Draft ECRIT requirements May 2005 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. 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Disclaimer of Validity This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Copyright Statement Copyright (C) The Internet Society (2005). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Schulzrinne & Marshall Expires November 6, 2005 [Page 38]