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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 ECRIT H. Schulzrinne 3 Internet-Draft Columbia U. 4 Intended status: Standards Track R. Marshall, Ed. 5 Expires: September 3, 2007 TCS 6 March 2, 2007 8 Requirements for Emergency Context Resolution with Internet 9 Technologies 10 draft-ietf-ecrit-requirements-13 12 Status of this Memo 14 By submitting this Internet-Draft, each author represents that any 15 applicable patent or other IPR claims of which he or she is aware 16 have been or will be disclosed, and any of which he or she becomes 17 aware will be disclosed, in accordance with Section 6 of BCP 79. 19 Internet-Drafts are working documents of the Internet Engineering 20 Task Force (IETF), its areas, and its working groups. Note that 21 other groups may also distribute working documents as Internet- 22 Drafts. 24 Internet-Drafts are draft documents valid for a maximum of six months 25 and may be updated, replaced, or obsoleted by other documents at any 26 time. It is inappropriate to use Internet-Drafts as reference 27 material or to cite them other than as "work in progress." 29 The list of current Internet-Drafts can be accessed at 30 http://www.ietf.org/ietf/1id-abstracts.txt. 32 The list of Internet-Draft Shadow Directories can be accessed at 33 http://www.ietf.org/shadow.html. 35 This Internet-Draft will expire on September 3, 2007. 37 Copyright Notice 39 Copyright (C) The IETF Trust (2007). 41 Abstract 43 This document defines terminology and enumerates requirements for the 44 context resolution of emergency calls placed by the public using 45 voice-over-IP (VoIP) and general Internet multimedia systems, where 46 Internet protocols are used end-to-end. 48 Table of Contents 50 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 51 2. Requirements Terminology . . . . . . . . . . . . . . . . . . . 5 52 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6 53 3.1. Emergency Services . . . . . . . . . . . . . . . . . . . . 6 54 3.2. Service Providers . . . . . . . . . . . . . . . . . . . . 6 55 3.3. Actors . . . . . . . . . . . . . . . . . . . . . . . . . . 7 56 3.4. Call Routing Entities . . . . . . . . . . . . . . . . . . 7 57 3.5. Location . . . . . . . . . . . . . . . . . . . . . . . . . 7 58 3.6. Identifiers, Numbers and Dial Strings . . . . . . . . . . 8 59 3.7. Mapping . . . . . . . . . . . . . . . . . . . . . . . . . 9 60 4. Basic Actors . . . . . . . . . . . . . . . . . . . . . . . . . 11 61 5. High-Level Requirements . . . . . . . . . . . . . . . . . . . 13 62 6. Identifying the Caller's Location . . . . . . . . . . . . . . 15 63 7. Emergency Service Identifier . . . . . . . . . . . . . . . . . 18 64 8. Mapping Protocol . . . . . . . . . . . . . . . . . . . . . . . 21 65 9. Security Considerations . . . . . . . . . . . . . . . . . . . 25 66 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26 67 11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 27 68 12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 28 69 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 29 70 13.1. Normative References . . . . . . . . . . . . . . . . . . . 29 71 13.2. Informative References . . . . . . . . . . . . . . . . . . 29 72 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 31 73 Intellectual Property and Copyright Statements . . . . . . . . . . 32 75 1. Introduction 77 Users of both voice-centric (telephone-like) and non-voice services 78 such as text communication for hearing disabled users (RFC 3351 79 [RFC3351]) expect to be able to initiate a request for help in case 80 of an emergency. 82 Unfortunately, the existing mechanisms to support emergency calls 83 that have evolved within the public circuit-switched telephone 84 network (PSTN) are not appropriate to handle evolving IP-based voice, 85 text and real-time multimedia communications. This document outlines 86 the key requirements that IP-based end systems and network elements, 87 such as Session Initiation Protocol (SIP) [RFC3261] proxies, need to 88 satisfy in order to provide emergency call services, which at a 89 minimum, offer the same functionality as existing PSTN services, with 90 the additional overall goal of making emergency calling more robust, 91 less costly to implement, and multimedia-capable. 93 This document only focuses on end-to-end IP-based calls, i.e., where 94 the emergency call originates from an IP end system and terminates in 95 an IP-capable PSAP, conveyed entirely over an IP network. 97 We first define terminology in Section 3. The document then outlines 98 various functional issues which relate to placing an IP-based 99 emergency call, including a description of baseline requirements 100 (Section 5), identification of the emergency caller's location 101 (Section 6), use of a service identifier to declare a call to be an 102 emergency call (Section 7), and finally, the mapping function 103 required to route the call to the appropriate PSAP (Section 8). 105 The primary purpose of the mapping protocol is to produce a PSAP URI 106 drawn from a preferred set of URI schemes such as SIP or SIPS URIs, 107 based on both location information [RFC4119] and a service identifier 108 in order to facilitate the IP end-to-end completion of an emergency 109 call. 111 Aside from obtaining a PSAP URI, the mapping protocol is useful for 112 obtaining other information as well. There may be a case, for 113 example, where an appropriate emergency number is not known, only 114 location. The mapping protocol can then return a geographically 115 appropriate emergency number based on the input. 117 Since some PSAPs may not immediately support IP, or because some user 118 equipment (UE) may not initially support emergency service 119 identifiers, it may be necessary to also support emergency service 120 identifiers that utilize less preferred URI schemes, such as a tel 121 URI in order to complete an emergency call via the PSTN. 123 Identification of the caller, while not incompatible with the 124 requirements for messaging outlined within this document, is 125 considered to be outside the scope of this document. 127 Location is required for two separate purposes, first, to support the 128 routing of the emergency call to the appropriate PSAP and second, to 129 display the caller's location to the call taker to help in 130 dispatching emergency assistance to the appropriate location. 132 This latter use, the display of location information to the PSAP, is 133 orthogonal to the mapping protocol, and is outside the scope of this 134 document. 136 2. Requirements Terminology 138 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 139 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 140 document are to be interpreted as described in RFC 2119 [RFC2119], 141 with the important qualification that, unless otherwise stated, these 142 terms apply to the design of the mapping protocol, not its 143 implementation or application. 145 3. Terminology 147 3.1. Emergency Services 149 Basic emergency service: Basic emergency service allows a caller to 150 reach a PSAP serving its current location, but the PSAP may not be 151 able to determine the identity or geographic location of the 152 caller, except by the call taker asking the caller. 154 Enhanced emergency service: In enhanced emergency service, the PSAP 155 call taker can determine the caller's current location. 157 3.2. Service Providers 159 Internet Access Provider (IAP): An organization that provides 160 physical and data link (layer 2) network connectivity to its 161 customers or users, e.g., through digital subscriber lines, cable 162 TV plants, Ethernet, leased lines or radio frequencies. Examples 163 of such organizations include telecommunication carriers, 164 municipal utilities, larger enterprises with their own network 165 infrastructure, and government organizations such as the military. 167 Internet Service Provider (ISP): An organization that provides IP 168 network-layer services to its customers or users. This entity may 169 or may not provide the physical-layer and data link (layer-2) 170 connectivity, such as fiber or Ethernet, i.e., it may or may not 171 play the role of an IAP. 173 Application Service Provider (ASP): The organization or entity that 174 provides application-layer services, which may include voice (see 175 "Voice Service Provider"). This entity can be a private 176 individual, an enterprise, a government, or a service provider. 177 An ASP is more general than a Voice Service Provider, since 178 emergency calls may use other media beyond voice, including text 179 and video. For a particular user, the ASP may or may not be the 180 same organization as his IAP or ISP. 182 Voice Service Provider (VSP): A specific type of Application Service 183 Provider which provides voice related services based on IP, such 184 as call routing, a SIP URI, or PSTN termination. In this 185 document, unless noted otherwise, any reference to "Voice Service 186 Provider" or "VSP" may be used interchangeably with "Application/ 187 Voice Service Provider" or "ASP/VSP". 189 3.3. Actors 191 (Emergency) caller: The term "caller" or "emergency caller" refer to 192 the person placing an emergency call or sending an emergency 193 instant message (IM). 195 User Equipment (UE): User equipment is the device or software 196 operated by the caller to place an emergency call. A SIP user 197 agent (UA) is an example of a UE. 199 Call taker: A call taker is an agent at the PSAP that accepts calls 200 and may dispatch emergency help. Sometimes the functions of call 201 taking and dispatching are handled by different groups of people, 202 but these divisions of labor are not generally visible to the 203 caller and thus do not concern us here. 205 3.4. Call Routing Entities 207 Emergency Service Routing Proxy (ESRP): An ESRP is an emergency call 208 routing support entity that invokes the location-to-PSAP URI 209 mapping function, to return an appropriate PSAP URI, or the URI 210 for another ESRP. Client mapping requests could also be performed 211 by a number of entities, including entities that instantiate the 212 SIP proxy role and the SIP user agent client role. 214 Public Safety Answering Point (PSAP): Physical location where 215 emergency calls are received under the responsibility of a public 216 authority. (This terminology is used by both ETSI, in ETSI SR 002 217 180, and NENA.) In the United Kingdom, PSAPs are called Operator 218 Assistance Centres, in New Zealand, Communications Centres. 219 Within this document, it is assumed, unless stated otherwise, that 220 PSAPs support the receipt of emergency calls over IP, using 221 appropriate application layer protocols such as SIP for call 222 signaling and RTP for media. 224 3.5. Location 226 Location: A geographic identification assigned to a region or 227 feature based on a specific coordinate system, or by other precise 228 information such as a street number and name. It can be either a 229 civic or geographic location. 231 Civic location: A described location based on some reference system, 232 such as jurisdictional region or postal delivery grid. A street 233 address is a common example of a civic location. 235 Geographic location: A reference to a point which is able to be 236 located as described by a set of defined coordinates within a 237 geographic coordinate system, such as latitude and longitude 238 within the WGS-84 datum. For example, 2-D geographic location is 239 defined as an (x,y) coordinate value pair according to the 240 distance north or south of the equator and east or west of the 241 prime meridian. 243 Location validation: A caller location is considered valid if the 244 civic or geographic location is recognizable within an acceptable 245 location reference system (e.g., United States Postal Address or 246 the WGS-84 datum) and can be mapped to one or more PSAPs. While 247 it is desirable to determine that a location exists, validation 248 may not ensure that such a location exists, but rather may only 249 ensure that the location falls within some range of known values. 250 Location validation ensures that a location is able to be 251 referenced for mapping, but makes no assumption about the 252 association between the caller and the caller's location. 254 3.6. Identifiers, Numbers and Dial Strings 256 (Emergency) service number: The (emergency) service number is a 257 string of digits used to reach the (emergency) service. The 258 emergency service number is often just called the emergency 259 number. It is the number typically dialed on devices directly 260 connected to the PSTN and the number reserved for emergency calls 261 by national or regional numbering authorities. It only contains 262 the digits 0 through 9, # and *. The service number may depend on 263 the location of the caller. For example, the general emergency 264 service number in the United States is 911 and the poison control 265 service number is 18002221222. In most cases, the service number 266 and dial string are the same; they may differ in some private 267 phone networks. A service number may be carried in tel URLs 268 [RFC3966], along with a context identifier. In the North American 269 numbering plan, some service numbers are also three-digit N11 or 270 service codes, but not all emergency numbers have three digits. A 271 caller may have to dial a service dial string (below) that differs 272 from the service number when using a PBX. 274 (Emergency) service dial string: The service dial string identifies 275 the string of digits that a caller must dial to reach a particular 276 (emergency) service. In devices directly connected to the PSTN, 277 the service dial string is the same as the service number and may 278 thus depend on the location of the caller. However, in private 279 phone networks, such as in PBXs, the service dial string consists 280 of a dialing prefix to reach an outside line, followed by the 281 emergency number. For example, in a hotel, the dial string for 282 emergency services in the United States might be 9911. Dial 283 strings may contain indications of pauses or wait-for-secondary- 284 dial-tone indications. Service dial strings are outside the scope 285 of this document. 287 (Emergency) service identifier: The (emergency) service identifier 288 describes the emergency service, independent of the user interface 289 mechanism, the signaling protocol that is used to reach the 290 service, or the caller's geographic location. It is a protocol 291 constant and used within the mapping and signaling protocols. An 292 example is the service URN [I-D.ietf-ecrit-service-urn]. 294 (Emergency) service URL: The service URL is a protocol-specific 295 (e.g., SIP) or protocol-agnostic (e.g., im: [RFC3860]) identifier 296 which contains the address of the PSAP or other emergency service. 297 It depends on the specific signaling or data transport protocol 298 used to reach the emergency service. 300 Service URN: A service URN is an implementation of a service 301 identifier, which can be applied to both emergency and non- 302 emergency contexts, e.g., urn:service:sos or 303 urn:service:counseling. Within this document, service URNs are 304 referred to as 'emergency service URNs' 305 [I-D.ietf-ecrit-service-urn]. 307 Home emergency number: A home emergency number is the emergency 308 number valid at the caller's customary home location, e.g., his 309 permanent residence. The home location may or may not coincide 310 with the service area of the caller's VSP. 312 Home emergency dial string: A home dial string is the dial string 313 valid at the caller's customary home location, e.g., his permanent 314 residence. 316 Visited emergency number: A visited emergency number is the 317 emergency number valid at the caller's current physical location. 318 We distinguish the visited emergency number if the caller is 319 traveling outside his home region. 321 Visited emergency dial string: A visited emergency dial string is 322 the dial string number valid at the caller's current physical 323 location. 325 3.7. Mapping 326 Mapping: Mapping is the process of resolving a location to one or 327 more PSAP URIs which directly identify a PSAP, or point to an 328 intermediary which knows about a PSAP and that is designated as 329 responsible for serving that location. 331 Mapping client: A mapping client interacts with the mapping server 332 to learn one or more PSAP URIs for a given location. 334 Mapping protocol: A protocol used to convey the mapping request and 335 response. 337 Mapping server: The mapping server holds information about the 338 location-to-PSAP URI mapping. 340 Mapping service: A network service which uses a distributed mapping 341 protocol to perform a mapping between a location and a PSAP, or 342 intermediary which knows about the PSAP, and is used to assist in 343 routing an emergency call. 345 4. Basic Actors 347 In order to support emergency services covering a large physical 348 area, various infrastructure elements are necessary, including 349 Internet Access Providers (IAPs), Application/Voice Service Providers 350 (ASP/VSPs), Emergency Service Routing Proxy (ESRP) providers, mapping 351 service providers, and PSAPs. 353 This section outlines which entities will be considered in the 354 routing scenarios discussed. 356 Location 357 Information +-----------------+ 358 |(1) |Internet | +-----------+ 359 v |Access | | | 360 +-----------+ |Provider | | Mapping | 361 | | | (3) | | Service | 362 | Emergency |<---+-----------------+-->| | 363 | Caller | | (2) | +-----------+ 364 | |<---+-------+ | ^ 365 +-----------+ | +----|---------+------+ | 366 ^ | | Location | | | 367 | | | Information<-+ | | 368 | +--+--------------+ |(5) | | (6) 369 | | | | | 370 | | +-----------v+ | | 371 | (4) | | | | | 372 +--------------+--->| ESRP |<--+---+ 373 | | | | | 374 | | +------------+ | 375 | | ^ | 376 | | (7) | | +----+--+ 377 | (8) | +------------>| | 378 +--------------+----------------------->| PSAP | 379 | | | | 380 |Application/ | +----+--+ 381 |Voice | 382 |Service | 383 |Provider | 384 +---------------------+ 386 Figure 1: Framework for emergency call routing 388 Figure 1 shows the interaction between the entities involved in the 389 call. There are a number of different deployment choices, as can be 390 easily seen from the figure. 392 Is the Internet Access Provider also the Application/Voice Service 393 Provider? In the Internet today these roles are typically provided 394 by different entities. As a consequence, the Application/Voice 395 Service Provider is typically not able to directly determine the 396 physical location of the emergency caller. 398 The overlapping squares in the figure indicate that some functions 399 can be collapsed into a single entity. As an example, the 400 Application/Voice Service Provider might be the same entity as the 401 Internet Access Provider. There is, however, no requirement that 402 this must be the case. Additionally, we consider that end systems 403 might act as their own ASP/VSP, e.g., either for enterprises or for 404 residential users. 406 Various potential interactions between the entities depicted in 407 Figure 1 are described below: 409 1. Location information might be available to the end host itself. 411 2. Location information might, however, also be obtained from the 412 Internet Access Provider. 414 3. The emergency caller might need to consult a mapping service to 415 determine the PSAP (or other relevant information) that is 416 appropriate for the physical location of the emergency caller, 417 possibly considering other attributes such as appropriate 418 language support by the emergency call taker. 420 4. The emergency caller might get assistance for emergency call 421 routing by infrastructure elements that are emergency call 422 routing support entities, such as an Emergency Service Routing 423 Proxy (ESRP) in SIP. 425 5. Location information is used by emergency call routing support 426 entities for subsequent mapping requests. 428 6. Emergency call routing support entities might need to consult a 429 mapping service to determine where to route the emergency call. 431 7. For infrastructure-based emergency call routing (in contrast to 432 UE-based emergency call routing), the emergency call routing 433 support entity needs to forward the call to the PSAP. 435 8. The emergency caller may interact directly with the PSAP, where 436 the UE invokes mapping, and initiates a connection, without 437 relying on any intermediary emergency call routing support 438 entities. 440 5. High-Level Requirements 442 Below, we summarize high-level architectural requirements that guide 443 some of the component requirements detailed later in the document. 445 Re1. Application/Voice service provider existence: The initiation 446 of an IP-based emergency call SHOULD NOT assume the existence of 447 an Application/Voice Service Provider (ASP/VSP). 449 Motivation: The caller may not have an application/voice service 450 provider. For example, a residence may have its own DNS domain 451 and run its own SIP proxy server for that domain. On a larger 452 scale, a university might provide voice services to its students 453 and staff, but might not be a telecommunication provider. 455 Re2. International applicability: Regional, political and 456 organizational aspects MUST be considered during the design of 457 protocols and protocol extensions which support IP-based emergency 458 calls. 460 Motivation: It must be possible for a device or software developed 461 or purchased in one country to place emergency calls in another 462 country. System components should not be biased towards a 463 particular set of emergency numbers or languages. Also, different 464 countries have evolved different ways of organizing emergency 465 services, e.g., either centralizing them or having smaller 466 regional subdivisions such as United States counties or 467 municipalities handle emergency calls within their jurisdiction. 469 Re3. Distributed administration: Deployment of IP-based emergency 470 services MUST NOT depend on a single central administrative 471 authority. 473 Motivation: The design of the mapping protocol must make it 474 possible to deploy and administer emergency calling features on a 475 regional or national basis without requiring coordination with 476 other regions or nations. The system cannot assume, for example, 477 that there is a single global entity issuing certificates for 478 PSAPs, ASP/VSPs, IAPs or other participants. 480 Re4. Multi-mode communication: IP-based emergency calls MUST 481 support multiple communication modes, including, for example, 482 audio, video and text. 484 Motivation: Within the PSTN, voice and text telephony (often 485 called TTY or text-phone in North America) are the only commonly 486 supported media. Emergency calling must support a variety of 487 media. Such media should include voice, conversational text (RFC 488 4103 [RFC4103]), instant messaging and video. 490 Re5. Mapping result usability: The mapping protocol MUST return one 491 or more URIs that are usable within a standard signaling protocol 492 (i.e., without special emergency extensions). 494 Motivation: For example, a SIP URI which is returned by the 495 mapping protocol needs to be usable by any SIP capable phone 496 within a SIP initiated emergency call. This is in contrast to a 497 "special purpose" URI, which may not be recognizable by a legacy 498 SIP device. 500 Re6. PSAP URI accessibility: The mapping protocol MUST support 501 interaction between the client and server where no enrollment to a 502 mapping service exists or is required. 504 Motivation: The mapping server may well be operated by a service 505 provider, but access to the server offering the mapping must not 506 require use of a specific ISP or ASP/VSP. 508 Re7. Common data structures and formats: The mapping protocol 509 SHOULD support common formats for location data. 511 Motivation: Location databases should not need to be transformed 512 or modified in any unusual or unreasonable way in order for the 513 mapping protocol to use the data. For example, a database which 514 contains civic addresses used by location servers may be used for 515 multiple purposes and applications beyond emergency service 516 location-to-PSAP URI mapping. 518 Re8. Anonymous mapping: The mapping protocol MUST NOT require the 519 true identity of the target for which the location information is 520 attributed. 522 Motivation: Ideally, no identity information is provided via the 523 mapping protocol. Where identity information is provided, it may 524 be in the form of an unlinked pseudonym (RFC 3693 [RFC3693]). 526 6. Identifying the Caller's Location 528 Location can either be provided directly (by value), or via a pointer 529 (by reference), and represents either a civic location, or a 530 geographic location. An important question is how and when to attach 531 location information to the VoIP emergency signaling messages. In 532 general, we can distinguish three modes of operation of how a 533 location is associated with an emergency call: 535 UA-inserted: The caller's user agent inserts the location 536 information into the call signaling message. 538 UA-referenced: The caller's user agent provides a pointer (i.e., a 539 location reference), via a permanent or temporary identifier, to 540 the location information, which is stored by a location server 541 somewhere else and then retrieved by the PSAP, ESRP, or other 542 authorized entity. 544 Proxy-inserted: A proxy along the call path inserts the location or 545 location reference. 547 The following requirements apply: 549 Lo1. Reference datum: The mapping protocol MUST support the WGS-84 550 coordinate reference system and MAY support other coordinate 551 reference systems. 553 Motivation: Though many different datums exist around the world, 554 this document recommends the WGS-84 datum since it is designed to 555 describe the whole earth, rather than a single continent or other 556 region, and is commonly used to represent Global Positioning 557 System coordinates. 559 Lo2. Location delivery by-value: The mapping protocol MUST support 560 the delivery of location information using a by-value method, 561 though it MAY also support de-referencing a URL that references a 562 location object. 564 Motivation: The mapping protocol is not required to support the 565 ability to de-reference specific location references. 567 Lo3. Alternate community names: The mapping protocol MUST support 568 both the jurisdictional community name and the postal community 569 name fields within the PIDF-LO [RFC4119] data. 571 Motivation: The mapping protocol must accept queries with either a 572 postal or jurisdictional community name field, or both, and 573 provide appropriate responses. If a mapping query contains only 574 one community name and the database contains both jurisdictional 575 and postal community names, the mapping protocol response SHOULD 576 return both community names. 578 Lo4. Validation of civic location: The mapping protocol MUST 579 support location validation for civic locations (street 580 addresses). 582 Motivation: Location validation provides an opportunity to help 583 ascertain ahead of time whether or not a successful mapping to the 584 appropriate PSAP will likely occur when it is required. 585 Validation may also help to avoid delays during emergency call 586 setup due to invalid location data. 588 Lo5. Information about location data used for mapping: The mapping 589 protocol MUST support the ability to provide ancillary information 590 about the resolution of location data used to retrieve a PSAP URI. 592 Motivation: The mapping server may not use all the data elements 593 in the provided location information to determine a match, or may 594 be able to find a match based on all of the information except for 595 some specific data elements. The uniqueness of this information 596 set may be used to differentiate among emergency jurisdictions. 597 Precision or resolution in the context of this requirement might 598 mean, for example, explicit identification of the data elements 599 that were used successfully in the mapping. 601 Lo6. Contact for location problems: The mapping protocol MUST 602 support a mechanism to contact an appropriate authority to resolve 603 mapping-related issues for the queried location. For example, the 604 querier may want to report problems with the response values or 605 indicate that the mapping database is mistaken on declaring a 606 civic location as non-existent. 608 Motivation: Initially, authorities may provide URLs where a human 609 user can report problems with an address or location. In 610 addition, web services may be defined to automate such reporting. 611 For example, the querier may wish to report that the mapping 612 database may be missing a newly-built or renamed street or house 613 number. 615 Lo7. Limits to validation: Successful validation of a civic 616 location MUST NOT be required to place an emergency call. 618 Motivation: In some cases, a civic location may not be considered 619 valid. This fact should not result in the call being dropped or 620 rejected by any entity along the call setup signaling path to the 621 PSAP. 623 Lo8. 3D sensitive mapping: The mapping protocol MUST implement 624 support for both 2D and 3D location information, and may accept 625 either a 2D or 3D mapping request as input. 627 Motivation: It is expected that queriers may provide either 2D or 628 3D data. When a 3D request is presented within an area only 629 defined by 2D data within the mapping server, the mapping result 630 would be the same as if the height or altitude coordinate had been 631 omitted from the mapping request. 633 Lo9. Database type indicator: The mapping protocol MAY support a 634 mechanism which provides an indication describing a specific type 635 of location database used. 637 Motivation: It is useful to know the source of the data stored in 638 the database used for location validation, either for civic or 639 geographic location matching. In the United States, sources of 640 data could include the United States Postal Service, the Master 641 Street Address Guide (MSAG) or commercial map data providers. 643 7. Emergency Service Identifier 645 Emergency service identifiers are protocol constants that allow 646 protocol entities such as SIP proxy servers to distinguish emergency 647 calls from non-emergency calls and to identify the specific emergency 648 service desired. Emergency service identifiers are a subclass of 649 service identifiers that more generally identify services reachable 650 by callers. An example of a service identifier is the service URN 651 [I-D.ietf-ecrit-service-urn], but other identifiers, such as tel URIs 652 [RFC3966], may also serve this role during a transition period. 654 Since this document only addresses emergency services, we use the 655 terms "emergency service identifier" and "service identifier" 656 interchangeably. Requirements for these identifiers include: 658 Id1. Multiple emergency services: The mapping protocol MUST be able 659 to distinguish between different emergency services, 660 differentiated by different service identifiers. 662 Motivation: Some jurisdictions may offer multiple types of 663 emergency services that operate independently and can be contacted 664 directly, for example, fire, police and ambulance services. 666 Id2. Extensible emergency service identifiers: The mapping protocol 667 MUST support an extensible list of emergency identifiers, though 668 it is not required to provide mappings for every possible service. 670 Motivation: Extensibility is required since new emergency services 671 may be introduced over time, either globally or in some 672 jurisdictions. The availability of emergency services depends on 673 the locations. For example, the Netherlands are unlikely to offer 674 a mountain rescue service. 676 Id3. Discovery of emergency number: The mapping protocol MUST be 677 able to return the location-dependent emergency number for the 678 location indicated in the query. 680 Motivation: Users are trained to dial the appropriate emergency 681 number to reach emergency services. There needs to be a way to 682 figure out the emergency number at the current location of the 683 caller. 685 Id4. Home emergency number recognition: User equipment MUST be able 686 to translate a home emergency number into an emergency service 687 identifier. 689 Motivation: The UE could be pre-provisioned with the appropriate 690 information in order to perform such a translation or could 691 discover the emergency number by querying the mapping protocol 692 with its home location. 694 Id5. Emergency number replacement: There SHOULD be support for 695 replacement of the emergency number with the appropriate emergency 696 service identifier for each signaling protocol used for an 697 emergency call, based on local conventions, regulations, or 698 preference (e.g., as in the case of an enterprise). 700 Motivation: Any signaling protocol requires the use of some 701 identifier to indicate the called party, and the user equipment 702 may lack the capability to determine the actual service URL (PSAP 703 URI). The use of local conventions may be required as a 704 transition mechanism. Since relying on recognizing local 705 numbering conventions makes it difficult for devices to be used 706 outside their home context and for external devices to be 707 introduced into a network, protocols should use standardized 708 emergency service identifiers. 710 Id6. Emergency service identifier marking: Signaling protocols MUST 711 support emergency service identifiers to mark a call as an 712 emergency call. 714 Motivation: Marking ensures proper handling as an emergency call 715 by downstream elements that may not recognize, for example, a 716 local variant of a logical emergency address. This marking 717 mechanism is related to, but independent of, marking calls for 718 prioritized call handling [RFC4412]. 720 Id7. Handling unrecognized emergency service identifiers: There 721 MUST be support for calls which are initiated as emergency calls 722 even if the specific emergency service requested is not recognized 723 by the ESRP. Such calls will then be routed to a generic 724 emergency service. 726 Motivation: Fallback routing allows new emergency services to be 727 introduced incrementally, while avoiding non-routable emergency 728 calls. For example, a call for marine rescue services would be 729 routed to a general PSAP if the caller's location does not offer 730 marine rescue services yet. 732 Id8. Return fallback service identifier: The mapping protocol must 733 be able to report back the actual service mapped if the mapping 734 protocol substitutes another service for the one requested. 736 Motivation: A mapping server may be configured to automatically 737 look up the PSAP for another service if the user-requested service 738 is not available for that location. For example, if there is no 739 marine rescue service, the mapping protocol might return the PSAP 740 URL for general emergencies and include the "urn:service.sos" 741 identifier in the response to alert the querier to that fact. 743 Id9. Discovery of visited emergency numbers: There MUST be a 744 mechanism to allow the end device to learn visited emergency 745 numbers. 747 Motivation: Travelers visiting a foreign country may observe the 748 local emergency number, e.g., seeing it painted on the side of a 749 fire truck, and then rightfully expect to be able to dial that 750 emergency number. Similarly, a local "good Samaritan" may use a 751 tourist's cell phone to summon help. 753 8. Mapping Protocol 755 There are two basic approaches to invoke the mapping protocol. We 756 refer to these as caller-based and mediated. In each case, the 757 mapping client initiates a request to a mapping server via a mapping 758 protocol. A proposed mapping protocol, LoST, is outlined in 759 [I-D.hardie-ecrit-lost]. 761 For caller-based resolution, the caller's user agent invokes the 762 mapping protocol to determine the appropriate PSAP based on the 763 location provided. The resolution may take place well before the 764 actual emergency call is placed, or at the time of the call. 766 For mediated resolution, an emergency call routing support entity, 767 such as a SIP (outbound) proxy or redirect server invokes the mapping 768 service. 770 Since servers may be used as outbound proxy servers by clients that 771 are not in the same geographic area as the proxy server, any proxy 772 server has to be able to translate any caller location to the 773 appropriate PSAP. (A traveler may, for example, accidentally or 774 intentionally configure its home proxy server as its outbound proxy 775 server, even while far away from home.) 777 Ma1. Baseline query protocol: A mandatory-to-implement protocol 778 MUST be specified. 780 Motivation: An over-abundance of similarly-capable choices appears 781 undesirable for interoperability. 783 Ma2. Extensible protocol: The mapping protocol MUST be designed to 784 support the extensibility of location data elements, both for new 785 and existing fields. 787 Motivation: This is needed, for example, to accommodate future 788 extensions to location information that might be included in the 789 PIDF-LO ([RFC4119]). 791 Ma3. Incrementally deployable: The mapping protocol MUST be 792 designed to support its incremental deployment. 794 Motivation: It must not be necessary, for example, to have a 795 global street level database before deploying the system. It is 796 acceptable to have some misrouting of calls when the database does 797 not (yet) contain accurate PSAP service area information. 799 Ma4. Any time mapping: The mapping protocol MUST support the 800 ability of the mapping function to be invoked at any time, 801 including while an emergency call is in process and before an 802 emergency call is initiated. 804 Motivation: Used as a fallback mechanism only, if a mapping query 805 fails at emergency call time, it may be advantageous to have prior 806 knowledge of the PSAP URI. This prior knowledge would be obtained 807 by performing a mapping query at any time prior to an emergency 808 call. 810 Ma5. Anywhere mapping: The mapping protocol MUST support the 811 ability to provide mapping information in response to an 812 individual query from any (earthly) location, regardless of where 813 the mapping client is located, either geographically or by network 814 location. 816 Motivation: The mapping client, such as an ESRP, may not 817 necessarily be anywhere close to the caller or the appropriate 818 PSAP, but must still be able to obtain mapping information. 820 Ma6. Appropriate PSAP: The mapping protocol MUST support the 821 routing of an emergency call to the PSAP responsible for a 822 particular geographic area. 824 Motivation: Routing to the wrong PSAP will result in delays in 825 handling emergencies as calls are redirected, and therefore will 826 also result in inefficient use of PSAP resources at the initial 827 point of contact. It is important that the location determination 828 mechanism not be fooled by the location of IP telephony gateways 829 or dial-in lines into a corporate LAN (and dispatch emergency help 830 to the gateway or campus, rather than the caller), multi-site LANs 831 and similar arrangements. 833 Ma7. Multiple PSAP URIs: The mapping protocol MUST support a method 834 to return multiple PSAP URIs which cover the same geographic area. 836 Motivation: Different contact protocols (e.g., PSTN via tel URIs 837 and IP via SIP URIs) may be routed to different PSAPs. Less 838 likely, two PSAPs may overlap in their coverage region. 840 Ma8. Single primary URI per contact protocol: Though the mapping 841 protocol may be able to include multiple URIs in the response, it 842 SHOULD return only one primary URI per contact protocol used, so 843 that clients are not required to select among different targets 844 for the same contact protocol. 846 Motivation: There may be two or more URIs returned when multiple 847 contact protocols are available (e.g., SIP and SMS). The client 848 may select among multiple contact protocols based on its 849 capabilities, preference settings, or availability. 851 Ma9. Non-preferred URI schemes: The mapping protocol MAY support 852 the return of a less preferred URI scheme, such as a tel URI. 854 Motivation: In order to provide incremental support to non-IP 855 PSAPs it may be necessary to be able to complete an emergency call 856 via the PSTN. 858 Ma10. URI properties: The mapping protocol MUST support the ability 859 to provide ancillary information about a contact that allows the 860 mapping client to determine relevant properties of the PSAP URI. 862 Motivation: In some cases, the same geographic area is served by 863 several PSAPs, for example, a corporate campus might be served by 864 both a corporate security department and the municipal PSAP. The 865 mapping protocol should then return URIs for both, with 866 information allowing the querying entity to choose one or the 867 other. This determination could be made by either an ESRP, based 868 on local policy, or by direct user choice, in the case of caller- 869 based methods. 871 Ma11. Mapping referral: The mapping protocol MUST support a 872 mechanism for the mapping client to contact any mapping server and 873 be referred to another mapping server that is more qualified to 874 answer the query. 876 Motivation: Referrals help mitigate the impact of incorrect 877 configuration that directs a client to the wrong initial mapping 878 server. 880 Ma12. Split responsibility: The mapping protocol MUST support the 881 division of data subset handling between multiple mapping servers 882 within a single level of a civic location hierarchy. 884 Motivation: For example, two mapping servers for the same city or 885 county may handle different streets within that city or county. 887 Ma13. URL for error reporting: The mapping protocol MUST support 888 the ability to return a URL that can be used to report a suspected 889 or known error within the mapping database. 891 Motivation: If an error is returned, for example, there needs to 892 be a URL which points to a resource which can explain or 893 potentially help resolve the error. 895 Ma14. Resilience to mapping server failure: The mapping protocol 896 MUST support a mechanism which enables the client to fail over to 897 different (replica) mapping server. 899 Motivation: The failure of a mapping server should not preclude 900 the mapping client from receiving an answer to its query. 902 Ma15. Traceable resolution: The mapping protocol SHOULD support the 903 ability of the mapping client to be able to determine the entity 904 or entities that provided the emergency address resolution 905 information. 907 Motivation: To improve reliability and performance, it is 908 important to be able to trace which servers contributed to the 909 resolution of a query. 911 Ma16. Minimal additional delay: Mapping protocol execution SHOULD 912 minimize the amount of delay within the overall call-setup time. 914 Motivation: Since outbound proxies will likely be asked to resolve 915 the same geographic coordinates repeatedly, a suitable time- 916 limited caching mechanism should be supported. 918 Ma17. Freshness indication: The mapping protocol SHOULD support an 919 indicator describing how current the information provided by the 920 mapping source is. 922 Motivation: This is especially useful when an alternate mapping is 923 requested, and alternative sources of mapping data may not have 924 been created or updated with the same set of information or within 925 the same timeframe. Differences in currency between mapping data 926 contained within mapping sources should be minimized. 928 9. Security Considerations 930 Threats and security requirements are discussed in a separate 931 document [I-D.ietf-ecrit-security-threats]. 933 10. IANA Considerations 935 This document does not require actions by the IANA. 937 11. Contributors 939 The information in this document is partially derived from text 940 written by the following contributors: 942 Nadine Abbott nabbott@telcordia.com 944 Hideki Arai arai859@oki.com 946 Martin Dawson Martin.Dawson@andrew.com 948 Motoharu Kawanishi kawanishi381@oki.com 950 Brian Rosen br@brianrosen.net 952 Richard Stastny Richard.Stastny@oefeg.at 954 Martin Thomson Martin.Thomson@andrew.com 956 James Winterbottom James.Winterbottom@andrew.com 958 12. Acknowledgments 960 In addition to thanking those listed above, we would like to also 961 thank Guy Caron, Barry Dingle, Keith Drage, Tim Dunn, Patrik 962 Faltstrom, Clive D.W. Feather, Raymond Forbes, Randall Gellens, 963 Michael Haberler, Michael Hammer, Ted Hardie, Gunnar Hellstrom, 964 Cullen Jennings, Marc Linsner, Rohan Mahy, Patti McCalmont, Don 965 Mitchell, John Morris, Andrew Newton, Steve Norreys, Jon Peterson, 966 James Polk, Benny Rodrig, John Rosenberg, Jonathan Rosenberg, John 967 Schnizlein, Shida Schubert, James Seng, Byron Smith, Barbara Stark, 968 Richard Stastny, Tom Taylor, Hannes Tschofenig, and Nate Wilcox for 969 their helpful input. 971 13. References 973 13.1. Normative References 975 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 976 Requirement Levels", BCP 14, RFC 2119, March 1997. 978 13.2. Informative References 980 [I-D.hardie-ecrit-lost] 981 Hardie, T., "LoST: A Location-to-Service Translation 982 Protocol", draft-hardie-ecrit-lost-00 (work in progress), 983 March 2006. 985 [I-D.ietf-ecrit-security-threats] 986 Taylor, T., "Security Threats and Requirements for 987 Emergency Call Marking and Mapping", 988 draft-ietf-ecrit-security-threats-03 (work in progress), 989 July 2006. 991 [I-D.ietf-ecrit-service-urn] 992 Schulzrinne, H., "A Uniform Resource Name (URN) for 993 Services", draft-ietf-ecrit-service-urn-05 (work in 994 progress), August 2006. 996 [I-D.ietf-sipping-toip] 997 Wijk, A. and G. Gybels, "Framework for real-time text over 998 IP using the Session Initiation Protocol (SIP)", 999 draft-ietf-sipping-toip-07 (work in progress), 1000 August 2006. 1002 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 1003 A., Peterson, J., Sparks, R., Handley, M., and E. 1004 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 1005 June 2002. 1007 [RFC3351] Charlton, N., Gasson, M., Gybels, G., Spanner, M., and A. 1008 van Wijk, "User Requirements for the Session Initiation 1009 Protocol (SIP) in Support of Deaf, Hard of Hearing and 1010 Speech-impaired Individuals", RFC 3351, August 2002. 1012 [RFC3693] Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and 1013 J. Polk, "Geopriv Requirements", RFC 3693, February 2004. 1015 [RFC3860] Peterson, J., "Common Profile for Instant Messaging 1016 (CPIM)", RFC 3860, August 2004. 1018 [RFC3966] Schulzrinne, H., "The tel URI for Telephone Numbers", 1019 RFC 3966, December 2004. 1021 [RFC4103] Hellstrom, G. and P. Jones, "RTP Payload for Text 1022 Conversation", RFC 4103, June 2005. 1024 [RFC4119] Peterson, J., "A Presence-based GEOPRIV Location Object 1025 Format", RFC 4119, December 2005. 1027 [RFC4412] Schulzrinne, H. and J. Polk, "Communications Resource 1028 Priority for the Session Initiation Protocol (SIP)", 1029 RFC 4412, February 2006. 1031 Authors' Addresses 1033 Henning Schulzrinne 1034 Columbia University 1035 Department of Computer Science 1036 450 Computer Science Building 1037 New York, NY 10027 1038 US 1040 Phone: +1 212 939 7004 1041 Email: hgs+ecrit@cs.columbia.edu 1042 URI: http://www.cs.columbia.edu 1044 Roger Marshall (editor) 1045 TeleCommunication Systems, Inc. 1046 2401 Elliott Avenue 1047 2nd Floor 1048 Seattle, WA 98121 1049 US 1051 Phone: +1 206 792 2424 1052 Email: rmarshall@telecomsys.com 1053 URI: http://www.telecomsys.com 1055 Full Copyright Statement 1057 Copyright (C) The IETF Trust (2007). 1059 This document is subject to the rights, licenses and restrictions 1060 contained in BCP 78, and except as set forth therein, the authors 1061 retain all their rights. 1063 This document and the information contained herein are provided on an 1064 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 1065 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 1066 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 1067 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 1068 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 1069 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 1071 Intellectual Property 1073 The IETF takes no position regarding the validity or scope of any 1074 Intellectual Property Rights or other rights that might be claimed to 1075 pertain to the implementation or use of the technology described in 1076 this document or the extent to which any license under such rights 1077 might or might not be available; nor does it represent that it has 1078 made any independent effort to identify any such rights. 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