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'5') (Obsoleted by RFC 6225) == Outdated reference: draft-ietf-ecrit-security-threats has been published as RFC 5069 == Outdated reference: draft-ietf-ecrit-service-urn has been published as RFC 5031 == Outdated reference: draft-ietf-geopriv-dhcp-civil has been published as RFC 4676 == Outdated reference: draft-ietf-sipping-toip has been published as RFC 5194 Summary: 3 errors (**), 0 flaws (~~), 8 warnings (==), 8 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 ECRIT H. Schulzrinne 3 Internet-Draft Columbia U. 4 Expires: December 3, 2006 R. Marshall, Ed. 5 TCS 6 June 2006 8 Requirements for Emergency Context Resolution with Internet 9 Technologies 10 draft-ietf-ecrit-requirements-11 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 December 3, 2006. 37 Copyright Notice 39 Copyright (C) The Internet Society (2006). 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 . . . . . . . . . . . . . . . . . . 14 62 6. Identifying the Caller's Location . . . . . . . . . . . . . 16 63 7. Emergency Service Identifier . . . . . . . . . . . . . . . . 19 64 8. Mapping Protocol . . . . . . . . . . . . . . . . . . . . . . 22 65 9. Security Considerations . . . . . . . . . . . . . . . . . . 27 66 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . 28 67 11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 29 68 12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 30 69 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 31 70 13.1 Normative References . . . . . . . . . . . . . . . . . . 31 71 13.2 Informative References . . . . . . . . . . . . . . . . . 31 72 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 32 73 Intellectual Property and Copyright Statements . . . . . . . 33 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 [3]) 79 expect to be able to initiate a request for help in case of an 80 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) [2] 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 [9] and a service identifier in 108 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 2. Requirements Terminology 134 In this document, the key words "MUST", "MUST NOT", "REQUIRED", 135 "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", 136 and "OPTIONAL" are to be interpreted as described in RFC 2119 [1], 137 with the qualification that unless otherwise stated these words apply 138 to the design of the mapping protocol, not its implementation or 139 application. 141 3. Terminology 143 3.1 Emergency Services 145 Basic emergency service: Basic emergency service allows a caller to 146 reach a PSAP serving its current location, but the PSAP may not be 147 able to determine the identity or geographic location of the 148 caller, except by the call taker asking the caller. 150 Enhanced emergency service: In enhanced emergency service, the PSAP 151 call taker can determine the caller's current location. 153 3.2 Service Providers 155 Internet Attachment Provider (IAP): An organization that provides 156 physical and data link (layer 2) network connectivity to its 157 customers or users, e.g., through digital subscriber lines, cable 158 TV plants, Ethernet, leased lines or radio frequencies. Examples 159 of such organizations include telecommunication carriers, 160 municipal utilities, larger enterprises with their own network 161 infrastructure, and government organizations such as the military. 163 Internet Service Provider (ISP): An organization that provides IP 164 network-layer services to its customers or users. This entity may 165 or may not provide the physical-layer and data link (layer-2) 166 connectivity, such as fiber or Ethernet, i.e., it may or may not 167 play the role of an IAP. 169 Application Service Provider (ASP): The organization or entity that 170 provides application-layer services, which may include voice (see 171 "Voice Service Provider"). This entity can be a private 172 individual, an enterprise, a government, or a service provider. 173 An ASP is more general than a Voice Service Provider, since 174 emergency calls may use other media beyond voice, including text 175 and video. For a particular user, the ASP may or may not be the 176 same organization as his IAP or ISP. 178 Voice Service Provider (VSP): A specific type of Application Service 179 Provider which provides voice related services based on IP, such 180 as call routing, a SIP URI, or PSTN termination. In this 181 document, unless noted otherwise, any reference to "Voice Service 182 Provider" or "VSP" may be used interchangeably with "Application/ 183 Voice Service Provider" or "ASP/VSP". 185 3.3 Actors 187 (Emergency) caller: The term "caller" or "emergency caller" refer to 188 the person placing an emergency call or sending an emergency 189 instant message (IM). 191 User Equipment (UE): User equipment is the device or software 192 operated by the caller to place an emergency call. A SIP user 193 agent (UA) is an example of a UE. 195 Call taker: A call taker is an agent at the PSAP that accepts calls 196 and may dispatch emergency help. Sometimes the functions of call 197 taking and dispatching are handled by different groups of people, 198 but these divisions of labor are not generally visible to the 199 caller and thus do not concern us here. 201 3.4 Call Routing Entities 203 Emergency Service Routing Proxy (ESRP): An ESRP is an emergency call 204 routing support entity that invokes the location-to-PSAP URI 205 mapping, to return either the URI for the appropriate PSAP, or the 206 URI for another ESRP. (In a SIP system, the ESRP would typically 207 be a SIP proxy, but may also be a back-to-back user agent 208 (B2BUA)). 210 Public Safety Answering Point (PSAP): Physical location where 211 emergency calls are received under the responsibility of a public 212 authority. (This terminology is used by both ETSI, in ETSI SR 002 213 180, and NENA.) In the United Kingdom, PSAPs are called Operator 214 Assistance Centres, in New Zealand, Communications Centres. 215 Within this document, it is assumed, unless stated otherwise, that 216 PSAPs support the receipt of emergency calls over IP, using 217 appropriate application layer protocols such as SIP for call 218 signaling and RTP for media. 220 3.5 Location 222 Location: A geographic identification assigned to a region or feature 223 based on a specific coordinate system, or by other precise 224 information such as a street number and name. It can be either a 225 civic or geographic location. 227 Civic location: A described location based on some reference system, 228 such as jurisdictional region or postal delivery grid. A street 229 address is a common example of a civic location. 231 Geographic location: A reference to a point which is able to be 232 located as described by a set of defined coordinates within a 233 geographic coordinate system, such as latitude and longitude 234 within the WGS-84 datum. For example, 2-D geographic location is 235 defined as an (x,y) coordinate value pair according to the 236 distance north or south of the equator and east or west of the 237 prime meridian. 239 Location validation: A caller location is considered valid if the 240 civic or geographic location is recognizable within an acceptable 241 location reference system (e.g., United States Postal Address or 242 the WGS-84 datum) and can be mapped to one or more PSAPs. While 243 it is desirable to determine that a location exists, validation 244 may not ensure that such a location exists, but rather may only 245 ensure that the location falls within some range of known values. 246 Location validation ensures that a location is able to be 247 referenced for mapping, but makes no assumption about the 248 association between the caller and the caller's location. 250 3.6 Identifiers, Numbers and Dial Strings 252 (Emergency) service number: The (emergency) service number is a 253 string of digits used to reach the (emergency) service. The 254 emergency service number is often just called the emergency 255 number. It is the number typically dialed on devices directly 256 connected to the PSTN and the number reserved for emergency calls 257 by national or regional numbering authorities. It only contains 258 the digits 0 through 9, # and *. The service number may depend on 259 the location of the caller. For example, the general emergency 260 service number in the United States is 911 and the poison control 261 service number is 18002221222. In most cases, the service number 262 and dial string are the same; they may differ in some private 263 phone networks. A service number may be carried in tel URLs [7], 264 along with a context identifier. In the North American numbering 265 plan, some service numbers are also three-digit N11 or service 266 codes, but not all emergency numbers have three digits. A caller 267 may have to dial a service dial string (below) that differs from 268 the service number when using a PBX. 270 (Emergency) service dial string: The service dial string identifies 271 the string of digits that a caller must dial to reach a particular 272 (emergency) service. In devices directly connected to the PSTN, 273 the service dial string is the same as the service number and may 274 thus depend on the location of the caller. However, in private 275 phone networks, such as in PBXs, the service dial string consists 276 of a dialing prefix to reach an outside line, followed by the 277 emergency number. For example, in a hotel, the dial string for 278 emergency services in the United States might be 9911. Dial 279 strings may contain indications of pauses or wait-for-secondary- 280 dial-tone indications. Service dial strings are outside the scope 281 of this document. 283 (Emergency) service identifier: The (emergency) service identifier 284 describes the emergency service, independent of the user interface 285 mechanism, the signaling protocol that is used to reach the 286 service, or the caller's geographic location. It is a protocol 287 constant and used within the mapping and signaling protocols. An 288 example is the service URN [12]. 290 (Emergency) service URL: The service URL is a protocol-specific 291 (e.g., SIP) or protocol-agnostic (e.g., im: [6]) contains the 292 address of the PSAP or other emergency service. It depends on the 293 specific signaling or data transport protocol used to reach the 294 emergency service. 296 Service URN: A service URN is an implementation of a service 297 identifier, which can be applied to both emergency and non- 298 emergency contexts, e.g., urn:service:sos or 299 urn:service:counseling. Within this document, service URNs are 300 referred to as 'emergency service URNs' [12]. 302 Home emergency number: A home emergency number is the emergency 303 number valid at the caller's customary home location, e.g., his 304 permanent residence. The home location may or may not coincide 305 with the service area of the caller's VSP. 307 Home emergency dial string: A home dial string is the dial string 308 valid at the caller's customary home location, e.g., his permanent 309 residence. 311 Visited emergency number: A visited emergency number is the emergency 312 number valid at the caller's current physical location. We 313 distinguish the visited emergency number if the caller is 314 traveling outside his home region. 316 Visited emergency dial string: A visited emergency dial string is the 317 dial string number valid at the caller's current physical 318 location. 320 3.7 Mapping 321 Mapping: Mapping is the process of resolving a location to one or 322 more PSAP URIs which directly identify a PSAP, or point to an 323 intermediary which knows about a PSAP and that is designated as 324 responsible for serving that location. 326 Mapping client: A mapping client interacts with the mapping server to 327 learn one or more PSAP URIs for a given location. 329 Mapping protocol: A protocol used to convey the mapping request and 330 response. 332 Mapping server: The mapping server holds information about the 333 location-to-PSAP URI mapping. 335 Mapping service: A network service which uses a distributed mapping 336 protocol to perform a mapping between a location and a PSAP, or 337 intermediary which knows about the PSAP, and is used to assist in 338 routing an emergency call. 340 4. Basic Actors 342 In order to support emergency services covering a large physical 343 area, various infrastructure elements are necessary, including 344 Internet Attachment Providers (IAPs), Application/Voice Service 345 Providers (ASP/VSPs), Emergency Service Routing Proxy (ESRP) 346 providers, mapping service providers, and PSAPs. 348 This section outlines which entities will be considered in the 349 routing scenarios discussed. 351 Location 352 Information +-----------------+ 353 |(1) |Internet | +-----------+ 354 v |Attachment | | | 355 +-----------+ |Provider | | Mapping | 356 | | | (3) | | Service | 357 | Emergency |<---+-----------------+-->| | 358 | Caller | | (2) | +-----------+ 359 | |<---+-------+ | ^ 360 +-----------+ | +----|---------+------+ | 361 ^ | | Location | | | 362 | | | Information<-+ | | 363 | +--+--------------+ |(5) | | (6) 364 | | | | | 365 | | +-----------v+ | | 366 | (4) | | | | | 367 +--------------+--->| ESRP |<--+---+ 368 | | | | | 369 | | +------------+ | 370 | | ^ | 371 | | (7) | | +----+--+ 372 | (8) | +------------>| | 373 +--------------+----------------------->| PSAP | 374 | | | | 375 |Application/ | +----+--+ 376 |Voice | 377 |Service | 378 |Provider | 379 +---------------------+ 381 Figure 1: Framework for emergency call routing 383 Figure 1 shows the interaction between the entities involved in the 384 call. There are a number of different deployment choices, as can be 385 easily seen from the figure. 387 How is location information provided to the end host? It might 388 either be known to the end host itself via manual configuration, 389 provided via GPS, made available via DHCP ([5], [14]) or some other 390 mechanism. Alternatively, location information is inserted by 391 intermediaries. 393 Is the Internet Attachment Provider also the Application/Voice 394 Service Provider? In the Internet today these roles are typically 395 provided by different entities. As a consequence, the Application/ 396 Voice Service Provider is typically not able to directly determine 397 the physical location of the emergency caller. 399 The overlapping squares in the figure indicate that some functions 400 can be collapsed into a single entity. As an example, the 401 Application/Voice Service Provider might be the same entity as the 402 Internet Attachment Provider. There is, however, no requirement that 403 this must be the case. Additionally, we consider that end systems 404 might act as their own ASP/VSP, e.g., either for enterprises or for 405 residential users. 407 Various potential interactions between the entities depicted in 408 Figure 1 are described below: 410 1. Location information might be available to the end host itself. 412 2. Location information might, however, also be obtained from the 413 Internet Attachment Provider (e.g., using DHCP or application 414 layer signaling protocols). 416 3. The emergency caller might need to consult a mapping service to 417 determine the PSAP (or other relevant information) that is 418 appropriate for the physical location of the emergency caller, 419 possibly considering other attributes such as appropriate 420 language support by the emergency call taker. 422 4. The emergency caller might get assistance for emergency call 423 routing by infrastructure elements that are emergency call 424 routing support entities, such as an Emergency Service Routing 425 Proxy (ESRP) in SIP. 427 5. Location information is used by emergency call routing support 428 entities for subsequent mapping requests. 430 6. Emergency call routing support entities might need to consult a 431 mapping service to determine where to route the emergency call. 433 7. For infrastructure-based emergency call routing (in contrast to 434 UE-based emergency call routing), the emergency call routing 435 support entity needs to forward the call to the PSAP. 437 8. The emergency caller may interact directly with the PSAP, where 438 the UE invokes mapping, and initiates a connection, without 439 relying on any intermediary emergency call routing support 440 entities. 442 5. High-Level Requirements 444 Below, we summarize high-level architectural requirements that guide 445 some of the component requirements detailed later in the document. 447 Re1. Application/Voice service provider existence: The initiation of 448 an IP-based emergency call SHOULD NOT assume the existence of an 449 Application/Voice Service Provider (ASP/VSP). 451 Motivation: The caller may not have an application/voice service 452 provider. For example, a residence may have its own DNS domain 453 and run its own SIP proxy server for that domain. On a larger 454 scale, a university might provide voice services to its students 455 and staff, but might not be a telecommunication provider. 457 Re2. International applicability: Regional, political and 458 organizational aspects MUST be considered during the design of 459 protocols and protocol extensions which support IP-based emergency 460 calls. 462 Motivation: It must be possible for a device or software developed 463 or purchased in one country to place emergency calls in another 464 country. System components should not be biased towards a 465 particular set of emergency numbers or languages. Also, different 466 countries have evolved different ways of organizing emergency 467 services, e.g., either centralizing them or having smaller 468 regional subdivisions such as United States counties or 469 municipalities handle emergency calls within their jurisdiction. 471 Re3. Distributed administration: Deployment of IP-based emergency 472 services MUST NOT depend on a single central administrative 473 authority. 475 Motivation: The design of the mapping protocol must make it 476 possible to deploy and administer emergency calling features on a 477 regional or national basis without requiring coordination with 478 other regions or nations. The system cannot assume, for example, 479 that there is a single global entity issuing certificates for 480 PSAPs, ASP/VSPs, IAPs or other participants. 482 Re4. Multi-mode communication: IP-based emergency calls MUST support 483 multiple communication modes, including, for example, audio, video 484 and text. 486 Motivation: Within the PSTN, voice and text telephony (often 487 called TTY or text-phone in North America) are the only commonly 488 supported media. Emergency calling must support a variety of 489 media. Such media should include voice, conversational text (RFC 490 4103 [8]), instant messaging and video. 492 Re5. Mapping result usability: The mapping protocol MUST return one 493 or more URIs that are usable within a standard signaling protocol 494 (i.e., without special emergency extensions). 496 Motivation: For example, a SIP URI which is returned by the 497 mapping protocol needs to be usable by any SIP capable phone 498 within a SIP initiated emergency call. This is in contrast to a 499 "special purpose" URI, which may not be recognizable by a legacy 500 SIP device. 502 Re6. PSAP URI accessibility: The mapping protocol MUST support 503 interaction between the client and server where no enrollment to a 504 mapping service exists or is required. 506 Motivation: The mapping server may well be operated by a service 507 provider, but access to the server offering the mapping must not 508 require use of a specific ISP or ASP/VSP. 510 Re7. Common data structures and formats: The mapping protocol SHOULD 511 support common formats for location data. 513 Motivation: Location databases should not need to be transformed 514 or modified in any unusual or unreasonable way in order for the 515 mapping protocol to use the data. For example, a database which 516 contains civic addresses used by location servers may be used for 517 multiple purposes and applications beyond emergency service 518 location-to-PSAP URI mapping. 520 Re8. Anonymous mapping: The mapping protocol MUST NOT require the 521 true identity of the target for which the location information is 522 attributed. 524 Motivation: Ideally, no identity information is provided via the 525 mapping protocol. Where identity information is provided, it may 526 be in the form of an unlinked pseudonym (RFC 3693 [4]). 528 6. Identifying the Caller's Location 530 Location can either be provided directly (by value), or via a poiner 531 (by reference), and represents either a civic location, or a 532 geographic location. An important question is how and when to attach 533 location information to the VoIP emergency signaling messages. In 534 general, we can distinguish three modes of operation of how a 535 location is associated with an emergency call: 537 UA-inserted: The caller's user agent inserts the location information 538 into the call signaling message. The location information is 539 derived from sources such as GPS, DHCP (see [5] for geographic 540 location information and [14] for civic location information) or 541 utilizing the Link Layer Discovery Protocol (LLDP) [16]. 543 UA-referenced: The caller's user agent provides a pointer (i.e., a 544 location reference), via a permanent or temporary identifier, to 545 the location information, which is stored by a location server 546 somewhere else and then retrieved by the PSAP, ESRP, or other 547 authorized entity. 549 Proxy-inserted: A proxy along the call path inserts the location or 550 location reference. 552 The following requirements apply: 554 Lo1. Reference datum: The mapping protocol MUST support the WGS-84 555 coordinate reference system and MAY support other coordinate 556 reference systems. 558 Motivation: Though many different datums exist around the world, 559 this document recommends the WGS-84 datum since it is designed to 560 describe the whole earth, rather than a single continent or other 561 region, and is commonly used to represent Global Positioning 562 System coordinates. 564 Lo2. Location delivery by-value: The mapping protocol MUST support 565 the delivery of location information using a by-value method, 566 though it MAY also support de-referencing a URL that references a 567 location object. 569 Motivation: The mapping protocol is not required to support the 570 ability to de-reference specific location references. 572 Lo3. Alternate community names: The mapping protocol MUST support 573 both the jurisdictional community name and the postal community 574 name fields within the PIDF-LO [9] data. 576 Motivation: The mapping protocol must accept queries with either 577 a postal or jurisdictional community name field, or both, and 578 provide appropriate responses. If a mapping query contains only 579 one community name and the database contains both jurisdictional 580 and postal community names, the mapping protocol response SHOULD 581 return both community names. 583 Lo4. Validation of civic location: The mapping protocol MUST support 584 location validation for civic locations (street addresses). 586 Motivation: Location validation provides an opportunity to help 587 ascertain ahead of time whether or not a successful mapping to the 588 appropriate PSAP will likely occur when it is required. 589 Validation may also help to avoid delays during emergency call 590 setup due to invalid location data. 592 Lo5. Validation resolution: The mapping protocol MUST support the 593 ability to provide ancillary information about the resolution of 594 location data used to retrieve a PSAP URI. 596 Motivation: The mapping server may not use all the data elements 597 in the provided location information to determine a match, or may 598 be able to find a match based on all of the information except for 599 some specific data elements. The uniqueness of this information 600 set may be used to differentiate among emergency jurisdictions. 601 Precision or resolution in the context of this requirement might 602 mean, for example, explicit identification of the data elements 603 that were used successfully in the mapping. 605 Lo6. Contact for location problems: The mapping protocol MUST 606 support a mechanism to contact an appropriate authority to resolve 607 mapping-related issues for the queried location. For example, the 608 querier may want to report problems with the response values or 609 indicate that the mapping database is mistaken on declaring a 610 civic location as non-existent. 612 Motivation: Initially, authorities may provide URLs where a human 613 user can report problems with an address or location. In 614 addition, web services may be defined to automate such reporting. 615 For example, the querier may wish to report that the mapping 616 database may be missing a newly-built or renamed street or house 617 number. 619 Lo7. Limits to validation: Successful validation of a civic location 620 MUST NOT be required to place an emergency call. 622 Motivation: In some cases, a civic location may not be considered 623 valid. This fact should not result in the call being dropped or 624 rejected by any entity along the call setup signaling path to the 625 PSAP. 627 Lo8. 3D sensitive mapping: The mapping protocol MUST implement 628 support for both 2D and 3D location information, and may accept 629 either a 2D or 3D mapping request as input. 631 Motivation: It is expected that queriers may provide either 2D or 632 3D data. When a 3D request is presented within an area only 633 defined by 2D data within the mapping server, the mapping result 634 would be the same as if the height or altitude coordinate had been 635 omitted from the mapping request. 637 Lo9. Database type indicator: The mapping protocol MAY support a 638 mechanism which provides an indication describing a specific type 639 of location database used. 641 Motivation: It is useful to know the source of the data stored in 642 the database used for location validation, either for civic or 643 geographic location matching. In the United States, sources of 644 data could include the United States Postal Service, the Master 645 Street Address Guide (MSAG) or commercial map data providers. 647 7. Emergency Service Identifier 649 Emergency service identifiers are protocol constants that allow 650 protocol entities such as SIP proxy servers to distinguish emergency 651 calls from non-emergency calls and to identify the specific emergency 652 service desired. Emergency service identifiers are a subclass of 653 service identifiers that more generally identify services reachable 654 by callers. An example of a service identifier is the service URN 655 [12], but other identifiers, such as tel URIs [7], may also serve 656 this role during a transition period. 658 Since this document only addresses emergency services, we use the 659 terms "emergency service identifier" and "service identifier" 660 interchangeably. Requirements for these identifiers include: 662 Id1. Multiple emergency services: The mapping protocol MUST be able 663 to distinguish between different emergency services, 664 differentiated by different service identifiers. 666 Motivation: Some jurisdictions may offer multiple types of 667 emergency services that operate independently and can be contacted 668 directly, for example, fire, police and ambulance services. 670 Id2. Extensible emergency service identifiers: The mapping protocol 671 MUST support an extensible list of emergency identifiers, though 672 it is not required to provide mappings for every possible service. 674 Motivation: Extensibility is required since new emergency 675 services may be introduced over time, either globally or in some 676 jurisdictions. The availability of emergency services depends on 677 the locations. For example, the Netherlands are unlikely to offer 678 a mountain rescue service. 680 Id3. Discovery of emergency number: The mapping protocol MUST be 681 able to return the location-dependent emergency number for the 682 location indicated in the query. 684 Motivation: Users are trained to dial the appropriate emergency 685 number to reach emergency services. There needs to be a way to 686 figure out the emergency number at the current location of the 687 caller. 689 Id4. Home emergency number recognition: User equipment MUST be able 690 to translate a home emergency number into an emergency service 691 identifier. 693 Motivation: The UE could be pre-provisioned with the appropriate 694 information in order to perform such a translation or could 695 discover the emergency number by querying the mapping protocol 696 with its home location. 698 Id5. Emergency number replacement: There SHOULD be support for 699 replacement of the emergency number with the appropriate emergency 700 service identifier for each signaling protocol used for an 701 emergency call, based on local conventions, regulations, or 702 preference (e.g., as in the case of an enterprise). 704 Motivation: Any signaling protocol requires the use of some 705 identifier to indicate the called party, and the user equipment 706 may lack the capability to determine the actual service URL (PSAP 707 URI). The use of local conventions may be required as a 708 transition mechanism. Since relying on recognizing local 709 numbering conventions makes it difficult for devices to be used 710 outside their home context and for external devices to be 711 introduced into a network, protocols should use standardized 712 emergency service identifiers. 714 Id6. Emergency service identifier marking: Signaling protocols MUST 715 support emergency service identifiers to mark a call as an 716 emergency call. 718 Motivation: Marking ensures proper handling as an emergency call 719 by downstream elements that may not recognize, for example, a 720 local variant of a logical emergency address. This marking 721 mechanism is related to, but independent of, marking calls for 722 prioritized call handling [10]. 724 Id7. Handling unrecognized emergency service identifiers: There MUST 725 be support for calls which are initiated as emergency calls even 726 if the specific emergency service requested is not recognized by 727 the ESRP. Such calls will then be routed to a generic emergency 728 service. 730 Motivation: Fallback routing allows new emergency services to be 731 introduced incrementally, while avoiding non-routable emergency 732 calls. For example, a call for marine rescue services would be 733 routed to a general PSAP if the caller's location does not offer 734 marine rescue services yet. 736 Id8. Return fallback service identifier: The mapping protocol must 737 be able to report back the actual service mapped if the mapping 738 protocol substitutes another service for the one requested. 740 Motivation: A mapping server may be configured to automatically 741 look up the PSAP for another service if the user-requested service 742 is not available for that location. For example, if there is no 743 marine rescue service, the mapping protocol might return the PSAP 744 URL for general emergencies and include the "urn:service.sos" 745 identifier in the response to alert the querier to that fact. 747 Id9. Discovery of visited emergency dial strings: There MUST be a 748 mechanism to allow the end device to learn visited emergency 749 numbers. 751 Motivation: Travelers visiting a foreign country may observe the 752 local emergency number, e.g., seeing it painted on the side of a 753 fire truck, and then rightfully expect to be able to dial that 754 emergency number. Similarly, a local "good Samaritan" may use a 755 tourist's cell phone to summon help. 757 8. Mapping Protocol 759 There are two basic approaches to invoke the mapping protocol. We 760 refer to these as caller-based and mediated. In each case, the 761 mapping client initiates a request to a mapping server via a mapping 762 protocol. A proposed mapping protocol, LoST, is outlined in [13]. 764 For caller-based resolution, the caller's user agent invokes the 765 mapping protocol to determine the appropriate PSAP based on the 766 location provided. The resolution may take place well before the 767 actual emergency call is placed, or at the time of the call. 769 For mediated resolution, an emergency call routing support entity, 770 such as a SIP (outbound) proxy or redirect server invokes the mapping 771 service. 773 Since servers may be used as outbound proxy servers by clients that 774 are not in the same geographic area as the proxy server, any proxy 775 server has to be able to translate any caller location to the 776 appropriate PSAP. (A traveler may, for example, accidentally or 777 intentionally configure its home proxy server as its outbound proxy 778 server, even while far away from home.) 780 Ma1. Baseline query protocol: A mandatory-to-implement protocol MUST 781 be specified. 783 Motivation: An over-abundance of similarly-capable choices appears 784 undesirable for interoperability. 786 Ma2. Extensible protocol: The mapping protocol MUST be designed to 787 support the extensibility of location data elements, both for new 788 and existing fields. 790 Motivation: This is needed, for example, to accommodate future 791 extensions to location information that might be included in the 792 PIDF-LO ([9]). 794 Ma3. Incrementally deployable: The mapping protocol MUST be designed 795 to support its incremental deployment. 797 Motivation: It must not be necessary, for example, to have a 798 global street level database before deploying the system. It is 799 acceptable to have some misrouting of calls when the database does 800 not (yet) contain accurate PSAP service area information. 802 Ma4. Any time mapping: The mapping protocol MUST support the ability 803 of the mapping function to be invoked at any time, including while 804 an emergency call is in process and before an emergency call is 805 initiated. 807 Motivation: Used as a fallback mechanism only, if a mapping query 808 fails at emergency call time, it may be advantageous to have prior 809 knowledge of the PSAP URI. This prior knowledge would be obtained 810 by performing a mapping query at any time prior to an emergency 811 call. 813 Ma5. Anywhere mapping: The mapping protocol MUST support the ability 814 to provide mapping information in response to an individual query 815 from any (earthly) location, regardless of where the mapping 816 client is located, either geographically or by network location. 818 Motivation: The mapping client, such as an ESRP, may not 819 necessarily be anywhere close to the caller or the appropriate 820 PSAP, but must still be able to obtain mapping information. 822 Ma6. Appropriate PSAP: The mapping protocol MUST support the routing 823 of an emergency call to the PSAP responsible for a particular 824 geographic area. 826 Motivation: Routing to the wrong PSAP will result in delays in 827 handling emergencies as calls are redirected, and therefore will 828 also result in inefficient use of PSAP resources at the initial 829 point of contact. It is important that the location determination 830 mechanism not be fooled by the location of IP telephony gateways 831 or dial-in lines into a corporate LAN (and dispatch emergency help 832 to the gateway or campus, rather than the caller), multi-site LANs 833 and similar arrangements. 835 Ma7. Multiple PSAP URIs: The mapping protocol MUST support a method 836 to return multiple PSAP URIs which cover the same geographic area. 838 Motivation: Different contact protocols (e.g., PSTN via tel URIs 839 and IP via SIP URIs) may be routed to different PSAPs. Less 840 likely, two PSAPs may overlap in their coverage region. 842 Ma8. Single primary URI per contact protocol: Though the mapping 843 protocol may be able to include multiple URIs in the response, it 844 SHOULD return only one primary URI per contact protocol used, so 845 that clients are not required to select among different targets 846 for the same contact protocol. 848 Motivation: There may be two or more URIs returned when multiple 849 contact protocols are available (e.g., SIP and SMS). The client 850 may select among multiple contact protocols based on its 851 capabilities, preference settings, or availability. 853 Ma9. URI alternate contact: In addition to returning a primary 854 contact, the mapping protocol MUST support the return of a PSAP 855 URI or contact method explicitly marked as an alternate contact 856 for use when a fallback contact is needed. 858 Motivation: There may be multiple ways to provide addresses of 859 backup PSAPs, including the mapping protocol, DNS lookup via NAPTR 860 and SRV, or call routing by SIP proxies. 862 Ma10. Non-preferred URI schemes: The mapping protocol MAY support 863 the return of a less preferred URI scheme, such as a tel URI. 865 Motivation: In order to provide incremental support to non-IP 866 PSAPs it may be necessary to be able to complete an emergency call 867 via the PSTN. 869 Ma11. URI properties: The mapping protocol MUST support the ability 870 to provide ancillary information about a contact that allows the 871 mapping client to determine relevant properties of the PSAP URI. 873 Motivation: In some cases, the same geographic area is served by 874 several PSAPs, for example, a corporate campus might be served by 875 both a corporate security department and the municipal PSAP. The 876 mapping protocol should then return URIs for both, with 877 information allowing the querying entity to choose one or the 878 other. This determination could be made by either an ESRP, based 879 on local policy, or by direct user choice, in the case of caller- 880 based methods. 882 Ma12. Mapping referral: The mapping protocol MUST support a 883 mechanism for the mapping client to contact any mapping server and 884 be referred to another mapping server that is more qualified to 885 answer the query. 887 Motivation: Referrals help mitigate the impact of incorrect 888 configuration that directs a client to the wrong initial mapping 889 server. 891 Ma13. Split responsibility: The mapping protocol MUST support the 892 division of data subset handling between multiple mapping servers 893 within a single level of a civic location hierarchy. 895 Motivation: For example, two mapping servers for the same city or 896 county may handle different streets within that city or county. 898 Ma14. URL for error reporting: The mapping protocol MUST support the 899 ability to return a URL that can be used to report a suspected or 900 known error within the mapping database. 902 Motivation: If an error is returned, for example, there needs to 903 be a URL which points to a resource which can explain or 904 potentially help resolve the error. 906 Ma15. Resiliance to failure: The mapping protocol MUST support a 907 mechanism which enables the client to fail over to different 908 (replica) mapping server. 910 Motivation: The failure of a mapping server should not preclude 911 the mapping client from receiving an answer to its query. 913 Ma16. Traceable resolution: The mapping protocol SHOULD support the 914 ability of the mapping client to be able to determine the entity 915 or entities that provided the emergency address resolution 916 information. 918 Motivation: To improve reliability and performance, it is 919 important to be able to trace which servers contributed to the 920 resolution of a query. 922 Ma17. Minimal additional delay: Mapping protocol execution SHOULD 923 minimize the amount of delay within the overall call-setup time. 925 Motivation: Since outbound proxies will likely be asked to 926 resolve the same geographic coordinates repeatedly, a suitable 927 time-limited caching mechanism should be supported. 929 Ma18. Alternate mapping sources: The mapping protocol MUST implement 930 a mechanism that allows for the retrieval of mapping information 931 from different sources. 933 Motivation: This provides the possibility of having available 934 alternative sources of mapping information when the normal source 935 is unavailable or unreachable. 937 Ma19. Freshness indication: The mapping protocol SHOULD support an 938 indicator describing how current the information provided by the 939 mapping source is. 941 Motivation: This is especially useful when an alternate mapping is 942 requested, and alternative sources of mapping data may not have 943 been created or updated with the same set of information or within 944 the same timeframe. Differences in currency between mapping data 945 contained within mapping sources should be minimized. 947 9. Security Considerations 949 Threats and security requirements are discussed in a separate 950 document [11]. 952 10. IANA Considerations 954 This document does not require actions by the IANA. 956 11. Contributors 958 The information contained in this document is a result of a several 959 original joint contributions of text, which was then discussed and 960 refined by those and many others within the working group. These 961 contributors to the early text include, Nadine Abbott, Hideki Arai, 962 Martin Dawson, Motoharu Kawanishi, Brian Rosen, Richard Stastny, 963 Martin Thomson, James Winterbottom. 965 The contributors can be reached at: 967 Nadine Abbott nabbott@telcordia.com 969 Hideki Arai arai859@oki.com 971 Martin Dawson Martin.Dawson@andrew.com 973 Motoharu Kawanishi kawanishi381@oki.com 975 Brian Rosen br@brianrosen.net 977 Richard Stastny Richard.Stastny@oefeg.at 979 Martin Thomson Martin.Thomson@andrew.com 981 James Winterbottom James.Winterbottom@andrew.com 983 12. Acknowledgments 985 In addition to thanking those listed above, we would like to also 986 thank Guy Caron, Barry Dingle, Keith Drage, Tim Dunn, Patrik 987 Faltstrom, Clive D.W. Feather, Raymond Forbes, Randall Gellens, 988 Michael Haberler, Michael Hammer, Ted Hardie, Gunnar Hellstrom, 989 Cullen Jennings, Marc Linsner, Rohan Mahy, Patti McCalmont, Don 990 Mitchell, John Morris, Andrew Newton, Steve Norreys, Jon Peterson, 991 James Polk, Benny Rodrig, John Rosenberg, Jonathan Rosenberg, John 992 Schnizlein, Shida Schubert, James Seng, Byron Smith, Barbara Stark, 993 Tom Taylor, Hannes Tschofenig, and Nate Wilcox for their helpful 994 input. 996 13. References 998 13.1 Normative References 1000 [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement 1001 Levels", BCP 14, RFC 2119, March 1997. 1003 13.2 Informative References 1005 [2] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., 1006 Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP: 1007 Session Initiation Protocol", RFC 3261, June 2002. 1009 [3] Charlton, N., Gasson, M., Gybels, G., Spanner, M., and A. van 1010 Wijk, "User Requirements for the Session Initiation Protocol 1011 (SIP) in Support of Deaf, Hard of Hearing and Speech-impaired 1012 Individuals", RFC 3351, August 2002. 1014 [4] Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and J. 1015 Polk, "Geopriv Requirements", RFC 3693, February 2004. 1017 [5] Polk, J., Schnizlein, J., and M. Linsner, "Dynamic Host 1018 Configuration Protocol Option for Coordinate-based Location 1019 Configuration Information", RFC 3825, July 2004. 1021 [6] Peterson, J., "Common Profile for Instant Messaging (CPIM)", 1022 RFC 3860, August 2004. 1024 [7] Schulzrinne, H., "The tel URI for Telephone Numbers", RFC 3966, 1025 December 2004. 1027 [8] Hellstrom, G. and P. Jones, "RTP Payload for Text 1028 Conversation", RFC 4103, June 2005. 1030 [9] Peterson, J., "A Presence-based GEOPRIV Location Object 1031 Format", RFC 4119, December 2005. 1033 [10] Schulzrinne, H. and J. Polk, "Communications Resource Priority 1034 for the Session Initiation Protocol (SIP)", RFC 4412, 1035 February 2006. 1037 [11] Taylor, T., "Security Threats and Requirements for Emergency 1038 Call Marking and Mapping", draft-ietf-ecrit-security-threats-03 1039 (work in progress), July 2006. 1041 [12] Schulzrinne, H., "A Uniform Resource Name (URN) for Services", 1042 draft-ietf-ecrit-service-urn-03 (work in progress), May 2006. 1044 [13] Hardie, T., "LoST: A Location-to-Service Translation Protocol", 1045 draft-hardie-ecrit-lost-00 (work in progress), March 2006. 1047 [14] Schulzrinne, H., "Dynamic Host Configuration Protocol (DHCPv4 1048 and DHCPv6) Option for Civic Addresses Configuration 1049 Information", draft-ietf-geopriv-dhcp-civil-09 (work in 1050 progress), January 2006. 1052 [15] Wijk, A. and G. Gybels, "Framework for real-time text over IP 1053 using the Session Initiation Protocol (SIP)", 1054 draft-ietf-sipping-toip-05 (work in progress), June 2006. 1056 [16] Institute of Electrical and Electronics Engineers, "Station and 1057 Media Access Control Connectivity Discovery", IEEE Standard 1058 802.1 AB, April 2005. 1060 Authors' Addresses 1062 Henning Schulzrinne 1063 Columbia University 1064 Department of Computer Science 1065 450 Computer Science Building 1066 New York, NY 10027 1067 US 1069 Phone: +1 212 939 7004 1070 Email: hgs+ecrit@cs.columbia.edu 1071 URI: http://www.cs.columbia.edu 1073 Roger Marshall (editor) 1074 TeleCommunication Systems 1075 2401 Elliott Avenue 1076 2nd Floor 1077 Seattle, WA 98121 1078 US 1080 Phone: +1 206 792 2424 1081 Email: rmarshall@telecomsys.com 1082 URI: http://www.telecomsys.com 1084 Intellectual Property Statement 1086 The IETF takes no position regarding the validity or scope of any 1087 Intellectual Property Rights or other rights that might be claimed to 1088 pertain to the implementation or use of the technology described in 1089 this document or the extent to which any license under such rights 1090 might or might not be available; nor does it represent that it has 1091 made any independent effort to identify any such rights. 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