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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) No issues found here. Summary: 0 errors (**), 0 flaws (~~), 1 warning (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 ECRIT B. Rosen 3 Internet-Draft 4 Intended status: Standards Track H. Schulzrinne 5 Expires: August 2, 2020 Columbia U. 6 H. Tschofenig 7 ARM Limited 8 R. Gellens 9 Core Technology Consulting 10 January 30, 2020 12 Non-Interactive Emergency Calls 13 draft-ietf-ecrit-data-only-ea-20 15 Abstract 17 RFC 6443 'Framework for Emergency Calling Using Internet Multimedia' 18 describes how devices use the Internet to place emergency calls and 19 how Public Safety Answering Points (PSAPs) handle Internet multimedia 20 emergency calls natively. The exchange of multimedia traffic for 21 emergency services involves a Session Initiation Protocol (SIP) 22 session establishment starting with a SIP INVITE that negotiates 23 various parameters for that session. These calls involve a person, 24 who uses the interactive media to communicate with the PSAP. 26 In some cases, however, the transmission of application data is all 27 that is needed, and no interactive media channel is established. 28 Examples of such environments include alerts issued by a temperature 29 sensor, burglar alarm, or chemical spill sensor. Often these alerts 30 are conveyed as one-shot data transmissions. These type of 31 interactions are called 'non-interactive emergency calls'. This 32 document describes use of a SIP MESSAGE transaction containing a 33 container for the data based on the Common Alerting Protocol (CAP). 34 MESSAGE does not establish a session, which differentiates this type 35 of emergency request from a SIP INVITE, which would. Any device that 36 needs to initiate a request for emergency services where no 37 interactive media channel will be established would use the 38 mechanisms in this document. 40 Status of This Memo 42 This Internet-Draft is submitted in full conformance with the 43 provisions of BCP 78 and BCP 79. 45 Internet-Drafts are working documents of the Internet Engineering 46 Task Force (IETF). Note that other groups may also distribute 47 working documents as Internet-Drafts. The list of current Internet- 48 Drafts is at https://datatracker.ietf.org/drafts/current/. 50 Internet-Drafts are draft documents valid for a maximum of six months 51 and may be updated, replaced, or obsoleted by other documents at any 52 time. It is inappropriate to use Internet-Drafts as reference 53 material or to cite them other than as "work in progress." 55 This Internet-Draft will expire on August 2, 2020. 57 Copyright Notice 59 Copyright (c) 2020 IETF Trust and the persons identified as the 60 document authors. All rights reserved. 62 This document is subject to BCP 78 and the IETF Trust's Legal 63 Provisions Relating to IETF Documents 64 (https://trustee.ietf.org/license-info) in effect on the date of 65 publication of this document. Please review these documents 66 carefully, as they describe your rights and restrictions with respect 67 to this document. Code Components extracted from this document must 68 include Simplified BSD License text as described in Section 4.e of 69 the Trust Legal Provisions and are provided without warranty as 70 described in the Simplified BSD License. 72 Table of Contents 74 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 75 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 76 3. Architectural Overview . . . . . . . . . . . . . . . . . . . 4 77 4. Protocol Specification . . . . . . . . . . . . . . . . . . . 6 78 4.1. CAP Transport . . . . . . . . . . . . . . . . . . . . . . 6 79 4.2. Profiling of the CAP Document Content . . . . . . . . . . 7 80 4.3. Sending a non-interactive Emergency Call . . . . . . . . 8 81 5. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 9 82 5.1. 425 (Bad Alert Message) Response Code . . . . . . . . . . 9 83 5.2. The AlertMsg-Error Header Field . . . . . . . . . . . . . 9 84 6. Call Backs . . . . . . . . . . . . . . . . . . . . . . . . . 11 85 7. Handling Large Amounts of Data . . . . . . . . . . . . . . . 11 86 8. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 87 9. Security Considerations . . . . . . . . . . . . . . . . . . . 15 88 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 89 10.1. Registration of the 90 'application/EmergencyCallData.cap+xml' MIME type . . . 17 91 10.2. IANA Registration of 'cap' Additional Data Block . . . . 18 92 10.3. IANA Registration for 425 Response Code . . . . . . . . 18 93 10.4. IANA Registration of New AlertMsg-Error Header Field . . 19 94 10.5. IANA Registration for the SIP AlertMsg-Error Codes . . . 19 95 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 20 96 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 20 97 12.1. Normative References . . . . . . . . . . . . . . . . . . 20 98 12.2. Informative References . . . . . . . . . . . . . . . . . 21 99 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22 101 1. Introduction 103 [RFC6443] describes how devices use the Internet to place emergency 104 calls and how Public Safety Answering Points (PSAPs) handle Internet 105 multimedia emergency calls natively. The exchange of multimedia 106 traffic for emergency services involves a SIP session establishment 107 starting with a SIP INVITE that negotiates various parameters for 108 that session. 110 In some cases, however, there is only application data to be conveyed 111 from the end devices to a PSAP or an intermediary. Examples of such 112 environments includes sensors issuing alerts, or certain types of 113 medical monitors. These messages may be one-shot alerts to emergency 114 authorities and do not require establishment of a session. These 115 type of interactions are called 'non-interactive emergency calls'. 116 In this document, we use the term "call" so that similarities between 117 non-interactive alerts and sessions with interactive media are more 118 obvious. 120 Non-Interactive emergency calls are similar to regular emergency 121 calls in the sense that they require the emergency indications, 122 emergency call routing functionality and may even have the same 123 location requirements. However, the communication interaction will 124 not lead to the exchange of interactive media, that is, Real-Time 125 Protocol packets, such as voice, video data or real-time text. 127 The Common Alerting Protocol (CAP) [cap] is a format for exchanging 128 emergency alerts and public warnings. CAP is mainly used for 129 conveying alerts and warnings between authorities and from 130 authorities to citizens/individuals. This document is concerned with 131 citizen to authority "alerts", where the alert is a call without any 132 interactive media. 134 This document describes a method of including a CAP message in a SIP 135 transaction by defining it as a block of "additional data" as defined 136 in [RFC7852]. The CAP message is included either by value (the CAP 137 message is in the body of the message, using a CID) or by reference 138 (a URI is included in the message, which when dereferenced returns 139 the CAP message). The additional data mechanism is also used to send 140 alert specific data beyond that available in the CAP message. This 141 document also describes how a SIP MESSAGE [RFC3428] transaction can 142 be used to send a non-interactive call. 144 2. Terminology 146 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 147 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 148 "OPTIONAL" in this document are to be interpreted as described in BCP 149 14 [RFC2119] [RFC8174] when, and only when, they appear in all 150 capitals, as shown here. 152 SIP is the Session Initiation Protocol [RFC3261] 154 PIDF-LO is Presence Information Data Format - Location Object, a data 155 structure for carrying location [RFC4119] 157 LoST is the Location To Service Translation protocol [RFC5222] 159 CID is Content InDirection [RFC2392] 161 CAP is the Common Alerting Protocol [cap] 163 PSAP is a Public Safety Answering Point, the call center for 164 emergency calls. 166 ESRP is an Emergency Services Routing Proxy, a type of SIP Proxy 167 Server used in some emergency services networks 169 3. Architectural Overview 171 This section illustrates two envisioned usage modes: targeted and 172 location-based emergency alert routing. 174 1. Emergency alerts containing only data are targeted to an 175 intermediary recipient responsible for evaluating the next steps. 176 These steps could include: 178 1. Sending a non-interactive call containing only data towards a 179 Public Safety Answering Point (PSAP); 181 2. Establishing a third-party initiated emergency call towards a 182 PSAP that could include audio, video, and data. 184 2. Emergency alerts may be targeted to a Service URN used for IP- 185 based emergency calls where the recipient is not known to the 186 originator. In this scenario, the alert may contain only data 187 (e.g., a CAP, Geolocation header field and one or more Call-Info 188 header fields containing Additional Data [RFC7852] in a SIP 189 MESSAGE). 191 Figure 1 shows a deployment variant where a sensor is pre-configured 192 (using techniques outside the scope of this document) to issue an 193 alert to an aggregator that processes these messages and performs 194 whatever steps are necessary to appropriately react to the alert. 195 For example, a security firm may use different sensor inputs to 196 dispatch their security staff to a building they protect or to 197 initiate a third-party emergency call. 199 +------------+ +------------+ 200 | Sensor | | Aggregator | 201 | | | | 202 +---+--------+ +------+-----+ 203 | | 204 Sensors | 205 trigger | 206 emergency | 207 alert | 208 | SIP MESSAGE with CAP | 209 |----------------------------->| 210 | | 211 | Aggregator 212 | processes 213 | emergency 214 | alert 215 | SIP 200 (OK) | 216 |<-----------------------------| 217 | | 218 | | 220 Figure 1: Targeted Emergency Alert Routing 222 In Figure 2 a scenario is shown whereby the alert is routed using 223 location information and a Service URN. An emergency services 224 routing proxy (ESRP) may use LoST (a protocol defined by [RFC5222] 225 which translates a location to a URI used to route an emergency call) 226 to determine the next hop proxy to route the alert message to. A 227 possible receiver is a PSAP and the recipient of the alert may be a 228 call taker. In the generic case, there is very likely no prior 229 relationship between the originator and the receiver, e.g., a PSAP. 230 A PSAP, for example, is likely to receive and accept alerts from 231 entities it has no previous relationship with. This scenario 232 corresponds to the classic emergency services use case and the 233 description in [RFC6881] is applicable. In this use case, the only 234 difference between an emergency call and an emergency non-interactive 235 call is that the former uses INVITE, creates a session, and 236 negotiates one or more media streams, while the latter uses MESSAGE, 237 does not create a session, and does not have interactive media. 239 +----------+ +----------+ +-----------+ 240 |Sensor or | | ESRP | | PSAP | 241 |Aggregator| | | | | 242 +----+-----+ +---+------+ +----+------+ 243 | | | 244 Sensors | | 245 trigger | | 246 emergency | | 247 alert | | 248 | | | 249 | | | 250 | SIP MESSAGE w/CAP | | 251 | (including Service URN, | 252 | such as urn:service:sos) | 253 |------------------>| | 254 | | | 255 | ESRP performs | 256 | emergency alert | 257 | routing | 258 | | MESSAGE with CAP | 259 | | (including identity info) | 260 | |----------------------------->| 261 | | | 262 | | PSAP 263 | | processes 264 | | emergency 265 | | alert 266 | | SIP 200 (OK) | 267 | |<-----------------------------| 268 | | | 269 | SIP 200 (OK) | | 270 |<------------------| | 271 | | | 272 | | | 274 Figure 2: Location-Based Emergency Alert Routing 276 4. Protocol Specification 278 4.1. CAP Transport 280 A CAP message may be sent in the initial message of any SIP 281 transaction. However, this document only addresses sending a CAP 282 message in a SIP MESSAGE transaction for a one-shot, non-interactive 283 emergency call. Behavior with other transactions is not defined. 285 The CAP message is included in a SIP message as an additional-data 286 block [RFC7852]. Accordingly, it is introduced to the SIP message 287 with a Call-Info header field with a purpose of 288 "EmergencyCallData.cap". The header field may contain a URI that is 289 used by the recipient (or in some cases, an intermediary) to obtain 290 the CAP message. Alternatively, the Call-Info header field may 291 contain a Content Indirect url [RFC2392] and the CAP message included 292 in the body of the message. In the latter case, the CAP message is 293 located in a MIME block of the type 'application/ 294 emergencyCallData.cap+xml'. 296 If the SIP server does not support the functionality required to 297 fulfill the request then a 501 Not Implemented will be returned as 298 specified in [RFC3261]. This is the appropriate response when a User 299 Agent Server (UAS) does not recognize the request method and is not 300 capable of supporting it for any user. 302 The 415 Unsupported Media Type error will be returned as specified in 303 [RFC3261] if the SIP server is refusing to service the request 304 because the message body of the request is in a format not supported 305 by the server for the requested method. The server MUST return a 306 list of acceptable formats using the Accept, Accept-Encoding, or 307 Accept-Language header fields, depending on the specific problem with 308 the content. 310 4.2. Profiling of the CAP Document Content 312 The usage of CAP MUST conform to the specification provided with 313 [cap]. For usage with SIP the following additional requirements are 314 imposed: 316 sender: The following restrictions and conditions apply to setting 317 the value of the element: 319 * Originator is a SIP entity, Author indication irrelevant: When 320 the alert was created by a SIP-based originator and it is not 321 useful to be explicit about the author of the alert, then the 322 element MUST be populated with the SIP URI of the user 323 agent. 325 * Originator is a non-SIP entity, Author indication irrelevant: 326 When the alert was created by a non-SIP based entity and the 327 identity of this original sender is to be preserved, then this 328 identity MUST be placed into the element. In this 329 situation it is not useful to be explicit about the author of 330 the alert. The specific type of identity being used will 331 depend on the technology used by the original originator. 333 * Author indication relevant: When the author is different from 334 the actual originator of the message and this distinction 335 should be preserved, then the element MUST NOT contain 336 the SIP URI of the user agent. 338 incidents: The element MUST be present. This incident 339 identifier MUST be chosen in such a way that it is unique for a 340 given combination. Note that the 341 element is optional and may not be present. 343 scope: The value of the element MAY be set to "Private" if 344 the alert is not meant for public consumption. The 345 element is, however, not used by this specification since the 346 message routing is performed by SIP and the respective address 347 information is already available in other SIP header fields. 348 Populating information twice into different parts of the message 349 may lead to inconsistency. 351 parameter: The element MAY contain additional 352 information specific to the sender, conforming to the CAP message 353 syntax. 355 area: It is RECOMMENDED to omit this element when constructing a 356 message. If the CAP message already contains an element, 357 then the specified location information SHOULD be copied into a 358 PIDF-LO structure (the data format for location used by emergency 359 calls on the Internet) referenced by the SIP 'Geolocation' header 360 field. If there is a need to copy the PIDF-LO structure 361 referenced by 'geolocation' to , implementers must be aware 362 that is limited to a circle or polygon, and conversion of 363 other shapes will be required. Points SHOULD be converted to a 364 circle with a radius equal to the uncertainty of the point. Arc- 365 bands and ellipses SHOULD be converted to an equivalent polygon. 366 3D locations SHOULD be converted to their equivalent 2D forms. 368 4.3. Sending a non-interactive Emergency Call 370 A non-interactive emergency call is sent using a SIP MESSAGE 371 transaction with a CAP URI or body part as described above in a 372 manner similar to how an emergency call with interactive media is 373 sent, as described in [RFC6881]. The MESSAGE transaction does not 374 create a session nor establish interactive media streams, but 375 otherwise, the header content of the transaction, routing, and 376 processing of non-interactive calls are the same as those of other 377 emergency calls. 379 5. Error Handling 381 This section defines a new error response code and a header field for 382 additional information. 384 5.1. 425 (Bad Alert Message) Response Code 386 This SIP extension creates a new location-specific response code, 387 defined as follows: 389 425 (Bad Alert Message) 391 The 425 response code is a rejection of the request due to its 392 included alert content, indicating that it was malformed or not 393 satisfactory for the recipient's purpose. 395 A SIP intermediary can also reject an alert it receives from a User 396 Agent (UA) when it detects that the provided alert is malformed. 398 Section 5.2 describes an AlertMsg-Error header field with more 399 details about what was wrong with the alert message in the request. 400 This header field MUST be included in the 425 response. 402 It is only appropriate to generate a 425 response when the responding 403 entity has no other information in the request that is usable by the 404 responder. 406 A 425 response code MUST NOT be sent in response to a request that 407 lacks an alert message, as the user agent in that case may not 408 support this extension. 410 A 425 response is a final response within a transaction, and MUST NOT 411 terminate an existing dialog. 413 5.2. The AlertMsg-Error Header Field 415 The AlertMsg-Error header field provides additional information about 416 what was wrong with the original request. In some cases the provided 417 information will be used for debugging purposes. 419 The AlertMsg-Error header field has the following ABNF [RFC5234]: 421 message-header /= AlertMsg-Error 422 ; (message-header from 3261) 423 AlertMsg-Error = "AlertMsg-Error" HCOLON 424 ErrorValue 425 ErrorValue = error-code 426 *(SEMI error-params) 427 error-code = 1*3DIGIT 428 error-params = error-code-text 429 / generic-param ; from RFC3261 430 error-code-text = "code" EQUAL quoted-string ; from RFC3261 432 HCOLON, SEMI, and EQUAL are defined in [RFC3261]. DIGIT is defined 433 in [RFC5234]. 435 The AlertMsg-Error header field MUST contain only one ErrorValue to 436 indicate what was wrong with the alert payload the recipient 437 determined was bad. 439 The ErrorValue contains a 3-digit error code indicating what was 440 wrong with the alert in the request. This error code has a 441 corresponding quoted error text string that is human readable. The 442 text string is OPTIONAL, but RECOMMENDED for human readability, 443 similar to the string phrase used for SIP response codes. The 444 strings in this document are recommendations, and are not 445 standardized -- meaning an operator can change the strings -- but 446 MUST NOT change the meaning of the error code. Similar to how RFC 447 3261 specifies, there MUST NOT be more than one string per error 448 code. 450 The AlertMsg-Error header field MAY be included in any response if an 451 alert message was in the request part of the same transaction. For 452 example, a UA includes an alert in a MESSAGE to a PSAP. The PSAP can 453 accept this MESSAGE, thus creating a dialog, even though its UA 454 determined that the alert message contained in the MESSAGE was bad. 455 The PSAP merely includes an AlertMsg-Error header field value in the 456 200 OK to the MESSAGE, thus informing the UA that the MESSAGE was 457 accepted but the alert provided was bad. 459 If, on the other hand, the PSAP cannot accept the transaction without 460 a suitable alert message, a 425 response is sent. 462 A SIP intermediary that requires the UA's alert message in order to 463 properly process the transaction may also sends a 425 with an 464 AlertMsg-Error code. 466 This document defines an initial list of AlertMsg-Error values for 467 any SIP response, including provisional responses (other than 100 468 Trying) and the new 425 response. There MUST be no more than one 469 AlertMsg-Error code in a SIP response. 471 AlertMsg-Error: 100 ; code="Cannot Process the Alert Payload" 473 AlertMsg-Error: 101 ; code="Alert Payload was not present or could 474 not be found" 476 AlertMsg-Error: 102 ; code="Not enough information to determine the 477 purpose of the alert" 479 AlertMsg-Error: 103 ; code="Alert Payload was corrupted" 481 Additionally, if an entity cannot or chooses not to process the alert 482 message from a SIP request, a 500 (Server Internal Error) SHOULD be 483 used with or without a configurable Retry-After header field. 485 6. Call Backs 487 This document does not describe any method for the recipient to call 488 back the sender of a non-interactive call. Usually, these alerts are 489 sent by automata, which do not have a mechanism to receive calls of 490 any kind. The identifier in the 'From' header field may be useful to 491 obtain more information, but any such mechanism is not defined in 492 this document. The CAP message may contain related contact 493 information for the sender. 495 7. Handling Large Amounts of Data 497 It is not atypical for sensors to have large quantities of data that 498 they may wish to send. Including large amounts of data (tens of 499 kilobytes) in a MESSAGE is not advisable, because SIP entities are 500 usually not equipped to handle very large messages. In such cases, 501 the sender SHOULD make use of the by-reference mechanisms defined in 502 [RFC7852], which involves making the data available via HTTPS (either 503 at the originator or at another entity), placing a URI to the data in 504 the 'Call-Info' header field, and the recipient uses HTTPS to 505 retrieve the data. The CAP message itself can be sent by-reference 506 using this mechanism, as well as any or all of the Additional Data 507 blocks that may contain sensor-specific data. 509 8. Example 511 The following example shows a CAP document indicating a BURGLARY 512 alert issued by a sensor called 'sensor1@example.com'. The location 513 of the sensor can be obtained from the attached location information 514 provided via the 'geolocation' header field contained in the SIP 515 MESSAGE structure. Additionally, the sensor provided some data along 516 with the alert message, using proprietary information elements 517 intended only to be processed by the receiver, a SIP entity acting as 518 an aggregator. 520 MESSAGE sip:aggregator@example.com SIP/2.0 521 Via: SIP/2.0/TCP sensor1.example.com;branch=z9hG4bK776sgdkse 522 Max-Forwards: 70 523 From: sip:sensor1@example.com;tag=49583 524 To: sip:aggregator@example.com 525 Call-ID: asd88asd77a@2001:DB8:0:0FF 526 Geolocation: 527 ;routing-allowed=yes 528 Supported: geolocation 529 Accept: application/pidf+xml,application/EmergencyCallData.cap+xml 530 CSeq: 1 MESSAGE 531 Call-Info: cid:abcdef2@example.com;purpose=EmergencyCallData.cap 532 Content-Type: multipart/mixed; boundary=boundary1 533 Content-Length: ... 535 --boundary1 537 Content-Type: application/EmergencyCallData.cap+xml 538 Content-ID: 539 Content-Disposition: by-reference;handling=optional 540 542 543 S-1 544 sip:sensor1@example.com 545 2008-11-19T14:57:00-07:00 546 Actual 547 Alert 548 Private 549 abc1234 550 551 Security 552 BURGLARY 553 Expected 554 Likely 555 Moderate 556 SENSOR 1 557 558 SENSOR-DATA-NAMESPACE1 559 123 560 561 562 SENSOR-DATA-NAMESPACE2 563 TRUE 564 565 566 568 --boundary1 570 Content-Type: application/pidf+xml 571 Content-ID: 572 Content-Disposition: by-reference;handling=optional 573 574 583 584 585 586 587 588 32.86726 -97.16054 589 590 591 592 593 false 594 595 2010-11-14T20:00:00Z 596 597 598 802.11 599 600 2010-11-04T20:57:29Z 601 602 603 --boundary1-- 605 Figure 3: Example Message conveying an Alert to an aggregator 607 The following shows the same CAP document sent as a non-interactive 608 emergency call towards a PSAP. 610 MESSAGE urn:service:sos SIP/2.0 611 Via: SIP/2.0/TCP sip:aggreg.1.example.com;branch=z9hG4bK776abssa 612 Max-Forwards: 70 613 From: sip:aggregator@example.com;tag=32336 614 To: 112 615 Call-ID: asdf33443a@example.com 616 Route: sip:psap1.example.gov 617 Geolocation: 618 ;routing-allowed=yes 619 Supported: geolocation 620 Accept: application/pidf+xml,application/EmergencyCallData.cap+xml 621 Call-info: cid:abcdef2@example.com;purpose=EmergencyCallData.cap 622 CSeq: 1 MESSAGE 623 Content-Type: multipart/mixed; boundary=boundary1 624 Content-Length: ... 626 --boundary1 628 Content-Type: application/EmergencyCallData.cap+xml 629 Content-ID: 630 632 633 S-1 634 sip:sensor1@example.com 635 2008-11-19T14:57:00-07:00 636 Actual 637 Alert 638 Private 639 abc1234 640 641 Security 642 BURGLARY 643 Expected 644 Likely 645 Moderate 646 SENSOR 1 647 648 SENSOR-DATA-NAMESPACE1 649 123 650 651 652 SENSOR-DATA-NAMESPACE2 653 TRUE 654 655 656 657 --boundary1 659 Content-Type: application/pidf+xml 660 Content-ID: 661 662 671 672 673 674 675 676 32.86726 -97.16054 677 678 679 680 681 false 682 683 2010-11-14T20:00:00Z 684 685 686 802.11 687 688 2010-11-04T20:57:29Z 689 690 691 --boundary1-- 693 Figure 4: Example Message conveying an Alert to a PSAP 695 9. Security Considerations 697 This section discusses security considerations when SIP user agents 698 issue emergency alerts utilizing MESSAGE and CAP. Location specific 699 threats are not unique to this document and are discussed in 700 [RFC7378] and [RFC6442]. 702 The ECRIT emergency services architecture [RFC6443] considers classic 703 individual-to-authority emergency calling where the identity of the 704 emergency caller does not play a role at the time of the call 705 establishment itself, i.e., a response to the emergency call does not 706 depend on the identity of the caller. In the case of emergency 707 alerts generated by devices such as sensors, the processing may be 708 different in order to reduce the number of falsely generated 709 emergency alerts. Alerts could get triggered based on certain sensor 710 input that might have been caused by factors other than the actual 711 occurrence of an alert-relevant event. For example, a sensor may 712 simply be malfunctioning. For this reason, not all alert messages 713 are directly sent to a PSAP, but rather may be pre-processed by a 714 separate entity, potentially under supervision by a human, to filter 715 alerts and potentially correlate received alerts with others to 716 obtain a larger picture of the ongoing situation. 718 In any case, for alerts initiated by sensors, the identity could play 719 an important role in deciding whether to accept or ignore an incoming 720 alert message. With the scenario shown in Figure 1 it is very likely 721 that only authorized sensor input will be processed. For this 722 reason, it needs to be possible to refuse to accept alert messages 723 from an unknown origin. Two types of information elements can be 724 used for this purpose: 726 1. SIP itself provides security mechanisms that allow the 727 verification of the originator's identity. These mechanisms can 728 be re-used, such as P-Asserted-Identity [RFC3325] or SIP Identity 729 [RFC8224]. The latter provides a cryptographic assurance while 730 the former relies on a chain of trust model. 732 2. CAP provides additional security mechanisms and the ability to 733 carry further information about the sender's identity. 734 Section 3.3.4.1 of [cap] specifies the signing algorithms of CAP 735 documents. 737 In addition to the desire to perform identity-based access control, 738 the classic communication security threats need to be considered, 739 including integrity protection to prevent forgery or replay of alert 740 messages in transit. To deal with replay of alerts, a CAP document 741 contains the mandatory , , elements and an 742 optional element. Together, these elements make the CAP 743 document unique for a specific sender and provide time restrictions. 744 An entity that has already received a CAP message within the 745 indicated timeframe is able to detect a replayed message and, if the 746 content of that message is unchanged, then no additional security 747 vulnerability is created. Additionally, it is RECOMMENDED to make 748 use of SIP security mechanisms, such as SIP Identity [RFC8224], to 749 tie the CAP message to the SIP message. To provide protection of the 750 entire SIP message exchange between neighboring SIP entities, the 751 usage of TLS is REQUIRED. 753 Note that none of the security mechanism in this document protect 754 against a compromised sensor sending crafted alerts. Privacy 755 provided for any emergency calls, including non-interactive messages, 756 is subject to local regulations. 758 10. IANA Considerations 760 10.1. Registration of the 'application/EmergencyCallData.cap+xml' MIME 761 type 763 To: ietf-types@iana.org 765 Subject: Registration of MIME media type application/ 766 EmergencyCallData.cap+xml 768 MIME media type name: application 770 MIME subtype name: cap+xml 772 Required parameters: (none) 774 Optional parameters: charset; Indicates the character encoding of 775 enclosed XML. Default is UTF-8 [RFC3629]. 777 Encoding considerations: Uses XML, which can employ 8-bit 778 characters, depending on the character encoding used. See 779 [RFC7303], Section 3.2. 781 Security considerations: This content type is designed to carry 782 payloads of the Common Alerting Protocol (CAP). RFC XXX [Replace 783 by the RFC number of this specification] discusses security 784 considerations for this. 786 Interoperability considerations: This content type provides a way to 787 convey CAP payloads. 789 Published specification: RFC XXX [Replace by the RFC number of this 790 specification]. 792 Applications which use this media type: Applications that convey 793 alerts and warnings according to the CAP standard. 795 Additional information: OASIS has published the Common Alerting 796 Protocol at http://www.oasis-open.org/committees/ 797 documents.php&wg_abbrev=emergency 799 Person and email address to contact for further information: Hannes 800 Tschofenig, hannes.tschofenig@gmx.net 802 Intended usage: Limited use 804 Author/Change controller: IETF ECRIT working group 806 Other information: This media type is a specialization of 807 application/xml [RFC7303], and many of the considerations 808 described there also apply to application/cap+xml. 810 10.2. IANA Registration of 'cap' Additional Data Block 812 This document registers a new block type in the sub-registry called 813 'Emergency Call Data Types' of the Emergency Call Additional Data 814 Registry defined in [RFC7852]. The token is "cap", the Data About is 815 "The Call" and the reference is this document. 817 10.3. IANA Registration for 425 Response Code 819 In the SIP Response Codes registry, the following is added 821 Reference: RFC-XXXX (i.e., this document) 823 Response code: 425 (recommended number to assign) 825 Default reason phrase: Bad Alert Message 826 Registry: 827 Response Code Reference 828 ------------------------------------------ --------- 829 Request Failure 4xx 830 425 Bad Alert Message [this doc] 832 This SIP Response code is defined in Section 5. 834 10.4. IANA Registration of New AlertMsg-Error Header Field 836 The SIP AlertMsg-error header field is created by this document, with 837 its definition and rules in Section 5, to be added to the IANA 838 Session Initiation Protocol (SIP) Parameters registry with two 839 actions: 841 1. Update the Header Fields registry with 843 Registry: 844 Header Name compact Reference 845 ----------------- ------- --------- 846 AlertMsg-Error [this doc] 848 2. In the portion titled "Header Field Parameters and Parameter 849 Values", add 851 Predefined 852 Header Field Parameter Name Values Reference 853 ----------------- ------------------- ---------- --------- 854 AlertMsg-Error code yes [this doc] 856 10.5. IANA Registration for the SIP AlertMsg-Error Codes 858 This document creates a new registry for SIP, called "AlertMsg-Error 859 Codes". AlertMsg-Error codes provide reasons for an error discovered 860 by a recipient, categorized by the action to be taken by the error 861 recipient. The initial values for this registry are shown below. 863 Registry Name: AlertMsg-Error Codes 865 Reference: [this doc] 867 Registration Procedures: Specification Required 868 Code Default Reason Phrase Reference 869 ---- --------------------------------------------------- --------- 870 100 "Cannot Process the Alert Payload" [this doc] 872 101 "Alert Payload was not present or could not be found" [this doc] 874 102 "Not enough information to determine 875 the purpose of the alert" [this doc] 877 103 "Alert Payload was corrupted" [this doc] 879 Details of these error codes are in Section 5. 881 11. Acknowledgments 883 The authors would like to thank the participants of the Early Warning 884 adhoc meeting at IETF#69 for their feedback. Additionally, we would 885 like to thank the members of the NENA Long Term Direction Working 886 Group for their feedback. 888 Additionally, we would like to thank Martin Thomson, James 889 Winterbottom, Shida Schubert, Bernard Aboba, Marc Linsner, Christer 890 Holmberg and Ivo Sedlacek for their review comments. 892 12. References 894 12.1. Normative References 896 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 897 Requirement Levels", March 1997. 899 [cap] Jones, E. and A. Botterell, "Common Alerting Protocol v. 900 1.2", October 2005, . 903 [RFC2392] Levinson, E., "Content-ID and Message-ID Uniform Resource 904 Locators", RFC 2392, DOI 10.17487/RFC2392, August 1998, 905 . 907 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 908 A., Peterson, J., Sparks, R., Handley, M., and E. 909 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 910 DOI 10.17487/RFC3261, June 2002, 911 . 913 [RFC3428] Campbell, B., Ed., Rosenberg, J., Schulzrinne, H., 914 Huitema, C., and D. Gurle, "Session Initiation Protocol 915 (SIP) Extension for Instant Messaging", RFC 3428, 916 DOI 10.17487/RFC3428, December 2002, 917 . 919 [RFC4119] Peterson, J., "A Presence-based GEOPRIV Location Object 920 Format", RFC 4119, DOI 10.17487/RFC4119, December 2005, 921 . 923 [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax 924 Specifications: ABNF", STD 68, RFC 5234, 925 DOI 10.17487/RFC5234, January 2008, 926 . 928 [RFC7303] Thompson, H. and C. Lilley, "XML Media Types", RFC 7303, 929 DOI 10.17487/RFC7303, July 2014, 930 . 932 [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 933 10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November 934 2003, . 936 [RFC6442] Polk, J., Rosen, B., and J. Peterson, "Location Conveyance 937 for the Session Initiation Protocol", RFC 6442, 938 DOI 10.17487/RFC6442, December 2011, 939 . 941 [RFC6881] Rosen, B. and J. Polk, "Best Current Practice for 942 Communications Services in Support of Emergency Calling", 943 BCP 181, RFC 6881, DOI 10.17487/RFC6881, March 2013, 944 . 946 [RFC7852] Gellens, R., Rosen, B., Tschofenig, H., Marshall, R., and 947 J. Winterbottom, "Additional Data Related to an Emergency 948 Call", RFC 7852, DOI 10.17487/RFC7852, July 2016, 949 . 951 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 952 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 953 May 2017, . 955 12.2. Informative References 957 [RFC7378] Tschofenig, H., Schulzrinne, H., and B. Aboba, Ed., 958 "Trustworthy Location", RFC 7378, DOI 10.17487/RFC7378, 959 December 2014, . 961 [RFC8224] Peterson, J., Jennings, C., Rescorla, E., and C. Wendt, 962 "Authenticated Identity Management in the Session 963 Initiation Protocol (SIP)", RFC 8224, 964 DOI 10.17487/RFC8224, February 2018, 965 . 967 [RFC3325] Jennings, C., Peterson, J., and M. Watson, "Private 968 Extensions to the Session Initiation Protocol (SIP) for 969 Asserted Identity within Trusted Networks", RFC 3325, 970 DOI 10.17487/RFC3325, November 2002, 971 . 973 [RFC5222] Hardie, T., Newton, A., Schulzrinne, H., and H. 974 Tschofenig, "LoST: A Location-to-Service Translation 975 Protocol", RFC 5222, DOI 10.17487/RFC5222, August 2008, 976 . 978 [RFC6443] Rosen, B., Schulzrinne, H., Polk, J., and A. Newton, 979 "Framework for Emergency Calling Using Internet 980 Multimedia", RFC 6443, DOI 10.17487/RFC6443, December 981 2011, . 983 Authors' Addresses 985 Brian Rosen 986 470 Conrad Dr 987 Mars, PA 16046 988 US 990 Phone: 991 Email: br@brianrosen.net 993 Henning Schulzrinne 994 Columbia University 995 Department of Computer Science 996 450 Computer Science Building 997 New York, NY 10027 998 US 1000 Phone: +1 212 939 7004 1001 Email: hgs+ecrit@cs.columbia.edu 1002 URI: http://www.cs.columbia.edu 1003 Hannes Tschofenig 1004 ARM Limited 1006 Austria 1008 Email: Hannes.Tschofenig@gmx.net 1009 URI: http://www.tschofenig.priv.at 1011 Randall Gellens 1012 Core Technology Consulting 1014 Email: rg+ietf@coretechnologyconsulting.com 1015 URI: http://www.coretechnologyconsulting.com