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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) ** Obsolete normative reference: RFC 3023 (Obsoleted by RFC 7303) -- Obsolete informational reference (is this intentional?): RFC 4474 (Obsoleted by RFC 8224) Summary: 1 error (**), 0 flaws (~~), 2 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 ECRIT B. Rosen 3 Internet-Draft NeuStar, Inc. 4 Intended status: Standards Track H. Schulzrinne 5 Expires: October 25, 2018 Columbia U. 6 H. Tschofenig 7 ARM Limited 8 R. Gellens 9 Core Technology Consulting 10 April 23, 2018 12 Data-Only Emergency Calls 13 draft-ietf-ecrit-data-only-ea-15 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. 25 In some cases, however, the transmission of application data is all 26 that is needed. Examples of such environments include alerts issued 27 by a temperature sensor, burglar alarm, or chemical spill sensor. 28 Often these alerts are conveyed as one-shot data transmissions. 29 These type of interactions are called 'data-only emergency calls'. 30 This document describes a container for the data based on the Common 31 Alerting Protocol (CAP) and its transmission using the SIP MESSAGE 32 transaction. 34 Status of This Memo 36 This Internet-Draft is submitted in full conformance with the 37 provisions of BCP 78 and BCP 79. 39 Internet-Drafts are working documents of the Internet Engineering 40 Task Force (IETF). Note that other groups may also distribute 41 working documents as Internet-Drafts. The list of current Internet- 42 Drafts is at http://datatracker.ietf.org/drafts/current/. 44 Internet-Drafts are draft documents valid for a maximum of six months 45 and may be updated, replaced, or obsoleted by other documents at any 46 time. It is inappropriate to use Internet-Drafts as reference 47 material or to cite them other than as "work in progress." 48 This Internet-Draft will expire on October 25, 2018. 50 Copyright Notice 52 Copyright (c) 2018 IETF Trust and the persons identified as the 53 document authors. All rights reserved. 55 This document is subject to BCP 78 and the IETF Trust's Legal 56 Provisions Relating to IETF Documents 57 (http://trustee.ietf.org/license-info) in effect on the date of 58 publication of this document. Please review these documents 59 carefully, as they describe your rights and restrictions with respect 60 to this document. Code Components extracted from this document must 61 include Simplified BSD License text as described in Section 4.e of 62 the Trust Legal Provisions and are provided without warranty as 63 described in the Simplified BSD License. 65 Table of Contents 67 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 68 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 69 3. Architectural Overview . . . . . . . . . . . . . . . . . . . 4 70 4. Protocol Specification . . . . . . . . . . . . . . . . . . . 6 71 4.1. CAP Transport . . . . . . . . . . . . . . . . . . . . . . 6 72 4.2. Profiling of the CAP Document Content . . . . . . . . . . 7 73 4.3. Sending a Data-Only Emergency Call . . . . . . . . . . . 8 74 5. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 8 75 5.1. 425 (Bad Alert Message) Response Code . . . . . . . . . . 9 76 5.2. The AlertMsg-Error Header Field . . . . . . . . . . . . . 9 77 6. Call Backs . . . . . . . . . . . . . . . . . . . . . . . . . 11 78 7. Handling Large Amounts of Data . . . . . . . . . . . . . . . 11 79 8. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 80 9. Security Considerations . . . . . . . . . . . . . . . . . . . 15 81 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 82 10.1. Registration of the 83 'application/EmergencyCallData.cap+xml' MIME type . . . 17 84 10.2. IANA Registration of 'cap' Additional Data Block . . . . 18 85 10.3. IANA Registration for 425 Response Code . . . . . . . . 18 86 10.4. IANA Registration of New AlertMsg-Error Header Field . . 19 87 10.5. IANA Registration for the SIP AlertMsg-Error Codes . . . 19 88 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 20 89 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 20 90 12.1. Normative References . . . . . . . . . . . . . . . . . . 20 91 12.2. Informative References . . . . . . . . . . . . . . . . . 21 92 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22 94 1. Introduction 96 RFC 6443 [RFC6443] describes how devices use the Internet to place 97 emergency calls and how Public Safety Answering Points (PSAPs) handle 98 Internet multimedia emergency calls natively. The exchange of 99 multimedia traffic for emergency services involves a SIP session 100 establishment starting with a SIP INVITE that negotiates various 101 parameters for that session. 103 In some cases, however, there is only application data to be conveyed 104 from the end devices to a PSAP or an intermediary. Examples of such 105 environments includes sensors issuing alerts, or certain types of 106 medical monitors. These messages may be one-shot alerts to emergency 107 authorities and do not require establishment of a session. These 108 type of interactions are called 'data-only emergency calls'. In this 109 document, we use the term "call" so that similarities between data- 110 only (non-interactive) alerts and sessions with interactive media are 111 more obvious. 113 Data-only emergency calls are similar to regular emergency calls in 114 the sense that they require the emergency indications, emergency call 115 routing functionality and may even have the same location 116 requirements. However, the communication interaction will not lead 117 to the exchange of interactive media, that is, Real-Time Protocol 118 packets, such as voice, video data or real-time text. 120 The Common Alerting Protocol (CAP) [cap] is a format for exchanging 121 emergency alerts and public warnings. CAP is mainly used for 122 conveying alerts and warnings between authorities and from 123 authorities to citizen/individuals. This document is concerned with 124 citizen to authority "alerts", where the alert is a call without any 125 interactive media. 127 This document describes a method of including a CAP message in a SIP 128 transaction by defining it as a block of "additional data" as defined 129 in [RFC7852]. The CAP message is included either by value (the CAP 130 message is in the body of the message, using a CID) or by reference 131 (a URI is included in the message, which when dereferenced returns 132 the CAP message). The additional data mechanism is also used to send 133 alert specific data beyond that available in the CAP message. This 134 document also describes how a SIP MESSAGE [RFC3428] transaction can 135 be used to send a data-only call. 137 2. Terminology 139 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 140 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 141 document are to be interpreted as described in RFC 2119 [RFC2119]. 143 3. Architectural Overview 145 This section illustrates two envisioned usage modes: targeted and 146 location-based emergency alert routing. 148 1. Emergency alerts containing only data are targeted to an 149 intermediary recipient responsible for evaluating the next steps. 150 These steps could include: 152 1. Sending a non-interactive call containing only data toward a 153 Public Safety Answering Point (PSAP); 155 2. Establishing a third-party initiated emergency call towards a 156 PSAP that could include audio, video, and data. 158 2. Emergency alerts may be targeted to a Service URN used for IP- 159 based emergency calls where the recipient is not known to the 160 originator. In this scenario, the alert may contain only data 161 (e.g., a CAP, Geolocation header field and one or more Call-Info 162 header fields containing Additional Data [RFC7852] in a SIP 163 MESSAGE). 165 Figure 1 shows a deployment variant where a sensor is pre-configured 166 (using techniques outside the scope of this document) to issue an 167 alert to an aggregator that processes these messages and performs 168 whatever steps are necessary to appropriately react to the alert. 169 For example, a security firm may use different sensor inputs to 170 dispatch their security staff to a building they protect or to 171 initiate a third-party emergency call. 173 +------------+ +------------+ 174 | Sensor | | Aggregator | 175 | | | | 176 +---+--------+ +------+-----+ 177 | | 178 Sensors | 179 trigger | 180 emergency | 181 alert | 182 | MESSAGE with CAP | 183 |----------------------------->| 184 | | 185 | Aggregator 186 | processes 187 | emergency 188 | alert 189 | 200 (OK) | 190 |<-----------------------------| 191 | | 192 | | 194 Figure 1: Targeted Emergency Alert Routing 196 In Figure 2 a scenario is shown whereby the alert is routed using 197 location information and a Service URN. An emergency services 198 routing proxy (ESRP) may use LoST to determine the next hop proxy to 199 route the alert message to. A possible receiver is a PSAP and the 200 recipient of the alert may be a call taker. In the generic case, 201 there is very likely no prior relationship between the originator and 202 the receiver, e.g., a PSAP. A PSAP, for example, is likely to 203 receive and accept alerts from entities it cannot authorize. This 204 scenario corresponds to the classic emergency services use case and 205 the description in [RFC6881] is applicable. In this use case, the 206 only difference between an emergency call and an emergency data-only 207 call is that the former uses INVITE, creates a session, and 208 negotiates one or more media streams, while the latter uses MESSAGE, 209 does not create a session, and does not have interactive media. 211 +----------+ +----------+ +-----------+ 212 |Sensor or | | ESRP | | PSAP | 213 |Aggregator| | | | | 214 +----+-----+ +---+------+ +----+------+ 215 | | | 216 Sensors | | 217 trigger | | 218 emergency | | 219 alert | | 220 | | | 221 | | | 222 | MESSAGE with CAP | | 223 | (including Service URN, | 224 | such as urn:service:sos) | 225 |-------------------| | 226 | | | 227 | ESRP performs | 228 | emergency alert | 229 | routing | 230 | | MESSAGE with CAP | 231 | | (including identity info) | 232 | |----------------------------->| 233 | | | 234 | | PSAP 235 | | processes 236 | | emergency 237 | | alert 238 | | 200 (OK) | 239 | |<-----------------------------| 240 | | | 241 | 200 (OK) | | 242 |<------------------| | 243 | | | 244 | | | 246 Figure 2: Location-Based Emergency Alert Routing 248 4. Protocol Specification 250 4.1. CAP Transport 252 A CAP message may be sent in the initial message of any SIP 253 transaction. However, this document only addresses sending a CAP 254 message in a SIP INVITE that initiates an emergency call, or in a SIP 255 MESSAGE transaction for a one-shot, data-only emergency call. 256 Behavior with other transactions is not defined. 258 The CAP message is included in a SIP message as an additional-data 259 block [RFC7852]. Accordingly, it is introduced to the SIP message 260 with a Call-Info header field with a purpose of 261 "EmergencyCallData.cap". The header field may contain a URI that is 262 used by the recipient (or in some cases, an intermediary) to obtain 263 the CAP message. Alternative, the Call-Info header field may contain 264 a Content Indirect url [RFC2392] and the CAP message included in the 265 body of the message. In the latter case, the CAP message is located 266 in a MIME block of the type 'application/emergencyCallData.cap+xml'. 268 If the SIP server does not support the functionality required to 269 fulfill the request then a 501 Not Implemented MUST be returned as 270 specified in RFC 3261 [RFC3261]. This is the appropriate response 271 when a User Agent Server (UAS) does not recognize the request method 272 and is not capable of supporting it for any user. 274 The 415 Unsupported Media Type error MUST be returned as specified in 275 RFC 3261 [RFC3261] if the SIP server is refusing to service the 276 request because the message body of the request is in a format not 277 supported by the server for the requested method. The server MUST 278 return a list of acceptable formats using the Accept, Accept- 279 Encoding, or Accept-Language header fields, depending on the specific 280 problem with the content. 282 4.2. Profiling of the CAP Document Content 284 The usage of CAP MUST conform to the specification provided with 285 [cap]. For usage with SIP the following additional requirements are 286 imposed: 288 sender: The following restrictions and conditions apply to setting 289 the value of the element: 291 Originator is a SIP entity, Author indication irrelevant: When 292 the alert was created by a SIP-based originator and it is not 293 useful to be explicit about the author of the alert, then the 294 element MUST be populated with the SIP URI of the user 295 agent. 297 Originator is a non-SIP entity, Author indication irrelevant: 298 When the alert was created by a non-SIP based entity and the 299 identity of this original sender is to be preserved, then this 300 identity MUST be placed into the element. In this 301 situation it is not useful to be explicit about the author of the 302 alert. The specific type of identity being used will depend on 303 the technology used by the original originator. 305 Author indication relevant: When the author is different from the 306 actual originator of the message and this distinction should be 307 preserved, then the element MUST NOT contain the SIP URI 308 of the user agent. 310 incidents: The element MUST be present. This incident 311 identifier MUST be chosen in such a way that it is unique for a 312 given combination. Note that the 313 element is optional and may not be present. 315 scope: The value of the element MAY be set to "Private" if 316 the alert is not meant for public consumption. The 317 element is, however, not used by this specification since the 318 message routing is performed by SIP and the respective address 319 information is already available in other SIP header fields. 320 Populating information twice into different parts of the message 321 may lead to inconsistency. 323 parameter: The element MAY contain additional 324 information specific to the sender. 326 area: It is RECOMMENDED to omit this element when constructing a 327 message. If the CAP message already contains an element, 328 then the specified location information SHOULD be copied into the 329 PIDF-LO structure referenced by the 'geolocation' header field. 331 4.3. Sending a Data-Only Emergency Call 333 A data-only emergency call is sent using a SIP MESSAGE transaction 334 with a CAP URI or body part as described above in a manner similar to 335 how an emergency call with interactive media is sent, as described in 336 [RFC6881]. The MESSAGE transaction does not create a session nor 337 establish interactive media streams, but otherwise, the header 338 content of the transaction, routing, and processing of data-only 339 calls are the same as those of other emergency calls. 341 5. Error Handling 343 This section defines a new error response code and a header field for 344 additional information. 346 5.1. 425 (Bad Alert Message) Response Code 348 This SIP extension creates a new location-specific response code, 349 defined as follows: 351 425 (Bad Alert Message) 353 The 425 response code is a rejection of the request due to its 354 included alert content, indicating that it was malformed or not 355 satisfactory for the recipient's purpose. 357 A SIP intermediary can also reject an alert it receives from a User 358 Agent (UA) when it understands that the provided alert is malformed. 360 Section 5.2 describes an AlertMsg-Error header field with more 361 details about what was wrong with the alert message in the request. 362 This header field MUST be included in the 425 response. 364 It is only appropriate to generate a 425 response when the responding 365 entity has no other information in the request that is usable by the 366 responder. 368 A 425 response code MUST NOT be sent in response to a request that 369 lacks an alert message, as the user agent in that case may not 370 support this extension. 372 A 425 response is a final response within a transaction, and MUST NOT 373 terminate an existing dialog. 375 5.2. The AlertMsg-Error Header Field 377 The AlertMsg-Error header field provides additional information about 378 what was wrong with the original request. In some cases the provided 379 information will be used for debugging purposes. 381 The AlertMsg-Error header field has the following ABNF [RFC5234]: 383 message-header /= AlertMsg-Error 384 ; (message-header from 3261) 385 AlertMsg-Error = "AlertMsg-Error" HCOLON 386 ErrorValue 387 ErrorValue = error-code 388 *(SEMI error-params) 389 error-code = 1*3DIGIT 390 error-params = error-code-text 391 / generic-param ; from RFC3261 392 error-code-text = "code" EQUAL quoted-string ; from RFC3261 394 HCOLON, SEMI, and EQUAL are defined in RFC3261 [RFC3261]. DIGIT is 395 defined in RFC5234 [RFC5234]. 397 The AlertMsg-Error header field MUST contain only one ErrorValue to 398 indicate what was wrong with the alert payload the recipient 399 determined was bad. 401 The ErrorValue contains a 3-digit error code indicating what was 402 wrong with the alert in the request. This error code has a 403 corresponding quoted error text string that is human understandable. 404 The text string is OPTIONAL, but RECOMMENDED for human readability, 405 similar to the string phrase used for SIP response codes. That said, 406 the strings are complete enough for rendering to the user, if so 407 desired. The strings in this document are recommendations, and are 408 not standardized -- meaning an operator can change the strings -- but 409 MUST NOT change the meaning of the error code. Similar to how RFC 410 3261 specifies, there MUST NOT be more than one string per error 411 code. 413 The AlertMsg-Error header field MAY be included in any response if an 414 alert message was in the request part of the same transaction. For 415 example, a UA includes an alert in a MESSAGE to a PSAP. The PSAP can 416 accept this MESSAGE, thus creating a dialog, even though its UA 417 determined that the alert message contained in the MESSAGE was bad. 418 The PSAP merely includes an AlertMsg-Error header field value in the 419 200 OK to the MESSAGE, thus informing the UA that the MESSAGE was 420 accepted but the alert provided was bad. 422 If, on the other hand, the PSAP cannot accept the transaction without 423 a suitable alert message, a 425 response is sent. 425 A SIP intermediary that requires the UA's alert message in order to 426 properly process the transaction may also sends a 425 with an 427 AlertMsg-Error code. 429 This document defines an initial list of AlertMsg-Error values for 430 any SIP response, including provisional responses (other than 100 431 Trying) and the new 425 response. There MUST be no more than one 432 AlertMsg-Error code in a SIP response. 434 AlertMsg-Error: 100 ; code="Cannot Process the Alert Payload" 436 AlertMsg-Error: 101 ; code="Alert Payload was not present or could 437 not be found" 439 AlertMsg-Error: 102 ; code="Not enough information to determine the 440 purpose of the alert" 441 AlertMsg-Error: 103 ; code="Alert Payload was corrupted" 443 Additionally, if an entity cannot or chooses not to process the alert 444 message from a SIP request, a 500 (Server Internal Error) SHOULD be 445 used with or without a configurable Retry-After header field. 447 6. Call Backs 449 This document does not describe any method for the recipient to call 450 back the sender of a data-only call. Usually, these alerts are sent 451 by automata, which do not have a mechanism to receive calls of any 452 kind. The identifier in the 'From' header field may be useful to 453 obtain more information, but any such mechanism is not defined in 454 this document. The CAP message may contain related contact 455 information for the sender. 457 7. Handling Large Amounts of Data 459 It is not atypical for sensors to have large quantities of data that 460 they may wish to send. Including large amounts of data in a MESSAGE 461 is not advisable, because SIP entities are usually not equipped to 462 handle very large messages. In such cases, the sender SHOULD make 463 use of the by-reference mechanisms defined in [RFC7852], which 464 involves making the data available via HTTPS (either at the 465 originator or at another entity), placing a URI to the data in the 466 'Call-Info' header field, and the recipient using HTTPS to retrieve 467 the data. The CAP message itself can be sent by-reference using this 468 mechanism, as well as any or all of the Additional Data blocks that 469 may contain sensor-specific data. 471 8. Example 473 The following example shows a CAP document indicating a BURGLARY 474 alert issued by a sensor called 'sensor1@domain.com'. The location 475 of the sensor can be obtained from the attached location information 476 provided via the 'geolocation' header field contained in the SIP 477 MESSAGE structure. Additionally, the sensor provided some data along 478 with the alert message, using proprietary information elements 479 intended only to be processed by the receiver, a SIP entity acting as 480 an aggregator. 482 MESSAGE sip:aggregator@domain.com SIP/2.0 483 Via: SIP/2.0/TCP sensor1.domain.com;branch=z9hG4bK776sgdkse 484 Max-Forwards: 70 485 From: sip:sensor1@domain.com;tag=49583 486 To: sip:aggregator@domain.com 487 Call-ID: asd88asd77a@2001:DB8:0:0FF 488 Geolocation: 489 ;routing-allowed=yes 490 Supported: geolocation 491 Accept: application/pidf+xml,application/EmergencyCallData.cap+xml 492 CSeq: 1 MESSAGE 493 Call-Info: cid:abcdef2@domain.com;purpose=EmergencyCallData.cap 494 Content-Type: multipart/mixed; boundary=boundary1 495 Content-Length: ... 497 --boundary1 499 Content-Type: application/EmergencyCallData.cap+xml 500 Content-ID: 501 Content-Disposition: by-reference;handling=optional 502 504 505 S-1 506 sip:sensor1@domain.com 507 2008-11-19T14:57:00-07:00 508 Actual 509 Alert 510 Private 511 abc1234 512 513 Security 514 BURGLARY 515 Expected 516 Likely 517 Moderate 518 SENSOR 1 519 520 SENSOR-DATA-NAMESPACE1 521 123 522 523 524 SENSOR-DATA-NAMESPACE2 525 TRUE 526 527 528 530 --boundary1 532 Content-Type: application/pidf+xml 533 Content-ID: 534 Content-Disposition: by-reference;handling=optional 535 536 545 546 547 548 549 550 32.86726 -97.16054 551 552 553 554 555 false 556 557 2010-11-14T20:00:00Z 558 559 560 802.11 561 562 2010-11-04T20:57:29Z 563 564 565 --boundary1-- 567 Figure 3: Example Message conveying an Alert to an aggregator 569 The following shows the same CAP document sent as a data-only 570 emergency call towards a PSAP. 572 MESSAGE urn:service:sos SIP/2.0 573 Via: SIP/2.0/TCP sip:aggreg.1.example.com;branch=z9hG4bK776abssa 574 Max-Forwards: 70 575 From: sip:aggregator@example.com;tag=32336 576 To: 112 577 Call-ID: asdf33443a@example.com 578 Route: sip:psap1.example.gov 579 Geolocation: 580 ;routing-allowed=yes 581 Supported: geolocation 582 Accept: application/pidf+xml,application/EmergencyCallData.cap+xml 583 Call-info: cid:abcdef2@domain.com;purpose=EmergencyCallData.cap 584 CSeq: 1 MESSAGE 585 Content-Type: multipart/mixed; boundary=boundary1 586 Content-Length: ... 588 --boundary1 590 Content-Type: application/EmergencyCallData.cap+xml 591 Content-ID: 592 594 595 S-1 596 sip:sensor1@domain.com 597 2008-11-19T14:57:00-07:00 598 Actual 599 Alert 600 Private 601 abc1234 602 603 Security 604 BURGLARY 605 Expected 606 Likely 607 Moderate 608 SENSOR 1 609 610 SENSOR-DATA-NAMESPACE1 611 123 612 613 614 SENSOR-DATA-NAMESPACE2 615 TRUE 616 617 618 620 --boundary1 622 Content-Type: application/pidf+xml 623 Content-ID: 624 625 634 635 636 637 638 639 32.86726 -97.16054 640 641 642 643 644 false 645 646 2010-11-14T20:00:00Z 647 648 649 802.11 650 651 2010-11-04T20:57:29Z 652 653 654 --boundary1-- 656 Figure 4: Example Message conveying an Alert to a PSAP 658 9. Security Considerations 660 This section discusses security considerations when SIP user agents 661 issue emergency alerts utilizing MESSAGE and CAP. Location specific 662 threats are not unique to this document and are discussed in 663 [RFC7378] and [RFC6442]. 665 The ECRIT emergency services architecture [RFC6443] considers classic 666 individual-to-authority emergency calling where the identity of the 667 emergency caller does not play a role at the time of the call 668 establishment itself, i.e., a response to the emergency call does not 669 depend on the identity of the caller. In the case of emergency 670 alerts generated by devices such as sensors, the processing may be 671 different in order to reduce the number of falsely generated 672 emergency alerts. Alerts could get triggered based on certain sensor 673 input that might have been caused by factors other than the actual 674 occurrence of an alert-relevant event. For example, a sensor may 675 simply be malfunctioning. For this reason, not all alert messages 676 are directly sent to a PSAP, but rather may be pre-processed by a 677 separate entity, potentially under supervision by a human, to filter 678 alerts and potentially correlate received alerts with others to 679 obtain a larger picture of the ongoing situation. 681 In any case, for alerts initiated by sensors, the identity could play 682 an important role in deciding whether to accept or ignore an incoming 683 alert message. With the scenario shown in Figure 1 it is very likely 684 that only authorized sensor input will be processed. For this 685 reason, it needs to be possible to refuse to accept alert messages 686 from an unknown origin. Two types of information elements can be 687 used for this purpose: 689 1. SIP itself provides security mechanisms that allow the 690 verification of the originator's identity. These mechanisms can 691 be re-used, such as P-Asserted-Identity [RFC3325] or SIP Identity 692 [RFC4474]. The latter provides a cryptographic assurance while 693 the former relies on a chain of trust model. 695 2. CAP provides additional security mechanisms and the ability to 696 carry further information about the sender's identity. 697 Section 3.3.2.1 of [cap] specifies the signing algorithms of CAP 698 documents. 700 In addition to the desire to perform identity-based access control, 701 the classic communication security threats need to be considered, 702 including integrity protection to prevent forgery or replay of alert 703 messages in transit. To deal with replay of alerts, a CAP document 704 contains the mandatory , , elements and an 705 optional element. Together, these elements make the CAP 706 document unique for a specific sender and provide time restrictions. 707 An entity that has already received a CAP message within the 708 indicated timeframe is able to detect a replayed message and, if the 709 content of that message is unchanged, then no additional security 710 vulnerability is created. Additionally, it is RECOMMENDED to make 711 use of SIP security mechanisms, such as SIP Identity [RFC4474], to 712 tie the CAP message to the SIP message. To provide protection of the 713 entire SIP message exchange between neighboring SIP entities, the 714 usage of TLS is REQUIRED. 716 Note that none of the security mechanism in this document protect 717 against a compromised sensor sending crafted alerts. Privacy 718 provided for any emergency calls, including data-only messages, is 719 subject to local regulations. 721 10. IANA Considerations 722 10.1. Registration of the 'application/EmergencyCallData.cap+xml' MIME 723 type 725 To: ietf-types@iana.org 727 Subject: Registration of MIME media type application/ 728 EmergencyCallData.cap+xml 730 MIME media type name: application 732 MIME subtype name: cap+xml 734 Required parameters: (none) 736 Optional parameters: charset; Indicates the character encoding of 737 enclosed XML. Default is UTF-8 [RFC3629]. 739 Encoding considerations: Uses XML, which can employ 8-bit 740 characters, depending on the character encoding used. See RFC 741 3023 [RFC3023], Section 3.2. 743 Security considerations: This content type is designed to carry 744 payloads of the Common Alerting Protocol (CAP). RFC XXX [Replace 745 by the RFC number of this specification] discusses security 746 considerations for this. 748 Interoperability considerations: This content type provides a way to 749 convey CAP payloads. 751 Published specification: RFC XXX [Replace by the RFC number of this 752 specification]. 754 Applications which use this media type: Applications that convey 755 alerts and warnings according to the CAP standard. 757 Additional information: OASIS has published the Common Alerting 758 Protocol at http://www.oasis-open.org/committees/ 759 documents.php&wg_abbrev=emergency 761 Person and email address to contact for further information: Hannes 762 Tschofenig, hannes.tschofenig@gmx.net 764 Intended usage: Limited use 766 Author/Change controller: IETF ECRIT working group 768 Other information: This media type is a specialization of 769 application/xml RFC 3023 [RFC3023], and many of the considerations 770 described there also apply to application/cap+xml. 772 10.2. IANA Registration of 'cap' Additional Data Block 774 This document registers a new block type in the sub-registry called 775 'Emergency Call Data Types' of the Emergency Call Additional Data 776 Registry defined in [RFC7852]. The token is "cap", the Data About is 777 "The Call" and the reference is this document. 779 10.3. IANA Registration for 425 Response Code 781 In the SIP Response Codes registry, the following is added 783 Reference: RFC-XXXX (i.e., this document) 785 Response code: 425 (recommended number to assign) 787 Default reason phrase: Bad Alert Message 789 Registry: 790 Response Code Reference 791 ------------------------------------------ --------- 792 Request Failure 4xx 793 425 Bad Alert Message [this doc] 795 This SIP Response code is defined in Section 5. 797 10.4. IANA Registration of New AlertMsg-Error Header Field 799 The SIP AlertMsg-error header field is created by this document, with 800 its definition and rules in Section 5, to be added to the IANA 801 Session Initiation Protocol (SIP) Parameters registry with two 802 actions: 804 1. Update the Header Fields registry with 806 Registry: 807 Header Name compact Reference 808 ----------------- ------- --------- 809 AlertMsg-Error [this doc] 811 2. In the portion titled "Header Field Parameters and Parameter 812 Values", add 814 Predefined 815 Header Field Parameter Name Values Reference 816 ----------------- ------------------- ---------- --------- 817 AlertMsg-Error code yes [this doc] 819 10.5. IANA Registration for the SIP AlertMsg-Error Codes 821 This document creates a new registry for SIP, called "AlertMsg-Error 822 Codes". AlertMsg-Error codes provide reasons for an error discovered 823 by a recipient, categorized by the action to be taken by the error 824 recipient. The initial values for this registry are shown below. 826 Registry Name: AlertMsg-Error Codes 828 Reference: [this doc] 830 Registration Procedures: Specification Required 831 Code Default Reason Phrase Reference 832 ---- --------------------------------------------------- --------- 833 100 "Cannot Process the Alert Payload" [this doc] 835 101 "Alert Payload was not present or could not be found" [this doc] 837 102 "Not enough information to determine 838 the purpose of the alert" [this doc] 840 103 "Alert Payload was corrupted" [this doc] 842 Details of these error codes are in Section 5. 844 11. Acknowledgments 846 The authors would like to thank the participants of the Early Warning 847 adhoc meeting at IETF#69 for their feedback. Additionally, we would 848 like to thank the members of the NENA Long Term Direction Working 849 Group for their feedback. 851 Additionally, we would like to thank Martin Thomson, James 852 Winterbottom, Shida Schubert, Bernard Aboba, and Marc Linsner for 853 their review comments. 855 12. References 857 12.1. Normative References 859 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 860 Requirement Levels", March 1997. 862 [cap] Jones, E. and A. Botterell, "Common Alerting Protocol v. 863 1.1", October 2005. 865 [RFC2392] Levinson, E., "Content-ID and Message-ID Uniform Resource 866 Locators", RFC 2392, DOI 10.17487/RFC2392, August 1998, 867 . 869 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 870 A., Peterson, J., Sparks, R., Handley, M., and E. 871 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 872 DOI 10.17487/RFC3261, June 2002, . 875 [RFC3428] Campbell, B., Ed., Rosenberg, J., Schulzrinne, H., 876 Huitema, C., and D. Gurle, "Session Initiation Protocol 877 (SIP) Extension for Instant Messaging", RFC 3428, 878 DOI 10.17487/RFC3428, December 2002, . 881 [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax 882 Specifications: ABNF", STD 68, RFC 5234, 883 DOI 10.17487/RFC5234, January 2008, . 886 [RFC3023] Murata, M., St. Laurent, S., and D. Kohn, "XML Media 887 Types", RFC 3023, DOI 10.17487/RFC3023, January 2001, 888 . 890 [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 891 10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November 892 2003, . 894 [RFC6442] Polk, J., Rosen, B., and J. Peterson, "Location Conveyance 895 for the Session Initiation Protocol", RFC 6442, 896 DOI 10.17487/RFC6442, December 2011, . 899 [RFC6881] Rosen, B. and J. Polk, "Best Current Practice for 900 Communications Services in Support of Emergency Calling", 901 BCP 181, RFC 6881, DOI 10.17487/RFC6881, March 2013, 902 . 904 [RFC7852] Gellens, R., Rosen, B., Tschofenig, H., Marshall, R., and 905 J. Winterbottom, "Additional Data Related to an Emergency 906 Call", RFC 7852, DOI 10.17487/RFC7852, July 2016, 907 . 909 12.2. Informative References 911 [RFC7378] Tschofenig, H., Schulzrinne, H., and B. Aboba, Ed., 912 "Trustworthy Location", RFC 7378, DOI 10.17487/RFC7378, 913 December 2014, . 915 [RFC4474] Peterson, J. and C. Jennings, "Enhancements for 916 Authenticated Identity Management in the Session 917 Initiation Protocol (SIP)", RFC 4474, 918 DOI 10.17487/RFC4474, August 2006, . 921 [RFC3325] Jennings, C., Peterson, J., and M. Watson, "Private 922 Extensions to the Session Initiation Protocol (SIP) for 923 Asserted Identity within Trusted Networks", RFC 3325, 924 DOI 10.17487/RFC3325, November 2002, . 927 [RFC6443] Rosen, B., Schulzrinne, H., Polk, J., and A. Newton, 928 "Framework for Emergency Calling Using Internet 929 Multimedia", RFC 6443, DOI 10.17487/RFC6443, December 930 2011, . 932 Authors' Addresses 934 Brian Rosen 935 NeuStar, Inc. 936 470 Conrad Dr 937 Mars, PA 16046 938 US 940 Email: br@brianrosen.net 942 Henning Schulzrinne 943 Columbia University 944 Department of Computer Science 945 450 Computer Science Building 946 New York, NY 10027 947 US 949 Phone: +1 212 939 7004 950 Email: hgs+ecrit@cs.columbia.edu 951 URI: http://www.cs.columbia.edu 953 Hannes Tschofenig 954 ARM Limited 955 Austria 957 Email: Hannes.Tschofenig@gmx.net 958 URI: http://www.tschofenig.priv.at 960 Randall Gellens 961 Core Technology Consulting 963 Email: rg+ietf@coretechnologyconsulting.com 964 URI: http://www.coretechnologyconsulting.com