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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: May 3, 2018 Columbia U. 6 H. Tschofenig 7 ARM Limited 8 R. Gellens 9 October 30, 2017 11 Data-Only Emergency Calls 12 draft-ietf-ecrit-data-only-ea-14 14 Abstract 16 RFC 6443 'Framework for Emergency Calling Using Internet Multimedia' 17 describes how devices use the Internet to place emergency calls and 18 how Public Safety Answering Points (PSAPs) handle Internet multimedia 19 emergency calls natively. The exchange of multimedia traffic for 20 emergency services involves a Session Initiation Protocol (SIP) 21 session establishment starting with a SIP INVITE that negotiates 22 various parameters for that session. 24 In some cases, however, the transmission of application data is all 25 that is needed. Examples of such environments include alerts issued 26 by a temperature sensor, burglar alarm, or chemical spill sensor. 27 Often these alerts are conveyed as one-shot data transmissions. 28 These type of interactions are called 'data-only emergency calls'. 29 This document describes a container for the data based on the Common 30 Alerting Protocol (CAP) and its transmission using the SIP MESSAGE 31 transaction. 33 Status of This Memo 35 This Internet-Draft is submitted in full conformance with the 36 provisions of BCP 78 and BCP 79. 38 Internet-Drafts are working documents of the Internet Engineering 39 Task Force (IETF). Note that other groups may also distribute 40 working documents as Internet-Drafts. The list of current Internet- 41 Drafts is at https://datatracker.ietf.org/drafts/current/. 43 Internet-Drafts are draft documents valid for a maximum of six months 44 and may be updated, replaced, or obsoleted by other documents at any 45 time. It is inappropriate to use Internet-Drafts as reference 46 material or to cite them other than as "work in progress." 48 This Internet-Draft will expire on May 3, 2018. 50 Copyright Notice 52 Copyright (c) 2017 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 (https://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 vehicles sending 106 crash data. 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 document format for 121 exchanging emergency alerts and public warnings. CAP is mainly used 122 for 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, either by value (the CAP message is in the body of the 129 message, using a CID) or by reference (a URI is included in the 130 message, which when dereferenced returns the CAP message) by defining 131 it as a block of "additional data" as defined in 132 [I-D.ietf-ecrit-additional-data]. The additional data mechanism is 133 also used to send alert specific data beyond that available in the 134 CAP message. This document also describes how a SIP MESSAGE 135 [RFC3428] transaction can 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 163 [I-D.ietf-ecrit-additional-data] in a SIP 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 media. 211 +-----------+ +----------+ 212 +--------+ | ESRP | | PSAP | 213 | Sensor | | | | | 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 [I-D.ietf-ecrit-additional-data]. Accordingly, it is 260 introduced to the SIP message with a Call-Info header field with a 261 purpose of "EmergencyCallData.cap". The header field may contain a 262 URI that is used by the recipient (or in some cases, an intermediary) 263 to obtain the CAP message. Alternative, the Call-Info header field 264 may contain a Content Indirect url [RFC2392] and the CAP message 265 included in the body of the message. In the latter case, the CAP 266 message is located in a MIME block of the type 'application/ 267 emergencyCallData.cap+xml'. 269 If the SIP server does not support the functionality required to 270 fulfill the request then a 501 Not Implemented MUST be returned as 271 specified in RFC 3261 [RFC3261]. This is the appropriate response 272 when a User Agent Server (UAS) does not recognize the request method 273 and is not capable of supporting it for any user. 275 The 415 Unsupported Media Type error MUST be returned as specified in 276 RFC 3261 [RFC3261] if the SIP server is refusing to service the 277 request because the message body of the request is in a format not 278 supported by the server for the requested method. The server MUST 279 return a list of acceptable formats using the Accept, Accept- 280 Encoding, or Accept-Language header fields, depending on the specific 281 problem with the content. 283 4.2. Profiling of the CAP Document Content 285 The usage of CAP MUST conform to the specification provided with 286 [cap]. For usage with SIP the following additional requirements are 287 imposed: 289 sender: The following restrictions and conditions apply to setting 290 the value of the element: 292 Originator is a SIP entity, Author indication irrelevant: When 293 the alert was created by a SIP-based originator and it is not 294 useful to be explicit about the author of the alert, then the 295 element MUST be populated with the SIP URI of the user 296 agent. 298 Originator is a non-SIP entity, Author indication irrelevant: 299 When the alert was created by a non-SIP based entity and the 300 identity of this original sender is to be preserved, then this 301 identity MUST be placed into the element. In this 302 situation it is not useful to be explicit about the author of the 303 alert. The specific type of identity being used will depend on 304 the technology used by the original originator. 306 Author indication relevant: When the author is different from the 307 actual originator of the message and this distinction should be 308 preserved, then the element MUST NOT contain the SIP URI 309 of the user agent. 311 incidents: The element MUST be present. This incident 312 identifier MUST be chosen in such a way that it is unique for a 313 given combination. Note that the 314 element is optional and may not be present. 316 scope: The value of the element MAY be set to "Private" if 317 the alert is not meant for public consumption. The 318 element is, however, not used by this specification since the 319 message routing is performed by SIP and the respective address 320 information is already available in other SIP header fields. 321 Populating information twice into different parts of the message 322 may lead to inconsistency. 324 parameter: The element MAY contain additional 325 information specific to the sender. 327 area: It is RECOMMENDED to omit this element when constructing a 328 message. If the CAP message already contains an element, 329 then the specified location information SHOULD be copied into the 330 PIDF-LO structure of the 'geolocation' header field. 332 4.3. Sending a Data-Only Emergency Call 334 A data-only emergency call is sent using a SIP MESSAGE transaction 335 with a CAP URI or body as described above in a manner similar to how 336 an emergency call with interactive media is sent, as described in 337 [RFC6881]. The MESSAGE transaction does not create a session nor 338 send media, but otherwise, the header content of the transaction, 339 routing, and processing of data-only calls are the same as those of 340 other emergency calls. 342 5. Error Handling 344 This section defines a new error response code and a header field for 345 additional information. 347 5.1. 425 (Bad Alert Message) Response Code 349 This SIP extension creates a new location-specific response code, 350 defined as follows: 352 425 (Bad Alert Message) 354 The 425 response code is a rejection of the request due to its 355 included alert content, indicating that it was malformed or not 356 satisfactory for the recipient's purpose. 358 A SIP intermediary can also reject an alert it receives from a User 359 Agent (UA) when it understands that the provided alert is malformed. 361 Section 5.2 describes an AlertMsg-Error header field with more 362 details about what was wrong with the alert message in the request. 363 This header field MUST be included in the 425 response. 365 It is only appropriate to generate a 425 response when the responding 366 entity has no other information in the request that is usable by the 367 responder. 369 A 425 response code MUST NOT be sent in response to a request that 370 lacks an alert message, as the user agent in that case may not 371 support this extension. 373 A 425 response is a final response within a transaction, and MUST NOT 374 terminate an existing dialog. 376 5.2. The AlertMsg-Error Header Field 378 The AlertMsg-Error header field provides additional information about 379 what was wrong with the original request. In some cases the provided 380 information will be used for debugging purposes. 382 The AlertMsg-Error header field has the following ABNF [RFC5234]: 384 message-header /= AlertMsg-Error 385 ; (message-header from 3261) 386 AlertMsg-Error = "AlertMsg-Error" HCOLON 387 ErrorValue 388 ErrorValue = error-code 389 *(SEMI error-params) 390 error-code = 1*3DIGIT 391 error-params = error-code-text 392 / generic-param ; from RFC3261 393 error-code-text = "code" EQUAL quoted-string ; from RFC3261 395 HCOLON, SEMI, and EQUAL are defined in RFC3261 [RFC3261]. DIGIT is 396 defined in RFC5234 [RFC5234]. 398 The AlertMsg-Error header field MUST contain only one ErrorValue to 399 indicate what was wrong with the alert payload the recipient 400 determined was bad. 402 The ErrorValue contains a 3-digit error code indicating what was 403 wrong with the alert in the request. This error code has a 404 corresponding quoted error text string that is human understandable. 405 The text string is OPTIONAL, but RECOMMENDED for human readability, 406 similar to the string phrase used for SIP response codes. That said, 407 the strings are complete enough for rendering to the user, if so 408 desired. The strings in this document are recommendations, and are 409 not standardized -- meaning an operator can change the strings -- but 410 MUST NOT change the meaning of the error code. Similar to how RFC 411 3261 specifies, there MUST NOT be more than one string per error 412 code. 414 The AlertMsg-Error header field MAY be included in any response if an 415 alert message was in the request part of the same transaction. For 416 example, a UA includes an alert in a MESSAGE to a PSAP. The PSAP can 417 accept this MESSAGE, thus creating a dialog, even though its UA 418 determined that the alert message contained in the MESSAGE was bad. 419 The PSAP merely includes an AlertMsg-Error header field value in the 420 200 OK to the MESSAGE, thus informing the UA that the MESSAGE was 421 accepted but the alert provided was bad. 423 If, on the other hand, the PSAP cannot accept the transaction without 424 a suitable alert message, a 425 response is sent. 426 A SIP intermediary that requires the UA's alert message in order to 427 properly process the transaction may also sends a 425 with an 428 AlertMsg-Error code. 430 This document defines an initial list of AlertMsg-Error values for 431 any SIP response, including provisional responses (other than 100 432 Trying) and the new 425 response. There MUST be no more than one 433 AlertMsg-Error code in a SIP response. 435 AlertMsg-Error: 100 ; code="Cannot Process the Alert Payload" 437 AlertMsg-Error: 101 ; code="Alert Payload was not present or could 438 not be found" 440 AlertMsg-Error: 102 ; code="Not enough information to determine the 441 purpose of the alert" 442 AlertMsg-Error: 103 ; code="Alert Payload was corrupted" 444 Additionally, if an entity cannot or chooses not to process the alert 445 message from a SIP request, a 500 (Server Internal Error) SHOULD be 446 used with or without a configurable Retry-After header field. 448 6. Call Backs 450 This document does not describe any method for the recipient to call 451 back the sender of a data-only call. Usually, these alerts are sent 452 by automata, which do not have a mechanism to receive calls of any 453 kind. The identifier in the 'From' header field may be useful to 454 obtain more information, but any such mechanism is not defined in 455 this document. The CAP message may contain related contact 456 information for the sender. 458 7. Handling Large Amounts of Data 460 It is not atypical for sensors to have large quantities of data that 461 they may wish to send. Including large amounts of data in a MESSAGE 462 is not advisable, because SIP entities are usually not equipped to 463 handle very large messages. In such cases, the sender SHOULD make 464 use of the by-reference mechanisms defined in 465 [I-D.ietf-ecrit-additional-data], which involves making the data 466 available via HTTPS (either at the originator or at another entity), 467 placing a URI to the data in the 'Call-Info' header field, and the 468 recipient using HTTPS to retrieve the data. The CAP message itself 469 can be sent by-reference using this mechanism, as well as any or all 470 of the Additional Data blocks that may contain sensor-specific data. 472 8. Example 474 The following example shows a CAP document indicating a BURGLARY 475 alert issued by a sensor called 'sensor1@domain.com'. The location 476 of the sensor can be obtained from the attached location information 477 provided via the 'geolocation' header field contained in the SIP 478 MESSAGE structure. Additionally, the sensor provided some data along 479 with the alert message, using proprietary information elements 480 intended only to be processed by the receiver, a SIP entity acting as 481 an aggregator. 483 MESSAGE sip:aggregator@domain.com SIP/2.0 484 Via: SIP/2.0/TCP sensor1.domain.com;branch=z9hG4bK776sgdkse 485 Max-Forwards: 70 486 From: sip:sensor1@domain.com;tag=49583 487 To: sip:aggregator@domain.com 488 Call-ID: asd88asd77a@2001:DB8:0:0FF 489 Geolocation: 490 ;routing-allowed=yes 491 Supported: geolocation 492 Accept: application/pidf+xml,application/EmergencyCallData.cap+xml 493 CSeq: 1 MESSAGE 494 Call-Info: cid:abcdef2@domain.com;purpose=EmergencyCallData.cap 495 Content-Type: multipart/mixed; boundary=boundary1 496 Content-Length: ... 498 --boundary1 500 Content-Type: application/EmergencyCallData.cap+xml 501 Content-ID: 502 Content-Disposition: by-reference;handling=optional 503 505 506 S-1 507 sip:sensor1@domain.com 508 2008-11-19T14:57:00-07:00 509 Actual 510 Alert 511 Private 512 abc1234 513 514 Security 515 BURGLARY 516 Expected 517 Likely 518 Moderate 519 SENSOR 1 520 521 SENSOR-DATA-NAMESPACE1 522 123 523 524 525 SENSOR-DATA-NAMESPACE2 526 TRUE 527 528 529 531 --boundary1 533 Content-Type: application/pidf+xml 534 Content-ID: 535 Content-Disposition: by-reference;handling=optional 536 537 546 547 548 549 550 551 32.86726 -97.16054 552 553 554 555 556 false 557 558 2010-11-14T20:00:00Z 559 560 561 802.11 562 563 2010-11-04T20:57:29Z 564 565 566 --boundary1-- 568 Figure 3: Example Message conveying an Alert to an aggregator 570 The following shows the same CAP document sent as a data-only 571 emergency call towards a PSAP. 573 MESSAGE urn:service:sos SIP/2.0 574 Via: SIP/2.0/TCP sip:aggreg.1.example.com;branch=z9hG4bK776abssa 575 Max-Forwards: 70 576 From: sip:aggregator@example.com;tag=32336 577 To: 112 578 Call-ID: asdf33443a@example.com 579 Route: sip:psap1.example.gov 580 Geolocation: 581 ;routing-allowed=yes 582 Supported: geolocation 583 Accept: application/pidf+xml,application/EmergencyCallData.cap+xml 584 Call-info: cid:abcdef2@domain.com;purpose=EmergencyCallData.cap 585 CSeq: 1 MESSAGE 586 Content-Type: multipart/mixed; boundary=boundary1 587 Content-Length: ... 589 --boundary1 591 Content-Type: application/EmergencyCallData.cap+xml 592 Content-ID: 593 595 596 S-1 597 sip:sensor1@domain.com 598 2008-11-19T14:57:00-07:00 599 Actual 600 Alert 601 Private 602 abc1234 603 604 Security 605 BURGLARY 606 Expected 607 Likely 608 Moderate 609 SENSOR 1 610 611 SENSOR-DATA-NAMESPACE1 612 123 613 614 615 SENSOR-DATA-NAMESPACE2 616 TRUE 617 618 619 621 --boundary1 623 Content-Type: application/pidf+xml 624 Content-ID: 625 626 635 636 637 638 639 640 32.86726 -97.16054 641 642 643 644 645 false 646 647 2010-11-14T20:00:00Z 648 649 650 802.11 651 652 2010-11-04T20:57:29Z 653 654 655 --boundary1-- 657 Figure 4: Example Message conveying an Alert to a PSAP 659 9. Security Considerations 661 This section discusses security considerations when SIP user agents 662 issue emergency alerts utilizing MESSAGE and CAP. Location specific 663 threats are not unique to this document and are discussed in 664 [RFC7378] and [RFC6442]. 666 The ECRIT emergency services architecture [RFC6443] considers classic 667 individual-to-authority emergency calling where the identity of the 668 emergency caller does not play a role at the time of the call 669 establishment itself, i.e., a response to the emergency call does not 670 depend on the identity of the caller. In the case of emergency 671 alerts generated by devices such as sensors, the processing may be 672 different in order to reduce the number of falsely generated 673 emergency alerts. Alerts may get triggered based on certain sensor 674 input that may have been caused by factors other than the actual 675 occurrence of an alert relevant event. For example, a sensor may 676 simply be malfunctioning. For this reason, not all alert messages 677 are directly sent to a PSAP, but rather may be pre-processed by a 678 separate entity, potentially under supervision by a human, to filter 679 alerts and potentially correlate received alerts with others to 680 obtain a larger picture of the ongoing situation. 682 In any case, for alerts initiated by sensors, the identity may play 683 an important role in deciding whether to accept or ignore an incoming 684 alert message. With the scenario shown in Figure 1 it is very likely 685 that only authorized sensor input will be processed. For this 686 reason, it needs to be possible to refuse to accept alert messages 687 from an unknown origin. Two types of information elements can be 688 used for this purpose: 690 1. SIP itself provides security mechanisms that allow the 691 verification of the originator's identity. These mechanisms can 692 be re-used, such as P-Asserted-Identity [RFC3325] or SIP Identity 693 [RFC4474]. The latter provides a cryptographic assurance while 694 the former relies on a chain of trust model. 696 2. CAP provides additional security mechanisms and the ability to 697 carry further information about the sender's identity. 698 Section 3.3.2.1 of [cap] specifies the signing algorithms of CAP 699 documents. 701 In addition to the desire to perform identity-based access control, 702 the classic communication security threats need to be considered, 703 including integrity protection to prevent forgery or replay of alert 704 messages in transit. To deal with replay of alerts, a CAP document 705 contains the mandatory , , elements and an 706 optional element. Together, these elements make the CAP 707 document unique for a specific sender and provide time restrictions. 708 An entity that has already received a CAP message within the 709 indicated timeframe is able to detect a replayed message and, if the 710 content of that message is unchanged, then no additional security 711 vulnerability is created. Additionally, it is RECOMMENDED to make 712 use of SIP security mechanisms, such as SIP Identity [RFC4474], to 713 tie the CAP message to the SIP message. To provide protection of the 714 entire SIP message exchange between neighboring SIP entities, the 715 usage of TLS is REQUIRED. 717 Note that none of the security mechanism in this document protect 718 against a compromised sensor sending crafted alerts. Privacy 719 provided for any emergency calls, including data-only messages, is 720 subject to local regulations. 722 10. IANA Considerations 723 10.1. Registration of the 'application/EmergencyCallData.cap+xml' MIME 724 type 726 To: ietf-types@iana.org 728 Subject: Registration of MIME media type application/ 729 EmergencyCallData.cap+xml 731 MIME media type name: application 733 MIME subtype name: cap+xml 735 Required parameters: (none) 737 Optional parameters: charset; Indicates the character encoding of 738 enclosed XML. Default is UTF-8 [RFC3629]. 740 Encoding considerations: Uses XML, which can employ 8-bit 741 characters, depending on the character encoding used. See RFC 742 3023 [RFC3023], Section 3.2. 744 Security considerations: This content type is designed to carry 745 payloads of the Common Alerting Protocol (CAP). RFC XXX [Replace 746 by the RFC number of this specification] discusses security 747 considerations for this. 749 Interoperability considerations: This content type provides a way to 750 convey CAP payloads. 752 Published specification: RFC XXX [Replace by the RFC number of this 753 specification]. 755 Applications which use this media type: Applications that convey 756 alerts and warnings according to the CAP standard. 758 Additional information: OASIS has published the Common Alerting 759 Protocol at http://www.oasis-open.org/committees/ 760 documents.php&wg_abbrev=emergency 762 Person and email address to contact for further information: Hannes 763 Tschofenig, hannes.tschofenig@gmx.net 765 Intended usage: Limited use 767 Author/Change controller: IETF ECRIT working group 769 Other information: This media type is a specialization of 770 application/xml RFC 3023 [RFC3023], and many of the considerations 771 described there also apply to application/cap+xml. 773 10.2. IANA Registration of 'cap' Additional Data Block 775 This document registers a new block type in the sub-registry called 776 'Emergency Call Data Types' of the Emergency Call Additional Data 777 Registry defined in [I-D.ietf-ecrit-additional-data]. The token is 778 "cap", the Data About is "The Call" and the reference is this 779 document. 781 10.3. IANA Registration for 425 Response Code 783 In the SIP Response Codes registry, the following is added 785 Reference: RFC-XXXX (i.e., this document) 787 Response code: 425 (recommended number to assign) 789 Default reason phrase: Bad Alert Message 791 Registry: 792 Response Code Reference 793 ------------------------------------------ --------- 794 Request Failure 4xx 795 425 Bad Alert Message [this doc] 797 This SIP Response code is defined in Section 5. 799 10.4. IANA Registration of New AlertMsg-Error Header Field 801 The SIP AlertMsg-error header field is created by this document, with 802 its definition and rules in Section 5, to be added to the IANA 803 Session Initiation Protocol (SIP) Parameters registry with two 804 actions: 806 1. Update the Header Fields registry with 808 Registry: 809 Header Name compact Reference 810 ----------------- ------- --------- 811 AlertMsg-Error [this doc] 813 2. In the portion titled "Header Field Parameters and Parameter 814 Values", add 816 Predefined 817 Header Field Parameter Name Values Reference 818 ----------------- ------------------- ---------- --------- 819 AlertMsg-Error code yes [this doc] 821 10.5. IANA Registration for the SIP AlertMsg-Error Codes 823 This document creates a new registry for SIP, called "AlertMsg-Error 824 Codes". AlertMsg-Error codes provide reasons for an error discovered 825 by a recipient, categorized by the action to be taken by the error 826 recipient. The initial values for this registry are shown below. 828 Registry Name: AlertMsg-Error Codes 830 Reference: [this doc] 832 Registration Procedures: Specification Required 833 Code Default Reason Phrase Reference 834 ---- --------------------------------------------------- --------- 835 100 "Cannot Process the Alert Payload" [this doc] 837 101 "Alert Payload was not present or could not be found" [this doc] 839 102 "Not enough information to determine 840 the purpose of the alert" [this doc] 842 103 "Alert Payload was corrupted" [this doc] 844 Details of these error codes are in Section 5. 846 11. Acknowledgments 848 The authors would like to thank the participants of the Early Warning 849 adhoc meeting at IETF#69 for their feedback. Additionally, we would 850 like to thank the members of the NENA Long Term Direction Working 851 Group for their feedback. 853 Additionally, we would like to thank Martin Thomson, James 854 Winterbottom, Shida Schubert, Bernard Aboba, and Marc Linsner for 855 their review comments. 857 12. References 859 12.1. Normative References 861 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 862 Requirement Levels", March 1997. 864 [cap] Jones, E. and A. Botterell, "Common Alerting Protocol v. 865 1.1", October 2005. 867 [RFC2392] Levinson, E., "Content-ID and Message-ID Uniform Resource 868 Locators", RFC 2392, DOI 10.17487/RFC2392, August 1998, 869 . 871 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 872 A., Peterson, J., Sparks, R., Handley, M., and E. 873 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 874 DOI 10.17487/RFC3261, June 2002, 875 . 877 [RFC3428] Campbell, B., Ed., Rosenberg, J., Schulzrinne, H., 878 Huitema, C., and D. Gurle, "Session Initiation Protocol 879 (SIP) Extension for Instant Messaging", RFC 3428, 880 DOI 10.17487/RFC3428, December 2002, 881 . 883 [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax 884 Specifications: ABNF", STD 68, RFC 5234, 885 DOI 10.17487/RFC5234, January 2008, 886 . 888 [RFC3023] Murata, M., St. Laurent, S., and D. Kohn, "XML Media 889 Types", RFC 3023, DOI 10.17487/RFC3023, January 2001, 890 . 892 [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 893 10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November 894 2003, . 896 [RFC6442] Polk, J., Rosen, B., and J. Peterson, "Location Conveyance 897 for the Session Initiation Protocol", RFC 6442, 898 DOI 10.17487/RFC6442, December 2011, 899 . 901 [RFC6881] Rosen, B. and J. Polk, "Best Current Practice for 902 Communications Services in Support of Emergency Calling", 903 BCP 181, RFC 6881, DOI 10.17487/RFC6881, March 2013, 904 . 906 [I-D.ietf-ecrit-additional-data] 907 Gellens, R., Rosen, B., Tschofenig, H., Marshall, R., and 908 J. Winterbottom, "Additional Data Related to an Emergency 909 Call", draft-ietf-ecrit-additional-data-38 (work in 910 progress), April 2016. 912 12.2. Informative References 914 [RFC7378] Tschofenig, H., Schulzrinne, H., and B. Aboba, Ed., 915 "Trustworthy Location", RFC 7378, DOI 10.17487/RFC7378, 916 December 2014, . 918 [RFC4474] Peterson, J. and C. Jennings, "Enhancements for 919 Authenticated Identity Management in the Session 920 Initiation Protocol (SIP)", RFC 4474, 921 DOI 10.17487/RFC4474, August 2006, 922 . 924 [RFC3325] Jennings, C., Peterson, J., and M. Watson, "Private 925 Extensions to the Session Initiation Protocol (SIP) for 926 Asserted Identity within Trusted Networks", RFC 3325, 927 DOI 10.17487/RFC3325, November 2002, 928 . 930 [RFC6443] Rosen, B., Schulzrinne, H., Polk, J., and A. Newton, 931 "Framework for Emergency Calling Using Internet 932 Multimedia", RFC 6443, DOI 10.17487/RFC6443, December 933 2011, . 935 Authors' Addresses 937 Brian Rosen 938 NeuStar, Inc. 939 470 Conrad Dr 940 Mars, PA 16046 941 US 943 Email: br@brianrosen.net 945 Henning Schulzrinne 946 Columbia University 947 Department of Computer Science 948 450 Computer Science Building 949 New York, NY 10027 950 US 952 Phone: +1 212 939 7004 953 Email: hgs+ecrit@cs.columbia.edu 954 URI: http://www.cs.columbia.edu 956 Hannes Tschofenig 957 ARM Limited 958 Austria 960 Email: Hannes.Tschofenig@gmx.net 961 URI: http://www.tschofenig.priv.at 963 Randall Gellens 965 Email: rg+ietf@randy.pensive.org