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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references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 3023 (Obsoleted by RFC 7303) == Outdated reference: draft-ietf-ecrit-additional-data has been published as RFC 7852 -- Obsolete informational reference (is this intentional?): RFC 4474 (Obsoleted by RFC 8224) Summary: 1 error (**), 0 flaws (~~), 3 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: September 2, 2016 Columbia U. 6 H. Tschofenig 7 ARM Limited 8 R. Gellens 9 March 1, 2016 11 Data-Only Emergency Calls 12 draft-ietf-ecrit-data-only-ea-11.txt 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 SIP session establishment starting with 21 a SIP INVITE that negotiates various parameters for that session. 23 In some cases, however, the transmission of application data is all 24 that is needed. Examples of such environments include alerts issued 25 by a temperature sensor, burglar alarm, or chemical spill sensor. 26 Often these alerts are conveyed as one-shot data transmissions. 27 These type of interactions are called 'data-only emergency calls'. 28 This document describes a container for the data based on the Common 29 Alerting Protocol (CAP) and its transmission using the SIP MESSAGE 30 transaction. 32 Status of This Memo 34 This Internet-Draft is submitted in full conformance with the 35 provisions of BCP 78 and BCP 79. 37 Internet-Drafts are working documents of the Internet Engineering 38 Task Force (IETF). Note that other groups may also distribute 39 working documents as Internet-Drafts. The list of current Internet- 40 Drafts is at http://datatracker.ietf.org/drafts/current/. 42 Internet-Drafts are draft documents valid for a maximum of six months 43 and may be updated, replaced, or obsoleted by other documents at any 44 time. It is inappropriate to use Internet-Drafts as reference 45 material or to cite them other than as "work in progress." 47 This Internet-Draft will expire on September 2, 2016. 49 Copyright Notice 51 Copyright (c) 2016 IETF Trust and the persons identified as the 52 document authors. All rights reserved. 54 This document is subject to BCP 78 and the IETF Trust's Legal 55 Provisions Relating to IETF Documents 56 (http://trustee.ietf.org/license-info) in effect on the date of 57 publication of this document. Please review these documents 58 carefully, as they describe your rights and restrictions with respect 59 to this document. Code Components extracted from this document must 60 include Simplified BSD License text as described in Section 4.e of 61 the Trust Legal Provisions and are provided without warranty as 62 described in the Simplified BSD License. 64 Table of Contents 66 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 67 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 68 3. Architectural Overview . . . . . . . . . . . . . . . . . . . 4 69 4. Protocol Specification . . . . . . . . . . . . . . . . . . . 6 70 4.1. CAP Transport . . . . . . . . . . . . . . . . . . . . . . 6 71 4.2. Profiling of the CAP Document Content . . . . . . . . . . 7 72 4.3. Sending a Data-Only Emergency Call . . . . . . . . . . . 8 73 5. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 8 74 5.1. 425 (Bad Alert Message) Response Code . . . . . . . . . . 9 75 5.2. The AlertMsg-Error Header Field . . . . . . . . . . . . . 9 76 6. Updates to the CAP Message . . . . . . . . . . . . . . . . . 11 77 7. Call Backs . . . . . . . . . . . . . . . . . . . . . . . . . 11 78 8. Handling Large Amounts of Data . . . . . . . . . . . . . . . 11 79 9. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 80 10. Security Considerations . . . . . . . . . . . . . . . . . . . 15 81 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 82 11.1. Registration of the 'application/emergencyCall.cap+xml' 83 MIME type . . . . . . . . . . . . . . . . . . . . . . . 17 84 11.2. IANA Registration of 'cap' Additional Data Block . . . . 18 85 11.3. IANA Registration for 425 Response Code . . . . . . . . 18 86 11.4. IANA Registration of New AlertMsg-Error Header Field . . 19 87 11.5. IANA Registration for the SIP AlertMsg-Error Codes . . . 19 88 12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 20 89 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 20 90 13.1. Normative References . . . . . . . . . . . . . . . . . . 20 91 13.2. 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 "emergencyCall.cap". The header field may contain a URI 262 that is used by the recipient (or in some cases, an intermediary) to 263 obtain the CAP message. Alternative, the Call-Info header field may 264 contain a Content Indirect url [RFC2392] and the CAP message included 265 in the body of the message. In either case, the CAP message is 266 located in a MIME block of the type 'application/ 267 emergencyCall.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 UAS does not recognize the request method and is not capable 273 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 sendor. 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 UA 359 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 are 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 an MESSAGE to a PSAP. The PSAP 417 can 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. Updates to the CAP Message 450 If the sender anticipates that the content of the CAP message may 451 need to be updated during the lifecycle of the event referred to in 452 the message, it may include an update block as defined in 453 [I-D.rosen-ecrit-addldata-subnot].If the sender includes an update 454 block and does not have a globally reachable URI, then the UA must 455 register it's contact with a Registrar, and include a GRUU in in the 456 update block 458 7. Call Backs 460 This document does not describe any method for the recipient to call 461 back the sender of a data-only call. Usually, these alerts are sent 462 by automata, which do not have a mechanism to receive calls of any 463 kind. The identifier in the 'From' header field may be useful to 464 obtain more information, but any such mechanism is not defined in 465 this document. The CAP message may contain related contact 466 information for the sender. 468 8. Handling Large Amounts of Data 470 It is not atypical for sensors to have large quantities of data that 471 they may wish to send. Including large amounts of data in a MESSAGE 472 is not advisable, because SIP entities are usually not equipped to 473 handle very large messages. In such cases, the sender SHOULD make 474 use of the by-reference mechanisms defined in 475 [I-D.ietf-ecrit-additional-data], which involves making the data 476 available via HTTPS (either at the originator or at another entity), 477 placing a URI to the data in the 'Call-Info' header field, and the 478 recipient using HTTPS to retrieve the data. The CAP message itself 479 can be sent by-reference using this mechanism, as well as any or all 480 of the Additional Data blocks that may contain sensor-specific data. 482 9. Example 484 Figure 3 shows a CAP document indicating a BURGLARY alert issued by a 485 sensor called 'sensor1@domain.com'. The location of the sensor can 486 be obtained from the attached location information provided via the 487 'geolocation' header field contained in the SIP MESSAGE structure. 488 Additionally, the sensor provided some data along with the alert 489 message, using proprietary information elements intended only to be 490 processed by the receiver, a SIP entity acting as an aggregator. 491 This example reflects the description in Figure 1. 493 MESSAGE sip:aggregator@domain.com SIP/2.0 494 Via: SIP/2.0/TCP sensor1.domain.com;branch=z9hG4bK776sgdkse 495 Max-Forwards: 70 496 From: sip:sensor1@domain.com;tag=49583 497 To: sip:aggregator@domain.com 498 Call-ID: asd88asd77a@1.2.3.4 499 Geolocation: 500 ;routing-allowed=yes 501 Supported: geolocation 502 Accept: application/pidf+xml, application/emergencyCall.cap+xml 503 CSeq: 1 MESSAGE 504 Call-Info: cid:abcdef2@domain.com;purpose=emergencyCall.cap 505 Content-Type: multipart/mixed; boundary=boundary1 506 Content-Length: ... 508 --boundary1 510 Content-Type: application/emergencyCall.cap+xml 511 Content-ID: 512 Content-Disposition: by-reference;handling=optional 513 515 516 S-1 517 sip:sensor1@domain.com 518 2008-11-19T14:57:00-07:00 519 Actual 520 Alert 521 Private 522 abc1234 523 524 Security 525 BURGLARY 526 Expected 527 Likely 528 Moderate 529 SENSOR 1 530 531 SENSOR-DATA-NAMESPACE1 532 123 533 534 535 SENSOR-DATA-NAMESPACE2 536 TRUE 538 539 540 542 --boundary1 544 Content-Type: application/pidf+xml 545 Content-ID: 546 Content-Disposition: by-reference;handling=optional 547 548 557 558 559 560 561 562 32.86726 -97.16054 563 564 565 566 567 false 568 569 2010-11-14T20:00:00Z 570 571 572 802.11 573 574 2010-11-04T20:57:29Z 575 576 577 --boundary1-- 579 Figure 3: Example Message conveying an Alert to an Aggregator 581 Figure 4 shows the same CAP document sent as a data-only emergency 582 call towards a PSAP. 584 MESSAGE urn:service:sos SIP/2.0 585 Via: SIP/2.0/TCP sip:aggreg.1.example.com;branch=z9hG4bK776abssa 586 Max-Forwards: 70 587 From: sip:aggregator@example.com;tag=32336 588 To: 112 589 Call-ID: asdf33443a@example.com 590 Route: sip:psap1.example.gov 591 Geolocation: 592 ;routing-allowed=yes 593 Supported: geolocation 594 Accept: application/pidf+xml, application/emergencyCall.cap+xml 595 Call-info: cid:abcdef2@domain.com;purpose=emergencyCall.cap 596 CSeq: 1 MESSAGE 597 Content-Type: multipart/mixed; boundary=boundary1 598 Content-Length: ... 600 --boundary1 602 Content-Type: application/emergencyCall.cap+xml 603 Content-ID: 604 606 607 S-1 608 sip:sensor1@domain.com 609 2008-11-19T14:57:00-07:00 610 Actual 611 Alert 612 Private 613 abc1234 614 615 Security 616 BURGLARY 617 Expected 618 Likely 619 Moderate 620 SENSOR 1 621 622 SENSOR-DATA-NAMESPACE1 623 123 624 625 626 SENSOR-DATA-NAMESPACE2 627 TRUE 628 629 630 632 --boundary1 633 Content-Type: application/pidf+xml 634 Content-ID: 635 636 645 646 647 648 649 650 32.86726 -97.16054 651 652 653 654 655 false 656 657 2010-11-14T20:00:00Z 658 659 660 802.11 661 662 2010-11-04T20:57:29Z 663 664 665 --boundary1-- 667 Figure 4: Example Message conveying an Alert to a PSAP 669 10. Security Considerations 671 This section discusses security considerations when SIP user agents 672 issue emergency alerts utilizing MESSAGE and CAP. Location specific 673 threats are not unique to this document and are discussed in 674 [RFC7378] and [RFC6442]. 676 The ECRIT emergency services architecture [RFC6443] considers classic 677 individual-to-authority emergency calling where the identity of the 678 emergency caller does not play a role at the time of the call 679 establishment itself, i.e., a response to the emergency call does not 680 depend on the identity of the caller. In the case of emergency 681 alerts generated by devices such as sensors, the processing may be 682 different in order to reduce the number of falsely generated 683 emergency alerts. Alerts may get triggered based on certain sensor 684 input that may have been caused by factors other than the actual 685 occurrence of an alert relevant event. For example, a sensor may 686 simply be malfunctioning. For this reason, not all alert messages 687 are directly sent to a PSAP, but rather may be pre-processed by a 688 separate entity, potentially under supervision by a human, to filter 689 alerts and potentially correlate received alerts with others to 690 obtain a larger picture of the ongoing situation. 692 In any case, for alerts initiated by sensors, the identity may play 693 an important role in deciding whether to accept or ignore an incoming 694 alert message. With the scenario shown in Figure 1 it is very likely 695 that only authorized sensor input will be processed. For this 696 reason, it needs to be possible to refuse to accept alert messages 697 from an unknown origin. Two types of information elements can be 698 used for this purpose: 700 1. SIP itself provides security mechanisms that allow the 701 verification of the originator's identity. These mechanisms can 702 be re-used, such as P-Asserted-Identity [RFC3325] or SIP Identity 703 [RFC4474]. The latter provides a cryptographic assurance while 704 the former relies on a chain of trust model. 706 2. CAP provides additional security mechanisms and the ability to 707 carry further information about the sender's identity. 708 Section 3.3.2.1 of [cap] specifies the signing algorithms of CAP 709 documents. 711 In addition to the desire to perform identity-based access control, 712 the classic communication security threats need to be considered, 713 including integrity protection to prevent forgery or replay of alert 714 messages in transit. To deal with replay of alerts, a CAP document 715 contains the mandatory , , elements and an 716 optional element. Together, these elements make the CAP 717 document unique for a specific sender and provide time restrictions. 718 An entity that has already received a CAP message within the 719 indicated timeframe is able to detect a replayed message and, if the 720 content of that message is unchanged, then no additional security 721 vulnerability is created. Additionally, it is RECOMMENDED to make 722 use of SIP security mechanisms, such as SIP Identity [RFC4474], to 723 tie the CAP message to the SIP message. To provide protection of the 724 entire SIP message exchange between neighboring SIP entities, the 725 usage of TLS is MANDATORY. 727 Note that none of the security mechanism in this document protect 728 against a compromised sensor sending crafted alerts. 730 11. IANA Considerations 732 11.1. Registration of the 'application/emergencyCall.cap+xml' MIME type 734 To: ietf-types@iana.org 736 Subject: Registration of MIME media type application/ 737 emergencyCall.cap+xml 739 MIME media type name: application 741 MIME subtype name: cap+xml 743 Required parameters: (none) 745 Optional parameters: charset; Indicates the character encoding of 746 enclosed XML. Default is UTF-8 [RFC3629]. 748 Encoding considerations: Uses XML, which can employ 8-bit 749 characters, depending on the character encoding used. See RFC 750 3023 [RFC3023], Section 3.2. 752 Security considerations: This content type is designed to carry 753 payloads of the Common Alerting Protocol (CAP). RFC XXX [Replace 754 by the RFC number of this specification] discusses security 755 considerations for this. 757 Interoperability considerations: This content type provides a way to 758 convey CAP payloads. 760 Published specification: RFC XXX [Replace by the RFC number of this 761 specification]. 763 Applications which use this media type: Applications that convey 764 alerts and warnings according to the CAP standard. 766 Additional information: OASIS has published the Common Alerting 767 Protocol at http://www.oasis-open.org/committees/ 768 documents.php&wg_abbrev=emergency 770 Person and email address to contact for further information: Hannes 771 Tschofenig, hannes.tschofenig@gmx.net 773 Intended usage: Limited use 775 Author/Change controller: IETF ECRIT working group 777 Other information: This media type is a specialization of 778 application/xml RFC 3023 [RFC3023], and many of the considerations 779 described there also apply to application/cap+xml. 781 11.2. IANA Registration of 'cap' Additional Data Block 783 This document registers a new block type in the sub-registry called 784 'Additional Data Blocks' defined in [I-D.ietf-ecrit-additional-data]. 785 The token is "cap" and the reference is this document. 787 11.3. IANA Registration for 425 Response Code 789 In the SIP Response Codes registry, the following is added 791 Reference: RFC-XXXX (i.e., this document) 793 Response code: 425 (recommended number to assign) 795 Default reason phrase: Bad Alert Message 797 Registry: 798 Response Code Reference 799 ------------------------------------------ --------- 800 Request Failure 4xx 801 425 Bad Alert Message [this doc] 803 This SIP Response code is defined in Section 5. 805 11.4. IANA Registration of New AlertMsg-Error Header Field 807 The SIP AlertMsg-error header field is created by this document, with 808 its definition and rules in Section 5, to be added to the IANA 809 Session Initiation Protocol (SIP) Parameters registry with two 810 actions: 812 1. Update the Header Fields registry with 814 Registry: 815 Header Name compact Reference 816 ----------------- ------- --------- 817 AlertMsg-Error [this doc] 819 2. In the portion titled "Header Field Parameters and Parameter 820 Values", add 822 Predefined 823 Header Field Parameter Name Values Reference 824 ----------------- ------------------- ---------- --------- 825 AlertMsg-Error code yes [this doc] 827 11.5. IANA Registration for the SIP AlertMsg-Error Codes 829 This document creates a new registry for SIP, called "AlertMsg-Error 830 Codes". AlertMsg-Error codes provide reasons for an error discovered 831 by a recipient, categorized by the action to be taken by the error 832 recipient. The initial values for this registry are shown below. 834 Registry Name: AlertMsg-Error Codes 836 Reference: [this doc] 838 Registration Procedures: Specification Required 839 Code Default Reason Phrase Reference 840 ---- --------------------------------------------------- --------- 841 100 "Cannot Process the Alert Payload" [this doc] 843 101 "Alert Payload was not present or could not be found" [this doc] 845 102 "Not enough information to determine 846 the purpose of the alert" [this doc] 848 103 "Alert Payload was corrupted" [this doc] 850 Details of these error codes are in Section 5. 852 12. Acknowledgments 854 The authors would like to thank the participants of the Early Warning 855 adhoc meeting at IETF#69 for their feedback. Additionally, we would 856 like to thank the members of the NENA Long Term Direction Working 857 Group for their feedback. 859 Additionally, we would like to thank Martin Thomson, James 860 Winterbottom, Shida Schubert, Bernard Aboba, and Marc Linsner for 861 their review comments. 863 13. References 865 13.1. Normative References 867 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 868 Requirement Levels", March 1997. 870 [cap] Jones, E. and A. Botterell, "Common Alerting Protocol v. 871 1.1", October 2005. 873 [RFC2392] Levinson, E., "Content-ID and Message-ID Uniform Resource 874 Locators", RFC 2392, DOI 10.17487/RFC2392, August 1998, 875 . 877 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 878 A., Peterson, J., Sparks, R., Handley, M., and E. 879 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 880 DOI 10.17487/RFC3261, June 2002, 881 . 883 [RFC3428] Campbell, B., Ed., Rosenberg, J., Schulzrinne, H., 884 Huitema, C., and D. Gurle, "Session Initiation Protocol 885 (SIP) Extension for Instant Messaging", RFC 3428, 886 DOI 10.17487/RFC3428, December 2002, 887 . 889 [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax 890 Specifications: ABNF", STD 68, RFC 5234, 891 DOI 10.17487/RFC5234, January 2008, 892 . 894 [RFC3023] Murata, M., St. Laurent, S., and D. Kohn, "XML Media 895 Types", RFC 3023, DOI 10.17487/RFC3023, January 2001, 896 . 898 [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 899 10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November 900 2003, . 902 [RFC6442] Polk, J., Rosen, B., and J. Peterson, "Location Conveyance 903 for the Session Initiation Protocol", RFC 6442, 904 DOI 10.17487/RFC6442, December 2011, 905 . 907 [RFC6881] Rosen, B. and J. Polk, "Best Current Practice for 908 Communications Services in Support of Emergency Calling", 909 BCP 181, RFC 6881, DOI 10.17487/RFC6881, March 2013, 910 . 912 [I-D.ietf-ecrit-additional-data] 913 Gellens, R., Rosen, B., Tschofenig, H., Marshall, R., and 914 J. Winterbottom, "Additional Data Related to an Emergency 915 Call", draft-ietf-ecrit-additional-data-37 (work in 916 progress), October 2015. 918 [I-D.rosen-ecrit-addldata-subnot] 919 Rosen, B., "Updating Additional Data related to an 920 Emergency Call using Subscribe/ Notify", draft-rosen- 921 ecrit-addldata-subnot-01 (work in progress), November 922 2013. 924 13.2. Informative References 926 [RFC7378] Tschofenig, H., Schulzrinne, H., and B. Aboba, Ed., 927 "Trustworthy Location", RFC 7378, DOI 10.17487/RFC7378, 928 December 2014, . 930 [RFC4474] Peterson, J. and C. Jennings, "Enhancements for 931 Authenticated Identity Management in the Session 932 Initiation Protocol (SIP)", RFC 4474, 933 DOI 10.17487/RFC4474, August 2006, 934 . 936 [RFC3325] Jennings, C., Peterson, J., and M. Watson, "Private 937 Extensions to the Session Initiation Protocol (SIP) for 938 Asserted Identity within Trusted Networks", RFC 3325, 939 DOI 10.17487/RFC3325, November 2002, 940 . 942 [RFC6443] Rosen, B., Schulzrinne, H., Polk, J., and A. Newton, 943 "Framework for Emergency Calling Using Internet 944 Multimedia", RFC 6443, DOI 10.17487/RFC6443, December 945 2011, . 947 Authors' Addresses 949 Brian Rosen 950 NeuStar, Inc. 951 470 Conrad Dr 952 Mars, PA 16046 953 US 955 Email: br@brianrosen.net 957 Henning Schulzrinne 958 Columbia University 959 Department of Computer Science 960 450 Computer Science Building 961 New York, NY 10027 962 US 964 Phone: +1 212 939 7004 965 Email: hgs+ecrit@cs.columbia.edu 966 URI: http://www.cs.columbia.edu 968 Hannes Tschofenig 969 ARM Limited 970 Austria 972 Email: Hannes.Tschofenig@gmx.net 973 URI: http://www.tschofenig.priv.at 974 Randall Gellens 976 Email: rg+ietf@randy.pensive.org