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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references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 3023 (Obsoleted by RFC 7303) == Outdated reference: A later version (-38) exists of draft-ietf-ecrit-additional-data-22 == Outdated reference: A later version (-14) exists of draft-ietf-ecrit-trustworthy-location-13 -- Obsolete informational reference (is this intentional?): RFC 4474 (Obsoleted by RFC 8224) Summary: 1 error (**), 0 flaws (~~), 4 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: January 25, 2015 Columbia U. 6 H. Tschofenig 7 Nokia Siemens Networks 8 July 24, 2014 10 Data-Only Emergency Calls 11 draft-ietf-ecrit-data-only-ea-08.txt 13 Abstract 15 RFC 6443 'Framework for Emergency Calling Using Internet Multimedia' 16 describes how devices use the Internet to place emergency calls and 17 how Public Safety Answering Points (PSAPs) can handle Internet 18 multimedia emergency calls natively. The exchange of multimedia 19 traffic typically involves a SIP session establishment starting with 20 a SIP INVITE that negotiates various parameters for that session. 22 In some cases, however, the transmission of application data is 23 everything that is needed. Examples of such environments include a 24 temperature sensors issuing alerts, or vehicles sending crash data. 25 Often these alerts are conveyed as one-shot data transmissions. 26 These type of interactions are called 'data-only emergency calls'. 27 This document describes a container for the data based on the Common 28 Alerting Protocol (CAP) and its transmission using the SIP MESSAGE 29 transaction. 31 Status of This Memo 33 This Internet-Draft is submitted in full conformance with the 34 provisions of BCP 78 and BCP 79. 36 Internet-Drafts are working documents of the Internet Engineering 37 Task Force (IETF). Note that other groups may also distribute 38 working documents as Internet-Drafts. The list of current Internet- 39 Drafts is at http://datatracker.ietf.org/drafts/current/. 41 Internet-Drafts are draft documents valid for a maximum of six months 42 and may be updated, replaced, or obsoleted by other documents at any 43 time. It is inappropriate to use Internet-Drafts as reference 44 material or to cite them other than as "work in progress." 46 This Internet-Draft will expire on January 25, 2015. 48 Copyright Notice 50 Copyright (c) 2014 IETF Trust and the persons identified as the 51 document authors. All rights reserved. 53 This document is subject to BCP 78 and the IETF Trust's Legal 54 Provisions Relating to IETF Documents 55 (http://trustee.ietf.org/license-info) in effect on the date of 56 publication of this document. Please review these documents 57 carefully, as they describe your rights and restrictions with respect 58 to this document. Code Components extracted from this document must 59 include Simplified BSD License text as described in Section 4.e of 60 the Trust Legal Provisions and are provided without warranty as 61 described in the Simplified BSD License. 63 Table of Contents 65 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 66 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 67 3. Architectural Overview . . . . . . . . . . . . . . . . . . . 4 68 4. Protocol Specification . . . . . . . . . . . . . . . . . . . 6 69 4.1. CAP Transport . . . . . . . . . . . . . . . . . . . . . . 6 70 4.2. Profiling of the CAP Document Content . . . . . . . . . . 7 71 4.3. Sending a Data-Only Emergency Call . . . . . . . . . . . 8 72 5. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 8 73 5.1. 425 (Bad Alert Message) Response Code . . . . . . . . . . 9 74 5.2. The AlertMsg-Error Header Field . . . . . . . . . . . . . 9 75 6. Updates to the CAP Message . . . . . . . . . . . . . . . . . 11 76 7. Call Backs . . . . . . . . . . . . . . . . . . . . . . . . . 11 77 8. Handling Large Amounts of Data . . . . . . . . . . . . . . . 11 78 9. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 79 10. Security Considerations . . . . . . . . . . . . . . . . . . . 15 80 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 81 11.1. Registration of the 'application/emergencyCall.cap+xml' 82 MIME type . . . . . . . . . . . . . . . . . . . . . . . 17 83 11.2. IANA Registration of Additional Data Block . . . . . . . 18 84 11.3. IANA Registration for 425 Response Code . . . . . . . . 18 85 11.4. IANA Registration of New AlertMsg-Error Header Field . . 19 86 11.5. IANA Registration for the SIP AlertMsg-Error Codes . . . 19 87 12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 20 88 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 20 89 13.1. Normative References . . . . . . . . . . . . . . . . . . 20 90 13.2. Informative References . . . . . . . . . . . . . . . . . 21 91 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22 93 1. Introduction 95 RFC 6443 [RFC6443] describes how devices use the Internet to place 96 emergency calls and how Public Safety Answering Points (PSAPs) can 97 handle Internet multimedia emergency calls natively. The exchange of 98 multimedia traffic typically involves a SIP session establishment 99 starting with a SIP INVITE that negotiates various parameters for 100 that session. 102 In some cases, however, there is only application data to be conveyed 103 from the end devices to a PSAP or some other intermediary. Examples 104 of such environments includes sensors issuing alerts, or vehicles 105 sending crash data. These messages may be one-shot alerts to 106 emergency authorities and do not require establishment of a session. 107 These type of interactions are called 'data-only emergency calls'. 108 In this document, we use the term "call" so that similarities between 109 full sessions with interactive media can be exploited. 111 Data-only emergency calls are similar to regular emergency calls in 112 the sense that they require the emergency indications, emergency call 113 routing functionality and may even have the same location 114 requirements. However, the communication interaction will not lead 115 to the exchange of interactive media, that is, Real-Time Protocol 116 packets, such as voice, video data or real-time text. 118 The Common Alerting Protocol (CAP) [cap] is a document format for 119 exchanging emergency alerts and public warnings. CAP is mainly used 120 for conveying alerts and warnings between authorities and from 121 authorities to citizen/individuals. This document is concerned with 122 citizen to authority "alerts", where the alert is sent without any 123 interactive media. 125 This document describes a method of including a CAP message in a SIP 126 transaction, either by value (CAP message is in the body of the 127 message, using a CID) or by reference (A URI is included in the 128 message, which when dereferenced returns the CAP message) by defining 129 it as a block of "additional data" as defined in 130 [I-D.ietf-ecrit-additional-data]. The additional data mechanism is 131 also used to send alert specific data beyond that available in the 132 CAP message. This document also describes how a SIP MESSAGE 133 [RFC3428] transaction can be used to send a data-only call. 135 2. Terminology 137 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 138 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 139 document are to be interpreted as described in RFC 2119 [RFC2119]. 141 3. Architectural Overview 143 This section illustrates two envisioned usage modes; targeted and 144 location-based emergency alert routing. 146 1. Emergency alerts containing only data are targeted to a 147 intermediary recipient responsible for evaluating the next steps. 148 These steps could include: 150 1. Sending an alert containing only data toward a Public Safety 151 Answering Point (PSAP); 153 2. Establishing a third-party initiated emergency call towards a 154 PSAP that could include audio, video, and data. 156 2. Emergency alerts targeted to a Service URN used for IP-based 157 emergency calls where the recipient is not known to the 158 originator. In this scenario, the alert may contain only data 159 (e.g., a CAP, Geolocation header and one or more Call-Info 160 headers containing Additional Data 161 [I-D.ietf-ecrit-additional-data] in a SIP MESSAGE). 163 Figure 1 shows a deployment variant where a sensor, is pre-configured 164 (using techniques outside the scope of this document) to issue an 165 alert to an aggregator that processes these messages and performs 166 whatever steps are necessary to appropriately react on the alert. 167 For example, a security firm may use different sensor inputs to 168 dispatch their security staff to a building they protect or to 169 initiate a third-party emergency call. 171 +------------+ +------------+ 172 | Sensor | | Aggregator | 173 | | | | 174 +---+--------+ +------+-----+ 175 | | 176 Sensors | 177 trigger | 178 emergency | 179 alert | 180 | MESSAGE with CAP | 181 |----------------------------->| 182 | | 183 | Aggregator 184 | processes 185 | emergency 186 | alert 187 | 200 (OK) | 188 |<-----------------------------| 189 | | 190 | | 192 Figure 1: Targeted Emergency Alert Routing 194 In Figure 2 a scenario is shown whereby the alert is routed using 195 location information and the Service URN. An emergency services 196 routing proxy (ESRP) may use LoST to determine the next hop proxy to 197 route the alert message to. A possible receiver is a PSAP and the 198 recipient of the alert may be call taker. In the generic case, there 199 is very likely no prior relationship between the originator and the 200 receiver, e.g. PSAP. A PSAP, for example, is likely to receive and 201 accept alerts from entities it cannot authorize. This scenario 202 corresponds more to the classical emergency services use case and the 203 description in [RFC6881] is applicable. In this use case, the only 204 difference between an emergency call, and an emergency data-only call 205 is that the former uses INVITE, creates a session and negotiates one 206 or more media streams, while the latter uses MESSAGE, does not create 207 a session and does not have media. 209 +-----------+ +----------+ 210 +--------+ | ESRP | | PSAP | 211 | Sensor | | | | | 212 +---+----+ +---+-------+ +---+------+ 213 | | | 214 Sensors | | 215 trigger | | 216 emergency | | 217 alert | | 218 | | | 219 | | | 220 | MESSAGE with CAP | | 221 | (including Service URN, | 222 | such as urn:service:sos) | 223 |------------------->| | 224 | | | 225 | ESRP performs | 226 | emergency alert | 227 | routing | 228 | | MESSAGE with CAP | 229 | | (including identity info) | 230 | |----------------------------->| 231 | | | 232 | | PSAP 233 | | processes 234 | | emergency 235 | | alert 236 | | 200 (OK) | 237 | |<-----------------------------| 238 | | | 239 | 200 (OK) | | 240 |<-------------------| | 241 | | | 242 | | | 244 Figure 2: Location-Based Emergency Alert Routing 246 4. Protocol Specification 248 4.1. CAP Transport 250 A CAP message may be sent on the initial message of any SIP 251 transaction. However, this document only describes specific behavior 252 when used with a SIP INVITE that would accompany a normal emergency 253 call and a SIP MESSAGE transaction for a one-shot, data-only 254 emergency call. Behavior with other transactions is not defined. 256 The CAP message included in a SIP message as an additional-data block 257 [I-D.ietf-ecrit-additional-data]. Accordingly, it is introduced to 258 the SIP message with a Call-Info header with a purpose of 259 "emergencyCall.cap". The header may contain a URI that is used by 260 the recipient (or in some cases, an intermediary) to obtain the CAP 261 message. Alternative, the Call-Info header may contain a Content 262 Indirect url [RFC2392] and the CAP message included in the body of 263 the message. In either case, the CAP message is located in a MIME 264 block. The MIME type is set to 'application/emergencyCall.cap+xml'. 266 If the server does not support the functionality required to fulfill 267 the request then a 501 Not Implemented MUST be returned as specified 268 in RFC 3261 [RFC3261]. This is the appropriate response when a UAS 269 does not recognize the request method and is not capable of 270 supporting it for any user. 272 The 415 Unsupported Media Type error MUST be returned as specified in 273 RFC 3261 [RFC3261] if the server is refusing to service the request 274 because the message body of the request is in a format not supported 275 by the server for the requested method. The server MUST return a 276 list of acceptable formats using the Accept, Accept-Encoding, or 277 Accept-Language header field, depending on the specific problem with 278 the content. 280 4.2. Profiling of the CAP Document Content 282 The usage of CAP MUST conform to the specification provided with 283 [cap]. For the usage with SIP the following additional requirements 284 are imposed: 286 sender: A few sub-categories for putting a value in the 287 element have to be considered: 289 Originator is a SIP entity, Author indication irrelevant: When 290 the alert was created by a SIP-based originator and it is not 291 useful to be explicit about the author of the alert then the 292 element MUST be populated with the SIP URI of the user 293 agent. 295 Originator is a non-SIP entity, Author indication irrelevant: In 296 case that the alert was created by a non-SIP based entity and 297 the identity of this original sender wants to be preserved then 298 this identity MUST be placed into the element. In 299 this category the it is not useful to be explicit about the 300 author of the alert. The specific type of identity being used 301 will depends on the technology being used by the original 302 originator. 304 Author indication relevant: In case the author is different from 305 the actual originator of the message and this distinction 306 should be preserved then the element MUST NOT contain 307 the SIP URI of the user agent. 309 incidents: The element MUST be present. This incident 310 identifier MUST be chosen in such a way that it is unique for a 311 given combination. Note that the 312 element is optional and may not be present. 314 scope: The value of the element MAY be set to "Private" if 315 the alert is not meant for public consumption. The 316 element is, however, not used by this specification since the 317 message routing is performed by SIP and the respective address 318 information is already available in other SIP headers. Populating 319 information twice into different parts of the message may lead to 320 inconsistency. 322 parameter: The element MAY contain additional 323 information specific to the sendor. 325 area: It is RECOMMENDED to omit this element when constructing a 326 message. In case that the CAP message already contained an 327 element then the specified location information SHOULD be copied 328 into the PIDF-LO structure of the 'geolocation' header. 330 4.3. Sending a Data-Only Emergency Call 332 A data-only emergency call is sent using a SIP MESSAGE transaction 333 with a CAP URI or body as described above in a manner similar to how 334 an emergency call with interactive media is sent, as described in 335 [RFC6881]. The MESSAGE transaction does not create a session or send 336 media, but otherwise, the header content of the transaction, routing, 337 and processing of data-only calls are the same as those of other 338 emergency calls. 340 5. Error Handling 342 This section defines a new error response code and a header field for 343 additional information. 345 5.1. 425 (Bad Alert Message) Response Code 347 This SIP extension creates a new location-specific response code, 348 defined as follows, 350 425 (Bad Alert Message) 352 The 425 response code is a rejection of the request due to its 353 included alert content, indicating that it was malformed or not 354 satisfactory for the recipient's purpose. 356 A SIP intermediary can also reject an alert it receives from a UA 357 when it understands that the provided alert is malformed. 359 Section 5.2 describes an AlertMsg-Error header field with more 360 details about what was wrong with the alert message in the request. 361 This header field MUST be included in the 425 response. 363 It is only appropriate to generate a 425 response when the responding 364 entity has no other information in the request that are usable by the 365 responder. 367 A 425 response code MUST NOT be sent in response to a request that 368 lacks an alert message entirely, as the user agent in that case may 369 not support this extension at all. 371 A 425 response is a final response within a transaction, and MUST NOT 372 terminate an existing dialog. 374 5.2. The AlertMsg-Error Header Field 376 The AlertMsg-Error header provides additional information about what 377 was wrong with the original request. In some cases the provided 378 information will be used for debugging purposes. 380 The AlertMsg-Error header field has the following ABNF [RFC5234]: 382 message-header /= AlertMsg-Error 383 ; (message-header from 3261) 384 AlertMsg-Error = "AlertMsg-Error" HCOLON 385 ErrorValue 386 ErrorValue = error-code 387 *(SEMI error-params) 388 error-code = 1*3DIGIT 389 error-params = error-code-text 390 / generic-param ; from RFC3261 391 error-code-text = "code" EQUAL quoted-string ; from RFC3261 393 HCOLON, SEMI, and EQUAL are defined in RFC3261 [RFC3261]. DIGIT is 394 defined in RFC5234 [RFC5234]. 396 The AlertMsg-Error header field MUST contain only one ErrorValue to 397 indicate what was wrong with the alert payload the recipient 398 determined was bad. 400 The ErrorValue contains a 3-digit error code indicating what was 401 wrong with the alert in the request. This error code has a 402 corresponding quoted error text string that is human understandable. 403 The text string are OPTIONAL, but RECOMMENDED for human readability, 404 similar to the string phrase used for SIP response codes. That said, 405 the strings are complete enough for rendering to the user, if so 406 desired. The strings in this document are recommendations, and are 407 not standardized - meaning an operator can change the strings - but 408 MUST NOT change the meaning of the error code. Similar to how RFC 409 3261 specifies, there MUST NOT be more than one string per error 410 code. 412 The AlertMsg-Error header field MAY be included in any response as an 413 alert message was in the request part of the same transaction. For 414 example, a UA includes an alert in an MESSAGE to a PSAP. The PSAP 415 can accept this MESSAGE, thus creating a dialog, even though his UA 416 determined the alert message contained in the MESSAGE was bad. The 417 PSAP merely includes an AlertMsg-Error header value in the 200 OK to 418 the MESSAGE informing the UA that the MESSAGE was accepted but the 419 alert provided was bad. 421 If, on the other hand, the PSAP cannot accept the transaction without 422 a suitable alert message, a 425 response is sent. 424 A SIP intermediary that requires the UA's alert message in order to 425 properly process the transaction may also sends a 425 with a 426 AlertMsg-Error code. 428 This document defines an initial list of error code ranges for any 429 SIP response, including provisional responses (other than 100 Trying) 430 and the new 425 response. There MUST be no more than one AlertMsg- 431 Error code in a SIP response. 433 AlertMsg-Error: 100 ; code="Cannot Process the Alert Payload" 435 AlertMsg-Error: 101 ; code="Alert Payload was not present or could 436 not be found" 438 AlertMsg-Error: 102 ; code="Not enough information to determine the 439 purpose of the alert" 440 AlertMsg-Error: 103 ; code="Alert Payload was corrupted" 442 Additionally, if an entity cannot or chooses not to process the alert 443 message from a SIP request, a 500 (Server Internal Error) SHOULD be 444 used with or without a configurable Retry-After header field. 446 6. Updates to the CAP Message 448 If the sender anticipates that the content of the CAP message may 449 need to be updated during the lifecycle of the event referred to in 450 the message, it may include an update block as defined in 451 [I-D.rosen-ecrit-addldata-subnot]. 453 7. Call Backs 455 This document does not describe any method for the recipient to call 456 back the sender of the data-only call. Usually, these alerts are 457 sent by automata, and do not have any mechanism to receive calls of 458 any kind. The identifier in the From header may be useful to obtain 459 more information, but any such mechanism is not defined in this 460 document. The CAP message may contain related contact information 461 for the sender. 463 8. Handling Large Amounts of Data 465 It is not atypical for sensor to have large quantities of data that 466 they may wish to send. Including large amounts of data in a MESSAGE 467 is not advisable, because SIP entities are usually not equipped to 468 handle very large messages. In such cases, the sender SHOULD make 469 use of the by-reference mechanisms defined for Additional Data which 470 involve sending a URI in the Call-Info header and using HTTPS to 471 retrieve the data. The CAP message itself can be sent by-reference 472 using this mechanism as well as any or all of the Additional Data 473 blocks that may contain sensor-specific data. 475 9. Example 477 Figure 3 shows a CAP document indicating a BURGLARY alert issued by a 478 sensor called 'sensor1@domain.com'. The location of the sensor can 479 be obtained from the attached location information provided via the 480 'geolocation' header contained in the SIP MESSAGE structure. 481 Additionally, the sensor provided some data long with the alert 482 message using proprietary information elements only to be processed 483 by the receiver, a SIP entity acting as an aggregator. This example 484 reflects the description in Figure 1. 486 MESSAGE sip:aggregator@domain.com SIP/2.0 487 Via: SIP/2.0/TCP sensor1.domain.com;branch=z9hG4bK776sgdkse 488 Max-Forwards: 70 489 From: sip:sensor1@domain.com;tag=49583 490 To: sip:aggregator@domain.com 491 Call-ID: asd88asd77a@1.2.3.4 492 Geolocation: 493 ;routing-allowed=yes 494 Supported: geolocation 495 Accept: application/pidf+xml, application/emergencyCall.cap+xml 496 CSeq: 1 MESSAGE 497 Call-Info: cid:abcdef2@domain.com;purpose=emergencyCall.cap 498 Content-Type: multipart/mixed; boundary=boundary1 499 Content-Length: ... 501 --boundary1 503 Content-Type: application/emergencyCall.cap 504 Content-ID: 505 Content-Disposition: by-reference;handling=optional 506 508 509 S-1 510 sip:sensor1@domain.com 511 2008-11-19T14:57:00-07:00 512 Actual 513 Alert 514 Private 515 abc1234 516 517 Security 518 BURGLARY 519 Expected 520 Likely 521 Moderate 522 SENSOR 1 523 524 SENSOR-DATA-NAMESPACE1 525 123 526 527 528 SENSOR-DATA-NAMESPACE2 529 TRUE 530 531 532 534 --boundary1 535 Content-Type: application/pidf+xml 536 Content-ID: 537 Content-Disposition: by-reference;handling=optional 538 539 548 549 550 551 552 553 32.86726 -97.16054 554 555 556 557 558 false 559 560 2010-11-14T20:00:00Z 561 562 563 802.11 564 565 2010-11-04T20:57:29Z 566 567 568 --boundary1-- 570 Figure 3: Example Message conveying an Alert to an Aggregator 572 Figure 4 shows the same CAP document sent as a data-only emergency 573 call towards a PSAP. 575 MESSAGE urn:service:sos SIP/2.0 576 Via: SIP/2.0/TCP sip:aggreg.1.example.com;branch=z9hG4bK776abssa 577 Max-Forwards: 70 578 From: sip:aggregator@example.com;tag=32336 579 To: 112 580 Call-ID: asdf33443a@example.com 581 Route: sip:psap1.example.gov 582 Geolocation: 583 ;routing-allowed=yes 584 Supported: geolocation 585 Accept: application/pidf+xml, application/emergencyCall.cap+xml 586 Call-info: cid:abcdef2@domain.com;purpose=emergencyCall.cap 587 CSeq: 1 MESSAGE 588 Content-Type: multipart/mixed; boundary=boundary1 589 Content-Length: ... 591 --boundary1 593 Content-Type: application/emergencyCall.cap+xml 594 Content-ID: 595 597 598 S-1 599 sip:sensor1@domain.com 600 2008-11-19T14:57:00-07:00 601 Actual 602 Alert 603 Private 604 abc1234 605 606 Security 607 BURGLARY 608 Expected 609 Likely 610 Moderate 611 SENSOR 1 612 613 SENSOR-DATA-NAMESPACE1 614 123 615 616 617 SENSOR-DATA-NAMESPACE2 618 TRUE 619 620 621 623 --boundary1 625 Content-Type: application/pidf+xml 626 Content-ID: 627 628 637 638 639 640 641 642 32.86726 -97.16054 643 644 645 646 647 false 648 649 2010-11-14T20:00:00Z 650 651 652 802.11 653 654 2010-11-04T20:57:29Z 655 656 657 --boundary1-- 659 Figure 4: Example Message conveying an Alert to a PSAP 661 10. Security Considerations 663 This section discusses security considerations when SIP user agents 664 issue emergency alerts utilizing MESSAGE and CAP. Location specific 665 threats are not unique to this document and are discussed in 666 [I-D.ietf-ecrit-trustworthy-location] and [RFC6442]. 668 The ECRIT emergency services architecture [RFC6443] considers 669 classical individual-to-authority emergency calling and the identity 670 of the emergency caller does not play a role at the time of the call 671 establishment itself, i.e., a response to the emergency call will not 672 depend on the identity of the caller. In case of emergency alerts 673 generated by devices, like sensors, the processing may be different 674 in order to reduce the number of falsely generated emergency alerts. 675 Alerts may get triggered based on certain sensor input that may have 676 been caused by other factors than the actual occurrence of an alert 677 relevant event. For example, a sensor may simply be malfunctioning. 679 For this purpose not all alert messages are directly sent to a PSAP 680 but rather may be pre-processed by a separate entity, potentially 681 under supervision by a human, to filter alerts and potentially 682 correlate received alerts with others to obtain a larger picture of 683 the ongoing situation. 685 In any case, for alerts that are initiated by sensors the identity 686 may play an important role in deciding whether to accept or ignore an 687 incoming alert message. With the scenario shown in Figure 1 it is 688 very likely that only authorized sensor input will be processed. For 689 this purpose it needs to be ensured that no alert messages from an 690 unknown origin are accepted. Two types of information elements can 691 be used for this purpose: 693 1. SIP itself provides security mechanisms that allow the 694 verification of the originator's identity. These mechanisms can 695 be re-used, such as P-Asserted-Identity [RFC3325] or SIP Identity 696 [RFC4474]. The latter provides a cryptographic assurance while 697 the former relies on a chain of trust model. 699 2. CAP provides additional security mechanisms and the ability to 700 carry additional information about the sender's identity. 701 Section 3.3.2.1 of [cap] specifies the signing algorithms of CAP 702 documents. 704 In addition to the desire to perform identity-based access control 705 the classical communication security threats need to be considered, 706 including integrity protection to prevent forgery and replay of alert 707 messages in transit. To deal with replay of alerts a CAP document 708 contains the mandatory , , elements and an 709 optional element. These attributes make the CAP document 710 unique for a specific sender and provide time restrictions. An 711 entity that has received a CAP message already within the indicated 712 timeframe is able to detect a replayed message and, if the content of 713 that message is unchanged, then no additional security vulnerability 714 is created. Additionally, it is RECOMMENDED to make use of SIP 715 security mechanisms, such as SIP Identity [RFC4474], to tie the CAP 716 message to the SIP message. To provide protection of the entire SIP 717 message exchange between neighboring SIP entities the usage of TLS is 718 mandatory. 720 Note that none of the security mechanism in this document protect 721 against a compromised sensor sending crafted alerts. 723 11. IANA Considerations 725 11.1. Registration of the 'application/emergencyCall.cap+xml' MIME type 727 To: ietf-types@iana.org 729 Subject: Registration of MIME media type application/ 730 emergencyCall.cap+xml 732 MIME media type name: application 734 MIME subtype name: cap+xml 736 Required parameters: (none) 738 Optional parameters: charset; Indicates the character encoding of 739 enclosed XML. Default is UTF-8 [RFC3629]. 741 Encoding considerations: Uses XML, which can employ 8-bit 742 characters, depending on the character encoding used. See RFC 743 3023 [RFC3023], Section 3.2. 745 Security considerations: This content type is designed to carry 746 payloads of the Common Alerting Protocol (CAP). 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@nsn.com 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 11.2. IANA Registration of Additional Data Block 774 This document registers a new block type in the sub-registry called 775 'Additional Data Blocks' defined in [I-D.ietf-ecrit-additional-data]. 776 The token is "cap" and the reference is this document. 778 11.3. IANA Registration for 425 Response Code 780 In the SIP Response Codes registry, the following is added 782 Reference: RFC-XXXX (i.e., this document) 784 Response code: 425 (recommended number to assign) 786 Default reason phrase: Bad Alert Message 788 Registry: 789 Response Code Reference 790 ------------------------------------------ --------- 791 Request Failure 4xx 792 425 Bad Alert Message [this doc] 794 This SIP Response code is defined in Section 5. 796 11.4. IANA Registration of New AlertMsg-Error Header Field 798 The SIP AlertMsg-error header field is created by this document, with 799 its definition and rules in Section 5, to be added to the IANA sip- 800 parameters registry with two actions: 802 1. Update the Header Fields registry with 804 Registry: 805 Header Name compact Reference 806 ----------------- ------- --------- 807 AlertMsg-Error [this doc] 809 2. In the portion titled "Header Field Parameters and Parameter 810 Values", add 812 Predefined 813 Header Field Parameter Name Values Reference 814 ----------------- ------------------- ---------- --------- 815 AlertMsg-Error code yes [this doc] 817 11.5. IANA Registration for the SIP AlertMsg-Error Codes 819 This document creates a new registry for SIP, called "AlertMsg-Error 820 Codes". AlertMsg-Error codes provide reason for the error discovered 821 by recipients, categorized by action to be taken by error recipient. 822 The initial values for this registry are shown below. 824 Registry Name: AlertMsg-Error Codes 826 Reference: [this doc] 828 Registration Procedures: Specification Required 829 Code Default Reason Phrase Reference 830 ---- --------------------------------------------------- --------- 831 100 "Cannot Process the Alert Payload" [this doc] 833 101 "Alert Payload was not present or could not be found" [this doc] 835 102 "Not enough information to determine 836 the purpose of the alert" [this doc] 838 103 "Alert Payload was corrupted" [this doc] 840 Details of these error codes are in Section 5. 842 12. Acknowledgments 844 The authors would like to thank the participants of the Early Warning 845 adhoc meeting at IETF#69 for their feedback. Additionally, we would 846 like to thank the members of the NENA Long Term Direction Working 847 Group for their feedback. 849 Additionally, we would like to thank Martin Thomson, James 850 Winterbottom, Shida Schubert, Bernard Aboba, and Marc Linsner for 851 their review comments. 853 13. References 855 13.1. Normative References 857 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 858 Requirement Levels", March 1997. 860 [cap] Jones, E. and A. Botterell, "Common Alerting Protocol v. 861 1.1", October 2005. 863 [RFC2392] Levinson, E., "Content-ID and Message-ID Uniform Resource 864 Locators", RFC 2392, August 1998. 866 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 867 A., Peterson, J., Sparks, R., Handley, M., and E. 868 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 869 June 2002. 871 [RFC3428] Campbell, B., Rosenberg, J., Schulzrinne, H., Huitema, C., 872 and D. Gurle, "Session Initiation Protocol (SIP) Extension 873 for Instant Messaging", RFC 3428, December 2002. 875 [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax 876 Specifications: ABNF", STD 68, RFC 5234, January 2008. 878 [RFC3023] Murata, M., St. Laurent, S., and D. Kohn, "XML Media 879 Types", RFC 3023, January 2001. 881 [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 882 10646", STD 63, RFC 3629, November 2003. 884 [RFC6442] Polk, J., Rosen, B., and J. Peterson, "Location Conveyance 885 for the Session Initiation Protocol", RFC 6442, December 886 2011. 888 [RFC6881] Rosen, B. and J. Polk, "Best Current Practice for 889 Communications Services in Support of Emergency Calling", 890 BCP 181, RFC 6881, March 2013. 892 [I-D.ietf-ecrit-additional-data] 893 Rosen, B., Tschofenig, H., Marshall, R., Randy, R., and J. 894 Winterbottom, "Additional Data related to an Emergency 895 Call", draft-ietf-ecrit-additional-data-22 (work in 896 progress), April 2014. 898 [I-D.rosen-ecrit-addldata-subnot] 899 Rosen, B., "Updating Additional Data related to an 900 Emergency Call using Subscribe/ Notify", draft-rosen- 901 ecrit-addldata-subnot-01 (work in progress), November 902 2013. 904 13.2. Informative References 906 [I-D.ietf-ecrit-trustworthy-location] 907 Tschofenig, H., Schulzrinne, H., and B. Aboba, 908 "Trustworthy Location", draft-ietf-ecrit-trustworthy- 909 location-13 (work in progress), June 2014. 911 [RFC4474] Peterson, J. and C. Jennings, "Enhancements for 912 Authenticated Identity Management in the Session 913 Initiation Protocol (SIP)", RFC 4474, August 2006. 915 [RFC3325] Jennings, C., Peterson, J., and M. Watson, "Private 916 Extensions to the Session Initiation Protocol (SIP) for 917 Asserted Identity within Trusted Networks", RFC 3325, 918 November 2002. 920 [RFC6443] Rosen, B., Schulzrinne, H., Polk, J., and A. Newton, 921 "Framework for Emergency Calling Using Internet 922 Multimedia", RFC 6443, December 2011. 924 Authors' Addresses 926 Brian Rosen 927 NeuStar, Inc. 928 470 Conrad Dr 929 Mars, PA 16046 930 US 932 Email: br@brianrosen.net 934 Henning Schulzrinne 935 Columbia University 936 Department of Computer Science 937 450 Computer Science Building 938 New York, NY 10027 939 US 941 Phone: +1 212 939 7004 942 Email: hgs+ecrit@cs.columbia.edu 943 URI: http://www.cs.columbia.edu 945 Hannes Tschofenig 946 Nokia Siemens Networks 947 Linnoitustie 6 948 Espoo 02600 949 Finland 951 Phone: +358 (50) 4871445 952 Email: Hannes.Tschofenig@gmx.net 953 URI: http://www.tschofenig.priv.at