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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references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 3023 (Obsoleted by RFC 7303) == Outdated reference: A later version (-38) exists of draft-ietf-ecrit-additional-data-33 -- Obsolete informational reference (is this intentional?): RFC 4474 (Obsoleted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: February 12, 2016 Columbia U. 6 H. Tschofenig 7 August 11, 2015 9 Data-Only Emergency Calls 10 draft-ietf-ecrit-data-only-ea-10.txt 12 Abstract 14 RFC 6443 'Framework for Emergency Calling Using Internet Multimedia' 15 describes how devices use the Internet to place emergency calls and 16 how Public Safety Answering Points (PSAPs) can handle Internet 17 multimedia emergency calls natively. The exchange of multimedia 18 traffic typically involves a SIP session establishment starting with 19 a SIP INVITE that negotiates various parameters for that session. 21 In some cases, however, the transmission of application data is 22 everything that is needed. Examples of such environments include a 23 temperature sensors issuing alerts, or vehicles sending crash data. 24 Often these alerts are conveyed as one-shot data transmissions. 25 These type of interactions are called 'data-only emergency calls'. 26 This document describes a container for the data based on the Common 27 Alerting Protocol (CAP) and its transmission using the SIP MESSAGE 28 transaction. 30 Status of This Memo 32 This Internet-Draft is submitted in full conformance with the 33 provisions of BCP 78 and BCP 79. 35 Internet-Drafts are working documents of the Internet Engineering 36 Task Force (IETF). Note that other groups may also distribute 37 working documents as Internet-Drafts. The list of current Internet- 38 Drafts is at http://datatracker.ietf.org/drafts/current/. 40 Internet-Drafts are draft documents valid for a maximum of six months 41 and may be updated, replaced, or obsoleted by other documents at any 42 time. It is inappropriate to use Internet-Drafts as reference 43 material or to cite them other than as "work in progress." 45 This Internet-Draft will expire on February 12, 2016. 47 Copyright Notice 49 Copyright (c) 2015 IETF Trust and the persons identified as the 50 document authors. All rights reserved. 52 This document is subject to BCP 78 and the IETF Trust's Legal 53 Provisions Relating to IETF Documents 54 (http://trustee.ietf.org/license-info) in effect on the date of 55 publication of this document. Please review these documents 56 carefully, as they describe your rights and restrictions with respect 57 to this document. Code Components extracted from this document must 58 include Simplified BSD License text as described in Section 4.e of 59 the Trust Legal Provisions and are provided without warranty as 60 described in the Simplified BSD License. 62 Table of Contents 64 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 65 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 66 3. Architectural Overview . . . . . . . . . . . . . . . . . . . 4 67 4. Protocol Specification . . . . . . . . . . . . . . . . . . . 6 68 4.1. CAP Transport . . . . . . . . . . . . . . . . . . . . . . 6 69 4.2. Profiling of the CAP Document Content . . . . . . . . . . 7 70 4.3. Sending a Data-Only Emergency Call . . . . . . . . . . . 8 71 5. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 8 72 5.1. 425 (Bad Alert Message) Response Code . . . . . . . . . . 9 73 5.2. The AlertMsg-Error Header Field . . . . . . . . . . . . . 9 74 6. Updates to the CAP Message . . . . . . . . . . . . . . . . . 11 75 7. Call Backs . . . . . . . . . . . . . . . . . . . . . . . . . 11 76 8. Handling Large Amounts of Data . . . . . . . . . . . . . . . 11 77 9. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 78 10. Security Considerations . . . . . . . . . . . . . . . . . . . 15 79 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 80 11.1. Registration of the 'application/emergencyCall.cap+xml' 81 MIME type . . . . . . . . . . . . . . . . . . . . . . . 17 82 11.2. IANA Registration of Additional Data Block . . . . . . . 18 83 11.3. IANA Registration for 425 Response Code . . . . . . . . 18 84 11.4. IANA Registration of New AlertMsg-Error Header Field . . 19 85 11.5. IANA Registration for the SIP AlertMsg-Error Codes . . . 19 86 12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 20 87 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 20 88 13.1. Normative References . . . . . . . . . . . . . . . . . . 20 89 13.2. Informative References . . . . . . . . . . . . . . . . . 21 90 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22 92 1. Introduction 94 RFC 6443 [RFC6443] describes how devices use the Internet to place 95 emergency calls and how Public Safety Answering Points (PSAPs) can 96 handle Internet multimedia emergency calls natively. The exchange of 97 multimedia traffic typically involves a SIP session establishment 98 starting with a SIP INVITE that negotiates various parameters for 99 that session. 101 In some cases, however, there is only application data to be conveyed 102 from the end devices to a PSAP or some other intermediary. Examples 103 of such environments includes sensors issuing alerts, or vehicles 104 sending crash data. These messages may be one-shot alerts to 105 emergency authorities and do not require establishment of a session. 106 These type of interactions are called 'data-only emergency calls'. 107 In this document, we use the term "call" so that similarities between 108 full sessions with interactive media can be exploited. 110 Data-only emergency calls are similar to regular emergency calls in 111 the sense that they require the emergency indications, emergency call 112 routing functionality and may even have the same location 113 requirements. However, the communication interaction will not lead 114 to the exchange of interactive media, that is, Real-Time Protocol 115 packets, such as voice, video data or real-time text. 117 The Common Alerting Protocol (CAP) [cap] is a document format for 118 exchanging emergency alerts and public warnings. CAP is mainly used 119 for conveying alerts and warnings between authorities and from 120 authorities to citizen/individuals. This document is concerned with 121 citizen to authority "alerts", where the alert is sent without any 122 interactive media. 124 This document describes a method of including a CAP message in a SIP 125 transaction, either by value (CAP message is in the body of the 126 message, using a CID) or by reference (A URI is included in the 127 message, which when dereferenced returns the CAP message) by defining 128 it as a block of "additional data" as defined in 129 [I-D.ietf-ecrit-additional-data]. The additional data mechanism is 130 also used to send alert specific data beyond that available in the 131 CAP message. This document also describes how a SIP MESSAGE 132 [RFC3428] transaction can be used to send a data-only call. 134 2. Terminology 136 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 137 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 138 document are to be interpreted as described in RFC 2119 [RFC2119]. 140 3. Architectural Overview 142 This section illustrates two envisioned usage modes; targeted and 143 location-based emergency alert routing. 145 1. Emergency alerts containing only data are targeted to a 146 intermediary recipient responsible for evaluating the next steps. 147 These steps could include: 149 1. Sending a call containing only data toward a Public Safety 150 Answering Point (PSAP); 152 2. Establishing a third-party initiated emergency call towards a 153 PSAP that could include audio, video, and data. 155 2. Emergency alerts may be targeted to a Service URN used for IP- 156 based emergency calls where the recipient is not known to the 157 originator. In this scenario, the alert may contain only data 158 (e.g., a CAP, Geolocation header and one or more Call-Info 159 headers containing Additional Data 160 [I-D.ietf-ecrit-additional-data] in a SIP MESSAGE). 162 Figure 1 shows a deployment variant where a sensor, is pre-configured 163 (using techniques outside the scope of this document) to issue an 164 alert to an aggregator that processes these messages and performs 165 whatever steps are necessary to appropriately react on the alert. 166 For example, a security firm may use different sensor inputs to 167 dispatch their security staff to a building they protect or to 168 initiate a third-party emergency call. 170 +------------+ +------------+ 171 | Sensor | | Aggregator | 172 | | | | 173 +---+--------+ +------+-----+ 174 | | 175 Sensors | 176 trigger | 177 emergency | 178 alert | 179 | MESSAGE with CAP | 180 |----------------------------->| 181 | | 182 | Aggregator 183 | processes 184 | emergency 185 | alert 186 | 200 (OK) | 187 |<-----------------------------| 188 | | 189 | | 191 Figure 1: Targeted Emergency Alert Routing 193 In Figure 2 a scenario is shown whereby the alert is routed using 194 location information and the Service URN. An emergency services 195 routing proxy (ESRP) may use LoST to determine the next hop proxy to 196 route the alert message to. A possible receiver is a PSAP and the 197 recipient of the alert may be call taker. In the generic case, there 198 is very likely no prior relationship between the originator and the 199 receiver, e.g. PSAP. A PSAP, for example, is likely to receive and 200 accept alerts from entities it cannot authorize. This scenario 201 corresponds more to the classical emergency services use case and the 202 description in [RFC6881] is applicable. In this use case, the only 203 difference between an emergency call, and an emergency data-only call 204 is that the former uses INVITE, creates a session and negotiates one 205 or more media streams, while the latter uses MESSAGE, does not create 206 a session and does not have media. 208 +-----------+ +----------+ 209 +--------+ | ESRP | | PSAP | 210 | Sensor | | | | | 211 +---+----+ +---+-------+ +---+------+ 212 | | | 213 Sensors | | 214 trigger | | 215 emergency | | 216 alert | | 217 | | | 218 | | | 219 | MESSAGE with CAP | | 220 | (including Service URN, | 221 | such as urn:service:sos) | 222 |------------------->| | 223 | | | 224 | ESRP performs | 225 | emergency alert | 226 | routing | 227 | | MESSAGE with CAP | 228 | | (including identity info) | 229 | |----------------------------->| 230 | | | 231 | | PSAP 232 | | processes 233 | | emergency 234 | | alert 235 | | 200 (OK) | 236 | |<-----------------------------| 237 | | | 238 | 200 (OK) | | 239 |<-------------------| | 240 | | | 241 | | | 243 Figure 2: Location-Based Emergency Alert Routing 245 4. Protocol Specification 247 4.1. CAP Transport 249 A CAP message may be sent on the initial message of any SIP 250 transaction. However, this document only describes specific behavior 251 when used with a SIP INVITE that would accompany a normal emergency 252 call and a SIP MESSAGE transaction for a one-shot, data-only 253 emergency call. Behavior with other transactions is not defined. 255 The CAP message included in a SIP message as an additional-data block 256 [I-D.ietf-ecrit-additional-data]. Accordingly, it is introduced to 257 the SIP message with a Call-Info header with a purpose of 258 "emergencyCall.cap". The header may contain a URI that is used by 259 the recipient (or in some cases, an intermediary) to obtain the CAP 260 message. Alternative, the Call-Info header may contain a Content 261 Indirect url [RFC2392] and the CAP message included in the body of 262 the message. In either case, the CAP message is located in a MIME 263 block. The MIME type is set to 'application/emergencyCall.cap+xml'. 265 If the server does not support the functionality required to fulfill 266 the request then a 501 Not Implemented MUST be returned as specified 267 in RFC 3261 [RFC3261]. This is the appropriate response when a UAS 268 does not recognize the request method and is not capable of 269 supporting it for any user. 271 The 415 Unsupported Media Type error MUST be returned as specified in 272 RFC 3261 [RFC3261] if the server is refusing to service the request 273 because the message body of the request is in a format not supported 274 by the server for the requested method. The server MUST return a 275 list of acceptable formats using the Accept, Accept-Encoding, or 276 Accept-Language header field, depending on the specific problem with 277 the content. 279 4.2. Profiling of the CAP Document Content 281 The usage of CAP MUST conform to the specification provided with 282 [cap]. For the usage with SIP the following additional requirements 283 are imposed: 285 sender: A few sub-categories for putting a value in the 286 element have to be considered: 288 Originator is a SIP entity, Author indication irrelevant: When 289 the alert was created by a SIP-based originator and it is not 290 useful to be explicit about the author of the alert then the 291 element MUST be populated with the SIP URI of the user 292 agent. 294 Originator is a non-SIP entity, Author indication irrelevant: In 295 case that the alert was created by a non-SIP based entity and 296 the identity of this original sender wants to be preserved then 297 this identity MUST be placed into the element. In 298 this category the it is not useful to be explicit about the 299 author of the alert. The specific type of identity being used 300 will depends on the technology being used by the original 301 originator. 303 Author indication relevant: In case the author is different from 304 the actual originator of the message and this distinction 305 should be preserved then the element MUST NOT contain 306 the SIP URI of the user agent. 308 incidents: The element MUST be present. This incident 309 identifier MUST be chosen in such a way that it is unique for a 310 given combination. Note that the 311 element is optional and may not be present. 313 scope: The value of the element MAY be set to "Private" if 314 the alert is not meant for public consumption. The 315 element is, however, not used by this specification since the 316 message routing is performed by SIP and the respective address 317 information is already available in other SIP headers. Populating 318 information twice into different parts of the message may lead to 319 inconsistency. 321 parameter: The element MAY contain additional 322 information specific to the sendor. 324 area: It is RECOMMENDED to omit this element when constructing a 325 message. In case that the CAP message already contained an 326 element then the specified location information SHOULD be copied 327 into the PIDF-LO structure of the 'geolocation' header. 329 4.3. Sending a Data-Only Emergency Call 331 A data-only emergency call is sent using a SIP MESSAGE transaction 332 with a CAP URI or body as described above in a manner similar to how 333 an emergency call with interactive media is sent, as described in 334 [RFC6881]. The MESSAGE transaction does not create a session or send 335 media, but otherwise, the header content of the transaction, routing, 336 and processing of data-only calls are the same as those of other 337 emergency calls. 339 5. Error Handling 341 This section defines a new error response code and a header field for 342 additional information. 344 5.1. 425 (Bad Alert Message) Response Code 346 This SIP extension creates a new location-specific response code, 347 defined as follows, 349 425 (Bad Alert Message) 351 The 425 response code is a rejection of the request due to its 352 included alert content, indicating that it was malformed or not 353 satisfactory for the recipient's purpose. 355 A SIP intermediary can also reject an alert it receives from a UA 356 when it understands that the provided alert is malformed. 358 Section 5.2 describes an AlertMsg-Error header field with more 359 details about what was wrong with the alert message in the request. 360 This header field MUST be included in the 425 response. 362 It is only appropriate to generate a 425 response when the responding 363 entity has no other information in the request that are usable by the 364 responder. 366 A 425 response code MUST NOT be sent in response to a request that 367 lacks an alert message entirely, as the user agent in that case may 368 not support this extension at all. 370 A 425 response is a final response within a transaction, and MUST NOT 371 terminate an existing dialog. 373 5.2. The AlertMsg-Error Header Field 375 The AlertMsg-Error header provides additional information about what 376 was wrong with the original request. In some cases the provided 377 information will be used for debugging purposes. 379 The AlertMsg-Error header field has the following ABNF [RFC5234]: 381 message-header /= AlertMsg-Error 382 ; (message-header from 3261) 383 AlertMsg-Error = "AlertMsg-Error" HCOLON 384 ErrorValue 385 ErrorValue = error-code 386 *(SEMI error-params) 387 error-code = 1*3DIGIT 388 error-params = error-code-text 389 / generic-param ; from RFC3261 390 error-code-text = "code" EQUAL quoted-string ; from RFC3261 392 HCOLON, SEMI, and EQUAL are defined in RFC3261 [RFC3261]. DIGIT is 393 defined in RFC5234 [RFC5234]. 395 The AlertMsg-Error header field MUST contain only one ErrorValue to 396 indicate what was wrong with the alert payload the recipient 397 determined was bad. 399 The ErrorValue contains a 3-digit error code indicating what was 400 wrong with the alert in the request. This error code has a 401 corresponding quoted error text string that is human understandable. 402 The text string are OPTIONAL, but RECOMMENDED for human readability, 403 similar to the string phrase used for SIP response codes. That said, 404 the strings are complete enough for rendering to the user, if so 405 desired. The strings in this document are recommendations, and are 406 not standardized - meaning an operator can change the strings - but 407 MUST NOT change the meaning of the error code. Similar to how RFC 408 3261 specifies, there MUST NOT be more than one string per error 409 code. 411 The AlertMsg-Error header field MAY be included in any response as an 412 alert message was in the request part of the same transaction. For 413 example, a UA includes an alert in an MESSAGE to a PSAP. The PSAP 414 can accept this MESSAGE, thus creating a dialog, even though his UA 415 determined the alert message contained in the MESSAGE was bad. The 416 PSAP merely includes an AlertMsg-Error header value in the 200 OK to 417 the MESSAGE informing the UA that the MESSAGE was accepted but the 418 alert provided was bad. 420 If, on the other hand, the PSAP cannot accept the transaction without 421 a suitable alert message, a 425 response is sent. 423 A SIP intermediary that requires the UA's alert message in order to 424 properly process the transaction may also sends a 425 with a 425 AlertMsg-Error code. 427 This document defines an initial list of error code ranges for any 428 SIP response, including provisional responses (other than 100 Trying) 429 and the new 425 response. There MUST be no more than one AlertMsg- 430 Error code in a SIP response. 432 AlertMsg-Error: 100 ; code="Cannot Process the Alert Payload" 434 AlertMsg-Error: 101 ; code="Alert Payload was not present or could 435 not be found" 437 AlertMsg-Error: 102 ; code="Not enough information to determine the 438 purpose of the alert" 439 AlertMsg-Error: 103 ; code="Alert Payload was corrupted" 441 Additionally, if an entity cannot or chooses not to process the alert 442 message from a SIP request, a 500 (Server Internal Error) SHOULD be 443 used with or without a configurable Retry-After header field. 445 6. Updates to the CAP Message 447 If the sender anticipates that the content of the CAP message may 448 need to be updated during the lifecycle of the event referred to in 449 the message, it may include an update block as defined in 450 [I-D.rosen-ecrit-addldata-subnot]. 452 7. Call Backs 454 This document does not describe any method for the recipient to call 455 back the sender of the data-only call. Usually, these alerts are 456 sent by automata, and do not have any mechanism to receive calls of 457 any kind. The identifier in the From header may be useful to obtain 458 more information, but any such mechanism is not defined in this 459 document. The CAP message may contain related contact information 460 for the sender. 462 8. Handling Large Amounts of Data 464 It is not atypical for sensor to have large quantities of data that 465 they may wish to send. Including large amounts of data in a MESSAGE 466 is not advisable, because SIP entities are usually not equipped to 467 handle very large messages. In such cases, the sender SHOULD make 468 use of the by-reference mechanisms defined for Additional Data which 469 involve sending a URI in the Call-Info header and using HTTPS to 470 retrieve the data. The CAP message itself can be sent by-reference 471 using this mechanism as well as any or all of the Additional Data 472 blocks that may contain sensor-specific data. 474 9. Example 476 Figure 3 shows a CAP document indicating a BURGLARY alert issued by a 477 sensor called 'sensor1@domain.com'. The location of the sensor can 478 be obtained from the attached location information provided via the 479 'geolocation' header contained in the SIP MESSAGE structure. 480 Additionally, the sensor provided some data long with the alert 481 message using proprietary information elements only to be processed 482 by the receiver, a SIP entity acting as an aggregator. This example 483 reflects the description in Figure 1. 485 MESSAGE sip:aggregator@domain.com SIP/2.0 486 Via: SIP/2.0/TCP sensor1.domain.com;branch=z9hG4bK776sgdkse 487 Max-Forwards: 70 488 From: sip:sensor1@domain.com;tag=49583 489 To: sip:aggregator@domain.com 490 Call-ID: asd88asd77a@1.2.3.4 491 Geolocation: 492 ;routing-allowed=yes 493 Supported: geolocation 494 Accept: application/pidf+xml, application/emergencyCall.cap+xml 495 CSeq: 1 MESSAGE 496 Call-Info: cid:abcdef2@domain.com;purpose=emergencyCall.cap 497 Content-Type: multipart/mixed; boundary=boundary1 498 Content-Length: ... 500 --boundary1 502 Content-Type: application/emergencyCall.cap 503 Content-ID: 504 Content-Disposition: by-reference;handling=optional 505 507 508 S-1 509 sip:sensor1@domain.com 510 2008-11-19T14:57:00-07:00 511 Actual 512 Alert 513 Private 514 abc1234 515 516 Security 517 BURGLARY 518 Expected 519 Likely 520 Moderate 521 SENSOR 1 522 523 SENSOR-DATA-NAMESPACE1 524 123 525 526 527 SENSOR-DATA-NAMESPACE2 528 TRUE 529 530 531 533 --boundary1 534 Content-Type: application/pidf+xml 535 Content-ID: 536 Content-Disposition: by-reference;handling=optional 537 538 547 548 549 550 551 552 32.86726 -97.16054 553 554 555 556 557 false 558 559 2010-11-14T20:00:00Z 560 561 562 802.11 563 564 2010-11-04T20:57:29Z 565 566 567 --boundary1-- 569 Figure 3: Example Message conveying an Alert to an Aggregator 571 Figure 4 shows the same CAP document sent as a data-only emergency 572 call towards a PSAP. 574 MESSAGE urn:service:sos SIP/2.0 575 Via: SIP/2.0/TCP sip:aggreg.1.example.com;branch=z9hG4bK776abssa 576 Max-Forwards: 70 577 From: sip:aggregator@example.com;tag=32336 578 To: 112 579 Call-ID: asdf33443a@example.com 580 Route: sip:psap1.example.gov 581 Geolocation: 582 ;routing-allowed=yes 583 Supported: geolocation 584 Accept: application/pidf+xml, application/emergencyCall.cap+xml 585 Call-info: cid:abcdef2@domain.com;purpose=emergencyCall.cap 586 CSeq: 1 MESSAGE 587 Content-Type: multipart/mixed; boundary=boundary1 588 Content-Length: ... 590 --boundary1 592 Content-Type: application/emergencyCall.cap+xml 593 Content-ID: 594 596 597 S-1 598 sip:sensor1@domain.com 599 2008-11-19T14:57:00-07:00 600 Actual 601 Alert 602 Private 603 abc1234 604 605 Security 606 BURGLARY 607 Expected 608 Likely 609 Moderate 610 SENSOR 1 611 612 SENSOR-DATA-NAMESPACE1 613 123 614 615 616 SENSOR-DATA-NAMESPACE2 617 TRUE 618 619 620 622 --boundary1 624 Content-Type: application/pidf+xml 625 Content-ID: 626 627 636 637 638 639 640 641 32.86726 -97.16054 642 643 644 645 646 false 647 648 2010-11-14T20:00:00Z 649 650 651 802.11 652 653 2010-11-04T20:57:29Z 654 655 656 --boundary1-- 658 Figure 4: Example Message conveying an Alert to a PSAP 660 10. Security Considerations 662 This section discusses security considerations when SIP user agents 663 issue emergency alerts utilizing MESSAGE and CAP. Location specific 664 threats are not unique to this document and are discussed in 665 [RFC7378] and [RFC6442]. 667 The ECRIT emergency services architecture [RFC6443] considers 668 classical individual-to-authority emergency calling and the identity 669 of the emergency caller does not play a role at the time of the call 670 establishment itself, i.e., a response to the emergency call will not 671 depend on the identity of the caller. In case of emergency alerts 672 generated by devices, like sensors, the processing may be different 673 in order to reduce the number of falsely generated emergency alerts. 674 Alerts may get triggered based on certain sensor input that may have 675 been caused by other factors than the actual occurrence of an alert 676 relevant event. For example, a sensor may simply be malfunctioning. 678 For this purpose not all alert messages are directly sent to a PSAP 679 but rather may be pre-processed by a separate entity, potentially 680 under supervision by a human, to filter alerts and potentially 681 correlate received alerts with others to obtain a larger picture of 682 the ongoing situation. 684 In any case, for alerts that are initiated by sensors the identity 685 may play an important role in deciding whether to accept or ignore an 686 incoming alert message. With the scenario shown in Figure 1 it is 687 very likely that only authorized sensor input will be processed. For 688 this purpose it needs to be ensured that no alert messages from an 689 unknown origin are accepted. Two types of information elements can 690 be used for this purpose: 692 1. SIP itself provides security mechanisms that allow the 693 verification of the originator's identity. These mechanisms can 694 be re-used, such as P-Asserted-Identity [RFC3325] or SIP Identity 695 [RFC4474]. The latter provides a cryptographic assurance while 696 the former relies on a chain of trust model. 698 2. CAP provides additional security mechanisms and the ability to 699 carry additional information about the sender's identity. 700 Section 3.3.2.1 of [cap] specifies the signing algorithms of CAP 701 documents. 703 In addition to the desire to perform identity-based access control 704 the classical communication security threats need to be considered, 705 including integrity protection to prevent forgery and replay of alert 706 messages in transit. To deal with replay of alerts a CAP document 707 contains the mandatory , , elements and an 708 optional element. These attributes make the CAP document 709 unique for a specific sender and provide time restrictions. An 710 entity that has received a CAP message already within the indicated 711 timeframe is able to detect a replayed message and, if the content of 712 that message is unchanged, then no additional security vulnerability 713 is created. Additionally, it is RECOMMENDED to make use of SIP 714 security mechanisms, such as SIP Identity [RFC4474], to tie the CAP 715 message to the SIP message. To provide protection of the entire SIP 716 message exchange between neighboring SIP entities the usage of TLS is 717 mandatory. 719 Note that none of the security mechanism in this document protect 720 against a compromised sensor sending crafted alerts. 722 11. IANA Considerations 724 11.1. Registration of the 'application/emergencyCall.cap+xml' MIME type 726 To: ietf-types@iana.org 728 Subject: Registration of MIME media type application/ 729 emergencyCall.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). 747 Interoperability considerations: This content type provides a way to 748 convey CAP payloads. 750 Published specification: RFC XXX [Replace by the RFC number of this 751 specification]. 753 Applications which use this media type: Applications that convey 754 alerts and warnings according to the CAP standard. 756 Additional information: OASIS has published the Common Alerting 757 Protocol at http://www.oasis-open.org/committees/ 758 documents.php&wg_abbrev=emergency 760 Person and email address to contact for further information: Hannes 761 Tschofenig, Hannes.Tschofenig@nsn.com 763 Intended usage: Limited use 765 Author/Change controller: IETF ECRIT working group 767 Other information: This media type is a specialization of 768 application/xml RFC 3023 [RFC3023], and many of the considerations 769 described there also apply to application/cap+xml. 771 11.2. IANA Registration of Additional Data Block 773 This document registers a new block type in the sub-registry called 774 'Additional Data Blocks' defined in [I-D.ietf-ecrit-additional-data]. 775 The token is "cap" and the reference is this document. 777 11.3. IANA Registration for 425 Response Code 779 In the SIP Response Codes registry, the following is added 781 Reference: RFC-XXXX (i.e., this document) 783 Response code: 425 (recommended number to assign) 785 Default reason phrase: Bad Alert Message 787 Registry: 788 Response Code Reference 789 ------------------------------------------ --------- 790 Request Failure 4xx 791 425 Bad Alert Message [this doc] 793 This SIP Response code is defined in Section 5. 795 11.4. IANA Registration of New AlertMsg-Error Header Field 797 The SIP AlertMsg-error header field is created by this document, with 798 its definition and rules in Section 5, to be added to the IANA sip- 799 parameters registry with two actions: 801 1. Update the Header Fields registry with 803 Registry: 804 Header Name compact Reference 805 ----------------- ------- --------- 806 AlertMsg-Error [this doc] 808 2. In the portion titled "Header Field Parameters and Parameter 809 Values", add 811 Predefined 812 Header Field Parameter Name Values Reference 813 ----------------- ------------------- ---------- --------- 814 AlertMsg-Error code yes [this doc] 816 11.5. IANA Registration for the SIP AlertMsg-Error Codes 818 This document creates a new registry for SIP, called "AlertMsg-Error 819 Codes". AlertMsg-Error codes provide reason for the error discovered 820 by recipients, categorized by action to be taken by error recipient. 821 The initial values for this registry are shown below. 823 Registry Name: AlertMsg-Error Codes 825 Reference: [this doc] 827 Registration Procedures: Specification Required 828 Code Default Reason Phrase Reference 829 ---- --------------------------------------------------- --------- 830 100 "Cannot Process the Alert Payload" [this doc] 832 101 "Alert Payload was not present or could not be found" [this doc] 834 102 "Not enough information to determine 835 the purpose of the alert" [this doc] 837 103 "Alert Payload was corrupted" [this doc] 839 Details of these error codes are in Section 5. 841 12. Acknowledgments 843 The authors would like to thank the participants of the Early Warning 844 adhoc meeting at IETF#69 for their feedback. Additionally, we would 845 like to thank the members of the NENA Long Term Direction Working 846 Group for their feedback. 848 Additionally, we would like to thank Martin Thomson, James 849 Winterbottom, Shida Schubert, Bernard Aboba, and Marc Linsner for 850 their review comments. 852 13. References 854 13.1. Normative References 856 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 857 Requirement Levels", March 1997. 859 [cap] Jones, E. and A. Botterell, "Common Alerting Protocol v. 860 1.1", October 2005. 862 [RFC2392] Levinson, E., "Content-ID and Message-ID Uniform Resource 863 Locators", RFC 2392, DOI 10.17487/RFC2392, August 1998, 864 . 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 DOI 10.17487/RFC3261, June 2002, 870 . 872 [RFC3428] Campbell, B., Ed., Rosenberg, J., Schulzrinne, H., 873 Huitema, C., and D. Gurle, "Session Initiation Protocol 874 (SIP) Extension for Instant Messaging", RFC 3428, DOI 875 10.17487/RFC3428, December 2002, 876 . 878 [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax 879 Specifications: ABNF", STD 68, RFC 5234, DOI 10.17487/ 880 RFC5234, January 2008, 881 . 883 [RFC3023] Murata, M., St. Laurent, S., and D. Kohn, "XML Media 884 Types", RFC 3023, DOI 10.17487/RFC3023, January 2001, 885 . 887 [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 888 10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November 889 2003, . 891 [RFC6442] Polk, J., Rosen, B., and J. Peterson, "Location Conveyance 892 for the Session Initiation Protocol", RFC 6442, DOI 893 10.17487/RFC6442, December 2011, 894 . 896 [RFC6881] Rosen, B. and J. Polk, "Best Current Practice for 897 Communications Services in Support of Emergency Calling", 898 BCP 181, RFC 6881, DOI 10.17487/RFC6881, March 2013, 899 . 901 [I-D.ietf-ecrit-additional-data] 902 Gellens, R., Rosen, B., Tschofenig, H., Marshall, R., and 903 J. Winterbottom, "Additional Data Related to an Emergency 904 Call", draft-ietf-ecrit-additional-data-33 (work in 905 progress), July 2015. 907 [I-D.rosen-ecrit-addldata-subnot] 908 Rosen, B., "Updating Additional Data related to an 909 Emergency Call using Subscribe/ Notify", draft-rosen- 910 ecrit-addldata-subnot-01 (work in progress), November 911 2013. 913 13.2. Informative References 915 [RFC7378] Tschofenig, H., Schulzrinne, H., and B. Aboba, Ed., 916 "Trustworthy Location", RFC 7378, DOI 10.17487/RFC7378, 917 December 2014, . 919 [RFC4474] Peterson, J. and C. Jennings, "Enhancements for 920 Authenticated Identity Management in the Session 921 Initiation Protocol (SIP)", RFC 4474, DOI 10.17487/ 922 RFC4474, August 2006, 923 . 925 [RFC3325] Jennings, C., Peterson, J., and M. Watson, "Private 926 Extensions to the Session Initiation Protocol (SIP) for 927 Asserted Identity within Trusted Networks", RFC 3325, DOI 928 10.17487/RFC3325, November 2002, 929 . 931 [RFC6443] Rosen, B., Schulzrinne, H., Polk, J., and A. Newton, 932 "Framework for Emergency Calling Using Internet 933 Multimedia", RFC 6443, DOI 10.17487/RFC6443, December 934 2011, . 936 Authors' Addresses 938 Brian Rosen 939 NeuStar, Inc. 940 470 Conrad Dr 941 Mars, PA 16046 942 US 944 Email: br@brianrosen.net 946 Henning Schulzrinne 947 Columbia University 948 Department of Computer Science 949 450 Computer Science Building 950 New York, NY 10027 951 US 953 Phone: +1 212 939 7004 954 Email: hgs+ecrit@cs.columbia.edu 955 URI: http://www.cs.columbia.edu 957 Hannes Tschofenig 958 Hall in Tirol 6060 959 Austria 961 Email: Hannes.tschofenig@gmx.net 962 URI: http://www.tschofenig.priv.at