idnits 2.17.1 draft-ietf-ecrit-data-only-ea-19.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (January 28, 2020) is 1543 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) No issues found here. Summary: 0 errors (**), 0 flaws (~~), 1 warning (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 ECRIT B. Rosen 3 Internet-Draft 4 Intended status: Standards Track H. Schulzrinne 5 Expires: July 31, 2020 Columbia U. 6 H. Tschofenig 7 ARM Limited 8 R. Gellens 9 Core Technology Consulting 10 January 28, 2020 12 Non-Interactive Emergency Calls 13 draft-ietf-ecrit-data-only-ea-19 15 Abstract 17 RFC 6443 'Framework for Emergency Calling Using Internet Multimedia' 18 describes how devices use the Internet to place emergency calls and 19 how Public Safety Answering Points (PSAPs) handle Internet multimedia 20 emergency calls natively. The exchange of multimedia traffic for 21 emergency services involves a Session Initiation Protocol (SIP) 22 session establishment starting with a SIP INVITE that negotiates 23 various parameters for that session. These calls involve a person, 24 who uses the interactive media to communicate with the PSAP. 26 In some cases, however, the transmission of application data is all 27 that is needed, and no interactive media channel is established. 28 Examples of such environments include alerts issued by a temperature 29 sensor, burglar alarm, or chemical spill sensor. Often these alerts 30 are conveyed as one-shot data transmissions. These type of 31 interactions are called 'non-interactive emergency calls'. This 32 document describes use of a SIP MESSAGE transaction containing a 33 container for the data based on the Common Alerting Protocol (CAP). 34 MESSAGE does not establish a session, which differentiates this type 35 of emergency request from a SIP INVITE, which would. Any device that 36 needs to initiate a request for emergency services where no 37 interactive media channel will be established would use the 38 mechanisms in this document. 40 Status of This Memo 42 This Internet-Draft is submitted in full conformance with the 43 provisions of BCP 78 and BCP 79. 45 Internet-Drafts are working documents of the Internet Engineering 46 Task Force (IETF). Note that other groups may also distribute 47 working documents as Internet-Drafts. The list of current Internet- 48 Drafts is at https://datatracker.ietf.org/drafts/current/. 50 Internet-Drafts are draft documents valid for a maximum of six months 51 and may be updated, replaced, or obsoleted by other documents at any 52 time. It is inappropriate to use Internet-Drafts as reference 53 material or to cite them other than as "work in progress." 55 This Internet-Draft will expire on July 31, 2020. 57 Copyright Notice 59 Copyright (c) 2020 IETF Trust and the persons identified as the 60 document authors. All rights reserved. 62 This document is subject to BCP 78 and the IETF Trust's Legal 63 Provisions Relating to IETF Documents 64 (https://trustee.ietf.org/license-info) in effect on the date of 65 publication of this document. Please review these documents 66 carefully, as they describe your rights and restrictions with respect 67 to this document. Code Components extracted from this document must 68 include Simplified BSD License text as described in Section 4.e of 69 the Trust Legal Provisions and are provided without warranty as 70 described in the Simplified BSD License. 72 Table of Contents 74 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 75 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 76 3. Architectural Overview . . . . . . . . . . . . . . . . . . . 4 77 4. Protocol Specification . . . . . . . . . . . . . . . . . . . 6 78 4.1. CAP Transport . . . . . . . . . . . . . . . . . . . . . . 6 79 4.2. Profiling of the CAP Document Content . . . . . . . . . . 7 80 4.3. Sending a non-interactive Emergency Call . . . . . . . . 8 81 5. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 9 82 5.1. 425 (Bad Alert Message) Response Code . . . . . . . . . . 9 83 5.2. The AlertMsg-Error Header Field . . . . . . . . . . . . . 9 84 6. Call Backs . . . . . . . . . . . . . . . . . . . . . . . . . 11 85 7. Handling Large Amounts of Data . . . . . . . . . . . . . . . 11 86 8. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 87 9. Security Considerations . . . . . . . . . . . . . . . . . . . 15 88 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 89 10.1. Registration of the 90 'application/EmergencyCallData.cap+xml' MIME type . . . 17 91 10.2. IANA Registration of 'cap' Additional Data Block . . . . 18 92 10.3. IANA Registration for 425 Response Code . . . . . . . . 18 93 10.4. IANA Registration of New AlertMsg-Error Header Field . . 19 94 10.5. IANA Registration for the SIP AlertMsg-Error Codes . . . 19 95 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 20 96 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 20 97 12.1. Normative References . . . . . . . . . . . . . . . . . . 20 98 12.2. Informative References . . . . . . . . . . . . . . . . . 21 99 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22 101 1. Introduction 103 [RFC6443] describes how devices use the Internet to place emergency 104 calls and how Public Safety Answering Points (PSAPs) handle Internet 105 multimedia emergency calls natively. The exchange of multimedia 106 traffic for emergency services involves a SIP session establishment 107 starting with a SIP INVITE that negotiates various parameters for 108 that session. 110 In some cases, however, there is only application data to be conveyed 111 from the end devices to a PSAP or an intermediary. Examples of such 112 environments includes sensors issuing alerts, or certain types of 113 medical monitors. These messages may be one-shot alerts to emergency 114 authorities and do not require establishment of a session. These 115 type of interactions are called 'non-interactive emergency calls'. 116 In this document, we use the term "call" so that similarities between 117 non-interactive alerts and sessions with interactive media are more 118 obvious. 120 Non-Interactive emergency calls are similar to regular emergency 121 calls in the sense that they require the emergency indications, 122 emergency call routing functionality and may even have the same 123 location requirements. However, the communication interaction will 124 not lead to the exchange of interactive media, that is, Real-Time 125 Protocol packets, such as voice, video data or real-time text. 127 The Common Alerting Protocol (CAP) [cap] is a format for exchanging 128 emergency alerts and public warnings. CAP is mainly used for 129 conveying alerts and warnings between authorities and from 130 authorities to citizens/individuals. This document is concerned with 131 citizen to authority "alerts", where the alert is a call without any 132 interactive media. 134 This document describes a method of including a CAP message in a SIP 135 transaction by defining it as a block of "additional data" as defined 136 in [RFC7852]. The CAP message is included either by value (the CAP 137 message is in the body of the message, using a CID) or by reference 138 (a URI is included in the message, which when dereferenced returns 139 the CAP message). The additional data mechanism is also used to send 140 alert specific data beyond that available in the CAP message. This 141 document also describes how a SIP MESSAGE [RFC3428] transaction can 142 be used to send a non-interactive call. 144 2. Terminology 146 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 147 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 148 document are to be interpreted as described in [RFC2119]. 150 SIP is the Session Initiation Protocol [RFC3261] 152 PIDF-LO is Presence Information Data Format - Location Object, a data 153 structure for carrying location [RFC4119] 155 LoST is the Location To Service Translation protocol [RFC5222] 157 CID is Content InDirection [RFC2392] 159 CAP is the Common Alerting Protocol [cap] 161 PSAP is a Public Safety Answering Point, the call center for 162 emergency calls. 164 ESRP is an Emergency Services Routing Proxy, a type of SIP Proxy 165 Server used in some emergency services networks 167 3. Architectural Overview 169 This section illustrates two envisioned usage modes: targeted and 170 location-based emergency alert routing. 172 1. Emergency alerts containing only data are targeted to an 173 intermediary recipient responsible for evaluating the next steps. 174 These steps could include: 176 1. Sending a non-interactive call containing only data towards a 177 Public Safety Answering Point (PSAP); 179 2. Establishing a third-party initiated emergency call towards a 180 PSAP that could include audio, video, and data. 182 2. Emergency alerts may be targeted to a Service URN used for IP- 183 based emergency calls where the recipient is not known to the 184 originator. In this scenario, the alert may contain only data 185 (e.g., a CAP, Geolocation header field and one or more Call-Info 186 header fields containing Additional Data [RFC7852] in a SIP 187 MESSAGE). 189 Figure 1 shows a deployment variant where a sensor is pre-configured 190 (using techniques outside the scope of this document) to issue an 191 alert to an aggregator that processes these messages and performs 192 whatever steps are necessary to appropriately react to the alert. 193 For example, a security firm may use different sensor inputs to 194 dispatch their security staff to a building they protect or to 195 initiate a third-party emergency call. 197 +------------+ +------------+ 198 | Sensor | | Aggregator | 199 | | | | 200 +---+--------+ +------+-----+ 201 | | 202 Sensors | 203 trigger | 204 emergency | 205 alert | 206 | SIP MESSAGE with CAP | 207 |----------------------------->| 208 | | 209 | Aggregator 210 | processes 211 | emergency 212 | alert 213 | SIP 200 (OK) | 214 |<-----------------------------| 215 | | 216 | | 218 Figure 1: Targeted Emergency Alert Routing 220 In Figure 2 a scenario is shown whereby the alert is routed using 221 location information and a Service URN. An emergency services 222 routing proxy (ESRP) may use LoST (a protocol defined by [RFC5222] 223 which translates a location to a URI used to route an emergency call) 224 to determine the next hop proxy to route the alert message to. A 225 possible receiver is a PSAP and the recipient of the alert may be a 226 call taker. In the generic case, there is very likely no prior 227 relationship between the originator and the receiver, e.g., a PSAP. 228 A PSAP, for example, is likely to receive and accept alerts from 229 entities it has no previous relationship with. This scenario 230 corresponds to the classic emergency services use case and the 231 description in [RFC6881] is applicable. In this use case, the only 232 difference between an emergency call and an emergency non-interactive 233 call is that the former uses INVITE, creates a session, and 234 negotiates one or more media streams, while the latter uses MESSAGE, 235 does not create a session, and does not have interactive media. 237 +----------+ +----------+ +-----------+ 238 |Sensor or | | ESRP | | PSAP | 239 |Aggregator| | | | | 240 +----+-----+ +---+------+ +----+------+ 241 | | | 242 Sensors | | 243 trigger | | 244 emergency | | 245 alert | | 246 | | | 247 | | | 248 | SIP MESSAGE w/CAP | | 249 | (including Service URN, | 250 | such as urn:service:sos) | 251 |-------------------| | 252 | | | 253 | ESRP performs | 254 | emergency alert | 255 | routing | 256 | | MESSAGE with CAP | 257 | | (including identity info) | 258 | |----------------------------->| 259 | | | 260 | | PSAP 261 | | processes 262 | | emergency 263 | | alert 264 | | SIP 200 (OK) | 265 | |<-----------------------------| 266 | | | 267 | SIP 200 (OK) | | 268 |<------------------| | 269 | | | 270 | | | 272 Figure 2: Location-Based Emergency Alert Routing 274 4. Protocol Specification 276 4.1. CAP Transport 278 A CAP message may be sent in the initial message of any SIP 279 transaction. However, this document only addresses sending a CAP 280 message in a SIP MESSAGE transaction for a one-shot, non-interactive 281 emergency call. Behavior with other transactions is not defined. 283 The CAP message is included in a SIP message as an additional-data 284 block [RFC7852]. Accordingly, it is introduced to the SIP message 285 with a Call-Info header field with a purpose of 286 "EmergencyCallData.cap". The header field may contain a URI that is 287 used by the recipient (or in some cases, an intermediary) to obtain 288 the CAP message. Alternative, the Call-Info header field may contain 289 a Content Indirect url [RFC2392] and the CAP message included in the 290 body of the message. In the latter case, the CAP message is located 291 in a MIME block of the type 'application/emergencyCallData.cap+xml'. 293 If the SIP server does not support the functionality required to 294 fulfill the request then a 501 Not Implemented MUST be returned as 295 specified in [RFC3261]. This is the appropriate response when a User 296 Agent Server (UAS) does not recognize the request method and is not 297 capable of supporting it for any user. 299 The 415 Unsupported Media Type error MUST be returned as specified in 300 [RFC3261] if the SIP server is refusing to service the request 301 because the message body of the request is in a format not supported 302 by the server for the requested method. The server MUST return a 303 list of acceptable formats using the Accept, Accept-Encoding, or 304 Accept-Language header fields, depending on the specific problem with 305 the content. 307 4.2. Profiling of the CAP Document Content 309 The usage of CAP MUST conform to the specification provided with 310 [cap]. For usage with SIP the following additional requirements are 311 imposed: 313 sender: The following restrictions and conditions apply to setting 314 the value of the element: 316 * Originator is a SIP entity, Author indication irrelevant: When 317 the alert was created by a SIP-based originator and it is not 318 useful to be explicit about the author of the alert, then the 319 element MUST be populated with the SIP URI of the user 320 agent. 322 * Originator is a non-SIP entity, Author indication irrelevant: 323 When the alert was created by a non-SIP based entity and the 324 identity of this original sender is to be preserved, then this 325 identity MUST be placed into the element. In this 326 situation it is not useful to be explicit about the author of 327 the alert. The specific type of identity being used will 328 depend on the technology used by the original originator. 330 * Author indication relevant: When the author is different from 331 the actual originator of the message and this distinction 332 should be preserved, then the element MUST NOT contain 333 the SIP URI of the user agent. 335 incidents: The element MUST be present. This incident 336 identifier MUST be chosen in such a way that it is unique for a 337 given combination. Note that the 338 element is optional and may not be present. 340 scope: The value of the element MAY be set to "Private" if 341 the alert is not meant for public consumption. The 342 element is, however, not used by this specification since the 343 message routing is performed by SIP and the respective address 344 information is already available in other SIP header fields. 345 Populating information twice into different parts of the message 346 may lead to inconsistency. 348 parameter: The element MAY contain additional 349 information specific to the sender, conforming to the CAP message 350 syntax. 352 area: It is RECOMMENDED to omit this element when constructing a 353 message. If the CAP message already contains an element, 354 then the specified location information SHOULD be copied into a 355 PIDF-LO structure (the data format for location used by emergency 356 calls on the Internet) referenced by the SIP 'Geolocation' header 357 field. If there is a need to copy the PIDF-LO structure 358 referenced by 'geolocation' to , implementers must be aware 359 that is limited to a circle or polygon, and conversion of 360 other shapes will be required. Points SHOULD be converted to a 361 circle with a radius equal to the uncertainty of the point. Arc- 362 bands and ellipses SHOULD be converted to an equivalent polygon. 363 3D locations SHOULD be converted to their equivalent 2D forms. 365 4.3. Sending a non-interactive Emergency Call 367 A non-interactive emergency call is sent using a SIP MESSAGE 368 transaction with a CAP URI or body part as described above in a 369 manner similar to how an emergency call with interactive media is 370 sent, as described in [RFC6881]. The MESSAGE transaction does not 371 create a session nor establish interactive media streams, but 372 otherwise, the header content of the transaction, routing, and 373 processing of non-interactive calls are the same as those of other 374 emergency calls. 376 5. Error Handling 378 This section defines a new error response code and a header field for 379 additional information. 381 5.1. 425 (Bad Alert Message) Response Code 383 This SIP extension creates a new location-specific response code, 384 defined as follows: 386 425 (Bad Alert Message) 388 The 425 response code is a rejection of the request due to its 389 included alert content, indicating that it was malformed or not 390 satisfactory for the recipient's purpose. 392 A SIP intermediary can also reject an alert it receives from a User 393 Agent (UA) when it detects that the provided alert is malformed. 395 Section 5.2 describes an AlertMsg-Error header field with more 396 details about what was wrong with the alert message in the request. 397 This header field MUST be included in the 425 response. 399 It is only appropriate to generate a 425 response when the responding 400 entity has no other information in the request that is usable by the 401 responder. 403 A 425 response code MUST NOT be sent in response to a request that 404 lacks an alert message, as the user agent in that case may not 405 support this extension. 407 A 425 response is a final response within a transaction, and MUST NOT 408 terminate an existing dialog. 410 5.2. The AlertMsg-Error Header Field 412 The AlertMsg-Error header field provides additional information about 413 what was wrong with the original request. In some cases the provided 414 information will be used for debugging purposes. 416 The AlertMsg-Error header field has the following ABNF [RFC5234]: 418 message-header /= AlertMsg-Error 419 ; (message-header from 3261) 420 AlertMsg-Error = "AlertMsg-Error" HCOLON 421 ErrorValue 422 ErrorValue = error-code 423 *(SEMI error-params) 424 error-code = 1*3DIGIT 425 error-params = error-code-text 426 / generic-param ; from RFC3261 427 error-code-text = "code" EQUAL quoted-string ; from RFC3261 429 HCOLON, SEMI, and EQUAL are defined in [RFC3261]. DIGIT is defined 430 in [RFC5234]. 432 The AlertMsg-Error header field MUST contain only one ErrorValue to 433 indicate what was wrong with the alert payload the recipient 434 determined was bad. 436 The ErrorValue contains a 3-digit error code indicating what was 437 wrong with the alert in the request. This error code has a 438 corresponding quoted error text string that is human readable. The 439 text string is OPTIONAL, but RECOMMENDED for human readability, 440 similar to the string phrase used for SIP response codes. That said, 441 the strings are complete enough for rendering to the user, if so 442 desired. The strings in this document are recommendations, and are 443 not standardized -- meaning an operator can change the strings -- but 444 MUST NOT change the meaning of the error code. Similar to how RFC 445 3261 specifies, there MUST NOT be more than one string per error 446 code. 448 The AlertMsg-Error header field MAY be included in any response if an 449 alert message was in the request part of the same transaction. For 450 example, a UA includes an alert in a MESSAGE to a PSAP. The PSAP can 451 accept this MESSAGE, thus creating a dialog, even though its UA 452 determined that the alert message contained in the MESSAGE was bad. 453 The PSAP merely includes an AlertMsg-Error header field value in the 454 200 OK to the MESSAGE, thus informing the UA that the MESSAGE was 455 accepted but the alert provided was bad. 457 If, on the other hand, the PSAP cannot accept the transaction without 458 a suitable alert message, a 425 response is sent. 460 A SIP intermediary that requires the UA's alert message in order to 461 properly process the transaction may also sends a 425 with an 462 AlertMsg-Error code. 464 This document defines an initial list of AlertMsg-Error values for 465 any SIP response, including provisional responses (other than 100 466 Trying) and the new 425 response. There MUST be no more than one 467 AlertMsg-Error code in a SIP response. 469 AlertMsg-Error: 100 ; code="Cannot Process the Alert Payload" 471 AlertMsg-Error: 101 ; code="Alert Payload was not present or could 472 not be found" 474 AlertMsg-Error: 102 ; code="Not enough information to determine the 475 purpose of the alert" 477 AlertMsg-Error: 103 ; code="Alert Payload was corrupted" 479 Additionally, if an entity cannot or chooses not to process the alert 480 message from a SIP request, a 500 (Server Internal Error) SHOULD be 481 used with or without a configurable Retry-After header field. 483 6. Call Backs 485 This document does not describe any method for the recipient to call 486 back the sender of a non-interactive call. Usually, these alerts are 487 sent by automata, which do not have a mechanism to receive calls of 488 any kind. The identifier in the 'From' header field may be useful to 489 obtain more information, but any such mechanism is not defined in 490 this document. The CAP message may contain related contact 491 information for the sender. 493 7. Handling Large Amounts of Data 495 It is not atypical for sensors to have large quantities of data that 496 they may wish to send. Including large amounts of data (tens of 497 kilobytes) in a MESSAGE is not advisable, because SIP entities are 498 usually not equipped to handle very large messages. In such cases, 499 the sender SHOULD make use of the by-reference mechanisms defined in 500 [RFC7852], which involves making the data available via HTTPS (either 501 at the originator or at another entity), placing a URI to the data in 502 the 'Call-Info' header field, and the recipient uses HTTPS to 503 retrieve the data. The CAP message itself can be sent by-reference 504 using this mechanism, as well as any or all of the Additional Data 505 blocks that may contain sensor-specific data. 507 8. Example 509 The following example shows a CAP document indicating a BURGLARY 510 alert issued by a sensor called 'sensor1@example.com'. The location 511 of the sensor can be obtained from the attached location information 512 provided via the 'geolocation' header field contained in the SIP 513 MESSAGE structure. Additionally, the sensor provided some data along 514 with the alert message, using proprietary information elements 515 intended only to be processed by the receiver, a SIP entity acting as 516 an aggregator. 518 MESSAGE sip:aggregator@example.com SIP/2.0 519 Via: SIP/2.0/TCP sensor1.example.com;branch=z9hG4bK776sgdkse 520 Max-Forwards: 70 521 From: sip:sensor1@example.com;tag=49583 522 To: sip:aggregator@example.com 523 Call-ID: asd88asd77a@2001:DB8:0:0FF 524 Geolocation: 525 ;routing-allowed=yes 526 Supported: geolocation 527 Accept: application/pidf+xml,application/EmergencyCallData.cap+xml 528 CSeq: 1 MESSAGE 529 Call-Info: cid:abcdef2@example.com;purpose=EmergencyCallData.cap 530 Content-Type: multipart/mixed; boundary=boundary1 531 Content-Length: ... 533 --boundary1 535 Content-Type: application/EmergencyCallData.cap+xml 536 Content-ID: 537 Content-Disposition: by-reference;handling=optional 538 540 541 S-1 542 sip:sensor1@example.com 543 2008-11-19T14:57:00-07:00 544 Actual 545 Alert 546 Private 547 abc1234 548 549 Security 550 BURGLARY 551 Expected 552 Likely 553 Moderate 554 SENSOR 1 555 556 SENSOR-DATA-NAMESPACE1 557 123 558 559 560 SENSOR-DATA-NAMESPACE2 561 TRUE 562 563 564 566 --boundary1 568 Content-Type: application/pidf+xml 569 Content-ID: 570 Content-Disposition: by-reference;handling=optional 571 572 581 582 583 584 585 586 32.86726 -97.16054 587 588 589 590 591 false 592 593 2010-11-14T20:00:00Z 594 595 596 802.11 597 598 2010-11-04T20:57:29Z 599 600 601 --boundary1-- 603 Figure 3: Example Message conveying an Alert to an aggregator 605 The following shows the same CAP document sent as a non-interactive 606 emergency call towards a PSAP. 608 MESSAGE urn:service:sos SIP/2.0 609 Via: SIP/2.0/TCP sip:aggreg.1.example.com;branch=z9hG4bK776abssa 610 Max-Forwards: 70 611 From: sip:aggregator@example.com;tag=32336 612 To: 112 613 Call-ID: asdf33443a@example.com 614 Route: sip:psap1.example.gov 615 Geolocation: 616 ;routing-allowed=yes 617 Supported: geolocation 618 Accept: application/pidf+xml,application/EmergencyCallData.cap+xml 619 Call-info: cid:abcdef2@example.com;purpose=EmergencyCallData.cap 620 CSeq: 1 MESSAGE 621 Content-Type: multipart/mixed; boundary=boundary1 622 Content-Length: ... 624 --boundary1 626 Content-Type: application/EmergencyCallData.cap+xml 627 Content-ID: 628 630 631 S-1 632 sip:sensor1@example.com 633 2008-11-19T14:57:00-07:00 634 Actual 635 Alert 636 Private 637 abc1234 638 639 Security 640 BURGLARY 641 Expected 642 Likely 643 Moderate 644 SENSOR 1 645 646 SENSOR-DATA-NAMESPACE1 647 123 648 649 650 SENSOR-DATA-NAMESPACE2 651 TRUE 652 653 654 655 --boundary1 657 Content-Type: application/pidf+xml 658 Content-ID: 659 660 669 670 671 672 673 674 32.86726 -97.16054 675 676 677 678 679 false 680 681 2010-11-14T20:00:00Z 682 683 684 802.11 685 686 2010-11-04T20:57:29Z 687 688 689 --boundary1-- 691 Figure 4: Example Message conveying an Alert to a PSAP 693 9. Security Considerations 695 This section discusses security considerations when SIP user agents 696 issue emergency alerts utilizing MESSAGE and CAP. Location specific 697 threats are not unique to this document and are discussed in 698 [RFC7378] and [RFC6442]. 700 The ECRIT emergency services architecture [RFC6443] considers classic 701 individual-to-authority emergency calling where the identity of the 702 emergency caller does not play a role at the time of the call 703 establishment itself, i.e., a response to the emergency call does not 704 depend on the identity of the caller. In the case of emergency 705 alerts generated by devices such as sensors, the processing may be 706 different in order to reduce the number of falsely generated 707 emergency alerts. Alerts could get triggered based on certain sensor 708 input that might have been caused by factors other than the actual 709 occurrence of an alert-relevant event. For example, a sensor may 710 simply be malfunctioning. For this reason, not all alert messages 711 are directly sent to a PSAP, but rather may be pre-processed by a 712 separate entity, potentially under supervision by a human, to filter 713 alerts and potentially correlate received alerts with others to 714 obtain a larger picture of the ongoing situation. 716 In any case, for alerts initiated by sensors, the identity could play 717 an important role in deciding whether to accept or ignore an incoming 718 alert message. With the scenario shown in Figure 1 it is very likely 719 that only authorized sensor input will be processed. For this 720 reason, it needs to be possible to refuse to accept alert messages 721 from an unknown origin. Two types of information elements can be 722 used for this purpose: 724 1. SIP itself provides security mechanisms that allow the 725 verification of the originator's identity. These mechanisms can 726 be re-used, such as P-Asserted-Identity [RFC3325] or SIP Identity 727 [RFC8224]. The latter provides a cryptographic assurance while 728 the former relies on a chain of trust model. 730 2. CAP provides additional security mechanisms and the ability to 731 carry further information about the sender's identity. 732 Section 3.3.4.1 of [cap] specifies the signing algorithms of CAP 733 documents. 735 In addition to the desire to perform identity-based access control, 736 the classic communication security threats need to be considered, 737 including integrity protection to prevent forgery or replay of alert 738 messages in transit. To deal with replay of alerts, a CAP document 739 contains the mandatory , , elements and an 740 optional element. Together, these elements make the CAP 741 document unique for a specific sender and provide time restrictions. 742 An entity that has already received a CAP message within the 743 indicated timeframe is able to detect a replayed message and, if the 744 content of that message is unchanged, then no additional security 745 vulnerability is created. Additionally, it is RECOMMENDED to make 746 use of SIP security mechanisms, such as SIP Identity [RFC8224], to 747 tie the CAP message to the SIP message. To provide protection of the 748 entire SIP message exchange between neighboring SIP entities, the 749 usage of TLS is REQUIRED. 751 Note that none of the security mechanism in this document protect 752 against a compromised sensor sending crafted alerts. Privacy 753 provided for any emergency calls, including non-interactive messages, 754 is subject to local regulations. 756 10. IANA Considerations 758 10.1. Registration of the 'application/EmergencyCallData.cap+xml' MIME 759 type 761 To: ietf-types@iana.org 763 Subject: Registration of MIME media type application/ 764 EmergencyCallData.cap+xml 766 MIME media type name: application 768 MIME subtype name: cap+xml 770 Required parameters: (none) 772 Optional parameters: charset; Indicates the character encoding of 773 enclosed XML. Default is UTF-8 [RFC3629]. 775 Encoding considerations: Uses XML, which can employ 8-bit 776 characters, depending on the character encoding used. See 777 [RFC7303], Section 3.2. 779 Security considerations: This content type is designed to carry 780 payloads of the Common Alerting Protocol (CAP). RFC XXX [Replace 781 by the RFC number of this specification] discusses security 782 considerations for this. 784 Interoperability considerations: This content type provides a way to 785 convey CAP payloads. 787 Published specification: RFC XXX [Replace by the RFC number of this 788 specification]. 790 Applications which use this media type: Applications that convey 791 alerts and warnings according to the CAP standard. 793 Additional information: OASIS has published the Common Alerting 794 Protocol at http://www.oasis-open.org/committees/ 795 documents.php&wg_abbrev=emergency 797 Person and email address to contact for further information: Hannes 798 Tschofenig, hannes.tschofenig@gmx.net 800 Intended usage: Limited use 802 Author/Change controller: IETF ECRIT working group 804 Other information: This media type is a specialization of 805 application/xml [RFC7303], and many of the considerations 806 described there also apply to application/cap+xml. 808 10.2. IANA Registration of 'cap' Additional Data Block 810 This document registers a new block type in the sub-registry called 811 'Emergency Call Data Types' of the Emergency Call Additional Data 812 Registry defined in [RFC7852]. The token is "cap", the Data About is 813 "The Call" and the reference is this document. 815 10.3. IANA Registration for 425 Response Code 817 In the SIP Response Codes registry, the following is added 819 Reference: RFC-XXXX (i.e., this document) 821 Response code: 425 (recommended number to assign) 823 Default reason phrase: Bad Alert Message 824 Registry: 825 Response Code Reference 826 ------------------------------------------ --------- 827 Request Failure 4xx 828 425 Bad Alert Message [this doc] 830 This SIP Response code is defined in Section 5. 832 10.4. IANA Registration of New AlertMsg-Error Header Field 834 The SIP AlertMsg-error header field is created by this document, with 835 its definition and rules in Section 5, to be added to the IANA 836 Session Initiation Protocol (SIP) Parameters registry with two 837 actions: 839 1. Update the Header Fields registry with 841 Registry: 842 Header Name compact Reference 843 ----------------- ------- --------- 844 AlertMsg-Error [this doc] 846 2. In the portion titled "Header Field Parameters and Parameter 847 Values", add 849 Predefined 850 Header Field Parameter Name Values Reference 851 ----------------- ------------------- ---------- --------- 852 AlertMsg-Error code yes [this doc] 854 10.5. IANA Registration for the SIP AlertMsg-Error Codes 856 This document creates a new registry for SIP, called "AlertMsg-Error 857 Codes". AlertMsg-Error codes provide reasons for an error discovered 858 by a recipient, categorized by the action to be taken by the error 859 recipient. The initial values for this registry are shown below. 861 Registry Name: AlertMsg-Error Codes 863 Reference: [this doc] 865 Registration Procedures: Specification Required 866 Code Default Reason Phrase Reference 867 ---- --------------------------------------------------- --------- 868 100 "Cannot Process the Alert Payload" [this doc] 870 101 "Alert Payload was not present or could not be found" [this doc] 872 102 "Not enough information to determine 873 the purpose of the alert" [this doc] 875 103 "Alert Payload was corrupted" [this doc] 877 Details of these error codes are in Section 5. 879 11. Acknowledgments 881 The authors would like to thank the participants of the Early Warning 882 adhoc meeting at IETF#69 for their feedback. Additionally, we would 883 like to thank the members of the NENA Long Term Direction Working 884 Group for their feedback. 886 Additionally, we would like to thank Martin Thomson, James 887 Winterbottom, Shida Schubert, Bernard Aboba, Marc Linsner, Christer 888 Holmberg and Ivo Sedlacek for their review comments. 890 12. References 892 12.1. Normative References 894 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 895 Requirement Levels", March 1997. 897 [cap] Jones, E. and A. Botterell, "Common Alerting Protocol v. 898 1.2", October 2005, . 901 [RFC2392] Levinson, E., "Content-ID and Message-ID Uniform Resource 902 Locators", RFC 2392, DOI 10.17487/RFC2392, August 1998, 903 . 905 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 906 A., Peterson, J., Sparks, R., Handley, M., and E. 907 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 908 DOI 10.17487/RFC3261, June 2002, 909 . 911 [RFC3428] Campbell, B., Ed., Rosenberg, J., Schulzrinne, H., 912 Huitema, C., and D. Gurle, "Session Initiation Protocol 913 (SIP) Extension for Instant Messaging", RFC 3428, 914 DOI 10.17487/RFC3428, December 2002, 915 . 917 [RFC4119] Peterson, J., "A Presence-based GEOPRIV Location Object 918 Format", RFC 4119, DOI 10.17487/RFC4119, December 2005, 919 . 921 [RFC5222] Hardie, T., Newton, A., Schulzrinne, H., and H. 922 Tschofenig, "LoST: A Location-to-Service Translation 923 Protocol", RFC 5222, DOI 10.17487/RFC5222, August 2008, 924 . 926 [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax 927 Specifications: ABNF", STD 68, RFC 5234, 928 DOI 10.17487/RFC5234, January 2008, 929 . 931 [RFC7303] Thompson, H. and C. Lilley, "XML Media Types", RFC 7303, 932 DOI 10.17487/RFC7303, July 2014, 933 . 935 [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 936 10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November 937 2003, . 939 [RFC6442] Polk, J., Rosen, B., and J. Peterson, "Location Conveyance 940 for the Session Initiation Protocol", RFC 6442, 941 DOI 10.17487/RFC6442, December 2011, 942 . 944 [RFC6881] Rosen, B. and J. Polk, "Best Current Practice for 945 Communications Services in Support of Emergency Calling", 946 BCP 181, RFC 6881, DOI 10.17487/RFC6881, March 2013, 947 . 949 [RFC7852] Gellens, R., Rosen, B., Tschofenig, H., Marshall, R., and 950 J. Winterbottom, "Additional Data Related to an Emergency 951 Call", RFC 7852, DOI 10.17487/RFC7852, July 2016, 952 . 954 12.2. Informative References 956 [RFC7378] Tschofenig, H., Schulzrinne, H., and B. Aboba, Ed., 957 "Trustworthy Location", RFC 7378, DOI 10.17487/RFC7378, 958 December 2014, . 960 [RFC8224] Peterson, J., Jennings, C., Rescorla, E., and C. Wendt, 961 "Authenticated Identity Management in the Session 962 Initiation Protocol (SIP)", RFC 8224, 963 DOI 10.17487/RFC8224, February 2018, 964 . 966 [RFC3325] Jennings, C., Peterson, J., and M. Watson, "Private 967 Extensions to the Session Initiation Protocol (SIP) for 968 Asserted Identity within Trusted Networks", RFC 3325, 969 DOI 10.17487/RFC3325, November 2002, 970 . 972 [RFC6443] Rosen, B., Schulzrinne, H., Polk, J., and A. Newton, 973 "Framework for Emergency Calling Using Internet 974 Multimedia", RFC 6443, DOI 10.17487/RFC6443, December 975 2011, . 977 Authors' Addresses 979 Brian Rosen 980 470 Conrad Dr 981 Mars, PA 16046 982 US 984 Phone: 985 Email: br@brianrosen.net 987 Henning Schulzrinne 988 Columbia University 989 Department of Computer Science 990 450 Computer Science Building 991 New York, NY 10027 992 US 994 Phone: +1 212 939 7004 995 Email: hgs+ecrit@cs.columbia.edu 996 URI: http://www.cs.columbia.edu 998 Hannes Tschofenig 999 ARM Limited 1001 Austria 1003 Email: Hannes.Tschofenig@gmx.net 1004 URI: http://www.tschofenig.priv.at 1005 Randall Gellens 1006 Core Technology Consulting 1008 Email: rg+ietf@coretechnologyconsulting.com 1009 URI: http://www.coretechnologyconsulting.com