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Checking references for intended status: Experimental ---------------------------------------------------------------------------- ** Obsolete normative reference: RFC 3023 (Obsoleted by RFC 7303) == Outdated reference: A later version (-20) exists of draft-ietf-ecrit-phonebcp-17 == Outdated reference: A later version (-09) exists of draft-ietf-sipcore-location-conveyance-08 ** Obsolete normative reference: RFC 3265 (Obsoleted by RFC 6665) == Outdated reference: A later version (-03) exists of draft-ietf-atoca-requirements-01 == Outdated reference: A later version (-14) exists of draft-ietf-ecrit-trustworthy-location-02 -- Obsolete informational reference (is this intentional?): RFC 4474 (Obsoleted by RFC 8224) Summary: 2 errors (**), 0 flaws (~~), 7 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: Experimental H. Schulzrinne 5 Expires: January 11, 2012 Columbia U. 6 H. Tschofenig 7 Nokia Siemens Networks 8 July 10, 2011 10 Common Alerting Protocol (CAP) based Emergency Alerts using the Session 11 Initiation Protocol (SIP) 12 draft-ietf-ecrit-data-only-ea-02.txt 14 Abstract 16 The Common Alerting Protocol (CAP) is a document format for 17 exchanging emergency alerts and public warnings. CAP is mainly used 18 for conveying alerts and warnings between authorities and from 19 authorities to citizen/individuals. This document describes how 20 devices use CAP to issue emergency alerts. 22 Status of this Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at http://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on January 11, 2012. 39 Copyright Notice 41 Copyright (c) 2011 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (http://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. Code Components extracted from this document must 50 include Simplified BSD License text as described in Section 4.e of 51 the Trust Legal Provisions and are provided without warranty as 52 described in the Simplified BSD License. 54 Table of Contents 56 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 57 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 58 3. Architectural Overview . . . . . . . . . . . . . . . . . . . . 5 59 4. Protocol Specification . . . . . . . . . . . . . . . . . . . . 7 60 4.1. CAP Transport . . . . . . . . . . . . . . . . . . . . . . 7 61 4.2. Profiling of the CAP Document Content . . . . . . . . . . 7 62 5. Error Handling . . . . . . . . . . . . . . . . . . . . . . . . 9 63 5.1. 425 (Bad Alert Message) Response Code . . . . . . . . . . 9 64 5.2. The AlertMsg-Error Header Field . . . . . . . . . . . . . 9 65 6. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 66 7. Security Considerations . . . . . . . . . . . . . . . . . . . 14 67 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 68 8.1. Registration of the 'application/cap+xml' MIME type . . . 16 69 8.2. IANA Registration for 425 Response Code . . . . . . . . . 17 70 8.3. IANA Registration of New AlertMsg-Error Header Field . . . 17 71 8.4. IANA Registration for the SIP AlertMsg-Error Codes . . . . 18 72 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 19 73 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20 74 10.1. Normative References . . . . . . . . . . . . . . . . . . . 20 75 10.2. Informative References . . . . . . . . . . . . . . . . . . 21 76 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 22 78 1. Introduction 80 The Common Alerting Protocol (CAP) [cap] is an XML document format 81 for exchanging emergency alerts and public warnings. CAP is mainly 82 used for conveying alerts and warnings between authorities and from 83 authorities to citizen/individuals. This document describes how 84 data-only emergency calls are able to utilize the same CAP document 85 format. 87 Emergency alerts containing data are similar to regular emergency 88 calls in the sense that they require emergency call routing 89 functionality and may even have the same location requirements. On 90 the other hand, the communication interaction may occur without 91 establishment of a voice or video channel. 93 Data-only emergency alerts are similar to regular emergency calls in 94 the sense that they require emergency call routing functionality and 95 may even have the same location requirements. On the other hand, the 96 initial communication interaction will not lead to the establishment 97 of a voice or video channel. 99 Based on the deployment experience with non-IP based systems, two 100 major deployment scenarios are envisaged: 102 1. Emergency alerts containing only data are targeted to a recipient 103 responsible for evaluating the next steps, which could include: 105 1. Sending an alert containing only data toward a Public Safety 106 Answering Point (PSAP); 108 2. Establishing an emergency call with a PSAP that could include 109 audio/video as well as data 111 2. Emergency alerts targeted to a Service URN used for IP-based 112 emergency calls where the recipient is not known to the 113 originator. In this scenario, the alert may contain only data 114 (e.g. a CAP and a PIDF-LO payload in a SIP MESSAGE) or could be 115 included along with establishment of an audio/video channel (e.g. 116 SIP INVITE) 118 We describe these two cases in more detail in Section 3. 120 2. Terminology 122 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 123 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 124 document are to be interpreted as described in RFC 2119 [RFC2119]. 126 This document utilizes terminology introduced in 127 [I-D.ietf-atoca-requirements]. In particular, the terms for author, 128 originator, receiver and recipient, are relevant for this document. 129 The originator and the receiver are SIP-based entities while the 130 author and the recipient are entities that relate to the alert 131 message delivery, when this is relevant for the communication. 133 3. Architectural Overview 135 This section illustrates two envisioned usage modes; targeted and 136 location-based emergency alert routing. Figure 1 shows a deployment 137 variant where a sensor, as the author and originator of the alert, is 138 pre-configured (using techniques outside the scope of this document) 139 to issue an alert to a receiver or an aggregator, a special form of 140 mediator, that processes these messages and performs whatever steps 141 are necessary to appropriately react on the alert. For example, a 142 security firm may use different sensor inputs to dispatch their 143 security staff to a building they protect or to initiate a third 144 party emergency call. 146 +------------+ +------------+ 147 | Sensor | | Aggregator | 148 | | | | 149 +---+--------+ +------+-----+ 150 | | 151 Sensors | 152 trigger | 153 emergency | 154 alert | 155 | MESSAGE with CAP | 156 |----------------------------->| 157 | | 158 | Aggregator 159 | processes 160 | emergency 161 | alert 162 | 200 (OK) | 163 |<-----------------------------| 164 | | 165 | | 167 Figure 1: Targeted Emergency Alert Routing 169 In Figure 2 a scenario is shown whereby the alert is routed using 170 location information and the Service URN. An emergency services 171 routing proxy (ESRP) may use LoST to determine the next hop proxy to 172 route the alert message to. A possible receiver is a PSAP and the 173 recipient of the alert may be call taker. In the generic case, there 174 is very likely no prior relationship between the originator and the 175 receiver, e.g. PSAP. A PSAP, for example, is likely to receive and 176 accept alerts from entities it cannot authorize. This scenario 177 corresponds more to the classical emergency services use case and the 178 description in [I-D.ietf-ecrit-phonebcp] is applicable. 180 +-----------+ +----------+ 181 +--------+ | ESRP | | PSAP | 182 | Sensor | | | | | 183 +---+----+ +---+-------+ +---+------+ 184 | | | 185 Sensors | | 186 trigger | | 187 emergency | | 188 alert | | 189 | | | 190 | | | 191 | MESSAGE with CAP | | 192 | (including Service URN, | 193 | such as urn:service:sos) | 194 |------------------->| | 195 | | | 196 | ESRP performs | 197 | emergency alert | 198 | routing | 199 | | MESSAGE with CAP | 200 | | (including identity info) | 201 | |----------------------------->| 202 | | | 203 | | PSAP 204 | | processes 205 | | emergency 206 | | alert 207 | | 200 (OK) | 208 | |<-----------------------------| 209 | | | 210 | 200 (OK) | | 211 |<-------------------| | 212 | | | 213 | | | 215 Figure 2: Location-Based Emergency Alert Routing 217 4. Protocol Specification 219 4.1. CAP Transport 221 Since alerts structured via CAP require a "push" medium. The 222 following SIP requests MAY carry the CAP payload defined in this 223 document: INVITE [RFC3261], UPDATE [RFC3311], MESSAGE [RFC3428], INFO 224 [RFC6086], NOTIFY [RFC3265], and PUBLISH [RFC3903]. The MIME type is 225 set to 'application/cap+xml'. 227 If the server does not support the functionality required to fulfill 228 the request then a 501 Not Implemented MUST be returned by RFC 3261 229 [RFC3261]. This is the appropriate response when a UAS does not 230 recognize the request method and is not capable of supporting it for 231 any user. 233 The 415 Unsupported Media Type error MUST be returned by RFC 3261 234 [RFC3261] if the server is refusing to service the request because 235 the message body of the request is in a format not supported by the 236 server for the requested method. The server MUST return a list of 237 acceptable formats using the Accept, Accept-Encoding, or Accept- 238 Language header field, depending on the specific problem with the 239 content. 241 4.2. Profiling of the CAP Document Content 243 The usage of CAP MUST conform to the specification provided with 244 [cap]. For the usage with SIP the following additional requirements 245 are imposed: 247 sender: A few sub-categories for putting a value in the 248 element have to be considered: 250 Originator is a SIP entity, Author indication irrelevant: When 251 the alert was created by a SIP-based originator and it is not 252 useful to be explicit about the author of the alert then the 253 element MUST be populated with the SIP URI of the user 254 agent. 256 Originator is a non-SIP entity, Author indication irrelevant: In 257 case that the alert was created by a non-SIP based entity and 258 the identity of this original sender wants to be preserved then 259 this identity MUST be placed into the element. In 260 this category the it is not useful to be explicit about the 261 author of the alert. The specific type of identity being used 262 will depends on the technology being used by the original 263 originator. 265 Author indication relevant: In case the author is different from 266 the actual originator of the message and this distinction wants 267 to be preserved then the element MUST NOT contain the 268 SIP URI. 270 incidents: The element MUST be present whenever there is 271 a possibility that alert information needs to be updated. The 272 initial message will then contain an incident identifier carried 273 in the element. This incident identifier MUST be 274 chosen in such a way that it is unique for a given combination. Note that the element 276 is optional and may not be present. 278 scope: The value of the element MUST be set to "Private" as 279 the alert is not meant for public consumption. The 280 element is, however, not used by this specification since the 281 message routing is performed by SIP and the respective address 282 information is already available in other SIP headers. Populating 283 information twice into different parts of the message may lead to 284 inconsistency. 286 parameter: The element MAY contain additional 287 information specific to the sensor. 289 area: It is RECOMMENDED to omit this element when constructing a 290 message. In case that the CAP message already contained an 291 element then the specified location information MUST be copied 292 into the PIDF-LO structure of the 'geolocation' header. 294 5. Error Handling 296 This section defines a new error response code and a header field for 297 additional information. 299 5.1. 425 (Bad Alert Message) Response Code 301 This SIP extension creates a new location-specific response code, 302 defined as follows, 304 425 (Bad Alert Message) 306 The 425 response code is a rejection of the request due to its 307 included alert content, indicating that it was malformed or not 308 satisfactory for the recipient's purpose. 310 A SIP intermediary can also reject an alert it receives from a UA 311 when it understands that the provided alert is malformed. 313 Section 5.2 describes a AlertMsg-Error header field with more details 314 about what was wrong with the alert message in the request. This 315 header field MUST be included in the 425 response. 317 It is only appropriate to generate a 425 response when the responding 318 entity has no other information in the request that are usable by the 319 responder. 321 A 425 response code MUST NOT be sent in response to a request that 322 lacks an alert message entirely, as the user agent in that case may 323 not support this extension at all. 325 A 425 response is a final response within a transaction, and MUST NOT 326 terminate an existing dialog. 328 5.2. The AlertMsg-Error Header Field 330 The AlertMsg-Error header provides additional information about what 331 was wrong with the original request. In some cases the provided 332 information will be used for debugging purposes. 334 The AlertMsg-Error header field has the following ABNF [RFC5234]: 336 message-header /= AlertMsg-Error 337 ; (message-header from 3261) 338 AlertMsg-Error = "AlertMsg-Error" HCOLON 339 ErrorValue 340 ErrorValue = error-code 341 *(SEMI error-params) 342 error-code = 1*3DIGIT 343 error-params = error-code-text 344 / generic-param ; from RFC3261 345 error-code-text = "code" EQUAL quoted-string ; from RFC3261 347 HCOLON, SEMI, and EQUAL are defined in RFC3261 [RFC3261]. DIGIT is 348 defined in RFC5234 [RFC5234]. 350 The AlertMsg-Error header field MUST contain only one ErrorValue to 351 indicate what was wrong with the alert payload the recipient 352 determined was bad. 354 The ErrorValue contains a 3-digit error code indicating what was 355 wrong with the alert in the request. This error code has a 356 corresponding quoted error text string that is human understandable. 357 The text string are OPTIONAL, but RECOMMENDED for human readability, 358 similar to the string phrase used for SIP response codes. That said, 359 the strings are complete enough for rendering to the user, if so 360 desired. The strings in this document are recommendations, and are 361 not standardized - meaning an operator can change the strings - but 362 MUST NOT change the meaning of the error code. Similar to how RFC 363 3261 specifies, there MUST NOT be more than one string per error 364 code. 366 The AlertMsg-Error header field MAY be included in any response as an 367 alert message was in the request part of the same transaction. For 368 example, a UA includes an alert in an MESSAGE to a PSAP. The PSAP 369 can accept this MESSAGE, thus creating a dialog, even though his UA 370 determined the alert message contained in the MESSAGE was bad. The 371 PSAP merely includes a AlertMsg-Error header value in the 200 OK to 372 the MESSAGE informing the UA that the MESSAGE was accepted but the 373 alert provided was bad. 375 If, on the other hand, the PSAP cannot accept the MESSAGE without a 376 suitable alert message, a 425 response is sent. 378 A SIP intermediary that requires the UA's alert message in order to 379 properly process the MESSAGE may also sends a 425 with a AlertMsg- 380 Error code. 382 This document defines an initial list of error code ranges for any 383 SIP response, including provisional responses (other than 100 Trying) 384 and the new 425 response. There MUST be no more than one AlertMsg- 385 Error code in a SIP response. 387 AlertMsg-Error: 100 ; code="Cannot Process the Alert Payload" 389 AlertMsg-Error: 101 ; code="Alert Payload was not present or could 390 not be found" 392 AlertMsg-Error: 102 ; code="Not enough information to determine the 393 purpose of the alert" 395 AlertMsg-Error: 103 ; code="Alert Payload was corrupted" 397 Additionally, if an LR cannot or chooses not to process the alert 398 message from a SIP request, a 500 (Server Internal Error) SHOULD be 399 used with or without a configurable Retry-After header field. 401 6. Example 403 Figure 3 shows a CAP document indicating a BURLARY alert issued by a 404 sensor with the identity 'sensor1@domain.com'. The location of the 405 sensor can be obtained from the attached location information 406 provided via the 'geolocation' header contained in the SIP MESSAGE 407 structure. Additionally, the sensor provided some data long with the 408 alert message using proprietary information elements only to be 409 processed by the receiver, a SIP entity acting as an aggregator. 410 This example reflects the description in Figure 1. 412 MESSAGE sip:aggregator@domain.com SIP/2.0 413 Via: SIP/2.0/TCP sensor1.domain.com;branch=z9hG4bK776sgdkse 414 Max-Forwards: 70 415 From: sip:sensor1@domain.com;tag=49583 416 To: sip:aggregator@domain.com 417 Call-ID: asd88asd77a@1.2.3.4 418 Geolocation: 419 ;routing-allowed=yes 420 Supported: geolocation 421 Accept: application/pidf+xml, application/cap+xml 422 CSeq: 1 MESSAGE 423 Content-Type: multipart/mixed; boundary=boundary1 424 Content-Length: ... 426 --boundary1 428 Content-Type: cap+xml 429 Content-ID: 430 432 433 S-1 434 sip:sensor1@domain.com 435 2008-11-19T14:57:00-07:00 436 Actual 437 Alert 438 Private 439 abc1234 440 441 Security 442 BURGLARY 443 Expected 444 Likely 445 Moderate 446 SENSOR 1 447 448 SENSOR-DATA-NAMESPACE1 449 123 450 451 452 SENSOR-DATA-NAMESPACE2 453 TRUE 454 455 456 458 --boundary1 460 Content-Type: application/pidf+xml 461 Content-ID: 462 463 471 472 473 474 475 476 32.86726 -97.16054 477 478 479 480 481 false 482 483 2010-11-14T20:00:00Z 484 485 486 802.11 487 488 2010-11-04T20:57:29Z 489 490 491 --boundary1-- 493 Figure 3: Example Message conveying an Alert 495 7. Security Considerations 497 This section discusses security considerations when SIP user agents 498 issue emergency alerts utilizing CAP. Location specific threats are 499 not unique to this document and are discussed in 500 [I-D.ietf-ecrit-trustworthy-location] and 501 [I-D.ietf-sipcore-location-conveyance]. 503 The ECRIT emergency services architecture [I-D.ietf-ecrit-phonebcp] 504 considers classical individual-to-authority emergency calling and the 505 identity of the emergency caller does not play a role at the time of 506 the call establishment itself, i.e., a response to the emergency call 507 will not depend on the identity of the caller. In case of emergency 508 alerts generated by devices, like sensors, the processing may be 509 different in order to reduce the number of falsely generated 510 emergency alerts. Alerts may get triggered based on certain sensor 511 input that may have been caused by other factors than the actual 512 occurrence of an alert relevant event. For example, a sensor may 513 simply be malfunctioning. For this purpose not all alert messages 514 are directly sent to a PSAP but are rather pre-processed by a 515 separate entity, potentially under supervision by a human, to filter 516 alerts and potentially correlate received alerts with others to 517 obtain a larger picture of the ongoing situation. These two message 518 routing examples are shown in Figure 1 and in Figure 2. 520 In any case, for alerts that are initiated by sensors the identity 521 may play an important role in deciding whether to accept or ignore an 522 incoming alert message. With the scenario shown in Figure 1 it is 523 very likely that only authorized sensor input will be processed. For 524 this purpose it needs to be ensured that no alert messages from an 525 unknown origin are accepted. Two types of information elements can 526 be used for this purpose: 528 1. SIP itself provides security mechanisms that allow the 529 verification of the originator's identity. These mechanisms can 530 be re-used, such as P-Asserted-Identity [RFC3325] or SIP Identity 531 [RFC4474]. The latter provides a cryptographic assurance while 532 the former relies on a chain of trust model. 534 2. CAP provides additional security mechanisms and the ability to 535 carry additional information about the sender's identity. 536 Section 3.3.2.1 of [cap] specifies the signing algorithms of CAP 537 documents. 539 In addition to the desire to perform identity-based access control 540 the classical communication security threats need to be considered, 541 including integrity protection to prevent forgery and replay of alert 542 messages in transit. To deal with replay of alerts a CAP document 543 contains the mandatory , , elements and an 544 optional element. These attributes make the CAP document 545 unique for a specific sender and provide time restrictions. An 546 entity that has received a CAP message already within the indicated 547 timeframe is able to detect a replayed message and, if the content of 548 that message is unchanged, then no additional security vulnerability 549 is created. Additionally, it is RECOMMENDED to make use of SIP 550 security mechanisms, such as SIP Identity [RFC4474], to tie the CAP 551 message to the SIP message. To provide protection of the entire SIP 552 message exchange between neighboring SIP entities the usage of TLS is 553 mandatory. 555 Note that none of the security mechanism in this document protect 556 against a compromised sensor sending crafted alerts. 558 8. IANA Considerations 560 8.1. Registration of the 'application/cap+xml' MIME type 562 To: ietf-types@iana.org 564 Subject: Registration of MIME media type application/ cap+xml 566 MIME media type name: application 568 MIME subtype name: cap+xml 570 Required parameters: (none) 572 Optional parameters: charset; Indicates the character encoding of 573 enclosed XML. Default is UTF-8 [RFC3629]. 575 Encoding considerations: Uses XML, which can employ 8-bit 576 characters, depending on the character encoding used. See RFC 577 3023 [RFC3023], Section 3.2. 579 Security considerations: This content type is designed to carry 580 payloads of the Common Alerting Protocol (CAP). 582 Interoperability considerations: This content type provides a way to 583 convey CAP payloads. 585 Published specification: RFC XXX [Replace by the RFC number of this 586 specification]. 588 Applications which use this media type: Applications that convey 589 alerts and warnings according to the CAP standard. 591 Additional information: OASIS has published the Common Alerting 592 Protocol at http://www.oasis-open.org/committees/ 593 documents.php&wg_abbrev=emergency 595 Person and email address to contact for further information: Hannes 596 Tschofenig, Hannes.Tschofenig@nsn.com 598 Intended usage: Limited use 600 Author/Change controller: IETF ECRIT working group 602 Other information: This media type is a specialization of 603 application/xml RFC 3023 [RFC3023], and many of the considerations 604 described there also apply to application/cap+xml. 606 8.2. IANA Registration for 425 Response Code 608 In the SIP Response Codes registry, the following is added 610 Reference: RFC-XXXX (i.e., this document) 612 Response code: 425 (recommended number to assign) 614 Default reason phrase: Bad Alert Message 616 Registry: 617 Response Code Reference 618 ------------------------------------------ --------- 619 Request Failure 4xx 620 425 Bad Alert Message [this doc] 622 This SIP Response code is defined in Section 5. 624 8.3. IANA Registration of New AlertMsg-Error Header Field 626 The SIP AlertMsg-error header field is created by this document, with 627 its definition and rules in Section 5, to be added to the IANA sip- 628 parameters registry with two actions: 630 1. Update the Header Fields registry with 632 Registry: 633 Header Name compact Reference 634 ----------------- ------- --------- 635 AlertMsg-Error [this doc] 637 2. In the portion titled "Header Field Parameters and Parameter 638 Values", add 640 Predefined 641 Header Field Parameter Name Values Reference 642 ----------------- ------------------- ---------- --------- 643 AlertMsg-Error code yes [this doc] 645 8.4. IANA Registration for the SIP AlertMsg-Error Codes 647 This document creates a new registry for SIP, called "AlertMsg-Error 648 Codes". AlertMsg-Error codes provide reason for the error discovered 649 by recipients, categorized by action to be taken by error recipient. 650 The initial values for this registry are shown below. 652 Registry Name: AlertMsg-Error Codes 654 Reference: [this doc] 656 Registration Procedures: Specification Required 658 Code Default Reason Phrase Reference 659 ---- --------------------------------------------------- --------- 660 100 "Cannot Process the Alert Payload" [this doc] 662 101 "Alert Payload was not present or could not be found" [this doc] 664 102 "Not enough information to determine 665 the purpose of the alert" [this doc] 667 103 "Alert Payload was corrupted" [this doc] 669 Details of these error codes are in Section 5. 671 9. Acknowledgments 673 The authors would like to thank the participants of the Early Warning 674 adhoc meeting at IETF#69 for their feedback. Additionally, we would 675 like to thank the members of the NENA Long Term Direction Working 676 Group for their feedback. 678 Additionally, we would like to thank Martin Thomson, James 679 Winterbottom, Shida Schubert, Bernard Aboba, and Marc Linsner for 680 their review comments. 682 10. References 684 10.1. Normative References 686 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 687 Requirement Levels", March 1997. 689 [cap] Jones, E. and A. Botterell, "Common Alerting Protocol v. 690 1.1", October 2005. 692 [RFC3023] Murata, M., St. Laurent, S., and D. Kohn, "XML Media 693 Types", RFC 3023, January 2001. 695 [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 696 10646", STD 63, RFC 3629, November 2003. 698 [I-D.ietf-ecrit-phonebcp] 699 Rosen, B. and J. Polk, "Best Current Practice for 700 Communications Services in support of Emergency Calling", 701 draft-ietf-ecrit-phonebcp-17 (work in progress), 702 March 2011. 704 [I-D.ietf-sipcore-location-conveyance] 705 Polk, J., Rosen, B., and J. Peterson, "Location Conveyance 706 for the Session Initiation Protocol", 707 draft-ietf-sipcore-location-conveyance-08 (work in 708 progress), May 2011. 710 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 711 A., Peterson, J., Sparks, R., Handley, M., and E. 712 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 713 June 2002. 715 [RFC3311] Rosenberg, J., "The Session Initiation Protocol (SIP) 716 UPDATE Method", RFC 3311, October 2002. 718 [RFC3428] Campbell, B., Rosenberg, J., Schulzrinne, H., Huitema, C., 719 and D. Gurle, "Session Initiation Protocol (SIP) Extension 720 for Instant Messaging", RFC 3428, December 2002. 722 [RFC6086] Holmberg, C., Burger, E., and H. Kaplan, "Session 723 Initiation Protocol (SIP) INFO Method and Package 724 Framework", RFC 6086, January 2011. 726 [RFC3265] Roach, A., "Session Initiation Protocol (SIP)-Specific 727 Event Notification", RFC 3265, June 2002. 729 [RFC3903] Niemi, A., "Session Initiation Protocol (SIP) Extension 730 for Event State Publication", RFC 3903, October 2004. 732 [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax 733 Specifications: ABNF", STD 68, RFC 5234, January 2008. 735 10.2. Informative References 737 [I-D.ietf-atoca-requirements] 738 Schulzrinne, H., Norreys, S., Rosen, B., and H. 739 Tschofenig, "Requirements, Terminology and Framework for 740 Exigent Communications", draft-ietf-atoca-requirements-01 741 (work in progress), January 2011. 743 [I-D.ietf-ecrit-trustworthy-location] 744 Tschofenig, H., Schulzrinne, H., and B. Aboba, 745 "Trustworthy Location Information", 746 draft-ietf-ecrit-trustworthy-location-02 (work in 747 progress), May 2011. 749 [RFC4474] Peterson, J. and C. Jennings, "Enhancements for 750 Authenticated Identity Management in the Session 751 Initiation Protocol (SIP)", RFC 4474, August 2006. 753 [RFC3325] Jennings, C., Peterson, J., and M. Watson, "Private 754 Extensions to the Session Initiation Protocol (SIP) for 755 Asserted Identity within Trusted Networks", RFC 3325, 756 November 2002. 758 Authors' Addresses 760 Brian Rosen 761 NeuStar, Inc. 762 470 Conrad Dr 763 Mars, PA 16046 764 US 766 Phone: 767 Email: br@brianrosen.net 769 Henning Schulzrinne 770 Columbia University 771 Department of Computer Science 772 450 Computer Science Building 773 New York, NY 10027 774 US 776 Phone: +1 212 939 7004 777 Email: hgs+ecrit@cs.columbia.edu 778 URI: http://www.cs.columbia.edu 780 Hannes Tschofenig 781 Nokia Siemens Networks 782 Linnoitustie 6 783 Espoo 02600 784 Finland 786 Phone: +358 (50) 4871445 787 Email: Hannes.Tschofenig@gmx.net 788 URI: http://www.tschofenig.priv.at