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Elwell 3 Internet-Draft Siemens Enterprise Communications 4 Updates: RFC 3325 GmbH & Co KG 5 (if approved) June 27, 2008 6 Intended status: Informational 7 Expires: December 29, 2008 9 Updates to Asserted Identity in the Session Initiation Protocol (SIP) 10 draft-ietf-sipping-update-pai-04.txt 12 Status of this Memo 14 By submitting this Internet-Draft, each author represents that any 15 applicable patent or other IPR claims of which he or she is aware 16 have been or will be disclosed, and any of which he or she becomes 17 aware will be disclosed, in accordance with Section 6 of BCP 79. 19 Internet-Drafts are working documents of the Internet Engineering 20 Task Force (IETF), its areas, and its working groups. Note that 21 other groups may also distribute working documents as Internet- 22 Drafts. 24 Internet-Drafts are draft documents valid for a maximum of six months 25 and may be updated, replaced, or obsoleted by other documents at any 26 time. It is inappropriate to use Internet-Drafts as reference 27 material or to cite them other than as "work in progress." 29 The list of current Internet-Drafts can be accessed at 30 http://www.ietf.org/ietf/1id-abstracts.txt. 32 The list of Internet-Draft Shadow Directories can be accessed at 33 http://www.ietf.org/shadow.html. 35 This Internet-Draft will expire on December 29, 2008. 37 Abstract 39 SIP has a mechanism for conveying the asserted identity of the 40 originator of a request by means of the P-Asserted-Identity header 41 field. This header field is specified for use in requests using a 42 number of SIP methods, in particular the INVITE method. However, RFC 43 3325 does not specify the insertion of this header field by a trusted 44 UAC, does not specify the use of this header field with certain SIP 45 methods such as UPDATE, REGISTER, MESSAGE, PUBLISH and ACK, and is 46 unclear on the use of this header field in responses. This document 47 extends RFC 3325 to cover these situations. 49 This work is being discussed on the sipping@ietf.org mailing list. 51 Table of Contents 53 1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 54 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 55 3. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . 3 56 3.1. Inclusion of P-Asserted-Identity by a UAC . . . . . . . . 4 57 3.2. Inclusion of P-Asserted-Identity in any request . . . . . 4 58 3.3. Inclusion of P-Asserted-Identity or 59 P-Preferred-Identity in a response . . . . . . . . . . . . 6 60 3.4. Dialog implications . . . . . . . . . . . . . . . . . . . 7 61 4. Behaviour . . . . . . . . . . . . . . . . . . . . . . . . . . 8 62 4.1. UAC Behaviour . . . . . . . . . . . . . . . . . . . . . . 8 63 4.1.1. Request handling . . . . . . . . . . . . . . . . . . . 8 64 4.1.2. Response handling . . . . . . . . . . . . . . . . . . 8 65 4.2. Proxy Behaviour . . . . . . . . . . . . . . . . . . . . . 9 66 4.2.1. Request handling . . . . . . . . . . . . . . . . . . . 9 67 4.2.2. Response handling . . . . . . . . . . . . . . . . . . 9 68 4.3. Registrar Behaviour . . . . . . . . . . . . . . . . . . . 10 69 4.4. UAS Behaviour . . . . . . . . . . . . . . . . . . . . . . 10 70 4.4.1. Request handling . . . . . . . . . . . . . . . . . . . 10 71 4.4.2. Response handling . . . . . . . . . . . . . . . . . . 10 72 5. IANA considerations . . . . . . . . . . . . . . . . . . . . . 10 73 6. Security considerations . . . . . . . . . . . . . . . . . . . 10 74 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11 75 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11 76 8.1. Normative References . . . . . . . . . . . . . . . . . . . 11 77 8.2. Informative References . . . . . . . . . . . . . . . . . . 12 78 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 12 79 Intellectual Property and Copyright Statements . . . . . . . . . . 13 81 1. Terminology 83 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 84 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 85 document are to be interpreted as described in [RFC2119]. 87 This document uses the concepts of Trust Domain and Spec(T), as 88 specified in section 2.3 of RFC 3324 [RFC3324]. 90 2. Introduction 92 The Session Initiation Protocol (SIP) is specified in RFC 3261 93 [RFC3261]. RFC 3325 [RFC3325] specifies a mechanism for conveying 94 within a Trust Domain the asserted identity of the originator of a 95 SIP request. This is achieved by means of the P-Asserted-Identity 96 header field, which is specified for use in requests using a number 97 of SIP methods, in particular the INVITE method. 99 RFC 3325 does not specify the insertion of the P-Asserted-Identity 100 header field by a UAC in the same Trust Domain as the first proxy. 101 Also RFC 3325 does not specify the use of the P-Asserted-Identity 102 header field with certain SIP methods such as UPDATE [RFC3311], 103 REGISTER, MESSAGE [RFC3428], PUBLISH [RFC3903] and ACK. Finally, RFC 104 3325 is unclear on the use of this header field in responses. There 105 are similar omissions concerning the P-Preferred-Identity header 106 field. 108 This document extends RFC 3325 by allowing inclusion of the 109 P-Asserted-Identity header field by a UAC in the same Trust Domain as 110 the first proxy, allowing use of this header field in any request 111 and, under certain conditions, allowing use of this header field in 112 SIP responses. This document also allows the use of the P-Preferred- 113 Identity header field in some of these situations. 115 This document does not alter the fact that the asserted identity 116 mechanism has limited applicability, i.e., within a Trust Domain. 117 For general applicability, including operation outside a Trust Domain 118 (e.g., over the public Internet) or between different Trust Domains, 119 a different mechanism is needed. RFC 4474 [RFC4474] specifies the 120 Identity header field, in conjunction with the From header field, for 121 providing authenticated identity in such circumstances. 123 3. Discussion 124 3.1. Inclusion of P-Asserted-Identity by a UAC 126 RFC 3325 does not include procedures for a UAC to include the 127 P-Asserted-Identity header field in a request. This can be 128 meaningful if the UAC is in the same Trust Domain as the first 129 downstream SIP entity. Examples of types of UAC that are often 130 suitable for inclusion in a Trust Domain are: 132 o PSTN gateways; 134 o media servers; 136 o application servers (or B2BUAs) that act as URI list servers 137 [I-D.ietf-sipping-uri-services]; 139 o application servers (or B2BUAs) that perform third party call 140 control. 142 In the particular case of a PSTN gateway, the PSTN gateway might be 143 able to assert an identity received from the PSTN, the proxy itself 144 having no means to authenticate such an identity. Likewise, in the 145 case of certain application server or B2BUA arrangements, the 146 application server or B2BUA may be in a position to assert an 147 identity of a user on the other side of that application server or 148 B2BUA. 150 In accordance with RFC 3325, nodes within a Trust Domain must behave 151 in accordance with a Spec(T), and this principle needs to apply 152 between a UAC and its proxy as part of the condition for considering 153 the UAC to be within the same Trust Domain. Normal proxy procedures 154 of RFC 3325 ensure that the header field is removed or replaced if 155 the first proxy considers the UAC to be outside the Trust Domain. 157 This update to RFC 3325 clarifies that a UAC may include a 158 P-Asserted-Identity header field in a request in certain 159 circumstances. 161 3.2. Inclusion of P-Asserted-Identity in any request 163 There are several use cases that would benefit from the use of the 164 P-Asserted-Identity header field in an UPDATE request. These use 165 cases apply within a Trust Domain where the use of asserted identity 166 is appropriate (see RFC 3325). 168 In one example, an established call passes through a gateway to the 169 PSTN. The gateway becomes aware that the remote party in the PSTN 170 has changed, e.g., due to call transfer. By including the 171 P-Asserted-Identity header field in an UPDATE request, the gateway 172 can convey the identity of the new remote party to the peer SIP UA. 174 Note that the (re-)INVITE method could be used in this situation. 175 However, this forces an offer-answer exchange, which typically is 176 not required in this situation. Also it involves 3 messages 177 rather than 2. 179 In another example, a B2BUA that provides third party call control 180 (3PCC) [RFC3725] wishes to join two calls together, one of which is 181 still waiting to be answered and potentially is forked to different 182 UAs. At this point in time it is not possible to trigger the normal 183 offer-answer exchange between the two joined parties, because of the 184 mismatch between a single dialog on the one side and potentially 185 multiple early dialogs on the other side, so this action must wait 186 until one of the called UAs answers. However, it would be useful to 187 give an early indication to each user concerned of the identity of 188 the user to which they will become connected when the call is 189 answered. In other words, it would provide the new calling UA with 190 the identity of the new called user and provide the new called UA(s) 191 with the identity of the new calling user. This can be achieved by 192 the B2BUA sending an UPDATE request with a P-Asserted-Identity header 193 field on the dialogs concerned. 195 Within a Trust Domain, a P-Asserted-Identity header field could 196 advantageously be used in a REGISTER request between an edge proxy 197 that has authenticated the source of the request and the registrar. 199 Within a Trust Domain, a P-Asserted-Identity header field could 200 advantageously be used in a MESSAGE request to assert the source of a 201 page mode instant message. This would complement its use in an 202 INVITE request to assert the source of an instant message session or 203 any other form of session. Similarly, between a UAC and first proxy 204 that are not within the same Trust Domain, a P-Preferred-Identity 205 header field could be used in a MESSAGE request to express a 206 preference when the user has several identities. 208 Within a Trust Domain, a P-Asserted-Identity header field could 209 advantageously be used in a PUBLISH request to assert the source of 210 published state information. This would complement its use in 211 SUBSCRIBE and NOTIFY requests. Similarly, between a UAC and first 212 proxy that are not within the same Trust Domain, a P-Preferred- 213 Identity header field could be used in a PUBLISH request to express a 214 preference when the user has several identities. 216 Within a Trust Domain, a P-Asserted-Identity header field could 217 advantageously be used in an ACK request. Considering the 3PCC 218 scenario in Flow I of [RFC3725], the asserted identity of user B may 219 not be known when the B2BUA (controller) sends the initial INVITE 220 request to UA A, but might be known when the B2BUA sends the ACK 221 request to UA A (having received it in the 200 response from UA B). 223 Thus there are several examples where P-Asserted-Identity could be 224 used in requests with methods that are not provided for in RFC 3325 225 or any other RFC. This leaves a few methods for which use cases are 226 less obvious, but the inclusion of P-Asserted Identity would not 227 cause any harm. In any requests, the header field would simply 228 assert the source of that request, whether or not this is of any use 229 to the UAS. Similarly there are examples where P-Preferred-Identity 230 could be used in requests with methods that are not provided for in 231 RFC 3325 or any other RFC. 233 This update to RFC 3325 allows a P-Asserted-Identity or P-Preferred- 234 Identity header field to be included in any request. 236 3.3. Inclusion of P-Asserted-Identity or P-Preferred-Identity in a 237 response 239 There are cases where the inclusion of the P-Asserted-Identity header 240 field in responses would be useful. Retargeting of a request can 241 result in the responding entity having a different identity from that 242 placed in the To URI of the request. Inclusion of asserted identity 243 in a response would provide the UAC with the identity of the 244 responder. Some examples of the benefits to be gained include: 246 o Asserted identity in a 2xx response to an INVITE request would 247 indicate the identity of the connected user. 249 o Asserted identity in a provisional response to an INVITE request 250 would indicate the contacted (e.g., alerted) user. 252 o Asserted identity in a 2xx response to a MESSAGE request would 253 provide confirmation of where the message was delivered to. 255 o Asserted identity in certain 4xx/5xx/6xx responses would provide 256 an indication of where the response originated. 258 In the case of a request that results in the formation of a dialog, a 259 mid-dialog request (e.g., UPDATE) in the reverse direction can 260 provide the identity of the user at the destination end of that 261 dialog, and therefore the need to include asserted identity in a 262 response to the dialog-forming request to identify the connected user 263 is debatable. There can be some benefits in terms of ease of 264 interworking with PSTN, where such information is placed in the 265 response to a call establishment request. For other responses, 266 including successful responses to requests such as MESSAGE and 267 PUBLISH and unsuccessful responses, the use of a request in the 268 reverse direction is unsuitable. 270 Note that when the authenticated identity of the connected user is 271 to be provided using the From and Identity header fields (as 272 opposed to providing asserted identity using the P-Asserted- 273 Identity header field), RFC 4916 [RFC4916] requires this to be 274 done in a mid-dialog request (e.g., UPDATE) in the reverse 275 direction. This is because the Identity header field is defined 276 only for use in requests. 278 RFC 3325 is ambiguous on inclusion of P-Asserted-Identity in a 279 response. For example, section 4 of RFC 3325 talks about inclusion 280 of the header field in messages, as opposed to requests. Moreover 281 section 5 explicitly mentions "message (request or response)". 282 However, there are other places (e.g., sections 6, 7 and 8) that only 283 mention requests. 285 Section 5 of RFC 3325 requires a proxy to authenticate the originator 286 of a message before adding a P-Asserted-Identity header field to the 287 forwarded message. In practice there is no SIP means to authenticate 288 the sender of a SIP response message. However, authentication may be 289 possible by other means. For example, if the proxy has TLS 290 connectivity with the originator of the response and has previously 291 authenticated the connected entity (e.g., using SIP digest 292 authentication at registration time), then the originator of the 293 response can be considered to be authenticated. In such 294 circumstances it is permissible for a proxy to insert a P-Asserted- 295 Identity header field in a SIP response. 297 It should also be permissible for a UAS to insert a P-Asserted- 298 Identity header field into a response if it is within the same Trust 299 Domain as the SIP entity from which the request was received. 301 Between a UAS and a SIP entity that are not within the same Trust 302 Domain, a P-Preferred-Identity header field could be used in a 303 response, in order to express a preference when the authenticated 304 user has several identities. 306 This update to RFC 3325 allows a P-Asserted-Identity or P-Preferred- 307 Identity header field to be included in a response in certain 308 circumstances. 310 3.4. Dialog implications 312 A P-Asserted-Identity header field in a received request or response 313 asserts the identity of the source of that request or response and 314 says nothing about the source of subsequent received requests or 315 responses claiming to relate to the same dialog. The recipient can 316 make its own deductions about the source of subsequent requests or 317 responses not containing a P-Asserted-Identity header field. This 318 document does not change RFC 3325 in this respect. 320 4. Behaviour 322 This document updates RFC 3325 by allowing a P-Asserted-Identity 323 header field to be included by a UAC within the same Trust Domain, by 324 allowing a P-Asserted-Identity or P-Preferred-Identity header field 325 to appear in any request, and by allowing a P-Asserted-Identity 326 header field to appear in a response in certain circumstances. 328 4.1. UAC Behaviour 330 4.1.1. Request handling 332 A UAC MAY include a P-Asserted-Identity header field in a request to 333 report the identity of the user on behalf of which the UAC is acting 334 and whose identity the UAC is in a position to assert. A UAC SHOULD 335 do so only in cases where it believes it is in the same Trust Domain 336 as the SIP entity to which it sends the request and is connected to 337 that SIP entity in accordance with the security requirements of RFC 338 3325. A UAC SHOULD NOT do so in other circumstances and might 339 instead use the P-Preferred-Identity header field. A UAC MUST NOT 340 include both header fields. 342 A UAC MAY include a P-Asserted-Identity or P-Preferred-Identity 343 header field in any request, i.e., not limited to the methods allowed 344 in RFC 3325. 346 4.1.2. Response handling 348 Typically a UA renders the value of a P-Asserted-Identity header 349 field that it receives in a response to its user. It may consider 350 the identity provided by a Trust Domain to be privileged, or 351 intrinsically more trustworthy than other information in the 352 response. However, any particular behaviour is specific to 353 implementations or services. This document also does not mandate any 354 UA handling for multiple P-Asserted-Identity header field values that 355 happen to appear in a response (such as a SIP URI alongside a tel 356 URL). 358 However, if a UAC receives a response from a previous element it does 359 not trust, it MUST NOT use the P-Asserted-Identity header field in 360 any way. 362 If a UA is part of the Trust Domain from which it received a response 363 containing a P-Asserted-Identity header field, then it can use the 364 value internally but it MUST ensure that it does not forward the 365 information to any element that is not part of the Trust Domain if 366 the responding user has requested that asserted identity information 367 be kept private. 369 4.2. Proxy Behaviour 371 4.2.1. Request handling 373 If a proxy receives a request from a UAC within the Trust Domain it 374 MUST behave as for a request from any other node within the Trust 375 Domain, in accordance with the rules of RFC 3325 for a proxy. 377 Note that this implies that the proxy must have authenticated the 378 sender of the request in accordance with the Spec(T) in force for 379 the Trust Domain and determined that the sender is indeed part of 380 the Trust Domain. 382 If a proxy receives a request containing a P-Asserted-Identity or 383 P-Preferred-Identity header field, it MUST behave in accordance with 384 the rules of RFC 3325 for a proxy, even if the method is not one for 385 which RFC 3325 specifies use of that header field. 387 4.2.2. Response handling 389 The proxy behaviour specified in RFC 3325 is applicable to responses 390 with the following qualifications. A proxy that receives a response 391 from a node outside the Trust Domain cannot directly authenticate the 392 UAS by SIP means. Therefore it MUST NOT include a P-Asserted- 393 Identity header field when forwarding the response unless it has 394 authenticated the UAS by other means. 396 One possible circumstance in which a proxy can include a 397 P-Asserted-Identity header field when forwarding a response from a 398 node outside the Trust Domain is when the proxy has direct TLS 399 connectivity with the UAS and has authenticated the UA by some 400 other means (e.g., SIP digest authentication) during that same TLS 401 session. 403 The proxy behaviour specified in RFC 3325 applies for handling a 404 P-Asserted-Identity header field in a response from a node within the 405 Trust Domain. 407 The proxy behaviour specified in RFC 3325 for handling a received 408 P-Preferred-Identity header field is applicable also to responses, 409 subject to the qualification above concerning authentication of the 410 UAS as a pre-requisite for inserting a P-Asserted-Identity header 411 field. 413 4.3. Registrar Behaviour 415 If a registrar receives a REGISTER request containing a P-Asserted- 416 Identity header field, it MUST disregard the asserted identity unless 417 received over a secure transport from a node within the Trust Domain. 418 Otherwise it MAY use this as evidence that the registering UA has 419 been authenticated as representing the identity asserted in the 420 header field. 422 4.4. UAS Behaviour 424 4.4.1. Request handling 426 If a UAS receives any request containing a P-Asserted-Identity header 427 field, it MUST behave as for any other request in accordance with the 428 rules of RFC 3325 for a UAS, even if the method is not one for which 429 RFC 3325 specifies use of that header field. 431 4.4.2. Response handling 433 A UAS MAY include a P-Asserted-Identity or P-Preferred-Identity 434 header field in a response to report the identity of the user on 435 behalf of which the UAS is acting and whose identity the UAS is in a 436 position to assert. A UAS SHOULD include a P-Asserted-Identity 437 header field only in cases where it believes it is in the same Trust 438 Domain as the SIP entity from which it received the request and is 439 connected to that SIP entity in accordance with the security 440 requirements of RFC 3325. 442 5. IANA considerations 444 This document requires no IANA actions. 446 6. Security considerations 448 The use of asserted identity raises a number of security 449 considerations, which are discussed fully in [RFC3325]. This 450 document raises the following additional security considerations. 452 When receiving a request or response containing a P-Asserted-Identity 453 header field, a proxy will trust the assertion only if the source is 454 known to be within the Trust Domain and behaves in accordance with a 455 Spec(T), which defines the security requirements. This applies 456 regardless of the nature of the resource (UA or proxy). One example 457 where a trusted source might be a UA is a PSTN gateway. In this case 458 the UA can assert an identity received from the PSTN, the proxy 459 itself having no means to authenticate such an identity. A SIP 460 entity must not trust an identity asserted by a source outside the 461 Trust Domain. Typically a UA under the control of an individual user 462 (such as a desk phone or mobile phone) should not be considered part 463 of a Trust Domain. 465 When receiving a response from a node outside the Trust Domain, a 466 proxy has no direct SIP means to authenticate the node. However, if 467 authentication has taken place by other means (e.g., an earlier use 468 of SIP digest authentication) and the entity sending the response is 469 known to be the same entity (e.g., connected via the same TLS 470 session) this can be sufficient grounds for asserting an identity. 471 In other circumstances a proxy must not assert identity for a 472 responding user. 474 When receiving a REGISTER request containing a P-Asserted-Identity 475 header field, a proxy will trust the asserted identity only if 476 received over a secure connection from a proxy within the Trust 477 Domain. 479 7. Acknowledgements 481 Useful comments were received from Francois Audet, Jeroen van Bemmel, 482 Hans Erik van Elburg, Vijay Gurbani, Cullen Jennings, Hadriel Kaplan, 483 Paul Kyzivat, Jonathan Rosenberg, Thomas Stach and Brett Tate during 484 drafting and review. 486 8. References 488 8.1. Normative References 490 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 491 Requirement Levels", BCP 14, RFC 2119, March 1997. 493 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 494 A., Peterson, J., Sparks, R., Handley, M., and E. 495 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 496 June 2002. 498 [RFC3311] Rosenberg, J., "The Session Initiation Protocol (SIP) 499 UPDATE Method", RFC 3311, October 2002. 501 [RFC3324] Watson, M., "Short Term Requirements for Network Asserted 502 Identity", RFC 3324, November 2002. 504 [RFC3325] Jennings, C., Peterson, J., and M. Watson, "Private 505 Extensions to the Session Initiation Protocol (SIP) for 506 Asserted Identity within Trusted Networks", RFC 3325, 507 November 2002. 509 [RFC3428] Campbell, B., Rosenberg, J., Schulzrinne, H., Huitema, C., 510 and D. Gurle, "Session Initiation Protocol (SIP) Extension 511 for Instant Messaging", RFC 3428, December 2002. 513 [RFC3903] Niemi, A., "Session Initiation Protocol (SIP) Extension 514 for Event State Publication", RFC 3903, October 2004. 516 [I-D.ietf-sipping-uri-services] 517 Camarillo, G. and A. Roach, "Framework and Security 518 Considerations for Session Initiation Protocol (SIP) 519 Uniform Resource Identifier (URI)-List Services", 520 draft-ietf-sipping-uri-services-07 (work in progress), 521 November 2007. 523 8.2. Informative References 525 [RFC3725] Rosenberg, J., Peterson, J., Schulzrinne, H., and G. 526 Camarillo, "Best Current Practices for Third Party Call 527 Control (3pcc) in the Session Initiation Protocol (SIP)", 528 BCP 85, RFC 3725, April 2004. 530 [RFC4474] Peterson, J. and C. Jennings, "Enhancements for 531 Authenticated Identity Management in the Session 532 Initiation Protocol (SIP)", RFC 4474, August 2006. 534 [RFC4916] Elwell, J., "Connected Identity in the Session Initiation 535 Protocol (SIP)", RFC 4916, June 2007. 537 Author's Address 539 John Elwell 540 Siemens Enterprise Communications GmbH & Co KG 541 Hofmannstrasse 51 542 D-81379 Munich 543 Germany 545 Phone: +44 115 943 4989 546 Email: john.elwell@siemens.com 548 Full Copyright Statement 550 Copyright (C) The IETF Trust (2008). 552 This document is subject to the rights, licenses and restrictions 553 contained in BCP 78, and except as set forth therein, the authors 554 retain all their rights. 556 This document and the information contained herein are provided on an 557 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 558 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 559 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 560 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 561 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 562 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 564 Intellectual Property 566 The IETF takes no position regarding the validity or scope of any 567 Intellectual Property Rights or other rights that might be claimed to 568 pertain to the implementation or use of the technology described in 569 this document or the extent to which any license under such rights 570 might or might not be available; nor does it represent that it has 571 made any independent effort to identify any such rights. Information 572 on the procedures with respect to rights in RFC documents can be 573 found in BCP 78 and BCP 79. 575 Copies of IPR disclosures made to the IETF Secretariat and any 576 assurances of licenses to be made available, or the result of an 577 attempt made to obtain a general license or permission for the use of 578 such proprietary rights by implementers or users of this 579 specification can be obtained from the IETF on-line IPR repository at 580 http://www.ietf.org/ipr. 582 The IETF invites any interested party to bring to its attention any 583 copyrights, patents or patent applications, or other proprietary 584 rights that may cover technology that may be required to implement 585 this standard. Please address the information to the IETF at 586 ietf-ipr@ietf.org.