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Crocker 3 Internet-Draft Brandenburg 4 Expires: June 6, 2003 J. Peterson 5 NeuStar 6 December 6, 2002 8 Common Profile: Presence 9 draft-ietf-impp-pres-01 11 Status of this Memo 13 This document is an Internet-Draft and is in full conformance with 14 all provisions of Section 10 of RFC2026. 16 Internet-Drafts are working documents of the Internet Engineering 17 Task Force (IETF), its areas, and its working groups. Note that 18 other groups may also distribute working documents as Internet- 19 Drafts. 21 Internet-Drafts are draft documents valid for a maximum of six months 22 and may be updated, replaced, or obsoleted by other documents at any 23 time. It is inappropriate to use Internet-Drafts as reference 24 material or to cite them other than as "work in progress." 26 The list of current Internet-Drafts can be accessed at http:// 27 www.ietf.org/ietf/1id-abstracts.txt. 29 The list of Internet-Draft Shadow Directories can be accessed at 30 http://www.ietf.org/shadow.html. 32 This Internet-Draft will expire on June 6, 2003. 34 Copyright Notice 36 Copyright (C) The Internet Society (2002). All Rights Reserved. 38 Abstract 40 Presence is defined in RFC2778 [5]. Today, numerous presence 41 protocols are in use (largely as components of commercial instant 42 messaging services), and little interoperability between services 43 based on these protocols has been achieved. This specification 44 defines common semantics and data formats for presence to facilitate 45 the creation of gateways between presence services. 47 Table of Contents 49 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 50 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3 51 3. Abstract Presence Service . . . . . . . . . . . . . . . . . 4 52 3.1 Overview of the Presence Service . . . . . . . . . . . . . . 4 53 3.2 Identification of PRESENTITIES and WATCHERS . . . . . . . . 6 54 3.3 Format of Presence Information . . . . . . . . . . . . . . . 6 55 3.4 The Presence Service . . . . . . . . . . . . . . . . . . . . 7 56 3.4.1 The Subscribe Operation . . . . . . . . . . . . . . . . . . 7 57 3.4.2 The Notify Operation . . . . . . . . . . . . . . . . . . . . 8 58 3.4.3 Subscribe Operation (with Zero Duration) . . . . . . . . . . 8 59 4. Security Considerations . . . . . . . . . . . . . . . . . . 8 60 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . 9 61 5.1 The PRES URI Scheme . . . . . . . . . . . . . . . . . . . . 9 62 6. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 9 63 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 10 64 A. PRES URI IANA Registration Template . . . . . . . . . . . . 10 65 A.1 URI scheme name . . . . . . . . . . . . . . . . . . . . . . 10 66 A.2 URI scheme syntax . . . . . . . . . . . . . . . . . . . . . 10 67 A.3 Character encoding considerations . . . . . . . . . . . . . 11 68 A.4 Intended usage . . . . . . . . . . . . . . . . . . . . . . . 11 69 A.5 Applications and/or protocols which use this URI scheme 70 name . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 71 A.6 Interoperability considerations . . . . . . . . . . . . . . 11 72 A.7 Security considerations . . . . . . . . . . . . . . . . . . 11 73 A.8 Relevant publications . . . . . . . . . . . . . . . . . . . 11 74 A.9 Person & email address to contact for further information . 12 75 A.10 Author/Change controller . . . . . . . . . . . . . . . . . . 12 76 A.11 Applications and/or protocols which use this URI scheme 77 name . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 78 B. Issues of Interest . . . . . . . . . . . . . . . . . . . . . 12 79 B.1 Address Mapping . . . . . . . . . . . . . . . . . . . . . . 12 80 B.2 Source-Route Mapping . . . . . . . . . . . . . . . . . . . . 12 81 Normative References . . . . . . . . . . . . . . . . . . . . 9 82 C. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 13 83 Full Copyright Statement . . . . . . . . . . . . . . . . . . 14 85 1. Introduction 87 Presence is defined in RFC2778 [5]. Today, numerous presence 88 protocols are in use (largely as components of commercial instant 89 messaging services, and little interoperability between services 90 based on these protocols has been achieved. This specification 91 defines semantics and data formats for common services of presence to 92 facilitate the creation of gateways between presence services. 94 Service behavior is described abstractly in terms of operations 95 invoked between the consumer and provider of a service. Accordingly, 96 each presence service must specify how this behavior is mapped onto 97 its own protocol interactions. The choice of strategy is a local 98 matter, providing that there is a clear relation between the abstract 99 behaviors of the service (as specified in this memo) and how it is 100 faithfully realized by a particular presence service. 102 The parameters for each operation are defined using an abstract 103 syntax. Although the syntax specifies the range of possible data 104 values, each Presence and IM service must specify how well-formed 105 instances of the abstract representation are encoded as a concrete 106 series of bits. 108 For example, one strategy might transmit presence information as key/ 109 value pairs, another might use a compact binary representation, and a 110 third might use nested containers. The choice of strategy is a local 111 matter, providing that there is a clear relation between the abstract 112 syntax (as specified in this memo) and how it is faithfully encoded 113 by an particular presence service. 115 In order to provide a means for the preservation of end-to-end 116 features (especially security) to pass through presence 117 interoperability gateways, this specification also provides 118 recommendations for presence document formats that could be employed 119 by presence protocols. 121 2. Terminology 123 In this document, the key words "MUST", "MUST NOT", "REQUIRED", 124 "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT 125 RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as 126 described in RFC2119 [1] and indicate requirement levels for 127 compliant implementations. 129 This memos makes use of the vocabulary defined in RFC2778 [5]. Terms 130 such as CLOSED, INSTANT INBOX, PRESENCE, and OPEN are used in the 131 same meaning as defined therein. 133 This document defines operations and attributes of a presence 134 service. In order for a protocol to interface with a presence 135 gateway, it must support all of the operations described in this 136 document (i.e. the presence protocol must have some message or 137 capability that provides the function described by this operation). 138 Similarly, the attributes defined for these operations must 139 correspond to information available in the presence protocol in order 140 for the protocol to interface with gateways defined by this 141 specification. Note that these attributes provide only the minimum 142 possible information that needs to be specified for interoperability 143 - the functions in a presence protocol that correspond to the 144 operations described in this document can contain additional 145 information that will not be mapped by CPP. 147 3. Abstract Presence Service 149 3.1 Overview of the Presence Service 151 When an application wants to (periodically) receive the presence 152 information associated with a PRESENTITY, it invokes the subscribe 153 operation, e.g., 155 +-------+ +-------+ 156 | | | | 157 | appl. | -- subscribe ----> | pres. | 158 | | | svc. | 159 +-------+ +-------+ 161 The subscribe operation has the following attributes: watcher, 162 target, duration, SubscriptID and TransID. The 'watcher' and 163 'target' identify the WATCHER and PRESENTITY, respectively, using the 164 identifiers described in Section 3.2. The duration specifies the 165 maximum number of seconds that the SUBSCRIPTION should be active 166 (which may be zero, in which case this is a one-time request for 167 presence information). The SubscriptID creates a reference to the 168 SUBSCRIPTION that is used when unsubscribing. The TransID is a 169 unique identifier used to correlate the subscribe operation with a 170 response operation. 172 Upon receiving a subscribe operation, the service immediately 173 responds by invoking the response operation containing the same 174 transaction- identifier, e.g., 175 +-------+ +-------+ 176 | | | | 177 | appl. | <----- response -- | pres. | 178 | | | svc. | 179 +-------+ +-------+ 181 The response operation has the following attributes: status, TransID, 182 and duration. 'status' indicates whether the subscribe operation has 183 succeeded or failed. The TransID of the response operation 184 corresponds to the TransID of the subscription operation to which it 185 is responding. The 'duration' attribute specifies the number of 186 seconds for which the subscription will be active (which may differ 187 from the value requested in the subscribe operation). 189 If the response operation indicates success, the service immediately 190 invokes the notify operation to communicate the presence information 191 to the WATCHER, e.g., 193 +-------+ +-------+ 194 | | | | 195 | appl. | <------- notify -- | pres. | 196 | | | svc. | 197 +-------+ +-------+ 199 The notify operation has the following attributes: watcher, target, 200 and TransID. The values of 'watcher' and 'target' are identical to 201 those given in the subscribe operation that triggered this notify 202 operation. The TransID is a unique identifier for this notification. 204 The notify operation also has content, namely PRESENCE INFORMATION. 205 Some further information on notify content is given in Section 3.3. 207 If the duration parameter is non-zero, then for up to the specified 208 duration, the service invokes the notify operation whenever there are 209 any changes to the PRESENTITY's presence information. Otherwise, 210 exactly one notify operation is invoked, achieving a one-time poll of 211 the presence information. Regardless, there is no application 212 response to the notify operation (i.e., the application does not 213 invoke a response operation when a notify operation occurs) defined 214 in CPP. 216 The application may prematurely cancel a subscription by re-invoking 217 the subscribe operation (as described above) with a duration of 0 and 218 the same SubscriptID as the original subscribe operation , e.g., 219 +-------+ +-------+ 220 | | | | 221 | appl. | -- subscribe 0 --> | pres. | 222 | | | svc. | 223 +-------+ +-------+ 225 Note that a notify operation will be invoke when a subscription is 226 prematurely canceled in this fashion; this notification may be 227 discarded by the watcher. 229 The service immediately responds by invoking the response operation 230 containing the same transaction- identifier, e.g., 232 +-------+ +-------+ 233 | | | | 234 | appl. | <----- response -- | pres. | 235 | | | svc. | 236 +-------+ +-------+ 238 3.2 Identification of PRESENTITIES and WATCHERS 240 A PRESENTITY is specified using the PRES URI scheme, which is further 241 described in Appendix A. An example would be: 242 "pres:fred@example.com" 244 To resolve presence URIs, a client determines the address of an 245 appropriate system running a server by resolving the destination 246 domain name that is part of the identifier to either an intermediate 247 relay system or a final target system. 249 Compliant implementations SHOULD follow the guidelines for 250 dereferencing URIs given in [2]. 252 3.3 Format of Presence Information 254 This specification defines an abstract interoperability mechanism for 255 presence protocols; the message content definition given here 256 pertains to semantics rather than syntax. However, some important 257 properties for interoperability can only be provided if a common end- 258 to-end format for presence is employed by the interoperating presence 259 protocols. Implementations therefore SHOULD support the format 260 defined in PIDF [4]. 262 3.4 The Presence Service 264 An implementation of the service must maintain information about both 265 presence information and in- progress operations in persistent 266 storage. 268 Note that the transaction-identifier parameter used by the service is 269 potentially long-lived. Accordingly, the values generated for this 270 parameter should be unique across a significant duration of time. 272 3.4.1 The Subscribe Operation 274 When an application wants to (periodically) receive the presence 275 information associated with a PRESENTITY, it invokes the subscribe 276 operation. 278 When the service is informed of the subscribe operation, it performs 279 these steps: 281 1. If the watcher or target parameter does not refer to a valid 282 PRESENTITY, a response operation having status "failure" is 283 invoked. 285 2. If access control does not permit the application to request this 286 operation, a response operation having status "failure" is 287 invoked. 289 3. If the duration parameter is non-zero, and if the watcher and 290 target parameters refer to an in-progress subscribe operation for 291 the application, a response operation having status "failure" is 292 invoked. 294 4. Otherwise, if the service is able to successfully deliver the 295 message: 297 A response operation having status "success" is immediately 298 invoked. (If the service chooses a different duration for the 299 subscription then it conveys this information in the response 300 operation.) 302 A notify operation, corresponding to the target's presence 303 information, is immediately invoked for the watcher. 305 For up to the amount of time indicated by the duration 306 parameter, if the target's presence information changes, and 307 if access control allows, a notify operation is invoked for 308 the watcher. 310 Note that if the duration parameter is zero-valued, then the 311 subscribe operation is making a one-time poll of the presence 312 information. Accordingly, the final step above (continued 313 notifications for the duration of the subscription) does not occur. 315 When the service invokes a response operation as a result of this 316 processing, the transID parameter is identical to the value found in 317 the subscribe operation invoked by the application. 319 3.4.2 The Notify Operation 321 The service invokes the notify operation whenever the presence 322 information associated with a PRESENTITY changes and there are 323 subscribers to that information. 325 There is no application response to the notify operation. 327 3.4.3 Subscribe Operation (with Zero Duration) 329 When an application wants to terminate a subscription, it issues a 330 SUBSCRIBE 0 with the SubscriptID of an existing subscription. Note 331 that an notify operation will be invoked by the presentity when a 332 subscription is canceled in this fashion; this notification can be 333 discarded by the watcher. There is no independent UNSUBSCRIBE 334 operation. 336 When an application wants to directly request presence information to 337 be supplied immediately without initiating any persistent 338 subscription, it issues a SUBSCRIBE 0 with a new SubscriptID. There 339 is no independent FETCH operation. 341 4. Security Considerations 343 Detailed security considerations for presence protocols given in 344 RFC2779 (in particular, requirements are given in sections 5.1 345 through 5.3 and some motivating discussion in 8.2). 347 CPP defines an interoperability function that is employed by gateways 348 between presence protocols. CPP gateways MUST be compliant with the 349 minimum security requirements of the presence protocols with which 350 they interface. 352 Note that end-to-end security properties (especially confidentiality 353 and integrity) between presentities and watchers that interface 354 through a CPP gateway can only be provided if a common presence 355 format (such as the format described in [4]) is supported by the 356 protocols interfacing with the CPP gateway. 358 5. IANA Considerations 360 The IANA assigns the "pres" URI scheme. 362 5.1 The PRES URI Scheme 364 The Presence (PRES) URI scheme designates an Internet resource, 365 namely a PRESENTITY or WATCHER. 367 The syntax of a PRES URI is given in Appendix A. 369 6. Contributors 371 The following individuals made substantial textual contributions to 372 this document: 374 Athanassios Diacakis (thanos.diacakis@openwave.com) 376 Florencio Mazzoldi (flo@networkprojects.com) 378 Christian Huitema (huitema@microsoft.com) 380 Graham Klyne (gk@ninebynine.org) 382 Jonathan Rosenberg (jdrosen@dynamicsoft.com) 384 Robert Sparks (rsparks@dynamicsoft.com) 386 Hiroyasu Sugano (suga@flab.fujitsu.co.jp) 388 Normative References 390 [1] Bradner, S., "Key words for use in RFCs to indicate requirement 391 levels", RFC 2119, March 1997. 393 [2] Crocker, D. and J. Peterson, "Address resolution for Instant 394 Messaging and Presence", draft-ietf-impp-srv-00 (work in 395 progress), October 2002. 397 [3] Resnick, P., "Internet Message Format", RFC 2822, STD 11, April 398 2001. 400 [4] Sugano, H., Fujimoto, S., Klyne, G., Bateman, A., Carr, W. and 401 J. Peterson, "CPIM Presence Information Data Format", draft- 402 ietf-impp-cpim-pidf-00 (work in progress), August 2001. 404 [5] Day, M., Rosenberg, J. and H. Sugano, "A Model for Presence and 405 Instant Messaging", RFC 2778, February 2000. 407 [6] Day, M., Aggarwal, S. and J. Vincent, "Instant Messaging / 408 Presence Protocol Requirements", RFC 2779, February 2000. 410 [7] Allocchio, C., "GSTN Address Element Extensions in Email 411 Services", RFC 2846, June 2000. 413 Authors' Addresses 415 Dave Crocker 416 Brandenburg InternetWorking 417 675 Spruce Drive 418 Sunnyvale, CA 94086 419 US 421 Phone: +1 408/246-8253 422 EMail: dcrocker@brandenburg.com 424 Jon Peterson 425 NeuStar, Inc. 426 1800 Sutter St 427 Suite 570 428 Concord, CA 94520 429 US 431 Phone: +1 925/363-8720 432 EMail: jon.peterson@neustar.biz 434 Appendix A. PRES URI IANA Registration Template 436 This section provides the information to register the pres: presence 437 URI . 439 A.1 URI scheme name 441 pres 443 A.2 URI scheme syntax 445 The syntax follows the existing mailto: URI syntax specified in 446 RFC2368. The ABNF is: 448 PRES-URI = "pres:" [ to ] [ headers ] 449 to = #mailbox 450 headers = "?" header *( "&" header ) 451 header = hname "=" hvalue 452 hname = *urlc 453 hvalue = *urlc 455 A.3 Character encoding considerations 457 Representation of non-ASCII character sets in local-part strings is 458 limited to the standard methods provided as extensions to RFC2822" 459 [3]. 461 A.4 Intended usage 463 Use of the pres: URI follows closely usage of the mailto: URI. That 464 is, invocation of an PRES URI will cause the user's instant messaging 465 application to start, with destination address and message headers 466 fill-in according to the information supplied in the URI. 468 A.5 Applications and/or protocols which use this URI scheme name 470 It is anticipated that protocols compliant with RFC2779, and meeting 471 the interoperability requirements specified here, will make use of 472 this URI scheme name. 474 A.6 Interoperability considerations 476 The underlying exchange protocol used to send an instant message may 477 vary from service to service. Therefore complete, Internet-scale 478 interoperability cannot be guaranteed. However, a service conforming 479 to this specification permits gateways to achieve interoperability 480 sufficient to the requirements of RFC2779. 482 A.7 Security considerations 484 When PRES URIs are placed in presence protocols, they convey the 485 identity of the sender and/or the recipient. In some cases, 486 anonymous messaging may be desired. Such a capability is beyond the 487 scope of this specification. 489 A.8 Relevant publications 491 RFC2779, RFC2778 493 A.9 Person & email address to contact for further information 495 Jon Peterson [mailto:jon.peterson@neustar.biz] 497 A.10 Author/Change controller 499 This scheme is registered under the IETF tree. As such, IETF 500 maintains change control. 502 A.11 Applications and/or protocols which use this URI scheme name 504 Instant messaging service; presence service 506 Appendix B. Issues of Interest 508 This appendix briefly discusses issues that may be of interest when 509 designing an interoperation gateway. 511 B.1 Address Mapping 513 When mapping the service described in this memo, mappings that place 514 special information into the im: address local-part MUST use the 515 meta-syntax defined in RFC2846 [7]. 517 B.2 Source-Route Mapping 519 The easiest mapping technique is a form of source- routing and 520 usually is the least friendly to humans having to type the string. 521 Source-routing also has a history of operational problems. 523 Use of source-routing for exchanges between different services is by 524 a transformation that places the entire, original address string into 525 the im: address local part and names the gateway in the domain part. 527 For example, if the destination INSTANT INBOX is "pepp://example.com/ 528 fred", then, after performing the necessary character conversions, 529 the resulting mapping is: 531 im:pepp=example.com/fred@relay-domain 533 where "relay-domain" is derived from local configuration information. 535 Experience shows that it is vastly preferable to hide this mapping 536 from end-users - if possible, the underlying software should perform 537 the mapping automatically. 539 Appendix C. Acknowledgments 541 The authors would like to acknowledge John Ramsdell for his comments, 542 suggestions and enthusiasm. Thanks to Derek Atkins for editorial 543 fixes. 545 Full Copyright Statement 547 Copyright (C) The Internet Society (2002). All Rights Reserved. 549 This document and translations of it may be copied and furnished to 550 others, and derivative works that comment on or otherwise explain it 551 or assist in its implementation may be prepared, copied, published 552 and distributed, in whole or in part, without restriction of any 553 kind, provided that the above copyright notice and this paragraph are 554 included on all such copies and derivative works. However, this 555 document itself may not be modified in any way, such as by removing 556 the copyright notice or references to the Internet Society or other 557 Internet organizations, except as needed for the purpose of 558 developing Internet standards in which case the procedures for 559 copyrights defined in the Internet Standards process must be 560 followed, or as required to translate it into languages other than 561 English. 563 The limited permissions granted above are perpetual and will not be 564 revoked by the Internet Society or its successors or assigns. 566 This document and the information contained herein is provided on an 567 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING 568 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING 569 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION 570 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF 571 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 573 Acknowledgement 575 Funding for the RFC Editor function is currently provided by the 576 Internet Society.