IMPP WG D. Crocker Internet-Draft Brandenburg Expires: June 6, 2003 J. Peterson NeuStar December 6, 2002 Common Profile: Presence draft-ietf-impp-pres-01 Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http:// www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on June 6, 2003. Copyright Notice Copyright (C) The Internet Society (2002). All Rights Reserved. Abstract Presence is defined in RFC2778 [5]. Today, numerous presence protocols are in use (largely as components of commercial instant messaging services), and little interoperability between services based on these protocols has been achieved. This specification defines common semantics and data formats for presence to facilitate the creation of gateways between presence services. Crocker & Peterson Expires June 6, 2003 [Page 1] Internet-Draft Common Profile: Presence December 2002 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Abstract Presence Service . . . . . . . . . . . . . . . . . 4 3.1 Overview of the Presence Service . . . . . . . . . . . . . . 4 3.2 Identification of PRESENTITIES and WATCHERS . . . . . . . . 6 3.3 Format of Presence Information . . . . . . . . . . . . . . . 6 3.4 The Presence Service . . . . . . . . . . . . . . . . . . . . 7 3.4.1 The Subscribe Operation . . . . . . . . . . . . . . . . . . 7 3.4.2 The Notify Operation . . . . . . . . . . . . . . . . . . . . 8 3.4.3 Subscribe Operation (with Zero Duration) . . . . . . . . . . 8 4. Security Considerations . . . . . . . . . . . . . . . . . . 8 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . 9 5.1 The PRES URI Scheme . . . . . . . . . . . . . . . . . . . . 9 6. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 10 A. PRES URI IANA Registration Template . . . . . . . . . . . . 10 A.1 URI scheme name . . . . . . . . . . . . . . . . . . . . . . 10 A.2 URI scheme syntax . . . . . . . . . . . . . . . . . . . . . 10 A.3 Character encoding considerations . . . . . . . . . . . . . 11 A.4 Intended usage . . . . . . . . . . . . . . . . . . . . . . . 11 A.5 Applications and/or protocols which use this URI scheme name . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 A.6 Interoperability considerations . . . . . . . . . . . . . . 11 A.7 Security considerations . . . . . . . . . . . . . . . . . . 11 A.8 Relevant publications . . . . . . . . . . . . . . . . . . . 11 A.9 Person & email address to contact for further information . 12 A.10 Author/Change controller . . . . . . . . . . . . . . . . . . 12 A.11 Applications and/or protocols which use this URI scheme name . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 B. Issues of Interest . . . . . . . . . . . . . . . . . . . . . 12 B.1 Address Mapping . . . . . . . . . . . . . . . . . . . . . . 12 B.2 Source-Route Mapping . . . . . . . . . . . . . . . . . . . . 12 Normative References . . . . . . . . . . . . . . . . . . . . 9 C. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 13 Full Copyright Statement . . . . . . . . . . . . . . . . . . 14 Crocker & Peterson Expires June 6, 2003 [Page 2] Internet-Draft Common Profile: Presence December 2002 1. Introduction Presence is defined in RFC2778 [5]. Today, numerous presence protocols are in use (largely as components of commercial instant messaging services, and little interoperability between services based on these protocols has been achieved. This specification defines semantics and data formats for common services of presence to facilitate the creation of gateways between presence services. Service behavior is described abstractly in terms of operations invoked between the consumer and provider of a service. Accordingly, each presence service must specify how this behavior is mapped onto its own protocol interactions. The choice of strategy is a local matter, providing that there is a clear relation between the abstract behaviors of the service (as specified in this memo) and how it is faithfully realized by a particular presence service. The parameters for each operation are defined using an abstract syntax. Although the syntax specifies the range of possible data values, each Presence and IM service must specify how well-formed instances of the abstract representation are encoded as a concrete series of bits. For example, one strategy might transmit presence information as key/ value pairs, another might use a compact binary representation, and a third might use nested containers. The choice of strategy is a local matter, providing that there is a clear relation between the abstract syntax (as specified in this memo) and how it is faithfully encoded by an particular presence service. In order to provide a means for the preservation of end-to-end features (especially security) to pass through presence interoperability gateways, this specification also provides recommendations for presence document formats that could be employed by presence protocols. 2. Terminology In this document, the key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as described in RFC2119 [1] and indicate requirement levels for compliant implementations. This memos makes use of the vocabulary defined in RFC2778 [5]. Terms such as CLOSED, INSTANT INBOX, PRESENCE, and OPEN are used in the same meaning as defined therein. Crocker & Peterson Expires June 6, 2003 [Page 3] Internet-Draft Common Profile: Presence December 2002 This document defines operations and attributes of a presence service. In order for a protocol to interface with a presence gateway, it must support all of the operations described in this document (i.e. the presence protocol must have some message or capability that provides the function described by this operation). Similarly, the attributes defined for these operations must correspond to information available in the presence protocol in order for the protocol to interface with gateways defined by this specification. Note that these attributes provide only the minimum possible information that needs to be specified for interoperability - the functions in a presence protocol that correspond to the operations described in this document can contain additional information that will not be mapped by CPP. 3. Abstract Presence Service 3.1 Overview of the Presence Service When an application wants to (periodically) receive the presence information associated with a PRESENTITY, it invokes the subscribe operation, e.g., +-------+ +-------+ | | | | | appl. | -- subscribe ----> | pres. | | | | svc. | +-------+ +-------+ The subscribe operation has the following attributes: watcher, target, duration, SubscriptID and TransID. The 'watcher' and 'target' identify the WATCHER and PRESENTITY, respectively, using the identifiers described in Section 3.2. The duration specifies the maximum number of seconds that the SUBSCRIPTION should be active (which may be zero, in which case this is a one-time request for presence information). The SubscriptID creates a reference to the SUBSCRIPTION that is used when unsubscribing. The TransID is a unique identifier used to correlate the subscribe operation with a response operation. Upon receiving a subscribe operation, the service immediately responds by invoking the response operation containing the same transaction- identifier, e.g., Crocker & Peterson Expires June 6, 2003 [Page 4] Internet-Draft Common Profile: Presence December 2002 +-------+ +-------+ | | | | | appl. | <----- response -- | pres. | | | | svc. | +-------+ +-------+ The response operation has the following attributes: status, TransID, and duration. 'status' indicates whether the subscribe operation has succeeded or failed. The TransID of the response operation corresponds to the TransID of the subscription operation to which it is responding. The 'duration' attribute specifies the number of seconds for which the subscription will be active (which may differ from the value requested in the subscribe operation). If the response operation indicates success, the service immediately invokes the notify operation to communicate the presence information to the WATCHER, e.g., +-------+ +-------+ | | | | | appl. | <------- notify -- | pres. | | | | svc. | +-------+ +-------+ The notify operation has the following attributes: watcher, target, and TransID. The values of 'watcher' and 'target' are identical to those given in the subscribe operation that triggered this notify operation. The TransID is a unique identifier for this notification. The notify operation also has content, namely PRESENCE INFORMATION. Some further information on notify content is given in Section 3.3. If the duration parameter is non-zero, then for up to the specified duration, the service invokes the notify operation whenever there are any changes to the PRESENTITY's presence information. Otherwise, exactly one notify operation is invoked, achieving a one-time poll of the presence information. Regardless, there is no application response to the notify operation (i.e., the application does not invoke a response operation when a notify operation occurs) defined in CPP. The application may prematurely cancel a subscription by re-invoking the subscribe operation (as described above) with a duration of 0 and the same SubscriptID as the original subscribe operation , e.g., Crocker & Peterson Expires June 6, 2003 [Page 5] Internet-Draft Common Profile: Presence December 2002 +-------+ +-------+ | | | | | appl. | -- subscribe 0 --> | pres. | | | | svc. | +-------+ +-------+ Note that a notify operation will be invoke when a subscription is prematurely canceled in this fashion; this notification may be discarded by the watcher. The service immediately responds by invoking the response operation containing the same transaction- identifier, e.g., +-------+ +-------+ | | | | | appl. | <----- response -- | pres. | | | | svc. | +-------+ +-------+ 3.2 Identification of PRESENTITIES and WATCHERS A PRESENTITY is specified using the PRES URI scheme, which is further described in Appendix A. An example would be: "pres:fred@example.com" To resolve presence URIs, a client determines the address of an appropriate system running a server by resolving the destination domain name that is part of the identifier to either an intermediate relay system or a final target system. Compliant implementations SHOULD follow the guidelines for dereferencing URIs given in [2]. 3.3 Format of Presence Information This specification defines an abstract interoperability mechanism for presence protocols; the message content definition given here pertains to semantics rather than syntax. However, some important properties for interoperability can only be provided if a common end- to-end format for presence is employed by the interoperating presence protocols. Implementations therefore SHOULD support the format defined in PIDF [4]. Crocker & Peterson Expires June 6, 2003 [Page 6] Internet-Draft Common Profile: Presence December 2002 3.4 The Presence Service An implementation of the service must maintain information about both presence information and in- progress operations in persistent storage. Note that the transaction-identifier parameter used by the service is potentially long-lived. Accordingly, the values generated for this parameter should be unique across a significant duration of time. 3.4.1 The Subscribe Operation When an application wants to (periodically) receive the presence information associated with a PRESENTITY, it invokes the subscribe operation. When the service is informed of the subscribe operation, it performs these steps: 1. If the watcher or target parameter does not refer to a valid PRESENTITY, a response operation having status "failure" is invoked. 2. If access control does not permit the application to request this operation, a response operation having status "failure" is invoked. 3. If the duration parameter is non-zero, and if the watcher and target parameters refer to an in-progress subscribe operation for the application, a response operation having status "failure" is invoked. 4. Otherwise, if the service is able to successfully deliver the message: A response operation having status "success" is immediately invoked. (If the service chooses a different duration for the subscription then it conveys this information in the response operation.) A notify operation, corresponding to the target's presence information, is immediately invoked for the watcher. For up to the amount of time indicated by the duration parameter, if the target's presence information changes, and if access control allows, a notify operation is invoked for Crocker & Peterson Expires June 6, 2003 [Page 7] Internet-Draft Common Profile: Presence December 2002 the watcher. Note that if the duration parameter is zero-valued, then the subscribe operation is making a one-time poll of the presence information. Accordingly, the final step above (continued notifications for the duration of the subscription) does not occur. When the service invokes a response operation as a result of this processing, the transID parameter is identical to the value found in the subscribe operation invoked by the application. 3.4.2 The Notify Operation The service invokes the notify operation whenever the presence information associated with a PRESENTITY changes and there are subscribers to that information. There is no application response to the notify operation. 3.4.3 Subscribe Operation (with Zero Duration) When an application wants to terminate a subscription, it issues a SUBSCRIBE 0 with the SubscriptID of an existing subscription. Note that an notify operation will be invoked by the presentity when a subscription is canceled in this fashion; this notification can be discarded by the watcher. There is no independent UNSUBSCRIBE operation. When an application wants to directly request presence information to be supplied immediately without initiating any persistent subscription, it issues a SUBSCRIBE 0 with a new SubscriptID. There is no independent FETCH operation. 4. Security Considerations Detailed security considerations for presence protocols given in RFC2779 (in particular, requirements are given in sections 5.1 through 5.3 and some motivating discussion in 8.2). CPP defines an interoperability function that is employed by gateways between presence protocols. CPP gateways MUST be compliant with the minimum security requirements of the presence protocols with which they interface. Note that end-to-end security properties (especially confidentiality and integrity) between presentities and watchers that interface through a CPP gateway can only be provided if a common presence format (such as the format described in [4]) is supported by the Crocker & Peterson Expires June 6, 2003 [Page 8] Internet-Draft Common Profile: Presence December 2002 protocols interfacing with the CPP gateway. 5. IANA Considerations The IANA assigns the "pres" URI scheme. 5.1 The PRES URI Scheme The Presence (PRES) URI scheme designates an Internet resource, namely a PRESENTITY or WATCHER. The syntax of a PRES URI is given in Appendix A. 6. Contributors The following individuals made substantial textual contributions to this document: Athanassios Diacakis (thanos.diacakis@openwave.com) Florencio Mazzoldi (flo@networkprojects.com) Christian Huitema (huitema@microsoft.com) Graham Klyne (gk@ninebynine.org) Jonathan Rosenberg (jdrosen@dynamicsoft.com) Robert Sparks (rsparks@dynamicsoft.com) Hiroyasu Sugano (suga@flab.fujitsu.co.jp) Normative References [1] Bradner, S., "Key words for use in RFCs to indicate requirement levels", RFC 2119, March 1997. [2] Crocker, D. and J. Peterson, "Address resolution for Instant Messaging and Presence", draft-ietf-impp-srv-00 (work in progress), October 2002. [3] Resnick, P., "Internet Message Format", RFC 2822, STD 11, April 2001. [4] Sugano, H., Fujimoto, S., Klyne, G., Bateman, A., Carr, W. and J. Peterson, "CPIM Presence Information Data Format", draft- ietf-impp-cpim-pidf-00 (work in progress), August 2001. Crocker & Peterson Expires June 6, 2003 [Page 9] Internet-Draft Common Profile: Presence December 2002 [5] Day, M., Rosenberg, J. and H. Sugano, "A Model for Presence and Instant Messaging", RFC 2778, February 2000. [6] Day, M., Aggarwal, S. and J. Vincent, "Instant Messaging / Presence Protocol Requirements", RFC 2779, February 2000. [7] Allocchio, C., "GSTN Address Element Extensions in Email Services", RFC 2846, June 2000. Authors' Addresses Dave Crocker Brandenburg InternetWorking 675 Spruce Drive Sunnyvale, CA 94086 US Phone: +1 408/246-8253 EMail: dcrocker@brandenburg.com Jon Peterson NeuStar, Inc. 1800 Sutter St Suite 570 Concord, CA 94520 US Phone: +1 925/363-8720 EMail: jon.peterson@neustar.biz Appendix A. PRES URI IANA Registration Template This section provides the information to register the pres: presence URI . A.1 URI scheme name pres A.2 URI scheme syntax The syntax follows the existing mailto: URI syntax specified in RFC2368. The ABNF is: Crocker & Peterson Expires June 6, 2003 [Page 10] Internet-Draft Common Profile: Presence December 2002 PRES-URI = "pres:" [ to ] [ headers ] to = #mailbox headers = "?" header *( "&" header ) header = hname "=" hvalue hname = *urlc hvalue = *urlc A.3 Character encoding considerations Representation of non-ASCII character sets in local-part strings is limited to the standard methods provided as extensions to RFC2822" [3]. A.4 Intended usage Use of the pres: URI follows closely usage of the mailto: URI. That is, invocation of an PRES URI will cause the user's instant messaging application to start, with destination address and message headers fill-in according to the information supplied in the URI. A.5 Applications and/or protocols which use this URI scheme name It is anticipated that protocols compliant with RFC2779, and meeting the interoperability requirements specified here, will make use of this URI scheme name. A.6 Interoperability considerations The underlying exchange protocol used to send an instant message may vary from service to service. Therefore complete, Internet-scale interoperability cannot be guaranteed. However, a service conforming to this specification permits gateways to achieve interoperability sufficient to the requirements of RFC2779. A.7 Security considerations When PRES URIs are placed in presence protocols, they convey the identity of the sender and/or the recipient. In some cases, anonymous messaging may be desired. Such a capability is beyond the scope of this specification. A.8 Relevant publications RFC2779, RFC2778 Crocker & Peterson Expires June 6, 2003 [Page 11] Internet-Draft Common Profile: Presence December 2002 A.9 Person & email address to contact for further information Jon Peterson [mailto:jon.peterson@neustar.biz] A.10 Author/Change controller This scheme is registered under the IETF tree. As such, IETF maintains change control. A.11 Applications and/or protocols which use this URI scheme name Instant messaging service; presence service Appendix B. Issues of Interest This appendix briefly discusses issues that may be of interest when designing an interoperation gateway. B.1 Address Mapping When mapping the service described in this memo, mappings that place special information into the im: address local-part MUST use the meta-syntax defined in RFC2846 [7]. B.2 Source-Route Mapping The easiest mapping technique is a form of source- routing and usually is the least friendly to humans having to type the string. Source-routing also has a history of operational problems. Use of source-routing for exchanges between different services is by a transformation that places the entire, original address string into the im: address local part and names the gateway in the domain part. For example, if the destination INSTANT INBOX is "pepp://example.com/ fred", then, after performing the necessary character conversions, the resulting mapping is: im:pepp=example.com/fred@relay-domain where "relay-domain" is derived from local configuration information. Experience shows that it is vastly preferable to hide this mapping from end-users - if possible, the underlying software should perform the mapping automatically. Crocker & Peterson Expires June 6, 2003 [Page 12] Internet-Draft Common Profile: Presence December 2002 Appendix C. Acknowledgments The authors would like to acknowledge John Ramsdell for his comments, suggestions and enthusiasm. Thanks to Derek Atkins for editorial fixes. Crocker & Peterson Expires June 6, 2003 [Page 13] Internet-Draft Common Profile: Presence December 2002 Full Copyright Statement Copyright (C) The Internet Society (2002). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Acknowledgement Funding for the RFC Editor function is currently provided by the Internet Society. Crocker & Peterson Expires June 6, 2003 [Page 14]