SIMPLE J. Rosenberg Internet-Draft Cisco Systems Expires: April 25, 2005 October 25, 2004 Presence Authorization Rules draft-ietf-simple-presence-rules-01 Status of this Memo By submitting this Internet-Draft, I certify that any applicable patent or other IPR claims of which I am aware have been disclosed, and any of which I become aware will be disclosed, in accordance with RFC 3668. 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 April 25, 2005. Copyright Notice Copyright (C) The Internet Society (2004). All Rights Reserved. Abstract Authorization is a key function in presence systems. Authorization policies, also known as authorization rules, specify what presence information can be given to which watchers, and when. This specification defines an Extensible Markup Language (XML) document format for expressing presence authorization rules. Such a document can be manipulated by clients using the XML Configuration Access Protocol (XCAP), although other techniques are permitted. Rosenberg Expires April 25, 2005 [Page 1] Internet-Draft Presence Authorization October 2004 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Structure of Permission Statements . . . . . . . . . . . . . 4 3.1 Conditions . . . . . . . . . . . . . . . . . . . . . . . . 4 3.1.1 Identity . . . . . . . . . . . . . . . . . . . . . . . 4 3.1.2 Anonymous . . . . . . . . . . . . . . . . . . . . . . 5 3.1.3 Sphere . . . . . . . . . . . . . . . . . . . . . . . . 5 3.2 Actions . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.2.1 Subscription Handling . . . . . . . . . . . . . . . . 6 3.3 Transformations . . . . . . . . . . . . . . . . . . . . . 7 3.3.1 Providing Access to Data Elements . . . . . . . . . . 7 3.3.1.1 Person Information . . . . . . . . . . . . . . . . 7 3.3.1.2 Device Information . . . . . . . . . . . . . . . . 7 3.3.1.3 Service Information . . . . . . . . . . . . . . . 8 3.3.2 Providing Access to Presence Attributes . . . . . . . 8 3.3.2.1 Provide Activities . . . . . . . . . . . . . . . . 8 3.3.2.2 Provide Class . . . . . . . . . . . . . . . . . . 8 3.3.2.3 Provide Mood . . . . . . . . . . . . . . . . . . . 9 3.3.2.4 Provide Place-type . . . . . . . . . . . . . . . . 9 3.3.2.5 Provide Privacy . . . . . . . . . . . . . . . . . 9 3.3.2.6 Provide Relationship . . . . . . . . . . . . . . . 9 3.3.2.7 Provide Sphere . . . . . . . . . . . . . . . . . . 9 3.3.2.8 Provide Status-Icon . . . . . . . . . . . . . . . 10 3.3.2.9 Provide Timezone . . . . . . . . . . . . . . . . . 10 3.3.2.10 Provide User Input . . . . . . . . . . . . . . . 10 3.3.2.11 Provide Unknown Attribute . . . . . . . . . . . 10 4. Example Document . . . . . . . . . . . . . . . . . . . . . . 11 5. XML Schema . . . . . . . . . . . . . . . . . . . . . . . . . 12 6. Schema Extensibility . . . . . . . . . . . . . . . . . . . . 15 7. XCAP Usage . . . . . . . . . . . . . . . . . . . . . . . . . 15 7.1 Application Unique ID . . . . . . . . . . . . . . . . . . 15 7.2 Structure of Permission Statements . . . . . . . . . . . . 15 7.3 Additional Constraints . . . . . . . . . . . . . . . . . . 15 7.4 Naming Conventions . . . . . . . . . . . . . . . . . . . . 15 7.5 Authorization Policies . . . . . . . . . . . . . . . . . . 16 7.6 XML Schema . . . . . . . . . . . . . . . . . . . . . . . . 16 8. Security Considerations . . . . . . . . . . . . . . . . . . 16 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . 16 9.1 XCAP Application Usage ID . . . . . . . . . . . . . . . . 16 9.2 URN Sub-Namespace Registration . . . . . . . . . . . . . . 17 9.3 XML Schema Registrations . . . . . . . . . . . . . . . . . 17 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 18 10.1 Normative References . . . . . . . . . . . . . . . . . . . 18 10.2 Informative References . . . . . . . . . . . . . . . . . . 19 Author's Address . . . . . . . . . . . . . . . . . . . . . . 19 Intellectual Property and Copyright Statements . . . . . . . 20 Rosenberg Expires April 25, 2005 [Page 2] Internet-Draft Presence Authorization October 2004 1. Introduction The Session Initiation Protocol (SIP) for Instant Messaging and Presence (SIMPLE) specifications allow a user, called a watcher, to subscribe to another user, called a presentity [15], in order to learn their presence information [18]. This subscription is handed by a presence agent. The logical processing of the presence agent is described in the presence data model [12]. In that model, the subscription authorization decision, the selection of the composition policy, and the governance of privacy filtering are all described by a presence authorization document. This specification defines a format for such a document. Typically, a user will place a multiplicity of authorization documents on a server, each one applying in certain situations. In addition to the user, the service provider may have its own authorization policies which apply in other situations. These documents are combined together to produce a single authorization policy which guides presence server processing. [10] specifies a framework for representing authorization policies, and is applicable to systems such as geo-location and presence. In that framework, an authorization document is a sequence of rules. Each rule contains conditions, actions, and transformations. The conditions specify under what conditions the rule is to be applied to presence server processing. The actions element tells the server what actions to take. In the context of the data model, these actions include the subscription authorization decision and the selection of the composition policy. The transformations element indicates how the presence data is to be manipulated before being presented to that watcher, and serves as the guide for the privacy filtering operation. [10] identifies a small number of specific conditions, actions and permissions common to presence and location services, and leaves it to other specifications, such as this one, to fill in usage specific details. These documents can be manipulated by clients using several means. One such mechanism is the XML Configuration Access Protocol (XCAP) [2]. This specification defines the details necessary for using XCAP to manage presence authorization documents. 2. Terminology In this document, the key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as described in RFC 2119 [1] and indicate requirement levels for compliant implementations. Rosenberg Expires April 25, 2005 [Page 3] Internet-Draft Presence Authorization October 2004 3. Structure of Permission Statements A permission statement is an XML document, formatted according to the schema defined in [10]. As described in [10], this document is composed of three parts - conditions, actions, and transformations. Each action or transformation, which is also called a permission, has the property of being a positive grant of information to the watcher. As a result, there is a well-defined mechanism for combining actions and transformations obtained from several sources. This mechanism is privacy safe, since the lack of any action or transformation can only result in less information being presented to a watcher. This section defines the new conditions, actions and transformations defined by this specification. 3.1 Conditions 3.1.1 Identity Although the element is defined in [10], that specification indicates that the interpretation of the element depends on the specific protocol in use and its authentication mechanisms. This sub-section defines that interpretation for systems based on [18]. For requests that are authenticated using SIP [9] digest authentication [8], the identity used for comparisons to the , and fields is set equal to the user and domain part of the SIP Address of Record (AOR) for the user that has authenticated themselves. For example, consider the following "user record": SIP AOR: sip:alice@example.com digest username: ali digest password: f779ajvvh8a6s6 digest realm: example.com If the presence server receives a SUBSCRIBE request, challenges it with the realm set to "example.com", and the subsequent SUBSCRIBE contains an Authorization header field with a username of "ali" and a digest response generated with the password "f779ajvvh8a6s6", the identity used in matching operations is "alice@example.com". For requests that are authenticated using RFC 3325 [19], the username and domain part of the URI are matched against the user and host parts of the SIP URI in the P-Asserted-Identity header field. Rosenberg Expires April 25, 2005 [Page 4] Internet-Draft Presence Authorization October 2004 For any other authentication mechanism in SIP which might be identified in other specifications, a similar pattern would be followed. The authentication mechanism would provide the recipient of the request with the AOR of the sender of the request. The user and domain parts of the AOR then form the identity used in this specification. In SIP systems, it is possible for a user to have aliases - that is, there are multiple SIP AOR "assigned" to a single user. In terms of this specification, there is no relationship between those aliases. Each would look like a different user. This will be the consequence for systems were the watcher is in a different domain than the presentity. However, even if the watcher and presentity are in the same domain, and the presence server knows that there are aliases for the watcher, these aliases are not mapped to each other or used in any way. 3.1.2 Anonymous The element, which is a boolean type, indicates whether or not the subscription request was sent from an anonymous sender. The value of TRUE means that the request was anonymous, and FALSE means it was not. The request is considered anonymous if it was authenticated using the username defined in RFC 3261, if the asserted identity has a URI in the "anonymous.invalid" domain [14], or if the request cannot be authenticated by any SIP authentication mechanisms. This implies that a request without any authentication, but with an otherwise valid From field, is still considered anonymous. 3.1.3 Sphere The element is defined in [10]. However, each application making use of the common policy specification needs to determine how the presence server computes the value of the sphere to be used in the evaluation of the condition. To compute the value of , the default composition policy is applied for the presentity [12]. The result will be a raw presence document with a single element, possibly containing a element, which is defined in the Rich Presence Information Data Format [11]. If the is present, that value is used in the evaluation of the condition. If the element is not present in the presence document, the value is set to undefined. 3.2 Actions Rosenberg Expires April 25, 2005 [Page 5] Internet-Draft Presence Authorization October 2004 3.2.1 Subscription Handling The element specifies the subscription authorization decision that the server should make, as described in [12]. It also specifies whether or not the composition policy should be the default value, or whether the "polite blocking" composition policy (the details of which are a matter of provider policy) is to be used. The two are specified jointly since proper privacy handling requires a correlation between them. As discussed in [10], since the combination algorithm runs independently for each permission, if correlations exist between permissions, they must be merged into a single variable. That is what is done here. The element is an enumerated Integer type. The defined values are: block: This action tells the server to place the subscription in the rejected state. It has the value of zero, and it represents the default value. No value of the sub-handling element can ever be lower than this. Strictly speaking, it is not necessary to every include an explicit block action, since the default in the absence of any action will be block. However, it is included for completeness. confirm: This action tells the server to place the subscription in the "pending" state, and await input from the presentity to determine how to proceed. It has a value of one. polite-block: This action tells the server to place the subscription into the "accepted" state. Furthermore, it selects the composition policy, and sets it to support a polite blocking operation. The specific composition policy to accomplish these goals is at the discretion of the service provider. In all cases, the result of the composition policy should produce a raw presence document that indicates that the user is unavailable for communication. A reasonable document would exclude device and person information elements, and include only a single service whose basic status is set to closed [3]. This action has a value of two. allow: This action tells the server to place the subscription into the "accepted" state. Furthermore, it selects the default composition policy as defined by [12]. This action has a value of three. NOTE WELL: Placing a value of block for this element does not guarantee that a subscription is denied! If any matching rule has any other value for this element, the subscription will receive treatment based on the maximum of those other values. This is based on the combining rules defined in [10]. Rosenberg Expires April 25, 2005 [Page 6] Internet-Draft Presence Authorization October 2004 Future specifications can define additional values for this permission, allowing for the selection of other composition policies. 3.3 Transformations The transformations defined here are used to drive the behavior of the privacy filtering operation described in [12]. Each transformation defines the visibility a watcher is granted to a particular component of the presence document. One group of transformations grant visibility to person, device and service data elements based on identifying information for those elements. Another group of transformations provide access to particular data elements in the presence document. 3.3.1 Providing Access to Data Elements The transformations in this section provide access to person, device and service data elements. Once access has been granted to such an element, access to specific presence attributes for that element is controlled by the permissions defined in Section 3.3.2. 3.3.1.1 Person Information The permission allows a watcher to see the information present in the presence document. It is a boolean variable. A value of TRUE means that permission is granted, and false means that it is not. OPEN ISSUE: The inclusion of multiple person elements in a document to report conflicting information would impact this permission. 3.3.1.2 Device Information The permission allows a watcher to see information present in the presence document. It is a set variable. Each value in the set is a member of the deviceIdentifier substitution group. Members of this group provide ways to identify a device or group of devices. This specification defines a single member of this substitution group, the element. This element identifies a device by its device ID. The element can also take on the special value which is a short-hand notation for all device IDs present in the presence document. Permission is granted to see a particular device if one of the device identifiers in the set identifies that device. For the device Rosenberg Expires April 25, 2005 [Page 7] Internet-Draft Presence Authorization October 2004 identifiers defined here, this is limited to the device ID. As such, a device is included in the filtered presence document if its device ID is listed in the set, or the value was used. 3.3.1.3 Service Information The permission allows a watcher to see service information present in elements in the presence document. Like , it is a set variable. Each member of the set is a member of the serviceIdentifier substitution group. Members of this group provide ways to identify a service or group of services. This specification defines two member elements for this substitution group. One, , identifies services by URI scheme. A service is a match for this identifier if the scheme of the contact URI of that service matches, based on case sensitive string comparison, the value of the element. The other member of the substitution group is . This element identifies a service by its contact URI. A service is a match for this identifier if the contact URI of that service matches, based on the equality rules for that scheme, the value of the element. Like , the element can also take on the special value , which is a short-hand notation for all services present in the presence document. 3.3.2 Providing Access to Presence Attributes The permissions of Section 3.3.1 provide coarse grained access to presence data by allowing or blocking specific services or devices, and allowing or blocking person information. Once person, device or service information is included in the document, the permissions in this section define which presence attributes are reported there. 3.3.2.1 Provide Activities This permission controls access to the element defined in [11]. The name of the element providing this permission is , and it is a boolean type. If its value is TRUE, then the element in the person data element is reported to the watcher. If FALSE, this presence attribute is removed if present. 3.3.2.2 Provide Class This permission controls access to the element defined in [11]. The name of the element providing this permission is Rosenberg Expires April 25, 2005 [Page 8] Internet-Draft Presence Authorization October 2004 , and it is a boolean type. If its value is TRUE, then the element in the person, service or device data element is reported to the watcher. If FALSE, this presence attribute is removed if present. 3.3.2.3 Provide Mood This permission controls access to the element defined in [11]. The name of the element providing this permission is , and it is a boolean type. If its value is TRUE, then the element in the person data element is reported to the watcher. If FALSE, this presence attribute is removed if present. 3.3.2.4 Provide Place-type This permission controls access to the element defined in [11]. The name of the element providing this permission is , and it is a boolean type. If its value is TRUE, then the element in the person data element is reported to the watcher. If FALSE, this presence attribute is removed if present. 3.3.2.5 Provide Privacy This permission controls access to the element defined in [11]. The name of the element providing this permission is , and it is a boolean type. If its value is TRUE, then the element in the service data element is reported to the watcher. If FALSE, this presence attribute is removed if present. 3.3.2.6 Provide Relationship This permission controls access to the element defined in [11]. The name of the element providing this permission is , and it is a boolean type. If its value is TRUE, then the element in the service data element is reported to the watcher. If FALSE, this presence attribute is removed if present. 3.3.2.7 Provide Sphere This permission controls access to the element defined in [11]. The name of the element providing this permission is , and it is a boolean type. If its value is TRUE, then the element in the person data element is reported to the watcher. If FALSE, this presence attribute is removed if present. Rosenberg Expires April 25, 2005 [Page 9] Internet-Draft Presence Authorization October 2004 3.3.2.8 Provide Status-Icon This permission controls access to the element defined in [11]. The name of the element providing this permission is , and it is a boolean type. If its value is TRUE, then any element in the person or service data element is reported to the watcher. If FALSE, this presence attribute is removed if present. 3.3.2.9 Provide Timezone This permission controls access to the element defined in [11]. The name of the element providing this permission is , and it is a boolean type. If its value is TRUE, then the element in the person data element is reported to the watcher. If FALSE, this presence attribute is removed if present. 3.3.2.10 Provide User Input This permission controls access to the element defined in [11]. The name of the element providing this permission is , and it is an enumerated integer type. Its value defines what information is provided to watchers: false: This value indicates that the element is removed from the document. It is assigned the numeric value of 0. bare: This value indicates that the element is to be retained. However, any "idle-threshold" and "since" attributes are to be removed. This value is assigned the numeric value of 1. thresholds: This value indicates that the element is to be retained. However, only the "idle-threshold" attribute is to be retained. This value is assigned to the numeric value of 2. full: This value indicates that the element is to be retained, including any attributes. This value is assigned to the numeric value of 3. 3.3.2.11 Provide Unknown Attribute It is important that systems be allowed to include proprietary or new presence information, and that users be able to set permissions for that information, without requiring an upgrade of the presence server and authorization system. For this reason, the permission is defined. This permission Rosenberg Expires April 25, 2005 [Page 10] Internet-Draft Presence Authorization October 2004 indicates that the unknown presence attribute with the given name (supplied as mandatory attribute of the element) should be included in the document. Its type is boolean. The value of the name attribute MUST be a qualified element name (meaning that the namespace prefix MUST be included), which will be matched to all unknown child elements of the PIDF , or rule from being applied to any of the presence status extensions defined by RPID. Another consequence of this definition is that the interpretation of the element can change should the presence server be upgraded with a new schema that defines authorization rules for elements included in a . The permissions for those elements will then be ignored, resulting in a removal of those elements from presence documents sent to watchers. The system remains privacy safe, but behavior might not be as expected. Developers of systems which allow clients to set policies are advised to check the capabilities of the server, as defined in [17], before uploading a new authorization document, to make sure that the behavior will be as expected. 4. Example Document The following presence authorization document specifies permissions for the user "user@example.com". Rosenberg Expires April 25, 2005 [Page 11] Internet-Draft Presence Authorization October 2004 user@example.com allow sip mailto true true bare true 5. XML Schema Rosenberg Expires April 25, 2005 [Page 12] Internet-Draft Presence Authorization October 2004 Rosenberg Expires April 25, 2005 [Page 14] Internet-Draft Presence Authorization October 2004 6. Schema Extensibility It is anticipated that future changes to this specification are accomplished through extensions that define new types of permissions. These extensions MUST exist within a different namespace. Furthermore, the schema defined above and the namespace for elements defined within it MUST NOT be altered by future specifications. Changes in the basic schema, or in the interpretation of elements within that schema, may result in violations of user privacy due to mis-interpretation of documents. This specification also defines two substitution groups. One is for service identifiers, and one is for device identifiers. It is expected that future extensions will specify new ways of identifying services and devices for inclusion in a document. These new permissions MUST be assigned to this substitution group. 7. XCAP Usage The following section defines the details necessary for clients to manipulate presence authorization documents from a server using XCAP. 7.1 Application Unique ID XCAP requires application usages to define a unique application usage ID (AUID) in either the IETF tree or a vendor tree. This specification defines the "pres-rules" AUID within the IETF tree, via the IANA registration in Section 9. 7.2 Structure of Permission Statements The structure of permission statements is defined in Section 3. 7.3 Additional Constraints There are no additional constraints defined by this specification. 7.4 Naming Conventions When a presence agent receives a subscription for some user foo within a domain, it will look for all documents within http://[xcap root]/ pres-rules/users/foo, and use all documents found beneath that point to guide authorization policy. Rosenberg Expires April 25, 2005 [Page 15] Internet-Draft Presence Authorization October 2004 7.5 Authorization Policies This application usage does not modify the default XCAP authorization policy, which is that only a user can read, write or modify their own documents. A server can allow priveleged users to modify documents that they don't own, but the establishment and indication of such policies is outside the scope of this document. 7.6 XML Schema The XML schema is defined in Section 5. 8. Security Considerations Presence authorization policies contain very sensitive information. They indicate which other users are "liked" or "disliked" by a user. As such, when these documents are transported over a network, they SHOULD be encrypted. Modification of these documents by an attacker can disrupt the service seen by a user, often in subtle ways. As a result, when these documents are transported, the transport SHOULD provide authenticity and message integrity. In the case where XCAP is used to transfer the document, clients SHOULD use HTTP over TLS, and servers SHOULD define the root services URI as an https URI. The server SHOULD authenticate the client over the resulting TLS connection using HTTP digest. 9. IANA Considerations There are several IANA considerations associated with this specification. 9.1 XCAP Application Usage ID This section registers an XCAP Application Usage ID (AUID) according to the IANA procedures defined in [2]. Name of the AUID: pres-rules Description: Presence rules are documents that describe the permissions that a presentity [15] has granted to users that seek to watch their presence. Rosenberg Expires April 25, 2005 [Page 16] Internet-Draft Presence Authorization October 2004 9.2 URN Sub-Namespace Registration This section registers a new XML namespace, per the guidelines in [13] URI: The URI for this namespace is urn:ietf:params:xml:ns:pres-rules. Registrant Contact: IETF, SIMPLE working group, (simple@ietf.org), Jonathan Rosenberg (jdrosen@jdrosen.net). XML: BEGIN Presence Rules Namespace

Namespace for Permission Statements

urn:ietf:params:xml:ns:pres-rules

See RFCXXXX.

END 9.3 XML Schema Registrations This section registers an XML schema per the procedures in [13]. URI: urn:ietf:params:xml:schema:pres-rules. Registrant Contact: IETF, SIMPLE working group, (simple@ietf.org), Jonathan Rosenberg (jdrosen@jdrosen.net). The XML for this schema can be found as the sole content of Section 5. Rosenberg Expires April 25, 2005 [Page 17] Internet-Draft Presence Authorization October 2004 10. References 10.1 Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [2] Rosenberg, J., "The Extensible Markup Language (XML) Configuration Access Protocol (XCAP)", draft-ietf-simple-xcap-03 (work in progress), July 2004. [3] Sugano, H., Fujimoto, S., Klyne, G., Bateman, A., Carr, W. and J. Peterson, "Presence Information Data Format (PIDF)", RFC 3863, August 2004. [4] Bray, T., Paoli, J., Sperberg-McQueen, C. and E. Maler, "Extensible Markup Language (XML) 1.0 (Second Edition)", W3C FirstEdition REC-xml-20001006, October 2000. [5] Moats, R., "URN Syntax", RFC 2141, May 1997. [6] Murata, M., St. Laurent, S. and D. Kohn, "XML Media Types", RFC 3023, January 2001. [7] Moats, R., "A URN Namespace for IETF Documents", RFC 2648, August 1999. [8] Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S., Leach, P., Luotonen, A. and L. Stewart, "HTTP Authentication: Basic and Digest Access Authentication", RFC 2617, June 1999. [9] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M. and E. Schooler, "SIP: Session Initiation Protocol", RFC 3261, June 2002. [10] Schulzrinne, H., "A Document Format for Expressing Privacy Preferences", draft-ietf-geopriv-common-policy-02 (work in progress), October 2004. [11] Schulzrinne, H., Gurbani, V., Kyzivat, P. and J. Rosenberg, "RPID: Rich Presence: Extensions to the Presence Information Data Format (PIDF)", draft-ietf-simple-rpid-03 (work in progress), March 2004. [12] Rosenberg, J., "A Data Model for Presence", draft-ietf-simple-presence-data-model-00 (work in progress), September 2004. Rosenberg Expires April 25, 2005 [Page 18] Internet-Draft Presence Authorization October 2004 [13] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, January 2004. [14] Peterson, J., "A Privacy Mechanism for the Session Initiation Protocol (SIP)", RFC 3323, November 2002. 10.2 Informative References [15] Day, M., Rosenberg, J. and H. Sugano, "A Model for Presence and Instant Messaging", RFC 2778, February 2000. [16] Day, M., Aggarwal, S., Mohr, G. and J. Vincent, "Instant Messaging / Presence Protocol Requirements", RFC 2779, February 2000. [17] Rosenberg, J., "An Extensible Markup Language (XML) Representation for Expressing Presence Policy Capabilities", draft-rosenberg-simple-pres-policy-caps-01 (work in progress), July 2004. [18] Rosenberg, J., "A Presence Event Package for the Session Initiation Protocol (SIP)", RFC 3856, August 2004. [19] Jennings, C., Peterson, J. and M. Watson, "Private Extensions to the Session Initiation Protocol (SIP) for Asserted Identity within Trusted Networks", RFC 3325, November 2002. Author's Address Jonathan Rosenberg Cisco Systems 600 Lanidex Plaza Parsippany, NJ 07054 US Phone: +1 973 952-5000 EMail: jdrosen@dynamicsoft.com URI: http://www.jdrosen.net Rosenberg Expires April 25, 2005 [Page 19] Internet-Draft Presence Authorization October 2004 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. 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Disclaimer of Validity This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM 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. Copyright Statement Copyright (C) The Internet Society (2004). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Rosenberg Expires April 25, 2005 [Page 20]