[Docs] [txt|pdf] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

Versions: (draft-ietf-simple-xcap-auth-usage) 00 01 02 03 04 05 06 07 08 09 10 RFC 5025

SIMPLE                                                      J. Rosenberg
Internet-Draft                                             Cisco Systems
Expires: April 25, 2007                                 October 22, 2006


                      Presence Authorization Rules
                  draft-ietf-simple-presence-rules-08

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
   have been or will be disclosed, and any of which he or she becomes
   aware will be disclosed, in accordance with Section 6 of BCP 79.

   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, 2007.

Copyright Notice

   Copyright (C) The Internet Society (2006).

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, 2007                 [Page 1]

Internet-Draft           Presence Authorization             October 2006


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Structure of Presence Authorization Documents  . . . . . . . .  4
     3.1.  Conditions . . . . . . . . . . . . . . . . . . . . . . . .  5
       3.1.1.  Identity . . . . . . . . . . . . . . . . . . . . . . .  5
         3.1.1.1.  Acceptable Forms of Authentication . . . . . . . .  5
         3.1.1.2.  Computing a URI for the Watcher  . . . . . . . . .  6
       3.1.2.  Sphere . . . . . . . . . . . . . . . . . . . . . . . .  7
     3.2.  Actions  . . . . . . . . . . . . . . . . . . . . . . . . .  8
       3.2.1.  Subscription Handling  . . . . . . . . . . . . . . . .  8
     3.3.  Transformations  . . . . . . . . . . . . . . . . . . . . . 10
       3.3.1.  Providing Access to Data Component Elements  . . . . . 10
         3.3.1.1.  Device Information . . . . . . . . . . . . . . . . 10
         3.3.1.2.  Person Information . . . . . . . . . . . . . . . . 11
         3.3.1.3.  Service Information  . . . . . . . . . . . . . . . 12
       3.3.2.  Providing Access to Presence Attributes  . . . . . . . 13
         3.3.2.1.  Provide Activities . . . . . . . . . . . . . . . . 13
         3.3.2.2.  Provide Class  . . . . . . . . . . . . . . . . . . 13
         3.3.2.3.  Provide DeviceID . . . . . . . . . . . . . . . . . 13
         3.3.2.4.  Provide Mood . . . . . . . . . . . . . . . . . . . 14
         3.3.2.5.  Provide Place-is . . . . . . . . . . . . . . . . . 14
         3.3.2.6.  Provide Place-type . . . . . . . . . . . . . . . . 14
         3.3.2.7.  Provide Privacy  . . . . . . . . . . . . . . . . . 14
         3.3.2.8.  Provide Relationship . . . . . . . . . . . . . . . 14
         3.3.2.9.  Provide Sphere . . . . . . . . . . . . . . . . . . 15
         3.3.2.10. Provide Status-Icon  . . . . . . . . . . . . . . . 15
         3.3.2.11. Provide Time-Offset  . . . . . . . . . . . . . . . 15
         3.3.2.12. Provide User-Input . . . . . . . . . . . . . . . . 15
         3.3.2.13. Provide Note . . . . . . . . . . . . . . . . . . . 16
         3.3.2.14. Provide Unknown Attribute  . . . . . . . . . . . . 16
         3.3.2.15. Provide All Attributes . . . . . . . . . . . . . . 17
   4.  When to Apply the Authorization Policies . . . . . . . . . . . 17
   5.  Example Document . . . . . . . . . . . . . . . . . . . . . . . 18
   6.  XML Schema . . . . . . . . . . . . . . . . . . . . . . . . . . 19
   7.  Schema Extensibility . . . . . . . . . . . . . . . . . . . . . 22
   8.  XCAP Usage . . . . . . . . . . . . . . . . . . . . . . . . . . 22
     8.1.  Application Unique ID  . . . . . . . . . . . . . . . . . . 23
     8.2.  XML Schema . . . . . . . . . . . . . . . . . . . . . . . . 23
     8.3.  Default Namespace  . . . . . . . . . . . . . . . . . . . . 23
     8.4.  MIME Type  . . . . . . . . . . . . . . . . . . . . . . . . 23
     8.5.  Validation Constraints . . . . . . . . . . . . . . . . . . 23
     8.6.  Data Semantics . . . . . . . . . . . . . . . . . . . . . . 23
     8.7.  Naming Conventions . . . . . . . . . . . . . . . . . . . . 23
     8.8.  Resource Interdependencies . . . . . . . . . . . . . . . . 23
     8.9.  Authorization Policies . . . . . . . . . . . . . . . . . . 24
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 24



Rosenberg                Expires April 25, 2007                 [Page 2]

Internet-Draft           Presence Authorization             October 2006


   10. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 24
     10.1. XCAP Application Usage ID  . . . . . . . . . . . . . . . . 24
     10.2. URN Sub-Namespace Registration . . . . . . . . . . . . . . 25
     10.3. XML Schema Registrations . . . . . . . . . . . . . . . . . 25
   11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 26
   12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 26
     12.1. Normative References . . . . . . . . . . . . . . . . . . . 26
     12.2. Informative References . . . . . . . . . . . . . . . . . . 27
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 28
   Intellectual Property and Copyright Statements . . . . . . . . . . 29









































Rosenberg                Expires April 25, 2007                 [Page 3]

Internet-Draft           Presence Authorization             October 2006


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 [16], in order to
   learn their presence information [17].  This subscription is handled
   by a presence agent.  However, presence information is sensitive, and
   a presence agent needs authorization from the presentity prior to
   handing out presence information.  As such, a presence authorization
   document format is needed.  This specification defines a format for
   such a document, called a presence authorization document.

   [8] specifies a framework for representing authorization policies,
   and is applicable to systems such as geo-location and presence.  This
   framework is used as the basis for presence authorization documents.
   In the framework, an authorization policy is a set 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.  The transformations element indicates how the
   presence data is to be manipulated before being presented to that
   watcher, and as such, defines a privacy filtering operation. [8]
   identifies a small number of specific conditions common to presence
   and location services, and leaves it to other specifications, such as
   this one, to fill in usage specific details.

   A presence authorization document 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.


3.  Structure of Presence Authorization Documents

   A presence authorization document is an XML document, formatted
   according to the schema defined in [8].  Presence authorization
   documents inherit the MIME type of common policy documents,
   application/auth-policy+xml.  As described in [8], this document is
   composed of rules which contain three parts - conditions, actions,
   and transformations.  Each action or transformation, which is also



Rosenberg                Expires April 25, 2007                 [Page 4]

Internet-Draft           Presence Authorization             October 2006


   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 <identity> element is defined in [8], that specification
   indicates that the specific usages of the framework document need to
   define details that are protocol and usage specific.  In particular,
   it is necessary for a usage of the common policy framework to:

   o  Define acceptable means of authentication.

   o  Define the procedure for representing the identity of the WR
      (Watcher/Requestor) as a URI or IRI [14].

   This sub-section defines those details for systems based on [17].

3.1.1.1.  Acceptable Forms of Authentication

   When used with SIP, a request is considered authenticated if one of
   the following techniques is used:

   SIP Digest: The presence agent has authenticated the watcher using
      SIP [5] digest authentication [4].  However, if the anonymous
      authentication described on page 194 of RFC 3261 [5] was used, the
      watcher is not considered authenticated.

   Asserted Identity: If a request contains a P-Asserted-ID header field
      [18] and the request is coming from a trusted element, the watcher
      is considered authenticated.

   Cryptographically Verified Identity: If a request contains an
      Identity header field as defined in [10], and it validates the
      From header field of the request, the request is considered to be
      authenticated.  Note that this is true even if the request
      contained a From header field of the form
      sip:anonymous@example.com.  As long as the signature verifies that
      the request legitimately came from this identity, it is considered
      authenticated.



Rosenberg                Expires April 25, 2007                 [Page 5]

Internet-Draft           Presence Authorization             October 2006


   An anonymous From header field with RFC 4474 [10] is considered
   authenticated, while anonymous digest is not considered
   authenticated, because the former still involves the usage of an
   actual username and credential as part of an authentication operation
   in the originating domain.

3.1.1.2.  Computing a URI for the Watcher

   For requests that are authenticated using SIP Digest, the identity of
   the watcher is set equal to the address of record (AoR) for the user
   that has authenticated themselves.  The AoR is always a URI, and can
   be either a SIP URI or tel URI [13].  For example, consider the
   following "user record" in a database:


   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 "sip:alice@example.com".

   For requests that are authenticated using RFC 3325 [18], the identity
   of the watcher is equal to the URI in the P-Asserted-ID header field.
   If there are multiple values for the P-Asserted-ID header field
   (there can be one sip URI and one tel URI [13]), then each of them is
   used for the comparisons outlined in [8], and if either of them match
   a <one> or <except> element, it is considered a match.

   For requests that are authenticated using the SIP Identity mechanism
   [10], identity of the WR is equal to the SIP URI in the From header
   field of the request, assuming that the signature in the Identity
   header field has been validated.

   In SIP systems, it is possible for a user to have aliases - that is,
   there are multiple SIP AoRs "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 where 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.




Rosenberg                Expires April 25, 2007                 [Page 6]

Internet-Draft           Presence Authorization             October 2006


   SIP also allows for anonymous requests.  If a request is anonymous
   because the digest challenge/response used the "anonymous" username,
   the request is considered unauthenticated and will match only an
   empty <identity> element.  If a request is anonymous because it
   contains a Privacy header field [15], but still contains a
   P-Asserted-ID header field, the identity in the P-Asserted-ID header
   field is still used in the authorization computations; the fact that
   the request was anonymous has no impact on the identity processing.
   However, if the request had traversed a trust boundary and the
   P-Asserted-ID header field and the Privacy header field had been
   removed, the request will be considered unauthenticated when it
   arrives at the presence server.  Finally, if a request contained an
   Identity header field that was validated, and the From header field
   contained a URI of the form sip:anonymous@example.com, then the
   watcher is considered authenticated, and it will have an identity
   equal to sip:anonymous@example.com.  Had such an identity been placed
   into a <one> or <except> element, there will be a match.

   It is important to note that SIP frequently uses both SIP URI and tel
   URI [13] as identifiers, and to make matters more confusing, a SIP
   URI can contain a phone number in its user part, in the same format
   used in a tel URI.  A WR identity that is a SIP URI with a phone
   number will NOT match the <one> and <except> conditions whose 'id' is
   a tel URI with the same number.  The same is true in the reverse.  If
   the WR identity is a tel URI, this will not match a SIP URI in the
   <one> or <except> conditions whose user part is a phone number.  URIs
   of different schemes are never equivalent.

3.1.2.  Sphere

   The <sphere> element is defined in [8].  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 <sphere>, the presence agent examines all
   published presence documents for the presentity.  If at least one of
   them includes the <sphere> element [9] as part of the person data
   component [11], and all of those containing the element have the same
   value for it, that is the value used for the sphere in presence
   policy processing.  If, however, the <sphere> element was not present
   in any of the published documents, or it was present but had
   inconsistent values, its value is considered undefined in terms of
   presence policy processing.

   Care must be taken in using <sphere> as a condition for determining
   the subscription handling.  Since the value of <sphere> changes
   dynamically, a state change can cause a subscription to be suddenly



Rosenberg                Expires April 25, 2007                 [Page 7]

Internet-Draft           Presence Authorization             October 2006


   terminated.  The watcher has no way to know, aside from polling, when
   their subscription would be re-instated as the value of <sphere>
   changes.  For this reason, <sphere> is primarily useful for matching
   on rules that define transformations.

3.2.  Actions

3.2.1.  Subscription Handling

   The <sub-handling> element specifies the subscription authorization
   decision that the server should make.  It also specifies whether or
   not the presence document for the watcher should be constructed using
   "polite blocking" or not.  Usage of polite blocking and the
   subscription authorization decision are specified jointly since
   proper privacy handling requires a correlation between them.  As
   discussed in [8], 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 <sub-handling> 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 ten.

   polite-block: This action tells the server to place the subscription
      into the "accepted" state, and to produce a presence document that
      indicates that the presentity is unavailable.  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 twenty.

   allow: This action tells the server to place the subscription into
      the "accepted" state.  This action has a value of thirty.

      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 [8].



Rosenberg                Expires April 25, 2007                 [Page 8]

Internet-Draft           Presence Authorization             October 2006


   Future specifications that wish to define new types of actions MUST
   define an entirely new action (separate from <sub-handling>), and
   define their own set of values for that action.  A document could
   contain both <sub-handling> and a subscription handling action
   defined by a future specification; in that case, since each action is
   always a positive grant of information, the resulting action is the
   least restrictive one across both elements.

   The exact behavior of a presence server upon a change in the sub-
   handling value can be described by utilizing the subscription
   processing state machine in Figure 1 of RFC 3857 [6].

   If the sub-handling permission changes value to "block", this causes
   a "rejected" event to be generated into the subscription state
   machine for all affected subscriptions.  This will cause the state
   machine to move into the terminated state, resulting in the
   transmission of a NOTIFY to the watcher with a Subscription-State
   header field with value "terminated" and a reason of "rejected" [7],
   which terminates their subscription.  If a new subscription arrives
   later on, and the value of sub-handling that applies to that
   subscription is "block", the subscription processing follows the
   "subscribe, policy=reject" branch from the init state, and a 403
   response to the SUBSCRIBE is generated.

   If the sub-handling permission changes value to confirm, the
   processing depends on the states of the affected subscriptions.
   Unfortunately, the state machine in RFC 3857 does not define an event
   corresponding to an authorization decision of "pending".  If the
   subscription is in the active state, it moves back into the pending
   state.  This causes a NOTIFY to be sent, updating the Subscription-
   State [7] to "pending".  No reason is included in the Subscription-
   State header field (none are defined to handle this case).  No
   further documents are sent to this watcher.  There is no change in
   state if the subscription is in the pending, waiting or terminated
   states.  If a new subscription arrives later on, and the value of
   sub-handling that apples to that subscription is "pending", the
   subscription processing follows the "subscribe, no policy" branch
   from the init state, and a 202 response to the SUBSCRIBE is
   generated, followed by a NOTIFY with Subscription-State of pending.
   No presence document is included in that NOTIFY.

   If the sub-handling permission changes value to "polite-block" or
   "allow", this causes an "approved" event to be generated into the
   state machine for all affected subscriptions.  This will cause the
   machine to move into the active state if it is currently in pending,
   resulting in the transmission of a NOTIFY with a Subscription-State
   header field of "active", and the inclusion of a presence document in
   that NOTIFY.  If a new subscription arrives later on, and the value



Rosenberg                Expires April 25, 2007                 [Page 9]

Internet-Draft           Presence Authorization             October 2006


   of sub-handling that applies to that subscription is "polite-block"
   or "allow", the subscription processing follows the "subscribe,
   policy=accept" branch from the init state, and a 200 OK response to
   the SUBSCRIBE is generated, followed by a NOTIFY with Subscription-
   State of "active" with a presence document in the body of the NOTIFY.

3.3.  Transformations

   The transformations defined here are used to drive the behavior of
   the privacy filtering operation.  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 Component Elements

   The transformations in this section provide access to person, device
   and service data component 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.  Device Information

   The <provide-devices> permission allows a watcher to see <device>
   information present in the presence document.  It is a set variable.
   Each member of the set provides a way to identify a device or group
   of devices.  This specification defines three types of elements in
   the set - <class>, which identifies a device occurrence by class,
   <deviceID>, which identifies a device occurrence by device ID, and
   <occurrence-id>, which identifies a device occurrence by occurrence
   ID.  The device ID and occurrence ID are defined in [11].  Each
   member of the set is identified by its type (class, deviceID or
   occurrence-id) and value (value of the class, value of the deviceID,
   or value of the occurrence-id).

   For example, consider the following <provide-devices> element:


   <provide-devices>
     <deviceID>urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6</deviceID>
     <class>biz</class>
   </provide-devices>

   This set has two members.  This is combined with a <provide-devices>
   element from a different rule:




Rosenberg                Expires April 25, 2007                [Page 10]

Internet-Draft           Presence Authorization             October 2006


   <provide-devices>
     <class>home</class>
     <class>biz</class>
   </provide-devices>

   The result of the set combination (using the union operation) is a
   set with three elements:


   <provide-devices>
     <class>home</class>
     <class>biz</class>
     <deviceID>urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6</deviceID>
   </provide-devices>

   The <provide-devices> element can also take on the special value
   <all-devices> which is a short-hand notation for all device
   occurrences present in the presence document.

   Permission is granted to see a particular device occurrence if one of
   the device identifiers in the set identifies that device occurrence.
   If a <class> permission is granted to the watcher, and the <class> of
   the device occurrence matches the value of the <class> permission
   based on case sensitive equality, the device occurrence is included
   in the presence document.  If a <deviceID> permission is granted to
   the watcher, and the <deviceID> of the device occurrence matches the
   value of the <deviceID> permission based on URI equivalence, the
   device occurrence is included in the presence document.  If a
   <occurrence-id> permission is granted to the watcher, and the
   <occurrence-id> of the device occurrence matches the value of the
   <occurrence-id> permission based on case sensitive equality, the
   device occurrence is included in the presence document.  In addition,
   a device occurrence is included in the presence document if the <all-
   devices> permission was granted to the watcher.

3.3.1.2.  Person Information

   The <provide-persons> permission allows a watcher to see the <person>
   information present in the presence document.  It is a set variable.
   Each member of the set provides a way to identify a person
   occurrence.  This specification defines two types of elements in the
   set - <class>, which identifies a person occurrence by class, and
   <occurrence-id>, which identifies an occurrence by its occurrence ID.
   Each member of the set is identified by its type (class or
   occurrence-id) and value (value of the class or value of the
   occurrence-id).  The <provide-persons> element can also take on the
   special value <all-persons> which is a short-hand notation for all
   person occurrences present in the presence document.  The set



Rosenberg                Expires April 25, 2007                [Page 11]

Internet-Draft           Presence Authorization             October 2006


   combination is done identically to the <provide-devices> element.

   Permission is granted to see a particular person occurrence if one of
   the person identifiers in the set identifies that person occurrence.
   If a <class> permission is granted to the watcher, and the <class> of
   the person occurrence matches the value of the <class> permission
   based on case sensitive equality, the person occurrence is included
   in the presence document.  If a <occurrence-id> permission is granted
   to the watcher, and the <occurrence-id> of the person occurrence
   matches the value of the <occurrence-id> permission based on case
   sensitive equality, the person occurrence is included in the presence
   document.  In addition, a person occurrence is included in the
   presence document if the <all-persons> permission was granted to the
   watcher.

3.3.1.3.  Service Information

   The <provide-services> permission allows a watcher to see service
   information present in <tuple> elements in the presence document.
   Like <provide-devices>, it is a set variable.  Each member of the set
   provides a way to identify a service occurrence.  This specification
   defines four types of elements in the set - <class>, which identifies
   a service occurrence by class, <occurrence-id>, which identifies a
   service by its occurrence ID, <service-uri>, which identifies a
   service by its service URI, and <service-uri-scheme>, which
   identifies a service by its service URI scheme.  Each member of the
   set is identified by its type (class, occurrence-id, service-uri or
   service-uri-scheme) and value (value of the class, value of the
   occurrence-id, value of the service-uri or value of the service-uri-
   scheme ).  The <provide-services> element can also take on the
   special value <all-services> which is a short-hand notation for all
   service occurrences present in the presence document.  The set
   combination is done identically to the <provide-persons> element.

   Permission is granted to see a particular service occurrence if one
   of the service identifiers in the set identifies that service
   occurrence.  If a <class> permission is granted to the watcher, and
   the <class> of the service occurrence matches the value of the
   <class> permission based on case sensitive equality, the service
   occurrence is included in the presence document.  If a <service-uri>
   permission is granted to the watcher, and the <service-uri> of the
   service occurrence matches the value of the <service-uri> permission
   based on URI equivalence, the service occurrence is included in the
   presence document.  If a <occurrence-id> permission is granted to the
   watcher, and the <occurrence-id> of the service occurrence matches
   the value of the <occurrence-id> permission based on case sensitive
   equality, the service occurrence is included in the presence
   document.  If a <service-uri-scheme> permission is granted to the



Rosenberg                Expires April 25, 2007                [Page 12]

Internet-Draft           Presence Authorization             October 2006


   watcher, and the scheme of the service URI for the service occurrence
   matches the value of <service-uri-scheme> based on case sensitive
   equality, the service occurrence is included in the presence
   document.  In addition, a service occurrence is included in the
   presence document if the <all-services> permission was granted to the
   watcher.

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.  Certain information is always
   reported.  In particular, the <contact>, <service-class> [9], <basic>
   status and <timestamp> elements in all <tuple> elements, if present,
   are provided to watchers .  The <timestamp> element in all <person>
   elements, if present, is provided to watchers.  The <timestamp> and
   <deviceID> elements in all <device> elements, if present, is provided
   to all watchers.

3.3.2.1.  Provide Activities

   This permission controls access to the <activities> element defined
   in [9].  The name of the element providing this permission is
   <provide-activities>, and it is a boolean type.  If its value is
   TRUE, then the <activities> 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 <class> element defined in
   [9].  The name of the element providing this permission is <provide-
   class>, and it is a boolean type.  If its value is TRUE, then any
   <class> element in a 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 DeviceID

   This permission controls access to the <deviceID> element in a
   <tuple> element, as defined in [9].  The name of the element
   providing this permission is <provide-deviceID>, and it is a boolean
   type.  If its value is TRUE, then the <deviceID> element in the
   service data element is reported to the watcher.  If FALSE, this



Rosenberg                Expires April 25, 2007                [Page 13]

Internet-Draft           Presence Authorization             October 2006


   presence attribute is removed if present.  Note that the <deviceID>
   in a device data element is always included, and not controlled by
   this permission.

3.3.2.4.  Provide Mood

   This permission controls access to the <mood> element defined in [9].
   The name of the element providing this permission is <provide-mood>,
   and it is a boolean type.  If its value is TRUE, then the <mood>
   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 Place-is

   This permission controls access to the <place-is> element defined in
   [9].  The name of the element providing this permission is <provide-
   place-is>, and it is a boolean type.  If its value is TRUE, then the
   <place-is> element in the person data element is reported to the
   watcher.  If FALSE, this presence attribute is removed if present.

3.3.2.6.  Provide Place-type

   This permission controls access to the <place-type> element defined
   in [9].  The name of the element providing this permission is
   <provide-place-type>, and it is a boolean type.  If its value is
   TRUE, then the <place-type> element in the person data element is
   reported to the watcher.  If FALSE, this presence attribute is
   removed if present.

3.3.2.7.  Provide Privacy

   This permission controls access to the <privacy> element defined in
   [9].  The name of the element providing this permission is <provide-
   privacy>, and it is a boolean type.  If its value is TRUE, then the
   <privacy> element in the person or service data element is reported
   to the watcher.  If FALSE, this presence attribute is removed if
   present.

3.3.2.8.  Provide Relationship

   This permission controls access to the <relationship> element defined
   in [9].  The name of the element providing this permission is
   <provide-relationship>, and it is a boolean type.  If its value is
   TRUE, then the <relationship> element in the service data element is
   reported to the watcher.  If FALSE, this presence attribute is
   removed if present.





Rosenberg                Expires April 25, 2007                [Page 14]

Internet-Draft           Presence Authorization             October 2006


3.3.2.9.  Provide Sphere

   This permission controls access to the <sphere> element defined in
   [9].  The name of the element providing this permission is <provide-
   sphere>, and it is a boolean type.  If its value is TRUE, then the
   <sphere> 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 Status-Icon

   This permission controls access to the <status-icon> element defined
   in [9].  The name of the element providing this permission is
   <provide-status-icon>, and it is a boolean type.  If its value is
   TRUE, then any <status-icon> element in the person or service data
   element is reported to the watcher.  If FALSE, this presence
   attribute is removed if present.

3.3.2.11.  Provide Time-Offset

   This permission controls access to the <time-offset> element defined
   in [9].  The name of the element providing this permission is
   <provide-time-offset>, and it is a boolean type.  If its value is
   TRUE, then the <time-offset> element in the person data element is
   reported to the watcher.  If FALSE, this presence attribute is
   removed if present.

3.3.2.12.  Provide User-Input

   This permission controls access to the <user-input> element defined
   in [9].  The name of the element providing this permission is
   <provide-user-input>, and it is an enumerated integer type.  Its
   value defines what information is provided to watchers in person,
   device or service data elements:

   false: This value indicates that the <user-input> element is removed
      from the document.  It is assigned the numeric value of 0.

   bare: This value indicates that the <user-input> element is to be
      retained.  However, any "idle-threshold" and "since" attributes
      are to be removed.  This value is assigned the numeric value of
      10.

   thresholds: This value indicates that the <user-input> element is to
      be retained.  However, only the "idle-threshold" attribute is to
      be retained.  This value is assigned to the numeric value of 20.






Rosenberg                Expires April 25, 2007                [Page 15]

Internet-Draft           Presence Authorization             October 2006


   full: This value indicates that the <user-input> element is to be
      retained, including any attributes.  This value is assigned to the
      numeric value of 30.

3.3.2.13.  Provide Note

   This permission controls access to the <note> element defined in [3]
   for <tuple> and [11] for <person> and <device>.  The name of the
   element providing this permission is <provide-note>, and it is a
   boolean type.  If its value is TRUE, then any <note> elements in the
   person, service or device data elements are reported to the watcher.
   If FALSE, this presence attribute is removed if present.

   This permission has no bearing on any <note> values present within
   <activities>, <mood>, <place-is>, <place-type>, <privacy>,
   <relationship> or <service-class> elements.  Notes there are
   essentially values for their respective elements, and are present if
   the respective element is permitted in the presence document.  For
   example, if an <activities> element is present in a presence
   document, and there is a <note> value for it, that note is present in
   the document sent to the watcher if the <provide-activities>
   permission is given, regardless of whether the <provide-note>
   permission is given.

3.3.2.14.  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 <provide-unknown-
   attribute> permission is defined.  This permission indicates that the
   unknown presence attribute with the given name and namespace
   (supplied as mandatory attributes of the <provide-unknown-attribute>
   element) should be included in the document.  Its type is boolean.

   The value of the name attribute MUST be an unqualified element name
   (meaning that a namespace prefix MUST NOT be included), and the the
   value of the ns attribute MUST be a namespace URI.  The two are
   combined to form a qualified element name, which will be matched to
   all unknown child elements of the PIDF <tuple>, <device> or <person>
   elements with the same qualified name.  In this context, "unknown"
   means that the presence server is not aware of any schemas that
   define authorization policies for that element.  By definition, this
   will exclude the <provide-unknown-attribute> rule from being applied
   to any of the presence status extensions defined by RPID, since
   authorization policies for those are defined here.

   Another consequence of this definition is that the interpretation of



Rosenberg                Expires April 25, 2007                [Page 16]

Internet-Draft           Presence Authorization             October 2006


   the <provide-unknown-attribute> element can change should the
   presence server be upgraded.  For example, consider a server which,
   prior to the upgrade, had an authorization document that used
   <provide-unknown-attribute> for some attribute, say foo.  This
   attribute was from a namespace and schema unknown to the server, and
   so the attribute was provided to watchers.  However, after upgrade,
   the server is now aware of a new namespace and schema for a
   permission that grants access to the foo attribute.  Now, the
   <provide-unknown-attribute> permission for the foo attribute will 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, (using the mechanism described in Section 7) before uploading
   a new authorization document, to make sure that the behavior will be
   as expected.

3.3.2.15.  Provide All Attributes

   This permission grants access to all presence attributes in all of
   the person, device and tuple elements that are present in the
   document (the ones present in the document are determined by the
   <provide-persons>, <provide-devices> and <provide-services>
   permissions).  It is effectively a macro that expands into a set of
   provide-activities, provide-class, provide-deviceID, provide-mood,
   provide-place-is, provide-place-type, provide-privacy, provide-
   relationship, provide-sphere, provide-status-icon, provide-time-
   offset, provide-user-input, provide-note and provide-unknown-
   attribute permissions such that each presence attribute in the
   document has a permission for it.  This implies that, so long as an
   entire person, service or device occurrence is provided, every single
   presence attribute, including ones not known to the server and/or
   defined in future presence document extensions, is granted to the
   watcher.


4.  When to Apply the Authorization Policies

   This specification does not mandate at what point in the processing
   of presence data the privacy filtering aspects of the authorization
   policy are applied.  However, they must be applied such that the
   final presence document sent to the watcher is compliant to the
   privacy policy described in the authorization documents that apply to
   the user (there can be more than one; the rules for combining them
   are described in [8]).  More concretely, if the presence document
   sent to a watcher is D, and the privacy filtering operation applied
   do a presence document x is F(x), then D MUST have the property that
   D = F(D).  In other words, further applications of the privacy



Rosenberg                Expires April 25, 2007                [Page 17]

Internet-Draft           Presence Authorization             October 2006


   filtering operation would not result in any further changes of the
   presence document, making further application of the filtering
   operation a no-op.  A corollary of this is that F(F(D)) = D for all
   D.

   The subscription processing aspects of the document get applied by
   the server when it decides to accept or reject the subscription.


5.  Example Document

   The following presence authorization document specifies permissions
   for the user "user@example.com".  The watcher is allowed to access
   presence information (the 'allow' value for <sub-handling>).  They
   will be granted access to all services whose contact URI schemes are
   sip and mailto.  Person information is also provided.  However, since
   there is no <provide-devices>, no device information will be given to
   the watcher.  Within the service and person information provided to
   the watcher, the <activities> element will be shown, as will the
   <user-input> element.  However, any "idle-threshold" and "since"
   attributes in the <user-input> element will be removed.  Finally, the
   presence attribute <foo> will be shown to the watcher.  Any other
   presence attributes will be removed.




























Rosenberg                Expires April 25, 2007                [Page 18]

Internet-Draft           Presence Authorization             October 2006


   <?xml version="1.0" encoding="UTF-8"?>
   <cr:ruleset xmlns="urn:ietf:params:xml:ns:pres-rules"
    xmlns:pr="urn:ietf:params:xml:ns:pres-rules"
    xmlns:cr="urn:ietf:params:xml:ns:common-policy">
    <cr:rule id="a">
     <cr:conditions>
      <cr:identity>
       <cr:one id="sip:user@example.com"/>
      </cr:identity>
     </cr:conditions>
     <cr:actions>
      <pr:sub-handling>allow</pr:sub-handling>
     </cr:actions>
     <cr:transformations>
      <pr:provide-services>
        <pr:service-uri-scheme>sip</pr:service-uri-scheme>
        <pr:service-uri-scheme>mailto</pr:service-uri-scheme>
      </pr:provide-services>
      <pr:provide-persons>
        <pr:all-persons/>
      </pr:provide-persons>
      <pr:provide-activities>true</pr:provide-activities>
      <pr:provide-user-input>bare</pr:provide-user-input>
       <pr:provide-unknown-attribute
        ns="urn:vendor-specific:foo-namespace"
        name="foo">true</pr:provide-unknown-attribute>
     </cr:transformations>
    </cr:rule>
   </cr:ruleset>



6.  XML Schema



   <?xml version="1.0" encoding="UTF-8"?>
   <xs:schema targetNamespace="urn:ietf:params:xml:ns:pres-rules"
    xmlns:xs="http://www.w3.org/2001/XMLSchema"
    xmlns:cr="urn:ietf:params:xml:ns:common-policy"
    xmlns:pr="urn:ietf:params:xml:ns:pres-rules"
    elementFormDefault="qualified" attributeFormDefault="unqualified">
    <xs:import namespace="urn:ietf:params:xml:ns:common-policy"/>
    <xs:simpleType name="booleanPermission">
     <xs:restriction base="xs:boolean"/>
    </xs:simpleType>
    <xs:element name="service-uri-scheme" type="xs:token"/>
    <xs:element name="class" type="xs:token"/>



Rosenberg                Expires April 25, 2007                [Page 19]

Internet-Draft           Presence Authorization             October 2006


    <xs:element name="occurrence-id" type="xs:token"/>
    <xs:element name="service-uri" type="xs:anyURI"/>
    <xs:complexType name="provideServicePermission">
     <xs:choice>
      <xs:element name="all-services">
       <xs:complexType/>
      </xs:element>
      <xs:sequence minOccurs="0" maxOccurs="unbounded">
       <xs:choice>
        <xs:element ref="pr:service-uri"/>
        <xs:element ref="pr:service-uri-scheme"/>
        <xs:element ref="pr:occurrence-id"/>
        <xs:element ref="pr:class"/>
        <xs:any namespace="##other" processContents="lax"/>
       </xs:choice>
      </xs:sequence>
     </xs:choice>
    </xs:complexType>
    <xs:element name="provide-services"
     type="pr:provideServicePermission"/>
    <xs:element name="deviceID" type="xs:anyURI"/>
    <xs:complexType name="provideDevicePermission">
     <xs:choice>
      <xs:element name="all-devices">
       <xs:complexType/>
      </xs:element>
      <xs:sequence minOccurs="0" maxOccurs="unbounded">
       <xs:choice>
        <xs:element ref="pr:deviceID"/>
        <xs:element ref="pr:occurrence-id"/>
        <xs:element ref="pr:class"/>
        <xs:any namespace="##other" processContents="lax"/>
       </xs:choice>
      </xs:sequence>
     </xs:choice>
    </xs:complexType>
    <xs:element name="provide-devices"
     type="pr:provideDevicePermission"/>
    <xs:complexType name="providePersonPermission">
     <xs:choice>
      <xs:element name="all-persons">
       <xs:complexType/>
      </xs:element>
      <xs:sequence minOccurs="0" maxOccurs="unbounded">
       <xs:choice>
        <xs:element ref="pr:occurrence-id"/>
        <xs:element ref="pr:class"/>
        <xs:any namespace="##other" processContents="lax"/>



Rosenberg                Expires April 25, 2007                [Page 20]

Internet-Draft           Presence Authorization             October 2006


       </xs:choice>
      </xs:sequence>
     </xs:choice>
    </xs:complexType>
    <xs:element name="provide-persons"
     type="pr:providePersonPermission"/>
    <xs:element name="provide-activities"
     type="pr:booleanPermission"/>
    <xs:element name="provide-class"
     type="pr:booleanPermission"/>
    <xs:element name="provide-deviceID"
     type="pr:booleanPermission"/>
    <xs:element name="provide-mood"
     type="pr:booleanPermission"/>
    <xs:element name="provide-place-is"
     type="pr:booleanPermission"/>
    <xs:element name="provide-place-type"
     type="pr:booleanPermission"/>
    <xs:element name="provide-privacy"
     type="pr:booleanPermission"/>
    <xs:element name="provide-relationship"
     type="pr:booleanPermission"/>
    <xs:element name="provide-status-icon"
     type="pr:booleanPermission"/>
    <xs:element name="provide-sphere"
     type="pr:booleanPermission"/>
    <xs:element name="provide-time-offset"
     type="pr:booleanPermission"/>
    <xs:element name="provide-user-input">
     <xs:simpleType>
      <xs:restriction base="xs:string">
       <xs:enumeration value="false"/>
       <xs:enumeration value="bare"/>
       <xs:enumeration value="thresholds"/>
       <xs:enumeration value="full"/>
      </xs:restriction>
     </xs:simpleType>
    </xs:element>
    <xs:element name="provide-note" type="pr:booleanPermission"/>
    <xs:element name="sub-handling">
     <xs:simpleType>
      <xs:restriction base="xs:token">
       <xs:enumeration value="block"/>
       <xs:enumeration value="confirm"/>
       <xs:enumeration value="polite-block"/>
       <xs:enumeration value="allow"/>
      </xs:restriction>
     </xs:simpleType>



Rosenberg                Expires April 25, 2007                [Page 21]

Internet-Draft           Presence Authorization             October 2006


    </xs:element>
    <xs:complexType name="unknownBooleanPermission">
     <xs:simpleContent>
      <xs:extension base="pr:booleanPermission">
       <xs:attribute name="name" type="xs:string" use="required"/>
       <xs:attribute name="ns" type="xs:string" use="required"/>
      </xs:extension>
     </xs:simpleContent>
    </xs:complexType>
    <xs:element name="provide-unknown-attribute"
     type="pr:unknownBooleanPermission"/>
    <xs:element name="provide-all-attributes">
     <xs:complexType/>
    </xs:element>
   </xs:schema>




7.  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.

   When extensions are made to the set of permissions, it becomes
   necessary for the agent constructing the permission document
   (typically a SIP user agent, though not necessarily) to know which
   permissions are supported by the server.  This allows the agent to
   know how to build a document which results in the desired behavior,
   since unknown permissions would be ignored by the server.  To handle
   this, when presence authorization documents are transported using
   XCAP, the XCAP capabilities document stored at the server SHOULD
   contain the namespaces for the permissions supported by the presence
   server.  This way, an agent can query for this list prior to
   constructing a document.


8.  XCAP Usage

   The following section defines the details necessary for clients to
   manipulate presence authorization documents from a server using XCAP.




Rosenberg                Expires April 25, 2007                [Page 22]

Internet-Draft           Presence Authorization             October 2006


8.1.  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 10.

8.2.  XML Schema

   XCAP requires application usages to define a schema for their
   documents.  The schema for presence authorization documents is in
   Section 6.

8.3.  Default Namespace

   XCAP requires application usages to define the default namespace for
   their documents.  The default namespace is
   urn:ietf:params:xml:ns:pres-rules.

8.4.  MIME Type

   XCAP requires application usages to defined the MIME type for
   documents they carry.  Presence authorization documents inherit the
   MIME type of common policy documents, application/auth-policy+xml.

8.5.  Validation Constraints

   There are no additional constraints defined by this specification.

8.6.  Data Semantics

   Semantics of a presence authorization document are discussed in
   Section 3.

8.7.  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.  If only a single document is
   used, it SHOULD be called "index".

8.8.  Resource Interdependencies

   There are no additional resource interdependencies defined by this
   application usage.





Rosenberg                Expires April 25, 2007                [Page 23]

Internet-Draft           Presence Authorization             October 2006


8.9.  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 privileged users to modify documents
   that they don't own, but the establishment and indication of such
   policies is outside the scope of this document.


9.  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.

   Authorization documents themselves exist for the purposes of
   providing a security function - privacy.  The SIP presence
   specifications [17] require the usage of an authorization function
   prior to the granting of presence information, and this specification
   meets that need.  Presence authorization documents inherit the
   privacy properties of the common policy format on which they are
   based.  This format has been designed to be privacy-safe, which means
   that failure of the presence server to obtain or understand an
   authorization document can never reveal more information than is
   desired about the user, only less.  This is a consequence of the fact
   that all permissions are positive grants of information, and not
   negative grants.


10.  IANA Considerations

   There are several IANA considerations associated with this
   specification.

10.1.  XCAP Application Usage ID

   This section registers an XCAP Application Usage ID (AUID) according



Rosenberg                Expires April 25, 2007                [Page 24]

Internet-Draft           Presence Authorization             October 2006


   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 [16] has granted to users that seek
      to watch their presence.

10.2.  URN Sub-Namespace Registration

   This section registers a new XML namespace, per the guidelines in
   [12]

      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
           <?xml version="1.0"?>
           <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN"
            "http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd">
           <html xmlns="http://www.w3.org/1999/xhtml">
           <head>
             <meta http-equiv="content-type"
                content="text/html;charset=iso-8859-1"/>
             <title>Presence Rules Namespace</title>
           </head>
           <body>
             <h1>Namespace for Permission Statements</h1>
             <h2>urn:ietf:params:xml:ns:pres-rules</h2>
           <p>See <a href="[[[URL of published RFC]]]">RFCXXXX</a>.</p>
           </body>
           </html>
           END

10.3.  XML Schema Registrations

   This section registers an XML schema per the procedures in [12].

      URI: urn:ietf:params:xml:schema:pres-rules.






Rosenberg                Expires April 25, 2007                [Page 25]

Internet-Draft           Presence Authorization             October 2006


      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 6.


11.  Acknowledgements

   The authors would like to thank Richard Barnes, Jari Urpalainen, Jon
   Peterson, and Martin Hynar for their comments.


12.  References

12.1.  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-11 (work in progress), May 2006.

   [3]   Sugano, H., Fujimoto, S., Klyne, G., Bateman, A., Carr, W., and
         J. Peterson, "Presence Information Data Format (PIDF)",
         RFC 3863, August 2004.

   [4]   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.

   [5]   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.

   [6]   Rosenberg, J., "A Watcher Information Event Template-Package
         for the Session Initiation Protocol (SIP)", RFC 3857,
         August 2004.

   [7]   Roach, A., "Session Initiation Protocol (SIP)-Specific Event
         Notification", RFC 3265, June 2002.

   [8]   Schulzrinne, H., "Common Policy: A Document Format for
         Expressing Privacy Preferences",
         draft-ietf-geopriv-common-policy-11 (work in progress),
         August 2006.




Rosenberg                Expires April 25, 2007                [Page 26]

Internet-Draft           Presence Authorization             October 2006


   [9]   Schulzrinne, H., Gurbani, V., Kyzivat, P., and J. Rosenberg,
         "RPID: Rich Presence Extensions to the Presence Information
         Data Format (PIDF)", RFC 4480, July 2006.

   [10]  Peterson, J. and C. Jennings, "Enhancements for Authenticated
         Identity Management in the Session Initiation Protocol (SIP)",
         RFC 4474, August 2006.

   [11]  Rosenberg, J., "A Data Model for Presence", RFC 4479,
         July 2006.

   [12]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
         January 2004.

   [13]  Schulzrinne, H., "The tel URI for Telephone Numbers", RFC 3966,
         December 2004.

   [14]  Duerst, M. and M. Suignard, "Internationalized Resource
         Identifiers (IRIs)", RFC 3987, January 2005.

   [15]  Peterson, J., "A Privacy Mechanism for the Session Initiation
         Protocol (SIP)", RFC 3323, November 2002.

12.2.  Informative References

   [16]  Day, M., Rosenberg, J., and H. Sugano, "A Model for Presence
         and Instant Messaging", RFC 2778, February 2000.

   [17]  Rosenberg, J., "A Presence Event Package for the Session
         Initiation Protocol (SIP)", RFC 3856, August 2004.

   [18]  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.

















Rosenberg                Expires April 25, 2007                [Page 27]

Internet-Draft           Presence Authorization             October 2006


Author's Address

   Jonathan Rosenberg
   Cisco Systems
   600 Lanidex Plaza
   Parsippany, NJ  07054
   US

   Phone: +1 973 952-5000
   Email: jdrosen@cisco.com
   URI:   http://www.jdrosen.net








































Rosenberg                Expires April 25, 2007                [Page 28]

Internet-Draft           Presence Authorization             October 2006


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.

   Copies of IPR disclosures made to the IETF Secretariat and any
   assurances of licenses to be made available, or the result of an
   attempt made to obtain a general license or permission for the use of
   such proprietary rights by implementers or users of this
   specification can be obtained from the IETF on-line IPR repository at
   http://www.ietf.org/ipr.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights that may cover technology that may be required to implement
   this standard.  Please address the information to the IETF at
   ietf-ipr@ietf.org.


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 (2006).  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, 2007                [Page 29]


Html markup produced by rfcmarkup 1.108, available from http://tools.ietf.org/tools/rfcmarkup/