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

Versions: 00 01

SIMPLE WG                                                  A. Niemi, Ed.
Internet-Draft                                                     Nokia
Expires: December 28, 2003                                 June 29, 2003


  Session Initiation Protocol (SIP) Extension for Presence Publication
                      draft-ietf-simple-publish-01

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups. Note that other
   groups may also distribute working documents as Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time. It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at http://
   www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on December 28, 2003.

Copyright Notice

   Copyright (C) The Internet Society (2003). All Rights Reserved.

Abstract

   This document describes an extension to the Session Initiation
   Protocol (SIP) for publishing event state used within the framework
   for SIP Event Notification. The first application of this extension
   is targeted at the publication of presence information.

   The mechanism described in this document can be extended to support
   publication of any event state, for which there exists an appropriate
   event package. It is not intended to be a general-purpose mechanism
   for transport of arbitrary data, as there are better suited
   mechanisms for this purpose (FTP, HTTP, etc.)






Niemi                  Expires December 28, 2003                [Page 1]

Internet-Draft          SIP Presence Publication               June 2003


Table of Contents

   1.    Introduction . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.    Terminology and Conventions  . . . . . . . . . . . . . . . .  3
   3.    Overall Operation  . . . . . . . . . . . . . . . . . . . . .  4
   4.    Prerequisites for Event Packages using PUBLISH . . . . . . .  5
   4.1   PUBLISH Bodies . . . . . . . . . . . . . . . . . . . . . . .  5
   4.2   PUBLISH Response Bodies  . . . . . . . . . . . . . . . . . .  5
   4.3   Partial Event State  . . . . . . . . . . . . . . . . . . . .  6
   4.4   Event State Decomposition  . . . . . . . . . . . . . . . . .  6
   4.5   Default Expiration of PUBLISH  . . . . . . . . . . . . . . .  6
   5.    Constructing the PUBLISH Request . . . . . . . . . . . . . .  7
   5.1   Creating Initial Publication . . . . . . . . . . . . . . . .  8
   5.2   Setting the Expiration Interval  . . . . . . . . . . . . . .  9
   5.3   Refreshing Event State . . . . . . . . . . . . . . . . . . .  9
   5.4   Modifying Event State  . . . . . . . . . . . . . . . . . . . 10
   5.5   Removing Event State . . . . . . . . . . . . . . . . . . . . 10
   5.6   Querying the Current Event State . . . . . . . . . . . . . . 11
   6.    Processing PUBLISH Requests  . . . . . . . . . . . . . . . . 11
   7.    Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
   7.1   New Methods  . . . . . . . . . . . . . . . . . . . . . . . . 14
   7.1.1 PUBLISH Method . . . . . . . . . . . . . . . . . . . . . . . 14
   7.2   New Response Codes . . . . . . . . . . . . . . . . . . . . . 16
   7.2.1 "412 Precondition Failed" Response Code  . . . . . . . . . . 16
   7.3   New Header Fields  . . . . . . . . . . . . . . . . . . . . . 16
   7.3.1 "ETag" Header  . . . . . . . . . . . . . . . . . . . . . . . 17
   7.3.2 "If-Match" Header  . . . . . . . . . . . . . . . . . . . . . 17
   7.4   Augmented BNF Definitions  . . . . . . . . . . . . . . . . . 17
   8.    IANA Considerations  . . . . . . . . . . . . . . . . . . . . 17
   8.1   Methods  . . . . . . . . . . . . . . . . . . . . . . . . . . 17
   8.2   Response Codes . . . . . . . . . . . . . . . . . . . . . . . 18
   8.3   Header Field Names . . . . . . . . . . . . . . . . . . . . . 18
   9.    Security Considerations  . . . . . . . . . . . . . . . . . . 18
   10.   Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 19
   11.   Open Issues  . . . . . . . . . . . . . . . . . . . . . . . . 25
   12.   Contributors . . . . . . . . . . . . . . . . . . . . . . . . 26
   13.   Changes from "draft-ietf-simple-publish-00"  . . . . . . . . 26
         Normative References . . . . . . . . . . . . . . . . . . . . 27
         Informative References . . . . . . . . . . . . . . . . . . . 27
         Author's Address . . . . . . . . . . . . . . . . . . . . . . 28
         Intellectual Property and Copyright Statements . . . . . . . 29










Niemi                  Expires December 28, 2003                [Page 2]

Internet-Draft          SIP Presence Publication               June 2003


1. Introduction

   The focus of this specification is to provide a framework for the
   publication of event state from a user agent to an entity that is
   responsible for compositing this event state and distributing it to
   interested parties through the SIP events [1] framework. This
   specification fills a gap in the SIP events framework to allow for a
   client to push its event state to the state agent that acts on its
   behalf.

   The first application of this mechanism is the publication of
   presence state by a presence user agent to a presence compositor
   which has a tightly coupled relationship to the presence agent. The
   requirements and model for presence publication are documented in
   [2]. This specification will address each of those requirements.

   The mechanism described in this document can be extended to support
   publication of any event state, for which there exists an appropriate
   event package as defined in [1]. It is not intended to be a
   general-purpose mechanism for transport of arbitrary data, as there
   are better suited mechanisms for this purpose (FTP [7], HTTP [8],
   etc.)

2. Terminology and Conventions

   In addition to the terminology of RFC 3265 [1] and RFC 3261 [3], this
   document introduces some new concepts:

   Event State: The composition state of a resource.

   Event Publication Agent (EPA): The UAC which issues a PUBLISH request
      to publish event state or event state segments. For presence, this
      corresponds to the PUA.

   Event State Compositor (ESC): The UAS which processes PUBLISH
      requests and is responsible of compositing event state or event
      state segments into a complete, composite event state. For
      presence, this corresponds to the PA.

   Event State Segment: For some event packages, there exists a natural
      decomposition of event state into event state segments. For
      presence, such decomposition is the presence tuple.

   Hard State: Hard state is the steady-state or default state version
      of event state at the ESC, which may be used in the absence of any
      other soft state publications.





Niemi                  Expires December 28, 2003                [Page 3]

Internet-Draft          SIP Presence Publication               June 2003


   Soft State: Soft state is a version of event state at the ESC, that
      is published by the EPA. Soft state has a defined lifetime and
      will expire after a negotiated amount of time.

   Version Identifier: A protocol element (i.e., an entity-tag) that is
      used to identify a specific soft state version of published event
      state at the ESC.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED",  "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [4] and
   indicate requirement levels for compliant implementations.

3. Overall Operation

   This document defines a new SIP method, PUBLISH, for publishing event
   state. PUBLISH is analogous to REGISTER in that it allows a user to
   add, modify, and remove state in another entity which manages this
   state on behalf of a user. The user may in turn have multiple UAs or
   endpoints. Each endpoint may publish its own unique state and through
   a subscription to that event package discover the event state of the
   other active endpoints.

   In the generic sense, a UAC which publishes event state is labelled
   an Event Publication Agent (EPA). For presence in particular, this is
   the familiar PUA role as defined in [5]. The entity which processes
   the PUBLISH request is known as an Event State Compositor (ESC). For
   presence in particular, this is the familiar PA role as defined in
   [5].

   PUBLISH requests create soft state in the state agent. This state has
   a defined lifetime and will expire after a negotiated amount of time,
   requiring the publication to be refreshed by subsequent PUBLISH
   requests. Local policy at the compositor may in turn define
   hard-state for a particular event package. That is, the steady-state
   of this event package in the absence of any other soft state provided
   through the PUBLISH method.

   Typically, the body of a PUBLISH request carries the published event
   state. In the response to a PUBLISH request, the EPA assigns a
   version identifier to the published event state or event state
   segment. This identifier is used by the EPA as part of a version
   precondition to subsequent refreshing PUBLISH requests of that event
   state. In the event that the publication refresh is to an outdated
   version of event state, the versioning precondition will fail. This
   enables an EPA to detect collisions between new and refresh
   publications of the same event state among a set of endpoints.




Niemi                  Expires December 28, 2003                [Page 4]

Internet-Draft          SIP Presence Publication               June 2003


   Event state publication inherently involves at least two parties: the
   source of the publication and the target of the publication. The
   source of the publication is naturally represented as an
   address-of-record (AOR).

   For some types of event state, namely presence, the target of the
   publication may not sufficiently be represented by an
   address-of-record (AOR) alone. Rather, the target is a combination of
   both an AOR and a unique identifier which acts to represent one of N
   possible sections of an overall event state for that AOR. In this
   specification, these sections are referred to as event state
   segments.

   In the context of presence publication, the event state segment is
   nothing more than the presence tuple associated with the presentity
   (AOR). It is the role of the compositor to aggregate these segments
   into a complete event state which is presented to the subscribers of
   that event state. This composition logic is a matter of local policy.

   For some event packages, there is no natural decomposition of event
   state into these segments and for these packages, an AOR is
   sufficient to identify the target of the publication.

4. Prerequisites for Event Packages using PUBLISH

   In order to make use of the event publication mechanism, certain
   prerequisites have to be fulfilled for each specific event package.
   In order to satisfy the requirements of [2], the body of the PUBLISH
   request must fulfill several requirements as well.

   This section outlines these prerequisites, and demonstrates how they
   are fulfilled specifically for presence publication.

4.1 PUBLISH Bodies

   Any application of the PUBLISH mechanism for a given event package
   MUST support a content type which fulfills the requirements in [2].
   Each event package MUST also describe the semantics associated with
   that content and MUST prescribe a default, mandatory to implement
   format.

   This document defines the semantics of the presence publication
   requests (event package "presence") when the CPIM PIDF [6] presence
   document format is used. A PUA which uses PUBLISH to publish presence
   state to the PA MUST support the CPIM PIDF presence format.

4.2 PUBLISH Response Bodies




Niemi                  Expires December 28, 2003                [Page 5]

Internet-Draft          SIP Presence Publication               June 2003


   The response to a PUBLISH request indicates whether the request was
   successful or not. In general, the body of such a response will be
   empty unless the event package defines explicit meaning for such a
   body.

   There is no such meaning for a response to a presence publication
   when the document format used is CPIM PIDF.

4.3 Partial Event State

   The content type MUST provide a way to publish partial state for an
   event package. The intention is to allow each device or client for an
   address-of-record to publish event state independently. To accomplish
   this, the event state that is published by these devices MUST be
   allowed to be only a portion of the complete state that the state
   agent advertises for that AOR.

      Note that sources for event state other than those using the
      PUBLISH mechanism are explicitly allowed. It is beyond the scope
      of this document to define such interfaces.

   For presence in particular, a PUA can publish presence state for just
   a subset of the tuples that may be composited into the presence
   document that watchers receive in a NOTIFY. The mechanism by which
   the ESC aggregates this information is a matter of local policy.

4.4 Event State Decomposition

   If the content type allows for event state segments to be
   represented, the content type MUST provide a means to uniquely
   identify each unique segment.

   For presence, the CPIM PIDF presence document provides a tuple-ID to
   distinguish the segments of the presence document associated with the
   encompassing presentity.

      OPEN ISSUE: The specifics of how the tuple-ID is used to identify
      specific segments of the composite state is still open. Currently,
      a specific naming convention for the tuple-ID seems like a
      reasonable approach. However, this naming convention is to be
      defined.


4.5 Default Expiration of PUBLISH

   PUBLISH establishes soft state which expires after a negotiated
   amount of time. Each event package MUST provide a default expiration
   value recommendation (SHOULD strength).



Niemi                  Expires December 28, 2003                [Page 6]

Internet-Draft          SIP Presence Publication               June 2003


   For presence publication, it is RECOMMENDED that the ESC use a
   default value of 3600 seconds (1 hour) for this default expiration
   value.

5. Constructing the PUBLISH Request

   PUBLISH requests create, remove, and modify event state. A PUBLISH
   request can create new event state in the state agent, associating
   this event state with an address-of-record and optionally with a
   unique identifier for segments of event state being published.
   Publication on behalf of a particular address-of-record may also be
   performed by a suitably authorized third party. To determine the
   current published state for a particular address-of-record, the
   client MAY create a subscription for this address-of-record and event
   package using the SUBSCRIBE/NOTIFY mechanism of RFC3265 [1].

      Note that in the case the event state is segmented, each segment
      logically represents an independent publication that may be added,
      removed, modified, and expired separately.

   Except as noted, the construction of the PUBLISH request and the
   behavior of clients sending a PUBLISH request is identical to the
   general UAC behavior described in Section 8.1 and Section 17.1 of RFC
   3261 [3].

   If necessary, clients may probe for the support of PUBLISH using the
   OPTIONS request defined in SIP [3]. The presence of "PUBLISH" in the
   "Allow" header field in a response to an OPTIONS request indicates
   support for the PUBLISH method. In addition, the "Allow-Events"
   header field indicates the supported event packages.

   A PUBLISH request does not establish a dialog.  A UAC MAY include a
   Route header field in a PUBLISH request based on a pre-existing route
   set as described in Section 8.1 of RFC3261. The Record-Route header
   field has no meaning in PUBLISH requests or responses, and MUST be
   ignored if present. In particular, the UAC MUST NOT create a new
   route set based on the presence or absence of a Record-Route header
   field in any response to a PUBLISH request. The PUBLISH request MUST
   NOT contain a Contact header.

   The following header fields are included in a PUBLISH request:

   Request-URI: The Request-URI initially contains the address-of-record
      whose publication is to be created, removed, or modified. The
      address-of-record MUST be a SIP URI or SIPS URI. Unlike the
      REGISTER request, the Request-URI SHOULD contain both "userinfo"
      and "@" components.




Niemi                  Expires December 28, 2003                [Page 7]

Internet-Draft          SIP Presence Publication               June 2003


   To: The To header field contains the address-of-record whose
      publication is to be created, removed, or modified. The To header
      field and the Request-URI field are typically the same. This
      address-of-record MUST be a SIP URI or SIPS URI.

   From: The From header field contains the address-of-record of the
      entity responsible for the publication.  The value is the same as
      the To header field unless the request is a third-party
      publication. This address-of-record MUST be a SIP URI or SIPS URI.

   Event: PUBLISH requests MUST contain a single Event header field. The
      value of this header field indicates the event package for which
      this request is publishing event state.

   Expires: PUBLISH requests SHOULD contain a single Expires header
      field. This value indicates the lifetime of the event state being
      published by this request. A special value of "0" indicates the
      removal of any prior soft state established by a prior PUBLISH
      request from this EPA.

   If-Match: PUBLISH requests MAY contain a single If-Match header
      field. This header field SHOULD contain one or more entity-tags
      provided by the ESC, to be used as a versioning precondition to a
      PUBLISH refresh.

   The PUBLISH request MAY contain a body, which contains event state
   that the client wishes to publish. The content format and semantics
   are dependent on the event package identified in the Event header.

   As with any other SIP message, the PUBLISH mechanism MAY use the
   content indirection mechanism defined in [9]. There are no additional
   requirements or restrictions on content indirection as applied to the
   PUBLISH request. Content indirection is a useful mechanism for
   communicating large event state information that cannot reasonably be
   carried directly within the SIP signaling (PUBLISH request).

5.1 Creating Initial Publication

   The PUBLISH request created by the EPA and sent to the Event State
   Compositor (ESC) establishes soft state in the state agent for the
   event package indicated in the request and bound to the
   address-of-record in the To header of the request. Additionally, the
   PUBLISH request may publish event state that is further sub-divided
   into segments of event state that may be manipulated independently.
   As an example, presence publication using the CPIM PIDF format may
   manipulate individual tuples related to a common presentity.





Niemi                  Expires December 28, 2003                [Page 8]

Internet-Draft          SIP Presence Publication               June 2003


      OPEN ISSUE: Atomicity of publication. How exactly is this handled?
      Can an initial "full" PIDF document be split into separate tuples
      later on? If the initial publication contains several tuples, do
      each of them inherit the version identifier? How can the EPA
      publish presentity level information, e.g., presentity note?

   Once the initial PUBLISH request has been processed by the ESC, the
   EPA MAY send subsequent PUBLISH requests to refresh, modify, or
   delete the publication state established by the first PUBLISH
   request. These operations will be described in subsequent sections.

   EPAs MUST NOT send a new PUBLISH request (not a re-transmission)
   until they have received a final response from the state agent for
   the previous one or the previous PUBLISH request has timed out.

5.2 Setting the Expiration Interval

   When a client sends a PUBLISH request, it SHOULD suggest an
   expiration interval that indicates how long the client would like the
   publication to be valid. The actual duration of the soft state is
   defined by local policy at the ESC.

   The expiration value is presented in the Expires header of the
   PUBLISH request. If an Expires header is not present, the client is
   indicating its desire for the server to choose. It is RECOMMENDED
   that the PA use a value of 3600 seconds (1 hour) for this default
   expiration value in the case of presence publication. The default
   value is generally event package specific.

   If an EPA receives a 423 (Interval Too Brief) response to a PUBLISH
   request, it MAY retry the publication after changing the expiration
   interval in the Expires header to be equal to or greater than the
   expiration interval within the Min-Expires header field of the
   423(Interval Too Brief) response.

5.3 Refreshing Event State

   Each EPA is responsible for refreshing the publications that it has
   previously established.

   The 200 (OK) response from the state agent MUST contain an Expires
   header indicating the expiration time interval for the publication.
   The EPA then issues a PUBLISH request for each of its publications
   before the expiration interval has elapsed.

   Also, the 200 (OK) response from the state agent MUST contain an ETag
   header with a single entity-tag indicating the version information of
   the publication. To refresh the event state, the EPA MUST include the



Niemi                  Expires December 28, 2003                [Page 9]

Internet-Draft          SIP Presence Publication               June 2003


   received entity-tag in an If-Match header field in a PUBLISH request.

      Note that for the EPA, the entity-tag is simply an opaque string.
      It carries no further semantics for the EPA.

   The If-Match header field with the version identifier entity-tag
   establishes a versioning precondition to the PUBLISH request. If the
   version identifier matches the version maintained by the ESC, the
   refresh is successful, and the EPA receives a 200 (OK) response. If
   there is no matching version at the ESC, i.e., the refreshed event
   state is out-of-date, the EPA receives a 412 (Precondition Failed)
   response to the PUBLISH request.

   If an EPA receives a 412 (Precondition Failed) response, it MUST NOT
   reattempt to refresh the event state. Instead, the EPA SHOULD query a
   principal for further actions.

      OPEN ISSUE: This may need some more thought. It's easy to see that
      in a presence system, the UA could prompt the user when a refresh
      fails. But there may be systems consisting of automata only, where
      such a concept does not make much sense.

   Also, to recover from this error, the client MAY determine the
   current version of the event state at the server by sending a
   SUBSCRIBE request to the server and re-issue the PUBLISH request if
   the event state changes again.

   A PUBLISH refresh SHOULD NOT contain a body.

5.4 Modifying Event State

   Modification of event state is considered a new publication similar
   to the creation of initial event state. Because the modification of
   event state is not a refresh publication, the EPA does not include a
   versioning precondition in the PUBLISH request. Therefore, the
   PUBLISH request MUST NOT include an If-Match header field, and the
   EPA MUST discard any previously received version identifier for this
   event state.

5.5 Removing Event State

   PUBLISH establishes soft state which expires unless refreshed. This
   event state may also be explicitly removed. A UA requests the
   immediate removal of event state by specifying an Expires value of
   "0" in the PUBLISH request. Such a request SHOULD NOT contain any
   body. UAs which support PUBLISH SHOULD support this mechanism for
   explicitly removing event state.




Niemi                  Expires December 28, 2003               [Page 10]

Internet-Draft          SIP Presence Publication               June 2003


5.6 Querying the Current Event State

   To query the event state that the state agent in fact delivers to the
   subscribers, the client may SUBSCRIBE to the event package for which
   it has sent a PUBLISH, indicating the same address-of-record in the
   To header. An Expires header value of "0" may be used in this
   SUBSCRIBE request to do a one-time fetch of this event state as
   defined in RFC3265.

6. Processing PUBLISH Requests

   The Event State Compositor (ESC) is a UAS that responds to PUBLISH
   requests and maintains a list of publications for a given
   address-of-record. The ESC MUST ignore the Record-Route header field
   if it is included in a PUBLISH request. The ESC MUST NOT include a
   Record-Route header field in any response to a PUBLISH request.

   The ESC has to know (for example, through configuration) the set of
   domain(s) for which it maintains event state.  PUBLISH requests MUST
   be processed in the order that they are received. PUBLISH requests
   MUST also be processed atomically, meaning that a particular PUBLISH
   request is either processed completely or not at all.

   A client may probe the ESC for the support of PUBLISH using the
   OPTIONS request defined in SIP [3]. In the response to an OPTIONS
   request, the ESC SHOULD include "PUBLISH" to the list of allowed
   methods in the "Allow" header field. Also, it SHOULD list the
   supported event packages in an "Allow-Events" header field.

      The "methods" parameter for Contact may also be used to
      specifically announce support for PUBLISH messages when
      registering. (See reference [10] for details on the "methods"
      parameter).

   When receiving a PUBLISH request, the ESC follows these steps:

   1.   The ESC inspects the Request-URI to determine whether this
        request is for a domain supported by the ESC. If not, the ESC
        SHOULD proxy the request to the addressed domain.

   2.   To guarantee that the ESC supports any necessary extensions, the
        ESC MUST process the Require header field values as described
        for UASs in Section 8.2.2 of RFC3261.

   3.   An ESC SHOULD authenticate the UAC.  Possible mechanisms for the
        authentication of SIP user agents are described in Section 22 of
        RFC3261.




Niemi                  Expires December 28, 2003               [Page 11]

Internet-Draft          SIP Presence Publication               June 2003


   4.   The ESC extracts the address-of-record from the To header field
        of the request.  If the address-of-record is not valid for the
        domain in the Request-URI, the ESC MUST send a 404 (Not Found)
        response and skip the remaining steps. Else, the URI MUST then
        be converted to a canonical form. To do that, all URI parameters
        MUST be removed (including the user-param), and any escaped
        characters MUST be converted to their unescaped form.  The
        result serves as an index into the list of publications
        maintained by the ESC.

   5.   The ESC SHOULD determine if the authenticated user is authorized
        to publish for the address-of-record of the To header field. If
        the authenticated user is not authorized to publish, the ESC
        MUST return a 403 (Forbidden).

           Note that this authorization may take into account third
           party publication of event state.

   6.   The ESC examines the Event header of the PUBLISH request. If the
        Event header is missing or contains an event package which the
        ESC does not support, the ESC MUST respond to the PUBLISH
        request with a 489 (Bad Event) response.

   7.   The ESC now processes the Expires header value from the PUBLISH
        request.

        *  If the request has an Expires header field, that value MUST
           be taken as the requested expiration.

        *  Else, a locally-configured default value MUST be taken as the
           requested expiration.

        *  The ESC MAY choose an expiration less than the requested
           expiration interval.  If and only if the requested expiration
           interval is greater than zero AND less than a
           locally-configured minimum, the ESC MAY reject the
           publication with a response of 423 (Interval Too Brief), and
           skip the rest of the remaining steps.  This response MUST
           contain a Min-Expires header field that states the minimum
           expiration interval the ESC is willing to honor.

   8.   The ESC examines the If-Match header of the PUBLISH request. If
        the If-Match header is absent, the request is a new publication;
        if the request contains a version precondition in the form of an
        If-Match header field, the request is a publication refresh. The
        ESC extracts any entity-tags contained in the If-Match header
        and then matches those entity-tags against all locally stored
        entity-tags for this address-of-record and event package. If no



Niemi                  Expires December 28, 2003               [Page 12]

Internet-Draft          SIP Presence Publication               June 2003


        match is found, the ESC MUST reject the publication with a
        response of 412 (Precondition Failed), and skip the remaining
        steps.

   9.   The ESC may then process the body of the PUBLISH request (the
        actual event state). If the request contains no body (when it
        should contain one), or the Content-Type of the request does not
        match the event-package, or is not understood by the ESC, the
        ESC MUST reject the request with an appropriate response.

        *  For each publication, the ESC will record the target of the
           publication (To URI), the source of the publication (From
           URI), and the version of the publication.

              Note that this version information will be generated by
              the ESC when receiving a new publication, and will be
              present in the If-Match header field in publication
              refreshes.

        *  For new publications, i.e., publications without a version
           precondition, the ESC MUST generate a locally unique
           entity-tag, and store it, replacing any existing entity-tags
           stored for that particular event state. The new entity-tag
           MUST be delivered to the EPA in an ETag header field of a 200
           (OK) response.

              Note that the exact way in which the ESC creates the
              version entity-tag is a matter of local policy. One
              reasonable implementation of a version entity-tag is a
              counter which is incremented by one for each new version.

        *  The processing of the PUBLISH request must be atomic. If
           internal errors (such as the inability to access a back-end
           database) occur before processing is complete, no portion of
           the PUBLISH document must be published and the ESC MUST fail
           with a 500 (Server Error) response.

   10.  The ESC returns a 200 (OK) response. The response MUST contain
        an Expires header indicating the expiration interval chosen by
        the ESC. The response MUST also contain an ETag header
        indicating the version of the published event state. The state
        agent associated with this ESC may then issue appropriate NOTIFY
        requests to any watchers of this event state.

           Note that the timing between the receipt of the PUBLISH
           request and the issuance of NOTIFY requests is implementation
           dependent and may also vary according to throttling policies
           at the state agent.



Niemi                  Expires December 28, 2003               [Page 13]

Internet-Draft          SIP Presence Publication               June 2003


7. Syntax

   This section describes the syntax extensions required for event
   publication in SIP. Note that the formal syntax definitions described
   in this section are expressed in the Augmented BNF format used in SIP
   [3], and contain references to elements defined therein.

7.1 New Methods

7.1.1 PUBLISH Method

   "PUBLISH" is added to the definition of the element "Method" in the
   SIP message grammar. As with all other SIP methods, the method name
   is case sensitive. PUBLISH is used to publish event state to an
   entity responsible for compositing this event state.

   Table 1 and Table 2 extend Tables 2 and 3 of RFC 3261 [3] by adding
   an additional column, defining the header fields that can be used in
   PUBLISH requests and responses.
































Niemi                  Expires December 28, 2003               [Page 14]

Internet-Draft          SIP Presence Publication               June 2003


            +---------------------+---------+-------+-----+
            | Header Field        |  where  | proxy | PUB |
            +---------------------+---------+-------+-----+
            | Accept              |    R    |       |  -  |
            | Accept              |   2xx   |       |  -  |
            | Accept              |   415   |       |  m* |
            | Accept-Encoding     |    R    |       |  -  |
            | Accept-Encoding     |   2xx   |       |  -  |
            | Accept-Encoding     |   415   |       |  m* |
            | Accept-Language     |    R    |       |  -  |
            | Accept-Language     |   2xx   |       |  -  |
            | Accept-Language     |   415   |       |  m* |
            | Alert-Info          |    R    |       |  -  |
            | Alert-Info          |   180   |       |  -  |
            | Allow               |    R    |       |  o  |
            | Allow               |   2xx   |       |  o  |
            | Allow               |    r    |       |  o  |
            | Allow               |   405   |       |  m  |
            | Authentication-Info |   2xx   |       |  o  |
            | Authorization       |    R    |       |  o  |
            | Call-ID             |    c    |   r   |  m  |
            | Call-Info           |         |   ar  |  o  |
            | Contact             |    R    |       |  -  |
            | Contact             |   1xx   |       |  -  |
            | Contact             |   2xx   |       |  -  |
            | Contact             |   3xx   |       |  o  |
            | Contact             |   485   |       |  o  |
            | Content-Disposition |         |       |  o  |
            | Content-Encoding    |         |       |  o  |
            | Content-Language    |         |       |  o  |
            | Content-Length      |         |   ar  |  t  |
            | Content-Type        |         |       |  *  |
            | CSeq                |    c    |   r   |  m  |
            | Date                |         |   a   |  o  |
            | Event               |    a    |   m   |     |
            | Error-Info          | 300-699 |   a   |  o  |
            | Expires             |         |       |  o  |
            | From                |    c    |   r   |  m  |
            | In-Reply-To         |    R    |       |  o  |
            | Max-Forwards        |    R    |  amr  |  m  |
            | Organization        |         |   ar  |  o  |
            +---------------------+---------+-------+-----+

                Table 1: Summary of header fields, A--O







Niemi                  Expires December 28, 2003               [Page 15]

Internet-Draft          SIP Presence Publication               June 2003


        +---------------------+-----------------+-------+-----+
        | Header Field        |      where      | proxy | PUB |
        +---------------------+-----------------+-------+-----+
        | Priority            |        R        |   ar  |  o  |
        | Proxy-Authenticate  |       407       |   ar  |  m  |
        | Proxy-Authenticate  |       401       |   ar  |  o  |
        | Proxy-Authorization |        R        |   dr  |  o  |
        | Proxy-Require       |        R        |   ar  |  o  |
        | Record-Route        |                 |   ar  |  -  |
        | Reply-To            |                 |       |  o  |
        | Require             |                 |   ar  |  c  |
        | Retry-After         | 404,413,480,486 |       |  o  |
        |                     |     500,503     |       |  o  |
        |                     |     600,603     |       |  o  |
        | Route               |        R        |  adr  |  o  |
        | Server              |        r        |       |  o  |
        | Subject             |        R        |       |  o  |
        | Timestamp           |                 |       |  o  |
        | To                  |       c(1)      |   r   |  m  |
        | Unsupported         |       420       |       |  o  |
        | User-Agent          |                 |       |  o  |
        | Via                 |        R        |  amr  |  m  |
        | Via                 |        rc       |   dr  |  m  |
        | Warning             |        r        |       |  o  |
        | WWW-Authenticate    |       401       |   ar  |  m  |
        | WWW-Authenticate    |       407       |   ar  |  o  |
        +---------------------+-----------------+-------+-----+

                Table 2: Summary of header fields, P--Z


7.2 New Response Codes

7.2.1 "412 Precondition Failed" Response Code

   The 412 response is added to the "Client-Error" header field
   definition. "412 Precondition Failed" is used to indicate that the
   precondition given for the request has failed.

7.3 New Header Fields

   Table 3 expands on Table 2 in SIP [3], as amended by the changes in
   Section 7.1.








Niemi                  Expires December 28, 2003               [Page 16]

Internet-Draft          SIP Presence Publication               June 2003


                 +--------------+-------+-------+-----+
                 | Header Field | where | proxy | PUB |
                 +--------------+-------+-------+-----+
                 | ETag         |  2xx  |       |  m  |
                 | If-Match     |   R   |       |  o  |
                 +--------------+-------+-------+-----+

                Table 3: Summary of header fields, A--O


7.3.1 "ETag" Header

   ETag is added to the definition of the element "general-header" in
   the SIP message grammar. Usage of this header is described in Section
   6.

7.3.2 "If-Match" Header

   If-Match is added to the definition of the element "general-header"
   in the SIP message grammar. Usage of this header is described in
   Section 5.

7.4 Augmented BNF Definitions

   This section describes the Augmented BNF definitions for the various
   new and modified syntax elements. The notation is as used in SIP [3]
   and the documents to which it refers.

      PUBLISHm           = %x50.55.42.4C.49.53.48 ; PUBLISH in caps.
      extension-method   = PUBLISHm / token
      ETag               = "ETag" HCOLON entity-tag
      If-Match           = "If-Match" HCOLON entity-tag
                           * (COMMA entity-tag)
      entity-tag         = quoted-string



8. IANA Considerations

   This document registers a new method name, a new response code and
   two new header field names.

8.1 Methods

   This document registers a new SIP method, defined by the following
   information which is to be added to the method and response-code
   sub-registry under http://www.iana.org/assignments/sip-parameters.




Niemi                  Expires December 28, 2003               [Page 17]

Internet-Draft          SIP Presence Publication               June 2003


       Method Name:   PUBLISH
       Reference:     [RFCYYYY]

      (Note to RFC Editor: Replace YYYY with the RFC number of this
      document when published).


8.2 Response Codes

   This document registers a new response code. This response code is
   defined by the following information, which is to be added to the
   method and response-code sub-registry under http://www.iana.org/
   assignments/sip-parameters.

       Response Code Number:   412
       Default Reason Phrase:  Precondition Failed


8.3 Header Field Names

   This document registers two new SIP header field names. These headers
   are defined by the following information, which is to be added to the
   header sub-registry under http://www.iana.org/assignments/
   sip-parameters.

       Header Name:    ETag
       Compact Form:   (none)

       Header Name:    If-Match
       Compact Form:   (none)


9. Security Considerations

   The state agent SHOULD authenticate the Event Publication Agent
   (EPA), and SHOULD apply its authorization policies to all requests.
   The composition model makes no assumptions that all input sources for
   a compositor (ESC) are on the same network, or in the same
   administrative domain.

   The ESC SHOULD throttle incoming publications and the corresponding
   notifications resulting from the changes in event state. As a first
   step, careful selection of default Expires: values for the supported
   event packages at a ESC can help limit refreshes of event state.
   Additional throttling and debounce logic at the ESC is advisable to
   further reduce the notification traffic produced as a result of a
   PUBLISH method.




Niemi                  Expires December 28, 2003               [Page 18]

Internet-Draft          SIP Presence Publication               June 2003


   Integrity protection and privacy of the PUBLISH requests can be
   ensured using the S/MIME mechanisms outlined in section 23 of
   RFC3261. Integrity protection of the To, From, Call-ID, CSeq, Event,
   ETag, If-Match, Route, and Expires headers should be done at a
   minimum.

   If the ESC receives a PUBLISH request which is integrity protected
   using a security association that is not with the ESC (for example,
   end-to-end S/MIME integrity protection), the state agent coupled with
   the ESC MUST NOT modify the event state before exposing it to the
   watchers of this event state in a NOTIFY request(s). This is to
   preserve the end-to-end integrity of the event state.

10. Examples

   The following section shows an example of the usage of the PUBLISH
   method in the case of publishing the presence document from a
   presence user agent to a presence agent. The watcher in this case is
   watching the PUA's presentity. The PUA will SUBSCRIBE to its own
   presence to see the composite presence state exposed by the PA. This
   is an optional but likely step for the PUA.


       PUA                     PA                      WATCHER
      (EPA)                   (ESC)
        |                       |                         |
        |                       | <---- M1: SUBSCRIBE --- |
        |                       |                         |
        |                       | ----- M2: 200 OK -----> |
        |                       |                         |
        |                       | ----- M3: NOTIFY -----> |
        |                       |                         |
        |                       | <---- M4: 200 OK ------ |
        |                       |                         |
        | --- M5: SUBSCRIBE --> |                         |
        |                       |                         |
        |<--- M6: 200 OK    --> |                         |
        |                       |                         |
        |<--- M7: NOTIFY  ----- |                         |
        |                       |                         |
        | --- M8: 200 OK    --> |                         |
        |                       |                         |
        | --- M9: PUBLISH ----> |                         |
        |                       |                         |
        | <-- M10: 200 OK ----  |                         |
        |                       |                         |
        |                       | ----- M11: NOTIFY ----> |
        |                       |                         |



Niemi                  Expires December 28, 2003               [Page 19]

Internet-Draft          SIP Presence Publication               June 2003


        |                       | <---- M12: 200 OK ----- |
        |                       |                         |
        |                       |                         |
        |<---- M13: NOTIFY ---- |                         |
        |                       |                         |
        |----- M14: 200 OK  --> |                         |
        |                       |                         |


   Message flow:

   M1: The watcher initiates a new subscription to the
      presentity@domain.com's presence agent.

      SUBSCRIBE sip:presentity@domain.com SIP/2.0
      Via: SIP/2.0/UDP 10.0.0.1:5060;branch=z9hG4bKnashds7
      To: <sip:presentity@domain.com>
      From: <sip:watcher@domain.com>;tag=12341234
      Call-ID: 12345678@10.0.0.1
      CSeq: 1 SUBSCRIBE
      Expires: 3600
      Event: presence
      Contact: <sip:watcher@domain.com>
      Content-Length: 0

   M2: The presence agent for presentity@domain.com processes the
      subscription request and creates a new subscription. A 200 (OK)
      response is sent to confirm the subscription.

      SIP/2.0 200 OK
      Via: SIP/2.0/UDP 10.0.0.1:5060;branch=z9hG4bKnashds7
      To: <sip:presentity@domain.com>;tag=abcd1234
      From: <sip:watcher@domain.com>;tag=12341234
      Call-ID: 12345678@10.0.0.1
      CSeq: 1 SUBSCRIBE
      Contact: <sip:pa@domain.com>
      Expires: 3600
      Content-Length: 0

   M3: In order to complete the process, the presence agent sends the
      watcher a NOTIFY with the current presence state of the
      presentity.

      NOTIFY sip:presentity@domain.com SIP/2.0
      Via: SIP/2.0/UDP pa.domain.com;branch=z9hG4bK8sdf2
      To: <sip:watcher@domain.com>;tag=12341234
      From: <sip:presentity@domain.com>;tag=abcd1234
      Call-ID: 12345678@10.0.0.1



Niemi                  Expires December 28, 2003               [Page 20]

Internet-Draft          SIP Presence Publication               June 2003


      CSeq: 1 NOTIFY
      Event: presence
      Subscription-State: active; expires=3599
      Content-Type: application/cpim-pidf+xml
      Content-Length: ...

      <?xml version="1.0" encoding="UTF-8"?>
      <presence xmlns="urn:ietf:params:xml:ns:cpim-pidf"
                entity="pres:presentity@domain.com">
         <tuple id="mobile-phone">
            <status>
               <basic>open</basic>
            </status>
            <timestamp>2003-02-01T16:49:29Z</timestamp>
         </tuple>
         <tuple id="desktop">
            <status>
               <basic>open</basic>
            </status>
            <timestamp>2003-02-01T12:21:29Z</timestamp>
         </tuple>
      </presence>

   M4: The watcher confirms receipt of the NOTIFY request.

      SIP/2.0 200 OK
      Via: SIP/2.0/UDP pa.domain.com;branch=z9hG4bK8sdf2
      To: <sip:watcher@domain.com>;tag=12341234
      From: <sip:presentity@domain.com>;tag=abcd1234
      Call-ID: 12345678@10.0.0.1
      CSeq: 1 NOTIFY
      Contact: <sip:watcher@domain.com>

   M5: To view its composite presence state, the PUA issues a SUBSCRIBE
      to the PA for itself.

      SUBSCRIBE sip:presentity@domain.com SIP/2.0
      Via: SIP/2.0/UDP 10.0.0.2:5060;branch=z9hG4bKjjsdfj
      To: <sip:presentity@domain.com>
      From: <sip:presentity@domain.com>;tag=43214321
      Call-ID: 87654321@10.0.0.2
      CSeq: 1 SUBSCRIBE
      Expires: 3600
      Event: presence
      Contact: <sip:pua@domain.com>
      Content-Length: 0





Niemi                  Expires December 28, 2003               [Page 21]

Internet-Draft          SIP Presence Publication               June 2003


   M6: The presence agent for presentity@domain.com processes the
      subscription request and creates a new subscription. A 200 (OK)
      response is sent to confirm the subscription.

      SIP/2.0 200 OK
      Via: SIP/2.0/UDP 10.0.0.2:5060;branch=z9hG4bKjjsdfj
      To: <sip:presentity@domain.com>;tag=abcd1235
      From: <sip:watcher@domain.com>;tag=43214321
      Call-ID: 87654321@10.0.0.2
      CSeq: 1 SUBSCRIBE
      Contact: <sip:pa@domain.com>
      Expires: 3600
      Content-Length: 0

   M7: In order to complete the process, the presence agent sends the
      PUA a NOTIFY with the current presence state of the presentity.

      NOTIFY sip:presentity@domain.com SIP/2.0
      Via: SIP/2.0/UDP pa.domain.com;branch=z9hG4bK8sdfk
      To: <sip:watcher@domain.com>;tag=abcd1235
      From: <sip:presentity@domain.com>;tag=43214321
      Call-ID: 87654321@10.0.0.2
      CSeq: 1 NOTIFY
      Event: presence
      Subscription-State: active; expires=3599
      Content-Type: application/cpim-pidf+xml
      Content-Length: ...

      <?xml version="1.0" encoding="UTF-8"?>
      <presence xmlns="urn:ietf:params:xml:ns:cpim-pidf"
                entity="pres:presentity@domain.com">
         <tuple id="mobile-phone">
            <status>
               <basic>open</basic>
            </status>
            <timestamp>2003-02-01T16:49:29Z</timestamp>
         </tuple>
         <tuple id="desktop">
            <status>
               <basic>open</basic>
            </status>
            <timestamp>2003-02-01T12:21:29Z</timestamp>
         </tuple>
      </presence>







Niemi                  Expires December 28, 2003               [Page 22]

Internet-Draft          SIP Presence Publication               June 2003


   M9: A presence user agent for the presentity detects a change in the
      user's presence state. It initiates a PUBLISH to the presentity's
      presence agent in order to update it with the new presence
      information. The timestamp element is updated to indicate the time
      of the change. The Expires header indicates the desired duration
      of this soft state. The "entity" attribute of the presence element
      in the PIDF document matches the To AOR.

      PUBLISH sip:presentity@domain.com SIP/2.0
      Via: SIP/2.0/UDP pua.domain.com;branch=z9hG4bK652hsge
      To: <sip:presentity@domain.com>;tag=1a2b3c4d
      From: <sip:presentity@domain.com>;tag=1234wxyz
      Call-ID: 81818181@pua.domain.com
      CSeq: 1 PUBLISH
      Expires: 3600
      Event: presence
      Content-Type: application/cpim-pidf+xml
      Content-Length: ...

      <?xml version="1.0" encoding="UTF-8"?>
      <presence xmlns="urn:ietf:params:xml:ns:cpim-pidf"
                entity="pres:presentity@domain.com">
         <tuple id="mobile-phone">
            <status>
               <basic>closed</basic>
            </status>
            <timestamp>2003-02-01T17:00:19Z</timestamp>
         </tuple>
      </presence>

   M10: The presence agent receives, and accepts the presence
      information. The published data is incorporated into the
      presentity's presence document. A 200 (OK) response is sent to
      confirm the publication.

      SIP/2.0 200 OK
      Via: SIP/2.0/UDP pua.domain.com;branch=z9hG4bK652hsge
      To: <sip:presentity@domain.com>;tag=1a2b3c4d
      From: <sip:presentity@domain.com>;tag=1234wxyz
      Call-ID: 81818181@pua.domain.com
      CSeq: 1 PUBLISH
      ETag: "dx200xyz"
      Expires: 1800

   M11: The presence agent determines that a reportable change has been
      made to the presentity's presence document, and sends another
      notification to those watching the presentity to update their
      information regarding the presentity's current presence status.



Niemi                  Expires December 28, 2003               [Page 23]

Internet-Draft          SIP Presence Publication               June 2003


      NOTIFY sip:presentity@domain.com SIP/2.0
      Via: SIP/2.0/UDP presence.domain.com;branch=z9hG4bK4cd42a
      To: <sip:watcher@domain.com>;tag=12341234
      From: <sip:presentity@domain.com>;tag=abcd1234
      Call-ID: 12345678@10.0.0.1
      CSeq: 2 NOTIFY
      Event: presence
      Subscription-State: active; expires=3400
      Content-Type: application/cpim-pidf+xml
      Content-Length: ...

      <?xml version="1.0" encoding="UTF-8"?>
      <presence xmlns="urn:ietf:params:xml:ns:cpim-pidf"
                entity="pres:presentity@domain.com">
         <tuple id="mobile-phone">
            <status>
               <basic>closed</basic>
            </status>
            <timestamp>2003-02-01T17:00:19Z</timestamp>
         </tuple>
         <tuple id="desktop">
            <status>
               <basic>open</basic>
            </status>
            <timestamp>2003-02-01T12:21:29Z</timestamp>
         </tuple>
      </presence>

   M12: The watcher confirms receipt of the NOTIFY request.

      SIP/2.0 200 OK
      Via: SIP/2.0/UDP presence.domain.com;branch=z9hG4bK4cd42a
      To: <sip:watcher@domain.com>;tag=12341234
      From: <sip:presentity@domain.com>;tag=abcd1234
      Call-ID: 12345678@10.0.0.1
      CSeq: 2 NOTIFY
      Content-Length: 0

   M13: The presence agent also sends a NOTIFY to the PUA.

      NOTIFY sip:presentity@domain.com SIP/2.0
      Via: SIP/2.0/UDP presence.domain.com;branch=z9hG4bK4cd42b
      To: <sip:watcher@domain.com>;tag=abcd1235
      From: <sip:presentity@domain.com>;tag=43214321
      Call-ID: 87654321@10.0.0.2
      CSeq: 2 NOTIFY
      Event: presence
      Subscription-State: active; expires=3400



Niemi                  Expires December 28, 2003               [Page 24]

Internet-Draft          SIP Presence Publication               June 2003


      Content-Type: application/cpim-pidf+xml
      Content-Length: ...

      <?xml version="1.0" encoding="UTF-8"?>
      <presence xmlns="urn:ietf:params:xml:ns:cpim-pidf"
                entity="pres:presentity@domain.com">
         <tuple id="mobile-phone">
            <status>
               <basic>closed</basic>
            </status>
            <timestamp>2003-02-01T17:00:19Z</timestamp>
         </tuple>
         <tuple id="desktop">
            <status>
               <basic>open</basic>
            </status>
            <timestamp>2003-02-01T12:21:29Z</timestamp>
         </tuple>
      </presence>

   M14: The PUA confirms receipt of the NOTIFY request.

      SIP/2.0 200 OK
      Via: SIP/2.0/UDP presence.domain.com;branch=z9hG4bK4cd42b
      To: <sip:watcher@domain.com>;tag=abcd1235
      From: <sip:presentity@domain.com>;tag=43214321
      Call-ID: 87654321@10.0.0.2
      CSeq: 2 NOTIFY


11. Open Issues

   o  Atomicity of publication. Should the segments of event state
      (presence tuples) be sent in separate PUBLISH requests or is it
      enough to treat these as implicitly separate publication requests?

   o  The exact naming convention used for the tuple-ID when publishing
      tuples.

   o  In case a refresh publication fails, what should the EPA do?
      Current suggestion is to query the principal, i.e., "prompt the
      user", but this is not quite specific.

   o  Does end-to-end S/MIME integrity protection make sense when an
      event compositor is used? Does it indicate that the segment should
      be carried to the watcher intact, or is another mechanism for this
      needed?




Niemi                  Expires December 28, 2003               [Page 25]

Internet-Draft          SIP Presence Publication               June 2003


   o  The examples seem a bit elaborate, and don't even cover the
      publication refresh case. We should probably work on them.

   o  Do we need another response code (new or some existing one) for
      the case when an EPA tries to refresh a publication, but the ESC
      has lost all version information it has, e.g., after e reboot?
      This seems a slightly different scenario from the usual
      "Precondition Failed".


12. Contributors

   The original contributors to this specification are:

      Ben Campbell
      dynamicsoft

      Sean Olson
      Microsoft

      Jon Peterson
      Neustar, Inc.

      Jonathan Rosenberg
      dynamicsoft

      Brian Stucker
      Nortel Networks, Inc.


13. Changes from "draft-ietf-simple-publish-00"

   The following changes were made since the last version:

   o  Merged with "draft-olson-simple-publish-02"

   o  Removed usage of Call-ID and CSeq for ordering

   o  Removed timestamp based versioning

   o  Added versioning based on entity-tag version information (ETag),
      and request precondition (If-Match)

   o  Changed reference to content-indirection as Informative

   o  Added section for ABNF definitions

   o  Editorial corrections, restructuring of document to improve



Niemi                  Expires December 28, 2003               [Page 26]

Internet-Draft          SIP Presence Publication               June 2003


      readability

   o  Moved the original authors into a new "Contributors" section

   o  Added new definitions in Terminology, and clarified EPA and ESC
      definitions

   o  Strengthened the IANA considerations section.

   o  Added text for announcing/probing support for publish, namely
      OPTIONS and "methods" parameter usage.

Normative References

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

   [2]  Campbell, B., "SIMPLE Presence Publication Requirements",
        draft-ietf-simple-publish-reqs-00 (work in progress), February
        2003.

   [3]  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.

   [4]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Levels", BCP 14, RFC 2119, March 1997.

   [5]  Rosenberg, J., "A Presence Event Package for the Session
        Initiation Protocol (SIP)", draft-ietf-simple-presence-10 (work
        in progress), January 2003.

   [6]  Fujimoto, S. and H. Sugano, "Common Presence and Instant
        Messaging (CPIM)Presence Information Data  Format",
        draft-ietf-impp-cpim-pidf-07 (work in progress), January 2003.

Informative References

   [7]   Postel, J. and J. Reynolds, "File Transfer Protocol", STD 9,
         RFC 959, October 1985.

   [8]   Fielding, R., Gettys, J., Mogul, J., Nielsen, H., Masinter, L.,
         Leach, P. and T. Berners-Lee, "Hypertext Transfer Protocol --
         HTTP/1.1", RFC 2616, June 1999.

   [9]   Olson, S., "A Mechanism for Content Indirection in SIP
         Messages", draft-olson-sip-content-indirect-mech-01 (work in
         progress), August 2002.



Niemi                  Expires December 28, 2003               [Page 27]

Internet-Draft          SIP Presence Publication               June 2003


   [10]  Rosenberg, J., Schulzrinne, H. and P. Kyzivat, "Caller
         Preferences and Callee Capabilities for the Session Initiation
         Protocol (SIP)", draft-ietf-sip-callerprefs-08 (work in
         progress), March 2003.


Author's Address

   Aki Niemi (editor)
   Nokia
   P.O. Box 321
   NOKIA GROUP, FIN  00045
   Finland

   Phone: +358 50 389 1644
   EMail: aki.niemi@nokia.com



































Niemi                  Expires December 28, 2003               [Page 28]

Internet-Draft          SIP Presence Publication               June 2003


Intellectual Property Statement

   The IETF takes no position regarding the validity or scope of any
   intellectual property 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; neither does it represent that it
   has made any effort to identify any such rights. Information on the
   IETF's procedures with respect to rights in standards-track and
   standards-related documentation can be found in BCP-11. Copies of
   claims of rights made available for publication 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 implementors or users of this specification can
   be obtained from the IETF Secretariat.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights which may cover technology that may be required to practice
   this standard. Please address the information to the IETF Executive
   Director.


Full Copyright Statement

   Copyright (C) The Internet Society (2003). All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works. However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assignees.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION



Niemi                  Expires December 28, 2003               [Page 29]

Internet-Draft          SIP Presence Publication               June 2003


   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.


Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.











































Niemi                  Expires December 28, 2003               [Page 30]


Html markup produced by rfcmarkup 1.107, available from http://tools.ietf.org/tools/rfcmarkup/