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Versions: 00 01 02 03 04 RFC 3842

SIPPING WG                                                       R. Mahy
Internet-Draft                                       Cisco Systems, Inc.
Expires: May 31, 2004                                           Dec 2003


   A Message Summary and Message Waiting Indication Event Package for
                 the Session Initiation Protocol (SIP)
                     draft-ietf-sipping-mwi-04.txt

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 May 31, 2004.

Copyright Notice

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

Abstract

   This document describes a SIP event package to carry message waiting
   status and message summaries from a messaging system to an interested
   User Agent.












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Table of Contents

   1.   Conventions  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.   Background and Appropriateness . . . . . . . . . . . . . . .   3
   3.   Event Package Formal Definition  . . . . . . . . . . . . . .   4
   3.1  Event Package Name . . . . . . . . . . . . . . . . . . . . .   4
   3.2  Event Package Parameters . . . . . . . . . . . . . . . . . .   4
   3.3  SUBSCRIBE Bodies . . . . . . . . . . . . . . . . . . . . . .   4
   3.4  Subscription Duration  . . . . . . . . . . . . . . . . . . .   4
   3.5  NOTIFY Bodies  . . . . . . . . . . . . . . . . . . . . . . .   4
   3.6  Subscriber generation of SUBSCRIBE requests  . . . . . . . .   6
   3.7  Notifier processing of SUBSCRIBE requests  . . . . . . . . .   6
   3.8  Notifier generation of NOTIFY requests . . . . . . . . . . .   7
   3.9  Subscriber processing of NOTIFY requests . . . . . . . . . .   7
   3.10 Handling of Forked Requests  . . . . . . . . . . . . . . . .   7
   3.11 Rate of notifications  . . . . . . . . . . . . . . . . . . .   7
   3.12 State Agents and Lists . . . . . . . . . . . . . . . . . . .   8
   3.13 Behavior of a Proxy Server . . . . . . . . . . . . . . . . .   8
   4.   Examples of Usage  . . . . . . . . . . . . . . . . . . . . .   8
   4.1  Example Message Flow . . . . . . . . . . . . . . . . . . . .   8
   4.2  Example Usage with Callee Capabilities and Caller
        Preferences  . . . . . . . . . . . . . . . . . . . . . . . .  14
   5.   Formal Syntax  . . . . . . . . . . . . . . . . . . . . . . .  14
   5.1  New event-package definition . . . . . . . . . . . . . . . .  14
   5.2  Body Format Syntax . . . . . . . . . . . . . . . . . . . . .  15
   6.   Security Considerations  . . . . . . . . . . . . . . . . . .  15
   7.   IANA Considerations  . . . . . . . . . . . . . . . . . . . .  15
   7.1  SIP Event Package Registration for message-summary . . . . .  16
   7.2  MIME Registration for application/simple-message-summary . .  16
   8.   Revision history . . . . . . . . . . . . . . . . . . . . . .  17
   8.1  Changes from draft-ietf-sipping-mwi-03 . . . . . . . . . . .  17
   8.2  Changes from draft-ietf-sipping-mwi-01 and -02 . . . . . . .  17
   8.3  Changes from draft-ietf-sipping-mwi-00 . . . . . . . . . . .  17
   8.4  Changes from draft-mahy-sipping-mwi-00 . . . . . . . . . . .  18
   8.5  Changes from draft-mahy-sip-mwi-01 . . . . . . . . . . . . .  18
   8.6  Changes from draft-mahy-sip-mwi-00 . . . . . . . . . . . . .  18
   9.   Contributors . . . . . . . . . . . . . . . . . . . . . . . .  19
   10.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . .  19
        Normative References . . . . . . . . . . . . . . . . . . . .  19
        Informational References . . . . . . . . . . . . . . . . . .  20
        Author's Address . . . . . . . . . . . . . . . . . . . . . .  20
        Intellectual Property and Copyright Statements . . . . . . .  21









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1. Conventions

   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 [3].

2. Background and Appropriateness

   Messaging Waiting Indication is a common feature of telephone
   networks.  It typically involves an audible or visible indication
   that messages are waiting, such as playing a special dial tone (which
   in telephone networks is called message-waiting dial tone), lighting
   a light or indicator on the phone, displaying icons or text, or some
   combination.

      Message-waiting dial tone is similar to but distinct from stutter
      dial tone.  Both are defined in GR-506 [12].

   The methods in the SIP [1] base specification were only designed to
   solve the problem of session initiation for multimedia sessions, and
   rendezvous.  Since Message Waiting Indication is really status
   information orthogonal to a session, it was not clear how an IP
   telephone acting as a SIP User Agent would implement comparable
   functionality.  Members of the telephony community viewed this as a
   shortcoming of SIP.

   Users want the useful parts of the functionality they have using
   traditional analog, mobile, and PBX telephones.  It is also desirable
   to provide comparable functionality in a flexible way that allows for
   more customization and new features. SIP Specific Event Notification
   (RFC 3265 -- SIP Events) [2] is an appropriate mechanism to use in
   this environment, as it preserves the user mobility and rendezvous
   features which SIP provides.

   Using SIP-Specific Event Notification, A Subscriber User Agent
   (typically an IP phone or SIP software User Agent) subscribes to the
   status of their messages.  A SIP User Agent acting on behalf of the
   user's messaging system then notifies the Subscriber whenever the
   messaging account's messages have changed. (This Notifier could be
   composed with a User Agent that provides a real-time media interface
   to send or receive messages, or it could be a standalone entitiy.)
   The Notifier sends a message summary in the body of a NOTIFY, encoded
   in a new MIME type defined later in this document.  A User Agent can
   also explicitly fetch the current status.

   A SIP User Agent MAY subscribe to multiple accounts (distinguished by
   the Request URI).  Multiple SIP User Agents MAY subscribe to the same
   account.



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   Before any subscriptions or notifications are sent, each interested
   User Agent must be made aware of its messaging notifier(s).  This MAY
   be manually configured on interested User Agents, manually configured
   on an appropriate SIP Proxy, or dynamically discovered based on
   requested caller preferences [4] and registered callee capabilities
   [5]. (For more information on usage with callee capabilities, see
   Section 4.2)

3. Event Package Formal Definition

3.1 Event Package Name

   This document defines a SIP Event Package as defined in RFC 3265 [2].
   The event-package token name for this package is:

        "message-summary"


3.2 Event Package Parameters

   This package does not define any event package parameters.

3.3 SUBSCRIBE Bodies

   This package does not define any SUBSCRIBE bodies.

3.4 Subscription Duration

   Subscriptions to this event package MAY range from minutes to weeks.
   Subscriptions in hours or days are more typical and are RECOMMENDED.
   The default subscription duration for this event package is one hour.

3.5 NOTIFY Bodies

   A simple text-based format is proposed to prevent an undue burden on
   low-end user agents, for example, inexpensive IP phones with no
   display.  Although this format is text-based, it is intended for
   machine consumption only.

   A future extension MAY define other NOTIFY bodies.  If no "Accept"
   header is present in the SUBSCRIBE, the body type defined in this
   document MUST be assumed.

   The format specified in this proposal attempts to separate orthogonal
   attributes of messages as much as possible.  Messages are separated
   by message-context-class (for example: voice-message, fax-message,
   pager-message, multimedia-message, text-message, and none); by
   message status (new and old); and by urgent and non-urgent type.



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   The text format begins with a simple status line, and optionally a
   summary line per message-context-class.  Message-context-classes are
   defined in [7].  For each message-context-class, the total number of
   new and old messages is reported in the new and old fields.

   In some cases, detailed message summaries are not available.  The
   status line allows messaging systems or messaging gateways to provide
   the traditional boolean message waiting notification.

        Messages-Waiting: yes

   If the Request-URI or To header in a message-summary subscription
   corresponds to a group or collection of individual messaging
   accounts, the notifier MUST specify to which account the
   message-summary body corresponds. Note that the account URI MUST NOT
   be delimited with angle brackets ("<" and ">").

          Message-Account: sip:alice@example.com

   In the example that follows, more than boolean message summary
   information is available to the User Agent.  There are two new and
   four old fax messages.

        Fax-Message: 2/4

   After the summary, the format can optionally list a summary count of
   urgent messages. In the next example there are one new and three old
   voice messages, none of the new messages are urgent, but one of the
   old messages is.  All counters have a maximum value of 4,294,967,295
   ((2^32) - 1).  Notifiers MUST NOT generate a request with a larger
   value.  Subscribers MUST treat a larger value as 2^32-1.

        Voice-Message: 1/3 (0/1)

   Optionally, after the summary counts, the messaging systems MAY
   append RFC 2822 [10]-style message headers, which further describe
   newly added messages.  Message headers MUST NOT be included in an
   initial NOTIFY, as new messages could be essentially unbounded in
   size.  Message headers included in subsequent notifications MUST only
   correspond to messages added since the previous notification for that
   subscription. A messaging system which includes message headers in a
   NOTIFY, MUST provide an administrator configurable mechanism for
   selecting which headers are sent. Likely headers for inclusion
   include To, From, Date, Subject, and Message-ID.  Note that the
   formatting of these headers in this body is identical to that of SIP
   extension-headers, not the (similar) format defined in RFC 2822.

   Implementations which generate large notifications are reminded to



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   follow the message size restrictions for unreliable transports
   articulated in Section 18.1.1 of SIP.

   Mapping local message state to new/old message status and urgency is
   an implementation issue of the messaging system.  However, the
   messaging notifier MUST NOT consider a message "old" merely because
   it generated a notification, as this could prevent another
   subscription from accurately receiving message-summary notifications.
   Likewise, the messaging system MAY use any suitable algorithm to
   determine that a message is "urgent".

   Messaging systems MAY use any algorithm for determining the
   approporiate message-context-class for a specific message.  Systems
   which use Internet Mail SHOULD use the contents of the
   Message-Context header [7] (defined in RFC 3458) if present as a hint
   to make a context determination.  Note that a composed messaging
   system does not need to support a given context in order to generate
   notifications identified with that context.

3.6 Subscriber generation of SUBSCRIBE requests

   Subscriber User Agents will typically SUBSCRIBE to message summary
   information for a period of hours or days, and automatically attempt
   to re-SUBSCRIBE well before the subscription is completely expired.
   If re-subscription fails, the Subscriber SHOULD periodically retry
   again until a subscription is successful, taking care to backoff to
   avoid network congestion.  If a subscription has expired, new
   re-subscriptions MUST use a new Call-ID.

   The Subscriber SHOULD SUBSCRIBE to that user's message summaries
   whenever a new user becomes associated with the device (a new login).
   The Subscriber MAY also explicitly fetch the current status at any
   time.  The subscriber SHOULD renew its subscription immediately after
   a reboot, or when the subscriber's network connectivity has just been
   re-established.

   The Subscriber MUST be prepared to receive and process a NOTIFY with
   new state immediately after sending a new SUBSCRIBE, a SUBSCRIBE
   renewal, an unsubscribe, or a fetch; or at any time during the
   subscription.

   When a user de-registers from a device (logoff, power down of a
   mobile device, etc.), subscribers SHOULD unsubscribe by sending a
   SUBSCRIBE message with an Expires header of zero.

3.7 Notifier processing of SUBSCRIBE requests

   When a SIP Messaging System receives SUBSCRIBE messages with the



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   message-summary event-type, it SHOULD authenticate the subscription
   request.  If authentication is successful, the Notifier MAY limit the
   duration of the subscription to an administrator defined amount of
   time as described in SIP Events.

3.8 Notifier generation of NOTIFY requests

   Immediately after a subscription is accepted, the Notifier MUST send
   a NOTIFY with the current message summary information.  This allows
   the Subscriber to resynchronize its state.  This initial
   synchronization NOTIFY MUST NOT include the optional RFC 2822
   [9]-style message headers.

   When the status of the messages changes sufficiently for a messaging
   account to change the number of new or old messages, the Notifier
   SHOULD send a NOTIFY message to all active subscribers to that
   account.  NOTIFY messages sent to subscribers of a group or alias,
   MUST contain the message account name in the notification body.

   A Messaging System MAY send a NOTIFY with an "Expires" header of "0"
   and a "Subscription-State" header of "terminated" before a graceful
   shutdown.

3.9 Subscriber processing of NOTIFY requests

   Upon receipt of a valid NOTIFY request, the subscriber SHOULD
   immediately render the message status and summary information to the
   end user in an implementation specific way.

   The Subscriber MUST be prepared to receive NOTIFYs from different
   Contacts corresponding to the same SUBSCRIBE.  (the SUBSCRIBE may
   have been forked).

3.10 Handling of Forked Requests

   Forked requests are allowed for this event type and may install
   multiple subscriptions.  The Subscriber MAY render multiple summaries
   which correspond to the same account directly to the user, or MAY
   merge them as described below.

   If any of the "Messages-Waiting" status lines report "yes", then the
   merged state is "yes"; otherwise the merged state is "no".

   The Subscriber MAY merge summary lines in an implementation-specific
   way if all notifications contain at least one msg-summary line.

3.11 Rate of notifications




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   A Notifier MAY choose to hold NOTIFY requests in "quarantine" for a
   short administrator-defined period (seconds or minutes) when the
   message status is changing rapidly.  Requests in the quarantine which
   become invalid are replaced by newer notifications, thus reducing the
   total volume of notifications.  This behavior is encouraged for
   implementations with heavy interactive use.  Note that timely
   notification which results in a change of overall state (messages
   waiting or not), and notification of newly added messages is probably
   more significant to the end user than a notification of newly deleted
   messages which do not affect the overall message waiting state (e.g.
   there are still new messages).

   Notifiers SHOULD NOT generate NOTIFY requests more frequently than
   once per second.

3.12 State Agents and Lists

   A Subscriber MAY use an "alias" or "group" in the Request-URI of a
   subscription if that name is significant to the messaging system.
   Implementers MAY create a service which consolidates and summarizes
   NOTIFYs from many Contacts.  This document does not preclude
   implementations from building state agents which support this event
   package.  One way to implement such a service is with the event list
   extension [11].

3.13 Behavior of a Proxy Server

   There are no additional requirements on a SIP Proxy, other than to
   transparently forward the SUBSCRIBE and NOTIFY methods as required in
   SIP.  However, Proxies SHOULD allow non-SIP URLs.  Proxies and
   Redirect servers SHOULD be able to direct the SUBSCRIBE request to an
   appropriate messaging notifier User Agent.

4. Examples of Usage

4.1 Example Message Flow

   The examples shown below are for informational purposes only.  For a
   normative description of the event package, please see sections 3 and
   5 of this document.

   In the example call flow below, Alice's IP phone subscribes to the
   status of Alice's messages. Via headers are omitted for clarity.

         Subscriber              Notifier
             |                       |
             |  A1: SUBSCRIBE (new)  |
             |---------------------->|



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             |  A2: 200 OK           |
             |<----------------------|
             |                       |
             |  A3: NOTIFY (sync)    |
             |<----------------------|
             |  A4: 200 OK           |
             |---------------------->|
             |                       |
             |                       |
             |  A5: NOTIFY (change)  |
             |<----------------------|
             |  A6: 200 OK           |
             |---------------------->|
             |                       |
             |                       |
             |  A7: (re)SUBSCRIBE    |
             |---------------------->|
             |  A8: 200 OK           |
             |<----------------------|
             |                       |
             |  A9: NOTIFY (sync)    |
             |<----------------------|
             |  A10: 200 OK          |
             |---------------------->|
             |                       |
             |                       |
             |  A11: (un)SUBSCRIBE   |
             |---------------------->|
             |  A12: 200 OK          |
             |<----------------------|
             |                       |
             |  A13: NOTIFY (sync)   |
             |<----------------------|
             |  A14: 200 OK          |
             |---------------------->|


       A1: Subscriber (Alice's phone) ->
             Notifier (Alice's voicemail gateway)
       Subscribe to Alice's message summary status for 1 day.

   SUBSCRIBE sip:alice@vmail.example.com SIP/2.0
   To: <sip:alice@example.com>
   From: <sip:alice@example.com>;tag=78923
   Date: Mon, 10 Jul 2000 03:55:06 GMT
   Call-Id: 1349882@alice-phone.example.com
   CSeq: 4 SUBSCRIBE
   Contact: <sip:alice@alice-phone.example.com>



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   Event: message-summary
   Expires: 86400
   Accept: application/simple-message-summary
   Content-Length: 0

       A2: Notifier -> Subscriber

   SIP/2.0 200 OK
   To: <sip:alice@example.com>;tag=4442
   From: <sip:alice@example.com>;tag=78923
   Date: Mon, 10 Jul 2000 03:55:07 GMT
   Call-Id: 1349882@alice-phone.example.com
   CSeq: 4 SUBSCRIBE
   Expires: 86400
   Content-Length: 0

       A3: Notifier -> Subscriber
       (immediate synchronization of current state:
        2 new and 8 old [2 urgent] messages)

   NOTIFY sip:alice@alice-phone.example.com SIP/2.0
   To: <sip:alice@example.com>;tag=78923
   From: <sip:alice@example.com>;tag=4442
   Date: Mon, 10 Jul 2000 03:55:07 GMT
   Call-Id: 1349882@alice-phone.example.com
   CSeq: 20 NOTIFY
   Contact: <sip:alice@vmail.example.com>
   Event: message-summary
   Subscription-State: active
   Content-Type: application/simple-message-summary
   Content-Length: 99

   Messages-Waiting: yes
   Message-Account: sip:alice@vmail.example.com
   Voice-Message: 2/8 (0/2)

       A4: Subscriber -> Notifier

   SIP/2.0 200 OK
   To: <sip:alice@example.com>;tag=78923
   From: <sip:alice@example.com>;tag=4442
   Date: Mon, 10 Jul 2000 03:55:08 GMT
   Call-Id: 1349882@alice-phone.example.com
   CSeq: 20 NOTIFY
   Content-Length: 0

       A5: Notifier -> Subscriber
       This is a notification of new messages.



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       Some headers from each of the new messages are appended.

   NOTIFY sip:alice@alice-phone.example.com SIP/2.0
   To: <sip:alice@example.com>;tag=78923
   From: <sip:alice@example.com>;tag=4442
   Date: Mon, 10 Jul 2000 04:28:53 GMT
   Contact: <sip:alice@vmail.example.com>
   Call-ID: 1349882@alice-phone.example.com
   CSeq: 31 NOTIFY
   Event: message-summary
   Subscription-State: active
   Content-Type: application/simple-message-summary
   Content-Length: 503

   Messages-Waiting: yes
   Message-Account: sip:alice@vmail.example.com
   Voice-Message: 4/8 (1/2)

   To: <alice@atlanta.com>
   From: <bob@biloxi.com>
   Subject: carpool tomorrow?
   Date: Sun, 09 Jul 2000 21:23:01 -0700
   Priority: normal
   Message-ID: 13784434989@vmail.example.com

   To: <alice@example.com>
   From: <cathy-the-bob@example.com>
   Subject: HELP! at home ill, present for me please
   Date: Sun, 09 Jul 2000 21:25:12 -0700
   Priority: urgent
   Message-ID: 13684434990@vmail.example.com

       A6: Subscriber -> Notifier

   SIP/2.0 200 OK
   To: <sip:alice@example.com>;tag=78923
   From: <sip:alice@example.com>;tag=4442
   Date: Mon, 10 Jul 2000 04:28:53 GMT
   Call-ID: 1349882@alice-phone.example.com
   CSeq: 31 NOTIFY
   Content-Length: 0

       A7: Subscriber  ->  Notifier
       Refresh subscription.

   SUBSCRIBE sip:alice@vmail.example.com SIP/2.0
   To: <sip:alice@example.com>;tag=4442
   From: <sip:alice@example.com>;tag=78923



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   Date: Mon, 10 Jul 2000 15:55:06 GMT
   Call-Id: 1349882@alice-phone.example.com
   CSeq: 8 SUBSCRIBE
   Contact: <sip:alice@alice-phone.example.com>
   Event: message-summary
   Expires: 86400
   Accept: application/simple-message-summary
   Content-Length: 0

       A8: Notifier -> Subscriber

   SIP/2.0 200 OK
   To: <sip:alice@example.com>;tag=4442
   From: <sip:alice@example.com>;tag=78923
   Date: Mon, 10 Jul 2000 15:55:07 GMT
   Call-Id: 1349882@alice-phone.example.com
   CSeq: 8 SUBSCRIBE
   Contact: <sip:alice@alice-phone.example.com>
   Expires: 86400
   Content-Length: 0

       A9: Notifier -> Subscriber
       (immediate synchronization of current state)

   NOTIFY sip:alice@alice-phone.example.com SIP/2.0
   To: <sip:alice@example.com>;tag=78923
   From: <sip:alice@example.com>;tag=4442
   Date: Mon, 10 Jul 2000 15:55:07 GMT
   Call-Id: 1349882@alice-phone.example.com
   CSeq: 47 NOTIFY
   Contact: <sip:alice@vmail.example.com>
   Event: message-summary
   Subscription-State: active
   Content-Type: application/simple-message-summary
   Content-Length: 99

   Messages-Waiting: yes
   Message-Account: sip:alice@vmail.example.com
   Voice-Message: 4/8 (1/2)

       A10: Subscriber -> Notifier

   SIP/2.0 200 OK
   To: <sip:alice@example.com>;tag=78923
   From: <sip:alice@example.com>;tag=4442
   Date: Mon, 10 Jul 2000 15:55:08 GMT
   Call-Id: 1349882@alice-phone.example.com
   CSeq: 47 NOTIFY



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   Contact: <sip:alice@vmail.example.com>


       A11: Subscriber  ->  Notifier
       Un-subscribe after "alice" logs out.

   SUBSCRIBE sip:alice@vmail.example.com SIP/2.0
   To: <sip:alice@example.com>;tag=4442
   From: <sip:alice@example.com>;tag=78923
   Date: Mon, 10 Jul 2000 19:35:06 GMT
   Call-Id: 1349882@alice-phone.example.com
   CSeq: 17 SUBSCRIBE
   Contact: <sip:alice@alice-phone.example.com>
   Event: message-summary
   Expires: 0
   Accept: application/simple-message-summary
   Content-Length: 0

       A12: Notifier -> Subscriber

   SIP/2.0 200 OK
   To: <sip:alice@example.com>;tag=4442
   From: <sip:alice@example.com>;tag=78923
   Date: Mon, 10 Jul 2000 19:35:07 GMT
   Call-Id: 1349882@alice-phone.example.com
   CSeq: 17 SUBSCRIBE
   Contact: <sip:alice@alice-phone.example.com>
   Expires: 0
   Content-Length: 0

       A13: Notifier -> Subscriber
      (immediate synchronization of current state,
       which the subscriber can now ignore)

   NOTIFY sip:alice@alice-phone.example.com SIP/2.0
   To: <sip:alice@example.com>;tag=78923
   From: <sip:alice@example.com>;tag=4442
   Date: Mon, 10 Jul 2000 19:35:07 GMT
   Call-Id: 1349882@alice-phone.example.com
   CSeq: 56 NOTIFY
   Contact: <sip:alice@vmail.example.com>
   Event: message-summary
   Subscription-State: terminated;reason=timeout
   Content-Type: application/simple-message-summary
   Content-Length: 99

   Messages-Waiting: yes
   Message-Account: sip:alice@vmail.example.com



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   Voice-Message: 4/8 (1/2)

       A14: Subscriber -> Notifier

   SIP/2.0 200 OK
   To: <sip:alice@example.com>;tag=78923
   From: <sip:alice@example.com>;tag=4442
   Date: Mon, 10 Jul 2000 19:35:08 GMT
   Call-Id: 1349882@alice-phone.example.com
   CSeq: 56 NOTIFY
   Event: message-summary
   Content-Length: 0


4.2 Example Usage with Callee Capabilities and Caller Preferences

   The use of callee capabilities is optional but encouraged.  If callee
   capabilities is used, a messaging notifier MAY REGISTER a Contact
   with an appropriate methods and events tag as shown in the example
   below.  To further distinguish itself, the messaging notifier MAY
   also REGISTER as a Contact with the actor="msg-taker" tag.  An
   example of this kind of registration follows below.

        REGISTER sip:sip3-sj.example.com SIP/2.0
        To: <sip:alice@example.com>
        From: <sip:alice@example.com>;tag=4442
        ...
           Contact: <sip:alice@vm13-sj.example.com>
            ;actor="msg-taker";methods="SUBSCRIBE"
            ;automata;events="message-summary"

   The following SUBSCRIBE message would find the Contact which
   registered in the example above.

           SUSBCRIBE sip:alice@example.com SIP/2.0
           ...
           Accept: application/simple-message-summary
        Event: message-summary
           Accept-Contact: *;automata;actor="msg-taker"


5. Formal Syntax

   The following syntax specification uses the augmented Backus-Naur
   Form (BNF) as described in RFC-2234 [6].

5.1 New event-package definition




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   This document defines a new event-package with the package name:

        message-summary


5.2 Body Format Syntax

   The formal syntax for the application/simple-message-summary MIME
   type is described below:

   messsage-summary = msg-status-line CRLF
                      [msg-account CRLF]
                      [*(msg-summary-line CRLF)]
                      [ *opt-msg-headers ]

   msg-status-line  = "Messages-Waiting" HCOLON msg-status
   msg-status = "yes" / "no"
   msg-account = "Message-Account" HCOLON Account-URI
   Account-URI = SIP-URI / SIPS-URI / absoluteURI

   msg-summary-line = message-context-class HCOLON newmsgs SLASH oldmsgs
                   [ LPAREN new-urgentmsgs SLASH old-urgentmsgs RPAREN ]

   opt-msg-headers = CRLF 1*(extension-header CRLF)

   newmsgs = msgcount
   oldmsgs = msgcount
   new-urgentmsgs = msgcount
   old-urgentmsgs  = msgcount
   msgcount = 1*DIGIT   ; MUST NOT exceed 2^32-1


6. Security Considerations

   Message summaries and optional message bodies contain information
   which is typically very privacy sensitive.  At minimum, subscriptions
   to this event package SHOULD be authenticated and properly
   authorized. Furthermore, notifications SHOULD be encrypted and
   integrity protected using either end-to-end mechanisms, or the
   hop-by-hop protection afforded messages sent to SIPS URIs.

   Additional and privacy security considerations are discussed in
   detail in SIP [1] and SIP Events [2].

7. IANA Considerations






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7.1 SIP Event Package Registration for message-summary

         Package name: message-summary

         Type: package

         Contact: [Mahy]

         Published Specification: This document.


7.2 MIME Registration for application/simple-message-summary

         MIME media type name: application

         MIME subtype name: simple-message-summary

         Required parameters: none.

         Optional parameters: none.

         Encoding considerations:   This MIME type was designed for
           use with protocols which can carry binary-encoded data.
           Although the format of this MIME type is similar to RFC2822,
           it is not identical.  (Specifically, line folding rules are
           SIP-specific and included URIs can contain non-ASCII
           characters.)  Protocols which do not carry binary data
           (which have line length or character-set restrictions
           for example) MUST use a reversible transfer encoding
           (such as base64) to carry this MIME type.

         Security considerations: See the "Security Considerations"
           section in this document.

         Interoperability considerations: none

         Published specification: This document.

   Applications which use this media: The simple-message-summary
   application subtype supports the exchange of message waiting and
   message summary information in SIP networks.

         Additional information:

              1. Magic number(s): N/A

              2. File extension(s): N/A




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              3. Macintosh file type code: N/A


8. Revision history

   ** Note to the RFC editor: please remove this entire section upon
   publication. **

8.1 Changes from draft-ietf-sipping-mwi-03

   1.  Updated MIME type registration to permit transfer encoding using
       any binary-clean encoding.

   2.  Changed caller preferences and callee capabilities usage to be
       consistent with change from msg-server="true" to
       actor="msg-taker".


8.2 Changes from draft-ietf-sipping-mwi-01 and -02

   1.  Updated the caller-preference section (now the callee
       capabilities section) to reflect the split of these drafts and
       the new tag ;msgserver="true".

   2.  Added some text in the overview to further clarify how message
       notifiers can be composed/decomposed with media processing.

   3.  Add a pointer to the event-list extension.


8.3 Changes from draft-ietf-sipping-mwi-00

   1.  Replaced the "media types" concept with message contexts. This is
       a better semantic match than what was in the draft before, and
       also controls extensibility and change control in a single
       document.  The list of valid message-context-classes are
       voice-message, fax-message, pager-message, multimedia-message,
       text-message, and none.

   2.  Completely updated the syntax to follow that of SIP instead of
       the previously more restrictive (and somewhat arbitrary) syntax.
       The SIP syntax adds line folding, for example.  The optional
       message-headers borrow the "extension-header" syntax and explicit
       whitespace separators defined in SIP (ex: HCOLON, SLASH).

   3.  Added a Message-Account field in the body format to provide the
       specific account name which corresponds to the notification when
       forking or state agents are used with group aliases (or



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       collections).

   4.  Changed caller preferences example to exclude methods="SUBSCRIBE"
       in the SUBSCRIBE request (removed redundant information).

   5.  Changed examples to be consistent with IESG recommendations


8.4 Changes from draft-mahy-sipping-mwi-00

   1.  Updated references and split into normative and informational

   2.  Removed normative behavior now specified in Events

   3.  Updated to address the event package sections now specified in
       Events.

   4.  Added the Subscription-State header field to the examples and
       removed the Event header field from responses.

   5.  Removed redundant BNF

   6.  Simplified text on how to choose the media type.  For Internet
       Mail, this now references the Message-Context header.


8.5 Changes from draft-mahy-sip-mwi-01

   1.  This document is now formatted as a SIP Event Package as defined
       in Section 4 of RFC 3265 (SIP Events) [2].

   2.  The event-package name is now "message-summary", to allow for
       other bodies to extend the package.

   3.  The "urgent" token was missing from the BNF.


8.6 Changes from draft-mahy-sip-mwi-00

   This draft greatly simplifies and shortens the -00 version.

   1.  The generic behavior of SUBSCRIBE/NOTIFY is now greatly clarified
       in SIP Events [2] and made consistent with PINT and SIP for
       presence.  This message waiting draft is now consistent with SIP
       Events.

   2.  The XML format has been removed due to lack of immediate
       interest.  At a future date, similar functionality may be added



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       as another body definition with an appropriate MIME type.

   3.  An IANA Considerations section was added to register the new
       "application/simple-message-summary" MIME type and the
       "simple-message-summary" SIP event package.

   4.  The "flag-list" was removed due to lack of interest and to
       encourage simplicity.

   5.  Due to synchronization issues, and the recommendation of the VPIM
       Working Group, support for message count "deltas" was removed.

   6.  The Messages-Waiting line in the body is now mandatory.

   7.  This version of the draft clarifies the role of caller
       preferences as optional but encouraged.

   8.  A set of SMTP-like headers from the triggering messages may now
       optionally follow the message summaries, provided that the
       resulting NOTIFY on UDP fits in a single datagram.


9. Contributors

   Ilya Slain came up with the initial format of the text body contained
   in this document.  He was previously listed as a co-author, however,
   he is no longer reachable.

10. Acknowledgments

   Thanks to Dan Wing, Dave Oran, Bill Foster, Steve Levy, Denise
   Caballero-McCann, Jeff Michel, Priti Patil, Satyender Khatter, Bich
   Nguyen, Manoj Bhatia, David Williams, and Bryan Byerly of Cisco;
   Jonathan Rosenberg and Adam Roach of Dynamicsoft; Eric Burger of
   Snowshore; Nir Chen of iComverse, and Eric Tremblay of Mediatrix.

Normative References

   [1]  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.

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

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




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   [4]  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.

   [5]  Rosenberg, J., "Indicating User Agent Capabilities in the
        Session Initiation Protocol  (SIP)",
        draft-ietf-sip-callee-caps-00 (work in progress), June 2003.

   [6]  Crocker, D. and P. Overell, "Augmented BNF for Syntax
        Specifications: ABNF", RFC 2234, November 1997.

   [7]  Burger, E., Candell, E., Eliot, C. and G. Klyne, "Message
        Context for Internet Mail", RFC 3458, January 2003.

Informational References

   [8]   Vaudreuil, G. and G. Parsons, "Voice Profile for Internet Mail
         - version 2", RFC 2421, September 1998.

   [9]   Freed, N. and N. Borenstein, "Multipurpose Internet Mail
         Extensions (MIME) Part Two: Media Types", RFC 2046, November
         1996.

   [10]  Resnick, P., "Internet Message Format", RFC 2822, April 2001.

   [11]  Rosenberg, J., Roach, A. and B. Campbell, "A Session Initiation
         Protocol (SIP) Event Notification Extension for  Resource
         Lists", draft-ietf-simple-event-list-04 (work in progress),
         June 2003.

   [12]  Telcordia, "GR-506: Signaling for Analog Interfaces, Issue 1,
         Revision 1", Nov 1996.


Author's Address

   Rohan Mahy
   Cisco Systems, Inc.
   101 Cooper Street
   Santa Cruz, CA  95060
   USA

   EMail: rohan@cisco.com







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   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
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