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Versions: 00                                                            
SIPPING Working Group                                       G. Camarillo
Internet-Draft                                                  Ericsson
Expires: March 1, 2004                                    September 2003


   A Session Initiation Protocol (SIP) Event Package for Media Policy
             draft-camarillo-sipping-policy-package-00.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 March 1, 2004.

Copyright Notice

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

Abstract

   This document defines a SIP event package for session policies. User
   agents can subscribe to this event package to obtain information
   about the session policy of a domain (e.g., allowed and disallowed
   codecs or maximum bandwidth).












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Table of Contents

   1.    Introduction . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.    Terminology  . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.    Package Definition . . . . . . . . . . . . . . . . . . . . .  3
   3.1   Event Package Name . . . . . . . . . . . . . . . . . . . . .  3
   3.2   Event Package Parameters . . . . . . . . . . . . . . . . . .  4
   3.3   SUBSCRIBE Bodies . . . . . . . . . . . . . . . . . . . . . .  4
   3.4   Subscription Duration  . . . . . . . . . . . . . . . . . . .  4
   3.5   NOTIFY Bodies  . . . . . . . . . . . . . . . . . . . . . . .  4
   3.6   Notifier Processing of SUBSCRIBE Requests  . . . . . . . . .  4
   3.7   Notifier Generation of NOTIFY Requests . . . . . . . . . . .  4
   3.8   Subscriber Processing of NOTIFY Requests . . . . . . . . . .  5
   3.9   Handling of Forked Request . . . . . . . . . . . . . . . . .  5
   3.10  Rate of Notifications  . . . . . . . . . . . . . . . . . . .  5
   3.11  State Agents . . . . . . . . . . . . . . . . . . . . . . . .  5
   4.    Session Policy Information Format  . . . . . . . . . . . . .  5
   5.    Structure of the Session Policy Information  . . . . . . . .  5
   6.    Protocols Element  . . . . . . . . . . . . . . . . . . . . .  6
   6.1   Methods Element  . . . . . . . . . . . . . . . . . . . . . .  6
   6.2   Option-tags Element  . . . . . . . . . . . . . . . . . . . .  6
   6.3   Feature-tags Element . . . . . . . . . . . . . . . . . . . .  6
   6.4   Bodies Element . . . . . . . . . . . . . . . . . . . . . . .  7
   6.5   Extensibility  . . . . . . . . . . . . . . . . . . . . . . .  7
   6.6   Example of a Protocol Element  . . . . . . . . . . . . . . .  7
   7.    Media Element  . . . . . . . . . . . . . . . . . . . . . . .  8
   7.1   Stream Element . . . . . . . . . . . . . . . . . . . . . . .  8
   7.1.1 Codecs Element . . . . . . . . . . . . . . . . . . . . . . .  8
   7.1.2 Transports Element . . . . . . . . . . . . . . . . . . . . .  8
   7.1.3 Directions Element . . . . . . . . . . . . . . . . . . . . .  9
   7.1.4 Extensibility  . . . . . . . . . . . . . . . . . . . . . . .  9
   7.2   Example of a Media Element . . . . . . . . . . . . . . . . .  9
   8.    Schema . . . . . . . . . . . . . . . . . . . . . . . . . . .  9
   9.    Example  . . . . . . . . . . . . . . . . . . . . . . . . . . 10
   10.   Security Considerations  . . . . . . . . . . . . . . . . . . 10
   11.   IANA Considerations  . . . . . . . . . . . . . . . . . . . . 10
   11.1  MIME Registration for application/session-policy+xml . . . . 10
   11.2  URN Sub-Namespace Registration for
         urn:ietf:params:xml:ns:sessionpolicy . . . . . . . . . . . . 11
         Normative References . . . . . . . . . . . . . . . . . . . . 12
         Informational References . . . . . . . . . . . . . . . . . . 12
         Author's Address . . . . . . . . . . . . . . . . . . . . . . 12
         Intellectual Property and Copyright Statements . . . . . . . 13








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1. Introduction

   Some domains have certain policies regarding the types of sessions
   users can establish. These policies are typically enforced somehow.
   For example, if the policy of a domain disallows the use of a
   particular codec, access routers will discard packets that transport
   media encoded with that codec. Unfortunatelly, enforcement mechanisms
   do not usually inform the user about what is happening. They silently
   keep the user from doing anything against the policy.

   Therefore, users need a means to obtain the policy of their domain in
   order not to try anything against it. Users also need to be informed
   about changes in this policy, since the session policy of a domain is
   a dynamic piece of information (e.g., high-bandwidth codecs are
   disallowed only in presence of a high number of users).

   Other domains have policies regarding the type of user agents that
   can use their network. For example, a domain could require that user
   agents using its network use a particular protocol (e.g., SIP) with a
   set of extensions (e.g., preconditions must be used). A user agent
   needs to know the exact policy of a domain in order to be able to use
   the right configuration to send and receive traffic in that domain.

   We define a SIP event package that allows a user agent to subscribe
   to the session policy information of a domain.

2. Terminology

   In this document, the key words "MUST", "MUST NOT", "REQUIRED",
   "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT
   RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as
   described in BCP 14, RFC 2119 [1] and indicate requirement levels for
   compliant implementations.

3. Package Definition

   This section fills in the details needed to specify an event package
   as defined in Section 4.4 of RFC 3265 [2].

3.1 Event Package Name

   The name of this package is "session-policy". As specified in RFC
   3265 [2], this value appears in the Event header field present in
   SUBSCRIBE and NOTIFY requests.

      Event: session-policy





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3.2 Event Package Parameters

   No package specific Event header field  parameters are defined for
   this event package.

3.3 SUBSCRIBE Bodies

   A SUBSCRIBE for session policy events MAY contain a body. This body
   would serve the purpose of filtering the subscription. The definition
   of such a body is outside the scope of this specification.

   A SUBSCRIBE for the session policy package MAY be sent without a
   body. This implies that the default session policy filtering policy
   has been requested. The default policy is that notifications are
   generated every time there is any change in the media policy for the
   user.

3.4 Subscription Duration

   The default expiration of subscriptions to session policy state is
   one hour (3600 seconds).

3.5 NOTIFY Bodies

   In this event package, the body of the notification contains a
   session policy document. This document describes the session policy
   of a domain for a user. All subscribers and notifiers MUST support
   the "application/session-policy+xml" data format described in Section
   4. The subscribe request MAY contain an Accept header field. If no
   such header field is present, it has a default value of "application/
   session-policy+xml". If the header field is present, it MUST include
   "application/session-policy+xml", and MAY include any other types
   capable of representing session policy state.

3.6 Notifier Processing of SUBSCRIBE Requests

   Session policy state can be sensitive information. Therefore, all
   subscriptions to it SHOULD be authenticated and authorized before
   approval. Authentication MAY be performed using any of the techniques
   available through SIP, including digest, S/MIME, TLS or other
   transport specific mechanisms. It is RECOMMENDED that a user be
   allowed to subscribe to their own session policy.

3.7 Notifier Generation of NOTIFY Requests

   Notifications SHOULD be generated for the session policy package
   whenever there is a change in the session policy for the user.




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3.8 Subscriber Processing of NOTIFY Requests

   NOTIFY requests contain the full session policy state. The subscriber
   does not need to perform any type of information aggregation.

3.9 Handling of Forked Request

   Session policy state is normally stored in some repository.
   Therefore, there is usually a single place where the session policy
   for a user is resident. This implies that a subscription for this
   information is readily handled by a single element with access to
   this repository. There is, therefore, no compelling need for a
   subscription to session policy information to fork. As a result, a
   subscriber MUST NOT create multiple dialogs as a result of a single
   subscription request. The required processing to guarantee that only
   a single dialog is established is described in Section 4.4.9 of RFC
   3265 [2].

3.10 Rate of Notifications

   For reasons of congestion control, it is important that the rate of
   notifications not become excessive. As a result, it is RECOMMENDED
   that the server not generate notifications for a single subscriber at
   a rate faster than once every 5 seconds.

3.11 State Agents

   State agents have no role in the handling of this package.

4. Session Policy Information Format

   Session policy information information is an XML document that MUST
   be well-formed and SHOULD be valid. Session policy documents MUST be
   based on XML 1.0 and MUST be encoded using UTF-8. This specification
   makes use of XML namespaces for identifying session policy documents.
   The namespace URI for elements defined by this specification is a URN
   [3], using the namespace identifier 'ietf' defined by RFC 2648 [4]
   and extended by [6]. This URN is:

      urn:ietf:params:xml:ns:sessionpolicy

   A session policy document begins with the root element tag
   "sessionpolicy".

5. Structure of the Session Policy Information

   A session policy document starts with a sessionpolicy element. This
   element has three mandatory attributes:



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      version: This attribute allows the recipient of session policy
      information documents to properly order them. Versions start at 0,
      and increment by one for each new document sent to a subscriber.
      Versions are scoped within a subscription. Versions MUST be
      representable using a 32 bit integer.

      domain: This attribute contains the domain the policy belongs to.

      entity: This attribute contains a URI that identifies the user
      whose media policy information is reported in the remainder of the
      document.

   The sessionpolicy element has a series of sessionpolicy sub-elements:
   zero or one protocols element and zero or one media element.

6. Protocols Element

   The protocols element contains a series of protocol sub-elements.
   Each protocol sub-element contains the policy related to the usage of
   a particular protocol.

   The protocol element has a single mandatory attribute, name. The name
   attribute identifies a protocol the policy of each protocol element
   is referring to. The protocol element has a series of sub-elements:
   methods, option-tags, feature-tags, and bodies.

6.1 Methods Element

   The methods element contains a default-policy attribute and method
   elements. The default-policy attribute contains the policy for
   methods that are not listed as method elements. A method element has
   two attributes: name and policy. The name attribute identifies a
   method, and the policy attribute contains the policy for that method
   (allowed or disallowed).

6.2 Option-tags Element

   The option-tags element contains a default-policy attribute and
   option-tag elements. The default-policy attribute contains the policy
   for option-tags that are not listed as option-tag elements. An
   option-tag element has two attributes: name and policy. The name
   attribute identifies a method, and the policy attribute contains the
   policy for that method (mandatory, allowed, or disallowed).

6.3 Feature-tags Element

   The feature-tags element contains a default-policy attribute and
   feature-tag elements. The default-policy attribute contains the



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   policy for feature-tags that are not listed as feature-tag elements.
   An feature-tag element has two attributes: name and policy. The name
   attribute identifies a method, and the policy attribute contains the
   policy for that method (allowed, or disallowed).

6.4 Bodies Element

   The bodies element contains a default-policy attribute, a
   default-encryption attribute and body-disposition elements. The
   default-policy attribute contains the policy for body dispositions
   that are not listed as body-disposition elements. The
   default-encryption attribute contains the encryption policy for body
   dispositions that are not listed as body-disposition elements.

   A body-disposition element can have a number of attributes: name,
   policy, default-policy, and encryption. The name attribute identifies
   a body-disposition, and the policy attribute contains the policy for
   that body-disposition (allowed, or disallowed). The default-policy
   attribute contains the policy for body formats that are not listed as
   body-format elements. The encryption attribute indicates whether or
   not encryption is allowed for a particular body disposition.

   A body-disposition element contains body-format elements.  A
   body-format element can have a two attributes: name and policy. The
   name attribute identifies a body-format, and the policy attribute
   contains the policy for that body-format (allowed or disallowed).

6.5 Extensibility

   Other elements from different namespaces MAY be present within a
   protocol element for the purposes of extensibility; elements or
   attributes from unknown namespaces MUST be ignored.

6.6 Example of a Protocol Element


   <protocols>
     <protocol name="SIP">
       <methods default-policy="allowed">
          <method name="MESSAGE" policy="disallowed"/>
       </methods>
       <option-tags default-policy="disallowed">
          <option-tag name="100rel" policy="mandatory"/>
          <option-tag name="preconditions" policy="allowed"/>
       </option-tags>
       <feature-tags default-policy="disallowed">
          <feature-tag name="video" policy="allowed"/>
       </feature-tags>



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       <bodies default-policy="allowed" default-encryption="allowed">
          <body-disposition name="session" policy="allowed"
                            encryption="disallowed" default-policy="disallowed">
             <body-format name="application/sdp" policy="allowed"/>
          </body-disposition>
       </bodies>
     </protocol>
   </protocols>


7. Media Element

   The media element contains the policy related to the characteristics
   of media streams of different types. It has three attributes:
   maxbandwidth, maxnostreams, and default-policy. They contain the
   maximum bandwidth the user can count on, the maximum number of media
   streams that the user is allowed to established at the same time, and
   the default policy (allowed or disallowed) for stream types that are
   not listed as stream elements.

   The media element contains a series of stream elements.

7.1 Stream Element

   A stream element can have a number of attributes: type, policy,
   maxbandwidth, and maxnostreams. The type attribute identifies a media
   type, and the policy attribute contains the policy for that media
   type (allowed or disallowed).

   The stream element has a number of optional sub-element: the codecs
   element, the transports element and the directions element.

7.1.1 Codecs Element

   The codecs element contains a default-policy attribute and codec
   elements. The default-policy attribute contains the policy for codecs
   that are not listed as codec elements. A codec element can have two
   attributes: name and policy. The name attribute identifies a codec,
   and the policy attribute contains the policy for that codec (allowed,
   or disallowed).

7.1.2 Transports Element

   The transports element contains a default-policy attribute and
   transport elements. The default-policy attribute contains the policy
   for transports that are not listed as transport elements. A tranport
   element can have two attributes: name and policy. The name attribute
   identifies a transport, and the policy attribute contains the policy



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   for that tranport (allowed, or disallowed).

7.1.3 Directions Element

   The directions element contains a default-policy attribute and
   direction elements. The default-policy attribute contains the policy
   for directions that are not listed as direction elements. A direction
   element can have two attributes: name and policy. The name attribute
   identifies a direction (sendrecv, sendonly, recvonly), and the policy
   attribute contains the policy for that direction (allowed, or
   disallowed).

7.1.4 Extensibility

   Other elements from different namespaces MAY be present within a
   stream element for the purposes of extensibility; elements or
   attributes from unknown namespaces MUST be ignored.

7.2 Example of a Media Element


   <media maxnostreams="4" default-policy="disallowed">
      <stream type="audio" policy="allowed">
           <codecs default-policy="allowed">
               <codec name="PCMU" policy="disallowed"/>
               <codec name="PCMA" policy="disallowed"/>
           </codecs>
           <transports default-policy="disallowed">
               <transport name="RTP/AVP" policy="allowed"/>
           </transports>
           <directions default-policy="disallowed">
               <direction name="sendonly" policy="allowed"/>
           </directions>
      </stream>
   </media>


8. Schema

   The following is the schema for the application/session-policy+xml
   type:



   <?xml version="1.0" encoding="UTF-8"?>
   TBD





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9. Example

   The following is is an example of an application/session-policy+xml
   document:


   <?xml version="1.0" encoding="UTF-8"?>
   <sessionpolicy xmlns="urn:ietf:params:xml:ns:sessionpolicy"
                  version="0"
                  domain="example.com"
                  entity="sip:alice@example.com">
    <protocols>
     <protocol name="SIP">
       <methods default-policy="allowed"/>
       <option-tags default-policy="allowed"/>
       <feature-tags default-policy="allowed"/>
       <bodies default-policy="allowed" default-encryption="allowed"/>
     </protocol>
    </protocols>
    <media default-policy="allowed"/>
   </sessionpolicy>


10. Security Considerations

   Session policy information can be sensitive information. The protocol
   used to distribute it SHOULD ensure privacy, message integrity and
   authentication. Furthermore, the protcol SHOULD provide access
   controls which restrict who can see who elses session policy
   information.

11. IANA Considerations

   This document registers a new MIME type, application/
   session-policy+xml, and registers a new XML namespace.

11.1 MIME Registration for application/session-policy+xml

   MIME media type name: application

   MIME subtype name: session-policy+xml

   Mandatory parameters: none

   Optional parameters: Same as charset parameter application/xml as
   specified in RFC 3023 [5].

   Encoding considerations: Same as encoding considerations of



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   application/xml as specified in RFC 3023 [5].

   Security considerations: See Section 10 of RFC 3023 [5] and Section
   10 of this specification.

   Interoperability considerations: none.

   Published specification: This document.

   Applications which use this media type: This document type has been
   used to download the session policy of a domain to SIP user agents.

   Additional Information:

   Magic Number: None

   File Extension: .wif or .xml

   Macintosh file type code: "TEXT"

   Personal and email address for further information: Gonzalo
   Camarillo, <Gonzalo.Camarillo@ericsson.com>

   Intended usage: COMMON

   Author/Change controller: The IETF.

11.2 URN Sub-Namespace Registration for
     urn:ietf:params:xml:ns:sessionpolicy

   This section registers a new XML namespace, as per the guidelines in
   [6]

   URI: The URI for this namespace is
   urn:ietf:params:xml:ns:sessionpolicy.

   Registrant Contact: IETF, SIPPING working group,<sipping@ietf.org>,
   Gonzalo Camarillo, <Gonzalo.Camarillo@ericsson.com>


           XML:

                BEGIN
                <?xml version="1.0"?>
                <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN"
                          "http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd">
                <html xmlns="http://www.w3.org/1999/xhtml">
                <head>



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                  <meta http-equiv="content-type"
                     content="text/html;charset=iso-8859-1"/>
                  <title>Session Policy Namespace</title>
                </head>
                <body>
                  <h1>Namespace for Session Policy Information</h1>
                  <h2>application/session-policy+xml</h2>
                  <p>See <a href="[[[URL of published RFC]]]">RFCXXXX</a>.</p>
                </body>
                </html>
                END

Normative References

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

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

   [3]  Moats, R., "URN Syntax", RFC 2141, May 1997.

   [4]  Moats, R., "A URN Namespace for IETF Documents", RFC 2648,
        August 1999.

   [5]  Murata, M., St. Laurent, S. and D. Kohn, "XML Media Types", RFC
        3023, January 2001.

   [6]  Mealling, M., "The IETF XML Registry",
        draft-mealling-iana-xmlns-registry-05 (work in progress), June
        2003.

Informational References


Author's Address

   Gonzalo Camarillo
   Ericsson
   Hirsalantie 11
   Jorvas  02420
   Finland

   EMail: Gonzalo.Camarillo@ericsson.com







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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
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   The IETF invites any interested party to bring to its attention any
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Full Copyright Statement

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

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   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION



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


Acknowledgment

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











































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