SIPREC                                                   R. Ravindranath
Internet-Draft                                             Cisco Systems
Intended status: Standards Track                Parthasarathi. Ravindran
Expires: August 2, 2016                                   Nokia Networks
                                                           Paul. Kyzivat
                                                                  Huawei
                                                        January 30, 2016


          Session Initiation Protocol (SIP) Recording Metadata
                     draft-ietf-siprec-metadata-19

Abstract

   Session recording is a critical requirement in many communications
   environments such as call centers and financial trading.  In some of
   these environments, all calls must be recorded for regulatory,
   compliance, and consumer protection reasons.  Recording of a session
   is typically performed by sending a copy of a media stream to a
   recording device.  This document describes the metadata model as
   viewed by Session Recording Server(SRS) and the Recording metadata
   format.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   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."

   This Internet-Draft will expire on August 2, 2016.

Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of



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   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Definitions . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Metadata Model  . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  Recording metadata Format . . . . . . . . . . . . . . . . . .   6
     5.1.  XML data format . . . . . . . . . . . . . . . . . . . . .   6
       5.1.1.  Namespace . . . . . . . . . . . . . . . . . . . . . .   7
       5.1.2.  recording . . . . . . . . . . . . . . . . . . . . . .   7
   6.  Recording Metadata classes  . . . . . . . . . . . . . . . . .   7
     6.1.  Recording Session . . . . . . . . . . . . . . . . . . . .   7
       6.1.1.  Attributes  . . . . . . . . . . . . . . . . . . . . .   8
       6.1.2.  Linkages  . . . . . . . . . . . . . . . . . . . . . .   8
     6.2.  Communication Session Group . . . . . . . . . . . . . . .   8
       6.2.1.  Attributes  . . . . . . . . . . . . . . . . . . . . .   9
       6.2.2.  Linkages  . . . . . . . . . . . . . . . . . . . . . .   9
     6.3.  Communication Session . . . . . . . . . . . . . . . . . .  10
       6.3.1.  Attributes  . . . . . . . . . . . . . . . . . . . . .  10
       6.3.2.  Linkages  . . . . . . . . . . . . . . . . . . . . . .  11
     6.4.  CSRSAssociation . . . . . . . . . . . . . . . . . . . . .  12
       6.4.1.  Attributes  . . . . . . . . . . . . . . . . . . . . .  13
       6.4.2.  Linkages  . . . . . . . . . . . . . . . . . . . . . .  13
     6.5.  Participant . . . . . . . . . . . . . . . . . . . . . . .  13
       6.5.1.  Attributes  . . . . . . . . . . . . . . . . . . . . .  14
       6.5.2.  Linkages  . . . . . . . . . . . . . . . . . . . . . .  14
     6.6.  ParticipantCSAssociation  . . . . . . . . . . . . . . . .  15
       6.6.1.  Attributes  . . . . . . . . . . . . . . . . . . . . .  15
       6.6.2.  Linkages  . . . . . . . . . . . . . . . . . . . . . .  16
     6.7.  Media Stream  . . . . . . . . . . . . . . . . . . . . . .  16
       6.7.1.  Attributes  . . . . . . . . . . . . . . . . . . . . .  17
       6.7.2.  Linkages  . . . . . . . . . . . . . . . . . . . . . .  17
     6.8.  ParticipantStream Association . . . . . . . . . . . . . .  17
       6.8.1.  Attributes  . . . . . . . . . . . . . . . . . . . . .  18
       6.8.2.  Linkages  . . . . . . . . . . . . . . . . . . . . . .  19
     6.9.  associate-time/disassociate-time  . . . . . . . . . . . .  19
     6.10. Unique ID format  . . . . . . . . . . . . . . . . . . . .  19
     6.11. Metadata version Indicator  . . . . . . . . . . . . . . .  19
   7.  Recording metadata snapshot Request format  . . . . . . . . .  20
   8.  SIP Recording Metadata Example  . . . . . . . . . . . . . . .  20
     8.1.  Complete SIP Recording Metadata Example . . . . . . . . .  20



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     8.2.  Partial Update of Recording metadata XML body . . . . . .  22
   9.  XML Schema definition for Recording metadata  . . . . . . . .  23
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  27
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  28
     11.1.  SIP recording metadata Schema Registration . . . . . . .  28
   12. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . .  28
   13. References  . . . . . . . . . . . . . . . . . . . . . . . . .  28
     13.1.  Normative References . . . . . . . . . . . . . . . . . .  28
     13.2.  Informative References . . . . . . . . . . . . . . . . .  30
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  30

1.  Introduction

   Session recording is a critical requirement in many communications
   environments such as call centers and financial trading.  In some of
   these environments, all calls must be recorded for regulatory,
   compliance, and consumer protection reasons.  Recording of a session
   is typically performed by sending a copy of a media stream to a
   recording device.  This document focuses on the Recording metadata
   which describes the communication session.  The document describes a
   metadata model as viewed by Session Recording Server(SRS) and the
   Recording metadata format, the requirements for which are described
   in [RFC6341] and the architecture for which is described in
   [RFC7245].

2.  Terminology

   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 [RFC2119].  This
   document only uses these key words when referencing normative
   statements in existing RFCs."

3.  Definitions

   Metadata Model: An abstract representation of metadata using a
   Unified Modelling Language(UML) class diagram.

   Metadata classes: Each block in the model represents a class.  A
   class is a construct that is used as a blueprint to create
   instances(called objects) of itself.  The description of each class
   also has representation of its attributes in a second compartment
   below the class name.

   Attributes: Attributes represent the elements listed in each of the
   classes.  The attributes of a class are listed in the second
   compartment below the class name.  Each instance of class conveys
   values for these attributes which adds to the recording's metadata.



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   Linkages: Linkages represent the relationship between the classes in
   the model.  Each represents a logical connection between classes(or
   objects) in class diagrams(or object diagrams).  The linkages used in
   the metadata model of this document are associations.

   This document also refers to the terminlogy defined in [RFC6341].

4.  Metadata Model

   Metadata is the information that describes recorded media and the
   Communication Session(CS) to which they relate.  The diagram below
   shows a model for metadata as viewed by a SRS.







































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             +-------------------------------+
             |    Recording Session (RS)     |
             +-------------------------------+
                   |1..*           | 1..*
                   |               |
                   |               | 0..*
                   |        +-----------------+
   +------------+  |        | Communication   |
   | CSRS       |  |        |  Session (CS)   |
   | Association|--+        |    Group        |
   |            |  |        +-----------------+
   +------------+  |              | 0..1
                   |              |
                   |0..*          | 1..*
   +-------------------------------+
   |   Communication Session (CS)  |
   |                               |
   +-------------------------------+
         | 1..*                   |0..1
   +-----+                        |
   |     | 0..*                   |0..*
   | +-------------+ receives +----------------+
   | | Participant |----------|  Media Streams |
   | |             |0..*  0..*|                |
   | |             |          |                |
   | |             |          |                |
   | |             |  sends   |                |
   | |             |----------|                |
   | |             |1.*   0..*|                |
   | +-------------+          +----------------+
   |        |                        |
   |        |                        |
   |        +------------------------+------------+
   |                                              |
   |                                              |
   |           +------------------+    +----------------------+
   |           |ParticipantCS     |    |  ParticipantStream   |
   +-----------|  Association     |    |    Association       |
               |                  |    |                      |
               +------------------+    +----------------------+



   The metadata model is a class diagram in Unified Modelling
   Language(UML).  The model describes the structure of metadata in
   general by showing the classes, their attributes, and the
   relationships among the classes.  Each block in the model above
   represents a class.  The linkages between the classes represent the



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   relationships which can be associations or composition.  The metadata
   is conveyed from SRC to SRS.

   The model allows the capture of a snapshot of a recording's metadata
   at a given instant in time.  Metadata changes to reflect changes in
   what is being recorded.  For example, if a participant joins a
   conference, then the SRC sends the SRS a snapshot of metadata having
   that participant information (with attributes like name/AoR pair and
   associate-time.)

   Some of the metadata is not required to be conveyed explicitly from
   the SRC to the SRS, if it can be obtained contextually by the
   SRS(e.g., from SIP or SDP signalling).

5.  Recording metadata Format

   This section gives an overview of the Recording metadata format.
   Some data from the metadata model is assumed to be made available to
   the SRS through Session Description Protocol (SDP)[RFC4566], and
   therefore this data is not represented in the XML document format
   specified in this document.  SDP attributes describe different media
   formats like audio, video.  The other metadata attributes, such as
   participant details, are represented in a new Recording specific XML
   document of type 'application/rs-metadata+xml'.  The SDP label
   attribute [RFC4574] provides an identifier by which a metadata XML
   document can refer to a specific media description in the SDP sent
   from the SRC to the SRS.

   The XML document format can be used to represent either the complete
   metadata or a partial update to the metadata.  The latter includes
   only elements that have changed compared to the previously reported
   metadata.

5.1.  XML data format

   Every recording metadata XML document MUST contain a <recording>
   element.  The <recording> element acts as a container for all other
   elements in this XML document.

   A recording object is an XML document.  It MUST have the XML
   declaration and it SHOULD contain an encoding declaration in the XML
   declaration, e.g., "<?xml version='1.0' encoding='UTF-8'?>".  If the
   charset parameter of the MIME content type declaration is present and
   it is different from the encoding declaration, the charset parameter
   takes precedence.

   Every application conforming to this specification MUST accept the
   UTF-8 character encoding to ensure the minimal interoperability.



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   Syntax and semantic errors in an XML document should be reported to
   the originator using application specific mechanisms.

5.1.1.  Namespace

   The namespace URI for elements defined by this specification is a
   Uniform Resource Namespace (URN) [RFC2141], using the namespace
   identifier 'ietf' defined by [RFC2648] and extended by [RFC3688].

   The URN is: urn:ietf:params:xml:ns:recording:1

5.1.2.  recording

   The <recording> element MUST contain an xmlns namespace attribute
   with value as urn:ietf:params:xml:ns:recording:1.  One recording
   element MUST be present in every recording metadata XML document.

   A recording element MAY contain a <dataMode> element indicating
   whether the XML document is a complete document or a partial update.
   If no <dataMode> element is present then the default value is
   "complete".

6.  Recording Metadata classes

   This section describes each class of the metadata model, and the
   attributes of each class.  This section also describes how different
   classes are linked and the XML element for each of them.

6.1.  Recording Session


   +-------------------------------+
   | Recording Session (RS)        |
   +-------------------------------+
   |                               |
   |     start-time                |
   |     end-time                  |
   |                               |
   |                               |
   +-------------------------------+
         |1..*            | 1..*
         |                |
         |0..*            | 0..*
    Communication    Communication
    Session          Session Group(CS Group)






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   Each instance of a Recording Session(RS) class namely the Recording
   Session Object represents a SIP session created between an SRC and
   SRS for the purpose of recording a Communication Session.

   RS object is represented in XML schema using <recording> element.
   That in turn relies on the SIP/SDP session with which the XML
   document is associated to provide the attributes of the RS element.

6.1.1.  Attributes

   A RS class has the following attributes:

   o  start-time - Represents the start time of a Recording Session
      object.

   o  end-time - Represents the end time of a Recording Session object.

   start-time and end-time attribute values are derivable from Date
   header(if present in SIP message) in RS.  In cases where Date header
   is not present, start-time is derivable from the time at which SRS
   receives the notification of SIP message to setup RS and and end-time
   is derivable from the time at which SRS receives disconnect on the RS
   SIP dialog.

6.1.2.  Linkages

   Each instance of RS has:

   o  Zero or more instances of Communication Session Group (CSG).

   o  Zero or more instances of Communication Session(CS) objects.

   CSs and CSGs are optional to accommodate persistent recording, where
   there may sometimes be none.

6.2.  Communication Session Group















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    Recording Session (RS)
              | 1..*
              |
              | 0..*
   +-------------------------------+
   | Communication Session         |
   |     Group                     |
   +-------------------------------+
   |  group_id                     |
   |  associate-time               |
   |  disassociate-time            |
   |                               |
   +-------------------------------+
              | 0..1
              |
              | 1..*
    Communication Session (CS)


   One instance of a Communication Session Group(CS-Group) class namely
   the Communication Session Group object provides association or
   linking of Communication Sessions.

   CS-Group object is represented in XML schema using <group> element.

6.2.1.  Attributes

   A CS-Group has the following attributes:

   o  group_id - This is to group different CSs that are related.  SRC
      (or SRS) is responsible for ensuring the uniqueness of group_id in
      case multiple SRC interacts with the same SRS.  The mechanism by
      which SRC groups the CS is outside the scope of SIPREC.

   o  associate-time - This is the time when a grouping is formed.  The
      rules that determine how a grouping of different CS objects is
      done by SRC is outside the scope of SIPREC.

   o  disassociate-time - disassociate-time for CS-Group is calculated
      by SRC as the time when the grouping ends.

6.2.2.  Linkages

   The linkages between CS-Group class and other classes are
   associations.  A CS-Group is associated with RS and CS in the
   following manner:

   o  There are one or more RS objects per CS-Group.



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   o  Each CS-Group object has to be associated with one or more RS.
      Here each RS can be setup by the potentially different SRCs.

   o  There are one or more CSs per CS-Group (for example, in case where
      the call is transferred).

6.3.  Communication Session



   Recording              Communication
   Session            Session Group(CS Group)
      |1..*                  | 0..1
      |                      |
      |0..*                  | 1..*
   +-------------------------------+
   |   Communication Session (CS)  |
   +-------------------------------+
   |   session_id                  |
   |   sipSessionID                |
   |   reason                      |
   |   group-ref                   |
   |   start-time                  |
   |   stop-time                   |
   +-------------------------------+
      |                      |
      | 0..*                 |0..1
      |                      |
      | 0..*                 |0..*
   Participant              Media Stream



   A Communication Session(CS) class and its object in the metadata
   model represents a Communication Session and its properties needed as
   seen by SRC.

   CS object is represented in XML schema using <session> element.

6.3.1.  Attributes

   A CS class has the following attributes:

   o  session_id - This attribute is used to uniquely identify an
      instance of CS object namely the session XML element with in the
      metadata XML document. session_id is generated using the rules
      mentioned in Section 6.10.




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   o  reason - This represents the reason why a CS was terminated.  The
      value for this attribute is derived from SIP Reason header
      [RFC3326] of CS.  There MAY be multiple instances of the reason
      XML element inside a session element.  The reason XML element has
      'protocol' as an attribute, which indicates the protocol from
      which the reason string is derived.  The default value for
      protocol attribute is "SIP".  The reason element can be derived
      from a SIP Reason header in the CS.

   o  sipSessionID - This attribute carries sip Session-ID defined in
      [I-D.ietf-insipid-session-id].  Each CS object can have zero or
      more sipSessionID elements.  More than one sipSessionID may be
      present in a CS for Conference flows.  For example, if three
      participants A, B and C are in a conference that has a focus
      acting as SRC, the metadata sent from the SRC to the SRS will
      likely have three sipSessionID elements that correspond to the SIP
      dialogs the focus has with each of the three participants.

   o  group-ref - A group-ref attribute MAY be present to indicate the
      group to which the enclosing session belongs.

   o  start-time - This optional attribute represents start time of CS
      as seen by SRC.

   o  Stop-time - This optional attribute represents stop time of CS as
      seen by SRC.

   This document does not specify attributes relating to what should
   happen to a recording of a CS after it has been delivered to the SRS
   (E.g., how long to retain the recording, what access controls to
   apply.)  The SRS is assumed to behave in accordance with its local
   policy.  The ability for the SRC to influence this policy is outside
   the scope of this document.  However if there are implementations
   where SRC desires to specify its own policy preferences, this could
   be sent as extension data attached to the CS.

6.3.2.  Linkages

   A CS is linked to CS-Group, Participant, Media Stream and RS classes
   using the association relationship.  Association between CS and
   Participant allows:

   o  CS to have zero or more participants

   o  Participant is associated with zero or more CSs.  This includes
      participants who are not directly part of any CS.  An example of
      such a case is participants in a premixed media stream.  The SRC
      may have knowledge of such participants, yet not have any



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      signaling relationship with them.  This might arise if one
      participant in CS is a conference focus.  To summarize, even if
      the SRC does not have direct signalling relationships with all
      participants in a CS, it should nevertheless create a participant
      object for each participant that it knows about.

   o  The model also allows participants in CS that are not participants
      in the media.  An example is the identity of a Third Party Call
      Control(3pcc) that has initiated a CS to two or more participants
      of the CS.  Another example is the identity of a conference focus.
      Of course a focus is probably in the media, but since it may only
      be there as a mixer, it may not report itself as a participant in
      any of the media streams.

   Association between CS and Media Stream allows:

   o  A CS to have zero or more streams

   o  A stream can be associated with at most one CS.  A stream in a
      persistent RS is not required to be associated with any CS before
      the CS is created and hence the zero associationa is allowed.

   Association between CS and RS allows:

   o  Each instance of RS has Zero or more instances of CS objects.

   o  Each CS has to be associated with one more RS.  Each RS can be
      potentially setup by different SRCs.

6.4.  CSRSAssociation



                        1..*            0..*
      Recording                             Communication
       Session        ----------+---------- Session
                                |
                                |
                                |
                      +-----------------------+
                      | CSRSAssociation       |
                      |                       |
                      +-----------------------+
                      | association-time      |
                      | disassociaton-time    |
                      | session_id            |
                      +-----------------------+




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   The CSRSAssociation class describes the association of a CS to an RS
   for a period of time.  A single CS may be associated with different
   RSs (perhaps by different SRCs) and may be associated and dissociated
   several times.

   The CSRSAssociation is represented in XML using sessionrecordingassoc
   XML element.

6.4.1.  Attributes

   CSRSAssociation class has the following attributes:

   o  associate-time - associate-time is calculated by SRC as the time
      it sees a CS is associated to a RS

   o  disassociate-time- disassociate-time is calculated by SRC as the
      time it see a CS disassociate from a RS.

   o  session_id - Each instance of this class MUST have session_id
      attribute that identifies the the CS to which this association
      belongs to.

6.4.2.  Linkages

   CSRSAssociation class is linked to CS and RS classes.

6.5.  Participant


    Communication Session (CS)
              | 0..*
              |
              | 0..*
   +-------------------------------+
   |          Participant          |
   +-------------------------------+
   |  nameID                       |
   |  participant_id               |
   |                               |
   +-------------------------------+
           | 0..*       1..*|
   receives|                |sends
           | 0..*       0..*|
             Media Stream







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   A Participant class and its objects has information about a device
   that is part of a CS and/or contributes/consumes media stream(s)
   belonging to a CS.

   Participant object is represented in XML schema using <participant>
   element.

6.5.1.  Attributes

   Participant has a single defined attribute:

   o  nameID - This attribute is a list of Name/AoR tuples.  An AoR can
      be one of SIP/SIPS/TEL URI, FQDN or IP address.  The AoR MAY be
      drawn from From header or P-Asserted-Identity header or Remote-
      Party-ID header.  SRCs local policy MAY also be used to decide on
      where to draw the AoR from.  Name represents participant name(SIP
      display name) or dialed number (DN) (when known).  Multiple tuples
      are allowed for cases where a participant has more than one AoR.
      (For example a P-Asserted-identity header [RFC3325] can have both
      SIP and TEL URIs.)

   o  participant_id - This attribute is used to identify the
      participant XML element with in the XML document.  It is generated
      using the rules mentioned in Section 6.10.  This attribute MUST be
      used for all references to a participant within a CSG, and MAY be
      used to reference the same participant more globally.

   This document does not specify other attributes relating to
   participant e.g. participant role, participant type.  An SRC which
   has information of these attributes can indicate the same as part of
   extension data to participant from SRC to SRS.

6.5.2.  Linkages

   The participant class is linked to MediaStream (MS) and CS class
   using association relationship.  The association between participant
   and MS allows:

   o  participant to receive zero or more media streams

   o  participant to send zero or more media streams.  (Same participant
      provides multiple streams e.g. audio and video)

   o  media stream to be received by zero or more participants.  Its
      possible, though perhaps unlikely, that a stream is generated but
      sent only to the SRC and SRS, not to any participant.  E.g.  In
      conferencing where all participants are on hold and the SRC is




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      collocated with the focus.  Also a media stream may be received by
      multiple participants (e.g.  Whisper calls, side conversations).

   o  media stream to be sent by one or more participants (pre-mixed
      streams).

   Example of a case where a participant receives zero or more streams -
   a supervisor may have side conversation with agent, while agent
   converses with customer.

6.6.  ParticipantCSAssociation



                        1..*            0..*
      Communication
       Session        ----------+---------- Participant
                                |
                                |
                                |
                      +-------------------------+
                      | ParticipantCSAssociation|
                      |                         |
                      |                         |
                      +-------------------------+
                      | associateTime           |
                      | disassociateTime        |
                      | param                   |
                      | participant_id          |
                      | session_id              |
                      +-------------------------+


   The ParticipantCSAssociation class describes the association of a
   participant to an CS for a period of time.  A participant may be
   associated and dissociated from a CS several times.  (For example,
   connecting to a conference, then disconnecting, then connecting
   again.)

   ParticipantCSAssociation object is represented in XML schema using
   <participantsessionassoc> element.

6.6.1.  Attributes

   ParticipantCS association class has the following attributes:

   o  associate-time - associate-time is calculated by SRC as the time
      it sees a participant is associated to CS



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   o  disassociate-time- disassociate-time is calculated by the SRC as
      the time it sees a participant disassociate from a CS.  It is
      possible that a given participant can have multiple associate/
      disassociate times within given communication session.

   o  param - An optional attribute describing the capabilities of a
      participant in a CS, as defined in [RFC3840].  The capablities are
      represented using param XML element in the metadata.  The 'param'
      XML element encoding defined in [RFC4235] is used to represent the
      capabilties attributes in metadata.  Each participant may have
      zero or more capabilities.  A participant may use different
      capabilities depending on the role it plays at a particular
      instance.  For example if a participant moves across different CSs
      (e.g., due to transfer) or is simultaneously present in different
      CSs with different roles.

   o  participant_id - This attribute identifies the participant to
      which this association belongs to.

   o  session_id - This attribute identifies the session to which this
      association belongs to.

6.6.2.  Linkages

   The participantCSAssociation class is linked to participant and CS
   classes.

6.7.  Media Stream


                                   Participant
                               | 0..*       1..*|
                       receives|                |sends
                               | 0..*       0..*|
                            +-------------------------+
                            |          Media Stream   |
   Communication 0..1  0..* +-------------------------+
     Session    ------------|                         |
                            |  label                  |
                            |  content-type           |
                            |  stream_id              |
                            |  session_id             |
                            +-------------------------+



   A MS class (and its objects) has the properties of media as seen by
   SRC and sent to SRS.  Different snapshots of a media stream object



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   may be sent whenever there is a change in media (e.g. direction
   change like pause/resume and/or codec change and/or participant
   change.).

   MS object is represented in XML schema using <stream> element.

6.7.1.  Attributes

   A MS class has the the following attributes:

   o  label - The label attribute within the stream XML element
      references an SDP "a=label" attribute that identifies an m-line
      within the RS SDP.  That m-line carries the media stream from the
      SRC to the SRS.

   o  content-type - The content of an MS element will be described in
      terms of value from the [RFC4796] registry.  If the SRC wishes to
      convey the Content-type to the SRS, it does so by including an
      'a=content' attribute with the m-line in the RS SDP.

   o  stream_id - Each stream element has unique 'stream_id' attribute
      which helps to uniquely identify stream.  This identifier is
      generated using the rules mentioned in Section 6.10.

   o  session_id - This attribute associates the stream with a specific
      session element.

   The metadata model should include media streams that are not being
   delivered to the SRS.  Examples include cases where SRC offered
   certain media types but SRS chooses to accept only a subset of them
   OR an SRC may not even offer a certain media type due it its
   restrictions to record

6.7.2.  Linkages

   A MS class is linked to participant and CS classes using the
   association relationship.  The details of association with the
   Participant are described in the Participant class section.  The
   details of association with CS is mentioned in the CS section.

6.8.  ParticipantStream Association










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   +-------------------------+
   | ParticipantStream       |
   | Association             |
   +-------------------------+   +----------Participant
   | association-time        |   |       0..*| 1..*|
   | disassociaton-time      |---+       recv|     |sends
   | send                    |   |       0..*| 0..*|
   | recv                    |   |           |     |
   | participant_id          |   |           |     |
   +-------------------------+   |           |     |
                                 +----------Media Stream



   A ParticipantStream association class describes the association of a
   Participant to a Media Stream for a period of time, as a sender or as
   a receiver, or both.

   This class is represented in XML using <participantstreamassoc>
   element.

6.8.1.  Attributes

   A ParticipantStream association class has the following attributes:

   o  associate-time: This attribute indicates the time a participant
      started contributing to a Media Stream

   o  disassociate-time: This attribute indicates the time a participant
      stopped contributing to a Media Stream

   o  send: This attribute indicates whether a participant is
      contributing to a stream or not.  This attribute has a value which
      points to stream represented by its unique_id.  The presence of
      this attribute indicates that a participant is contributing to a
      stream represented by the Unique_id.  If due to changes in CS if a
      participant stops contributing to a stream, a snapshot MUST be
      sent from SRC to SRS with no Send element for that stream.

   o  recv: This attribute indicates whether a participant is receiving
      a media stream or not.  This attribute has a value which points to
      a stream represented by its Unique_id.  The presence of this
      attribute indicates that a participant is receiving a stream
      represented by the Unique_id.  If due to changes in CS(like hold)
      the participants stops receiving a stream, a snapshot MUST be sent
      from SRC to SRS with no Recv element for that stream.





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   o  participant_id - This attributes points to the participant to
      which this streams are associated with.

   This XML element is used to represent a snapshot of a participant
   association with a stream.  The send and recv XML elements MUST be
   used to indicate whether a participant is contributing to a stream or
   receiving a stream.  There MAY be multiple instances of the send and
   recv XML elements inside a particpantstreamassoc element.  If a
   metadata snapshot is sent with a participantstreamassoc that does not
   have any send and recv elements, it means that participant is neither
   contributing to any streams nor receiving any streams.

6.8.2.  Linkages

   The participantStream association class is linked to participant and
   Stream classes.

6.9.  associate-time/disassociate-time

   The XML <associate-time> and <disassociate-time> elements contain
   strings indicating the date and time of the status change of this
   tuple.  The value of these elements MUST follow the IMPP datetime
   format [RFC3339].  Timestamps that contain 'T' or 'Z' MUST use the
   capitalized forms.  At a time, any of the time tuple associate-time
   or disassociate-time MAY exist in the element namely group, session,
   participant and not both timestamp at the same time.

   As a security measure, the timestamp element SHOULD be included in
   all tuples unless the exact time of the status change cannot be
   determined.

6.10.  Unique ID format

   A Unique id is generated in two steps:

   o  the UUID is created using [RFC4122]

   o  the UUID is encoded using base64 as defined in [RFC4648]

   The above mentioned unique-id mechanism SHOULD be used for each
   metadata element.  Multiple SRCs can refer to the same element/UUID
   (how each SRC learns the UUID here is out of scope of SIPREC)

6.11.  Metadata version Indicator

   This section defines a version indicator for metadata XML.





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   This version value allows the SRS to know the exact metadata XML
   schema used by the SRC.  This document describes version 1.
   Implementations may not interoperate if the version implemented by
   the sender is not known by the receiver.  No negotiation of versions
   is provided.  There is no significance to the version number although
   documents which update or obsolete this document (possibly including
   drafts of such documents) should include a higher version number if
   the metadata XML schema changes.

7.  Recording metadata snapshot Request format

   This section gives an details of metadata snapshot request format.
   When SRS wishes to request metadata snapshot from SRC it MUST follow
   the syntax described in this section.  The SRS requests metadata
   snapshot in a request message and SHOULD insert a XML document having
   the namespace urn:ietf:params:xml:ns:recording:1.  The Request can
   have the following elements.

   A <requestsnapshot> XML element MUST be present as the top level
   element in the XML document.  A <requestreason> XML element that
   indicates the reason for requesting snapshot as a string MAY be
   present as a child XML element of <requestsnapshot>.

8.  SIP Recording Metadata Example

8.1.  Complete SIP Recording Metadata Example

   The following example provides all the tuples involved in Recording
   Metadata XML body.


<?xml version="1.0" encoding="UTF-8"?>
<recording xmlns='urn:ietf:params:xml:ns:recording:1'>
  <datamode>complete</datamode>
        <group group_id="7+OTCyoxTmqmqyA/1weDAg==">
                <associate-time>2010-12-16T23:41:07Z</associate-time>
                <!-- Standardized extension -->
                <call-center xmlns='urn:ietf:params:xml:ns:callcenter'>
                        <supervisor>sip:alice@atlanta.com</supervisor>
                </call-center>
                <mydata xmlns='http://example.com/my'>
                        <structure>FOO!</structure>
                        <whatever>bar</whatever>
                </mydata>
        </group>
        <session session_id="hVpd7YQgRW2nD22h7q60JQ==">
                <sipSessionID>ab30317f1a784dc48ff824d0d3715d86;
                  remote=47755a9de7794ba387653f2099600ef2</sipSessionID>



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                <group-ref>7+OTCyoxTmqmqyA/1weDAg==
                </group-ref>
                <!-- Standardized extension -->
                <mydata xmlns='http://example.com/my'>
                        <structure>FOO!</structure>
                        <whatever>bar</whatever>
                </mydata>
        </session>
        <participant
              participant_id="srfBElmCRp2QB23b7Mpk0w==">
                <nameID aor="sip:bob@biloxi.com">
                        <name xml:lang="it">Bob B</name>
                </nameID>
                <!-- Standardized extension -->
                <mydata xmlns='http://example.com/my'>
                        <structure>FOO!</structure>
                        <whatever>bar</whatever>
                </mydata>
        </participant>
        <participant
               participant_id="zSfPoSvdSDCmU3A3TRDxAw==">
                <nameID aor="sip:Paul@biloxy.com">
                        <name xml:lang="it">Paul</name>
                </nameID>
                <!-- Standardized extension -->
                <mydata xmlns='http://example.com/my'>
                        <structure>FOO!</structure>
                        <whatever>bar</whatever>
                </mydata>
        </participant>
        <stream stream_id="UAAMm5GRQKSCMVvLyl4rFw=="
               session_id="hVpd7YQgRW2nD22h7q60JQ==">
                <label>96</label>
        </stream>
        <stream stream_id="i1Pz3to5hGk8fuXl+PbwCw=="
               session_id="hVpd7YQgRW2nD22h7q60JQ==">
                <label>97</label>
        </stream>
        <stream stream_id="8zc6e0lYTlWIINA6GR+3ag=="
               session_id="hVpd7YQgRW2nD22h7q60JQ==">
                <label>98</label>
        </stream>
        <stream stream_id="EiXGlc+4TruqqoDaNE76ag=="
               session_id="hVpd7YQgRW2nD22h7q60JQ==">
                <label>99</label>
        </stream>
        <sessionrecordingassoc session_id="hVpd7YQgRW2nD22h7q60JQ==">
                <associate-time>2010-12-16T23:41:07Z</associate-time>



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        </sessionrecordingassoc>
        <participantsessionassoc
              participant_id="srfBElmCRp2QB23b7Mpk0w=="
              session_id="hVpd7YQgRW2nD22h7q60JQ==">
                <associate-time>2010-12-16T23:41:07Z</associate-time>
        </participantsessionassoc>
        <participantsessionassoc
               participant_id="zSfPoSvdSDCmU3A3TRDxAw=="
               session_id="hVpd7YQgRW2nD22h7q60JQ==">
                <associate-time>2010-12-16T23:41:07Z</associate-time>
        </participantsessionassoc>
        <participantstreamassoc
              participant_id="srfBElmCRp2QB23b7Mpk0w==">
                <send>i1Pz3to5hGk8fuXl+PbwCw==</send>
                <send>UAAMm5GRQKSCMVvLyl4rFw==</send>
                <recv>8zc6e0lYTlWIINA6GR+3ag==</recv>
                <recv>EiXGlc+4TruqqoDaNE76ag==</recv>
        </participantstreamassoc>
        <participantstreamassoc
               participant_id="zSfPoSvdSDCmU3A3TRDxAw==">
                <send>8zc6e0lYTlWIINA6GR+3ag==</send>
                <send>EiXGlc+4TruqqoDaNE76ag==</send>
                <recv>UAAMm5GRQKSCMVvLyl4rFw==</recv>
                <recv>i1Pz3to5hGk8fuXl+PbwCw==</recv>
        </participantstreamassoc>
</recording>


                  SIP Recording Metadata Example XML body

8.2.  Partial Update of Recording metadata XML body

   The following example provides partial update in Recording metadata
   XML body for the above example.  The example has a snapshot that
   carries the disassociate-time for a participant from a session.
















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    <?xml version="1.0" encoding="UTF-8"?>
       <recording xmlns='urn:ietf:params:xml:ns:recording:1'>
         <dataMode>partial</dataMode>
         <participant
            participant_id="srfBElmCRp2QB23b7Mpk0w==">
            <name ID="sip:bob@biloxi.com">
                      <name xml:lang="it">Bob R</name>
                    </nameID>
             <structure>FOO!</structure>
             <whatever>bar</whatever>
         </participant>
         <participantsessionassoc
               participant_id="srfBElmCRp2QB23b7Mpk0w=="
               session_id="hVpd7YQgRW2nD22h7q60JQ==">
             <disassociate-time>2010-12-16T23:41:07Z</disassociate-time>
          </participantsessionassoc>
       </recording>


             Partial update of SIP Recording Example XML body

9.  XML Schema definition for Recording metadata

   This section defines XML schema for Recording metadata document


<?xml version="1.0" encoding="UTF-8"?>
   <xs:schema targetNamespace="urn:ietf:params:xml:ns:recording:1"
      xmlns:xs="http://www.w3.org/2001/XMLSchema"
      xmlns:tns="urn:ietf:params:xml:ns:recording:1"
      elementFormDefault="qualified"
      attributeFormDefault="unqualified">
     <!-- This import brings in the XML language attribute xml:lang-->
     <xs:import namespace="http://www.w3.org/XML/1998/namespace"/>
     <xs:element name="recording" type="tns:recording"/>
     <xs:complexType name="recording">
         <xs:sequence>
             <xs:element name="datamode" type="tns:dataMode"
                  minOccurs="0"/>
           <xs:element name="group" type="tns:group"
                  minOccurs="0" maxOccurs="unbounded"/>
             <xs:element name="session" type="tns:session"
                  minOccurs="0" maxOccurs="unbounded"/>
             <xs:element name="participant" type="tns:participant"
                  minOccurs="0" maxOccurs="unbounded"/>
             <xs:element name="stream" type="tns:stream"
                 minOccurs="0" maxOccurs="unbounded"/>
            <xs:element name="sessionrecordingassoc"



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                 type="tns:sessionrecordingassoc"
                 minOccurs="0" maxOccurs="unbounded"/>
            <xs:element name="participantsessionassoc"
                 type="tns:participantsessionassoc"
                 minOccurs="0" maxOccurs="unbounded"/>
            <xs:element name="participantstreamassoc"
                 type="tns:participantstreamassoc"
                 minOccurs="0" maxOccurs="unbounded"/>
            <xs:any namespace='##other'
                     minOccurs='0'
                     maxOccurs='unbounded'
                     processContents='lax'/>
         </xs:sequence>
     </xs:complexType>
     <xs:complexType name="group">
         <xs:sequence>
           <xs:element name="associate-time" type="xs:dateTime"
              minOccurs="0"/>
           <xs:element name="disassociate-time" type="xs:dateTime"
              minOccurs="0"/>
          <xs:any namespace='##other'
                     minOccurs='0'
                     maxOccurs='unbounded'
                     processContents='lax'/>
         </xs:sequence>
         <xs:attribute name="group_id" type="xs:base64Binary"
              use="required"/>
     </xs:complexType>
     <xs:complexType name="session">
         <xs:sequence>
           <xs:element name="sipSessionID" type="xs:string" minOccurs="0"
                   maxOccurs="unbounded"/>
           <xs:element name="reason" type="tns:reason" minOccurs="0"
                   maxOccurs="unbounded"/>
           <xs:element name="group-ref" type="xs:base64Binary"
                  minOccurs="0" maxOccurs="1"/>
           <xs:element name="start-time" type="xs:dateTime"
                  minOccurs="0" maxOccurs="1"/>
           <xs:element name="stop-time" type="xs:dateTime"
                  minOccurs="0" maxOccurs="1"/>
              <xs:any namespace='##other'
                     minOccurs='0'
                     maxOccurs='unbounded'
                     processContents='lax'/>
         </xs:sequence>
         <xs:attribute name="session_id" type="xs:base64Binary"
              use="required"/>
     </xs:complexType>



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     <xs:complexType name="sessionrecordingassoc">
         <xs:sequence>
           <xs:element name="associate-time" type="xs:dateTime"
                  minOccurs="0"/>
           <xs:element name="disassociate-time" type="xs:dateTime"
                  minOccurs="0"/>
           <xs:any namespace='##other'
                     minOccurs='0'
                     maxOccurs='unbounded'
                     processContents='lax'/>
         </xs:sequence>
         <xs:attribute name="session_id" type="xs:base64Binary"
              use="required"/>
     </xs:complexType>
     <xs:complexType name="participant">
         <xs:sequence>
             <xs:element name="nameID" type="tns:nameID"
                     maxOccurs='unbounded'/>
          <xs:any namespace='##other'
                     minOccurs='0'
                     maxOccurs='unbounded'
                     processContents='lax'/>
         </xs:sequence>
         <xs:attribute name="participant_id" type="xs:base64Binary"
              use="required"/>
  </xs:complexType>
     <xs:complexType name="participantsessionassoc">
         <xs:sequence>
         <xs:element name="associate-time" type="xs:dateTime"
                  minOccurs="0"/>
         <xs:element name="disassociate-time" type="xs:dateTime"
                  minOccurs="0"/>
          <xs:element name="param" minOccurs="0" maxOccurs="unbounded">
               <xs:complexType>
                  <xs:attribute name="pname" type="xs:string" use="required"/>
                  <xs:attribute name="pval" type="xs:string" use="required"/>
                </xs:complexType>
             </xs:element>
           <xs:any namespace='##other'
                     minOccurs='0'
                     maxOccurs='unbounded'
                     processContents='lax'/>
         </xs:sequence>
         <xs:attribute name="participant_id" type="xs:base64Binary"
              use="required"/>
         <xs:attribute name="session_id" type="xs:base64Binary"
              use="required"/>
     </xs:complexType>



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     <xs:complexType name="participantstreamassoc">
         <xs:sequence>
             <xs:element name="send" type="xs:base64Binary"
               minOccurs="0" maxOccurs="unbounded"/>
             <xs:element name="recv" type="xs:base64Binary"
               minOccurs="0" maxOccurs="unbounded"/>
               <xs:element name="associate-time" type="xs:dateTime"
                  minOccurs="0"/>
            <xs:element name="disassociate-time" type="xs:dateTime"
                  minOccurs="0"/>
               <xs:any namespace='##other'
                     minOccurs='0'
                     maxOccurs='unbounded'
                     processContents='lax'/>
         </xs:sequence>
         <xs:attribute name="participant_id" type="xs:base64Binary"
              use="required"/>
     </xs:complexType>
     <xs:complexType name="stream">
         <xs:sequence>
           <xs:element name="label" type="xs:string"
               minOccurs="0" maxOccurs="1"/>
            <xs:any namespace='##other'
                     minOccurs='0'
                     maxOccurs='unbounded'
                     processContents='lax'/>
         </xs:sequence>
         <xs:attribute name="stream_id" type="xs:base64Binary"
              use="required"/>
         <xs:attribute name="session_id" type="xs:base64Binary"/>
     </xs:complexType>
       <xs:simpleType name="dataMode">
           <xs:restriction base="xs:string">
              <xs:enumeration value="complete"/>
                      <xs:enumeration value="partial"/>
           </xs:restriction>
     </xs:simpleType>
     <xs:complexType name="nameID">
      <xs:sequence>
         <xs:element name="name" type ="tns:name" minOccurs="0"
                            maxOccurs="1"/>
      </xs:sequence>
      <xs:attribute name="aor" type="xs:anyURI" use="required"/>
    </xs:complexType>
   <xs:complexType name="name">
   <xs:simpleContent>
          <xs:extension base="xs:string">
           <xs:attribute ref="xml:lang" use="optional"/>



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          </xs:extension>
         </xs:simpleContent>
    </xs:complexType>
    <xs:complexType name="reason">
      <xs:simpleContent>
       <xs:extension base="xs:string">
          <xs:attribute type="xs:short" name="cause" use="required"/>
          <xs:attribute type="xs:string" name="protocol" default="SIP"/>
       </xs:extension>
      </xs:simpleContent>
    </xs:complexType>
    <xs:element name="requestsnapshot" type="tns:requestsnapshot"/>
     <xs:complexType name="requestsnapshot">
       <xs:sequence>
          <xs:element name="requestreason" type="tns:name"  minOccurs="0"/>
          <xs:any namespace='##other'
            minOccurs='0'
            maxOccurs='unbounded'
            processContents='lax'/>
       </xs:sequence>
     </xs:complexType>
</xs:schema>


10.  Security Considerations

   This document describes an extensive set of metadata that may be
   recorded by the SRS.  Most of the metadata could be considered
   private data.  For this reason, it is RECOMMENDED that a SRC use a
   strong means for authentication and metadata information protection
   and that it apply comprehensive authorization rules when using the
   metadata format defined in this document.

   It is RECOMMENDED that a SRC authenticate the SRS using the normal
   SIP authentication mechanisms, such as Digest as defined in
   Section 22 of [RFC3261].  The mechanism used for conveying the
   metadata information MUST ensure integrity and confidentially of the
   information.  In order to achieve these, an end-to-end SIP encryption
   mechanism, such as S/MIME described in [RFC3261], SHOULD be used.

   If a strong end-to-end security means (such as above) is not
   available, it is RECOMMENDED that a SRC use mutual hop-by-hop
   Transport Layer Security (TLS) authentication and encryption
   mechanisms described in "SIPS URI Scheme" and "Interdomain Requests"
   of [RFC3261].

   Some implementations may have the SRC choose parts of metadata that
   can be sent to the SRS.  In other cases, SRCs may send metadata that



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   is not appropriate for the SRS to record.  Which metadata is actually
   recorded by the SRS must be carefully considered to balance privacy
   concerns with usability.  Implementations MUST control what metadata
   is recorded, and MUST NOT save metadata sent by the SRC that does not
   conform to the recording policy of the SRS.  Metadata in storage
   needs to be provided with a level of security that is comparable to
   that of the recording session.

11.  IANA Considerations

   This specification registers a new XML namespace, and a new XML
   schema.

11.1.  SIP recording metadata Schema Registration

   URI: urn:ietf:params:xml:ns:recording:1

   Registrant Contact: IETF SIPREC working group, Ram mohan
   R(rmohanr@cisco.com)

   XML: the XML schema to be registered is contained in Section 8.

   Its first line is <?xml version="1.0" encoding="UTF-8"?> and its last
   line is </xs:schema>

12.  Acknowledgement

   Thanks to John Elwell, Henry Lum, Leon Portman, De Villers, Andrew
   Hutton, Deepanshu Gautam,Charles Eckel, Muthu Arul Mozhi, Michael
   Benenson, Hadriel Kaplan, Brian Rosen, Scott Orton, Ofir Roth, Mary
   Barnes, Ken Rehor, Gonzalo Salgueiro, Yaron Pdut and Alissa Cooper
   for their valuable comments and inputs.

   Thanks to Joe Hildebrand, Peter Saint-Andre, Matt Miller for helping
   in writing the XML schema and Martin Thompson for validating the XML
   schema and providing comments on the same.

13.  References

13.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC2141]  Moats, R., "URN Syntax", RFC 2141, DOI 10.17487/RFC2141,
              May 1997, <http://www.rfc-editor.org/info/rfc2141>.



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   [RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
              A., Peterson, J., Sparks, R., Handley, M., and E.
              Schooler, "SIP: Session Initiation Protocol", RFC 3261,
              DOI 10.17487/RFC3261, June 2002,
              <http://www.rfc-editor.org/info/rfc3261>.

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              DOI 10.17487/RFC3688, January 2004,
              <http://www.rfc-editor.org/info/rfc3688>.

   [RFC3339]  Klyne, G. and C. Newman, "Date and Time on the Internet:
              Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,
              <http://www.rfc-editor.org/info/rfc3339>.

   [RFC4566]  Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
              Description Protocol", RFC 4566, DOI 10.17487/RFC4566,
              July 2006, <http://www.rfc-editor.org/info/rfc4566>.

   [RFC4574]  Levin, O. and G. Camarillo, "The Session Description
              Protocol (SDP) Label Attribute", RFC 4574,
              DOI 10.17487/RFC4574, August 2006,
              <http://www.rfc-editor.org/info/rfc4574>.

   [RFC4796]  Hautakorpi, J. and G. Camarillo, "The Session Description
              Protocol (SDP) Content Attribute", RFC 4796,
              DOI 10.17487/RFC4796, February 2007,
              <http://www.rfc-editor.org/info/rfc4796>.

   [RFC3840]  Rosenberg, J., Schulzrinne, H., and P. Kyzivat,
              "Indicating User Agent Capabilities in the Session
              Initiation Protocol (SIP)", RFC 3840,
              DOI 10.17487/RFC3840, August 2004,
              <http://www.rfc-editor.org/info/rfc3840>.

   [RFC4122]  Leach, P., Mealling, M., and R. Salz, "A Universally
              Unique IDentifier (UUID) URN Namespace", RFC 4122,
              DOI 10.17487/RFC4122, July 2005,
              <http://www.rfc-editor.org/info/rfc4122>.

   [RFC4648]  Josefsson, S., "The Base16, Base32, and Base64 Data
              Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
              <http://www.rfc-editor.org/info/rfc4648>.

   [I-D.ietf-insipid-session-id]
              Jones, P., Salgueiro, G., and C. Pearce, "End-to-End
              Session Identification in IP-Based Multimedia
              Communication Networks", draft-ietf-insipid-session-id-16
              (work in progress), October 2015.



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13.2.  Informative References

   [RFC6341]  Rehor, K., Ed., Portman, L., Ed., Hutton, A., and R. Jain,
              "Use Cases and Requirements for SIP-Based Media Recording
              (SIPREC)", RFC 6341, DOI 10.17487/RFC6341, August 2011,
              <http://www.rfc-editor.org/info/rfc6341>.

   [RFC7245]  Hutton, A., Ed., Portman, L., Ed., Jain, R., and K. Rehor,
              "An Architecture for Media Recording Using the Session
              Initiation Protocol", RFC 7245, DOI 10.17487/RFC7245, May
              2014, <http://www.rfc-editor.org/info/rfc7245>.

   [RFC2648]  Moats, R., "A URN Namespace for IETF Documents", RFC 2648,
              DOI 10.17487/RFC2648, August 1999,
              <http://www.rfc-editor.org/info/rfc2648>.

   [RFC3326]  Schulzrinne, H., Oran, D., and G. Camarillo, "The Reason
              Header Field for the Session Initiation Protocol (SIP)",
              RFC 3326, DOI 10.17487/RFC3326, December 2002,
              <http://www.rfc-editor.org/info/rfc3326>.

   [RFC3325]  Jennings, C., Peterson, J., and M. Watson, "Private
              Extensions to the Session Initiation Protocol (SIP) for
              Asserted Identity within Trusted Networks", RFC 3325,
              DOI 10.17487/RFC3325, November 2002,
              <http://www.rfc-editor.org/info/rfc3325>.

   [RFC4235]  Rosenberg, J., Schulzrinne, H., and R. Mahy, Ed., "An
              INVITE-Initiated Dialog Event Package for the Session
              Initiation Protocol (SIP)", RFC 4235,
              DOI 10.17487/RFC4235, November 2005,
              <http://www.rfc-editor.org/info/rfc4235>.

Authors' Addresses

   Ram Mohan Ravindranath
   Cisco Systems
   Cessna Business Park
   Bangalore, Karnataka
   India

   Email: rmohanr@cisco.com









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   Parthasarathi Ravindran
   Nokia Networks
   Bangalore, Karnataka
   India

   Email: partha@parthasarathi.co.in


   Paul Kyzivat
   Huawei
   Hudson, MA
   USA

   Email: pkyzivat@alum.mit.edu





































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