SIPREC                                                    A. Hutton, Ed.
Internet-Draft                                        Siemens Enterprise
Intended status:  Informational                           Communications
Expires:  May 25, 2013                                   L. Portman, Ed.
                                                            NICE Systems
                                                                 R. Jain
                                                             IPC Systems
                                                                K. Rehor
                                                     Cisco Systems, Inc.
                                                       November 21, 2012


    An Architecture for Media Recording using the Session Initiation
                                Protocol
                   draft-ietf-siprec-architecture-07

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 architectures for
   deploying session recording solutions in an environment which is
   based on the Session Initiation Protocol (SIP).

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 May 25, 2013.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.



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   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
   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.  Definitions  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Session Recording Architecture . . . . . . . . . . . . . . . .  5
     3.1.  Location of the Session Recording Client . . . . . . . . .  5
       3.1.1.  B2BUA acts as a Session Recording Client . . . . . . .  5
       3.1.2.  Endpoint acts as Session Recording Client  . . . . . .  7
       3.1.3.  A SIP Proxy cannot be a Session Recording Client . . .  7
       3.1.4.  Interaction with MEDIACTRL . . . . . . . . . . . . . .  8
       3.1.5.  Interaction with Conference Focus  . . . . . . . . . .  9
     3.2.  Establishing the Recording Session . . . . . . . . . . . . 10
       3.2.1.  Session Recording Client Initiated Recording . . . . . 11
       3.2.2.  Session Recording Server Initiated Recording . . . . . 11
       3.2.3.  Pause/Resume Recording Session . . . . . . . . . . . . 12
       3.2.4.  Media Stream Mixing  . . . . . . . . . . . . . . . . . 12
       3.2.5.  Media Transcoding  . . . . . . . . . . . . . . . . . . 12
     3.3.  Recording Metadata . . . . . . . . . . . . . . . . . . . . 12
       3.3.1.  Contents of recording metadata . . . . . . . . . . . . 13
       3.3.2.  Mechanisms for delivery of metadata to Session
               Recording Server . . . . . . . . . . . . . . . . . . . 13
     3.4.  Notifications to the Recorded User Agents  . . . . . . . . 13
     3.5.  Preventing the recording of a SIP session  . . . . . . . . 13
   4.  IANA considerations  . . . . . . . . . . . . . . . . . . . . . 13
   5.  Security considerations  . . . . . . . . . . . . . . . . . . . 14
   6.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 14
   7.  Informative References . . . . . . . . . . . . . . . . . . . . 15
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16












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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 describes architectures for
   deploying session recording solutions in an environment which is
   based on the Session Initiation Protocol (SIP) the requirements for
   which are described in [RFC6341].

   This document focuses on how sessions are established between a
   Session Recording Client (SRC) and the Session Recording Server (SRS)
   for the purpose of conveying the Replicated Media and Recording
   Metadata (e.g.  Identity of parties involved) relating to the
   Communication Session.

   Once the Replicated Media and Recording Metadata have been received
   by the Session Recording Server they will typically be archived for
   retrieval at a later time.  The procedures relating to the archiving
   and retrieval of this information is outside the scope of this
   document.

   This document only considers active recording, where the Session
   Recording Client purposefully streams media to a Session Recording
   Server.  Passive recording, where a recording device detects media
   directly from the network (E.g. using port mirroring techniques), is
   outside the scope of this document.  In addition, lawful intercept is
   outside the scope of this document which takes account of the IETF
   policy on wiretapping [RFC2804].

   The Recording Session that is established between the Session
   Recording Client and the Session Recording Server uses the normal
   procedures for establishing INVITE initiated dialogs as specified in
   [RFC3261] and uses SDP for describing the media to be used during the
   session as specified in [RFC4566].  However it is intended that some
   extensions to SIP (E.g.  Headers, Option Tags, Etc.) will be defined
   to support the requirements for media recording.  The Replicated
   Media is required to be sent in real-time to the Session Recording
   Server and is not buffered by the Session Recording Client to allow
   for real-time analysis of the media by the Session Recording Server.









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2.  Definitions

   Session Recording Server (SRS):  A Session Recording Server (SRS) is
   a SIP User Agent (UA) that is a specialized media server or collector
   that acts as the sink of the recorded media.  An SRS is typically
   implemented as a multi-port device that is capable of receiving media
   from multiple sources simultaneously.  An SRS is the sink of the
   communication session metadata.

   Session Recording Client (SRC):  A Session Recording Client (SRC) is
   a SIP User Agent (UA) that acts as the source of the recorded media,
   sending it to the SRS.  An SRC is a logical function.  Its
   capabilities may be implemented across one or more physical devices.
   In practice, an SRC could be a personal device (such as a SIP phone),
   a SIP Media Gateway (MG), a Session Border Controller (SBC) or a SIP
   Media Server (MS) integrated with an Application Server (AS).  This
   specification defines the term SRC such that all such SIP entities
   can be generically addressed under one definition.  The SRC provides
   comunication session metadata to the SRS.

   Communication Session (CS):  A session created between two or more
   SIP User Agents (UAs) that is the subject of recording.

   Recording Session (RS):  The SIP session created between an SRC and
   SRS for the purpose of recording a Communication Session.

   Recording aware User Agent (UA):  A SIP User Agent that is aware of
   SIP extensions associated with the Communication Session.  Such
   extensions may be used to notify the Recording aware UA that a
   session is being recorded, or by a Recording aware UA to express
   preferences as to whether a recording should be started, paused,
   resumed or stopped.

   Recording unaware User Agent (UA):  A SIP User Agent that is unaware
   of SIP extensions associated with the Communication Session.  Such
   Recording unaware UA will be notified that a session is being
   recorded or express preferences as to whether a recording should be
   started, paused, resumed or stopped via some other means that is out
   of scope of SIPREC.

   Recording Metadata:  The metadata describing the communication
   session that is required by the Session Recording Server.  This will
   include for example the identity of users that participate in the
   Communication Session and dialog state.  Typically this metadata is
   archived with the replicated media at the Session Recording Server.
   The recording metadata is delivered in real-time to the Session
   Recording Server.




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   Replicated Media:  A copy of the media associated with the
   Communication Session created by the Session Recording Client and
   sent to the Session Recording Server.  It may contain all the media
   associated with the communication session (E.g.  Audio and Video) or
   just a subset (E.g.  Audio).  Replicated Media is part of Recording
   Session.


3.  Session Recording Architecture

3.1.  Location of the Session Recording Client

   This section contains some example session recording architectures
   showing how the Session Recording Client is a logical function that
   can be located in or split between various physical components.

3.1.1.  B2BUA acts as a Session Recording Client

   A SIP Back to Back User Agent (B2BUA) which has access to the media
   that is to be recorded may act as a Session Recording Client.  The
   B2BUA may already be aware that a session needs to be recorded before
   the initial establishment of the communication session or the
   decision to record the session may occur after the session has been
   established.

   If the SRC makes the decision to initiate the Recording Session (RS),
   then it will initiate the establishment of a SIP RS by sending an
   INVITE to the SRS.

   If the SRS makes the decision to initiate the recording session, then
   it will initiate the establishment of a SIP RS by sending an INVITE
   to the SRC.

   The RS INVITE contains information which identifies the session as
   being established for the purposes of recording and prevents the
   session from being accidentally rerouted to a UA which is not an SRS
   if the RS was initiated by SRC or vice-versa.

   The B2BUA/SRC is responsible for notifying the UAs involved in the
   communication session that the session is being recorded.

   The B2BUA/SRC is responsible for complying with requests from
   recording aware UAs or through some configured policies indicating
   that the communication session should not be recorded.







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                                              +-----------+
                          (Recording Session) |  Session  |
                             +------SIP------>| Recording |
                             |                |  Server   |
                             |  +--RTP/RTCP-->|  (SRS)    |
                             |  |             +-----------+
                             V  V                   ^
                        +-------------+             |
                        |             |             |
                        |             |-- Metadata -+
                        |             |
                        |    B2BUA    |
                        |             |
                        |   Session   |
     +--------+         |  Recording  |         +---------+
     |        |<- SIP ->|   Client    |<- SIP ->|         |
     |  UA-A  |         |   (SRC)     |         |  UA-B   |
     |        |<- RTP/->|             |<- RTP/->|         |
     +--------+   RTCP  |             |   RTCP  +---------+
                        +-------------+
     |____________________________________________________|
                    (Communication Session)

          Figure 1: B2BUA Acts as the Session Recording Client.



























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3.1.2.  Endpoint acts as Session Recording Client

   A SIP Endpoint / UA may act as a Session Recording Client in which
   case the endpoint sends the Replicated Media to the Session Recording
   Server

   If the endpoint makes the decision to initiate the Recording Session
   then it will initiate the establishment of a SIP Session by sending
   an INVITE to the Session Recording Server.

   If the Session Recording Server makes the decision to initiate the
   Recording Session then it will initiate the establishment of a SIP
   Session by sending an INVITE to the endpoint.  The actual decision
   mechanism is out of scope of SIPREC.



          (Recording Session) +-----------+
         +----------SIP------>|           |
         |  +----RTP/RTCP---->|  Session  |
         |  |                 | Recording |
         |  |                 |  Server   |
         |  | +-- Metadata -->|   (SRS)   |
         |  | |               |           |
         |  | |               +-----------+
         |  | |
         |  | |
         |  | |
         |  | |
         V  V |  (Communication Session)
      +--+------+                     +---------+
      |         |<-------SIP--------->|         |
      |  UA-A   |                     |  UA-B   |
      |  (SRC)  |<-----RTP/RTCP------>|         |
      +---------+                     +---------+


      Figure 2: SIP Endpoint acts as the Session Recording Client



3.1.3.  A SIP Proxy cannot be a Session Recording Client

   A SIP Proxy is unable to act as an SRC because it does not have
   access to the media and therefore has no way of enabling the delivery
   of the replicated media to the SRS





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3.1.4.  Interaction with MEDIACTRL

   The MEDIACTRL architecture [RFC5567] describes an architecture in
   which an Application Server (AS) controls a Media Server (MS) which
   may be used for purposes such as conferencing and recording media
   streams.  In the [RFC5567] architecure the AS typically uses SIP
   Third Party Call Control (3PCC) to instruct the SIP UAs to direct
   their media to the Media Server.

   The SRC or the SRS described in this document may be architected
   according to [RFC5567]; and therefore, when further decomposed, they
   may be made up of an application server (AS) which uses a mediactrl
   interface to control a media server (MS).

   As shown in figure 3, when the SRS is architected according to
   [RFC5567] the MS acts as a sink of the recording media and the AS
   acts as a sink of the metadata and the termination point for RS SIP
   signaling.  As shown in figure 4, when the SRC is architected
   according to [RFC5567] the MS acts as a source of recording media and
   the AS acts as a sink of the metadata and the termination point for
   RS SIP signaling.


                                     Session Recording Server (SRS)
                              +----------------------------------------+
                              |                                        |
          (Recording Session) |  +-----------+          +------------+ |
          +------------SIP----|->|           |          |            | |
          |                   |  | MEDIACTRL |MEDIACTRL |   Media    | |
          |                   |  |Application|<-------->|   Server   | |
          |    +-----Metadata--->|  Server   |          |  (Recorder)| |
          |    |              |  |           |          |            | |
          |    |              |  +-----------+          +------------+ |
          |    |              |                              ^         |
          |    |              +------------------------------|---------+
          |    |  +--------------- RTP/RTCP -----------------+
          |    |  |
          V    |  V
        +---+------+                          +---------+
        |          |<-------SIP-------------->|         |
        |   UA-A   | (Communication Session)  |  UA-B   |
        |   (SRC)  |<-------RTP/RTCP--------->|         |
        +----------+                          +---------+

           Figure 3: Example of Session Recording Server using MEDIACTRL






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                                                    +----------+
                 (Recording Session)                | Session  |
           +-----------SIP------------------------->|Recording |
           | +----------Metadata------------------->|  Server  |
           | |                                      |   (SRS)  |
           V | UA-A Session Recording Client (SRC)  +----------+
    +----------------------------------------+         ^
    |                                        |         |
    |  +-----------+          +------------+ |         |
    |  |           | Control  |            |<-RTP/RTCP-+    +---------+
    |  |    UA     | Protocol |   Media    | |              |         |
    |  |Application|<-------->|  Server    | |<----SIP----->|  UA-B   |
    |  |  Server   |          |            |<-----RTP------>|         |
    |  |           |          |            | |              +---------+
    |  +-----------+          +------------+ |
    |                                        |
    +----------------------------------------+
           Figure 4: Example of Session Recording Client decomposition


3.1.5.  Interaction with Conference Focus

   In the case of a centralised conference a combination of the
   conference focus and mixer [RFC4353] may act as a SRC and therefore
   provide the SRS with the replicated media and associated recording
   metadata.  In this arrangement the SRC is able to provide media and
   metadata relating to each of the participants, including, for
   example, any side conversations where the media passes through the
   mixer.

   Conference Focus can either provide mixed replicated media or
   separate streams per conference participant (as depicted in the
   Figure 5).

   The conference focus may also act as a Recording Aware UA in the case
   when one of the participants acts as a SRC.

   In an alternative arrangement a SIP endpoint which is a conference
   participant can act as an SRC.  The SRC will in this case have access
   to the media and metadata relating to that particular participant and
   may be able to obtain additional metadata from the conference focus.
   The SRC may for example use the conference event package as described
   in [RFC4575] to obtain information about other participants which it
   provides to the SRS within the recording metadata.

   The SRC may be involved in the conference from the very beginning or
   may join at some later point of time.




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                                User 1
                            +-----------+
                            |           |
                            |           |
                            |Participant|
                            |     1     |
                            |           |
                            +-----------+
                                ^ ^SIP
                            RTP | |Dialog
                                | |1
       User 2                   V V       Recording
    +-----------+           +-----------+  Session     *************
    |           |           |           |<------------>*           *
    |           |<-- RTP -->|           |<-RTP/RTCP 1->*           *
    |Participant|<--------->| Focus/SRC |<-RTP/RTCP 2->*    SRS    *
    |     2     |  SIP      |           |<-RTP/RTCP 3->*           *
    |           |  Dialog   |           |              *           *
    +-----------+  2        +-----------+              *************
                                 ^ ^
                                 | |SIP
                             RTP | |Dialog
                                 | |3
                                 V V
                            +-----------+
                            |           |
                            |           |
                            |Participant|
                            |    3      |
                            |           |
                            +-----------+
                               User 3

           Figure 5: Conference Focus acting as an SRC.


3.2.  Establishing the Recording Session

   The Session Recording Client or the Session Recording Server may
   initiate the Recording Session.

   It should be noted that the Recording Session is independent from the
   Communication Session that is being recorded at both the SIP dialog
   level and at the session level.

   Concerning media negotiation, regular SIP/SDP capabilities should be
   used, and existing transcoding capabilities and media encryption
   should not be precluded.



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3.2.1.  Session Recording Client Initiated Recording

   When the Session Recording Client initiates the Recording Session for
   the purpose of conveying media to the Session Recording Server it
   performs the following actions:

   o  The SRC is provisioned with a Unified Resource Identifier (URI)
      for the SRS, which is resolved through normal [RFC3263]
      procedures.

   o  Initiates the dialog by sending an INVITE request to the Session
      Recording Server.  The dialog is established according to the
      normal procedures for establishing an INVITE initiated dialog as
      specified in [RFC3261].

   o  Include in the INVITE an indication that the session is
      established for the purpose of recording the associated media.

   o  If the Replicated Media is to be started immediately then the
      Session Recording Client will include an SDP attribute of
      "a=sendonly" for each media line or "a=inactive" if it is not
      ready to transmit the media.

   o  The Recording Session may replicate all media associated with the
      Communication Session or only a subset.

   o  Replicates the media streams that are to be recorded and transmits
      the media to the Session Recording Server.

3.2.2.  Session Recording Server Initiated Recording

   When the Session Recording Server initiates the media recording
   session with the Session Recording Client it performs the following
   actions:

   o  The SRS is provisioned with a Unified Resource Identifier (URI)
      for the SRC, which is resolved through normal [RFC3263]
      procedures.

   o  Sends an INVITE request to the Session Recording Client

   o  Includes in the INVITE an indication that the session is
      established for the purpose of recording the associated media.
      Possible mechanisms for this include using the Require header or a
      media feature tag as defined in [RFC3840].

   o  Identifies the sessions that is to be recorded.  The actual
      mechanism of the identification depends on SRC policy.



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   o  If the Recording Session is to be started immediately then the
      Session Recording Client will include an SDP attribute of
      "a=recvonly" for each media line or "a=inactive" if it is not
      ready to receive the media

   If the SRS does not have prior knowledge of what media streams are
   available to be recorded it can make use of an offerless INVITE which
   allows the SRC to make the initial Session Description Protocol (SDP)
   offer.

3.2.3.  Pause/Resume Recording Session

   The SRS or the Session Recording Client may pause the recording by
   changing the SDP direction attribute to "inactive" and resume the
   recording by changing the direction back to "recvonly" or "sendonly".

3.2.4.  Media Stream Mixing

   In a basic session involving only audio there are typically two
   audio/RTP streams between the two UAs involved transporting media in
   each direction.  When recording this media the two streams may be
   mixed at the SRC before being transmitted to the SRS or it may be
   required that the media streams are not mixed and are sent to the SRS
   as two separate streams.  The case when media is mixed at the SRC is
   simple as only a single media stream is required to be sent to the
   SRS.  However in the case when the media streams are not mixed then
   the SDP offer sent to the SRS must describe two separate media
   streams.

3.2.5.  Media Transcoding

   The communication session (CS) and the recording session (RS) are
   negotiated separately using the standard SDP offer/answer exchange
   which may result in the SRC having to perform media transcoding
   between the two sessions.  If the SRC is not capable of performing
   media transcoding it may limit the media formats in the offer to the
   SRS depending on what media is negotiated on the CS or may limit what
   it includes in the offer on the CS if it has prior knowledge of the
   media formats supported by the SRS.  However typically the SRS will
   be a more capable device which can provide a wide range of media
   format options to the SRC and may also be able to make use of a media
   transcoder as detailed in [RFC5369].

3.3.  Recording Metadata







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3.3.1.  Contents of recording metadata

   The metadata model is defined in [I-D.ietf-siprec-metadata].

3.3.2.  Mechanisms for delivery of metadata to Session Recording Server

   The SRS obtains session recording metadata from the SRC.  The
   metadata is transported via SIP based mechanisms as specified in
   [I-D.ietf-siprec-protocol]

   It is also possible that metadata is transported via non SIP based
   mechanisms but these are considered out of scope.

   It is also possible to have RS session without the metadata, in such
   case SRS will be receiving it by some other means or not at all.

3.4.  Notifications to the Recorded User Agents

   Typically a user that is involved in a session that is to be recorded
   is notified by an announcement at the beginning of the session or may
   receive some warning tones within the media.  However the
   standardization of media recording protocols when using SIP enable an
   indication that the call is being recorded to be included in the SIP
   requests and responses associated with that communication session.

   It is the Session Recording Client that provides the notification to
   all SIP UAs for which it is replicating received media for the
   purpose of recording including the local user if the Session
   Recording Client is a SIP endpoint.

3.5.  Preventing the recording of a SIP session

   A Recording Aware UA may during the initial session establishment or
   during an established session provide an indication of their
   preference with regard to recording the media in the communication
   session.  The mechanism for this are specified in
   [I-D.ietf-siprec-protocol]


4.  IANA considerations

   This document has no actions for IANA.  This draft mentions SIP/SDP
   extensions.  The associated IANA considerations are addressed in
   [I-D.ietf-siprec-protocol] that defines them.







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5.  Security considerations

   The Recording Session is fundamentally a standard SIP dialog and
   media session and therefore makes use of existing SIP security
   mechanisms for securing the Recording Session and Recording Metadata.

   The intended use of this architecture is only for the case where the
   users are aware that they are being recorded, and the architecture
   provides the means for the Session Recording Client to notify users
   that they are being recorded.

   This architectural solution is not intended to support lawful
   intercept which in contrast requires that users are not informed.

   It is the responsibility of the Session Recording Server to protect
   the Replicated Media and Recording Metadata once it has been received
   and archived.  The mechanism for protecting the storage and retrieval
   from the SRS is out of scope of this work.

   Protection of the RS should not be weaker than protection of the CS,
   and may need to be stronger because the media is retransmitted
   (allowing more possibility for interception).  This applies to both
   the signaling and media paths.

   It is essential that the SRC will authenticate the SRS because the
   client must be certain that it is recording on the right recording
   system.  It is less important that the SRS authenticate the SRC, but
   implementations must have the ability to perform mutual
   authentication.

   In some environments, it is desirable to not decrypt and re-encrypt
   the media.  This means the same media encryption key is negotiated
   and used within the CS and RS.  If for any reason the media are
   decrypted on the CS, and are re-encrypted on the RS, a new key must
   be used.

   The retrieval mechanism for media recorded by this protocol is out of
   scope.  Implementations of retrieval mechanisms should consider the
   security implications carefully as the retriever is not usually a
   party to the call that was recorded.  Retrievers should be
   authenticated carefully.  The crypto suites on the retrieval should
   be no less strong than used on the RS, and may need to be stronger.


6.  Acknowledgements

   Thanks to John Elwell, Brian Rosen, Alan Johnson, Cullen Jennings,
   Hadriel Kaplan, Henry Lum, Paul Kyzivat, Parthasarathi R, Ram Mohan



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   R, Charles Eckel, Friso Feenstra and Dave Higton for their
   significant contributions and assistance with this document and
   Working Group, and to all the members of SIPREC WG mailing list for
   providing valuable input to this work.


7.  Informative References

   [RFC3261]  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.

   [RFC3263]  Rosenberg, J. and H. Schulzrinne, "Session Initiation
              Protocol (SIP): Locating SIP Servers", RFC 3263,
              June 2002.

   [RFC4566]  Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
              Description Protocol", RFC 4566, July 2006.

   [RFC6341]  Rehor, K., Portman, L., Hutton, A., and R. Jain, "Use
              Cases and Requirements for SIP-Based Media Recording
              (SIPREC)", RFC 6341, August 2011.

   [I-D.ietf-siprec-metadata]
              R, R., Ravindran, P., and P. Kyzivat, "Session Initiation
              Protocol (SIP) Recording Metadata",
              draft-ietf-siprec-metadata-10 (work in progress),
              November 2012.

   [I-D.ietf-siprec-protocol]
              Portman, L., Lum, H., Eckel, C., Johnston, A., and A.
              Hutton, "Session Recording Protocol",
              draft-ietf-siprec-protocol-08 (work in progress),
              October 2012.

   [RFC3840]  Rosenberg, J., Schulzrinne, H., and P. Kyzivat,
              "Indicating User Agent Capabilities in the Session
              Initiation Protocol (SIP)", RFC 3840, August 2004.

   [RFC4353]  Rosenberg, J., "A Framework for Conferencing with the
              Session Initiation Protocol (SIP)", RFC 4353,
              February 2006.

   [RFC4575]  Rosenberg, J., Schulzrinne, H., and O. Levin, "A Session
              Initiation Protocol (SIP) Event Package for Conference
              State", RFC 4575, August 2006.




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   [RFC5567]  Melanchuk, T., "An Architectural Framework for Media
              Server Control", RFC 5567, June 2009.

   [RFC5369]  Camarillo, G., "Framework for Transcoding with the Session
              Initiation Protocol (SIP)", RFC 5369, October 2008.

   [RFC2804]  IAB and IESG, "IETF Policy on Wiretapping", RFC 2804,
              May 2000.


Authors' Addresses

   Andrew Hutton (editor)
   Siemens Enterprise Communications
   Hofmannstrasse 51
   Munich D-81379
   Germany

   Email:  andrew.hutton@siemens-enterprise.com


   Leon Portman (editor)
   NICE Systems
   8 Hapnina
   Ra'anana  43017
   Israel

   Email:  leon.portman@gmail.com


   Rajnish Jain
   IPC Systems
   777 Commerce Drive
   Fairfield, CT  06825
   USA

   Email:  rajnish.jain@ipc.com


   Ken Rehor
   Cisco Systems, Inc.
   170 West Tasman Drive
   San Jose, CA  95134-1706
   USA

   Email:  krehor@cisco.com





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