path: root/doc/rfc/rfc7245.txt

Internet Engineering Task Force (IETF)                    A. Hutton, Ed.
Request for Comments: 7245                                         Unify
Category: Informational                                  L. Portman, Ed.
ISSN: 2070-1721                                             NICE Systems
                                                                 R. Jain
                                                             IPC Systems
                                                                K. Rehor
                                                     Cisco Systems, Inc.
                                                                May 2014


                  An Architecture for Media Recording
                 Using the Session Initiation Protocol

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 that is based
   on the Session Initiation Protocol (SIP).

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7245.











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Copyright Notice

   Copyright (c) 2014 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
   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 SRC . . . . . . . . . . . . . . . . . . .   5
       3.1.1.  B2BUA Acts as a SRC . . . . . . . . . . . . . . . . .   5
       3.1.2.  Endpoint Acts as SRC  . . . . . . . . . . . . . . . .   6
       3.1.3.  A SIP Proxy Cannot Be a SRC . . . . . . . . . . . . .   7
       3.1.4.  Interaction with MEDIACTRL  . . . . . . . . . . . . .   7
       3.1.5.  Interaction with Conference Focus . . . . . . . . . .   9
     3.2.  Establishing the Recording Session  . . . . . . . . . . .  10
       3.2.1.  SRC-Initiated Recording . . . . . . . . . . . . . . .  11
       3.2.2.  SRS-Initiated Recording . . . . . . . . . . . . . . .  11
       3.2.3.  Pause/Resume Recording Session  . . . . . . . . . . .  12
       3.2.4.  Media Stream Mixing . . . . . . . . . . . . . . . . .  12
       3.2.5.  Media Transcoding . . . . . . . . . . . . . . . . . .  12
       3.2.6.  Lossless Recording  . . . . . . . . . . . . . . . . .  12
     3.3.  Recording Metadata  . . . . . . . . . . . . . . . . . . .  13
       3.3.1.  Contents of Recording Metadata  . . . . . . . . . . .  13
       3.3.2.  Mechanisms for Delivery of Metadata to SRS  . . . . .  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  . . . . . . . . . . . . . . . . . . . . . .  15
   7.  Informative References  . . . . . . . . . . . . . . . . . . .  15









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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 as defined in "Use Cases and
   Requirements for SIP-Based Media Recording (SIPREC)" [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 the parties involved) relating to the
   Communication Session.

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

   This document only considers active recording, where the SRC
   purposefully streams media to a SRS.  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 SRC and the SRS
   uses the normal procedures for establishing INVITE-initiated dialogs
   as specified in [RFC3261] and uses the Session Description Protocol
   (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 SRS and is not buffered by
   the SRC to allow for real-time analysis of the media by the SRS.













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2.  Definitions

   The first four definitions are quoted from RFC 6341.

   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 recorded 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 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 CS.

   The following terms are defined by this document.

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








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   Recording Metadata:  The metadata describing the CS that is required
      by the SRS.  This will include, for example, the identities of
      users that participate in the CS and dialog state.  Typically,
      this metadata is archived with the Replicated Media at the SRS.
      The recording metadata is delivered in real-time to the SRS.

   Replicated Media:  A copy of the media that is associated with the
      CS, was created by the SRC, and was sent to the SRS.  It may
      contain all the media associated with the CS (e.g., audio and
      video) or just a subset (e.g., audio).  Replicated Media is part
      of the Recording Session.

3.  Session Recording Architecture

3.1.  Location of the SRC

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

3.1.1.  B2BUA Acts as a SRC

   A SIP Back-to-Back User Agent (B2BUA) that has access to the media to
   be recorded may act as an SRC.  The B2BUA may already be aware that a
   session needs to be recorded before the initial establishment of the
   CS, or the decision to record the session may occur after the session
   has been established.

   If the SRC makes the decision to initiate the RS, then it will do so
   by sending a SIP INVITE request 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 that identifies the session as
   being established for the purposes of recording and prevents the
   session from being accidentally rerouted to a UA that is not an SRS
   if the RS was initiated by the SRC or vice versa.

   The B2BUA/SRC is responsible for notifying the UAs involved in the CS
   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 CS 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

3.1.2.  Endpoint Acts as SRC

   A SIP endpoint / UA may act as a SRC.  In that case, the endpoint
   sends the Replicated Media to the SRS.

   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 SRS.

   If the SRS 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 for the SIP media recording architecture.













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          (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 SRC

   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.

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 architecture described in [RFC5567], 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]; therefore, when further decomposed, they may
   be made up of an AS that uses a MEDIACTRL interface to control an 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 source of the metadata and the termination point
   for RS SIP signaling.




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                                     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

                                                    +----------+
                 (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









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3.1.5.  Interaction with Conference Focus

   In the case of a centralized 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.

   The conference focus can either provide mixed Replicated Media or
   separate streams per conference participant (as depicted in
   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 that 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
   that 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 SRC or the SRS may initiate the Recording Session.

   It should be noted that the Recording Session is independent from the
   CS 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.  SRC-Initiated Recording

   When the SRC initiates the Recording Session for the purpose of
   conveying media to the SRS, it performs the following actions:

   o  Is provisioned with a Unified Resource Identifier (URI) for the
      SRS; the URI is resolved through normal [RFC3263] procedures.

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

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

   o  Includes an SDP attribute of "a=sendonly" for each media line if
      the Replicated Media is to be started immediately, or includes
      "a=inactive" if it is not ready to transmit the media.

   o  Replicates the media streams that are to be recorded and transmits
      the media to the SRS.

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

3.2.2.  SRS-Initiated Recording

   When the SRS initiates the media Recording Session with the SRC, it
   performs the following actions:

   o  Is provisioned with a Unified Resource Identifier (URI) for the
      SRC; the URI is resolved through normal [RFC3263] procedures.

   o  Sends an INVITE request to the SRC.

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

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

   o  Includes an SDP attribute of "a=recvonly" for each media line if
      the Recording Session is to be started immediately, or includes
      "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 SDP offer.



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3.2.3.  Pause/Resume Recording Session

   The SRS or the SRC 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 in transporting media
   in each direction.  When recording this media, the two streams may be
   mixed or not mixed at the SRC before being transmitted to the SRS.
   In the case when they are not mixed, two separate streams are sent to
   the SRS, and the SDP offer sent to the SRS must describe two separate
   media streams.  In the mixed case, a single mixed media stream is
   sent to the SRS.

3.2.5.  Media Transcoding

   The CS and the 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].

3.2.6.  Lossless Recording

   Session recording may be a regulatory requirement in certain
   communication environments.  Such environments may impose a
   requirement generally known as "lossless recording".  An overall
   solution for lossless recording may involve multiple layers of
   solutions.  Individual aspects of the solutions may range from
   administering networks for appropriate QoS, reliable transmission of
   recorded media, and perhaps certain SIPREC protocol-level
   capabilities in SRC and SRS.











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3.3.  Recording Metadata

3.3.1.  Contents of Recording Metadata

   The metadata model is defined in [REC-METADATA].

3.3.2.  Mechanisms for Delivery of Metadata to SRS

   The SRS obtains session recording metadata from the SRC.  The
   metadata is transported via SIP-based mechanisms as specified in
   [REC-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 an RS session without the metadata; in
   that case, the SRS will be receiving the metadata 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,
   SIPREC enables an indication that the call is being recorded to be
   included in the SIP requests and responses associated with that CS.

   The SRC provides the notification to all SIP UAs for which it is
   replicating received media for the purpose of recording.  If the SRC
   is acting as a SIP endpoint, as described in Section 3.1.2, then it
   also provides a notification to the local user.

3.5.  Preventing the Recording of a SIP Session

   During the initial session establishment or during an established
   session, a recording-aware UA may provide an indication of its
   preference with regard to recording the media in the CS.  The
   mechanisms for this are specified in [REC-PROTOCOL]

4.  IANA Considerations

   This document has no actions for IANA.  This document mentions
   SIP/SDP extensions.  The associated IANA considerations are addressed
   in [REC-PROTOCOL], which 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 SRC 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 SRS to protect the Replicated Media
   and Recording Metadata once it has been received and archived.  The
   stored content must be protected using a cipher at least as strong
   (or stronger) than the original content; however, the mechanism for
   protecting the storage and retrieval from the SRS is out of scope of
   this work.  The keys used to store the data must also be securely
   maintained by the SRS and should only be released, securely, to
   authorized parties.  How to secure these keys, properly authorize a
   receiving party, or securely distribute the keying material is also
   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 cryptosuites on the retrieval should be
   no less strong than those used on the RS and may need to be stronger.



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6.  Acknowledgements

   Thanks to John Elwell, Brian Rosen, Alan Johnson, Cullen Jennings,
   Hadriel Kaplan, Henry Lum, Paul Kyzivat, Parthasarathi R., Ram Mohan
   R., Charles Eckel, Friso Feenstra, and Dave Higton for their
   significant contributions and assistance with this document and
   working group.  Also, thanks to all the members of the 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.

   [REC-METADATA]
              Ravindranath, R., Ravindran, P., and P. Kyzivat, "Session
              Initiation Protocol (SIP) Recording Metadata", Work in
              Progress, February 2014.

   [REC-PROTOCOL]
              Portman, L., Lum, H., Eckel, C., Johnston, A., and A.
              Hutton, "Session Recording Protocol", Work in Progress,
              February 2014.

   [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.

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




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   [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)
   Unify
   Hofmannstrasse 51
   81359 Munich
   Germany

   EMail: andrew.hutton@unify.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@outlook.com


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

   EMail: krehor@cisco.com









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