SIPREC                                                   L. Portman, Ed.
Internet-Draft                                              NICE Systems
Intended status: Informational                               H. Lum, Ed.
Expires: January 9, 2012                         Genesys, Alcatel-Lucent
                                                             A. Johnston
                                                                   Avaya
                                                               A. Hutton
                                                      Siemens Enterprise
                                                          Communications
                                                            July 8, 2011


                       Session Recording Protocol
                    draft-portman-siprec-protocol-05

Abstract

   The Session Recording Protocol is used for establishing recording
   session and reporting of the metadata of the communication session.

   This document specifies the Session Recording Protocol.  The protocol
   is used between Session Recording Client (SRC) and Session Recording
   Server (SRS).

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 January 9, 2012.

Copyright Notice

   Copyright (c) 2011 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



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   (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  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Scope  . . . . . . . . . . . . . . . . . . . . . . . . . . . .  5
   4.  Overview of operations . . . . . . . . . . . . . . . . . . . .  5
     4.1.  Delivering recorded media  . . . . . . . . . . . . . . . .  5
     4.2.  Conference focus as an SRC . . . . . . . . . . . . . . . .  6
     4.3.  Delivering recording metadata  . . . . . . . . . . . . . .  7
   5.  SIP Extensions for Recording Session . . . . . . . . . . . . .  8
     5.1.  Callee Capabilities Extensions for SIP Recording . . . . .  9
       5.1.1.  src Feature Tag  . . . . . . . . . . . . . . . . . . .  9
       5.1.2.  srs Feature Tag  . . . . . . . . . . . . . . . . . . . 10
     5.2.  SDP handling . . . . . . . . . . . . . . . . . . . . . . . 10
     5.3.  RTP handling . . . . . . . . . . . . . . . . . . . . . . . 12
     5.4.  Metadata . . . . . . . . . . . . . . . . . . . . . . . . . 12
     5.5.  Requesting for metadata snapshot . . . . . . . . . . . . . 14
       5.5.1.  Formal Syntax  . . . . . . . . . . . . . . . . . . . . 15
     5.6.  Recording Pause and Resume . . . . . . . . . . . . . . . . 15
   6.  SIP Extensions for Recording-aware User Agents . . . . . . . . 15
     6.1.  Providing recording indication . . . . . . . . . . . . . . 15
     6.2.  Recording awareness  . . . . . . . . . . . . . . . . . . . 17
     6.3.  Recording preference . . . . . . . . . . . . . . . . . . . 17
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 18
     7.1.  New Content-Disposition Parameter Registrations  . . . . . 18
     7.2.  Media Type Registration  . . . . . . . . . . . . . . . . . 18
       7.2.1.  Registration of MIME Type application/rs-metadata  . . 18
       7.2.2.  Registration of MIME Type
               application/rs-metadata-request  . . . . . . . . . . . 19
     7.3.  Registration of record-aware Option Tag  . . . . . . . . . 19
     7.4.  SDP Attributes . . . . . . . . . . . . . . . . . . . . . . 19
       7.4.1.  'record' SDP Attribute . . . . . . . . . . . . . . . . 19
       7.4.2.  'recordpref' SDP Attribute . . . . . . . . . . . . . . 19
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 20
     8.1.  Authentication and Authorization . . . . . . . . . . . . . 20
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 20
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 20
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 21
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 22



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1.  Introduction

   Communication Session (CS) recording requires establishment of the
   recording session between communication system and recording system.
   In order to allow access to such recordings, the metadata about the
   CS shall be sent from the SRC to the SRS.

   The SIP-based Media Recording Requirements [I-D.ietf-siprec-req] list
   a set of requirements that need to be met by session recording
   protocols.  The Session Recording Protocol, which is specified in
   this document, meets these requirements.

   The Session Recording Protocol uses SIP as the protocol for session
   establishment with special attention to reducing size of the required
   SIP messages.  In addition, it is designed for future extendability
   and protocol version management to ensure backward compatability.

   The remainder of this document is organized as follows: Section 2
   defines the terminology used throughout this document, Section 3
   discusses the scope of the Session Recording Protocol, Section 4
   provides a non-normative overview of recording operations, Section 5
   provides normative description of SIP extensions for the Recording
   Session, Section 6 provides normative description of SIP extensions
   for recording-aware user agents.


2.  Definitions

   The core defintions are taken from the requirements document
   [I-D.ietf-siprec-req].

      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
      a logical function that typically archives media for extended
      durations of time and provides interfaces for search and retrieval
      of the archived media.  An SRS is typically implemented as a
      multi-port device that is capable of receiving media from several
      sources simultaneously.  An SRS is typically also 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



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      Application Server (AS).  This specification defines the term SRC
      such that all such SIP entities can be generically addressed under
      one definition.  The SRC itself or another entity working on its
      behalf (such as a SIP Application Server) may act as the source of
      the recording metadata.

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

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

   Metadata  Information that describes recorded media and the CS to
      which they relate.

   Session Recording Protocol  The set of SIP extensions that supports
      recording of Communication Sessions.

   Pause during a Communication Session:  The action of temporarily
      discontinuing the transmission and collection of RS media.

   Resume during a Communication Session:  The action of recommencing
      the transmission and collection of RS media.

   Figure 1 shows the relationship between the defintions.


     +-------------+                                      +-----------+
     |             |        Communication Session         |           |
     |     A       |<------------------------------------>|     B     |
     |             |                                      |           |
     +-------------+                                      +-----------+
     ..................................................................
     .                             Session                            .
     .                            Recording                           .
     .                             Client                             .
     ..................................................................
                                      |
                                      | Recording
                                      | Session
                                      |
                                      v
                               +------------+
                               |   Session  |
                               |  Recording |
                               |   Server   |
                               +------------+




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              Figure 1: Relationship between CS, SRC, SRS, and RS



3.  Scope

   The scope of the Session Recording Protocol includes the
   establishment of the recording sessions and the reporting of the
   metadata.  The following items, which is not an exhaustive list, do
   not represent the protcol itself and are considered out of the scope
   of the Session Recording Protocol:

   o  Recording policies that determine whether the CS should be
      recorded

   o  Retention policies that determine how long a recording is stored

   o  Searching and accessing the recorded media and metadata

   o  Delivering recording session metadata through non-SIP mechanism


4.  Overview of operations

   This section is informative and provides a description of recording
   operations.

   As mentioned in the architecture document
   [I-D.ietf-siprec-architecture], there are a couple of types of call
   flows based on the location of the Session Recording Client.  The
   following sample call flows provide a quick overview of the
   operations between the SRC and the SRS.

4.1.  Delivering recorded media

   When the SRC is deployed as a B2BUA, the SRC can route call requests
   from UA(A) to UA(B).  As a SIP B2BUA, the SRC has access to the media
   path between the user agents.  When the SRC is aware that it should
   be recording the conversation, the SRC may bridge the media between
   UA(A) and UA(B).  The SRC then establishes the Recording Session with
   the SRS and sends replicated media towards the SRS.

   An endpoint can also be acting as the SRC, and the endpoint itself
   will be establishing the Recording Session to the SRS.  Since the
   endpoint has access to the media in the Communication Session, the
   endpoint can send replicated media towards the SRS.

   The following is a sample call flow that shows the SRC establishing a



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   recording session towards the SRS.  The call flow is essentially
   identical when the SRC is a B2BUA or as the endpoint itself.  Note
   that the SRC can choose when to establish the Recording Session
   independent of the Communication Session, even though the following
   call flow suggests that the Recording Session is established after
   the Communication Session is established.


   UA A           SRC                    UA B                    SRS
    |(1)CS INVITE  |                       |                      |
    |------------->|                       |                      |
    |              |(2)CS INVITE           |                      |
    |              |---------------------->|                      |
    |              |               (3)OK   |                      |
    |              |<----------------------|                      |
    |        (4)OK |                       |                      |
    |<-------------|                       |                      |
    |              |(5)RS INVITE with SDP  |                      |
    |              |--------------------------------------------->|
    |              |                       |       (6)OK with SDP |
    |              |<---------------------------------------------|
    |(7)CS RTP     |                       |                      |
    |=============>|======================>|                      |
    |<=============|<======================|                      |
    |              |(8)RS RTP              |                      |
    |              |=============================================>|
    |              |=============================================>|
    |(9)CS BYE     |                       |                      |
    |------------->|                       |                      |
    |              |(10)CS BYE             |                      |
    |              |---------------------->|                      |
    |              |(11)RS BYE             |                      |
    |              |--------------------------------------------->|
    |              |                       |                      |

            Figure 2: Basic Recording Call flow


4.2.  Conference focus as an SRC

   A conference focus may also act as an SRC since it has access to all
   the media from each conference participant.  In this example, a user
   agent may REFER the conference focus to the SRS, and the SRC may
   choose to mix media streams from all participants as a single media
   stream towards the SRS.  In order to tell the conference focus to
   start a recording session to the SRS, the user agent can include the
   srs feature tag in the Refer-To header as per [RFC4508].




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    UA A                 Focus                 UA B                SRS
      |                  (SRC)                  |                   |
      |                    |                    |                   |
      |      (already in a conference)          |                   |
      |<==================>|<==================>|                   |
      |(1)REFER sip:Conf-ID Refer-To:<SRS>;srs  |                   |
      |------------------->|                                        |
      |(2)202 Accepted     |                                        |
      |<-------------------|                                        |
      |  (3)NOTIFY (Trying)|                                        |
      |<-------------------|                                        |
      |(4)200 OK           |                                        |
      |------------------->|                                        |
      |                    |(5)RS INVITE Contact:Conf-ID;isfocus    |
      |                    |--------------------------------------->|
      |                    |                              (6)200 OK |
      |                    |<---------------------------------------|
      |                    | (7)RTP (mixed or unmixed)              |
      |                    |=======================================>|
      |     (8)NOTIFY (OK) |                                        |
      |<-------------------|                                        |
      |(9)200 OK           |                                        |
      |------------------->|                                        |

     Figure 3: Recording call flow - SRC as a conference focus


4.3.  Delivering recording metadata

   Certain metadata, such as the attributes of the recorded media
   stream, are already included in the SDP of the recording session.
   This information is reused as part of the metadata.  The SRC may
   provide an initial metadata snapshot about recorded media streams in
   the initial INVITE content in the recording session.  Subsequent
   metadata updates can be represented as a stream of events in UPDATE
   or reINVITE requests sent by the SRC.  These metadata updates are
   normally incremental updates to the initial metadata snapshot to
   optimize on the size of updates, however, the SRC may also decide to
   send a new metadata snapshot anytime.

   The SRS also has the ability to sent a request to the SRC to request
   to receive a new metadata snapshot update when the SRS fails to
   understand the current stream of incremental updates for whatever
   reason (ie.  SRS gets a syntax/semantic error in metadata update, the
   SRS crashes and restarts), and the SRS may attach a reason along with
   the snapshot request.  This request allows both SRC and SRS to
   restart the states with a new metadata snapshot so that further
   metadata incremental updates will be based on the latest metadata



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   snapshot.  Similar to the metadata content, the metadata snapshot
   request is transported as content in UPDATE or INVITE sent by the SRS
   in the recording session.


     SRC                                                   SRS
      |                                                     |
      |(1) INVITE (metadata snapshot)                       |
      |---------------------------------------------------->|
      |                                           (2)200 OK |
      |<----------------------------------------------------|
      |(3) ACK                                              |
      |---------------------------------------------------->|
      |(4) RTP                                              |
      |====================================================>|
      |(5) UPDATE (metadata update 1)                       |
      |---------------------------------------------------->|
      |                                          (6) 200 OK |
      |<----------------------------------------------------|
      |(7) UPDATE (metadata update 2)                       |
      |---------------------------------------------------->|
      |                                          (8) 200 OK |
      |<----------------------------------------------------|
      |              (9) UPDATE (metadata snapshot request) |
      |<----------------------------------------------------|
      |                   (10) 200 OK (metadata snapshot 2) |
      |---------------------------------------------------->|
      |(11) UPDATE (metadata update 1 based on snapshot 2)  |
      |---------------------------------------------------->|
      |                                         (12) 200 OK |
      |<----------------------------------------------------|

          Figure 4: Delivering metadata via SIP UPDATE


   In some cases session metadata can be conveyed through non-SIP
   mechanism such as HTTP or JTAPI.  These non-SIP mechanisms are
   considered out of the scope of the Session Recording Protocol,
   however, it is envisoned that a link with a URI can be provided in
   the recording session INVITE message so that the SRS can access the
   session metadata via the URI provided that the SRS supports the type
   of URI.


5.  SIP Extensions for Recording Session

   The following sections describe SIP extensions for the Recording
   Session.



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   The From header must contain the identity of the SRC.  Participants
   information is not recorded in the From or To header; they are
   included in the metadata information.

   Note that a recording session does not have to live within the scope
   of a single communication session.  As outline in REQ-005 of
   [I-D.ietf-siprec-req], the recording session can be established in
   the absence of a communication session.  In this case, the SRC must
   pre-allocate a recorded media stream and offer an SDP with at least
   one m= line to establish a persistent recording session.  When the
   actual call arrives, the SRC can map recorded media stream to
   participant media and minimize media clipping.

   Recorded media from multiple communication sessions may be handled in
   a single recording session.  The SRC provides a reference of each
   recorded media stream to the metadata described in the next section.

5.1.  Callee Capabilities Extensions for SIP Recording

   This section discusses how the callee capabilities defined in
   [RFC3840] can be extended for SIP call recording.

   SIP Callee Capabilities defines feature tags which are used to
   represent characteristics and capabilities of a UA.  From RFC 3840:

      "Capability and characteristic information about a UA is carried
      as parameters of the Contact header field.  These parameters can
      be used within REGISTER requests and responses, OPTIONS responses,
      and requests and responses that create dialogs (such as INVITE)."

   Note that feature tags are also used in dialog modifying requests and
   responses such as re-INVITE and responses to a re-INVITE, and UPDATE.
   The 'isfocus' feature tag, defined in [RFC4579] is similar
   semantically to this case: it indicates that the UA is acting as a
   SIP conference focus, and is performing a specific action (mixing) on
   the resulting media stream.  This information is available from
   OPTIONS queries, dialog package notifications, and the SIP
   registration event package.

   We propose the definition of two new feature tags: 'src' and 'srs'.

5.1.1.  src Feature Tag

   The 'src' feature tag is used in Contact URIs by the Session
   Recording Client (SRC) related to recording sessions.  A Session
   Recording Server uses the presence of this feature tag in dialog
   creating and modifying requests and responses to confirm that the
   dialog being created is for the purpose of a Recording Session.  In



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   addition, a registrar could discover that a UA is an SRC based on the
   presence of this feature tag in a registration.  Other SIP Recording
   extensions and behaviors can be triggered by the presence of this
   feature tag.

   Note that we could use a single feature tag, such as 'recording' used
   by either an SRC or SRS to identify that the session is a recording
   session.  However, due to the differences in functionality and
   behavior between an SRC and SRS, using only one feature tag for both
   is not ideal.  For instance, if a routing mistake resulted in a
   request from a SRC being routed back to another SRC, if only one
   feature tag were defined, they would not know right away about the
   error and could become confused.  With separate feature tags, they
   would realize the error immediately and terminate the session.  Also,
   call logs would clearly show the routing error.

5.1.2.  srs Feature Tag

   The 'srs' feature tag is used in Contact URIs by the Session
   Recording Server (SRS) related to recording sessions.  A Session
   Recording Client uses the presence of this feature tag in dialog
   creating and modifying requests and responses to confirm that the
   dialog being created is for the purpose of a Recording Session
   (REQ-30).  In addition, a registrar could discover that a UA is an
   SRS based on the presence of this feature tag in a registration.
   Other SIP Recording extensions and behaviors can be triggered by the
   presence of this feature tag.

   To ensure a recording session is redirected to an SRS, an SRC can
   utilize the SIP Caller Preferences extensions, defined in [RFC3841].
   The presence of a Accept-Contact: *;sip.srs allows a UA to request
   that the INVITE be routed to an SRS.  Note that to be completely
   sure, the SRC would need to include a Require: prefs header field
   field in the request.

5.2.  SDP handling

   Following the SDP offer/answer model in [RFC3264], this section
   describes the conventions used in the recording session for SDP
   handling.

   SRC must provide an SDP offer in the initial INVITE to the SRS.  SRC
   can include one or more media streams to the SRS.  The SRS must
   respond with the same number of media descriptors in the SDP body of
   the 200 OK.

   The SRC should use a=sendonly attribute as the SRC does not expect to
   receive media from the SRS.  As SRS only receives RTP streams from



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   SRC, the 200 OK response will normally contain SDP with a=recvonly
   attribute.

   Since the SRC may send recorded media of different participants (or
   even mixed streams) to the SRS, the SDP must provide a label on each
   media stream in order to identify the recorded stream with the rest
   of the metadata.  The a=label attribute [RFC4574] will be used to
   identify each recorded media stream, and the label name is mapped to
   the Media Stream Reference in the metadata in
   [I-D.ietf-siprec-metadata].  Note that a participant may have
   multiple streams (audio and video) and each stream is labeled
   separately.


              v=0
              o=SRS 0 0 IN IP4 172.22.3.8
              s=SRS
              c=IN IP4 172.22.3.8
              t=0 0
              m=audio 12241 RTP/AVP 0 4 8
              a=sendonly
              a=label:1
              m=audio 12242 RTP/AVP 98
              a=rtpmap:98 H264/90000
              a=fmtp:98 ...
              a=sendonly
              a=label:2
              m=audio 12243 RTP/AVP 0 4 8
              a=sendonly
              a=label:3
              m=audio 12244 RTP/AVP 98
              a=rtpmap:98 H264/90000
              a=fmtp:98 ...
              a=sendonly
              a=label:4

       Figure 6: Sample SDP with audio and video streams


   To remove a recorded media stream from the recording session, send a
   reINVITE and set the port to zero in the m= line.

   To add a recorded media stream, send a reINVITE and add a new m=
   line.

   The SRS may respond with a=inactive attribute as part of the SDP in
   the 200 OK response when the SRS is not ready to receive recorded
   media.  The SRS can send re-INVITE to update the SDP with a=recvonly



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   when it is ready to receive media.

   The following sequence diagram shows an example of SRS responds with
   SDP that contain a=inactive, and then later update media information
   update with re-INVITE.


     SRC                                                   SRS
      |                                                     |
      |(1) INVITE (SDP offer)                               |
      |---------------------------------------------------->|
      |                         (2)200 OK with SDP inactive |
      |<----------------------------------------------------|
      |(3) ACK                                              |
      |---------------------------------------------------->|
      |                      ...                            |
      |                     (4) re-INVITE with SDP recvonly |
      |<----------------------------------------------------|
      |(5)200 OK with SDP sendonly                          |
      |---------------------------------------------------->|
      |                                             (6) ACK |
      |<----------------------------------------------------|
      |(7) RTP                                              |
      |====================================================>|
      |                      ...                            |
      |(8) BYE                                              |
      |---------------------------------------------------->|
      |                                             (9) OK  |
      |<----------------------------------------------------|

              Figure 7: SRS to offer with a=inactive


5.3.  RTP handling

   [This is a placeholder section to specify any protocol impacts or
   recommendations for RTP usage in the session recording protocol.  The
   details are listed in [I-D.eckel-siprec-rtp-rec]]

5.4.  Metadata

   The format of the full metadata will be described as part of the
   mechanism in [I-D.ietf-siprec-metadata].

   As mentioned in the previous section, the SDP of the recording
   session is the metadata for all recorded media streams.  The label
   attribute contains a reference to the rest of the metadata
   information.



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   For all basic metadata information such as communication session,
   participants, call identifiers and direction, they can be included in
   the initial INVITE request sent by the SRC.  Metadata can be included
   as content in the INVITE or UPDATE request.  A new "disposition-type"
   of Content-Disposition is defined for this purpose and the value is
   "recording-session".

   The following SIP example for RS establishment between SRC and SRS
   with metadata as content.


     INVITE sip:97753210@10.240.3.10:5060 SIP/2.0
     From: <sip:2000@10.226.240.3>;tag=35e195d2-947d-4585-946f-098392474
     To: <sip:Recorder@10.240.3.10>
     Call-ID: d253c800-b0d1ea39-4a7dd-3f0e20a@10.226.240.3
     CSeq: 101 INVITE
     Date: Thu, 26 Nov 2009 02:38:49 GMT
     Supported: timer
     Supported: replaces
     User-Agent: B2BUA
     Max-Forwards: 70
     Allow: INVITE,OPTIONS,INFO,BYE,CANCEL,ACK,PRACK,UPDATE,
       REFER,SUBSCRIBE,NOTIFY,PUBLISH
     Allow-Events: presence,kpml
         Min-SE: 90
     Contact: <sip:2000@10.226.240.3:5060;transport=tcp>;isfocus;src
     Via: SIP/2.0/TCP 10.226.240.3:5060;branch=z9hG4bKdf6b622b648d9
     Session-Expires: 1800
     Content-Type: multipart/mixed;boundary=foobar
     Content-Length: [length]

     --foobar
     Content-Type: application/sdp

     v=0
     o=SRS 0 0 IN IP4 10.226.240.3
     c=IN IP4 10.226.240.3
     t=0 0
     m=audio 12241 RTP/AVP 0 4 8
     a=sendonly
     a=label:1

     --foobar
     Content-Type: application/rs-metadata
     Content-Disposition: recording-session

     [metadata content]




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         Figure 8: Sample INVITE request for the recording session


   Further updates to recording metadata can be deliverd as a sequence
   events reported in SIP UPDATE or reINVITE requests and the SRS must
   receive the sequence of events in order.  Since there can only be a
   single INVITE or UPDATE transaction happening at a time within a SIP
   dialog, using sequence number CSeq in the dialog can be a reliable
   way for the SRS to identify the receipt of the next metadata update.

   At any time during Recording Session, the SRC may send a new metadata
   snapshot in SIP UPDATE or reINVITE request.  All subsequent metadata
   updates will be based on the new metadata snapshot.

5.5.  Requesting for metadata snapshot

   The SRS may send a request for metadata snapshot any time after the
   Recording Session has been established.  Typically, the SRS sends
   such as request in the case where the SRS is failing to process
   further metadata incremental updates.  Failure scenarios can include
   failure to parse metadata information (syntax error), failure to
   match metadata information with the current metadata snapshot
   (semantic error), or failure at the SRS.

   Similar to delivering metadata, the SRS sends the metadata snapshot
   request as content in UPDATE or INVITE requests or responses.  The
   same disposition type "recording-session" is used to note that the
   content represents content sent by the SRS.  The format of the
   content is application/rs-metadata-request, and the body format is
   chosen to be a simple text-based format with header and values.  The
   following shows an example:


       SRS-Status: SRS failure


   The SRS MUST include the reason why a metadata snapshot request is
   being made to the SRC in the SRS-Status header.  This header is free
   form text to allow the SRS to provide a descriptive reason.  The body
   format also allows additional extension headers to be included by the
   SRS in the snapshot request to convey additional information to the
   SRC.

   When the SRC receives the request for a metadata snapshot, the SRC
   may provide the metadata snapshot in the response or as a separate
   INVITE/UPDATE transaction.  All subsequent metadata updates sent by
   the SRC MUST be based on the new metadata snapshot.




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5.5.1.  Formal Syntax

   The formal syntax for the application/rs-metadata-request MIME is
   described below using the augmented Backus-Naur Form (BNF) as
   described in [RFC2234].

   snapshot-request = srs-status-line CRLF [ *opt-srs-headers ]

   srs-status-line = "SRS-Status" HCOLON srs-status

   srs-status = [TEXT-UTF8-TRIM]

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

5.6.  Recording Pause and Resume

   To temporarily discontinue streaming and collection of recorded media
   from the SRC to the SRS, the SRC must send a reINVITE and set
   a=inactive for each recorded media stream to be paused.

   To resume streaming and collection of recorded media, the SRC must
   send a reINVITE and set a=sendonly for each recorded media stream to
   resume.

   Note that when a media stream in the CS is muted/unmuted, this
   information may be conveyed in the metadata by the SRC.  The SRC
   should not modify the recorded media stream with a=inactive for mute
   since this operation is reserved for pausing the RS media.


6.  SIP Extensions for Recording-aware User Agents

   The following sections describe SIP extensions for recording-aware
   UA.

6.1.  Providing recording indication

   While there are existing mechanisms for providing an indication that
   a CS is being recorded, these mechanisms are usually delivered on the
   CS media streams such as playing an in-band tone or an announcement
   to the participants.  A new SDP attribute is introduced to allow a
   recording-aware UA to render recording indication at the user
   interface.

   The 'record' SDP attribute appears at the media level, and may appear
   in either SDP offer or answer.  The recording indication applies to
   the specified media stream only, for example, the audio portion of
   the call may be recorded in a audio/video call.  The following is the



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   ABNF of the 'record' attribute:

      record-attr = "a=record:" indication

      indication = "on" / "off" / "paused"

   on Recording is in progress.

   off  No recording is in progress.

   paused  Recording is in progress by media is paused.

   The recording attribute is a declaration by the endpoints in the
   session to indicate whether recording is taking place.  For example,
   if a UA (A) is initiating a call to UA (B) and UA (A) is also an SRC
   that is performing the recording, then UA (A) provides the recording
   indication in the SDP offer with a=record:on.  When UA (B) receives
   the SDP offer, UA (B) will see that recording is happening on the
   other endpoint of this session.  If UA (B) does not wish to perform
   recording itself, UA (B) provides the recording indication as
   a=record:off in the SDP answer.

   Whenever the recording indication needs to change, such as
   termination of recording, then the UA must initiate a reINVITE to
   update the SDP attribute to a=record:off.  The following call flow
   shows an example of the offer/answer with the recording indication
   attribute.


    UA A                                                   UA B
    (SRC)                                                   |
      |                                                     |
      |                [SRC recording starts]               |
      |(1) INVITE (SDP offer + a=record:on)                 |
      |---------------------------------------------------->|
      |                  200 OK (SDP answer + a=record:off) |
      |<----------------------------------------------------|
      |(3) ACK                                              |
      |---------------------------------------------------->|
      |(4) RTP                                              |
      |<===================================================>|
      |               [SRC stops recording]                 |
      |(5) re-INVITE (SDP + a=record:off)                   |
      |---------------------------------------------------->|
      |                      (6) 200 OK (SDP + a=record:off)|
      |<----------------------------------------------------|
      |                                             (6) ACK |
      |---------------------------------------------------->|



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              Figure 9: Recording indication example


   If a call is traversed through one or more SIP B2BUA, and it happens
   that there are more than one SRC in the call path, the recording
   indication attribute does not provide any hint as to which SRC is
   performing the recording, meaning the endpoint only knows that the
   call is being recorded.  This attribute is also not used as an
   indication to negotiate which SRC in the call path will perform
   recording if there are multiple SRCs in the call path.

6.2.  Recording awareness

   A recording-aware UA may indicate that it can accept reporting of
   recording indication in media level SDP provided in the previous
   section.  A new option tag "record-aware" is introduced to indicate
   such awareness.

   A UA that has indicated recording awareness by including the record-
   aware option tag in a transmitted Supported header field MUST provide
   at its user interface an indication whether recording is on or off
   for a given medium based on the most recently received a=record SDP
   attribute for that medium.

   Some user agents that are automatons (eg.  IVR, media server, PSTN
   gateway) may not have an user interface to render recording
   indication.  When such user agent indicates recording awareness,
   these UA may render recording indication through other means, such as
   passing an inband tone on the PSTN gateway, putting the recording
   indication in a log file, or raising an application event in a
   VoiceXML dialog.  These user agents may also choose not to indicate
   recording awareness, thereby relying on whatever mechansim an SRC
   chooses to indicate recording, such as playing a tone inband.

   When a UA has not indicated that it is recording aware, an SRC must
   provide recording indications, where SRC is required to do so based
   on policies, through other means such as playing a tone inband.

6.3.  Recording preference

   A recording-aware UA involved in a CS may request the CS to be
   recorded or not recorded.  This indication of recording preference
   may be sent at session establishment time or during the session.

   A new SDP attribute "recordpref" is introduced.  The SDP attribute
   appears at the media level and can only appear in an SDP offer.  The
   recording indication applies to the specified media stream only.  The
   following is the ABNF of the recordpref attribute:



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      recordpref-attr = "a=recordpref:" pref

      pref = "on" / "off" / "pause" / "nopreference"

   on Request for recording if it has not already been started.  If the
      recording is currently paused, request to resume recording.

   off  Request for no recording.  If recording has already been
      started, then this preference indicates a request to stop
      recording.

   pause  Request to pause recording if recording is currently in
      progress.

   nopreference  To indicate that the UA has no preference on recording.
      While the absence of this attribute indirectly implies the lack of
      preference, using this value allows the UA to explicitly state no
      preference to being recorded.


7.  IANA Considerations

7.1.  New Content-Disposition Parameter Registrations

   This document registers a new "disposition-type" value in Content-
   Disposition header: recording-session.

   recording-session the body describes the metadata information about
   the recording session

7.2.  Media Type Registration

7.2.1.  Registration of MIME Type application/rs-metadata

   This document registers the application/rs-metadata MIME media type
   in order to describe the recording session metadata.  This media type
   is defined by the following information:

   Media type name: application

   Media subtype name: rs-metadata

   Required parameters: none

   Options parameters: none






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7.2.2.  Registration of MIME Type application/rs-metadata-request

   This document registers the application/rs-metadata-request MIME
   media type in order to describe a recording session metadata snapshot
   request.  This media type is defined by the following information:

   Media type name: application

   Media subtype name: rs-metadata-request

   Required parameters: none

   Options parameters: none

7.3.  Registration of record-aware Option Tag

   This document registers the "record-aware" option tag.

   Name: record-aware

   Description: This option tag is to indicate the ability for the user
   agent to receive recording indicators in media level SDP.  When
   present in a Supported header, it indicates that the UA can receive
   recording indicators in media level SDP.

7.4.  SDP Attributes

   This document registers the following new SDP attributes.

7.4.1.  'record' SDP Attribute

   Attribute name: record

   Long form attribute name: Recording Indication

   Type of attribute: media level

   Subject to charset: no

   This attribute provides the recording indication for the session or
   media stream.

   Allowed attribute values: on, off, paused

7.4.2.  'recordpref' SDP Attribute

   Attribute name: recordpref




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   Long form attribute name: Recording Preference

   Type of attribute: media level

   Subject to charset: no

   This attribute provides the recording indication for the session or
   media stream.

   Allowed attribute values: on, off, pause, nopreference


8.  Security Considerations

   The recording session is fundamentally a standard SIP dialog
   [RFC3261], therefore, the recording session can reuse any of the
   existing SIP security mechanism available for securing the recorded
   media as well as metadata.

8.1.  Authentication and Authorization

   The recording session reuses the SIP mechanism to challenge requests
   that is based on HTTP authentication.  The mechanism relies on 401
   and 407 SIP responses as well as other SIP header fields for carrying
   challenges and credentials.

   The SRS may have its own set of recording policies to authorize
   recording requests from the SRC.  The use of recording policies is
   outside the scope of the Session Recording Protocol.


9.  References

9.1.  Normative References

   [I-D.ietf-siprec-metadata]
              R, R., R, P., and P. Kyzivat, "Session Initiation Protocol
              (SIP) Recording Metadata", draft-ietf-siprec-metadata-03
              (work in progress), July 2011.

   [I-D.ietf-siprec-req]
              Rehor, K., Portman, L., Hutton, A., and R. Jain, "Use
              Cases and Requirements for SIP-based Media Recording
              (SIPREC)", draft-ietf-siprec-req-12 (work in progress),
              June 2011.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.



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   [RFC2234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", RFC 2234, November 1997.

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

   [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.

   [RFC3264]  Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
              with Session Description Protocol (SDP)", RFC 3264,
              June 2002.

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

   [RFC3841]  Rosenberg, J., Schulzrinne, H., and P. Kyzivat, "Caller
              Preferences for the Session Initiation Protocol (SIP)",
              RFC 3841, August 2004.

   [RFC4574]  Levin, O. and G. Camarillo, "The Session Description
              Protocol (SDP) Label Attribute", RFC 4574, August 2006.

9.2.  Informative References

   [I-D.eckel-siprec-rtp-rec]
              Eckel, C., "Real-time Transport Protocol (RTP)
              Recommendations for SIPREC", draft-eckel-siprec-rtp-rec-01
              (work in progress), June 2011.

   [I-D.ietf-siprec-architecture]
              Hutton, A., Portman, L., Jain, R., and K. Rehor, "An
              Architecture for Media Recording using the Session
              Initiation Protocol", draft-ietf-siprec-architecture-02
              (work in progress), April 2011.

   [RFC4508]  Levin, O. and A. Johnston, "Conveying Feature Tags with
              the Session Initiation Protocol (SIP) REFER Method",
              RFC 4508, May 2006.

   [RFC4579]  Johnston, A. and O. Levin, "Session Initiation Protocol
              (SIP) Call Control - Conferencing for User Agents",
              BCP 119, RFC 4579, August 2006.





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Authors' Addresses

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

   Email: leon.portman@nice.com


   Henry Lum (editor)
   Genesys, Alcatel-Lucent
   1380 Rodick Road, Suite 200
   Markham, Ontario  L3R4G5
   Canada

   Email: henry.lum@genesyslab.com


   Alan Johnston
   Avaya
   St. Louis, MO  63124

   Email: alan.b.johnston@gmail.com


   Andrew Hutton
   Siemens Enterprise Communications

   Email: andrew.hutton@siemens-enterprise.com




















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