SIPREC                                                   L. Portman, Ed.
Internet-Draft                                              NICE Systems
Intended status: Informational                                    H. Lum
Expires: September 2, 2011                       Genesys, Alcatel-Lucent
                                                             A. Johnston
                                                                   Avaya
                                                               A. Hutton
                                       Siemens Enterprise Communications
                                                           March 1, 2011


            The SIP-based Media Recording Protocol (SIPREC)
                    draft-portman-siprec-protocol-03

Abstract

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

   This document specifies the SIPREC Protocol (SIPREC).  SIPREC 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
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   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
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   This Internet-Draft will expire on September 2, 2011.

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
   (http://trustee.ietf.org/license-info) in effect on the date of



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


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  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 . . . . . . . . . . . . .  9
     5.1.  Callee Capabilities Extensions for SIP Recording . . . . .  9
       5.1.1.  src Feature Tag  . . . . . . . . . . . . . . . . . . . 10
       5.1.2.  srs Feature Tag  . . . . . . . . . . . . . . . . . . . 10
     5.2.  SDP handling . . . . . . . . . . . . . . . . . . . . . . . 10
     5.3.  Metadata . . . . . . . . . . . . . . . . . . . . . . . . . 12
       5.3.1.  Requesting for metadata snapshot . . . . . . . . . . . 14
       5.3.2.  Recording Pause and Resume . . . . . . . . . . . . . . 14
   6.  SIP Extensions for Recording-aware User Agents . . . . . . . . 15
     6.1.  Recording awareness  . . . . . . . . . . . . . . . . . . . 15
     6.2.  Providing recording indication . . . . . . . . . . . . . . 15
     6.3.  Recording preference . . . . . . . . . . . . . . . . . . . 16
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 16
     7.1.  New Content-Disposition Parameter Registrations  . . . . . 16
     7.2.  Media Type Registration  . . . . . . . . . . . . . . . . . 16
       7.2.1.  Registration of MIME Type application/rs-metadata  . . 16
       7.2.2.  Registration of MIME Type
               application/rs-metadata-request  . . . . . . . . . . . 17
     7.3.  Info Package . . . . . . . . . . . . . . . . . . . . . . . 17
     7.4.  SDP Attributes . . . . . . . . . . . . . . . . . . . . . . 17
       7.4.1.  'recording-aware' SDP Attribute  . . . . . . . . . . . 17
       7.4.2.  'record' SDP Attribute . . . . . . . . . . . . . . . . 18
       7.4.3.  'recordpref' SDP Attribute . . . . . . . . . . . . . . 18
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 18
     8.1.  Authentication and Authorization . . . . . . . . . . . . . 18
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 19
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 19
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 19
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20





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1.  Introduction

   Communication Session recording requires establishment of the
   recording session between communication system and recording system.
   In order to allow access to such recordings, information about the
   communication session (metadata) is also shared between SRC and SRS.

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

   The SIPREC 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 SIPREC (i.e., which tasks fall within the
   scope of SIPREC and which ones are performed using different
   mechanisms), Section 4 provides a non-normative overview of SIPREC
   operation, and subsequent sections provide the normative
   specification of SIPREC.


2.  Definitions

   The core SIPREC 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.

   SIPREC  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 SIPREC 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 SIPREC
   protcol itself and are considered out of the scope of the SIPREC
   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 SIPREC
   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 basic call flow shows the SRC establishing a recording



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   session towards the SRS.  The call flow is essentially identical when
   the SRC is a B2BUA or as the endpoint itself.


   UA A           SRC                    UA B                    SRS
    |(1)CS INVITE  |                       |                      |
    |------------->|                       |                      |
    |              |(2)CS INVITE           |                      |
    |              |---------------------->|                      |
    |              |               (3)OK   |                      |
    |              |<----------------------|                      |
    |        (4)OK |                       |                      |
    |<-------------|                       |                      |
    |              |(5)RS INVITE (CallId + Participants) 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)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.  The metadata snapshot request will be provided as an INFO
   package [RFC6086] and sent as mid-dialog messages within the
   recording session by the SRS.


     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) INFO (metadata snapshot request) |
      |<----------------------------------------------------|
      |                                         (10) 200 OK |
      |---------------------------------------------------->|
      |(11) UPDATE (metadata snapshot 2)                    |
      |---------------------------------------------------->|
      |                                         (12) 200 OK |
      |<----------------------------------------------------|
      |(13) UPDATE (metadata update 1 based on snapshot 2)  |
      |---------------------------------------------------->|
      |                                         (14) 200 OK |
      |<----------------------------------------------------|

          Figure 4: Delivering metadata via SIP INFO


   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 SIPREC 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.






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5.  SIP Extensions for Recording Session

   The following sections describe SIP extensions for the Recording
   Session.

   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 have 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
   offer an SDP with zero m= lines.

   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.

   The SRC must be able to accept re-INVITE from SRS with the updated
   SDP as part of the session timer mechanism.

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'.






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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
   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

   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.




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   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
   SRS, 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 will be used
   as the reference for the 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



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   media.  The SRS can send re-INVITE to update the SDP with a=recvonly
   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 (no offer)                                |
      |---------------------------------------------------->|
      |                         (2)200 OK with SDP inactive |
      |<----------------------------------------------------|
      |(3) ACK with SDP inactive                            |
      |---------------------------------------------------->|
      |                      ...                            |
      |                     (4) re-INVITE with SDP recvonly |
      |<----------------------------------------------------|
      |(5)200 OK with SDP sendonly                          |
      |---------------------------------------------------->|
      |                                  (6) ACK with SDP   |
      |<----------------------------------------------------|
      |(7) RTP                                              |
      |====================================================>|
      |                      ...                            |
      |(8) BYE                                              |
      |---------------------------------------------------->|
      |                                             (9) OK  |
      |<----------------------------------------------------|

              Figure 7: SRS to offer with a=inactive


5.3.  Metadata

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

   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"



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   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]

         Figure 8: Sample INVITE request for the recording session


   Further updates to recording metadata can be deliverd as a sequence



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   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.

5.3.1.  Requesting for metadata snapshot

   The SRS may send an INFO request to request for a metadata snapshot
   any time after the Recording Session has been established.  The INFO
   package is "recording-session-srs".  The format of the metadata
   snapshot request is described in [I-D.ram-siprec-metadata].  This
   request allows the SRS to request for a metadata snapshot from the
   SRC, and is used in scenarios 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.  The SRS should include the
   reason why a snapshot request is being made.

   When the SRC receives the INFO request for a metadata snapshot, the
   SRC should wait for any existing dialog modifying transactions to
   complete and then send a UPDATE request with a new metadata snapshot.
   All subsequent metadata updates sent by the SRC will be based on the
   new metadata snapshot.

5.3.2.  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 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.







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6.  SIP Extensions for Recording-aware User Agents

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

6.1.  Recording awareness

   A recording-aware UA MUST include the 'a=recording-aware' SDP
   attribute to indicate that the user agent can accept other recording
   SDP attributes listed in this section.  This is a session level
   attribute.

   If the offerer is recording-aware and the answerer is also recording-
   aware, the answer MUST contain the recording-aware attribute.

   If the offerer is not recording-aware, the answerer MUST be prepared
   to provide recording indication through other existing mechanisms
   such as in-band media.

6.2.  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 may appear at the session level or the
   media level, and may appear in either SDP offer or answer.  When the
   attribute is set at the session level, then the recording indication
   applies to all media streams within the session.  When the attribute
   is set at the media level, then the recording indication applies to
   the specified media stream only.  The following is the 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.






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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
   may appear at the session level or the media level and can only
   appear in an SDP offer.  When the attribute is set at the session
   level, then the recording indication applies to all media streams
   within the session.  When the attribute is set at the media level,
   then the recording indication applies to the specified media stream
   only.  The following is the ABNF of the recordpref attribute:

      recordpref-attr = "a=recordpref:" pref

      pref = "record" / "norecord" / "pause" / "resume"

   record  Request for recording if it has not already been started.

   norecord  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.

   resume  Request to resume recording if recording is currently paused.


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:




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   Media type name: application

   Media subtype name: rs-metadata

   Required parameters: none

   Options parameters: none

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.  Info Package

   This document registers a new INFO package for transpoting metadata
   requests from the SRS within a Recording Session.

   Info Package Name: recording-session-srs

   Reference: [RFCXXXX]

7.4.  SDP Attributes

   This document registers the following new SDP attributes.

7.4.1.  'recording-aware' SDP Attribute

   Attribute name: recording-aware

   Type of attribute: session level

   Subject to charset: no

   This attribute indicates that the user agent supports recording
   extensions.  This is a property attribute which does not take a
   value.





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7.4.2.  'record' SDP Attribute

   Attribute name: record

   Long form attribute name: Recording Indication

   Type of attribute: session level or media level

   Subject to charset: no

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

   Allowed attribute values: on, off, paused

7.4.3.  'recordpref' SDP Attribute

   Attribute name: recordpref

   Long form attribute name: Recording Preference

   Type of attribute: session level or media level

   Subject to charset: no

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

   Allowed attribute values: nopref, record, norecord, pause, resume


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 SIPREC protocol.



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9.  References

9.1.  Normative References

   [I-D.ietf-siprec-req]
              Rehor, K., Portman, L., Hutton, A., and R. Jain,
              "Requirements for SIP-based Media Recording (SIPREC)",
              draft-ietf-siprec-req-06 (work in progress),
              December 2010.

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

   [RFC3265]  Roach, A., "Session Initiation Protocol (SIP)-Specific
              Event Notification", RFC 3265, 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.

   [RFC6086]  Holmberg, C., Burger, E., and H. Kaplan, "Session
              Initiation Protocol (SIP) INFO Method and Package
              Framework", RFC 6086, January 2011.

9.2.  Informative References

   [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-01
              (work in progress), October 2010.

   [I-D.ram-siprec-metadata]



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              R, R., R, P., and P. Kyzivat, "Session Initiation Protocol
              (SIP) Recording Metadata", draft-ram-siprec-metadata-03
              (work in progress), January 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.


Authors' Addresses

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

   Email: leon.portman@nice.com


   Henry Lum
   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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