SIPREC                                                   L. Portman, Ed.
Internet-Draft                                              NICE Systems
Intended status: Standards Track                             H. Lum, Ed.
Expires: April 28, May 3, 2012                             Genesys, Alcatel-Lucent
                                                             A. Johnston
                                                                   Avaya
                                                               A. Hutton
                                                      Siemens Enterprise
                                                          Communications
                                                        October 26, 31, 2011

                       Session Recording Protocol
                     draft-ietf-siprec-protocol-01
                     draft-ietf-siprec-protocol-02

Abstract

   This document specifies the use of the Session Initiation Protocol
   (SIP), the Session Description Protocol (SDP), and the Real Time
   Protocol (RTP) for delivering real-time media and metadata from a
   communication session
   Communication Session (CS) to a recording device.  The Session
   Recording Protocol specifies the use of SIP, SDP, and RTP to
   establish a Recording Session (RS) from the Session Recording Client
   (SRC), which is on the path of the CS, to a Session Recording Server
   (SRS) at the recording device.

Status of this Memo

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   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on April 28, May 3, 2012.

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   Copyright (c) 2011 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Definitions  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Scope  . . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   4.  Overview of operations . . . . . . . . . . . . . . . . . . . .  5
     4.1.  Delivering recorded media  . . . . . . . . . . . . . . . .  5
     4.2.  Delivering recording metadata  . . . . . . . . . . . . . .  7
   5.  Initiating a Recording Session . . . . . . . . . . . . . . . .  8
     5.1.  Procedures at the SRC  . . . . . . . . . . . . . . . . . .  8
     5.2.  Procedures at the SRS  . . . . . . . . . . . . . . . . . .  9
   6.  SDP Handling . . . . . . . . . . . . . . . . . . . . . . . . . 10  9
     6.1.  Procedures at the SRC  . . . . . . . . . . . . . . . . . . 10
       6.1.1.  Handling media stream updates  . . . . . . . . . . . . 11
     6.2.  Procedures at the SRS  . . . . . . . . . . . . . . . . . . 12
   7.  RTP Handling . . . . . . . . . . . . . . . . . . . . . . . . . 13
   8.  Metadata . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
     8.1.  Procedures at the SRC  . . . . . . . . . . . . . . . . . . 13
     8.2.  Procedures at the SRS  . . . . . . . . . . . . . . . . . . 14 15
       8.2.1.  Formal Syntax  . . . . . . . . . . . . . . . . . . . . 16 17
   9.  Persistent Recording . . . . . . . . . . . . . . . . . . . . . 16 17
   10. Extensions for Recording-aware User Agents . . . . . . . . . . 16 17
     10.1. Procedures at the record-aware user agent  . . . . . . . . 17
       10.1.1. Recording preference . . . . . . . . . . . . . . . . . 17 18
     10.2. Procedures at the SRC  . . . . . . . . . . . . . . . . . . 18 19
       10.2.1. Recording indication . . . . . . . . . . . . . . . . . 18 19
       10.2.2. Recording preference . . . . . . . . . . . . . . . . . 20
   11. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 20 21
     11.1. Registration of Option Tags  . . . . . . . . . . . . . . . 20 21
       11.1.1. siprec Option Tag  . . . . . . . . . . . . . . . . . . 20 21
       11.1.2. record-aware Option Tag  . . . . . . . . . . . . . . . 20 21
     11.2. Registration of media feature tags . . . . . . . . . . . . 20 21
       11.2.1. src feature tag  . . . . . . . . . . . . . . . . . . . 20 21
       11.2.2. srs feature tag  . . . . . . . . . . . . . . . . . . . 21 22
     11.3. New Content-Disposition Parameter Registrations  . . . . . 21 22
     11.4. Media Type Registration  . . . . . . . . . . . . . . . . . 22
       11.4.1. Registration of MIME Type application/rs-metadata  . . 22
       11.4.2. Registration of MIME Type
               application/rs-metadata-request  . . . . . . . . . . . 22 23
     11.5. SDP Attributes . . . . . . . . . . . . . . . . . . . . . . 22 23
       11.5.1. 'record' SDP Attribute . . . . . . . . . . . . . . . . 22 23
       11.5.2. 'recordpref' SDP Attribute . . . . . . . . . . . . . . 23
   12. Security Considerations  . . . . . . . . . . . . . . . . . . . 23 24
     12.1. Authentication and Authorization . . . . . . . . . . . . . 23 24
   13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 23 24
   14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 24
     14.1. Normative References . . . . . . . . . . . . . . . . . . . 24
     14.2. Informative References . . . . . . . . . . . . . . . . . . 25
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 25 26

1.  Introduction

   This document specifies the mechanism to record a Communication
   Session (CS) by delivering real-time media and metadata from the CS
   to a recording device.  In accordance to the architecture
   [I-D.ietf-siprec-architecture], the Session Recording Protocol
   specifies the use of SIP, SDP, and RTP to establish a Recording
   Session (RS) from the Session Recording Client (SRC), which is on the
   path of the CS, to a Session Recording Server (SRS) at the recording
   device.

   SIP is also used to deliver metadata to the recording device, as
   specified in [I-D.ietf-siprec-metadata].  Metadata is information
   that describes recorded media and the CS to which they relate.

   The Session Recording Protocol intends to satisfy the SIP-based Media
   Recording requirements listed in [RFC6341].

2.  Definitions

   This document refers to the core definitions provided in the
   architecture document [I-D.ietf-siprec-architecture].

3.  Scope

   The scope of the Session Recording Protocol includes the
   establishment of the recording sessions and the reporting of the
   metadata.  The scope also includes extensions supported by User
   Agents participating in the CS such as indication of recording.  The
   user agents need not be recording-aware in order to participate in a
   CS being recorded.

   The following items, which are not an exhaustive list, do not
   represent the protocol itself and are considered out of the scope of
   the Session Recording Protocol:

   o  Delivering recorded media in real-time as the CS media

   o  Specifications of criteria to select a specific CS to be recorded
      or triggers to record a certain CS in the future

   o  Recording policies that determine whether the CS should be
      recorded and whether parts of the CS are to be recorded

   o  Retention policies that determine how long a recording is stored
   o  Searching and accessing the recorded media and metadata

   o  Policies governing how CS users are made aware of recording

   o  Delivering additional 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 number 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 a B2BUA SIP Back-to-back User Agent (B2BUA) with SRC functionality
   routes a call from UA(A) to UA(B), 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 can cause the B2BUA to 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 may also have SRC functionality, where the endpoint
   itself establishes 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
   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 SRC is establishing the Recording Session
   (message #5) after the Communication Session is established.

   UA A           SRC                    UA B                    SRS
    |(1)CS INVITE  |                       |                      |
    |------------->|                       |                      |
    |              |(2)CS INVITE           |                      |
    |              |---------------------->|                      |
    |              |               (3)OK           (3) 200 OK  |                      |
    |              |<----------------------|                      |
    |        (4)OK   (4) 200 OK |                       |                      |
    |<-------------|                       |                      |
    |              |(5)RS INVITE with SDP  |                      |
    |              |--------------------------------------------->|
    |              |                       |       (6)OK  (6) 200 OK with SDP |
    |              |<---------------------------------------------|
    |(7)CS RTP     |                       |                      |
    |=============>|======================>|                      |
    |<=============|<======================|                      |
    |              |(8)RS RTP              |                      |
    |              |=============================================>|
    |              |=============================================>|
    |(9)CS BYE     |                       |                      |
    |------------->|                       |                      |
    |              |(10)CS BYE             |                      |
    |              |---------------------->|                      |
    |              |(11)RS BYE             |                      |
    |              |--------------------------------------------->|
    |              |                       |                      |

            Figure 1: Basic Recording Call flow

   The above call flow can also apply to the case of a centralized
   conference with a mixer.  For clarity, ACKs to INVITEs and 200 OKs to
   BYEs are not shown.  The conference focus can provide the SRC
   functionality since the conference focus has access to all the media
   from each conference participant.  When a recording is requested, the
   SRC delivers the metadata and the media streams to the SRS.  Since
   the conference focus has access to a mixer, the SRC may choose to mix
   the media streams from all participants as a single mixed media
   stream towards the SRS.

   An SRC can use a single recording session to record multiple
   communication sessions.  Every time the SRC wants record a new call,
   the SRC updates the recording session with a new SDP offer to add new
   recorded streams to the recording session, and correspondingly also
   update the metadata for the new call.

4.2.  Delivering recording metadata

   The SRC is responsible to deliver for the delivery of metadata to the SRS.  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.

   Metadata is transported in the body of INVITE or UPDATE messages.
   Certain metadata, such as the attributes of the recorded media stream
   are located in the SDP of the recording session.

   The SRS has the ability to send a request to the SRC to request for a
   new metadata snapshot update from the SRC.  This can happen when the
   SRS fails to understand the current stream of incremental updates for
   whatever reason, for example, when SRS loses the current state due to
   internal failure.  The SRS may optionally 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
   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  |
      |---------------------------------------------------->|
      |      (11) INVITE (metadata snapshot 2 + SDP offer)  |
      |---------------------------------------------------->|
      |                            (12) 200 OK (SDP answer) |
      |<----------------------------------------------------|
      | (13) UPDATE (metadata update 1 based on snapshot 2) |
      |---------------------------------------------------->|
      |                                         (14) 200 OK |
      |<----------------------------------------------------|

          Figure 3: Delivering metadata via SIP UPDATE

5.  Initiating a Recording Session

5.1.  Procedures at the SRC

   The SRC can initiate a recording session by sending a SIP INVITE
   request to the SRS.  In this case, the From header MUST contain the
   identity of the SRC, and the To header MUST contain the identity of
   the SRS.  Participants information is not recorded in the From or To
   header; they are included in the metadata.

   The SRC MUST include the 'src' feature tag in the Contact URI,
   defined in this specification as per an extension to [RFC3840], for all
   recording sessions.  An SRS uses the presence of the 'src' 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.

   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 in
   the request.

   Since SIP Caller Preferences extensions are optional to implement for
   routing proxies, there is no guarantee that a recording session will
   be routed to an SRC or SRS.  A new options tag is introduced:
   "siprec".  As per [RFC3261], only an SRC or an SRS can accept this
   option tag in a recording session.  An SRC SHOULD include the
   "siprec" option tag in the Require header when initiating a Recording
   Session so that other types of user agents can simply reject the
   INVITE request with a 420 Bad Extension.

5.2.  Procedures at the SRS

   The SRS can initiate a recording session by sending a SIP INVITE
   request to the SRC.  In this case, the From header MUST contain the
   identity of the SRS, and the To header MUST contain the identity of
   the SRC.

   The SRS MUST include the 'srs' feature tag in the Contact URI, as per
   [RFC3840], for all recording sessions.  An SRC 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 SRC, an SRS can
   utilize the SIP Caller Preferences extensions, defined in [RFC3841].
   The presence of a Accept-Contact: *;sip.src allows a UA to request
   that the INVITE be routed to an SRC.  Note that to be completely
   sure, the SRS would need to include a Require: prefs header field in
   the request.

   An SRS SHOULD include the "siprec" option tag in the Require header
   as per [RFC3261] when initiating a Recording Session so that other
   types of user agents can simply reject the INVITE request with a 420
   Bad Extension.

6.  SDP Handling

   The SRC and SRS follows the SDP offer/answer model in [RFC3264].  The
   rest of this section describes conventions used in a recording
   session.

6.1.  Procedures at the SRC

   Since the SRC does not expect to receive media from the SRS, the SRC
   typically sets each media stream of the SDP offer to only send media,
   by qualifying them with the a=sendonly attribute, according to the
   procedures in [RFC3264].

   The SRC sends recorded streams of participants to the SRS, and the
   SRC MUST provide a label attribute (a=label), as per [RFC4574], on
   each media stream in order to identify the recorded stream with the
   rest of the metadata.  The a=label attribute identifies 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
   recorded stream is different than a CS stream; the metadata provides
   a list of participants that contributes to each recorded stream.

   The following is an example of SDP with both audio and video recorded
   streams.  Note that the following example contain unfolded lines
   longer than 72 characters.  These are captured between <allOneLine>
   tags.

       v=0
       o=SRS 2890844526 2890844526 IN IP4 198.51.100.1
       s=-
       c=IN IP4 198.51.100.1
       t=0 0
       m=audio 12240 RTP/AVP 0 4 8
       a=sendonly
       a=label:1
       m=video 22456 RTP/AVP 98
       a=rtpmap:98 H264/90000
       <allOneLine>
       a=fmtp:98 profile-level-id=42A01E;
                 sprop-parameter-sets=Z0IACpZTBYmI,aMljiA==
       </allOneLine>
       a=sendonly
       a=label:2
       m=audio 12242 RTP/AVP 0 4 8
       a=sendonly
       a=label:3
       m=audio 22458 RTP/AVP 98
       a=rtpmap:98 H264/90000
       <allOneLine>
       a=fmtp:98 profile-level-id=42A01E;
                 sprop-parameter-sets=Z0IACpZTBYmI,aMljiA==
       </allOneLine>
       a=sendonly
       a=label:4

       Figure 4: Sample SDP with audio and video streams

6.1.1.  Handling media stream updates

   Over the lifetime of a recording session, the SRC can add and remove
   recorded streams from the recording session for various reasons.  For
   example, when a CS stream is added or removed from the CS, or when a
   CS is created or terminated if a recording session handles multiple
   CSes.  To remove a recorded stream from the recording session, the
   SRC sends a new SDP offer where the port of the media stream to be
   removed is set to zero, according to the procedures in [RFC3264].  To
   add a recorded stream to the recording session, the SRC sends a new
   SDP offer by adding a new media stream description or by reusing an
   old media stream which had been previously disabled, according to the
   procedures in [RFC3264].

   The SRC can temporarily discontinue streaming and collection of
   recorded media from the SRC to the SRS for reason such as masking the
   recording.  In this case, the SRC sends a new SDP offer and sets the
   media stream to inactive (a=inactive) for each recorded stream to be
   paused, as per the procedures in [RFC3264].  To resume streaming and
   collection of recorded media, the SRC sends a new SDP offer and sets
   the media streams with a=sendonly attribute.  Note that when a CS
   stream is muted/unmuted, this information is conveyed in the metadata
   by the SRC.  The SRC SHOULD not modify the media stream with
   a=inactive for mute since this operation is reserved for pausing the
   RS media.

6.2.  Procedures at the SRS

   The SRS only receives RTP streams from the SRC, the SDP answer
   normally sets each media stream to receive media, by setting them
   with the a=recvonly attribute, according to the procedures of
   [RFC3264].  When the SRS is not ready to receive a recorded stream,
   the SRS sets the media stream as inactive in the SDP offer or answer
   by setting it with a=inactive attribute, according to the procedures
   of [RFC3264].  When the SRS is ready to receive recorded streams, the
   SRS sends a new SDP offer and sets the media streams with a=recvonly
   attribute.

   The following sequence diagram shows an example where the SRS is
   initially not ready to receive recorded streams, and later updates
   the recording session when the SRS is ready to record.

     SRC                                                   SRS
      |                                                     |
      |(1) INVITE (SDP offer)                               |
      |---------------------------------------------------->|
      |                                           [not ready to record]
      |                         (2)200 OK with SDP inactive |
      |<----------------------------------------------------|
      |(3) ACK                                              |
      |---------------------------------------------------->|
      |                      ...                            |
      |                                             [ready to record]
      |                     (4) re-INVITE with SDP recvonly |
      |<----------------------------------------------------|
      |(5)200 OK with SDP sendonly                          |
      |---------------------------------------------------->|
      |                                             (6) ACK |
      |<----------------------------------------------------|
      |(7) RTP                                              |
      |====================================================>|
      |                      ...                            |
      |(8) BYE                                              |
      |---------------------------------------------------->|
      |                                             (9) OK  |
      |<----------------------------------------------------|

              Figure 5: SRS to offer with a=inactive

7.  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]

8.  Metadata

8.1.  Procedures at the SRC

   The SRC is responsible to deliver metadata to the SRS in a recording
   session.  Metadata can be provided by the SRC in the initial INVITE
   request when establishing the recording session, and subsequent
   metadata updates can be provided by the SRC in reINVITE and UPDATE
   requests and responses in the recording session.

   Certain metadata attributes are contained in the SDP, and others are
   contained in a new content type "application/rs-metadata".  The
   format of the metadata is described as part of the mechanism in
   [I-D.ietf-siprec-metadata].  A new "disposition-type" of Content-
   Disposition is defined for the purpose of carrying metadata and the
   value is "recording-session".  The "recording-session" value
   indicates that the "application/rs-metadata" content contains
   metadata to be handled by the SRS, and the disposition can be carried
   in either INVITE or UPDATE requests or responses sent by the SRC.

   Metadata sent by the SRC can be categorized as either a full metadata
   snapshot or partial update.  A full metadata snapshot describes all
   the recorded streams and all metadata associated with the recording
   session.  When the SRC sends a full metadata snapshot, the SRC MUST
   send an INVITE request with an SDP offer and the "recording-session"
   disposition.  A partial update represents an incremental update since
   the last metadata update sent by the SRC.  A partial update sent by
   the SRC can be an INVITE request or response with an SDP offer, or an
   INVITE/UPDATE request or response containing a "recording-session"
   disposition, or an INVITE request containing both an SDP offer and
   the "recording-session" disposition.

   The following is an example of a full metadata snapshot sent by the
   SRC in the initial INVITE request:

      INVITE sip:97753210@10.240.3.10:5060 sip:recorder@example.com SIP/2.0
      Via: SIP/2.0/TCP src.example.com;branch=z9hG4bKdf6b622b648d9
      From: <sip:2000@10.226.240.3>;tag=35e195d2-947d-4585-946f-098392474 <sip:2000@example.com>;tag=35e195d2-947d-4585-946f-098392474
      To: <sip:Recorder@10.240.3.10> <sip:recorder@example.com>
      Call-ID: d253c800-b0d1ea39-4a7dd-3f0e20a@10.226.240.3 d253c800-b0d1ea39-4a7dd-3f0e20a
      CSeq: 101 INVITE
     Date: Thu, 26 Nov 2009 02:38:49 GMT
     Supported: timer
      Max-Forwards: 70
     Min-SE: 90
     Session-Expires: 1800
      Require: siprec
      Accept: application/sdp, application/rs-metadata,
        application/rs-metadata-request
      Contact: <sip:2000@10.226.240.3:5060;transport=tcp>;src
     Via: SIP/2.0/TCP 10.226.240.3:5060;branch=z9hG4bKdf6b622b648d9 <sip:2000@src.example.com>;src
      Content-Type: multipart/mixed;boundary=foobar
      Content-Length: [length]

      --foobar
      Content-Type: application/sdp

      v=0
      o=SRS 2890844526 2890844526 IN IP4 198.51.100.1
      s=-
      c=IN IP4 198.51.100.1
      t=0 0
      m=audio 12240 RTP/AVP 0 4 8
      a=sendonly
      a=label:1

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

      [metadata content]

          Figure 6: Sample INVITE request for the recording session

8.2.  Procedures at the SRS

   The SRS receives metadata updates from the SRC in INVITE and UPDATE
   requests.  Since the SRC can send partial updates based on the
   previous update, the SRS needs to keep track of the sequence of
   updates from the SRC.

   In the case of an internal failure at the SRS, the SRS may fail to
   recognize a partial update from the SRC.  The SRS may be able to
   recover from the internal failure by requesting for a full metadata
   snapshot from the SRC.  Certain errors, such syntax errors or
   semantic errors in the metadata information, are likely caused by an
   error on the SRC side, and it is likely the same error will occur
   again even when a full metadata snapshot is requested.  In order to
   avoid repeating the same error, it is RECOMMENDED that the SRS
   terminate the recording session when a syntax error or semantic error
   is detected in the metadata.

   When the SRS requires a full metadata snapshot, the SRS sends a
   metadata snapshot request to the SRC in an INVITE/UPDATE request or
   in an INVITE/UPDATE response.  The metadata snapshot request is
   contained the content with the disposition type "recording-session".
   The format of the content is "application/rs-metadata-request", and
   the body format is chosen to be a simple text-based format.  The
   following shows an example:

       UPDATE sip:2000@10.226.240.3:5060 sip:2000@src.exmaple.com SIP/2.0
       Via: SIP/2.0/UDP srs.example.com;branch=z9hG4bKdf6b622b648d9
       To: <sip:2000@10.226.240.3>;tag=35e195d2-947d-4585-946f-098392474 <sip:2000@exmaple.com>;tag=35e195d2-947d-4585-946f-098392474
       From: <sip:Recorder@10.240.3.10>;tag=1234567890 <sip:recorder@example.com>;tag=1234567890
       Call-ID: d253c800-b0d1ea39-4a7dd-3f0e20a@10.226.240.3 d253c800-b0d1ea39-4a7dd-3f0e20a
       CSeq: 1 UPDATE
       Supported: timer
       Max-Forwards: 70
       Min-SE: 90
       Session-Expires: 1800
       Require: siprec
       Contact: <sip:Recorder@10.240.3.10:5060>;srs
       Via: SIP/2.0/UDP 10.240.3.10:5060;branch=z9hG4bKdf6b622b648d9 <sip:recorder@srs.example.com>;srs
       Accept: appliation/sdp, application/rs-metadata
       Content-Disposition: recording-session
       Content-Type: application/rs-metadata-request
       Content-Length: [length]

       SRS internal error

           Figure 7: Metadata Request

   The SRS MAY include the reason why a metadata snapshot request is
   being made to the SRC in the reason line.  This reason line is free
   form text, mainly designed for logging purposes on the SRC side.  The
   processing of the content by the SRC is entirely optional since the
   content is for logging only, and the snapshot request itself is
   indicated by the use of the application/rs-metadata-request content
   type.

   When the SRC receives the request for a metadata snapshot, the SRC
   MUST provide a full metadata snapshot in a separate INVITE
   transaction, along with an SDP offer.  All subsequent metadata
   updates sent by the SRC MUST be based on the new metadata snapshot.

8.2.1.  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-reason-line CRLF

   srs-reason-line = [TEXT-UTF8-TRIM]

9.  Persistent Recording

   Persistent recording is a specific use case outlined in REQ-005 or
   Use Case 4 in [RFC6341], where a recording session can be established
   in the absence of a communication session.  The SRC continuously
   sends recorded media to the SRS in the absence of a CS for certain
   allocated devices; allocated devices can include a specific physical
   device, a specific person or contact registered, or a set of trunks
   or ports of a gateway.  To continuously record, the SRC adds recorded
   streams into the recording session for all devices with persistent
   recording.  By allocating recorded streams and continuously sending
   recorded media to the SRS, the SRC does not have to prepare new
   recorded streams with new SDP offer when a new communication session
   is created and also does not impact the timing of the CS.  The SRC
   only needs to update the metadata when new communication sessions are
   created.

   When there is no communication sessions running on the devices with
   persistent recording, there is no recorded media to stream from the
   SRC to the SRS.  In certain environments where Network Address
   Translator (NAT) is used, typically a minimum of flow activity is
   required to maintain the NAT binding for each port opened.  In order
   not to lose the NAT bindings for the RTP/RTCP ports opened for the
   recorded streams, the SRC and SRS SHOULD follow the recommendations
   provided in [RFC6263] to maintain the NAT bindings.

10.  Extensions for Recording-aware User Agents

   The following sections describe the SIP and SDP extensions for
   recording-aware user agents.

10.1.  Procedures at the record-aware user agent

   A recording-aware UA SHOULD indicate that it can accept reporting of
   recording indication provided by the SRC.  A new option tag "record-
   aware" is introduced to indicate such awareness.  The recording-aware
   UA SHOULD include the "record-aware" option tag in the Supported
   header when initiating or establishing a CS.  A recording-aware UA
   that has indicated recording awareness MUST provide at recording
   indication to the end user through an appropriate 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 a user interface to render recording
   indication.  When such user agent indicates recording awareness, the
   UA SHOULD 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 mechanism an SRC
   chooses to indicate recording, such as playing a tone inband.

10.1.1.  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
   can 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. offer or answer.
   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 = "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.

10.2.  Procedures at the SRC

   When a UA has indicated that it is recording-aware through the
   "record-aware" option tag, the SRC MUST provide recording indications
   in a new SDP attribute described in the following section.  In the
   absence of the "record-aware" option tag, meaning that the UA is not
   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.

10.2.1.  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 in either SDP
   offer or answer.  The recording indication applies to the specified
   media stream only, for example, only the audio portion of the call is
   recorded in an audio/video call.  The following is the ABNF of the
   'record' attribute:

      attribute /= record-attr

      ; attribute defined in RFC 4566

      record-attr = "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 an endpoint in the CS 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) answer) |
      |<----------------------------------------------------|
      |(3) ACK                                              |
      |---------------------------------------------------->|
      |(4) RTP                                              |
      |<===================================================>|
      |               [SRC stops recording]                 |
      |(5) re-INVITE (SDP + a=record:off)                   |
      |---------------------------------------------------->|
      |                      (6) 200 OK (SDP + a=record:off)|
      |<----------------------------------------------------|
      |                                             (6) ACK |
      |---------------------------------------------------->|

              Figure 8: 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 and is not used as a request to start/stop recording if
   there are multiple SRCs in the call path.

10.2.2.  Recording preference

   When the SRC receives the a=recordpref SDP in an SDP offer or answer,
   the SRC MAY choose to honor such request to record the request based
   on local policy on the SRC.  When the SRC honors the request, the SRC
   MUST also update the recording indication to reflect the current
   state of the recording (on/off/paused).

11.  IANA Considerations

11.1.  Registration of Option Tags

   This specification registers two option tags.  The required
   information for this registration, as specified in [RFC3261], is as
   follows.

11.1.1.  siprec Option Tag

      Name: siprec

      Description: This option tag is for identifying the SIP session
      for the purpose of recording session only.  This is typically not
      used in a Supported header.  When present in a Require header in a
      request, it indicates that the UAS MUST be either a SRC or SRS
      capable of handling the contexts of a recording session.

11.1.2.  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.

11.2.  Registration of media feature tags

   This document registers two new media feature tags in the SIP tree
   per the process defined in [RFC2506] and [RFC3840]

11.2.1.  src feature tag

      Media feature tag name: sip.src

      ASN.1 Identifier: 25

      Summary of the media feature indicated by this tag: This feature
      tag indicates that the user agent is a Session Recording Client
      for the purpose for Recording Session.

      Values appropriate for use with this feature tag: boolean

      The feature tag is intended primarily for use in the following
      applications, protocols, services, or negotiation mechanisms: This
      feature tag is only useful for a Recording Session.

      Examples of typical use: Routing the request to a Session
      Recording Server.

      Security Considerations: Security considerations for this media
      feature tag are discussed in Section 11.1 of RFC 3840.

11.2.2.  srs feature tag

      Media feature tag name: sip.srs

      ASN.1 Identifier: 26

      Summary of the media feature indicated by this tag: This feature
      tag indicates that the user agent is a Session Recording Server
      for the purpose for Recording Session.

      Values appropriate for use with this feature tag: boolean

      The feature tag is intended primarily for use in the following
      applications, protocols, services, or negotiation mechanisms: This
      feature tag is only useful for a Recording Session.

      Examples of typical use: Routing the request to a Session
      Recording Client.

      Security Considerations: Security considerations for this media
      feature tag are discussed in Section 11.1 of RFC 3840.

11.3.  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

11.4.  Media Type Registration

11.4.1.  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

11.4.2.  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

11.5.  SDP Attributes

   This document registers the following new SDP attributes.

11.5.1.  'record' SDP Attribute

   Contact names: Leon Portman leon.portman@nice.com, Henry Lum
   henry.lum@genesyslab.com

   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

11.5.2.  'recordpref' SDP Attribute

   Contact names: Leon Portman leon.portman@nice.com, Henry Lum
   henry.lum@genesyslab.com

   Attribute name: recordpref

   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

12.  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.  Other security considerations are
   outlined in the use cases and requirements document [RFC6341].

12.1.  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.

13.  Acknowledgements

   We want to thank John Elwell, Paul Kyzivat, Partharsarathi R, Ram
   Mohan R, Charles Eckel, Hadriel Kaplan, Adam Roach, Miguel Garcia for
   their valuable comments and inputs to this document.

14.  References

14.1.  Normative References

   [I-D.ietf-siprec-metadata]
              R, R., Ravindran, P., and P. Kyzivat, "Session Initiation
              Protocol (SIP) Recording Metadata",
              draft-ietf-siprec-metadata-04
              draft-ietf-siprec-metadata-05 (work in progress),
              September
              October 2011.

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

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

   [RFC2506]  Holtman, K., Mutz, A., and T. Hardie, "Media Feature Tag
              Registration Procedure", BCP 31, RFC 2506, March 1999.

   [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.

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

14.2.  Informative References

   [I-D.eckel-siprec-rtp-rec]
              Eckel, C., "Real-time Transport Protocol (RTP)
              Recommendations for SIPREC", draft-eckel-siprec-rtp-rec-02
              (work in progress), September 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-03
              (work in progress), October 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.

   [RFC6263]  Marjou, X. and A. Sollaud, "Application Mechanism for
              Keeping Alive the NAT Mappings Associated with RTP / RTP
              Control Protocol (RTCP) Flows", RFC 6263, June 2011.

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