SIPREC                                                   L. Portman, Ed.
Internet-Draft                                              NICE Systems
Intended status: Standards Track                             H. Lum, Ed.
Expires: February 16, April 28, 2012                          Genesys, Alcatel-Lucent
                                                             A. Johnston
                                                                   Avaya
                                                               A. Hutton
                                                      Siemens Enterprise
                                                          Communications
                                                         August 15,
                                                        October 26, 2011

                       Session Recording Protocol
                     draft-ietf-siprec-protocol-00
                     draft-ietf-siprec-protocol-01

Abstract

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

   This document specifies the use of the Session Recording Protocol.  The protocol
   is used between Initiation Protocol
   (SIP), the Session Recording Client (SRC) Description Protocol (SDP), and Session Recording
   Server (SRS). the Real Time
   Protocol (RTP) for delivering real-time media and metadata from a
   communication session to a recording device.

Status of this Memo

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   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on February 16, April 28, 2012.

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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.  Conference focus as an SRC  Delivering recording metadata  . . . . . . . . . . . . . .  7
   5.  Initiating a Recording Session . .  6
     4.3.  Delivering recording metadata . . . . . . . . . . . . . .  7
   5.  SIP Extensions for Recording Session  8
     5.1.  Procedures at the SRC  . . . . . . . . . . . . . . . . . .  8
     5.1.  Callee Capabilities Extensions for SIP Recording
     5.2.  Procedures at the SRS  . . . . .  9
       5.1.1.  src Feature Tag . . . . . . . . . . . . .  9
   6.  SDP Handling . . . . . .  9
       5.1.2.  srs Feature Tag . . . . . . . . . . . . . . . . . . . 10
     5.2.  recording-session Options Tag
     6.1.  Procedures at the SRC  . . . . . . . . . . . . . . . . . . 10
     5.3.  SDP handling
       6.1.1.  Handling media stream updates  . . . . . . . . . . . . 11
     6.2.  Procedures at the SRS  . . . . . . . . . . . . 11
     5.4. . . . . . . 12
   7.  RTP handling Handling . . . . . . . . . . . . . . . . . . . . . . . . . 13
     5.5.
   8.  Metadata . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
     5.6.  Requesting for metadata snapshot
     8.1.  Procedures at the SRC  . . . . . . . . . . . . . . . 15
       5.6.1.  Formal Syntax . . . 13
     8.2.  Procedures at the SRS  . . . . . . . . . . . . . . . . . 16
     5.7.  Recording Pause and Resume . 14
       8.2.1.  Formal Syntax  . . . . . . . . . . . . . . . . . . . . 16
   6.  Extensions for Recording-aware User Agents
   9.  Persistent Recording . . . . . . . . . . . . . . . . 16
     6.1.  SIP Extensions . . . . . 16
   10. Extensions for Recording-aware User Agents . . . . . . . . . . 16
     10.1. Procedures at the record-aware user agent  . . . . . . . . 17
       6.1.1.
       10.1.1. Recording awareness preference . . . . . . . . . . . . . . . . . 17
     6.2.  SDP Extensions
     10.2. Procedures at the SRC  . . . . . . . . . . . . . . . . . . 18
       10.2.1. Recording indication . . . . 17
       6.2.1.  Providing recording indication . . . . . . . . . . . . 17
       6.2.2. . 18
       10.2.2. Recording preference . . . . . . . . . . . . . . . . . 19
   7. 20
   11. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 19
     7.1. 20
     11.1. Registration of Option Tags  . . . . . . . . . . . . . . . 19
       7.1.1.  recording-session 20
       11.1.1. siprec Option Tag  . . . . . . . . . . . . . . . . . . 20
       7.1.2.
       11.1.2. record-aware Option Tag  . . . . . . . . . . . . . . . 20
     7.2.
     11.2. Registration of media feature tags . . . . . . . . . . . . 20
       7.2.1.
       11.2.1. src feature tag  . . . . . . . . . . . . . . . . . . . 20
       7.2.2.
       11.2.2. srs feature tag  . . . . . . . . . . . . . . . . . . . 21
     7.3.
     11.3. New Content-Disposition Parameter Registrations  . . . . . 21
     7.4.
     11.4. Media Type Registration  . . . . . . . . . . . . . . . . . 21
       7.4.1. 22
       11.4.1. Registration of MIME Type application/rs-metadata  . . 21
       7.4.2. 22
       11.4.2. Registration of MIME Type
               application/rs-metadata-request  . . . . . . . . . . . 22
     7.5.
     11.5. SDP Attributes . . . . . . . . . . . . . . . . . . . . . . 22
       7.5.1.
       11.5.1. 'record' SDP Attribute . . . . . . . . . . . . . . . . 22
       7.5.2.
       11.5.2. 'recordpref' SDP Attribute . . . . . . . . . . . . . . 22
   8. 23
   12. Security Considerations  . . . . . . . . . . . . . . . . . . . 23
     8.1.
     12.1. Authentication and Authorization . . . . . . . . . . . . . 23
   9.
   13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 23
   10.
   14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 23
     10.1. 24
     14.1. Normative References . . . . . . . . . . . . . . . . . . . 23
     10.2. 24
     14.2. Informative References . . . . . . . . . . . . . . . . . . 24 25
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 24 25

1.  Introduction

   Communication Session (CS) recording requires establishment of

   This document specifies the
   recording session between communication system and recording system.
   In order to allow access mechanism to such recordings, the record a Communication
   Session (CS) by delivering real-time media and metadata about the
   CS shall be sent from the SRC CS
   to a recording device.  In accordance to the SRS.

   The SIP-based Media architecture
   [I-D.ietf-siprec-architecture], the Session Recording Requirements [RFC6341] list a set Protocol
   specifies the use of
   requirements that need SIP, SDP, and RTP to be met by session recording protocols.  The establish a Recording
   Session (RS) from the Session Recording Protocol, Client (SRC), which is specified in this document,
   meets these requirements.

   The remainder of this document is organized as follows: Section 2
   defines the terminology used throughout this document, Section 3
   discusses on the scope
   path of the CS, to a Session Recording Protocol, Section 4
   provides a non-normative overview of Server (SRS) at the recording operations, Section 5
   provides normative description of
   device.

   SIP extensions for is also used to deliver metadata to the recording device, as
   specified in [I-D.ietf-siprec-metadata].

   The Session Recording
   Session, Section 6 provides normative description of SIP extensions
   for recording-aware user agents. 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 Record-
   aware 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 specific CS to be recorded or
      triggers to record 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 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 B2BUA with SRC can route functionality routes a call requests from UA(A) to UA(B).  As a SIP B2BUA,
   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 may 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 can may also be acting as the SRC, and have SRC functionality, where the endpoint
   itself
   will be establishing 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   |                      |
    |              |<----------------------|                      |
    |        (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 1: Basic Recording Call flow

4.2.  Conference focus as an SRC

   A conference focus may

   The above call flow can also act as an apply to the case of a centralized
   conference with a mixer.  The conference focus can provide the SRC
   functionality since it the conference focus has access to all the media
   from each conference participant.  In this example,  When a user
   agent may REFER recording is requested, the
   SRC delivers the metadata and the media streams to the SRS.  Since
   the conference focus has access to the SRS, and a mixer, the SRC may choose to mix
   the media streams from all participants as a single mixed media
   stream towards the SRS.  In order to tell the conference focus to
   start

   An SRC can use a single recording session to record multiple
   communication sessions.  Every time the SRS, the user agent can include the
   srs feature tag in the Refer-To header as per [RFC4508].

    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 2: Recording call flow - SRC as wants record a conference focus

4.3.  Delivering recording metadata

   Certain metadata, such as new call,
   the attributes of SRC updates the recording session with a new SDP offer to add new
   recorded media
   stream, are already included in streams to the SDP of recording session, and correspondingly also
   update the metadata for the new call.

4.2.  Delivering recording session.
   This information metadata

   The SRC is reused as part of responsible to deliver metadata to the metadata. 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 also has the ability to send a request to the SRC to request
   to receive 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 (ie.  SRS gets a syntax/semantic error in metadata update, the reason, for example, when SRS crashes and restarts), and 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.  SIP Extensions for  Initiating a Recording Session

5.1.  Procedures at the SRC

   The following sections describe SRC can initiate a recording session by sending a SIP extensions for INVITE
   request to the SRS.  In this case, the Recording
   Session.

   The From header must MUST contain the
   identity of the SRC or 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 information.

   Note that a recording session does not have to live within metadata.

   The SRC MUST include the scope
   of a single communication session.  As outline 'src' feature tag in REQ-005 of
   [RFC6341], the Contact URI, as per
   [RFC3840], for all recording session can be established in sessions.  An SRS uses the absence presence of
   a communication session.  In this case,
   the SRC MUST pre-allocate a
   recorded media stream 'src' feature tag in dialog creating and offer an SDP with at least one m= line modifying requests and
   responses to
   establish a persistent recording session.  When confirm that the actual call
   arrives, dialog being created is for the SRC can map recorded media stream to participant media
   and minimize media clipping.

   Recorded media from multiple communication sessions MAY be handled in purpose
   of a single recording session.  The SRC provides Recording Session.  In addition, a reference of each
   recorded media stream to registrar could discover that
   a UA is an SRC based on the metadata described presence of this feature tag in the next section.

5.1.  Callee Capabilities Extensions for a
   registration.  Other SIP Recording

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

   SIP Callee Capabilities defines feature tags which are used to
   represent characteristics and capabilities
   triggered by the presence of this feature tag.

   To ensure a UA.  From RFC 3840:

      "Capability and characteristic information about a UA recording session is carried
      as parameters of redirected to an SRS, an SRC can
   utilize 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, SIP Caller Preferences extensions, 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.

   Two new feature tags are introduced: 'src' and 'srs'.

5.1.1.  src Feature Tag [RFC3841].
   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 Accept-Contact: *;sip.srs allows a UA is an SRC based on to request
   that the
   presence of this feature tag in a registration.  Other SIP Recording
   extensions and behaviors can INVITE be triggered by the presence of this
   feature tag. routed to an SRS.  Note that we could use a single feature tag, such as 'recording' used
   by either an to be completely
   sure, the SRC or SRS would need to identify that include a Require: prefs header field in
   the session request.

   Since SIP Caller Preferences extensions are optional to implement for
   routing proxies, there is no guarantee that a recording
   session.  However, due session will
   be routed to the differences in functionality and
   behavior between an SRC and SRS, using only one feature or SRS.  A new options tag for both is not ideal.  For instance, if a routing mistake resulted introduced:
   "siprec".  As per [RFC3261], only an SRC or an SRS can accept this
   option tag in a
   request from a recording session.  An SRC being routed back to another SRC, if only one
   feature tag were defined, they would not know right away about SHOULD include the
   error and could become confused.  With separate feature tags, they
   would realize
   "siprec" option tag in the error immediately and terminate Require header when initiating a Recording
   Session so that other types of user agents can simply reject the session.  Also,
   call logs would clearly show
   INVITE request with a 420 Bad Extension.

5.2.  Procedures at the routing error.

   To ensure SRS

   The SRS can initiate a recording session is redirected by sending a SIP INVITE
   request to an SRS, an SRC can
   utilize the SIP Caller Preferences extensions, defined in [RFC3841].
   The presence SRC.  In this case, the From header MUST contain the
   identity 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, SRS, and the SRC would need to include a Require: prefs To header field in MUST contain the request.

5.1.2.  srs Feature Tag identity of
   the SRC.

   The SRS MUST include the 'srs' feature tag is used in Contact URIs by the Session
   Recording Server (SRS) related to Contact URI, as per
   [RFC3840], for all recording sessions.  A Session
   Recording Client  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.

5.2.  recording-session Options Tag

   Since SIP Caller Preferences extensions are optional to implement for
   routing proxies, there is no guarantee that a recording session will
   be routed an SRC or SRS.  We introduce the use of the recording-
   session option tag as a mechanism to ensure only an SRC or an SRS
   would be able to accept recording sessions.

   An SRC or an SRS SHOULD include the recording-session "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.

5.3.

6.  SDP handling

   Following Handling

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

6.1.  Procedures at the SRC

   Since the SRC does not expect to receive media from the SRS.  As SRS only receives RTP streams from
   SRC, SRS, the SRC
   typically sets each media stream of the 200 OK response will normally contain SDP offer to only send media,
   by qualifying them with a=recvonly
   attribute.

   Since the a=sendonly attribute, according to the
   procedures in [RFC3264].

   The SRC may send sends recorded media streams of different participants (or
   even mixed streams) to the SRS, and the SDP must
   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 [RFC4574] will be used to
   identify 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 participant may have
   multiple streams (audio and video) and each
   recorded stream is labeled
   separately. 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.

       v=0
       o=SRS 0 0 2890844526 2890844526 IN IP4 172.22.3.8
              s=SRS 198.51.100.1
       s=-
       c=IN IP4 172.22.3.8 198.51.100.1
       t=0 0
       m=audio 12241 12240 RTP/AVP 0 4 8
       a=sendonly
       a=label:1
              m=audio 12242
       m=video 22456 RTP/AVP 98
       a=rtpmap:98 H264/90000
       a=fmtp:98 ... profile-level-id=42A01E;
                 sprop-parameter-sets=Z0IACpZTBYmI,aMljiA==
       a=sendonly
       a=label:2
       m=audio 12243 12242 RTP/AVP 0 4 8
       a=sendonly
       a=label:3
       m=audio 12244 22458 RTP/AVP 98
       a=rtpmap:98 H264/90000
       a=fmtp:98 ... profile-level-id=42A01E;
                 sprop-parameter-sets=Z0IACpZTBYmI,aMljiA==
       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 media stream from the recording session, send the
   SRC sends a
   reINVITE and set 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 zero 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 m= line. procedures in [RFC3264].  To add a resume streaming and
   collection of recorded media stream, send media, the SRC sends a reINVITE new SDP offer and add sets
   the media streams with a=sendonly attribute.  Note that when a new m=
   line. CS
   stream is muted/unmuted, this information is conveyed in the metadata
   by the SRC.  The SRS may respond SRC SHOULD not modify the media stream with
   a=inactive attribute as part of 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 in answer
   normally sets each media stream to receive media, by setting them
   with the 200 OK response when a=recvonly attribute, according to the procedures of
   [RFC3264].  When the SRS is not ready to receive a recorded
   media.  The stream,
   the SRS can send re-INVITE to update sets the media stream as inactive in the SDP with a=recvonly
   when offer or answer
   by setting it with a=inactive attribute, according to the procedures
   of [RFC3264].  When the SRS is ready to receive media. 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 of where the SRS responds with
   SDP that contain a=inactive, is
   initially not ready to receive recorded streams, and then later update media information
   update with re-INVITE. 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

5.4.

7.  RTP handling

   [This Handling

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

5.5.  Metadata a new content type "application/rs-metadata".  The
   format of the full metadata will be is described as part of the mechanism in
   [I-D.ietf-siprec-metadata].

   As mentioned in the previous section, the SDP  A new "disposition-type" of Content-
   Disposition is defined for the recording
   session describes the properties purpose of media for all recorded media
   streams. carrying metadata and the
   value is "recording-session".  The label attribute "recording-session" value
   indicates that the "application/rs-metadata" content contains a reference
   metadata to be handled by the rest of the
   metadata information.

   For all basic metadata information such as communication session,
   participants SRS, and call identifiers, they the disposition can be included carried
   in the
   initial either INVITE request or UPDATE requests or responses sent by the SRC.

   Metadata sent by the SRC can be included categorized as
   content in 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 or UPDATE request. request with an SDP offer and the "recording-session"
   disposition.  A new "disposition-type" of
   Content-Disposition is defined for this purpose 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 value is
   "recording-session". "recording-session" disposition.

   The following is an example for RS establishment between SRC and SRS
   with of a full metadata as content. snapshot sent by the
   SRC in the initial INVITE request:

     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
     Max-Forwards: 70
     Min-SE: 90
     Session-Expires: 1800
     Require: recording-session siprec
     Contact: <sip:2000@10.226.240.3:5060;transport=tcp>;src
     Via: SIP/2.0/TCP 10.226.240.3:5060;branch=z9hG4bKdf6b622b648d9
     Content-Type: multipart/mixed;boundary=foobar
     Content-Length: [length]

     --foobar
     Content-Type: application/sdp

     v=0
     o=SRS 0 0 2890844526 2890844526 IN IP4 10.226.240.3 198.51.100.1
     s=-
     c=IN IP4 10.226.240.3 198.51.100.1
     t=0 0
     m=audio 12241 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

   Further updates to recording metadata can be delivered as a sequence
   events reported in SIP UPDATE or reINVITE requests and Sample INVITE request for the recording session

8.2.  Procedures at the SRS must
   receive

   The SRS receives metadata updates from the sequence of events SRC in order.  Since there can only be a
   single INVITE or and 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,
   requests.  Since the SRC can send a new metadata
   snapshot in a SIP reINVITE request along with an SDP offer.  All
   subsequent metadata partial updates will be based on the new metadata
   snapshot.

5.6.  Requesting for metadata snapshot

   The
   previous update, the SRS can send a request for metadata snapshot any time after needs to keep track of the
   Recording Session has been established.  Typically, sequence of
   updates from the SRS sends
   such as request in SRC.

   In the case where of an internal failure at the SRS, the SRS is failing may fail to process
   further metadata incremental updates.  Failure scenarios can include
   failure
   recognize a partial update from the SRC.  The SRS may be able to
   recover from the internal SRS error or failure to match by requesting for a full metadata update
   sequence.
   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 new full metadata snapshot is requested.  In order to
   avoid repeating the same error
   with snapshot requests, error, it is RECOMMENDED that the SRS
   terminate the recording session when a syntax error or semantic error occurs
   is detected in the metadata.

   Similar to delivering metadata,

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

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

       Reason:

       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 header.  This header is free form
   text mainly designed for logging purposes on the SRC side.  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. 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.

5.6.1.

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 [ *opt-srs-headers ]

   srs-reason-line = "Reason" HCOLON srs-reason

   srs-reason = [TEXT-UTF8-TRIM]

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

5.7.

9.  Persistent Recording Pause and Resume

   To temporarily discontinue streaming and collection

   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
   from the SRC to the SRS, SRS in the SRC sends absence of a reINVITE and set a=inactive CS for each recorded media stream to be paused.

   To resume streaming and collection certain
   allocated devices; allocated devices can include a specific physical
   device, a specific person or contact registered, or a set of recorded media, trunks
   or ports of a gateway.  To continuously record, the SRC sends a
   reINVITE and set a=sendonly adds recorded
   streams into the recording session for each all devices with persistent
   recording.  By allocating recorded streams and continuously sending
   recorded media stream to resume.

   Note that the SRS, the SRC does not have to prepare new
   recorded streams with new SDP offer when a media stream in the CS is muted/unmuted, this
   information new communication session
   is conveyed in created and also does not impact the metadata by timing of the SRC. CS.  The SRC SHOULD
   not modify
   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 with a=inactive for mute since
   this operation from the
   SRC to the SRS.  In certain environments where Network Address
   Translator (NAT) is reserved used, typically a minimum of flow activity is
   required to maintain the NAT binding for pausing each port opened.  In order
   not to lose the RS media.

6. 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 UA.

6.1.  SIP Extensions

6.1.1.  Recording awareness
   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 in media level SDP provided in by the previous
   section. SRC.  A new option tag "record-aware" "record-
   aware" is introduced to indicate such awareness.

   A  The recording-aware
   UA that has indicated recording awareness by including SHOULD include the record-
   aware "record-aware" option tag in a transmitted the Supported
   header field when initiating or establishing a CS.  A recording-aware UA
   that has indicated recording awareness MUST provide at its 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.  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 not indicated that it 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 recording aware, 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.

6.2.  SDP Extensions

6.2.1.  Providing recording

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 = "a=record:" "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 an endpoint in the
   session 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) |
      |<----------------------------------------------------|
      |(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.

6.2.2.

10.2.2.  Recording preference

   A recording-aware UA involved in a CS MAY request

   When the CS to be
   recorded or not recorded.  This indication of recording preference
   can be sent at session establishment time or during SRC receives the session.

   A new SDP attribute "recordpref" is introduced.  The a=recordpref 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:

      recordpref-attr = "a=recordpref:" pref

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

   on Request for recording if it has not already been started.  If offer or answer,
   the
      recording is currently paused, request SRC MAY choose to resume recording.

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

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

   nopreference  To indicate that record the UA has no preference request based
   on local policy on recording.
      While the absence of this attribute indirectly implies SRC.  When the lack of
      preference, using this value allows SRC honors the UA request, the SRC
   MUST also update the recording indication to explicitly reflect the current
   state no
      preference to being recorded.

7. of the recording (on/off/paused).

11.  IANA Considerations

7.1.

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.

7.1.1.  recording-session

11.1.1.  siprec Option Tag

      Name: recording-session 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.

7.1.2.

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.

7.2.

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]

7.2.1.

11.2.1.  src feature tag

      Media feature tag name: sip.src

      ASN.1 Identifer: 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.

7.2.2.

11.2.2.  srs feature tag

      Media feature tag name: sip.srs

      ASN.1 Identifer: 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.

7.3.

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

7.4.

11.4.  Media Type Registration

7.4.1.

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

7.4.2.

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

7.5.

11.5.  SDP Attributes

   This document registers the following new SDP attributes.

7.5.1.

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

7.5.2.

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

8.

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.

8.1.  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.

9.

13.  Acknowledgements

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

10.

14.  References

10.1.

14.1.  Normative References

   [I-D.ietf-siprec-metadata]
              R, R., R, Ravindran, P., and P. Kyzivat, "Session Initiation
              Protocol (SIP) Recording Metadata", draft-ietf-siprec-metadata-03
              draft-ietf-siprec-metadata-04 (work in progress), July
              September 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.

10.2.

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-01 draft-eckel-siprec-rtp-rec-02
              (work in progress), June 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-02 draft-ietf-siprec-architecture-03
              (work in progress), April 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