SIPREC L. Portman, Ed.
Internet-Draft NICE Systems
Intended status: Informational H. Lum
Expires: June 17, 2011 Genesys, Alcatel-Lucent
December 14, 2010
The SIP-based Media Recording Protocol (SIPREC)
draft-portman-siprec-protocol-01
Abstract
SIPREC Session Recording Protocol is used for establishing recording
session and reporting of the metadata of the communication session.
This document specifies the SIPREC Protocol (SIPREC). SIPREC is used
between Session Recording Client (SRC) and Session Recording Server
(SRS).
Status of this Memo
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Overview of operations . . . . . . . . . . . . . . . . . . . . 5
4.1. Delivering recorded media . . . . . . . . . . . . . . . . 6
4.2. Delivering recording metadata . . . . . . . . . . . . . . 8
5. SIP Extensions . . . . . . . . . . . . . . . . . . . . . . . . 11
5.1. SDP handling . . . . . . . . . . . . . . . . . . . . . . . 11
5.2. Metadata . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.3. Recording Pause and Resume . . . . . . . . . . . . . . . . 15
6. Transport . . . . . . . . . . . . . . . . . . . . . . . . . . 15
7. Failover and Recovery . . . . . . . . . . . . . . . . . . . . 15
8. Error Handling . . . . . . . . . . . . . . . . . . . . . . . . 15
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
9.1. New Content-Disposition Parameter Registrations . . . . . 15
9.2. MIME Type . . . . . . . . . . . . . . . . . . . . . . . . 15
10. Security Considerations . . . . . . . . . . . . . . . . . . . 16
10.1. Authentication and Authorization . . . . . . . . . . . . . 16
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
11.1. Normative References . . . . . . . . . . . . . . . . . . . 16
11.2. Informative References . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17
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1. Introduction
Communication Session recording requires establishment of the
recording session between communication system and recording system.
In order to allow access to such recordings, information about the
communication session (metadata) is also shared between SRC and SRS.
The SIPREC Requirements [I-D.ietf-siprec-req] list a set of
requirements that need to be met by session recording protocols. The
SIPREC protocol, which is specified in this document, meets these
requirements.
The SIPREC protocol uses SIP as the protocol for session
establishment with special attention to reducing size of the required
SIP messages. In addition, it is designed for future extendability
and protocol version management to ensure backward compatability.
The remainder of this document is organized as follows: Section 2
defines the terminology used throughout this document, Section 3
discusses the scope of SIPREC (i.e., which tasks fall within the
scope of SIPREC and which ones are performed using different
mechanisms), Section 4 provides a non-normative overview of SIPREC
operation, and subsequent sections provide the normative
specification of SIPREC.
2. Definitions
The core SIPREC defintions are taken from the requirements document
[I-D.ietf-siprec-req].
[Henry's note: do we really need this section since this is just a
copy and paste?]
Session Recording Server (SRS): A Session Recording Server (SRS)
is a SIP User Agent (UA) that is a specialized media server or
collector that acts as the sink of the recorded media. An SRS is
a logical function that typically archives media for extended
durations of time and provides interfaces for search and retrieval
of the archived media. An SRS is typically implemented as a
multi-port device that is capable of receiving media from several
sources simultaneously. An SRS is typically also the sink of the
recorded session metadata.
Session Recording Client (SRC) A Session Recording Client (SRC) is a
SIP User Agent (UA) that acts as the source of the recorded media,
sending it to the SRS. An SRC is a logical function. Its
capabilities may be implemented across one or more physical
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devices. In practice, an SRC could be a personal device (such as
a SIP phone), a SIP Media Gateway (MG), a Session Border
Controller (SBC) or a SIP Media Server (MS) integrated with an
Application Server (AS). This specification defines the term SRC
such that all such SIP entities can be generically addressed under
one definition. The SRC itself or another entity working on its
behalf (such as a SIP Application Server) may act as the source of
the recording metadata.
Communication Session (CS) A session created between two or more SIP
User Agents (UAs) that is the target for recording.
Recording Session (RS) The SIP session created between an SRC and
SRS for the purpose of recording a Communication Session.
Metadata Information that describes recorded media and the CS to
which they relate.
SIPREC The set of SIP extensions that supports recording of
Communication Sessions.
Pause during a Communication Session: The action of temporarily
discontinuing the transmission and collection of RS media.
Resume during a Communication Session: The action of recommencing
the transmission and collection of RS media.
Figure 1 shows the relationship between the defintions.
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+-------------+ +-----------+
| | Communication Session | |
| A |<------------------------------------>| B |
| | | |
+-------------+ +-----------+
..................................................................
. Session .
. Recording .
. Client .
..................................................................
|
| Recording
| Session
|
v
+------------+
| Session |
| Recording |
| Server |
+------------+
Figure 1: Relationship between CS, SRC, SRS, and RS
3. Scope
The scope of the SIPREC protocol includes the establishment of the
recording sessions and the reporting of the metadata. The following
items, which is not an exhaustive list, do not represent the SIPREC
protcol itself and are considered out of the scope of the SIPREC
protcol:
o Recording policies that determine whether the CS should be
recorded
o Retention policies that determine how long a recording is stored
o Searching and accessing the recorded media and metadata
o Delivering recording session metadata through non-SIP mechanism
4. Overview of operations
This section provides a description of SIPREC operations.
As mentioned in the architecture document
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[I-D.ietf-siprec-architecture], there are a couple of types of call
flows based on the location of the Session Recording Client. The
following sample call flows provide a quick overview of the
operations between the SRC and the SRS.
4.1. Delivering recorded media
When the SRC is deployed as a B2BUA, the SRC can route call requests
from UA(A) to UA(B). As a SIP B2BUA, the SRC has access to the media
path between the user agents. When the SRC is aware that it should
be recording the conversation, the SRC may bridge the media between
UA(A) and UA(B). The SRC then establishes the Recording Session with
the SRS and sends replicated media towards the SRS.
UA A SRC UA B SRS
|(1)CS INVITE | | |
|------------->| | |
| |(2)CS INVITE | |
| |---------------------->| |
| | (3)OK | |
| |<----------------------| |
| (4)OK | | |
|<-------------| | |
| |(5)RS INVITE (CallId + Participants) with SDP |
| |--------------------------------------------->|
| | | (6)OK with SDP |
| |<---------------------------------------------|
|(7)CS RTP | | |
|=============>|======================>| |
|<=============|<======================| |
| |(8)RS RTP | |
| |=============================================>|
| |=============================================>|
|(9)CS BYE | | |
|------------->| | |
| |(10)CS BYE | |
| |---------------------->| |
| |(11)RS BYE | |
| |--------------------------------------------->|
| | | |
Figure 3: Recording Call flow - SRC as a B2BUA
When one of the endpoint is also acting as the SRC, the endpoint
itself will be establishing the Recording Session to the SRS. Since
the endpoint has access to the media in the communication session,
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the endpoint can send replicated media towards the SRS.
UA A UA B SRS
(SRC) | |
|(1)CS INVITE | |
|---------------------->| |
| (2)OK | |
|<----------------------| |
|(3)RS INVITE (CallId + Participants) with SDP |
|--------------------------------------------->|
| | (4)OK with SDP |
|----------------------------------------------|
|(5)CS RTP | |
|======================>| |
|<======================| |
|(6)RS RTP | |
|=============================================>|
|=============================================>|
|(7)CS BYE | |
|---------------------->| |
|(8)RS BYE | |
|--------------------------------------------->|
| | |
Figure 4: Recording Call flow - SRC as the endpoint
A conference focus may also act as an SRC since it has access to all
the media from each conference participant. In this example, a user
agent may REFER the conference focus to the SRS, and the SRC may
choose to mix media streams from all participants as a single media
stream towards the SRS.
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UA A Focus UA B SRS
| (SRC) | |
| | | |
| (already in a conference) | |
|<==================>|<==================>| |
|(1)REFER sip:Conf-ID Refer-To:SRS | |
|------------------->| |
|(2)202 Accepted | |
|<-------------------| |
| (3)NOTIFY (Trying)| |
|<-------------------| |
|(4)200 OK | |
|------------------->| |
| |(5)INVITE Contact:Conf-ID;isfocus |
| |--------------------------------------->|
| | (6)200 OK |
| |<---------------------------------------|
| | (7)RTP (mixed or unmixed) |
| |=======================================>|
| (8)NOTIFY (OK) | |
|<-------------------| |
|(9)200 OK | |
|------------------->| |
Figure 5: Recording call flow - SRC as a conference focus
4.2. Delivering recording metadata
Certain metadata, such as the attributes of the recorded media
stream, are already included in the SDP of the recording session.
This information is reused as part of the metadata. The SRC may
update or add additional metadata about recorded media streams in
requests such as INVITE, reINVITE, and UPDATE in the Recording
Session.
The rest of the metadata will be delivered as content. Metadata can
also be represented as a stream of events. There are 4 ways to
transport metadata events as outlined in the architecture document:
SIP INVITE Content: for a simple call recording use case where no
mid-dialog events are required to be delivered after the RS is
established, the SIP INVITE may include content for all the metadata
needed for the call.
SIP INFO Package: metadata can be provided as an INFO package and
sent as mid-dialog messages within the recording session.
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UA A UA B SRS
(SRC) | |
|(1)CS INVITE | |
|---------------------->| |
| (2)OK | |
|<----------------------| |
|(3)RS INVITE (SDP) | |
|--------------------------------------------->|
| | (4)OK with SDP |
|----------------------------------------------|
|(5)CS RTP | |
|======================>| |
|<======================| |
|(6)RS RTP | |
|=============================================>|
|=============================================>|
|(7)RS INFO (metadata) | |
|--------------------------------------------->|
|(8)CS BYE | |
|---------------------->| |
|(9)RS BYE | |
|--------------------------------------------->|
| | |
Figure 6: Delivering metadata via SIP INFO
Event Package: Metadata can also be conveyed from the SRC to the SRS
using the SIP event notification mechanism [RFC3265]. Using a
subscription allows the SRC to deliver metadata to the SRS when the
lifecycles of the CS and RS are different. This also allows the SRC
to deliver session metadata and recorded media separately, for
example, an SRS that reports metadata for multiple recording sessions
as a single subscription.
[Henry's note: is it the responsibility of the SRS to find the URI of
the SRC when sending the SUBSCRIBE request?]
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UA A SRC UA B SRS
| |(1)SUBSCRIBE Event: rs-metadata |
| |<---------------------------------------------|
| | | (2)OK |
| |--------------------------------------------->|
| |(3)NOTIFY |
| |--------------------------------------------->|
| | | (4)OK |
| |<---------------------------------------------|
|(5)CS INVITE | | |
|------------->| | |
| |(6)CS INVITE | |
| |---------------------->| |
| | (7)OK | |
| |<----------------------| |
| (8)OK | | |
|<-------------| | |
| |(9)RS INVITE (CallId + Participants) with SDP |
| |--------------------------------------------->|
| | | (10)OK with SDP |
| |<---------------------------------------------|
|(11)CS RTP | | |
|=============>|======================>| |
|<=============|<======================| |
| |(12)RS RTP | |
| |=============================================>|
| |=============================================>|
| |(13)NOTIFY (metadata) |
| |--------------------------------------------->|
| | | (14)OK |
| |<---------------------------------------------|
|(15)CS BYE | | |
|------------->| | |
| |(16)CS BYE | |
| |---------------------->| |
| |(17)RS BYE | |
| |--------------------------------------------->|
| | | |
Figure 7: Delivering metadata via Events
In some cases session metadata can be conveyed through non-SIP
mechanism such as HTTP or JTAPI. These non-SIP mechanisms are
considered out of the scope of the SIPREC protocol, however, it is
envisoned that a link with a URI can be provided in the recording
session INVITE message so that the SRS can access the session
metadata via the URI provided that the SRS supports the type of URI.
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5. SIP Extensions
The recording session is a SIP Session and negotiates recorded media
streams sent from the SRC to the SRS. In order to identify itself as
a recording session, the SRC MUST include the src media feature tag
[I-D.johnston-siprec-cc-rec] in the Contact header of the initial
INVITE request. When the SRS provides the response, the SRS MUST
include the srs media feature tag in the Contact header.
The From header MUST contain the identity of the SRC. Participants
information is not recorded in the From or To header; they are
included in the metadata information.
Note that a recording session does not have to have live within the
scope of a single communication session. As outline in REQ-004 of
[I-D.ietf-siprec-req], the recording session can be established in
the absence of a communication session. In this case, the SRC MUST
offer an SDP with zero m= lines.
Recorded media from multiple communication sessions may be handled in
a single recording session. The SRC provides a reference of each
recorded media stream to the metadata described in the next section.
The SRC MUST be able to accept re-INVITE from SRS with the updated
SDP as part of the session timer mechanism.
5.1. SDP handling
SRC can include one or more media streams to the SRS. The SRS MUST
respond with the same number of media descriptors in the SDP body of
the 200 OK.
The SRC should use a=sendonly attribute as the SRC does not expect to
receive media from the SRS. As SRS only receives RTP streams from
SRS, the 200 OK response will normally contain SDP with a=recvonly
attribute.
Since the SRC may send recorded media of different participants (or
even mixed streams) to the SRS, the SDP MUST provide a label on each
media stream in order to identify the recorded stream with the rest
of the metadata. The a=label attribute [RFC4574] will be used to
identify each recorded media stream, and the label name will be used
as the reference for the metadata. Note that a participant may have
multiple streams (audio and video) and each stream is labeled
separately.
[Henry's note: I think the direction of media should be provided in
the metadata as long as we have a label to reference it in the
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metadata?]
v=0
o=SRS 0 0 IN IP4 172.22.3.8
s=SRS
c=IN IP4 172.22.3.8
t=0 0
m=audio 12241 RTP/AVP 0 4 8
a=sendonly
a=label:1
m=audio 12242 RTP/AVP 98
a=rtpmap:98 H264/90000
a=fmtp:98 ...
a=sendonly
a=label:2
m=audio 12243 RTP/AVP 0 4 8
a=sendonly
a=label:3
m=audio 12244 RTP/AVP 98
a=rtpmap:98 H264/90000
a=fmtp:98 ...
a=sendonly
a=label:4
Figure 8: Sample SDP with audio and video streams
To remove a recorded media stream from the recording session, send a
reINVITE and set the port to zero in the m= line.
To add a recorded media stream, send a reINVITE and add a new m=
line.
The SRS may respond with a=inactive attribute as part of the SDP in
the 200 OK response when the SRS is not ready to receive recorded
media. The SRS can send re-INVITE to update the SDP with a=recvonly
when it is ready to receive media.
The following sequence diagram shows an example of SRS responds with
SDP that contain a=inactive, and then later update media information
update with re-INVITE.
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SRC SRS
| |
|(1) INVITE (no offer) |
|---------------------------------------------------->|
| (2)200 OK with SDP inactive |
|<----------------------------------------------------|
|(3) ACK with SDP inactive |
|---------------------------------------------------->|
| ... |
| (4) re-INVITE with SDP recvonly |
|<----------------------------------------------------|
|(5)200 OK with SDP sendonly |
|---------------------------------------------------->|
| (6) ACK with SDP |
|<----------------------------------------------------|
|(7) RTP |
|====================================================>|
| ... |
|(8) BYE |
|---------------------------------------------------->|
| (9) OK |
|<----------------------------------------------------|
Figure 9: SRS to offer with a=inactive
5.2. Metadata
The format of the full metadata will be described as part of the
mechanism in [I-D.ram-siprec-metadata].
As mentioned in the previous section, the SDP of the recording
session is the metadata for all recorded media streams. The label
attribute contains a reference to the rest of the metadata
information.
For all basic metadata information such as communication session,
participants, call identifiers and direction, they can be included in
the initial INVITE request sent by the SRC. Metadata can be included
as content in the INVITE request. A new "dispoition-type" of
Content-Disposition is defined for this purpose and the value is
"recording-session".
Recording metadata can also be a stream of events. The metaadata
events can be reported using SIP SUBSCRIBE/NOTIFY mechanism.
[Henry's note: should we support both INFO packages and Event
packages assuming both effectively contains the same content for
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metadata?]
The following SIP example for RS establishment between SRC and SRS
with metadata as content.
INVITE sip:97753210@10.240.3.10:5060 SIP/2.0
From: <sip:2000@10.226.240.3>;tag=35e195d2-947d-4585-946f-098392474
To: <sip:Recorder@10.240.3.10>
Call-ID: d253c800-b0d1ea39-4a7dd-3f0e20a@10.226.240.3
CSeq: 101 INVITE
Date: Thu, 26 Nov 2009 02:38:49 GMT
Supported: timer
Supported: replaces
User-Agent: B2BUA
Max-Forwards: 70
Allow: INVITE,OPTIONS,INFO,BYE,CANCEL,ACK,PRACK,UPDATE,
REFER,SUBSCRIBE,NOTIFY,PUBLISH
Allow-Events: presence,kpml
Min-SE: 90
Contact: <sip:2000@10.226.240.3:5060;transport=tcp>;isfocus;src
Via: SIP/2.0/TCP 10.226.240.3:5060;branch=z9hG4bKdf6b622b648d9
Session-Expires: 1800
Content-Type: multipart/mixed;boundary=foobar
Content-Length: [length]
--foobar
Content-Type: application/sdp
v=0
o=SRS 0 0 IN IP4 10.226.240.3
c=IN IP4 10.226.240.3
t=0 0
m=audio 12241 RTP/AVP 0 4 8
a=sendonly
a=label:1
--foobar
Content-Type: application/rs-metadata
Content-Disposition: recording-session
[metadata content]
Figure 10: Sample INVITE request for the recording session
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5.3. Recording Pause and Resume
To temporarily discontinue streaming of recorded media from the SRC
to the SRS, the SRC MUST send a reINVITE and set a=inactive for each
recorded media stream to be paused.
To resume streaming of recorded media, the SRC must send a reINVITE
and set a=sendonly for each recorded media stream to resume.
[Henry's note: how do we tell the difference between pause/resume of
recorded media and mute/unmute of the communication session?]
6. Transport
TBD
7. Failover and Recovery
TBD
8. Error Handling
TBD
9. IANA Considerations
9.1. New Content-Disposition Parameter Registrations
This document registers a new "disposition-type" value in Content-
Disposition header: recording-session.
recording-session the body describes the metadata information about
the recording session
9.2. MIME Type
This document registers the [TBD] 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
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Required parameters: none
Options parameters: none
10. 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.
10.1. Authentication and Authorization
The recording session reuses the SIP mechanism to challenge requests
that is based on HTTP authentication. The mechanism relies on 401
and 407 SIP responses as well as other SIP header fields for carrying
challenges and credentials.
The SRS may have its own set of recording policies to authorize
recording requests from the SRC. The use of recording policies is
outside the scope of the SIPREC protocol.
11. References
11.1. Normative References
[I-D.ietf-siprec-req]
Rehor, K., Portman, L., Hutton, A., and R. Jain,
"Requirements for SIP-based Media Recording (SIPREC)",
draft-ietf-siprec-req-05 (work in progress),
December 2010.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2804] IAB and IESG, "IETF Policy on Wiretapping", RFC 2804,
May 2000.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261,
June 2002.
[RFC3265] Roach, A., "Session Initiation Protocol (SIP)-Specific
Event Notification", RFC 3265, June 2002.
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[RFC4574] Levin, O. and G. Camarillo, "The Session Description
Protocol (SDP) Label Attribute", RFC 4574, August 2006.
11.2. Informative References
[I-D.ietf-siprec-architecture]
Hutton, A., Portman, L., Jain, R., and K. Rehor, "An
Architecture for Media Recording using the Session
Initiation Protocol", draft-ietf-siprec-architecture-01
(work in progress), October 2010.
[I-D.johnston-siprec-cc-rec]
Johnston, A. and A. Hutton, "SIP Call Control - Recording
Extensions", draft-johnston-siprec-cc-rec-00 (work in
progress), July 2010.
[I-D.ram-siprec-metadata]
R, R., R, P., and P. Kyzivat, "Session Initiation Protocol
(SIP) Recording Metadata", draft-ram-siprec-metadata-01
(work in progress), October 2010.
Authors' Addresses
Leon Portman (editor)
NICE Systems
8 Hapnina
Ra'anana 43017
Israel
Email: leon.portman@nice.com
Henry Lum
Genesys, Alcatel-Lucent
1380 Rodick Road, Suite 200
Markham, Ontario L3R4G5
Canada
Email: henry.lum@genesyslab.com
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