draft-ietf-siprec-protocol-00.txt   draft-ietf-siprec-protocol-01.txt 
SIPREC L. Portman, Ed. SIPREC L. Portman, Ed.
Internet-Draft NICE Systems Internet-Draft NICE Systems
Intended status: Standards Track H. Lum, Ed. Intended status: Standards Track H. Lum, Ed.
Expires: February 16, 2012 Genesys, Alcatel-Lucent Expires: April 28, 2012 Genesys, Alcatel-Lucent
A. Johnston A. Johnston
Avaya Avaya
A. Hutton A. Hutton
Siemens Enterprise Siemens Enterprise
Communications Communications
August 15, 2011 October 26, 2011
Session Recording Protocol Session Recording Protocol
draft-ietf-siprec-protocol-00 draft-ietf-siprec-protocol-01
Abstract Abstract
The Session Recording Protocol is used for establishing recording This document specifies the use of the Session Initiation Protocol
session and reporting of the metadata of the communication session. (SIP), the Session Description Protocol (SDP), and the Real Time
Protocol (RTP) for delivering real-time media and metadata from a
This document specifies the Session Recording Protocol. The protocol communication session to a recording device.
is used between Session Recording Client (SRC) and Session Recording
Server (SRS).
Status of this Memo Status of this Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on February 16, 2012. This Internet-Draft will expire on April 28, 2012.
Copyright Notice Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
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publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 3, line 12 skipping to change at page 2, line 17
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Overview of operations . . . . . . . . . . . . . . . . . . . . 5 4. Overview of operations . . . . . . . . . . . . . . . . . . . . 5
4.1. Delivering recorded media . . . . . . . . . . . . . . . . 5 4.1. Delivering recorded media . . . . . . . . . . . . . . . . 5
4.2. Conference focus as an SRC . . . . . . . . . . . . . . . . 6 4.2. Delivering recording metadata . . . . . . . . . . . . . . 7
4.3. Delivering recording metadata . . . . . . . . . . . . . . 7 5. Initiating a Recording Session . . . . . . . . . . . . . . . . 8
5. SIP Extensions for Recording Session . . . . . . . . . . . . . 8 5.1. Procedures at the SRC . . . . . . . . . . . . . . . . . . 8
5.1. Callee Capabilities Extensions for SIP Recording . . . . . 9 5.2. Procedures at the SRS . . . . . . . . . . . . . . . . . . 9
5.1.1. src Feature Tag . . . . . . . . . . . . . . . . . . . 9 6. SDP Handling . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.1.2. srs Feature Tag . . . . . . . . . . . . . . . . . . . 10 6.1. Procedures at the SRC . . . . . . . . . . . . . . . . . . 10
5.2. recording-session Options Tag . . . . . . . . . . . . . . 10 6.1.1. Handling media stream updates . . . . . . . . . . . . 11
5.3. SDP handling . . . . . . . . . . . . . . . . . . . . . . . 11 6.2. Procedures at the SRS . . . . . . . . . . . . . . . . . . 12
5.4. RTP handling . . . . . . . . . . . . . . . . . . . . . . . 13 7. RTP Handling . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.5. Metadata . . . . . . . . . . . . . . . . . . . . . . . . . 13 8. Metadata . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.6. Requesting for metadata snapshot . . . . . . . . . . . . . 15 8.1. Procedures at the SRC . . . . . . . . . . . . . . . . . . 13
5.6.1. Formal Syntax . . . . . . . . . . . . . . . . . . . . 16 8.2. Procedures at the SRS . . . . . . . . . . . . . . . . . . 14
5.7. Recording Pause and Resume . . . . . . . . . . . . . . . . 16 8.2.1. Formal Syntax . . . . . . . . . . . . . . . . . . . . 16
6. Extensions for Recording-aware User Agents . . . . . . . . . . 16 9. Persistent Recording . . . . . . . . . . . . . . . . . . . . . 16
6.1. SIP Extensions . . . . . . . . . . . . . . . . . . . . . . 17 10. Extensions for Recording-aware User Agents . . . . . . . . . . 16
6.1.1. Recording awareness . . . . . . . . . . . . . . . . . 17 10.1. Procedures at the record-aware user agent . . . . . . . . 17
6.2. SDP Extensions . . . . . . . . . . . . . . . . . . . . . . 17 10.1.1. Recording preference . . . . . . . . . . . . . . . . . 17
6.2.1. Providing recording indication . . . . . . . . . . . . 17 10.2. Procedures at the SRC . . . . . . . . . . . . . . . . . . 18
6.2.2. Recording preference . . . . . . . . . . . . . . . . . 19 10.2.1. Recording indication . . . . . . . . . . . . . . . . . 18
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 10.2.2. Recording preference . . . . . . . . . . . . . . . . . 20
7.1. Registration of Option Tags . . . . . . . . . . . . . . . 19 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
7.1.1. recording-session Option Tag . . . . . . . . . . . . . 20 11.1. Registration of Option Tags . . . . . . . . . . . . . . . 20
7.1.2. record-aware Option Tag . . . . . . . . . . . . . . . 20 11.1.1. siprec Option Tag . . . . . . . . . . . . . . . . . . 20
7.2. Registration of media feature tags . . . . . . . . . . . . 20 11.1.2. record-aware Option Tag . . . . . . . . . . . . . . . 20
7.2.1. src feature tag . . . . . . . . . . . . . . . . . . . 20 11.2. Registration of media feature tags . . . . . . . . . . . . 20
7.2.2. srs feature tag . . . . . . . . . . . . . . . . . . . 21 11.2.1. src feature tag . . . . . . . . . . . . . . . . . . . 20
7.3. New Content-Disposition Parameter Registrations . . . . . 21 11.2.2. srs feature tag . . . . . . . . . . . . . . . . . . . 21
7.4. Media Type Registration . . . . . . . . . . . . . . . . . 21 11.3. New Content-Disposition Parameter Registrations . . . . . 21
7.4.1. Registration of MIME Type application/rs-metadata . . 21 11.4. Media Type Registration . . . . . . . . . . . . . . . . . 22
7.4.2. Registration of MIME Type 11.4.1. Registration of MIME Type application/rs-metadata . . 22
11.4.2. Registration of MIME Type
application/rs-metadata-request . . . . . . . . . . . 22 application/rs-metadata-request . . . . . . . . . . . 22
7.5. SDP Attributes . . . . . . . . . . . . . . . . . . . . . . 22 11.5. SDP Attributes . . . . . . . . . . . . . . . . . . . . . . 22
7.5.1. 'record' SDP Attribute . . . . . . . . . . . . . . . . 22 11.5.1. 'record' SDP Attribute . . . . . . . . . . . . . . . . 22
7.5.2. 'recordpref' SDP Attribute . . . . . . . . . . . . . . 22 11.5.2. 'recordpref' SDP Attribute . . . . . . . . . . . . . . 23
8. Security Considerations . . . . . . . . . . . . . . . . . . . 23 12. Security Considerations . . . . . . . . . . . . . . . . . . . 23
8.1. Authentication and Authorization . . . . . . . . . . . . . 23 12.1. Authentication and Authorization . . . . . . . . . . . . . 23
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 23 13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 23
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 23 14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 24
10.1. Normative References . . . . . . . . . . . . . . . . . . . 23 14.1. Normative References . . . . . . . . . . . . . . . . . . . 24
10.2. Informative References . . . . . . . . . . . . . . . . . . 24 14.2. Informative References . . . . . . . . . . . . . . . . . . 25
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 24 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 25
1. Introduction 1. Introduction
Communication Session (CS) recording requires establishment of the This document specifies the mechanism to record a Communication
recording session between communication system and recording system. Session (CS) by delivering real-time media and metadata from the CS
In order to allow access to such recordings, the metadata about the to a recording device. In accordance to the architecture
CS shall be sent from the SRC to the SRS. [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.
The SIP-based Media Recording Requirements [RFC6341] list a set of SIP is also used to deliver metadata to the recording device, as
requirements that need to be met by session recording protocols. The specified in [I-D.ietf-siprec-metadata].
Session Recording Protocol, which is specified in this document,
meets these requirements.
The remainder of this document is organized as follows: Section 2 The Session Recording Protocol intends to satisfy the SIP-based Media
defines the terminology used throughout this document, Section 3 Recording requirements listed in [RFC6341].
discusses the scope of the Session Recording Protocol, Section 4
provides a non-normative overview of recording operations, Section 5
provides normative description of SIP extensions for the Recording
Session, Section 6 provides normative description of SIP extensions
for recording-aware user agents.
2. Definitions 2. Definitions
This document refers to the core definitions provided in the This document refers to the core definitions provided in the
architecture document [I-D.ietf-siprec-architecture]. architecture document [I-D.ietf-siprec-architecture].
3. Scope 3. Scope
The scope of the Session Recording Protocol includes the The scope of the Session Recording Protocol includes the
establishment of the recording sessions and the reporting of the establishment of the recording sessions and the reporting of the
metadata. The scope also includes extensions supported by Record- metadata. The scope also includes extensions supported by User
aware User Agents such as indication of recording. The following Agents participating in the CS such as indication of recording. The
items, which are not an exhaustive list, do not represent the user agents need not be recording-aware in order to participate in a
protocol itself and are considered out of the scope of the Session CS being recorded.
Recording Protocol:
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 o Recording policies that determine whether the CS should be
recorded recorded and whether parts of the CS are to be recorded
o Retention policies that determine how long a recording is stored o Retention policies that determine how long a recording is stored
o Searching and accessing the recorded media and metadata o Searching and accessing the recorded media and metadata
o Delivering recording session metadata through non-SIP mechanism 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 4. Overview of operations
This section is informative and provides a description of recording This section is informative and provides a description of recording
operations. operations.
As mentioned in the architecture document As mentioned in the architecture document
[I-D.ietf-siprec-architecture], there are a couple of types of call [I-D.ietf-siprec-architecture], there are a couple of types of call
flows based on the location of the Session Recording Client. The flows based on the location of the Session Recording Client. The
following sample call flows provide a quick overview of the following sample call flows provide a quick overview of the
operations between the SRC and the SRS. operations between the SRC and the SRS.
4.1. Delivering recorded media 4.1. Delivering recorded media
When the SRC is deployed as a B2BUA, the SRC can route call requests When a B2BUA with SRC functionality routes a call from UA(A) to
from UA(A) to UA(B). As a SIP B2BUA, the SRC has access to the media UA(B), the SRC has access to the media path between the user agents.
path between the user agents. When the SRC is aware that it should When the SRC is aware that it should be recording the conversation,
be recording the conversation, the SRC may bridge the media between the SRC can cause the B2BUA to bridge the media between UA(A) and
UA(A) and UA(B). The SRC then establishes the Recording Session with UA(B). The SRC then establishes the Recording Session with the SRS
the SRS and sends replicated media towards the SRS. and sends replicated media towards the SRS.
An endpoint can also be acting as the SRC, and the endpoint itself An endpoint may also have SRC functionality, where the endpoint
will be establishing the Recording Session to the SRS. Since the itself establishes the Recording Session to the SRS. Since the
endpoint has access to the media in the Communication Session, the endpoint has access to the media in the Communication Session, the
endpoint can send replicated media towards the SRS. endpoint can send replicated media towards the SRS.
The following is a sample call flow that shows the SRC establishing a The following is a sample call flow that shows the SRC establishing a
recording session towards the SRS. The call flow is essentially recording session towards the SRS. The call flow is essentially
identical when the SRC is a B2BUA or as the endpoint itself. Note identical when the SRC is a B2BUA or as the endpoint itself. Note
that the SRC can choose when to establish the Recording Session that the SRC can choose when to establish the Recording Session
independent of the Communication Session, even though the following independent of the Communication Session, even though the following
call flow suggests that the SRC is establishing the Recording Session call flow suggests that the SRC is establishing the Recording Session
(message #5) after the Communication Session is established. (message #5) after the Communication Session is established.
skipping to change at page 6, line 34 skipping to change at page 6, line 34
|(9)CS BYE | | | |(9)CS BYE | | |
|------------->| | | |------------->| | |
| |(10)CS BYE | | | |(10)CS BYE | |
| |---------------------->| | | |---------------------->| |
| |(11)RS BYE | | | |(11)RS BYE | |
| |--------------------------------------------->| | |--------------------------------------------->|
| | | | | | | |
Figure 1: Basic Recording Call flow Figure 1: Basic Recording Call flow
4.2. Conference focus as an SRC The above call flow can also apply to the case of a centralized
conference with a mixer. The conference focus can provide the SRC
A conference focus may also act as an SRC since it has access to all functionality since the conference focus has access to all the media
the media from each conference participant. In this example, a user from each conference participant. When a recording is requested, the
agent may REFER the conference focus to the SRS, and the SRC may SRC delivers the metadata and the media streams to the SRS. Since
choose to mix media streams from all participants as a single media the conference focus has access to a mixer, the SRC may choose to mix
stream towards the SRS. In order to tell the conference focus to the media streams from all participants as a single mixed media
start a recording session to the SRS, the user agent can include the stream towards the SRS.
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 a conference focus 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.
4.3. Delivering recording metadata 4.2. Delivering recording metadata
Certain metadata, such as the attributes of the recorded media The SRC is responsible to deliver metadata to the SRS. The SRC may
stream, are already included in the SDP of the recording session.
This information is reused as part of the metadata. The SRC may
provide an initial metadata snapshot about recorded media streams in provide an initial metadata snapshot about recorded media streams in
the initial INVITE content in the recording session. Subsequent the initial INVITE content in the recording session. Subsequent
metadata updates can be represented as a stream of events in UPDATE metadata updates can be represented as a stream of events in UPDATE
or reINVITE requests sent by the SRC. These metadata updates are or reINVITE requests sent by the SRC. These metadata updates are
normally incremental updates to the initial metadata snapshot to normally incremental updates to the initial metadata snapshot to
optimize on the size of updates, however, the SRC may also decide to optimize on the size of updates, however, the SRC may also decide to
send a new metadata snapshot anytime. send a new metadata snapshot anytime.
The SRS also has the ability to send a request to the SRC to request Metadata is transported in the body of INVITE or UPDATE messages.
to receive a new metadata snapshot update when the SRS fails to Certain metadata, such as the attributes of the recorded media stream
understand the current stream of incremental updates for whatever are located in the SDP of the recording session.
reason (ie. SRS gets a syntax/semantic error in metadata update, the
SRS crashes and restarts), and the SRS may attach a reason along with The 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 the snapshot request. This request allows both SRC and SRS to
restart the states with a new metadata snapshot so that further restart the states with a new metadata snapshot so that further
metadata incremental updates will be based on the latest metadata metadata incremental updates will be based on the latest metadata
snapshot. Similar to the metadata content, the metadata snapshot snapshot. Similar to the metadata content, the metadata snapshot
request is transported as content in UPDATE or INVITE sent by the SRS request is transported as content in UPDATE or INVITE sent by the SRS
in the recording session. in the recording session.
SRC SRS SRC SRS
| | | |
|(1) INVITE (metadata snapshot) | |(1) INVITE (metadata snapshot) |
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|---------------------------------------------------->| |---------------------------------------------------->|
| (12) 200 OK (SDP answer) | | (12) 200 OK (SDP answer) |
|<----------------------------------------------------| |<----------------------------------------------------|
| (13) UPDATE (metadata update 1 based on snapshot 2) | | (13) UPDATE (metadata update 1 based on snapshot 2) |
|---------------------------------------------------->| |---------------------------------------------------->|
| (14) 200 OK | | (14) 200 OK |
|<----------------------------------------------------| |<----------------------------------------------------|
Figure 3: Delivering metadata via SIP UPDATE Figure 3: Delivering metadata via SIP UPDATE
5. SIP Extensions for Recording Session 5. Initiating a Recording Session
The following sections describe SIP extensions for the Recording
Session.
The From header must contain the identity of the SRC or 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 the scope
of a single communication session. As outline in REQ-005 of
[RFC6341], the recording session can be established in the absence of
a communication session. In this case, the SRC MUST pre-allocate a
recorded media stream and offer an SDP with at least one m= line to
establish a persistent recording session. When the actual call
arrives, the SRC can map recorded media stream to participant media
and minimize media clipping.
Recorded media from multiple communication sessions MAY be handled in
a single recording session. The SRC provides a reference of each
recorded media stream to the metadata described in the next section.
5.1. Callee Capabilities Extensions for SIP Recording
This section discusses how the callee capabilities defined in
[RFC3840] can be extended for SIP call recording.
SIP Callee Capabilities defines feature tags which are used to
represent characteristics and capabilities of a UA. From RFC 3840:
"Capability and characteristic information about a UA is carried
as parameters of the Contact header field. These parameters can
be used within REGISTER requests and responses, OPTIONS responses,
and requests and responses that create dialogs (such as INVITE)."
Note that feature tags are also used in dialog modifying requests and
responses such as re-INVITE and responses to a re-INVITE, and UPDATE.
The 'isfocus' feature tag, defined in [RFC4579] is similar
semantically to this case: it indicates that the UA is acting as a
SIP conference focus, and is performing a specific action (mixing) on
the resulting media stream. This information is available from
OPTIONS queries, dialog package notifications, and the SIP
registration event package.
Two new feature tags are introduced: 'src' and 'srs'.
5.1.1. src Feature Tag 5.1. Procedures at the SRC
The 'src' feature tag is used in Contact URIs by the Session The SRC can initiate a recording session by sending a SIP INVITE
Recording Client (SRC) related to recording sessions. A Session request to the SRS. In this case, the From header MUST contain the
Recording Server uses the presence of this feature tag in dialog identity of the SRC, and the To header MUST contain the identity of
creating and modifying requests and responses to confirm that the the SRS. Participants information is not recorded in the From or To
dialog being created is for the purpose of a Recording Session. In header; they are included in the metadata.
addition, a registrar could discover that a UA is an SRC based on the
presence of this feature tag in a registration. Other SIP Recording
extensions and behaviors can be triggered by the presence of this
feature tag.
Note that we could use a single feature tag, such as 'recording' used The SRC MUST include the 'src' feature tag in the Contact URI, as per
by either an SRC or SRS to identify that the session is a recording [RFC3840], for all recording sessions. An SRS uses the presence of
session. However, due to the differences in functionality and the 'src' feature tag in dialog creating and modifying requests and
behavior between an SRC and SRS, using only one feature tag for both responses to confirm that the dialog being created is for the purpose
is not ideal. For instance, if a routing mistake resulted in a of a Recording Session. In addition, a registrar could discover that
request from a SRC being routed back to another SRC, if only one a UA is an SRC based on the presence of this feature tag in a
feature tag were defined, they would not know right away about the registration. Other SIP Recording extensions and behaviors can be
error and could become confused. With separate feature tags, they triggered by the presence of this feature tag.
would realize the error immediately and terminate the session. Also,
call logs would clearly show the routing error.
To ensure a recording session is redirected to an SRS, an SRC can To ensure a recording session is redirected to an SRS, an SRC can
utilize the SIP Caller Preferences extensions, defined in [RFC3841]. utilize the SIP Caller Preferences extensions, defined in [RFC3841].
The presence of a Accept-Contact: *;sip.srs allows a UA to request 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 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 sure, the SRC would need to include a Require: prefs header field in
the request. the request.
5.1.2. srs Feature Tag 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.
The 'srs' feature tag is used in Contact URIs by the Session 5.2. Procedures at the SRS
Recording Server (SRS) related to recording sessions. A Session
Recording Client uses the presence of this feature tag in dialog The SRS can initiate a recording session by sending a SIP INVITE
creating and modifying requests and responses to confirm that the request to the SRC. In this case, the From header MUST contain the
dialog being created is for the purpose of a Recording Session identity of the SRS, and the To header MUST contain the identity of
(REQ-30). In addition, a registrar could discover that a UA is an the SRC.
SRS based on the presence of this feature tag in a registration.
Other SIP Recording extensions and behaviors can be triggered by the The SRS MUST include the 'srs' feature tag in the Contact URI, as per
presence of this feature tag. [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 To ensure a recording session is redirected to an SRC, an SRS can
utilize the SIP Caller Preferences extensions, defined in [RFC3841]. utilize the SIP Caller Preferences extensions, defined in [RFC3841].
The presence of a Accept-Contact: *;sip.src allows a UA to request 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 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 sure, the SRS would need to include a Require: prefs header field in
the request. the request.
5.2. recording-session Options Tag 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.
Since SIP Caller Preferences extensions are optional to implement for 6. SDP Handling
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 option tag in the Require header so
that other types of user agents can simply reject the INVITE request
with a 420 Bad Extension.
5.3. 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.
Following the SDP offer/answer model in [RFC3264], this section 6.1. Procedures at the SRC
describes the conventions used in the recording session for SDP
handling.
SRC must provide an SDP offer in the initial INVITE to the SRS. SRC Since the SRC does not expect to receive media from the SRS, the SRC
can include one or more media streams to the SRS. The SRS must typically sets each media stream of the SDP offer to only send media,
respond with the same number of media descriptors in the SDP body of by qualifying them with the a=sendonly attribute, according to the
the 200 OK. procedures in [RFC3264].
The SRC should use a=sendonly attribute as the SRC does not expect to The SRC sends recorded streams of participants to the SRS, and the
receive media from the SRS. As SRS only receives RTP streams from SRC MUST provide a label attribute (a=label), as per [RFC4574], on
SRC, the 200 OK response will normally contain SDP with a=recvonly each media stream in order to identify the recorded stream with the
attribute. 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.
Since the SRC may send recorded media of different participants (or The following is an example of SDP with both audio and video recorded
even mixed streams) to the SRS, the SDP must provide a label on each streams.
media stream in order to identify the recorded stream with the rest
of the metadata. The a=label attribute [RFC4574] will be used to
identify each recorded media stream, and the label name is mapped to
the Media Stream Reference in the metadata in
[I-D.ietf-siprec-metadata]. Note that a participant may have
multiple streams (audio and video) and each stream is labeled
separately.
v=0 v=0
o=SRS 0 0 IN IP4 172.22.3.8 o=SRS 2890844526 2890844526 IN IP4 198.51.100.1
s=SRS s=-
c=IN IP4 172.22.3.8 c=IN IP4 198.51.100.1
t=0 0 t=0 0
m=audio 12241 RTP/AVP 0 4 8 m=audio 12240 RTP/AVP 0 4 8
a=sendonly a=sendonly
a=label:1 a=label:1
m=audio 12242 RTP/AVP 98 m=video 22456 RTP/AVP 98
a=rtpmap:98 H264/90000 a=rtpmap:98 H264/90000
a=fmtp:98 ... a=fmtp:98 profile-level-id=42A01E;
a=sendonly sprop-parameter-sets=Z0IACpZTBYmI,aMljiA==
a=label:2 a=sendonly
m=audio 12243 RTP/AVP 0 4 8 a=label:2
a=sendonly m=audio 12242 RTP/AVP 0 4 8
a=label:3 a=sendonly
m=audio 12244 RTP/AVP 98 a=label:3
a=rtpmap:98 H264/90000 m=audio 22458 RTP/AVP 98
a=fmtp:98 ... a=rtpmap:98 H264/90000
a=sendonly a=fmtp:98 profile-level-id=42A01E;
a=label:4 sprop-parameter-sets=Z0IACpZTBYmI,aMljiA==
a=sendonly
a=label:4
Figure 4: Sample SDP with audio and video streams Figure 4: Sample SDP with audio and video streams
To remove a recorded media stream from the recording session, send a 6.1.1. Handling media stream updates
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= Over the lifetime of a recording session, the SRC can add and remove
line. 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 SRS may respond with a=inactive attribute as part of the SDP in The SRC can temporarily discontinue streaming and collection of
the 200 OK response when the SRS is not ready to receive recorded recorded media from the SRC to the SRS for reason such as masking the
media. The SRS can send re-INVITE to update the SDP with a=recvonly recording. In this case, the SRC sends a new SDP offer and sets the
when it is ready to receive media. 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.
The following sequence diagram shows an example of SRS responds with 6.2. Procedures at the SRS
SDP that contain a=inactive, and then later update media information
update with re-INVITE. 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 SRC SRS
| | | |
|(1) INVITE (SDP offer) | |(1) INVITE (SDP offer) |
|---------------------------------------------------->| |---------------------------------------------------->|
| [not ready to record]
| (2)200 OK with SDP inactive | | (2)200 OK with SDP inactive |
|<----------------------------------------------------| |<----------------------------------------------------|
|(3) ACK | |(3) ACK |
|---------------------------------------------------->| |---------------------------------------------------->|
| ... | | ... |
| [ready to record]
| (4) re-INVITE with SDP recvonly | | (4) re-INVITE with SDP recvonly |
|<----------------------------------------------------| |<----------------------------------------------------|
|(5)200 OK with SDP sendonly | |(5)200 OK with SDP sendonly |
|---------------------------------------------------->| |---------------------------------------------------->|
| (6) ACK | | (6) ACK |
|<----------------------------------------------------| |<----------------------------------------------------|
|(7) RTP | |(7) RTP |
|====================================================>| |====================================================>|
| ... | | ... |
|(8) BYE | |(8) BYE |
|---------------------------------------------------->| |---------------------------------------------------->|
| (9) OK | | (9) OK |
|<----------------------------------------------------| |<----------------------------------------------------|
Figure 5: SRS to offer with a=inactive Figure 5: SRS to offer with a=inactive
5.4. RTP handling 7. RTP Handling
[This is a placeholder section to specify any protocol impacts or This is a placeholder section to specify any protocol impacts or
recommendations for RTP usage in the session recording protocol. The recommendations for RTP usage in the session recording protocol. The
details are listed in [I-D.eckel-siprec-rtp-rec]] details are listed in [I-D.eckel-siprec-rtp-rec]
5.5. Metadata 8. Metadata
The format of the full metadata will be described as part of the 8.1. Procedures at the SRC
mechanism in [I-D.ietf-siprec-metadata].
As mentioned in the previous section, the SDP of the recording The SRC is responsible to deliver metadata to the SRS in a recording
session describes the properties of media for all recorded media session. Metadata can be provided by the SRC in the initial INVITE
streams. The label attribute contains a reference to the rest of the request when establishing the recording session, and subsequent
metadata information. metadata updates can be provided by the SRC in reINVITE and UPDATE
requests and responses in the recording session.
For all basic metadata information such as communication session, Certain metadata attributes are contained in the SDP, and others are
participants and call identifiers, they can be included in the contained in a new content type "application/rs-metadata". The
initial INVITE request sent by the SRC. Metadata can be included as format of the metadata is described as part of the mechanism in
content in the INVITE or UPDATE request. A new "disposition-type" of [I-D.ietf-siprec-metadata]. A new "disposition-type" of Content-
Content-Disposition is defined for this purpose and the value is Disposition is defined for the purpose of carrying metadata and the
"recording-session". 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.
The following is an example for RS establishment between SRC and SRS Metadata sent by the SRC can be categorized as either a full metadata
with metadata as content. 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/2.0 INVITE sip:97753210@10.240.3.10:5060 SIP/2.0
From: <sip:2000@10.226.240.3>;tag=35e195d2-947d-4585-946f-098392474 From: <sip:2000@10.226.240.3>;tag=35e195d2-947d-4585-946f-098392474
To: <sip:Recorder@10.240.3.10> To: <sip:Recorder@10.240.3.10>
Call-ID: d253c800-b0d1ea39-4a7dd-3f0e20a@10.226.240.3 Call-ID: d253c800-b0d1ea39-4a7dd-3f0e20a@10.226.240.3
CSeq: 101 INVITE CSeq: 101 INVITE
Date: Thu, 26 Nov 2009 02:38:49 GMT Date: Thu, 26 Nov 2009 02:38:49 GMT
Supported: timer Supported: timer
Max-Forwards: 70 Max-Forwards: 70
Min-SE: 90 Min-SE: 90
Session-Expires: 1800 Session-Expires: 1800
Require: recording-session Require: siprec
Contact: <sip:2000@10.226.240.3:5060;transport=tcp>;src Contact: <sip:2000@10.226.240.3:5060;transport=tcp>;src
Via: SIP/2.0/TCP 10.226.240.3:5060;branch=z9hG4bKdf6b622b648d9 Via: SIP/2.0/TCP 10.226.240.3:5060;branch=z9hG4bKdf6b622b648d9
Content-Type: multipart/mixed;boundary=foobar Content-Type: multipart/mixed;boundary=foobar
Content-Length: [length] Content-Length: [length]
--foobar --foobar
Content-Type: application/sdp Content-Type: application/sdp
v=0 v=0
o=SRS 0 0 IN IP4 10.226.240.3 o=SRS 2890844526 2890844526 IN IP4 198.51.100.1
c=IN IP4 10.226.240.3 s=-
c=IN IP4 198.51.100.1
t=0 0 t=0 0
m=audio 12241 RTP/AVP 0 4 8 m=audio 12240 RTP/AVP 0 4 8
a=sendonly a=sendonly
a=label:1 a=label:1
--foobar --foobar
Content-Type: application/rs-metadata Content-Type: application/rs-metadata
Content-Disposition: recording-session Content-Disposition: recording-session
[metadata content] [metadata content]
Figure 6: Sample INVITE request for the recording session Figure 6: Sample INVITE request for the recording session
Further updates to recording metadata can be delivered as a sequence 8.2. Procedures at the SRS
events reported in SIP UPDATE or reINVITE requests and the SRS must
receive the sequence of events in order. Since there can only be a
single INVITE or UPDATE transaction happening at a time within a SIP
dialog, using sequence number CSeq in the dialog can be a reliable
way for the SRS to identify the receipt of the next metadata update.
At any time during Recording Session, the SRC can send a new metadata
snapshot in a SIP reINVITE request along with an SDP offer. All
subsequent metadata updates will be based on the new metadata
snapshot.
5.6. Requesting for metadata snapshot 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.
The SRS can send a request for metadata snapshot any time after the In the case of an internal failure at the SRS, the SRS may fail to
Recording Session has been established. Typically, the SRS sends recognize a partial update from the SRC. The SRS may be able to
such as request in the case where the SRS is failing to process recover from the internal failure by requesting for a full metadata
further metadata incremental updates. Failure scenarios can include snapshot from the SRC. Certain errors, such syntax errors or
failure to internal SRS error or failure to match metadata update semantic errors in the metadata information, are likely caused by an
sequence. Certain errors, such syntax errors or semantic errors in error on the SRC side, and it is likely the same error will occur
the metadata information, are likely caused by an error on the SRC again even when a full metadata snapshot is requested. In order to
side, and it is likely the same error will occur again when a new avoid repeating the same error, it is RECOMMENDED that the SRS
snapshot is requested. In order to avoid repeating the same error terminate the recording session when a syntax error or semantic error
with snapshot requests, it is RECOMMENDED that the SRS terminate the is detected in the metadata.
recording session when a syntax error or semantic error occurs in the
metadata.
Similar to delivering metadata, the SRS sends the metadata snapshot When the SRS requires a full metadata snapshot, the SRS sends a
request as content in UPDATE or INVITE requests or responses. The metadata snapshot request to the SRC in an INVITE/UPDATE request or
same disposition type "recording-session" is used to note that the in an INVITE/UPDATE response. The metadata snapshot request is
content represents content sent by the SRS. The format of the contained the content with the disposition type "recording-session".
content is application/rs-metadata-request, and the body format is The format of the content is "application/rs-metadata-request", and
chosen to be a simple text-based format with header and values. The the body format is chosen to be a simple text-based format. The
following shows an example: following shows an example:
UPDATE sip:2000@10.226.240.3:5060 SIP/2.0 UPDATE sip:2000@10.226.240.3:5060 SIP/2.0
To: <sip:2000@10.226.240.3>;tag=35e195d2-947d-4585-946f-098392474 To: <sip:2000@10.226.240.3>;tag=35e195d2-947d-4585-946f-098392474
From: <sip:Recorder@10.240.3.10>;tag=1234567890 From: <sip:Recorder@10.240.3.10>;tag=1234567890
Call-ID: d253c800-b0d1ea39-4a7dd-3f0e20a@10.226.240.3 Call-ID: d253c800-b0d1ea39-4a7dd-3f0e20a@10.226.240.3
CSeq: 1 UPDATE CSeq: 1 UPDATE
Supported: timer Supported: timer
Max-Forwards: 70 Max-Forwards: 70
Min-SE: 90 Min-SE: 90
Session-Expires: 1800 Session-Expires: 1800
Require: recording-session Require: siprec
Contact: <sip:Recorder@10.240.3.10:5060>;srs Contact: <sip:Recorder@10.240.3.10:5060>;srs
Via: SIP/2.0/UDP 10.240.3.10:5060;branch=z9hG4bKdf6b622b648d9 Via: SIP/2.0/UDP 10.240.3.10:5060;branch=z9hG4bKdf6b622b648d9
Content-Disposition: recording-session Content-Disposition: recording-session
Content-Type: application/rs-metadata-request Content-Type: application/rs-metadata-request
Content-Length: [length] Content-Length: [length]
Reason: SRS internal error SRS internal error
Figure 7: Metadata Request Figure 7: Metadata Request
The SRS MAY include the reason why a metadata snapshot request is 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 being made to the SRC in the reason line. This reason line is free
text mainly designed for logging purposes on the SRC side. The body form text, mainly designed for logging purposes on the SRC side. The
format also allows additional extension headers to be included by the processing of the content by the SRC is entirely optional since the
SRS in the snapshot request to convey additional information to the content is for logging only, and the snapshot request itself is
SRC. The processing of the content by the SRC is entirely optional indicated by the use of the application/rs-metadata-request content
since the content is for logging only, and the snapshot request type.
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 When the SRC receives the request for a metadata snapshot, the SRC
MUST provide a metadata snapshot in a separate INVITE transaction, MUST provide a full metadata snapshot in a separate INVITE
along with an SDP offer. All subsequent metadata updates sent by the transaction, along with an SDP offer. All subsequent metadata
SRC MUST be based on the new metadata snapshot. updates sent by the SRC MUST be based on the new metadata snapshot.
5.6.1. Formal Syntax 8.2.1. Formal Syntax
The formal syntax for the application/rs-metadata-request MIME is The formal syntax for the application/rs-metadata-request MIME is
described below using the augmented Backus-Naur Form (BNF) as described below using the augmented Backus-Naur Form (BNF) as
described in [RFC2234]. described in [RFC2234].
snapshot-request = srs-reason-line CRLF [ *opt-srs-headers ] snapshot-request = srs-reason-line CRLF
srs-reason-line = "Reason" HCOLON srs-reason
srs-reason = [TEXT-UTF8-TRIM]
opt-srs-headers = CRLF 1*(extension-header CRLF)
5.7. Recording Pause and Resume
To temporarily discontinue streaming and collection of recorded media srs-reason-line = [TEXT-UTF8-TRIM]
from the SRC to the SRS, the SRC sends a reINVITE and set a=inactive
for each recorded media stream to be paused.
To resume streaming and collection of recorded media, the SRC sends a 9. Persistent Recording
reINVITE and set a=sendonly for each recorded media stream to resume.
Note that when a media stream in the CS is muted/unmuted, this Persistent recording is a specific use case outlined in REQ-005 or
information is conveyed in the metadata by the SRC. The SRC SHOULD Use Case 4 in [RFC6341], where a recording session can be established
not modify the recorded media stream with a=inactive for mute since in the absence of a communication session. The SRC continuously
this operation is reserved for pausing the RS media. 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.
6. Extensions for Recording-aware User Agents 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.
The following sections describe SIP and SDP extensions for recording- 10. Extensions for Recording-aware User Agents
aware UA.
6.1. SIP Extensions The following sections describe the SIP and SDP extensions for
recording-aware user agents.
6.1.1. Recording awareness 10.1. Procedures at the record-aware user agent
A recording-aware UA SHOULD indicate that it can accept reporting of A recording-aware UA SHOULD indicate that it can accept reporting of
recording indication in media level SDP provided in the previous recording indication provided by the SRC. A new option tag "record-
section. A new option tag "record-aware" is introduced to indicate aware" is introduced to indicate such awareness. The recording-aware
such awareness. UA SHOULD include the "record-aware" option tag in the Supported
header when initiating or establishing a CS. A recording-aware UA
A UA that has indicated recording awareness by including the record- that has indicated recording awareness MUST provide at recording
aware option tag in a transmitted Supported header field MUST provide indication to the end user through an appropriate user interface an
at its user interface an indication whether recording is on or off indication whether recording is on or off for a given medium based on
for a given medium based on the most recently received a=record SDP the most recently received a=record SDP attribute for that medium.
attribute for that medium.
Some user agents that are automatons (eg. IVR, media server, PSTN Some user agents that are automatons (eg. IVR, media server, PSTN
gateway) may not have a user interface to render recording gateway) may not have a user interface to render recording
indication. When such user agent indicates recording awareness, the indication. When such user agent indicates recording awareness, the
UA SHOULD render recording indication through other means, such as UA SHOULD render recording indication through other means, such as
passing an inband tone on the PSTN gateway, putting the recording passing an inband tone on the PSTN gateway, putting the recording
indication in a log file, or raising an application event in a indication in a log file, or raising an application event in a
VoiceXML dialog. These user agents MAY also choose not to indicate VoiceXML dialog. These user agents MAY also choose not to indicate
recording awareness, thereby relying on whatever mechanism an SRC recording awareness, thereby relying on whatever mechanism an SRC
chooses to indicate recording, such as playing a tone inband. chooses to indicate recording, such as playing a tone inband.
When a UA has not indicated that it is recording aware, an SRC MUST 10.1.1. Recording preference
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 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.
6.2.1. Providing recording indication 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 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 While there are existing mechanisms for providing an indication that
a CS is being recorded, these mechanisms are usually delivered on the 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 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 to the participants. A new SDP attribute is introduced to allow a
recording-aware UA to render recording indication at the user recording-aware UA to render recording indication at the user
interface. interface.
The 'record' SDP attribute appears at the media level in either SDP The 'record' SDP attribute appears at the media level in either SDP
offer or answer. The recording indication applies to the specified offer or answer. The recording indication applies to the specified
media stream only, for example, only the audio portion of the call is 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 recorded in an audio/video call. The following is the ABNF of the
'record' attribute: 'record' attribute:
record-attr = "a=record:" indication attribute /= record-attr
; attribute defined in RFC 4566
record-attr = "record:" indication
indication = "on" / "off" / "paused" indication = "on" / "off" / "paused"
on Recording is in progress. on Recording is in progress.
off No recording is in progress. off No recording is in progress.
paused Recording is in progress by media is paused. paused Recording is in progress by media is paused.
The recording attribute is a declaration by the endpoints in the The recording attribute is a declaration by an endpoint in the CS to
session to indicate whether recording is taking place. For example, indicate whether recording is taking place. For example, if a UA (A)
if a UA (A) is initiating a call to UA (B) and UA (A) is also an SRC is initiating a call to UA (B) and UA (A) is also an SRC that is
that is performing the recording, then UA (A) provides the recording performing the recording, then UA (A) provides the recording
indication in the SDP offer with a=record:on. When UA (B) receives 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 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 other endpoint of this session. If UA (B) does not wish to perform
recording itself, UA (B) provides the recording indication as recording itself, UA (B) provides the recording indication as
a=record:off in the SDP answer. a=record:off in the SDP answer.
Whenever the recording indication needs to change, such as Whenever the recording indication needs to change, such as
termination of recording, then the UA MUST initiate a reINVITE to termination of recording, then the UA MUST initiate a reINVITE to
update the SDP attribute to a=record:off. The following call flow update the SDP attribute to a=record:off. The following call flow
shows an example of the offer/answer with the recording indication shows an example of the offer/answer with the recording indication
skipping to change at page 19, line 14 skipping to change at page 20, line 5
If a call is traversed through one or more SIP B2BUA, and it happens 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 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 indication attribute does not provide any hint as to which SRC is
performing the recording, meaning the endpoint only knows that the performing the recording, meaning the endpoint only knows that the
call is being recorded. This attribute is also not used as an call is being recorded. This attribute is also not used as an
indication to negotiate which SRC in the call path will perform indication to negotiate which SRC in the call path will perform
recording and is not used as a request to start/stop recording if recording and is not used as a request to start/stop recording if
there are multiple SRCs in the call path. there are multiple SRCs in the call path.
6.2.2. Recording preference 10.2.2. 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. When the SRC receives the a=recordpref SDP in an SDP offer or answer,
While the absence of this attribute indirectly implies the lack of the SRC MAY choose to honor such request to record the request based
preference, using this value allows the UA to explicitly state no on local policy on the SRC. When the SRC honors the request, the SRC
preference to being recorded. MUST also update the recording indication to reflect the current
state of the recording (on/off/paused).
7. IANA Considerations 11. IANA Considerations
7.1. Registration of Option Tags 11.1. Registration of Option Tags
This specification registers two option tags. The required This specification registers two option tags. The required
information for this registration, as specified in [RFC3261], is as information for this registration, as specified in [RFC3261], is as
follows. follows.
7.1.1. recording-session Option Tag 11.1.1. siprec Option Tag
Name: recording-session Name: siprec
Description: This option tag is for identifying the SIP session Description: This option tag is for identifying the SIP session
for the purpose of recording session only. This is typically not for the purpose of recording session only. This is typically not
used in a Supported header. When present in a Require header in a 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 request, it indicates that the UAS MUST be either a SRC or SRS
capable of handling the contexts of a recording session. capable of handling the contexts of a recording session.
7.1.2. record-aware Option Tag 11.1.2. record-aware Option Tag
Name: record-aware Name: record-aware
Description: This option tag is to indicate the ability for the Description: This option tag is to indicate the ability for the
user agent to receive recording indicators in media level SDP. user agent to receive recording indicators in media level SDP.
When present in a Supported header, it indicates that the UA can When present in a Supported header, it indicates that the UA can
receive recording indicators in media level SDP. receive recording indicators in media level SDP.
7.2. Registration of media feature tags 11.2. Registration of media feature tags
This document registers two new media feature tags in the SIP tree This document registers two new media feature tags in the SIP tree
per the process defined in [RFC2506] and [RFC3840] per the process defined in [RFC2506] and [RFC3840]
7.2.1. src feature tag 11.2.1. src feature tag
Media feature tag name: sip.src Media feature tag name: sip.src
ASN.1 Identifer: 25 ASN.1 Identifier: 25
Summary of the media feature indicated by this tag: This feature Summary of the media feature indicated by this tag: This feature
tag indicates that the user agent is a Session Recording Client tag indicates that the user agent is a Session Recording Client
for the purpose for Recording Session. for the purpose for Recording Session.
Values appropriate for use with this feature tag: boolean Values appropriate for use with this feature tag: boolean
The feature tag is intended primarily for use in the following The feature tag is intended primarily for use in the following
applications, protocols, services, or negotiation mechanisms: This applications, protocols, services, or negotiation mechanisms: This
feature tag is only useful for a Recording Session. feature tag is only useful for a Recording Session.
Examples of typical use: Routing the request to a Session Examples of typical use: Routing the request to a Session
Recording Server. Recording Server.
Security Considerations: Security considerations for this media Security Considerations: Security considerations for this media
feature tag are discussed in Section 11.1 of RFC 3840. feature tag are discussed in Section 11.1 of RFC 3840.
7.2.2. srs feature tag 11.2.2. srs feature tag
Media feature tag name: sip.srs Media feature tag name: sip.srs
ASN.1 Identifer: 26 ASN.1 Identifier: 26
Summary of the media feature indicated by this tag: This feature Summary of the media feature indicated by this tag: This feature
tag indicates that the user agent is a Session Recording Server tag indicates that the user agent is a Session Recording Server
for the purpose for Recording Session. for the purpose for Recording Session.
Values appropriate for use with this feature tag: boolean Values appropriate for use with this feature tag: boolean
The feature tag is intended primarily for use in the following The feature tag is intended primarily for use in the following
applications, protocols, services, or negotiation mechanisms: This applications, protocols, services, or negotiation mechanisms: This
feature tag is only useful for a Recording Session. feature tag is only useful for a Recording Session.
Examples of typical use: Routing the request to a Session Examples of typical use: Routing the request to a Session
Recording Client. Recording Client.
Security Considerations: Security considerations for this media Security Considerations: Security considerations for this media
feature tag are discussed in Section 11.1 of RFC 3840. feature tag are discussed in Section 11.1 of RFC 3840.
7.3. New Content-Disposition Parameter Registrations 11.3. New Content-Disposition Parameter Registrations
This document registers a new "disposition-type" value in Content- This document registers a new "disposition-type" value in Content-
Disposition header: recording-session. Disposition header: recording-session.
recording-session the body describes the metadata information about recording-session the body describes the metadata information about
the recording session the recording session
7.4. Media Type Registration 11.4. Media Type Registration
7.4.1. Registration of MIME Type application/rs-metadata 11.4.1. Registration of MIME Type application/rs-metadata
This document registers the application/rs-metadata MIME media type This document registers the application/rs-metadata MIME media type
in order to describe the recording session metadata. This media type in order to describe the recording session metadata. This media type
is defined by the following information: is defined by the following information:
Media type name: application Media type name: application
Media subtype name: rs-metadata Media subtype name: rs-metadata
Required parameters: none Required parameters: none
Options parameters: none Options parameters: none
7.4.2. Registration of MIME Type application/rs-metadata-request 11.4.2. Registration of MIME Type application/rs-metadata-request
This document registers the application/rs-metadata-request MIME This document registers the application/rs-metadata-request MIME
media type in order to describe a recording session metadata snapshot media type in order to describe a recording session metadata snapshot
request. This media type is defined by the following information: request. This media type is defined by the following information:
Media type name: application Media type name: application
Media subtype name: rs-metadata-request Media subtype name: rs-metadata-request
Required parameters: none Required parameters: none
Options parameters: none Options parameters: none
7.5. SDP Attributes 11.5. SDP Attributes
This document registers the following new SDP attributes. This document registers the following new SDP attributes.
7.5.1. 'record' SDP Attribute 11.5.1. 'record' SDP Attribute
Contact names: Leon Portman leon.portman@nice.com, Henry Lum
henry.lum@genesyslab.com
Attribute name: record Attribute name: record
Long form attribute name: Recording Indication Long form attribute name: Recording Indication
Type of attribute: media level Type of attribute: media level
Subject to charset: no Subject to charset: no
This attribute provides the recording indication for the session or This attribute provides the recording indication for the session or
media stream. media stream.
Allowed attribute values: on, off, paused Allowed attribute values: on, off, paused
7.5.2. 'recordpref' SDP Attribute 11.5.2. 'recordpref' SDP Attribute
Contact names: Leon Portman leon.portman@nice.com, Henry Lum
henry.lum@genesyslab.com
Attribute name: recordpref Attribute name: recordpref
Long form attribute name: Recording Preference Long form attribute name: Recording Preference
Type of attribute: media level Type of attribute: media level
Subject to charset: no Subject to charset: no
This attribute provides the recording indication for the session or This attribute provides the recording indication for the session or
media stream. media stream.
Allowed attribute values: on, off, pause, nopreference Allowed attribute values: on, off, pause, nopreference
8. Security Considerations 12. Security Considerations
The recording session is fundamentally a standard SIP dialog The recording session is fundamentally a standard SIP dialog
[RFC3261], therefore, the recording session can reuse any of the [RFC3261], therefore, the recording session can reuse any of the
existing SIP security mechanism available for securing the recorded existing SIP security mechanism available for securing the recorded
media as well as metadata. media as well as metadata. Other security considerations are
outlined in the use cases and requirements document [RFC6341].
8.1. Authentication and Authorization 12.1. Authentication and Authorization
The recording session reuses the SIP mechanism to challenge requests The recording session reuses the SIP mechanism to challenge requests
that is based on HTTP authentication. The mechanism relies on 401 that is based on HTTP authentication. The mechanism relies on 401
and 407 SIP responses as well as other SIP header fields for carrying and 407 SIP responses as well as other SIP header fields for carrying
challenges and credentials. challenges and credentials.
The SRS may have its own set of recording policies to authorize The SRS may have its own set of recording policies to authorize
recording requests from the SRC. The use of recording policies is recording requests from the SRC. The use of recording policies is
outside the scope of the Session Recording Protocol. outside the scope of the Session Recording Protocol.
9. Acknowledgements 13. Acknowledgements
We want to thank John Elwell, Paul Kyzivat, Partharsarathi R, Ram We want to thank John Elwell, Paul Kyzivat, Partharsarathi R, Ram
Mohan R, Charles Eckel, Hadriel Kaplan, Adam Roach for their valuable Mohan R, Charles Eckel, Hadriel Kaplan, Adam Roach, Miguel Garcia for
comments and inputs to this document. their valuable comments and inputs to this document.
10. References 14. References
10.1. Normative References 14.1. Normative References
[I-D.ietf-siprec-metadata] [I-D.ietf-siprec-metadata]
R, R., R, P., and P. Kyzivat, "Session Initiation Protocol R, R., Ravindran, P., and P. Kyzivat, "Session Initiation
(SIP) Recording Metadata", draft-ietf-siprec-metadata-03 Protocol (SIP) Recording Metadata",
(work in progress), July 2011. draft-ietf-siprec-metadata-04 (work in progress),
September 2011.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax [RFC2234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997. Specifications: ABNF", RFC 2234, November 1997.
[RFC2506] Holtman, K., Mutz, A., and T. Hardie, "Media Feature Tag [RFC2506] Holtman, K., Mutz, A., and T. Hardie, "Media Feature Tag
Registration Procedure", BCP 31, RFC 2506, March 1999. Registration Procedure", BCP 31, RFC 2506, March 1999.
skipping to change at page 24, line 27 skipping to change at page 25, line 5
Preferences for the Session Initiation Protocol (SIP)", Preferences for the Session Initiation Protocol (SIP)",
RFC 3841, August 2004. RFC 3841, August 2004.
[RFC4574] Levin, O. and G. Camarillo, "The Session Description [RFC4574] Levin, O. and G. Camarillo, "The Session Description
Protocol (SDP) Label Attribute", RFC 4574, August 2006. Protocol (SDP) Label Attribute", RFC 4574, August 2006.
[RFC6341] Rehor, K., Portman, L., Hutton, A., and R. Jain, "Use [RFC6341] Rehor, K., Portman, L., Hutton, A., and R. Jain, "Use
Cases and Requirements for SIP-Based Media Recording Cases and Requirements for SIP-Based Media Recording
(SIPREC)", RFC 6341, August 2011. (SIPREC)", RFC 6341, August 2011.
10.2. Informative References 14.2. Informative References
[I-D.eckel-siprec-rtp-rec] [I-D.eckel-siprec-rtp-rec]
Eckel, C., "Real-time Transport Protocol (RTP) Eckel, C., "Real-time Transport Protocol (RTP)
Recommendations for SIPREC", draft-eckel-siprec-rtp-rec-01 Recommendations for SIPREC", draft-eckel-siprec-rtp-rec-02
(work in progress), June 2011. (work in progress), September 2011.
[I-D.ietf-siprec-architecture] [I-D.ietf-siprec-architecture]
Hutton, A., Portman, L., Jain, R., and K. Rehor, "An Hutton, A., Portman, L., Jain, R., and K. Rehor, "An
Architecture for Media Recording using the Session Architecture for Media Recording using the Session
Initiation Protocol", draft-ietf-siprec-architecture-02 Initiation Protocol", draft-ietf-siprec-architecture-03
(work in progress), April 2011. (work in progress), October 2011.
[RFC4508] Levin, O. and A. Johnston, "Conveying Feature Tags with [RFC4508] Levin, O. and A. Johnston, "Conveying Feature Tags with
the Session Initiation Protocol (SIP) REFER Method", the Session Initiation Protocol (SIP) REFER Method",
RFC 4508, May 2006. RFC 4508, May 2006.
[RFC4579] Johnston, A. and O. Levin, "Session Initiation Protocol [RFC4579] Johnston, A. and O. Levin, "Session Initiation Protocol
(SIP) Call Control - Conferencing for User Agents", (SIP) Call Control - Conferencing for User Agents",
BCP 119, RFC 4579, August 2006. 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 Authors' Addresses
Leon Portman (editor) Leon Portman (editor)
NICE Systems NICE Systems
8 Hapnina 8 Hapnina
Ra'anana 43017 Ra'anana 43017
Israel Israel
Email: leon.portman@nice.com Email: leon.portman@nice.com
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