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IETF RFC 6341
Last modified on Saturday, August 13th, 2011
 Permanent link to RFC 6341
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Internet Engineering Task Force (IETF) K. Rehor, Ed.
Request for Comments: 6341 Cisco Systems
Category: Informational L. Portman, Ed.
ISSN: 2070-1721 NICE Systems
A. Hutton
Siemens Enterprise Communications
R. Jain
IPC Systems
August 2011
Use Cases and Requirements for SIP-Based Media Recording (SIPREC)
 Abstract
Session recording is a critical requirement in many business
communications environments, such as call centers and financial
trading floors. In some of these environments, all calls must be
recorded for regulatory and compliance reasons. In others, calls may
be recorded for quality control or business analytics.
Recording is typically performed by sending a copy of the session
media to the recording devices. This document specifies requirements
for extensions to SIP that will manage delivery of RTP media to a
recording device. This is being referred to as SIP-based Media
Recording.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/RFC 6341.
Rehor, et al. Informational PAGE 1 
RFC 6341 Requirements for SIPREC August 2011
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction ....................................................2
2. Requirements Notation ...........................................4
3. Definitions .....................................................4
4. Use Cases .......................................................5
5. Requirements ...................................................10
6. Privacy Considerations .........................................13
7. Security Considerations ........................................14
8. Acknowledgements ...............................................15
9. Normative References ...........................................15
1. Introduction
Session recording is a critical operational requirement in many
businesses, especially where voice is used as a medium for commerce
and customer support. A prime example where voice is used for trade
is the financial industry. The call recording requirements in this
industry are quite stringent. The recorded calls are used for
dispute resolution and compliance. Other businesses, such as
customer support call centers, typically employ call recording for
quality control or business analytics, with different requirements.
Depending on the country and its regulatory requirements, financial
trading floors typically must record all calls. In contrast, call
centers typically only record a subset of the calls, and calls must
not fail, regardless of the availability of the recording device.
Respecting the privacy rights and wishes of users engaged in a call
is of paramount importance. In many jurisdictions, participants have
a right to know that the session is being recorded or might be
recorded, and they have a right to opt out, either by terminating the
call or by demanding that the call not be recorded. Therefore, this
Rehor, et al. Informational PAGE 2
RFC 6341 Requirements for SIPREC August 2011
document contains requirements for being able to notify users that a
call is being recorded and for users to be able to request that a
call not be recorded. Use cases where users participating in a call
are not informed that the call is or might be recorded are outside
the scope of this document. In particular, lawful intercept is
outside the scope of this document.
Furthermore, a one-size-fits-all model will not fit all markets where
the scale and cost burdens vary widely and where needs differ for
such solution capabilities as media injection, transcoding, and
security. If a standardized solution supports all of the
requirements from every recording market but doing so would be
expensive for markets with lesser needs, then proprietary solutions
for those markets will continue to propagate. Care must be taken,
therefore, to make a standards-based solution support optionality and
flexibility.
This document specifies requirements for using SIP [RFC 3261] between
a Session Recording Client and a Session Recording Server to control
the recording of media that has been transmitted in the context of a
Communication Session. A Communication Session is the "call" between
participants. The Session Recording Client is the source of the
recorded media. The Session Recording Server is the sink of recorded
media. It should be noted that the requirements for the protocol
between a Session Recording Server and Session Recording Client have
very similar requirements (such as codec and transport negotiation,
encryption key interchange, and firewall traversal) as compared to
regular SIP media sessions. The choice of SIP for session recording
provides reuse of an existing protocol.
The recorded sessions can be any RTP media sessions, including voice,
dual-tone multifrequency (DTMF) (as defined by [RFC 4733]), video, and
text (as defined by [RFC 4103]).
An archived session recording is typically comprised of the
Communication Session media content and the Communication Session
Metadata. The Communication Session Metadata allows recording
archives to be searched and filtered at a later time and allows a
session to be played back in a meaningful way, e.g., with correct
synchronization between the media. The Communication Session
Metadata needs to be conveyed from the Session Recording Client to
the Session Recording Server.
This document only considers active recording, where the Session
Recording Client purposefully streams media to a Session Recording
Server. Passive recording, where a recording device detects media
directly from the network, is outside the scope of this document.
Rehor, et al. Informational PAGE 3
RFC 6341 Requirements for SIPREC August 2011
2. Requirements Notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC 2119] and indicate
requirement levels for compliant mechanisms.
3. Definitions
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
typically implemented as a multi-port device that is capable of
receiving media from multiple sources simultaneously. An SRS is
the sink of the recorded session metadata.
Session Recording Client (SRC): A Session Recording Client (SRC) is a
SIP User Agent (UA) that acts as the source of the recorded media,
sending it to the SRS. An SRC is a logical function. Its
capabilities may be implemented across one or more physical
devices. In practice, an SRC could be a personal device (such as
a SIP phone), a SIP Media Gateway (MG), a Session Border
Controller (SBC), or a SIP Media Server (MS) integrated with an
Application Server (AS). This specification defines the term
"SRC" such that all such SIP entities can be generically addressed
under one definition. The SRC provides metadata to the SRS.
Communication Session (CS): A session created between two or more SIP
User Agents (UAs) that is the subject of recording.
Recording Session (RS): The SIP session created between an SRC and
SRS for the purpose of recording a Communication Session.
Figure 1 pictorially represents the relationship between a Recording
Session and Communication Session.
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RFC 6341 Requirements for SIPREC August 2011
+-------------+ +-----------+
| | Communication Session | |
| A |<------------------------------------>| B |
| | | |
+-------------+ +-----------+
..................................................................
. Session .
. Recording .
. Client .
..................................................................
|
| Recording
| Session
|
v
+------------+
| Session |
| Recording |
| Server |
+------------+
Figure 1
Metadata: Information that describes recorded media and the CS to
which they relate.
Pause and Resume during a Communication Session:
Pause: The action of temporarily discontinuing the transmission
and collection of RS media.
Resume: The action of recommencing the transmission and collection
of RS media.
Most security-related terms in this document are to be understood in
the sense defined in [RFC 4949]; such terms include, but are not
limited to, "authentication", "confidentiality", "encryption",
"identity", and "integrity".
4. Use Cases
Use Case 1: Full-time Recording: One Recording Session for each
Communication Session.
For example, the diagram below shows the life cycle of
Communication Sessions (CSs) and the relationship to the Recording
Sessions (RS).
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CS |--- CS 1 ---| |--- CS 2 ---| |--- CS 3 ---|
RS |--- RS 1 ---| |--- RS 2 ---| |--- RS 3 ---|
t--->
Figure 2
Record every CS for each specific extension/person.
The need to record all calls is typically due to business process
purposes (such as transaction confirmation or dispute resolution)
or to ensure compliance with governmental regulations.
Applications include enterprise, contact center, and financial
trading floors.
This is also commonly known as Total Recording.
Use Case 2: Selective Recording: Start a Recording Session when a
Communication Session to be recorded is established.
In this example, Communication Sessions 1 and 3 are recorded but
CS 2 is not.
CS |--- CS 1 ---| |--- CS 2 ---| |--- CS 3 ---|
RS |--- RS 1----| |--- RS 2 ---|
t--->
Figure 3
Use Case 3: Start/Stop a Recording Session during a Communication
Session.
The Recording Session starts during a Communication Session,
either manually via a user-controlled mechanism (e.g., a button on
a user's phone) or automatically via an application (e.g., a
contact center customer service application) or business event. A
Recording Session ends either during the Communication Session or
when the Communication Session ends. One or more Recording
Sessions may record each Communication Session.
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CS |------------- Communication Session -----------|
RS |---- RS 1 ----| |---- RS 2 -----|
t--->
Figure 4
Use Case 4: Persistent Recording: A single Recording Session captures
one or more Communication Sessions.
|--- CS 1 ---| |--- CS 2 ---| |--- CS 3 ---|
RS |------------------- Recording Session ------------------|
t--->
Figure 5
A Recording Session records continuously without interruption.
Periods when there is no CS in progress must be reproduced upon
playback (e.g., by recording silence during such periods, or by
not recording such periods but marking them by means of metadata
for utilization on playback, etc.). Applications include
financial trading desks and emergency (first-responder) service
bureaus. The length of a Persistent Recording Session is
independent from the length of the actual Communication Sessions.
Persistent Recording Sessions avoid issues such as media clipping
that can occur due to delays in Recording Session establishment.
The connection and attributes of media in the Recording Session
are not dynamically signaled for each Communication Session before
it can be recorded; however, codec re-negotiation is possible.
In some cases, more than one concurrent Communication Session (on
a single end-user apparatus, e.g., trading-floor turret) is mixed
into one Recording Session:
|-------- CS 1 -------|
|-------- CS 2 -------|
|-------- CS 3 -------|
RS |----------- Recording Session --------------|
t--->
Figure 6
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RFC 6341 Requirements for SIPREC August 2011
Use Case 5: Real-time Recording Controls.
For an active Recording Session, privacy or security reasons may
demand not capturing a specific portion of a conversation. An
example is for PCI (payment card industry) compliance where credit
card information must be protected. One solution is not to record
a caller speaking their credit card information.
An example of a real-time control is Pause/Resume.
Use Case 6: IVR / Voice Portal Recording.
Self-service Interactive Voice Response (IVR) applications may
need to be recorded for application performance tuning or to meet
compliance requirements.
Metadata about an IVR session recording must include session
information and may include application context information (e.g.,
VoiceXML session variables, dialog names, etc.).
Use Case 7: Enterprise Mobility Recording.
Many agents and enterprise workers whose calls are to be recorded
are not located on company premises.
Examples:
o Home-based agents or enterprise workers.
o Mobile phones of knowledge workers (e.g., insurance agents,
brokers, or physicians) when they conduct work-related (and
legally required recording) calls.
Use Case 8: Geographically distributed or centralized recording.
Enterprises such as banks, insurance agencies, and retail stores
may have many locations, possibly up to thousands of small sites.
Frequently, only phones and network infrastructure are installed
in branches, without local recording services. In cases where
calls inside or between branches must be recorded, a centralized
recording system in data centers together with telephony
infrastructure (e.g., Private Branch Exchange (PBX)) may be
deployed.
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Use Case 9: Record complex call scenarios.
The following is an example of a scenario where one call that is
recorded must be associated with a related call that also must be
recorded.
o A Customer is in a conversation with a Customer Service Agent.
o The Agent puts the Customer on hold in order to consult with a
Supervisor.
o The Agent enters into a conversation with the Supervisor.
o The Agent disconnects from the Supervisor, then reconnects with
the Customer.
o The Supervisor call must be associated with the original
Customer call.
Use Case 10: High availability and continuous recording.
Specific deployment scenarios present different requirements for
system availability, error handling, etc., including the
following:
o An SRS must always be available at call setup time.
o No loss of media recording can occur, including during failure
of an SRS.
o The Communication Session must be terminated (or suitable
notification given to parties) in the event of a recording
failure.
Use Case 11: Record multi-channel, multimedia session.
Some applications require the recording of more than one media
stream, possibly of different types. Media are synchronized,
either at storage or at playback.
Speech analytics technologies (e.g., word spotting, emotion
detection, speaker identification) may require speaker-separated
recordings for optimum performance.
Multi-modal contact centers may include audio, video, IM, or other
interaction modalities.
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In trading-floor environments, in order to minimize storage and
recording system resources, it may be preferable to mix multiple
concurrent calls (Communication Sessions) on different handsets/
speakers on the same turret into a single recording session.
Use Case 12: Real-time media processing.
It must be possible for an SRS to support real-time media
processing, such as speech analytics of trading-floor
interactions. Real-time analytics may be employed for automatic
intervention (stopping interaction or alerting) if, for example, a
trader is not following regulations.
Speaker separation is required in order to reliably detect who is
saying specific phrases.
5. Requirements
The following are requirements for SIP-based Media Recording:
o REQ-001: The mechanism MUST provide a means for using the SIP
protocol for establishing, maintaining, and terminating Recording
Sessions between a Session Recording Client and a Session
Recording Server.
o REQ-002: The mechanism MUST support the ability to record all CSs
in their entirety.
o REQ-003: The mechanism MUST support the ability to record selected
CSs in their entirety, according to policy.
o REQ-004: The mechanism MUST support the ability to record selected
parts of selected CSs.
o REQ-005: The mechanism MUST support the ability to record a CS
without loss of media of RS (for example, clipping media at the
beginning of the CS) due to RS recording preparation and also
without impacting the quality or timing of the CS (for example,
delaying the start of the CS while preparing for a recording
session). See Use Case 4 in Section 4 for more details.
o REQ-006: The mechanism MUST support the recording of IVR sessions.
o REQ-007: The mechanism MUST support the recording of the following
RTP media types: voice, DTMF (as defined by [RFC 4733]), video, and
text (as defined by [RFC 4103]).
Rehor, et al. Informational PAGE 10
RFC 6341 Requirements for SIPREC August 2011
o REQ-008: The mechanism MUST support the ability for an SRC to
deliver mixed audio streams from multiple Communication Sessions
to an SRS.
Note: A mixed audio stream is where several related Communication
Sessions are carried in a single Recording Session. A mixed-media
stream is typically produced by a mixer function. The RS MAY be
informed about the composition of the mixed streams through
session metadata.
o REQ-009: The mechanism MUST support the ability for an SRC to
deliver mixed audio streams from different parties of a given
Communication Session to an SRS.
o REQ-010: The mechanism MUST support the ability to deliver to the
SRS multiple media streams for a given CS.
o REQ-011: The mechanism MUST support the ability to pause and
resume the transmission and collection of RS media.
o REQ-012: The mechanism MUST include a means for providing the SRS
with metadata describing CSs that are being recorded, including
the media being used and the identifiers of parties involved.
o REQ-013: The mechanism MUST include a means for the SRS to be able
to correlate RS media with CS participant media.
o REQ-014: Metadata format must be agnostic of the transport
protocol.
o REQ-015: The mechanism MUST support a means to stop the recording.
o REQ-016: The mechanism MUST support a means for a recording-aware
UA involved in a CS to request at session establishment time that
the CS should be recorded or should not be recorded, the honoring
of such a request being dependent on policy.
o REQ-017: The mechanism MUST support a means for a recording-aware
UA involved in a CS to request during a session that the recording
of the CS should be started, paused, resumed, or stopped, the
honoring of such a request being dependent on policy. Such
recording-aware UAs MUST be notified about the outcome of such
requests.
o REQ-018: The mechanism MUST NOT prevent the application of tones
or announcements during recording or at the start of a CS to
support notification to participants that the call is being
recorded or may be recorded.
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RFC 6341 Requirements for SIPREC August 2011
o REQ-019: The mechanism MUST provide a means of indicating to
recording-aware UAs whether recording is taking place, for
appropriate rendering at the user interface.
o REQ-020: The mechanism MUST provide a way for metadata to be
conveyed to the SRS incrementally during the CS.
o REQ-021: The mechanism MUST NOT prevent high-availability
deployments.
o REQ-022: The mechanism MUST provide means for facilitating
synchronization of the recorded media streams and metadata.
o REQ-023: The mechanism MUST provide means for facilitating
synchronization among the recorded media streams.
o REQ-024: The mechanism MUST provide means to relate recording and
recording controls, such as start/stop/pause/resume, to the wall
clock time.
o REQ-025: The mechanism MUST provide means for an SRS to
authenticate the SRC on RS initiation.
o REQ-026: The mechanism MUST provide means for an SRC to
authenticate the SRS on RS initiation.
o REQ-027: The mechanism MUST include a means for ensuring that the
integrity of the metadata sent from the SRC to the SRS is an
accurate representation of the original CS metadata.
o REQ-028: The mechanism MUST include a means for ensuring that the
integrity of the media sent from the SRC to the SRS is an accurate
representation of the original CS media.
o REQ-029: The mechanism MUST include a means for ensuring the
confidentiality of the metadata sent from the SRC to the SRS.
o REQ-030: The mechanism MUST provide a means to support RS
confidentiality.
o REQ-031: The mechanism MUST support the ability to deliver to the
SRS multiple media streams of the same media type (e.g., audio,
video). One example is the case of delivering unmixed audio for
each participant in the CS.
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RFC 6341 Requirements for SIPREC August 2011
6. Privacy Considerations
Respecting the privacy rights and wishes of users engaged in a call
is of paramount importance. In many jurisdictions, participants have
a right to know that the session is being recorded or might be
recorded, and they have a right to opt out, either by terminating the
call or by demanding that the call not be recorded. Therefore, this
document contains requirements for being able to notify users that a
call is being recorded and for users to be able to request that a
call not be recorded. Use cases where users participating in a call
are not informed that the call is or might be recorded are outside
the scope of this document. In particular, lawful intercept is
outside the scope of this document.
Requirements for participant notification of recording vary widely by
jurisdiction. In a given deployment, not all users will be
authorized to stop the recording of a CS (although any user can
terminate its participation in a CS). Typically, users within the
domain that is carrying out the recording will be subject to policies
of that domain concerning whether CSs are recorded. For example, in
a call center, agents will be subject to policies of the call center
and may or may not have the right to prevent the recording of a CS or
part of a CS. Users calling into the call center, on the other hand,
will typically have to ask the agent not to record the CS. If the
agent is unable to prevent recording, or if the caller does not trust
the agent, the only option generally is to terminate the CS.
Privacy considerations also extend to what happens to a recording
once it has been created. Typical issues are who can access the
recording (e.g., receive a copy of the recording, view the metadata,
play back the media, etc.), for what purpose the recording can be
used (e.g., for training purposes, for quality control purposes,
etc.), and for how long the recording is to be retained before
deletion. These are typically policies of the domain that makes the
recording, rather than policies of individual users involved in a
recorded CS, whether those users be in the same domain or in a
different domain. Taking the call center example again, agents might
be made aware of call center policy regarding retention and use of
recordings as part of their employment contract, and callers from
outside the call center might be given some information about policy
when notified that a CS will be recorded (e.g., through an
announcement that says that calls may be recorded for quality
purposes).
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RFC 6341 Requirements for SIPREC August 2011
This document does not specify any requirements for a user engaged in
a CS to be able to dictate policy for what happens to a recording, or
for such information to be conveyed from an SRC to an SRS. It is
assumed that the SRS has access to policy applicable to its
environment and can ensure that recordings are stored and used in
accordance with that policy.
7. Security Considerations
Session recording has substantial security implications, for the SIP
UAs being recorded, the SRC, and the SRS.
For the SIP UAs involved in the Communication Session, the
requirements in this document enable the UA to identify that a
Communication Session is being recorded and to request that a given
Communication Session not be subject to recording.
Since humans don't typically look at or know about protocol signaling
such as SIP, and indeed the SIP session might have originated through
a Public Switched Telephone Network (PSTN) gateway without any
ability to pass on in-signaling indications of recording, users can
be notified of recording in the media itself through voice
announcements, a visual indicator on the endpoint, or other means.
With regard to security implications of the protocol(s), clearly
there is a need for authentication, authorization, and eavesdropping
protection for the solution. The SRC needs to know the SRS it is
communicating with is legitimate, and vice versa, even if they are in
different domains. Both the signaling and media for the Recording
Session need the ability to be authenticated and protected from
eavesdropping. Requirements are detailed in Section 5.
Communication Sessions and Recording Sessions can require different
security levels both for signaling and media, depending on deployment
configurations. For some environments, e.g., the SRS and SRC will be
collocated in a secure network region, and therefore the RS will not
require the same protection level as a CS that extends over a public
network, for example. For other environments, the SRS can be located
in a public cloud, for example, and the RS will require a higher
protection level than the CS. For these reasons, there is not a
direct relationship between the security level of Communication
Sessions and the security level of Recording Sessions.
A malicious or corrupt SRC can tamper with media and metadata
relating to a CS before sending the data to an SRS. Also, CS media
and signaling can be tampered with in the network prior to reaching
an SRC, unless proper means are provided to ensure integrity
protection during transmission on the CS. Means for ensuring the
Rehor, et al. Informational PAGE 14
RFC 6341 Requirements for SIPREC August 2011
correctness of media and metadata emitted by an SRC are outside the
scope of this work. Other organizational and technical controls will
need to be used to prevent tampering.
8. Acknowledgements
Thanks to Dan Wing, Alan Johnson, Vijay Gurbani, Cullen Jennings,
Hadriel Kaplan, Henry Lum, Dave Smith, Martin Palmer, Alissa Cooper,
Deepanshu Gautam, Paul Kyzivat, Parthasarathi R, Ram Mohan R, and
Charles Eckel for their significant contributions and assistance with
this document and the SIPREC WG, and to all the members of the
DISPATCH WG and SIPREC WG mailing lists for providing valuable input
to this work.
9. Normative References
[RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC 3261] 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.
[RFC 4103] Hellstrom, G. and P. Jones, "RTP Payload for Text
Conversation", RFC 4103, June 2005.
[RFC 4733] Schulzrinne, H. and T. Taylor, "RTP Payload for DTMF
Digits, Telephony Tones, and Telephony Signals", RFC 4733,
December 2006.
[RFC 4949] Shirey, R., "Internet Security Glossary, Version 2",
FYI 36, RFC 4949, August 2007.
Rehor, et al. Informational PAGE 15
RFC 6341 Requirements for SIPREC August 2011
Authors' Addresses
Ken Rehor (editor)
Cisco Systems
170 West Tasman Dr.
Mail Stop SJC30/2/
San Jose, CA 95134
USA
EMail: krehor@cisco.com
Leon Portman (editor)
NICE Systems
8 Hapnina
Ra'anana 43017
Israel
EMail: leon.portman@nice.com
Andrew Hutton
Siemens Enterprise Communications
EMail: andrew.hutton@siemens-enterprise.com
URI: http://www.siemens-enterprise.com
Rajnish Jain
IPC Systems
777 Commerce Drive
Fairfield, CT 06825
USA
EMail: rajnish.jain@ipc.com
Rehor, et al. Informational PAGE 16
RFC TOTAL SIZE: 34155 bytes
PUBLICATION DATE: Saturday, August 13th, 2011
LEGAL RIGHTS: The IETF Trust (see BCP 78)
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