SIST ETS 300 747 E1:2003

• Abstract:

  This ETS describes the functions of the Multipoint Control Unit, the acces control of a session and the synchronisation of the Confidentiality System.

• Status: Published
• Publication Date: 30-Nov-2003
• ICS: 33.020 - Telecommunications in general
• ICS: 33.160.01 - Audio, video and audiovisual systems in general
• Technical Committee: SS EIT - Technical Board for the electrotechnical, information technology and telecommunications fields
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-Dec-2003
• Due Date: 01-Dec-2003
• Completion Date: 01-Dec-2003
• Ref Project: ETSI ETS 300 747 ed.1 (1997-05) - Telecommunications security; Service access control and synchronization for audiovisual services

SIST ETS 300 747 E1:2003 is the Slovenian standard identical to ETS 300 747 Edition 1 from ETSI. It specifies service access control and synchronization for audiovisual services over ISDN, with confidentiality-related protocol extensions for setting up, changing, and ending conferences that use one or more Multipoint Control Units (MCUs). It is aimed at audiovisual conference systems that need chair control, authentication, key exchange, and synchronized key activation.

What does SIST ETS 300 747 E1:2003 specify?

SIST ETS 300 747 E1:2003 covers the functions needed to manage confidential audiovisual conferences over the Integrated Services Digital Network (ISDN). The standard builds on ITU-T H.233 and H.234 and focuses on how an MCU, a Chair-Control Terminal (CCT), and the participating terminals handle access control and synchronization during a session.

Clause	Topic
1	Scope
2	Normative references
3	Abbreviations
4	General functions
5	Access control
6	Synchronization of the confidentiality system

What are the key requirements of SIST ETS 300 747 E1:2003?

Clause 4 separates two operating models: Trusted MCU (TMCU) and Non-trusted MCU (NMCU). In a TMCU, signals are decrypted at the MCU inputs; in an NMCU, the MCU cannot decrypt audio, video, or other data and must switch encrypted traffic instead. In practice, this determines whether the conference controller handles content directly or only relays encrypted streams.

General functions and chair control

Clause 4.2 assigns chair-control functions to the CCT when an NMCU is used. The CCT is responsible for participant authentication, key distribution at regular or irregular intervals, renewal of keys when participants join or leave, and speaker switching. For implementers, this means the chair terminal is part of the security workflow, not just the conference UI.

Clause 4.3 requires participants, including the session chair, to authenticate before joining. With a TMCU, the MCU performs authentication; with an NMCU, the CCT performs it, and the CCT itself is not authenticated in the same way. Once the MCU-CCT link is established, the conference is treated as running and later participants join it as modifications to the session.

Clause 4.4 requires routing of the Encryption Control Signal (ECS) channel in an NMCU. The MCU uses routing information carried in the IV blocks, with the terminal number encoded in the available bits, so the CCT can exchange keys and related control information with specific terminals. This is the part that makes point-to-point control work inside a multipoint conference.

Session setup, changes, and termination

Clause 5.1 says that session initialization in a TMCU follows ITU-T H.234 and H.243, while an NMCU starts with the first connected terminal that has Chair Control capability. If that terminal cannot take chair control, the connection is dropped. This gives a clear rule for who may start the conference.

Clause 5.2.1 and 5.2.2 cover joining and leaving. A joining terminal goes through authentication and/or key exchange, and in an NMCU the CCT is informed before the new participant is admitted. When a participant leaves, the MCU - or the CCT in an NMCU - initiates a new key exchange, distributes new session keys, and then synchronizes the remaining terminals. This is the mechanism that limits the impact of membership changes on confidentiality.

Clause 5.2.3 describes chair handover in restricted and flexible modes. In restricted mode, the initial terminal remains the CCT for the whole session; in flexible mode, chair control can move to another participant. Clause 5.3 uses the Chair Command Kill (CCK) BAS code from the CCT to end the conference and release resources. Clause 5.4 says an abrupt CCT termination ends the session in an NMCU, while a TMCU may continue with the remaining terminals.

Synchronization after changes

Clause 6 requires synchronization after every session modification. The MCU broadcasts new session keys using message P6, each participant confirms receipt with P12, and the MCU repeats the process until confirmation is received or the time limit expires. After all confirmations, the key-loading synchronization flag is set in the IV block. In practice, this ensures all terminals activate the same session key at the same time.

What terms does SIST ETS 300 747 E1:2003 define?

Multipoint Control Unit (MCU) - the conference control unit that manages or routes audiovisual conference traffic between terminals.

Trusted MCU (TMCU) - an MCU model in which signals are decrypted at the MCU inputs, so the MCU needs a secure location.

Non-trusted MCU (NMCU) - an MCU model that cannot decrypt the media and therefore operates by switching encrypted data.

Chair-Control Terminal (CCT) - the terminal that handles chair control functions such as authentication, key distribution, and speaker switching in an NMCU.

Encryption Control Signal (ECS) - the control channel used to exchange key and routing information between participants and the CCT.

Chair Command Kill (CCK) - the BAS code used by the CCT to terminate the conference and release MCU resources.

Who uses SIST ETS 300 747 E1:2003?

SIST ETS 300 747 E1:2003 is used by designers and integrators of audiovisual conferencing systems over ISDN. It is also relevant for MCU implementers, terminal vendors, and security engineers who need to define authentication, key management, chair control, and synchronization behavior in multipoint conferences.

Which standards are used with SIST ETS 300 747 E1:2003?

The standard relies on these referenced publications:

• ITU-T Recommendation H.233 - the confidentiality system foundation for audiovisual services.
• ITU-T Recommendation H.234 - encryption key management and authentication for audiovisual services.
• ITU-T Recommendation H.243 - procedures for establishing communication, participant changes, and chair control behavior.
• ITU-T Recommendation H.231 - MCU functions for audiovisual systems.
• ITU-T Recommendation H.230 - frame-synchronous control and indication signals, including BAS codes.
• ETS 300 840 - confidentiality system for audiovisual services.
• ETS 300 840 - encryption key management and authentication system for audiovisual services.

What does the SIST ETS 300 747 E1:2003 document contain?

The document contains clause-by-clause procedures for general MCU functions, access control, and synchronization of the confidentiality system. It includes the routing model for the ECS channel and a figure showing how ECS messages are forwarded between the CCT and specific terminals in an NMCU.

It also defines the message P12, Key Received Confirmation, and describes how it is used after the MCU sends session keys with P6. The document uses these procedures to show how conference setup, participant changes, and termination are handled without losing synchronization of the confidentiality system.

SLOVENSKI STANDARD
01-december-2003
Telekomunikacijska varnost – Krmiljenje in sinhronizacija dostopa do storitev pri
avdiovizualnih storitvah
Telecommunications security; Service access control and synchronization for audiovisual
services
Ta slovenski standard je istoveten z: ETS 300 747 Edition 1
ICS:
33.020 Telekomunikacije na splošno Telecommunications in
general
33.160.01 Avdio, video in avdiovizualni Audio, video and audiovisual
sistemi na splošno systems in general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN ETS 300 747
TELECOMMUNICATION May 1997
STANDARD
Source: ETSI TC-Security Reference: DE/SEC-002308
ICS: 33.020
Key words: Audio, security, service
Telecommunications Security;
Service access control and synchronization
for audiovisual services
ETSI
European Telecommunications Standards Institute
ETSI Secretariat
Postal address: F-06921 Sophia Antipolis CEDEX - FRANCE
Office address: 650 Route des Lucioles - Sophia Antipolis - Valbonne - FRANCE
X.400: c=fr, a=atlas, p=etsi, s=secretariat - Internet: [e-mail]
Tel.: [phone] - Fax: [phone]
Copyright Notification: No part may be reproduced except as authorized by written permission. The copyright and the
foregoing restriction extend to reproduction in all media.
© European Telecommunications Standards Institute 1997. All rights reserved.

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ETS 300 747: May 1997
Whilst every care has been taken in the preparation and publication of this document, errors in content,
typographical or otherwise, may occur. If you have comments concerning its accuracy, please write to
"ETSI Editing and Committee Support Dept." at the address shown on the title page.

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ETS 300 747: May 1997
Contents
Foreword .5
1 Scope .7
2 Normative references.7
3 Abbreviations.7
4 General functions .8
4.1 Trusted MCUs (TMCUs) versus Non-trusted MCUs (NMCUs) .8
4.1.1 TMCU.8
4.1.2 NMCU.8
4.2 Chair-Control Functions for Confidentiality .8
4.3 Authentication .8
4.4 Routeing of ECS channel messages.9
5 Access control.9
5.1 Initialization of a session .9
5.2 Modifications during a session.9
5.2.1 Participants joins a session.9
5.2.2 Participant leaves a session.9
5.2.3 Handover of session responsibility.10
5.3 Termination of a session. 10
5.4 Abnormal events.10
6 Synchronization of the confidentiality system.10
6.1 Introduction .10
6.2 Synchronization of session key activation.10
History.11

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ETS 300 747: May 1997
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ETS 300 747: May 1997
Foreword
This European Telecommunication Standard (ETS) has been produced by the Security Technical
Committee of the European Telecommunications Standards Institute (ETSI).
Transposition dates
Date of adoption: 18 April 1997
Date of latest announcement of this ETS (doa): 31 August 1997
Date of latest publication of new National Standard
or endorsement of this ETS (dop/e): 28 February 1998
Date of withdrawal of any conflicting National Standard (dow): 28 February 1998

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ETS 300 747: May 1997
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ETS 300 747: May 1997
1 Scope
This European Telecommunication Standard (ETS) fits into the series of standards about audiovisual
communication over the Integrated Services Digital Network (ISDN), which is introduced in the
ITU-T H.200 series of Recommendations.
In ITU-T Recommendations H.233 [1] and H.234 [2], the basic mechanisms for confidentiality and key
exchange are specified.
On top of these, this ETS specifies the confidentiality related protocol extensions needed for the
establishment, modification and termination of audiovisual conferences using one or more Multipoint
Control Units (MCUs).
2 Normative references
This ETS incorporates by dated and undated reference, provisions from other publications. These
normative references are cited at the appropriate places in the text and the publications are listed
hereafter. For dated references, subsequent amendments to or revisions of any of these publications
apply to this ETS only when incorporated in it by amendment or revision. For undated references the latest
edition of the publication referred to applies.
[1] ITU-T Recommendation H.233: "Confidentiality system for audiovisual services".
NOTE 1: ITU-T Recommendation H.233 forms the basis of ETS 300 840 [6].
[2] ITU-T Recommendation H.234: "Encryption key management and
authentication system for audiovisual services".
NOTE 2: ITU-T Recommendation H.234 forms the basis of ETS 300 841 [7].
[3] ITU-T Recommendation H.243: "Procedures for establishing communication
between three or more audiovisual terminals using digital channels up to
2 Mbit/s".
[4] ITU-T Recommendation H.231: "Multipoint control units for audiovisual systems
using digital channels up to 2 Mbit/s".
[5] ITU-T Recommendation H.230: "Frame-synchronous control and indication
signals for audiovisual systems".
[6] ETS 300 840: "Telecommunications Security; Integrated Services Digital
Network (ISDN); Confidentiality system for audiovisual services".
[7] ETS 300 840: "Telecommunications Security; Integrated Services Digital
Network (ISDN); Encryption key management and authentication system for
audiovisual services".
3 Abbreviations
For the purposes of this ETS, the following abbreviations apply:
CCK Chair Command Kill
CCT Chair-Control Terminal
ECS Encryption Control Signal
MCU Multipoint Control Unit
NMCU Non-trusted MCU
TMCU Trusted MCU
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