IEC 60839-7-4:2001

INTERNATIONAL IEC
STANDARD
60839-7-4
First edition
2001-03
Alarm systems –
Part 7-4:
Message formats and protocols for serial data
interfaces in alarm transmission systems –
Common transport layer protocol
Systèmes d'alarme –
Partie 7-4:
Formats de message et protocoles pour les interfaces de
données série dans les systèmes de transmission d'alarme –
Protocole de la couche commune de transport

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INTERNATIONAL IEC
STANDARD
60839-7-4
First edition
2001-03
Alarm systems –
Part 7-4:
Message formats and protocols for serial data
interfaces in alarm transmission systems –
Common transport layer protocol
Systèmes d'alarme –
Partie 7-4:
Formats de message et protocoles pour les interfaces de
données série dans les systèmes de transmission d'alarme –
Protocole de la couche commune de transport

 IEC 2001  Copyright - all rights reserved
No part of this publication may be reproduced or utilized in any form or by any means, electronic or
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International Electrotechnical Commission
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– 2 – 60839-7-4 © IEC:2001(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
ALARM SYSTEMS –
Part 7-4: Message formats and protocols for serial data interfaces

in alarm transmission systems –

Common transport layer protocol

FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of the IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, the IEC publishes International Standards. Their preparation is
entrusted to technical committees; any IEC National Committee interested in the subject dealt with may
participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. The IEC collaborates closely with the International Organization
for Standardization (ISO) in accordance with conditions determined by agreement between the two
organizations.
2) The formal decisions or agreements of the IEC on technical matters express, as nearly as possible, an
international consensus of opinion on the relevant subjects since each technical committee has representation
from all interested National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical specifications, technical reports or guides and they are accepted by the National
Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject
of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60839-7-4 has been prepared by IEC technical committee 79: Alarm
systems.
The text of this standard is based on the following documents:
FDIS Report on voting
79/201/FDIS 79/211/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 3.
Annex A forms an integral part of this standard.
The committee has decided that the contents of this publication will remain unchanged until
2004. At this date, the publication will be
reconfirmed;
withdrawn;
replaced by a revised edition, or
amended.
60839-7-4 © IEC:2001(E) – 3 –
A bilingual version of this standard may be issued at a later date.

IEC 60839-7-4 forms one of a number of related parts presented under the general title: Alarm

systems – Part 7: Message formats and protocols for serial data interfaces in alarm

transmission systems:
IEC 60839-7-1: General
IEC 60839-7-2: Common application layer protocol

IEC 60839-7-3: Common data link layer protocol

IEC 60839-7-4: Common transport layer protocol

IEC 60839-7-5: Alarm system interfaces employing a two-wire configuration in accordance
with ISO/IEC 8482
IEC 60839-7-6: Alarm system interfaces employing ITU-T Recommendation V.24/V.28
signalling
IEC 60839-7-7: Alarm system interfaces for plug-in alarm system transceivers
IEC 60839-7-11: Serial protocol for use by digital communicator systems using ITU-T
Recommendation V.23 signalling at interfaces with the PSTN
IEC 60839-7-12: PTT interfaces for dedicated communications using ITU-T
Recommendation V.23 signalling
IEC 60839-7-20: Terminal interfaces employing ITU-T Recommendation V.24/V.28
signalling
– 4 – 60839-7-4 © IEC:2001(E)
ALARM SYSTEMS –
Part 7-4: Message formats and protocols for serial data interfaces

in alarm transmission systems –

Common transport layer protocol

1 Scope
This part of IEC 60839 specifies the transport layer message structure, formats and
transmission procedures to be used at standard interfaces in alarm transmission systems. This
should be used at all such interfaces where equipment from one supplier is intended to inter-
work with equipment from other suppliers, and where the underlying system architecture does
not provide the necessary facilities to support the common application layer.
The structure follows the OSI recommendations for a layered protocol to allow flexibility in the
choice and use of lower level transmission media and protocols, whilst maintaining support for
the common application layer protocol.
This standard applies equally to the transmission of alarms and other messages to/from
intrusion, fire, access control and social alarm systems, and to the transmission of information
to/from other similar systems.
The physical management of the authentication keys required by this standard is not included.
2 Normative references
The following normative documents contain provisions which, through reference in this text,
constitute provisions of this part of IEC 60839. For dated references, subsequent amendments
to, or revisions of, any of these publications do not apply. However, parties to agreements
based on this part of IEC 60839 are encouraged to investigate the possibility of applying the
most recent editions of the normative documents indicated below. For undated references, the
latest edition of the normative document referred to applies. Members of IEC and ISO maintain
registers of currently valid International Standards.
IEC 60839-7-1, Alarm systems – Part 7-1: Message formats and protocols for serial data
interfaces in alarm transmission systems – General

3 Definitions
For the purpose of this part of IEC 60839, the definitions in IEC 60839-7-1 apply.
4 Abbreviations
The abbreviations in IEC 60839-7-1 apply.

60839-7-4 © IEC:2001(E) – 5 –
5 General
The transport layer is responsible for the formatting of messages from the application layer into

a form suitable for transmission to the remote location, and for the addition of facilities not

available from the underlying transport mechanism.

Although a link using this protocol may be point-multipoint, or multipoint-multipoint, the

transport layer described here presumes that such systems will comprise a number of logical

point-point communications which will proceed independently.

In such communications, one device is defined as the ORIGINATOR and one as the

RECEIVER in order that the standard may be defined generally. The calling standard shall
identify which of these functions is assigned to which equipment.
6 Transport layer message format
Each application layer message or transport layer data block shall be formatted into transport
layer message with the addition of a header as defined below.
6.1 Transmission of transport layer data block
Transport layer data shall be formatted in accordance with annex A and transmitted with a
transport layer header as defined in 6.2.
6.2 Transport layer header
The transport layer header shall be as follows:
FLAGS
SOURCE ID DESTINATION ID
(FIRST OCTET)
7 0
bit 0 : Reserved  (must be unset (=0))
bit 1 : 1 = source identity follows
0 = no source identity included
bit 2 : 1 = destination identity follows
0 = no destination identity included
bit 3 : 1 = transport layer data block follows
0 = application layer message follows

bit 4 : 00 1 1
bit 5 : 01 0 1
Reserved
message contains encrypted data
Message Authentication Code (MAC) appended
no encryption or MAC
bit 6 : 1 = special encryption algorithm used
0 = no special encryption algorithm used
bit 7 :  Reserved must be set (=1)
Bit 4 should be set when the application message or the transport data are encrypted. Bit 5
should be set to indicate that the message contains a message authentication code (MAC).
The option of using encryption and a MAC should not be used since this effectively lowers the
security. Where a special high security algorithm is used for either the encryption or the MAC
bit 6 should be set, otherwise the standard algorithm defined in this standard should be used.

– 6 – 60839-7-4 © IEC:2001(E)
Bit 3 indicates whether the data is a transport layer data block or an application layer message.

The transport layer header may include the source identity, the destination identity, both or

neither as defined in bits 1 and 2.

Maximum length for SOURCE ID and DESTINATION ID is eight octets equal to seven digits

each.
Where both identities are included, the source identity shall always be first.

The format of the identity is as follows:

No of 1st 2nd 3rd
nibbles digit digit digit
74307430 7430
The first nibble (bits 4-7 of the first octet) is the number of digits in the address. The actual
identity digits shall be contained in subsequent nibbles in HEX format, starting with the lower
nibble of the first octet. The identity shall contain only sufficient octets to include the number of
digits required. If the number of digits is even, the last nibble (bits 0-3 of the last octet) shall be
zero.
As an example, if the identity is 1234 this would be transmitted as:
0 100 000 100 100 011 010 000 00
4 digits 1 2 3 4
7 Authentication
The following procedure shall be adopted following the establishment of the connection in order
to confirm the identity of the equipment.
7.1 Configuration
As part of their initialization/configuration each item of equipment shall be programmed with a
master key (Mk).
7.2 Initialization
With a connection established, the ORIGINATOR shall generate two random numbers R1 and
Rs, and shall transmit R1 to the RECEIVER encrypted with Mk as transport layer message
type 1 (see annex A). Rs is the random seed used by the encryption algorithm for the
transmission of R1.
The RECEIVER shall decode R1 and shall then generate a random number R2, together with a
secondary key Ki. It shall then return a transport layer message type 2 to the ORIGINATOR
which contains R2 together with R1 and Ki. This message shall be encrypted using Mk and Ki
as shown below and in annex A.

60839-7-4 © IEC:2001(E) – 7 –
The value of the secondary key (Ki) and the random numbers R1 and R2 shall only be stored in

volatile memory and should not be capable of being displayed in either the RECEIVER or

ORIGINATOR.
The ORIGINATOR shall decode the message to evaluate R1, R2 and Ki. The correct reception

of R1 confirms the identity of the RECEIVER. If correct, it shall then send a transport layer

message type 3 containing R2 encrypted using Ki. The correct decoding of R2 at the

RECEIVER confirms the identity of the ORIGINATOR.

A message shall be generated to both the alarm system and the annunciation equipment to

indicate that the value of Ki has been set.

A
...