ETSI ETS 300 403-1 ed.1 (1995-11)

Integrated Services Digital Network (ISDN); Digital Subscriber Signalling System No. one (DSS1) protocol; Signalling network layer for circuit-mode basic call control; Part 1: Protocol specification [ITU-T Recommendation Q.931 (1993), modified]

DE/SPS-05034-1

Digitalno omrežje z integriranimi storitvami (ISDN) - Protokol digitalne naročniške signalizacije št. 1 (DSS1) - Signalizacijska omrežna plast za krmiljenje vodovnega osnovnega klica - 1. del: Specifikacija protokola (preoblikovano priporočilo ITU-T Q.931 (1993))

General Information

• Status: Published
• Publication Date: 20-Nov-1995
• Technical Committee: SPS 5 - Digital access signalling
• Current Stage: 12 - Completion
• Due Date: 01-Dec-1995
• Completion Date: 21-Nov-1995
• Mandate: T-234B
• Ref Project: SIST ETS 300 403-1:1999 - Integrated Services Digital Network (ISDN); Digital Subscriber Signalling System No. one (DSS1) protocol; Signalling network layer for circuit-mode basic call control; Part 1: Protocol specification [ITU-T Recommendation Q.931 (1993), modified]

Standards Content (Sample)

SLOVENSKI STANDARD
SIST ETS 300 403-1:1999
01-maj-1999
'LJLWDOQRRPUHåMH]LQWHJULUDQLPLVWRULWYDPL,6'13URWRNROGLJLWDOQHQDURþQLãNH
VLJQDOL]DFLMHãW'666LJQDOL]DFLMVNDRPUHåQDSODVW]DNUPLOMHQMHYRGRYQHJD
RVQRYQHJDNOLFDGHO6SHFLILNDFLMDSURWRNRODSUHREOLNRYDQRSULSRURþLOR,787
4
Integrated Services Digital Network (ISDN); Digital Subscriber Signalling System No. one
(DSS1) protocol; Signalling network layer for circuit-mode basic call control; Part 1:
Protocol specification [ITU-T Recommendation Q.931 (1993), modified]
Ta slovenski standard je istoveten z: ETS 300 403-1 Edition 1
ICS:
33.080 Digitalno omrežje z Integrated Services Digital
integriranimi storitvami Network (ISDN)
(ISDN)
35.100.30 Omrežni sloj Network layer
SIST ETS 300 403-1:1999 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST ETS 300 403-1:1999

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SIST ETS 300 403-1:1999
EUROPEAN ETS 300 403-1
TELECOMMUNICATION November 1995
STANDARD
Source: ETSI TC-SPS Reference: DE/SPS-05034-1
ICS: 33.080, 35.100.30
ISDN, DSS1, layer 3
Key words:
Integrated Services Digital Network (ISDN);
Digital Subscriber Signalling System No. one (DSS1) protocol;
Signalling network layer for circuit-mode basic call control;
Part 1: Protocol specification
[ITU-T Recommendation Q.931 (1993), modified]
ETSI
European Telecommunications Standards Institute
ETSI Secretariat
F-06921 Sophia Antipolis CEDEX - FRANCE
Postal address:
650 Route des Lucioles - Sophia Antipolis - Valbonne - FRANCE
Office address:
c=fr, a=atlas, p=etsi, s=secretariat - [e-mail]
X.400: Internet:
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 1995. All rights reserved.

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SIST ETS 300 403-1:1999
Page 2
ETS 300 403-1: November 1995
Foreword
This European Telecommunication Standard (ETS) has been produced by the Signalling Protocols and
Switching (SPS) Technical Committee of the European Telecommunications Standards Institute (ETSI).
This ETS which is based on ITU-T Recommendation Q.931 (1993) is an extended and updated version of
ETS 300 102-1 (1990) which was based on CCITT Recommendation Q.931 (1988). Annex ZA identifies
the relevant differences between this ETS and ETS 300 102-1.
This ETS is part 1 of a multi-part standard covering the Digital Subscriber Signalling System No. one
(DSS1) protocol specification for the Integrated Services Digital Network (ISDN) signalling network layer
for circuit-mode basic call control, as described below:
Part 1: "Protocol specification";
Part 2: "Specification and Description Language (SDL) diagrams";
Part 3: "Protocol Implementation Conformance Statement (PICS) proforma specification";
Part 4: "Test Suite Structure and Test Purposes (TSS&TP) specification for the user";
Part 5: "Abstract Test Suite (ATS) and partial Protocol Implementation eXtra Information for Testing
(PIXIT) proforma specification for the user";
Part 6: "TSS&TP specification for the network";
Part 7: "ATS and partial PIXIT proforma specification for the network".
Transposition dates
Date of adoption of this ETS: 10 November 1995
Date of latest announcement of this ETS (doa): 28 February 1996
Date of latest publication of new National Standard
or endorsement of this ETS (dop/e): 31 August 1996
Date of withdrawal of any conflicting National Standard (dow): 31 August 1996
Endorsement notice
The text of ITU-T Recommendation Q.931 (1993) was approved by ETSI as an ETS with agreed
modifications as given below.
NOTE: New or modified text is indicated using sidebars. In addition, underlining and/or strike-
out are used to highlight detailed modifications where necessary.
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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SIST ETS 300 403-1:1999
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ETS 300 403-1: November 1995
Page 1, clause 1
Delete clause 1 (General) and subclause 1.1 (Scope of the Recommendation).
Insert the following three clauses (Scope, Normative references, Definitions) at the start of the text:
Scope
This European Telecommunication Standard (ETS) specifies the stage three of circuit-mode on-demand
basic telecommunication services for the pan-European Integrated Services Digital Network (ISDN) as
provided by European telecommunications operators at the T reference point or coincident S and T
reference point (as defined in ITU-T Recommendation I.411 [91] by means of the Digital Subscriber
Signalling System No. one (DSS1). Stage three identifies the protocol procedures and switching functions
needed to support a telecommunication service (see CCITT Recommendation I.130 [88]).
In addition, this ETS specifies the protocol requirements at the T reference point where the service is
provided to the user via a private ISDN.
NOTE 1: Procedures at the T reference point, to support the access of a private ISDN to the
public ISDN, are not explicitly identified in this ETS, however some procedures are
applicable only to the T reference point.
This ETS does not specify the additional protocol requirements where the service is provided to the user
via a telecommunication network that is not an ISDN.
A basic telecommunication service is a fundamental type of service. It forms the basis on which
supplementary services may be added.
NOTE 2: Specific requirements of individual circuit-mode basic telecommunication services are
not covered in this ETS. However, ETR 018 gives guidance on the use of service
specific information elements to implement individual basic telecommunication
services.
Further parts of this ETS specify the Specification and Description Language (SDL) diagrams, the method
of testing and detailed application specific requirements to determine conformance based on this ETS.
This ETS is applicable to equipment supporting circuit-mode on-demand basic telecommunication
services, to be attached at either side of a T reference point or coincident S and T reference point when
used as an access to the public ISDN.
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.
[87] ITU-T Recommendation I.112 (1993): "Vocabulary of terms for ISDNs".
[88] CCITT Recommendation I.130 (1988): "Method for characterization of
telecommunication services supported by an ISDN and network capabilities of
an ISDN".
[89] ITU-Recommendation I.140 (1993): "Attribute technique for the characterization
of telecommunication services supported by an ISDN and network capabilities of
an ISDN".
[90] ITU-T Recommendation I.210 (1993): "Principles of telecommunication services
supported by an ISDN and the means used to describe them".

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SIST ETS 300 403-1:1999
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ETS 300 403-1: November 1995
[91] ITU-T Recommendation I.411 (1993): "ISDN user network interfaces - reference
configurations".
[92] CCITT Recommendation Q.9 (1988): "Vocabulary of switching and signalling
terms".
[93] ETS 300 007 (1991): "Integrated Services Digital Network (ISDN); Support of
packet-mode terminal equipment by an ISDN".
[94] ETS 300 011 (1990): "Integrated Services Digital Network (ISDN); Primary rate
user-network interface layer 1 specification and test principles".
[95] ETS 300 012 (1990): "Integrated Services Digital Network (ISDN); Basic user-
network interface layer 1 specification and test principles".
[96] ETS 300 058-1: "Integrated Services Digital Network (ISDN); Call Waiting (CW)
supplementary service; Digital Subscriber Signalling System No. one (DSS1)
protocol; Part 1: Protocol specification".
[97] ETS 300 075: "Terminal Equipment (TE); Processable data; File transfer".
[98] ETS 300 092-1: "Integrated Services Digital Network (ISDN); Calling Line
Identification Presentation (CLIP) supplementary service; Digital Subscriber
Signalling System No. one (DSS1) protocol; Part 1: Protocol specification".
[99] ETS 300 093-1: "Integrated Services Digital Network (ISDN); Calling Line
Identification Restriction (CLIR) supplementary service; Digital Subscriber
Signalling System No. one (DSS1) protocol; Part 1: Protocol specification".
[100] ETS 300 122-1: "Integrated Services Digital Network (ISDN); Generic keypad
protocol for the support of supplementary services; Digital Subscriber Signalling
System No. one (DSS1) protocol; Part 1: Protocol specification".
[101] ETS 300 196-1: "Integrated Services Digital Network (ISDN); Generic functional
protocol for the support of supplementary services; Digital Subscriber Signalling
System No. one (DSS1) protocol; Part 1: Protocol specification".
[102] ETS 300 207-1: "Integrated Services Digital Network (ISDN); Diversion
supplementary services; Digital Subscriber Signalling System No. one (DSS1)
protocol; Part 1: Protocol specification".
[103] ETS 300 286-1: "Integrated Services Digital Network (ISDN); User-to-User
Signalling (UUS) supplementary service; Digital Subscriber Signalling System
No. one (DSS1) protocol; Part 1: Protocol specification".
[104] ETS 300 402-1 (1995): "Integrated Services Digital Network (ISDN); Digital
Subscriber Signalling System No. one (DSS1) protocol; Data link layer; Part 1:
General aspects [ITU-T Recommendation Q.920 (1993), modified]".
[105] ETS 300 402-2 (1995): "Integrated Services Digital Network (ISDN); Digital
Subscriber Signalling System No. one (DSS1) protocol; Data link layer; Part 2:
General protocol specification [ITU-T Recommendation Q.921 (1993),
modified]".
[106] ETS 300 403-2 (1995): "Integrated Services Digital Network (ISDN); Digital
Subscriber Signalling System No. one (DSS1) protocol; Signalling network layer
for circuit-mode basic call control; Part 2: Specification and Description
Language (SDL) diagrams".
[107] ETS 300 485 (1995): "Integrated Services Digital Network (ISDN); Definition and
usage of cause and location in Digital Subscriber Signalling System No. one
(DSS1) and Signalling System No. 7 ISDN User Part (ISUP)".

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ETS 300 403-1: November 1995
NOTE: The references listed in this ETS are a continuation of publications referenced in ITU-T
Recommendation Q.931.
Definitions
For the purposes of this ETS, the following definitions apply, together with those given in the referenced
publications:
access channel; channel: See CCITT Recommendation Q.9 [92], definition 0008.
B-channel: A 64 kbit/s channel accompanied by timing intended to carry a wide variety of user
information streams. A B-channel does not carry signalling information for circuit switching by the ISDN.
basic access: See CCITT Recommendation Q.9 [92], definition 1551.
basic service; basic telecommunication service: See CCITT Recommendation Q.9 [92], definition
7018.
call: See CCITT Recommendation Q.9 [92], definition 2201.
call control message: A message as defined in subclause 3.1 of this ETS, which on sending or receipt
causes a change of the call state at either the network or the user; and also PROGRESS and
INFORMATION messages.
call establishment; connection establishment: See CCITT Recommendation Q.9 [92], definition 2207.
call reference: An identifier of a signalling transaction. The signalling transaction may either be bearer
related, in which case the signalling transaction can be used to control that bearer, or bearer independent,
in which case there is no bearer associated with that signalling transaction. All signalling transactions in
this ETS are bearer related except those associated with the global call reference. Where there is only
one bearer required for a call, then the call reference of the associated bearer related signalling
transaction may be used to identify the call. In this ETS there is only one bearer for each call.
call state: A state as defined in subclause 2.1 of this ETS, for either the user side or network side as
appropriate. A call state may exist for each call reference value (and at the network side for each
additional responding CEI in the incoming call states).
circuit switched; circuit switching: See CCITT Recommendation Q.9 [92], definition 1125.
comprehension required: The requirement that the coding structure and meaning of an information
element shall be understood by its receiver for the message to be processed. A specific range of values
for information element identifiers is provided for those information elements for which comprehension is
required.
connection: See CCITT Recommendation Q.9 [92], definition 0011. In this ETS, the term is taken to
include a bearer and its associated control signalling.
D-channel: A channel primarily intended to carry signalling information for circuit switching by the ISDN.
data link connection endpoint identifier: Identifier used by a layer 3 protocol entity to address its peer
entity.
dummy call reference: A call reference value of one octet length encoded as "0000 0000".

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ETS 300 403-1: November 1995
en bloc receiving: A procedure, used in call establishment of an incoming call, to enable the network to
send called party number digits to the user in a single message.
en bloc sending: A procedure, used in call establishment of an outgoing call, to enable the user to send
called party number digits to the network in a single message.
global call reference: A Call reference information element with a call reference value of zero. The length
of the call reference value is encoded in the first octet of the information element. The Global call
reference identifies all call references currently associated with the appropriate data link connection
endpoint identifier.
Incoming (call): A call incoming to the user side of the interface.
Integrated Services Digital Network (ISDN): See ITU-T Recommendation I.112 [87], definition 308.
interface: See CCITT Recommendation Q.9 [92], definition 4001.
Network Service Access Point (NSAP) address; OSI NSAP address: See CCITT Recommendation
Q.9 [92], definition 2083.
network: The DSS1 protocol entity at the network side of the user-network interface.
on demand: See ITU-T Recommendation I.140 [89], annex A, clause A.2.
Open System Interconnection (OSI): The concept of interconnecting systems in accordance with the
architecture described in the Open System Interconnection Reference model (CCITT Recommendation
X.200 [78]).
outgoing (call): A call outgoing from the user side of the interface.
overlap receiving: A procedure, used in call establishment of an incoming call, to enable the network to
send called party number digits to the user in successive messages, as and when they are made available
from the remote network.
overlap sending: A procedure, used in call establishment of an outgoing call, to enable the user to send
called party number digits to the network in successive messages, as and when they are made available
by the user.
point-to-multipoint configuration; multipoint terminal configuration; multipoint configuration: A
terminal configuration in which there is more than one signalling entity.
point-to-multipoint data link; broadcast data link: A data link connection with the capability to support
more than two connection endpoints.
point-to-point configuration; single-point terminal configuration; single-point configuration: A
terminal configuration in which there is one signalling entity.
point-to-point data link: A data link on which a frame is directed to a single endpoint.
primary rate access: See CCITT Recommendation Q.9 [92], definition 1552.
service; telecommunication service: See ITU-T Recommendation I.112 [87], definition 201.
supplementary service: See ITU-T Recommendation I.210 [90], subclause 2.4.
user: The DSS1 protocol entity at the user side of the user-network interface.

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ETS 300 403-1: November 1995
Throughout the text of ITU-T Recommendation Q.931
Replace references throughout the text as shown below.
Reference in ITU-T Modified reference
Recommendation Q.931
ITU-T Recommendation I.430 [46] ETS 300 012 [95]
ITU-T Recommendation I.431 [27] ETS 300 011 [94]
ITU-T Recommendation Q.850 [67] ETS 300 485 [107]
ITU-T Recommendation Q.920 [45] ITU-T Recommendation Q.920 as modified by ETS 300 402-1 [104]
ITU-T Recommendation Q.921 [3] ITU-T Recommendation Q.921 as modified by ETS 300 402-2 [105]
ITU-T Recommendation Q.931 ITU-T Recommendation Q.931 as modified by this ETS
ITU-T Recommendation Q.951 [85], ETS 300 092-1 [98]
section 3
ITU-T Recommendation Q.951 [85], ETS 300 093-1 [99]
section 4
ITU-T Recommendation Q.952 [86] ETS 300 207-1 [102]
ITU-T Recommendation Q.953 [84] ETS 300 058-1 [96]
section 1
ITU-T Recommendation Q.957 [54] ETS 300 286-1 [103]
section 1
Pages 1 and 2, clause 2
Replace the second paragraph by:
In the paragraphs which follow, states are defined for circuit switched calls in subclause 2.1 (call states)
and for the interface in subclause 2.4 (global call reference states).
Replace the three last paragraphs by:
A detailed description of the procedures for call control are given in clause 5 in terms of:
a) the messages defined in clause 3 which are transferred across the user-network interface;
b) the information processing and actions that take place at the user side and the network side.
Detailed SDL diagrams for call control of circuit switched calls are contained in
ETS 300 403-2 [106].
Page 2, subclause 2.1, last paragraph
Delete the last paragraph referring to annex D.
Pages 4 to 6, subclause 2.2
Delete subclause 2.2 and all of its subclauses. The basic packet-mode access connection control states
for access to the ISDN virtual bearer service are defined in ETS 300 007 [93] and are outside the scope of
this ETS.
Pages 6 to 8, subclause 2.3
Delete subclause 2.3 and all of its subclauses. It is outside the scope of this ETS.
Page 8, subclause 2.4, last paragraph
Replace the last paragraph by:
The global call reference shall be handled independently for incoming and outgoing sides, i.e. two
independent state machines in an entity shall be referenced by the global call reference.

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ETS 300 403-1: November 1995
Page 8, subclause 2.4.1.1, subclause heading
Replace the subclause heading by the following:
2.4.1.1 Restart Null (Rest 0)
Page 9, subclause 2.4.2.1, subclause heading
Replace the subclause heading by the following:
2.4.2.1 Restart Null (Rest 0)
Page 9, clause 3, note 1
Delete the last sentence "Annex D . interfaces".
Page 10, table 3-1/Q.931
Include SEGMENT as a message in the Miscellaneous messages: part of table 3-1/Q.931 with a
reference to subclause 3.5.1.
Page 11, table 3-2/Q.931
Modify table 3-2/Q.931 as follows:
Message type: ALERTING
Significance: global
Direction: both
Information element Reference Direction Type Length
Protocol discriminator 4.2 both M 1
Call reference 4.3 both M 2 - 3
Message type 4.4 both M 1
Bearer capability 4.5 both O (note 1) 4 - 12
Channel identification 4.5 both (note 2) O (note 3) 2 - 34
u → n
Progress indicator 4.5 both O (note 4) 2 - 4
Display 4.5 O (note 5) 2 - 82
n → u
(note 6)
Signal 4.5 n → u O (note 7) 2 - 3
High layer compatibility 4.5 both O (note 8) 2 - 5
NOTE 1: The Bearer capability information element is included when the procedures of subclause
5.11 for bearer capability selection apply. When present, progress description #5
"interworking has occurred and has resulted in a telecommunication service change" shall
also be present.
NOTE 2:    Included in the network-to-user direction for support of the procedures in annex D.
NOTE 3: Mandatory if this message is the first message in response to SETUP, unless the user
accepts the B-channel indicated in the SETUP message.
NOTE 4: Included in the event of interworking. Included in the network-to-user direction in connection
with the provision of in-band information/patterns. Included in the user-to-network direction in
connection with the provision of in-band information/patterns if annex K is implemented or in
accordance with the procedures of subclause 5.11.3 and subclause 5.12.3.
NOTE 5: Included if the network provides information that can be presented to the user.
NOTE 6: The minimum length is 2 octets; the maximum length is network dependent and is either 34
or 82 octets.
NOTE 7:    Included if the network optionally provides information describing tones or alerting signals.
NOTE 8: The High layer compatibility information element is included when the procedures of
subclause 5.12 for high layer compatibility selection apply. When present, progress
description #5, "interworking has occurred and has resulted in a telecommunication service
change", shall also be present.

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ETS 300 403-1: November 1995
Page 12, table 3-3/Q.931
Modify table 3-3/Q.931 as follows:
Message type: CALL PROCEEDING
Significance: local
Direction: both
Information element Reference Direction Type Length
Protocol discriminator 4.2 both M 1
Call reference 4.3 both M 2 - 3
Message type 4.4 both M 1
Bearer capability 4.5 both O (note 5) 4 - 12
Channel identification 4.5 both O (note 1) 2 - 34
Progress indicator 4.5 both O (note 2) 2 - 4
Display 4.5 O (note 3) 2 - 82
n → u
(note 4)
High layer compatibility 4.5 both O (note 6) 2 - 5
NOTE 1: Mandatory in the network-to-user direction if this message is the first message in response
to SETUP. Mandatory in the user-to-network direction if this message is the first message in
response to SETUP, unless the user accepts the B-channel indicated in the SETUP
message.
NOTE 2: Included in the event of interworking. Included in the network-to-user direction in connection
with the provision of in-band information/patterns. Included in the user-to-network direction in
connection with the provision of in-band information/patterns if annex K is implemented or in
accordance with the procedures of subclause 5.11.3 and subclause 5.12.3.
NOTE 3: Included if the network provides information that can be presented to the user.
NOTE 4: The minimum length is 2 octets; the maximum length is network dependent and is either 34
or 82 octets.
NOTE 5: The Bearer capability information element is included when the procedures of subclause
5.11 for bearer capability selection apply. When present, progress description #5
"interworking has occurred and has resulted in a telecommunication service change", shall
also be present.
NOTE 6: The High layer compatibility information element is included when the procedures of
subclause 5.12 for high layer compatibility selection apply. When present, progress
description #5, "interworking has occurred and has resulted in a telecommunication service
change", shall also be present.

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ETS 300 403-1: November 1995
Page 13, table 3-4/Q.931
Modify table 3-4/Q.931 as follows:
Message type: CONNECT
Significance: global
Direction: both
Information element Reference Direction Type Length
Protocol discriminator 4.2 both M 1
Call reference 4.3 both M 2 - 3
Message type 4.4 both M 1
Bearer capability 4.5 both O (note 1) 4 - 12
Channel identification 4.5 both (note 2) O (note 3) 2 - 34
u → n
Progress indicator 4.5 both O (note 4) 2 - 4
Display 4.5 O (note 5) 2 - 82
n → u
(note 6)
Date/time 4.6 O (note 7) 2 - 7
n → u
Signal 4.5 O (note 8) 2 - 3
n → u
Low layer compatibility 4.5 both O (note 9) 2 - 18 16
High layer compatibility 4.5 both O (note 10) 2 - 5
NOTE 1: The Bearer capability information element is included when the procedures of subclause
5.11 for bearer capability selection apply.
NOTE 2:    Included in the network-to-user direction for support of the procedures in annex D.
NOTE 3: Mandatory if this message is the first message in response to SETUP, unless the user
accepts the B-channel indicated in the SETUP message.
NOTE 4: Included in the event of interworking or in connection with the provision of in-band
information/patterns.
NOTE 5: Included if the network provides information that can be presented to the user.
NOTE 6: The minimum length is 2 octets; the maximum length is network dependent and is either 34
or 82 octets.
NOTE 7: As a network option, may be included to provide date and time information to the calling user
for all calls or for calls involving specific telecommunication services.
NOTE 8:    Included if the network optionally provides information describing tones.
NOTE 9: Included in the user-to-network direction when the answering user wants to return low layer
compatibility information to the calling user. Included in the network-to-user direction if the
user awarded the call included a Low layer compatibility information element in the
CONNECT message. Optionally included for low layer compatibility negotiation, but some
networks may not transport this information element to the calling user (see annex J).
NOTE 10: The High layer compatibility information element is included when the procedures of
subclause 5.12 for high layer compatibility selection apply.

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ETS 300 403-1: November 1995
Page 14, table 3-5/Q.931
Modify table 3-5/Q.931 as follows:
Message type: CONNECT ACKNOWLEDGE
Significance: global
Direction: both
Information element Reference Direction Type Length
Protocol discriminator 4.2 both M 1
Call reference 4.3 both M 2 - 3
Message type 4.4 both M 1
Display 4.5 O (note 1) 2 - 82
n → u
(note 2)
Signal 4.5 O (note 3) 2 - 3
n → u
NOTE 1: Included if the network provides information that can be presented to the user.
NOTE 2: The minimum length is 2 octets; the maximum length is network dependent and is either 34
or 82 octets.
NOTE 3:    Included if the network optionally provides additional information describing tones.
Page 15, table 3-6/Q.931
Modify table 3-6/Q.931 as follows:
Message type: DISCONNECT
Significance: global
Direction: both
Information element Reference Direction Type Length
Protocol discriminator 4.2 both M 1
Call reference 4.3 both M 2 - 3
Message type 4.4 both M 1
Cause 4.5 both M 4 - 32
Progress indicator 4.5 (note 1) O (note 2) 2 - 4
n → u
Display 4.5 O (note 3) 2 - 82
n → u
(note 4)
Signal 4.5 O (note 5) 2 - 3
n → u
NOTE 1: Included in the network-to-user direction if the network provides in-band tones. See annex D
for usage in the user-to-network direction.
NOTE 2: Included by the network if in-band tones are provided. However, the user may include the
Progress Indicator and provide in-band tones (see annex D). In such cases the network will
ignore this information element and will not convey the in-band tones.
NOTE 3: Included if the network provides information that can be presented to the user.
NOTE 4: The minimum length is 2 octets; the maximum length is network dependent and is either 34
or 82 octets.
NOTE 5:    Included if the network optionally provides additional information describing tones.

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ETS 300 403-1: November 1995
Page 16, table 3-7/Q.931
Modify table 3-7/Q.931 as follows:
Message type: INFORMATION
Significance: local (note 1)
Direction: both
Information element Reference Direction Type Length
Protocol discriminator 4.2 both M 1
Call reference 4.3 both M 2 - 3
(note 2)
Message type 4.4 both M 1
Sending complete 4.5 both O (note 3) 1
Cause 4.5 O (note 9) 2 - 32
n → u
Display 4.5 O (note 4) 2 - 82
n → u
(note 5)
Keypad facility 4.5 O (note 6) 2 - 34
u → n
(note 10)
Signal 4.5 O (note 7) 2 - 3
n → u
Called party number 4.5 O (note 8) 2 - 23
u → n
both
NOTE 1: This message has local significance, but may carry information of global significance.
NOTE 2:    This message may be set with the dummy call reference defined in § 4.3 when feature key
management procedures are used (see Recommendation Q.932); otherwise the minimum
length in 2 octets.
NOTE 3: Included if the user optionally indicates completion of overlap sending to the network, or if
the network optionally indicates completion of overlap receiving to the user.
NOTE 4: Included if the network provides information that can be presented to the user.
NOTE 5: The minimum length is 2 octets; the maximum length is network dependent and is either 34
or 82 octets.
NOTE 6: Either The Called party number or the Keypad facility information element is included by the
user to convey called party number information to the network during overlap sending. The
Keypad facility information element may also be included if the user wants to convey other
call establishment information to the network or to convey supplementary service information
(see clause 7).
NOTE 7:    Included if the network optionally provides additional information describing tones.
NOTE 8: Either The Called party number or the Keypad facility information element is included by the
user to c
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