ETSI EN 300 369-1 V1.2.1 (1998-10)

Integrated Services Digital Network (ISDN); Explicit Call Transfer (ECT) supplementary service; Digital Subscriber Signalling System No. one (DSS1) protocol; Part 1: Protocol specification

REN/SPS-05116-1

Digitalno omrežje z integriranimi storitvami (ISDN) - Dopolnilna storitev: nedvoumna predaja klica (ECT) - Protokol digitalne naročniške signalizacije št. 1 (DSS1) - 1. del: Specifikacija protokola

General Information

• Status: Published
• Publication Date: 08-Oct-1998
• Technical Committee: SPS 5 4 - Supplementary Services
• Current Stage: 12 - Completion
• Due Date: 23-Oct-1998
• Completion Date: 09-Oct-1998
• Ref Project: SIST EN 300 369-1 V1.2.4:2005 - Integrated Services Digital Network (ISDN); Explicit Call Transfer (ECT) supplementary service; Digital Subscriber Signalling System No. one (DSS1) protocol; Part 1: Protocol specification

Standards Content (Sample)

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Integrated Services Digital Network (ISDN); Explicit Call Transfer (ECT) supplementary
service; Digital Subscriber Signalling System No. one (DSS1) protocol; Part 1: Protocol
specification
Ta slovenski standard je istoveten z: EN 300 369-1 Version 1.2.4
ICS:
33.080 Digitalno omrežje z Integrated Services Digital
integriranimi storitvami Network (ISDN)
(ISDN)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN 300 369-1 V1.2.4 (1998-10)
European Standard (Telecommunications series)
Integrated Services Digital Network (ISDN);
Explicit Call Transfer (ECT) supplementary service;
Digital Subscriber Signalling System No. one (DSS1) protocol;
Part 1: Protocol specification

2 EN 300 369-1 V1.2.4 (1998-10)
Reference
REN/SPS-05116-1 (3f090iqo.PDF)
Keywords
ISDN, DSS1, supplementary service, ECT,
stage 3
ETSI
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The copyright and the foregoing restriction extend to reproduction in all media.
© European Telecommunications Standards Institute 1998.
All rights reserved.
ETSI
3 EN 300 369-1 V1.2.4 (1998-10)
Contents
Intellectual Property Rights. 5
Foreword. 5
1 Scope . 7
2 Normative references. 7
3 Definitions. 8
4 Abbreviations.9
5 Description . 9
6 Operational requirements . 10
6.1 Provision and withdrawal.10
6.2 Requirements on the originating network side.10
6.3 Requirements on the destination network side .10
7 Coding requirements. 10
7.1 Coding of the Facility information element components.10
7.2 Coding of the Notification indicator information element .12
7.3 Coding of the Redirection number information element .12
8 State definitions. 12
9 Signalling procedures at the coincident S and T reference point . 13
9.1 Activation, deactivation and registration .13
9.2 Invocation and operation.13
9.2.1 Explicit call transfer request using implicit linkage procedures.14
9.2.1.1 Normal operation.14
9.2.1.2 Exceptional procedures .14
9.2.2 Explicit call transfer request using explicit linkage procedures .14
9.2.2.1 Requesting a LinkId value.14
9.2.2.1.1 Normal operation.14
9.2.2.1.2 Exceptional procedures.15
9.2.2.2 Requesting call transfer .15
9.2.2.2.1 Normal operation.15
9.2.2.2.2 Exceptional procedures.15
9.2.3 Confirmation of call transfer .16
9.2.3.1 Normal operation.16
9.2.3.2 Exceptional procedures .16
9.2.4 Procedures for remote interfaces when both calls are in the Active call state.16
9.2.4.1 Normal operation.16
9.2.4.2 Exceptional procedures .17
9.2.5 Procedures for remote interfaces with one of the calls in the Call Delivered call state .17
9.2.5.1 Normal operation.17
9.2.5.2 Exceptional procedures .17
9.3 Content of notification information.18
10 Procedures for interworking with private ISDNs . 21
10.1 Call transfer performed in the private network, served user is connected to the private ISDN.21
10.1.1 Normal operation .21
10.1.2 Exceptional procedures.22
10.2 Call transfer performed in the public network, remote user is connected to the private ISDN.22
10.2.1 Normal operation .22
10.2.2 Exceptional procedures.23
10.3 Procedures for the mechanism to avoid looping of uncontrolled circuits.23
10.3.1 Procedures at the served network side .23
10.3.1.1 Normal operation.23
10.3.1.2 Exceptional procedures .24
ETSI
4 EN 300 369-1 V1.2.4 (1998-10)
10.3.2 Procedures at the remote network side.24
10.3.2.1 Normal operation.24
10.3.2.2 Exceptional procedures .24
10.4 Call transfer performed by the public ISDN, served user is connected to the private ISDN.24
11 Interactions with other networks. 25
12 Interaction with other supplementary services. 25
13 Parameter values (timers). 25
14 Dynamic description (SDL diagrams). 25
14.1 User side SDL diagrams .25
14.2 Network side SDL diagrams.30
Annex A (informative): Signalling flows . 34
Annex B (informative): Assignment of object identifier values . 45
Annex C (informative): Identification of changes since ETS 300 369-1 (1995). 46
History. 47
ETSI
5 EN 300 369-1 V1.2.4 (1998-10)
Intellectual Property Rights
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found in
SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in respect
of ETSI standards", which is available free of charge from the ETSI Secretariat. Latest updates are available on the
ETSI Web server (http://www.etsi.fr/ipr or http://www.etsi.org/ipr).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee can
be given as to the existence of other IPRs not referenced in SR 000 314 (or the updates on the ETSI Web server) which
are, or may be, or may become, essential to the present document.
Foreword
This European Standard (Telecommunications series) has been produced by ETSI Technical Committee Signalling
Protocols and Switching (SPS).
The present document 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) diversion supplementary services, as
described below:
Part 1: "Protocol specification";
Part 2: "Protocol Implementation Conformance Statement (PICS) proforma specification";
Part 3: "Test Suite Structure and Test Purposes (TSS&TP) specification for the user";
Part 4: "Abstract Test Suite (ATS) and partial Protocol Implementation eXtra Information for Testing (PIXIT)
proforma specification for the user";
Part 5: "Test Suite Structure and Test Purposes (TSS&TP) specification for the network";
Part 6: "Abstract Test Suite (ATS) and partial Protocol Implementation eXtra Information for Testing (PIXIT)
proforma specification for the network".
In accordance with CCITT Recommendation I.130 [3], the following three level structure is used to describe the
supplementary telecommunication services as provided by European public telecommunications operators under the
pan-European ISDN:
- Stage 1: is an overall service description, from the user's standpoint;
- Stage 2: identifies the functional capabilities and information flows needed to support the service described in
stage 1; and
- Stage 3: defines the signalling system protocols and switching functions needed to implement the service described
in stage 1.
The present document details the stage 3 aspects (signalling system protocols and switching functions) needed to support
the ECT supplementary service. The stage 1 and stage 2 aspects are detailed in EN 300 367 [15] and ETS 300 368 [16],
respectively.
ETSI
6 EN 300 369-1 V1.2.4 (1998-10)
National transposition dates
Date of adoption of this EN: 9 October 1998
Date of latest announcement of this EN (doa): 31 January 1999
Date of latest publication of new National Standard
or endorsement of this EN (dop/e): 31 July 1999
Date of withdrawal of any conflicting National Standard (dow): 31 July 1999
ETSI
7 EN 300 369-1 V1.2.4 (1998-10)
1 Scope
This first part of EN 300 369 specifies the stage three of the Explicit Call Transfer (ECT) supplementary service for the
pan-European Integrated Services Digital Network (ISDN) as provided by European public telecommunications operators
at the T reference point or coincident S and T reference point (as defined in ITU-T Recommendation I.411 [5]) by means
of the Digital Subscriber Signalling System No. one (DSS1) protocol. Stage three identifies the protocol procedures and
switching functions needed to support a telecommunication service (see CCITT Recommendation I.130 [3]).
In addition, the present document specifies the protocol requirements at the T reference point where the service is
provided to the user via an intermediate private ISDN.
The present document does not specify the additional protocol requirements where the service is provided to the user via
a telecommunications network that is not an ISDN.
The ECT supplementary service enables a user who has two calls, each of which can be an incoming call or an outgoing
call, to connect together the other users in the two calls, into one call. One of the two calls shall be answered, the other
call can be either answered or, as a network option, in the alerting phase.
The ECT supplementary service is applicable to all circuit-switched basic telecommunication services using one
B-channel.
Further parts of EN 300 369 specify the method of testing required to identify conformance to the present document.
The present document is applicable to equipment supporting the ECT supplementary service, 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.
2 Normative references
References may be made to:
a) specific versions of publications (identified by date of publication, edition number, version number, etc.), in which
case, subsequent revisions to the referenced document do not apply; or
b) all versions up to and including the identified version (identified by "up to and including" before the version
identity); or
c) all versions subsequent to and including the identified version (identified by "onwards" following the version
identity); or
d) publications without mention of a specific version, in which case the latest version applies.
A non-specific reference to an ETS shall also be taken to refer to later versions published as an EN with the same
number.
[1] ITU-T Recommendation E.164 (1997): "The international public telecommunication numbering
plan".
[2] ITU-T Recommendation I.112 (1993): "Vocabulary of terms for ISDNs".
[3] CCITT Recommendation I.130 (1988): "Method for the characterization of telecommunication
services supported by an ISDN and network capabilities of an ISDN".
[4] ITU-T Recommendation I.210 (1993): "Principles of telecommunication services supported by an
ISDN and the means to describe them".
[5] ITU-T Recommendation I.411 (1993): "ISDN user-network interfaces; Reference Configurations".
[6] CCITT Recommendation X.208 (1988): "Specification of Abstract Syntax Notation One (ASN.1)".
[7] CCITT Recommendation X.219 (1988): "Remote operations: Model, notation and service
definitions".
ETSI
8 EN 300 369-1 V1.2.4 (1998-10)
[8] CCITT Recommendation Z.100 (1988): "Specification and Description Language (SDL)".
[9] ETS 300 092-1 including amendment A2: "Integrated Services Digital Network (ISDN); Calling
Line Identification Presentation (CLIP) supplementary service; Digital Subscriber Signalling System
No. one (DSS1) protocol; Part 1: Protocol specification".
[10] ETS 300 097-1 including amendment A1: "Integrated Services Digital Network (ISDN); Connected
Line Identification Presentation (COLP) supplementary service; Digital Subscriber Signalling
System No. one (DSS1) protocol; Part 1: Protocol specification".
[11] ETS 300 141-1: "Integrated Services Digital Network (ISDN); Call Hold (HOLD) supplementary
service; Digital Subscriber Signalling System No. one (DSS1) protocol; Part 1: Protocol
specification".
[12] EN 300 195-1: "Integrated Services Digital Network (ISDN); Supplementary service interactions;
Digital Subscriber Signalling System No. one (DSS1) protocol; Part 1: Protocol specification".
[13] EN 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".
[14] EN 300 207-1: "Integrated Services Digital Network (ISDN); Diversion supplementary services;
Digital Subscriber Signalling System No. one (DSS1) protocol; Part 1: Protocol specification".
[15] EN 300 367 (V1.2): "Integrated Services Digital Network (ISDN); Explicit Call Transfer (ECT)
supplementary service; Service description".
[16] ETS 300 368: "Integrated Services Digital Network (ISDN); Explicit Call Transfer (ECT)
supplementary service; Functional capabilities and information flows".
[17] ETS 300 402-1: "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]".
[18] EN 300 403-1: "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]".
[19] ETS 300 403-2: "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".
3 Definitions
For the purposes of the present document, the following definitions apply:
call A-C: The call between user A and user C.
call A-B: The call between user A and user B.
call state: A state as defined in EN 300 403-1 [18], subclause 2.1 for either the user side or the network side as
appropriate. A call state may exist for each call reference value (and for each additional responding CEI in the incoming
call state).
component: See EN 300 196-1 [13], subclause 8.2.2.
Connection Endpoint Identifier (CEI): See subclause 3.4.1 of ITU-T Recommendation Q.920 as modified by
ETS 300 402-1 [17].
Integrated Services Digital Network (ISDN): See ITU-T Recommendation I.112 [2], definition 308.
invoke component: See EN 300 196-1 [13], subclause 8.2.2.1. Where reference is made to a "xxxx" invoke component,
an invoke component is meant with its operation value set to the value of the operation "xxxx".
ETSI
9 EN 300 369-1 V1.2.4 (1998-10)
ISDN number: A number conforming to the numbering plan and structure specified in ITU-T Recommendation E.164 [1].
network: The DSS1 protocol entity at the network side of the user-network interface.
network A: The network to which the served user is attached.
network B: The network to which user B is attached.
network C: The network to which user C is attached.
public network: The DSS1 protocol entity at the network side of the user-network interface at the T reference point.
private network: The DSS1 protocol entity at the user side of the user-network interface at the T reference point.
reject component: See EN 300 196-1 [13], subclause 8.2.2.4.
remote user: User B or user C.
return error component: See EN 300 196-1 [13], subclause 8.2.2.3. Where reference is made to a "xxxx" return error
component, a return error component is meant with its operation value set to the value of the operation "xxxx".
return result component: See EN 300 196-1 [13], subclause 8.2.2.2. Where reference is made to a "xxxx" return result
component, a return result component is meant with its operation value set to the value of the operation "xxxx".
served user; user A: The served user is the user who invokes the ECT supplementary service.
service; telecommunication service: See ITU-T Recommendation I.112 [2], definition 201.
supplementary service: See ITU-T Recommendation I.210 [4], subclause 2.4.
user: The DSS1 protocol entity at the user side of the user-network interface.
user B: The other user in one of user A's calls. By convention, in the present document, it is considered that the
connection has been established on this call.
user C: The other user in another of user A's calls.
NOTE: In this context, the sequence of the call setups is of no consequence, i.e. call A-C may exist before the call
A-B.
4 Abbreviations
For the purposes of the present document, the following abbreviations apply:
CEI Connection Endpoint Identifier
CLIR Calling Line Identification Restriction
COLR Connected Line Identification Restriction
DSS1 Digital Subscriber Signalling System No. one
ECT Explicit Call Transfer
HOLD Call Hold
ISDN Integrated Services Digital Network
NIE Notification indicator Information Element
RDNIE Redirection Number Information Element
SDL Specification and Description Language
5 Description
The ECT supplementary service enables a user (user A) who has two calls, each of which can be an incoming call or an
outgoing call, to connect together the other users in the two calls, into one call. One of the two calls shall be answered, the
other call can be either answered or, as a network option, in the alerting phase. At the coincident S and T reference point,
the two calls shall be controlled using the same data link connection identified by the same CEI value.
ETSI
10 EN 300 369-1 V1.2.4 (1998-10)
As a network provider option the ECT supplementary service can be provided at the T reference point.
When the ECT supplementary service is invoked, the served user shall send a message to the network, identifying the
users to be connected. The network responds by releasing both calls at user A and establishing a connection between
user B and user C, and at the same time sending a notification of the transfer to both users B and C. See also
EN 300 367 [15], clause 5.
The procedures are currently restricted to basic telecommunication services involving a single 64 kbit/s connection. The
present document is not applicable to a video telephony call involving two 64 kbit/s connections.
6 Operational requirements
6.1 Provision and withdrawal
The ECT supplementary service is provided by prior arrangements with the service provider.
Withdrawal of the service is made by the service provider upon request by the subscriber or for service provider reasons.
6.2 Requirements on the originating network side
The originating network (served user side) shall provide the Call Hold (HOLD) supplementary service
ETS 300 141-1 [11] in connection with the ECT supplementary service
In the case where the network supports the option allowing the transfer of an alerting call, the other user shall be notified
when the alerting call is answered.
6.3 Requirements on the destination network side
The destination network (remote user sides) shall be able to:
- receive an indication of the transfer from the originating network and convey notification of the transfer, and a
request for subaddress to the user who remains part of the transferred call;
- receive a subaddress from the remote user and convey it to the network of the other remote user;
- receive a subaddress from the network of the other remote user and convey it to the user.
7 Coding requirements
7.1 Coding of the Facility information element components
Table 1 shows the definition of the operations and errors required for the ECT supplementary service using Abstract
Syntax Notation one (ASN.1) as defined in CCITT Recommendation X.208 [6] and using the OPERATION and ERROR
macro as defined in CCITT Recommendation X.219 [7], figure 4/X.219.
The formal definition of the component types to encode these operations and errors is provided in EN 300 196-1 [13],
annex D, clause D.1. The inclusion of components in Facility information elements is defined in EN 300 196-1 [13],
subclause 11.2.2.1.
All components (invoke, return result, return error and reject) shall be included within a Facility information element.
This Facility information element may be included in any appropriate message as specified in EN 300 196-1 [13],
subclause 8.3.1.1, unless a more restrictive specification is given in clause 9.
ETSI
11 EN 300 369-1 V1.2.4 (1998-10)
Table 1: Operation and error definitions for the ECT supplementary service
Explicit-Call-Transfer-Operations-and-Errors {ccitt identified-organization etsi(0) 369
version(2) operations-and-errors(1)}
DEFINITIONS ::=
BEGIN
EXPORTS EctLinkIdRequest,
EctExecute,
RequestSubaddress,
SubaddressTransfer,
ExplicitEctExecute,
LinkIdNotAssignedByNetwork,
EctLoopTest,
EctInform;
IMPORTS OPERATION,
ERROR
FROM Remote-Operation-Notation
{joint-iso-ccitt remote-operations(4) notation(0)}
notAvailable,
notSubscribed,
resourceUnavailable,
supplementaryServiceInteractionNotAllowed,
invalidCallState
FROM General-Errors
{ccitt identified-organization etsi(0) 196 general-errors(2)}
PartySubaddress,
PresentedNumberUnscreened
FROM Addressing-Data-Elements
{ccitt identified-organization etsi(0) 196 addressing-data-elements(6)};
EctExecute ::= OPERATION
RESULT
ERRORS {notAvailable,
notSubscribed,
invalidCallState,
supplementaryServiceInteractionNotAllowed}
EctInform ::= OPERATION
ARGUMENT SEQUENCE {
ENUMERATED {
alerting (0),
active (1)},
redirectionNumber PresentedNumberUnscreened OPTIONAL}
EctLinkIdRequest ::= OPERATION
RESULT LinkId
ERRORS {resourceUnavailable}
EctLoopTest ::= OPERATION
ARGUMENT CallTransferIdentity
RESULT LoopResult
ERRORS {notAvailable}
ExplicitEctExecute ::= OPERATION
ARGUMENT LinkId
RESULT
ERRORS {notAvailable,
notSubscribed,
invalidCallState,
supplementaryServiceInteractionNotAllowed,
LinkIdNotAssignedByNetwork}
RequestSubaddress ::= OPERATION
SubaddressTransfer ::= OPERATION
ARGUMENT transferredToSubaddress PartySubaddress
CallTransferIdentity ::= INTEGER (-128.127)
LinkId ::= INTEGER (-32768.32767)
LoopResult ::= ENUMERATED {
insufficientInformation (0),
noLoopExists (1),
simultaneousTransfer (2)}
LinkIdNotAssignedByNetwork ::= ERROR
eCTOID OBJECT IDENTIFIER ::= {ccitt identified-organization etsi(0) 369
operations-and-errors(1)}
ectExecute EctExecute ::= localValue 6
ETSI
12 EN 300 369-1 V1.2.4 (1998-10)
Table 1 (concluded): Operation and error definitions for the ECT supplementary service
explicitEctExecute ExplicitEctExecute ::= globalValue {eCTOID explicitEctExecute-operation(1)}
requestSubaddress RequestSubaddress ::= globalValue {eCTOID requestSubaddress-operation (2)}
subaddressTransfer SubaddressTransfer ::= globalValue {eCTOID subaddressTransfer-operation(3)}
ectLinkIdRequest EctLinkIdRequest ::= globalValue {eCTOID ectLinkIdRequest-operation (4)}
ectInform EctInform ::= globalValue {eCTOID ectInform-operation (5)}
ectLoopTest EctLoopTest ::= globalValue {eCTOID ectLoopTest-operation (6)}
linkIdNotAssignedByNetwork LinkIdNotAssignedByNetwork ::= globalValue {eCTOID
linkIdNotAssignedByNetwork-error(21)}
END -- Explicit-Call-Transfer-Operations-and-Errors
7.2 Coding of the Notification indicator information element
For the coding of the Notification indicator Information Element (NIE), see EN 300 403-1 [18], subclause 4.5.21.
For the ECT supplementary service, the notification description (octet 3) of the Notification indicator information element
shall be coded "call transferred, active" or "call transferred, alerting". The coding is shown in table 2.
Table 2: Notification description
Bits
7 6 5 4 3 2 1
1 1 0 1 0 0 1 Call transferred, alerting
1 1 0 1 0 1 0 Call transferred, active
7.3 Coding of the Redirection number information element
The purpose of the Redirection Number Information Element (RDNIE) is to identify the ISDN number of the transferred
user. The coding of the Redirection number information element shall be as defined in EN 300 207-1 [14],
subclause 7.2.3.
8 State definitions
The call states as specified in EN 300 403-1 [18], subclause 2.1 shall apply. The auxiliary states as specified in
EN 300 196-1 [13], subclause 7.1.2 shall apply. For the associated use of the HOLD supplementary service, the auxiliary
states are defined in ETS 300 141-1 [11].
Table 3 defines the states for the ECT supplementary service.
Table 3: States for user A and network A associated to the ECT supplementary service
User A states
ECT Idle An instance of the ECT supplementary service has not been requested.
ECT LinkId Request A request for a link identifier has been initiated.
ECT LinkId Assigned A LinkId value is assigned.
Await ECT LinkId A LinkId value has not yet been assigned.
ECT Implicit Request The ECT supplementary service has been requested using the implicit linkage
procedure, confirmation is awaited.
ECT Explicit Request The ECT supplementary service has been requested using the explicit linkage
procedure, confirmation is awaited.
Network A state
ECT Idle An instance of the ECT supplementary service has not been requested.
ETSI
13 EN 300 369-1 V1.2.4 (1998-10)
9 Signalling procedures at the coincident S and T
reference point
9.1 Activation, deactivation and registration
Not applicable.
9.2 Invocation and operation
To perform an explicit call transfer, the states at user A shall be one of the combinations indicated in tables 4 or 5
depending on the linkage procedure used.
Table 4: States at user A for the invocation of the ECT supplementary service
using either the implicit or the explicit linkage procedure
Call A«B Call A«C Examples of signalling flow
for information
(Active call state, (Active call state, Figures A.1 and A.6
Call Held auxiliary state) Idle auxiliary state)
(Active call state, (Active call state, Figures A.1 and A.6
Idle auxiliary state) Call Held auxiliary state)
(Active call state, (Call Delivered call state, Figures A.2 and A.7
Call Held auxiliary state) Idle auxiliary state) (notes 1 and 2)
(Active call state, (Call Delivered call state, Figures A.3 and A.8
Idle auxiliary state) Call Held auxiliary state) (notes 1 and 2)
NOTE 1: Only applicable for an outgoing call (from the served user).
NOTE 2: The support of the call transfer with this combination is dependant on a network option for transfer of a call
in the alerting phase.
Table 5: Additional states at user A for the invocation of the ECT supplementary service
in which the explicit linkage procedure shall be used
Call A«B Call A«C Examples of signalling
flow for information
(Active call state, (Active call state, Figures A.9 and A.11
Idle auxiliary state) Idle auxiliary state) (note 1)
(Active call state, (Call Delivered call state, Figures A.10 and A.12
Idle auxiliary state) Idle auxiliary state) (notes1, 2 and 3)
NOTE 1: The support of call transfer with this combination is dependant on a network option for transfer of calls
without prior hold.
NOTE 2: The support of the call transfer with this combination is dependant on a network option for transfer of a call
in the alerting phase.
NOTE 3: Only applicable for an outgoing call (from the served user).
NOTE: In tables 4 and 5 and throughout the text, the term "Idle auxiliary state" is used for a call which is not on
hold, and also in cases where the HOLD supplementary service does not apply.
In order to invoke the ECT supplementary service, an implicit or, an explicit linkage mechanism may be used in the
invocation procedure to identify the two calls to be transferred. The support of the explicit linkage mechanism is both a
network and an user option. The implicit linkage mechanism or explicit linkage mechanism can be used if the served user
has only one call in the Idle auxiliary state and at least one call in the Call Held auxiliary state. The explicit linkage
mechanism shall be used if the served user has more than one call in the Idle auxiliary state.
ETSI
14 EN 300 369-1 V1.2.4 (1998-10)
9.2.1 Explicit call transfer request using implicit linkage procedures
9.2.1.1 Normal operation
In order to transfer the two calls into one call between user B and user C using the implicit linkage procedure, one of the
combination of the states in table 4 shall apply. User A shall send a FACILITY message according to the procedures of
subclause 8.3.1.1 of EN 300 196-1 [13] with the call reference of the call in the Call Held auxiliary state and with a
Facility information element containing an EctExecute invoke component.
Network A, on receiving such a transfer request, shall follow the procedure of subclause 9.2.3.
9.2.1.2 Exceptional procedures
If network A cannot accept the transfer request, network A shall send a FACILITY message containing an EctExecute
return error component to user A, within a Facility information element, using the procedures in subclause 8.3.1.1 of
EN 300 196-1 [13], and indicating one of the following error values:
- "notSubscribed", if the ECT supplementary service is not subscribed to;
- "notAvailable", if the ECT supplementary service is invoked on a non-circuit-switched connection;
- "notAvailable", if network A recognizes a looping condition;
- "notAvailable", if network A cannot accept the transfer request due to internal network restrictions;
- "invalidCallState", if the ECT supplementary service is invoked when the call indicated by the call reference is
not in the Active call state (N10) or, as a network option, in the Call Delivered call state (N4);
- "invalidCallState", if the ECT supplementary service is invoked when the call indicated by the call reference is
not in the Call Held auxiliary state;
- "invalidCallState", if the ECT supplementary service is invoked when the call in the Idle auxiliary state is not in a
compatible call state or if there are more than one call in the Idle auxiliary state;
- "supplementaryServiceInteractionNotAllowed", if the ECT supplementary service is invoked when another
supplementary service is already activated and network A does not allow this supplementary service interaction.
At user A, on receiving the FACILITY message containing the EctExecute return error component, the calls A-C and A-B
shall remain in the call states in which they were before transfer was attempted.
At user A, on receiving the FACILITY message containing a reject component, the calls A-C and A-B shall remain in the
call states in which they were before transfer was attempted.
9.2.2 Explicit call transfer request using explicit linkage procedures
9.2.2.1 Requesting a LinkId value
9.2.2.1.1 Normal operation
In order to initiate the explicit linkage procedure, user A shall send a FACILITY message to network A according to the
procedures of subclause 8.3.1.1 of EN 300 196-1 [13] with the call reference of a call to be transferred and with a
Facility information element containing an EctLinkIdRequest invoke component.
Network A, on receiving such a request shall:
- issue a LinkId value and associate this value with that call. The LinkId value shall be unique within the data link
connection used to control the call; and
- send a FACILITY message according to the procedures of subclause 8.3.1.1 of EN 300 196-1 [13] to user A, with
a Facility information element containing an EctLinkIdRequest return result component carrying the LinkId value.
ETSI
15 EN 300 369-1 V1.2.4 (1998-10)
User A, on receiving a FACILITY message with a Facility information element containing the issued LinkId value in the
EctLinkIdRequest return result component, shall store this value for use in subsequent explicit call transfer requests.
When the call associated with a LinkId value is cleared, the LinkId value shall be released by network A and user A.
9.2.2.1.2 Exceptional procedures
If network A receives the EctLinkIdRequest invoke component and is unable to allocate a LinkId value, then network A
shall send a FACILITY message according to the procedures of subclause 8.3.1.1 of EN 300 196-1 [13] with a Facility
information element containing an EctLinkIdRequest return error component to the served user. The error shall indicate
"resourceUnavailable".
If network A receives the EctLinkIdRequest invoke component when the call indicated by the call reference has already
allocated a LinkId value, then network A shall send a FACILITY message according to the procedures of
subclause 8.3.1.1 of EN 300 196-1 [13] with the Facility information element containing a EctLinkIdRequest return result
component. The EctLinkIdRequest return result component shall indicate the current LinkId value. At user A, on receiving
the FACILITY message with the EctLinkIdRequest return result component indicating the current LinkId value, normal
procedures shall apply.
At user A, on receiving the FACILITY message with the EctLinkIdRequest return error component, the calls A-C and A-B
shall remain in the basic call states in which they were before the LinkId value was requested.
At user A, on receiving the FACILITY message with a reject component, the calls A-C and A-B shall remain in the basic
call states in which they were before the LinkId value was requested.
9.2.2.2 Requesting call transfer
9.2.2.2.1 Normal operation
In order to transfer the two calls into one call between user B and user C one of the combinations of the states in table 4 or
5 shall apply. A LinkId value shall have been assigned for one of the calls to be transferred. This call shall be in the Idle
auxiliary state. User A shall send a FACILITY message according to the procedures of subclause 8.3.1.1 of
EN 300 196-1 [13] with the call reference of the call for which a LinkId value has not been assigned. The FACILITY
message shall contain a Facility information element with an ExplicitEctExecute invoke component including the LinkId
value received using the procedures in subclause 9.2.2.1.
Network A, on receiving such a transfer request, shall release the LinkId value and follow the procedures of
subclause 9.2.3.
9.2.2.2.2 Exceptional procedures
If network A cannot accept the transfer request, network A shall send a FACILITY message containing an
ExplicitEctExecute return error component to user A, within a Facility information element, using the procedures in
subclause 8.3.1.1 of EN 300 196-1 [13], and indicating one of the following error values:
- "notSubscribed", if the ECT supplementary service is not subscribed to;
- "notAvailable", if the ECT supplementary service is invoked on a non-circuit-switched connection;
- "notAvailable", if network A recognizes a looping condition;
- "notAvailable", if network A cannot accept the transfer request due to internal network restrictions;
- "invalidCallState", if the ECT supplementary service is invoked when the call indicated by the call reference is
not in the Active call state (N10) or, as a network option, in the Call Delivered call state (N4);
- "invalidCallState", if the ECT supplementary service is invoked when the call identified by the LinkId value is not
in a compatible call state;
- "supplementaryServiceInteractionNotAllowed", if the ECT supplementary service is invoked when another
supplementary service is already activated and network A does not allow this supplementary service interaction;
- "LinkIdNotAssignedByNetwork", if the received LinkId value has not been assigned.
ETSI
16 EN 300 369-1 V1.2.4 (1998-10)
At user A, on receiving an ExplicitEctExecute return error component, the calls A-C and A-B shall remain in the basic
call states in which they were before transfer was attempted.
At user A, on receiving a reject component, the calls A-C and A-B shall remain in the basic call states in which they were
before transfer was attempted.
9.2.3 Confirmation of call transfer
9.2.3.1 Normal operation
If the request for call transfer is accepted, network A shall:
- through-connect between the networks of user B and user C;
- send a DISCONNECT message with the call reference of the call on which the EctExecute or ExplicitEctExecute
invoke component was received, and with a Facility information element containing an EctExecute return result
component (if the procedure in subclause 9.2.1 has been used) or an ExplicitEctExecute return result component (if
the procedure in subclause 9.2.2 has been used), thereby initiating clearing of the call towards user A according to
the procedures of EN 300 403-1 [18], subclause 5.3.4;
- initiate normal clearing towards user A of the other call (i.e. the call associated with the LinkId value in case of
explicit linkage procedure or the call in the Idle auxiliary state in case of implicit linkage procedure) in
accordance with the procedures of EN 300 403-1 [18], subclause 5.3.4.
User A on receiving the DISCONNECT messages shall continue call clearing in accordance with EN 300 403-1 [18],
subclause 5.3.4.
9.2.3.2 Exceptional procedures
Not applicable.
9.2.4 Procedures for remote interfaces when both calls are in the Active
call state
9.2.4.1 Normal operation
When call transfer is indicated to the remote networks while the call to user C is in the Active call state:
- network C shall send a FACILITY message to user C according to the procedures of subclause 8.3.1.1 of
EN 300 196-1 [13], with a Noti
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