SIST ETS 300 201 E1:2003

• Abstract:

  Stage 1 of CFNR supplementary service

• Status: Published
• Publication Date: 30-Nov-2003
• ICS: 33.080 - Integrated Services Digital Network (ISDN)
• 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 300 201 ed.1 (1994-12) - Integrated Services Digital Network (ISDN); Call Forwarding No Reply (CFNR) supplementary service; Service description

SIST ETS 300 201 E1:2003 is the Slovenian adoption of ETS 300 201 Edition 1 for Integrated Services Digital Network (ISDN) Call Forwarding No Reply (CFNR). It is a stage 1 service description from the user's point of view, defining when the network redirects unanswered calls, who is informed, and how the service behaves on public ISDN and in private ISDN interworking.

What does SIST ETS 300 201 E1:2003 specify?

SIST ETS 300 201 E1:2003 specifies the stage 1 description of the CFNR supplementary service for the pan-European ISDN. It sets out the service behavior, not the signaling protocol details or the human-machine interface.

The standard covers:

• how the service is provided and withdrawn,
• normal and exceptional procedures for activation, deactivation, registration, erasure, invocation, and interrogation,
• intercommunication with non-ISDNs and private ISDNs,
• interaction with other supplementary services listed in clause 8.

A useful way to read the structure is:

Part	What it covers
Foreword	Stage 1, stage 2, and stage 3 context for ISDN supplementary services
Clauses 1-6	Scope, references, definitions, service description, and procedures
Clause 7	Intercommunication with non-ISDNs and private ISDNs
Clause 8	Interaction with other supplementary services
Annex A	Interaction between user-to-user signalling and CFNR

The scope is user-focused. The standard says CFNR lets the network redirect calls addressed to the served user's ISDN number if the call is not established within a defined time. The served user's ability to originate calls is not affected.

What are the key requirements of SIST ETS 300 201 E1:2003?

SIST ETS 300 201 E1:2003 gives the service rules that determine when forwarding happens, what users can configure, and what information is shown during call handling. In practice, these clauses tell a service provider what must be available in provisioning, what notifications may be sent, and how to handle edge cases.

Service availability and trigger conditions

Clause 5 states that CFNR shall be available to users connected by basic access or primary rate access. The service can apply to all calls or only to calls associated with specified basic services.

The service is invoked only after the call has been offered to the served user and the network has received the indication that the called user is being informed. This matters because CFNR is not a pre-answer diversion - it is a no-reply action after alerting has started.

The served user's ability to make outgoing calls remains unchanged. For a buyer or operator, that means CFNR is an incoming-call handling feature, not a line barring feature.

Provisioning, activation, and interrogation

Clause 6.1 says CFNR is provided after prior arrangement with the service provider. It can be subscribed to per ISDN number or for the whole access, and it can apply to all basic services or selected basic services.

Activation in clause 6.2.1 requires the ISDN number of the forwarded-to user, optionally with a subaddress, plus the scope of the activation across basic services. When the access has several ISDN numbers, the served user may also need to identify which number the activation applies to.

Interrogation in clause 6.2.4 lets the served user check whether CFNR is active, see the forwarded-to address, and see which basic services are covered. If the option is offered, the user can also query which ISDN numbers on the access have CFNR active. That is important for service desks and administrators who need to confirm customer settings.

Deactivation, replacement, and rejection cases

Clause 6.2.1.2 allows deactivation for individual basic services or for all basic services, and a later activation can replace earlier registered information. Clause 6.3 lists rejection cases, including wrong served-user number, missing information, an invalid or special forwarded-to number, or a request for a basic service where CFNR does not apply.

These rules matter because provisioning systems need to reject inconsistent requests cleanly and report the reason to the terminal that issued the request. They also show that a provider may block forwarding to numbers with special significance, such as emergency or operator services.

Notification and forwarding behavior

Clause 6.2.3 and 6.3.3 describe what happens when no reply occurs. The network sets up the call to the forwarded-to user, and the served user may either keep the original call until the forwarding attempt is underway or have the original call removed immediately, depending on a network option.

Subscription options control whether:

• the served user receives notice that forwarding has happened,
• the calling user receives notice that the call has been forwarded,
• the calling user receives the forwarded-to ISDN number,
• the forwarded-to user receives the served user's ISDN number.

In practice, this is the part that determines customer-facing privacy and traceability behavior. The standard also says that if a number cannot be shown, the recipient of the notification should be told why no number is available.

Limits, interworking, and related services

Clause 5 and clause 6.2.3 set a service provider option for the maximum number of diversions per call, with an upper limit of five and with all diversion types counted. Clause 7 extends CFNR to interworking with non-ISDNs and private ISDNs, while keeping the total diversion limit in force across network boundaries.

Clause 8 records key interactions with other supplementary services. Examples include:

• call forwarding unconditional taking precedence over CFNR,
• call waiting still being offered before the no-reply timer expires,
• closed user group parameters from the original call being used for the forwarded part,
• subaddress not being forwarded,
• user-to-user signalling behavior being controlled by Annex A.

What terms does SIST ETS 300 201 E1:2003 define?

• Integrated Services Digital Network (ISDN) - the digital network environment for the service, defined by reference to the ISDN vocabulary standard.
• CFNR - Call Forwarding No Reply, the supplementary service that redirects a call when the called user does not answer in time.
• served user - the user who subscribes to CFNR and whose incoming calls are handled by the service.
• user A - the calling user whose call is subject to diversion.
• user B - the served user when a call from user A is subject to CFNR.
• user C - the forwarded-to user who receives the redirected call.
• diversion - the broader family of forwarding behavior, including forwarding and deflection.
• ISDN number - a number that follows the ISDN numbering plan and structure used in the standard.

Who uses SIST ETS 300 201 E1:2003?

SIST ETS 300 201 E1:2003 is used by public telecommunications operators, ISDN service providers, and network engineers who configure and verify supplementary services. It is also relevant to private ISDN administrators, interoperability teams, and quality managers who need to understand how unanswered calls are redirected and what information is presented to each user. Buyers of telecom platforms can use it to check whether a system supports the expected CFNR behavior and interworking options.

What changed in SIST ETS 300 201 E1:2003 from the previous edition?

SIST ETS 300 201 E1:2003 is identified as identical to ETS 300 201 Edition 1. The history notes the first edition dated December 1994.

Which standards are used with SIST ETS 300 201 E1:2003?

Reference	What it contributes
CCITT Recommendation I.130	The three-stage method used to describe telecommunication services
CCITT Recommendation I.112	ISDN vocabulary, including key ISDN terms
CCITT Recommendation E.164	ISDN numbering plan and number structure
CCITT Recommendation I.210	Principles of telecommunication services and how to describe them
CCITT Recommendation Q.9	Switching and signalling vocabulary, including access terms
ETS 300 205	The stage 2 description for CFNR
ETS 300 207	The stage 3 description for CFNR

What does the SIST ETS 300 201 E1:2003 document contain?

The document contains the service description, procedure clauses, intercommunication rules, and interaction rules needed to understand CFNR at stage 1. Table 1 summarizes subscription options, including notification and presentation choices, while Annex A and Table A.1 describe how user-to-user signalling interacts with CFNR.

It also includes the normal and exceptional procedures for activation, deactivation, interrogation, and call forwarding operation. These sections are the parts a network planner or implementer would use to map service behavior to product features and provisioning logic.

SLOVENSKI STANDARD
01-december-2003
Digitalno omrežje z integriranimi storitvami (ISDN) – Dopolnilna storitev: podaja
klica, ko ni odziva (CFNR) – Opis storitve
Integrated Services Digital Network (ISDN); Call Forwarding No Reply (CFNR)
supplementary service; Service description
Ta slovenski standard je istoveten z: ETS 300 201 Edition 1
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.

EUROPEAN ETS 300 201
TELECOMMUNICATION December 1994
STANDARD
Source: ETSI TC-NA Reference: T/NA1(89)23
ICS: 33.080
ISDN, supplementary service
Key words:
Integrated Services Digital Network (ISDN);
Call Forwarding No Reply (CFNR) supplementary service
Service description
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 1994. All rights reserved.
New presentation - see History box

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ETS 300 201: December 1994
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 300 201: December 1994
Contents
Foreword .5
1 Scope .7
2 Normative references.7
3 Definitions.8
4 Symbols and abbreviations .9
5 Description .9
6 Procedures.9
6.1 Provision and withdrawal .9
6.2 Normal procedures .10
6.2.1 Activation, deactivation and registration.10
6.2.1.1 Activation .10
6.2.1.2 Deactivation.11
6.2.1.3 Registration.12
6.2.2 Erasure.12
6.2.3 Invocation and operation .12
6.2.3.1 Served user's view.12
6.2.3.2 Forwarded-to user's view.13
6.2.3.3 Calling user's view .13
6.2.4 Interrogation .14
6.3 Exceptional procedures .15
6.3.1 Activation, deactivation and registration.15
6.3.1.1 Activation .15
6.3.1.2 Deactivation.16
6.3.1.3 Registration.16
6.3.2 Erasure.17
6.3.3 Invocation and operation .17
6.3.4 Interrogation .17
7 Intercommunication considerations.18
7.1 Interworking with non-ISDNs .18
7.2 Interworking with private ISDNs.18
8 Interaction with other supplementary services .19
8.1 Advice of charge services.19
8.1.1 Charging information at call set-up time.19
8.1.2 Charging information during the call.19
8.1.3 Charging information at the end of the call.19
8.2 Call waiting.19
8.3 Call hold .19
8.4 Explicit call transfer.20
8.5 Number identification services.20
8.5.1 Calling line identification presentation .20
8.5.2 Calling line identification restriction .20
8.5.3 Connected line identification presentation.20
8.5.4 Connected line identification restriction.20
8.6 Closed user group.21
8.7 Completion of calls to busy subscriber .21
8.8 Conference services .21
8.8.1 Conference call, add-on .21
8.8.2 Meet me-conference .21

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8.9 Direct dialling in . 21
8.10 Diversion services . 22
8.10.1 Call forwarding unconditional. 22
8.10.2 Call forwarding busy . 22
8.10.3 Call forwarding no reply . 22
8.10.4 Call deflection . 22
8.11 Freephone. 22
8.12 Malicious call identification. 22
8.13 Multiple subscriber number . 23
8.14 Subaddressing . 23
8.15 Terminal portability. 23
8.16 Three party. 23
8.17 User-to-user signalling . 23
Annex A (informative): Interaction between user-to-user signalling and the CFNR supplementary
service. 25
History. 26

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Foreword
This European Telecommunication Standard (ETS) has been produced by the Network Aspects (NA)
Technical Committee of the European Telecommunications Standards Institute (ETSI).
In accordance with CCITT Recommendation I.130 [1], the following three level structure is used to
describe the supplementary telecommunications services as provided by European public
telecommunications operators under the pan-European Integrated Services Digital Network (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.
This ETS details the stage 1 aspects (overall service description) for the Call Forwarding No Reply
(CFNR) supplementary service. The stage 2 and stage 3 aspects are detailed in ETS 300 205 (1994) and
ETS 300 207 (1994), respectively.
Proposed transposition dates
Date of latest announcement of this ETS (doa): 31 March 1995
Date of latest publication of new National Standard
or endorsement of this ETS (dop/e): 30 September 1995
Date of withdrawal of any conflicting National Standard (dow): 30 September 1995

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1 Scope
This standard defines the stage one of the Call Forwarding No Reply (CFNR) supplementary service for
the pan-European Integrated Services Digital Network (ISDN) as provided by European public
telecommunications operators. Stage one is an overall service description from the user's point of view
(see CCITT Recommendation I.130 [1]), but does not deal with the details of the human interface itself.
This standard defines the interworking requirements of private ISDNs with the public ISDN.
In addition this standard specifies the base functionality where the service is provided to the user via a
private ISDN.
This standard does not specify the additional requirements where the service is provided to the user via a
telecommunications network that is not an ISDN but does include interworking requirements of other
networks with the public ISDN.
Interactions with supplementary services not listed in clause 8 are outside the scope of this standard.
Charging principles are outside the scope of this standard.
The CFNR supplementary service enables a served user to have the network redirect to another user
calls which are addressed to the served user's ISDN number, and for which the connection is not
established within a defined period of time. The CFNR supplementary service may operate on all calls, or
just those associated with specified basic services. The served user's ability to originate calls is unaffected
by the CFNR supplementary service.
The CFNR supplementary service is applicable to all circuit-switched telecommunication services.
This standard is applicable to the stage two and stage three standards for the ISDN CFNR supplementary
service. The terms "stage two" and "stage three" are also defined in CCITT Recommendation I.130 [1].
Where the text indicates the status of a requirement (i.e. as strict command or prohibition, as authorization
leaving freedom, or as a capability or possibility), this shall be reflected in the text of the relevant stage two
and stage three standards.
Furthermore, conformance to this standard is met by conforming to the stage three standards with the
field of application appropriate to the equipment being implemented. Therefore, no method of testing is
provided for this standard.
2 Normative references
This standard incorporates by dated or 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 standard only when incorporated in it by amendment or revision. For dated references the
latest edition of the publication referred to applies.
[1] CCITT Recommendation I.130 (1988): "Method for the characterization of
telecommunication services supported by an ISDN and network capabilities of
an ISDN".
[2] CCITT Recommendation I.112 (1988): "Vocabulary of terms for ISDNs".
[3] CCITT Recommendation E.164 (1991): "Numbering plan for the ISDN era".
[4] CCITT Recommendation I.210 (1988): "Principles of telecommunication
services supported by an ISDN and the means to describe them".
[5] CCITT Recommendation Q.9 (1988): "Vocabulary of switching and signalling
terms".
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3 Definitions
For the purpose of this standard the following definitions apply:
Integrated Services Digital Network (ISDN): See CCITT Recommendation I.112 [2], § 2.3, definition
308.
(basic) service; Telecommunications service: See CCITT Recommendation I.112 [2], § 2.2, definition
201.
supplementary service: See CCITT Recommendation I.210 [4], § 2.4.
ISDN number: A number conforming to the numbering plan and structure specified in CCITT
Recommendation E.164 [3].
served user: The user to whom the CFNR supplementary service is provided.
user A: The calling user in a call which is subject to diversion.
user B: The served user when a call (from user A) is subject to the CFNR supplementary service.
NOTE: In the context of multiple diversions, a suffix is used, e.g. 1, 2, . n, n+1, . m, to
denote the successive diverting users. For example, user B3 is also the diverted-to
user with respect to the diversion applied at user B2.
user C: The forwarded-to user in a call which is subject to the CFNR supplementary service. In the case
of a call which is subject to multiple diversions, user C is the forwarded-to user with respect to the final call
forwarding.
forwarded-to user: A user to whom the call is redirected as a result of forwarding.
diverted-to user: A user to whom a call is redirected as a result of diversion.
basic access: See CCITT Recommendation Q.9 [5], § 1, definition 1551.
primary rate access: See CCITT Recommendation Q.9 [5], § 1, definition 1552.
address: See CCITT Recommendation E.164 [3], § 12.
subaddress: See CCITT Recommendation E.164 [3], § 12.2.
(call) forwarding: A general term applied to any functionality whereby a call is redirected automatically by
the service provider to another user. The forms of forwarding are: unconditional, whereby all calls are
redirected; busy, whereby calls encountering busy are redirected; and, no reply, whereby calls which are
not answered within a time period are redirected.
diversion: A general term which includes all forms of forwarding, and includes deflection whereby calls
are redirected by the user instead of being answered.
basic call procedures: The procedures by which a call (as an instance of a basic telecommunication
service) is established and terminated.
diverting user: A user for whom the call is subjected to diversion.

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4 Symbols and abbreviations
CFNR Call Forwarding No Reply
ISDN Integrated Services Digital Network
PSTN Public Switched Telephone Network
5 Description
The CFNR supplementary service shall be available to users who are connected to the network via a
basic access or a primary rate access.
The CFNR supplementary service enables a served user to have the network redirect to another user
calls which are addressed to the served user's ISDN number, and for which the connection is not
established within a defined period of time. The CFNR supplementary service may operate on all calls, or
just those associated with specified basic services. The served user's ability to originate calls is unaffected
by the CFNR supplementary service.
The CFNR supplementary service can only be invoked by the network after the call has been offered to
the served user and an indication that the called user is being informed of the call has been received.
As a service provider option, a subscription option can be provided to enable the served user to receive an
indication that the CFNR supplementary service has been activated. This indication shall be provided
when the served user originates a call if the CFNR supplementary service has been activated for the
served user's ISDN number and for the basic service requested for the call.
The maximum number of diversions permitted for each call is a service provider option with an upper limit
of five diversions. When counting the number of diversions, all types of diversion are included.
6 Procedures
6.1 Provision and withdrawal
The CFNR supplementary service shall be provided after prior arrangement with the service provider.
As a service provider option, the CFNR supplementary service can be provided on a per ISDN number
basis, or the CFNR supplementary service can apply to the whole access. If a service provider offers both
of these options, then it shall be a subscription option to choose which of these options applies.
In addition, the CFNR supplementary service (including options) can be subscribed to for all basic
services subscribed to by the user, or as a service provider option, the user can identify particular basic
service(s) for which the CFNR supplementary service shall apply.
As a service provider option, the service can be offered with one or more of four subscription options,
which can apply separately to each basic service subscribed to. If the CFNR supplementary service is
provided on a per ISDN number basis, then these options can apply separately to each ISDN number. For
each subscription option, only one value can be selected. Subscription options are summarized in table 1.

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Table 1
Subscription options Value
Served user receives notification -no
that the call has been forwarded - yes
Calling user receives notification -no
that the call has been forwarded - yes, without the ISDN
number of the forwarded-to
user
- yes, with the ISDN number of
the forwarded-to user
Served user receives notification -no
that the CFNR supplementary - yes
service is currently activated
The served users ISDN number can-no
be presented to the forwarded-to - yes
user
The value of the no reply timer shall be set by the service provider as a default value applying for all users.
As a service provider option, a subscription option can be offered to served users, to enable the CFNR
supplementary service to be activated, deactivated and interrogated for all ISDN numbers on the same
access. ISDN numbers for which the CFNR supplementary service is not subscribed to shall not be
affected.
The CFNR supplementary service shall be withdrawn by the service provider upon request of the
subscriber or for service provider reasons.
6.2 Normal procedures
6.2.1 Activation, deactivation and registration
6.2.1.1 Activation
The served user shall supply the following information when requesting the activation of the CFNR
supplementary service:
- the ISDN number of the forwarded-to user, which can be accompanied by a subaddress for
additional identification of the forwarded-to user; and
- information as to whether the activation of the CFNR supplementary service is for all basic services
to which the CFNR supplementary service applies, or for a specific basic service out of the basic
services to which the CFNR supplementary service applies.

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When subscription applies on a per ISDN number basis and more than one ISDN number is allocated to
the access, then:
- the served user shall also supply the ISDN number for which the activation of the CFNR
supplementary service shall apply, or;
- as a service provider option, the served user can, if subscribed to, indicate that the activation of the
CFNR supplementary service shall apply for all ISDN numbers for which the CFNR supplementary
service is subscribed to. In this case, this activation shall replace any previous activation of the
CFNR supplementary service which may be in force on individual ISDN numbers on the access, for
the basic services indicated at activation.
When subscription applies for the whole access, or only one ISDN number is allocated to the access, the
served user need not provide an ISDN number to identify the served user. If the served user includes an
ISDN number allocated to that access, or indicates that the activation of the CFNR supplementary service
shall apply to all ISDN numbers (if this functionality is offered by the service provider and subscribed to by
the served user) then the ISDN number, or the indication of all ISDN numbers, shall be ignored. Activation
of the CFNR supplementary service shall proceed as normal.
The served user can separately activate the CFNR supplementary service for each basic service to which
the CFNR supplementary service applies and thereby request a different ISDN number and/or subaddress
to identify the forwarded-to user for each basic service to which the CFNR supplementary service applies.
When the CFNR supplementary service is activated for all basic services, this activation shall replace any
previous activation of the CFNR supplementary service which may be in force on individual basic services.
Verification of the ISDN number of the forwarded-to user can be carried out before accepting the request
to activate the CFNR supplementary service. This verification can be limited, e.g. a simple check of the
ISDN number of the forwarded-to user to see if the ISDN number is within the allowed number range.
When the served user's request to activate the CFNR supplementary service is accepted, the service
provider shall inform the served user. The information shall include the address of the forwarded-to user
to whom the served user has activated the CFNR supplementary service. All affected users shall be
informed.
6.2.1.2 Deactivation
The CFNR supplementary service can be deactivated in any of the following ways:
- the served user can request the deactivation of the CFNR supplementary service for individual
basic services. The service provider shall inform the served user that the previous activation of the
CFNR supplementary service has been deactivated. All affected users shall be informed;
- the served user can request the deactivation of the CFNR supplementary service for all basic
services. The service provider shall inform the served user that the previous activation of the CFNR
supplementary service has been deactivated. All affected users shall be informed;
- the served user can request the activation of the CFNR supplementary service indicating a basic
service for which the CFNR supplementary service has already been activated. This shall replace
the previous information registered for that basic service. In this case, users shall not be specifically
informed of the deactivation. The procedures of subclause 6.2.1.1 for informing the served user
apply;
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- the served user can request the activation of the CFNR supplementary service for all basic
services. This shall replace the information registered for all of the basic services for which the
CFNR supplementary service has already been activated. In this case, users shall not be
specifically informed of the deactivation. The procedures of subclause 6.2.1.1 for informing the
served user apply.
When subscription applies on a per ISDN number basis and more than one ISDN number is allocated to
the access, then:
- the served user shall also supply the ISDN number for which the deactivation of the CFNR
supplementary service shall apply, or;
- as a service provider option, the served user can, if subscribed to, indicate that the deactivation of
the CFNR supplementary service shall apply for all ISDN numbers for which the CFNR
supplementary service is subscribed to.
When subscription applies for the whole access, or only one ISDN number is allocated to the access, the
served user need not provide an ISDN number to identify the served user. If the served user includes an
ISDN number allocated to that access, or indicates that the deactivation of the CFNR supplementary
service shall apply to all ISDN numbers (if this functionality is offered by the service provider and
subscribed to by the served user) then the ISDN number, or the indication of all ISDN numbers, shall be
ignored. Deactivation of the CFNR supplementary service shall proceed as normal.
6.2.1.3 Registration
Registration of information is performed on activation of the CFNR supplementary service.
There are no separate registration procedures for the CFNR supplementary service.
6.2.2 Erasure
Not applicable.
6.2.3 Invocation and operation
The maximum number of diversions for each call shall be limited. The maximum number of diversions is a
service provider option with an upper limit of five diversions for each call. When counting the number of
diversions, all types of diversions shall be included.
6.2.3.1 Served user's view
If the CFNR supplementary service has been activated, then if the connection is not established within a
specified time interval after the served user has been informed of the call, then the service provider shall
attempt to forward the call.
The call shall be offered to the served user by means of basic call procedures.
According to the value of a subscription option, the served user shall be informed that the CFNR
supplementary service has been invoked on the call. This information shall be given when the network
originates the call to the forwarded-to user.

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When the CFNR supplementary service is invoked, the network shall set up a call to the forwarded-to
user. According to a network option, one of the following shall occur:
a) the call to the served user shall be retained until the network receives an indication that the
forwarded-to user is being informed of the call, or that the connection is established at the
forwarded-to user, whereupon the call shall be removed from the served user. If, on a multipoint
access, another terminal requests the establishment of the connection prior to the removal of the
call, then the connection shall be established and the forwarding ceased; or
b) the call shall be removed from the served user when the CFNR supplementary service is invoked.
6.2.3.2 Forwarded-to user's view
The forwarded-to user shall receive an indication that the CFNR supplementary service has been invoked
on the call. Depending on the value of one of the served user's subscription options the forwarded-to user
can also receive the ISDN number of the served user.
If multiple diversions have occurred, then the forwarded-to user can also be given the originally called
user's ISDN number provided that the presentation has been permitted by the diversion service invoked
for the originally called user. When multiple diversions occur the reason for forwarding given to the
forwarded-to user shall indicate the last type of forwarding (i.e. the invocation of the CFNR supplementary
service).
6.2.3.3 Calling user's view
Depending on the value of the served user's subscription option "calling user receives notification that the
call has been forwarded", user A can be given an indication that the call is being forwarded. In that case,
this information shall be given when the network originates the call to the forwarded-to user. Depending on
the value of this subscription option, user A can also be given the ISDN number of the forwarded-to user.
When calls are forwarded once, i.e. due to a single invocation of the CFNR supplementary service, the
following information shall be given to user A based on the value of the served user's subscription option
"calling user receives notification that the call has been forwarded":
- if the value of the subscription option is "no", then no information shall be sent to user A;
- if the value of the subscription option is "yes, without the ISDN number of the forwarded-to user",
then an indication that the call is being forwarded shall be sent to user A. The ISDN number of the
forwarded-to user shall not be sent; and
- if the value of the subscription option is "yes, with the ISDN number of the forwarded-to user", then
an indication that the call is being forwarded shal
...