ETSI ETS 300 357 ed.1 (1995-10)

Integrated Services Digital Network (ISDN); Completion of Calls to Busy Subscriber (CCBS) supplementary service; Service description

DE/NA-012211

Digitalno omrežje z integriranimi storitvami (ISDN) – Dopolnilna storitev: dokončanje klicanja zasedenega naročnika (CCBS) – Opis storitve

General Information

• Status: Published
• Publication Date: 12-Oct-1995
• Technical Committee: NA 1 - User Interfaces, Services and Charging
• Current Stage: 12 - Completion
• Due Date: 13-Oct-1995
• Completion Date: 13-Oct-1995
• Ref Project: SIST ETS 300 357 E1:2005 - Integrated Services Digital Network (ISDN); Completion of Calls to Busy Subscriber (CCBS) supplementary service; Service description

Standards Content (Sample)

SLOVENSKI STANDARD
SIST ETS 300 357 E1:2005
01-april-2005
'LJLWDOQRRPUHåMH]LQWHJULUDQLPLVWRULWYDPL,6'1±'RSROQLOQDVWRULWHY
GRNRQþDQMHNOLFDQMD]DVHGHQHJDQDURþQLND&&%6±2SLVVWRULWYH
Integrated Services Digital Network (ISDN); Completion of Calls to Busy Subscriber
(CCBS) supplementary service; Service description
Ta slovenski standard je istoveten z: ETS 300 357 Edition 1
ICS:
33.080 Digitalno omrežje z Integrated Services Digital
integriranimi storitvami Network (ISDN)
(ISDN)
SIST ETS 300 357 E1:2005 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST ETS 300 357 E1:2005

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SIST ETS 300 357 E1:2005
EUROPEAN ETS 300 357
TELECOMMUNICATION October 1995
STANDARD
Source: ETSI TC-NA Reference: DE/NA-012211
ICS: 33.080
ISDN, supplementary service
Key words:
Integrated Services Digital Network (ISDN);
Completion of Calls to Busy Subscriber (CCBS)
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 1995. All rights reserved.
New presentation - see History box

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ETS 300 357: October 1995
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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Contents
Foreword .5
1 Scope .7
2 Normative references.8
3 Definitions.8
4 Symbols and abbreviations .9
5 Description .10
6 Procedures.10
6.1 Provision and withdrawal .10
6.2 Normal procedures .11
6.2.1 Activation, deactivation and registration.11
6.2.1.1 Activation .11
6.2.1.2 Deactivation.12
6.2.1.3 Registration.12
6.2.2 Erasure.12
6.2.3 Invocation and operation .12
6.2.4 Interrogation .13
6.3 Exceptional procedures .14
6.3.1 Activation, deactivation and registration.14
6.3.1.1 Activation .14
6.3.1.2 Deactivation.14
6.3.1.3 Registration.14
6.3.2 Erasure.14
6.3.3 Invocation and operation .15
6.3.3.1 Exceptional situation at destination B's side.15
6.3.3.2 Exceptional situation at user A's side .15
6.3.3.3 Network congestion .16
6.3.4 Interrogation .16
7 Intercommunication considerations.16
7.1 Interworking with non-ISDNs .16
7.2 Interworking with private ISDNs.17
8 Interaction with other supplementary services .17
8.1 Advice of charge services.17
8.1.1 Charging information at call set-up time.17
8.1.2 Charging information during the call.17
8.1.3 Charging information at the end of a call.17
8.2 Call waiting.17
8.3 Call hold .18
8.4 Explicit call transfer.18
8.5 Number identification services.18
8.5.1 Calling line identification presentation .18
8.5.2 Calling line identification restriction .18
8.5.3 Connected line identification presentation.18
8.5.4 Connected line identification restriction.18
8.6 Closed user group.18
8.7 Completion of calls to busy subscriber .19
8.8 Conference services .19
8.8.1 Conference call, add-on .19
8.8.2 Meet-me conference .19

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8.9 Direct dialling in . 19
8.10 Diversion services . 19
8.10.1 Call forwarding unconditional. 19
8.10.2 Call forwarding busy . 20
8.10.3 Call forwarding no reply . 20
8.10.4 Call deflection . 21
8.11 Freephone. 21
8.12 Malicious call identification. 21
8.13 Multiple subscriber number . 21
8.14 Subaddressing . 22
8.15 Terminal portability. 22
8.16 Three party. 22
8.17 User-to-user signalling . 22
Annex A (normative): Determination of the existence of compatible terminals. 23
Annex B (informative): Bibliography . 24
History. 25

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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 Completion of Calls to Busy
Subscriber (CCBS) supplementary service. The stage 2 aspects are detailed in ETS 300 358 (1994) and
the stage 3 aspects are detailed in ETS 300 359 (1994) and ETS 300 356-18 (1994).
Proposed transposition dates
Date of adoption of this ETS 31 October 1995
Date of latest announcement of this ETS (doa): 31 January 1996
Date of latest publication of new National Standard
or endorsement of this ETS (dop/e): 31 July 1996
Date of withdrawal of any conflicting National Standard (dow): 31 July 1996

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1 Scope
This standard defines the stage one of the Completion of Calls to Busy Subscriber (CCBS) 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 CCBS supplementary service enables user A, encountering a busy destination B, to have the call
completed without having to make a new call attempt when the destination B becomes not busy.
The CCBS supplementary service is applicable to all circuit-switched telecommunications services with
the following exceptions:
a) call 2, of the videotelephony teleservice (see ETS 300 264);
b) all other circuit-switched telecommunications services requiring the use of more than one
B-channel.
This standard is applicable to the stage two and stage three standards for the ISDN CCBS 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
authorisation 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 standard with the field
of application appropriate to the equipment being implemented. Therefore, no method of testing is
provided for this standard.

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2 Normative references
This standard 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 standard only when incorporated in it by amendment or revision. For undated references the
latest edition of the publication referred to applies.
[1] CCITT Recommendation I.130 (1988): "Method for the characterisation 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 I.210 (1988): "Principles of telecommunication
services supported by an ISDN and the means to describe them".
[4] CCITT Recommendation E.164 (1991): "Numbering plan for the ISDN era".
[5] CCITT Recommendation Q.9 (1988): "Vocabulary of switching and signalling
terms".
[6] CCITT Recommendation I.221 (1988): "Common specific characteristics of
services".
3 Definitions
For the purposes of this standard the following definitions apply:
Integrated Services Digital Network (ISDN): see CCITT Recommendation I.112 [2], § 2.3, definition
308.
Service; telecommunications service: see CCITT Recommendation I.112 [2], § 2.2, definition 201.
Supplementary service: see CCITT Recommendation I.210 [3], § 2.4.
ISDN number: a number conforming to the numbering plan and structure specified in CCITT
Recommendation E.164 [4].
User A: the user who originated the call and to whom the CCBS supplementary service is provided.
ISDN number: a number conforming to the numbering plan and structure specified in CCITT
Recommendation E.164 [4].
Subaddress: see CCITT Recommendation E.164 [4], § 11.2.
Basic access: see CCITT Recommendation Q.9 [5], § 1, definition 1551.
Primary rate access: see CCITT Recommendation Q.9 [5], § 1, definition 1552.
Busy: see CCITT Recommendation I.221 [6], § 3.
Destination B: the entity addressed in the original call.
Basic call procedures: the procedures by which a call (as an instance of a telecommunications service)
is established and terminated.

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Retention timer: this timer specifies the amount of time that the network retains all of the information
supplied by the calling user when the call encounters busy. This timer is part of the basic call procedures.
Although this timer is optional for the basic call procedures, it is needed for the operation of the CCBS
supplementary service. The value shall be greater than 15 seconds.
CCBS service duration timer: the maximum time the CCBS supplementary service will remain activated
for user A within the network. The value of this timer shall be a minimum of 15 minutes and a maximum of
45 minutes.
CCBS recall timer: the maximum time the network will wait for user A to respond to a CCBS recall. The
value of this timer shall be a minimum of 10 seconds and a maximum of 20 seconds.
Destination B idle guard timer: the time the network will wait after destination B has become not busy
before informing user A. The value of this timer shall be a maximum of 15 seconds.
CCBS busy: any one of the following conditions will cause user A to be considered as CCBS busy:
- maximum number of calls reached at user A;
- no B-channels available at user A;
- CCBS recall pending on user A.
CCBS call: a call generated by the network from user A to destination B resulting from user A's
acceptance of a CCBS recall.
CCBS recall: an indication informing user A that the network is ready to initiate a CCBS call to destination
B and that the network is awaiting a response to this indication.
CCBS request: an instance of an activation of the CCBS supplementary service which is held in a queue
pending the correct conditions for the CCBS supplementary service to be completed.
Suspended CCBS request: a CCBS request which cannot be served even if destination B is not busy,
because user A is busy or CCBS busy.
Compatible terminal: a terminal which can support the bearer service or teleservice requested for the
original call to destination B and which can accept calls to the ISDN number and subaddress identifying
the called user in the original call to destination B.
4 Symbols and abbreviations
CCBS Completion of Calls to Busy Subscriber
ISDN Integrated Services Digital Network

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5 Description
The CCBS supplementary service enables user A, encountering a busy destination B, to have the call
completed without having to make a new call attempt when the destination B becomes not busy.
When user A requests the CCBS supplementary service, the network will monitor for destination B
becoming not busy.
When destination B becomes not busy (i.e. access resources, e.g. at least one B-channel, are not busy)
then the network will wait a short time in order to allow the resources to be re-used for originating a call. If
the resources are not re-used by destination B within this time, then the network will automatically recall
user A.
When user A accepts the CCBS recall, then the network will automatically generate a CCBS call to
destination B.
The CCBS supplementary service shall be available to users who are connected to the network via a
basic access or a primary rate access.
NOTE: A supplementary service provided to destination B which prevents the registration of
CCBS requests is outside the scope of this standard.
6 Procedures
6.1 Provision and withdrawal
The CCBS supplementary service shall be provided to user A after prior arrangement with the service
provider or shall be generally available.
The CCBS supplementary service shall be withdrawn by the service provider upon request of the
subscriber or for service provider reasons.
As a service provider option, the CCBS supplementary service can be offered with a subscription option
which shall apply to the whole access of user A. The subscription option is detailed in table 1.
Table 1
Subscription option Values
Recall mode - Global, i.e. CCBS recall offered to all terminals.
- Specific, i.e. CCBS recall offered to the terminal which
activated the CCBS supplementary service.
If the subscription option is not offered, one of the two values shall be chosen by the service provider.

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6.2 Normal procedures
6.2.1 Activation, deactivation and registration
6.2.1.1 Activation
When the network encounters a busy destination B, it shall retain the call information for the CCBS
supplementary service for the period defined by the retention timer. During this time user A can activate
the CCBS supplementary service. The value of the retention timer shall be a minimum of 15 seconds.
Upon receipt of a request for the activation of the CCBS supplementary service the network shall check
that a compatible terminal exists at destination B (see annex A).
When it has been established that a compatible terminal exists at destination B, the network shall register
the CCBS request based on the retained call information and user A shall be informed that the activation
was successful. Multiple requests against destination B shall be queued.
When the activation of the CCBS supplementary service is accepted the CCBS service duration timer
shall be started. The value of this timer shall be a minimum of 15 minutes and a maximum of 45 minutes.
The network shall monitor for destination B becoming not busy.
User A can have a limited number of CCBS requests outstanding. This limit shall apply in general for all
users and its value shall be a network provider option with a maximum value of 5. The requests can be to
different destinations, or can be to the same destination B with different service requirements (e.g. bearer
service and teleservice requirements), or as a network option, the same service requirements.
Destination B can have a limited number of incoming CCBS requests outstanding. This limit shall apply in
general for all users and its value shall be a destination network option with a maximum value of 5.
As a further destination network option, the size of the destination B CCBS queue can be reduced for
individual users. The reduced size can have zero length.
NOTE 1: Reducing the queue length allows a network operator to balance the interaction
between the CCBS supplementary service and other supplementary services (e.g. the
call waiting supplementary service and the freephone supplementary service).
NOTE 2: As a consequence of the queue having zero length, the CCBS supplementary service
will be unavailable to users calling destination B.
Having activated the CCBS supplementary service, user A can originate calls and receive calls as normal.

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6.2.1.2 Deactivation
User A can send any of the following deactivation requests:
a) deactivate all outstanding CCBS requests; or
b) deactivate a specific CCBS request. This request shall contain enough information to correlate with
the initial activation.
Upon successful deactivation, the corresponding CCBS request shall be discarded.
User A shall be informed that the deactivation is successful. If a specific CCBS request is deactivated, the
network shall indicate which specific CCBS request has been deactivated.
If the value of the subscription option "recall mode" is "specific" then the user can deactivate only those
outstanding CCBS requests made from that terminal.
If the value of the subscription option "recall mode" is "global", then from any of user A's terminals, user A
can deactivate any outstanding CCBS request stored for that user.
6.2.1.3 Registration
Not applicable.
6.2.2 Erasure
Not applicable.
6.2.3 Invocation and operation
When destination B becomes not busy (e.g. a call is terminated) or destination B is not busy when either
of the following occur:
- a CCBS request is received; or
- a CCBS request becomes not suspended,
then the destination B CCBS queue shall be processed, provided that an entry in the destination B CCBS
queue is not currently being processed. Entries shall not be processed in parallel.
The first request which is not suspended shall be selected and the network shall reserve on destination
B's interface the resources (e.g. a B-channel) which are necessary to complete the CCBS call. Destination
B can use the reserved access resources or other free resources, in order to originate a call. An incoming
call shall not use these reserved resources.
A check for a compatible terminal which is not busy at destination B shall be performed (see annex A). If
such a terminal does not exist, further requests which are not suspended shall be examined. When a
terminal is found, the network shall start the destination B idle guard timer. The value of this timer shall be
a maximum of 15 seconds.
NOTE: This timer enables destination B to initiate a call before any CCBS request is
processed.
When the destination B idle guard timer expires, then provided that interface resources are still available
at destination B, and a compatible terminal at destination B is still not busy, user A shall be informed.

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If user A is neither busy nor CCBS busy, user A shall be recalled with an indication that it is a CCBS recall
and with an indication of which CCBS request it applies to, and the CCBS recall timer shall be started. The
value of this timer shall be a minimum of 10 seconds and a maximum of 20 seconds.
If user A accepts the recall before the CCBS recall timer expires, then the network shall initiate the CCBS
call to destination B. When the network receives an indication that the destination B is being informed of
the CCBS call, the corresponding CCBS request shall be considered as completed.
Whilst the idle guard timer is running, and also whilst awaiting the CCBS call to destination B, a new
incoming call shall not be offered to destination B if it has service requirements and destination selection
information identical to the (not suspended) request which is currently being processed in the
destination B CCBS queue.
For such incoming calls, the called user shall be considered as being busy and the calling user shall be
informed as for basic call procedures.
The CCBS requests in the destination B CCBS queue shall be processed in the order they are received,
although the actual mechanism for processing the queue is outside the scope of this standard. During the
processing of the destination B CCBS queue, CCBS requests which are currently suspended shall be
ignored.
If, for any reason, no CCBS call results from the processing of a CCBS request, then provided that access
resources are still available at destination B, the next request in the destination B CCBS queue shall be
selected for processing. This procedure shall be repeated until the processing of the destination B CCBS
queue is complete.
If, for any reason, no CCBS call results from the processing of a CCBS request and the access resources
are no longer available at destination B, then the resources reserved for the CCBS supplementary service
shall be released and the network shall monitor for destination B becoming not busy.
If all of the destination B CCBS queue has been processed and no CCBS call results, then processing is
complete and the resources reserved for the CCBS supplementary service shall be released. If requests
which are not suspended exist in the destination B CCBS queue, then:
- if destination B is busy, the network shall monitor for destination B becoming not busy; or,
- if destination B is not busy, then the destination B CCBS queue shall be processed when another
call is terminated, or a CCBS request is received, or a CCBS request becomes not suspended.
6.2.4 Interrogation
User A can request the status of the CCBS supplementary service. In response to the request the
following information shall be provided:
a) in response to a general request user A shall be given a list of the addresses against which CCBS
requests are outstanding;
b) in response to a specific request concerning one particular address, user A shall be informed
whether or not user A has a CCBS request outstanding against that address.
NOTE: In both cases, the network provides information relating to CCBS requests and it is a
matter for terminal implementation whether or not the user is given information about
CCBS requests which are not compatible with the terminal.

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6.3 Exceptional procedures
6.3.1 Activation, deactivation and registration
6.3.1.1 Activation
The activation of the CCBS supplementary service shall be rejected if the CCBS supplementary service is
not provided to the user.
The activation of the CCBS supplementary service shall be rejected if there is no compatible terminal at
destination B.
If the network cannot accept user A's request to activate the CCBS supplementary service, the network
shall inform user A and give one of the following reasons:
a) short term denial: the network temporarily cannot accept user A's request to activate the CCBS
supplementary service. A later attempt to acti
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