ISO/IEC 15991:1998

Information technology — Telecommunications and information exchange between systems — Private Integrated Services Network — Specification, functional model and information flows — Call priority interruption and call priority interruption protection supplementary services

Technologies de l'information — Télécommunications et échange d'information entre systèmes — Réseau privé à intégration de services — Spécification, modèle fonctionnel et flux d'informations — Services supplémentaires d'interruption de priorité d'appel et de protection d'interruption de priorité d'appel

General Information

• Status: Withdrawn
• Publication Date: 19-Dec-1998
• Withdrawal Date: 19-Dec-1998
• ICS: 33.040.35 - Telephone networks
• Technical Committee: ISO/IEC JTC 1/SC 6 - Telecommunications and information exchange between systems
• Drafting Committee: ISO/IEC JTC 1/SC 6 - Telecommunications and information exchange between systems
• Current Stage: 9599 - Withdrawal of International Standard
• Completion Date: 21-Mar-2003

Relations

• Revised: ISO/IEC 15991:2003 - Information technology — Telecommunications and information exchange between systems — Private Integrated Services Network — Specification, functional model and information flows — Call Priority Interruption and Call Priority Interruption Protection supplementary services
• Effective Date: 15-Apr-2008

Standards Content (Sample)

INTERNATIONAL ISO/IEC
STANDARD 15991
First edition
1998-12-15
Information technology —
Telecommunications and information
exchange between systems — Private
Integrated Services Network —
Specification, functional model and
information flows — Call priority
interruption and call priority interruption
protection supplementary services
Technologies de l'information — Télécommunications et échange
d'information entre systèmes — Réseau privé à intégration de services —
Spécification, modèle fonctionnel et flux d'informations — Services
supplémentaires d'interruption de priorité d'appel et de protection
d'interruption de priorité d'appel
Reference number
B C
ISO/IEC 15991:1998(E)

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ISO/IEC 15991:1998(E)
Contents
Foreword vi
Introduction vii
1 Scope 1
2 Conformance 1
3 Normative references 1
4 Definitions 2
4.1 External definitions 2
4.2 Additional network feature 3
4.3 Call, Basic call 3
4.4 Call Priority Interruption Capability Level (CPICL) 3
4.5 Call Priority Interruption Protection Level (CPIPL) 3
4.6 Established call 3
4.7 Impending priority interruption state 3
4.8 Impending priority interruption warning notification 3
4.9 Non-priority call 3
4.10 Priority call 3
4.11 Protected call 3
4.12 Served user 3
4.13 Time to priority interruption 3
4.14 Unprotected call 3
5 List of acronyms 3
6 SS-CPI stage 1 specification 4
6.1 Description 4
6.1.1 General description 4
6.1.2 Qualifications on applicability to telecommunication services 4
6.2 Procedure 4
6.2.1 Provision/withdrawal 4
6.2.2 Normal procedures 4
6.2.3 Exceptional procedures 5
6.3 Interaction with other supplementary services and ANFs 6
6.3.1 Calling Name Identification Presentation (SS-CNIP) 6
6.3.2 Connected Name Identification Presentation (SS-CONP) 6
6.3.3 Completion of Call to Busy Subscriber (SS-CCBS) 6
6.3.4 Completion of Call on No Reply (SS-CCNR) 6
6.3.5 Call Transfer (SS-CT) 6
6.3.6 Call Forwarding Unconditional (SS-CFU) 6
©  ISO/IEC 1998
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or
utilized in any form or by any means, electronic or mechanical, including photocopying and micro-
film, without permission in writing from the publisher.
ISO/IEC Copyright Office • Case postale 56 • CH-1211 Genève 20 • Switzerland
Printed in Switzerland
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ISO/IEC ISO/IEC 15991:1998(E)
6.3.7 Call Forwarding Busy (SS-CFB) 6
6.3.8 Call Forwarding No Reply (SS-CFNR) 6
6.3.9 Call Deflection (SS-CD) 6
6.3.10 Path Replacement (ANF-PR) 6
6.3.11 Call Offer (SS-CO) 6
6.3.12 Call Intrusion (SS-CI) 6
6.3.13 Do not Disturb (SS-DND) 6
6.3.14 Do not Disturb Override (SS-DNDO) 6
6.3.15 Advice of Charge (SS-AOC) 6
6.3.16 Recall (SS-RE) 6
6.3.17 Call Interception (ANF-CINT) 6
6.3.18 Transit Counter (ANF-TC) 7
6.3.19 Cordless Terminal Location Registration (SS-CTLR) 7
6.3.20 Cordless Terminal Incoming Call (ANF-CTMI) 7
6.3.21 Cordless Terminal Outgoing Call (ANF-CTMO) 7
6.3.22 Authentication of a CTM User (SS-CTAU) 7
6.3.23 Authentication of the PISN (SS-CTAN) 7
6.3.24 Message Waiting Indication (SS-MWI) 7
6.3.25 Common Information (ANF-CMN) 7
6.3.26 Call Priority Interruption Protection (SS-CPIP) 7
6.4 Interworking considerations 7
6.5 Overall SDL 7
7 SS-CPIP stage 1 specification 11
7.1 Description 11
7.1.1 General description 11
7.1.2 Qualifications on applicability to telecommunication services 11
7.2 Procedure 11
7.2.1 Provision/withdrawal 11
7.2.2 Normal procedures 11
7.2.3 Exceptional procedures 12
7.3 Interaction with other supplementary services and ANFs 12
7.3.1 Calling Name Identification Presentation (SS-CNIP) 12
7.3.2 Connected Name Identification Presentation (SS-CONP) 12
7.3.3 Completion of Call to Busy Subscriber (SS-CCBS) 12
7.3.4 Completion of Call on No Reply (SS-CCNR) 12
7.3.5 Call Transfer (SS-CT) 12
7.3.6 Call Forwarding Unconditional (SS-CFU) 12
7.3.7 Call Forwarding Busy (SS-CFB) 12
7.3.8 Call Forwarding No Reply (SS-CFNR) 12
7.3.9 Call Deflection (SS-CD) 12
7.3.10 Path Replacement (ANF-PR) 12
7.3.11 Call Offer (SS-CO) 12
7.3.12 Call Intrusion (SS-CI) 12
7.3.13 Do not Disturb (SS-DND) 12
7.3.14 Do not Disturb Override (SS-DNDO) 12
7.3.15 Advice of Charge (SS-AOC) 13
7.3.16 Recall (SS-RE) 13
7.3.17 Call Interception (ANF-CINT) 13
7.3.18 Transit Counter (ANF-TC) 13
7.3.19 Cordless Terminal Location Registration (SS-CTLR) 13
7.3.20 Cordless Terminal Incoming Call (ANF-CTMI) 13
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ISO/IEC 15991:1998(E) ISO/IEC
7.3.21 Cordless Terminal Outgoing Call (ANF-CTMO) 13
7.3.22 Authentication of a CTM User (SS-CTAU) 13
7.3.23 Authentication of the PISN (SS-CTAN) 13
7.3.24 Message Waiting Indication (SS-MWI) 13
7.3.25 Common Information (ANF-CMN) 13
7.3.26 Call Priority Interruption (SS-CPI) 13
7.4 Interworking considerations 13
7.5 Overall SDL 13
8 SS-CPI stage 2 specification 15
8.1 Functional model 15
8.1.1 Functional model description 15
8.1.2 Description of Functional Entities 15
8.1.3 Relationship of functional model to basic call functional model 16
8.2 Information flows 16
8.2.1 Definition of information flows 16
8.2.2 Relationship of information flows to basic call information flows 18
8.2.3 Information flow sequences 18
8.3 Functional Entity actions 21
8.3.1 Actions of FE1 21
8.3.2 Actions of FE2 21
8.3.3 Actions of FE3 21
8.3.4 Actions of FE4 22
8.3.5 Actions of FE5 22
8.4 Functional entity behaviour 22
8.4.1 Behaviour of FE1 22
8.4.2 Behaviour of FE2 24
8.4.3 Behaviour of FE3 25
8.4.4 Behaviour of FE4 27
8.4.5 Behaviour of FE5 28
8.5 Allocation of Functional Entities to physical equipment 29
8.6 Interworking considerations 29
9 SS-CPIP stage 2 specification 29
9.1 Functional model 29
9.1.1 Functional model description 29
9.1.2 Description of Functional Entities 30
9.1.3 Relationship of functional model to basic call functional model 31
9.2 Information flows 31
9.2.1 Definition of information flows 31
9.2.2 Relationship of information flows to basic call information flows 32
9.2.3 Information flow sequences 32
9.3 Functional Entity actions 35
9.3.1 Actions of FE1 35
9.3.2 Actions of FE2 35
9.3.3 Actions of FE3 35
9.3.4 Actions of FE4 36
9.3.5 Actions of FE5 36
9.4 Functional entity behaviour 36
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ISO/IEC ISO/IEC 15991:1998(E)
9.4.1 Behaviour of FE1 37
9.4.2 Behaviour of FE2 38
9.4.3 Behaviour of FE3 39
9.4.4 Behaviour of FE4 40
9.4.5 Behaviour of FE5 41
9.5 Allocation of Functional Entities to physical equipment 42
9.6 Interworking considerations 42
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ISO/IEC 15991:1998(E) ISO/IEC
Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical Commission) form the
specialized system for worldwide standardization. National bodies that are members of ISO or IEC participate in the
development of International Standards through technical committees established by the respective organization to deal with
particular fields of technical activity. ISO and IEC technical committees collaborate in fields of mutual interest. Other
international organizations, governmental and non-governmental, in liaison with ISO and IEC, also take part in the work.
In the field of information technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1. Draft
International Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the national bodies casting a vote.
International Standard ISO/IEC 15991 was prepared by ECMA (as ECMA-263) and was adopted, under a special “fast-track
procedure”, by Joint Technical Committee ISO/IEC JTC 1, Information technology, in parallel with its approval by national
bodies of ISO and IEC.
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ISO/IEC ISO/IEC 15991:1998(E)
Introduction
This International Standard is one of a series of International Standards defining services and signalling procedures applicable
to Private Integrated Services Networks (PISNs). The series uses the ISDN concepts as developed by ITU-T and conforms to
the framework of International Standards for Open Systems Interconnection as defined by ISO/IEC.
This International Standard specifies the Call Priority Interruption (CPI) and Call Priority Interruption Protection (CPIP)
supplementary services.
This International Standard is based upon the practical experience of ECMA member companies and the results of their active
and continuous participation in the work of ISO/IEC JTC1, ITU-T, ETSI and other international and national standardization
bodies. It represents a pragmatic and widely based consensus.
There are currently no equivalent services specified by ITU-T or ETSI for public ISDN.
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©
INTERNATIONAL STANDARD  ISO/IEC ISO/IEC 15991:1998(E)
Information technology - Telecommunications and information exchange between
systems - Private Integrated Services Network - Specification, functional model and
information flows - Call priority interruption and call priority interruption
protection supplementary services
1 Scope
This International Standard specifies the Supplementary Services Call Priority Interruption (SS-CPI) and Call Priority
Interruption Protection (SS-CPIP), which are applicable to various basic services supported by Private Integrated Services
Networks (PISN). Basic services are specified in ISO/IEC 11574.
Note 1 - This edition of this International Standard does not apply to the circuit-mode Multiple Rate Bearer Service.
SS-CPI is a supplementary service that allows a call request for a priority call to proceed successfully in the case that there is
no user information channel available. This is accomplished by force releasing an established call of lower priority.
SS-CPIP is a supplementary service that allows for the protection of calls against interruption from other, priority, calls.
SS-CPI and SS-CPIP are described separately because SS-CPI is a service used by a calling user, and SS-CPIP is a service
used by either a calling user or a called user.
Supplementary service specifications are produced in three stages, according to the method described in CCITT Rec. I.130.
This International Standard contains the stage 1 and stage 2 specifications of SS-CPI. The stage 1 specification (clause 6)
specifies the general feature principles and capabilities. The stage 2 specification (clause 7) identifies the Functional Entities
involved in the supplementary service and the information flows between them.
2 Conformance
In order to conform to this International Standard, a stage 3 standard shall specify signalling protocols and equipment
behaviour that are capable of being used in a PISN which supports the supplementary service specified in this International
Standard. This means that, to claim conformance, a stage 3 standard is required to be adequate for the support of those aspects
of clause 6 (stage 1) and clause 7 (stage 2) which are relevant to the interface or equipment to which the stage 3 standard
applies.
3 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this International
Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to
agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent
editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International
Standards.
ISO/IEC 11574:1994, Information technology - Telecommunications and information exchange between systems -
Private Integrated Services Network - Circuit-mode 64 kbit/s bearer services - Service description,
functional capabilities and information flows.
ISO/IEC 11579-1:1994, Information technology - Telecommunications and information exchange between systems -
Private Integrated Services Network - Part 1: Reference configuration for PISN Exchanges
(PINX).
ISO/IEC 13863:1995, Information technology - Telecommunications and information exchange between systems -
Private Integrated Services Network - Specification, functional model and information flows -
Path replacement additional network feature.
ISO/IEC 13865:1995, Information technology - Telecommunications and information exchange between systems -
Private Integrated Services Network - Specification, functional model and information flows - Call
transfer supplementary service.
ISO/IEC 13866:1995, Information technology - Telecommunications and information exchange between systems -
Private Integrated Services Network - Specification, functional model and information flows - Call
completion supplementary services.
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ISO/IEC 15991:1998(E) ISO/IEC
ISO/IEC 13872:1995, Information technology - Telecommunications and information exchange between systems -
Private Integrated Services Network - Specification, functional model and information flows - Call
diversion supplementary services.
ISO/IEC 15053:1997, Information technology - Telecommunications and information exchange between systems -
Private Integrated Services Network - Specification, functional model and information flows - Call
interception additional network feature.
1)
ISO/IEC 15430:— , Information technology - Telecommunications and information exchange between systems - PISN -
Specifications, functional model and information flows - Wireless Terminal call handling
additional network features.
ITU-T Rec. I.112:1993, Vocabulary of terms for ISDNs.
CCITT Rec. I.130:1988, Method for the characterization of telecommunication services supported by an ISDN and network
capabilities of an ISDN.
ITU-T Rec. I.210:1993, Principles of telecommunication services supported by an ISDN and the means to describe them.
ITU-T Rec. Z.100:1993, Specification and description language.
4 Definitions
For the purposes of this International Standard, the following definitions apply.
4.1 External definitions
This International Standard uses the following terms defined in other documents:
− Basic service (ITU-T Rec. I.210)
− Private Integrated Services Network (PISN) (ISO/IEC 11579-1)
− Private Integrated Services Network Exchange (PINX) (ISO/IEC 11579-1)
− Service (ITU-T Rec. I.112)
− Signalling (ITU-T Rec. I.112)
− Supplementary Service (ITU-T Rec. I.210)
− User (ISO/IEC 11574)
This International Standard refers to the following basic call Functional Entities (FE) defined in ISO/IEC 11574:
− Call Control (CC)
− Call Control Agent (CCA)
This International Standard refers to the following basic call inter-FE relationships defined in ISO/IEC 11574:
− r1
− r2
− r3
This International Standard refers to the following basic call information flows defined in ISO/IEC 11574:
− DISCONNECT request/indication
− RELEASE request/indication
− SETUP request/indication
____________
1)  To be published.
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ISO/IEC ISO/IEC 15991:1998(E)
4.2 Additional network feature : A capability, over and above that of a basic service, provided by a PISN, but not directly to
a PISN user.
4.3 Call, Basic call : An instance of the use of a basic service.
4.4 Call Priority Interruption Capability Level (CPICL) : A parameter indicating the priority of a call.
4.5 Call Priority Interruption Protection Level (CPIPL) : A parameter indicating a level of protection of a call against
interruption from other calls.
4.6 Established call : The active call that is selected for interruption.
4.7 Impending priority interruption state : The condition of an established call and a priority call after provision of an
Impending priority interruption warning notification and before the release of the established call.
4.8 Impending priority interruption warning notification : A notification provided before the release of the established call.
4.9 Non-priority call : A call that has not been assigned a CPICL value.
4.10 Priority call : A call that has a CPICL value greater than zero.
Note 2 - A priority call may also be a protected call.
4.11 Protected call : A call that has a CPIPL value greater than zero.
Note 3 - A protected call may also be a priority call.
4.12 Served user : The user who requests SS-CPI and/or SS-CPIP.
4.13 Time to priority interruption : The duration of the impending priority interruption state.
4.14 Unprotected call : A call which has not been assigned a CPIPL value or has a CPIPL value equal to zero.
5 List of acronyms
ANF Additional Network Feature
AOC Advice Of Charge
CC Call Control (Functional Entity)
CCA Call Control Agent (Functional Entity)
CCBS Call Completion to Busy Subscriber
CCNR Call Completion on No Reply
CD Call Deflection
CFB Call Forwarding Busy
CFNR Call Forwarding No Reply
CFU Call Forwarding Unconditional
CI Call Intrusion
CICL Call Intrusion Capability Level
CINT Call INTerception
CLIP Calling Line Identification Presentation
CLIR Calling/Connected Line Identification Restriction
CMN CoMmoN Information
CNIP Calling Name Identification Presentation
CNIR Calling/Connected Name Identification Restriction
CO Call Offer
COLP Connected Line Identification Presentation
CONP Connected Name Identification Presentation
CPI Call Priority Interruption
CPICL Call Priority Interruption Capability Level
CPIP Call Priority Interruption Protection
CPIPL Call Priority Interruption Protection Level
CT Call Transfer
CTAU Cordless Terminal AUthentication
CTLR Cordless Terminal Location Registration
CTMI Cordless Terminal Mobility Incoming call
CTMO Cordless Terminal Mobility Outgoing call
DND Do Not Disturb
DNDO Do Not Disturb Override
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ISO/IEC 15991:1998(E) ISO/IEC
FE Functional Entity
ISDN Integrated Services Digital Network
MWI Message Waiting Indication
PINX Private Integrated Services Network Exchange
PISN Private Integrated Services Network
PR Path Replacement
RE REcall
SDL Specification and Description Language
SS Supplementary Service
TC Transit Counter
TE Terminal Equipment
6 SS-CPI stage 1 specification
6.1 Description
6.1.1 General description
Call Priority Interruption (SS-CPI) is a supplementary service that allows a call request for a priority call to proceed
successfully in the case that there is no user information channel available.
A priority interruption only occurs if the served user has a higher Call Priority Interruption Capability Level (CPICL) than the
Call Priority Interruption Protection Level (CPIPL) of at least one of the active calls on the selected route.
6.1.2 Qualifications on applicability to telecommunication services
SS-CPI is applicable to all basic services defined in ISO/IEC 11574.
6.2 Procedure
6.2.1 Provision/withdrawal
SS-CPI shall be provided or withdrawn after pre-arrangement with the service provider.
SS-CPI shall be provided on a per PISN number basis for one or more basic services.
One or more Call Priority Interruption Capability Levels (CPICL) shall be allocated to the served user. The procedure by
which CPICL is allocated is outside the scope of this International Standard.
CPICL shall have a value in the range 1 (lowest priority) to 3 (highest priority). An implementation may offer one or more
CPICL values.
Note 4 - It is not precluded that CPICL values can be variable, e. g. a user may have the possibility to change the value with a user procedure. The details of
such capabilities are outside the scope of this International Standard.
At least one of the methods of invoking SS-CPI (see 6.2.2.2) shall be offered.
6.2.2 Normal procedures
6.2.2.1 Activation/deactivation/registration/interrogation
SS-CPI shall be activated upon provision and deactivated upon withdrawal.
Registration and interrogation shall not apply.
6.2.2.2 Invocation and operation
There are two different ways to invoke SS-CPI. A PISN may offer one or both of these ways.
These are:
i) Consultation: the served user, on being informed that a call has failed because of congestion en route to the destination,
shall be able, within a defined period (consultation timer), to request SS-CPI.
ii) Immediate invocation: the served user shall be able to request SS-CPI as part of the initial call set-up, or as an
implementation option, the network can invoke SS-CPI automatically on behalf of the user.
On invocation, CPICL, if provided, shall be assigned one of the offered values.
Note 5 - As an example, this assignment may be based on a class of service.
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ISO/IEC ISO/IEC 15991:1998(E)
6.2.2.2.1 Verification and selection of an established call
If the consultation method is provided to the served user, the following procedure shall apply. If a call fails due to congestion
en route to the destination and the PISN is not aware that call priority interruption is not allowed (e. g. because of insufficient
CPICL), the PISN shall notify the served user that the call has failed because of congestion and that priority interruption may
be possible. The served user may then request SS-CPI.
If the immediate invocation method is provided to the served user, the served user may request SS-CPI with the initial call set-
up.
For both invocation alternatives the following shall apply. Upon receiving a call priority interruption request, the PISN shall
check that at least one user information channel is available on the selected route.
If a user information channel is available on the selected route, the call shall proceed in accordance with basic call procedures.
If no user information channel is available on the selected route, and in order to determine that interruption is allowed, the
PISN shall check that the CPICL value of the received call request is greater than zero (priority call). It shall then check that
the Call Priority Interruption Protection Level (CPIPL) value of an active call on the selected route is lower than the CPICL
value of the served user. If the PISN does not have knowledge of the CPIPL value of an active call, this call shall be treated as
if the call has no protection (i.e. CPIPL value equal to zero).
Note 6 - CPIPL values are allocated when SS-CPIP is invoked. See 7.2.2.2.
The call that passes these checks shall be selected as the established call. If more than one call passes these checks, the PISN
shall select the active call with the lowest CPIPL value as the established call. If more than one call has the same lowest
CPIPL, the method used to select the established call from this group of calls shall be implementation dependent. If no active
call passes these checks the priority call request may be rejected or some other implementation dependent action may be taken.
Note 7 - One example of an implementation dependent action is to establish the call on another route, if such a route is available.
When the established call has been selected, the users in the established call may as an option be provided with an Impending
priority interruption warning notification and a short delay before the user connection is broken. If this notification is
provided, it shall be sent to the users in the established call and the impending priority interruption state shall be entered.
Note 8 - The Impending priority interruption warning notification can be accompanied by an in-band tone or announcement to all users in the established
call.
SS-CPI shall terminate when the call request reaches its destination or leaves the PISN.
6.2.2.2.2 Actions during impending priority interruption state
6.2.2.2.2.1 Impending priority interruption state ends
A time period, time to priority interruption (1-10 seconds as an implementation option), after the Impending priority
interruption warning notification has been provided, the users involved in the established call shall be notified of the forced
release. The impending priority interruption state shall be terminated, the established call shall be released and the priority call
request shall proceed in accordance with basic call procedures selecting the newly available user information channel.
6.2.2.2.2.2 Release of priority call request
If the priority call request is released by the served user during the impending priority interruption state, the users involved in
the established call shall be notified that the priority interruption request has been terminated and SS-CPI shall be terminated.
6.2.2.2.2.3 Release of established call
If the established call is released by a user during the impending priority interruption state, the priority call request shall
proceed in accordance with basic call procedures selecting the newly available user information channel.
6.2.2.2.2.4 User information channel becomes available
If another user information channel becomes available for this call during the impending priority interruption state, the users
involved in the established call shall be notified that the impending priority interruption state has been terminated. The priority
call request shall proceed in accordance with basic call procedures selecting the newly available user information channel.
6.2.3 Exceptional procedures
6.2.3.1 Activation/deactivation/registration/interrogation
Not applicable.
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ISO/IEC 15991:1998(E) ISO/IEC
6.2.3.2 Invocation and operation
If the interruption request cannot be accepted the request shall be ignored.
6.3 Interaction with other supplementary services and ANFs
Interactions with other supplementary services and ANFs for which PISN standards were available at the time of publication
of this International Standard are specified below.
6.3.1 Calling Name Identification Presentation (SS-CNIP)
No Interaction.
6.3.2 Connected Name Identification Presentation (SS-CONP)
No interaction.
6.3.3 Completion of Call to Busy Subscriber (SS-CCBS)
SS-CPI may apply to a call resulting from the use of SS-CCBS.
6.3.4 Completion of Call on No Reply (SS-CCNR)
SS-CPI may apply to a call resulting from the use of SS-CCNR.
6.3.5 Call Transfer (SS-CT)
SS-CPI shall not be invoked to interrupt other calls during establishment of the new connection.
6.3.6 Call Forwarding Unconditional (SS-CFU)
SS-CPI may be invoked when establishing the diverted call.
6.3.7 Call Forwarding Busy (SS-CFB)
SS-CPI may be invoked when establishing the diverted call.
6.3.8 Call Forwarding No Reply (SS-CFNR)
SS-CPI may be invoked when establishing the diverted call.
6.3.9 Call Deflection (SS-CD)
SS-CPI may be invoked when establishing the diverted call.
6.3.10 Path Replacement (ANF-PR)
SS-CPI shall not be invoked to interrupt other calls during establishment of the new connection.
6.3.11 Call Offer (SS-CO)
No interaction.
6.3.12 Call Intrusion (SS-CI)
No interaction.
Note 9 - SS-CI may be used in conjunction with SS-CPI to provide for intrusion if a called user busy condition is determined.
6.3.13 Do not Disturb (SS-DND)
No interaction.
6.3.14 Do not Disturb Override (SS-DNDO)
No interaction.
6.3.15 Advice of Charge (SS-AOC)
No interaction.
6.3.16 Recall (SS-RE)
No interaction.
6.3.17 Call Interception (ANF-CINT)
A SS-CPI request shall have priority over any ANF-CINT request on a network congestion condition. There is no interaction
with ANF-CINT for other invocation conditions.
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ISO/IEC ISO/IEC 15991:1998(E)
6.3.18 Transit Counter (ANF-TC)
No interaction.
6.3.19 Cordless Terminal Location Registration (SS-CTLR)
No interaction.
6.3.20 Cordless Terminal Incoming Call (ANF-CTMI)
SS-CPI may be invoked when establishing a call to a CTM user.
6.3.21 Cordless Terminal Outgoing Call (ANF-CTMO)
No interaction.
6.3.22 Authentication of a CTM User (SS-CTAU)
No interaction.
6.3.23 Authentication of the PISN (SS-CTAN)
No interaction.
6.3.24 Message Waiting Indication (SS-MWI)
No interaction.
6.3.25 Common Information (ANF-CMN)
No interaction.
6.3.26 Call Priority Interruption Protection (SS-CPIP)
See 6.2.
6.4 Interworking considerations
When interworking with another network which supports an equivalent feature, it may be possible to cooperate with the other
network to provide SS-CPI.
6.5 Overall SDL
Figure 1 contains the dynamic description of SS-CPI using the Specification and Description Language (SDL) defined in ITU-
T Rec. Z.100 (1993). The SDL process represents the behaviour of the PISN in providing SS-CPI to a served user.
Input symbols from the left and output symbols to the left represent primitives from and to the served user.
Input symbols from the right represent inputs from the basic call process or inputs from an internal process.
Output symbols to the right represent primitives to the users in the established call, outputs to the basic call process or outputs
to an internal process.
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
ISO/IEC 15991:1998(E) ISO/IEC
Process SS_CPI 1(3)
CPI Idle
Call request Call request
From calling
with SS−CPI From calling user without
user
request SS−CPI req.
Network
Wait
congested?
No Yes
Call request
with SS−CPI 1
request
CPI Idle
Wait
Basic call Basic call
released; released
reason other due to
than congestion congestion
SS−CPI
CPI Idle
allowed?
Yes No
SS−CPI
CPI Idle
possible
Start
consultation
timer
Consultation
Figure 1 - SS-CPI, overall SDL - Part 1 of 3
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
ISO/IEC ISO/IEC 15991:1998(E)
Process SS_CPI 2(3)
Consultation
Consultation Basic
SS−CPI
timer call
request
expiry cleared
Stop Stop
consultation consultation
CPI Idle
timer timer
Ntwk. still
1 CPI Idle
congested?
No Yes
Call request
Interruption
with SS−CPI
allowed?
request
Yes No
Select
CPI Idle established CPI Idle
call
Warning No warning
Notify users Notify u
...