SIST-TS ETSI/TS 101 818-1 V1.1.1:2005

• Abstract:

  The Trunk Hunting supplementary service enables calls to an ISDN number assigned to the private ISDN (hunt group number) to be offered to a free access within that hunt group of accesses.

• Status: Published
• Publication Date: 31-Dec-2004
• ICS: 33.080 - Integrated Services Digital Network (ISDN)
• Technical Committee: SPN - Services and Protocols for Networks
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-Jan-2005
• Due Date: 01-Jan-2005
• Completion Date: 01-Jan-2005
• Ref Project: ETSI TS 101 818-1 V1.1.1 (2000-07) - Integrated Services Digital Network (ISDN); Digital Subscriber Signalling System No. one (DSS1); Trunk Hunting (TH) supplementary service; Part 1: Protocol specification

SIST-TS ETSI/TS 101 818-1 V1.1.1:2005 is the Slovenian adoption of ETSI TS 101 818-1, a Technical Specification for the Integrated Services Digital Network (ISDN) Digital Subscriber Signalling System No. one (DSS1) Trunk Hunting (TH) supplementary service. It specifies the stage 3 signalling procedures and switching functions for offering calls to a hunt group number to a free access within the hunt group, and for temporary hunt group withdrawal and cancellation at the T reference point or coincident S and T reference point. It is written for ISDN network operators, equipment implementers, and test teams that need interoperable call handling and control behavior.

What does SIST-TS ETSI/TS 101 818-1 V1.1.1:2005 specify?

SIST-TS ETSI/TS 101 818-1 V1.1.1:2005 specifies the DSS1 protocol for the TH supplementary service on a pan-European ISDN, including the protocol requirements when the service is provided through an intermediate private ISDN. It focuses on the user-network signalling and the network state behavior needed to support hunt group call presentation and temporary withdrawal control.

The document covers the service at the T reference point and at the coincident S and T reference point. It also applies to all circuit-switched telecommunication services, while the selection of a free channel within an access remains a basic call matter handled by the network provider.

The main body is organized into clauses on scope, references, definitions, service description, operational requirements, coding requirements, state definitions, signalling procedures, interworking, interactions, timers, and SDL diagrams. Annex A is informative and gives examples of signalling flows.

Annex	What it covers
Annex A	Examples of signalling flows for withdrawal and cancellation of withdrawal

What are the key requirements of SIST-TS ETSI/TS 101 818-1 V1.1.1:2005?

The standard sets out a few practical requirements that matter directly to implementation and testing.

• Clause 4 defines how TH is provisioned and used. The service is provided after prior arrangement with the network provider and withdrawn at the network provider’s or subscriber’s request. In practice, operators need a clear provisioning process and a withdrawal process before the service can be offered.
• Clause 4 also defines hunt group structure and selection behavior. A hunt group can include basic accesses, primary rate accesses, or both, and an access may belong to more than one hunt group, up to a network-defined maximum of 15. The access-selection method can be sequential, cyclic, or uniform hunting. This matters because equipment must support the operator’s chosen hunt-group behavior.
• Clause 4 and Clause 9 define how incoming calls are handled. The TH service is invoked automatically on calls to the hunt group number or any DDI number associated with it, and the network selects a free access according to the subscribed selection method. If no free access is available, call establishment stops and the calling user is informed by basic call procedures.
• Clause 5 defines subscription options for the whole hunt group. If hunt group withdrawal is supported, it must be available to all accesses in that hunt group. If the selection method is not subscribed as an option, the network determines the selection method. This affects how the service is presented and what the user can control.
• Clause 6 defines the Facility information element coding for the service. The operations and errors are encoded with ASN.1 and carried as invoke, return result, return error, or reject components in a Facility information element. Implementers need this for interoperability at the signalling level.
• Clause 9 defines temporary hunt group withdrawal and cancellation. The served user sends WithdrawTHG or CancelWithdrawTHG invoke components and starts timer T-WITHDRAWAL or T-CANCELLATION. The network responds with a return result on success or a return error on failure. The procedure is stateful, so both ends must track the current TH state.
• Clause 9 also defines how the huntGroupNr parameter is used. When an access belongs to more than one hunt group, the user must identify the affected hunt group or request allNumbers. That matters in multi-hunt-group deployments, where the wrong group identifier would lead to an error.
• Clause 12 sets both timers, T-WITHDRAWAL and T-CANCELLATION, to 4 seconds. In practice, this bounds how long the user waits for a network response before treating the request as failed.

What terms does SIST-TS ETSI/TS 101 818-1 V1.1.1:2005 define?

• Access - A general term for a basic access or a primary rate access.
• Hunt group - The set of accesses over which TH applies for the assigned ISDN number.
• Hunt group number - The ISDN number to which TH and related services are allocated.
• Free access - An access where channels are not busy and one or more information channels are available.
• Hunt group withdrawal - A request to temporarily prevent an access from receiving calls to the hunt group, without affecting existing calls.
• Cyclic hunting - A method where the next free access search starts after the last one used and continues in fixed order.
• Sequential hunting - A method where the search always starts at the same access and then follows a fixed order.
• Served user - The private ISDN to which the TH service is provided.

Who uses SIST-TS ETSI/TS 101 818-1 V1.1.1:2005?

SIST-TS ETSI/TS 101 818-1 V1.1.1:2005 is used by ISDN network operators, switch and signalling equipment vendors, and engineers who implement supplementary services on private ISDN connections. It is also used by conformance and interoperability testers who need to verify the withdrawal, cancellation, and call-offering procedures defined for TH.

Service providers use it to configure hunt groups, subscription options, and user control of temporary withdrawal. Designers and testers use it to align message coding, state handling, and error handling across network and user equipment.

What changed in SIST-TS ETSI/TS 101 818-1 V1.1.1:2005 from the previous edition?

This Slovenian standard is identical to TS 101 818-1 Version 1.1.1. The document history identifies the version as V1.1.1, July 2000, and the standard presents that version as the adopted text.

Which standards are used with SIST-TS ETSI/TS 101 818-1 V1.1.1:2005?

The document cites these referenced standards and recommendations as part of its technical framework:

Reference	What it contributes
ETSI EN 300 195-1	Supplementary service interactions
ETSI EN 300 196-1	Generic functional protocol for supplementary services, including Facility information element handling
ETSI EN 300 403-1	DSS1 signalling network layer for circuit-mode basic call control
ITU-T Recommendation I.112	ISDN vocabulary and basic access / primary rate access definitions
ITU-T Recommendation I.210	Principles of telecommunication services supported by ISDN
CCITT Recommendation I.130	Service characterization method and stage structure
ITU-T Recommendation I.221	Common service characteristics, including channels busy
CCITT Recommendation Z.100	Specification and Description Language (SDL)
ITU-T Recommendation E.164	International public telecommunications numbering plan
ITU-T Recommendation X.680	ASN.1 basic notation
ITU-T Recommendation X.880	Remote operations concepts, model and notation
CCITT Recommendation I.411	ISDN user-network interface reference configurations
ETSI EN 301 484	Testing method for conformance to the TH service specification

The foreword also places this part in a six-part set: Part 2 covers the PICS proforma, Part 3 the user TSS&TP, Part 4 the user ATS and partial PIXIT proforma, Part 5 the network TSS&TP, and Part 6 the network ATS and partial PIXIT proforma.

What does the SIST-TS ETSI/TS 101 818-1 V1.1.1:2005 document contain?

SIST-TS ETSI/TS 101 818-1 V1.1.1:2005 contains the service description, operational rules, coding requirements, state definitions, signalling procedures, timer values, and SDL diagrams needed to implement TH. Clause 6 gives the ASN.1 operation and error definitions for WithdrawTHG and CancelWithdrawTHG, together with the Facility information element treatment.

Tables in the document collect the network options, subscription options, state definitions, and operation/error definitions. Clause 13 provides SDL diagrams for user and network control behavior, and Annex A gives example signalling flows for withdrawal and cancellation. These parts are especially useful for implementation, debugging, and conformance testing.

SLOVENSKI STANDARD
01-januar-2005
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Integrated Services Digital Network (ISDN); Digital Subscriber Signalling System No. one
(DSS1); Trunk Hunting (TH) supplementary service; Part 1: Protocol specification
Ta slovenski standard je istoveten z: TS 101 818-1 Version 1.1.1
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.

Technical Specification
Integrated Services Digital Network (ISDN);
Digital Subscriber Signalling System No. one (DSS1);
Trunk Hunting (TH) supplementary service;
Part 1: Protocol specification

2 ETSI TS 101 818-1 V1.1.1 (2000-07)
Reference
DTS/SPAN-05172-1
Keywords
ISDN, DSS1, supplementary service, TH,
protocol
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ETSI
3 ETSI TS 101 818-1 V1.1.1 (2000-07)
Contents
Intellectual Property Rights.4
Foreword .4
1 Scope.5
2 References.5
3 Definitions and abbreviations .6
3.1 Definitions.6
3.2 Abbreviations .7
4 Description .7
5 Operational Requirements.7
5.1 Provision and Withdrawal .7
5.2 Requirements on the originating network side.8
5.3 Requirements on the destination network side .8
6 Coding requirements .8
6.1 Coding of the Facility information element components.8
7 State Definitions.10
8 Signalling Procedures at the coincident S and T reference point .10
9 Procedures for interworking with private ISDNs.10
9.1 Activation, deactivation and interrogation.10
9.1.1 Temporary Hunt Group withdrawal.11
9.1.1.1 Normal operation .11
9.1.1.2 Exceptional procedures .12
9.1.2 Cancellation of Temporary Hunt Group withdrawal.12
9.1.2.1 Normal operation .12
9.1.2.2 Exceptional procedures .13
9.1.3 Interrogation .14
9.2 Invocation and Operation .14
9.2.1 Normal operation.14
9.2.2 Exceptional procedures.14
10 Interactions with other networks.14
11 Interaction with other supplementary services.14
12 Parameter values (timers).14
13 Dynamic description (SDL diagrams).15
Annex A (informative): Examples of Signalling flows.22
History.23
ETSI
4 ETSI TS 101 818-1 V1.1.1 (2000-07)
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 ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (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 ETSI 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 Technical Specification (TS) has been produced by ETSI Technical Committee Services and Protocols for
Advanced Networks (SPAN).
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) Trunk Hunting (TH) supplementary
service, 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: "TSS&TP specification for the network";
Part 6: "ATS and partial PIXIT proforma specification for the network".
In accordance with CCITT Recommendation I.130 [6], 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 Trunk Hunting supplementary service. The stage 2 aspects of the Trunk Hunting supplementary service have
not been specified.
ETSI
5 ETSI TS 101 818-1 V1.1.1 (2000-07)
1 Scope
The present document specifies the stage three of the Trunk Hunting (TH) 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 CCITT Recommendation I.411 [12] ) by means of
the Digital Subscriber System No. one (DSS1). Stage three identifies the protocol procedures and switching functions
needed to support a telecommunications service (see CCITT Recommendation I.130 [6]).
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 TH supplementary service enables calls to a single ISDN number to be offered to a free access in a group of
accesses to which a private ISDN is connected (T reference point).
The principles for the selection of a free channel within an access are a network provider matter as part of the basic call
procedures and so are outside the scope of the present document.
The TH service is applicable to all circuit-switched telecommunication services.
Further parts of EN 301 484 [13] specify the method of testing required to identify conformance to the present
document.
2 References
The following documents contain provisions which, through reference in this text, constitute provisions of the present
document.
• References are either specific (identified by date of publication, edition number, version number, etc.) or
non-specific.
• For a specific reference, subsequent revisions do not apply.
• For a non-specific reference, 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] ETSI EN 300 195-1: "Integrated Services Digital Network (ISDN); Supplementary service
Interactions; Digital Subscriber Signalling System No. one (DSS1) protocol; Part 1: Protocol
Specification".
[2] ETSI 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".
[3] ETSI 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]".
[4] ITU-T Recommendation I.112: "Vocabulary of terms for ISDNs".
[5] ITU-T Recommendation I.210: "Principles of telecommunication services supported by an ISDN
and the means to describe them".
[6] CCITT Recommendation I.130: "Method for the characterization of telecommunication services
supported by an ISDN and network capabilities of an ISDN".
[7] ITU-T Recommendation I.221 (1993): "Common specific characteristics of services".
ETSI
6 ETSI TS 101 818-1 V1.1.1 (2000-07)
[8] CCITT Recommendation Z.100: "Specification and Description Language (SDL)".
[9] ITU-T Recommendation E.164: "The International public telecommunications Numbering plan".
[10] ITU-T Recommendation X.680: "Information technology – Abstract Syntax Notation One
(ASN.1): Specification of basic notation".
[11] ITU-T Recommendation X.880: "Information technology – remote operations: concepts, model
and notation".
[12] CCITT Recommendation I.411: "ISDN user-network interfaces - Reference configurations".
[13] ETSI EN 301 484: "Integrated Services Digital Network (ISDN); Line Hunting (LH)
supplementary service; Digital Subscriber Signalling System No. one (DSS1)".
3 Definitions and abbreviations
3.1 Definitions
For the purposes of the present document, the following terms and definitions apply:
Access: General term, used in the present document, denoting basic accesses and/or primary rate accesses.
Basic access: See ITU-T Recommendation I.112 [4], subclause 2.4, definition 425.
Basic call procedures: Procedures by which a call (as an instance of a basic telecommunications service) is established
and terminated.
Channels busy: See ITU-T Recommendation I.221 [7], subclause 2.1.3.
Cyclic hunting: Selection of a free access always starts at the next access after the one used last, and follows a fixed
order. When the last access in the group is reached, the search continues from the beginning of the group until all
accesses in the group have been searched.
Free access: Access for which the channels busy condition does not exist (i.e., one or more information channels are
available).
Hunt group: Number of accesses over which the TH supplementary service applies for the assigned ISDN number.
Hunt group number: The ISDN number to which the TH supplementary service is allocated and to which ISDN basic
services and supplementary services relating to the hunt group are allocated.
Hunt group withdrawal: Request by the private ISDN in order to temporarily prevent an access from receiving calls to
the hunt group (existing calls are not affected).
Integrated Services Digital Network (ISDN): See ITU-T Recommendation I.112 [4], subclause 2.3, definition 308.
ISDN number: Number conforming to the numbering plan and structure specified in
ITU-T Recommendation E.164 [9].
Primary rate access: See ITU-T Recommendation I.112 [4], subclause 2.4, definition 426.
Sequential hunting: Selection of a free access always starts with the same access and then follows a fixed order until all
accesses in the hunt group have been searched or a free access is found.
Served user: User (i.e., a private ISDN) to whom the TH service is provided.
Service; telecommunications service: See ITU-T Recommendation I.112 [4], subclause 2.2, definition 201.
Supplementary service: See ITU-T Recommendation I.210 [5], subclause 2.4.
ETSI
7 ETSI TS 101 818-1 V1.1.1 (2000-07)
Uniform Hunting:
NOTE: Uniform hunting is not explicitly identified but not necessarily excluded for future enhancement.
3.2 Abbreviations
For the purpose of the present document, the following abbreviations apply:
HG Hunt Group
ISDN Integrated Services Digital Network
TH Trunk Hunting
4 Description
The TH supplementary service is intended for use on accesses to which a private ISDN is connected to the public ISDN
at the T reference point.
The TH supplementary service enables calls to an ISDN number assigned to the private ISDN (i.e. the hunt group
number and any DDI number associated with the hunt group number) to be offered to a free access in a hunt group. The
hunt group can comprise basic accesses, primary rate accesses, or a mixture of these types of accesses.
The TH supplementary service applies to accesses within a hunt group that are connected to the same exchange. As a
network operator option the TH supplementary service can be used to create a multi-nodal service that allows Trunk
Hunting across accesses on multiple exchanges. The specification of the multi-nodal service is outside the scope of the
present document.
As a network option an access can be member of more than one hunt group. The maximum number of hunt groups of
which an access can be a member, shall be a network option with an upper limit of 15.
The method of selecting the access shall be either sequential, uniform or cyclic hunting.
As a service provider option, the TH supplementary service can be offered with the possibility for hunt group
withdrawal. If the option of "hunt group withdrawal" is supported by the service provider, the served user can request
that an access can be temporarily prevented from receiving calls to the hunt group.
Services can be subscribed to on the hunt group identified by the hunt group number.
5 Operational Requirements
5.1 Provision and Withdrawal
The TH supplementary service shall be provided after prior arrangement with the network provider.
The TH supplementary service shall be withdrawn at the network provider or subscriber's request.
The network option having an impact on the protocol is described in Table 1.
Table 1: Network options
Network option Values
Max number of HGs for which one access may be a member 1 to 15
As a network option, the TH supplementary service can be offered with subscription options which are provided on a
hunt group basis. The subscription options are summarized in Table 2.
If the network supports the option "hunt group withdrawal" then the subscription option for "hunt group withdrawal"
shall be available to all accesses of the hunt group.
ETSI
8 ETSI TS 101 818-1 V1.1.1 (2000-07)
Table 2: Subscription option applying for the whole hunt group
Subscription Option Values
Selection Method - sequential hunting
- cyclic hunting
- uniform hunting (see Note)
Hunt group withdrawal - available
- not available
NOTE: Uniform hunting is not explicitly identified as an option but is not necessarily excluded for
future enhancement.
If the TH supplementary service is provided without the subscription option "selection method", the network shall
determine the selection method.
If the network does not offer the subscription option "hunt group withdrawal", then the accesses cannot be withdrawn
from the hunt group by the user.
5.2 Requirements on the originating network side
The procedures at the T reference point in EN 300 403-1 [3], subclause 5.1 and the procedures of Clause 9 in the
present document shall apply.
5.3 Requirements o
...