ETSI ETR 018 ed.4 (1995-11)

SLOVENSKI STANDARD
SIST-TP ETSI/ETR 018 E4:2005
01-april-2005
Digitalno omrežje z integriranimi storitvami (ISDN) - Aplikacija informacijskih

elementov: nosilna zmožnost (BC), združljivost zgornjih plasti (HCL) in združljivost

Integrated Services Digital Network (ISDN); Application of the Bearer Capability (BC),

High Layer Compatibility (HLC) and Low Layer Compatibility (LLC) information elements

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

Copyright Notification: No part may be reproduced except as authorized by written permission. The copyright and the

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.

Foreword .......................................................................................................................................................7

Introduction....................................................................................................................................................7

1 Scope ..................................................................................................................................................9

2 References..........................................................................................................................................9

3 Abbreviations.....................................................................................................................................10

4 General principles applicable to all services .....................................................................................11

5 Impact of interworking situations.......................................................................................................12

5.1 Incoming calls from non-ISDNs .........................................................................................12

5.2 BC and LLC application guidelines ....................................................................................12

6 Request and recognition of a basic telecommunication service in an ISDN environment ................13

6.1 Request and recognition of a circuit-mode bearer service ................................................13

speech information transfer...........................................................................13

category.........................................................................................................15

3,1 kHz audio information transfer ................................................................16

category.........................................................................................................17

6.2 Packet mode bearer service categories ............................................................................18

Case B)) ........................................................................................................18

6.2.1.1 Access through the B-channel.............................................18

6.2.1.2 Access through the D-channel ............................................19

6.3 Request and recognition of a teleservice...........................................................................20

6.3.1 Telephony 3,1 kHz teleservice ......................................................................20

6.3.2 Telefax G4 service (using circuit-mode bearer capability) ............................22

6.3.3 Syntax-based videotex teleservice ............................................................... 26

Case A) ............................................................................... 30

6.3.4 Telephony 7 kHz teleservice......................................................................... 34

6.3.5 Videotelephony teleservice........................................................................... 36

6.3.6 Facsimile group 2/3 service.......................................................................... 45

6.3.7 File Transfer & Access Management (FTAM) teleservice............................ 46

6.3.8 Eurofile transfer teleservice .......................................................................... 50

6.3.8.1 Request by a calling terminal.............................................. 50

7 Coding examples applicable to specific user applications................................................................ 54

7.1 Specific user applications of the circuit-mode 64 kbit/s unrestricted 8 kHz structured

bearer service.................................................................................................................... 54

7.1.1 Support of terminal adapters V.110/X.30 ..................................................... 54

7.1.1.1 Synchronous mode of operation ......................................... 54

7.1.1.2 Asynchronous mode of operation ....................................... 58

access unit (ITU-T Recommendation X.31, Case A)....................................62

8 kHz-structured bearer capability.................................................................66

7.2 Specific user applications of the circuit mode 64 kbit/s 8 kHz structured bearer service

category usable for 3,1 kHz audio information transfer .....................................................70

7.2.1 Voice band data via modem..........................................................................70

8 Interworking with non-European ISDNs supporting restricted 64 kbit/s transfer capability...............73

8.1 Request by a calling terminal connected to a network supporting 64 kbit/s unrestricted

digital information transfer .................................................................................................73

8.2 Compatibility at the called terminal equipment connected to a network supporting

64 kbit/s unrestricted digital information transfer ...............................................................73

64 kbit/s restricted digital information transfer ...................................................................74

8.4 Compatibility at the called terminal equipment connected to a non-European network

using restricted digital information transfer........................................................................74

9 Codings in the case where non-ISDNs are involved.........................................................................75

9.1 Calls from PSTN to ISDN ..................................................................................................75

9.2 Calls from PSPDN to ISDN................................................................................................75

9.3 Calls from CSPDN to ISDN ...............................................................................................75

Annex A: Bibliography ............................................................................................................................76

History..........................................................................................................................................................77

This ETSI Technical Report (ETR) has been produced by the Signalling Protocols and Switching (SPS)

Technical Committee of the European Telecommunications Standards Institute (ETSI).

ETRs are informative documents resulting from ETSI studies which are not appropriate for European

Telecommunication Standard (ETS) or Interim European Telecommunication Standard (I-ETS) status. An

ETR may be used to publish material which is either of an informative nature, relating to the use or the

application of ETSs or I-ETSs, or which is immature and not yet suitable for formal adoption as an ETS or

This fourth edition of ETR 018 replaces the third edition issued in January 1995.

- examples for the use of the File Transfer & Access Management (FTAM) teleservice have been

- examples for the use of the Eurofile transfer teleservice have been added (see subclause 6.3.8).

Further enhancements of this ETR will (most likely) become necessary. Candidates for inclusion in a

- an adjustment of the examples for the use of the FTAM teleservice following a possible amendment

- examples to support channel aggregation as an application of the 64 kbit/s unrestricted bearer

This ETR specifies the coding of the information elements Bearer Capability (BC), High Layer

Compatibility (HLC) and Low Layer Compatibility (LLC) to be used by terminals supporting the ISDN

telecommunication services so far specified within ETSI and operating in the demand mode. It is based on

ITU-T Recommendation Q.931 (1993) as modified by ETS 300 403-1, including its relevant annexes (B, I

For each service it is specified which field values the calling user is requested to send and which field

values the called user could expect to receive in a pure ISDN environment (clauses 6 and 7). Clause 8

specifies the codings to be used in the case of inter-working with non European ISDNs supporting

restricted 64 kbit/s transfer capability. Furthermore, interworking with the Public Switched Telephone

Unless otherwise stated, the use of the term "terminal" refers to customer's terminal apparatus which may

be a Terminal Equipment type 1 (TE1), a Terminal Adapter (TA) together with a Terminal Equipment

type 2 (TE2) or a Network Termination type 2 (NT2) as defined in ITU-T Recommendation I.411.

The exact bit patterns correlated with the named field values can be found in the following subclauses of

Generally, the information elements BC, HLC and LLC serve the following purposes:

At the calling side, the network checks that the bearer service requested by the calling user in the Bearer

capability information element matches with the bearer service provided to that user by the network (see

At the called side, the called user performs network-to-user compatibility checking based on the content of

the BC-information element, and user-to-user compatibility checking based on the content of the HLC-

This ETSI Technical Report (ETR) provides supplementary information on the usage of the compatibility

information elements Bearer Capability (BC), High layer Compatibility (HLC) and Low Layer Compatibility

(LLC) for individual telecommunication services. It considers the telecommunications services as they are

specified for public Integrated Services Digital Networks (ISDNs). It does not specify additional codings of

the compatibility information elements which might be required to support the request and provision of

Since some bearer services can be used to support various user applications, additional information on

- in subclause 7.1 for the circuit-mode 64 kbit/s unrestricted 8 kHz structured bearer service;

- in subclause 7.2 for the circuit-mode 64 kbit/s 8 kHz structured 3,1 kHz audio bearer service.

The specific objective of this ETR is to provide guidance on the correct usage of ETS 300 403-1 [7]

codepoints to the different ETSI Technical Committees or Technical Subcommittees dealing with services,

ISDN terminals, Terminal Adapters (TAs) and documents on testing. This ETR shall help to assure inter-

operability of terminals supporting the same telecommunication service and shall enable terminals to

The typical codings specified in clause 6 should be supported by all users and networks supporting the

corresponding telecommunications service. Other variants of these codings may be supported in addition,

however, these variants might not provide for world-wide interoperability and might not guarantee terminal

The coding examples given in clause 7 are not exhaustive. They illustrate typical user applications

Clause 8 is devoted to examples showing the interworking of European ISDNs with non-European ISDNs

This ETR incorporates by dated or undated reference, provisions from other publications. These

references are cited at the appropriate places in the text and the publications listed hereafter. For dated

references, subsequent amendments to or revisions of any of these publications apply to this ETR only

when incorporated in it by amendment or revision. For undated references the latest edition of the

[3] ETS 300 218 (1993): "Integrated Services Digital Network (ISDN); Syntax-based

[5] ETS 300 383 (1995): "Integrated Services Digital Network (ISDN); File transfer

[6] ETS 300 388 (1995): "Integrated Services Digital Network (ISDN); File Transfer

[7] ETS 300 403-1: "Integrated Services Digital Network (ISDN); Digital Subscriber

a) the LLC information element is transferred transparently through an ISDN between the calling entity

and the addressed entity. However, dependent on the charging principles applied, some networks

b) the HLC information element is transferred transparently through an ISDN between the calling entity

and the addressed entity. However, some networks may check its content, e.g., to associate a

c) where bearer services are specified, the HLC information element will normally not be present

d) the coding examples consider the general case. In special terminal arrangements the user may

need to rely on address information only. In these cases, the Multiple Subscriber Number (MSN)

e) a Terminal Equipment type 2 (TE2) together with a TA are assumed to provide the same

functionality as a Terminal Equipment type 1 (TE1). Therefore, a TA should not generate and send

a progress indicator when setting-up a connection. Consequently, a TA, e.g., adapting a two-wire

analogue Public Switched Telephone Network (PSTN) user-network interface to the ISDN user-

network interface will generate the BC and, if appropriate, the HLC and LLC information elements in

accordance with the type of equipment it serves at the interface at the R reference point, namely:

- octets 1 and 2 of the compatibility information elements, indicating the information element identifier

and length respectively, are omitted from the considerations and therefore not shown in the

- field values in brackets ( ) may or may not be included at the calling side and therefore not be

In the case of interworking with non-ISDNs, HLC and LLC information elements may be absent, and this

interworking is shown with the presence of the Progress indicator information element. When this occurs,

the terminal should accept the incoming call according to annex B of ETS 300 403-1 [7], i.e. it should

regard the compatibility as successful if it is compatible with the included information, which as a minimum

In many cases, the same low layer information (e.g., the user rate and the rate adaption technique

applied) can be coded in either the BC or the LLC information element. However, the provision of

information in the one or the other information element has consequences with respect to the selection or

The following guidelines exist for the application of BC and LLC information elements according to annex I

Type I Information used only at the destination end to allow decision regarding terminal

compatibility. This information, if required, shall be coded into octets (3a and) 5 to 7 of the

Type II Information to permit the network to select the bearer service. This information shall be

Type III Information used by the addressed user to determine terminal compatibility and used by the

network to facilitate interworking with other ISDNs or other dedicated networks. This

information is encoded into octet 5 (including octets 5a-5d if appropriate) of the BC

Case 1 If the originating user wishes to transfer information end-to-end to ensure end user

compatibility without invoking network interworking, then type I information together with

Case 2 If the originating user either requires network interworking or is willing to accept network

interworking, should it be necessary in order to complete the call, then type III information

Consequently, if interworking with a PSTN, Circuit Switched Public Data Network (CSPDN) or the pan-

European mobile cellular system is supported by the network by providing the appropriate functions (i.e.

data extraction, modem pool) at the interworking unit, then those calls carrying the rate adaption