ETSI ETS 300 080 ed.1 (1992-09)

SLOVENSKI STANDARD
01-december-2003
Digitalno omrežje z integriranimi storitvami (ISDN) – Protokoli za nižje ravni
sistema ISDN za telematske terminale
Integrated Services Digital Network (ISDN); ISDN lower layer protocols for telematic
terminals
Ta slovenski standard je istoveten z: ETS 300 080 Edition 1
ICS:
33.080 Digitalno omrežje z Integrated Services Digital
integriranimi storitvami Network (ISDN)
(ISDN)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN ETS 300 080
TELECOMMUNICATION September 1992
STANDARD
Source: ETSI TC-TE Reference: T/TE 12-04
ICS: 33.080
ISDN, Terminal Equipment
Key words:
Integrated Services Digital Network (ISDN);
ISDN lower layer protocols for telematic terminals
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 - secretariat@etsi.fr
X.400: Internet:
Tel.: +33 92 94 42 00 - Fax: +33 93 65 47 16
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 1992. All rights reserved.
New presentation - see History box

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ETS 300 080: September 1992
Whilst every care has been taken in the preparation and publication of this document, errors in content,
typographical or otherwise, may occur. If you have comments concerning its accuracy, please write to
"ETSI Editing and Committee Support Dept." at the address shown on the title page.

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ETS 300 080: September 1992
Contents
Foreword.9
1 Scope . 11
2 Normative references . 11
3 Abbreviations. 13
4 Model description. 14
4.1 Protocol pillars. 14
4.2 Co-ordination between B-channel and D-channel . 15
4.2.1 Multiple B-channels. 15
4.2.2 Active B-channel connection. 15
4.2.3 Established B-channel. 15
4.2.4 B-channel disconnection by the network . 16
4.3 Mapping of ETS 300 102-1 causes to OSI CONS reasons. 16
5 Layer 1 protocols. 18
5.1 Basic access . 18
5.2 Primary rate access. 18
6 D-channel layer 2 . 18
7 D-channel layer 3 . 18
7.1 The access protocol. 18
7.2 Terminal selection and compatibility checking . 18
7.2.1 Compatibility information provided by the calling terminal. 18
7.2.1.1 Bearer capability . 19
7.2.1.2 Low layer compatibility. 19
7.2.1.3 High layer compatibility. 20
7.2.2 Compatibility checking by the called terminal . 21
7.2.3 Call acceptance conditions. 21
7.3 Service specific use of supplementary services . 22
7.3.1 Supplementary services for addressing. 22
7.3.2 Supplementary services for identification. 22
7.3.3 Other supplementary services . 22
8 B-channel protocols. 22
8.1 B-channel Layer 2 . 22
8.1.1 Base protocols. 22
8.1.2 General rules for base protocol CCITT Recommendation X.75 . 23
8.1.2.1 STE - DTE. 23
8.1.2.2 Single link procedure. 23
8.1.2.3 Data link layer address procedure. 23
8.1.2.4 Mode of operation . 23
8.1.3 Specific rules for base protocol CCITT Recommendation X.75 . 24
8.1.4 Application rules for base protocol ISO 7776. 26
8.1.5 Synchronisation. 28
8.2 B-channel layer 3 . 28
8.2.1 DTE/DCE role. 28
8.2.2 Logical channels to be used . 29
8.2.3 Packet sizes . 29
8.2.4 Default packet level window size . 29
8.2.5 Default throughput class. 29

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ETS 300 080: September 1992
8.2.6 D-bit.29
8.2.7 Q-bit.30
8.2.8 Protocol identifier .30
8.2.9 INTERRUPT packet.30
8.2.10 Packet Data Units (PDUs).30
8.2.11 Encoding of Network Service Access Point (NSAP) addresses .31
8.2.12 Optional user facilities and CCITT specified DTE facilities.31
8.2.12.1 Facilities that shall be implemented .32
8.2.12.1.1 On-line facility registration .32
8.2.12.1.2 Fast select facility. 32
8.2.12.1.3 Expedited data negotiation facility .33
8.2.12.2 Facilities that shall not be used .33
8.2.12.3 Allowed Facilities which are not recommended.33
9 Layer 4 transport protocol.33
9.1 Additional application rules for the transport protocol in CCITT Recommendation T.70
(layer 4) .33
9.1.1 Transport Protocol Data Unit (TPDU) size negotiation.33
9.1.2 Timer values .33
9.1.3 Handling of Transport Service Access Point Identifier (TSAP-ID) as
initiator of a transport connection establishment.34
9.1.4 Handling of TSAP-ID responding to a transport connection establishment
attempt.34
9.1.5 Use of N-CONNECT primitives for transport protocol identification.34
9.2 Specification of the additional application rules for the transport protocol in ISO/IEC
8073 and CCITT Recommendation X.224 (layer 4) .34
9.2.1 Protocol classes. 34
9.2.2 Timer supervision .34
9.2.3 Timer values .34
9.2.4 Basic length indicator value .34
9.2.5 Handling of TSAP-ID as initiator of a transport connection establishment .35
9.2.6 Handling of TSAP-ID responding to a transport connection establishment
attempt.35
9.2.7 Use of N-CONNECT primitives for transport protocol identification.35
Annex A (informative): Comparison between ISO 7776 and CCITT Recommendation X.75 Layer 2 .36
A.1 Referenced documents .36
A.1.1 ISO 7776.36
A.1.2 ISO/IEC JTC 1/SC 6 N 5571.36
A.1.3 CCITT Recommendation X.75 (1988) .36
A.1.4 CCITT Recommendation X.75.36
A.2 Introduction.36
A.3 Table of differences.37
A.4 Details of the differences .38
A.4.1 Unnumbered frames modulo 128 (CCITT Recommendation X.75, table 2).38
A.4.2 Invalid frame (ISO 7776, subclause 3.8 - CCITT Recommendation X.75, § 2.3.5.3) .38
A.4.3 SABM control byte encoding (ISO 7776, table 6).38
A.4.4 DM as mode set request (ISO 7776, subclause 4.3.8).38
A.4.5 Conditions to send FRMR (ISO 7776, subclause 4.3.9 - CCITT Recommendation X.75,
§ 2.3.4.9) .38
A.4.6 Busy condition/Receiving a RNR.39
A.4.7 N(S) sequence error recovery .39
A.4.8 Start T1 after transmitted REJ (ISO 7776, subclause 4.4.2.2 - CCITT
Recommendation X.75, § 2.3.5.2.1) .40
A.4.9 Answer to received REJ (ISO 7776, subclause 4.4.2.2 - CCITT Recommendation X.75,
§ 2.3.5.2.1).40

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ETS 300 080: September 1992
A.4.10 Receiving frames in FRMR condition (ISO 7776, subclause 4.4.4/5.6.2 - CCITT
Recommendation X.75, § 2.3.5.4/2.4.7.3). 40
A.4.11 Excessive idle channel state (ISO 7776, subclause 3.11.2 - CCITT Recommendation
X.75, § 2.3.5.5) . 40
A.4.12 SABM with P=1 (ISO 7776, subclause 5.3.1, 3rd paragraph) . 41
A.4.13 Information phase/T4 (ISO 7776, subclause 5.3.2, 2nd paragraph). 41
A.4.14 DISC with P=1 (ISO 7776, subclause 5.3.3, 2nd paragraph). 41
A.4.15 Transmitted DISC (ISO 7776, subclause 5.3.3 - CCITT Recommendation X.75, §
2.4.4.3) . 41
A.4.16 Collision of unnumbered commands (ISO 7776, subclause 5.3.5 - CCITT
Recommendation X.75, § 2.4.4.5). 41
A.4.17 Retransmission using k (ISO 7776, subclause 5.4.1 - CCITT Recommendation
max
X.75, § 2.4.5.1) . 42
A.4.18 Waiting for I-frame acknowledgement (ISO 7776, subclause 5.4.9 - CCITT
Recommendation X.75, § 2.4.5.9). 42
A.4.19 Conditions for link reset (ISO 7776, subclause 5.5 - CCITT Recommendation X.75,
§ 2.4.6). 42
A.4.20 Request for link reset by FRMR (ISO 7776, subclause 5.6.2 - CCITT Recommendation
X.75, § 2.4.7.3) . 42
A.4.21 Timer T1 (ISO 7776, subclause 5.7.1.1 - CCITT Recommendation X.75, § 2.4.8.1). 43
A.4.22 Timer T2 (ISO 7776, subclause 5.7.1.2 - CCITT Recommendation X.75, § 2.4.8.2). 43
A.4.23 Timer T3 (ISO 7776, subclause 5.7.1.3 - CCITT Recommendation X.75, § 4.8.3). 43
A.4.24 Timer T4 (ISO 7776, subclause 5.7.1.4). 43
A.4.25 N1 (ISO 7776, subclause 5.7.3 - CCITT Recommendation X.75, § 2.4.8.5). 43
A.4.26 Window size k (ISO 7776, subclause 5.7.4 - CCITT Recommendation X.75, § 2.4.8.6). 43
Annex B (informative): Comparison of the Red Book (1984) and Blue Book (1988) version of CCITT
Recommendation X.75, Layer 2. 44
B.1 Introduction. 44
B.2 Receiving acknowledgement (§ 2.4.5.5). 44
B.3 Receiving an RNR frame (§ 2.4.5.7) . 44
Annex C (informative): Valuation of the application rules for the layer 2 protocols . 45
C.1 Introduction. 45
C.1.1 Referenced documents. 45
C.1.2 Procedure . 45
C.2 Table of application rules . 46
C.3 Evaluation of the application rules. 48
C.3.1 Link layer address procedure. 48
C.3.2 Recommendation version. 48
C.3.3 STE/DTE. 48
C.3.4 Parameter negotiation . 48
C.3.5 Mode of operation. 48
C.3.6 Single link procedure . 49
C.3.7 Length of information field. 49
C.3.8 FRMR causes. 49
C.3.9 Bits X, Y, Z, W . 49
C.3.10 Invalid frame condition . 49
C.3.11 Expiration of T3. 50
C.3.12 "Corresponding response" . 50
C.3.13 Active channel state . 50
C.3.14 SABM with P=1 . 50
C.3.15 Condition for entering the disconnected phase. 50
C.3.16 Initiator of link setup . 50

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ETS 300 080: September 1992
C.3.17 Timer recovery after received RNR.51
C.3.18 Sending I-frames after received RNR.51
C.3.19 N2 unsuccessful transmission attempts .51
C.3.20 Check commands in FRMR condition.52
C.3.21 Clearing of FRMR condition. 52
C.3.22 Originator of reset in FRMR condition .52
C.3.23 N2 unsuccessful transmissions of FRMR.52
C.3.24 Timer T1. 52
C.3.25 Timer T2. 53
C.3.26 Timer T3.53
C.3.27 Timer T4. 53
C.3.28 Maximum transmission number N2.53
C.3.29 Maximum frame length N1.53
C.3.30 Window size k. 54
C.3.31 Independent LAPB protocol on each channel.54
C.3.32 Use of unsolicited DM as mode setting command .54
C.3.33 Disconnecting the B-channel.55
C.3.34 Synchronising the activation of the B-channel.55
C.3.35 Acknowledging I-frames.56
C.4 Overall valuation of the interworking.56
C.4.1 Qualification table.57
C.4.2 Statement of interworking .59
Annex D (informative): Differences between the CCITT Recommendation X.224 and the International
Standard ISO/IEC 8073.60
D.1 General . 60
D.2 Additional items in CCITT Recommendation X.224.60
D.2.1 Additional annexes and appendices.60
D.2.2 Additional notes and paragraphs.60
D.3 Other differences .61
D.3.1 Protocol identifier .61
D.3.2 Sending a DC TPDU.61
D.3.3 Conformance statements. 61
D.3.3.1 Class 0/Class 2. 61
D.3.3.2 Class 0/Class 1. 61
D.3.3.3 Explicit indication of alternative class.61
D.3.4 Tables in Annex A.62
D.3.4.1 Table 17 (ISO/IEC) - table A-8 (CCITT).62
D.3.4.2 Table 19 (ISO/IEC) - table A-10 (CCITT) .62
D.3.5 Annex B (ISO/IEC 8073) - Appendix I (CCITT Recommendation X.224) .63
D.4 Conclusion for Class 0 .63
Annex E (informative): Differences between the CCITT Recommendation T.70 and ISO/IEC 8073 .64
E.1 Referenced documents .64
E.2 Introduction.64
E.3 Structure and terminology of the documents .64
E.4 Differences in the contents of CCITT Recommendation T.70 and ISO/IEC 8073.65
E.4.1 Invalid TPDUs and protocol errors .65
E.4.1.1 Invalid TPDUs .65
E.4.1.2 Protocol errors.65
E.4.2 Description of transport protocol by state tables and state transition diagrams.66

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ETS 300 080: September 1992
E.4.3 Handling of Timers . 66
E.4.4 Correspondence of transport layer states in CCITT Recommendation T.70 and
ISO/IEC 8073. 66
Annex F (informative): Bibliography. 68
History. 69

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ETS 300 080: September 1992
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ETS 300 080: September 1992
Foreword
This European Telecommunication Standard (ETS) has been produced by the Terminal Equipment (TE)
Technical Committee of the European Telecommunications Standards Institute (ETSI).
This ETS specifies a common set of protocols up to layer 4 of the Open Systems Interconnection (OSI)
model to be used by telematic terminals attached to the pan-European Integrated Services Digital Network
(ISDN). It bears a close relationship to CCITT Recommendation T.90 [8] and the Functional Standard
T/1112 (ENV 41 112) [20]. Full details of these and other normative references are given in Clause 2 of
this ETS.
A number of the references given in Clause 2 also involves work currently being carried out within ETSI. All
of the ETSI drafts listed should be available from your ETSI agreed National Standards Organisation
(NSO).
Reference to this ETS will be made by specifying attachment approval requirements and type approval
test suites in the terminal NETs.

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ETS 300 080: September 1992
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ETS 300 080: September 1992
1 Scope
This ETS specifies the usage of all protocols and supplementary services up to and including layer 4 for
telematic terminals in the ISDN. The scope of this ETS is limited to demand circuit-switched calls using the
64 kbit/s unrestricted digital information bearer capability and the DTE/DTE case of the Network Layer
peer entities in B-channel connection. This ETS is based on other ETSs, International Standards or
CCITT Recommendations and, where necessary, it adds new or other requirements as application rules.
The telematic services considered are:
a) teletex;
b) facsimile group 4; and
c) ISDN syntax-based Videotex.
The ETS is applicable to terminals using either basic access or primary rate access to the ISDN. Basic
access and primary rate access refer to different ETSs for layer 1.
NOTE: In the context of this ETS, and in the case of Videotex, a terminal is either a real
terminal equipment, a Videotex service centre, a Videotex access point or a Videotex
host.
Conformance testing to verify to which extent a terminal conforms with this ETS is to be specified in a
separate ETS which will cover both the Protocol Implementation Conformance Statement (PICS)
proformas and the Abstract Test Suites (ATS).
Interworking capabilities and limitations with implementations following similar Standards such as
Functional Standards are described in informative annexes.
2 Normative references
This ETS incorporates by dated or undated reference, provisions from other publications. These normative
references are cited at the appropriate places in the text and the publications are listed hereafter. For
dated references, subsequent amendments to or revisions of any of these publications apply to this ETS
only when incorporated in it by amendment or revision. For undated references the latest edition of the
publication referred to applies.
[1] CCITT Recommendation F.184 (1988): "Operational provision for the
international public facsimile service between subscriber stations with group 4
facsimile machines (telefax 4)".
[2] CCITT Recommendation F.200 (1988): "Teletex service".
[3] CCITT Recommendation F.220 (1988): "Service requirements unique to the
processable mode number 1 (PM1) used within the teletex service".
[4] CCITT Recommendation F.230 (1988): "Service requirements unique to the
mixed mode (MM) used within the teletex service".
[5] CCITT Recommendation I.333 (1988): "Terminal selection in ISDN".
[6] CCITT Recommendation Q.931 (1988): "ISDN user-network interface layer 3
specification for basic call control".
[7] CCITT Recommendation T.70 (1988): "Network-independent basic transport
service for the telematic services".

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ETS 300 080: September 1992
[8] CCITT Recommendation T.90 (1988): "Characteristics and protocols for
terminals for telematic services in ISDN".
[9] CCITT Recommendation T.101 (1988): "International interworking for videotex
services".
[10] CCITT Recommendation X.25 (1988): "Interface between data terminal
equipment (DTE) and data circuit terminating equipment (DCE) for terminals
operating in the packet mode and connected to public data networks by
dedicated circuits".
[11] CCITT Recommendation X.75 (1984): "Packet-switched signalling system
between public networks providing data transmission services".
[12] CCITT Recommendation X.224 (1988): "Transport protocol specification for
Open Systems Interconnection for CCITT Applications".
[13] ETS 300 102-1 (1990): "Integrated Services Digital Network (ISDN);
User-network interface layer 3, Specification for basic call control".
[14] ETS 300 102-2 (1991): "Integrated Services Digital Network (ISDN);
User-network interface layer 3 Specification for basic call control Specification
Description Language (SDL) diagrams".
[15] ETS 300 011 (1992): "Integrated Services Digital Network (ISDN); Primary rate
user-network interface, Layer 1 specification and test principles".
[16] ETS 300 012 (1992): "Integrated Services Digital Network (ISDN); Basic user-
network interface, Layer 1 specification and test principles".
[17] ETS 300 125 (1991): "Integrated Services Digital Network (ISDN); User-network
interface data link layer specifications Application of CCITT Recommendations
Q.920/I.440 and Q.921/I.441".
[18] prETS 300 196: "Integrated Services Digital Network (ISDN); Generic Functional
protocol for the support of supplementary services Digital Subscriber Signalling
No one (DSS1) protocol".
[19] prETS 300 195: "Integrated Services Digital Network (ISDN); Digital Subscriber
Signalling No. one (DSS1); Supplementary services interactions protocol".
[20] FS T/1112: " Provision of the OSI Connection-mode Transport Service and the
OSI Connection-mode Network Service by using an ISDN circuit-mode 64 kbit/s
unrestricted Bearer Service: Demand Case (ENV 41 112)".
[21] ISO 7776 (1986): "Information processing systems - Data communications -
Description of the X.25 LAPB-compatible DTE data link procedures".
[22] ISO/IEC 7776: "Addendum 1 Information processing systems - Data
communication - High level data link control procedures - Description of the X.25
LAPB-compatible DTE data link procedure - Addendum 1: PICS proforma".
[23] ISO/IEC 8073 (1988): "Information processing systems - Open Systems
Interconnection - Connection oriented transport protocol specification".
[24] ISO/IEC 8073 Addendum x: "Information processing systems; Open Systems
Interconnection; Connection oriented transport protocol specification Addendum
x: PICS".
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ETS 300 080: September 1992
[25] ISO/IEC 8208 (1990): "Information technology - Data communications - X.25
Packet Level Protocol for Data Terminal Equipment".
[26] ISO/IEC 8208 Addendum 3: "Information processing systems; Data
communication; X.25 Packet Level Protocol for Data Terminal Equipment
Addendum 3: Conformance requirements".
[27] ISO/IEC 8878 (1987): "Information processing systems - Data communications -
Use of X.25 to provide OSI connection-mode network service".
[28] ISO/IEC DIS 9574 (1989): "Information technology - Telecommunications and
information exchange between systems - Provision of the OSI connection-mode
network service by packet mode terminal equipment connected to an Integrated
Services Digital Network (ISDN)".
[29] ISO/IEC DIS 9574 PDAD 1: "Information technology - Telecommunications and
information exchange between systems - Provision of the OSI connection-mode
network service by packet mode terminal equipment connected to an Integrated
Services Digital Network (ISDN) ADDENDUM 1: Operation over an ISDN
circuit-switched channel connecting directly to the remote terminal".
[30] ISO/IEC 10025: "Transport conformance testing (temporary title)".
In the Standards and Recommendations listed above, further normative references are given which are not
listed here.
3 Abbreviations
The following abbreviations shall apply:
CC Call Connect
CLIP Calling Line Identification Presentation
CR Connection Request
DCE Data Circuit-terminology Equipment
DDI Direct Dialling-In
DISC Disconnect
DM Disconnected Mode
DTE Data Terminology Equipment
FRMR Frame Reject
HLC Higher Layer Compatibility
ISDN Integrated Services Digital Network
LAPB Link Access Procedure - Balanced
LAPD Link Access Procedure on the D-channel
LI Length indicator
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ETS 300 080: September 1992
LLC Lower Layer Compatibility
MLP Multilink Procedure
MSN Multiple Subscriber Number
NSAP Network Service Access Point
OSI Open Systems Interconnection
PDU Protocol Data Unit
RNR Receive Not Ready
SABM Set Asynchronous Balanced Mode
SABME Set Asynchronous Balanced Mode Extended
SPI Subsequent Protocol Identifier
TBR Transport Block Reject
4 Model description
4.1 Protocol pillars
Either CCITT Recommendation X.75 [11] or ISO 7776 [21], plus some additional rules in each case as
indicated in subclause 7.1, shall serve as the layer 2 protocol in the B-channel. Either CCITT
Recommendation T.70 [7] or ISO/IEC 8073 [23] plus some application rules in either case as indicated in
Clause 8, shall serve as the layer 4 protocol in the B-channel. Therefore, each of the protocol pillars shown
in figure 1a and figure 1b is allowed to conform with this ETS:
OSI
Layer
�˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜¿ ˜˜˜˜˜ �˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜¿
‡   [CCITT T.70] (NOTE 3)      ‡  4  ‡  [ISO/IEC 8073] (NOTE 3)    ‡
ˆ˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜· ˜˜˜˜˜ ˆ˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜·
‡     (NOTE 1)          ‡     ‡     (NOTE 1)        ‡
‡        �˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜·     ‡        �˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜·
‡        ‡ [ISO 8878]      ‡  3  ‡        ‡ [ISO 8878]    ‡
ˆ˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜¯˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜·     ˆ˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜¯˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜·
‡[ETS 300 102-1]‡ [ISO 8208]      ‡     ‡[ETS 300 102-1]‡ [ISO 8208]    ‡
ˆ˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜¯˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜· ˜˜˜˜˜ ˆ˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜¯˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜·
‡ [ETS 300 125] ‡[CCITT X.75] NOTES 2+4‡  2  ‡ [ETS 300 125] ‡ [ISO 7776] NOTE 2‡
ˆ˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜`˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜· ˜˜˜˜˜ ˆ˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜`˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜·
‡     [ETS 300 011 or       ‡  1  ‡     [ETS 300 011 or     ‡
‡     ETS 300 012]        ‡     ‡     ETS 300 012]      ‡
�˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜� ˜˜˜˜˜ �˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜�
D-channel      B-channel          D-channel     B-channel
Figure 1a                             Figure 1b
NOTE 1: This function, called co-ordinating function and detailed below, specifies the relationship
between the B-channel and D-channel protocol pillars, and is consistent with ISO/IEC
9574 PDAD 1 [29], the scope of which does not include the functions defined in this
document.
NOTE 2: Additional rules are imposed on the protocol (see subclause 7.1). In the case of CCITT
Recommendation X.75 [11], the rules are modifying the protocol, while in the case of
ISO 7776 [21] the rules are in conformance with the protocol. The two protocols plus
their additional rules are still different. However, it is shown in Annex C that they can
interwork.
NOTE 3: The layer 4 protocol is not applicable to Videotex.

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ETS 300 080: September 1992
NOTE 4: CCITT Recommendation T.90 [8] uses a modified version of CCITT Recommendation
X.75 [11], the usage of other protocols as alternative options being indicated for further
study. ISO 7776 [21] is such a candidate in CCITT Recommendation T.90 [8] and is
already allowed to be implemented to conform with this ETS.
At layer 1, ETS 300 012 [16] is used for ISDN basic access and ETS 300 011 [15] is used for ISDN
primary rate access. At layer 2, ETS 300 125 [17] provides the Link Access Procedure - Balanced (LAPB)
Data Link procedures for the D-channel and CCITT Recommendation X.75 [11] or ISO 7776 [21] (both
with additional rules imposed as indicated in subclause 7.1) provides the LAPB Data Link procedures for
the B-channel. At layer 3, ETS 300 102-1 [13] signalling procedures are used in the D-channel, and the
ISO/IEC 8208 [25] packet level protocol is used in DTE/DTE operation in the B-channel. The provisions of
ISO/IEC 8878 [27] apply with regard to the mappings of the OSI CONS primitives and parameters to and
from the elements of the ISO/IEC 8208 [25] packet level protocol.
NOTE: The provision of the full OSI CONS for Videotex is for further study.
For the application of teletex and facsimile group 4, transport connections are provided by CCITT
Recommendation T.70 [7] or ISO/IEC 8073 [23] (both with application rules imposed as indicated in
Clause 8), while in Videotex no transport protocol is employed at all.
Additional conformance requirements to the standards in figure 1a and figure 1b can be found in Clauses 7
and 8.
4.2 Co-ordination between B-channel and D-channel
Independently of the choice made at layer 2 of the B-channel (taking figure 1a or figure 1b as the protocol
pillar), the terminal implements two protocol stacks below layer 4. One stack is used over the ISDN
D-channel for establishing, maintaining and clearing circuit-switched B-channel connections. The other is
used over the B-channel(s) for establishing, maintaining and clearing virtual calls, and for the information
transfer itself.
The co-ordination function provides the synchronisation mechanism required between the usage of the
D-channel protocol stack and the B-channel protocol stack.
4.2.1 Multiple B-channels
If a terminal operates more than one B-channel with one or more than one other end system, the layer 2
and 3 entities shall be processed independently in each B-channel (e.g. Data Link disconnection, active/idle
channel state, DTE/DCE role assignment, logical channel range, etc.).
4.2.2 Active B-channel connection
If a B-channel connection is not already established (or if Quality of Service or other considerations dictate
that an additional B-channel connection is needed to support the additional traffic), the receipt by layer 3 of
an N-CONNECT request primitive shall first cause the ISDN D-channel signalling procedure for full
circuit-switched connection to be used as defined in Clause 6, to establish a B-channel connection.
4.2.3 Established B-channel
When a B-channel connection is established in layer 1, the co-ordinating function shall inform the Network
Layer entity and the Data Link Layer entity. The Data Link Layer shall then perform synchronisation with
the peer Data Link Layer entity as described in subclause 8.1.5 and inform the Network Layer entity after
successful synchronisation.
NOTE: The supervision by the co-ordinating function of the B-channel establishment and Data
Link initialisation is a local matter.

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ETS 300 080: September 1992
4.2.4 B-channel disconnection by the network
If one or more OSI Network Service connections are established or in the process of being established on
an established B-channel and that B-channel is disconnected, this disconnection shall be indicated to the
Network Service user by means of an N-DISCONNECT indication primitive with the originator parameter
indicating "Network Service provider" and the reason parameter as defined in table 1, for each OSI
Network connection established or in the process of being established.
If a cause different from all causes in table 1 is detected on the D-channel, either a value in table 1 that
suits shall be selected, or the cause "Normal, unspecified" shall be chosen.
NOTE 1: Table 1 is compatible to "table 2 - Mapping of CCITT Recommendation Q.931 causes
to OSI CONS reasons", contained in ISO/IEC 9574 [28], except for the fact that the
"not applicable" causes have been removed and the causes "Normal call clearing"
(value = 16), "Call rejected" (value = 21) and "Normal, unspecified" (value = 31) have
been appended.
NOTE 2: The Diagnostic field of the CCITT Recommendation Q.931 [6] cause information
element may contain an indication of the permanence or transience of the condition.
The Network Service reason passed to the Network Service user may be modified to
transfer this additional information.
4.3 Mapping of ETS 300 102-1 causes to OSI CONS reasons
Table 1: Mapping of causes to reasons
�˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝�˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝»
” ETS 300 102-1 [13] cause         ‡ Network Service Reason    ”
�˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝�˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝„
” 1 : Unassigned or unallocated number   ‡ Connection rejection - NSAP  ”
”                      ‡ unreachable - permanent    ”
˙˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜¯˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜”
” 3 : No route to destination       ‡ Connection rejection - NSAP  ”
”                      ‡ unreachable - permanent    ”
˙˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜¯˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜”
” 6 : Channel unacceptable         ‡ Connection rejection - reason ”
”                      ‡ unspecified - transient    ”
˙˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜¯˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜”
” 16 : Normal call clearing         ‡ Disconnection - transient   ”
˙˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜¯˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜”
” 17 : User busy              ‡ Connection rejection - reason ”
”                      ‡ unspecified - transient    ”
˙˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜¯˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜”
” 18 : No user responding          ‡ Connection rejection - reason ”
”                      ‡ unspecified - permanent    ”
˙˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜¯˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜”
” 21 : Call rejected            ‡ Connection rejection - reason ”
”                      ‡ unspecified - transient    ”
˙˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜¯˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜”
” 22 : Number changed            ‡ Connection rejection - reason ”
”                      ‡ unspecified - permanent
...