SIST ETS 300 125:1996

Integrated Services Digital Network (ISDN); User-network interface data link layer specification; Application of CCITT Recommendations Q.920/I.440 and Q.921/I.441

ISDN User-Network Layer 2 Signalling Protocols and associated Test Specifications

Digitalno omrežje z integriranimi storitvami (ISDN) - Specifikacija podatkovne povezovalne plasti vmesnika uporabnik-omrežje - Aplikacija priporočil CCIT Q.920/I.440 in Q.921/I.441

General Information

• Status: Published
• Publication Date: 30-Nov-1996
• Withdrawal Date: 30-Nov-1996
• ICS: 33.080 - Integrated Services Digital Network (ISDN)
• ICS: 35.100.20 - Data link layer
• Technical Committee: SPS - Signalling protocols and switching
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-Dec-1996
• Due Date: 01-Dec-1996
• Completion Date: 01-Dec-1996
• Ref Project: ETSI ETS 300 125 ed.1 (1991-09) - Integrated Services Digital Network (ISDN); User-network interface data link layer specification; Application of CCITT Recommendations Q.920/I.440 and Q.921/I.441

Standards Content (Sample)

SLOVENSKI STANDARD
SIST ETS 300 125:1996
01-GHFHPEHU-1996
'LJLWDOQRRPUHåMH]LQWHJULUDQLPLVWRULWYDPL,6'16SHFLILNDFLMDSRGDWNRYQH
SRYH]RYDOQHSODVWLYPHVQLNDXSRUDEQLNRPUHåMH$SOLNDFLMDSULSRURþLO&&,7
4,LQ4,
Integrated Services Digital Network (ISDN); User-network interface data link layer
specification; Application of CCITT Recommendations Q.920/I.440 and Q.921/I.441
Ta slovenski standard je istoveten z: ETS 300 125 Edition 1
ICS:
33.080 Digitalno omrežje z Integrated Services Digital
integriranimi storitvami Network (ISDN)
(ISDN)
35.100.20 Podatkovni povezovalni sloj Data link layer
SIST ETS 300 125:1996 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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PSIST ETS 300 125:1996

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PSIST ETS 300 125:1996
EUROPEAN ETS 300 125
TELECOMMUNICATION September 1991
STANDARD
Source: ETSI TC-SPS Reference: T/S 46-20 [CC]
ICS: 33.080
Key words: ISDN, data link layer, Q.920, Q.921
Integrated Services Digital Network (ISDN);
User-network interface data link layer specification;
Application of CCITT Recommendations Q.920/I.440
and Q.921/I.441
ETSI
European Telecommunications Standards Institute
ETSI Secretariat
Postal address: F-06921 Sophia Antipolis CEDEX - FRANCE
Office address: 650 Route des Lucioles - Sophia Antipolis - Valbonne - FRANCE
X.400: c=fr, a=atlas, p=etsi, s=secretariat - Internet: [e-mail]
Tel.: [phone] - Fax: [phone]
Copyright Notification: No part may be reproduced except as authorized by written permission. The copyright and the
foregoing restriction extend to reproduction in all media.
© European Telecommunications Standards Institute 1991. All rights reserved.

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PSIST ETS 300 125:1996
Page 2
ETS 300 125: September 1991
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 Standards Approval Dept." at the address shown on the title page.

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PSIST ETS 300 125:1996
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ETS 300 125: September 1991
Contents
Foreword .9
Scope .9
PART 1: Application of CCITT Recomendation Q.920(I.440) .11
ISDN user-network interface data link layer - General aspects.11
1 General.11
2 Concepts and terminology.11
3 Overview description of LAPD functions and procedures .15
3.1 General .15
3.2 Unacknowledged operation .17
3.3 Acknowledged operation.17
3.4 Establishment of information transfer modes .17
3.4.1 Data link connection identification.17
3.4.2 Data link states.18
3.4.3 TEI administration .19
3.4.4 Establishment of multiple frame operation.20
4 Service characteristics .20
4.1 General .20
4.2 Services provided to layer 3.20
4.2.1 Unacknowledged information transfer service .20
4.2.2 Acknowledged information transfer service .20
4.3 Services provided to layer management.21
4.4 Administrative services .22
4.5 Model of the data link service: .22
4.5.1 General.22
4.5.2 Data link layer representation as seen by layer 3.23
4.5.2.1 Data Link Connection Endpoint States.23
4.5.2.2 Broadcast data link layer connection services.23
4.5.2.3 Point-to-point data link connection endpoint services .23
4.5.2.4 Sequences of primitives at one point-to-point data link
connection endpoint.23
4.6 Services required from the physical layer.24
5 Data link layer - Management structure .24
5.1 Data link procedure.26
5.2 Multiplex procedure.26
5.3 Structure of the data link procedure.26
5.4 Additions for European networks.27
5.4.1 General.27
5.4.2 Enhanced functional block diagram and block interaction diagram .27
References (used in Q.920) .31
PART 2: Application of CCITT Recomendation Q.921(I.441) .32
ISDN user-network interface - Data link layer specification .32
1 General.32
2 Frame structure for peer-to-peer communication .32

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ETS 300 125: September 1991
2.1 General. 32
2.2 Flag sequence. 32
2.3 Address field. 32
2.4 Control field . 33
2.5 Information field. 33
2.6 Transparency . 33
2.7 FCS field. 33
2.8 Format convention .34
2.8.1 Numbering Convention. 34
2.8.2 Order of bit transmission . 34
2.8.3 Field mapping convention. 34
2.9 Invalid frames. 35
2.10 Frame abort. 35
3 Elements of procedures and formats of fields for data link layer peer-to-peer communication . 35
3.1 General. 35
3.2 Address field format . 35
3.3 Address field variables .36
3.3.1 Address field extension bit (EA). 36
3.3.2 Command/Response field bit (C/R). 36
3.3.3 Service Access Point Identifier (SAPI). 36
3.3.4 Terminal Endpoint Identifier (TEI). 37
3.3.4.1 TEI for broadcast data link connection. 37
3.3.4.2 TEI for point-to-point data link connection . 37
3.4 Control field formats. 37
3.4.1 Information transfer (I) format. 38
3.4.2 Supervisory (S) format. 38
3.4.3 Unnumbered (U) format. 38
3.5 Control field parameters and associated state variables . 38
3.5.1 Poll/Final bit . 38
3.5.2 Multiple frame operation - variables and sequence numbers. 39
3.5.2.1 Modulus. 39
3.5.2.2 Send state variable V(S) . 39
3.5.2.3 Acknowledge state variable V(A) . 39
3.5.2.4 Send sequence number N(S) . 39
3.5.2.5 Receive state variable V(R) . 39
3.5.2.6 Receive sequence number N(R). 39
3.5.3 Unacknowledged operation - variables and parameters . 39
3.6 Frame types . 39
3.6.1 Commands and responses. 39
3.6.2 Information (I) command . 40
3.6.3 Set asynchronous balanced mode extended (SABME) command. 40
3.6.4 DISConnect (DISC) command . 41
3.6.5 Unnumbered Information (UI) command. 41
3.6.6 Receive Ready (RR) command/response . 41
3.6.7 REJect (REJ) command/response . 41
3.6.8 Receive Not Ready (RNR) command/response. 41
3.6.9 Unnumbered Acknowledgement (UA) response . 42
3.6.10 Disconnected Mode (DM) response . 42
3.6.11 Frame reject (FRMR) response. 42
3.6.12 Exchange identification (XID) command/response . 43
4 Elements for layer-to-layer communication .44
4.1 General. 44
4.1.1 Generic names . 44
4.1.1.1 DL-ESTABLISH. 44
4.1.1.2 DL-RELEASE. 44
4.1.1.3 DL-DATA. 44
4.1.1.4 DL-UNIT DATA . 44
4.1.1.5 MDL-ASSIGN. 44
4.1.1.6 MDL-REMOVE. 45
4.1.1.7 MDL-ERROR . 45
4.1.1.8 MDL-UNIT DATA . 45

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4.1.1.9 MDL-XID.45
4.1.1.10 PH-DATA.45
4.1.1.11 PH-ACTIVATE.45
4.1.1.12 PH-DEACTIVATE.45
4.1.1.13 MPH-ACTIVATE (See Appendix III) .45
4.1.1.14 MPH-DEACTIVATE (See Appendix III) .45
4.1.1.15 MPH-INFORMATION .45
4.1.2 Primitive types .45
4.1.2.1 REQUEST .46
4.1.2.2 INDICATION.46
4.1.2.3 RESPONSE.46
4.1.2.4 CONFIRM.46
4.1.3 Parameter definition .46
4.1.3.1 Priority indicator .46
4.1.3.2 Message unit .46
4.2 Primitive procedures .47
4.2.1 General.47
4.2.2 Layer 3 - data link layer interactions.47
5 Definition of the peer-to-peer procedures of the data link layer .49
5.1 Procedure for the use of the P/F bit.50
5.1.1 Unacknowledged information transfer.50
5.1.2 Acknowledged multiple frame information transfer .50
5.2 Procedures for unacknowledged information transfer.50
5.2.1 General.50
5.2.2 Transmision of unacknowledged information.51
5.2.3 Receipt of unacknowledged information .51
5.3 Terminal Endpoint Identifier (TEI) management procedures.51
5.3.1 General.51
5.3.2 TEI assignment procedure .52
5.3.2.1 Expiry of timer T202 .54
5.3.3 TEI check procedure .54
5.3.3.1 Use of the TEI check procedure.54
5.3.3.2 Operation of the TEI check procedure .55
5.3.4 TEI removal procedure.56
5.3.4.1 Action taken by the data link layer entity receiving the
MDL-REMOVE-REQUEST primitive .56
5.3.4.2 Conditions for TEI removal.56
5.3.5 TEI identity verify procedure.57
5.3.5.1 General.57
5.3.5.2 Operation of the TEI identity verify procedure .57
5.3.5.3 Expiry of timer T202 .58
5.3.6 Formats and codes .58
5.3.6.1 General.58
5.3.6.2 Layer management entity identifier.59
5.3.6.3 Reference number (Ri).59
5.3.6.4 Message type .59
5.3.6.5 Action indicator (Ai).59
5.4 Automatic negotiation of data link layer parameters.60
5.5 Procedures for establishment and release of multiple frame operation .60
5.5.1 Establishment of multiple frame operation.60
5.5.1.1 General.60
5.5.1.2 Establishment procedures.60
5.5.1.3 Procedure on expiry of timer T200 .61
5.5.2 Information transfer .61
5.5.3 Termination of multiple frame operation.61
5.5.3.1 General.61
5.5.3.2 Release procedure .61
5.5.3.3 Procedure on expiry of timer T200 .62
5.5.4 TEI-assigned state .62
5.5.5 Collision of unnumbered commands and responses .62
5.5.5.1 Identical transmitted and received commands .62
5.5.5.2 Different transmitted and received commands.63

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5.5.6 Unsolicited DM response and SABME or DISC command . 63
5.6 Procedures for information transfer in multiple frame operation. 63
5.6.1 Transmitting I frames. 63
5.6.2 Receiving I frames. 63
5.6.2.1 P bit set to 1 . 63
5.6.2.2 P bit set to 0 . 64
5.6.3 Sending and receiving acknowledgements . 64
5.6.3.1 Sending acknowledgements . 64
5.6.3.2 Receiving acknowledgements . 64
5.6.4 Receiving REJ frames . 64
5.6.5 Receiving RNR frames . 65
5.6.6 Data link layer own receiver busy condition. 67
5.6.7 Waiting acknowledgement. 67
5.7 Re-establishment of multiple frame operation . 68
5.7.1 Criteria for re-establishment . 68
5.7.2 Procedures . 68
5.8 Exception condition reporting and recovery . 69
5.8.1 N(S) sequence error . 69
5.8.2 N(R) sequence error. 69
5.8.3 Timer recovery condition . 69
5.8.4 Invalid frame condition. 70
5.8.5 Frame rejection condition . 70
5.8.6 Receipt of an FRMR response frame. 70
5.8.7 Unsolicited response frames . 70
5.8.8 Multiple-assignment of TEI value. 71
5.9 List of system parameters. 71
5.9.1 Timer T200 . 71
5.9.2 Maximum number of retransmissions (N200) . 71
5.9.3 Maximum number of octets in an information field (N201). 72
5.9.4 Maximum number of transmission of the TEI identity request message
(N202). 72
5.9.5 Maximum number of outstanding I frames (k). 72
5.9.6 Timer T201 . 72
5.9.7 Timer T202 . 72
5.9.8 Timer T203 . 72
5.10 Data link layer monitor function. 73
5.10.1 General . 73
5.10.2 Data link layer supervision in the multiple-frame-established state. 73
5.10.3 Connection verification procedures . 73
5.10.3.1 Start timer T203 . 73
5.10.3.2 Stop Timer T203 . 74
5.10.3.3 Expiry of timer T203. 74
Annex A (to Recommendation Q.921) Provision of point-to-point signalling connections. 75
Annex B (to Recommendation Q.921) SDL for point-to-point procedures . 76
B.1 General. 76
B.2 An overview of the states of the point-to-point data link layer entity. 76
B.3 Cover notes . 79
B.4 The use of queues. 80
B.5 SDL representation. 81
Annex C (to Recommendation Q.921) An SDL representation of the broadcast procedures of the data
link layer . 109
Annex D (to Recommendation Q.921) State transition table of the point-to-point procedures of the data
link layer . 110

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D.1 State transition table.110
D.2 Key to the state transition table .111
D.2.1 Definition of a cell of the state transition table .111
D.2.2 Key to the contents of a cell.111
Appendix I (to Recommendation Q.921) Retransmission of REJ response frames .143
I.1 Introduction.143
I.2 Procedure.143
Appendix II (to Recommendation Q.921) Occurence of MDL-ERROR-INDICATION within the basic
states and actions to be taken by the management entity.144
II.1 Introduction.144
II.2 Layout of table II-1/Q.921 .144
II.3 Preferred management actions.144
Appendix III (to Recommendation Q.921) Optional basic access deactivation procedures.146
III.1 Introduction.146
III.2 Description of the conceptual model .146
III.3 Deactivation procedure with MPH-DEACTIVATE-INDICATION .147
III.4 Deactivation procedure without MPH-DEACTIVATE-INDICATION .149
Appendix IV (to Recommendation Q.921) Automatic negotiation of data link layer parameters .150
IV.1 General .150
IV.2 Parameter initialisation.150
IV.3 Internal parameter initialisation .150
IV.4 Automatic notification of data link layer parameter values.150
History.153
...

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Integrated Services Digital Network (ISDN); User-network interface data link layer specification; Application of CCITT Recommendations Q.920/I.440 and Q.921/I.44135.100.20Podatkovni povezovalni slojData link layer33.080Digitalno omrežje z integriranimi storitvami (ISDN)Integrated Services Digital Network (ISDN)ICS:Ta slovenski standard je istoveten z:ETS 300 125 Edition 1PSIST ETS 300 125:1996en01-oktober-1996PSIST ETS 300 125:1996SLOVENSKI
STANDARD



PSIST ETS 300 125:1996



EUROPEANETS 300 125TELECOMMUNICATIONSeptember 1991STANDARDSource: ETSI TC-SPSReference: T/S 46-20 [CC]ICS:33.080Key words:ISDN, data link layer, Q.920, Q.921Integrated Services Digital Network (ISDN);User-network interface data link layer specification;Application of CCITT Recommendations Q.920/I.440and Q.921/I.441ETSIEuropean Telecommunications Standards InstituteETSI SecretariatPostal address: F-06921 Sophia Antipolis CEDEX - FRANCEOffice address: 650 Route des Lucioles - Sophia Antipolis - Valbonne - FRANCEX.400: c=fr, a=atlas, p=etsi, s=secretariat - Internet: [e-mail].: [phone] - Fax: [phone]Copyright Notification: No part may be reproduced except as authorized by written permission. The copyright and theforegoing restriction extend to reproduction in all media.© European Telecommunications Standards Institute 1991. All rights reserved.PSIST ETS 300 125:1996



Page 2ETS 300 125: September 1991Whilst 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 Standards Approval Dept." at the address shown on the title page.PSIST ETS 300 125:1996



Page 3ETS 300 125: September 1991ContentsForeword.9Scope.9PART 1: Application of CCITT Recomendation Q.920(I.440).11ISDN user-network interface data link layer - General aspects.111General.112Concepts and terminology.113Overview description of LAPD functions and procedures.153.1General.153.2Unacknowledged operation.173.3Acknowledged operation.173.4Establishment of information transfer modes.173.4.1Data link connection identification.173.4.2Data link states.183.4.3TEI administration.193.4.4Establishment of multiple frame operation.204Service characteristics.204.1General.204.2Services provided to layer 3.204.2.1Unacknowledged information transfer service.204.2.2Acknowledged information transfer service.204.3Services provided to layer management.214.4Administrative services.224.5Model of the data link service:.224.5.1General.224.5.2Data link layer representation as seen by layer 3.234.5.2.1Data Link Connection Endpoint States.234.5.2.2Broadcast data link layer connection services.234.5.2.3Point-to-point data link connection endpoint services.234.5.2.4Sequences of primitives at one point-to-point data linkconnection endpoint.234.6Services required from the physical layer.245Data link layer - Management structure.245.1Data link procedure.265.2Multiplex procedure.265.3Structure of the data link procedure.265.4Additions for European networks.275.4.1General.275.4.2Enhanced functional block diagram and block interaction diagram.27References (used in Q.920).31PART 2: Application of CCITT Recomendation Q.921(I.441).32ISDN user-network interface - Data link layer specification.321General.322Frame structure for peer-to-peer communication.32PSIST ETS 300 125:1996



Page 4ETS 300 125: September 19912.1General.322.2Flag sequence.322.3Address field.322.4Control field.332.5Information field.332.6Transparency.332.7FCS field.332.8Format convention.342.8.1Numbering Convention.342.8.2Order of bit transmission.342.8.3Field mapping convention.342.9Invalid frames.352.10Frame abort.353Elements of procedures and formats of fields for data link layer peer-to-peer communication.353.1General.353.2Address field format.353.3Address field variables.363.3.1Address field extension bit (EA).363.3.2Command/Response field bit (C/R).363.3.3Service Access Point Identifier (SAPI).363.3.4Terminal Endpoint Identifier (TEI).373.3.4.1TEI for broadcast data link connection.373.3.4.2TEI for point-to-point data link connection.373.4Control field formats.373.4.1Information transfer (I) format.383.4.2Supervisory (S) format.383.4.3Unnumbered (U) format.383.5Control field parameters and associated state variables.383.5.1Poll/Final bit.383.5.2Multiple frame operation - variables and sequence numbers.393.5.2.1Modulus.393.5.2.2Send state variable V(S).393.5.2.3Acknowledge state variable V(A).393.5.2.4Send sequence number N(S).393.5.2.5Receive state variable V(R).393.5.2.6Receive sequence number N(R).393.5.3Unacknowledged operation - variables and parameters.393.6Frame types.393.6.1Commands and responses.393.6.2Information (I) command.403.6.3Set asynchronous balanced mode extended (SABME) command.403.6.4DISConnect (DISC) command.413.6.5Unnumbered Information (UI) command.413.6.6Receive Ready (RR) command/response.413.6.7REJect (REJ) command/response.413.6.8Receive Not Ready (RNR) command/response.413.6.9Unnumbered Acknowledgement (UA) response.423.6.10Disconnected Mode (DM) response.423.6.11Frame reject (FRMR) response.423.6.12Exchange identification (XID) command/response.434Elements for layer-to-layer communication.444.1General.444.1.1Generic names.444.1.1.1DL-ESTABLISH.444.1.1.2DL-RELEASE.444.1.1.3DL-DATA.444.1.1.4DL-UNIT DATA.444.1.1.5MDL-ASSIGN.444.1.1.6MDL-REMOVE.454.1.1.7MDL-ERROR.454.1.1.8MDL-UNIT DATA.45PSIST ETS 300 125:1996



Page 5ETS 300 125: September 19914.1.1.9MDL-XID.454.1.1.10PH-DATA.454.1.1.11PH-ACTIVATE.454.1.1.12PH-DEACTIVATE.454.1.1.13MPH-ACTIVATE (See Appendix III).454.1.1.14MPH-DEACTIVATE (See Appendix III).454.1.1.15MPH-INFORMATION.454.1.2Primitive types.454.1.2.1REQUEST.464.1.2.2INDICATION.464.1.2.3RESPONSE.464.1.2.4CONFIRM.464.1.3Parameter definition.464.1.3.1Priority indicator.464.1.3.2Message unit.464.2Primitive procedures.474.2.1General.474.2.2Layer 3 - data link layer interactions.475Definition of the peer-to-peer procedures of the data link layer.495.1Procedure for the use of the P/F bit.505.1.1Unacknowledged information transfer.505.1.2Acknowledged multiple frame information transfer.505.2Procedures for unacknowledged information transfer.505.2.1General.505.2.2Transmision of unacknowledged information.515.2.3Receipt of unacknowledged information.515.3Terminal Endpoint Identifier (TEI) management procedures.515.3.1General.515.3.2TEI assignment procedure.525.3.2.1Expiry of timer T202.545.3.3TEI check procedure.545.3.3.1Use of the TEI check procedure.545.3.3.2Operation of the TEI check procedure.555.3.4TEI removal procedure.565.3.4.1Action taken by the data link layer entity receiving theMDL-REMOVE-REQUEST primitive.565.3.4.2Conditions for TEI removal.565.3.5TEI identity verify procedure.575.3.5.1General.575.3.5.2Operation of the TEI identity verify procedure.575.3.5.3Expiry of timer T202.585.3.6Formats and codes.585.3.6.1General.585.3.6.2Layer management entity identifier.595.3.6.3Reference number (Ri).595.3.6.4Message type.595.3.6.5Action indicator (Ai).595.4Automatic negotiation of data link layer parameters.605.5Procedures for establishment and release of multiple frame operation.605.5.1Establishment of multiple frame operation.605.5.1.1General.605.5.1.2Establishment procedures.605.5.1.3Procedure on expiry of timer T200.615.5.2Information transfer.615.5.3Termination of multiple frame operation.615.5.3.1General.615.5.3.2Release procedure.615.5.3.3Procedure on expiry of timer T200.625.5.4TEI-assigned state.625.5.5Collision of unnumbered commands and responses.625.5.5.1Identical transmitted and received commands.625.5.5.2Different transmitted and received commands.63PSIST ETS 300 125:1996



Page 6ETS 300 125: September 19915.5.6Unsolicited DM response and SABME or DISC command.635.6Procedures for information transfer in multiple frame operation.635.6.1Transmitting I frames.635.6.2Receiving I frames.635.6.2.1P bit set to 1.635.6.2.2P bit set to 0.645.6.3Sending and receiving acknowledgements.645.6.3.1Sending acknowledgements.645.6.3.2Receiving acknowledgements.645.6.4Receiving REJ frames.645.6.5Receiving RNR frames.655.6.6Data link layer own receiver busy condition.675.6.7Waiting acknowledgement.675.7Re-establishment of multiple frame operation.685.7.1Criteria for re-establishment.685.7.2Procedures.685.8Exception condition reporting and recovery.695.8.1N(S) sequence error.695.8.2N(R) sequence error.695.8.3Timer recovery condition.695.8.4Invalid frame condition.705.8.5Frame rejection condition.705.8.6Receipt of an FRMR response frame.705.8.7Unsolicited response frames.705.8.8Multiple-assignment of TEI value.715.9List of system parameters.715.9.1Timer T200.715.9.2Maximum number of retransmissions (N200).715.9.3Maximum number of octets in an information field (N201).725.9.4Maximum number of transmission of the TEI identity request message(N202).725.9.5Maximum number of outstanding I frames (k).725.9.6Timer T201.725.9.7Timer T202.725.9.8Timer T203.725.10Data link layer monitor function.735.10.1General.735.10.2Data link layer supervision in the multiple-frame-established state.735.10.3Connection verification procedures.735.10.3.1Start timer T203.735.10.3.2Stop Timer T203.745.10.3.3Expiry of timer T203.74Annex A (to Recommendation Q.921) Provision of point-to-point signalling connections.75Annex B (to Recommendation Q.921) SDL for point-to-point procedures.76B.1General.76B.2An overview of the states of the point-to-point data link layer entity.76B.3Cover notes.79B.4The use of queues.80B.5SDL representation.81Annex C (to Recommendation Q.921) An SDL representation of the broadcast procedures of the datalink layer.109Annex D (to Recommendation Q.921) State transition table of the point-to-point procedures of the datalink layer.110PSIST ETS 300 125:1996



Page 7ETS 300 125: September 1991D.1State transition table.110D.2Key to the state transition table.111D.2.1Definition of a cell of the state transition table.111D.2.2Key to the contents of a cell.111Appendix I (to Recommendation Q.921) Retransmission of REJ response frames.143I.1Introduction.143I.2Procedure.143Appendix II (to Recommendation Q.921) Occurence of MDL-ERROR-INDICATION within the basicstates and actions to be taken by the management entity.144II.1 Introduction.144II.2 Layout of table II-1/Q.921.144II.3 Preferred management actions.144Appendix III (to Recommendation Q.921) Optional basic access deactivation procedures.146III.1 Introduction.146III.2 Description of the conceptual model.146III.3 Deactivation procedure with MPH-DEACTIVATE-INDICATION.147III.4 Deactivation procedure without MPH-DEACTIVATE-INDICATION.149Appendix IV (to Recommendation Q.921) Automatic negotiation of data link layer parameters.150IV.1 General.150IV.2 Parameter initialisation.150IV.3 Internal parameter initialisation.150IV.4 Automatic notification of data link layer parameter values.150History.153PSIST ETS 300 125:1996



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Page 9ETS 300 125: September 1991ForewordThis European Telecommunication Standard (ETS) has been produced by the Signalling, Protocols andSwitching (SPS) Technical Committee of the European Telecommunications Standard Institute (ETSI),and was adopted, having passed through the ETSI standards approval procedure.This ETS is a revised version of CEPT Recommendation T/CS 46-20 (Edition of December 15, 1987;Revision 1988). It is based on the CCITT Recommendations Q.920/I.440 and Q.921/I.441 versionsaccording to the BLUE BOOK, Vol. VI, Fascicle VI.10. It is intended to reduce the number of options whichexist within CCITT Recommendations Q.920/I.440 and Q.921/I.441 and to provide the additionalspecification text necessary for clarification as well as to ensure harmonisation of the ISDN user-networkinterface within Europe.All procedures at the ISDN user-network interface apply to both, the S and T reference points.CCITT Recommendations Q.920/I.440 and Q.921/I.441 apply with the modifications specified below. Themodifications are presented based on the CCITT Recommendations according to the BLUE BOOK, Vol.VI, Fascicle VI.10.The following editorial conventions have been applied:-the layout of this standard is aligned with CCITT Recommendations Q.920/I.440 and Q.921/I.441according to the
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