ETSI ETS 300 297 ed.1 (1995-05)

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Digitalno omrežje z integriranimi storitvami (ISDN)
– Digitalni dostopovni odsek za osnovni dostop v sistemu ISDNIntegrated Services Digital Network (ISDN); Access digital section for ISDN basic access33.080Digitalno omrežje z integriranimi storitvami (ISDN)Integrated Services Digital Network (ISDN)ICS:Ta slovenski standard je istoveten z:ETS 300 297 Edition 1SIST ETS 300 297 E1:2003en01-december-2003SIST ETS 300 297 E1:2003SLOVENSKI
STANDARD
EUROPEANETS 300 297TELECOMMUNICATIONMay 1995STANDARDSource: ETSI TC-TMReference: DE/TM-03004ICS:33.080Key words:ISDN, basic accessIntegrated Services Digital Network (ISDN);Access digital section for ISDN basic accessETSIEuropean 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: secretariat@etsi.frTel.: +33 92 94 42 00 - Fax: +33 93 65 47 16Copyright 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 1995. All rights reserved.SIST ETS 300 297 E1:2003

Page 2ETS 300 297: May 1995Whilst 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.SIST ETS 300 297 E1:2003

Page 3ETS 300 297: May 1995ContentsForeword.71Scope.92Normative references.93Definitions and abbreviations.103.1Definitions.103.2Abbreviations.104Configuration and application.104.1Configuration.104.2Application.114.3Modelling and relationship between the access digital section and the ET.135Functions.145.1B-channel.145.2D-channel.145.3Bit timing.145.4Octet timing.145.5Activation.155.5.1Activation from ET.155.5.2Request for activation from TE.155.6Deactivation.155.7Power feeding.155.8Operation and maintenance.156Signal transfer delay.157Jitter.167.1Output/input jitter at the T reference point.167.2Jitter at V1 reference point.168Activation/deactivation.168.1Functional capabilities.168.1.1Customer installation at the user side of the T reference point.168.1.2Installation at the network side of V1 reference point.168.2Modelling.178.2.1General.178.2.2Partitioning of functions.188.2.3Location of timer T2.188.3Activation/deactivation procedures.198.3.1Basic characteristics of the procedures.198.3.1.1Priority.198.3.1.2System management.198.3.1.3Loopbacks.198.3.1.4Protection of layer 2 frames.198.3.1.5Structure of the tables.198.4Description of the state transition table.208.4.1Access digital section states (DS-states).208.4.1.1State DS 1.0 (access deactivated).208.4.1.2State DS 1.1 (access activation initiated).208.4.1.3State DS 1.2 (access activation: DS synchronised LT -->NT).208.4.1.4State DS 1.3 (access activation: DS activated).208.4.1.5State DS 1.4 (access activated).20SIST ETS 300 297 E1:2003

Page 4ETS 300 297: May 19958.4.1.6State DS 1.5 (LOS/LFA at T).208.4.1.7State DS 1.6 (access deactivation initiated).218.4.1.8State DS 1.7 (defect condition).218.4.1.9State DS 2.0 (loopback 1 or 1a initiated).218.4.1.10State DS 2.1 (loopback 1 or 1a activated).218.4.1.11State DS 2.2 (loopback 2 initiated).218.4.1.12State DS 2.3 (DS synchronised LT --> NT).218.4.1.13State DS 2.4 (DS activated).218.4.1.14State DS 2.5 (loopback 2 activated).218.4.2Set of signals sent across the T reference point.218.4.3Set of function elements sent across the V1 reference point.228.4.4Assumptions made in specifying the procedures in table 2.228.5Activation time.258.5.1Warm start time.258.5.2Cold start time.259Operation and maintenance.259.1Control facilities.259.1.1Loopbacks.259.1.1.1Loopback implementation.259.1.1.2Loopback procedure.269.1.2Information request.269.1.3Power switch on/off to the line.269.1.4Continuity test.269.2Monitoring.269.2.1Functions.269.2.2Defect conditions and consequent actions.269.2.2.1Detection of defect conditions.269.2.2.2Consequent actions.279.2.3Error detection and reporting.279.2.4Status report functions.279.2.5System dependent status report functions.27Annex A (normative):System management requirements.28A.1Introduction.28A.2System management requirements.28A.2.1General.28A.2.2Error indications.28A.2.3Loopback operations.28A.2.4Continuity test.28A.2.5Information to be sent in the D-channel during loopback operation.28A.2.6Configuration control.29A.3Description of the ET layer 1 state transition table.29A.3.1ET layer 1 states (ET-states).29A.3.1.1State ET 1.0 (access deactivated).29A.3.1.2State ET 1.1 (access activation initiated).29A.3.1.3State ET 1.2 (access activated):.29A.3.1.4State ET 2.0 (access in loopback state).29A.3.1.5State ET 2.1 (loopback requested).29A.3.2Set of primitives within the ET for the support of functions associated with the accessdigital section.30A.3.3Assumptions made in specifying the procedures in table A.1 (ET 1.x states).30Annex B (informative):Partial activation of the access digital section.32B.1Introduction.32B.2Description of DS 3.x states for the partial DS activation of the access digital section mode ofoperation.32B.2.1State DS 3.0 (partial activation initiated).32SIST ETS 300 297 E1:2003

Page 5ETS 300 297: May 1995B.2.2State DS 3.1 (DS activated, T interface deactivated).32B.2.3State DS 3.2 (DS activated, T interface activating).32B.2.4State DS 3.3 (access activated).32B.2.5State DS 3.4 (LOS/LFA at T).32B.2.6State DS 3.5 (T interface deactivating).33B.3Description of ET 3.x states for the partial activation of the access digital section mode ofoperation.38B.3.1State ET 3.0 (partial activation initiated).38B.3.2State ET 3.1 (DS partially activated, interface at T deactivated).38B.3.3State ET 3.2 (DS partially activated, interface at T activation initiated).38B.3.4State ET 3.3 (DS partially activated, interface at T activated).38B.4Set of primitives within the ET for the support of functions associated with the partial activation ofthe access digital section.38Annex C (informative):Bibliography.39History.40SIST ETS 300 297 E1:2003

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Page 7ETS 300 297: May 1995ForewordThis European Telecommunication Standard (ETS) has been produced by the Transmission andMultiplexing (TM) Technical Committee of the European Telecommunications Standards Institute (ETSI).Proposed transposition datesDate of latest announcement of this ETS (doa):31 August 1995Date of latest publication of new National Standardor endorsement of this ETS (dop/e):29 February 1996Date of withdrawal of any conflicting National Standard (dow):29 February 1996SIST ETS 300 297 E1:2003

Page 8ETS 300 297: May 1995Blank pageSIST ETS 300 297 E1:2003

Page 9ETS 300 297: May 19951ScopeThis European Telecommunication Standard (ETS) specifies the characteristics of an access digitalsection for the Integrated Services Digital Network (ISDN) basic access between the user-networkinterface (at T reference point, as defined in ETS 300 012 [6] and the local exchange (at V1 referencepoint defined in CCITT Recommendation Q.512 [4]) supporting the basic access interface channelstructure (defined in CCITT Recommendation I.412 [1] and ETS 300 012 [6]) and the additional functionsrequired for operation and maintenance of the access digital section. This ETS is based on CCITTRecommendation G.960 [7].The requirements of this ETS and subsequently for the transmission systems based on this ETS, satisfynetwork performance requirements of CCITT Recommendation G.821 on error performance as well asCCITT Recommendations G.801 and I.350 with regard to availability. Annex A to this ETS is normativeand specifies requirements for working with the Exchange Termination (ET) and the definition of the ETlayer 1 state machine which are outside the scope of this ETS, but nevertheless are important for theunderstanding of the behaviour of the access digital section.Annex B specifies an optional procedure for partial activation and deactivation of the access digitalsection.Annex C provides a bibliography of informative references used in this ETS.A further annex is under development which will specify conformance testing for this ETS. This will beadded to this ETS using the ETSI standards maintenance procedures.2Normative referencesThis ETS incorporates, by dated or undated reference, provision from other publications. These normativereferences are cited at the appropriate places in the text and the publications are listed hereafter. Fordated references, subsequent amendments to or revisions of any of these publications apply to this ETSonly when incorporated in it by amendment or revision. For undated references the latest edition of thepublication referred applies.[1]CCITT Recommendation I.412 (1988): "ISDN user-network interfaces - Interfacestructures and access capabilities".[2]ETS 300 125 (1990): "Integrated Services Digital Network (ISDN); User-networkinterface data link layer specification; Application of CCITT RecommendationsQ.920/I.440 and Q.921/I.441".[3]ETR 001 (1990): "Integrated Services Digital Network (ISDN); Customer accessmaintenance".[4]CCITT Recommendation Q.512 (1988): "Exchange interfaces for subscriberaccess".[5]CCITT Recommendation G.114 (1988): "Mean one-way propagation time".[6]ETS 300 012 (1991): "Integrated Services Digital Network (ISDN); Basic user-network interface Layer 1 specification and test principles".[7]CCITT Recommendation G.960 (1988): "Digital section for ISDN basic rateaccess".[8]ETR 080 (1992): "Transmission and Multiplexing (TM); Integrated ServicesDigital Network (ISDN) basic rate access Digital transmission system on metalliclocal lines".[9]CCITT Recommendation I.430 (1988): "Basic user-network interface - Layer 1specification".SIST ETS 300 297 E1:2003

Page 10ETS 300 297: May 19953Definitions and abbreviations3.1DefinitionsAccess: The ISDN customer access as defined in CCITT Recommendation G.960 [7], annex B. TheAccess consists of the ET, the access digital section and the terminal equipment.full activation: Activation of the access in order to establish a layer 2 service between the user and thenetwork.partial activation: Partial activation of the access digital section under control from the ET. No signalshall be sent from the NT1 to the interface at the T reference point, but signals can be received for theactivation from the user side.TE: In this ETS, unless otherwise indicated, the term TE is used to indicate terminating layer 1 aspects ofTE1, TA and NT2 functional groups. When the term TE indicates terminating layer 1 aspects of TE1, then,according to CCITT Recommendation I.411, figure 2, the S and T reference points coincide. However, forthe purposes of this ETS, the terminology used is in accordance with annex B of CCITT RecommendationG.960 [7].3.2AbbreviationsFor the purposes of this ETS, the following abbreviations apply.AIAction IndicatorDSaccess Digital SectionETExchange TerminationFEFunction Element used between the ET and LTHDLCHigh level Data Link ControlINFOInformation element defined at the user-network interfaceISDNIntegrated Services Digital NetworkLFALoss of Frame AlignmentLOSLoss Of SignalLTLine TerminationMPHCommunication between Management and Physical layerNTNetwork TerminationPHCommunication between data link layer and Physical layerREGRegeneratorSIGSignal between LT and NT1TETerminal Equipment (see also subclause 3.1)4Configuration and application4.1ConfigurationFigure 1 shows the boundaries of the access digital section in relation to the digital system definition.NOTE 1:From a functional point of view the information transferred via the reference points Tand V1 are different and, therefore, the access digital section is not symmetrical.NOTE 2:The T and V1 reference points are defined in CCITT Recommendations I.411 andQ.512 [4].SIST ETS 300 297 E1:2003

Page 11ETS 300 297: May 1995Digital transmission systemTENT1LTETV1ReferencepointReferencepointAccess Digital SectionDSTNOTE 1:Digital transmission system refers to a line system using metallic pairs, optical fibres orradio systems.NOTE 2:The line transceivers in the Network Termination (NT) and the Line Termination (LT)are part of the digital transmission system.Figure 1: Access digital section and transmission system boundariesThe concept of the access digital section is used in order to allow a functional and procedural descriptionand a definition of the network requirements.The concept of a digital transmission system is used in order to describe the characteristics of animplementation, using a specific medium, in support of the access digital section.4.2ApplicationThe basic access digital section may be applied as given in figure 2 for:-direct access to the local exchange (V1 reference point);-access via a basic access multiplex equipment (V5 interface) to the local exchange;-access via a basic access concentrator (V5 interface) to the local exchange.NOTE:Other applications may also be possible and may be defined in the relevant standard,e.g. flexible access network. However, it is assumed that the functionality of the basicaccess section will be maintained.SIST ETS 300 297 E1:2003

Page 12ETS 300 297: May 1995 TETNT1(note 2)access digital section(note 2)access digital sectionTETETNT1NT1LTLT(note 2)access digital sectionV1MultiplexerConcentrator(note 3)V5ETETETLTLocal exchange(note 1)V1(note 3)V5TV1NOTE 1:The LT may be integrated together with the ET or separate (as integral part or outsideof the local exchange).NOTE 2:An access digital section using a digital transmission system for metallic pairs theapplication of one regenerator may be foreseen.NOTE 3:Local and remote applications are envisaged. For the remote case, a transparent linkbetween the remote multiplexer or concentrator and the local exchange shall be used.NOTE 4:Depending of the functionality implemented in the multiplexer or concentrator theremay be a part of the ET function implemented in this equipment.Figure 2: Examples of equipment configuration in the ISDN basic accessThis model includes primitive procedures between ET layer 1, ET layer 2 and system management:a)ETS 300 012 [6] and ETS 300 125 [2] interactions between ET layer 1 and ET layer 2 and systemmanagement based on PH and MPH primitives, respectively, as defined in ETS 300 012 [6]. Theseinteractions are for the support of functions specified in ETS 300 125 [2];b)interactions between ET layer 1 and system management for the support of functions associatedwith the access digital section, based on MPH primitives.The primitive procedures within TE comply with the specification according to ETS 300 012 [6].This model does not constrain layer 1 arrangements between LT and NT1, (it is also applicable to remoteaccess as shown in figure 2), or the digital transmission system technology.SIST ETS 300 297 E1:2003

Page 13ETS 300 297: May 19954.3Modelling and relationship between the access digital section and the ETPH primitivesaccording toETS 300 012PH primitivesaccording toETS 300 012B channelsMPH primitivesaccording to ETS 300 012MPH primitivesaccording to ETS 300 012INFOs(note 1)MPH primitivesassociated with line systemTSIGs (note 2)Digital transmissionsystem(note 1)TElayer 1NT1LTETlayer 1B channels(note 2)
FEs access digital sectionV1System management (note 3)TE layer 2ET layer 2System management (note 3)NOTE 1:The digital transmission system refers to a digital line transmission system using eithera metallic pair of wires, optical fibre or radio system.NOTE 2:SIG, Function Element (FE) and primitives refer to an exchange of information. Theydo not imply any specific coding nor implementation. Some of these functions may beterminated in the LT and do not pass through the digital transmission system.NOTE 3:The term system management corresponds to both system management and layermanagement as defined in CCITT Recommendation Q.940 (see also clause A.1 ofthis ETS).Figure 3: General model of ISDN customer access layer 1 and adjacent entitiesThe general model shown in figure 3 depicts the whole ISDN customer access layer 1 and adjacententities, and provides the basis to describe the functions performed by the access digital section andthose performed by TE, ET and system management and how various functions are grouped. Inparticular, according to this model, the activation/deactivation procedures and maintenance functionsspecified in this ETS are not confined to functions performed by the access digital section but includefunctions associated with ET layer 1.SIST ETS 300 297 E1:2003

Page 14ETS 300 297: May 19955FunctionsFigure 4 shows the functions which need to be supported by the basic access digital section.T reference pointAccess Digital SectionV
reference point1 B-ChannelsD-ChannelBit timingOctet timingActivation (note)Deactivation (note)Power feedingOperation andMaintenanceNOTE:The activation and deactivation functions are concerned with the operation of theaccess digital section and the user-network interface. However, for consistency withETS 300 012 [6], they are described as separate functions.Figure 4: Functions supported in the access digital section5.1B-channelThis function provides, for each direction of transmission, two independent 64 kbit/s channels for use asB-channels (as defined in CCITT Recommendation I.412 [1]).5.2D-channelThis function provides, for each direction of transmission, one D-channel at a bit rate of 16 kbit/s (asdefined in CCITT Recommendation I.412 [1]).5.3Bit timingThis function provides bit (signal element) timing to enable the receiving equipment to recover informationfrom the aggregate bit stream. For the V1 reference point, the bit timing function is used for both transmitand receive data.5.4Octet timingThis function provides 8 kHz octet timing for the B-channels.SIST ETS 300 297 E1:2003

Page 15ETS 300 297: May 19955.5Activation5.5.1Activation from ETThis function places all the functions of the access digital section into a normal operating mode andsupports the activation of the interface at the T reference point according to ETS 300 012 [6]. This takesinto account:-power down mode;-initial power up;-a failure condition.The procedures and exchange of information are described in clause 8 of this ETS.An activation should be possible to a state which allows maintenance actions to be performed in theaccess digital section even when there is no customer equipment connected to the T reference point.5.5.2Request for activation from TEThis function supports activation of the access digital section and of the interface at the T reference pointaccording to ETS 300 012 [6].5.6DeactivationThis function is specified in order to permit the interface at the T reference point and the access digitalsection or the T reference point only to be placed in a low power consumption mode. The procedures andexchange of information are described in clause 8 of this ETS.Deactivation should be initiated only by the ET.5.7Power feedingThis function provides for remote power feeding of NT1. This function is dependent on the transmissionmedium used. The power feeding through the interface at the T reference point is defined inETS 300 012 [6].5.8Operation and maintenanceThis function supports required actions and information for operating and maintaining the access digitalsection controlled by the ET as defined in ETR 001 [3].Four categories of functions have been identified:-commands regarding LT, regenerator, or NT1;-information from LT, regenerator, or NT1;-indications of fault conditions;-control of access digital section power feeding.6Signal transfer delayThe mean one-way delay between the T and V1 reference points shall not exceed 1 250 ms when noregenerator is implemented. In accordance with CCITT Recommendation G.114 [5], this value is themean of the propagation times in the two directions of transmission.SIST ETS 300 297 E1:2003

Page 16ETS 300 297: May 19957Jitter7.1Output/input jitter at the T reference pointThe requirements are specified in ETS 300 012 [6], subclause A.8.3.7.2Jitter at V1 reference pointJitter on timing signals provided at V1 reference point to the LT shall be limited to values which do notrequire jitter reduction in the LT.Jitter limits at the V1 reference point from LT are not required, because the timing at the V1 referencepoint is defined as contra-directional.Jitter requirements additional to those given in CCITT Recommendation G.960 [7], § 4.4.2 are systemdependent and outside the scope of this ETS and may be as defined in ETR 080 [8].8Activation/deactivation8.1Functional capabilitiesThe access digital section provides the layer 1 signalling capability and the necessary procedures toenable the installations described in subclauses 8.1.1 and 8.1.2.8.1.1Customer installation at the user side of the T reference pointTo activate the layer 1 of the user-network interface at the T reference point and, if not already activated,at the access digital section.8.1.2Installation at the network side of V1 reference pointInstallation at the network side of V1 reference point to:a)activate:1)the layer 1 of the user-network interface at the T reference point and, if not already activated,at the access digital section (this activation is related to call control); or2)the access digital section partially (this activation is related to controlling the configuration ofthe access: it is a network option);b)deactivate:1)the layer 1 of the user-network interface at the T reference point and at the access digitalsection; or2)the layer 1 of the user-network interface at the T reference point only.SIST ETS 300 297 E1:2003

Page 17ETS 300 297: May 1995(DS states. timer T2)DS state machineETlayer 1statemachine(ET states.timer T1)ETlayer 2ETS 300 012ETS 300 012Primitivesaccess digital sectionFEsTRelated tocall controlRelated toconfigurationcontrolRelated toloopbackcontrolAdditionalAdditionalV1System
managementFigure 5: State machinesThe functional capabilities defined in subclause 8.1.2 a2) allow maintenance actions in the access digitalsection which do not affect the deactivated user-network interface at the T reference point to beperformed. If required in some applications, they also permit the access digital section to be placed in amode where the full information transfer capability is available while the user-network interface at the Treference point remains deactivated.The procedures for the activation or deactivation of the layer 1 of the user-network interface at the Treference point comply with the ETS 300 012 [6], annex A, table A.1, subclause A.6.2. These proceduresare based on a set of INFO signals as defined in ETS 300 012 [6] (annex A, table A.1, subclause A.6.2).The procedures at the V1 reference point are based on a set of Function Elements (FEs). These FEs havespecific relationships to primitives between the ET layer 1 and ET layer 2, and ET layer 1 and systemmanagement for the activation or deactivation of the layer 1 of the user-network interface in accordancewith ETS 300 012 [6], annex A, table A.1, subclause A.6.2 and ETS 300 125 [2]. The means for definingthese interactions are the primitive procedures (see annex A, table A.1, subclause A.6.2.1.6 ofETS 300 012 [6]) based on a set of PH and MPH primitives.8.2Modelling8.2.1GeneralThe model for activation/deactivation procedures is given in subclause 4.3.It is recognised that activation/deactivation is a process between subscriber installation and localexchange, requiring appropriate functionality at both ends. The model contained in subclause 4.3 includesthe functional blocks relevant to activation/deactivation and depicts the primitives related to theactivation/deactivation procedures.SIST ETS 300 297 E1:2003

Page 18ETS 300 297: May 19958.2.2Partitioning of functionsETS 300 012 [6] defines the network side of the user-network interface at the T reference point as onefunctional block which supports the layer 1 activation/deactivation procedures across the T reference pointand the primitive procedures at the ET layer 1/ET layer 2 boundary and ET layer 1/system managementboundary. This block includes the functional groupings NT1, LT and ET layer 1.This concept is described in terms of a state machine, called the G state machine in ETS 300 012 [6].MPH-AIMPH-DIMPH-DRMPH-primitives foraccess digital sectionDS state machine(DS states. timer T2)ET layer 2LT statemachine(LT states)NT1 statemachine(NT states)SIGs(ET states.timer T1)ET layer 1statemachineaccess digital sectionSystemmanagementDeactivationprocedureaccording to CCITTRecommendationI.441, Appendix IIIV1V1TTFEsINFOsPH-ARPH-AIPH-DIFigure 6: Partitioning of the access Digital Section (DS) state machineIn order to describe the relationship between signals across the user-network interface at the T referencepoint and function elements across reference point V1, and the relationship between function elementsacross reference point V1 and primitives, two state machines are defined. One in the access digitalsection (DS state machine), and one at the network side of the V1 reference point (ET layer 1 statemachine). Figure 5 illustrates this approach.In addition to primitives defined in ETS 300 012 [6] and in ETS 300 125 [2] related to call control, figure 5also introduces a new set of primitives related to configuration control and the control of loopbacks.Partitioning of activation/deactivation procedures between two state machines is used for the convenienceof easy and accurate description. The ET layer 1 state machine is to be viewed as conceptual and doesnot imply any particular implementation.However, in order to implement a customer access the DS state machine shall be partitioned further.Figure 6 shows the partition of the DS state machine into NT1 state machine (NT-states) and LT statemachine (LT-states).The NT1 state machine supports user-network interface procedure in accordance with ETS 300 012 [6],based on the INFOs, and interacts with the LT state machine by means of a set of signals (SIGs) whichshall be supported by the line transmission system. The LT state machine interacts with the ET layer 1state machine by means of a set of FEs. The ET layer 1 state machine contains those states whichrepresent the local exchange view of the status of the interface at the T reference point and the accessdigital section. It supports the already specified primitive procedures to provide services to ET layer 2 andsystem management in accordance with ETS 300 012 [6], and additional primitive procedures for thesupport of functions associated with the access digital section.8.2.3Location of timer T2The exact location of timer T2 within the access digital section has no impact on the description of the DSstate machine.SIST ETS 300 297 E1:2003

Page 19ETS 300 297: May 19958.3Activation/deactivation proceduresThe procedures allow the activation/deactivation of the user-network interface at the T reference point.The activation may be invoked by either side while deactivation can only be invoked by the network. Theoverall activation/deactivation procedures can be divided into two classes:a)basic procedures for call control used to activate the access digital section;b)procedures to control loopbacks.8.3.1Basic characteristics of the procedures8.3.1.1PriorityPriority refers to contention resolution between activation/deactivation requests which have been invokedconcurrently.If contention between conflicting activation/deactivation requests from ET side and user side occurs it isresolved in the DS state machine. Table 1 shows the DS state machine priority order.8.3.1.2System managementSome assumptions related to the system management are described in annex A.8.3.1.3LoopbacksIn case a transparent loopback 2 is applied, the NT1 shall send INFO 4 frames toward the user with the D-echo-channel set to binary ZERO.With a transparent loopback 1, the NT1 (when able to activate the user-network interface at the Treference point) shall send INFO 4 frames towards the user with the D-echo-channel set to binary ZEROor operating normally.Table 1: Priority order of request in the DS state machineType of requestPriority orderCall control activation request from ET side2 (highest)Call control activation request from user side1access digital section partial activation/deactivation requestfrom the ET side0 (lowest)8.3.1.4Protection of layer 2 framesAccording to ETS 300 012 [6] annex A, table A.1, subclause A.6.2.6.1, a TE is allowed to take up to 100ms to synchronise on INFO 2, no lower time limit is defined. The different time each TE may take tosynchronise on INFO 2 affects the offering of an incoming call in layer 1 multiple terminal arrangements.The fastest TE notifies the network that the access is activated and the message offering the incomingcall (SET-UP) may be transmitted (TE ready to receive the message) while other TEs are not yet ready toreceive the message.This could result in the slow TEs losing all, or part of, the incoming messages (layer 2 frames).Concerning the full activation procedure, reference is made to CCITT Recommendation G.960 [7], table 2,note 5 and to CCITT Recommendation I.430 [9], table 6, note 4, where some information concerning layer1 methods to protect layer 2 frames can be found. With regard to partial activation, the notification of thereceipt of INFO3 by the NT to the ET could be delayed either by the definition of the procedure or adefinite timer value to reduce the risk of a loss of layer 2 message.8.3.1.5Structure of the tablesThe DS state transition table is structured such that the two classes of the activation/deactivationprocedures described at the beginning of subclause 8.3 are clearly separated.SIST ETS 300 297 E1:2003

Page 20ETS 300 297: May 19958.4Description of the state transition table8.4.1Access digital section states (DS-states)Defined below are the states that the access digital section may enter as a result of INFOs received fromthe user across the T reference point, FEs received from the ET across the V1 reference point, or internalevents. They are classified according to the functionality they support as follows:a) DS 1.X states for the support of functionality according to ETS 300 012 [6];b) DS 2.X states for the support of functionality related to loopbacks;c)DS 3.X states for the optional support of functionality related to partial activation of the accessdigital section (as defined in annex B).8.4.1.1State DS 1.0 (access deactivated)The access digital section is in its non-operational mode. INFO 0 is sent to the user and FE
6 is sent tothe ET. Viewed from the user side of the T reference point, the network is in state G1 according toETS 300 012 [6], annex A, table A.1, subclause A.6.2.1.2.1.8.4.1.2State DS 1.1 (access activation initiated)Activation of the access digital section has been requested either by the receipt of FE
1 from the ET or bythe receipt of INFO 1 from the user. The first stage of activation, namely, the activation of the digitaltransmission system, has been initiated. INFO 0 is sent to the user and FE
2 is sent to the ET. Viewedfrom the user side of the T reference point, the network is in state G1 according to ETS 300 012 [6],annex A, table A.1, subclause A.6.2.1.2.1.8.4.1.3State DS 1.2 (access activation: DS synchronised LT --> NT)In this second state of the access digital section activation, the NT has been synchronised with the LT.INFO 2 is sent to the user and FE
2 is sent to the ET while the DS is synchronising NT®LT. Viewed fromthe user side of the T reference point, the network is in state G2 according to ETS 300 012 [6], annex A,table A.1, subclause A.6.2.1.2.2.8.4.1.4State DS 1.3 (access activation: DS activated)In this third stage of the access digital section activation, the DS has been synchronised in both directions.INFO 2 continues to be sent to the user, but FE
3 is sent to the ET while the receipt of INFO 3 from theuser is awaited. Viewed from the user side of the T reference point, the network is in state G2 according toETS 300 012 [6], annex A, table A.1, subclause A.6.2.1.2.2.8.4.1.5State DS 1.4 (access activated)The access digital section is in its stable active state, INFO 3 having been received from the user. FE
4 issent to the ET and INFO 4 is sent to the user (see note 4 to table 2). Viewed from the user side of the Treference point, the network is in state G3 according to ETS 300 012 [6], annex A, table A.1, subclauseA.6.2.1.2.3.8.4.1.6State DS 1.5 (LOS/LFA at T)The signal or frame alignment has been lost on the user side of the T reference point while the accessdigital section is in its stable active state. This may have been caused, for example, by the temporaryremoval of the terminal (the terminal portability facility). INFO 2 is sent to the user to assist rapidresynchronization of the terminal, and FE
12 is sent to the ET while awaiting either the receipt of INFO 3from the user, or FE
5 from the ET (instruction to deactivate). Viewed from the user side of the Treference point, the network is in state G2 according to ETS 300 012 [6], annex A, table A.1, subclauseA.6.2.1.2.2. Upon receipt of INFO 3 from the user, the access digital section returns to state DS 1.4.SIST ETS 300 297 E1:2003

Page 21ETS 300 297: May 19958.4.1.7State DS 1.6 (access deactivation initiated)The access digital section has been instructed by the ET to deactivate by the receipt of FE
5. The FE sent to the network is identical to the FE
sent prior to the issue of FE
5 from the network and INFO 0 issent to the user. Viewed from the user side of the T reference point, the network is in state G4 accordingto ETS 300 012 [6], annex A, table A.1, subclause A.6.2.1.2.4. Upon the receipt of INFO 0 from the user,the deactivation of the DS or the expiry of timer T2, the access digital section changes to state DS 1.0.8.4.1.8State DS 1.7 (defect condition)Loss of Signal/Loss of Frame Alignment (LOS/LFA) has occurred on the transmission system, or powerhas been lost at the NT. The defect condition is reported to the ET by sending FE
7. The INFO sent to theuser shall depend on the NT state prior to the defect condition. Viewed from the user side of the Treference point, the network is in the same G state prior to the defect condition according toETS 300 012 [6], annex A, table A.1, subclause A.6.2.1.2. Upon the receipt of FE
5 from the ET, theaccess digital section changes to state DS 1.0.8.4.1.9State DS 2.0 (loopback 1 or 1a initiated)Activation of loopback 1 or 1a has been requested by the receipt of FE
9 or FE
10 respectively from thenetwork. Activation has been initiated and FE
2 is sent to the ET.8.4.1.10State DS 2.1 (loopback 1 or 1a activated)The appropriate loopback is in its stable state. FE
4 is sent to the ET. The control of the NT is not part ofthe loopback procedure, so the INFO sent to the user cannot be defined.8.4.1.11State DS 2.2 (loopback 2 initiated)Activation of loopback 2 has been requested by the receipt of FE
8 from the network. Activation has beeninitiated and FE
2 is sent to the ET.8.4.1.12State DS 2.3 (DS synchronised LT --> NT)NT has recognised the request of loopback 2. INFO2 is sent in the user direction.8.4.1.13State DS 2.4 (DS activated)NT has recognised looped back INFO 2, acting in this case as INFO 3 for normal activation. FE
3 is sentto the ET.8.4.1.14State DS 2.5 (loopback 2 activated)NT sends INFO 4 frames as described in subclause 8.3.1.3. FE
4 is sent to the ET.8.4.2Set of signals sent across the T reference pointThe INFO signals used in the activation/deactivation of
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