SIST ETS 300 752:2001

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Radio Equipment and Systems (RES); Terrestrial Flight Telecommunications System (TFTS); Packet mode data49.060Aerospace electric equipment and systems33.060.20Sprejemna in oddajna opremaReceiving and transmitting equipmentICS:Ta slovenski standard je istoveten z:ETS 300 752 Edition 13SIST ETS 300 752:2001en01-IHEUXDU-20013SIST ETS 300 752:2001SLOVENSKI
STANDARD
EUROPEAN ETS 300 752TELECOMMUNICATION September 1997STANDARDSource: RES Reference: DE/RES-05-01/2ICS:33.020Key words:Aeronautical, data, packet mode, radio, TFTSRadio Equipment and Systems (RES);Terrestrial Flight Telecommunications System (TFTS);Packet mode dataETSIEuropean 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 4 92 94 42 00 - Fax: +33 4 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 1997. All rights reserved.SIST ETS 300 752:2001

Page 2ETS 300 752: September 1997Whilst 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 300 752:2001

Page 3ETS 300 752: September 1997ContentsForeword.71Scope.92Normative references.93Abbreviations.103.1Definitions.103.2Abbreviations.103.3Symbols.114Service definition.114.1Packet mode services.115Network architecture.125.1Support of multiple network layer protocols.125.2Data transmission.125.3AT functionality.135.3.1Interworking function.135.3.2Location registration procedure.135.3.3Dynamic resource management.135.4GSS functionality.135.4.1Administrative aspects.145.4.1.1Data call phases and activities.145.4.1.2Collection of data for call charging.155.5CIF functionality.155.5.1Interworking with GSSs.165.5.2TFTS packet messages conversion.165.5.3Address conversion.166End to end data flow.176.1CALL management procedures.176.1.1AT originated call establishment.176.1.2CIF originated call establishment.176.1.3Data transfer.186.1.4Handover procedures.186.1.5Call clearing procedures.186.2Scenarios.187AT to GSS interface aspects.187.1General.187.2Layer 2 aspects.197.3AT location registration procedure.207.4Data transfer services provided by signalling layer 3 on the AT side.207.4.1General.207.4.2Service states at the AT side of the AT-GSS interface.217.5Data transfer services provided by signalling layer 3 on the GSS side.217.5.1General.217.5.2Service states at the GSS side of the AT-GSS interface.217.6Dynamic resource management.227.6.1General.227.6.2Varying throughput transmission.227.6.2.1Aircraft-originated throughput modification.227.6.2.2Ground initiated throughput modification.237.6.3Decision strategy.247.6.3.1Throughput increase.247.6.3.2Throughput decrease.25SIST ETS 300 752:2001

Page 4ETS 300 752: September 19977.7Elementary procedures for packet switched data transfer.257.7.1General.257.7.2DTM states.257.7.2.1Call states at the AT side of the interface (see figure C.1).257.7.2.2Call states at the GSS side of the interface (see figureC.2).257.7.2.3Packet-switched DTM procedures.267.7.3Aircraft location management.267.7.3.1General.267.7.3.2Location registration.267.7.3.2.1General.267.7.3.2.2Connection request.277.7.3.2.3Connection confirmation.277.7.3.2.4Connection rejection.277.7.3.2.5Connection release.277.7.3.3Location update.277.7.4Aircraft originating call establishment procedures.277.7.4.1General.277.7.4.2Call request.287.7.4.3Call connected.287.7.4.4Call rejection.287.7.5Ground originating call establishment procedures.287.7.5.1General.287.7.5.2Call connected.297.7.6Call clearing.297.7.6.1Exception conditions.297.7.6.2Clearing initiated by the AT.297.7.6.3Clearing initiated by the GSS.297.7.6.4Completion of clearing.307.7.6.5Clear collision.307.7.7Miscellaneous procedures.307.7.7.1Data transfer air-to-ground.307.7.7.2Data transfer ground-to-air.307.7.7.3Timer expiry.307.7.7.4Handover.307.7.7.4.1AT side.307.7.7.4.2GSS side.317.7.7.5Resource management.317.7.7.5.1General.317.7.7.5.2Throughput increase.317.7.7.5.3Throughput decrease.327.8Handling of error conditions.337.8.1General treatment of error conditions.337.8.2Message type error.337.8.3Mandatory information element error.337.9Message functional definitions and contents.347.9.1DTM messages.347.9.1.1Connect.347.9.1.2Disconnect.357.9.1.3Packet data transfer (PD1).357.9.1.4Packet data transfer (PD2).367.9.2Supplementary RRM messages.367.9.2.1Throughput modification request.367.9.2.2Throughput modification command.377.9.2.3Throughput modification reject.377.10General message format and information elements coding.377.10.1Overview.387.10.2Protocol discriminator.387.10.3Transaction identifier.387.10.4Message type.387.10.5Supplementary RRM information elements.397.10.5.1Capacity request.397.10.5.2Slot allocation.40SIST ETS 300 752:2001

Page 5ETS 300 752: September 19977.10.6DTM information elements.407.10.6.1DTM-cause.407.10.6.2Data information.417.11List of system parameters.417.11.1Timers for data transfer on the AT side.417.11.2Timers for data transfer on the GSS side.417.12Definition of primitive parameters.427.12.1Primitive parameters for DTM.427.12.2Additional primitive parameters for the RR service.428Interworking at the GSS.438.1General.438.2Relay function description.438.3DTM states at the GSS side of the AT-GSS and GSS-CIF interfaces.439GSS to CIF interface aspects.449.1General.449.2Data transfer services provided by signalling layer 3 on GSS side.449.2.1General GSS.449.2.2Service state diagram GSS.459.3Data transfer services provided by signalling layer 3 on the CIF side.459.3.1General.459.3.2Service state diagram CIF.459.4Elementary procedures for packet switched DT.469.4.1Overview.469.4.1.1General.469.4.2DTM states.469.4.2.1Call states at the GSS side of the interface.469.4.2.2Call states at the CIF side of the interface.469.4.2.3Packet-switched DTM procedures.479.4.3GSS originating call establishment procedures.479.4.3.1Call request.479.4.3.2Call connected.479.4.4CIF originating call establishment procedures.489.4.4.1Call request.489.4.4.2Call connected.489.4.5Call clearing.489.4.5.1Clearing initiated by the CIF.489.4.5.2Clearing initiated by the GSS.499.4.5.3Completion of clearing.499.4.6Miscellaneous procedures.499.4.6.1Data transfer GSS-to-CIF.499.4.6.2Data transfer ground to air.499.4.6.3Handover.499.4.6.3.1GSS side.499.4.6.3.2CIF side.509.5Handling of error conditions.509.5.1General treatment of error conditions.509.5.2Message type error.509.5.3Mandatory information element error.509.6Message functional definitions and contents.519.6.1X.25 layer 3 sublayer.519.6.2Data transfer management sublayer.519.6.2.1Message type.519.6.2.2Packet data transfer (PD1).529.6.2.3Packet data transfer (PD2).529.6.2.4Connect.529.6.2.5Disconnect.529.7General message format and information elements coding.539.7.1CIF indicator.539.7.2DTM cause.539.7.3Data information.549.8List of system parameters.54SIST ETS 300 752:2001

Page 6ETS 300 752: September 19979.8.1 Timers for data transfer on the GSS side.549.8.2Timers for data transfer on the CIF side.549.9Definition of primitive parameters.55Annex A (informative):Information on expected usage of data service.56A.1Status update information.56A.2File transfer.56A.3Information update.56A.4Interactive services.56Annex B (informative):Scenarios.57Annex C (informative):SDL of TFTS layer 3 DTM processes.74History.125SIST ETS 300 752:2001

Page 7ETS 300 752: September 1997ForewordThis European Telecommunication Standard (ETS) has been produced by the Radio Equipment andSystems (RES) Technical Committee of the European Telecommunications Standards Institute (ETSI).Transposition datesDate of adoption:5 September 1997Date of latest announcement of this ETS (doa):31 December 1997Date of latest publication of new National Standardor endorsement of this ETS (dop/e):30 June 1998Date of withdrawal of any conflicting National Standard (dow):30 June 1998SIST ETS 300 752:2001

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Page 9ETS 300 752: September 19971ScopeThis European Telecommunication Standard (ETS) deals with the procedures allowing the technicalrealization of packet mode data with the Terrestrial Flight Telecommunications System (TFTS)environment using transparent network support according to the teleservice definitions contained inETS 300 326-1 [1].The TFTS packet data transmission services build on the existing architecture defined in ETS 300 326 [1], [2]and [3] introducing a new network function termed the Centralised Interworking Function (CIF). The selectionof a networking protocol, and its definition is outside the scope of this ETS. The use of a particularprotocol does not constrain the actual implementation of CIF functionality.Transport layer aspectsIn order to ensure the resolution of lost or duplicated packets arising from handover, it is assumed that thehigher layers implement an end to end acknowledgement function.2Normative referencesThis ETS incorporates by dated and undated reference, provisions from other publications. Thesenormative references are cited at the appropriate places in the text and the publications are listedhereafter. For dated references, subsequent amendments to or revisions of any of these publicationsapply to this ETS only when incorporated in it by amendment or revision. For undated references the latestedition of the publication referred to applies.[1]ETS 300 326-1: "Radio Equipment and Systems (RES); Terrestrial FlightTelephone System (TFTS); Part 1: Speech services, facilities andrequirements".[2]ETS 300 326-2 (1996): "Radio Equipment and Systems (RES); Terrestrial FlightTelephone System (TFTS); Part 2: Speech services, radio interface".[3]ETS 300 326-3: "Radio Equipment and Systems (RES); Terrestrial FlightTelephone System (TFTS); Part 3: Speech services, network aspects".[4]ITU-T Recommendation X.25: "Interface between Data Terminal Equipment(DTE) and Data Circuit-terminating Equipment (DCE) for terminals operating inthe packet mode and connected to public data networks by dedicated circuit".[5]ITU-T Recommendation X.121: "International numbering plan for public datanetworks".[6]ARINC Characteristic 746-4: "Cabin Communication Systems (CCS)".[7]ISO 9577: "Information technology - Protocol identification in the network layer".[8]ITU-T Recommendation Q.931: "Digital subscriber Signalling System No. 1(DSS1) - ISDN user-network interface layer 3 specification for basic call control".[9]Internet Architecture Board RFC 791: "Internet Protocol - DARPA InternetProgram protocol specification".[10]Internet Architecture Board RFC 793: "Transmission Control Protocol - DARPAInternet Program protocol specification".SIST ETS 300 752:2001

Page 10ETS 300 752: September 19973Abbreviations3.1DefinitionsFor the purposes of this ETS, the following definitions apply:Ba channel: A channel which carries either:-a 9,6 kbit/s bit stream with an error structure and transmission delay suitable to carry voiceencoded information; or-a bit stream at a gross rate of 9,6 kbit/s with an error structure and transmission delayadapted to a wider range of services.La channel: A channel with a gross data rate of 2,4 kbit/s.Ma channel: A channel with a gross data rate of 4,8 kbit/s.PACKET DATA TRANSFER: The mechanism of transporting messages between the avionic terminationand the ground station system.Ua interface: The interface between the Avionic Termination (AT) and the Ground Station System (GSS)(ETS 300 326-2 [2]).3.2AbbreviationsFor the purposes of this ETS, the following abbreviations apply:ACARSAircraft Communications, Addressing and Reporting SystemASAircraft StationATAvionic TerminationATEIAvionic Termination Equipment IdentifierBCCH(D)Broadcast Control CHannel (Data)CCCall ControlCIFCentralised Interworking FunctionCMConnection ManagementCTUCabin Telecommunication UnitDCCHDedicated Control CHannelDTData TransmissionDTMData Transmission ManagementDTM-SAPData Transmission Management Service Access PointFACCHFast Associated Control CHannel (a case of a DCCH)FCTFlow Control ThresholdGSGround StationGSCGround Switching CentreGSICGround Station Identity CodeGSSGround Station SystemIEInformation ElementIEIInformation Element IdentifierIPIInitial Protocol IdentifierMFMandatory with Fixed lengthMN-SAPMobile Network Service Access PointMVMandatory with Variable lengthOFOptional with Fixed lengthOVOptional with Variable lengthPSDNPacket Switched Data NetworkRRRadio ResourcesRRMRadio Resource ManagementSACCHSlow Associated Control CHannel (a case of a DCCH)SAPService Access PointSAPIService Access Point IdentifierSDLSystem Description LanguageSIST ETS 300 752:2001

Page 11ETS 300 752: September 1997TCTThroughput Control ThresholdTETerminal EquipmentTFTSTerrestrial Flight Telecommunications SystemTITransaction IdentifierVCVirtual CircuitX.25 RNRX.25 [4] Receiver Not Ready messageX.25 RRX.25 [4] Receiver Ready message3.3SymbolsFor the purposes of this ETS, the following symbols apply:bpsbits per secondclrclearcnfconfirmconnconnectionCONNCONNECTDISCDISCONNECTest establishindindicationkbit/skilobits per secondPDPacket Datapendpendingrelreleasereqrequestrespresponsetranstransport4Service definitionThis ETS specifies support for the following data types:-packet transport on the TFTS radio interface.The TFTS packet data transmission service allows an aircraft application to send and receive data in anend-to-end, point-to-point, connection-oriented mode.4.1Packet mode servicesThe types of packet mode services supported by the TFTS packet transport service may include thefollowing:-status update information;-file transfer;-information update;-interactive services.Annex A provides further information.SIST ETS 300 752:2001

Page 12ETS 300 752: September 19975Network architectureThe TFTS packet data transmission services builds on the existing architecture defined in ETS 300 326 [1],[2] and [3] introducing a new network function termed the Centralised Interworking Function (CIF). Thisfunction provides the interworking between the transport mode used between the Avionic Termination (AT)and the Ground Station System (GSS), and that used in the public data network. The interface between theAT and the GSS for the TFTS packet data transmission is defined in clause 7 of this ETS. The interfacebetween the GSS and the CIF is defined in clause 9 of this ETS. The interface between the CIF and thepublic network is not defined in this ETS but is assumed to be compliant with international standards for dataservices and in particular for packet data, e.g. ITU-T Recommendation X.25 [4]. Similarly, the interfacebetween the AT and the aircraft Terminal Equipment (TE) is not defined in this ETS, but is assumed to becompliant with international standards for data services and in particular for packet data, e.g. ITU-TRecommendation X.25 [4] or ARINC Characteristic 746-4 [6].This ETS defines the basic packet transport mechanism required to transport packets from the AT to theGSS and the reverse. It does not address the way in which the end-to-end packet service operates.Figure 1: Packet mode architectureFigure 1 shows the architecture of the system showing the Ua interface defined in ETS 300 326-2 [2],subclause 6.2 figure 5 and a new interface 1d between the GSS and CIF.5.1Support of multiple network layer protocolsThe TFTS packet mode service provides for the transparent transfer of arbitrary binary data betweenonboard avionics equipment and the ground user. The TFTS packet mode service provides no constraintson network protocol used. Typical examples of protocols that may be used are ITU-T RecommendationX.25 [4] and Internet Architecture Board RFC 791 [9] and RFC 793 [10].The interworking between the ground user and the TFTS network is carried out by the CIF. The first octetof the data field defined in subclause 7.9.1 shall be an Initial Protocol Identifier (IPI). IPIs can conform toISO 9577 [7], in which case the message shall conform to subclause 7.9.1.3; or be defined within TFTS, inwhich case the message shall conform to subclause 7.9.1.4.5.2Data transmissionData transmission is managed, both on the Avionic Termination (AT) side and on the ground side by theData Transmission Management (DTM) entity.The Data Transmission Management (DTM) is part of the Connection Management Layer, i.e. upper partof layer 3.To distinguish Call Control (CC) messages, Maintenance Resource messages and Data Transmission(DT) messages, a specific protocol discriminator is used.TEATGSSCIFPSDNTETHIS SPECIFICATIONX.25 OR OTHERX.25 OR OTHERUa1dSIST ETS 300 752:2001

Page 13ETS 300 752: September 1997Maintenance ResourceManagementCall Control ManagementData TransmissionManagementRadio Resources ManagementLayer 2Layer 1Figure 2: Sublayer relationshipFigure 2 illustrates the relationship between the components of layer 3.5.3AT functionality5.3.1Interworking functionThe AT shall provide an interworking function between the application messages and the PACKET DATATRANSFER messages.For air-to-ground transfer, the interworking function shall encapsulate the application message into aPACKET DATA TRANSFER message.For ground-to-air messages the AT shall strip off the PACKET DATA TRANSFER message header andforward the resultant application message to the TE.There are two cases of PACKET DATA TRANSFER message dependent upon the coding standard of theIPI employed (see subclause 7.9.1).5.3.2Location registration procedureThe AT shall carry out the location registration procedure (see subclause 7.7.3) if it is to provide ground-initiated data transfer service.The location registration procedure allows the AT to inform the CIF that it is capable of receiving data. Themessage shall be sent every time the AT selects a new cell.Furthermore, each AT shall also send a periodic location registration message (using the samemechanism) after a pre-defined timeout period (T350).To differentiate between location registration messages and other services a specific IPI value is used asspecified in table 11.The mandatory contents of the location registration message is defined in subclause 7.9.1.4 with the IPIidentifying the TFTS location registration protocol.The location registration procedure is optional. However, the functionality required for the support of thisprocedure shall be implemented in all equipment. It shall be possible to enable and disable the locationregistration functions defined in this ETS in both airborne and CIF equipment in service.5.3.3Dynamic resource managementThe AT shall dynamically manage Radio Resources (RR) in conjunction with the GSS based on theamount of traffic. This shall be achieved using the mechanism defined in subclause 7.6.5.4GSS functionalityThe GSS shall provide a gateway function between the AT and the CIF.On the air interface side (Ua), when receiving a PACKET DATA TRANSFER message (seesubclause 9.6.2.2 or subclause 9.6.2.3), the GSS function shall extract the user data transferred andencapsulate it in the corresponding PACKET DATA TRANSFER message (see subclause 9.6.2.2 or9.6.2.3) before sending it on the ground interface.SIST ETS 300 752:2001

Page 14ETS 300 752: September 1997On the ground interface side, when a PACKET DATA TRANSFER message is received, the GSS functionshall extract the user data transferred and encapsulate it in the corresponding PACKET DATATRANSFER message and send it on the air interface.The GSS shall establish, upon request, a Virtual Circuit (VC) for each AT and maintain this until it receivesa clear down message or internal time-out.Routing to the appropriate aircraft shall be achieved by the one-to-one mapping between AT and VC.For air to ground calls the VC shall be established on receipt of the first PACKET DATA TRANSFERmessage from a particular aircraft. All subsequent PACKET DATA TRANSFER messages to or from aparticular AT shall be passed over this virtual circuit.For ground to air calls to registered aircraft, if no VC is present then the GSS shall accept the requestfrom the CIF for establishment of a VC.Additional functionality is required if no RR are available. The GSS shall buffer the first message receivedfrom the CIF whilst it sends a PAGE REQUEST message to the AT alerting it that it has data for it. Once aDedicated Control CHannel (DCCH) is established the GSS shall forward the PACKET DATA TRANSFERmessage to the aircraft.The GSS shall dynamically manage RR in collaboration with the AT based on the amount of traffic. Thisshall be achieved using the mechanism defined in subclause 7.6 of this ETS.5.4.1Administrative aspects5.4.1.1Data call phases and activitiesA chargeable packet data call is assumed to begin when an aircraft first makes contact with the groundstation network in order to log on to the CIF which handles its interface between the GSS and ground datanetworks. The call ends when the aircraft is no longer accessible to the ground network and its associatedVC between GSS and CIF has been cleared. During this time, the GSS may repeatedly establish andclear RR as required in order to allow transmission of data packets between the aircraft and the groundnetwork. The following diagram gives an example of how resources might be used during a packet datacall:Aircraft logged on to CIF and X.25 VCestablished between GSS and CIFTimeAircraftCallRequestCallReleasedTotal duration of packet callResourcesAllocatedDataTransResourcesAllocatedDataTransResourcesAllocatedDataTransFigure 3: Phases of a packet data callThe phases of a packet data call are illustrated in figure 3.SIST ETS 300 752:2001

Page 15ETS 300 752: September 19975.4.1.2Collection of data for call chargingThe GSS shall collect call data for use for billing. The following paragraphs are for guidance only.Operators may base call charges on a number of factors associated with the above packet data callprofile. The following elements may be identified as cost/utility factors during a call:1)initiation and clearing of a packet data call, including establishment and clearing ITU-TRecommendation X.25 [4] virtual circuits with the CIF;2)occupancy of Slow Associated Control CHannel (SACCH) channels during those phases of a callwhen Radio Resources (RR) are in use;3)occupancy of Fast Associated Control CHannel (FACCH) channels during those phases of a callwhen Radio Resources (RR) are in use;4)amount of data transmitted air to ground and onwards to the CIF;5)amount of data transmitted from the CIF and onwards from the GSS to the aircraft.The occupancy of radio channels may be expressed as the number of seconds a data call occupies agiven class of channel and its bandwidth. For example, use of a SACCH associated with a voice call mayuse no extra RR. Thus, a 9 600 bps channel would accumulate "La seconds" four times faster than a2 400 bps channel. Charges for the use of packet data networks generally depend on the time duringwhich a VC is established and on the amount of data transmitted. This is accounted for in blocks of 64bytes (segments) or kilosegments.The content and format of the call record for data calls are defined by the TFTS Forum.5.5CIF functionalityThe following subclause defines the functionality of the CIF assuming an end-to-end service using astandard networking protocol, such as ITU-T Recommendation X.25 [4].The CIF shall perform the interworking between the TFTS network and public or private data networks.The gateway shall be connected to public and/or private networks as required by the CIF operator andshall have addressing schemes which allow individual aircraft to be called.The CIF shall provide the following functionality:-interworking with the Ground Switching Centre (GSC) network;-conversion between TFTS packet messages and public and/or private message formats;-address conversion between TFTS network addressing and public and/or private networks;-support of dynamic routing tables.The CIF may provide support for:-billing functions;-closed user groups.SIST ETS 300 752:2001

Page 16ETS 300 752: September 1997Figure 4 illustrates the functionality of the CIF.X.25 SwitchTFTS MessageConversionX.25 SwitchDynamicRouting TablesAddressConversionX.25 Call RequestX.25 Data PacketGSC SIDEPDN SIDEFigure 4: CIF functional overview (X.25)5.5.1Interworking with GSSsTogether with the GSSs, the CIF shall manage a set of X.25 [4] Virtual Circuits (VCs) corresponding to theactive set of ATs currently using its facilities. The CIF shall accept VCs requested by GSSs and shallmaintain these until internal processes dictate that they are released. The CIF shall accept requests fromthe GSS to release a VC. The CIF may also establish and release VCs to the GSS.It is possible that two GSSs will set up a virtual circuit for a particular AT (e.g. as the aircraft moves fromthe coverage of one GSS to that of another). Under these circumstances, the CIF shall retain the mostrecently established virtual circuit and clear down the other.Clause 9 of this ETS presents details of the protocol used for communication and data transmissionbetween GSC and CIF.5.5.2TFTS packet messages conversionThe CIF shall convert the TFTS message format into the format required for communication on the datanetwork side of the CIF (as opposed to the TFTS side). On receipt of a data packet from a GSC the CIFshall perform the following procedures:1)remove the PACKET DATA TRANSFER header message (see subclauses 9.6.2.1 and 9.6.2.2);2)examine the contents of the message to determine whether to set up a network data call (in thecase of a Call Request packet) or to route the information to the appropriate port or circuit (if it is adata message).On receipt of a message from a terrestrial user the CIF shall add a PACKET DATA TRANSFER (seesubclauses 9.6.2.2 and 9.6.2.3) message header and envelop the whole message in an X.25 [4] datapacket and forward the resultant packet to the appropriate GSC (determined from the internal dynamicrouting table).5.5.3Address conversionThe CIF shall convert the private aircraft addressing scheme to public or private addressing schemesdepending on the networks used for terrestrial user access. For example, the CIF may convert an aircraftaddress to an X.121 [5] address if using an X.25 [4] Packet Switched Data Network (PSDN). In such acase, the calling DTE address would be changed to one assigned to the CIF by the packet data network.For ground to air calls this procedure shall be reversed.SIST ETS 300 752:2001

Page 17ETS 300 752: September 1997Ground to air callAT <-------> CIFNetwork (note) <----> CIFCalling addressTerminal numberTerminal numberCalled addressPrivate terminal numberPublic terminal addressNOTE:Illustrated assuming X.25 [4] packet data network on terrestrial user side.Figure 5: Ground to air number translationAir to ground callAT <-------> CIFNetwork (note) <----> CIFCalling addressPrivate terminal numberPublic terminal addressCalled addressTerminal numberTerminal numberNOTE:Illustrated assuming X.25 [4] packet data network on terrestrial user side.Figure 6: Air to ground number translationThe CIF shall provide translation between addresses known by the terrestrial network user and the privateaddressing scheme that achieves correct routing to the application on the aircraft. Figures 5 and 6illustrate the number relationships on the ground to air and air to ground calls.6End to end data flow6.1CALL management proceduresThis clause defines the transfer mechanism between the Air Termination (AT) and the CentralInterworking Function (CIF).Two types are defined:-AT originated;-CIF originated.6.1.1AT originated call establishmentWhen the AT receives a request from a higher layer to send packet mode data, it shall establish anappropriate connection to the GSS (see subclause 7.7.4). The GSS responds with the establishment of anappropriate connection to the CIF (see subclause 9.1).6.1.2CIF originated call establishmentWhen the CIF receives a DTM_DATA_REQUEST from a higher layer to send packet mode data, it shallestablish an appropriate connection to the GSS (see subclause 7.4). The GSS responds in one of two waysdepending upon whether or not it has physical resources to the target AT.On receipt of PACKET DATA TRANSFER, the GSS shall determine whether a Data Transmission (DT)connection exists between itself and the target AT.If physical RR exist between the GSS and target AT, the GSS establishes a connection in accordance withsubclause 7.7.5 of this ETS.If physical RR do not exist between the GSS and the target AT, the GSS initiates a page messageaddressing the target AT using procedures defined in clause 10 of ETS 300 326-2 [2] and subclause 7.7.5 ofthis ETS.On receipt of a DTM-PAGE REQUEST for data transmission the AT shall establish RR to the GSS by usingthe Data Transmission (DT) connection establishment as defined in subclause 6.1.1.SIST ETS 300 752:2001

Page 18ETS 300 752: September 19976.1.3Data transferThe AT and GSS shall support transparent transfer of data packets between the aircraft application and theCIF. These processes are illustrated in scenarios 7 and 8 in annex B. This shall be achieved by themechanisms defined in subclauses 7.7.7.1, 7.7.7.2, 9.4.6.1 and 9.4.6.2 of this ETS.6.1.4Handover proceduresWhen a change of cell is necessary, the AT and the network shall ensure that any association betweenthe AT and the CIF shall be maintained. This shall be the case irrespective of whether dedicated RR areallocated to the AT.If dedicated resources are allocated to the AT, these shall be maintained as the AT moves from thecoverage of one cell to another using the handover procedures defined in clause 10 of ETS 300 326-2 [2].Handover aspects specific to the packet data service on the radio interface are defined insubclause 7.7.7.4.The network shall ensure that the flow of packet data between AT and CIF shall be by the most directroute through the TFTS network. This shall be achieved by maintaining only a single GSC in the pathbetween AT and CIF. The procedures for the network handling of handover of TFTS packet dataconnections are defined in subclause 9.4.6.3.6.1.5Call clearing proceduresClearing of packet mode data connections shall be supported in both air-to-ground and ground-to-airdirections. Call clearing procedures shall utilize the Radio Resources Management (RRM) proceduresdefined in clause 10 of ETS 300 326-2 [2]. Clearing of the Radio Resource (RR) shall be as detailed insubclause 7.7.6, whilst clearing of the GSS-CIF resource shall be as described in subclause 9.4.5.6.2ScenariosInformation flows are provided in annex B for the most common scenarios.7AT to GSS interface aspects7.1GeneralOn the AT-GSS layer 3 interface, the TFTS packet Data Transmission (DT) is an additional signallingfunction using the services provided by the layer 2 as defined in clause 9 of ETS 300 326-2 [2].Data Transfer is an additional part of the Connection Management (CM) sublayer as defined insubclause 10.1.1 of ETS 300 326-2 [2].In addition to the objectives and basic groups of functions defined in subclause 10.1.
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