SIST EN 300 937 V8.0.1:2003
(Main)Digital cellular telecommunications system (Phase 2+) (GSM); Data Link (DL) layer; General aspects (GSM 04.05 version 8.0.1 Release 1999)
- Abstract
Upgrade to R99
- Status
- Published
- Publication Date
- 30-Nov-2003
- Current Stage
- 6060 - National Implementation/Publication (Adopted Project)
- Start Date
- 01-Dec-2003
- Due Date
- 01-Dec-2003
- Completion Date
- 01-Dec-2003
SIST EN 300 937 V8.0.1:2003 is the Slovenian adoption of ETSI EN 300 937 V8.0.1, published by SIST for GSM Phase 2+ Release 1999. It specifies the Data Link (DL) layer general aspects for the GSM Dm channel on the mobile station-network radio interface, so engineers can see how layer 3 signalling is carried, prioritized and recovered.
What does SIST EN 300 937 V8.0.1:2003 specify?
SIST EN 300 937 V8.0.1:2003 sets out the general behaviour of LAPDm on the Dm channel and relates it to the GSM radio interface, layer 3 and the physical layer. It is written for the mobile station (MS)-network interface and is organized into six clauses plus one informative annex.
The scope states that the document is an upgrade to R99 and that details are provided in GSM 04.06. The annex gives the change request history.
| Annex | What it covers |
|---|---|
| Annex A | Informative change request history |
What are the key requirements of SIST EN 300 937 V8.0.1:2003?
Clause 3 says LAPDm carries information between layer 3 entities across the GSM PLMN radio interface using the Dm channel. In practice, this is the protocol that moves signalling messages between the MS and the network over the relevant control channels.
Clause 3 also defines two transfer modes: unacknowledged operation and acknowledged multiple frame operation. The BCCH and PCH+AGCH only support unacknowledged operation, while SDCCH, SACCH and FACCH support both. That matters because channel choice determines whether the network can expect acknowledgements and retransmissions.
Clause 4 defines the services offered to layer 3 and those required from the physical layer. It includes priority handling, segmentation in acknowledged mode, and random access support on the RACH. This tells implementers what the link layer must do before a layer 3 message can be sent or accepted.
Clause 4.2.2 gives priority rules, with SAPI 0 taking precedence over SAPI 3 on SDCCH, and specific SACCH priority constraints. In practice, these rules control which signalling traffic is sent first when resources are limited.
Clause 4.2.5 defines the acknowledged multiple frame service using I frames and the SABM establishment procedure, plus suspend, resume, reconnect and release primitives. This is the part that matters when a signalling link must be established, moved to another channel, or closed cleanly.
Clause 5 explains how the data link layer is structured. The Data Link Connection Identifier (DLCI) combines the Service Access Point Identifier (SAPI) and the control channel type, and the layer uses this to deliver each message to the right endpoint.
Clause 6 states which SAPIs and modes are allowed on each channel type. It also fixes the acknowledged-mode window size k to 1 for SAPI 0 and SAPI 3, and requires enough processing capacity to avoid receiver busy states for SAPI 0. In practice, this limits implementation choices and protects signalling reliability.
What terms does SIST EN 300 937 V8.0.1:2003 define?
- LAPDm - Link Access Procedures on the Dm channel; the GSM data link protocol described by this standard.
- Dm channel - The collection of signalling channels used to carry layer 3 information across the GSM radio interface.
- Service Access Point Identifier (SAPI) - The identifier used to select the service access point for a data link connection.
- Data Link Connection Identifier (DLCI) - The identifier for a data link endpoint, built from the SAPI and channel type.
- BCCH - Broadcast Control Channel, used only for network-to-MS broadcast signalling.
- SACCH - Slow Associated Control Channel, one of the dedicated control channels used for signalling.
- RACH - Random Access Channel, used for random access bursts rather than normal LAPDm user transfer.
Who uses SIST EN 300 937 V8.0.1:2003?
SIST EN 300 937 V8.0.1:2003 is used by GSM radio access engineers, protocol implementers, terminal and network equipment designers, and test teams. It is also relevant to quality managers and buyers who need to check whether an implementation supports the correct GSM signalling behaviour on the MS-network interface. Operators use it when validating interoperability, channel handling and signalling capacity in GSM Phase 2+ systems.
What changed in SIST EN 300 937 V8.0.1:2003 from the previous edition?
The change request history notes one substantive change before publication: addition of preemption capability for SAPI 0 in LAPDm. The document was then updated to version 8.0.1 for publication.
Which standards are used with SIST EN 300 937 V8.0.1:2003?
| Reference | What it contributes |
|---|---|
| GSM 01.04 | Abbreviations and acronyms used in the document |
| GSM 04.01 | General layering principles for the GSM MS-BSS interface |
| GSM 04.03 | Channel structures and access capabilities, including control channels |
| GSM 04.04 | Layer 1 general requirements on the radio interface |
| GSM 04.06 | Detailed LAPDm specification referenced for procedures and framing |
| GSM 04.07, GSM 04.08, GSM 04.10, GSM 04.11 | Layer 3 and service specifications that define the signalling carried over LAPDm |
| GSM 07.01, GSM 07.02, GSM 07.03, GSM 07.05, GSM 07.06 | Terminal adaptation and DTE-DCE interface references for related MS functions |
| CCITT X.200, X.210, Q.920, Q.921, X.25 | OSI, ISDN and packet-mode data link concepts used as the protocol basis |
| ISO 3309, ISO/IEC 4335 | HDLC frame structure and procedural elements used by LAPDm |
What does the SIST EN 300 937 V8.0.1:2003 document contain?
The document contains a scope, references, abbreviations, terminology, an overview of LAPDm functions and procedures, service characteristics, data link layer structure, and specific requirements. Figures show the entity and SAP relationships, the primitive exchange model, the reference model, and an example MS configuration. Clause 4 describes service primitives such as DL-UNITDATA, DL-DATA, DL-ESTABLISH, DL-SUSPEND, DL-RESUME, DL-RECONNECT, DL-RELEASE, DL-RANDOMACCESS, PH-DATA and PH-RANDOMACCESS, while Clause 5 explains endpoint identification, distribution and random access handling.
Get Certified
Connect with accredited certification bodies for this standard
ANCE
Mexican certification and testing association.
Intertek Slovenia
Intertek testing, inspection, and certification services in Slovenia.
LNE (Laboratoire National de Métrologie et d'Essais)
French national laboratory for metrology and testing.
Sponsored listings
Frequently Asked Questions
SIST EN 300 937 V8.0.1:2003 is a standard published by the Slovenian Institute for Standardization (SIST). Its full title is "Digital cellular telecommunications system (Phase 2+) (GSM); Data Link (DL) layer; General aspects (GSM 04.05 version 8.0.1 Release 1999)". This standard covers: Upgrade to R99
Upgrade to R99
SIST EN 300 937 V8.0.1:2003 is classified under the following ICS (International Classification for Standards) categories: 33.070.50 - Global System for Mobile Communication (GSM). The ICS classification helps identify the subject area and facilitates finding related standards.
SIST EN 300 937 V8.0.1:2003 is available in PDF format for immediate download after purchase. The document can be added to your cart and obtained through the secure checkout process. Digital delivery ensures instant access to the complete standard document.
Standards Content (Sample)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Digital cellular telecommunications system (Phase 2+) (GSM); Data Link (DL) layer; General aspects (GSM 04.05 version 8.0.1 Release 1999)33.070.50Globalni sistem za mobilno telekomunikacijo (GSM)Global System for Mobile Communication (GSM)ICS:Ta slovenski standard je istoveten z:EN 300 937 Version 8.0.1SIST EN 300 937 V8.0.1:2003en01-december-2003SIST EN 300 937 V8.0.1:2003SLOVENSKI
STANDARD
ETSIEN300937V8.0.1(2000-09)EuropeanStandard(Telecommunicationsseries)Digitalcellulartelecommunicationssystem(Phase2+);DataLink(DL)layer;Generalaspects(GSM04.05version8.0.1Release1999)GLOBALSYSTEMFORMOBILECOMMUNICATIONSRSIST EN 300 937 V8.0.1:2003
ETSIETSIEN300937V8.0.1(2000-09)2(GSM04.05version8.0.1Release1999)ReferenceREN/SMG-020405Q8KeywordsDigitalcellulartelecommunicationssystem,GlobalSystemforMobilecommunications(GSM)ETSI650RoutedesLuciolesF-06921SophiaAntipolisCedex-FRANCETel.:+33492944200Fax:+33493654716SiretN°34862356200017-NAF742CAssociationàbutnonlucratifenregistréeàlaSous-PréfecturedeGrasse(06)N°7803/88ImportantnoticeIndividualcopiesofthepresentdocumentcanbedownloadedfrom:http://www.etsi.orgThepresentdocumentmaybemadeavailableinmorethanoneelectronicversionorinprint.Inanycaseofexistingorperceiveddifferenceincontentsbetweensuchversions,thereferenceversionisthePortableDocumentFormat(PDF).Incaseofdispute,thereferenceshallbetheprintingonETSIprintersofthePDFversionkeptonaspecificnetworkdrivewithinETSISecretariat.Usersofthepresentdocumentshouldbeawarethatthedocumentmaybesubjecttorevisionorchangeofstatus.InformationonthecurrentstatusofthisandotherETSIdocumentsisavailableathttp://www.etsi.org/tb/status/Ifyoufinderrorsinthepresentdocument,sendyourcommentto:editor@etsi.frCopyrightNotificationNopartmaybereproducedexceptasauthorizedbywrittenpermission.Thecopyrightandtheforegoingrestrictionextendtoreproductioninallmedia.©EuropeanTelecommunicationsStandardsInstitute2000.Allrightsreserved.SIST EN 300 937 V8.0.1:2003
ETSIETSIEN300937V8.0.1(2000-09)3(GSM04.05version8.0.1Release1999)ContentsIntellectualPropertyRights.4Foreword.41Scope.51.1References.61.2Abbreviations.72Conceptsandterminology.73OverviewdescriptionofLAPDmfunctionsandprocedures.103.1General.103.2Unacknowledgedoperation.113.3Acknowledgedoperation.113.4Informationtransfermode.113.4.1InformationtransferontheBCCH.113.4.2InformationtransferonthePCH+AGCH.113.4.3InformationtransferontheDCCHs.113.5Releaseofdatalinks.114Servicecharacteristics.124.1General.124.2Servicesprovidedtolayer3.124.2.1General.124.2.2Priority.124.2.3Segmentation.124.2.4Unacknowledgedinformationtransferservice.134.2.5Acknowledgedinformationtransferservices.134.2.6Randomaccessprocedure.144.3Servicesrequiredfromthephysicallayer.154.4Administrativeservices.164.4.1Generaldescriptionofadministrativeservices.164.4.2Definitionofprimitivesforadministrativeservices.165Overviewofdatalinklayerstructure.165.1Functionalcomposition.165.2Identificationofdatalinkendpoints.165.3Datalinkprocedure.175.4Datalinkdistributionprocedure.175.5Randomaccessprocedures.176Specificrequirements.186.1ModeofoperationandallowedSAPIs.186.2Acknowledgedmodeofoperation.196.2.1Windowsize.196.2.2Processingcapacity.19AnnexA(informative):ChangeRequesthistory.20History.21SIST EN 300 937 V8.0.1:2003
ETSIETSIEN300937V8.0.1(2000-09)4(GSM04.05version8.0.1Release1999)IntellectualPropertyRightsIPRsessentialorpotentiallyessentialtothepresentdocumentmayhavebeendeclaredtoETSI.TheinformationpertainingtotheseessentialIPRs,ifany,ispubliclyavailableforETSImembersandnon-members,andcanbefoundinETSISR000314:"IntellectualPropertyRights(IPRs);Essential,orpotentiallyEssential,IPRsnotifiedtoETSIinrespectofETSIstandards",whichisavailablefromtheETSISecretariat.LatestupdatesareavailableontheETSIWebserver(http://www.etsi.org/ipr).PursuanttotheETSIIPRPolicy,noinvestigation,includingIPRsearches,hasbeencarriedoutbyETSI.NoguaranteecanbegivenastotheexistenceofotherIPRsnotreferencedinETSISR000314(ortheupdatesontheETSIWebserver)whichare,ormaybe,ormaybecome,essentialtothepresentdocument.ForewordThisEuropeanStandard(Telecommunicationsseries)hasbeenproducedbyETSITechnicalCommitteeSpecialMobileGroup(SMG).Thepresentdocumentdefinesingeneraltermsthedatalinklayer(layer2)oftheMobileStation(MS)-networkinterfacewithinthedigitalcellulartelecommunicationssystem.TheETSfromwhichthepresentdocumenthasevolvedisPhase2GSMETS300554(GSM04.05version4.0.3).ThecontentsofthepresentdocumentissubjecttocontinuingworkwithinSMGandmaychangefollowingformalSMGapproval.ShouldSMGmodifythecontentsofthepresentdocument,itwillbere-releasedwithanidentifyingchangeofreleasedateandanincreaseinversionnumberasfollows:Version8.x.ywhere:8indicatesRelease1999ofGSMPhase2+.xtheseconddigitisincrementedforallchangesofsubstance,i.e.technicalenhancements,corrections,updates,etc.ythethirddigitisincrementedwheneditorialonlychangeshavebeenincorporatedinthespecification.ThespecificationfromwhichthepresentdocumenthasbeenderivedwasoriginallybasedonCEPTdocumentation,hencethepresentationofthepresentdocumentmaynotbeentirelyinaccordancewiththeETSIdraftingrules.NationaltranspositiondatesDateofadoptionofthisEN:18August2000DateoflatestannouncementofthisEN(doa):30November2000DateoflatestpublicationofnewNationalStandardorendorsementofthisEN(dop/e):31May2001DateofwithdrawalofanyconflictingNationalStandard(dow):31May2001SIST EN 300 937 V8.0.1:2003
ETSIETSIEN300937V8.0.1(2000-09)5(GSM04.05version8.0.1Release1999)1ScopeThepresentdocumentdescribesingeneraltermstheLinkAccessProceduresontheDmchannel,LAPDm.Theapplicationofthisprotocoltootherchanneltypesisforfurtherstudy.DetailsareprovidedinGSM04.06.ThepurposeofLAPDmistoconveyinformationbetweenlayer3entitiesacrosstheGSMPLMNradiointerface(MStonetworkinterface)usingtheDmchannel.NOTE1:ThetermDmchannelisusedforconveniencetodesignatethecollectionofallthevarioussignallingchannelsrequiredintheGSMsystem.SeealsoGSM04.03.ThedefinitionofLAPDmisbasedontheprinciplesandterminologyof:-CCITTRecommendationsX.200andX.210:thereferencemodelforOpenSystemsInterconnection(OSI);-CCITTRecommendationsQ.920andQ.921:thespecificationofLAPDfortheuser-networkinterfaceinISDN;-CCITTRecommendationX.25LAPB:user-networkinterfaceforpacketmodeterminals;and-ISO3309andISO4335:High-levelDataLinkControl(HDLC)standardsforframestructureandelementsofprocedures.LAPDmisaprotocolthatoperatesatthedatalinklayeroftheOSIarchitecture.Therelationshipbetweenthedatalinklayerandotherprotocollayersisdefinedbelow.NOTE2:Theinterfacebetweenthemobilestationandexternalterminalequipment/terminaladaptersisdefinedintheTechnicalSpecificationsoftheGSM07-series.NOTE3:ThephysicallayerontheradiointerfaceisdefinedinGSM04.04andlayer3isdefinedinGSM04.07,04.08,04.10and04.11.ReferenceshouldbemadetotheseTechnicalSpecificationsforthecompletedefinitionsoftheprotocolsandproceduresacrosstheGSMPLMNradiointerface.NOTE4:Theterm"datalinklayer"isusedinthemaintextofthepresentdocument.However,mainlyinfiguresandtables,theterms"layer2"and"L2"areusedabbreviations.Furthermore,inaccordancewithGSM04.07and04.08theterm"layer3"isusedtoindicatethelayerabovethedatalinklayer.LAPDmisindependentofthetransmissionbitrate.ItrequiresphysicalchannelswithcharacteristicsasdefinedinGSM04.03.Section2belowdescribesbasicconceptsusedinthepresentdocumentandGSM04.06.Section3givesanoverviewdescriptionofLAPDmfunctionsandprocedures.Section4summarizestheservicesthatthedatalinklayerprovidestolayer3andtheservicesthatthedatalinklayerrequiresfromthephysicallayer.Section5providesanoverviewofthedatalinklayerstructure.SIST EN 300 937 V8.0.1:2003
ETSIETSIEN300937V8.0.1(2000-09)6(GSM04.05version8.0.1Release1999)1.1ReferencesThefollowingdocumentscontainprovisionswhich,throughreferenceinthistext,constituteprovisionsofthepresentdocument.• Referencesareeitherspecific(identifiedbydateofpublication,editionnumber,versionnumber,etc.)ornon-specific.• Foraspecificreference,subsequentrevisionsdonotapply.• Foranon-specificreference,thelatestversionapplies.• Anon-specificreferencetoanETSshallalsobetakentorefertolaterversionspublishedasanENwiththesamenumber.• ForthisRelease1999document,referencestoGSMdocumentsareforRelease1999versions(version8.x.y).[1]GSM01.04:"Digitalcellulartelecommunicationssystem(Phase2+);Abbreviationsandacronyms".[2]GSM04.01:"Digitalcellulartelecommunicationssystem;MobileStation-BaseStationSystem(MS-BSS)interfaceGeneralaspectsandprinciples".[3]GSM04.03:"Digitalcellulartelecommunicationssystem(Phase2+);MobileStation-BaseStationSystem(MS-BSS)interfaceChannelstructuresandaccesscapabilities".[4]GSM04.04:"Digitalcellulartelecommunicationssystem;Layer1Generalrequirements".[5]GSM04.06:"Digitalcellulartelecommunicationssystem;MobileStation-BaseStationSystem(MS-BSS)interfaceDataLink(DL)layerspecification".[6]GSM04.07:"Digitalcellulartelecommunicationssystem(Phase2);Mobileradiointerfacesignallinglayer3Generalaspects".[7]GSM04.08:"Digitalcellulartelecommunicationssystem(Phase2+);Mobileradiointerfacelayer3specification".[8]GSM04.10:"Digitalcellulartelecommunicationssystem;Mobileradiointerfacelayer3SupplementaryservicesspecificationGeneralaspects".[9]GSM04.11:"Digitalcellulartelecommunicationssystem(Phase2+);Point-to-Point(PP)ShortMessageService(SMS)supportonmobileradiointerface".[10]GSM07.01:"Digitalcellulartelecommunicationssystem(Phase2+);GeneralonTerminalAdaptationFunctions(TAF)forMobileStations(MS)".[11]GSM07.02:"Digitalcellulartelecommunicationssystem(Phase2+);TerminalAdaptationFunctions(TAF)forservicesusingasynchronousbearercapabilities".[12]GSM07.03:"Digitalcellulartelecommunicationssystem(Phase2+);TerminalAdaptationFunctions(TAF)forservicesusingsynchronousbearercapabilities".[13]GSM07.05:"Digitalcellulartelecommunicationssystem(Phase2+);UseofDataTerminalEquipment-DataCircuitterminatingEquipment(DTE-DCE)interfaceforShortMessageService(SMS)andCellBroadcastService(CBS)".[14]GSM07.06:"Digitalcellulartelecommunicationssystem(Phase2);UseoftheVseriesDataTerminalEquipment-DataCircuitterminatingEquipment(DTE-DCE)interfaceattheMobileStation(MS)forMobileTermination(MT)configuration".[15]CCITTRecommendationX.25:"Interfacebetweendataterminalequipment(DTE)anddatacircuit-terminatingequipment(DCE)forterminalsoperatinginthepacketmodeandconnectedtopublicdatanetworksbydedicatedcircuit".SIST EN 300 937 V8.0.1:2003
ETSIETSIEN300937V8.0.1(2000-09)7(GSM04.05version8.0.1Release1999)[16]CCITTRecommendationX.200:"ReferenceModelofOpenSystemsInterconnectionforCCITTApplications".[17]CCITTRecommendationX.210:"OpenSystemsInterconnectionlayerservicedefinitionconventions".[18]CCITTRecommendationQ.920:"Integratedservicesdigitalnetwork(ISDN)user-networkinterface-DatalinklayerGeneralaspects".[19]CCITTRecommendationQ.921:"Integratedservicesdigitalnetwork(ISDN)user-networkinterface-Datalinklayerspecification".[20]ISO3309:"Informationtechnology-Telecommunicationsandinformationexchangebetweensystems-Highleveldatalinkcontrol(HDLC)procedures-Framestructure".[21]ISO/IEC4335:"Informationtechnology-Telecommunicationsandinformationexchangebetweensystems-Highleveldatalinkcontrol(HDLC)procedures-Elementsofprocedures".1.2AbbreviationsAbbreviationsusedinthepresentdocumentarelistedinGSM01.04.2ConceptsandterminologyThegenerallayeringprinciplesusedinthepresentdocumentandotherspecificationsinthe04seriesaregiveninGSM04.01.ThedatalinklayeristhenexttolowestlayeroftheOSIreferencemodel.Thedatalinklayerreceivesservicesfromthephysicallayerandprovidesservicestolayer3.Theservicesprovidedbythedatalinklayerarethecombinationoftheservicesandfunctionsprovidedbyboththedatalinklayerandthephysicallayer.AdatalinklayerServiceAccessPoint(SAP)isthepointatwhichthedatalinklayerprovidesservicestolayer3.TheServiceAccessPointisidentifiedbyaServiceAccessPointIdentifier(SAPI).OneormoredatalinkconnectionendpointscanbeassociatedwitheachdatalinklayerSAP.Seefigure1.Adatalinkconnectionendpointisidentifiedbyadatalinkconnectionendpointidentifier(asseenfromlayer3)andbyaDataLinkConnectionIdentifierDLCI(asseenfromthedatalinklayer).SAPIsandDLCIsusedbyLAPDmaredefinedinsection5.2.Layer3Layer3entityDatalinklayerserviceaccesspointDatalinkconnectionendpointDatalinklayerDatalinklayerentity*Figure1:Entities,serviceaccesspointsandendpointsSIST EN 300 937 V8.0.1:2003
ETSIETSIEN300937V8.0.1(2000-09)8(GSM04.05version8.0.1Release1999)Co-operationbetweendatalinklayerentitiesisgovernedbyapeer-to-peerprotocolspecifictothelayer.Forinformationexchangebetweentwoormorelayer3entities,anassociationmustbeestablishedbetweenthelayer3entitiesinthedatalinklayerusingadatalinklayerprotocol.Thisassociationiscalledadatalinkconnection.DatalinkconnectionsareprovidedbythedatalinklayerbetweentwoormoreSAPs(seefigure2).Layer3entityLayer3entityDatalinklayerserviceaccesspointDatalinkconnectionendpointDatalinkrelationshipFigure2:Peer-to-peerrelationshipDatalinklayermessageunitsareconveyedbetweendatalinklayerentitiesbymeansofphysicalconnection.Layer3requestsservicesfromthedatalinklayerviaserviceprimitives.Thesameappliesfortheinteractionbetweenthedatalinklayerandthephysicallayer.Theprimitivesrepresent,inanabstractway,thelogicalexchangeofinformationandcontrolbetweenthedatalinklayeranditsadjacentlayers.Theydonotspecifyorconstrainimplementations.Theprimitivesthatareexchangedbetweenthedatalinklayerandadjacentlayersareofthefollowingfourtypes(seealsofigure3).**Layer3ConfirmIndicationSAPDatalinklayerLayer2peer-to-peerprotocolRequestResponseNOTE:Thesameprincipleappliesfordatalinklayer-physicallayerinteractions.Figure3:PrimitiveactionsequenceSIST EN 300 937 V8.0.1:2003
ETSIETSIEN300937V8.0.1(2000-09)9(GSM04.05version8.0.1Release1999)TheREQUESTprimitivetypeisusedwhenahigherlayerisrequestingaservicefromthenextlowerlayer.TheINDICATIONprimitivetypeisusedbyalayerprovidingaservicetonotifythenexthigherlayerofactivitiesrelatedtotheprimitivetypeREQUEST.TheRESPONSEprimitivetypeisusedbyalayertoacknowledgereceipt,fromalowerlayer,oftheprimitivetypeINDICATION.TheCONFIRMprimitivetypeisusedbythelayerprovidingtherequestedservicetoconfirmthattheactivityhasbeencompleted.TheprecisespecificationofLayer-to-layerinteractionsisgiveninGSM04.06.InformationbetweenpeerentitiesandbetweenentitiesinadjacentlayersattachedtothesameSAPistransferredintwodifferenttypesofmessageunits:-messageunitsofapeer-to-peerprotocol;and-messageunitsthatcontainlayer-to-layerinformationconcerningstatusandspecializedservicerequests.Themessageunitsofthelayer3peer-to-peerprotocolarecarriedbythedatalinkconnection.Themessageunitscontaininglayer-to-layerinformationconcerningstatusandspecializedservicerequestsareneverconveyedoveradatalinkconnectionoraphysicalconnection.Thepresentdocumentintroduces(seealsofigure4):a)thepeer-to-peerprotocolforthetransferofinformationandcontrolbetweenanypairofdatalinklayerserviceaccesspoints;b)theinteractionsbetweenthedatalinklayerandlayer3,andbetweenthedatalinklayerandthephysicallayer.Layer3entityLayer3entityDatalinklayerentityDatalinklayerentitylayerlayerentityentityPhysicalPhysicalDatalinklay
...