Frame Relay - for Faster and More Efficient Data Communications ...

49TERMINATION POINT FRAGMENTThe Termination Point Fragment decribesManaged Objects which are closely relatedto Resources in the vicinity of endpoints of Trails and Connections. Theseclose relationships are illustrated by comparingFig. 6, showing the Functional Model,with Fig. 18, showing the Entity Relationshipdiagram of the corresponding InformationModel. Table 2 lists TransportFunctions, Transport Reference Points,and relationships between Transport ReferencePoints and related ManagedObjects.Fig. 20Inheritance Hierarchy for Generic TerminationPointsSINK, SOURCE and BIDIRECTIONALTPTTPCTPTermination PointTrail Termination PointConnection Termination PointThe process that leads from the FunctionalModel of the transport network, Fig. 6,to the corresponding Information Model isdescribed below. The Functional Model ofthe transport network describes ConnectionPoints that are related to accessible ornon-accessible points in transmission networkimplementations. It also describesTransport Functions performed by theseimplementations, in which the Resourcesrequired for management are found too.The Network Element aspect provides adetailed description of the NEs, while theNetwork aspect uses only those detailsthat are required for network management.The Functional Model provides an abstractview of telecommunications equipment,based on the essential functions that suchequipment must perform. These functionalcomponents are modelled by ManagedObjects in the Information Model. ManagedObjects represent implementationindependentaspects of equipment andnetworks.Several Resources can be combined intoa Managed Object. The particular Resourcescombined to form a Managed Objectcan be chosen so that they permit- the use of appropriate facilities for themonitoring and controlling of functions- iterative usage of management informationleading to subclasses in hierarchies-the name and the naming structure ofManaged Objects leading to namingtrees.A relationship between Managed Objectscan be expressed either as a Managed Objector as an attribute of one or both of theManaged Objects associated by the relationship.In Fig. 18 two types of relationshipare shown:- Connectivity Pointer relationship, definingthe one-to-one association betweenTermination Points, appears as attributesin both Termination Points- Naming (containing) relationship, definingthe association between n TerminationPoints in the client layer and one TerminationPoint in the server layer,appears as an attribute in the TerminationPoint of the server layer.Fig. 19 illustrates signal transport to andfrom functional units in a network. Resourcesinvolved in signal receiving leadto "SINK" type Managed Objects. Resourcesinvolved in signal sending lead to"SOURCE" type Managed Objects. Forsignal transmission 2 to 140 Mbit/s acrossthe PDH multiplexer shown in Fig. 13,Functions 1-4 lead to "SINK" type andFunctions 10-19 to "SOURCE" type ManagedObjects. In the reverse direction,Functions 10-19 are related to "SINK" andFunctions 1-4 to "SOURCE". Resourcesfor signal receiving and sending lead to "BI­DIRECTIONAL" type Managed Objects."SINK" and "SOURCE" characterisingManaged Objects should not be confusedwith "in" and "out" characterising TransportFunctions.Fig. 20 shows the Inheritance Hierarchy ofTermination Points (TP). Bidirectional TPsinherit the properties from SINK andSOURCE TPs through a multiple inheritancemechanism. This is valid, in principle,for all PDH and SDH Inheritance Hierarchies(but not shown in all the figures).PDH Information modelContrary to the SDH case, for which RecommendationG.774 specifies the InformationModel, no CCITT recommendationfor the PDH Information Model exists atpresent. The Model described below is basedon the principles used in the SDH case.ERICSSON REVIEW No. 1-2, 1992